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  • 1995-1999  (906)
  • 1985-1989
  • 1996  (906)
  • Industrial Chemistry  (438)
  • Chemical Engineering  (437)
  • Genetics
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta diabetologica 33 (1996), S. 257-262 
    ISSN: 1432-5233
    Keywords: Key words NIDDM ; Candidate genes ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta diabetologica 33 (1996), S. 257-262 
    ISSN: 1432-5233
    Keywords: NIDDM ; Candidate genes ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 382-387 
    ISSN: 1432-2242
    Keywords: Genetics ; Blacking resistance ; Brassica napus ; Brassica juncea ; Leptosphaeria maculans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetic control of adult-plant blackleg (Leptosphaeria maculans) resistance in a Brassica napus line (579NO48-109-DG-1589), designated “R13” possessing Brassica juncea-like resistance (JR), was elucidated by the analysis of segregation ratios in F2 and F3 populations from a cross between “R13” and the highly blackleg-susceptible B. napus cultivar “Tower”. The F2 segregration ratios were bimodal, demonstrating that blackleg resistance in “R13” was controlled by major genes. Analysis of the segregation ratios for 13 F3 families indicated that blackleg resistance in these families was controlled by three nuclear genes, which exhibited a complex interaction. Randomly sampled plants of F3 progeny all had the normal diploid somatic chromosome number for B. napus. The similarities between the action of the three genes found in this study with those controlling blackleg resistance in B. juncea is discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 817-826 
    ISSN: 1432-2242
    Keywords: Zea mays ; RFLPs ; Plant breeding ; Genetics ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F2∶3 and F6∶7 recombinant inbred (RI) lines from the same population. One hundred and eighty-six F6∶7 RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F2∶3 lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F2∶3 seem to be dissected into multiple, linked QTL in the F6∶7 generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F6∶7 generation for all traits.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1920
    Keywords: Key words Myotonic dystrophy ; Magnetic resonance imaging ; Brain ; Muscles ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Amplification of an unstable CTG trinucleotide repeat sequence in a protein kinase gene on chromosome 19 has recently been recognised as the molecular basis of myotonic dystrophy (DM), a multisystem disorder with a wide spectrum of muscular and extramuscular manifestations. The CTG expansion of 40 patients was assessed by direct genotype analysis of the white blood cell DNA and correlated with MRI of the brain and muscles, and with functional clinical data. Cerebral pathology on MRI consisted of diffuse atrophy (68 %), subcortical white matter lesions (65 %), wide Virchow-Robin spaces (38 %) and thickening of the skull (35 %). Cerebral atrophy and extent of white matter disease correlated significantly with mental retardation, duration of disease and CTG fragment amplification. MRI of the muscular system showed fatty degeneration of different degrees in neighbouring muscles causing a mosaic pattern of the thigh in 38 % and the calf in 44 %. Muscular changes on MRI were strongly correlated with muscular impairment but less strongly with CTG expansion. Changes on MRI reflect the stage of development of tissue pathology in DM, modified by defect of the DM gene. Pathology on MRI is strongly correlated with functional deficits.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 108 (1996), S. 419-423 
    ISSN: 1432-1939
    Keywords: Barnyard grass ; Seed dormancy ; Geographic variation ; Genetics ; Ecophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1991–1993, we investigated the incidence of seed dormancy in 25 local populations of barnyard grass, Echinochloa crus-galli (L.) P.Beauv., in the western Czech Republic. The percentage of germination after 4 months afterripening of dry seeds at 25°C varied between 0.0 and 83.6%. Although there were significant annual differences in the percentage of germination at some localities, typical proportions of dormant seeds persisted over 3 years at field sites where the seed bank was not disturbed. One-way ANOVA (using data from 14 cultivated or abandoned fields) revealed that 73.0% of variance in seed dormancy incidence could be attributed to the effect of locality (P〈0.001). Incidence of dormancy was not correlated with mother plant stature (dry above-ground biomass, number of tillers, maximal stem height) nor seed mass. There was a significant correlation (r 2=0.403, P〈0.005) between dormancy incidence at natural localities in 1991 and in F1 offspring sown at experimental grounds at Praha-Ruzyně in 1992. The results indicate that heredity is important in maintaining local variation in seed dormancy, probably favoured by the self-pollinating reproduction of barnyard grass.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 74 (1996), S. 515-521 
    ISSN: 1432-1440
    Keywords: Key words Emotionality ; Behaviour ; Genetics ; Animal models ; QTL analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It seems that the genetic basis of common psychiatric diseases such as schizophrenia and manic-depressive psychosis is amenable to the genetic mapping strategies that have been successful in other complex disorders such as diabetes. The next challenge is the genetic dissection of quantitative behavioural traits such as mood, personality and intelligence. Quantitative traits pose new problems for gene cloning experiments. We argue that one way forward is by using animal models. One of the features of quantitative traits is that the DNA sequence variants which are responsible for them are unlikely to be immediately recognizable. In contrast to many qualitative traits where a discrete phenotypic difference is often the consequence of an inactivating mutation, the allelic variation responsible for quantitative traits probably has a more subtle basis. This distinction means that strategies to clone the genetic basis of quantitative behavioural traits will have to rely on functional assays of alleles thought to be important in determining the phenotype. We suggest that an efficient strategy for detecting sequences that give rise to quantitative behavioural traits can be devised in the mouse. The importance and utility of the mouse for quantitative trait analysis make it worthwhile to investigate mouse models of human behaviour; these advantages outweigh the difficulties that arise in attempts to validate the animal models. As an example we review the evidence that validates rodent emotionality as an animal model for susceptibility to human anxiety. We show that there is good evidence that rodent emotionality is a central nervous system state with a genetic basis, and that there are neuropharmacological and neuroanatomical parallels with human anxiety. Furthermore, our own work has shown that the genetic basis of the trait is relatively simple, and that the task of characterizing it at a molecular level is feasible. We expect that future experiments will show us how genetic variation gives rise to quantitative behavioural traits.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 74 (1996), S. 515-521 
    ISSN: 1432-1440
    Keywords: Emotionality ; Behaviour ; Genetics ; Animal models ; QTL analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It seems that the genetic basis of common psychiatric diseases such as schizophrenia and manic-depressive psychosis is amenable to the genetic mapping strategies that have been successful in other complex disorders such as diabetes. The next challenge is the genetic dissection of quantitative behavioural traits such as mood, personality and intelligence. Quantitative traits pose new problems for gene cloning experiments. We argue that one way forward is by using animal models. One of the features of quantitative traits is that the DNA sequence variants which are responsible for them are unlikely to be immediately recognizable. In contrast to many qualitative traits where a discrete phenotypic difference is often the consequence of an inactivating mutation, the allelic variation responsible for quantitative traits probably has a more subtle basis. This distinction means that strategies to clone the genetic basis of quantitative behavioural traits will have to rely on functional assays of alleles thought to be important in determining the phenotype. We suggest that an efficient strategy for detecting sequences that give rise to quantitative behavioural traits can be devised in the mouse. The importance and utility of the mouse for quantitative trait analysis make it worthwhile to investigate mouse models of human behaviour; these advantages outweigh the difficulties that arise in attempts to validate the animal models. As an example we review the evidence that validates rodent emotionality as an animal model for susceptibility to human anxiety. We show that there is good evidence that rodent emotionality is a central nervous system state with a genetic basis, and that there are neuropharmacological and neuroanatomical parallels with human anxiety. Furthermore, our own work has shown that the genetic basis of the trait is relatively simple, and that the task of characterizing it at a molecular level is feasible. We expect that future experiments will show us how genetic variation gives rise to quantitative behavioural traits.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Der Nervenarzt 67 (1996), S. 837-845 
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Migräne ; Genetik ; Familiäre Hemiplegische Migräne ; Linkageanalyse ; Zwillingsstudien ; Assoziationsstudien ; Key words Migraine ; Familial Hemiplegic Migraine ; Genetics ; Linkage analysis ; Twin studies ; Association studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Several historical reports focusing on the heredity of migraine, as well as recent studies on its epidemiology and molecular biology, have revealed evidence for a decisive role of genetic factors in the aetiopathogenesis of familial migraine. Indeed, family studies, segregation analyses and twin studies have shown that genetic factors play an important role in disposition towards migraine but could not explain the entire aetiopathogenesis. The influence of extragenetic factors, however, remains mostly unknown. Recent linkage analyses have provided evidence for genetic heterogeneity. A locus for Familial Hemiplegic Migraine (FHM), the only known type of migraine that follows autosomal-dominant transmission, has been linked to chromosome 19p13 but genetic heterogeneity has also been shown, i. e. different types of migraine could be excluded from this locus. Further investigations should concentrate on identifying the FHM gene on chromosome 19p13, on linkage analyses with markers for different susceptibility genes, and on genomic analyses of highly informative pedigrees. This would lead to further clues to the pathogenesis underlying migraine and, thus, to therapeutic developments.
