Grain size--dependent alteration and the magnetization of oceanic basalts

Unblocking temperatures of natural remanent magnetization were found to extend well above the dominant Curie points in samples of oceanic basalts from the axis of the East Pacific Rise. This phenomenon is attributed to the natural presence in the basalts of three related magnetic phases: an abundant fine-grained and preferentially oxidized titanomagnetite that carries most of the natural remanent magnetism, a few coarser and less oxidized grains of titanomagnetite that account for most of the high-field magnetic properties, and a small contribution to both the natural remanent magnetism and high-field magnetic properties from magnetite that may be due to the disproportionation of the oxidized titanomagnetite under sea-floor conditions. This model is consistent with evidence from the Central Anomaly magnetic high that the original magnetization acquired by oceanic basalts upon cooling is rapidly altered and accounts for the lack of sensitivity of bulk rock magnetic parameters to the degree of alteration of the remanence carrier in oceanic basalts.     

Stable lead isotopes as a tracer in coastal waters

The natural abundances of the stable isotopes of lead are used to identify natural and industrial sources of lead in the coastal waters of British Columbia, Canada. The (206)Pb/(207)Pb ratios, used to characterize the lead source, had values of approximately 1.24 for coastal oceanic water, approximately 1.22 for fjord waters receiving lead from mine tailings, and approximately 1.163 for waters near urban centers. The lead concentration data are in agreement with presently accepted seawater values.     

Thorium-uranium fractionation by garnet: evidence for a deep source and rapid rise of oceanic basalts

Mid-ocean ridge basalts (MORBs) and ocean island basalts (QIBs) are derived by partial melting of the upper mantle and are marked by systematic excesses of thorium-230 activity relative to the activity of its parent, uranium-238. Experimental measurements of the distribution of thorium and uranium between the melt and solid residue show that, of the major phases in the upper mantle, only garnet will retain uranium over thorium. This sense of fractionation, which is opposite to that caused by clinopyroxene-melt partitioning, is consistent with the thorium-230 excesses observed in young oceanic basalts. Thus, both MORBs and QIBs must begin partial melting in the garnet stability field or below about 70 kilometers. A calculation shows that the thorium-230-uranium-238 disequilibrium in MORBs can be attributed to dynamic partial melting beginning at 80 kilometers with a melt porosity of 0.2 percent or more. This result requires that melting beneath ridges occurs in a wide region and that the magma rises to the surface at a velocity of at least 0.9 meter per year.     

Reciprocal inhibition as indicated by a differential staining reaction

Neurohistological and neurophysiological studies have shown that the bilaterally represented Mauthner's cells in teleosts are related both structurally and functionally. The VIIIth nerve afferents, as well as the axoaxonal collaterals, display a distribution pattern which supports the concept of polar function of the neuron. Inasmuch as it is possible to alter the staining reaction of both the Mauthner's cells by unilateral stimulation of the entering VIIIth nerve roots, it is proposed that the synaptic endings serve principally as activators and that neuronal excitation or inhibition is determined by the chemical state of the dendrites, the cell body, and the axon hillock region.     

Hydroxyl orientation in muscovite as indicated by electrostatic energy calculations

The electrostatic energy of the 2M(1) muscovite structure, KAl(2)(Si(3)Al)- O(10)(OH)(2), has been calculated as a function of the orientation of the hydroxyl group (O-H distance = 0.97 angstrom). The minimum in the electrostatic energy occurs when the OH bond makes an angle of 18 degrees with the cleavage plane and an angle of 31 degrees with the b-axis (in the a-b plane), which is 2.5 degrees away from the orientation of the transition moment as determined from infrared measurements on single crystals. If the K+ ion is excluded from the calculation, the O-H bond makes an angle of 53 degrees with the cleavage plane. This indicates the strong influence that the interlayer cation exerts on the hydroxyl hydrogen in mica structures.     

Volcanic production rates: comparison of oceanic ridges, islands, and the columbia plateau basalts

New potassium-argon age data from the Columbia Plateau suggest a basalt production rate of 108 cubic meters per year during a middle Miocene volcanic episode. This is two to three times the production rate in some oceanic islands, and about four to six times the production rate in spreading mid-oceanic ridge systems.     

