退火温度对MgB_2超导薄膜的影响

本实验是研究退火温度对MgB2超导薄膜的影响。在多晶Al2O3衬底上,以B2H6作为硼源,化学气相沉积先驱硼薄膜,采用Mg扩散方法,在不同退火温度条件下制备了MgB2超导薄膜;还采用了测量电阻-温度曲线、X射线衍射分析和扫描电子显微镜形貌观测方法。结果表明,退火温度对MgB2薄膜的超导特性、晶体结构和相纯、表面形貌有影响。退火温度高,生成的MgB2晶粒较大,晶形好,正常态电阻也增大,杂相越少。

Interaction among deformation, recrystallization and phase transformation of TA2 pure titanium during hot compression

TA2 pure titanium was chosen to research the interaction among deformation, recrystallization and phase transformation during hot compression. The samples were hot compressed by thermal simulation method with different processing parameters. Variant selection induced by stress during cooling after compression was found. The prismatical texture component which featured that the [0001] direction perpendicular to the compressing direction produced preferentially under the compressing stress. As a result, the transformedα phase possesses strong prismatical texture which is different with the basal texture of compressed αphase. The minimum elastic strain energy is demonstrated to be the main reason that causes the variant selection. Dynamic recrystallization behavior and microstructure evolution during hot compression were also studied.

A High Purity Integer-N Frequency Synthesizer in 0.35μm SiGe BiCMOS

An integer-N frequency synthesizer in 0.35μm SiGe BiCMOS is presented. By implementing different building blocks with different types of devices,a high purity frequency synthesizer with excellent spur and phase noise performance has been realized. All the building blocks are implemented with differential topology except for the off-chip loop filter. To further reduce the phase noise,bonding wires are used to form the resonator in the LC-VCO. The frequency synthesizer operates from 2.39 to 2.72GHz with output power of about 0dBm. The measured closed-loop phase noise is - 95dBc/Hz at 100kHz offset and - 116dBc/Hz at 1MHz offset from the carrier. The power level of the reference spur is less than - 72dBc. With a 3V power supply, the whole chip including the output buffers consumes 60mA.

Isolation of Plasma and Thylakoid Membranes from the Heterocystous Cyanobacterium Anabaena sp. PCC 7120

利用水溶性多聚体双相法分离蓝细菌Anabaenasp .PCC 712 0质膜和类囊体膜两种膜系统。吸收光谱分析表明 ,质膜相和类囊体膜相的主要色素分别为类胡萝卜素和叶绿素。SDS_凝胶电泳显示这两种膜系统蛋白组成有很大差别。这种分离方法容易操作 ,对研究蓝细菌的膜蛋白和膜脂非常有用。

Purification of Sulfuric and Hydriodic Acids Phases in the Iodine-sulfur Process

Iodine-sulfur （IS） thermochemical water-splitting cycle is the most promising massive hydrogen production process. To avoid the undesirable side reactions between hydriodic acid（HI） and sulfuric acid （H2SO4）, it is necessary to purify the two phases formed by the Bunsen reaction. The purification process could be achieved by reverse reaction of the Bunsen reaction. In this study, the purification of the H2SO4 and HI Phases was studied. The purification proceeded in both batches and the continuous mode, the influences of operational parameters, including the reaction temperature, the flow rate of nitrogen gas, and the composition of the raw material solutions, on the purification effect, were investigated. Results showed that the purification of the H2SO4 phase was dominantly-affected by the reaction temperature, and iodine ion in the sulfuric acid phase could be removed completely when the temperature was above 130℃; although, the purification effect of the HI phase improved with increasing of both the flow rate of nitrogen gas and temperature.

