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排序方式: 共有186条查询结果,搜索用时 234 毫秒
111.
Briere RA Chen GP Ferguson T Tatishvili G Vogel H Adam NE Alexander JP Bebek C Berger BE Berkelman K Blanc F Boisvert V Cassel DG Drell PS Duboscq JE Ecklund KM Ehrlich R Gibbons L Gittelman B Gray SW Hartill DL Heltsley BK Hsu L Jones CD Kandaswamy J Kreinick DL Magerkurth A Mahlke-Krüger H Meyer TO Mistry NB Nordberg E Palmer M Patterson JR Peterson D Pivarski J Riley D Sadoff AJ Schwarthoff H Shepherd MR Thayer JG Urner D Valant-Spaight B Viehhauser G Warburton A Weinberger M Athar SB 《Physical review letters》2002,89(8):081803
We determine the weak coupling /V(cb)/ between the b and c quarks using a sample of 3 x 10(6) BB; events in the CLEO detector at the Cornell Electron Storage Ring. We determine the yield of reconstructed B-->D*l nu; decays as a function of w, the boost of the D* in the B rest frame, and from this we obtain the differential decay rate d Gamma/dw. By extrapolating d Gamma/dw to w=1, the kinematic end point at which the D* is at rest relative to the B, we extract the product /V(cb)/F(1), where F(1) is the form factor at w=1. Combined with theoretical results for F(1) we determine /V(cb)/=0.0469+/-0.0014(stat)+/-0.0020(syst)+/-0.0018(theor). 相似文献
112.
Mahapatra R Nelson HN Briere RA Chen GP Ferguson T Tatishvili G Vogel H Adam NE Alexander JP Bebek C Berkelman K Blanc F Boisvert V Cassel DG Drell PS Duboscq JE Ecklund KM Ehrlich R Gibbons L Gittelman B Gray SW Hartill DL Heltsley BK Hsu L Jones CD Kandaswamy J Kreinick DL Magerkurth A Mahlke-Krüger H Meyer TO Mistry NB Nordberg E Palmer M Patterson JR Peterson D Pivarski J Riley D Sadoff AJ Schwarthoff H Shepherd MR Thayer JG Urner D Valant-Spaight B Viehhauser G Warburton A Weinberger M 《Physical review letters》2002,88(10):101803
We report the first observation of the exclusive decays B-->D((*))K(*-), using 9.66 x 10(6) BB pairs collected at the Upsilon(4S) with the CLEO detector. We measure the following branching fractions: B(B--->D(0)K(*-)) = (6.1+/-1.6+/-1.7)x10(-4), B(B(0)-->D(+)K(*-)) = (3.7+/-1.5+/-1.0)x10(-4), B(B(0)-->D(*+)K(*-)) = (3.8+/-1.3+/-0.8)x10(-4), and B(B--->D(*0)K(*-)) = (7.7+/-2.2+/-2.6)x10(-4). The B-->D(*)K(*-) branching ratios are the averages of those corresponding to the 00 and 11 helicity states. The errors shown are statistical and systematic, respectively. 相似文献
113.
Briere RA Chen GP Ferguson T Vogel H Gritsan A Alexander JP Baker R Bebek C Berger BE Berkelman K Blanc F Boisvert V Cassel DG Drell PS Duboscq JE Ecklund KM Ehrlich R Gaidarev P Gibbons L Gittelman B Gray SW Hartill DL Heltsley BK Hopman PI Hsu L Jones CD Kandaswamy J Kreinick DL Lohner M Magerkurth A Meyer TO Mistry NB Nordberg E Palmer M Patterson JR Peterson D Riley D Romano A Thayer JG Urner D Valant-Spaight B Viehhauser G Warburton A Avery P Prescott C Rubiera AI Stoeck H Yelton J 《Physical review letters》2001,86(17):3718-3721
We have studied two-body charmless hadronic decays of B mesons into the final states straight phiK and phiK(*). Using 9.7 million B&Bmacr; pairs collected with the CLEO II detector, we observe the decays B- --> phiK- and B0--> phiK(*0) with the following branching fractions: B(B--->phiK-) = (5.5(+2.1)(-1.8)+/-0.6)x10(-6) and B(B0--> phiK(*0)) = (11.5(+4.5+1.8)(-3.7-1.7))x10(-6). We also see evidence for the decays B0-->phiK0 and B---> phiK(*-). However, since the statistical significance is not overwhelming for these modes, we determine upper limits of <12.3x10(-6) and <22.5x10(-6) ( 90% confidence level), respectively. 相似文献
114.
RajnikantEmail author Vivek?K.?Gupta Dinesh Rachna?Gupta Samir?V.?Mistry Suresh?M.?Desai S.?S.?Madhava?Rao Amrish?C.?Shah 《Journal of chemical crystallography》2004,34(11):735-741
Claisen rearrangement of ethyl-2,4-diallyloxy--carbethoxycinnamate (1) in refluxing DMA afforded ethyl-9-allyl-2-methyl-2,3-dihydrofuro(2,3-h)benzopyran-5H-one-6-carboxylate (2) in a single step. Dehydrogenation with Pd/C (10%) in DPE furnished an unexpected isomeric compound, 9-(1,2-propenyl)-6-carbethoxy-2-methyl-2,3-dihydrofuro[2,3-h]-benzopyran-5H-one (3). This compound, C18H18O5, crystallizes in the monoclinic space group P21/n with unit cell parameters, a = 7.346(1), b = 16.482(3), c = 12.653(2),Å, and = 92.71(1)°. The structure has been solved by direct methods and refined to R = 0.056 for 1719 observed reflections. The coumarin nucleus is planar. The five-membered ring is in envelope-conformation. The crystal structure is stabilized by intra- and intermolecular CHO hydrogen bonds. 相似文献
115.
