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El uso de rayos X juega un papel esencial en el diagnóstico y planificación de tratamientos dentales. Los avances tecnológicos de los equipos de rayos X han contribuido al mayor uso de este tipo de radiación en la práctica odontológica. Aunque la exposición a la radiación es baja en estos procedimientos, todavía existe un riesgo que debe reducirse al mínimo necesario a fin de obtener una imagen adecuada para el diagnóstico y a la vez evitar efectos nocivos para el paciente y el personal involucrado. Debido al alto y creciente número de radiografías dentales, el hecho de que niños y adolescentes sean el foco de la mayoría de estas, la subestimación de la cantidad de exámenes radiológicos reportados y la supuesta baja conciencia de estudiantes y profesionales de la odontología sobre los peligros del uso indiscriminado de los rayos X, es necesario adoptar medidas de protección radiológica para mitigar los efectos biológicos radioinducidos. Este artículo tiene como objetivo revisar los principios básicos de la radioprotección que deben considerarse en la práctica dental, con el fin de garantizar el menor daño posible a trabajadores ocupacionalmente expuestos, pacientes y miembros del público.

No presente trabalho são 1 apresentados os resultados de estudos por fluorescência de raios X de tijolos brasileiros. Neste estudo foram avaliados 22 tijolos, sendo sete de Igarassu, dois do Forte do Brum e 13 de Olinda. Um equipamento portátil de fluorescência de raios X por dispersão de energia foi desenvolvido para este estudo. Análises por difração de raios X também foram efetuadas para determinar as fases cristalinas presentes nos tijolos. Os resultados mostraram a existência de fases minerais, como quartzo, em todos os tijolos avaliados. A Análise da Componente Principal foi aplicada aos dados dos espectros de fluorescência de raios X obtidos. Os resultados mostraram que a partir do gráfico de scores das componentes principais CP1 e CP3, respectivamente representadas pelo Fe e Ca, foi possível separar os tijolos de Igarassu e do Forte do Brum em cinco grupos, que estavam associados com o século de fabricação. Por sua vez, os tijolos de Olinda foram separados em dois grupos, sendo um formado por um único tijolo e o outro grupo pelos demais tijolos. Estes resultados sugerem que os tijolos foram produzidos com diferentes matérias primas ou em diferentes locais. ENERGY DISPERSIVE X-RAY FLUORESCENCE APPLIED TO THE CHARACTERIZATION OF BRICKS OF PERNAMBUCO HISTORICAL SITESABSTRACTThis work presents the results of X-ray fluorescence analysis of Brazilian bricks, collected from several historical sites of the State of Pernambuco, Brazil. In this study, twenty two bricks were analyzed; seven from Igarassu, two from Forte do Brum in Recife, and thirteen from Olinda. A portable X-ray fluorescence system was assembled and used for the qualitative determination of the chemical elements present in the samples. X-ray diffraction analysis was also carried out to determine the crystal mineral phases in the bricks. All the bricks studied showed several minerals, such as quartz A Principle Component Analysis was applied to the full X-ray fluorescence spectra. In the score plot of

No presente trabalho são 1 apresentados os resultados de estudos por fluorescência de raios X de tijolos brasileiros. Neste estudo foram avaliados 22 tijolos, sendo sete de Igarassu, dois do Forte do Brum e 13 de Olinda. Um equipamento portátil de fluorescência de raios X por dispersão de energia foi desenvolvido para este estudo. Análises por difração de raios X também foram efetuadas para determinar as fases cristalinas presentes nos tijolos. Os resultados mostraram a existência de fases minerais, como quartzo, em todos os tijolos avaliados. A Análise da Componente Principal foi aplicada aos dados dos espectros de fluorescência de raios X obtidos. Os resultados mostraram que a partir do gráfico de scores das componentes principais CP1 e CP3, respectivamente representadas pelo Fe e Ca, foi possível separar os tijolos de Igarassu e do Forte do Brum em cinco grupos, que estavam associados com o século de fabricação. Por sua vez, os tijolos de Olinda foram separados em dois grupos, sendo um formado por um único tijolo e o outro grupo pelos demais tijolos. Estes resultados sugerem que os tijolos foram produzidos com diferentes matérias primas ou em diferentes locais. ENERGY DISPERSIVE X-RAY FLUORESCENCE APPLIED TO THE CHARACTERIZATION OF BRICKS OF PERNAMBUCO HISTORICAL SITESABSTRACTThis work presents the results of X-ray fluorescence analysis of Brazilian bricks, collected from several historical sites of the State of Pernambuco, Brazil. In this study, twenty two bricks were analyzed; seven from Igarassu, two from Forte do Brum in Recife, and thirteen from Olinda. A portable X-ray fluorescence system was assembled and used for the qualitative determination of the chemical elements present in the samples. X-ray diffraction analysis was also carried out to determine the crystal mineral phases in the bricks. All the bricks studied showed several minerals, such as quartz A Principle Component Analysis was applied to the full X-ray fluorescence spectra. In the score plot of

