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Chemical speciation

Laura C Merrill, Jennifer L Schaefer
Magnesium batteries are a promising alternative to lithium-ion batteries due to the widespread abundance of magnesium and its high specific volumetric energy capacity. Ethereal solvents such as tetrahydrofuran (THF) are commonly used for magnesium-ion electrolytes due the chemical compatibility with magnesium metal, but the volatile nature of THF is a concern for practical application. Herein, we investigate magnesium bis(hexamethyldisilazide) plus aluminum chloride (Mg(HMDS)2-AlCl3) electrolytes in THF, diglyme, and tetraglyme at varying temperature...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Etienne Loire, Sergio Tusso, Pierre Caminade, Dany Severac, Pierre Boursot, Guila Ganem, Carole M Smadja
Expression divergence, rather than sequence divergence, has been shown to be important in speciation, particularly in the early stages of divergence of traits involved in reproductive isolation. In the two European subspecies of house mice, Mus musculus musculus and M. m. domesticus, earlier studies have demonstrated olfactory-based assortative mate preference in populations close to their hybrid zone. It has been suggested that this behaviour evolved following the recent secondary contact between the two taxa (~3,000 years ago) in response to selection against hybridisation...
June 19, 2017: Molecular Ecology
Petr Drahota, Karel Raus, Eva Rychlíková, Jan Rohovec
Historical mining activities in the village of Kaňk (in the northern part of the Kutná Hora ore district, Czech Republic) produced large amounts of mine wastes which contain significant amounts of metal(loid) contaminants such as As, Cu, Pb, and Zn. Given the proximity of residential communities to these mining residues, we investigated samples of mine waste (n = 5), urban soil (n = 6), and road dust (n = 5) with a special focus on the solid speciation of As, Cu, Pb, and Zn using a combination of methods (XRD, SEM/EDS, oxalate extractions), as well as on in vitro bioaccessibility in simulated gastric and lung fluids to assess the potential exposure risks for humans...
June 15, 2017: Environmental Geochemistry and Health
Zeeshan Ali Syed, Martik Chatterjee, Manas Arun Samant, Nagaraj Guru Prasad
Promiscuity can drive the evolution of sexual conflict before and after mating occurs. Post mating, the male ejaculate can selfishly manipulate female physiology, leading to a chemical arms race between the sexes. Theory suggests that drift and sexually antagonistic coevolution can cause allopatric populations to evolve different chemical interactions between the sexes, thereby leading to postmating reproductive barriers and speciation. There is, however, little empirical evidence supporting this form of speciation...
June 13, 2017: Scientific Reports
Florian Werner, Carsten W Mueller, Jürgen Thieme, Alessandra Gianoncelli, Camille Rivard, Carmen Höschen, Jörg Prietzel
Soils comprise various heterogeneously distributed pools of lithogenic, free organic, occluded, adsorbed, and precipitated phosphorus (P) forms, which differ depending on soil forming factors. Small-scale heterogeneity of element distributions recently has received increased attention in soil science due to its influence on soil functions and soil fertility. We investigated the micro-scale distribution of total P and different specific P binding forms in aggregates taken from a high-P clay-rich soil and a low-P sandy soil by combining advanced spectrometric and spectroscopic techniques to introduce new insights on P accessibility and availability in soils...
June 9, 2017: Scientific Reports
Anna Leavey, Sameer Patel, Raul Martinez, Dhruv Mitroo, Claire Fortenberry, Michael Walker, Brent Williams, Pratim Biswas
Residential solid fuel combustion in cookstoves has established health impacts including bladder and lung cancers, cataracts, low birth weight, and pneumonia. The chemical composition of particulate matter (PM) from 4 commonly-used solid fuels (coal, dung, ambient/dry applewood, and oakwood pellets), emitted from a gasifier cookstove, as well as propane, were examined. Temporal changes between the different cookstove burn-phases were also explored. Normalized concentrations of non-refractory PM1, total organics, chloride, ammonium, nitrate, sulfate, and 41 particle-phase polycyclic aromatic hydrocarbons (PAHs) were measured using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a Thermal desorption Aerosol Gas chromatograph (TAG), respectively...
