National Nuclear Energy Commission

About: National Nuclear Energy Commission is a government organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Dosimetry & Laser. The organization has 3816 authors who have published 4694 publications receiving 59951 citations.

PtSn/C alloyed and non-alloyed materials: Differences in the ethanol electro-oxidation reaction pathways

Abstract: In the present work, the ethanol oxidation reaction (EOR) was investigated using PtSn/C electrocatalysts in the following two phases: 92% alloyed prepared by the polymeric precursor method (PPM) and 6% alloyed prepared by a sol–gel method (SGM). The TEM experiments show particle sizes of 3–5 nm for both catalysts. The electrocatalytic activity for both materials was investigated using chronoamperometry, and at 0.5 V vs. RHE, the current density for the EOR on the PPM material was approximately 5 times higher than on the SGM material. From in situ ATR-FTIR experiments, it can be seen that the non-alloyed materials led to CO 2 formation with slow kinetics, whereas alloyed materials led to acetic acid formation with fast kinetics. The enhancement in the electrocatalytic behavior for ethanol oxidation was explained by acetic acid formation.

Use of radiation in the production of hydrogels

Abstract: The first hydrogel for wound dressing processed by radiation left the laboratories in Poland in 1986 by the hands of its inventor Janusz M. Rosiak and soon, after formal tests, arrived in the local market (1992). It was a technological breakthrough due to its product characteristics as pain reliever and enhanced healing properties besides its clever production process combining sterilization and crosslinking in a simultaneous operation. IAEA invited professor Rosiak to support the transference of his technology for many laboratories around the world. The laboratories of developing countries, which face all kinds of restrictions, were seduced by the simplicity of the process and low cost of its raw materials. This was the seed of the flourishing activities in hydrogel dressings in Brazil and other developing countries. The technology transfer of the radiation production of hydrogel dressings and other hydrogels to the Brazilian industry is under way. The usual issues associated with radiation processing arise from this experience, i.e. capital costs, misinformation about radiation and lack of expertise on radiation processing. Some other issues concerning local market and social peculiarities also add to the problem. Notwithstanding, many different opportunities arise from those challenges. These technical and commercial issues are roughly: (i) There are plenty of new hydrogels in the market and all say the same. What else radiation processed hydrogels can say? (ii) Regarding to hydrogels and its industrial production as market product, what are the unique characteristics of radiation processing? It was shown that the radiation is a powerful tool for producing hydrogels the same basic formula with improved flexibility, control and purity.

Determination of the geographical origin of green coffee by principal component analysis of carbon, nitrogen and boron stable isotope ratios

Abstract: In this study we show that the continental origin of coffee can be inferred on the basis of coupling the isotope ratios of several elements determined in green beans. The combination of the isotopic fingerprints of carbon, nitrogen and boron, used as integrated proxies for environmental conditions and agricultural practices, allows discrimination among the three continental areas producing coffee (Africa, Asia and America). In these continents there are countries producing 'specialty coffees', highly rated on the market that are sometimes mislabeled further on along the export-sale chain or mixed with cheaper coffees produced in other regions. By means of principal component analysis we were successful in identifying the continental origin of 88% of the samples analyzed. An intra-continent discrimination has not been possible at this stage of the study, but is planned in future work. Nonetheless, the approach using stable isotope ratios seems quite promising, and future development of this research is also discussed.

The in vitro antifungal activity of some dithiocarbamate organotin(IV) compounds on Candida albicans— a model for biological interaction of organotin complexes

Abstract: The in vitro antifungal activity of the dithiocarbamate organotin complexes [Sn{S2CN(CH2)4}2Cl2] (1), [Sn{S2CN(CH2)4}2Ph2] (2), [Sn{S2CN(CH2)4}Ph3] (3), [Sn{S2CN(CH2)4}2n-Bu2] (4), [Sn{S2CN(CH2)4}Cy3] {Cy = cyclohexyl} (5), [Sn{S2CN(C2H5)2}2Cl2] (6), [Sn{S2CN(C2H5)2}2Ph2] (7), [Sn{S2CN(C2H5)2}Ph3] (8), [Sn{S2CN(C2H5)2}3Ph] (9) and [Sn{S2CN(C2H5)2}Cy3] (10) has been screened against Candida albicans (ATCC 18804), Candida tropicalis (ATCC 750) and resistant Candida albicans collected from HIV-positive Brazilian patients with oral candidiasis. All compounds exhibited antifungal activities and complexes 3 and 8 displayed the best results. We have investigated the effect of compounds 1–10 on the cellular activity of the yeast cultures. Changes in mitochondrial function have not been detected. However, all drugs reduced ergosterol biosynthesis. Preliminary studies on DNA integrity indicated that the compounds do not cause gross damage to yeast DNA. The data suggest that these compounds share some mechanisms of action on cell membranes similar to that of polyene but not with azole drugs, normally used in Candida infections. Copyright © 2008 John Wiley & Sons, Ltd.

Effect of the type of ceria dopant on the performance of Ni/CeO2 SOFC anode for ethanol internal reforming

Abstract: This work studied the effect of the type of ceria dopant on the performance of Ni/CeO2 SOFC anode for ethanol conversion reaction. Ni-based catalysts supported on CeO2 doped with different cations (Gd, Y, Pr, Zr, Nb) were prepared by the hydrothermal method. The addition of dopant to ceria led to the formation of the solid solutions during calcination for all samples, except for CeNb sample due to the low solubility limit. In spite of the high oxygen mobility of ceria-based supports, all catalysts deactivated for ethanol decomposition reaction at 1123 K due to carbon deposition. The large Ni0 and CeO2 crystallites formed during calcination at high temperature reduced the effectiveness of the mechanism of carbon removal because of the low metal-support interfacial area. The lowest formation of carbon on Ni/CeNb catalyst was attributed to the presence of NiNb2O6 phase. The reduction of this phase leads to the formation of Ni particles covered by NbOx species, which inhibits carbon formation.