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Inorganic
Terms modified by Inorganic Selected AbstractsMolecular Characteristics of Poly(N -isopropylacrylamide) Separated from Nanocomposite Gels by Removal of Clay from the Polymer/Clay NetworkMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2010Kazutoshi Haraguchi Abstract The extraordinary mechanical and swelling/deswelling properties of nanocomposite (NC) gels are attributed to their unique organic (polymer)/inorganic (clay) network structure. In this study, poly(N -isopropylacrylamide) (PNIPA) was successfully separated from an NC gel network by decomposing the clay (hectorite) using hydrofluoric acid (HF). A very low HF concentration (0.2,wt.-%) was adequate for the decomposition of the clay without causing any damage to PNIPA. The separated PNIPA had a high (=5.5,×,106 g,·,mol,1). Also, was almost constant regardless of the clay concentration (Cclay,=,1,25,×,10,2 mol,·,l,1), even though the properties of the NC gel varied widely over this Cclay range. Comparisons of NC gels, PNIPA, and SiO2 -NC gels indicated that the clay platelets specifically play an important role in NC gels. [source] Tunable Colors in Opals and Inverse Opal Photonic CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Carlos I. Aguirre Abstract Colloidal photonic crystals and materials derived from colloidal crystals can exhibit distinct structural colors that result from incomplete photonic band gaps. Through rational materials design, the colors of such photonic crystals can be tuned reversibly by external physical and chemical stimuli. Such stimuli include solvent and dye infiltration, applied electric or magnetic fields, mechanical deformation, light irradiation, temperature changes, changes in pH, and specific molecular interactions. Reversible color changes result from alterations in lattice spacings, filling fractions, and refractive index of system components. This review article highlights the different systems and mechanisms for achieving tunable color based on opaline materials with close-packed or non-close-packed structural elements and inverse opal photonic crystals. Inorganic and polymeric systems, such as hydrogels, metallopolymers, and elastomers are discussed. [source] Polyphenylene Dendrimer-Templated In Situ Construction of Inorganic,Organic Hybrid Rice-Shaped ArchitecturesADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Xiaoying Qi Abstract A novel dendrimer-templating method for the synthesis of CuO nanoparticles and the in situ construction of ordered inorganic,organic CuO,G2Td(COOH)16rice-shaped architectures (RSAs) with analogous monocrystalline structures are reported. The primary CuO nanoparticles are linked by the G2Td(COOH)16 dendrimer. This method provides a way to preserve the original properties of primary CuO nanoparticles in the ordered hybrid nanomaterials by using the 3D rigid polyphenylene dendrimer (G2Td(COOH)16) as a space isolation. The primary CuO nanoparticles with diameter of (6.3,±,0.4) nm are synthesized via four successive reaction steps starting from the rapid reduction of Cu(NO3)2 by using NaBH4 as reducer and G2Td(COOH)16 as surfactant. The obtained hybrid CuO,G2Td(COOH)16 RSA, formed in the last reaction step, possesses a crystal structure analogous to a monocrystal as observed by transmission electron microscopy(TEM). In particular, the formation process of the RSA is monitored by UV,vis, TEM, and X-ray diffraction. Small angle X-ray scattering and Fourier transform infrared spectroscopy are used to investigate the role of the dendrimer in the RSA formation process. The obtained results illuminate that Cu2+COO, coordination bonds play an indispensable role in bridging and dispersing the primary CuO nanoparticles to induce and maintain the hybrid RSA. More importantly, the RSA is retained through the Cu2+COO,coordination bonds even with HCl treatment, suggesting that the dendrimers and Cu2+ ions may form rice-shaped polymeric complexes which could template the assembly of CuO nanoparticles towards RSAs. This study highlights the feasibility and flexibility of employing the peculiar dendrimers to in-situ build up hybrid architectures which could further serve as templates, containers or nanoreactors for the synthesis of other nanomaterials. [source] Generation of Monodisperse Inorganic,Organic Janus Microspheres in a Microfluidic DeviceADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Naveen Prasad Abstract This study presents a simple synthetic approach for the in situ preparation of monodisperse hybrid Janus microspheres (HJM) having organic and inorganic parts in a PDMS-based microfluidic device. Based on the mechanism of shear-force-driven break-off, merged droplets of two photocurable oligomer solutions having distinctive properties are generated into an immiscible continuous phase. Functionalized perfluoropolyether (PFPE) as the organic phase and hydrolytic allylhydridopolycarbosilane (AHPCS) as the inorganic phase are used for the generation in aqueous medium of HJM with well-defined morphology and high monodispersity (average diameter of 162,µm and a 3.5% coefficient of variation). The size and shape of the HJM is controlled by varying the flow rate of the disperse and continuous phases. The HJM have two distinctive regions: a hydrophobic hemisphere (PFPE) having a smooth surface and a relatively hydrophilic region (AHPCS) with a rough, porous surface. In addition, pyrolysis and subsequent oxidation of these HJM convert them into SiC-based ceramic hemispheres through the removal of the organic portion and etching off the silica shell. The selective incorporation of magnetic nanoparticles into the inorganic part shows the feasibility of the forced assembly of HJM in an applied magnetic field. [source] Luminescence Modulation of Ordered Upconversion Nanopatterns by a Photochromic Diarylethene: Rewritable Optical Storage with Nondestructive ReadoutADVANCED MATERIALS, Issue 5 2010Chao Zhang Inorganic,organic composite films for rewritable optical storage are fabricated base on the reversible luminescence modulation of ordered upconversion nanopatterns via a photochromic diarylethene. The near-IR excitation for reading the upconversion emission does not affect the recorded data bits. Moreover, the spatially well-defined 2D nanopatterns promise future applications in ultrahigh-density storage. [source] A Hybrid Inorganic,Organic Semiconductor Light-Emitting Diode Using ZrO2 as an Electron-Injection LayerADVANCED MATERIALS, Issue 34 2009Nurlan Tokmoldin A hybrid inorganic,polymer light-emitting diode that uses ZrO2 and MoO3 charge-injection layers exhibits enhanced electron injection and allows the use of a variety of red-, green-, and blue-light-emitting polymers. [source] Synthesis of Inorganic,Organic Diblock Copolymers as a Precursor of Ordered Mesoporous SiCN Ceramic,ADVANCED MATERIALS, Issue 17 2007D. Nghiem A novel poly(vinyl)silazane- block -polystyrene diblock copolymer is successfully synthesized by living free-radical polymerization via a reversible addition fragmentation chain transfer (RAFT) route (see figure). The obtained diblock copolymer, having an inorganic volume fraction of 0.69, leads to phase-separation at the nanoscale to form an ordered nanostructure, which is converted to well-ordered mesoporous SiCN ceramic after heating at 800,°C and maintained up to 1400,°C. [source] Computational Inorganic and Bioinorganic Chemistry.ANGEWANDTE CHEMIE, Issue 18 2010Herausgegeben von Edward John Wiley & Sons, Hoboken 2009. 614,S., geb., 155.00,,.,ISBN 978-0470699973 [source] Supramolecular Interactions at the Inorganic,Organic Interface in Hybrid Nanomaterials,ANGEWANDTE CHEMIE, Issue 15 2010Huibiao Liu Dr. Taschendieb: Perylen kann mithilfe anorganisch-organischer Nanomaterialien aus ZnO-Nanostäben (grauer Zylinder) und Perylendiimiden (rotes Rechteck) nachgewiesen werden. Die Interkalation von Perylen (gelbes Rechteck) in eine Molekültasche an der anorganisch-organischen Grenzfläche führt bei allen drei Komponenten zur Fluoreszenzlöschung, wobei die Nachweisgrenze 10,12,M ist. [source] Synthesis of Modular "Inorganic,Organic,Inorganic" Polyoxometalates and Their Assembly into Vesicles,ANGEWANDTE CHEMIE, Issue 44 2009Chullikkattil Verknüpfte Cluster: Eine neue Klasse anorganisch-organisch-anorganischer Hybride mit Größen von etwa 3.4,nm wurde durch kovalente Funktionalisierung V3 -überdachter Wells-Dawson-Cluster mit linearen Bis(tris)-Liganden hergestellt (siehe Schema; TBA=nBu4N+) sowie röntgenkristallographisch und mit ESI-MS charakterisiert. Die Verbindungen weisen Tensideigenschaften auf (dynamische Lichtstreuung) und bilden in Lösung supramolekulare Vesikel. [source] Kazuo Nakamoto Infrared and Raman Spectra of Inorganic and Coordination Compounds, Part B, Applications in Coordination, Organometallic, and Bioinorganic Chemistry, 6th edn Wiley, 2009, 424 pp. (hardback) ISBN 978-0-471-74493-1APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Alan Brisdon No abstract is available for this article. [source] ChemInform Abstract: Synthesis of Modular "Inorganic,Organic,Inorganic" Polyoxometalates and Their Assembly