Fabrication of the 19-filament Fe/Cu clad MgB2 wire via in situ powder-in-tube method

Using commercial amorphous B powder (92% in purity) and Mg powder (99% in purity) as starting materials, 19-filament Fe/Cu clad MgB2 wires were fabricated by an in situ powder-in-tube method. Heat treatment was performed at 700℃ for 1 h under an argon gas atmosphere. The influence of Mg/B ratio on the microstructure and superconducting properties of the wires was investigated. It was found that the major phases of MgB2 wires were MgB2 accompanied with relatively small amounts of MgO and Fe2B impurities. With 5% excess Mg addition, the onset TC slightly decreased. However, the transport JC at 4.2 K and 4 T reached 1.07×104 A·cm-2, increasing by a factor of 1.4 compared to the stoichiometric sample. Moreover, the Mg1.05B2 sample showed an improved field dependence of JC, suggesting that less voids and smaller grain size of the Mg1.05B2 core lead to better grain connectivity and stronger flux pinning.     

Fabrication of visible-light responsive S-F-codoped TiO<Subscript>2</Subscript> nanotubes

Fabrication and S-F-codoping of TiO2 nanotubes were carried out by a one-step electrochemical anodization process to extend the photoresponse of TiO2 to the visible-light region. The prepared samples were annealed in air and detected by SEM, XRD, XPS and UV-vis DRS spectrophotometer. The results showed that the average tube diameter of the nanotubes was 150 nm and the average tube length was 400 nm. The doped TiO2 nanotubes exhibited strong absorption in visible-light region. Photoelectrocatalytic degradation efficiency of 4-CP over S-F-codoped TiO2 nanotubes was 39.7% higher than that of only-F-doped sample. Moreover, sulfur and fluorine codoped into substitutional sites of TiO2 had been proven to be indispensable for strong response and high photocatalytic activity under visible light, as assessed by XPS.     

Character and fabrication of Al/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al tunnel junctions for qubit application

The superconductive Josephson junction is the key device for superconducting quantum computation. We have fabricated Al/Al2O3/Al tunnel junctions using a double angle evaporation method based on a suspended shadow mask. The Al2O3 junction barrier has been formed by introducing pure oxygen into the chamber during the fabrication process. We have adjusted exposure conditions by changing either the oxygen pressure or the oxidizing time during the formation of tunnel barriers to control the critical current density Jc and the junction specific resistance Rc. Measurements of the leakage in Al/Al2O3/Al tunnel junctions show that the devices are suitable for qubit applications.     

High pressure effects on the crystal structure and electric conductivity of perovskite like（Ca/Sr）2CuO2Cl2 compounds

The crystal structure stability as well as electric conductance of （Sr/Ca）2CuO2Cl2 compound with K2NiF4 structure was investigated up to 31 GPa using diamond anvil technique. It seems that （Sr/Ca）2CuO2Cl2 is quite stable under pressure but with obvious anisotropic compressibility. The equation of state （EOS） obtained shows relative large bulk modulus.     

Supercondcuting properties in MgB2／Fe wires prepared by PIT method

The discovery of superconductivity at 39 K in MgB2has attracted a lot of interest in the world[15]. Recently, many results on the magnetic and transport properties of bulks have been reported. And high critical currentdensities (Jc) in polycrystalline MgB2 materials indicate that Jc is not limited by the weak link of grain boundaries as high temperature superconductor (HTS), suggestingthat MgB2 has a good potential for electrical engineering applications[2,48]. The fabrication of high qua…     

Comparison between P25 and anatase-based TiO<Subscript>2</Subscript> quasi-solid state dye sensitized solar cells

Pure anatase TiO2 films have been made via hydration of titanium isopropoxide using a sol-gel tech-nique, while mixed TiO2 films which contained both anatase and rutile TiO2 were made from commercial P25 powder. Quasi-solid state dye-sensitized solar cells were fabricated with these two kinds of mesoporous films and a comparison study was carried out. The result showed that the open-circuit photovoltages （Voc） for both kinds of cells were essentially the same, whereas the short-circuit photo-currents （1sc） of the anatase-based cells were about 33% higher than that of the P25-based cells. The highest photocurrent intensity of the anatase-based cell was 6.12 mA/cm^2 and that of the P25-based cell was 4.60 mA/cm^2. Under an illumination with the light intensity of 30 mW/cm^2, the corresponding energy conversion efficiency was measured to be 7.07% and 6.89% for anatase-based cells and P25-based cells, respectively.     