An empirical model that describes the dependence of hot-carrier lifetime on the effective channel length of an n-channel MOSFET, allowing the estimation of the lifetimes of transistors of a given length based on data from a limited number of channel lengths, is presented. The model takes into account the localization of hot-carrier induced damage and shows that the size of the damaged region relative to the total length of the transistor is important in determining the effect of hot-carrier-damage-induced transistor characteristics. The results are integrated into two commonly used equations for hot-carrier lifetimes of MOSFETs of a given channel length under DC operation. The model is experimentally verified for MOSFETs of effective channel lengths between 0.45 and 2.7 μm 相似文献
116.
J. Eickmeyer S. Michalowski N. Mistry R. Talman K. Ueno 《Physics letters. [Part B]》1976,63(1):104-106
The total cross-section for production of hadrons by inelastic electron scattering at 3.2° from hydrogen and deuterium has been measured in the Q2 range 0.015 GeV2 to 0.1 GeV2, at virtual photon energies ranging from 2 GeV to 8.5 GeV. The transition to photoproduction is observed to be smooth, the ratio σD/σH being about 1.85 in this range. No evidence is seen for a conjectured rapid Q2-dependence of this ratio at low Q2. 相似文献
117.
Syntheses,Structures, and Magnetic Behavior of New Azide Linked Compounds with One‐ and Two‐Dimensional Structures
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Three azide based compounds were synthesized employing aliphatic amines as site blocking agents: [Ni(N3)(C6H16N2)2]ClO4 ( I ) [C6H16N2 = N,N′‐diethylethylenediamine (DEDA)], [Cu8(N3)16(C6H18N4)2] ( II ) [C6H18N4 = tris(2‐aminoethyl) amine (TREN)], and [Cu7(N3)14(C7H19N3)2] · 2H2O ( III ) [C7H19N3 = 3,3′‐diamino‐N‐methyldipropylamine (DMDA)]. The compounds I and II have one‐dimensional structure and III has a two‐dimensional structure. Compound I is a simple linear cationic Ni–azide chain and compound II has Cu6 azide units forming a column terminated by the copper‐metalloligand generated in‐situ during the course of the reaction. The charge compensation perchlorate anions occupy spaces in between the chains in I . Compound II packs in a herringbone arrangement, which is not commonly observed in low‐dimensional structures. Compound III has one‐dimensional copper‐azide chains connected through copper‐metalloligand forming the two‐dimensional structure. All the three compounds exhibit anti‐ferromagnetic behavior. 相似文献
118.
Mathew S.K. Krishnamurthy R.K. Anders M.A. Rios R. Mistry K.R. Soumyanath K. 《Solid-State Circuits, IEEE Journal of》2001,36(11):1636-1646
In this paper, we present: 1) design of a single-rail energy-efficient 64-b Han-Carlson ALU, operating at 482 ps in 1.5 V, 0.18-μm bulk CMOS; 2) direct port of this ALU to 0.18-μm partially depleted SOI process; 3) SOI-optimal redesign of the ALU using a novel deep-stack quaternary-tree architecture; 4) margining for max-delay pushout due to reverse body bias in SOI designs; and 5) performance scaling trends of the ALU designs in 0.13-μm generation. We show that a direct port of the Han-Carlson ALU to 0.18-μm SOI offers 14% performance improvement after margining. A redesign of the ALU, using an SOI-favored deep-stack architecture improves the margined speedup to 19%. A 10% margin was required for the SOI designs, to account for reverse body-bias-induced max-delay pushout. Preconditioning the intermediate stack nodes in the dynamic ALU designs reduced this margin to 2%. Scaling the ALUs to 0.13-μm generation reduces the overall SOI speedup for both architectures to 9% and 16%, respectively, confirming the trend that speedup offered by SOI technology decreases with scaling 相似文献
119.
120.
Mistry MK Choudhury NR Dutta NK Knott R 《Langmuir : the ACS journal of surfaces and colloids》2010,26(24):19073-19083
The high-temperature morphology of supported liquid membranes (SLMs) prepared from perfluorinated membranes such as Nafion and Hyflon and hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-TFSI) has been investigated by small-angle X-ray scattering (SAXS). Proton conductivity results of SLMs before and after leaching show an increase in conductivity with temperature up to 160 °C in an anhydrous environment. DSC results show that crystallites within perfluorinated membranes are thermally stable up to 196 °C. High-temperature SAXS results have been used to correlate structure and morphology of supported liquid membranes with high-temperature conductivity data. The ionic liquid essentially acts as a proton solvent in a similar way to water in hydrated Nafion membranes and increases size of clusters, which allow percolation to be achieved more easily. The cation of the ionic liquid interacts with sulfonate groups within ionic domains through electrostatic interactions and displaces protons. Protons can associate with free anions of the ionic liquid, which are loosely associated with cations and can transport by hopping from anion sites within the membrane. The ionic liquid contributes to proton conductivity at high temperature through achievement of long-range ordering and subsequent percolation. 相似文献