A disposição de resíduos sólidos é um dos temas mais discutidos na atualidade. A queima controlada dos resíduos possibilita a redução do volume a ser depositado e a geração de energia. Este trabalho estudou o emprego de uma nova tecnologia no atual processo de queima de uma série de resíduos carbonosos. Um sistema de catálise foi utilizado para sintetizar nanotubos de carbono (CNTs) a partir dos gases gerados pela pirólise/combustão dos resíduos. Os CNTs são materiais com alto valor de mercado devido às suas excepcionais propriedades. Foram alvos de estudo os resíduos da indústria do etanol (bagaço da cana-de-açúcar e grãos secos de destilaria com solúveis - DDGS), borracha de pneus inservíveis e garrafas de poli(tereftalato de etileno) pós-consumo. Amostras dos resíduos foram incineradas em um forno de fluxo contínuo com atmosfera controlada através da injeção de N2 e temperaturas de 600-1000°C, sendo que jatos de O2 foram adicionados em alguns experimentos. O efluente gasoso da queima foi submetido a um filtro de SiC e repassado a um segundo forno com temperatura constante de 1000°C. Telas de aço inoxidável foram dispostas no forno secundário para atuarem como catalisador. A cromatografia gasosa foi utilizada para a comparação dos efluentes com e sem o uso do catalisador, sendo constatado que o emprego das telas ocasionou uma significativa redução na emissão de poluentes. Após os experimentos, foi verificada a formação de partículas de carbono sólido na superfície do catalisador. As partículas formadas foram submetidas a análises por MEV, MET, TG e Raman. Os resultados apontaram a formação de nanotubos de carbono de parede múltiplas com comprimentos de 20 a 50 µm e diâmetros entre 20 e 50 nm quando empregados pneus e bagaço da cana como matérias-primas. Experimentos que empregaram DDGS e garrafas PET produziram microfibras de carbono com comprimentos em torno de 40 µm e diâmetros entre 80 e 200 nm. / The disposal of solid wastes is one of the most discussed topics nowadays. Controlled burning allows the reduction of waste volumes to be deposited, and the energy generation. This study examined the use of a new technology in the current burn processes of several carbonaceous wastes. A catalyst system was used to synthesize carbon nanotubes (CNTs) from the gases generated by pyrolysis/combustion of wastes. CNTs are materials with high market value due to its exceptional properties. Residues of the ethanol industry (sugarcane bagasse and distillers dried grains with solubles - DDGS), scrap tire rubbers and post-consumer polyethylene terephthalate bottles were subject of study. Waste samples were incinerated in a laminar-flow furnace with controlled atmosphere by injection of N2, and temperatures of 600-1000°C, while jets of O2 were added in some experiments. The effluent gases were subjected to a SiC filter and channeled into the second furnace with constant temperature of 1000°C. Stainless steel meshes were placed in the second furnace in order to work as catalyst. Gas chromatography was used to compare the effluent with and without the catalyst use, wherein was showed that the use of meshes caused a significant reduction in the emissions. After the experiments, the formation of solid carbon particles was verified on the catalyst surface. The formed particles were analyzed by SEM, TEM, TG and Raman. Results showed the formation of multi-wall carbon nanotubes with lengths of 20-50 µm and diameters in the range of 20-50 nm when tires and sugarcane bagasse were used as raw materials. Experiments using DDGS and PET bottles produced carbon microfibers with lengths of about 40 µm and diameters of 80-200 nm.

