Abstract Sisal (Agave sisalana) is a plant exploited in semi-arid regions of Brazil for fiber production, but the floral scape of sisal (peduncle) is collected and often burned, causing environmental problems, even through irregular disposal. To circumvent this scenario, the objective of this work was to produce reconstituted panels using the sisal arrow and castor-based polyurethane resin. The panels were obtained using 175 g of crushed sisal arrow core with dimensions smaller than 2 mm and adopting 10% castor-based polyurethane resin and The samples were pressed under tension of 2 MPa. The properties of reconstituted panel were evaluated through NBR 14810-1 (ABNT, 2013) and NBR 14810-2 (ABNT, 2018), the physical properties were investigated: moisture, density, thickness swelling and absorption; as well as mechanical properties: MOR, MOE, internal bond and parallel compression. The found results show that the panel is classified as low density (419.8 kg/m³), and with physical and mechanical properties similars to other panels of the same classification in the literature. For average values of MOR and MOE it was found 5.24 MPa and 147.49 MPa, respectively. For internal bonding it was found 0.14 MPa and for parallel compression properties it was found 1.14 MPa.

Resumo O sisal (Agave sisalana) é uma planta explorada nas regiões semiáridas do Brasil para produção de fibras, mas o escapo floral do sisal (flecha) é coletado e frequentemente queimado causando problemas ambientais, até mesmo pelo descarte irregular. Para contornar este cenário, o objetivo deste trabalho foi produzir painéis reconstituídos usando a flecha do sisal e resina poliuretana à base de mamona. Os painéis foram obtidos empregando 175 g do miolo da flecha de sisal triturada com dimensões inferiores a 2 mm e adotando 10% de resina poliuretana à base de mamona e as amostras foram prensadas com tensão de 2 MPa. Avaliou-se no painel reconstituído, através da NBR 14810-1 (ABNT, 2013) e NBR 14810-2 (ABNT, 2018) as propriedades físicas: umidade, densidade, inchamento e absorção; bem como as propriedades mecânicas: MOR, MOE, força de ligação e compressão paralela. Os resultados encontrados mostram que o painel é classificado como de baixa densidade (419,8 kg/m³), e de propriedades físicas e mecânicas semelhantes a outros painéis de mesma classificação da literatura. Para MOR e MOE foram encontrados 5,24 MPa e 147,49 MPa de média, respectivamente. Já os ensaios de tração perpendicular e compressão paralela obtiveram resultados de 0,14 MPa e 1,14 MPa, respectivamente.

Litografie-gebaseerde keramiekvervaardiging (LCM) is 'n laagvervaardigingstegnologie (LV) wat pasgemaakte, driedimensionele keramiekonderdele laag vir laag bou. Die vlak van akkuraatheid van die proses maak voorsiening vir die druk van pasgemaakte intern-aaneenlopende roosterstrukture en ontwerpe wat geskik is vir beenimplantate. Hierdie studie het die LCM-veraardigbaarheid van verskeie roosterstrukture ondersoek met die hidroksieapatiet (HA480) verskaf deur Lithoz. Verskillende roosterstrukture is gekarakteriseer. Die mikroskopiese struktuur, die samestelling en die oppervlakrofheid van die toetsmonsters is bepaal. Om die meganiese eienskappe van die strukture te verkry, is druktoetse uitgevoer. Die waargenome mikroporieë van ±3 µm en die makroporieë van ±320 µm was geskik vir beenselgroei. Die gemete mikrohardheid van HA480 was 556±25 HV in die bourigting en 559±27 HV loodreg op die bourigting. Die druksterkte van die rombiese dodekaëderroosterstruktuur was 4±0.5 MPa, en was beter as ander getoetste roosters. Uit die resultate is tot die gevolgtrekking gekom dat roosterstrukture wat deur LCM vervaardig word, die potensiaal het om gebruik te word vir vervaardiging van pasgemaakte beenregenererende steiers.

