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  • Artikel: DFG Deutsche Nationallizenzen  (2.826)
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  • Artikel: DFG Deutsche Nationallizenzen  (2.826)
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  • 2005-2009
  • 1995-1999  (1.155)
  • 1990-1994  (1.671)
  • 1970-1974
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  • 101
    Digitale Medien
    Digitale Medien
    Intracerebral penetration of carteolol hydrochloride in rats (1997)
    Springer
    Psychopharmacology 131 (1997), S. 388-393 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Carteolol hydrochloride ; β-Blocker ; Penetrability ; Brain ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract To elucidate the penetrability of carteolol, a β-adrenoceptor antagonist (β-blocker) into the brain of rats, intracerebral and serum concentrations of the compound were determined in male rats receiving single or repetitive oral administration of carteolol hydrochloride at 30 mg/kg. The time-course of the intracerebral concentration of carteolol following single IV administration of the compound at 10 and 30 mg/kg was also studied in male rats. A high-performance liquid chromatography method was used to determine the intracerebral and serum concentrations. Following single oral dosing, the intracerebral concentration of carteolol reached a maximum of 0.074 μg/g at 2 h postdosing and declined with a half-life of 3.7 h, and the Cmax and AUC of carteolol in the brain were 12.5% and 19.8% of those in serum. The intracerebral and serum concentrations of carteolol were determined in male rats receiving repetitive oral dosing of the compound once daily for 7 days. The concentration of carteolol in the brain and serum at 1 h postdosing varied within a range of 0.059–0.091 μg/g and 0.321–0.443 μg/ml, respectively, throughout the dosing period, showing no changes in the penetrability of the compound into the brain due to repeated dosing. The concentration of carteolol in the brain and serum increased in a dose-dependent manner in rats receiving a single IV administration of the compound. The elimination half-life of carteolol in the serum and brain was 0.6–0.8 h and 1.3–1.7 h, respectively, in rats following single IV dosing of the compound. The half-life in the brain was about twice as long as that in the serum. The brain to serum concentration ratio was 0.306:0.499. From the above results, it was concluded that carteolol is distributed from the circulation to the brain with low penetrability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050307
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  • 102
    Digitale Medien
    Digitale Medien
    Effects of imipramine on raphe nuclei and prefrontal cortex extracellular serotonin levels in the rat (1997)
    Springer
    Psychopharmacology 134 (1997), S. 401-405 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Imipramine ; Serotonin ; Raphe nuclei ; Prefrontal cortex ; Microdialysis ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  The effect of acute administrations of three doses of imipramine (1, 5 and 10 mg/kg SC), a widely used tricyclic antidepressant, on extracellular levels of serotonin (5-HT) has been studied by intracerebral microdialysis in raphe nuclei and prefrontal cortex of conscious rats. Imipramine 1 mg/kg SC did not change extracellular 5-HT in either raphe nuclei and prefrontal cortex. However, with the dose of 5 mg/kg SC imipramine induced in raphe nuclei, a brief increase of extracellular 5-HT followed by a lowering (55–65% basal release) of the neurotransmitter. The same dose of imipramine decreased (60–70% of basal value) extracellular 5-HT in prefrontal cortex. Imipramine 10 mg/kg SC significantly increased 5-HT levels in both raphe nuclei (190 ± 20% above basal value) and prefrontal cortex (280 ± 15% above basal value). Pretreatment with (-)pindolol (5 mg/kg SC), a non-selective 5-HT1A subtype receptor antagonist, 30 min before imipramine 5 mg/kg, modified the effect of the antidepressant: an increase, instead of a decrease, on prefrontal cortex dialysate 5-HT was observed. (-)Pindolol (10 mg/kg SC) increased extracellular 5-HT in both raphe nuclei (155 ± 20% above basal value) and prefrontal cortex (160 ± 8% above basal value). These data show that acute administration of imipramine modifies extracellular 5-HT at the level of the raphe nuclei and prefrontal cortex. 5-HT1A autoreceptors in the raphe nuclei, which this study suggests to be tonically active, may be stimulated after systemic administration of high doses of imipramine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050477
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  • 103
    Digitale Medien
    Digitale Medien
    Changes in baroreceptor vagal reflex performance in the developing rat (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 438-444 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Key words Baroreceptor reflex ; Nucleus tractus solitarii ; Neonatal ; Maturation ; Cardiac vagal tone ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Ontogenesis of both vagal control of heart rate and the baroreceptor vagal reflex were evaluated in rats at postnatal ages (P) of 5/6, 10, 15, 20, 25 and 〉42 days anaesthetised with urethane (1.5 g/kg). Between P5/6 and P25 heart rate rose from 372 ± 12 to 448 ± 20 beats per minute and mean arterial pressure increased from 33.9 ± 3.1 to 74.59 ± 3.25 mm Hg (mean ± SEM, n = 7 and 11 respectively). Cardiac vagal tone was absent at P10 but significant at P20 (P 〈 0.05) as revealed with atropine (0.5–1 mg/kg i.v.). Baroreceptor cardiac reflex sensitivity, tested with phenylephrine (10–50 μg/kg i.v.), was attenuated significantly in P10–20 rats compared with P5/6, P25 and mature animals. In P14–17 rats stimulation of neurones in either the solitary tract or ambiguual nuclei, by microinjection of L-glutamate (100–200 pmol), evoked an atropine-sensitive bradycardia indicating a functional integrity of central and peripheral efferent pathways mediating the baroreceptor reflex. Thus, the baroreceptor vagal reflex is functional in P5/6 rats but becomes attenuated between P10–P20, which is coincident with the maturational rise in arterial pressure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004240050418
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  • 104
    Digitale Medien
    Digitale Medien
    Absence of evidence for a powerful tonic baroreflex-mediated inhibition on catechol activity in the rat rostral ventrolateral medulla: in vivo voltammetric evidence during sino-aortic deafferentation (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 599-608 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Key words Baroreceptor reflex ; Rostral ventrolateral medulla ; C1 cell group ; In vivo voltammetry ; Sino-aortic deafferentation ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  To test in a catechol-specific and dynamic manner for the existence of a powerful long-lasting inhibition arising from barosensitive afferents that depresses the activity of adrenergic neurons in the rostral ventrolateral medulla (RVLM), in vivo voltammetry was used before and after acute sino-aortic deafferentation. Rats were anaesthetized with pentobarbital or halothane and ventilated with a mixture of air and oxygen. Snares were inserted around the vagus, the glossopharyngeal and the superior laryngeal nerves. After placing the animal prone in the stereotaxic frame and stabilization at a high mean arterial pressure (MAP ≈ 120 mmHg), the snares were rapidly closed to produce complete barodeafferentation, assessed by loss of heart rate responses and changes in renal nerve sympathetic activity in response to vasoactive agents. Recording of a catechol signal was maintained in the RVLM during deafferentation. Under pentobarbital-induced anaesthesia (n = 5), deafferentation did not lead to a significant change in the catechol signal within the deafferented group. Under halothane-induced anaesthesia and phenylephrine-induced high baseline pressure (n = 5), no changes in the catechol signal were observed upon deafferentation (not significant vs sham animals: n = 5). This failure to demonstrate a major increase in catechol activity upon deafferentation does not fit with the hypothesis that a powerful tonic baroreflex-mediated inhibition depresses the activity of adrenergic RVLM barosensitive bulbospinal neurons, even when the baseline MAP is high. Rather, these data are compatible with weak or no inhibition of catechol activity by the baroreceptors and a nonessential role of adrenergic neurons within the baroreceptor reflex arc itself: the adrenergic neurons may not be in series within this arc but in parallel with the arc. This interpretation is in keeping with newer schemas of autonomic core circuitry that are devoid of adrenergic neurons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004240050442
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  • 105
    Digitale Medien
    Digitale Medien
    A single administration of d-amphetamine prior to stimulus pre-exposure and conditioning attenuates latent inhibition (1997)
    Springer
    Psychopharmacology 130 (1997), S. 79-84 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Latent inhibition ; Conditioned emotional response ; Amphetamine ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of a single administration of d-amphetamine (0.32 mg/kg, SC) upon latent inhibition (LI) in a one-session pre-exposure and conditioning procedure was investigated in rats in a conditioned emotional response paradigm. It was found that amphetamine attenuated LI. The effects could not be attributed to differences in unconditioned suppression nor to differences in response rates between the experimental groups. These results support the observations of Dunn and suggest that the disruption of LI may not depend upon a complex interaction between changes in neuronal processes consequent upon repetitive amphetamine administration and the schedule with which the drug is administered during the experimental procedure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050213
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  • 106
    Digitale Medien
    Digitale Medien
    Additive deficits in the choice accuracy of rats in the delayed non-matching to position task after cholinolytics and serotonergic lesions are non-mnemonic in nature (1997)
    Springer
    Psychopharmacology 130 (1997), S. 303-312 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Working memory ; Motor activity ; Serotonergic ; Muscarinic ; Nicotinic ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The role of serotonin (5-HT) and its interaction with the muscarinic or nicotinic receptor-mediated mechanisms in the modulation of working memory and motor activity was investigated by assessing the effects of 5-HT lesion and cholinergic receptor blockade on the performance of rats in a working memory (delayed non-matching to position, DNMTP) task. A global serotonergic lesion was induced by the intracerebroventricular adminstration of 5,7-dihydroxytryptamine (5,7-DHT). Post-mortem neurochemical analysis revealed that serotonin and 5-hydroxyindoleacetic acid (5-HIAA) levels were reduced in frontal and parieto-occipital cortices and in hippocampi of 5,7-DHT lesioned rats. 5-HIAA levels were also reduced in striatum. 5,7-DHT lesion slightly impaired choice accuracy of rats in the DNMTP task and also transiently reduced motor activity in rats. Even the lower dose of scopolamine (0.075 mg/kg), a muscarinic receptor antagonist, impaired the choice accuracy already at the shortest delay (i.e. not indicative of a working memory impairment per se), and caused a marked disruption of motor activity (lengthened response latencies, increased probability of omissions and decreased trials completed). Furthermore, the quaternary analogue, N-methylscopolamine (0.150 mg/kg), affected the motor activity of rats to the same extent as scopolamine. Mecamylamine (1.0; 3.0 mg/kg) also interfered with motor activity and it slightly decreased the choice accuracy, which was not dependent on the delay. Although mecamylamine disrupted the performance of rats in the DNMTP task, the disruption was not as severe as that seen with scopolamine. Moreover, both scopolamine and mecamylamine augmented the slight impairment on the choice accuracy of 5,7-DHT lesioned rats, but this was non-mnemonic in character. We conclude that there is no evidence for any major interaction between the serotonergic system and muscarinic or nicotinic cholinergic mechanisms in working memory per se, but muscarinic and nicotinic receptor antagonists may act additively with the 5,7-DHT lesion to disrupt the choice accuracy of rats.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050244
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  • 107
    Digitale Medien
    Digitale Medien
    (−)Alprenolol potentiates the disrupting effects of dizocilpine on sensorimotor function in the rat (1997)
    Springer
    Psychopharmacology 132 (1997), S. 281-288 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Acoustic startle response ; Prepulse inhibition ; Schizophrenia ; Dopamine ; Serotonin ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The β-adrenoceptor antagonist as well as serotonin 5-HT1 receptor antagonist, (−)alprenolol, was found to potentiate the disrupting effect of the non-competitive NMDA receptor antagonist, dizocilpine, on prepulse inhibition (PPI) of the acoustic startle response (ASR) in the rat. The facilitating effect of dizocilpine on ASR amplitude was also potentiated by (−)alprenolol. (−)Alprenolol by itself did not affect either of these measures. These effects did not seem to be related to the unselective β-adrenoceptor antagonist property of (−)alprenolol, since combined pretreatment with the β1- and β2-adrenoceptor antagonists, metoprolol and ICI 118551, did not alter the effects of dizocilpine on startle behaviour. However, a serotonergic influence was suggested by the fact that a facilitating effect of dizocilpine on ASR amplitude was also obtained by pretreatment with the 5-HT precursor, L-5-HTP, in benserazide-pretreated rats. Furthermore, pretreatment with the 5-HT2 selective receptor antagonist, MDL 100907, significantly reduced the (−)alprenolol-induced potentiation of the effects of dizocilpine on startle behaviour, while the 5-HT3 selective receptor antagonist, ondansetron, failed to do that. Finally, the (−)alprenolol-induced potentiation of the effects of dizocilpine was significantly reduced by pretreatment with the atypical antipsychotic, clozapine, and by the potential antipsychotic and selective dopamine D2 receptor antagonist, raclopride. This study suggests that altered 5-HT activity may influence the effects of psychotomimetic drugs such as dizocilpine on sensorimotor function, and this observation may have implications for the pharmacological treatment of schizophrenia in humans.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050346
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  • 108
    Digitale Medien
    Digitale Medien
    Neonatal lesions of the rat ventral hippocampus result in hyperlocomotion and deficits in social behaviour in adulthood (1997)
    Springer
    Psychopharmacology 132 (1997), S. 303-310 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Hyperactivity ; Hippocampus ; Neonate ; Negative symptoms ; Positive symptoms ; Rat ; Schizophrenia ; Social behaviour
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The neonatal ibotenic acid lesion of the ventral hippocampus in the rat is an animal model of several aspects of schizophrenia. This lesion produces a number of behavioural abnormalities, such as hyperlocomotion and deficits in prepulse inhibition of startle, that present themselves relatively late in development, i.e. after puberty. Some of these abnormalities, which are thought to model the positive symptoms of schizophrenia, can be normalized by chronic treatment with neuroleptics. In the present study, we examined the effects of the neonatal hippocampal lesion on social behaviour. Social withdrawal and isolation are key components of the negative symptoms of schizophrenia that have not been previously addressed in this model. Rats were lesioned on postnatal day 7 (PD7) and tested for social interaction on PD35 and PD65. They were then treated with clozapine (1.9 and 7.4 μmol/kg or 0.63 and 2.5 mg/kg) for 21 days and retested. The results show that although, as previously reported, spontaneous hyperlocomotion emerged in the lesioned rats only after puberty (PD65), social interaction deficits and behaviors that may reflect anxiety were present at both PD35 and PD65. Clozapine normalized locomotion, but did not ameliorate putative anxiety or social interaction deficits in the neonatally lesioned rats. Our results indicate that the neonatal hippocampal lesion in the rat models some aspects of both positive and negative symptoms of schizophrenia. The effects of clozapine appear inconsistent with its putative benefit for negative symptoms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050349
