Critical behavior of multifragmentation in finite nuclei and extraction of critical exponents

Using a phenomenological asymmetric nuclear equation of state, we obtained pressure-density isotherms of the finite nucleus Sn-112 simulated in r-space and in p-space and constructed the nuclear fragments by using the coalescence model. After correlatively analysing the fragments, the signal of critical behavior has been found and critical exponents were also extracted.

Production mechanism of superheavy nuclei in massive fusion reactions

Within the concept of the dinuclear system (DNS), a dynamical model is used for describing the formation of superheavy residues in massive fusion reactions, in which the capture of two colliding nuclei, the formation and de-excitation of the compound nucleus are described by using a barrier distribution method, solving master equations numerically and statistical approach, respectively. Using the DNS model, the production cross sections of superheavy nuclei are calculated and compared with the available experimental data. The isotopic dependence of the cross sections to produce the superheavy element Z=116 by the two types of the reactions is discussed and the possible reasons influencing the isotopic trends are analyzed systematically.

Probing high-density behavior of symmetry energy from pion emission in heavy-ion collisions

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The total pion multiplicities and the pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6. Ska and SIB, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI Collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Dynamics of strangeness production in heavy-ion collisions near threshold energies

Within the framework of the improved isospin-dependent quantum molecular dynamics (ImIQMD) model, the dynamics of strangeness (K-0,K-+, Lambda, and Sigma(-,0,+)) production in heavy-ion collisions near threshold energies is investigated systematically, with the strange particles considered to be produced mainly by inelastic collisions of baryon-baryon and pion-baryon. Collisions in the region of suprasaturation densities of the dense baryonic matter formed in heavy-ion collisions dominate the yields of strangeness production. Total multiplicities as functions of incident energies and collision centralities are calculated with the Skyrme parameter SLy6. The excitation function of strangeness production is analyzed and also compared with the KaoS data for K+ production in the reactions C-12 + C-12 and Au-197 + Au-197.

Dynamics of pion production in heavy-ion collisions around 1A GeV energies

Within the framework of the improved isospin-dependent quantum molecular dynamics model, the dynamics of pion emission in heavy-ion collisions in the region of 1A GeV energies as a probe of nuclear symmetry energy at suprasaturation densities is investigated systematically. The total pion multiplicities and the pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6, Ska, and SIII and also for the cases of different stiffness of symmetry energy with the parameter SLy6. The influence of Coulomb potential, symmetry energy, and in-medium pion potential on the pion production is investigated and compared to each other by analyzing the distributions of transverse momentum and longitudinal rapidity and also the excitation functions of the total pion and the pi(-)/pi(+) ratio. The directed flow, elliptic flow, and polar-angle distributions are calculated for the cases of different collision centralities and also the various stiffnesses of the symmetry energies. A comparison of the calculations with the available experimental data is performed.

Influence of entrance channels on the formation of superheavy nuclei in massive fusion reactions

Within the framework of the dinuclear system (DNS) model, the production cross sections of superheavy nuclei Hs (Z=108) and Z=112 combined with different reaction systems are analyzed systematically. It is found that the mass asymmetries and the reaction Q values of the projectile target combinations play a very important role on the formation cross sections of the evaporation residues. Both methods to obtain the fusion probability by nucleon transfer by solving a set of microscopically derived master equations along the mass asymmetry degree of freedom (ID) and distinguishing protons and neutrons of fragments (2D) are compared with each other and also with the available experimental data. (C) 2010 Elsevier B.V. All rights reserved.

Hemizygosity for Atm and Brca1 influence the balance between cell transformation and apoptosis

Background: In recent years data from both mouse models and human tumors suggest that loss of one allele of genes involved in DNA repair pathways may play a central role in genomic instability and carcinogenesis. Additionally several examples in mouse models confirmed that loss of one allele of two functionally related genes may have an additive effect on tumor development. To understand some of the mechanisms involved, we examined the role of monoallelic loss or Atm and Brca1 on cell transformation and apoptosis induced by radiation. Methods: Cell transformation and apoptosis were measured in mouse embryo fibroblasts (MEF) and thymocytes respectively. Combinations of wild type and hemizygous genotypes for ATM and BRCA1 were tested in various comparisons. Results: Haploinsufficiency of either ATM or BRCA1 resulted in an increase in the incidence of radiation-induced transformation of MEF and a corresponding decrease in the proportion of thymocytes dying an apoptotic death, compared with cells from wild-type animals. Combined haploinsufficiency for both genes resulted in an even larger effect on apoptosis. Conclusions: Under stress, the efficiency and capacity for DNA repair mediated by the ATM/BRCA1 cell signalling network depends on the expression levels of both proteins.

