Fragmentation of 2,2,2-triphenylethoxychlorocarbene: evidence for ultrafast fragmentation-rearrangement in excited diazirines

[reaction: see text] Photolysis of 3-(2,2,2-triphenylethoxy)-3-chlorodiazirine gives 2,2,2-triphenylethoxychlorocarbene which fragments with 1,2-phenyl migration and loss of CO and Cl(-) to yield the 1,1,2-triphenylethyl cation and thence 1,1,2-triphenylethene by proton loss. However, ps and fs laser flash photolysis provides evidence that up to 25% of the alkene product stems from carbocation that arises directly from excited diazirine rather than from the carbene.     

位移和速度反馈的数学模型及实现方法

本文提出了位移和速度同时反馈的数学模型 .并给出了位移和速度反馈的实现方法 ,该方法用传统的差动变压器实现了位移和速度的同时反馈     

Surface modification of polypropylene microfiltration membranes by graft polymerization of N-vinyl-2-pyrrolidone

A hydrophilic polymer, poly(N-vinyl-2-pyrrolidone), was tethered on the surface of polypropylene microfiltration membrane (PPMM) by UV photo-assisted and γ-ray pre-irradiation induced graft polymerizations. Results revealed that the γ-ray pre-irradiation graft polymerization was more efficient in view of the grafting degree. The chemical changes of the membrane surface were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Pure water contact angle on poly(N-vinyl-2-pyrrolidone)-grafted PPMM decreased with the increase of grafting degree, which indicated an enhanced hydrophilicity for the modified membrane. Both bovine serum albumin adsorption and static platelets adhesion were measured to evaluate the bio-compatibility of the poly(N-vinyl-2-pyrrolidone)-modified PPMM. The statistical amounts of adsorbed bovine serum albumin and adhered platelets on unit membrane area decreased significantly, which to a certain degree demonstrated that the hemocompatibility of PPMM was improved. The N₂ permeability and the mean pore diameters of different PPMMs increased at first, then decreased after certain grafting degree. The changes of water flux followed a similar tendency. These indicated that at low grafting degree pore degradation induced by γ-ray irradiation had a major impact on permeability, while this was overcompensated by the grafted polymer at high grafting degrees.     

LD泵浦固体激光器基模振荡光的场分布噪音

通过调整泵浦光直径,使得LD端面泵浦固体激光器的振荡光工作于基模.在排除高阶横模的条件下,测量了由于热透镜的不稳定引起的光场场分布的噪音.实验发现,基模振荡光的高斯半径、光束指向角都在波动,而且光斑存在畸变波动.对一个未采取抑制措施的2W连续LD端面泵浦Nd:YAG固体激光器进行了测量.结果表明,在总功率不变的情况下,激光束峰值点附近的光强波动达到6.3%;激光的高斯半径波动达到5.8%;激光的指向角波动达到0.3mrad.     

水热法合成纳米花状二硫化钼及其微观结构表征

本文以钼酸钠、硫代乙酰胺为前驱体, 硅钨酸为添加剂, 成功用水热法合成高纯度纳米花状二硫化钼. 产物特性用X射线衍射(XRD)、能量色散谱(EDS)、扫描电子显微镜(SEM)进行表征. XRD和EDS图显示实验产物为二硫化钼, 且其结晶度和层状堆垛良好. SEM图谱则表明二硫化钼为纳米花状结构, 颗粒直径300 nm左右, 由几十上百片花瓣组成, 每片花瓣厚度十个纳米左右. 通过以硅钨酸为变量的梯度实验, 研究发现, 硅钨酸对于纳米花状MoS₂的形成具有重要作用, 不添加硅钨酸, 无法形成纳米花状MoS₂, 此外, 硅钨酸的剂量会影响合成MoS₂的大小和形貌. 本文还对纳米花状二硫化钼的形成机理做了初步的讨论.     

聚左旋乳酸/聚消旋乳酸共混物的结晶行为

非晶态聚消旋乳酸(PDLLA)对PLLA的结晶行为有较大的影响。本文利用差示扫描量热仪(DSC)和偏光显微镜(POM)对不同分子量PLLA、PDLLA按不同比例制得的共混物结晶进行了系统研究。结果表明随PDLLA含量的增大PLLA冷结晶温度升高,且越接近熔融温度。PDLLA分子量较小时PLLA球晶特征被明显破坏,PDLLA分子量较大时PLLA更易形保持球晶特征且易形成环带球晶形貌,这与结晶速率与非晶组分的扩散速率匹配程度有关。低分子量的PDLLA使PLLA的最大生长速率对应的温度出现在较低温度。     

Carbon Nanotubes Grown on Sepiolite as Catalyst Carrier

Multi-walled carbon nanotubes were synthesized by the catalytic decomposition of acetylene at 750℃ over sepiolite powder,which was treated with aqueous cobalt nitrate. It is expected that the composite with high specific area will have high capacity of hydrogen storage.     

乙醇在杂多酸上的氧化、脱水和程序升温脱附研究

合成了两个系列具有Keggin结构的12-钒钼磷酸和钨钼磷酸,研究了它们对乙醇氧化、脱水的催化反应。借助程序升温脱附技术研究了反应物及产物乙醇、乙烯、乙醚等在样品上的程脱作用。讨论了钨、钒取代部分钼原于后对杂多酸酸性及氧化性能的影响。     

Simultaneous determination of preservatives,sweeteners and antioxidants in foods by paired-ion liquid chromatography

Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethyl-para-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous α-hydroxyisobutyric acid solution (pH 4.5) (2.2 : 3.4 or 2.4 : 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C₁₈ column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 μg. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and α-hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.     

Delipidation‐based solid‐phase extraction pretreatment technique for plasma broad‐coverage metabolomic profiling to reveal the potential pathogenesis of yeast‐induced fever in rats

During the process of metabolomics profiling by using ultra high performance liquid chromatography coupled with time‐of flight mass spectrometry, blood sample pretreatment is a crucial step for biomarker discovery. Herein, in order to prevent the potential loss of metabolites and ion suppression phenomena caused by the proteins and phospholipids contained in blood fluids, a delipidation‐based solid‐phase extraction pretreatment technique for plasma broad‐coverage metabolomic profiling was performed. This technique can be summarized as a single extraction, a single elution of solid‐phase extraction plate, followed by four times measuring with electrospray ionization in positive and negative ion mode, respectively. This approach significantly increased the number of features detected in plasma, and 1572 features in positive mode and 1352 features in negative mode were detected, respectively. Besides, the stability and repeatability of the approach were greatly improved. For these advantages, the approach was employed to elucidate the potential pathogenesis of yeast‐induced fever in rats. The biomarkers associated with the pathogenesis of fever were shown to be related to amino acids metabolism and lipid metabolism. The delipidation‐based solid‐phase extraction pretreatment approach can provide a useful tool to reveal the pathological mechanisms of such systemic pathological process.