A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids....A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).展开更多
The hexagonal boron nitride has been well investigated. Its layered structure is similar to that of graphite. In the manufacture of cosmetics, this structure is intended to improve the appearance, sensory aspect and m...The hexagonal boron nitride has been well investigated. Its layered structure is similar to that of graphite. In the manufacture of cosmetics, this structure is intended to improve the appearance, sensory aspect and makes it easy to mix excipients contained in the formulation in the mixture process. In cosmetology, the efficiency and the penetration of active substances into skin are known to be directly related to the particle size. However, only recently their nanostructured properties have been explored. In this work, the synthesis of hexagonal boron nitride in the nanoscale, its composition, structure, morphology and potential for future application in sunscreens are being investigated. The boron nitride was synthesized from boric acid and melamine to a heat treatment at 1600℃. The crystal structure was characterized by (XRD) and its morphology was examined by (SEM) and (TEM);the chemical composition was studied by (FTIR), (EDS) and (EELS), the texture characterization by (BET) and its potential in sunscreens by (FTIR and UV/VIS). Results have shown that boron nitride may be synthesized in the nanoscale and that this material has the potential to be incorporated into cosmetics.展开更多
The Brazilian repository is being planned to be a near-surface one. In Brazil, the low and intermediate level radioactive wastes are immobilized using cement and bitumen for nuclear plant Angra 1 and Angra 2, respecti...The Brazilian repository is being planned to be a near-surface one. In Brazil, the low and intermediate level radioactive wastes are immobilized using cement and bitumen for nuclear plant Angra 1 and Angra 2, respectively. The major problems due to the disposal of bituminized wastes in repositories are swelling of the waste products and their degrad^ttion in the long term. To accommodate the swelling of the bituminized wastes, the drums are filled up to 70-90% of their volume, which reduces the structural the repository stability and the disposal availability. Countries, which use bitumen in the solidification of NPP＇s radioactive waste and have near-surface repositories, need to immobilize this bituminized waste within other drums containing cement pastes or mortars to disposal them. This study aims to evaluate the properties of bitumen, cement pastes and mortars to be used in the encapsulation of bituminized wastes. The formulations of two pastes and two mortars were selected for the pilot scale tests. The laboratory and pilot scales results were very similar, indicating that any of these formulations could be used. However, the better formulation will be chosen after the leaching test results, because it is an essential parameter in the long-term repository performance.展开更多
In this paper, the evaluation of a preliminary design of a PGAA （prompt gamma activation analysis） facility based on Monte Carlo simulations is presented and discussed. The implementation of the PGAA method at the C...In this paper, the evaluation of a preliminary design of a PGAA （prompt gamma activation analysis） facility based on Monte Carlo simulations is presented and discussed. The implementation of the PGAA method at the CDTN （nuclear technology development centre） would increase the applications of the TRIGA reactor. The preliminary design is based on a quasi vertical hollow cylinder （called neutron extractor） in the reactor pool to extract the neutron flux. This study evaluates the neutron flux in the upper position of the cylinder in the suggested position of the samples to be analyzed by the PGAA. The calculations of the radioactive capture reaction rates and of the detection limits for some isotopes were performed. Through all these calculations, the feasibility of the application of the PGAA method at the IPR-R1 installations was evaluated. According to the obtained results, it can be concluded that is possible to apply the PGAA method at the IPR-R1 reactor, even with its design restrictions.展开更多
Peptides have an important role in organism and its high quantity present in tumors leading to development of radiolabeled peptides for tumor-specific imaging. Once the traditional methodologies used for radiofluorina...Peptides have an important role in organism and its high quantity present in tumors leading to development of radiolabeled peptides for tumor-specific imaging. Once the traditional methodologies used for radiofluorination do not work with peptides, due to their harsh conditions, other radiolabeling strategies had to be developed to supply the need. Direct radiofluorination is either an inefficient method, and the use of bidirectional groups, or prosthetic groups, is needed to enable the binding between the radionuclide fluorine-18 and a peptide functionalized. New peptides radiolabeling strategies have been developed sourcing increase the synthesis yield, its chemoselectivity, and the binding stability, and reduce the total process time and the number of steps required. The progress of radiofluorination methodologies led to development of the amidation, acylation, imidation, and alkylation techniques, the use of thiol groups, photochemical conjugation, chemoselective reactions, and “click chemistry”, in addition to use of FDG molecule and heteroatoms as linkers. This paper presents the main strategies used for peptides radiofluorination, presenting their positive and negative points, and the prosthetic groups most used in each method.展开更多
文摘A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).