June 6, 2017: Environmental Research
F Penen, M P Isaure, D Dobritzsch, I Bertalan, H Castillo-Michel, O Proux, E Gontier, P Le Coustumer, D Schaumlöffel
The green micro-alga Chlamydomonas reinhardtii is commonly used as a model to investigate metallic stress in photosynthetic organisms. The aim of this study was to explore processes implemented by three C. reinhardtii strains to cope with cadmium (Cd), and particularly to evidence Cd sequestration in the cell. For that, we used a combination of subcellular fractionation and chemical imaging (micro X-ray fluorescence (μXRF) and transmission electron microscopy (TEM/X-EDS)) to identify subcellular compartments of Cd accumulation, and X-ray absorption spectroscopy (XAS) to determine chemical Cd speciation...
June 9, 2017: Metallomics: Integrated Biometal Science
C Mérot, C Salazar, R M Merrill, C D Jiggins, M Joron
The process by which species evolve can be illuminated by investigating barriers that limit gene flow between taxa. Recent radiations, such as Heliconius butterflies, offer the opportunity to compare isolation between pairs of taxa at different stages of ecological, geographical, and phylogenetic divergence. Here, we report a comparative analysis of existing and novel data in order to quantify the strength and direction of isolating barriers within a well-studied clade of Heliconius Our results highlight that increased divergence is associated with the accumulation of stronger and more numerous barriers to gene flow...
June 14, 2017: Proceedings. Biological Sciences
Forrest D Heller, Amanda J Casella, Gregg J Lumetta, Kenneth L Nash, Sergey I Sinkov, Samuel A Bryan
A Lewis cell was designed and constructed for investigating solvent extraction systems by spectrophotometrically monitoring both the organic and aqueous phases in real time. This new Lewis cell was tested and shown to perform well compared to other previously reported Lewis cell designs. The advantage of the new design is that the spectroscopic measurement allows determination of not only metal ion concentrations, but also information regarding chemical speciation - information not available with previous Lewis cell designs...
June 7, 2017: Analyst
Khadijah A Isimekhai, Hemda Garelick, John Watt, Diane Purchase
Informal E-waste recycling can pose a risk to human health and the environment which this study endeavours to evaluate. The distribution of a number of heavy metals in soil from an informal recycling site in the largest market for used and new electronics and electrical equipment in West Africa was investigated. The potential bioavailability of heavy metals, extent of contamination, potential risk due to the recycling activities and impact of external factors such as rainfall were also assessed. The concentrations of all the heavy metals tested were higher in the area where burning of the waste occurred than at the control site, suggesting an impact of the recycling activities on the soil...
June 6, 2017: Environmental Science and Pollution Research International
David Hilario Gonzalez, Christopher K Cala, Qiaoyun Peng, Suzanne E Paulson
Oxidative stress mediated by reactive oxygen species (ROS) is a hypothesized mechanism for particulate-matter related health effects. Fe(II) is a key player in ROS formation in the presence of lung antioxidants is not known. We use Suwanee River Fulvic Acid (SRFA) as a surrogate for HULIS and investigate its effect on OH formation from Fe(II). For the first time, a chemical kinetics model was developed to explain behavior of Fe(II) and SRFA in SLF. Model and experimental results are used to find best-fit rate coefficients for key reactions...
June 5, 2017: Environmental Science & Technology
Nora Expósito, Vikas Kumar, Jordi Sierra, Marta Schuhmacher, Gemma Giménez Papiol
Microalgae growth inhibition assays are candidates for referent ecotoxicological assays, and are a fundamental part in the strategy to reduce the use of fish and other animal models in aquatic toxicology. In the present work, the performance of Raphidocelis subcapitata exposed to heavy metals following standardized growth inhibition assays has been assessed in three different scenarios: 1) dilutions of single heavy metals, 2) artificial mixture of heavy metals at similar levels than those found in natural rivers and, 3) natural samples containing known mixtures of contaminants (heavy metals)...
June 1, 2017: Science of the Total Environment
Daniel R Fröhlich, Alena Kremleva, André Rossberg, Andrej Skerencak-Frech, Carsten Koke, Sven Krüger, Notker Rösch, Petra J Panak
The complexation of Am(III) with formate in aqueous solution is studied as a function of the pH value using a combination of extended X-ray absorption fine structure (EXAFS) spectroscopy, iterative transformation factor analysis (ITFA), and quantum chemical calculations. The Am LIII-edge EXAFS spectra are analyzed to determine the molecular structure (coordination numbers; Am-O and Am-C distances) of the formed Am(III)-formate species and to track the shift of the Am(III) speciation with increasing pH. The experimental data are compared to predictions from density functional calculations...
