Shaking Table Test of U-Shaped Walls Made of Fiber-Reinforced Foamed Concrete.

Fiber-reinforced foamed concrete (FRFC) is a lightweight material that has the potential to perform well in seismic applications due to its low density and improved mechanical properties. However, studies focused on the seismic assessment of this material are limited. In this work, U-shaped wall specimens, made of FRFC reinforced with henequen fibers and plain foamed concrete (PFC) with a density of 900 kg/m3, were subjected to shaking table tests. PFC and FRFC were characterized using compression and tension tests. FRFC exhibited enhanced mechanical properties, which were attributed to the fibers. The dynamic tests showed that U-shaped walls made of FRFC performed better than those made of PFC. The time period prior to the collapse of the FRFC U-shaped walls was longer than that of the PFC specimens, which was attributed to the enhanced specimen integrity by the fibers. Finite element simulations of the shaking table test allowed for the prediction of the stress concentration and plastic strain that may lead to the failure of the U-shaped wall. These results showed that U-shaped walls made of FRFC have the potential to perform well in seismic applications, however, these results are preliminary and further studies are needed to support the findings of this work.

Surface Plasmon Resonance and Bending Loss-Based U-Shaped Plastic Optical Fiber Biosensors.

Escherichia coli (E. coli) is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being in the feces of animals and humans, its presence in water and food is used as indicator of fecal contamination. The main method for this microorganism detection is the bacterial culture medium that is time-consuming and requires a laboratory with specialized personnel. Other sophisticated methods are still not fast enough because they require sending samples to a laboratory and with a high cost of analysis. In this paper, a gold-coated U-shaped plastic optical fiber (POF) biosensor for E. coli bacteria detection is presented. The biosensor works by intensity modulation principle excited by monochromatic light where the power absorption is imposed by predominant effect of either bending loss or surface plasmon resonance (SPR), depending on the gold thickness. Bacterial selectivity is obtained by antibody immobilization on the fiber surface. The biosensor showed a detection limit of 1.5 × 10³ colony-forming units (CFU)/mL, demonstrating that the technology can be a portable, fast response and low-cost alternative to conventional methodologies for quality analysis of water and food.

Stress amplifications in dental non-carious cervical lesions.

This study aims to investigate the influence of the presence, shape and depth of NCCLs on the mechanical response of a maxillary second premolar subjected to functional and non-functional occlusal loadings using 3-D finite element (FE) analysis. A three-dimensional model of a maxillary second premolar and its supporting bone was constructed based on the contours of their cross-sections. From the sound model, cervical defects having either V- or U-shapes, as found clinically, were subtracted in three different depths. The models were loaded with 105 N to simulate normal chewing forces according to a functional occlusal loading (F1) vertically applied and two non-functional loadings (F2 and F3) obliquely oriented. Two alveolar bone crest heights were tested. Ansys™ FE software was used to compute stress distributions and maximum principal stress for each of the models. The presence of a lesion had no effect on the overall stress distribution of the system, but affected local stress concentrations. Non-functional loadings exhibited tensile stresses concentrating at the cervical areas and root surfaces, while the functional loading resulted in homogeneous stress distributions within the tooth. V-shaped lesions showed higher stress levels concentrated at the zenith of the lesion, whereas in U-shaped defect stresses concentrated over a wider area. As the lesions advanced in depth, the stress was amplified at their deepest part. A trend of stress amplification was observed with decreasing bone height. These results suggest a non-linear lesion progression with time, with the progression rate increasing with patient's age (deeper lesions and lower bone support).

Lumbopelvic fixation and sacral decompression for a U-shaped sacral fracture: case report

BACKGROUND: U-shaped sacral fractures are highly unstable, can cause significant neurological deficits, lead to progressive deformity and chronic pain if not treated appropriately. OBJECTIVE: To report a case of a U-shaped sacral fracture treated with lumbopelvic fixation and decompression of sacral roots in a 23-years-old man. METHOD: Decompression of the sacral roots combined with internal reduction and lumbopelvic fixation using iliac screws. RESULTS: Restitution of lumbosacropelvic stability and recovery of sphincter function. CONCLUSION: Lumbopelvic fixation is effective in restoring lumbosacralpelvic stability and allows full mobilization in the postoperative period. Good neurological recovery can be expected in the absence of discontinuity of the sacral roots.

INTRODUÇÃO: As fraturas sacrais em U são instáveis e podem causar significativa lesão neurológica, deformidade progressiva e dor crônica se não tratadas apropriadamente. OBJETIVO: Relatar caso de um homem de 23 anos com fratura em U do sacro tratada com fixação lombopélvica e descompressão das raízes sacrais. MÉTODO: Descompressão da cauda equina associada a redução interna e fixação lombopélvica usando parafusos ilíacos. RESULTADOS: Reconstituição da estabilidade lombosacropélvica e recuperação da continência esfincteriana CONCLUSÃO: A fixação lombopélvica é eficaz em restaurar a estabilidade lombo-sacro-pélvica e permite mobilização imediata no pós-operatório. Recuperação neurológica pode ser esperada na ausência de neurotmese das raízes sacrais.