The Universidad Nacional del Sur is the largest national university in southern Argentina. Its motto is Ardua Veritatem, which means "through the difficulties to the truth".The university was founded on January 5, 1956, and absorbed what had been the Instituto Tecnológico del Sur, a former Universidad Nacional de La Plata affiliate established in 1946. Located in the city of Bahía Blanca, the school became the seventh in Argentina's national university system. Wikipedia.
Sieben J.M.,National University of the South |
Duarte M.M.E.,National University of the South
International Journal of Hydrogen Energy | Year: 2012
Pt and Pt-Ru catalysts supported on oxidized multi-walled carbon nanotubes with different ruthenium content ranging from 19 to 30 at.% were prepared by pulse electrodeposition and tested for methanol, ethanol and ethylene glycol oxidation in H 2SO 4 electrolyte. The catalysts were mainly composed by small 3D irregular-shaped agglomerates of nano-sized particles. Electrocatalytic activity measurements indicated that the bimetallic catalyst with 30 at.% Ru was the most active electrode for methanol, ethanol and ethylene glycol oxidation. This behavior can be associated with a synergistic effect between the facilitation of alcohol oxidation via oxygen-containing species adsorbed on Ru atoms, the suitable Pt ensemble size and the modification of the electronic structure of Pt atoms at the Fermi level that weakens the adsorption of CO and other intermediates. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Gonzalez M.B.,National University of the South |
Saidman S.B.,National University of the South
Corrosion Science | Year: 2011
The electrosynthesis of polypyrrole films onto 316L stainless steel from near neutral and alkaline solutions containing molybdate and nitrate is reported. The corrosion behavior of the coated electrodes was investigated in NaCl solutions by electrochemical techniques and scanning electron microscopy. The polymer formed potentiostatically in a solution of pH 12 is the most efficient in terms of adhesion and corrosion protection. The coating significantly reduces the pitting corrosion of the substrate. The results are interpreted in terms of the nature of dopants, the good electroactivity of the polymer formed in alkaline solution and the passivating properties of the oxide layer. © 2010 Elsevier Ltd.
Miller M.W.,National University of the South |
Sadeh N.,National University of the South
Molecular Psychiatry | Year: 2014
Post-Traumatic stress disorder (PTSD) is associated with elevated risk for a variety of age-related diseases and neurodegeneration. In this paper, we review evidence relevant to the hypothesis that chronic PTSD constitutes a form of persistent life stress that potentiates oxidative stress (OXS) and accelerates cellular aging. We provide an overview of empirical studies that have examined the effects of psychological stress on OXS, discuss the stress-perpetuating characteristics of PTSD, and then identify mechanisms by which PTSD might promote OXS and accelerated aging. We review studies on OXS-related genes and the role that they may have in moderating the effects of PTSD on neural integrity and conclude with a discussion of directions for future research on antioxidant treatments and biomarkers of accelerated aging in PTSD. © 2014 Macmillan Publishers Limited All rights reserved.
Brigante M.,National University of the South |
Schulz P.C.,National University of the South
Journal of Hazardous Materials | Year: 2011
Removal of the antibiotic tetracycline (TC) by TiO 2 and the mesoporous binary system TiO 2-SiO 2 have been studied in batch experiments by performing adsorption isotherms/kinetics and photodegradation kinetics under different conditions of pH, supporting electrolyte concentration, temperature, adsorbent amount, and TiO 2-loading. On the one hand, the adsorption of TC on the studied materials is strongly dependent on pH, increasing as pH decreases. The adsorption mechanism, controlled by diffusion processes, is strongly related to electrostatic attractions and H-bond formations mainly between amide, carbonylic and phenolic groups of the antibiotic and the functional groups of TiO 2. The adsorption capacity at constant pH increases in the order TiO 2
Safari B.,National University of the South
Renewable and Sustainable Energy Reviews | Year: 2010
During the last two decades, Rwanda has experienced an energy crisis mostly due to lack of investment in the energy sector. With the growing of the population and increasing industrialization in urban areas, energy provided by existing hydro and thermal power plants has been increasingly scarce with high energy costs, and energy instability. Furthermore, as wood fuel is the most important source of energy in Rwanda, the enduring dependence on it and fossil fuel consumption as well, will continue to impact on the process of environmental degradation. Rwanda is rich with abundant renewable energy resources such as methane gas in Lake Kivu, solar, biomass, geothermal; and wind energy resource is currently being explored. Recently, the Government has given priority to the extension of its national electrical grid through development of hydro power generation projects, and to rural energy through development of alternative energy projects for rural areas where access to national grid is still difficult. This paper presents a review of existing energy resources and energy applications in Rwanda. Recent developments on renewable energy are also presented. © 2009 Elsevier Ltd. All rights reserved.
