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141.
Aromatic, allylic, and aliphatic compounds containing a chlorohydrin group were selected as substrates for the enzymatic kinetic resolution mediated by Amano AK lipase from Pseudomonas fluorescens immobilized in silk friboin-alginate spheres. Thus, the enantioselectivity of the process was sufficient for the production of the desired alcohols and acetates in good yields and high enantiomeric purities. This Letter provides a simple, cheap, and practical protocol for enantioselective synthesis of chlorohydrins and reinforces the versatility of silk fibroin as supports for heterogeneous catalysts.  相似文献   
142.
Hybrid organic–inorganic lead halide perovskite APbX3 pigments, such as methylammonium lead iodide, have recently emerged as excellent light harvesters in solid‐state mesoscopic solar cells. An important target for the further improvement of the performance of perovskite‐based photovoltaics is to extend their optical‐absorption onset further into the red to enhance solar‐light harvesting. Herein, we show that this goal can be reached by using a mixture of formamidinium (HN=CHNH3+, FA) and methylammonium (CH3NH3+, MA) cations in the A position of the APbI3 perovskite structure. This combination leads to an enhanced short‐circuit current and thus superior devices to those based on only CH3NH3+. This concept has not been applied previously in perovskite‐based solar cells. It shows great potential as a versatile tool to tune the structural, electrical, and optoelectronic properties of the light‐harvesting materials.  相似文献   
143.
Metal hydrides are of fundamental importance in chemistry, both as solid‐state materials and molecular compounds. The first low‐valent molecular metal cluster containing an interstitial four‐coordinate hydride in a tetrahedral site is decribed, which undergoes hydride migration from the surface to the tetrahedral cavity of the cluster upon coordination of a [AuPPh3]+ fragment. The [HFe4(CO)12(AuPPh3)2]? mono‐anion, which contains a surface μ3‐H, was obtained from the reaction of [HFe4(CO)12]3? with two equivalents of [Au(PPh3)Cl]. This is, in turn, transformed into the neutral [HFe4(CO)12(AuPPh3)3] upon addition of a third [AuPPh3]+ fragment, with concomitant migration of the unique hydride from the surface of the cluster to its tetrahedral cavity. All of these species have been fully characterized in solution by means of IR and multinuclear NMR spectroscopy, and in the solid state by single‐crystal X‐ray diffractometry.  相似文献   
144.
A concise synthesis of (R)-4-amino-3-hydroxybutanoic acid, starting from L-malic acid, is reported. The approach is based on the conversion of the oxazolidin-2-one 9 into a full protected form of (®)-GABOB by an Arndt-Eistert reaction.  相似文献   
145.
146.
The formation of clay intercalates with three different kinds of organic ammonium salts, when mixed in the presence of synthetic or natural polyisoprene rubber, has been investigated. X‐ray diffraction and transmission electron microscopy (TEM) experiments have shown that intercalates with organic bilayers, rather than with interdigitated organic monolayers, are obtained only for the ammonium salts presenting two long alkyl chains and only in the presence of the natural rubber (NR). These results have been qualitatively rationalized on the basis of suitable interlayer densities. Both monolayer and bilayer clay intercalates remain stable for short‐term heating procedures at temperatures lower than 250°C. For treatments at higher temperatures, where the decomposition of the organic ammonium salt occurs, both kinds of clay intercalates maintain intralayer crystalline order. However, the decomposition of the organic modifier leads to the formation of pristine and exfoliated clay for the intercalates with organic monolayers and bilayers, respectively. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
147.
148.
Recently a one-dimensional closed ladder of Josephson junctions has been studied [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Phys. Lett. A 372 (2008) 2464] within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. That led us to predict the emergence of a topological order in such a system [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter we analyze the ground states and the topological properties of fully frustrated Josephson junction arrays (JJA) arranged in a Corbino disk geometry for a variety of boundary conditions. In particular minimal configurations of fully frustrated JJA are considered and shown to exhibit the properties needed in order to build up a solid state qubit, protected from decoherence. The stability and transformation properties of the ground states of the JJA under adiabatic magnetic flux changes are analyzed in detail in order to provide a tool for the manipulation of the proposed qubit.  相似文献   
149.
In this paper we answer two questions raised by M. A. Erceg [J. Math. Anal. Appl. 69 (1979), 205–230]: precisely we show that the fuzzy unit interval is never T0 except in the standard case and that a fuzzy pseudo-metrizable T0 space is metrizable in the sense of Erceg (ibid.); hence the two definitions of metrizable space given in B. Hutton and I. Reilly [Fuzzy Sets and Systems3 (1980), 93–104] and Erceg (ibid.) are equivalent.  相似文献   
150.
Summary We have investigated the electronic states of some Pt-W alloys by means of the relativistic KKR-CPA theory in order to gain some insights on the many interesting physical properties of such a system. In particular we were interested in studying the role of the Fermi surface topology in the ordering phenomena shown by this alloy. It turns out that the broadening of the states at the Fermi energy makes the Fermi surface concept questionable. Reasons for that are understood in terms of our scheme and approximations, even though to give an exhaustive answer one should pursue the full-charge self-consistency obtainable in the SCF-KKR-CPA theory.  相似文献   
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