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  • Digitale Medien  (5.585)
  • 1985-1989  (4.461)
  • 1965-1969  (1.124)
  • 1988  (4.461)
  • 1969  (1.124)
  • Life and Medical Sciences  (2.184)
  • Analytical Chemistry and Spectroscopy  (1.527)
  • Biochemistry and Biotechnology  (781)
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  • Digitale Medien  (5.585)
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  • 1985-1989  (4.461)
  • 1965-1969  (1.124)
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  • 1
    Digitale Medien
    Digitale Medien
    The minimum alveolar concentration of sevoflurane in cats (1988)
    Springer
    Journal of anesthesia 2 (1988), S. 113-114 
    Details
    ISSN: 1438-8359
    Schlagwort(e): Sevoflurane ; Minimum alveolar concentration ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Eight adult cats of either sex were studied. The minimal alveolar concentration (MAC) for sevoflurane in the cats was found to be 2.58 ± 0.30% (mean ± SD). The ratios of MAC values between sevoflurane and halothane, enflurane and isoflurane in cats were very similar to those ratios found in humans and dogs. This observation suggests that the results of this study are correct and allows us to estimate unknown MAC values for sevoflurane in other species using known MAC values for other anesthetic agents. (Doi M, Yunoki H, Ikeda K: The minimum alveolar concentration of sevoflurane in cats. J Anesth 2: 113–114, 1988)
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s0054080020113
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  • 2
    Digitale Medien
    Digitale Medien
    Experimental hydrocephalus and hydrosyringomyelia. Computertomographic studies (1988)
    Springer
    Neurosurgical review 11 (1988), S. 87-94 
    Details
    ISSN: 1437-2320
    Schlagwort(e): Cat ; CSF ; CT scans ; experimental hydrocephalus ; syringomyelia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Two methods were used to induce a model of experimental hydrocephalus and hydrosyringomyelia in the cat: a) injection of kaolin into the cisterna magna and b) closure of the lateral apertures of the fourth ventricle with cotton swabs. The pathological changes in the brain ventricles and the central canal of the spinal cord were monitored and documented at regular intervals by computed tomography (CT). The CT method is particularly advantageous for studies of this kind because the animals can be examined frequently without risking disturbances in cerebro-spinal fluid dynamics or tissue damage that would result from introduction of contrast media into the ventricular system. Our results and others reported earlier suggest that the dilated central canal acts as a kind of spontaneous CSF deviation route from the ventricles to the subarachnoid space. In spite of the tendency of the animals to recover in a clinical sense, the internal CSF space continued to expand; in cats the disease is progressive, a fact that is readily evident in follow-up CTs. This characteristic indicates that the spontaneous “shunt system” from the fourth ventricle through the dilated central canal to the spinal CSF spaces does not function well enough. Possible explanations for hydrocephalus compensation and the development of hydrosyringomyelia in experimental animals are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01795699
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  • 3
    Digitale Medien
    Digitale Medien
    Pattern of in vivo release of endogenous histamine in the mamillary body and the amygdala (1988)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 337 (1988), S. 53-57 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Endogenous histamine release ; Mamillary body ; Medial amygdaloid nucleus ; Ultradian rhythm ; Suprachiasmatic nucleus ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The mamillary body and the medial amygdaloid nucleus of cats anaesthetized with sodium pentobarbital were bilaterally and simultaneously superfused through push-pull cannulae with CSF and the release of endogenous histamine was determined in the superfusates. Collection of the superfusates in 10 min time periods revealed that histamine was rhythmically released in the two areas with frequencies of one cycle/90 min (mamillary body) or one cycle/135 min (medial amygdaloid nucleus). Collection of the superfusates in time periods of 2 min revealed the existence of an additional ultradian rhythm with a frequency of approximately one cycle/19 min in both areas. Bilateral lesions of the suprachiasmatic nucleus did not seem to influence the pattern of histamine release in the mamillary body and the medial amygdaloid nucleus, but the rate of histamine release was decreased in the mamillary body. It is concluded that the ultradian rhythms of histamine release in the mamillary body and the medial amygdaloid nucleus are not dependent on the integrity of the suprachiasmatic nucleus. The rate of histamine release in the mamillary body seems to be under the influence of excitatory neurons which originate from the suprachiasmatic nucleus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00169476
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  • 4
    Digitale Medien
    Digitale Medien
    Afferents to the lateral reticular nucleus from the oculomotor region (1988)
    Springer
    Anatomy and embryology 177 (1988), S. 277-283 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Lateral reticular nucleus ; Oculomotor region ; Retrograde transport of WGA-HRP ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary By means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex, afferent fibres to the lateral reticular nucleus from the oculomotor and accessory oculomotor nuclei were demonstrated in the cat. Small iontophoretic ejections were made into the main part of the lateral reticular nucleus from a ventral approach. Significant numbers of retrogradely labelled neurons were found bilaterally in all parts of the oculomotor nucleus. The majority was of small size and distributed along the dorsal and lateral boundaries of the nucleus. Some labelled neurons were located just outside these boundaries, in the periaqueductal gray and the adjacent mesencephalic reticular formation. Retrogradely labelled neurons were also found in the accessory oculomotor nuclei: The interstitial nucleus of Cajal featured a substantial number of labelled neurons. Some labelled neurons were consistently found also in the nucleus of the posterior commissure, but no labelled neurons were found in the nucleus of Darkschewitch. The labelled neurons in the interstitial nucleus of Cajal were of different sizes and located bilaterally, mainly in its rostral part. Caudal as well as rostral parts of the main lateral reticular nucleus appear to receive the descending afferents from the oculomotor region, but higher numbers of labelled neurons were found subsequent to ejections in the rostral part. The findings are discussed and some comments are made concerning the lateral reticular nucleus as a possible relay nucleus for oculomotor input to the cerebellum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00321138
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  • 5
    Digitale Medien
    Digitale Medien
    The accessory optic system of the rabbit, cat, dog and monkey: a whole-mount HRP study (1988)
    Springer
    Anatomy and embryology 177 (1988), S. 285-295 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Accessory optic system ; Rabbit ; Cat ; Dog Monkey
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The three-dimensional fiber pathways of the accessory optic system in the rabbit, cat, dog and monkey were studied in whole-mounted preparations of the diencephalon and the midbrain, without sectioning, by anterograde labeling of retinal axons with horseradish peroxidase (HRP). HRP histochemical studies on alternate serial coronal sections were also performed. The rabbit accessory optic system exhibited two fasciculi (the inferior fasciculus, and the superior fasciculus consisting of the anterior fibers and the posterior fibers) and three terminal nuclei (the medial terminal nucleus, and the anterior and posterior porcions of the lateral terminal nucleus), but lacked the dorsal terminal nucleus. In the cat and dog, only the posterior fibers of the superior fasciculus were detected. The inferior fasciculus and the anterior fibers of the superior fasciculus were absent. The medial terminal nucleus and the posterior portion of the lateral terminal nucleus were commonly observed in the cat and dog. The cat accessory optic system possessed the dorsal terminal nucleus, and the dog accessory optic system possessed the anterior portion of the lateral terminal nucleus. The monkey (Macaca fuscata) accessory optic system consisted of the posterior fibers of the superior fasciculus, but blacked the inferior fasciculus and the anterior fibers of the superior fasciculus. Most of the posterior fibers terminated in the well-developed posterior portion of the lateral terminal nucleus located on the upper surface of the cerebral peduncle. A small number of posterior fibers projected to the poorly-developed medial terminal nucleus. Based on these findings, species differences in the mammalian accessory optic system were discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315835
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  • 6
    Digitale Medien
    Digitale Medien
    The feline oculomotor nucleus: morphological subdivisions and projection to the cerebellar cortex and nuclei (1988)
    Springer
    Anatomy and embryology 178 (1988), S. 67-75 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Retrograde transport of WGA-HRP ; Oculomotor nucleus ; Cerebellar nuclei ; Cerebellar cortex ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The cytoarchitecture of the feline oculomotor nucleus was examined in sections stained with thionin and neutral red. Five different subdivisions (caudal central, paramedian, ventral, dorsomedial and dorsolateral divisions) can be identified on each side of the midline. This observation is discussed, and our findings are compared to previous studies of the cytoarchitecture or central muscular representation of the oculomotor nucleus in which different subgroups have been distinguished. Implants or injections of the wheat germ agglutinin-horseradish peroxidase complex have revealed that all five subdivisions project to different parts of the cerebellar cortex and nuclei. Retrogradely labelled cells were found in the oculomotor nucleus in 18 cases following deposition of tracer in the fastigial and interposed nuclei and certain regions of the anterior, posterior and flocculonodular lobes. The projection is bilateral and appears to have its main termination in flocculus. It originates from small neurons, especially from those located along the dorsal border of the oculomotor nucleus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305016
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  • 7
    Digitale Medien
    Digitale Medien
    The distribution of infrahyoid motoneurons in the cat: a retrograde horseradish peroxidase study (1988)
    Springer
    Anatomy and embryology 177 (1988), S. 445-450 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Motoneurons ; Infrahyoid muscles ; Spinal cord ; HRP ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The distribution of cell bodies and the peripheral course of axons of infrahyoid motoneurons were examined in the cat by the retrograde horseradish peroxidase method after application of the enzyme to the peripheral nerve branches supplying the infrahyoid muscles. Infrahyoid motoneurons were observed to constitute a slender cell column, which extended from a level of the caudal part of the hypoglossal nucleus usually to the most caudal level of the C1 cord segment, or occasionally to the lower levels of the C2 cord segment. The cell column was located immediately lateral to that of motoneurons of the spinal accessory nerve. In the cell column, thyrohyoid motoneurons were distributed in the medulla oblongata; sternohyoid motoneurons were located somewhat more cranially than sternothyroid motoneurons in the medulla oblongata and cervical cord. However, the level of craniocaudal distribution of thyrohyoid, sternohyoid or sternothyroid motoneurons highly overlapped. The experiments involving severance of the hypoglossal and/or cervical nerves indicated that axons of thyrohyoid and sternohyoid motoneurons passed via the roots of both hypoglossal and C1 nerves, that axons of sternohyoid motoneurons passed via the C1 nerve roots, and that axons of infrahyoid motoneurons innervating the conjugated part of the sternohyoid and sternothyroid muscles passed usually via the C1 nerve roots, or occasionally via the roots of both C1 and C2 nerves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00304742
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  • 8
    Digitale Medien
    Digitale Medien
    Cerebellar cortical and nuclear afferents from the Edinger-Westphal nucleus in the cat (1988)
    Springer
    Anatomy and embryology 178 (1988), S. 59-65 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Retrograde transport of WGA-HRP ; Edinger-Westphal nucleus ; Cerebellar nuclei ; Cerebellar cortex ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The cerebellar projection from the Edinger-Westphal nucleus was studied in the cat by means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex. The present findings give evidence that the flocculus is the main terminal area. However, small tracer implants and injections into various parts of the cerebellar nuclei and cortex revealed projections also to the fastigial and interposed nuclei and to most parts of the anterior and posterior lobe cortices. The projecting neurons are small and located bilaterally throughout the Edinger-Westphal nucleus. No topical differences between the projections to different parts of the cerebellum were found.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305015
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  • 9
    Digitale Medien
    Digitale Medien
    Routes of entry into the cerebellum of spinocerebellar axons from the lower part of the spinal cord (1988)
    Springer
