3,674 research outputs found

    The constant-velocity highly collimated outflows of the planetary nebula He 2-90

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    We present high-dispersion echelle spectroscopic observations and a narrow-band [N II] image of the remarkable jet-like features of He 2-90. They are detected in the echelle spectra in the H-alpha and [N II] lines but not in other nebular lines. The [N II]/H-alpha ratio is uniformly high, ~1. The observed kinematics reveals bipolar collimated outflows in the jet-like features and shows that the southeast (northwest) component expands towards (away from) the observer at a remarkably constant line-of-sight velocity, 26.0+-0.5 km/s. The observed expansion velocity and the opening angle of the jet-like features are used to estimate an inclination angle of ~5 degrees with respect to the sky plane and a space expansion velocity of ~290 km/s. The spectrum of the bright central nebula reveals a profusion of Fe lines and extended wings of the H-alpha line, similar to those seen in symbiotic stars and some young planetary nebulae that are presumed to host a mass-exchanging binary system. If this is the case for He 2-90, the constant velocity and direction of the jets require a very stable dynamic system against precession and warping.Comment: 8 pages (emulate ApJ), 5 figure, 1 tabl

    Red ruby glass from gold nanoparticles obtained by LASiS – a new approach

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    Currently, most of the red colored glasses are still produced using cadmium sulfoselenide, despite its high toxicity. Alternative solutions, more environmentally friendly, have been sought, most of them going through the use of gold or copper nanoparticle, the color being obtained by striking. This work presents a new methodology for production of a red colored glass by the incorporation of gold nanoparticles in the melt, trying to take advantage of an amorphous silica layer involving the nanoparticles. Gold nanoparticles (AuNP) were produced by laser ablation synthesis in solution (LASiS), using a solution of tetraethyl orthosilicate (TEOS) and isopropanol (IPA). A xerogel was prepared using the TEOS:IPA:AuNp suspension, mixed with a alkaline-earth aluminosilicate colorless glass and melted at 1350 °C producing a glass with an intense and homogeneous ruby red color without the need of a striking stage.publishe

    Forest patch conservation indicators.

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    This work presents indicators to assess the conservation status of forest patches in fragmented landscapes. However, how can we evaluate the conservation status of forest patches in order to compare it to a hypothetical situation of well-preserved vegetation without human disturbance? It is possible to measure some ecological processes, like nutrient cycling, canopy, edaphic, topographic and hydrological parameters, as well as landscape attributes, and associate them to conservation status. When the attributes of original well-preserved forest are unknown because they are seldom found, it is possible to compare patches by assessing the variability of their attributes. To this end, parameters related to canopy, soil, topography and landscape were analyzed to establish indicators and their integrated analysis was developed to assess the conservation status of forest patches and identify possible causes of shortcomings or obstacles to reach the conservation status. The study area is located in a Semidecidual Forest region, in Brazil. The methodology was developed considering plots distributed in sites within forest patches. The results allowed the identification of patches in different conditions of conservation and provided information of the factors that contribute to this status, in order to help guide and select the most appropriate measures to mitigate degradation and identify forest conservation strategies
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