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1.
Three crystalline forms of calcium carbonate were identified in washings of the hamster vagina. Spherical concretions of vaterite and hexagonal concretions of calcite predominate on days 3 and 4 of the 4-day estrous cycle. Dumbbell-like concretions of aragonite predominate during pregnancy and pseudopregnancy. Each polymorph is associated with an acid-insoluble matrix. Concretions disappear after ovariectomy and reappear during daily injections of estrogen and progesterone. 相似文献
2.
Phosphorite concretions have been detected in the kidneys of two widespread species of mollusks, Mercenaria mercenaria and Argopecten irradians, which have relatively high population densities. These concretions are the first documentation of the direct biogenic formation of phosphorite grains. The concretions are principally amorphous calcium phosphate, which upon being heated yields an x-ray diffraction pattern which is essentially that of chlorapatite. These concretions appear to be a normal formation of the excretory process of mollusks under reproductive, environmental, or pollutant-induced stress. Biogenic production of phosphorite concretions over long periods of time and diagenetic change from amorphous to crystalline structure, coupled with secondary enrichment, may account for the formation of some marine phosphorite desposits which are not easily explained by the chemical precipitation-replacement hypothesis. 相似文献
3.
Alewives, Alosa pseudoharengus, wash ashore from Onondaga Lake, N.Y., in the form of combustible concretions in which the mnuscles are replaced by calcium salts of fatty acids. In both distribution pattern and total concentration of fatty acids the concretions differ strikingly from normal carcasses. Carbon-13: carbon-12 ratios indicate that the concretions may have formed from lipids of terrestrial or freshwater organisms or from organic pollutants of nonmarine origin, or from lipids and pollutants. 相似文献
4.
Greenslate J 《Science (New York, N.Y.)》1974,186(4163):529-531
Incipient manganese concretions occur in microcavities of planktonic skeletal debris (especially diatom frustules) in some Pacific Basin deep-sea sediments. These concretions contain over 50 percent manganese and very little iron (< 1 percent). There is a continuum of growth stages in the concretions having a diameter between 0 and approximately 2 millimeters, and a genetic relationship is suggested between the very small and the centimeter sized concretions. 相似文献
5.
从古土壤中碳酸钙淀积深度、钙结核中氧同位素组成、磁化率、全铁、地球化学元素等替代性指标方面回顾了国内外对古气候定量化研究的现状,并对研究中存在的一些问题进行了讨论。 相似文献
6.
R A Berner 《Science (New York, N.Y.)》1968,159(811):195-197
Bacterial decomposition of butterfish and smelts in small sealed jars containing seawater and other solutions, for periods ranging from 65 to 205 days, results in a large increase in concentrations of dissolved bicarbonate, carbonate, and ammonia (plus volatile amines). Accompanying this is a rise in pH and the precipitation of Ca(++) ion from solution. The Ca(++) is not precipitated as CaCO(3) but instead as a mixture of calcium fatty acid salts or soaps with from 14 to 18 carbon atoms. This can be explained by the thermodynamic instability of CaCO(3) relative to Ca soaps in the presence of excess free fatty acid. It is suggested that some ancient CaCO(3) concretions, especially those enclosing fossils of soft-bodied organisms, may have formed rapidly after death in the form of natural Ca soap (adipocere) which was later converted to CaCO(3). 相似文献
7.
铁锰结核的元素组成及微形态特征 总被引：8，自引：0，他引：8
本文研究了钙质变性土中铁锰结核的矿质全量组成、微量元素丰度，微形态特征以及土壤和铁锰结核中各形态铁锰氧化物的组成特点，结果表明，铁锰结核中仍以ＳｉＯ２含量最高，但Ｆｅ２Ｏ３含量增加超过了Ａｌ２Ｏ３、ＭｎＯ含量大大超过了Ｋ２Ｏ、Ｎａ２Ｏ、ＴｉＯ２和ＭｇＯ的含量，所测定的９种微量元素中以Ｂａ含量最高，其次是Ｖ、Ｎｉ、Ｃｏ３种铁族元素，Ｃｕ和Ｐｂ含量也较高，但Ｚｎ和Ｃｒ含量较低，一般黑土层中的结核较小， 相似文献
8.
土壤中的钙质结核可分为软结核、硬结核和钙质硬盘３种形态，其化学组成以ＣａＣＯ３为主，矿质全量组成的各氧化物平均含量水平的顺序为：ＣａＯ〉ＳｉＯ２〉Ａｌ２Ｏ３〉Ｆｅ２Ｏ３〉ＭｇＯ〉Ｋ２Ｏ〉Ｎａ２Ｏ〉ＴｉＯ２〉ＭｎＯ〉Ｐ２Ｏ５。但在某些软结核中，ＳｉＯ２含量仍大于ＣａＯ含量。微形态分析结果表明，软结核为碳酸盐颗粒的胶结体，常嵌埋较多的土壤基质、石英、长石等粗颗粒；硬结核多为碳酸盐和方解石的胶结体，许多 相似文献
9.
