Navegando por Autor "Melo, C."
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Artigo A catalog of rotational and radial velocities for evolved stars(EDP Sciences, 2006-07-20) Martins, Bruno Leonardo Canto; de Medeiros, José Renan; Silva, J. R. P.; Nascimento Júnior, José Dias do; da SIlva, L.; Melo, C.; Burnet, M.Aims.The present paper describes the first results of an observational program intended to refine and extend the existing measurements of metal-poor stars, with an emphasis on field evolved stars. Methods.The survey was carried out with the FEROS and CORALIE spectrometers. For the measurements, obtained from spectral synthesis, we estimate an uncertainty of about 2.0. Results.Precise rotational velocities are presented for a large sample of 100 metal-poor stars, most of them evolving off the main–sequence. For the large majority of the stars composing the present sample, rotational velocities have been measured for the first timeArtigo Reversible cerebral vasoconstriction syndrome as a cause of simultaneously ischemic and hemorrhagic stroke(Journal of the Neurological Sciences, 2015) Correia, Carlos Eduardo Rocha; Godeiro, Clécio de Oliveira; Loureiro, C.; Loureiro, A.; Linard, V.; José, J.; Laurentino, M.; Santiago, P.; Dourado, M.E.; Melo, C.; Marinho, M.Introduction: Reversible cerebral vasoconstriction syndrome(RCVS) is characterized by multifocal segmental vasoconstriction of cerebral arteries, which resolve spontaneously within 3 months, typically heralded by a sudden, severe headache with or without neurologic deficit. The main complications are intracranial hemorrhage, ischemic disturbance of the cerebral circulation, hypertensive encephalopathy (PRES) or epileptic seizures. Case: Female, 47 years old, hypertensive and no history of previous migraine, suddenly developed headache associated with paresis of the right upper limb. After a few hours of the onset of symptoms, a CT scan was performed and showed intraparenchymal hemorrhage in left temporal and parietal lobes. The patient evolved with partial and progressive improvement of the symptoms. A week later, a CT scan revealed ischemic area at the right parietal lobe. Magnetic Resonance Angiography was performed, which found narrowing of the right posterior and middle cerebral artery. The patient was treated with prednisone and nimodipine for 3 months. A 90 days later MRA revealed no vascular irregularity anymore. Discussion: Stroke, either hemorrhagic or ischemic is a relatively frequent presentation in RCVS, but simultaneously manifestations of intracerebral hemorrhage, and cerebral infarction was not described. More than half the cases (60%) are secondary to exposure to vasoactive substances or occur in the postpartum period. Cortical subarachnoid hemorrhage (22%), intracerebral hemorrhage (6%), seizures (3%), and reversible posterior leukoencephalopathy (9%) are early complication. Ischemic events, including TIAs (16%) and cerebral infarction (4%), occur later than hemorrhagic strokes. Several case series have reported success with calcium channel blockers or short term glucocorticoids medications.Artigo Search for giant planets in M67 III. Excess of hot Jupiters in dense open clusters(EDP Sciences, 2016) Brucalassi, A.; Pasquini, v; Saglia, R.; Ruiz, M. T.; Bonifacio, v; Leão, I.; Martins, B. L. Canto; Medeiros, José Renan de; Bedin, L. R.; Biazzo, v; Melo, C.; Lovis, C.; Randich, S.Since 2008 we used high-precision radial velocity (RV) measurements obtained with different telescopes to detect signatures of massive planets around main-sequence and evolved stars of the open cluster (OC) M67. We aimed to perform a long-term study on giant planet formation in open clusters and determine how this formation depends on stellar mass and chemical composition. A new hot Jupiter (HJ) around the main-sequence star YBP401 is reported in this work. An update of the RV measurements for the two HJ host-stars YBP1194 and YBP1514 is also discussed. Our sample of 66 main-sequence and turnoff stars includes 3 HJs, which indicates a high rate of HJs in this cluster (5.6+5.4-2.6% for single stars and 4.5%+4.5-2.5% for the full sample). This rate is much higher than what has been discovered in the field, either with RV surveys or by transits. High metallicity is not a cause for the excess of HJs in M67, nor can the excess be attributed to high stellar masses. When combining this rate with the non-zero eccentricity of the orbits, our results are qualitatively consistent with a HJ formation scenario dominated by strong encounters with other stars or binary companions and subsequent planet-planet scattering, as predicted by N-body simulations.