Low-lying non-normal parity states in B-8 measured by proton elastic scattering on Be-7

A new measurement of proton resonance scattering on Be-7 was performed tip to the center-of-mass energy of 6.7 MeV using the low-energy RI beam facility CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study of the University of Tokyo. The excitation function of Be-7 + p elastic scattering above 3.5 MeV was measured Successfully for the first time, providing important information about the resonance structure of the B-8 nucleus. The resonances are related to the reaction rate of Be-7(p.gamma)B-8. which is the key reaction in solar B-8 neutrino production. Evidence for the presence of two negative parity states is presented. One of them is a 2(-) state observed as a broad s-wave resonance, the existence of which had been questionable. Its possible effects on the determination of the astrophysical S-factor of Be-7(p.gamma)B-8 at solar energy are discussed. The other state had not been observed in previous measurements, and its spin and parity were determined as 1(-). (C) 2009 Elsevier B.V. All rights reserved.

Optical absorption spectra of Na-5, Na-6 and Na-7 clusters: a theoretical study

In the frame of time-dependent density functional theory, the: dynamical polarizabilities of Na-5, Na-6 and Na-7 clusters are calculated using a time-dependent local density approximation. By using Fourier transformation, the optical absorption spectra of Na-5, Na-6 and Na-7 clusters are obtained from their dynamical polarizabilities. It is shown that experimentally measured optical absorption spectra of Na-5, Na-6 and Na-7 clusters are reproduced in our calculations. Furthermore, the calculations of Na-6 and Na-7 clusters are in good agreement with the results of configuration interaction method. Compared with the three-dimensional structure of Na-6, the calculated optical absorption spectra of Na-6 with the two-dimensional structure are more close to the experimental data.

Optimal design of a 7 T highly homogeneous superconducting magnet for a Penning trap

A Penning trap system called Lanzhou Penning Trap (LPT) is now being developed for precise mass measurements at the Institute of Modern Physics (IMP). One of the key components is a 7 T actively shielded superconducting magnet with a clear warm bore of 156 mm. The required field homogeneity is 3 x 10(-7) over two 1 cubic centimeter volumes lying 220 mm apart along the magnet axis. We introduce a two-step method which combines linear programming and a nonlinear optimization algorithm for designing the multi-section superconducting magnet. This method is fast and flexible for handling arbitrary shaped homogeneous volumes and coils. With the help of this method an optimal design for the LPT superconducting magnet has been obtained.

Design of a 7 T Superconducting Magnet for Lanzhou Penning Trap

A penning trap system called LPT (LANZHOU PENNING TRAP) is now being developed for precise mass measurements in IMP (Institute of Modern Physics). The most key component of LPT is a superconducting magnet. A Phi 156 mm warm bore and two cylinder good field regions with a distance of 220 mm are required for trapping ions and measurements. As the required homogeneity is better than 0.5 ppm, several complicated coaxial coils are used to produce such a magnetic field. The size and position of these coils are optimized by using a method combining linear program with multiobjective optimization. Superconducting shim coils and passive shim pieces are used to eliminate inevitable winding tolerances and environmental influence. The fringe field is decreased to 5 Gs at 2 m line from the center of the magnet by active shielding coils. The designs of the mechanical structure, the quench protection system are also introduced in this paper.

Quench Protection Design and Simulation of a 7 Tesla Superconducting Magnet

A 7 Tesla superconducting magnet with a clear warm bore of 156 mm in diameter has been developed for Lanzhou Penning Trap at the Institute of Modern Physics for high precision mass measurement. The magnet is comprised of 9 solenoid coils and operates in persistent mode with a total energy of 2.3 MJ. Due to the considerable amount of energy stored during persistent mode operation, the quench protection system is very important when designing and operating the magnet. A passive protection system based on a subdivided scheme is adopted to protect the superconducting magnet from damage caused by quenching. Cold diodes and resistors are put across the subdivision to reduce both the voltage and temperature hot spots. Computational simulations have been carried in Opera-quench. The designed quench protection circuit and the finite element method model for quench simulations are described; the time changing of temperature, voltage and current decay during the quench process is also analysed.

