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  • 1995-1999  (7)
  • 1970-1974
  • 1998  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray studies of Pseudomonas putida histidine ammonium-lyase (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 681-683 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Histidine ammonium-lyase from P. putida was expressed in Escherichia coli, purified to homogeneity, and crystallized by the vapour-diffusion method using polyethylene glycol 3350 as the precipitant. The crystals, which diffract to at least 2.5 Å resolution, exhibit the symmetry of space group P212121, with unit-cell parameters a = 89.7, b = 138.2 and c = 164.8 Å. The asymmetric unit contains a tetramer, and the crystals have a Vm value of 2.41 Å3 Da−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444997017848
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Density-of-states anomaly and tunneling conductance of Au/p-GaAs0.94Sb0.06 contacts near the metal-insulator transition (1998)
    Springer
    Semiconductors 32 (1998), S. 1270-1276 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The tunneling-current anomaly in Au/p-GaAs0.94Sb0.06 contacts at zero bias voltage (V) → 0) is investigated. Epitaxial layers of the solid solution GaAs0.94Sb0.06 are doped with germanium and have a conductivity close to that at the metal-insulator transition. The square-root dependence of the differential conductance G(V)=(dV/dI)−1 at small values of eV〉kT TT predicted by the Al’tshuler-Aronov theory of quantum corrections to the density of states at the Fermi level in disordered conductors is observed. Satisfactory agreement between the experimental data and theory is observed at hole densities (p) in the layers greater than the critical density for the metal-insulator transition p c , but the relative magnitude of the anomaly is sharply smaller at p〈p c . This confirms the specificity of the condition k F l⩾1 (instead of ) for applicability of the theory for the density-of-states anomaly appearing as a result of electron-electron interactions in a three dimensional electron gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187613
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Differential resistance of Au/GaAs1−x Sbx tunneling contacts near the zero-bias anomaly. II. Contacts to p-GaAs1−x Sbx (1998)
    Springer
    Semiconductors 32 (1998), S. 517-520 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The differential resistance R(V)=dV/dI of Au/p-GaAs1−x Sbx tunneling contacts was investigated. Schottky barriers were prepared on epitaxial layers of the solid solution p-GaAs1−x Sbx (0.045〈x〈0.125), which were doped with Ge from 0.01 to 5 at.%. It was shown that substantial features are present in the voltage dependences R(V) for Au/p-GaAs1−x Sbx contacts as compared with the data for Au/n-GaAs1−x Sbx structures. A square-root voltage dependence was observed for the conductance G(V)5(dV/dI)−1 versus the bias voltage V near the zero-bias anomaly, in agreement with Al’tshuler-Aronov theory for quantum corrections introduced in the density of states at the Fermi level by the characteristic features of the electron-electron interaction in disordered metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187431
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Differential resistance of Au/GaAs1−x Sbx tunneling contacts in the zero-bias anomaly region. I. Contacts to n-GaAs1−x Sbx (1998)
    Springer
    Semiconductors 32 (1998), S. 513-516 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The current-voltage characteristics and the differential resistance R(V)=dV/dI of Au/n-GaAs1−x Sbx tunneling contacts were investigated. Schottky barriers were prepared on n-GaAs1−x Sbx epitaxial layers, which were specially not doped, in the composition range 0.01〈x〈0.125. It was shown that the curves R(V) in the electron density range 2×1018⩽n⩽7×1018 cm−3 and temperature range 4.2⩽T⩽295 K are described well by the tunneling theory employing a self-consistent calculation of the potential in the Schottky barrier region. A square-root dependence of the conductance G(V)=(dV/dI)−1 on the bias voltage V was observed in the zero-bias anomaly region in accordance with the Al’tshuler-Aronov theory of quantum corrections introduced in the density of states at the Fermi level by the characteristic features of the electron-electron interaction in disordered metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187430
