Showing papers by "National Nuclear Energy Commission published in 2002"
TL;DR: In this article, the authors investigated the physicochemical properties of cross-linked proteins and showed that the properties of these proteins improved significantly the puncture strength for all types of films.
130 citations
TL;DR: In this paper, the changes in total β-carotene and flavonoids upon the radiation treatment were tested in herbs used as food products, and the alterations in the active principles in the herbs were analyzed employing various methods of extraction and chromatography.
104 citations
TL;DR: In this paper, the half-life values of spontaneous nuclear decay processes are presented in the framework of the effective liquid drop model (ELDM) using the combination of varying mass asymmetry shape description for the mass transfer (VMAS) and Werner-Wheeler's inertia coefficient (WW).
103 citations
TL;DR: A generic system for 137Cs is described, mainly based on a reference soil-to-plant transfer factor which depends solely on soil properties such as nutrient status, exchangeable K-content, pH and moisture content.
86 citations
TL;DR: In this article, a simple and efficient procedure for the preconcentration and determination of molybdenum in sea-water was developed using solid phase extraction (SPE), which was carried out using two-level full factorial and Doehlert matrix designs.
Abstract: A simple and efficient procedure for the preconcentration and determination of molybdenum in sea-water was developed using solid-phase extraction (SPE) of molybdenum(V) ion as the thiocyanate complex by polyurethane foam and inductively coupled plasma optical emission spectrometry (ICP-OES). The optimization process was carried out using two-level full factorial and Doehlert matrix designs. Four variables (solution volume, shaking time, thiocyanate concentration and hydrochloric acid concentration) were regarded as factors in the optimization. Results of the two-level full factorial design, 24 with 16 runs based on the variance analysis (ANOVA), demonstrated that all four factors, as well as the interactions between thiocyanate concentration and time and hydrochloric acid concentration and time, are statistically significant. Doehlert designs were applied in order to determine the optimum conditions for
molybdenum preconcentration. The proposed procedure allowed molybdenum determination with a detection limit of 1.5 µg L−1 and a precision, calculated as relative standard deviation (RSD), of 1.8% for a set of 10 measurements for a molybdenum concentration of 10.0 µg L−1 in synthetic sea-water solution. The recovery of molybdenum in the presence of several cations achieved demonstrated that this procedure improved the required selectivity for sea-water analysis. The studied procedure was applied to molybdenum determination in surface sea-water samples collected in Salvador City, Brazil. Results showed good agreement with other reported data from the literature, including data obtained for samples from this same city by another procedure.
71 citations
TL;DR: In this article, the effect of irradiation on the hygienic quality of meat and meat products is considered as related to the control of meat-borne parasites of humans; elimination of pathogens from fresh meat and poultry; and elimination of organisms from processed meat.
71 citations
TL;DR: An investigation was made of the in vitro cytotoxic effect of calcium phosphate cement based on a-tricalcium phosphate immersed for different lengths of time in simulated body fluid (SBF), based on the ISO-10993 ‘‘Biological Evaluation of Medical Devices’’ standard.
66 citations
TL;DR: In this article, a radiation dynamics electron beam accelerator with 1.5 MeV energy and 37kW power was used to destroy organic compounds delivered in industrial effluents, mainly chloroform, dichloroethane, methyl isobutyl ketone, toluene, xylene and phenol.
61 citations
TL;DR: Results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zIRconia-hydroxyapatites composites with potential for future use as orthopedic and dental implants are presented.
Abstract: Materials and devices intended for end-use applications as implants and medical devices must be evaluated to determine their biocompatibility potential in contact with physiological systems. The use of standard practices of biological testing provides a reasonable level of confidence concerning the response of a living organism to a given material or device, as well as guidance in selecting the proper procedures to be carried out for the screening of new or modified materials. This article presents results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zirconia-hydroxyapatite composites (Z4H6 and Z6H4) with potential for future use as orthopedic and dental implants. They indicate that these materials present potential for this type of application because they meet the requirements of the standard practices recommended for evaluating the biological reactivity of ATCC cell cultures (CCL1 NCTC clone 929 of mouse connective tissue and CCL 81 of monkey connective tissue) and animals (rabbit and mouse) with direct or indirect patient contact, or by the injection of specific extracts prepared from the material under test. In addition, studies involving short-term intramuscular and long-term implantation assays to estimate the reaction of living tissue to the composites studied, and investigations on long-term effects that these materials can cause on the cellular metabolism, are already in progress.
