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  • 2005-2009
  • 2000-2004  (6)
  • 2002  (6)
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Years
  • 2005-2009
  • 2000-2004  (6)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Nanoscale tungsten aerosol particles embedded in GaAs (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2976-2978 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs containing buried nanoscale tungsten particles has been characterized electrically. The particles were produced using a special aerosol process and were embedded in GaAs by epitaxial overgrowth. Two different particle sizes were investigated separately. When the particle concentration was increased, a conductance drop of about 500 times was observed. A simulation model, based on a random distribution of the particles, was developed and used to support our findings. The major advantage of our method is the simplicity and low processing cost. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1470701
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A Monte Carlo simulation for the stripping of the (square root of)3×(square root of)3 R30° alkanethiol lattice from Au(111) terraces and steps (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 2293-2298 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulations of a model for the stripping of (square root of)3×(square root of)3 R30° alkanethiol lattices from terraces and steps of a (111) metal face in aqueous solutions are presented. In the model the stripping probability of an adsorbed alkanethiolate molecule depends on the applied potential, on intermolecular forces that stabilize the alkanethiol layer, and on the presence of substrate defects. Stabilizing intermolecular forces are also responsible for alkanethiolate aggregate formation during the stripping process. Snapshots and voltammograms derived from the model reproduce experimental STM images and electrochemical data for alkanethiol stripping from the Au(111) surface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490922
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    On quantum effects near the liquid–vapor transition in helium (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1621-1628 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The liquid–vapor transition in 3He and 4He is investigated by means of path-integral molecular dynamics and the quantum virial expansion. Both methods are applied to the critical isobar and the critical isochore. While previous path-integral simulations have mainly considered the lambda transition and superfluid regime in 4He, we focus on the vicinity of the critical point and obtain good agreement with experimental results for the molar volume and the internal energy down to subcritical temperatures. We find that an effective classical potential that properly describes the two-particle radial distribution function exhibits a strong temperature dependence near the critical temperature. This contrasts with the behavior of essentially classical systems like xenon, where the effective potential is independent of temperature. It is conjectured that, owing to this difference in behavior between classical and quantum-mechanical systems, the crossover behavior observed for helium in the vicinity of the critical point differs qualitatively from that of other simple liquids. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429957
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Frontal brain activation in anxious school children (2002)
    Oxford UK : Blackwell Publishers
    The @journal of child psychology and psychiatry 43 (2002), S. 0 
    Details
    ISSN: 1469-7610
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Background: An atypical EEG pattern of frontal brain activation has been found in infants and adults with emotional disorders. Eighty-two 8-year-old children and 56 11-year-old children were examined with regard to the following questions: 1. Do children who are diagnosed with anxiety disorder exhibit an atypical pattern of frontal brain activation? 2. Can this pattern be demonstrated in children of different ages? and 3. Are there gender differences in these patterns similar to those that have been demonstrated in adults? Baseline EEG activity was subjected to power spectral analysis. Results: In 8- and 11-year-old anxious girls, the well-known pattern of greater right than left frontal activation emerged that has been found previously in internalizing preschoolers. Healthy girls showed no frontal asymmetry at 8 years of age, and a greater left than right frontal brain activation at 11 years. In contrast, healthy boys demonstrated a significantly greater right than left frontal activation, whereas anxious boys displayed no frontal asymmetry at the age of 8, and a greater left than right frontal activation at the age of 11. Conclusions: Children suffering from anxiety disorders exhibited a significantly different pattern of frontal brain activation than healthy children without any lifetime diagnosis of mental disorder. Distinct gender differences in frontal activation were found in anxious as well as in healthy children. This could be demonstrated in two samples of different ages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-7610.00019
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Field-scale 13C-labeling of phospholipid fatty acids (PLFA) and dissolved inorganic carbon: tracing acetate assimilation and mineralization in a petroleum hydrocarbon-contaminated aquifer (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 41 (2002), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This study was conducted to determine the feasibility of labeling phospholipid-derived fatty acids (PLFA) of an active microbial population with a 13C-labeled organic substrate in the denitrifying zone of a petroleum hydrocarbon-contaminated aquifer during a single-well push-pull test. Anoxic test solution was prepared from 500 l of groundwater with addition of 0.5 mM Br− as a conservative tracer, 0.5 mM NO3−, and 0.25 mM [2-13C]acetate. At 4, 23 and 46 h after injection, 1000 l of test solution/groundwater mixture were sequentially extracted. During injection and extraction phases we measured Br−, NO3− and acetate concentrations, characterized the microbial community structure by PLFA and fluorescent in situ hybridization (FISH) analyses, and determined 13C/12C ratios in dissolved inorganic carbon (DIC) and PLFA. Computed first-order rate coefficients were 0.63±0.08 day−1 for NO3− and 0.70±0.05 day−1 for acetate consumption. Significant 13C incorporation in DIC and PLFA was detected as early as 4 h after injection. At 46 h we measured δ13C values of up to 5614‰ in certain PLFA (especially monounsaturated fatty acids), and up to 59.8‰ in extracted DIC. Profiles of enriched PLFA and FISH analysis suggested the presence of active denitrifiers. Our results demonstrate the applicability of 13C labeling of PLFA and DIC in combination with FISH to link microbial structure and activities at the field scale during a push-pull test.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2002.tb00987.x
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Sulfate-reducing bacterial community response to carbon source amendments in contaminated aquifer microcosms (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 42 (2002), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Microbial sulfate reduction is an important metabolic activity in many reduced habitats. However, little is known about the sulfate-reducing communities inhabiting petroleum hydrocarbon (PHC)-contaminated freshwater aquifer sediments. The purpose of this study was to identify the groups of sulfate-reducing bacteria (SRB) selectively stimulated when sediment from a PHC-contaminated freshwater aquifer was incubated in sulfate-reducing aquifer microcosms that were amended with specific carbon sources (acetate, butyrate, propionate, lactate, and citrate). After 2 months of incubation, the SRB community was characterized using phospholipid fatty acid (PLFA) analysis combined with multivariate statistics as well as fluorescence in situ hybridization (FISH). Molybdate was used to specifically inhibit SRB in separate microcosms to investigate the contribution of non-SRB to carbon source degradation. Results indicated that sulfate reduction in the original sediment was an important process but was limited by the availability of sulfate. Substantially lower amounts of acetate and butyrate were degraded in molybdate treatments as compared to treatments without molybdate, suggesting that SRB were the major bacterial group responsible for carbon source turnover in microcosms. All of the added carbon sources induced changes in the SRB community structure. Members of the genus Desulfobulbus were present but not active in the original sediment but an increase of the fatty acids 15:1ω6c and 17:1ω6c and FISH results showed an enrichment of these bacteria in microcosms amended with propionate or lactate. The appearance of cy17:0 revealed that bacteria affiliated with the Desulfobacteriaceae were responsible for acetate degradation. Desulfovibrio and Desulfotomaculum spp. were not important populations within the SRB community in microcosms because they did not proliferate on carbon sources usually favored by these organisms. Metabolic, PLFA, and FISH results provided information on the SRB community in a PHC-contaminated freshwater environment, which exhibited stimulation patterns similar to other (e.g. marine) environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2002.tb01000.x
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    Paper (German National Licenses)
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