Lithography-based ceramic manufacturing (LCM) is an additive manufacturing (AM) technology that builds custom-designed, three-dimensional ceramic parts layer by layer. The level of precision of the process allows for the printing of custom-made interconnected lattices and designs suitable for bone implants. This study investigated the LCM printability of various lattice structures with the hydroxyapatite (HA480) supplied by Lithoz. Different lattice structures were characterised. The microscopic structure, the composition, and the surface roughness of the test specimens were determined. To obtain the mechanical properties of the structures, compression tests were performed. The observed micropores of ±3 µm and the macropores of ±320 µm were suitable for bone cell growth. The measured microhardness of HA480 was 556±25 HV in the built direction and 559±27 HV perpendicular to the built direction. The compressive strength of the rhombic dodecahedron lattice structure was 4±0.5 MPa, and was superior to other tested lattices. From the results it was concluded that lattice structures produced through LCM have the potential to be used to produce customised bone-regenerating scaffolds.

Abstract This research evaluated the flexo-compression behavior in the rigidity of the beam-pillar connection with the use of bamboo armor of the species bamboo vulgaris as an alternative replacement to conventional steel reinforcement, in the expectation of using an alternative material with ecological biases. They have manufactured reinforced concrete pillars of length 1,600 mm and cross-sections (140 x 140) mm² and (140 x 310) mm² were made, respectively, in the internal stretch and at the ends of the pillar, simulating the beam-pillar connection. The pillars had as their only variable the longitudinal reinforcement rate, of 1.03% for the conventional pillar, of 2.14%, 3.21% and 4.29% for the pillars with the bamboo. The results regarding the resistant capacity showed that the pillar with the bamboo rate of 4.29%, that is, with the reinforcement area four times the steel area, presented similar behavior to the pillar with conventional reinforcement and had the lowest ductility index, considerably reducing the propagation of cracks. And the theoretical estimates showed variability of only 9%. Thus, bamboo, with an adequate rate and adhesion, revealed a technically viable and sustainable alternative to steel in the manufacture of reinforced concrete structural elements.

Resumo Esta pesquisa avaliou o comportamento de flexocompressão na rigidez da conexão viga-pilar com o uso de armadura de bambu da espécie Bambusa vulgaris como alternativa de substituição à armadura convencional de aço, na expectativa de utilizar um material com viés ecológico. Foram confeccionados 4 pilares de concreto armado de comprimento 1.600 mm e de seções transversais de 140x140 mm² e de 140x310 mm² no trecho interno e nas extremidades do pilar respectivamente, simulando a conexão viga-pilar. Os pilares tinham como única variável a taxa de armadura longitudinal, de 1,03% para o pilar convencional, de 2,14%, 3,21% e 4,29% para os pilares com o bambu. Os resultados quanto à capacidade resistente mostraram que o pilar com a taxa de bambu de 4,29%, ou seja, com a área de armadura quatro vezes a área do aço, apresentou comportamento similar ao pilar com armadura convencional e teve o menor índice de ductilidade, reduzindo consideravelmente a propagação das fissuras. As estimativas teóricas apresentaram variabilidade de apenas 9%. Assim, o bambu, com taxa e aderência adequadas, revelou-se uma alternativa tecnicamente viável e sustentável ao aço na fabricação de elementos estruturais de concreto armado.

Abstract Additive manufacturing has evolved from a rapid prototyping technology to a technology with the ability to produce highly complex parts with superior mechanical properties than those obtained conventionally. The processing of metallic powders by means of a laser makes it possible to process any type of alloy and even metal matrix composites. The present work analyzes the tensile and compressive response of 316L stainless steel processed by laser-based powder bed fusion. The resulting microstructure was evaluated by optical microscopy. Regarding the mechanical properties, the yield strength, ultimate tensile strength, percentage of elongation before breakage, compressive strength and microhardness were determined. The results show that the microstructure is constituted by stacked micro molten pools, within which cellular sub-grains are formed due to the high thermal gradient and solidification rate. The compressive strength (1511.88 ± 9.22 MPa) is higher than the tensile strength (634.80 ± 11.62 MPa). This difference is mainly associated with strain hardening and the presence of residual stresses. The initial microhardness was 206.24 ± 11.96 HV; after the compression test, the hardness increased by 23%.