    Experimental brain research 72 (1988), S. 543-561 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Spinocerebellar neurons ; Cerebellar peduncles ; Axonal course ; Horseradish peroxidase ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Among the newly discovered spinocerebellar cell groups, those at lumbar and more caudal levels of the cat's spinal cord were studied with regard to which of the two cerebellar peduncles, the restiform body or the superior cerebellar peduncle, is used by their axons. Bilateral injections with horseradish peroxidase were made into either of the anterior lobe or the posterior cerebellar termination area for spinocerebellar fibers, following unilateral transections of either the superior cerebellar peduncle or the restiform body, combined with low contralateral transections of the lateral and ventral funiculi. Following transection of the superior cerebellar peduncle, labeled neurons were found ipsilateral to the transection in the column of Clarke and in laminae IV–VI at L 3–L 7. Contralaterally, labeled neurons were found in the ventromedial nucleus and lamina VIII of the ventral horn in the sacro-coccygeal segments and in the medial part of lamina VII at L 6 and more caudal levels. All these neurons were regarded as sending their axons through the restiform body. Following transection of the restiform body, labeled neurons were found in the following areas contralateral to the transection: the dorsolateral nucleus of the L 3–L 6 segments, the lateral part of lamina VII at L 3–L 5/6, the medial part of lamina VII in L 6 and more caudal segments, and the ventrolateral nucleus of L 4–L 5. Ipsilaterally, labeled neurons were found in lamina VIII at L 4–L 6. All these neurons were regarded as sending their axons through the superior cerebellar peduncle. In addition to new information about the peduncular routes of spinocerebellar neurons, the study has given confirming evidence as to the crossing conditions for different spinocerebellar cell groups. The findings should be useful in future studies on the organization of the spinocerebellar systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00250600
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  • 10
    Digitale Medien
    Digitale Medien
    Collateral projections of neurons from the lower part of the spinal cord to anterior and posterior cerebellar termination areas (1988)
    Springer
    Experimental brain research 72 (1988), S. 562-576 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Spinocerebellar neurons ; Cerebellar cortex ; Fluorescent tracers ; Double labeling ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The collateral projections of spinocerebellar neurons located in the L 2 to Ca 1 spinal segments in the cat were investigated by retrograde fluorescent double labeling technique. Rhodamine labeled latex microspheres (Rm) and Fast Blue (FB) were used for injections into the cerebellum in 8 cats. Two additional cats, with injections of Fluoro-Gold (FG) combined with Rm were excluded because lipofuchsin autofluorescence obscured the labeling. After injections with one tracer unilaterally in the paramedian lobule and another tracer bilaterally in the anterior lobe, double labeled neurons were found on the side of the paramedian lobule injection in the column of Clarke at L 2–L 4, laminae IV–VI at L 2–L 5 and the dorsolateral nucleus at L 2–L 6. After bilateral injections of one tracer in lobule VIII B and another in the anterior lobe, double labeled neurons were found bilaterally in the column of Clarke at L 2–L 4, laminae IV–VI at L 2–L 5, the medial part of lamina VII at L 6–L 7 and in certain cell groups at sacro-coccygeal levels. Neurons in the lateral part of lamina VII at L 3–L 5 and the ventrolateral nucleus of L 4–L 5 were labeled exclusively from injections in the anterior lobe. The findings indicate that spinocerebellar neurons at lumbar and more caudal levels of the cat spinal cord have different projection patterns in the cerebellum. A certain number of neurons which project to the anterior lobe have divergent axon collaterals supplying also the posterior vermis and/or the paramedian lobule. Other neurons project to the anterior or to the posterior lobe only.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00250601
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  • 11
    Digitale Medien
    Digitale Medien
    Properties and localization of the anterior semicircular canal-activated vestibulocollic neurons in the cat (1988)
    Springer
    Experimental brain research 71 (1988), S. 345-352 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Anterior semicircular canal ; Vestibular nuclei ; Vestibulo-collic ; Neck motoneuron ; Unitary EPSP ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Unit activites of secondary vestibular neurons that selectively responded to stimulation of the anterior semicircular canal nerve (ACN) were recorded extracellularly in the anesthetized cat. Axonal pathways and projections in the spinal cord of the ACN-activated neurons were examined by recording their antidromic responses to stimulation of the lateral and medial vestibulospinal tracts (LVST and MVST), and the bilateral neck extensor motoneuron pools in the C1segment (C1dorsal rami [DR] motoneuron pools). In order to determine whether the neurons had ascending axon collaterals to the extraocular motoneurons, the contralateral (c-) inferior oblique (IO) motoneuron pool was also stimulated. Twenty-seven neurons sent their axons to the ipsilateral (i-) C1DR motoneuron pool via the LVST without any projection to the extraocular motoneuron pool. All the cells except one were located in the ventral part of the lateral vestibular nucleus. This pathway produced monosynaptic EPSPs with short time-to-peak and short half-width in C1DR motoneurons (16/16 motoneurons). Eight neurons sent axons to the i-C1DR motoneuron pool via the MVST without any to the extraocular motoneuron pool. Cell somata were located in the descending nucleus or in the ventral part of the lateral nucleus. These neurons did not produce postsynaptic potentials (PSPs) in any C1DR motoneurons. All thirty-five neurons sending axons to the c-C1DR motoneuron pool have ascending axon collaterals to the c-IO motoneuron pool.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247494
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  • 12
    Digitale Medien
    Digitale Medien
    The organization of receptive fields in area 18 neurones of the cat varies with the spatio-temporal characteristics of the visual stimulus (1988)
    Springer
    Experimental brain research 71 (1988), S. 1-7 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Area 18 ; Receptive field ; Velocity ; Spatial frequency ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The spatial frequency tuning curves of neurones of area 18 depend upon the velocity of the visual stimulus. The higher the velocity the lower the spatial frequencies to which the cell is tuned. Since in area 17 the size of the cell receptive field is inversely related with the optimal spatial frequency to which the cell responds, we have investigated whether the shift of the optimal spatial frequency with the velocity corresponds to a “change” in the receptive field size. We recorded extracellularly from neurones in area 18; for each cell we selected two gratings, one of high spatial frequency drifting at low velocity and another of low spatial frequency drifting at high velocity to which the cell gave comparable responses. The results show that the masking of the cells receptive field which abolishes the response to the high frequency low velocity grating does not prevent the cell from responding to the low frequency high velocity grating. We conclude that the size of the receptive field of neurones in area 18 depends upon the characteristics (spatial frequency and velocity) of the visual stimulus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247517
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  • 13
    Digitale Medien
    Digitale Medien
    Topographic relations between ocular dominance and orientation columns in the cat striate cortex (1988)
    Springer
    Experimental brain research 71 (1988), S. 33-46 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Columns ; Visual cortex ; Orientation ; Ocular dominance ; Maps ; Cat ; Development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the visual cortex of four adult cats ocular dominance and orientation columns were visualized with (3H)proline and (14C)deoxyglucose autoradiography. The two columnar systems were reconstructed from serial horizontal sections or from flat-mount preparations and graphically superimposed. They share a number of characteristic features: In both systems the columns have a tendency to form regularly spaced parallel bands whose main trajectory is perpendicular to the border between areas 17 and 18. These bands frequently bifurcate or terminate in blind endings. The resulting irregularities are much more pronounced in the ocular dominance than in the orientation system. The periodicity of the columnar patterns was assessed along trajectories perpendicular to the main orientation of the bands and differed in the two columnar systems. The spacing of the ocular dominance stripes was significantly narrower than the spacing of orientation bands. The mean periodicity of a particular columnar system was virtually identical in the two hemispheres of the same animal but it differed substantially in different animals. However, the spacing of orientation columns covaried with that of the ocular dominance columns, the ratios of the mean spacings of the two columnar systems being similar in the four cats. The superposition of the two columnar systems revealed no obvious topographic relation between any of the organizational details such as the location of bifurcations, blind endings and intersections. We suggest the following conclusions: 1. The developmental processes generating the two columnar systems seem to obey the same algorithms but they act independently of each other. 2. The space constants of the two systems are rigorously specified and appear to depend on a common variable. 3. The main orientation of the bands in both columnar systems is related to a) the representation of the vertical meridian, b) the anisotropy of the cortical magnification factor, and c) the tangential spread of intracortical connections.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247520
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  • 14
    Digitale Medien
    Digitale Medien
    Automatic postural responses in the cat: responses of hindlimb muscles to horizontal perturbations of stance in multiple directions (1988)
    Springer
    Experimental brain research 71 (1988), S. 93-102 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Postural reflexes ; Unexpected postural perturbations ; Electromyographic activity ; Muscle synergies ; Motor control ; Hindlimb muscles ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of the direction of unexpected horizontal perturbations of stance on the organization of automatic postural responses was studied in cats. We recorded EMG activity in eight proximal and distal muscles of the hindlimb along with vertical forces imposed by the limbs in awake behaving cats while they stood on an hydraulic platform. Postural responses to motion of the platform in 16 different horizontal directions were recorded. Vertical force changes were consistent with passive shifts of the center of mass and active correction of stance by the animals. When the perturbation was in the sagittal plane, vertical force changes began about 65 ms following initial platform movement. When the perturbation contained a component in the lateral direction, latency for vertical force changes was about 25 ms and an inflection in the vertical force trace was observed at 65 ms. No EMG responses were observed with latencies that were short enough to account for the early force component and it was concluded that this force change was due to passive shifts of the center of mass. The amplitude of the EMG responses of each muscle recorded varied systematically as perturbation direction changed. The directions for which an individual muscle showed measurable EMG activity were termed the muscle's “angular range of activation.” No angular range of activation was oriented strictly in the A-P or lateral directions. Most muscles displayed angular ranges of activation that encompassed a range of less than 180°. Onset latencies of EMG responses also varied systematically with perturbation direction. The amplitude and latency relationships between muscles, which made up the organization of postural responses, also varied systematically as perturbation direction was changed. This result suggests that direction of perturbation determines organizational makeup of postural responses, and for displacements in the horizontal plane, is considered a continuous variable by the nervous system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247525
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  • 15
    Digitale Medien
    Digitale Medien
    Spared-root deafferentation of a cat's hindlimb: hierarchical regulation of pathways mediating recovery of motor behavior (1988)
    Springer
    Experimental brain research 73 (1988), S. 329-342 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Dorsal roots ; Locomotion ; Sprouting ; Cat ; Plasticity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Previous studies showed that after complete hindlimb deafferentation in cats, the ipsilateral descending pathways mediated recovery of overground, goal-directed locomotion and accurate placement of the deafferented limb. In the present study deafferentations sparing one dorsal root (L6) were performed to see if the descending systems would still be responsible for the recovery. The partially deafferented hindlimb is initially impaired in postural reflexes and accurate placement during locomotion but considerable recovery occurs. A similar pattern of severe impairment and subsequent recovery is observed in cats in which the only lesion is L1 hemisection. When a hemisection is added 6 months later to chronic spared-root deafferentation the recovery (from the latter lesion) is temporarily reversed but the animals recover again in a fashion similar to that after hemisection alone. Since there is no recovery of overground locomotion when hemisection is added to complete deafferentation but there is when deafferentation is incomplete, the descending pathways apparently are not responsible for maintaining the recovery when one dorsal root is spared as they are when all are cut. The results suggest that a competitive or hierarchical control over residual systems may regulate recovery of motor function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00248225
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  • 16
    Digitale Medien
    Digitale Medien
    Axonal trajectories of posterior canal-activated secondary vestibular neurons and their coactivation of extraocular and neck flexor motoneurons in the cat (1988)
    Springer
    Experimental brain research 70 (1988), S. 181-191 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Axonal branching ; Vestibulo-ocular ; Vestibulo-collic ; Neck motoneurons ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Unit activities of 148 secondary vestibular neurons related to the posterior semicircular canal were recorded extracellularly in anesthetized cats. Axonal projections of these neurons were examined by their antidromic responses to stimulation of the excitatory target motoneurons of the contralateral (c-) inferior rectus muscle (IR) and bilateral (bi-) motoneuron pools of longus capitis muscles, neck flexors, in the C1 segment (C1LC). The neurons were classified into 4 groups according to their axonal projections. The first group of neurons, termed vestibulo-oculo-collic (VOC) neurons, sent axon collaterals both to the c-IR motoneuron pool and to the c-C1LC motoneuron pool. The majority of them (72%) were located in the descending nucleus. The second group of neurons were termed vestibuloocular (VO) neurons and sent their axons to the c-IR motoneuron pool but not to the cervical cord. Most of them (86%) were located in the medial nucleus. The third group of neurons, termed vestibulo-collic (contralateral) (VCc) neurons, sent axons to the cC 1LC motoneuron pool via the contralateral ventral funiculus but not to the oculomotor nuclei. They were mostly (75%) found in the descending nucleus. The last group of neurons were vestibulo-collic (ipsilateral) (VCi) neurons, which gave off axons to the ipsilateral (i-) C1LC motoneuron pool via the ipsilateral ventral funiculus but not to the oculomotor nuclei. One of them also sent an axon collateral to the c-C1LC motoneuron pool. The majority of them (74%) were located in the ventral part of the lateral nucleus. It was also observed in some of the VOC and VCi neurons that they produced unitary EPSPs in the c-C1LC and i-C1LC motoneurons, respectively. Their synaptic sites were estimated to be on the cell somata and/or proximal dendrites of the motoneurons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00271859
