30MeV/u~(40)Ar+~(112,124)Sn反应中的同位素产额比与核温度

系统研究了 3 0MeV u40 Ar+ 1 1 2 ,1 2 4 Sn反应中的轻粒子同位素产额比随角度和初始激发能的变化关系 .对于两个反应体系 ,均观察到3He 4He和6Li 7Li的产额比随角度的增加而增加 ,6He 4He和8Li 7Li随角度的增加而减小 .统计发射的运动学效应不能完全符合实验结果 .各种单同位素产额比与靶核的N Z比有关 ,表现出同位旋效应 ,而由双同位素比提取的核温度几乎没有靶核相关性

改进的Glauber理论和核-核反应总截面

利用Glauber理论系统计算了中、低能条件下核 -核反应总截面 .讨论了量子效应、库仑效应以及核子 -核子碰撞同位旋效应对Glauber理论的修正 .发现在应用Glauber理论计算中、低能核 -核反应截面时 ,量子修正是重要的 .利用修正了的Glauber理论 ,系统计算了从低能到高能大量稳定线附近的核 -核反应总截面 ,在没有可调参数的情况下 ,都与实验结果较好地符合

介质型脉冲高能中子探测器

首次报道一种基于反冲质子法和高速带电粒子在物质表面引起二次电子发射的高能中子探测方法 ,研制成功的新一代强流脉冲高能中子探测器 ,即介质型脉冲高能中子探测器 .与传统的强流脉冲中子探测器相比 ,该探测器对中子的探测及信号的传输过程是在介质中完成的 ,因而不需要真空和高压也可以正常工作 ,并具有多项优异的物理性能 .该探测器的输出信号来自于高能中子在聚乙烯转换靶产生的高能反冲质子和这些质子穿越电荷收集极表面时产生的部分二次电子 .选择适当的卡阈吸收片和电荷收集极材料 ,二次电子在探测灵敏度中的份额及其随能量的变化可由实验测定

毛细管式的靶-离子源系统在线实验研究

讨论了在线同位素分离器使用激光离子源的必要性 ,分析研究了毛细管式激光离子源对电离器的要求及热毛细管电离器的工作原理 ,并给出了在线实验的结果 .为了在较低温度下形成等离子体鞘势和降低热电离效率 ,采用了低电子逸出功的耐高温材料Nb作毛细管材料 .在线实验获得成功 ,使用毛细管式的靶 -离子源的在线同位素分离器的总效率约达 0 2 % ,满足了激光离子源电离器和靶室的工作要求

枸杞体细胞胚发生中对痕量金属离子吸收的动态研究

以药用植物宁夏枸杞 (LyciumbarbarumL .)愈伤组织为材料 ,离体培养诱导体细胞胚发生。采用多重示踪技术和γ射线能谱分析法研究枸杞体细胞胚发生中对多种痕量金属离子的吸收动态。结果表明 :( 1)体胚发生中对多种痕量金属离子的吸收呈选择性。对多重示踪剂溶液中的 2 3种核素 ,只吸收了其中的 16种 (Mn_5 2、Zn_65、Co_5 6、Co_60、As_74、Se_75、mTc_95、Rh_99、V_4 8、Rb_83、Rb_84、Sr_85、Y_87、Y_88、Zr_88和Zr_89) ,而对另 7种未吸收 (Be_7、Tc_96、Ru_97、mRh_10 1、Sc_4 6、Ga_67和Cr_5 1)。 ( 2 )吸收呈动态变化 ,在同一发育期对不同的金属离子吸收率不同 ,如第 10天 ,大部分金属离子的吸收率在 5 % /g左右 ,而Se_75、Rb_83、Sr_85和Zr_89的则是 10 %～ 3 0 % /g ;在不同发育期对同一种金属离子的吸收率不同 ,如对Se_75的吸收总体呈上升趋势。第 5天达第 1峰值 14 % /g。随后缓慢下降 ,基本稳定 ,第 15天后急剧上升 ,至第 2 0天达第 2个峰值 2 0 % /g ;随着胚性细胞的分化与分裂 ,吸收既存在一致性 ,也存在非一致性。Se_75、Rb_83、Sr_85、Co_5 6和V_4 8等核素的吸收趋势相似 ,基本上呈上升曲线。而Mn_5 2的吸收趋势则类似正态分布曲线。

