Relationship between vessel parameters and cleavage associated with checking in eucalyptus grandis wood

In this work, the relationship between vessels parameters and the wood cleavage strength were studied to clarify the process of formation of this type of check, very common in Eucalyptus wood. The objective was to identify the relationship between the wood cleavage strength, the average area of the vessel, and the percentage area of vessels on the wood transverse surface. For this, two Eucalyptus grandis trees at 22 years old were felled and specimens for the cleavage test were produced to determine the wood cleavage strength. From these specimens, samples were taken to determine the average area of the vessel and the percentage area of vessels, aiming at adjusting mathematical models that explain the variation in the cleavage strength. The results showed that the higher the average area of the vessel and the percentage of area occupied by vessels in the wood, the lower its cleavage strength. The multiple linear regression model can estimate the cleavage strength as a function of the average area of the vessel, and the percentage area of the vessels

MICOBIOTA ASSOCIADA À MADEIRA SERRADA DE Eucalyptus grandis HILL EX MAIDEN DURANTE A SECAGEM AO AR LIVRE

O objetivo principal deste trabalho foi o de acompanhar a secagem ao ar livre da madeira serrada de Eucalyptus grandis conduzida na região de Lavras, MG e identificar a micobiota associada à madeira em diversas fases da secagem. As tábuas foram cortadas de oito toras de 3,0 m de comprimento, oriundas de três árvores, com 27 anos de idade, plantadas em área experimental da UFLA. Dos resultados, pôde-se concluir que a secagem da madeira de Eucalyptus grandis ao ar livre, iniciada em janeiro, consumiu 158 dias até atingir umidade próxima a 12,5%. A curva de secagem foi representada por uma equação logarítmica com coeficiente de determinação (R2) igual a 98,3%. Os fungos causadores de bolores superficiais e de manchas tiveram maior ocorrência no início da secagem. As mais altas freqüências de fungos, verificadas no início da secagem, foram observadas para Penicillium spp. e Pestalotiopsis sp. O fungo Lentinus lepideus ocorreu com maior freqüência no final da secagem

Relationships between microfibril angle, modulus of elasticity and compressive strength in Eucalyptus wood

Many traits are known to be important in determining the value of Eucalyptus wood as sawn tim-ber. The commercial importance of the microfi bril angle (MFA) for wood quality is well established for a range of softwoods, but is less clear for hardwood species. For instance, the relationships of MFA with wood stiffness and compressive strength are unknown in Eucalyptus. Therefore, the aim of this study was to evaluate the correlation between MFA and the modulus of elasticity (Ec0,m) in compres-sion parallel to grain and compressive strength (Fc0,k) using juvenile wood of Eucalyptus grandis from fast-growing plantations. The correlation between wood stiffness and compressive strength was high (0.91). The cellulose microfi bril angle presented a correlation of -0.67 with wood stiffness and of -0.52 with compressive strength in Eucalyptus juvenile wood. MFA was found to be important in de-termining the mechanical behaviour of wood and appears to be a useful parameter to indicate wood stiffness and strength in juvenile Eucalyptus from short-rotation plantations

Application of a strain gauge to assess drying stresses in normal and tension wood of corymbia citriodora

The quantitative evaluation of longitudinal drying strain can provide relevant information for the processing wood and lumber industry, especially with regard to reaction wood in Corymbia, since little has been published. The objective of this work was to evaluate the effect of the steam conditioning and the cooling on the longitudinal drying strain (LDS) obtained from a strain gauge, called extensometer, in boards of both normal and tension wood of Corymbia citriodora. Lumbers 30 mm thick were produced and kiln dried at the initial temperature of 40 °C, final temperature of 65 °C and drying potential of 2,1. The LDS were measured before and after steam conditioning on hot and cold lumbers. It was observed that the conditioning did not reduce the LDS. Hot lumbers showed higher LDS values than the cold lumbers. The LDS values measured in normal, tension and opposite woods were statistically similar, indicating that the type of wood was not an influential factor in the appearance of longitudinal drying stresses. Extensometer proved to be feasible for measuring LDS, allowing its easy and quick quantification

Correlation between feeding methods, non-nutritive sucking and orofacial behaviors

