Was wissen wir über Neutronensterne?

There are 10^9±0.5 neutron stars in the Galaxy. They are born in supernova explosions. Isolated neutron stars are observed as (radio-)pulsars, in some cases also as γ-ray pulsars and as IR-, optical and X-ray pulsars. Binary neutron stars, when accreting mass from their companion, become flickering, periodic and/or bursting X-ray sources, and probably also γ-ray bursters. They may all derive from binary star systems. The masses of population-I-neutron stars are compatible with (1.4 ±0.2)M _⊙; their surface magnetic fields fall almost exclusively within 10^12.2 and 10^13.2 Gauss (at birth). The radii of population-II-neutron stars are (10 _-3 ⁺⁶ )km. Even in exotic sources like SS 433 and Cyg X-1, the compact core may well be a neutron star.     

锆英石基An4+放射性核素固化体性能研究

为研究锆英石基An4+(四价锕系核素)放射性核素固化体的性能,利用Ce4+作为An4+的模拟替代物质,以ZrO2、SiO2和CeO2粉体为原料,采用高温固相法制备出包容20%(物质的量,下同)Ce4+的锆英石基固化体,利用60Co源γ射线辐照装置对其进行572.1kGy的γ射线辐照.利用粉末X射线衍射仪、扫描电子显微镜和电感耦合等离子体质谱仪对γ射线辐照前后固化体的物相、结构、微观形貌及模拟核素的浸出行为进行了研究.结果表明,固化体中虽包容有20%的Ce4+,但其主物相仍以锆英石物相为主,与标准样品相比晶胞参数发生10-4nm量级的变化,经γ射线辐照后样品晶胞参数仅发生了10-5~10-4nm量级的微弱变化,在pH6.5的HCI浸出液中Ce4+的平衡浓度低于0.30μg/L.     

New radio sky surveys

A new all-sky radio continuum survey at 408 MHz has recently been completed, which up to now represents the most accurate map of radio emission from the whole sky. This map forms a new standard for comparison with other astronomical observations. To study the physical nature of the radio emission from different areas in our Galaxy, further observations at higher frequencies are required. A companion 1420 MHz survey will cover the whole sky too, while at 2700 MHz high-resolution observations concentrate on complex radio sources along the galactic plane.     

Coherence in X-ray physics

Highly brilliant synchrotron radiation sources have opened up the possibility of using coherent X-rays in spectroscopy and imaging. Coherent X-rays are characterized by a large lateral coherence length. Speckle spectroscopy is extended to hard X-rays, improving the resolution to the nm range. It has become possible to image opaque objects in phase contrast with a sensitivity far superior to imaging in absorption contrast. All the currently available X-ray sources are chaotic sources. Their characterization in terms of coherence functions of the first and second order is introduced. The concept of coherence volume, defined in quantum optics terms, is generalized for scattering experiments. When the illuminated sample volume is smaller than the coherence volume, the individuality of the defect arrangement in a sample shows up as speckle in the scattered intensity. Otherwise, a configurational average washes out the speckle and only diffuse scattering and possibly Bragg reflections will survive. The loss of interference due to the finite detection time, to the finite detector pixel size and to uncontrolled degrees of freedom in the sample is discussed at length. A comparison between X-ray scattering, neutron scattering and mesoscopic electron transport is given. A few examples illustrate the possibilities of coherent X-rays for imaging and intensity correlation spectroscopy.     

Degradation of nitrobenzene in wastewater by γ-ray irradiation

The degradation of nitrobenzene(NB) by γ-ray irradiation was studied. The influences of dose rate and initial NB concentration were investigated in details. At a dose rate of 55 Gy/min, the degradation kinetics was pseudo-first-order at NB concentrations from 0.2 mmol/L to 4.0 mmol/L. At an initial NB concentration of 0.8 mmol/L, the degradation of NB at various dose rates also followed pseudo-first-order kinetics. Dissolved oxygen was found to have a positive effect on NB degradation. The degradation products were identified as nitrophenol, nitrosobenzene, and hydroquinone, and so on. Based on the product analysis, possible degradation pathways of nitrobenzene were proposed.     

γ-射线对不同含水率剩余污泥的影响

采用溶解性化学需氧量(SCOD)、紫外可见光谱及污泥内源呼吸耗氧速率等指标,探讨了不同剂量γ-射线对不同含水率剩余污泥的辐照效果.结果表明,经γ-射线辐照处理后,污泥上清液的SCOD随着辐照剂量的升高而不断增加;相同辐照剂量下,污泥含水率越低,SCOD值增幅越大:原污泥SCOD均不足100mg/L,经20kGy辐照后,...     

