Ground state spin orderings of the triangular Ising model with the nearest and next nearest neighbor interaction

Low temperature Monte Carlo results are used as an indicator of the size of the repeating unit. An energy minimization is then carried out for a number of configurations. It is proposed that, in the presence of a magnetic field, there are five spin orderings according to the relative sizes of the exchange integrals.     

Cleavage of tert-butyldimethylsilyl ethers by tetrafluoroborate salts

Primary and secondary alcohols can be regenerated from their corresponding $\text{tert}$-butyl silyl ethers by treatment with tetrafluoroborate salts.     

A new measurement of the ratio of the cross sections of muon-neutrino and muon-antineutrino scattering on electrons

A new experimental determination of the electro-weak mixing angle θ_W is reported based on a second exposure of the CHARM calorimeter to the CERN-SPS wide-band beam. The ratio R of muon-neutrino- and muon-antineutrino-electron scattering cross section has been determined from a sample of 37 ± 10 and 35 ± 10 events. The experimental result is R = 1.26_?0.45^+0.72, corresponding to a value of sin²θ_W = 0.216 ± 0.055. The total sample of events collected in the CHARM calorimeter during the two exposures is $\text{(83 ± 16)ν}{}_{\mathrm{\mu }}\text{e}\text{events and}\text{(112 ± 21)}\text{ν}{}_{\mathrm{\mu }}\text{e}$ events, leadint to the final result sin²θ_W = 0.215 ± 0.032. The systematic error is estimated to be ± 0.012.     

Experimental study of neutral-current and charged-current neutrino cross sections

Samples of 9200 muon-neutrino and 3800 muon-antineutrino interactions on nuclei were obtained with the fine-grain calorimeter of the CHARM Collaboration at the CERN 200 GeV narrow-band neutrino beam. The interactions were classified as either neutral-current or charged-current processes on an event-by-event basis. Neutral-current and charged-current cross sections in neutrino and antineutrino interactions are presented. From these results we deduce a statistically significant contribution of right-handed coupling to the neutral hadronic current, and a value of the electroweak mixing angle corresponding to sin²θ = 0.220 ± 0.014.     

First observation of nonreciprocal X-Ray gyrotropy

We report the first observation of a nonreciprocal x-ray linear dichroism caused by the time-reversal odd, real part zeta of the complex gyrotropy tensor zeta(*) which is dominated by electric dipole-electric quadrupole E1E2 interference terms. A nonreciprocal transverse anisotropy was observed in the low temperature insulating phase of a Cr doped V2O3 Mott crystal when a single antiferromagnetic domain was grown by magnetoelectric annealing along the hexagonal c axis. This new element (edge) specific spectroscopy could nicely complement x-ray magnetic circular dichroism which is silent for antiferromagnetic materials.     

Experimental determination of the structure function of the pion

It was shown in the preceeding letter that dimuon production by 22 GeV pions proceeds in part through qq? annihilations in agreement with the Drell-Yan model. Using these data we extract the quark distribution function of the pion. Comparison of our structure function with that obtained from data at higher energy reveals differences compatible with the QCD calculations of the Q²-dependence (scale breaking) of the pion structure function.     

Experimental study of differential cross sections dσdy in neutral current neutrino and antineutrino interactions

We present differential cross sections dσ/dy corrected for resolution and acceptance, for events induced by both the neutral- and charged-current interactions of neutrinos and antineutrinos. They are based on 8553 neutrino and 3578 antineutrino events obtained using the CHARM fine-grain calorimeter in the CERN 200 GeV narrow-band beam. From these differential cross sections we demonstrate that the coupling strength of the weak neutral current to the strange quark is compatible with being equal to that of the down quark. Assuming this equality we then describe the weak neutral current in terms of one parameter, sin²θ, which we find to be 0.222 ± 0.016. The charged-current differential cross sections yield values of the fractional momentum-weighted content of the nucleon for non-strange (0.12 ± 0.04) and strange (0.06 ± 0.04) sea quarks. Furthermore, from the strength of the allowed y² term in the neutral-current differential cross sections we put a limit of 3% on the presence of scalar or pseudoscalar contributions to the weak neutral current. This can alternatively be expressed in terms of the Callan-Gross violation parameter R, where we find R = 0 .10 ± 0.10.     

空间频率域超声背散射参量用于骨质状况的评价*

在超声背散射骨质评价中,不同测量感兴趣区域(ROI)的超声背散射信号会有波动,致使诊断准确度降低。该文目的是研究超声背散射信号随测量区域的变化规律。采用空间扫描方法离体测量了35块骨样本,将超声背散射参数从空间域变换到空间频率域。结果表明,超声背散射参数的主要空间频率成分集中于低频部分;空间频率域超声背散射参量最大值(MASF)与骨矿密度等参数具有中高度显著相关性(R2=0.45~0.83,p0.001);空间频率域超声背散射参量衰减系数(AC)也与松质骨密度及结构特征有显著相关性(R2=0.41~0.72,p0.001)。研究表明空间频率域变换方法有助于明确超声背散射信号随测量ROI的变化规律,空间频率域的超声背散射相关新参量评价松质骨状况具有可行性。     

Reflection and transmission characteristics of ultrasonic guided waves in fractured long bone

Assessment of fractured long bone using ultrasonic guided wave（GW） has gained considerable attention.This paper focuses on using the hybrid boundary element method （HBEM） to analyze the propagation characteristics of ultrasonic GW in fractured long bones. The reflection coefficients（RC） and transmission coefficients（TC） for different depth-to-width ratio（d/w） cracks were numerically calculated and analyzed.It has been shown that the primary output modes,which include the transmission and reflection modes,are the same as the incidence modes.For some cracks,different TC curves always got the local maxima in adjacent frequencies.For different d/w cracks,most of the TC curves had local maxima which are not overlapped.These simulation results are helpful to optimize the modes and frequencies of the incidence GWs for quantitatively evaluating the bone quality and providing the numeral results of the cracks in long cortical bones.     

超声轴向传播技术评价长骨的研究

用超声轴向传播技术评价长骨状况已成为近年来的一个研究热点。本文首先介绍了第一到达波(FAS)法、超声Lamb波及柱面导波法在评价长骨皮质骨状况方面的研究进展,最后分析和讨论了当前研究中存在的问题及应该研究的方向。