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  • 17
    Digitale Medien
    Digitale Medien
    Stimulus contrast and visual cortical lesions (1988)
    Springer
    Experimental brain research 72 (1988), S. 191-194 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Visual cortex ; Ablation ; Orientation discrimination ; Contrast ; Redundancy ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Intact animals can make fine orientation discriminations over a wide range of contrasts. After ablation of area 17 deficits in orientation discrimination are observed only at low contrast. The relevance of this finding for the design of sensitive ablation experiments is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00248515
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  • 18
    Digitale Medien
    Digitale Medien
    Distribution and projection of single units in the cat preoptic region responding to stimulation of the medial amygdala (1988)
    Springer
    Experimental brain research 70 (1988), S. 449-454 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Preoptic area ; Amygdala ; Medial forebrain bundle ; Medial basal hypothalamus ; LH ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Neuronal responses were recorded extracellularly in the preoptic region of 11 male castrate cats following stimulation in the ‘medial’ group of amygdalar nuclei (medial, basomedial, basolateral). The latency of responses varied with the site of stimulation and could be explained if connections to the preoptic region were made through both the stria terminalis and the ventral amygdalofugal pathway. Projection of 13% of orthodromically excited preoptic units to the medial basal hypothalamus was established by collision tests following stimulation in these regions. The amygdalar excitation was probably exerted through the amygdalofugal pathway. In 5/6 cats the amygdalar stimulation was successfully used to raise plasma LH levels. In one cat no preoptic units projecting to the medial basal hypothalamus were found and in the cat which failed to increase plasma LH in response to amygdala stimulation, 5 such units were found. We conclude the pathway from the amygdala through the preoptic region to the hypothalamus may not be the way in which amygdalar stimulation affects LH release in the cat. Projection of 10% of orthodromically excited preoptic units in the medial forebrain bundle was established by collision tests in 3 cats. These identified units were driven from amygdalar sites thought to project to the preoptic region by ventral amygalofugal pathways.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247592
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  • 19
    Digitale Medien
    Digitale Medien
    Dopamine and serotonin in cat retina: electroretinography and histology (1988)
    Springer
    Experimental brain research 71 (1988), S. 231-240 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat ; Retinal electrophysiology ; Electroretinogram ; Neurotransmitters ; Dopamine ; Serotonin ; Aminophosphonobutyric acid (APB)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Anatomical structures of the cat retina were related to functional changes induced by the application of dopaminergic and serotonergic substances. We report on the contribution of dopaminergic and serotonin accumulating retinal neurones to retinal activity as reflected by the electroretinogram. The effect of dopaminergic neurones was investigated by the application of the neurotoxin 6-hydroxydopamine (6-OHDA) which is known to destroy dopaminergic neurones, and injections of either serotonin (5-HT) or the analogue 5,6-dihydroxytryptamine (5,6-DHT) were used to monitor the effects of indoleamines. In control experiments aminophosphonobutyric acid (APB), an agonist of glutamate transmission, was injected. Conventional immunohistochemical methods identified dopaminergic and serotonin accumulating neurones, and the electrophysiological data obtained from the same animals were related to the anatomical structures influenced by the respective substances. Destruction of dopaminergic amacrine cells by 6-OHDA increased the ERG b-wave amplitude. Accumulation of indoleamines by certain amacrine cells also caused an increase of the ERG b-wave. However, intravitreal injection of APB completely blocked the bwave. The data show that ERG mass responses can be used to monitor transmitter-specific effects on retinal circuitry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247483
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  • 20
    Digitale Medien
    Digitale Medien
    Distribution of opiate receptors within visual structures of the cat brain (1988)
    Springer
    Experimental brain research 73 (1988), S. 523-532 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Opiate ; Receptor ; Vision ; Cat ; Mu ; Kappa ; Delta
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The distributions of μ, δ, and χ opiate receptors within visual regions in the cat cortex, thalamus and midbrain were determined by in vitro autoradiography. The overall distribution of receptors was examined using [3H]-etorphine, a ligand that nonselectively labels all types of opiate receptors. [3H]-[D-Ala2, N-Me-Phe4, Gly(ol)5]-enkephalin (DAGO) was used to selectively label μ receptors, [3H]-[D-Pen2,5]-enkephalin (DPDPE) for δ receptors, and [3H]-bremazocine for χ receptors. Each of the areas examined showed clear opiate receptor binding with [3H]-etorphine and a differential distribution of μ, δ, and χ receptors. Compared to other cortical regions, opiate binding in layers 3 and 4 of areas 17 and 18 was sparse. In the adjacent areas a more uniform distribution across layers was observed. The density of χ opiate receptors was greater in cortex than in subcortical structures, whereas the reverse was the case for μ receptors. Nevertheless, all three types of opiate receptors were found in the ventral and dorsal subdivisions of the lateral geniculate (LGN), the pulvinar complex, and the suprageniculate nucleus. In the midbrain, the superficial layers of the superior colliculus were heavily labelled with the μ, receptor ligand, and modestly with the χ ligand. Compared with other midbrain and diencephalic areas, δ binding was low in the superior colliculus. These results suggest that the diverse effects of opiates on visual perception are mediated by the unique distributions of opiate receptor types throughout the visual areas in the brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00406610
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  • 21
    Digitale Medien
    Digitale Medien
    Binocular interaction in the perigeniculate nucleus of the cat (1988)
    Springer
    Experimental brain research 69 (1988), S. 497-508 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Binocular interaction ; Perigeniculate nucleus ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have recorded from single cells in the perigeniculate nucleus (PGN) of the cat to determine their response properties. Quantitative tests have been conducted with sinusoidal gratings. Using optimal stimulus parameters, determined monocularly, we explored binocular interaction by varying the relative phase between dichoptically presented gratings. Monocularly, cells exhibit varying degrees of response specificities with respect to stimulus orientation and spatial frequency. Binocularly, we have identified six types of response. The most prominent, type 1, found for half the cells, is phase-specific binocular interaction at the fundamental frequency component of the drifting grating. For these cells, mean response rate is independent of interocular phase. The remaining types of binocular responses involve varying degrees of interaction at different harmonic components. For a quarter of the sample, no binocular interaction was observed. To investigate the role of cortical input to PGN, visual cortex was removed from some cats. Subsequent study of PGN cells indicated that response properties were generally similar to those found in intact animals. We conclude that PGN response properties are determined primarily by subcortical inputs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247304
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  • 22
    Digitale Medien
    Digitale Medien
    Relationships between nucleus medialis dorsalis, pericruciate cortex, ventral tegmental area and nucleus accumbens in cat: an electrophysiological study (1988)
    Springer
    Experimental brain research 69 (1988), S. 559-566 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat ; Nucleus medialis dorsalis ; Ventral tegmental area ; Nucleus accumbens ; Pericruciate cortex ; Attentional mechanisms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In anaesthetized cats, single units were recorded from the ventrolateral part of n. medialis dorsalis (MD) of the thalamus. Cells were tested for their ortho- or antidromic short latency responses to single electrical shocks applied to the pericruciate cortex (PCx) and to either the mesencephalic ventral tegmental area (VTA) or the nucleus accumbens (ACC). Some reciprocal direct connections were thus shown to exist between MD and PCx, i.e. a cortical area posterior to the main classical MD “prefrontal” projection zone. Reciprocal direct connections were also identified physiologically between MD and VTA and between MD and ACC. Coupled stimulations showed that some MD cells could serve as a relay for a pathway from VTA to cortex, others for a reciprocal pathway from PCx to VTA, and still others, for a pathway from PCx to ACC. These findings are compared to previous — mostly anatomical — data obtained in other species, mainly rat. Their functional meaning is also discussed, in the light of previous results on the roles of MD, VTA and ACC in the control of immobility during focused attentive behaviour in cat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247309
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  • 23
    Digitale Medien
    Digitale Medien
    Evidence for a nicotinic component to the actions of acetylcholine in cat visual cortex (1988)
    Springer
    Experimental brain research 73 (1988), S. 553-568 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat ; Visual cortex ; Acetylcholine ; Nicotinic receptors ; Iontophoresis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Radioligand binding assays, receptor autoradiography and iontophoresis have been used to look for evidence of a nicotinic component to the actions of acetylcholine in cat visual cortex. [3H]Nicotine bound to a uniform population of high affinity binding sites in cat primary visual cortex. This binding was inhibited by nicotine agonists and antagonists but not muscarinic antagonists. The concentration of nicotinic binding sites was about 10% of that of muscarinic binding sites measured with [3H]N-methylscopolamine. The muscarinic sites were resolved into M1 and M2 subtypes. Quantitative receptor autoradiography showed that there were muscarinic sites in all layers, although they were least abundant in layer IV of area 17. In contrast, the nicotinic sites were most concentrated in layer IV in area 17. The concentration of this labelling was reduced at the 17/18 border and also at the 18/19 border. Layer I of the cingulate and suprasylvian gyri were also labelled. Electrolytic lesions of the lateral geniculate nucleus (LGN) led to a loss of nicotinic binding sites in layer IV of area 17, indicating that these sites are most likely located on the LGN terminals. Iontophoresis of mecamylamine, a nicotinic antagonist, decreased evoked responses in visual cortex, providing evidence that the [3H]nicotine binding sites are functional receptors and suggesting that the release of acetylcholine onto these receptors on the LGN terminals facilitates the input of visual information into visual cortex.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00406614
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  • 24
    Digitale Medien
    Digitale Medien
    Vestibulo-ocular reflex adaptation in cats before and after depletion of norepinephrine (1988)
    Springer
    Experimental brain research 69 (1988), S. 509-521 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Vestibulo-ocular reflex ; Cat ; Norepinephrine ; Neuronal adaptation ; 6-hydroxydopamine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The vestibulo-ocular reflex (VOR) operates to stabilize the eyes in space during movements of the head. The system has been described as having a gain of approximately -1 since stimulation of the semi-circular canals brought about by head movements will have the effect of causing the eyes to rotate an equal amount in the opposite direction. Change in the gain of the VOR has been put forth as a model to study plasticity in the central nervous system. Since numerous studies have implicated norepinephrine (NE) in neuroplasticity and modifiability of neural circuits, we attempted to determine the effect of NE depletion (via 6-hydroxydopamine (6-OHDA) intra-cisternal injection) on the modifiability of the VOR. We have found that cats increase the gain of their VOR over a four hour period when rotated in the horizontal plane in a manner equal but opposite to the rotation of a surrounding opto-kinetic drum. The entire group of animals manifests a statistically significant decrement in their ability to increase VOR gain when central stores of norepinephrine are depleted via intra-cisternal injection of 6-OHDA. Individual animals manifest a wide variety of gain changes (0.98 to 1.62). We have found that there were two groups of cats — high and low gain modifiers. The greatest reduction in VOR gain increase after NE depletion was observed in the high gain modifiers. No difference was observed in the low gain modifiers. These same animals tested for VOR modification after amphetamine injection, produced similar results. Alertness during the VOR modification task, as estimated by saccadic eye movement counts, was unchanged after NE depletion. NE levels, measured by HPLC-EC, after depletion were reduced to the greatest extent in the cerebellum. There was also a substantial reduction of NE in the visual cortex with less of a reduction in the brain stem.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247305
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  • 25
    Digitale Medien
    Digitale Medien
    Voiced calls evoked by hypothalamic stimulation in the cat (1988)
