Le doctorant n'a pas fourni de résumé en français. / The research described in this thesis is directed to study an externally stimulated DDS that incorporates a hydrogel as the matrix for the therapeutic agent. The research does not investigate a particular site for the delivery of the therapeutic agent. However, the aim of this research program is to develop various hydrogel formulations with desirable characteristics and structures from which the drug release can be controlled with applied external energy in the form of low-frequency ultrasound. To accomplish this, two types of natural hydrogels from agarose and chitosan and one type of synthetic hydrogel from PVA were fabricated. Parameters that affect the structure were varied for each type of hydrogel in order to study the effect of structural changes on drug loading and release capacity of hydrogels. Next, the obtained hydrogels were assessed for the delivery of Theophylline as the model drug.Among the three types of hydrogels, chitosan was found to have the fastest swelling rates and the higher water uptakes while the least swelling was found with PVA hydrogels and then agarose hydrogels crosslinked at pH 12. Regarding the mechanical stability of hydrogels, the ranking of the elastic modulus was PVA hydrogels (highest), then agarose hydrogels and chitosan copolymers (lowest). It seemed that the more mechanically stable structure of the PVA hydrogels correlated with a reduced mobility of water, in comparison to the greater mobility of water in the mechanically weaker chitosan copolymers.The stimulated and passive release of Theophylline from those hydrogel carriers showed how ultrasound, as an external energy, stimulates and controls the release of the drug. The measurements confirmed that it is only the energy imparted by the longitudinal ultrasonic waves that act on the polymeric network. The mechanism by which the ultrasound affects the release is considered as a form of a ratchet motor. The polymer chains play the role of the “ratchet” steps and the ultrasonic waves accelerate the particle movement in the release media. Hence, once the ultrasound is applied, the particles descend chain-to-chain (i.e. step-by-step) driven down their concentration gradient by the applied energy until they reach the surface of the hydrogel and hence are released into the surrounding media.Increasing the ultrasound intensity vastly accelerates the drug release. Indeed a higher intensity equals a higher energy transferred from the ultrasonic waves to the drug particles, resulting in faster and less controlled release. This also depends on the type of drug carrier structure. If the hydrogel carrier is mechanically stable, such as the PVA samples or the agarose hydrogels crosslinked at pH 12, the effect of high ultrasound intensity is much less compared to a less mechanically stable carrier such as the chitosan blends. Ultrasound applied for a longer period of time increases the amount of drug released, with the consequent effect of increasing the amount of heat generated in the hydrogel. Generally, a longer duration of the applied energy results in a greater amount of energy absorption, and an increase in friction and heat generation. These effects are important considerations in relation to the heat sensitivity of the drug to be delivered and the thermal characteristics of the polymeric carrier.This PhD research has demonstrated that both natural and synthetic hydrogels coupled to an ultrasonic energy source provides a controllable DDS, which provide some novel outcomes and contributions to the body of knowledge in the field of controlled drug delivery.

Calls for history teachers to adopt inquiry methods continue to go unabated in educational research and curricular initiatives. In recent years, there has been increased recognition of the important role teacher reflection plays in managing the uncertainty that accompanies such pedagogy in history classrooms. Accordingly, this dissertation was situated within theories of reflection and reflective teaching, which acknowledge teaching to be endemically problematic and teachers as autonomous in their curricular- instructional decisions and thereby resistive to certainty-driven models of history teaching. This dissertation sought to investigate the reflections of inquiry-oriented history teachers by examining how and upon what they reflect throughout a unit of study. Using an interpretive multiple-case design with video-stimulated recall methodology, reflective interviews were conducted with participants in four different schools within the same urban public school district. A cross-case analysis of the data led to several key findings. First, the process of reflection for teachers in practice revealed itself to be more affective and messy than conventional rational models of reflection found in the literature. Second, the results showed that history teachers’ reflections were prioritized in accordance with their values and sense of purpose. Third, the inclusiveness of teachers’ classroom environments and curricular-instructional decisions were a focal point of their reflections. Fourth, the teachers’ reflections were influenced by their understandings of their school cultures, with three of the four teachers finding their school norms and policies as oppositional to the promotion of inquiry methods with their students. Finally, the findings showed that reflection aided teachers’ examination of assumptions embedded within their professional routines and pedagogical decisions, particulary with regard to the selection and use of the essential questions that framed their units. This dissertation highlights the need for more and better reflective opportunites for pre- and in-service history teachers and for better research that might yield further insights into the nature of inquiry-based history teaching.

