As câmaras de extrapolação são câmaras de ionização com volume variável e são utilizadas principalmente como detectores de radiação beta. Neste trabalho foram caracterizadas duas câmaras de extrapolação, uma comercial da marca PTW, e uma outra desenvolvida no Laboratório de Calibração do IPEN, para aplicação como sistemas de referência em feixes de mamografia, radiodiagnóstico convencional e radioterapia. Os resultados obtidos nos testes de caracterização da resposta das câmaras de extrapolação: corrente de fuga, estabilidade de curto e médio prazos, determinação das correntes de saturação e das eficiências de coleção de íons, dependência angular e energética, mostram que estas câmaras de extrapolação podem ser utilizadas em dosimetria de feixes de radiação X de energias baixas. Os fatores de transmissão no tecido e os fatores de calibração foram também determinados para todas as qualidades de radiação citadas. Finalmente, foi estabelecido um procedimento de calibração de detectores de radiação em feixes padronizados de radiação X, utilizando as câmaras de extrapolação. / The extrapolation chambers are ionization chambers with variable volume, and they are mainly utilized as beta radiation detectors. In this work two extrapolation chambers were characterized, a commercial PTW extrapolation chamber and another extrapolation chamber developed at the Calibration Laboratory of IPEN, for application as reference systems in mammography, conventional diagnostic radiology and radiotherapy beams. The results obtained from the characterization tests of the chamber response: leakage current, short- and medium terms stability, determination of the saturation currents and the ion collection efficiencies, angular and energy dependence, show that these extrapolation chambers may be utilized for low-energy X radiation beam dosimetry. The transmission factors in tissue and the calibration factors were also determined for all cited radiation qualities. Finally, a procedure was established for calibration of radiation detectors in standard X radiation beams, using the extrapolation chambers.

Os equipamentos de radiação X, por estarem ligados à rede elétrica, podem apresentar flutuações na intensidade de seus feixes de radiação. Essas variações na intensidade, podem, por sua vez, modificar a taxa de kerma no ar produzida por este feixe de radiação. Em um laboratório de calibração de instrumentos, onde são realizadas calibrações de diversos equipamentos detectores de radiação, utilizados principalmente em clínicas ou hospitais, essa possível variação na intensidade do feixe de radiação pode causar um erro na determinação da dose absorvida. As câmaras de ionização monitoras são utilizadas para verificar a constância da intensidade de feixes de radiação, e fornecer uma correção para possíveis oscilações. Neste trabalho foram projetadas, construídas e caracterizadas câmaras de ionização monitoras para feixes de radiação X. As câmaras de ionização desenvolvidas possuem formato inovador, anelar, com eletrodos de alumínio ou de grafite. Essas câmaras de ionização anelares apresentam a vantagem de não interferirem no feixe direto de radiação. Foi ainda construída uma câmara de ionização com volume duplo e eletrodos de grafite, similar à câmara de ionização monitora comercial utilizada no Laboratório de Calibração de Instrumentos do Instituto de Pesquisas Energéticas e Nucleares. Essas câmaras de ionização foram testadas em diversos feixes de radiação padronizados e seus desempenhos foram comparados aos de câmaras de ionização comerciais. Os resultados obtidos mostram que duas dentre as quatro câmaras de ionização desenvolvidas apresentaram desempenho comparável ao das câmaras de ionização comerciais testadas. Além de apresentarem bons resultados, as câmaras de ionização desenvolvidas foram feitas artesanalmente e utilizando materiais de baixo custo, que são facilmente encontrados no mercado. / X radiation equipment may show fluctuations in the radiation beam intensity, as they are connected to the power net. These intensity variations can, in turn, modify the air kerma rate produced by this radiation beam. In a calibration laboratory, where radiation detectors (from clinics and hospital services) are calibrated, variations in the radiation beam intensity may cause an error in the absorbed dose determination. The monitor ionization chambers are used to verify the radiation beam intensity constancy, and to provide a correction for possible fluctuations. In this work, monitor ionization chambers for X radiation beams were designed, assembled and characterized. The developed ionization chambers have an innovative design, ring-shaped, with aluminium or graphite electrodes. These ring-shaped ionization chambers have the advantage of not interfering in the direct radiation beams. A double-volume ionization chamber with graphite electrodes was also developed. This ionization chamber is similar to the commercial monitor ionization chamber used in the Calibration Laboratory of the Instituto de Pesquisas Energéticas e Nucleares. All developed ionization chambers were tested in several standardized radiation beams and their performances were compared with those of commercial ionization chambers. The results show that two of the four ionization chambers developed showed performance comparable to that of the commercial ionization chambers tested. Besides presenting good results, the ionization chambers were designed and manufactured using low cost materials, which are easily found on the Brazilian market.

