Resumo Este artigo teve como foco a estimativa de propriedades mecânicas essenciais à concepção de estruturas de concreto mediante um modelo confiável de predição da resistência à compressão, à tração e à flexão de concreto reforçado com fibra de aço (CRFA) utilizando redes neurais artificias (RNA), bem como avaliar a influência do teor de fibras nessas propriedades. A pesquisa utilizou um banco de dados com 57 estudos experimentais descritos na literatura, sendo implementado um modelo de rede neural com 12 variáveis de entrada, 1 de saída e 2 camadas ocultas com 16 neurônios. Como resultados, obtiveram-se as seguintes métricas indicadoras da qualidade do ajuste: um erro quadrático médio (MSE) de 22,63, 0,08 e 0,80, e um erro absoluto médio (MAE) de 3,64, 0,24 e 0,74 respectivamente para as resistências à compressão, à tração e à flexão. A análise da sensibilidade evidenciou que houve aumento considerável nas resistências à tração e à flexão com uso de fibras, o que é esperado. Os resultados confirmaram a capacidade de o modelo reproduzir de forma confiável as propriedades mecânicas do CRFA.

Abstract The aim of this paper was to estimate the mechanical properties essential to the design of concrete structures through a reliable prediction model of the compressive, tensile and flexural strengths of concrete steel fiber reinforced concrete (CFRC) using Artificial Neural Networks (ANN), and also to evaluate the influence of the fiber content on these properties. The study used a database with 57 experimental studies from the literature, implementing a neural network model with 12 input variables, 1 output and 2 hidden layers with 16 neurons. The results obtained were a mean square error (MSE) of 22.63, 0.08 and 0.80, and a mean absolute error (MAE) of 3.64, 0.24 and 0.74, respectively, for the compressive, tensile and flexural strengths. The sensitivity analysis showed that there was a considerable increase in tensile and flexural strengths with the use of fibers, which was expected. The results confirmed the model's ability to reliably reproduce the mechanical properties of the CFRC.

SUMMARY OBJECTIVE: A multicentric, cross-sectional study was carried out to determine the prevalence and risk factors for Coronavirus disease 2019 in medical students and residents from four universities and affiliated hospitals in Brazil. METHODS: A survey about contamination risk and symptoms was sent to all participants through email and WhatsApp. Prevalence was measured by the self-report of positive polymerase chain reaction or serological test. Univariate and multivariate analyses were performed, and odds ratio and 95% confidence interval were calculated. RESULTS: Prevalence of infection by Sars-CoV-2 was 14.9% (151/1011). The disease was more prevalent in residents and interns than in undergraduate students. Contact with an infected relative outside the hospital or with colleagues without using personal protective equipment was associated with higher contamination. Contact with patients without wearing goggles and higher weekly frequency of contact were the two factors independently associated with the infection by Coronavirus disease 2019 in the multivariate analysis. CONCLUSIONS: Medical students, interns, and residents have a higher prevalence of Coronavirus disease 2019 than the general population, in which the last two groups are significantly at higher risk. Contacting patients at a higher weekly frequency increases the risk for infection. The use of goggles should be reinforced when contacting patients.

Resumo Racional A colite de desuso é frequente em nosso meio e o tratamento de maior eficácia é de alto custo, havendo necessidade de se encontrar uma terapêutica eficaz e de baixo custo. Objetivo Avaliar a eficácia da Baccharis dracunculifolia (alecrim-do-campo) no tratamento da colite de exclusão em ratos. Método Utilizou-se 18 ratos Wistar, os quais foram anestesiados e submetidos à colostomia; em seguida distribuídos em 2 grupos: Grupo Controle, recebendo infusão intrarretal de solução salina (n = 8) e Grupo BD, recebendo infusão intrarretal de extrato de Baccharis dracunculifolia (n = 10); após 21 dias de tratamento foram submetidos a eutanásia, o segmento intesinal excluso de trânsito intestinal foi ressecado e submetido a estudo histopatológico classificando-se o grau de inflamação e grau de congestão vascular de 0 a 3. Resultados Verificou-se média de inflamação 2,7 no Grupo Controle vs. 2,1 no Grupo BD (p = 0,049), enquanto as médias de congestão vascular foram 2,3 e 2, respectivamente, nos grupos controle e BD (p = 0,1642). Conclusão A infusão intrarretal do extrato de Baccharis dracunculifolia minimizou significantemente o processo inflamatório na colite de exclusão de ratos submetidos à colostomia, sem alterar o grau de congestão vascular.