    Springer
    Experimental brain research 71 (1988), S. 21-32 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Voiced vocalization ; Hypothalamic stimulation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Voiced vocalizations evoked by hypothalamic stimulation were studied in a series of six awake adult cats. Electrical stimulation was found to evoke vocalizations at numerous sites within the hypothalamus, ranging from A+8 to A+16. Regions showing the largest number of responsive sites were the preoptic region, the ventromedial area, the perifornical region, the lateral and the dorso-medial hypothalamus. The form of the evoked calls was generally similar to the spontaneous calls of the same animal. Call latency, duration, and intensity were not significantly affected by changes in stimulus intensity or duration but all three of these call parameters were significantly affected by changes in stimulus frequency. In general, call latency was longest at sites in the rostral hypothalamus and shortest at sites in the caudal hypothalamus. This study is the first to investigate systematically voiced call producing areas in the hypothalamus of awake cats and to document similarities between these calls and spontaneously produced voiced calls.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247519
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  • 26
    Digitale Medien
    Digitale Medien
    Effects of convergent strabismus on spatio-temporal response properties of neurons in cat area 18 (1988)
    Springer
    Experimental brain research 72 (1988), S. 264-278 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Convergent strabismus ; Cat ; Area 18 ; Temporal properties ; Contrast sensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Single-cell recording experiments were carried out to determine whether rearing kittens with surgically induced convergent strabismus (esotropia) alters the development of receptive field (RF) properties of neurons in area 18. In agreement with previous work on kittens with divergent strabismus (exotropia), there was a marked loss of binocularly driven cells in area 18 of esotropic cats. In contrast to the striate cortex of strabismic cats, the spatial properties of area 18 neurons, including receptive-field size and spatial frequency tuning, did not differ from those in normal controls. On the other hand, we found that contrast thresholds, measured at an optimal spatial frequency, were significantly elevated, and that the contrast gain in many cells was reduced in strabismic cats. These deficits were observed in both eyes, though the cells dominated by the deviating eye had a lower response amplitude at all contrasts. Furthermore, temporal frequency tuning curves were abnormal in strabismic cats in that the optimal frequencies and temporal resolutions were shifted to lower values. These effects were also bilateral. Velocity tuning, measured with a high-contrast bar stimulus, revealed that area 18 neurons in strabismic cats were unable to respond to very high velocities compared to normals. This reduced response was more severe when measured with the deviating eye in spite of the bilateral nature of the deficit. Finally, latencies to electrical stimulation of the optic chiasm or the optic radiation were significantly longer in strabismic cats. The magnitude of these effects was virtually the same for both eyes. From these observations, we conclude that the temporal properties of area 18 neurons, particularly the cells abilities to follow fast temporal modulations, are affected by raising kittens with surgically induced convergent strabismus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00250249
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  • 27
    Digitale Medien
    Digitale Medien
    Neural site of strabismic amblyopia in cats: X-cell acuities in the LGN (1988)
    Springer
    Experimental brain research 72 (1988), S. 503-509 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Strabismic amblyopia ; Cat ; Lateral geniculate nucleus ; Acuity ; X-cell ; VEP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The acuities of X-cells from the dorsal lateral geniculate nucleus (LGN) were measured in five cats raised with a convergent strabismus, surgically induced by tenotomy. The acuities of cells driven by the strabismic eye were not significantly different from the acuities of cells driven by the non-deviating eye over the range of eccentricities in the visual field studied (from the area centralis to over 20°). The data were also similar to X-cell acuities in the LGN of 3 normal cats. Lowered acuities of LGN X-cells driven by the deviating eye of an esotropic cat in which the strabismus was created by myectomy confirm a previous finding of a retinal locus of amblyopia associated with that preparation. In contrast, the results here implicate the visual cortex as the initial site of the deficit in spatial processing in amblyopia arising from tenotomy strabismus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00250595
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  • 28
    Digitale Medien
    Digitale Medien
    The contribution of the horizontal semicircular canals to the response to off-vertical-axis rotation in the cat (1988)
    Springer
    Experimental brain research 71 (1988), S. 147-152 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Eye movements ; Vestibulo-ocular reflex ; Otoliths ; Off-vertical-axis rotation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The response to off-vertical-axis rotation (OVAR) was measured in cats under circumstances in which the signals from the horizontal semicircular canals and otoliths were opposed. Opposition was achieved by sudden acceleration or deceleration during constant velocity OVAR. The degree of opposition was expressed as a canal/otolith ratio where a ratio of unity indicated agreement. For a canal/otolith ratio of 1, the OVAR gain (eye velocity/ stimulus velocity) was 0.73 (±0.13). The steady-state OVAR response was, however, reduced if the canals and otoliths were opposed. The reduction depended on the degree of opposition with a fall-off of 0.15 gain/(unit of canal/otolith ratio). These findings are discussed with respect to the central velocity store and the mechanism underlying the generation of the OVAR response.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247529
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  • 29
    Digitale Medien
    Digitale Medien
    Excitatory and inhibitory postsynaptic potentials in cat hypoglossal motoneurons during swallowing (1988)
    Springer
    Experimental brain research 71 (1988), S. 262-272 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Swallowing ; Synaptic potential ; Hypoglossal motoneuron ; Extrinsic tongue muscle ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The postsynaptic potentials produced in cat genioglossus and styloglossus motoneurons (GG- and SG-Mns) during swallowing were studied. During swallowing elicited by placing water on the dorsum of the tongue, the GG-muscle discharged for 80–210 ms (mean±S. D. 123±31 ms, N=59) and was abruptly suppressed, and the SG-muscle began discharging in synchrony with the GG-muscle and discharged for 200–360 ms (mean+ S. D. 247±36 ms, N=59). The GG and the SG-Mns were identified if unitary muscle activity followed the induced spike of the motoneuron one-for-one. During swallowing, excitatory postsynaptic potentials (EPSPs) were evoked in the SG-Mns regardless of the respiratory drive on the SG-Mns, and inhibitory postsynaptic potential (IPSP) or EPSP-IPSP was evoked on the GG-Mns regardless of the respiratory drive on the GG-Mns. By increasing the intracellular concentration of chloride ions, the IPSP elicited in the GG-Mn during swallowing was turned into a depolarizing potential. In immobilized cats, a depolarizing potential and a depolarizing-hyperpolarizing potential sequence was evoked successively on a tongue retractor motoneuron and a tongue protruder motoneuron by repetitive electrical stimulation of the superior laryngeal nerve.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247486
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  • 30
    Digitale Medien
    Digitale Medien
    Nystagmus induced by off-vertical rotation axis in the cat (1988)
    Springer
    Experimental brain research 73 (1988), S. 78-90 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Otoliths ; Nystagmus ; Labyrinth ; Eye movements ; Velocity storage mechanism ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1) In the alert cat, nystagmus induced by off-vertical axis rotation (OVAR) was recorded following steps in head velocity or ramps of velocity at constant acceleration below canal threshold. Dependence of nystagmus characteristics on tilt angle of rotation axis and head velocity was studied. Similar results were obtained with both types of stimulation. 2) Mean and modulation amplitude of horizontal eye velocity increased with tilt angle in the range 0–30 degrees. 3) Both variables increased also with head velocity, but with different trends, probably because they are set by different mechanisms. When head rotational velocity was increased above 80°/s, mean eye velocity progressively decreased to zero. 4) In spite of variations from one animal to another, some regularity was observed in the phase of eye velocity modulation. In several cases, a reduction in phase lead of eye velocity with respect to conventional origin of phases (nose-down position) was observed when head velocity increased. 5) Time constant of post-OVAR nystagmus decreased with the tilt angle of the rotation axis from gravity, but not with the orientation of the head with respect to rotation axis. 6) The results could be accounted for by a general equation describing the vestibulo-ocular reflex, provided that estimates of kinematic variables of head movement (head rotational and translational velocities), and visual target distance could be computed by the Central Nervous System.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279663
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  • 31
    Digitale Medien
    Digitale Medien
    Effects of the dopamine antagonists haloperidol and domperidone on the normoxic ventilatory response to CO2 in cats (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 278-282 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Peripheral chemoreceptors ; Central chemoreceptors ; Control of respiration ; Dopamine ; Haloperidol ; Domperidone ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We investigated the effects of the dopamine antagonists haloperidol and domperidone on the ventilatory response following square-wave changes in end-tidal CO2 during normoxia in chloralose-urethane anaesthetized cats. In 7 cats these responses were measured before (control, 28 runs) and after the administration of 1 mg/kg haloperidol i.v. (26 runs) and in 8 other cats before (39 runs) and after 0.5 mg/kg domperidone i.v. (34 runs). Each response was separated into a slow central and a fast peripheral part by fitting two exponential functions to the measured ventilation. These functions have as parameters a CO2 sensitivity, a time constant, a time delay and an apnoeic threshold B (extrapolated PETCO2 of the steady-state response curve at zero ventilation). Haloperidol significantly diminished the peripheral (Sp) and the central (Sc) ventilatory sensitivity to CO2 and the B-value (P〈0.001). The ratio Sp/Sc, the time constants and the time delays were not significantly changed. Domperidone only diminished the B-value significantly (P〈0.001). Since domperidone does not readily cross the blood-brain barrier, its effect was a CO2 independent increase of the ventilation mediated by the peripheral chemoreceptors. Haloperidol exhibited, besides the peripheral stimulatory effect a depressant central effect due to an action on the central integrative structure, resulting in a proportional decrease of Sp and Sc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00585115
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  • 32
    Digitale Medien
    Digitale Medien
    Apomorphine-induced limb flicks in cats: the role of dopamine receptors located outside the blood-brain barrier (1988)
    Springer
    Psychopharmacology 95 (1988), S. 268-270 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Aminotetralin ; Apomorphine ; Cat ; Emesis ; Limb flicks
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Apomorphine-induced limb flicks in cats have been ascribed to a central dopamino-mimetic action of the drug. In these experiments we investigated the role of receptors located outside the blood-brain barrier (BBB) in the induction of limb flicking. Domperidone, a dopamine-receptor blocker which does not readily pass through the BBB, antagonised the induction of limb-flicks induced by apomorphine. This suggests that limb flicking behaviour may involve interactions with receptors located before the BBB. In contrast, 6-amino-5,6,7,8-tetrahydro-1,2-naphtalenediol HBr (6-ATN), a dopamine-agonist which does not penetrate the BBB, did not induce limb flicks, indicating that receptor stimulation outside the BBB alone is not sufficient to induce limb flicks. We suggest that limb flicks in cats is a behaviour which can be elicited by combined activation of centrally located dopamine receptors and dopamine receptors in the area postrema.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00174522
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  • 33
    Digitale Medien
    Digitale Medien
    Neurokinin A-like immunoreactivity in feline dental pulp: its distribution, origin and coexistence with substance P-like immunoreactivity (1988)
    Springer
    Cell & tissue research 251 (1988), S. 565-569 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Neurokinin A ; Substance P ; Dental pulp ; Immunohistochemistry ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The distribution and origin of neurokinin A (NKA)-like immunoreactivity were investigated in feline dental pulp by an indirect immunofluorescence method. NKA-containing nerve fibres with varicosities, which entered the dental pulp via apical foramen, were distributed throughout this tissue. Many NKA-containing nerve fibres were localized around blood vessels, but some were observed apart therefrom. At the odontoblastic layer, thin NKA-containing nerve fibres were observed running straight toward the pulp-predentinal border between odontoblasts. After inferior alveolar nerve section, all NKA-containing nerve fibres disappeared in the dental pulp, while the removal of the superior cervial ganglion resulted in no change in the distribution of these fibres. The correlation of NKA-like immunoreactivity and substance P (SP)-like immunoreactivity was also investigated by double-immunofluorescence technique. The distribution of NKA-containing nerve fibres was very similar to that of SP-containing nerve fibres; it appeared that all NKA-containing nerve fibres contained SP.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00214004
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  • 34
    Digitale Medien
    Digitale Medien
    Immunocytochemical analysis of calcitonin gene-related peptide and vasoactive intestinal polypeptide in Merkel cells and cutaneous free nerve endings of cats (1988)
