Study of the reactione + e −→K + K − in the energy range1350 \leqq \sqrt s \leqq 2400 MeV

Thee ⁺ e ^?→K ⁺ K ^? cross section has been measured from about 750 events in the energy interval \(1350 \leqq \sqrt s \leqq 2400 MeV\) with the DM2 detector at DCI. TheK ^± form factor |F _F ^±| cannot be explained by the ρ, ω, ? and ρ′(1600). An additional resonant amplitude at 1650 MeV has to be added as suggested by a previous experiment.     

Comprehensive analysis of the chromatin landscape in Drosophila melanogaster

Chromatin is composed of DNA and a variety of modified histones and non-histone proteins, which have an impact on cell differentiation, gene regulation and other key cellular processes. Here we present a genome-wide chromatin landscape for Drosophila melanogaster based on eighteen histone modifications, summarized by nine prevalent combinatorial patterns. Integrative analysis with other data (non-histone chromatin proteins, DNase I hypersensitivity, GRO-Seq reads produced by engaged polymerase, short/long RNA products) reveals discrete characteristics of chromosomes, genes, regulatory elements and other functional domains. We find that active genes display distinct chromatin signatures that are correlated with disparate gene lengths, exon patterns, regulatory functions and genomic contexts. We also demonstrate a diversity of signatures among Polycomb targets that include a subset with paused polymerase. This systematic profiling and integrative analysis of chromatin signatures provides insights into how genomic elements are regulated, and will serve as a resource for future experimental investigations of genome structure and function.     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

Non-planar smoulder propagation governed by diffusion

The steady propagation of a thin smouldering front in a half-spacehas been considered. A suitable coordinate transformation hasallowed the region near the leading edge of the front to beexamined for both a maintained planar surface and with surfacecollapse due to material shrinkage. The change in the oxidizerconcentration for a small increment in the propagation speedfor large time and surface collapse has been determined. Theinfluence of two types of nonlinear diffusion on the shape ofthe smouldering front has been found; other cases can be dealtwith in a similar manner.     

火花放电三维路径的分形特征分析

提出了一种记录空气中火花放电三维路径图像及其处理的方法．根据实验数据，分析了火花放电路径及其发展过程的分形特征，计算了分形参数的数值范围，讨论了各个分形参数的物理意义．     

Comparison of methods for determining corona inception voltages of transmission line conductors

Corona inception voltages are important parameters for power transmission-line conductors. However, there is no specific criterion for the determination of the corona inception voltage on such conductors. A corona cage is an effective and economical means for testing transmission-line conductors as it allows the duplication of surface electric fields, and hence the corona phenomena, at lower conductor voltages. Measurements with an ultraviolet imager, a partial discharge detector, a current-measuring radio-frequency interference receiver, and a sound level meter were used to observe the transition region between no corona and strong corona and hence determine the corona inception voltages of two practical conductors, types LGJ500/35 and LGJ400/50. Good agreement was found between the four approaches. The corona inception voltage was also calculated from first principles after determining the electric field near the surface strands using a charge simulation method, and compared with the peak inception voltages found from the measurements. Comparison was also made with the values obtained be applying Peek's equation. In both the calculations, Peek's surface roughness factor ‘m’ was applied with a value of 0.81 giving close agreement with the measurements.     

The effect of floating-potential conductors on the electric field near overhead transmission lines

The use of helicopters as platforms equipped with infrared and UV detection, digital cameras and other inspection equipment is an effective method of increasing the efficiency and effectiveness of transmission line inspection. However, as a 'floating-potential conductor' near to a high-voltage transmission line, a helicopter causes distortion of the local electric field, with regions of high electric field near the helicopter's surface where the curvature is high. In this paper, these fields are investigated both by calculation and experimentally, using a simple metal sphere, and then a model of a helicopter, placed near to a short length of energized transmission line conductor.     

KMgF3:Ni2+晶体的占位、局部结构、吸收光谱和顺磁g因子的统一解释

利用完全对角化方法和强场耦合方案,采用半自洽场(semi-SCF)自由Ni2+的d轨道模型和Ni2+-6X-(x=F,Cl,Br,I)络合物的μ-κ-α模型研究,建立了含有过渡族金属离子的晶体的局域结构与吸收光谱和顺磁g因子之间的定量关系,对KMgF3:Ni2+晶体的占位、局域结构、吸收光谱和顺磁g因子作出了统一解释,预测了KMgF3:Ni2+晶体的光谱精细结构.所得理论计算结果与实验值符合得很好.