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.     

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.     

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.     

The ISNaS incompressible Navier-Stokes solver: invariant discretization

The ISNaS-project aims at providing tools for computer aided design and engineering in aerodynamics and hydrodynamics by developing an Information System for the simulation of complex flows based on the Navier-Stokes equations. Major components of the project are the development of a method-shell and of accurate as well as robust solvers for both compressible and incompressible flows. For the incompressible case, guided by typical applications in the field of river and coastal hydrodynamics, a solution procedure is being developed that is capable of handling complicated geometries, including free surface effects, in particular for high-Reynolds number flow regimes. In the present paper the invariant discretization of the incompressible Navier-Stokes equations in general boundary-fitted coordinate systems is discussed. It is found to be important that certain rules are followed concerning the choice of unknowns and the approximation of the geometric quantities. This is illustrated by some preliminary results. Extensions to moving coordinate systems and time-varying computational grids are indicated.     

Baryon pairs production ine + e − annihilation at\sqrt s = 2.4 GeV

Search for baryon pairs production ine ⁺ e ^? annihilation at \(\sqrt s = 2386 MeV\) is reported. The data relate to a luminosity of 161 nb^?1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe ⁺ e ^? annihilation into \(\Lambda \bar \Lambda \) and ofe ⁺ e ^?→ \(p\bar p\) at this energy are presented. First observation of a goode ⁺ e ^?→ \(n\bar n\) candidate is reported and upper limits are given fore ⁺ e ^?→ \(n\bar n, \Lambda \bar \sum ^0 + c.c.\) and \(\Sigma ^0 \bar \Sigma ^0 \) .     

Cooperative behavior between oscillatory and excitable units: the peculiar role of positive coupling-frequency correlations

We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.