PV型HgCdTe光电探测器中的混沌及其诊断

 对激光辐照半导体光电探测器的实验研究，发现当一束不太强的稳定连续波激光照射在PV型HgCdTe光电探测器上时，可以引起探测器出现混沌行为。利用光电探测器的光电压信号随时间变化的实验数据，通过求功率谱、计算Lyapunov指数对混沌进行了诊断。     

激光辐照PC型HgCdTe探测器的实验研究

 分别用连续波1.319μm激光和10.6μm激光辐照PC型HgCdTe红外探测器时，得到了不同辐照光功率密度下，探测器输出的一系列实验结果。给出了在波长为1.319μm的波段内激光辐照下PC型HgCdTe探测器的饱和阈值；用波长为10.6μm的波段外CO₂激光辐照探测器时，发现了一些与波段内激光辐照探测器时大不相同的实验现象；对实验结果进行了分析。简要总结了PC型HgCdTe探测器对于波段内和波段外激光辐照的响应机制。     

激光与材料参数对瞬态SBS 诱导的激光超声破坏效果的影响

 通过数值求解一维瞬态受激布里渊散射（SBS）声光耦合波方程，从理论上分析了泵浦激光参数及光学材料参数对SBS过程发生阈值的影响。以SBS过程中建立起来的应力场抗拉（压）强度和散射场的反射率为判据，分析了激光脉宽及作用区域长度对激光超声破坏材料效果的影响，探讨了短脉冲激光（约ns）引起的激光超声对材料的破坏机理；讨论了通过参数配置有效遏制SBS过程激光超声对光学材料的破坏问题。     

Beam wander of J 0- and I 0-Bessel Gaussian beams propagating in turbulent atmosphere

Root mean square (rms) beam wander of J ₀-Bessel Gaussian and I ₀-Bessel Gaussian beams, normalized by the rms beam wander of the fundamental Gaussian beam, is evaluated in atmospheric turbulence. Our formulation is based on the first and the second statistical moments obtained from the Rytov series. It is found that after propagating in atmospheric turbulence, the collimated J ₀-Bessel Gaussian and the I ₀-Bessel Gaussian beams have smaller rms beam wander than that of the Gaussian beam, regardless of the choice of Bessel width parameter. However, the extent of such an advantage depends on the chosen width parameter, Gaussian source size, propagation distance and the wavelength. Focusing at finite distances of the considered beams causes the rms beam wander to decrease sharply at the propagation distances equal to the focusing parameter.     

New results on the melting thermodynamics of a circular DNA chain

We investigate the impact of supercoil period and nonzero supercoil formation energy on the thermal denaturation of a circular DNA. Our analysis is based on a recently proposed generalization of the Poland-Scheraga model that allows the DNA melting to be studied for plasmids with circular topology, where denaturation is accompanied by formation of supercoils. We find that the previously obtained first-order melting transition persists under the generalization discussed. The dependence of the size of the order-parameter jump at the transition point and the associated melting temperature are obtained analytically.     

Rayleigh Scattering of 59.5 keV γ-Rays by Mo and Sn

The differential cross sections for coherent scattering of 59.5 keV γ-rays by Mo and Sn were measured using a high-purity germanium detector. The results were compared with predictions of form factor theories and S-matrix calculations.     

苯乙双胍在人体内形成一氧化氮的机理研究

探讨了一氧化氮(NO)在一氧化氮合酶(NOS)的作用下通过氧化苯乙双胍的末端氮原子N1而合成的机理.在这个过程中,化合物的氧化是通过过氧甲酸HCOOOH(Performic acid)来实现的.我们以AM1计算为基础,在NO形成的反应路径上,研究了化合物的中间产物(speciesB、C、D、E),并得到了这些分子的最优化结构.此机制所释放的产物为HNO,它很容易产生NO.通过研究C3-O15和C3-N1原子间距离的变化,我们讨论了这个机制的合理性.     

Propagation factors of Hermite–Gaussian beams in turbulent atmosphere

Based on the extended Huygens–Fresnel integral and the second-order moments of the Wigner distribution function, an analytical formulae for the propagation factors (M²-factors) of coherent and partially coherent one-dimensional Hermite–Gaussian beams in a turbulent atmosphere are derived. Evolution properties of the M²-factor of the Hermite–Gaussian beam in a turbulent atmosphere are studied numerically in detail. Our results show that the M²-factor of the Hermite–Gaussian beam increases upon propagation in a turbulent atmosphere. The M²-factor of the Hermite–Gaussian beam with larger beam order (or lower coherence) increases slower that of the Hermite–Gaussian beam with smaller beam order (or higher coherence) in a turbulent atmosphere, which means that the Hermite–Gaussian beam with a larger beam order and lower coherence is less affected by a turbulent atmosphere. Our results will be useful in long-distance free-space optical communications.     

Scintillation advantages of lowest order Bessel–Gaussian beams

For a weak turbulence propagation environment, the scintillation index of the lowest order Bessel–Gaussian beams is formulated. Its triple and single integral versions are presented. Numerical evaluations show that at large source sizes and large width parameters, when compared at the same source size, Bessel–Gaussian beams tend to exhibit lower scintillations than the Gaussian beam scintillations. This advantage is lost however for excessively large width parameters and beyond certain propagation lengths. Large width parameters also cause rises and falls in the scintillation index of off-axis positions toward the edges of the received beam. Comparisons against the fundamental Gaussian beam are made on equal source size and equal power basis. PACS  42.25.Dd; 42.25.Bs; 42.68.Bz; 42.68.-w