Marinocyanins,cytotoxic bromo-phenazinone meroterpenoids from a marine bacterium from the streptomycete clade MAR4

Six cytotoxic and antimicrobial metabolites of a new bromo-phenazinone class, the marinocyanins A-F (1–6), were isolated together with the known bacterial metabolites 2-bromo-1-hydroxyphenazine (7), lavanducyanin (8, WS-9659A) and its chlorinated analog WS-9659B (9). These metabolites were purified by bioassay-guided fractionation of the extracts of our MAR4 marine actinomycete strains CNS-284 and CNY-960. The structures of the new compounds were determined by detailed spectroscopic methods and marinocyanin A (1) was confirmed by crystallographic methods. The marinocyanins represent the first bromo-phenazinones with an N-isoprenoid substituent in the skeleton. Marinocyanins A-F show strong to weak cytotoxicity against HCT-116 human colon carcinoma and possess modest antimicrobial activities against Staphylococcus aureus and amphotericin-resistant Candida albicans.     

An overview of analytical methodologies for the determination of antibiotics in environmental waters

The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes.     

High‐energy X‐ray diffraction using the Pixium 4700 flat‐panel detector

The Pixium 4700 detector represents a significant step forward in detector technology for high‐energy X‐ray diffraction. The detector design is based on digital flat‐panel technology, combining an amorphous Si panel with a CsI scintillator. The detector has a useful pixel array of 1910 × 2480 pixels with a pixel size of 154 µm × 154 µm, and thus it covers an effective area of 294 mm × 379 mm. Designed for medical imaging, the detector has good efficiency at high X‐ray energies. Furthermore, it is capable of acquiring sequences of images at 7.5 frames per second in full image mode, and up to 60 frames per second in binned region of interest modes. Here, the basic properties of this detector applied to high‐energy X‐ray diffraction are presented. Quantitative comparisons with a widespread high‐energy detector, the MAR345 image plate scanner, are shown. Other properties of the Pixium 4700 detector, including a narrow point‐spread function and distortion‐free image, allows for the acquisition of high‐quality diffraction data at high X‐ray energies. In addition, high frame rates and shutterless operation open new experimental possibilities. Also provided are the necessary data for the correction of images collected using the Pixium 4700 for diffraction purposes.     

The Phase Morphology of 2,5 DI-Substituted Pyridine Derivatives: A Quantum Mechanical Analysis

A comparative analysis of some mesogenic and nonmesogenic molecules of 2, 5 di-substituted pyridine derivatives molecules has been carried out. The multicenter multipole expansion method is used to obtain the various interaction energy terms. The phase morphology of the mesogenic molecular system has been further investigated with the aid of various energy terms of configurations. The multicenter multipole expansion method is satisfactory and predicts the mesogenic behavior of molecular systems.     

膜吸附反应器（MAR）对饮用水系统中病毒的去除

以尺寸与人体肠道病毒相近的f2噬菌体作为模型病毒,本研究采用膜吸附反应器（Membrane adsorption reactor,MAR）,考察膜分离与纳米TiO2耦合工艺对饮用水中病毒的去除效果．两种不同孔径的PVDF（0．20μm）、PAN（0．05μm）平板膜在自来水体系中对f2噬菌体的截留效果分别为1．88～2．56log和4．78～5．95log,大大超过理论计算值,这与膜具有不规则孔型的重叠筛网状结构直接相关．吸附实验结果表明,纳米TiO2对f2噬菌体的吸附在60min内即可达到吸附平衡,符合Freundlich等温吸附模型qe=27．4·Ce1.24．两组MAR系统对f2噬菌体的总去除率分别高达3．88log与6．40log,这主要是由于纳米TiO2的吸附作用,以及运行中在膜表面形成有效的滤饼层．纳米材料与膜系统的耦合既保持了系统对病毒的高效去除,又实现了纳米颗粒的有效分离回收,操作简单、费用低．     

Maximum likelihood inference for the Cox regression model with applications to missing covariates

In this paper, we carry out an in-depth theoretical investigation for existence of maximum likelihood estimates for the Cox model [D.R. Cox, Regression models and life tables (with discussion), Journal of the Royal Statistical Society, Series B 34 (1972) 187–220; D.R. Cox, Partial likelihood, Biometrika 62 (1975) 269–276] both in the full data setting as well as in the presence of missing covariate data. The main motivation for this work arises from missing data problems, where models can easily become difficult to estimate with certain missing data configurations or large missing data fractions. We establish necessary and sufficient conditions for existence of the maximum partial likelihood estimate (MPLE) for completely observed data (i.e., no missing data) settings as well as sufficient conditions for existence of the maximum likelihood estimate (MLE) for survival data with missing covariates via a profile likelihood method. Several theorems are given to establish these conditions. A real dataset from a cancer clinical trial is presented to further illustrate the proposed methodology.     

缺失数据下EV模型的调整最小二乘估计

该文考虑协变量缺失时的多元线性EV模型参数的估计, 其中协变量的缺失机制是Rubin(1976)提出的随机缺失(MAR). 利用加权调整最小二乘方法给出参数估计, 证明了估计的相合性和渐近正态性. 数值模拟结果表明所给的估计性态良好.