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排序方式: 共有419条查询结果,搜索用时 164 毫秒
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2.
The gas-sensing mechanism of an n-type semiconductor (tin dioxide) gas sensor is reviewed in this paper. It is demonstrated
that very high sensitivity can be obtained only when the crystallite size is less than -10 nm. Various mechanisms involving
the surface and the bulk modifications of the semiconductor oxide gas sensors are discussed to improve the gas sensitivity.
Current challenges and problems in nanocrystalline oxide gas sensors are also presented. 相似文献
3.
Nano-crystal embedded PbO-P2O5 glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within
the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region.
The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment
of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature.
A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic
elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic
velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination
of the size of nano-crystals from the ultrasonic attenuation data. 相似文献
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Rodrigo F. Ortiz-Meoz Liping Wang Rosalie Matico Anna Rutkowska-Klute Martha De la Rosa Sabrina Bedard Robert Midgett Katrin Strohmer Douglas Thomson Cunyu Zhang Makda Mebrahtu Jeffrey Guss Rachel Totoritis Thomas Consler Nino Campobasso David Taylor Tia Lewis Kurt Weaver Marcel Muelbaier John Seal Richard Dunham Wieslaw Kazmierski David Favre Giovanna Bergamini Lisa Shewchuk Alan Rendina Guofeng Zhang 《Chembiochem : a European journal of chemical biology》2021,22(3):516-522
Indoleamine-2,3-dioxygenase 1 (IDO1) is a heme-containing enzyme that catalyzes the rate-limiting step in the kynurenine pathway of tryptophan (TRP) metabolism. As it is an inflammation-induced immunoregulatory enzyme, pharmacological inhibition of IDO1 activity is currently being pursued as a potential therapeutic tool for the treatment of cancer and other disease states. As such, a detailed understanding of the mechanism of action of IDO1 inhibitors with various mechanisms of inhibition is of great interest. Comparison of an apo-form-binding IDO1 inhibitor (GSK5628) to the heme-coordinating compound, epacadostat (Incyte), allows us to explore the details of the apo-binding inhibition of IDO1. Herein, we demonstrate that GSK5628 inhibits IDO1 by competing with heme for binding to a heme-free conformation of the enzyme (apo-IDO1), whereas epacadostat coordinates its binding with the iron atom of the IDO1 heme cofactor. Comparison of these two compounds in cellular systems reveals a long-lasting inhibitory effect of GSK5628, previously undescribed for other known IDO1 inhibitors. Detailed characterization of this apo-binding mechanism for IDO1 inhibition might help design superior inhibitors or could confer a unique competitive advantage over other IDO1 inhibitors vis-à-vis specificity and pharmacokinetic parameters. 相似文献
7.
Dilip Chandra Ghimire Sudip Adhikari Hideo Uchida Masayoshi Umeno 《Diamond and Related Materials》2006,15(11-12):1792
We report the effects of gas composition pressure (GCP) on the optical, structural and electrical properties of thin amorphous carbon (a-C) films grown on p-type silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (MW SWP CVD). The films, deposited at various GCPs ranging from 50 to 110 Pa, were studied by UV/VIS/NIR spectroscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and current–voltage characteristics. The optical band gap of the a-C film was tailored to a relatively high range, 2.3–2.6 eV by manipulating GCPs from 50 to 110 Pa. Also, spin density strongly depended on the band gap of the a-C films. Raman spectra showed qualitative structured changes due to sp3/sp2 carbon bonding network. The surfaces of the films are found to be very smooth and uniform (RMS roughness < 0.5 nm). The photovoltaic measurements under light illumination (AM 1.5, 100 mW/cm2) show that short-circuit current density, open-circuit voltage, fill factor and photo-conversion efficiency of the film deposited at 50 Pa were 6.4 μA/cm2, 126 mV, 0.164 and 1.4 × 10− 4% respectively. 相似文献
8.
Sudip Adhikari Sunil Adhikary Ashraf M.M. Omer Mohamad Rusop Hideo Uchida Tetsuo Soga Masayoshi Umeno 《Diamond and Related Materials》2005,14(11-12):1824
Nitrogenated diamond-like (DLC:N) carbon thin films have been deposited by microwave surface wave plasma chemical vapor deposition on silicon and quartz substrates, using argon gas, camphor dissolved in ethyl alcohol composition and nitrogen as plasma source. The deposited DLC:N films were characterized for their chemical, optical, structural and electrical properties through X-ray photoelectron spectroscopy, UV/VIS/NIR spectroscopy, Raman spectroscopy, atomic force microscope and current–voltage characteristics. Optical band gap decreased (2.7 to 2.4 eV) with increasing Ar gas flow rate. The photovoltaic measurements of DLC:N / p-Si structure show that the open-circuit voltage (Voc) of 168.8 mV and a short-circuit current density (Jsc) of 8.4 μA/cm2 under light illumination (AM 1.5 100 mW/cm2). The energy conversion efficiency and fill factor were found to be 3.4 × 10− 4% and 0.238 respectively. 相似文献
9.
We developed surface‐modified silica fillers by coating these with an acrylate monomer, trimethylolpropane triacrylate, or a silane coupling agent, triethoxyvinyl silane, followed by electron‐beam irradiation at room temperature. These were incorporated in an ethylene–octene copolymer rubber. Thermorheological studies of the unvulcanized ethylene–octene copolymer and its untreated and modified silica‐filled composites were done with a shear dynamic oscillating rheometer. Modification of the silica filler, especially via the silanization process followed by electron beam treatment, significantly reduced filler–filler networking as revealed from the log–log plots of storage modulus and complex shear viscosity, and its real component. The rheological complexity of the compositions was analyzed from a double logarithmic plot of the storage modulus and loss modulus. The results obtained from the master curves constructed on the basis of the time–temperature superposition principle and the activation energy calculated from the Arrhenius equation for the flow of above these compounds further supported these findings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2453–2459, 2003 相似文献
10.
Arvind Agarwal Tim McKechnie Sudipta Seal 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(9):42-44
Research Summary Nanostructured ceramics and their composites possess improved properties such as tensile strength, fatigue
strength, hardness, and wear resistance. Freestanding, near-net shape, nanostructured Al2O3 components can be synthesized via plasma-spray forming. In this study, plasma-spray parameters were optimized and an innovative
substrate cooling technique was developed to retain nanosize Al2O3 in the spray deposit. Nanosize Al2O3 particles were partially melted and trapped between the fully melted coarser, micrometersize Al2O3grains. Densification of the spray-deposited Al2O3occurred via solidification and sintering. A similar processing approach can be adopted for fabrication of near-net shapes
of a variety of nanostructured materials (metals, ceramics, and intermetallics) and their combinations by selecting suitable
powder-treatment and plasmaspray parameters. 相似文献