用随机过程方法研究耀变体4C 01.02的射电和γ射线光变特征时标

使用不同于传统的类傅里叶方法的celerite方法分析耀变体4C 01.02的γ射线和射电波段的长期光变特征。结果表明celerite中最简单的阻尼随机游走模型(damped random walk,DRW)可以成功地拟合射电和γ射线的长期光变曲线,而较为复杂的二阶随机过程(stochastically-driven,damped harmonic oscillator,SHO)并没有显著提升拟合优度。得到的内禀的γ射线光变特征时标约为3 a,如此长的时标不能在轻子辐射模型中产生,但是在强子模型中是可能存在的,由此推测4C 01.02长期的γ射线辐射可能起源于强子过程。射电光变的内禀特征时标约为10 a,它可能对应于射电辐射区的逃逸时标,这表明射电辐射产生于大尺度喷流。

Evolution of Surface Oxide Film of Typical Aluminum Alloy During Medium-Temperature Brazing Process

The evolution of the surface oxide film along the depth direction of typical aluminum alloy under mediumtemperature brazing was investigated by means of X-ray photoelectron spectroscopy(XPS). For the alloy with Mg content below 2.0wt%, whether under cold rolling condition or during medium-temperature brazing process, the enrichment of Mg element on the surface was not detected and the oxide film was pure Al2O3. However, the oxide film grew obviously during medium-temperature brazing process, and the thickness was about 80 nm. For the alloy with Mg content above 2.0wt%, under cold rolling condition, the original surface oxide film was pure Al2O3. However, the Mg element was significantly enriched on the outermost surface during medium-temperature brazing process, and MgO-based oxide film mixed with small amount of MgAl2O4 was formed with a thickness of about 130 nm. The alloying elements of Mn and Si were not enriched on the surface neither under cold rolling condition nor during mediumtemperature brazing process for all the selected aluminum alloy, and the surface oxide film was similar to that of pure aluminum, which was almost entire Al2O3.

Characterization of Pyrolytic Lignin Extracted from Bio-oil

Bio-oil is a new liquid fuel produced by fast pyrolysis,which is a promising technology to convert bio-mass into liquid. Pyrolytic lignin extracted from bio-oil,a fine powder,contributes to the instability of bio-oil. The paper presents the structural features of three kinds of pyrolytic lignin extracted from bio-oil with different methods(WIF,HMM,and LMM) . The pyrolytic lignin samples are characterized by Fourier transform infrared spectrometer(FTIR) and X-ray photoelectron spectroscopy(XPS) . FTIR data indicate that the three pyrolytic lignin samples have similar functional groups,while the absorption intensity is different,and show characteristic vibra-tions of typical lignocellulosic material groups O H(3340-3380 cm-1) ,C H(2912-2929 cm-1) and C O(1652-1725 cm-1) . Comparison in the region(3340-3380 cm-1) indicates that WIF has more O H stretch groups than HMM and LMM. The carbon spectra are fitted to four peaks:C1,C C or C H,BE 283.5 eV;C2,C OR or C OH,BE 284.5-285.8 eV;C3,C O or HO C OR,BE 286.10-287.10 eV;C4,O C O,BE 287.5-287.7 eV. The absence of C1,C C or C H indicates the dominant polymerization structure of aro-matic carbon in pyrolytic lignin samples. For HMM and WIF,C2a and C2b can not be separated,so there is no free hydroxyl group in the samples. The oxygen peaks are also fitted to four peaks:O1,OH,BE = 530.3 eV;O2,RC O,BE 531.45-531.72 eV;O3,O C O,BE = 532.73-533.74 eV;O4,H2O,BE 535 eV. The absence of O1 and O4 indicates that little hydroxyl groups and adsorbed water are present in the samples.

类星体PKS 1510-089的射电流量变化周期特性研究

介绍了一种用运用小波分析寻找类星体PKS1510-089射电波段光变周期的方法.收集了PKS1510-089在射电37和22GHz波段较为完备的观测数据,获得了从1990～2005年的射电光变曲线.使用小波分析方法较好地分析和认证了类星体PKS1510-089的光变周期值,结果表明:(ⅰ)PKS1510-089在射电37GHz有T1=(1.80±0.06)a和T2=(0.90±0.07)a的周期,(ⅱ)在射电22GHz有T1=(1.80±0.06)a的周期,(ⅲ)从等值线图的连续性,发现T1=(1.80±0.06)a为PKS1510-089的主周期,T2=(0.90±0.07)a可能为T1=(1.80±0.06)a的半周期.这些结果与Xie在2004,2005,2008年以及Wu在2005年,Liu和Fan在2007年采取其他数据分析方法获得的结果是一致的.预测最近的一次大爆发将发生在2011年1月.

