Role of the nature of support on the structure of Au-Rh bimetallic nanoparticles

Au, Rh, and Au-Rh clusters were studied on Al₂O₃, TiO₂ powders and titania nanowire by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). On the XP spectra of the Au-Rh/TiO₂ and Au-Rh/Al₂O₃ powders and wires the binding energy of the Au 4f emission was practically unaffected by the presence of Rh, the position of Rh 3d remained also constant on alumina, while it shifted to lower binding energy with gold admixture on titania. New emission for Rh 3d at 309.2 eV and for Au 4f at 85.6 eV developed on titania wire case. The bands due to Rho-CO and (Rho)₂-CO were observed on IR spectra of titania supported bimetallic samples. The peak due to Rh⁺-(CO)₂ was less intense on bimetallic nanowire. All three bands however are intense on Au-Rh/Al₂O₃. The results were interpreted by electron donation from titania through gold to rhodium. “Core-shell” bimetallic structures are supposed on Au-Rh/titania wire.     

Ion beam modifications of defect sub-structure of calcite cleavages

Experimental investigations on the defect sub-structure and surface modifications, brought about by He⁺ ion-bombardment of calcite cleavages (100), have been carried out. Optical and scanning electron microscopic investigations revealed drastic modifications on the surface morphology, local symmetry and defect concentration. Additional structural defects on ion-bombardment of calcite surfaces also have been observed. Changes in shape and form of chemical etch pits are found to be a function of ion-beam energy, as studied by optical microscopy. Radiation damage in calcite has been attributed mainly due to desorption of CO₃⁻² ions from the calcite surfaces, on irradiation. Measurements of surface conductivity on irradiated calcite surfaces have been made employing a four-probe technique. Enhancement of surface conductivity has been considered to be due to an increase in concentration of CO₃⁻² ions formed, on ion irradiation and subsequent thermal stimulation. Planar plastic anisotropy has been studied on irradiated calcite cleavages by measurement of microhardness.     

Mathematical modeling of the optical characteristics of carbon dioxide

A method of calculating the absorption coefficient in CO₂ rotational-vibrational bands, taking account of the rotational structure, is outlined. Account is taken of the effect of Fermi resonance on the position and intensity of the spectral lines.In the present issue (pp. 121–262), papers on the current state and main lines of development in methods of the mathematical modeling of radiation and complex heat transfer are published; this subject was considered at a combined session of the section on radiant heat transfer of the Scientific Council on Mass and Heat Transfer in Technological Processes of the State Committee of the USSR on Science and Technology and the section on heat and mass transfer of the Scientific Council on Complex Problems of Thermophysics of the Academy of Sciences of the USSR (Minsk, Apr. 6–7, 1978), A report of the session is given on p. 261.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 2, pp. 197–203, February, 1979.     

Effect of silicon on corrosion resistance of Ti-Si alloys

The corrosion resistance of Ti-Si alloys has been studied in acid solutions and the alloys exhibit a high resistance to corrosion. SEM examinations combined with EDAX allowed to conclude that the passive films on Ti-Si alloys are mainly composed of TiO₂/SiO₂ oxides. XPS analysis indicated the formation of Si-O and Si-O-Ti bonds in the passive film, respectively corresponding to SiO₂ and Si-doping TiO₂. The effect of silicon on the corrosion was correlated to the formation of a stable SiO₂ film, Si-doping on TiO₂ and the extended lattice imperfections formed along TiO₂/SiO₂ grain boundaries and phase-boundaries. The calculated donor densities based on the point defect model were shown to depend exponentially on pH and linearly on potential.     

Specific features of deuterium and tritium labeling of SB258585

Samples of SB258 585 labeled with hydrogen isotopes were synthesized. [²H]SB258 585 containing one ²H atom per molecule and [³H]SB258585 with the molar radioactivity of 15 Ci mmol^?1 were obtained in preparative amounts. From 0.18 to 1.5 ²H atoms were incorporated, on the average, into an SB 258 585 molecule depending on the reaction conditions. The isotope exchange efficiency strongly depends not only on the catalyst-substrate ratio and on the reaction temperature, but also on processes occurring on the support surface. The isotope effects strongly influence the degree of deuterium or tritium incorporation into the samples in cases when the organic compound largely decomposes in the course of the reaction.     

