First results from KamLAND: evidence for reactor antineutrino disappearance

KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.     

Time-resolved measurements of self-focusing pulses in air

The spatial, spectral, and temporal properties of self-focusing 798-nm 100-fs pulses in air are experimentally measured with high-resolution, single-shot techniques at a set propagation distance of 10.91 m. The data, obtained with an initially collimated Gaussian beam, show significant evolution of spatial narrowing as well as temporal and spectral changes at intensities lower than those required for significant ionization of air.     

Search for direct CP violation in nonleptonic decays of charged Xi and lambda hyperons

A search for direct CP violation in the nonleptonic decays of hyperons has been performed. In comparing the product of the decay parameters, alpha(Xi)alpha(Lambda), in terms of an asymmetry parameter, A(XiLambda), between hyperons and antihyperons in the charged Xi-->Lambdapi and Lambda-->ppi decay sequence, we found no evidence of direct CP violation. The parameter A(XiLambda) was measured to be 0.012+/-0.014.     

Stability and boundedness conditions for the motions of discrete-time mechanical systems

The paper establishes sufficient conditions for the stability and uniform boundedness of the solutions of a large-scale discrete system for weaker restrictions (compared those available in the literature) on the first differences of auxiliary functions     

Control problem for the holling-tanner model

We examine the design of optimal control for the Holling—Tanner system in the case when the goal set is the neighborhood of a limit cycle and the objective function is minimum time. We prove the existence of an optimal control and study its structure. A bound on the number of switchings is obtained for an arbitrary initial point in the phase space. Numerical algorithms are proposed to calculate the curves that form the design picture. Calculation results are reported.Translated from Nelineinaya Dinamika i Upravlenie, No. 2, pp. 139–146, 2002.     

Picture change error correction of radon atom electron density

The importance of the picture change error (PCE) correction in the quasirelativistic electron density of radon atom is presented. PCE correction is considered for the infinite order two-component (IOTC) and second order Douglas-Kroll-Hess (DKH2) wave functions. Implementation details of PCE correction of electron density are outlined. The result section presents the radial distributions of electron density ρ(r) and the 4πr(2)ρ(r) function of the radon atom in the nuclear region. The PCE corrected and contaminated DKH2, IOTC electron densities are presented and compared with the Dirac-Coulomb Hamiltonian and nonrelativistic electron densities. Besides, some additional effects in electron density and SCF energy are considered, such as spin-orbit coupling, the inclusion of the Gaunt term, and the finite nucleus model effects. The effects of p(2)Vp(2) and p(2)ρ(r)p(2) analytic integral classes within IOTC Hamiltonian and PCE correction of IOTC electron density are considered.     

Synthesis and antimicrobial activity of a series of optically active quaternary ammonium salts derived from phenylalanine

We synthesized nine quaternary ammonium compounds (QUATs) starting from phenylalanine, N-alkyl-N,N-dimethyl-(1-hydroxy-3-phenylpropyl)-2-ammonium bromides, which were prepared as optically pure substances. Five compounds were prepared as S-enantiomers and four compounds as R-enantiomers. These compounds were evaluated by their activities against bacteria and fungi. Three microbial strains were used in the study: the gram-negative bacteria Escherichia coli, the gram-positive bacteria Staphylococcus aureus and the fungi Candida albicans. The activities were expressed as minimum bactericidal or fungicidal concentrations (MBC). The most active compounds were (2S)-N-tetradecyl-N,N-dimethyl-(1-hydroxy-3-phenylpropyl)-2-ammonium bromide and (2R)-N-tetradecyl-N,N-dimethyl-(1-hydroxy-3-phenylpropyl)-2-ammonium bromide, with MBC values exceeding those of commercial benzalkoniumbromide (BAB) used as standard. The relationships between structure and biological activity of the tested QUATs were quantified by the bilinear model (QSAR) and are discussed.     

Octaarginine-modified chitosan as a nonviral gene delivery vector: properties and in vitro transfection efficiency

Protein transduction domains (PTD) have been identified to have the capacity to facilitate molecular cargo to translocate through cell membrane. This study aims to utilize the cell membrane penetrating ability of octaarginine oligopeptide, a simplified prototype of the PTD, to enhance the transfection efficiency of chitosan. Octaarginine-modified chitosan (R₈-CS) was synthesized as a gene transfer carrier by carbodiimide chemistry. The structure and composition of R₈-CSs were characterized using FTIR and ¹H NMR. Agarose gel electrophoresis assay showed that R₈-CS could efficiently condense the DNA. The particle size of R₈-CS/DNA complexes were determined to be around 100–200 nm. The nanoparticle complexes exhibited a spherical and compact morphology. R₈-CS demonstrated higher transfection activity and lower cytotoxicity as compared to the unmodified chitosan and also showed good serum resistance.