Effect of the modification of alumina supports with chloride on the structure and catalytic performance of Ag/Al_(2)O_(3)catalysts for the selective catalytic reduction of NO_(x)with propene and H_(2)/propene

The effect of the modification of an alumina support with chloride on the structure and the catalytic performance of Ag/Al_(2)O_(3)catalysts(SA)was investigated for the selective catalytic reduction(SCR)of NO using C_(3)H_(6)or H_(2)/C_(3)H_(6)as reductants.The Ag/Al_(2)O_(3)catalyst and Cl^(–)-modified Ag/Al_(2)O_(3)catalysts(SA-Cl)were prepared by a conventional impregnation method and characterized by X-ray diffraction,Brunauer-Emmett-Teller isotherm analysis,electron probe microanalysis,transmission electron microscopy,UV-Vis diffuse reflectance spectroscopy,X-ray photoelectron spectroscopy,and hydrogen temperature-programmed reduction.The catalytic activities in the C3H6-SCR and H_(2)/C3H6-SCR reactions were evaluated,and the reaction mechanism was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy and synchrotron vacuum ultraviolet photoionization mass spectroscopy(SVUV-PIMS).We found that Cl^(-)modification of the alumina-supported Ag/Al_(2)O_(3)catalysts facilitated the formation of oxidized silver species(Ag_(n)^(ᵟ+))that catalyze the moderate-temperature oxidation of hydrocarbons into partial oxidation products(mainly acetate species)capable of participating in the SCR reaction.The low-temperature promoting effect of H_(2)on the C3H6-SCR("hydrogen effect")was found to originate from the enhanced decomposition of strongly adsorbed nitrates on the catalyst surface and the conversion of these adsorbed species to–NCO and–CN species.This"H_(2)effect"occurs in the presence of Ag_(n)^(ᵟ+)species rather than the metallic Ag^(0)species.A gaseous intermediate,acrylonitrile(CH_(2)CHCN),was also identified in the H_(2)/C3H6-SCR reaction using SVUV-PIMS.These findings provide novel insights in the structure-activity relationship and reaction mechanisms of the SA-catalyzed HC-SCR reaction of NO.

Characterization of calcium deposition induced by Synechocystis sp. PCC6803 in BG11 culture medium

Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate deposition were investigated. Inoculated BGll in different calcium ion concentrations was used for the experimental group, while the BGll culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium （Ca）, carbon （C）, oxygen （O）, phosphorus （P）, iron （Fe）, copper （Cu）, zinc （Zn）, and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BGll culture media. There may be more calcium- containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.

Adsorption of cadmium ions from aqueous solutions by activated carbon with oxygen-containing functional groups

The adsorption of aqueous cadmium ions(Cd(Ⅱ)) have been investigated for modified activated carbon(AC-T)with oxygen-containing functional groups.The oxygen-containing groups of AC-T play an important role in Cd(Ⅱ) ion adsorption onto AC-T.The modified activated carbon is characterized by scanning electron microscopy,Fourier transform infrared spectroscopy(FT-IR) and X-ray photoelectron spectroscopy(XPS).The results of batch experiments indicate that the maximal adsorption could be achieved over the broad pH range of 4.5 to 6.5.Adsorption isotherms and kinetic study suggest that the sorption of Cd(Ⅱ) onto AC-T produces monolayer coverage and that adsorption is controlled by chemical adsorption.And the adsorbent has a good reusability.According to the FT-IR and XPS analyses,electrostatic attraction and cation exchange between Cd(Ⅱ) and oxygen-containing functional groups on AC-T are dominant mechanisms for Cd(Ⅱ) adsorption.