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  • 109
    Digitale Medien
    Digitale Medien
    Effects of the AMPA receptor antagonist NBQX on the development and expression of behavioral sensitization to cocaine and amphetamine (1997)
    Springer
    Psychopharmacology 134 (1997), S. 266-276 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words AMPA ; NBQX ; Behavioral sensitization ; Cocaine ; Amphetamine ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  We examined the effect of 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX), an antagonist of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) subtype of glutamate receptor, on the development and expression of behavioral sensitization to amphetamine and cocaine in rats. A single injection of NBQX (12.5 mg/kg) administered 30 min prior to cocaine during the induction phase (days 1–5) prevented the development of cocaine sensitization, assessed by responsiveness to cocaine challenge on day 8. This NBQX regimen did not affect development of amphetamine sensitization. Two pretreatment injections of NBQX, one 20 min before and one 70 min after amphetamine on each day of the induction phase (days 1–6), did not affect sensitization of stereotypy but prevented sensitization of post-stereotypy ambulatory hyperactivity (both assessed by responsiveness to amphetamine challenge on day 8). The effect of NBQX on ambulatory sensitization was dose-dependent (attenuation with 12.5 mg/kg, complete prevention with 25 mg/kg). In contrast to its effects on development, NBQX (25 mg/kg) did not prevent expression of sensitization to cocaine or amphetamine. NBQX itself exerted no significant effects on locomotor activity in either drug-naive rats or rats that had received either NBQX or amphetamine repeatedly. These findings support a requirement for AMPA receptor stimulation in the development of locomotor sensitization to cocaine and amphetamine, but suggest a different mechanism for sensitization of amphetamine stereotypy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050449
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  • 110
    Digitale Medien
    Digitale Medien
    Gamma-vinyl GABA attenuates cocaine-induced lowering of brain stimulation reward thresholds (1997)
    Springer
    Psychopharmacology 133 (1997), S. 383-388 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Intracranial self stimulation (ICSS) ; Dopamine ; Rat ; GABA transaminase inhibitor ; Vigabatrin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Gamma-vinyl GABA (GVG, also referred to as vigabatrin), an irreversible inhibitor of GABA transaminase (GABA-T), raises levels of GABA in nerve terminals, inhibits striatal dopamine release, and attenuates cocaine-induced increases in extracellular dopamine in the striatum and nucleus accumbens. In order to determine the action of GVG on dopamine-mediated reward, we examined its effects on the threshold for rewarding brain stimulation in male F-344 rats. GVG dose-dependently raised brain stimulation reward (BSR) thresholds at doses of 200, 300, and 400 mg/kg without significant effects on motor performance as measured by response latencies. In order to determine if GVG had similar modulatory effects on cocaine-induced lowering of BSR thresholds, the effective doses of GVG were co-administered with 2.5 and 5.0 mg/kg cocaine, doses that significantly lower BSR thresholds. The 400 mg/kg dose of GVG significantly blocked the lowering of thresholds seen at each dose of cocaine. Cocaine in combination with 200 or 300 mg/kg GVG, doses of GVG that significantly raise BSR thresholds, resulted in thresholds not significantly different from those obtained with cocaine alone. These data demonstrate that, at the doses tested, GVG is more effective at modulating basal reward thresholds than at modulating thresholds lowered by cocaine, implying that as dopaminergic activity increases, GABAergic activity must also increase in order to exert its inhibitory influence on dopaminergic activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050418
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  • 111
    Digitale Medien
    Digitale Medien
    Behavioral sensitization and extracellular dopamine responses to amphetamine after various treatments (1997)
    Springer
    Psychopharmacology 134 (1997), S. 221-229 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Behavioral sensitization ; Dopamine ; Amphetamine ; Rat ; Microdialysis ; Caudate putamen ; Nucleus accumbens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The repeated administration of amphetamine (AMPH) results in a pattern of behavioral changes which includes an augmentation of some behaviors, generally referred to as behavioral sensitization. Some investigators have suggested that an increased dopamine (DA) response to AMPH challenge may underlie behavioral sensitization, while others have reported behavioral sensitization in the absence of an enhanced DA response. Because temporal and dosage parameters of the AMPH pretreatment regimen have been suggested to play a role in the appearance of an enhanced DA response, we utilized a variety of AMPH pretreatment regimens to assess the relationship between pretreatment dose of AMPH, duration of withdrawal and the DA response in caudate-putamen and nucleus accumbens to a subsequent AMPH challenge. Under our experimental conditions, behavioral sensitization was observed after each of these treatments in the absence of an enhanced DA response in either brain region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050445
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  • 112
    Digitale Medien
    Digitale Medien
    Validity, reliability and utility of the chronic mild stress model of depression: a 10-year review and evaluation (1997)
    Springer
    Psychopharmacology 134 (1997), S. 319-329 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Animal model of depression Chronic mild stress ; Predictive validity ; Face validity Construct validity ; Reliability ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This paper evaluates the validity, reliability and utility of the chronic mild stress (CMS) model of depression. In the CMS model, rats or mice are exposed sequentially, over a period of weeks, to a variety of mild stressors, and the measure most commonly used to track the effects is a decrease in consumption of a palatable sweet solution. The model has good predictive validity (behavioural changes are reversed by chronic treatment with a wide variety of antidepressants), face validity (almost all demonstrable symptoms of depression have been demonstrated), and construct validity (CMS causes a generalized decrease in responsiveness to rewards, comparable to anhedonia, the core symptom of the melancholic subtype of major depressive disorder). Overall, the CMS procedure appears to be at least as valid as any other animal model of depression. The procedure does, however, have two major drawbacks. One is the practical difficulty of carrying out CMS experiments, which are labour intensive, demanding of space, and of long duration. The other is that, while the procedure operates reliably in many laboratories, it can be difficult to establish, for reasons which remain unclear. However, once established, the CMS model can be used to study problems that are extremely difficult to address by other means.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050456
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  • 113
    Digitale Medien
    Digitale Medien
    A rat model of monitoring liver allograft rejection (1997)
    Springer
    Transplant international 10 (1997), S. 103-108 
    Details
    ISSN: 1432-2277
    Schlagwort(e): Key words Liver transplantation ; rat model ; Rat ; liver transplantation ; fine needle aspiration ; Fine needle aspiration ; liver ; rat ; Rejection ; liver ; rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Rat models are often used to study liver allograft rejection. We have established a model for rat liver allograft rejection, monitored by fine needle aspiration biopsy (FNAB), in the strain combination PVG-to-BN with a mean survival time of 37 ± 20 days. In this model, we observed acute rejection with an intense peak of lymphoid blasts and lymphocyte-dominated inflammation in the FNAB [9.1 ± 3.0 corrected increment units (CIU)], and an eventual increase in macrophages (up to 4.2 ± 4.4 CIU), together with fibrosis and parenchymal necrosis in the graft. Markers of immune activation, such as an increase in IL-2-receptor (from 1 % ± 2 % to 21 % ± 13 %) and class II (from 20 % ± 9 % to 43 % ± 13 %) expressing lymphoid cells and induction of ICAM-1 in the graft, were consistent with the overall cellular response. The FNAB correlated well with parallel graft histology. In this rat model, the atraumatic monitoring makes a close follow-up possible without having to sacrifice the experimental animals. This saves work, animals, and costs in the study of liver rejection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001470050020
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  • 114
    Digitale Medien
    Digitale Medien
    The characterization of reconstituted passenger leukocytes on the induction of tolerance in rat liver transplantation (1997)
    Springer
    Transplant international 10 (1997), S. 350-356 
    Details
    ISSN: 1432-2277
    Schlagwort(e): Key words Liver transplantation ; passenger leukocytes ; rat ; Passenger leukocytes ; liver transplantation ; rat ; Rat ; liver transplantation ; passenger leukocytes ; Tolerance ; liver transplantation ; rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The tolerance induced by orthotopic liver transplantation [DA (RT1a) rats to PVG (RT1c) rats] can be prevented by total body irradiation of the donor rat. Reconstitution of the irradiated donor with DA splenic leukocytes reintroduces this tolerance. To investigate the major histocompatibility complex (MHC) specificity of passenger leukocytes, irradiated DA donors were reconstituted by third-party BN (RT1n) splenic leukocytes. The reconstitution with BN splenocytes re-established DA-specific tolerance in PVG recipients, as confirmed by subsequent DA cardiac allografting, while BN hearts were rejected with second-set tempo. To determine which cell components play an important role in re-establishing liver graft tolerance, DA splenic leukocytes were further purified into three types: T, B, and adherent cells. Only “T-cell-enriched” preparations restored liver graft tolerance in three out of five PVG recipients. These results suggest that passenger leukocytes of differing MHC types can help to induce liver-specific tolerance and that T cells in the liver graft may be essential to regulate tolerance induction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001470050069
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  • 115
    Digitale Medien
    Digitale Medien
    Integrated intestinal capacity and nutritional status following small bowel transplantation (1997)
    Springer
    Transplant international 10 (1997), S. 386-391 
    Details
    ISSN: 1432-2277
    Schlagwort(e): Key words Intestinal transplantation ; function ; rat ; Small bowel function ; intestinal transplantation ; rat ; Rat ; small bowel function ; intestinal transplantation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Successful small bowel transplantation requires normal functional capacity of the graft and unaltered metabolism of the host. Weight gain and wet weight of muscle groups and intra-abdominal fat pads were compared between transplanted, sham-operated, short bowel-operated, and normal rats that were fed either standard chow or fat-enriched (15 %) pellets. Weight gain and wet weight of muscle groups and fat pads for the control, transplanted, and sham-operated rats were identical, while short bowel animals showed reduced weight. Transplanted rats receiving fat-enriched food had lower wet weight of fat pads than control animals on the high-fat diet. We conclude that small bowel transplantation makes it possible to overcome the intestinal failure associated with short bowel syndrome, leading to overall normal weight gain and development of the recipient. However, altered fat metabolism, reflected in changed body composition, was observed in transplanted animals on the high-fat diet.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001470050075
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  • 116
    Digitale Medien
    Digitale Medien
    Prevention of graft rejection and graft-versus-host reaction by a novel immunosuppressant, FTY 720, in rat small bowel transplantation (1997)
    Springer
    Transplant international 10 (1997), S. 343-349 
    Details
    ISSN: 1432-2277
    Schlagwort(e): Key words Immunosuppression ; FTY 720 ; rat ; small bowel transplantation ; FTY 720 ; immunosuppression ; rat ; small bowel transplantation ; Rat ; small bowel transplantation ; FTY 720 ; Small bowel transplantation ; rat ; FTY 720
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In the present study, we examined the immunosuppressive effect of a new drug, FTY 720, on small bowel transplantation (SBT) in rats. Grafts from (LEW × BN) F 1-to-LEW rats treated with FTY 720 at 0.5 mg/kg from day 0 to 14 post-SBT survived significantly longer than untreated grafts. In addition, the administration of FTY 720 combined with cyclosporin (CyA; 5 mg/kg per day) had a synergistic effect on allograft survival. The graft-versus-host reaction (GVHR) that occurred in the LEW-to-F 1 rats was markedly reduced after the administration of FTY 720. FTY 720 combined with a low dose of CyA completely abrogated GVHR without any adverse reaction. FTY 720 treatment resulted in a significant decrease in the number of lymphocytes in the peripheral blood and the spleen, but the number of peripheral neutrophils was unchanged. Thus, FTY 720 would appear to be an ideal drug to combine with CyA in order to control the immune reaction after SBT.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001470050068
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  • 117
    Digitale Medien
    Digitale Medien
    Oxytocin innervation of spinal preganglionic neurons projecting to the superior cervical ganglion in the rat (1997)
    Springer
    Cell & tissue research 287 (1997), S. 481-486 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Oxytocin ; Immunocytochemistry ; Paraventricular nucleus ; Superior cervical ganglion ; Spinal cord ; Sympathetic nervous system ; Retrograde tracing ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The paraventricular nucleus of the hypothalamus is a major integrative nucleus for relaying information from the suprachiasmatic nucleus to the autonomic system. The precise pathway by which this information can influence autonomic functions, such as melatonin synthesis in the pineal gland, is not clear. In the present study, we used a retrograde tracer injected in the superior cervical ganglion to identify spinal preganglionic neurons. One of the main neurotransmitters present in descending projections of the paraventricular nucleus of the hypothalamus, oxytocin, was detected with immunocytochemistry to visualise possible contacts with the neurons located in the intermediolateral column of the spinal cord and projecting to the superior cervical ganglion. Although many appositions could be seen at the light-microscopic level, this abundance could not be confirmed at the electron-microscopic level. The implications of these observations for the overall timing message received by the spinal preganglionic neurons are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050772
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  • 118
    Digitale Medien
    Digitale Medien
    HSP72 induction of systemic organs of rats after severe burn injury (1997)
    Springer
    European journal of plastic surgery 20 (1997), S. 136-140 
    Details
    ISSN: 1435-0130
