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排序方式: 共有773条查询结果,搜索用时 375 毫秒
31.
A branching point is a point on a reaction path leading from reactants to products (via a transition state) at which it is energetically favorable for the system to break symmetry. Such a point can be defined in terms of normal modes along the reaction path and corresponds to zero curvature (a zero Hessian eigenvalue) along a symmetry-breaking mode. An effective method for the location of such points is presented and realized in an efficient, practical algorithm designed for use in the ab initio program package Gaussian 82. 相似文献
32.
Capon RJ Skene C Liu EH Lacey E Gill JH Heiland K Friedel T 《Natural product research》2004,18(4):305-309
Bioassay directed fractionation of a Raspailia (Raspailia) sp. (Order Poecilosclerida; Family Raspailiidae) collected during scientific trawling operations off the Northern Rottnest Shelf yielded as nematocidal agents the known metabolites, phorboxazoles A (1) and B (2). Further examination revealed the new natural product but known synthetic compound, esmodil (3). The structure for 3 was confirmed by spectroscopic analysis and total synthesis. 相似文献
33.
Solid state radioluminescent lighting 总被引:1,自引:0,他引:1
C. L. Renschler J. T. Gill R. J. Walko C. S. Ashley T. J. Shepodd S. T. Reed G. M. Malone L. E. Leonard R. E. Ellefson R. L. Clough 《Radiation Physics and Chemistry》1994,44(6):629-644
We have demonstrated novel types of tritium-powered, solid-phase radioluminescent (RL) light sources. These lights include: (1) all-organic formulations comprised of polystyrene and fluorescent organic dyes; (2) polydimethylsiloxane-based systems incorporating inorganic phosphors; and (3) inorganic aerogel-based systems doped with phosphors. Three principal design consideration for these new RL lights are described. These include: (1) incorporation of tritium into the solid matrix; (2) molecular engineering to maximize light-output efficiency; and (3) strategies for increasing longevity. The advanced RL lights, which are of interest due to potential advantages in efficiency, brightness and safety, are being developed for emergency lighting uses and for battery and lighting applications in remote locations. 相似文献
34.
In a combination of cobalt-mediated cationic and free radical chemistry, treatment of the allyl silane substituted β-hydroxycobaloxime 13 with pTSA led predominantly to the trans-disubstituted cyclopentane 14, which on irradiation with TEMPO produced 15. In a similar manner, the cobaloxime 18 was cyclised to 19 in the presence of pTSA which, on irradiation with a sunlamp then underwent radical mediated cyclisation to the substituted indane 20. 相似文献
35.
R. D. Gill 《Probability Theory and Related Fields》1980,53(1):97-116
Summary Uniform consistency and weak convergence is proved of estimators of the transition probabilities of an arbitrary finite state space Markov renewal process, based on n independent and identically distributed right censored realizations of the process. The approach uses the theory of stochastic integrals and counting processes. It is shown how the results may be extended to the non-identically distributed case and to general censorship under suitable conditions. 相似文献
36.
Nisar Ahmad M. Akram K.P. Gill S.P. Asdaq R.M. Akhtar M. Saleem M.A. Baig 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,41(3):159-163
A narrow bandwidth ring dye laser pumped by an argon ion laser has been used to investigate the hyperfine structure of the even and odd parity levels of tantalum by optogalvanic spectroscopy in the wavelength range 5640 to 6050 Å. Seventeen transitions have been observed and eight of these have not been reported in the literature so far. These transitions involve 27 levels with 15 odd and 12 even parity configurations. The magnetic dipole hyperfine interaction constants A and the electric quadrupole interaction constants B for these levels have been computed and compared with the data available in literature. The results for the levels at 34799.71 cm?1, 26960.46 cm?1 and 19657.78 cm?1 are reported for the first time. 相似文献
37.
The standard enthalpies of solution of rare gases (helium, neon, argon, krypton, and xenon) in water at 25°C have been measured by a high precision steady-state calorimetric method. The aqueous solvation process is energetically favorable at 25°C for the gases studied. Values of the standard free energy, enthalpy, and entropy changes are found to be well correlated with cavity surface areas and the number of water molecules in the first solvation shell. Also, the values of the standard enthalpy and entropy of solution for the rare gases are found to have the same dependence on the number of solvation shell water molecules as inorganic and hydrocarbon gases. These results imply that the dominant source of enthalpy and entropy change resides in the first solvation shell. 相似文献
38.
Peter M.W. Gill Darragh P. O'Neill Nicholas A. Besley 《Theoretical chemistry accounts》2003,109(5):241-250
Two-electron distribution functions and intracules are functions of electronic coordinates and occupy an important, and frequently
overlooked, middle ground between the beguiling simplicity of electron densities and the bewildering complexity of wavefunctions.
We survey the functions that have been considered by earlier workers and introduce two new ones, the Wigner intracule and
the action intracule, that have not previously been discussed. To illustrate their usefulness, we consider the intracules
of jellium, a few small atoms and the dissociating hydrogen molecule.
Received: 26 July 2002 / Accepted: 20 October 2002 /
Published online: 30 January 2003
Correspondence to: P.M.W. Gill e-mail: peter.gill@nott.ac.uk 相似文献
39.
Dip Singh Gill 《Journal of solution chemistry》1979,8(10):691-699
Precise conductances for tetrabutylammonium tetrabutylboride (Bu4NBBu4) at 25°C have been measured in a number of nonaqueous solvents, and the data have been analyzed by the 1957 Fuoss-Onsager conductance equation. Limiting ion conductances for the Bu4N+ ion at infinite dilution 0(Bu
4
N
+) in various solvents have been evaluated by dividing 0 values of the salt into two equal parts. The 0(Bu
4
N
+) values so obtained are in fairly good agreement (within±0.1–3.5%) with the corresponding values determined from direct transference number measurements in these solvents. 相似文献