Study of transport behavior for Fe-doping La<Subscript>0.67</Subscript>Ca<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript> perovskite manganese

Systematic studies of the transport properties of La_0.67Ca_0.33Mn_1?xFe _x O₃ (x=0–0.3) systems showed that with increasing Fe-doping contentx the resistance increases and the insulator-metal transition temperature moves to lower temperature. For small doping content, the transport property satisfies metal transport behavior below the transition temperature, and above the transition temperature it satisfies the small polaron model. This behavior can be explained by Fe³⁺ doping, which easily forms Fe³⁺?O^2??Mn⁴⁺ channel, suppressing the double exchange Mn³⁺?O^2??Mn⁴⁺ channel and enhancing the spin scattering of Mn ions induced by antiferromagnetic clusters of Fe ions.     

Electrochemical properties of CoFe<Subscript>3</Subscript>Sb<Subscript>12</Subscript> as potential anode material for lithium-ion batteries

A skutterudite-related antimonide, CoFe₃Sb₁₂, was prepared with vacuum melting. XRD analysis showed the material contained Sb, FeSb₂, CoSb₂ and CoSb₃ phases. The electrochemical properties of the ball-milled CoFe₃Sb₁₂−10 wt% graphite composite were studied using pure lithium as the reference electrode. A maximal lithium inserting capacity of about 860 mAh/g was obtained in the first cycle. The reversible capacity of the material was about 560 mAh/g in the first cycle and decreased toca. 320 mAh/g and 250 mAh/g after 10 and 20 cycles respectively.Ex-situ XRD analyses showed that the antimonides in the pristine material were decomposed after the first discharge and that antimony was the active element for lithium to insert into the host material. Project supported by the National Natural Foundation of China (No. 59771032) and the RFDP of the Education Ministry of China (No. 20010335045)     

Science Letters：Nitrogen doping of activated carbon loading Fe2O3 and activity in carbon-nitric oxide reaction

Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime (<500 °C) because of the cooperative effect of Fe2O3 and the surface nitrogen species.     

Catalytic properties of CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Ti0.3O2 in NO＋CO reaction

Using SnxTi1-xO2 as carriers, CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Ti0.3O2 catalysts with different loading amounts of copper oxide (CuO) were prepared by an impregnation method. The catalytic properties of CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Ti0.3O2 were examined using a microreactor-gas chromatography (GC) NO CO reaction system and the methods of BET (Brun- auer-Emmett-Teller), TG-DTA (themogravimetric and differential thermal analysis), X-ray diffraction (XRD) and H2-temperature programmed reduction (TPR). The results showed that NO conversions of Sn0.9Ti0.1O2 and Sn0.7Ti0.3O2 were 47.2% and 43.6% respectively, which increased to 95.3% and 90.9% at 6 wt% CuO loading. However, further increase in CuO loading caused a decrease in the catalytic activity. The nitrogen adsorption-desorption isotherm and pore-size distribution curve of Sn0.9Ti0.1O2 and Sn0.7Ti0.3O2 represented type IV of the BDDT (Brunauer, Deming, Deming and Teller) system and a typical mesoporous sample. There were two CuO diffraction peaks (2θ 35.5° and 38.7°), and the diffraction peak areas increased with increasing CuO loading. TPR analysis also detected three peaks (α, β and γ) from the CuO-loaded catalysts, suggesting that the α peak was the reduction of the highly dispersed copper oxide, the β peak was the reduction of the isolated copper oxide, and the γ peak was the reduction of crystal phase copper oxide. In addition, a fourth peak (δ) of the catalysts meant that the SnxTi1-xO2 mixed oxides could be reductive.     

Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> as indicator of heavy metal enrichment in Zhujiang (Pearl River) estuary sediments

A part of the heavy metals in estuary and coastal zone occurs naturally in the environment; the other part is due to human activity; so the directly measured concentration of heavy metal does not automatically indicate anthropogenic enrichment. Fe₂O₃ was used in this study as conservative tracer to distinguish natural components from anthropogenic components of heavy metal sediment concentration in the Zhujiang estuary. Compared with clay and Al₂O₃, Fe₂O₃ is more suitable as reference element. The final results showed that two zones in the Zhujiang estuary were seriously contaminated by heavy metals. One nearby the Humen mouth; the other around the west coast of the estuary. The horizontal distribution of heavy metals indicates that Zn, Ni and Cu have wider contaminating areas than TiO₂, V and Cr in the estuary.     