PROBING THE SYMMETRY ENERGY AT SUPRA-SATURATION DENSITIES FROM PION EMISSION IN HEAVY-ION COLLISIONS

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6, Ska and SIII, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2.

奇奇核158Ho和124Cs高自旋态的实验研究

奇奇核作为研究准质子和准中子间相互作用的独特侯选核，近年来，人们给予了越来越多的关注。奇奇核高j组态带中观测到的低自旋旋称反转现象(Signature inversion)已成为原子核高自旋态领域中一个十分活跃的研究课题。近十年来，一系列基于二准粒子加转子模型框架的计算结果表明，奇奇核中这两个准粒子之间的相互作用与旋称反转现象的发生密切相关。相对于偶偶核和奇A核，奇奇核的能级结构更复杂一些，实验上对其高自旋态的研究比较困难，这主要体现在实验上所提供的许多奇奇核的能级纲图存在着一定程度的不确定性，例如能级的激发能位置、转动带的组态、自旋和宇称的指定，甚至在纲图结构、级联系列的核素归属等方面都有一些问题。其中，转动带能级自旋的指定直接关系到准粒子能量的劈裂属性(即正常劈裂还是反常劈裂、旋称反转发生在低自旋区还是高自旋区及旋称反转的发生位置等)：自旋的奇偶性定错了，会导致本来是反转的旋称劈裂变成不反转的(反之亦然)；自旋值定错了△I，会导致旋称反转的位置发生相应的漂移。由于实验上奇奇核转动带能级自旋指定的混乱局面，掩盖了旋称反转现象的客观规律，使得相关理论模型的计算结果得不到及时检验。基于激发能系统学分析方法、以顺排角动量相加性为判据，我们曾对A～160轻稀土区的πhl_(11/2)direct X vi_(13/2)转动带(17个核素)和A～130过渡区的πh_(11/2)direct XVh_(ll/2)转动带(20个核素)进行了系统研究，对其中20个核的自旋数据提出质疑、并提出了相应的修正方案，在此基础上总结了两核区旋称反转现象的系统规律。利用激发能系统学方法指定奇奇核转动带的能级自旋，主要遵循以下三点原则：①自旋奇偶性：根据推转壳模型的描述，当准粒子处于优惠态(Favored)时、较非优惠态(Unfavored)具有更大的顺排角动量。这样，通过对转动带中两signature分支系列的i_x大小的比较，可以辅助推断能级自旋的奇偶性；②顺排角动量相加性：在忽略p-n剩余相互作用条件下，奇奇核中总的顺排角动量近似等于相邻奇A核中相应组态带提取的准粒子顺排角动量之和。这样，利用i_x对自旋值比较敏感的特点，可以推断出能级自旋取值的大致范围；③激发能系统性分析：由于集体转动反映大量核子的集体行为，少数核子的改变不会对这种运动产生明显影响，利用转动惯量的组态相关特性，在一组同位素或同中子素系列链中，对应一定内禀结构的转动带，随着质子数或中子数的均匀递增，能级能量应表现光滑的变化趋势(即不发生突变)。这三个方面基于不同角度、相对独立地指定转动带自旋。其结论的统一、往往可以给出正确的自旋数据。然而，必须指出的是：系统学分析过程是一种经验方法，并不具有严格的理论基础，上述的自旋修正以及总结出的旋称反转规律，必须得到实验核谱学测量的支持。基于这一思想，针对两核区，我们分别选择情况较为阿典型的奇奇核~(158)Ho和~(124)Cs进行了集中的实验测量。本论文的主要研究目标就是要建立两核中晕带与低激发态或基态的联系，找出原纲图中错误自旋指定的原因所在，验证系统学结论的有效性，并用旋称反转的实验规律性对理论模型的系统计算结果进行检验。(一)奇奇核~(158)58Ho高自旋态的实验研究在原子能研究院的HI-13串列加速器上，通过~(152)Sm(~(11)B，5nγ)~(158)Ho融合蒸发反应(束流轰击能E_(lab)=60 MeV)、对目标核~(158)Ho的高自旋态进行布居。探测阵列由八个高纯锗探测器构成，为了提高低能射线的收集效率，使用了一个平面型高纯锗探测器。分别进行了激发函数曲线测量、γ-γ-t符合测量和剩余放射性测量。数据反演后，两重符合总记数～120x10~6。