Application of microwave energy to wood can increase permeability in order to improve the impregnation of treatments, particularly important in refractory species such as eucalyptus. However, microwave treatment can also affect the physical and mechanical properties of wood. This paper discusses the application of microwave treatments of different intensities to improve impregnability (uptake and retention) and examines the effects on the mechanical properties of eucalyptus wood (Eucalyptus globulus). Microwave treatments significantly improve uptake and retention of the protective agent, especially in the most severe treatment. In contrast, there was a clear decrease in mechanical properties (modulus of elasticity and bending, compression, tension and shear strength) as a function on the energy applied. The effect of microwaves on the properties of wood varies depending on moisture content at the time of treatment.
The main objective of this work was to study the structural viability of using small-diameter logs of Uruguayan Loblolly/Slash pine, mainly from thinning operations, to design cross-laminated timber (CLT) panels. A visual grade named “CTH” (coniferous thinning) was proposed, and 45 specimens of sawn timber boards were tested, resulting in 51% lower bending strength than that of the minimum strength class C14. Subsequently, 20 CLT panels were manufactured and experimentally tested, the results showed that the bending strength of the CLT panels was 43% above that of the individual layers. Additionally, the structural performance of the CLT panels for use in floors was calculated, and the thickness-span relationship depending on strength class and imposed load are presented. Results showed than the use of CTH timber to design CLT floors implies a volume (m3/m2) 17% higher than that using C24 timber.
Variations of the nutritional condition of lobsters Panulirus argus (Decapoda: Palinuridae) in Eastern region of the Gulf of Batabanó, Cuba. Nutritional condition can affect survival and growth rate of crustaceans, and this is mostly affected by habitat conditions. This study describes the space-temporary nutritional changes in this commercially important species. With this aim, the variations in the nutritional condition (K) of lobsters from four zones (1, 2, 4 and 5) in the Gulf of Batabanó, Cuba, were determined. For this, the weight/length ratio (K=Pt/Lt) was calculated using animals captured in 1981 and 2010. The nutritional condition between areas and sexes, and years and sexes, was contrasted by a bifactorial ANOVA, and the overall length and weight of lobsters were compared using a t-Test for independent samples and unifactorial ANOVA. It was found that the nutritional condition was significantly greater in males than in females. In addition, significant variations between zones were detected for both years. Nutritional condition of lobsters from Zone five was the highest for 1981, while it was Zone two for 2010. Lobsters nutritional state showed significant variations between years, being greater in 1981 (2.34±0.84g/mm) than in 2010 (1.96±0.49g/mm). The inter-zones variations as well as the inter-annual ones seem to be related to the reported variations of the bottom type and the vegetation cover. Seasonal variations in the abundance and distribution of benthic organisms, that constitute food for lobsters, could also be influencing. The differences between sexes, however, were assumed as a consequence of the methodology used and the sexual dimorphism of the species. Due to other K estimation methods, that do not include morphometric measurements, these differences were not detected. We suggested that the P. argus nutritional condition is a good estimator of the habitat condition. Besides, according to the applied K estimation methodology, it was found that different groups of lobsters that have resemblant nutritional condition, did not necessarily observe similarities in the overall mean length or weight, so they could exist under different habitat conditions.
A partir de nueve muestreos efectuados en meses lluviosos del 2009 en aguas de los golfos de Ana María y Guacanayabo, región suroriental de Cuba, se realizaron comparaciones (ANOVA) entre ambos golfos de concentración de sustancias nutrientes y otras variables oceanográficas, así como se estimó el grado de eutrofia y se confeccionaron cartas de distribución horizontal del índice de eutrofización del nitrógeno total inorgánico y el fósforo inorgánico. Se analizaron las variaciones de la concentración media de nutrimentos en tres periodos diferentes (1972-1973, 1988-1991 y 2009). Entre ambos golfos, se encontró diferencia significativa (P < 0.05) en la salinidad, el fósforo inorgánico y los silicatos. La distribución espacial del índice de eutrofización del nitrógeno total inorgánico y del fósforo inorgánico mostró gradientes que disminuyeron a medida que se incrementó la distancia a la costa. El Golfo de Guacanayabo presentó una mayor distribución y extensión de valores mesotróficos y características menos halinas que el Golfo de Ana María, con índice de eutrofización del nitrógeno total inorgánico de 3.05, superior al del Golfo de Ana María (2.99); el fosforo inorgánico mostró un índice de 2.80 en el Golfo de Guacanayabo, mayor que en el Golfo de Ana María (2.57). En el análisis por períodos, en ambos golfos las concentraciones medias de nitrógenos oxidados (NOx) disminuyeron en 2009 con respecto al periodo 1988-1991, el fósforo inorgánico mostró tendencia al incremento, mientras que los silicatos mostraron un decrecimiento escalonado desde 1972-73. Abstract Nutrient concentrations and other oceanographic variables were compared (ANOVA) between the Gulfs of Ana María and Guacanayabo in the Southeastern region of Cuba based on nine samples taken during the rainy months in 2009. In addition, the degree of eutrophication was estimated, and horizontal distribution charts were prepared for the eutrophication index of total inorganic nitrogen and phosphorus. The variations of the mean concentration of nutrients were analyzed for three different periods (1972-1973, 1988-91, and 2009). There were significant differences (P < 0.05) in salinity, inorganic phosphorus and silicate between the two gulfs. The spatial distribution of the eutrophication index of total inorganic nitrogen and phosphorus showed gradients that decreased as distance to the coast increased. The Gulf of Guacanayabo showed greater distribution and extension of mestrophic values, less haline characteristics, and higher eutrophication index of total inorganic nitrogen (3.05) than the Gulf of Ana María (2.99). The inorganic phosphorus also showed a higher mean rate in relation with the Ana María Gulf (2.57). In the analysis by periods for both gulfs, the mean concentrations of nitrogen oxides (NOx) decreased in 2009 compared to the 1988-1991 period, the inorganic phosphorus showed an increasing trend, while silicate showed a stepwise decrease from 1972-1973.
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