First measurement of inclusive B→Xsη decays

We report a first measurement of inclusive B→Xsη decays, where Xs is a charmless state with unit strangeness. The measurement is based on a pseudoinclusive reconstruction technique and uses a sample of 657×10(6)BB pairs accumulated with the Belle detector at the KEKB e+e- collider. For MXs < 2.6 GeV/c2, we measure a branching fraction of [26.1±3.0(stat)-2.1+1.9(syst)-7.1+4.0(model)]×10(-5) and a direct CP asymmetry of ACP=-0.13±0.04-0.03+0.02. Over half of the signal occurs in the range MXs > 1.8 GeV/c2.     

All-optical control of gigahertz acoustic resonances by forward stimulated interpolarization scattering in a photonic crystal fiber

We report the observation of a novel nonlinear optoacoustic phenomenon, that we name forward stimulated interpolarization scattering. When two frequency-offset laser signals are colaunched into orthogonally polarized guided modes of a birefringent small-core (1.8 μm diameter) photonic crystal fiber, a pattern of axially moving polarization fringes is produced, with a velocity and spacing that depends on the frequency offset. At values of frequency offset in the few-GHz range, the pattern of moving fringes can perfectly match the phase velocity and axial wavelength (3.9 mm) of the torsional-radial acoustic mode tightly guided in the core. An intense optoacoustic interaction ensues, leading to efficient nonlinear exchange of power from the higher frequency (pump) mode to the orthogonally polarized lower frequency (Stokes) mode. A full-vectorial theory is developed to explain the observations.     

Investigation on shape variation of Au nanocrystals

A variety of shapes, such as rod, tripod, -shape and cube, of Au nanocrystals were synthesized by employing different reaction conditions. The nanocrystals and their shape variation were characterized by transmission electron microscopy and UV–vis spectrophotometry. The evolution of shape was accomplished by controlling the parameters used in their synthesis, the concentration of reducing agent and surface capping agent. The effect of synthetic parameters on shape was explored, to determine suitable conditions for producing each shape of nanocrystals. Nanocrystals with different shapes have different plasmon bands in the visible region of the spectrum, which is a valuable property for sensor applications.     

On the synchronization of a hyperchaotic system based on adaptive method

This Letter researches the adaptive synchronization of a hyperchaotic system. Based on Lyapunov method, a general adaptive method via a driving vector and an original adaptive method via a single driving variable are presented to achieve the chaos synchronization. Especially, the latter makes the structure of adaptive controller simple and has more practical value compared with the former. Some typical numerical examples are included to demonstrate the effectiveness of the method proposed.     

Non-Commutative Fock--Darwin System and Magnetic Field Limits

A Fock--Darwin system in noncommutative quantum mechanics is studied. By constructing Heisenberg algebra we obtain the levels on noncommutative space and noncommutative phase space, and give the corrections to the results in usual quantum mechanics. Moreover, to search the difference among the three spaces, the degeneracy is analysed by two ways, the valueof ω/ω_c and certain algebra realization (SU(2)and SU(1,1)), and some interesting properties in the magnetic field limit are exhibited, such as totally different degeneracy and magic number distribution for the given frequency or mass of a system in strong magnetic field.     

黄石市板岩山危岩体成因机理分析与防治对策研究

本文论述了黄石板岩山危岩体地形、地貌及地质构造特征 ,分析讨论了其成因机理 ,得出危岩体已处于蠕变后期 ,位移变形趋于稳定。不会再次发生大规模的整体倾倒破坏 ,提出了活石清理、裂缝顶部加盖排水指导的防治措施。     

Hysteresis suppression improvement of polycrystalline silicon thin-film transistors by two-step hydrogenation

The effect of two-step hydrogenation, consisting of plasma hydrogenation and annealing in hydrogen, on the hysteresis phenomenon of metal-induced unilaterally crystallized silicon thin-film transistors (MIUC-Si TFTs) was investigated. The large hysteresis level of the conventional MIUC-Si TFTs caused a wide variation of the drain current with the previous gate voltage. As the plasma exposure time increased, the plasma hydrogenation commonly used for stability in poly-Si TFTs was found to increase the hysteresis level of MIUC-Si TFTs after a minimum point. This is because plasma-induced damages correlated with unique defects of MIUC-Si such as metal-related weak bonds, are accompanied by passivation. The following annealing repaired the damages. Consequently the hysteresis level was lower, which resulted in a narrower variation of the drain current.     

激发态Cs2和H2的电子-振转能级的碰撞转移

利用相干反斯托克斯拉曼光谱(CARS)探测技术, 研究了激发态Cs2与H2间的电子-振转能级的碰撞转移。用波长为532 nm和中心波长为716 nm的两束激光同时聚焦到样品池中, 扫描CARS谱确认了H2分子的S支(△v =1, △J=2)仅在v=1, J=4,5及v=2, J=3,4能级上有布居, 用n1、n2、n3、n4分别表示(2,4)、(2,3)、(1,4)及(1,5)上的粒子数密度。从CARS线的峰值得到n2/n1、n3/n1、n4/n1分别为6.34±1.27、3.66±0.73和1.45±0.29。转移能配置到振动、转动和平动的比例分别为0.44、0.06和0.50, 能量主要分配在振动和平动上。在T=523 K和PH2=2.5×103 Pa条件下, 通过求解速率方程组和对时间分辨CARS线轮廓的分析, 得到碰撞转移速率系数k1=(6.0±1.2)×10-14 cm-3s-1和k2=(4.0±0.8)×10-13cm-3 s-1。     

Temperature dependent narrow-band terahertz pulse generation in periodically poled crystals via difference frequency generation

Femtosecond optical pulse is used to generate narrow-band terahertz pulses depending on a quasi-phase-matched condition in periodically poled lithium niobate (PPLN) and stoichiometric lithium tantalate (PPSLT) crystals by difference frequency generation. The origin of narrow-band THz generation proved that the two frequency components of the fs pulse contribute to the frequency mixing. By cryogenic cooling, the absorption of THz waves in the crystal is significantly reduced which results in efficient THz generation. Simultaneously generated forward and backward THz pulses were 1.38 and 0.65 THz with as narrow as the bandwidth of 32 GHz in the PPSLT sample. Temperature dependence of the generated THz waveforms had good agreement with the simulation result using one dimensional plane-wave propagation model.