Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

数学史上的三次重大危机

在教学发展史上,无理数的出现,无穷小量以及集合悖论的困惑,引起人们极大的混乱,给数学的发展以深刻的影响,俗称数学史上的三次重大危机。依据历史事实研究它们产生和突破的过程,从中分析理论和实践的关系,数学与逻辑的关系,运用唯物辩证法来指导数学的教学与研究工作。     

Ferritinophagy and α-Synuclein: Pharmacological Targeting of Autophagy to Restore Iron Regulation in Parkinson’s Disease

A major hallmark of Parkinson’s disease (PD) is the fatal destruction of dopaminergic neurons within the substantia nigra pars compacta. This event is preceded by the formation of Lewy bodies, which are cytoplasmic inclusions composed of α-synuclein protein aggregates. A triad contribution of α-synuclein aggregation, iron accumulation, and mitochondrial dysfunction plague nigral neurons, yet the events underlying iron accumulation are poorly understood. Elevated intracellular iron concentrations up-regulate ferritin expression, an iron storage protein that provides cytoprotection against redox stress. The lysosomal degradation pathway, autophagy, can release iron from ferritin stores to facilitate its trafficking in a process termed ferritinophagy. Aggregated α-synuclein inhibits SNARE protein complexes and destabilizes microtubules to halt vesicular trafficking systems, including that of autophagy effectively. The scope of this review is to describe the physiological and pathological relationship between iron regulation and α-synuclein, providing a detailed understanding of iron metabolism within nigral neurons. The underlying mechanisms of autophagy and ferritinophagy are explored in the context of PD, identifying potential therapeutic targets for future investigation.     

油-气管道检测机器人技术现状及展望

为提高油-气管道检测的效果,结合国内外典型管道机器人的特点,综合分析了管道机器人运动控制技术、定位技术和实时检测技术3个方面的现状,并指出了核心技术的不足;针对石油化工行业高温带压管道环境,提出管道检测机器人的研究重点为分层模糊神经网络运动控制技术、CCD视觉定位技术、低频电磁定位技术和分层图像分割的优化方法等。为进一步提高化工油-气管道内检测机器人的检测效果提供了理论依据。     

Enhancing compatibilizer function by controlled distribution in hydrophobic polylactic acid/hydrophilic starch blends

Various polylactic acid (PLA)/cornstarch blends, with and without the compatibilizer methylenediphenyl diisocyanate (MDI), were prepared by melt processing using a twin‐screw extruder. In the blends where it was included, MDI was distributed in either the PLA or starch phase through controlling processes conditions. The effects of MDI inclusion and its distribution on the resultant microstructures, mechanical properties, and thermal and rheological behaviors of the blends were studied via scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, mechanical testing, and Haake rheometer. The results showed that when the MDI was distributed in the starch phase before blending with PLA, the highly reactive isocyanate groups in the MDI were most probably consumed by water, resulting in an overall weakening of its compatibilizing effect. However, when the MDI was distributed in the PLA phase before blending with starch, modulus, yield strength, and impact strength were all increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of pigmentation on siloxane–polyurethane coatings and their performance as fouling-release marine coatings

Siloxane–polyurethane paints were formulated and characterized for coating properties and performance as fouling-release (FR) marine coatings. Paints were formulated at 20 and 30 pigment volume concentrations with titanium dioxide, and aminopropyl-terminated poly(dimethylsiloxane) (APT-PDMS) loadings were varied from 0 to 30% based on binder mass. The coatings were characterized for water contact angle, surface energy (SE), gloss, and pseudobarnacle (PB) adhesion. The assessment of the FR performance compared with polyurethane (PU) and silicone standards through the use of laboratory biological assays was also performed. Biofilm retention and adhesion were conducted with the marine bacterium Cellulophaga lytica, and the microalgae diatom Navicula incerta. Live adult barnacle reattachment using Amphibalanus amphitrite was also performed. The pigmented coatings were found to have properties and FR performance similar to those prepared without pigment. However, a higher loading of PDMS was required, in some cases, to obtain the same properties as coatings prepared without pigment. These coatings rely on a self-stratification mechanism to bring the PDMS to the coating surface. The slight reduction in water contact angle (WCA) and increase in pseudobarnacle release force with pigmentation suggests that pigmentation slowed or interfered with the self-stratification mechanism. However, increasing the PDMS loading is an apparent method for overcoming this issue, allowing for coatings having similar properties as those of clear coatings and FR performance similar to those of silicone standard coatings.     

