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  • 1995-1999
  • 1985-1989  (151)
  • 1870-1879
  • 1987  (151)
  • Genetics  (99)
  • Industrial Chemistry
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 69-75 
    ISSN: 1432-198X
    Schlagwort(e): Blood pressure ; Essential hypertension ; Genetics ; Epidemiology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This paper presents a review of the genetic transmission of normal blood pressure and of essential hypertension. Familial aggregation of normal blood pressure has been reported in adults, in children and even in newborns. Blood pressure aggregation phenomenon, however, is the result of both a genetic component and shared environmental factors. More specific for each etiological factor were the studies of blood pressure aggregation in twins and in adopted children. Attention was focused on the Montreal Adoption Study. In essential hypertension, a Japanese study is reviewed showing the occurrence of hypertension in the offspring of hypertensive parents. The heterogeneity of essential hypertension is underlined and two of the multiple etiological factors are particularly considered for their genetic component: the response to salt intake and erythrocyte cation fluxes. The conclusion from the literature reviewed is that essential hypertension is a polygenic disease transmitted by polygenic systems.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 136-139 
    ISSN: 1432-198X
    Schlagwort(e): IgA nephropathy ; Genetics ; Complement ; C4 ; Glomerulonephritis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract C4 and factor B typing were performed in 37 pediatric patients with primary IgA nephropathy. Null alleles for C4B occurred with a frequency of 26% in patients, as compared to 15% in healthy controls (NS). The phenotype of C4B deficiency (homozygous C4B null), however, was found in 16% of patients and 4% of controls (P〈0.05). Comparison of observed C4B phenotypes with those predicted from the Hardy-Weinberg equilibrium also confirmed an excess of C4B deficiency (P〈0.0005). In contrast, there was no evidence of distortion in the frequencies of the C4A null allele or phenotype, or of the factor B alleles. The data suggest that C4B deficiency may be one of multiple interacting factors contributing to the development of this glomerulopathy.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 397-404 
    ISSN: 1432-198X
    Schlagwort(e): Cystic kidneys ; Genetics ; Prenatal diagnosis ; Linkage studies ; Potter sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Despite the high incidence of cystic kidney diseases, affected families are not usually well informed of the inheritance of these disorders. Genetic counselling must be based on precise diagnostic criteria. Detailed information on the different types of cystic kidney disease is summarized, including clinical features, pathology, radiology, prenatal diagnosis and the risk of recurrence. In addition, a genetic interpretation is given of the Caroli syndrome, Potter sequence as well as congenital hepatic fibrosis.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 436-438 
    ISSN: 1432-198X
    Schlagwort(e): Alport's syndrome ; Genetics ; Heterogeneity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The pattern of inheritance in Alport's syndrome has been controversial for some time. Recent studies have clarified the mode of inheritance in this disease. Alport's syndrome is a heterogeneous disorder made up of a number of genetically distinct syndromes, with an autosomal dominant, an X-linked dominant and a rare autosomal recessive form. Clinical analysis shows that there are many distinct forms with or without nerve deafness, and with early or late occurrence of end-stage renal disease.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 149 (1987), S. 36-42 
    ISSN: 1432-072X
    Schlagwort(e): Catabolite repression ; Genetics ; Malate dehydrogenase ; Molecular cloning ; Sequence ; CRP binding site ; Escherichia coli
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The malate dehydrogenase gene of Escherichia coli, which is susceptible to catabolite and anaerobic repression, has been cloned using plasmic pLC32-38 of Clarke and Carbon (1976). The nucleotide sequence was determined of a 2.47 kbp fragment, containing the mdh structural gene. All information necessary for expression of the mdh structural gene was mapped within a 1.3 kbp SphI-BstEII fragment. Compared with the untransformed wild type, transformations with pUC19 vector, containing this fragment, gave up to 40-fold more malate dehydrogenase activity in both E. coli wild type and mdh mutant recipients. Catabolite repression was not affected in the transformants. A possible CRP binding site in the promotor region of the mdh gene provides evidence for a co-regulation with fumA gene, the structural gene of fumarase, which is also subject to catabolite repression. The structures for transcription initiation and termination were similar to those previously described for E. coli. Amino acid sequence homologies between pro- and eucaryotic malate dehydrogenases are discussed.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 146 (1987), S. 283-287 
    ISSN: 1432-1076
    Schlagwort(e): Pena-Shokeir I syndrome ; Facial anomalies ; Ankylosis ; Pulmonary hypoplasia ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Two siblings whose clinical and pathologic features were consistent with the “Syndrome of camptodactyly, multiple ankyloses and pulmonary hypoplasia” originally described by Pena and Shokeir were examined at autopsy. Additional features were intrauterine growth retardation, immaturity of the central nervous system (CNS) and atrophy of skeletal muscles. Our data suggest that CNS damage may cause the complicated phenotypic abnormalities of the syndrome.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 146 (1987), S. 550-554 
    ISSN: 1432-1076
    Schlagwort(e): Epilepsy ; Genetics ; Myoclonic-astatic seizures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This paper presents case reports of patients suffering from myoclonic-astatic and stimulus-sensitive myoclonic seizures, respectively. It gives details of clinical and EEG data in the pertinent families. This is discussed in the context of controversial nosographic concepts of epilepsies with myoclonic seizures, and of the results of extensive family investigations. The findings demonstrate the decisive importance of hereditary factors in the pathogenesis of myoclonic and myoclonic-astatic epilepsy, the genetic background of which is probably polygenic.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 73 (1987), S. 440-444 
    ISSN: 1432-2242
    Schlagwort(e): Secale cereale L. ; Genetics ; α-Amylase ; Isozymes ; Modifiers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Fifteen inbred lines of rye, F1 and F2 progenies from crosses between lines were studied using polyacrylamide gel electrophoresis. Conventional genetic analysis of α-amylase zymograms showed that the 19 bands detected in the endosperm of germinating caryopses were controlled by three linked structural loci and one independent modifying locus, which influenced the electrophoretic mobility of isozymes. Two codominant alleles were found at the α-Amy1, α-Amy2 structural loci and the M-α-Amy modifying locus while the α-Amy3 locus had three alleles. Double-banded expression of the α-amylase alleles was probably due to the simultaneous presence of modified and unmodified forms of isozymes on the zymogram.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 74 (1987), S. 177-187 
    ISSN: 1432-2242
    Schlagwort(e): Barley ; Grain development ; Mutants ; Ultrastructure ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Eleven Na-azide induced barley shrunken endosperm mutants expressing xenia (sex) were characterized genetically and histologically. All mutants have reduced kernel size with kernel weights ranging from 11 to 57% of the wild type. With one exception, the mutant phenotypes are ascribable to single recessive mutant alleles, giving rise to a ratio of 3∶1 of normal and shrunken kernels on heterozygous plants. One mutant (B10), also monofactorially inherited, shows a gene dosage dependent pattern of expression in the endosperm. Among the 8 mutants tested for allelism, no allelic mutant genes were discovered. By means of translocation mapping, the mutant gene of B10 was localized to the short arm of chromosome 7, and that of B9 to the short arm of chromosome 1. Based on microscopy studies, the mutant kernel phenotypes fall into three classes, viz. mutants with both endosperm and embryo affected and with a non-viable embryo, mutants with both endosperm and embryo affected and with a viable embryo giving rise to plants with a clearly mutant phenotype, and finally mutants with only the endosperm affected and with a normal embryo giving rise to plants with normal phenotype. The mutant collection covers mutations in genes participating in all of the developmental phases of the endosperm, i.e. the passage from syncytial to the cellular endosperm, total lack of aleurone cell formation and disturbance in the pattern of aleurone cell formation. In the starchy endosperm, varying degrees of cell differentiation occur, ranging from slight deviations from wild type to complete loss of starchy endosperm traits. In the embryo, blocks in the major developmental phases are represented in the mutant collection, including arrest at the proembryo stage, continued cell divisions but no differentiation, and embryos deviating only slightly from the wild type.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 65 (1987), S. 101-109 
    ISSN: 1432-1440
    Schlagwort(e): Blood Pressure ; Hypertension ; Salt ; Sodium ; Genetics ; Twin Model ; Salt Restriction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To examine the effect of genetic variance on blood pressure, sodium homeostasis, and its regulatory determinants, we studied 37 pairs of monozygotic twins and 18 pairs of dizygotic twins under conditions of volume expansion and contraction. We found that, in addition to blood pressure and body size, sodium excretion in response to provocative maneuvers, glomerular filtration rate, the renin-angiotensin system, and the sympathetic nervous system are influenced by genetic variance. To elucidate the interaction of genetic factors and an environmental influence, namely, salt intake, we restricted dietary sodium in 44 families of twin children. In addition to a modest decrease in blood pressure, we found heterogeneous responses in blood pressure indicative of sodium sensitivity and resistance which were normally distributed. Strong parent-offspring resemblances were found in baseline blood pressures which persisted when adjustments were made for age and weight. Further, mother-offspring resemblances were observed in the change in blood pressure with sodium restriction. We conclude that the control of sodium homeostasis is heritable and that the change in blood pressure with sodium restriction is familial as well. These data speak to the interaction between the genetic susceptibility to hypertension and environmental influences which may result in its expression.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 18 (1987), S. 249-256 
    ISSN: 1573-5133
    Schlagwort(e): Developmental rate ; Genetics ; Inheritance ; Meristic ; Salmonidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Deviations from morphological intermediacy in six first generation hybrids between three hatchery strains of rainbow trout, raised in a common environment, are reported. Hybrids have higher mean counts of four meristic characters than their maternal parental strain in a significantly greater number of cases (18 out of 24). Furthermore, eight of eleven hybrid indices are not intermediate. These results are discussed in reference to several mechanisms and models proposed to account for observed responses of meristic characters to environmental and genetic influences.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 74 (1987), S. 439-444 
    ISSN: 1432-2242
    Schlagwort(e): Wheat ; Callus ; Regeneration ; Tissue culture ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Calli were initiated from immature embryos of nine lines of hexaploid wheat (Triticum aestivum L. em. Thell). These were the euploid lines Chinese Spring and Cappelle-Desprez, a line of Chinese Spring ditelocentric for the long arm of 4B, four substitution lines of Chinese Spring in which chromosome 4B has been replaced by its homologues from different wheat varieties and substituted into Chinese Spring and a substitution line of Besostaya I 4B into Cappelle-Desprez. The calli from these lines were found to differ in their growth rates and morphogenic and regenerative activities. The substitution of different 4B chromosomes into Chinese Spring significantly increased morphogenesis and shoot regeneration from callus. The potential for developing wheat lines with improved culture characteristics is discussed.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 208 (1987), S. 279-287 
    ISSN: 1617-4623
    Schlagwort(e): NAD metabolism ; Regulation ; nadR ; Salmonella typhimurium ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nadR locus (99 min) controls the transcription of several genes involved with either the biosynthesis (nadAB) or recycling (pncB) of NAD in Salmonella typhimurium. Point mutations in this locus were found to cause defects either in the transport of nicotinamide mononucleotide (PnuA-), the regulation of nadAB (NadR-) or both transport and regulation (PnuA-NadR-). Deletions or insertions into nadR always resulted in the PnuA- NadR- phenotypes. Merodiploids constructed with various combiminations of PnuA-, NadR- or PnuA-NadR- strains indicate a single complementation group. The results suggest the NadR product is a bifunctional regulatory protein. Operon fusions to lacZ (nadR:: Mud1-8) were used to show that nadR is not autoregulated and is transcribed in a clockwise direction. The gene was also cloned and located within a 2 kb EcoR1-BglII fragment.