High critical current density in powder-in-tube processed MgB2/Ta/Cu wire

The magnetization of dense MgB₂/Ta/Cu wires prepared by the powder-in-tube method is measured by a SQUID magnetometer. The results indicate that the critical temperature of MgB₂/Ta/Cu is around 38.4 K with a sharp transition width of 0.6 K. The MgB₂/Ta/Cu wire shows a strong flux pinning and the critical current density is higher than 10⁵ A/cm² (5 K, self-field) and 10⁴ A/cm² (20 K, 1 T). Also, the irreversibility field of the sample reaches 6.6 T at 5 K.     

Performances improvement of eosin Y sensitized solar cells by modifying TiO2 electrode with silane-coupling reagent

Chemical fixing of xanthene dye （eosin Y） on the surface of TiO2 electrode was carried out by modifying the electrode with silane-coupling reagent to obtain stable dye-sensitized TiO2 electrode. Such silane modification can not only evidently enhance the stability of dye-sensitized TiO2 electrode but also improve the energy conversion efficiency of the assembled cells by increasing short-circuit photocurrent （Jsc） and open-circuit photovoltage （Voc）. It was found that the improvements of cell performances differ depending on the composition of the electrolyte. The optimum cell of the cell performance was achieved in the electrolyte with 0.5 mol/L TBAI/0.05 mol/L 12/EC：PC（3：1 w/w）, yielding Jsc of 4.69 mA. cm-2, Voc of 0,595 V, fill factor （FF） of 0.64 and ηof 1,78%, Different spectroscopic techniques including UV-Vis spectra, fluorescence spectra, EIS and dark current measurements were employed to derive reasonable analysis and explanations.     

Compression behavior and equation of state of Ni77P23 amorphous alloy

The compression behavior of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using insitu high pressure energy dispersive X-ray diffraction with a syn- chrotron radiation source. The equation of state is determined by fitting the experimental data accord- ing to Birch-Murnaghan equation: -ΔV/V0=0.08606P-3.2×10-4P2 5.7×10-6P3. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa.     

Measurement of Magnetization Curve and Magnetic Relaxation for 2H-NbSe2 Crystals

The characteristics of electronic transport properties: behaviors of magnetization curve and magnetic relaxation of a typical normal superconductor 2H-NbSe2 are investigated. The results show that Tc and △Tc of the samples are 7. 2,0. 18 K, indicating that superconducting energy gap at zero temperature is 1. 1 meV. No fish tail shape is found in the magnetization curves at several temperatures. The relationship between remnant magnetic moment and time reveals that the magnetic flux creep of the sample agrees with the Kim-Anderson thermal activation model with the relaxation rate S=0.000 36 at T=6 K.     

dr1127： A novel gene of Deinococcus radiodurans responsible for oxidative stress

The functional analysis of dr1127,a novel gene in Deinococcus radiodurans was performed in this pa-per. The dr1127 gene was found occasionally in our microarray and 2-DE gel experiments. Mutation of the dr1127 gene decreased the γ-radiation and H2O2 resistance of D. radiodurans,and weakened the scavenging abilities of cell extracts for free radicals (superoxide anion,hydrogen peroxide,and hy-droxyl radical). Further oxidative damage assays demonstrated that the purified DR1127 protein of D. radiodurans could bind to double stranded DNA in vitro and protect DNA from oxidative damage in this way. These results suggest that the dr1127 gene is an important gene that can maintain γ-radiation and oxidative resistance in D. radiodurans and may take part in the oxidative stress process.     

