Photoredox mediated CN cross coupling of sulfoximines with aryl iodides

A new photoredox-catalyzed CN coupling reaction of sulfoximines with aryl halides has been developed for a general N-arylation of sulfoximines. The reactions proceed in the presence of visible light with high levels of chemoselectivity and a wide range of functionality is tolerated. There is a rapidly increasing interest in sulfoximines as pharmacophores in drug discovery and this new method offers potential in terms of high functional group tolerance and late-stage functionalization of compounds.     

Determination of beryllium in solid samples by flame atomic absorption spectrometry after preconcentration on activated carbon.

It is generally supposed that the preconcentration procedure is used for the determination of metal concentrations under the sensitivity of the measurement method. This study showed that preconcentration is also need for the beryllium (Be) concentration over the sensitivity of atomic absorption spectrometry. For this purpose, a simple and selective method for the determination of Be in solid samples is modified. The method is based on the preconcentration of the complexes of beryllium-acetylacetone plus morin, oxine, PAN and PAR on activated carbon at different pH values. The adsorbed beryllium was eluted with aqua regia and measured by flame atomic absorption spectrometry (FAAS). Recoveries of up to 85% were achieved. For removing chemical interferences and applying the method to Be determination in solid samples, the masking studies and reproducibility were examined. The detection limit was found to be 0.12 ng mL(-1). The relative sandard deviations (RSD) were found to be 8% for 60 mL of 10.0 ng mL(-1) using 10 replicate enrichment procedures. Beryllium concentrations in the studied solid samples were found in the range of 0.28 - 3.95 mg kg(-1).     

Water-soluble green perylenediimide (PDI) dyes as potential sensitizers for photodynamic therapy

[reaction: see text] A series of water-soluble green perylenediimide (PDI) dyes have been synthesized. On red light excitation, these dyes were shown to be efficient generators of singlet oxygen, and in cell culture media, they were shown to display significant light-induced cytotoxic effects on the human erythroleukemia cell line (K-562). It appears that highly versatile PDI dyes are likely to find new applications in photodynamic therapy.     

Variations in Toxic Metal Levels of Two Fish Species,Pomatomus saltatrix and Dicentrarchus labrax,and Risk Estimation for Children

The concentrations of five toxic metals were monthly determined in two fish species,obtained from fish markets in Turkey during 2010—2011.For the determinations,AAS and ICP-AES were used.The obtained lead concentrations for all studied Pomatomus saltatrix(mean 635μg·kg-1)and Dicentrarchus labrax(mean 463μg·kg-1)samples were found to be significantly higher than the maximum allowances concentration(MAC)of 300μg·kg-1.Mean chromium(324μg·kg-1)and Cu(940μg·kg-1)concentrations in Pomatomus saltatrix were higher than in Dicentrarchus labrax(268μg Cr·kg-1 and 600μg Cu·kg-1)while Ni in Pomatomus saltatrix(216μg·kg-1)was lower in Dicentrarchus labrax(291μg·kg-1).The estimated non-carcinogenic and carcinogenic health risks by the Target Hazard Quotient and target carcinogenic risk indicate that there are no sytemic effects,and the risk of developing cancer over a human lifetime is between 2~9in 1 000 000.     

Can Extensional Flow Rupture Macromolecules in an Electrospinning Process?

The fracture of high molecular weight poly(ethylene oxide) (PEO) chains under extensional stretching during the electrospinning of aqueous solutions was investigated by measuring solution viscosities and monitoring the change of molecular weight. The degree of macromolecular chain fractures in 1.0% polymer solutions increased with the increase in molecular weight. The strain rates for stretching and fracturing of macromolecules are critical for the degradation of polymers along with experimental elongational strain rates. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1051–1054     

Quantitative characterization of chemical degradation of heat‐treated wood surfaces during artificial weathering using XPS

The X‐ray photoelectron spectroscopy (XPS) study of three heat‐treated North American wood species (jack pine, birch and aspen) was carried out to evaluate chemical modifications occurring on the wood surface during artificial weathering for different times. The results suggest that the weathering reduces lignin content (aromatic rings) at the surface of heat‐treated wood, consequently, the carbohydrates content increases. This results in surfaces richer in cellulose and poorer in lignin. Heat‐treated wood surfaces become acidic due to weathering, and the acidity increases as the weathering time increases. Three possible reasons are given to account for the increase of acidity during weathering. The lignin content increases, whereas the hemicelluloses content decrease due to heat treatment. Heat‐treated woods have lower acidity to basicity ratios than the corresponding untreated woods for all three species because of the decrease in carboxylic acid functions mainly present in hemicelluloses. The wood composition changes induced by weathering are more significant compared to those induced by heat treatment at wood surface. Exposure to higher temperatures causes more degradation of hemicelluloses, and this characteristic is maintained during weathering. However, the wood direction has more effect on chemical composition modification during weathering compared to that of heat treatment temperature. The heat‐treated jack pine is affected most by weathering followed by heat‐treated aspen and birch. This is related to differences in content and structure of lignin of softwood and hardwood. The use of XPS technique has proved to be a reliable method for wood surface studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyhedral Analysis for Concentrator Location Problems

The concentrator location problem is to choose a subset of a given terminal set to install concentrators and to assign each remaining terminal node to a concentrator to minimize the cost of installation and assignment. The concentrators may have capacity constraints. We study the polyhedral properties of concentrator location problems with different capacity structures. We develop a branch and cut algorithm and present computational results.     

系综Monte Carlo方法

本文系统地给出了Monte Carlo模拟的一般方法在各种系综条件下的表述以及它们的算法。     

Development of enhanced ultrafiltration methodologies for the resolution of racemic benzoin

In the scope of achieving the separation of chiral molecules, enzyme enhanced ultrafiltration (EEUF), a new method based on polymer enhanced ultrafiltration (PEUF), utilizing apoenzymes as ligands, was developed. Benzoin was chosen as the model chiral molecule. Bovine serum albumin (BSA) and apo form of benzaldehyde lyase (BAL) (E.C. 4.1.2.38) were used as chiral ligands in PEUF and EEUF experiments, respectively. In order to bind to the target enantiomer well, the addition of ligand to the benzoin solution was followed by ultrafiltration. With the use of BSA as ligand, adaptation of PEUF for chiral target molecules and process parameter optimization was carried out; whereas, in EEUF studies the effect of ligand concentration was focused on. In PEUF experiments, although total benzoin retention values reached to 48.7% and 41.3% at pH 10, for 15% (v/v) PEG 400 and 30% (v/v) DMSO cosolvents, respectively; obtained enantiomeric excess (ee) % values were all less than 20%. In EEUF experiments, at BAL concentrations greater than 158 ppm, total benzoin retention and ee% remained constant at ca. 75% and 60%, respectively. On the other hand, at 61 ppm BAL concentration, total benzoin retention was kept at ca. 75%, but ee% decreased to ca. 30%, probably due to the nonspecific binding of benzoin to DNA and other proteins. Thus, the method developed enzyme enhanced ultrafiltration, functioned with its intended purpose effectively in chiral separation.