Spin Dependent Hopping in Ti Doped La0.67 Ca0.33 MnO3

A systematic investigation of the magnetic and transport properties of Ti doped La0.67Ca0.33MnO3 was reported. The Ti substitution for Mn ions results in a reduction in ferromagnetism and conductivity. The metal-insulator transition temperature is close to Curie temperature which decreases from 274 to 82 K as x increases from 0 to 0.17. The most important effect of Ti doping is to introduce spin clusters in the samples due to the distortion of local lattice and the inhomogeneous magnetic structure induced primarily by the random distribution of Mn ions. A maximum magnetoresistance ratio as large as 90% in 1 T at 122 K was obtained for the sample with x =0. 055, which is four times larger than that obtained for LCMO sample at 272 K. There is a remarkable field-history dependent MR in the cooling process for the doped samples while such phenomenon disappears in the warming run. The resistivity follows well the variable range hopping behavior in paramagnetic state. Both the size effect and spin dependent hopping of carriers between the spin clusters should be considered in this system.     

Synthesis, Characterization and Crystal Structure of Quaternary Complex of Gadolinium （Ⅲ）

Ａｎｕｍｂｅｒｏｆｌａｎｔｈａｎｉｄｅｔｅｒｎａｒｙｃｏｍｐｌｅｘｅｓｃｏｎ ｔａｉｎｉｎｇｈｅｔｅｒｏｃｙｃｌｉｃａｍｉｎｅｓｈａｖｅｂｅｅｎｒｅｐｏｒｔｅｄｓｉｎｃｅ1960 [1] .Ｉｎｒｅｃｅｎｔｙｅａｒｓｍｕｃｈａｔｔｅｎｔｉｏｎｈａｓｂｅｅｎｐａｉｄｔｏｑｕａｔｅｒｎａｒｙｃｏｍｐｌｅｘｅｓｏｆｌａｎｔｈａｎｉｄｅｓｂｅｃａｕｓｅｏｆｉｎ ｔｅｒｅｓｔｉｎｇｓｔｒｕｃｔｕｒｅ ,ｃｏｏｒｄｉｎａｔｉｏｎｍｏｄｅ ,ｃｏｍｐｅｔｉｔｉｏｎｒｅ ａｃｔｉｏｎａｎｄｐｒｏｐｅｒｔｙ[2～ 9] .ＥＳＲｃａｎｅ…     

Improved Matrix-Filler Adhesion

Enhanced matrix-filler adhesion is realized after filler treatment with a surface treatment process. The hydrosol/coupling agent treatment was applied to a wide range of inorganic and organic fillers, and adhesion to a variety of matrix resins was improved. Scanning Electron Microscopy (SEM) was used to determine the locus of failure in the filled systems. The locus of failure shows the relative degree of adhesion between the filler and the polymer matrix. Significant improvement in adhesion in humid environments is also observed.     

Capture of Airborne Particulate Using Surface Applied Emulsions: Potential for Postdetonation Dirty Bomb Cleanup

Recent research has proposed the use of asphalt and tall-oil-pitch emulsions for stabilizing radioactive contamination deposited on surfaces in urban areas. The objective of this project was to investigate whether surface applied emulsions could capture airborne radioactive particulate. Laboratory experiments included wind-blown particulate capture studies using an acrylic column and particulate retainment experiments using a wind box capable of producing wind speeds of 96?km/h. A probe methodology was developed to relate particulate retainment to a tack force on the emulsion surface. Experiments were also performed to determine the potential for such emulsions to absorb particulate matter into their emulsion matrix. Tall-oil-pitch emulsions outperformed asphalt emulsions in terms of particulate retention, tack force, and the ability to absorb magnesium silicate. Both tall-oil-pitch and asphalt emulsions were capable of extracting 22–24?g?m?2 of powder from particulate-laden airflow. Tall-oil-pitch emulsions were capable of retaining as much as 5–10% of magnesium silicate powder applied (i.e., retainment densities of 10–20?g?m?2) even after seven?days of curing and after applying 96.5?km/h (60?mph) wind. Tall-oil-pitch emulsions were able to absorb surface-applied magnesium silicate (approximately 0.1–0.2?g of magnesium silicate per 1.0?g of emulsion within three?days) into their emulsion matrix, preventing the magnesium silicate from being exposed to the external environment. Initial results with these five different emulsion formulations suggested particulate capture was feasible. Future emulsion formulations (i.e., longer curing times with greater acid concentrations) should be tested to optimize this postdetonation response strategy.     

