Desenvolvimento de materiais para reatores eletroquímicos cerâmicos de temperatura reduzida

Electrochemical membrane reactors using proton-conducting ceramics are promising and efficient technologies for the production of valuable chemical products by the promotion of hydrogenation/dehydrogenation reactions. Due to a very high equilibrium constant for hydration, yttrium-doped barium cerate, BaCe0.9Y0.1O3-δ (BCY10) presents one of the highest proton conductivities at low temperatures of the known proton-conducting ceramic oxides (e.g. ~ 10-3 S cm-1 at 400 °C under humidified atmospheres, pH2O ~ 10-2 atm). Nonetheless, BCY10 is commonly discarded for such applications due to its poor chemical stability towards hydroxide or carbonate formation. Moreover, the use of humidified atmospheres may not be feasible for many chemical syntheses, due to undesired side reactions. The current work, therefore, focus on the electrochemical transport properties of BCY10 in conditions of very low humidity (pH2O < 10-4 atm and at low temperatures < 600 °C). The analyses include the study of the defect chemistry for this composition as a function of potential working conditions, and its relation to the partial conductivities of the bulk properties. Further work corresponds to the examination of the specific grain boundary conductivities in terms of space charge properties, as a function of temperature and atmosphere. The implications of all these properties of BCY10 are then exemplified in two working examples: i) the study of new La4Ni3O10-d-based cathodes for proton ceramic applications, using symmetrical cells made of BCY10 substrates, where the polarisation resistance of the electrode must be corrected for significant electronic leakage by taking into account the electronic transport number of the electrolyte; ii) the study of a single-cell made of thin film BCY10 electrolyte under both electrolyser and fuel cell/ion pump modes, where these modes of operation are shown to cause variations in both electrolyte and electrode resistances. The conditions used to study BCY10 are comprehensively justified in each chapter by thermodynamic calculations to be able to prevent the decomposition of the ceramic phase in contact with atmospheres containing hydrocarbons or acidic gases such as CO2 and H2O. Moreover, the relevance of such conditions is highlighted with respect to potential to apply this material to industrially relevant chemical synthesis reactions, while retaining hydration and high protonic conductivity. This work, thereby, unlocks a new application area for proton-conducting ceramics to a wide range of hydrogenation/de-hydrogenation reactions at low temperatures under minimum water vapour partial pressures.Os reatores eletroquímicos de membrana cerâmica protónica são tecnologias promissoras e eficientes para a produção de produtos químicos valiosos através da promoção eletroquímica de reações de hidrogenação/desidrogenação. Devido à sua elevada constante de equilíbrio para a hidratação, o cerato de bário dopado com ítria, BaCe0,9Y0,1o3-δ (BCY10) apresenta uma das mais altas condutividades protónicas a baixas temperaturas, entre os óxidos cerâmicos condutores protónicos mais conhecidos (p.e., ~ 10-3 S cm-1 a 400 °C em atmosferas humidificadas, pH2O ~ 10-2 atm). Contudo, o BCY10 é comumente descartado para tais aplicações devido à sua fraca estabilidade química para a formação de hidróxido ou carbonato. Além disso, o uso de atmosferas humidificadas pode não ser viável para muitas sínteses químicas, devido a reações secundárias indesejáveis. Este trabalho, portanto, centra-se nas propriedades de transporte eletroquímico do BCY10 em condições de humidade muito baixa (pH2O < 10-4 atm e baixas temperaturas < 600 °C). As análises incluem o estudo da química de defeitos para esta composição em função das possíveis condições de trabalho, e a sua relação com as condutividades parciais das propriedades em bulk. O trabalho prossegue com a análise das condutividades específicas da fronteira de grão em termos das propriedades da dupla camada elétrica em função da temperatura e da atmosfera. As implicações de todas estas propriedades do BCY10 são então exemplificadas em dois exemplos de trabalho: i) o estudo de novos cátodos à base de La4Ni3O10-d para aplicações de cerâmicos protónicos, utilizando células simétricas de substratos BCY10, em que a resistência de polarização do eléctrodo deve ser corrigida devido à existência de curto-circuito no eletrólito, tendo em conta o número de transporte eletrónico do mesmo; ii) o estudo de uma célula completa feita de uma película fina de BCY10 em ambos os modos eletrolizador e pilha de combustível/bombagem iónica, em que cada um pode causar diferentes alterações nas resistências do eletrólito e dos elétrodos. As condições utilizadas para o estudo do BCY10 são justificadas de forma compreensível em cada capítulo através de cálculos termodinâmicos, mostrando que é possível prevenir a decomposição da fase cerâmica em contato com atmosferas contendo hidrocarbonetos ou gases ácidos, p.e. CO2 e H2O. Além disso, destaca-se a relevância de tais condições no que diz respeito à possibilidade de aplicar este material em reações de síntese química industrialmente relevantes, mantendo hidratação e condutividade protónica elevadas. Este trabalho desbloqueia, assim, uma nova área de aplicação para os cerâmicos condutores protónicos a uma vasta gama de reações de hidrogenação/de-hidrogenação a baixas temperaturas e pressões parciais mínimas de vapor de água.Programa Doutoral em Engenharia da Refinação, Petroquímica e Químic