    Notes: Zusammenfassung Nachdem bereits in historischen Beschreibungen eine genetische Verursachung der Migräne vermutet worden war, haben epidemiologische und molekularbiologische Forschungen in den letzten Jahren differenzierte Ergebnisse über genetische Faktoren in der Ätiopathogenese der familiären Migräne geliefert. Aufgrund von Familien- und Segregationsanalysen und von Zwillingsstudien wird dargestellt, daß genetische Faktoren mit größter Wahrscheinlichkeit eine Rolle in der Pathogenese der typischen Migräne spielen. Inwieweit extragenetische Faktoren auf die Ätiopathogenese der Migräne Einfluß nehmen, ist weitgehend offen. Linkageanalysen haben in jüngster Zeit gezeigt, daß möglicherweise mehrere verschiedene Gene für diese Erkrankung verantwortlich sind. Für die Familiäre Hemiplegische Migräne (FHM), der einzigen Migräneform, für die ein autosomal-dominanter Erbgang nachgewiesen ist, konnte ein Genlocus auf Chromosom 19p13 gefunden werden, gleichzeitig wurde aber auch genetische Heterogenität nachgewiesen. Verschiedene andere Formen der Migräne zeigten keine Linkage zu diesem Locus. Weitere Forschungen sollten neben der Identifizierung des FHM-Gens auch Linkageanalysen für Kandidatengene und Genomanalysen an großen informativen Familien zum Ziel haben. Letztlich werden die Ergebnisse genaueren Einblick in die Pathophysiologie der Migräne liefern und damit therapeutisch relevant sein.
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  • 10
    ISSN: 1433-2965
    Keywords: Bone density ; Femor geometry ; Genetics ; Twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To estimate genetic effects on femoral neck geometry and the distribution of bone mineral within the proximal femur a cross-sectional twin analysis was carried out at a university hospital that compared correlations in these traits in pairs of mono- and dizygo-tic female twins. Monozygotic (MZ, n=51 pairs, age 49.1±9.3 years) and dizygotic (DZ, n=26 pairs, age 45.7±11.3 years) twins were randomly selected from a larger sample of twins previously studied. Measurements of bone mineral density (BMD), femoral neck angles and length, cross-sectional area and moment of interia, the center of mass of the narrowest cross-section of the femoral neck, and BMDs of regions within the femoral neck were made. A summary index of the resistance of the femoral neck to forces experienced in a fall with impact on the greater trochanter (Fall Index, FI) was calculated. MZ pair intraclass correlations (rMZ) were significantly (p〈0.05) different from zero for all bone mass and femoral geometry variables (0.35〈rMZ〈0.82). DZ pair correlations (rDZ) were lower thanrMZ for all variables (0.04〈rDZ〈0.52) except femoral neck length (rDZ=0.38, rMZ=0.36). After adjustment for BMD of the femoral neck,rMZ was significantly greater thanrDZ, yielding high heritability estimates for regional BMDs (0.72〈H 2〈0.78), the center of mass of the femoral neck (H 2=0.70, −0.04 to 1.43 95% CI) and the resistance of the femoral neck to forces experienced in a fall (FI,H 2=0.94, 0.06 to 1.85 95% CI), but not for femoral neck length. Adjustments for age did not alter these findings. It is concluded that there are significant familial influences on the distribution of femoral bone mass and on the calculated structural strength of the proximal femur, but not on femoral neck length. If the assumptions of the twin model are correct, this is evidence for genetic factors influencing these traits.
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  • 11
    ISSN: 1432-0533
    Keywords: Key words Alzheimer’s disease ; Clinicopathological ; correlations ; Early-onset dementia ; Genetics ; Pick’s ; disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 39 (1996), S. 375-382 
    ISSN: 1432-0428
    Keywords: Genetics ; maternally inherited diabetes and deafness ; NIDDM ; IDDM ; mitochondria ; MELAS syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Diabetes mellitus is a common disease with many forms of clinical expression. In addition, the development of diabetic complications is not only dependent on glycaemic control but also on individual factors which may be related to genetic heterogeneity. At present, multiple genetic factors are being recognized as contributing to the development of diabetes or possibly modulating its clinical expression. The purpose of this review is to give an overview of our current knowledge on a subtype of diabetes which is apparently caused by a single mutation in the mitochondrial DNA.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 155 (1996), S. 540-544 
    ISSN: 1432-1076
    Keywords: Key words Amyloidosis ; Arab ; children ; Familial Mediterranean ; fever ; Genetics ; Recurrent ; abdominal pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Over a period of 3 years, 192 children with familial Mediterranean fever were prospectively studied. Of these, 106 (55%) were girls and 86 (45%) were boys. The prevalence was 1 : 2600 children with a gene frequency of 1 : 50. The age at onset ranged between 4 months and 16 years. Of these patients 24% started their illness below the age of 2 years and 88% were symptomatic before the age of 10 years; 82% had recurrent abdominal pain, 43% had pleurisy, 37% had arthritis, 15% had cutaneous manifestations, 12% had splenomegaly and 4% had hepatomegaly. The presenting symptoms were abdominal pain in 51%, unilateral chest pain in 23% and arthritis in 26%. The family history was positive in 62%. Of 12 affected families 19 members had/have renal failure and amyloidosis was confirmed in 7 patients. Conclusion Our data show a high prevalence of familial Mediterranean fever and a high gene frequency in Arab children similar to that reported in Jews and Armenians.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 155 (1996), S. 540-544 
    ISSN: 1432-1076
    Keywords: Amyloidosis ; Arab children ; Familial Mediterranean fever ; Genetics ; Recurrent abdominal pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Over a period of 3 years, 192 children with familial Mediterranean fever were prospectively studied. Of these, 106 (55%) were girls and 86 (45%) were boys. The prevalence was 1∶2600 children with a gene frequency of 1∶50. The age at onset ranged between 4 months and 16 years. Of these patients 24% started their illness below the age of 2 years and 88% were symptomatic before the age of 10 years: 82% had recurrent abdominal pain, 43% had pleurisy, 37% had arthritis, 15% had cutaneous manifestations, 12% had splenomegaly and 4% had hepatomegaly. The presenting symptoms were abdominal pain in 51%, unilateral chest pain in 23% and arthritis in 26%. The family history was positive in 62%. Of 12 affected families 19 members had/have renal failure and amyloidosis was confirmed in 7 patients.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 817-826 
    ISSN: 1432-2242
    Keywords: Key words  Zea mays ; RFLPs ; Plant breeding ; Genetics ; Recombination ; Abbreviations  RFLPs Restriction fragment length polymorphisms ; QTL quantitative trait loci ; RIs recombinant inbreds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F2:3 and F6:7 recombinant inbred (RI) lines from the same population. One hundred and eighty-six F6:7 RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F2:3 lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F2:3 seem to be dissected into multiple, linked QTL in the F6:7 generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F6:7 generation for all traits.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 124 (1996), S. 332-339 
    ISSN: 1432-2072
    Keywords: Nicotine ; Genetics ; Self-administration ; Reinforcement ; Seizures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Inbred mouse strains differ in sensitivity to a first dose of nicotine and in the development of tolerance to nicotine. The experiments reported here used six inbred mouse strains (A, BUB, C3H, C57BL/6, DBA/2, ST/b) that differ in sensitivity to an acute challenge dose of nicotine to determine whether differences in oral self-selection of nicotine exist. Animals were presented with solutions containing nicotine or vehicle (water or 0.2% saccharin) and their daily intake of the two fluids was measured for 4 days starting with a 10 µg/ml nicotine solution. This was followed by sequential 4-day testing with 20, 35, 50, 65, 80, 100, 125, 160, and 200 µg/ml nicotine solutions. The strains differed dramatically in their self-selection of nicotine and in maximal daily dose (mg/kg); the rank order of the strains was C57BL/6〉DBA〉BUB〉A≥C3H≥ST/b for both the tap water and 0.2% saccharin choice experiments. Correlations between nicotine consumption and sensitivity to nicotine, as measured by a battery of behavioral and physiological responses, were also calculated. Strain differences in nicotine intake were highly correlated with senstivity to nicotine-induced seizures. As senstivity to nicotine-in-duced seizures increases, oral self-selection of nicotine decreases. This finding may suggest that this toxic action of nicotine serves to limit intake.
