The field of numerically controlled (NC) machining has long been interested with predicting and measuring the errors in machining. Creating a simulation of NC machining is one way of achieving this. This thesis presents one such implementation of an NC simulation. It also runs a number of numerical and physical tests to verify the simulation?s correctness. The numerical tests show that the simulator work correctly as well as providing guide lines for appropriate simulation parameters. The physical tests show that the results of the simulation match the results of real NC machines. It is hoped that this thesis can provide a guide for the creation of machining simulators and their verification.

The field of numerically controlled (NC) machining has long been interested with predicting and measuring the errors in machining. Creating a simulation of NC machining is one way of achieving this. This thesis presents one such implementation of an NC simulation. It also runs a number of numerical and physical tests to verify the simulation?s correctness. The numerical tests show that the simulator work correctly as well as providing guide lines for appropriate simulation parameters. The physical tests show that the results of the simulation match the results of real NC machines. It is hoped that this thesis can provide a guide for the creation of machining simulators and their verification.

Measuring student learning is fundamental to any educational endeavor. A primary goal of many computer science education projects is to determine the extent to which a given instructional intervention has had an impact on student learning. However, the field of computing lacks valid and reliable assessment instruments for pedagogical or research purposes. Without such valid assessments, it is difficult to accurately measure student learning or establish a relationship between the instructional setting and learning outcomes. The goal of assessment research in computer science is to have valid ways of measuring student conceptions of fundamental topics, which will enable both research into how understanding of knowledge in the domain develops as well as enable curricular innovation and reform grounded in this knowledge. My dissertation work focused on three questions regarding assessment of introductory concepts in computer science. How can existing test development methods be applied and adapted to create a valid assessment instrument for CS1 conceptual knowledge? To what extent can pseudo-code be used as the mechanism for achieving programming language independence in an assessment instrument? And to what extent does the language independent instrument provide a valid measure of CS1 conceptual knowledge? I developed the Foundational CS1 (FCS1) Assessment instrument, the first assessment instrument for introductory computer science concepts that is applicable across a variety of current pedagogies and programming languages. I applied methods from educational and psychological test development, adapting them as necessary to fit the disciplinary context. I conducted think aloud interviews and a large scale empirical study to demonstrate that pseudo-code was an appropriate mechanism for achieving programming language independence. Student participants were able to read and reason in the pseudo-code syntax without difficulty and were able to transfer conceptual knowledge from their CS1 programming language to pseudo-code. Finally, I established the validity of the assessment using a multi-faceted argument, combining interview data, statistical analysis of results on the assessment, and exam scores. The contributions of this research are: (1) An example of how to bootstrap the process for developing the first assessment instrument for a disciplinary specific design-based field. (2) Identification that although it may not be possible to correlate scores between computer science exams created with different measurement goals, the validity claims of the individual assessments are not diminished. (3) A demonstration that novice computing students, at an appropriate level of development, can transfer their understanding of fundamental concepts to pseudo-code notation. (4) A valid assessment of introductory computing concepts for procedurally-based introductory computing courses taught in Java, Matlab, or Python at the university level.

Submitted by Pedro Barros (pedro.silvabarros@ufpe.br) on 2018-08-22T20:42:01Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Antônio Luiz Gonçalves Ferreira Júnior.pdf: 1647720 bytes, checksum: 85ed14b32797084b7b0a5a878256a1fc (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-08-29T21:26:30Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Antônio Luiz Gonçalves Ferreira Júnior.pdf: 1647720 bytes, checksum: 85ed14b32797084b7b0a5a878256a1fc (MD5) / Made available in DSpace on 2018-08-29T21:26:30Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Antônio Luiz Gonçalves Ferreira Júnior.pdf: 1647720 bytes, checksum: 85ed14b32797084b7b0a5a878256a1fc (MD5) Previous issue date: 2017-06-07 / Este trabalho trata do processo de desertificação, assunto que vem sendo discutido nos âmbitos governamental e acadêmico pelo menos desde os anos 1970. O tema envolve, aspectos ambientais, sociais e econômicos, com desdobramentos no longo prazo. Frente à complexidade da desertificação, tornou-se necessário elaborar sistemas de avaliação do fenômeno, procurando traçar indicadores de mensuração ou de estimativa que sejam compostos por dados de fácil obtenção e sistematização, resultando em sistemas mais operacionais. No caso da degradação ambiental, o indicador de maior relevância é a erosão do solo, podendo ser irreversível e tornar improdutiva a área de ocorrência. As metodologias para estimar a erosão são de dois tipos: por medição direta