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排序方式: 共有396条查询结果,搜索用时 140 毫秒
81.
Partha P. Bera Kurt W. Sattelmeyer Martin Saunders Henry F. III Schaefer Paul von Rague Schleyer 《ChemInform》2006,37(30):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献
82.
83.
We compare different discreted DCF Raman amplifier configurations, including single-stage and dual-stage. The optimum design with respect to SNR degradation, compromise linear and nonlinear impairments. 相似文献
84.
The polycrystalline samples of Pb(Li1/4Dy1/4W1/2)O3 have been synthesized by high-temperature solid-state reaction techniques. Room temperature X-ray diffraction (XRD) studies
of the compound provided preliminary structural data, and hence formation of a single phase desired material was confirmed.
Detailed studies of dielectric constant (ε) and loss (tanδ) as a function of frequency (100 Hz to 10 kHz) at room temperature (298 K) and also as a function of temperature (liquid
nitrogen to 403 K) at 10 kHz suggest that the compound undergoes a ferroelectric phase transition of diffuse type. 相似文献
85.
Moon Sig Joo Byung Jin Cho Chia Ching Yeo Siu Hung Chan D. Sung Jin Whoang Mathew S. Kanta Bera L. Balasubramanian N. Dim-Lee Kwong 《Electron Devices, IEEE Transactions on》2003,50(10):2088-2094
We demonstrate that a high quality metal organic chemical vapor deposition (MOCVD) HfAl/sub x/O/sub y/ (hereafter HfAlO) dielectric film can successfully be deposited with a wide range of composition controllability between HfO/sub 2/ and Al/sub 2/O/sub 3/ in HfAlO using a single cocktail liquid source HfAl(MMP)/sub 2/(OiPr)/sub 5/. A composition ratio between 45 to 90% of HfO/sub 2/ in HfAlO is achieved by controlling deposition process parameters. The effect of the composition ratio between HfO/sub 2/ and Al/sub 2/O/sub 3/ on the electrical properties of the film is also investigated. The HfAlO film with 90% HfO/sub 2/ (10% Al/sub 2/O/sub 3/), which has minimum sacrifice of K value (around 19), shows a great improvement in thermal stability and significant reduction of interfacial layer growth during subsequent thermal processes, leading to the reduction in leakage current by around 2 orders of magnitude compared to pure HfO/sub 2/ film. The HfAlO film also shows good compatibility with TaN metal gate electrode under high temperature annealing process. 相似文献
86.
Rajendra K. Bera 《国际流体数值方法杂志》1988,8(7):759-768
An accurate numerical scheme has been devised to study the self-induced motion of an infinitely thin, free vortex sheet of finite span in an unbounded, inviscid, incompressible fluid. The new numerical scheme has been tested against two vortex sheet problems for which exact solutions have also been obtained. The agreement between the numerical and exact solutions is excellent. The scheme has been further tested against two more examples for which analytical solutions for small times were available. Here too the agreement is excellent. 相似文献
87.
Nanobimetallic particles consisting of Au-Pd, Au-Ag, and Au-Pt have been synthesized in a single step by a sol-gel process and stabilized in liquid and solid matrices. Organically modified silicates (Ormosils) that play a dual role of a matrix and of a stabilizer have been used to obtain very stable dispersions in the form of sols, gels, and monoliths. The simultaneous reduction of metal ions leads to either a surface enriched with one component or an alloy type of structure depending on the bimetal combination. The nanometallic dispersions are characterized by absorbance, TEM, XRD, IR, XPS, and CO adsorption studies. The stabilized nanoparticles are found to be good electrocatalysts and the preliminary results on the electrochemical reduction of oxygen are reported. 相似文献
88.
Campos-Fernández CS Schottel BL Chifotides HT Bera JK Bacsa J Koomen JM Russell DH Dunbar KR 《Journal of the American Chemical Society》2005,127(37):12909-12923
Reactions of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with solvated first-row transition metals M(II) (M(II) = Ni, Zn, Mn, Fe, Cu) have been explored with emphasis on the factors that influence the identity of the resulting cyclic products for Ni(II) and Zn(II). The relatively small anions, namely [ClO4]- and [BF4]-, lead to the formation of molecular squares [{M4(bptz)4(CH3CN)8} subsetX][X]7, (M = Zn(II), Ni(II); X = [BF4]-, [ClO4]-), whereas the larger anion [SbF6]- favors the molecular pentagon [{Ni5(bptz)5-(CH3CN)10} subsetSbF6][SbF6]9. The molecular pentagon easily converts to the square in the presence of excess [BF4]-, [ClO4]-, and [I]- anions, whereas the Ni(II) square can be partially converted to the less stable pentagon under more forcing conditions in the presence of excess [SbF6]- ions. No evidence for the molecular square being in equilibrium with the pentagon was observed in the ESI-MS spectra of the individual square and pentagon samples. Anion-exchange reactions of the encapsulated ion in [{Ni4(bptz)4(CH3CN)8} subsetClO4][ClO4]7 reveal that a larger anion such as [IO4]- cannot replace [ClO4]- inside the cavity, but that the linear [Br3]- anion is capable of doing so. ESI-MS studies of the reaction between [Ni(CH3CN)6][NO3]2 and bptz indicate that the product is trinuclear. Mass spectral studies of the bptz reactions with Mn(II), Fe(II), and Cu(II), in the presence of [ClO4]- anions, support the presence of molecular squares. The formation of the various metallacyclophanes is discussed in light of the factors that influence these self-assembly reactions, such as choice of metal ion, anion, and solvent. 相似文献
89.
90.
Dr. Debobrata Sheet Abhijit Bera Yang Fu Antonin Desmecht Prof. Olivier Riant Prof. Sophie Hermans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(39):9191-9196
Poly(amidoamine) dendrimers grafted on carbon nanotubes have been appended with iron(II)-α-keto acid (benzoylformate) complex of polypyridyl ligand to design artificial non-heme oxygenase model. This nano-enzyme was applied for selective catalytic oxidation of organic molecules. Although the carbon nanotubes serve as a robust heterogeneous platform, the amine terminals of dendrimers provide catalysts binding sites and the amide bonds provide a necessary second coordination sphere similar to the enzymatic polypeptide chains. Such a hybrid design prevented the deactivation of the primary active sites leading to 8 times faster oxidative decarboxylation rates than those of its homogeneous analogue. An electrophilic iron(IV)-oxo intermediate has been intercepted, which catalyzes the selective oxidation of alcohols to aldehydes and incorporates single oxygen atoms into sulfides and olefins by using aerial oxygen with multiple turnover numbers. The catalyst was consecutively regenerated three times by mild chemical treatment and showed negligible loss of activity. 相似文献