铀箔测量~（238）U裂变率的修正研究

用中子束照射铀箔测量２３８Ｕ裂变率时，由于铀箔含有少量的２３５Ｕ原子，所以测量结果必须去掉２３８Ｕ的裂变率而加以修正。本文介绍一种箔活化法测量２３８Ｕ裂变率的修正方法，它用于修正用铀箔测量２３８Ｕ裂变率分布，修正后的２３８Ｕ裂变率和用包镉裂变室测量数据进行了比较，其结果是令人满意的。     

The tectonic uplift of the Hua Shan in the Cenozoic

Six granite samples were collected from six difference elevation locations at the Hua Shan in a main ridge of the Qinling Mountain. Apatite and zircon separated from these six samples were dated by the fission track technique. An assessment of the Cenozoic uplift or exhumation rate was obtained from the altitude difference of sampling samples dated by fission track, and from the difference of fission track dates of both apatite and zircon for a sample. The preliminary results suggest that the beginning of uplift of the Hua Shan was as early as 68.2 MaBP and the uplift rates for different periods are 0.02–0.19 mm/a (from the elevation difference) or 0.12–0.16 mm/a (from two mineral fission track dates). The average uplift rate is 0.12 mm/a (from the elevation difference) or 0.14 mm/a (from two mineral fission track dates). The uplift of the Hua Shan might accelerate since (17.8±2.0) MaBP, and the average uplift rate is about 0.19 mm/a.     

复合核裂变与微观裂变理论进展

核裂变过程是一个复杂的大幅度的量子多体动力学过程,对其理论描述一直是一个挑战.为了描述实验上的裂变可观测量,理论上发展了一些半唯象与近似的模型,但这些模型依赖唯象的参数.从有效核力出发发展微观的裂变理论,原则上无需自由参数,但要达到定量计算的阶段还很困难.本文介绍了复合核裂变的理论进展,特别讨论了微观计算复合核存活概率在超重核合成研究中的关键影响.此外比较了绝热和非绝热的微观裂变动力学模型.其中绝热裂变模型对低激发裂变的实验可观测量能较好描述,而非绝热动力学模型对深入研究裂变机制非常有用.本文分析了核裂变理论的问题和挑战,意识到裂变过程极其复杂,并展望了裂变理论的发展方向.     

Novel cell cycle control of RNA synthesis in yeast

During the fission yeast cell cycle, the rate of polyadenylated messenger RNA synthesis doubles when the cell reaches a critical size. This size-related control maintains average mRNA content in balance with total cell mass during exponential growth, even in cells growing at different absolute growth rates per cell.     

CtBP/BARS induces fission of Golgi membranes by acylating lysophosphatidic acid

Membrane fission is essential in intracellular transport. Acyl-coenzyme As (acyl-CoAs) are important in lipid remodelling and are required for fission of COPI-coated vesicles. Here we show that CtBP/BARS, a protein that functions in the dynamics of Golgi tubules, is an essential component of the fission machinery operating at Golgi tubular networks, including Golgi compartments involved in protein transport and sorting. CtBP/BARS-induced fission was preceded by the formation of constricted sites in Golgi tubules, whose extreme curvature is likely to involve local changes in the membrane lipid composition. We find that CtBP/BARS uses acyl-CoA to selectively catalyse the acylation of lysophosphatidic acid to phosphatidic acid both in pure lipidic systems and in Golgi membranes, and that this reaction is essential for fission. Our results indicate a key role for lipid metabolic pathways in membrane fission.     

应用磷灰石裂变径迹研究沉积盆地的热史

磷灰石裂变径迹是研究沉积盆地地热史的强有力工具。胜利油区东营凹陷磷灰石裂变径迹分析表明该盆地的古热作用比现今热作用强。盆地形成初期经历的热事件使其具有较高的热流，随后热流缓慢衰减；３号样品径迹长度的混和型分布说明东营组（Ｅｄ）和馆陶组（Ｎｇ）之间的沉积间断曾引起了盆地古地温的降低。东营凹陷磷灰石裂变径迹退火带位置在２０００～３４００ｍ左右，和生油窗是一致的。     

Meso-Cenozoic uplifting and exhumation on Yunkaidashan： Evidence from fission track thermochronology

