Electrophilic cyclization of N-alkenylamides using a chloramine-T/I2 system

A new protocol for the cyclization of N-alkenylamides using chloramine-T and iodine is described. When N-alkenylsulfonamides are treated with chloramine-T and iodine, three- to six-membered N-heterocycles are obtained with complete stereoselectivity. The method is compatible with the cyclization of the allylbenzamide or allylbenzthioamide to afford an oxazoline or thiazoline derivative, respectively. Mechanistic studies indicate that the chloramine-T/I₂ system functions as an effective iodonium species.     

Aggregation behavior of polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer in N‐methylpyrrolidone

Solution property of hydrogenated polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer (SEBS copolymer) was studied by using static light scattering and dynamic light scattering for cyclohexane and N‐methylpyrrolidone (NMP) solutions. From the values of dimensionless parameters ρ, defined as the ratio of radius of gyration 〈S²〉^1/2 to hydrodynamic radius R_H, and solubility parameters, SEBS copolymer proved to exist as single chain close to random coil in nonpolar cyclohexane, whereas aggregate into the core‐shell micelle consisting of poly(ethylene/butylene) (PEB) core surrounded by PS shell in polar NMP. The core‐shell micelle formed in NMP is composed of 65 polymer chains, having three times larger average chain density (d = 0.12 g cm^?3) than a single polymer chain (d = 0.04 g cm^?3) in cyclohexane. The comparison with the aggregation behaviors in other solvents demonstrated that the aggregate compactness of the copolymer depended largely on solvent polarity, resulting in formation of the highly dense PEB core (R_c = 4.5 nm) and the thick PS shell (ΔR = 22.9 nm) in high‐polar NMP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 588–594, 2010     

Relations of electronic energies and magnetic moments of tetra-3d metal (Mn, Fe, Co and Ni) nitrides calculated using a plane-wave basis method

Geometrical optimization of tetra-3d metal nitrides (Mn₄N, Fe₄N, Co₄N, and Ni₄N) has been performed and the relations of their energies (E) and their total magnetic moments (M) are obtained by plane-wave-basis density-functional calculations without any assumption of specific spin arrangement. The E vs. M relations obtained for Fe₄N and Mn₄N have a bimodal character. The ground state of Fe₄N is a high-spin state, which would correspond to the ferromagnetic character, while that of Mn₄N is a low-spin state, which would correspond to the observed ferrimagnetic character. Lattice constants and total magnetic moments of these tetra-3d metal nitrides are almost accurately predicted. From the spin-polarized densities of states curves, Co₄N would have the largest spin polarization ratio of 0.88, which suggests Co₄N can be a candidate material for ferromagnetic electrodes for spin-injection.     

Effects of oxygen vacancy on adhesion of incoherent metal/oxide interface by first-principles calculations

We investigate effects of oxygen vacancies on adhesion behavior of incoherent Ni/MgO(0 0 1) interface with large misfit, based on the density functional theory. We demonstrate that oxygen vacancies at any local atomic configuration of the incoherent geometry enhance the image-chargelike interaction between the ions in MgO and the ion-induced images in Ni, and stabilize adhesion of the Ni/MgO(0 0 1) interface. The adhesion energy of the defective interface is remarkably larger than that of the perfect interface. We also show that force constants of the adhesive interactions near the oxygen vacancies are comparable to the Ni-Mg bond at the perfect interface. The vacancy-induced enhancement of the image electron accumulation hardly contributes to the interfacial stiffness, while it is reduced by losing the covalent Ni-O interaction due to an ontop oxygen vacancy.     

Optimization of capillary array electrophoresis single-strand conformation polymorphism analysis for routine molecular diagnostics

Mutation screening is widely used for molecular diagnostics of inherited disorders. Furthermore, it is anticipated that the present and future identification of genetic risk factors for complex disorders will increase the need for high-throughput mutation screening technologies. Capillary array electrophoresis (CAE) SSCP analysis is a low-cost, automated method with a high throughput and high reproducibility. Thus, the method fulfills many of the demands to be met for application in routine molecular diagnostics. However, the need for performing the electrophoresis at three temperatures between 18 degrees C and 35 degrees C for achievement of high sensitivity is a disadvantage of the method. Using a panel of 185 mutant samples, we have analyzed the effect of sample purification, sample medium and separation matrix on the sensitivity of CAE-SSCP analysis to optimize the method for molecular diagnostic use. We observed different effects from sample purification and sample medium at different electrophoresis temperatures, probably reflecting the complex interplay between sequence composition, electrophoresis conditions and sensitivity in SSCP analysis. The effect on assay sensitivity from three different polymers was tested using a single electrophoresis temperature of 27 degrees C. The data suggest that a sensitivity of 98-99% can be obtained using a 10% long chain poly-N,N-dimethylacrylamide polymer.     

Derivations and invariant forms of Jordan and alternative tori

Jordan and alternative tori are the coordinate algebras of extended affine Lie algebras of types and . In this paper we show that the derivation algebra of a Jordan torus is a semidirect product of the ideal of inner derivations and the subalgebra of central derivations. In the course of proving this result, we investigate derivations of the more general class of division graded Jordan and alternative algebras. We also describe invariant forms of these algebras.

     

Syntheses of some 2-hydroxypyrazine 1-oxides

A series of 2-hydroxypyrazine 1-oxides were prepared from the corresponding chloropyrazines by two methods, including oxidation processes in satisfactory yields. The treatment of 2,3-diphenylpyrazine 1,4-dioxide ( 6 ) led to 2,3-dichloro-5,6-diphenylpyrazine ( 7 ) and 2-chloro-5,6-diphenylpyrazine 1-oxide ( 8 ), and the latter was converted to 5,6-diphenyl-2-hydroxypyrazine 1-oxide ( 9 ) by an alkaline hydrolysis.     

Sol-Gel Preparation of Silica Films with Controlled Surface Morphology and Their Application to a Low Reflective Glass

Silica coating films with various surface morphologies, such as flat, porous (with deep pores), concave-convex (with hills and valleys), and convex (with hills on flat plane) structure were prepared from a mixture of two kinds of sols derived from polymerized tetraethoxy-silane (TEOS) and methyltriethoxysilane (MTES). Different surface morphologies were obtained by varying the molar ratio r = MTES/TEOS of the coating solution. The surface was flat for r less than 2.5, porous for 2.5 r < 5, concave-convex for 5 r < 7.5, convex for 7.5 r < 13, and again flat for r larger than 13. For 2.5 r < 5, the apparent refractive index of the silica film with porous morphology was decreased to 1.23 by selecting the solvent and by controlling the relative humidity of the coating atmosphere and the heat treatment temperature. Coating of glass with silica films of low refractive index of 1.23 led to the low reflective glasses with visible light reflectance Rvis of less than 0.2%.     

Electrochemical and structural investigations of the reaction of lithium with tin-based composite oxide glasses

Tin-based composite oxide materials have received considerable attention as potential anode materials for rechargeable lithium batteries. In this contribution we present the results of our investigations of the SnOB₂O₃P₂O₅ system. We have investigated its electrochemical properties and especially its cycling performance. A focus of our interest was to explain the structural changes which occur during lithium cycling and their strong dependence on the preparation method. A part of the SnO component was converted into a very stable metallic phase. In addition, a decrease was observed in capacity owing to the formation of isolated and inactive tin grains. We also report on structural changes in the B₂O₃P₂O₅ matrix. Received: 2 October 1997  / Accepted: 3 July 1998