The study’s objective was to assess whether resting-state regional functional connectivity and current source density (CSD) measured during smoking abstinence predict smoking progression across 18 months, depressive traits, and nicotine-enhanced reward sensitivity (NERS) in young light-nicotine (NIC) smokers using low-resolution brain electromagnetic tomography analysis (LORETA). A secondary goal was to assess whether depressive traits moderate the ability of connectivity and regional CSD to predict NERS. Brain regions of interest (ROIs) hypothesized to predict smoking progression, NERS, and depressive traits include structures with high-density nicotinic acetylcholine receptors (nAChRs) and reward-related areas. A total of N=108, 14-hour NIC-deprived young (age 18-24) light (5-35 NIC uses/week) smokers underwent electroencephalogram (EEG) recording while at rest (i.e., viewed a white crosshair on a black background) for 8 minutes then completed the PRT, an assessment of reward sensitivity, after smoking a placebo (0.05 mg NIC) and NIC (0.8 mg NIC) cigarette using a within-subjects design allowing for the assessment of NIC-induced changes in reward sensitivity. All EEG power and LORETA activity bands underwent regression analysis to discover if EEG-assessed brain activity can predict smoking progression, depressive traits, NERS, and their potential interaction. Localized brain regions include 1) reward-related structures, 2) depressive trait-related structures, and 3) large-scale neural (e.g., salience network (SN), default mode network (DMN), executive control network (ECN)) and substance use disorder networks (e.g., orbital frontal cortex (OFC), insula, dorsal lateral prefrontal cortex (dlPFC) anterior cingulate cortex (ACC)). Weaker resting-state connectivity (rsC) between the insula and ACC (i.e., SN) predicted greater smoking progression at 18 months (theta1 and theta2) and greater depressive traits (delta and theta1), while greater rsC within the SN predicted greater NERS (alpha2 and beta 2/3[23.19 – 25.14 Hz]). Greater NERS was also predicted by greater alpha2 connectivity between the 1) ACC and posterior cingulate cortex (PCC) and 2) ACC and left dlPFC. Greater depressive traits were also predicted by 1) weaker delta and theta2 connectivity between the bilateral insula, 2) weaker delta, theta1, and theta2 between the insula and dlPFC, 3) weaker delta and theta1 between the insula and subgenual cortex, 4) greater theta2 in the right vs. left default mode, and 5) greater delta (2.44 – 3.41 Hz) in the left vs. right default mode network. Both greater depressive traits and greater NERS were predicted by weaker 1) theta2/alpha1 (6.59 – 9.52 Hz) between the insula and dlPFC and 2) alpha1 (7.5 – 9.5 Hz) between the left orbital frontal cortex and right dlPFC. These findings provide the first evidence that differences in EEG-assessed brain connectivity in young light smokers are associated with nicotine-enhanced reward sensitivity, depressive traits, and smoking progression. Notably, weaker low-frequency rsC within the salience network predicted depressive traits and smoking progression, while greater high-frequency rsC predicted greater nicotine-enhanced reward sensitivity. These findings suggest that salience network rsC and drug-enhanced reward sensitivity may be useful tools and potential endophenotypes for reward sensitivity and drug-dependence research.

No / To determine the accuracy of radiographer plain radiograph reporting in clinical practice. MATERIALS AND METHODS Studies were identified from electronic sources and by hand searching journals, personal communication and checking reference lists. Eligible studies assessed radiographers' plain radiograph reporting in clinical practice compared with a reference standard, and provided accuracy data to construct 2×2 contingency tables. Data were extracted on study eligibility and characteristics, quality and accuracy. Summary estimates of sensitivity and specificity and receiver operating characteristic curves were used to pool the accuracy data. RESULTS Radiographers compared with a reference standard, report plain radiographs in clinical practice at 92.6% (95% CI: 92.0¿93.2) and 97.7% (95% CI: 97.5¿97.9) sensitivity and specificity, respectively. Studies that compared selectively trained radiographers and radiologists of varying seniority against a reference standard showed no evidence of a difference between radiographer and radiologist reporting accuracy of accident and emergency plain radiographs. Selectively trained radiographers were also found to report such radiographs as accurately as those not solely from accident and emergency, although some variation in reporting accuracy was found for different body areas. Training radiographers improved their accuracy when reporting normal radiographs. CONCLUSION This study systematically synthesizes the literature to provide an evidence-base showing that radiographers can accurately report plain radiographs in clinical practice.