Termini and main-chain composition of monomethoxy-terminated poly(ethylene glycol) studied by two-dimensional column chromatography

Samples of poly(ethylene glycol) especially those with functionalized ends have dimeric, trimeric, and tetrameric components at twice, three times, and four times as high a molecular weight (MW) as that of the main component. We used two-dimensional column chromatography to evaluate the MW and identify the terminal groups in each component. The first step is high osmotic pressure chromatography to prepare a sufficient amount of fractions that contain different percentages of the multimeric components. In the second step, each of the fractions was characterized by using regular size exclusion chromatography and high-resolution NMR. Decomposition of the chromatogram combined with isolation of the terminal methoxy peak in the NMR spectrum led to unique identification of the terminal groups. We thus found that the monomeric component is monomethoxy-terminated whereas the dimeric and other multimeric components are mostly dihydroxy-terminated.     

(Z,Z)-4,7-tridecadien-(S)-2-yl acetate: sex pheromone of Douglas-fir cone gall midge,Contarinia oregonensis

Our objectives were to identify and field test the sex pheromone of female Douglas-fir cone gall midge, Contarinia oregonensis (Diptera: Cecidomyiidae). Coupled gas chromatographic–electroantennographic detection (GC-EAD) analyses of pheromone extract revealed a single compound (A) that elicited responses from male antennae. Hydrogenation of pheromone extract, followed by renewed GC-EAD analysis, revealed a new EAD-active compound with chromatographic characteristics identical to those of tridecan-2-yl acetate on five fused silica columns (DB-5, DB-210, DB-23, SP-1000, and Cyclodex-B). Syntheses, chromatography, and retention index calculations of all possible tridecen-2-yl acetates suggested that the candidate pheromone A was a tridecadien-2-yl acetate with nonconjugated double bonds. Synthetic candidate pheromone component (Z,Z)-4,7-tridecadien-2-yl acetate (Z4Z7) cochromatographed with A on all analytical columns and elicited comparable antennal activity. In GC-EAD analyses that separated the enantiomers (Z,Z)-4,7-tridecadien-(S)-2-yl acetate (2S-Z4Z7) and (Z,Z)-4,7-tridecadien-(R)-2-yl acetate (2R-Z4Z7) with baseline resolution, only 2S-Z4Z7 as a component in a racemic standard or in pheromone extract elicited antennal responses. In Douglas-fir seed orchards, sticky traps baited with 2S-Z4Z7 captured male C. oregonensis, whereas 2R-Z4Z7 was behaviorally benign. Comparable catches of males in traps baited with racemic Z4Z7 (50 g) or virgin female C. oregonensis suggested that synthetic pheromone baits could be developed for monitoring C. oregonensis populations in commercial Douglas-fir seed orchards.     

Characterization of the adipose tissue atrophy induced by peroxisome proliferators in mice

In the present study, we characterized the effects of peroxisome proliferators (PP) on adipose tissue in mice. Treatment with potent PP, such as perfluorooctanoic acid (PFOA), 2-methyl-2-(p(1,2,3,4-tetrahydroxy-naphthyl)-phenoxy)propionic acid, (4-chloro-6-(2,3-xylidino)2-pyrimidinylthio) acetic acid, and di(2-ethylhexyl)phthalate, caused dramatic decreases in adipose tissue weight, whereas the moderately potent PP, acetylsalicylic acid, had a relatively weak effect. This decrease in weight reflects a loss of fat from adipocytes rather than a loss of cells, as demonstrated by constant DNA content. The dose-dependency and time-course experiments indicate that peroxisome proliferation occurs simultaneously with or prior to adipose tissue atrophy. Thus, hepatic peroxisome proliferation might result in the increased mobilization of lipids and lipid utilization in liver. The enhanced adipose tissue hormonesensitive lipase (HSL) activity and down-regulated lipoprotein lipase (LPL) activity observed upon PP treatment might, at least in part, explain the loss of fat via increase FA release from adipocytes and/or decreased FA uptake from the circulation, respectively. In addition, the possible involvement of the increased tumor necrosis factor α expression found upon PFOA treatment in reducing the insulin sensitivity of adipose tissue and thereby altering LPL and HSL activities is discussed.     

耐盐型聚丙烯酸钠高吸水树脂的合成研究

以过硫酸铵(APS)为引发剂,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,采用反相悬浮乳液聚合法合成了丙烯酸(AA)-丙烯酰胺(AM)-2-丙烯酰胺基辛烷基磺酸钠(NaAMC8S)三元共聚高吸水树脂,研究了引发剂含量、交联剂含量、AA中和度对树脂吸液性能的影响。结果表明:磺酸基单体NaAMC8S的加入显著提高了吸水树脂的盐水吸收能力,当引发剂含量为0.2%,交联剂含量为0.02%,中和度为75%,加入NaAMC8S为0.5%时,共聚树脂吸自来水的量为601mL/g,吸0.9%Nacl水溶液的量为154mL/g。