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  • Articles: DFG German National Licenses  (4,533)
  • 1985-1989  (2,892)
  • 1965-1969  (1,641)
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  • Insulin
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  • Articles: DFG German National Licenses  (4,533)
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  • 1
    Electronic Resource
    Electronic Resource
    Insulin and insulin-like growth factor (IGF I) modulate the effects of bTSH on3H-thymidine incorporation in human thyroid cells in primary culture (1989)
    Springer
    Journal of molecular medicine 67 (1989), S. 976-979 
    Details
    ISSN: 1432-1440
    Keywords: Human thyroid cells ; Thyroid cell growth ; bTSH ; Insulin ; Insulin-like growth factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of TSH in thyroid cell growth and the pathogenesis of goiter has become a matter of recent debate, since many investigators have failed to demonstrate a growth-promoting effect of TSH in human thyroid cells in culture. While those studies have focused on the action of TSH in human thyroid cells, the influence of assay conditions and cofactors has received scant attention. In the present study, we have therefore undertaken to elucidate the effects of insulin and insulin-like growth factor (IGF I) on3H-thymidine uptake in human thyroid cells, particularly with respect to their relation to the actions of bTSH. We could demonstrate a considerable, dose-dependent stimulation of3H-thymidine incorporation in the cells by bTSH that was dependent on the presence of insulin or IGF I; bTSH alone was ineffective in that respect. The concentrations of insulin and IGF I required to facilitate the TSH response were of a magnitude at which both peptides were totally ineffective by themselves. At concentrations of insulin or IGF I that produced a maximum stimulation of3H-thymidine incorporation, the addition of bTSH did result in a slight decrease rather than a further increase of that stimulation. We conclude from these findings, first, that TSH appears to be a growth factor for human thyroid cells under the conditions described, and, second, the effects of TSH on thyroid cell proliferation are under the control of cofactors like insulin and IGF I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01716060
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  • 2
    Electronic Resource
    Electronic Resource
    Insulin and C-peptide co-localization in theβ granules of normal human pancreas and insulinomas (1989)
    Springer
    Virchows Archiv 416 (1989), S. 19-23 
    Details
    ISSN: 1432-2307
    Keywords: C-peptide ; Insulin ; Pancreaticβ cells ; Insulinoma morphometry ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It has been shown, by using the immunogold technique, that C-peptide and insulin are co-localized in the mature granules of human pancreaticβ cells and insulinomas with typical granules. The mean gold bead densities of both C-peptide and insulin were at least twice as high in the normal pancreas when compared with the insulinomas. The mean granule diameter of the insulinoma cells (D=0.30 ±0.12 μm) was smaller than that of human pancreatic cells (D=0.45 ±0.15 μm). The morphometric data indicate that each of the antigens (C-peptide and insulin) is distributed similarly in the halos and the dense cores of theβ granules. Thus, no topological segregation of these two antigens occurs within theβ granules of either normal human pancreas or insulinomas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606466
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  • 3
    Electronic Resource
    Electronic Resource
    Feline sporotrichosis: A case report (1989)
    Springer
    Mycopathologia 108 (1989), S. 149-154 
    Details
    ISSN: 1573-0832
    Keywords: Sporotrichosis ; Sporothrix schenckii ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The isolation of Sporothrix schenckii from a female European cat it is described. The cat showed lengthened alopecic areas, with prominent nodules in the external surface of the thighs and abdomen. A mycological and histopathological studies of the lesions were carried out. The lesions resolved under treatment with 20% potassium iodide in doses of 0'1 ml/kg oral route in a 8 weeks period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00436219
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  • 4
    Electronic Resource
    Electronic Resource
    The cerebellar nuclear afferent and efferent connections with the lateral reticular nucleus in the cat as studied with retrograde transport of WGA-HRP (1989)
    Springer
    Anatomy and embryology 179 (1989), S. 471-483 
    Details
    ISSN: 1432-0568
    Keywords: Lateral reticular nucleus ; Cerebellar nuclei ; Retrograde transport of WGA-HRP ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cerebellar nuclear projection from the lateral reticular nucleus (NRL) was studied in 29 cats by means of retrograde axonal transport after implantation of the crystalline wheat germ agglutinin-horseradish peroxidase (WGA-HRP) complex in the cerebellar nuclei. It was confirmed that all the cerebellar nuclei receive afferent fibres from the NRL with the strongest termination in the ipsilateral interposed nuclei. In addition, these experiments give evidence of a previously unrecognized topical pattern in the projection to the interposed nuclei, arranged according to the same principle as in the projection to the immediately overlying cerebellar cortex. Thus, the anterior interposed nucleus receives fibres from all parts of the main NRL, its rostral part especially from laterally situated neurons, while subsequent more caudal parts from more medially situated neurons, while the posterior interposed nucleus receives fibres mainly from the dorsomedial part of the main NRL. The cerebellar nuclear projection to the NRL was investigated in 15 cats using retrograde transport after ventral microiontophoretical ejections of the WGA-HRP complex in the main NRL. The contralateral rostral fastigial nucleus was confirmed as the main origin of this projection, but projecting neurons were, in addition, discovered rostrally in the anterior interposed and dentate nuclei on the same side. No topical differences could be observed following ejections in different parts of the NRL; the majority of the projecting neurons were always concentrated along the ventral and lateral borders of the fastigial nucleus and in the adjacent medial part of the anterior interposed nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319590
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  • 5
    Electronic Resource
    Electronic Resource
    Neurovisceral sphingomyelinosis in a Siamese cat (1989)
    Springer
    Acta neuropathologica 79 (1989), S. 330-332 
    Details
    ISSN: 1432-0533
    Keywords: Sphingomyelinosis ; Neuropathology ; Histochemistry ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This report presents the clinical, morphological and biochemical findings on an 11-month-old female Siamese cat with neurovisceral sphingomyelinosis. Gross pathological features and histochemical findings are compared with the human disease counterpart and the previously described animal models. Hepatomegaly was observed while splenomegaly was not. Although sphingomyelin in liver and spleen was biochemically elevated, histochemical results in this case were slightly different from those previously recorded in human and feline Niemann-Pick disease. These results suggest that this feline case might be a different type of animal Niemann-Pick disease to that reported previously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294670
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  • 6
    Electronic Resource
    Electronic Resource
    Cytochemical studies of normal feline blood and bone marrow cells (1989)
    Springer
    Annals of hematology 58 (1989), S. 195-199 
    Details
    ISSN: 1432-0584
    Keywords: Cytochemistry ; Blood ; Bone marrow ; Leukocytes ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Blood and bone marrow cells of ten clinically healthy cats were stained for alkaline phosphatase (ALP), peroxidase (PO), chloroacetate esterase (CAE), alpha-naphthyl butyrate esterase (NBE), sudanophilia, and periodic acid-Schiff (PAS) reaction. Mature neutrophils in blood and bone marrow were devoid of ALP and NBE, but exhibited modest to strong PO, CAE, sudanophilia, and PAS reaction. In bone marrow, sudanophilia, PO, and CAE were prominent at the promyelocyte stage and diminished with cellular differentiation and maturation, while PAS reactivity increased with cell maturation usually from the myelocyte stage onwards. Myeloblasts were negative for all cytochemical reactions, but some large unidentifiable cells reacted strongly for ALP. Eosinophils were slightly reactive for ALP, CAE, and PAS, but not for PO, sudanophilia, and NBE. Basophil granules stained strongly for CAE, revealed PAS positivity, and stained negatively for PO, NBE, ALP, and sudanophilia. Slight ALP activity was detected in the intergranular cytoplasm of basophils. Lymphocytes and monocytes, with few exceptions, stained negatively. An occasional lymphocyte revealed slight globular NBE activity (NaF-resistant) and diffuse PAS reaction, while an occasional monocyte contained a few PO-positive and sudanophilic granules. Monocytes reacted modestly, whereas bone marrow macrophages reacted strongly for NBE (NaF-sensitive). Cells of the erythroid series stained negatively for all cytochemical reactions, megakaryocytes were PAS-positive, and platelets gave positive reactions for PAS and CAE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320772
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  • 7
    Electronic Resource
    Electronic Resource
    Biological activity of des-(B26-B30)-insulinamide and related analogues in rat hepatocyte cultures (1989)
    Springer
    Diabetologia 32 (1989), S. 416-420 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; des-(B26-B30)-insulinamide ; [TyrB25]des-(B26-B30)insulinamide ; [HisB25]des-(B26-B30)-insulinamide ; liver metabolism ; rat hepatocyte culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Short-term and long-term biological activities were studied in adult rat hepatocytes cultured in the presence of the insulin analogues des-(B26-B30)-insulinamide, [TyrB25]des-(B26-B30)-insulinamide and [HisB25]des-(B26-B30)-insulinamide. When compared to insulin, full potency of des-(B26-B30)-insulinamide has been reported in rat adipocytes and an enhanced potency has been reported for the other analogues. Steady state binding characteristics of the analogues to hepatocytes were indistinguishable from those of native insulin with half-maximal binding occurring at concentrations of about 0.8 nmol/l. Half-maximal effects for the stimulation of glycolysis and inhibition of basal and glucagon-activated glycogenolysis required identical concentrations for insulin and all 3 analogues. Induction of the key glycolytic enzymes glucokinase and pyruvate kinase as well as the inhibition of glucagon-dependent induction of phosphenolpyruvate carboxykinase also required identical concentrations of insulin and the 3 analogues. These data confirm that in cultured hepatocytes the C-terminal amidation of des-(B26-B30)-insulin results in a molecule with full in vitro potency. In contrast to data obtained in adipocytes, the des-(B26-B30)-insulin-amidated analogues with tyrosine or histidine substitutions at position B25 are equally as potent as native insulin in eliciting biological responses in rat hepatocyte culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271260
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  • 8
    Electronic Resource
    Electronic Resource
    The insulin secretory granule (1989)
    Springer
    Diabetologia 32 (1989), S. 271-281 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; granule ; vesicle ; proton pump ; prohormone conversion ; autocrine ; chromogranin A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The insulin secretory granule of the pancreatic B cell is a complex intracellular organelle comprised of a many proteins with different catalytic activities and messenger functions. With the advent of tumour models of the B cells and the application of immunological and molecular cloning techniques considerable progress has been made in recent years towards the elucidation of the structure and function of these granule proteins. A number of examples are selected here for review. Particular emphasis given to how the activities of quite different granule proteins are interdependent and how this contributes to the co-ordination and integration of the organelle's biological functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265542
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  • 9
    Electronic Resource
    Electronic Resource
    Projections from the rostral mesencephalic reticular formation to the spinal cord (1989)
    Springer
    Experimental brain research 75 (1989), S. 265-279 
    Details
    ISSN: 1432-1106
    Keywords: Rostral interstitial nucleus of the MLF ; Interstitial nucleus of Cajal ; Spinal cord ; Motoneurons ; Neck muscles ; Axial muscles ; Vertical eye and head movements ; Autoradiography ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eye and head movements are strongly interconnected, because they both play an important role in accurately determining the direction of the visual field. The rostral brainstem includes two areas which contain neurons that participate in the control of both movement and position of the head and eyes. These regions are the caudal third of Field H of Forel, including the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and the interstitial nucleus of Cajal with adjacent reticular formation (INC-RF). Lesions in the caudal Field H of Forel in monkey and man result in vertical gaze paralysis. Head tilt to the opposite side and inability to maintain vertical eye position follow lesions in the INC-RF in cat and monkey. Projections from these areas to extraocular motoneurons has previously been observed. We reported a study of the location of neurons in Field H of Forel and INC-RF that project to spinal cord in cat. The distribution of these fiber projections to the spinal cord are described. The results indicate that: 1. Unlike the neurons projecting to the extra-ocular muscle motoneurons, the major portion of the spinally projecting neurons are not located in the riMLF or INC proper but in adjacent areas, i.e. the ventral and lateral parts of the caudal third of the Field H of Forel and in the INCRF. A few neurons were also found in the nucleus of the posterior commissure and ventrally adjoining reticular formation. 2. Neurons in caudal Field H of Forel project, via the ventral part of the ventral funiculus, to the lateral part of the upper cervical ventral horn. This area includes the laterally located motoneuronal cell groups, innervating cleidomastoid, clavotrapezius and splenius motoneurons. At lower cervical levels labeled fibers are distributed to the medial part of the ventral horn. Projections from the caudal Field H of Forel to thoracic or more caudal spinal levels are sparse. 3. Neurons in the INC-RF, together with a few neurons in the area of the nucleus of the posterior commissure, project bilaterally to the medial part of the upper cervical ventral horn, via the dorsal part of the ventral funiculus. This area includes motoneurons innervating prevertebral flexor muscles and some of the motoneurons of the biventer cervicis and complexus muscles. Further caudally, labeled fibers are distributed to the medial part of the ventral horn (laminae VIII and adjoining VII) similar to the projections of Field H of Forel. A few INC-RF projections were observed to low thoracic and lumbosacral levels. It is argued that the neurons in the caudal Field H of Forel, which project to the spinal cord are especially involved in the control of those fast vertical head movements which occur in conjunction with saccadic eye movements. In contrast the INC-RF projections to the spinal cord are responsible for slower, smaller movements controlling the position of the head in the vertical plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247933
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  • 10
    Electronic Resource
    Electronic Resource
    Short latency somaesthetic responses in motor cortex, transmitted through the spino-thalamic system, in the cat (1989)
    Springer
    Experimental brain research 75 (1989), S. 639-643 
    Details
    ISSN: 1432-1106
    Keywords: Motor cortex ; Somaesthetic responses ; Spinothalamic system ; Intracellular recording ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Evidence is presented that in the cat, the spinothalamic system contributes to short latency somaesthetic responses in motor cortex efferent cells. Intracellular recordings performed on identified pyramidal tract cells and corticospinal cells show that these cells are still activated and/or inhibited from the periphery after a set of central nervous lesions leaving intact only the ventral half of the spinal cord. The responses were attributed to the spinothalamic system. The ascending system is activated through collaterals of afferent fibres running in the dorsal columns of the spinal cord. This peripheral link to the motor cortex might participate in updating the motor command on the basis of information feedback from the periphery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249915
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  • 11
    Electronic Resource
    Electronic Resource
    Orientation bias of cat retinal ganglion cells: a reassessment (1989)
    Springer
    Experimental brain research 76 (1989), S. 182-186 
    Details
    ISSN: 1432-1106
