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  • 1995-1999  (8)
  • 1990-1994  (19)
  • 1955-1959
  • 1920-1924
  • 1910-1914
  • Chemistry  (24)
  • 27.90.+b  (3)
  • 1
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 14.60.Ef ; 25.85.Ge ; 27.90.+b ; 36.10.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ratios of prompt to delayed fission yields for the isotopes233U,234U,235U,236U,238U,237Np,242Pu, and244Pu and the fission probabilities relative to each other have been investigated experimentally. Using the value of the total fission probability for237Np the absolute probabilities for prompt and delayed fission have been determined. The fission probabilities per muon captureP fc have been derived for all the isotopes and compared with an evaluation based on excitation functions from theory.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 13.10.+9 ; 14.60.Ef ; 25.30.−C ; 25.85.−W ; 27.90.+b ; 36.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The probabilities of muon attachment to fission fragments in the prompt fission of237Np have been determined as a function of fragment mass and total kinetic energy release in a (μ −,f 1 f 2 e −)-coincidence measurement. A strong dependence of the attachment probability on the fragment mass is observed. The experimental results are compared with theoretical predictions.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 14.60.Ef ; 23.20.−g ; 25.30.−c ; 25.85.−w ; 27.90.+b ; 36.10.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study of muonic238U has been performed in a combined (μ −,γ f) and (μ −,γγ) coincidence experiment to investigate the role of non-radiative transitions and their fission probabilities. An augmentation of the outer fission barrier ofΔE b =(0.6±0.1) MeV due to the presence of the muon is deduced. A significant contribution to the prompt fission yield not only results from the (2p→1s) and (3d→1s) non-radiative transitions, but also from other radiationless transitions. Specifically, the measured fission probabilities of the transitions (2p→1s), (3d→1s), and (3p→1s) are (1.5±0.4)%, (5.7±1.7)%, and (5.3±1.9)%, respectively.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 7 (1990), S. 16-31 
    ISSN: 0887-3585
    Keywords: BPTI ; dithiothreitol ; DTT-sensitive mutants ; protein folding ; random mutagenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A genetic screening procedure has been developed to identify mutant forms of bovine pancreatic trypsin inhibitor (BPTI) that can fold to an active conformation but are inactivated more rapidly than the wild type protein. Small cultures of Escherichia coli containing plasmids with mutagenized BPTI genes were grown in microtiter plates, lysed, and treated with dithiothreitol (DTT). Under these conditions, unfolding and inactivation of wild-type protein has a half-time of about 10 hours. Variants of BPTI that are inactivated within 1 hour were identified by adding trypsin and a chromogenic substrate. Approximately 11,000 mutagenized clones were screened in this way and 75 clones that produce proteins that can fold but are inactivated by DTT were isolated. The genes coding for 68 “DTT-sensitive” mutant proteins were sequenced, and 25 different single amino acid substitutions at 15 of the 58 residues of the protein were identified. Most of the altered residues are largely buried in the core of the naive wild-type structure and are highly conserved among proteins homologous to BPTI. These results indicate that a large fraction of the sequence of the protein contributes to the kinetic stability of the active conformation, but it also appears that substitutions can be tolerated a most sites without completely preventing folding Because this genetics, further studies of the isolated mutants are expected to provide information about the roles of the altered residues in folding and unfolding.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 15 (1993), S. 322-329 
    ISSN: 0887-3585
    Keywords: unfolded proteins ; mutations ; BPTI ; gel electrophoresis ; disulfide-formation kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The effects of amino acid replacements on the hydrodynamic volume of reduced and unfolded bovine pancreatic trypsin inhibitor (BPTI) have been examined by gel electrophoresis. The electrophoretic mobilities of the reduced forms of 46 BPTI variants were compared at room temperature in the absence of denaturants. The single substitutions examined include many different types of replacements at sites throughout the polypeptide, and, collectively, alter 22 of the 58 residues of the wild-type protein. The only substitutions found to alter the electrophoretic mobility of the reduced protein by more than ∼3% are those that change the net charge of the protein. For nine mutants, the rates of disulfide formation in the reduced protein were also examined and found to be very similar to that of the wild-type protein. These results suggest that any structure that may be present in the reduced protein is either relatively insensitive to amino acid replacements or does not greatly influence the averaged properties of the polypeptide chain. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2441-2451 
    ISSN: 0887-624X
    Keywords: fluorinated diaminobiphenyls ; poly(amic acid)s ; polyimides ; spin-coated films ; physical property characterization ; thermal expansion coefficient ; electronics applications ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new fluorinated diamine monomers, 3,3′-diamino-5,5′-bis(trifluoromethyl)biphenyl and 3,3′-diamino-6,6′-bis(trifluoromethoxy)biphenyl, as well as a known nonfluorinated analog, 3,3′-diaminobiphenyl, were synthesized. Reaction of these diamines with rigid, highly rod-like dianhydrides produced poly(amic acid)s and polyimides, which were spin coated and thermally treated to produce polyimide films for evaluation in electronics applications. It was hoped that these polyimide films would exhibit an ideal combination of low thermal expansion, reduced water absorption, and low dielectric constant but with improved elongation due to the “crankshaft” nature of the 3,3′-biphenyl unit. Unlike polyimide films from analogous 4,4′-diaminobiphenyls, however, the 3,3′-diaminobiphenyl-based polyimides did not yield low in-plane thermal expansion coefficient in spin-coated films. In some cases high elongation was achieved, but with high thermal expansion. These new diamines may nevertheless find utility in polyimides and polyaramides for membrane, fiber, and other applications. Additionally, they may be useful in modifying the properties of polymer backbones via copolymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2441-2451, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0887-3585
