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  • American Chemical Society  (25)
  • Wiley  (18)
  • Wiley-Blackwell  (7)
  • Annual Reviews  (4)
  • Institute of Physics
  • 2010-2014
  • 1995-1999  (53)
  • 1955-1959  (2)
  • 1935-1939
  • 1998  (28)
  • 1996  (25)
  • 1957  (2)
  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Analytical chemistry 29 (1957), S. 154-155 
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 32 (1998), S. 1-6 
    ISSN: 0066-4197
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Anthropology 25 (1996), S. 105-126 
    ISSN: 0084-6570
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Ethnologie , Biologie
    Notizen: Abstract Any understanding of contemporary biodiversity change in the Americas is likely to be uninformative and misleading if it employs a prehistoric baseline imbued with pristine characteristics. Archaeological evidence clearly displays a protracted history of environmental transformations at varying geographical and temporal scales throughout the Holocene (that is, the past 10,000 years). Because of problems inherent to the interpretation of the archaeological record, the genesis of these transformations often can only be ambiguously attributed to environmental and/or anthropogenic origins. However, at any given time or place, both the distribution of the numbers of different kinds of organisms and their relative abundances were in a constant state of flux since the retreat of glacial cover some 10,000 years ago. Here I review archaeological evidence to illustrate the dynamism of prehistoric biodiversity, which can be attributed to environmental events, to anthropogenic causation, or as a response of these to each other.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The methanolysis of the epimeric 7-chloro-7H-yohimbine derivatives 2 and 3 was reinvestigated. In case of the 7α-epimer 2, the reaction was uneventful and conformed with earlier observations, i.e., under sufficiently mild conditions, only the imino ether 4 (= imino ether A) was produced. Under the same conditions, the less reactive β-isomer 3 furnished a mixture of both imino ethers 4 and 5, accompanied by the elimination product 11, and by equal amounts of yohimbine (1) and 3,4,5,6-tetradehydroyohimbine (12), which are believed to arise through a disproportionation process of the putative intermediate 5,6-didehydroyhimbine (23). The nature of this divergent reactivity and of the ready equilibration of 4 and 5 was investigated by means of extensive force-field and semi-empirical calculations (AM1 and PM3) of various conformers of the compounds 2-5 and of some possible reaction intermediates.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 869-876 
    ISSN: 0947-6539
    Schlagwort(e): ab initio calculations ; silaguanidinium cations ; silylium cations ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quantium mechanical calculations at the MP2/6-31 G(d) level are reported for the silaguanidinium cation Si(NH2)3+ (1) and derivatives thereof. The equilibrium structure 1a has D3 symmetry with planar amino groups rotated out of the SiN3 plane by 19.60. The Si-N bond length of 1 a (1.658 Å) is intermediate between a single and a double bond. Isodesmic reactions show that the stabilization of the silylium cation 1 a by the amino groups (63.5 kcal mol-1) is about 40% of the resonance stabilization of the guanidinium cation (159.3 kcal mol-1), but 1 a is clearly better stabilized than alkyl-substituted silylium cations. The electronic stabilization of 1 a by the amino groups is also made obvious by the calculated complexation energy with one molecule of water. The calculated stabilization through complexation of water at HF/6- 31 G(d) is markedly lower for Si(NH2)3-(H2O)+ (6) (28.8 kcal mol-1) than for SiMe3(H2O)+ (40.6 kcal mol-1). The tris(dimethylamino) silylium cation Si(N-Me2)3+ (8) is even more stable than 1 a. The complexation energy of Si(NMe2)3-(H2O)+ (10) is only 17.3 kcal mol-1. IGLO calculations of the 29Si N M R chemical shifts predict that 1 a and 8 should not show the same extremely low shielding that is calculated for alkyl-sub-stituted silylium ions. The calculated 29Si resonances for 8 are in reasonable agreement with the experimental N M R spectrum of (Me2N)3 SiB(C6F5)4. AM 1 calculations predict that the substituted tripyrrolidino silylium cation 12 would be an even better candidate for a stable tricoordinate silylium cation in condensed phases. One of the pyrrolidine rings of 12 has tert-butyl groups in the 2 and 5 positions, which serve as a steric fence around the silicon atom.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 732-746 
