646 research outputs found

    VIVO and VIV Species Formed in Aqueous Solution by the Tridentate Glutaroimide–Dioxime Ligand – An Instrumental and Computational Characterization

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    Complexation of VIV in aqueous solution with glutaroimide–dioxime (H3L), a ligand proposed for the possible sequestration of uranium from seawater, was studied by the combined application of spectroscopic (EPR and UV/Vis), spectrometric (ESI‐MS), electrochemical (CV), and computational (DFT) techniques. The results indicate that a rare non‐oxido VIV species, with formula [VIVL2]2–, is formed in the pH range 3–5. It transforms into a usual VIVO complex, [VIVOL(OH)]2–, at pH > 6. The non‐oxido species is characterized by a "type 3" EPR spectrum with Az ≈ 126 × 10–4 cm–1 and a UV/Vis signal with ε > 2000 m–1 cm–1 in the visible region. The detection of VV species by ESI‐MS spectrometry was related to two possible oxidation processes, the first one in solution and the second one in‐source during the recording of the spectra. The cyclic voltammogram of [VIVL2]2– shows two quasi‐reversible processes, at E1/2 = –0.75 V and E1/2 = 0.03 V, assigned to the VIV/VIII reduction and VIV/VV oxidation, respectively. All the experimental results were verified by DFT calculations, which indicated that the geometry of the non‐oxido VIV complex is intermediate between an octahedron and a trigonal prism and allowed us to predict its 51V hyperfine coupling (HFC) tensor A, the electron absorption spectrum, the two redox processes in the cyclic voltammogram, and the electronic structure that, in turn, determines its EPR and UV/Vis behavior

    Quasinormal modes of a Schwarzschild black hole surrounded by free static spherically symmetric quintessence: Electromagnetic perturbations

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    In this paper, we evaluated the quasinormal modes of electromagnetic perturbation in a Schwarzschild black hole surrounded by the static spherically symmetric quintessence by using the third-order WKB approximation when the quintessential state parameter wq w_{q} in the range of −1/3<wq<0-1/3<w_{q}<0. Due to the presence of quintessence, Maxwell field damps more slowly. And when at −1<wq<−1/3-1<w_{q}<-1/3, it is similar to the black hole solution in the ds/Ads spacetime. The appropriate boundary conditions need to be modified.Comment: 6 pages, 3 figure

    Constraints on accelerating universe using ESSENCE and Gold supernovae data combined with other cosmological probes

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    We use recently observed data: the 192 ESSENCE type Ia supernovae (SNe Ia), the 182 Gold SNe Ia, the 3-year WMAP, the SDSS baryon acoustic peak, the X-ray gas mass fraction in clusters and the observational H(z)H(z) data to constrain models of the accelerating universe. Combining the 192 ESSENCE data with the observational H(z)H(z) data to constrain a parameterized deceleration parameter, we obtain the best fit values of transition redshift and current deceleration parameter zT=0.632−0.127+0.256z_{T}=0.632^{+0.256}_{-0.127}, q0=−0.788−0.182+0.182q_{0}=-0.788^{+0.182}_{-0.182}. Furthermore, using Λ\LambdaCDM model and two model-independent equation of state of dark energy, we find that the combined constraint from the 192 ESSENCE data and other four cosmological observations gives smaller values of Ω0m\Omega_{0m} and q0q_{0}, but a larger value of zTz_{T} than the combined constraint from the 182 Gold data with other four observations. Finally, according to the Akaike information criterion it is shown that the recently observed data equally supports three dark energy models: Λ\LambdaCDM, wde(z)=w0w_{de}(z)=w_{0} and wde(z)=w0+w1ln⁡(1+z)w_{de}(z)=w_{0}+w_{1}\ln(1+z).Comment: 18 pages, 8 figure

    The Accelerating Growth of Online Tagging Systems

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    Research on the growth of online tagging systems not only is interesting in its own right, but also yields insights for website management and semantic web analysis. Traditional models that describing the growth of online systems can be divided between linear and nonlinear versions. Linear models, including the BA model (Brabasi and Albert, 1999), assume that the average activity of users is a constant independent of population. Hence the total activity is a linear function of population. On the contrary, nonlinear models suggest that the average activity is affected by the size of the population and the total activity is a nonlinear function of population. In the current study, supporting evidences for the nonlinear growth assumption are obtained from data on Internet users' tagging behavior. A power law relationship between the number of new tags (F) and the population (P), which can be expressed as F ~ P ^ gamma (gamma > 1), is found. I call this pattern accelerating growth and find it relates the to time-invariant heterogeneity in individual activities. I also show how a greater heterogeneity leads to a faster growth.Comment: 8 pages, 3 figure

    Prenatal exposure to traffic and ambient air pollution and infant weight and adiposity: The Healthy Start study