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  • 17
    ISSN: 1530-0358
    Keywords: Colorectal neoplasms ; Genetics ; K-ras ; Gene mutations ; Early diagnosis ; Polymerase chain reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: Best chances of a cure from colorectal cancer are obtained before metastatic spread. Lack of specific tests allowing early diagnosis of the tumor accounts for investigation of gene alterations involved in carcinogenesis by a noninvasive method. In the present study, K-ras codons 12 and 13 mutations were studied in neoplastic cells shed from the bowel into the stool and those contained in the tumor and normal mucosa. Moreover, healthy patients and a few others with precancerous conditions were examined. METHODS: Stool, tumor, and mucosa samples were taken from 25 patients with colorectal adenocarcinoma. Stool and mucosa samples were obtained from 11 healthy patients, and stool, pathologic bowel tissue, and normal mucosa samples were obtained from 3 patients with adenoma (1) or ulcerative colitis (2). Polymerase chain reaction amplification and restriction enzyme analysis were performed. RESULTS: K-ras codon 12 mutations were detected in both tumor and stool samples of 10 cancer patients, and no gene alterations were observed in 14 patients. In one patient with a tumor, a mutation was shown in only the tumor tissue. The agreement rate in tumor and stool analysis was 96 percent. A normal pattern of K-ras codons 12 and 13 was observed in the bowel mucosa. All stool and mucosa samples from healthy patients were not altered in K-ras.Agreement was registered between samples taken from patients with preneoplastic lesions. CONCLUSIONS: These preliminary findings show a high rate of accuracy in the investigation of K-ras alterations in the colorectal cells shed into the feces, suggesting that such an approach could be used to study other gene alterations and, prospectively, to identify early colorectal cancers.
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  • 18
    ISSN: 1437-160X
    Keywords: SLE ; Apoptosis ; bcl-2 gene ; Susceptibility ; Linkage ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by the production of a large number of autoantibodies. It has been postulated that this may be the result of prolonged longevity of auto-reactive B cells due to defective regulation of programmed cell death (apoptosis). The proto-oncogenebcl-2 is involved in the control of apoptosis in immunocompetent cells, and its over-expression is noted in T and B cells from SLE patients. This study examined the genetic linkage between thebcl-2 gene locus and SLE susceptibility using the affected sib-pair method in SLE families. Seventeen caucasian multiplex families were evaluated. A polymorphic microsatellite marker closely linked to thebcl-2 gene on 18g21.3 was used to determine thebcl-2 genotype. We demonstrated that haplotype sharing among the affected sibling pairs was not statistically different from random (P〉0.5). This suggests that thebcl-2 gene locus does not confer a genetic susceptibility to SLE expression.
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  • 19
    ISSN: 1573-0905
    Keywords: Compensation ; Dyslexia ; Environment ; Familial aggregation ; Genetics ; Risk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Education
    Notes: Abstract When one or both parents have a history of developmental reading disorder (RD) in childhood, the risk to their offspring for developing reading problems is substantially increased. However, risk research has usually assumed a stability of reading problems across the lifespan (i.e., if a parent was affected in childhood, he or she remains affected in adulthood). Yet, some individuals with RD in childhood compensate for the disorder as they grow older. Both an environmental and genetic hypothesis would predict that the risk for RD in offspring will vary as a function of parental compensation. This study examined whether risk to offspring was dependent on the parents' successful or unsuccessful compensation for their childhood reading problems. Two large family data sets were analyzed (N=907). Diagnoses with either an age discrepant or IQ discrepant criteria essentially showed that having at least one still affected parent (i.e., RD both as a child and as an adult) put the offspring at a higher risk for RD than having at least one compensated parent (i.e., RD as a child but not as an adult). The lowest risk to an offspring occurred when both parents were never affected (i.e., not RD as a child or as an adult). The implications of these findings are discussed with regard to counseling and early diagnosis of reading problems.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    European archives of psychiatry and clinical neuroscience 246 (1996), S. 175-181 
    ISSN: 1433-8491
    Keywords: Schizophrenia ; Genetics ; Liability ; Vulnerability ; Eye-tracking dysfunction ; Eye movements ; Smooth-pursuit eye movements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is increasing evidence that the genetic predisposition for schizophrenia in families affects more individuals than those fulfilling the criteria for schizophrenia. This finding is supposed to be one of the major problems in molecular genetic schizophrenia research, especially when linkage studies are employed. Eye-tracking dysfunction (ETD), which is conceived as a possible phenotypic marker for genetic liability to schizophrenia, may offer considerable advantages. However, there is only little information from families with multiple occurrence of schizophrenia. It is still unclear whether in these families ETD aggregates with diagnoses from the schizophrenia spectrum. This first report from an ongoing study presents the results of 48 individuals from 6 multiplex families. Smooth-pursuit eye movements were recorded by infrared reflectometry and assessed by quantitative measurement techniques. Along with the high degree of psychiatric morbidity in these families, in 56.3% of the individuals ETD was assessed. Reduced mean pursuit gain was present in 39.6%. The distribution of eye-tracking dysfunction resembles the distribution of schizophrenia-related psychiatry morbidity.
    Type of Medium: Electronic Resource
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 267-272 
    ISSN: 1432-2242
    Keywords: Cerrado ; Savannah ; Acid soils ; Hydroponics ; Nutrient ; Variety ; Genetics ; Inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The soybean is a major crop in the agricultural systems of the Brazilian Cerrados (Savannahs), whose soils are acidic, devoid of nutrients and need to be amended before they are cultivated. However, below the ploughed layer there is a scarcity of nutrients and toxic aluminium (Al). These limit root growth, subsequently causing nutritional imbalance and drought stress. Our aim in the investigation described here was to identify genetic differences in the aluminium tolerance of soybeans by a 9 × 9 diallel cross among contrasting varieties grown in high-Al areas and in hydroponics. Combining ability analysis indicated predominantly additive gene effects, and the additive-dominance model explained most of the genetic differences in this germ plasm for mineral element absorption and root growth under aluminium stress. The relationship between the two factors suggest that conjugation hydroponics and field evaluations in breeding programmes would further improve soybeans with respect to yield stability under tropical cultivation conditions.
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 93 (1996), S. 301-306 
    ISSN: 1432-2242
    Keywords: Leptosphaeria maculans ; Brassica napus ; Blackleg ; Genetics ; Virulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetic basis of virulence of 24 isolates of L. maculans collected from various sites throughout south-eastern and south-western Australia were studied using five clone-lines of B. napus. The experimental design allowed the estimation of the environmental and genetic components of variance using a standard analysis of variance. Virulence of these isolates (as measured by the percentage of stem girdling, %G) on the clonelines NCII and Tap was found to be most likely controlled by a small number of genes; the broad-sense heritabilities were 79.7% and 67.5% for virulence on NCII and Tap, respectively. The significance of these results in relation to the potential of L. maculans in adapting to new resistant B. napus cultivars is discussed.
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  • 23
    ISSN: 1432-2242
    Keywords: Extreme virus resistance ; Potyviruses ; Genetics ; Genes Ry and Ra ; New gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extreme resistance in cultivated potato (Solanum tuberosum) to potato viruses Y and A (PVY and PVA) conditioned by the presence of Ry genes introduced from Solanum stoloniferum was described by Cockerham (1970). Cockerham detailed a number of genes which controlled a variety of reactions, including extreme resistance to both viruses (i.e. little or no visible reaction of plants and no viral replication following graft and manual inoculation) controlled by gene Ry sto. In the present study, cvs ‘Pirola’ and ‘Barbara’, which contain a Ry gene, were found to have extreme resistance to PVY isolates from the ordinary (PVY°), veinal necrosis (PVYN) and potato tuber necrotic ringspot (PVYNTN) subgroups, and PVA. The inheritance of this phenotype was examined in seedling progenies obtained by crossing ‘Barbara’ and ‘Pirola’ with susceptible cultivars. Segregation data for resistance to PVY and PVA in a progeny involving cv ‘Pirola’ best fitted a genetical model of one gene controlling extreme resistance to both PVY and PVA, although the possibility that there are two genes, each controlling resistance to one virus but closely linked, cannot be excluded. Segregation data from progenies involving cv ‘Barbara’ best fitted a genetical model in which there are two independent genes, one controlling extreme resistance to PVA and PVY and a second gene controlling extreme resistance to PVA but not to PVY. This previously unrecognised gene conferring extreme resistance to PVA only, should be given the notation Ra in keeping with nomenclature used for other resistance genes.
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  • 24
    ISSN: 1432-2242
    Keywords: Aluminum toxicity ; Diallel analysis ; Genetics ; Rice ; Variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was undertaken to investigate the variability among lowland rice cultivars and the mode of gene action of aluminum (Al) toxicity tolerance in rice. Pregerminated seeds were grown in a nutrient solution containing 30 ppm Al and in normal nutrient solution, and relative root length (RRL) was determined at the 14-day-old stage to characterize genotypes for tolerance. Sixty-two traditional rice cultivars grown on lowland acid sulfate soil areas of Asia and West Africa were tested. Tolerant varieties ‘Azucena’, ‘IRAT104’, and ‘Moroberekan’, moderately sensitive ‘IR29’ and ‘IR43’, and sensitive ‘IR45’ and ‘IR1552’ were used to investigate the genetics of tolerance by diallel analysis. Of the 62 cultivars tested, only 3 were found to be sensitive to A l toxicity. Among the tolerant cultivars identified, 11 (‘Siyam Kuning’, ‘Gudabang Putih’, ‘Siyam’, ‘Lemo’, ‘Khao Daeng’, ‘Siyamhalus’, ‘Bjm-12’, ‘Ketan’, ‘Seribu Gantang’, ‘Bayer Raden Rati’, and ‘Padi Kanji’) were found to possess higher levels of tolerance than the improved tolerant upland cultivar ‘IRAT104’. Diallel analysis revealed that high RRL is governed by both additive and dominance effects with a preponderance of additive effects. The trait exhibited partial dominance, and one group of genes was detected. Heritability was high, and environmenal effects were low. Findings suggest that when breeding for A1 toxicity tolerance, selection can be made in early generations. The pedigree method of breeding would be suitable. Combining ability analysis revealed the importance of both general combining ability (GCA) and specific combining ability (SCA) in the genetics of A1 toxicity tolerance in rice. GCA was more prevalent than SCA. Tolerant parens ‘Azucena’, ‘IRAT104’, and ‘Moroberekan’ were the best general combiners. The presence of reciprocal effects among crosses suggested the proper choice of parents in hybridization programs. Results indicated that ‘Azucena’, ‘IRAT 104’, and ‘Moroberekan’ should be used as the female in crosses for A1 toxicity tolerance.