Made available in DSpace on 2016-03-15T19:36:43Z (GMT). No. of bitstreams: 1 Anderson dos Santos Mesquita.pdf: 7340501 bytes, checksum: ff5f2b956484062f42f8187d057664f3 (MD5) Previous issue date: 2014-06-13 / IPEN - Instituto de Pesquisas Energéticas e Nucleares / This work is intended to obtain and characterize the polym er-based poly(ethylene terephthalate) (PET) loaded with carbon black and compare their physical and chemical properties with other polymers loaded with carbon black, more particularly polypropylene and polysty rene, traditionally used in antistatic packaging. PET compounds were obtained containing 10, 0; 11,0; 12,0 and 15,0% of carbon black with a particle size 325 mesh. We determined the thermo mechanical properties, electrical and morphological of the compounds obtained. The result showed that the compound based on PET filled with 15% carbon black may be used in the handling, transportation and storage of electronic components because their mechanical properties, thermal and resistivity are satisfactory for this purpose. / Este trabalho teve como objetivo obter e caracterizar compostos à base de poli(tereftalato de etileno) (PET) carregado com negro de fumo e comparar suas propriedades físico-químicas com os demais polímeros carregados com negro de fumo, mais especificamente o polipropileno (PP) e o poliestireno (PS), tradicionalmente utilizados em embalagens antiestáticas. Foram obtidos compostos de PET contendo 10,0; 11,0; 12,0 e 15,0% de negro de fumo com granulometria de 325 mesh. Foram determinadas as propriedades termomecânicas, elétricas e morfológicas dos compostos obtidos. Os resultados mostraram que o composto à base de PET carregado com 15% de negro de fumo (NF) pode ser utilizado no manuseio, transporte e armazenagem de componentes eletrônicos visto que suas propriedades mecânicas, térmicas e de resistividade são satisfatórias para este fim.

Apesar do recente conhecimento do papel anti-inflamatório e anti-nociceptivo do H2S na artrite induzida por carragenina (CGN) em rato, os mecanismos envolvidos ainda não são conhecidos. Tampouco se sabe se compostos híbridos antiinflamatórios não esteroides (AINEs) doadores de H2S possuem vantagens farmacológicas adicionais quando comparados aos doadores de H2S clássicos. Apesar de H2S exercer um efeito anti-nociceptivo em modelos de inflamação e dor aguda, pouco se sabe sobre o papel deste gás na dor crônica. Neste estudo investigou-se os mecanismos do H2S no modelo de sinovite e participação desse gás na dor crônica. Verificou-se que os canais de K+ATP, canais de Ca2+ tipo L ou receptores TRPV1 não estão envolvidos no mecanismo protetor do H2S na sinovite, diminuição da IL-1b e aumento da IL-10 e não houve diferença em relação a participação das enzimas oxidantes GPx e GR. Ainda, o tratamento agudo com o doador de H2S não reverteu o desconforto do teste do Rota Rod e alodinia térmica. / Despite recent knowledge of the anti-inflammatory and anti-nociceptive role of H2S in the carrageenin-induced arthritis (CGN) in rats, the mechanisms involved are not yet known. Nor is it known whether hybrid compounds antiinflammatory drugs (NSAIDs) H2S donors have additional pharmacological advantages when compared to classical H2S donors. Although H2S exert an anti-nociceptive effect in models of inflammation and acute pain, little is known about the role of this gas in chronic pain . In this study we investigated the protective mechanisms of H2S in the model of synovitis and chronic pain . It was found that the K+ATP channel, L type Ca2+ channel or TRPV1 receptors are not involved in the protective mechanism of H2S in synovitis , decreased IL-1b and increased IL-10 and there was no difference in the participation of oxidant enzymes GPx and GR . Still, the acute treatment with H2S donor did not reverse the discomfort of the Rota Rod test and thermal allodynia.

Cette étude présente la conception d’agents pour la radiothérapie et la Tomographie par Emission de Positrons (TEP). Les agents bimodaux envisagés sont constitués de deux parties : la partie uracile et la partie diamsar (1,8-diamino-3,6,10,13,16,19- hexaazabicyclo[6.6.6]eicosane) qui complexerait le 64Cu2+ ou le 67Cu2+. Durant la conception de ces agents bimodaux, nous avons examiné indépendamment les deux parties. Dans un premier temps, l’introduction de différents groupements benzyliques sur les amines primaires du diamsar ont permis d’étudier les changements dans les propriétés de complexation des ions métalliques (Cu2+, Co2+ et Cd2+) par les ligands. Quant aux dérivés correspondant à la partie uracile, leur stabilité a été étudiée à pression atmosphérique puis dans un système de vide à très basse pression par entraînement dans un jet d’hélium. Lors de l’introduction à leur état gazeux par le jet d’hélium, aucune dissociation thermique ne fut observée par spectrométrie de masse couplée avec la technique de « time of flight ». La réussite de cette introduction démontre clairement que les études d’interactions entre l’électron ou le positron de basse énergie et ces dérivés de l’uracile peuvent être réalisées pour des études ultérieures de l’attachement dissociatif des électrons ou de l’annihilation de positron. / The design of PET-radiotherapy agent investigation is reported. These envisaged bimodal agents are based on two moieties: the uracil moiety and the diamsar (1,8-diamino-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane) moiety that could complex 64Cu2+ or 67Cu2+. In the design of bimodal agents, the two moieties are investigated independently. Firstly, diamsar derivatives with various benzyl groups linked to the primary amines are synthesized. Therefore, the influence of these changes on the complexation of metal ions (Cu2+, Co2+ and Cd2+) is established. In the other hand, the stability of the synthesized uracil derivatives is first investigated at atmospheric pressure followed by their introduction into a high vacuum system by seeding into a helium jet. Through time of flight mass spectroscopy (TOFMS), no thermal dissociation is observed in their gas phase during the heating phase of introduction in the helium jet. This successful introduction clearly demonstrates that interaction studies between low energy electron or positron and these uracil derivatives could be performed for dissociative electron attachment (DEA) or positron annihilation studies.

