Removal of Cd, Cu, Pb, and Zn from aqueous solutions by biochars

Sorption and desorption of heavy metals (Cd, Cu, Pb, and Zn) was evaluated in biochars derived from sugarcane bagasse (SB), eucalyptus forest residues (CE), castor meal (CM), green coconut pericarp (PC), and water hyacinth (WH) as candidate materials for the treatment of contaminated waters and soils. Solid-liquid distribution coefficients depended strongly on the initial metal concentration, with K d,max values mostly within the range 10(3)-10(4) L kg(-1). For all biochars, up to 95 % removal of all the target metals from water was achieved. The WH biochar showed the highest K d,max values for all the metals, especially Cd and Zn, followed by CE (for Cd and Pb) and PC (for Cd, Pb, and Zn). Sorption data were fitted satisfactorily with Freundlich and linear models (in the latter case, for the low concentration range). The sorption appeared to be controlled by cationic exchange, together with specific surface complexation at low metal concentrations. The low desorption yields, generally less than 5 %, confirmed that the sorption process was largely irreversible and that the biochars could potentially be used in decontamination applications.

An empirical model for calculation of the collimator contamination dose in therapeutic proton beams

Collimators are used as lateral beam shaping devices in proton therapy with passive scattering beam lines. The dose contamination due to collimator scattering can be as high as 10% of the maximum dose and influences calculation of the output factor or monitor units (MU). To date, commercial treatment planning systems generally use a zero-thickness collimator approximation ignoring edge scattering in the aperture collimator and few analytical models have been proposed to take scattering effects into account, mainly limited to the inner collimator face component. The aim of this study was to characterize and model aperture contamination by means of a fast and accurate analytical model. The entrance face collimator scatter distribution was modeled as a 3D secondary dose source. Predicted dose contaminations were compared to measurements and Monte Carlo simulations. Measurements were performed on two different proton beam lines (a fixed horizontal beam line and a gantry beam line) with divergent apertures and for several field sizes and energies. Discrepancies between analytical algorithm dose prediction and measurements were decreased from 10% to 2% using the proposed model. Gamma-index (2%/1 mm) was respected for more than 90% of pixels. The proposed analytical algorithm increases the accuracy of analytical dose calculations with reasonable computation times.

Persistent natural acidification drives major distribution shifts in marine benthic ecosystems

Ocean acidification is receiving increasing attention because of its potential to affect marine ecosystems. Rare CO2 vents offer a unique opportunity to investigate the response of benthic ecosystems to acidification. However, the benthic habitats investigated so far are mainly found at very shallow water (less than or equal to 5 m depth) and therefore are not representative of the broad range of continental shelf habitats. Here, we show that a decrease from pH 8.1 to 7.9 observed in a CO2 vent system at 40 m depth leads to a dramatic shift in highly diverse and structurally complex habitats. Forests of the kelp Laminaria rodriguezii usually found at larger depths (greater than 65 m) replace the otherwise dominant habitats (i.e. coralligenous outcrops and rhodolith beds), which are mainly characterized by calcifying organisms. Only the aragonite-calcifying algae are able to survive in acidified waters, while high-magnesium-calcite organisms are almost completely absent. Although a long-term survey of the venting area would be necessary to fully understand the effects of the variability of pH and other carbonate parameters over the structure and functioning of the investigated mesophotic habitats, our results suggest that in addition of significant changes at species level, moderate ocean acidification may entail major shifts in the distribution and dominance of key benthic ecosystems at regional scale, which could have broad ecological and socio-economic implications.

Sorption behaviour of nonylphenol and nonylphenol monoethoxylate in soils

Sorption behaviour of two alkylphenolic compounds (APCs), nonylphenol (NP) and nonylphenol monoethoxylate (NP1EO), was studied in five soils with contrasting characteristics. Sorption isotherms were obtained by equilibrating the soil samples with 0.01 mol L(-1) CaCl2 solutions containing different initial concentrations of NP or NP1EO. Linear fitting was generally appropriate for describing the sorption behaviour of NP and NP1EO in the soils, with the exception of two cases, for which the Freundlich model was more suitable for describing the sorption pattern of NP1EO. Solid-liquid distribution coefficients derived from sorption isotherms (Kd) varied from 24 to 1059 mL g(-1) for NP and from 51 to 740 mL g(-1) for NP1EO. For most soils, sorption Kd values were higher for NP than for NP1EO due to the higher hydrophobicity of NP. Sorption reversibility of NP and NP1EO was also tested from desorption isotherms. Desorption solid-liquid distribution coefficients (Kd,des), obtained from linear fitting, were between 130 and 1467 mL g(-1) for NP and between 24 and 1285 mL g(-1) for NP1EO. Kd,des values were higher than Kd values, which demonstrated that target compounds were irreversibly sorbed into soils, with the exception of the high desorption yield (45%) of NP1EO in the soil with the lowest content of organic matter. The fraction of soil organic carbon (FOC) was a key parameter that influenced the sorption of NP and NP1EO in soils, with logKOC values of 4.0 and 3.8, respectively.

Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element V_{tb}

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb^{-1} per experiment. The t-channel cross section is measured to be σ_{t}=2.25_{-0.31}^{+0.29} pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ_{s+t}=3.30_{-0.40}^{+0.52} pb, without assuming the standard model value for the ratio σ_{s}/σ_{t}. The resulting value of the magnitude of the top-to-bottom quark coupling is |V_{tb}|=1.02_{-0.05}^{+0.06}, corresponding to |V_{tb}|>0.92 at the 95% C.L.

Fluorescence of the Flavin group in choline oxidase. Insights and analytical applications for the determination of choline and betaine aldehyde

Choline oxidase (ChOx) is a flavoenzyme catalysing the oxidation of choline (Ch) to betaine aldehyde (BA) and glycine betaine (GB). In this paper a fundamental study of the intrinsic fluorescence properties of ChOx due to Flavin Adenine Dinucleotide (FAD) is presented and some analytical applications are studied in detail. Firstly, an unusual alteration in the excitation spectra, in comparison with the absorption spectra, has been observed as a function of the pH. This is ascribed to a change of polarity in the excited state. Secondly, the evolution of the fluorescence spectra during the reaction seems to indicate that the reaction takes place in two consecutive, but partially overlapped, steps and each of them follows a different mechanism. Thirdly, the chemical system can be used to determine the Ch concentration in the range from 5×10(-6)M to 5×10(-5)M (univariate and multivariate calibration) in the presence of BA as interference, and the joint Ch+BA concentration in the range 5×10(-6)-5×10(-4)M (multivariate calibration) with mean errors under 10%; a semiquantitative determination of the BA concentration can be deduced by difference. Finally, Ch has been successfully determined in an infant milk sample.

Importance of salt fingering for new nitrogen supply in the oligotrophic ocean

The input of new nitrogen into the euphotic zone constrains the export of organic carbon to the deep ocean and thereby the biologically mediated long-term CO₂ exchange between the ocean and atmosphere. In low-latitude open-ocean regions, turbulence-driven nitrate diffusion from the ocean's interior and biological fixation of atmospheric N₂ are the main sources of new nitrogen for phytoplankton productivity. With measurements across the tropical and subtropical Atlantic, Pacific and Indian oceans, we show that nitrate diffusion (171±190 μmol m⁻² d⁻¹) dominates over N₂ fixation (9.0±9.4 μmol m⁻² d⁻¹) at the time of sampling. Nitrate diffusion mediated by salt fingers is responsible for ca. 20% of the new nitrogen supply in several provinces of the Atlantic and Indian Oceans. Our results indicate that salt finger diffusion should be considered in present and future ocean nitrogen budgets, as it could supply globally 0.23–1.00 Tmol N yr⁻¹ to the euphotic zone.

The relative contribution of nitrogen fixation and nitrogen diffusion to marine biomes is presently debated. Here, the authors evaluate the contribution of these pathways across the tropics and subtropics of the global ocean and show that nitrogen diffusion, reinforced by salt fingers, is the dominant process.

Search for Resonances Decaying to Top and Bottom Quarks with the CDF Experiment

We report on a search for charged massive resonances decaying to top (t) and bottom (b) quarks in the full data set of proton-antiproton collisions at a center-of-mass energy of √[s]=1.96  TeV collected by the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.5  fb(-1). No significant excess above the standard model background prediction is observed. We set 95% Bayesian credibility mass-dependent upper limits on the heavy charged-particle production cross section times branching ratio to tb. Using a standard model extension with a W'→tb and left-right-symmetric couplings as a benchmark model, we constrain the W' mass and couplings in the 300-900  GeV/c(2) range. The limits presented here are the most stringent for a charged resonance with mass in the range 300-600  GeV/c(2) decaying to top and bottom quarks.

Tevatron constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quark pairs

Combined constraints from the CDF and D0 Collaborations on models of the Higgs boson with exotic spin J and parity P are presented and compared with results obtained assuming the standard model value JP=0+. Both collaborations analyzed approximately 10  fb(-) of proton-antiproton collisions with a center-of-mass energy of 1.96 TeV collected at the Fermilab Tevatron. Two models predicting exotic Higgs bosons with JP=0- and JP=2+ are tested. The kinematic properties of exotic Higgs boson production in association with a vector boson differ from those predicted for the standard model Higgs boson. Upper limits at the 95% credibility level on the production rates of the exotic Higgs bosons, expressed as fractions of the standard model Higgs boson production rate, are set at 0.36 for both the JP=0- hypothesis and the JP=2+ hypothesis. If the production rate times the branching ratio to a bottom-antibottom pair is the same as that predicted for the standard model Higgs boson, then the exotic bosons are excluded with significances of 5.0 standard deviations and 4.9 standard deviations for the JP=0- and JP=2+ hypotheses, respectively.

Constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quarks in the full CDF data set

A search for particles with the same mass and couplings as those of the standard model Higgs boson but different spin and parity quantum numbers is presented. We test two specific alternative Higgs boson hypotheses: a pseudoscalar Higgs boson with spin-parity J^{P}=0^{-} and a gravitonlike Higgs boson with J^{P}=2^{+}, assuming for both a mass of 125  GeV/c^{2}. We search for these exotic states produced in association with a vector boson and decaying into a bottom-antibottom quark pair. The vector boson is reconstructed through its decay into an electron or muon pair, or an electron or muon and a neutrino, or it is inferred from an imbalance in total transverse momentum. We use expected kinematic differences between events containing exotic Higgs bosons and those containing standard model Higgs bosons. The data were collected by the CDF experiment at the Tevatron proton-antiproton collider, operating at a center-of-mass energy of sqrt[s]=1.96  TeV, and correspond to an integrated luminosity of 9.45  fb^{-1}. We exclude deviations from the predictions of the standard model with a Higgs boson of mass 125  GeV/c^{2} at the level of 5 standard deviations, assuming signal strengths for exotic boson production equal to the prediction for the standard model Higgs boson, and set upper limits of approximately 30% relative to the standard model rate on the possible rate of production of each exotic state.

[Ocular involvement with Candida albicans: report of 2 cases]

INTRODUCTION

Ocular involvement by Candida albicans is rare and may present as endogenous endophthalmitis or choroiditis. It occurs in the context of C. albicans septicemia, in the context of intensive care unit hospitalization or intravenous drug use. We report two cases referred to our department with different characteristics, background, diagnostic modalities and different courses.

OBSERVATIONS

A 37-year-old woman, with a history of intravenous drug use, presented with C. albicans endophthalmitis. Intravenous combination antifungal therapy was begun, but vitrectomy and intravitreal amphotericin B were performed due to worsening of the endophthalmitis. The second case was a 53-year-old man who was hospitalized in the intensive care unit for C. albicans septicemia with a left macular chorioretinitis. Intravenous antifungal therapy was initiated and allowed regression of the ocular lesion.

DISCUSSION

Our cases illustrate both types of ophthalmic involvement by candidiasis requiring different treatments with well-described recommendations: in the case of endophthalmitis, the use of vitrectomy and intravitreal amphotericin B injection in association with intravenous antifungal treatment, whereas parenteral antifungal treatment is often sufficient in the case of chorioretinitis.

CONCLUSION

Early detection, initiation of treatment and ophthalmologic monitoring are difficult but necessary in these populations non-compliant with follow-up or in intensive care units. The management of ocular candidiasis requires good collaboration between the ophthalmology, infectious diseases and intensive care unit departments.

Giant enhancement of the optical second-harmonic emission of WSe(2) monolayers by laser excitation at exciton resonances

We show that the light-matter interaction in monolayer WSe_{2} is strongly enhanced when the incoming electromagnetic wave is in resonance with the energy of the exciton states of strongly Coulomb bound electron-hole pairs below the electronic band gap. We perform second harmonic generation (SHG) spectroscopy as a function of laser energy and polarization at T=4  K. At the exciton resonance energies we record an enhancement by up to 3 orders of magnitude of the SHG efficiency, due to the unusual combination of electric dipole and magnetic dipole transitions. The energy and parity of the exciton states showing the strong resonance effects are identified in 1- and 2-photon photoluminescence excitation experiments, corroborated by first principles calculations. Targeting the identified exciton states in resonant 2-photon excitation allows us to maximize k-valley coherence and polarization.

Viability of organic wastes and biochars as amendments for the remediation of heavy metal-contaminated soils

Composts derived from municipal (MOW and MSW) and domestic wastes (DOM), wastes from the olive oil industry (OWH and OP), green waste (GW), and biochars (BF and BS) were investigated to test their viability for remediating metal-contaminated soils. In addition to common analyses, the characterisation included structural analyses (FTIR and (13)C NMR), determination of the acid neutralisation capacity (ANC) and the construction of sorption isotherms for target metals (Pb, Zn, Cd, Ni and Cu). MOW and GW had the highest ANC values (4280 and 7100 meq kg(-1), respectively), and MOW, GW, DOM, BF and BS exhibited the highest solid-liquid distribution coefficients (Kd) with maximum values in the 10(4) L kg(-1) range. Sorption isotherms were fitted using linear and Freundlich models for better comparison of the sorption capacities of the materials. Based on their basic pH, high ANC and high sorption capacity, MOW, GW and biochars are the most promising materials.