into Vesicles.CHEMINFORM, Issue 51 2009Chullikkattil P. Pradeep 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: The Layered Thiostannate (dienH2)Cu2Sn2S6: A Photoconductive Inorganic,Organic Hybrid Compound.CHEMINFORM, Issue 2 2009Nicole Pienack 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: 0-D and 1-D Inorganic,Organic Composite Polyoxotungstates Constructed from in situ Generated MonocopperII -Substituted Keggin Polyoxoanions and CopperII,Organoamine Complexes.CHEMINFORM, Issue 51 2008Jun-Wei Zhao 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: A Polyoxometalate-Templated Inorganic,Organic Hybrid Compound Containing a Crown-Like Metallamacrocyclic Cation [Ag6(1,2,4-Triazole)6]6+.CHEMINFORM, Issue 30 2008Xiang-Min Chen 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Two Unprecedented Inorganic,Organic Boxlike and Chainlike Hybrids Based on Arsenic,Vanadium Clusters Linked by Nickel Complexes.CHEMINFORM, Issue 21 2007Yanfei Qi 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] ChemInform Abstract: Hydrothermal Synthesis and Structural Characterization of the (CnH2n+6N2) [Mn3(HPO3)4] (n = 3,8) New Layered Inorganic,Organic Hybrid Manganese(II) Phosphites.CHEMINFORM, Issue 37 2001Crystal Structure, Magnetic Properties of (C3H12N2) [Mn3(HPO3)4]., Spectroscopic Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Inorganic,Organic Hybrid Structures: Open-Framework Iron Phosphite,Oxalates of Varying DimensionalityCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2007Sukhendu Mandal Abstract Inorganic,organic hybrid structures belonging to the family of iron phosphite,oxalates have been prepared by employing hydrothermal methods. Their structures, determined by single-crystal X-ray diffraction, show a hierarchy within the family. While compounds I and II are low dimensional, III,VI have three-dimensional structures. Compound I has edge-shared ladders of iron phosphite with oxalate units hanging from the iron centers. Compound II has a layer structure with a honeycomb-like arrangement. The three-dimensional hybrid structures have the oxalate units connected in both in-plane and out-of-plane modes. A newly identified secondary building unit (SBU-7) and the oxalate units satisfying the valence and coordination requirements in the structure of V are novel and noteworthy structural features. Magnetic studies show that the dominant interactions between the iron centers are antiferromagnetic. Similar to other known hybrid structures, the phosphite,oxalate structures appear to show wide compositional and structural diversity. [source] Synthesis and crystal structure of a new inorganic , organic complex: (4-ClC7H6NH3)9[Nd(P6O18)2]·9H2OCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2007O. Amri Abstract Single crystals of (4-ClC7H6NH3)9[Nd(P6O18)2]·9H2O were synthesized in aqueous solution. This compound crystallizes in a triclinic P1 unit-cell, with a = 14.898(6), b = 18.049(7), c = 20.695(6)Å, , = 102.04(3), , = 100.49(3), , = 98.82(3)°, V = 5245(4) Å3 and Z = 2. The crystal structure has been solved and refined to R = 0.043 (Rw = 0.061) for 20420 observed reflections. The atomic arrangement of the title compound can be described as infinite layers built by complex of Neodyme [Nd(P6O18)2] and nine water molecules. The organic cations are located in the space delimited by the successive inorganic layers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Diversity of native and alien plant species on rubbish dumps: effects of dump age, environmental factors and toxicityDIVERSITY AND DISTRIBUTIONS, Issue 3 2003Antonín Py Abstract. The flora of 96 rubbish dumps consisting of organic, inorganic and industrial wastes was studied in the Czech Republic. Some dumps contained toxic substances (heavy metals, chlorethylenes, phenols, polychlorinated biphenyls, oil hydrocarbons and biogas). Statistically significant factors explaining the number and proportional representation of native plant species, archaeophytes (introduced before 1500) and neophytes (introduced later) were determined. In total, 588 species of vascular plants were recorded, with archaeophytes (133 species) over-represented and native species (322 species) and neophytes (133 species) under-represented compared to their proportions in the national flora. Minimum adequate models were used to determine the effects of several factors on species numbers and proportions, independent of other factors. Dump area, human density in the region and altitude (non-significant only in archaeophytes) were correlated positively with species numbers. Dump