59 resultados para hyperpolarisierte Gase, He-3, MRT, Lunge, Applikator

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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Using a transport model coupled with a phase-space coalescence afterburner, we study the triton-He-3 (t-He-3) ratio with both relative and differential transverse flows in semicentral Sn-132 + Sn-124 reactions at a beam energy of 400 MeV/nucleon. The neutron-proton ratios with relative and differential flows are also discussed as a reference. We find that similar to the neutron-proton pairs, the t-He-3 pairs also carry interesting information regarding the density dependence of the nuclear symmetry energy. Moreover, the nuclear symmetry energy affects more strongly the t-He-3 relative and differential flows than the pi(-)/pi(+) ratio in the same reaction. The t-He-3 relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.

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The single charge transfer process in He-3(2+)+He-4 collisions is investigated using the quantum-mechanical molecular-orbital close-coupling method, in which the adiabatic potentials and radial couplings are calculated by using the ab initio multireference single- and double-excitation configuration interaction methods. The differential cross sections for the single charge transfer are presented at the laboratorial energies E = 6 keV and 10 keV for the projectile He-3(2+). Comparison with the existing data shows that the present results are better in agreement with the experimental measurements than other calculations in the dominant small angle scattering, which is attributed to the accurate calculations of the adiabatic potentials and the radial couplings.

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Using a transport model coupled with a phase-space coalescence after-burner we study the triton-He-3 relative and differential transverse flows in semi-central Sn-132 + Sn-124 reactions at a beam energy of 400 MeV/nucleon. We find that the triton-He-3 pairs carry interesting information about the density dependence of the nuclear symmetry energy. The t-He-3 relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.

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利用适用于低能电子入射的反应显微成像谱仪,对电子入射He原子近阈值下的双电离过程进行了研究,实验测量了反应后3个粒子的全部动量,获得了出射电子间的关联信息.主要介绍近阈值下的双电离实验装置及实验技术,集中分析反应后出射电子的动量能量关系,对描述近阈值双电离的Wannier理论进行了检验,发现在入射电子能量为106eV时,实验结果具有Wannier理论预言的性质.

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Helium, rieon and argon isotope compositions of fluid inclusions have been measured in hydrothermal sulfide samples from the TAG hydrothermal field at the Mid-Atlantic Ridge. Fluid-inclusion He-3/He-4 ratios are 2.2-13.3 times the air value (Ra), and with a mean of 7.2 Ra. Comparison with the local vent fluids (He-3/He-4=7.5-8.2 Ra) and mid-ocean ridge basalt values (He-3/He-4=6-11 Ra) shows that the variation range of He-3/He-4 ratios from sulfide-hosted fluid inclusions is significantly large. Values for Ne-20/Ne-22 are from 10.2 to 11.4, which are significantly higher than the atmospheric ratio (9.8). And fluid-inclusion Ar-40/Ar-36 ratios range from 287 to 359, which are close to the atmospheric values (295.5). These results indicate that the noble gases of fluid inclusions in hydrothermal sulfides are a mixture of mantle- and seawater-derived noble gases; the partial mantle-derived components of trapped hydrothermal fluids may be from the lower mantle; the helium of fluid inclusions is mainly from upper mantle; and the Ne and Ar components are mainly from seawater.

