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  • 1990-1994  (4)
  • 1960-1964
  • 1990  (4)
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  • 1990-1994  (4)
  • 1960-1964
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  • 1
    Electronic Resource
    Electronic Resource
    Rovibrational excitation of carbon monoxide by energy transfer from metastable nitrogen (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1758-1767 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The CO fundamental vibration–rotation spectra resulting from the interaction of discharged nitrogen with carbon monoxide at low pressure (∼3 mTorr) exhibit bimodal rotational distributions. We have identified 14 vibrational levels of a rotationally relaxed (80 K) component and eight vibrational levels from a rotationally excited component. The eight rotationally excited bands are best reproduced by a statistical distribution E=ER+EV=3.7 eV, which provides sufficient population in the region of the Fortrat reversal (J∼90) to account for the observed R-branch bandhead formation. The rotationally relaxed vibrational levels are populated by single- and two-quantum transfer from N2(v), N2(v)+CO→N2(v−1,2)+CO(v=1,2), and radiative cascade from CO(A) produced by quenching of N2(a'), N2(a' 1Σ−u) +CO→N2(X,v)+CO(A 1Π)→CO(v≤9)+hν, and relaxation of the rotationally excited component. Kinetic and energetic arguments indicate that a branch of N2(a') quenching N2(a' 1Σ−u) +CO→N2(X,v)+CO(v≤14,J) is responsible for the rotationally excited component. Surprisal analysis indicates two dynamic mechanisms are responsible for the rotationally excited component. We have modeled the vibrational distribution of the rotationally excited component with equal contributions from a statistical (all v) process and a process favoring excitation of low vibrational levels (v≤4).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458057
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Towards an understanding of the structural basis of ‘forbidden’ transport pathways in the Escherichia coli lactose carrier: mutations probing the energy barriers to uncoupled transport (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Recent progress in the analysis of mutants of the Eschenchia coli lactose carrier function is reviewed, with special emphasis on the structural basis for energy barriers which prevent ‘forbidden’ con-formational changes. Mutations which break down the barriers to forbidden isomerizations involving the binary carrier:sugar (CS) and carrier:proton (CH) complexes have been obtained in several laboratories. These mutants allow uncoupled transport of H+ or galactoside in the lactose carrier which normally couples cation and sugar movement in a 1:1 stoichiometry. These uncoupled mutants appear to be associated with changes in both sugar and cation recognition, suggesting that the physical interactions forming the basis for co-substrate recognition and uncoupling are not independently variable.By postulating that translocation involves transformation of the stable intermediate of the co-transport cycle to unstable transition state conformations of the carrier, it is possible to consider the consequences of mutagenesis in terms of transition state theory. Consistent with several experimental observations, the analysis predicts in each mutant the occurrence of more than one abnormality in the transport cycle (such as changes in sugar recognition, cation recognition or the coupling reaction). We have called the general phenomenon a ‘mutational double-effect’ because any mutation which alters the Gibbs free energy change of one reaction in the transport
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb02053.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Breakdown of cytoplasmic vacuoles (1990)
    Springer
    Protoplasma 155 (1990), S. 144-152 
    Details
    ISSN: 1615-6102
    Keywords: Motile vacuoles ; Vesiculation ; Mathematical model ; Fixation ; Osmotic conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plant cells possess an extensive motile vacuolar system (MVS) easily observed with dark field, Nomarski or phase contrast optics. The elements of the MVS are long cylindrical vacuoles, 1–6 μm in diameter, but are transformed into spherical vesicle upon fixation with non-coagulant fixatives (e.g., glutaraldehyde). A mathematical model is developed to describe the vesiculation event, taking into account osmotic properties of the fixing solution. A computer simulation is prepared, using the model equations, to examine response of vesicle radius and number under weak to strong osmotic conditions. Vesicle radius is strictly dependent upon initial vacuolar radius, while vesicle number is found to depend upon initial vacuole length as well as radius. However, vesicle number is more dependent upon initial vacuolar radius as osmotic influences increase. The model points out important basic properties of membrane cylinders and spheres that can be scaled up or down to include similar structures at various magnitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322624
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Multiple transitions in a dimethacrylate network (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1195-1208 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Triethylene glycol dimethacrylate, TEGDM, was cured to various dose levels (0.15-2.0 Mrad) by γ-irradiation at 40°C and its dynamic mechanical properties were evaluated. The resultant products had up to four transition phenomena dependent upon dose. The highest temperature transition (IV) was due to the ultimate glass transition. Transition III (ca. 40°C) was due to additional reaction occuring just above the cure temperature. Transition 1 (ca. -60°C) occurred at low doses and was associated with residual monomer. Transition II (ca. -10°C) is due to association of —(CH2CH2O)— units in TEGDM monomer, and the associated regions persist in the crosslinked polymer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400710
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    Paper (German National Licenses)
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