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  • 25
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    Springer
    Theoretical and applied genetics 93 (1996), S. 932-940 
    ISSN: 1432-2242
    Keywords: Genetics ; Adult-plant ; Blackleg resistance ; Brassica napus ; Leptosphaeria maculans ; Australian cultivar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetic control of adult-plant blackleg [Leptosphaeria maculans (Desm.) Ces. et De Not.] resistance in rapeseed (Brassica napus L.) was studied in the F2 and first-backcross populations of the cross “Maluka” (blackleg-resistant) x “Niklas” (highly susceptible). A L. maculans isolate possessing high levels of host specificity (MB2) was used in all inoculations. Resistance/susceptibility was evaluated using three separate measures of crown-canker size, i.e. the percentage of crown girdled (%G), external lesion length (E) and internal lesion area (%II). Disease severity scores for the F2 and first-backcross populations based on E and %II gave discontinuous distributions, indicating major-gene control for these measures of resistance; but those for %G were continuous, indicating quantitative genetic control for this measure. Chi-square tests performed on the (poorly-defined) resistance classes, based on E, in the F2 and first-backcross populations indicated the likelihood for resistance being governed by a single, incompletely dominant major gene. Although the distributions of the F2 and first-backcross populations, based on%II, were clearly discontinuous, the observed segregation ratios for resistance and susceptibility did not fit any of the numerous Mendelian ratios which were considered. Differences in inheritance of resistance according to the assessment method and blackleg isolate used, were discussed.
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  • 26
    ISSN: 1573-0905
    Keywords: Differential diagnosis ; Etiology ; Genetics ; Mathematics performance ; Reading disability ; Twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Education
    Notes: Abstract In order to assess the etiology of reading disability as a function of mathematics performance, data from 168 monozygotic (MZ) and 127 same-sex dizygotic (DZ) twin pairs in which at least one member of each pair was reading-disabled were subjected to quantitative genetic analyses. MZ and DZ concordance rates for reading disability were computed for different levels of mathematics performance, and reading performance data were fitted to an extension of the basic multiple regression model for the analysis of selected twin data. Results of these analyses suggest that genetic factors may be especially salient as a cause of reading disability in children with borderline deficits in mathematics performance: thus, mathematics performance may be a valid dimension for diagnosing subtypes of reading disability.
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  • 27
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    AIChE Journal 42 (1996), S. 538-546 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nuclear magnetic resonance (NMR) spin-lattice relaxation measurements are used to investigate pore structures and fluid phase distributions in porous media. A new method for estimating relaxation time distribution functions from measured relaxation data is presented using a B-spline basis to represent the distribution function and Tikhonov regularization to stabilize the estimation problem. Surface relaxivity, which is required to convert relaxation time distributions to pore-size distributions of fluid phase distributions at partial saturations, is determined using pore volume-to-surface-area ratios estimated by NMR diffusion measurements. This approach was validated by analyzing certain model porous media with known pore volume-to-surface-area ratios. The method is demonstrated by determining pore-size and fluid phase distributions of sandstone and carbonate samples, as well as by comparing the pore-size distributions of chalk samples obtained by this methodology with those estimated by mercury porosimetry.
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  • 28
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    AIChE Journal 42 (1996), S. 547-561 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Emulsion liquid membrane separation processes remain excessively vulnerable to one or more of four major problems. Difficulties lie in developing liquid membranes that combine high levels of both stability and permeability with acceptably low levels of swelling and ease of subsequent demulsification for membrane and solute recovery. This article provides a new technique for simultaneously overcoming the first three problems, while identifying physical indications that the proposed solution may have little adverse effect on the fourth problem (demulsification) and may even alleviate it. Numerous benefits of optimized conversion of the membrane phase into suitable non-Newtonian form are identified, their mechanisms outlined, and experimental verifications provided. These include increased stability, retained (or enhanced) permeability, reduced swelling, increased internal phase volume, and increased stirrer speeds. The highly favorable responsiveness of both aliphatic and aromatic membranes to the new technique is demonstrated.
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  • 29
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 30
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    AIChE Journal 42 (1996), S. 585-594 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comprehensive equation of state was developed to represent the phase equilibria and volumetric properties of aqueous calcium chloride solutions at temperatures above 523 K. The equation consists of a reference part and a perturbation contribution. The reference function is developed from the statistical mechanical theory for mixtures of dipolar and quadrupolar hard spheres, which agrees well with the Monte Carlo simulation results. In this treatment, calcium chloride is described by the completely undissociated model. The empirical perturbation function is a truncated series of virial expansion terms. Thus, mixing rules are guided by those of virial coefficients, which are derived rigorously from statistical mechanics. The equation reproduces experimental saturated vapor pressures and volumetric data within experimental uncertainty for temperatures to 623 K. At higher temperatures, few and less accurate experimental data are available, but values of the saturated vapor pressures of the liquid have been reported and are represented satisfactorily.
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  • 31
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    AIChE Journal 42 (1996), S. 601-612 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A previously developed mathematical wetting model is generalized and applied to the following two closely related situations: the spreading of a liquid over a prewet solid surface and the receding contact-line motion with a microscopic residual film, remaining behind the contact line. An analytical expression for the velocity dependence of the dynamic contact angle is derived. Macroscopic characteristics (the dynamic contact angle and drag force) and the flow field corresponding to the spreading of a liquid over a wet solid surface differ considerably from those calculated for a dry surface. Under certain conditions the flow in the reference frame fixed with respect to the contact line has a region with closed streamlines. The region appears due to the flow-induced Marangoni effect, the reverse influence of the surface tension gradient along the liquid-solid interface caused by the flow on the flow, which gives rise to the gradient. The results are compared qualitatively with experimental data.
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  • 32
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    AIChE Journal 42 (1996), S. 638-648 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The full Navier-Stokes equations were employed with a single-fluid model and a front tracking scheme to study a large cylindrical bubble in a free shear layer. A general formulation based on work by Auton et al. of the hydrodynamic forces on a finite Reynolds number large bubble in an unsteady, nonuniform and rotational flow was then used to investigate the effects of nonlinear spatial and temporal gradients on dispersion. The resulting bubble dispersion in the full Navier-Stokes solution significantly differ from that by a conventional bubble dynamic equation based on linear spatial gradients and quasi-steady flow. This was due to the adjunct forces not accounted for by such a formulation, which are related to regions of high nonuniformity and unsteadiness. These adjunct forces in the drag/lift direction were correlated with rapid variations of relative bubble velocity and high gradients of the liquid velocity.
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  • 33
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    AIChE Journal 42 (1996), S. 623-637 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The evolution of a film with insoluble surfactant on a wavy horizontal wall differs from flow without surfactant (the way it usually is studied) in that the film passes through different stages. The first stage is as if the surfactant were absent. Once the surface tension gradient - induced by the nonuniform surfactant concentration adsorbed at the free surface - starts resisting the flow effectively, the evolution enters a transitional stage. A final stage is reached once the free surface becomes rigid due to the surface-tension gradient (high elasticity limit) or becomes virtually leveled before the surface-tension gradient is released (low elasticity limit). The velocity profile through the film changes with time, sol fluid is depleted or accumulated at different strata in the film as the flow evolves. The velocity profile and resulting deformations throughout the film can be influenced significantly by the viscosity distribution or stratification, which occurs, for example, when multiple layers of different viscosity are coated simultaneously. A model and applications for the leveling of such a film are presented. The evolution is described in general terms for a film of uniform viscosity and for a film of two discrete layers of different viscosity. Then the three limiting cases are established. For two of these limits, the effect on the exponential decay rate of the flow and the deformation of the different strata or layers is examined when the viscosity is changed in an infinitesimally thin layer or stratum, and in a layer of finite thickness in films of two and three discrete layers.