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The noble gas nuclide abundances and isotopic ratios of the upmost layer of Fe-Mn crusts from the western and central Pacific Ocean have been determined. The results indicate that the He and Ar nuclide abundances and isotopic ratios can be classified into two types: low He-3/He-4 type and high He-3/He-4 type. The low He-3/He-4 type is characterized by high He-4 abundances of 191x10(-9) cm(3.)STP(.)g(-1) on average, with variable He-4, Ne-20 and Ar-40 abundances in the range (42.8-421)x10(-9) cm(3.)STP(.)g(-1), (5.40-141)x10(-9)cm(3.)STP(.)g(-1), and (773-10976)x10(-9) cm(3.)STP(.)g(-1), respectively. The high He-3/He-4 samples are characterized by low He-4 abundances of 11.7x10(-9) cm(3.)STP(.)g(-1) on average, with He-4, Ne-20 and Ar-40 abundances in the range of (7.57-17.4)x10(-9) cm(3.)STP(.)g(-1), (110.4-25.5)x10(-9) cm(3.)STP(.)g(-1) and (5354-9050)x10(-9) cm(3.)STP(.)g(-1), respectively. The low He-3/He-4 samples have He-3/He-4 ratios (with RIRA ratios of 2.04-2.92) which are lower than those of MORB (R/R-A=8 +/- 1) and Ar-40/Ar-36 ratios (447-543) which are higher than those of air (295.5). The high He-3/He-4 samples have He-3/He-4 ratios (with R/R-A ratios of 10.4-12.0) slightly higher than those of MORB (R/R-A=8 +/- 1) and Ar-40/Ar-36 ratios (293-299) very similar to those of air (295.5). The Ne isotopic ratios (Ne-20/Ne-22 and Ne-21/Ne-22 ratios of 10.3-10.9 and 0.02774-0.03039, respectively) and the Ar-38/Ar-36 ratios (0.1886-0.1963) have narrow ranges which are very similar to those of air (the Ne-20/Ne-22, Ne-21/Ne-22, Ar-38/Ar-36 ratios of 9.80, 0.029 and 0.187, respectively), and cannot be differentiated into different groups. The noble gas nuclide abundances and isotopic ratios, together with their regional variability, suggest that the noble gases in the Fe-Mn crusts originate primarily from the lower mantle. The low He-3/He-4 type and high He-3/He-4 type samples have noble gas characteristics similar to those of HIMU (High U/Pb Mantle)- and EM (Enriched Mantle)-type mantle material, respectively. The low He-3/He-4 type samples with HIMU-type noble gas isotopic ratios occur in the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain and the Mid-Pacific Seamounts whereas the high He-3/He-4 type samples with EM-type noble gas isotopic ratios occur in the Line Island Chain. This difference in noble gas characteristics of these crust types implies that the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain, and the Mid-Pacific Seamounts originated from HIMU-type lower mantle material whereas the Line Island Chain originated from EM-type lower mantle material. This finding is consistent with variations in the Pb-isotope and trace element signatures in the seamount lavas. Differences in the mantle surce may therefore be responsible for variations in the noble gas abundances and isotopic ratios in the Fe-Mn crusts. Mantle degassing appears to be the principal factor controlling noble gas isotopic abundances in Fe-Mn crusts. Decay of radioactive isotopes has a negligible influence on the nuclide abundances and isotopic ratios of noble gases in these crusts on the timescale of their formation.

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In 1990 JET operated with a number of technical improvements which led to advances in performance and permitted the carrying out of experiments specifically aimed at improving physics understanding of selected topics relevant to the "NEXT STEP". The new facilities include beryllium antenna screens, a prototype lower hybrid current drive system, and modification of the NI system to enable the injection of He-3 and He-4. Continued investigation of the hot-ion H-mode produced a value of n(D)(0)tau-E(T)(i)(0) = 9 x 10(20)m-3s keV, which is near conditions required for Q(DT) = 1, while a new peaked density profile H-mode was developed with only slightly lower performance. Progress towards steady state operation has been made by achieving ELMy H-modes under certain operating conditions, while maintaining good tau-E values. Experimental simulation of He ash transport indicates effective removal of alpha-particles from the plasma core for both L and H mode plasmas. Detailed analyses of particle and energy transport have helped establish a firmer link between particle and energy transport, and have suggested a connection between reduced energy transport and reversed shear. Numerical and analytic studies of divertor physics carried out for the pumped divertor phase of JET have helped clarify the key parameters governing impurity retention, and an intensive model validation effort has begun. Experimental simulation of alpha-particle effects with beta-fast up to 8% have shown that the slowing down processes are classical, and have given no evidence of deleterious collective effects.

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During its 1990 operation, 2 large RF systems were available on JET. The Ion Cyclotron Resonance Heating (ICRH) system was equipped with new beryllium screens and with feedback matching systems. Specific impurities generated by ICRH were reduced to negligible levels even in the most stringent H-mode conditions. A maximum power of 22 MW was coupled to L-mode plasmas. High quality H-modes (tau-E greater-than-or-equal-to 2.5 tau-EG) were achieved using dipole phasing. A new high confinement mode was discovered. It combines the properties of the H-mode regime to the low central diffusivities obtained by pellet injection. A value of n(d) tau-E T(i) = 7.8 x 10(20) m-3 s keV was obtained in this mode with T(e) approximately T(i) approximately 11 keV. In the L-mode regime, a regime, a record (140 kW) D-He-3 fusion power was generated with 10 - 14 MW of ICRH at the He-3 cyclotron frequency. Experiments were performed with the prototype launcher of the Lower Hybrid Current Drive (LHCD) systems with coupled power up to 1.6 MW with current drive efficiencies up to < n(e) > R I(CD)/P = 0.4 x 10(20) m-2 A/W. Fast electrons are driven by LHCD to tail temperatures of 100 keV with a hollow radial profile. Paradoxically, LHCD induces central heating particularly in combination with ICRH. Finally we present the first observations of the synergistic acceleration of fast electrons by Transit Time Magnetic Pumping (TTMP) (from ICRH) and Electron Landau Damping (ELD) (from LHCD). The synergism generates TTMP current drive even without phasing the ICRH antennae.