O presente trabalho tem como objetivo a reconstrução da história evolutiva ao longo do Holoceno da planície costeira de cordões litorâneos estabelecidos sobre o vale fluvial do Rio Itabapoana/ES. A partir desse objetivo, foram realizadas as seguintes etapas metodológicas: Sensoriamento Remoto, Topografia, Geofísica e Geocronologia. Através da análise da imagem de satélite RapidEye, na composição colorida R5-G3-B1, foram discriminadas classes de cobertura vegetal. A relação entre a vegetação e o solo exposto proporcionou a identificação de três padrões distintos na planície costeira de cordões litorâneos. A obtenção de dados contínuos de altimetria através de um sistema global de navegação por satélite (GNSS), concentrado no caminhamento perpendicular à linha de costa, permitiu a elaboração e análise do perfil altimétrico dos cordões litorâneos, identificando-se três principais características: 1) nos primeiros 600 m tem-se um acréscimo na elevação; 2) em seguida, uma longa faixa “estável”, de pouca mudança na elevação; 3) por fim, o decréscimo da elevação nos últimos 500 m. Para caracterizar a arquitetura deposicional em subsuperfície dos cordões litorâneos, utilizou-se um Radar de Penetração no Solo (GPR) O registro obtido com GPR possibilitou a identificação de três padrões, representados pelas unidades retrogradacional e progradacional, onde o padrão de empilhamento compõe uma sequência de barreira regressiva ou progradante. Para a obtenção de uma relação cronoestratigráfica, seis amostras de sedimentos da fração arenosa de deposição eólica foram coletadas para a obtenção de idades absolutas a partir de Luminescência Opticamente Estimulada (LOE). Os cordões datados apresentaram idades holocênicas, com idades inferiores a 5.261 ± 396 anos. A integração dos resultados obtidos através dos métodos aplicados permitiu o reconhecimento de três padrões que levaram à interpretação de três fases decorrentes das variações do nível relativo do mar e do aporte sedimentar na evolução da planície. Essas fases representam os períodos de transgressão, regressão normal e regressão forçada. / The aim of this study is the reconstruction of the evolutionary history along the Holocene of the of beach ridges coastal plain established on the fluvial valley of Itabapoana River/ES. From this objective, the following methodological steps were performed: Remote Sensing, Topography, Geophysics and Geochronology. Through the analysis of the RapidEye satellite image, in the color composition R5-G3-B1, classes of vegetal cover were discriminated. The relationship between vegetation and exposed soil provided the identification of three distinct patterns of the beach ridges coastal plain. Obtaining continuous data of altimetry with a GNSS system, concentrated in the path perpendicular to the coastline, allowed the elaboration and analysis of the altimetric profile of the beach ridges. It was identified three main characteristics: 1) in the first 600 m there is an increase in elevation; 2) then along “stable” stretch, with little change in elevation; 3) lastly, the decrease of the elevation in the last 500 m. A Ground Penetrating Radar (GPR) was used to characterize the depositional architecture in the subsurface of the beach ridges The GPR record allowed the identification of three patterns, represented by the retrogradational and progradational units, in which the stacking pattern consists of a regressive or progradational barrier sequence. Six sediment samples of the sandy fraction of wind deposition were collected to obtain absolute ages from Optically Stimulated Luminescence (OSL). The dated ridges presented Holocene ages, with ages lower than 5,261 ± 396 years. The integration of the results obtained allowed the recognition of three patterns that led to the interpretation of three phases due to the variations of the relative sea level and the sedimentary budget in the evolution of the plain. These phases represent periods of transgression, normal regression and forced regression.

