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Metal Content (metal + content)
Kinds of Metal Content Selected AbstractsCHANGES IN THE METAL CONTENT OF HUMAN HAIR DURING DIAGENESIS FROM 500 YEARS, EXPOSURE TO GLACIAL AND AQUEOUS ENVIRONMENTSARCHAEOMETRY, Issue 3 2010I. M. KEMPSON Scanning electron microscopy, inductively coupled plasma mass spectroscopy and time-of-flight secondary ion mass spectrometry have been used to examine the extent and possible mechanisms by which the metal content of human hair is altered by exposure to aqueous environments. The results, using both modern hair and samples from 500-year-old hair associated with glacier-entombed remains, show that the metal content has been altered sufficiently so that the interpretation of the metal signature in terms of diet or disease is problematic. While endogenous information is difficult to glean from these data, interesting observations have been made of possible early stages of mineral authigenic deposition. The chemistry of the outer hair surface was found to be consistent with deposition of Fe and Al silicates, as well as other mineral phases. The ancient hair was analysed at the root region and included a comparison of the internal versus external composition to assist in identifying the diagenetic processes. [source] Low-Alkali Metal Content in ,-Vanadium Mixed Bronzes: The Crystal Structures of ,-Kx(V,Mo)6O15 (x = 0.23 and 0.32) by Single-Crystal X-Ray Diffraction.CHEMINFORM, Issue 51 2007Michele Zema Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Agaricus macrosporus as a potential bioremediation agent for substrates contaminated with heavy metalsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2005MA García Abstract This study investigated the potential use of the mushroom Agaricus macrosporus for bioextraction of heavy metals from contaminated substrates. Mushrooms were grown (1) in a non-contaminated control substrate, (2) in a substrate with added Cd (10 mg per kg dw), and (3) in a multi-contaminated substrate (Cd, Hg and Pb each at 10 mg kg,1; Cu and Zn each at 20 mg kg,1). Metal contents were determined in fruiting bodies by anodic stripping voltammetry (ASV). In the control substrate, three production waves (,breaks') were obtained, compared with only two in the contaminated substrates; however, total biomass in the Cd-contaminated substrate was similar to that in the control substrate, and only 40% lower (ie still considerable) in the Hg-containing multi-contaminated substrate. Within each break, metal contents were higher in young than in adult individuals. Metal contents were also higher in the hymenophore than in other parts of the fruiting body. The metal content data indicate that A macrosporus effectively extracted Cd, Hg and Cu (though not Pb) from the contaminated substrates. Of particular interest is the tolerance and extraction of Hg, in contrast with plants. These results suggest that fungi such as A macrosporus may be effective for bioremediation of metal-contaminated substrates, though bearing in mind that in many contaminated environments cultivation of mushrooms of this type may be difficult. Copyright © 2005 Society of Chemical Industry [source] Influence of supported vanadium catalyst on ethylene polymerization reactionsPOLYMER INTERNATIONAL, Issue 2 2008Sutapa Ghosh Abstract BACKGROUND: In the research area of homogeneous Ziegler,Natta olefin polymerization, classic vanadium catalyst systems have shown a number of favourable performances. These catalysts are useful for (i) the preparation of high molecular weight polymers with narrow molecular weight distributions, (ii) the preparation of ethylene/R -olefin copolymers with high R -olefin incorporation and (iii) the preparation of syndiotactic polypropylenes. In view of the above merits of vanadium-based catalysts for polymerization reactions, the development of well-defined single-site vanadium catalysts for polymerization reactions is presently an extremely important industrial goal. The main aim of this work was the synthesis and characterization of a heterogeneous low-coordinate non-metallocene (phenyl)imido vanadium catalyst, V(NAr)Cl3, and its utility for ethylene polymerization. RESULTS: Imido vanadium complex V(NAr)Cl3 was synthesized and immobilized onto a series of inorganic supports: SiO2, methylaluminoxane (MAO)-modified SiO2 (4.5 and 23 wt% Al/SiO2), SiO2 Al2O3, MgCl2, MCM-41 and MgO. Metal contents on the supported catalysts determined by X-ray fluorescence spectroscopy remained between 0.050 and 0.100 mmol V g,1 support. Thermal stability of the catalysts was determined by differential scanning calorimetry (DSC). Characterization of polyethylene was done by gel permeation chromatography and DSC. All catalyst systems were found to be active in ethylene polymerization in the presence of MAO or triisobutylaluminium/MAO mixture (Al/V = 1000). Catalyst activity was found to depend on the support nature, being between 7.5 and 80.0 kg PE (mol V),1 h,1. Finally, all catalyst systems were found to be reusable for up to three cycles. CONCLUSION: Best results were observed in the case of silica as support. Acid or basic supports afforded less active systems. In situ immobilization led to higher catalyst activity. The resulting polyethylenes in all experiments had ultrahigh