The effects of substrates on the thin-film structures of BaTiO3

Barium titanate (BaTiO₃) thin films prepared on magnesia, silicon and strontium titanate substrates by r.f. sputtering has been investigated. As a function of substrate and annealing temperatures, the crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy. Thin films were grown on both MgO and silicon substrates; they were amorphous when deposited on MgO if the substrate temperature was less than 450 °C, while for those grown on silicon the temperature had to be less than 500 °C. Above these elevated temperatures, the films were crystalline, with cubic symmetry. After annealing the thin films on magnesia, the crystal structure changed from cubic to tetragonal phase above 1100 °C; thebe c-axis or annealing thus caused the grain growth of the BaTiO₃. The thin films on SrTiO₃ were found toc-axis oriented tetragonal films for a substrate temperature above 500 °C.     

Standardization Administration of the People's Republic of China (SAC)

Main Responsibilities of SAC 1.To draft and revise the state laws and regulations on standardization, to formulate and implement the policies on standardization; to formulate the national administrative rules on standardization and develop relevant systems; to organize the implementation of laws, rules and systems on standardization; 2.To be responsible for formulating the development programs on standardization of China; to organize, coordinate and draft the programs on the development and revision of national standards;     

Ag基底织构和表面状况对YBCO薄膜性能的影响

采用MOD方法在三种不同织构和表面状态的Ag基底上制备了YBCO薄膜,研究了Ag基底的织构和表面状态对YBCO超导薄膜的影响.在真空中退火的Ag基底上沉积的YBCO薄膜仅有c轴取向,且薄膜表面有很多平行条纹,薄膜的连接性不好,J_c不高;在氩气气氛中退火的Ag基底上沉积的YBCO薄膜,具有很强的c轴取向和良好的面内织构,J_c相对较高为1.2×10⁴A/cm²;冷轧Ag基底沉积的YBCO薄膜织构没有氩气退火的Ag基底上的强,但薄膜的表面平整,连接性好,临界电流密度最高为1.5×10⁴A/cm².     

Investigation of the effect of a microwave field on the curing process and properties of epoxy compositions

We present experimental data on the rate and degree of curing of epoxy compositions discretely reinforced with alumina fibers and filled with barium titanate powder on exposure to microwave radiation. We observed the enhancement of the process of epoxy polymer formation, revealed the dominating effect of the filler—polymer interface on the extent of the conversion of a binder and on the properties of heterogeneous compositions cured in a microwave field. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 6, pp. 1014–1019, November–December, 1997.     

Webometric analysis of Iranian universities of medical sciences

Introduction  There are many researches have been conducted on webometrics, especially the impacts of websites on each other and the web impact factor. However, there are few studies focusing on the websites of Iranian universities. This study analyzed the websites of Iranian universities of medical sciences according to the webometric indicators. Method and materials  In a cross-sectional study, the number of web pages, inlinks, external inlinks and also the overall and absolute web impact factors for Iranian universities of medical sciences with active exclusive websites were calculated and compared using AltaVista search engine. Finally, the websites were ranked based on these webometric indicators. Results  The results showed that the website of Tehran university of medical sciences with 49,300 web pages and 9860 inlinks was ranked first for the size and number of inlinks, while its impact factor was ranked 38th. Rafsanjan UMS with 15 web pages and 211 links had the highest rank for the web impact factor among Iranian universities of medical sciences. Discussions and conclusions  The study revealed that Iranian universities of medical sciences did not have much impact on the web and were not well known internationally. The major reason relies on linguistic barriers. Some of them also suffer from technical problems in their web design.     