    Springer
    Cell & tissue research 254 (1988), S. 429-437 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Calcitonin gene-related peptide (CGRP) ; Vasoactive intestinal polypeptide (VIP) ; Merkel cells ; Free nerve endings ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Calcitonin gene-related peptide (CGRP)-and vasoactive intestinal polypeptide (VIP)-immunoreactivity were observed to coexist in Merkel cells of cats. No differences in peptide content were found between Merkel cells located in epithelia of the hard palate, in hairy and glabrous skin of the upper lip, and in vibrissae follicles. CGRP-and VIP-immunoreactive nerve fibres were also found near CGRP/VIP-immunoreactive Merkel cells. In the vibrissae follicles some CGRP-and VIP-immunoreactive nerve terminals end abutting on the glassy membrane. Other CGRP immunoreactive nerve fibres penetrate the epithelium of the skin and end within it. Electron microscopy of vibrissae follicles revealed that Merkel cell neuntes are not immunostained and that immunostained nerve fibres form unmyelinated bundles before ending freely. Thus, CGRP-and VIP immunoreactive nerve fibres in cat skin do not end as Merkel cell neuntes but as different kinds of free nerve endings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00225816
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  • 35
    Digitale Medien
    Digitale Medien
    Localization of CRF-immunoreactive neurons in the cat medulla oblongata: their presence in the inferior olive (1988)
    Springer
    Cell & tissue research 251 (1988), S. 137-143 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Corticotropin-releasing factor (CRF) ; Medulla oblongata ; Inferior olive ; Immunohistochemistry ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Corticotropin releasing factor (CRF)-immunoreactive (IR) perikarya, visualized by the indirect immunoperoxidase method in colchicine-pretreated cats, were localized in many discrete regions of the medulla oblongata. They were found mainly in the dorsal aspect and midline of the medulla oblongata, and more rostrally in the ventrolateral portion. Our results also demonstrated CRF-IR neurons in the rostrocaudal extent of the inferior olive, probably projecting to the cerebellar cortex via thick axons visualized along the lateral edge of the medulla. CRF-IR olivary cells were also found in the pontine cat from which the forebrain was removed, but neither in hypophysectomized nor adrenalectomized cats.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215458
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  • 36
    Digitale Medien
    Digitale Medien
    Neuropeptide distribution in the cervico-thoracic paravertebral ganglia of the cat with particular reference to calcitonin gene-related peptide immunoreactivity (1988)
    Springer
    Cell & tissue research 252 (1988), S. 463-471 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Calcitonin gene-related peptide ; Regulatory peptides ; Paravertebral ganglia ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Paraffin sections of cervical and upper thoracic paravertebral ganglia of the cat were investigated by immunohistochemistry using antisera directed against calcitonin gene-related peptide (CGRP). The relationships of CGRP-immunoreactive structures to those exhibiting immunoreactivity to antisera against other regulatory peptides and dopamine-β-hydroxylase (DBH), respectively, were studied in consecutive sections. Singly scattered CGRP-immunoreactive neuronal perikarya were observed in the superior and middle cervical ganglia as well as in the stellate ganglion. These neurons also displayed immunoreactivity to vasoactive intestinal polypeptide (VIP), and some additionally exhibited faint substance-P immunoreactivity. DBH- and neuropeptide Y-immunoreactive ganglion cells were not identical with CGRP-immunoreactive neuronal cell bodies. According to the immunoreactive properties of varicosities, which abut on CGRP/VIP-immunoreactive perikarya, three types of CGRP/VIP-immunoreactive ganglion cells could be distinguished: (1) CGRP/VIP-immunoreactive neurons being surrounded by somatostatin-immunoreactive nerve fibers, (2) neurons being approached by both DBH- and met-enkephalin-immunoreactive varicosities, and (3) neurons receiving both DBH- and neurotensin-immunoreactive fibers. The stellate and upper thoracic ganglia harbored clusters of intensely VIP-immunoreactive somata, which lacked CGRP-immunoreactivity. Fine somatostatin-immunoreactive and coarse CGRP-immunoreactive fibers were distributed within these clusters, whereas patches of neurotensin-immunoreactive fibers were complementarily arranged. At all segmental levels investigated, a few postganglionic neurons were approached by both CGRP-immunoreactive and substance P-immunoreactive varicosities, but lacked a VIP-immunoreactive innervation. Therefore, CGRP/substance P-immunoreactive fiber baskets appeared rather to be of extraganglionic origin than to emerge from intraganglionic CGRP/VIP/SP neurons. CGRP-immunoreactive cell bodies or fibers were absent in clusters of small paraganglionic cells, but some of the solitary paraganglionic cells displayed CGRP-immunoreactivity. Our findings establish the presence of CGRP-immunoreactivity in a population of sympathetic neurons in the cat. A highly differentiated, segment-dependent organizational pattern of neuropeptides in cervico-thoracic paravertebral ganglia was demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00214390
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  • 37
    Digitale Medien
    Digitale Medien
    A re-evaluation of the cytology of cat Pacinian corpuscles (1988)
    Springer
    Cell & tissue research 253 (1988), S. 83-93 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Pacinian corpuscle ; Axonal spines ; Inner core lamella ; Inner core cleft ; Elastica ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructure of cat mesenteric Pacinian corpuscles in cross and longitudinal sections has been examined. The terminal ends of lamellar cells of the inner core have been identified in longitudinal sections through the proximal portion of the inner core. These terminal bulbous expansions contain characteristic concentric membranes of rough endoplasmic reticulum and in some cases masses of oval membranous inclusions. The central axon as seen in cross section is oval in profile, having X-(short) and Y-(long) axes, and each axonal face is characterized by specializations of the axolemma. At the X-axis, the inner lamellae of the inner core tightly abut a smooth axolemma, with no intervening connective tissue matrix, in a manner reminiscent of a neuroepithelium. The axolemma of the Y-axis has numerous axonal spines (microspikes) that project into the cleft in the inner core. The extent of the axolemma having axonal spines can only be appreciated in longitudinal sections. The clefts contain a specialized connective tissue with elastic and collagen fibrils. The connective tissue compartment of fibers and matrix separating individual inner core lamellae is unique, in that it contains extremely thin collagen fibrils measuring approximately 15 nm in diameter. The diameter of collagen fibrils increases as the cleft is approached. Here the fibrils resemble typical endoneural collagen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00221743
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  • 38
    Digitale Medien
    Digitale Medien
    A re-evaluation of the cytology of cat Pacinian corpuscles (1988)
    Springer
    Cell & tissue research 253 (1988), S. 95-103 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Pacinian corpuscle ; Axonal spines ; Axonal extreme tip ; Inner core lamella ; Basal lamina-like material ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The present report is the second of two studies re-evaluating the cytological characteristics of Pacinian corpuscles. The extreme tip of the axon of a Pacinian corpuscle has been identified and is quite different from the previously described ultraterminal region. The latter is the site where the inner core lamellae begin to terminate and is characterized by a smooth axolemma. The extreme tip lacks inner core lamellae directly abutting the axolemma and is instead characterized by the presence of many axonal spines projecting into a matrix of basal lamina-like material. The extreme tip of the axon thus resembles the organization of the axolemma facing the clefts of the inner core. The axonal spines at the cleft and extreme tip are proposed as a site of restricted current flow due to the tight apposition of inner core lamellae to the axolemma of X-axis. The hemiinner cores thus could restrict current flow to the cleft. These anatomical specializations could represent both a source and a sink for K+ ions during mechano-electric transduction and account in part for the exquisite sensitivity of Pacinian corpuscles to complex pressure waves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00221744
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  • 39
    Digitale Medien
    Digitale Medien
    The influence of middle ear pressure on the otolith system in cats (1988)
    Springer
    European archives of oto-rhino-laryngology and head & neck 245 (1988), S. 321-324 
    Details
    ISSN: 1434-4726
    Schlagwort(e): Otoliths ; Middle ear pressure ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The influence of varying middle ear pressure on the otolith system was investigated in anesthetized cats. Extra-axonal recordings of action potentials were performed in the vestibular nerve fibers and in the neurons in the lateral vestibular nucleus that responded to lateral or anteroposterior steadystate tilt. Positive or negative pressure was applied to the ipsilateral middle ear during the recordings. Seventy-three percent of the fibers and 63% of the neurons responded to changes in the middle ear pressure. These response rates were higher than those previously reported on the units innervating semicircular canals. Findings suggest that the otolith organs are more sensitive to changes in the middle ear pressure than are the semicircular canals. The units responding to lateral tilt were more sensitive to middle ear pressure than those that responded to anteroposterior tilt. Displacement of endolymph caused by pressure changes in the middle ear was considered to have affected the activities of hair cells in otolith organs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00464641
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  • 40
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988) 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250101
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  • 41
    Digitale Medien
    Digitale Medien
    Error estimation and adaptivity in flow formulation for forming problems (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 23-42 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A very simple and reliable error estimator has recently been developed for problems of linear elasticity.1 This leads naturally toa predication of an h-mesh refinement required for a given accuracy and with a suitable mesh generator2 for an efficient adaptive process. In this paper we extend the methodology developed previously to incompresible plastic flow of metals or polymers using the ‘flow formulation’ approach.3The examples of application include steady state extrusion problems for which exact solutions are available and hence allow the efficiency of the error estimates to be tested as well as more complex problems of upsetting in which the mesh is updated. It is found that the estimator performs well under various circumstances and provides an economical adaptive process.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250105
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  • 42
    Digitale Medien
    Digitale Medien
    Ignition phase transition of a polymer: Convective exposure (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 373-386 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The ignition of a semi-infinite solid polymer under convective exposure is investigated. A quasi-steady approximation is used for the gas phase and the transient effect is accounted for in the solid phase only. Both surface and gas phase chemical reactions are included simultaneously. The ignition mechanism is studied in terms of the concurrent heat transfer, mass transfer, mass transfer and chemical processes at the surface as well as in the gas phase. The gas phase governing equations are integrated independently from the solid phase energy equation using the Adams-Moulton subroutine. Corrections to the iterative procedure are carried out by establishing a set of perturbation equations and using the Newton-Raphson and least-squares methods. The results indicate that ignition occurs in the heterogeneous mode within a narrow range of low flow velocities and high temperatures. An ignition phase transition point exists, and within a wide range of high flow velocities, ignition switches to the homogeneous mode.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250208
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  • 43
    Digitale Medien
    Digitale Medien
    Shape design sensitivity analysis for non-linear anisotropic heat conducting solids and shape optimization by the BEM (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 109-120 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Shape design sensitivity analysis (SDSA) expressions have been derived for non-linear anisotropic heat conducting solid bodies by following the material derivative concept and adjoint variable method of optimal shape design given in the literature. The variation of a general integral functional has been described in terms of primary and adjoint quantities evaluated at the varying boundaries. As an example problem in shape optimization, optimal outer boundary profiles of an orthotropic solid body are obtained by the boundary element method (BEM), after reformulating the SDSA equations in a form which is most suitable for the BEM.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260108
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  • 44
    Digitale Medien
    Digitale Medien
    Analyses of steady-state visco-elastic fluids using the penalty function method (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 43-54 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The application of the penalty-function formulation of the finite element method is made possible for analysing visco-elastic fluid flows by the method which decouples the momentum and continuity equations from the constitutive equation. An upwind finite element scheme is combined with the method in order to solve the constitutive equation. As visco-elastic fluid models, Jaumann derivative, upper and lower convected derivatives are considered. The Poiseuille flow and the flow through a plane converging channel are analysed.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250106
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  • 45
    Digitale Medien
    Digitale Medien