Optimization for Purification and Characterization of Recombinant Hirudin Ⅲ from E. coli

Aim To optimize purification conditions of recombinant hirudin 3 in thefermentation broth and characterize the product. Methods Reambinant hirudin 3 was isolated andpurified from the fermentation broth by three column chromatography steps with macroporous resin,DEAE cellulose DES2 and preparative RP-HPLC, respectively, and the optimal conditions were obtained.Purity of the product was determined by SDS-PAGE and analytical RP-HPLC. The molecular weight wasdetermined by mass spec-trometry. The structure of the product was analyzed by peptide map.ResultsThe product with purity of 95.4786% was obtained after three purification steps in the optimumconditions with a total yield of 39%. The molecular weight of the product was 6 913.32 ± 6.55 Da,coincident to the theoretical molecular weight of r-hirudin 3. The structure of the product wascoincident to r-hirudin 3 either. Conclusion The optimized purification steps can be successfullyemployed for purification of r-hirudin 3 from E. coli using batch-type approaches. The productobtained with high purity was confirmed to be r-hirudin 3.

Functional characterization of a novel microbial esterase identified from the Indian Ocean and its use in the stereoselective preparation of(R)-methyl mandelate

Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmol/L substrate, p H 6.0, 2 h at 40 ℃）, this esterase can hydrolyze racemic methyl mandelate to（ R）-methyl mandelate with very high optical purity（e. e. 〉99%） and yield（nearly 90%）. Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate（ S）-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the fi nal chiral product（R）-methyl mandelate, which can potentially simplify the production procedure of（ R）-methyl mandelate catalyzed by esterase.

A ROBUST PHASE-ONLY DIRECT DATA DOMAIN ALGORITHM BASED ON GENERALIZED RAYLEIGH QUOTIENT OPTIMIZATION USING HYBRID GENETIC ALGORITHM

A robust phase-only Direct Data Domain Least Squares (D3LS) algorithm based on gen- eralized Rayleigh quotient optimization using hybrid Genetic Algorithm (GA) is presented in this letter. The optimization efficiency and computational speed are improved via the hybrid GA com- posed of standard GA and Nelder-Mead simplex algorithms. First, the objective function, with a form of generalized Rayleigh quotient, is derived via the standard D3LS algorithm. It is then taken as a fitness function and the unknown phases of all adaptive weights are taken as decision variables. Then, the nonlinear optimization is performed via the hybrid GA to obtain the optimized solution of phase-only adaptive weights. As a phase-only adaptive algorithm, the proposed algorithm is sim- pler than conventional algorithms when it comes to hardware implementation. Moreover, it proc- esses only a single snapshot data as opposed to forming sample covariance matrix and operating matrix inversion. Simulation results show that the proposed algorithm has a good signal recovery and interferences nulling performance, which are superior to that of the phase-only D3LS algorithm based on standard GA.

Formation of interfacial brittle phases sigma phase and IMC in hybrid titanium-to-stainless steel joint

The microstructures of the brazed joints for commercially pure Ti and stainless steel were investigated by the applications of various filler alloys including Ag-, Ti-, Zr- and Ni-based alloys. Generally, the dissimilar joints between Ti and stainless steel were dominated by the Ti-based intermetallic compounds （IMCs）, e.g. （Ti, Zr）2（Fe, Ni）, TiFe, TiCu, and Ti2（Fe, Ni）, due to a significant dissolution of Ti from the base metal. The （Fe-Cr） cr phase was also observed near the stainless steel due to a segregation of Cr into the interface region. This research demonstrates empirically that the brittleness of the Ti and stainless steel joint can not be avoided only by applying single braze alloy or single insert metal, and thus an introduction of additional suitable interlayer between the filler alloy and the base metal is necessary to prevent the brittleness of the joint.

