The anatomy and the physical, mechanical, acoustical and chemical properties of pernambuco wood (Caesalpinia echinata Lam.) were investigated to determine factors that could explain the different quality of sticks used in bow manufacture. Eighteen sticks were classified into four classes (A to D with A being the best) according to their potential quality for bow manufacture. Selection of samples was based on the experience of a bow maker and on some nondestructive tests. The A-class sticks had a lower frequency of vessels and rays and a higher percentage of fibers when compared to the other classes. They also had higher values of density, speed of sound propagation, modulus of elasticity and modulus of rupture. Klason lignin content was higher in the A-class sticks but the quantity of hydrosoluble and ethanol/benzene soluble extractives was lower. The values of density and speed of sound propagation obtained by nondestructive and destructive methods were similar showing the applicability of the former in the prior selection process of the sticks.

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Effect of bismuth oxide as a buffer layer on metal-lanthanum-substituted bismuth titanate-insulator-semiconductor structures

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Amorphous samples of Vitrovac(R) 6025 metallic alloys were nanocrystallized by thermal annealing at temperatures in the range 576–716 K, well below the crystallization temperature (831 K, as obtained by differential scanning calorimetry at 20 K/min) and times in the range 10–90 min. Initial magnetic permeability exhibited a maximum of ∼109 000 (from ∼20 000 for the as-quenched state) for annealing times of ∼15 min, and then a decrease toward a plateau value (30 000–40 000) for longer times. Domain wall relaxation frequency showed the opposite behavior, a minimum of ∼9 kHz (from 40 kHz for the as-quenched value) for the permeability maximum, and then a stabilization at ∼15 kHz. Transmission electron microscopy observations confirmed that for annealing times up to 60 min., crystallite size is smaller than 30 nm. Permeability and relaxation frequency results are interpreted in terms of the dependence of wall bulging on anisotropy and free-wall surface area between pinning sites.

RESUMO -(Madeiras utilizadas na fabricação de arcos para instrumentos de corda: aspectos anatômicos). A madeira de pau-brasil (Caesalpinia echinata Lam.) é mundialmente empregada na confecção de arcos para instrumentos de corda, uma vez que apresenta características únicas de ressonância, densidade, durabilidade, beleza, entre outras qualidades, que a tornam ideal para tal uso. Diferentes amostras de pau-brasil, contudo, fornecem arcos com qualidades distintas. No comércio nacional outras madeiras estão sendo empregadas na produção de arcos. Realizou-se, neste estudo, uma análise qualitativa e quantitativa de diferentes amostras de pau-brasil com o objetivo de apontar diferenças na estrutura da madeira que possam contribuir para o entendimento das causas da variação na qualidade do arco, além da análise de outras espécies objetivando determinar, do ponto de vista estrutural, semelhanças ou diferenças com o paubrasil. Conclui-se que variações no diâmetro dos vasos, distribuição e quantidade de parênquima axial e orientação dos elementos axiais e radiais são parâmetros que devem ser considerados quando se busca determinar as causas das diferenças na qualidade dos arcos de paubrasil. Constatou-se que arcos de boa qualidade apresentam grã linheira e textura fina. Esta última característica decorre da menor proporção de vasos cujo diâmetro é reduzido, raios homogêneos e fibras com paredes espessas e/ou muito espessas. Assim, a relação entre a estrutura e a qualidade do arco está diretamente relacionada com as dimensões, a distribuição e a proporção das células do lenho.Palavras-chave : anatomia da madeira, arcos para violino, Caesalpinia echinata, pau-brasil, madeiras substitutas ABSTRACT -(Anatomical features of woods used in the manufacture of bows for stringed instruments). Pernambuco wood (Caesalpinia echinata Lam.) has special characteristics like resonance, density, durability, and beauty; for this reason, it is considered the best material for stringed instruments bows. Besides pernambuco wood has been used around the world, some samples, and consequently some bows, are better than others. In Brazil, others woody species have been used in the manufacture of bows. In this paper some wood samples of pernambuco wood were analysed in order to verify if it is possible to find differences in their anatomical qualitative and quantitative characteristics that explain the bow quality. The comparative analysis of pernambuco wood samples showed variations in vessel diameter, quantity and distribution of axial parenchyma and orientation of axial and radial wood elements.

Key message We demonstrate that tropical trees growing in wet climates can have a marked seasonality in cambium activity and stem growth associated with high temperature and day length of summer. Abstract Monitoring the rhythm of tree growth associated with the growth rings can contribute substantially to understanding forest dynamics and the management of tropical forests. In this study, we monitored the girth increment rhythm and described the wood characteristics (anatomy of growth rings, wood specific gravity) in 10 tropical tree species (103 individuals) naturally occurring in a wet and weakly seasonal region of Atlantic Forest in southern Brazil. We aimed to verify whether tree growth dynamics are associated with climate and woody anatomy in tropical trees with contrasting ecological characteristics. We installed permanent dendrometer bands and monthly assessed the girth increment for 22 months. We collected wood samples (non-destructive method), measured wood specific gravity and prepared permanent slides to characterize the growth ring markers. We found growth rings in all species (distinct in six species); deciduous species produced more distinguishable tree rings compared with semi-deciduous and evergreen tree species. Species varied in their accumulated girth growth (in average, from 1.83 to 62.64 mm), growth rates (1-15 %), and annual radial increment (0.16-5.44 mm). Girth increment was positively related to temperature and day length in five out of ten tree species, indicating the possible effects of these climatic variables in triggering cambial activity in these species. The growth pattern varied among species and was marginally associated to the tree deciduousness. We concluded that even in wet and less seasonal climates, there can be an association in the cambium activity and stem growth with the hotter and longer days of summer months.

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