Characterization of Acrocarpus fraxinifolius wood submitted to heat treatment

Aiming to provide greater visibility for the wood species Acrocarpus fraxinifolius, the present study sought to analyze the influence of heat treatment on an industrial scale applied to wood species, also popularly known as Indian cedar. The heat treatment was carried out in an autoclave, with temperature and pressure control, and with saturated steam injection, for temperatures 155 ºC, 165 ºC, 175 ºC, and 185 ºC. Physical, chemical, and mechanical tests were carried out for the analyzed wood. The content of holocellulose and total lignin decreased, while the content of extractives showed a substantial increase. The density increased after the heat treatment, however the treated wood showed cracks, and these cracks influenced the significant loss of the values of the mechanical properties of compression, tension, and flexion. The shear showed strength gain for the temperature of 155 ºC, and the wood treated at 165 ºC was equivalent to untreated wood. The woods submitted to temperatures of 175 ºC and 185 ºC presented strength losses. The heat treatment in question contributes to increase the visibility, use and market value of wood

Estudo analítico da estabilidade dimensional longitudinal das espécies de madeira tropicais brasileiras

Brazil owns a large vegetal covering and the best utilization of these materials requires physical and mechanical characterization procedures. Equations found in the literature make easier the wood properties determination. At this context, well known authors developed the equation βl = βt/23, being βl and βt the longitudinal and tangential shrinkage percentages, for βl estimation based on the βt value specially for wood species from the Northern hemisphere. This paper aims to investigate the accuracy of this equation for fifteen tropical Brazilian wood species covering the entire range of hardwood strength classes according to the Brazilian Normative ABNT NBR7190. The average experimental values of βl and βt were 7.71% (CV = 26,71%) and 0.73% (CV = 38,76%), respectively. The non-parametric Kruskal-Wallis ANOVA refuted the hypothesis of equivalence between theoretical and experimental βl values (p-value = 0.0000). A linear regression model fitted to experimental values provided βl = βt/9,84 as optimal solution (p-value = 0.0000, R2 = 47,23%). According to results it is possible to conclude that the value of longitudinal shrinkage percentage of tropical Brazilian wood species is statistically 2,34 times greater than the value found in the literature, which impacts the design of timber structures procedures increasing the internal stresses in timber structural elements.O Brasil possui grande cobertura vegetal e o melhor aproveitamento desses materiais requer procedimentos de caracterização física e mecânica. Equações encontradas na literatura facilitam a determinação das propriedades da madeira. Nesse contexto, autores conhecidos desenvolveram a equação βl = βt/23, sendo βl e βt as porcentagens de retração longitudinal e tangencial, para estimativa de βl com base no valor de βl especialmente para espécies de madeira do hemisfério Norte. Este trabalho tem como objetivo investigar a precisão desta equação para quinze espécies de madeiras tropicais brasileiras cobrindo toda a faixa de classes de resistência da madeira de lei de acordo com o Norma Brasileira ABNT NBR 7190. Os valores experimentais médios de βl e βt foram 7,71% (CV = 26,71 %) e 0,73% (CV = 38,76%), respectivamente. A ANOVA não paramétrica de Kruskal-Wallis refutou a hipótese de equivalência entre os valores de βl  teórico e experimental (p-valor = 0,0000). Um modelo de regressão linear ajustado aos valores experimentais forneceu βl  =βt/9,84 como solução ótima (p-valor = 0,0000, R² = 47,23%). De acordo com os resultados, é possível concluir que o valor da porcentagem de retração longitudinal das espécies de madeira tropical brasileira é estatisticamente 2,34 vezes maior que o valor encontrado na literatura, o que impacta nos procedimentos de dimensionamento de estruturas de madeira aumentando as tensões internas nas estruturas de madeira

Influência dos parâmetros de fabricação nas Propriedades Físicas e Mecânicas de Paineis de Partícula de Média Densidade

