National Institute of Nuclear Research

Marina di Pisa, Italy

National Institute of Nuclear Research

Marina di Pisa, Italy
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Gonzalez-Ramirez D.F.,National Polytechnic Institute of Mexico | Avila-Perez P.,National Institute of Nuclear Research | Torres-Bustillos L.G.,National Polytechnic Institute of Mexico | Aguilar-Lopez R.,National Polytechnic Institute of Mexico | And 3 more authors.
Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering | Year: 2017

Surface interactions with pollutants and photons are key factors that affect the applications of TiO2 in environmental remediation. In this study, the solubilizing agents dimethylsulfoxide and polyoxyethylene sorbitan monooleate, which act as photon competitors, had no effect on the photocatalytic activity of TiO2–C–Ag film in phenanthrene (PHE) removal. Fiberglass with TiO2–C–Ag coating removed 91.1 ± 5.2 and 99.7 ± 0.4% of PHE in treatments using UVA (365–465 nm) and UVC (254 nm) irradiation, respectively. The use of fiberglass as a support increased the superficial area, thus allowing PHE sorption. C and Ag, which are electrically active impurities in TiO2, enhanced its photocatalytic activity and thus the attraction of the pollutant to its surface. The use of high-frequency UV light (UVC) decreased the amount of carbon species deposited on the TiO2CAg film surface. X-ray photoelectron spectroscopy of the TiO2–C–Ag film revealed extensive oxidation of the carbon deposited on the film under UVC light and loss of electrons from Ag clusters by conversion of Ag0 to Ag3+. © 2017 Taylor & Francis Group, LLC

Ortiz-Arzate Z.,National Institute of Nuclear Research | Ortiz-Arzate Z.,Mexico State University | Santos-Cuevas C.L.,National Institute of Nuclear Research | Ocampo-Garcia B.E.,National Institute of Nuclear Research | And 6 more authors.
Nuclear Medicine Communications | Year: 2014

Background In breast cancer, a(n)b(3) and/or a(n)b(5) integrins are overexpressed in both endothelial and tumour cells. Radiolabelled peptides based on the Arg-Gly-Asp (RGD) sequence are radiopharmaceuticals with high affinity and selectivity for these integrins. The RGD-dimer peptide (E-[c(RGDfK)]2) radiolabelled with 99mTc has been reported as a radiopharmaceutical with a 10-fold higher affinity for the a(n)b(3) integrin compared with the RGD-monomer. Ethylenediamine- N,N0-diacetic acid (EDDA) is a hydrophilic molecule that may favour renal excretion when used as coligand in the 99mTc labelling of hydrazinonicotinamide (HYNIC) peptides and can easily be formulated in a lyophilized kit. Aim The aim of this study was to establish a biokinetic model for 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2 prepared from lyophilized kits and evaluate its dosimetry as a tumour-imaging agent in seven healthy women and three breast cancer patients. Materials and methods 99mTc labelling was performed by adding sodium pertechnetate solution and 0.2 mol/l phosphate buffer (pH 7.0) to a lyophilized formulation containing E-[c(RGDfK)]2, EDDA, tricine, mannitol and stannous chloride. The radiochemical purity was evaluated using reverse-phase high-performance liquid chromatography and instant thin-layer chromatography on silica gel analyses. Stability studies in human serum were carried out using size-exclusion high-performance liquid chromatography. In-vitro cell uptake was tested using breast cancer cells (MCF7, T47D and MDA-MB-231) with blocked and nonblocked receptors. Biodistribution and tumour uptake were determined in MCF7 tumour-bearing nude mice with blocked and nonblocked receptors, and images were obtained using a micro-SPECT/PET/CT. Whole-body images from seven healthy women were acquired at 0.5, 1, 3, 6 and 24 h after 99mTc-EDDA/HYNIC-E- [c(RGDfK)]2 administration with radiochemical purities greater than 94%. Regions of interest were drawn around the source organs at each time frame. Each region of interest was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate the 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2 time- activity curves of each organ to adjust the biokinetic model and calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. In three breast cancer patients with histologically confirmed cancer, static images were obtained at 1 h in the supine position with hands placed behind the head. Results 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2 obtained from lyophilized kits demonstrated high stability in human serum and specific cell receptor binding. The biodistribution data from mice showed rapid blood clearance, with both renal and hepatobiliary excretion, and specific binding towards a(n)b(3) integrins in the MCF7 tumours. In women, the blood activity showed a half-life value of 1.60 min for the fast component (T 1/2a = ln2/26.01) and half-life values of 1.0 h for the first slow component (T1/2b =ln2/0.69) and 4.03 h for the second slow component (T 1/2c =ln2/0.16). Images from patients showed an average tumour/heart (blood) ratio of 3.61±0.62 at 1 h. The average equivalent doses calculated for a study using 740MBq were 4.9, 6.2, 20.7, 34.5 and 57.0mSv for the liver, intestines, spleen, kidneys and thyroid, respectively, and the effective dose was 6.1mSv. Conclusion All absorbed doses were comparable to those known from most of the 99mTc studies. 99mTc-EDDA/ HYNIC-E-[c(RGDfK)]2 obtained from kit formulations showed high tumour uptake in patients with malignant lesions, making it a promising imaging radiopharmaceutical for targeting site-specific breast cancer. The results obtained in this study warrant further clinical studies to determine the specificity and sensitivity of 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2. © 2014 Wolters Kluwer Health Lippincott Williams & Wilkins.