Theoretic study of the reaction mechanism between （Me）3CO· radical and trans-3-hexene

The reaction mechanism between （Me）3CO· radical and trans-3-hexene in benzene was studied for the first time at the B3LYP/6-311＋＋G（d,p）//B3LYP/6-31G（d）＋ZPVE level. Two distinct elementary channels were identified as： （1） abstraction-addition; （2） addition-addition-elimination. Analysis of the potential energy surface demonstrates that for the title reaction, channels （1） and （2） have the major and minor contribution, respectively. Our calculated results can well explain the recently observed product distribution by Coseri et al. （J. Org. Chem. 2005, 70, 4629）. However, we found that the addition-abstraction channel proposed by Coseri et al. is kinetically infeasible.     

Novel trichromatic phosphor Co-doped with Eu, Tb in SiO2 gel matrix

The Eu, Tb co-doped SiO2 matrix tricolor fluorescence system was prepared by sol-gel technique. Red emission at 618 nm, green emission at 543 nm and blue emission at 350-500 nm were observed in the PL spectra of the sample, indicating that Eu^3＋, Eu^2＋ and Tb^3＋ ions coexisted in the matrix. In the co-doped sample, the blue emission of Eu^2＋ was much stronger than that of the sample single doped with Eu, which implied that the electron transfer between Eu^3＋ and Tb^3＋ maybe happened in the SiO2 matrix. The influences of the annealing temperature and Tb concentration on the PL spectra of the samples were investigated. The optimal doped concentration of Tb was determined to be 0.2% and the optimal annealing temperature 850℃. Annealed at 600℃, Tb^3＋ had a sensitizing effect on Eu^3＋ in the SiO2 matrix, and the emission intensity of Eu^3＋ in the Eu, Tb co-doped sample was more than four times that of the single doped sample, which could be attributed to the energy transfer from Tb^3＋ to Eu^3＋.     

Mutagenesis of Ser24 of Cytochrome b559 α Subunit Affects PSII Acitivies in Chlamydomonas reinhardtii

In order to study the functions of cytochrome b559 (Cyt b559) in photosystem two (PSII) activity, mutant S24F of Chlamydomonas reinhardtii was constructed using site directed mutagenesis, in which Serine24 (Ser24) locating downstream of Histidine23 (His23) in α subunit of Cyt b559 was replaced by Phenylalanine (Phe). Physiological and biochemical analysis showed that mutant S24F could be grown photoautotrophically or photoheterotrophically. However, their growth rate was slower either on HSM or TAP medium than that of the control; Analysis of PSII activity revealed that its oxygen evolution was about 71% of wild type (WT); The Photochemical efficiency of PSII (Fv/Fm) of S24F was reduced 0.23 compared with WT; S24F was more sensitive to strong light irradiance than the wild type; Furthermore, SDS-PAGE and Western-blotting analysis indicated that the expression levels of α subunit of Cyt b559, LHCII and PsbO of S24F were a little less than those of the wild type. Overall, these data suggests that Ser24 plays a significant role in making Cyt b559 structure maintain PSII complex activity of oxygen evolution although it is not directly bound to heme group.     

Development and characterization of interspecific hybrids between <Emphasis Type="Italic">Oryza sativa</Emphasis> and <Subscript>O. latifolia</Subscript> by <Subscript>in situ</Subscript> hybridization

Oryza sativa and O. latifolia belong to the AA and CCDD genomes of Oryza, respectively. In this study, interspecific hybrids of these species were obtained using the embryo rescue technique. Hybrid panicle traits, such as long awns, small grain, exoteric large purple stigma, grain shattering and dispersed panicles, resemble that of the paternal parent, O. latifolia, whereas there is obvious heterosis in such respects as plant height, tillering ability and vegetative vigor. Chromosome pairing and the genomic components of the hybrid were subsequently investigated using genomic in situ hybridization （GISH） and fluorescent in situ hybridization （FISH） analysis. Based on the mitotic metaphase chromosome numbers of the root tips investigated, the hybrid is a triploid with 36 chromosomes. The genomic constitution of the hybrid is ACD. In the meiotic metaphase Ⅰ of the hybrid pollen mother cell, poor chromosome pairing was identified and most of the chromosomes were univalent, which resulted in complete male sterility in the hybrid.     