实验结果概括如下：1．建立了基态带，组态指定为：{πh_(11/2)[523]7／2-direct Xvh_(9/2)[521]3／2~-}K~π=5~+；2．建立了一个强度仅次于晕带的强耦合带结构(亚晕带：yrare band)。通过转动参数、跃迁几率、顺排角动量、带交叉频率等特征参量的分析，其组态指定为：{πg_(7／2)[404】7／2]~+ direct X vi_(3／2)[651]3／2~+}K~π=5~+。 尽管该带带头附近的结构还不完整，但观测到了带内几条能级退激、分别贯入到晕带和基态带，从而将晕带和亚晕带同基态联系起来，固定了晕带和亚晕带中能级的激发能位置，并通过对这些连接跃迁多极性的分析，指定了两个带中的能级自旋和宇称；3.晕带(πh_(11/2)direct X vi~(13/2))向高自旋端拓展了7条能级，最高自旋态达到26h，激发 能4．9MeV。肯定了原纲图中不确定的617kev跃迁的存在和放置，观测到了反转点(I_(inv.)≈16h)，肯定了系统学研究对该核的自旋修正。基于本实验建立的连接关系，晕带中观测到的最低态(即70.8kev跃迁贯入能级)激发能为207．6kev，而对应该能级，原纲图中激发能为156．9kev。这意味着原能级纲图中，晕带向基态退激途径中漏掉了一个～5lkeV的"能隙"(Energy gap)，自旋差|△I|=3。根据晕带与退激5-同质异能态的跃迁(156．9kev)的快符合关系，该"能隙"至少由两个跃迁构成。该结果否定了原纲图中对晕带带头处理的三种可能性(①70．8kev为连接跃迁，其退激的能级为带头；②70．8kev为带内跃迁，156．9kev、5-同质异能态为带头：⑨70．8kev为带内跃迁，156．9kev、5-同质异能态为带头，但带头附近仍存在尚未观测的跃迁)。不确切的连接关系是过去实验中无法正确指定晕带自旋的原因；4．建立了一个强耦合的转动带结构，其能级间距(跃迁E_γ)随角动量的增加均匀递增，组态指定为{πh_(11/2)[523]7／2~-direct Xvh_(11/2)[505]11／2~-}K~π=9~+；同时，观测到了另一高K激发态退激到该转动带。其内禀结构指定为：{πg_(7／2)[404]7／2~+direct Xvh_(11/2)[505]1 l／2~-}K~π=9~-；5．建立了基于156．9 kev(I~π=5~-、T_(1/2)=29 ns)同质异能态上的转动带，该带观测完整，具有较强耦合的结构特点。其内禀准粒子轨道指定为：{πh_(11/2)[523]_(7／2)~-direct X vd_(3／2)[402]3／2~+}K~π=5~-，与处于较低激发能(67．3 kev)的2~-态(T_(1／2)=27 min．)构成了一对GM伙伴态。否定了过去的实验中把该态指定为{πg_(7/2)~2+direct Xvh_(9/2)[521]3／2~-}K~π=2~-组态；6．观测到了一个基于65．5 kev激发态的转动带，通过理论模型预言的带头激发能及转动参数与实验值的比较、考虑到其较弱的布居强度和很低的顺排角动量、以及较强耦合的结构特点， 其组态指定为： {πd~(5／2)[402]5／2~direct X vh_(9／2)[521]3／2~-}K~π=4~-。这一结果肯定了过去放射性测量中对处于较高激发能(139．2 kev)、T_(1／2)=1．85 ns、I~π=1~-激发态的讨论，即二者构成了一对GM伙伴态；7．建立了基于{πh_(11／2)[523]7／2~-direct X v_(7／2)[523]5／2~-}K~π=6~+激发态的强耦合转动带结构，其带头激发能为450．1 kev，与I~π=1~+、激发能为146．9 kev的同质异能态构成了一对GM伙伴态；8．在过去的放射性衰变测量中，提供了三个2~+激发态(激发能分别为117．7 kev、74．95 kev和316 kev)。其中两个2~+态(117．7和74．95 kev)同时指定具有{πh_(11／2)[523↑]7／2~-direct X vh_(9／2)[521↓]3／2~-}K~π=2~+组态。这里，我们指定1 17．