Direct observation of the Aharonov-Casher phase

Ring structures fabricated from HgTe/HgCdTe quantum wells have been used to study Aharonov-Bohm type conductance oscillations as a function of Rashba spin-orbit splitting strength. We observe nonmonotonic phase changes indicating that an additional phase factor modifies the electron wave function. We associate these observations with the Aharonov-Casher effect. This is confirmed by comparison with numerical calculations of the magnetoconductance for a multichannel ring structure within the Landauer-Büttiker formalism.     

Microscopic analysis of the valence band and impurity band theories of (Ga,Mn)As

We analyze microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with conventional parametrization and the full potential local-density approximation+U calculations give a very similar band structure whose microscopic spectral character is consistent with the physical premise of the k·p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character. By adapting the tight-binding Anderson calculations individually to each of the impurity band pictures in the single Mn impurity limit and then by exploring the entire doping range, we find that a detached impurity band does not persist in any of these models in ferromagnetic (Ga,Mn)As.     

Gevrey vectors in involutive tube structures and Gevrey regularity for the solutions of certain classes of semilinear systems

In this work, we introduce the notion of s-Gevrey vectors in locally integrable structures of tube type. Under the hypothesis of analytic hypoellipticity, we study the Gevrey regularity of such vectors and also show how this notion can be applied to the study of the Gevrey regularity of solutions of certain classes of semilinear equations.     

Synthesis of novel 5-aryl-6-cyano-3H,8H-pyrido[2,3-d]pyrimidine-4,7-diones in the reaction of 6-amino-4-pyrimidinones with benzaldehyde and ethyl cyanoacetate

The title compounds 4 and 5 have been prepared in one-step reaction from 6-amino-4-pyrimidinones 1 , the corresponding 4-substituted benzaldehyde 2 and ethyl cyanoacetate 3 in very good yields. The structure of the final compounds was determined on the basis of nmr measurements, especially by ¹H, ¹H-, ¹H,¹³C COSY, and DEPT.     

Synthesis of 5-cyanopyrazolo[3,4-b]pyridines in the reaction of 5-amino-3-methyl-1-phenylpyrazole with arylidene derivatives of malonodinitrile and ethyl cyanoacetate

This paper describes the synthesis of a new series of 6-amino-4-aryl-5-cyanopyrazolo[3,4-b]pyridines 4 and 4-aryl-5-cyano-6H-pyrazolo[3,4-b]pyridin-6-ones 5 from the reaction of 5-amino-3-methyl-1-phenylpyrazole 1 with arylidene derivatives of malonodinitrile 2 and ethyl cyanoacetate 3 . The structure of the final compounds was determined on the basis of nmr measurements, especially by ¹H, ¹H-, ¹H, ¹³C-COSY, DEPT and X-ray diffraction.     

cis‐Bis­[1,3‐bis(2‐fluoro­phenyl)­triazenido‐κ2N1,N3]­bis­(pyridine‐κN)cadmium(II)

In the title compound, [Cd(C₁₂H₈F₂N₃)₂(C₅H₅N)₂], the Cd atom lies on a crystallographic twofold axis in space group Iba2. The coordination geometry about the Cd^II ion corresponds to a rhombically distorted octahedron, with two deprotonated 1,3‐bis(2‐fluoro­phenyl)­triazenide ions, viz. FC₆H₄NNNC₆H₄F⁻, acting as bidentate ligands (four‐electron donors). Two neutral pyridine (py) mol­ecules complete the coordination sphere in positions cis with respect to one another. The triazenide ligand is not planar (r.m.s. deviation = 0.204 Å), the dihedral angle between the phenyl rings of the terminal 2‐fluoro­phenyl substituents being 24.6 (1)°. The triazenide and pyridine Cd—N distances are 2.3757 (18)/2.3800 (19) and 2.3461 (19) Å, respectively. Intermolecular C—H⋯F interactions generate sheets of mol­ecules in the (010) plane.     

A computational study of stereospecifity in the thermal elimination reaction of menthyl benzoate in the gas phase

This paper reports a theoretical study, at the B3LYP/6–31 + G(d,p) and M05‐2X/6–31G + (d,p) levels, on the thermal decomposition of menthyl benzoate (2‐isopropyl‐5‐methylcyclohexyl benzoate). It undergoes a unimolecular first‐order elimination to give 3‐menthene (1‐isopropyl‐4‐methylcyclohexene), 2‐menthene (3‐isopropyl‐6‐methylcyclohexene), and benzoic acid. We studied two possible mechanisms trying to explain the formation of 2‐ and 3‐menthene, via six‐membered or four‐membered cyclic transition states. Rate constants were calculated at two temperatures, 587.1 and 598.6 K, and they agree well with the experimentally determined values. We verify that 3‐menthene is the product mainly formed at both temperatures. The progress of the reactions has been followed by means of the Wiberg bond indices. Intrinsic reaction coordinate (IRC) calculations have been carried out to verify that the localized transition state structures connect with the reactants and products and also to verify that the parent compound, menthyl benzoate, is taking the cis‐configuration needed in the reaction. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of 6‐(2‐hydroxybenzoyl)pyrazolo[1,5‐a]pyrimidines by reaction of 5‐amino‐1h‐pyrazoles and 3‐formylchromone

Reaction of 3‐formylchromone ( 1 ) with 5‐amino‐1H‐pyrazoles ( 2 ) in ethanol, afforded 6‐(2‐hydroxy‐benzoyl)pyrazolo[1,5‐a]pyrimidines ( 3a‐g ) in good yields. The structures and the regiospecificity of the reaction were established by nmr measurements and X‐ray analysis, in which soft intermolecular hydrogen‐bonded networks were found.     

Synthesis of musafluorone: a naphthoxanthenone isolated from Musa acuminata

5-Methoxy-3H-naphtho[2,1,8-mna]xanthen-3-one (musafluorone, 1), the only naphthoxanthenone reported so far from Musaceae, was synthesized starting from 2-naphthol in nine steps and resulted in an overall yield of 3%. Grignard addition of phenylmagnesium bromide to 4-methoxyperinaphthenone afforded the corresponding 4-methoxy-9-phenylphenalenone which, after epoxidation and methyl transposition, was subjected to a photochemical cyclization procedure to furnish 1.