    Materialart: Digitale Medien
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  • 14
    ISSN: 1617-4623
    Schlagwort(e): E. coli ; Genetics ; Polysaccharide biosynthesis ; Secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Transposon and deletion analysis of the cloned K1 capsule biosynthesis genes of Escherichia coli revealed that approximately 17 kb of DNA, split into three functional regions, is required for capsule production. One block (region 1) is required for translocation of polysaccharide to the cell surface and mutations in this region result in the intracellular appearance of polymer indistinguishable on immunoelectrophoresis to that found on the surface of K1 encapsulated bacteria. This material was released from the cell by osmotic shock indicating that the polysaccharide was probably present in the periplasmic space. Insertions in a second block (region 2) completely abolished polymer production and this second region is believed to encode the enzymes for the biosynthesis and polymerisation of the K1 antigen. Addition of exogenous N-acetylneuraminic acid to one insertion mutant in this region restored its ability to express surface polymer as judged by K1 phage sensitivity. This insertion probably defines genes involved in biosynthesis of N-acetylneuraminic acid. Insertions in a third block (region 3) result in the intracellular appearance of polysaccharide with a very low electrophoretic mobility. The presence of the cloned K1 capsule biosynthesis genes on a multicopy plasmid in an E. coli K-12 strain did not increase the yields of capsular polysaccharide produced compared to the K1+ isolate from which the genes were cloned.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987) 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 33-37 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: All the present experiments confirm that there is some liquid channelling on trays. Liquid channelling is extensive on trays of large diameters. It largely depends on the tilting of the plate, modifications of the inlet weirs and on non-uniform bubble cap spacing. Consequences of liquid channelling for plate efficiency are clear; the higher the degree of liquid channelling the lower the plate efficiency. However, own experimental and theoretical investigations indicate that plate efficiency never falls below the value of point efficiency. Therefore, liquid channelling only affects the crossflow on trays. Liquid channelling reduces the mass transfer performance to a similar extent as does the backmixing of liquid. Consequently, plate efficiency is not very sensitive to liquid channelling. Since the liquid is completely mixed in the downcomer, the effects of liquid channelling are restricted to a single tray. The behaviour of tray columns completely differs from that of packed columns, where the effects of liquid channelling are cumulative over the packed height. Consequently, trays represent a suitable design for columns of large diameters.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 16-27 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Although carbon dixoide is important as an abundant carbonaceous raw material, so far, its utilization in chemical processes has been rather limited. This review covers the reactions of CO2 employed in industry, such as the production of urea, the Kolbe-Schmitt reaction, the synthesis of cyclic organic carbonates and the use of CO2 in methanol synthesis. Interesting recent developments in CO2 chemistry, such as the reactions catalyzed by transition metals, are also described. Apart from the synthesis of polymers and hydrocarbons, the production of oxygen-containing substances appears to be very profitable and attractive for future industrial applications. Not only can derivatives of formic and carbonic acids be produced but also longer-chain carboxylic acids and their derivatives by reactions of carbon dioxide with hydrocarbons such as alkynes, alkenes and 1,3-dienes.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 18
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The present contribution illustrates a way of developing a continuous separation process for near critical fluid extraction, on the example of separation of soya oil from lecithin. First, a suitable solvent was selected. Phase equilibria were measured in autoclaves. Operating conditions for a pilot plant were derived from the phase equilibrium data. The pilot plant experiments provided the necessary data for designing a production plant. Computer programs for phase equilibrium, stage to stage and mass and heat balance calculations were used in order to minimize the number of experiments. A production plant with a capacity of 500 t/a of raw lecithin was designed on the basis of experimental and computational results. A cost estimation, based on tenders, showed that it is more economical to produce lecithin by near critical fluid extraction than by conventional acetone extraction.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 56-63 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Ideal flow conditions are generally assumed for the reactor design. If stoichiometry, reaction mechanism and kinetics are known, the balance equations for the ideal flow tube, the ideal steady-state continuous stirred tank reactor or the ideal, completely mixed stirred batch reactor are often applied. In many cases, formal kinetics, which forms the basis of reaction modelling, is so uncertain that the idealization of the flow field can be accepted. In practice, however, deviations from the ideally calculated conversions, yields and product qualities, often occur. In these cases, it is necessary to consider the real flow conditions. In general, a distinction is made between macroand micromixing processes.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 1-15 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Using pilot-scale test plant, the interfacial area per unit volume was investigated in different gasliquid reactors, i.e. packed column, bubble column and free jet reactor. The interfacial area was studied as a function of liquid viscosity and of operating parameters. As a rule, identical test conditions were maintained in all the measurements, in order to obtain comparable results. The interfacial area was determined by chemical means using the sulphite system (a solution of sodium sulphite in water as model liquid and air as gaseous medium). The viscosity of the solution can be increased by adding carboxymethyl cellulose without significantly affecting the reaction kinetics. The addition of a surfactant to the sulphite system allowed comparative measurements at reduced surface tension. Based on a large number of measurements, the correlations of the interfacial area are expressed as power laws. The inclusion of experiments with a jet tube reactor and a stirring vessel allows an extensive comparison of all reactors. All tests were carried out with the same material system and the same method was used to determine the interfacial area per unit volume. Therefore, a comparison with respect to mass transfer is possible.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 27-32 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new measurement method for determining the local liquid-phase velocities in multiphase flows is presented. It is based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer. The input of heat pulses and measurement of temperature at an adjacent point is performed by small probes. As an intermediate result, the flow time distribution of the heat-labelled fluid elements is calculated on-line as a cross-correlation function between the pseudo-random input and the measured output signals. This calculation and the automatic control of measurements is carried out by a simple microprocessor unit. The device produced excellent results in gas-liquid flows at high gas throughputs and high liquid-phase velocities.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 63-72 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Among other processes, adsorption is used for the removal of hydrogen sulphide from natural gases. Hereby, competitive adsorption of the different gas components plays an important role, e.g., that of carbon dioxide. Data of equilibrium loading and adsorption kinetics are required for the design of adsorbers, filled with molecular sieve. In order to obtain these data under the prevailing operating conditions, hydrogen sulphide was removed from gas mixtures H2S/CH4 and H2S/CO2/CH4, in a pilot plant, by adsorption on molecular sieve 5A. The equilibrium loading, the height of transfer zone, and the length of unused bed were determined from the measured breakthrough curves of H2S. With these data, the breakthrough time and the optimum process conditions were calculated for a practical example.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 43-55 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The oxidation of carbon monoxide by air in a turbulent flow was investigated under experimental conditions where the rates of turbulent mixing and of chemical reaction are comparable. For this purpose, carbon monoxide was admixed into the completely burnt gas of a natural gas flame operated with excess of air. Measurements of mean values of axial velocity, temperature and volume fractions of carbon monoxide and oxygen were compared with computational simulations involving the k - ∊ turbulence model and several turbulent reaction models for the oxidation of carbon monoxide. The comparison of measurements and numerical calculations demonstrated that the k - ∊ turbulence model is suitable for prediction of the turbulent flow field in the flow system investigated. Furthermore, it could be shown that one-variable turbulent reaction models, such as the flamesheet or the eddy-break-up model, cannot explain the measured carbon monoxide volume fraction profiles. Two-variable turbulent reaction models with a probability density function closure of the source term of the transport equation for the mass fraction of the chemical species result in a better agreement between the measured and simulated volume fraction profiles, particularly in predicting the clear influence of the initial temperature on carbon monoxide volume fractions. Weighting of the kinetic rate expression for the oxidation of carbon monoxide with different presumed probability density functions yields slightly different predictions of the carbon monoxide volume fractions, reflecting the assumed different character of turbulent fluctuations.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 92-98 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Distillation columns with vertical partitions can separate a feed mixture into 3 or 4 pure fractions. Compared to other column arrangements, their investment costs and energy consumption are lower. Production columns show good results and are easily controlled. Conventional distillation columns produce only 2 pure product streams at the top and at the bottom of the column. Side products are contaminated by light or heavy components, depending on the location of the side stream in the rectifying or stripping section. This disadvantage is set aside by using a distillation column with a vertical partition. The internal separation wall prevents lateral mixing of liquid and vapour in the central part of the column, forming there separate feed and outlet sections. In the presence of a vertical partition, 3 or 4 pure fractions can be obtained in a single distillation step. This is particularly advantageous when heat sensitive components are to be separated. On account of good thermodynamic properties, the energy consumption is 20 to 35% lower than that of other distillation arrangements. The control behaviour is similar or better than that of conventional distillation columns.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 86-92 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The Carman-Arnell equation relates the rate of flow of a fluid through a packed bed to the pressure drop across the bed. This equation is the basis for surface area determination by permeametry. It is found that the surface area measured at sub-atmospheric pressure varies with the bed porosity, so a porosity was selected where the rate of change was at a minimum. The study suggests that, at reduced pressures, the gas flow rate is a linear function of the mean pressure.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 104-112 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A 0.5 MW spray-dry scrubbing FGD pilot plant was used in the study of spray dryer performance over a wide range of operating conditions. Experimental findings were compared with a spray dryer model. During operation with large excesses of lime, the SO2 absorption was limited by gas phase diffusion. At operation with a shortage of lime, the rate limiting step was the dissolution rate of lime. In addition, the flow regime in a spray dryer can be best described as well mixed. The SO2 level in the flue gas was found to exert no direct effect on the efficiency of SO2 removal. The observed effects are attributed solely to the changes in the drying process, due to the inter-dependence of slurry composition and SO2 concentration.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 73-86 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: As a part of a research project on the mass transfer in liquid pulsed sieve-tray extraction columns (PSE), the diameters and hold-ups of the drops were measured: the drop size using a suction technique, with photoelectric detection, which was adapted to the special boundary conditions of the PSE; the integral hold-up by the pressure difference between the lower and upper parts of the column. Since experimental results cannot be described by known calculation formulae for the Sauter mean diameter and the hold-up, a new method of calculation was developed. It is phenomenologically based on high-speed photographs of the drop motion on a sieve tray. The mathematical-physical model allows the prediction of drop size and hold-up within certain limits, while the possible different operating regimes of the PSE, i.e. the mixer-settler and dispersion regimes can also be estimated.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 125-131 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: When crude oil is vacuum distilled, about 30% of the feed remain as low value residue. Hydrocracking can upgrade this residue into valuable light hydrocarbons. The hydrocracking could be optimized catalytically, if the residue were not to contain the metals vanadium and nickel that poison the catalyst. This contribution shows that continuous extraction of the residue with ethyl acetate yields a fraction with low metal content, while an asphaltene fraction with the remaining metal content is filtered off.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 29
