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Siddheswaran R.,University of Concepción | Mangalaraja R.V.,University of Concepción | Gomez M.E.,University of Valle | Avila R.E.,Chilean Commission of Nuclear Energy | And 2 more authors.
Journal of Alloys and Compounds | Year: 2013

Pure and Co, Al co-doped ZnO(Zn1-x-PCoxAlyO; x = 0.04, 0.03, 0.02; y = 0.01, 0.02, 0.03) nanoparticles were synthesized by wet chemical combustion method at 500 °C for various doping levels using zinc, cobalt and aluminium nitrates as precursors. The synthesized powders were calcined at 600 °C and sintered at 1000 °C after uni-axial compaction. Structure, morphology and the presence of magnetism in combusted and sintered materials of pure and doped ZnO were examined. At room temperature, both the calcined nanoparticles and sintered compacts of pure ZnO exhibited paramagnetism. But, ferromagnetism was observed for Co and Al co-doped ZnO (diluted magnetic semiconductor) nanoparticles calcined at 600 °C. Also, it was found that the ferromagnetism increased correspondingly for the calcined particles with Co concentration. Whereas, a strong paramagnetic behavior was observed for the sintered compacts of various concentrations of Co and Al dopants due to grain growth. © 2013 Elsevier B.V. All rights reserved.


Mangalaraja R.V.,University of Concepción | Ananthakumar S.,Indian National Institute for Interdisciplinary Science and Technology | Schachtsiek A.,TU Darmstadt | Lopez M.,University of Concepción | And 2 more authors.
Materials Science and Engineering A | Year: 2010

Nanocrystalline Ce0.9Sm0.1O1.95 electrolyte was prepared by nitrate-fuel combustion technique using urea, citric acid, glycine and polyethylene glycol as organic fuels. The combusted precursors were calcined at 700°C/2h and then compacted to cylindrical pellets and sintered at 1200°C for 2, 4 and 6h durations. The sintered samples were tested for the mechanical hardness and fracture toughness and the results were compared within the fuel sources. Dense nanocrystalline ceria electrolyte membranes having theoretical sintered densities of 98% and the sintered grain sizes below 1μm were successfully achieved at 1200°C. Ceria electrolytes derived from the glycine and citric acid fuels have maximum microhardness of 7.94±0.2 and 7.63±0.2GPa. Whereas high toughness is observed for the samples prepared from the urea and polyethylene glycol fuels. They were estimated as 3.06±0.3 and 3.17±0.3MPam1/2 respectively at 20N. The study significantly contributes to select the fuels appropriately so that the advantages of low temperature densification and mechanically durability can be achieved in ceria electrolyte membranes for IT-SOFC applications. © 2010 Elsevier B.V.


Ubeda C.,University of Tarapacá | Vano E.,Complutense University of Madrid | Gonzalez L.,Complutense University of Madrid | Miranda P.,Luis Calvo Mackenna Hospital | And 3 more authors.
Radiation Protection Dosimetry | Year: 2010

Interventional cardiology procedures usually imply high doses to the staff, as paediatric cardiologists need to stay closer to the patient than during adult procedures. Also, biplane systems are used that imply an additional source of staff doses. The objective of this paper is to measure scatter doses in four X-ray systems, using polymethyl methacrylate phantoms with thicknesses ranging from 4 to 16 cm to simulate paediatric patients, for the different acquisition modes. Scatter dose rates measured at the position of cardiologist's eyes ranged from 0.8 to 12 mSv h-1, and about twice the above values at lower extremities, as a linear function of the surface air kerma at the phantom, keeping the irradiated area constant. Therefore, the respective personal dose equivalent for the lens of the eyes may be around 0.5 and 1 mSv throughout the procedure, if additional protection is not used. Simultaneous cine acquisition in biplane systems yielded scatter doses to cardiologists, increased by factors from 5 to 21, compared with a single C-arm acquisition case and depending on geometry. Knowledge of scatter doses for different operation modes, patient thicknesses and the biplane operation should help paediatric cardiologists to adopt conservative attitudes in respect of their occupational radiation risks. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org.