    Keywords: Retinal ganglion cells ; Orientation bias ; Receptive field centre ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary For cat retinal ganglion cells whose receptive field centres were distributed in specified sections of the left visual field, the deviations of the major axis from the radial, horizontal, and circumferential directions were determined. The percentage of cells with deviations within ± 20° from the radial, horizontal, and circumferential directions were, respectively, 33%, 68%, 16%. In addition, comparison between values of deviation from the horizontal direction for cells located at eccentricities of 10° and 20° from the area centralis showed a statistically significant trend: the bias for the horizontal increased with eccentricity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253635
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  • 12
    Electronic Resource
    Electronic Resource
    Unitary characteristics of presumptive cholinergic tegmental neurons during the sleep-waking cycle in freely moving cats (1989)
    Springer
    Experimental brain research 76 (1989), S. 519-529 
    Details
    ISSN: 1432-1106
    Keywords: Pontine tegmentum ; Cholinergic neurons ; Single units ; Sleep-waking states ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A total of 260 neurons were recorded in the rostral pontine tegmentum of freely moving cats during the sleep-waking cycle. Of these, 207 neurons (80%) were located in the dorsal pontine tegmentum containing monoaminergic and choline acetyltransferase (ChAT)-immunoreactive, or cholinergic neurons. In addition to presumably monoaminergic PS-off cells (n = 51) showing a cessation of discharge during paradoxical sleep (PS) and presumably cholinergic PGO-on cells (n = 40) exhibiting a burst of discharge just prior to and during ponto-geniculo-occipital (PGO) waves, we observed tonic (n = 108) and phasic (n = 61) neurons exhibiting, respectively, tonic and phasic patterns of discharge during wakefulness and/or paradoxical sleep. Of 87 tonic cells histologically localized in the dorsal pontine tegmentum rich in cholinergic neurons, 46 cells (53%) were identified as giving rise to ascending projections either to the intralaminar thalamic complex (n = 26) or to the ventrolateral posterior hypothalamus (n = 13) or to both (n = 9). Two types of tonic neurons were distinguished: 1) tonic type I neurons (n = 28), showing a tonic pattern and high rates of discharge during both waking and paradoxical sleep as compaired with slow wave sleep; and 2) tonic type II neurons (n = 20), exhibiting a tonic pattern of discharge highly specific to the periods of paradoxical sleep. Tonic type I neurons were further divided into two subclasses on the basis of discharge rates during waking: a) rapid (Type I-R; n = 17); and b) slow (Type I-S; n = 11) units with a discharge frequency of more than 12 spikes/s or less than 5 spikes/s, respectively. Like monoaminergic PS-off and cholinergic PGO-on cells, both tonic type II and type I-S cells were characterized by a long spike duration (median: 3.3 and 3.5 ms), as well as by a slow conduction velocity (median: 1.8 and 1.7 m/s). In the light of these data, we discuss the possible cholinergic nature and functional significance of these ascending tonic neurons in the generation of neocortical electroencephalographic desynchronization occurring during waking and paradoxical sleep.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248908
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  • 13
    Electronic Resource
    Electronic Resource
    Cat red nucleus activity preceding movement depends on initiation conditions (1989)
    Springer
    Experimental brain research 77 (1989), S. 271-282 
    Details
    ISSN: 1432-1106
    Keywords: Red nucleus ; Motor initiation ; Single-unit activity ; Reaction time ; Delayed movement ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of 98 Red Nucleus neurons was recorded in 3 cats operantly conditioned to perform a ballistic forelimb flexion movement triggered after a brief sound in a simple Reaction Time condition, or Delayed after the same sound in the presence of a tone cue. Fifty-eight task related neurons presented changes of activity in either one or both conditions. Forty-four of them were studied quantitatively and classified in 3 categories: 1) only 16% of the units presented similar changes of firing preceding the triggered or delayed movement; 2) most units (55%) presented different changes of activity in the two conditions: in the Delayed condition, the activation occurred earlier before the movement, and/or the change in magnitude was reduced or the pattern of activity was modified; 3) moreover, for 29% of the units, the change of activity observed before movement in the Reaction Time condition was severely reduced or even absent in the Delayed condition. For some of these neurons a building-up of activity was observed very early in the Reaction Time condition, during the preparatory period, well before the occurrence of the conditioned stimulus. These results show that the Red Nucleus activity preceding a movement is clearly dependent on its initiation conditions. The distinct patterns of unit firing observed in the Reaction Time condition and in the Delayed condition are tentatively related to the different preparation and initiation constraints determined by the behavioral conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00274984
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  • 14
    Electronic Resource
    Electronic Resource
    The effects of postsynaptic inhibition on the monosynaptic reflex of the cat at different levels of motoneuron pool activity (1989)
    Springer
    Experimental brain research 77 (1989), S. 577-584 
    Details
    ISSN: 1432-1106
    Keywords: Motoneuron pool ; Inhibition ; Monosynaptic reflex ; Recruitment level ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The motoneurons to the Soleus muscle in the decerebrate cat were activated by the crossed extensor reflex, elicited by stimulation of the contralateral common peroneal (CP) nerve. Monosynaptic reflexes were obtained from the Soleus motoneuron pool by stimulation of the cut L7-S1 dorsal roots. The amplitude of the reflex increased approximately linearly with the recruitment level of the motoneuron pool. Tonic postsynaptic inhibition was induced in the Soleus moto-neuron pool by repetitive antidromic stimulation of the Lateral Gastrocnemius (LG) and Medial Gastrocnemius (MG) nerves at a rate of 17–47 stimuli/s. This reduced the size of the monosynaptic reflex at rest by at least 40%. However, when the motoneurons were active, the amplitude of the monosynaptic reflex obtained during repetitive stimulation of the LG-MG nerve increased with the recruitment level along the same curve as the control reflexes. Thus, tonic postsynaptic inhibition of the motoneurons per se cannot control the amplitude of the monosynaptic reflex independently of the recruitment level of the motoneuron pool. These experimental results verify predictions from computer simulations and suggest by exclusion that presynaptic inhibition is needed to control the amplitude of the monosynaptic reflex independently of the recruitment level of the motor pool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249610
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  • 15
    Electronic Resource
    Electronic Resource
    Note on the tonotopic organization in the cat medial geniculate body: influence of sampling of units (1989)
    Springer
    Experimental brain research 74 (1989), S. 220-226 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; Medial geniculate body ; Hearing ; Tonotopic organization ; Single unit recording
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The tonotopic organization observed in the present study for the pars lateralis (LV) of the medial geniculate body (MGB) in nitrous oxide anesthetized cats is generally consistent with that previously reported under barbiturate anesthesia. The present data, however, provide evidence for local deviations in characteristic frequency (CF) using appropriate sampling procedures of single units. Although the majority of pairs of units recorded simultaneously with the same microelectrode showed comparable CFs, a few pairs of such neighbouring units displayed CF disparities of up to 1.5 octaves. In addition, some units characterized by an elevated threshold had a CF deviating significantly from the general CF progression observed for the majority of units having low thresholds. This study points out the influence of the sampling procedure on the quality of the tonotopic organization observed in the MGB in addition to a possible effect of the level of anesthesia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248295
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  • 16
    Electronic Resource
    Electronic Resource
    Axis of preferred motion is a function of bar length in visual cortical receptive fields (1989)
    Springer
    Experimental brain research 76 (1989), S. 307-314 
    Details
    ISSN: 1432-1106
    Keywords: Moving stimuli ; Orientation specificity ; Preferred axes ; Spot-response-axis ; Striate cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The responses of 82 simple cells and 41 complex cells in area 17 of anesthetized and paralysed cats were examined with light bars of different length. For 84% of the simple cells and 66% of the complex cells the preferred axis of orientation of a stationary flashing long bar (orientational selectivity) and the preferred axis of movement of a small spot were parallel. As a consequence, the axis of maximal response to a moving light spot was mostly orthogonal to the optimal axis of a moving bar. Thus, a single cell responds to two perpendicular axes of preferred movement one for a long bar and one for a light spot, respectively. For both axes independent direction preferences could be distinguished. Additional preferred axes of movement between the two orthogonal extremes could be found with moving bars of intermediate lengths. This can be explained by the fact that cells with a pronounced response to a moving spot showed a strong tendency for intermediate bar length to elicit responses consisting of a superposition of both components. Therefore, decreasing bar length resulted in a gradual rotation of the preferred direction of movement from orthogonal to parallel with respect to the orientational axis, rather than to a mere widening of the tuning curve. Accordingly, the change in orientation selectivity with decreasing bar length is a regular transition from the orientation dependent response to a response type that depends only on the movement axis of the spot. Thus, in a simple model, the resulting response characteristic can be interpreted as an average of both components weighted according to the length of the stimulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247890
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  • 17
    Electronic Resource
    Electronic Resource
    Eye movements evoked by microstimulations in the brainstem of the alert cat (1989)
    Springer
    Experimental brain research 77 (1989), S. 94-102 
    Details
    ISSN: 1432-1106
    Keywords: Eye movement ; Brainstem ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study maps the eye movements evoked by microstimulations in the medulla of 9 alert cats. Trains of square waves (20 μA amplitude, 0.2 msec duration, 200 Hz) were delivered through glass-covered tungsten microelectrodes (0.5–1 MΩ). Movements of both eyes were recorded by the magnetic field/eye coil technique. Stimulation of the prepositus hypoglossi nucleus (PH) evoked nystagmus with ipsilaterally-directed slow phases followed by after-nystagmus with contralaterally-directed slow phases. Stimulation of the medial vestibular nucleus (MVN) induced nystagmus whose slow phases were more often ipsilaterally-directed but at time contralaterally-directed. At nearly all sites where we stimulated the reticular formation underlying prepositus and vestibular nuclei (from P4.5 to P12), we recorded versional conjugate movements. They were most often ipsilaterally-directed. Some microstimulations in the region of the medial longitudinal fasciculus evoked recentering eye movements: regardless of the initial position of the gaze (to the left as well as to the right), microstimulations given at the same place induced a movement of both eyes toward their neutral position. The amplitude of this movement was proportional to the eccentricity of the pre-stimulation position of the gaze.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250571
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  • 18
    Electronic Resource
    Electronic Resource
    Central distributions of the efferent and afferent components of the pharyngeal branches of the vagus and glossopharyngeal nerves: an HRP study in the cat (1989)
    Springer
    Experimental brain research 78 (1989), S. 327-335 
    Details
    ISSN: 1432-1106
    Keywords: Pharyngeal vagus nerve ; Pharyngeal glossopharyngeal nerve ; Nucleus ambiguus ; Retrofacial nucleus ; Lateral reticular formation ; Nucleus of solitary tract ; Alaminar spinal trigeminal nucleus ; Horseradish peroxidase ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The central distributions of efferent and afferent components of the pharyngeal branches of the vagus (PH-X) and glossopharyngeal (PH-IX) nerves in the cat were studied by soaking their central cut ends in a horseradish peroxidase (HRP) solution. HRP-labelled PH-X neurones were distributed ipsilaterally in the rostral part of the nucleus ambiguus (NA) and the retrofacial nucleus (RFN); HRP-labelled PH-IX neurones were found in the ipsilateral RFN and the bulbopontine lateral reticular formation (RF). Vagal pharyngeal neurones constituted a large population of brainstem motoneurones. The population of HRP-labelled glossopharyngeal neurones was divided into two components. Indeed, on the basis of their location and somal morphology, the most ventral cells were identified as cranial motoneurones and those scattered in the lateral RF as parasympathetic preganglionic neurones. Application of HRP to the PH-IX nerve resulted also in the labelling of fibres and terminals in the alaminar spinal trigeminal nucleus and the nucleus of the solitary tract (NTS). The afferent fibres entered the lateral medulla with the glossopharyngeal roots, ran dorsomedially, then turned caudally toward the NTS and the caudal part of the alaminar spinal trigeminal motor (V) nucleus. In the NTS, labelled fibres ran mainly along the solitary tract, projecting to terminals in the dorsal and dorsolateral nuclei of the NTS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228904
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  • 19
    Electronic Resource
    Electronic Resource
    Response to rates of luminance change of sustained and transient cells in the cat lateral geniculate nucleus and optic tract (1989)
    Springer
    Experimental brain research 74 (1989), S. 116-130 
    Details
    ISSN: 1432-1106
    Keywords: Lateral geniculate nucleus ; Optic tract ; Sustained cells ; Transient cells ; Temporal luminance modulation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We recorded the response of sustained (X) and transient (Y) cells in the cat lateral geniculate nucleus (LGN) and optic tract to a stationary spot while the spot luminance was increased and decreased with a constant rate (linear luminance functions), or modulated sinusoidally. The spot filled the receptive field center, and was surrounded by an annulus of fixed luminance. The LGN X cells seemed to perform a differentiation-like operation in the time domain at slow temporal modulations, giving information about rate of luminance change. To the linear luminance functions the cells responded with a constant firing rate. The on-center cells were activated during increasing luminance, the off-center cells during decreasing luminance. This firing rate increased monotonically with rate of luminance change. To low-frequency sinusoidal modulations the cells had a marked negative phase shift. The response of the LGN Y cells had a transient component shortly after the luminance started to increase (on-center cells) or decrease (off-center cells), followed by a secondary, gradually changing component. The peak of the transient component occurred on average when the response of the X cells increased most rapidly. To low-frequency sinusoidal modulation the average negative phase shift of this peak was twice the average of the X cells. The Y system could accordingly provide information about rate of change in the response of the X system. In the optic tract the X fiber response resembled the LGN X cell response in most respects. The Y fibers had only a weak transient response component, so this component was accentuated in the thalamic relay. Also the sensitivity for rate of luminance change was increased in LGN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248285
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  • 20
    Electronic Resource
    Electronic Resource
    Excitatory interactions between phrenic motoneurons: intracellular study in the cat (1989)
    Springer
    Experimental brain research 74 (1989), S. 131-138 
    Details
    ISSN: 1432-1106
