Ethylene Oligomerization Promoted by Nickel Complexes with 8-Iminoquinoline Derivatives

In the past decades, the great progress has been witnessed in chemical industry, and chain olefins have played important roles in substantial technical interests of detergents, plastics, lubricants, oil additives and a variety of fine chemicals. Ethylene oligomerization is the fast developing process to get chain olefins. Shell Company did the pioneer pilot process work1, which was based on the nickel complexes with remarkable activity and selectivity. The chelating ligands are considered to p…     

HEAT FLOW FOR YANG-MILLS-HIGGS FIELDS, PART I HEAT FLOW FOR YANG-MILLS-HIGGS FIELDS, PART I

1. IntroductionLet (M, g) be a four dimensional Riemannian manifold and let P be a principal bundlewith compact Lie structure group G over M. The Yang-Mills functional is defined bywhere F denotes the curvature of a connection D and dM is the volume form induced bythe metric g on M. All integrals on M in this paper will be with the volume form dM, sowe will not write it explicitly.Donaldsonl3] and K. Uhlenbeck[18'19] obtained many important results about Yang-Millsequations (see also […     

Status of the scalar singlet dark matter model

One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a \(\mathbb {Z}_2\) symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above \(\sim \)1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned.     

中国数学规划学科发展概述

数学规划又称数学优化, 是运筹学的一个重要分支. 它主要研究在一定约束条件下, 如何求一个实数或者整数变量的实函数的最大值或者最小值. 它是运筹学和管理科学中最常用的一种建模工具和求解问题的方法, 在工程、经济和金融等领域有非常广泛的应用. 首先简单介绍数学规划的发展历史、应用领域及其主要研究方向; 然后简述数学规划的发展现状和在中国的发展进程; 最后, 讨论数学规划若干研究前沿问题与研究展望.     

激光相干控制选态激发的理论研究

系统地研究了三色相位干的激光场与三能级体系的相互作用过程，证明了态的布居几率依赖于光场的相的相位和振幅属性，从理论上指出用于相干光场实现选态激发的可能性，并首次提出用相干光场去实现泛频激发的可行性和优点。     

Recession cones and the domination property in vector optimization

This paper presents a study of recession cones of nonconvex sets in infinite dimensional spaces. The results are then applied to investigate efficiency conditions and the domination property in vector optimization.This paper was written when the author was at the University of Erlangen-Nürnberg under a grant of the Alexander von Humboldt-Stiftung.On leave from the Institute of Mathematics, Hanoi, Vietnam.     

Study of tau-pair production in photon-photon collisions at LEP and limits on the anomalous electromagnetic moments of the tau lepton

Tau-pair production in the process was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^-1. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Received: 18 September 2003, Revised: 26 March 2004, Published online: 11 May 2004     

Measurement of anti-deuteron photoproduction and a search for heavy stable charged particles at HERA

The cross section for anti-deuteron photoproduction is measured at HERA at a mean centre-of-mass energy of GeV in the range 0.2 < p _T /M < 0.7 and |y| < 0.4, where M, p _T and y are the mass, transverse momentum and rapidity of the anti-deuteron in the HERA laboratory frame, respectively. The numbers of anti-deuterons per event are found to be similar in photoproduction to those in central proton-proton collisions at the CERN ISR but much lower than those in central Au-Au collisions at RHIC. The coalescence parameter B ₂, which characterizes the likelihood of anti-deuteron production, is measured in photoproduction to be , which is much higher than in Au-Au collisions at a similar nucleon-nucleon centre-of-mass energy. No significant production of particles heavier than deuterons is observed and upper limits are set on the photoproduction cross sections for such particles.Received: 31 March 2004, Revised: 23 June 2004, Published online: 30 July 2004     

$\overline pp$ annihilation into four charged pions at rest and in flight

The spin-parity analysis of the data on the annihilation reaction at rest in liquid and in gaseous hydrogen at 3 bar pressure and in flight at momentum of MeV/c, collected by the Obelix spectrometer at the LEAR complex of CERN, is presented. The relative branching ratios and are obtained. It is also shown that the inclusion of the exotic meson , J^PC = 1^{- +} , mass and width , GeV/c², in its decay to , improves the fit and some implications of these results are briefly discussed. The relative S and P-wave annihilation percentages in four charged pions at two target densities are obtained.Received: 2 December 2003, Published online: 23 April 2004     

Studies of QCD at ${\rm e}^ + {\rm e}^-$ centre-of-mass energies between 91 and 209 GeV

The hadronic final states observed with the ALEPH detector at LEP in annihilation are analysed using 730 pb^-1 of data collected between 91 and 209 GeV in the framework of QCD. In particular event-shape variables and inclusive charged particle spectra are measured. The energy evolution of quantities derived from these measurements is compared to analytic QCD predictions. The mean charged particle multiplicity, the charged particle momentum spectrum and its peak position are compared to predictions of the modified-leading-logarithmic approximation. The strong coupling constant is determined from a fit of the QCD prediction to distributions of six event-shape variables at eight centre-of-mass energies. A study of non-perturbative power law corrections is presented.Received: 18 May 2004, Published online: 23 June 2004