有限核多重碎裂的同位旋效应和临界现象的分析

利用非对称核物质状态方程及同位旋相关的量子分子动力学模型对有限核112Sn和132Sn在不同温度下多重碎裂的同位旋效应进行了研究,发现随着温度的升高同位旋效应逐渐消失,并给出了在一定温度下不同密度对产生中等质量碎片的影响.通过碎片的关联分析,对中高能重离子碰撞中的临界现象做了初步研究.

200kV电子帘加速器的电子束轨迹的计算

采用法国的MAFIA程序计算电场 .编制了TRAJ程序 ,用逐点跟踪计算电子轨迹 ,得到了束流包络 .观察了在高压电场中栅压对束流光学传输的影响 ,并获得了在不同能量范围内的栅压聚焦作用 ,为栅压调节提供了理论依据 ,也为将来对其它规格的电子帘加速器的物理设计积累了十分宝贵的经验

Alterations of immune functions induced by 12C6+ion irradiation in mice

Purpose: To estimate the biological risks to the immune system of the type of space radiation, 12C6+, encountered by cosmonauts during long-term travel in space. Materials and methods: The Kun-Ming strain mice were whole-body irradiated by 12C6+ ion with 0, 0.01, 0.05, 0.075, 0.2, 0.3, 0.5, 0.75, 1 or 2 Gy, at a dose rate of 1 Gy/min. At 35 days after irradiation, the thymus and spleen weights were measured, the natural killer (NK) cells activity of spleen was determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT), and the interferon-gamma (IFN-gamma) levels in serum and thymus were detected with enzyme-linked immunosorbent assays (ELISA). Results: The results showed that the thymus weight, IFN-gamma levels in serum and the activity of splenic NK-cells had significantly increased at a dose of 0.05 Gy. With further dose increase, the weight of spleen continued to increase but the weight of thymus, IFN-gamma level and NK-cells activity declined. Conclusions: These results suggest that the dose of 0.05 Gy irradiation has a stimulatory effect on mouse immunity; this effect declined with increasing dose.

强子有效质量与核子内夸克性质

论文包括两部分内容：利用强子动力学模型和相对论平均场近似方法研究了强子的有效质量；扩展了夸克质量密度相关的模型，讨论了核子的基本性质。 从非线性σ-ω-ρ模型拉氏量出发,给出了核物质标量密度和矢量密度的关系,利用其修正了K介子有效质量；在不变耦合系数和密度相关耦合系数下，研究了Θ+的有效质量，并发现在密度相关的耦合系数下，标量介子与重子的相互作用在高密度区域被削弱。 在改进的夸克质量密度相关(IQMDD)模型的基础上，引入了ω介子来描述夸克间排斥作用，给出了夸克和σ,ω场函数满足的方程, 通过自洽求解，分B^(1/4)=145MeV和c2=0两种情况，研究了在不同条件下夸克波函数和夸克密度的变化情况，给出了σ,ω场函数的分布。计算了rp，磁矩μp，以及核子的轴矢量与矢量的β衰变耦合系数之比gA/gv，发现与实验值有较好的吻合

短期菲胁迫对大豆幼苗超氧化物歧化酶活性及丙二醛含量的影响

研究了不同浓度 ( 0～ 2 0 0 μg·g-1)菲胁迫和恢复培养后大豆幼苗生长、超氧化物歧化酶 (SOD)活性及丙二醛 (MDA)含量的变化 .结果表明 ,2 0 0 μg·g-1菲处理 5d后大豆幼苗生长受到抑制 ,但幼苗恢复培养后经短暂停滞期后仍可恢复生长 .菲污染对大豆幼苗SOD活性变化的剂量 效应关系的作用形式比较复杂 ,胁迫 2d时为线性关系 ,胁迫 5d和 8d时为抛物线型 .在菲处理前期 ( 2d) ,幼苗SOD活性被 10 0和2 0 0 μg·g-1菲显著诱导 [分别为对照的 1.15倍 (P <0 .0 5 )和 1.2 6倍 (P <0 .0 1) ].菲暴露 8d时 ,SOD活性显著降低 ,2 0 0 μg·g-1菲处理组SOD活性为对照的 88% (P <0 .0 5 ) .菲处理 5d后恢复培养 2d和 4d ,5 0和10 0 μg·g-1菲处理组幼苗SOD活性得到恢复 ,而 2 0 0 μg·g-1菲处理组幼苗SOD活性仍明显高于对照 (P <0 .0 5 ) .试验亦反映出 ,10 0和 2 0 0 μg·g-1菲处理 5d和 8d ,幼苗MDA含量均比对照显著增加 (P <0 .0 5和P <0 .0 1) .可以认为 ,SOD活性可作为大豆幼苗遭受短期菲胁迫的生物标记物 .