58 citations
TL;DR: It was found that the corrosion potential of uncoated sample is always more noble than that of coated one, and the corrosion rate determined from polarization curves is higher for HA-coated alloys, but it still can be considered negligible.
Abstract: The electrochemical behavior of Ti-6Al-7Nb alloy with and without plasma-sprayed hydroxyapatite (HA) coating was investigated in Hank's balanced salt solution at 37 degrees C. This behavior was evaluated by analyzing both corrosion potential variation with time curves and potentiodynamic polarization curves. The polarization curves were determined both in aerated and deaerated solutions. It was found that the corrosion potential of uncoated sample is always more noble than that of coated one. In aerated solutions the polarization curve of a coating-free alloy presents a typical passive/transpassive behavior, which is absent in the HA-coated alloy and in deaerated solution for both coated and uncoated conditions. In the latter polarization curves, the current density continuously increases with the increase of the potential. The corrosion rate determined from polarization curves is higher for HA-coated alloys, but it still can be considered negligible (less than 1 microA/cm(2)).
52 citations
TL;DR: The high osteoconductive potential of the HA foams provides a potential structure for use as bone substitute in orthopedic, oral, and cranio-maxillofacial reconstructive surgery, and as dento-alveolar implants.
Abstract: Hydroxyapatite (HA) is widely applied as bone graft material due to its osteoconductive potential and well-established biocompatibility. In this work, macroporous hydroxyapatite structures made through foaming of aqueous suspensions and gelcasting were tested for in vivo osteointegration. These foams are composed of a three-dimensional array of spherical pores with diameters of approximately 100–500 μm, interconnected by windows of smaller size in the range of 30–120 μm. The HA foams were implanted in the tibia of albino New Zealand rabbits and removed after a period of 8 weeks. Histological analysis revealed that the pores in the foams were partially or completely filled progressively with mature new bone tissue and osteoid after the implanted period. No immune or inflammatory reactions were detected. The high osteoconductive potential of the HA foams provides a potential structure for use as bone substitute in orthopedic, oral, and cranio-maxillofacial reconstructive surgery, and as dento-alveolar implants. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 587–592, 2002
TL;DR: This work investigated the influence of a low-intensity, linearly polarized Nd:YLF laser beam on skin wound healing, considering two orthogonal directions of polarization, and shown that lesion 1 healed faster than the control lesions, which presented a smaller degree of healing after 14 days postwounding.
Abstract: Previous research in our laboratory has shown that the polarization component of the electrical field plays an important role on the healing process of inflammatory lesions created in the end of the spinal column of Lewis rats, using a He-Ne laser at lambda = 632.8 nm. It is well known that polarization is lost in a turbid medium, such as living tissue. However, the Nd:YLF wavelength (lambda = 1,047 nm) allows more polarization preservation than lambda = 632.8 nm, and the Nd:YLF laser beam has been used in clinical trials as a biostimulating agent. In this work, we investigated the influence of a low-intensity, linearly polarized Nd:YLF laser beam on skin wound healing, considering two orthogonal directions of polarization. We have considered a preferential axis as the animals' spinal column, and we aligned the linear laser polarization first parallel, then perpendicular to this direction. Burns of about 6 mm in diameter were created with liquid N2 on the back of the animals, and the lesions were irradiated on days 3, 7, 10, and 14 postwounding, D = 1.0 J/cm2. Lesions 1 and 2 were illuminated using Nd:YLF pulsed laser radiation. Lesion 1 was irradiated with linear polarization parallel with the rat spinal column. Lesion 2 was irradiated using the same protocol, but the light polarization was aligned with the perpendicular relative orientation. Control lesions were not irradiated. We have taken photographs from the wound areas on the 3rd, 7th, 10th, 14th, and 17th postoperative day for a biometrical analysis. The results have shown that lesion 1 healed faster than the control lesions (p < 0,05), which presented a smaller degree of healing after 14 days postwounding.
