Kinetic model for the chiral symmetry breaking transition in the growth front of a conglomerate crystal phase

In its molten phase, 1,1'-binaphthyl is racemic due to its high racemization rate, but it can crystallize as a conglomerate of R and S crystals. Our experiments have indicated that, under some conditions, the crystal growth front of 1,1'-binaphthyl shows many of the characteristics of an open system in which chiral symmetry is broken; i.e., the growing solid phase becomes predominantly R or S. Here we present a kinetic model to explain the observed chiral symmetry breaking. The model is based on growth due to attachment of R or S growth units to a crystal surface in a supercooled melt. Chiral symmetry breaking occurs due to chirally autocatalytic formation of R or S growth units on the growth surface. Unlike the many models suggested and studied in the 1980s, there is no cross-inhibition between R- and S-enantiomer in the model presented here. In our model, asymmetric and symmetric steady-state solutions that do not intersect were found. Through linear stability analysis, the critical point, at which a symmetric solution becomes unstable and makes a transition to an asymmetric solution, is determined.     

Mechanisms of electron injection from retinoic acid and carotenoic acids to TiO2 nanoparticles and charge recombination via the T1 state as determined by subpicosecond to microsecond time-resolved absorption spectroscopy: dependence on the conjugation length

To examine the mechanisms of electron injection to TiO2 in retinoic acid (RA) and carotenoic acids (CAs), including RA5, CA6, CA7, CA8, CA9, and CA11 having the number of conjugated double bonds n = 5, 6, 7, 8, 9, and 11, respectively, their subpicosecond time-resolved absorption spectra were recorded free in solution and bound to TiO2 nanoparticles in suspension. The time-resolved spectra were analyzed by singular-value decomposition (SVD) followed by global fitting based on an energy diagram consisting of the 3A(g)(-), 1B(u)(-), 1B(u)(+), and 2A(g)(-) singlet excited states, whose energies had been determined as functions of 1/(2n + 1) by the use of carotenoids with n = 9-13. It was found that electron injection took place from both the 1B(u)(+) and 2A(g)(-) states in RA5, CA6, CA7, and CA8, whereas only from the 1B(u)(+) state in CA9 and CA11. The electron-injection efficiencies were determined, by the use of the relevant time constants determined by the SVD and global-fitting analyses, to be in the following order: RA5 approximately CA6 < CA7 > CA8 > CA9 > CA11. To determine the mechanism of charge recombination via the T(1) state, submicrosecond time-resolved absorption spectra of RA5, CA6, CA7, and CA8 bound to TiO2 nanoparticles in suspension were recorded. The SVD and global-fitting analyses lead us to a new scheme, which includes the formation of the D(0)(*+) - T(1) complex followed by transformation to both the D(0)(*+) and T(1) states. On the other hand, their one-electron oxidation potentials were determined, and their singlet and triplet levels were scaled to the conduction band edge (CBE) of TiO2. The T(1) level was lower than, but closest to, the CBE in RA5, and it became lower in the order RA5, CA6, CA7, and CA8. Consistent with the energy gap between the CBE and the T(1) levels, the generation of the T(1) state (or in other words, charge recombination) decreased in the order RA5 > CA6 > CA7 > CA8.     

Colorimetric SNP analysis using oligonucleotide-modified nanoparticles

A point mutation in the p53 gene has been detected by means of fluorescence microscopy and fluorescent resonance energy transfer (FRET) through sequence selective aggregation of DNA-modified nanoparticles, in which fluorescent dyes were impregnated.     

Ustalic acid as a toxin and related compounds from the mushroom Tricholoma ustale

A toxin and related compounds were isolated from a poisonous mushroom Tricholoma ustale. Their structures were determined by analyses of the spectral data and synthesis.     

Efficient photocyclization of dithienylethene dimer, trimer, and tetramer: quantum yield and reaction dynamics

Multi-dithienylethene arrays, in which two, three, or four 1,2-bis(2,4-dimethylthiophen-3-yl)perfluorocyclopentenes are ethynylene-bridged, were synthesized. Upon irradiation with ultraviolet light the hexane solutions of the arrays turned violet-blue and the color disappeared by irradiation with visible light. The quantum yields of photocyclization reactions successively increased from 0.21 to 0.40 by increasing the number of the dithienylethene moieties in the arrays from one to four. Picosecond laser photolysis as well as the fluorescence depolarization experiment confirmed that efficient excited energy migration in the arrays from the photochemically inactive parallel conformer to the photoactive antiparallel conformer resulted in the high quantum yields.     

