Synthesis of Iodinated Naphthoquinones Using Morpholine-Iodine Complex

artículo (arbitrado)--Universidad de Costa Rica. Escuela de Química, 2004. Este documento es privado debido a limitaciones de derechos de autor.

Assessment of iodine intake and related cognitive function impairments in elementary schoolchildren from Terceira Island, Azores (Portugal)

Dissertação de Mestrado, Ciências Biomédicas, 28 de Junho de 2016, Universidade dos Açores.

Report to the director, National Center for Radiological Health, Public Health Service, on environmental contamination by radioactive substances, December 1, 1967.

Mode of access: Internet.

Monitoring of specific activities of long-lived radioactive elements along the Mini- Okoro/Oginigba Creek, Port Harcourt

Presence and concentrations of radionuclides could be as a result of natural and human activities. This study examined the associations and differences among soil, sediment and water specific activities of long-lived radioactive element (LLRE). Gamma spectroscopy was used to measure the concentration of the LLRE along the Mini Okoro/Oginigba Creek, Port Harcourt. Specific activities of three selected LLRE were derived. Correlation analysis was carried out to examine associations among the specific activities across different substrates. A strong and a significant negative correlation exists between the specific activities of Water 40K and Soil 232Th (r =-0.721, p<0.05); Water 238U and Soil 238U (r = -0.717, p<0.05) and Water 40K and Sediment 238U (r=-0.69, p<0.05). Comparison using Mann-Whitney U test shows that, soil and sediment are similar in their specific activities with Z values of -0.408, -1.209 and -1.021 (p > 0.05) for 40K, 232Th and 238U respectively. The concentration of solid samples (soil and sediment) is different from the liquid (water) samples. These associations can be attributed to some specific underlying factors. And in other to understand them there is need for more studies.

Development of iodine and air chemistry models for the simulation of plasma in Helicon Plasma Thrusters

The aim of this work is to analyse the chemistry models of low pressure Helicon discharges fed with iodine and air. In particular the focus of this research is to understand the plasma dynamics in order to predict propulsive performances of iodine and air-breathing Helicon Plasma Thrusters. The two systems have been simulated and analysed with the use of global models, i.e. a 0 dimensional tool to solve the set of governing equations by assuming that all quantities are volume averaged. Furthermore, some strategies have been implemented to improve the accuracy of this approach. A verification have been accomplished on the global models for both iodine and air, comparing results against simulations taken from literature. Moreover, the iodine global model has been validated against the experimental measurements of REGULUS, an helicon plasma thruster developed by the Italian company T4i, with a good agreement. From the analysis of iodine model, it has been found a significantly higher density for atomic positive ions with respect to molecular ions. Negative ions, instead, have shown to have negligible effect on the propulsive results. Also, the influence of reactions between heavy particles has been analysed with the global model. Results have demonstrated that, in the iodine case, chemistry is almost entirely affected by electronic collisions. For what concerns air-breathing results, it has been investigated the effects of the orbital height on propulsive performances. In particular, the global model has shown that at lower height, the values of thrust and specific impulse are lower due a change in atmosphere concentration. Finally, the iodine chemistry model has been introduced in the fluid code 3D-VIRTUS in order to preliminary assess the plasma properties of a Helicon discharge chamber for electric propulsion.

The Conformational Analysis Of 2-halocyclooctanones.

The establishment of the most stable structures of eight membered rings is a challenging task to the field of conformational analysis. In this work, a series of 2-halocyclooctanones were synthesized (including fluorine, chlorine, bromine and iodine derivatives) and submitted to conformational studies using a combination of theoretical calculation and infrared spectroscopy. For each compound, four conformations were identified as the most important ones. These conformations are derived from the chair-boat conformation of cyclooctanone. The pseudo-equatorial (with respect to the halogen) conformer is preferred in vacuum and in low polarity solvents for chlorine, bromine and iodine derivatives. For 2-fluorocyclooctanone, the preferred conformation in vacuum is pseudo-axial. In acetonitrile, the pseudo-axial conformer becomes the most stable for the chlorine derivative. According to NBO calculations, the conformational preference is not dictated by electron delocalization, but by classical electrostatic repulsions.

Marcos da história da radioatividade e tendências atuais

The first days of radioactivity, the discoveries of X-rays, radioactivity, of alpha- and beta- particles and gamma- radiation, of new radioactive elements, of artificial radioactivity, the neutron and positron and nuclear fission are reviewed as well as several adverse historical marks, such as the Manhattan project and some nuclear and radiological accidents. Nuclear energy generation in Brazil and the world, as an alternative to minimize environmental problems, is discussed, as are the medicinal, industrial and food applications of ionizing radiation. The text leads the reader to reflect on the subject and to consider its various aspects with scientific and technological maturity.