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A one-stage model of the formation of primary bubbles is presented in which the bubble volume is deduced from an equilibrium of buoyancy, viscosity, inertia and surface tension forces. In contrast to the two-stage model, presented by Kumar and Kuloor, it was not assumed that the drag coefficient in bubble expansion can be described by the same constants as in the steady-state bubble ascent. The constants were adapted in such a way that the introduction of an additional bubble volume was not necessary. It was demonstrated that this model describes the bubble formation in gravitational and centrifugal fields equally well and, furthermore, is also applicable to structurally viscous liquids, provided that the effective shear gradient \documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop {\rm \gamma }\limits^. = \frac{1}{6}({\rm \Delta \rho }gzd_{\rm B} /{\rm \eta }) $$\end{document} is calculated from the equilibrium of shearing and buoyancy forces. The model is based on the assumption of a constant volumetric flow rate during bubble formation and, for this reason, a minimum Froude number is necessary in analogy to the weeping limit for sieve plates. The normalized presentation permits simple operation. The possibility of applying the model to drop formation was confirmed by comparison of experimental values with those, predicted by the model.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 143-150 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new equipment for the measurement of virial coefficients of pure substances and binary mixtures is described. It consists of an improved modification of the set-up proposed by Eucken and Meyer in 1929. The development is based on a critical review of the existing methods particularly with respect to adsorption effects. In order to reduce the influence of adsorption on the accuracy of virial coefficients, an optimum range for gas density is recommended. The accuracy of the virial coefficients is better than 20 cm3 mol-1. The set-up was employed for the measurement of virial coefficients of acetone and hexane in the range from 352.95 to 393.85 K. The results are in excellent agreement with data published in literature. Furthermore, cross-virial coefficients of the binary system acetone/hexane were measured and interpreted.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 113-125 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Fouling and/or scaling of heat transfer surfaces causes serious problems in industry. Prevention of fouling is therefore essential for technical (considerable deterioration of heat transfer) and also economic reasons (increased costs). In order to provide successful countermeasures, it is, however, necessary to obtain more detailed information on the physical, chemical and biological processes which produce fouling. Based on the already known fouling mechanisms, it is shown that a satisfactory prediction of fouling behaviour of heat exchangers is not yet possible. This contribution presents a physical model for the description of fouling, caused by sedimentation and crystallization. It is assumed that, during fouling, deposition and removal processes overlap. In order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments. Aqueous CaSO4 solutions served as experimental liquids. A comparison of experimental and calculated fouling factors shows a satisfactory agreement.
    Zusätzliches Material: 23 Ill.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 157-164 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Based on a paper by Hein, a dimensioning program for tube-bundle heat exchangers with straight tubes and fixed tube sheets has been developed. The equipment to be dimensioned is tested at 14 critical points, with regard to permissible stresses. The optimum thickness of the tube sheet, the shell and channel are subsequently selected on the basis of economic criteria. Compared to dimensioning according to AD-data sheet, it is possible to save between 10 and 25% of production costs. With the aid of a finite-element (FE) program, complex structures such as heat exchangers can be calculated accurately. Several mesh-generation programs were written for the data input. The structure of a tube-bundle heat exchanger with straight tubes is generated with 3/D elements with only some geometrical data. An FE-calculation of a heat exchanger is explained with the aid of an example and stress analysis is presented.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
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  • 33
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The present contribution reports on a new method for the simulation of the dispersed phase behaviour in liquid-liquid extraction columns. The fluid dynamic description is based on a mathematical model which explicitly takes into account drop transport, break-up and coalescence mechanisms, via a drop population balance along the column. Application of the model requires some simple measurements on single drops in order to determine transport and break-up laws, which are required by the model, and possibly also coalescence parameters. In this study the model is applied to pulsed sieve plate columns. The specific example considered here is based on systematic studies on the determination of break-up rates from the corresponding probabilities of break-up and the generated daughter drop size distributions by means of high-speed photography. The validity of the model was subsequently tested by comparison with some experimental results from studies on two different pulsed columns 80 and 225 mm in diameter for the water/toluene system without mass transfer. The satisfactory agreement between the results justifies the use of such a method for the description of the behaviour of liquid-liquid extraction columns in a wide range of operating conditions. Furthermore, application of the model may help to dispense with long and expensive pilot tests.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 34
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Microbial desulphurization of coal by pyrite oxidizing enrichment cultures containing predominantly Thiobacillus ferrooxidans was performed in an air-agitated slurry reactor, 20 l in volume. A model of microbiological and chemical reactions, occurring at various points within the coal, was set up taking into account the pore structure of the coal. The influence of parameters relevant to industrial processes, such as superficial gas velocity, particle size, initial pyrite concentration, and slurry density of the coal, on the conversion of pyrite was examined. Variation of the superficial gas velocity in the range of 0.01 to 0.04 m/s confirmed that the reaction is not controlled by oxygen transfer from gaseous to liquid phase. The rate of pyrite oxidation depends mainly on the accessibility of pyrite to micro-organisms which is determined by the particle size of the coal as well as the distribution of pyrite crystals in the coal matrix. The accessibility of pyrite to the micro-organisms is described by the ratio of effective to maximum microbial activity, measured as oxygen consumption. Starting with higher initial concentration of pyrite in the coal increases the oxidation rate, according to first order kinetics. Enhanced slurry densities lead to a decrease of pyrite conversion, in spite of higher pyrite concentration. The maximum pyrite oxidation rate was measured at 15% (v/v) slurry density and 25°C as 1800 mg Spyr/kg coal per day, or 360 mg Spyr/l reactor volume per day.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 131-142 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The influence of electrolytes, which are dissolved in the aqueous absorbent and do not react with nitrogen oxides, on the absorption kinetics of both these components was investigated experimentally. In addition to demineralized water, various salt solutions of different concentrations as well as sodium hydroxide solution were used as absorbents. The term H \documentclass{article}\pagestyle{empty}\begin{document}$ H\sqrt {k_1 D} $\end{document} for N2O4 and N2O3, which is important for the design of industrial absorbers, was determined as a function of composition and concentration of the absorbents. In the case of N2O4, the chosen measuring and evaluation methods permitted a separate determination of the rate constant k of the pseudo first order reaction and of the solubility H. The diffusion coefficient D of the gas in the absorbent can be obtained only by calculation. Experimental results showed that \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document} decreases with increasing ionic strength I, however, without a clear indication of any ion-specific effects. This decrease does not appear to be caused simply by a reduction in solubility (salting out effect), or in diffusion coefficient, but at least, to the same extent, through a decrease of the rate constant k with increasing electrolyte content in the absorbent. The measurements permitted the determination of the gas-based salting out parameter for N2O4. The investigations on the absorption of N2O3 in water and in an Na2SO4 solution showed no experimentally detectable influence of dissolved salts on \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document}. The numerical value of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document} is six times that of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document}.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 36
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Slurry bubble columns are widely used in biotechnology. Therefore, the effects of solid particles on fluidization characteristics, gas hold-up and volumetric liquid-side mass transfer coefficient were measured in a slurry bubble column (i.d. 0.14 m). The density and diameter of the suspended particles were similar to those applied in biotechnology with immobilized bacteria. Based on models of turbulence and of liquid circulation induced by rising gas bubbles, equations for critical gas velocity, gas hold-up and volumetric liquid-side mass transfer coefficient were obtained by dimensional analysis.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 37
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The detailed dynamic simulation of coupled process units in chemical plants is gaining an increasing importance as a useful tool in plant engineering and operation. The outline of the program package DIVA (Dynamische Simulation verfahrenstechnischer Anlagen) which is currently under development is presented in the following. The dynamic plant equations and the corresponding Jacobian matrix are generated automatically. The full exploitation of sparse matrix techniques in combination with stiff ODE (ordinary differential equation) solvers allows an efficient solution of all the equations simultaneously. The possibilities offered by the simulator are demonstrated by the simulation of two laboratory plants.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 190-203 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Spatially resolved oxygen concentration measurements were performed in premixed hydrocarbon flames by using laser induced spontaneous Raman scattering. The measurements demonstrate the performance of a relatively simple pulsed laser Raman probe for fundamental combustion studies and also for the control of the equivalence ratio in flames (best spatial resolution: 0.2 mm3; theoretical detection limit: 0.8% of O2). Comparison of the results with those obtained by a mechanical suction probe (Magnos 2 T) confirmed a good agreement. At present, control of different stoichiometric conditions is possible at a minimum O2 concentration of 1.3%.