Solvothermal synthesis of nanosized CoSb<Subscript>3</Subscript> skutterudite

Nanostructures enhance phonon scattering and improve the figure of merit of thermoelectric materials. Nanosized CoSb₃ skutterudite was synthesized by solvothermal methods using CoCl₂ and SbCl₃ as the precursors. A “two-step” model was suggested for the formation of CoSb₃ based on the X-ray diffraction analysis. The first step is the formation of cobalt diantimonide in the earlier stage during the synthesis process. Diantimonide was then combined with antimony atoms to form the skutterudite structured triantimonide, CoSb₃, in the later stage of the synthesis process as the second step. The synthesized CoSb₃ powders consist of irregular particles with sizes of about 20 nm and sheets of about 80 nm. Project supported by the National Natural Science Foundation of China (No. 50171064) and the Hi-Tech Research and Development Program (863) of China (No. 2002AA302406)     

PE/CaCO3-nanocomposites synthesized by in-situ polymerization

Polyethylene-nanocomposites with CaCO3-weight fractions from 0 to 15 wt.% were prepared by in-situ polymeriza- tion with Me2Si(Ind)2ZrCl2/MAO metallocene catalysts. A high activity especially in the presence of TIBA was observed. The morphology was investigated by using raster electron microscopy (REM) showing that the CaCO3-nanoparticles are uniformly distributed. The melting temperatures and the crystallization temperatures are not much influenced by increasing filler content.     

Green epoxidation of cyclooctene with molecular oxygen over an ecofriendly heterogeneous polyoxometalate-gold catalyst Au/BW<Subscript>11</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

An ecofriendly heterogeneous polyoxometalate (POM)-gold catalyst Au/BW₁₁/Al₂O₃ was synthesized and used for solvent-free epoxidation of cyclooctene under mild reaction conditions using molecular oxygen as an oxidant and t-butyl hydroperoxide (TBHP) as an initiator. The catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), induced coupled plasma optical emission spectrometry (ICP-OES), and Brunauer-Emmett-Teller (BET). The catalyst showed good conversion and high selectivity without use of solvents or environmentally harmful oxidants. Moreover, the catalyst is recyclable up to three cycles with no significant loss in selectivity towards epoxide.     

Thermodynamic Optimization of DyCl3 -NaCl System

In this paper, the phase diagram of the DyCl3 -NaCl system is optimized and calculated with CALPHAD ( calculation of phase diagram ) technology. A set of thermodynamic functions of compounds Na3 DyCl6, NaDyCl4, and NaDY2 Cl7 have been optimized and calculated based on an interactive computer-assisted analysis. The optimized thermodynamic parameters, calculated phase diagram and experimental phase diagram are thermodynamically serf-consistent.     

V2O5-CaCo3-Nb2O5掺杂对低损耗功率Mn-Zn铁氧体的影响

Effect of the content of dopants in the manganese-zinc ferrites on the low power loss is studied by measuring magnetic properties and observing the grain boundary structures. The Mn0.738Zn0.206Fe2.066O4 composition powders were prepared by using conventional ceramic powder processing technique. The microstructure of grain boundary was observed by scanning electron microscope （SEM）. It has been found that power loss is greatly dependent upon the content of the additives.     

Fabrication of LaAlO<Subscript>3</Subscript> film by sol-gel process with corresponding inorganic

Well-cubic perovskite lanthanum aluminate (LaAlO₃) film on (110) silicon substrate was fabricated by sol-gel method with corresponding inorganic salts. Lanthanum acetate and aluminum acetate glacial acetic acid solutions were prepared via ligand exchange starting from lanthanum nitrate hexahydrate and aluminum nitrate hexahydrate after being refluxed. (CH₃CO)₂O removed nitrates and the crystallized H₂O completely, acetylacetone (AcAc) was partially bidentated with metallic ion of the metallic acetates and formed La(OAc)_3−x (AcAc) _x which were hydrolyzed into La(AcAc)_3−x(OH) _x by adding 10 ml 0.4% methyl cellulose (MCL) solution. The La(AcAc)_3−x (OH) _x , polymerizing and combining with MCL, formed the LaAlO₃ sol precursor with heteropolymeric structure and formed film easily. The epitaxial LaAlO₃ film on Si(110) substrate was crystallized after being annealed in thermal annealing furnace for 650–750 °C/30 min. The morphologies and microstructures were characterized. The refractive index of the LAO film was 1.942 to 2.007; the dielectric constant and the dissipation factors were estimated to be 23–26 and 2.1×10⁻⁴−2.4×10⁻⁴ respectively. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China     

