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161.
R. L. Lichti K. H. Chow D. W. Cooke S. F. J. Cox E. A. Davis R. C. DuVarney T. L. Estle B. Hitti S. R. Kreitzman R. Macrae C. Schwab A. Singh 《Hyperfine Interactions》1994,86(1):711-716
Longitudinal-field muon-spin depolarization rates in high-purityGe and semiinsulatingGaAs are reported and compared to similar data for intrinsicSi. Depolarization onset temperatures provide a comparison of charge carrier concentrations leading to rapid charge exchange and a shift in the onset, for n-typeGaAs verifies anelectron process. The temperature dependence of the low-field rate constants imply more complicated dynamics inGe than observed earlier inSi. Features near 750K inGaAsTe appear consistent with dissociation of aMu-Te pair.This work was supported by the US National Science Foundation (DMR-8917639 [TLE, BH]), the Science and Engineering Research Council of the UK (EAD, AS, SFJC), the Robert A. Welch Foundation (D-1053 [RLL], and C-1048 [TLE]), and a NATO Collaborative Research Grant (RLL, SFJC, RCD, CS). We wish to thank D.A. Vanderwater of Hewlett Packard for providing theGaAsTe sample. 相似文献
162.
We present a systematic analysis on the helium projectile fragments produced from 10.6 A GeV197Auemulsion interactions in an experiment conducted at the Brookhaven AGS. Total charge changing and partial production cross-sections are measured experimentally on the basis of helium multiplicity. The multiplicity distribution of helium fragments which are produced collectively obey a KNO scaling. The transverse momentum distribution of these particles indicates that they are produced from two different independent sources.We are thankful to the BNL technical staff and specially to Dr. D. Beavis for his help in the exposure of emulsion stacks. Thanks are due to Profs. Y. Takahashi and G. Romano for their help in the preparation and development of the emulsion stacks. We appreciate the discussions with Prof. H. Stocker and J. Aichelin. This work was supported by D.O.E. under Grant No. DE-FGO2-90ER 40566. 相似文献
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Summary CuII complexes of the [CuL2(SO4)]·nH2O and [CuL(SO4)(H2O)2]·nH2O type, where L = benzoylhydrazine (PhCONHNH2; BH) or iso-propanone benzoylhydrazone (PhCONHN:CMe2; IBH), L= iso-nicotinoylhydrazine (NC5H4CONHNH2; INH) or isopropanone iso-nicotinoylhydrazone (NC5H4CONHN: CMe2; IINH); n = 0–2, were prepared and characterized by elemental analyses, molar conductances, and electronic, e.s.r. and i.r. spectral measurements. The electronic and e.s.r. spectra suggest a tetragonally distorted octahedral geometry in the solid state as well as in DMSO solution. The e.s.r. data also reveal an axial symmetry for most of the complexes in the solid state and in DMSO solution at 300 and 77 K, while the complex of IBH is isotropic at 300 K. The Ms = 2 transition observed for this complex suggests that it is a dimer. BH and INH bond to CuII through the C-O and NH2 groups, whereas IBH and IINH bond through C-O and C-N groups. 相似文献
167.
Singh SB Ball RG Bills GF Cascales C Gibbs JB Goetz MA Hoogsteen K Jenkins RG Liesch JM Lingham RB Silverman KC Zink DL 《The Journal of organic chemistry》1996,61(22):7727-7737
Farnesyl-protein transferase (FPTase) is an enzyme responsible for the farnesylation of Ras protein. Farnesylation is required for cell-transforming activity in several tumor-types, and therefore, inhibition of FPTase activity may be a potential target for anticancer drugs. Our continued search for novel inhibitors led to the isolation of a number of bicyclic resorcinaldehyde cyclohexanone derivatives named here cylindrols A(1) to A(4), cylindrols B and B(1), and a number of known compounds, from Cylindrocarpon lucidum. The compounds were isolated by bioassay-guided separation using Sephadex LH-20, silica gel, and reverse phase HPLC. Structures were elucidated by extensive application of 2D NMR and X-ray crystallography. The determination of absolute stereochemistry was accomplished by CD measurements. Chemical transformations of the most abundant compound resulted in a number of key derivatives which were critical for the evaluation of structure activity relationship. These compounds are members of ascochlorin family and showed a wide range of inhibitory activity (0.7 &mgr;M to >140 &mgr;M) against FPTase. The FPTase activity was noncompetitive with respect to both substrates. Isolation, structures, chemical transformations, and FPTase activity are discussed in detail. 相似文献
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A note on smoothed estimating functions 总被引:1,自引:0,他引:1
A. Thavaneswaran Jagbir Singh 《Annals of the Institute of Statistical Mathematics》1993,45(4):721-729
The kernel estimate of regression function in likelihood based models has been studied in Staniswalis (1989,J. Amer. Statist. Assoc.,84, 276–283). The notion of optimal estimation for the nonparametric kernel estimation of semimartingale intensity (t) is proposed. The goal is to arrive at a nonparametric estimate
of 0=(t
0) for a fixed pointt
0 [0, 1]. We consider the estimator that is a solution of the smoothed optimal estimating equation
is the optimal estimating function as in Thavaneswaran and Thompson (1986,J. Appl. Probab.,23, 409–417). 相似文献
170.