Nas últimas décadas cresceu o número de pesquisas que defendem os benefícios do uso da História da Ciência na educação científica, entretanto, surgiram também estudos apontando diversas dificuldades para tal fim, inclusive quanto à carência de propostas efetivas para a sala de aula. A partir deste impasse, desenvolvemos uma pesquisa que elabora e analisa o processo de construção de uma abordagem didática da história da radioatividade para o Ensino Médio para ser utilizada por professores de química e de física. Selecionamos aspectos da pesquisa sobre radioatividade, desde seu inicio -- entre as décadas de 1890 e de 1900 -- às suas aplicações, durante o século XX, como tema para a construção de uma proposta didático-metodológica para ensino de física e de química. Além de conceitos científicos, tais episódios permitem discussões metacientíficas, por exemplo, diferenciando a descoberta de um fenômeno natural da construção de explicações sobre ele e a compreensão da ciência enquanto fazer coletivo. Utilizamos como apoio metodológico uma proposta que se propõe a lidar com obstáculos apontados pela literatura, fundamentando a seleção e adaptação de conteúdos históricos na proposição de atividades didáticas, a partir de cada contexto educacional e dos objetivos epistemológicos estabelecidos pelo autor/pesquisador. Oferecemos como resultados desta pesquisa o planejamentos para as aulas, os textos para os alunos (material didático) e para o professor e a análise sobre a construção da proposta, que pode auxiliar outras pesquisas na área. / In recent decades has grown the number of research defending the benefits of using the History of Science in science education, however, there were also studies pointing out the difficulties for that purpose, including proposals for the classroom. From this impasse, we developed a survey that establishes and analyzes the process of building a didactic approach of radioactivity history for the high school for be used by teachers of chemical and physical. We selected aspects of research on radioactivity, since its beginning -- between the 1890s and 1900s -- to their applications, during the twentieth century, as the theme for the construction of a didactic-methodological proposal for physics and chemistry teaching. In addition to scientific concepts such episodes allow metascientific discussions, for example, differentiating the discovery of a natural phenomenon of building explanations about it and understanding of science while making collective. The methodology used, which proposes to deal with obstacles mentioned by the literature, supporting the selection and adaptation of historical contents in proposing educational activities, from every educational context and epistemological objectives set by the author / researcher. We offer as a result of this research the plans for classes, the texts for students (teaching materials) and for the teacher and the analysis on the construction of proposal, that can assist other research in the area.

A radiogeochemical exploration in the area of Chrastava - Bogatynia belonging into lugic region was conducted in the years 2012 - 2013. This exploration's objective was to search for and investigate radioactive water manifestations with radioactivity concentration reaching minimal value of 1500 Bq/l 222Rn. This boundary is set in the spa law no. 164/2001 Sb. as a minimal radioactivity concentration for radioactive mineral water. In this area, 30 water manifestations were discovered meeting the boudary of >1500 Bq/l 222Rn. The most significant cluster is located in Albrechtice by Frýdlant. Close to Kančí vrch (Boar Hill) 12 radioactive water springs were discovered. In the town of Albrechtice, a discovery of dissolved salts- rich radioactive mineral water was made, concerning springs Soumar and Matka. The most mineralized spring Soumar contains more than 1 g/l of dissolved salts (hydrochemical type Na-Ca-Cl water with total mineralization up to 1,5 g/l) combined with it's 222Rn activity surpassing 1500 Bq/l. Another significant cluster is located near the town of Nová Ves by Chrastava, where the most active source of the whole area, Mikulášský pramen (Mikulash Spring), with activity up to 2821 Bq/l 222Rn, was found. Another three radioactive water springs were found in this area. Also, probable dry...

