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71.
72.
Wang X Zeng L Wiens M Schlossmacher U Jochum KP Schröder HC Müller WE 《Micron (Oxford, England : 1993)》2011,42(5):401-411
In the present study we examined material from the Ashikule Basin of Tibet. Chemical analyses were performed by use of energy dispersive X-ray spectroscopy and electron probe microanalysis to clarify whether the varnish layers that had developed on the surface of the rhyolite are indeed composed of varnish bodies and silica glaze. Electron microscopic analyses revealed that the surface of the varnish is covered both by filamentous hyphae bacterial and cocci-shaped forms. Within the varnish mineral layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterial aggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish matrix, that surrounds the varnish bodies]. The bacillus-like forms are embedded in a network of filaments that have diameters between 35 and 45 nm. These bacilli with the surrounding filaments are assumed to have been involved in biofilm formation (synthesis of extracellular polymeric substances) prior to their live burial. We concluded that the formation of the varnish layers was for the most part biogenically driven by microorganisms. 相似文献
73.
Quantum-enhanced metrology infers an unknown quantity with accuracy beyond the standard quantum limit (SQL). Feedback-based metrological techniques are promising for beating the SQL but devising the feedback procedures is difficult and inefficient. Here we introduce an efficient self-learning swarm-intelligence algorithm for devising feedback-based quantum metrological procedures. Our algorithm can be trained with simulated or real-world trials and accommodates experimental imperfections, losses, and decoherence. 相似文献
74.
Andreas Hilgeroth Günter Hempel Ute Baumeister Detlef Reichert 《Solid state nuclear magnetic resonance》1999,13(4):4125-243
13C CPMAS NMR spectroscopy has been applied to monitor the solid-state reaction of two different photodimerizing 4-phenyl-1,4-dihydropyridines yielding a cage dimer in one case and an anti-dimer in the other case. The spectra of the reacting monomers exhibit a magnetical inequivalence of chemically equivalent CO and C2/4 carbon atoms caused by a rotation of the pseudoaxially oriented 4-phenyl substituent out off the plane through N1, C3, C8 which could be determined by X-ray crystal structure analyses of the centrosymmetrically arranged monomers. The 13C CPMAS NMR monitoring of the cage dimer formation proves that the reaction takes place in two steps via a syn-dimer for which a non-symmetrical structure was derived from the spectrum. The non-symmetrical structure was confirmed by X-ray crystal structure analysis of one structurally related derivative. A centrosymmetric structure for both the finally formed cage dimer and the anti-dimer of the other monitored photoreaction was proved by their spectra with one set of signals for each half of the dimers, respectively. Thus, conformational properties of the molecules as well as the symmetry of the products can be directly derived from the 13C CPMAS NMR spectra. 相似文献
75.
76.
We study the validity of the Born–Oppenheimer approximation in chaotic dynamics. Using numerical solutions of autonomous Fermi accelerators, we show that the general adiabatic conditions can be interpreted as the narrowness of the chaotic region in phase space. 相似文献
77.
78.
Ingo Brasack Horst Böttcher Ute Hempel 《Journal of Sol-Gel Science and Technology》2000,19(1-3):479-482
Biocomposite layers of silica and various bone-relevant proteins such as collagen, gelatine and commercial collagen hydrolysate can be obtained from coatings of silica sols mixed with proteins in water/dioxane. Investigations into the mechanical and cell proliferation properties for different sol parameters (pH, solvent), type and concentration of proteins, annealing and crosslinking of the biocomposite layers revealed that such coatings are highly biocompatible with excellent mechanical properties. 相似文献
79.
A system of independent electrons interacting with an arbitrary number of fixed point scatterers on the surface of an infinitely long cylinder is considered. It is shown that (at zero temperature) the equilibrium Byers-Yang Hall current takes the same value as for free electrons if the Fermi energy lies in an energy gap. 相似文献
80.