Promoting effect of sol-gel method and pre-treatment on the activity of SnO2/Al2O3 catalyst for NO reduction by propene

SnO₂/Al₂O₃ catalyst prepared by sol-gel method showed higher activity than those prepared by impregnation method, and their activity was significantly improved by pre-treatment in the reaction gas. The increased activity is closely related to the agglomeration of SnO₂ species and the re-exposure of Al₂O₃, which was previously covered by dispersed SnO₂ species. This revised version was published online in June 2006 with corrections to the Cover Date.     

苯酚、马尿酸和甲基马尿酸的反相高效液相色谱分析

本文提出了人体内苯、甲苯和二甲苯的代谢产物苯酚、马尿酸和甲基马尿酸的反相高效液相色谱分析法,讨论了其保留机制和样品预处理技术.以ODS为固定相,甲醇-水-醋酸为流动相时可实现良好分离.方法回收率为97.3%,相对标准偏差为1.02%.提出的方法可用于尿样分析,适用于临床与职业病防治的监测分析.     

利用1 064 nm激光预处理提高pickoff镜损伤阈值

 激光预处理是提高光学元件损伤阈值的有效方法之一。利用输出1 064 nm基频激光的SAGA激光器,采用光栅刻线式扫描的方式对镀多层高反物理膜的pickoff镜进行了能量周期递增的预处理,验证激光预处理对其损伤阈值的提高效果。结果表明：零几率损伤阈值平均提高38.8%,而50%几率损伤阈值提高了7.6%,经过激光预处理后pickoff镜抗损伤能力较处理前有了一定提高。     

Effects of Ultra-sonification Assisting Polyethylene Glycol Pre-treatment on the Crystallinity and Accessibility of Cellulose Fiber

In order to prepare the advanced cellulosic super-absorbent polymer with high grafting level, we tried the novel ultrasound wave assisting polyethylene glycol (PEG) pre-treatment method to decrease the crystallinity and increase the accessibility of cellulose fiber. The effects of ultrasonification assisting PEG method on the crystallinity and swelling capacity of cellulose fiber were investigated. To optimize the experimental condition, the Taguchi method was employed in the treatment process. The influence factors such as ultrasonic wave power, ultrasonic wave time and PEG molecular weight relative to the crystallinity of cellulose fiber were studied systematically. The degree of crystallinity of cellulose fiber was measured by wide-angle X-ray diffraction (WAXD). The morphology of cellulose fiber was observed by environment scanning electron microscopy (ESEM). The effects of pre-treatment variables on the water absorbency and water retention values of cellulose fiber were also investigated. The research results revealed that, under the optimal experimental condition (ultrasonic powder, 500 W; ultrasonic time, 150 s; PEG molecular weight, 600 g/mol), the crystallinity of cellulose fiber decreased from 72.16 to 42.95%. Accordingly, the absorbency of cellulose fiber increased from 1.436 to 2.063 g/g, and the water retention value increased from 47.21 to 113.4%. However, the morphology of cellulose fiber did not change thoroughly compared with the original cellulose fiber. It can be hypothesized that the original inter- and intra-macromolecular hydrogen bonds in cellulose network were weakened, resulting from the high level dispersion of PEG within cellulose network without breaking the surface morphology of fiber.     

Effects of process severity on the chemical structure of Miscanthus ethanol organosolv lignin

Ethanol organosolv lignin extracted from Miscanthus × giganteus with differing levels of severity (1.75 < CS<2.8) were subjected to comprehensive structural characterization by ¹³C, ³¹P NMR, FTIR spectroscopy and gel permeation chromatography. The results were compared to those from milled wood lignin from the same feedstock. The results showed that an increase in the severity of the treatment enhanced the dehydration reactions on the side chain and the condensation of lignin, increased the concentration of phenol groups and decreased the molecular mass of lignin fragments. It appeared that for the experimental conditions generally employed the cleavage of α-aryl ether bonds is primarily reaction responsible for lignin depolymerization under the organosolv conditions examined.     

Significant enhancement of the photoelectrochemical activity of TiO2 nanotubes

In the present work, we report on a facile and effective approach to significantly enhance the photocatalytic activity of TiO₂ nanotubes. The TiO₂ nanotubes prepared by the electrochemical oxidation of titanium in dimethyl sulfoxide (DMSO) with 2% HF were treated in a methanol solution under UV light irradiation. In comparison with the untreated TiO₂ nanotubes, the treatment resulted in a dramatic increase in the donor density of the TiO₂ nanotubes by approximately 3 orders of magnitude. The treated TiO₂ nanotubes exhibited a 15-fold enhancement in photocurrent and a 6.8-fold increase in the photoelectrochemical degradation of 4-nitrophenol, significant for hydrogen generation and wastewater treatment.     