Multiphoton ionization of pyrrole-water mixed clusters

Multiphoton ionization of the hydrogen,bonded pyrrole-water clusters (C4H5N)(n)(H2O)(m) is studied with a reflectron-time of flight mass spectrometer at 355 mn. With increasing partial concentration of pyrrole in a gas mixture source, a series of poly-pyrrole-water binary-mixed cluster ions can be observed, including unprotonated cluster ions [(C4H5N)(x)(H2O)(y)](+), protonated cluster ions [(C4H5N)(x)(H2O)(y)](+) and dehydrogenated cluster ions [(C4H4N)(C4H5N)(x)(H2O)(y)](+). Ab initio calculations of their structures, bond strengths, charge distributions and reaction energies are carried out. Stable structures of these clusters are obtained from the calculations. A probable formation mechanism of the cluster ions [(C4H5N)(x)(H2O)(y)](+), [(C4H5N)(x)(H2O)(y)]H+ and [(C4H4N)(C4H5N)(x) (H2O)(y)](+) is supposed to be the ionization of clusters followed by dissociation.

黄土丘陵区典型群落特征及其与环境因子的关系

研究了安塞县黄土丘陵区4种典型群落分布、物种多样性、生物量变化与环境因子的关系。结果表明,所选群落的盖度和地上、地下生物量随退耕年限增加而明显增加,土壤水分、粘粒含量也有增加趋势;典范对应、多元回归和通径分析表明,群落的分布及变化受环境因子综合影响,土壤有机质、恢复年限、粘粒含量、坡向、海拔、硝态氮含量等是影响退耕地典型群落特征及分布的主要因子;土壤全磷含量对生态优势度,有机质、全氮含量分别对地上、地下生物量有最大正效应。本研究为黄土丘陵半干旱区退耕地植被恢复重建提供了理论依据。

碳同位素技术在土壤碳循环研究中的应用

碳在土壤中的储量和存储时间是陆地生态系统碳库中最大和最长的,而土地利用方式会影响到土壤碳储量及其循环周期,因此有效的土地利用管理可使土壤成为一个碳汇。土壤储存碳的过程就是土壤有机碳动态平衡的变化,因此认识土壤有机碳的动态变化是揭示土壤碳循环过程及其调控机制的重要方面。首先介绍了碳的一种稳定性同位素(13C)和放射性同位素(14C)在生态系统长期动态过程的重建(如C3/C4植被的历史格局)、土壤有机碳周转周期等方面的应用,探讨了同位素示踪技术在土壤有机碳来源、周转周期、土壤CO2通量的变化和组分区分、同位素

Fe3O4 magnetic nanoparticles as peroxidase mimetics and their applications in H2O2 and glucose detection

Artificial enzyme mimetics are a current research interest because natural enzymes bear some serious disadvantages, such as their catalytic activity can be easily inhibited and they can be digested by proteases. A very recently study reported by Yan et al. has proven that Fe3O4 magnetic nanoparticles (MNPs) exhibit an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, though MNPs are usually thought to be biological and chemical inert (Gao, L. Z.; Zhuang, J.; Nie, L.; Zhang, J. B.; Zhang, Y.; Gu, N.; Wang, T. H.; Feng, J.; Yang, D. L.; Perrett, S.; Yan, X. Y. Nat. Nanotechnol. 2007, 2, 577-583).

Structural stability and electronic properties of Ba2MIrO6 (M = La, Y) by first principles

We investigate the structural stability and electronic properties of ordered perovskite-type compounds Ba2MIrO6 (M = La, Y) by use of density functional theory. Cubic (Fm-3m), rhombohedral (R-3) and monoclinic (P2(1)/n) phases are considered for each compound. It was found that the most energetically stable phase for Ba2YIrO6 and Ba2LaIrO6 is P2(1)/n andR-3, respectively. It is also interesting to find that Ba2YIrO6 in R-3 phase, which was not reported in experiment, has a slightly lower energy than experimentally observed cubic Fm-3m phase.