A presente pesquisa tem por objetivo avaliar a influência de três fatores de produção (densidade nominal, temperatura e pressão) na produção de paineis de partículas de média densidade da madeira de Eucalyptus saligna com resina ureia-formaldeído e catalisadores e verificar se os paineis atendem ao requisito normativo da ABNT NBR 14810. A influência dos fatores nos paineis MDP foram analisados por intermédio de 12 tratamentos experimentais. Foram fabricadas 48 chapas ao total, com 4 chapas com dimensões 300 mm x 300 mm x 15 mm, determinando 7 propriedades físicas e mecânicas, totalizando 336 determinações experimentais. Foram avaliadas as seguintes propriedades: teor de umidade, densidade aparente, inchamento em espessura após 2h e 24h, tração perpendicular, módulo de elasticidade e módulo de resistência. Os tratamentos, em grande parte, atenderam aos requisitos normativos, com três tratamentos atendendo plenamente. Para a maioria das propriedades os fatores de produção não foram significativos do ponto de vista estatístico, possibilitando que possa haver redução de algum fator a fim de manter o mesmo desempenho atendendo aos requisitos normativos. Palavras-chave: Painéis de partículas de média densidade (MDP), Eucalyptus, fator de produção, desempenho, análise de variância (ANOVA)

Alternative model to determine the characteristic strength value of wood in the compression parallel to the grain

Wood strength values are calculated based on the characteristic value, which corresponds to the 5 % percentile of a given probability distribution model. For a few number of samples (12 samples), the Brazilian standard ABNT NBR (7190) establishes an estimator of the characteristic compressive strength parallel to grain of the wood, which may provide a different result when compared with the characteristic value coming from a suitable probability distribution model. Considering the strength results in the parallel compression to the grain of 45 wood species of the hardwood group, Normal, LogNormal, Weibull and Exponential probability distribution models were used for each specie with the purpose of determining the one with the highest adhesion. Calculated the characteristic values by the best probability model distribution, an analysis of variance (ANOVA) was performed in the estimation of the characteristic value of compressive strength, making it possible to identify the most significant terms of the models as well as the quality of the adjustment obtained on such models. The proposed regression model (R2 adj= 96,56 %) proved to be equivalent to the empirical model of the Brazilian standard. The model proposed here only depends on the mean and the lowest value obtained from the compressive strength in the parallel direction to the grain

Carbon fiber-reinforced polymers as a tensile reinforcement of the Pinus elliotti and Manilkara huberi wood species

In wood structures, the elements subjected to bending stresses, such as the beams, present a fracture initiated in the tensile region, and under these conditions, the use of laminated composite materials is presented as an alternative solution in the form of repair or reinforcement. This research aimed to evaluate the influence of the use of carbon fibers laminated composites in tensile reinforcement in the direction parallel to grain of Pinus elliotti and Manilkara huberi wood species. The Viapol two-component epoxy adhesive was used in the lamination and fixation of the unidirectional carbon fiber in the wood species. Ten specimens with no defects (reference) and 10 specimens were prepared for each crack length (25 and 50mm) with and without the reinforcement (60mm × 50mm) by the laminated composite. The tensile tests were performed in accordance with the requirements of the Brazilian standard ABNT NBR 7190 (1997). From the results of the statistical analysis, the use of the carbon fiber composite was able to restore the tensile strength of the cracked samples (partial or total) in relation to samples without defects, demonstrating the potential of the laminates in carbon fibers as an alternative solution in repair for both wood species

Do Diabetes à Doença Renal: Uma Revisão Sistemática dos Benefícios Nefroprotetores dos Inibidores de SGLT2

Esta revisão sistemática aborda o papel nefroprotetor dos inibidores do cotransportador de sódio-glicose tipo 2 (SGLT2) em pacientes com diabetes. A análise compreensiva de estudos clínicos e diretrizes atuais destaca não apenas a eficácia desses agentes no controle glicêmico, mas também seus efeitos diretos na prevenção da progressão da doença renal crônica (DRC). Os inibidores de SGLT2 demonstraram consistentemente redução significativa da proteinúria, efeitos hemodinâmicos benéficos, e uma associação clara com a redução do risco cardiovascular. As diretrizes da KDIGO reconhecem o papel integral desses medicamentos na gestão da nefropatia diabética. Esses achados sugerem que os inibidores de SGLT2 representam uma abordagem terapêutica promissora para pacientes com diabetes e risco de complicações renais

Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil

The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others

Analysis of relations between physical and mechanical properties in different harvest regions of Cambará wood (Erisma Uncinatum Warm)

