Improved lithium cyclability and storage in a multi-sized pore (''differential spacers'') mesoporous SnO2

A wide pore distribution mesoporous morphology stabilizes SnO2 structure during lithium insertion and removal and in the process remarkably enhances the lithium storage and cyclability.

Synthesis of DEF ring skeleton of naulafine alkaloid

6, 8-Dichloro-4, 5-dihydro-2-methyl-[2, 7]acenaphthyridin-1-one (5), obtained from the. reaction of 5-cyano-2, 6-dihydroxy-3, 4-cyclopentenopyridine with Vilsmeier reagent, has been transformed to the key synthon 4a in two steps.

Synthesis of taxanes - The carvone approach; A simple, efficient stereo- and enantio-selective synthesis of the functionalised A ring

A highly stereo- and enantio-selective methodology for the construction of the chiral functionalised A-ring of taxanes, starting from (R)-carvone employing a short, simple and efficient sequence is described.

The reaction of lambda 3-cyclotriphosphazanes with tetrachloro-ortho-benzoquinone: An unusual ring contraction-rearrangement

Oxidative addition of tetrachloro-ortho-benzoquinone to lambda(3)-cyclotriphosphazanes, [EtNP(OR)](3) results in an unprecedented ring contraction-rearrangement to give diazadiphosphetidines (EtN)(2)[P(OR)(O2C6Cl4)] [P(O2C6Cl4)-[N(Et)P(OR)(2)}] (R = C6H4Br-4 or C(6)H(3)Me(2)-2,6), a process indicated to be thermodynamically favourable on the basis of PM3 calculations.

The unusual formation of methyl alpha-(5,6-dimethoxycarbonyl-2,3-dimethoxyazepin-7-ylidene)-alpha-[5-methoxycarbonyl-2,3-dimethoxypyrid-6-yl)acetate during the pyrolysis of ''azido-meta-hemipinate'' - First example of a reaction involving a concomitant ring expansion and ring extrusion

he ortho methoxycarbonyl substituent constitutes a sole exception in the ring closure reactions of ortho substituted aryl azides, as it provides no rate acceleration to this reaction. Pyrolysis of ''azido-meta-hemipinate'', an aryl azide containing such a substituent, led us to the title compound, a new azepinylidenepyridylacetic ester, whose structure has been established unambiguously by a single crystal X-ray diffraction study. This is the first report of a reaction involving both a ring expansion to an azaheptafulvalene and a ring extrusion to a pyridyl ring residue.

Enhanced charge and spin currents in the one-dimensional disordered mesoscopic Hubbard ring

We consider a one-dimensional mesoscopic Hubbard ring with and without disorder and compute charge and spin stiffness as a measure of the permanent currents. For finite disorder we identify critical disorder strength beyond which the charge currents in a system with repulsive interactions are larger than those for a free system. The spin currents in the disordered repulsive Hubbard model are enhanced only for small U, where the magnetic state of the system corresponds to a charge-density wave pinned to the impurities. For large U, the state of the system corresponds to localized isolated spins and the spin currents are found to be suppressed. For the attractive Hubbard model we find that the charge currents are always suppressed compared to the free system at all length scales.

Synthesis Based on Cyclohexadienes. 5. A New Approach to the Synthesis of a-Ring Aromatic Steroids - a Formal Total Synthesis of (+/-)-Estrone

A new strategy for the construction of A-ring aromatic steroids which resulted in the formal total synthesis of estrone is described. Thus reaction of the adduct (9), obtained from 1-methoxy-4-methylcyclohexa-1,4-diene and acrolein, with 3-(m-methoxyphenyl)propylmagnesium bromide followed by oxidation afforded the bicyclo[2.2.2]octene derivative (14). Acid-catalysed rearrangement of (14) followed by an intramolecular Michael addition resulted in the cis tetraenone (18) which was dehydrogenated with palladium chloride to the pentaenone (22). Li/NH3 reduction of (22) gave 3-methoxy-D-homoestra-1,3,5(10)-trien-16-one (31) which has been converted into the methyl ether (37) of marrianolic acid, and its methyl ester (38).

Synthesis of amino thiols and isocysteines via regioselective ring opening of sulfamidates with tetrathiomolybdate

Herein we present a simple and highly efficient method for the synthesis of beta and gamma-amino thiols via regioselective ring opening of sulfamidates with tetrathiomolybdate 1. The generality of this methodology has been shown by synthesizing carbohydrate derived beta-amino thiol. The scope and versatility of this methodology has been demonstrated by synthesizing biologically important unnatural amino acids like isocysteines in optically pure form. (C) 2011 Elsevier Ltd. All rights reserved.

On the performance of stabilized ?-nickel hydroxide as a nickel-positive electrode in alkaline storage batteries

The internal resistance of a stabilized alpha-nickel hydroxide electrode is found to be lower than that of a beta-nickel hydroxide electrode as shown from studies of the open-circuit potential-time transients at all states-of-charge. Nevertheless, the self-discharge rates of the former is higher. Gasometric studies reveal that the charging efficiency of the alpha-nickel hydroxide electrode is higher than that of the beta-nickel hydroxide electrode.

Persistent currents in a one-dimensional ring for a disordered Hubbard model

We consider a one-dimensional Hubbard model in the presence of disorder. We compute the charge stiffness for a mesoscopic ring as a function of the size L, which is a measure of the persistent currents. We find that for finite disorder the persistent currents of the system with repulsive interactions are larger than those of the system with attractive interactions. This counterintuitive result is due to the fact that local-density fluctuations are reduced in the presence of repulsive interactions.

Advances in storage batteries

Over the years, new power requirements for telecommunication, space, automotive and traction applications have arisen which need to be met. Although lead-acid and nickel-cadmium storage batteries continue to be the work horses with limited advances, associated environmental hazards and recycling are still the issues to be resolved. As a result, lead-acid and nickel-cadmium storage batteries have declined in importance whilst nickel-metal hydride and lithium secondary batteries with superior performances have shown greater acceptability in newer applications. These developments are reflected in this article.

Model studies directed towards the synthesis of functionalised chiral A-ring derivatives of taxanes

Model studies, starting from the monoterpene R-carvone, directed towards the synthesis of chiral A-ring derivatives of taxanes with oxygen functionalities at C-2, 9 and 13 carbon atoms as in taxol is described.

Mapping adaptive resonance theory onto ring and mesh architectures

In recent years, parallel computers have been attracting attention for simulating artificial neural networks (ANN). This is due to the inherent parallelism in ANN. This work is aimed at studying ways of parallelizing adaptive resonance theory (ART), a popular neural network algorithm. The core computations of ART are separated and different strategies of parallelizing ART are discussed. We present mapping strategies for ART 2-A neural network onto ring and mesh architectures. The required parallel architecture is simulated using a parallel architectural simulator, PROTEUS and parallel programs are written using a superset of C for the algorithms presented. A simulation-based scalability study of the algorithm-architecture match is carried out. The various overheads are identified in order to suggest ways of improving the performance. Our main objective is to find out the performance of the ART2-A network on different parallel architectures. (C) 1999 Elsevier Science B.V. All rights reserved.