Hybrid titanium-CFRP laminates for high-performance bolted joints

This paper presents an experimental and numerical investigation of the mechanical response of bolted joints manufactured using new hybrid composite laminates based on the substitution of CFRP plies with titanium plies. The local hybridization of the material is proposed to increase the efficiency of the bolted joints in CFRP structures. Two modeling strategies, based on non-linear finite element methods, are proposed for the analysis of the bolt-bearing and transition regions of the hybrid laminates. The bolt-bearing region is simulated using a three-dimensional finite element model that predicts ply failure mechanisms, whereas the free-edge of the transition region is simulated using plane stress and cohesive elements. The numerical and experimental results indicate that the use of hybrid composites can drastically increase the strength of CFRP bolted joints and therefore increase the efficiency of this type of connection. In addition, the numerical models proposed are able to predict the failure mechanisms and the strength of hybrid composite laminates with a good accuracy

Causality Constraints on Massive Gravity

The de Rham-Gabadadze-Tolley massive gravity admits pp-wave backgrounds on which linear fluctuations are shown to undergo time advances for all values of the parameters. The perturbations may propagate in closed time-like curves unless the parameter space is constrained to a line. These classical phenomena take place well within the theory's validity regime.Comment: 6 pages, 4 figures; to appear in PR

Acute knee pain in elderly patients

A dor aguda no joelho de pacientes idosos é freqüente, sendo caracterizada por seu aparecimento súbito, sem causa aparente, com exame radiográfico dentro dos padrões da normalidade, na maioria dos casos. A etiologia da dor aguda no joelho é decorrente de insuficiência das estruturas, e seu quadro clínico difere completamente daquele determinado pela osteoartrose, sendo sempre unilateral e ocorre na grande maioria em pacientes do sexo feminino, após a quinta década de vida, e na região medial do joelho (local de maior carga). Com o propósito de analisar as possíveis etiologias para a dor aguda do joelho de pacientes acima de 60 anos de idade, suas características e tratamento, os autores discutem as etiologias relacionadas à dor aguda: lesão meniscal, fratura por fadiga e osteonecrose idiopática.Acute knee pain in elderly patients is not uncommon, and is characterized by a sudden onset, no apparent cause, and by normal radiographic findings in most cases. The etiology of acute knee pain is the result of insufficient structures, and clinical symptoms are totally different from the symptoms seen in osteoarthrosis. This acute pain in the knee is always unilateral and in the medial region of the knee joint (site with the heaviest load), predominantly in females after the fifth decade of live. In order to consider the possible etiologies for acute knee joint pain in patients older than 60 years, its characteristics and treatment, the authors discuss etiologies related to acute pain: lesion of the meniscus, stress fracture, and idiopathic osteonecrosis

Total arthroplasty in ankylosed knees: a case series

OBJECTIVE: To present nine patients with ankylosis in their knees that were submitted to a total arthroplasty to lessen their pain and improve their functional limitation. For these patients, arthrodesis remained a possibility in the event of arthroplasty failure. INTRODUCTION: Ankylosis of the knee is a severe functional limitation that becomes worse when pain is present. Arthrodesis of the knee is a classical indication for such patients, since it resolves the pain; however, the severe functional limitation remains. METHODS: In the present study, we evaluated the clinical course of nine patients who underwent total arthroplasty of the knee, and were followed up for at least five years. RESULTS: The results demonstrate that all of the patients experienced a significant reduction in pain and some improvement in the degree of knee flexion and extension. CONCLUSION: Based on the latest follow-up, there has been no need to perform arthrodesis for any of our patients, showing that a total arthroplasty could be a option for treatment in knee ankylosis

Phase transitions in general gravity theories

Phase transitions between two competing vacua of a given theory are quite common in physics. We discuss how to construct the space-time solutions that allow the description of phase transitions between different branches (or asymptotics) of a given higher curvature gravity theory at finite temperature.Comment: 4 pages, 1 figure, Contribution to the Conference Proceedings of the Spanish Relativity Meeting in Portugal (ERE2012