The incidence of gastrointestinal (GI) cancers has been steadily increasing in the UK since the mid 1970’s. These include cancers of the colon and oesophagus. Colon cancers have a high incidence rate, being the fourth most common cancer in the UK for both men and women. Oesophageal cancers in comparison are much rarer, however they have a poor survival rate primarily due to a late diagnosis. The key to improving survival for these cancers and many others is to detect and remove the disease at the early stages, to prevent the cancer from advancing. At present the ‘gold standard’ for diagnosis is a biopsy followed by histopathology. This technique is invasive, time consuming and highly subjective. It is therefore important to look towards non-invasive methods for early and rapid diagnosis. Optical techniques have begun to show such promise. By probing the interactions of tissues with light, diagnostic information is able to be obtained non-invasively. Techniques such as Raman spectroscopy utilise inherent molecular vibrations to extract biochemical information from tissues. Raman spectroscopy, however, is currently fundamentally limited by long acquisition times, due to the inherently weak signals produced. Using coherent Raman techniques such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), the molecular vibrations are coherently driven to provide an enhancement in signal. This thesis explored spectral signatures from snap frozen oesophageal sections in the fingerprint (450 cm-1 to 1850 cm-1) and high wavenumber (2800 cm-1 to 3050 cm-1) regions using spontaneous Raman and compared with spectra from hyperspectral SRS. The diagnostic potential for each technique was assessed for four major pathology groups, normal, Barrett’s oesophagus, dysplasia and adenocarcinoma. Samples were classified using a principal component fed linear discriminant analysis (PCA-LDA) approach with a leave-one-out cross validation. Comparisons were made to haematoxylin and eosin (H&E) stained sections. Raman in the fingerprint region was found to be the most promising for diagnosis. There were minimal changes in the high wavenumber region between pathology groups which was also reflected in the SRS spectra and proved to be insufficient for classification. Further comparisons were made between spontaneous and coherent Raman techniques using frozen colon sections. The morphological and structural information available was explored using a k-means cluster analysis. Both spontaneous and coherent Raman were able to distinguish important structural features in the colon, such as the epithelial cells that form the colonic glands and surrounding connective tissue. Both are important visual markers for cancer diagnosis in the current approach. SRS demonstrated higher spatial resolution and faster acquisition times in comparison to spontaneous Raman. This work has discussed the many advantages of using coherent Raman techniques for tissue applications, but has also highlighted some of the limitations for spectral measurements, arising from the complexity of the system.

abstract: In disordered soft matter system, amorphous and crystalline components might be coexisted. The interaction between the two distinct structures and the correlation within the crystalline components are crucial to the macroscopic property of the such material. The spider dragline silk biopolymer, is one of such soft matter material that exhibits exceptional mechanical strength though its mass density is considerably small compare to structural metal. Through wide-angle X-ray scattering (WAXS), the research community learned that the silk fiber is mainly composed of amorphous backbone and $\beta$-sheet nano-crystals. However, the morphology of the crystalline system within the fiber is still not clear. Therefore, a combination of small-angle X-ray scattering experiments and stochastic simulation is designed here to reveal the nano-crystalline ordering in spider silk biopolymer. In addition, several density functional theory (DFT) calculations were performed to help understanding the interaction between amorphous backbone and the crystalline $\beta$-sheets. By taking advantage of the prior information obtained from WAXS, a rather crude nano-crystalline model was initialized for further numerical reconstruction. Using Markov-Chain stochastic method, a hundreds of nanometer size $\beta$-sheet distribution model was reconstructed from experimental SAXS data, including silk fiber sampled from \textit{Latrodectus hesperus}, \textit{Nephila clavipes}, \textit{Argiope aurantia} and \textit{Araneus gemmoides}. The reconstruction method was implemented using MATLAB and C++ programming language and can be extended to study a broad range of disordered material systems. / Dissertation/Thesis / Doctoral Dissertation Physics 2015

A dosimetria in vivo têm se tornado um papel importante para o tratamento da irradiação total da pele dentro de um rigoroso programa de garantia de qualidade que deve ser parte integrante nos departamentos radioterápicos. A dosimetria em TSI é difícil, devido à complexidade do tratamento em avaliar a uniformidade da dose e medir a dose absorvida em profundidades rasas em toda extensão da superfície cutânea, tendo como consequência uma ampla variação na distribuição da dose. Os TLDs tem provado ser muito úteis para a distribuição e verificação da dose prescrita para o paciente, pois a dose pode diferir de local para local devido a geometria do corpo do paciente, sobreposições de estruturas e assimetrias do campo de radiação. A utilização de TLDs in vivo pode identificar variações da dose prescrita por apresentarem uma grande exatidão e precisão nas medidas. Nos setores de radioterapia vêm sendo empregado vários tipos de dosímetros, os mais utilizados são o Flureto de Lítio (TLD-100), onde obtém uma longa história neste tipo de