    Schlagwort(e): Burn injury ; Stress protein ; HSP72 ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In order to understand the stress response of systemic organs to severe burn injury, the induction of 72-kD heat shock protein (HSP72) in various organs (brain, hypophysis, lung, heart, liver, pancreas, spleen, kidney, adrenal gland, and skeletal muscle) was investigated in rats with severe burns. A full-thickness burn was induced on the rats' skin by immersing the rats in hot water (90° C) for 3 s. At 0, 24, and 48 h after the burn injury, the HSP72 expression of various organs was examined using the Western blot analysis. At 24 h after the burn injury, the level of HSP72 had increased in the hypophysis, lung, heart, and kidney. In all organs examined, the expression of HSP72 had increased at 48 h after the burn injury. The level of HSP72 was highest in the hypophysis (3.3-fold compared to the control), and lowest in the brain and adrenal gland (1.7-fold of the control) at 48 h after the burn injury. These results confirm that severe burn injury causes a stress response in systemic organs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01002047
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  • 119
    Digitale Medien
    Digitale Medien
    Specific [3H] Glutamate Binding in the Cerebral Cortex and Hippocampus of Rats During Development: Effect of Homocysteine-Induced Seizures (1997)
    Springer
    Neurochemical research 22 (1997), S. 637-646 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Rat ; early development ; cerebral cortex ; hippocampus ; homocysteine seizures ; glutamate binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Specific [3H]glutamate binding to synaptic membranes from the cerebral cortex and hippocampus of 7-, 12- and 18-day-old rats was examined, both in control animals and during seizures induced by homocysteine. In the cerebral cortex a transient peak of glutamate binding was observed in 7-day-old group, whereas in the hippocampus it occurred in 12-day-old animals. Total specific [3H]glutamate binding was not influenced by preceding seizure activity in either of the age groups and both the studied regions. NMDA- and QA-sensitive glutamate bindings represent the highest portion of the total binding. Moreover, NMDA-sensitive binding in the cerebral cortex of 7-day-old rats is significantly higher as compared to the two more mature groups. The proportion of individual receptor subtypes on total binding in each age group was not influenced by preceding seizure activity. However, NMDA-sensitive binding in the hippocampus of 12-day-old rats, sacrificed during homocysteine-induced seizures, was significantly increased as compared to corresponding controls. In contrast to the effect of NMDA, AMPA, kainate and quisqualate which displaced to a different extent [3H]glutamate binding, homocysteine had no effect when added to membrane preparations. Similarly, [3H]CPP and [3H]AMPA bindings were not affected in the presence of homocysteine. It thus seems unlikely that homocysteine is an effective agonist for conventional ionotropic glutamate receptors. Its potential activity at some of the modulatory sites at the NMDA receptor channel complex or at metabotropic receptors has to be clarified in further experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022434406400
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  • 120
    Digitale Medien
    Digitale Medien
    Verhalten postoperativer Adhäsionen nach intraperitonealer Applikation von Fibrinolytika in einem Rattenmodell (1997)
    Springer
    Langenbeck's archives of surgery 382 (1997), S. 33-36 
    Details
    ISSN: 1435-2451
    Schlagwort(e): Key words Fibrin ; Fibrinolysis ; Peritoneum ; Adhesions ; Rat ; Schlüsselwörter Fibrin ; Fibrinolyse ; Peritoneum ; Adhäsionen ; Ratte
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In einem Rattenmodell wurde die Beeinflussung der Adhäsionsentstehung nach Laparotomien durch intraperitoneale Applikation verschiedener Fibrinolytika untersucht. Streptokinase und TPA verminderten die sero-serosale Haftung signifikant, nicht aber Urokinase. Die intravasale Gerinnung blieb unbeeinflußt.
    Notizen: Abstract In a rat model, the effect of the intraperitoneal application of fibrinolytic agents on the development of adhesions was examined. Streptokinase and TPA reduced sero-serosal adhesions significantly, whereas urokinase did not reduce them. Intravascural coagulation was not affected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00008008
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  • 121
    Digitale Medien
    Digitale Medien
    Rate-dependent prolongation of action potential duration in isolated rat ventricular myocytes (1997)
    Springer
    Basic research in cardiology 92 (1997), S. 123-128 
    Details
    ISSN: 1435-1803
    Schlagwort(e): Rat ; ventricular myocyte ; action potential duration ; transient outward current ; 4-aminopyridine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Rate-dependent alterations of action potential duration (APD) in rat ventricular myocytes were investigated. Action potentials of the isolated myocytes were recorded with patch electrodes containing EGTA (11 mM), and showed a marked rate-dependent prolongation in the APD (0.2–5 Hz). This prolongation was significantly inhibited in the presence of 4-aminopyridine (4-AP), a blocker of the transient outward K+ current (Ito). Thus, the rate-dependent decrease in Ito may underlie the change in APD. In contrast, the action potentials recorded from rat ventricular papillary muscles with conventional microelectrodes did not show rate-dependent alterations in the APD, i.e., the APD remained practically unaltered at the frequency range of 0.2–5 Hz. These results suggest that the rate-dependent prolongation of APD (due to rate-dependent blockade of Ito) becomes evident when the intracellular Ca2+ was chelated by the internal application of EGTA via patch pipette. We speculate that the rate-dependent prolongation of APD (via decreases in Ito) is masked in the ventricular papillary muscles, probably due to rate-dependent decreases in the inward current (e.g., electrogenic Na+−Ca2+ exchange current) that is regulated by the intracellular calcium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00788629
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  • 122
    Digitale Medien
    Digitale Medien
    Ca transport during contraction and relaxation in mammalian ventricular muscle (1997)
    Springer
    Basic research in cardiology 92 (1997), S. 1-10 
    Details
    ISSN: 1435-1803
    Schlagwort(e): Rat ; rabbit ; ferret ; shortening ; fluorescence ; cardiac myocyte ; sarcoplasmic reticulum ; cardiac hypertrophy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract During relaxation of cardiac muscle four Ca transport systems can compete to remove Ca from the myoplasm. These are 1) the SR Ca-ATPase, 2) the sarcolemmal Na/Ca exchange, 3) the sarcolemmal Ca-ATPase, and 4) the mitochondrial Ca uniporter. Isolated ventricular myocytes loaded with the intracellular fluorescent Ca indicator indo-1 were used to study [Ca]i decline during relaxation. By selective inhibition of the various Ca transporters above the dynamic interaction of these systems during relaxation was evaluated. Quantitatively the SR Ca-ATPase and Na/Ca exchange are clearly the most important (accounting for 〉95% of Ca removal). However, the balance of Ca fluxes between these systems vary in a species dependent manner. For example, the SR is much more strongly dominant in rat ventricular myocytes, where ∼92% of Ca removal is via SR Ca-ATPase and only 7% via Na/Ca exchange during a twitch. In other species (rabbit, ferret, cat, and guinea-pig) the balance is more in the range of 70–75% SR Ca-ATPase and 25–30% Na/Ca exchange. Ferret ventricular myocytes also exhibit a unusually strong sarcolemmal Ca-ATPase. During the normal steady state cardiac contraction-relaxation cycle the same amount of Ca must leave the cell as enters over a cardiac cycle. This implies that 25–30% of the Ca required to activate contraction must enter the cell at each cardiac cycle. Experiments using voltage clamp to measure both Ca current and Na/Ca exchange current demonstrate that this amount of Ca may be supplied by the L-type Ca current. The ability of the SR Ca-ATPase to reduce [Ca]i may also be modified both acutely (e.g. by catecholamines) as well as chronically (e.g. during cardiac hypertrophy and heart failure). Using tissue cultured neonatal rat ventricular myocytes, we studied the effect of chronic arrest or stimulation with phorbol esters (to stimulate protein kinase C). Verapamil-induced arrest increased the SR Ca-ATPase at the level of mRNA, protein expression and functional ability to lower [Ca]i in intact cells. Conversely, stimulation or protein kinase C reduced SR Ca-ATPase at all three of these levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00794062
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  • 123
    Digitale Medien
    Digitale Medien
    An animal model for external otitis (1997)
    Springer
    European archives of oto-rhino-laryngology and head & neck 254 (1997), S. 115-119 
    Details
    ISSN: 1434-4726
    Schlagwort(e): External auditory canal ; External otitis ; Pathogenesis ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract External otitis was produced in 12 Sprague-Dawley rats by mechanical stimulation through a plastic micropipette inserted into the right external auditory canal (EAC). The EAC was later evaluated regarding the color of the skin, swelling and the presence of fluid. Within 1 day all rats developed an external otitis that was characterized by a red, swollen ear canal containing an opalescent fluid. The tympanic membrane and middle ear cavity appeared to be normal. No healed EACs were seen within the initial 10 days of follow-up and 4 of 6 rats still exhibited external otitis at day 21. Light microscopy of biopsy specimens revealed pronounced edema of the dermis of the ear canal. Mast cells were more numerous in the early phase of the otitis present, although very few inflammatory cells were found in tissues despite the marked inflammatory reaction produced. Findings show that this animal model for external otitis can be used to investigate pathogenesis as well as to test various treatment strategies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02471273
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  • 124
    Digitale Medien
    Digitale Medien
    Dose-dependent protective effect of BPC 157 on capsaicin-induced rhinitis in rats (1997)
    Springer
    European archives of oto-rhino-laryngology and head & neck 254 (1997), S. S9 
    Details
    ISSN: 1434-4726
    Schlagwort(e): Capsaicin ; Rhinitis ; BPC 157 ; Mastocytes ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Protection of BPC 157 on capsaicin-induced rhinitis was studied in Wistar rats for its effect on mastocyte infiltration, degranulation and inflammatory cell infiltration. Animals were pretreated with 10 μg/kg, 10 ng/kg or 2 ml saline i.p. and capsaicin (0.05 ml/nostril of 1750 nmol/l sol.) was applied intranasally. They were then euthanized at 1, 3 and 12 h after capsaicin provocation. Nasal mucosa was analyzed and scored for mastocyte infiltration, degranulation and inflammatory cell infiltration. BPC 157 pretreatment significantly prevented mastocyte infiltration at 1 h. Polymorphonuclear leukocyte infiltration was significantly reduced in rats pretreated with 10 μg/kg BPC 157. A dose-dependent effect of BPC 157 pretreatment was demonstrated only for polymorphonuclear leukocyte infiltration at 12 h.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02439711
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  • 125
    Digitale Medien
    Digitale Medien
    Inhibition of the development of myringosclerosis by local administration of fenspiride, an anti-inflammatory drug (1997)
    Springer
    European archives of oto-rhino-laryngology and head & neck 254 (1997), S. 425-429 
    Details
    ISSN: 1434-4726
    Schlagwort(e): Tympanic membrane ; Myringotomy ; Myringosclerosis ; Fenspiride ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Earlier studies have revealed a relationship between the development of myringosclerosis and oxygen-derived free radicals. The latter can be blocked by the anti-inflammatory drug fenspiride. The present study was undertaken to test the ability of fenspiride to prevent myringosclerosis from developing during healing of the tympanic membrane. Myringotomized rats were treated with either topical applications or intraperitoneal injections of fenspiride for 12 days, after which the tympanic membranes were examined by otomicroscopy and studied histologically by light microscopy. Topically applied fenspiride was found to inhibit the development of sclerotic lesions, whereas intraperitoneal injections were ineffective.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02439973
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  • 126
    Digitale Medien
    Digitale Medien
    Effect of focal cerebral ischemia on nitric oxide synthase expression in rats (1997)
    Springer
    Medical molecular morphology 30 (1997), S. 55-62 
    Details
    ISSN: 1860-1499
    Schlagwort(e): Nitric oxide ; Nitric oxide synthase ; Immunohistochemistry ; Rat ; Cerebral ischemia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Time- and cell-type-dependent immunohistochemical activity of nitric oxide synthase (NOS) was investigated in rat cerebral cortex following focal ischemia and the local concentration of nitric oxide (NO) was measured. NO concentration increased 2 min after the ischemia. Brain NOS-immunoreactive neurons increased in number 5 min after the ischemia. Endothelial cell NOS immunoreactivity was first detected in vascular endothelial cells and astrocytes 5 min after the ischemia, and it increased again during 60 min to 4 days after the ischemia in reactive astrocytes. Inducible NOS immunoreactivity was detected in astrocytes, vascular endothelium, and microglia/macrophages at the periphery of the ischemic core during 2–4 days after the ischemia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01545082
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  • 127
    Digitale Medien
    Digitale Medien
    Ultrastructural localization of calcium in rat retina with oxalate pyroantimonate and energy-dispersive X-ray detector (1997)
    Springer
    Medical molecular morphology 30 (1997), S. 76-80 
    Details
    ISSN: 1860-1499
    Schlagwort(e): Ultrastructure ; Retina ; Rat ; Oxalate ; Potassium pyroantimonate ; X-ray analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Intracellular calcium plays an important role in the intracellular signal transduction as one of the second messengers. In this study, we examined the ultrastructural distribution of calcium in rat retina, using the oxalate pyroantimonate technique and X-ray microanalysis. Large amounts of precipitates were observed inside the disc of outer segments of photoreceptor cells (OS) and the synaptic vesicles of the inner (IPL) and outer plexiform layer (OPL). Precipitates also were observed in the ribosome-rich regions in the cytoplasm and the euchromatinic part in the cell nuclei of the ganglion, amacrine, and bipolar and horizontal cells. However, few precipitates were found in the inner segment of the photoreceptor cells and the retinal pigment epithelium (RPE). X-ray microanalysis with an energydispersive X-ray detector revealed that these precipitates had a peak of antimony and calcium. Therefore, it was suggested that these precipitates were Ca[Sb(OH)6]2, the reaction products of the oxalate-pyroantimonate technique. Our findings showed that calcium precipitates are abundant in retinal regions that are related to visual transmission.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01545085
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  • 128
    Digitale Medien
    Digitale Medien
    Thermoxidized Palm Oil Induces reproductive Toxicity in Healthy and Malnourished Rats (1997)
    Springer
    Plant foods for human nutrition 51 (1997), S. 159-166 
    Details
    ISSN: 1573-9104
    Schlagwort(e): Thermoxidized palm oil ; Rat ; Kwashiorkor ; Fertility ; Fetotoxicity ; Reproduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Repeatedly thermoxidized palm oil (TPO), simulating local culinary practice, was fed for eight weeks at 15% of a balanced basal diet to two sets of male and female weanling albino rats of Wistar strain. The first set of animals were normal and healthy while the second set were kwashiorkoric. Primary controls (PC) of all rats were fed a balanced basal diet of commercial rat pellets while secondary controls (SC) were fed the balanced basal diet supplemented with 15% untreated palm oil. The findings indicate that fertility, as expressed by the pregnancy rate of healthy test rats, was 78% when compared with 80% in PC (p 〈 0.05). Fetotoxicity was additionally observed in that neonatal birth weights and litter size in test rats (4.92 g and 6.70, respectively) were inferior (p 〈 0.05) to both SC and PC (4.96 g and 8.40; 5.38 g and 9.25, respectively). Protein energy malnutrition worsened the observed TPO-induced reproductive toxicities in that reproductive capacities of the rehabilitated animals were inferior to that of the healthy animals. Pregnancy rates in test animals were reduced by as much as 55% (p 〈 0.01) while fetotoxicities were also more pronounced (p 〈 0.05).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007985529125
