Telomerization by free-radical mercaptan chain transfer. IV. Effects of structure,solvent and initiator variation on the stereochemistry of acrylate ester–mercaptan telomers

Chain-transfer constants for radicals one to five units in length were determined for the methyl acrylate–isopropanethiol system. Effects of varying ester alkyl group, mercaptan solvent and initiator on three-unit diastereomer ratio were also investigated. It was found that the proportion of syndiotactic isomer increased as the size of either the ester alkyl group or the mercaptan increased, the latter result being equivalent to a penultimate effect. Polar solvents, on the other hand, favored the formation of the isotactic form. This effect was observed in the free-radical telomerization and to an even greater degree in the base-initiated anionic telomerization. Possible reasons for solvent effects are discussed.     

Satisfactory solution concepts and their relations for Stochastic Multiobjective Programming problems

This work deals with the concept of satisfactory solution for Stochastic Multiobjective Programming (SMP) problems. Based on previous literature, we will introduce different concepts of satisfactory solutions for SMP problems, define a new concept of solution (where the decision maker (DM) sets his/her preferences in terms of two aspiration levels for the stochastic objective and two probabilities to reach those levels), and establish some relationship between these concepts. The results will aim at featuring these concepts and determine the differences between them. Moreover, the paper proposes a new step by step procedure to exchange information between the analyst and DM prior to solving the problem. Thus, the DM will be able to choose the transformation criterion for each stochastic objective and the aspiration level.     

New Insights into Sulfur Deposition on Gold Using Dithiobisphthalimide as a New Precursor

Dithiobisphthalimide is used as a new precursor for the spontaneous deposition of sulfur on gold surfaces in acetonitrile. Characterization of the modified surfaces is achieved using X‐ray photoelectron spectroscopy (XPS), electrochemistry and scanning tunneling microscopy (STM). The reported results indicate that the sulfur deposition is an efficient and fast process and that high coverages can be reached very quickly. Sequential high‐resolution STM in air allows the direct observation, for the first time, of the mobility of the usually observed rectangular structures as individual units. It also shows the reversible association/dissociation of these rectangles. The nature of these structures is highly debated in the literature and the present work provides new insights into their nature through the use of a new sulfur precursor under non‐traditional conditions. To explain our results we consider these structures as simple sulfur adlayers on the gold surface.     

Recent advances in surface engineering of superparamagnetic iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising materials for various biomedical applications including targeted drug delivery and imaging, hyperthermia, magneto-transfections, gene therapy, stem cell tracking, molecular/cellular tracking, magnetic separation technologies (e.g. rapid DNA sequencing), and detection of liver and lymph node metastases. The most recent applications for SPIONs for early detection of inflammatory, cancer, diabetes and atherosclerosis have also increased their popularity in academia. In order to increase the efficacy of SPIONs in the desired applications, especial surface coating/characteristics are required. The aim of this article is to review the surface properties of magnetic nanoparticles upon synthesis and the surface engineering by different coatings. The biological aspects, cytotoxicity, and health risks are addressed. Special emphasis is given to organic and inorganic-based coatings due to their determinant role in biocompatibility or toxicity of the final particles.     

Crystal Structure,Thermal Analysis and IR Spectroscopic Investigation of Bis Benzyl Ammonium Monohydrogentetraoxoarsenate(V) Monohydrate

Abstract  

The salt bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate [C₆H₅CH₂NH₃ ⁺]₂HAsO₄ ²⁻·H₂O, M = 373.92, Triclinic, P−1. a = 6.514(1), b = 8.910(2), c = 15.061(3) ?, α = 99.26(2), β = 93.93(1), γ = 97.64(1)°, V = 851.5(3), Z = 2, D _x  = 1.460, λ (MoKα) = 0.71073 ?, μ = 0.99 mm⁻¹, F(000) = 126, T = 20(2)  °C, final R = 0.673 for 5488 unique reflections. Planes of HAsO₄ ²⁻ alternate with planes of C₆H₅CH₂NH₃ ⁺ groups. The structure consists of infinite parallel two-dimensional planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers. Differential scanning calorimetry study on bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate was carried out. The infrared of polycrystalline samples of this compound have been recorded at room temperature.     