Electron acceleration by laser produced wake field: Pulse shape effect

Analytical expressions are obtained for the longitudinal field (wake field: E_x), density perturbations () and the potential () behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular–triangular (RT) pulse and rectangular–Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory (), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10¹⁸ W/m². The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.     

Weibull Raindrop-Size Distribution and its Application to Rain Attenuation from 30 GHz to 1000 GHz

A weibull raindrop-size distribution is fitted to the measurements of rainfall observed using a distrometer in Tokyo. A propagation experiment at 103 GHz is also introduced. The rain attenuation is calculated by considering the Mie scattering for the Marshall-Palmer, Best, Joss-Thomas-Waldvogel, Gamma and Weibull raindrop-size distributions. The results of frequency characteristics from the Weibull raindrop-size distribution agrees well with some experimental data for the millimeter and submillimeter waves above 30 GHz. The quick read table is calculated for the rain attenuation from 30 GHz to 1000 GHz.     

Synthesis and conformational properties of oligonucleotides incorporating 2'-O-phosphorylated ribonucleotides as structural motifs of pre-tRNA splicing intermediates

To synthesize oligonucleotides containing 2'-O-phosphate groups, four kinds of ribonucleoside 3'-phosphoramidite building blocks 6a-d having the bis(2-cyano-1,1-dimethylethoxy)thiophosphoryl (BCMETP) group were prepared according to our previous phosphorylation procedure. These phosphoramidite units 6a-d were not contaminated with 3'-regioisomers and were successfully applied to solid-phase synthesis to give oligodeoxyuridylates 15, 16 and oligouridylates 21, 22. Self-complementary Drew-Dickerson DNA 12mers 24-28 replaced by a 2'-O-phosphorylated ribonucleotide at various positions were similarly synthesized. In these syntheses, it turned out that KI(3) was the most effective reagent for oxidative desulfurization of the initially generated thiophosphate group to the phosphate group on polymer supports. Without using this conversion step, a tridecadeoxyuridylate 17 incorporating a 2'-O-thiophosphorylated uridine derivative was also synthesized. To investigate the effect of the 2'-phosphate group on the thermal stability and 3D-structure of DNA(RNA) duplexes, T(m) measurement of the self-complementary oligonucleotides obtained and MD simulation of heptamer duplexes 33-36 were carried out. According to these analyses, it was suggested that the nucleoside ribose moiety phosphorylated at the 2'-hydroxyl function predominantly preferred C2'-endo to C3'-endo conformation in DNA duplexes so that it did not significantly affect the stability of the DNA duplex. On the other hand, the 2'-modified ribose moiety was expelled to give a C3'-endo conformation in RNA duplexes so that the RNA duplexes were extremely destabilized.     

强激光辐照下纳米晶体铜薄膜层裂破坏的实验研究

采用强激光辐照加载技术和激光速度干涉(VISAR)测试技术，对纳米晶体铜薄膜的层裂特性进行实验测量和分析.基于VISAR实测的自由面速度波形，计算得到纳米晶体铜薄膜在超高拉伸应变率下的层裂强度高达3 GPa，明显高于多晶铜的层裂强度, 其原因归咎于纳米晶体材料中存在大量晶界阻碍了位错运动.     

Binding evaluation of the combination between the superconductor and matrix by ultrasonic spectra

Combination of the superconductor and high conductive normal metal is now indispensable in the practical use of superconducting magnet. And the binding property of both materials is one of the key points whether superconductive characteristics are fully attained or the current fails prematurely in the practical magnet. But this binding evaluation is not so easy, because even in the mechanically well-jointed conductor, it often appears poor in electric and magnetic joint in cryogenic temperature. Since we have examined and reported fundamental AE properties of superconductor from UI-91, UI-93, UI-95, and UI-97, we have found the simple but important discovery for getting new information about the binding evaluation. Here we report a new technique for evaluating these bindings by observing ultrasonic spectra when a normal transition is propagated along the superconductor. We have discovered that a good contacting conductor has an emission of this sound with sharp resonating frequency peak or peaks at around the highest spectrum area; from 0.5 to 1.0 MHz. Our interpretation of the evaluations are so simple that we can say that binding degrees are best, good or bad, according to the resonating Q-value at around the highest spectrum of the ultrasonic sound.