Preparation of Organic/Inorganic Hybrid Polymer Emulsions with High Silicon Content and Sol-gel-derived Thin Films

A novel polymer/SiO2 hybrid emulsion(PAES)was prepared by directly mixing colloidal silica with polyacrylate emulsion(PAE)modified by a saline coupling agent.The sol-gel-derived thin films were obtained by addition of co-solvents into the PAES.The effects ofγ-methacryloxypropyltrimethoxysilane(KH-570)content and co-solvent on the properties of PAES films were investigated.Dynamic laser scattering(DLS)data indicate that the average diameter of PAES(96 nm)is slightly larger than that of PAE(89 nm).Transmission electron microscopy (TEM)photo discloses that colloidal silica particles are dispersed uniformly around polyacrylate particles and some of the colloidal silica particles are adsorbed on the surface of PAE particles.The crosslinking degree data and Fourier transform infrared(FT-IR)spectra confirm that the chemical structure of the PAES is changed to form Si-O-Si-polymer crosslinking networks during the film formation.Atomic force microscope(AFM)photos show the solvent induced sol-gel process of colloidal silica and the Si-based polymer distribution on the film surface of the dried PAES.Thermogravimetric analysis(TGA)curves demonstrate that the PAES films display much better thermal stability than PAE.

Influences of Uncaptured Electron on Energy Conversion of Photon Compton Scattering in High Power Laser-plasma

Using the single particle theory and the non-flexibility collision model of electron and photon, the influence of the uncaptured electrons on the energy conversion efficiency of multi-photon nonlinear Compton scattering in the extra stationary laser-plasma is investigated. It shows that in extra stationary laser-plasma,the uncaptured electrons make the Δω of the scattering frequency of the multi-photon Compton fall down with the increases of the incident radiation electron speed,the materials of the incident collision of electron and photon, and the number of the photons which work with the electrons at the same time. Under the modulation of the uncaptured electrons to the laser field, the energy conversion efficiency between electrons and photons will fall down with the increase of the electron incident radiation speed, using the low-power electrons for incident source, the loss can be efficiently reduced.

Continuous Flow Reactor for Hydroxylation of Benzene to Phenol by Hydrogen Peroxide

The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe （Fe/AC） in acetonitrile using H2O2 as the oxidant was studied in a continuous flow reactor. Results showed that the continuous operation could obtain high phenol yield of 28.1%, coupled with the turnover frequency of 3 h^-1, and high selectivity of 98% under mild condition. The catalyst was characterized by N2 adsorption/desorption, Boehm titration, X-ray photoelectron spectra, and Fourier transform infrared spectroscopy. It was observed that iron may interact with the carboxyl group forming iron-carboxylate like species, which act as the active phase. The apparent activation energy obtained by fitting an Arrhenius model to the experimental data was 13.4 kJ/mol. The reaction order was calculated to be about i, 0.2 for benzene and 0.7 for H202.

Grafting of Chitosan and Chitosantrimethoxylsilylpropyl Methacrylate on Single Walled Carbon Nanotubes-Synthesis and Characterization

Acid functionalized single walled carbon nanotubes （CNTs） were grafted to chitosan by first reacting the oxidized CNTs with thionyl chloride to form acyl-chlorinated CNTs. This product was subsequently dispersed in chitosan and covalently grafted to form CNT-chitosan. CNT-chitosan was further grafted onto 3-trimethoxysilylpropyl methacrylate by free radical polymerization conditions, to yield CNT-g-chitosan-g-3-trimethoxysilylpropyl methacrylate （TMSPM）, hereafter referred to as CNT-chitosan-3-TMSPM. These composites were characterized by Fourier Transform Infrared Resonance Spectroscopy （FTIR）, carbon-13 nuclear magnetic resonance （13C NMR）, Yhermogravimetric Analysis （TGA）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The composite showed improved thermal stability and could be of great potential use in bone tissue engineering.

Sodium Citrate： A Universal Reducing Agent for Reduction/ Decoration of Graphene Oxide with Au Nanoparticles

A facile method is proposed for the synthesis of reduced graphene oxide nanosheets （RGONS） and Au nanoparticle-reduced graphene oxide nanosheet （Au-RGONS） hybrid materials, using graphene oxide （GO） as precursor and sodium citrate as reductant and stabilizer. The resulting RGONS and Au-RGONS hybrid materials were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy, and X-ray diffraction. It was found that the RGONS and Au-RGONS hybrid materials formed stable colloidal dispersions through hydrogen bonds between the residual oxygen-containing functionalities on the surface of RGONS and the hydroxyl/carboxyl groups of sodium citrate. The electrochemical responses of RGONS and Au-RGONS hybrid material-modified glassy carbon electrodes （GCE） to three kinds of biomolecules were investigated, and all of them showed a remarkable increase in electrochemical performance relative to a bare GCE.