Ubeda C.,University of Tarapacá | Vano E.,Complutense University of Madrid | Miranda P.,Luis Calvo Mackenna Hospital | Leyton F.,Diego Portales University | And 2 more authors.
Radiation Protection Dosimetry | Year: 2011

Radiation dose and image quality for paediatric protocols in all five X-ray fluoroscopy systems used for interventional cardiology procedures existing in Chile have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object (TO) and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4-16 cm of PMMA). Images from fluoroscopy (low (FL), medium and high) and cine (CI) modes have been archived in DICOM format. Signal-to-noise ratio (SNR), figure of merit (FOM) and high-contrast spatial resolution (HCSR) have been computed from the images. The ratio between the maximum and the minimum value of ESAK per frame for a given fluoroscopy mode between the five systems ranges from 2 to 5 and from 14 to 38 for CI mode. SNR, FOM and HCSR showed a great variability for the different acquisition modes (AMs) and PMMA thickness. In the near future, it is urgent to upgrade Chilean legislation on radiation protection to incorporate quality assurance programmes that will allow us to evaluate and optimise the X-ray systems used in medical applications. Increments in doses per frame when increasing phantom thickness and when used CI runs instead of FL runs can be considered by the cardiologist in the good management of patient dose and allow them to select the best imaging AM during clinical procedures. © The Author 2010. Published by Oxford University Press. All rights reserved.


Ronco A.M.,University of Chile | Gutierrez Y.,University of Chile | Gras N.,Chilean Commission of Nuclear Energy | Munoz L.,Chilean Commission of Nuclear Energy | And 2 more authors.
Biological Trace Element Research | Year: 2010

The objective of this study was to evaluate whether lead (Pb) and arsenic (As) levels in biological fluids were associated to the body composition in a group of reproductive-age women. Voluntary childbearing-age women (n = 107) were divided into three groups according to their body mass index (BMI: weight/height2 (kg/m2): low weight (BMI<18.5 kg/m 2), normal (BMI > 19 < 24.9 kg/m2), and overweight (BMI>25 kg/m2). Body composition and fat mass percentage were determined by the isotopic dilution method utilizing deuterated water. Blood lead concentrations were determined by graphite furnace atomic absorption spectrometry and urinary arsenic (AsU) concentrations by inductively coupled plasma mass spectrometry. The type and frequency of food consumption and lifestyle-related factors were also registered. Most women had PbBlevels > 2 < 10 μ/dl, and only 2.6% had AsU concentrations above 50 μg/L. The levels of these toxic elements were not found to be associated with the fat mass percentage. © 2009 Humana Press Inc.


Akbari-Fakhrabadi A.,University of Concepción | Mangalaraja R.V.,University of Concepción | Sanhueza F.A.,University of Concepción | Avila R.E.,Chilean Commission of Nuclear Energy | And 2 more authors.
Journal of Power Sources | Year: 2012

Gadolinia-doped ceria (Ce 0.9Gd 0.1O 1.95, GDC) electrolyte was fabricated by aqueous-based tape casting method for solid oxide fuel cells (SOFCs). The ceramic powder prepared by combustion synthesis was used with poly acrylic acid (PAA), poly vinyl alcohol (PVA), poly ethylene glycol (PEG), Octanol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate and double distilled water as dispersant, binder, plasticizer, defoamer, surfactant and solvent respectively, to prepare stable GDC slurry. The conditions for preparing stable GDC slurries were studied and optimized by sedimentation, zeta potential and viscosity measurements. Green tapes with smooth surface, flexibility, thickness in the range of 0.35-0.4 mm and 45% relative green density were prepared. Conventional and flash sintering techniques were used and compared for densification which demonstrated the possibility of surpassing sintering at high temperatures and retarding related grain growth. © 2012 Elsevier B.V.


Akbari-Fakhrabadi A.,University of Concepción | Avila R.E.,Chilean Commission of Nuclear Energy | Carrasco H.E.,University of Concepción | Ananthakumar S.,Indian National Institute for Interdisciplinary Science and Technology | Mangalaraja R.V.,University of Concepción
Journal of Alloys and Compounds | Year: 2012

NiO-Ce 0.9Gd 0.1O 1.95 (NiO-10GDC) nanocomposite anode material was synthesized through combustion technique for possible low temperature solid oxide fuel cells (LT-SOFCs). A low weight loss is seen in the TG/DTA thermogram that indicates the complete combustion of the reactant mixtures. The powder X-ray diffraction patterns showed that the presence of NiO, GDC and Ni crystallite phases in the as combusted product. Upon calcination at 600 °C, the metallic Ni oxidized to NiO. TEM images showed a wide size distribution of fine spherical GDC and large irregularly shaped NiO particles. This NiO-10GDC anode material was applied over GDC electrolyte as a porous thin layer. Using this surface engineered GDC electrolyte a semi-cell (electrode/electrolyte structure) was fabricated. The electrical conductivity of the semi-cell was characterized with respect to temperature. © 2012 Published by Elsevier B.V.