Studies by optical microscopy, x-ray diffraction, and electron probe techniques of ferromanganese concretions from three Canadian lakes reveal chemical banding of amorphous hydrated iron and manganese oxides. The average ratio of iron to manganese in concretions from these lakes varies from 0.43 to 2.56. The concentrations of cobalt, nickel, copper, and lead are one to two orders of magnitude below those reported for oceanic ferromanganese concretions. 相似文献
10.
Saturnine gout: lead-induced formation of guanine crystals 总被引：1，自引：0，他引：1
Intravenous injection of a sublethal dose of lead acetate into a domestic pig resulted in a 4.5-fold increase of guanine in the urine, indicating an impairment in the conversion of guanine to xanthine. This impairment is probably due to the inhibition of guanine aminohydrolase (guanase), since the activity of this enzyme is inhibited by Pb2+ (the inhibition constant being 3.0 X 10(-6)M). Postmortem histological examination revealed concretions of crystalline material in the epiphyseal plate of the femoral head. Extraction of the section containing the concretions showed that they were guanine. The relation of these findings to saturnine gout is discussed. 相似文献
11.
以曼氏皮海鞘Molgula manhattensis为试验对象,采用静水方法在不同饵料种类(湛江等鞭金藻、扁藻、小新月菱形藻、小球藻、螺旋藻粉、稚参饵料)、盐度梯度(20、25、30、32、35、40)、pH梯度(4、5、6、7、8、9、10)和规格[大、中、小3种规格,平均湿重分别为(0.2276±0.0023)、(0.9302±0.0093)、(1.8857±0.1004)g]的条件下对其摄食率进行了研究。结果表明:(1)6种饵料对曼氏皮海鞘摄食率的影响极显著(P<0.01),摄食率大小依次为螺旋藻粉>稚参配合饵料>扁藻>湛江等边金藻>小球藻>小新月菱形藻;(2)盐度对曼氏皮海鞘摄食率的影响显著(P<0.05),在盐度为30、32时,曼氏皮海鞘对6种饵料的摄食率均较高,在盐度为20和40时,其摄食率均较低;(3)pH对曼氏皮海鞘的摄食率的影响显著(P<0.05),在pH为6、7、8和8.36(天然海水)时,曼氏皮海鞘对6种饵料的摄食率均较高,在pH为4、9、和10时,其摄食率均较低;(4)规格对曼氏皮海鞘摄食率的影响显著(P<0.05),曼氏皮海鞘对6种饵料的摄食率随其规格的增大而增大。 相似文献
12.
Squyres SW Grotzinger JP Arvidson RE Bell JF Calvin W Christensen PR Clark BC Crisp JA Farrand WH Herkenhoff KE Johnson JR Klingelhöfer G Knoll AH McLennan SM McSween HY Morris RV Rice JW Rieder R Soderblom LA 《Science (New York, N.Y.)》2004,306(5702):1709-1714
Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features include hematite-rich concretions and crystal-mold vugs. We interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history. The environmental conditions that they record include episodic inundation by shallow surface water, evaporation, and desiccation. The geologic record at Meridiani Planum suggests that conditions were suitable for biological activity for a period of time in martian history. 相似文献
13.
对广东省２个花岗岩赤红壤的微形态研究表明：骨骼颗粒以蚀变石英为主：呈斑晶状分布;土体棱块状结构发育明显,微团聚体轻微发育;细粒物质以其红色、具轻微双折射现象为主要特征;土体中亦可见少量铁锰结核体及粉质体的出现。 相似文献
14.
Yu. N. Vodyanitskii 《Russian Agricultural Sciences》2009,35(3):185-188
It is suggested to characterize concretions in contaminated soils by geochemical modules based on the affinity of heavy metals and metalloids with carrier phases, which is indicated by significant positive correlation coefficients between them. The modules include molar ratios Cu: Fe, Ni: Fe, As: Fe, P: Fe, and Pb: Mn, with increase of which the strength of fixation of the trace element by the corresponding carrier phase decreases. 相似文献
15.
在50 kpa、100 kpa、150 kpa、200 kpa四种固结压力下,分别对双王城水库坝基土原状土样进行了动三轴试验,得到了最大动剪切模量Gmax和GGdmax γd曲线以及λλmax γd曲线,可供岩土和其他水利工程的地震安全性评价工作参考和借鉴。 相似文献
16.