Ce travail est une étude expérimentale et de modélisation d’une configuration de puce microfluidique réalisée par photoablation laser d’un polymère diélectrique, le polyéthylène téréphtalate (PET) pour des applications en bioanalyse. C’est une configuration dite « non-contact » dans laquelle deux microélectrodes sont galvaniquement isolées dans le PET sans contact avec l’électrolyte du microcanal. La caractérisation par spectroscopie d’impédance de la réponse diélectrique du PET seul a permis de conclure que le film de PET peut être considéré comme un élément à phase constante (CPE). Cela a permis la compréhension des impédances mesurées sur puce microfluidique suivant une perturbation alternative de 100 mV dans la gamme de fréquence comprise entre 1MHz à 1Hz est effectuée pour : un microcanal vide, et un microcanal rempli avec des solutions de différentes conductivités ioniques. Les résultats obtenus ont montré une grande sensibilité des mesures d’impédances par rapport aux variations de la conductivité électrique de la solution électrolytique. Un des résultats surprenant concernant les impédances identifiées a été le comportement CPE observé avec un exposant de 0,5 que nous avons relié à l’impédance de surface rugueuse due la microstructuration en surface du PET photoablaté. Tous ces résultats expérimentaux ont été confortés par la modélisation en utilisant les circuits électriques équivalents puis par les éléments finis. Ce qui a permis de modéliser à la fois les phénomènes physiques dans le microcanal et à l’interface PET/µ-canal photoablaté. Enfin, deux applications capteur puis biocapteur ont été mises en œuvre en suivant le module de l’impédance à fréquence fixe et en fonction du temps. Comme exemple ; l’étude de la cinétique d’adsorption de la BSA sur le PET et l’étude de la cinétique d’association/ dissociation entre la BSA et l’anti-BSA. / This work is an experimental study and modeling of a microfluidic chip configuration produced by laser photoablation process on a dielectric polymer, polyethylene terephthalate (PET) for new bioanalytical development. This configuration is named "non- contact" wherein two microelectrodes are galvanically isolated in the PET without contact with the streaming electrolyte. Characterization by impedance spectroscopy of the dielectric response of PET alone has concluded that the PET film can be regarded as a constant phase element (CPE). This has permitted a best understanding of the measured impedances in a microfluidic chip under a 100 mV AC excitation in the frequency range between 1 Hz to 1 MHz, which are performed for: an empty microchannel, and a filled microchannel with electrolytes at various ionic conductivities. The results obtained showed a high sensitivity of the impedance measurements in correlation with the electrical conductivity change of the electrolyte. One of the surprising results relating to the identified impedances was a CPE behavior observed with an exponent of 0.5. This latter has been connected to the impedance due to the PET surface roughness. All these experimental results were supported by modeling using the equivalent circuits and by the finite elements. This was used to model both the physical phenomena in the microchannel and at PET interface/? - channel photoablated. Finally, both sensor and biosensor applications have been implemented in the microchip by recording the impedance module at fixed frequency with time. As examples, the investigating of the kinetics of BSA adsorption on the PET and the kinetics of association / dissociation between BSA and anti?BSA have been demonstrated.