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  • 34
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    AIChE Journal 42 (1996), S. 809-819 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general theory for the adsorption of self-associating molecules in microporous structures is developed. The approach is similar to the “chemical” interpretation of nonideality of vapor and liquid phases. The theory displays Type 5 isotherm behavior and can explain Types 1 and 5 transition. Isothermal data are represented by only three parameters: Henry's law constant, saturation capacity, and reaction constant for “cluster” formation in the micropores. When isotherms at different temperatures are available, the theory can be used with five temperature-independent parameters to describe the entire phase behavior including the heat of adsorption. Water adsorption on activated carbon, the most common display of Type 5 behavior, is used to test the theory. Analysis of several data sets indicates that the theory can closely correlate data, provide physically meaningful parameter values in line with carbon properties, and it is highly effective in correlating temperature variation. The reaction enthalpy for water dimerization in the carbon micropores is lower than that in vapor phase. This preliminary conclusion with the theory needs to be supported with more accurate data when available.
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  • 35
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    AIChE Journal 42 (1996), S. 820-828 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The new application of nuclear magnetic resonance imaging (MRI) techniques for characterizing fractures and flow in fractured media is investigated. Specifically, a relaxation-weighted imaging technique is used for selectively highlighting either fracture or porous matrix regions. Many advantages over conventional spin-density MRI techniques for characterizing fractured media are demonstrated. Its use to speed image acquisition is also demonstrated. In addition, a multislice profile imaging technique is used to investigate imbibition and drainage displacement experiments in fractured porous media. These images demonstrate that the fractures can have profound effects on the fluid distributions in multiphase flow.
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  • 36
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    AIChE Journal 42 (1996), S. 829-836 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many living organisms store iron in solid form, Fe(III), as a crystal in the inner cavity of the ferritin molecule. When iron is needed for biosynthesis, a reducing agent reduces Fe(III) into the soluble form Fe2+ released by ferritin. Crystallization and release processes are reversible, and their rates evolve in an identical way as a function of the number n of iron atoms in the molecule. The rate increases with n, showing a maximum value when n is approximately 1,300, and then stabilizes for the highest values of n, which can reach 4,500. On the other hand, plotting the amount of released iron as a function of time gives curves with a sigmoid shape. The proposed model was based on the theoretical description of different steps involved in crystal growth inside the protein shell: several independent crystals grow freely at the inner protein wall, and then a distribution function takes into account possible overlapping of different crystallite clusters, whose further growth is limited by diminution of the available space inside the cavity. The kinetics derived was then used to calculate the release curve as a function of time. Solving the system of differential mass-balance equations was simplified by describing the ferritin population as a large discrete distribution of species. The model fully fitted and explained the variation in the crystallization rate with n, and the sigmoid shape of the release curve as a function of time obtained experimentally in a thin-layer electrochemical cell.
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  • 37
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    AIChE Journal 42 (1996), S. 837-849 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new group-contribution lattice-fluid equation of state (GCLF-EOS), which is capable of predicting the equilibrium properties of polymer-solvent solutions, was developed by modifying the original GCLF-EOS of High and Danner. The GCLF-EOS is a group-contribution form of the Panayiotou-Vera equation of state based on the lattice-hole theory. Group contributions for the interaction energy and reference volume were developed based only on the saturated vapor pressure and liquid densities of low molecular weight compounds. For a mixture, a binary interaction parameter was introduced into the mixing rules. Group contributions for the binary interaction parameter were developed from the binary vapor-liquid equilibria of low molecular weight compounds. This modified GCLF-EOS model gives excellent predictions of solvent activity coefficients both at infinite dilution and at finite concentrations. It is significantly better than the original GCLF-EOS model in its prediction capability. The only input required for the model is the structure of the molecules in terms of their functional groups. No other pure component or mixture properties of the polymer or solvent are needed.
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  • 38
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    AIChE Journal 42 (1996), S. 249-258 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ion-selective electrodes were used to measure the activity coefficients at 298.2 K of individual ions in aqueous solutions of NaCl and NaBr up to of 5 molal and of KCl up to 4 molal. The mean ionic activity coefficients of NaCl, NaBr, and KCl, obtained from the values of the activity coefficients of the individual ions, show good agreement with values reported in the literature. The experimental results show that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte and that, as expected from the ion-ion and ion-solvent interactions, the activity coefficient of an ion depends on the nature of its counterion. A modified form of the Pitzer's model, which distinguishes between the activity coefficients of the anion and the cation, was used to correlate the experimental results.
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  • 39
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    AIChE Journal 42 (1996), S. 850-860 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cartilage constructs were grown using isolated chondrocytes and biodegradable polymer scaffolds made of fibrous polyglycolic acid in the form of 1-cm-dia × 5-mm-thick discs. The scaffolds were seeded in a mixed cell suspension and cultured for up to 8 weeks under static or mixed tissue culture conditions in petri dishes and spinner flasks. Turbulent mixing significantly improved the biochemical compositions and altered morphologies of the cartilage constructs, which were the thickest ones cultured to date in vitro. Constructs from mixed cultures were more regular in shape and contained up to 70% more cells, 60% more sulfated glycosaminoglycan, and 125% more total collagen when compared to constructs from static cultures. Mixing also induced the formation of an outer capsule with multiple layers of elongated cells and collagen fibrils around the inner tissue phase, while statically grown constructs consisted of round cells embedded in cartilaginous matrix. Mixing during cell seeding and tissue culture is thus an important parameter for the cultivation of tissue-engineered cartilage in a range of sizes, shapes and compositions for a variety of clinical applications (e.g., fibrous cartilage for reconstructive surgery or articular cartilage for joint resurfacing).
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  • 40
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    AIChE Journal 42 (1996), S. 876-883 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A solid-state carbon monoxide sensor was fabricated using a 9% yttria-stabilized zirconia (YSZ) disc sandwiched between two platinum thin-film electrodes. One of the electrodes was coated with a thin layer of 7 CuO · 10 ZnO · 3 Al2O3 catalyst. The sensor showed limiting current behavior at an applied voltage between 0.5 and 1.2 V. Linear response was observed with carbon monoxide in a nitrogen-oxygen mixture at high temperature and limiting current conditions. The linear carbon monoxide concentration range increased with increase in the operating temperature and its sensitivity increased from 2.437 mA · atm-1 CO at 1,023 K to 10.771 at 1,093 K. These characteristics were adequately described by the proposed mathematical model relating the response to the rate processes occurring in the catalyst layer and in the electrochemical cell under limiting current conditions. The model showed that effective sensing and high sensitivity are best obtained using a catalyst with high catalytic activity toward the test solute and proper design and fabrication of the sensor to ensure its high diffusivity in the catalyst.
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  • 41
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    AIChE Journal 42 (1996), S. 889-891 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 42
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    AIChE Journal 42 (1996), S. 892-895 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 43
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    AIChE Journal 42 (1996), S. 884-888 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 44
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    AIChE Journal 42 (1996), S. 896-900 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 45
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    AIChE Journal 42 (1996) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 46
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    AIChE Journal 42 (1996), S. 910-920 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New data on the variation of the diffusion coefficient with concentration in binary nonideal liquid mixtures are presented. The diffusion coefficients were measured with laser holography with an improved analysis procedure and are primarily in systems that form two liquid phases. The results show that for such systems the diffusion coefficient is constant if a chemical-potential driving force is used. If, however, the miscibility gap is wide, the Schreiner equation (Schreiner, 1922) is shown to be more accurate than relations that consider the variation of viscosity. Cluster theories developed for diffusion behavior near critical points were found to explain the data well only in water-organic systems on the water-rich side.
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  • 47
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    AIChE Journal 42 (1996), S. 277-284 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 48
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    AIChE Journal 42 (1996), S. 285-289 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 49
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    AIChE Journal 42 (1996), S. 1041-1068 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The study of spatial structures in heterogeneous reactors is a challenging academic topic, revealing patterns that differ from those known to exist in reaction-diffusion systems exposed to uniform conditions, as well as a practical problem that should affect design and operation procedures of commercial reactors like the catalytic convertor. Experimental observations and mathematical models of spatiotemporal patterns in high-pressure catalytic reactors are reviewed. Patterns in high-pressure reactors, in which thermal effects provide the positive feedback, as well as the long-range communication, usually emerge due to global interaction. Patterns are classified comprehensively by considering reactors of increasing degree of complexity: a wire or ribbon exposed to uniform conditions, a globally coupled catalyst in a mixed reactor or in a control loop, and a fixed bed in which interaction by convection occurs only in one direction. Catalytic wires are not expected to exhibit sustained patterns in the absence of global interaction. Global interactions by external control or gas-phase coupling are shown experimentally and analytically to induce a rich plethora of patterns. Complex motions were simulated to occur due to the interaction of convection, conduction and reaction in a fixed-bed; only a few of these patterns were experimentally observed. Directions for future research are suggested.