    Keywords: Phrenic motoneurons ; Intracellular recording ; Interactions ; Recurrent EPSPs ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Intracellular recordings were made from 220 Phrenic Motoneurons (PM) in anaesthetized, spontaneously breathing cats, deafferented from C3 to C7, in order to look for somatic events related to the Recurrent Responses (RR) evoked in PM axons by repetitive stimulation of the phrenic nerve. RR appear sporadically at a constant latency, originate from a spinal nicotinic mechanism and can be evoked in a PM without the presence of an antidromic volley in its axon (Khatib et al. 1986). 2. Using stimuli effective for eliciting RR in axons, we failed to observe intracellularly somatic events corresponding to RR after the occurence of an antidromic action potential. RR were observed extracellularly in two cases, but in both cases the recording originated from axons. 3. We attempted to elicit somatic RR without a preceding antidromic action potential, using either parathreshold stimulation of the impaled PM, or suprathreshold stimulation of a phrenic strand which excluded the axon of the impaled PM. In both cases, RR-like events, with very stable latencies, appeared sporadically in 4/142 and 2/15 PMs respectively. 4. Parathreshold stimuli or stimulation of a strand were coupled with averaging of the synaptic noise in order to look for small events temporally related to the stimuli. Short latency small depolarizations, looking-like recurrent EPSPs, were revealed in 22/142 and 5/15 PMs respectively. 5. These results confirm the existence of interrelations between PMs, providing for re-excitation and coupling within the phrenic pool, in addition to centrally imposed synchronization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248286
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  • 21
    Electronic Resource
    Electronic Resource
    Binocular depth perception, visual acuity and visual fields in cats following neonatal section of the optic chiasm (1989)
    Springer
    Experimental brain research 74 (1989), S. 272-278 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; Corpus callosum ; Optic chiasm ; Stereoacuity ; Visual acuity ; Visual fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied the role of the transcallosal pathway in stereopsis by measuring binocular and monocular depth perception in two cats that had undergone section of the optic chiasm at the age of 21 d. To ensure that the surgery did not impair vision to the extent that depth perception could not be evaluated, visual acuity and visual fields were also measured. In both of the chiasm-sectioned animals the visual fields were reduced and the visual acuity was substantially lower than in normal cats, with a maximum of about 2 cyc deg-1. Binocular depth thresholds of the chiasm-sectioned cats were worse than those of the normal cat but were better than their own monocular thresholds. These results suggest that the chiasm-sectioned animals were still able to use binocular cues to judge depth and indicate that the indirect pathway through the corpus callosum is sufficient to mediate binocular depth perception.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248860
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  • 22
    Electronic Resource
    Electronic Resource
    Demonstration of axonal branching of fibres from certain precerebellar nuclei to the cerebellar cortex and nuclei: a retrograde fluorescent double-labelling study in the cat (1989)
    Springer
    Experimental brain research 75 (1989), S. 15-27 
    Details
    ISSN: 1432-1106
    Keywords: Precerebellar nuclei ; Cerebellar cortex and nuclei ; Fluoro-Gold ; Rhodamine-B-isothiocyanate (RITC) ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The projections from certain brain stem precerebellar nuclei to the cerebellar cortex and nuclei have been examined in the cat by using the retrograde fluorescent double-labelling technique. Crystalline Fluoro-Gold was implanted into the left cerebellar nuclei from the contralateral side and rhodamine-B-isothiocyanate was injected into the overlying cerebellar cortex. The inferior olive, the lateral reticular nucleus, and the reticular tegmental pontine nucleus all contained double- as well as single-labelled neurons, and it was concluded that these nuclei have a high number of neurons whose axons branch to both the cerebellar cortex and nuclei. The neurons in the paramedian reticular nucleus and the pontine nuclei proper appear to project only to the cerebellar cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248525
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  • 23
    Electronic Resource
    Electronic Resource
    Modulation of short latency cutaneous excitation in flexor and extensor motoneurons during fictive locomotion in the cat (1989)
    Springer
    Experimental brain research 77 (1989), S. 57-68 
    Details
    ISSN: 1432-1106
    Keywords: Cutaneous EPSPs ; Fictive locomotion ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We examined modulation of transmission in short-latency, distal hindlimb cutaneous reflex pathways during fictive locomotion in 19 decerebrate cats. Fictive stepping was produced either by electrical stimulation of the mesencephalic locomotor region (MLR) or by administration of Nialamide and 1-DOPA to acutely spinalized animals. Postsynaptic potentials (PSPs) produced by electrical stimulation of low threshold afferents (〈 2.5 times threshold) in the superficial peroneal (SP), sural, saphenous or medial plantar nerves were recorded intracellularly from various extensor (n = 28) and flexor (n = 24) motoneurons and averaged throughout the step cycle, together with voltage responses to intrasomatic constant current pulses (in order to monitor relative cell input resistance). Each motoneuron studied displayed rhythmic background oscillations in membrane potential and correlated variations in input resistance. The average input resistance of extensor motoneurons was lowest during mid-flexion, when the cells were relatively hyperpolarized and silent. Conversely, average input resistance of flexor motoneurons was highest during mid-flexion, when they were depolarized and active. The amplitude of the minimum-latency excitatory components of PSPs produced by cutaneous nerve stimulation were measured from computer averaged records representing six subdivisions of the fictive step cycle. Oligosynaptic EPSP components were consistently modulated only in the superficial peroneal responses in flexor motoneurons, which exhibited enhanced amplitude during the flexion phase. With the other skin nerves tested (sural, saphenous, and plantar), no consistent patterns of modulation were observed during fictive locomotion. We conclude that transmission through some, but not all, oligosynaptic excitatory cutaneous pathways is enhanced by premotoneuronal mechanisms during the flexion phase of fictive stepping in several cat hindlimb motor nuclei. The present results suggest that the patterns of interaction between the locomotor central pattern generator and excitatory cutaneous reflex pathways depend on the source of afferent input and on the identity of the target motoneuron population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250567
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  • 24
    Electronic Resource
    Electronic Resource
    Pharyngeal motoneurones: respiratory-related activity and responses to laryngeal afferents in the decerebrate cat (1989)
    Springer
    Experimental brain research 78 (1989), S. 336-344 
    Details
    ISSN: 1432-1106
    Keywords: Vagal pharyngeal nerve ; Glossopharyngeal nerve ; Single fibre recordings ; Respiratory-related units ; Superior laryngeal nerve ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In decerebrate, paralyzed and artificially ventilated cats, we recorded the discharge of 64 motor axons supplying the pharyngeal muscles. Filaments containing motor axons, with discharges related to the respiratory cycle (phrenic nerve activity), were teased from the pharyngeal branches of the vagus and glossopharyngeal nerves. Most units (n = 41) fired only during expiration and exhibited a steady, a decreasing or a late augmenting discharge pattern. These units were found only in vagal filaments. Twenty three units discharged during inspiration and exhibited a steady, a late augmenting or a tonic discharge pattern. The inspiratory-related units were present in both the vagus (n=13) and glossopharyngeal (n=10) nerves. Nineteen of 20 pharyngeal inspiratoryrelated units tested were activated at short latency (range 3.4 to 8.0 ms) by stimulation of afferents in the superior laryngeal nerve (SLN). In 13 of these, such stimulation also suppressed their spontaneous activity. SLN stimulation elicited in all 17 pharyngeal expiratory-related units tested a short latency (range 0 to 8 ms) reduction of activity, followed in 7 units by an increase in activity. SLN stimulation occasionally evoked single or rhythmic multifibre bursts in the vagal pharyngeal filaments. These bursts, involving expiratory-related units, likely correspond to the buccopharyngeal stage of swallowing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228905
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  • 25
    Electronic Resource
    Electronic Resource
    Quantitative measurements of receptive field changes during antagonism of GABAergic transmission in primary somatosensory cortex of cats (1989)
    Springer
    Experimental brain research 78 (1989), S. 514-532 
    Details
    ISSN: 1432-1106
    Keywords: Bicuculline ; Inhibition ; Latency ; Receptive field profile ; Somatosensory cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In cortical area 3b of cats, responses of 76 single neurons to punctate indentations were recorded before and during iontophoretic administration of bicuculline methiodide (BMI), a GABAergic antagonist, at levels that did not affect spontaneous activity. Constant amplitude indentations were applied to selected sites along distalproximal and radial-ulnar axes that intersected the most sensitive area in the receptive field. Profiles of response magnitudes were used to measure receptive field dimensions before and during antagonism of GABAergic inhibition. Blockade of GABAergic transmission caused receptive field dimensions of 48 rapidly-adapting neurons to increase an average 141%, or nearly 2.5 times their original size. Analysis of the spatial distribution of inhibition indicated that in-field inhibition was larger than surround inhibition. During BMI administration, response latency was significantly longer for response elicited from the expanded territory than for responses elicited from within the original receptive field, suggesting that receptive field expansion might be mediated by multisynaptic intracortical connections. The magnitude of receptive field expansion was independent of receptive field size or peripheral location. In a substantial number of neurons, however, BMI produced asymmetric expansions that extended only in the proximal direction. For 9 slowly-adapting neurons, BMI produced measureable increases in receptive field dimensions, but these changes were significantly smaller than the changes in rapidly-adapting neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230239
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  • 26
    Electronic Resource
    Electronic Resource
    Actions of excitatory amino acid antagonists on synaptic potentials of layer II/III neurons of the cat's visual cortex (1989)
    Springer
    Experimental brain research 78 (1989), S. 489-500 
    Details
    ISSN: 1432-1106
    Keywords: NMDA receptor ; Visual cortex ; Excitatory amino acid ; Slice ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Actions of excitatory amino acid (EAA) antagonists on the responses of cells in layers II/III and IV of the cat's visual cortex to stimulation of layer VI and the underlying white matter were studied in slice preparations. Antagonists used were 2-amino-5-phosphonovalerate (APV), a selective antagonist for the N-methyl-D-aspartate (NMDA) type of EAA receptors, and kynurenate, a broadspectrum antagonist for the three types of EAA receptors. In extracellular recordings it was demonstrated that most of the layer II/III cells were sensitive to APV, while the great majority of the layer IV cells were not, By contrast, kynurenate suppressed the responses completely in both layers. Excitatory post-synaptic potentials (EPSPs) evoked by stimulation of layer VI and the while matter were recorded intracellularly from layer II/III neurons. To determine whether the EPSPs were elicited mono- or polysynaptically, the synaptic delay for each EPSP was calculated from a pair of onset latencies of EPSPs evoked by stimulation of the two sites. Forty-two percent of the layer II/III cells were classified as having monosynaptic EPSPs. In 60% of these monosynaptic cells, the rising slope of the EPSPs was reduced by APV while in the other 40%, it was not. In the former (APV-sensitive cells), subtraction of the APV-sensitive component from the total EPSP indicated that the onset latency of the NMDA receptor-mediated component was roughly equal to that of the non-NMDA component. In the latter (APV-resistant cells), only the slowly-decaying component was in part mediated by NMDA receptors. The conduction velocities of the afferent fibers innervating APV-resistant cells were slower than those of the APV-sensitive cells, suggesting that both types of cells are innervated by different types of afferents. The polysynaptic EPSPs of almost all layer II/III cells were sensitive to APV. The subtraction method indicated that the NMDA component had about the same magnitude as the non-NMDA components. When the slices were superfused by a Mg2+-free solution, the EPSPs were potentiated dramatically, but this potentiation was reduced to the control level during the administration of APV. Similarly, APV-sensitive components were potentiated during the administration of bicuculline, a selective antagonist for gamma-aminobutyric acid receptors of A type. These results suggest that NMDA receptors participate, at varying degrees, in excitatory synaptic transmission at most layer II/III cells in the cat's visual cortex, and their actions appear to be regulated by intracortical inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230237
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  • 27
    Electronic Resource
    Electronic Resource
    Behavioural thermosensitivity after bilateral lesions of the lateral funiculi in the cervical spinal cord of the cat (1989)
    Springer
    Experimental brain research 78 (1989), S. 374-379 
    Details
    ISSN: 1432-1106
    Keywords: Thermosensitivity ; Spinal cord ; Ascending pathways ; Behaviour ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The behavioural thermosensitivity of six cats was measured before and after single stage, symmetrical, bilateral, surgical lesions of the cervical spinal cord. The lesions were aimed at an area in the most ventral parts of the dorsal halves of the lateral funiculi. Unilateral lesions of that area have previously been found to cause reproducible, although subtotal, contralateral thermosensory defects, which were attributed to interruption of the thermosensory spinothalamic pathway. The lesions of three of the present cats were found to be incomplete, and those animals showed no postoperative thermosensory deficiency. Two of the cats with complete lesions showed marked post-operative defects, especially immediately after the operations, but the third cat with a complete lesion showed no postoperative thermosensory defect at all. The differences between the last three animals have been compared to the irregularity of previous reports about thermosensitivity after spinal cord lesions in man and animals, and may depend on the testing technique, rather than differences of thermosensitivity per se.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228909
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  • 28
    Electronic Resource
    Electronic Resource
    The distribution of intrinsic cortical axons in area 3b of cat primary somatosensory cortex (1989)
    Springer
    Experimental brain research 78 (1989), S. 501-513 
    Details
    ISSN: 1432-1106
    Keywords: Somatosensory cortex ; Interlaminar ; Corticortical ; SI ; Area 3b ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The morphology of single neurons in area 3b of cat primary somatosensory (SI) cortex was examined after horseradish peroxidase (HRP) injections. Neurons were labeled either by intracellular injection of HRP following intracellular recording or by small extracellular iontophoretic HRP injections. Both pyramidal and nonpyramidal neurons were labeled and reconstructed from serial sections. Their axons had local, interlaminar and interareal patterns of termination. Most neurons formed local axonal fields around their cell bodies and dendrites. Pyramidal neurons in cortical layer IV sent axons up into layers II and III, neurons in layers II and III sent axons down to layer V, and layer V neurons sent axons to layer VI as well as back to the upper layers. Layer VI neurons sent axons back to the upper cortical layers in a unique bowl-shaped pattern. The horizontal distribution of axons of pyramidal cells in layer III was extremely widespread. Axons of layer III neurons in area 3b terminated within 3b and area 1, but not in other areas of SI. Layer III neurons in area 1 distributed axon collaterals to all fields of SI as well as projecting a main axon to motor cortex. In general, the axon collaterals of area 3b pyramidal cells outside layer III remained confined to area 3b. Most of the nonpyramidal neurons labeled were basket cells in layers III and VI. These neurons formed dense axonal fields around their cell bodies, and none of their axons could be followed into the underlying white matter. The results of the present study demonstrate that area 3b somatosensory cortical neurons and their axons are vertically organized in a manner similar to that reported for other sensory cortical areas. They also show that widespread horizontal connections are formed by pyramidal neurons of layer III, and that these horizontal axons can travel for great distances in the cortical grey matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230238
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  • 29
    Electronic Resource
    Electronic Resource
    Role of the sensorimotor cortex in postural adjustments accompanying a conditioned paw lift in the standing cat (1989)
    Springer
