Single-shot grating-based x-ray differential phase contrast imaging with a modified analyzer grating

X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping information extraction method reduces system stability and prolongs data acquisition time by several times compared with conventional x-ray absorptionbased imaging. The mechanical stepping can be avoided by using a staggered grating, but at the cost of low vertical spatial resolution. In this paper, employing a modified staggered grating and the angular signal radiography, we proposed a single-shot grating-based x-ray differential phase contrast imaging with decent vertical spatial resolution. The theoretical framework was deduced and proved by numerical experiments. Absorption, phase, and scattering computed tomography can be performed without phase stepping. Therefore, we believe this fast and highly stable imaging method with decent resolution would be widely applied in x-ray grating-based phase contrast imaging.     

A three‐crystal spectrometer for high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy and X‐ray emission spectroscopy at SSRF

A Johann‐type spectrometer for the study of high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy, X‐ray emission spectroscopy and resonant inelastic X‐ray scattering has been developed at BL14W1 X‐ray absorption fine structure spectroscopy beamline of Shanghai Synchrotron Radiation Facility. The spectrometer consists of three crystal analyzers mounted on a vertical motion stage. The instrument is scanned vertically and covers the Bragg angle range of 71.5–88°. The energy resolution of the spectrometer ranges from sub‐eV to a few eV. The spectrometer has a solid angle of about 1.87 × 0^?3 of 4π sr, and the overall photons acquired by the detector could be 10⁵ counts per second for the standard sample. The performances of the spectrometer are illustrated by the three experiments that are difficult to perform with the conventional absorption or emission spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

盐酸特拉唑嗪降解产物的结构鉴定

盐酸特拉唑嗪是一种新型选择性 α₁-肾上腺能受体拮抗剂,用于治疗高血压和良性前列腺增生。采用高效液相色谱-高分辨多级质谱(HPLC-HRMSⁿ)联用法对强氧化条件下盐酸特拉唑嗪原料药的降解产物进行了详细的解析和结构确证。共检测到15种降解产物,其中7种与文献报道的有关物质相同,另外8种为新检测到的降解产物,其主要降解途径为酰胺键水解、羟基化、羰基化及3种途径组合的次级降解途径。     

地尔硫卓的合成工艺改进

以对甲氧基苯甲醛和氯乙酸甲酯为原料,经Darzens缩合、环氧开环、酒石酸拆分、环合、N-烃基化、O-乙酰化、成盐等7步反应制得地尔硫卓盐酸盐,其结构经 ¹H NMR,IR, MS（ESI）和元素分析确证。     

Derivative artificial compression method for conservation laws with multi-dimensional extension

A new resolution-enhancing technique called derivative artificial compression method is developed with multi-dimensional extension. The method is constructed via applying high-resolution difference schemes on derivative equations of conservation laws. In this way, one could overcome the defect of accuracy decay at extreme points that has plagued almost all high-resolution schemes. The new method has high resolution, low dissipation and low diffusion properties, and could enhance the resolution (of numerical solution) both at discontinuities and at extreme points. Numerical experiments are implemented using initial value problems of single conservation law, one-dimensional shock-tube problem, two-dimensional Riemann problems, double Mach reflection problem, and a shock reflection from a wedge. Resolutions of discontinuities, extremes and fine structures are compared between the original TVD scheme, TVD scheme with artificial compression method and TVD scheme with derivative artificial compression method.     

非对称空间外差光谱技术研究

传统空间外差光谱技术存在光谱分辨率、光谱范围与探测器象元数之间的制约关系。非对称空间外差光谱技术相比传统空间外差光谱技术主要区别在于增加单臂光栅到分束器的距离,能够在系统参数不变的情况下大大的增加光谱分辨率。首先阐述了非对称空间外差光谱技术的基本原理,并给出相应的系统参数计算公式推导结果,从理论上推导出单臂光栅偏置量增加和光谱分辨率增加之间的关系。偏置量作为非对称空间外差光谱技术的重要参数,受短双边象元数和光谱分辨率需求的制约。根据实验室现有实验平台参数,给出偏置量选择原则及结果。在元器件参数相同的情况下,分别计算了两种形式的理论光学性能参数,并且进行了仿真验证,得出非对称空间外差光谱仪与传统空间外差光谱仪光谱范围相同,但具有更高的光谱分辨率,并且分辨率提高与偏置量增加关系与理论计算相符。最后通过单色光扫描方法对非对称空间外差光谱仪实验室装置进行光谱范围和光谱分辨率的定标,定标结果与理论计算值吻合较好。     

