985 resultados para commerce au loin


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We report a measurement of high-p(T) inclusive pi(0), eta, and direct photon production in p + p and d + Au collisions at root s(NN) = 200 GeV at midrapidity (0 < eta < 1). Photons from the decay pi(0) -> gamma gamma were detected in the barrel electromagnetic calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The eta -> gamma gamma decay was also observed and constituted the first eta measurement by STAR. The first direct photon cross-section measurement by STAR is also presented; the signal was extracted statistically by subtracting the pi(0), eta, and omega(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading-order perturbative QCD calculations.

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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.

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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.

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用47MeV/u12C离子轰击天然铋靶,通过炮弹和靶核之间的核子转移反应产生Au同位素。使用放射化学方法从大量Bi和复杂反应产物中分离、纯化Au,并制备Au的γ射线测量源。使用HPGe探测器测量放射性Au同位素的γ活性。根据照射结束时Au同位素的活度和其他相关数据,确定每个Au同位素的产生截面。分析发现,缺中子Au同位素的产生截面与Qgg值之间不遵从指数依赖关系,这可用重离子碰撞中的次级过程加以解释。

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利用能量为164-180MeV的35Cl束流,通过重离子核反应149Sm(35Cl,5n) 研究了179Au的高自旋态能级结构。实验进行了γ射线的激发函数、X-γ和γ-γ-t符合测量。基于实验测量结果,首次建立了179Au的1/2[660](πi13/2)转动带。结合已有的实验数据,着重讨论了奇-A Au核中1/2[660](πi13/2) 转动带的形变和带头激发能随中子数的变化。用能量为140MeV的29Si束流轰击159Tb金属靶,布居了183Au核的高自旋态。实验中要求至少有3个高纯锗和2个BGO探测器同时点火,在此符合条件下,记录高纯锗探测器探测到的γ射线的能量和相对时间、BGO探测到的γ射线的总能量和多重性。通过对实验数据的分析,扩展并更新了183Au的能级纲图。首次建立了183Au的πi13/2转动带的能量非优先带。分析并讨论了缺中子奇-A Au中πh9/2转动带的能量非优先带和πf7/2转动带间的相互作用

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本实验工作是在兰州重离子加速器国家实验室ECR离子源完成。实验采用能量为336keV的低能高电荷态Ar16+离子轰击Au、Mo金属靶,入射离子与靶表面之间的夹角分别是20°,25°,……,80°,入射角与出射角之和为90°。测量了不同角度下Mo的Lα、Lβ,Au的Mα和Ar的Kα特征X射线谱,对实验谱进行了高斯拟合,计算了不同入射角下的各条X射线的产额和产生截面,并将靶原子发射出的X射线截面与ECPSSR和带结合能修正的BEA理论计算的结果进行了比较。发现当入射角较小时,Ar16+与金属靶相互作用时所产生出的各条特征X射线截面随入射角的增加而增加,当入射角达到40°左右后X射线截面基本上保持不变。与ECPSSR计算值相比,本实验中Au的X射线截面比较接近,实验值比ECPSSR计算值小不到一个量级;而Mo的X射线截面实验值比ECPSSR计算值大3-4个量级,但产额与带结合能修正的BEA计算值很接近

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本实验工作是在中国原子能科学研究院的HI-13串列加速器国家实验室第二测量厅原子物理实验平台上完成。本工作采用能量为20-50MeV的高电荷态O5+离子去轰击Au, 测量了不同能量下Au的L1、Lα、Lβ、Lγ的X射线谱,计算了不同能量下各条X射线的产生截面,并与ECPSSR理论计算结果进行了比较。实验结果表明σ(Ll)/σ(Lα) 和σ(Lγ)/σ(Lα)与ECPSSR理论计算结果符合比较好,而对于σ(Lβ)/σ(Lα),在较低能区实验值略高于理论值。在中国科学院近代物理研究所320kV高电荷态离子实验研究平台上测量了Xeq+ (q=17-29)入射Al、Ti和Ni等表面诱发的可见光和红外光。通过对靶原子光谱线的研究,实验发现,随着入射离子的电荷态增高,原子和离子的各种光谱线可得到有效地激发。低速高电荷态离子入射金属固体表面,靶原子的特征谱线的激发强度,与入射离子的电荷态q密切相关。qc的实验测量值和理论计算值符合的较好

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利用能量为164-180MeV的35Cl束流,通过重离子核反应149Sm(35Cl,5n) 研究了179Au的高自旋态能级结构。实验进行了γ射线的激发函数、X-γ和γ-γ-t符合测量。基于实验测量结果,首次建立了179Au的1/2[660](πi13/2)转动带。结合已有的实验数据,着重讨论了奇-A Au核中1/2[660](πi13/2) 转动带的形变和带头激发能随中子数的变化。用能量为140MeV的29Si束流轰击159Tb金属靶,布居了183Au核的高自旋态。实验中要求至少有3个高纯锗和2个BGO探测器同时点火,在此符合条件下,记录高纯锗探测器探测到的γ射线的能量和相对时间、BGO探测到的γ射线的总能量和多重性。通过对实验数据的分析,扩展并更新了183Au的能级纲图。首次建立了183Au的πi13/2转动带的能量非优先带。分析并讨论了缺中子奇-A Au中πh9/2转动带的能量非优先带和πf7/2转动带间的相互作用