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    Background: Prenatal exposures to ambient air pollution and traffic have been associated with adverse birth outcomes, and may also lead to an increased risk of obesity. Obesity risk may be reflected in changes in body composition in infancy. Objective: To estimate associations between prenatal ambient air pollution and traffic exposure, and infant weight and adiposity in a Colorado-based prospective cohort study. Methods: Participants were 1125 mother-infant pairs with term births. Birth weight was recorded from medical records and body composition measures (fat mass, fat-free mass, and adiposity [percent fat mass]) were evaluated via air displacement plethysmography at birth (n = 951) and at ~5 months (n = 574). Maternal residential address was used to calculate distance to nearest roadway, traffic density, and ambient concentrations of fine particulate matter (PM2.5) and ozone (O3) via inverse-distance weighted interpolation of stationary monitoring data, averaged by trimester and throughout pregnancy. Adjusted linear regression models estimated associations between exposures and infant weight and body composition. Results: Participants were urban residents and diverse in race/ethnicity and socioeconomic status. Average ambient air pollutant concentrations were generally low; the median, interquartile range (IQR), and range of third trimester concentrations were 7.3 μg/m3 (IQR: 1.3, range: 3.3–12.7) for PM2.5 and 46.3 ppb (IQR: 18.4, range: 21.7–63.2) for 8-h maximum O3. Overall there were few associations between traffic and air pollution exposures and infant outcomes. Third trimester O3 was associated with greater adiposity at follow-up (2.2% per IQR, 95% CI 0.1, 4.3), and with greater rates of change in fat mass (1.8 g/day, 95% CI 0.5, 3.2) and adiposity (2.1%/100 days, 95% CI 0.4, 3.7) from birth to follow-up. Conclusions: We found limited evidence of an association between prenatal traffic and ambient air pollution exposure and infant body composition. Suggestive associations between prenatal ozone exposure and early postnatal changes in body composition merit further investigation

    Effects of red grape, wild grape and black raspberry wines on ground pork during refrigerated storage

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    The effects of red grape, wild grape and black raspberry wines on the quality of ground pork during a 15 days refrigerated storage period were investigated. The levels of phenolic compounds were the highest in black raspberry wine (P0.05). The addition of 5% and 10% wine influenced the quality of ground pork by decreasing pH, inhibiting the progression of lipid oxidation and the formation of total volatile basic nitrogen (TVB-N), and stabilizing the red colour of the ground pork compared to control samples to which no wine was added. In ground pork, addition of red grape wine led to lower concentrations of thiobarbituric acid reactive substances (TBARS, 0.19–0.39 mg kg−1) and TVB-N values (69.1–119.9 mg kg−1) than wild grape (0.16–0.43 mg kg−1 and 72.0–194.1 mg kg−1, respectively) or black raspberry wine (0.33–0.58 mg kg−1 and 81.7–225.4 mg kg−1, respectively) up to 10 days of storage. Results from the present study suggested that the quality of ground pork was affected by wine type and storage period. These effects could be due to phenolic compounds as well as other chemical components of the wines

    Metal enrichment processes

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    There are many processes that can transport gas from the galaxies to their environment and enrich the environment in this way with metals. These metal enrichment processes have a large influence on the evolution of both the galaxies and their environment. Various processes can contribute to the gas transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy interactions and others. We review their observational evidence, corresponding simulations, their efficiencies, and their time scales as far as they are known to date. It seems that all processes can contribute to the enrichment. There is not a single process that always dominates the enrichment, because the efficiencies of the processes vary strongly with galaxy and environmental properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 17; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

    Tobacco Retail Outlets, Neighborhood Deprivation and the Risk of Prenatal Smoke Exposure

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    INTRODUCTION: Smoking and smoke exposure among pregnant women remain persistent public health issues. Recent estimates suggest that approximately one out of four nonsmokers have measurable levels of cotinine, a marker indicating regular exposure to secondhand smoke. Epidemiological research has attempted to pinpoint individual-level and neighborhood-level factors for smoking during pregnancy. However, most of these studies have relied upon self-reported measures of smoking. AIMS AND METHODS: To more accurately assess smoke exposure resulting from both smoking and secondhand exposure in mothers during pregnancy, we used Bayesian regression models to estimate the association of cotinine levels with tobacco retail outlet (TRO) exposure and a neighborhood deprivation index (NDI) in six counties in North Carolina centered on Durham County. RESULTS: Results showed a significant positive association between TRO exposure (β = 0.008, 95% credible interval (CI) = [0.003, 0.013]) and log cotinine after adjusting for individual covariates (eg, age, race/ethnicity, education, marital status). TRO exposure was not significant after including the NDI, which was significantly associated with log cotinine (β = 0.143, 95% CI = [0.030, 0.267]). However, in a low cotinine stratum (indicating secondhand smoke exposure), TRO exposure was significantly associated with log cotinine (β = 0.005, 95% CI = [0.001, 0.009]), while in a high cotinine stratum (indicating active smoking), the NDI was significantly associated with log cotinine (β = 0.176, 95% CI = [0.005, 0.372]). CONCLUSIONS: In summary, our findings add to the evidence that contextual factors are important for active smoking during pregnancy. IMPLICATIONS: In this study, we found several significant associations that suggest a more nuanced understanding of the potential influence of environmental- and individual-level factors for levels of prenatal smoke exposure. Results suggested a significant positive association between TRO exposure and cotinine levels, after adjusting for the individual factors such as race, education, and marital status. Individually, NDI was similarly positively associated with cotinine levels as well. However, when combining TRO exposure alongside NDI in the same model, TROs were no longer significantly associated with overall cotinine levels
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