age, expressed as time since dump establishment, interacted with the dump toxicity; species numbers increased with dump age on non-toxic dumps, whereas on toxic dumps no increase in numbers was noted. For neophytes, dump toxicity also interacted with human density; the increase in numbers of neophytes with human density is more pronounced on toxic than on non-toxic dumps. The variables measured failed to explain observed differences in proportional representation of native species, archaeophytes and neophytes. This suggests that the occurrence of species growing in such extreme habitats is driven overwhelmingly by factors such as anthropogenic disturbance. A possible explanation for the positive effect of altitude on species numbers on dumps is that the effect of heating of the deposited substrate by microbiological processes, documented by previous studies, overrides the effect of altitude which was shown repeatedly to have a negative effect on species richness. Neophyte distribution is driven by an interplay of factors distinct from those influencing the distribution of native species, namely toxicity and human density (the latter we interpret as a surrogate for propagule pressure). Their distribution on studied dumps is more restricted than that of native taxa and archaeophytes, and they are more limited by toxic substrata; more intensive propagule pressure is required for their establishment at dumps with higher toxicity levels. [source] Novel Potentiometric Sensors of Molecular Imprinted Polymers for Specific Binding of ChlormequatELECTROANALYSIS, Issue 2 2008Ayman Abstract Molecularly imprinted polymers (MIP) were used as potentiometric sensors for the selective recognition and determination of chlormequat (CMQ). They were produced after radical polymerization of 4-vinyl pyridine (4-VP) or methacrylic acid (MAA) monomers in the presence of a cross-linker. CMQ was used as template. Similar non-imprinted (NI) polymers (NIP) were produced by removing the template from reaction media. The effect of kind and amount of MIP or NIP sensors on the potentiometric behavior was investigated. Main analytical features were evaluated in steady and flow modes of operation. The sensor MIP/4-VP exhibited the best performance, presenting fast near-Nernstian response for CMQ over the concentration range 6.2×10,6,1.0×10,2,mol L,1 with detection limits of 4.1×10,6,mol L,1. The sensor was independent from the pH of test solutions in the range 5,10. Potentiometric selectivity coefficients of the proposed sensors were evaluated over several inorganic and organic cations. Results pointed out a good selectivity to CMQ. The sensor was applied to the potentiometric determination of CMQ in commercial phytopharmaceuticals and spiked water samples. Recoveries ranged 96 to 108.5%. [source] Self-Assembled Monolayers into the 21st Century: Recent Advances and ApplicationsELECTROANALYSIS, Issue 2 2003Justin Gooding Abstract The modification of an interface on a molecular level with more than one molecular ,building block' is essentially an example of the ,bottom,up' fabrication principle of nanotechnology. The fabrication of such integrated molecular systems in electrochemistry has seen rapid progress in recent years via the development of sensing interfaces fabricated using self-assembled monolayers (SAMs). This review outlines recent advances and applications of self-assembled monolayers for modifying electrodes with an emphasis on the development of integrated molecular systems. First, some basic issues regarding fabricating integrated molecular systems, such as the role of the surface topography of the electrode and patterning surfaces, are discussed. Subsequently an overview of recent developments in pH, inorganic and bio sensing involving the use of SAMs is given. Finally emerging trends in using molecular building blocks in the fabrication of integrated molecular systems, such as nanotubes, dendrimers and nanoparticles, are reviewed. [source] Iodide-Selective Electrode Based on Copper PhthalocyanineELECTROANALYSIS, Issue 23 2002Saeed Shahrokhian Abstract Copper phthalocyanine was used as ion carrier for preparing polymeric membrane selective sensor for detection of iodide. The electrode was prepared by incorporating the ionophore into plasticized poly(vinyl chloride) (PVC) membrane, coated on the surface of graphite electrode. This novel electrode shows high selectivity for iodide with respect to many common inorganic and organic anions. The effects of membrane composition, pH and the influence of lipophilic cationic and anionic