ANALYSIS OF THE NATURAL VIBRATION FREQUENCY TEST METHOD TO OBTAIN THE MODULUS OF ELASTICITY OF WOOD STRUCTURAL COMPONENTS

There are several techniques to characterize the elastic modulus of wood and those currently using the natural frequencies of vibration stand out as they are non-destructive techniques, producing results that can be repeated and compared over time. This study reports on the effectiveness of the testing methods based on the natural frequencies of vibration versus static bending to obtain the elastic properties of reforested structural wood components usually employed in civil construction. The following components were evaluated: 24 beams of Eucalyptus sp. with nominal dimensions (40 x 60 x 2.000 mm) and 14 beams of Pinus oocarpa with nominal dimensions (45 x 90 x 2.300 mm) both without treatment; 30 boards with nominal dimensions (40 x 240 x 2.010 mm) and 30 boards with nominal dimensions (40 x 240 x 3.050 mm), both of Pinus oocarpa and with chromate copper arsenate (CCA) preservative treatment. The results obtained in thiswork show good correlation when compared to the results obtained by the static bending mechanical method, especially when applying the natural frequency of longitudinal vibration. The use of longitudinal frequency was reliable and practical, therefore recommended for determining the modulus of elasticity of wood structural elements. It was also found that no specific support is needed for the specimens using the longitudinal frequency, as well as no previous calibrations, reducing the execution time and enabling to test many samples.

A nonlinear elasticity phantom containing spherical inclusions

The strain image contrast of some in vivo breast lesions changes with increasing applied load. This change is attributed to differences in the nonlinear elastic properties of the constituent tissues suggesting some potential to help classify breast diseases by their nonlinear elastic properties. A phantom with inclusions and long-term stability is desired to serve as a test bed for nonlinear elasticity imaging method development, testing, etc. This study reports a phantom designed to investigate nonlinear elastic properties with ultrasound elastographic techniques. The phantom contains four spherical inclusions and was manufactured from a mixture of gelatin, agar and oil. The phantom background and each of the inclusions have distinct Young's modulus and nonlinear mechanical behavior. This phantom was subjected to large deformations (up to 20%) while scanning with ultrasound, and changes in strain image contrast and contrast-to-noise ratio between inclusion and background, as a function of applied deformation, were investigated. The changes in contrast over a large deformation range predicted by the finite element analysis (FEA) were consistent with those experimentally observed. Therefore, the paper reports a procedure for making phantoms with predictable nonlinear behavior, based on independent measurements of the constituent materials, and shows that the resulting strain images (e. g., strain contrast) agree with that predicted with nonlinear FEA.

DETERMINATION OF THE E/G RATIO OF WOOD LOGS USING TRANSVERSE VIBRATION

The Bernoulli's model for vibration of beams is often used to make predictions of bending modulus of elasticity when using dynamic tests. However this model ignores the rotary inertia and shear. Such effects can be added to the solution of Bernoulli's equation by means of the correction proposed by Goens (1931) or by Timoshenko (1953). But to apply these corrections it is necessary to know the E/G ratio of the material. The objective of this paper is the determination of the E/G ratio of wood logs by adjusting the analytical solution of the Timoshenko beam model to the dynamic testing data of 20 Eucalyptus citriodora logs. The dynamic testing was performed with the logs in free-free suspension. To find the stiffness properties of the logs, the residue minimization was carried out using the Genetic Algorithm (GA). From the result analysis one can reasonably assume E/G = 20 for wood logs.

Particulate composite based on coconut fiber and castor oil polyurethane adhesive: An eco-efficient product

This paper presents a study on the potential use of coconut fiber as material to produce particleboards, with two different densities (0.8 g/cm(3) and 1.0 g/cm3), using castor oil-based polyurethane adhesive and urea-formaldehyde. The quality of the product that can be produced by industry was evaluated according to the normative NBR 14.810:2006, where density, thickness swell (TS), absorption, modulus of elasticity (MOE), modulus of rupture (MOR) in static bending and internal bond (IB) were determined. From the results, there was a decrease in TS and increase in MOR of coconut fiber panels with polyurethane resin panels compared with coconut fiber and resin urea-formaldehyde. Scanning microscopy electronic images (SEM) indicated that castor oil-based polyurethane adhesive occupies the gaps between the particles, a factor that contributes to improved physical and mechanical properties of the panels. The assessment of durability through accelerated aging tests shows that panels protected with waterproofing material can be used in environments that have contact with moisture. (C) 2012 Elsevier B.V. All rights reserved.