No / Lymphocyte responses from 208 individuals: 20 with melanoma, 34 with colon cancer, and 4 with lung cancer (58), 18 with suspected melanoma, 28 with polyposis, and 10 with COPD (56), and 94 healthy volunteers were examined. The natural logarithm of the Olive tail moment (OTM) was plotted for exposure to UVA through 5 different agar depths (100 cell measurements/depth) and analyzed using a repeated measures regression model. Responses of patients with cancer plateaued after treatment with different UVA intensities, but returned toward control values for healthy volunteers. For precancerous conditions and suspected cancers, intermediate responses occurred. ROC analysis of mean log OTMs, for cancers plus precancerous/suspect conditions vs. controls, cancer vs. precancerous/suspect conditions plus controls, and cancer vs. controls, gave areas under the curve of 0.87, 0.89, and 0.93, respectively (P<0.001). Optimization allowed test sensitivity or specificity to approach 100% with acceptable complementary measures. This modified comet assay could represent a stand-alone test or an adjunct to other investigative procedures for detecting cancer.

Chronic nicotine use has been linked to increased sensitivity to nondrug rewards as well as improvement in mood among individuals with depression, and these effects have been hypothesized to be mediated through alternations in striatal dopamine activity. Similarly, chronic nicotine use is hypothesized to influence the mechanisms by which healthy and depressed individuals learn about rewards in their environment. However, the specific behavioral and neural mechanisms by which nicotine influences the learning process is poorly understood. Here, we use a probabilistic learning task, functional magnetic resonance imaging and neurocomputational analyses, to show that chronic smoking is associated with higher reward sensitivity, along with lower learning rate and striatal prediction error signal. Further, we show that these effects do not differ between individuals with and without major depressive disorder (MDD). In addition, a negative correlation between reward sensitivity and striatal prediction error signal was found among smokers, consistent with the suggestion that enhanced tonic dopamine associated with increased reward sensitivity leads to an attenuation of phasic dopamine activity necessary for updating of reward value during learning. / Master of Science / Nicotine use has been associated with increased sensitivity to nondrug rewards and improvement in mood among individuals with depression, and these effects maybe attributed to neural activity in the striatum, a brain region related to reward perception and learning. Chronic nicotine may also influence reward learning in healthy and depressed individuals but this influence is poorly understood. Therefore, we use a computerized learning task to measure participants’ behavioral performance, functional magnetic resonance imaging to collect their brain activity data and neurocomputational analyses to examine their learning process. We showthat, compared to nonsmokers, chronic smokers perceive rewards as more rewarding (higher reward sensitivity), they learn the value of a reward slower (lower learningrate) and the neural activity in their striatum is weaker in the learning process. Moreover, we show that these effects do not differ between individuals with and without depression.

