542 research outputs found

    Avaliação do período de floração e frutificação do banco ativo de germoplasma do jaborandi.

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    O jaborandi (Pilocarpus microphyllus Stapf ex wardleworth) pertencente à família Rutaceae está entre as plantas com efeito medicinal comprovado, sendo considerada uma espécie prioritária em programas de conservação. O Banco Ativo de Germoplasma (BAG) do jaborandi foi estabelecido em 1992, no Horto de Plantas Medicinais da EMBRAPA Amazônia Oriental, ano em que o jaborandi entrou na lista do IBAMA de espécies ameaçadas de extinção. Através do acompanhamento diário dessa espécie, foi possível avaliar o seu período de floração e frutificação no período de 2009 a 2010, buscando conhecer o melhor momento para a coleta de material vegetal. O BAG jaborandi teve floração e frutificação durante todo o período avaliado. O mês de setembro de 2010 foi o mês com maior número de dias de floração e o menor o mês de novembro de 2009. Os meses de abril e julho de 2009 e maio, junho e julho de 2010 foram os meses que apresentaram o maior número de acessos floridos. Quanto à frutificação, setembro de 2010 foi o mês onde ocorreu o maior número de dias de frutificação e o mês de junho de 2009 foi o menor. O maior número de acessos que frutificaram ocorreu nos meses de maio e julho de 2009 e maio, junho e julho de 2010.PIBIC-2011

    Avaliação da regeneração de ramos de jaborandi (Pilocarpus microphyllus Stapf ex wardleworth).

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    Entre as plantas que possuem efeito medicinal comprovado, o jaborandi (Pilocarpus microphyllus Stapf ex wardleworth) é considerado planta obrigatória em programas de conservação. Das folhas, são extraídas sais de pilocarpina, cuja principal ação ocorre no tratamento contra o glaucoma. Nesse sentido, estudos relacionados com a regeneração de ramos de jaborandi são fundamentais no manejo para a colheita de folhas dessa espécie. Os acessos avaliados na pesquisa foram: Maisa, Merck cultivado a pleno sol e Merck cultivado à sombra; foram utilizados dois tipos de corte nos ramos, respectivamente, a 10 e 20 cm das bifurcações dos ramos. O acesso Merck cultivado a pleno sol obteve maiores resultado em relação ao número de folíolos e comprimento da brotação na altura de corte de 10 cm. Na altura de corte de 20 cm, o maior número de folíolos foi obtido pelos acessos Merck cultivado a pleno sol e na sombra e em relação ao comprimento da brotação o acesso, que sobressaio sobre os demais foi o Merck cultivado a pleno sol.PIBIC-2011

    Avaliação fenológica e screening fitoquímico de Mansoa alliacea (LAM.) A. Gentry - Bignoniaceae.

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    O trabalho teve como objetivo determinar o período de floração e frutificação do cipó d?alho cultivado no horto de plantas medicinais da Embrapa Amazônia Oriental. O estudo foi realizado no período de agosto de 2010 a maio de 2011. O cipó d?alho apresentou um período de 3 a 20 dias de floração sem ocorrer frutificação, favorecendo a coleta de folhas. O screening fitoquímico identificou a presença de oito compostos químicos naturais do metabolismo secundário da Mansoa alliacea.PIBIC-2011

    Avaliação fenológica e screening fitoquímico de Averrhoa carambola L.- Oxalidaceae.

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    O trabalho teve como objetivo determinar o período de floração e frutificação da carambola cultivada no horto de plantas medicinais da Embrapa Amazônia Oriental. O estudo foi realizado no período de agosto de 2010 a maio de 2011. A carambola apresentou um período de 15 a 21 dias de floração e frutificação, favorecendo a coleta de folhas por mês, sendo que o mês de janeiro apresentou o maior número de dias em que a espécie floresceu e frutificou. Enquanto, o mês de dezembro foi o que apresentou o menor número (15 dias). O screening fitoquímico identificou a presença de 14 compostos químicos naturais do metabolismo secundário da Averrhoa carambola.PIBIC-2011

    Dynamical masses of the low-mass stellar binary AB Doradus B

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    Context. ABDoradus is the main system of the ABDoradus moving group. It is a quadruple system formed by two widely separated binaries of pre-main-sequence (PMS) stars: ABDorA/C and ABDor Ba/Bb. The pair ABDorA/C has been extensively studied and its dynamical masses have been determined with high precision, thus making of ABDorC a benchmark for calibrating PMS stellar models. If the orbit and dynamical masses of the pair ABDor Ba/Bb can be determined, they could not only play a similar role to that of ABDorC in calibrating PMS models, but would also help to better understand the dynamics of the whole ABDoradus system. Aims. We aim to determine the individual masses of the pair ABDor Ba/Bb using VLBI observations and archive infrared data, as part of a larger program directed to monitor binary systems in the ABDoradus moving group. Methods. We observed the system ABDor B between 2007 and 2013 with the Australian Long Baseline Array (LBA), at a frequency of 8.4 GHz in phase-reference mode. Results. We detected, for the first time, compact radio emission from both stars in the binary, ABDor Ba and ABDor Bb. This result allowed us to determine the orbital parameters of both the relative and absolute orbits and, consequently, their individual dynamical masses: 0.28±0.05M_sun and 0.25±0.05M_sun, respectively. Conclusions. Comparisons of the dynamical masses with the prediction of PMS evolutionary models show that the models underpredict the dynamical masses of the binary components Ba and Bb by ~30 and 40%, respectively, although they all still agree at the 2-sigma level. The same stellar models favour an age between 50 and 100 Myr for this system. We also discuss the evolutionary status of ABDor Ba/Bb in terms of an earlier double-double star scenario that might explain the strong radio emission detected in both components

