Induction of genomic instability after an acute whole-body exposure of mice to Fe ions

The purpose of this study was to evaluate dose–response relationships for the in vivo induction of micronuclei (MN) as a measure of both initial radiation damage and the induction of genomic instability. These measurements were made in mouse blood erythrocytes as a function of radiation dose, radiation quality, time after irradiation, and the genetic background of exposed individuals. Blood samples were collected from two strains of mouse (CBA/CaJ and C57BL/6J) at different times up to 3 months following a whole-body exposure to various doses of 1 GeV/amu ⁵⁶Fe ions (0, 0.1, 0.5 and 1.0 Gy, at the dose rate of a 1 Gy/min) or ¹³⁷Cs gamma rays (0, 0.5, 1.0 and 3.0 Gy, at the dose rate of 0.72 Gy/min). Blood-smear slides were stained with acridine orange (AO). The frequencies of MN were measured in mature normochromatic-erythrocytes (MN-NCEs) and in immature polychromatic-erythrocytes (MN-PCEs). Effects of both types of radiation on erythropoiesis were also evaluated. As a measure of cell progression delay, a dose-dependent decrease in numbers of PCEs was observed at day 2 post-exposure in both strains, regardless of radiation quality. Subsequently, the levels of PCEs increased in all exposed mice, reaching control levels (or higher) by day 7 post-exposure. Further, at day 2 after the exposure, there was no increase in the frequency of MN-PCEs in CBA/CaJ mice exposed to ⁵⁶Fe ions while the frequency of MN-PCEs elevated as a function of dose in the C57BL/6J mice. At day 4, there was no dose related increase in MN-NCEs in either strain of mouse exposed to ¹³⁷Cs gamma rays. Additionally, at the early sacrifice times (days 2 and 4), ⁵⁶Fe ions were slightly more effective (per unit dose) in inducing MN-NCEs than ¹³⁷Cs gamma rays in CBA/CaJ mice. However, there was no increase in the frequency of MN-NCEs at late times after an acute exposure to either type of radiation. In contrast, both types of radiation induced increased MN-PCEs frequencies in irradiated CBA/CaJ mice, but not C57BL/6J mice, at late times post-exposure. This finding indicates the potential induction of genomic instability in hematopoietic cells of CBA/CaJ mice by both types of radiation. The finding also demonstrates the influence of genetic background on radiation-induced genomic instability in vivo.     

Atmospheric Ion-induced Aerosol Nucleation

Ion-induced nucleation has been suggested to be a potentially important mechanism for atmospheric aerosol formation. Ions are formed in the background atmosphere by galactic cosmic rays. A possible connection between galactic cosmic rays and cloudiness has been However, the predictions of current atmospheric nucleation models are highly uncertain because the models are usually based on the liquid drop model that estimates cluster thermodynamics based on bulk properties (e.g., liquid drop density and surface tension). Sulfuric acid (H₂SO₄) and water are assumed to be the most important nucleating agents in the free troposphere. Measurements of the molecular thermodynamics for the growth and evaporation of cluster ions containing H₂SO₄ and H₂O were performed using a temperature-controlled laminar flow reactor coupled to a linear quadrupole mass spectrometer as well as a temperature-controlled ion trap mass spectrometer. The measurements were complemented by quantum chemical calculations of the cluster ion structures. The analysis yielded a complete set of H₂SO₄ and H₂O binding thermodynamics extending from molecular cluster ions to the bulk, based on experimental thermodynamics for the small clusters. The data were incorporated into a kinetic aerosol model to yield quantitative predictions of the rate of ion-induced nucleation for atmospheric conditions. The model predicts that the negative ion-H₂SO₄-H₂O nucleation mechanism is an efficient source of new particles in the middle and upper troposphere.     

磁层氧离子向磁鞘泄漏的机制和效应

１９９７年 １月 １０日磁暴期间， Ｇｅｏｔａｉｌ卫星在向阳侧的磁鞘中观测到了磁层氧离子突增事件．这些氧离子的出现和磁鞘中存在很强的南向行星际磁场有关．事件期间向阳面发生了准静态的磁重联，氧离子流存在由北向南的速度分量．通量突增过程具有逆向和正向能量色散现象，磁层内部只有氧离子有可能被梯度漂移输送到重联区，所以只有氧离子在磁鞘中持续地被观测到．估计氧离子的逃逸速率为 ０．６１× １０２３／ｓ，大约为环电流氧离子输入率的 ３３％．大量的环电流氧离子由磁层跑到了磁鞘，导致环电流指数 ＡＳＹ－Ｈ呈现明显的非对称性．     

Investigation of the Influence of Magnetic Anomalies on Ion Distributions at Mars

Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This ion flow does not significantly affect the overall distribution of ion beams around Mars.     