    Experimental brain research 78 (1989), S. 588-596 
    Details
    ISSN: 1432-1106
    Keywords: Motor cortex ; Conditioned movement ; Posture ; Balance control ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of the sensorimotor cortex in the postural adjustments associated with conditioned paw lifting movements was investigated in the cat. Cats were trained to stand quietly on four strain gauge equipped platforms and to perform a lift-off movement with one forelimb when a conditioned tone was presented. The parameters recorded were the vertical forces exerted by the paws on each platform, the lateral and antero-posterior displacements of rods implanted on the T2, T12, L5 vertebrae as well as their rotation, and the EMG of triceps and biceps of both forelimbs. Before lesion, the postural adjustment consisted of a “nondiagonal” pattern where the CG was displaced laterally inside the triangle formed by the three remaining supporting limbs. Here a lateral bending of the thoracic column toward the supporting forelimb could be observed. The associated EMG pattern consisted of an early activation of the triceps lateral head in the moving limb which was probably responsible for the body displacement toward the opposite side, and a late biceps activation associated with the lift. In the supporting forelimb, a coactivation of the biceps and triceps was usually present. After contralateral sensorimotor lesion, the conditioned lifting movements were lost for 4–15 days after the lesion, before being subsequently recovered. The same lateral CG displacement and bending of the back was seen after lesion as before, which indicates that the goal of postural adjustment was preserved. However, the means of reaching it were modified. In most of the intact animals, the CG displacement was achieved in one step, whereas in the animals with lesions, the displacement was made either according to a slow ramp mode or in a discontinuous manner involving several steps. The mechanisms responsible for this disturbance are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230246
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  • 30
    Electronic Resource
    Electronic Resource
    The role of inhibitory processes in the formation of functional properties of neurons in vibrissal projection zone of the cat somatosensory cortex (1989)
    Springer
    Experimental brain research 76 (1989), S. 198-206 
    Details
    ISSN: 1432-1106
    Keywords: Somatosensory cortex ; Directional sensitivity ; GABA inhibition ; Picrotoxin ; Bicuculline ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of intracortical inhibitory processes in the formation of neuronal receptive fields in the vibrissal projection zone of the somatosensory cortex was studied. Iontophoretic application of picrotoxin and bicuculline blocks the inhibition and causes the loss of directional sensitivity in neurons. Activation of inhibition by distant glutamate application gives opposite results — neurons become direction sensitive. A dependence was found between spatial location of activated cells and the pattern of changes of their detector properties. Inhibitory processes caused by natural afferent stimulation lead to similar changes in the functional properties of neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253637
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  • 31
    Electronic Resource
    Electronic Resource
    Effects of dark rearing on the development of visual callosal connections (1989)
    Springer
    Experimental brain research 78 (1989), S. 203-213 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Development ; Vision ; Dark rearing ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is now well established that during normal postnatal development there is a partial elimination of the callosal projections of cortical areas 17 and 18 in the cat and that visual experience early in life can modulate this process. In the present experiments, we quantitatively studied the influence of light, per se, by rearing cats in total darkness. Dark rearing exaggerates the normally occurring partial elimination of immature callosal projections: it causes a significant reduction in the total number of neurons in both the supra-and infragranular layers that send an axon through the corpus callosum and slightly narrows the distribution of these neurons across areas 17 and 18. These data demonstrate that visual stimulation is not necessary either to initiate the partial elimination of immature callosal projections or to stabilize a large fraction of the callosal projections present at birth. However, normal visual stimulation is necessary for the stabilization of the normal complement of callosal projections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230700
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  • 32
    Electronic Resource
    Electronic Resource
    Intercostal and abdominal muscle afferent influence on caudal medullary expiratory neurons that drive abdominal muscles (1989)
    Springer
    Experimental brain research 78 (1989), S. 219-222 
    Details
    ISSN: 1432-1106
    Keywords: Control of respiration ; Intercostal muscle afferents ; Phrenic nerve ; Abdominal muscle afferents ; Expiratory neurons ; Abdominal muscle control ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Our objective was to determine if caudal ventral respiratory group (VRG) expiratory (E) neurons that drive abdominal expiratory motoneurons in the lumbar cord respond to intercostal and lumbar nerve afferent stimulation. Results showed that 92% of medullary E-neurons that were antidromically activated from the upper lumbar cord reduced their activity in response to stimulation of external and internal intercostal and lumbar nerve afferents. We conclude that afferent information from intercostal and abdominal muscle tendon organs has an inhibitory effect on caudal VRG E-neurons that drive abdominal expiratory motoneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230702
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  • 33
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    Electronic Resource
    Synaptic potentials induced by postganglionic stimulations in cat bladder parasympathetic neurones (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 235-244 
    Details
    ISSN: 1432-2013
    Keywords: Cat ; Urinary bladder ; Parasympathetic ganglion neurone ; Postganglionic stimulation ; Synaptic potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intracellular recording techniques were used to examine and compare synaptic potentials evoked by stimulating pre- and postganglionic nerve trunks in cat bladder parasympathetic ganglia. In the 76 ganglion cells exammed, two types of responses were recorded on stimulating the postganglionic nerve: an antidromic action potential (type Post NS1;n=30) or a fast excitatory postsynaptic potential (f-EPSP; type PostNS2;n=46) which resulted in an orthodromic-like action potential. In some of the cells exhibiting a PostNS1 response (n=19), a fast depolarization was superimposed on the antidromic spike. This depolarization was due to the synaptic activation of nicotinic receptors. In many of the cells exhibiting either PostNS1 or PostNS2 responses, repetitive stimulation of the postganglionic nerve induced a slow hyperpolarization. Applying nicotinic (hexamethonium, methonium, 0.5–1 mM), muscarinic (atropine, 1 μM), alpha-adrenergic (phentolamine, 1 μM) and purinergic (caffeine, 0.5–1 mM) receptor antagonists completely inhibited the tetanus-induced slow hyperpolarization in some cells (n=5). In other cells (n=15), a slow hyperpolarization persisted in the presence of these antagonists. These results indicate that stimulation of the postganglionic nerve trunk of cat bladder parasympathetic ganglia can elicit not only an antidromic action potential, but also synaptic potentials which are mediated by the activation of cholinergic (nicotinic and muscarinic), noradrenergic and purinergic receptors, as well as a non-cholinergic, non-alpha-adrenergic and non-purinergic synaptic potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580969
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  • 34
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    Electronic Resource
    Oro-facial dyskinesia and the sub-commissural part of the globus pallidus in the cat: role of acetylcholine and its interaction with GABA (1989)
    Springer
    Psychopharmacology 99 (1989), S. 381-385 
    Details
    ISSN: 1432-2072
    Keywords: Oro-facial dyskinesia ; Globus pallidus ; GABA ; Acetylcholine ; Behaviour ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The possible role of cholinergic mechanisms in the sub-commissural part of the globus pallidus (scGP) in the induction of oro-facial dyskinesia (OFD) was studied in cats. Local injections of the cholinergic agonist carbachol into the scGP elicited tongue protrusions in a dose dependent way (100–1000 ng/0.5 μl). The effect elicited by 1000 ng carbachol was selectively antagonized by the cholinergic antagonist scopolamine (10 μg/0.5 μl); this dose of scopolamine was ineffective when injected alone. The tongue protrusions resulted from both normal and abnormal movements: whereas normal movements simply consisted of protruding the flat tongue, abnormal movements implied a variety of movements, especially curling upwards the lateral side(s) or tip of the tongue inside or outside the oral cavity. The abnormal carbachol-induced tongue protrusions formed part of a syndrome marked by dyskinetic movements of the muscles of the eye, ear and cheek, and were identical to those seen previously after local injections of picrotoxin (250–500 ng). Intra-pallidal injections of the abovementioned dose of scopolamine had no effect on the tongue protrusions induced by local injections of 375 ng picrotoxin. However, local injections of 100 ng muscimol, which was previously found to attenuate significantly the effect of 375 ng picrotoxin and which was ineffective when injected alone, significantly attenuated the tongue protrusions induced by local injections of 1000 ng carbachol. These data suggest that the cholinergic effects are mediated via a GABAergic mechanism, but not vice versa. The results are discussed in view of GABAergic and anticholinergic therapies used in oro-facial dyskinesia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00445562
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  • 35
    Electronic Resource
    Electronic Resource
    [3H]ICS 205-930 labels 5-HT3 recognition sites in membranes of cat and rabbit vagus nerve and superior cervical ganglion (1989)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 340 (1989), S. 396-402 
    Details
    ISSN: 1432-1912
    Keywords: 5-HT3 receptors ; Radioligand binding ; [3H]ICS 205-930 ; Cat ; Rabbit ; Vagus nerve ; Superior cervical ganglion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The binding characteristics of [3H]ICS 205-930, a 5-hydroxytryptamine 5-HT3 receptor antagonist, were investigated in membranes prepared from cat and rabbit vagus nerve (VN) and superior cervical ganglion (SCG). The autoradiographic localisation of 5-HT3 recognition sites was also assessed using [3H]ICS 205-930 in slices from cat medulla oblongata, nodose ganglion and vagus nerve. [3H]ICS 205-930 bound to a homogeneous population of high affinity recognition sites in cat VN: Bmax = 201 ± 43 fmol/mg protein, pKD = 9.26 ± 0.17 and SCG: Bmax = 291 ± 40 fmol/mg, pKD = 9.35 ± 0.80 (n = 3). Competition experiments performed in membranes from cat VN and SCG with agonists and antagonists suggested the presence of a homogeneous population of [3H]ICS 205-930 recognition sites. Competition curves were steep and monophasic and were best fitted by a 1 receptor site model. The following rank order of affinity for [3H]ICS 205-930 binding sites was observed with antagonists: SDZ 206-830 = ICS 205-930 〉 BRL 43694 〉 SDZ 206–792 〉 quipazine 〉 MDL 72222 〉 metoclopramide 〉 mCPP and agonists: 2-methyl-5-HT = 5-HT 〉 phenylbiguanide. A similar profile was observed for a limited series of compounds in rabbit membranes. Drugs acting at 5-HT1, 5-HT2 and dopamine receptors (domperidone, spiperone and metergoline) showed very low affinities for [3H]ICS 205-930 recognition sites. The sites labelled with [3H]ICS 205-930 in vagus nerve and superior cervical ganglion of both species displayed the pharmacological profile of a 5-HT3 receptor. There was a significant correlation between the rank order of affinity of the tested compounds for [3H]ICS 205-930 recognition sites in cat and rabbit membranes and their rank order of affinity for 5-HT3 receptors from neuroblastoma-glioma NG 108-15 cells. Autoradiographic studies suggest that [3H]ICS 205-930 binding sites are present over and around the nodose ganglion cell somata, along certain fibers of the vagus nerve and in the terminal areas of this nerve in the medullar nucleus of the vagus. The present data demonstrate that [3H]ICS 205-930 identifies 5-HT3 receptors in preparations of cat and rabbit vagus nerve and superior cervical ganglion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167040
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  • 36
    Electronic Resource
    Electronic Resource
    Carotid occlusion increases the release of endogenous GABA in the nucleus of the solitary tract (1989)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 340 (1989), S. 764-766 
    Details
    ISSN: 1432-1912
    Keywords: Nucleus of the solitary tract (NTS) ; GABA release ; Carotid occlusion ; Blood pressure ; Push-pull cannula ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized cats, the nucleus of the solitary tract was bilaterally superfused through push-pull cannulae with artificial cerebrospinal fluid (CSF) and the effect of carotid occlusion on the release of endogenous GABA was investigated. Bilateral carotid occlusion led to a rise in blood pressure which was associated with a very pronounced increase in the release rate of GABA in the nucleus of the solitary tract. The results demonstrate the hypertensive function of GABA in the nucleus of the solitary tract and the importance of GABAergic neurons of this nucleus for the central cardiovascular control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169687
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  • 37
    Electronic Resource
    Electronic Resource
    Ultrastructure and immunocytochemistry of endocrine cells in the midgut of the desert locust, Schistocerca gregaria (Forskal) (1989)
    Springer
    Cell & tissue research 258 (1989), S. 577-583 
    Details
    ISSN: 1432-0878
    Keywords: Gut hormones ; Insulin ; Bombesin ; Immunocytochemistry ; Pancreatic polypeptide ; Cholecystokinin (CCK) ; Gastrin ; Schistocerca gregaria (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The endocrine cells of the midgut epithelium of the desert locust are found dispersed among the digestive cells and are similar to those of the vertebrate gut. According to their reactivity to silver impregnation techniques and the ultrastructural features of the secretory granules (shape, electron-density, size, and structure) 10 types of endocrine cell have been identified, of which seven are located in the main segment of the midgut or in the enteric caeca, and the other three seem to be present only in the ampullae through which the Malpighian tubules drain into the gut. The endocrine cells have a slender cytoplasmic process that reaches the gut lumen, a feature that supports the receptosecretory nature postulated for this cellular type in insects as well as vertebrates. Antisera directed against mammalian gastrin, CCK, insulin, pancreatic polypeptide and bombesin reacted with some of the endocrine cells. This is the first time that insulin- and bombesin-like immunoreactive cells have been described in the midgut of an insect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218870
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  • 38
    Electronic Resource
    Electronic Resource
    Gap junctions between odontoblasts revealed by transjunctional flux of fluorescent tracers (1989)
    Springer
    Cell & tissue research 258 (1989), S. 611-616 
    Details
    ISSN: 1432-0878
    Keywords: Cell communication ; Dye-coupling ; Odontoblasts ; Gap junctions ; Dentin sensitivity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cell communication between odontoblasts was investigated with the use of fluorescent-dye tracers; Lucifer Yellow CH (molecular weight = 457.3), and dextran-Lucifer Yellow CH (average molecular weight = 10000). Dyes were injected into cell bodies of individual odontoblasts via an intracellular microelectrode or into a group of cells through their processes, and passage to adjacent cells was examined with a fluorescence microscope. Lucifer Yellow CH appeared to diffuse very easily among odontoblasts, while dextran-Lucifer Yellow remained within the injected cell or cells. This efficient migration of Lucifer Yellow CH can be considered a functional manifestation of gap junctions between odontoblasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218874
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  • 39
    Electronic Resource
    Electronic Resource
    Localisation of islet amyloid peptide in lipofuscin bodies and secretory granules of human B-cells and in islets of type-2 diabetic subjects (1989)
    Springer
    Cell & tissue research 257 (1989), S. 179-185 
    Details
    ISSN: 1432-0878