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    AIChE Journal 42 (1996), S. 1088-1094 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ignited state is associated with a thin reaction zone and a steep temperature gradient ahead of the front. The stability of this front is analyzed for small radial and azimuthal perturbations. The near-equidiffusional assumption is made, and the deviation of the Lewis number from unity is considered as the bifurcation parameter. The analysis shows that the planar front becomes unstable at Lewis numbers above unity after a Hopf bifurcation. The oscillatory front collapses into hot spots or rings which oscillate around the axial axis. For Lewis numbers less than one, a steady-state cellular front structure is found.
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  • 51
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    AIChE Journal 42 (1996), S. 1095-1100 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel reactor for the modification of a porous hollow-fiber membrane up to 1 m in length is presented. The polyethylene hollow fiber irradiated with an electron beam was exposed to the vapor of an epoxy-group-containing vinyl monomer (glycidyl methacrylate) in a cylindrical reactor rotated at 1 rpm. Construction of the hollow fibers resulted in a diffusion-controlled reaction system, which led to the nonuniformity of degree of grafting (dg), whereas the shuffling of the hollow fibers by rotating the cylindrical reactor provided a higher reactivity (dg = 110% for 100 min at 300 K) and uniformity (standard deviation = 4.5%) of dg.
    Additional Material: 7 Ill.
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  • 52
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    AIChE Journal 42 (1996), S. 359-368 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model of simultaneous heat and mass transfer presented describes drying with internal heat generation. Since a liquid expulsion phase is observed, a numerical procedure was developed to account for saturated and unsaturated zones and to model the liquid expulsion. The model was validated by a drainage experiment. An experimental rig was built to conduct microwave drying experiments in well-controlled conditions using capillary porous body (light concrete) as test material. Two types of drying (high and low power) were distinguished, depending on whether or not boiling occurred in the sample. The heat source term in the medium was determined from the experimental results. The numerical results agree with the experimental observations in terms of drying kinetics and transfer mechanisms. This allows a very accurate description of the transport phenomena and the liquid expulsion phase associated with high-power drying.
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  • 53
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    AIChE Journal 42 (1996), S. 1116-1126 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Helmholtz energy F is written as the sum F = FH + FA + FPol, where FH is the hard-body contribution, FA the attractive dispersion force contribution, and FPol either the quadrupolar or dipolar contribution. Here, a new expression for FA is constructed by a simultaneous correlation of experimental data of methane, oxygen, and ethane. The resulting equations for F with only three or four substance-specific parameters are tested for several nonpolar, quadrupolar, and dipolar fluids. In the correlation of large data sets good results are obtained. The significance of the approach, however, is in the good to excellent prediction of all thermodynamic properties in the whole fluid region based on a parameter fit to only four experimental data - two vapor pressures and two saturated liquid densities.
    Additional Material: 8 Ill.
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  • 54
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    AIChE Journal 42 (1996), S. 1108-1115 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A lab-scale nonflowing reactor was built to study chemical vapor deposition reactions. Mass spectrometry is used to follow reaction pathways and to determine instantaneous reaction rates throughout film growth. In each experiment, the kinetic rate dependence on concentration for a wide range of concentrations is observed as reactants convert to products. This method of obtaining kinetic data is efficient in terms of sample loading, gas usage, and time, since over 200 instantaneous rate/composition pairs can be determined from one 30-min deposition. Because the rate is determined from gas-mass balance, rather than film-thickness measurements, an unlimited number of rate studies can be made on one sample. As a test case, the SiH4 reduction of WF6, used to deposit tungsten during integrated-circuit production, was investigated in the 0.64-L nonflowing laboratory reactor. Gas compositions were measured 2 mm from the growing surface, throughout time, with a mass spectrometer equipped with a capillary sampling tube. Tungsten was deposited on the 95°C surface, and SiHF3 was the primary silicon fluoride reaction product for most tested conditions. A multiple-regression analysis of 1,975 instantaneous composition/rate pairs gives orders of 1.22 in silane, 0.27 in hydrogen, and -2.17 in WF6. The ratio of SiF4 to SiHF3 stays low and constant until the gas becomes silane-rich. The evolution of the instantaneous rate over time implies that a minimal level of thermal activation of the reactive gases is necessary for the deposition to be surface-rate-limited. Preliminary heat-transfer models of the wire substrate imply that heat transfer to the gas phase is in the Knudsen regime.
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  • 55
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    AIChE Journal 42 (1996), S. 1139-1148 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The behavior of a reverse-flow reactor was studied for the purification of polluted air by catalytic combustion. A heterogeneous one-dimensional model was extended with a heat balance for the reactor wall. An overall heat transport term is included to account for the small heat losses in radial direction.The calculations are compared to experimental data without using fit parameters. The agreement between simulations and experiments is generally good. Discrepancies can be explained mainly by inaccurate kinetic data and experimental uncertainties. At low gas velocities and for small reactor diameters, the one-dimensional model failed and a two-dimensional model must be developed to improve the predictive potential.
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  • 56
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    AIChE Journal 42 (1996), S. 1149-1152 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No Abstarct.
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  • 57
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    AIChE Journal 42 (1996), S. 1127-1138 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dynamic projections from the surface of many motile cell types provide for variable contact with the extracellular environment and can be important in regulating cell migration events. For example, during nerve development and regeneration, the sensory motile tip of the axon exhibits long, slender filopodia projecting from the growth cone periphery. Extension and retraction of these filopodia continually remodel the points of contact between axon and surroundings. Experimental studies show that filopodial contact with specific extracellular features can guide subsequent growth cone migration, suggesting a potentially important means of engineering nerve growth to repair nerve injury or construct biological neural networks. A simulation model is presented of the dynamic filopodial structure on the nerve growth cone based on recent experimental characterization. The model is analyzed to obtain quantitative relationships between average filopodial characteristics, which are commonly measured experimental quantities, and the underlying parameters of individual filopodium dynamics. It is then applied to simulate encounter between a growth cone and its target due to filopodial dynamics alone. Filopodial contribution to growth cone-target encounter is summarized in terms of a mean encounter time that is reminiscent of a first passage time for a diffusing particle. The parametric relationships in this study provide a basis for further investigation of filopodial-mediated mechanisms in nerve growth and other cellular processes.
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  • 58
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    AIChE Journal 42 (1996), S. 1153-1156 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 59
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    AIChE Journal 42 (1996), S. 1157-1163 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 60
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    AIChE Journal 42 (1996), S. 1170-1173 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 61
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    AIChE Journal 42 (1996), S. 1033-1040 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Necessary and sufficient conditions for the robust stability and performance of the Smith-predictor controller, modeled under a norm-bounded uncertainty, are given in a general formulation. In addition, a practical stability condition is obtained as a special corollary of the main results. These conditions provide useful and practical guidelines for the development of a systematic robust design method. In particular, an application is developed for the robust control of first-order deadtime systems with simultaneous uncertainties in all three parameters of the model. A simulation example and the results of a case study on the robust level control of a coupled-tanks apparatus are provided for illustration.
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  • 62
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    AIChE Journal 42 (1996), S. 1181-1186 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 8 Ill.
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  • 63
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    AIChE Journal 42 (1996), S. 1187-1190 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 64
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    AIChE Journal 42 (1996), S. 2540-2554 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For multiinput-multioutput nonlinear plants whose state-feedback control problem is solvable with complete or partial output linearization, the output-feedback problem is addressed by combining the state-feedback controller with a suitable closed-loop state inferer (detector). A candidate closed-loop detector was built to study the stability of the resulting plant-controller interconnection. As a result, sufficient conditions for closed-loop asymptotic nominal stability, as well as a systematic and simple design-tuning procedure, are obtained. The stabilization of an open-loop, unstable, free-radical homopolymerization reactor was studied as an application example.
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  • 65
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    AIChE Journal 42 (1996), S. 2627-2634 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comprehensive experimental study of gas holdup in bubble columns of varying diameters, fitted with different distributor types, using several liquids is presented. Air was used as the gas phase. Experiments to test the influence of gas density were also carried out with He, Ar, and SF6. A generalization of the two-phase model for gas-solid fluidized beds was used to interpret the experimental data where the “dilute” phase is identified with the “large” bubble population and the “dense” phase with the liquid phase where the “small” bubble population is entrained. Gas holdups in dilute and dense phases were determined from dynamic gas disengagement experiments.In the churn-turbulent regime of operation, voidage of the gas in the dense phase was independent of the superficial gas velocity. Reilly et al.'s correlations for the gas holdup and superficial gas velocity at the regime transition point estimate the gas voidage of the dense phase and the superficial gas velocity well through this phase. Corresponding correlations of Wilkinson et al. significantly underpredict dense-phase parameters. The experiment showed that the dilute phase or large bubble holdup in bubble columns, operating at superficial gas velocities 〉 0.1 m/s, is independent of liquid properties, how the gas is distributed and the density of the gas phase. But it is affected significantly by the column diameter. Relying on hydrodynamic analogies with a gas-solid-fluid bed, a simple correlation was developed that is considerably more accurate than the Wilkinson correlation that significantly overpredicts large bubble holdup.