Boland R.L.,National University of the South
Molecular and Cellular Endocrinology | Year: 2011
The purpose of this article is to review the activation of signal transduction pathways in skeletal muscle cells by the hormone 1α,25(OH) 2-vitamin D 3 [1α,25(OH) 2D 3], focusing on the role of the vitamin D receptor (VDR). The hormone induces fast, non transcriptional responses, involving stimulation of the transmembrane second messenger systems adenylyl cyclase/cAMP/PKA, PLC/DAG+IP 3/PKC, Ca 2+ messenger system and MAPK cascades. Short treatment with 1α,25(OH) 2D 3 induces reverse translocation of the VDR from the nucleus to plasma membranes. Accordingly, a complex is formed in the caveolae between the VDR and TRCP3, integral protein of capacitative Ca 2+ entry (CCE), suggesting an association between both proteins and a functional role of the VDR in 1α,25(OH) 2D 3 activation of CCE. Stimulation of tyrosine phosphorylation cascades by 1α,25(OH) 2D 3 have demonstrated the formation of complexes between Src and the VDR. Through these mechanisms, 1α,25(OH) 2D 3 plays an important function in contractility and myogenesis. © 2011 Elsevier Ireland Ltd.
Fernandez G.,National University of the South
Investigative ophthalmology & visual science | Year: 2013
Eye movements follow a reproducible pattern during normal reading. Each eye movement ends up in a fixation point, which allows the brain to process the incoming information and to program the following saccade. Alzheimer disease (AD) produces eye movement abnormalities and disturbances in reading. In this work, we investigated whether eye movement alterations during reading might be already present at very early stages of the disease. Twenty female and male adult patients with the diagnosis of probable AD and 20 age-matched individuals with no evidence of cognitive decline participated in the study. Participants were seated in front of a 20-inch LCD monitor and single sentences were presented on it. Eye movements were recorded with an eye tracker, with a sampling rate of 1000 Hz and an eye position resolution of 20 arc seconds. Analysis of eye movements during reading revealed that patients with early AD decreased the amount of words with only one fixation, increased their total number of first- and second-pass fixations, the amount of saccade regressions and the number of words skipped, compared with healthy individuals (controls). They also reduced the size of outgoing saccades, simultaneously increasing fixation duration. The present study shows that patients with mild AD evidenced marked alterations in eye movement behavior during reading, even at early stages of the disease. Hence, evaluation of eye movement behavior during reading might provide a useful tool for a more precise early diagnosis of AD and for dynamical monitoring of the pathology.