重离子辐照诱导DNA双链断裂的剂量率效应

利用不同剂量率的 5 0MeV/u12C6+ 辐照B16黑色素瘤细胞的脱蛋白DNA ,采用脉冲场凝胶电泳技术对DNA双链断裂 (DSB)的诱导和片段的分布进行了研究。结果发现 ,在剂量率分别为3Gy/min和 30Gy/min的情况下 ,DNA片段释放百分比 (PR)都随着剂量的增加而增加 ,并在超过一定剂量之后趋于相似的准阈值 ;3Gy/min辐照诱导DSB的产额为 0 .4 0DSBs/ (10 0Mbp .Gy) ,30Gy/min辐照诱导的DSB产额准确值无法得到 ;30Gy/min辐照诱导DSB的截面为 2 .14μm2 ,是 3Gy/min的 3.1倍。所有结果都表明剂量率越高 ,诱导DSB越有效。另外 ,3Gy/min辐照诱导DSB片段在 -86 0kbp处有一个片段峰 ,而 30Gy/min没有 ,说明剂量率可以影响DSB片段的分布。

彗星分析法检测γ射线诱导的人肝癌细胞DNA链断裂

以人肝癌SMMC - 772 1细胞为材料 ,用彗星分析法研究了γ射线诱导的DNA链断裂 ,结果表明 ,随着剂量的增加 ,彗尾逐渐变长 ,彗尾的细胞数也越来越多 ;彗尾与彗头的长度比和面积比与剂量成线性正相关 ,尤以长度比随剂量的增加变化为明显 ,可反映γ射线诱导的DNA链断裂程度。

高能Ar~+辐照P型CdZnTe的电学特性和光致发光

采用能量 2 Ge V、剂量 10 1 0— 10 1 3cm- 2的 Ar+辐照 P型 Cd0 .96 Zn0 .0 4Te材料 ,对辐照前后和不同辐照剂量的样品进行了电学测试和光致发光研究 .实验结果和分析表明 ,Ar+ 辐照在 Cd0 .96 Zn0 .0 4Te中产生了更大密度的受主型缺陷和散射中心 ,引起材料载流子 (空穴 )浓度的增大和迁移率的降低 .随着辐照剂量的增大 ,载流子迁移率的降低要比载流子浓度增大得快 ,导致材料电阻随辐照剂量增大而增大

基于APACK的额济纳天然绿洲景观空间格局分析

基于研究区2001年Landsat7ETM+遥感影像资料,综合运用遥感与GIS技术手段,利用景观格局分析软件APACK分别从景观生态类型面积统计、景观水平指数、斑块类型水平指数及斑块类型间水平指数定量化分析了2001年额济纳天然绿洲景观空间格局特征,并结合研究区1987年和1994年的景观格局指数进一步探讨了关于格局指数间的相关性问题。研究结果表明:①研究区景观具有典型的“基质—廊道—斑块”结构特征;②研究区景观具有较高破碎化、较低多样性及粗糙质地特征,景观稳定性差;③各景观格局指数相互之间并不完全独立,有些指数之间具有明显的相关性。

Nanocluster-containing mesoporous magnetoceramics from hyperbranched organometallic polymer precursors

Pyrolysis of hyperbranched poly[1,1'-ferrocenylene(methyl)silyne] (5) yields mesoporous, conductive, and magnetic ceramics (6). Sintering at high temperatures (1000-1200 degrees C) under nitrogen and argon converts 5 to 6N and 6A, respectively, in similar to 48-62% yields. The ceramization yields of 5 are higher than that (similar to 36%) of its linear counterpart poly[1,1'-ferrocenylene(dimethyl)silylene] (1), revealing that the hyperbranched polymer is superior to the linear one as a ceramic precursor. The ceramic products 6 are characterized by SEM, XPS, EDX, XRD, and SQUID. It is found that the ceramics are electrically conductive and possess a mesoporous architecture constructed of tortuously interconnected nanoclusters. The iron contents of 6 estimated by EDX are 36-43%, much higher than that (11%) of the ceramic 2 prepared from the linear precursor 1. The nanocrystals in 6N are mainly alpha-Fe2O3 whereas those in 6A are mainly Fe3Si. When magnetized by an external field at room temperature, 6A exhibits a high-saturation magnetization (M-s similar to 49 emu/g) and near-zero remanence and coercivity; that is, 6A is an excellent soft ferromagnetic material with an extremely low hysteresis loss.