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稻属(Oryza L.)隶属于禾本科(Gramineae)Ehrhartoideae亚科的稻族(Oryzeae),包括两个栽培种(亚洲栽培稻O. sativa和非洲栽培稻O. glaberrima)和大约20多个野生种,广布于热带亚洲、非洲、大洋洲、中美洲和南美洲。药用野生稻复合体(O. officinalis complex)是稻属中最大、也是最复杂的一个复合体,共包括9个种,含有5种染色体组类型(B、C、BC、CD 和E)。作为栽培稻品质改良的重要基因库,药用野生稻复合体在稻属中具有重要的地位。但是,相似的形态和重叠的地理分布使部分物种的分类和鉴定一直较为困难;种内染色体组构成和倍性的不同更增加了分类鉴定的复杂性。这种情况阻碍了对这些野生稻遗传优势的有效利用。另外,由于物种间断分布和缺乏明确的二倍体亲本等原因,药用野生稻复合体内的异源多倍体起源一直存在争议。本文通过细胞核乙醇脱氢酶基因(Adh)和nrDNA的内转录间隔区(ITS)限制性片段长度多态性(RFLP)分析;叶绿体matK 基因、trnL 内含子和trnL-trnF 基因间隔区、核基因Adh和GPA1以及核糖体DNA ITS片段等序列比较的方法,对药用野生稻复合体中染色体组和物种的鉴定、种间系统发育关系,以及异源多倍体CCDD物种的起源和多倍体ITS的分子进化等进行了研究。主要研究结果如下: 1. 利用核Adh 基因限制性片段长度多态性,检测了来自国际水稻研究所基因库的64份药用野生稻复合体的样品。结果证明,所有O. rhizomatis样品都是含C染色体组的二倍体,所有O. minuta样品都是含BC 染色体组的四倍体。但是,种子库中鉴定为O. officinalis、O. punctata和O. eichingeri的样品中,同时都发现了含C染色体组的二倍体和含BC染色体组的四倍体。四倍体的O. officinalis只在印度分布,而且曾被描述为另一个种O. malampuzhaensis。 四倍体的O. punctata,也被一些学者称为O. schweinfurthiana,被发现和其二倍体一样分布广泛。值得注意的是,有两个曾被作为O. officinalis 四倍体的样品实际上是含有CD染色体组的物种O. latifolia。我们的结果增进了对国际水稻研究所种子库中部分野生稻样品染色体组构成的理解, 纠正了以往对药用野生稻复合体样品的错误鉴定,为今后进一步研究和利用这部分资源提供了种质编目的重要基础。 2. 对稻属中代表不同地理分布区的、含CD染色体组的11个样品(包括77个克隆)的ITS片段进行了测序。基于这些ITS序列的限制性片段长度多态性,提出一个快速而可靠的区分稻属CD 染色体组物种的方法。这个方法的具体步骤是:(1)利用通用引物扩增ITS 片段;(2)利用限制性内切酶FokI和/或DraⅢ消化PCR扩增产物;(3)用1%的琼脂糖胶电泳并根据消化产物的片段长度多态性来区分不同物种。 3. 利用包括两个叶绿体片段(matK和 trnL-trnF)、nrDNA内转录间隔区(ITS)和三个核基因(Adh1、Adh2和GPA1)的同源序列分析,探讨了药用野生稻复合体中二倍体物种和它们所代表的染色体组之间的系统发育关系。独立和合并的基因系统发育树都显示了一致的结果,即C染色体组和B染色体组的亲缘关系要比它们和E染色体组的近。三个含C染色体组的二倍体中,O. officinalis 和O. rhizomatis表现出较近的亲缘关系。值得注意的是,在O. eichingeri种内,尽管基于多基因的数据支持来自斯里兰卡的样品和来自非洲的样品聚成一个分支,但是较低的支持率表明, 两个地区的样品之间存在着较高的遗传分化。 4. 稻属中含CD染色体组的物种特产于拉丁美洲,包括O. alta、 O. grandiglumis 和O. latifolia。由于具有相同的染色体组类型、相似的形态特征和重叠的地理分布,这3个物种间的系统发育关系一直存在争论。另外,因为美洲大陆上没有含C和D染色体组的二倍体物种存在,对这些含CD染色体组物种的可能起源也有不同的假设被提出。使这个问题更具挑战性的是,尽管开展了世界范围的收集,至今仍没有找到含D 染色体组的二倍体物种。在本研究中,代表含C、CD和E染色体组以及含G染色体组的外类群共7个物种,共15份样品的2个叶绿体片段(matK和trnL-trnF)和3个核基因(Adh1,Adh2 和 GPA1)部分片段被测序。基于简约法、距离法和最大似然法的系统发育分析都充分支持含CD染色体组的物种起源于一次杂交事件的推论,并且显示,在物种形成时,含C染色体组的物种(O. officinalis 或O. rhizomatis 而非O. eichingeri)可能承担了母本,而含E染色体组的物种(O. australiensis)则可能承担了父本。另外,CCDD物种间非常一致的系统发育关系表明,非常大的分歧存在于 O. latifolia 和其它两个种(O. alta和O. grandiglumis)之间,这个结果倾向于将后两个种处理为同种或同种下不同分类群。 5. 基于178个克隆序列比较,探讨了ITS在稻属多倍体中的致同进化及其系统学意义。研究发现稻属异源四倍体的ITS存在不同形式的进化方式:首先,非洲BBCC四倍体O. eichingeri和O. punctata 的ITS片段同时保留了双亲拷贝,而且系统发育研究表明,二倍体的O. eichingeri和O. punctata 可能是这两个四倍体的直接祖先;其次,亚洲四倍体O. malampuzhaensis和O. minuta 的ITS仅定向保留母本ITS拷贝;另外,美洲CCDD四倍体的ITS序列发生了双向致同进化,即O. alta和O. grandiglumis的ITS位点一致化成C染色体组类型,而O. latifolia一致化成 D/E 染色体组类型。我们的研究进一步表明在利用ITS片段进行系统发育分析时,特别是涉及异源多倍体时必须慎重。 6. 利用栽培稻的微卫星引物,对含B/C染色体组的6个物种,157个体的SSR位点进行扩增。结果在这些亲缘关系稍远的野生稻中得到7个SSR位点,其中5个位点表现出多态性。比较BB、CC和BBCC物种SSR位点的每位点平均等位基因数A、多态位点百分率P和期望杂合度He ,3项指标发现,四倍体物种的遗传多样性,总体上要高于二倍体物种;二倍体物种内部,O. officnalis的遗传变异最大。另外,以遗传相关性为标准,讨论了B/C染色体组物种间的系统发育关系,同时推测了现存二倍体物种和4个BBCC四倍体物种的遗传关系。

