Electrochemical and photo-electrochemical processes of Methylene blue oxidation by Ti/TiO2 electrodes modified with Fe-allophane

Indexación: Scopus.This work reports the degradation of methylene blue (MB) on Ti/TiO2 and Ti/TiO2/Fe-allophane electrodes in a pH 3 using 0.1 M Na2SO4 as support electrolyte. SEM micrographs show a homogeneous distribution of TiO2 over the whole electrode surface forming nanotubes and nanopores. Fe-allophane modified electrode shows the formation of large-grains agglomerate on the electrode surface due to allophane, which provides a greater surface area to the electrode due to meso and micropore structures. Preliminary cyclic voltammetry show that Ti/TiO2 has the typical voltammetric response due to Ti(III)/Ti(IV) pair. Diffusional problems were observed through of the film when the electrode is modified with Fe-allophane modifying the quasi-reversible process Ti(III)/Ti(IV). Different kind of methodologies in the degradation process were used: Electrochemistry (EC), Photochemistry (PC), Photoelectrochemistry (PEC) and Adsorption (Ads). These methods were developing to discard any reaction or interaction that is not of interest. On Ti/TiO2 with PC and Ads methodologies was not observed any activity to MB degradation showing that is not photosensitive and that the interaction between this and surface electrode is low. But with EC and PEC degradation to 55% is reached after 3 hours of electrolysis. With Ti/TiO2-Fe-allophane electrodes are observed a higher activity for all methodologies. The PC and Ads methods show that the MB degradation reaches to ∼20 % of the initial concentration. As mentioned above, the PC and Ads processes no show degradation on Ti/TiO2, therefore the degradation it only due to the adsorption of MB in/on allophane coat behaving as concentrator matrix. A lower improvement is observed with EC process when is incorporated Ti/TiO2-Fe-allophane is due to the barrier of the electrode surface by oxidation products. With PEC is reached the higher degradation value of ∼88 %, showing an improvement of the degradation with the presence of Fe-allophane. The results indicate that the main role of Fe-allophane on the electrode is similar to a concentrator matrix.http://ref.scielo.org/shz7t

The occurrence of Calanidae species in waters off Argentina

As food of planktivorous fish and likely good predictors of natural perturbations, members of the family Calanidae are recognised to be key species in ecosystems worldwide. The distribution and seasonal relative abundance of the Calanidae species occurring in the Argentine Sea were reviewed from published and unpublished data collected over the last three decades. Species are also figured in order to elucidate any possible taxonomic uncertainty. Calanoides ef. carinatus, Calanus australis and Calanus simillimus are the most abundant calanids in the region. The former two species typically inhabit inner and middle shelf waters decreasing offshore, while Calanus simillimus is distributed in the middle and outer shelf, its abundance increasing towards the shelf-break. The southern limit of the distribution of Calanoides ef. carinatus appears to be ∼46° S. Calanus australis is the most common large copepod in coastal and inner shelf waters off southern Patagonia. Neocalanus tonsus and Calanoides patagoniensis are a much rarer species. The latter is recorded in the southwestern Atlantic, for the first time, immediately east of Magallanes Strait and the Beagle Channel. The taxonomic status and worldwide biogeographic distribution of the region's calanids are briefly described and the patterns identified off Argentina are discussed in relation to the major hydrographic characteristics.Fil: Ramírez, F. C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Sabatini, Marina Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentin

Bilepton effects on the WWV^* vertex in the 331 model with right-handed neutrinos via a SU_L(2)XU_Y(1) covariant quantization scheme

In a recent paper, we investigated the effects of the massive charged gauge bosons (bileptons) predicted by the minimal 331 model on the off-shell vertex WWV^* (V=gamma, Z) using a SU_L(2) X U_Y(1) covariant gauge-fixing term for the bileptons. We proceed along the same lines and calculate the effects of the gauge bosons predicted by the 331 model with right-handed neutrinos. It is found that the bilepton effects on the WWV^* vertex are of the same order of magnitude than those arising from the SM and several of its extensions, provided that the bilepton mass is of the order of a few hundred of GeVs. For heavier bileptons, their effects on the WWV^* vertex are negligible. The behavior of the form factors at high energies is also discussed as it is a reflect of the gauge invariance and gauge independence of the WWV^* Green function obtained via our quantization method.Comment: Replaced to match published versio