文摘The hexagonal boron nitride has been well investigated. Its layered structure is similar to that of graphite. In the manufacture of cosmetics, this structure is intended to improve the appearance, sensory aspect and makes it easy to mix excipients contained in the formulation in the mixture process. In cosmetology, the efficiency and the penetration of active substances into skin are known to be directly related to the particle size. However, only recently their nanostructured properties have been explored. In this work, the synthesis of hexagonal boron nitride in the nanoscale, its composition, structure, morphology and potential for future application in sunscreens are being investigated. The boron nitride was synthesized from boric acid and melamine to a heat treatment at 1600℃. The crystal structure was characterized by (XRD) and its morphology was examined by (SEM) and (TEM);the chemical composition was studied by (FTIR), (EDS) and (EELS), the texture characterization by (BET) and its potential in sunscreens by (FTIR and UV/VIS). Results have shown that boron nitride may be synthesized in the nanoscale and that this material has the potential to be incorporated into cosmetics.
文摘The Brazilian repository is being planned to be a near-surface one. In Brazil, the low and intermediate level radioactive wastes are immobilized using cement and bitumen for nuclear plant Angra 1 and Angra 2, respectively. The major problems due to the disposal of bituminized wastes in repositories are swelling of the waste products and their degrad^ttion in the long term. To accommodate the swelling of the bituminized wastes, the drums are filled up to 70-90% of their volume, which reduces the structural the repository stability and the disposal availability. Countries, which use bitumen in the solidification of NPP＇s radioactive waste and have near-surface repositories, need to immobilize this bituminized waste within other drums containing cement pastes or mortars to disposal them. This study aims to evaluate the properties of bitumen, cement pastes and mortars to be used in the encapsulation of bituminized wastes. The formulations of two pastes and two mortars were selected for the pilot scale tests. The laboratory and pilot scales results were very similar, indicating that any of these formulations could be used. However, the better formulation will be chosen after the leaching test results, because it is an essential parameter in the long-term repository performance.
文摘In this paper, the evaluation of a preliminary design of a PGAA （prompt gamma activation analysis） facility based on Monte Carlo simulations is presented and discussed. The implementation of the PGAA method at the CDTN （nuclear technology development centre） would increase the applications of the TRIGA reactor. The preliminary design is based on a quasi vertical hollow cylinder （called neutron extractor） in the reactor pool to extract the neutron flux. This study evaluates the neutron flux in the upper position of the cylinder in the suggested position of the samples to be analyzed by the PGAA. The calculations of the radioactive capture reaction rates and of the detection limits for some isotopes were performed. Through all these calculations, the feasibility of the application of the PGAA method at the IPR-R1 installations was evaluated. According to the obtained results, it can be concluded that is possible to apply the PGAA method at the IPR-R1 reactor, even with its design restrictions.
文摘Peptides have an important role in organism and its high quantity present in tumors leading to development of radiolabeled peptides for tumor-specific imaging. Once the traditional methodologies used for radiofluorination do not work with peptides, due to their harsh conditions, other radiolabeling strategies had to be developed to supply the need. Direct radiofluorination is either an inefficient method, and the use of bidirectional groups, or prosthetic groups, is needed to enable the binding between the radionuclide fluorine-18 and a peptide functionalized. New peptides radiolabeling strategies have been developed sourcing increase the synthesis yield, its chemoselectivity, and the binding stability, and reduce the total process time and the number of steps required. The progress of radiofluorination methodologies led to development of the amidation, acylation, imidation, and alkylation techniques, the use of thiol groups, photochemical conjugation, chemoselective reactions, and “click chemistry”, in addition to use of FDG molecule and heteroatoms as linkers. This paper presents the main strategies used for peptides radiofluorination, presenting their positive and negative points, and the prosthetic groups most used in each method.
