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311.
A simple Kronig-Penney model for 1D mesoscopic systems with δ peak potentials is used to study numerically the influence of spatial disorder on conductance fluctuations and distribution at different regimes. The Lévy laws are used to investigate the statistical properties of the eigenstates. It is found that an Anderson transition occurs even in 1D meaning that the disorder can also provide constructive quantum interferences. The critical disorder Wc for this transition is estimated. In these 1D systems, the metallic phase is well characterized by a Gaussian conductance distribution. Indeed, the results relative to conductance distribution are in good agreement with the previous works in 2D and 3D systems for other models. At this transition, the conductance probability distribution has a system size independent shape with large fluctuations in good agreement with previous works. 相似文献
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Mhamed El Achhab Andreas Erbe Georg Koschek Rachid Hamouich Klaus Schierbaum 《Applied Physics A: Materials Science & Processing》2014,116(4):2039-2044
The structure and distribution of TiO2 rutile and anatase phases of anodized titanium foil, subjected to a special high-voltage electrochemical preparation technique, are reported. We applied X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy on samples that were oxidized for various times. Combining data from the different techniques led to a model in which the initially formed porous, micrometer-thick TiO2 layer, consisting in a large part of anatase, is transformed into rutile. The result is a porous rutile layer on top of anatase, which is in direct contact with the Ti metal. The first structural model is derived from the evaluated data and the phenomena that occurred during preparation are clarified. 相似文献
314.
Rachid Essehli Brahim El Bali Mohammed Lachkar Michael Dusek Fejfarova Karla Michael Bolte 《Journal of chemical crystallography》2006,36(10):655-660
(C2N2H10)2Mg(HP2O7)2·2H2O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO4(H2O)2] octahedra resulting in chains, which are linked via [HP2O7] units to form [Mg(HP2O7)2(H2O)2]4− layers. The Mg2+ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation. 相似文献
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Abdelwaheb Hamdi Rachid Souane Lidia Kim Rym Abidi Lucia Mutihac Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》2009,64(1-2):95-100
Calixarenes 2–4, 6 and 7 in the cone conformation variously substituted by acid or amido functions, glycolic chains and hydroxyl groups were synthesised. They have been used in extraction of native amino acid and amino acid esters. 相似文献
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As a continuation of our studies directed at the development of straightforward and sustainable methodologies, we describe herein an original example of a combined effect of ultrasonic activation and iron–copper dual catalysis that allows an efficient and ecofriendly one-pot, three-step route to a new series of nucleoside-substituted triazoles. The reactions were carried out under both conventional and ultrasonic irradiation conditions. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
320.
Dr. José Justicia Dr. Tania Jiménez Dr. Delia Miguel Rafael Contreras‐Montoya Dr. Rachid Chahboun Prof. Enrique Álvarez‐Manzaneda Daniel Collado‐Sanz Prof. Diego J. Cárdenas Dr. Juan M. Cuerva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(43):14484-14495
In this article, a complete study on the selectivity of titanocene(III) cyclization of epoxypolyprenes is presented. The requirements for the formation of six‐ or seven‐membered rings during these cyclizations are determined, taking into account the different substitution pattern in the epoxypolyprene precursor. Thus, a complete selectivity to 6‐exo or 7‐endo cyclization process has been achieved, yielding mono‐, bi‐, and even tricyclic compounds, constituting a new and efficient access to this type of derivative. Additionally, this procedure opens the possibility to prepare excellent building blocks for the synthesis of polycyclic compounds with a trisubstituted oxygenated function, which is present in several natural terpenes. 相似文献