Identified particle production, azimuthal anisotropy, and interferometry measurements in Au plus Au collisions at root s(NN)=9.2 GeV

We present the first measurements of identified hadron production, azimuthal anisotropy, and pion interferometry from Au + Au collisions below the nominal injection energy at the BNL Relativistic Heavy-Ion Collider (RHIC) facility. The data were collected using the large acceptance solenoidal tracker at RHIC (STAR) detector at root s(NN) = 9.2 GeV from a test run of the collider in the year 2008. Midrapidity results on multiplicity density dN/dy in rapidity y, average transverse momentum < p(T)>, particle ratios, elliptic flow, and Hanbury-Brown-Twiss (HBT) radii are consistent with the corresponding results at similar root s(NN) from fixed-target experiments. Directed flow measurements are presented for both midrapidity and forward-rapidity regions. Furthermore the collision centrality dependence of identified particle dN/dy, < p(T)>, and particle ratios are discussed. These results also demonstrate that the capabilities of the STAR detector, although optimized for root s(NN) = 200 GeV, are suitable for the proposed QCD critical-point search and exploration of the QCD phase diagram at RHIC.

Observation of an Antimatter Hypernucleus

Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons-comprising an antiproton, an antineutron, and an antilambda hyperon-produced by colliding gold nuclei at high energy. Our analysis yields 70 +/- 17 antihypertritons (3/Lambda(H) over bar) and 157 +/- 30 hypertritons (H-3(Lambda)). The measured yields of H-3(Lambda) (3/Lambda(H) over bar) and He-3 ((3)(He) over bar) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and of nuclei containing strange quarks, have implications spanning nuclear and particle physics, astrophysics, and cosmology.

Longitudinal scaling property of the charge balance function in Au plus Au collisions at root s(NN)=200 GeV

We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at root S-NN = 200 GeV using the STAR detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage vertical bar-1.3, 1.3 vertical bar. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes. (c) 2010 Elsevier B.V. All rights reserved.

Center of mass energy and system-size dependence of photon production at forward rapidity at RHIC

We present the multiplicity and pseudorapidity distributions of photons produced in Au + Au and Cu + Cu collisions at root(NN)-N-s = 62.4 and 200 GeV. The photons are measured in the region -3.7 < eta < -2.3 using the photon Multiplicity detector in the STAR experiment at RHIC. The number of photons produced per average number of participating nucleon pairs increases with the beam energy and is independent of (lie collision centrality. For collisions with similar average numbers of participating nucleons the photon multiplicities are observed to be similar for An + Au and Cu + Cu collisions at a given beam energy. The ratios of the number of charged particles to photons in the measured pseudorapidity range are found to be 1.4 +/- 0.1 and 1.2 +/- 0.1 for root(NN)-N-s = 62.4 and 200 GeV, respectively. The energy dependence of this ratio could reflect varying contributions from baryons to charged particles, while mesons are the dominant contributors to photon production in the given kinematic region. The photon pseudorapidity distributions normalized by average number of participating nucleon pairs, when plotted as a function of eta-Y-beam, are found to follow a longitudinal scaling independent of centrality and colliding ion species at both beam energies. (C) 2009 Elsevier B.V. All rights reserved.

Loss of p15/Ink4b accompanies tumorigenesis triggered by complex DNA double-strand breaks

DNA double-strand breaks (DSBs) are the most deleterious lesion inflicted by ionizing radiation. Although DSBs are potentially carcinogenic, it is not clear whether complex DSBs that are refractory to repair are more potently tumorigenic compared with simple breaks that can be rapidly repaired, correctly or incorrectly, by mammalian cells. We previously demonstrated that complex DSBs induced by high-linear energy transfer (LET) Fe ions are repaired slowly and incompletely, whereas those induced by low-LET gamma rays are repaired efficiently by mammalian cells. To determine whether Fe-induced DSBs are more potently tumorigenic than gamma ray-induced breaks, we irradiated 'sensitized' murine astrocytes that were deficient in Ink4a and Arf tumor suppressors and injected the surviving cells subcutaneously into nude mice. Using this model system, we find that Fe ions are potently tumorigenic, generating tumors with significantly higher frequency and shorter latency compared with tumors generated by gamma rays. Tumor formation by Fe-irradiated cells is accompanied by rampant genomic instability and multiple genomic changes, the most interesting of which is loss of the p15/Ink4b tumor suppressor due to deletion of a chromosomal region harboring the CDKN2A and CDKN2B loci. The additional loss of p15/Ink4b in tumors derived from cells that are already deficient in p16/Ink4a bolsters the hypothesis that p15 plays an important role in tumor suppression, especially in the absence of p16. Indeed, we find that reexpression of p15 in tumor-derived cells significantly attenuates the tumorigenic potential of these cells, indicating that p15 loss may be a critical event in tumorigenesis triggered by complex DSBs.