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  • 66
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    AIChE Journal 42 (1996), S. 2654-2660 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The coalescence of isotropic etch pits observed in the dissolution of semiconductor substrates is studied using a discrete model for the evolution of the surface under reaction-rate-limited conditions. The model discretizes the solid into cubic elements and repetitively applies dissolution rules to the individual elements. The rate of mass removal is based on the number and arrangement of the element's exposed faces and the specified reaction-rate parameters. Detailed knowledge of the surface normal is not required. The model shows that even at moderate etch pit densities, the effects of the coalescence do not significantly alter the trends observed for noncoalescing etch pits.
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  • 67
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    AIChE Journal 42 (1996), S. 2687-2691 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 68
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    AIChE Journal 42 (1996), S. 2683-2686 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 69
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    AIChE Journal 42 (1996), S. 2698-2698 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 70
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    AIChE Journal 42 (1996), S. 2926-2940 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of turbulent mixing in the reaction zone of a tubular low-density polyethylene reactor was studied by combining a Lagrangian composition probability density function (LCPDF) code with a computational fluid-dynamics code. Because the LCPDF code can treat the chemical reaction terms in a turbulent flow without resorting to moment closures, it is used to describe the temperature and scalar fields of reactants including initiator and monomer molar concentrations, and the moments of the molecular weight distribution. The chemical reaction terms are efficiently dealt with using a three-parameter chemical lookup table that contains the temperature and composition changes as functions of initiator and monomer concentrations and temperature over a small time step. The reaction-rate constants from the study of Lee and Marano (1979) are functions of temperature and pressure. The flow fields are obtained using the k - ε turbulence model. Because the temporal and spatial evolution of all fields in the reactor can be simulated, it is possible to study the effect of the initiator injection location, flow rate and temperature of the monomer and initiator feed streams on polymerization in considerable detail. Moreover, by observing the probability distribution of the composition fields, a better understanding of hot-spot formation is achieved, leading to improved reactor designs.
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  • 71
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    AIChE Journal 42 (1996), S. 1621-1626 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow visualization of flowing particles around a tube of various types of tube arrangements in a moving bed was studied using X-ray video films to obtain a relation between particles behavior and local heat-transfer coefficients. A stagnant part of solid particles was observed on the tube in the case of a staggered arrangement. This part did not appear in the case of the single tube and the single row of tubes. The measured local heat-transfer coefficients around a tube was decreased in this stagnant part. Furthermore, influences of different tube arrangements both on flow patterns of particles and on local heat-transfer coefficients between tubes and bed were examined.
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  • 72
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    AIChE Journal 42 (1996), S. 1600-1611 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method for generating theoretical breakage distribution functions for multiple particle breakage is presented. It starts with the joint probability function that accounts for all the child particles; it is then reduced to the marginal probability function commonly used in the breakage equation. This method is flexible enough to allow the user to choose the number of child particles and the functional form to be used. The method is demonstrated with both product and summation functions with a power-law form. To facilitate the use of these theoretical functions for statistical analyses, a companion discretized breakage equation is developed. The new equation guarantees the conservation of mass and correct prediction of the total number of particles despite discretization. It is easy to use because it is a set of ordinary differential equations and applicable to both equal-size and geometric-size intervals. Simulation results show that different breakage distribution functions coupled with different breakage rates can produce almost indistinguishable particle-size distributions, signifying the need for further work in this area.
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  • 73
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    AIChE Journal 42 (1996), S. 1612-1620 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A population balance model presented describes simultaneous coagulation and fragmentation during shear-induced flocculation. Given sufficient time, a floc-size distribution reaches steady state that reflects the balance between coagulation and fragmentation. The model agrees with experimental data for the evolution of the average floc size. Higher shear shifts the steady-state size distribution to smaller sizes. When the steady-state size distributions obtained at various shear rates are scaled with the average floc size, however, they collapse onto a single line. This indicates that the steady-state floc-size distribution is self-preserving with respect to fluid shear. This distribution is universal for the employed coagulation and fragmentation rates provided that less than 5% (by number) of the particles remain unflocculated. This result is supported with experimental data on shear-induced flocculation of polystyrene particles, although a detailed quantitative comparison is limited by the irregular structure of the flocs.
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  • 74
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    AIChE Journal 42 (1996), S. 2668-2682 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bioartificial pancreas, consisting of immobilized islets encapsulated within hollow fibers, is investigated as an alternative treatment for insulin-dependent diabetes. A mathematical model is developed to determine whether this configuration of the bioartificial pancreas can yield an insulin response to a glucose challenge with the appropriate dynamics in diabetic humans. The model consists of the 2-D mass-conservation equations for glucose and insulin within the hollow fiber and capillaries. The equations contain terms for insulin-production kinetics by porcine islets and glucose-consumption kinetics. The boundary conditions account for transport resistances of the fiber membrane, the tissue surrounding the implant, and a thin film within the capillaries. The equations are coupled to a pharmacokinetic model of the circulatory system. The calculations show that an optimized design with this configuration will be feasible for human use and requires a total volume of 4.6 mL to reach the target insulin concentration in the bloodstream following a glucose challenge. The parameters and processes controlling the system performance are discussed.
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  • 75
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  • 76
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    AIChE Journal 42 (1996), S. 2977-2983 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 42 (1996), S. 2987-2989 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 78
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    AIChE Journal 42 (1996), S. 2994-2995 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 79
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    AIChE Journal 42 (1996), S. 3001-3007 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the first time, a macroscopic method was used to measure directly diffusivity of fast diffusing species such as methane in silicalite. A form of Wicke-Kallenbach technique was applied to measure intracrystalline diffusivity. The technique uses a single embedded zeolite crystal as a membrane and a mass-selective detector to determine the transient mass response and hence the diffusion flux passing through the membranne. A concentration-difference driving force is used rather than a pressure-difference driving force. The diffusivities calculated from both adsorption and desorption transients were in excellent agreement, thus providing a check for the self-consistency of the data. The diffusivities of carbon dioxide, methane, ethane, propane and butane in silicalite between 30 and 70°C have been compared with those from the literature. The diffusivities reported here are between those measured with microscopic methods and those measured with other macroscopic methods.
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  • 80
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    AIChE Journal 42 (1996), S. 3041-3054 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The axial and transverse apparent dispersion coefficients of three solvents in two packed chromatographic columns were determined by pulsed-field-gradient nuclear-magnetic resonance in a range of mobile phase velocity. The column beds were packed with 5- μm particles of porous C18 silica or 30-μm particles of silica. The solvents used were methanol and acetonitrile (in an 80:20 ACN/water solution) in the former case and acetone in the latter. The coefficients were determined over a range of particle Peclet numbers from less than 0.1 to approximately 10 in the former case and 40 in the latter. The data obtained with short dispersion times were fitted to the correlations suggested by Giddings, Horvath and Lin, Huber, and Knox. These data agreed well only with the Giddings equation.
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    AIChE Journal 42 (1996), S. 3087-3101 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article introduces the novel concept of synthesizing waste-interception networks (WINs) and incorporates it within a mass-integration framework for the global allocation of pollutants. The essence of this notion is to provide selective interception and rerouting of undersirable species at the heart of the process instead of dealing with the pollutants in the terminal waste streams. It also provides a unified framework for simultaneously tackling gaseous and liquid pollution. Several tools are developed to track the pollutant throughout the process and determine the optimal interception policies. The problem is formulated as an optimization program that seeks to determine the optimum locations for intercepting the pollutants, extent of separation, and separating agents to carry out the interception tasks. Furthermore, the WINs can be used within a mass-integration scheme for the global allocation of species throughout the plant. These new concepts and associated mathematical formulation are demonstrated using a case study on the removal of a chlorinated hydrocarbon. This approach has benefits over conventional recycle/reuse (such as MEN synthesis).
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    AIChE Journal 42 (1996), S. 3146-3152 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A newly developed gas-induced reactor for gas-liquid heterogeneous reactions presented here has no baffle on the inner wall of the tank body. Inside the reactor tank, two in-series 45° pitched blade downward turbines enclosed by a draft tube were employed. As the turbines rotate at high speeds, a central gas vortex is formed downwardly along the central shaft from the free surface of the liquid toward the upper turbine. The gas is then induced by the upper turbine and mixes with the input gas. After that, the mixed gas is broken into bubbles by the lower turbine and dispersed through the liquid vortex. With the formation of gas and liquid vortexes, the reactive gas was able to circulate in the liquid phase to achieve high gas utilization. The experimental studies were on the heterogeneous ozonation reaction of a reactive dye (C.I. Reactive Blue 19). Major experimental parameters, such as impeller speed, input concentration of ozone, input flow rate of ozone and liquid volume, were changed to investigate the characteristics of the gas-induced reactor. This gas-induced reactor achieved high gas utilization ratio, short reaction time, and high recovery of the unreactive gas.
    Additional Material: 8 Ill.