TL;DR: In this paper, the residual compressive strength and modulus of elasticity of concrete concretes were analyzed at a temperature of 600 °C after cooling down to room temperature.
Abstract: In this work we analyzed the "residual" performance of Portland cement concretes heat-treated at 600 °C after cooling down to room temperature. Concretes with characteristic compressive strength at 28 days of 45 MPa and of 60 MPa were studied. The heat-treatment was carried out without any imposed load. We measured the residual compressive strength and modulus of elasticity. The geometry of the structure was described by mercury intrusion porosimetry and nitrogen sorption tests. We observed a decrease of residual compressive strength and modulus of elasticity, with the raise of heat-treatment temperature, as a result of heat-induced material degradation. The results also indicated that the microstructural damage increased steadily with increasing temperature. Based on the results of this experimental work we concluded that residual mechanical properties of concrete are dependent of their original non heat-treated values.
TL;DR: In this paper, bovine powder gelatin was submitted to γ-radiation from a 60Co source, dose rate about 7kGy/h and to electron beam irradiation, dose level about 11k Gy/s.
01 Jan 2002-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a Neural Network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set, which is calibrated at the National Physical Laboratory, United Kingdom, and uses gold activation foils as thermal neutron detectors.
Abstract: A Neural Network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set. The present work used the “Stuttgart Neural Network Simulator” as the interface for designing, training and validation of a MultiLayer Perceptron network. The back-propagation algorithm was applied. The Bonner Sphere set chosen has been calibrated at the National Physical Laboratory, United Kingdom, and uses gold activation foils as thermal neutron detectors. The neutron energy covered by the response functions goes from 0.0001 eV to 10 MeV. Two types of neutron spectra were numerically investigated: monoenergetic and continuous. Good results were obtained, indicating that the Neural Network can be considered an interesting alternative among the neutron spectrum unfolding methodologies.
TL;DR: The neural network was a powerful tool, able to recognize prompt gamma-ray explosive patterns in spite of the presence of occluding materials, and was revealed as a potential tool for in situ inspection systems.
TL;DR: In this article, the effectiveness of low-dose gamma-irradiation combined with edible coatings to produce shelf-stable foods was evaluated using a nine-point hedonic scale to evaluate the organoleptic characteristics.
TL;DR: Human thyroid‐stimulating hormone (hTSH), a heterodimeric glycoprotein composed of non‐covalently linked α‐ and β‐subunits, was expressed in Chinese hamster ovary cells using a system based on dicistronic expression vectors.
Abstract: The utilization of dicistronic mRNA expression vectors, containing the gene of interest upstream of an amplifiable marker gene, has shown success in rapidly, efficiently and reproducibly obtaining stable cell lines that express high levels of the protein of interest. For this reason, human thyroid-stimulating hormone (hTSH), a heterodimeric glycoprotein composed of non-covalently linked alpha- and beta-subunits, was expressed in Chinese hamster ovary (CHO) cells using a system based on dicistronic expression vectors. These contained the genes of interest and the amplifiable gene markers dihydrofolate reductase (DHFR) and adenosine deaminase (ADA), separated by an internal ribosome entry site isolated from the encephalomyocarditis virus. After the cells (CHO-DHFR-) had been co-transfected with the expression vectors and submitted to gene amplification in culture medium containing stepwise increments of methotrexate, it was possible to isolate clones that presented a secretion level of up to 7.2+/-1.3 microg/10(6) cells per day, the highest ever reported for the expression of this glycoprotein hormone. A second treatment, involving the utilization of deoxycoformycin, directed to amplify the ADA marker gene, provided a clone with an additional 2-3-fold increase in hTSH secretion, reaching a secretion level of 17.8+/-7.6 microg/10(6) cells per day. Cell culture and hTSH production in a hollow-fibre bioreactor were set up in order to carry out a preliminary physico-chemical, immunological and biological characterization of this hormone in comparison with pituitary-extracted hTSH (from the National Institute of Diabetes and Digestive and Kidney Diseases) and the only recombinant hTSH now available (Thyrogen). The availability of recombinant hTSH is very important in the diagnosis and therapy of thyroid carcinoma, via stimulation of radioiodine uptake.
