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  • 2005-2009  (2)
  • 1995-1999  (7)
  • 1970-1974  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Rydberg transitions in X-ray absorption spectroscopy of alkanes: The importance of matrix effects (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6834-6845 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Precise ab initio electronic structure calculations on isolated alkanes (propane, butane) and on propane embedded in a matrix of several propane molecules were used in order to characterize the near-edge x-ray absorption fine structure (NEXAFS) resonances of condensed saturated hydrocarbons. The results demonstrate that upon condensation the dominating NEXAFS spectral features, i.e., the Rydberg resonances located between 287.4 and 288.1 eV, have a significant blue shift from the corresponding transition energies of an isolated alkane molecule. Furthermore, the theoretical results confirm the excitonic character of the final state. Additional calculations carried out for different conformations (trans/gauche) of isolated butane demonstrate that the transition energies of the corresponding NEXAFS resonances do not differ significantly. Previously observed changes in the electronic structure of disordered thin organic films of calciumarachidate are thus attributed to changes in the intermolecular spacing of the molecules rather than to changes in the electronic structure of the different, trans and gauche, conformations of the alkane chain. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479976
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  • 2
    Electronic Resource
    Electronic Resource
    Study of partial oxidation of Cu clusters by HRTEM (1997)
    Springer
    Catalysis letters 49 (1997), S. 101-108 
    Details
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cu clusters of diameters less than 10 nm were selected as models to study oxidation as a function of size, chemical composition, and structure. The investigations were performed with high-resolution electron microscopy. It was shown that beginning with multiply twinned particles as stable structures for particles with diameters less than 5 nm and of cuboctahedra for larger particles, in the transitional state between pure metal and oxide both states can coexist within the same particle; this latter can be proved by HRTEM. It was also demonstrated that this is due to incorporating distortions as step dislocations within grain boundaries which can be shown in electron micrographs of high resolution better than 0.18 nm after image processing. The creation of sub-oxides with less reactivity than the pure metal clusters could also be demonstrated leading to morphologies which are different from those of the pure metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019080516212
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  • 3
    Electronic Resource
    Electronic Resource
    A Study of Polymer Degradation Using Doppler Broadening Positron Annihilation Spectroscopy (1997)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 255-257 (Sept. 1997), p. 278-280 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/02/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.255-257.278.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of molecular orientation in ultrathin liquid crystal. films on solid substrates using X-ray absorption spectroscopy (1997)
    Springer
    Applied physics 65 (1997), S. 231-234 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 42 H60O6, HBT) deposited on a (111)-oriented Au single crystal and a polycrystalline indium tin oxide (ITO) substrate has been carried out using X-ray absorption spectroscopy. Films of thicknesses between 2 nm and 15 nm were prepared in UHV by evaporation of HBT [which exhibits a discotic liquid crystalline (LC) bulk phase] from a Knudsen cell. Thickness and composition of the HBT films were determined using X-ray photoelectron spectroscopy (XPS). For the thinnest films with thicknesses in the monolayer regime, the orientational analysis reveals a pronounced orientation of the disc-shaped HBT molecules parallel to the Au surface. For thicker films, a significantly reduced anisotropy is observed with the molecular plane oriented more normal to the Au surface. In the case of the ITO-substrates, no significant differences were observed between different thickn esses and the average orientation of the molecular planes was predominantly normal to the surfaces, as for the thicker films on the Au substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050571
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  • 5
    Electronic Resource
    Electronic Resource
    Trisomy 7 in synovial fibroblasts obtained from arthritic joints (1999)
    Springer
    Inflammation research 48 (1999), S. 132-133 
    Details
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000110050553
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  • 6
    Electronic Resource
    Electronic Resource
    From Solidification Simulation to Virtual Product Development (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 508 (Mar. 2006), p. 523-530 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Although the use of the Finite Elements Method (FEM) has more and more become a natural course of action for the creation of component parts, not yet the whole potential of numerical simulation is used. The absences of interfaces between the different calculations, missing or inaccurate physical data as well as the lack of theoretical background in certain areas prevent a complete virtual product development. Design, solidification simulation, calculation of mechanical properties, stress calculations, and the prediction of the operating life of a component are at present almost exclusively regarded as separate solutions. Necessary however is a meshed computation loop, where the solutions of previous steps are moved on to the following ones. Due to improvements in the area of solidification simulation and with the help of new theoretical concepts for the prediction of mechanical properties of casted aluminum parts, it is now possible to do all the technical analysis with just one software package. This solves the interface problem and especially the error-prone change between different numerical calculation processes
