X-ray absorption contrast images of binary chemical reactions     

D. Walker  O.T. Lord  M.J. Walter  S.M. Clark   《Chemical Geology》2009,260(3-4):211-220

Low-divergence synchrotron-sourced X-rays enable a radiographic imaging scheme for full characterization of binary chemical reactions and characterization by type of more complex reactions, in situ, in diamond anvil cells (DAC). Spatially resolved reactants are induced to react by laser heating of their interface. The spatially intermediate products are observed through X-ray absorption contrast. Limits to the technique include the ability to maintain controlled experiment geometry during compression and the ability to resolve chemical differences between reactants and products by X-ray absorption. The ability to make in situ observations at experimental pressure and temperature obviates the problem with quenching techniques for capturing liquid compositions in experiments with dimensions smaller than the diffusion length during quenching time. Partially molten Fe-alloy systems, of poor quenchability, are examined at DAC pressures and temperatures for relevance to Earth's core constitution and evolution. Determinations of eutectic melting in Fe–FeS match known results. Of the probable light elements that may alloy with Fe in the Earth's liquid outer core, Fe–FeS experiments show only modest quenching problems, but C and Si alloy experiments are highly vulnerable to quenching artifacts. The observed reactivity of FeS, Fe₃C, FeSi, and FeO(OH) with Fe in DAC makes the observed non-reactivity between Fe and FeO more significant, reducing the probability that oxygen alone is the major alloy in Earth's molten outer core.  相似文献   

Comparison of laboratory testing protocols to field observations of the weathering of sulfide-bearing mine tailings   总被引：1，自引：0，他引：1  

Carla Ardau  David W. Blowes  Carol J. Ptacek 《Journal of Geochemical Exploration》2009,100(2-3):182-191

A laboratory weathering study using a humidity cell procedure was conducted on two sulfide-bearing tailing samples from a metallurgical site in Ontario (Canada). The test was accompanied by microbiological studies to enumerate the major groups of sulfur-oxidizing bacteria and determine their potential role at different stages during the oxidation process. To evaluate the utility of this method, results were compared with those of previous laboratory and field studies on the same materials. The mineralogy of the laboratory samples differs only by the addition of a small amount of hydronium-bearing natrojarosite [(Na,H₃O)Fe₃(SO₄)₂(OH)₆] to one sample. The progress of sulfide oxidation and the rates of solute release were determined to evaluate the extent of mineral dissolution. These processes were influenced strongly by the capacity of the material to generate acidity, which was enhanced by the presence of hydronium-bearing natrojarosite. Acid-neutralization processes occurring during the laboratory tests were affected by reaction kinetics, consistent with field observations. In particular, the extent of carbonate-mineral dissolution appears to be different in the laboratory than in the field, where more prolonged rock–water interaction allowed more complete chemical equilibration. As a consequence, the capacity of this test procedure to predict weathering reactions in mine tailings is limited by its inability to reproduce the weathering sequence observed in the field. The results of the microbiological study showed that distinct groups of sulfur-oxidizing bacteria operate at different stages of the oxidative process, as was observed in field studies where tailings oxidation occurred under natural conditions, suggesting that microbiological tests performed for laboratory studies are reflective of field conditions.  相似文献   

Modelling the effects of motion on primary production in the mixed layer of lakes     

John C. Patterson 《Aquatic Sciences - Research Across Boundaries》1991,53(2-3):218-238

A model of the time dependent relationship between productivity and light intensity following changes in light intensity is briefly described. The model incorporates two response timescales simulating initial response and photoinhibition, although additional timescales could easily be incorporated. The model is calibrated against one set of time dependent data, and applied to two simple models of motion in the upper mixed layer of a lake. The two models are: organised motion simulating Langmuir cells, and disorganised motion simulating the turbulent velocity field associated with surface wind stirring. The depth and therefore light histories for a number of photosynthesising particles are calculated by these models, and used by the productivity model to calculate mean productivities. The results show that the influence of the time dependent nature of the productivity relationship depends on the ratio of the mixed layer depth to the euphotic depth, and to a less extent, on the rate at which the particles circulate in the mixed layer.  相似文献   