Typhoon effects on DOC dynamics in a phosphate-limited reservoir

To explore typhoon effects on dissolved organic carbon (DOC) dynamics, field investigations (tributary and dam site) and laboratory experiments (bioassay and DOC consumption) were conducted in a subtropical reservoir. A tributary survey indicated that after typhoon disruption, upstream areas were the sources of phosphate (P) but not DOC for the dam site located downstream. Bioassay experiments verified P-limitation on bacteria and phytoplankton during summer stratification, and bacteria showed a faster response than algae to added P. Experiments indicated that DOC consumption was determined by the availability of P. The 4 yr typhoon period (June-September) data of the dam site denoted that DOC concentration (27 to 270 mu M C) and its rate of change (-13 to 24 mu M C d(-1)) varied more dramatically in the weak (2006 and 2007) than in the strong (2004 and 2005) typhoon years. The negative correlation of DOC with the ratio of bacterial production (BP) to primary production (PP) in the euphotic zone (0 to 10 m) signified the interactive effects of auto- and heterotrophic processes on DOC variation. In the aphotic zone, the variation of DOC could be ascribed to the change of BP, which showed a positive correlation with P concentrations. This study documents that DOC concentration in the studied system varied at multiple time scales. Such variation can be explained by the decoupling between BP and PP, which is believed to be a function of the limiting nutrient's availability. More importantly, this study suggests that the P supply introduced by strong typhoons might have substantiated a tighter coupling between BP and PP, so that the amplitude of DOC oscillation during the summer period was effectively reduced.

渤海湾盆地前第三系构造演化与煤成气成藏研究

The disequilibrium between supply and demand the east part of North China accelerated natural gas exploration in Bohai bay basin. Exploration practice showed that coal-derived gas is important resource. In searching of big to middle scaled coal derived gas field, and realize successive gas supply, the paper carried out integrated study on structural evolution of Pre-Tertiary and evaluation of reservoir forming condition of coal-derived gas. Study work of the paper was based on the following condition: available achievement in this field at present, good understanding of multiphase of tectonic movement. Study work was focused on geological evolution, source rock evaluation and dissection key factors controlling reservoir forming. Based on analysis of seismic data, drilling data, tectonic style of Pre-Tertiary was subdivided, with different tectonic style representing different tectonic process. By means of state of the art, such as analysis of balanced cross section, and erosion restoration, the paper reestablished tectonic history and analyzed basin property during different tectonic phase. Dynamic mechanism for tectonic movement and influence of tectonic evolution on tectonic style were discussed. Study made it clear that tectonic movement is intensive since Mesozoic including 2 phase of compressional movement (at the end of Indo-China movement, and Yanshan movement), 2 phase of extensional movement (middle Yanshan movement, and Himalayan movement), 2 phase of strike slip movement, as well as 2 phase of reversal movement (early Yanshan movement, and early Himalayan movement). As a result, three tectonic provinces with different remnant of strata and different tectonic style took shape. Based on afore mentioned study, the paper pointed out that evolution of Bohai bay basin experienced the following steps: basin of rift valley type (Pt2+3)-craton basin at passive continental margin (∈1－2)-craton basin at active continental margin (∈3- O)-convergent craton basin (C-T1+2)-intracontinental basin (J＋K). Superposition of basins in different stage was discussed. Aimed at tectonic feature of multiple phases, the paper put forward concept model of superposition of tectonic unit, and analyzed its significance on reservoir forming. On basis of the difference among 3 tectonic movements in Mesozoic and Cenozoic, superposition of tectonic unit was classified into the following 3 categories and 6 types: continuous subsidence type (I), subsidence in Mesozoic and uplift for erosion in Cenozoic (II1), repeated subsidence and uplift in Mesozoic and subsidence in Cenozoic (II2), repeated subsidence and uplift in Mesozoic and uplift for erosion in Cenozoic (II3), uplift for erosion in Mesozoic and subsidence in Cenozoic (II4), and continuous uplift (III). Take the organic facies analysis as link, the paper established relationship between sedimentary environment and organic facies, as well as organic facies and organic matter abundance. Combined information of sedimentary environment and logging data, the paper estimated distribution of organic matter abundance. Combined with simulation of secondary hydrocarbon generation, dynamic mechanism of hydrocarbon generation, and thermal history, the paper made static and dynamic evaluation of effective source rock, i.e. Taiyuan formation and Shanxi formation. It is also pointed out that superposition of tectonic unit of type II2, type II4, and type I were the most favorable hydrocarbon generation units. Based on dissection of typical primary coal-derived gas reservoir, including reservoir forming condition and reservoir forming process, the paper pointed out key factors controlling reservoir forming for Carboniferous and Permian System: a. remnant thickness and source rock property were precondition; b. secondary hydrocarbon generation during Himalayan period was key factor; c. tectonic evolution history controlling thermal evolution of source rock was main factor that determine reservoir forming; d. inherited positive structural unit was favorable accumulation direction; e. fault activity and regional caprock determined hydrocarbon accumulation horizon. In the end, the paper established reservoir forming model for different superposition of tectonic units, and pointed out promising exploration belts with 11 of the first class, 5 of the second class and 6 of the third class.

