1,856,360 research outputs found
ruoyusun/GBM-Hg-ISO-EPME: GBM-Hg-ISO-EPME
No full textWe develop a global box model of Hg isotopes (GBM-Hg-ISO-EPME) to investigate the mechanism of Hg enrichment and Hg isotopic variations across the EPME.
Full Changelog: https://github.com/ruoyusun/GBM-Hg-ISO-EPME/commits/v1.
Together, not separately, OH and O3 oxidize Hg(0) to Hg(II) in the atmosphere
No full textMercury, a highly toxic metal, is emitted to the atmosphere mostly as gaseous Hg(0). Atmospheric Hg(0) enters ecosystems largely through via uptake by vegetation, while Hg(II) largely enters ecosystems in oceans and via rainfall. Consequently, the redox chemistry of atmospheric mercury strongly influences its fate and its global biogeochemical cycling. Here we report on the oxidation and reduction of Hg(I) (BrHg and HOHg radicals) in reactions with ozone, and how the electronic structure of these Hg(I) species affects the kinetics of these reactions. The oxidation reactions lead to XHgO• + O2 (X=Br and OH), while the reduction reaction produces Hg(0), HOX, and O2. According to our calculations with CCSD(T), NEVPT2, and CAM-B3LYP-D3BJ, the kinetics of both oxidation reactions are very similar. These two oxidation reactions are much faster than their reduction counterparts, and this effect is remarkably stronger for the oxidation of HOHg(I) by ozone. Modeling of field data supports the idea that OH and/or O3 (rather than Br) dominates Hg(II) production in the continental boundary layer. Almost all models invoking OH- and ozone-initiated oxidation of Hg(0) assume that these reactions directly produces Hg(II), despite the lack of plausible mechanism for these oxidation reactions. The present work helps reconcile modeling results with mechanistic insights
HG-induced osteoblast cells utilize both mitochondrial respiration and Glycolysis more efficiently than healthy cells.
No full textA. Oxygen consumption rate is indicative of mitochondrial respiration in healthy and HG-treated cells. B. Four channels of sequential injections exhibited an increase in OCR levels in HG-treated bone cells. C. Extracellular acidification rate is indicative of glycolysis in healthy and HG-treated cells. D. Four channels of sequential injections exhibited an increased in ECAR levels in HG-treated bone cells. Abbreviations: OCR = Oxygen Consumption Rate; ECAR = Extracellular Acidification rate. Error bars indicate SD (standard deviation). Data were analyzed using Two-way ANOVA. A total of N = 3 independent experiments per culture condition were performed. All experiments were performed in triplicates.</p
Experimental studies of Hg(II)-Hg(0) transformations and their effects on Hg isotope fractionation
No full textUnderstanding the redox transformations of inorganic forms of mercury (Hg) is necessary for understanding the fate of mercury in environmental systems. In this study, the interactions of Hg(0) and Hg(II) with organic and inorganic substances were characterized using mercury stable isotopes. Interactions of a mixed Hg(0)-Hg(II) solution with thiol and humic substances were observed, with no net changes to redox speciation. In the presence of mercaptoacetic acid (MCA), an equilibrium isotope enrichment factor (ε202Hg = δ202HgHg(II) - δ202HgHg(0)) of 1.34‰ between the Hg(II) and Hg(0) fractions was observed, similar with previously published values for Hg(0) oxidation by thiols. The equilibrium ε202Hg values similarly determined for 2-mercaptopropionic acid (MPA) and Suwannee River humic acids were 2.03‰ and 1.50‰, respectively. Reduction of mercury by siderite (FeCO3) was also characterized with respect to isotope fractionation over the course of the reaction. This reaction resulted in an 87% reduction of Hg(II) over 30 minutes, with change in mercury isotope ratios of the reactant. Kinetic ε202Hg values for the reduction of Hg(II) by siderite (ε202Hg = δ202HgHg(0) - δ202HgHg(II)) were determined by closed-system model (-1.59‰) and Rayleigh distillation model (-1.07‰; product enrichment in light isotopes). The final equilibrium state exhibited an equilibrium ε202Hg of -0.67‰. The results from the experiments conducted suggest that there is equilibrium isotope exchange between thiol-bound Hg(II) and dissolved Hg(0), and that the reduction by siderite is rapid and may involve multiple processes through the reaction.M.S.Includes bibliographical reference
Hessische Beiträge zur Gelehrsamkeit und Kunst. Stück 1-4
No full textLayoutgetreues Digitalisat der Ausg.: Frankfurt, M. : Varrentrapp und Wenner, 1784 Zentralbibliothek Sign.: VIII C 10 (Hassiaca
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Hg-Stable Isotope Variations in Marine Top Predators of the Western Arctic Ocean
No full textRecent studies on mercury (Hg)-stable
isotopes in Alaskan seabird
eggs and ringed seal livers illustrated the control of sea ice cover
on marine methyl-Hg photochemistry. Here, complementary marine mammal
tissues have been analyzed to document variations in Hg-, carbon (C)-,
and nitrogen (N)-stable isotope compositions of Arctic marine food
webs. Hg-stable isotope ratios were measured in liver samples of 55
beluga whales (Delphinapterus leucas) and 15 polar bears (Ursus maritimus) collected since 1990. Large variations in δ202Hg (≈2.1‰) and Δ199Hg (≈1.7‰)
are observed between species and within species stocks covering the
Gulf of Alaska–Bering Sea–Arctic Ocean regions. Polar
bears, mainly feeding on ringed seal (δ15N shift
of 4.2‰), show identical liver Δ199Hg of 0.5‰,
confirming the absence of metabolic mass-independent fractionation,
and 0.33 ± 0.11‰ enrichment in heavy Hg isotopes. Beluga
whale liver total Hg concentrations increase with age, reflecting
lifetime bioaccumulation, while Hg speciation shifts to inorganic
Hg with age as a result of hepatic methyl-Hg breakdown. Δ200Hg variations in biota show a small, 0.1‰ decrease
from North Pacific Ocean to Arctic Ocean habitats, suggesting atmospheric
Hg deposition to be important in the Pacific and terrestrial Hg inputs
to dominate in the Arctic Ocean. Similar to seabird eggs, a consistent
south to north gradient in Δ199Hg baseline is seen
in mammal liver tissues, confirming sea ice cover as a control factor
on marine Hg photoreduction and Δ199Hg. Arctic Ocean
beluga whales have near zero Δ199Hg, indicating that
terrestrial Hg and in-situ-produced methyl-Hg are
not measurably photoreduced in the Arctic Ocean before entering the
marine food web
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