    ISSN: 0006-3592
    Schlagwort(e): Desulfovibrio vulgaris ; hydrogen cycling ; kinetics ; thermodynamics ; modeling ; anaerobic ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A unified model for the growth of Desulfovibrio vulgaris under different environmental conditions is presented. The model assumes the existence of two electron transport mechanisms functioning simultaneously. One mechanism results in the evolution and consumption of hydrogen, as in the hydrogen-cycling model. The second mechanism assumes a direct transport of electrons from the donor to the acceptor, without the participation of H2. A combination of kinetic and thermodynamic conditions control the flow of electrons through each pathway. The model was calibrated using batch experiments with D. vulgaris grown on lactate, in the presence and absence of sulfate, and was verified using additional batch experiments under different conditions. The model captured the general trends of consumption of substrates and accumulation of products, including the transient accumulation and consumption of H2. Furthermore, the model estimated that 48% of the electrons transported from lactate to sulfate involved H2 production, indicating that hydrogen cycling is a fundamental process in D. vulgaris. The presence of simultaneous electron transport mechanisms might provide D. vulgaris with important ecological advantages, because it facilitates a rapid response to changes in environmental conditions. This model increases our ability to study the microbial ecology of anaerobic environments and the role of Desulfovibrio species in a variety of environments. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:732-746, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 0009-286X
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 63-72 
    ISSN: 0941-1216
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1,3-Dithienium and 1,3-Dithiolenium Salts. IX. Reactions of 1,3-Dithiane-2-ylium Tetrafluoroborates with C-Nucleophiles1,3-Dithian-2-ylium tetrafluoroborates (1), which can be easily obtained by variable methods, react in good to excellent yields with variable C-nucleophiles to new geminal disubstituted 1,3-dithianes. The latter compounds are potential precursors of interesting synthetic building blocks. Reactions are described with 2-lithio-1,3-dithianes 2, sodium cyanide 4, sodium salts of the nitro alkanes 7 and CH-acids of the type of the 1,3-dicarbonyl compounds 9. The reduction of 3-oxo-2-(2-phenyl-1,3-dithian-2-yl)-ethoxybutanoat-following a diastereoselective pathway - leads to the Cram product 11. Further presented is the crystal structure of 2-phenyl-1,3-dithiane-2-ylium tetrafluoroborate (1b).
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 68 (1996), S. 1074-1075 
    ISSN: 0009-286X
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 1331-1337 
    ISSN: 0749-503X
    Schlagwort(e): pyruvate decarboxylase ; glycerol-3-phosphate dehydrogenase ; glycerol production ; Saccharomyces cerevisiae ; Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: This investigation deals with factors affecting the production of glycerol in Saccharomyces cerevisiae. In particular, the impact of reduced pyruvate-decarboxylase (PDC) and increased NAD-dependent glycerol-3-phosphate dehydrogenase (GPD) levels was studied. The glycerol yield was 4·7 times (a pdc mutant exhibiting 19% of normal PDC activity) and 6·5 times (a strain exhibiting 20-fold increased GPD activity resulting from overexpression of GPD1 gene) that of the wild type. In the strain carrying both enzyme activity alterations, the glycerol yield was 8·1 times higher than that of the wild type. In all cases, the substantial increase in glycerol yield was associated with a reduction in ethanol yield and a higher by-product formation.The rate of glycerol formation in the pdc mutant was, due to a slower rate of glucose catabolism, only twice that of the wild type, and was increased by GPD1 overexpression to three times that of the wild-type level. Overexpression of GPD1 in the wild-type background, however, led to a six- to seven-fold increase in the rate of glycerol formation. The experimental work clearly demonstrates the rate-limiting role of GPD in glycerol formation in S. cerevisiae.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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