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1.
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
2.
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
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.
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
5.
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
6.
Four Paleozoic bivalved genera are assigned to the new molluscan class Rostroconchia: Eopteria, Euchasma, Conocardium, and Pseudoconocardium. These mollusks have ani uncoiled univalved larval shell; an untorted bivalved adult shell; no hinge teeth, ligament, or adductor muscles; and a fused, almost inflexible. hinge. Rostroconchianis developed separately from the pelecypods through the ribeirioids, but are regarded as more closely related to the Pelecypoda and Scaphopoda than to other known classes of mollusks. 相似文献
7.
We have attempted to demonstrate a possible relationship between phosphorite deposition and an increase in marine denitrification. The studies of others indicate that major phosphorite deposits are often associated with black shales and accumulated during only a few epochs of geologic history. Some of these epochs were also marked by mass extinctions of organisms. Such events are not as precisely nor as strongly correlated as we would like. Nevertheless, the correlations are strong enough to encourage further consideration of the effects of possible changes in the rate of denitrification within ancient oceans on the origin of phosphorite deposits, the extinctions of marine organisms, variations in the overall level of biological activity, and temporal fluctuations in the organic carbon content of sedimentary rocks (36). 相似文献
8.
Weddellite (calcium oxalate dihydrate) and calcite (anhydrous calcium carbonate phase) are components of concretions in the renal sac of the ascidian tunicate Molgula manhattensis. The presence of weddellite along with urate in the concretions suggests a resemblance to human kidney stones, although, unlike the latter, the concretions in Molgula do not seem to be pathologic deposits. 相似文献
9.
10.
Stanley SM 《Science (New York, N.Y.)》1969,166(3905):634-635
Oblique and chevron-like ridges on the shell surfaces of certain burrowing bivalve mollusks grip the sediment during shell-rocking movements to aid in sediment penetration. These ridges (characterized by steep dorsal slopes and gentle ventral slopes) have evolved through convergence in several families in association with particular behavioral and ecological traits. 相似文献
11.
In sewage sludge composting,adding ash from stove(FA20)inactivated active Cu effectively and the results were significantly better than control.For Zn,Mn,Pb and Cd,satisfying results was achieved by adding ash from stove and phosphorite powder(FA20,PR10),phosphorite powder and lime(PR15,CL10),ash from stove and phosphorite powder(FA10,PR10),and ash from stove and peat(FA20,PT10).Based on their effects of inactivating available forms of heavy metals,ash from stove,phosphorite powder and peat were supposed to be effective inactivators with optimum percentages of 20%,15% and 10%(FA20,PR15,PT10). 相似文献
12.
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
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14.
Modern sea-floor phosphorite nodules sampled from off the coast of Peru are shown to grow at rates of millimeters per thousand years in spite of the fact that the measured accumulation rates of the underlying sediment are two to four orders of magnitude faster. Phosphate nodules grow downward into soft sediment, and the rates of phosphorus accumulation into nodules are approximately equal to the upward diffusive flux of dissolved phosphate inferred from pore water profiles. These results demonstrate that phosphorus in nodules originates from regeneration in sediments rather than as a result of direct precipitation from bottom waters. 相似文献
15.
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
16.
The origin and possible antiquity of faunas at deep-sea hydrothermal vents and seeps have been debated since their discovery. We used the fossil record of seep mollusks to show that the living seep genera have significantly longer geologic ranges than the marine mollusks in general, but have ranges similar to those of deep-sea taxa, suggesting that seep faunas may be shaped by the factors that drive the evolution of life in the deep sea in general. Our data indicate that deep-sea anoxic/dysoxic events did not affect seep faunas, casting doubt on the suggested anoxic nature and/or global extent of these events. 相似文献
17.
Messenger S Keller LP Stadermann FJ Walker RM Zinner E 《Science (New York, N.Y.)》2003,300(5616):105-108
We have identified six circumstellar silicate grains within interplanetary dust particles (IDPs). Their extrasolar origins are demonstrated by their extremely anomalous oxygen isotopic compositions. Three 17O-rich grains appear to originate from red giant or asymptotic giant branch stars. One 16O-rich grain may be from a metal-poor star. Two 16O-poor grains have unknown stellar sources. One of the grains is forsterite, and two are amorphous silicate "GEMS" (glass with embedded metal and sulfides), which is consistent with astronomical identifications of crystalline and amorphous silicates in the outflows of evolved stars. These observations suggest cometary origins of these IDPs and underscore the perplexing absence of silicates among circumstellar dust grains from meteorites. 相似文献
18.
硅酸盐细菌对磷矿石风化作用机理的探讨 总被引：1，自引：0，他引：1
[目的]以1株硅酸盐细菌为例研究微生物对磷矿石的风化作用。[方法]在装有100目磷矿石粉的液体培养基中接种硅酸盐细菌,按不同时间取样处理后,用原子吸收光谱仪测定培养液上清液中Ca2+的质量浓度,磷钼比色法测定水溶性磷(DP)的质量浓度;细菌作用后的残留物用电子探针、透射电镜和能谱仪进行分析。[结果]结果表明,硅酸盐细菌对磷矿石粉风化后,培养液中Ca2+和DP的质量浓度随作用时间延长而增加,细菌作用后的矿粉颗粒浑圆,边缘模糊不清,菌体及有机物对矿物有较强的剥蚀作用。[结论]经分析认为细菌对磷矿石的风化作用源自细菌生长导致的机械破坏作用、胞外分泌物的生化降解作用以及多种因素之间的协同作用。 相似文献
19.
A method is described for increasing luminescence in poly(p-phenylene vinylene) (PPV) light-emitting diodes. Cis linkages were engineered into the PPV chain. These linkages interrupt conjugation and interfere with the packing of the polymer chains, which results in the formation of amorphous PPV. Large-area electroluminescent devices were prepared from this polymer. Devices made of an aluminum electrode, PPV as the luminescent layer, and an electron-transporting layer have internal quantum efficiencies of 2 percent, a turn-on voltage of 20 volts, and can carry current densities of 2000 milliamperes per square centimeter. The current density is at least an order of magnitude higher than previously obtained. 相似文献
20.
The fossil record of fungi and lichens is scarce. Here we report the discovery of lichen-like fossils, involving filamentous hyphae closely associated with coccoidal cyanobacteria or algae, preserved in marine phosphorite of the Doushantuo Formation (between 551 and 635 million years old) at Weng'an, South China. These fossils indicate that fungi developed symbiotic partnerships with photoautotrophs before the evolution of vascular plants. 相似文献