丰水期渤海湾水体中DOM的分布特征及来源

为了解丰水期渤海湾水体中污染物的来源,采用三维荧光光谱和紫外光谱,结合平行分子模型和相关性分析研究了渤海湾水体中DOM（溶解性有机质）的分布特征和来源,以期间接了解其他污染物的来源.结果表明：渤海湾水体DOM对荧光强度贡献率表现为近岸海域高,而远离海岸的海域低.DOM荧光光谱主要有高激发光色氨酸（S峰）、低激发光色氨酸（T峰）、类腐殖酸（A峰）和类富里酸（C峰）这四类荧光峰,类蛋白类荧光峰（S峰和T峰）在研究海域北部荧光强度贡献率较高,类腐殖质类（A峰和C峰）呈现近海岸高、远离海岸低的特征;渤海湾和入海河流荧光指数（FI）均在1.4左右,说明类腐殖质主要受到外源影响,大部分显示出强腐殖质化特征（HIX >3.0）,只有子研究区北部区域由于藻类暴发显示出强自生源特征（BIX >1.0）.紫外特征吸收波长结果显示渤海湾近岸海域类富里酸和类腐殖酸对紫外吸收系数的贡献率（20.18±4.04）%显著低于入海河流中的类富里酸和类腐殖酸贡献率（26.43±3.85）%,可能是由于入海河流输入DOM受到了海水盐度作用,高盐度海水会使DOM产生絮凝作用,随着悬浮物汇入海底沉积物中,使DOM中类富里酸和类腐殖酸对紫外吸收系数的贡献率降低.整体上渤海湾水体中DOM在丰水期受到外源河流输入影响较为显著,应加强对外源输入河流污染物的控制和管理.     

水流紊动特性对活性污泥沉降性能的影响

为优化活性污泥处理系统的设计和运行,在SBR反应器中通过改变搅拌浆的转速,调整水流的紊动条件,借助粒子图像测速技术分析了反应器内水流的紊动特性,研究了反应器内不同区域紊动强度对活性污泥沉降性能的影响.结果表明,搅拌浆叶周围15mm的范围内,紊动强度远高于距桨叶更远的区域,距离浆板5mm的1-1断面和距离浆板60mm的3-3断面搅拌轴心处的紊动强度值分别反映了反应器搅拌主体区和其他区的紊动特征.随搅拌浆转速的增加,反应器内各区域的紊动强度逐渐增加,活性污泥的沉降性能表现出先改善后恶化的规律.当反应器搅拌主体区紊动强度1.51%,其他区紊动强度0.31%时,本试验条件下形成的活性污泥沉降指数(SVI)达到最小值67mL/g,界面沉降速率(ZSV)达到最大值0.20mm/s,活性污泥的沉降性能最佳.搅拌主体区范围较小,紊动强度较高,增强该区的紊动强度会加剧污泥的侵蚀破坏;其他区范围较大,紊动强度较低,增强该区的紊动强度对改善污泥的沉降效果作用明显.工程中可通过降低搅拌主体区的紊动强度,选择其他区适当的紊动强度,改善活性污泥的沉降性能.     

中国大气降水δ~(18)O区域特征及其对古气候研究的意义

系统地收集和分析IAEA/WMO数据库GNIP/ISOHIS与文献报道的中国及周边大气降水和石笋的δ18O等数据,发现大气降水δ18O值和降水量效应在大尺度上均与前人研究结果相似,但在小尺度上具有显著的区域性特征:以塔里木盆地、鄂尔多斯盆地和潢川-合肥盆地等为中心的区域大气降水δ18O值明显高于其它地区,而以拉萨和川-滇-黔为中心的区域明显低于其它地区;在川-滇-黔三省交界地区和湖南中东部分别出现了强和弱降水量效应。大气降水出现δ18O较高值或降低值的主要原因可能与当地蒸发和季风等因子控制的水汽来源特征有关;而降水量效应的区域性特征可能与水汽来源结构变化密切相关。对区域上的大气降水和石笋δ18O进行比较分析表明,以单一水汽来源为主的地区,石笋δ18O值能较好地反映太阳辐射强度或季风强度;两种水汽来源强度相当的地区,石笋δ18O值反映的是两种水汽来源的综合信息;在太阳辐射强度变化对不同水汽影响差异性明确之前很难直接解析为太阳辐射或季风强度信息。     

The catchment sediment budget as a management tool

There is increasing recognition that fine sediment represents an important diffuse source pollutant in surface waters, due to its role in governing the transfer and fate of many substances, including nutrients, heavy metals, pesticides and other organic contaminants, and because of its impacts on aquatic ecology. Catchment management strategies therefore frequently need to include provision for the control of sediment mobilisation and delivery. The sediment budget concept provides a valuable framework for assisting the management and control of diffuse source sediment pollution and associated problems, by identifying the key sources and demonstrating the importance of intermediate stores and the likely impact of upstream mitigation strategies on downstream suspended sediment and sediment-associated contaminant fluxes. Accordingly, the utility of the sediment budget concept for catchment management is further discussed, by introducing examples from several contrasting river basins.     