O objetivo deste trabalho foi estabelecer uma metodologia de calibração em termos de dose absorvida na água para câmaras de ionização de placas paralelas a serem utilizadas em feixes de radiação X de energia baixa (10 kV a 100 kV) para fins terapêuticos. Atualmente, no Brasil nenhum laboratório de calibração está oferecendo este tipo de serviço. Para o estabelecimento desta metodologia de calibração foram utilizadas duas câmaras de ionização PTW modelos 23344. Ambas as câmaras foram caracterizadas e testadas qualitativamente segundo recomendações de normas internacionais. Os testes de caracterização realizados foram: a medição da taxa de dose mínima efetiva, a curva de saturação, a eficiência da coleção de íons, a resposta quanto ao efeito da polaridade e a linearidade da câmara com a resposta. Os testes de controle de qualidade aplicados foram: estabilidade em curto e longo prazos, fuga de corrente sem irradiação, fuga de corrente após-irradiação e tempo de estabilização. Para a implantação da metodologia, foram estabelecidas as qualidades de radiação de T-10 a T-100, seguindo as recomendações do código de prática da AIEA. Desta forma, foi possível determinar a grandeza de referência, dose absorvida na água, utilizando-se as duas câmaras de ionizações e em todas as qualidades estabelecidas. / The objective of this study was to establish a calibration methodology in terms of absorbed dose to water for parallel plate ionization chambers to be used in low energy X rays beams (10kV to 100kV) for therapy purposes. Currently, in Brazil no calibration laboratory is offering this type of service. In order to establish this calibration methodology was used two ionization chambers PTW models 23344. Both chambers were characterized and tested qualitatively according to recommendations of international standards. The characterization tests performed were: measuring the effective minimum dose rate, the saturation curve, the efficiency of ions collection, polarity effect and the linearity of the ionization chamber with the response. The quality control tests applied were: stability in the short and long term, leakage current without irradiation, leakage current after irradiation and settling time. For the implementation of the methodology, the radiation qualities the T- 10 to T-100 were established, following the recommendations of the IAEA code of practice. Thus, it was possible to determine the magnitude of reference absorbed dose in water, using the two ionization chambers in the all established qualities.

O uso de Tomografia Computadorizada (CT) para procedimentos de imagiologia vem crescendo cada vez mais devido aos avanços da tecnologia dos equipamentos de CT, que permitem a obtenção de imagens com melhor resolução do que por outras técnicas, sendo consequentemente responsável pelo aumento da dose de radiação no paciente durante o procedimento. Isso acarretou uma maior preocupação com as doses recebidas pelos pacientes que se submetem a esse tipo de exame. Para a realização da dosimetria de feixes de CT, o instrumento mais utilizado é a câmara de ionização do tipo lápis, pois este dosímetro apresenta uma resposta uniforme ao feixe de radiação incidente em todos os ângulos. A câmara convencional que se encontra disponível no mercado apresenta um comprimento de volume sensível de 10 cm; entretanto, alguns estudos têm mostrado que esse dosímetro tem subestimado os valores de dose. Portanto, neste trabalho optou-se por desenvolver no Laboratório de Calibração de Instrumentos do Instituto de Pesquisas Energéticas e Nucleares (LCI-IPEN/CNEN) duas câmaras de ionização, fazendo uso de materiais nacionais de baixo custo, com comprimentos de volume sensível de 10 cm e 30 cm. A caracterização destas câmaras foi realizada e os resultados se apresentaram dentro dos limites recomendáveis internacionais. Como uma aplicação, as câmaras desenvolvidas, juntamente com uma câmara comercial, foram testadas em um tomógrafo clínico. As câmaras de ionização desenvolvidas foram analisadas de maneira completa, para os seus possíveis usos. / The use of computed tomography (CT) for imaging procedures is growing due to advances in the CT equipment technology, because they allow the obtention of images with better resolution than through other techniques. Therefore, they are responsible for increasing the dose radiation of patients during the procedure. This fact led to a greater concern about the doses received by patients who undergo this type of examination. To perform the dosimetry in CT beams, the most widely used instrument is the pencil type ionization chamber, because this dosimeter has a uniform response to the incident radiation beam for all angles. The conventional ionization chamber, which is available on the market, has a sensitive volume length of 10 cm; however, some studies have shown that this dosimeter has underestimated the dose values. Therefore, in this study two ionization chambers with sensitive volume lengths of 10 cm and 30 cm, making use of low cost national materials, were developed at the Calibration Laboratory of Instruments (LCI-IPEN/CNEN). The characterization of these chambers was performed, and the results were obtained within the international recommended limits. As an application, the developed ionization chambers and a commercial chamber were tested in a clinical tomographer. The developed ionization chambers were analyzed in a complete way for their possible uses.

