992 resultados para RARE EARTH ELEMENTS


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Metabolic profiles caused by rare earth complex were investigated using NMR and ICP-MS techniques. Male and female Wistar rats were treated orally with Changle (A kind of rare earth complex applied in agriculture to raise the production of crops) at dose of 2, 5 and 20 mg (.) kg(-1) body weight/day respectively for 90 d. Urine and serum samples are collected on 90 d. The relative concentrations of important endogenous metabolites in urine and serum are determined from H-1 NMR spectra and the contents of the four rare earth elements ( La, Ce, Pr and Nd) constituting Changle in the serum samples are measured by ICP-MS technique. Changle-induced renal and liver damage in rats is found based on the increase in the amounts of the amino acids, trimethylamine N-oxide, N, N-dimethyglycine, dimethylamine, succinate, aketoglutarate and ethanol as well as rare earth concentrations. The similarities and differentiations are found in the alteration patterns of metabolites and rare earth concentrations in serum.

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The effect of La3+ on the electrochemical behavior and structure of heme undecapeptide-microperoxidase-11 (MP-11)-in the aqueous solution was investigated using cyclic voltammetry, circular dichroism (CD) and UV-vis absorption spectrometry. It was found for the first time that La3+ would promote the electrochemical reaction of MP-11 at the glassy carbon (GC) electrode. This is mainly due to the fact that La3+ would induce more beta-turn and alpha-helical conformations from the random coil conformation of MP-11 and increase the non-planarity of the heme.

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Recent important applications of inductively coupled plasma mass spectrometry in biological samples analysis are reviewed. The sample preparation, sample introduction techniques, interference correction and typical applications are introduced in detail with 154 references.

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An information system for inductively coupled plasma atomic emission spectrometry (TCP-BES) in MS Windows environment was developed based on the previous work in the laboratory. The system contains the data of about 28 000 spectral lines and a function of ICP spectral simulation,so it would be very helpful for line selection. The system also contains the Kalman filter and factor analysis programmes written with MS Visual Basic(version 4.0), which can be used for spectral interference correction and peak position optimization. A large amount of real spectral scanning data of rare earth elements were included in the system for user's references. All these characteristics made the system more useful and practical.

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From the chemical bond viewpoint, second-order nonlinear optical (NLO) tensor coefficients of the family of new oxoborates Ca4ReO(BO3)(3) (CReOB, Re = La, Nd, Sm, Gd, Er, and Y) have been theoretically predicted. The d(11) tensor coefficient of CReOB is predicted to be -11 d(36)(KDP), which is the largest d(ij) tensor that has been found in borate crystals. From the structural characteristic of CReOB, we find the isolated BO33- clusters play a dominant role in contributions to the total nonlinearity, and the largest d(11) tensor of CReOB-type crystals is also ascribed to these BO33- clusters. We also find the NLO property of this family does not change dramatically for different rare-earth elements. The details of the calculation of CGdOB only are presented.

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A series of LnSrNiO(4)(A(2)BO(4), Ln = La, Pr, Nd, Sm, Gd) mixed oxides with K2NiF4 structure, in which A-site(Sr) was partly substituted by individual light rare earth element, was prepared. The solid state physico-chemical properties including crystal structure, defect structure, IR spectrum, valence state of H-site ion, nonstoichiometric oxygen, oxygenous species, the properties of oxidation and reduction etc. as well as the catalytic behavior for NO decomposition on these mixed oxides were investigated. The results show that all of these mixed oxide catalysts have high activity for the direct decomposition of NO(at 900 degrees C the conversion of NO is more than 90%). The effect of the substitution of light rare earth elements at A-site on catalytic behavior for NO decomposition was elucidated.

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A new and efficient extraction method of endohedral metallofullerenes, especially of rare-earth elements encapsulated metallofullerenes, has been reported in this paper. Soxhlet-extraction of raw soot with toluene was used in the first step to wash away most accompanying C-60, C-70. Then pyridine was chosen as solvent to obtain high-temperature and high pressure extract. Two kinds of extract were analysed by DEI-MS and LDI-MS, the results indicate that this two-step method can provide the extract which has the highest fraction of endohedral metallofullerenes. So it will greatly simplify the following separation and purification processes of metallofullerenes.