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  • 83
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1706-1714 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental studies of polymer melt flow in the filling and post-filling stages of the injection molding process were performed using the sequential injection of transparent and colored polystyrene resin. Effects of fountain flow in the filling stage, geometrical factors caused by edges and corners, as well as flow through contractions and expansions, were identified. Significant polymer melt flow which increases with increased packing pressure was observed in the post-filling process. The melt flow is more concentrated around the gate area than away from the gate. It was also found that the polymer melt flows across the gap center, resulting in partial annihilation of the weld line. Simulations based on the control-volume/finite-element method employed within each gapwise layer combined with the dual-filling-parameter technique were developed to trace the advancements in melt fronts for both skin and core materials. Numerical simulations show reasonable consistency with experimental results in both skin and core material distribution. If the edge effect is taken into account using a shape factor as a geometrical correction, the simulation accuracy is further improved.
    Additional Material: 15 Ill.
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  • 84
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1715-1722 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mass transport during pyrolysis of the degradation product of a polymeric binder used for ceramic molding is analyzed. Two series resistances to transport are incorporated: the diffusion of the product of degradation through its parent polymer during decomposition and the permeation of vapor through a static powder bed used to support the molding. The model predicts the critical rate of heating, Zc, above which defects caused by boiling of the organic phase occur at the center of the molding. For the system modeled, the permeability of the powder bed has little effect on Zc if the moldings are small but this is not the case for large moldings where well-packed fine powders should be avoided and the thickness of the powder bed should be kept to a minimum.
    Additional Material: 7 Ill.
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  • 85
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 86
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3333-3339 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new semiempirical model for prediction of self-diffusion phenomena in liquids is proposed. Assuming anlogy between the concept of a free volume in liquids and a porosity of a granular medium, a capillary model of the granular bed and the Kozeny-Carman theory was applied to determine self-diffusion coefficients in liquids. The dimensionless free volume in liquids was evaluated using a combination of the proposed dependence and an appropriate formula available in the literature. The new model was tested for 89 sets of data concerning self-diffusion of different chemical substances at several values of a temperature. The average error of a prediction was between ± 1% and about 3% for some data points.
    Additional Material: 4 Ill.
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  • 87
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1771-1771 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 88
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1765-1771 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modeling of supercritical CO2 extraction of essential oils from leaves was studied using sage at 90 bar (9 MPa) and 50°C. The fractional separation of the extracts enabled essential oil to be obtained. Four mean sage particle sizes ranging from 0.25 to 3.10 mm were tested. The model proposed was based on differential mass balances performed along the extraction bed. Experimental data suggest that the internal mass transfer was the controlling stage for the extraction process. Different hypotheses were tested on vegetable matter geometry, and their incidence on the model performance was evaluated. The particle shape proved to be a key factor in fitting experimental results, which were fairly good when the conventional spherical geometry was replaced by a realistic slab geometry. Diffusivity of the solute in the solid matrix was used as the only adjustable parameter of the model; its best fit value was 6.0 × 10-13 m2/s. The effect of the introduction of particle-size distribution into calculations was also tested. To verify if the external mass-transfer mechanisms influence the extraction process, experiments at two different CO2 flow rates were also performed. Simplified models were also considered, and the extent of approximations was evaluated.
    Additional Material: 6 Ill.
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  • 89
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1789-1792 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 90
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1793-1797 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 91
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1772-1788 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The vapor-liquid equilibrium (VLE) of aqueous-organic mixtures is important in understanding the physical chemistry behind the contamination and remediation of contaminated surface water, ground water and unsaturated soils. The state of the science is assessed, and available VLE and solubility data are reviewed comprehensively for several organic compounds. Benzene, toluene, o-, m-, p-xylene, ethylbenzene, chloroform, 1,1,1-trichloroethane (TCA), and trichloroethylene (TCE) were included in this study. Correlations are provided for estimation of VLE as a function of temperature. A new VLE apparatus was developed to extend experimental techniques found in the literature. Partitioning data for several aqueous-organic systems were measured. The collected data compared very favorably to data available in the literature. The new procedure is capable of providing high-quality data over a wide range of liquid concentrations and temperatures.
    Additional Material: 15 Ill.
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  • 92
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 93
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1798-1799 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 94
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3550-3553 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 95
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3533-3543 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Attempts to model asphaltene solubility with Scatchard-Hildebrand theory were hampered by uncertainty in molar volume and solubility parameter distribution within the asphaltenes. By considering asphaltenes as a series of polyaromatic hydrocarbons with randomly distributed associated functional groups, molar volume and solubility parameter distributions are calculated from experimental measurements of molar mass and density. The molar mass distribution of Athabasca asphaltenes is determined from interfacial tension and vapor pressure osmometry measurements together with plasma desorption mass spectrometry determinations from the literature. Asphaltene desnities are calculated indirectly from mixtures of known concentration of asphaltene in toluene. Asphaltene density, molar volume, and solubility parameter are correlated with molar mass. Solid-liquid equilibrium calculations based on solubility theory and the asphaltene property correlations successfully predict experimental data for both the precipitation point and the amount of precipitated asphaltenes in toluene-hexane solvent mixtures.
    Additional Material: 12 Ill.
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  • 96
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3554-3558 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 97
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3567-3570 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 98
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1968-1976 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: NO reduction through heterogeneous mechanisms is a major concern when coal or lignite is used as reburning fuel. Reburning was simulated in an alumina flow reactor operated with a synthetic flue gas at a stoichiometric ratio of 1.1, at 1,100°C and with a residence time of approximately 0.2 s. Reburning fuels used include methane, one bituminous coal, two lignites, chars derived from the bituminous coal and two lignites, and the bituminous coal char impregnated with CaO. Reburning with chars indicates that heterogeneous mechanisms are more important than homogeneous mechanisms when lignites are used. This high reactivity renders lignite char an even more effective reburning fuel than the parent lignite, while char from the bituminous coal produces little activities at stoichiometric ratios above 0.75. Bituminous coal char impregnated with CaO demonstrates higher NO reduction efficiency than the original char. Effects of SR on NO reductions imply that oxygen atoms, required for the NO and HCN conversions in homogeneous mechanisms, are not required in heterogeneous mechanisms. In fact, they inhibit the surface NO reduction. The first-level kinetic analysis indicates that the surface area is not the only contributor to a remarkable increase in NO reduction of lignite char, and chars of different origins seem to follow different mechanisms or to have different controlling steps in the overall reaction scheme.
    Additional Material: 8 Ill.
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  • 99
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2014-2024 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Geometrical properties of the pore-solid interfaces of devolatilized charcoals from the pyrolysis of fuel woods in a bench-scale fluidized-bed reactor were investigated through small-angle X-ray scattering. Specifically, surface morphological features of the interfaces were characterized by a single parameter indicative of the degree of surface roughness, that is, the surface fractal dimension, dSF, at various retention times. The surface fractal dimensions of the original wood samples prior to devolatilization were approximately identical for all species within the range between 2.00 and 2.15, over a length scale from 55 to 600 Å, and those for the respective charcoals from these wood samples were influenced to different degrees by the retention time, τ, in the reactor. The dSF's of the mesopores of charcoals of all the species attained maxima at a value of τ equal to 35 s and decreased subsequently with an increase in τ. The analysis of this unexpected trend was facilitated by the values of the mean radii of gyration of the pores, estimated through the Guinier plots. The results imply that when the retention time of the charcoals in the reactor is prolonged, the mechanism of pore enlargement and smoothening of the interfaces can play a dominant role in altering the surface morphology and thereby influence significantly the kinetics of chemical reactions in heterogeneous porous systems.
    Additional Material: 12 Ill.
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  • 100
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2005-2013 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thin liquid films stabilized by surfactants above the critical micelle concentration exhibit stratification or stepwise dynamic thinning. A continuum hydrodynamic model is outlined for stepwise film thinning that incorporates equilibrium micellar structuring through self-consistent oscillatory disjoining pressures and effective viscosities. Effective viscosities as functions of thickness are evaluated with an extension of the local average density model, considering dilute colloidal suspension shear viscosities and solvent effects. To establish local shear viscosities, structured DFT micellar profiles, coarse-grained densities, and disjoining pressure are used. Ionic micelles and other colloidal systems with repulsive interactions show structured effective viscosities that are generally less than the corresponding homogeneous solution shear viscosity, bounded by the pure solvent viscosity and that of the bulk micellar solution. For 0.1 and 0.2-M sodium dodecylsulfate micellar solutions, the effective viscosities are less than 5 and 10%, respectively, below the homogeneous fluid viscosity, except at small thicknesses, indicating that the micellar film thins faster than a pure water film of the same thickness.Calculated thinning curves closely resemble experimental observations in the stepwise thinning behavior, displaying decreasing slopes and increased step durations at later times. Despite the micellar structuring within the film, the ionic micelles do not contribute appreciably to the viscous resistance of the thinning film. Rather, Reynolds' film thinning is obeyed, with the equilibrium oscillatory disjoining pressures driving the stepwise dynamics. The shear viscosity of the ionic micellar film is well approximated by that of the bulk solution.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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