    Approximate methods for analysing the cold drawing of polymeric fibres and films (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 99-112 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Approximate methods for analysing steady-state cold drawing processes in polymer forming are discussed. These methods are applied to both axisymmetric and plane-strain drawing. The cold drawing process is associated with steady-state neck propagation along the specimen. Modifications are introduced in the approximate steady-state analysis which reflect the neck initiation and localization phases prior to steady-state drawing. This is accomplished without resorting to an analysis of the entire load-deformation history of the process. Finite element results are also presented and compared with those of the proposed approximate analyses. These comparisons show the approximate analysis to be an extremely efficient and quite accurate computational scheme for the analysis of steady-state cold drawing processes.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250110
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  • 46
    Digitale Medien
    Digitale Medien
    Analysis of stress and strain distributions in slab rolling using an elastic-plastic finite-element method (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 55-66 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The cold rolling of rectangular section slabs is analysed for a range of width-to-height ratios (one to three) for which spread of the workpiece is appreciable. This necessitates the use of a three-dimensional model. An elastic-plastic finite-element method is used to provide a complete description of the slab rolling process.The pressure distribution at the workpiece/roll interface is found to show the typical ‘friction-hill’ observed in near-plane-strain experiments, but the pressure varies across the width of the interface. The shear-stress distribution at the roll interface provides detailed information about the ‘neutral line’ which is usually assumed to occur where the shear stress changes direction. The 3-D analysis shows clearly that there is a flow divide in both longitudinal and transverse directions.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250107
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  • 47
    Digitale Medien
    Digitale Medien
    Numerical simulation of the densification behaviour of metal powder during hot isostatic pressing (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 213-225 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A numerical method is introduced which is based on metal flow theory and simulates the densification of metal powder during hot isostatic pressing.The method, in which nodal velocities are variables, takes into consideration the dependence of flow stress on the temperature, strain rate and relative density of the material. The compressibility of porous metal as well as the incompressibility of fully dense metal are also taken into account.Porous specimens of the superalloy MERL76 were subjected to uniaxial compression tests at high temperature in order to determine the parameters of the equations on which the method is based. The densification behaviour of a turbine disk and two cylindrical components was numerically simulated and compared with experimental results.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250117
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  • 48
    Digitale Medien
    Digitale Medien
    Preface (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. i 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250202
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  • 49
    Digitale Medien
    Digitale Medien
    Coarse-fine mesh method for heat and mass transfer in locally complex flows (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 347-355 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Combined forced and free convective flows having locally complicated geometries or boundary conditions were numerically studied with a finite difference method of coarse and fine meshes. The coarse-and-fine mesh method developed can be used for numerical calculations of both unsteady and steady processes of heat and mass transfer in convective and diffusion flows which are strongly influenced by locally fine flows. The method was applied to a numerical calculation of the steady flow field of a CVD (chemical vapour deposition) reactor which has locally complicated flows caused by small inlet nozzles. The results of the calculation showed a considerable contribution of locally fine flows to the overall flow field, which is well predicted with the present method.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250206
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  • 50
    Digitale Medien
    Digitale Medien
    Thermal analysis of human body-clothing-environment system (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 357-371 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: For the solution of thermal comfort problems a coupled model is presented consisting of the thermal model of the human body and of the clothing, with boundary conditions of the third kind.For thermal modelling the human body is divided into 16 parts according to the special character of the internal heat generation, of the blood vessel system and of the sweat secretion mechanism. Part models are connected by the flow paths of arteries and veins.Transport phenomena in the clothing are treated by a coupled heat and mass transfer model which permits various kinds of clothing for the different parts of the body.The equation system of the full model has been solved numerically by using time stepping schemes. As the results of the computations an approximative temperature field of the human body is produced.Calculated results have been compared with Experimental data.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250207
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  • 51
    Digitale Medien
    Digitale Medien
    Finite element simulation of hot isostatic pressing of metal powders (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 191-212 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Rate form constitutive equations of elasto-viscoplastic type are expressed in a manner similar to that of classical metals, but the viscoplastic part, which is no longer incompressible, is related to the rate of variation of porosity. An incremental and implicit algorithm has been implemented in a finite element program in order to simulate hot isostatic pressing of an Astroloy powder. Temperature distributions are shown to induce strong density variations in real parts during hot isostatic pressing (HIP). For one particular turbine disk, we tested the sensitivity of the final shape to different processing parameters. Computed final shapes compare well with experimental ones.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250116
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  • 52
    Digitale Medien
    Digitale Medien
    Analysis of bending effects in sheet forming operations (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 253-267 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The majority of work in numerical analyses of sheet metal forming operations is based on the simple membrane-shell theory which neglects the effect of sheet bending. While useful information can be extracted from these analyses, especially for stretch-dominated operations, the membrane theory is basically inadequate for analysing the draw-type operations where sheet metal bends, slides and unbends over a draw radius.This paper presents axisymmetric and plane-strain finite element analyses of stretch/draw of sheet metal over a die corner radius. Numerical solutions obtained from a total Lagrangian formulation of a finite-strain thin shell theory are used to indicate the relative significance of including the bending effects in various simple forming operations. Comparisons of the calculated results with available experimental data are also given.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250119
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  • 53
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    Digitale Medien
    A finite element simulation of the sheet metal forming process (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 283-292 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A finite element simulation code of the sheet metal forming process has been developed. This simulation code plays an important role in the computer aided engineering (CAE) system for an automobile parts forming process, which includes the pre- and post-processes. The paper presents the development of an updated Lagrangian type finite element modelling, based on the elastic-plastic (J2 flow law) membrane shell theory. An attempt is made to calculate the strain distribution incurred by peripherally clamped or non-clamped square plates when impressed by rigid punches. These are the cases of square box-shape punch drawing and arbitrary shaped panel stretch forming.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250121
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  • 54
    Digitale Medien
    Digitale Medien
    Punch stretching of sheet metal and differential equations on manifolds (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 269-282 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The goal of mathematical modelling of sheet metal forming processes is to provide predictive tools for use in the design of stamping processes and the selection of sheet materials. Most current approaches to finite element modelling of large deformation, elastic-plastic sheet metal forming problems use a rate form of the virtual work (equilibrium) equations, and a single-field finite element representation of the displacement components. Called the incremental method, this approach does not produce approximations which satisfy the discrete equilibrium equations at all times, and consequently it demands small time steps to insure stability and numerical accuracy. This paper describes a variant of the mixed method in which displacements, stresses, effective strain and pressures are all given separate finite element representations. The equilibrium equations in non-rate form are discretized to produce a system of algebraic equations which are coupled with the constitutive equations and then integrated using state-of-the-art numerical software. When used to model rate sensitive sheet materials in hydrostatic bulging, plane strain punch stretching and hemispherical punch stretching, the new approach proved to be between 6 and 26 times as fast as the old incremental method.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250120
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  • 55
    Digitale Medien
    Digitale Medien
    Buoyant flow calculations with non-orthogonal curvilinear co-ordinates for vertical and horizontal parallelepiped enclosures (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 331-345 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A control-volume-based finite-difference formulation is developed for heat transfer and fluid flow in arbitrary three-dimensional parallelepiped enclosures. The governing equations in Cartesian co-ordinates are first transformed to those in non-orthogonal curvilinear co-ordinates by tensor transformations. After introducing the properties of the parallelepiped geometry, equations are obtained in the primitive variables for which all vectors and tensors are based on the curvilinear co-ordinates. With proper treatment of the heat flux and stress tensor terms, the finite-difference equations, analogous to those in the Cartesian coordinates, are formed. Examples are utilized to show the validity of the methodology and the results are found to compare well with existing experimental data. The differences in heat transfer and fluid flow inside parallelepiped enclosures and rectangular enclosures are delineated and discussed from a physical point of view.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250205
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  • 56
    Digitale Medien
    Digitale Medien
    Finite element analysis of turbulent forced convection in lid-driven rectangular cavities (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 313-329 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Turbulent fluid flow and heat transfer in lid-driven rectangular cavities are analysed by a finite element procedure for the prediction of the turbulent forced convection in two-dimensional recirculating flows. The (k-ε) model is used to compute effective viscosities and thermal conductivities. The fluid flow and turbulence model parabolic equations are solved sequentially, one after the other. Then, the calculated velocity distribution is used in the solution of the steady state energy equation to yield the temperature field. Aspect ratios e=0·75, 1·0 and 1·5 and Reynolds numbers ranging from 5 × 104 to 4 × 105 are considered in the numerical examples.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250204
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  • 57
    Digitale Medien
    Digitale Medien
    Non-linear simulation of dendritic solidification of an undercooled melt (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 415-444 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Two-dimensional finite element simulations of solidification for quiescent undercooled pure metals are presented. The full non-linear, transient heat equation is used with phase front tracking which is subject to local curvature and interfacial kinetics. During early stages of the waveform instability the simulated solutions match the linear stability analysis with fidelity. Beyond the valid range of that analysis the numerical solution continues to demonstrate the physically observed exponential growth behaviour and characteristic spacing between fingers. Whereas the simulations show the sensitivity of dendritic growth to initial conditions, as expected for an unstable process, the overall pattern formation preserves the characteristic spacing. The simulations are terminated after the onset of bifurcation. Thereafter, the numerical model is inappropriate for physical comparison owing to the planar, two-dimensional limitation.
    Zusätzliches Material: 24 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250211
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  • 58
    Digitale Medien
    Digitale Medien
    A regular indirect boundary element method for thermal analysis (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 495-515 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A Regular Indirect Boundary Element formulation is developed following a weighted residual approach. In this formulation, the fictitious source density, which appears in the integral equations of the method, is distributed on a surface which is exteriorly separated from the physical field boundary of the problem. This approach does not require the evaluation of singular integrals and produces undeteriorated solutions at geometric discontinuities. The formulation is presented here as applied to two dimensional and axisymmetric thermal problems. It includes a different subregioning scheme which treats each subregion, of a multidomain problem, separately, thereby eliminating the need for a sophisticated reduction scheme.