地下水潜在污染源危害性评价方法研究

地下水污染源危害性评价对地下水资源保护及地下水污染防控区划具有重要意义,然而现有区域尺度地下水污染源荷载危害性评价弱化了点源污染复合强度对地下水的影响.因此,为更准确地进行区域地下水潜在污染源危害性评价,引入污染复合强度要素.选取工业源、农业源、生活源、地表排污河、垃圾场和加油站为研究对象,构建以污染源种类、污染物排放量、污染源释放可能性、缓冲区半径和污染复合强度为指标的综合评价模型,采用层次分析法确定各类污染源权重,基于ArcGIS 10.2软件对沧州市进行地下水综合潜在污染源荷载危害性评价.结果表明:Ⅳ、Ⅴ级风险区面积为5 560.0 km2,占总面积的41.6%,主要位于沧州市中部、北部地区,其危害性受工业源影响最大;Ⅰ、Ⅱ级风险区面积为3 303.4 km2,占总面积的25.2%,主要位于沧州市东部地区.研究显示,该评价方法强化了点源污染复合强度对地下水危害性的影响,可为区域地下水潜在污染源危害性评价提供参考,对地下水资源保护及污染防控区划具有重要意义.      

β射线法与重量法监测环境空气PM_(2.5)的应用比较

重量法是测量PM_(2.5)的传统手工经典方法,而β射线法加动态加热系统联用光散射法作为自动在线监测技术的常用方法被广泛使用。将5030-SHARP型β射线法加动态加热系统联用光散射法PM_(2.5)自动监测设备监测结果与手工法测量结果进行比对、分析,结果表明:β射线法与重量法监测结果具有一致性,测量结果不存在显著性差异;β射线法与重量法相对偏差值与温度、相对湿度、风速等气象因子的相关性不明显;β射线法与重量法监测结果的差异性与PM_(2.5)质量浓度、季节等条件有关;随着PM_(2.5)质量浓度逐渐升高,β射线法与重量法相对偏差的绝对值|RD|也随之增大,不同季节的|RD|平均值差异较大,春季、冬季的|RD|平均值大于夏季、秋季。     

利用三维荧光技术分析太湖水体溶解性有机质的分布特征及来源

利用三维荧光光谱法研究了太湖125个样点表层(0.5m)和底层(1.5m)水体溶解性有机质(DOM)的组成和分布特征,并对不同湖区DOM的来源进行了分析.结果表明,太湖大部分湖区水体DOM以类蛋白物质为主,其中,竺山湾DOM中的腐殖质和类蛋白物质含量均较其它湖区高.太湖水体DOM的分布存在区域差异性,即:竺山湾湖区西部湖区梅梁湾湖心区贡湖湾南部湖区.分析认为,太湖DOM的来源具有陆源输入与内源微生物降解的双重特征,但竺山湾和西部湖区以陆源输入为主,而梅梁湾、贡湖、南部湖区及湖心区以内源微生物降解为主.分析各类荧光峰强度与水质参数的相关性发现,太湖水体DOM4类荧光峰之间呈显著正相关关系,DOM的4类荧光峰均与总氮(TN)、总磷(TP)、硝酸根离子(NO3-)、铵根离子(NH4+)呈显著正相关关系(p0.01),DOM的各类荧光峰强度和溶解氧呈显著负相关(p0.01),这可能是由于水体DOM含量升高后,微生物比较活跃,消耗大量的溶解氧所致;DOM的各类荧光峰强度和溶解性有机碳(DOC)之间的相关性不显著,可能与不同湖区样品中一些非荧光物质在DOM中的比例不同有关.     

朗伯表面材料实现地面目标雷达隐身的可行性分析

将描述光学漫散射现象的朗伯体概念和分析方法应用在兵器目标的雷达散射截面积计算上．通过对朗伯表面的散射强度计算和实例模拟分析．提出了利用散射一吸收型材料构造朗伯表面实现地面兵器目标雷达波隐身的一条新途径。     

广州市北部土壤天然放射性水平研究

用高纯锗g能谱分析仪测量了广州市北部土壤中放射性核素238U,226Ra,232Th和40K的含量,分别为167.5(43.0~605.0)Bq/kg, 171.7(47.8~603.6)Bq/kg,183.2(45.4~447.1)Bq/kg和871.7(70.5~1967.2)Bq/kg,与全国和广东省的平均值相比明显偏高.测量了采样点1m高空气γ辐射吸收剂量率,并与利用Beck公式的计算值进行了对比,计算值普遍高于实际测量值.还计算了等效镭浓度、外照射指数和年有效剂量率,平均值分别为502.0Bq/kg,1.4,284.7μSv/a,表明广州市的γ辐射外照射水平远高于全国和广东省平均值.     