É crescente o interesse e a necessidade de substituição de materiais preparados a partir de matéria-prima obtida de fontes fósseis, por materiais oriundos de fontes renováveis, como os compósitos poliméricos reforçados com fibras naturais. Adicionalmente, é acelerada a geração de descarte de embalagens plásticas no país, comparativamente à reciclagem de materiais. Neste contexto, o presente trabalho consistiu na busca pelo aprimoramento de processos de preparação de compósitos baseados em poli (tereftalato de etileno) reciclado (PET reciclado) e fibras de sisal. As fibras de sisal foram caracterizadas segundo o teor de componentes químicos majoritários, difração de raios X, microscopia eletrônica de varredura (MEV), análise térmica (calorimetria exploratória diferencial (DSC) e termogravimetria (TG)) e espectroscopia na região do infravermelho (IV). O PET reciclado foi caracterizado por DSC, TG, IV e determinação do índice de fluidez. Inicialmente, compósitos de PET reciclado/fibras de sisal foram processados via reometria de torque, com posterior termoprensagem, à temperatura de 260ºC, porém foi observada a decomposição térmica das fibras, ou seja, o recobrimento pela matriz não retardou a decomposição das fibras. Consequentemente, visando uma diminuição da temperatura de fusão do PET reciclado (~265ºC), a fim de evitar a decomposição térmica das fibras durante o processamento, os plasticizantes acetil tributil citrato (ATBC), tributil citrato (TBC), glicerol, óleo de mamona (OM) e óleo de soja epoxidado (OSE) foram acrescentados às formulações dos compósitos. Adicionalmente, polibutadieno hidroxilado líquido (PBHL) foi acrescentado à formulação do material, visando avaliar sua ação como agente compatibilizante/de acoplamento na interface fibra-matriz. Destaca-se que estes plasticizantes foram escolhidos por serem oriundos de fontes renováveis, assim como por possuírem grupos nas respectivas estruturas com afinidade tanto por grupos presentes nos componentes da fibra como na matriz. Desta forma a possível ação dos mesmos como compatibilizantes também foi considerada. Os plasticizantes foram caracterizados por DSC, TG e IV. A exploração de parâmetros de processamento, usando plasticizantes, foi feita misturando os componentes usando pás rotativas, seguido de moldagem por compressão. A composição da mistura e parâmetros de processamento, que levaram ao melhor conjunto de resultados, foi considerada para processamento via reometria de torque/termoprensagem. Os compósitos foram caracterizados por MEV, DSC, TG, absorção de água, e com relação às suas propriedades mecânicas por análise térmica dinâmico-mecânica (DMTA), e ensaios de resistência ao impacto e à flexão. Analisando-se os resultados obtidos, observa-se que, com relação aos diferentes processamentos dos compósitos, a moldagem por compressão foi mais adequada para a preparação dos compósitos de PET reciclado/fibras de sisal, principalmente em relação ao superior desempenho mecânico apresentado por estes materiais, em comparação aos compósitos processados por reometria de torque e posterior termoprensagem. O PET reciclado não reforçado, dentre as propriedades mecânicas apresentadas, não apresentou boa resistência ao impacto, assim como os compósitos preparados a partir dele, ou seja, a propriedade do PET reciclado foi predominante nos compósitos. No entanto, o uso de plasticizantes viabilizou não só o processamento dos compósitos à menor temperatura, assim como aumentou a molhabilidade da fibra pelo polímero, por diminuir a viscosidade da mistura. Ainda, no geral, as micrografias das superfícies de fratura dos compósitos demonstraram uma boa adesão na interface fibra-matriz, indicando atuação dos plasticizantes também como compatibilizantes entre fibra e matriz. Destaca-se que, no geral, os resultados de resistência à flexão e DMTA apontaram no sentido de que a presença das fibras e plasticizantes levaram a materiais menos rígidos e mais flexíveis. Dentre os compósitos, pode-se considerar que a mistura PET reciclado/fibras de sisal/glicerol/ TBC apresentou o melhor desempenho mecânico, que levou, no geral, ao melhor resultado de resistência ao impacto, boa resistência à flexão e deformação na ruptura. O compósito de PET reciclado/fibras de sisal, contendo em sua composição somente o plasticizante TBC, também apresentou um bom desempenho frente aos demais compósitos, com o melhor resultado de resistência à flexão, maior módulo de armazenamento e baixo teor de água absorvida. Assim, como pretendido, viabilizou-se o preparo de compósitos de PET reciclado/fibras de sisal, com a adição de diferentes tipos e misturas de plasticizantes, avaliando-se não somente a influência destes, assim