    Zusätzliches Material: 25 Ill.
    Materialart: Digitale Medien
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  • 39
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: During the sudden unheated vessel top venting of initially saturated two-component gas/liquid mixtures, in which the gas is also extensively dissolved in the non-evaporating liquid phase, a solubility inequilibrium develops between the phases; re-equilibration can set in only after a so-called desorption delay time. Laboratory measurements of this delay time were under-taken with model mixtures of CO2 and water and viscous aqueous (Newtonian) solutions by high speed cinematography. The parameters of the experiments are relief cross-section, initial liquid level, pressure, temperature, and concentration. The shortest deley time obtained lasts approximately 75 ms. It differs substantially from the minimum boiling delay time previously measured with various refrigerants in the same test facility. The experimental results are correlated by a semi-empirical dimensionless power relationship, which includes all independent primary design variables generally availble in a physically consistent interrelationship. Reasonable extrapolations to other test conditions and aqueous two-component systems with an acceptable accuracy systems can therefore be expected.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 40
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Correlations for pressure drop and upper capacity limit (flooding) are useful for the design of packed columns. Available correlations are based on the results of measurements made at atmospheric pressure. Extrapolation to higher pressures is not recommended. Therefore, systematic experimental investigations were carried out in a pilot plant at pressures of up to 100 bar. The experimental equipment and techniques, evaluation methods, and some characteristic experimental results are presented.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 224-230 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This paper describes a pilot plant for entrainment measurements on various types of column trays. The data obtained from different trays differ by up to a factor of 10. The measurements were compared with the theoretical model of Stichlmair. The Stichlmair entrainment diagram permits a fairly accurate prediction for most types of trays if the height of the two-phase layer is known. Prediction of the height and relative liquid hold-up in this two-phase system should be modified by a term reflecting the vapour flow profile, which requires further testing. These tests should examine the effect of tray spacing, fractional free area and, in particular, the influence of different media.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 204-215 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In three-phase systems, where the liquid constitutes the continuous phase, solid is the catalyst and gas represents the dispersed phase, there are decisive criteria which have to be observed in reactor design. These are e.g. the interfacial area per unit volume between gas and liquid, the volumetric mass transfer coefficient and the mass transfer coefficient. The basic aim of the present work was therefore the investigation of these parameters in relation to the main influencing parameters. Process parameters stirrer speed and superficial gas velocity were varied as well as the physical properties such as liquid viscosity, solids concentration, particle diameter and a geometrical parameter, i.e. reactor diameter. The sulphite method was employed for the determination of these values. The test results confirmed the known relationships of power consumption and superficial gas velocity. An increase in the liquid viscosity leads to a decrease in all the tested values. In most cases, suspended solid particles lead to a lowering of the test values. The influence of the tank diameter on the plots of the test values against specific power consumption turned out to be invariant so that a scale-up of geometrically similar systems can be carried out at constant power consumption, superficial gas velocity and liquid viscosity.
    Zusätzliches Material: 27 Ill.
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 242-248 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Pool boiling data of multicomponent mixtures show that the heat transfer coefficients can be considerably lower than those of a corresponding pure fluid with the same physical properties as the mixture. The proposed model, which assumes maximum mass transfer resistance in the liquid boundary layer, is confirmed by the comparison between calculated and experimental data. The model allows the prediction of heat transfer coefficients in pool boiling of mixtures using only single component properties and vapour-liquid equilibrium data. Judging by experience with a number of different systems, the method should be sufficiently accurate for most practical applications.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 248-255 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The development of heat resistant permeation membranes has opened up new possibilities for the conversion of fossil energy resources. In steam reforming of natural gas, such membranes even permit a direct production of hydrogen at high temperatures during the conversion of feed hydrocarbons. Further gas processing, such as required for reformer gas in existing hydrogen production processes, is not necessary. Due to continuous hydrogen discharge directly in the reformer tube, the chemical equilibrium of the occurring reactions becomes displaced towards the products, resulting in more favourable process conditions and, consequently, in improved by 36% utilization of the feed hydrocarbons. At the same time, the hydrogen yield increases by 44%. The heat required, which is provided by a high temperature reactor, is 17% in excess of that in conventional plants. It can be expected that the simplified process design will produce substantial cost advantages over the existing processes for the production of hydrogen.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 45
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the present paper, models are developed for the description of coalescence and splitting of bubbles in gas fluidized beds. The distinction between slow and fast bubbles, which originates from the Davidson model of gas flow in and around a rising bubble, was found to be decisive for the modelling of coalescence processes. On the basis of the respective models, it is shown that a change in bed temperature does influence the mechanisms of both bubble coalescence and splitting. In cases of both slow and fast bubbles undergoing splitting, the theory predicts a decrease of bubble size with temperature whereas in the case of a non-splitting system with fast bubbles, typically encountered with Geldart type B particles, no significant temperature effect on bubble size is expected. The theoretical predictions are shown to be in agreement with own measurements as well as with the results of other workers.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 262-271 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Pressure pulsations in hydraulic systems, generated by reciprocating pumps, can cause serious problems with regard to plant safety and reliability. In particular, fatigue problems arise in high-pressure piping systems. The available knowledge is not sufficient for an accurate computation of pressure peaks in the piping of reciprocating pumps. A number of calculation models are available which, however, neglect both fluid compressibility and friction. This contribution presents a calculation method which allows a precise modelling of various pump installations. Comparison of calculated and experimental data shows a good agreement and provides a validation of the computational model.
    Zusätzliches Material: 18 Ill.