7 kev的2~+激发态为{πg_(7／2)[404↓]7／2~+ direct X vi_(l3／2)[651↓]3／2~+}K~π=2+组态，即与本实验建立的亚晕带内禀激发态构成了一对GM伙伴态，而74．95 kev的2~+激发态指定为 {πh_(11/2)[523↑]7／2~-direct X vh_(9/2)[521↓]3／2~-}K~π=2~+组态，即与基态构成了一对GM伙伴态。基于本实验中K~π=9~+激发态的观测及其转动带的建立，我们指定激发能为3 1 6 kev的2~+激发态具有{πh_(11/2)[523↓]7／2~-direct X vh_(11/2)[505个]1 1／2~-}K~π=2~+组态，即这两个态构成了一对GM伙伴态；9．通过本实验、提供了~(158)Ho中各能态的跃迁强度和跃迁几率等数据。概括起来，奇奇核~(158)Ho的能级纲图大大完善了。综合本实验观测到的高自旋转动带结构和放射性测量中的部分激发态信息，我们可以整理出10对GM伙伴态，并提供了四个分别对应自旋平行和反平行耦合的GM能量漂移(GM Shift)，即：{πh_(ll／2)[523]7／2~-direct Xvh_(9／2)[521]3／2~-}K~π=5~+、2~+，EGM=101．4 kev；{πh_(11/2)[523] 7／2~-direct X vd_(3／2)[402]3／2~+}K~π=5~-、2~-，E_(GM)=64．1 kev；{πd_(5/2)[402]5／2~+direct X vh_(9／2)[521]3／2~-}K~π =4~-、1~-，E_(GM)=113．3 kev；{πh_(11/2)[523]7／2~-direct Xvf_(7/2)[523]5／2~-}K~π=6~+、1~+，EGM=255．7 keV。(二)奇奇核~(124)Cs高自旋态的实验研究在原子能院的HI-13串列加速器上，利用~（116）Sn（~（11)B，3nγ)~(124)Cs融合蒸发反应(束流轰击能E_(lab.)=45 MeV)，对奇奇核~(124)Cs的高自旋态进行了布居。探测阵列由10个高纯锗探测器和一个小平面探测器组成。数据反演后，总的两重符合事件数达到160x10~6。实验结果概括如下：1．高自旋转动带的信息更丰富了：建立了三个新的转动带结构，其中两个耦合带、一个退耦带，组态分别为：{πh_(11／2)[550]1／2~- direct X vhd_(5/2)[413]5／2~+}K~π=3~-、{πg_(7／2)[413]5／2~+direct X vg_(7/2)[402】5／2~+}K~π=5~+以及{πh_(11/2)[550]1／2~- direct X vd_(3/2)[400]l／2~+}K~π=1~-；2．低激发态的信息更丰富了：观测到了20多条新的低激发态跃迁，增加了10多个新的低激发态；3．转动带之间以及转动带与低激发态间耦合的信息大大丰富了：在过去的研究中观测到了三个彼此孤立、悬空的转动带结构，这里指定它们的组态为：{πh_(11／2) [550]1／2~-direct X vh_(11/2)[523]7／2~-}K~π=4~+(晕 带) ； {πh_(11/2)[550]1／2~- (direct X)vg_(7/2)[402]5/2~+}K~π=3~-(亚晕带：布居强度仅次于晕带)；{πh_(11/2)[550]1/2~-(direct X)vs_(1/2)[411]1／2~+}K~π=1~-(双退耦结构)。其中，亚晕带(yrare band)通过至少三个独立的退激路径与低激发态联系起来；同时，建立了晕带与亚晕带间的多条连接关系。其它转动带分别与晕带和亚晕带联系起来，从而，在奇奇核~(124)Cs中，转动带的"悬空"不再存在，限定了各转动带中能级的激发能位援，并通过这些连接跃迁多极性的分析，分别指定了各能态的自旋和宇称。4．基于本实验建立的连接关系，晕带的最低态(124kev射线贯入能级)的激发能为618．9kev，该能量值比过去研究中的同一能级高出11．7kev。这表明原能级纲图中晕带的退激途径漏掉了一个11．7kev的"能隙"(根据Weisskopf估计，该能隙很可能由两个偶极跃迁构成)。该"能隙"的漏观测，正是导致过去实验中无法正确指定晕带自旋的原因所在；