Bending stiffness evaluation of Teca and Guajara lumber through tests of transverse and longitudinal vibration

The grading of structural lumber besides contributing for increasing the structure's safety, due to the reduction of the material variability, also allows its rational use. Due to the good correlation between strength and bending stiffness, the latter has been used in estimating the mechanical strength of lumber pieces since the 60's. For industrial application, there are equipment and techniques to evaluate the bending stiffness of lumber, through dynamic tests such as the longitudinal vibration technique, also known as stress wave, and the transverse vibration technique. This study investigated the application of these two techniques in the assessment of the modulus of elasticity in bending of Teca beams (Tectona grandis), from reforestation, and of the tropical species Guajara (Micropholis venulosa). The modulus of elasticity estimated by dynamic tests showed good correlation with the modulus measured in the static bending test. Meantime, we observed that the accuracy of the longitudinal vibration technique was significantly reduced in the evaluation of the bending stiffness of Teca pieces due to the knots existing in this species.

Extracellular Matrix Composition of the Cricopharyngeus Muscle

The aim of this study was to analyze the presence and distribution of total collagen, type I and type III collagen, elastic fibers, fibronectin, and versican in the endomysium of cricopharyngeus muscles from adults of various ages. The study was a cross-sectional analysis of human cricopharyngeus muscles. Twenty-seven muscles obtained from autopsies of men and women ranging in age from 28 to 92 years were analyzed with the Picrosirius method, oxidized Weigert resorcin-fuchsin, immunohistochemistry, and image analysis. Collagen had the highest density among the analyzed components. Elastic fibers surrounded each muscle cell; they were aligned longitudinally by their long axis and associated with traversing fibers, thereby forming a fiber network with embedded muscle cells. The fibronectin and versican contents varied widely among the specimens. We found no statistically significant differences between the proportion of extracellular matrix (ECM) components and factors such as gender and race. We conclude that the higher proportion of type I and type III collagen is compatible with the cricopharyngeus muscle's sphincteric behavior, and the arrangement of the elastic fibers may also contribute to the muscle's elasticity. We found no statistically significant correlation between the ECM components and age.

REALISTIC IVUS IMAGE GENERATION IN DIFFERENT INTRALUMINAL PRESSURES

Intravascular ultrasound (IVUS) phantoms are important to calibrate and evaluate many IVUS imaging processing tasks. However, phantom generation is never the primary focus of related works; hence, it cannot be well covered, and is usually based on more than one platform, which may not be accessible to investigators. Therefore, we present a framework for creating representative IVUS phantoms, for different intraluminal pressures, based on the finite element method and Field II. First, a coronary cross-section model is selected. Second, the coronary regions are identified to apply the properties. Third, the corresponding mesh is generated. Fourth, the intraluminal force is applied and the deformation computed. Finally, the speckle noise is incorporated. The framework was tested taking into account IVUS contrast, noise and strains. The outcomes are in line with related studies and expected values. Moreover, the framework toolbox is freely accessible and fully implemented in a single platform. (E-mail: fernando.okara@gmail.com) (c) 2012 World Federation for Ultrasound in Medicine & Biology.

RELATIONSHIP AMONG EXTRACTIVES, LIGNIN AND HOLOCELLULOSE CONTENTS WITH PERFORMANCE INDEX OF SEVEN WOOD SPECIES USED FOR BOWS OF STRING INSTRUMENTS

In this paper we investigate the influence of extractives, lignin and holocellulose contents on performance index (PI) of seven woods used or tested for violin bows. Woods with higher values of this index (PI = root MOE/rho, where MOE is modulus of elasticity and rho is density) have a higher bending stiffness at a given mass, which can be related to bow wood quality. Extractive content was negatively correlated with PI in Caesalpinia echinata, Hanclroanthus sp. and Astronium lecointei. In C. echinata holocellulose was positively correlated with PI. These results need to be further explored with more samples and by testing additional wood properties. Although the chemical constituents could provide an indication of quality, it is not possible to establish appropriate woods for bows solely by examining their chemical constituents.

In vitro analysis of the influence of surface treatment of dental implants on primary stability

Surface treatment interferes with the primary stability of dental implants because it promotes a chemical and micromorphological change on the surface and thus stimulates osseointegration. This study aimed to evaluate the effects of different surface treatments on primary stability by analyzing insertion torque (IT) and pullout force (PF). Eight samples of implants with different surface treatments (TS - external hexagon with acid surface treatment; and MS - external hexagon, machined surface), all 3.75 mm in diameter x 11.5 mm in length, were inserted into segments of artificial bones. The IT of each sample was measured by an electronic torquemeter, and then the pullout test was done with a universal testing machine. The results were subjected to ANOVA (p < 0.05), followed by Tukey's test (p < 0.05). The IT results showed no statistically significant difference, since the sizes of the implants used were very similar, and the bone used was not highly resistant. The PF values (N) were, respectively, TS = 403.75 +/- 189.80 and MS = 276.38 +/- 110.05. The implants were shown to be different in terms of the variables of maximum force (F = 4.401, p = 0.0120), elasticity in maximum flexion (F = 3.672, p = 0.024), and relative stiffness (F = 4.60, p = 0.01). In this study, external hexagonal implants with acid surface treatment showed the highest values of pullout strength and better stability, which provide greater indication for their use.