Noncommutative 6D Gauge Higgs Unification Models

The influence of higher dimensions in noncommutative field theories is considered. For this purpose, we analyze the bosonic sector of a recently proposed 6 dimensional SU(3) orbifold model for the electroweak interactions. The corresponding noncommutative theory is constructed by means of the Seiberg-Witten map in 6D. We find in the reduced bosonic interactions in 4D theory, couplings which are new with respect to other known 4D noncommutative formulations of the Standard Model using the Seiberg-Witten map. Phenomenological implications due to the noncommutativity of extra dimensions are explored. In particular, assuming that the commutative model leads to the standard model values, a bound -5.63 10^{-8} GeV^{-2}< theta <1.06 10^{-7}GeV^{-2} on the corresponding noncommutativity scale is derived from current experimental constraints on the S and T oblique parameters. This bound is used to predict a possibly significant impact of noncommutativity effects of extra dimensions on the rare Higgs boson decay H-> gamma gamma.Comment: Latex file, 11 pages, 1 figur

Kinetic energy of protons in ice Ih and water: a path integral study

The kinetic energy of H and O nuclei has been studied by path integral molecular dynamics simulations of ice Ih and water at ambient pressure. The simulations were performed by using the q-TIP4P/F model, a point charge empirical potential that includes molecular flexibility and anharmonicity in the OH stretch of the water molecule. Ice Ih was studied in a temperature range between 210-290 K, and water between 230-320 K. Simulations of an isolated water molecule were performed in the range 210-320 K to estimate the contribution of the intramolecular vibrational modes to the kinetic energy. Our results for the proton kinetic energy, K_H, in water and ice Ih show both agreement and discrepancies with different published data based on deep inelastic neutron scattering experiments. Agreement is found for water at the experimental melting point and in the range 290-300 K. Discrepancies arise because data derived from the scattering experiments predict in water two maxima of K_H around 270 K and 277 K, and that K_H is lower in ice than in water at 269 K. As a check of the validity of the employed water potential, we show that our simulations are consistent with other experimental thermodynamic properties related to K_H, as the temperature dependence of the liquid density, the heat capacity of water and ice at constant pressure, and the isotopic shift in the melting temperature of ice upon isotopic substitution of either H or O atoms. Moreover, the temperature dependence of K_H predicted by the q-TIP4P/F model for ice Ih is found to be in good agreement to results of path integral simulations using ab initio density functional theory.Comment: 11 pages, 6 figures, 2 table

Unexpected impact of D waves in low-energy neutral pion photoproduction from the proton and the extraction of multipoles

Contributions of $D$ waves to physical observables for neutral pion photoproduction from the proton in the near-threshold region are studied and means to isolate them are proposed. Various approaches to describe the multipoles are employed --a phenomenological one, a unitary one, and heavy baryon chiral perturbation theory. The results of these approaches are compared and found to yield essentially the same answers. $D$ waves are seen to enter together with $S$ waves in a way that any means which attempt to obtain the $E_{0+}$ multipole accurately must rely on knowledge of $D$ waves and that consequently the latter cannot be dismissed in analyses of low-energy pion photoproduction. It is shown that $D$ waves have a significant impact on double-polarization observables that can be measured. This importance of $D$ waves is due to the soft nature of the $S$ wave and is a direct consequence of chiral symmetry and the Nambu--Goldstone nature of the pion. $F$-wave contributions are shown to be negligible in the near-threshold region.Comment: 38 pages, 13 figures, 19 tables. Version to be published in Physical Review