    Keywords: electrospray ionization mass spectrometry ; noncovalent complexes ; protease ; integrase ; nucleocapsid protein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Mass spectrometry (MS) with electrospray ionization (ESI) has shown utility for studying noncovalent protein complexes, as it offers advantages in sensitivity, speed, and mass accuracy. The stoichiometry of the binding partners can be easily deduced from the molecular weight measurement. In many examples of protein complexes, the gas phase-based measurement is consistent with the expected solution phase binding characteristics. This quality suggests the utility of ESI-MS for investigating solution phase molecular interactions. Complexes composed of proteins from the human immunodeficiency virus (HIV) have been studied using ESI-MS. Multiply charged protein dimers from HIV integrase catalytic core (F185K) and HIV protease have been observed. Furthermore, the ternary complex between HIV protease dimer and inhibitor pepstatin A was studied as a function of solution pH. Zinc binding to zinc finger-containing nucleocapsid protein (NCp7) and the NCp7-psi RNA 1:1 stoichiometry complex was also studied by ESI-MS. No protein-RNA complex was observed in the absence of zinc, consistent with the role of the zinc finger motifs for RNA binding. Proteins Suppl. 2:28-37, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2112-2122 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transport of moisture in shrinking food gels during drying is studied based on a novel thermomechanical theory accounting for a structural transition in the material - from the rubbery to the galssy state - during drying. The proposed theory is applied to the drying of a model cylindrical starch-gluten gel system. The predicted drying characteristics depend on the Deborah number, a ratio of the characteristic relaxation time to the characteristic diffusion time. At low Deborah numbers, drying is Fickian. At intermediate and high Deborah numbers, however, drying is non-Fickian, leading to an apparent mass-transfer shutdown, which is a result of surface dryout and skin/shell formation. Based on a time-dependent surface boundary condition, the model proposes that surface drying is not only a function of the Biot number but also a function of the “Shell” number, a ratio of the Deborah and Biot numbers. The model is verified by comparing its predictions with experimental data from drying of starch-gluten gels at 22.5 and 40°C. The model predictions agree with experimental data and capture the observed sigmoidal shape of the experimental drying curves in the saturated flow regime. The predicted moisture profiles show shell formation and growth during drying, compatible with the experimental moisture profiles from the literature.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1151-1160 
    ISSN: 0006-3592
    Keywords: fluorescence ; monitoring ; methane ; fermentation ; NAD(P)H ; F420 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line in situ fluorescence measurements of the methanogenic fermentation were conducted with reactors receiving either glucose or a mixture of volatile fatty acids as the substrate. The reactors were perturbed from steady-state conditions in order to assess the response of fluorescencemonitoring probes. Two fluorescence-monitoring probes were evaluated over a period of 8 months; they performed in a consistent manner, and their response was not significantly affected by the changes in pH and redox potential encountered during routine reactor operation. A commercially available probe, designed to measure NAD(P)H, demonstrated particular promise for detecting imbalance caused by the entry of air, inhibitor addition and was capable of distinguishing between different substrates. This fluorescence-monitoring probe detected imbalance more rapidly than other on-line measurements such as pH, Eh, or gas production, or off-line measurements such as volatile fatty acid concentration or gas composition. An experimental fluorescence-monitoring probe, designed to measure coenzyme F420, also showed some promise in this regard. The response of the fluorescence-monitoring probes also revealed details of the metabolic routes in the reactors and the probes represent a useful research tool. For example, a failure to observe the characteristic response of the NAD(P)H-monitoring probe to formate addition during the metabolism of acetate, propionate, or glucose strongly suggests that any formate liberated during their catabolism is degraded via a different route to exogenously added formate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 251-257 
    ISSN: 0887-6266
    Keywords: poly(aryl-ether-ether-ketone) (PEEK), solvent-induced crystallinity in ; crystallization of PEEK, solvent-induced ; sorption of solvents in PEEK, crystallinity induced by ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The amount and structure of the crystals formed by the solvent-induced crystallization (SIC) following a sorption-desorption cycle of five fluids (benzene, toluene, chloroform, methylene chloride, and carbon disulfide) in amorphous PEEK was determined by wideangle x-ray scattering (WAXS). The SIC crystal structure was compared with that produced by thermal methods, both those formed at low temperature by heating the amorphous material 10-20°C above Tg or by cooling from the melt. Although smaller in size, the SIC crystals are tighter and more organized than those produced thermally. The WAXS data indicates that all five fluids produce approximately 35% crystallinity in PEEK. Gravimetric data suggest that a low-density region, consisting of either microvoids or highly disordered amorphous region, surrounds the crystals.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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