Showing papers by "National Nuclear Energy Commission published in 2010"

Study of the corrosion resistance and in vitro biocompatibility of PVD TiCN-coated AISI 316 L austenitic stainless steel for orthopedic applications

Abstract: The aim of the present work was to study the corrosion resistance in Hanks' solution and the in vitro biocompatibility of a TiCN-coated AISI 316 L stainless steel. The electrochemical behavior was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy. Cytotoxicity and genotoxicity tests were performed to evaluate the potential biocompatibility of the specimens. TiCN morphology was investigated using scanning electron microscopy (SEM). Bare 316 L specimens were also evaluated for comparison. The results showed that the film morphology strongly influences the electrochemical behavior of the coated underlying metal. TiCN-coated specimens presented neither cytotoxicity nor genotoxicity.

Colorectal cancer chemoprevention by 2 β-cyclodextrin inclusion compounds of auraptene and 4′-geranyloxyferulic acid

Abstract: The inhibitory effects of novel prodrugs, inclusion complexes of 3-(4'-geranyloxy-3'-methoxyphenyl)-2-trans propenoic acid (GOFA) and auraptene (AUR) with beta-cyclodextrin (CD), on colon carcinogenesis were investigated using an azoxymethane (AOM)/dextran sodium sulfate (DSS) model. Male CD-1 (ICR) mice initiated with a single intraperitoneal injection of AOM (10 mg/kg body weight) were promoted by the addition of 1.5% (w/v) DSS to their drinking water for 7 days. They were then given a basal diet containing 2 dose levels (100 and 500 ppm) of GOFA/beta-CD or AUR/beta-CD for 15 weeks. At Week 18, the development of colonic adenocarcinoma was significantly inhibited by feeding with GOFA/beta-CD at dose levels of 100 ppm (63% reduction in multiplicity, p < 0.05) and 500 ppm (83% reduction in the multiplicity, p < 0.001), when compared with the AOM/DSS group (multiplicity: 3.36 +/- 3.34). In addition, feeding with 100 and 500 ppm (p < 0.01) of AUR/beta-CD suppressed the development of colonic adenocarcinomas. The dietary administration with GOFA/beta-CD and AUR/beta-CD inhibited colonic inflammation and also modulated proliferation, apoptosis and the expression of several proinflammatory cytokines, such as nuclear factor-kappaB, tumor necrosis factor-alpha, Stat3, NF-E2-related factor 2, interleukin (IL)-6 and IL-1beta, which were induced in the adenocarcinomas. Our findings indicate that GOFA/beta-CD and AUR/beta-CD, especially GOFA/beta-CD, are therefore able to inhibit colitis-related colon carcinogenesis by modulating inflammation, proliferation and the expression of proinflammatory cytokines in mice.

Natural antioxidants protecting irradiated beef burgers from lipid oxidation

Abstract: The effect of butylated hydroxytoluene/butylated hydroxyanisole blend (BHT/BHA), and rosemary and oregano extracts, added individually or in combination, on lipid oxidation and fatty acid composition was investigated on irradiated frozen beef burgers. Irradiation treatment was carried out using a 60CO semi-industrial irradiator at doses of 6, 7 and 8 kGy, and then the treated meat samples were stored at −20 °C for 90 days. Lipid oxidation and fatty acid composition of beef samples were evaluated by measurement of TBARS and gas chromatography, respectively. The results of the experiment showed that rosemary extract, applied alone and in combination with either BHT/BHA or oregano extract, was more effective in maintaining a low oxidation level in the samples compared to oregano extract used individually or in combination with BHT/BHA. Results also showed no significant differences (p > 0.05) in fatty acid composition in all analyzed samples, although some changes in terms of decreased PUFA and MUFA, beside of slight increase of SFA content were observed. However, these differences do not correlate positively neither with the irradiation dose nor the type of antioxidant. Thus, there is a potential application of these spices as natural antioxidants in irradiated meats.

