The group of commutativity preserving maps on strictly upper triangular matrices

Let N = N _n (R) be the algebra of all n × n strictly upper triangular matrices over a unital commutative ring R. A map φ on N is called preserving commutativity in both directions if xy = yx ? φ(x)φ(y) = φ(y)φ(x). In this paper, we prove that each invertible linear map on N preserving commutativity in both directions is exactly a quasi-automorphism of N, and a quasi-automorphism of N can be decomposed into the product of several standard maps, which extains the main result of Y. Cao, Z. Chen and C. Huang (2002) from fields to rings.     

胶束毛细管电泳在线扫集技术同时分离测定穿心莲内酯和脱水穿心莲内酯的研究

采用胶束毛细管电泳在线扫集技术分离测定了中药穿心莲中脱水穿心莲内酯和穿心莲内酯.电泳条件:以20 mmol/L H3BO310 mmol/L NaH2PO4-50mmol/L SDS(含体积分数20%甲醇,pH 2.4)为电泳运行缓冲溶液,未涂层石英毛细管(58 cm×50 μm i.d.,有效长度为41.2 cm)为分离通道,重力进样,进样高度为11 cm,-20 kV恒压,检测波长为246 nm.富集倍数可以达到200倍以上.在5.70～91.20 mg/L,和3.96～31.68 mg/L范围内呈良好的线性关系,对两种内酯分别进行了定量分析.加标平均回收率脱水穿心莲内酯为100.80%,穿心莲内酯为98.06%.     

Binary and ternary recombination of para-H3(+) and ortho-H3(+) with electrons: state selective study at 77-200 K

Measurements in H(3)(+) afterglow plasmas with spectroscopically determined relative abundances of H(3)(+) ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77-200 K) para-H(3)(+) ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that H(3)(+) recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states. Electron-stabilized (collisional-radiative) recombination appears to make only a small contribution.     

Bioavailability of metallic impurities in carbon nanotubes is greatly enhanced by ultrasonication

Metallic impurities within carbon nanotubes (CNTs) are considered as the main cause of their toxicity. Ultrasonication is a common procedure used to purify and obtain homogeneous dispersions of CNTs as well as to mix them with other components for further processing into composites. Herein, the influence of ultrasonication upon the bioavailability of metallic impurities in CNTs was investigated. We showed that even ultrasonication times as short as 5?min significantly enhanced the bioavailability of metallic impurities, which can therefore interact more actively with biologically important molecules. These findings will have profound impact on the processing of CNTs as well as on nanotoxicity studies.     

Assessing calcareous sponges and their associated bacteria for the discovery of new bioactive natural products

An overview of the chemistry and microbiology of calcareous sponges (Calcispongiae) is provided, highlighting the potential of these sessile filter-feeding marine invertebrates and their associated bacteria for the discovery of new bioactive natural products. 103 compounds are presented and 116 references cited.     

Photoelectrocatalytic Oxidation of Glutathione Based on Porous TiO(2)-Pt Nanowhiskers

The performance of TiO(2) nanoparticles is extremely attractive in various areas of chemical and biochemical engineering as they can effectively work by combining the photocatalytic property with various superior properties of the related nanostructure. The relevant photoelectrochemical detection has attracted considerable interest and shown potential applications in a wide range of areas. In this study, we have prepared new nanowhiskers of platinum-doped titanium dioxide (TiO(2)-Pt), which could be further used to fabricate a novel nanointerface for the sensitive detection of biomolecules including glutathione (GSH). Our observations demonstrate that the sensitive TiO(2)-Pt nanowhiskers biointerface could be readily fabricated by casting the TiO(2)-Pt nanowhiskers suspension on a glassy carbon electrode (GCE), which could readily combine the photocatalytic and eletrocatalytic properties of TiO(2) nanocomposites to introduce a novel photoelectrocatalytic biosensor for GSH detection in real samples. Compared to other analysis strategies, the TiO(2)-Pt nanowhiskers-modified GCE showed a considerably high sensitivity for the detection of GSH due to the excellent photoelectrocatalytic ability of the porous TiO(2)-Pt nanowhiskers. Scanning electron microscopy (SEM), Raman spectroscopy, and electrochemical impedance spectroscopy have shown that Pt can readily blend with porous TiO(2) nanowhiskers and facilitate the relevant catalysis property of TiO(2), resulting in the enhanced photoelectrocatalytic effect. Thus, through the new strategy of the utilization of the excellent photoelectrocatalytic property of TiO(2)-Pt nanocomposites, it is possible to realize the rapid electrochemical detection of glutathione with high sensitivity, low cost, and good reproducibility.     

Enhanced solubilization of bovine serum albumin in reverse micelles by compressed CO2

The effect of compressed CO2 on the solubilization of bovine serum albumin (BSA) in water/sodium bis-(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles was studied by observing phase behavior and recording UV-visible spectra under different conditions. The pH values within the water cores of reverse micelles at different CO2 pressures were also determined. The solubilization capacity of the reverse micelles for the protein increased considerably as CO2 pressure increased within the low-pressure range, but decreased at higher CO2 pressures, so that the micelles eventually lost their ability to solubilize the protein. The effect of CO2 on the stability of the reverse micelles played an important role in the relationship between pressure and protein solubility. A "multicomplex" model was proposed to explain these effects. The different solublization capacities within different pressure ranges demonstrates the unique advantage of using compressed CO2 in the extraction of proteins with reverse micelles.     

Synthesis and growth mechanism of zirconia nanotubes by anodization in electrolyte containing Cl−

The formation and growth of a self-organized zirconia porous layer can be achieved directly by anodization of Zr in chloride containing electrolytes. The morphology of the porous layers is affected by electrochemical conditions such as Cl⁻ concentration. Zirconia nanotubes with diameters ranging from 250 to 300 nm and a length of 33 μm were formed under proper conditions. The nanotubes have smooth and straight walls. The composition of the nanotubes was characterized by using an energy dispersive spectrometer. Selected area electron diffraction investigation reveals that the as-anodized zirconia nanotubes have an amorphous structure. Crystal phase transition and structural stability of the ZrO₂ nanotubes after heat treatment were characterized. A possible growth mechanism is presented.     

2,4-二硝基酚分光光度法测定氯氮卓

在水溶液中 ,氯氮卓与 2 ,4 二硝基酚发生荷移反应 ,生成稳定的 1∶1的配合物 .最大吸收波长为 44 4nm ,表观摩尔吸光系数为ε =1.48× 10 3L/ (mol·cm) ,线性范围 3～ 96 μg/mL ,回收率为 99.95 %～ 99.97% ,相对标准偏差为 0 .5 5 %