    Zusätzliches Material: 24 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250214
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  • 59
    Digitale Medien
    Digitale Medien
    Warping torsion in thin-walled open section beams using the semiloof beam element (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 231-243 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Many structural members including metallic, reinforced polymer and concrete members must be modelled, in the simplest approximation, as thin-walled beams whose cross-sections exhibit significant, out-of-plane warping owing to torsion. The elastic capabilities of the semiloof beam element are extended to include warping torsion of thin-walled open section beams. The performance of the extended element is compared with that of the original formulation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260116
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  • 60
    Digitale Medien
    Digitale Medien
    Partial eigensolution of damped structures by non-linear optimization (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 143-152 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The partial solution of damped structures involves the determination of only a few of the resonant frequencies and corresponding damping characteristics and mode shapes. The procedure outlined here uses a modification of the variable metric solution algorithm, in which the dicision variables are elements of the complex eigenvector and the eigenvalue. The quadratic eigenvalue problem is reformulated as a sequential unconstrained minimization problem. Both normality and orthogonality constraints are incorporated in the objective function. The method is compared to an adaptation of the subspace iteration technique, also applicable to the quadratic eigenvalue problem.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260110
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  • 61
    Digitale Medien
    Digitale Medien
    An element-by-element method for heat conduction CAE including composite problems (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 199-215 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Mechanical computer aided engineering (CAE) implies large finite element problems due to the geometric complexity of the ‘true’ 3D designs. Application of the standard finite element technique is not practical for such problems because the direct solution of the global matrix equations is too costly. This paper considers the element-by-element implicit algorithm for the CAE application of transient heat conduction. The direct solution is avoided by an operator splitting or approximate factorization technique. This results in both the execution time and storage requirements for each time step being linearly proportional to the number of elements while retaining unconditional stability. However, the approximate factorization introduces additional truncation error and incorrect jump conditions at material interfaces. Detailed analyses and numerical experiments are carried out in one dimension to assess the nature and mechanism of these inaccuracies. A three dimensional implementation is then compared with one dimensional results. The need for an additional predictor-corrector element-by-element algorithm for 3D composite problems is also presented.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260114
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  • 62
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    Digitale Medien
    Letters to the editor (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 281-282 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260119
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  • 63
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    Digitale Medien
    Conference diary (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 291-292 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260124
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  • 64
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    Digitale Medien
    Plastic design. An imposed hinge-rotation approach, P. Zeman and H. M. Irvine, Allen & Unwin, London, 1986, 86, pages (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 290-290 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260123
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  • 65
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    Digitale Medien
    Finite elements and solution procedures for structural analysis. vol. I: Linear analysis. M. A. Crisfield, Pineridge Press, Swansea, 1986. No. of pages: 272 (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 289-289 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260122
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  • 66
    Digitale Medien
    Digitale Medien
    Hybrid finite element-Monte Carlo method for coupled conduction and gas radiation enclosure heat transport (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 361-378 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A hybrid two-dimensional finite element-Monte Carlo numerical solution method has been developed for solving complex transient non-linear gas radiation enclosure problems. Solid conducting media are coupled to conducting gaseous or particulate participating media and both may be internally energy generating. Bilinear isoparametric elements are used, allowing geometrically complex enclosures with internal objects to be present. Radiative energy transport within the gaseous enclosures is accounted for using a Monte Carlo method which permits a broad range of complexities. Included here are: diffuse-grey and specularly reflecting walls with temperature and spectrally dependent, and non-homogeneous emissivities or absorptivities; absorbing/emitting gases with temperature and spectrally dependent, and non-homogeneous emissivities or absorptivities; and isotropic or anisotropic scattering gases or particles. This method was verified by solving several standard steady state problems and comparing the solutions to those found using the conventional finite element, the P-N and the exchange factor methods. Solution times are comparable to those of the finite element method. A more complex transient problem solution is then given to demonstrate the versatility and power of the method.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260206
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  • 67
    Digitale Medien
    Digitale Medien
    Derivatives of eigenvalues and eigenvectors of a general complex matrix (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 293-311 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A survey of methods for sensitivity analysis of the algebraic eigenvalue problem for non-Hermitian matrices is presented. In addition, a modification of one method based on a better normalizing condition is proposed. Methods are classified as Direct or Adjoint and are evaluated for efficiency. Operation counts are presented in terms of matrix size, number of design variables and number of eigenvalues and eigenvectors of interest. The effect of the sparsity of the matrix and its derivatives is also considered, and typical solution times are given. General guidelines are established for the selection of the most efficient method.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260202
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  • 68
    Digitale Medien
    Digitale Medien
    Convergence of curved shell elements based on assumed covariant strain interpolations (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 329-347 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A C0 9-node shell element based on assumed interpolations of covariant strain components defined with respect to the element natural co-ordinate system has recently been proposed. In this formulation, the covariant strains are obtained directly from the Cartesian strains by tensor transformation without any need to compute laminar co-ordinate based strains. In the present work, the interpolated covariant strains used in this element are analysed to determine their satisfaction of the basic requirements for successful strain interpolation. These basic requirements are stated as invariance to rigid body motions and ability to represent constant and linear strain states. In the finite element formulation, the weak form of momentum balance is expressed in terms of covariant strains and contravariant stresses. The corresponding elasticity tensor is a function of the components of the metric tensor associated with the element natural co-ordinate system. The invariance properties of the metric tensor in the context of the finite element approximation are also discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260204
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  • 69
    Digitale Medien
    Digitale Medien
    Spline collocation in the flow of non-Newtonian fluids (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 413-421 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Natural convection flow of a non-Newtonian fluid between two vertical infinite parallel flat plates forms the case study of the present work. Velocity profiles for the Prandtl-Eyring and Powell-Eyring fluid models are obtained through the method of spline collocation.The applicability and reliability of the techniques employed here are discussed in detail with a suggested error estimate and analysis. Accuracy in the successive iterations in the results is of the fourth order. To maintain this accuracy the help of a computer is not required for carrying out the calculation of velocity profiles. Thus the simplicity of the spline collocation technique is demonstrated in its application to flow problems.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260209
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  • 70
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    Digitale Medien
    Computation of hybrid element matrices by elimination techniques (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 423-435 
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    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Three functionals, the modified forms of the Hu-Washizu, Hellinger-Reissner, and complementary energy principles, as developed by Pian, Chen, and Kang1.2 are stated. Finite element discretization of each is presented and the ensuing computations developed, resulting in the element stiffness matrix, with displacement degrees-of-freedom only, and the stress recovery matrices. Subroutines are presented for this purpose where the close relationship of the three principles is exploited to result in a compact hybrid element technique. The techniques herein reviewed are assumed applicable at the individual element level. The usual summation over all elements in the model is implied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260210
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  • 71
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    Digitale Medien
    Accuracies of numerical solution methods for the pressure-modified von Mises modelThe paper was presented at Tenth U.S. National Congress of Applied Mechanics, June 16-20, 1986, Austin, Texas, U.S.A. (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 453-465 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The accuracy of three numerical algorithms - the tangent-stiffness radial-return, secant-stiffness radial-return and simple radial-return methods - is analysed against exact solutions for the pressure-modified von Mises yield criterion with the associated flow rule. The governing equations of the exact solutions are derived using a simple and innovative geometrical approach, in terms of a pair of non-linear, first order differential equations, in rate change of the deviatoric radius and in rate change of angular locations on the deviatoric plane. For both accuracy and efficiency, and for small and large time steps, the secant-stiffness radial-return method is the best of all.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260212
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  • 72
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    Digitale Medien
    Three-dimensional elastic finite element study of the skid resistance of grooved pavement (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 437-452 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A three-dimensional finite element model has been developed to simulate the sliding of a rubber block over a grooved road surface. The model makes use of the symmetries of the problem to simplify the analysis, so that two-dimensional isoparametric elements of both rectangular and triangular configuration have been extended into the third dimension. A procedure for analysing the behaviour of any one groove to groove unit of the pavement is also developed, and this is extended so that the contact between the sliding rubber block and the leading edge of each raised pavement section is analysed. Preliminary comparisons between theoretical calculations and experimental measurements indicate that the finite element procedure provides an accurate and economical estimate of the behaviour of the rubber slider as it is pressed into a grooved pavement. Elastic predictions of sliding resistance seem reasonable at low sliding speeds, but viscoelastic rubber analysis appears necessary if higher speed skid resistance is to be predicted.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260211
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  • 73
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    Digitale Medien
    Analysis of steady free convection from an axisymmetric heat-generating body embedded in a semi-infinite porous medium (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 467-487 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: An analysis is presented for the steady state free convective flow and heat transfer from an axisymmetric heat-generating body that is embedded in a fluid-saturated, semi-infinite, porous medium. The porous medium is assumed to be rigid, homogeneous and isotropic, and be in thermal equilibrium with the fluid. The fluid is assumed to be incompressible, with the density changes contributing only towards the buoyancy forces via the Boussinesq approximation. The governing equations for the fluid consist of the equation of continuity, Darcy's law and the equation of energy. After introducing the stream function concept, the equations governing the stream function and pressure are derived. Using the non-dimensional variables, the non-dimensional equations governing the non-dimensional forms of the temperature, stream function and pressure are dervied and the appropriate boundary conditions are stated. The mathematical formulation contains two parameters; D, the non-dimensional depth of the body from the surface of the porous medium, and a product Raθs of Rayleigh number (Ra) and the non-dimensional surface temperature of the body (θs). The Galerkin finite element method, with linear, isoparametric, quadrilateral elements, is used to reduce the mathematical formulation into a set of algebraic equations. The expressions to calculate the non-dimensional surface temperature and Nusselt number of the body, and the non-dimensional velocity of the fluid, are derived. A computer code has been developed to solve the algebraic equations, using Gauss elimination procedure, in a banded matrix form. The computer code, in addition to the non-dimensional temperature, stream function and pressure, calculates the isothermal lines, non-dimensional surface temperature of the body, Nusselt number of the body, velocity field and isobars.To demonstrate the application of the code, a spherical heat-generating body is considered as an example. Numerical results are obtained for D = 3 and 6, and Raθs = 0.001, 0.1, 1 and 5, and presented.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260213
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  • 74
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    Digitale Medien
    Masthead (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988) 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260301
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  • 75
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    Announcements (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 527-530 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260217
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  • 76
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    An integrated approach to the synthesis of geometrically non-linear structures (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 555-570 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: An integrated approach to the minimum weight design of geometrically non-linear three dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The non-linear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the contraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically non-linear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260304
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  • 77
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    Digitale Medien
    Theoretical basis of the finite element iterative method for the eigenvalue problem in stationary cracks (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 531-539 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In a recently published paper a finite element based iterative method was introduced for the solution of the eigenvalue problem of stationary cracks.1 In this paper we give the theoretical basis of this iterative method and we show why it converges and how it could be extended to more complex fracture problems. The cases of cracks at interfaces are illustrated.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260302
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  • 78
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    Digitale Medien
    Application of the finite element iterative method to the eigenvalue problem of a crack between dissimilar media (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 541-554 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The finite element iterative method is applied to the eigenvalue problem of a crack between dissimilar media. In this case the transfer matrix is non-symmetric, which leads to complex eigenvalues. The singularity obtained agrees with the analytical results of r(-1/2+ie). The method of evaluating the eigenfunctions is general and can be applied to more complex cases of material and geometry, which are frequently encountered in composite materials. A powerful method for evaluating stress intensities in dissimilar media is given in the Appendix. The method is also reduced for homogeneous media to give stress intensity factors for modes I, II and III.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260303
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  • 79
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    Digitale Medien
    Elasto-plastic large deformation analysis of space-frames: A plastic-hinge and stress-based explicit derivation of tangent stiffnesses (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 589-615 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper deals with elasto-plastic large deformation analysis of space-frames. It is based on a complementary energy approach. A methodology is presented wherein: (i) each member of the frame, modelled as an initially straight space-beam, is sought to be represented by a single finite element, (ii) each member can undergo arbitrarily large rigid rotations, but only moderately large relative rotations; (iii) a plastic-hinge method, with arbitrary locations of the hinges along the beam, is used to account for plasticity, (iv) the non-linear bendin-stretching coupling is accounted for in each member, (v) the applied loading may be non-conservative and (vi) an explicit expression for the tangent stiffness matrix of each element is given under conditions (i) to (v). Several examples, with both quasi-static and dynamic loading, are given to illustrate the accuracy and efficiency of the approaches presented.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260306