TEMA: o desenvolvimento do controle motor oral depende em parte das experiências sensoriais e motoras. OBJETIVO: analisar a relação entre a duração do aleitamento natural, artificial e da sucção e destas com o desempenho motor orofacial. MÉTODO: cento e setenta e seis crianças, de 6 a 12 anos de idade, passaram por avaliação miofuncional orofacial, empregando o protocolo com escores, e os responsáveis foram entrevistados a respeito do aleitamento e hábitos de sucção de suas crianças. As correlações foram calculadas pelo teste de Spearman. RESULTADOS: na amostra estudada, a média de duração do aleitamento natural foi de 10,30 meses (variando de zero a 60 meses), do aleitamento artificial 44,12 (zero a 122 meses) e dos hábitos de sucção de 39,32 meses (zero a 144 meses). Houve correlação negativa da duração do aleitamento natural com a duração do aleitamento artificial e a duração dos hábitos de sucção (p < 0,001). A maior duração do aleitamento artificial correspondeu à maior duração dos hábitos de sucção, apresentando, assim, correlação positiva (p < 0,001). A duração do aleitamento natural foi correlacionada positivamente com a mobilidade orofacial (p = 0,05). Houve correlação negativa da duração do aleitamento artificial e da duração dos hábitos de sucção com, respectivamente, o desempenho na mastigação e na deglutição, bem como da duração de ambos os tipos de sucção com a prova de diadococinesia (p = 0,05). CONCLUSÃO: a duração do aleitamento natural mostrou efeito positivo sobre a mobilidade das estruturas orofaciais. Os efeitos deletérios da duração dos hábitos de sucção no controle motor orofacial foram confirmados.BACKGROUND: the development of oral motor control depends partially on motor and sensory experiences. AIM: to analyze the relationship between the duration of breastfeeding, artificial feeding and sucking habits, and of these parameters with the orofacial motor performance. METHOD: participants of this study were one hundred and seventy-six children aged 6 to 12 years. All subjects were submitted to an orofacial myofunctional clinical examination, using a protocol with scores, and parents/care takers were interviewed in respect to the feeding and sucking habits of their children. Correlations were calculated using the Spearman Test. RESULTS: in the studied sample, the mean duration of breastfeeding was of 10.30 months (ranging from zero to 60 months), of artificial feeding was of 44.12 months (zero to 122 months) and of sucking habits was of 39.32 months (0 to 144 months). There was a negative correlation of breastfeeding duration with artificial feeding duration and sucking habits duration (p < 0001). The duration of the artificial feeding was positively correlated to the duration of sucking habits (p < 0001). The duration of breastfeeding was positively correlated with the mobility of the tongue and jaw (p = 0.05). There was a negative correlation of the duration of artificial feeding and the duration of sucking habits with the performance in mastication and swallowing, respectively, as well as with the duration of both types of sucking with the performance in the diadochokinesia test (p = 0.05). CONCLUSION: the duration of natural breastfeeding presented a positive effect over the mobility of the orofacial structures. Deleterious effects of the prolonged duration of artificial feeding and sucking habits in the oral motor control were confirmed

Micobiota associada à madeira serrada de Eucalyptus grandis Hill ex Maiden durante a secagem ao ar livre.

This work’s main objective was to follow the air-drying of Eucalyptus grandis lumber, carried out in Lavras, MG, and to identify the mycobiota associated with the lumber at various phases of drying. The lumbers were obtained from eight 3.0 meter long logs from 27 year-old trees, planted in an experimental area of UFLA. Results showed that the air-drying of Eucalyptus grandis, started in January, demanded 158 days to achieve moisture content around 12.5 %. The moisture content-time curve was represented by a logarithmic equation with coefficient of determination equal to 98.3 %. The highest occurrence of fungi that cause surface mold and stain was observed at the beginning of the drying. The highest frequencies of fungi were verified at the beginning of the drying for Penicillium spp and Pestalotiopsis sp. The fungus Lentinus lepideus occurred with higher frequency at the end of the drying.O objetivo principal deste trabalho foi o de acompanhar a secagem ao ar livre da madeira serrada de Eucalyptus grandis conduzida na região de Lavras, MG e identificar a micobiota associada à madeira em diversas fases da secagem. As tábuas foram cortadas de oito toras de 3,0 m de comprimento, oriundas de três árvores, com 27 anos de idade, plantadas em área experimental da UFLA. Dos resultados, pôde-se concluir que a secagem da madeira de Eucalyptus grandis ao ar livre, iniciada em janeiro, consumiu 158 dias até atingir umidade próxima a 12,5%. A curva de secagem foi representada por uma equação logarítmica com coeficiente de determinação (R2) igual a 98,3%. Os fungos causadores de bolores superficiais e de manchas tiveram maior ocorrência no início da secagem. As mais altas freqüências de fungos, verificadas no início da secagem, foram observadas para Penicillium spp. e Pestalotiopsis sp. O fungo Lentinus lepideus ocorreu com maior freqüência no final da secagem

Analysing the drying behavior of juvenile and mature Eucalyptus saligna wood in drastic drying test for optimal drying schedule

The heterogeneity of characteristics observed in the pith-bark direction within a log causes sawn pieces of wood have different behaviors during water removal. Understanding these differences is important for the industry regarding the possibility of classification of the lumber into juvenile wood and mature wood, facilitating the drying in separate loads. Thus, this study aimed to evaluate the behavior of juvenile and mature wood samples of Eucalyptus saligna when subjected to drastic drying. In order to do this, test specimens were submitted to drastic drying at 100°C to obtain the drying times, drying rates and dimensions of end checks. These data were applied in equations to obtain the parameters initial temperature, final temperature and drying potential, used in the elaboration of drying schedules. In juvenile wood we observed that the basic density was lower and the initial moisture content was higher. Mature wood showed a lower drying rate. Drying schedules were developed separately for juvenile and mature wood, the drying schedule for the latter considered milder than the drying schedule developed for juvenile wood