em campo ou por medição indireta. Para medição indireta, uma das opções é a técnica do ¹³⁷Cs, consistindo em estimar perdas e ganhos de solo por erosão hídrica, conforme sua movimentação na área pesquisada. Tem como vantagem a obtenção de resultados em período de tempo mais curto. Considerando a relação existente entre desertificação e erosão, a presente pesquisa teve como primeiro objetivo avaliar a possibilidade de empregar a técnica do ¹³⁷Cs na estimativa de erosão enquanto indicador do subíndice de degradação ambiental para mensuração de desertificação. Para tanto, foi aplicada a técnica numa área semiárida, suscetível à desertificação, especificamente o município de São Bento do Una, situado no Agreste de Pernambuco, região Nordeste do Brasil. O propósito foi estimar perdas e ganhos de solo por erosão a partir da avaliação dos estoques do radionuclídeo. O segundo objetivo foi verificar a aplicabilidade da metodologia proposta por Sampaio et al. (2003) para obtenção de índices de propensão à desertificação e de ocorrência da desertificação no Núcleo de Desertificação (Vasconcelos Sobrinho,1983), formado pelos municípios de Afrânio, Araripina, Belém do São Francisco, Cabrobó, Itacuruba, Ouricuri, Parnamirim, Petrolina e Salgueiro, em Pernambuco. Tínhamos como hipóteses que a técnica do ¹³⁷Cs seria um instrumento válido de estimativa da erosão no Agreste de Pernambuco e que a metodologia de Sampaio et al. (2003) seria pertinente para avaliação do processo de desertificação. A partir da análise dos dados, chegamos a conclusões de duas ordens. Em relação à aplicação da técnica do ¹³⁷Cs, não foi possível estimar as perdas de solo por erosão, pois os estoques obtidos nos transectos não corresponderam ao comportamento do radionuclídeo verificado em outras pesquisas. Isso nos levou a perceber a necessidade de melhor padronização nos procedimentos de coleta de amostras de solo, bem como de realização de novos estudos para geração de dados mais abrangentes no Brasil. Quanto à metodologia proposta por Sampaio et al. (2003), de um lado, verificamos importante fator limitante, que foi a defasagem temporal de dados secundários entre as fontes consultadas, o que exigiria atualização mais constante das bases de dados. Por outro, constatou-se a consistência da metodologia, pois atende a alguns requisitos básicos necessários, como facilidade de coleta e sistematização dos dados, consideração das dimensões social, ambiental e econômica, definição de níveis de classificação (baixo-1; moderado-2 e alto-3), tanto para a propensão, quanto para a ocorrência da desertificação. / This paper deals with the desertification process, a topic that has been discussed in the governmental and academic spheres at least since the 1970s. The theme involves environmental, social and economic aspects, with long-term consequences. Faced with the complexity of desertification, it became necessary to develop systems for assessing the phenomenon, seeking to draw indicators of measurement or estimation that are composed of data that are easily obtained and systematized, resulting in more operational systems. In the case of environmental degradation, the most relevant indicator is soil erosion, which may be irreversible and render the area of occurrence unproductive. The methodologies for estimating erosion are of two types: by direct field measurement or by indirect measurement. For indirect measurement, one of the options is the 137Cs technique, consisting of estimating soil losses and gains due to water erosion, according to its movement in the surveyed area. It has the advantage of obtaining results in a shorter period of time. Considering the relationship between desertification and erosion, the present study had as its first objective to evaluate the possibility of using the 137Cs technique in the erosion estimation as an indicator of the subindex of environmental degradation to measure desertification. For this purpose, the technique was applied in a semi-arid area, susceptible to desertification, specifically the São Bento do Una municipality, located in the Agreste of Pernambuco, Northeastern region of Brazil. The purpose was to estimate soil losses and erosion gains from the assessment of radionuclide stocks. The second objective was to verify the applicability of the methodology proposed by Sampaio et al. (2003) to obtain desertification propensity indexes and desertification occurrence in the Desertification Nucleus (Vasconcelos Sobrinho, 1983), formed by the municipalities of. Salgueiro, in Pernambuco. We hypothesized that the 137Cs technique would be a valid tool for estimating erosion in the Agreste of Pernambuco and that the methodology of Sampaio et al. (2003) would be relevant for assessing the desertification process. From the analysis of the data, we arrive at conclusions of two orders. Regarding the application of the 137Cs technique, it was not possible to estimate soil losses due to erosion, since the transects obtained did not correspond to the radionuclide behavior verified in other studies. This led us to understand the need for better standardization of soil sampling procedures, as well as new studies for the generation of more comprehensive data in Brazil. As for the methodology proposed by Sampaio et al. (2003), on the one hand, we found an important limiting factor, which was the temporal lag of secondary data between the sources consulted, which would require a more constant updating of the databases. On the other hand, it was verified the consistency of the methodology, as it meets some basic requirements, such as ease of collection and systematization of data, consideration of social, environmental and economic dimensions, definition of classification levels (low-1; And high-3), both for propensity and for the occurrence of desertification.