弹核碎裂反应中类弹碎片产生机制研究

远离稳定线核素的性质研究是当前核物理和天体物理研究的热点之一，作为推进这一研究的重要工具，放射性束产生装置却由于对相关反应机制的缺乏了解，在应用过程中受到很大制约。因而前角区类弹碎片的产生机制研究对于放射性束产生装置的改进和实验设计具有重要的意义。 本论文工作利用兰州重离子加速器国家实验室的次级束流产生装置RIBLL，对57AMeV的40Ar束流在9Be和181Ta靶上反应产生的前角区类弹碎片进行了研究。通过磁刚度扫描方法，实验测量得到了Z>8核区近百种核素的动量分布和截面信息。 实验结果表明，在这一能区，碎片的高能部分主要来源于弹核碎裂过程，而在低能端，存在弹核碎裂和核子转移等其它过程的竞争。实验测量得到的碎片产生截面同EPAX2经验公式和AA模型计算相比较，在稳定线附近符合较好，但在远离稳定线区域，特别是丰质子区域，计算结果过高的估计了碎片截面。研究表明，在这一能区，碎片产生截面同弹核能量无关，但同靶核种类的关系不同于“factorization”假设的预计。 本工作对系统同位旋对碎片截面的影响也进行了研究，发现除弹核同位旋外，靶核同位旋对碎片同位素分布也有影响，这种影响随弹核能量的提高而减小。这是核子-核子作用截面的能量相关性等多种因素共同起作用的结果

CMC聚合物对重金属离子的吸附性能

通过正交试验得出制备羧甲基纤维素(CMC)聚合物的最佳工艺条件:丙烯酸(AA)/羧甲基纤维素=10,引发剂(硫酸铵)和交联剂(N,N′-亚甲基双丙烯酰胺)用量分别为单体的0.0014倍和0.0015倍.吸胀平衡后,将CMC聚合物在400~450℃下完全灰化16h,消解并用火焰原子吸收法测定聚合物对Zn2+、Cu2+、Pb2+、Cd2+、Cr2+、Ni2+和Mn2+的吸附性能.结果表明,CMC聚合物对重金属离子具有一定的吸附能力,其吸附量随着溶液pH值和重金属离子质量浓度的增加而增大,当pH为9时达到最大;并且CMC聚合物对Pb2+和Cu2+的吸附量要大于其他金属离子.

淀粉与丙烯酸/丙烯酰胺共聚物的合成及表征

以淀粉(St)、丙烯酸(AA)和丙烯酰胺(AM)为原料,采用过硫酸钾-亚硫酸氢钠氧化还原引发体系,合成了二元接枝共聚物St-g-pAA和三元接枝共聚物St-g-p(AA-co-AM).通过正交试验,研究了单体浓度、引发剂用量等因素对接枝共聚物吸水率的影响,得到了优化反应条件.红外光谱和扫描电子显微镜对接枝共聚物的表征结果证实了接枝共聚物的存在.

低温弱光下类囊体腔内质子由CF_0渗漏引起黄瓜类囊体耦联度降低

毫秒延迟发光测定结果表明低温弱光处理黄瓜叶片导致类囊体原位 (in situ)耦联度显著降低。DCCD可以恢复低温弱光处理的黄瓜叶片的毫秒延迟发光的慢相强度和反映类囊体膜质子吸收的 9- AA(9- Aminoacridine)荧光猝灭能力 ,说明类囊体耦联度降低的原因是质子由 CF0 大量快速渗漏。进一步研究结果表明 ,活性氧和 CF1的脱落不是低温弱光引起黄瓜类囊体耦联度降低的根本原因。

低温弱光对黄瓜类囊体膜耦联状态的影响

与低温黑暗处理相比 ,低温弱光处理使黄瓜叶片的放氧活性显著降低 ,2℃黑暗处理 6.5h后黄瓜叶片的放氧活性降低到处理前的 66% ,2℃ 35μmol/(m2· s)处理6.5h后则降低到处理前的 - 50 %。研究结果显示 ,在 5℃低温条件下 1 0 0 μmol/(m2· s)光照使黄瓜发生下列变化 :叶片毫秒延迟发光的慢相强度显著降低 ;从叶片中提取的叶绿体的PS 及 PS +PS 的电子传递速率显著升高 ;加 NH4 Cl和加 ADP+Pi的 Hill反应活性与基础 Hill反应活性相差不大 ;从叶片中提取的叶绿体 9- AA荧光猝灭能力消失。以上结果证明低温下光照处理使黄瓜类囊体膜解耦联。

