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Hosseini-Benhangi P.,University of British Columbia | Garcia-Contreras M.A.,National Institute of Nuclear Research | Garcia-Contreras M.A.,University of British Columbia | Alfantazi A.,University of British Columbia | Gyenge E.L.,University of British Columbia
Journal of the Electrochemical Society | Year: 2015

The bifunctional oxygen reduction and evolution reaction (ORR and OER, respectively) electrocatalytic activity and durability of mixed oxides MnO2-LaCoO3and MnO2-Nd3IrO7, are investigated. The goal is to identify possible beneficial synergistic catalytic effects between the two oxides and to investigate the role of alkali-metal ions (Li+,Na+,K+ and Cs+) for promotion of electrocatalytic activity and durability. The combination of the two, structurally different, oxides, improves the bifunctional activity compared to the individual oxide components, as shown by either lower apparent Tafel slopes or higher exchange current densities for ORR and OER in 6 M KOH. Insertion of potassium ion in the oxide structure either by longer-term exposure to 6 M KOH or by an accelerated potential driven intercalation method, lowers further both the OER and ORR overpotentials. At constant current density of 5 mA cm-2 (or 5 A g-1 catalyst) for two hours, the OER overpotential is lowered by 110 mV and 152 mV due to potential driven potassium ion insertion in MnO2-LaCoO3 and MnO2-Nd3IrO7, respectively. For ORR, at -2 mA cm-2 (or -2 A g-1 catalyst) the overpotential on MnO2-LaCoO3 is decreased by 75 mV. In addition, the stability of the potassium ion activated catalysts is also improved. The ORR activity promotion effect is specific to potassium compared to all other investigated alkali metal hydroxides (LiOH, NaOH, CsOH), whereas for OER, cesium ion also has a beneficial effect. The electrode kinetic results are supported by surface analysis showing the presence of potassium in the catalyst. © 2015 The Electrochemical Society. Source


Gonzalez-Acevedo Z.I.,Instituto Nacional de Investigaciones Nucleares | Gonzalez-Acevedo Z.I.,National Institute of Nuclear Research | Olguin M.T.,Instituto Nacional de Investigaciones Nucleares | Rodriguez-Martinez C.E.,Instituto Nacional de Investigaciones Nucleares | And 2 more authors.
Water, Air, and Soil Pollution | Year: 2012

The sorption and desorption processes of Se(VI) onto non-living Eichhornia crassipes (E. crassipes) and Lemna minor (L. minor) were evaluated. Different pH values of the initial Se solution (20 μg L -1) were tested at static conditions. At dynamic conditions of horizontal flow, biomass-packed columns (BPC) were estimated as prepared (pH 4) and unprepared (pH 6-7) and at different flow rates. The desorption process was tested using HCl (0.1 M) as the eluent. The maximum Se uptake took place at a pH of 4 for both biomasses. The lowest flow rate improves major Se removal due to the increase in contact time. The Se was desorbed from the biomass with elution efficiencies of 5 and 18 % for E. crassipes and L. minor, respectively. Nevertheless, more time was needed to increase these efficiencies and reach desaturation times. The breakthrough curves showed that unprepared E. crassipes and L. minor BPC at horizontal flow, with a flow rate of 6 and 4 mL min -1 respectively, had a biomass removal capacity of 0.135 and 0.743 μg g -1 correspondingly. The system of E. crassipes is more efficient, suggesting an ion exchange sorption mechanism. This demonstrates that non-living E. crassipes and L. minor have the capacity to remove Se from very dilute solutions. © 2012 Springer Science+Business Media B.V. Source


Paredes L.,National Institute of Nuclear Research | Azorin J.,Metropolitan Autonomous University | Balcazar M.,National Institute of Nuclear Research | Franois J.L.,National Autonomous University of Mexico
Radiation Measurements | Year: 2010

Neutron kerma coefficients were calculated in different media: 4 malignant tumours, 5 normal tissues and 3 tissue substitute in the range 11 eV-29 MeV. The objective was to identify which is the material that better reproduces the behavior of these tumours and tissues. These tissues have clinical interest in interstitial brachytherapy applications with fast neutron source (Cf-252). The small differences of elemental composition among these tissues produce variation in the neutron kerma coefficients. The results show that the neutron kerma coefficients for malignant tumours are smaller than soft tissue from 6% to 9%. Also, the muscle is the tissue that best represents the dosimetric behavior for the tumours and tissues analyzed in this paper for neutron energies >1 keV, where this coefficients show minor variation. © 2010 Published by Elsevier Ltd. All rights reserved. Source


Spinella F.,National Institute of Nuclear Research | Angelucci B.,University of Pisa | Lamanna G.,National Institute of Nuclear Research | Minuti M.,National Institute of Nuclear Research | And 5 more authors.
2014 19th IEEE-NPSS Real Time Conference, RT 2014 - Conference Records | Year: 2014

The main goal of the NA62 experiment at CERN SPS is to measure the branching ratio of the ultra-rare K+→π+νν decay, collecting about 100 events in two years of data taking to test the Standard Model of Particle Physics. Readout uniformity of sub-detectors, scalability, efficient online selection and lossless high rate readout are key issues. The TEL62 boards are the common blocks of the NA62 Trigger and Data AcQuisition (TDAQ) system. TEL62s process and store hits coming from the subdetectors in a buffer according to their timestamp, extracting only those requested by the trigger system, which merges trigger primitives also produced by TEL62s. The complete dataflow and firmware organization are described. © 2014 IEEE. Source


Martinez T.,National Autonomous University of Mexico | Tejeda S.,National Institute of Nuclear Research | Estanol B.,National Autonomous University of Mexico | Zuniga M.A.,National Autonomous University of Mexico | Zarazua G.,National Institute of Nuclear Research
Journal of Radioanalytical and Nuclear Chemistry | Year: 2016

Sediments collected from the North Coast of the Gulf of Mexico got carefully mixed, dried, and finally subjected to physical and chemical analysis. Metal concentration was determined by energy dispersive X-ray fluorescence (EDXRF). Sequential chemical analysis was performed by modified TESSIER technique. Results and statistical analysis (α = 0.05) show concentrations of most elements (excepting Mn, Ca, Ga, As and Pb) in the range of those of the earth crust’s values, which set a sampling zone base line. Sequential extraction shows the potential risk of mobilization of metals sequestered in particulate phases by oxidation of anoxic sediments or intense organic matter degradation. © 2016 Akadémiai Kiadó, Budapest, Hungary Source

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