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Lanthanide chlorides have been found to catalyze the Diels-Alder synthesis of 2-butoxy-3, 4-dihydro-2H-pyran and several norbornene derivatives under mild conditions. In particular, the heavier lanthanide chlorides are very active catalysts for some (4 + 2) cycloaddition reactions. The catalyst activities and selectivities generally increase with increasing atomic number of the rare earth elements.

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The Research on Electroanalytical chemistry in China started mainly from the beginning of new China in 1949. It has already good basis and development nowadays. A review with references to the end of seventies has been published in "Reviews in Analytical Chemistry" 1) and in a book titled "Fifty years of Chinese Chemistry" edited by the Chinese Chemical Society in 1985 2). Since then more than thousand papers have been published, and it is impossible and also not necessary to describe all of them. This review only deals with the main progress of electroanalytical chemistry in China in recent years. Some new developed methodologies will be reviewed by S. Dong in the next article.

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Sediment samples were collected from the lower channel of the Yangtze River and the Yellow River and the contents of rare earth elements (REEs) were measured. In addition, some historical REEs data were collected from published literatures. Based on the delta Eu-N-I REEs pound plot, a clear boundary was found between the sediments from the two rivers. The boundary can be described as an orthogonal polynomial equation by ordinary linear regression with sediments from the Yangtze River located above the curve and sediments from the Yellow River located below the curve. To validate this method, the REEs contents of sediments collected from the estuaries of the Yangtze River and the Yellow River were measured. In addition, the REEs data of sediment Core 255 from the Yangtze River and Core YA01 from the Yellow River were collected. Results show that the samples from the Yangtze River estuary and Core 255 almost are above the curve and most samples from the Yellow River estuary and Core YA01 are below the curve in the delta Eu-N-I REEs pound plot. The plot and the regression equation can be used to distinguish sediments from the Yangtze River and the Yellow River intuitively and quantitatively, and to trace the sediment provenance of the eastern seas of China. The difference between the sediments from two rivers in the delta Eu-N-I REEs pound plot is caused by different mineral compositions and regional climate patterns of the source areas. The relationship between delta Eu-N and I REEs pound is changed little during the transport from the source area to the river, and from river to the sea. Thus the original information on mineral compositions and climate of the source area was preserved.

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Peridotites from the southern Mariana forearc were sampled on the landward trench slope of the Izu-Bonin-Mariana (IBM) subduction zone by dredging. These mantle wedge peridotites underwent hydration by fluid derived from a dehydrated descending slab, and later interacted with seawater after emplacement at or near the seafloor. This study investigates how these two different rock-fluid interaction processes influenced trace element distribution in the southern Mariana forearc peridotites. We measured trace element concentrations of peridotites from the southern Mariana forearc. The southern Mariana forearc peridotites are characterized by a distinct seawater-like REE pattern with an obvious negative Ce anomaly, and La shows good correlation with other REEs (except Ce). In addition, there is a great enrichment of U, Pb, Sr and Li elements, which show a distinct positive anomaly relative to adjacent elements in the multi-element diagram. For the seawater-like REE pattern, we infer that REEs are mainly influenced by seawater during peridotite-seawater interactions after their emplacement at or near the seafloor, by serpentinization or by marine weathering. Furthermore, the anomalous behavior of Ce, compared with other rare earth elements in these samples, may indicate that they have undergone reactions involving Ce (IV) when the peridotites interacted with seawater. Positive U, Pb, Sr and Li anomalies are inferred to be related to seawater and/or fluids released during dehydration of the subducting slab.