Efeito da composição no transporte iónico em eletrólitos compósitos

Mestrado em Engenharia de MateriaisOs eletrólitos compósitos constituídos por uma matriz cerâmica de céria e uma mistura de carbonatos alcalinos têm vindo a justificar algum interesse na área das pilhas de combustível. A possibilidade de funcionarem a temperaturas intermédias (400 - 600 °C) permite a utilização de materiais convencionais na construção destes dispositivos, uma das vantagens destes novos sistemas. Contudo, o mecanismo de condução nestes materiais permanece ainda incerto. Conhece-se o transporte de iões óxido e carbonatos, mas não é claro o possível papel da condução protónica. O presente trabalho pretendeu explorar a modificação desta região por via composicional, testando o efeito de óxidos alternativos na condutividade iónica do eletrólito. Estes óxidos foram selecionados numa lógica de afinidade com alguns dos eletrólitos mais utilizados em pilhas de combustível (ZrO2 e CeO2) e caráter ácido-base diverso (a saber: Y2O3, La2O3, Gd2O3, Dy2O3, Yb2O3, Ce0,9Gd0,1O2-, HfO2 e TiO2). Os novos compósitos foram avaliados em termos de estabilidade química entre os seus dois componentes por uma combinação de técnicas analíticas, nomeadamente difração de raios X, espetroscopia do infravermelho e Raman. O comportamento elétrico de misturas selecionadas foi caracterizado por espetroscopia de impedância, estudando-se a influência da atmosfera (ar, CO2, O2 e N2-H2) na condutividade. Os resultados mostram uma forte dependência da condutividade em função da atmosfera envolvente, verificando-se um notável efeito ligado à instabilidade química do compósito. De todos os materiais estudados, o compósito à base de Yb2O3 é o único estável nas diferentes atmosferas e temperaturas, apresentando uma condutividade na ordem dos 0,1 S.cm-1 a 580 °C, semelhante ao valor para o eletrólito de referência à base de Ce0,9Gd0,1O2-. Esta descoberta abre uma pista promissora para o estudo deste tipo de materiais e fenómenos relacionados.Composite electrolytes based on a ceria ceramic matrix and a mixture of alkaline carbonates deserve growing interest in field of fuel cells. The target intermediate operating temperature (400-600 °C) is sufficiently low to avoid the use of expensive cell and stack materials, being one of the advantages of these systems. However, the conduction mechanism in these materials still remains uncertain. The transport of oxide and carbonate ions is expected, but the possibility of proton conduction is still under debate. This work attempted the modification of this region by compositional effects, testing various possibilities of alternative ceramic materials with affinity with some of the best known electrolytes used in fuel cells (ZrO2 and CeO2), and screening a wide range of acid-basic oxides (exactly Y2O3, La2O3, Gd2O3, Dy2O3, Yb2O3, Ce0.9Gd0.1O2-, HfO2 and TiO2). The new composites were assessed with respect to their chemical stability, namely by X-ray diffraction and Raman and infra-red spectroscopies. The electrical behavior was studied by impedance spectroscopy in air, CO2, N2, O2 and N2-H2 gas mixtures. The impedance results showed a strong dependence of the conductivity on the surrounding environment, with remarkable effects related to the chemical stability of the composites. Amongst the oxides tested, Yb2O3 is apparently the only one stable under different atmospheres and temperatures, showing conductivity in the order of 0,1 S.cm-1 at 580 °C, identical to that of the conventional Ce0.9Gd0.1O2--based composite. This finding opens a promising research direction to proceed with the study of these materials and related effects

Destilador solar destinado a fornecer água potável para as famílias de agricultores de base familiar.