慢生大豆根瘤菌(Bradyrhizobiumjaponicum)聚羟丁酸合成酶基因(phbC)的克隆和序列测定

以苜蓿根瘤菌Rm10 2 1的 phaC基因突变体菌株Rm1114 4 (phaC ::Tn5 - 2 33)为受体菌 ,通过功能互补 ,成功地从构建的Bradyrhizobium japonicum USDA110基因文库中 ,筛查到能与Rm1114 4互补 ,使之恢复在以乙酰乙酸为唯一碳源的M9培养基 (M9-AA)平板上 5d形成明显可见菌落 ,以及在MOPS平板上形成粘液型菌落的表型的重组粘粒 pDC2 ;经证实 ,该粘粒带有 phbC基因 .完成了该基因的全序列测定并已在GenBank登记 ,登记号为AY0 775 80 .B .japonicumphbC基因由 180 3碱基对组成 ,GC含量 6 1.8% ,AT含量 38.2 % ;编码 6 0 0个氨基酸 ,Mr=6 6 .95× 10 3 .图 3表 3参 13

苜蓿根瘤菌聚羟丁酸解聚酶基因(phbD)突变体的构建及其特性

根据苜蓿根瘤菌(Sinorhizobiummeliloti )Rm1021基因组中与RalstoniaeutrophaphaZ基因同源部分序列设计1对引物,从S.meliloti基因组中用PCR扩增出835bpphbD 基因片段并克隆到载体pGEM-TEasy上;通过在phbD基因内插入ΩSmSp和基因置换构建了phbD突变体。该突变体可积累比野生型菌株多1.0~2.6倍的聚羟丁酶(PHB)。在YMA和TY平板上形成非粘液型菌落,而在以乙酰乙酸或3-羟丁酸为唯一碳源的M9基本培养基(M9-AA,M9-HB)上形成粘液型菌落。碱性磷酸酶测定结果表明,通过接合引入phbD突变体菌株中的exoF-phoA融合基因在YMB培养基中低量表达,而在M9-AA和M9-HB中高量表达。

拓扑异构酶的结构、功能与进化的结构生物信息学研究

拓扑异构酶（topoisomerase）是一类控制和修改双螺旋DNA复制和转录过程中的拓扑结构的酶，是生命活动中最重要的酶。以IA类和II类拓扑异构酶中共存的toprim以及CAP-like结构域为研究对象，对拓扑异构酶中的三大类酶的分子进化情况进行了分析。结果显示在IA类和II类酶之间序列保守性很低，但是具有两个保守的结构域，在IIB类拓扑异构酶中toprim结构域中存在着和其他toprim结构域相同的四个保守位点，而在CAP-like结构域中IA类和II类中存在较大差异，没有明显的序列保守性，IIB类和IIA类的CAP-like结构域在二级结构上非常相似。从toprim结构域系统进化研究中我们发现IIA类和皿类中toprim结构域的进化关系很近，两类酶的toprim结构域在亲缘关系上和primase较远，而以上三者和IA类的进化关系最远。CAP-like结构域的系统进化研究发现IIA类以及IA类的domain4的CAP-like结构域进化关系比较近，IIB类和他们之间关系稍微远一些，IA类的domain3和以上几个结构域的关系较远，这也与他们的二级结构上的一致性是相同的。通过分析，IIA、IIB类起源于类似IA类的古老的拓扑异构酶，'在IA类进化中经过基因复制产生了两个不同的CAP-like结构域。然后祖先拓扑异构酶发生了变化，N'端加入了ATPase结构域和DNAgyrase/Mutlsecond结构域，形成了严格依赖ATP供能的真核生物IIA类，在细菌中断开成为两个亚基的细菌中IIA类。IIB类是祖先细胞的IIA类的一个或者是两个亚单位在古细菌以及真核生物中通过复制、重组和缺失造成的，IIB类中的toprim结构域很接近IIA类，可以认为，llB类中的toPrim结构域直接由IIA类转移而来，而IIB类中的cAP一1汰e结构域较IIA类中产生更早一些，应该是由拓扑异构酶祖先中产生的二级结构为aβaaββ的CAP-like结构域直接进化而来。然而，两个结构域的基因在连接到一起时候发生了不同于一般顺序的拼接，于是nB类中两个结构域形成了不同于现在的IA类和IIA类的顺序。

Synthesis and properties of two kinds of CPVC carboxylated ionic copolymers

In the present work, two kinds of CPVC carboxylated ionic copolymers were prepared by a new method. First, a graft copolymer (CPVC-cg-AA) comprising of polyacrylic acid (PAA) as branched chains and chlorinated polyvinyl chloride (CPVC) as backbone was synthesized by in-situ chlorinating graft copolymerization (ISCGC). Second, the acid groups of the graft copolymer were neutralized by sodium hydroxide and aluminium hydroxide, respectively in order to prepare carboxylated ionic copolymers.

Platinum-coated gold nanoporous film surface: Electrodeposition and enhanced electrocatalytic activity for methanol oxidation

This report describes the preparation of Pt-nanoparticle-coated gold-nanoporous film (PGNF) on a gold substrate via a simple "green" approach. The gold electrode that has been anodized under a high potential of 5 V is reduced by freshly prepared ascorbic acid (AA) solution to obtain gold nanoporous film electrode. Then the Pt nanoparticle is grown on the electrode by cyclic voltammetry (CV).