碳纳米管表面修饰程度对碳纳米管载Pt电催化性能的影响

比较了用不同温度的浓HNO₃处理的碳纳米管(CNTs)作载体的Pt(Pt/CNTs)对甲醇氧化的电催化活性. 结果表明浓HNO₃处理使CNTs表面修饰上的含氧基团对CNTs上沉积Pt粒子的平均粒径有较大影响. 表面修饰程度适当时, 制得的Pt/CNTs中Pt粒子较小, 因此, 对甲醇氧化的电催化活性较高. 而表面修饰程度过大, 易使Pt粒子团聚, 从而降低Pt/CNTs催化剂对甲醇氧化的电化学活性.     

Mid-infrared generation based on a periodically poled LiNbO3 optical parametric oscillator

We report a nanosecond Nd:YVO_4-pumped optical parametric oscillator (OPO) based on periodically poled LiNbO_3 (PPLN). Tuning is achieved in this experiment by varying the temperature and period of the PPLN. The design of double-pass singly resonant oscillator (DSRO) and confocal cavity enables the OPO threshold to be lowered considerably, resulting in a simple, compact, all-solid-state configuration with the mid-infrared idler powers of up to 466mW at 3.41μm.     

Interaction of an electron bunch with a laser pulse in vacuum

The output properties of electrons accelerated by the vacuum laser acceleration scheme CAS (capture and acceleration scenario) are addressed. The transport process of the electron bunch, the fraction of the CAS electrons of the incident electrons, the correlation of electron energy with position and scattering angle, the energy spectrum and angular distributions as well as the emittance of the outgoing electrons are studied at a laser intensity of a₀=10. In addition, the effects of the laser intensity, beam width, and pulse duration on the properties of the output electrons are also examined. Physical explanations of those output characteristics are presented based on the mechanism behind the CAS scheme. The feasibility of CAS to become a realistic laser accelerator scheme is explored. PACS 41.75.Jv; 42.60.Jf; 41.85.Ja     

Two new monodesmosidic triterpene saponins from Gypsophila oldhamiana

Two new monodesmosidic triterpene saponins were isolated from the roots of Gypsophila oldhamiana (Caryophyllaceae). Their structures were elucidated on the basis of spectral data to be quillaic acid, alpha-L-arabinopyranosyl-(1-->4)-alpha-L-arabinopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (1), and vaccaric acid, beta-D-glucopyranosyl-(1-->3)-[beta-D-xylopyranosyl-(1-->4)]-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (2). Compound 1 showed a significant enhancement of granulocyte phagocytosis in vitro.     

Direct determination of nucleosides in the urine of patients with breast cancer using column-switching liquid chromatography-tandem mass spectrometry

We developed an analytical method for a simple, sensitive and simultaneous determination of oxidized nucleosides in urine using column-switching liquid chromatography-electrospray/tandem mass spectrometry (LC-ESI/MS/MS). We connected two columns through a six-way switching valve and effectively separated nucleosides in the urine from the interference by column-switching liquid chromatography. We monitored separated nucleosides using positive ionization tandem mass spectrometry in selective reaction monitoring (SRM) mode. The calibration ranges of nucleosides were 0.2-100 nmol/mL. The linearity of the method was 0.994-0.999, and the limits-of-detection (LOD) at a signal-to-noise (S/N) ratio of 3 were 0.1-0.2 nmol/mL. The coefficients of variation were in the range 2.28-11.74% for within-day variation and 4.36-11.15% for day-to-day variation, respectively. To explore the relationship between breast cancer and the nucleosides level in human urine, we measured the concentrations of nucleosides in female patients with breast cancer (n = 30) and in normal female subjects (n = 30). The concentration of nucleosides was significantly increased in patients with breast cancer when compared with the normal controls (1-methyladenosine; p < 0.005, N(2),N(2)-dimethylguanosine; p < 0.01, 5-hydroxymethyl-2'-deoxyuridine; p < 0.001, 8-hydroxy-2-deoxyguanosine; p < 0.001). Therefore, the elevated levels of nucleosides could be used as an important biomarker for breast-cancer research.     

Non-affine structural evolution of soft colloidal crystalline latex films under stretching as observed via synchrotron X-ray scattering

A polymer dispersion consisting of soft latex spheres with a diameter of 135 nm was used to produce a crystalline film with face-centered cubic (fcc) packing of the spheres. Different from conventional small-molecule and hard-sphere colloidal crystals, the crystalline latex film in the present case is soft (i.e., easily deformable). The structural evolution of this soft colloidal latex film under stretching was investigated by in-situ synchrotron ultra-small-angle X-ray scattering. The film exhibits polycrystalline scattering behavior corresponding to fcc structure. Stretching results not only in a large deformation of the crystallographic structure but also in considerable nonaffine deformation at high draw ratios. The unexpected nonaffine deformation was attributed to slippage between rows of particles and crystalline grain boundaries. The crystalline structure remains intact even at high deformation, suggesting that directional anisotropic colloidal crystallites can be easily produced.     

Self-assembly of an amphiphilic derivative of chitosan and micellar solubilization of puerarin

A kind of amphiphilic derivatives of chitosan (2-hydroxyl-3-butoxyl)-propylcarboxymethyl-chitosan (HBP-CMCHS), has been synthesized, and the critical micelle concentration (cmc) of HBP-CMCHS was detected by the fluorescence method. The puerarin-loaded HBP-CMCHS micellar system was prepared by physical entrapped method. Result showed that when adding the same amount of puerarin, the solubilizing capacity was enhanced by increasing the concentration of HBP-CMCHS and temperature. Puerarin-loaded micellar system of HBP-CMCHS was characterized by TEM and DLS. TEM photograph revealed that the micelles were spherical and puerarin was solubilized in the cores of the spherical polymeric micelles. DLS showed that after solubilization the size of the micelles became bigger. In vitro tests showed that puerarin was slowly released from micellar solution and the release lasted up to 60 h by means of the dialysis method.     

杂环烯酮缩胺:构筑分子多样性稠杂环化合物的合成先导分子

杂环烯酮缩胺（HKAs）是一类构建分子多样性稠杂环化合物的多功能合成砌块,已被广泛应用于构筑多种多样的类天然杂环化合物和合成药物中。随着杂环烯酮缩胺研究的深入开展,其作为双亲核试剂与多种亲电底物反应取得了较大的进展。本文将基于HKAs的结构特征、反应性能,对以HKAs及1,1-烯二胺为合成子构建各种类型具有潜在生物活性的类天然多环稠杂环化合物进行综述。     

微波辅助-顶空液相微萃取/高效液相色谱分析水样中的邻硝基苯酚

建立了基于微波辅助-顶空液相微萃取在线联用、高效液相色谱法测定水样中邻硝基苯酚的分析方法。采用L16(45)正交实验设计对影响萃取的各种因素,如萃取有机溶剂、微波辐射功率、萃取时间、离子强度、样品液体积,进行了优化。优化后萃取条件为,以乙酸丁酯作为萃取溶剂,功率和时间分别为100W和12min条件下,离子强度为0的样品溶液体积为20mL。在优化萃取条件下,邻硝基苯酚的检出限LOD(S/N=3)为0.94μg/L,萃取富集倍数为30,实际水样的加标回收率为85.2%。理论分析和实验结果表明,微波辅助-顶空液相微萃取在线联用方法具有简便、快速、高效、节省溶剂、选择性好、应用范围广的特点。