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  • 129
    Digitale Medien
    Digitale Medien
    Simulations of a LDPE reactor using computational fluid dynamics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 104-117 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Computational fluid dynamics methods are used to provide three-dimensional simulations of a low-density polyethylene (LDPE) autoclave reactor under normal operating conditions. For the conditions used, the reactor is not very well mixed; thus, the common model approximation of a perfectly stirred reactor is not warranted. The simulations verify the sensitive nature of the polymerization reactors and indicate a need for optimizing operating parameters.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430113
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  • 130
    Digitale Medien
    Digitale Medien
    Simulation of decoking of thermal cracking coils by steam/air-mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 118-126 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A rigorous approach was developed for the simulation of the decoking of an industrial cracking furnace. A one-dimensional heterogeneous reactor model, which accounts for the interfacial gradients between the process gas and the coke surface, was used to simulate reactor coils. Both the combustion and steam gasification of the coke layer were taken into account. The reactor model for the decoking was coupled with a detailed firebox simulation model. The initial profile of the coke layer thickness, required for the decoking calculations, was obtained by a run-length simulation. The evolution with time of the temperature distribution inside the cracking coil and in the furnace was generated simultaneously, which made it possible to understand the decoking operation in detail and to predict its duration accurately.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430114
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  • 131
    Digitale Medien
    Digitale Medien
    Dynamics of semibatch polymerization reactors: II. Pilot-plant study (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 157-165 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A semibatch flow scheduling strategy proposed by Teymour and Ray (1989, 1996) is evaluated for a polymerization reaction conducted in a pilot-plant reactor. The reaction used is the free radical terpolymerization of styrene, α-methyl styrene, and acrylic acid monomers initiated by an organic peroxide initiator and carried out in the presence of a reactive glycol ether solvent. This strategy was tested in both single batch and sequential semibatch modes. The process was shown to produce polymer of constant molecular weight properties and composition as inferred from acid number and monomer conversion measurements. This process could be used for obtaining polymer products from a semibatch reactor that are of comparable quality to CSTR products. Results indicate success of this process at meeting this objective; however, practical considerations relating to agitation and temperature control need to be properly addressed to ensure this success.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430118
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  • 132
    Digitale Medien
    Digitale Medien
    Steady-state multiplicity in cocurrently cooled autothermal reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 127-134 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The steady-state simulation of a cocurrently cooled autothermal fixed-bed reactor was carried out using a 2-D heterogeneous mathematical model. The ammonia synthesis was chosen as a case study. Unlike the not-autothermal cocurrent reactor, which is unconditionally stable, the autothermal cocurrent reactor shows multiple steady states within a broad range of operating conditions. This finding, not reported in the literature, is explained through the mass transport from the bottom to the top of the reactor, associated with a feedback of energy. The feedback of heat, which is inherent to autothermal reactors, leads to an ignition-extinction phenomenon similar to that found in the countercurrent configuration. The influence of different parameters on the stability of the autothermal cocurrent reactor was analyzed. The regions where steady-state multiplicity occurs were compared with those presented by the autothermal countercurrent reactor. The influence of an additional heat exchanger on the reactor stability was considered.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430115
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  • 133
    Digitale Medien
    Digitale Medien
    Analysis of νi/κTx in solvent mixtures at the critical line (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 277-280 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430133
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  • 134
    Digitale Medien
    Digitale Medien
    Rheological simulation of in-line bubble interactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 265-267 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430130
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  • 135
    Digitale Medien
    Digitale Medien
    Analysis of nucleation and crystal growth data using the interfacial supersaturation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 268-272 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430131
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  • 136
    Digitale Medien
    Digitale Medien
    Boiling heat transfer of Nitrogen in a thermosyphon condenser-reboiler (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 339-344 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An experimental investigation was conducted to determine the boiling heat-transfer characteristics in a thermosyphon condenser-reboiler of air-separation plants. The test section was a plate-fin heat exchanger of practical size of 0.106 m width and 2.56 m length. The testing fluid was nitrogen. Experiments were carried out within a range of pressure from 150 to 300 kPa, submergence from 1.95 to 2.80 m, and heat flux up to 11 kW/m2 under constant wall-temperature condition. The liquid superheat at the onset of boiling was rather significant. The boiling heat-transfer coefficients obtained agreed well with Chen's correlation modified by Colburn's J factor within a mean deviation of 9.3%.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430207
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  • 137
    Digitale Medien
    Digitale Medien
    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430101
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  • 138
    Digitale Medien
    Digitale Medien
    Efficient sampling technique for optimization under uncertainty (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 440-447 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The concept of robust design involves identification of design settings that make the product performance less sensitive to the effects of seasonal and environmental variations. This concept is discussed in this article in the context of batch distillation column design with feed stock variations, and internal and external uncertainties. Stochastic optimization methods provide a general approach to robust/parameter design as compared to conventional techniques. However, the computational burden of these approaches can be extreme and depends on the sample size used for characterizing the parametric variations and uncertainties. A novel sampling technique is presented that generates and inverts the Hammersley points (an optimal design for placing n points uniformly on a k-dimensional cube) to provide a representative sample for multivariate probability distributions. The example of robust batch-distillation column design illustrates that the new sampling technique offers significant computational savings and better accuracy.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430217
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  • 139
    Digitale Medien
    Digitale Medien
    Analysis of cake growth in cake filtration: Effect of fine particle retention (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 33-44 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Equations were derived that describe the dynamics of cake growth in cake filtration, and methods for their solutions were developed. In deriving the equations, the moving boundary nature of the cake formation process and the effect of fine particle retention were considered. It was shown that fine particle retention may contribute significantly to the decrease of cake permeability and thus alters the performance of cake filtration even if the amount of fine particles involved is small. Through numerical examples, it was also demonstrated that fine particle retention in filter cakes may cause serious errors in determining the constitutive relationships from filter test data.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430106
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  • 140
    Digitale Medien
    Digitale Medien
    Characteristics of high-pressure liquid-solid fluidization (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 45-57 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Fundamental characteristics of liquid-solid fluidization at high pressures (up to 21 MPa) and moderate temperatures (up to 89°C) are investigated. Properties under study include minimum fluidization velocity (umf), bed voidage at minimum fluidization, and bed expansion. Devices for in-situ measurements of physical properties of the liquid in the bed are developed, and measurements are carried out to quantify the pressure and temperature effects on the fluidization behavior. The results indicate that under high pressures and moderate temperatures, liquid-solid fluidization behavior is affected significantly by the variation of liquid density and viscosity with pressure. As the pressure increases, the liquid viscosity and density increase, yielding an increased drag force and buoyancy force on the particles, and hence a decreasing umf and an increasing bed expansion for a given liquid flow rate. An increase in temperature has an opposite effect on the physical properties of the liquid, increasing umf and decreasing the bed expansion for a given liquid flow rate. Various correlations proposed in the literature for umf and bed expansion, including those by Richardson and Zaki (1954) and Chitester et al. (1984), are applicable to high-pressure and high-temperature conditions when proper account is made of the liquid physical properties under bed operating conditions.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430107
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  • 141
    Digitale Medien
    Digitale Medien
    Asymptotic models for H2S absorption into single and blended aqueous amines (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 58-63 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Asymptotic power series solutions for the mass-transfer enhancement factor for absorption of a gas component into a liquid where it undergoes irreversible instantaneous chemical reaction(s) with one and two liquid-phase reactants are developed in this work. The Padé technique is used to extend the region of applicability (accelerate the convergence) of the four-term asymptotic power series solutions. The resulting modified asymptotic expressions for the enhancement factor show excellent accuracy over a wide range and can be used to predict enhancement factors as low as 2 with an error of about 5% compared to the exact numerical solution. Predictions of these new asymptotic solutions are compared with experimental absorption data for H2S absorption into aqueous methyldiethanolamine and H2S absorption into aqueous mixtures of methyldiethanolamine and diethanolamine obtained in a laminar-jet absorber. The absolute mean deviations of the predictions from the experimental absorption data for the single and mixed amine solutions were 4.6% and 2.4%, respectively.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430108
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  • 142
    Digitale Medien
    Digitale Medien
    Analysis of rate enhancement in a periodically operated trickle-bed reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 166-172 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: When a trickle-bed reactor (TBR) is operated periodically, the bed is fed with liquid on and off, while the gas phase passes continuously. Rates and conversions could be higher than those corresponding to the steady-state operation. In the “dry cycles” the heat generated by the reaction can drive the vaporization of the liquid phase, and a much more rapid “gas phase” reaction may occur. There is a trade-off between the potential for hot-spot formation and the fact that overall rates are higher during cycling. A qualitative understanding of the phase transition in TBRs is obtained by a simple phenomenological model that takes into account different transport and reaction mechanisms occurring in a catalytic particle under different cycling conditions. A mathematical model is used to predict results.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430119
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  • 143
    Digitale Medien
    Digitale Medien
    Recent advances in modeling thermodynamic properties of aqueous strong electrolyte systems (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 180-195 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Theoretical and engineering models for the thermodynamic properties of strong electrolyte solutions have advanced significantly since 1985. This progress is notable in the ability to calculate selected properties of single and mixed strong electrolyte solutions over a wide range of temperatures and compositions, including effects of various nonelectrolytes, solvents and supercritical components. Theoretical studies have begun to consider more realistic fundamental interactions between various components in these systems. There have been several successful conversions of theories based on the mean spherical approximation and perturbation methods into engineering equations, without large numbers of empirical parameters. Other theoretical models seem almost ready for application to real systems. The capability to estimate a wide variety of thermodynamic properties accurately with a consistent set of equations and a small number of adjustable parameters has been achieved by several groups over limited temperature and composition ranges. Much work remains to be done, however, to understand completely the interplay and relative importance of various contributing energy effects.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430121
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  • 144
    Digitale Medien
    Digitale Medien
    Vapor-liquid equilibria of the ternary mixture CH4 + C2H6 + CO2 from molecular simulation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 212-217 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The NpT + test-particle method for the calculation of vapor-liquid equilibria by molecular simulations is extended to ternary mixtures. It is applied to the system methane + ethane + carbon dioxide, for which all binary molecular interaction models are available from previous work. Methane is described as one-center Lennard-Jones fluid, ethane as two-center Lennard-Jones fluid, and carbon dioxide as two-center Lennard-Jones plus point quadrupole fluid. The unlike interactions are treated in the same way as the binary mixtures, using two parameters for each binary interaction. No ternary parameters are introduced. Vapor-liquid phase equilibria are calculated for the ternary mixture at the following temperature-pressure pairs: 233.15 K - 2 MPa; 250.5 K - 2 MPa; and 250.5 K - 3.04 MPa. Comparison of the simulation data with experimental and equation-of-state results shows excellent agreement. Bubble and dew densities are also reported.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430123