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  • 47
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 256-261 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the separation of gaseous mixtures by gas permeation, it is in some cases impossible to achieve the desired product quality in a single stage and, therefore, several stages may be necessary. Multistage processes can be implemented by membrane modules arranged in the form of a cascade or by a membrane column design. On the basis of an economic analysis, this paper discusses different possible module arrangements for 2 cases, i.e. the enrichment of oxygen from air and the separation of methane from biogas. Present calculations indicate that, in the first case, two-stage cascades with or without recycle and, in the second case, one-stage cascade without recycle constitute the optimum module arrangements. However, depending on the selling price of the methane enriched gas, one- or two-stage cascades with recycle have to be considered. Finally, It was shown that, in the permeation of non-ideal gases, the Joule-Thomson effect has to be taken into account.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 48
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 281-289 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Fundamental investigations of coalescence processes in settlers with plate packages for the separation of liquid-liquid dispersions prompted an analysis of the drop motion on the interface of a stratified two-phase flow. Therefore, a physical model was developed, which permits the calculation of drop velocity along the interface of an inclined trickling film. Starting from a balance of forces around a single particle, the model provides the equation of motion for a steady motion of single particles in a stratified two-phase flow. Several assumptions and considerations were necessary to solve this equation, such as taking into account the influence of the wall and of flow resistance. The model calculation assumes Newtonian liquids and laminar, smooth trickling films. A comparison with experimental results confirms that the drop motion behaviour is well reproduced.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 49
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 291-296 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The kinetics of extraction processes with chemical reaction was studied experimentally on the system copper/Acorga PT 5050 and quantified according to meaningful kinetic models. These were coupled with other models describing the behaviour of dispersions in columns in order to permit a computer aided simultation of reactive extraction. Thus, a better prediction of column performance is achieved.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 312-322 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Existing heat exchanger design criteria do not satisfy the continually increasing requirements for greater efficiency or mass flux and energy throughput. Occasionally, failures appear even after only a few hours of operation, as shown in section 3. A long series of experiments, often carried out on original scale, did lead to the derivation of a large number of empirical expressions; however, physical explanations of the complex tube-failure interactions could not as yet be found. In contrast, experiments with a well defined simple model, whereby the tube deflections were recorded digitally and, at the same time, tube-fluid interactions were registered on a high-speed film, show that elementary “fluid transport mechanisms” control the stability behaviour of the heat exchanger tubes. Vibration excitation mechanisms such as “galloping”, “jet switching” and “whirling” (fluid elastic coupling) proved, with their characteristics, as typical for the vibration behaviour of single rows within the tube array, but not for the vibration phenomena of tube bundles.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 297-305 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Against the background of long-term availability of natural gas, its present technology and future prospects are described. Particular emphasis is put on the oxidative coupling of methane to C2+ hydrocarbons: (1) Catalyst development, activity, selectivity and deactivation as well as reactor operation are discussed; (2) a tentative process scheme is put forward and its economics evaluated with respect to ethylene production.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 323-329 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The conversion of a number of alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and cyclic compounds and their mixtures on H-ZSM-5 at 673 K was investigated. These compounds can be easily converted to aromatic hydrocarbons if the C/H ratio of the molecule fragment, remaining after elimination of oxygen as water, is less than 0.62. At higher C/H ratios, coking of the catalyst increases, thus reducing its lifetime, a difficulty which can be overcome by hydrogenation of these compounds prior to their conversion over H-ZSM-5. A procedure is proposed for converting at least a part of organic waste chemicals to valuable products instead of burning them.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 53
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An experimental study of the flow of phosphate mine tailings was carried out in order to characterize these suspensions of fine particles for pipeline transport. Rheological measurements with a rotating cylinder viscometer indicate a viscoplastic behaviour which can be represented by a Herschell-Bulkley or by a Casson model. The variation of the parameters of these models with solids concentration reveals a change in the behaviour at a concentration of 10 to 15%. The pressure drops were measured during flow in capillary tubes, in both laminar and turbulent regimes. The variation of the pressure drop coefficient (Fanning friction factor) as a function of the generalized Reynolds number confirms the validity of the employed rheological models. The results are in good agreement with measurements made in pipes of industrial size. The velocity profiles measured with a novel ultrasonic velocimeter demonstrate the influence of the rheological behaviour on the yield and wall stresses.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 330-337 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The aim of this investigation is to show the demarcation of two possible mechanisms for surface deposition of fine particles on the rear surface of single spheres. By means of single particle trajectory computation, based on numerically determined flow fields (Remax = 103), it is shown that the mere existence of a wake is not in itself sufficient to produce eddy deposition. In addition, the particle's motion must undergo a lateral transfer promoted by fluid trubulence, in order to effect eddy deposition commencing at a Reynolds number of about 100. On the other hand, rear deposition, influenced by electrostatic forces, especially by the Coulomb force, is possible at any Reynolds number. Consequently, for Reynolds numbers of less than 100, only electrostatic effects can produce rear surface deposition. In the range of high Reynolds numbers, the coexistence of both mechanisms is possible. Very high Reynolds numbers (Re 〉 103) and low Stokes numbers indicated the predominance of the electrostatic effect over eddy deposition, whereas at very high Reynolds numbers and medium to high Stokes numbers the electrostatic effect is only predominant in presence of high electrostatic charges.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 349-352 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A simplified reactor model can be used for predicting the performance of an industrial VGO-treater. Laboratory-scale experiments performed on the same feed and catalyst as those in the industrial unit lead to a reactor simulation which agrees well with the data from this unit. In the laboratory experiments, it is possible to overcome the specific hydrodynamic problems of tricklebed reactors by appllying the catalyst dilution technique. Results obtained by this technique allowed the development of a reactor model which enables the user to simulate the adiabatic behaviour of the industrial reactor. In this way, the significant gap between the reaction temperature in the isothermal laboratory reactor and the WABT of the industrial adiabatic reactor can be bridged.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 361-367 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The rate behaviour of multi-step reaction systems is difficult to model. Concentration-controlled investigations in a recycle reactor provide new tools for this purpose, e.g. the possibility to decompose a network into single reaction steps. Methanation of carbon monoxide over a supported Ni catalyst could be shown to be accompanied to a considerable extent by the shift reaction, and to a lesser extent by direct hydrogenation of carbon dioxide. Deactivation of the catalyst was measured at definite gas compositions. The two main steps show different responses to deactivation: Separable kinetics was found only for the methanation step. Power law rate equations were fitted to the rate data of the individual reaction steps to represent the main features of their kinetic behaviour. Some aspects of deactivation kinetics are also discussed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 368-375 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This contribution presents the measurements of bubble behaviour in presence of A, B and D powders in a semi-industrial scale pressurized fluidized bed. Local measurements were taken at static pressures of 0.2, 1.0 and 2.5 MPa, using capacitance probes. Quartz sand with mean particle diameter of 157 μm was fluidized in small “two-dimensional” transparent equipment with Frigen R 115. In addition, pressure fluctuations in the bulk of the fluidized bed with inner diameter of 0.4 m were studied experimentally.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 353-360 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Correlation flowmeters have been used in the scientific field for many years and are actually gaining greater commercial importance due to an increasing number of applications in industrial plants. The importance of the correlation method is based on the fact that essentially no alternatives exist for measuring velocity and mass flow rate in pneumatic conveyors. However, the hitherto employed transit time correlation method leads to results which are clouded by uncertainties. The commonly used theoretical model of the measurement process does not explain these effects satisfactorily. Therefore, the theory of non-intrusive flow sensors is reinvestigated from a physical standpoint. The derived model permits a discussion of the transit time correlation method in some detail. Furthermore, this model leads to an alternative sensor arrangement and signal processing scheme which makes it possible to measure the true mean velocities. Examples of experimental results are given.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 59
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: For the simulation of steady- and non-steady-state behaiour of separation columns, a simulation program was developed and employed for the calculation and optimization of methanol-water separation. The demand for increasingly higher purities and energy-saving optimization of plants results in complex column configurations and thus in complex control schemes. The number of possible control schemes was reduced on the basis of heuristic rules. By simulating the process, the optimum control and manipulative variables and measuring points were determined from the reduced number of control concepts. A control scheme was introduced. The model was verified by simulation of the dynamic behaviour of the process. The investigation included the effects of computing technique, time interval, model reduction and tray hold-up on the results. Thus, various effects and interactions were verified theoretically with respect to the robustness of the model. This was followed by a simulation of the non-ontrolled and controlled column. By implementing the controllers in the existing column program, the computer can predict the control parameters. These parameters were checked and corrected when the metahnol-ater column was put in operation. In the start-up phase, major problems were caused by the sensitivity and failure rate of density, throughput and pump measuring sensors. Feed impurities were another source of problems. Operation with high product purities is possible, with a side stream to discharge impurities.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 382-389 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Phase equilibria in the n-hexadecane-water-hydrogen and n-hexadecane-benzene-water-hydrogen systems were determined experimentally at temperatures between 200 and 350°C and pressures between 100 and 300 bar. At high water concentrations, three-phase equilibria were observed. Two-phase regions could be correlated with a modified Redlich-Kwong equation of state. The influence of interaction parameters on the calculated miscibility gaps was investigated. On application of mean interaction parameters, it is possible to calculate phase equilibria at different pressures or temperatures with the same set of parameters. In the ternary system, the three-phase regions could be calculated from the correlated binodal curves of two-phase regions. In the quaternary system, cross-sections through the vapour-liquid miscibility gap could be successfully correlated.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 375-382 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the extraction literature, no attention has been given so far to differential calculation models for countercurrent extraction columns which take into account the changes in flow rates of the phases as a result of transferred mass, and which also reflect the variations in interfacial area per unit volume and in axial dispersion coefficients since these depend on the flow rates. The present contribution puts forward a formulation of such a model; this results in a set of non-linear differential equations with separated boundary conditions, representing the feeds at either side of the extraction column. This set of differential equations must be solved numerically. The model is illustrated by a sample calculation on the extraction of benzene with furfural. In this (realistic) example, the interfacial area per unit volume varies from bottom to top by a factor of 3. Ignoring this effect would obviously result in serious under- or overdesign.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 405-410 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Starting from the assumption that the growth of desublimed layers is governed mainly by heat and mass transfer, the authors present a model based on conditions in the diffusion boundary layer and suggest that the “hoarfrost”Hereafter the term frost will be used instead of hoarfrost. density depends on only one parameter. The discussion accounts for the process determining factors, i.e. the growth rate, mass transfer and gas concentration. The theoretical relationship is confirmed by the authors' own experiments on two systems and data from literature. The relationship can be established by a few laboratory experiments and permits the calculation of frost density and of associated variables, thus facilitating the optimization of desublimator design.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 411-419 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This contribution reviews the work performed mainly at Bergbau-Forschung during the past few years. First, it deals with the quantitative description of gasification kinetics, taking into account the pressure of the gasifying agent and partial pressures of product gases. Thereby, a method and quantitative data are provided for the calculation of reaction rates for uncatalyzed and potassium-catalyzed gasification, on the example of chars from high volatile bituminous coals. In addition, a method for characterization of internal surface area by oxygen chemisorption with respect to char reactivity has been improved. Progress has also been achieved in the assessment of the impact of pyrolysis conditions, especially the time-temperature profile during char formation, on its chemical activity during subsequent use.
    Zusätzliches Material: 12 Ill.
