Theoretical Calculations and Experimental Verification of the Antibacterial Potential of Some Monocyclic β-Lactams Containing Two Synergetic Buried Antibacterial Pharmacophore Sites

A new series of N-thiazole, 3-phenyl, 4-substituted phenyl azetidine-2-ones 4(a–h) have been synthesized in good yields starting from 2-aminothiazole 1. In the first step, then Schiff's bases 3(a–h) are prepared by the condensation of 2-aminothiazole 1 with different aryl aldehydes 2(a–h). Finally, monocyclic β-lactams, i.e. substituted azetidinones 4(a–h), were the products formed using three different methods by the dehydrative cyclocondensation of 3(a–h) with phenyl acetyl chloride in dioxane, phenyl acetic acid–thionyl chloride in dichloromethane and phenyl acetic acid–phosphorus oxychloride in dichloromethane in the presence of triethylamine. We found that latter method is the best as compared with the former two methods. The synthesized molecules 4(a–h) were screened for their antibacterial activity against four microorganisms: Staphylococcus aureus (Gram positive), Pseudomonas vulgaris (Gram positive), Pseudomonas aeruginosa (Gram negative), and Escherichia coli (Gram negative). Their antibacterial activities are reported, and on the basis of the screening data available, attempt is also made to elucidate the structure–activity relationship.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

基于尺度分离的SAR图像梯度反演海面风向

基于数字图像处理知识和大气边界层理论,提出了一种利用合成孔径雷达图像局部梯度反演海面风向的新方法.该方法定义尺度分离后的合成孔径雷达图像梯度方向与风向垂直,而风向就是由所选图像区域出现最多频率的局部梯度所确定.实例研究表明由梯度方法所确定的风向结果与数值预报值十分吻合,其风向均方根误差为3.414°.并且梯度方法在使用谱方法无法获得结果的情况下,仍然能求得正确的风向结果,为提高海面风场反演率奠定了应用基础.     

Luminescence sensitivity changes of polymineral fine grains during IRSL and [post-IR] OSL measurements

Sensitivity changes during measurement sequences of infra-red-stimulated luminescence (IRSL) and post-IR optically stimulated luminescence (OSL) are presented for a sample of loess from northwestern China. Together with a dose recovery experiment, the results are used to investigate the ratio of 2.4 found for the D_e values (for IRSL and [post-IR] OSL) obtained when using a single-aliquot regenerative-dose (SAR) protocol in which both D_e values are obtained in a single sequence of measurements. Responses to test doses for both the IRSL and [post-IR] OSL show progressive luminescence sensitivity changes with repeated measurement cycles, with a slight dose dependence for the IRSL. In addition, five modified SAR procedures were used, varying preheats, filter combinations and method of measuring the luminescence signal. The D_e values for all IRSL measurements were at least 50% greater than those for the [post-IR] OSL signal. A modified SAR sequence was also applied in which 0.1 s stimulations (using both IR and blue light sources) were made between all sample treatments. A lack of consistency in the measured luminescence sensitivity of the natural IRSL signal suggests that the [post-IR] OSL signal provides the more reliable value of D_e.     

模拟合成孔径雷达数据片波差的测量和胶片、波差的容限

本文介绍一种用马赫-陈德干涉系统测量模拟合成孔径雷达数据片波差的方法.该法能把两种原因产生的波差区分开来,即把通过胶片变形的波面与平面参考波面比较,求出胶片厚度不平产生的波差;把合成孔径雷达数据片的一级衍射波面与两个半径不等的参考球面波比较,分别求出由模拟装置产生的方位维和斜距维波差.本文给出一些实验结果和分析.这种方法还可以用于测量真实合成孔径雷达数据片的波差.由胶片厚度变化产生的波差可以用液体门补偿.但是,在实际中使用液体门是很繁复的,有时也没有必要.因此,我们认瑞利准则出发导出合成孔径雷达数据片胶片厚度变化产生的波差的容限,以此作为判断是否要用液体门的依据.     

Calculated ionization energies for a series of sesquiterpenes: comparisons with experimental vertical ionization energies and comments on related structure–activity relationships (SARs)

The energies of the highest-occupied molecular orbitals (HOMOs) are known to be excellent predictors of the reactivities of biogenic hydrocarbons, such as terpenes, with reactive atmospheric oxidants including O₃, OH, and NO₃. Structure–Activity Relationships (SARs) have also been effectively employed in such studies and related to HOMO energies and lowest ionization energies (ionization potentials). This study employs density function theory (DFT), at the B3LYP/6-31G** level, to predict vertical ionization energies (IP_v) for a structurally diverse group of sesquiterpenes, each of which has been reported in air samples collected in the lower troposphere. The availability of published UV photoelectron spectra for nine sesquiterpenes permits comparison of experimental and theoretical vertical ionization energy data. The experimental and theoretical data show a good correlation (average discrepancy ± 0.07 eV). This enables predictions of reactivities for sesquiterpenes whose tropospheric lifetimes may last only a few hours before their transformations into secondary organic aerosols (SOA) close to their emission sources.     

肿瘤射频热疗SAR场与瞬时温度分布模拟

本文针对非侵入性射频热疗的SAR场及瞬态温度分布进行建模和数值模拟计算。采用了能正确反映电磁波在生物组织中衰减的电磁场模型。在温度场模拟中考虑了血液灌流项随组织温度变化和肿瘤区低血液灌流的特点,这些措施使模拟计算结果更加符合临床实际。还对射频热疗电磁能量分布和温度分布的特点及其影响因素等作了细致的分析和讨论。     

A Class of Global Optimization Problems as Models of the Phase Unwrapping Problem

Let I={(i,j) i=1, 2,..., N ₁, j=1, 2,..., N ₂} and let U=U_i,j, (i,j)I be a discrete real function defined on I. Let []₂ be modulus 2, we define W:I , ) as follows W=[U]₂. The function U will be called phase function and the function W will be called wrapped phase function. The phase unwrapping problem consists in recovering U from some knowledge of W. This problem is not well defined, that is infinitely many functions U correspond to the same function W, and must be `regularized' to be satisfactorily solvable. We propose several formulations of the phase unwrapping problem as an integer nonlinear minimum cost flow problem on a network. Numerical algorithms to solve the minimum cost flow problems obtained are proposed. The phase unwrapping problem is the key problem in interferometry, we restrict our attention to the SAR (Synthetic Aperture Radar) interferometry problem. We compare the different formulations of the phase unwrapping problem proposed starting from the analysis of the numerical experience obtained with the numerical algorithms proposed on synthetic and real SAR interferometry data. The real data are taken from the ERS missions of the European Space Agency (ESA).     

基于渐进核图割的SAR图像自动分割

合成孔径雷达(Synthetic Aperture Radar,SAR)图像是遥感目标检测与分割等研究的重要数据源。提出了一种渐进核图割分割方法,该方法通过迭代进行二类聚类分割,自动实现合成孔径雷达SAR图像中多目标的分割。实验结果表明,该方法能够有效地实现复杂场景SAR图像的多目标分割。