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The variolitic andesite from the Susong County in the Dabie Mountains implies that it was erupted in water. The mineralogy of the varioles is primarily radiate plagioclase (albite sind oligoclase), with little pyroxene, hornblende and quartz (derived from alteration). The pyroxene, hornblende and quartz are in the interstices between plagiocalse. The matrix consists of glass, hornblende, chlorite, epidote and zoisite. It is clearly subjected an extensive alteration. The andesite has an uncommon chemical composition. The SiO2 content is about 56.8%, TiO2 = 0.9%, MgO = 6.4%, Fe2O3 (tot) = 6.7%similar to 7.6%, 100Mg/(Mg + Fe) = 64.1 similar to 66.2. Mg-# is significantly high. The andesite has high abundances of large-lithophile trace elements (e.g. K, Ba. Sr, LREE), e.g. La/Nb = 5.56 similar to 6.07, low abundances of high-strength-field elements (HFSE e.g. Ta, Nb, P, Ti), particularly Ta and Nb strongly depleted. These are consistent with the characteristics of subduction-related magmas. In the spider diagram of trace elements, from Ce to right hand, the abundances of elements decrease quickly, showing a character of the continental margins. There has a strong punishment of light-rare-earth elements, with a significant diffraction of REEs (the mean value of (La/Yb)(N) is 32.84). No Eu anomaly, but there are anomaly high (La/Yb)(N) = 28.63 similar to 36.74, (La/Y)(N) = 70.33 similar to 82.4. The elements Y and Yb are depleted greatly, Y<20 g/g, Y-N = 2.74 similar to 2.84, Yb-N = 2.18 similar to 2.35. From the La-(La/Sm) diagram, the andesite is derived from partial melting. But the epsilone value of Nd is - 18.7 similar to -19.2, so that the material source may be the mantle materials affected by the crustal materials. The Nd model age is 1.9 Ga indicating that the variolitic basaltic andesite was resulted from the mantle wedge of North China block, which had the Nd model age of 2.5Ga, when the Yangze block which had the Nd model age of 1.7Ga subducted beneath it. So the variolitic andesite has characteristics of the island-are volconic rocks oil a continental basement in the vicinity of the destructive continental margin.

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Based upon analyses of grain-size, rare earth element (REE) compositions, elemental occurrence phases of REE, and U-series isotopic dating, the sediment characteristics and material sources of the study area were examined for the recently formed deep-sea clays in the eastern Philippine Sea. The analytical results are summarized as follows. (1) Low accumulation rate, poor sorting and roundness, and high contents of grains coarser than fine silt indicate relatively low sediment input, with localized material source without long distance transport. (2) The REE Contents are relatively high. Shale-normalized patterns of REE indicate weak enrichment in heavy REE (HREE), Ce-passive anomaly, and Eu-positive anomaly. (3) Elemental occurrence phases of REE between the sediments with and without crust are similar. REE mainly concentrate in residual phase and then in ferromanganese oxide phase. The light REE (LREE) enrichment, Ce-positive anomaly, and Eu-positive anomaly occur in residual phase. Ferromanganese oxide phase shows the characteristics of relatively high HREE content and Ce-passive anomaly. (4) There are differences in each above mentioned aspect between the sediments with and without ferromanganese crust. (5) Synthesizing the above characteristics and source discriminant analysis, the study sediments are deduced to mainly result from the alteration of local and nearby volcanic materials. Continental materials transported by wind and/or river (ocean) flows also have minor contributions.

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Volcanic rocks both from the northern East China Sea (NECS) shelf margin and the northern Okinawa Trough are subalkaline less aluminous, and lower in High Field Strength Elements (HFSE). These rocks are higher in Large Ion Lithophile Elements (LILE), thorium and uranium contents, positive lead anomalies, negative Nb-Ta anomalies, and enrichment in Light Rare Earth Elements (LREE). Basalts from the NECS shelf margin are akin to Indian Ocean Mid-Ocean Ridge Basalt (MORB), and rhyolites from the northern Okinawa Trough have the highest Pb-207/Pb-208 and Pb-208/Pb-204 ratios. The NECS shelf margin basalts have lower Sr-87/Sr-86 ratios, epsilon(Nd) and sigma O-18 than the northern Okinawa Trough silicic rocks. According to K-40-Ar-40 isotopic ages of basalts from the NECS shelf margin, rifting of the Okinawa Trough may have been active since at least 3.65-3.86 Ma. The origin of the NECS shelf margin basalt can be explained by the interaction of melt derived from Indian Ocean MORB-like mantle with enriched subcontinental lithosphere. The basalts from both sides of the Okinawa Trough may have a similar origin during the initial rifting of the Okinawa Trough, and the formation of basaltic magmas closely relates to the thinning of continental crust. The source of the formation of the northern Okinawa Trough silicic rocks was different from that of the middle Okinawa Trough, which could have been generated by the interaction of basaltic melt with an enriched crustal component. From the Ryukyu island arc to East China, the Cenozoic basalts have apparently increasing trends of MgO contents and ratios of LREE to Heavy Rare Earth Elements (HREE), suggesting that the trace element variabilities of basalts may have been influenced by the subduction of the Philippine Sea plate, and that the effects of subduction of the Philippine Sea plate on the chemical composition of basaltic melts have had a decreasing effect from the Ryukyu island arc to East China.