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  • 64
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 398-404 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Previous investigations have shown that the specific energy input is the overall parameter of influence on product size during communition in agitated ball mills, from laboratory up to industrial scale. The specific energy input is the introduced energy related to the amount of comminuted material. This parameter can be used for mill scale-up. Consequently, a method had to be found of introducing power into the mill so as to obtain a given specific energy input. For this purpose, stirring tests with purely Newtonian liquids were carried out in absence of solids and hence, without comminution. Mathematical models are presented which describe the power consumption in agitated ball mills in absence of grinding beads. In addition, tests with grinding beads filling were also performed, leading to scale-up guidelines with respect to power consumption. Finally, the influence of size and material of grinding beads was investigated.
    Zusätzliches Material: 9 Ill.
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  • 65
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A pressure swing adsorption process for hydrogen recovery from coke oven gases comprises the steps of adsorption at pressures above 6 bar, cocurrent and countercurrent depressurization, purging with hydrogen at ambient pressure and repressurization. The process was investigated in the cyclic mode, on a laboratory scale, using an adsorber filled with 1.3 litres of carbon molecular sieve. Based on the test results of concentrations and pressures within the adsorber during complete cycles, a pseudo-homogeneous model was developed for the adsorption step. Adsorption equilibrium parameters were determined by separate measurements, while the transport parameters were evaluated by fitting the experiments of the fixed bed adsorber. It was possible to consider the residual load, resulting from an incomplete regeneration, by the assumption of a load distribution in the inlet region of the adsorber.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 10 (1987), S. 420-426 
    ISSN: 0930-7516
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: An important aspect of nuclear and chemical reactor safety is the ability to predict the maximum or critical mass flow rate from a break or leak in a pipe system. At the beginning of such a blowdown, if the stagnation condition of the fluid is subcooled or slightly saturated thermodynamic non-equilibrium exists in the downstream, e.g. the fluid becomes superheated to a degree determined by the liquid pressure. A simplified non-equilibrium model, explained in this report, is valid for rapidly decreasing pressure along the flow path. It presumes that fluid has to be superheated by an amount governed by physical principles before it starts to flash into steam. The flow is assumed to be homogeneous, i.e. the steam and liquid velocities are equal. An adiabatic flow calculation mode (Fanno lines) is employed to evaluate the critical flow rate for long pipes. The model is found to satisfactorily describe critical flow tests. Good agreement is obtained with the large scale Marviken tests as well as with small scale experiments.
    Zusätzliches Material: 12 Ill.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    International journal of anthropology 2 (1987), S. 141-149 
    ISSN: 1824-3096
    Schlagwort(e): Absolute finger ridge count ; Genetics ; Dermatoglyphics ; India ; Major gene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In order to test the hypothesis of a major gene effect on absolute total finger ridge count (ATFRC), the nature of relationship between mean ATFRC and its variability was evaluated in a series of 47 population samples from India. Regression analysis showed that both the standard deviation and the coefficient of variation are significantly related to mean ATFRC, and about 35% of the variation in ATFRC is explained by the dependent variable coefficent of variation. These results support the hypothesis of a major gene effect on the trait ATFRC.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 5-9 
    ISSN: 0749-503X
    Schlagwort(e): Schizosaccharomyces pombe ; sterile mutants ; ste genes ; protoplast fusion ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: In previous experiments of Girgsdies (1982), eight sterile (ste) mutants of Schizosaccharomyces pombe did not sporulate when fused with h+ or h- protoplasts. We succeeded in achieving sporulation with these mutants. Two hitherto unknown ste genes, ste7 and ste8, were found.
    Zusätzliches Material: 3 Tab.
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 1-4 
    ISSN: 0749-503X
    Schlagwort(e): Cell cycle ; sporulation ; meiosis ; nuclear division ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The cell division age dependency of sporulation was investigated in a diploid strain of Saccharomyces cerevisiae (19el) which undergoes a single equational nuclear division during sporulation with consequent formation of asci containing two uninucleate diploid spores (apomictic dyads). Under modified nutritional conditions which partially restore meiosis and hence normal tetrad formation, newly formed (age 0) daughter cells were observed to be capable of formation of apomictic dyads but not of meiotic tetrads. Even under conditions in which only apomictic dyads developed, approximately 20% of the asci resulted from differentiation of newborn ‘inexperienced’ cells. Thus, the data indicated production of at least one bud to be a prerequisite for meiosis but not for apomixis; however, occurrence of at least one complete mitotic cell division cycle was evidently insufficient for the morphogenetic switch from diploid to haploid spore formation, since older cells bearing several bud scars often underwent apomictic dyad development, and some produced no spores.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 70
    ISSN: 0749-503X
    Schlagwort(e): Yeast protein map ; carbon metabolism machinery ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Using a modification of the basic two-dimensional polyacrylamide gel electrophoresis technique, we have undertaken a systematic identification of the polypeptides of the protein map of Saccharomyces cerevisiae corresponding to components of the carbon metabolism machinery. To the previous location of nine glycolytic enzyme polypeptides on the yeast protein map we add the location of 23 polypeptides. Ten of them were identified as corresponding to cytoplasmic enzymes of the carbon metabolism machinery and 13 were characterized as mitochondrial proteins. The criteria used to establish the identification of these polypeptides spots include migration with purified proteins, immunodetection, overproduction by plasmid-carrying strains and physiological behaviour.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987) 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 72
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 263-270 
    ISSN: 0749-503X
    Schlagwort(e): Lodderomyces elongisporus ; Rhodotorula gracilis ; Saccharomyces cerevisiae ; accumulation ratio ; membrane transport ; suspension density ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The previously described effect of cell suspension density on metabolic and transport phenomena in yeast, apparently caused by inhibition by dissolved carbon dioxide, is also observed with the accumulation ratio of both sugars and amino acids where not only a kinetic but also an energetic factor comes into play. Unlike all previously measured metabolic and transport parameters, the dependence of the accumulation ratio on suspension density is not monotonic but shows a pronounced maximum in the range of 4-8 mg dry wt/ml, depending on yeast species and on cultivation conditions. In Rhodotorula gracilis and in Lodderomyces elongisporus it is not due to CO2 but is semiquantitatively related to the proton-motive force across the plasma membrane as well as to the intracellular ATP content. It is observed both in oxygen and in argon, over a wide range of pH values and of temperatures, but it is suppressed by metabolic inhibitors. It is expressed only in a range of transported solute concentrations between about 0·1 and 10 mM.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 43-49 
    ISSN: 0749-503X
    Schlagwort(e): Heterologous gene expression ; Hepatitis B ; protein estimation ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Purified recombinant hepatitis B surface antigen separated on polyacrylamide gels in the presence of sodium dodecyl sulphate has a very low staining index with Coomassie blue relative to a number of standard proteins. In contrast the protein stains better than average with silver nitrate. This property has been used to develop a semi-quantitative method of estimation of recombinant surface antigen in extracts of Saccharomyces cerevisiae producing this protein. The method can be used to follow purification protocols. It is quick, simple and since it measures the surface antigen biochemically, is independent of the aggregation state or conformation of the protein, a factor which can affect enzyme-linked immunoassays which rely on antigen-antibody interactions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 33-42 
    ISSN: 0749-503X
    Schlagwort(e): Yeast ; acid phosphatase ; gene regulation ; upstream activating sequences ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: To identify the sequences involved in the regulation of the yeast acid phosphatase gene (PHO5) we constructed a series of hybrid promoters. Increasing lengths of 5′-flanking sequences of the PHO5 gene were placed in front of the TATA-box of constitutively expressed acid phosphatase gene (PHO3).The PHO5/PHO3 promoter constructions were used to replace the entire PHO5, PHO3 gene cluster on chromosome II. Depending on the length of PHO5 5′-flanking sequences present the PHO3 gene driven by the hybrid promoter could now be derepressed in response to inorganic phosphate (low Pi) exactly as the PHO5 wild type gene. A critical regulatory element was located between position -402 to -351 (upstream from ATG) and sequences further downstream (from -351 to -300) could increase transcriptional activation. The transcription levels of PHO3 were determined by northern blot analysis, under repressed (high Pi) and derepressed (low Pi) conditions which was paralleled by an increase in extra-cellular acid phosphatase activity. Fully regulated promoter hybrids showed a 40-fold induction of mRNA levels, comparable to wild type PHO5 promoter. S1-nuclease protection experiments revealed that the PHO5 5′-flanking sequences, placed in front of PHO3, did not change the PHO3 transcription initiation site/s.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987) 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 117-129 
    ISSN: 0749-503X
    Schlagwort(e): Killer ; virus-like particles ; nucleotides ; pyrophosphatase ; RNA polymerase ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The intracellular killer virions of yeast co-purify with an RNA polymerase activity which catalyzes the synthesis of fulllength transcripts of the two viral genomic double-stranded RNA segments. This polymerase utilizes ribonucleoside diphosphates or triphosphates as substrates. The virions have other associated nucleotide-metabolizing enzyme activities, including nucleoside diphosphate kinase, adenosine monophosphate kinase, and nucleoside triphosphate phosphotransferase, an activity which catalyzes the exchange of gamma-phosphate from any ribonucleoside triphosphate with any ribonucleoside or deoxyribonucleoside triphosphate. The purified virions also contain an inorganic pyrophosphatase activity. These enzymes may allow the virus to utilize nucleotide pools distinct from those utilized in host cell transcription.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 77