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  • 145
    Digitale Medien
    Digitale Medien
    Recovery and purification of paclitaxel using low-pressure liquid chromatography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 232-242 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An efficient and economical low-pressure liquid chromatography process has been developed for paclitaxel recovery and purification directly from plant-tissue culture (PTC) broth. PTC broth is first diluted with ethanol to ensure padlitaxel dissolution and then passed through a column packed with a high-capacity polystyrene divinyl-benzene sorbent. A step increase in ethanol concentration in the mobile phase (ethanol:water) is used to concentrate and compress the taxane bands to as high as 29-fold of influent concentrations (about 1 mg/L). A recycle technique is then used to separate the concentrated paclitaxel band from other taxane bands, achieving 95% purity with more than 90% recovery and 99% purity with more than 80% recovery. In this process, the same low-pressure columns are used to capture, concentrate and purify paclitaxel. Theoretical predictions agree closely with the stepwise elution and recycle chromatography data. After validation, simulations are used to explore various design and operating alternatives. Analysis of the alternatives shows that the process cost can be further reduced by using higher feed concentration, larger loading volume, smaller particle size, and optimal gradient and recycle strategies.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430125
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  • 146
    Digitale Medien
    Digitale Medien
    Phase equilibria for the mean-force potential of globular protein solutions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 218-231 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: When polymers are added to a solution containing proteins, the protein may deposit as an amorphous precipitate or as crystals. Experimental evidence indicates that from a thermodynamic viewpoint, an amorphous precipitate should be treated as a liquid phase dense in the protein and crystals as true solids. To understand the conditions under which protein precipitation or crystallization may occur, Gibbs-ensemble Monte Carlo simulation and Gibbs-Duhem integration techniques are used to calculate the liquid-liquid and liquid-solid phase boundaries for protein precipitation induced by polymers. In these simulations, the system is modeled using the pseudo-one-component approximation with an appropriate potential of mean force. The critical point for fluid-fluid phase equilibrium disappears as the attractive part of the mean-force potential becomes very short ranged. The accuracy of the second-order Barker and Henderson perturbation theory is examined by comparing the phase diagram predicted using this method with the simulation results. Perturbation theory is able to predict the general trends observed in the simulations but not with quantitative accuracy. Perturbation theory is then used to examine a broader range of conditions for protein deposition.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430124
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  • 147
    Digitale Medien
    Digitale Medien
    Influence of particle-size distribution on entrainment solid rate in fluidized bed (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 260-262 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430128
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  • 148
    Digitale Medien
    Digitale Medien
    Simulated moving bed under linear conditions: Experimental vs. calculated results (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 935-945 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A simulated moving bed (SMB) was operated for the separation of mixtures of 2-phenyl ethanol and 3-phenyl-1-propanol on columns packed with Zorbax C18 bonded silica, using a 60:40 (v/v) solution of methanol and water as the mobile phase. Series of four or eight columns were used. The experiments were carried out with low concentration mixtures, that is, under linear conditions. Band profiles of both compounds eluted from one of the columns during successive periods after steady state had been reached were recorded, as were the concentration histories at the extract and raffinate ports. These experimental results are compared to those predicted by two models: the linear ideal and the linear equilibrium-dispersive models of chromatography, applied to the SMB separator. These two models give excellent agreement between the experimental profiles and those calculated with the model. As expected, the profiles predicted by the ideal and the equilibrium-dispersive models differ only by the lack of dispersion in the profiles given by the former. The latter model is demonstrated to be a solid, reliable tool for further studies of the SMB design and optimization.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430409
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  • 149
    Digitale Medien
    Digitale Medien
    Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 311-316 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: To study the influence of particle concentration on the hydrodynamics of bubble-column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38-m-dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol. %. To interpret experimental results a generalization of the “two-phase” model for gas-solid fluid beds was used to describe bubble hydrodynamics. The two phase identified are: a dilute phase consisting of fast-rising large bubbles that traverse the column virtually in plug flow and a dense phase that is identified with the liquid phase along with solid particles and entrained small bubbles. The dense phase suffers backmixing considerably. Dynamic gas disengagement was experimented in the heterogeneous flow regime to determine the gas voidage in dilute and dense phases. Experimental data show that increasing the solid concentration decreases the total gas holdup significantly, but the influence on the dilute-phase gas holdup is small. The dense-phase gas voidage significantly decreases gas holdup due to enhanced coalescene of small bubbles resulting from introduction of particles. The dense-phase gas voidage is practically independent of the column diameter. The dilute-phase gas holdup, on the other hand, decreases with increasing column diameter, and this dependence could be described adequately with a slight modification of the correlation of Krishna and Ellenberger developed for gas-liquid systems.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430204
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  • 150
    Digitale Medien
    Digitale Medien
    Intraparticle diffusion in hydrogenation of 3-hydroxypropanal (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 475-485 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Strong intraparticle diffusion resistance was observed and the apparent effectiveness factors were measured for the hydrogenation of 3-hydroxypropanal (HPA) to 1,3-propanediol (PD) over Ni/SiO2/Al2O3 catalyst pellets at 45 to 80°C and 2.60 to 5.15 MPa in a stirred reactor with a spinning basket. A mathematical model was proposed to describe the intraparticle diffusion and to estimate the effective diffusion coefficients of HPA, PD and hydrogen under reaction conditions by a maximum likelihood function of the apparent effectiveness factors of HPA and PD. The calculated concentration distributions of HPA, PD and hydrogen in catalyst particles reveal an excess of hydrogen at 80°C and higher temperatures, but an excess of HPA at 45°C. It results in a weak dependence of the consumption formation rate of HPA and PD on the partial pressure of hydrogen at high temperature.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430220
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  • 151
    Digitale Medien
    Digitale Medien
    Perturbation solution to the convection-diffusion equation with moving fronts (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 631-644 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Electrophoresis of a solute through a column in which its transport is governed by the convection - diffusion equation is described. Approximate solutions to the convection - diffusion equation in the limit of small diffusion are developed using perturbation methods. The diffusion coefficient and velocity are assumed to be functions of space and time such that both undergo a sudden change from one constant value to another within a thin transition zone that itself translates with a constant velocity. Two cases are considered: (1) the thickness ∊f of the transition zone is negligible compared to the diffusional length scale, so the zone may be treated as a singular boundary across which the diffusion constant and velocity suffer discontinuous changes; (2) the transition zone is considerably wider than the diffusional length scale, so the diffusion coefficient and velocity, although sharply varying, are smooth functions of position and time. A systematic perturbation expansion of the concentration distribution is presented for case 1 in terms of the small parameter ∊ = 1/Pe. A lowest order approximation is given for case 2. A suitably configured system analyzed here can lead to progressive accumulation, or focusing, of the transported solute. The degree of focusing in case 1 scales with ∊-1, whereas in case 2 it scales with (∊f∊)-1/2, and thus increases much more weakly with increasing Pe. A separation based on this concept requires development of materials and devices that allow dynamic tuning of the mass-transport properties of a medium. This would make it possible to achieve progressive focusing and separation of solutes, such as proteins and DNA fragments, in electrophoretic media with an unprecedented degree of control.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430309
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  • 152
    Digitale Medien
    Digitale Medien
    Continuous drying of a solid wetted with ternary mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 681-692 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The influence on drying selectivity of the continuous-contact mode between a solid wetted with ternary mixtures and a gas stream was theoretically studied. The liquid mixtures, ethanol-isopropanol-water and water-ethanol-acetone, were used. A mathematical model describing a gas-phase-controlled process was developed, and the influence of the process variables was studied by simulations. In addition to the inlet composition of the moisture and temperature of the solid, gas composition has the most important effect on selectivity. Small changes of gas composition, either imposed or spontaneous, may modify completely the process trajectory. The extent of these effects depends on the ratio between the flow rates of inlet gas and liquid contained in the solid. Because of their effects on the evolution of temperature and composition, the operating pressure and energy sources other than convection are also useful in controlling the selectivity. Since all these variables determine the composition of the remaining liquid and thereby product quality, their influence should be predictable. The model may be a valuable tool for exploring the process, provided that drying is gas-phase-controlled.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430314
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  • 153
    Digitale Medien
    Digitale Medien
    Sherwood number for a swarm of adsorbing spheroidal particles at any peclet number (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 844-846 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430330
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  • 154
    Digitale Medien
    Digitale Medien
    Finite-element simulation of mixing: 1. Two-dimensional flow in periodic geometry (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 577-587 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Complex mixing flows and mixing parameters are calculated to evaluate mixing quality on the basis of kinematic parameters together with a statistical analysis. The results allow for a comparative evaluation in terms of geometry and flow parameters. The evaluation is limited to two-dimensional flows with moving boundaries in periodic motion such as the flow in the cross section of a twin-cam mixer. The finite-element calculation requires a remeshing procedure for every time step with special techniques to upgrade mixing variables from one time step to the next. The relative mixing quality of single cam and co: or counterrotating cam devices are compared by evaluating segregation scale, length stretch, and efficiency. The numerical results exhibit a good correspondence with their experimental counterpart.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430303
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  • 155
    Digitale Medien
    Digitale Medien
    Resonant microwave power absorption in slabs and cylinders (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 615-624 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Resonant power absorption is an important phenomenon during microwave heating. The resonances that occur when plane electromagnetic waves are incident on infinitely long cylinders and slabs are investigated as a function of sample dimensions. For cylinders two kinds of incident waves are studied: TMz when the electric field is oriented along the axis of the cylinder and TEz when the magnetic field is oriented along the axis. At a resonant condition the overage power absorbed by the sample is a local maximum. Due to attenuation within the sample the resonances decrease in intensity as the sample size increases. Using the dielectric properties of water, resonances are found to be a function of the ratio of the sample dimension to the wavelength of radiation, λs, in the sample. For slabs of thickness L and integer values of n, resonances occurred at L/λs = 0.5n; for cylinders of diameter D, resonances occurred at D/λs = 0.5n - 0.257. The generality of these relations to predict resonances in other food samples are shown using existing dielectric data. Resonances in cylinders for both polarizations occurred at similar radii. However, the radius at which the first resonance occurred for the TMz case was absent in the TEz case.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430307
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  • 156
    Digitale Medien
    Digitale Medien
    Transient behavior of pulsed particulate fluidized beds (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 625-630 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Transient phenomena in solid-liquid fluidized-bed systems are important in designing pulsed, countercurrent (multistage) fluidized-bed contactors of the Cloete-Streat type at high-solids flow rate. Of particular interest are the residence times or corresponding velocities of porosity gradients in the bed and the excess or overshoot height of the bed after refluidization. Theory assuming local equilibrium between holdup and velocity of the phases (local-equilibrium model) for stepwise perturbations in the liquid flow is readily available. It is investigated whether the local-equilibrium theory can be used for more complex perturbations and whether inertia effects, such as are encountered in countercurrent multistage fluidized-bed systems, can be ignored. Therefore, the detailed particle-bed model of Foscolo and Gibilaro, which incorporates inertia effects, was applied to investigate the transient behavior of fluidized-bed systems. Transient fluidization experiments were performed with a broad range of water-fluidized particles in a laboratory-scale multistage fluidized-bed contactor. The operating conditions corresponded to those for countercurrent contact.Numerical simulations with the particle-bed model predict satisfactory experimental results. The “overshoot” heights of the fluidized bed were estimated correctly by the particle-bed model, whereas the local-equilibrium model only provides a conservative estimate. However, the local-equilibrium model allows an analytical solution that is more interesting for design, as it avoids tedious calculations. The residence time of the last perturbation before the fluidized bed relaxes to steady state was estimated with similar accuracy by both models.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430308
