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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5837-5837 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have shown theoretically, by means of a full-potential LMTO method in a slab geometry, that the topmost surface layer of α-Ce is γ-like. The calculations are fully relativistic and include all electrons. Also an orbital correction to the f-electron states is included to allow for f localization. For the topmost layer the spin moment is found to be 0.70 μB for the f electrons and 0.08 μB for the d-electron states while the orbital moment from the f electrons is found to be −1.07 μB. These moments correspond well to the moments calculated for bulk γ-Ce which are 0.63, 0.07, and −0.87 μB, respectively. The subsurface and lower lying layers are calculated to have spin and orbital moments close to zero. We therefore conclude that the topmost layer on the α-Ce surface is γ-like while the subsurface and lower lying layers are similar to bulk α-Ce. Our findings explain recent photoemission experiments on this material and provide a theoretical foundation for the interpretation of these experiments. The fact that our theory assumes that α-Ce has delocalized f electrons, and the agreement with the interpretation of photoemission experiments, gives support that the Mott transition model for the α→γ phase transition is correct. © 1996 American Institute of Physics.
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By combining MCXD experiments with first principles electronic structure calculations, we demonstrate that the orbital contribution to magnetism can be strongly enhanced at surfaces. This effect is illustrated for Co grown on a Cu(100) surface. The MCXD measurements were performed using the SX 700 plane grating monochromators at BESSY. The Co films were evaporated and characterized in situ, for their cleanness, thickness (1.6–50 ML), and structural order. For a film thickness up to 2.2 ML, measurements of the ac MCXD susceptibility response at a fixed photon energy allowed one to measure the critical temperature, Tc, of the films and their critical properties were characterized in situ. For several samples the MCXD response as a function of the x-ray incidence angle was investigated as well. This allows one to quantify and correct saturation effects that can occur in the measurements. Data were taken in a temperature range between 40 and 350 K, and for many samples measurements were performed at several reduced temperatures, T/Tc. The first layer of Co on the Cu(100) surface shows an enhanced orbital moment, in contrast to the subsequent layers where the orbital moment is bulklike. The lowering of the symmetry, the enhanced spin moment, and the increased value of the density of states at the Fermi level are factors that combine to give the observed enhancements. © 1996 American Institute of Physics. [S0021-8979(96)679608-0]
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3498-3500 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With the use of first principles theory we confirm the semiconducting ground state of the technologically interesting YH3 compound. Thus, unlike previously published theories, we demonstrate that density functional theory in the local density approximation reproduces the existence of a band gap. We also show that the HoD3 structure is the stable structure at ambient conditions, in agreement with experiment. In addition, we predict that moderate applied pressure will drive YH3 into the cubic structure. © 1997 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4891-4904 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young's modulus, and Poisson's ratio for ideal polycrystalline TiSi2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young's modulus for single crystal TiSi2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the experimental results. The shear anisotropic factors and anisotropy in the linear bulk modulus are obtained from the single crystal elastic constants. From the site and angular momentum decomposed density of states combined with a charge density analysis and the elastic anisotropies, the chemical bonding nature between the constituents in TiSi2 is analyzed. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal. The calculated elastic properties are found to be in good agreement with experimental values when the generalized gradient approximation is used for the exchange and correlation potential. © 1998 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 400 (1999), S. 46-49 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In 1897 Guillaume discovered that face-centred cubic alloys of iron and nickel with a nickel concentration of around 35 atomic per cent exhibit anomalously low (almost zero) thermal expansion over a wide temperature range. This effect, known as the Invar effect, has since been found in various ...
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  • 6
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Following the discovery of stishovite (the highest-pressure polymorph of silica known from natural samples), many attempts have been made to investigate the possible existence of denser phases of silica at higher pressures. Based on the crystal structures observed in chemical analogues of ...