molecular weight. Finally, this work explains the synthesis and characterization of reusable supported novel vanadium catalysts, which are useful in the synthesis of very high molecular weight ethylene polymers. Copyright © 2007 Society of Chemical Industry [source] Working Electrodes from Amalgam Paste for Electrochemical MeasurementsELECTROANALYSIS, Issue 4 2008Bogdan Yosypchuk Abstract Paste electrode with paste amalgam as an active electrode material is described here for the first time. Designed electrode from silver paste amalgam (AgA-PE) is solely metallic and does not contain any organic binder. Mechanical surface regeneration of AgA-PE is performed in the same way as for classical carbon paste electrodes and reproducibility of such regeneration is about 10%. Electrochemical surface regeneration appeared very efficient for most measurements. In dependence on paste metal content, the electrode surface can be liquid (resembling a film) or rather solid. The hydrogen overvoltage on AgA-PE is high, and the electrode allows measurements at highly negative potentials. AgA-PE is well suited for study of reduction or oxidation processes without an accumulation step. Anodic stripping voltammetry of some metals tested on the electrode is influenced by formation of intermetallic compounds. The measurement based on cathodic stripping voltammetry (adenine, cysteine) and on catalytic processes from adsorbed state (complex of osmium tetroxide with 2,2,-bipyridine) can be performed on AgA-PE practically under the same conditions as found earlier for HMDE and for silver solid amalgam electrode. The working electrode from paste amalgam combines the advantages of paste and metal electrodes. [source] Structural diversity of bacterial communities in a heavy metal mineralized granite outcropENVIRONMENTAL MICROBIOLOGY, Issue 3 2006Deirdre Gleeson Summary This laboratory study of a variably mineralized and hydrothermally altered granite outcrop investigated the influences of rock-surface chemistry and heavy metal content on resident bacterial populations. Results indicated that elevated heavy metal concentrations had a profound impact on bacterial community structure, with strong relationships found between certain ribotypes and particular chemical/heavy metal elements. Automated ribosomal intergenic sequence analysis (ARISA) was used to assess the nature and extent of bacterial diversity, and this was combined with chemical analysis and multivariate statistics to identify the main geochemical factors influencing bacterial community structure. A randomization test revealed significant changes in bacterial structure between samples, while canonical correspondence analysis (CCA) related each individual ARISA profile to linear combinations of the chemical variables (mineralogy, major element and heavy metal concentrations) revealing the geochemical factors that correlated with changes in the ARISA data. anova was performed to further explore interactions between individual ribotypes and chemical/heavy metal composition, and revealed that a high proportion of ribotypes correlated significantly with heavy metals. [source] Accumulation of toxic metals (Pb and Cd) in the sea urchin Diadema aff. antillarum Philippi, 1845, in an oceanic island (Tenerife, Canary Islands)ENVIRONMENTAL TOXICOLOGY, Issue 3 2010Ofelia Dolores Hernández Abstract This document shows the results obtained from a study on the concentration of toxic heavy metals in the internal tissue and exoskeleton of sea urchins, collected from their natural habitat. The levels of lead and cadmium were measured by Graphite Furnace Atomic Absorption Spectrometry. The mean concentrations of lead and cadmium in the internal tissue were 304.04 and 260.54 ,g/kg respectively, whereas in the shell they were 185.02 and 142.48 ,g/kg. We also performed a statistical analysis of the differences in the distribution of metals between their exoskeleton and their internal content, a correlation study of the metal content in internal tissue and shell and sampling areas, and a correlation study between the metal content and sample size. Since the sea urchin Diadema antillarum presents a wide range of variation in metal content, this study suggests that this species is an excellent bioindicator of heavy metal contamination. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010. [source] Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft-shell clam, Mya arenariaENVIRONMENTAL TOXICOLOGY, Issue 3 2002C. Blaise Abstract A spatial and temporal survey of six sites in the Saguenay Fjord and of one adjacent site in the St. Lawrence River estuary (Quebec, Canada) was undertaken to study the possible effects of anthropogenic contaminant input on soft-shell clam (Mya arenaria) populations. Bivalve sampling sites were selected because they reflected a range of areas representative of either no known (or apparent) pollution sources or of areas potentially influenced by different gradients and types of contamination sources. The most upstream site selected in the Saguenay Fjord, nearest to a highly populated and industrialized sector, and the most downstream site, near its mouth with the St. Lawrence River estuary, spanned a distance of some 70 km and encompassed the entire intertidal area suitable for Mya arenaria habitat. To