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  • Springer  (53)
  • International Union of Crystallography (IUCr)  (4)
  • 1990-1994  (57)
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  • 1
    ISSN: 1432-0630
    Keywords: 61.10 ; 68.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Single crystals of iodine-intercalated C60 have been examined by transmission electron microscopy. Tilting series of Electron Diffraction Patterns (EDP) confirm that it has a simple hexagonal structure with c/a≈1 in accordance with the results of X-ray diffraction, which allows higher precision c/a=1.0024. Cooling and heating experiments were performed in the vacuum of the microscope to investigate the order — disorder phenomena. High-Resolution Electron Microscopy (HREM) images and electron diffraction patterns reveal that the c/2-displacement along the c-direction plays an important role in the transition from the simple hexagonal structure into the fcc structure when iodine is lost from the specimen or “vice versa”. The orientation relationship between the intercalate and the C60 structure is [01 $$\overline {\text{1}}$$ 10]h∥[1 $$\overline {\text{1}}$$ 10]fcc and (001)h∥(110)fcc. A model is proposed to interpret the features observed in EDP and HREM consistently.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Aequationes mathematicae 40 (1990), S. 248-260 
    ISSN: 1420-8903
    Keywords: Primary 05B05 ; Secondary 05C20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary Letv andK be positive integers. A (v, k, 1)-Mendelsohn design (briefly (v, k, 1)-MD) is a pair (X,B) whereX is av-set (ofpoints) andB is a collection of cyclically orderedk-subsets ofX (calledblocks) such that every ordered pair of points ofX are consecutive in exactly one block ofB. A necessary condition for the existence of a (v, k, 1)-MD isv(v−1) ≡ 0 (modk). If the blocks of a (v, k, 1)-MD can be partitioned into parallel classes each containingv/k blocks wherev ≡ ) (modk) or (v − 1)/k blocks wherev ≡ 1 (modk), then the design is calledresolvable and denoted briefly by (v, k, 1)-RMD. It is known that a (v, 3,1)-RMD exists if and only ifv ≡ 0 or 1 (mod 3) andv ≠ 6. In this paper, it is shown that the necessary condition for the existence of a (v, 4, 1)-RMD, namelyv ≡ 0 or 1 (mod 4), is also sufficient, except forv = 4 and possibly exceptingv = 12. These constructions are equivalent to a resolvable decomposition of the complete symmetric directed graphK v * onv vertices into 4-circuits.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0392-6737
    Keywords: Flux pinning ; flux motion ; fluxon-defect interactions ; Critical currents ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The results of low-temperature magnetic-relaxation experiments in TlBaCaCuO superconductors (2212 and 2223 phase) are reported. They give evidence of a crossover from a thermally activated regime of flux motion to a nonthermally activated one. The magnetic-relaxation rate is found to become temperature independent below ≅7K and ≅3K, for the 2212 and 2223 phase, respectively. Its value compares well with that predicted by the theories of flux motion by quantum tunnelling.
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  • 4
    ISSN: 1434-6079
    Keywords: 34.80.D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Distorted-wave Born approximation calculations are reported for electron impact ionization of He, Ne, Ar, Kr and Xe in coplanar symmetric geometry at energies of 100, 500 and 1000 eV. Of special interest is double scattering effect at large angles.
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  • 5
    ISSN: 1434-6079
    Keywords: 03.65. ; 36.40.+d ; 21.60.-n
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Simulating the one-particle spectra of the infinite-well potential by a model, we study the symmetry and the shell-structure of octupole deformations as well as the possible occurrence of octupole (and quadrupole) instabilities. Among various types of octupole deformations investigated theY 32-type deformation is found to have a strong shell-structure as well as a very interesting symmetry which leads to the occurrence of highly-degenerate single-particle levels. One particle spectra of the octupole-coupled two-level model (withl andl + 3) are analytically studied in the limit of large angular-momentum,l.
