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  • 1995-1999  (6)
  • 1999  (6)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7053-7057 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Inelastic neutron scattering spectra of DNA-fibers are analyzed using ideas formulated recently in the field of the glass transition. The analysis reveals two temperatures, namely, T∼180–200 K and T∼230 K, at which the dynamics of DNA exhibits qualitative changes. The former is similar to the glass transition temperature, whereas the latter is similar to the crossover temperature recognized now as an important point for the dynamics of the glass transition. Exactly in this temperature range many other hydrated biopolymers show some dynamic transition and strong slowing down of their functions. The crossover temperature appears to be close to the crossover temperature of bulk water. A possible relation of the dynamic transition to functions of biomolecules and also to the dynamic transition in the hydration shell is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 401 (1999), S. 549-555 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Kyoto Protocol allows reductions in emissions of several ‘greenhouse’ gases to be credited against a CO2-equivalent emissions limit, calculated using ‘global warming potential’ indices for each gas. Using an integrated global-systems model, it is shown that a ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic properties of the intermetallic compounds Gd1−x YxMn2Ge2 (0≤x≤0.5) (tetragonal crystal structure of the type ThCr2Ge2) have been measured in fields up to 40 T in the temperature range 4.2–120 K on free powders (whose particles are free to rotate in a magnetic field), fixed powders, and polycrystalline bulk samples. The temperature dependence of the crystal structure parameters of some of these intermetallic compounds was determined from x-ray diffraction measurements. It was found that the temperatures of magnetic disordering of the gadolinium magnetic subsystem and the transition of the manganese subsystem from the ferromagnetic to the antiferromagnetic state decrease as the gadolinium content is decreased, so that in compositions with x〈0.3 this transition is a first-order phase transition, and with further decrease of the gadolinium content it becomes second-order. In intermetallic compounds of this system with x=0.3 and 0.4 another spontaneous first-order transition is observed at lower temperatures. In a magnetic field the magnetization of all the investigated intermetallic compounds except for the composition x=0.5 undergo a metamagnetic transition. The T-x, H-x, and H-T magnetic phase diagrams are constructed. The experimental data are interpreted with allowance for the fact that according to the results of previous studies, the Mn-Mn exchange interaction is antiferromagnetic, and thus the examined intermetallic compounds are two-sublattice ferrimagnets with negative exchange interaction in one of the sublattices. Calculations performed within the framework of this model in the Yafet-Kittel approximation, which assumes that the sublattice with negative exchange can be divided into two sub-sublattices, permit a quantitative description of the experimental results in most cases.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical sciences 96 (1999), S. 3327-3331 
    ISSN: 1573-8795
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The acoustic field of a source moving at a subsonic velocity in a regular waveguide with perfectly reflecting boundaries is considered. The acceleration of the source is assumed to be small. In a moving coordinate system, the asymptotics of the wave field is obtained. This asymptotics is inapplicable near the critical cross sections, for which the Doppler frequency of the source coincides with the frequency of the waveguide mode under consideration. It is demonstrated that, in this case, the wave field can be represented locally by a special type of integral, which is analyzed by the saddle-point method.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-8221
    Keywords: myocardial ischemia ; cardiac arrhythmias ; opioid receptors ; laser irradiation ; sympathetic regulation of the heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of intravenous administration of different opioid peptides on the development of ischemic cardiac arrhythmias under conditions of intraatrial laser irradiation (λ=632.8 nm) were studied in cats with transected cardiac branches of the right stellate ganglion and preserved sympathetic innervation of the ischemized area. Ischemia was caused by occlusion of the circumflex branch of the left coronary artery. It was found that the protective effects of dalargin were most powerful when sympathetic influences on the ischemic area were intestified by laser irradiation. Under these conditions DAGO showed more pronounced antiarrhythmic effects than DSLET.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Alternative policies to address global climate change are being debated in many nations and within the United Nations Framework Convention on Climate Change. To help provide objective and comprehensive analyses in support of this process, we have developed a model of the global climate system consisting of coupled sub-models of economic growth and associated emissions, natural fluxes, atmospheric chemistry, climate, and natural terrestrial ecosystems. The framework of this Integrated Global System Model is described and the results of sample runs and a sensitivity analysis are presented. This multi-component model addresses most of the major anthropogenic and natural processes involved in climate change and also is computationally efficient. As such, it can be used effectively to study parametric and structural uncertainty and to analyze the costs and impacts of many policy alternatives. Initial runs of the model have helped to define and quantify a number of feedbacks among the sub-models, and to elucidate the geographical variations in several variables that are relevant to climate science and policy. The effect of changes in climate and atmospheric carbon dioxide levels on the uptake of carbon and emissions of methane and nitrous oxide by land ecosystems is one potentially important feedback which has been identified. The sensitivity analysis has enabled preliminary assessment of the effects of uncertainty in the economic, atmospheric chemistry, and climate sub-models as they influence critical model results such as predictions of temperature, sea level, rainfall, and ecosystem productivity. We conclude that uncertainty regarding economic growth, technological change, deep oceanic circulation, aerosol radiative forcing, and cloud processes are important influences on these outputs.
    Type of Medium: Electronic Resource
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