It has been proposed several times in the past that one can obtain an equivalent, but in many aspects simpler description of fermions by first reformulating their first-order (Dirac) Lagrangian in terms of two-component spinors, and then integrating out the spinors of one chirality (e.g.primed or dotted). The resulting new Lagrangian is second-order in derivatives, and contains two-component spinors of only one chirality. The new second-order formulation simplifies the fermion Feynman rules of the theory considerably, e.g. the propagator becomes a multiple of an identity matrix in the field space. The aim of this thesis is to work out the details of this formulation for theories such as Quantum Electrodynamics, and the Standard Model of elementary particles. After having developed the tools necessary to establish the second-order formalism as an equivalent approach to spinor field theories, we proceed with some important consistency checks that the new formulation is required to pass, namely the presence or absence of anomalies in their perturbative and non-perturbative description, and the unitarity of the S-Matrix derived from their Lagrangian. Another aspect which is studied is unification, where we seek novel gauge-groups that can be used to embed all of the Standard Model content: forces and fermionic representations. Finally, we will explore the possibility to unify gravity and the Standard Model when the former is seen as a diffeomorphism invariant gauge-theory.

We study the chiral anomaly by solving the Dirac equation for fermions in parallel electric and magnetic fields. In such case, only the lowest-energy Landau levels are relevant to the anomaly. Specifically, for massless fermions, the chiral anomaly is a result of the production of particles of one chirality, and no creation of particles of the other chirality. For massive fermions, we find that the chiral anomaly equation can be simply obtained via a proper regularization of the range of the momentum. We extend the method to anomaly cancellation, and conclude that the conservation of the baryon number plus lepton number must be violated as a quantum anomaly in the context of the Standard Model. Accordingly, such baryon number non-conservation can play a vital role during the electroweak transition to achieve the baryon asymmetry of the Universe. Through real-time lattice simulations, we refine the implementation of ensemble fermions for a cold electroweak transition, involving the SU (2) gauge field, Higgs field and one generation of fermions. We find that the dynamics and most observables converge quickly with a reasonable number of fermion realizations, and the method of ensemble fermions for the entire electroweak sector becomes numerically tractable. We apply the method to the computation of the effective preheating temperature during a fast electroweak transition, relevant for Cold Electroweak Baryogenesis. We find that the fermion temperature is never below 20 GeV, and this can indirectly rule out Standard Model CP -violation as the origin of the baryon asymmetry of the Universe, as Standard Model cold baryogenesis requires a temperature of at most of order of 1 GeV. For this reason, new CP -violation source from physics beyond the Standard Model is required in order to explain the baryon asymmetry. We further present a first-principles numerical computation of the baryon asymmetry in electroweak-scale baryogenesis, where the CP -violation is obtained as a consequence of including another Higgs doublet. For one particularly favourable scalar potential that could provide a high sphaleron transition rate, we calculate the asymmetry through large-scale computer simulations. The numerical signal is at the boundary of what is numerically discernible with the available computer resources, but we tentatively find an asymmetry of |η| ≤ 3.5 × 10−7 . We also find it is attainable to include the complete electroweak SU (2) × U (1) gauge fields in the reduced Standard Model that we are using in practical simulations, so that in further studies we can measure the cosmic magnetic field generated during the electroweak phase transition.