<p> This thesis is concerned with control procedures employed in Pavlovian conditioning, in particular, the "truly random" control. Pilot work indicated that this procedure employed in a CER paradigm resulted in response suppression. Our first objective then was to examine this finding in a more formal experiment, as well as attempting to determine the cause of the observed suppression. In a second experiment, a variable predicted to affect the amount of conditioning within traditional conditioning theory was employed to determine the possible role of this variable in suppression produced by the random control procedure.</p> <p> It was found, in the first experiment, that two variations of the random procedure resulted in suppression in testing. The results of a third group indicated that the suppression was not due to a between-session discriminative function of the CS. A fourth group demonstrated, within contingency logic, inhibitory control, but this group, like the others, showed suppression.</p> <p> In the second experiment, variations of stimulus conditions, none of which made the US contingent on the CS, resulted in marked differences in suppression in testing. Further, significantly different recovery rates of the operant baseline were noted both as a function of the recovery condition and of the CS employed in training.</p> / Thesis / Master of Arts (MA)

Computer Science students need to understand the mechanism of programming systems that involve computation, automation, and information. Computer scientists need to know how to design and analyze a problem and solve it with an algorithm. We study students' behaviors in CS education to find out patterns of those who need help. Several behaviors are examined: Time Management, Incremental development, Self-checking, Persistence, and Planning. Help-seeking, when done correctly, is known as a good strategy related to self-regulated learning. This behavior includes online searching, coming to office hours for help from instructional staff, and asking instructors and peers publicly on online forums. Some of these sources of help can be tracked more easily than others. We present efforts to collect and analyze data related to the help-seeking behavior of students in a second-semester programming course. The goal of this work is to establish mechanisms that will permit us to collect sufficient data from a variety of sources so that we can determine what help-seeking behavior patterns are associated with successful course outcomes. Our current data collection efforts are tied in part to the effects of the COVID-19 pandemic, which caused courses to be taught online during our data collection period that normally would be taught face-to-face. Data includes logs of viewing or posting questions to the online forum system Piazza, office hour visit logs, Zoom logs, and grades from the Canvas LMS. We present initial analysis such as comparing course grades with the number of times students received help from instructional staff both in office hours and online forum Piazza. / Master of Science / Computer Science students need to understand the mechanism of programming systems that involve computation, automation, and information. Computer scientists need to know how to design and analyze a problem and solve it with an algorithm. We study students' behaviors in CS education to find out patterns of those who need help. Several behaviors are examined: Time Management, Incremental development, Self-checking, Persistence, and Planning. Help-seeking, when done correctly, is known as a good strategy related to self-regulated learning. This behavior includes online searching, coming to office hours for help from instructional staff, and asking instructors and peers publicly on online forums. Some of these sources of help can be tracked more easily than others. We present efforts to collect and analyze data related to the help-seeking behavior of students in a second-semester programming course. The goal of this work is to establish mechanisms that will permit us to collect sufficient data from a variety of sources so that we can determine what help-seeking behavior patterns are associated with successful course outcomes. Our current data collection efforts are tied in part to the effects of the COVID-19 pandemic, which caused courses to be taught online during our data collection period that normally would be taught face-to-face. Data includes logs of viewing or posting questions to the online forum system Piazza, office hour visit logs, Zoom logs, and grades from the Canvas LMS. We present initial analysis such as comparing course grades with the number of times students received help from instructional staff both in office hours and online forum Piazza.