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 131-137 
    ISSN: 0749-503X
    Schlagwort(e): Transformation ; Saccharomyces ; plasmid ; DNA uptake ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: We have studied the mechanism of DNA transformation of whole yeast cells in Saccharomyces cerevisiae with particular emphasis on the role of the cell wall complex in DNA uptake. Two new aspects of the process have been investigated in order to evaluated its specificity. Such aspects are: (i) effect of monovalent vs. divalent cations during incubation with the transforming DNA and (ii) timing of DNA adsorption and uptake. We found that the specificity for cation requirement is a strain-dependent characteristic influenced by the presence of transforming DNA in the cell suspension. This finding is supported by reports from several laboratories that some yeast strains show mutually exclusive transformability with monovalent vs. divalent cations. While irreversible adsorption of plasmid DNA molecules is induced by both heat shock and polyethylene-glycol(PEG), DNA uptake seems to occur only after the removal of PEG. In the course of this study we have developed a new, alternative method of whole cell DNA transformation with CaCl2 able to transform strains that do not respond to other methods.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 139-148 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 187-200 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 161-174 
    ISSN: 0749-503X
    Schlagwort(e): Saccharomyces cerevisiae ; mitochondria ; cAMP-dependent protein kinase ; submitochondrial localization ; topology ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: We describe the identification and submitochondrial localization of four protein kinases and of their target proteins in derepressed yeast mitochondria. The activity of one of the kinases depends on the presence of cyclic AMP (cAMP). It is soluble and localized in the mitochondrial intermembrane space. Its natural target is a polypeptide of 40 kDa molecular mass, which is bound to the inner membrane. Besides this natural target this kinase phosphorylates acidic heterologous proteins, like casein, with high efficiency. The other protein kinases identified so far are cAMP-independent. At least one is localized in the matrix having its natural substrates (49 and 24 kDa) in the same compartment. Two others are firmly bound to the inner membrane phosphorylating target proteins in the inner membrane (52·5 kDa) and in the intermembrane space (17·5 kDa), respectively.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 149-160 
    ISSN: 0749-503X
    Schlagwort(e): DNA repair ; RAD2 ; Saccharomyces ; gene expression ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The cloned RAD2 gene of S. cerevisiae was tailored into regulatable expression vectors for overexpression of Rad2 protein in E. coli and in yeast. In E. coli both Rad2/β-galactosidase fusion protein and native Rad2 protein are insoluble, but are extractable with 1% Sarkosyl. In yeast some of the overexpressed native Rad2 protein is also insoluble; however, soluble protein is readily detected by immunoblotting with Rad2-specific antibodies. All forms of the protein detected in transformed or untransformed yeast cells and the insoluble species in E. coli migrate in denaturing polyacrylamide gels with an apparent molecular weight considerably larger than the size predicted from the sequence of the RAD2 coding region. This property is not the result of post-translational glycosylation detectable by binding of concanavalin A, or of phosphorylation of the protein. Overexpression of the RAD2 gene is toxic to yeast. Transformed yeast cells grow much more slowly than untransformed controls and when yeast transformants are serially propagated cultures show considerable colony heterogeneity and concomitant selection for rapidly growing variants which express less Rad2 protein. Antisera raised against Rad2/β-galactosidase fusion protein expressed in E. coli do not cross-react with Rad1, Rad3 or Rad10 protein in crude extracts of yeast, nor with purified E. coli UvrA, UvrB or UvrC proteins.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 82
    ISSN: 0749-503X
    Schlagwort(e): Cellulases ; Endoglucanases ; Trichoderma reesei ; Saccharomyces cerevisiae ; Cellulolytic yeast ; secretion ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The cDNA copies of the two endo-β-1,4-glucanase genes, egl1 and egl3, from the filamentous fungus Trichoderma reesei were expressed in yeast Saccharomyces cerevisiae under the control of the yeast phosphoglycerate kinase gene promoter. Active EGI and EGIII enzyme was produced and secreted by yeast into the growth medium. The recombinant EGI enzyme was larger and more heterogeneous in size than the native enzyme secreted by Trichoderma, due to differences in the extent of N-glycosylation between these two organisms. The morphology of the yeast cells producing EGI or EGIII was clearly different from control strain.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 209-221 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 84
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Materialart: Digitale Medien
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  • 85
    ISSN: 0749-503X
    Schlagwort(e): Pichia pinus ; alcohol oxidase ; catabolite repression ; metabolic regulation ; methanol ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The effect of various carbon compounds on the synthesis of alcohol oxidase in a medium with methanol was studied in the wild type strain of Pichia pinus as well as in gcr1 and ecr1 mutants defective in glucose and ethanol repression of methanol metabolic enzymes, respectively. Compounds repressing the synthesis of alcohol oxidase in the wild type strain were divided into four groups. Repression of alcohol oxidase by compounds of the first group (glucose, fructose, mannose, galactose, L-sorbose and xylose) was impaired only in the gcr1 mutant and that by compounds of the second group (ethanol, acetate, 2-oxoglutarate and erythritol) only in the ecr1 mutant. Repression by compounds of the third group (malate, dihydroxyacetone) was not impaired in both these regulatory mutants and that by compounds of the fourth group (succinate, fumarate, L-arabinose, sorbitol, salicin, xylitol and cellobiose) was partially reduced in both gcr1 and ecr1 strains.Mutation gcr1 causes a significant decrease in phosphofructokinase activity. It also led to a six- to seven-fold increase in intracellular pools of glucose-6-phosphate and fructose-6-phosphate and to a two-fold decrase in the intracellular pool of fructose-1,6-bisphosphate. In ecr1 strains, a decrese in 2-oxoglutarate dehydrogenase activity accompanied by an increae in activities of NAD- and NADP-dependent isocitrate dehydrogenases and NAD- and NADP-dependent glutamate dehydrogenases was demonstrated. The intracellular pool of 2-oxoglutarate was increased 2·5-fold in ecr1 strains. Genes GCR1 and ECR1 are not linked.The mechanisms of catabolite repression of alcohol oxidase in methylotrophic yeasts are discussed.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987) 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 87
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 23-32 
    ISSN: 0749-503X
    Schlagwort(e): Zygosaccharomyces ; weak-acid resistance ; intracellular pH ; yeast ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Weak acids and hydrogen ions in different concentration combinations affect the intracellular pH value (pHi) of Zygosaccharomyces bailii. The lowest pHi value measured was not at the most extreme, but at intermediate conditions of inhibition. Proton and organic-acid ejection, on a cell volume basis, is greater in cells grown under inhibitory conditions and is stimulated by weak acids, whilst in cells not grown under inhibitory conditions acid efflux is lower and is depressed by weak acids; this may be important in the maintenance of tolerable pHi values in the presence of weak acids. The concentration of benzoic acid measured internally is identical to the value expected from its pK, external pH and pHi. Addition of fructose to starved cells causes both a decreased pHi and a concomitant efflux of previously loaded benzoic acid, quantitatively in accord with the shift in equilibrium of the freely permeable undissociated acid. There is no evidence that weak acids are actively extruded. Protoplast volume also varies with hydrogen-ion and weak-acid concentration and this too may play a role in intracellular pH maintenace.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 62-62 
    ISSN: 0749-503X
    Schlagwort(e): Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Materialart: Digitale Medien
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  • 89
    ISSN: 0749-503X
    Schlagwort(e): Genome organization ; Saccharomyces cerevisiae ; chromosome I ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: MAK16 is an essential gene on chromosome I defined by the thermosensitive lethal mak16-1 mutation. MAK16 is also necessary for M double-stranded RNA replication at the permissive temperature for cell growth. As part of an effort to clone all the DNA from chromosome I, plasmids that complemented both the temperature-sensitive growth defect, and the M1 replication defects of mak16-1 strains were isolated from a plasmid YCp50: Saccharomyces cerevisiae recombinant DNA library. The two plasmids analysed contained overlapping inserts that hybridized proportionally to strains carrying different dosages of chromosome I. Furthermore, integration of a fragment of one of these clones occurred at a site linked to ade1, confirming that this clone was derived from the appropriate region of chromosome I. An open reading frame adjacent to MAK16 potentially coding for a 468 amino acid protein was defined by sequence analysis. 185 amino acids of this open reading frame were replaced with a 1·2 kb fragment carrying the S. cerevisiae URA3 gene by a one-step gene disruption. The resulting strains grew at a rate indistinguishable from the wild type at 20°C, 30°C, or 37°C, but could not grow at 8°C. The deleted region is thus essential only at 8°C, and we name this gene LTE1 (low temperature essential).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 71-76 
    ISSN: 0749-503X
    Schlagwort(e): OFAGE ; X-ray damage ; DNA repair ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Orthogonal field alternation gel electrophoresis (OFAGE) allows separation of DNA molecules in the size range of 200 kb to 3000 kb. These sizes encompass the chromosome sizes of the genome of Saccharomyces cerevisiae. Using this technique, we have found that yeast cells exposed to X-rays generate a smear of DNA fragments corresponding to the products of random, independent double strand breaks, and that the bands corresponding to unbroken chromosomes decrease in intensity in direct proportion to chromosome size. If exposed wild type cells are permitted time to repair (5 h at 30°C on YEPD), the fragments partially disappear and the chromosome bands reappear, although at less than normal intensity. In certain radiation-sensitive mutants (rad51, rad52 and rad54), the fragment smear appears following X-ray exposure but no repair of broken chromosomes occurs. In fact, loss of the fragments occurs; this could appear as partial repair using other procedures.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 77-84 
    ISSN: 0749-503X