A novel reduction of diketones with i-RMgBr catalyzed by Cp<Subscript>2</Subscript>TiCl<Subscript>2</Subscript> and deoxygenation of sulfoxides by Cp<Subscript>2</Subscript>TiCl<Subscript>2</Subscript>/Al system

α-diketones and β-diketones react with Grignard reagents in the presence of a catalytic amount of Cp₂TiCl₂ to yield α-ketols and corresponding ketones respectively. Sulfoxides can be deoxygenated by Cp₂TiCl₂/Al system. The possible mechanisms are also discussed. Project (No. 20072033) supported by the National Natural Science Foundation of China and the Specialized Research Fund for the Doctoral Program of Higher Education Ministry, China     

过冷液相区内轧制温度对Zr52.5Al10Ni10Cu15Be12.5大块金属玻璃表面形貌的影响

Surface morphologies of Zr52.5 Al10 Ni10 Cu15 Be12.5 bulk metallic glass after being rolled at both a temperature around T9 and near （ Tx - 50） K were investigated with a scanning electron microscopy. Macroscopic and microscopic observation results show that squamae, cracks, steps and wedges exist on the surface when the samples were rolled at temperatures around Ty. However, a smooth and fiat surface appears when the samples were rolled at temperatures near （ Tx - 50） K. These results indicate that the mode of deformation in the supercooled liquid region is a partially homogeneous flow at a temperature around T9, and a fully homogeneous one at temperatures near （ Tx - 50） K. According to the results, it is more feasible to roll the amorphous alloys at temperatures near （ Tx - 50） K to obtain parts with smooth and fiat surface.     

The Electrochemical Performance of Ml0.7Mm0.3Ni3.7Co0.7Mn0.4Al0.2 Nanocrystalline Hydrogen Storage Alloy as Metal Hydride Electrode

Ml0.7Mm0.3Ni3.7Co0.7Mn0.4Al0.2 nanocrystalline hydrogen storage materials are prepared by melt-spinning(MS).X-ray diffraction is used for the measurement of the nanocrystalline size.Compared to the electrode of polycrystalline alloys,the property of activation MH9metal hydride)electrode of the alloys with nanometer scale became worse and the inital discharge capacity decreased.It may be ascribed to the decrease of the total amount of rare earth metals and the increase of oxygen on the surface from the analysis of components of the alloys.After heat-treatment,the electrochemical performance of MH electrode of as-spun alloys could be improved,which could be attributed to the alleviation of the lattice strain.     

A SISO mixed<Emphasis Type="Italic">H</Emphasis><Subscript>2</Subscript>/l<Subscript>1</Subscript> optimal control problem and its solution

Study of the SISO mixedH ₂/l₁ problem for discrete time systems showed that there exists a unique optimal solution which can be approximated within any prescribed missing error bound inl ₂ norm with solvable suboptimal solutions and solvable superoptimal solutions. Project supported by the National Natural Science Foundation of China (No. 60174026) and the Scientific Research Foundation for Returned Overseas Chinese Scholars of Zhejiang Province (No. J20020546)     

ZnS<Subscript>0.8</Subscript>Se<Subscript>0.2</Subscript> film for high resolution liquid crystal light valve

The structural characteristics and optical and electrical properties of molecular-beam-epitaxy (MBE) grown ZnS_0.8Se_0.2 thin films on indium-tin-oxide(ITO) glas substrates were investigated in this work. TheX-ray diffraction (XRD) results indicated that high quality polycrystalline ZnS_0.8Se_0.2 thin film grown at the optimized temperature had a prefered orientation along the (111) planes. The transmission electron microscopy (TEM) cross-sectional micrograph of the sample showed a well defined columnar structure with lateral crystal dimension in the order of a few hundred angstroms. Ultraviolet (UV) photoresponsivity as high as 0.01 A/W had been demonstrated and for wavelengths longer than 450 nm, the response was down from the peak response by more than 3 orders of magnitude. The thin ZnS_0.8Se_0.2 photosensor layer, with a wide energy gap and anisotropic electrical property, makes a transmission UV liquid crystal light valve (LCLV) with high resolution feasible. Project supported by the National Natural Science Foundation of China (No. 59910161981) and RGC grant from the Hong Kong Government Grant (No. NSFC/HKUST 35), China     