The aim of this study was to investigate the perception of personalization on news applications and to examine to what extent it is seen as an optimal solution for users to receive information. Due to the growth of online news and digital journalism the amount of information that is being published online is significantly higher nowadays than it has previously been. Therefore, a recommendation system called personalization has been introduced to choose content for the reader. Many concerns of personalization have already been brought to light, these concerns are believed to be contributing to filter bubbles and echo chambers. This study will investigate these concerns further in order to understand the users. The methodology used in the study were semi-structured interviews and an analysis based on the concerns brought forward by Borgesius et al. Six interviews were conducted with users and two were conducted with major news organizations in Sweden. The results of the study indicate that users fear personalization will cause filter bubbles and polarization due to them only being subjected to one perspective. The users are unaware as to how personalization works and therefore question why it is being introduced into news applications. Due to personalization being a new phenomenon news applications it is not yet seen as an optimal solution by users or news organizations. There are, however, many factors that can assist in its development such as transparency and awareness of the phenomenon.

Dans un contexte de réchauffement climatique, la fonction " puits " de carbone (C) des tourbières est susceptible de changer en fonction " source " libérant ainsi de grandes quantités de C dans l'atmosphère sous l'effet d'une dégradation accrue de la matière organique (MO). Ainsi cette thèse se sont attachés à étudier la dynamique de dégradation de la MO labile (MOL) et récalcitrante (MOR) en fonction de 3 facteurs contrôlant (le niveau relatif de la nappe, un réchauffement simulé in situ et des variations saisonnières) dans la tourbière ombrotrophe du Forbonnet (25, Jura). Basés sur des analyses biogéochimiques et moléculaires de (i) la tourbe (50cm d'épaisseur), (ii) la fraction organique extractible à l'eau (WEOM) et (iii) les eaux piézométriques, les résultats acquis montrent une dégradation accrue de la MOL (e.g. polysaccharides et produits de son hydrolyse tels que le fructose,le glucose et le saccharose) et de la MOR sous l'effet d'une diminution du niveau de la nappe. Les conditions hydrologiques affectent également les processus de dégradation (sénescence et un éventuel priming effect) et d'humification de la MO pouvant conditionner le piégeage potentiel de laMOL. Après 13 mois d'incubation, l'effet du réchauffement simulé se traduirait par une hausse de l'évapotranspiration dans la condition la plus humide, là où l'étude de la WEOM indique une moindre dégradation de la MOL en surface contrairement aux niveaux profonds. Enfin, les travaux portant sur la dynamique saisonnière du C des eaux piézométriques soulignent le besoin d'intégrer la notion d'interactions entre facteurs contrôlant le cycle du C dans les tourbières pour comprendre leur réponse aux changements climatiques.

