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61.
Visart de Bocarmé T Kruse N Gaspard P Kreuzer HJ 《The Journal of chemical physics》2006,125(5):054704
We report a study of the adsorption and reaction of CO on a gold nanotip in high electrostatic fields. Field ion microscopy is used to investigate the emergence of a Au-carbonyl wave that is made visible with oxygen as the imaging gas. We set up a simple kinetic model that reproduces the adsorption wave and confirms that the presence of oxygen merely serves as an imaging gas and does not lead to field-induced oxidation of CO. 相似文献
62.
Visart de Bocarmé T Chau TD Tielens F Andrés J Gaspard P Wang RL Kreuzer HJ Kruse N 《The Journal of chemical physics》2006,125(5):054703
We have studied oxygen interaction with Au crystals (field emitter tips) using time-resolved (atom-probe) field desorption mass spectrometry. The results demonstrate no adsorption to take place on clean Au facets under chosen conditions of pressures (p < 10(-4) m/bar) and temperatures (T = 300-350 K). Steady electric fields of 6 V/nm do not allow dissociating the oxygen molecule. The measured O2+ intensities rather reflect ionization of O2 molecules at critical distances above the Au tip surface. Certain amounts of Au-O2 complex ions can be found at the onset of Au field evaporation. Calculations by density functional theory (DFT) show weak oxygen end-on interaction with Au10 clusters (Delta E = 0.023 eV) and comparatively stronger interaction with Au1/Au(100) model surfaces (Delta E = 0.25 eV). No binding is found on {210} facets. Including (positive) electric fields in the DFT calculations leads to an increase of the activation energy for oxygen dissociation thus providing an explanation for the absence of atomic oxygen ions from the field desorption mass spectra. 相似文献
63.
64.
We report on the fact that microscopically enforcing fulfillment of thermodynamics’ third law on a system of fermions automatically yields the values of the external parameter (here coupling strengths in the pertinent Hamiltonian) at which quantum phase transitions take place. Our considerations are illustrated via an exactly solvable model of Plastino and Moszkowski [Il Nuovo Cimento 47, 470 (1978)]. 相似文献
65.
Volume Contents
Contents of Volume 74 (2002) 相似文献66.
67.
Summary The D-(resp. R) configuration of isovaline (=2-ethylalanine) was proved for the peptide antibiotics antiamoebin, Tü 165 (CBS 382.62), stilbellin, samarosporin (=emerimicin IV), suzukacillin B (A), trichotoxin A-40 and A-50. This contradicts the previously reported L-configuration for isovaline in antiamoebin and emerimicin IV. The configuration was determined by GC of the N-trifluoroacetyl-isovaline n-propyl ester on glass capillary columns coated with the chiral stationary phase N-propionyl-L-valine tert.-butylamide polysiloxane (Chirasil Val). The D-configuration of the isovaline from trichotoxin A-40 was also established independently using GC of N-pentafluoro-propionyl-isovaline (+)-3-methyl-2-butyl esters on glass capillary columns coated with OV 17. 相似文献
68.
A set of several automatic and interactive computer programs for instrumental neutron activation analysis is discussed. The
system allows fast and precise evaluation of data obtained from counting samples on a large number of different Ge(Li) detectors. 相似文献
69.
Raisa V. Talroze Eugene R. Zubarev Marina A. Rogunova Igor A. Litvinov Nicolai A. Plate Kishore Udipi Robert Kruse 《先进技术聚合物》1996,7(3):182-186
Peculiarities of the rheological properties of blends composed of thermoplastic polymer and polyacrylates are studied. The comparison of blends containing comb-shaped polymers of differing side-chain lengths shows that the flow mechanism changes with shortening side-group length. This leads to higher viscosity and elasticity of the combshaped component and, at the same time, results in the dramatic decrease in the blend viscosity, even at combshaped additive low content. 相似文献
70.
Determination of chlorophenols in urine of children and suggestion of reference values 总被引:1,自引:0,他引:1
P. Bartels E. Ebeling B. Krämer H. Kruse N. Osius K. Vowinkel O. Wassermann J. Witten C. Zorn 《Analytical and bioanalytical chemistry》1999,365(5):458-464
During the course of a human biomonitoring project (Biebesheim in Hessen, Germany) we elaborated a simple but sensitive method
for the determination of tri- (TCP), tetra- (TeCP) and pentachlorophenol (PCP) in human urine. Urine samples, spiked with
internal standards, were treated by acid hydrolysis. After a steam bath distillation the distillates were extracted using
solid phase extraction. Derivatization of the chlorophenols was not carried out. GC/ECD system was used for detection. Detection
limits of the chlorophenols were found in the range of 0.02 μg/L urine (detection limits of the ECD: 0.52 to 2.76 μg/L). By
this method mono- and dichlorophenols cannot be detected. We investigated 24h-urine samples of 339 pupils (age 10 to 12 years).
The children live either in the surroundings of a hazardous waste incinerator (SVA) in Biebesheim (n = 193), or controls (i.e.
regions without waste incinerator) in the non polluted areas of Odenwald (n = 90) and Rheintal (n = 56). Between these three
groups we did not find statistically significant differences in chlorophenol concentrations of the urine samples. The 95-percentiles
of the analyzed samples are 0.74 μg/L (2,3,4-TCP), 1.24 μg/L (2,3,5-TCP), 0.70 μg/L (2,3,6–TCP), 1.10 μg/L (2,4,5–TCP), 1.74
μg/L (2,4,6–TCP), 2.84 μg/L (3,4,5–TCP), 4.78 μg/L (2,3,4,5-TeCP), 1.86 μg/L (2,3,4,6-TeCP), 2.90 μg/L (2,3,5,6-TeCP) and
4.39 μg/L (PCP).
Received: 24 February 1999 / Revised: 3 May 1999 / Accepted: 6 May 1999 相似文献