    Keywords: Islet amyloid peptide ; Pancreatic islets ; Type-2 diabetes ; Insulin ; Lysosomes ; Secretory granules ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Islet amyloid peptide (or diabetes-associated peptide), the major component of pancreatic islet amyloid found in type-2 diabetes, has been identified by electronmicroscopic immunocytochemistry in pancreatic B-cells from five non-diabetic human subjects, and in islets from five type-2 diabetic patients. The greatest density of immunoreactivity for islet amyloid peptide was found in electrondense regions of some lysosomal or lipofuscin bodies. The peptide was also localised by quantification of immunogold in the secretory granules of B-cells, and was present in cytoplasmic lamellar bodies. Acid phosphatase activity was also demonstrated in these organelles. Immunoreactivity for insulin was found in some lysosomes. These results suggest that islet amyloid peptide is a constituent of normal pancreatic B-cells, and accumulates in lipofuscin bodies where it is presumably partially degraded. In islets from type-2 diabetic subjects, amyloid fibrils and lipofuscin bodies in B-cells showed immunoreactivity for the amyloid peptide. Abnormal processing of the peptide within B-cells could lead to the formation of islet amyloid in type-2 diabetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221649
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  • 40
    Electronic Resource
    Electronic Resource
    NPY-, galanin-, VIP/PHI-, CGRP- and substance P-immunoreactive neuronal subpopulations in cat autonomic and sensory ganglia and their projections (1989)
    Springer
    Cell & tissue research 256 (1989), S. 259-273 
    Details
    ISSN: 1432-0878
    Keywords: Autonomic ganglia ; Spinal ganglia ; Sensory neurons ; Neurotransmitters ; Sweat glands ; Blood vessels ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The neuronal subpopulations in the cat stellate, lower lumbar and sacral sympathetic ganglia were studied with regard to the cellular distribution of immunoreactivity to tyrosine hydroxylase (TH), acetylcholinesterase (AChE) and various neuronal peptides. Coexistence of neuropeptide Y (NPY)- and galanin (GAL)-like immunoreactivity (LI) was found in a high proportion of the neuronal cell bodies; these cells also contained immunoreactivity to TH, confirming their presumably noradrenergic nature. Some TH- and GAL-immunoreactive principal ganglion cells lacked NPY-LI. Two populations (scattered and clustered) of vasoactive intestinal polypeptide (VIP)- and peptide histidine isoleucine (PHI)-positive cell bodies were found in the sympathetic ganglia studied. The scattered VIP/PHI neurons also contained AChE-LI, calcitonin gene-related peptide (CGRP)-and, following culture, substance P (SP)-LI. The clustered type only contained AChE-LI. In the submandibular and sphenopalatine ganglia, neurons were AChE- and VIP/ PHI-immunoreactive but lacked CGRP- and SP-LI. Many GAL- and occasional TH-positive neurons were found in these ganglia. In the spinal ganglia, single NPY-immunoreactive sensory neuronal cells were observed, in addition to CGRP- and SP-positive neurons. The present results show that there are at least two populations of sympathetic cholinergic neurons in the cat. Retrograde tracing experiments indicate that the scattered type of cholinergic neurons contains four vasodilator peptides (VIP, PHI, CGRP, SP) and provides an important input to sweat glands, whereas the clustered type (containing VIP and PHI) mainly innervates blood vessels in muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218883
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  • 41
    Electronic Resource
    Electronic Resource
    Nerve-induced secretion of parotid acinar granules in cats (1989)
    Springer
    Cell & tissue research 257 (1989), S. 549-554 
    Details
    ISSN: 1432-0878
    Keywords: Salivary secretion ; Parotid gland ; Exocytosis ; Secretory granules ; Autonomic nerve-stimulation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscopy of cat parotid glands revealed great heterogeneity in the secretory granules of normal unstimulated acinar cells. Electrical stimulation of the parasympathetic nerve to the gland evoked a copious flow of parotid saliva which was accompanied by an extensive depletion of the secretory granules from the acinar cells. Exocytosis was captured as it was occurring by means of perfusion-fixation, and showed that the events occur in a conventional manner. Stimulation of the sympathetic nerve caused only a very small flow of saliva, and no acinar degranulation was detected. It can be concluded that the parasympathetic secretomotor axons provide the main drive for parotid acinar degranulation in the cat. This contrasts with the rat in which sympathetic impulses provide the main stimulus for parotid acinar degranulation. These dissimilarities serve to emphasise how extensively species differences may influence autonomic responses in salivary glands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221465
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  • 42
    Electronic Resource
    Electronic Resource
    Abstracts of Dutch doctoral theses (1989)
    Springer
    Pharmacy world & science 11 (1989), S. 236-243 
    Details
    ISSN: 1573-739X
    Keywords: Absorption ; Diabetes mellitus, insulin-dependent ; Injections, subcutaneous ; Insulin ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01959418
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  • 43
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    Electronic Resource
    Histologic and physiologic evaluation of electrically stimulated peripheral nerve: Considerations for the selection of parameters (1989)
    Springer
    Annals of biomedical engineering 17 (1989), S. 39-60 
    Details
    ISSN: 1573-9686
    Keywords: Electrical stimulation ; Neural damage ; Peripheral nerve electrode ; Peroneal nerve ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Helical electrodes were implanted around the left and right common peroneal nerves of cats. Three weeks after implantation one nerve was stimulated for 4–16 hours using charge-balanced, biphasic, constant current pulses. Compound action potentials (CAP) evoked by the stimulus were recorded from over the cauda equina before, during and after the stimulation. Light and electron microscopy evaluations were conducted at various times following the stimulation. The mere presence of the electrode invariably resulted in thickened epineurium and in some cases increased peripheral endoneurial connective tissue beneath the electrodes. Physiologic changes during stimulation included elevation of the electrical threshold of the large axons in the nerve. This was reversed within one week after stimulation at a frequency of 20 Hz, but often was not reversed following stimulation at 50–100 Hz. Continuous stimulation at 50 Hz for 8–16 hours at 400 μA or more resulted in neural damage characterized by endoneurial edema beginning within 48 hours after stimulation, and early axonal degeneration (EAD) of the large myelinated fibers, beginning by 1 week after stimulation. Neural damage due to electrical stimulation was decreased or abolished by reduction of the duration of stimulation, by stimulating at 20 Hz (vs. 50 Hz) or by use of an intermittent duty cycle. These results demonstrate that axons in peripheral nerves can be irreversely damaged by 8–16 hours of continuous stimulation at 50 Hz. However, the extent to which these axons may subsequently regenerate is uncertain. Therefore, protocols for functional electrical stimulation in human patients probably should be evaluated individually in animal studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02364272
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  • 44
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    Electronic Resource
    Selective hydrogenation: Kinetic investigation of 1, 3-cyclo-octadiene and cyclo-octene hydrogenationDedicated to Prof. Dr.-Ing. Hanns Hofmann on the occasion of his 65th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 45-53 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The vapour phase hydrogenation of 1,3-cyclo-octadiene (COD) over Pd on alumina has been studied in the gas phase, using a recycle reactor. The dependences of COD hydrogenation rates and those of the consecutive cyclo-octene (COE) hydrogenation on the reaction conditions are well described by a model which takes into account mass transfer in the porous layer of palladium. The kinetics of the COE hydrogenation is of a Langmuir-Hinshelwood type. The hydrogenation of COD is of first order with respect to hydrogen. The reaction order with respect to COD is -0.15. If the catalyst surface is completely covered by COD, the hydrogenation of COE is totally suppressed. This indicates a much stronger adsorption of COD than of COE. Hydrogenation of COE can only occur in the innermost part of the pores when the transport of COD by diffusion is insufficient to supply the entire active surface of the catalyst. This happens if the ratio PH2/PCOD exceeds 2/ϕ2 with ϕ being the Thiele's modulus. This relationship permits a simple evaluation of the effective diffusion coefficient in the porous Pd-layer.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120109
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  • 45
    Electronic Resource
    Electronic Resource
    Advances in modelling and design of multitubular fixed-bed reactorsII. A Mathematical Model of the Cocurrent Multitubular Reactor System (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 170-175 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents a method mathematical modelling of cocurrent multitubular fixed-bed reactors. The method is adapted to the most widespread type of industrial reactor design, i.e. the system fitted with disk-and-doughnut baffles. The proposed model makes it possible to estimate the influence of non-uniformity of the heat carrier flow on the reactor characteristics, taking into account the coolant streams by-passing via the tube-to-baffle clearances. Based on the model, the effect of the operating parameters as well as of some more important geometrical parameters of the reactor on an exemplary highly exothermic process of partial benzene oxidation to maleic anhydride is discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120123
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  • 46
    Electronic Resource
    Electronic Resource
    A new model of the effect of stirring intensity on the rate of secondary nucleationPaper presented at the Anual Meeting of the “GVC-Fachausschuß Kristallisation”, The Hague, March 10 to 12, 1986. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 137-146 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Secondary nucleation in industrial crystallizers depends on both supersaturation and mechanical stress by stirring. Most models which consider mechanical stress assume that nucleation is proprotional to the energy transferred to the crystals during collisions. This is not based on any physical relationship and, in addition, the models do not satisfactorily reproduce the experimental results. Own model, based on the theory of Hertz/Huber, which accounts for the stress of the crystals caused by impact, gave better results. This well-known and proven theory allows the calculation of the volume abraded during collisions between crystals and stirrer or walls. Introducing a nucleate efficienncy, the effect of mechanical stress on the rate of secondary nucleation, due to stirring intensity and crystallizer size, can be determined.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120119
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  • 47
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    Electronic Resource
    Effects of turbulence on heat and mass transfer in stagnation flowsPaper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987.Dedicated to Professor Dr. Josef Kestin on the occasion of his 75th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 176-187 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of turbulence on local heat and mass transfer is systematically analyzed. Essential prerequisite is the availability of measurement methods, based on convective mass transfer, which allow the visualization of heat and mass transfer distributions. The results show that, even at low turbulence intensities, the flow and transport phenomena are decisively influenced by the specific design of turbulence grids and the orientation of the grid wires with respect to the stagnation line. Thereby, two different flow mechanisms occur which may interact. The anisotropy of grid turbulence leads to the “wire-gap effect” depending on the actual position of the grid wires in relation to the stagnation line. The other mechanism is based on the wavy wake velocity distribution behind screens and grid which, in conjunction with the centrifugal instability of stagnation flows, may lead to longitudinal vortices. The results indicate why turbulence has not been sufficiently considered in the available (semi-) empirical correlations. Information needed for an accurate prediction of heat and mass transfer in turbulence flows is discussed.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120124
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  • 48
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    Reduction of energy requirements in distillationExtended version of a paper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 163-169 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Distillation has been, up to now, the standard method for separating fluid mixtures in the process industry and the consensus is that it will remain so for years to come. The only disadvantage of distillation is its high energy requirement. In the following, it will be demonstrated on the example of an ideal ternary mixture, how the energy requirement of distillation process can be reduced. Very effective are some modifications of single columns, optimization of column sequences and direct or indirect column coupling. It will be shown that, just by column coupling, the energy requirement can be reduced to a third.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120122
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  • 49
    Electronic Resource
    Electronic Resource
    Venturi scrubber calculation and optimization (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 188-195 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Collection efficiency and pressure loss of a venturi scrubber can usually be determined from the calculation models of Barth and Calvert. However, this only leads to reasonable results if the droplets are uniformly distributed throughout each cross-section of the washing zone. In this work, a two-zone models is developed which allows the calculation of the venturi scrubber at operating conditions with a non-uniform droplet distribution. The scrubber geometry is also taken into account. A venturi scrubber was developed on the basis of this new model. Its energy consumption is significantly lower than the well-Known optimum characteristic of Wicke and Holzer. For ideal operating conditions, a new optimum characteristic is given which should be the aim of future optimizations.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120125
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  • 50
    Electronic Resource
    Electronic Resource
    Model concept of floc disintegration in centrifugal fields (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 200-204 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model of floc destruction resulting form mass forces in a centrifugal field is postulated and its validity examined. This model is to be regarded as a supplement to the existing shear-loading disagglomeration models. In order to verify this additional floc disintegration mechanism, appropriate investigations were carried out with flocculated suspensions of silica and Hamburg dock sludge. As a result, in addition to floc disintegration by shear forces within a turbulent flow and in the centrifuge inlet, the existence of another mechanism was demonstrated. This consists in the floc destruction in a centrifugal field where particles in excess of a certain size, or specifically heavier components, are preferentially torn out of the floc. This floc disintegration by mass forces can lead to a classification effect in centrifuges which also subject the flocs to instant high centrifugal forces.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120127
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  • 51
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    Mass transfer and chemical reaction in fluid two-phase systemsPresented in part at the 21th meeting of the Dechema-Arbeitsausschuß “Technische Reaktionen” together with the GVC-Fachausschuß “Technische Reaktionsführung” in Aronoldsheim/Taunus, 10-11th February 1982. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 195-199 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steady-state concentrations of the transferred reactant in the bulk phase and the non-flowing diffusion boundary layer of an isothermal, isobaric two-phase reactor with an irreversible first-order reaction and constant composition of one phase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120126
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  • 52
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    Electronic Resource
    Measurement of aeration capacity of fermenters (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 213-217 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Important aspects of K1a measurement in agitated aerated vessels are briefly characterized from the standpoint of reliability of the measured data. An analysis of the shortcomings of dynamic methods for measuring the K1a is given. A new modification of the dynamic method is proposed, which excludes these inadequacies through a special experimental arrangement. This was verified by comparing the data with those obtained by an independent steady-state method. The new method can serve as a standard of reference, suitable for testing newly developed methods for K1a measurement. The initial response method was tested in this way in non-coalescent liquids, and shown to lead to errors of the order of hundreds of percent. K1a values obtained with the initial response method were found to depend strongly on the probe's location in the vessel.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120129