The method of Continuum Sensitivity Analysis (CSA) with Spatial Gradient Reconstruction (SGR) is presented for calculating the sensitivity of fluid, structural, and coupled fluid-structure (aeroelastic) response with respect to shape design parameters. One of the novelties of this work is the derivation of local CSA with SGR for obtaining flow derivatives using finite volume formulation and its nonintrusive implementation (i.e. without accessing the analysis source code). Examples of a NACA0012 airfoil and a lid-driven cavity highlight the effect of the accuracy of the sensitivity boundary conditions on the flow derivatives. It is shown that the spatial gradients of flow velocities, calculated using SGR, contribute significantly to the sensitivity transpiration boundary condition and affect the accuracy of flow derivatives. The effect of using an inconsistent flow solution and Jacobian matrix during the nonintrusive sensitivity analysis is also studied. Another novel contribution is derivation of a hybrid adjoint formulation of CSA, which enables efficient calculation of design derivatives of a few performance functions with respect to many design variables. This method is demonstrated with applications to 1-D, 2-D and 3-D structural problems. The hybrid adjoint CSA method computes the same values for shape derivatives as direct CSA. Therefore accuracy and convergence properties are the same as for the direct local CSA. Finally, we demonstrate implementation of CSA for computing aeroelastic response shape derivatives. We derive the sensitivity equations for the structural and fluid systems, identify the sources of the coupling between the structural and fluid derivatives, and implement CSA nonintrusively to obtain the aeroelastic response derivatives. Particularly for the example of a flexible airfoil, the interface that separates the fluid and structural domains is chosen to be flexible. This leads to coupling terms in the sensitivity analysis which are highlighted. The integration of the geometric sensitivity with the aeroelastic response for obtaining shape derivatives using CSA is demonstrated. / Ph. D. / Many natural and man-made systems exhibit behavior which is a combination of the structural elastic response, such as bending or twisting, and aerodynamic or fluid response, such as pressure; for example, flow of blood in arteries, flapping of a bird’s wings, fluttering of a flag, and flight of a hot-air balloon. Such a coupled fluid-structure response is defined as aeroelastic response. Flight of an aircraft through turbulent weather is another example of an aeroelastic response. In this work, a novel method is proposed for calculating the sensitivity of an aircraft’s aeroelastic response to changes in the shape of the aircraft. These sensitivities are numbers that indicate how sensitive the aircraft’s responses are to changes in the shape of the aircraft. Such sensitivities are essential for aircraft design. The method presented in this work is called Continuum Sensitivity Analysis (CSA). The main goal is to accurately and efficiently calculate the sensitivities which are used by optimization tools to compute the best aircraft shape that suits the customers needs. The key advantages of CSA, as compared to the other methods, are that it is more efficient and it can be used effectively with commercially available (nonintrusive) tools. A unique contribution is that the proposed method can be used to calculate sensitivities with respect to a few or many shape design variables, without much effort. Integration of structural and fluid sensitivities is carried out first by applying CSA individually for structural and fluid systems, followed by connecting these together to obtain the coupled aeroelastic sensitivity. We present the first application of local formulation of CSA for nonintrusive implementation of high-fidelity aeroelastic sensitivities. The following challenging tasks are tackled in this research: (a) deriving the sensitivity equations and boundary conditions, (b) developing and linking computer codes written in different languages (C++, MATLAB, FORTRAN) for solving these equations, and (c) implementing CSA using commercially available tools such as NASTRAN, FLUENT, and SU2. CSA can improve the design process of complex aircraft and spacecraft. Owing to its modularity, CSA is also applicable to multidisciplinary areas such as biomedical, automotive, ocean engineering, space science, etc.

