Do the seasonal forests in northeastern Brazil represent a single floristic unit?

Floristic analyses (Principal Component Analysis and Analysis of Group Indicators) at the genus level were employed to characterize and compare seasonal forest formations in northeastern Brazil. The presence - absence of 248 genera of woody plants occurring in 24 floristic surveys was correlated with geomorphology and climatic variables. The analyses were consistent and point to the existence of two floristic groups of seasonal forests in the region, one more closely related to the Atlantic Coastal Forest (mata atlântica) and the other to the xerophytic formations (caatinga) of the region. The driest seasonal forest group experiences more than 8 dry months per year and/or a total annual rainfall of <1000 mm, and is found on the ancient eroded peaks in the semi-arid core and on the western slopes of the Borborema Plateau

Comparison of chemical composition of packable resin composites by scanning electron microscopy Comparação da composição química de resinas compostas compactáveis através de microscopia eletrônica de varredura

OBJECTIVES: the purpose of this study was to compare the chemical composition of four different shades (incisal/extra-light, A2, A3 and B3) of two packable resin composites (SOLITAIRE®, and PRODIGY CONDENSABLE TM). METHODS AND MATERIALS: the specimens measured 4mm in diameter and 4mm in thickness. Five specimens were made for each shade of the materials. They were light cured for 40 seconds at a power of 600mW/cm&sup2;. Subsequently, the specimens were removed from the plates and ground to powder and then pressed into holes measuring 4mm in diameter in a Teflon matrix, using the plates of the same material as base and cover. Specimens were evaluated under SEM with an x-ray detector for the spectroscopic test by energy dispersing. RESULTS: the chemical components found in both materials were practically the same, but in different proportions. Carbon, Oxygen, Aluminum, Silica, Fluoride and Barium were found. CONCLUSIONS: the chemical composition of each same material varied according to each shade analyzed.<br>OBJETIVO: comparar a composição química de duas resinas compostas compactáveis (SOLITAIRE®, Kulzer, e PRODIGY CONDENSABLE TM, Kerr) em quatro diferentes cores (incisal/extra-light, A2, A3 e B3). MATERIAIS E MÉTODO: as amostras foram confeccionadas em placas de acrílico transparente com 4mm de espessura. Os materiais foram inseridos e compactados em orifícios de 4mm de diâmetro. Para cada cor de cada material foram confeccionadas 5 amostras, as quais foram fotopolimerizadas durante 40 segundos a uma potência de 600mW/cm&sup2;. Logo após, estas foram removidas das placas e trituradas até apresentarem uma consistência de pó, foram prensadas, para colocação das diferentes cores em nichos de 4mm de diâmetro de uma matriz de Teflon, tendo como base e cobertura duas placas do mesmo material. As amostras foram montadas em stubs para a metalização, ou deposição de íons, sendo suas imagens importadas ao microscópio eletrônico de varredura com detector de raios X, para o teste de espectroscopia por dispersão de energia. RESULTADO: foram encontrados Carbono, Oxigênio, Alumínio, Sílica, Flúor, e Bário em diferentes proporções nos materiais estudados. CONCLUSÃO: a composição química de um mesmo material variou de acordo com a cor analisada e os componentes químicos encontrados foram praticamente os mesmos, mas em diferentes proporções