Ising自旋体系的非平衡动态相变

在平均场理论架构下, 以含时金兹堡-朗道和Glauber动力学这两类动态模型为基础，研究 了受外场和温度共同驱动的Ising自旋体系的非平衡动态相变.确定了界定动态无序(动态顺 磁相P)和动态有序(动态铁磁相F)转变的动态相界.并根据动态序参量Q和Binder参数U随系统 温度t(r₀)、驱动外场频率ω和振幅h₀的变化规律，就上述两类模 型的动态相界上是否存在区分连续动态转变和非连续动态转变的三临界点这一引发争议的问 题做出了进一步分析说明. 关键词： Ising自旋体系 非平衡动态相变 含时金兹堡-朗道模型 Glauber 动力学模型     

Quantum Cosmology in CGBD Theory

We apply the theory developed in quantum cosmology to a model of charged generalized Brans–Dicke gravity. This is a quantum model of gravitation interacting with a charged Brans–Dicke type scalar field which is considered in the Pauli frame. The Wheeler–DeWitt equation describing the evolution of the quantum Universe is solved in the semiclassical approximation by applying the WKB approximation. The wave function of the Universe is also obtained by applying both the Vilenkin-like and the Hartle–Hawking-like boundary conditions. We then make predictions from the wave functions and infer that the Vilenkin's boundary condition is more reasonable in the Brans–Dicke gravity models leading a large vacuum energy density at the beginning of the inflation.     

3-D echo planar (1)HMRS imaging in MS: metabolite comparison from supratentorial vs. central brain

To determine if metabolite ratios as measured by 3-dimensional echo planar spectroscopy imaging (3D-EPSI) from central brain regions of interest (ROI) centered at the corpus callosum reflect imaging metrics of large volumes of supratentorial brain (STB) from patients with multiple sclerosis. METHODS: 48 MS patients with relapsing-remitting, secondary progressive, and primary progressive disease underwent a 3D-EPSI sequence covering large volumes of STB. Metabolite ratios were first estimated from all voxels within a STB mask using a linear regression of N-acetylaspartate (NAA) over Creatine (Cr), NAA over choline (Cho) and Cho over Cr. Secondly, spectroscopic voxels from a central brain (CB) ROI centered at the corpus callosum were selected within the STB. Ratios were compared using Bland-Altman regression analysis and Spearman's correlation coefficients between STB versus central brain. Ratios from studied ROIs were correlated with the EDSS and compared to normal controls. RESULTS: Very strong correlations ranging from 0.884 and 0.938 (p < 0.0001) were found for all metabolite ratios between STB versus central brain. NAA/Cr ratios were similarly and negatively correlated with the EDSS across all ROIs, trends ranging from -0.257 to -0.314 (p < 0.1). NAA/Cr from all MS patients was similarly decreased compared to controls across all ROIs (p < 0.01). CONCLUSION: Metabolite ratios from a central brain ROI were statistically equivalent and highly correlated with ratios from the STB. The study of NAA/Cr using (1)HMRS from a central brain ROI centered at the corpus callosum seems to be representative of brainwide axonal changes in patients with MS.     

Beam propagation method using a [(p- 1)/ p] Padé approximant of the propagator

A new beam propagation method (BPM) is developed based on a direct approximation to the propagator by its [(p-1)/p] Padé approximant. The approximant is simple to construct and has the desired damping effect for the evanescent modes. The method is applied to a tapered waveguide for TM-polarized waves, based on the energy-conserving improvement of the one-way Helmholtz equation. Numerical results are compared with those obtained with other variants of the BPM.     

Temperature dependence of excitonic luminescence from nanocrystalline ZnO films

The properties of the excitonic luminescence for nanocrystalline ZnO thin films are investigated by using the dependence of excitonic photoluminescence (PL) spectra on temperature. The ZnO thin films are prepared by thermal oxidation of ZnS films prepared by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The X-ray diffraction (XRD) indicates that ZnO thin films have a polycrystalline hexagonal wurtzite structure with a preferred (0 0 2) orientation. A strong ultraviolet (UV) emission peak at 3.26 eV is observed, while the deep-level emission band is barely observable at room temperature. The strength of the exciton-longitudinal-optical (LO) phonon coupling is deduced from the temperature dependence of the full-width at half-maximum (FWHM) of the fundamental excitonic peak, decrease in exciton-longitudinal-optical (LO) phonon coupling strength is due to the quantum confinement effect.     

透镜的粘接固定技术

本文对透镜固定技术作了分析,提出了以透镜粘接固定法代替传统的包边法和压圈固定法。对粘接剂的选择、粘接固定形式、粘接工艺及质量验证等问题均作了较详细的介绍,并列举了有关试验结果。     

微微秒自动调谐参量激光的研究

采用一对MgO:LiNbO_3角度调谐覆盖了红近外波段0.7～2.2μm,并配以自动波长扫描。文中分析了影响脉冲宽度与线宽的因素,与实验结果相吻合。脉宽<30ps,线宽～1nm(简并波长附近～10nm),单脉冲峰功率达MW级,参量光总能量转换效率达5.4％。     

云南甘草中齐墩果烷型五环三萜化合物的NMR谱的研究

本文研究了云南甘草皂甙元(glyyunnansapogenin)等oleanane类化合物的核磁共振谱。运用PBB,INEPT,DEPT方法,并结合化学位移值规律归属了这些化合物的¹³C-NMR信号。总结出用角甲基的化学位移植范围判定角甲基的取代位置的方法,分析了角甲基被氧取代后对环的化学位移值的影响。按类似olean-12-en,18α-H方式考虑,归属了oleana-11,13(18)-diene化合物的¹³C-NMR信号。讨论了具30→18β内酯或2929→18α内酯类化合物的核磁谱规律。另外,还发现了DE环上有1个OAC取代时,与其偕碳质子的化学位移值规律。