measure effects in collected animals, we used a comprehensive battery of biomarkers composed of metallothionein-like proteins (MT), 7-ethoxyresorufin O-deethylase activity (EROD), DNA damage (DD), lipid peroxidation (LPO), vitellinlike proteins (Vn), phagocytosis (PHAG), nonspecific esterase (NspE) activity, and condition factor (weight-to-length ratio of clams). Vn, PHAG, DD, and NspE biomarkers were assayed in hemolymph (or hemocytes), whereas others (MT, EROD, LPO) were determined in the digestive gland. Whole-tissue metal content was also quantified in clams collected in the spatial survey. The spatial survey conducted in June 1997 showed significant effects at all sites, and principal component analysis indicated in addition that the more important responses were linked to the MT, LPO, and NspE biomarkers. Clams collected from sites closest to the upstream reaches of the fjord generally displayed higher levels of tissue metals (cadmium, manganese), as well as greater responses of NspE activity, MT, LPO, and PHAG. Animals collected from sites influenced by municipal wastewaters had higher levels of Vn, suggesting the presence of environmental estrogens. The results of the temporal survey (six monthly samplings of clams at three sites from May through October, 1997) showed that the bivalve reproductive cycle (vitellogenesis and spawning) can modulate the expression of several biomarkers. Vn levels, for example, were positively correlated with DD and EROD and negatively correlated with MT, suggesting that reproduction can influence the susceptibility of clams to some contaminants. Discrimination analysis over the 6 months of sampling revealed that the mean value of the discriminant function changed significantly over time, suggesting important changes in the relative contribution of each biomarker. In short, this study has provided evidence that clam populations in the Saguenay Fjord are impacted by multiple sources of contamination whose effects can be modulated by reproduction. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 170,186, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10048 [source] Creating metal-spiked bed sediments: A case study from Orewa estuary, New Zealand,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008Xueqiang Lu Abstract Spiking sediments to achieve target concentrations of heavy metal pollutants is a key step in sediment toxicity tests. It is difficult, however, to ensure that metals in an artificially spiked sediment will behave naturally. A method has been developed in the present study to create Cu-, Pb-, and Zn-spiked sediments in which naturally occurring adsorption onto sediment surfaces is the dominant process binding the metals and in which precipitation of readily redissolved minerals and other metal-bearing phases (artifacts of the spiking procedure) are avoided. Uncontaminated bed sediment from an intertidal mudflat in the Orewa estuary, New Zealand, was characterized in terms of existing metal content, optimal adsorption pH, and adsorption capacity. Competitive adsorption between Cu and Pb as well as complexation by seawater anions only slightly affected metal adsorption from seawater. Surface complexation modeling indicated that iron oxide surfaces in the sediment likely were dominating metal adsorption processes. Spiking experiments were designed using these established adsorption characteristics but with significantly higher (>100-fold) concentrations of sediments and dissolved metals and a liquid to solid (L:S) ratio of approximately 5.5. An equilibration time of at least 36 h was required to achieve a reproducible target metal concentration, which could be reliably predicted from the L:S ratio and the initial metal concentration in the spiking solution. Adsorption equilibrium remained the process governing metal binding to the sediment, and no indication was observed that the adsorption capacity of the sediment had been exceeded or that additional metal-bearing phases had been formed. [source] Relation between metal concentration in water and metal content of marine mussels (Mytilus galloprovincialis): Impact of physiology,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2008Stellio Casas Abstract The present study constitutes an in situ investigation of metal kinetics within soft tissue of mussels (Mytilus gallo-provincialis), which solves the problem of the decoupling of the effect of animal physiology and metal bioavailability in water. Field experiments were conducted to measure uptake and elimination kinetics for four metals (Hg, Pb, Cd, and Cu) in three Mediterranean sites with different contamination and nutritive levels. At each site, metal concentrations were monitored in soft tissues of mussels and in the surrounding waters. The experimental conditions were completely characterized: Lazaret Bay (located between Nice and Marseille, France) is a hot spot for Hg (6.3 ng/L) and Pb (163 ng/L) concentrations and is an oligotrophic, stable site; Bages Lagoon (located to the west of Montpellier, France) is particularly contaminated by Cd (1.5 ng/L) and Cu (1.5,g/L) and is a mesotrophic site where variability of trophic and physicochemical parameters is significant; and Port-Cros Island (located in the Hyeres National Park, France) is considered to be a reference