additives and also nature of plasticizer on the response characteristics of the electrode were investigated. A calibration plot with near-Nernestian slope for iodide was observed over a wide linear range of five decades of concentration (5×10,6,1×10,1,M). The electrode has a fast response time, and micro-molar detection limit (ca. 1×10,6,M iodide) and could be used over a wide pH range of 3.0,8.0. Application of the electrode to the potentiometric titration of iodide ion with silver nitrate is reported. This sensor is used for determination of the minute amounts of iodide in lake water samples. [source] Microfluidic chip-capillary electrophoresis for two orders extension of adjustable upper working range for profiling of inorganic and organic anions in urineELECTROPHORESIS, Issue 18 2010Wen Peng Guo Abstract To meet the need for onsite monitoring of urine anions, a microfluidic chip-capillary electrophoresis device was designed, fabricated and tested to extend the upper CE working range for an enhancement up to 500 fold (100 fold for sample dilution and 5 folds for CE injection) in order to analyze highly variable anionic metabolites in urine samples. Capillaries were embedded between two PMMA plates with laser-fabricated microchannel patterns to produce the microfluidic chip-capillary electrophoresis to perform standard/sample dilution and CE injection with adjustable dilution ratios. A circular ferrofluid valve was incorporated on-chip to perform cleanup and conditioning, mixing and dilution, injection and CE separation. Under optimized conditions, a complete assay for four samples can be achieved within an hour for 15 anions commonly found in urines. Satisfactory working ranges (0.005,500,mM) and low detection limits (0.5,6.5,,M based on S/N =2) are obtained with satisfactory repeatability (RSD, n=5) 0.52,0.87% and 4.1,6.5% for migration time and peak area, respectively. The working ranges with two orders adjustable upper extension are adequate to cover all analytes concentrations commonly found in human urine samples. The device fabricated shows sufficiently large experimentally verifiable enhancement factor to meet the application requirements. Its reliability was established by more than 94% recoveries of spiked standards and agreeable results from parallel method comparison with conventional ion chromatography method. The extension of the upper CE working range enables flexible onsite dilution on demand, a quick turn-around of results, and a low-cost device suitable for bedside monitoring of patients under critical conditions for metabolic disorders. [source] Cover Picture: Electrophoresis 22'2009ELECTROPHORESIS, Issue 22 2009Article first published online: 25 NOV 200 Issue no. 22 is a Special Issue on "CE and CEC Innovations" consisting of 24 important contributions in various areas of CE and CEC that are grouped into five different parts. Part I has 7 articles on novel "Stationary Phases for CEC". Part II is on "CE of Microorganisms and their Components and Interactions", and has 4 research articles. "Enantioseparations" constitute part III and has 3 research articles dealing with different chiral species and chiral CE systems. Part IV has 3 contributions on "Detection Approaches in CE". Part V is on "Capillary Coating, Affinity and Separation Media , Applications" and contains 7 research articles dealing with the separations of proteins, lipoproteins, bioactive inflammatory cytokines, inorganic and small organic anions, non-steroidal anti-inflammatory drugs, cell culture media and ancient DNA samples." [source] The role of Variovorax and other Comamonadaceae in sulfur transformations by microbial wheat rhizosphere communities exposed to different sulfur fertilization regimesENVIRONMENTAL MICROBIOLOGY, Issue 6 2008Achim Schmalenberger Summary Sulfonates are a key component of the sulfur present in agricultural soils. Their mobilization as part of the soil sulfur cycle is mediated by rhizobacteria, and involves the oxidoreductase AsfA. In this study, the effect of fertilization regime on rhizosphere bacterial asfA distribution was examined at the Broadbalk long-term wheat experiment, Rothamsted, UK, which was established in 1843, and has included a sulfur-free treatment since 2001. Direct isolation of desulfonating rhizobacteria from the wheat rhizospheres led to the identification of several Variovorax and Polaromonas strains, all of which contained the asfA gene. Rhizosphere DNA was isolated from wheat rhizospheres in plots fertilized with inorganic fertilizer with and without sulfur, with farmyard manure or