Short echo time in vivo prostate ¹H-MRSI

Visualization of short echo time (TE) metabolites in prostate magnetic resonance spectroscopic imaging is difficult due to lipid contamination and pulse timing constraints. In this work, we present a modified pulse sequence to permit short echo time (TE=40ms) acquisitions with reduced lipid contamination for the detection of short TE metabolites. The modified pulse sequence employs the conformal voxel MRS (CV-MRS) technique, which automatically optimizes the placement of spatial saturation planes to adapt the excitation volume to the shape of the prostate, thus reducing lipid contamination in prostate magnetic resonance spectroscopic imaging (MRSI). Metabolites were measured and assessed using a modified version of LCModel for analysis of in vivo prostate spectra. We demonstrate the feasibility of acquiring high quality spectra at short TEs, and show the measurement of short TE metabolites, myo-inositol, scyllo-inositol, taurine and glutamine/glutamate for both single and multi-voxel acquisitions. In single voxels experiments, the reduction in TE resulted in 57% improvement in the signal-to-noise ratio (SNR). Additional 3D MRSI experiments comparing short (TE=40 ms), and long (TE=130 ms) TE acquisitions revealed a 35% improvement in the number of adequately fitted metabolite peaks (775 voxels over all subjects). This resulted in a 42 ± 24% relative improvement in the number of voxels with detectable citrate that were well-fitted using LCmodel. In this study, we demonstrate that high quality prostate spectra can be obtained by reducing the TE to 40 ms to detect short T2 metabolites, while maintaining positive signal intensity of the spin-coupled citrate multiplet and managing lipid suppression.     

Comparing the efficiency of Wolbachia driven Aedes mosquito suppression strategies

Wolbachia is an endosymbiotic bacterium which manipulates host reproduction by cytoplasmic incompatibility, and restrains the transmission of dengue virus in Aedes mosquitoes. A novel strategy for dengue control involves releasing Wolbachia infected males into nature to suppress wild Aedes mosquito population. We develop a model of delay differential equations, integrating larval density-dependent competition and diapausing eggs, to compare the efficiency of different suppression strategies. The global asymptotical stability of the complete suppression state identifies the releasing amount threshold ascertaining suppression. Based on the experimental data for Aedes albopictus population in Guangzhou, our simulations show that the mosquito density in the highest peak season can be reduced by more than $95\%$ when the number of released males is above the releasing threshold. The best time to initiate the suppression is in early March, lasting until the end of June, followed by the parallel releasing policy from July to November. However, the egg bank has neglectable effects on the control of dengue vector in Guangzhou.     

空气－乙炔火焰中铝对铂的干扰规律、干扰机理及其应用研究

在不同介质中，少量铝对铂的吸光度均有抑制作用，随着铝的浓度增加，则表现为增感作用，其中在硝酸和硫酸介质中５０００μｇ／ｍｌ的铝可使铂的吸光度分别增加９０％和１７８％，铝对铂的干扰可分为与浓度有关及与浓度无关的化学干扰，在硝酸介质中５０００μｇ／ｍｌ的铝对０～５０μｇ／ｍｌ铂的干扰与浓度无关，在该条件下可使用标准加入法。在硝酸介质中，５０００μｇ／ｍｌ的铝还可用作２５μｇ／ｍｌ钠对２５μｇ／ｍｌ铂干扰的缓冲剂。同时探讨了铝对铂的干扰机理。     

干涉法测量掺铒光纤的非线性折射率

本文提出一种测量掺铒光纤非线性折射率的方法,该方法使氩离子激光通过一根掺铒光纤和另一根并排的普通光纤产生干涉.由掺铒光纤的非线性折射率导致的位相差变化将使干涉条纹发生位移,通过位移的测量可以得出光纤的非线性折射率.     

干涉超光谱图像分析与近无损压缩CPLD实现

介绍了干涉超光谱卫星遥感图像的成像特性，计算、比较分析了干涉超光谱图象的空间维与光谱维的相关性，提出了一种近无损压缩的局部DPCM算法.选用CPLD在Maxplus Ⅱ使用VHDL语言对该压缩算法进行了硬件描述和仿真.仿真结果表明该压缩算法简单可行，易由硬件实现.     

Experimental investigation and numerical validation of explosion suppression by inert particles in large-scale duct

A large-scale duct with an explosion suppressor was designed to investigate experimentally the explosion suppression by inert particles for a CH₄/O₂/N₂ mixture. The duct is 25 m long and has an internal diameter of 700 mm. Pressure and flame signals were recorded some distance away from ignitor in the duct. Pressure tracking lines of the shock front for the different inert particle cloud densities and the inert particle diameters were made. The measured results indicate that the shock front is decoupled from the flame front in the inert particle cloud, which leads to a suppression of explosion. Also, the experiments suggest that increasing the inert particle cloud density or decreasing the inert particle diameter can enhance the ability to suppress explosion. For the purpose of validation, a two-dimensional numerical model coupled with the element chemical reaction mechanism for the simulations of the CH₄/O₂/N₂ mixture explosion suppression by the inert particles has been developed. This model makes use of the second-order TVD scheme and the MacCormack scheme to calculate gas-phase and particle-phase equations, respectively. The Strang splitting technique is used to treat the stiffness due to the coupling of the governing equations, while the implicit Gear algorithm is used to treat the stiffness due to the chemical reactions. The effect of inert particle cloud density on explosion suppression was investigated using the model. The calculated results indicate that the accumulation of inert particles slows the propagation of the gas-phase shock front and results in explosion suppression. With increased inert particle cloud density, the explosion suppression is more prominent. The calculated results show a qualitative agreement with the measured results in the large-scale duct experiment.     

透光率导数光谱与吸光度导数光谱的比较

研究了糖精钠在220－260nm的1－6阶透光率导数光谱和吸光度导数光谱，透光率导数光谱的灵敏度大大高于吸光度导数光谱，但其抗干扰能力比吸光度导数光谱差，两者特征峰强度与浓度的线性关系接近。     

基于细菌视紫红质光子逻辑门的实验研究

研究了基于细菌视紫红质(简称BR或菌紫质)变种材料D96N的3种光逻辑操作.在633nm激发光照射下，菌紫质分子会被激发到M态，处于M态的菌紫质对412nm的紫光呈较大吸收，会抑制同时入射的紫光.选择合适的紫光强度，通过CCD观测被抑制的412nm检测光透射强度分布，模拟了“非”、“或非”、“与非”几种基本的光子逻辑操作. 关键词： 细菌视紫红质 光子逻辑门 互补抑制     

核物质中粲偶素粒子的形成与压低

用微扰方法系统求解了cc各态之间的耦合Schroedinger方程,讨论了粲粒子的形成时间和核吸收的关联. 通过计算J/ψ及ψ′在不同核子-核过程中的压低并与实验结果比较,发现形成时间对J/ψ,特别是ψ′的核吸收过程有重要的影响     

锰石墨炉原子吸收分析中氯化钙干扰机理研究

本文用时间分辨技术考察了氯化钙对锰测定过程的干扰情况。干扰包括三个方面：抑制效应，延迟效应和背景吸收。选用硝酸作为基体改进剂，ＨＣｌ的形成和挥发减少了锰的损失，消除了ＣａＣｌ２的分子吸收，硝酸的加入还改进了锰吸收峰形，改善了测定灵敏度。Ｃａ（Ⅱ）－Ｍｎ－ＨＮＯ３的共存体系使锰的原子化移向高温，原子化效率提高。镁，锶，钡具有类似钙的作用。