Low-level laser therapy in collagenase-induced Achilles tendinitis in rats: Analyses of biochemical and biomechanical aspects

NSAIDs are widely prescribed and used over the years to treat tendon injuries despite its well-known long-term side effects. In the last years several animal and human trials have shown that low-level laser therapy (LLLT) presents modulatory effects on inflammatory markers, however the mechanisms involved are not fully understood. The aim of this study was to evaluate the short-term effects of LLLT or sodium diclofenac treatments on biochemical markers and biomechanical properties of inflamed Achilles tendons. Wistar rats Achilles tendons (n?=?6/group) were injected with saline (control) or collagenase at peritendinous area of Achilles tendons. After 1?h animals were treated with two different doses of LLLT (810?nm, 1 and 3?J) at the sites of the injections, or with intramuscular sodium diclofenac. Regarding biochemical analyses, LLLT significantly decreased (p?<?0.05) COX-2, TNF-a, MMP-3, MMP-9, and MMP-13 gene expression, as well as prostaglandin E2 (PGE2) production when compared to collagenase group. Interestingly, diclofenac treatment only decreased PGE2 levels. Biomechanical properties were preserved in the laser-treated groups when compared to collagenase and diclofenac groups. We conclude that LLLT was able to reduce tendon inflammation and to preserve tendon resistance and elasticity. (c) 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:19451951, 2012

Sugar-Sweetened Beverage Taxes in Brazil

Objectives. We investigated whether taxing sugar-sweetened beverages (SSBs) would improve the diets of households in Brazil. Methods. We used household food consumption data that the Brazilian Institute of Geography and Statistics collected in 2002-2003 from a nationally representative sample of 48470 Brazilian households. The consumption of SSBs is expressed as the total SSB calories consumed and as the SSB percentage of the total calories purchased. We investigated price elasticity with regression models, controlling for demographic variables, income, and prices of all other foods and drinks. Results. Increases in the price of SSBs led to reductions in consumption. A 1.00% increase in the price of SSBs led to a 0.85% reduction of SSB calories consumed (1.03% reduction for the poor and 0.63% for the nonpoor). Increased income had a positive effect on SSB consumption, but the effect was less than half the size of the price elasticity (0.41% increase in SSB calories consumed for every 1.00% increase in income). Conclusions. High SSB price elasticity in Brazil indicates that a tax on purchased weight or volume would lead to reductions in SSB consumption. (Am J Public Health. 2012;102:178-183. doi:10.2105/AJPH.2011.300313)

Nuts and seed: A natural yet dangerous foreign body

Rationale and aim: This paper has the object to present the impact of nuts' and seeds' injuries withdrawing data from the Susy Safe registry, highlighting that as for other foreign bodies the main item efficiently and substantially susceptible to changes to decrease the accidents' rates is the education of adults and children, that can be shared with parents both from pediatricians and general practitioners. Indeed labeling and age related warnings have also a fundamental relevance in prevention. Methods: The present study draws its data from the Susy Safe registry. Details on injuries are entered in the Susy Safe Web-registry through a standardized case report form, that includes information regarding: children age and gender, features of the object, circumstances of injury (presence of parents and activity) and hospitalization's details (lasting, complications and removal details). Cases are prospectively collected using the Susy Safe system from 06/2005; moreover, also information regarding past consecutive cases available in each centre adhering to the project have been entered in the Susy Safe registry. Results: Nuts and seeds are one of the most common food item retrieved in foreign bodies injuries in children. In Susy Safe registry they represent the 38% in food group, and almost the 10% in general cases. Trachea, bronchi and lungs were the main location of FB's retrieval, showing an incidence of 68%. Hospitalization occurred in 83% of cases, showing the major frequency for foreign bodies located in trachea. This location was also the principal site of complications, with a frequency of 68%. There were no significant associations between these outcomes and the age class of the children. The most common complications seen (22.4%) was bronchitis, followed by pneumonia (19.7%). Adult presence was recorded as positive in 71.2% of cases, showing an association (p value 0.009) between the adult supervision and the hospitalization outcome. On the contrary there was a non significant association between adult presence and the occurrence of complications. In 80.7% of cases, the incident happened while the child was eating. Among those cases, 88.6% interested trachea, lungs and bronchi. Conclusions: Food-related aspiration injuries are common events for young children, particularly under 4 years of age, and may lead to severe complication. There is a need to study in more depth specific characteristics of foreign bodies associated with increased hazard, such as size, shape, hardness or firmness, lubricity, pliability and elasticity, in order to better identify risky foods, and more precisely described the pathogenetic pathway. Parents are not adequately conscious and aware toward this risk; therefore, the number and severity of the injuries could be reduced by educating parents and children. Information about food safety should be included in all visits to pediatricians in order to make parents able to understand, select, and identify key characteristics of hazardous foods and better control the hazard level of various foods. Finally, preventive measures including warning labels on high-risk foods could be implemented. (C) 2012 Elsevier Ireland Ltd. All rights reserved.

