O2Activation over Ag-Decorated CeO2(111) and TiO2(110) Surfaces: A Theoretical Comparative Investigation

Periodic spin-polarized hybrid density functional theory calculations have been performed to investigate the reactivity of pristine, O-defective, and Ag-decorated CeO2(111) and TiO2(110) surfaces with a small Ag10 cluster toward O2. The adsorption of O2 and its subsequent dissociation have been studied in order to provide a better understanding of the role of the oxide, the metallic nanoparticle, and their interaction in the reactivity of composite metal/metal oxide materials toward O2, as potential catalysts to this reaction. Structural, energetic, electronic, and vibrational properties of all species involved in the different reaction paths considered have been fully characterized. On the stoichiometric surfaces, Ag10 is oxidized and reduces surface Ce4+/Ti4+ ions, while on the O-defective surfaces, the adhesion of silver is promoted only on CeO2 but unfavored on TiO2. On the other hand, on the silver-free supports, O2 strongly adsorbs at vacancies and preferentially reduces to peroxide. When no O vacancies are considered on the Ag10-decorated supports, the net positive charge on Ag10 actually prevents the adsorption and reduction of O2. Instead, when O vacancies are included, two reaction pathways are observed; oxygen molecules can weakly absorb on the silver cluster as a superoxide moiety or strongly adsorb at the vacancy as peroxide. The dissociation of the O-O bond of the peroxide is favored both from the thermodynamic and kinetic points of view in silver-decorated surfaces, in contrast with the silver-free cases. In addition, Ag10/CeO2 shows higher activity toward the O2 adsorption and dissociation than Ag10/TiO2, which can be related both to the higher ionicity and superior electron storage/release ability of ceria with respect to titania, thus leading to the weakening of the O-O bond and providing lower activation barriers for oxygen reduction. These results deepen the current understanding of the reactivity of metal/metal oxide composites toward O2, especially elucidating how the surface stoichiometry affects the charge state of the metal clusters, and hence the reactivity of these interfaces toward O2, with potential important consequences when such composites are considered for catalytic applications

Іван Франко - публіцист

Проаналізовано соціально-економічну і культурно-освітню публіцистику І. Франка, зокрема, його ставлення до податкової політики Австро-Угорщини, діяльності банківської системи, еміграції з Галичини, кооперативного руху, майбутнього української держави.The article analyses social and economic and cultural and educational publications by Ivan Franko, as well as his attitude to tax policies in Austro-Hungarian Empire, banking system activities, emigration from Halychyna, co-operative societies movement, and the future of Ukraine

The endothelial mineralocorticoid receptor regulates vasoconstrictor tone and blood pressure

Pathophysiological aldosterone (aldo)/mineralocorticoid receptor (MR) signaling has significant effects on the cardiovascular system, resulting in hypertension and cardiovascular remodeling; however, the specific contribution of the vascular MR to blood pressure regulation remains to be established. To address this question, we generated a mouse model with conditional overexpression of the MR in endothelial cells (MR-EC). In basal conditions, MR-EC mice developed moderate hypertension that could be reversed by canrenoate, a pharmacological MR antagonist. MR-EC mice presented increased contractile response of resistance arteries to vasoconstrictors (phenylephrine, thromboxane A(2) analog, angiotensin II, and endothelin 1) in the absence of vascular morphological alterations. The acute blood pressure response to angiotensin II or endothelin 1 infusion was increased in MR-EC mice compared with that in littermate controls. These observations demonstrate that enhanced MR activation in the endothelium generates an increase in blood pressure, independent of stimulation of renal tubular Na(+) transport by aldo/MR or direct activation of smooth muscle MR and establish one mechanism by which endothelial MR activation per se may contribute to impaired vascular reactivity

Systematic calibration of N2O emissions from a full-scale WWTP including a tracer test and a global sensitivity approach

Altres ajuts: Acord transformatiu CRUE-CSICBorja Solís is grateful for the PIF PhD grant funded by Universitat Autònoma de Barcelona.Nitrous oxide (NO) is a greenhouse gas (GHG) emitted during biological nitrogen removal from wastewater treatment plants (WWTPs). Some modelling tools have been proposed to predict NO emissions during the design and operation of WWTPs. In this study, the novel ASM2d-NO model, which accounts for the production of NO in nutrient removal WWTPs, was used to study the associated emissions from a full-scale WWTP with two independent lines. Firstly, the hydraulics of the WWTP was characterized by a residence time distribution test, showing the flow was equally divided into the two treatment lines (49.3 vs. 50.7%), that each reactor worked as an ideal continuous stirred tank reactor and the secondary settler model flux was similar to a plug-flow reactor. The ASM2d-NO model was then calibrated using experimental data obtained under dynamic conditions. A global sensitivity analysis was used to select, among 59 model parameters, five candidates that resulted to be related to nitrifying organisms. Different parameter subsets up to four parameters were evaluated, being the subset [µ, q, K, K] the best, achieving 53.3% reduction of the calibration cost function. The model fit obtained provided a reasonably description of nutrients and NO emission trends, considering the inherent operational variability suffered in full-scale WWTPs. Finally, a simulation-based study showed that, for the given WWTP and operational conditions, an unbalanced distribution of flow-rate between the two treatment lines did not result in a significant increase on NO emissions. The results obtained show that this model can be a suitable tool for predicting NO emissions in full-scale WWTPs, and can therefore be used to find operational conditions that help to minimise these emissions