中国西部大气和雪冰黑碳及其传输过程研究

Glaciers in west China are the sources of the major great rivers in Asia, and the solid water resources are crucial to China and South Asia. Black carbon (BC) results in very complex climate effects not only in the atmosphere, but accelerates the melting after its deposit on the surface of snow/ice. As the main distributed area of glaciers in China, the Tibetan Plateau (TP) and Xinjiang region are abutted by South Asia, Central Asia, and Russia, and east China, and the atmospheric environment would be influenced by the BC emitted from these regions. Whereas, the BC’s temporal and spatial distributions for concentration in the mid and top troposphere in west China, its transport, and its radiative forcing after deposited on the snow/ice surface are not well understood at the present. In the field, we collected samples from surface snow, snow pits, ice core, and aerosol in the glaciers, analyzed BC content mainly by the thermo-oxidized method in the laboratory, and discussed temporal and spatial distributions for BC concentrations in glaciers, the transport, and its impacts on the environment. Several conclusions were derived as follows: 1_Spatial distribution and the impact on albedos for BC concentrations in snow/ice: the BC concentrations in the surface snow for the investigated glaciers could be placed in areas, the Tianshan Mountains ＞ the central TP ＞ the Pamirs ＞ the Qilian Mountians ＞ the Himalayas. This distribution could be attributed to the elevation of the glaciers, the topography of the TP, and more regional emissions. Probably significant impacts on the albedos of the glacier surface could be caused by BC deposits, and the estimated reduced albedos on the glaciers are 9.8% (the Zhadang glacier), 8.7% (the Miao’ergou Riverhead No.3 glacier), and 6.8% (the Kuitun River Haxilegen No.48 glacier), and 6.2% (the Dongkemadi glacier), and 5.3% (the La’nong glacier), and 4.2% (the Muztagata glacier), etc. 2_The temporal variance of BC concentrations in ice of the East Rongbuk Glacier (ERG) and its climatic implications: major cations and anions (e.g., SO42- and Ca2+) concentrations in aerosols during summer monsoon seasons showed their close relationships with the sources of air masses, in which the variance of SO42- concentrations suggested the atmospheric environment over the ERG was significantly influenced by the aerosols from South Asia. BC record based on an ice core suggested its deposit was dominantly transported by monsoons in summers and by westerlies in other seasons, and the BC from South Asia in summers dominated the varying trend of its concentrations in the ice core and caused higher concentrations in summers than those in other seasons. In the past 50 yrs, BC concentrations showed fluctuations, whereas showed an increasing tread in the most recent decade, and exceeded 50 μg kg-1 in the summer of 2001; correspondingly, the radiative forcing caused by BC showed an increasing trend since 1990s, and exceeded 4.5 W m-2 in the summer of 2001. 3_Cabonaceous aerosols in the Nam Co region: organic carbon (OC) concentration accounted for ～95% and BC for ～5% in the total carbonaceous aerosol concentration, which was significantly influenced by summer precipitations. OC was dominantly derived from fossil fuel burning and BC from both fossil fuel and biomass burning. Trajectory analysis and aerosol optical depth suggested the atmospheric environment in the Nam Co region was most probably influenced by the emissions from South Asia. The potential source regions of air pollutants in the Nam Co regions in summers might be Bangladesh and east India, and in winters might be the Indo-gangetic basin. The scavenging ratio of atmospheric BC by rainfalls was less than those at other sites. West China is a less-developed region for industry, where BC concentrations in the atmosphere and snow/ice could be significantly influenced by the emissions from the abutted regions with rising industries (South Asia, Central Asia, and Russia). For example, snow/ice BC concentrations in the glaciers of the Parmirs, the Tianshan Mountains, and the Qilian Mountains in the northeast margin of the TP might be more influenced by the emissions from Centrial Asia (transported by the westerlies), those in the glaciers of the Himalayas might be more influenced by the emissions from South Asia (transported by the monsoons and the westerlies), and atmospheric carbonaceous aerosols might also be more influenced by the emissions from South Asia (transported by the monsoons and the westerlies). The BC concentrations in some glaciers might cause significant impacts on the albedos for the glaciers, and therefore enhanced the radiative forcings, for example, the ERG. The research on the relationships among atmospheric and snow/ice BC and its radiative forcing, variance of snow cover, mass balance of glaciers, and climate forcing would be needed in future.