Abstract Rationale Disuse colitis is frequent in our country and the most effective treatment is high cost and there is a need for effective and low cost therapy. Objective To evaluate the efficacy of Baccharis dracunculifolia (field rosemary) in the treatment of exclusion colitis in rats. Method Eighteen Wistar rats were anesthetized and submitted to colostomy; they were then distributed into two groups: Control Group, receiving intrarectal saline infusion (n = 8) and Group BD receiving intrarectal infusion ofBaccharis dracunculifolia extract (n = 10); after 21 days of treatment they were euthanized, the intestinal segment excluded from intestinal transit was resected and submitted to histopathological study, classifying the degree of inflammation and degree of vascular congestion from 0 to 3. Results Mean inflammation was 2.7 in Control Group versus 2.1 in BD Group (p = 0.049), while mean vascular congestion was 2.3 and 2, respectively, in Control and BD groups (p = 0.1642). Conclusion Intra-rectal infusion ofBaccharis dracunculifolia extract significantly minimized the inflammatory process in the exclusion colitis of rats submitted to colostomy, without altering the degree of vascular congestion.

ABSTRACT Expansive clay soils are a problem for agriculture and engineering because they are susceptible to change in volume due to seasonal variation in water content and temperature. One of its morphological properties is slickensides, which result from the ability to contract and crack when dry and expand by wetting. The objective of this study was to evaluate the processes of expansion and formation and propagation of cracks due to the change in water content over time. The expansion process was evaluated through simple edometric tests with different external stress values applied to undisturbed soil samples. To evaluate the shrinking process, a device was developed to monitor the process of crack propagation. The mechanisms through which cracks begin and develop were studied using molded soil samples at the liquidity limit and at 1.25 times the liquidity limit with a drying and wetting cycle. Crack initiation conditions and development of geometric crack indices were measured with the water content and drying time. The soil presented medium to high expansion that depends on the overburden and suction applied, and the swelling stress was found to increase as suction increases. The changes in volume due to wetting and the propagation of cracks due to drying developed in three stages: initial, primary, and secondary. In the initial stage, few cracks or swelling occur with gradual variation in water content. As the water content approaches the limit of soil contraction (in the drying process) or the limit of soil saturation (in the wetting process), cracks and expansion developed slowly and approach a secondary stage. In the primary stage, cracks and expansion occurred rapidly with drying or wetting, respectively. Drying and wetting cycles showed similar crack patterns with the appearance of new micro-cracks during each new drying cycle.

RESUMO Racional: A colite de exclusão é ainda muito frequente em nosso meio, uma vez que a confecção de estomas é prática comum especialmente em situações de trauma. Em consequência, há necessidade de tratamento para a colite de desuso. Objetivo: Avaliar o efeito terapêutico da infusão retal de Curcuma longa (açafrão-da-terra) no segmento intestinal excluso de ratos. Método: Utilizou-se 18 ratos Wistar submetidos à colostomiae distribuídos em dois grupos: grupo controle, recebendo infusão intrarretal de solução salina (n=8) e grupo CL, recebendo infusão intrarretal de extrato de Curcuma longa (n=10). Após 21 dias de tratamento foram submetidos a eutanásia; o segmento intestinal excluso de trânsito intestinal foi ressecado e submetido a estudo histopatológico classificando-se os graus de inflamação e de congestão vascular. Resultados: Verificou-se média de inflamação 2,7 no grupo controle vs. 2,6 no grupo CL (p=0,3125), enquanto as médias de congestão vascular foram 2,3 e 2,1, respectivamente, nos grupos controle e CL (p=0,1642). Conclusão: A infusão intrarretal do extrato de Curcuma longa não foi capaz de minimizar o processo inflamatório ou a congestão vascular na colite de exclusão de ratos submetidos a colostomia.