Uranium removal by chitosan impregnated with magnetite nanoparticles: adsorption and desorption

Abstract: A magnetic biosorbent composed of nanoparticles of magnetite covered with chitosan, denominated magnetic chitosan, was prepared. The magnetic chitosan showed a magnetic response of intense attraction in the presence of a magnetic field without becoming magnet, a typical behaviour of superparamagnetic material. Its adsorption performance was evaluated by the adsorption isotherm models of Langmuir and Freundlich for uranium ions, and the desorption behaviour using carbonate and oxalate ions was investigated. The adsorption equilibrium data fitted well to the Langmuir model, being the maximum adsorption capacity equal 42 mg g -1 . In the desorption studies, 94% of recovered UO2 2+ with carbonate ion was verified under the conditions studied. The chitosan, available as a byproduct of marine food processing, is environmentally safe and can be a low cost adsorbent for U removal from wastewater. The magnetic chitosan as adsorbent of U to treat radioactive wastewater is a sustainable technology.

Study on application of PTFE, FEP and PFA fluoropolymers on radiation dosimetry

Abstract: Changes induced by radiation in the UV–vis and Infrared absorbance spectra of fluoropolymer films were investigated. Samples (3×1 cm2) of commercially available fluoropolymers, tetrafluoropolymer homopolymer (PTFE–Tecnofluor/DuPont) and its copolymers with hexafluoropropylene (FEP 1000 C–DuPont) and perfluoroalkoxy (PFA 500 CLP–Dupont) were irradiated with 60Co gamma radiation in free air at electronic equilibrium conditions with absorbed doses between 1 and 150 kGy. Studies of environmental condition effects, such as temperature and light, pre- and post-irradiation stability and dose range useful response were carried out. Fluoropolymers are very stable when exposed to different ambient conditions; the dosimetric wavelength is characteristic for each type of fluoropolymer and a linear correlation was found between gamma radiation dose and optical response.

Electro-oxidation of ethanol using PtSnRh/C electrocatalysts prepared by an alcohol-reduction process

Abstract: PtRh/C (90:10), PtRh/C (50:50), PtSn/C (50:50), and PtSnRh/C (50:40:10) electrocatalysts were prepared by an alcohol-reduction process using ethylene glycol as solvent and reduction agent and Vulcan Carbon XC72 as supports. The electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy. The electro-oxidation of ethanol was studied by cyclic voltammetry chronoamperometry at room temperature and on a single cell of a direct ethanol fuel cell at 100 °C. Cyclic voltammetry and chronoamperometry experiments showed that PtSnRh/C and PtSn/C electrocatalysts have similar performance for ethanol oxidation at room temperature, while the activity of PtRh/C electrocatalysts was very low. At 100 °C on a single cell, PtSnRh/C showed superior performance compared to PtSn/C and PtRh/C electrocatalysts.

Synthesis and characterization of mesoporous silica/poly(N-isopropylacrylamide) functional hybrid useful for drug delivery

Abstract: Recent studies indicate the use of mesoporous silica and polymeric sensitive hydrogels as suitable for drug delivery systems due to their specific characteristics. Polymeric hydrogels, such as poly(N-isopropylacrylamide) [P(N-iPAAm)], show volumetric expansion/contraction behaviour at 306 K, which that can be used to develop a thermosensitive drug delivery system. In this study, we report a facile and direct synthesis route to obtain hybrid functional nanosystems based on silica-P(N-iPAAm) by using a neutral surfactant and without any functionalization method and the assessment of its release rate of a model drug. The materials were characterized by Fourier transform infrared spectroscopy, nitrogen adsorption, scanning electron microscopy, transmission electron microscopy and thermal analysis. A release assay with atenolol monitored by UV–Vis spectroscopy was performed for pure SBA-15 and a hybrid system at different temperatures in order to evaluate the influence of the thermosensitive behaviour of the polymer on the release kinetics. The response of the hybrid system as a drug delivery device is influenced by the volumetric contraction of P(N-iPAAm) up to the lower critical solution temperature (LCST) due to phase transition. Above the LCST, drug release depends essentially on the temperature.