Resumen La fabricación aditiva ha evolucionado desde una tecnología de prototipado rápido hasta una con la capacidad de producir piezas altamente complejas con propiedades mecánicas que superan las logradas de manera convencional. El procesamiento de polvos metálicos mediante tecnología láser permite el tratamiento de una amplia gama de aleaciones e incluso materiales compuestos. Este estudio analiza la respuesta a tracción y compresión del acero inoxidable 316L fusionado mediante fusión selectiva láser. La microestructura resultante fue analizada mediante microscopía óptica. En cuanto a las propiedades mecánicas, se determinaron la resistencia a la fluencia, la resistencia última a la tracción, el porcentaje de elongación antes de la fractura, la resistencia a la compresión y la microdureza. Los resultados muestran que la microestructura está compuesta por micropiletas fundidas apiladas, dentro de las cuales se generan subgranos celulares debido al alto gradiente térmico y la alta velocidad de solidificación. La resistencia a la compresión (1511.88 ± 9.22 MPa) es superior a la resistencia a tracción (634.80 ± 11.62 MPa). Esta diferencia está principalmente asociada con el endurecimiento por deformación y las tensiones residuales. La microdureza inicial fue de 206.24 ± 11.96 HV, y después de la prueba de compresión, la dureza aumentó en un 23 %.

Abstract May-Thurner syndrome is defined as the set of clinical manifestations secondary to anatomical extrinsic compression of the common iliac vein by the iliac artery, which can trigger recurrent thrombotic events and post-thrombotic syndrome. This anatomical variation can occur in approximately 1 in 4 people, who will develop the syndrome once they are faced with a triggering noxa, which is why the approach based on contrasted abdomen imaging in patients with unilateral recurrent venous thrombosis is accurate to identify said anomaly in time, given the requirement of minimally invasive interventions as described in the present case.

Resumen El síndrome de May-Thurner se define como el conjunto de manifestaciones clínicas secundarias a la compresión anatómica extrínseca de la vena ilíaca común por la arterial ilíaca, lo cual puede desencadenar eventos trombóticos recurrentes y síndrome postrombótico. Dicha variación anatómica se puede presentar en aproximadamente una de cada cuatro personas, quienes desarrollarán el síndrome una vez se encuentren ante una noxa desencadenante, es por esto que el enfoque basado en imagen de abdomen contrastado en pacientes con trombosis venosa recurrente unilateral es acertado para identificar a tiempo dicha anomalía, dado el requerimiento de intervenciones mínimamente invasivas tal y como se describe en el presente caso.

RESUMEN Numerosos autores han interpretado el margen pacífico colombiano como sucesivas acreciones de terrenos oceánicos, con la generación de cuencas de antearco bajo un régimen tectónico compresivo-transpresivo vigente durante el Cretácico tardío-Mioceno. Existe nueva información adquirida en la última década, consistente en nuevas secciones sísmicas y geológicas reprocesadas, además de información de pozos y columnas estratigráficas. En el presente trabajo se analiza esta nueva información y se hace notar que no presenta coherencia con los modelos de sucesivas acreciones de terrenos oceánicos propuestos a la fecha. Los nuevos datos sugieren que, entre el Cretácico tardío y el Eoceno Medio-tardío, las cuencas costa adentro (onshore basins) estuvieron regidas por una extensa plataforma marina, con crecimiento de carbonatos arrecifales hacia el final de ese periodo. Coetáneo a la sedimentación del Cretácico tardío, se presentó magmatismo efusivo, principalmente basáltico. A partir del Oligoceno, la evolución de las cuencas estuvo dominada por procesos diferentes durante tres periodos. Primero, en el Oligoceno-Mioceno temprano, en la cuenca Tumaco y subcuenca San Juan ocurrió un evento transtensional acompañado del emplazamiento de cuerpos ígneos hacia sus bordes orientales, con la generación de estructuras de pilares tectónicos, fosas tectónicas y fallas tipo dominó. En tanto, la subcuenca Atrato presentó hacia su límite sur deformación con fallas inversas locales concentradas en su flanco oriental. Segundo, durante el Mioceno Medio-tardío se levantó el flanco occidental de la cuenca Tumaco, mientras que en la subcuenca San Juan tuvo lugar deformación transpresiva dada por la interacción del sistema de fallas San Juan y Garrapatas. Tercero, durante el Pleistoceno, en la subcuenca Atrato se generó el anticlinal de Baudó asociado a un régimen transpresional. Los resultados aquí expuestos sugieren que no hay evidencia de acreción de terrenos oceánicos en las cuencas estudiadas; tampoco se observan los efectos generados por la presencia de un sistema de subducción durante el Cretácico tardío-Eoceno Medio. Esto abre la posibilidad de que el sistema de subducción en el margen pacífico colombiano haya comenzado en el Oligoceno temprano.