aplicação. Novos materiais dosímetricos vêm ganhado grande importância na aplicação da dosímetria de feixes clínicos de elétrons, como o Sulfato de Cálcio dopado com Disprósio (TL) e o Óxido de Alumínio dopado com Carbono (OSL), este trabalho avalia o desempenho dosímetrico dos respectivos dosímetros termoluminescentes e a luminescência opticamente estimulada na aplicação da dosímetria de feixes clínicos de elétrons utilizados na irradiação total da pele. / In vivo dosimetry has become an important role for the treatment of total skin irradiation within a rigorous quality assurance program that should be an integral part of the radiotherapy departments. TSI dosimetry is difficult because of the complexity of the treatment in assessing dose uniformity and measuring the dose absorbed at shallow depths throughout the skin surface extent, resulting in a wide variation in dose distribution. The TLDs have proven to be very useful for the distribution and verification of the dose prescribed for the patient as the dose may differ from place to place due to patient body geometry, overlapping of structures and asymmetries of the radiation field. The use of TLDs in vivo can identify variations in the prescribed dose because its measurement accuracy and great precision. Several types of dosimeters have been used in the radiotherapy sectors, the most commonly used are Lithium Fluride (TLD-100), where it obtains a long history in this type of application. New dosimetric materials have gained great importance in the dosimetry of clinical electron beams, such as Dysprosium-doped Calcium Sulphate (TL) and Carbon doped (OSL) based Aluminum Oxide, This work evaluates the performance of the respective thermoluminescent dosimeters and the optically stimulated luminescence in the dosimetry of clinical electron beams used in total irradiation of the skin.

O presente trabalho tem como objetivo a reconstrução da história evolutiva ao longo do Holoceno da planície costeira de cordões litorâneos estabelecidos sobre o vale fluvial do Rio Itabapoana/ES. A partir desse objetivo, foram realizadas as seguintes etapas metodológicas: Sensoriamento Remoto, Topografia, Geofísica e Geocronologia. Através da análise da imagem de satélite RapidEye, na composição colorida R5-G3-B1, foram discriminadas classes de cobertura vegetal. A relação entre a vegetação e o solo exposto proporcionou a identificação de três padrões distintos na planície costeira de cordões litorâneos. A obtenção de dados contínuos de altimetria através de um sistema global de navegação por satélite (GNSS), concentrado no caminhamento perpendicular à linha de costa, permitiu a elaboração e análise do perfil altimétrico dos cordões litorâneos, identificando-se três principais características: 1) nos primeiros 600 m tem-se um acréscimo na elevação; 2) em seguida, uma longa faixa “estável”, de pouca mudança na elevação; 3) por fim, o decréscimo da elevação nos últimos 500 m. Para caracterizar a arquitetura deposicional em subsuperfície dos cordões litorâneos, utilizou-se um Radar de Penetração no Solo (GPR) O registro obtido com GPR possibilitou a identificação de três padrões, representados pelas unidades retrogradacional e progradacional, onde o padrão de empilhamento compõe uma sequência de barreira regressiva ou progradante. Para a obtenção de uma relação cronoestratigráfica, seis amostras de sedimentos da fração arenosa de deposição eólica foram coletadas para a obtenção de idades absolutas a partir de Luminescência Opticamente Estimulada (LOE). Os cordões datados apresentaram idades holocênicas, com idades inferiores a 5.261 ± 396 anos. A integração dos resultados obtidos através dos métodos aplicados permitiu o reconhecimento de três padrões que levaram à interpretação de três fases decorrentes das variações do nível relativo do mar e do aporte sedimentar na evolução da planície. Essas fases representam os períodos de transgressão, regressão normal e regressão forçada. / The aim of this study is the reconstruction of the evolutionary history along the Holocene of the of beach ridges coastal plain established on the fluvial valley of Itabapoana River/ES. From this objective, the following methodological steps were performed: Remote Sensing, Topography, Geophysics and Geochronology. Through the analysis of the RapidEye satellite image, in the color composition R5-G3-B1, classes of vegetal cover were discriminated. The relationship between vegetation and exposed soil provided the identification of three distinct patterns of the beach ridges coastal plain. Obtaining continuous data of altimetry with a GNSS system, concentrated in the path perpendicular to the coastline, allowed the elaboration and analysis of the altimetric profile of the beach ridges. It was identified three main characteristics: 1) in the first 600 m there is an increase in elevation; 2) then along “stable” stretch, with little change in elevation; 3) lastly, the decrease of the elevation in the last 500 m. A Ground Penetrating Radar (GPR) was used to characterize the depositional architecture in the subsurface of the beach ridges The GPR record allowed the identification of three patterns, represented by the retrogradational and progradational units, in which the stacking pattern consists of a regressive or progradational barrier sequence. Six sediment samples of the sandy fraction of wind deposition were collected to obtain absolute ages from Optically Stimulated Luminescence (OSL). The dated ridges presented Holocene ages, with ages lower than 5,261 ± 396 years. The integration of the results obtained allowed the recognition of three patterns that led to the interpretation of three phases due to the variations of the relative sea level and the sedimentary budget in the evolution of the plain. These phases represent periods of transgression, normal regression and forced regression.