Combustion instabilities are a significant problem in combustion systems, particularly in Low NOx Gas Turbine combustors. These instabilities result in large-scale pressure oscillations in the combustor, leading to degraded combustor performance, shortened lifetime, and catastrophic combustor failure. The objective of this research was to develop a practical adaptive active control system that, coupled with an appropriate actuator, is capable of controlling the combustor pressure oscillations without a priori knowledge of the combustor design, operating conditions or instability characteristics. The adaptive controller utilizes an observer that determines the frequencies, phases and amplitudes of the dominant modes of the oscillations in real time. The research included development and testing of the adaptive controller on several combustors and on an unstable acoustic feedback system in order to analyze its performance. The research also included investigations of combustor controllability and combustor stability margin, which are critical issues for practical implementation of an active control system on an industrial combustor. The results of this research are directly applicable to a variety of combustors and can be implemented on full-scale industrial combustion systems.

<p>Syftet med studien är att undersöka hur pojkar med ett svagt läsintresse upplever boksamtal samt om det främjar deras läsintresse. För att få en uppfattning om hur eleverna upplevde boksamtalen så har jag genomfört kvalitativa intervjuer med eleverna. Urvalet gick till så att samtliga elever i den klass som jag själv undervisar i fick ett erbjudande om att få vara med i ett boksamtalsprojekt under hösten 2009. Det huvudsakliga kriteriet för att delta i projektet/studien var att man väldigt sparsamt eller aldrig hade läst någon form av skönlitteratur på sin fritid under de senaste åren. Sju pojkar visade sitt intresse och under hösten 2009 genomförde vi, de sju eleverna och jag, boksamtal kring fantasyboken <em>Över näktergalens golv – Sagan om klanen Otori – </em>av Lian Hearn.¹ </p><p>     Jag har utgått ifrån Chambers modell för boksamtal. Den främsta anledningen till detta är att jag anser att modellen bygger på ett enkelt och tydligt samtalskoncept såtillvida att fördjupningsstrukturen i Chambers boksamtal går från det allmänna till det mer specifika.²</p><p>    I Skolverkets Rapport 305 framgår det att lärandet i skolan än mer borde ske i ett meningsfyllt sammanhang. Vidare så lyfts det fram i samma rapport att boksamtal i mindre grupper är ett positivt exempel på en metod som gynnar det meningsfyllda lärandet.³Litteraturöversikten kretsar därför i mångt och mycket kring de olika beståndsdelar som är centrala för att boksamtal skall upplevas som ett meningsfyllt lärande. </p><p>    Resultatet och analysen visar att eleverna är positiva till boksamtal och att de upplever att läsintresset har ökat under tiden som boksamtalsprojektet pågick. Eleverna upplever också att lärarens stöd behövs i bokvalsprocessen samt att presentationen av boken är betydelsefull för att läsintresset skall gynnas. Likaså nämner eleverna att de tyckte att boksamtalen hade en öppen samtalskaraktär genom att alla tankar och idéer beaktades.</p><p> </p><p><strong>Nyckelord: </strong>Boksamtal, skönlitteratur, läsintresse, Chambers inriktning---------------------------------</p><p>¹Hearn Lian, <em>Över näktergalens golv. Sagan klanen Otori</em>, 2009.</p><p>²Aidan Chambers, Böcker inom oss. Om boksamtal, 1993</p><p>³Skolverket, PIRLS 2006. Läsförmågan hos elever i årskurs 4 – i Sverige och i världen 2001-2006.  Rapport 305, 2007:114.</p><p> </p> / <p>The study aims to examine how the boys with a faint interest in reading experience booktalks, and if it promotes their interest in reading. To get an idea of how the students felt about booktalks, I have conducted qualitative interviews with the  students. The selection was made among the students in the class that I teach, who were all invited to participate in the project in the autumn 2009, which revolved around discussions about the content of a literary book. The main criterion for participation in the project/study was that they very sparingly or never had read any fiction in their spare time during recent years. Seven boys showed their interest and in autumn 2009 we carried out, the seven students and I, to have booktalks about the fantasy book Across the Nightingale Floor - Tales of the Otori - Lian of Hearn.¹</p><p>     I have proceeded from Chamber's model for booktalk. The main reason for this is that I think the model is based on a simple and transparent conversation concept provided that the  deeper structure of Chamber's booktalk goes from the general to the more specific.²</p><p>    The School Board Report 305 shows that learning in school should be done in a more meaningful context. Furthermore. as it is presented in the same report, the booktalk in small groups is a positive example of a method that favors a meaningful learning. Literature review therefore circuits very much around the various elements that are central to discussions around the books as to be perceived as meaningful learning.³</p><p>    The results and analysis show that students are positive about the booktalks and that they feel that their interest in reading has increased over the time that the study lasted. Students also experienced that teacher support is needed in the process during the selection of the book. In addition, the presentation of the book promotes the interest in reading. Similarly, the students mentioned that they thought that booktalks had a character of open conversation where all ideas were accepted.</p>