Capillary array electrophoresis with confocal fluorescence rotary scanner

A capillary array electrophoresis system with rotary corifocal fluorescence scanner was reported. High speed direct current rotary motor combined with a rotary encoder and the reflection mirror has been designed to direct exactly the excitation laser beam. to the array of capillaries, which are symmetrically distributed around the motor. The rotary encoder is introduced to accurately orient the position of each capillary and its output signal triggers the data acquiring system to record. the fluorescence signal corresponding to each capillary. Separations of several amino acids are demonstrated by eight-channel capillary array electrophoresis built by ourselves.

Optimizing the formation of in vitro sponge primmorphs from the Chinese sponge Stylotella agminata (Ridley)

The establishment and optimization of in vitro primmorph formation from a Chinese sponge, Stylotella agminata (Ridley), collected from the South China Sea, were investigated. Our aims were to identify the key factors affecting primmorph formation in this species and to optimize the technique for developing an in vitro primmorph culture system. The size of dissociated cells from S. agminata is relatively small, in the range between 5 and 10 mum. Round-shaped primmorphs of less than 100 gm were formed 3 days after transferring the dissociated cells into seawater containing Ca2+ and Mg2+. The effect of various cell dissociation conditions, inoculum. cell density, concentration of antibiotics, pH, and temperature was further investigated upon the formation of primmorphs. The time required for primmorph formation, primmorph size distribution, and the proliferating capability were microscopically documented. Healthy sponge S. agminata, inoculum. cell density and culture temperature play a critical role for the successful formation of primmorphs and that the microbial contamination will have to be controlled. (C) 2002 Elsevier Science B.V. All rights reserved.

CO2 Flux Estimation by Different Regression Methods from an Alpine Meadow on the Qinghai-Tibetan Plateau

National Key Research and Development Program [2010CB833500]; National Natural Science Foundation of China [30590381]; Chinese Academy of Sciences [KZCX2-YW-432]

Short-term effect of increasing nitrogen deposition on CO2, CH4 and N2O fluxes in an alpine meadow on the Qinghai-Tibetan Plateau, China

National Key Research and Development Program [2010CB833500]; Natural Science Foundation of China [30590381]; Knowledge Innovation Project of Chinese Academy of Sciences [KZCX2-YW-432]

Crystallization Behaviors of n-Octadecane in Confined Space: Crossover of Rotator Phase from Transient to Metastable Induced by Surface Freezing

In this paper, the confined crystallization and phase transition behaviors of n-octadecane in microcapsules with a diameter of about 3 Pm were studied with the combination of differential scanning calorimetry (DSC), temperature dependent Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD).

Preparation and characterization of As-cast and hot-rolled Mg-3Al-0.5Mn-0.5Zn-1MM alloy

Mg-3Al-0.5Mn-0.5Zn-1MM alloy was prepared by metal mould casting method. The as-cast ingot was homogenized and then hot-rolled at 673 K with total thickness reduction of 65%. Microstructure and mechanical properties of the as-cast and hot-rolled samples were investigated. The results showed that the as-cast sample mainly consisted of alpha-Mg, beta-Mg17Al12, Al10Ce2Mn7, and Al11RE3 (RE = La and Ce) phases. The average grain size of the sample homogenized at 673 K was about 240 gm, and it was greatly refined to about 7 mu m by dynamic recrystallization for the hot-rolled sample.