Aromatic hydrocarbons in the murchison meteorite

Polynuclear aromatic hydrocarbons in the Murchison meteorite have been identified by the combined techniques of gas chromatography and mass spectrometry. The distribution of the aromatic compounds suggests that they are the products of a high-temperature synthesis.     

Spatially resolved organic analysis of the allende meteorite

The distribution of polycyclic aromatic hydrocarbons(PAHs) in the Allende meteorite has been probed with two-step laser desorption/laser multiphoton ionization mass spectrometry. This method allows direct in situ analysis with a spatial resolution of 1 square millimeter or better of selected organic molecules. Spectra from freshly fractured interior surfaces of the meteorite show that PAH concentrations are locally high compared to the average concentrations found by wet chemical analysis of pulverized samples. The data suggest that the PAHs are primarily associated with the fine-grained matrix, where the organic polymer occurs. In addition, highly substituted PAH skeletons were observed. Interiors of individual chondrules were devoid of PAHs at our detection limit(about 0.05 parts per million).     

The organic content of the Tagish Lake meteorite

The Tagish Lake meteorite fell last year on a frozen lake in Canada and may provide the most pristine material of its kind. Analyses have now shown this carbonaceous chondrite to contain a suite of soluble organic compounds (approximately 100 parts per million) that includes mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic hydrocarbons. The insoluble carbon exhibits exclusive aromatic character, deuterium enrichment, and fullerenes containing "planetary" helium and argon. The findings provide insight into an outcome of early solar chemical evolution that differs from any seen so far in meteorites.     

Origin and evolution of prebiotic organic matter as inferred from the Tagish Lake meteorite

The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites' asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration. At least some molecules of prebiotic importance formed during the alteration.     

Amino Acid analyses of the murchison, murray, and allende carbonaceous chondrites

Three carbonaceous chondrites were examined for water-extractable amino acids. The Murchison Murray specimens were found to be of similar amino acid composition. This similarity suggests that these amino acids in are indigenous to type II carbonaceous chondrites. The Allende (type III) carbonaceous chondrite was found to be essentially devoid of amino acids on the basis of on identical analysis.     

Templating organic semiconductors via self-assembly of polymer colloids

A route for producing semiconducting polymer blends is demonstrated in which a doped pi-conjugated polymer is forced into a three-dimensionally continuous minor phase by the self-assembly of colloidal particles and block copolymers. The resulting cellular morphology can be viewed as a high-internal phase polymeric emulsion. Compared with traditional blending procedures, this process reduces the percolation threshold for electrical conductivity by a factor of 10, increases the conductivity by several orders of magnitude, and simultaneously improves thermal stability. Following this route, new applications can be envisaged for semiconducting polymer blends that require only minimal concentrations of doped pi-conjugated polymer.     

The convergence of synthetic organic and polymer chemistries

Several recent conceptual advances, which take advantage of the design criteria and practical techniques of molecular-level control in organic chemistry, allow preparation of well-defined polymers and nanostructured materials. Two trends are clear: the realization that synthesis of complex macromolecules poses major challenges and opportunities and the expectation that such materials will exhibit distinctive properties and functions. Polymer synthesis methods now being developed will yield well-defined synthetic macromolecules that are capable of mimicking many of the features of proteins (for example, three-dimensional folded structure) and other natural materials. These macromolecules have far-reaching potential for the study of molecular-level behavior at interfaces, in thin films, and in solution, while also enabling the development of encapsulation, drug-delivery, and nanoscale-patterning technologies.     

Melting relations of the aliende meteorite

The proportions of major oxides in the Allende carbonaceous chondrite after partial reduction are remarkably similar to those in possible mantle material of the earth. When heated, the Allende meteorite generates a sulfide melt (47 percent iron, 25 percent nickel, and 24 percent sulfur by weight), a ferrobasaltic melt, and olivine with or without pyroxene, over a wide pressure range (5 to 25 kilobars). The silicate melt contains more sodium and less titanium than lunar ferrobasalts. An aggregate of the Allende chondrite rich in calcium and aluminum produces silica-undersaturated, calcium-rich melt and spinel over a wide pressure and temperature range. From these studies, it is suggested that the earth's core contains significant amounts of both nickel and sulfur and that a 3 : 2 mixture of Allende bulk sample and calcium- and aluminum-rich aggregates is closer in major element abundances than either of these components to the average composition of the moon.     

Exsolution in ferromagnesian olivine of the divnoe meteorite

Ferromagnesian olivine, one of the most common minerals in the solar system, has been widely regarded as a continuous solid solution, although several thermodynamic analyses have suggested the possibility of a miscibility gap at low temperatures. Natural ferromagnesian olivine from the Divnoe meteorite contains compositionally different exsolution lamellae, providing direct evidence for the existence of a miscibility gap in iron-magnesium olivine solid solutions.     

