Spiraling multivortex solitons in nonlocal nonlinear media

We demonstrate the existence of a broad class of higher-order rotating spatial solitons in nonlocal nonlinear media. We employ the generalized Hermite-Laguerre-Gaussian ansatz for constructing multivortex soliton solutions and study numerically their dynamics and stability. We discuss in detail the tripole soliton carrying two spiraling phase dislocations, or self-trapped optical vortices.     

2′-Deoxyisoguanosine and Base-Modified Analogues: Chemical and Photochemical Synthesis

The synthesis of 2′-deoxyisoguanosine ( 2 ), and the pyrrolo[2,3-d]pyrimidine and pyrazolo[3,4-d]pyrimidine 2′-deoxyribonucleosides 3 and 4 is described. Condensation of the imidazole precursor 5 with benzoyl isocyanate followed by reaction with ammonia gave 2 . Its N(7) regioisomer was obtained from 6 . Compound 2 was also prepared by the photochemically induced conversion of 2-Chloro- and 2-bromopurine 2′-deoxyribofuranosides 9a and 10 , respectively, in aqueous solution, The photo reaction was further used for the synthesis of the compounds 3 and 4 starting with the amino-chloro-2′-deoxynucleosides 9b and 9c , respectively.     

The structure of the b-completion of space-time

Structured space, as a natural generalization of the manifold concept, is defined to be a topological space with a sheaf of real function algebras which are suitably localized and closed with respect to composition with smooth Euclidean functions. Vector fields, differential forms, linear connection and curvature are introduced on structured spaces. It is shown that structured spaces correctly model space-times with singularities. Schmidt's b-boundary of space-time is constructed in the category of structured spaces, and well known difficulties with the b-boundaries of the closed Friedman and Schwarzschild space-times are disentangled. It is argued that the b-boundary of space-time, when considered in the category of structured spaces, can serve as a good definition of classical singularities.     

SITE-TO-SITE DIFFUSION IN PROTEINS AS OBSERVED BY ENERGY TRANSFER AND FREQUENCY-DOMAIN FLUOROMETRY *

Abstract We report measurements of the site-to-site diffusion coefficients in proteins and model compounds, which were measured using time-dependent energy transfer and frequency-domain fluorometry. The possibility of measuring these diffusion coefficients were shown from simulations, which demonstrate that donor (D)-to-acceptor (A) diffusion alters the donor frequency response, and that this effect is observable in the presence of a distribution of donor-to-acceptor distances. For decay times typical of tryptophan fluorescence, the simulations indicate that D-A diffusion coefficients can be measured ranging from ^?7 to ^?5 cm²/s. This possibility was verified by studies of a methylenechain linked D-A pair in solutions of varying viscosity. The D-A diffusion was also measured for two labeled peptides and two proteins, melittin and troponin I. In most cases we used global analysis of data sets obtained with varying amounts of collisional quenchers to vary the donor decay time. Unfolding of troponin I results in more rapid D-A diffusion, whereas for melittin more rapid diffusion was observed in the α-helical state but over a limited range of distances.     

Substituted 1,4-diazepino[5,6,7-kl]acridines as unexpected side products in reaction of 2-(dialkylamino)ethylamine with 1-chloro-7-methyoxy-4-nitro-9-phenoxyacridine

Substituted 1,4-diazepino[5,6,7-kl]acridines were obtained in reaction of 2-(dialkylamino)ethylamine with 1-chloro-7-methoxy-4-nitro-9-phenoxyacridine. The mechanism of their formation was studied. The correct structure of these compounds was established on the basis of their ¹H nmr studies.     

Optimization of sequencing conditions using near-infrared lifetime identification methods in capillary gel electrophoresis

We have investigated the sample preparation and electrophoresis conditions necessary to prepare DNA sequencing samples appropriate for use with near-infrared (IR) fluorescent labels with dye identification accomplished via lifetime techniques. It was found that several sample preparation protocols required attention to maximize the fluorescence yields of the labeling dyes, such as thermal cycling conditions, choice of counter ion used for the ethanol precipitation step and also, dye-primer versus dye-terminator chemistries. In addition, several different sieving matrices were investigated for their effects on both the fluorescence properties of the labeling dyes and electrophoretic resolution. Extended times used for the high temperature denaturing of duplexed DNA fragments during cycle sequencing produced cleavage products, in which the covalently attached dye to the sequencing primer was released through attack by dithiothreitol (DTT). Even under optimized thermal cycling conditions, free dye was generated that masked readable data from the sequencing traces. Ethanol precipitation was necessary to remove this free dye with the proper choice of counter ion (sodium). The results using different sieving matrices indicated that linear polyacrylamides (LPAs) were appropriate for any fluorescence measurement, since they could readily be replaced between runs minimizing deleterious memory effects associated with cross-linked polyacrylamide gels. After investigation of several different sieving LPAs, the commercially available POP6 was found to be particularly attractive, since it produced good electrophoretic resolution, single exponential behavior for the near-IR dye series investigated herein, and also, discernible lifetime differences within the dye set. Finally, dye-terminator chemistry was also found to minimize bleeding in the gel matrix produced by large amounts of unextended dye-primer within the gel lane.     

Conversion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (mptp) and its 5-methyl analog into pyridinium salts

Monoamine oxidase B metabolizes 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 1 ) first to 1-methyl-4-phenyl-2,3-dihydropyridinium salt (MPDP⁺; 5 ), and then to 1-methyl-4-phenylphridinium salt (MPP⁺; 7 ). Chemical synthesis of MPDP⁺ and its 5-methyl analog 6 was accomplished from the N-oxides 3 and 4 of MPTP and its 5-methyl analog, respectively, by a Polonovski reaction. Oxidation of MPDP⁺ to MPPM⁺ was accomplished with air, and greatly accelerated by Pt catalyst. Reduction of MPDP⁺ and MPP⁺ with NaBH₄ afforded MPTP.     

Heteroleptic metal alkoxide "oxoclusters" as molecular models for the sol-gel synthesis of perovskite nanoparticles for bio-imaging applications

Systematic structural study of the molecules, resulting from microhydrolysis of heterometallic beta-diketonate alkoxides of barium and strontium (single-source precursors of perovskite oxide materials), demonstrates that the structures of these products result from a thermodynamically driven self-assembly of metal cations and ligands directed towards the most densely packed cores. The ratio between metal cations, and of the cations to bidentate heteroligands, is easily changed to enable the highest packing density. The key to the application of single-source precursors appears to be the use of stoichiometric or superstoichiometric water amounts together with solvents preventing diffusion of possible homometallic intermediates. Eu-doped BaTiO3 nanoparticles have been successfully obtained and characterized.     

A compact group which is not Valdivia compact

A compact space is Valdivia compact if it can be embedded in a Tikhonov cube in such a way that the intersection is dense in , where is the sigma-product ( the set of points with countably many non-zero coordinates). We show that there exists a compact connected Abelian group of weight which is not Valdivia compact, and deduce that Valdivia compact spaces are not preserved by open maps.