The ARC-EN-CIEL radiation sources

MOPC005International audienceThe ARC-EN-CIEL (Accelerator-Radiation for Enhanced Coherent Intense Extended Light) project proposes a panoply of light sources for the scientific community on a 1 GeV superconducting LINAC (phase 2) on which two ERL loops (1 and 2 GeV) are added in phase 3. LEL1 (200-1.5 nm), LEL2 (10-0.5 nm) and LEL4 (2-0.2 nm) are three kHz High Gain Harmonic Generation Free Electron Laser sources seeded with the High order Harmonics generated in Gas, with 100-30 FWHM pulses. A collaboration, which has been set-up with the SCSS Prototype Accelerator in Japan to test this key concept of ARC-EN-CIEL, has led to the experimental demonstration of the seeding with HHG and the observation up the 7th non linear harmonic with a seed at 160 nm. LEL3 (40-8 nm) installed on the 1 GeV loop is a MHz FEL oscillator providing higher average power and brilliance. In addition, in vacuum undulator spontaneous emission source extend the spectral range above 10 keV and intense THz radiation is generated by edge radiation of bending magnets. Optimisations and light sources characteristics are described

Aggregation effects on pigment coatings: Pigment red 179 as a case study

Here, we have studied, with a combined experimental and computational approach, the effect of the crystal environment and aggregation on the electronic properties of Pigment Red 179, which affect both its color and optical energy gap. Spectra acquired in the near-infrared and visible range of energies suggest that this molecule is indeed a "cool" dye, which can be employed as a red pigment that provides effective color coverage to different substrates without contributing to their heating during light irradiation. Spectra acquired on different polymer mixtures at different pigment concentrations (i.e., 2.5-10 wt %) suggest that absorption features depend on chromophoric arrangements promoted by the strong intermolecular I -\u3c0interactions. Calculations, performed at the time-dependent density functional theory level, allowed to both attribute the nature of the electronic transitions causing the observed spectra involved and understand the effect of the environment. Indeed, the visible spectra of the pigment is dominated by two localized transitions, with negligible charge transfer for both a dye monomer and dimer either in vacuum or acetonitrile solution. Instead, models including the crystal environment of the pigment show the presence of a high-wavelength S1 \ue2 S0 charge transfer transition between two adjacent molecules, in quantitative agreement with the experimental absorption energy of the crystal pigment

Ovarian steroid hormones: what's hot in the stem cell pool?

The vital role of ovarian hormones in the development of the normal breast foreshadowed their importance in mammary stem cell regulation. Two recent papers reveal that 17β-estradiol and progesterone control the size and repopulating ability of the mammary stem cell compartment. This likely occurs via paracrine signaling from steroid receptor-positive luminal cells to steroid receptor-negative stem cells. These findings illuminate roles for the female sex steroids in mobilizing the stem cell pool in the normal breast, and also provide a crucial link between the known hormonal risks of breast cancer and the potential stem cell origin of this disease

Stability and Electronic Properties of TiO2 Nanostructures With and Without B and N Doping

We address one of the main challenges to TiO2-photocatalysis, namely band gap narrowing, by combining nanostructural changes with doping. With this aim we compare TiO2's electronic properties for small 0D clusters, 1D nanorods and nanotubes, 2D layers, and 3D surface and bulk phases using different approximations within density functional theory and GW calculations. In particular, we propose very small (R < 0.5 nm) but surprisingly stable nanotubes with promising properties. The nanotubes are initially formed from TiO2 layers with the PtO2 structure, with the smallest (2,2) nanotube relaxing to a rutile nanorod structure. We find that quantum confinement effects - as expected - generally lead to a widening of the energy gap. However, substitutional doping with boron or nitrogen is found to give rise to (meta-)stable structures and the introduction of dopant and mid-gap states which effectively reduce the band gap. Boron is seen to always give rise to n-type doping while depending on the local bonding geometry, nitrogen may give rise to n-type or p-type doping. For under coordinated TiO2 surface structures found in clusters, nanorods, nanotubes, layers and surfaces nitrogen gives rise to acceptor states while for larger clusters and bulk structures donor states are introduced