como parâmetros de processo, uso de diferentes tipos de processamento e propriedades finais dos materiais gerados. / There is an increasing interest and need for the replacement of materials prepared from raw material obtained from fossil sources by those from renewable sources, such as polymeric composites reinforced with natural fibers. Additionally, the generation of plastic packaging disposal is accelerated in the country compared to materials recycling. In this context, the focus of this investigation was on the search for developing processes for the preparation of composites based on recycled poly (ethylene terephthalate) (recycled PET) and sisal fibers. The sisal fibers were characterized according to the content of major chemical components by X-ray diffraction, scanning electron microscopy (SEM), thermal analysis (differential scanning calorimetry (DSC) and thermogravimetry (TG)) and by infrared spectroscopy (IR). The recycled PET was characterized by DSC, TG, IV and melt index determination. Initially, composites of recycled PET/sisal fibers were processed in a Haake torque rheometer with subsequent thermopressing, at 260ºC, but this method proved to be inefficient, since fiber decomposition was observed, i.e., the decomposition of the fibers was not delayed by the matrix coating. Consequently, by aiming at obtaining a decrease of the melting temperature of the recycled PET (~ 265ºC) in order to avoid thermal decomposition of the fibers during processing, the plasticizers, acetyl tributyl citrate (ATBC), tributyl citrate (TBC), glycerol, castor oil (CO) and epoxidized soybean oil (OSE) were added to the formulations of the composites. In addition, hydroxylated liquid polybutadiene (PBHL) was added to the formulation of the material to evaluate its action as a compatibilizer/coupling agent in the fiber-matrix interface. It is emphasized that these plasticizers were chosen because they come from renewable sources, as well as having groups in the respective structures with affinity for both groups present in components of the fiber and the matrix. Thus the possible action of plasticizers as compatibilizers was also considered. The plasticizers were characterized by DSC, TG and IV. The exploitation of processing parameters using plasticizers was made by mixing the components using shovels, followed by compression molding. The composition of the mixture and the processing parameters, which led to the best set of results, were considered for processing via torque rheometry/thermopressing. The composites were characterized by SEM, DSC, TG, water absorption, and regarding their mechanical properties, by dynamic mechanical thermal analysis (DMTA) and impact and flexural strength. Analyzing the results, it is observed that when it comes to different processes of composites, compression molding was the most suitable for the preparation of the composites of recycled PET/sisal fibers, especially in relation to the superior mechanical performance presented by these materials compared to composites processed by torque rheometry and subsequent thermopressing. The non-reinforced recycled PET, among the mechanical properties shown, did not show a good impact strength, nor did the composites prepared from it, i.e., the property of recycled PET in the composites was predominant. However, not only did the use of plasticizers allow the processing of the composites at a lower temperature, but also it increased the wettability of the polymer-fiber by reducing the viscosity of the mixture. Still, in general, the SEM images of fractured surfaces of the composites showed a good adhesion between fiber-matrices, indicating activity of plasticizers and also compatibilizers between fiber and matrix. It is noteworthy that, in general, the results of flexural strength and DMTA pointed out that the presence of plasticizers led to less rigid and more flexible materials. Among the composites, it can be assumed that the mixture recycled PET/sisal fibers/glycerol/TBC presented the best mechanical performance, which in general led to the best result of impact strength, good flexural strength and fracture strain. The composite of recycled PET/sisal fibers in its composition, containing only the TBC plasticizer, also performed well compared to other composites, with the best result of flexural strength, higher storage modulus and low moisture absorption. Thus, as desired, the preparation of composites based on recycled PET/sisal fibers with the addition of different types and mixtures of plasticizers was enabled, evaluating not only their influence but also process parameters, the use of different types of processing and the final properties of the generated materials.