Human Multipotent Mesenchymal Stromal Cells from Distinct Sources Show Different In Vivo Potential to Differentiate into Muscle Cells When Injected in Dystrophic Mice

Abstract: Limb-girdle muscular dystrophies are a heterogeneous group of disorders characterized by progressive degeneration of skeletal muscle caused by the absence or deficiency of muscle proteins. The murine model of Limb-Girdle Muscular Dystrophy 2B, the SJL mice, carries a deletion in the dysferlin gene. Functionally, this mouse model shows discrete muscle weakness, starting at the age of 4-6 weeks. The possibility to restore the expression of the defective protein and improve muscular performance by cell therapy is a promising approach for the future treatment of progressive muscular dystrophies (PMD). We and others have recently shown that human adipose multipotent mesenchymal stromal cells (hASCs) can differentiate into skeletal muscle when in contact with dystrophic muscle cells in vitro and in vivo. Umbilical cord tissue and adipose tissue are known rich sources of multipotent mesenchymal stromal cells (MSCs), widely used for cell-based therapy studies. The main objective of the present study is to evaluate if MSCs from these two different sources have the same potential to reach and differentiate in muscle cells in vivo or if this capability is influenced by the niche from where they were obtained. In order to address this question we injected human derived umbilical cord tissue MSCs (hUCT MSCs) into the caudal vein of SJL mice with the same protocol previously used for hASCs; we evaluated the ability of these cells to engraft into recipient dystrophic muscle after systemic delivery, to express human muscle proteins in the dystrophic host and their effect in functional performance. These results are of great interest for future therapeutic application.

Low-level laser therapy in burning mouth syndrome patients: a pilot study.

Abstract: Objective: The aim of this study was to investigate the effect of low-level laser therapy (LLLT) on the treatment of burning mouth syndrome (BMS). In addition, the laser effect was compared on the different affected oral sites. Materials and Methods: Eleven subjects with a total of 25 sites (tongue, lower lip, upper lip, and palate) affected by a burning sensation were selected. The affected areas were irradiated once a week for three consecutive weeks with an infrared laser (λ = 790 nm). The probe was kept in contact with the tissue, and the mucosal surface was scanned during the irradiation. The exposure time was calculated based on the fluence of 6 J/cm2, the output power of 120 mW, and the area to be treated. Burning intensity was recorded through a visual analog scale before and after the treatment and at the 6-week follow-up. The percentage of the improvement in symptoms was also obtained. Results: Burning intensity at the end of the laser therapy was statistically lower than at the beginni...

Harmonised framework for ecological risk assessment of sediments from ports and estuarine zones of North and South Atlantic.

Abstract: This paper presents a harmonised framework of sediment quality assessment and dredging material characterisation for estuaries and port zones of North and South Atlantic. This framework, based on the weight-of-evidence approach, provides a structure and a process for conducting sediment/dredging material assessment that leads to a decision. The main structure consists of “step 1” (examination of available data); “step 2” (chemical characterisation and toxicity assessment); “decision 1” (any chemical level higher than reference values? are sediments toxic?); “step 3” (assessment of benthic community structure); “step 4” (integration of the results); “decision 2” (are sediments toxic or benthic community impaired?); “step 5” (construction of the decision matrix) and “decision 3” (is there environmental risk?). The sequence of assessments may be interrupted when the information obtained is judged to be sufficient for a correct characterisation of the risk posed by the sediments/dredging material. This framework brought novel features compared to other sediment/dredging material risk assessment frameworks: data integration through multivariate analysis allows the identification of which samples are toxic and/or related to impaired benthic communities; it also discriminates the chemicals responsible for negative biological effects; and the framework dispenses the use of a reference area. We demonstrated the successful application of this framework in different port and estuarine zones of the North (Gulf of Cadiz) and South Atlantic (Santos and Paranagua Estuarine Systems).

New materials for photocatalytic degradation of Indigo Carmine—Synthesis, characterization and catalytic experiments of nanometric tin dioxide-based composites

