Development of the FTIR properties of nano-structure silica gel doped with different rare earth elements,prepared by sol-gel route

Structural characteristics of pure silica gel (silica-xerogel, SiO₂) and silica gel doped with some rare earth elements (REEs) such as, praseodymium Pr³⁺, and Europium Eu³⁺, Erbium Er³⁺ and Holmium Ho³⁺ ions, with different concentrations ranging from 1 up to 6%, in the form of monolith materials were prepared by sol-gel technique, Using tetra-ethoxysilane as precursor materials, which are of particular interest for sol-gel integrated optics applications. Some structural features of sol-gel derived monolith are analyzed, namely the structure of nano-particle momolith samples, based on X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR). We show that the XRD spectra of α-crystobalite are obtained for the pure samples at 1100°C and even by doping with the four REEs ions.     

偏氟乙烯的聚合反应

本文研究了用有机引发剂引发偏氟乙烯的水相聚合,并对制得的聚偏氟乙烯的性质进行了研究。有机引发剂引发聚合的聚偏氟乙烯的热稳定性、强度、结晶度和熔点均比用过硫酸盐引发聚合的聚偏氟乙烯高。     

Phase separation in the formation of hollow particles by suspension polymerization for divinylbenzene/toluene droplets dissolving polystyrene

Phase-separation behavior within polymerizing divinylbenzene/toluene droplet dissolving polystyrenes (PS) was investigated to clarify the formation mechanism of the hollow polymer particles by suspension polymerization. No hollow particles were obtained at a low content of low-molecular-weight PS where phase separation occurred at high conversion. On the other hand, hollow particles were obtained at a high content of high-molecular-weight PS where phase separation occurred at low conversion. The phase separation in an early stage of the polymerization, which was promoted by the presence of PS and cross-links of polydivinylbenzene, was a key factor for the formation of the hollow structure.     

磁疗手术胆结石的红外光谱观测

本文报道用Nicolet 170 SXFT-IR红外光谱仪观测磁疗手术胆结石、磁疗破碎排出胆结石及服中草药破碎胆结石的红外光谱,分析并比较了它们的光谱特征。     

Synthesis and Investigation of Indium Dodecatungstosilicate

Indium dodecatungstosilicate of the composition [In(OH)⋅5H₂O]₂ [SiW₁₂O₄₀]⋅H₂O is synthesized and studied by means of IR spectroscopy, thermogravimetry, and X-ray phase analysis. The crystals of this compound are triclinic, space group P1, a 13.079(3), b 13.795(3), c 13.967(3) Å, α 90.08(3)°, β 103.76(3)°, ψ107.76(3)°, Z 2, and π_calc 4.900 g cm⁻³.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 21–23.Original Russian Text Copyright © 2005 by Kaziev, Dutov, Quinones, Ita, Sychkin.     

Modeling the reaction mechanisms for redox regulation of protein tyrosine phosphatase 1B activity

Protein tyrosine phosphatase 1B (PTP1B) functions by removing the phosphoryl group from tyrosinephosphorylated proteins in insulin signaling and metabolism. The regeneration of the active site involves a sulphenylamide intermediate derived from the intrastrand cross-linking between the catalytic serine and the neighboring backbone nitrogen. Two mechanisms have been proposed for the formation of the sulphenylamide intermediate and the subsequent reactivation of the catalytic site. In the current work, the proposed mechanisms have been investigated by the use of density functional theory calculations. Our results suggest that these two mechanisms have similar overall energy barriers and that the preferred route will be determined by the availability of hydrogen peroxide or other oxidizing reagents.     

Water as an Efficient Solvent for Oxygenation Transformations with 34% Hydrogen Peroxide Catalyzed by some Heteropolyoxometalates

Summary. A highly efficient, selective, fast, and cheap protocol is developed for oxidation of aromatic amines and alcohols utilizing 34% hydrogen peroxide in water catalyzed by some W- and Mo-based heteropolyoxometalates. Findings showed that dodecatungstophosphoric acid, H₃PW₁₂O₄₀, was the most efficient catalyst in the examined oxidation reactions. This methodology may prove to be a valuable alternative for eco-friendly green oxidation. Inherent simplicity, easy work up, and using regenerable catalysts were other key aspects of this oxidation protocol.     

Identification of a chemical indicator of the rupture of 1,4-β-glycosidic bonds of cellulose in an oil-impregnated insulating paper system

In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded (TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with 2-furfuraldehyde, which is the current reference in the domain.     

Organic–inorganic nanocomposites prepared from fluoro-aramid and silica

Fluoro-aramid-based sol/gel-derived nanocomposites were synthesized by condensing a mixture of 4,4′-(hexafluoro-isopropylidene)dianiline and 1,3-phenylenediamine with terephthaloylchloride (TPC) in dimethylacetamide. TPC was added in slight excess to produce amide chains with carbonyl chloride end groups and then replaced with alkoxy groups using aminophenyltrimethoxysilane to develop bonding with the silica network. Mechanical, dynamic mechanical thermal, water absorption and morphological measurements were carried out on the thin hybrid films. Increase in the tensile strength and modulus was observed as compared to pristine polyamide. The thermal decomposition temperature was found in the range of 400–500 °C. The water absorption was found to be reduced with higher silica content. The glass transition temperature and the storage moduli increased with increasing silica concentration. The maximum increase in the T _g value (345 °C) was observed with 20 wt% silica. Scanning electron microscopy revealed the uniform distribution of silica in the matrix with an average particle size ranging from 8 to 50 nm.     

酞菁锰-表面活性剂薄膜电极的电化学表征及其对三氯乙酸的电化学催化作用的研究

将酞菁锰（ＭｎＰｃ）掺入阳离子表面活性剂双十二烷基二甲基溴化铵（ＤＤＡＢ）的氯仿溶液，并涂布于热解石墨电极表面，待氯仿挥发后即制得ＭｎＰｃ－ＤＤＡＢ薄膜电极。循环伏安实验表明，在ＫＢｒ溶液中，该薄膜电极有两对还原氧化峰，第一对峰的Ｅｐｃ１＝－０．２７Ｖ，Ｅｐａ１＝０．０１Ｖ；第二对峰的Ｅｐｃ２＝－０．７６Ｖ，Ｅｐａ２＝－０．６２Ｖ（ｖｓ．ＳＣＥ）。本文着重探讨了第二对峰的电化学行为，估计了该体系的电荷传递扩散系数Ｄｃｔ和表观非均相电极反应速率常数Ｋ０′等电化学参数，并可将该薄膜电极用于催化三氯乙酸的电化学还原。