ABSTRACT Background: Diversion colitis is still very common in our country, since the stoma creation is a common practice especially in situations of trauma. needing treatment for this condition. Aim: To evaluate the therapeutic effect of rectal infusion of Curcuma longa (turmeric) in the excluded intestinal segment of rats. Method: Eighteen Wistar rats were used and submitted to colostomy: control group (n=8) under rectal saline infusion and group CL, receiving intra-rectal infusion of Curcuma longa extract (n=10). After 21 days of treatment they were submitted to euthanasia; the intestinal segment excluded from intestinal transit was resected and sent to histopathological evaluation, classifying the degree of inflammation and of vascular congestion. Results: The average of inflammation was 2.7 in the control group vs. 2.6 in the CL group (p=0.3125), while the mean vascular congestion was 2.3 and 2.1, respectively, in the control and CL groups (p=0.1642). Conclusion: Intra-rectal infusion of Curcuma longa extract was not able to minimize the inflammatory process or vascular congestion in the diversion colitis of rats subjected to colostomy.

OBJETIVO: Estudar o efeito do sildenafil, administrado previamente à isquemia/reperfusão (I/R) renal, em avaliações cintilográficas e histopatológicas em ratos. MÉTODOS: Vinte e quatro ratos Wistar foram aleatoriamente distribuídos em dois grupos. Os animais receberam 0,1 ml IV de 99mTecnécio-Etilenodicisteína, foram submetidos à cintilografia renal inicial e em seguida submetidos a isquemia no rim esquerdo, com oclusão da artéria renal, durante 60 minutos, com posterior reperfusão. O grupo sildenafil (n=12) recebeu previamente 1mg/kg de sildenafil em suspensão 60 minutos antes da isquemia. Solução salina 0,9% foi administrada no grupo controle (n=12). Metade dos animais de cada grupo foi avaliada após 24 horas e a outra metade após sete dias de reperfusão, com nova cintilografia renal. Após eutanásia, os rins foram retirados e submetidos a exame histopatológico. Na avaliação estatística foram empregados os testes t de Student e de Mann-Whitney. RESULTADOS: Foi observado no rim esquerdo (submetido a I/R) do grupo controle déficit funcional diferencial nas imagens cintilográficas após sete dias, com padrão de necrose tubular aguda, quando comparado com a cintilografia inicial (p<0,05). O tratamento com sildenafil resultou em melhor função diferencial do rim esquerdo 24h após reperfusão, comparado com os controles. Na histopatologia, os rins esquerdos dos animais do grupo controle (24 horas pós-I/R), apresentaram maior grau de necrose celular quando comparados com o grupo tratado com o sildenafil (p<0,05). CONCLUSÃO: O sildenafil teve efeito protetor em rins de ratos submetidos à isquemia/reperfusão normotérmica, demonstrado por cintilografia e histomorfometria.

PURPOSE: To evaluate the effect of sildenafil, administered prior to renal ischemia/reperfusion (I/R), by scintigraphy and histopathological evaluation in rats. METHODS: Twenty-four rats were divided randomly into two groups. They received 0.1 ml of 99mTechnetium-etilenodicisteine intravenous, and a baseline (initial) renal scintigraphy was performed. The rats underwent 60 minutes of ischemia by left renal artery clamping. The right kidney was not manipulated. The sildenafil group (n=12) received orally 1 mg/kg of sildenafil suspension 60 minutes before ischemia. Treatment with saline 0.9% in the control group (n=12). Half of the rats was assessed after 24 hours and half after seven days I/R, with new renal scintigraphy to study differential function. After euthanasia, kidneys were removed and subjected to histopathological examination. For statistical evaluation, Student t and Mann-Whitney tests were used. RESULTS: In the control group rats, the left kidneys had significant functional deficit, seven days after I/R, whose scintigraphic pattern was consistent with acute tubular necrosis, compared with the initial scintigraphy (p<0.05). Sildenafil treatment resulted in better differential function of the left kidneys 24h after reperfusion, compared with controls. Histopathologically, the left kidney of control rats (24 hours after I/R) showed a higher degree of cellular necrosis when compared with the sildenafil treated rats (p<0.05). CONCLUSION: Sildenafil had a protective effect in rat kidneys subjected to normothermic I/R, demonstrated by scintigraphy and histomorphometry.