TL;DR: An object oriented algorithm, written in the Java programming language, which performs a Monte Carlo calculation of the evaporation-fission process taking place inside an excited nucleus, shows that this nuclear physics problem is very suited for the object oriented programming.
TL;DR: Reversed-phase high-performance liquid chromatography methodology for the determination of human prolactin (hPRL) in bacterial periplasmic space or in purified preparations has been developed, based on the high hydrophobicity of the hPRL molecule, which allows its separation from the bulk of bacterial proteins.
TL;DR: In this article, the synthesis of ternary electrocatalysts Pt/Ru/Mo type were performed according to the Bonnemann method and characterized by the following techniques: energy dispersive analysis (EDX), X-rays diffraction (XRD), cyclic voltammetry (CV) and polarization curves (E vs. i) for the oxidation of H2, H2/CO and methanol in a Proton Exchange Membrane Fuel Cell (PEMFC).
Abstract: The synthesis of ternary electrocatalysts Pt/Ru/Mo type were performed according to the Bonnemann method and characterized by the following techniques: energy dispersive analysis (EDX), X-rays diffraction (XRD), cyclic voltammetry (CV) and polarization curves (E vs. i) for the oxidation of H2, H2/CO and methanol in a Proton Exchange Membrane Fuel Cell (PEMFC). Catalysts structure consists of highly dispersed nanocrystals in carbon support, with an average particle size of 2 nm. The results of cyclic voltammetry suggest an enhancement of the catalyst electroactivity with the addition of cocatalysts. Polarization curves indicate that Pt/Ru/Mo systems could be employed as electrode material for PEM fuel cell for technological application.
TL;DR: In this article, the preconcentration of thorium from natural water and its determination directly by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) were attempted.
Abstract: The preconcentration of thorium from natural water and its determination directly by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) were attempted. The first step consists of thorium preconcentration from slightly acid solutions on polyurethane foam (PUF) loaded with 2-etilhexylphosphonic acid (EHPA) reagent as solid phase. PUF held up to 50% (w/w) of the reagent and the preconcentration was maximum at the acidity of 0.25 mol.l-1 hydrochloric solution. Sorption on PUF had fast kinetics and 4.0 and 10 mg.l-1 detection and quantitation limits of thorium were achieved, respectively, as well as a R.S.D. of 4.2% at 21.7 mg.l-1. This method was successfully applied to natural water analyses. The results were in good agreement with reference values of water samples at 95% confidence level.
Journal Article•
TL;DR: According to the preliminary results, biomechanical characteristics of the samples irradiated seem to be maintained with regard to the non irradiated group, and skin sterilization by ionizing radiation may reduce the quarentine period for transplantation in patients.
Abstract: The skin has a fundamental role in the viability of human body. In the case of extensive wounds, skin allografts provide an altemative to cover temporarily the damaged areas. After donor screening and preservation in glycerol 85%, the skin can be stored in a Skin Bank. Glycerol at this concentration has a bacteriostatic effect after certain time of preservation. On the other hand, skin sterilization by ionizing radiation may reduce the quarentine period for transplantation in patients. The objective of this work was to evaluate allograft sterilization using two sources of ionizing radiation. Through the analysis of stress-strain, it was intended to verify possible effects of the radiation on the structure of preserved grafts. Three groups of skin samples were selected. The first group was maintained in the initial conditions, not irradiated. The second was exposed to cobalt-60, while the third one was irradiated using an Dynamitron Accelerator JOB 188 electron beam. The irradiation dose was 25 kGy for both tests. Both irradiation sources, and the Instron Universal Machine used for biomechanical experiments, are installed at the Centro de Tecnologia das Radiacoes / Instituto de Pesquisas Energeticas e Nucleares (Sao Paulo, Brazil). According to the preliminary results, biomechanical characteristics of the samples irradiated seem to be maintained with regard to the non irradiated group.