A major challenge in neuroscience is to reverse engineer the brain and understand its information processing and learning capabilities. While the pace of discovery and untangling of the brain's staggering dynamics is advancing at unprecedented speed especially with the recently developed tools and imaging techniques, this advancement is not devoid of risk: the arsenal of novel techniques carries a huge mass of data that may complicate further the unraveling of brain function. Is every ion channel, every spine, every dendrite, every neuron and every synaptic connection necessary to achieve the computational capabilities of the central nervous system? Answering this question rises the need for a two-way communication between experiments and mathematical theoretical work. Neural networks composed of point neurons and endowed with biologically inspired synaptic learning rules have been successfully applied to a variety of challenging learning- related tasks, namely in problems of pattern recognition, associative memory, map formation, among others. While these networks are good at tasks they are built for, there still exists a gap separating us from fully understanding how the brain is good at the large multitude of tasks it can perform. When we reflect upon most efforts in building and simulating neural networks, we ask ourselves about the appropriate scale for modeling: Given the complexity of the nervous system, is it enough to model the neurons as point-like units in which a weighted sum of synaptic inputs is passed through a single spike-generating mechanism? From a modern perspective, the point neuron seems likely to be a poor representation of synaptic integration in neurons with large, profusely branched, active dendrites that populate brain structures associated with advanced cognitive functions and learning. These dendrites are endowed with nonlinear active conductances that modulate synaptic integration and somatic activity. Does the increased nonlinearity at

A major challenge in neuroscience is to reverse engineer the brain and understand its information processing and learning capabilities. While the pace of discovery and untangling of the brain's staggering dynamics is advancing at unprecedented speed especially with the recently developed tools and imaging techniques, this advancement is not devoid of risk: the arsenal of novel techniques carries a huge mass of data that may complicate further the unraveling of brain function. Is every ion channel, every spine, every dendrite, every neuron and every synaptic connection necessary to achieve the computational capabilities of the central nervous system? Answering this question rises the need for a two-way communication between experiments and mathematical theoretical work. Neural networks composed of point neurons and endowed with biologically inspired synaptic learning rules have been successfully applied to a variety of challenging learning- related tasks, namely in problems of pattern recognition, associative memory, map formation, among others. While these networks are good at tasks they are built for, there still exists a gap separating us from fully understanding how the brain is good at the large multitude of tasks it can perform. When we reflect upon most efforts in building and simulating neural networks, we ask ourselves about the appropriate scale for modeling: Given the complexity of the nervous system, is it enough to model the neurons as point-like units in which a weighted sum of synaptic inputs is passed through a single spike-generating mechanism? From a modern perspective, the point neuron seems likely to be a poor representation of synaptic integration in neurons with large, profusely branched, active dendrites that populate brain structures associated with advanced cognitive functions and learning. These dendrites are endowed with nonlinear active conductances that modulate synaptic integration and somatic activity. Does the increased nonlinearity at

OBJECTIVE. The purpose of this study was to assess the frequency of pediatric CT in 40 less-resourced countries and to determine the level of appropriateness in CT use. MATERIALS AND METHODS. Data on the increase in the number of CT examinations during 2007 and 2009 and appropriate use of CT examinations were collected, using standard forms, from 146 CT facilities at 126 hospitals. RESULTS. The lowest frequency of pediatric CT examinations in 2009 was in European facilities (4.3%), and frequencies in Asia (12.2%) and Africa (7.8%) were twice as high. Head CT is the most common CT examination in children, amounting to nearly 75% of all pediatric CT examinations. Although regulations in many countries assign radiologists with the main responsibility of deciding whether a radiologic examination should be performed, in fact, radiologists alone were responsible for only 6.3% of situations. Written referral guidelines for imaging were not available in almost one half of the CT facilities. Appropriateness criteria for CT examinations in children did not always follow guidelines set by agencies, in particular, for patients with accidental head trauma, infants with congenital torticollis, children with possible ventriculoperitoneal shunt malfunction, and young children ( LT 5 years old) with acute sinusitis. In about one third of situations, nonavailability of previous images and records on previously received patient doses have the potential to lead to unnecessary examinations and radiation doses. CONCLUSION. With increasing use of CT in children and a lack of use of appropriateness criteria, there is a strong need to implement guidelines to avoid unnecessary radiation doses to children.

OBJECTIVE. The purpose of this study was to assess the frequency of pediatric CT in 40 less-resourced countries and to determine the level of appropriateness in CT use. MATERIALS AND METHODS. Data on the increase in the number of CT examinations during 2007 and 2009 and appropriate use of CT examinations were collected, using standard forms, from 146 CT facilities at 126 hospitals. RESULTS. The lowest frequency of pediatric CT examinations in 2009 was in European facilities (4.3%), and frequencies in Asia (12.2%) and Africa (7.8%) were twice as high. Head CT is the most common CT examination in children, amounting to nearly 75% of all pediatric CT examinations. Although regulations in many countries assign radiologists with the main responsibility of deciding whether a radiologic examination should be performed, in fact, radiologists alone were responsible for only 6.3% of situations. Written referral guidelines for imaging were not available in almost one half of the CT facilities. Appropriateness criteria for CT examinations in children did not always follow guidelines set by agencies, in particular, for patients with accidental head trauma, infants with congenital torticollis, children with possible ventriculoperitoneal shunt malfunction, and young children ( LT 5 years old) with acute sinusitis. In about one third of situations, nonavailability of previous images and records on previously received patient doses have the potential to lead to unnecessary examinations and radiation doses. CONCLUSION. With increasing use of CT in children and a lack of use of appropriateness criteria, there is a strong need to implement guidelines to avoid unnecessary radiation doses to children.

Nos sítios arqueológicos do Nordeste brasileiro é comum serem encontrados materiais cerâmicos e sedimentos, cuja datação é importante para a compreensão do desenvolvimento dos povos nesta região.