STRUCTURE FEATURES AND COMPOSITE ANALYSIS OF CONVECTIVE CELLS IN A WARM SECTOR HEAVY RAINFALL EVENT OVER SOUTHERN CHINA     

钱磊  丁治英  赵向军  夏蘩 《热带气象学报(英文版)》2017,23(3):245-258

This paper uses the ARW-WRF model to carry out a numerical simulation of a warm-sector heavy rainfall event over southern China on the 22–23 May, 2014. A composite analysis method was used to analyze the evolution process and structural features of the convective cells on a convection line during this rainfall event. This analysis identified three stages: (1) Stage of activation: the equivalent potential temperature surfaces as lower layers start to bulge and form warm cells and weak vertical convective cloud towers which are subject to the impact of low-level warm moist updrafts in the rainfall sector; (2) Stage of development: the warm cells continue to bulge and form warm air columns and the convective cloud towers develop upwards becoming stronger as they rise; (3) Stage of maturity: the warm air columns start to connect with the stable layer in the upper air; the convective cloud tower will bend and tilt westward with each increasing in height, and the convection cell is characterized by a “crescent-shaped echo” above the 700hPa plane. During this stage the internal temperature of the cell is higher than the ambient temperature and the dynamic structural field is manifested as intensive vertical upward movement. The large-value centers of the northerly and westerly winds in the middle layer correspond to the warm moist center in the cells and the relatively cold center south of the warm air column. Further analysis shows that the formation of the “crescent-shaped” convective cell is associated with horizontal vorticity. Horizontal vorticity in the center and west of the warm cell experiences stronger cyclonic and anticyclonic shear transformation over time; this not only causes the original suborbicular cell echo shape to develop into a crescent-like shape, but also makes a convection line consisting of cells that develop to the northwest.  相似文献   

环境因子对三种常见微藻细胞中二甲基硫丙酸含量影响的初步研究   总被引：2，自引：0，他引：2  

李炜  焦念志 《海洋与湖沼》1999,30(6):635-639

以3种常见的海洋浮游藻类──扁藻、杜氏藻和牟氏角刺藻作为实验材料,采用正交方法设计实验条件,研究盐度、温度和光强的变化对藻类细胞内二甲基硫丙酸（DMSP）含量的影响。结果表明,3种藻类细胞DMP含量相差很大。扁藻DMSP含量最高,其次为杜氏藻,牟氏角刺藻含量最低。种间差别的影响明显高于环境条件的变化对藻细胞DMSP含量的影响。3种环境因子对藻细胞DMSP含量的影响效果不同,盐度变化引起藻细胞DMP含量的变化最为显著,其次为温度和光强。随着盐度的增加,扁藻、杜氏藻和牟氏角刺藻细胞内DMSP含量均呈上升趋势。  相似文献   

鲎血细胞提取物生物活性的初步研究   总被引：7，自引：0，他引：7  

张海涛  梁景耀  翁云  祝其锋 《海洋科学》2000,24(10):48-50

采用酸抽提法和Ｓｅｐｈａｄｅｘ Ｇ－５０凝胶层析从鲎血细胞中分离出含有一低分子量组分的提取物,ＳＤＳ－ＰＡＧＥ显示一条区带。提取物可以抑制内毒素诱导的鲎试剂（ＴＡＬ）反应,抑制金色葡萄菌和大肠杆菌的生长,并发现２５ｍｇ／Ｌ的提取物对ＨＬ－６０细胞的生长有强烈的抑制作用。  相似文献   

褐藻多糖硫酸酯对脂多糖诱导大鼠肾小球系膜细胞NO产生量的影响   总被引：2，自引：2，他引：0  

王雪妹  王晶  张全斌 《海洋科学》2014,38(10):1-5

慢性肾衰的进程中伴随着肾脏炎症的发生,研究表明褐藻多糖硫酸酯具有抗炎作用,且对于慢性肾衰的早期治疗具有一定的作用。本文通过脂多糖(lipopolysaccharide,LPS)诱导,建立大鼠肾小球系膜细胞的炎症模型,用来源于海带的高分子质量褐藻多糖硫酸酯F1和低分子质量褐藻多糖硫酸酯F2对细胞进行处理,24 h后MTT法检测各组细胞活力,Griess法检测24 h及48 h后细胞培养液中NO的含量。结果表明,各组间细胞活力无明显差异;脂多糖可以诱导大鼠肾小球系膜细胞NO产量增加,F1和F2均可在一定程度上抑制脂多糖诱导的NO产量的增加,从而减轻细胞炎症反应。剂量为25μg/m L的F1和F2处理细胞48 h后,与模型组相比,F1和F2组细胞培养液中NO含量分别下降22.52%和38.65%,低分子质量褐藻多糖硫酸酯抗炎效果明显高于高分子质量褐藻多糖硫酸酯。  相似文献   

Effects of sulfate chitosan derivatives on nonalcoholic fatty liver disease     

Mingming Yu  Yuanhong Wang  Tingfu Jiang  Zhihua Lv 《中国海洋大学学报(英文版)》2014,13(3):531-537