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 807-811 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Residual biomass, produced by the thermophilic fungus, Talaromyces emersonii CBS 814.70, following growth on glucose-containing media, was examined for its ability to take up uranium from aqueous solution. It was found that the biomass had a relatively high observed biosorption capacity for the uranium (280 mg/g dry weight biomass). The calculated maximum biosorption capacity obtained by fitting the data to a Langmuir model was calculated to be 323 mg uranium/g dry weight biomass. Pretreatment of the biomass with either dilute HCl or NaOH brought about a significant decrease in biosorptive capacity for uranium. Studies on the effects of variation in temperature on the biosorptive capacity demonstrated no significant change in binding between 20°C and 60°C. However, a significant decrease in biosorptive capacity was observed at 5°C. Binding of uranium to the bio mass at all temperatures reached equilibrium within 2 min. While the routine binding assays were performed at pH 5.0, adjustment of the pH to 3.0 gave rise to a significant decrease in biosorption capacity by the biomass. The biosorptive capacity of the biomass for uranium was increased when extraction from solution in sea-water was examined.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 807-811 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Residual biomass, produced by the thermophilic fungus, Talaromyces emersonii CBS 814.70, following growth on glucose-containing media, was examined for its ability to take up uranium from aqueous solution. It was found that the biomass had a relatively high observed biosorption capacity for the uranium (280 mg/g dry weight biomass). The calculated maximum biosorption capacity obtained by fitting the data to a Langmuir model was calculated to be 323 mg uranium/g dry weight biomass. Pretreatment of the biomass with either dilute HCl or NaOH brought about a significant decrease in biosorptive capacity for uranium. Studies on the effects of variation in temperature on the biosorptive capacity demonstrated no significant change in binding between 20°C and 60°C. However, a significant decrease in biosorptive capacity was observed at 5°C. Binding of uranium to the biomass at all temperatures reached equilibrium within 2 min. While the routine binding assays were performed at pH 5.0, adjustment of the pH to 3.0 gave rise to a significant decrease in biosorption capacity by the biomass. The biosorptive capacity of the biomass for uranium was increased when extraction from solution in sea-water was examined.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 112 (1999), S. 291-299 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The aim of this investigation was to study, with immunohistochemical methods, the distribution of the novel cytoskeletal protein smoothelin in human cardiovascular tissues, the possible changes during the development of the cardiovascular system and its correlation to the intermediate filament proteins desmin and vimentin. Smoothelin was detected in smooth muscle cells of the fetal coronary arteries. In very young subjects (up to 3 months of age), only a few cells in the media of the elastic arteries contained smoothelin, whereas it was present in most smooth muscle cells in the muscular arteries. In individuals older than 1 year, most smooth muscle cells in the media of all blood vessels contained smoothelin. In vessels with a developed intima, smoothelin was present in a variable proportion of the smooth muscle cells. With few exceptions, smoothelin was more frequently detected than desmin in medial smooth muscle cells. Smoothelin and vimentin were codistributed in the smooth muscle cells of the media in most vessels. In the cardiomyocytes (fetal to adult age), the smoothelin antibody detected epitopes located at the Z-disc level but not in the intercalated discs. In conclusion, smoothelin is more widely distributed in the muscular arteries than in the elastic arteries early in life, and thus exhibits a variable distribution during postnatal development of vascular tissues. In the adult, smoothelin is detected in the media of most vascular smooth muscle cells, both in muscular and elastic arteries, and is not necessarily codistributed with either desmin or vimentin. Evidence that smoothelin is present in human striated cardiomyocytes is also presented.
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  • 10
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A fast and simple method of determining the mean velocity vector of complex three-dimensional flow fields is outlined. Straight and slanted single hot-wires are rotated in two perpendicular planes. This method increases the angular resolution, which is of importance in flow situations where one of the velocity components dominates and the other changes rapidly from one point to another. The method was calibrated in a wind tunnel and assessed in the internal flow field at the outlet of a fan in a defroster channel. It is shown that the hot-wire method yields good agreement with corresponding flow visualizations determined using a textile thread, and an integration of the measured mean flow yields a flow rate which agrees within a few percent with corresponding direct measurements on an orifice plate.
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