Synthesis and Re-refinement of Cu_3PSe_4

The title compound Cu3PSe4 was synthesized by the reaction of CuCl, P2Se5 and Se in a molar ratio of 1:1:1 at 500 C and structurally characterized by X-ray crystallography. The crystal belongs to orthorhombic, space group Pmn21 with cell parameters: a = 7.685(2), b = 6.656(1), c = 6.377(1) , V = 326.2(1) 3, Z = 2, Dc = 5.472 g/cm3, Mr = 537.43, F(000) = 476, m = 32.12 mm-1, R = 0.0642, wR = 0.1481 and S = 1.037. The 3-D structure can be regarded as constructed from the alternately stacking of [Cu(2)Se4] tetrahedral layers and Cu(1)PSe tetrahedral layers along the b direction, in which the Cu(2)Se layer is comprised of corner-sharing [Cu(2)Se4] tetrahedra along the a and c directions, and the Cu(1)PSe layer is consisted of alternately corner-sharing [Cu(1)Se4] tetrahedra and [PSe4] tetrahedra along the a and c directions.

3-D fracture network dynamic simulation based on error analysis in rock mass of dam foundation

Accurate 3-D fracture network model for rock mass in dam foundation is of vital importance for stability,grouting and seepage analysis of dam foundation.With the aim of reducing deviation between fracture network model and measured data,a 3-D fracture network dynamic modeling method based on error analysis was proposed.Firstly,errors of four fracture volume density estimation methods(proposed by ODA,KULATILAKE,MAULDON,and SONG)and that of four fracture size estimation methods(proposed by EINSTEIN,SONG and TONON)were respectively compared,and the optimal methods were determined.Additionally,error index representing the deviation between fracture network model and measured data was established with integrated use of fractal dimension and relative absolute error(RAE).On this basis,the downhill simplex method was used to build the dynamic modeling method,which takes the minimum of error index as objective function and dynamically adjusts the fracture density and size parameters to correct the error index.Finally,the 3-D fracture network model could be obtained which meets the requirements.The proposed method was applied for 3-D fractures simulation in Miao Wei hydropower project in China for feasibility verification and the error index reduced from 2.618 to 0.337.

Behavior of Hydrogen and Nitrogen in Tungsten, as Divertor Wall of a Fusion Reactor

The analysis of the interaction of hydrogen, nitrogen （and their isotopes） with tungsten is important, since this material is a strong candidate to form the first wall of fusion reactors for both magnetic and inertial confinement, and these atoms have a very sensitive （desired and unwanted） interaction with it. For this purpose, we study the effects and electronic state densities of atomic hydrogen and nitrogen in pure tungsten, in order to analyze some important properties such as the density of states of the system. Focusing on this application, this work is a preliminary study of the behavior of atoms of hydrogen and nitrogen, on a surface of tungsten on the three sites of the cell： top, hollow and bridge. We use a program simulation based on the DFT （density functional theory） implemented in the Open-Source Code Quantum Espresso, in order to obtain the adsorption energy and the density of states of the systems.

Preparation of National CRMs of Active Compounds from Natural Products

According to the standard of GB/T1500.3-2008 and the guidelines of ISO/REMCO, the preparation of National Certified Reference Materials （CRMs） of active compounds was composed of the following two aspects： preparation and certification. This paper presents an example of the preparation of biochanin A to illustrate the preparation of National CRMs of active compounds from natural products. Firstly, the target compound was extracted and purified from crude materials. Then, its chemical structure was identified by UV spectrum, IR spectrum, ESI-MS, and NMR. The purity of the compound was determined by HPLC with the area normalization method. The certified value assessed by comparing the purity values from six independent qualified laboratories and the value of uncertainty were given. Thermal analysis, residual solvent, homogeneity testing and stability testing was tested in the process.

HPLC determination of Nimodipine in plasma with an improved sample refining method and its application in pharmacokinetic studies

In order to prepare samples for HPLC analysis with maximum drug recovery and impurity elimination, a revised method for the extraction and purification of a target substance from plasma was developed and applied in a pharmacokinetic study with Nimodipine as a model drug. After protein precipitation of a plasma sample using pure methanol and evaporation of the supernatant to dryness, methanol of various concentrations from 10% to 100% were used to dissolve the remaining residues with the goal of maximizing drug recovery and impurity elimination. Through rigorous screening with HPLC peaks from residual impurity and recovered drug as the criteria, a methanol concentration of 30% was chosen. The standard curve was linear （r2〉 0.999） over the range of 2-160 ng/mL with a limit of quantification （LOQ） of 2 ng/mL. Intra- and inter-day precision values were below 15%, and the accuracy ranged from -1.70% to 5.88% at all three quality control （QC） levels. The wavelength of maximum absorption was 238 nm, and a smaller LOQ value of 2 ng/mL was achieved compared with the reported method. The revised method was successfully applied in a pharmacokinetic study of Nimodipine in rats and sample preparations of lidocaine hydrochloride.