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  • 157
    Digitale Medien
    Digitale Medien
    Steady spontaneous capillary flow in partially coated tubes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 645-654 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A spontaneous, steady capillary flow is produced for a liquid index in a circular tube that is partially coated with a surface modifier to create a discontinuous wetting condition between upstream and downstream portions of the tube. As a means of demonstrating that the flow configuration may prove useful as a diagnostic tool in studies concerning capillarity and the physics associated with the moving contact line, average steady velocities are predicted and compared against a large experimental data set that includes the effects of tube dimensions and fluid properties. To access a wider range of tube diameters (0.516-9.88 mm), experiments are performed employing “U-tubes” tested in the low-gravity environment of a drop tower, in addition to straight capillary tubes tested horizontally in a laboratory. The sensitivity of the steady capillary flow to surface cleanliness is dramatic.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430310
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  • 158
    Digitale Medien
    Digitale Medien
    Permeability of filter cakes of palm oil in relation to mechanical expression (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 673-680 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Permeability and compressibility data are required for an adequate process model for compressible-cake filtration and mechanical expression. Experimental and modeling results of the permeability of palm-oil filter cakes (a highly compressible viscoelastic material) are combined with compressibility data, leading to a model for the expression step. Permeability measurements show that permeability depends strongly on the quantity of fine particles in the cake. Removal of fine particles from the slurry before expression significantly increases the solid-phase content during expression due to higher permeability. Modeling results of the expression step show that for palm-oil filter cakes there is a pressure above which the attainable mass fraction of solids becomes independent of pressure. Decrease in specific cake resistance has two effects: a higher mass fraction of solids at the same pressure and a higher pressure at which the mass fraction of solids is not affected further.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430313
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  • 159
    Digitale Medien
    Digitale Medien
    Modeling and optimization of a semiregenerative catalytic naphtha reformer (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 740-753 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Modeling and optimization of a semiregenerative catalytic naphtha reformer has been carried out considering most of its key constituent units. A detailed kinetic scheme involving 35 pseudocomponents connected by a network of 36 reactions in the C5-C10 range was modeled using Hougen-Watson Langmuir-Hinshelwood-type reaction-rate expressions. Deactivation of the catalyst was modeled by including the corresponding equations for coking kinetics. The overall kinetic model was parameterized by bench-marking against industrial plant data using a feed-characterization procedure developed to infer the composition of the chemical species in the feed and reformate from their measured ASTM distillation data. For the initial optimization studies, a constant reactor inlet temperature configuration that would lead to optimum operation over the entire catalyst life cycle was identified. The analysis was extended to study the time-optimal control profiles of decision variables over the run length. In addition, the constant octane case was also studied. The improvement in the objective function achieved in each case was determined. Finally, the sensitivity of the optimal results to uncertainty in reactor-model parameters was evaluated.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430319
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  • 160
    Digitale Medien
    Digitale Medien
    Microwave heating of the continuous flow catalytic reactor in a nonuniform electric field (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 754-760 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Temperature profiles in the continuous-flow reactor with a fixed bed placed in a nonuniform microwave field are predicted by considering specific on - off regulation of the microwave power and local distribution of the electric-field intensity. The spatial and temperature dependence of the electric-field intensity affects the heating appreciably, as shown by indirect measurements. Results of numerical calculations agree with experimental data of outlet temperature and explain temperature oscillations in the outlet flow. The model developed allows an accurate description of microwave heating in the continuous-flow reactor associated with specific regulation of microwave power. The hydrolysis of sucrose catalyzed by the strongly acidic cation-exchange resin Amberlite 200C in R-H form was chosen as the reaction system. Calculated conversions of sucrose based on predicted temperature profiles agree with experimental data.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430320
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  • 161
    Digitale Medien
    Digitale Medien
    Oxidative dehydrogenation of butane using membrane reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 777-784 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The oxidative dehydrogenation of butane was studied at temperatures between 450 and 550°C using a conventional fixed-bed reactor and inert membrane catalytic reactors with different feed arrangements. When inert membrane reactors were employed, a ceramic membrane was used to distribute oxygen to a fixed bed of V-Mg-O catalyst. The membrane reactor was found to be more efficient than a fixed-bed reactor under most of the conditions investigated. In addition, in the membrane reactor the formation of hot spots decreased considerably, leading to a more stable and safer operation.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430322
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  • 162
    Digitale Medien
    Digitale Medien
    Reaction rates in fractal vs. uniform catalysts with linear and nonlinear kinetics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1691-1699 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Pore fractal objects are expected to be optimal catalysts, since material is supplied to the narrower pores, which are also shorter through the larger pores where diffusion resistance is smaller. To demonstrate this, diffusion and reaction were simulated on Sierpinski-gasket-type fractal objects and on the corresponding nonfractal uniform-pore structures of the same size, porosity and reactive area. Positive order reactions limited by Knudsen diffusion were shown to exhibit larger rates in fractal than in uniform-pore objects. Fractal catalysts also exhibited a new intermediate domain in which the rate depends only weakly on the kinetics parameters. In nonmonotomic kinetics the branching point (bifurcation point) was extremely sensitive to the pore structure.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430706
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  • 163
    Digitale Medien
    Digitale Medien
    Electrochemically modulated complexation process for ethylene/ethane separation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1709-1716 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An electrochemically modulated complexation (EMC) process was designed to selectively extract and concentrate ethylene from a feed-phase mixture with ethane. Unlike previous EMC processes, where the separation was based on equilibrium solubility differences, this separation was based on differences in the rate of complexing with copper(I) solution between the two gases. The EMC process employed flowthrough electrolysis cells that electrochemically modulate aqueous-phase copper chlorides between high, copper(I), and low, copper(II), affinity states. The liquid phase in the high affinity form contracts a feed gas phase in a hollow-fiber membrane module for selective extraction and contacts the receiving gas phase in the low affinity form for concentration. Experimental results and modeling of the process are reported.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430708
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  • 164
    Digitale Medien
    Digitale Medien
    Synthesis of crystallization-distillation hybrid separation processes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1751-1762 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A systematic method to synthesize crystallization-distillation hybrid separation processes is presented. Two classes of hybrids are identified for binary mixtures. The first bypasses azeotropes and tangent pinches, while the second bypasses eutectics. Guidelines for flow-sheet selection are proposed based on an analysis of simple eutectic, constant relative volatility systems. In addition, the hybrids are compared to both extractive and adductive crystallization in order to determine the conditions under which solvent-based crystallization techniques outperform the proposed hybrid configurations. The method is extended to ternary mixture. The use of stream combination and complex distillation columns is also considered.
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430712
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  • 165
    Digitale Medien
    Digitale Medien
    Dehydrogenation of propane using a packed-bed catalytic membrane reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1819-1827 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In a high-temperature catalytic membrane reactor, a plug-flow reactor is combined with a gas-separative membrane. By selectively removing one of the reaction products, the reaction mixture is prevented from reaching equilibrium, and a higher conversion can be obtained. This concept is only valid for reactions that are limited by the thermodynamic equilibrium, such as the direct dehydrogenation of propane to propene. A tubular H2-selective silica membrane was characterized [αH2/C3H8 = 70-90 at 500°C] and used as the gas-separative membrane. The membrane reactor was filled with a chromia/alumina catalyst. The kinetics of the catalyst was studied. At 500°C the deactivation of the catalyst is slow, and the propene yield is almost constant for at least 10 h of operation. Under well-chosen process conditions, the propene yield is at least twice as high as the value obtained at thermodynamic equilibrium in a conventional reactor.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430717
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  • 166
    Digitale Medien
    Digitale Medien
    Measurement of ultrasonic forces for particle-liquid separations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1727-1736 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The magnitude and direction of the ultrasonic radiation forces that act on individual particles in a standing-wave field were determined using a microscope-based imaging system. The forces are calculated from measured particle velocities assuming that the drag force, given by Stokes' law, is exactly counterbalanced by the imposed ultrasonic forces. The axial primary radiation force was found to vary sinusoidally with axial position and to be proportional to the local acoustic energy density, as predicted by theory. The magnitude of the transverse primary force was determined by two independent methods to be about 100-fold weaker than the axial force. Separation concepts exploiting the transverse force for cell retention have been successful despite the great disparity in magnitude between the axial and transvers-force components. This may be explained by the reduced hydrodynamic forces on aggregated particles in transverse flow due to their alignment in the sound field.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430710
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  • 167
    Digitale Medien
    Digitale Medien
    Surfactant effects on absorption in the presence of induced interfacial turbulence (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1909-1913 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430726
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  • 168
    Digitale Medien
    Digitale Medien
    Improving clay-based tailings disposal: Case study on coal tailings (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1894-1903 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The role of swelling clays in hindering the compressional dewatering characteristics of coal-mine tailings is examined. The effects of electrolyte concentration and ion exchange in improving the shear and compressional rheology are compared. Suspensions studies include actual mine tailings (thickener feed and thickener underflow) as well as synthetic clay dispersions made from clay collected from the coal seam. It was shown that the most important parameter in controlling the properties of the tailings suspension is “controlled” dispersion in the presence of a Ca2+ electrolyte concentration in excess of that required to (1) prevent initial swelling and (2) provide full cation exchange of the clay. Under these electrolyte conditions, complete delamination of the clay did not occur, and both the dewatering and handling characteristics of the resultant suspensions improved dramatically.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430724
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  • 169
    Digitale Medien
    Digitale Medien
    Spread and rebound of liquid droplets upon impact on flat surfaces (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2169-2179 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The spread and rebound of droplets upon impact on flat surfaces at room temperature were studied over a wide range of impact velocities (0.5-6 m/s), viscosities (1-100 mPa.s), static contact angles (30-120°), droplet sizes (1.5-3.5 mm), and surface roughnesses using a fast-shutter-speed CCD camera. The maximum spread of a droplet upon impact depended strongly on the liquid viscosity and the impact velocity. The tendency of a droplet to deposit or to rebound is determined primarily by the liquid viscosity and the liquid/substrate static contact angle. A model more broadly applicable than existing models was developed to predict maximum spread as a function of the Reynolds number, the Weber number, and the static contact angle. Based on the conservation of energy, a rebound model is proposed that predicts the tendency to rebound as a function of maximum spread and static contact angle.The maximum-spread model prediction agrees to within 10% with more than 90% of the experimental data from different sources. In the current study, the rebound model successfully predicts the tendency of a droplet to rebound.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430903
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  • 170
    Digitale Medien
    Digitale Medien
    Mass and thermal transport analysis of oscillating flow with absorbent polymers (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2157-2168 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new concept for removing toxic gases with respirator applications based on inhalation and exhalation through absorbent polymer-lined tubes was studied. The two-way oscillatory flow through the respirator element enables capture and expulsion of toxic vapors, which is not feasible with activated charcoal because of the adverse effect of moist breath on the charcoal efficiency. To study the influence of various material, design and operating parameters on the performance of such a respirator, a numerical model that solves the governing equations of mass and heat transport in an oscillatory flow through an absorbent polymer-lined tube was developed and utilized with experimentally measured property data. Factors investigated include respirator element geometry, polymer and toxic vapor characteristics, and flowthrough speed. Results show a large delay in toxic gas penetration over that obtained by conventional one-way flow, and define the importance of partition coefficient, flow passage size, and length and velocity. Results are compared with data from simulated breathing experiments.