Analysis of active sites for N2 and H^＋ reduction on FeMo-cofactor of nitrogenase

Dinitrogen (N2) and proton (H ),which act as physiological substrates of nitrogenase,are reduced on FeMo-co of the MoFe protein. However,researchers have different opinions about their exact reduction sites. Nitrogenases were purified from the wild type (WT) and five mutants of Azotobacter vinelandii (Av),including Qα191K,Hα195Q,nifV-,Qα191K/nifV- and Hα195Q/nifV-; and the activities of these en-zymes for N2 and H reduction were analyzed. Our results suggest that the Fe2 and Fe6,atoms closed to the central sulfur atom (S2B) within FeMo-co,are sites for N2 binding and reduction and the Mo atom of FeMo-co is the site for H reduction. Combining these data with further bioinformatical analysis,we propose that two parallel electron channels may exist between the 8Fe7S cluster and FeMo-co.     

Detection of infrared photons with a superconductor

A superconductor single photon detector based on NbN nanowire was fabricated using electron beam lithography （EBL） and reactive ion etching （RIE） for infrared photon detection. When biased well below its critical current at 4.2 K, NbN nanowire is very sensitive to the incident photons. Typical telecommunication photons with a wavelength of 1550 nm were detected by this detector. Data analysis indicates the repeating rate of the device with 200 nm NbN nanowire may be up to 100 MHz, and the quantum efficiency is about 0,01% when biased at 0.95/c.     

Inhibition of DNA restrictive endonucleases and Taq DNA polymerase by trimalonic acid C60

Activities of trimalonic acid fullerene (TMA C_60) on DNA restrictive enzymatic reaction were investigated by using two restrictive endonucleases Hind III and EcoR I and plasmid pEGFP-N1 with single restric-tive site for both enzymes. Meanwhile, TMA C60 was also tested to clarify its effects on polymerase chain reaction (PCR) with the catalyst of Taq DNA polymerase and the template of plasmid pEGFP-N1. The products from restrictive reactions or PCR were detected by agarose gel electrophoresis. It was found that the product amounts from restrictive reactions or PCR decreased significantly with addition of TMA C60. The inhibition by TMA C60 was dose-dependent and IC50 values for reactions of Hind III, EcoR I and PCR were 16.3, 6.0 and 6.0 μmol/L, respectively. Addition of two scavengers of reactive oxygen species (ROS), L-ascorbic acid-2-phosphate ester magnesium and sodium azide at the con-centrations of 2―10 mmol/L did not antagonize the activities of TMA C60 against PCR and two restrictive reactions. However, increase of Taq DNA polymerase amounts in PCR system antagonized the activities of TMA C60. These data implied that TMA C60 was able to inhibit the activities of the three above-mentioned enzymes involved in DNA metabolism, and that this inhibition probably did not correlate to ROS.     

Rate constants for the reaction of ozone with <Emphasis Type="Italic">n</Emphasis>-butyl, <Emphasis Type="Italic">s</Emphasis>-butyl and <Emphasis Type="Italic">t</Emphasis>-butyl methyl sulfides

The rate constants for the ozone reactions with n-butyl methyl sulfide （n-BMS, CHaCH2CH2CH2SCH3）, sec-butyl methyl sulfide （s-BMS, CH3CH2（CH3）CHSCHa） and tert-butyl methyl sulfide （t-BMS, （CH3）3CSCH3） were measured using our smog chamber under supposedly pseudo-first-order conditions at 30002 K and 760 Torr. The experimental determined rate constants for n-butyl, s-butyl and t-butyl methyl sulfide are （1.23 ± 0.06）×10-19, （5.08 ± 0.19）×10-20 and （2.26 ± 0.14）×10-20 cm3 molecule-1· s-1, respectively. The reactivity-structure relationship of the reactions was discussed and used to illustrate the mechanism of the ozone reaction with thioethers. The results enrich the kinetics data of atmospheric chemistry.     

Enhanced parametric amplification in slow-light photonic crystal waveguides

We demonstrate both theoretically and numerically that slow light can enhance the parametric process of silicon in photonic crystal line-defect waveguides. Specifically, to get the desired gain, the pump power for a given gain medium length or the gain medium length for given pump power can be reduced by （c/vgn）^2 when slow light waveguides are used, where n is the material index of conventional waveguide, vg is the group velocity of the slow light waveguide and c is the light velocity in vacuum.