from unfertilized plots. Genetic profiling of 16S rRNA gene fragments [denaturing gradient gel electrophoresis (DGGE)] from the wheat rhizospheres revealed that the level of inorganic sulfate in the inorganic fertilizer was correlated with changes in the general bacterial community structure and the betaproteobacterial community structure in particular. Community analysis at the functional gene level (asfA) showed that 40% of clones in asfAB clone libraries were affiliated to the genus Variovorax. Analysis of asfAB -based terminal restriction fragment length polymorphism (T-RFLP) fingerprints showed considerable differences between sulfate-free treatments and those where sulfate was applied. The results suggest the occurrence of desulfonating bacterial communities that are specific to the fertilization regime chosen and that arylsulfonates play an important role in rhizobacterial sulfur nutrition. [source] Investigation of the derived fuel rod formation from auto shredder residue using an extrusion apparatusENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2006Hua-Shan Tai Abstract The objective of this study was to form auto shredder residue,derived fuel (ASRDF) by using an extrusion apparatus, to solve the disposal problems of auto shredder residue (ASR) and to recover the heat value in its combustible content. ASR is the waste material produced by shredding vehicles. In general, these materials contain 20,30% of each vehicle by weight. ASR should be preprocessed into extruded rods before being used for fuel to remove about 20,30% inorganic, incombustible materials and to accommodate easy transportation and storage. The analytical results of ASR indicated the moisture content to be <2%, ash was <20%, and combustibles were nearly 80% by weight. Concentrations of N and S in the ASR were very low, although the chlorine content of ASR was in the range of 1.32,2.79%, which is the main burden of the ASR utilization. The heat content of ASR was about 5000,6000 kcal kg,1 (9000,10,800 BTU lb,1). Particle size had no significant effect on the analytical chemical composition. All the data indicated that ASR had a significant potential use as RDF. Through observations of the appearance and density of the ASRDF rod, we found that better appearance and higher densities could be achieved at higher extrusion temperature and pressure. The heat content of ASRDF was much lower than that of ASR, and it decreased with increasing extrusion temperature and pressure. The reasons for the better appearance, higher densities, and heat loss on the conditions of higher extrusion temperature and pressure may be explained by the proposed die swell ratio and skin,core effect. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] Bioaccumulation and biotransformation of arsenic in the Mediterranean polychaete Sabella spallanzanii experimental observationsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2007Alessandra Notti Abstract The Mediterranean fan worm Sabella spallanzanii is characterized by elevated basal levels of arsenic in branchial crowns (>1,000 ,g/g) and an unusual prevalence of dimethylarsinic acid (DMA), a relatively toxic compound with a possible antipredatory role. The aim of this work was to obtain further insights on the capability of this polychaete to accumulate arsenic from different compounds and to operate biotransformation reactions. Laboratory exposures to arsenate (AsV), dimethylarsinic acid (DMA), trimethylarsine (TMA), and arsenobetaine (AsB) revealed significant differences among tissues and kind of experiments. The highest increases of arsenic content were observed in branchial crowns of organisms treated with arsenate, which can enter the cell through the phosphate carrier system; lower variations were measured with DMA and TMA, while not-significant changes of total As occurred after treatments with AsB. In body tissues, exposure to AsV, DMA, and TMA confirmed a progressively lower accumulation of total arsenic, while a marked increase was caused by AsB. Obtained results suggested that accumulated arsenic could be chemically transformed, thus explaining the elevated basal levels of DMA typical of S. spallanzanii; during all the experiments, DMA was the most accumulated molecule, suggesting that this species possesses the enzymatic pathways for methylation and demethylation reactions of inorganic and trimethylated arsenicals. Only arsenobetaine was not converted into DMA, which would confirm a microbial pathway for degradation for this molecule, particularly important in body tissues of S. spallanzanii for