Microfibril angle of Eucalyptus grandis wood in relation to the cambial age

The microfibril angle (MFA) of wood is an important feature, which helps to explain the physical and mechanical behaviour of wood in use. It has been little investigated for wood produced in Brazil, mainly for mature trees. Thus, the objective of this study was to analyze the MFA of Eucalyptus grandis at age 25 years in relation to the cambial age. One disk was cut from the base of the stem from each of three trees, where growth rings were marked. From a central strip 3,0 cm wide, 1 cm3 blocks were removed from each growth ring. After sectioned on the tangential face with a sliding microtome, sections of 8 μm thick were macerated. The individual fibres were observed by polarized light microscopy for measurement of MFA. According to the results, i) the MFA decreased from 29,3° (ring nº 1) to 18,9° (ring nº 25); ii) MFA can be estimated by the cambial age – a, according to the equation MFA = 28,1 – 0,35 × a, with R2 = 94,7%

Efecto del ángulo microfibrilar en las características tecnológicas de la madera de Pinus pseudostrobus var. apulcensis

El ángulo microfibrilar es la inclinación de las microfibrillas de celulosa en la pared celular en relación al eje vertical de la célula. Esta característica contribuye en explicar las variaciones en propiedades físicas y mecánicas de la madera y fibra procesada. Pinus pseudostrobus var. apulcensis es una especie forestal nativa de México con importancia económica e industrial. Se seleccionaron al azar 10 árboles sanos de esta especie en una plantación en Texcoco, Estado de México, México. De cada árbol se extrajo un tarugo a 1,3 m de altura de fuste. Se midió el ángulo microfibrilar, la densidad básica (DB), la longitud de traqueidas&nbsp; y la contracción volumétrica con el objetivo de determinar el efecto del ángulo microfibrilar sobre dichas características tecnológicas en esta madera. Se obtuvo un ángulo microfibrilar promedio de 28,8°; densidad básica promedio de 0,43 g·cm-3; longitud de traqueidas promedio de 3516 µm y contracción volumétrica promedio de 10,3 %. &nbsp;Se ajustaron modelos aditivos generalizados entre el ángulo microfibrilar como variable explicativa y cada una de las tres variables respuesta por separado. Finalmente se ajustó un modelo aditivo generalizado para conocer el comportamiento de la densidad básica, longitud de traqueidas y contracción volumétrica en función del ángulo microfibrilar. Este modelo generado tuvo una capacidad explicativa de 88,2 %. La variable mejor explicada por el ángulo microfibrilar fue la longitud de traqueidas (capacidad explicativa de 83,3 %). Sería interesante observar si este comportamiento se presenta en otras especies de pino mexicanas

Eficiência na estimativa do peso seco para árvores individuais e definição do ponto ótimo de amostragem para determinação da densidade básica de Eucalyptus camaldulensis.

The objectives of this study were to test the efficiency of models of double entrance, simple entrance, double entrance associated to hypsometric relationship, and the method of the two diameters, and also to define the optimum sampling point along the tree for obtaining the wood  basic density from just one sample. The study was carried out in the João Pinheiro region, MG, belonging to “Mannesman Florestal” LTDA. Data from 127 cubed trees were used with ages ranging from 28 to 76 months. Cross sections cuttings at every meter of the stem were taken for basic density determination. The estimates of the total dry weigth outside and inside bark were obtained from the proposed methods. The comparison of estimated with observed values was made by randon block design. It was observed that any of tested methods resulted in dry weight estimates similar to the observed values. Meanwhile, the precision of the estimates from the simple entrance equation were inferior to those one obtained through the other tested methods. The optimum sampling point to obtain the basic density was at 1 m from the ground. It was also verified that a greatter precision can be obtained if the sample for basic density is taken obtained at the heights of 1, 3 and 6 meters from the ground.Os objetivos deste estudo foram testar a eficiência dos modelos de dupla entrada, de simples entrada, de dupla entrada associados a relação hipsométrica e o método dos dois diâmetros; e também definir o ponto ótimo de amostragem na árvore para obter a densidade básica da madeira, a partir de uma amostra. O estudo foi conduzido na região de João Pinheiro, MG, em propriedade da Mannesman Florestal Ltda. Foram utilizadas 127 árvores cubadas rigorosamente com idades variando de 28 a 76 meses. Foram também retirados discos de metro em metro ao longo do fuste, para a determinação da densidade básica. As estimativas do peso seco total com e sem casca foram obtidas para as quatro metodologias em estudo. A comparação destas com os valores reais se deu através de um delineamento em blocos ao acaso. Foi constatado que qualquer dos procedimentos testados propiciam estimativas do peso seco semelhantes aos valores reais. No entanto, as medidas de precisão da equação de simples entrada são inferiores aos demais métodos testados. O ponto ótimo de amostragem na árvore para obter a densidade básica foi a 1m de altura. Maior precisão pode ser conquistada se a amostra for tomada a 1; 3 e 6 metros de altura