Theoretical investigation of the transition temperature of dirty proximity-effect sandwich systems

The influence of impurities and of an interface barrier on the critical temperature of a superconductor-normal (SN) metal sandwich is studied in the Cooper limit. The investigations are based on new equations which allow us to deal with inhomogeneous, dirty superconducting systems near the critical temperature. In contrast with previous treatments, it is shown that at finite film thicknesses,T _c is not only dependent on the N to S thickness ratio, but also on the absolute thickness values, the transmission probability of the interface barrier, and the mean free electron paths. Our results permit the determination of the stay probabilities of McMillan 's tunneling model and the effective length of de Gennes' extended boundary condition on the integral kernel which determinesT _c. Finally, it is shown how the conventional Cooper limit result forT _c by de Gennes is approached.     

Measurement of optical properties of highly scattering ceramic materials

Radiation transfer in highly scattering ceramics is described by a diffusion approximation based on the asymptotic relation of the radiant flux and the radiant energy density in material depth. In this approximation, a calculation of the effective absorption coefficient k and the radiation diffusion coefficient D is based on the measurement of normal-hemispherical transmission of specimens shaped as various-thickness disks. Taken into account are radiation field, twodimensionality, and the radiation boundary reflection effect. The optical property measurements have been performed on the experimental apparatus based on an integrating sphere, a collimated radiation source, and a twochannel data acquisition and processing system. Results of the measurements of k and D for the silica ceramic are given at room temperature.     

The effect of seed layer thickness on alignment and morphology of ZnO nanorods

Thin films of ZnO of 20, 40,160 and 320 nm thickness were deposited on Si (100) substrates by rf-magnetron sputtering and then nanorods were grown on the seed layer at 95 °C for 2 h. The ZnO nanorods were synthesized in C₆H₁₂N₄ and Zn (NO₃)₂·6H₂O solution by a hydrothermal method and the effect of seed layer thickness on the alignment, diameter, density and growth rate of nanorods was studied.The results revealed that the alignment of nanorods depended on crystallinity, grain size and roughness frequency of the sputtered seed layer, so that, with increase of seed layer thickness, crystallinity improved. In addition the grain size increased and the roughness frequency decreased and hence alignment and diameter of nanorods increased.Finally, we present a model for the effect of seed layer thickness on the alignment and diameter of the nanorods.     

Proliferation of osteoblasts and fibroblasts on model surfaces of varying roughness and surface chemistry

Physical and chemical properties of the surfaces of implants are of considerable interest for dental and orthopedic applications. We used self-assembled monolayers (SAMs) terminated by various functional chemical groups to study the effect of surface chemistry on cell behavior. Cell morphology and proliferation on silicon wafers of various roughnesses and topographies created by chemical etching in caustic solution and by corundum sandblasting were analyzed as well. Water contact angle data indicated that oxidized wafer surfaces displayed high hydrophilicity, modification with poly(ethylene glycol) (PEG) created a hydrophilic surface, and an amino group (NH₂) led to a moderately wettable surface. A hydrophobic surface was formed by hydrocarbon chains terminated by CH₃, but this hydrophobicity was even further increased by a fluorocarbon (CF₃) group. Cell proliferation on these surfaces was different depending primarily on the chemistry of the terminating groups rather than on wettability. Cell proliferation on CH₃ was as high as on NH₂ and hydrophilic oxidized surfaces, but significantly lower on CF₃. Precoating of silicon wafers with cell culture serum had no significant influence on cell proliferation. Scanning electron microscopy indicated a very weak initial cell-surface contact on CF₃. The cell number of osteoblasts was significantly lower on sandblasted surfaces compared with other rough surfaces but no differences were detected with 3T3 mouse fibroblasts. The different surface roughnesses and topographies were recognized by MG-63 osteoblasts. The cells spread well on smooth surfaces but appeared smaller on a rough and unique pyramid-shaped surface and on a rough sandblasted surface.     