Barrantes F.J.,National University of the South
Sub-Cellular Biochemistry | Year: 2010
Cholesterol is an essential partner of the nicotinic acetylcholine receptor (AChR). It is not only an abundant component of the postsynaptic membrane but also affects the stability of the receptor protein in the membrane, its supramolecular organization and function. In the absence of innervation, early on in ontogenetic development of the muscle cell, embryonic AChRs occur in the form of diffusely dispersed molecules. At embryonic day 13, receptors organize in the form of small aggregates. This organization can be mimicked in mammalian cells in culture. Trafficking to the plasmalemma is a cholesterol-dependent process. Receptors acquire association with the sterol as early as the endoplasmic reticulum and the Golgi apparatus. Once AChRs reach the cell surface, their stability is also highly dependent on cholesterol levels. Acute cholesterol depletion reduces the number of receptor domains by accelerating the rate of endocytosis. In muscle cells, AChRs are internalized via a recently discovered dynamin- and clathrin-independent, cytoskeleton-dependent endocytic mechanism. Unlike other endocytic pathways, cholesterol depletion accelerates internalization and re-routes AChR endocytosis to an Arf6-dependent pathway. Cholesterol depletion also results in ion channel gain-of-function of the remaining cell-surface AChRs, whereas cholesterol enrichment has the opposite effect. Wide-field microscopy shows AChR clusters as diffraction-limited puncta of ∼200 nm diameter. Stimulated emission depletion (STED) fluorescence microscopy resolves these puncta into nanoclusters with an average diameter of ∼55 nm. Exploiting the enhanced resolution, the effect of acute cholesterol depletion can be shown to alter the short- and long-range organization of AChR nanoclusters. In the short range, AChRs form bigger nanoclusters. On larger scales (0.5–3.5 μm) nanocluster distribution becomes non-random, attributable to the cholesterol-related abolition of cytoskeletal physical barriers normally preventing the lateral diffusion of AChR nanoclusters. The dependence of AChR numbers at the cell surface on membrane cholesterol raises the possibility that cholesterol depletion leads to AChR conformational changes that alter its stability and its long-range dynamic association with other AChR nanoclusters, accelerate its endocytosis, and transiently affect the channel kinetics of those receptors remaining at the surface. Cholesterol content at the plasmalemma may thus homeostatically modulate AChR dynamics, cell-surface organization and lifetime of receptor nanodomains, and fine tune the ion permeation process. © Springer ScienceBusiness Media B.V. 2010.
Sieben J.M.,National University of the South |
Duarte M.M.E.,National University of the South
International Journal of Hydrogen Energy | Year: 2011
Pt and Pt-Sn catalysts supported on oxidized carbon nanotubes were prepared by multiple potentiostatic pulses and tested for ethanol and ethylene glycol electro-oxidation in sulfuric acid. The composed nanostructured materials were characterized via SEM, TEM, EDX and XRD analysis. Small metal nanoparticles (4-6 nm) forming 3-D nanostructured agglomerates (25-100 nm) distributed over the carbon substrate were formed. XRD results showed that the bimetallic electrocatalysts consisted of a Pt single-phase material, suggesting the formation of solid solutions over the entire composition range. The tin content in the alloys was between 10 and 40 at. %. Cyclic voltammetry and chronoamperometry measurements at room temperature showed that at potentials below 0.5 V, the bimetallic catalyst with 40 at. % Sn exhibited the highest activity for ethanol and ethylene glycol oxidation, whereas at potentials above 0.5 V, the alloy with 25 at. % Sn displayed better performance. This behavior can be explained by the synergistic effect between the facilitation of alcohol oxidation via oxygen-containing species adsorbed on Sn atoms, the alteration of the electronic structure of Pt atoms that weakens CO and intermediates adsorption, and the adequate Pt ensembles size. Besides, the increment of the lattice parameter and the presence of grain boundaries can enhance the adsorption of the alcohols and favor the splitting of the C-C bond. © 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Safari B.,National University of the South
Renewable and Sustainable Energy Reviews | Year: 2011
Utilization of wind energy as an alternative energy source may offer many environmental and economical advantages compared to fossil fuels based energy sources polluting the lower layer atmosphere. Wind energy as other forms of alternative energy may offer the promise of meeting energy demand in the direct, grid connected modes as well as stand alone and remote applications. Wind speed is the most significant parameter of the wind energy. Hence, an accurate determination of probability distribution of wind speed values is very important in estimating wind speed energy potential over a region. In the present study, parameters of five probability density distribution functions such as Weibull, Rayleigh, lognormal, normal and gamma were calculated in the light of long term hourly observed data at four meteorological stations in Rwanda for the period of the year with fairly useful wind energy potential (monthly hourly mean wind speed v̄2ms-1). In order to select good fitting probability density distribution functions, graphical comparisons to the empirical distributions were made. In addition, RMSE and MBE have been computed for each distribution and magnitudes of errors were compared. Residuals of theoretical distributions were visually analyzed graphically. Finally, a selection of three good fitting distributions to the empirical distribution of wind speed measured data was performed with the aid of a χ2 goodness-of-fit test for each station. © 2010 Elsevier Ltd. All rights reserved.