Com o objetivo de fornecer água potável aos agricultores do Semiárido do Nordeste Brasileiro, estudou-se a viabilidade técnica de um destilador solar no processo de dessalinização de água para consumo humano constituído de um coletor solar para aquecimento de água salina. Foram avalizados dois métodos de condução do fluxo de água do coletor solar para o tanque de evaporação. No Método 1 (M1) o fluxo de água foi constante (1L h-1), mantendo-se um lâmina de 10mm no interior da caixa de alvenaria. No Método 2 (M2) o fluxo de água, advindo do coletor solar, ocorria apenas às 15 horas quando o destilador/condensador era abastecido com água quente advinda do coletor solar, e após o abastecimento o fluxo de água era interrompido. Os volumes de água destilada produzida no sistema são suficientes para atender as necessidades de água destinada ao consumo direto de uma família na zona rural. Em termos médios a produção de água destilada por radiação solar incidente no sistema em M2 foi 46,87% maior que em M1

Prevalence of asymptomatic urethritis by Chlamydia trachomatis and Neisseria gonorrhoeae and associated risk factors among males living with HIV-1

Objectives The increase in HIV transmissibility in non-ulcerative sexually transmitted infection is already well-established. It is estimated that symptomatic carriers of N. gonorrhoeae and C. trachomatis have a relative risk of 4.8-fold and 3.6-fold, respectively, for the sexual acquisition of HIV. This type of evaluation for asymptomatic urethritis is necessary to reinforce strategies to combat HIV transmission. This study aims to assess the prevalence of patients with asymptomatic urethritis among men diagnosed with HIV-1 and determine the risk factors associated with this infection. Methods We enrolled a total of 115 male patients aged 18 years or older who have been diagnosed with HIV infection and have no symptoms of urethritis or other sexually transmitted infections and who have been evaluated between May and August 2015 in a follow-up visit at the Immunology Outpatient Clinic of a Brazilian University Hospital. Results Four asymptomatic patients were positive for C. trachomatis and were considered asymptomatic carriers of urethritis. Prevalence was 3.47%. Patients who were positive for C. trachomatis urethritis had a lower mean age (p = 0.015). Conclusion The presence of asymptomatic sexually transmitted infection is a challenge in clinical practice. We recommend that, in outpatient practice, the habit of inquiring on previous sexual behavior to obtain more information about risks and associations with asymptomatic sexually transmitted infection, a routine physical examination and complementary tests to detect STI pathogens should be performed to discard these conditions. The development of rapid tests for this purpose should also be encouraged

Chlamydia trachomatis asymptomatic urethritis recurrence among males living with HIV-1

A prevalence of 3.47% of asymptomatic Chlamydia trachomatis urethritis has been previously reported among males living with HIV infection in Brazil. This study aims to assess the recurrence of C. trachomatis urethritis three years later in the same cohort of patients and analyze associated risk factors. A total of 115 male patients diagnosed with HIV infection, with no symptoms of urethritis and observed since May of 2015 in followup visits were enrolled. They had urine samplers tested by PCR for C. trachomatis and N. gonorrhoeae between February and March 2018. Results: Three of the four patients who had asymptomatic C. trachomatis urethritis three years before were recurrently positive for C. trachomatis urethritis. Two new patients were diagnosed as positives, accounting for a total asymptomatic C. trachomatis urethritis prevalence of 4.34%. The prevalence during the whole study was 5.21%. The relative risk for a new urethritis episode among those previously diagnosed with urethritis is RR=41.62 (95% CI: 9.42-183.84), p &lt; 0.01. Patients who presented asymptomatic urethritis anytime and who were recurrently positive for C. trachomatis had a lower mean age (p&lt;0.01). Married individuals were protected regarding asymptomatic urethritis [p&lt;0.01, OR = 0.04 (0.005-0.4)] and had lower risk to develop recurrence [p&lt;0.01, RR = 0.86 (0.74-0.99)]. Illicit drugs users had risk associated to asymptomatic urethritis [p=0.02, OR= 5.9 (1.03-34)] and higher risk to develop recurrence [p&lt;0.01, RR=1.1 (1-1.22)]. Conclusion: The recurrence of asymptomatic C. trachomatis urethritis after treatment among males living with HIV infection in Brazil can be considered high and should not be neglected