Effect of Rare Earth Element Cerium on Mechanical Properties and Morphology of TiN Coating Prepared by Arc Ion Plating

TiN coatings were deposited on polished substrates of W18Cr4V high speed steel by means of vacuum arc ion plating. The effect of cerium on adhesion between TiN coating and substrate was studied. The microstructures and composition of TiN coatings were also investigated by means of scanning electron microscope (SEM), Auger electron spectroscopy (AES), and X-ray diffraction (XRD) technique. It was found that cerium is an effective modifying agent and the addition of suitable amount of cerium to TiN coatings can produce relatively excellent properties such as micro-hardness, wear resistance, oxidation resistance and porosity. The experimental results show that the added cerium in TiN coatings makesa contribution to form the preferred direction along with a (111 ) or (222) close packed face, which may be one of the reasons that improves some properties mentioned above.     

Femtochemistry of Guest Molecules Hosted in Colloidal Zeolites

The ultrafast deprotonation of 2‐(2′‐hydroxyphenyl)benzothiazole (HBT) hosted in nanometer‐sized FAU and MFI zeolites is reported. Samples are prepared via in‐situ incorporation of HBT in the precursor colloidal solutions resulting in the formation of nanometer‐sized zeolites under hydrothermal treatment. The diameter of the zeolite particles formed in the crystalline suspensions is determined by dynamic light scattering and high‐resolution transmission microscopy to lie in the range 40–100 nm. It is shown that the HBT loading does not influence the degree of the zeolite crystallinity but does change the size and the morphology of the individual zeolite nanoparticles. Colloidal suspensions containing the crystalline nanoparticles are well suited for optical investigations since they are sufficiently transparent and clear. The photochemical properties of the HBT guest in the zeolite‐host systems are studied with femtosecond transient transmission spectroscopy. Depending on the acid–base properties either the enol or the keto tautomer of HBT is found to be hosted in the internal voids of the zeolites; upon UV excitation, the HBT‐keto tautomer is converted to the enol form in both MFI‐ and FAU‐type hosts. The HBT photoconversion takes place via an ultrafast deprotonation within 1.5 ps as detected by femtosecond transient absorption spectroscopy.     

Preparation of glucose oxidase immobilized in different carriers using radiation polymerization

Glucose oxidase (EC 1.1.3.4) was immobilized on different polymeric materials using different immobilization techniques (entrapping by γ‐irradiation, and covalent binding using epichlorohydrin). Studies were carried out to increase the thermal stability of glucose oxidase (GOD) for different applications. The activity and stability of the resulting biopolymers have been compared with those of free GOD. The effect of different polyvinyl alcohol/polyacrylamide (PVA/PAAm) compositions of the copolymer carrier on the enzymatic activity of the immobilized GOD was studied. The maximum enzymatic activity was obtained with the composition ratio of PVA/PAAm of 60:40. The behaviour of the free and immobilized enzyme was analysed as a function of pH. A broadening in the pH profile (5.5–8) was observed for immobilized preparations. The activity and stability of the resulting biopolymers produced by immobilization of GOD onto different carriers have been compared, in both aqueous and organic media, with those of the free GOD. The enzyme's tolerance toward both heat and organic solvent was enhanced by immobilization onto polymers. The addition of different concentrations of organic solvents (10–50%, v/v) to the enzyme at higher temperature (60 °C) was found to stabilize the enzyme molecule. The strongest stabilizing effect on the enzymatic activity was achieved at a concentration of 10%. Copyright © 2005 Society of Chemical Industry     

WC对Cu/WC_P复合材料性能及组织的影响

通过ＷＣ含量对ＷＣ／Ｃｕ复合材料性能的影响，确定了冷压－烧结法制备Ｃｕ／ＷＣ材料的适宜ＷＣ含量为１０ｖｏｌ％左右。并就ＷＣ对该材料组织和再结晶行为的影响进行了有益的探讨。     

Equipment for Testing Sheet Structural Materials under Biaxial Tension. Part 2. Testing by Biaxial Loading in the Plane of the Sheet

We analyze specific features of the design of equipment used for mechanical testing of sheet structural materials under the conditions of biaxial static, cyclic, or dynamic loading. We propose original solutions of the problems related to the fatigue testing of crosslike specimens performed without using complex hydraulic systems and their dynamic testing carried out by using very simple testing machines for uniaxial tension–compression.