中国特有针叶树种对气候变化的敏感性研究

About 214 trees in 9 sampling sites, representing 5 endemic conifer species, were collected from the western Sichuan Province and eastern Qinghai Province, China. In this study, structure we try to investigate tree-ring sensitivity to climate in order to obtain primary information of reconstructing past climate from the trees in this region. All the 5 species present distinct ring boundaries ^ few ABS(absent rings) and available for cross-dating,which are all past the test by program COFECHA. Statistics for all the 8 tree-ring width residual chronologies present significant inter-correlation between series and high values of mean sensitivity. As well as the maximum latewood density of Picea crassifolia Kom and Pinus densata Mast. These results indicate usefulness of these chronologies for dendrochronological studies. Pearson correlation analyses were applied to provide a basic estimate of the causal relationships between tree-ring width and climate factors. We found some significant relationships between tree-ring width> maximum density and temperature as well as precipitation. Especially, there is high correlation between the maximum density of the Picea crassifolia Kom and the index of moisture, the ratio of precipitation and temperature, which can indicate well the climate; however the higher correlation can be see between the maximum density of Pinus densata Mast and the total temperature from June to September. Regardless of tree species, chronologies in our study region presented accordant variations of which may reveal strong common climate signal. Thus these chronologies are shown to be dependable for building tree-ring network in the nearly future. However, there are limitations in this study, only monthly mean of temperature and precipitation were available. Also, for this typical subtropical mountain system, meteorological stations are usually located in valley and biased to represent moisture conditions on the slopes. Thus the estimation of precipitation both in temporal and spatial domain was rather restricted. Further study, such as wood anatomy, physiology and densitometry, are needed for better understanding the environmental and climatic history in this area.

当代大学生消费价值观与消费行为的调查研究——北京大学生中的消费主义倾向及有关影响因素研究

The aim of this study was to investigate consuming values and behaviors in Chinese college students, to detect the factorial structure in consuming values, and to explore possible determinants of those values and their effects on consuming behaviors. A total of 778 students from various universities in Beijing were investigated with questionnaire survey. The main results and conclusions are as follows: (1) College students were basically satisfied with their current life and study conditions in university, and their main pressures or stresses were from their studies. They were highly motivated in the development of their academic and life careers, and also valued the importance of family and having children in the future. About 11% of the students had pressures due to less favorable financial conditions of their families. (2) Five basic consuming values were found among college students, namely, “industrious and thrifty-aimed value”, “status and brand-aimed value”, “personal and unique-oriented value”, “relation-aimed value”, and “autonomous-aimed value”. The “industrious and thrifty-aimed value” stands for the traditional consuming values in the culture, and the “status and brand-aimed value” shows an explicit tendency of consumerism. The other three consuming values had moderate relations with both of the two values. (3) There was a high negative correlation between the first two values, which showed both a general acceptance and the main trend of “industrious and thrifty-aimed value” among the students. The basic “status and brand-aimed value” was shown among 3.3% of the students. (4) The consuming values were significantly correlated with life values, indicating that consuming values could be in consistence with or be determined by basic life values. The “industrious and thrifty-aimed value” and the “autonomous-aimed value” were shown as collectivistic values, while the “status and brand-aimed value” and “relation-aimed value” were shown as individualistic values. (5) Consuming values had significant influences on consuming behaviors. (6) The demographic factors such as financial conditions of parents, children of number in family, urban-rural location of family, gender, age, and campus culture could affect consuming values and consuming behaviors of college students in both direct and indirect ways.