ABSTRACT Several authors have interpreted the Colombian Pacific margin as a succession of oceanic terrane accretions, with generation of forearc basins under a compressive-transpressive tectonic regime during the Late Cretaceous-Miocene. New data acquired in the last decade, consisting of reprocessed seismic lines, geological cross-sections, stratigraphic data from wells, and new stratigraphic columns, are analyzed in this study. We suggest that the proposed models of successive terrane accretions are not supported by the new data; rather, the onshore basins were likely controlled by a marine platform from the Late Cretaceous to the Middle-Late Eocene, with reef growth to the end of this period. In the Late Cretaceous, contemporary to the sedimentation stage, effusive magmatism, mainly basaltic, also occurred. Since Oligocene time, the basins were affected by three different tectonic processes. First, during the Oligocene-Early Miocene, an extensional-transtensional event occurred in the Tumaco Basin and San Juan Sub-basin, which produced horst and graben structures and domino faults, along with the emplacement of igneous bodies in the eastern flank of the basins. The Atrato Sub-basin was affected by local reverse faulting towards its eastern edge. Second, during the Mid-Late Miocene, the western side of the Tumaco Basin was uplifted, and transpressive deformation occurred in the San Juan Sub-basin as evidenced by the San Juan and Garrapatas fault systems. Finally, in the Atrato Sub-basin, a transpressional regime is evidenced by the Baudó anticline. Our results suggest there is no evidence of oceanic terrane accretions in the abovementioned basins during the Late Cretaceous-Middle Eocene. Furthermore, we do not see evidence of a subduction system during that period. We conclude that subduction in western Colombia could have begun during the Early Oligocene instead.

Abstract With the advent of critical state Soil Mechanics (CSSM), the void ratio began to be recognized as a key parameter, along with the stress state, which defines the mechanical behavior of soils and other particulate geomaterials by using the state parameter. The state parameter is the difference between the current and critical void ratio so that its definition requires the critical state line (CSL) identification. This work presents numerical calibration results, using the NorSand constitutive model, from three sets of triaxial compression tests selected from the literature. The SIGMA/W module of the Geostudio® System was adopted to perform the simulations of the triaxial compression tests, and the results showed adequate fit between real tests and numerical simulations. The parameters necessary for the modeling with NorSand model, defined from the numerical calibration, were used in a stress-strain evaluation of a hypothetical upstream tailings dam. These simulations allowed the evaluation of the differences in the tailings storage facility (TSF) responses in terms of both deformation behavior and flow liquefaction instability. Flow liquefaction instability is described in the literature as a complete loss in shear strength and the development of excessive strains due to the contractive response of tailings when subjected to low confining stress. The results suggest that the use of the NorSand model is, in general, a good option to reproduce the typical strain-softening behavior of such structures. Furthermore, it was clear the high sensitivity of the constitutive model parameters, drawing attention to the importance of best laboratory practices for carrying out triaxial tests to obtain reliable parameters for NorSand modeling.