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；

46.7 MeV/u~(12)C轰击~(58)Ni、~(115)In、~(197)Au反应中粒子发射研究中子皮及中子分布弥散度对核势的影响

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

阿魏氯仿提取物对7种玉米病害的离体抑菌活性比较

采用生长速率法和孢子萌发法测定了阿魏氯仿提取物对引起玉米病害的7种病原菌(小斑病菌、弯孢霉叶斑病菌、链格孢叶斑病病菌、圆斑病菌、顶腐病菌、青枯病菌和瘤黑粉病菌)的菌丝生长和孢子萌发的影响。结果表明,对于同一种病原菌来说,阿魏氯仿提取物对其菌丝生长的抑制效果好于对其孢子萌发的抑制效果;对顶腐病菌菌丝生长的抑制效果最好,EC50只有46.66 mg/L;可引起大中型分生孢子畸形。

Calorimetric study on two biphenyl liquid crystals

The molar heat capacities of the two biphenyl liquid crystals, 3BmFF and 3BmFFXF3, with a purity of 99.7 mol% have been precisely measured by a fully automated precision adiabatic calorimeter in the temperature range between T = 80 and 350 K. Nematic phase-liquid phase transitions were found between T = 297 K and 300 K with a peak temperature of T-peak = (298.071 +/- 0.089) K for 3BmFF, and between T = 316 and 319 K with a peak temperature of T-peak = (315.543 +/- 0.043) K for 3BmFFXF3. The molar enthalpy (Delta(trs)H(m)) and entropy (Delta(trs)S(m)) corresponding to these phase transitions have been determined by means of the analysis of the heat capacity curves, which are (15.261 +/- 0.023) U mol(-1) and (51.202 +/- 0.076) J K-1 mol(-1) for 3BmFF, (31.624 +/- 0.066) kJ mol(-1) and (100.249 +/- 0.212) J K-1 mol(-1) for 3BmFFXF3, respectively. The real melting points (TI) and the ideal melting points (TO) with no impurities of the two compounds have been obtained from the fractional melting method to be (298.056 +/- 0.018) K and (298.165 +/- 0.038) K for 3BmFF, (315.585 +/- 0.043) K and (315.661 +/- 0.044) K for 3BmFFXF3, respectively. In addition, the transitions of these two biphenyl liquid crystals from nematic phase to liquid phase have further been investigated by differential scanning calorimeter (DSC) technique; the repeatability and reliability for these phase transitions were verified. (C) 2004 Elsevier B.V. All rights reserved.

汞和两种农药复合污染对土壤转化酶活性的影响

通过模拟方法研究了豆磺隆,呋喃丹2种农药与重金属汞(Hg)单一及复合污染对草甸棕壤和黑土4个土壤转化酶活性的影响.结果显示,在试验浓度范围内,土壤添加豆磺隆和呋喃丹后,转化酶变化幅度分别为-12%~7%和-6%~7%,表明2种农药对土壤转化酶的毒性较小;Hg对转化酶最大抑制率为22%~35%,二者之间呈显著的对数负相关关系,表明Hg对转化酶的毒性较大,转化酶在一定程度上可作为Hg污染的监测指标,通过对数方程计算出4个土样的生态剂量(ED50)分别为76.68,727.49,236.52,316.59mg/kg;Hg和2种农药之间普遍存在交互作用,豆磺隆与Hg复合污染引起土壤转化酶最大净变化量(?I)为对照的-12%~15%,呋喃丹和Hg为-25%~-6%,有机质对复合污染产生的毒性有明显的缓冲作用.

江苏省云台山7种野生中草药植物根区土壤真菌多样性研究

通过对江苏省云台山地区7种不同野生中草药植物烟台百里香(T.quinquecostatusCelak.)、掌叶半夏(P.pedatisectaSchott.)、何首乌(P.multiflorumThunb.)、海洲香薷(E.splendensNakai ex F.)、野葛[P.lobata(Willd)Ohwi]、紫金牛(A.japonicaBl.)和菝葜(S.sieboldiiMiq.)根区土壤真菌进行分离鉴定,共分离出真菌16属126种。多样性分析结果表明,7种野生中草药植物根区土壤真菌种群多样性丰富,其中青霉属(Penicillium)、曲霉属(Asper-gillus)和木霉属(Trichoderma)是中草药植物根区土壤中的优势种群,镰孢菌属(Fusarium)、交链孢属(Alternaria)、腐霉属(Pythium)、毛霉属(Mucor)真菌分布丰度也较高。结果也表明根区土壤真菌群落在一定程度上受到中草药植物的影响,大部分野生中草药植物根区土壤的真菌群落的均匀度指数低于裸地非根区土壤,而丰富度指数却高于裸地非根区土壤。不同野生中草药植物根区土壤真菌区系的结构和组成存在一定的差异性,紫金牛根区土壤中真菌种类最多,达到14属,而野葛根区土壤中真菌种类最少,只有8属。