Light neutralino dark matter in the pMSSM

We present an investigation of the dependence of searches for boosted Higgs bosons using jet substructure on the perturbative and non-perturbative parameters of the Herwig++ Monte Carlo event generator. Values are presented for a new tune of the parameters of the event generator, together with the an estimate of the uncertainties based on varying the parameters around the best-fit values.     

A New Procedure to Measure Near Yield Residual Stresses Using the Deep Hole Drilling Technique

Mechanical strain relief techniques for estimating the magnitude of residual stress work by measuring strains or displacements when part of the component is machined away. The underlying assumption is that such strain or displacement changes result from elastic unloading. Unfortunately, in components containing high levels of residual stress, elastic-plastic unloading may well occur, particularly when the residual stresses are highly triaxial. This paper examines the performance of one mechanical strain relief technique particularly suitable for large section components, the deep hole drilling (DHD) technique. The magnitude of error is calculated for different magnitudes of residual stress and can be substantial for residual stress states close to yield. A modification to the technique is described to allow large magnitudes of residual stress to be measured correctly. The new technique is validated using the case of a quenched cylinder where use of the standard DHD technique leads to unacceptable error. The measured residual stresses using the new technique are compared with the results obtained using the neutron diffraction technique and are shown to be in excellent agreement.     

Antibacterial and antioxidant properties of phyto-synthesized silver nanoparticles using Lavandula stoechas extract

Due to environmentally friendly and cost- effective issues, biological methods for silver nanoparticles (AgNPs) synthesis are advantageous over chemical and physical ones. In this study, AgNPs synthesized using Lavandula stoechas extract as a reductant and its antioxidant capacity, antibacterial property and cytotoxicity effect were investigated. The phyto-synthesized AgNPs were characterized using various analyses such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) as well as Fourier transform infrared (FT-IR). The prepared nanoparticles were spherical on shape with the size about 20–50 nm. Antibacterial studies through agar disk diffusion method confirmed the antibacterial potential of phyto-synthesized AgNPs toward two clinical Staphylococus aureus and Pseudomonas aeruginosa bacteria, although MTT assay demonstrated that S. aureus (MIC = 125 μg/ml) was more susceptible to AgNPs than P. aeruginosa (MIC = 250 μg/ml). Moreover, the cytotoxicity assay of phyto-synthezied AgNPs showed a low cytotoxic effect on RAW264 cell line at 62.5 μg/ml as an effective concentration. Also the considerable antioxidant capacity of the AgNPs confirmed through DPPH assay. Great antibacterial and antioxidant properties along with biocompatibility make the suggested phyto-synthesized AgNPs a great candidate for different biomedical applications including wound healing.     

Multi-shock structure of roll wavesStructure multi-chocs d'ondes à rouleaux

The special class of periodic travelling waves which is known as roll waves is investigated for nonhomogeneous hyperbolic equations of gas dynamics type. In this Note these equations are applied to shallow water flows in inclined open channels, but the results obtained are more general and far-reaching. The necessary conditions for the existence of a roll wave are derived. It is shown that for a nonconvex pressure term, multi-shock configurations of roll waves of finite amplitude exist. A new type of periodic travelling wave, which corresponds to the slug flow regime in two-layer flows, is found. To cite this article: A. Boudlal, V.Yu. Liapidevskii, C. R. Mecanique 332 (2004).     

Rapid Sonosynthesis of N‐Doped Nano TiO2 on Wool Fabric at Low Temperature: Introducing Self‐cleaning,Hydrophilicity, Antibacterial/Antifungal Properties with low Alkali Solubility,Yellowness and Cytotoxicity

Nano nitrogen‐doped titanium dioxide was rapidly prepared by hydrolysis of titanium isopropoxide at 75–80°C using in situ sonochemical synthesis by introducing ammonia. Various concentrations of titanium isopropoxide were examined to deposit nano nitrogen‐doped titanium dioxide through impregnation of the wool fabric in ultrasound bath followed by curing. The antibacterial/antifungal activities of wool samples were assessed against two common pathogenic bacteria including Escherichia coli and Staphylococcus aureus and the diploid fungus Candida albicans. The sonotreated wool fabrics indicated no adverse effects on human dermal fibroblasts. The presence of nanoparticles on the sonotreated wool fabrics were confirmed by FE‐SEM images and EDS patterns and X‐ray mapping and the crystalline size of nanoparticles were estimated through XRD results. The role of both pH and precursor concentration on the various properties of the fabric was investigated and the optimized conditions introduced using response surface methodology.