Sulfate chitosan derivatives have good solubility and therapeutic effect on the cell model of NAFLD. The aim of this study was to examine the therapeutic effect of sulfate chitosan derivatives on NAFLD. The male Wistar rats were orally fed high fat emulsion and received sulfate chitosan derivatives for 5 weeks to determine the pre-treatment effect of sulfate chitosan derivatives on NAFLD. To evaluate the therapeutic effect of sulfate chitosan derivatives on NAFLD, the rats were orally fed with high concentration emulsion for 5 weeks, followed by sulfate chitosan derivatives for 3 weeks. Histological analysis and biomedical assays showed that sulfate chitosan derivatives can dramatically prevent the development of hepatic steatosis in hepatocyte cells. In animal studies, pre-treatment and treatment with sulfate chitosan derivatives significantly protected against hepatic steatohepatitis induced by high fat diet according to histological analysis. Furthermore, increased TC, ALT, MDA, and LEP in NAFLD were significantly ameliorated by pre-treatment and treatment with sulfate chitosan derivatives. Furthermore, increased TG, AST, and TNF-α in NAFLD were significantly ameliorated by treatment with sulfate chitosan derivatives. Sulfate chitosan derivatives have good pre-treatment and therapeutic effect on NAFLD.  相似文献   

螺旋藻多糖对CD₃AK细胞增殖能力的影响   总被引：7，自引：0，他引：7  

王友顺  黎露刚  吴侃  谢宗华  唐庆  李新岗  祁铁流  李长亮  汪洋  汪庭  方光如 《海洋科学》1998,22(3):37-39

研究了螺旋藻多糖（ＰＳ）对ＣＤ３ＭｃＡｂ激活的杀伤细胞（ＣＤ３ＭｃＡｂ Ａｃｔｉｖａｔｅｄ Ｋｉｌｌｅｒ Ｃｅｌｌｓ,ＣＤ３ＡＫ Ｃｅｌｌｓ）增殖能力的影响。结果表明,当ＰＳ浓度为２．５μｇ·ｍｌ＾－１培养体系条件下,对ＣＤ３ＡＫ细胞具有明显的刺激细胞增殖作用（Ｐ〈０．０２）;对培养长达２３ｄ的ＣＤ３ＡＫ细胞杀伤肿瘤细胞（Ｋ５６２细胞）的活性仍维持在较高的水平（４６．５％￣５０％）。提示ＰＳ对辐射  相似文献   

Cascades of sub-decadal,channel-floodplain changes in low-gradient,non-vegetated reaches near a dryland river terminus: Salar de Uyuni,Bolivia     

Jiaguang Li  Stephen Tooth  Guangqing Yao 《地球表面变化过程与地形》2019,44(2):490-506

The terminus of the ephemeral Río Colorado is located at the margins of Salar de Uyuni, Bolivia, the world's largest salt lake. The low-gradient (<0.0006 m m^-1), non-vegetated reaches approaching the terminus provide an excellent natural laboratory for investigating cascades of channel-floodplain changes that occur in response to quasi-regular flows (at least once annually) and fine-grained sediment supply (dominantly silt and clay). High-resolution satellite imagery (<0.65 m, various dates from 2004 onwards) and field data reveal widespread, pronounced and rapid morphodynamics on sub-decadal timescales, including channel erosion and chute cutoff formation, and development of crevasse channels and splays, floodouts (unchannelled surfaces at channel termini), and erosion cells (floodplain scour-transport-fill features). In particular, following high annual precipitation (>400 mm) in 2004–2005 and two subsequent high magnitude daily precipitation events (~40 mm), all of which led to widespread flooding, numerous crevasse splays formed between 2004 and 2016, avulsions occurred at nearby floodouts, and erosion cells downstream of the splays and floodouts underwent striking morphological changes. High-precision GPS data reveal two preferential localities for erosion cell development: partially or fully abandoned channels with crevasse splay remnants, and topographic lows between channels. In this overall low-gradient setting, comparatively high gradients (up to ~0.0006 m m^-1) at the edge of splay deposits and topography created by crevasses and abandoned channels may initiate knickpoint retreat and thereafter erosion cell development. Abandoned channels with splays tend to give rise to narrow, deep erosion cells, while topographic lows promote relatively shallow, wide erosion cells. In both situations, erosion cells may extend upslope and downslope, and eventually connect to form straight channels. The channel-floodplain morphodynamics near the Río Colorado terminus extend previous analyses of low-gradient, dryland river systems, particularly because the lack of vegetation and quasi-regular floods drive cascades of rapid changes on sub-decadal timescales. © 2018 John Wiley & Sons, Ltd.  相似文献