低分子量有机酸及其共聚物去除土壤重金属研究

为探究低分子有机酸以及其共聚物对土壤中重金属的去除效果,通过振荡淋洗法研究了富马酸和丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物在不同浓度、pH和时间条件下对土壤中Cd、Pb和Zn的去除率,并采用传统人工螯合剂乙二胺四乙酸做对比。结果表明,土壤中Cd、Pb和Zn的去除率随着有机酸浓度的增加呈现先上升后趋于平稳的趋势。丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物和富马酸在浓度为10 g·L-1时对Cd、Pb和Zn的去除率分别为54.75%、69.60%、51.42%和42.03%、55.00%、46.97%,乙二胺四乙酸对Cd和Pb的去除率与富马酸趋于一致,但其对Zn的去除率显著低于富马酸(P0.05),仅为34.11%。两种有机酸对重金属去除率受pH的影响较大,其在pH为4~5时能有效去除土壤中Cd、Pb和Zn;富马酸在60 min时达到最大去除率,而丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物在大于120 min时去除率最高。此外,经过两种有机酸和人工螯合剂乙二胺四乙酸淋洗后,土壤中Cd、Pb和Zn的可交换态和碳酸盐结合态含量大幅度下降。因此,富马酸和丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物对重金属污染土壤具有潜在修复能力。     

Olivine-garnet transformation in a meteorite

Garnet has been identified for the first time as a meteorite mineral in the Coorara chondrite from Western Australia. It replaces olivine grains in a 1-millimeter veinlet traversing the body of the meteorite. The associated olivine has abnormally low birefringence, which suggests a highly shocked condition. Microprobe analyses do not distinguish the garnet from the associated olivine, which has the composition (Mg(.75)Fe(.25))(2) SiO(4); the garnet may have the composition Mg(3)Fe(2)Si(3)O(12) but be unresolvable from the accompanying olivine, or alternatively is nonstoichiometric. Transformation of olivine to garnet under high pressure could have significant implications for the phase composition of the Earth's mantle.     

Evidence for a phytotoxic hydroxy-aluminum polymer in organic soil horizons

The toxicity of A1 that has been mobilized in soil, streams, and lakes through acid deposition primarily has been attributed to mononuclear A1 species. Polynuclear A1 species are more toxic than mononuclear species, but they have not been considered to be significant in the environment. Aluminum-27 nuclear magnetic resonance (NMR) spectra of forested spodosol soil horizon samples show the presence of polynuclear A1O(4)A1(12)(OH)(24)(H(2)O)(12)(7+). The AlO(4)A1(12)(OH)(24)(H(2)O)(12)(7+) species accounted for 30 percent of the aqueous A1 observable by NMR, and this could make a significant contribution to the toxicity of the A1 in these soils.     

Pyroxene-garnet transformation in coorara meteorite

Majorite is a new garnet in a veinlet of the Coorara meteorite. Its chemical composition is compatible with derivation mostly from original pyroxene, not from olivine as originally reported. Silicon is partly in sixfold coordination. Ringwoodite, a spinel of olivine composition, occurs as purple grains set in a matrix of fine-grained garnet. The similar mineralogy and texture of the Coorara and Tenham meteorites suggest a common parent body.     

The frequency of meteorite falls on the Earth

Photographic observations from a network of 60 cameras in western Canada are used to derive the influx rate of meteorites on the earth's surface, the first time instrumental data have been used for this purpose. Forty-three observed events are believed to have dropped between 0.1 and 12 kilograms of meteorites each. The flux values are corrected for a minor latitude effect and agree with earlier estimates near 10 kilograms but vary more slowly with mass. Eight events per year drop at least 1 kilogram of meteorites in an area of 10(6) square kilometers.     

A monoclinic post-stishovite polymorph of silica in the shergotty meteorite

A post-stishovite phase of silica was identified in the Shergotty meteorite by x-ray diffraction and field emission scanning electron microscopy. The diffraction pattern revealed a monoclinic lattice, similar to the baddeleyite-structured polymorph with the cell parameters a = 4.375(1) angstroms, b = 4.584(1) angstroms, c = 4. 708(1) angstroms, beta= 99.97(3), rho = 4.30(2) grams per cubic centimeter, where the numbers in parentheses are the maximum deviations. Transmission electron microscopy investigations indicate the presence of the alpha-lead dioxide-like polymorph, stishovite, and secondary cristobalite in the same silica grain. The mixture of high-density polymorphs suggests that several post-stishovite phases were formed during the shock event on the Shergotty parent body.     

Amino acids indigenous to the murray meteorite

Analysis of the Murray meteorite, a type II carbonaceous chondrite, has led to the identification of 17 amino acids. For seven of the amino acids nearly equal amounts of the D and L isomers are present, and 11 of the amino acids are not found in protein. These results suggest that these amino acids, like the amino acids of the Murchison meteorite, are extraterrestrial in origin.     

有机高分子材料添加对沼渣颗粒肥理化特性的影响

采用造粒方法,将羟乙基纤维素、羟丙甲基纤维素、聚乙烯醇及羧甲基纤维素钠4种有机高分子材料应用到沼渣颗粒造粒中,测定沼渣颗粒肥的粒径、成球率、颗粒强度、吸水率以及保水率等指标,研究有机粘结剂的种类及其含量对沼渣颗粒肥的影响规律。结果表明:沼渣颗粒成球率方面,聚乙烯醇作为粘结材料其质量分数为9.09%时,制备的牛粪沼渣颗粒肥造粒成球率达到82.31%。在沼渣颗粒强度方面,羟乙基纤维素质量分数为6.25%时制备的肥料颗粒最低强度为6.3N;聚乙烯醇质量分数为9.09%时,沼渣肥料颗粒强度可以达到90.3N。在沼渣颗粒肥吸水方面,牛粪沼渣颗粒肥的吸水能力与有机粘结材料的质量分数呈正相关关系。沼渣颗粒肥崩解时间试验显示,羟乙基纤维素适用于制备速效沼渣颗粒肥料,聚乙烯醇适用于制备缓释沼渣颗粒肥料。