PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Further conventions for NMR shielding and chemical shifts (IUPAC Recommendations 2008)

IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the (1)H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3-(trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating (13)C NMR chemical shifts in solids to the scales used for high-resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice.     

RESEARCH ON SOME CHARACTERISTICS AND IMPROVEMENTS OF A 70cm STREAMER CHAMBER

In this paper the influence of various proportion of Ne-He gases and the time delay on the quality of streamer tracks has been studied. The diameterand density of streamers under these mixed-gas conditions have been measured.
The time resolution of this streamer chamber was determined to be 2.1μs in 69% Ne+31% He+8×10^－8 SF₆, and as 177μs in pure neon by using the exponentially decreasing relation of streamer desity with delay time. The spatial resolution was determined to be 0.32mm in Ne+3×10^－8 SF₆ by measuring the streamer diameters, and the method of track standard deviation was also used.
Some results show that the diameter and brightness increase with increasing high voltage, but become rather even when high voltage continues increasing.
Photographs were taken with domestically produced special film (32 DIN, 60 lines/mm), being similar to Kodak SO-143.
A special designed central electrode of the streamer chamber with its wires inlaid in lucite plate is successful for preventing gas from breakdown near wires. Besides, delay time has been reduced to 1.3μs, mainly by the Marx generator and its trigger system the parameters of which have been chosen by a series of experiments.     

High Sensitive Long Period Fiber Grating Sensor for Detection of Nitrite

A high sensitive long period fiber grating(LPFG) sensor for the detection of nitrite is proposed, which is realized by coating multiple poly(sodium 4-styrensulfonate)(PSS) and poly(diallyldimethylammonium) chloride (PDDA) layers on the fiber grating surface. The sensitivity of this LPFG sensor is maximum when the number of assembled layers is 70. Under this condition, a nitrite concentration of 3×10-3 mol/L, which is lower than the National Food Additive Standard, 4.2×10-3 mol/L, can be distinguished. The s...     

Simultaneous determination of 20 food additives by high performance liquid chromatography with photo-diode array detector

An efficient and accurate analytical method was developed for the simultaneous determination of 20 synthetic food additives, including three sweeteners,seven food colorants,nine synthetic preservatives and caffeine,by high performance liquid chromatography (HPLC) with photodiode array detector(PDA).This method permits the detection of food additives at very low concentrations(0.005-0.150μg/mL).The applicability was verified by the determination of food additives present in various foodstuffs.     

用扫描电镜研究工程塑料的断裂行为

本文研究了工程塑料——聚碳酸酯及聚对苯二甲酸丁二醇酯的微观断裂行为。研究中采用了静载和动载破断实验,用扫描电镜观察断裂形态特征,并结合宏观力学试验过程分析其断裂行为。实验结果表明,热塑性工程塑料,在加载速率及环境温度固定条件下,其微观断裂行为受材料损伤体积空间分布的影响,材料损伤体积宏观空间分布范围宽,则大分子相互协同动作强,应变均匀,微观塑性形变差别小,断口表面趋于平坦;反之,大分子相互协同动作差,应变易于集中,微观塑性形变差异大,断口表面高低起伏大。     

万年蒿中二萜类化合物的结构研究

自菊科蒿属植物万年蒿(Artemisia Sacrorum Ledeb)地上部分首次分得三个贝壳杉烷型(Kauranetape)二萜类化合物,经理化常数测定及光谱分析(IR,’H-NMR,~(13)C-NMR,MS,二维核磁共振光谱)鉴定其结构分别为:3α,16α,17-三羟基贝壳杉烷[I],3α,16α-二羟基贝壳杉烷-17-0-β-D-葡萄糖甙[Ⅱ]和16α-羟基贝壳杉-3-酮-17-0-β-D-葡萄糖甙[Ⅲ]。其中[Ⅰ]为一新天然产物,[Ⅱ]为一未见报道的新化合物。通过对该三个化合物的~(13)C-NMR光谱分析,讨论了不同位置取代基对其~(13)C-NMR光谱化学位移的影响。     

Catalytic applications of nano β-PbO in Paal-Knorr reaction

Several 2,5-dimethyl-N-substituted pyrroles were prepared by the condensation of different substituted anilines with 2,5- hexanedione using nano lead oxide as an efficient and recyclable catalyst.All the synthesized compounds are confirmed through IR, ¹H NMR,¹³C NMR and mass spectral data.Nano lead oxide β-PbO（P85） was prepared by dissolving lead acetate dihydrate in 1- propanol at a pH 9.0 under stirring at 85℃.The structural study and surface morphology of the lead oxide（PbO） were characterized using X-ray diffraction（XRD）,Scanning electron microscopy（SEM） and the functional groups of the PbO sample were investigated using infrared spectrophotometer.