Subsolidus binary phase diagram of the bilayer compounds [n-C_nH_(2n+1)N(CH_3)_3]_2ZnCl_4(n = 16, 18)

The bilayer compounds[n-CnH2n+1N(CH3)3]2Zn Cl4(n=16,18)experience solid-solid phase transition within the temperature range of 310 to 340 K.The low-temperature crystal structures of the pure compounds are characteristic of the piling effect in which a 2D macro-anion Zn Cl42- is sandwiched between two alkylammonium layers.These layers become conformationally disordered in the high-temperature phases.The structures can alternatively be viewed as a double layer of alkylammonium ions between Zn Cl42- sheets and can be considered as crystalline models of lipid bilayers.The experimental subsolidus binary phase diagram of[n-C16H33N(CH3)3]2Zn Cl4-[n-C18H37N(CH3)3]2Zn Cl4 has also been established over the whole composition range by differential scanning calorimetry(DSC)and X-ray diffraction.In the phase diagram,one intermediate compound[n-C16H33N(CH3)3][n-C18H37N(CH3)3]Zn Cl4 at WC16C3Zn%47.50 and two eutectoid invariants points at WC16C3Zn%35.10 and75.70 were observed;the respective temperatures of the two eutectoids are 320±1 and 315±1 K.In addition,there are three noticeable solid solution ranges in the phase diagram:α-phase at the left,β-phase at the right,andγ-phase in the middle.

The Degenerated Second Main Theorem and Schmidt's Subspace Theorem

In this paper, we establish a Second Main Theorem for an algebraically degenerate holomorphic curve f : C → Pn(C) intersecting hypersurfaces in general position. The related Diophantine problems are also considered.

Rotationally symmetric pseudo-Khler metrics of constant scalar curvatures

We study the ordinary differential equations related to rotationally symmetric pseudo-Khler metricsof constant scalar curvatures. We present various solutions on various holomorphic line bundles over projectivespaces and their disc bundles, and discuss the phase change phenomenon when one suitably changes initialvalues.

HSV-1 stimulation-related protein HSRG1 inhibits viral gene transcriptional elongation by interacting with Cyclin T2

The protein encoded by HSRG1(HSV-1 stimulation-related gene 1) is a virally induced protein expressed in HSV-1-infected cells.We have already reported that HSRG1 is capable of interacting with transcriptional regulator proteins.To further analyze the effects of HSRG1 on the regulation of viral gene transcription,we expressed the HSRG1 protein in transfected cells and found that it postpones the proliferation of HSV-1.CAT(chloramphenicol acetyltransferase) assays also revealed that HSRG1 reduces transcription from HSV-1 promoters.Yeast two-hybrid and immunoprecipitation assays indicated that HSRG1 interacts with Cyclin T2,the regulatory subunit of P-TEFb,which is required for transcription elongation by RNA Pol II(RNAP II) ,and that amino acid residues 1-420 in Cyclin T2 are important for binding with HSRG1.Fluorescence assays suggested that the cellular localizations of those two proteins are influenced by their interaction.Further analyses with CAT assays revealed that HSRG1 inhibits the transcriptional activation by Cyclin T2 of viral promoters.Our results suggested that the inhibitory effects of HSRG1 on viral replication and proliferation are probably induced by its binding to Cyclin T2.Therefore,it is likely that HSRG1 inhibits viral gene transcriptional elongation by interacting with Cyclin T2.