Determination of berberine in Rhizoma coptidis and its preparations by non-aqueous capillary electrophoresis

A non-aqueous capillary electrophoretic method was established for the determination of berberine in Rhizoma coptidis and its preparations. The effects of organic solvent and the concentrations of sodium acetate were studied, which showed that berberine in extracts of traditional Chinese medicine can be separated successfully in a buffer solution of 75 mmol/L of sodium acetate in methanol containing 1 mol/L of acetic acid. The simple and rapid method was linear in the range 25-200 microgram/mL of berberine and had a good reproducibility, with the relative standard deviation below 2%. Non-aqueous capillary electrophoresis is a satisfactory system for the analysis of alkaloids in traditional Chinese medicine.     

Sm2-xCexCuO4的物性研究

制备了Sm2-xCexCuO4的多晶样品.X-射线粉末衍射结果表明,该系列样品为K2NiF4214结构,当0.090.17时,为T'相.电阻率测量在0.15,0.17,0.19样品上观测到超导转变.最高Tc对应于x=0.17为13.6K,均远低于(Pr0.8La1.2)1.85Ce1.2CuO4 的超导转变温度(30K).这是由于该系列样品在远高于超导转变温度时就存在更强的载流子局域化效应.磁化率测量结果表明x=0.17的样品为体超导.该体系样品的Tc低、抗磁信号小与载流子的强局域化效应有关.热电势测量结果表明,在最佳超导组份附近斜率改变符号,欠掺杂区域载流子为电子型,过掺杂区域载流子为空穴型.     

A partition coefficient calculation method with the SFED model

The Solvation Free Energy Density (SFED) model, a solvation model proposed by No et al. was modified to give better solvation free energies of the molecules having high polarizable groups. The SFED at a point around the molecule was represented by a linear combination of four basis functions, the contribution from the cavitation free energy of a solvent, and a constant. As an application of the SFED model, the linear expansion coefficients of the Hydration Free Energy Density (HFED) and the 1-Octanol Free Energy Density (1-OFED) were determined. Both calculated hydration free energy and 1-octanol solvation free energy of selected 95 organic molecules agreed well with experimental values. The standard errors were 0.47 and 0.39 kcal/mol, respectively. 1-Octanol/water partition coefficients (P) of the molecules were calculated from the difference of the HFE and 1-OFE of the molecules. At the same time, the logP density (LPD) of a molecule was represented by the same basis functional form with the SFED model. The logP of a molecule can be obtained by the integration of the LPD of the molecule. The coefficients of the basis functions were determined by using experimental logP as constraints through an optimization procedure. Both logPs calculated from the free energy difference and from the LPD agreed well with the experimental data. The absolute mean errors were obtained as 0.34 and 0.32, respectively.     

Measurement of nonrandom event-by-event fluctuations of average transverse momentum in square root of (sNN)=200 GeV Au+Au and p+p collisions

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in square root of (sNN)=200 GeV Au+Au, and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the pT range over which the average is calculated. Both the centrality and pT dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard-scattering processes.     

Lyotropic liquid crystalline phases formed in an ionic liquid

Lyotropic liquid crystalline phases of an amphiphilic block copolymer are constructed and characterized in an ionic liquid with comparison of component and temperature effects.     

Midrapidity neutral-pion production in proton-proton collisions at square root s = 200 GeV

The invariant differential cross section for inclusive neutral-pion production in p+p collisions at sqrt[s]=200 GeV has been measured at midrapidity (|eta|<0.35) over the range 1相似文献   

Elliptic flow of identified hadrons in Au+Au collisions at sqrt sNN =200 GeV

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.     

Scaling properties of proton and antiproton production in sqrt[s(NN)]=200 GeV Au+Au collisions

We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at sqrt[s(NN)]=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5相似文献   

Transverse asymmetry AT' from the quasielastic 3He(e,e') process and the neutron magnetic form factor

We have measured the transverse asymmetry A(T') in 3He(e,e(')) quasielastic scattering in Hall A at Jefferson Laboratory with high precision for Q2 values from 0.1 to 0.6 (GeV/c)(2). The neutron magnetic form factor G(n)(M) was extracted based on Faddeev calculations for Q2 = 0.1 and 0.2 (GeV/c)(2) with an experimental uncertainty of less than 2%.