The absorption enhancing ability of chitosan, a linear polysaccharide, is mediated by protonated amino groups on the C-2 position of the molecules that induce interaction with the anionic sites on the cell membranes to subsequently alter tight junction integrity. In neutral and basic environments, such as those found in the small and large intestines, most chitosan molecules will lose their charge and precipitate from solution rendering it ineffective as an absorption enhancer. To increase the solubility of this polymer, methylation of the amino groups on the C- 2 position was proposed. A partially quaternised and water soluble derivative of chitosan, N-trimethyl chitosan chloride (TMC), which exhibits superior solubility in a basic environment compared with other chitosan salts was synthesised and included in a chitosan microbead solid drug delivery system. Two TMC derivatives were synthesised by reductive methylation from high and medium molecular weight Chitoclear™ chitosan respectively. The degree of quaternisation calculated from the 1H-NMR spectra for the medium molecular weight TMC (TMC-M) and the high molecular weight TMC (TMC-H) polymers were 74.7 % and 48.5 % respectively. The mean molecular weights of the synthesised TMC-M and TMC-H polymers were 64 100 g/mole and 233 700 g/mole respectively. The effect of different concentrations TMC-M and TMC-H on chitosan microbeads was studied with results obtained from scanning electron microscopy (SEM), TMC loading capacity and microbead swelling behaviour. After selection of the most suitable TMC concentration, the effect of varying concentration (0.1, 0.2 and 0.5 %) additives on TMC and ibuprofen release was studied. Commonly used modified cellulose gum (Ac-di-sol®(ADS)), sodium starch glycolate (Explotab®(EXP)) and ascorbic acid (AA) were added as disintegrants to different microbead formulations to promote release of both the ibuprofen as model drug and TMC from the beads. It was noticed that the loading (% drug loading capacity) of TMC-M was much lower than that obtained with TMC-H while the inclusion of different additives in varying concentrations did not seem to have a profound influence on the loading of either TMC-M or TMC-H. It was further noticed from the fit factors (f1 and f2) for dissolution profiles of eighteen chitosan microbead variations that the formulation containing TMC-H and 0.5% (w/v) ascorbic acid was the only formulation with a significantly higher ibuprofen and TMC-H release profile compared to all other formulations tested. The chitosan microbead formulation containing 2%(w/v) TMC-H and 0.5 % (w/v) ascorbic acid (H-AA-0.5) was used for in vitro absorption studies through rat intestine in Sweetana-Grass diffusion chambers. Chitosan containing TMC-H (no ascorbic acid) (CHIT-H) only and a plain chitosan microbead (CHIT) formulation was used as control formulations during the in vitro studies. Although the H-AA-0.5 formulation exhibited the highest transport rate for ibuprofen, the mean rate of transport (P app) obtained from the two formulations containing TMCH (CHIT-H and H-AA-0.5) showed no significant difference in the transport rate of ibuprofen. Compared to the CHlT formulation as control, both formulations containing TMC-H exhibited increased ibuprofen transport across in vitro rat jejunum. However, a statistical significant increase in transport was obtained only from the H-AA-0.5 formulation in comparison with the CHlT formulation. It can be concluded that the combination of high molecular weight TMC with a low degree of quaternisation and ascorbic acid (0.5% w/v) in a chitosan microbead lead to a statistical significant increase in the in vitro transport rate of ibuprofen through rat jejunum. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2006.

No description available.