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430902
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  • 171
    Digitale Medien
    Digitale Medien
    Analytical description of the Lennard-Jones fluid and its application (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2215-2226 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A simplified exponential (SEXP) approximation, combining the exponential approximation and the first-order mean spherical approximation, is proposed to improve the equation of state for the Lennard-Jones (LJ) fluid. The SEXP approximation, which can be implemented in an analytical manner, yields better radial distribution functions of the LJ fluid. Extensive comparisons with two typical perturbation theories show that the SEXP approximation is more appropriate to describe the behaviors of the LJ fluid. The latest 33-parameter modified Benedict-Webb-Rubin equation, also calculated, is inadequate in the region of phase coexistence. The SEXP approximation is applied to the calculation of methane properties with much better results than the Peng-Robinson equation of state for saturated liquid densities and second virial coefficients.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430908
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  • 172
    Digitale Medien
    Digitale Medien
    Temperature dependence of one-component permeation through a silicalite-1 membrane (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2203-2214 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The one-component steady-state permeation of gases through a silicalite-1 zeolite composite membrane as a function of the temperature is studied from 190 to 680 K for light hydrocarbons, noble gases, and some inorganic gases. In general, with increasing temperature the permeance shows a maximum followed by a minimum. For gases weakly adsorbed the permeance has only a minimum and for gases strongly adsorbed only a maximum is observed in the permeance. The permeance for various gases, for a feed pressure of 101 kPa, span four orders of magnitude. The lowest permeation is for i-butane at 300 K: a permeance of 0.07 × 10-8 mol. m-2.s-1.Pa-1. The highest value is observed for methane: a permeance of 70 × 10-8 mol. m-2.s-1.Pa-1 at about 240 K. A comparison between the isobars and the temperature dependence of the steady-state permeance, both at 101 kPa, shows that at the temperature where the amount adsorbed vanishes the permeance starts to increase. The temperature dependence of the steady-state fluxes through the silicalite-1 membrane can be described only if two diffusion mechanisms are taken into account. For high occupancies the mass transport can be described by equilibrium adsorption followed by surface diffusion and for low occupancies the mass transport can be described by activated gaseous diffusion. With increasing temperature the mass-transport mechanism shifts from the surface diffusion regime to the activated gaseous diffusion regime. With these two diffusivities modeling results agree well with experimental results for the one-component flux through the silicalite-1 zeolite membrane.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430907
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  • 173
    Digitale Medien
    Digitale Medien
    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431101
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  • 174
    Digitale Medien
    Digitale Medien
    Gas-filled cavity structures and local void fraction distribution in aerated stirred vessel (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2921-2931 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The local structural function obtained by a microresistivity probe at different hydrodynamic regimes is examined. The structures, such as the vortex-clinging structure, the appearance of one and two large cavities, small 3-3 structure, large 3-3 structure, and ragged cavities were recognized by frequency transformation of the time-domain structural function. An optimized phase discrimination in signal processing was used. The distribution of the local void fraction (α) in a pilot-size stirred tank was experimentally investigated, because almost no such data can be found in the literature. The two-phase mixture was composed of air and water; α was measured at 190 nodes in the vertical half-section plane of the vessel. Relative differences smaller than 9% between integrated values of α and measured gas holdups agreed reasonably well under all conditions.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431105
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  • 175
    Digitale Medien
    Digitale Medien
    Constrained MPCI: A weak persistent excitation approach (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2279-2288 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Model-predictive control and identification (MPCI) introduced by Genceli and Nikolaou in 1996 is a novel approach to the identification of processes under constrained model-predictive control. MPCI solves an on-line optimization problem that involves (a) a standard MPC objective; (b) standard MPC constraints; and (c) persistent excitation (PE) constraints. The on-line optimization problem is computationally demanding. To alleviate that problem, we take a frequency-domain approach to formulating the PE constraints. This approach relies on the following fact: a signal is persistently exciting of order n, if its two-sided power spectrum is nonzero at no fewer than n points. Therefore, persistently exciting input signals can be parametrized over a finite horizon as a sum of sinusoid terms with nonzero coefficients. Used in the MPCI framework, the last requirement generates a set of completely decoupled reverse-convex constraints that are combinatorially tractable from a computational point of view. The effectiveness of the proposed MPCI method is demonstrated through simulations. For the SISO systems studied, computation of the global optimum could be handled combinatorially in real-time using PC hardware.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430913
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  • 176
    Digitale Medien
    Digitale Medien
    Design and retrofit of sensor networks in process plants (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2300-2306 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A novel procedure to find cost-optimal sensor networks is proposed. Cost is minimized subject to qualifying constraints that are related to certain requirements of data reconciliation. One basic qualifying constraint is a desired level of precision of reconciled values for a selected set of variables. Since precision requirements lead to multiple solutions, other qualifying constraints are proposed. These constraints are availability, resilience, and error detectability. Definitions for these terms are given and their impact on the results is presented.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430915
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  • 177
    Digitale Medien
    Digitale Medien
    Pore-structure optimization of calcium carbonate for enhanced sulfation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2323-2335 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A modified CaCO3 sorbent with an open internal pore structure is prepared and its sulfation characteristics are investigated in an entrained flow reactor at high temperatures (900-1,100°C) and short contact times (20-600 ms) using small particle sizes (〈 5 μm). The most distinguishing feature of this modified carbonate (MC) is its 70-75% sulfation conversion within 0.5 s, which is substantially higher than any other sorbents published. The MC is prepared by carbonation-precipitation from a calcium hydroxide suspension by optimizing the operating parameters to generate carbonate particles of the desired pore structural properties. The high initial surface area combined with its open pore structure and pore-size distribution of its calcine contribute to its high reactivity. The calcined MC possesses a significant portion of its pore volume in the 50-200 Å range. This size range represents an optimum pore size for sulfation since it provides a reasonably high surface area and is less susceptible than 〈 50 Å pore sizes, to pore filling, or pore-mouth plugging due to the formation of higher molar volume CaSO4. Investigation with other carbonates reveals that a much higher portion of their calcines' porosity lies in the smaller pores, which leads to premature termination of sulfation. Results show the impact of internal pore structure on initial reactivity and ultimate sorbent conversion.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430917
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  • 178
    Digitale Medien
    Digitale Medien
    Analysis of bacterial swimming speed approaching a solid-liquid interface (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1341-1347 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Previous experimental studies have found that surface interactions significantly affect the transport of motile bacteria through small tubes, along solid surfaces, and through porous media. However, the role that hydrodynamic forces play in the interactions between solid surfaces and motile bacteria remains unclear. In this study, the swimming speeds of populations of Escherichia coli bacteria were measured near (〈 10 μm) and far (〉10 μm) from a flat glass surface at four ranges of orientations to the surface (0°-45°, 45°-90°, 90°-135°, and 135°-180°). Populations of bacteria close to the surface and moving in the orientation range most perpendicular (0-45°) to the surface experienced the greatest change in the swimming speed when compared to the population in the same orientation range located far from the surface. The decrease in swimming speed experienced by this population was on the same order as that predicted by hydrodynamic models of bacterial swimming near surfaces.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430523
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  • 179
    Digitale Medien
    Digitale Medien
    Lagrangian simulation of turbulent particle dispersion in electrostatic precipitators (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1403-1413 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Industrial design of electrostatic precipitators is based on the transport theory developed by Deutsch (1922), which assumes that transverse turbulent mixing is effective enough to maintain the concentration profile uniform throughout the cross section (i.e., turbulent diffusivity is assumed infinite). To improve understanding of turbulent particle dispersion under the influence of electrostatic forces, a database on particle trajectories was first generated, based on the flow field from a direct numerical simulation of a plate-plate precipitator (Soldati et al., 1993). The effect of various parameters, such as particle size, charge and particle migration velocity, on dispersion and collection efficiency was investigated. Results show that particle concentration profiles are not uniform due to finite values of “turbulent diffusion” coefficient. The simulations indicate that the early stages of particle collection are controlled by particle migration velocity, while final stages are controlled by turbulence diffusion mechanisms.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430604
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  • 180
    Digitale Medien
    Digitale Medien
    Gas-holdup measurements in bubble columns using computed tomography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1414-1425 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A computed tomographic scanner was developed for imaging gas-holdup distributions in two-phase flow systems such as bubble columns and fluidized beds. The scanner has been used to study the effects of various operating parameters (such as column diameter, superficial gas velocity, and distributor type) on the gas holdup and its distribution in an air-water bubble column. The experimental investigation shows that the column dimensions have no significant effect on the void fraction when the column diameter is greater than 0.15 m. Differences in the holdup distribution due to the kind of distributor used are significant only at low gas flow rates. Surface tension of the liquid has a profound influence on the gas holdup and its distribution.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430605
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  • 181
    Digitale Medien
    Digitale Medien
    Crystallization of nanosized silicon powder prepared by plasma-induced clustering reactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2610-2615 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Nanosized silicon powders were prepared by gas-phase cluster agglomeration reactions in a low-pressure silane plasma. The formation and agglomeration of clusters leading to the growth of primary particles of powder were studied by in-situ techniques including mass spectroscopy and laser light-scattering experiments. These powders, generally amorphous and crystallized in a reducing atmosphere, were studied in detail by Raman spectroscopy and high-resolution electron microscopy, which revealed a very rough surface of as-prepared single powder particles with structures of 1 to 2 nm. Upon 1-h annealing at temperatures between 300 and 600°C, circular contrast features, 1.5 to 2.5 nm in size, are observed in the amorphous particles, which show medium-range order. A distinct onset of crystallization is observed at 700°C with structures ranging from very small crystalline ordered regions of 2.5-3.5 nm in size to fast-grown multipletwinned crystallites. The crystallization behavior is influenced by the clusters that form primary particles. Observed sintering behavior cannot be explained by a classical approach; hence, theoretical models need to be adapted to nanosized powders.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431303
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  • 182
    Digitale Medien
    Digitale Medien
    Carbothermally prepared nanophase SiC/ Si3N4 composite powders and densified parts (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2624-2635 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Nanophase SiC/Si3N4 composite powders were synthesized by the carbothermal nitridation of SiO2. These powders have desirable characteristics of high quality with oxygen contents on the order of 1.5 to 2 wt. %, surface area of ∼ 10 m2/g, submicron α-Si3N4, low metallic impurity levels, and a homogeneous distribution of the nanophase SiC phase. High-resolution TEM analysis has shown that the content and size of the nanophase SiC can be varied from 0.5 to 50 wt. % and 25 to 500 nm, respectively, through proper control of raw materials and reactor conditions. To determine how the nanophase SiC reinforcement affects the mechanical properties of Si3N4, densified components were fabricated using both pressureless and pressure-assisted densification methods. TEM analysis revealed that the nanophase SiC particles are distributed both intergranularly and intragranularly throughout the Si3N4, matrix. By controlling the sintering additive package and the sintering conditions, the ratio of inter- to intragranular SiC can be adjusted. Mechanical property measurements at elevated temperatures showed a dramatic improvement in high-temperature strength and creep resistance over components made with commercially available powders.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431305
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  • 183
    Digitale Medien
    Digitale Medien
    Generation of unagglomerated, Dense, BaTiO3 particles by flame-spray pyrolysis (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2665-2669 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Fine particles of dense, high-purity, crystalline BaTiO3were produced by flame-spray pyrolysis. A 0.5-M (Ba:Ti = 1:1) solution of barium acetate, titanium lactate, and water was aerosolized using an ultrasonic generator, and the droplets were delivered into the core of an annular diffusion flame (H2/air) reactor. For all investigated temperatures [∼1,000-∼2,000°C adiabatic], the generated powders were chemically pure, crystalline (primarily tetragonal phase with hexagonal and cubic polymorphs), and unagglomerated. At a low-flame temperature (∼1,000°C ad.), the particles produced were hollow and irregularly shaped. Particles produced at higher flame temperatures (〉∼1,500°C ad.) were dense and homogeneous. Particles showed a transition from a nonspherical porous morphology to a spherical dense morphology with increasing temperature. By increasing residence time, the temperature at which particles became spherical and dense was reduced. Flame-spray pyrolysis provides a useful method for forming dense particles of high melting point materials by aerosol-phase densification.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431310
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  • 184
    Digitale Medien
    Digitale Medien
    Perovskite-type oxide membranes for the oxidative coupling of methane (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2731-2740 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A series of ion-conducting perovskites of the form [La1-xAx] [Co0.2Fe0.8] O3-δ (x = 0.4, 0.6 for A = Sr; × = 0.8 for A = Ba) were investigated for their use as a catalytic membrane for the oxidative coupling of methane (OCM). A-site cations consisting of La0.4Sr0.6 and La0.2Ba0.8 produce materials with the highest oxygen fluxes and result in C2+ selectivities of 50% at 1,098 K, which are significantly higher than those achieved with a powdered catalyst in a packed-bed reactor configuration. Selectivities in these materials appear to be limited by high oxygen ion recombination rates that compete for oxygen with the desired coupling reaction(s). The results also indicate that oxygen fluxes are not limited by diffusion, but by surface exchange rates at the oxygen-lean side of the membrane. The study on stability of these materials showed that all three perovskites could be reduced in a pure methane or ethane stream at 1,023 K, but they were totally stable under reaction conditions where oxygen is present.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431319
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  • 185
    Digitale Medien
    Digitale Medien
    Fabrication of conductometric gas-sensing films by selected area chemical-vapor deposition (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2760-2764 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new selected-area chemical-vapor deposition (CVD) process to fabricate thin sensing films on a micromachined silicon-based, conductometric gas-sensor structure is reported. The CVD method is self-lithographic and does not require the use of masks to define the thin-film region. Since the films are deposited after silicon processing, the selection of film materials is not constrained by their compatibility with the etchants used in silicon micromachining. The presence of conductance electrodes underneath the growing film permits in-situ monitoring of film resistance. The rapid thermal response of the device allows precise termination of film growth once the film resistance has reached a value suitable for gas sensing. The application of this new CVD method is demonstrated for growth of thin platinum films, which are used for sensing of O2 and H2 gases.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431322