Les agents anti-microtubules (MTAs), comme les taxanes et les vinca-alcaloïdes, sont des anticancéreux largement utilisés en pratique clinique. Ils agissent d'une part en perturbant les fonctions du réseau microtubulaire, conduisant à un arrêt du cycle cellulaire. D'autre part, à côté de cet effet anti-prolifératif, les MTAs sont capables d'induire divers signaux responsables de l'exécution du programme apoptotique via la voie mitochondriale intrinsèque. La famille Bcl-2 joue un rôle primordial dans l'induction de l'apoptose par ces agents. Aussi, au cours de ce travail, nous nous sommes d'abord intéressés à l'origine de la diminution de Bcl-2 lors de l'apoptose médiée par la vinorelbine. Nous avons ainsi mis en évidence la régulation transcriptionnelle de bcl-2 grâce à l'identification d'un nouveau site de liaison de p53 sur le promoteur de bcl-2. Dans un second temps, nous avons évalué l'influence de la famille Bcl-2 dans la réponse aux MTAs. En effet, nous nous sommes focalisés sur la sensibilité paradoxale aux MTAs de certaines tumeurs surexprimant Bcl-2, in vitro et in vivo chez la souris nude. Nous avons montré l'implication de Bim dans cette augmentation de sensibilité, qui agit en perturbant le réseau mitochondrial. Enfin, nous avons investigué le mécanisme moléculaire liant la surexpression de Bcl-2 et celle de Bim. Nous avons montré que la surexpression de Bcl-2, en inhibant l'activité transcriptionnelle de p53, permettait une meilleure activité du facteur de transcription FoxO3a, principal acteur de la régulation génique de Bim. / Microtubule targeting agents (MTAs), such as taxanes and vinca-alkaloïds, are anticancer drugs widely used in clinical practice. Firstly, they are known to disturb functions of microtubular network, leading to cell cycle arrest. On the other hand, beside this anti-proliferative effect, MTAs are able to trigger signaling cascades leading to apoptosis execution, through intrinsic mitochondrial pathway. Bcl-2 family proteins play a crucial role in induction of MTAs-induced apoptosis. In this work, we first studied the origin of Bcl-2 downregulation in vinorelbine-mediated apoptosis. We thus highlighted a transcriptional mechanism through the identification of a novel p53 binding site in the bcl-2 promoter. Second, we evaluated the influence of Bcl-2 family in response to MTAs. Indeed, we focused on paradoxical sensitivity to MTAs of some tumors overexpressing Bcl-2, in vitro and in vivo in nude mouse. Bim was involved in this enhanced sensitivity, by disrupting the mitochondrial network. We then investigated the molecular mechanism linking Bcl-2 and Bim overexpressions. We showed that Bcl-2 overexpression, by inhibiting the transcriptional activity of p53, leads to an increase in activity of the transcription factor FoxO3a, the main actor in Bim transcriptional regulation. Our work underlines the importance of Bcl-2 family and especially Bim as potential biomarker in predicting MTA's efficacy.

The main aim of this thesis was to evaluate the performance of the contrast sensitivity clock (CSC), a new screening device for measuring contrast sensitivity (CS) and glare. This device allows CS without glare, with glare and disability glare scores to be recorded. After initial data collection the design of the CSC was slightly amended improving the performance of the device. The amended design of the CSC was shown to be a valid, discriminative and repeatable measure for purpose. The CSC is also a quick test to perform and is relatively cheap to produce. If all these factors are considered it shows potential to become the test of choice for the assessment of visual glare. A head-mounted display system was also evaluated in terms of the glare effects it may cause. The monocular display screen of the device significantly reduced the CS of the eye directly exposed but also had an effect on binocular performance, reducing amounts of binocular summation. Electronic devices, including head-mounted displays and satellite navigation systems can seriously affect CS at low luminance levels, similar to those found when driving at night.

