Search for D0-D(-)0 mixing and a measurement of the doubly Cabibbo-suppressed decay rate in D0-->Kpi decays

We present results of a search for D0-D(-)0 mixing and a measurement of R(D), the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays, using D0-->K+pi- decays from 57.1 fb(-1) of data collected near sqrt[s]=10.6 GeV with the BABAR detector at the PEP-II collider. At the 95% confidence level, allowing for CP violation, we find the mixing parameters x('2)<0.0022 and -0.056相似文献   

Barium azacryptand sodide,the first alkalide with an alkaline Earth cation,also contains a novel dimer, (Na(2))(2-)

The first barium sodide, with stoichiometry Ba(2+)(H(5)Azacryptand[2.2.2](-))Na(-).2MeNH(2), was synthesized by the reaction of Ba, Na, and H(6)Azacryptand[2.2.2] in NH(3)-MeNH(2) solution. It was characterized by X-ray crystallography, (23)Na MAS NMR, hydrogen evolution, DSC, optical spectroscopy, and magnetic susceptibility. This is the first sodide in which the sodium anions form (Na(2))(2)(-) dimers. Previous theoretical predictions were verified by a calculation of the potential energy curve for the dimer in the field of the surrounding charges, whose positions were determined from the crystal structure.     

Inert site in a protein zinc cluster: isotope exchange by high resolution mass spectrometry

Using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, we show that one Zn2+ ion in the Zn4 cluster of cyanobacterial metallothionein is inert to exchange with 67Zn2+. We suggest that this is zinc in site A, which together with the surrounding alpha and beta secondary structure forms a zinc-finger fold.     

Measuring extraocular muscle volume using dynamic contours

The effect of medical treatment on extraocular muscle enlargement in thyroid associated ophthalmopathy (TAO) may be monitored by measuring the change in volume of the extraocular muscles on serial orbital MRI examinations. In theory, 3D image sets offer the opportunity to minimise errors due to poor repositioning and partial volume effects. This study describes an automated technique for estimating extraocular muscle volumes from 3D datasets. Operator input is minimal and the technique is robust. Verification of the technique on both simulated and real datasets is described. For simulated image sets, both automated segmentation and manual outlining produced estimates of volume which were on average 4% less than "true" volume. For real patient data, extraocular muscle volumes measured by the automated technique were 1.6% (SD 13%) less than volumes measured by manual outlining. Coefficient of variation for repeat outlining of the same image dataset for the automated technique was 1.0%, compared with 4% for manual outlining. The manual technique took an experienced operator approximately 20 min to perform, compared to 7 min for the automated technique. The automated method is therefore rapid, reproducible and at least as accurate as other available methods.     

Constancy of loudness of pipe organ sounds at different locations in an auditorium

Pipe organ sounds, as judged by ear, tend to remain constant across different locations in an auditorium, yet the SPL of line spectra may vary by a maximum of 26 dB (mean 8.98 dB, s.d. 2.5), and the overall level may vary, typically, 10 to 12 dB from location to location. However, organs are designed, listened to, and regulated using the psychophysical units of loudness and timbre, and it is possible that the heard sound constancy exists at the psychophysical level. The present work recorded the sound of the C's and G's of pipe organ stops at three different locations in a church. The sound pressure levels were transformed to loudness. Similarity of loudness across the locations was measured two ways. First, the bass to treble distribution of loudness across the compass was measured using cross-correlation functions across pairs of locations. Second, the degree of similarity of loudness at the different locations was quantified by calculating ratios of loudness between the different locations. By these measures, the bass to treble loudness distribution and absolute loudness of the reeds were found to be nearly identical at the three locations. Two psychophysical processes were shown to be responsible for the loudness constancy. The first depended upon the power summation of harmonics within each third octave band above band 9 which contain two or more harmonics. The power summation of these harmonics greatly reduced the effect of SPL variability of the line spectra contained within these higher numbered bands. The second depended upon interharmonic loudness summation and upward masking of the first six harmonics. Greater loudness variability at the different locations was found after transforming the SPL measurements of two 8-ft diapasons to loudness compared with the reeds. The larger loudness variability was due to the smaller number of harmonics above the third of the diapasons compared with the reeds. The psychoacoustic measures indicate what a listener will hear as he/she moves among the locations.     

Reflection and transmission of waves near the localization threshold

A theory is presented for propagation of waves in bounded media near the mobility edge, based on the self-consistent theory for localization. It predicts a spatially inhomogeneous diffusion constant that leads to scale dependence in enhanced backscattering and transmission.     

两种气液两相流模型的应用和比较

本文应用MUSIG模型[1]和均一直径模型对某溶液堆台架模型堆芯内气液流动传热进行了数值模拟.在MUSIG模型中堆芯内离散相气泡被分为5组不同直径的气泡,用于分析堆芯内气泡的流动变化和大小分布,采用Luo and Svendsen[2]和Prince and Blanch[3]模型描述不同直径气泡组间的破裂和聚合.在均一直径模型中,堆芯内的气体被考虑为同一直径的组分,并且不考虑其破裂与聚合现象.计算得到采用两个模型的模拟结果并且对其进行了对比研究.结果显示应用MUSIG模型的计算结果与台架实验结果吻合更好.     

Six-Fold Degenerate Dark States in a Four-Level Atomic System

With all driving fields on Raman resonance, a tripod-type atomic system quickly evolves into a dark state decoupled from the lossy excited level. The dark state depends strongly on field Rabi frequencies, spontaneous decay rates, and the initial atomic population in a complicated way. Analytical results reveal that it is a sixfold degenerate dark state with its three components superposed both coherently and incoherently due to population redistribution from spontaneous emission.     

Local currents for the GL(N,C) self-dual Yang-Mills equation

By using a simple Bäcklund-like transformation which linearizes the GL(N, C) self-dual Yang-Mills equation, an infinite number of local conservation laws for this equation are constructed. In the SL(N, C) case, the currents become trivial, which explains why these currents are not found in SU(N) gauge theory.