O poli(tereftalato de etileno), PET, é um material polimérico importante, largamente utilizado na produção de garrafas para refrigerante e água mineral. Entretanto, a destinação das embalagens de PET pós-consumo vem criando sérias preocupações econômicas e ambientais. Uma das alternativas de destino desse material é a reciclagem química por glicólise, tendo como objetivo a produção do monômero tereftalato de bis-hidroxietila (BHET). Esta reação, embora referenciada, ainda apresenta problemas como rendimento de BHET e tempo de reação, entre outros, tendo como desafio o desenvolvimento de novos catalisadores eficientes e altamente seletivos. Dentro deste contexto, o presente trabalho busca estudar a atividade catalítica de um material nanoestruturado, os nanotubos de titanatos (TNT), na glicólise de PET (virgem e pós-consumo) comparado ao acetato de zinco (catalisador mais utilizado citado em literatura), a otimização de alguns parâmetros reacionais (granulometria de PET pós-consumo, razão Etilenoglicol:PET, porcentagem molar de TNT) e uma modificação dos nanotubos com zinco (ZnTNT) na despolimerização do PET Para a caracterização dos produtos as principais técnicas utilizadas foram a Calorimetria Exploratória Diferencial (DSC), Análise Termogravimétrica (TGA) e Ressonância Magnética Nuclear (RMN), além de resultados de rendimento, turnover number (TON) e turnover frequency (TOF). A despolimerização ocorreu por reação de glicólise utilizando PET virgem e pós-consumo e etilenoglicol para diferentes tempos a uma temperatura de 196°C. Os principais resultados mostram os TNT como catalisadores promissores, apresentando rendimentos em BHET de 83,9 e 76,7%, para PET virgem e pós-consumo, respectivamente, para 3 horas de reação. Esses valores são equiparáveis aos obtidos quando utilizado acetato de zinco, em que foi alcançado 79,4% (PET virgem) e 80,8% (PET pós-consumo). Após a modificação dos TNT com zinco, os resultados de rendimento em BHET alcançaram 87,1% para 3 horas de reação na menor granulometria estudada, demonstrando ser um catalisador ainda mais eficiente para essa reação. / Polyethylene terephthalate, PET, is an important polymer material, widely used in the production of bottles for soda and mineral water. However, the disposal of post-consumer PET packaging has created serious economic and environmental concerns. One of the alternatives for the disposal of this material is the chemical recycling by glycolysis, aiming the production of the monomer bis-(2hydroxyethyl) terephthalate (BHET). This reaction, although referenced, still presents problems such as BHET yield and reaction time, among others, having as challenge the development of new efficient and highly selective catalysts. In this context, the present work aims to study the catalytic activity of a nanostructured material, the titanate nanotubes (TNT) in PET glycolysis (virgin and post-consumer) compared to zinc acetate (the most used catalyst cited in literature), the study of some reaction parameters (post-consumer PET granulometry, Ethylene glycol:PET ratio and TNT molar percentage) and a modification of the catalyst with zinc (ZnTNT) in the depolymerization of PET For the characterization of the products, the main techniques used were Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Nuclear Magnetic Resonance (NMR), as well as yield, turnover number (TON) and turnover frequency (TOF) results. The depolymerization occurred by glycolysis reaction using virgin and post-consumer PET and ethylene glycol at different times at a temperature of 196°C. The main results show TNT as promising catalysts, with yields of BHET yields of 83.9 and 76.7%, for virgin and post-consumer PET, respectively, for 3 hours of reaction. These values are similar to those obtained when zinc acetate was used, in which 79.4% (virgin PET) and 80.8% (post-consumer PET) were reached. After the modification of the TNT with zinc, the yield results in BHET reached 87.1% for 3 hours of reaction at the smaller particle size studied, proving itself to be an even more efficient catalyst for this reaction.

