Development and physicochemical characterization of modified polymeric surfaces for bacterial adhesion

Radiation‐induced graft polymerization was used to modify the surfaces of polypropylene (PP) sheets for bacterial adhesion. For the experiments, two monomers were mixed: the quaternary ammonium salt (QAS) [2‐(methacryloyloxy)ethyl]trimethylammonium chloride and acrylic acid (AAc). The PP sheets were activated by electron‐beam radiation before the grafting reaction. Different AAc/QAS comonomer mixture ratios (50 : 10, 40 : 20, 30 : 30, 20 : 40, and 10 : 50) were used to determine the degree of grafting and to make the PP surfaces hydrophilic. The graft level increased with an increase in the percentage of AAc in the comonomer mixtures. Synergism was investigated during graft polymerization to quantify the poly(acrylic acid) and poly{[2‐(methacryloyloxy)ethyl]trimethylammonium chloride} graft fractions in the resulting graft copolymers. An approximation of the graft fractions was made with an analytical technique based on acid–base volumetric titration. The wettability of the modified surfaces was determined by the measurement of the water contact angles. The surfaces prepared with higher percentages of QAS in the comonomer mixtures had lower contact angles than those prepared with lower percentages of QAS. The presence of oxygen and nitrogen on the modified PP surfaces was investigated with X‐ray photoelectron spectroscopy. Structural changes in unmodified and modified PP were characterized with differential scanning calorimetry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

人脸特征点定位的自适应窗回归方法

针对显式形状回归（ESR）对于一些面部遮挡、面部表情过大样本定位精度低的问题，提出一种自适应窗回归方法。首先，应用先验信息为每张图片生成精确的人脸框，用人脸框的中心点对人脸进行特征映射，并进行相似变换得到多个初始形状；其次，提出一种自适应窗口调整策略，基于先前回归的均方误差自适应地调整特征窗口大小；最后，基于互信息（MI）的特征选择策略，提出新的相关性计算方法，在候选像素集中选出最相关的特征。在三个公开数据集LFPW、HELEN、COFW上，相较于ESR算法，所提方法的定位精度分别提升7.52%、5.72%和5.89%。实验结果表明，自适应窗回归方法可以有效提高人脸特征点定位精度。     

Effect of iron counter-ions on the redox properties of the Keggin-type molybdophosphoric heteropolyacid Part I. An experimental study on isobutane oxidation catalysts

Keggin-type molybdophosphoric heteropolyacid with protons partially substituted by iron cations in a bulk form (Fe_0.85H_0.45PMo₁₂O₄₀) or supported on the cesium salt (Cs₂Fe_0.2H_0.4PMo₁₂O₄₀) have been synthesized and characterized by different techniques like the Mössbauer spectroscopy and the electron spin resonance (ESR). The effect of iron on the redox and catalytic properties for the oxidation of isobutane into methacrylic acid (MAA) has also been studied. Iron has been shown to have a different effect whether acts as a counter-cation in the bulk acid or in the acid supported on the cesium salt. In the first case, it increases both the selectivity in methacrylic acid and methacrolein (MA) and the activity of the acid phase whereas in the second case, it increases only the selectivity. This difference has been explained by the existence of an electron transfer between iron and molybdenum occurring only in the bulk acid. This electron transfer was related to a combined hydration-oxidation mechanism which promotes the reducibility of the solid and consequently its catalytic activity.     

铸造高速钢轧辊研究进展与前景展望

介绍了铸造高速钢轧辊的主要制造方法和使用效果，其中着重介绍了ＣＰＣ工艺制造高速钢轧辊的性能、特点、存在的问题及改进方向。     

低温电子自旋共振Al芯测年

对低温Ａｌ芯电子自旋共振测年进行了初步的探讨。在９８Ｋ的低温条件下，得到了分辨率较高的Ａｌ芯ＥＳＲ全峰图形。通过对三块不同深度的花岗片麻岩中Ａｌ芯的测定，从浅到深分别得到１．１４，１．１０，０．５０Ｍａ的实验结果。这个结果与岩石形成的地质背景相一致。由此证明用ＥＳＲ的Ａｌ芯来测定浅成变质岩的年龄是完全可行的。     

冷却水温对GH4169合金电渣重熔凝固过程参数的影响

借助模拟软件MeltFlow,模拟了GH4169合金电渣重熔凝固过程参数的变化,分析了冷却水温变化对凝固过程参数的影响.结果表明,凝固过程参数随冷却水温的升高变化不明显；凝固过程参数沿重熔锭中心至边缘随冷却速度增大逐渐减小；局部凝固时间、二次枝晶间距、Rayleigh数变化趋势一致,在判断凝固组织优劣方面是等同的；计算模拟结果与硫印实验结果吻合良好.     