ABSTRACT When the only information available is the issue parameters, and the intended outwards, machine learning techniques like ANN (Artificial Neural Networks) and ANFIS (Adaptive neuro-fuzzy inference system) been proven to address the complex problems without duplicating the phenomena under investigation. The main prompting characteristics are the height-to-the-thicknesses ratio of prisms and the strength under compression of prisms and mortar were analyzed. As inputs, the prototypes are used as blocks and mortars. Both prototypes were accomplished and evaluated. Thirty-six data sets were gathered for testing in addition to verified technical and subsequently comparison with other empirical computation methods served to validate. The outwards show that the suggested prototypes have good forecast capabilities with negligible error rates. To assess and compare the structural behavior of structural completion of AAC block with the other types. At last, both the machine learning tools are good application and dependability.

ABSTRACT Knowledge of the physical and mechanical properties of wood is crucial for the safety and efficiency of structural design. In addition to promoting diversification and supply in the timber market, determining these properties for different types of native woods can contribute to reduce the concentrated overexploitation of tropical woods. Among the woods available for construction purposes in the Tocantina region of Maranhão State is tuturubá (Pouteria oblanceolata Pires). In this context, the present study aimed to evaluate the physical and mechanical properties of tuturubá wood for its use in building structures. The characterizations carried out were: moisture content, apparent density, compressive strength parallel and perpendicular to the grain, shear strength parallel to the grain, flexural strength, modulus of elasticity in compression parallel to the grain and three-point bending test. For the average moisture content, a percentage value of 13.88% was checked, and for the average apparent density, a value of 992.04 kg.m-3 was obtained. For the compressive strength parallel to the grain, an average value of 60.03 MPa was determined, while the characteristic value was 56.86 MPa. The compressive modulus of elasticity parallel to the grain determined was equal to 22761 MPa. The average values for compressive strength perpendicular to the grain and shear strength parallel to the grain were 10.74 MPa and 10.47 MPa, respectively. For flexural strength, average and characteristic values were 154.82 and 128.37 MPa, respectively. For the flexural modulus of elasticity, an average value of 21026 MPa was determined. The results allowed tuturubá wood to be classified in mechanical resistance class D50. Compared to other commercially available wood species, tuturubá has better mechanical properties than pequiá (Cary-ocar villosum) and tauari (Couratari oblongifolia) woods. This physical-mechanical characterization high-lights the potential of tuturubá wood for use in building structures.

RESUMO O conhecimento das propriedades físicas e mecânicas da madeira é crucial para a segurança e eficácia do dimensionamento das estruturas. Além de favorecer a diversificação e abastecimento do mercado madeireiro, a determinação de tais propriedades, para diferentes espécies nativas, pode contribuir para a redução da exploração concentrada de madeiras tropicais. Entre as madeiras disponíveis para a construção civil na Região Tocantina do Maranhão encontra-se o tuturubá (Pouteria oblanceolata Pires). Neste contexto, este estudo teve como objetivo determinar as propriedades físicas e mecânicas da madeira de tuturubá, visando o seu uso em estruturas de edificações. Foram determinados: o teor de umidade, a densidade aparente, as resistências à compressão paralela e perpendicular às fibras, a resistência ao cisalhamento paralelo às fibras, a resistência à flexão e os módulos de elasticidade à compressão paralela às fibras e à flexão. Obteve-se um teor de umidade médio de 13,88%, uma densidade aparente média de 992,04 kg.m-3, o valor médio da resistência à compressão paralela às fibras igual a 60,03 MPa e o valor característico de 56,86 MPa, sendo o módulo de elasticidade à compressão paralela às fibras de 22761 MPa. A resistência média à compressão perpendicular às fibras foi de 10,74 MPa e a resistência média ao cisalhamento paralelo às fibras foi igual a 10,47 MPa. A resistência à flexão média foi de 154,82 MPa e o valor característico igual a 128,37 MPa, enquanto o valor médio do módulo de elasticidade à flexão foi de 21026 MPa. Os resultados permitiram classificar a madeira de tuturubá como pertencente à classe de resistência mecânica D50. Comparativamente com outras espécies disponíveis no mercado madeireiro, a madeira de tuturubá apresentou propriedades mecânicas superiores às madeiras de pequiá (Caryocar villosum) e tauari (Couratari oblongifolia). Esta caracterização físico-mecânica evidencia o potencial da madeira de tuturubá para utilização em estruturas de edificações.

