Synchrotron radiation X-ray multiple diffraction in the study of KDP phase transition induced by electric field

In this work, the application of the X-ray multiple diffraction technique using synchrotron radiation at Laboratório Nacional de Luz Síncrotron (LNLS) to study KDP phase transition induced by electric field is discussed. A Huber three-axis (omega, phi, 2theta) diffractometer mounted on a table which rotates around the incident beam allows to measure Renninger scans (RS) at the XRD station of LNLS using the adequate polarization for the experiments. Prior results indicated (080) as the best choice for the KDP primary reflection and the (440)(<img src="http:/img/fbpe/mr/v4n1/quatro.gif" alt="quatro.gif (94 bytes)"> 40) four-beam case for the secondary. Two Bragg-surface diffraction (BSD) reflections, where the secondary beam is propagated parallel to the sample surface, are involved in this multiple diffraction case. A RS interval of 3.3° around phi = 0° position was measured while the electric field was increased up to 6 kV/cm. At this value, a phase transition was observed and the secondary peaks became narrower and changed their RS position indicating possible occurrence of a metastable ferroelectric phase

Ecofisiologia da germinação de sementes de Campomanesia pubescens Ecophysiology of Campomanesia pubescens seed germination

A gabiroba de arbusto [Campomanesia pubescens (DC.) O. Berg. (Myrtaceae)], espécie nativa do Cerrado é considerada uma planta com potencial melífero, ornamental e medicinal. Com o objetivo de avaliar a influência de diferentes temperaturas, substratos e condições de luminosidade e da secagem, na qualidade fisiológica de suas sementes foram conduzidos dois experimentos. No primeiro utilizou-se sementes com 13% de teor de água, o qual foi realizado em delineamento experimental inteiramente casualizado em esquema fatorial (4x3x2), composto por quatro temperaturas (15-25, 20-30&deg;C alternadas, 25 e 30&deg;C constantes), três substratos (sobre papel, entre areia e entre vermiculita) e duas condições de luminosidade (claro e escuro) e, o segundo com sementes recém extraídas dos frutos e secas superficialmente, contendo 35% de teor de água e após a secagem em estufa com ventilação forçada de ar a temperatura de 30&deg;C por 30, 60, 90, 120, 150, 180, 260, 360, 750 e 810 minutos. Para a avaliação da qualidade fisiológica de sementes de gabiroba de arbusto, a semeadura sobre papel, no escuro e a 30&deg;C possibilita uma melhor expressão do vigor. As sementes de gabiroba de arbusto são intolerantes a secagem, podendo ser classificadas como recalcitrantes.<br>The gabiroba bush [Campomanesia pubescens (DC.) O. Berg. (Myrtaceae)], a native species of the Cerrado is considered a plant with melliferous, ornamental and medicinal potential. Aiming to evaluate the influence of abiotic factors on seed germination, two experiments were conducted. The first was conducted in a completely randomized design in a factorial design(4x3x2), composed of four temperatures (15-25, 20-30&deg;C alternate, 25 and 30&deg;C constant), 3 substrates (paper, sand and vermiculite) and two light conditions (light and dark). The second experiment aimed to evaluate the tolerance to desiccation of fresh seeds dried superficially, with 35% of water, by drying it in oven with forced ventilation of air at 30&deg;C for 30, 60, 90, 120, 150, 180, 260, 360, 750 and 810 minutes. To evaluate the physiological quality of seeds gabiroba, shrub planting on paper, in the dark and 30&deg;C, enables a better expression of the force. The seeds of bush gabiroba are intolerant to desiccation and can be classified as recalcitrant