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371.
Sterrer M Heyde M Novicki M Nilius N Risse T Rust HP Pacchioni G Freund HJ 《The journal of physical chemistry. B》2006,110(1):46-49
Localized electronic defects on the surface of a 4 monolayer (ML) thin MgO(001) film deposited on Ag(001) have been investigated by low-temperature scanning tunneling microscopy and spectroscopy. Depending on the location of the defect, we observe for the first time different defect energy levels in the band gap of MgO. The charge state of defects can be manipulated by interactions with the scanning tunneling microscope tip. Comparison with ground state energy levels of color centers on the MgO surface obtained from embedded cluster calculations corroborates the assignment of the defects to singly and doubly charged color centers. 相似文献
372.
Gottfried JM Flechtner K Kretschmann A Lukasczyk T Steinrück HP 《Journal of the American Chemical Society》2006,128(17):5644-5645
We demonstrate that well-defined monolayers of a metal complex on a surface can be prepared by direct vapor deposition of the metal atoms on monolayers of the ligand. In particular, ordered monolayers of adsorbed tetraphenylporphyrin (2H-TPP) on a silver surface were exposed to cobalt vapors, resulting in the complexation of the metal by the porphyrin. The formation of the metal complexes was monitored by means of X-ray photoelectron spectroscopy (XPS), which reveals that this metalation reaction leads to a chemical equivalence of all four nitrogen atoms. The described in situ metalation provides a convenient way to produce adsorbed monolayers of more reactive (e.g., air- or solvent-sensitive) or thermally unstable metalloporphyrins that are difficult to evaporate or even to obtain as pure compounds at room temperature. 相似文献
373.
We study conditions under which the Hausdorff quasi-uniformity UH of a quasi-uniform space (X,U) on the set P0(X) of the nonempty subsets of X is bicomplete.Indeed we present an explicit method to construct the bicompletion of the T0-quotient of the Hausdorff quasi-uniformity of a quasi-uniform space. It is used to find a characterization of those quasi-uniform T0-spaces (X,U) for which the Hausdorff quasi-uniformity of their bicompletion on is bicomplete. 相似文献
374.
Various K-, L- and M-shell X-ray production cross sections are measured for heavy ion impact on elements in the range Z
2 = 13 to 83. The ion species range from Z
1 = 10 to 36, and ion energies from 1 to 16 MeV are used. Enhanced cross sections are observed when the projectile K- or L-
binding energy is similar to the energy of the target K-, L- or M-shell. This effect is used to improve the analysis sensitivity
for selected elements. As an example trace analysis of Fe in glass with V, Mn, Co and Ni ions is investigated. Results are
compared with proton induced X-ray emission analysis on the same samples. In these samples Fe-Kα X-ray production is similar for irradiation with 3 MeV protons and 14 MeV Ni ions. However the signal to background ratio
is four times higher for the irradiation with Ni ions as compared to irradiation with protons. Advantages and drawbacks of
heavy ion induced X-ray emission for quantitative analysis compared to proton induced X-ray emission analysis are discussed. 相似文献
375.
Hans-Peter Scheffler 《Probability Theory and Related Fields》2000,116(2):257-271
For a random vector belonging to the (generalized) domain of operator semistable attraction of some nonnormal law we prove
various variants of Chover's law of the iterated logarithm for the partial sum. Furthermore we also derive some large deviation
results necessary for the proof of our main theorems.
Received: 30 September 1998 / Revised version: 28 May 1999 相似文献
376.
Let ? be a simply connected nilpotent Lie group with Lie Algebra ? and let τ be a contraction on ?. A probability measure
μ on ? is strongly τ-decomposable iff it is representable as the limit of for some probability ν on ?. We show that such a limit exists if and only if ν possesses a finite logarithmic moment with
respect to a homogeneous norm on ?. This result is then generalized to the class of selfdecomposable laws on ?. We also show
that selfdecomposable laws on ? correspond in a 1–1 way to operator selfdecomposable laws on the tangent space ?.
Received 1 October 1998; in revised form 29 March 1999 相似文献
377.
Condensation of o-xylylene bis(triphenylphosphorane) 4 with [(Me3Si)2N]2Sn yields the 1,3-bis(triphen-ylphosphoranediyl)-2σ2-stannaindene 2 , which is orange as a solid and red in solution and which demonstrates stannylene reactivity. Alkyl bromides andiodides add to 2 to give the corresponding 2σ4-stannaindanes. In the reaction with PCl3, the tin atom in 2 is replaced by a phosphenium ring member. A secondary product in the preparation of 2 is the spirocyclic 2σ4-stannaindane 12. Its structure has been determined by X-ray analysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:103–108, 1998 相似文献
378.
379.
Bernd Jung Hans-Peter Lenhof Peter Müller Christine Rüb 《Macromolecular theory and simulations》1997,6(2):507-521
A parallel algorithm is developed that allows efficient Langevin-dynamics simulations of macromolecular coils, which is the usual structure of synthetic polymers in solution and in bulk. Contrary to usual so-called spatial decomposition algorithms, we map the one-dimensional topology of the chain molecule on the parallel computer. The speedup of the algorithm is measured on different multi-processor systems. The reliability of the parallel calculations is shown by comparison with sequential simulations. 相似文献
380.
Hans-Peter Fink Hans Joachim Purz Andreas Bohn Jürgen Kunze 《Macromolecular Symposia》1997,120(1):207-217
Supramolecular structure of initially wet bacterial cellulose of Acetobacter xylinum has been investigated by X-ray scattering including synchrotron radiation, transmission electron microscopy, and 13C-CP/MAS-NMR-spectroscopy. As a result a model is given of never dried swollen microfibrillar ribbons consisting of 5 to 12 waterfree Iα-crystalline subunits with a cross-section of about 7 nm × 13 nm and of water solvating the subunits. Lateral aggregation of these crystalline units was found along the smaller (110)-lattice planes with a layer of water between adjacent crystallites. The NMR-spectrum of wet bacterial cellulose exhibits an additional C-1 line component indicating cellulose-water interactions. During drying lateral dimensions of the microfibrillar ribbons, crystallite sizes, as well as the overall crystalline order decrease, whereas the Iα/Iβ-ratio of about 80/20 remains approximately unchanged. Conclusions were drawn with regard to the early states of structure formation of bacterial cellulose. 相似文献