Klingelhöfer G Morris RV Bernhardt B Schröder C Rodionov DS de Souza PA Yen A Gellert R Evlanov EN Zubkov B Foh J Bonnes U Kankeleit E Gütlich P Ming DW Renz F Wdowiak T Squyres SW Arvidson RE 《Science (New York, N.Y.)》2004,306(5702):1740-1745
Mossbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions. 相似文献
17.
Squyres SW Knoll AH Arvidson RE Clark BC Grotzinger JP Jolliff BL McLennan SM Tosca N Bell JF Calvin WM Farrand WH Glotch TD Golombek MP Herkenhoff KE Johnson JR Klingelhöfer G McSween HY Yen AS 《Science (New York, N.Y.)》2006,313(5792):1403-1407
The Mars Exploration Rover Opportunity has spent more than 2 years exploring Meridiani Planum, traveling approximately 8 kilometers and detecting features that reveal ancient environmental conditions. These include well-developed festoon (trough) cross-lamination formed in flowing liquid water, strata with smaller and more abundant hematite-rich concretions than those seen previously, possible relict "hopper crystals" that might reflect the formation of halite, thick weathering rinds on rock surfaces, resistant fracture fills, and networks of polygonal fractures likely caused by dehydration of sulfate salts. Chemical variations with depth show that the siliciclastic fraction of outcrop rock has undergone substantial chemical alteration from a precursor basaltic composition. Observations from microscopic to orbital scales indicate that ancient Meridiani once had abundant acidic groundwater, arid and oxidizing surface conditions, and occasional liquid flow on the surface. 相似文献
18.
Herkenhoff KE Squyres SW Arvidson R Bass DS Bell JF Bertelsen P Ehlmann BL Farrand W Gaddis L Greeley R Grotzinger J Hayes AG Hviid SF Johnson JR Jolliff B Kinch KM Knoll AH Madsen MB Maki JN McLennan SM McSween HY Ming DW Rice JW Richter L Sims M Smith PH Soderblom LA Spanovich N Sullivan R Thompson S Wdowiak T Weitz C Whelley P 《Science (New York, N.Y.)》2004,306(5702):1727-1730
The Microscopic Imager on the Opportunity rover analyzed textures of soils and rocks at Meridiani Planum at a scale of 31 micrometers per pixel. The uppermost millimeter of some soils is weakly cemented, whereas other soils show little evidence of cohesion. Rock outcrops are laminated on a millimeter scale; image mosaics of cross-stratification suggest that some sediments were deposited by flowing water. Vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis. Microscopic images support the hypothesis that hematite-rich spherules observed in outcrops and soils also formed diagenetically as concretions. 相似文献
19.
以野生欧李Prunus humilis为试材,采用不同浸提剂（水,1 mol·L－1氯化钠,20 g·kg－1乙酸,50 g·kg－1盐酸）逐级提取方法,研究了欧李实生类型（大果型和小果型）和嫁接类型（高位嫁接和低位嫁接）果实采后常温储藏过程中不同形态钙的质量分数及组成比率的变化,为欧李钙素研究和质量评价提供基础资料。结果表明：采收期果实中不同形态钙的提取率为98.24% ~ 99.32%,且以水溶钙和果胶钙形态组成为主,约占总钙量的70%左右;大果型果实中果胶钙质量分数显著高于小果型果实（P＜0.01）,小果型果实中水溶钙、磷酸钙和草酸钙质量分数显著高于大果型果实（P＜0.01）,小果型果实中钙总量显著高于大果型果实（P＜0.05）;与实生类型比较,嫁接类型果实中水溶钙提取率增加,果胶钙提取率下降;采后果实储藏后水溶钙形态组成比率增加,果胶钙和草酸钙形态组成比例下降,磷酸钙和剩余钙形态组成比例无明显改变。图4表1参17 相似文献
20.
During activation of visceral smooth muscle there is an increase in cytosolic-free calcium, but the source (intracellular calcium release or calcium influx), kinetics, and stoichiometry of this increase have not been determined. Here, the fluorescent indicator, quin2-acetoxymethyl ester, was used to measure directly cytosolic-free calcium during contraction of isolated stomach muscle cells induced by the two neuropeptides cholecystokinin-octapeptide and Met-enkephalin as well as acetylcholine. An increase in cytosolic-free calcium was seen that was (i) dependent on the concentration of contractile agonist, (ii) derived from intracellular sources (that is, not significantly affected by removal of ambient calcium or addition of a calcium channel blocker), and (iii) kinetically and stoichiometrically related to net calcium efflux and contraction. In contrast, the increase in cytosolic-free calcium induced by depolarizing concentrations of potassium was caused by influx of calcium through voltage-dependent calcium channels. 相似文献