Difluorocarbene-Induced Ring-Opening Difluoromethylation-Halogenation of Cyclic (Thio)Ethers with TMSCF2X (X=Br,Cl)**

The ring-opening difluoromethylation-halogenation of cyclic (thio)ethers is reported through a simple strategy relying on carbon-chalcogen bond activation with difluorocarbene. The reaction proceeds through in situ protonation of the previously little-known difluoromethylene oxonium or sulfonium ylide intermediate followed by ring-opening with halide ion to afford halogenated acyclic difluoromethyl (thio)ethers that can then be employed for further elaboration. TMSCF₂X (X=Br, Cl) are unique reagents to achieve this synthetic purpose, which serve as both the difluorocarbene source and the halide ion source.     

Double Orthogonal Click Reactions for the Development of Antimicrobial Peptide Nanotubes

A new class of amphipathic cyclic peptides, which assemble in bacteria membranes to form polymeric supramolecular nanotubes giving them antimicrobial properties, is described. The method is based on the use of two orthogonal clickable transformations to incorporate different hydrophobic or hydrophilic moieties in a simple, regioselective, and divergent manner. The resulting cationic amphipathic cyclic peptides described in this article exhibit strong antimicrobial properties with a broad therapeutic window. Our studies suggest that the active form is the nanotube resulted from the parallel stacking of the cyclic peptide precursors. Several techniques, CD, FTIR, fluorescence, and STEM, among others, confirm the nanotube formation.     

大面阵激光二极管阵列端面泵浦耦合技术

为了满足常温Yb:YAG激光放大器对泵浦功率密度的要求,设计了一种高缩束比的耦合系统。根据激光二极管（LD）的发光特性,将输出功率为80 kW的LD阵列进行拟球面排列,采用正交柱面透镜配合空心导光管进行泵浦耦合,耦合系统的面积缩束比高达86∶1。模拟计算表明,该耦合系统的耦合效率对导光管反射板的反射率依赖性较低,且脱离耦合系统后的泵浦光传输8.5 mm后,依然可以保持泵浦光场的轮廓,满足端面泵浦的常温Yb:YAG片状放大器对泵浦耦合系统的要求。     

Nonlinear vertical accelerations of a floating torus in regular waves

The longitudinal motions and vertical accelerations of a floating torus as well as wave motion inside the torus are studied by model tests in regular deep-water waves. Comparisons are made with linear and partly with second-order potential-flow theory for the smallest examined experimental wave height-to-wave length ratio 1/120. Reasonable agreement is obtained, in particular for the linear problem. The importance of 3D flow, hydroelasticity and strong hydrodynamic frequency dependency is documented. Experimental precision errors and bias errors, for instance, due to tank-wall interference are discussed. Numerical errors due to viscous effects are found to be secondary. Experiments show that the third and fourth harmonic accelerations of the torus matter and cannot be explained by a perturbation method with the wave steepness as a small parameter.     

用于考察外源添加剂对卷烟常规烟气指标影响的样品制备因子筛选

为筛选用于考察外源添加剂对卷烟常规烟气指标影响的样品制备关键控制因子,采用L_8(2~7)正交试验设计进行香兰素及乙基麦芽酚的添加实验.卷烟常规烟气指标变化数值通过极差分析、方差分析,结果显示:参比卷烟种类是影响卷烟烟气总粒相物、焦油、水分的高度显著因子,就试验采用的1R5F和3R4F参比卷烟而言,添加剂在高焦油3R4F卷烟中对常规烟气指标的影响比其在低焦油1R5F卷烟中的影响大;添加剂种类与浓度的交互作用不仅对卷烟烟气总粒相物有高度显著影响,而且对总粒相物中的水分也有显著影响;因此,规范样品制备,可减少误差、保证后续外源添加剂加入对卷烟常规烟气指标影响评价结果和推断的可靠性及科学性.     

Simultaneous determination of boscalid and fludioxonil in grape and soil under field conditions by gas chromatography/tandem triple quadrupole mass spectrometry

A gas chromatography–tandem mass spectrometry method was developed and validated to simultaneously determine boscalid and fludioxonil in grape and soil samples. These samples were extracted with 10 mL of acetonitrile and purified using a mixed primary secondary amine/octadecylsilane sorbent. The method showed good linearity (R² > 0.99) in the calibration range 0.005–2 μg/mL for both pesticides. The limits of detection and quantification for the two analytes in grape and soil were 0.006 and 0.02 mg/kg, respectively. Fungicide recoveries in grape and soil were 81.18–92.11% for boscalid and 82.73–97.67% for fludioxonil with relative standard deviations of 1.31–10.31%. The established method was successfully applied to the residual analysis of boscalid and fludioxonil in real grape and soil samples. The terminal residue concentrations of boscalid and fludioxonil in grape samples collected from Anhui and Guizhou were <5 mg/kg (the maximum residue limit set by China) 7 days after the last application and 1 mg/kg (the maximum residue limit set by USA) 14 days after the last application. These results could provide guidance for the proper and safe use of boscalid and fludioxonil in grape and help the Chinese government to establish an MRL for fludioxonil in grape.     

An improved algorithm for the shallow water equations model reduction: Dynamic Mode Decomposition vs POD

We propose an improved framework for dynamic mode decomposition (DMD) of 2‐D flows for problems originating from meteorology when a large time step acts like a filter in obtaining the significant Koopman modes, therefore, the classic DMD method is not effective. This study is motivated by the need to further clarify the connection between Koopman modes and proper orthogonal decomposition (POD) dynamic modes. We apply DMD and POD to derive reduced order models (ROM) of the shallow water equations. Key innovations for the DMD‐based ROM introduced in this paper are the use of the Moore–Penrose pseudoinverse in the DMD computation that produced an accurate result and a novel selection method for the DMD modes and associated amplitudes and Ritz values. A quantitative comparison of the spatial modes computed from the two decompositions is performed, and a rigorous error analysis for the ROM models obtained is presented. Copyright © 2015 John Wiley & Sons, Ltd.     

Quadratic decomposition of symmetric semi-classical polynomial sequences of even class: an example from the case s = 2

In the present work, we deal with the quadratic decomposition of symmetric semi-classical polynomial sequences of even class. An example from class 2 is settled. We give an integral representation of the considered symmetric form.     

Importance Sampling for p-value Computations in Multivariate Tests

Abstract

An importance sampling procedure is developed to approximate the distribution of an arbitrary function of the eigenvalues for a matrix beta random matrix or a Wishart random matrix. The procedure is easily implemented and provides confidence intervals for the p-values of many of the commonly used test statistics in multivariate analysis. An adaptive procedure allows for the control of either absolute error or relative error in this p-value estimation through the choice of importance sample size.