The human foot has been accepted over the years as an important source of afferent input, used not only in the recognition of the surrounding environment (e.g. hard and soft surfaces), but also in the fine regulation of common daily-live movements (e.g. gait and balance control). The performance of these movements is usually accompanied by fluctuations in foot skin temperature as well as reciprocal blood flow changes at the foot area. Moreover, both variables are likely to be affected by footwear usage. Although these three factors are constantly present during the performance of daily live movements, only little and partially controversial information regarding the effects of foot skin temperature, blood flow at the foot area and footwear on foot sensitivity can be found in the literature. Therefore, the goal of the thesis was to investigate the effects of foot skin temperature, blood flow at the foot area and footwear on plantar foot vibration sensitivity of healthy young subjects. Three single studies were performed in order to investigate each variable separately. The first study investigated the influence of foot sole skin temperature on plantar foot sensitivity of 40 healthy subjects. Vibration thresholds were measured at 200Hz at a initial baseline temperature and after cooling/warming the foot skin 5-6 °C. The second study investigated the influence of short-time lower leg ischemia on plantar foot vibration sensitivity of 39 young adults. Lower leg ischemia was evoked with a pneumatic tourniquet, placed about 10cm above the popliteus cavity. Vibration thresholds were measured at 200 Hz in three different cuff pressure conditions: baseline (0 mmHg), low (50 mmHg) and high (150 mmHg). Finally, the influence of footwear on foot sensitivity was investigated in the third study, using specific Formula 1 shoes. Twenty-five male subjects participated in the study. Plantar foot vibration thresholds were measured at 30 and 200 Hz in five different foot/shoe conditions (barefoot and four shoe conditions). In all studies, vibration thresholds were measured at three anatomical locations of the plantar foot: heel, first metatarsal head (MET I) and hallux. The main results of the three studies show that the analysed variables significantly influence plantar foot vibration sensitivity. Data from the first study show that 5-6 °C alterations in foot skin temperature significantly influence the foot sensitivity of healthy young adults, whereby skin cooling results in reduced foot sensitivity, whereas skin warming improves plantar foot vibration sensitivity. The results of the second study indicate that short-time lower leg ischemia; especially regarding the high cuff pressure condition (150 mmhg), significantly reduces plantar foot sensitivity. Data from the third study show that the footwear effects on foot sensitivity are frequency-dependent. While barefoot sensitivity is better than shod sensitivity at 30Hz, shod sensitivity is better than barefoot sensitivity when measured at 200Hz. In conclusion, foot sole skin temperature, blood flow at the foot area and footwear significantly influence the plantar foot vibration sensitivity of healthy young adults. The alterations in foot sensitivity caused by these variables have important consequences for future clinical as well as movement-related research. Future clinical applications of quantitative sensory testing should consider the influence of these three factors during the assessment of sensory data, in order to standardize the measurement procedures as well as to enhance the quality of the collected data. Regarding the movement-related research, further studies should try to identify the importance of foot sensitivity for the performance of different types of movements (including sport-related activities). Additionally, the combined effects of movement-related changes in foot skin temperature and blood flow should be analysed and integrated in the development process of functional footwear, which is able to fulffill the foot sensitivity requirements of different movements. / Die Rolle des menschlichen Fußes als wichtiger „Mediator“ sensorischer Reize wird zunehmen in der Literatur akzeptiert. Die vom Fuß aufgenommenen afferenten Informationen werden im Zentralen Nervensystem integriert und weitergeleitet, um die Regulation