Rotation-driven prolate-to-oblate shape phase transition in W-190: A projected shell model study

A shape phase transition is demonstrated to occur in W-190 by applying the projected shell model, which goes beyond the usual mean-field approximation. Rotation alignment of neutrons in the high-j, i(13/2) orbital drives the yrast sequence of the system, changing suddenly from prolate to oblate shape at angular momentum 10h. We propose observables to test the picture.

Separation of potential and kinetic electron emission from Si and W induced by multiply charged neon and argon ions

T he total secondary electron emission yields, gamma(T), induced by impact of the fast ions Neq+ (q = 2-8) and Arq+ (q = 3-12) on Si and Neq+ (q = 2-8) on W targets have been measured. It was observed that for a given impact energy, gamma(T) increases with the charge of projectile ion. By plotting gamma(T) as a function of the total potential energy of the respective ion, true kinetic and potential electron yields have been obtained. Potential electron yield was proportional to the total potential energy of the projectile ion. However, decrease in potential electron yield with increasing kinetic energy of Neq+ impact on Si and W was observed. This decrease in potential electron yield with kinetic energy of the ion was more pronounced for the projectile ions having higher charge states. Moreover, kinetic electron yield to energy-loss ratio for various ion-target combinations was calculated and results were in good agreement with semi-empirical model for kinetic electron emission.

Excitation and dissociation of tungsten hexacarbonyl W(CO)(6): Statistical and nonstatistical dissociation processes

We have studied the excitation and dissociation processes of the molecule W(CO)(6) in collisions with low kinetic energy (3 keV) protons, monocharged fluorine, and chlorine ions using double charge transfer spectroscopy. By analyzing the kinetic energy loss of the projectile anions, we measured the excitation energy distribution of the produced transient dications W(CO)(6)(2+). By coincidence measurements between the anions and the stable or fragments of W(CO)(6)(2+), we determined the energy distribution for each dissociation channel. Based on the experimental data, the emission of the first CO was tentatively attributed to a nonstatistical direct dissociation process and the emission of the second or more CO ligands was attributed to the statistical dissociation processes. The dissociation energies for the successive breaking of the W-CO bond were estimated using a cascade model. The ratio between charge separation and evaporation (by the loss of CO+ and CO, respectively) channels was estimated to be 6% in the case of Cl+ impact. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3523347]

重离子与~(nat)W相互作用中Hf的生成研究

用放射化学方法研究了6.3、8.5、11.8、14.7、18.4、24.6、40 MeV/nucleon ~(40)Ar + ~(nat)W、10.5 MeV/nucleon ~(84)Kr + ~(nat)W、80 MeV/nucleon ~(16)O + ~(nat)W、135 MeV/nucleon ~(12)C + ~(nat)W反应中的Hf的生成，得到了Hf同位素的激发函数、反冲性质和同位素分布。研究结果指出利用HIRFL能量的重离子和丰中子靶核作用，能以一定的截面生成A > 170区丰中子新核素。重炮弹更有利于丰中子新核素的生成。使用厚靶，可以明显地提高丰中子新核素的产额。过高的入射能量对丰中子新核素的生成无明显贡献，相反却极大地增加了缺中子同位素产额，这对丰中子新核素的分离和鉴别是非常不利的

SFC 200K W高频系统计算机控制的改进探讨

本文是关于对HIRFL SFC 200KW 高频系统实施计算机控制的专题讨论。首先对HIRFL SFC 200KW 高频系统各部分的运行情况进行了详细分析，在此基础上对原有计算机控制系统进行了剖解，并针对原有计算机控制系统存在的缺陷进行了一些改进和实验，使之投入实际运行工作中；然后，对计算机控制系统中普遍采用的电路从理论上进行了讨论，给出了一些有益于工程实践的结论；最后，为了实现对整个SFC 200KW 高频系统的计算机控制，从软、硬件两个方面，提出了对HIRFL SFC 200KW 高频系统进行该造的方案。

Dinoflagellate cysts as potential indicators of industrial pollution in a Norwegian Fjord

Variation in dinoflagellate cyst assemblages through the last approximately 300 years was studied in two sediment cores, one from the heavily polluted Frierfjord, and one from the adjoining, relatively unpolluted Brevikfjord, in order to docu1ent possible dinoflagellate responses to pollution. Changes in the cyst-flora were compared with historical information on the development of industry and also with geochemistry of the sediments, reflecting aspects of pollution. In the Frierfjord core, increasing pollution was accompanied by a decrease in cyst concentration, possibly reflecting reduced production, at least of dinoflagellates, and a shift toward more heterotrophic species, possibly reflecting reduced light penetration in the euphotic zone, or increased production of prey for the heterotrophs. These trends seem to have reversed as pollution decreased after about 1975, suggesting that cyst assemblages contain signals that may prove useful for tracing the development of pollution. Cyst assemblages in the Brevikfjord core only showed minor changes.

Boundary Characterization Experiment Series Overview

Ocean acoustic propagation and reverberation in continental shelf regions is often controlled by the seabed and sea surface boundaries. A series of three multi-national and multi-disciplinary experiments was conducted between 2000-2002 to identify and measure key ocean boundary characteristics. The frequency range of interest was nominally 500-5000 Hz with the main focus on the seabed, which is generally considered as the boundary of greatest importance and least understood. Two of the experiments were conducted in the Mediterranean in the Strait of Sicily and one experiment in the North Atlantic with sites on the outer New Jersey Shelf (STRATAFORM area) and on the Scotian Shelf. Measurements included seabed reflection, seabed, surface, and biologic scattering, propagation, reverberation, and ambient noise along with supporting oceanographic, geologic, and geophysical data. This paper is primarily intended to provide an overview of the experiments and the strategies that linked the various measurements together, with detailed experiment results contained in various papers in this volume and other sources