浙江省2008~2018年人为源氨排放清单及分布特征

以浙江省为研究区域,通过收集11个地级市各类氨排放的活动水平数据,采用排放因子法建立了2008~2018年浙江省人为源氨排放清单,并利用ArcGIS进行1 km×1 km空间网格分配.结果表明,2008~2018年浙江省人为源氨排放量总体呈现下降趋势,年均下降率约3.97%;2018年浙江省氨排放量为108.52 kt,其中农业源为90.02 kt,非农业源为18.50 kt,排放强度为1.03 t ·km^-2;杭州市、嘉兴市和温州市的氨排放量高于其他城市,分别占全省总量的14.72%、11.86%和11.80%;空间分布特征显示,氨排放主要分布在浙江省北部区域,呈现出"北高南低"的排放趋势;不确定性分析表明,氨排放量模拟平均值为108.37 kt,在95%置信区间的不确定度范围为-5.40%~5.60%.     

水泥厂粉尘防治的环境经济效益分析

以雎水煤矿水泥厂技改为例，分别对新、老生产线粉尘污染进行了预测和调查监测。用无组织和有组织源强，计算了技改后的粉尘削减量，求得直接效益及环保投资回收期，并试用人力资本法、市场价值法，概算了间接效益。最后对无组织源强确定法作了讨论。     

苏州市人为源氨排放清单及其分布特征

通过调研分析苏州大市范围内的农业、工业、生活及交通等相关活动水平数据,采用排放因子法建立了2013年苏州市人为源氨排放清单. 结果表明:2013年苏州市人为源氨排放总量为22 020.18 t,排放强度为3.06 t/km2;畜禽养殖、工业源、氮肥施用是苏州市氨排放的主要来源,排放量分别为8 080.99、7 103.50、4 841.23 t,共占氨排放总量的90.94%. 其中,工业源的氨排放分担率为32.25%,高于全国平均值,火电行业和化肥制造行业的氨排放占工业源排放总量的90.14%,烟气脱硝过程的氨逃逸值得关注;在畜禽源中,肉鸡和生猪是最大的氨排放源,二者排放量分别占畜禽养殖氨排放总量的42.59%和37.14%. 太仓、张家港、常熟依次为苏州市氨排放量和排放强度最大的3个地区,共占氨排放总量的69.02%,苏州市区氨排放量位列第四但排放强度最低. 空间分布特征表明,苏州市东北部氨排放较集中,中部排放量较小,周边地区特别是沿江县级市的排放量较大. 研究显示,氨排放清单的建立可为苏州市氨排放控制提供基础数据.      

珠三角一次重空气污染过程特征分析及数值模拟

以珠江三角州地区(珠三角)2009年11月23─29日一次重空气污染过程为例,利用常规观测资料及中尺度气象模式(MM5)、污染源排放模式(SMOKE)和空气质量模式(CMAQ)的模拟,研究此次重空气污染过程的特征. 结果表明,造成此次重污染的主要原因有:①前期高压脊带来的稳定层结和静小风条件使得大气污染物逐日累积,难以扩散;②西太平洋台风向南海附近发展移动时,其外围下沉气流导致珠三角大气污染物向低层输送并积累. 珠三角区域污染分布特征表明,广州和佛山的本地贡献明显,而肇庆等地受外地源输送的影响更为显著.      

Getting ready for the manned mission to Mars: the astronauts’ risk from space radiation

Space programmes are shifting towards planetary exploration and, in particular, towards missions by human beings to the Moon and to Mars. Radiation is considered to be one of the major hazards for personnel in space and has emerged as the most critical issue to be resolved for long-term missions both orbital and interplanetary. The two cosmic sources of radiation that could impact a mission outside the Earth’s magnetic field are solar particle events (SPE) and galactic cosmic rays (GCR). Exposure to the types of ionizing radiation encountered during space travel may cause a number of health-related problems, but the primary concern is related to the increased risk of cancer induction in astronauts. Predictions of cancer risk and acceptable radiation exposure in space are extrapolated from minimal data and are subject to many uncertainties. The paper describes present-day estimates of equivalent doses from GCR and solar cosmic radiation behind various shields and radiation risks for astronauts on a mission to Mars.