the presence of bacteria associated to digestive tracts. Overall, the present study suggests future investigations on the biological role of arsenic and DMA in S. spallanzanii as a potential adaptive mechanism against predation in more vulnerable tissues. [source] Complete elimination of carbonates: A critical step in the accurate measurement of organic and black carbon in sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2005Marta T. Lukasewycz Abstract Accurate measurement of organic carbon (OC) and black carbon (BC) in sediments requires the complete removal of coexisting inorganic carbonates from the sample before instrumental analysis. The removal of carbonates from sediments is achieved with acidification, which causes the dissolution and decomposition of carbonates with accompanying effervescence. This effervescence, or the lack of it, is commonly used as an indicator for the presence or absence of carbonates. We have found that the lack of effervescence endpoint used with the direct acidification method (adding aliquots of acid to samples) is not a reliable indicator for complete removal of carbonates from sediment samples. The ineffectiveness of the lack of effervescence endpoint, we believe, is caused by the presence of carbonates with dissolution rates much slower than those of calcite, resulting in much slower rates of visible effervescence. We propose and demonstrate a method for determining the amount of acid required for complete elimination of all carbonates using Lake Michigan (USA) sediment samples. Based on our experiences with the lack of effervescence endpoint, we recommend that in any scheme for analysis of OC and/or BC, a minimum of two samples be treated with three different levels of acidification, with the lowest level being the same as that planned for all the OC and/or BC analyses. There can be no significant differences among the OC and BC contents measured using the three different levels of acidification. [source] Interactions between metabolism of trace metals and xenobiotic agonists of the aryl hydrocarbon receptor in the antarctic fish Trematomus bernacchii: Environmental perspectivesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2005Francesco Regoli Abstract Although Antarctica is a pristine environment, organisms are challenged with contaminants either released locally or transported from industrialized regions through atmospheric circulation and marine food webs. Organisms from Terra Nova Bay also are exposed to a natural enrichment of cadmium, but to our knowledge, whether such environmental conditions influence biological responses to anthropogenic pollutants has never been considered. In the present study, the Antarctic rock cod (Trematomus bernacchii) was exposed to model chemicals, including polycyclic aromatic hydrocarbons (benzo[a]pyrene), persistent organic pollutants (2,3,7,8-tetrachlorodibenzo- p -dioxin [TCDD]), cadmium, and a combination of cadmium and TCDD. Analyzed parameters included chemical bioaccumulation, activity, and levels of biotransformation enzymes (cytochrome P4501A); metallothioneins and the efficiency of the antioxidant system measured as individual defenses (catalase, glutathione, glutathione reductase, glutathione S -transferases, and glutathione peroxidases); and total scavenging capacity toward peroxyl and hydroxyl radicals. Reciprocal interactions between metabolism of inorganic and organic pollutants were demonstrated. Dioxin enhanced the accumulation of cadmium, probably stored within proliferating endoplasmic reticulum, and cadmium suppressed the inducibility of cytochrome P4501A, allowing us to hypothesize a posttranscriptional mechanism as the depletion of heme group availability. Clear evidence of oxidative perturbation was provided by the inhibition of antioxidants and enhanced sensitivity to oxyradical toxicity in fish exposed to organic chemicals. Exposure to cadmium revealed counteracting responses of glutathione metabolism; however, these responses did not prevent a certain loss of antioxidant capacity toward peroxyl radicals. The pattern of antioxidant responses exhibited by fish coexposed to cadmium and TCDD was more similar to that observed for cadmium than to that observed for TCDD. The overall results suggest that elevated natural levels of cadmium in Antarctic organisms from Terra Nova Bay can limit biotransformation capability of polycyclic (halogenated) hydrocarbons, thus influencing the bioaccumulation and biological effects of these chemicals in key sentinel species. [source] | ||||||||||||||||||||||||||||||||||||||||