Magister Scientiae - MSc / The Environmental Radioactivity Laboratory (ERL) at iThemba LABS undertakes experimental work using a high purity germanium (HPGe) detector for laboratory measurements. In this study the Monte Carlo transport code, MCNPX, which is a general-purpose Monte Carlo N − Particle code that extends the capabilities of the MCNP code, developed at the Los Alamos National Laboratory in New Mexico, was used. The study considers how various parameters such as (1) coincidence summing, (2) volume, (3) atomic number (Z) and (4) density, affects the absolute photopeak efficiency of the ERL’s HPGe detector in a close geometry (Marinelli beaker) for soil, sand, KCl and liquid samples. The results from these simulations are presented here, together with an intercomparison exercise of two MC codes (MCNPX and a C++ program developed for this study) that determine the energy deposition of a point source in germanium spheres of radii 1 cm and 5 cm. A sensitivity analysis on the effect of the detector dimensions (dead layer and core of detector crystal) on the photopeak detection efficiency in a liquid sample and the effect of moisture content on the photopeak detection efficiency in sand and soil samples, was also carried out. This study has shown evidence that the dead layer of the ERL HPGe detector may be larger than stated by the manufacturer, possibly due to warming up of the detector crystal. This would result in a decrease in the photopeak efficiency of up to 8 % if the dead layer of the crystal were doubled from its original size of 0.05 cm. This study shows the need for coincidence summing correction factors for the gamma lines (911.1 keV and 968.1 keV) in the 232Th series for determining accurate activity concentrations in environmental samples. For the liquid source the gamma lines, 121.8 keV, 244.7 keV, 444.1 keV and 1085.5 keV of the 152Eu series, together with the 1173.2 keV and 1332.5 keV gamma lines of the 60Co, are particularly prone to coincidence summing. In the investigation into the effects of density and volume on the photopeak efficiency for the KCl samples, it has been found that the simulated results are in good agreement with experimental data. For the range of sample densities that are dealt with by the ERL it has been found that the drop in photopeak efficiency is less than 5 %. This study shows that the uncertainty of the KCl sample activity measurement due to the effect of different filling volumes in a Marinelli beaker is estimated in the range of 0.6 % per mm and is not expected to vary appreciably with photon energy. In the case of the effect of filling height on the efficiency for the soil sample, it was found that there is a large discrepancy in the trends of the simulated and experimental curves. This discrepancy could be a result of the use of only one sand sample in this study and therefore the homogeneity of the sample has to be investigated. The effect of atomic number has been found to be negligible for the soil and sand compositions for energies above 400 keV, however if the composition of the heavy elements is not properly considered when simulating soil and sand samples, the effect of atomic number on the absolute photopeak efficiency in the low energy (< 400 keV) region can make a 14 % difference. / South Africa

Magister Scientiae - MSc / The natural 238U, 232Th and 40K radioactive content of vineyard soil was measured with an in-situ gamma-ray detector. The activity concentrations measured with the in-situ detector are normalized using the laboratory-determined activity concentrations of several samples from the vineyard site. To determine the activity concentration of a particular soil sample, the gamma-ray photopeak detection efficiencies are required. In this work, the detection efficiencies were derived for each soil sample using gamma-ray photopeaks associated with the radionuclides of 238U and 232Th present in the sample, and the 40K, 1460.8 keV gamma-ray peak, from KCl salt. The systematic effects related to the gamma ray photopeaks used, the sample moisture and sealing, sample volume or filling height, and sample density, were determined and applied in order to obtain the accurate sample activity concentrations. Assessment of the effect of using specific gamma photopeaks on the activity concentrations was done to confirm that the gamma-ray photopeaks highly prone to coincidence summing were omitted from the efficiency analysis. The effect of sample moisture and sealing suggested that in order to optimize the accuracy of each radioactivity measurement each sample must be oven dried and then hermitically sealed. The effect of volume or filling height variations of 0.47 % per mm between the sample and KCl standard was derived and this figure was incorporated into the uncertainty in each of the sample activity concentrations. The effect of density variations of less than 5 %, for sample densities ranging from 0.7 g.cm-3 to 1.6 g.cm-3, was determined and incorporated in the efficiency analysis and activity concentration uncertainties. After taking into account all these systematic effects, the soil sample activity concentration uncertainty was found to be no more than 10.4 % at the 95 % confidence level. / South Africa

No description available.

Mycobacter avium complex serovars 4 and 20 were cultured in the presence of [3H] fucose, [3H]-methionine, and [3H]-mannose to specifically radiolabel the oligosaccharide of the glycopeptidolipid (GPL) antigens. Distribution of radioactivity in lipid was determined by thin-layer chromatographic methods. Examination of acid hydrolysates from radiolabeled antigens revealed that [3H]-methionine incorporated into methylated sugars in polar and apolar GPL components, whereas [3H]-mannose incorporated exclusively into the oligosaccharide of polar GPL antigens. Least incorporation of radiolabel into antigens was observed with [3H]-fucose. Use of radiolabeled serovar 4 antigens in macrophage uptake studies revealed maximum uptake to be slightly above 250 gg/ 3.2 x 105 cells. Timed experiments demonstrated that GPL antigens were relatively inert to degradation by resident peritoneal macrophages.

