用混凝土模型校正伽玛能谱仪的经验     

Gras.  RL 陆士立 《国外铀金地质》1993,10(3):261-266

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车载伽玛能谱测量数据处理方法探讨   总被引：1，自引：1，他引：0  

李必红  陆士立  韩绍阳 《华东地质学院学报》2008,31(3):265-268

放射性测量过程中,受仪器本身和外界环境的影响,需要对仪器性能进行检查.介绍了GR-660车载伽玛能谱测量系统,对仪器的稳定性和重复性进行了实验分析.介绍了噪声调整后奇异值分解方法和自适应神经网络模糊系统分析方法,通过处理航空标准模型实测数据来对两种方法进行了比较分析,应用变异系数方法对区域铀含量进行了分析.  相似文献   

Stress-induced apoptosis in sea urchin embryogenesis     

Vega RL  Epel D 《Marine environmental research》2004,58(2-5):799-802

We find that early sea urchin embryos have the capability to induce programmed cell death, or apoptosis, in response to chemical and physical stress. Strongylocentrotus purpuratus embryos (fertilized, 4 cell, 16 cell, 64 cell, and early blastula) were exposed to known cytotoxins, in order to determine when apoptosis occurs naturally and in response to stress. Using cell permeability as an indicator of early stage apoptosis, caspase activation as a mid-stage indicator, and DNA fragmentation as a late stage indicator, we find that during the cleavage stage of embryogenesis apoptosis is almost completely absent. However, a statistically significant (p<0.001) rise in apoptosis in stressed embryos is evident around 24 h after fertilization, during the early blastula stage and shortly after hatching. Before this stage, exposed embryos show no statistically significant increases in apoptosis in comparison to the controls. This pattern of apoptosis in development is similar to that seen in lower vertebrate models in which stress-induced apoptosis occurs only around the mid-blastula transition. We conclude that apoptosis may be used to rid embryos of aberrant or damaged cells in early development, but this response is stage-dependant. Repair, rather than apoptosis, may be utilized during earlier stages, or alternatively, embryos exposed to such stressors may continue development with damaged cells and perhaps damaged DNA. Our continued studies will focus on these alternative hypotheses.  相似文献   

Shock chemistry in the molecular clouds associated with SNR IC 443     

Ziurys LM  Snell RL  Dickman RL 《The Astrophysical journal》1989,341(2):857-866

Several interstellar molecules have been detected toward the highly perturbed B and G clouds associated with the supernova remnant IC 443 via their 3 mm transitions, including N2H+, SiO, SO, CN, HNC, and H13CO+. The (J, K) = (1, 1) and (2, 2) inversion lines of metastable ammonia have also been observed, as well as the J = 3-2 transition of HCO+ at 1.2 mm. Analysis of the (1, 1) and (2, 2) inversion lines of NH3 indicates minimum gas kinetic temperatures of TK = 70 K toward cloud B, and TK = 33 K in cloud G. Modeling of the J = 1-0 and J = 3-2 transitions of HCO+ implies densities greater than 10(5) cm-3 toward both positions. These data clearly show that hot and dense material is present in IC 443, and they suggest the presence of shocks in both regions. A careful analysis of the HCO+ lines indicates that the HCO+ abundance is at most enhanced by factors of a few over that found in cold, quiescent gas. This conclusion contradicts past claims of HCO+ abundance enhancements of several orders of magnitude in the perturbed regions. The N2H+ abundance was also found to be similar to that in cold gas, suggesting that there is no increase in ionization in the clouds. The abundances of SO and CS, as well as CN and NH3, do not appear to differ significantly from those found in cold dark clouds, although chemistry models predict sulfur-containing species to undergo high-temperature enhancements. SiO, however, is found to have an abundance in the perturbed gas 100 times larger than the upper limits observed in the dark cloud TMC 1, a result in agreement with high temperature chemistry models. In addition, the HNC/HCN ratio in both IC 443 B and G was found to be approximately 0.1--far from the ratio of 1 predicted by low-temperature ion-molecule chemistry, but similar to the values observed in clouds where elevated temperatures are present.  相似文献   

Sediment oxygen profiles in a super-oxygenated antarctic lake     

Wharton RA  Meyer MA  McKay CP  Mancinelli RL  Simmons GM 《Limnology and oceanography》1994,39(4):839-853

Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column.  相似文献   

HD-4002型综合测井仪     

陆士立  袁明  焦仓文  马艳芳  谢海宁  赵志明  李继红  于延斌 《铀矿地质》2005,21(3):183-192

HD 4002型综合测井仪是核工业北京地质研究院于1998年开始研制的, 其目标是为铀矿地质系统提供适合砂岩型铀矿勘查的轻便型数字测井仪, 满足测井生产的需要。该仪器于2001 年3月通过部级鉴定, 2002至2003年投入海拉尔盆地铀矿勘查测井试生产。本文介绍了仪器的用途、功能及特点、性能指标, 简要说明了各部分的工作原理。  相似文献   

伽玛射线测量中上现探测器的标定     

Gras.  RL 《物探化探译丛》1997,(A02):94-97

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北美中部和东部地区震源参数的地质意义     

Whee.  RL 张康富 《地壳构造与地壳应力》1994,(5):16-24,29

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科学家认为每一个大震都会引起另一个大震     

Hotz  RL 曾包红 《地震科技情报》1995,(1):28-29

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地面伽玛谱仪标定及含量计算的若干问题     

陆士立 《铀矿地质》1983,(1)

本文讨论模型不纯对地面伽玛谱仪标定结果的影响,含量近似计算公式的误差,并介绍一种含量速算图。一、模型不纯对标定及含量计算的影响迄今为止,各种地面伽玛谱仪都在石家庄的2.2×0.6米标准模型上进行标定。但是前一时期该套模型除了主元素含量外只给出了两种杂质元素含量,即铀模型中的钍和钍模型中的  相似文献