typischer Bewegungsmuster (z.B. Gang und Gleichgewichtskontrolle) mitzusteuern. Während der Durchführung derartiger Bewegungen werden oftmals Änderungen der Hauttemperatur oder auch des Blutflusses im Fußbereich provoziert. Diese werden wiederum durch das Tragen von Schuhen beeinflusst. Obwohl Hauttemperatur, Blutfluss im Fußbereich und Schuhwerk wichtige Faktoren bei der Bewegungsdurchführung darstellen, können nur wenige und teilweise konträre Informationen über den Einfluss dieser Faktoren auf die Fußsensibilität in der Literatur gefunden werden. Somit hat diese Dissertation zum Ziel, den Einfluss der Temperatur der Fußsohle, des Blutflusses am Fußbereich sowie des Schuhwerkes auf die Vibrationssensibilität des plantaren Fußes gesunder Probanden zu untersuchen. Um den Einfluss der einzelnen Parameter auf die Fußsensibilität untersuchen zu können, wurden drei Studien durchgeführt. Die erste Studie hatte zum Ziel, den Einfluss der Temperatur der Fußsohle auf die Vibrationssensibilität von 40 Probanden zu untersuchen. Dabei wurden die Vibrationsschwellen, - mit einer Frequenz von 200 Hz -, bei einer Ausgangsmessung sowie nach einer 5-6 °C Abkühlung/Erwärmung der Haut der Fußsohle gemessen. In der zweiten Studie wurde der Einfluss einer Kurzzeitischämie des Unterschenkels auf die plantare Fußsensibilität von 39 Probanden getestet. Die Ischämie im Unterschenkel wurde mit Hilfe eines im Bereich der fossa popliteal platzierten pneumatischen Tourniquets hervorgerufen. Die plantaren Vibrationsschwellen wurden mit einer Frequenz von 200Hz in drei verschiedenen Druckbedingungen ermittelt: Ausgang (0 mmHg), niedrig (50 mmHg) und hoch (150 mmHg). Schließlich beschäftigt sich die dritte Studie mit dem Einfluss vom Schuhwerk auf die Fußsensibilität. Fünfundzwanzig Probanden haben an der Studie teilgenommen. Die Vibrationsschwellen wurden mit Frequenzen von 30 und 200 Hz bei fünf verschiedenen Bedingungen gemessen (eine Barfuss- und vier Schuhbedingungen). In allen Studien wurden die Vibrationsschwellen im plantaren Fußbereich unter der Ferse, dem Metatarsalkopf I sowie unter dem Hallux ermittelt. Die Ergebnisse der drei Studien zeigen, dass die analysierten Parameter einen signifikanten Einfluss auf die plantare Vibrationssensibilität der Probanden haben. Die erste Studie zeigt, dass eine 5-6° C - Schwankung der Hauttemperatur der Fußsohle die Fußsensibilität signifikant beeinflusst, wobei die Erwärmung der Haut eine Zunahme der Fußsensibilität verursacht und die Abkühlung eine Abnahme der Fußsensibilität hervorruft. Die Ergebnisse der zweiten Studie demonstrieren, dass die im Unterschenkel hervorgerufene Ischämie eine Verschlechterung der Fußsensibilität verursacht, insbesondere bei den Messungen der Hochdruckbedingung (150 mmHG). Die Daten der dritten Studie weisen darauf hin, dass der Einfluss vom Schuhwerk auf die Vibrationssensibilität des plantaren Fußes frequenzabhängig ist. Bei einer Vibrationsfrequenz von 30Hz ist die Sensibilität barfuss besser als die mit Schuhen gemessene Vibrationssensibilität. Hingegen ist bei einer Frequenz von 200 Hz die mit Schuhen gemessenen Sensibilität besser als die Sensibilität barfuss. Anhand der Ergebnisse der drei Studien konnte festgestellt werden, dass die Temperatur der Fußsohle, Blutfluss im Fußbereich und Schuhwerk einen signifikanten Einfluss auf die plantare Vibrationssensibilität gesunder Probanden haben. Daraus folgen wichtige Hinweise für zukünftige klinische- sowie bewegungsorientierte Forschung. Der Einfluss der drei analysierten Parameter sollte künftig bei der Beurteilung sensorischer Daten mit einbezogen werden. Dies würde zum einem eine Standardisierung der Messverfahren gewährleisten, zum anderen die Qualität der im klinischen Bereich gemessenen Daten erhöhen. Im Rahmen bewegungsorientierter Forschung soll die Wichtigkeit der Fußsensibilität bei der Durchführung unterschiedlicher Bewegungsformen, auch sportlicher Bewegung, näher untersucht werden. Weiterhin sollte eine gemeinsame Analyse der bewegungsbezogenen Änderungen der Hauttemperatur bzw. des Blutflusses im Fußbereich in künftiger Forschung angestrebt werden. Folglich können diese Änderungen in die Entwicklung funktionellen Schuhwerkes eingesetzt werden, um den Anforderungen der Fußsensibilität bei unterschiedlichen Bewegungsformen möglichst gerecht zu werden.