Organization of DNA in dipteran polytene chromosomes as indicated by polarized fluorescence microscopy

Analysis of the polarization of fluorescence from Drosophila virilis polytene chromosomes stained with acridine orange suggests that the DNA in the interband regions of these chromosomes cannot be in a supercoiled configuration, but must lie parallel to the chromosome axis.     

Steelhead migration: potential temperature effects as indicated by gill adenosine triphosphatase activities

Yearling steelhead trout held in fresh water at cold temperatures (6.5 degrees or 10 degrees C) showed an increase in gill microsomal Na(+), K(+)-stimulated adenosine triphosphatase activity during parr-smolt transformation, whereas trout held in warm water (15 degrees or 20 degrees C) did not. Adenosine triphosphatase activity increased and other indications of transformation were observed in fish transferred from warm to cold water, whereas the reverse occurred on transfer from cold to warm water.     

万寿菊属品种资源遗传关系的ISSR分析

【目的】通过ISSR分子标记研究品种资源遗传关系,探讨其种群遗传多样性水平和遗传结构,为了解品种间遗传多样性、品种间亲缘关系、育种及科学合理保存和利用现有万寿菊属种质资源提供理论依据和技术支持。【方法】对29份万寿菊材料及2份孔雀草材料利用ISSR分子标记进行遗传关系分析。【结果】用11个引物对31份万寿菊属材料进行PCR扩增,每个引物扩增的ISSR条带数在5—11条,平均每条引物能扩增出6.8条带,多态位点百分率为40%—100%。聚类分析结果表明,ISSR分类结果与传统分类的结果基本一致,31份材料按照万寿菊及孔雀草分为两大类,并且同系列万寿菊品种被划为同一亚组。【结论】利用ISSR标记技术可较准确分析万寿菊属材料间的亲缘关系及遗传多样性。     

Petroleum pollutants in surface and groundwater as indicated by the carbon-14 activity of dissolved organic carbon

The (14)C activity of dissolved organic carbon (DOC) can be used to distinguish between the fossil organic carbon due to petrochemical effluents and modern organic carbon due to domestic wastes and natural decaying organic matter. Rivers polluted by petrochemical effluents show varying amounts of depression of the DOC (14)C activity, reflecting concentrations of (14)C-deficient fossil carbon of as much as about 40 percent of the total DOC.     

Microaggregations of oceanic plankton observed by towed video microscopy

Oceanic plankton have been hypothesized to occur in micropatches (<10 meters) that can have a large impact on marine ecosystem dynamics. Towed video microscopy was used to unobtrusively determine distributions of oceanic plankton over a continuum of scales from microns to hundreds of meters. Distinct, taxa-specific aggregations measuring less than 20 centimeters were found for copepods but not for nonmotile (cyanobacterial colonies) or asexual (doliolid phorozooids) forms, which suggests that these small patches are related to mating. Significant patchiness was also found on larger scales and was correlated among taxa, indicating physical control. These video observations provide new insights into basic plankton ecology by allowing quantitative assessment of individual plankton in their natural, undisturbed state.     

崇明白山羊遗传多样性的ISSR分析

应用ISSR分子标记对崇明白山羊3个群体和黄淮山羊群体进行遗传多样性分析。用筛选出的12条引物对127个个体进行扩增,共扩增出147条谱带,其中多态性谱带67条。分析结果显示:崇明白山羊遗传多样性较为丰富,在物种水平上平均多态位点百分率(PPB)=42.18%,Shannon's信息指数(Ho)=0.2085;在群体水平上,PPB=38.55%,Ho=0.1946。崇明白山羊各群体间遗传差异较小,遗传稳定性较高。UPGMA聚类分析显示:崇明白山羊3个群体间亲缘关系较近,优先聚为1支,再与黄淮山羊相聚。     

Production of isotopic variability in continental basalts by cryptic crustal contamination

Regional variations in the Nd, Sr, and Pb isotopic compositions of Neogene basalts from the western United States are commonly interpreted to originate in the subcontinental mantle. In southern California, isotopic variability is restricted to lavas that lack mantle-derived xenoliths; xenolith-bearing basalts have uniform isotopic compositions similar to those of ocean-island basalts (OIBs). Combined with available geochemical data, these observations suggest that isotopic variability at these volcanoes results from subtle crustal contamination, locally by mafic crust, of primitive OIB-like magma. Recognition of such cryptic contamination may help to reconcile local discrepancies between tectonic and isotopic views of the subcontinental mantle.     

