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41.
C. Olivier J. W. McMillan T. B. Pierce 《Journal of Radioanalytical and Nuclear Chemistry》1976,31(2):515-523
A technique has been developed to permit the distribution of boron isotopes in metal samples to be measured with the nuclear
microprobe. Samples are irradiated with focussed beams of α-particles, and protons from the (α, p) reactions on both10B and11B are counted. Particle spectroscopy enables contributions from the two isotopes to be determined separately from the same
spectrum and distributions can be followed by varying the position of the ion beam on the sample surface. 相似文献
42.
A study of the condensation of a metal vapor in an inert carrier gas is made. Superheated zinc vapor is generated in a hot
shot wind tunnel in a helium carrier gas and expanded in a converging-diverging nozzle. Static pressure measurements along
the length of the nozzle are made to determine the location of the onset of condensation. A conical nominal Mach 5 (helium)
nozzle is employed. The amount of supercooling before the onset of condensation is found to be approximately 430 K, measured
along the isentrope over a range of initial zinc mass fractions of .35 to .70 for saturation partial pressures of zinc between
10 psia and 70 psia. The measurements are compared with results of an analysis based on the classical liquid drop model of
nucleation. The computed results agree reasonably well with the measurements. 相似文献
43.
Stephen Pierce 《Linear and Multilinear Algebra》1992,33(3):305-306
Topics in Matrix Analysis, Roger A. Horn and Charles R. Johnson, Cambridge University Press, New York, 1991, viii+607 pages. ISBN 0-521-30587-X 相似文献
44.
We find that the topography and composition of a reactive surface can evolve during epitaxy via motion of point and line defects within the material. We observe the response of a NiAl surface to an Al atom flux with low-energy electron microscopy. Initially, new NiAl layers grow as Al atoms exchange with bulk Ni atoms. When the surface is critically enriched in Al, condensation occurs at dislocations. They dissociate, move linearly, and leave tracks of altered composition and new atomic steps. We show how these dynamics depend on the identity and quantity of point defects near the surface. 相似文献
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A biased potential molecular dynamics simulation approach, accelerated molecular dynamics (AMD), has been implemented in the framework of ab initio molecular dynamics for the study of chemical reactions. Using two examples, the double proton transfer reaction in formic acid dimer and the hypothetical adiabatic ring opening and subsequent rearrangement reactions in methylenecyclopropane, it is demonstrated that ab initio AMD can be readily employed to efficiently explore the reactive potential energy surface, allowing the prediction of chemical reactions and the identification of metastable states. An adaptive variant of the AMD method is developed, which additionally affords an accurate representation of both the free-energy surface and the mechanism associated with the chemical reaction of interest and can also provide an estimate of the reaction rate. 相似文献
47.
Frantz MC Pierce JG Pierce JM Kangying L Qingwei W Johnson M Wipf P 《Organic letters》2011,13(9):2318-2321
JP4-039 is a novel nitroxide conjugate capable of crossing lipid bilayer membranes and scavenging reactive oxygen species (ROS). An efficient and scalable one-pot hydrozirconation-transmetalation-imine addition methodology has been developed for its asymmetric preparation. Furthermore, this versatile methodology allows for the synthesis of cyclopropyl and fluorinated analogs of the parent lead structure. 相似文献
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