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.508.523.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    New Algorithm to Calculate Liquid – Solid Shrinkage and Graphite Expansion (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 508 (Mar. 2006), p. 509-514 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Meanwhile the calculation of cooling and solidification is a well introduced tool into thefoundry industry for calculating gating and riser systems. However, knowing the areas of last solidification is often no answer to the question if there are any defects in the casting or not. Of course one requirement is an exact description of the heat flow and the heat transfer between melt and mould. But furthermore the liquid/liquid and liquid/solid shrinkage influence the temperature fields due to a convective heat flux. Also auxiliary material influence the liquid/solid behaviour. Auxiliary materials can be on one hand the inoculation material and on the other chills with and without coating. This is the reason, why defects near the gating often can not be detected by a conventional solidification calculation, which doesn’t take into account the impact of the auxiliary material on the convective flow. With new algorithms within the FEM program SIMTEC/WinCast it is possible to respect this behaviour during the simulation of solidification. Special attention was turned to the expansion of graphite in ductile irons. The graphite first nucleates in the liquid, and then continues to grow in the solid phase depending on the alloy compositions and the solidification parameters. With the knowledge about the physical properties of the alloy the location and the size of defects can be predicted precisely
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.508.509.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Heat exchange in liquid helium by phonon tunneling through very thin plates (1971)
    Springer
    Journal of low temperature physics 4 (1971), S. 263-271 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thin plates with a thicknessd smaller than the phonon mean-free path can be used to increase the heat exchange in 3 He- 4 He refrigerators at very low temperatures. The resistanceR for the heat current density of these plates is theoretically investigated. For plates withd still larger than the dominant thermal-phonon wavelength λ T in the plate,R is given by twice the Kapitza resistance. Ford ≈ λ T the resistanceR decreases due to phonon tunneling. Ford ≪ λ T there exists a region whereR varies asT −1, in contrast to theT −3 dependence for thicker plates. Numerical calculations are carried out for copper plates immersed in pure 4 He. The results show that one obtains a large increase of the heat exchange due to phonon tunneling for plates with a thickness of a few microns at temperatures in the millidegree range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00629713
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  • 9
    Electronic Resource
    Electronic Resource
    The Effects of Chemical Doping and Hydrostatic Pressure on T c of Y1−y Ca y Ba2Cu3O x and NdBa2Cu3O x Single Crystals (1999)
    Springer
    Journal of low temperature physics 117 (1999), S. 921-925 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Westudied T c of Y Ba 2 Cu 3 O x (Y123), Y 0.89 Ca 0.11 Ba 2 Cu 3 O x (YCa123) and NdBa 2 Cu 3 O x (Nd123) single crystals with various oxygen contents x. Compared to T c (x) of Y123 the T c (x) curves of YCa123 are shifted to lower oxygen contents and the maximum transition temperature T c,max decreases with increasing Ca content whereas in Nd123 T c (x) is shifted to higher oxygen contents and T c,max is increased. According to the universal parabolic T c (n h ) behavior the differences in T c (x) of Y123, YCa123 and Nd123 can be ascribed to different hole concentrations n h in the CuO 2 planes caused by doping via changes in chemistry or structure. In order to study the influence of structural changes on T c we examined the hydrostatic pressure effect dT c /dp (p ≤0.6GPa). In the underdoped region, at n h ≈0.11, the examined compounds show a peak in dT c /dp which is very pronounced for systems with well ordered CuO chains. As this peak occurs at the same n h in all investigated systems it is not caused by oxygen ordering, but its origins might be found in a strong influence of lattice deformations on the electronic structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022559025868
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  • 10
    Electronic Resource
    Electronic Resource
    A quantum mechanical determination of the superfluid density (1972)
    Springer
    The European physical journal 14 (1972), S. 324-335 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The constituting conservation laws for a superfluid are quantum mechanically derived. Using thermodynamic relations the superfluid density is model-independently expressed in terms of reduced-density matrices. The general relation is illustrated for the Bogolubov model, and for two other approximations for the two-particle reduced-density matrix. The resulting relations between the densities of the super component and of the condensate are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02422689
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