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Tazhong-Bachu region is located in the Western Tarim basin.The early Permian magmatic rocks occur in the earth surface of Tazhong-Bachu region are mainly distributed in Kepintag,Mazhartag and Wajilitag region. There are a lot of wells, in which researchers found the early Permian magmatic rocks,in desert cover area.Most magmatic rocks are basic rocks, a few of which are ultrabasic rocks and intermediate-acid magmatic rocks.The ultrabasic rocks are are mainly occur in the Cryptoexplosive Breccia Pipes ,which is located in the volcanic complex body of Wajilitag region.The basic rocks can be divided into three rock types:The first type of the magmatic rocks in Tazhong-Bachu region is volcanic rock ,which occurs in the Lower Permian Kupukuziman Formation and Kaipaizileike Formation. Most Volcanic rocks are basalts,a few of which are volcanic breccias and pyroclastic rocks.The basalts are distributed in stratiform occurrences and interbeded the clastic rocks in Kepintag region.The attitudes of the basalts are nearly horizontal.Columnar Joints, gas pore textures and amygdaloidal structure are to develop in basalts.The second type of the magmatic rocks in Tazhong-Bachu region is diabase,which occurs in Mazhartag region.Diabase dike swarms occur in the stratums of Silurian, Devonian, Carboniferous and Lower Permian.They make from NNW direction to SSE direction, the obliquity of stratum is greater than 60°, and the dike thickness is form several cm to several meters. Diabasic texture is found in the rocks .The first type of the magmatic rocks in Tazhong-Bachu region are gabbro- pyroxenite rocks ,which occur in the Wajilitag igneous complex body. The intermediate-acid magmatic rocks, which are mainly syenites, are located in Mazhartag and Wajiltag region. But they are small in the whole Tazhong-Bachu region.There are intermediate-acid magmatic rocks,which are mainly dacite,in the northeast part of the wells in Tazhong-Bachu region.But ,it is not found in earth surface.Through systematical geochemical research of early Permian magmatic rocks,which are distributed in Kepintag,Mazhartag, Wajilitag region and the wells such as F1 well、Z1 well、Z13 well、TZ18 well、H3 well、H4 well et al., the focus on the geochronologic characteristics, the main element,trace element and REE geochemistry, the mineralogic characteristics, the Sr-Nd and Pb isotopic characteristics are put forward. The main points are: 1、A combined study of CL imaging and LA-ICP-MS U-Pb dating were carried out for zircon grains of the magmatic rocks in the Tazhong-Bachu region from the Tarim basin.The results of the systematic zircon LA-ICP-MS U-Pb dating reveal 272±6Ma to 291±10Ma for the magamatic rocks. It indicated that Early Permian is an important period of magmatic acvivity in the Tazhong-Bachu region. 2、There are a big hunch in the curves of primitive mantle-normalized trace element concentrations in the early Permian magmatic rocks from Kepintag, Mazhartag, Wajilitag region and the 14 wells. Light rare earth elements are comparatively rich and heavy rare earth elements are comparatively poor. The slope rates are same between light rare erath elements and heavy rare earth elements. It is not like the curves of the basalts in the convergent margin of plate , in which the slope rates of light rare erath elements is bigger than the alope rates of heavy rare erath elements, and the curves of heavy rare earth elements are comparatively flat. The magmatic rocks of Tazhong-Bachu region rarely have the characteristics of the basalts in the convergent margin of plate, which is that Tantalum, Niobium and Titanium are much poor, and Zirconium, Hafnium and Phosphorus are moderately poor. The magamatic rocks are mostly alkaline, which is indicated by the dots of the (Na2O+K2O)-SiO2 identification diagram. All of these indicate that the early Permian magmatic rocks were formed in an extension environment of intraplate. 3、The Thorium abundance is high and Tantalum abundance is low in most magmatic rocks from Tazhong-Bachu reguion, which is formed for crustal contamination.In the Th/Yb-Ta/Yb identification diagram,most dots are in the region, which means active continental margin, but a few dots are in the region, which means mantle source. It indicated the feeding of continental crust materials. 4、The magnesium content of the olvines from Wagilitag region is richest, and the olvines from Kepintag region is poorest in the tree region. 5、Through the the Sr-Nd and Pb isotopic study of the basalts and diabases from the F1 well core, Z1 well core, Z13 well core,TZ18 well core, and the basalts,gabbros, diabases(diabase-prophyrites) and pl-peridotites from Kepintag,Mazhartag, Wajilitag region , it indicated that all isotopic data is similar and close to enriched mantle.