Siddheswaran R.,University of Concepción | Mangalaraja R.V.,University of Concepción | Tijerina E.P.,Autonomous University of Nuevo León | Menchaca J.-L.,Autonomous University of Nuevo León | And 4 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

Effect of transition metal oxides (TM = Co and Ni) co-doping on the crystallinity, surface morphology, grain growth and magnetic properties of nanostructure Al:ZnO thin films has been studied for diluted magnetic semiconductor applications. Al:ZnO thin films were fabricated by sol-gel spin coating on p-type Si (100) substrates. Fabrication of hexagonal wurtzite TM co-doped Al:ZnO thin films having thickness 2 μm was successfully achieved. The Raman spectra of the TM co-doped Al:ZnO thin films showed a broad vibrational mode in the range 520-540 cm-1 due to crystal defects created co-doping elements in the ZnO host lattice. Scanning electron microscopy (SEM) revealed that the films are composed of uniform size, polycrystalline dense ZnO particles with defect free, smooth surfaces. The surface roughness was further verified with atomic force microscopy (AFM). The energy dispersive X-ray spectroscopic analysis (EDX) confirmed the stoichiometric compositions of the TM co-doped Al:ZnO films. The magnetic measurements exhibited that the Co, Al:ZnO and Ni, Al:ZnO thin films were ferromagnetic at room temperature. © 2013 Elsevier B.V. All rights reserved.


Yianatos J.,University of Santa María in Ecuador | Contreras F.,University of Santa María in Ecuador | Diaz F.,Chilean Commission of Nuclear Energy
Minerals Engineering | Year: 2010

In this work, the measurement of the axial gas holdup profile and gas residence time distribution (RTD), in a 130 m 3 self-aerated flotation cell, is presented. For this purpose, a radioactive tracer gas was activated in the Nuclear Reactor of the Chilean Commission of Nuclear Energy. The gas tracer, Freon 13B1, was injected as an impulse signal at the gas (air) inlet point, located at the top of the cell, from which the gas tracer circulates first through the rotor, where the bubble dispersion occurs, and then the gas becomes well distributed over the whole cross-sectional area before leaving the cell. The axial gas holdup profile was estimated from the transient gas concentration measurement at different depths inside the cell. From these experiments it was found that the air entering the cell was preferentially distributed in the upper half of the cell, while the gas entrainment into tailings was negligible. The mean gas holdup was 8.8%, and consequently the effective pulp volume of collection zone was 91.2%. The gas concentration on top of froth was recorded for RTD measurement of the gas leaving the cell. It was found that the mean gas residence time was around 42 s and the mixing condition for gas and pulp was similar. © 2009 Elsevier Ltd. All rights reserved.


Yianatos J.,University of Santa María in Ecuador | Bergh L.,University of Santa María in Ecuador | Vinnett L.,University of Santa María in Ecuador | Contreras F.,University of Santa María in Ecuador | Diaz F.,Chilean Commission of Nuclear Energy
Minerals Engineering | Year: 2010

The batch flotation process has been commonly characterized assuming a flotation rate distribution function F(k), e.g.: Dirac delta, Rectangular, Gamma or Weibull functions. The identification of F(k) for the collection zone of continuous industrial cells is more complex and to the authors knowledge, has not been reported yet. In this work, a novel procedure to estimate the flotation rate distribution from the collection zone of industrial flotation cells, using the radioactive tracer technique, is presented. The approach consists of measuring the impulse response of the floatable mineral tracer concentration, and non-floatable gangue tracer concentration (Residence Time Distribution, RTD), in the cell tailings. Then, the floatable tracer concentration can be compared with the model prediction, using the Gamma function and the RTD of the non-floatable tracer. Thus, the F(k) distribution parameters were obtained by means of the least-square estimation. The new approach was successfully tested in industrial rougher flotation cells of large size. © 2010 Elsevier Ltd. All rights reserved.

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