MAMMALS IN PORTUGAL : A data set of terrestrial, volant, and marine mammal occurrences in P ortugal

Mammals are threatened worldwide, with 26% of all species being includedin the IUCN threatened categories. This overall pattern is primarily associatedwith habitat loss or degradation, and human persecution for terrestrial mam-mals, and pollution, open net fishing, climate change, and prey depletion formarine mammals. Mammals play a key role in maintaining ecosystems func-tionality and resilience, and therefore information on their distribution is cru-cial to delineate and support conservation actions. MAMMALS INPORTUGAL is a publicly available data set compiling unpublishedgeoreferenced occurrence records of 92 terrestrial, volant, and marine mam-mals in mainland Portugal and archipelagos of the Azores and Madeira thatincludes 105,026 data entries between 1873 and 2021 (72% of the data occur-ring in 2000 and 2021). The methods used to collect the data were: live obser-vations/captures (43%), sign surveys (35%), camera trapping (16%),bioacoustics surveys (4%) and radiotracking, and inquiries that represent lessthan 1% of the records. The data set includes 13 types of records: (1) burrowsjsoil moundsjtunnel, (2) capture, (3) colony, (4) dead animaljhairjskullsjjaws, (5) genetic confirmation, (6) inquiries, (7) observation of live animal (8),observation in shelters, (9) photo trappingjvideo, (10) predators dietjpelletsjpine cones/nuts, (11) scatjtrackjditch, (12) telemetry and (13) vocalizationjecholocation. The spatial uncertainty of most records ranges between 0 and100 m (76%). Rodentia (n=31,573) has the highest number of records followedby Chiroptera (n=18,857), Carnivora (n=18,594), Lagomorpha (n=17,496),Cetartiodactyla (n=11,568) and Eulipotyphla (n=7008). The data setincludes records of species classified by the IUCN as threatened(e.g.,Oryctolagus cuniculus[n=12,159],Monachus monachus[n=1,512],andLynx pardinus[n=197]). We believe that this data set may stimulate thepublication of other European countries data sets that would certainly contrib-ute to ecology and conservation-related research, and therefore assisting onthe development of more accurate and tailored conservation managementstrategies for each species. There are no copyright restrictions; please cite thisdata paper when the data are used in publications.info:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Mammals in Portugal: a data set of terrestrial, volant, and marine mammal occurrences in Portugal

Mammals are threatened worldwide, with ~26% of all species being included in the IUCN threatened categories. This overall pattern is primarily associated with habitat loss or degradation, and human persecution for terrestrial mammals, and pollution, open net fishing, climate change, and prey depletion for marine mammals. Mammals play a key role in maintaining ecosystems functionality and resilience, and therefore information on their distribution is crucial to delineate and support conservation actions. MAMMALS IN PORTUGAL is a publicly available data set compiling unpublished georeferenced occurrence records of 92 terrestrial, volant, and marine mammals in mainland Portugal and archipelagos of the Azores and Madeira that includes 105,026 data entries between 1873 and 2021 (72% of the data occurring in 2000 and 2021). The methods used to collect the data were: live observations/captures (43%), sign surveys (35%), camera trapping (16%), bioacoustics surveys (4%) and radiotracking, and inquiries that represent less than 1% of the records. The data set includes 13 types of records: (1) burrows | soil mounds | tunnel, (2) capture, (3) colony, (4) dead animal | hair | skulls | jaws, (5) genetic confirmation, (6) inquiries, (7) observation of live animal (8), observation in shelters, (9) photo trapping | video, (10) predators diet | pellets | pine cones/nuts, (11) scat | track | ditch, (12) telemetry and (13) vocalization | echolocation. The spatial uncertainty of most records ranges between 0 and 100 m (76%). Rodentia (n =31,573) has the highest number of records followed by Chiroptera (n = 18,857), Carnivora (n = 18,594), Lagomorpha (n = 17,496), Cetartiodactyla (n = 11,568) and Eulipotyphla (n = 7008). The data set includes records of species classified by the IUCN as threatened (e.g., Oryctolagus cuniculus [n = 12,159], Monachus monachus [n = 1,512], and Lynx pardinus [n = 197]). We believe that this data set may stimulate the publication of other European countries data sets that would certainly contribute to ecology and conservation-related research, and therefore assisting on the development of more accurate and tailored conservation management strategies for each species. There are no copyright restrictions; please cite this data paper when the data are used in publications