site. Those kinetics permit us to decouple physiological, chemical, and environmental interactions. After normalizing mussel metal content for similar physiological conditions, application of the local weighted regression (LOWESS) statistical treatment shows a parallelism between the time trends of metal concentrations in the bivalve and metal concentrations in water. The results enabled us to obtain in situ kinetic parameters and realistic bioaccumulation factors. Their logarithmic values were 4.6 for Hg, 4.3 for Pb, 4.9 for Cd, and 3.9 for Cu. The importance of physiological processes such as spawning is discussed as a factor influencing the bioaccumulation factor. This information may be useful in refining monitoring tools for risk assessment and, more generally, in environmental management strategies. [source] Soil-solution speciation of CD as affected by soil characteristics in unpolluted and polluted soilsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2005Erik Meers Abstract Total metal content by itself is insufficient as a measure to indicate actual environmental risk. Understanding the mobility of heavy metals in the soil and their speciation in the soil solution is of great importance for accurately assessing environmental risks posed by these metals. In a first explorative study, the effects of general soil characteristics on Cd mobility were evaluated and expressed in the form of empirical formulations. The most important factors influencing mobility of Cd proved to be pH and total soil content. This may indicate that current legislation expressing the requirement for soil sanitation in Flanders (Belgium) as a function of total soil content, organic matter, and clay does not successfully reflect actual risks. Current legal frameworks focusing on total content, therefore, should be amended with criteria that are indicative of metal mobility and availability and are based on physicochemical soil properties. In addition, soil-solution speciation was performed using two independent software packages (Visual Minteq 2.23 and Windermere Humic Aqueous model VI [WHAM VI]). Both programs largely were in agreement in concern to Cd speciation in all 29 soils under study. Depending on soil type, free ion and the organically complexed forms were the most abundant species. Additional inorganic soluble species were sulfates and chlorides. Minor species in solution were in the form of nitrates, hydroxides, and carbonates, the relative importance of which was deemed insignificant in comparison to the four major species. [source] Soil solution concentration of Cd and Zn canbe predicted with a CaCl2 soil extractEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2003F. Degryse Summary Risk assessment of heavy metals in soil requires an estimate of the concentrations in the soil solution. In spite of the numerous studies on the distribution of Cd and Zn in soil, few measurements of the distribution coefficient in situ, Kd, have been reported. We determined the Kd of soils contaminated with Cd and Zn by measuring metal concentrations in the soil and in the soil solution and attempted to predict them from other soil variables by regression. Soil pH explained most of the variation in logKd (R2 = 0.55 for Cd and 0.70 for Zn). Introducing organic carbon content or cation exchange capacity (CEC) as second explanatory variable improved the prediction (R2 = 0.67 for Cd and 0.72 for Zn), but these regression models, however, left more than a factor of 10 of uncertainty in the predicted Kd. This large degree of uncertainty may partly be due to the variable degree of metal fixation in contaminated soils. The labile metal content was measured by isotopic dilution (E value). The E value ranged from 18 to 92% of the total metal content for Cd and from 5 to 68% for Zn. The prediction of Kd improved when metals in solution were assumed to be in equilibrium with the labile metal pool instead of the total metal pool. It seems necessary therefore to discriminate between ,labile' and ,fixed' pools to predict Kd for Cd and Zn in field contaminated soils accurately. Dilute salt extracts (e.g. 0.01 m CaCl2) can mimic soil solution and are unlikely to extract metals from the fixed pool. Concentrations of Cd and Zn in the soil solution were predicted from the concentrations of Cd and Zn in a 0.01 m CaCl2 extract. These predictions were better correlated with the observations for field contaminated soils than the predictions based on the regression equations relating logKd to soil properties (pH, CEC and organic C). [source] Lead and cadmium uptake in the marine fungi Corollospora lacera and Monodictys pelagicaFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Michael A.S. Taboski Abstract This study provides observations on the effects of lead and cadmium ions on the growth of two species of marine fungi, Corollospora lacera and Monodictys pelagica. On solid media lead appeared to have no effect on the radial rate of growth of fungi. Exposure to increasing cadmium concentrations on solid media resulted in significant reduction (P < 0.05) in the radial mycelial growth rates of both fungi, especially in M. pelagica. These results reveal significant difference in species sensitivity toward cadmium and, essentially, insensitivity toward lead exposure. In liquid