Introduction: Despite the relatively low dose (0.5 mSv – 1 mSv) generated by Attenuation Correction CT (ACCT) in PET examinations, the ALARA principle is still applicable. The currently used ACCT standard protocol at the Karolinska University Hospital in Solna uses 7.6 effective mAs (mAseff) and 120 kVp, but reducing mAseff and/or kVp would decrease patient dose as well as facilitate an increased number of research subjects. A CT reconstruction algorithm called Quantification Achieved Consistently (Q.AC.) (Lonn, 2012) has recently been developed to enable reduced doses from ACCT, while preserving quantitative PET data. The purposes of this study were to investigate possible limitations of the Q.AC. with respect to patient size, and to optimise protocols, aiming at minimising ACCT dose in terms of Volumetric Computer Tomography Dose Index CTDIvol. Methods: Measurements were performed with a GE PET/CT Discovery system, which offers Q.AC. reconstruction. The NEMA NU-2 protocol was followed to quantify PET quality, including evaluations of relative count error in the artificial lung in the phantom centre (lung), hot- and cold-sphere contrast (Q), and background variability (N). Two phantoms were used; the NEMA body phantom (elliptical cross section sized 30 cm laterally and 23 cm anterior-posterior (AP)), here representing paediatric patients and small-sized adults, and the same phantom with an additional (20 cm laterally and 4 cm AP) ellipsoid plastic (PMMA) extension ring, representing mid- and large-sized patients. ACCTs were acquired with 15 mAseff values, range [2.3 - 260], in combination with four kVp values [80, 100, 120, 140] and reconstructed with two algorithms (Q.AC. and a regular soft CT algorithm). Consequently, PET reconstructions were performed based on each mAseff, kVp and CT-reconstruction combination. Results: Quantitatively similar PET results to the standard protocol were achieved with the Q.AC. CT reconstruction algorithm using a CTDIvol = 0.06 mGy (2.3 mAseff and 80 kVp) for the NEMA body phantom, respectively a CTDIvol = 0.20 mGy (2.3 mAseff and 120 kVp) for the phantom with additional extension ring. Conclusions: This study indicates that the Q.AC. CT reconstruction algorithm enables accurate PET results at lower ACCT mAseff and kVp settings than the currently used clinical standard protocol. For paediatric patients and small-sized adults, a reduction of CTDIvol by approximately 90% may be achieved, while for mid- and large-sized patients, the CTDIvol can be reduced by approximately 70% without loss of quantitative PET data.

Alterations in the dopaminergic system have been implicated in both animal and human obesity. However, to date, a comprehensive model on the nature and functional relevance of this relationship is missing. In particular, human data remain equivocal in that seemingly inconsistent reports exist of positive, negative or even no relationships between dopamine D2/D3 receptor availability in the striatum and measures of obesity. Further, data on receptor availability have been commonly interpreted as reflecting receptor density, despite the possibility of an alternative interpretation, namely alterations in the basal levels of endogenous dopaminergic tone. Here, we provide a unifying framework that is able to explain the seemingly contradictory findings and offer an alternative and novel perspective on existing data. In particular, we suggest (i) a quadratic relationship between alterations in the dopaminergic system and degree of obesity, and (ii) that the observed alterations are driven by shifts in the balance between general dopaminergic tone and phasic dopaminergic signalling. The proposed model consistently integrates human data on molecular and behavioural characteristics of overweight and obesity. Further, the model provides a mechanistic framework accounting not only for the consistent observation of altered (food) reward–responsivity but also for the differences in reinforcement learning, decision-making behaviour and cognitive performance associated with measures of obesity.

Background: Serotonin (5-HT) and its neurotrophic support system, specifically brain-derived neurotrophic factor (BDNF), are thought to modulate energy homeostasis and susceptibility to obesity. Moreover, a polymorphism (5-HTTLPR) in the serotonin reuptake transporter (5-HTT) gene impairs its transcription, thereby altering serotonergic tone and potentially contributing to such susceptibility. This study aims to investigate the effect of BDNF, biallelic 5-HTTLPR, and central in-vivo 5-HTT availability in highly obese versus non-obese subjects using positron emission tomography (PET) and 5-HTT selective [11C]DASB. Methods: Thirty-eight subjects, 24 obese (body mass index, BMI, >35 kg/m2), otherwise mentally and physically healthy, and 14 non-obese (BMI ≤ 25 kg/m2), age- and sex-matched healthy controls were included in this study. Parametric images of binding potential were generated from PET data. Central 5-HTT availability, 5-HTTLPR genotype, and serum BDNF concentrations were analyzed, first in a volume of interest, then in a voxel-wise manner. Results: Overall, our results showed an absence of a linear correlation between BDNF, in-vivo central 5-HTT availability, and body mass index (BMI). 5-HTTLPR genotyping revealed BDNF and hippocampal 5-HTT availability to be negatively correlated (r = −0.57, p = 0.007) in long allelic homozygotes. However, obese subjects exhibited opposing effects of BDNF levels on 5-HTT availability in the nucleus accumbens (NAcc) relative to our non-obese controls. Conclusions: Our data did not confirm an overall correlation between serum BDNF, in-vivo central 5-HTT availability, 5-HTTLPR, and BMI. However, there is evidence that serotonergic tone linked to BDNF, specifically in the NAcc, is involved in the pathophysiology of obesity, although this needs further exploration over a wide range of reward-related eating behaviors.