Dans le cadre de la mission de surveillance radiologique de l’environnement de l’Institut de Radioprotection et de Sûreté Nucléaire (IRSN), le Laboratoire de Mesure de la Radioactivité dans l’Environnement (LMRE) réalise la mesure de la concentration en activité dans différentes matrices environnementales. Il s’agit de matrices biologiques (mousses aquatiques, algues, lait, légumes …), de sols, d’eaux ou encore de filtres de prélèvement d’aérosols.Les radionucléides artificiels recherchés sont en très faible proportion par rapport à certains radionucléides naturels : le potassium 40 dans les matrices biologiques ou encore les descendants particulaires du radon dans les filtres d’aérosols. L’important fond Compton induit par ces radionucléides naturels dans le spectre gamma complique la détermination des radionucléides présents au niveau trace.Un moyen de s’affranchir de ce fond Compton est de faire une mesure par spectrométrie $gamma$ en coïncidence en utilisant au moins deux détecteurs. La méthode a été développée sur un système existant, le système anti-Compton constitué d’un détecteur germanium entouré d’un scintillateur NaI(Tl), avec le développement d’un algorithme d’analyse et de l’étalonnage par simulation Monte Carlo si nécessaire. De plus, un nouveau système de mesure en coïncidence a été conçu par simulation Monte Carlo puis mis en service pour pallier les limites du système anti-Compton. Ce nouveau système de mesure, nommé Léda, est composé de deux détecteurs germanium face à face, entourés d’un scintillateur NaI(Tl) ; il possède plusieurs voies de mesure, chacune présentant une amélioration en termes de limite de détection pour tous les radionucléides mesurés. / The French Institute of Radiation Protection and Nuclear Safety (IRSN) is in charge of the radiological surveillance of the environment. In this framework the Laboratory of Environment Radioactivity Measurement (LMRE) measures the radioactivity concentrations in various environmental samples: biological matrices (aquatic moss, seaweed, milk, vegetables …), soils, waters or aerosol filters.Artificial radionuclides searched are in low proportion compared to natural radionuclides: potassium 40 in biological matrices or radon particular daughters in aerosol filters. The significant Compton continuum induced in the gamma spectrum makes difficult the identification and the quantification of radionuclides present at trace level.The use of two detectors enables to make coincident spectrometry in order to decrease this Compton background. This technique was developed with an existing system of the laboratory, the anti-Compton system, composed of a germanium detector surrounded by a NaI(Tl) scintillator. A data analysis algorithm was developed and also a Monte Carlo calibration if radionuclides measured are not available in standard source. Moreover a new coincident measurement system was designed by Monte Carlo simulation, called Leda consisting of two germanium detectors face to face surrounded by a NaI(Tl) scintillator. This new system overcomes the limits of the anti-Compton system. Different measurement channels improve the detection limits for all radionuclides measured in our laboratory.

This thesis deals with the areal survey of water resources in the area of Priessnitz baths, to search for natural medicinal sources and advanced data collection for evaluation radiohydrogeochemical situation of the area. The area of interest is situated in the Hrubý Jeseník mountains. Hydrogeologically it is a hard rock, which consists mainly of metamorphic rocks of the Bohemian Massif, the Moravian-Silesian region, presented as the methamorfic envelope of the desen group of Silenics. Altogether, 83 objects were recorded and many of them were visited repeatedly. Physical parameters (temperature, pH, Eh, conductivity), activity 222Rn and flow rate were measured. In addition, the chemical composition and tritium contents were determined on selected sources. Conductometry, thermometry, and probes for peloids were conducted. There was no source of water (or peloid) that would reach the criteria of a natural healing source (according to the Czech spa law). However, the overall hydrogeological and hydrochemical situation is quite complicated. Both the genesis of water and its chemical composition is highly heterogeneous and influenced by the heterogenical geological structure. Generally, we have distinguished three types of water according to the chemical composition. We also divided the water sources...