A espectrometria de absorção atômica (AAS) é consolidada como uma técnica robusta, cujas aplicações estendem-se a diversos analitos e matrizes. Sua limitação encontra-se na região do UV distante (~ 190 nm), por isso ela permaneceu exclusiva à determinação de metais durante vários anos: não-metais geralmente absorvem na região de UV de vácuo. Com o advento da AAS de alta resolução com fonte contínua, houve a implementação de uma terceira dimensão (comprimento de onda) nas análises: a visualização da região espectral da linha analítica. Esta nova característica permitiu um maior número de informações espectrais, principalmente em relação às bandas estruturadas de moléculas diatômicas, o que resultou na determinação de absorção molecular (HR CS MAS). Destarte, o objetivo deste trabalho foi a elaboração de novos procedimentos analíticos para determinação de não-metais por HR CS MAS, especificadamente Br, Cl e S, com atomizador de forno de grafite. O bromo foi avaliado via CaBr em componentes plásticos de amostras eletrônicas, extraído por extração Soxhlet com tolueno, e obteve limites de detecção (LD) e quantificação (LQ) de 4,3 e 14 ng de Br, respectivamente, com Pd como modificador químico. Duas matrizes foram estudadas para a quantificação de enxofre via CS: carvão e diesel. O carvão foi injetado em HR CS MAS como uma suspensão com Triton X-100 0,04 % m v-1, e (NH4)2SO4 foi empregado como padrão de enxofre. Os LD e LQ obtidos para o método foram 0,01 e 0,05 % m m-1, respectivamente. Para o diesel, dois métodos foram estudados: (i) emulsão alcoólica com etanol 50 % v v-1, a qual apresentou LD de 0,12 g kg-1 e LQ de 0,40 g kg-1, adequados para determinação de altos teores de S em diesel; e (ii) injeção direta de diesel no sistema de HR CS MAS, cujos LD e LQ foram 3 e 9 mg kg-1, respectivamente. Ambos empregaram nanopartículas de Pd como modificador químico, das quais a análise direta de diesel obteve melhores resultados. Finalmente, um novo conceito foi investigado em HR CS MAS: o deslocamento isotópico em moléculas diatômicas. Os estados vibracionais e rotacionais presentes na transição eletrônica observada em HR CS MAS confere esta propriedade. As moléculas de AlCl e CaBr, cujos isótopos de interesse foram 35Cl e 37Cl, e 79Br e 81Br, respectivamente, foram estudadas. Os deslocamentos isotópicos observados foram de 15,6 pm para AlCl e 41,6 pm para CaBr nos comprimentos de onda selecionados, suficientes para implementação de calibração por diluição isotópica, a qual apresentou LDs de 2,5 e 64 ng, respectivamente. Amostras de água natural e mineral foram empregadas para o Cl, enquanto o Br foi determinado em amostras de PVC e folhas de tomate, as quais foram introduzidas diretamente como sólidos. A diluição isotópica corrigiu adequadamente as interferências espectrais acarretadas pelas matrizes de ambos os analitos. / Atomic Absorption Spectrometry (AAS) is a robust analytical technique whose applications extend to many different analytes and matrices. Its limitation lies on the far UV region (~ 190 nm) and therefore it remained exclusive for metal determination as non-metals typically absorb within the vacuum-UV region. With the invention of the High-Resolution Continuum Source AAS (HR CS AAS), the AAS analysis has been upgraded and a new dimension (wavelength) was added: the visualization of the analytical lines vicinity. This new feature allowed improved spectral information, mainly related to the structured bands of diatomic molecules, giving rise to the HR CS Molecular Absorption Spectrometry (MAS). The goal of this thesis was the evaluation of new analytical procedures for non-metals determination by HR CS MAS, specifically Br, Cl, and S, using graphite furnace as the atomizer. Bromine in plastic electronic components was evaluated as CaBr after Soxhlet extraction with toluene. This method had limits of detection (LD) and quantification (LQ) of 4.3 and 14 -ng, respectively, using Pd as chemical modifier. Sulfur determination via CS molecule employed two distinct matrices: coal and diesel. Coal samples were prepared as a slurry with Triton X-100 0.04% m v1 for injection in the HR CS MAS and the external calibration employed was (NH4)2SO4as sulfur standard. The method LD and LQ were 0.01% m m1 and 0.05% m m1, respectively. Two methods were studied for diesel samples: (i) alcoholic emulsion with ethanol 50% v v1, with an LD of 0.12 g kg1 and an LQ of 0.40 g kg1, suitable for sulfur high concentration determination in diesel; and (ii) direct diesel injection in the HR CS MAS system, whose LD and LQ were 3 mg kg-1and 9 mg kg-1, respectively. Both methods employed Pd nanoparticles as chemical modifier, with better results for direct diesel analysis. Ultimately, a new concept was investigated in HR CS MAS: the isotopic shift of diatomic molecules. An absorption profile consisted of multiple peaks was due to vibrational and rotational energy couplings within the electronic transition observed by HR CS MAS, which provided the isotopic shift. This effect was detected on AlCl and CaBr molecules, whose target isotopes were, respectively, 35Cl &37Cl and 79Br &81Br. The observed isotopic shifts were 15.6 pm (AlCl) and 41.6 pm (CaBr) at the selected wavelengths, appropriate for isotopic dilution calibration, which featured LDs of 2.5 ng and 64 ng, respectively. Natural and mineral water samples were evaluated for Cl determination; and Br was found in PVC and tomato leaves samples, both introduced as solid samples in HR CS GFMAS. Isotopic dilution adequately corrected the spectral interferences derived from the matrices of both analytes.