This research had the purpose of evaluating the relationship between the physical and mechanical properties of Cambará wood extracted from three distinct sites: Vera, Mucajaí and south of Rondônia. The possibility of estimating (linear regression, exponential, geometric and logarithmic models) the physical and mechanical properties as a function of apparent density will also be evaluated. This research was motivated by the fact that there is no consideration in the normative code the influence of the extraction regions on the physical and mechanical properties of timber, since different climatic conditions, vegetation and soil in which the tree can influence their growth and, consequently, the values of its physical and mechanical properties. The ABNT NBR 7190, the Kruskal-Wallis variance analysis and the resampling technique were considered in the accomplishment of the procedures. The results of ANOVA indicated an equivalence index equal to 100% for the properties of the Vera region, 94% for the regions of Mucajaí and South of Rondônia. The resampling technique led to similar results for the Vera and Mucajaí regions and for the southern region of Rondônia, the equivalence index was equal to 89%. The results of the ANOVA to estimate the physical and mechanical properties in function of the apparent density indicated that it was not possible to make such estimates for Cambará wood.Não recebi financiamentoEsta pesquisa teve a finalidade de avaliar de relação existente entre as propriedades físicas e mecânicas da madeira de Cambará extraída de três locais distintos: Vera, Mucajaí e sul de Rondônia. Também será avaliado a possibilidade de se estimar (modelos de regressão linear, exponencial, geométrico e logarítmico) as propriedades físicas e mecânicas em função da densidade aparente. Tal pesquisa foi motivada por não haver no dispositivo normativo nenhuma consideração acerca da influência das regiões de extração nas propriedades físicas e mecânicas das madeiras, uma vez que diferentes condições climáticas, vegetação e solo na qual a árvore medra podem influenciar seu crescimento e, por consequência, os valores de suas propriedades. Considerou-se na realização dos procedimentos a ABNT NBR 7190, a análise de variância de Kruskal-Wallis e a técnica de reamostragem. Os resultados da ANOVA indicaram índice de equivalência igual a 100% para as propriedades da região de Vera, 94% para as regiões de Mucajaí e Sul de Rondônia. A técnica de reamostragem levou a resultados semelhantes para as regiões de Vera e Mucajaí e para a região Sul de Rondônia, o índice de equivalência foi igual a 89%. Os resultados da ANOVA para estimativa de propriedades físicas e mecânicas em função da densidade aparente indicaram que não foi possível fazer tais estimativas para a madeira de Cambará

Effect of fatigue on tropical wood species

The aim of present study was to create a theoretical model that allowed, with security and reliability, to obtain values of strength and stiffness to which the structural element will be submitted throughout its useful life. The effect was studied for strength and stiffness properties, and the modulus of elasticity (EM) and bending strength (fM) on static bending test were evaluated according to the increasing number of cycles of the fatigue test for the five classes of hardwoods, recommended by NBR 7190 Standard Code. A reduction in strength and stiffness properties was observed with increasing loading Ncycles applied at two frequency levels. From the multivariate regression models and the respective determination coefficients, a generic model was obtained for the set involving the five wood species, emphasizing the insertion of the apparent density as an independent variable, which allowed a greater generalization of the use of the adjustments in the estimation of the EM and fM properties, presenting significant determination coefficients, ranging between 67.89% and 70.58%

Effect of fatigue on tropical wood species

The aim of present study was to create a theoretical model that allowed, with security and reliability, to obtain values of strength and stiffness to which the structural element will be submitted throughout its useful life. The effect was studied for strength and stiffness properties, and the modulus of elasticity (EM) and bending strength (fM) on static bending test were evaluated according to the increasing number of cycles of the fatigue test for the five classes of hardwoods, recommended by NBR 7190 Standard Code. A reduction in strength and stiffness properties was observed with increasing loading Ncycles applied at two frequency levels. From the multivariate regression models and the respective determination coefficients, a generic model was obtained for the set involving the five wood species, emphasizing the insertion of the apparent density as an independent variable, which allowed a greater generalization of the use of the adjustments in the estimation of the EM and fM properties, presenting significant determination coefficients, ranging between 67.89% and 70.58%