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1.
We present a review of our recent measurements of total cross sections (Q
T's) for the scattering of positrons by Na, K, and Rb, and positronium-formation cross sections (Q
Ps's) for Na and K. For our total cross section measurements, a beam transmission technique has been used. For ourQ
Ps measurements, our approach involves setting upper and lower limits onQ
Ps using a combination of (1) measuring the transmission of the positron beam with the angular discrimination of the apparatus made as poor as possible, and (2) measuring the 511 keV annihilation gamma rays in coincidence produced by the decay of para-Ps formed in the scattering cell. Comparison with theoretical calculations shows that our measuredQ
T's andQ
Ps's for Na and K agree reasonably well with a close coupling approximation (CCA) calculation which takes into account the formation of Ps in then=1 andn=2 states. In the 3–10 eV energy range, this calculation predicts a peak in theQ
T's andQ
Ps's for K which also appears in our measurements. The absence of such a peak in our measuredQ
T's andQ
Ps's (preliminary) for Na in this energy range is also consistent with the same theory. Comparisons with five-state CCA calculations ofQ
T which do not take Ps-formation into account also show good agreement with our positron-Na, K, and RbQ
T measurements for energies above 20 eV, but show dramatic departures from our measurements below 10 eV for K and Rb. 相似文献
2.
The role of filamentation instability of quark-gluon plasma, in explaining collective phenomena in relativistic heavy-ion
collisions, has been analyzed. Using equations of SU(2) two fluid color hydrodynamics it is shown that this instability can
significantly enhance nuclear stopping and might contribute to collective sideward flows. 相似文献
3.
4.
The aminolysis of a novel activated ester resin was utilized for kinetic study via continuous in situ fluorescence measurements. A variety of resin compositions (polystyrene, JandaJel, ArgoPore, TentaGel, NovaGel, and PEGA) and solvents (dimethylformamide, acetonitrile, tetrahydrofuran, 1,2-dichlorethane, and toluene) were tested to compare their effects on the reaction rate. A linear relationship between the reaction rate and (solvent polarity x swelling of resin) was elucidated for the aminolysis reaction. 相似文献
5.
R. S. Saxena Reshma D. Parikh K. C. Gupta 《Monatshefte für Chemie / Chemical Monthly》1984,115(2):141-146
Potentiometric and conductometric studies on the zinc, cadmium, lead—methylene bis thio acetic acid system in aqueous media reveal the formation of 1:1 and 1:2 (M:L) complexes in thepH range 3.4–5.1. Their stability constants have been determined at 20°, 30° and 40 °C by applyingCalvin andMelchior's extension ofBjerrum's method. The overall changes in thermodynamic function H, G and S accompanying complexation have been evaluated at 30 °C.
Elektrochemische Untersuchungen über Zusammensetzung, Stabilität und Thermodynamik von Zn(II)-, Cd(II)- und Pb(II)-Komplexen mit Methylen-bisthioessigsäure
Zusammenfassung Potentiometrische und konduktometrische Untersuchungen an Zink-, Cadmium- und Blei-Methylen-bis-thioessigsäure-Systemen in wäßrigem Medium zeigten die Bildung von 1:1 und 1:2 (M:L)-Komplexen impH-Bereich 3,4–5,1. Die Stabilitätskonstanten wurden bei 20°, 30° und 40 °C mittels derCalvin-Melchior-Methode (erweiterteBjerrum-Methode) bestimmt. Die thermodynamischen Parameter H, G und S der Komplexierung wurden für 30 °C ermittelt.相似文献
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9.
Brozell AM Muha MA Parikh AN 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11588-11591
We report the formation of microscopic patterns of substrate-supported, 3D planar colloidal crystals using physical confinement in conjunction with surfaces displaying predetermined binary patterns of hydropholicity. The formation process involves a primary self-assembly wherein nano- and microscale colloids order into a photonic fcc lattice via capillary interactions followed by a secondary template-induced crystal cleavage step. Following this method, arbitrary arrays of pattern elements, which preserve structural and orientational properties of the parent crystal, can be easily obtained. 相似文献
10.