RPC-ICA: The Ion Composition Analyzer of the Rosetta Plasma Consortium

The Ion Composition Analyzer (ICA) is part of the Rosetta Plasma Consortium (RPC). ICA is designed to measure the three-dimensional distribution function of positive ions in order to study the interaction between the solar wind and cometary particles. The instrument has a mass resolution high enough to resolve the major species such as protons, helium, oxygen, molecular ions, and heavy ions characteristic of dusty plasma regions. ICA consists of an electrostatic acceptance angle filter, an electrostatic energy filter, and a magnetic momentum filter. Particles are detected using large diameter (100 mm) microchannel plates and a two-dimensional anode system. ICA has its own processor for data reduction/compression and formatting. The energy range of the instrument is from 25 eV to 40 keV and an angular field-of-view of 360° × 90° is achieved through electrostatic deflection of incoming particles.     

工程数值优化方法研究进展

回顾与分析了工程数值优化方法研究的发展历程 ,着重介绍与讨论了优化问题的几种数学列式、近似问题的保真度与近似函数 ,以及复杂优化问题的求解策略等。指出优化问题的对偶列式变式 DFOP-V2与高精度多点近似函数和二级近似概念结合而产生的数值优化解法 ,具有通用性 ,高的计算效率 ,并易于与市场现有分析软件结合使用等显著优点     

对叔丁基苯甲酸稀土杂化发光材料的研究

本文合成了几种稀土金属离子（Eu^3＋，Tb^3＋，Dy^3＋）与对叔丁基苯甲酸的二元有机配合物，且将其不同浓度的光活性组分引入TEOS（正硅酸乙酯）基质中利用溶胶-凝胶法水解缩聚得到粉末状固体材料。同时采用了紫外吸收，荧光激发与发射光谱，扫描电镜等手段对样品进行了表征，表明该材料具较高的发光性能，得到了理想的稀土离子特征荧光且发射强度随配合物浓度增加而递增，没有出现明显的浓度淬灭现象。     

“嫦娥一号”卫星观测近月太阳风离子特征

"嫦娥一号"卫星的太阳风离子探测器(SWIDs)的科学目标是研究太阳风与月球的相互作用以及相应的近月空间等离子体环境。文章利用"嫦娥一号"卫星SWIDs探测器在2007年12月30日的观测数据对近月太阳风等离子体环境,包括向阳侧太阳风离子、"拾起"离子以及在月球尾迹边界处的太阳风离子的特征进行分析,得到以下主要观测结果:1)在慢速太阳风中观测到双峰结构,分别为太阳风中的氢离子和二价氦离子;2)在行星际磁场具有明显昏向(+By)分量期间,在月球向阳侧持续观测到有月表散射或反射后被拾起的太阳风离子;3)与入射的太阳风离子不同,这些拾起的太阳风离子具有明显的角度分布特征;4)在行星际磁场昏向(晨向)期间,太阳风中的氢离子在月球尾迹北半球的边界处呈现减速(加速)特征并进入尾迹;而并未发现氦离子进入尾迹的特征。"嫦娥一号"卫星的这些观测数据对于认识近月空间等离子体环境有着重要的意义。     

电负性气体等离子体推力器研究进展

目前广泛应用的电推力器中,大多采用加速单一正离子的方式来获得推力和相应比冲。该加速方式需要增设中和器,对喷射出的正离子进行中和以保持羽流电中性,否则将导致航天器自充电,对其通信和电子器件造成损害,并减弱加速场。为了简化系统结构,延长推力器寿命,提出了一种能够交替加速正、负离子来获得推力的电负性气体等离子体推力器。分析了该推力器的工作原理和加速过程,指明了包括电负性气体种类选取、电子过滤装置设计要求、如何施加周期性栅极偏置电压加速正、负离子以及合理诊断离子数密度等关键技术,为后续研究工作提供了参考。     

离子发动机栅极系统中束流离子的三维模拟

应用网格质点法,对离子发动机栅极系统进行了三维数值模拟.模拟得到了离子发动机栅极系统中的电场分布、离子运动轨迹、离子在计算域内的空间分布和相空间分布等.计算结果表明,屏栅的离子透明度为69.3%,大于其物理透明度67.1%,加速栅的离子透明度为100%,远大于其物理透明度31.1%,说明所选模拟工况参数合理.模拟结果可以为离子发动机栅极的初步设计提供理论参考.