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  • 186
    Digitale Medien
    Digitale Medien
    Thermochemistry of aqueous silicate solution precursors to ceramics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2773-2784 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A quantitative understanding of the thermochemistry of silicate solution systems is necessary for the design, optimization and control of sol-gel, colloid and zeolite preparations. This review is intended to be a compendium of ready information for the growing number of chemical engineers active in solution-based materials synthesis. Experimental measurements of silica solubility, silicate speciation and silanol deprotonation in aqueous solutions are summarized and critiqued. The thermochemical properties of monomeric and dimeric silicate anions are also assessed. The trends that are then evident are compared with expectations from simplistic gas-phase molecular orbital calculations to illustrate the importance of solvation. Finally, the equilibrium behavior of simple silicate oligomers is rationalized, and the future direction to quantitative modeling of the behavior of more complex oligomers is suggested.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431324
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  • 187
    Digitale Medien
    Digitale Medien
    Inorganic and organically modified rare-earth-doped silica gels (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2785-2792 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The fluorescence properties of inorganic and organically-modified rare-earth-doped sol-gel silica are presented. Eu3+-doped ormosils were prepared from Si(OCH3)4 and CH3Si(OCH3)3, (CH3)2Si(OCH3)2, (CH3)2Si(OC2H5)2, or (n-C3H7)Si(OCH3)3 in various proportions. Er3+-doped ormosils were prepared using Si(OC2H5)4 and CH3Si(OC2H5)3, (CH3)2Si(OC2H5)2 or C2H5Si(OC2H5)3. Gels derived from Si(OCH3)4 were also doped with the fluorinated Eu3+ precursors Eu(fod)3, (CF3SO3)3Eu, and (CF3CO2)3Eu·3H2O. The effect of metal ion codopants, which are known to inhibit clustering of Eu3+ in sol-gel silica, on Er3+ fluorescence is also considered. Fluorescence line-narrowing studies of Eu3+-doped samples indicated that significant Eu3 clustering occurs in both the ormosils and fluorinated precursor compositions. Lifetime measurements of the Eu3+-and Er3+ -doped ormosils showed longer lifetimes at low heat treatment temperatures relative to purely inorganic sol-gel silica, but no significant difference remained in fully densified samples. The longest lifetimes were observed for samples doped with the fluorinated precursors, indicating that the fluorinated ligands are effective at reducing the water content in densified gels.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431325
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  • 188
    Digitale Medien
    Digitale Medien
    Nanoparticle synthesis of titanium silicalite for fiber, film, and monolith formation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2802-2808 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Zeolite fiber, film, and monolith were prepared by using nanosize titanium silicalite (TS-1) crystals. Films and fibers of TS-1 zeolite were optically transparent, which might be important for advanced optozeolitic materials. A permeation result of gases on monolith indicates that the gas permeation is governed by the Knudsen mechanism. All types of TS-1 zeolites manufactured in this work are observed to be MFI structure with an orthorhombic symmetry. These results suggest that nanosize zeolites have potential to allow morphological design with applications for advanced functional materials.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431327
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  • 189
    Digitale Medien
    Digitale Medien
    Covalent grafting of optically active molecules on silica gels (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2820-2826 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Active organic molecules are grafted on the xerogel silica matrix by using functionalized alkoxides f-R′-Si(OEt)3, where f is a chemical function and R′ is an alkyl spacer to limit the degrees of freedom of the molecules. Organic-inorganic hybrid films are prepared in which optically nonlinear DRl chromophores are covalently bound to the silica network. These films exhibit a large and stable second-order nonlinear coefficient from second harmonic generation experiments. Protoporphyrin molecules are attached double covalently to the xerogel matrix via flexible organic spacers. Persistent spectral holes are still burnt with moderate fluency at 120 K.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431329
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  • 190
    Digitale Medien
    Digitale Medien
    Forsterite powder prepared from water-soluble hybrid precursor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2832-2836 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Partially polycondensed γ-aminopropylsilanetriol (APSTOL) was used as the silica precursor to prepare magnesium orthosilicate in the form of crystalline forsterite. Aqueous solutions of APSTOL and magnesium acetate were mixed and dried forming a water-soluble product that was converted into forsterite by heating to 1,000°C. The thermal evolution of the system was studied using TGA, FTIR, UV-VIS spectrophotometry, and XRD techniques, especially for the acetate decomposition and transformation of CSiO3-tetrahedra into the orthosilicate anions. The combustion of organics and the crystallization of forsterite proceed at temperatures 350 and 870°C, respectively. At intermediate temperatures, the system contains amorphous silicates with oligomeric and polymeric anions, which gradually depolymerize as temperature increases. The resulting crystalline product contains less impurities (periclase and enstatite) than samples prepared using other wet-chemistry techniques.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431331
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  • 191
    Digitale Medien
    Digitale Medien
    Thermal decomposition of barium titanate precursor prepared by a wet chemical method (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2837-2843 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: As a part of fundamental study on the kinetics of electroceramics processing by wet chemical methods, barium titanate precursor gel was prepared using barium acetate and titanium tetra-isopropapoxide as starting materials. Experimental results indicated that barium acetate was distributed uniformly in the gel matrix formed by hydrolysis and polymerization of titanium tetra-isopropoxide. In the subsequent calcination of the gel, rapid formation of barium titanate was observed above 823 K, which resulted from the reaction between titania and barium carbonate or barium oxide(s). The dynamics of barium titanate formation under different heat-up programs was successfully simulated based on a proposed reaction model that incorporates a specified reactive portion of barium acetate in the gel matrix.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431332
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  • 192
    Digitale Medien
    Digitale Medien
    Macroporous ceramics from ceramic-polymer dispersion methods (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2878-2888 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Porous ceramics were fabricated by firing ceramic-polymer composites prepared by casting dispersions containing cellulose acetate, water and colloidal ceramic particles (alumina and silica). Composite microstructures were determined by polymer phase separation. Polymer adsorption on the ceramic particles was necessary for the formation of controlled porosity in the composite and fired ceramic. Cellulose acetate adsorbed on alumina, but not silica particles. The microstructure of alumina-cellulose acetate composites was characterized by unagglomerrated alumina particles in a polymer matrix; relatively large pores (pore diameter ∼ 15 μm) formed when the alumina concentration was low (〈50 vol. % relative to the polymer in the dried composite), and smaller pores (pore diameter ∼2μm) developed at higher alumina contents. By contrast, silica-cellulose acetate composites contained agglomerated silica particles and a large pore structure invariant to silica content. Firing of alumina-cellulose acetate composites with ceramic contents greater than 40 vol. % resulted in crack-free porous ceramics with pore structures comparable to the original composites.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431339
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  • 193
    Digitale Medien
    Digitale Medien
    Experimental study of the influence of the flow rates in SMB chromatography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2970-2983 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A Sorbex-type SMB separation instrument was operated for the separation of mixtures of 2-phenyl ethanol and 3-phenyl-l-propanol on a series of eight columns packed with Zorbax C18 bonded silica, using a 60:40 (u/v) solution of methanol and water as the mobile phase. The experiments were carried out with low-concentration mixtures under linear conditions. The elution profiles of both compounds between any two successive columns of the set under steady-state conditions were recorded while compositions of the raffinate and extract were measured. The four safety margin factors, βj, were divided into two groups: β1 and β4; β2 and β3 with different influence. Within the framework of the linear, ideal model of chromatography, a range of flow rates enables an SMB to operate successfully by completely separating the feed into its two components. The influence of different flow rates on the performance of the separator was studied by calculations and experiments with excellent agreement between both sets. With a simple optimization strategy, the four flow rates are selected to maximize the production rate or the concentration of extract and raffinate products, or to minimize the desorbent consumption. These optimum conditions are obtained by controlling the locations of concentration profiles inside the SMB. A reliable model for SMB operation allows a rapid and easy selection of the optimum experimental conditions.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431110
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  • 194
    Digitale Medien
    Digitale Medien
    Multiscale integration hybrid algorithms for homogeneous-heterogeneous reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 3031-3041 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Despite many available models at different reactor length scales, no models exist for designing homogeneous-heterogeneous reactors from first principles by linking molecular with macroscopic scales. Hybrid algorithms, based on a domain decomposition method, are proposed to couple a continuum fluid-phase transport/reaction model with a new efficient, real-time surface Monte Carlo model suitable for stiff problems. These algorithms properly treat surface heterogeneities and morphology and provide the exact boundary condition to the continuum fluid-phase model. In this way, molecular-scale information is integrated into a macroscopic chemical system. The methods are applied at atmospheric pressure to a stagnant boundary layer near a catalytic surface where heterogeneities are caused by adsorbate-adsorbate interactions. Both steady-state and transient simulations are performed. Such numerical methods have the potential for microscopic control of chemical processes through macroscopic control of experimental parameters. Applications to homogeneous-heterogeneous processes such as catalytic reactors, control of morphology of solid materials with atomic resolution, and corrosion processes are also discussed.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431115
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  • 195
    Digitale Medien
    Digitale Medien
    Molecular dynamics study of epitaxial growth and cluster formation on MgO(001) (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2765-2772 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new molecular dynamics (MD) code was developed to simulate the continuous deposition process of various molecules on substrates. In this methodology, various molecules can be deposited over substrate surfaces one by one in regular time intervals with definite velocity. It enables us to simulate homo- and hetero-epitaxial growth process as well as cluster formation process on various substrates. This new MD code has been already applied to study the homoepitaxial growth and Au cluster formation processes on MgO(00l). This article compares such phenomena as growth mode, temperature effect, and influence of surface defects in the homoepitaxial growth and Au cluster formation processes on the MgO(001), based on previous results. The continuous deposition process of MgO molecules was simulated. A 2-D smooth MgO layer without any defects was formed at 1,000 K, which was not realized at 300 K. High temperature is favorable for the complete layer-by-layer homoepitaxial growth. The deposition process of Au atoms on the Mg(001) differed significantly from that of MgO molecules. A 3-D hemispherical Au cluster was constructed on the MgO(001) and low temperature was found to be desired for the fabrication of highly active supported Au catalysts. The origin of the different growth mode and the different temperature effect in the homo-epitaxial growth and Au cluster formation on the MgO(001) was clarified.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431323
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  • 196
    Digitale Medien
    Digitale Medien
    Intrazeolite nanocomposite catalysts: Co-Mo Sulfides for Hydrodesulfurization (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2809-2819 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: It was, for the first time, demonstrated by means of FTIR, EXAFS, XPS, and XRF techniques that thermally stable Co-Mo binary sulfide clusters were synthesized in NaY zeolite cavities using Co and Mo carbonyls as precursors. The hydrodesulfurization (HDS) and hydrogenation activities of the intrazeolite nanocomposite sulfide clusters were examined as a function of composition. It was found that the highest HDS activity was attained at Co/Mo ≃ 1 (2 Mo/super cage or 12 wt. % Mo) and that the Co sites of the clusters were responsible for the reactions. The composition of the catalytically active intrazeolite Co-Mo sulfide clusters was implied to be Co2Mo2S6. The present intrazeolite nanostructure approach strongly suggested that the Co-Mo binary sulfide formation played a prominent role in the catalytic synergy generation. Metal carbonyl techniques were used in the preparation of intrazeolite Fe-Mo binary sulfides.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431328
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  • 197
    Digitale Medien
    Digitale Medien
    Improved NLO properties through a liquid crystal phase poling (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2827-2831 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Cross-linkable organic NLO chromophore called DRS was chemically incorporated into silica matrices using the sol-gel process. A number of electrically poled DRS/silica matrix systems were studied to elucidate the relaxation of the oriented organic chromophore by following the decay of UV absorption as a function of time and temperatures. The value of the second harmonic coefficient d33 was 47 pm/V for the DRS/silica matrix films (0.4 μm thickness). From the dramatic decrease in the UV absorption after poling at 80°C, it is speculated that the DRS may act as a liquid crystalline mesogenic group and is effectively oriented in poling at the phase (nematic) transition temperature (80°C). This argument was substantiated by investigating the phase behavior of DRS itself using both DSC and a polarized optical microscope. The DRS/silica system contained the ideal matrices to retain the oriented chromophore because of optical clarity, thermal stability and effective poling at the nematic liquid crystalline phase.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431330
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  • 198
    Digitale Medien
    Digitale Medien
    Characterization of sputtered BZT thin films for MCM: Multichip module (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2844-2848 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Ba(Zr, Ti)O3 [BZT] thin films were prepared for potential use as a decoupling capacitor for a multichip module (MCM). The crystal structure of BZT thin films on Pt(100)/MgO(100) and MgO(100) deposited from Ba(Zr0.2Ti0.8)O3 powder targets has a perovskite structure and is strongly (100) oriented. The crystal structure of BZT thin films on Pt(111) coated substrates differ from that of Pt(100)/MgO(100) and MgO(100) substrates. The degree of preferred (100) orientation on Pt(111)/SiO2/Si increased with increasing deposition temperature. We obtained a maximum dielectric constant of 150 at 600°C deposition. The loss tangent, leakage current and temperature dependence of capacitance of these BZT thin films were very small.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431333
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  • 199
    Digitale Medien
    Digitale Medien
    Development of fine-scale piezoelectric composites for transducers (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2849-2856 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Piezoelectric ceramic/polymer composites, also known as piezocomposites, have been developed over the past two decades for electromechanical transducers to be used in both military and civilian applications. Recently, the thrust in these transducers is toward high operating frequencies, requiring fine-scale (〈200-μm ceramic-phase dimension) piezocomposites. Methods for processing these fine-scale piezocomposites are discussed. Current capabilities, as well as strengths and weaknesses of each method, are compared. The fundamentals of medical imaging and the importance of spatial scale in composite performance are reviewed. Several processing methods demonstrated composites with fine-scale ceramic phases (〈50 μm), and others have shown the potential to form composites with a ceramic scale of under 20 μm.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431334
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  • 200
    Digitale Medien
    Digitale Medien
    La-Ni-oxide films, fibers and powders by La(MOE)3-Ni(acac)2 precursors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2874-2877 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The preparation of LaNiO3, La4Ni3O10, La3Ni2O7-δ and La2NiO4 via La-methoxy-ethanolato-Ni(acac)2 precursor was investigated. From these precursors films, fibers and powders were prepared and heat treated to form LaNiO3 at temperatures as low as 750°C with a heating time of 4 h. The formation of La4Ni3O10 and La2NiO4 was complete at 1,000°C, for 4 h, while monophasic La3Ni2O7 required heating to 1,150°C, for 1 h. Pathways yielding various phases were also discussed briefly. The techniques used in this study are TGA, mass-spectroscopy, SEM-EDS, TEM-EDS, powder-XRD, and FT-IR spectroscopy.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431338
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