中籼杂交稻遗传多样性的RAPD分析

选用20个随机引物对15个在生产和育种上广泛使用的中籼杂交稻亲本进行遗传多样性分析。20个引物共扩增出205条带纹，其中多态性带为165条。不同引物的多态性频率有较大差异，但普遍较高，平均达95．33％。亲本间的遗传距离小，在0．1210－0．3913之间，平均0．2455。15个亲本按UPGMA法可明显地分为不育系（I类）和恢复系（Ⅱ类）两类，其中Ⅱ类又分为两个亚类（Ⅱ－1和Ⅱ－2）。类群内和类群间的遗传距离分析表明，不育系与恢复系内的遗传差异都较小，而且不育系的遗传变异较恢复系小；不育系和恢复系间的遗传距离只有0．2906，而且与恢复系两个亚类间遗传差异不显著，这说明杂交水稻亲本的遗传资源匮乏。亲本间的遗传差异小，这可能是限制当前杂交水稻产量的重要因素。增加亲本遗传多样性和扩大亲本间遗传差异是当前中籼杂交稻育种的重要任务之一。     

Separation of calcium isotopes by liquid phase thermal diffusion

Significant separation of the isotopes of calcium was obtained by thermogravitational thermal diffusion of an aqueous calcium nitrate solution. A flow of solvent was used to partially offset the large solute-solvent separation effect in the experimental column. Further development of this technique may lead to separation of the isotopes of calcium and of other elements on a practical scale.     

不同解吸剂对污染土娄土铜铅的解吸动力学研究

【目的】研究螯合剂和表面活性剂作用下污染土娄土中Cu、Pb的解吸动力学特征。【方法】在Cu单一污染、Pb单一污染和Cu、Pb复合污染土娄土中,分别加入2种螯合剂(乙二胺四乙酸(EDTA)、柠檬酸(CIT))和2种表面活性剂(十二烷基磺酸钠(SDS)、鼠李糖脂(RL2))作为解吸剂,采用批次试验方法,研究螯合剂和表面活性剂对污染土娄土中Cu、Pb不同形态及其含量的影响,并对其解吸动力学方程进行拟合。【结果】2种螯合剂对Cu、Pb的解吸是一个相对慢速的过程,240min左右时解吸基本达到平衡;而2种表面活性剂对Cu、Pb的解吸是一个相对快速的过程,在60min左右达到平衡。4种解吸剂对Cu的解吸量依次表现为EDTA>CIT>RL2>SDS;对Pb的解吸量依次表现为EDTA>CIT>SDS>RL2。【结论】4种解吸剂中,EDTA对污染土娄土中Cu、Pb的解吸效果最好;准二级方程能较好地描述4种解吸剂解吸污染土娄土中Cu、Pb的动力学特征。     

盐碱化土壤对铅的吸附特性

为进一步明确盐碱土对重金属的吸附累积规律,本研究以盐碱化土壤为研究对象,探讨不同盐碱化程度土壤对重金属铅的吸附行为,以及施用水稻秸秆、堆肥后盐碱化土壤对铅的吸附特征变化。结果表明:施用水稻秸秆、堆肥前后的盐碱化土壤样品,对铅的等温吸附曲线更符合Freundlich方程,且决定系数均大于0.9;盐碱化土壤对铅有较强的吸附能力,其强弱顺序为:轻度盐碱化土壤重度盐碱化土壤中度盐碱化土壤;在盐碱化土壤中施用一定量水稻秸秆能促进其对铅的吸附,而施用一定量污泥堆肥能抑制盐碱化土壤对铅的吸附。     

土壤污染的防治技术

本文概述了土壤铅污染的特点及现状,并分析评论了铅污染防治的三种主流技术,即:物理控制法、化学控制法和生物修复法,指出了各自优缺点.并在此基础上提出一些见解和看法,为今后这方面的研究提供一些参考.