ABSTRACT Turbochargers have proven to be essential in the automotive field as they are machines responsible for increasing power, reducing fuel consumption, and generating less carbon dioxide in an internal combustion engine. This article presents the development of a mathematical model based on a plenum to obtain the dynamic characteristics of the mass flow generated by a turbocharger. To comply with the proposal, it was based on the theoretical-practical knowledge of the laws and concepts that make up a turbocharger, resulting in the simulation of a mathematical model using the Simulink tool. For the development of the mathematical model, theoretical and test data in stable and dynamic regimes were used, as well as the behavior of the plenum subjected to the compression system. This proposed model will contribute to the scientific community by obtaining the characteristics between the compression ratio and the compressor mass flow of a turbocharger and will also contribute to the field of detection and diagnosis of targeted failures in vehicle turbochargers.

RESUMEN Los turbocargadores en la actualidad han demostrado ser imprescindibles en el campo automotriz por ser máquinas que se encargan de aumentar la potencia, reducir el consumo de combustible y generar menos dióxido de carbono en un motor de combustión interna. En este artículo se presenta el desarrollo de un modelo matemático en base a un plenum, con el propósito de obtener las características dinámicas del flujo másico que genera un turbocargador. Para cumplir con lo propuesto se fundamentó en el conocimiento teórico-práctico de las leyes y conceptos que conforman un turbocargador, dando como resultado la simulación de un modelo matemático utilizando la herramienta Simulink. Para el desarrollo del modelo matemático se utilizaron datos teóricos y de pruebas en régimen estable y dinámico, así como el comportamiento del plenum sometido al sistema de compresión. Este modelo planteado contribuirá a la comunidad científica a través de la obtención de las características entre la relación de compresión y el flujo de masa del compresor de un turbocargador, también, aportará en el futuro al campo de la detección y diagnósticos de fallos orientados a los turbocargadores vehiculares.

Abstract Clayey soils are spread in many countries and require significant improvement. Recently, nanomaterial have been entered to the geotechnical research as a treatment material. Current study utilized magnesium oxide (MgO) as an additive to enhance swelling potential, compressibility characteristics, and index properties of clayey soil from Mosul city using different content of nano-MgO and under varies curing periods. The results showed that the free swell and swell pressure of the soil specimens have been reduced by 25%, and 19%, respectively for 0.25, and 0.75% content of nano material under 3 days of curing time at 25C. Results also showed that the compressibility characteristic represented by the compression index parameter has been reduced by 20.3% for 0.75% of nano-MgO material. Moreover, the soil plasticity index exhibited a maximum increase at 0.75% of nano content. Moreover, results showed that the pH value increased while the electrical conductivity (EC) decreased with the nano-MgO content. To evaluate the curing time effect, specimens were cured for varies curing time under curing temperature of 25 ºC. Then, the free swell, swell pressure, compression index, and Atterberg limits were measured. The results revealed that the free swell and swell pressure for both untreated and treated specimens were reduced during different periods of curing time. Furthermore, the compression index of treated soil was reduced by approximately half for curing time of 28 days. In sum, the swelling and consolidation reduction with curing brought significant improvement and promising results for the treated samples.