O crescimento do consumo energético trouxe a necessidade do desenvolvimento de fontes alternativas de energia, uma vez que os combustíveis fósseis, além dos impactos ambientais, constituem uma fonte finita, cuja formação leva milhares de anos para ocorrer. Neste contexto, surge o biodiesel, uma fonte de energia renovável e que pode ser obtido através da reação de transesterificação dos triglicerídeos presentes em óleos vegetais e gorduras animais com álcoois de cadeia curta. Assim como os combustíveis derivados do petróleo, o biodiesel deve seguir alguns parâmetros de qualidade estabelecidos pela Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP). A estabilidade e a qualidade do biocombustível são afetadas por uma série de fatores, dentre os quais as concentrações de magnésio, cálcio, sódio, potássio, enxofre e fósforo. Visando unificar a determinação destes analitos através da espectrometria de absorção atômica e da espectrometria de absorção molecular de alta resolução e fonte contínua, foram propostos como métodos de preparo de amostra a digestão ácida e a fotodegradação para determinação de Mg, Ca, Na e K por FAAS, e análise direta para determinação de S e P por GF MAS. O preparo de amostra influenciou no limite de detecção dos elementos, visto que os melhores LOD para Na, K e Ca foram observados através da digestão ácida, especialmente na condição 2, empregando 6,0 mL de HNO3, 2,0 mL de H2O2 e 2,0 mL de HCl, enquanto que para Mg o menor LOD ocorreu para a fotodegradação por reação foto-Fenton. Os menores valores de RSD para Mg e Ca foram obtidos por fotodegradação foto-Fenton e por TiO2, respectivamente, e para Na e K por fotodegradação foto-Fenton e digestão ácida na condição 2, respectivamente. O biodiesel estava dentro das especificações exigidas pela legislação, então foram realizados testes de adição e recuperação para avaliar a exatidão dos métodos propostos. O Mg foi o analito cuja determinação apresentou as menores concentrações características, indicando maior sensibilidade, e também os menores LOD, enquanto que o cálcio apresentou a menor sensibilidade. A digestão ácida com 6,0 mL de HNO3 e 4,0 mL de H2O2 e a fotodegração foto-Fenton possibilitaram as melhores recuperações de analito considerando o conjunto dos 4 elementos, com variação de 88 % a 108 %. O padrão de enxofre a base de óleo mineral demonstrou não ser apropriado para a determinação de enxofre em biodiesel por análise direta. O uso de 2-mercaptoetanol como padrão, no entanto, possibilitou o estudo da molécula CS na amostra de biodiesel, apresentando-se mais compatível e com ganho de sensibilidade nas medidas. O emprego de Ir como modificador químico permanente e da mistura Pd/Mg permitiu boa estabilização da molécula CS, um LOD de 1,8 µg g-1 de biodiesel foi obtido, e a concentração de S na amostra não enriquecida foi de 6,2 µg g-1, abaixo do limite máximo permitido. Para o fósforo, somente foi possível obter sinal analítico em 246,40 nm, correspondente a uma transição rotacional da molécula PO, utilizando W como modificador químico. O LOD obtido foi de 2,2 µg g-1, e a concentração estimada na amostra pura pela curva de adição padrão estava entre o LOD e o LOQ calculados, abaixo do limite máximo permitido. Os métodos desenvolvidos mostraram-se apropriados para a determinação dos analitos na amostra de biodiesel via espectrometria de absorção atômica/molecular por chama e forno de grafite, atendendo a legislação vigente / The increase in the energy consumption over the last years led to the research and development of alternatives sources of energy, once the fossil fuels, besides their environmental effects, represent a finite source which takes thousands of years to be formed. In this context, biodiesel arises as a renewable source that can be produced by the transesterification reaction between triglycerides of vegetable oils or animal fat and short chain alcohols. As well as for oil-derived fuels, biodiesel must obey some quality specifications established by the National Petroleum, Natural Gas and Biofuel Agency (NPA). The stability and quality of biofuels are influenced by conditions such as the concentration of magnesium, calcium, sodium, potassium, sulfur and phosphorus. This study aims