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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5756-5777 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dissociation of CH4 physisorbed on Ni(111) at 46 K is observed to be induced by the impact of incident inert gas atoms. The dynamics and mechanism of this new process, collision induced dissociative chemisorption, are studied by molecular beam techniques coupled with ultrahigh vacuum electron spectroscopies. The absolute cross section for collision induced dissociation is measured over a wide range of kinetic energies (28–109 kcal/mol) and incident angles of Ne, Ar, and Kr atom beams. The cross section displays a complex dependence on the energy of the impinging inert gas atom characteristic of neither total nor normal energy scaling. Quantitative reproduction of the complex dependence of the cross section on the Ar and Ne incident energy by a two-step, dynamical model establishes the mechanism for collision induced dissociation. Collision induced dissociation occurs by the impulsive transfer of kinetic energy upon collision of Ar or Ne with CH4, followed by the translationally activated dissociative chemisorption of the CH4 upon its subsequent collision with the Ni surface. The dependence of the probability of activated dissociation on the resultant CH4 normal energy derived from the fit of the model to the experimental cross section is in excellent agreement with the results of a previous study of the translationally activated dissociative chemisorption of CH4 on Ni(111). Collision induced activation and translational activation are shown to be consistent mechanisms for providing energy to CH4 to surmount the barrier to dissociative chemisorption.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 111 (1989), S. 8748-8749 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 16 (1989), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Kaposi's sarcoma is associated with an increased frequency of HLA-DR5. The hypothesized model of a susceptibility gene in linkage disequilibrium with DR5 may be tested by haplotype analysis in familial Kaposi's sarcoma. Our finding of no common haplotype among afflicted members of a family provides evidence against the hypothesized linkage.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 1114-1115 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Landscape ecology 3 (1989), S. 193-205 
    ISSN: 1572-9761
    Keywords: hierarchy theory ; nonequilibrium ; thermodynamics ; catastrophe theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Landscapes are complex ecological systems that operate over broad spatiotemporal scales. Hierarchy theory conceptualizes such systems as composed of relatively isolated levels, each operating at a distinct time and space scale. This paper explores some basic properties of scaled systems with a view toward taking advantage of the scaled structure in predicting system dynamics. Three basic properties are explored: (1) hierarchical structuring, (2) disequilibrium, and (3) metastability. These three properties lead to three conclusions about complex ecological systems. First, predictions about landscape dynamics can often be based on constraints that directly result from scaled structure. Biotic potential and environmental limits form a constraint envelope, analogous to a niche hypervolume, within which the landscape system must operate. Second, within the constraint envelope, thermodynamic and other limiting factors may produce attractors toward which individual landscapes will tend to move. Third, because of changes in biotic potential and environmental conditions, both the constraint envelope and the local attractors change through time. Changes in the constraint structure may involve critical thresholds that result in radical changes in the state of the system. An attempt is made to define measurements to predict whether a specific landscape is approaching a critical threshold.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 332 (1989), S. 241-242 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The level scheme of the yrast band of124Ba has been extended up to spin 32ħ. Transitions in the two negative parity side bands are observed up to spin 27ħ and tentatively 20ħ. The second backbend observed in the S-band and the backbends in the side bands are explained as due to neutrons. The structure of the sidebands is discussed and compared with deformation self-consistent calculations, Total Routhian Surfaces (TRS).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical microbiology & infectious diseases 8 (1989), S. 706-710 
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The haemolytic activity of several clinical and reference strains ofCampylobacter pylori was determined using cell-free preparations of broth-grown organisms and human, horse, guinea pig, rabbit and sheep erythrocytes. Significant levels of haemolysis were produced only when the cell-free preparations were concentrated tenfold. However, three of 14 strains still gave haemolysis values of less than 50% when tested with guinea pig erythrocytes. Significant haemolytic activity could not be demonstrated with preparations derived from bacteria cultured on solid medium. Irrespective of the strain examined or the type of preparation, strong urease activity was demonstrable. Purified urease had no effect on erythrocytes, and thiourea failed to inhibit the haemolytic activity ofCampylobacter pylori cell-free preparations. It was concluded that ureolytic activity was not implicated in the lysis of erythrocytes, either by direct action or via the generation of ammonia. Furthermore, the haemolytic activity produced byCampylobacter pylori was found to be due to a secreted factor, possibly a haemolysin.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-7284
    Keywords: Neisseria gonorrhoeae ; Munich isolates ; Plasmid content ; Serotyping ; Antimicrobial susceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eighty-four strains of Neisseria gonorrhoeae isolated in Munich between January 1987 and June 1988 were characterized in terms of their plasmid content, protein I serovar and susceptibility or resistance to four antimicrobial agents. Eighty two percent of the strains belonged to serogroup 1B, the three most prevalent serovars being 1B-1, 1B-2 and 1B-6. Among the serogroup 1A strains, 1A-2 was the commonest serovar. Fourteen strains (16.7%) lacked the 2.6 Md cryptic plasmid, although two of these strains contained the conjugative gonococcal plasmid. Although some degree of resistance to penicillin and tetracycline was noted, all the strains were sensitive to spectinomycin and cefotiam.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-2568
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Conclusion The dyspeptic patient presents a common and difficult problem in clinical practice. Careful evaluation of symptoms may be unrewarding; however, a thorough clinical and screening psychiatric evaluation are essential. Upper gastrointestinal endoscopy or upper gastrointestinal radiology and ultrasonic examination of the biliary tract and pancreas should be the first investigations. In patients in whom these are noncontributory and in whom symptoms persist, evaluation of upper gastrointestinal function (secretory, motor, provocation tests) may be indicated to determine the cause of functional dyspepsia and to allow appropriate management.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 36 (1989), S. 19-33 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A set of 18 aryltriazenes and the antitumor drug DTIC, whose mutagenicity has been determined in the Ames test, has been studied using octanol-water partition coefficients (P) as a measure of relative hydrophobicity and MNDO molecular orbital energies and electron distributions to account for variation in their electronic characteristics. A good structure-activity relationship was found using log P in combination with either εHOMO, or qHOMO, where the latter is defined as the HOMO electron density on N1 of the triazene. The dependence of mutagenicity on hydrophobicity is similar to what had been found earlier by Venger, Hansch, Hatheway, and Amrein [4] for the aryltriazenes alone using σ+ as a descriptor of electronic characteristics. A consistent role for electronic factors is found using σ+, εHOMO and qHOMO, namely, increased mutagenicity is associated with structural variations that increase the electron donating ability of the triazenes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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