Resumen: Los anillos vasculares son malformaciones congénitas infrecuentes. Dentro de ellas, el doble arco aórtico (DAA) suele ser de difícil diagnóstico debido a su baja incidencia de síntomas. El DAA puede asociarse a compresión traqueal o esofágica y en casos severos, requerir intubación traqueal o uso crónico de sonda nasogástrica. Esto último, favorece el desarrollo de fístulas aortotraqueales (FAT) y/o aortoesofágicas (FAE). Objetivo: Presentar un caso con una inusual asociación de DAA con FAT y reforzar la importancia de mantener una alta sospecha diagnóstica en pacientes con hemorragia aerodigestiva masiva sin foco evidente. Caso Clínico: Se presenta caso de RNPT de 32 semanas de gestación que requirió ventilación mecánica prolongada con episodios intermitentes de hemorragia orofaríngea masiva, con compromiso hemodinámico, asociado a obstrucción de vía aérea inferior sin hemorragia pulmonar. Endoscopía digestiva alta y laparotomía exploradora sin evidencia de sangrado. Nasofaringolaringoscopía flexible y laringoscopía directa tampoco detectaron anomalías. Angiotomografía computada demostró DAA completo con indentación de arco dominante izquierdo sobre tráquea, sin estenosis severa ni evidencia de fístula. Se sospechó FAE y se planteó exploración quirúrgica. Sin embargo, el paciente falleció previo al procedimiento por hemorragia pulmonar masiva. La autopsia demostró la presencia de FAT. Conclusiones: En pacientes con hemorragia aerodigestiva masiva sin foco evidente se debe considerar la presencia de un DAA y posible FAE/FAT. Los estudios imagenológicos no tienen buen rendimiento para este diagnóstico, por lo que debe considerarse la cirugía como parte del proceso diagnóstico y tratamiento.

Abstract: Vascular rings are unusual congenital malformations. Among them, double aortic arch (DAA) is often difficult to diagnose due to its low incidence of symptoms. DAA can be associated with tracheal or esophageal compression and, in severe cases, could require tracheal intubation or chronic use of a nasogastric tube. This scenario favors the development of aortotracheal fistulas (ATF) or aortoe-sophageal fistulas (AEF). Objective: To present a clinical case with an unusual association of DAA with ATF and to reinforce the importance of maintaining high diagnostic suspicion in patients with massive aerodigestive bleeding without an obvious source. Clinical Case: A 32-week preterm newborn who required prolonged mechanical ventilation and presented intermittent episodes of massive oropharyngeal bleeding with hemodynamic compromise associated with lower airway obstruction without pulmonary hemorrhage. The patient underwent upper endoscopy and exploratory laparotomy without evidence of bleeding. Flexible nasopharyngolaryngoscopy and direct laryngoscopy also showed no abnormalities. A CT angiography showed complete DAA with indentation of the left dominant arch over the trachea, without severe stenosis or evidence of a fistula. AEF was suspected, so exploratory surgery was considered. However, the patient died before surgery due to a massive pulmonary hemorrhage. The autopsy revealed the presence of ATF. Conclusions: In patients with massive aerodigestive bleeding without an obvious source, the presence of DAA and possible AEF/ ATF should be considered. Imaging studies have a poor performance for this diagnosis, so surgery should be considered for diagnosis and treatment in these patients.

BACKGROUND: Thirty-day readmission rate and 30-day reoperation rate are recognised indicators of perioperative quality of care. While these indicators have been reported in numerous studies from developed countries, little is known about readmission and reoperation following spinal surgery in South Africa. The main aim of this study was to describe the overall rate of 30-day reoperation and 30-day readmission following spine surgery in a large open medical scheme. Secondary aims were to describe the reasons for 30-day reoperation and 30-day reoperation by spine region and for certain procedures. METHODS: This retrospective cohort study was based on an anonymised dataset of spine surgeries funded by the largest open medical scheme in South Africa between 2008 and 2017. The dataset was processed to identify descriptors of each surgery, including the year of operation, patient demographics, spinal pathology, spine region and certain procedures. The primary outcome was reoperation within 30 days, which was identified based on the time to the second operation, diagnostic codes and procedure codes. RESULTS: A total of 49 395 spine surgeries were included in the study, of which at least 38 218 (77%) were for degenerative pathology. Overall, 3 204 (6.5%) surgeries were associated with 30-day readmission for any cause and 415 (0.8%) patients underwent a second unplanned spine surgery within 30 days of the initial spine procedure. The most common reasons for the 415 reoperations were neural compression (n = 160, 39%) and infection (n = 79, 19%). CONCLUSION: Spine surgery in the South African private sector is associated with low rates of 30-day readmission and reoperation, suggesting good quality of perioperative care. Furthermore, the findings compare favourably with those from developed countries. Future studies should investigate long-term reoperation following spinal surgery to provide more comprehensive insight into the quality of spinal surgery care in the South African private healthcare setting. Level of evidence: Level 3

