Astrometry of mutual approximations between natural satellites. Application to the Galilean moons

Typically we can deliver astrometric positions of natural satellites with errors in the 50-150 mas range. Apparent distances from mutual phenomena, have much smaller errors, less than 10 mas. However, this method can only be applied during the equinox of the planets. We developed a method that can provide accurate astrometric data for natural satellites -- the mutual approximations. The method can be applied when any two satellites pass close by each other in the apparent sky plane. The fundamental parameter is the central instant $t_0$ of the passage when the distances reach a minimum. We applied the method for the Galilean moons. All observations were made with a 0.6 m telescope with a narrow-band filter centred at 889 nm with width of 15 nm which attenuated Jupiter's scattered light. We obtained central instants for 14 mutual approximations observed in 2014-2015. We determined $t_0$ with an average precision of 3.42 mas (10.43 km). For comparison, we also applied the method for 5 occultations in the 2009 mutual phenomena campaign and for 22 occultations in the 2014-2015 campaign. The comparisons of $t_0$ determined by our method with the results from mutual phenomena show an agreement by less than 1-sigma error in $t_0$, typically less than 10 mas. This new method is particularly suitable for observations by small telescopes.Comment: 13 pages, 11 figures and 8 tables. Based on observations made at the Laborat\'orio Nacional de Astrof\'isica (LNA), Itajub\'a-MG, Brazi

Estratégia para redução do uso da água em arroz irrigado: cultivar superprecoce BRS Atalanta.

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Fungos associados a sementes de araucária coletadas em três municípios do Estado do Paraná.

Resumo

Avaliação técnica e operacional do sistema de classificação de pele bovina estabelecido pelo Ministério da Agricultura, Pecuária e Abastecimento (MAPA).

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Astrometry of the main satellites of Uranus: 18 years of observations

We determine accurate positions of the main satellites of Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those of these satellites, are also determined. The observational period spans from 1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil. We used the software called Platform for Reduction of Astronomical Images Automatically (PRAIA) to minimise (digital coronography) the influence of the scattered light of Uranus on the astrometric measurements and to determine accurate positions of the main satellites. The positions of Uranus were then indirectly determined by computing the mean differences between the observed and ephemeris positions of these satellites. A series of numerical filters was applied to filter out spurious data. These filters are mostly based on the comparison between the positions of Oberon with those of the other satellites and on the offsets as given by the differences between the observed and ephemeris positions of all satellites. We have, for the overall offsets of the five satellites, -29 (+/-63) mas in right ascension and -27 (+/-46) mas in declination. For the overall difference between the offsets of Oberon and those of the other satellites, we have +3 (+/-30) mas in right ascension and -2 (+/-28) mas in declination. Ephemeris positions for the satellites were determined from DE432+ura111. Comparisons using other modern ephemerides for the solar system -INPOP13c- and for the motion of the satellites -NOE-7-2013- were also made. They confirm that the largest contribution to the offsets we find comes from the motion of the barycenter of the Uranus system around the barycenter of the solar system, as given by the planetary ephemerides. Catalogues with the observed positions are provided.Comment: 13 pages, 21 figure

POTENTIAL OF ILMENITE AS A SOLAR ABSORBER

Titanium is considered the fourth most widely used material in industry worldwide. Titanium minerals are currently being applied in various branches of industry, mainly in the field of pigmentation. Ilmenite (FeTiO3) is an iron and titanium oxide of more common and abundant occurrence, with theoretical composition of Fe (36.8%), Ti (31.6%) and O (31.6%). Having regard to the potential of titanium minerals and the abundance of ilmenite, together with the importance of validating direct applications of this ore, since the processing of titanium is still complex and expensive, it is necessary to study this mineral and the knowledge of its main characteristics. This work brings thermal, chemical and mineralogical characterizations of ilmenite, in order to know the potential of application of this ore as a solar absorbing material. The characterization techniques used were: X-ray diffraction (XRD) and Rietveld refinement for phase quantification, X-ray fluorescence (XRF), optical spectroscopy in the middle infrared region with Fourier Transformation by Transmittance (FTIR) and thermogravimetric thermal analysis (TGA). The analyzed sample obtained X-ray diffractogram, ilmenite (80.6%) and rutile (19.4%) as significant phases, corroborating the FRX results that indicated greater presence of Fe and titanium oxide in the ilmenite chemical composition under study. The TGA, DTA and DSC analyses indicated good thermal stability of the material in medium and high temperatures. The integration of the obtained data shows that the application of this ore as a precursor material of absorber films for selective purposes is considerable

α - to - β transformation on PVDF films obtained by uniaxial stretch

The α to β phase transformation of PVDF through the stretching process at different temperatures was investigated. The optimum stretching conditions were studied and characterised by infrared spectroscopy and differential scanning calorimetry. The maximum β−phase content was achieved at 80ºC and a stretch ratio of 5. Accompanying the phase transformation, a orientation of the polymer chains and a packing of the crystalline structure is observed. The stretch ratio does not significantly affect the degree of crystallinity.GRICES/FAPESP (Proc. 4.1.3/FAPESP).EU-ALFA project Plastinet.Fundação para a Ciência e a Tecnologia (FCT) - Grants POCTI/CTM/33501/99, POCI/CTM/59425/2004

Orbit determination of Transneptunian objects and Centaurs for the prediction of stellar occultations

The prediction of stellar occultations by Transneptunian objects and Centaurs is a difficult challenge that requires accuracy both in the occulted star position as for the object ephemeris. Until now, the most used method of prediction involving tens of TNOs/Centaurs was to consider a constant offset for the right ascension and for the declination with respect to a reference ephemeris. This offset is determined as the difference between the most recent observations of the TNO and the reference ephemeris. This method can be successfully applied when the offset remains constant with time. This paper presents an alternative method of prediction based on a new accurate orbit determination procedure, which uses all the available positions of the TNO from the Minor Planet Center database plus sets of new astrometric positions from unpublished observations. The orbit determination is performed through a numerical integration procedure (NIMA), in which we develop a specific weighting scheme. The NIMA method was applied for 51 selected TNOs/Centaurs. For this purpose, we have performed about 2900 new observations during 2007-2014. Using NIMA, we succeed in predicting the stellar occultations of 10 TNOs and 3 Centaurs between 2013 and 2015. By comparing the NIMA and JPL ephemerides, we highlighted the variation of the offset between them with time. Giving examples, we show that the constant offset method could not accurately predict 6 out of the 13 observed positive occultations successfully predicted by NIMA. The results indicate that NIMA is capable of efficiently refine the orbits of these bodies. Finally, we show that the astrometric positions given by positive occultations can help to further refine the orbit of the TNO and consequently the future predictions. We also provide the unpublished observations of the 51 selected TNOs and their ephemeris in a usable format by the SPICE library.Comment: 12 pages, 9 figures, accepted in A&

A lei da inovação tecnológica na Embrapa Clima Temperado.

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