Atualmente a utilização de fótons de raios X e gama na Medicina (radiodiagnóstico e radioterapia) gerou a necessidade do conhecimento da dose absorvida nos tecidos dos pacientes. Para isso, utiliza-se detectores com diversas funcionalidades a fim de conhecer a deposição de energia. Para ser possível a utilização destes materiais, é necessário caracterizá-los tanto quanto à resposta em função da dose absorvida, quanto à dependência com a energia. Neste trabalho foi estudada a dependência energética da resposta OSL dos dosímetros compostos por BeO e Al2O3 em feixes de raios X convencional com espectro largo, feixes de raios X de aceleradores clínicos e do acelerador Microtron do Instituto de Física da USP e fontes gama de Cs-137 e Co-60, em uma faixa de doses desde centenas de mGy até aproximadamente 2 Gy. Foram utilizadas em conjunto simulações em Monte Carlo com o código PENELOPE, que simula o transporte de fótons e elétrons na matéria, a fim de conhecer a deposição de energia nos materiais. Os espectros utilizados nas simulações foram validados através da comparação das características dos feixes tais como a deposição de dose com a profundidade, camada semirredutora, energia média e resolução espectral. Utilizando um sistema de varredura por câmara de ionização controlado remotamente, foi estudada a distribuição de doses no campo de irradiação para definir uma região de irradiação com dose uniforme para pode realizar a irradiação de um conjunto de dosímetros simultaneamente. Foram encontrados valores do fator de dependência energética experimental para os feixes mais energéticos (Co-60, Microtron 5 MeV e aceleradores clínicos de 6 e 15 MeV), com desvio menor que 3% para o Al2O3 e 5% para o BeO, indicando independência com a energia do feixe de irradiação. Já nos feixes de baixa energia, os fatores de dependência energética relativos à energia do Co-60 para o Al2O3 foram de 1,68 e 1,42, e, para o BeO, de 0,78 e 0,90 para os feixes W150 e W200 respectivamente. Estes valores indicam que, nesta faixa de energia, a resposta OSL depende mais fortemente da energia do feixe. As simulações em Monte Carlo feitas para os fatores de dependência energética se mostraram bem consistentes com os valores experimentais para o BeO em toda faixa de energia e para o Al2O3, excetuando-se os feixes de baixa energia, possivelmente pelo não completo conhecimento de todos os elementos constituintes do dosímetro empregado (fita de Luxel®). Quanto às curvas de emissão OSL para as diferentes energias de irradiação, foi observado que o sinal decai mais rápido quanto mais elevada é a energia média do feixe para o BeO. Para o Al2O3, o efeito foi mais sutil e oposto. Os estudos do feixe do Microtron mostraram que, desde que a corrente seja monitorada durante as irradiações para posterior correção da dose, é possível realizar estudos utilizando um feixe de fótons de Bremsstrahlung produzido com alvo externo e energias médias (simuladas e ainda não validadas experimentalmente) próximas às energias das fontes gama de Cs-137 e Co-60. Os resultados experimentais para as respostas OSL dos dois materiais foram compatíveis com as simulações. / Nowadays the use of X and gamma-ray photons in Medicine (radiodiology and radiotherapy) has generated the necessity of knowing the absorbed dose to the tissues of patients. For this purpose, detectors with diverse functionalities are used to know the energy deposition. To make possible the use of these materials, it is necessary to characterize the dose response, as well as the energy dependence of the response. In this work the energy dependence of the OSL response of the BeO and Al2O3 dosimeters was studied for conventional X-ray beams with wide energy spectrum, X-ray beams from clinical accelerators and from the Microtron accelerator of the Institute of Physics (University of São Paulo), and for gamma sources of Cs-137 and Co-60, in a dose range from hundreds of mGy to about 2 Gy. Monte Carlo simulations were used with the PENELOPE code, which simulates the photons and electrons transport of in the matter, to know the energy deposition in the materials. The energy spectra used in simulations were validated by comparison with beam characteristics such as depth dose deposition, half-value layer, mean energy and spectral resolution. Using a remotely controlled ionization chamber scanning system, the dose distribution within the irradiation field was evaluated to define a uniform dose region for irradiation or a set of dosimeters simultaneously. Experimental energy dependence factor values were obtained for the high-energy