    Schlagwort(e): Microbodies ; Saccharomyces cerevisiae ; oleic acid ; β-oxidation ; catalase ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The development of microbodies in the yeast Saccharomyces cerevisiae was studied in response to different conditions of growth. Various strains of S. cerevisiae were investigated, using cells from the exponential growth phase on glucose as an inocullum in all transfer experiments. Electron microscopy, including serial sectioning, revealed that these cells generally contained one to four small microbodies which were localized in the vicinity of the cell wall and characterized by the presence of catalase. Transfer of these glucose-grown cells into media supplemented with various compounds known to induce microbody proliferation in other yeasts - i.e. uric acid, alkylated amines, amino acids, C2-compounds such as ethanol or acetate, in the presence or absence of compounds that induce oxygen radical formation - did not result in a significant change in the number of microbody profiles observed. Marked microbody proliferation was, however, observed after a shift of cells into media containing oleic acid and was associated with the induction of activities of β-oxidation enzymes. In addition, catalase and isocitrate lyase were present in enhanced levels. Kinetic experiments suggested that these microbodies developed from those originally present in the inoculum cells. In thin sections up to 14 microbody profiles were occasionally observed, often present in small clusters. Their ultimate volume fraction amounted to 8-10% of the cytoplasmic volume.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 92
    ISSN: 0749-503X
    Schlagwort(e): Cyclic AMP ; nitrogen limitation ; resting state ; cell cycle ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: We have identified a mutation called rcal (for rescue by cAMP) which allows adenylate cyclase-deficient mutants to divide in the presence of cAMP. We took advantage of this rcal mutation to study the effect of externally added cAMP on the onset of the resting state when cells are starved for ammonium. We measured the resistance of the cells to zymolyase treatment as a parameter of the resting state. We observed that the onset of the resting state is reversibly blocked by cAMP. This inhibitory effect of cAMP is discussed together with the cAMP control of the start. This leads us to propose a model in which the cAMP level, controlled by the availability of nutrients, should trigger the choice between the entry of the cell into the resting state and the initiation of a new division cycle.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 95-105 
    ISSN: 0749-503X
    Schlagwort(e): Saccharomyces cerevisiae ; tryptophan accumulation ; genetic engineering ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Plasmid pME559, carrying all five yeast TRP genes, was constructed. This plasmid is a yeast/Escherichia coli shuttle vector based on pBR322 and 2 μm-DNA sequences derived from plasmid pJDB207. We studied in yeast (i) the stability of the plasmid under selective and non-selective conditions, (ii) expression of all five TRP genes and (iii) tryptophan accumulation in yeast transformants. These studies were conducted in comparison with an earlier construction, pME554, which differs from plasmid pME559 in the expression of the TRP1 gene and which carries the TRP2 wild type instead of the TRP2fbr mutant allele. For stable maintenance of the plasmids in yeast a selection was necessary. Plasmid pME559 displayed normal expression of all TRP genes, and enzyme levels on average 23-fold higher than in the wild type strain were found. In comparison, the maximal tryptophan flux observed in such a plasmid-carrying strain was about ten-fold higher than the maximal flux capacity in the wild type strain.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 107-115 
    ISSN: 0749-503X
    Schlagwort(e): DNA replication ; ARS elements ; histone genes ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: We have previously identified an autonomously replicating segment (ARS) near the 3′ end of the histone H4 gene at the copy-I H3-H4 locus. We have now searched for additional autonomously replicating segments and sequences homologous with the ARS core consensus sequence near the copy-II histone H4 gene and both of the histone H3 genes. No new ARS elements were identified by functional cloning assays. However, several matches to the ARS core consensus element were found within the DNA sequencs of the copy-I and copy-II genes. An exact match to the ARS core consensus was identified in the region downstream from the copy-I histone H3 gene and a set of sequences with weak homology was also locatd within the copy-II region. However, restriction fragments including these sequences did not demonstrate ARS activity on a plasmid in transformed cells.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 3 (1987), S. 201-206 
    ISSN: 0749-503X
    Schlagwort(e): Flocculation ; yeast ; shaking ; activation-energy ; surface-charge ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Flocculent yeast cells have an absolute requirement for mechanical energy input in order for flocculation to occur. Flocculation is arrested by cessation of energy input. The initial rate of flocculation increases as the square of the cell concentration. There is a minimum shaking speed to initiate flocculation and thereafter the initial rate of flocculation increases exponentially with the shaking speed. The minimum shaking speed for flocculation to occur increases with pH value. Activation energy for flocculation, derived from Arrhenius-like plots, varies with pH value. We propose that activation energy is required to overcome mutual repulsion between charged yeast cells and allow flocculent bonds to be formed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 1-9 
    ISSN: 0192-253X
    Schlagwort(e): T/t-complex ; LT mice ; parthenogenesis ; recombination ; gene-mapping ; primitive streak ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Ovarian teratomas that result from parthenogenetic activation of oocytes provide a double tool for developmental geneties. First, they provide a way of measuring recombination between a gene and its centromere. Second, in the absence of crossing over there is the potential of producing tumors that are homozygous for genes that would be lethal in the course of in utero embryonic development. We have applied both aspects to several t- haplotypes containing different early acting t-lethal genes. In a study of 26 tumors, genotyped by Southern blot analysis of the major histocompatibility complex (MHC), we measured the distance between the centromere and the start of the t-complex as 5.6 ± 2.3 cM. We found a marked deficiency of t-homozygous genotypes among the tumors we studied, although T/T genotypes formed teratomas at levels comparable to controls. None of the lethal t-haplotypes we studied permit homozygous embryos to develop to the primitive streak stage, while T/T embryos do develop essentially normally through that stage. Thus, although the total number of tumors observed from t-bearing mice was small, the great difference in the incidence of t/t tumors versus the incidence of T/T tumors suggests strongly that the parthenogeretic embryos that convert to teratocarcinomas must first pass through some of the stages of normal early development, including the formation of three germ layers and the primitive streak.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 97
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 35-43 
    ISSN: 0192-253X
    Schlagwort(e): development ; isozymes ; murine trisomy ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: We examined developmental changes in the relative activities of three different isozyme systems: aldolase, enolase and phosphoglycerate mutase, in tissues of fetal mice with trisomy 16 and of fetal euploid littermates. We wanted to determine whether morphological abnormalities such as reduced weight and size, which are generally observed in murine trisomy, are reflected at the molecular level. Following electrophoretic separation and subsequent measurement of relative activities of enolase isozymes in brain and phospho-glycerate mutase isozymes in heart, we found no significant differences between trisomy 16 fetuses and their euploid littermates. Synthesis of liver-specific aldolase was, however, delayed in trisomy 16 fetuses.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 83-89 
    ISSN: 0192-253X
    Schlagwort(e): chick blastula ; hypoblast-epiblast interaction ; transcriptional control ; α-amanitin ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Interaction between the epiblast and the primary hypoblast in chick blastula results in induction of the primitive streak (PS) in the epiblast. Alpha-amanitin, a specific inhibitor of poly A-containing RNA synthesis, inhibits formation of the definitive PS. This inhibition is associated with qualitative changes in the pattern of protein synthesis in the hypoblast but not in the epiblast. The protein pattern of the component areas of the epiblast shows increase in some polypeptides after treatment with α-amanitin. By contrast, α-amanitin resulted in a decrease in synthesis of several polypeptides, which are either undetectable or weakly present in the hypoblast. The α-amanitin-sensitive translational products of the embryonic genome that are observed in the hypoblast may have specific functions in the control of PS induction and stabilization.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 207-218 
    ISSN: 0192-253X
    Schlagwort(e): chimeras ; ovotestes ; sex differentiation ; sex mosaics ; hermaphrodites ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The majority of XX ↔ XY chimeric mice develop into fertile males. The sexual differentiation of the gonads in these animals has been examined on days 12-14 postcoitum to determine if their development parallels that of normal testes. It was found that 50% of chimeric fetuses, the proportion predicted to be XX ↔ XY, had neither normal testes nor ovaries. Instead, ovotestes were present, with varying proportions of presumptive ovarian and testicular tissue. On day 12 the ovotestes were organized with testicular tissue in the central region and ovarian tissue at the craniad and/or caudad poles. In the more advanced fetuses there was evidence of regression of the ovarian portion, which would account for the testes found in adults. These results are discussed in light of current theories of sex determination and differentiation and what was previously known about gonads of sex mosaics.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 249-265 
    ISSN: 0192-253X
    Schlagwort(e): trisomy ; trisomy 16 mouse ; trisomy 19 mouse ; Down syndrome ; gene dosage effects ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Autosomal aneuploidy in mammals adversely affects developmental processes. In human beings, for example, trisomy 21 is the most frequent aneuploidy detected among newborns and the most common known genetic cause of mental retardation. In this review, several hypotheses are discussed that have been proposed to explain the mechanisms by which aneuploidy (especially trisomy) disrupts development. These mechanisms included specific gene dosage effects, generalized disruption of genetic homeostasis, and the influence of the parental origin of the duplicated chromosome. The availability of specific chromosomal rearrangements in mice, coupled with selective breeding schemes, permits generation of aneuploidy of specific chromosomes or chromosomal segments on controlled genetic backgrounds, thus enabling the systematic study of the causes and consequences of defined aneuploidy. Phenotypic characteristics associated with a number of specific aneuploidies in the mouse are discussed. Emphasis is placed on the effects of trisomy 16. Genetic homology between mouse chromosome 16 and human chromosome 21 has led investigators to suggest that analogous mechanisms will be responsible for the developmental abnormalities produced in these respective aneuploidies. Analysis of trisomy 16 mice from the organismal to the subcellular level has revealed a number of phenotypic characteristics (particularly neurobiologic ones) shared with human trisomy 21. The dosage effects of shared genes (or their products) may contribute to the development of these features.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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