June 2, 2017: Inorganic Chemistry
Myriam Lazard, Marc Dauplais, Sylvain Blanquet, Pierre Plateau
Selenium is an essential trace element due to its incorporation into selenoproteins with important biological functions. However, at high doses it is toxic. Selenium toxicity is generally attributed to the induction of oxidative stress. However, it has become apparent that the mode of action of seleno-compounds varies, depending on its chemical form and speciation. Recent studies in various eukaryotic systems, in particular the model organism Saccharomyces cerevisiae, provide new insights on the cytotoxic mechanisms of selenomethionine and selenocysteine...
May 24, 2017: Biomolecular Concepts
Ugras Kaplan, Samer Amayri, Jakob Drebert, Andre Rossberg, Daniel Grolimund, Tobias Reich
Plutonium plays an important role within nuclear waste materials because of its long half-life and high radiotoxicity. The aim of this study was to investigate with high spatial resolution the reactivity of the more oxidized forms of Pu(V,VI) within Opalinus Clay (OPA) rock, a heterogeneous, natural argillaceous rock considered as potential repository host. A combination of synchrotron based X-ray microprobe and bulk techniques were used to study the spatial distribution and molecular speciation of Pu within OPA after diffusion and sorption processes...
May 30, 2017: Environmental Science & Technology
Brecht Verstraete, Steven Janssens, Nina Rønsted
Every plant species on Earth interacts in some way or another with microorganisms and it is well known that certain forms of symbiosis between different organisms can drive evolution. Within some clades of Rubiaceae (coffee family), a specific plant-bacteria interaction exists in which non-pathological endophytes are present in the leaves of their hosts. It is hypothesized that the bacterial endophytes, either alone or by interacting with the host, provide chemical protection against herbivory or pathogens by producing toxic or otherwise advantageous secondary metabolites...
May 25, 2017: Molecular Phylogenetics and Evolution
J Paluch, J Kozak, M Wieczorek, M Kozak, J Kochana, K Widurek, M Konieczna, P Kościelniak
The proposed approach to two-component speciation analysis relies on simultaneous application of two calibration methods to determination of two different forms of an analyte. One form is determined in extrapolative way, whereas the second form is determined in interpolative way, with the use of the same calibration graph, after appropriate chemical treatment, e.g. oxidation or reduction. The applicability of the approach has been verified on the examples of spectrophotometric determinations of Fe(II)/Fe(III) and Cr(VI)/Cr(III) using 1,10-phenanthroline and 1,5-diphenylcarbazide methods, respectively...
August 15, 2017: Talanta
Evgeniya Soldatova, Natalia Guseva, Zhanxue Sun, Valeriy Bychinsky, Pascal Boeckx, Bai Gao
Nitrogen contamination of natural water is a typical problem for various territories throughout the world. One of the regions exposed to nitrogen pollution is located in the Poyang Lake basin. As a result of agricultural activity and dense population, the shallow groundwater of this area is characterised by a high concentration of nitrogen compounds, primarily NO3(-), with the concentration varying from 0.1mg/L to 206mg/L. Locally, high ammonium content occurs in the shallow groundwater with low reduction potential Eh (<100mV)...
July 2017: Journal of Contaminant Hydrology
Estefanía Nunez-Bajo, M Carmen Blanco-López, Agustín Costa-García, M Teresa Fernández-Abedul
This paper describes the development of simple, sustainable, and low-cost strategies for signal enhancement on paper-based carbon platforms through gold nanoparticles electrogenerated from small volumes of tetrachloroauric (III) acid solutions. Carbon ink is deposited on a hydrophilic working area of the paper delimited with hydrophobic wax. This maskless procedure is fast and cuts down ink waste. The connection of this working electrode to the potentiostat is ensured with the use of screen-printed electrodes (SPEs)...
June 6, 2017: Analytical Chemistry
Ankur Jamwal, Som Niyogi
The present study evaluated the mechanistic underpinnings of the interactive effects of selenium (Se), both inorganic (selenite) and organic (selenomethionine (SeMet)), against arsenite (As-III) cytotoxicity using rainbow trout (Oncorhynchus mykiss) hepatocytes in primary culture. Arsenite is known to induce cytotoxic effects by disrupting cellular redox homeostasis. In contrast, Se is essential for the maintenance of cellular anti-oxidative machinery, but when present above a threshold concentration, can also induce reactive oxygen species (ROS) generation and cause oxidative damage...
June 21, 2017: Metallomics: Integrated Biometal Science
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