cultures, the metal content of mycelia (metal mass found in mycelium, in mg), and the concentration of metal in dry mycelium (metal mass in 1 g of mycelium, in mg g,1) were both found to increase (P < 0.05) with the increase in the metal cation concentration, while mycelium dry mass decreased. As it was observed on solid media, cadmium cation affected more severely (P < 0.05) the growth of M. pelagica in liquid cultures. Ergosterol content of mycelia of C. lacera exposed to increasing cadmium cation concentration decreased, similarly to the trend observed for dry mycelial mass. It was found that ca. 93% of all lead sequestered by C. lacera is located extracellularly. M. pelagica was found to bioaccumulate over 60 mg of cadmium and over 6 mg of lead per 1 g of mycelium, while C. lacera bioaccumulated over 7 mg of cadmium and up to 250 mg of lead per 1 g of mycelium. Overall, the results indicate that both metal ions affect the growth of marine fungi with lead being accumulated extracellularly in the mycelia. Both metals accumulated by fungi may then enter the marine ecosystem food web, of which marine fungi are integral members. [source] Manganese in biogenic magnetite crystals from magnetotactic bacteriaFEMS MICROBIOLOGY LETTERS, Issue 2 2009Carolina N. Keim Abstract Magnetotactic bacteria produce either magnetite (Fe3O4) or greigite (Fe3S4) crystals in cytoplasmic organelles called magnetosomes. Whereas greigite magnetosomes can contain up to 10 atom% copper, magnetite produced by magnetotactic bacteria was considered chemically pure for a long time and this characteristic was used to distinguish between biogenic and abiogenic crystals. Recently, it was shown that magnetosomes containing cobalt could be produced by three strains of Magnetospirillum. Here we show that magnetite crystals produced by uncultured magnetotactic bacteria can incorporate manganese up to 2.8 atom% of the total metal content (Fe+Mn) when manganese chloride is added to microcosms. Thus, chemical purity can no longer be taken as a strict prerequisite to consider magnetite crystals to be of biogenic origin. [source] Diphosphines of dppf-Type Incorporating Electron-Withdrawing Furyl Moieties Substantially Improve the Palladium-Catalysed Amination of Allyl AcetatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Aziz Fihri Abstract Highly active Pd/diphosphine catalytic systems incorporating new, air-stable ferrocenyl-furylphosphines allow nucleophilic allylic amination at room temperature with unprecedented turnover frequencies. For instance, in the presence of 0.01,mol,% catalyst the coupling of aniline to allyl acetate occurs at a TOF of more than 10,000,h,1; even the addition of the less nucleophile morpholine to allyl acetate is observed with a TOF of 4250,h,1. The amination of the sterically demanding geranyl acetate, a monoterpene derivative of interest in the flavour industry, at low catalyst loadings demonstrates the scope of this methodology, which provides in addition noticeable advantages in terms of economical (resource- and energy-saving) and sustainable chemistry (high selectivity, no additive, low metal content, and thus easier purification). [source] Synthesis, characterization, and electrical properties of diazophenylene bridged Co, Ni, Cu, Ce, and Er phthalocyanine polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Cemil Alkan Abstract In this research, diazophenylene bridged metal-phthalocyanine (Pc) polymers were produced from diazonium salt of 1,4-diaminophenylene and presynthesized 1,8,15,22-tetraamino metal-Pcs. 1,8,15,22-Tetraamino metal-Pc complexes of Co, Ni, Cu, Ce, and Er were obtained by reducing 1,8,15,22-tetranitro metal-Pc complexes synthesized from 3-nitrophthalic anhydride, urea, metal salt, and ammonium molybdate catalyst. Complexes and polymers were characterized by Fourier transform infrared (FTIR), ultraviolet,visible (UV,vis), and X-ray powder diffraction spectroscopes. X-ray analysis of the polymers showed that there were short-range orientations in the polymers. Thermal analysis of the complexes and the polymers were done by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10°C min,1 under nitrogen atmosphere. Ash analysis was performed to determine the metal content of the polymers. Viscosimetry and ebullioscopy measurements of the soluble part of the polymers were done for molecular weight analysis of the soluble part in tetrahydrofuran (THF) at 25°C. Four-probe conductivity measurements on isothermal conditions revealed that the polymer samples showed 104 fold increases in their electrical conductivities when doped with iodine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Zirconia-Based Metastable Solid Solutions through Self-Propagating High-Temperature Synthesis: Synthesis, Characterization, and Mechanistic InvestigationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2000Filippo Maglia Cubic Zr1,xMexOy(Me = Fe, Co, Ni, Cu) metastable solid solutions with metal content significantly higher than equilibrium levels have been synthesized by the self-propagating high-temperature synthesis method based on a thermite reaction between metallic zirconium and the transition-metal oxides CoO, Fe2O3, CuO, and NiO. Through in situ XRD analysis, it was determined that when heated to 1100°C, the cubic solid solution