beams (Co-60, Microtron 5 MeV, and clinical accelerators of 6 and 15 MeV), with a deviation of less than 3% for Al2O3 and 5% for BeO, indicating independence with the beam energy. For the low-energy X-ray beams, the energy dependence factors, relative to the Co-60 energy, for Al2O3 were 1.68 and 1.42, and, for BeO, 0.78 and 0.90 for W150 and W200 beams respectively. These values indicate that, in this energy range, the OSL response depends on beam energy. Monte Carlo simulations for the energy dependence factors were consistent with experimental values for the BeO in entire energy range and for the Al2O3, with the exception of low energy beams, possibly due to the incomplete knowledge of all the elements that constitute the Luxel®. As for the shape of OSL emission curves for the different irradiation energies, it was observed that the signal decays faster the higher is the average beam energy for BeO. For Al2O3, the effect was more subtle and opposite. The Microtron beam scanning has shown that, as long as the current is monitored during irradiation for further dose-rate correction, it is possible to carry out studies using a beam of Bremsstrahlung photons produced with external target and mean energies (simulated but still not validated experimentally) close to the energies of the Cs-137 and Co-60 sources. The experimental results for the OSL responses of both materials were compatible with simulations.

Neste trabalho desenvolvemos um método de controle e aquisição de dados, particularmente aplicado a medidas de correntes termoestimuladas (TSC), mas que podem ser estendidas a sistemas semelhantes. O sistema automatizado de medidas TSC em plataforma GUI, foi implementado de modo a realizar o controle da temperatura de uma estufa, de forma que seja possível gerar rampas lineares com taxas programáveis, e também a leitura de sinais analógicos referentes ao sistema, como corrente e temperatura, e processar os sinais obtendo como resultado curvas gráficas (sinais processados em função do tempo). Os resultados são armazenados e podem ser exibidos, ou impressos e transferidos para o padrão de arquivo de entrada de outros aplicativos. Os dados são obtidos em tempo real e o sistema utiliza conceitos da tecnologia GUI, onde provemos um estudo desta, gerando janelas com interação orientada a eventos e uma interface gráfica com o usuário bastante interativa. O sistema faz uso de microcomputador padrão IBM PC AT e utiliza o MS-Windows 3.1 como plataforma GUI (\"GraphicsUser Interface\"). / A method for control and data acquisition using GUI environment, applied to thermal and electrical measurements was developed. The method was specifically applied to thermal stimulated current (TSC), but it can be extended to similar systems. The GUI - based automated TSC system maked possible the accurate control of the oven temperature, at different heating rates. This system performs the data acquisition of analogic signals (current and temperature, for instance), and those signals are processed generating functions of time and/or temperature (TSC curves, for example). Stored results can be displayed, printed, as well as transferred to files, which are compatible to standard applicative for data treatment. Data are obtained in real time and the system uses GUI concepts, which are extensively studied in this work, generating events oriented windows and a user-friendly graphical interface. The system configuration consists of an IBM PC AT microcomputer and the MS-Windows 3.1 is used as the GUI environment.

Encontrou-se que a relaxação dielétrica dos dipolos impureza-vacância em KI dopado com pequenas quantidades de KCl é extremamente diferente da relaxação dielétrica na matriz KI não contendo íons Cl&#8254.Os novos picos de relaxação, atribuídos à presença do Cl&#8254 na vizinhança imediata do íon divalente, tem um tempo de relaxação 103 vezes menor que o normal na temperatura ambiente.Foi proposto um modelo para o aprisionamento dos íons divalentes pelo Cl&#8254 e estudado a influência dos raios atômicos do divalente e do anion estranho neste processo de aprisionamento. / The dielectric relaxation due to I-V dipoles in KI doped with small amounts of KCl was found to be strongly different than in KI crystals not containing Cl&#8254.The new relaxation peak attributed to the presence of the Cl&#8254 in the close neighborhood of the divalent ion has a relax¬ation time 103 greater than the normal one.A model for the trapping of the divalent ions by the Cl&#8254 is proposed. The influence of atomic radius of the divalent and the impurity anion is discussed.