Yunkaidashan, located at the southern South China block (SCB) and closely adjacent to the Indochina block, is an ideal region for better understanding the temporal and spatial framework of tectonothermal overprinting at the southern SCB since Mesozoic. Apatite and zircon fission track thermochronology of various-type rocks from Yunkaidashan is presented in this paper. The results show, no matter what rocks are, the apparent ages of zircon fission track range from 97.4 to 133.0 Ma, and those of apatite fission track from 43.2 to 68.4 Ma. The length of apatite fission track yields an average confined track length of -13 μm andshows normal distribution of unimodal frequency. It is inferred that the uplifting amplitude has been more than 5 km in Yunkaidashan since late Mesozoic. The difference of fission track apparent ages at different locations in Yunkaidashan suggests a paleophysiognomic scenario of the heterogeneous uplift/denudation. These data of the fission track thermochronology provide new constraints for better understanding the tectonophysiognomic pattern of the SCB sincelate Mesozoic.     

Late Cretaceous-Cenozoic exhumation history of Tiantangzhai region of Dabieshan Orogen： Constraints from （U-Th）／He and fission track analysis

Integrated fission track and (U-Th)/He analysis is carried out on 6 apatite and 6 zircon samples from a near vertical section in The Tiantangzhai region at the core of the present Dabieshan orogen. The result shows that the region experienced cooling/exhumation during the Late Cretaceousand Early Tertiary period. Age-elevation relationships for different dating systems and different minerals suggest a pulse of rapid exhumation at ～110 Ma before present, preserved in the structurally highest samples. At lower elevations, ages begin to decrease with decreasing elevation, suggesting lower exhumation rates since 90 Ma. Two periods of different exhumation rates are identified since 90 Ma. The average apparent exhumation rate for the period of 43.4—22.5 is 0.062 km/Ma, whereas that for the period of 76.4—47.4 Ma is 0.039 km/Ma.     

Evidences of rapid erosion driven by climate in the Yarlung Zangbo （Tsangpo） Great Canyon, the eastern Himalayan syntaxis

Climate and tectonism are both particularly intense in the Yarlung Zangbo (Tsangpo) Great Canyon in the eastern Himalayan syntaxis,which is characterized by the most rapid landscape evolution of anywhere in the world.Thus,the eastern Himalayan syntaxis is one of the best locations to study the interactions between climate and tectonics.This paper investigates the cooling ages of the Doxong La-Baibung profile using apatite fission track (AFT) dating on 11 bedrock samples at elevations ranging from 4210 to 710 m.There are topographic,climatic,metamorphic,and thermochronological gradients in the profile,providing good conditions to study interactions between climate and tectonics.AFT ages ranged from 4.6±0.6 Ma to 1.7±0.3 Ma,and the mean fission track lengths ranged from 11.0 to 12.4 μm.It was found that the cooling rates revealed by AFT ages increased with decreasing elevation.However,the tendency of the cooling rates revealed by the 40 Ar-39 Ar ages was different from that indicated by the AFT ages.Moreover,for most districts of the eastern Himalayan syntaxis,the compiled AFT age distribution correlates well with the annual average precipitation,indicating the coupling of the cooling and erosion rates of the near-surface rock and precipitation.The geothermal history modeling results indicate an obvious increase in the cooling and erosion rate between 1.0 and 0.5 Ma.This age is consistent with other research findings for this time,when the vapor channel of the Yarlung Zangbo Great Canyon began to take effect.These evidences suggest that climate,especially precipitation,has acting as a key factor influencing the rapid cooling and erosion in the Yarlung Zangbo Great Canyon since 1-0.5 Ma.     

Nuclear fission modes and fragment mass asymmetries in a five-dimensional deformation space

Nuclei undergoing fission can be described by a multi-dimensional potential-energy surface that guides the nuclear shape evolution--from the ground state, through intermediate saddle points and finally to the configurations of separated fission fragments. Until now, calculations have lacked adequate exploration of the shape parameterization of sufficient dimensionality to yield features in the potential-energy surface (such as multiple minima, valleys, saddle points and ridges) that correspond to characteristic observables of the fission process. Here we calculate and analyse five-dimensional potential-energy landscapes based on a grid of 2,610,885 deformation points. We find that observed fission features--such as the distributions of fission fragment mass and kinetic energy, and the different energy thresholds for symmetric and asymmetric fission--are very closely related to topological features in the calculated five-dimensional energy landscapes.