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Vitamin D3 enhances mood in healthy subjects during winter (1998)
    Springer
    Psychopharmacology 135 (1998), S. 319-323 
    Details
    ISSN: 1432-2072
    Keywords: Key words Seasonality ; Seasonal affective disorder ; Vitamin D3 ; Serotonin ; Circadian rhythms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Mood changes synchronised to the seasons exist on a continuum between individuals, with anxiety and depression increasing during the winter months. An extreme form of seasonality is manifested as the clinical syndrome of seasonal affective disorder (SAD) with carbohydrate craving, hypersomnia, lethargy, and changes in circadian rhythms also evident. It has been suggested that seasonality and the symptoms of SAD may be due to changing levels of vitamin D3, the hormone of sunlight, leading to changes in brain serotonin. Forty-four healthy subjects were given 400 IU, 800 IU, or no vitamin D3 for 5 days during late winter in a random double-blind study. Results on a self-report measure showed that vitamin D3 significantly enhanced positive affect and there was some evidence of a reduction in negative affect. Results are discussed in terms of their implications for seasonality, SAD, serotonin, food preference, sleep, and circadian rhythms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050517
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of temperature on human L-type cardiac Ca2+ channels expressed in Xenopus oocytes (1998)
    Springer
    Pflügers Archiv 436 (1998), S. 238-247 
    Details
    ISSN: 1432-2013
    Keywords: Key words Calcium ; Heart ; Hypothermia ; Phosphorylation ; Protein kinase A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Temperature normally affects peak L-type Ca2+ channel (CaCh) current with a temperature coefficient (Q 10) of between 1.8 and 3.5; in cardiomyocytes attenuating protein kinase A activity increases Q 10 whilst activating it lowers Q 10. We examine temperature effects using cloned human cardiac CaChs expressed in Xenopus oocytes. Peak inward currents (I Ba) through expressed CaChs (i.e. α1Cα2/δaβ1b) exhibited a Q 10 of 5.8±0.4 when examined between 15 and 25°C. The nifedipine-sensitive I Ba exhibited a higher Q 10 of 8.7±0.5, whilst the nifedipine-insensitive I Ba exhibited Q 10 of 3.7±0.3. Current/voltage (I/V) relationships shifted to negative potentials on warming. Using instead a different CaCh β subunit isoform, β2c, gave rise to an I Ba similar to those expressed using β1b. We utilized a carboxyl deletion mutant, α1C-Δ1633, to determine the temperature sensitivity of the pore moiety in the absence of auxiliary subunits; I Ba through this channel exhibited a Q 10 of 9.3±0.3. However, the Q 10 for macroscopic conductance was reduced compared to that of heteromeric channels; decreasing from 5.0 (i.e. α1Cα2/δaβ1b) and 3.9 (i.e. α1Cα2/δaβ2c) to 2.4 (α1C-Δ1633). These observations differ markedly from those made in studies of cardiomyocytes, and suggest that enhanced sensitivity may depend on the membrane environment, channel assembly or other regulatory factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050628
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    An Initial-Value Problem for Fully Three-Dimensional Inflectional Boundary Layer flows (1998)
    Springer
    Theoretical and computational fluid dynamics 12 (1998), S. 131-148 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. In a recent paper the present authors considered the effects of small cross-flow upon the nonlinear evolution of two oblique waves of unequal amplitude. The present analysis extends this work in two ways: (i) the cross-flow is increased to O(1) making it of comparable magnitude to the streamwise component and (ii) by taking the long-wavelength limit of Rayleigh's equation a whole spectrum of wave numbers can now be catered for. Thus (ii) allows a fairly general initial disturbance to be accommodated. Another significant effect due to the presence of a whole spectrum of wave numbers is that the critical layer jump is now forced by a quadratic, as opposed to the usual cubic, nonlinearity. Numerical solutions of the new nonlinear amplitude evolution equation are presented for a special class of initial disturbance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001620050103
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