849 research outputs found
Spiral structure of the Third Galactic Quadrant and the solution to the Canis Major debate
With the discovery of the Sagittarius dwarf spheroidal (Ibata et al. 1994), a
galaxy caught in the process of merging with the Milky Way, the hunt for other
such accretion events has become a very active field of astrophysical research.
The identification of a stellar ring-like structure in Monoceros, spanning more
than 100 degrees (Newberg et al. 2002), and the detection of an overdensity of
stars in the direction of the constellation of Canis Major (CMa, Martin et al.
2004), apparently associated to the ring, has led to the widespread belief that
a second galaxy being cannibalised by the Milky Way had been found. In this
scenario, the overdensity would be the remaining core of the disrupted galaxy
and the ring would be the tidal debris left behind. However, unlike the
Sagittarius dwarf, which is well below the Galactic plane and whose orbit, and
thus tidal tail, is nearly perpendicular to the plane of the Milky Way, the
putative CMa galaxy and ring are nearly co-planar with the Galactic disk. This
severely complicates the interpretation of observations. In this letter, we
show that our new description of the Milky Way leads to a completely different
picture. We argue that the Norma-Cygnus spiral arm defines a distant stellar
ring crossing Monoceros and the overdensity is simply a projection effect of
looking along the nearby local arm. Our perspective sheds new light on a very
poorly known region, the third Galactic quadrant (3GQ), where CMa is located.Comment: 5 pages, 2 figures. Quality of Fig 1 has been degraded to make it
smaller. Original fig. available on request. accepted for publication in
MNRAS letter
A Link Between the Semi-Major Axis of Extrasolar Gas Giant Planets and Stellar Metallicity
The fact that most extrasolar planets found to date are orbiting metal-rich
stars lends credence to the core accretion mechanism of gas giant planet
formation over its competitor, the disc instability mechanism. However, the
core accretion mechanism is not refined to the point of explaining orbital
parameters such as their unexpected semi-major axes and eccentricities. We
propose a model, which correlates the metallicity of the host star with the
original semi-major axis of its most massive planet, prior to migration,
considering that the core accretion scenario governs giant gas planet
formation. The model predicts that the optimum regions for planetary formation
shift inward as stellar metallicity decreases, providing an explanation for the
observed absence of long period planets in metal-poor stars. We compare our
predictions with the available data on extrasolar planets for stars with masses
similar to the mass of the Sun. A fitting procedure produces an estimate of
what we define as the Zero Age Planetary Orbit (ZAPO) curve as a function of
the metallicity of the star. The model also hints that the lack of planets
circling metal-poor stars may be partly caused by an enhanced destruction
probability during the migration process, since the planets lie initially
closer to the central stars.Comment: Nature of the replacement: According to recent simulations, the
temperature profile, T, is more adequately reproduced by beta = 1 rather than
beta = 2. We have introduced a distance scale factor that solves the very
fast drop of T for low metallicity and introduces naturally the inferior
distance limit of our ZAPO. Under this modification all the fitting process
was altere
Modelo de hargreaves-samani ajustado as condições climáticas do estado do Rio de Janeiro para estimativa da evapotranspiração de referência.
Utilizando-se como padrão para determinação da evapotranspiração de referência (ETo) o modelo de Penman-Monteith parametrizado no boletim Nº 56 de irrigação e drenagem da FAO (PM-FAO56) ajustou-se o modelo de Hargreaves-Samani (HS) para as condições climáticas do Estado do Rio de Janeiro. Nas estimativas da ETo foram utilizadas séries climáticas de 10 estações meteorológicas convencionais pertencentes ao Instituto Nacional de Meteorologia. Os valores dos coeficientes do modelo de HS ajustados para o Estado do Rio de Janeiro não variaram significativamente (cv 3,4%), sendo indicado a utilização de um valor médio (0,0116 ± 0,0004) para todo o Estado. O modelo de Hargreaves-Samani ajustado e o original apresentaram elevada precisão (r2 = 0,94) das estimativas de ETo. Contudo, a acurácia das estimativas de ETo foram superiores com o modelo HS ajustado (d = 0,99 e EPE = 0,25 mm d-1) em relação ao original (d = 0,93 e EPE = 0,65 mm d-1)
Weak insensitivity to initial conditions at the edge of chaos in the logistic map
We extend existing studies of weakly sensitive points within the framework of
Tsallis non-extensive thermodynamics to include weakly insensitive points at
the edge of chaos. Analyzing tangent points of the logistic map we have
verified that the generalized entropy with suitable entropic index q correctly
describes the approach to the attractor.Comment: 6 pages, 3 figure
Efektivitas Pemberian Jus Tomat Terhadaptekanan Darah pada Penderita Hipotensi
The aim of this research is to determinedthe effectivenessoftomato juiceonblood pressure of hypotensionpatients. The design of thisresearch is quasy experimentdesigned byNon-equivalent control groupweredivided intoexperiment groupandcontrol group. The research was conductedofhypotension patientinthe PuskesmasRumbai. The total sample are 50peoplewhowere takenby usingsimple randomtechniquesby noticing tothe inclusion criteria.Measuring instruments usedin the two groupsisthe observation sheet.The analysis usedwas univariateandbivariatealternativetestandWilcoxonMannWhitney.The results showeda significant differencebetween the meanbloodpressurebefore and afteradministration oftomatojuiceto the increase inbloodpressurep(0.000) <α (0.05).It'smeans thatin patent with hypotension effective to increase blood pressure. The results of this study recommend to apply tomato juice as an herbaltreatment to increase blood pressure
Variabilidade mesoclimática da chuva no norte e noroeste do estado do Rio de Janeiro.
Resumo: A chuva é um dos elementos climáticos mais importantes. Na quantidade e no período adequado pode trazer benefícios para, por exemplo, a agricultura, mas em situações adversas pode causar prejuízos, como inundações e deslizamentos de terra. Nesse sentido, este estudo analisou a variabilidade climática da altura pluviométrica sazonal nas mesorregiões Norte e Noroeste do estado do Rio de Janeiro. Foram utilizados dados trimestrais de chuva de onze estações hidrológicas. Os métodos da Análise de Regressão e, de Kendall foram utilizados para testar a tendência da altura pluviométrica sazonal. Os resultados mostraram que no verão e inverno foram observadas as maiores e menores tendências significativas da altura pluviométrica, respectivamente. Abstract: Rain is one of the most important climatic elements. In the quantity and at the right time can benefit, for example, agriculture, but in adverse situations can cause damage such as floods and landslides. In this perspective, this study analyzed the climate viability of seasonal rainfall in the North and Northwest mesoregions, from the state of Rio de Janeiro. Quarterly rainfall data from eleven hydrological stations were used. Methods of Regression Analysis and Kendall were used to test the trend of seasonal rainfall. The results showed that in the summer and in the winter the highest and the lowest significant trends in rainfall height were observed, respectively
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