The reaction of phosphinyl radicals with 1,3-dienes

The stabilized radical, [(Me₃Si)₂CH]₂P·, reacts with 1,3-dienes to afford 1,4-diphosphino-2-butenes.     

Differential and total cross sections for proton impact excitation of He

An extended form of the Vainshtein-Presnyakov-Sobelman approximation is used to calculate differential and total cross sections for proton impact excitation of the n = 2 level in He. Agreement with experiment is very good.     

Graphene‐coated cotton fibers as a sorbent for the extraction of multiclass pesticide residues from water and their determination by gas chromatography with mass spectrometry

A straightforward functionalization procedure is proposed for synthesizing a cotton‐supported graphene as an extraction material, which is effectively employed for the extraction of multiclass pesticides from environmental waters prior to their determination by gas chromatography with mass spectrometry. Different experimental parameters that affect the extraction efficiency, including pH of the extraction, stirring rate, extraction time, ionic strength, presence of humic acid, sample volume, amount of sorbent, and elution conditions, were investigated and properly established. The advantages of the present extraction method are the simplicity of implementation, rapidity, and low consumption of sorbent per extraction. Moreover, the pesticides on the adsorbent are stable, under certain storage conditions, rendering the cotton‐supported graphene suitable for environmental field studies. The applicability of the cotton–graphene‐based procedure for routine analysis was demonstrated by the determination of pesticides in a lake water sample. The recoveries ranged from 83 to 107%, the limits of quantitation were in the range of 0.02–0.09 μg/L, and the calculated relative standard deviations varied from 3 to 8% (data obtained with the same batch of sorbent). Because of the acceptable analytical characteristics, the developed method shows great prospects in determining certain classes of pesticides in water.     

Comparison of topological, shape, and docking methods in virtual screening

Virtual screening benchmarking studies were carried out on 11 targets to evaluate the performance of three commonly used approaches: 2D ligand similarity (Daylight, TOPOSIM), 3D ligand similarity (SQW, ROCS), and protein structure-based docking (FLOG, FRED, Glide). Active and decoy compound sets were assembled from both the MDDR and the Merck compound databases. Averaged over multiple targets, ligand-based methods outperformed docking algorithms. This was true for 3D ligand-based methods only when chemical typing was included. Using mean enrichment factor as a performance metric, Glide appears to be the best docking method among the three with FRED a close second. Results for all virtual screening methods are database dependent and can vary greatly for particular targets.     

Co-electrospinning of core-shell fibers using a single-nozzle technique

Co-electrospinning is ideally suited for fabricating continuous fibers encasing materials within a polymer sleeve, but requires relatively complex coannular nozzles. A single-nozzle co-electrospinning technique is demonstrated using blends of poly(methyl methacrylate) (PMMA)/polyacrylonitrile (PAN) solutions in dimethylformamide (DMF). The as-spun fibers have outer diameters in the range of 0.5-5 microm and possess a core-shell structure similar to that attained via coannular nozzles. The technique relies on the precipitation of PMMA solution droplets, which become trapped at the base of the Taylor cone issuing the PAN solution jet from its tip. A theoretical analysis shows that the outer shell flow is sufficiently strong to stretch the inner droplet into the Taylor cone, thus forming a core-shell jet. The method seems attractive for technological applications involving macroscopically long and radially inhomogeneous or hollow nano/micro fibers.     

Hyperbolic balance laws with dissipative source relaxing to adiabatic conservation laws

The paper discusses the long time behavior of BV solutions to the Cauchy problem for hyperbolic systems of balance laws with partial dissipation, when the relaxed system is adiabatic.