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101.
Nora C. Hopkins Michael K. Kinyon 《Transactions of the American Mathematical Society》1999,351(11):4545-4559
Quadratic differential equations whose associated algebra has an automorphism of order two are studied. Under hypotheses that naturally generalize the cases where the even or odd part of the algebra is one dimensional, the following are examined: structure theory of the associated algebra (ideal structure, simplicity, solvability, and nilpotence), derivations and first integrals, trajectories given by derivations, and Floquet decompositions.
102.
103.
Harry P. Hopkins Jr. David D. Hamilton W. D. Wilson Cynthia T. McMurray 《Journal of solution chemistry》1999,28(6):759-768
Two complementary 23 base-pair oligomers with sequences analogous to the 3, 5-cyclic adenosine monophosphate (cAMP) inducible enhancer region of the human enkaphalin gene were shown previously(6) to undergo reversible conformational transformation from duplex to two individual hairpin structures, with two GT and two AC base mismatches, respectively. The present study uses differential scanning calorimetry (DSC) to determine H values for both the dissociation of the duplex formed by the complementary stands and the melting of each hairpin structure. Melting of the hairpins was studied at several different pH values and both the H and cooperative unit (CU) parameters for the hairpin with the AC base mismatches was found to be pH dependent. Increased values for H of melting and cooperative unit size at lower pH values supports the possibility of protonation of adenosine bases and formation of stable AC base pairs in this latter hairpin. 相似文献
104.
105.
R.H. Hopkins R.G. Seidensticker J.R. Davis P. Rai-Choudhury P.D. Blais J.R. McCormick 《Journal of Crystal Growth》1977
The use of lower purity, lower cost, “solar grade” silicon for crystal growth feed stock has been proposed as one means to reduce the cost of solar cells. The metallic impurities in this material have a deleterious effect on cell efficiency; however, the maximum tolerable impurity concentrations depend not only on the acceptable cell efficiency, but also on the details of the crystal growth process. We wuantitatively analyze the problem using data on relative solar cell efficiency as a function of metallic impurity concentration and the effective segregation coefficients for Czochralski growth. We find, for example, that solar cell performance rather than interface breakdown during crystal growth will most likely determine the permissable impurity content in solar grade silicon. We also show that continuous rather than sequential melt replenishment is advantageous for Czochralski growth. 相似文献
106.
An improved, more general method for performing multicentred integrated QM/QM calculations is presented. The new approach allows the multicentred approximation to be extended to overlapping model systems, removing a significant limitation of the original approach. The usefulness and numerical accuracy of the equations presented are confirmed via some applications to dipole–dipole, charge–dipole and charge–charge complexes. The method performs well for all of these complexes, which range from very weakly to very strongly bound and in which non-additivity effects on interaction energies range from 0.2 to 17kcalmol?1. 相似文献
107.
J. Scott Parent Greg D. F. White Darren J. Thom Ralph A. Whitney William Hopkins 《Journal of polymer science. Part A, Polymer chemistry》2003,41(13):1915-1926
The sulfuration and reversion products of brominated poly(isobutylene‐co‐isoprene) (BIIR) were characterized through the use of a model compound, brominated 2,2,4,8,8‐pentamethyl‐4‐nonene (BPMN). The reaction of BPMN with S8 produced bisallylic polysulfides of various ranks, yielding sulfur bromide intermediates that likely contributed to the rapid oxidation of allylic sulfides into thiophenes. Reductive cure reversion to pentamethylnonene was also observed in the latter stages of vulcanization. The reaction of 2,2′‐dithiobisbenzothiazole with BIIR and BPMN produced a stable adduct that reduced the concentration of allylic bromide available for vulcanization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1915–1926, 2003 相似文献
108.
We have observed a three-dimensional gyroscopic effect associated with a vortex in a dilute Bose-Einstein condensed gas. A condensate with a vortex possesses a single quantum of circulation, and this causes the plane of oscillation of the scissors mode to precess around the vortex line. We have measured the precession rate of the scissors oscillation. From this we deduced the angular momentum associated with the vortex line and found a value close to Planck's over 2pi per particle, as predicted for a superfluid. 相似文献
109.
For all integers m3 and all natural numbers a1,a2,…,am−1, let n=R(a1,a2,…,am−1) represent the least integer such that for every 2-coloring of the set {1,2,…,n} there exists a monochromatic solution to
a1x1+a2x2++am−1xm−1=xm.