The occurrence of antibiotics in the aquatic environment is an important emerging issue due to potential adverse effect of these compounds on ecosystem and human health. For a correct environmental ...risk assessment there is a need for appropriate analytical methods for monitoring antibiotic residues in a variety of water matrices. This paper describes a method for the determination of eleven sulphonamide compounds in surface and drinking waters using solid-phase extraction and liquid chromatography-tandem mass spectrometry. Recoveries of the analytes in both surface and drinking water matrices at different fortification levels, always exceed 87%; the limits of quantification in surface water samples are between 0.005 and 0.021 µg L−1 depending on the compound, and the interday method precision is less than 12%. Matrix effects were evaluated in drinking and surface water samples. The method has been applied to a small scale reconnaissance of river, lake, mineral and municipal water samples; results indicate the occurrence of sulphonamides in some surface and mineral waters analyzed.
157Gd is a potential agent for neutron capture cancer therapy (GdNCT). We directly observed the microdistribution of Gd in cultured human glioblastoma cells exposed to ...Gd-diethylenetriaminepentaacetic acid (Gd-DTPA). We demonstrated, with three independent techniques, that Gd-DTPA penetrates the plasma membrane, and we observed no deleterious effect on cell survival. A systematic microchemical analysis revealed a higher Gd accumulation in cell nuclei compared with cytoplasm. This is significant for prospective GdNCT because the proximity of Gd to DNA increases the cell-killing potential of the short-range, high-energy electrons emitted during the neutron capture reaction. We also exposed Gd-containing cells to thermal neutrons and demonstrated the GdNC reaction effectiveness in inducing cell death. These results in vitro stimulated in vivo Gd-DTPA uptake studies, currently underway, in human glioblastoma patients.
Context.
Polarimetric imaging is one of the most effective techniques for high-contrast imaging and for the characterization of protoplanetary disks, and it has the potential of becoming instrumental ...in the characterization of exoplanets. The Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument installed on the Very Large Telescope (VLT) contains the InfraRed Dual-band Imager and Spectrograph (IRDIS) with a dual-beam polarimetric imaging (DPI) mode, which offers the capability of obtaining linear polarization images at high contrast and resolution.
Aims.
We aim to provide an overview of the polarimetric imaging mode of VLT/SPHERE/IRDIS and study its optical design to improve observing strategies and data reduction.
Methods.
For
H
-band observations of TW Hydrae, we compared two data reduction methods that correct for instrumental polarization effects in different ways: a minimization of the “noise” image (
U
ϕ
), and a correction method based on a polarimetric model that we have developed, as presented in Paper II of this study.
Results.
We use observations of TW Hydrae to illustrate the data reduction. In the images of the protoplanetary disk around this star, we detect variability in the polarized intensity and angle of linear polarization that depend on the pointing-dependent instrument configuration. We explain these variations as instrumental polarization effects and correct for these effects using our model-based correction method.
Conclusions.
The polarimetric imaging mode of IRDIS has proven to be a very successful and productive high-contrast polarimetric imaging system. However, the instrument performance is strongly dependent on the specific instrument configuration. We suggest adjustments to future observing strategies to optimize polarimetric efficiency in field-tracking mode by avoiding unfavorable derotator angles. We recommend reducing on-sky data with the pipeline called IRDAP, which includes the model-based correction method (described in Paper II) to optimally account for the remaining telescope and instrumental polarization effects and to retrieve the true polarization state of the incident light.
This study investigates the effect of iron oxide Fe2O3 on the homogeneity, viscosity, and glass transition temperature (Tg) of peraluminous glasses. As-quenched glass samples elaborated at 1350 °C ...show an incorporation limit around 17.5 wt% of Fe2O3 (10.4 mol%), while slowly cooled glass samples show a limit of 7.5 wt% of Fe2O3 (4.2 mol%). Iron in the peraluminous glasses investigated was detected under three configurations: 6-fold coordinated 6Fe3+ in majority, 4-fold coordinated 4Fe3+ and 6-fold coordinated 6Fe2+. It was observed that Fe2O3 addition has a strong fluidifying effect on peraluminous glasses and tends to slightly decrease the glass transition temperature Tg, depending on its thermal history.
Chromium is a multivalent element with very low solubility in silica-based glasses. It is incorporated into glass via the solubilisation of Cr2O3 as Cr3+ through an acido-basic reaction, and is in ...redox equilibrium with Cr6+ and Cr2+ oxidation states depending on the surrounding atmosphere. The least soluble form of chromium is Cr3+, which is also the most common form of chromium in glass elaborated in air. This study investigated the behavior of chromium in peraluminous glasses, which are potential matrices for nuclear waste containment. Chromium is often present in nuclear waste solutions as a corrosion product coming from the waste reprocessing steps. Consequently, it is important to understand the effect of chromium addition to peraluminous glasses, both in terms of the microstructure and the processing ability of the glass melt. The study investigated the effect of chromium added as a Cr2O3 chromium (+III) oxide on the homogeneity, the viscosity, and the glass transition temperature (Tg) of peraluminous glasses. The chromium redox state and its effect on the incorporation limit of chromium was determined. Peraluminous glasses have an incorporation limit of between 0.50 and 0.55 wt% Cr2O3 in air, and between 1.25 and 1.50 wt% Cr2O3 in a reducing environment. Chromium (+III) oxide was found to have a limited effect on the viscosity of peraluminous glasses up to 2 wt% of Cr2O3, despite the presence of crystals above 0.5 wt%. The addition of chromium oxide had no significant effect on the Tg of the glass, except after a slow cooling of the sample containing the highest content of 2.0 wt% Cr2O3. Two forms of chromium were identified under UV-visible spectroscopy for the glasses elaborated in air: Cr3+ (6-fold) and Cr6+ (4-fold).
A suite of analytical techniques were combined to study the chemical speciation of Fe and Pb in the water column of a lake characterized by a biogenic meromixis (Paul Lake, MI). Depth profiles of Fe
...2+ and “dissolved” Pb display significant concentration gradients below the chemocline, i.e., they increase from below detection limit to ca. 100 μM for Fe
2+ and 2 nM for Pb
d. Significant correlations between particulate organic matter, hydrous iron oxides, and particulate Pb suggest that Pb is scavenged by Fe-rich particles formed at the oxic-anoxic transition. Transmission electron microscopy shows that particles of hydrous iron oxides form complex aggregates with natural organic matter at and below the oxic-anoxic transition. Experiments with batch reactors show that these organo-mineral moieties remove Pb rapidly during their formation. Thermodynamic calculations predict that FeS and PbS are respectively saturated and oversaturated in the monimolimnion, although the presence of neither FeS nor PbS was observed. This suggests that the solubilities of Fe and Pb are influenced by complexation. Voltammetric experiments on filtered samples show that Pb is weakly complexed in the mixolimnion and strongly complexed in the monimolimnion. A conditional stability constant for Pb complexation is determined using metal titration curves assuming a simple 1:1 stoichiometry and gives logK
cond = 9.4 ± 0.8 M
−1 in the monimolimnion. These speciation results are confirmed by ion exchange chromatography, which demonstrates that more than 98% of Pb is complexed by natural organic matter.
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