Martinez T.,National Autonomous University of Mexico | Lartigue J.,National Autonomous University of Mexico | Zarazua G.,National Institute of Nuclear Research | Avila-Perez P.,National Institute of Nuclear Research | And 2 more authors.
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2010

Trace metals concentrations in food are significant for nutrition, due either to their nature or toxicity. Sweets, including chewing gum and candies, are not exactly a food, but they usually are unwearied consumed by children, the most vulnerable age-group to any kind of metal contamination in the food chain. The presence of relatively high concentrations of heavy metals such as Lead elicits concern since children are highly susceptible to heavy metals poisoning. Trace-metals concentrations were determined for six different flavors of a Mexican candy by means of Total X-ray Fluorescence Spectrometry. Triplicate samples of the various candy's flavours (strawberry, pineapple, lemon, blackberry, orange and chilli) were digested in 8 mL of a mix of supra-pure HNO3 and H2O2 (6 mL: 2 mL) in a microwave oven MARS-X. Results show the presence of essential and toxic elements such as Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, and Pb. All metal concentrations were higher and significantly different (α=0.05) in chilli candy, compared to other candy flavours. Lead concentration fluctuated in the range of 0.102 to 0.342 μg g-1. A discussion about risk consumption and concentration allowed by Mexican and International Norms is made. As a part of the Quality Control Program, a NIST standard of "Citrus Leaves" and a blank were treated in the same way. © 2010 Elsevier B. V. All rights reserved.

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

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.

Martinez T.,National Autonomous University of Mexico | Tejeda S.,National Institute of Nuclear Research | Lartigue J.,National Autonomous University of Mexico | Zarazua G.,National Institute of Nuclear Research | And 4 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2014

Marine sediments from Mexico's West coast in the Pacific Ocean from Sinaloa to Jalisco were analyzed by energy-dispersive X-ray fluorescence technique. Ten sediment samples were collected in May, 2010 between 55.5 and 1264 m water depth with a Reinneck type box nucleate sampler. Sediments were dried and fractioned by granulometry. Their physical and chemical properties were determined in laboratory by standard methods, pH, and conductivity. Concentration and distribution of K, Ca, Ti Mn, Fe, Cu, Zn, Ga, Pb, Br and Sr were analyzed. In order to determine the status of the elements, enrichment factors were calculated. Total, organic carbon and CaCO3 were also determined. Scanning electron microscopy and X-ray diffraction show predominant groups of compounds. As quality-control method, Certified Reference Material was both processed and analyzed at even conditions. Enrichment factors for K, Ca, Ti, Mn Fe, Cu, Zn, Ga, Ni, and Sr show they are conservative elements having concentrations in the range of unpolluted sites giving a base data line for the sampling zone In spite of moderately enrichment factors <100 μm size and bulk fractions, first Pb concentration fraction was similar to those found in not influenced by anthropogenic activities sites nearby Mazatlan Harbor. Bulk fraction concentration (52-133 μg g-1) and enrichment factor show the influence of anthropogenic sources with values between lowest effect level and a third part of 250 μg g-1value, which is considered to have severe effect levels for aquatic life. © 2013 Akadémiai Kiadó, Budapest, Hungary.

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.

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.

Garcia-Contreras M.A.,National Institute of Nuclear Research | Fernandez-Valverde S.M.,National Institute of Nuclear Research | Basurto-Sanchez R.,National Institute of Nuclear Research
Journal of Applied Electrochemistry | Year: 2015

Pt, PtCo, and PtNi electrocatalysts were prepared by mechanical alloying, and their activity for oxygen reduction reaction in 0.5 M KOH was investigated using cyclic voltammetry (CV) and rotating ring-disk electrode techniques. Electrocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Physical characterization showed that all electrocatalysts are alloys in the form of agglomerated particles that consist of nanocrystals. To perform an electrocatalytic evaluation, polarization curves, Koutecky–Levich and Tafel plots were obtained to calculate the kinetic parameters. Additionally, the molar fraction of the generated HO2 − and the number of transferred electrons were determined. PtCo alloy showed a better performance for oxygen reduction reaction with a higher exchange current density, a lower overpotential, as well as higher specific and mass activities due to a synergistic effect between Pt and Co atoms as a result of the alloying process. © 2015, Springer Science+Business Media Dordrecht.

Mondragon-Contreras L.,National Institute of Nuclear Research | Ramirez-Jimenez F.J.,National Institute of Nuclear Research | Garcia Hernandez J.M.,National Institute of Nuclear Research | Torres Bribiesca M.A.,National Institute of Nuclear Research
IEEE Nuclear Science Symposium Conference Record | Year: 2012

The accurate dose determination for gamma ray fields is considered, a p-i-n diode is taken as the basic detector for the implementation of a gamma ray monitor. This determination is fundamental for a further application in the evaluation of dose from photon fields generated for medical applications in Radiotherapy with LINAC's. © 2012 IEEE.

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