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101.
Van De Walle CG 《Physical review letters》2000,85(5):1012-1015
Zinc oxide, a wide-band-gap semiconductor with many technological applications, typically exhibits n-type conductivity. The cause of this conductivity has been widely debated. A first-principles investigation, based on density functional theory, produces strong evidence that hydrogen acts as a source of conductivity: it can incorporate in high concentrations and behaves as a shallow donor. This behavior is unexpected and very different from hydrogen's role in other semiconductors, in which it acts only as a compensating center and always counteracts the prevailing conductivity. These insights have important consequences for control and utilization of hydrogen in oxides in general. 相似文献
102.
S. Sugunan D. John N. K. Renuka M. Varghese K. Sreekumar C. G. Ramankutty 《Reaction Kinetics and Catalysis Letters》1999,66(1):39-45
The electron donating properties of manganese ferrospinels of various compositions (MnFe2O4, Mn1.2Fe1.8O4, Mn2FeO4 and Mn2.5Fe0.5O4) were studied from the adsorption of electron acceptors of various electron affinity values from acetonitrile as solvent.
The limit of electron transfer from the oxide surface is from 1.77 to 2.40 eV in terms of the electron affinity of the electron
acceptor. The data have been correlated with the catalytic activity of these oxides towards autoxidation of sulfites. Both
weak and strong electron donor sites catalyze the reaction. 相似文献
103.
A dispersion relation for the perpendicular propagation of the electromagnetic ion cyclotron wave around the second harmonic
of the deuterium ion gyrofrequency in a mildly relativistic, anisotropic Maxwellian plasma with hydrogen as the majority species
and deuterium as the minority component has been derived. The work has been carried out in the frame of reference of the majority
hydrogen ions; to these ions the waves at 2ΘD would be at its own gyrofrequency.
Using a small quantityɛ to order all relevant parameters of the plasma, it was possible to derive the dispersion relations in a simple form. To the
lowest order the relativistic factors do not enter the dispersion relation. The plasma can now support two modes—one above
and the other below the hydrogen gyrofrequency in agreement with the assumptions. This was also verified numerically using
a standard root solver thereby justifying the correctness of the ordering scheme.
In the next higher order, the dispersion relation is a quartic equation and is sensitively dependent on the relativistic factors.
The plasma can now support four modes, both above and below the hydrogen gyrofrequency and consistent with the ordering scheme
used. However the modes can now coalesce resulting in complex conjugate roots to the dispersion relation thereby indicating
an instability.
The advantage of such a scheme is that two dispersion relations — one of which is independent of the relativistic factors
and the other which is sensitively dependent on them can be separated out. 相似文献
104.
Sarma V. Markandeya Ch. Renuka Parvathi K. Lakshmi A. Rajesh Korupolu Raghu Babu 《合成通讯》2018,48(2):135-145
This article describes the synthesis of a new phosphine free tetradentate Pd catalyst using dl-2,3-diaminopropionic acid. The complex was characterized by Mass, IR, and 1H NMR. The catalyst is air stable at room temperature and non-hygroscopic. Application of this new catalyst to regioselective C–H activation on 1-substituted 1,2,3-triazole and indoles with aryl iodides to get corresponding C-5 and C-2 arylated products with satisfactory yields. All the products were characterized by spectroscopic studies. 相似文献
105.
Renuka Charugandla Markandeya Sarma Vangala Sridhar Chidara Raghu Babu Korupolu 《Tetrahedron letters》2018,59(34):3283-3287
The nickel catalyzed, palladium/phosphine free carbonylative Sonogashira reaction of terminal alkynes with substituted aryl and heteroaryl iodides is described. This protocol provides mild and robust conditions to synthesize a variety of substituted aryl α,β-alkynyl ketones and flavones in good to excellent isolated yields. This methodology tolerates several functional groups such as electron donating (methyl, isopropyl, tert-butyl, methoxy) as well as electron withdrawing (trifluoromethyl, nitro, esters, nitrile) groups on the terminal alkynes and iodides. 相似文献
106.
107.
Koster S Duursma MC Boon JJ Nielen MW de Koster CG Heeren RM 《Journal of mass spectrometry : JMS》2000,35(6):739-748
The molecular structure of a series of homo- and copolyesters was studied using sustained off-resonance irradiation collisionally activation dissociation on a Fourier transform ion cyclotron resonance mass spectrometer. Electrospray ionization was used as an ionization technique. The most important fragmentation pathways of the homopolyesters poly(dipropoxylated bisphenol-A/adipic acid) and poly(dipropoxylated bisphenol-A/isophthalic acid) were studied. Six different dissociation mechanisms were observed which are very similar to the mechanisms found to occur during pyrolysis of these compounds. Four of these mechanisms are a result of cleavages of the ester bond and the others are due to cleavages of the ether bond or bisphenol-A unit. Some of the fragments expected are not present in the spectrum, indicating that each fragment has a specific sodium affinity. Sequence-specific fragments of two of the three copolyester sequences that theoretically can exist were experimentally observed. Fragments that originate from the third sequence are not unique and can also be formed from other sequences. Therefore, it was not possible to determine the presence of the third sequence. Copyright 2000 John Wiley & Sons, Ltd. 相似文献
108.
Einstein equations describing gravitational fields are expressed as a compact exterior system of spinor-valued forms. It is
pointed out that Clifford algebra-valued differential forms provide a natural formalism for Einstein gravitational fields.
Finally we try to express these equations in a real spacetime. 相似文献
109.
Sankaran Sugunan Neeroli Kizhakayil Renuka 《Reaction Kinetics and Catalysis Letters》2002,76(1):171-178
Supported vanadia systems synthesized by the excess solvent technique were characterized by different analytical methods. The selective oxidation activity of the system was examined towards the decomposition of ethanol. 相似文献
110.
采用逐步蔓延采样点和三角形的方法,给出了3个算法用于隐函数曲面的采样和三角化,这些算法使得隐函数曲面的重复绘制和控制都能实时进行,其采样方法具有局部适应性,能随着曲率的变化自动控制采样点的疏密程度,从而使得采样点尽量少,但又不至于遗漏表面细节,提出的三角化方法能用于其它散乱数据点的表面重构,它的算法复杂度仅为O(n)。 相似文献