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在绝缘体衬底中金属纳米颗粒的制备,常采用金属离子直接注入的方法,这一方法存在的问题主要是,所形成的金属颗粒尺寸离散较大,使这类材料的应用受到了限制。惰性气体离子注入到某些材料中所形成的纳米气泡或空腔的尺寸分布较均一,且纳米空腔具有吸附金属离子的性质。在此基础上我们提出:利用惰性气体离子注入预先在材料中形成尺寸分散较小的纳米空腔埋层,然后在样品表面沉积Au膜,再尝试通过高温扩散或离子束附加辐照的方法制备Au纳米颗粒。实验结果表明,高温退火的方法未在样品内部形成Au颗粒,离子束附加辐照的方法在样品内形成了尺寸分散较小的Au纳米颗粒,这为制备尺寸分散小的金属纳米颗粒复合材料提供了借鉴和新方法。论文中用多种测试方法(PL、UV-VIS、RBS、SEM、TEM)分析讨论了Ar的注入剂量、热处理温度、样品表面取向等参量对制备Au纳米颗粒的影响,并利用M-G理论对所研究体系的光吸收性质进行了模拟计算和定性解释

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用能量密度公式及小液滴模型给出的费米密度分布,并引入中子皮及中子分布弥散度随中子过剩自由度增加而增加这一因素,计算了重离子反应在相互作用势及熔合位垒。熔合位垒的计算值和实验值符合很好,特别是在中重核区域,改善了以前的计算结果。详细研究了亲近势标度,发现用中子皮及中子分布弥散度的变化能较好地解释中子过剩自由度对新近势标度偏离的影响。本工作对奇异核结构与核反应性质的研究无疑是有用的。我们利用HIRFL提供的46.7MeV/u ~(12)C束轰击~(58)Ni、~(115)In、~(197)Au研究了反应中发射的α粒子角分布和能谱。从速度表象中洛仑兹不变截面等高图中明显看到发射α粒子的三个源。用这三个源的运动模型成功拟合了α粒子能谱,所提取的参数符合费米气体模型计算结果,并讨论了能谱及拟合参数对靶的依赖关系。认为快速源实质上来自弹核碎裂或类弹核碎裂

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本论文的工作:利用两体裂变角关联技术,辅之以飞行时间测量,测定了47MeV/u的~(12)C轰击~(197)Au和~(209)Bi靶中心碰撞对应的线性动量转移(LMT),得到了关联裂片出射的共面歧离分布,同时还发现了关联角很小且共面歧离很大的裂变事件,并得到了其相对速度分布。从测到的LMT分布中,得到中心碰撞对应的最可几线性动量转移约占入射动量的65%,相应于单核子线性动量转移约为192MeV/c.A,进而还估算出了所形成热核的激发能上限。在对关联裂片出射的共面歧离效应研究中,发现了共面歧离宽度是热核激发能的较好量度之一。并给出了共面歧离宽度跟热核单核子激发能的经验关系;还用简化的裂片级联蒸发模型估算了蒸发中子、质子和α粒子的平均多重性

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通过对中能区Ar+Au/Tb/Ag反应中高激发核的发射时标、发射次序、发射机制、核温度、集体运动等衰变特性的研究,提取了轻粒子和中等质量碎片(IMF)的发射时间,IMF发射时间随束流能的升高而变短,发射机制逐渐由相继衰变过渡至多重碎裂。研究了轻粒子和碎片间的发射次序,对高能粒子和碎片,轻粒子先于碎片发射,而低能时,则为碎片先于轻粒子发射。IMF发射成分与角度和碰撞参数有关,前角区来自于弹核碎裂,后角区来自于类靶热核的蒸发。在平面和出平面研究表明,中速粒子和碎片为在平面发射占主导,即存在类转动效应;对轻粒子,转动效应随粒子质量增加而增加;对中速产物均观测到该效应随碰撞参数饿增大而增大。采用几种不同的方法提取了热核的核温度,研究了不同方法之间的区别。

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We described the use of silica nanoparticles as building blocks for the immobilization of electrogenerated chemiluminescence (ECL) reagent Ru(bpy)3" and the fabrication of layer-by-layer assembly film by alternating the deposition of the Ru(bpy)3 2'-doped silica nanoparticles and Au nanoparticles.

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A novel hydrogen peroxide biosensor was fabricated that is based on horseradish peroxidase-Au nanoparticles immobilized on a viologen-modified glassy carbon electrode (GCE) by amino cation radical oxidation in basic solution. The immobilized BAPV acts as a mediator and a covalent linker between GCE and the Au nanoparticles. The biosensor exhibited fast response, good reproducibility, and long-term stability.

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A simple, rapid and ultrasensitive colorimetric detection of protein using aptamer-Au nanoparticles (AuNPs) conjugates based on a dot-blot array has been developed, which was combined with the unique optical properties of AuNPs, enabling the visual detection of protein within minutes without any instrument.