Aplicação do método de ensaio das frequências naturais de vibração para obtenção do módulo de elasticidade de peças estruturais de madeira

Existem diversas técnicas para caracterização do módulo de elasticidade de madeiras e, dentre as atualmente empregadas, destacam-se aquelas que utilizam as frequências naturais de vibração, por serem técnicas não destrutivas e, portanto, apresentarem resultados que podem ser repetidos e comparados ao longo do tempo. Este trabalho teve como objetivo avaliar a eficácia, dos métodos de ensaios baseados nas frequências naturais de vibração comparando-os aos resultados obtidos na flexão estática na obtenção das propriedades elásticas em peças estruturais de madeira de reflorestamento que são usualmente empregadas na construção civil. Foram avaliadas 24 vigas de Eucalyptus sp. com dimensões nominais (40 x 60 x 2.000 mm) e 14 vigas de Pinus oocarpa com dimensões nominais (45 x 90 x 2.300 mm), ambas sem tratamento; 30 pranchas com dimensões nominais (40 x 240 x 2.010 mm) e 30 pranchas com dimensões nominais (40 x 240 x 3.050 mm), ambas de Pinnus oocarpa e com tratamento preservativo à base de Arseniato de Cobre Cromatado - CCA. Os resultados obtidos apresentaram boa correlação quando comparados aos resultados obtidos pelo método mecânico de flexão estática, especialmente quando empregada a frequência natural de vibração longitudinal. O emprego da frequência longitudinal mostrou-se confiável e prático, portanto recomendada para a determinação do módulo de elasticidade de peças estruturais de madeira. Verificou-se ainda que, empregando a frequência longitudinal, não há necessidade de um suporte específico para os corpos de prova ou calibrações prévias, reduzindo assim o tempo de execução e favorecendo o ensaio de grande quantidade de amostras.

Emprego de ferramentas numéricas na avaliação do módulo de elasticidade em vigas roliças de madeira

Vigas são elementos estruturais encontrados na maioria das construções civis. Dentre os materiais de engenharia, destaca-se a madeira, por ter resistência mecânica satisfatória aliada a baixa densidade. A madeira roliça apresenta-se como boa solução na confecção de vigas, uma vez que não precisa ser processada, como é o caso da madeira serrada. O projeto de elementos estruturais de madeira requer o conhecimento de suas propriedades físicas e mecânicas, obtidas segundo as premissas de documentos normativos. Em se tratando da madeira roliça, os documentos normativos nacionais que tratam da determinação das propriedades de resistência e rigidez estão vigentes há mais de vinte anos sem revisão técnica. De forma geral, tanto as normas nacionais como as internacionais idealizam geometria troncocônica para as peças roliças de madeira, implicando equações simplificadas incapazes de prever a influência das irregularidades da forma na determinação do módulo de elasticidade longitudinal. Este trabalho objetiva avaliar a influência das irregularidades da geometria em peças roliças de madeira Corymbia citriodora e Pinus caribaea no cálculo do módulo de elasticidade longitudinal. Para tanto, utilizou-se do ensaio de flexão estática a três pontos, considerando também um modelo matemático simplificado, assumindo seção circular constante para a forma do elemento. As irregularidades das peças são consideradas nos modelos numéricos, constituídos de elementos finitos de barra e tridimensionais. Os resultados encontrados revelam equivalência estatística entre os módulos de elasticidade para ambas as formas de cálculo, indicando ser plausível a consideração de seção circular constante para as peças de madeira aqui avaliadas.

Análise de concorrência no mercado mundial de café verde

A literatura argumenta que o Brasil, embora ainda seja o maior exportador mundial de café verde, tem perdido poder neste mercado, pois a concorrência (rivalidade e probabilidade de entrada) imposta por países como a Colômbia e o Vietnã é forte o suficiente para tornar este mercado bastante competitivo. Assim, este artigo avalia o padrão recente de concorrência do mercado mundial de café verde utilizando uma metodologia econométrica mais usualmente empregada em análise antitruste. Para avaliar o comportamento dos consumidores, foram estimadas as elasticidades-preço da demanda mundial de café verde, por tipo de café, usando o modelo de demanda Logit Multinomial Antitruste. Para avaliar o comportamento de equilíbrio de mercado foram realizados testes de instabilidade de share de quantidade por meio de análise de cointegração em painel. Os resultados apontam para aumento da concorrência à variedade de café brasileiro por parte da demanda e manutenção de sharede quantidades como configuração de equilíbrio de mercado.