TL;DR: In this paper, an analytical method for the determination of traces of rare earth elements (REE) as impurities in high pure lanthanum oxide (La2O3) produced in the Instituto de Pesquisas Energeticas e Nucleares (IPEN) and compared with the oxide of commercial Lanthanum as a certified reference is discussed.
TL;DR: Results have shown that such exercises are necessary to improve the quality of the measurements and to identify those instruments that are producing incorrect values.
TL;DR: An analytical procedure was developed to determine the concentration of some elements regarded as trace impurities in nuclear fuel using inductively coupled plasma mass spectrometry (ICPMS) associated to the matrix matching method.
Abstract: An analytical procedure was developed to determine the concentration of some elements regarded as trace impurities in nuclear fuel using inductively coupled plasma mass spectrometry (ICPMS) associated to the matrix matching method. The assessment of this approach was carried out using a set of certified reference materials produced by the New Brunswick Laboratory (NBL). Eighteen out of the twenty-four elements in the reference materials could be easily determined. It was found that the mean values for reproducibility and accuracy were 5.0% and 15.0%. The remaining six elements provided mean values of 11.0% and 37.0%, respectively. They could not be adequately determined due to the effects of analyte signal suppression and spectral interference.
TL;DR: In this article, the use of a GA for the determination of the optimal fraction of mass flow rate to be extracted from each stage of the turbines of a typical PWR secondary side, in order to increase cycle efficiency was proposed.
TL;DR: Investigation of the influence of irradiation process on the original painting and on the products used in the restoration process concluded that the irradiation with the appropriated dose of 6.0 kGy, according to the literature, will not damage the restored painting.
TL;DR: In this paper, the effects of carbonation on the microstructure of Portland cement concrete for long-term durability applications were discussed, showing that carbonation provoked a reduction of 5% to 12% of the concrete open porosity accessible to water.
Abstract: This paper discusses the effects of carbonation on the microstructure of Portland cement concrete for long-term durability applications. A class C40 concrete (characteristic compression strength between 40 MPa and 44 MPa on the 28th day, according to Brazilian standard NBR 8953) was chosen for the experimental study of the carbonation effects, from which test samples were molded for accelerated test under a 100%-CO2 atmosphere after physical and mechanical characterization. It was observed that carbonation provoked a reduction of 5% to 12% of the concrete open porosity accessible to water. Flexural strength values obtained after the carbonation tests revealed a decrease of 12% and 25% in relation to the values obtained before tests on the 28th and 91st days, respectively.
TL;DR: A graft random copolymer of N-vinyl-2-pyrrolidone and N,N′-dimethylacrylamide onto polypropylene was synthesized using a simultaneous gamma radiation technique from a 60Co source, so that the hydrogel poly(propylene-g,vinylpyrlidone-co-n,N,N-dimethylamide) [PP-g-(VP- co-DMAM)], thus produced by grafting, could be used as a support for enzyme immobilization.
Abstract: A graft random copolymer of N-vinyl-2-pyrrolidone and N,N′-dimethylacrylamide onto polypropylene was synthesized using a simultaneous gamma radiation technique from a 60Co source, so that the hydrogel poly(propylene-g-vinylpyrrolidone-co-N,N′-dimethylacrylamide) [PP-g-(VP-co-DMAM)], thus produced by grafting, could be used as a support for enzyme immobilization. The grafted spheres showed very good swelling behavior in water due to the incorporation of hydrophilicity in the PP spheres. The influence of pH and temperature on as well as the determination of the kinetic parameters, KM and Vmax, for both immobilized and soluble invertase were determined. PP-g-(VP-co-DMAM) grafting onto the PP spheres caused a significant change in the water content of the support and was more pronounced for the spheres with a high degree of grafting. A porous structure of the polymeric spheres was observed by scanning electron microscopy (SEM). The porous structure contributed to the reaction rate decrease due to diffusional effects, as shown by the larger KM value observed for immobilized invertase relative to the free enzyme. The enzyme affinity for the substrate (KM/Vmax) remains quite good after immobilization. The thermal stability of immobilized invertase was significatively higher than that of the free enzyme and a displacement of 20°C was observed for the immobilized enzyme. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 767–777, 2002; DOI 10.1002/app.10326