Effects of elastic and inelastic NN scattering cross sections on pi(-)/pi(+) ratios in heavy-ion collisions at intermediate energies

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model and the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross sections on pi(-)/pi(+) in the neutron-rich reaction of Ca-48 + Ca-48 at a beam energy of 400 MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect Delta(1232), pi(-) and pi(+) production, as well as the value of pi(-)/pi(+).

Medium effects on pi(-)/pi(+) in heavy-ion collisions at intermediate energies

Based on the isospin-dependent transport model IBUU and on the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross-sections on pi(-)/pi(+) in the neutron-rich reaction Ca-48 + Ca-48 at a beam energy of 400MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect Delta(1232), pi(-) and pi(+) productions as well as the value of pi(-)/pi(+).

CONSISTENT THREE-BODY FORCE WITH BONN B POTENTIAL AND NEUTRON STAR STRUCTURE

Microscopic three-nucleon force consistent with the Bonn B two-nucleon potential is constructed, which includes Delta(1232), Roper, and nucleon-antinucleon excitation contributions. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined. At the high densities,the nuclear equation of state and the symmetry energy are calculated. The corresponding neutron star mass-radius relations are presented.

PROBING THE SYMMETRY ENERGY AT SUPRA-SATURATION DENSITIES FROM PION EMISSION IN HEAVY-ION COLLISIONS

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6, Ska and SIII, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2.

强子的介质效应

本论文简述了强子介质效应的研究现状，理论方法以及实验探测技术。系统的介绍了相对论平均场理论和手征有效场论。利用相对论平均场研究了Pentaquark的介质效应，利用手征有效场论研究了△(1232)共振态的介质效应。 在密度相关的平均场理论基础上，计算出的Pentaquark的有效质量随核物质密度的增加而减小。一定的Pentaquark含量导致每核子的结合能减小，这使得核物质系统更加稳定。 在手征有效场论的框架下，利用泡利不相容原理对核子传播子的修正，以及核子有效质量在核物质中的改变，通过计算△共振态一阶自能，讨论了△共振态的有效质量和衰变宽度对核物质密度的依赖关系。结果表明：△共振态的有效质量随核物质密度的增加而减小，在正常核密度下为1221MeV，而在3倍正常核密度时为1186MeV，其减小幅度与美国Lawrence Berkeley国家实验室上做的58Ni+Cu（能量为1.97GeV/u）碰撞实验给出的结果大致相符；△粒子的衰变宽度在核物质中的变化主要决定于核子以及△粒子的有效质量的变化

The shape parameter of Liposomes and DNA-lipid complexes determined by viscometry utilizing small sample volumes

A minicapillary viscometer utilizing <0.5 ml of sample at a volume fraction of <0.1% is described. The calculated a/b of DPPC/DPPG multilamellar liposome was 1.14 as prolate ellipsoids and a/b of dioleoylpropyltrimethyl ammonium methylsulfate-DNA complex at a charge ratio of 4: 1 (+/-) was 3.7 as prolate ellipsoids or 4.9 as oblate ellipsoids. The deviation of shape from perfect sphere is thus expressed quantitatively in more than two significant figures. In these measurement, the necessary amount of DNA is <0.5 mg.

黄土丘陵区藓结皮生物量测定方法及其随发育年限的变化

通过野外调查黄土丘陵区不同发育年限退耕地上藓结皮发育状况,结合室内测定,提出了藓类植物生物量测定的回归方程法.运用该方法测定了研究区9个不同发育年限藓类植物的生物量,并分析了其随发育年限的变化趋势.结果表明,研究区藓类植物个体微小,株高相同的藓类植物生物量变异很小,不同株高的藓类植物的株数与其生物量之间呈显著的线性相关关系(R2>0.96,n=7).因此,可以利用藓类植物株数与生物量之间的统计回归关系式估测生物结皮中藓类植物的生物量.用所建立的回归方程估测的研究区不同年限退耕地藓类植物生物量的绝对误差为1.3%～27.3%.研究区藓类植物生物量随结皮发育年限而变化,在退耕的前11年里,藓类植物生物量随发育年限的延长而增加,至11年时藓类植物生物量达到最大值(303.8g/m2),此后藓类植物生物量变化不大甚至还有下降趋势.

气候变化对三北防护林的影响与应对策略

分析20世纪90年代以来有关气候变暖及其影响的研究数据,得出如下结论:中国三北地区气候正经历着暖干化的变化,未来几十年此种趋势将更加明显,位于三北东部的东北地区尤为突出。气候暖干化将带给三北防护林工程3方面的压力:1)干旱区和荒漠化面积扩增;2)自然植被分布格局发生变化,自西向东的植被逆向演替,众多的过渡带变化敏感;3)现存的防护林在气候变异的干扰下衰退的风险加剧。应对气候变化,三北防护林建设宜采取如下策略:1)增加建设规模;2)植被疏林化和灌丛化作为过渡带防护林设计的目标;3)在水土流失区以原生化建设模式设计油松人工林;4)制订三北防护林经营技术方案。

AlCl_3对细颗粒泥沙絮凝沉降的影响

铝类絮凝剂对细颗粒泥沙絮凝沉降有重要作用 ,常应用于浑水澄清、农业污水处理等研究中。在AlCl3 浓度为 0～ 1 7mmol/L ,泥沙浓度为 1 0g/L时 ,用吸管法研究了AlCl3 对细颗粒泥沙絮凝沉降的影响 ,结果表明 :在液面下同一深度 ,泥沙浓度随时间呈指数衰减 ;悬液经多次搅拌后再沉降 ,其沉速减缓 ;当AlCl3 浓度为 0 9～ 1 7mmol/L时 ,出现明显的清浑水交界面 ,交界面随时间等速下降 ,平均沉速为 4 75 6cm/min ,对应的絮团平均粒径为 0 0 31 5mm ;土娄土絮凝临界粒径为 0 0 2 7mm。

植物生殖物候研究进展

概述了植物生殖物候的近期研究趋势、研究内容和研究进展。近十几年,生殖物候研究体现了从物种尺度到群落尺度、由野外观察到模拟实验、从孤立研究到关联研究过渡的趋势。主要研究内容包括:(1)特定植物的生殖物候;(2)群落尺度的生殖物候;(3)生殖物候与系统发生的关系;(4)生殖物候的可塑性;(5)生殖物候对气候变化的响应;(6)生殖物候与动物食源供应的关系;(7)生殖物候与花粉过敏症的关系;(8)生殖物候与植物保护和植被管理的关系。控制实验和长期观测将在未来研究中占有重要地位,以植物多样性保护和退化生态系统恢复为目的的研究将趋于增多,有关温带植物和草本植物以及特殊生态系统的研究将得到进一步加强,群落尺度的研究将继续增多。