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排序方式: 共有297条查询结果,搜索用时 15 毫秒
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The oscillating CO oxidation on Pt is examined as a possible candidate for the Takoudis, Schmidt and Aris (TSA) model. Moreover the results of our Monte Carlo simulation of this model reaction are tentatively compared to TSA numerical results. 相似文献
56.
Stannyl and silyl alkylselenides have been efficiently transformed to the corresponding alkylselenolates on reaction with butyllithiums. Other conditions proved to be limited. 相似文献
57.
This paper is concerned with the piecewise linear finite element approximation of Hamilton–Jacobi–Bellman equations. We establish the optimal L ∞-error estimate, combining the concepts of subsolution and discrete regularity. 相似文献
58.
V. Th venot V. Souliere H. Dumont Y. Monteil J. Bouix P. Regreny Tran-Minh Duc 《Journal of Crystal Growth》1997,170(1-4):251-256
InP substrates and epilayers grown by MOVPE have been studied by AFM. For different misorientation angles, we observed the surface of the substrate after annealing under phosphine (PH3) and of the epilayers under different growth conditions such as growth temperature Tg and trimethylindium (TMI) partial pressure. After annealing the terrace width corresponds to the nominal value of misorientation angle measured by X-ray diffraction. We observed different topographies and roughnesses for the grown layers corresponding to different growth modes. We propose, taking into account the roughness of the surface, a calculation of the step height and terrace width. For 2D nucleation (θ ≤ 0.2° and Tg = 500°C) and step flow mode, the roughness is low while it is increased by step bunching (θ ≥ 0.5° and Tg ≥ 580°C). Moreover we have examined the surface morphology for different misorientation angles and determined the influence of growth conditions (growth temperature, indium partial pressure) on the growth mechanism. At Tg = 580°C the increase of the TMI partial pressure in the reactor enhances the step bunching and leads to larger terraces. 相似文献
59.
Integrated molecular orbital-molecular orbital (IMOMO) calculations on 17 short disulfide-bridged peptides (up to 16 residues, with at most five intraloop residues) were performed to elucidate some factors controlling their electron capture. These illustrative systems display contrasted behaviors, shedding light on several criteria of differentiation: size, shape, and rigidity of the disulfide-linking loop, intramolecular hydrogen bonds, etc. The geometrical malleability of disulfide radical anions, whose existence and role as intermediate have been evidenced, is discussed. The disulfide elongation (by ca. 0.7 A) upon electron capture induces "soft" structural damages for these turn structures, with a weakening or cleavage of vicinal hydrogen bond(s). On the basis of a series of six Cys-Alan-Cys peptides, it is proposed that electron affinity reflects the topological frustration of these short and highly constrained structures. Results for a series of amino acid mutations are analyzed for the Cys-Xxx-Yyy-Cys motif, common to redox enzymes of the thioredoxin superfamily. 相似文献
60.
MJ Singh DO Kataria N Madhavan P Sugathan JJ Das DK Awasthi AK Sinha R Shanker 《Pramana》1999,53(4):743-764
A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer
processes in collisions of 60–120 MeV Si
q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization,
electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated.
The data reported on the present collision system result from a direct measurement in the considered impact energy for the
first time. The total ionization cross-sections for the recoil ions are shown to scale as q
1.7/E
p
0.5
, where E
p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing
recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j
2 upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing
cross-sections σ
qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow
our data for different ionization processes is reviewed and discussed. 相似文献