to unify the determination of these elements by atomic absorption spectrometry and high-resolution continuum source molecular absorption spectrometry techniques. The proposed methods of sample treatment are the acid digestion and the photodegradation for Mg, Ca, Na and K by FAAS, and the direct analysis for S and P by GF MAS. The limits of detection were influenced by the sample treatment. The lowest LOD values for Na, K and Ca were observed through acid digestion, especially second condition (6,0 mL of HNO3, 2,0 mL of H2O2 and 2,0 mL of HCl), while for Mg the lowest LOD was achieved by photo-Fenton photodegradation. The lowest RSD values for Mg and Ca were observed by photo-Fenton and TiO2 photodegradations, respectively, and for Na and K by photo-Fenton photodegradation and acid digestion (condition 2), respectively. The biodiesel sample was within the specifications legally required, therefore recovery tests were used to evaluate the accuracy of the proposed methods. Magnesium was the analyte whose determination showed the lowest characteristic concentrations, which indicates the best sensitivity, and also the lowest detection limits, while calcium was the least sensitive analyte. The acid digestion (6.0 mL of HNO3 and 4.0 mL of H2O2) and photodegradation by photo-Fenton reaction allowed the best recoveries, considering the set of 4 analytes, ranging from 88 % to 108 %. The oil-based standard was not appropriated for sulfur determination in biodiesel sample by direct analysis. The use of 2-mercaptoethanol as a standard led to a better sensitivity, in addition to the compatibility with the sample. Iridium as permanent chemical modifier, along with a mixture of Pd/Mg, provided good stabilization of CS molecule, a LOD of 1.8 µg g-1 was achieved, and the sulfur concentration in the biodiesel sample, obtained by standard addition method, was 6.2 µg g-1, below the limit legally established. Regarding phosphorus study for determination in biodiesel, an acceptable analytic signal was obtained at 246.40 nm, which corresponds to a rotational transition of PO molecule. The calculated LOD was 2.2 µg g-1, and the estimated concentration in the pure sample, obtained by a standard addition curve, was between the LOD and LOQ, below the limit legally established. The developed methods were appropriated for determination of the proposed analytes set in biodiesel sample by atomic/molecular absorption spectrometry, in agreement with current legislation

Os radionuclídeos artificiais e naturais podem ser comumente encontrados em diversos compartimentos da crosta terrestre. Algumas espécies de cogumelos têm uma alta capacidade em absorver radionuclídeos e elementos tóxicos vindos do solo. A dieta alimentar destaca-se como uma das principais vias de contaminação radioativa. Portanto, a medida da radioatividade no ambiente e em alimentos é extremamente importante para monitorar os níveis de radiação aos quais o homem possa estar exposto de forma direta ou indireta. A biomonitoração ambiental tem demonstrado que diversos organismos como os crustáceos, peixes e cogumelos são usados para avaliar a contaminação e a qualidade dos ecosssistemas. Existem vários radionuclídeos que podem ser acumulados por cogumelos, incluindo 40 K, 137Cs, 232Th e 238U. No entanto há poucos estudos em países do hemisfério Sul, sobre os níveis de radioatividade natural e artificial em cogumelos. Este trabalho consistiu na determinação das atividades específicas de elementos radioativos naturais e 137Cs em cogumelos comestíveis comercializados em São Paulo-Brasil. As amostras de cogumelos comestíveis foram adquiridas em diferentes pontos comerciais da cidade de São Paulo, especialmente em mercados municipais, porém algumas foram adquiridas diretamente de produtores de algumas regiões como Mogi das Cruzes, Mirandópolis, Suzano e Juquitiba. Cerca de 400 g de cada espécie de cogumelos comestíveis foram coletadas, incluindo Agaricus sp, Lentinula sp e Pleurotus sp. Todas as amostras foram preparadas e acondicionadas em recipientes de polietileno, seladas e armazenadas por aproximadamente 35 dias, para que fosse estabelecido o equilíbrio radioativo secular, antes que se iniciassem as contagens. As atividades gama do 40K, 