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.

A key gene of the RNA interference pathway in the black tiger shrimp, Penaeus monodon: Identification and functional characterisation of Dicer-1

RNA interference (RNAi) is an evolutionarily conserved mechanism by which double-stranded RNA (dsRNA) initiates post-transcriptional silencing of homologous genes. Here we report the amplification and characterisation of a full length cDNA from black tiger shrimp (Penaeus monodon) that encodes the bidentate RNAase III Dicer, a key component of the RNAi pathway. The full length of the shrimp Dicer (Pm Dcr1) cDNA is 7629 bp in length, including a 51 untranslated region (UTR) of 130 bp, a 3' UTR of 77 bp, and an open reading frame of 7422 bp encoding a polypeptide of 2473 amino acids with an estimated molecular mass of 277.895 kDa and a predicted isoelectric point of 4.86. Analysis of the deduced amino acid sequence indicated that the mature peptide contains all the seven recognised functional domains and is most similar to the mosquito (Aedes aegypti) Dicer-1 sequence with a similarity of 34.6%. Quantitative RT-PCR analysis showed that Pm Dcr1 mRNA is most highly expressed in haemolymph and lymphoid organ tissues (P 0.05). However, there was no correlation between Pm Dcr1 mRNA levels in lymphoid organ and the viral genetic loads in shrimp naturally infected with gill-associated virus (GAV) and Mourilyan virus (P > 0.05). Treatment with synthetic dsRNA corresponding to Pm Dcr1 sequence resulted in knock-down of Pm Dcr1 mRNA expression in both uninfected shrimp and shrimp infected experimentally with GAV. Knock-down of Pm Dcr1 expression resulted in more rapid mortalities and higher viral loads. These data demonstrated that Dicer is involved in antiviral defence in shrimp. (c) 2007 Elsevier Ltd. All rights reserved.

中国东部近海温度锋面的分布特征和变化规律

海洋锋面既是各种物理过程，如环流、上升流、混合等的结果，也是这些物理过程的指标，还是影响流场结构、海洋热量和动量交换、海气相互作用以及生物化学过程的重要因素。同时，海洋锋面研究还与海洋产业活动，如海洋渔业、环境保护、海洋倾废等密切相关，也是军事海洋学必须考虑的问题。所以，海洋锋面的研究也成为物理海洋学和海洋交叉学科研究中的一个重要内容。 本研究以中国东部近海（渤海、黄海、东海及南海北部）锋面的分布特征、变化规律、动力机制及对相应过程的影响为研究对象，以1985~2002年AVHRR Pathfinder的卫星海表面温度数据为基础，辅以POM模式，通过数据分析、模式验证和动力机制分析相结合的方法，既全面描述了中国东部近海锋面分布和变化的总体特征，又深入研究了三个典型锋面，即南黄海西部沿岸锋面、黄海暖流源区陆架锋面和东海黑潮陆坡锋面的具体特点，结果如下： 1，中国东部近海温度锋面分布状况的季节变化明显。冬季，锋面丰富，形状规则，位置稳定，可以明确区分出14条沿岸流锋面和暖流锋面。春季及夏初，锋区分布范围广，没有规则的锋面形态，也没有固定的发生区域，不能明确分辨出具体锋面，锋区大体按黑潮流域—长江河口沿岸区域—南黄海区域的方向和渤海—北黄海—南黄海的方向转移。夏季在沿岸区域产生潮汐锋，秋季则很少有锋面出现。对于冬季锋面的位置来讲，沿岸锋面的年际变化小，暖流锋面的年际变化大；受地形限制的锋面年际变化小，脱离地形控制的锋面年际变化大。 2，冬季山东半岛南部（即南黄海西部）温度锋面的完整形态为“N”形，东、西两部分平行岸线和等深线，中间部分跨越等深线。表层以下的黄海沿岸流和黄海暖流及分支是此锋面生成和维持的直接原因：南下沿岸流与北上的黄海暖流形成了锋面的东部部分，反气旋性回流的沿岸流与被沿岸流挟入南黄海西部的黄海暖流暖水及进入南黄海西部的黄海暖流分支形成了锋面的中部和西部部分。通过强烈的垂直混合，此锋面形态特征从表层以下传播到表层。沿岸流和暖流的强弱会影响此锋面的位置，锋面的形成会反过来影响上述流态。冬季风是维持相关环流和锋面结构的间接原因。 3，暖舌西移和双暖舌温度结构是冬季南黄海温度分布的主要特征，黄海暖流源区暖舌南北两侧形成的双锋面是南黄海锋面结构的主要特征，这两条锋面有时也可在西端连为一体，形成环绕黄海暖水舌前锋区的弧形锋面。南侧锋面大致沿长江浅滩边缘，北侧锋面大致呈东西走向，横跨黄海海槽入口，在此锋面的阻挡下，黄海暖舌无法沿海槽中央北上，在两锋面之间沿着黄海海槽西侧进入黄海。统计结果表明，北侧锋面的位置、强度变化，是驱使暖舌沿海槽西侧进入黄海、并控制其西移程度的主要因素。当北侧锋面偏南或强度大时，暖舌西移程度大，当两条锋面间隔距离大时，暖舌的西移程度弱，暖舌主体北侵的程度就越大，双暖舌结构越不明显。源区黄海暖流的东西向质量和热量输运，黄海内部的风应力等通过影响锋面的位置和强度而间接影响暖舌西移程度。黄海暖舌甚至黄海暖流的起源值得进一步探讨。 4，东海黑潮锋在台湾岛东北部和九州岛西南部的平均经向位置之间存在着反位相的年际变化规律。长期观测资料和数值试验结果都表明，进入东海的黑潮流量的改变能够导致黑潮锋面位置在两地反位相的变化：当黑潮流量增大时，黑潮在台湾岛东北部的向陆架入侵减小，锋面向南偏移，而同时黑潮在九州岛西南部的向陆架入侵增大，锋面向北偏移；冬季风应力在台湾岛东北部以东北风为主，在九州岛西南部以西北风为主。当风应力增大时，黑潮锋面在台湾岛东北部向西北偏移，在九州岛西南部向西南方向偏移。黑潮流轴位置的改变也可能是导致反位相变化的原因。位涡输运方程中的地形和斜压联合效应项以及风应力项（主要是Ekman输运）在两地的不同表现可能是控制这种变化的机制。