Preparation and electrochemical application of praseodymium modified TiO<Subscript>2</Subscript>-NTs/SnO<Subscript>2</Subscript>-Sb anode by cyclic voltammetry method

A Pr-doped TiO₂-NTs/SnO₂-Sb electrode was prepared by a simple method, cyclic voltammetry(CV). The methyl orange(MO)aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO₂-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseodymium oxide was successfully doped into the SnO₂-Sb film by CV method. Due to the doped Pr, the oxygen evolution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The C _t /C ₀ (φ) was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.099 3 min^-1. The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.     

Adjuvant effects mediated by the carbohydrate recognition domain of <Emphasis Type="Italic">Agrocybe aegerita</Emphasis> lectin interacting with avian influenza H<Subscript>9</Subscript>N<Subscript>2</Subscript> viral surface glycosylated proteins

Objective

To evaluate the potential adjuvant effect of Agrocybe aegerita lectin (AAL), which was isolated from mushroom, against a virulent H₉N₂ strain in vivo and in vitro.

Methods

In trial 1, 50 BALB/c male mice (8 weeks old) were divided into five groups (n=10 each group) which received a subcutaneous injection of inactivated H₉N₂ (control), inactivated H₉N₂+0.2% (w/w) alum, inactivated H₉N₂+0.5 mg recombinant AAL/kg body weight (BW), inactivated H₉N₂+1.0 mg AAL/kg BW, and inactivated H₉N₂+2.5 mg AAL/kg BW, respectively, four times at 7-d intervals. In trial 2, 30 BALB/c male mice (8 weeks old) were divided into three groups (n=10 each group) which received a subcutaneous injection of inactivated H₉N₂ (control), inactivated H₉N₂+2.5 mg recombinant wild-type AAL (AAL-wt)/kg BW, and inactivated H₉N₂+2.5 mg carbohydrate recognition domain (CRD) mutant AAL (AAL-mutR63H)/kg BW, respectively, four times at 7-d intervals. Seven days after the final immunization, serum samples were collected from each group for analysis. Hemagglutination assay, immunogold electron microscope, lectin blotting, and co-immunoprecipitation were used to study the interaction between AAL and H₉N₂ in vitro.

Results

IgG, IgG1, and IgG2a antibody levels were significantly increased in the sera of mice co-immunized with inactivated H₉N₂ and AAL when compared to mice immunized with inactivated H₉N₂ alone. No significant increase of the IgG antibody level was detected in the sera of the mice co-immunized with inactivated H₉N₂ and AAL-mutR63H. Moreover, AAL-wt, but not mutant AAL-mutR63H, adhered to the surface of H₉N₂ virus. The interaction between AAL and the H₉N₂ virus was further demonstrated to be associated with the CRD of AAL binding to the surface glycosylated proteins, hemagglutinin and neuraminidase.

Conclusions

Our findings indicated that AAL could be a safe and effective adjuvant capable of boosting humoral immunity against H₉N₂ viruses in mice through its interaction with the viral surface glycosylated proteins, hemagglutinin and neuraminidase.

     

在室温和常压下用机械合金化方法制备Fe5C2金属间化合物

Single phase Fe5C2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X-ray differaction spectrum. The decomposing temperature of the Fe5C2 compound is 596.4℃ determined by the DSC curve. It is further shown that the size of nanometer crystal grain is an important condition for carrying out the solid state reaction at room temperature and normal pressure.     

Fall and rise of a D<Subscript>2</Subscript>O ice cube in liquid H<Subscript>2</Subscript>O

In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. “Classroom” is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science.The demonstration described in this article is to show that while H₂O ice floats in water, D₂O ice sinks in water, proving the higher density of ‘heavy water’. This experiment can be done in a classroom or in an auditoriam.