transformed to the tetragonal phase with the concomitant formation of iron oxide. When cooled to lower temperatures, the tetragonal phase transformed to the monoclinic phase at or below 500°C. Results of auxiliary experiments strongly suggest that the formation of the solid solution takes place behind the combustion front by a reaction between zirconia and the metal. [source] The nature of high-redshift galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001Rachel S. Somerville Using semi-analytic models of galaxy formation set within the cold dark matter (CDM) merging hierarchy, we investigate several scenarios for the nature of the high-redshift ) Lyman-break galaxies (LBGs). We consider a ,collisional starburst' model in which bursts of star formation are triggered by galaxy,galaxy mergers, and find that a significant fraction of LBGs are predicted to be starbursts. This model reproduces the observed comoving number density of bright LBGs as a function of redshift and the observed luminosity function at and with a reasonable amount of dust extinction. Model galaxies at have star formation rates, half-light radii, colours and internal velocity dispersions that are in good agreement with the data. Global quantities such as the star formation rate density and cold gas and metal content of the Universe as a function of redshift also agree well. Two ,quiescent' models without starbursts are also investigated. In one, the star formation efficiency in galaxies remains constant with redshift, while in the other, it scales inversely with disc dynamical time, and thus increases rapidly with redshift. The first quiescent model is strongly ruled out, as it does not produce enough high-redshift galaxies once realistic dust extinction is accounted for. The second quiescent model fits marginally, but underproduces cold gas and very bright galaxies at high redshift. A general conclusion is that star formation at high redshift must be more efficient than locally. The collisional starburst model appears to accomplish this naturally without violating other observational constraints. [source] CHANGES IN THE METAL CONTENT OF HUMAN HAIR DURING DIAGENESIS FROM 500 YEARS, EXPOSURE TO GLACIAL AND AQUEOUS ENVIRONMENTSARCHAEOMETRY, Issue 3 2010I. M. KEMPSON Scanning electron microscopy, inductively coupled plasma mass spectroscopy and time-of-flight secondary ion mass spectrometry have been used to examine the extent and possible mechanisms by which the metal content of human hair is altered by exposure to aqueous environments. The results, using both modern hair and samples from 500-year-old hair associated with glacier-entombed remains, show that the metal content has been altered sufficiently so that the interpretation of the metal signature in terms of diet or disease is problematic. While endogenous information is difficult to glean from these data, interesting observations have been made of possible early stages of mineral authigenic deposition. The chemistry of the outer hair surface was found to be consistent with deposition of Fe and Al silicates, as well as other mineral phases. The ancient hair was analysed at the root region and included a comparison of the internal versus external composition to assist in identifying the diagenetic processes. [source] Crystallization and preliminary X-ray diffraction analysis of thermophilic imidase from pig liverACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2003Cheng-Yang Huang Imidase is an enzyme, also known as dihydropyrimidinase (EC 3.5.2.2), hydantoinase, dihydropyrimidine hydrase or dihydropyrimidine amidohydrolase, that catalyzes the reversible hydrolysis of 5,6-dihydrouracil to 3-ureidopropionate and many other imides. Substrate specificity, metal content and amino-acid sequence all differ significantly between bacterial and mammalian imide-hydrolyzing enzymes. In this study, a thermophilic imidase was isolated from pig liver and crystallized. Two kinds of imidase crystals were grown by the hanging-drop vapour-diffusion method using polyethylene glycol MME 5000 and 2-propanol as precipitants. One belongs to the triclinic P1 space group, with unit-cell parameters a = 96.35, b = 96.87, c = 154.87,Å, , = 82.10, , = 72.54, , = 77.19°, and the other belongs to the orthorhombic C2221 space group, with unit-cell parameters a = 113.92, b = 157.22, c = 156.21,Å. [source] Accumulation and solubility of metals during leaf litter decomposition in non-polluted and polluted soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2009S. Scheid Summary The decomposition of alder (Alnus glutinosa) and poplar (Populus tremula) leaf litter placed in direct contact with non-polluted and metal-polluted soil was investigated over 25 months in a controlled model-ecosystem experiment using the litterbag method. In addition to mass loss, we monitored the total and soluble concentrations of carbon, Cu, Zn, Cd and Pb. Leaves from trees grown on polluted soil had larger initial Zn, Cd and dissolved organic carbon concentrations. Neither the origin of the leaves (from trees grown on non-polluted or polluted soil) nor the placement of the leaves in polluted or unpolluted soil affected the decomposition process. Total metal contents increased in leaves placed on polluted soil over time. The solubility of metals in the leaf litter