Abstract: Herein we describe experiments of photocatalytic degradation of Indigo Carmine dye, carried out by new composites containing nanometric SnO 2 supported on Al 2 O 3 . The composites were prepared in a sequence of procedures which involved reactions of SnBuCl 3 , aluminium hydroxide with NH 4 OH in ethanol in order to impregnate organotin oxide in Al 2 O 3 in different stoichiometry. Hence, the obtained materials were employed in experiments of thermal decomposition in O 2 at different temperatures, yielding nanoparticles of SnO 2 supported on Al 2 O 3 , with ratios of Sn/Al 2 O 3 of 30% ( 1 ), 40% ( 2 ) and 60% ( 3 ) in weight, respectively. XRD experiments revealed diffraction patterns of SnO 2 , and those of Al 2 O 3 were not observed due to their low crystallinity. 119 Sn Mossbauer experiments suggested the formation of SnO 2 in all experiments. Studies of scanning electron microscopies (SEM) showed the formation of tin(IV) oxide on the surface of Al 2 O 3 in composites ( 1 )–( 3 ). The crystallite average size ( D ) was calculated employing Scherrer equation, revealing the presence of nanometric SnO 2 in all samples. Photocatalytic degradation of Indigo Carmine in aqueous medium, induced by composites ( 1 )–( 3 ), was monitored by electronic spectroscopy, and composite ( 3 ) displayed the higher activity. In addition, results from electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) allowed us to propose a degradation route for the dye.

Mesoporous silica-magnetite nanocomposite: facile synthesis route for application in hyperthermia

Abstract: The synthesis of nanostructured magnetic materials has been intensively researched because of their large field of applications as magnetic carriers in drug targeting, hyperthermia in tumor treatment, among others. Much effort has been invested in magnetic nanoparticles for bioapplications. However, as these nanoparticles present high specific surface area, unprotected nanoparticles can easily form aggregates and react with oxygen in the air. They can also rapidly biodegrade when directly exposed to biological systems. In this context, we have explored the possibility of synthesizing a mesoporous SiO2–Fe3O4 nanocomposite and its AC magnetic-field-induced heating properties. The magnetite nanocomposite was obtained by impregnation of an iron precursor into a silica framework. The proposed method involves the preparation of an iron oxide precursor in ethanol and the subsequent impregnation of SBA-15 mesoporous hexagonal silica. Iron oxide was formed inside the porous structure, thus producing the magnetic device. The nanocomposite was characterized by X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), N2 adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Measurements of AC magnetic-field-induced heating properties of the obtained nanocomposite, both of the solid form and in aqueous solution, under different applied magnetic fields showed that it is suitable as a hyperthermia agent for biological applications.

Preparation of PtRuNi/C electrocatalysts by an alcohol-reduction process for electro-oxidation of methanol

Abstract: PtRuNi/C electrocatalysts with 20 wt% metals loading and Pt:Ru:Ni atomic ratio of 50:40:10 were prepared by an alcohol-reduction process. The electrocatalysts were characterized using energy-dispersive X-ray analysis, X-ray diffraction analysis and thermogravimetric analysis. The electro-oxidation of methanol was studied in sulfuric acid solution by chronoamperometry. It was found that when the initial pH of the reaction medium was acidic, only Pt(IV) and Ru(III) ions were reduced, while the reduction of Ni(II) ions did not take place. Changing the pH of the reaction medium by addition of OH − ions resulted in the reduction of Pt(IV), Ru(III) and Ni(II) ions, which crystallized in the face-centered cubic (fcc) structure. This was observed for OH − /metals ratios ≥6, however, under these conditions the metals loading on the carbon support was only half the nominal value. The PtRuNi/C electrocatalyst prepared with OH − /metals = 6 showed superior performance for methanol oxidation at room temperature compared to commercial PtRu/C electrocatalyst.

Analytical Solution for Multi-Species Contaminant Transport in Finite Media with Time-Varying Boundary Conditions

Abstract: Most analytical solutions available for the equations governing the advective- dispersivetransportofmultiplesolutesundergoingsequentialfirst-orderdecayreactionshave been developed for infinite or semi-infinite spatial domains and steady-state boundary con- ditions. In this study, we present an analytical solution for a finite domain and a time-varying boundary condition. The solution was found using the Classic Integral Transform Technique (CITT) in combination with a filter function having separable space and time dependen- cies, implementation of the superposition principle, and using an algebraic transformation that changes the advection-dispersion equation for each species into a diffusion equation. The analytical solution was evaluated using a test case from the literature involving a four radionuclide decay chain. Results show that convergence is slower for advection-dominated transport problems. In all cases, the converged results were identical to those obtained with the previous solution for a semi-infinite domain, except near the exit boundary where dif- ferences were expected. Among other applications, the new solution should be useful for benchmarking numerical solutions because of the adoption of a finite spatial domain.