Higgs mediated Double Flavor Violating top decays in Effective Theories

The possibility of detecting double flavor violating top quark transitions at future colliders is explored in a model-independent manner using the effective Lagrangian approach through the $t \to u_i\tau \mu$ ($u_i=u,c$) decays. A Yukawa sector that contemplates $SU_L(2)\times U_Y(1)$ invariants of up to dimension six is proposed and used to derive the most general flavor violating and CP violating $q_iq_jH$ and $l_il_jH$ vertices of renormalizable type. Low-energy data, on high precision measurements, and experimental limits are used to constraint the $tu_iH$ and $H\tau \mu$ vertices and then used to predict the branching ratios for the $t \to u_i\tau \mu$ decays. It is found that this branching ratios may be of the order of $10^{-4}-10^{-5}$, for a relative light Higgs boson with mass lower than $2m_W$, which could be more important than those typical values found in theories beyond the standard model for the rare top quark decays $t\to u_iV_iV_j$ ($V_i=W,Z,\gamma, g$) or $t\to u_il^+l^-$. %% LHC experiments, by using a total integrated luminosity of $\rm 3000 fb^{-1}$ of data, will be able to rule out, at 95% C.L., DFV top quark decays up to a Higgs mass of 155 GeV/$c^2$ or discover such a process up to a Higgs mass of 147 GeV/$c^2$.Comment: 24 pages, 11 figure

Actividades intersectoriales en la prevención de accidentes de tráfico

ResumenSe describen las líneas de trabajo priorizadas y algunos resultados obtenidos en la implantación del programa de prevención y reducción de lesiones por accidentes de tráfico en un área de salud. A partir de 1999 el Centro de Salud Pública priorizó la identificación y búsqueda de aliados en otros sectores (Asociación de policías locales y educación), la construcción de la capacidad de trabajo conjunta y la formación de un grupo intersectorial. Se llevaron a cabo actividades docentes y jornadas. Se formó una red de personas en 17 de un total de 39 ayuntamientos que participan con actividades en el grupo intersectorial. Un total de 10 de estos ayuntamientos participaron con actividades educativas y siete, además, exigieron al cumplimiento de la legislación.El grupo intersectorial potenció la visibilidad de sus actividades a través de los medios de comunicación local. Estas actividades no están dirigidas a reducir las lesiones por tráfico, sino a crear un marco de trabajo para la movilización de los sectores implicados. Se pretende potenciar más el compromiso entre los niveles políticos, técnicos y civiles incidiendo en valores sociales de respeto para una vida más saludable.AbstractWe describe priority issues and some of the results obtained from the implementation of the «Prevention and Reduction of Traffic Accident Injuries» program in a health area. Since 1999 the public health center has made a priority of identifying and recruiting partners from other sectors (the local police association and the local education authority), increasing its capacity for working together, and setting up an intersectorial working group. Teaching activities and meetings were held. A network of people was created from 17 of a total of 39 town halls that participate in activities supported by the intersectorial group. Ten are involved in educational activities and a further seven focus on ensuring compliance with the law. The intersectorial group promoted their visibility through the local media. These activities are not aimed at reducing injuries from road traffic accidents, but rather at creating an action framework through which all the sectors involved can be mobilized. The aim is to strengthen commitment among political, technical and civil sectors by focussing on social values of respect for a healthier life

Asymptotic solvers for ordinary differential equations with multiple frequencies

We construct asymptotic expansions for ordinary differential equations with highly oscillatory forcing terms, focusing on the case of multiple, non-commensurate frequencies. We derive an asymptotic expansion in inverse powers of the oscillatory parameter and use its truncation as an exceedingly effective means to discretize the differential equation in question. Numerical examples illustrate the effectiveness of the method

The night-sky at the Calar Alto Observatory

We present a characterization of the main properties of the night-sky at the Calar Alto observatory for the time period between 2004 and 2007. We use optical spectrophotometric data, photometric calibrated images taken in moonless observing periods, together with the observing conditions regularly monitored at the observatory, such as atmospheric extinction and seeing. We derive, for the first time, the typical moonless night-sky optical spectrum for the observatory. The spectrum shows a strong contamination by different pollution lines, in particular from Mercury lines, which contribution to the sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25 mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a particularly dark site for optical observations up to the I-band. The fraction of astronomical useful nights at the observatory is ~70%, with a ~30% of photometric nights. The typical extinction at the observatory is k_V~0.15 mag in the Winter season, with little dispersion. In summer the extinction has a wider range of values, although it does not reach the extreme peaks observed at other sites. The median seeing for the last two years (2005-6) was ~0.90", being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude in general that after 26 years of operations Calar Alto is still a good astronomical site, being a natural candidate for future large aperture optical telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of Astronomical Society of the Pacific (PASP