137Cs, 232Th e 238U foram medidas por espectrometria gama. O equipamento utilizado consistiu de um detector de Germânio Hiperpuro conectado a um sistema eletrônico. As medidas foram de aproximadamente 200000 segundos. A eficiência do detector foi medida utilizando os materiais de referência: IAEA-300, IAEA-327 e IAEA-375. Os resultados obtidos para as amostras de cogumelos comestíveis variaram de 461 a 1535 Bq kg 1, 1,4 a 10,6 Bq kg 1, 6,2 a 54,2 Bq kg 1 e 14 a 66 Bq kg 1 em peso seco, para 40K,137Cs, 232Th e 238U, respectivamente. Os níveis de 137Cs estão de acordo com o fallout radioativo do hemisfério Sul, apresentando concentrações abaixo dos níveis máximos estabelecidos pela CNEN. Comparando os resultados obtidos com outros trabalhos da literatura, comprovou-se que os valores das atividades encontradas para os radionuclíddeos naturais estão dentro dos níveis normais de radioatividade para este produto. As espécies de cogumelos analisadas podem ser consumidas sem riscos de contaminação. O método de análise empregado neste estudo demonstrou-se adequado para estimar a atividade 232Th e 238U e determinar as atividades de 40K e 137Cs, em amostras biológicas. Este estudo assinala a primeira vez em que cogumelos comestíveis, no Brasil foram estudados para avaliar o conteúdo radioativo e, como tal, é uma contribuição para investigações futuras nesta área. / Artificial and natural radionuclides are commonly found in several compartments of the earth\'s crust. Some mushroom species have a high capacity to absorb radionuclides and toxic elements from the soil. Diet is considered as one of the main routes of radioactive contamination. Therefore, radioactivity measurements in the environment and in food are extremely important to monitor the radiation levels that human can be exposed to either directly or indirectly. Environmental biomonitoring has demonstrated that diverse organisms such as crustaceans, fish and mushrooms are useful when evaluating both the contamination and the quality of the ecosystems. There are actually several radionuclides that can be accumulated in mushrooms, including 40 K, 137Cs, 232Th and 238U. There are few studies in the Southern hemisphere countries, on the natural and artificial radioactivity levels in mushrooms. The present study evaluated 40K, 137Cs, 232Th and 238U in commercialized edible mushrooms in the state of São Paulo, Brazil. The edible mushroom samples were acquired in different commercial establishments in the São Paulo metropolitan region, specifically in Municipal Markets. Some samples were acquired directly from producers located in the cities of Mogi das Cruzes, Mirandópolis, Suzano and Juquitiba. About 400g were colleted for each edible mushroom species, which included Agaricus sp, Pleurotus sp and Lentinula sp species. All the samples were prepared and stored in polyethylene bottles for approximately 35 days, so that secular equilibrium could be established before counting. The 40K, 137Cs, 232Th and 238U gamma activities were measured by gamma spectrometry. The equipment consisted of a Hiperpure Germanium detector connected to an electronic system. The detector efficiency was obtained from measurements of reference materials: IAEA-300, IAEA-327 and IAEA-375. The results for the specific activities in edible mushrooms samples ranged from 461 to 1535 Bq kg1, 1.4 to 10.6 Bq kg1, 6.2 to 54.2 Bq kg1 and 14 to 66 Bq kg1 d.w., for 40K,137Cs, 232Th e 238U, respectively. The 137Cs levels are in accordance with the Southern hemisphere radioactive fallout, the concentrations are below the maximum levels established by CNEN. Comparing the result values with these found in published literature, the values of the activities found for natural radionuclides are within the normal radioactivity levels for this kind of food. Hence, the studied mushroom species can be consumed without risk of contamination. The employed methodology in this study showed adequate to estimate 232Th and 238U specific activities and to determine 40K and 137Cs activities in biological samples. This study marks the first time that edible mushrooms in Brazil have been studied to evaluate their radioactivity contents and as such is a contribution for future research in this area.