decreased over time, indicating that leaves acted as a temporary pool for metals from the soil in direct contact with the leaves. The sorbed metals were strongly bound in the litter even after two years of decomposition. The strong binding and thus reduced bioavailability of the metals provides an explanation for why they had no observable effects on litter decomposition. [source] Survival of Escherichia coli O157:H7 in private drinking water wells: influences of protozoan grazing and elevated copper concentrationsFEMS MICROBIOLOGY LETTERS, Issue 1 2002Rebekka R.E Artz Abstract The survival characteristics of Escherichia coli O157:H7 in private drinking water wells were investigated to assess the potential for human exposure. A non-toxigenic, chromosomally lux -marked strain of E. coli O157:H7 was inoculated into well water from four different sites in the North East of Scotland. These waters differed significantly in their heavy metal contents as well as nutrient and bacterial grazer concentrations. Grazing and other biological factors were studied using filtered (3 and 0.2 ,m) and autoclaved water. The survival of E. coli O157:H7 was primarily decreased by elevated copper concentrations. This hypothesis was supported by acute toxicity assay data. In addition, significant protozoan predation effects were observed in untreated water when compared with survival rates in filtered water. The combination of these two factors in particular determines the survival time of the pathogen in a private water well. It therefore appears that wells with higher water quality as assessed using the European Union Drinking Water Directive standards will also allow survival of E. coli O157:H7 for much longer periods. [source] Agaricus macrosporus as a potential bioremediation agent for substrates contaminated with heavy metalsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2005MA García Abstract This study investigated the potential use of the mushroom Agaricus macrosporus for bioextraction of heavy metals from contaminated substrates. Mushrooms were grown (1) in a non-contaminated control substrate, (2) in a substrate with added Cd (10 mg per kg dw), and (3) in a multi-contaminated substrate (Cd, Hg and Pb each at 10 mg kg,1; Cu and Zn each at 20 mg kg,1). Metal contents were determined in fruiting bodies by anodic stripping voltammetry (ASV). In the control substrate, three production waves (,breaks') were obtained, compared with only two in the contaminated substrates; however, total biomass in the Cd-contaminated substrate was similar to that in the control substrate, and only 40% lower (ie still considerable) in the Hg-containing multi-contaminated substrate. Within each break, metal contents were higher in young than in adult individuals. Metal contents were also higher in the hymenophore than in other parts of the fruiting body. The metal content data indicate that A macrosporus effectively extracted Cd, Hg and Cu (though not Pb) from the contaminated substrates. Of particular interest is the tolerance and extraction of Hg, in contrast with plants. These results suggest that fungi such as A macrosporus may be effective for bioremediation of metal-contaminated substrates, though bearing in mind that in many contaminated environments cultivation of mushrooms of this type may be difficult. Copyright © 2005 Society of Chemical Industry [source] Cadmium and zinc accumulation in willow and poplar species grown on polluted soils,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2007Maria N. Dos Santos Utmazian Abstract Woody plant species that produce high biomass have been proposed for use in phytoremediation technology. We investigated the accumulation of cadmium (Cd) and zinc (Zn) in Salix babylonica, S. caprea, S. dasyclados, S. matsudana × alba, S. purpurea, S. smithiana, Populus tremula, and P. nigra clones grown in a pot experiment on a Calcaric and a Eutric Cambisol (pH 7.2 and 6.4) of different levels of contamination (total metal concentrations in mg,kg,1 in soil A: 32.7 Cd, 1760 Zn; soil B: 4.34 Cd, 220 Zn). Generally, the tested clones tolerated large metal concentrations in soils and had larger Cd and Zn concentrations in leaves compared to the roots. The largest Cd concentrations in leaves were found in two clones of S. smithiana (440 mg,kg,1 on soil A; 70 mg,kg,1 on soil B). One of the S. smithiana clones had also the largest Zn concentrations (870 mg,kg,1) on soil B but accumulated slightly less Zn than a S. matsudana × alba clone (2430 mg,kg,1) on soil A. The Cd concentrations in leaves of both S. smithiana clones on soil A are the largest ever reported for soil-grown willows. The bioconcentration factors of the best performing clone reached 15.9 for Cd and 3.93 for Zn on the less contaminated soil B. Also based on the metal contents in leaves, this clone was identified as the most promising for phytoextraction. The metal concentrations in leaves observed in the pot experiment do not reflect those found in a previous hydroponic study and the leaf-to-root ratios are clearly underestimated in hydroponic conditions. This demonstrates the need for testing candidates for phytoextraction crops on soils rather than in hydroponics. Our data also show that the phytoextraction potential should be tested on different soils to avoid misleading