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  • 53
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    Characterization of mixing and residence time distributions in nozzle-type reactors (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 262-269 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Studies of flow characteristics and residence time distribution, (RTD), have been undertaken in a range of geometrically similar, laboratory nozzle-type reactors. High-speed cine-photography was employed to record the complex phenomena of liquid mixing in the reactor and also to record on film the colour of an injected tracer solution leaving in the effluent. A novel atomic absorption spectrophotometric (AAS) technique was applied to transform the results of the latter film into response curves. This technique provide detailed quantitative data on the residence time distributions (RTD) for different feed rates. A multiparameter model, comprising a network of CSTR's and plug flows, was developed to simulate the experimental response data. Good agreement was obtained between model predictions and experimental results. The experimental technique and theoretical approach are recommended for analyzing the flow patterns and mixing mechanisms in such reactors.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120136
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    Streamline-upwind/Petrov-galerkin finite element methods in polymer processing (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 269-273 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120137
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    Vapour-liquid equilibria of hydrogen/coal liquid and methane/coal liquid systems at elevated temperatures and pressures (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 280-288 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A cubic equation of state is modified in such a way that prediction of PVT data from 40 model compounds, typical of coal oil, becomes possible with an absolute mean deviation of less than 2% for saturated liquid volumes and vapour pressures 〉 1 bar. Additional correlations for binary interaction parameters are obtained by an optimization procedure using vapour-liquid euilibrium (VLE) data from known heavy hydrocarbon liquid/light gas systems. When the modified equation is applied to coal-derived liquids, only specific gravity and boiling analysis data of the coal liquids are required, primarily in order to determine the equation-of-state parameters. The proposed equation is shown to allow a good prediction of VLE data for systems consisting of wide-boiling-range coal oils and light gases. Experimental values were obtained at elevated temperatures and pressures with a circulation flow apparatus.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120139
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  • 56
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    Heat transfer enhancement in fin-plate heat exchangers by wing type vortex generatorsDedicated to Professor Dr. Klaus Gersten on the occasion of his birthday. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 288-294 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heat transfer and fluid mechanical data were computed for laminar channel flows containing strong longitudinal vortex pairs. The strong vortices are generated by thin delta wings and delta winglet pairs of low aspect ratios and large angles of attack. These wings are attached to the channel walls. The data show that longitudinal vortices cause high local peaks in heat transfer and marked increases in the overall channel heat transfer. These increases occur over a wide region of channel wall, compared to the vortex generating wing area. The results are of special interest for compact heat exchangers. The heat transfer enhancement allows a considerable reduction in the heat transfer area which, in turn, reduces the manufacturing and operating costs.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120140
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    Fluid dynamic description of jet-loop reactors in multiphase operationModified version of a paper presented by K.H. Tebel at the “Jahrestreffen der Verfahrens-Ingenieure”, Strasbourg, September 17 to 19, 1986. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 274-280 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A superposition of simple physical equations allows a satisfactory, comprehensive fluid dynamic description of jet-loop reactors in multiphase operation up to a dispersed phase hold-up of 15%. In the case of higher concentrations, there are further interactions which are not yet included in the model description. Apart from the drag coefficient of the single-phase jet loop, information on the particle swarm behaviour, i.e. on the slip velocity of the dispersed phase is required. Explicit formulation of the influence of the relevant geometrical parameters permits a reliable scale-up without additional adaptation parameters.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120138
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    Incorporation of gradient into random search optimizationPresented at the Second Canadian-German Workshop on Chemical Engineering Mathematics, Bad Honnef, Fr Germany, May 30-June 2, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 309-318 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To improve the rate of convergence of random search optimization procedures, the incorporation of a gradient-oriented one-dimensional search is investigated. With this modification to the random search procedure based on uniform sampling and region contraction [1], convergence to within 0.01% of the global optimum was obtained substantially faster for typical chemical engineering problems. It was also found that the reliability of obtaining the global optimum was improved.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120143
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    Particle collection in small laboratory cyclones as a basis for the design of large-scale cyclonesPaper presented by H. Büttner at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg September 30 to October 2, 1987. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 295-301 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Grade efficiencies must be measured in order to characterize particle collection in cyclones. For real, irregularly shaped partcles, the grade efficiencies depend on the shape and orientation of the particles and the flow around them. Therefore, the collection characteristics of cyclones should be defined in relation to spherical particles. Deviations occurring on the use of real, irregularly shaped dusts can then be attributed to a material influence. A fast and accurate measuring technique to determine the collection characteristic for spherical particles is described, followed by the presentation of results of extensive investigations on small model cyclones. A similarity relationship is presented. The validity of this relationship was confirmed by investigations with similar, larger cyclones.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120141
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    Leakage rates of refrigerants through cracksPaper presented by F. Westphal at the European Two-Phase Flow Group Meeting, Université Catholique de Louvain, Brussels, May 30 to June 1, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 301-308 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An independent preliminary mechanistic prediction method for leakage rates through small slit-shaped through-wall cracks, based on coupled pressure drop and (critical) mass flux calculation is presented. The predictions are verified against initially subcooled liquid refrigerants and water data collected during experiments in real and model cracks in a wide range of parameters. The achieved accuracy of prediction is already comparable to that of the experimental results. Further model modifications are put forward.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120142
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    Parameter estimation from integral Mars-van Krevelen type of kinetic data of a reaction networkDedicated to Professor Dr. Horst Langemann on the occasion of his 60th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 11-14 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120103
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  • 62
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    Micromixing limits in an MSMPR crystallizer (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 1-11 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of micromixing limits on a process of crystallization in an MSMPR crystallizer is studied with respect to power law growth and nucleation kinetics. Three limiting cases corresponding to maximum mixedness and complete segregation in an MSMPR crystallizer and plug flow configuration were analyzed for processes in which supersaturation is generated by conventional techniques. The sensitivity of these three limiting cases to the supersaturation generation term in each mode of operation was investigated using several numerical examples. The study demonstrates the effects of mixing on the overall crystallizer performance and, in particular, the enormous micromixing influence at high supersaturation generation rates. The difference in the product CSD arise from the variations of supersaturation profiles experienced by the elementary volumes throughout their sojourn. Characterization of mixing in a real crystallizer at some intermediate levels is emphasized with the aid of relevant industrial examples.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120102
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    Coupled simulation of heat transfer and reaction in a steam reforming furnaceDedicated to Professor Dr. Hanns Hofmann on the occasion of his 65th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 20-26 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For design and simulation of chemical process furnaces in accordance with present-day standards, the temperature distributions in the firebox and in the reactors must be generated simultaneously. This calls for coupling of the simulations of the firebox and of the reactor. For the calculation of heat transfer in the firebox, a generalized furnace simulations program, based on the zone method, is applied. Monte Carlo simulation techniques are used to determine the view factors. The location of the burners is explicitly accounted for. Absorption and emission of radiation by the flue gas are calculated by considering band contributions for carbon dioxide and water. For the simulation of the steam reforming reactors, a one-dimensional heterogeneous model, which accounts for the presence of intraparticle partial pressure gradients, is used. The simulated temperature distribution in the furnace is in excellent agreement with industrial results, as is the simulated product distribution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120105
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    Performance of an RTL contactor for gas-liquid systems: Effective interfacial area and volumetric mass transfer coefficient by oxidation of sodium sulphite solution (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 15-19 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effective interfacial area a and volumetric liquid-side mass transfer coefficient kLa of an RTL contactor were obtained at different stirring speeds by absorption of oxygen from air into 0.8 kmol/m3 sodium sulphite solution, in the presence of Co++ ions. The values of a and kLa ranged from 80 to 150 m2/m3 and 0.0003 to 0.00053 s-1, respectively, when stirrer speed was increased from 8 to 40 rpm. When kL alone was evaluated, it was found to be practically constant, irrespective of stirring speed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120104
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    IR study of chlorination of alumina employing mixtures of gaseous chlorine and carbon monoxideDedicated to Professor Dr.-Ing. Hanns Hofmann on the occasion of his 65th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 27-32 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The chlorination of an alumina with BET surface area of 100 m2/g has been studied in situ by transmission IR measurements at about 670 K. The chlorinating gases consisting of Cl2 and CO were employed individually and in equimolar proportion. The IR results do not reveal the presence of a phosgene surface species which could support the only mechanism proposed so far to explain the chlorination. A detailed alternative reaction mechanism is suggested for the high temperature chlorination reaction, taking into account the IR results, together with the known electron donor-acceptor properties of the activated alumina and the reaction gases: Cl2 molecules accept electrons from oxide ions with a lower coordination number on the alumina surface, leading to the formation of Cl-and Oad. While Cl- yields AlCl3, Oad reacts further with CO producing CO2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120106
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    Heat transfer to submerged surfaces in coarse-grained pressurized fluidized beds and fixed bedsPaper presented by J. Schweinzer at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 38-44 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution reports on the theory underlying a uniform representation of heat transfer to submerged surfaces in fixed bed reactors and of gas convective part of heat transfer in fluidized beds with coarse-grained bulk solids and/or at elevated pressure. Based on an analysis of the pressure drop behaviour of fixed bed percolation at different gas pressures and with different bulk solids, a new dimensionless pressure drop parameter was developed. Fixed bed heat transfer data are very well correlated by this new dimensionless number. As soon as fluid throughput is in excess of minimum fluidization velocity, the pressure drop parameter transforms into the well-known Archimedes number. These two dimensionless numbers are connected by the condition of equilibrium for pressure drop and mass of practices in a fluidized bed. This equilibrium is fulfilled as soon as fluidization commences. Up to now, the Archimedes number has been generally accepted as the significant parameter, determining the gas convective part of heat transfer in fluidized beds; however, without any physical interpretation of this parameter. Introduction of the pressure drop number, which is consistent with the Archimedes number, reduces the heat transfer behaviour to pressure drop characteristics. The usefulness of this concept is proven by the comparison of experimental results and prediction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120108
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    Reversible absorption of nitric oxide in low volatile organic liquids containing cupric halides (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 33-37 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The absorption of nitric oxide (NO) in phosphoric acid esters and polyethylene glycol ethers which contain cupric halides has been investigated. Due to high solubility of cupric halides and high equilibrium constants of formed nitrosyl complexes, the effective solubility of nitric oxide can be enhanced to about 100-fold its solubility in the salt-free organic liquid which itself amounts to only about 5-fold the NO-solubility in water. Calculations taking into account flue gas conditions indicate that the required gas-liquid ratio in industrial absorption processes will lie in the normal range of flue gas scrubbing processes, namely in the region of 400:1 to 1000:1 in volume. Thus, such a reversible absorption process could a viable alternative to SCR-processes in flue gas denitrification.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120107
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    Increase in viscosity and its influence on polymerization processesDedicated to Prof. Dr. Heinz Gerrens on the occasion of his 65th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 71-87 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the course of polymerization in homogeneous systems, the viscosity of the reaction mass increases by several orders of magnitude. The viscosity increase is affected by reaction conditions, concentration and properties of the formed polymer. Empirical correlations for homogeneous and heterogeneous polymerizations are given. Viscosity significantly affects the polymerization kinetics as well as heat, mass and momentum balances of the polymerization reactor. The influence of viscosity and its increase on conductive heat transfer, stirrer power input and cooling capacity, molecular diffusion and mass transfer coefficients, mixing time and residence time distribution in homogeneous and heterogeneous polymerizations in stirred tank and tubular reactors is reviewed.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120112
