Stuctural, optical and radiation shielding properties of zinc boro-tellurite alumina glasses

In this work, boro-telluride glasses with additional zinc, aluminum, and alkali–alkaline modifiers have been synthesized using the melt-quenching–annealing method. Six glasses were fabricated with composition of [(60 − x)B₂O₃–(10 + x)TeO₂–10ZnO–10Al₂O₃ 5Li₂O–5MgO] all in mol% and x varied from 0, 10, 20, 30, 40 and 50. The aim of this work is to understand the effect of changing the main glass former from B₂O₃ → TeO₂, to obtain new optical materials. To confirm the amorphous nature of these six glasses, X-ray diffraction was characterized for all six glasses from 10° to 80°. Optical absorption with wavelength range 200–800 nm in room temperature was measured, and the optical absorption coefficient α(λ) calculated to obtain the cutoff wavelength. In addition, gamma photons shielding features of the prepared K1–K6 glasses were evaluated by means of some essential parameters such as mass attenuation coefficients (μ/ρ) and effective atomic number (Zeff) at five energies between 0.356 and 1.33 MeV. No significant difference between the theoretical and simulation μ/ρ values was found. The effective atomic number results indiacte that as the TeO₂ content increases, the photons’ attenuation increases. The number of interactions of gamma photons with K6 sample (which contains the maximum amount of TeO₂) is relatively high (in comparison to the rest of the samples), which results in more attenuation and thus better shielding features for K6

Evaluation of theoretical approaches for describing the interaction of water with linear acenes

The interaction of a water monomer with a series of linear acenes (benzene, anthracene, pentacene, heptacene, and nonacene) is investigated using a wide range of electronic structure methods, including several "dispersion"- corrected density functional theory (DFT) methods, several variants of the random phase approximation (RPA), DFT-based symmetry-adapted perturbation theory with density fitting (DF-DFT-SAPT), MP2, and coupled-cluster methods. The DF-DFT-SAPT calculations are used to monitor the evolution of the electrostatics, exchange-repulsion, induction, and dispersion contributions to the interaction energies with increasing acene size and also provide the benchmark data against which the other methods are assessed. © 2010 American Chemical Society

Mercury-Induced Chromosomal Damage in Wild Fish (Dicentrarchus labrax L.) Reflecting Aquatic Contamination in Contrasting Seasons

Ria de Aveiro (mainly Laranjo basin, Portugal) has been subjected to mercury contamination from a chlor-alkali plant, currently presenting a well-described mercury gradient. This study aimed to assess mercury genotoxicity in this area by measuring the frequency of erythrocytic nuclear abnormalities (ENA) in the European sea bass (Dicentrarchus labrax), addressing the relation with total mercury concentration in the blood and the modulatory role of seasonal variables. Fish were collected, in warm and cold periods, at three locations differing in their distances to the main mercury source: reference (R), moderately (M), and highly (H) contaminated sites. Genotoxicity was detected in both degrees of contamination (M and H) and in both periods of the year (warm and cold), which is in line with the greater levels of mercury measured in fish blood. No significant seasonal variations were observed for mercury bioaccumulation or ENA frequency. The apparent low imperviousness of ENA frequency to seasonal factors reinforced its consistency as a genotoxicity biomarker, thus enabling a clearer identification of cause-and-effect relationships. Overall, the results reflected a serious environmental risk to native ichthyofauna at Laranjo basin due to mercury contamination, showing a potential of mercury to induce genetic damage in fish blood cells through clastogenic and/or aneugenic actions