Resumo Esse trabalho apresenta uma nova alternativa para a obtenção de Modelos de Bielas e Tirantes para estruturas de Concreto Armado através do Método de Otimização Topológica Híbrida, já proposto na literatura técnica, sendo aqui refinado para utilizar elementos finitos poligonais e acelerar a solução do problema da não linearidade material. Nesse método, o concreto é aproximado como meio contínuo, utilizando elementos finitos bidimensionais poligonais, e as barras de aço como elementos de treliça, utilizando elementos finitos unidimensionais com dois nós. Para uma representação mais próxima da realidade, implementou-se um modelo constitutivo ortotrópico para o concreto, considerando rigidezes distintas para a compressão e tração, sendo uma das vantagens do modelo. O método híbrido também limita a disposição final das barras de aço, gerando estruturas melhores do ponto de vista construtivo, enquanto permite uma maior liberdade para a forma e a inclinação das bielas de concreto. Como desvantagem, o método é mais complexo, aumentando o custo computacional, que porém foi substancialmente reduzido através da implementação de um procedimento. Os resultados obtidos para alguns domínios se aproximaram bastante dos resultados de outras metodologias, mas pequenas diferenças são notadas que podem ser relevantes para o resultado final. Outros domínios apresentaram resultados com maiores diferenças mudando de forma significativa o modelo de bielas e tirantes final, apresentando, assim, uma nova alternativa de dimensionamento. Híbrida técnica material contínuo treliça nós realidade implementouse implementou tração construtivo desvantagem complexo computacional procedimento metodologias apresentando assim dimensionamento

Abstract This work introduces a new alternative to obtain strut-and-tie models using the hybrid topology optimization method, which is already proposed in the technical literature and is refined here to use polygonal finite elements and accelerate the solution of the material nonlinearity problem. In this method, concrete is approached as a continuum, using polygonal two-dimensional finite elements, and steel bars as truss elements, using one-dimensional finite elements with two nodes. For a closer representation of reality, an orthotropic constitutive model for concrete was implemented considering different compression and tensile stiffness values, which is one of the advantages of the model. Further, the hybrid method limits the final layout of steel bars, thereby generating better structures from a constructive point of view, while allowing greater freedom for the shape and concrete strut slope. However, this method is more complex, and it increases the computational cost, which was substantially minimized through the implementation of an algorithm. Results obtained for some domains were very close to the results of other methodologies; however, small differences were noted that may be relevant to the final result. Other domains showed results with greater differences, thereby significantly changing the final strut-and-tie model and presenting a new structural design alternative. strutandtie tie problem continuum twodimensional dimensional onedimensional nodes reality values Further view slope However complex cost algorithm methodologies however result

Abstract: Hydraulic testing of isolated sapwood from mature tree trunks is time-consuming and prone to errors, whereas the measurement of compression strength is a standardized and rapid wood technological application. In this study, we aimed to analyze if compression stress perpendicular to the grain relates to hydraulic vulnerability of mature Norway spruce (Picea abies) trunk wood with an expected narrow vulnerability range. The sample-set comprised 52 specimens originating from 34 trees harvested in Sweden. Before mechanical testing, the P 50, i.e., the water potential resulting in 50 % of hydraulic conductivity loss, was estimated on small sapwood beams employing the air injection method. Compression strength perpendicular to the grain was defined as the first peak of a stress-strain curve (peak stress) when the wood is subjected to radial compression. Peak stress ranged between 1,65 MPa and 5,07 MPa, P 50 between -2,98 MPa and -1,98 MPa. We found a good correlation between the peak stress and P 50 (r = 0,80; P < 0,0001). This provides further evidence that peak stress in radial compression and P 50 are both extremely dependent on the characteristics of the “weakest” wood part, i.e., the highly conductive earlywood. We conclude that the radial compression strength is a good proxy for P 50 of mature Norway spruce trunk wood.