Children with Developmental Language Disorder (DLD) have difficulties in acquiring language in the absence of other neurodevelopmental issues (e.g. autism, hearing impairment) and despite growing up in an adequate language-learning environment. Previous characterisations of DLD have focused on grammatical processing, phonological memory or rapid auditory processing. This thesis approaches the language-learning difficulties of children with DLD from a novel perspective by considering the potential contribution made by differing levels of sensitivity to the rhythmic properties of language. Children with DLD have been shown to have reduced sensitivity to some of the acoustic cues present in speech which are thought to be important for rhythmic perception. Since rhythm forms the basis of language processing in early development, poorer sensitivity to language rhythm may result in later language problems. To investigate whether children with DLD demonstrate difficulties in processing language rhythm, this thesis explores five areas of language processing which could be affected by poor rhythmic sensitivity: locating word-boundaries, processing novel words, storing lexical stress patterns, representing sentence level structures and the integration of rhythm and syntax. As part of the investigation, measures were also taken of acoustic threshold sensitivity to see whether task performance related to acoustic sensitivity. A parallel strand of the study investigated whether provision of an entraining rhythm prior to task stimuli could support task performance. Three groups of children participated in the study: children with DLD, age-matched TD children (AMC) and younger, language-matched TD children (YLC). The results indicate that rhythmic manipulation of language stimuli affects task responses across the five language areas under investigation. The findings are then discussed in terms of the contribution made to our understanding of the role of rhythm in language and language disorder.

Os transtornos de ansiedade representam uma das formas mais comuns de psicopatologia em crianças e adolescentes e estão associados com prejuízos no funcionamento acadêmico, social e familiar. Porém, permanecem frequentemente subdiagnosticados e subtratados. O bullying escolar é muito comum e está associado com um amplo espectro de problemas psiquiátricos, incluindo sintomas de ansiedade. O principal objetivo desta tese foi examinar a prevalência de bullying em uma grande amostra comunitária de crianças e adolescentes brasileiros e investigar a associação entre bullying e sintomatologia ansiosa de acordo com o DSM-IV. Esse estudo transversal consistiu no preenchimento de um questionário sobre bullying e de sua frequência e de um instrumento auto-aplicativo de triagem para transtornos de ansiedade que é a Screen for Child Anxiety Related Emotional Disorders (SCARED) por 2.353 estudantes entre 9 e 18 anos provenientes de seis escolas pertencentes à área de captação da Unidade Básica de Saúde do Hospital de Clínicas de Porto Alegre. Um total de 22,9% da amostra relatou envolvimento com bullying frequente, como agressor (7,6%), como vítima (5,7%) ou como agressor-vítima (9,6%). Em geral, meninos foram mais envolvidos como agressores e como agressores-vítimas e meninas como vítimas. Nossos achados demonstraram que estudantes envolvidos com bullying, como vítimas ou agressores-vítimas, apresentavam maiores escores na SCARED total e em suas subescalas do que agressores ou do que os estudantes sem envolvimento com bullying. A prevalência do bullying encontrada no nosso estudo está na média quando comparada com estudos prévios na literatura. Vítimas e agressores-vítimas, mas não agressores, são grupos associados com uma sintomatologia ansiosa mais alta. Embora no Brasil as taxas para as prevalências dos transtornos de ansiedade na infância e adolescência sejam substanciais, há uma carência de instrumentos para avaliar os sintomas de ansiedade e constructos relacionados à ansiedade em crianças e adolescentes. Adicionalmente, essa tese avaliou as propriedades psicométricas de duas escalas que são utilizadas na avaliação da ansiedade em crianças e adolescentes. A SCARED é um instrumento auto-aplicativo que foi originalmente desenvolvido como uma ferramenta de triagem para avaliar os transtornos de ansiedade na infância e adolescência de acordo com o DSM-IV. Os resultados encontrados em nosso estudo evidenciam que a SCARED apresenta propriedades psicométricas apropriadas e é um instrumento válido e confiável para avaliar sintomas de ansiedade em jovens no Brasil. O Childhood Anxiety Sensitivity Index (CASI) é o principal instrumento