conclusions. [source] Novel polymerase chain reaction primers for the specific detection of bacterial copper P-type ATPases gene sequences in environmental isolates and metagenomic DNALETTERS IN APPLIED MICROBIOLOGY, Issue 6 2010R. De la Iglesia Abstract Aims:, In the last decades, the worldwide increase in copper wastes release by industrial activities like mining has driven environmental metal contents to toxic levels. For this reason, the study of the biological copper-resistance mechanisms in natural environments is important. Therefore, an appropriate molecular tool for the detection and tracking of copper-resistance genes was developed. Methods and Results:, In this work, we designed a PCR primer pair to specifically detect copper P-type ATPases gene sequences. These PCR primers were tested in bacterial isolates and metagenomic DNA from intertidal marine environments impacted by copper pollution. As well, T-RFLP fingerprinting of these gene sequences was used to compare the genetic composition of such genes in microbial communities, in normal and copper-polluted coastal environments. New copper P-type ATPases gene sequences were found, and a high degree of change in the genetic composition because of copper exposure was also determined. Conclusions:, This PCR based method is useful to track bacterial copper-resistance gene sequences in the environment. Significance and Impact of the Study:, This study is the first to report the design and use of a PCR primer pair as a molecular marker to track bacterial copper-resistance determinants, providing an excellent tool for long-term analysis of environmental communities exposed to metal pollution. [source] Magmatic Fluid Inclusions from the Zaldivar Deposit, Northern Chile: The Role of Early Metal-bearing Fluids in a Porphyry Copper SystemRESOURCE GEOLOGY, Issue 1 2006Eduardo A. Campos Abstract. The occurrence of a distinct type of multi-solid, highly-saline fluid inclusions, hosted in igneous quartz phe-nocrysts from the Llamo porphyry, in the Zaldivar porphyry copper deposit of northern Chile is documented. Total homoge-nization of the multi-solid type inclusions occurs at magmatic temperatures (over 750d,C), well above the typical temperatures of hydro thermal fluids (less than 600d,C) usually recorded in porphyry copper systems. The analysis of this type of fluid inclusions, using a combination of non-destructive microthermometry, Raman and PIXE techniques and the identification of daughter minerals by SEM method, indicates that the trapped fluid was a dense, complex chloride brine in which Cl, Na, K, Fe, Cu, and Mn are dominant. The high chlorine and metal contents indicate that the metals were separated from the crystallizing magma as homogeneous aqueous chloride-rich solutions that represent the primary magmatic fluids exsolved at high temperatures and depth during the crystallization of the parental intrusive. The multi-solid type inclusion illustrates the mechanism by which ore components are sequestered from the crystallizing parental magma and concentrated in the exsolved magmatic aqueous fluids. These fluids are significant with respect to the origin of porphyry copper deposits, as they are responsible for the first enrichment of metals and represent the precursors of metal-bearing hydrothermal fluids in a porphyry copper system. [source] Geochemistry and Radioactive Potentiality of Um Naggat Apogranite, Central Eastern Desert, EgyptRESOURCE GEOLOGY, Issue 1 2000AFANDY, Adel H. EL Abstract: The northern part of Um Naggat granite massif (UNGM) has suffered extensive post-magmatic metasomatic reworking which results into the development of (Zr, Hf, Nb, Ta, U, Th, F), and albite-enriched and greisenized apogranite body (UNAP) of 600 m thick, and more than 3 km in the strike length. Albitization produced an enrichment in Zr (av. 2384 ppm), Hf (61), Nb (419), and U (43). The Th/U ratio ranges between 1. 33 and 1. 90. Extreme albitization (i. e. the albitite rock) is characterized by sharp decrease in the rare metals contents. However, extreme greisenization (i. e. endogreisen bodies) is characterized by a considerable enrichment in Zr (av. 5464 ppm), Hf (143), Nb (2329), Ta (152), U (66) and Th (178). The Th/U ratio ranges between 1. 57 and 3. 60. In contrast to extreme greisenization, it seems that extreme albitization does not apparently change the fluid pH and therefore poor amounts of rare metals are localized in the albitites. It is suggested that the presence of Na+, H+ and F - in the ore fluids was essential to stablize complexes of Zr, Hf, Nb, Ta, U, Th, and HREE during extraction and transportation. In contrast, contemporaneous decrease of temperature and increasing pH due to decreasing pressure are considered the essential factors for localization of disseminated mineralization of Zr and Nb in the apical parts of the UNAP. The enhanced uranium content in the alteration facies of UNAP coupled with the absence of significant uranium mineralization may indicate the metalliferous rather than mineralized nature for the UNAP. The high uranium contents are stabilized in refractory accessory minerals. However, with repect to Zr and Nb, the UNAP especially the albitized and greisen facies, can be categorized as a mineralized productive granite. [source] | |||||||||||||||||||