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    The pressure ratio of critical two-phase flowsDedicated to Professor Dr. h.c. Dr.-Ing. Heinz Brauer on the occasion of his 65th birthday (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 89-96 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Depressurization of a pressure vessel, containing a liquid or a gas is limited by the maximum possible mass flux. This flux occurs at a certain drop in pressure. The ratio of ambient pressure to that inside the vessel must be less than a certain critical value. The critical pressure ratio depends on the thermodynamic state of the fluid inside the vessel and on the geometry of the outlet cross-section. The outlet can be a pipeline, a safety valve or a rupture disk. The results of known theoretical and experimental work are presented. In previous experiments, saturated liquids, two-phase flows or pure vapours were examined. In order to predict the critical pressure ratio, certain assumptions are necessary. These are derived for three well-defined cross-sections of the vessel outlet.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120113
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    Effects of pretreatments on semi-continuous anaerobic digestion of wheat straw (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 96-102 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of alkali treatment, nitrogen supplement and hydraulic retention time on methane production rate from semi-continuous anaerobic digestion of 5% wheat straw-water mixtures were investigated. The experiments were carried out in laboratory scale fermenters, fed with 1 1 of basic, alkali treated and nitrogen supplemented 5% wheat straw-water mixtures, respectively, and maintained at 55 °C. Digestion experiments were performed for hydraulic retention times of 8, 10 and 15 days. The amount and composition of produced gas were measured until steady state was attained in each run. The steady-state methane production rates were found to increase with hydraulic retention time and with the type of slurry in the following order; basic, nitrogen supplemented and alkali treated slurry. Data obtained from the experiments were employed to determine the kinetics of methane production from anaerobic digestion of wheat straw, for the assessment of pretreatment effects on process kinetics. The predicted methane production rates were found to be in a reasonably good agreement with the measurements.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120114
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    Simulation of sintering of model supported metal catalysts (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 103-109 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the past decade, the sintering of model supported metal catalysts, i.e. catalysts consisting of metal deposited on very thin and flat oxide films, has been intensively investigated by transmission electron microscopy. In the current paper, a mathematical model, based on an atomic migration mechanism, for the sintering of these catalysts is presented. The predictions of the model, based on Monte Carlo simulations, are in very good agreement with the experimental observations, i.e. phenomena such as ‘apparent’ particle migration, splitting and neck formation between particles are predicated by the model.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120115
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  • 72
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    Dispersion behaviour of droplets in circular loop reactors (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 205-212 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A circular loop reactor was built for application to a heterogeneous liquid-liquid reaction. In order to investigate the dispersion behaviour of droplets in the reactor, basic experiments were performed using a number of liquid-liquid dispersions. Droplets discharged form the impeller region were found to grow due to coalescence in the circulation region. Mean droplet diameter decreased exponentially with elapsing time. An expression correlating the steady-state mean droplet diameter with the operating conditions was derived. Moreover, the transition time required for the droplet diameter to reach the equilibrium value was determined and correlated with the operating conditions.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120128
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    The contradiction in the theory of desorption phenomena: A new interpretation of the classical concept for its avoidance (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 218-225 
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    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Most chemical engineers presently accept that the mass transfer rate in desorption from the solid to the gas phase or from the liquid to the gas phase is accelerated with increasing temperature in the liquid or the solid phase, or increasing partial pressure of inert gas in the gas phase, and/or decreasing total system pressure in the gas phase. Nevertheless, many reports about such mass transfer are still based on the former concept, which completely contradicts the actual phenomena mentioned above. Here, we discuss the contradiction and suggest a way of resolving it in terms of diffusion theory.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120130
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    Thermally stabilized combustionPaper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 249-254 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermally stabilized combustion has a number of unique characteristics which permit the generation of steam or other forms of process energy from the heat of combustion of a gaseous or clean liquid fuel in remarkably compact, integrated apparatus while truly minimizing the concentrations of NOx, CO and unburnt fuel in the effluent. These characteristics, which have been identified by a long-range program of research, are described and the advantages and limitations of this process are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120134
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    Heat and mass transfer during condensation of steam in the presence of air at pressures of up to 21 bar (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 235-244 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Film theory under consideration of one-sided diffusion is a satisfactory basis for the calculation of vapour condensation from a flowing turbulent mixture with non-condensable gases. At atmospheric pressure and low condensate flow rates, coefficient equations for smooth tubes are used as a rule. At higher pressures and thus, at higher temperatures and gas densities, there are additional parameters. For instance, non-ideal behaviour of the gas phase or the surface roughness affects the condensation process. These parameters were examined in a test plant under variation of pressure, steam concentration and temperature in a vapour/air mixture. At pressures of up to 21 bar, the Reynolds number of the gaseous phase reaches a maximum value of 128 000 and of 720 for the condensed phase. After description of the test facility, the experimental results are explained and discussed. It is shown that the experimental results are not in a good agreement with the common calculating methods. Taking into account the non-ideal behaviour of the steam/air mixture and the roughness of condensate surface by using a friction factor ξr, all the results could be calculated with an accuracy of ± 20%. This was achived with a modification of the coefficient equation of Gnielinski [1] and by using the equation of Andreussi [2] for the friction factor of a cocurrent annular flow. With respect to one-sided diffusion, the film theory is still applicable. The described method for the determination of local transfer coefficients includes the common calculating method. It represents an extension of the general validity of the film theory.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120132
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    Influence of turbulence on transient premixed flame propagation inside closed vessels (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 226-233 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The explosion behaviour of CH4/air mixtures inside a closed 0.065 m3 spherical and a 1 m3 cylindrical vessel was investigated to determine the effect of turbulence on the structure and propagation rate of transient turbulent flames for different initial turbulence levels generated by 4 ventilators installed inside the equipment. Laser-Doppler and hot wire anemometry were used to measure the turbulent motion. It was found that fairly uniform turbulence could be achieved in the central zones of the vessels and that the RMS-values of flow velocity were proportional to the ventilator speed. The evaluation of burning velocity from the pressure/time records showed that, starting from an initial burning velocity which depends on the initial turbulence level, the flame accelerates as a result of pressure, temperature and turbulence effects. Maximum burning velocity coincides with the inflexion point of the pressure/time curve, and is followed by a rapid deceleration of the flame front. A linear relationship between burning velocity and measured RMS-velocity is recognized in the observed range of RMS-values.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120131
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  • 77
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    Study of mass transfer in a centrifugal film apparatus (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 245-248 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer data are presented for absorption of oxygen in a centrifugal film apparatus. The apparatus was designed to exclude the formation of foam by gas dispersion in liquid. Cells and micro-organisms are not subjected to high shear stress. Therefore, this equipment can be applied in fermentation processes. In the present work, experimental data and correlations were obtained on splitting of the liquid film and oxygen absorption into the film through a spiral ridge formed on the conical surface. The performance of the apparatus is found to be equivalent to those of other types of absorbers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120133
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  • 78
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    Porosity and permeametry at sub-atmospheric pressures (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 255-261 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Carman-Kozeny equation is applicable in the viscous flow regime but, as the powder becomes finer, this equation fails. The controlling factor is the ratio of the hydraulic diameter to the mean free path of gas molecules (rH/λ) and, as this approaches unity, “slip flow” occurs. This effect increases with (a) increasing fineness, i.e. rH reduced, (b) decreasing porosity, i.e. rH reduced, and (c) decreasing pressure, i.e. λ increased. In order to account for the enhanced flow arising as a result of this failure, a second term is introduced into the equation and this includes an unknown “constant” (δK0/K), the coefficient of slip. It was considered probable that this so-called constant was a function of (rH/λ), and an attempt was made to investigate this relationship.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120135
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  • 79
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    A new load cell for measuring normal and shear stresses (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 318-323 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A special stress measuring device for determining the normal and shear stresses acting on silo walls was developed and tested. The load cell can be used for measuring simultaneously the normal stress as well as the intensity and direction of the shear stress.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120144
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  • 80
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    Heat transfer to liquids and suspensions in agitated narrow vesselsPaper presented by D.-H. Frobese at the “Jahrestreffen der Verfahrensingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 324-332 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The knowledge of the heat transfer coefficient on the inner side of a heated vessel wall is of the utmost importance for the design of agitated vessels. In the case of large Reynolds numbers, the heat transfer is mainly determined by these numbers whereas, with small Reynolds numbers, the heat transfer is better described by considering the Grashof number. Investigations of heat transfer in agitated narrow vessels have shown that the height/diameter ratio exerts virtually no influence on the heat transfer when multi-impeller stirrers are used. The heat transfer to stirred suspensions can be described by relationships valid for liquids if the characteristic data of the liquid are replaced by those of the suspension and when the solids volume concentration is also taken into account. This relationship allows the heat transfer coefficient to be calculated for given solids volume concentrations of up to 60%.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120145
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  • 81
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    Design and analysis of a state observer for the temperature front of a retification columnExtended version of a paper presented by G. Feig at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 339-344 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to achieve optimal energy-saving, load-dependent operation of rectification columns, development and implementation of model-based control concepts are necessary. This paper reports on the design and step-by-step testing of a state observer for the estimation of two state variables which cannot be measured directly, namely the vapour rate and the location of mass transfer zone (temperature front) in the stripping section of a production column. The procedure is described, and the relevant simulation and operation results are presented and discussed. Initial experience, gained when the concept was put into practical operation, is reported.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120147
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  • 82
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    Directional specific shear-rate measurements in gas-liquid two-phase flow (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 374-378 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wall shear rate vectors in a bubble column and an airlift-loop reactor were measured using the limiting-current electrodiffusion technique. In connection with a new circular three-segment probe, the magnitudes and directions of shear rates were determined. The results for the bubble column are in good agreement with hot film-anemometry measurements in the same column. Moreover, the spiral flow structure, postulated in the shear-zone model of Franz, has been confirmed. In addition, the measuring technique was used to determine the flow structure in an airlift-loop reactor employed for the cultivation of animal cells. The region above the gas distributor of this fermenter has been identified as critical for mechanical damage to the cells.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120153
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  • 83
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    Effect of transfer on droplet size in liquid-liquid dispersions (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 395-399 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mean droplet diameter of the dispersed phase in pulsed plate extraction columns was measured for binary and ternary systems. A change in the droplet size in the presence of solute, dependent on such factors as the direction of mass transfer, droplet size in the binary system, radio of diffusion coefficients, viscosity of the continuous phase, interfacial tension and driving force for extraction was observed. Two new empirical correlations of mean droplet sizes in mass transfer conditions are proposed. These correlations have been successfully applied to other extraction columns.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120156
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  • 84
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    Flow phenomena and local heat and mass transfer in corrugated passagesPaper presented by G. Gaiser at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 400-405 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow phenomena, local heat and mass transfer and pressure drop of corrugated passages in process equipment are examined. Based on a method for measuring local heat and mass transfer, developed in previous investigations, a procedure has been formulated for the determination of local heat and mass transfer in corrugated passages. Using the analogy between heat and mass transfer, this technique allows the determination of heat transfer distributions in any structures with high local resolution. The corresponding pressure drop is presented together with the local and integral heat and mass transfer of different structures. It is shown that differences in heat and mass transfer as well as in pressure drop are due to different flow phenomena which also characterize mixing behaviour.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120157
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  • 85
