铁镧复合氧化物纳米米微粒的制备及其光催化性能

以溶胶-凝胶法制备了纳米铁镧复合氧化物.通过了XRD、TG-DTA等手段,对该氧化物进行了分析.研究了焙烧温度、光催化剂的用量、光照等因素对催化剂光催化降解活性染料的影响.并用红外光谱分析方法验证光催化降解效果.结果表明在适当的用量和700C焙烧并在紫外光照射下铁镧复合氧化物对活性翠蓝KGL和活性B-GFF黑有较强的光催化降解活性.     

AAS测定紫皮石斛中5种重金属元素的含量

对天然紫皮石斛(Dendrobium devoninum Paxt.)根和茎中Cr、Cd、Pb、Hg、Cu 5种重金属元素的含量进行了测定,旨在为该资源的药(食)利用提供基础数据.利用干法灰化处理样品,采用原子吸收光谱法(AAS)分别测定紫皮石斛根和茎中Cr、Cd、Pb、Hg、Cu 5种重金属元素的含量.根中Cr、Hg和Cu 3种元素含量分别为122.8043士39.02、311.5152士24.28、0.2890士0.19mg·kg-1,相对标准偏差(RSD)在3.20％-14.07％之间;茎中Cr、Hg和Cu 3种元素的含量分别为139.3997士14.72、276.0101士45.61、0.2854士0.29mg·kg-1,相对标准偏差(RSD)在4.83％-10.99％之间;根和茎中均未检出Cd、Pb两种元素,可能与地球化学背景有关.与人工种植石斛中重金属元素含量相比,Cr、Hg两种元素含量相对较高,Cu元素含量较低.本法操作简便,重复性好,测定结果满意.     

Stability of Nonlinear Wave of Kadomtsev-Petviashvili-Type Equation

For ion-acoustic waves in a plasma with non-isothermal electrons,the MKP equation is its governing equation.The instability of a soliton solution of MKP equation to two-dimensional long-wavelength perturbations is investigated up to the third order.It indicates that the one-soliton solution of MKP equation is unstable if v = -1wheras it is stable if v = 1 until the third order approximation has been considered.     

Smoothly embedded spheres in symplectic 4-manifolds

We characterize rational or ruled surfaces among all symplectic 4-manifolds by the existence of certain smoothly embedded spheres.

     

Preparation of Cyclodextrin Type Stationary Phase Based on Graphene Oxide and Its Application in Enantioseparation and Hydrophilic Interaction Chromatography

Graphene oxide (GO) was covalently coupled to the surface of amino silica gel by amide bond. β-cyclodextrin (β-CD) was further chemically bonded with GO to prepare a novel chiral stationary phase. The resulting material was characterized by Fourier transform-infrared (FT-IR) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis and thermogravimetric analysis (TGA). The separation of seven enantiomers was improved in varying degrees. Meanwhile, the stationary phase showed typical characteristics of hydrophilic interaction chromatography (HILIC), and four small nucleoside molecules were separated with the mobile phase of methanol-acetonitrile-water (45:45:10, V/V) in the HILIC mode. In addition, the separation mechanism of the stationary phase was further explored by studying the effects of mobile phase composition, temperature and pH value on the analyte retention. The low temperature was conducive to the separation of analytes at 20–60 °C. The addition of protonated solvent methanol significantly decreased the retention time of the four analytes. The change of pH affected the degree of protonation of the analyte, the interaction between analytes and the stationary phase, and retention time of analytes. The results showed that GO and β-CD played a synergistic effect in the chiral resolution of the chromatographic stationary phase. The retention of analytes in HILIC was attributed to their mixed-mode retention mechanisms including hydrophilic interaction, electrostatic interaction, hydrogen bonding, π-π stacking and so on.     

Electric dipole moment and chromoelectric dipole moment of the top quark inSU(3)C×SU(3)L×U(1)X model

We show that inSU(3) _C ×SU(3) _L ×U(1) _X model, the leading contribution to the electric and chromolelectric dipole moment of the top quark is due to the one-loop diagrams which come from exchanging the charged and neutral Higgs bosons. The dipole moments are typically of the order of 10^?19 e-cm and 10^?19 g-cm respectively, for the values of relative phases of the vev's such that CP violation is maximal. From an experimental point of view, theq ² dependence of dipole moment form factors is given.     

Copper-catalyzed trifluoromethylation of terminal alkenes through allylic C-H bond activation

An unprecedented type of reaction for Cu-catalyzed trifluoromethylation of terminal alkenes is reported. This reaction represents a rare instance of catalytic trifluoromethylation through C(sp(3))-H activation. It also provides a mechanistically unique example of Cu-catalyzed allylic C-H activation/functionalization. Both experimental and theoretical analyses indicate that the trifluoromethylation may occur via a Heck-like four-membered-ring transition state.     

Synthesis of dibenzofurans via palladium-catalyzed phenol-directed C-H activation/C-O cyclization

A practical, Pd(0)/Pd(II)-catalyzed reaction was developed for phenol-directed C-H activation/C-O cyclization using air as an oxidant. The turnover-limiting step of the process was found to be C-O reductive elimination instead of C-H activation. This reaction can tolerate a variety of functional groups and is complementary to the previous methods for the synthesis of substituted dibenzofurans.