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  • 6
    ISSN: 1573-2568
    Keywords: chronic hepatitis ; interferon ; mononuclear cells ; MHC antigen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Twenty-four subjects with chronic HCV infection were treated with IFN for six months. Liver biopsies were obtained before and after therapy. The number of mononuclear cells staining for CD3, CD4, CD8, 3G8, and the number of mononuclear cells, liver cells, and bile duct cells staining for class I and II MHC antigens in the biopsies was determined. NK cells increased from 16±3 to 28±3 cells per 5 high-power fields (HFP) (P≤0.03). The number of bile duct cells expressing class I and II MHC Ag and liver cells expressing class II MHC Ag increased (allP≤0.03). The only parameter that distinguished responders from nonresponders was the number of NK cells. Following IFN withdrawal, expression of these antigens declined. Based upon these data, it is concluded that IFN treatment of HCV increases: (1) the NK cells number; (2) the expression of class I MHC Ag on bile duct cells and the expression of class II MHC Ag on liver and bile duct cells; and (3) with IFN withdrawal, these changes disappear.
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  • 7
    ISSN: 1434-6036
    Keywords: 75.70.-i ; 76.90.+d ; 73.40.GK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetic relaxation measurements of very thin Dy films of thickness 20 Å and 40 Å have been performed in the temperature range 1.8 K–20 K. Below the blocking temperature, the magnetic viscosity decreases when decreasing the temperature and becomes non-thermal below a few Kelvins.
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  • 8
    ISSN: 1573-5117
    Keywords: zooplankton ; grazing ; Coulter Counter ; 14C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both the Coulter Counter and 14C method were used to measure the grazing (clearance rates) of the marine calanoid copepod Acartia tonsa on different concentrations of a Chlamydomonas sp. culture. In most cases, clearance rates measured by the Coulter Counter method were higher than those measured by the 14C method by factors of 2 to 3. We explore several possibilities for the differences obtained between the two methods. We suggest that loss of radioactivity through grazer egestion might be the main reason for the discrepancy between methods. Food concentration did not affect the comparability of both methods' measurements.
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  • 9
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We report new results on the modulation characteristics of GaAs/AlGaAs asymmetric Fabry-Perot modulators grown on silicon substrates. We discuss factors affecting device performance and evaluate these by growing p-i-n quantum well diodes, and multilayer reflector stacks on silicon. Using data from these test structures we have designed an asymmetric microresonator modulator and achieve, experimentally, a 40% reflection change with only 5 V and a contrast ratio of 7.4 dB, also with 5 V.
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  • 10
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The relationship between surface pressure fluctuations and the velocity field associated with turbulent coherent structures is examined for flow within and above a deciduous forest. Measurements were taken with tower-mounted sonic anemometer/thermometers at six heights, Lyman-alpha humidiometers at three heights, and a pressure sensor at the forest floor. We find a strong, near-linear relationship between the mean square turbulent velocity and the standard deviation of the high-pass-filtered pressure fluctuations. Lagged cross-correlations between vertical velocity fluctuations and those of pressure show maximum correlations of ± 0.5 but with a phase offset. Examination of surface pressure during the passage of coherent structures, which are characterized by a transition from ejection to sweep, reveals a period of overpressure about 20 s in duration roughly centered on the time of passage of the scalar microfront at the top of the canopy. Pressure patterns associated with coherent structures appear to be largely responsible for the form of the correlations stated above. Pressure patterns calculated from an integrated Poisson equation, using observed velocity and temperature signals during coherent structures, match the main features of the observed pressure. Retrieval of the pressure fluctuations in this manner reveals that the mean wind shear/turbulence interaction term is dominant, but that important contributions arise from two other terms in the equation. Buoyancy effects are negligible. We show that the surface pressure signal is mainly created by the velocity field near the top of the forest, and present evidence to suggest that features of the sub-crown air movement result directly from this pressure field.
    Type of Medium: Electronic Resource
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