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981.
982.
Richard F. Smith Lisa A. Dennis William J. Ryan George Rodriguez Keith A. Brophy 《Journal of heterocyclic chemistry》1992,29(1):181-183
Three mechanistic pathways are considered for the hydroxide-promoted conversion of 1,1-disubstituted-3-amino-4,5-dihydro-1H-pyrazolium halides 1 to 1,1-disubstituted hydrazines, ammonia and sodium 3-hydroxypropanoate. Evidence presented in this paper supports a hydrolysis mechanism c that is initiated by hydroxide ion addition to the 3-position of 1 to form a tetrahedral intermediate 7 . 相似文献
983.
Christopher G MoorePatrick J Murphy Harri L WilliamsAlan T McGown Nigel K Smith 《Tetrahedron letters》2003,44(2):251-254
A potentially biomimetic synthesis of the guanidine-containing marine natural product crambescidin 359 via a double Michael addition of guanidine to a suitably functionalised bis-enone is reported. 相似文献
984.
E. D. Minor T. A. Armstrong B. Chen R. A. Lewis G. A. Smith 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(4):447-454
Spectra of protons with momenta greater than 500 MeV/c following antiproton annihilation at rest in carbon and uranium nuclei have been measured. They are compared to recent results from other experiments and to predictions of an intranuclear cascade model. Evidence is presented for a substantialB>0 component in the annihilation process, and an estimate of the magnitude of that component is made. 相似文献
985.
986.
Gregory R. Lumpkin Katherine L. Smith Mark G. Blackford Reto Gier C. Terry Williams 《Micron (Oxford, England : 1993)》1994,25(6):581-587
In this paper we describe a technique for the determination of 25 elements in natural zirconolite using energy-dispersive analytical electron microscopy (AEM). The method presented here allows one to quantitatively investigate the chemistry of submicron-scale zones in complex oxide minerals. The effects of electron channeling, thickness variability and variations in detector resolution were minimized by using a controlled set of operating procedures and instrument parameters. To provide a high level of accurayy, kATI-factors were determined from standards for most of the 25 elements of interest, including all of the major elements. Each analytical spectrum is reduced to a set of raw peak counts (and errors) using a digital top-hat filter to suppress background followed by multiple least squares fitting of reference spectra. Counting times of 12–15 min per analysis were required to provide suitable counting statistics. Results are presented for zirconolite samples from the contact metamorphic aureole of the Bergell granodiorite intrusion, Switzerland-Italy. A comparison of 43 AEM analyses with 15 analyses obtained by wavelength-dispersive electron probe microanalysis (EPMA) shows that there is excellent agreement between the two data sets in the amounts of individual elements present, chemical trends and overall stoichiometry. An assessment of the combined data set shows that the major substitution mechanisms in the Bergell samples are coupled substitutions involving the M5,6- and M8-sites of the zirconolite structure: M8Ca2+ + M5,6Ti4+→M8REE3+ + M5,6(Al,Fe)3+ and M8Ca2+ + M5,6Ti4+→M8(Th,U)4+ + M5,6 (Mg,Fe)2+. 相似文献
987.
E. Oltman P. Auchincloss R. E. Blair C. Haber S. R. Mishra M. Ruiz F. J. Sciulli M. H. Shaevitz W. H. Smith F. S. Merritt M. J. Oreglia P. G. Reutens R. Coleman H. E. Fis D. Levinthal W. Marsh P. A. Rapidis H. B. White D. Yovanovitch A. Bodek F. Borcherding N. Giokaris K. Lang I. E. Stockdale 《Zeitschrift fur Physik C Particles and Fields》1992,53(1):51-71
Structure functions obtained from high energy neutrino and antineutrino scattering from an iron target are presented. These were extracted from the combined data of Fermilab experiments E616 and E701; these utilized narrow band beam runs between 1979–1982. The structure functions are used to test the validity of quarkparton model (QPM) predictions and to extract the QCD scale parameter Λ from fits to the Altarelli-Parisi equations. 相似文献
988.
Christopher M. Collins Shizhe Li Qing X. Yang Michael B. Smith 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,125(2):233-241
A method for calculatingB1field strength and homogeneity as functions of radiofrequency shield geometry is presented. The method requires use of three-dimensional finite-element analysis, birdcage-coil theory, and antenna-array theory. Calculations were performed for a 12-element birdcage coil (19 cm diameter, 21 cm length) at 125 MHz. CalculatedB1field strengths and homogeneities for the coil in 25 different shields and in no shield are given. For configurations where the shield is longer than the coil, bothB1field strength and homogeneity decrease as shield diameter decreases or as shield length increases. In configurations where the shield is shorter than the coil and has a diameter of 25.6 cm,B1homogeneity is greater than in an unshielded coil.B1field strength was measured experimentally at 125 MHz in a birdcage coil of the same geometry as the model within shields of four different diameters. Calculated results very closely matched experimental measurement. 相似文献
989.
Jianjun Liu Chun-gang DuanM.M Ossowski W.N MeiR.W Smith J.R Hardy 《Journal of Physics and Chemistry of Solids》2002,63(3):409-414
Structural phase transition in AgNO3 at high temperature is simulated by molecular dynamics. The simulations are based on the potentials calculated from the Gordon-Kim modified electron-gas formalism extended to molecular ionic crystals. AgNO3 transforms into rhombohedral structure at high temperature and the phase transition is associated with the rotations of the NO3 ions and displacements of the NO3 and Ag ions. 相似文献
990.
Isaac Dyner Ricardo A. Smith Gloria E. Peña 《The Journal of the Operational Research Society》1995,46(10):1163-1173
A System Dynamics model to simulate the substitution of installed household appliances by more efficient ones is presented. The model allows the construction of scenarios and also the analyses of several other issues such as: alternatives for technology penetration, electricity consumption growth, gas consumption growth and effects of pricing policies on various energy demands. The proposed methodology has been applied to assist the decision process in relation to gas penetration policies. The model also supports policy making on energy efficiency and it allows the calculation of total energy savings under different scenarios. Furthermore, government underpricing policies on tariffs and appliance acquisition (longer loan terms, lower interest rates and grace periods) may also be analysed. 相似文献