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  • 80
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    Digitale Medien
    Multi-grid solutions to the elastic plastic torsion problem in multiply connected domains (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 631-646 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The elastic plastic torsion problem for an elastic, perfectly plastic cylinder with multiply connected cross section twisted around its longitudinal axis is formulated as an obstacle problem for an associated stress potential, the obstacle being defined in terms of a generalized distance function. Based upon the reformulation of the obstacle problem as an equivalent linear complementarity problem, the latter is discretized by means of finite difference techniques, and a monotonically convergent iterative scheme for its numerical solution is developed. At each step of the iteration the solution of a reduced system of discrete Poisson equations is required which is done by applying multi-grid techniques with respect to a hierarchy of grid-point sets. Combined with a suitably chosen nested iteration process this results in a computationally very efficient algorithm for the approximate solution of the elastic plastic torsion problem.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260308
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  • 81
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    Digitale Medien
    Application of spline strip method to analyse vibration of open cylindrical shells (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 663-676 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper deals with the vibration of open cylindrical shells by the spline strip method based on Novozhilov's shell theory. Convergence of the solutions is investigated in a few examples and is found to be satisfactory. The accuracy of the results is compared with those calculated by other numerical methods and found to be in good agreement.The effect of inlcuded angles and inplane constraints on vibrating characteristics of simply supported cylindrical shells is shown.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260310
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  • 82
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    Digitale Medien
    A quadrilateral finite element including vertex rotations for plane elasticity analysis (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 717-730 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A finite element of arbitrary quadrilateral shape is presented for plane elasticity analysis. The element is derived from triangular fields of compatible quadratic displacements with vertex connectors which include rotations. All rigid body movements and constant strain states are recovered exactly. Results from several test problems demonstrate that very good numerical accuracy is obtained for both displacements and stresses, even for quite coarse finite element meshes.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260314
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  • 83
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    Digitale Medien
    A numerical case study of a non-Newtonian flow problem (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 695-704 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper addresses some of the theoretical aspects involved in the numerical study of non-Newtonian flow problems. We consider the second-order Rivlin-Erickson constitutive model due to the simple differential form that emerges for the system of equations that govern the flow when expressed in stream function-vorticity variables. This model describes slightly elastic fluids that exhibit a constant viscosity behaviour. A steady two-dimensional flow is studied through a planar contraction geometry.An auxiliary variable is introduced into the problem formulation producing a non-linear system of differential equations comprising two elliptic equations and one hyperbolic equation. This system is discretized by finite difference methods and the resulting system of non-linear algebraic equations is solved iteratively by successive substitutions. The simple structure of this iteration permits a convergence analysis which is presented in Section 2. This analysis is performed prior to the spatial discretization and establishes the dependence of the iteration upon the material parameters. At the discrete linearized equation level a combination of inner iterations for elliptic equations and direct marching for the hyperbolic equation is used. The stability of the marching scheme is considered in Section 4.3 and a discussion on the results is given in Section 5.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260312
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  • 84
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    Digitale Medien
    A nine node finite element for analysis of geometrically non-linear shells (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1945-1962 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A nine node finite element is presented for the analysis of thin shell structures undergoing large deflection. The finite element formulation is based on the concept of degenerate solid shell element and the Hellinger-Reissner principle with independent strain. Three versions of assumed independent strain are selected to suppress spurious kinematic modes. One version leads to a finite element model which is kinematically stable at element level while the other two give globally stable models. Numerical tests indicate that the finite element model which is stable at element level may reveal the locking effect in certain cases. However, the other two models are free of locking.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260905
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  • 85
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    Digitale Medien
    Finite element approximations of singular parabolic problems (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1989-2007 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: An efficient implementation of finite element methods for free boundary parabolic problems in general two dimensional space domains is presented. The Stefan problem, the Hele-Shaw problem and the porous medium equation are included. Backward differences or linearization techniques are used for the time discretization of the problem. The performances of these schemes are discussed with several numerical tests.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260907
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  • 86
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    Digitale Medien
    A new hybrid transfinite element computational methodology for applicability to conduction/convection/radiation heat transfer (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1087-1100 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper describes new and recent advances in the development of a hybrid transfinite element computational methodology for applicability to conduction/convection/radiation heat transfer problems. The transfinite element methodology, while retaining the modelling versatility of contemporary finite element formulations, is based on application of transform techniques in conjunction with classical Galerkin schemes and is a hybrid approach. The purpose of this paper is to provide a viable hybrid computational methodology for applicability to general transient thermal analysis. Highlights and features of the methodology are described and developed via generalized formulations and applications to several test problems. The proposed transfinite element methodology successfully provides a viable computational approach and numerical test problems validate the proposed developments for conduction/convection/radiation thermal analysis.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260507
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  • 87
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    Digitale Medien
    A robust triangular plate bending element of the Reissner-Mindlin type (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1169-1184 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A new triangular plate element is presented. This new element is based on independent interpolations for slopes, displacement and shear forces, and it is shown that it does not suffer from any defect common to other Mindlin plate elements. Several examples are presented to illustrate the behaviour of this new element.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260511
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  • 88
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    Digitale Medien
    Computer analysis of structures matrix structural analysis, structured programming, Siegfried M. Holzer, Elsevier, 1985, pp. 426. ISBN 0-444-00943-4 (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1235-1236 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260515
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  • 89
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    Formulation and solution of hierarchical finite element equations (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1213-1233 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper presents a general hierarchical formulation applicable to both elliptic and hyperbolic problems. Static and eigenvalue linear elastic problems as well as convection-diffusion problems are studied. The hierarchical formulation is well suited for adaptive procedures.For the convection-diffusion problem the hierarchical approximation is made in time only. Different hierarchical functions are proposed for different types of problems. Both weighted residual and least-squares formulations are applied. A combination of these two gives a penalty method with a constraint equation corresponding to the least-squares method. A whole class of time integration formulae is obtained. These are all suitable for adaptive procedures owing to the hierarchical approximation in the time domain. If a linear discontinuous hierarchical base function is used in the Galerkin weak formulation, the method so obtained corresponds to the discontinuous Galerkin method in time and is especially suited for convection dominated problems. The streamline-diffusion method is found to be the aforementioned penalty method.This paper also examines the sequence of nested equation systems that results from a hierarchical finite element formulation. Properties of these systems arising from static problems are investigated. The paper presents some new possibilities for iterative solution of hierarchic element equations, and different procedures are compared in a numerical example. Finally, a simple ID convection-diffusion problem clearly shows that the proposed hierarchical formulation in time gives a stable and accurate solution even for convection dominated flow.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260514
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  • 90
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    Digitale Medien
    Announcement (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1240-1240 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260518
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  • 91
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    Digitale Medien
    Masthead (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988) 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260601
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  • 92
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    Digitale Medien
    Exact numerical solutions for radiative heat transfer in cylindrical furnaces (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 1201-1212 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Exact expressions for the distributions of the components of radiative flux density and the radiative energy source term in terms of wall and medium temperature distributions have been formulated for an emitting absorbing medium of constant properties bounded by black walls of a cylindrical enclosure. The accuracy of numerical solutions has been tested on an idealized enclosure for which exact analytical solution of the expressions is possible and shown to have six-figure accuracy. The exact expressions have then been solved numerically for an enclosure problem based on data reported previously on a large scale experimental furnace. The principal feature of the data is highly non-uniform temperature distributions which are typical of the conditions encountered in industrial furnaces. These data have been chosen because of their practical importance and the non-availability of exact solutions for such data. The resulting exact solutions have been tabulated and are intended to serve in the future as standards for testing the accuracy of the approximate predictions produced using various three-dimensional flux models in cylindrical configurations.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260513
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  • 93
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    Digitale Medien
    Three-dimensional finite element analysis of open-die forging (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 67-85 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Three-dimensional finite element analysis is applied to operation sequences in open-die forging. Flat tools with rounded edges for open-die forging are geometrically modelled using Bézier curves. With this technique, the problems at the die-workpiece interface, such as the integration of frictional stress, node touching on dies and node separating from dies, can be handled effectively. It is shown that in solving general symmetric problems computation time can be saved by reducing variables and rearranging them in the stiffness matrix. One-bite operations and operation sequences for producing two-size bars and two-size pipes in several bites are investigated in regard to geometry, load, energy and deformation distribution.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250108
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  • 94
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    Digitale Medien
    On the development of a general purpose finite element program for analysis of forming processes (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 113-131 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250111
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  • 95
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    Digitale Medien
    On the use of the boundary element method for elastoplastic, large deformation problems (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 165-176 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The boundary element method is applied to large deformation problems typical in industrial forming problems. A form of Betti's theorem relevant to an updated Lagrangian type of solution procedure is established as the basis for the boundary element formulation. Equilibrium iterations are needed in each load step. All non-linear terms are moved to the right-hand side and the boundary element method can be used. Cross-anisotropy is assumed where Hill's yield criterion is adopted together with isotropic hardening. The investigation has shown that the boundary element method is applicable to this type of problem, giving good results within reasonable computer time.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250114
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  • 96
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    Digitale Medien
    Transient analysis of forging operations by the pseudo-concentration method (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 177-189 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The pseudo-concentration method is used to follow the flow of metal during the transient analysis of an axisymmetric forging problem. The technique requires a minimum of user interaction and appears to be ideal for computer aided design of dies. An analysis of an engine disc blocker die is presented and compared with experimental results. The same problem is analysed using a Newtonian fluid which is shown to give good qualitative results which would be acceptable in the initial stages of die design.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250115
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  • 97
    Digitale Medien
    Digitale Medien
    Plastic and viscoplastic flow of void-containing metals. Applications to axisymmetric sheet forming problems (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 227-251 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A formal analogy between the equations of pure plastic and viscoplastic flow theory for void-containing metals and those of standard non-linear elasticity is presented. The formulation is particularized for the analysis of axisymmetric sheet metal forming problems using simple two node linear finite elements. Details of the treatment of friction and strain hardening phenomena, time increment computation and elastic effects are also given. Examples of the effect of void porosity on the hemispherical stretching of a circular sheet are presented.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250118
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  • 98
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988) 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250201
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  • 99
    Digitale Medien
    Digitale Medien
    Computation of low-speed compressible flows with time-marching procedures (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 293-311 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The extension of time-marching procedures to low Mach number and low Reynolds number conditions is considered. It is shown that the disparate speeds of the acoustic and particle waves prevent convergence at high Reynolds numbers, while the requirement that both the Courant and the von Neumann numbers be of order one prevents convergence in very viscous flows. A perturbation expansion is used to introduce pseudo-acoustic waves that propagate at speeds similar to the particle speed at high Reynolds numbers and that allows both the inviscid and viscous time step parameters to be of order one at low Reynolds numbers. The resulting algorithm is shown to give convergence rates that are independent of either Mach number or Reynolds number over a range of five orders of magnitude in both parameters. Results are shown for strong heat addition in low-speed flow encompassing this broad range of variables.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620250203
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  • 100
    Digitale Medien
    Digitale Medien
    Optimization of actively controlled structures using goal programming techniques (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 26 (1988), S. 183-197 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The problem of design of actively controlled structures subject to restrictions on the damping parameters of the closed-loop system is formulated and solved as a multiobjective optimization problem. The purpose of control is to effectively suppress structural vibrations due to initial excitation. The cross-sectional areas of the members are treated as design variables. The structural weight and the controlled system energy are considered as objective functions for minimization. The goal programming approach is used for the solution of the multiobjective optimization problems. The procedure is illustrated through numerical simulations using two-bar and twelve-bar truss structures.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620260113
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