Short monolithic columns for purification and fractionation of peptide samples for matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry analysis in proteomics

This study records a novel application of methacrylate-based monolithic columns for MALDI-TOF/TOF MS analyses in proteomics for pre-concentration and separation of peptides derived from protein digestion. Reversed-phase monolithic capillary columns (30 mm × 0.32 mm i.d.) were created inside the fused silica capillary via thermal-initiated free-radical polymerization of ethylene glycol dimethacrylate and lauryl methacrylate monomers in the presence of 1-propanol and 1,4-butandiol as a porogen system. The elution of peptides was achieved using a linear gradient of acetonitrile from 0 to 60% in water with 0.1% trifluoroacetic acid formed in a microsyringe. Individual fractions of separated peptides were collected on the MALDI target spots covered with alpha-cyano-4-hydroxycinnamic acid used as a matrix and then they were analyzed using MALDI-TOF/TOF mass spectrometry. The developed method was tested with a mixture of tryptic peptides from bovine serum albumin and its applicability was also tested for tryptic in-gel digests from barley grain extracts of water soluble proteins separated using SDS gel electrophoresis. The number of detected peptides was approximately three to four times higher compared to the analysis without previous separation. These results show an improved quality of sample information with the higher amount of identified peptides which increased protein sequence coverage and improved sensitivity of mass spectrometry measurements.     

Imidazole Processing of Wheat Straw and Eucalyptus Residues—Comparison of Pre-Treatment Conditions and Their Influence on Enzymatic Hydrolysis

Biomass pre-treatment is a key step in achieving the economic competitiveness of biomass conversion. In the present work, an imidazole pre-treatment process was performed and evaluated using wheat straw and eucalyptus residues as model feedstocks for agriculture and forest-origin biomasses, respectively. Results showed that imidazole is an efficient pre-treatment agent; however, better results were obtained for wheat straw due to the recalcitrant behavior of eucalyptus residues. The temperature had a stronger effect than time on wheat straw pre-treatment but at 160 °C and 4 h, similar results were obtained for cellulose and hemicellulose content from both biomasses (ca. 54% and 24%, respectively). Lignin content in the pre-treated solid was higher for eucalyptus residues (16% vs. 4%), as expected. Enzymatic hydrolysis, applied to both biomasses after different pre-treatments, revealed that results improved with increasing temperature/time for wheat straw. However, these conditions had no influence on the results for eucalyptus residues, with very low glucan to glucose enzymatic hydrolysis yield (93% for wheat straw vs. 40% for eucalyptus residues). Imidazole can therefore be considered as a suitable solvent for herbaceous biomass pre-treatment.     

Application of ultrasound technology in the drying of food products

This study presents a state-of-the-art overview on the application of ultrasound technology in the drying of food products, including the ultrasound pre-treatment and ultrasound assisted drying. The effect of main parameters and ultrasound technology on the drying kinetics and food quality were discussed. Inconsistencies were pointed out and analyzed in detail. Results showed that for ultrasound pre-treatment, the food products may lose or gain water and increase of ultrasonic parameters (sonication time, amplitude and ultrasound power) promoted the water loss or water gain. When ultrasound technology was applied prior to drying, an increase in drying kinetics was always observed, though some different results were also presented. For ultrasound assisted drying, the ultrasound power always gave a positive effect on the drying process, however, the magnitude of ultrasound improvement was largely dependent on the process variables, such as air velocity, air temperature, microwave power and vacuum pressure, etc. The application of ultrasound technology will somehow affect the food quality, including the physical and chemical ones. Generally, the ultrasound application can decrease the water activity, improve the product color and reduce the nutrient loss.     

Studies on the influence of surface pre-treatments on electroless copper coating of boron carbide particles

Boron carbide is one of the hard ceramic particles which find application as structural materials and neutron shielding material due to its high neutron capture cross section. Copper coating on boron carbide particle is essential for the synthesis of metal-ceramic composites with enhanced sinterability and dispersibility. Surface characteristics of the substrate and the coating parameters play a foremost role in the formation of effective electroless coating. The effect of surface pre-treatment conditions and pH on electroless copper coating of boron carbide particles has been studied. Surface pre-treatement of B₄C when compared to acid treated and alkali treated particles were carried out. Uniform copper coating was observed at pH 12 in alkali treated particles when compared to others due to the effective removal of inevitable impurities during the production and processing of commercially available B₄C. A threshold pH 11 was required for initiation of copper coating on boron carbide particles. The growth pattern of the copper coating also varies depending on the surface conditions from acicular to spherical morphology.