    The Electrical-Thermal Switching in Carbon Black-Polymer Composites as a Local Effect

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    Following the lack of microscopic information about the intriguing well-known electrical-thermal switching mechanism in Carbon Black-Polymer composites, we applied atomic force microscopy in order to reveal the local nature of the process and correlated it with the characteristics of the widely used commercial switches. We conclude that the switching events take place in critical interparticle tunneling junctions that carry most of the current. The macroscopic switched state is then a result of a dynamic-stationary state of fast switching and slow reconnection of the corresponding junctions.Comment: 14 pages, 5 figures,Typographic correctio

    New constraints on the presence of debris disks around G 196-3 B and VHS J125601.92–125723.9 b

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    Context. The existence of warm (protoplanetary) disks around very young isolated planetary and brown dwarf mass objects is known based on near- and mid-infrared flux excesses and millimeter observations. These disks may later evolve into debris disks or rings, although none have been observed or confirmed so far. Little is known about circum(sub)stellar and debris disks around substellar objects. Aims. We aim to investigate the presence of debris disks around two of the closest (~20 pc), young substellar companions, namely G196-3 B and VHS J125601.92–125723.9 b (VHS J1256–1257 b), whose masses straddle the borderline between planets and brown dwarfs. Both are companions at wide orbits (≥100 au) of M-type dwarfs and their ages (50–100 Myr and 150–300 Myr, respectively) are thought to be adequate for the detection of second-generation disks. Methods. We obtained deep images of G196-3 B and VHS J1256–1257 b with the NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm. These data were combined with recently published Atacama Large Millimeter Array (ALMA) and Very Large Array (VLA) data of VHS J1256–1257 b at 0.87 mm and 0.9 cm, respectively. Results. Neither G196-3 B nor VHS J1256–1257 b were detected in the NOEMA, ALMA, and VLA data. At 1.3 mm, we imposed flux upper limits of 0.108 mJy (G196-3 B) and 0.153 mJy (VHS J1256–1257 b) with a 3-σ confidence. Using the flux upper limits at the millimeter and radio wavelength regimes, we derived maximum values of 1.38×10−2 MEarth and 5.46 × 10−3 MEarth for the mass of any cold dust that might be surrounding G196-3 B and VHS J1256–1257 b, respectively. Conclusions. We put our results in the context of other deep millimeter observations of free-floating and companion objects with substellar masses smaller than 20 MJup and ages between approximately one and a few hundred million years. Only two very young (2–5.4 Myr) objects are detected out of a few tens of them. This implies that the disks around these very low-mass objects must have small masses, and possibly reduced sizes, in agreement with findings by other groups. If debris disks around substellar objects scale down (in mass and size) in a similar manner as protoplanetary disks do, millimeter observations of moderately young brown dwarfs and planets must be at least two orders of magnitude deeper to be able to detect and characterize their surrounding debris disks

    Annihilation of structural defects in chalcogenide absorber films for high-efficiency solar cells

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    Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In polycrystalline semiconductor absorbers for thin-film solar cells, structural defects may enhance electron-hole recombination and hence lower the resulting energy conversion efficiency. To be able to efficiently design and optimize fabrication processes that result in high-quality materials, knowledge of the nature of structural defects as well as their formation and annihilation during film growth is essential. Here we show that in co-evaporated Cu(In,Ga)Se-2 absorber films the density of defects is strongly influenced by the reaction path and substrate temperature during film growth. A combination of high-resolution electron microscopy, atomic force microscopy, scanning tunneling microscopy, and X-ray diffraction shows that Cu(In,Ga)Se-2 absorber films deposited at low temperature without a Cu-rich stage suffer from a high density of - partially electronically active - planar defects in the {112} planes. Real-time X-ray diffraction reveals that these faults are nearly completely annihilated during an intermediate Cu-rich process stage with [Cu]/([In] + [Ga]) > 1. Moreover, correlations between real-time diffraction and fluorescence analysis during Cu-Se deposition reveal that rapid defect annihilation starts shortly before the start of segregation of excess Cu-Se at the surface of the Cu(In,Ga)Se-2 film. The presented results hence provide direct insights into the dynamics of the film-quality-improving mechanism
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