The effect of seed layer thickness on alignment and morphology of ZnO nanorods

Thin films of ZnO of 20, 40,160 and 320 nm thickness were deposited on Si (100) substrates by rf-magnetron sputtering and then nanorods were grown on the seed layer at 95 °C for 2 h. The ZnO nanorods were synthesized in C₆H₁₂N₄ and Zn (NO₃)₂·6H₂O solution by a hydrothermal method and the effect of seed layer thickness on the alignment, diameter, density and growth rate of nanorods was studied.The results revealed that the alignment of nanorods depended on crystallinity, grain size and roughness frequency of the sputtered seed layer, so that, with increase of seed layer thickness, crystallinity improved. In addition the grain size increased and the roughness frequency decreased and hence alignment and diameter of nanorods increased.Finally, we present a model for the effect of seed layer thickness on the alignment and diameter of the nanorods.     

Effect of thicknesses of copper catalyst and oxide sublayer on morphology of ZnO nanorods

The influence of thicknesses of a ZnO sublayer and a copper catalyst film on the morphology of ZnO nanorods grown by carbothermal synthesis on α-Al₂O₃(11–20) substrates has been studied. An increase in the Cu catalyst film thickness leads to a growth in the diameters, heights, and surface density of nanorods. As the ZnO sublayer thickness is increased, the average diameter of nanorods also increases, while their lengths and surface density decrease. The effect of elevated temperatures on the thermal decomposition of ultrathin Cu films deposited on α-Al₂O₃ substrates has been studied. The photoluminescence characteristics of nanorod arrays have been measured at high levels of optical pumping. An increase in the pumping level to 250–280 kW/cm² leads to superluminescence of the nanorods.     

Effect of Adventitious Carbon on Pit Formation of Monolayer MoS2

Forming pits on molybdenum disulfide (MoS₂) monolayers is desirable for (opto)electrical, catalytic, and biological applications. Thermal oxidation is a potentially scalable method to generate pits on monolayer MoS₂, and pits are assumed to preferentially form around undercoordinated sites, such as sulfur vacancies. However, studies on thermal oxidation of MoS₂ monolayers have not considered the effect of adventitious carbon (C) that is ubiquitous and interacts with oxygen at elevated temperatures. Herein, the effect of adventitious C on the pit formation on MoS₂ monolayers during thermal oxidation is studied. The in situ environmental transmission electron microscopy measurements herein show that pit formation is preferentially initiated at the interface between adventitious C nanoparticles and MoS₂, rather than only sulfur vacancies. Density functional theory (DFT) calculations reveal that the C/MoS₂ interface favors the sequential adsorption of oxygen atoms with facile kinetics. These results illustrate the important role of adventitious C on pit formation on monolayer MoS₂.     

Effect of dilution gases in methane on the deposition of diamond-like carbon in a microwave discharge II: Effect of hydrogen

The effect of hydrogen as a dilution gas on the deposition of diamond-like carbon by the decomposition of methane in a microwave discharge was studied from surface analysis of the substrate and from plasma diagnostics. When carbon deposited from a CH₄-Ar plasma and consisting of large amounts of graphite and small amounts of diamond, was placed in the hydrogen plasma chemical sputtering of carbon to form hydrocarbons and adsorption of hydrogen on the carbon substrate were observed. The reaction occured only on graphite and not on diamond. The effects of hydrogen as a dilution gas on the deposition of diamond-like carbon from CH₄-H₂ plasma are to cause the formation of CH₃ radicals in the plasma, the removal of graphite from the deposit and the adsorption of atomic hydrogen on the deposit as an active participant in the diamond crystallization process.     

审美体验对用户可用性感知影响的元分析

目的 对审美体验与用户可用性感知的影响进行元分析。方法 以22项实证研究为数据来源,考察了审美体验对用户可用性感知的总体综合效用,并对与其相关的三大调节变量测量时机、地域文化和实际可用性等效用进行整合分析。结果 审美体验对用户可用性感知具有中等程度的积极影响。其中,审美体验对可用性感知的影响在实际使用物品之前比实际使用物品之后更为有效。审美体验对用户可用性感知的影响在亚洲最优,在美洲次之,而在欧洲最弱。物品实际可用性方面的差异,也会在一定程度上影响审美体验对可用性的感知。结论 用户对物品可用性的感知总是随着审美体验这一因素的提高而上升,其具体效果受测量时机、地域文化、物品实际可用性的影响,且其中测量时机和地域文化两因素所产生的差异显著。