Radio spectral index of BL Lac objects

In this paper, the preliminary data from University of Michigan Radio Astronomy Observatory database （UMRAO） are used to discuss the radio spectral index properties of 8 BL Lacs. To do so, we calculated the radio spectral index, a （F oc va）, which was obtained by fitting the averaged flux densities in the bands （4.8 GHZ, 8 GHz, and 14.5 GHz） by binning the original for 7 d. We also calculated the time delay between the averaged lightcurves and the spectral variance. Our calculations and analysis give the following results. 1） The averaged logarithmic flux density at 8 GHz （logF） and the corresponding spectral index （or） have strong correlation for all the BL Lacs; 2） the lightcurves and the spectral variability have the similar profile for all the BL Lacs; 3） the lightcurves delay spectral variability for all sources but PKS 0735＋178, with the delay time ranging from 31 d to 125 d.

In-situ interaction of nano-PbS with gelatin

Water-soluble gelatin-PbS bionanocomposites （BNCs） were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, UV-vis absorption spectra （UV-vis）, Fourier transform infrared spectra （FT-IR） and circular dichroism （CD）. FT-IR data were used to envis- age the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2＋ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less c^-helix content and more open structures （[3-sheet, r-turn, or expanded）. A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K （298/303/308 K： 3.11/2.00/1.60 × 10^6 tool/L） at three different temperatures were calculated based on this formula. Thermodynamic parameters such as AG^θ, △Hθ and △S^θ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous （AG^θ 〈 0）, and enthalpy-driven （△H^8 〈 0）.

Enhancing the selective hydrogenation of benzene to cyclohexene over Ru/TiO_2 catalyst in the presence of a very small amount of ZnO

Highly efficient and greener hydrogenation of benzene to cyclohexene is of great importance but is challenging.In this work,Ru/Ti O2 catalyst was prepared by a simple chemical-reduction method.The catalyst was characterized by transmission electron spectroscopy(TEM),X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),and nitrogen adsorption-desorption techniques.It was shown that the Ru nanoparticles with average size of about 2.2 nm were dispersed uniformly on the surface of the Ti O2 support.The effect of a very small amount of Zn O in Na OH solution on the selectivity to cyclohexene was investigated under different conditions by using Ru/Ti O2 catalyst.It was found that the addition of a small amount of Zn O to the Na OH solution could effectively enhance the selectivity to cyclohexene and that the yield of cyclohexene could reach 41.5%.Control experiments revealed that the main reason for the enhancement of the selectivity to cyclohexene was the presence of Zn O in the form of Na2Zn(OH)4 in the alkaline solution,which effectively retarded the further hydrogenation of cyclohexene.A recycling experiment showed that the yield of cyclohexene was not obviously decreased after four reuses.

Laser-Plasma Interaction in Presence of an Obliquely External Magnetic Field:Application to Laser Fusion without Radioactivity

In this paper, the nonlinear interaction of ultra-high power laser beam with fusion plasma at relativistic regime in the presence of obliquely external magnetic field has been studied. Imposing an external magnetic field on plasma can modify the density profile of the plasma so that the thermal conductivity of electrons reduces which is considered to be the decrease of the threshold energy for ignition. To achieve the fusion of Hydrogen–Boron(HB) fuel,the block acceleration model of plasma is employed. Energy production by HB isotopes can be of interest, since its reaction does not generate radioactive tritium. By using the inhibit factor in the block model acceleration of plasma and Maxwell's as well as the momentum transfer equations, the electron density distribution and dielectric permittivity of the plasma medium are obtained. Numerical results indicate that with increasing the intensity of the external magnetic field, the oscillation of the laser magnetic field decreases, while the dielectric permittivity increases. Moreover, the amplitude of the electron density becomes highly peaked and the plasma electrons are strongly bunched with increasing the intensity of external magnetic field. Therefore, the magnetized plasma can act as a positive focusing lens to enhance the fusion process. Besides, we find that with increasing θ-angle(from oblique external magnetic field) between 0 and 90°, the dielectric permittivity increases, while for θ between 90° and 180°, the dielectric permittivity decreases with increasing θ.