Os radionuclídeos artificiais e naturais podem ser comumente encontrados em diversos compartimentos da crosta terrestre. Algumas espécies de cogumelos têm uma alta capacidade em absorver radionuclídeos e elementos tóxicos vindos do solo. A dieta alimentar destaca-se como uma das principais vias de contaminação radioativa. Portanto, a medida da radioatividade no ambiente e em alimentos é extremamente importante para monitorar os níveis de radiação aos quais o homem possa estar exposto de forma direta ou indireta. A biomonitoração ambiental tem demonstrado que diversos organismos como os crustáceos, peixes e cogumelos são usados para avaliar a contaminação e a qualidade dos ecosssistemas. Existem vários radionuclídeos que podem ser acumulados por cogumelos, incluindo 40 K, 137Cs, 232Th e 238U. No entanto há poucos estudos em países do hemisfério Sul, sobre os níveis de radioatividade natural e artificial em cogumelos. Este trabalho consistiu na determinação das atividades específicas de elementos radioativos naturais e 137Cs em cogumelos comestíveis comercializados em São Paulo-Brasil. As amostras de cogumelos comestíveis foram adquiridas em diferentes pontos comerciais da cidade de São Paulo, especialmente em mercados municipais, porém algumas foram adquiridas diretamente de produtores de algumas regiões como Mogi das Cruzes, Mirandópolis, Suzano e Juquitiba. Cerca de 400 g de cada espécie de cogumelos comestíveis foram coletadas, incluindo Agaricus sp, Lentinula sp e Pleurotus sp. Todas as amostras foram preparadas e acondicionadas em recipientes de polietileno, seladas e armazenadas por aproximadamente 35 dias, para que fosse estabelecido o equilíbrio radioativo secular, antes que se iniciassem as contagens. As atividades gama do 40K, 137Cs, 232Th e 238U foram medidas por espectrometria gama. O equipamento utilizado consistiu de um detector de Germânio Hiperpuro conectado a um sistema eletrônico. As medidas foram de aproximadamente 200000 segundos. A eficiência do detector foi medida utilizando os materiais de referência: IAEA-300, IAEA-327 e IAEA-375. Os resultados obtidos para as amostras de cogumelos comestíveis variaram de 461 a 1535 Bq kg 1, 1,4 a 10,6 Bq kg 1, 6,2 a 54,2 Bq kg 1 e 14 a 66 Bq kg 1 em peso seco, para 40K,137Cs, 232Th e 238U, respectivamente. Os níveis de 137Cs estão de acordo com o fallout radioativo do hemisfério Sul, apresentando concentrações abaixo dos níveis máximos estabelecidos pela CNEN. Comparando os resultados obtidos com outros trabalhos da literatura, comprovou-se que os valores das atividades encontradas para os radionuclíddeos naturais estão dentro dos níveis normais de radioatividade para este produto. As espécies de cogumelos analisadas podem ser consumidas sem riscos de contaminação. O método de análise empregado neste estudo demonstrou-se adequado para estimar a atividade 232Th e 238U e determinar as atividades de 40K e 137Cs, em amostras biológicas. Este estudo assinala a primeira vez em que cogumelos comestíveis, no Brasil foram estudados para avaliar o conteúdo radioativo e, como tal, é uma contribuição para investigações futuras nesta área. / Artificial and natural radionuclides are commonly found in several compartments of the earth\'s crust. Some mushroom species have a high capacity to absorb radionuclides and toxic elements from the soil. Diet is considered as one of the main routes of radioactive contamination. Therefore, radioactivity measurements in the environment and in food are extremely important to monitor the radiation levels that human can be exposed to either directly or indirectly. Environmental biomonitoring has demonstrated that diverse organisms such as crustaceans, fish and mushrooms are useful when evaluating both the contamination and the quality of the ecosystems. There are actually several radionuclides that can be accumulated in mushrooms, including 40 K, 137Cs, 232Th and 238U. There are few studies in the Southern hemisphere countries, on the natural and artificial radioactivity levels in mushrooms. The present study evaluated 40K, 137Cs, 232Th and 238U in commercialized edible mushrooms in the state of São Paulo, Brazil. The edible mushroom samples were acquired in different commercial establishments in the São Paulo metropolitan region, specifically in Municipal Markets. Some samples were acquired directly from producers located in the cities of Mogi das Cruzes, Mirandópolis, Suzano and Juquitiba. About 400g were colleted for each edible mushroom species, which included Agaricus sp, Pleurotus sp and Lentinula sp species. All the samples were prepared and stored in polyethylene bottles for approximately 35 days, so that secular equilibrium could be established before counting. The 40K, 137Cs, 232Th and 238U gamma activities were measured by gamma spectrometry. The equipment consisted of a Hiperpure Germanium detector connected to an electronic system. The detector efficiency was obtained from measurements of reference materials: IAEA-300, IAEA-327 and IAEA-375. The results for the specific activities in edible mushrooms samples ranged from 461 to 1535 Bq kg1, 1.4 to 10.6 Bq kg1, 6.2 to 54.2 Bq kg1 and 14 to 66 Bq kg1 d.w., for 40K,137Cs, 232Th e 238U, respectively. The 137Cs levels are in accordance with the Southern hemisphere radioactive fallout, the concentrations are below the maximum levels established by CNEN. Comparing the result values with these found in published literature, the values of the activities found for natural radionuclides are within the normal radioactivity levels for this kind of food. Hence, the studied mushroom species can be consumed without risk of contamination. The employed methodology in this study showed adequate to estimate 232Th and 238U specific activities and to determine 40K and 137Cs activities in biological samples. This study marks the first time that edible mushrooms in Brazil have been studied to evaluate their radioactivity contents and as such is a contribution for future research in this area.