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    A study of gas and liquid distributions in structured packingsPaper presented by R. Stikkelman at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 445-449 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study describes the gas and liquid distributions in a column with structured packings. The column is 0.5 m in diameter. It is equipped with a total of 1289 detectors in the top and bottom cross-sections. These detectors provide a detailed picture of the gas and liquid flows through elements of only 25 × 25 mm2. The maldistribution in the gas bulk flow is negligible. Only the observed wall can contribute to malperformance. The gas flows in parallel to sheet orientation, thus introducing a radial transport. Together with the change in the orientation of subsequent packing elements, this results in good gas mixing. It was observed that the liquid wall flow rate decreases when the gas velocity exceeds 1.7 m/s. Up to the loading point, the maldistribution of the liquid is constant. Above this point, the equality of the distribution deteriorates rapidly, due to the occurrence of large-scale liquid segregation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120164
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  • 86
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    Investigation of a wet dust scrubber with a pneumatic nozzle: Dust collection based on turbulent diffusionPaper presented by P. Centner at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 439-444 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The “nozzle scrubber” is a wet scrubber in which the scrubbing water is dispersed in dust laden gas stream by means of one or more pneumatic nozzle. This scrubber is distinguished by an excellent collection efficiency for submicron dust at an unusually low energy and water consumption. So far, the physical effects affecting the separation cannot be explained by a well-defined theory. Therefore, it is sensible to investigate the collection efficiency with regard to the mechanisms of inertial impaction, turbulent diffusion and coalescence induced by turbulence. The experimental equipment is of a very simple design. A light scattering device was used to measure the particle distributions. In addition, electron micrographs were analyzed to obtain information about the submicron particles. The influence of operating parameters on grade efficiency has been demonstrated by their systematic variation. The contribution of turbulent diffusion to the collection efficiency has been confirmed; nevertheless, grade efficiencies were also measured when inertial impaction prevailed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120163
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  • 87
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    On-line measurement of partical size distribution and partical concentration in suspensions by ultrasonic spectrometryPaper presented by U. Riebel at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 433-438 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The principle of ultrasonic spectrometry is based on the measurement of the ultrasonic extinction caused by the presence of particles. From measurements at different frequencies and with the knowledge of the ultrasonic extinction cross section of the particles, a system of linear equations can be established and solved to obtain the particle size distribution and particle concentration. With an experimental apparatus covering the frequency range from 1.7 MHz to 81 MHz, particles ranging from 20 to 1000 μm in diameter may be analyzed. The measurements can be carried out with particle concentrations as high as 10% by volume.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120162
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  • 88
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    Masthead (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120101
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  • 89
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    Separation of liquid from vapour upon pressure relief (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 54-63 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a chemical reactor is depressurized or pressure in a vessel, filled with saturated liquid, has to be decreased, generally both vapour and liquid flow out through the relief valve. Since chemical reactors are usually operated with toxic and explosive fluids, the discharged liquid which vaporizes on the ground around the vessel may reach dangerous concentrations, causing explosions or accidents with the poisonous gas. During a research project, some fundamentals were developed for the design of separation systems which separate liquid from vapour and store it in a receiver. The requirement for a separation efficiency of a least 80% is related to the condition that the separated liquid should flow back into the reactor still during the pressure relief phase. For safety reasons, both separation and re-storage are to be carried out without the supply of external energy. Theoretical and experimental investigations of pressure distribution within the piping to the relief valve and in an integrated separator show that re-storage of the separated liquid in the vessel can be achieved under certain flow conditions. Therefore, the separator must be integrated in the pipe at a certain height above the vessel, so that the hydrostatic pressure of the separated liquid, corresponding to the difference in height, is sufficient to lead it back through another pipe against the internal pressure of the vessel. First, several separators were tested with air-water mixtures. A swirl separator and a reversing separator have been developed to such an extent that they appear suitable for the set task. Experimental results with air-water mixtures and refrigerant R12 upon pressure relief show separation efficiencies of between 90 and 100% at low pressure drops within the whole operating range. As an alternative to separation outside the vessel, a rotary separator was also developed which is fixed to the outlet opening in the vessel. A centrifugal field is produced by the separator rotor and the heavier liquid is largely separated from the vapour so that only drops in the range 〈 100 μm flow together with the vapour towards the central standpipe. The outflowing vapour leaves the separator via 4 tangentially arranged nozzles, under critical conditions. The vapour flow momentum drives the separator rotor. The arrangement was developed and tested during various series of experiments, under conditions or pressure relief with refrigerant R12. So far, separation efficiencies between 60 and 95% have been achieved at stirring speeds of up to 2500 min-1.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120110
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  • 90
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    Absorption process for the removal of organic solvents from exhaust air (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 63-70 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown in this report that, under certain conditions, cleaning of exhaust air by absorption presents an interesting alternative to the existing methods. In particular, this process can be used with advantage for small quantities of exhaust air, high and strongly fluctuating solvent concentrations and solvent mixtures such as those occurring in batch operation. A washing agent was employed which had not been previously used for this purpose. Its properties, which were investigated in the laboratory, were confirmed during a 15-months' trial period in a semi-industrial plant. The process and plant were optimized for practical use. Through its option of solvent recovery from exhaust air, this physical absorption process contributes to environmental control.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120111
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  • 91
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    Advances in modelling and design of multitubular fixed- bed reactorsI. Description of Interaction Between Reactants and Coolant (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 113-130 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Starting from the review of current industrial designs, the present paper analyzes thermal interaction between reactants and coolant in multitubular fixed-bed reactors. The interaction can be described quantitatively in terms of parameters characterizing transport processes both on the tube side and in the intertubular space. The study provides a detailed discussion of existing methods and correlations used for the evaluation of these parameters. The methods presented here can be considered as a basis for the development of a more comprehensive approach to the modeling and design of multitubular catalytic reactors.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120117
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  • 92
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    Determination of size and stress intensity factors for leaks in nozzle attachmentsPaper presented by G. Wiedemann at the “Jahrestreffen der Verfahrens-Ingenieure”, Freiburg, September 30 to October 2, 1987. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 131-137 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The prediction of leak areas in pressure vessels is an important objective in the safety analysis of chemical plants. Using suitable design rules, a leak-before-break behaviour can be achieved. This contribution outlines a procedure for the leak-before-break design of nozzle attachments and the determination of the size of the corresponding opening area. In addition, K1-factors and leak areas for a number of nozzle geometries have been calculated and plotted.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120118
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  • 93
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    Combined process treatment of molasses fermentation waste water for biogas generation (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 109-112 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anaerobic fermentation of molasses distillery slops to biogas was carried out with the aid of an adapted and selected anaerobic mixed culture. Two different types of fermenters were used, namely an agitated pretreatment fermenter and a column fermenter with glass rings as carriers for micro-organisms. The production of biogas in both fermenters amounted to between 0.6 and 0.8 dm3/g COD. The aerobic pretreatment of distillery slops by T. fermentans, yeast during a 4 to 6 h period allows a high reduction of COD in the subsequent anaerobic phase of the process. After treatment of the distillery slops by T. fermentans, it was possible to convert between 85 and 93% of the organic matter to methane. Conversion was about 93% with loading rate of 25g COD/litre day.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120116
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  • 94
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    A new particle size effect (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 147-154 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The sintering effect of highly dispersed metals is the reason for the following phenomena: thermal deactivation, particle size effect, separable or non-separable kinetics and the isokinetic relationship ( = compensation effect). A comparison of these phenomena reveals a contradiction which can be reconciled by a new particle size effect. This effect is characterized in the following way: The dependence of specific activity on particle size is always connected with a variation of the activation energy, caused by the particle size distribution. Therefore, this effect is referred to as the partical size and distribution effect, P.S.D.E. This new concept describes all the observed phenomena of the conventional partical size effect. Moreover, it is consistent with similar effects such as non-separable kinetics and the isokinetic relationship. In consequence, the method of isothermal measurement of specific activity is inadequate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120120
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  • 95
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    Conversion of methanol to light olefins over zeolite H-T (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 155-161 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conversion of methanol over zeolite H-T was investigated in a fixed bed reactor. H-T was prepared from Na-T by ion exchange with HCl and NH4Cl solutions. The HCl solution caused appreciable dealumination. High yields of ethene were obtained with NH4Cl exchangeed zeolites Na-T with 45% decationization, high proprne yields with low HCl or NH4Cl Exchanged catalysts. Low methanol partial pressures and short residence times favoured the formation of lower olefins. Lowest coking rates were observed at a reaction temperature of 693 K. The catalytic activity decrased slowly with the number of reaction/regeneration cycles. The distribution of procucts 〉 C2 could be described by the most probable distribution of Schulz and Flory.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120121
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  • 96
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    Generalization of AIChE and colburn models for tray efficiency (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 333-339 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The most important investigations on liquid weeping and entrainment in plate columns with downcomers are reveiwed. The formulae for calculating column plate efficiency under conditions of liquid weeping and entrainment have been derived on the basis of mass balance equations. The presented model is a generalization of the models of AIChE and Colburn. Sample results are shown graphically. The effect of liquid entrainment on tray efficiency predicted by the model is in agreement with experimental data of FRI.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120146
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  • 97
    Electronic Resource
    Electronic Resource
    Selective absorption of ethylene by methanol solutions of Copper(I) chloride-ethylenediamine complex (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 356-357 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120150
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  • 98
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    Electronic Resource
    Continuous crystallization of potassium carbonate (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 345-350 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous crystallization of potassium carbonate was investigated in a mixed suspension mixed product removal (MSMPR) crystallizer with 7.0 1 working volume. Highly polydispersed product was obtained, with x50 varying between 320 and 670 μm. Crystal growth rates can be described by the model of Abegg, Stevens and Larson (ASL) (size dependent crystal growth rate). Values of G0 = 8.6 × 10-9 to 3.6 × 10-8 m/s and B0/ϕ = 2.7 × 108 to 4.2 × 109 1/m3s were obtained for mT = 45 to 92 kg/m3 and ε = 0.45 ± 0.05 W/kg. Nucleation kinetics at 27 °C can be described by the equation: B0/ϕ = kBϕsε0.73G02.5. Since G0 ∝ σ, convection and/or diffusion rather than surface integration are the crystal growth controlling mechanisms.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120148
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  • 99
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    Electronic Resource
    Experienmental and theoretical combustion rates of graphite plates in hot parallel flows of air and O2/N2 mixturesPaper presented by H. Wilhelmi at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 351-356 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Combustion rate of flat graphite plates in oxidizing flows with velocities of up to 80 m/s and stagnation temperatures between 1600 and 2500 K were investigated. The flow field and its local properties were recorded in addition to surface temperature of the solid sample and change in surface structure. The experiments, in which the surface temperature of graphite was adjusted and carefully controlled by radiation shields, indicated that, under these experimental conditions, between 15 and 20 wt-% of carbon was lost as particles of up to 100 μm which burnt rapidly in the boundary layer region. Subtraction of erosion rates from the recorded global combustion rates yield the heterogeneous chemical reaction rates, which are approximated by an Arrhenius type function for the mathematical modelling. Since steep temperature and concentration gradients occur in the boundary layer, the local values of the multicomponent transport coefficients were evaluated in order to design a more realistic computational procedure which, in addition, also includes radiative heat transfer. Computational checks revealed that, in the past, the assumption of mean constant values for the transport coefficients has led to errors of up to 100% in the evaluation of the chemical reaction and global combustion rates.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120149
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  • 100
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    Electronic Resource
    Simulation of primary and secondary reformers for improved energy performance of an ammonia plant (1989)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 358-364 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The energy consumption of ammonia plants based on steam reforming of naphtha or natural gas can be reduced by shifting the reforming load from the primary to the secondary reformer. It is shown that lowering of the primary reformer operating temperature 20 °C results in 2% increase of unconverted methane content in the outlet stream. The increased methane content can be processed in the secondary reformer if the process air inlet temperature is increased to 400 °C. The lower operating temperature reduces the energy consumption of the primary reformer by about 6% (and the overall consumption by about 2%) and also prolongs the service life of reformer tubes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270120151
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