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We discuss the non-Abelian topological objects, in particular the non-Abrikosov vortex and the magnetic knot made of the twisted non-Abrikosov vortex, in two-gap superconductor. We show that there are two types of non-Abrikosov vortex in Ginzburg-Landau theory of two-gap superconductor, the D-type which has no concentration of the condensate at the core and the N-type which has a non-trivial profile of the condensate at the core, under a wide class of realistic interaction potential. We prove that these non-Abrikosov vortices can have either integral or fractional magnetic flux, depending on the interaction potential. We show that they are described by the non-Abelian topology pi(2)(S-2) and pi(1)(S-1), in addition to the well-known Abelian topology pi(1)(S-1). Furthermore, we discuss the possibility to construct a stable magnetic knot in two-gap superconductor by twisting the non-Abrikosov vortex and connecting two periodic ends together, whose knot topology pi(3)(S-2) is described by the Chern-Simon index of the electromagnetic potential. We argue that similar topological objects may exist in multi-gap or multi-layer superconductors and multi-component Bose-Einstein condensates and superfluids, and discuss how these topological objects can be constructed in MgB2, Sr2RuO4, He-3, and liquid metallic hydrogen.

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We present a numerical study of shear viscosity and thermal conductivity of symmetric nuclear matter, pure neutron matter, and beta-stable nuclear matter, in the framework of the Brueckner theory. The calculation of in-medium cross sections and nucleon effective masses is performed with a consistent two- and three-body interaction. The investigation covers a wide baryon density range as needed in the applications to neutron stars. The results for the transport coefficients in beta-stable nuclear matter are used to make preliminary predictions on the damping time scales of nonradial modes in neutron stars.

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We discuss experimental evidence for a nuclear phase transition driven by the different concentrations of neutrons to protons. Different ratios of the neutron to proton concentrations lead to different critical points for the phase transition. This is analogous to the phase transitions occurring in He-4-He-3 liquid mixtures. We present experimental results that reveal the N/A (or Z/A) dependence of the phase transition and discuss possible implications of these observations in terms of the Landau free energy description of critical phenomena.

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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.

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The experimental results reveal the isospin dependence of the nuclear phase transition in terms of the Landau Free Energy description of critical phenomena. Near the critical point, different ratios of the neutron to proton concentrations lead to different critical points for the phase transition which is analogous to the phase transitions in He-4-He-3 liquid mixtures. The antisymmetrized molecular dynamics (AMD) and GEMINI models calculations were also performed and the results will be discussed as well.