基于经验模态分解提高太赫兹频率分辨率的方法

太赫兹频率分辨率是影响物质鉴别的重要因素,但是由于太赫兹时域光谱系统中存在器件反射,使得参考信号和测量信号出现多个反射峰,时域信号长度截断导致频率分辨率很低。为了去除反射峰的影响,提出基于经验模态分解去除时域反射峰,从而提高太赫兹频率分辨率的方法。通过与太赫兹主峰的互相关定位时域反射峰,计算反射峰的上下包络和求平均值,获取本征模函数并代替反射峰,增加时域信号有效长度,提高太赫兹频域分辨率。空气中水蒸汽的太赫兹透射谱实验结果表明,该方法具有自适应去除多个反射峰的能力,对太赫兹时域信号修复效果良好,频率分辨率提高了12倍,而且未丢失有用的吸收谱信息,吸收峰的位置和个数与真实谱一致,很好地保留了太赫兹谱的鉴别能力。     

Sensitivity study of(10,100) GeV gamma-ray bursts with double shower front events from ARGO-YBJ

ARGO-YBJ, located at the Yangbajing Cosmic Ray Observatory(4300 m a.s.l., Tibet, China), is a full coverage air shower array, with an energy threshold of ~300 Ge V for gamma-ray astronomy. Most of the recorded events are single front showers, satisfying the trigger requirement of at least 20 particles detected in a given time window. However, in ~11.5% of the events, two randomly arriving showers may be recorded in the same time window,and the second one, generally smaller, does not need to satisfy the trigger condition. These events are called double shower front events. By using these small showers, well under the trigger threshold, the detector primary energy threshold can be lowered to a few tens of Ge V. In this paper, the angular resolution that can be achieved with these events is evaluated by a full Monte Carlo simulation. The ARGO-YBJ sensitivity in detecting gamma-ray bursts(GRBs) by using double shower front events is also studied for various cutoff energies, time durations, and zenith angles of GRBs in ARGO's field of view.     

基于双波前传感器自适应光学技术的太阳光栅光谱仪

为了研究不同太阳大气高度的热力学特性,具有良好成像质量的成像型光栅光谱仪是实现这个目标的重要仪器。然而作为地基式太阳望远镜重要的终端仪器之一,光栅光谱仪的光谱成像性能不可避免的会受到动态波前像差和系统静态像差的影响。动态波前像差常通过在太阳望远镜系统中集成自适应光学系统进行补偿。针对光学系统中的由装调和光学元件加工等引起的静态波前像差,提出了一种基于自适应光学技术校正光栅光谱仪中静态波前像差的方法,并进行了数值模拟仿真和实验验证。实验结果表明,校正后系统的残余波前像差RMS≈0.025λ,此时波前像差对光谱分辨率和能量利用率的影响可忽略,提高了光栅光谱仪的光谱成像质量,证明了所提出的方法的有效性。此外它具有降低光学系统装调精度和光学元件加工精度要求的优点。     

Engineering of Yeast Old Yellow Enzyme OYE3 Enables Its Capability Discriminating of (E)-Citral and (Z)-Citral

The importance of yeast old yellow enzymes is increasingly recognized for direct asymmetric reduction of (E/Z)-citral to (R)-citronellal. As one of the most performing old yellow enzymes, the enzyme OYE3 from Saccharomyces cerevisiae S288C exhibited complementary enantioselectivity for the reduction of (E)-citral and (Z)-citral, resulting in lower e.e. value of (R)-citronellal in the reduction of (E/Z)-citral. To develop a novel approach for the direct synthesis of enantio-pure (R)-citronellal from the reduction of (E/Z)-citral, the enzyme OYE3 was firstly modified by semi-rational design to improve its (R)-enantioselectivity. The OYE3 variants W116A and S296F showed strict (R)-enantioselectivity in the reduction of (E)-citral, and significantly reversed the (S)-enantioselectivity in the reduction of (Z)-citral. Next, the double substitution of OYE3 led to the unique variant S296F/W116G, which exhibited strict (R)-enantioselectivity in the reduction of (E)-citral and (E/Z)-citral, but was not active on (Z)-citral. Relying on its capability discriminating (E)-citral and (Z)-citral, a new cascade reaction catalyzed by the OYE3 variant S296F/W116G and glucose dehydrogenase was developed, providing the enantio-pure (R)-citronellal and the retained (Z)-citral after complete reduction of (E)-citral.