Radical annihilation of γ‐ray‐irradiated contact lens blanks made of a 2‐hydroxyethyl methacrylate copolymer at elevated temperatures

The annihilation of the radicals in irradiated 2‐hydroxyethyl methacrylate copolymer was analyzed by the use of electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra were deconvoluted into three radicals: a quartet (Ra), a triplet (Rb), and a broad singlet (Rc). Radical Ra was attributed to coupling with a methyl radical and/or a doublet or triplet with about the same hyperfine coupling due to a methylene radical. Radical Rb was due to a methylene radical produced by main‐chain scission. Radical Rc was attributed to various free radicals without coupling to protons. By comparing the EPR spectra of radicals Ra, Rb, and Rc with the spectrum of a 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) standard with a known spin number, we calculated the spin numbers of the radicals, which decreased with time in the temperature range 25–45°C, regardless of the irradiation dose. The annealing of Ra and Rb and the annealing of Rc at longer times followed second‐order kinetics; these were different from the kinetics for the color formation and defect‐controlled hardening of polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of sage and garlic on lipid oxidation in high-pressure processed chicken meat

Sage was found to protect minced chicken breast processed with high hydrostatic pressure up to 800 MPa for 10 min against lipid oxidation during subsequent chilled storage for 2 weeks. Garlic showed prooxidative effects especially at moderate high pressure around 300 MPa, an effect partly counteracted by simultaneous addition of sage. From the rate of lipid oxidation, measured as thiobarbituric acid reactive substances, the apparent volume of activation for pressure-induced lipid oxidation during subsequent chilled storage was estimated, which showed that the prooxidative effect of garlic and pressure-induced lipid oxidation were additive. Based on electron spin resonance (ESR) spectroscopy radical formation was measured in pressurized lipid and aqueous phases of minced chicken thighs, and a high radical scavenging capacity of sage in the lipid phase was identified as most important for the protective effect of sage.     

Investigation on photogenerated radicals of some carboxylates in solution and in aqueous dispersions of AgBr

Abstract

The photogenerated free radicals from formate, oxalate and acetate in aqueous solutions without and with dispered AgBr grains under illuminations of 355 nm laser light, natural light and monochromatic red, green or blue light were detected by electron spin resonance with spin-trap DMPO. The results showed that: (a) ·CO₂^? radicals were produced in the formate solution by all of these illuminations; (b) the signals of ·CO₂^? radicals were greatly intensified when an AgBr dispersion was present in the formate solution; (c) the signals of ·CO₂^? radicals in the oxalate solution were also detected and intensified when an AgBr dispersion was present, but only after illumination by the 355 nm laser; (d) ·CH₃ radicals, instead of ·CO₂^?, were weakly detected in the acetate solution, but only in the presence of AgBr under illumination by the 355 nm laser. The photochemical behaviour of these carboxylates, particularly formate and oxalate, perhaps implies their capability for trapping photogenerated holes and their potential for acting as a hole converter to an effective electron carrier.     

Structure of Drawn Gel-Crystallized UHMWPE as Revealed by Spin-Probe Technique

Abstract

The volume distribution and molecular dynamics of spin-probe (nitroxyl radical) in the gel-crystallized UHMWPE of different draw ratios (DR = 12,100) have been investigated. The spin-probes were found to occupy approximately 50% of the polymer volume in the necked samples and 20–30% in the samples drawn up to DR = 100. The mobility of the spin-probe in the samples studied is higher than that in the drawn and even in the undrawn samples of conventional melt-crystallized PE. This fact along with a low value of activation energy of spin-probe rotation (less than 10 kJ/mole) enables a conclusion that the regions of spin-probe localization are those with a significantly reduced density, such as pores, for examples. The analysis of the data obtained and the results of the structural study of the gel-crystallized samples by a SAXS and WAXS technique suggest that these pores are localized in interfibrillar space.