utilizado para avaliar sensibilidade à ansiedade em crianças e adolescentes. A sensibilidade à ansiedade é um constructo temperamental que pode ser conceitualizado como o medo de que sintomas de ansiedade possam ter graves consequências físicas, psicológicas ou sociais para o indivíduo. A sensibilidade à ansiedade está associada com outras medidas de ansiedade, principalmente àquelas que avaliam sintomas relacionados ao transtorno do pânico, e pode ser considerada um fator de risco para o desenvolvimento de sintomas de ansiedade e de transtornos de ansiedade em jovens. Nossos achados demonstraram uma confiabilidade apropriada e evidência de validade convergente entre a CASI e a SCARED em uma subamostra do nosso estudo, sugerindo que a CASI possa ser uma ferramenta útil na avaliação da sensibilidade à ansiedade nessa população. Tendo em vista os limitados recursos em relação à saúde mental e a pouca atenção clínica aos transtornos de ansiedade, acredita-se que tais instrumentos possam 11 se tornar ferramentas úteis na triagem de crianças e adolescentes com sintomas de ansiedade e que poderão necessitar de avaliações adicionais e de tratamento. / Anxiety disorders are one of the most common forms of psychopathology among children and adolescents and are associated with impairments in academic, social, and family functioning. Although very prevalent, the anxiety disorders are often undetected or untreated. School bullying is common and is associated with a broad spectrum of psychiatric problems, including anxiety symptomatology. The main objective of this study was to examine the prevalence of bullying behaviors in a large communitarian sample of Brazilian children and adolescents and to investigate the association between bullying behaviors and DSM-IV anxiety symptomatology. This cross-sectional study involved completion of a self-report questionnaire about bullying behaviors and their frequency and the Screen for Child Anxiety Related Emotional Disorders (SCARED) that is also a self-report screening tool for childhood anxiety disorders by 2353 students aged 9-18 years from 6 schools located in the catchment area of the Primary Care Unit from the Hospital de Clínicas de Porto Alegre. A total of 22.9% of the sample reported frequent involvement in bullying, as a bully (7.4%), as a victim (5.7%), or as a bully-victim (9.5%). In general, boys were more likely to be involved as bully and as bully-victim, and girls were more likely to be involved as victims. Our findings showed that students involved in bullying behaviors, as victims or bully-victims, were more likely to have higher total scores in SCARED scale, as well as in its subscales than bullies and than uninvolved students. The prevalence of bullying behaviors found in our sample is about average when compared with previous studies described in the literature. Victims and bully-victims, but no bullies, are groups associated with higher anxiety symptomatology. Although prevalence rates of anxiety disorders in Brazilian youth are significant, there is a lack of validated instruments to assess anxiety symptoms and related constructs in children and adolescents. In addition, this study verified the psychometrics properties of two scales that are frequently used in the assessment of anxiety in children and adolescents. The SCARED is a self-report instrument that was originally developed as a screening tool for DSM-IV childhood anxiety disorders. Our study suggested that the SCARED has appropriate psychometric properties and is a useful and reliable instrument to assess anxiety symptoms in Brazilian youth. The Childhood Anxiety Sensitivity Index (CASI) is the principal instrument used to assess anxiety sensitivity in children and adolescents. Anxiety Sensitivity refers to the tendency to fear anxiety-related sensations and is thought to arise from beliefs about their harmful physical, cognitive, or social consequences. Anxiety sensitivity is associated with other anxiety measurements, mainly those evaluating panic symptoms. It is also considered a risk factor for the development of anxious symptomatology and anxiety disorders in youth. Our findings demonstrated an appropriate reliability and evidence of convergent validity in the CASI with the SCARED in a subsample of our study, suggesting that the CASI could be a suitable tool for evaluating anxiety sensitivity in this population. Given the limited mental health resources and the paucity of clinical attention to childhood anxiety disorders in Brazil, these instruments may be a valuable tool for screening Brazilian children and adolescents with anxiety symptoms who may need further assessment and treatment.