Measuring stellar differential rotation with high-precision space-borne photometry

We introduce a method of measuring a lower limit to the amplitude of surface differential rotation from high-precision, evenly sampled photometric time series. It is applied to main-sequence late-type stars whose optical flux modulation is dominated by starspots. An autocorrelation of the time series was used to select stars that allow an accurate determination of starspot rotation periods. A simple two-spot model was applied together with a Bayesian information criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty were obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov Chain approach. We applied our method to the Sun and eight other stars for which previous spot modelling had been performed to compare our results with previous ones. We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite for successfully measuring differential rotation through spot modelling. For a proper Monte Carlo Markov Chain analysis, it is necessary to take the strong correlations among different parameters that exist in spot modelling into account. For the planet-hosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation of \Delta P / P = 0.0523 \pm 0.0016. We confirm that the Sun as a star in the optical passband is not suitable for measuring differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison to more sophisticated and time-consuming approaches.Comment: Accepted to Astronomy and Astrophysics, 15 pages, 13 figures, 4 tables and an Appendi

Assessment models in two project based learning (PBL) approaches: An exploratory study

Project Based Learning approach (PBL) has been a curricular and pedagogical asset in several engineering programs. According to the literature, PBL is based on a project being developed by teams of students in order to solve a problem connected with the profession, linking theory and practice. This learning context create opportunities for students to develop a set of technical and transversal competences related to engineering professional practice. In PBL there is no universal models, but a diversity of approaches. They are similar by the main principles of PBL, but different by the way they happen in practice. Implementing PBL implies rethinking the teaching and learning approach, in terms of contents, faculty collaboration, pedagogical spaces, and strategies for students’ support, amongst other. Particularly, assessment has been widely discussed in several studies. In order to contribute for an in-deep reflection about this topic, this paper aim to present two PBL assessment models in different contexts: a) PIEGI – Master Degree in Industrial Engineering and Management at University of Minho, Portugal; b) 100% PBL model in Engineering courses at UNISAL, Lorena, SP, Brazil. The assessment model in both contexts were analysed, based on documental analysis (pedagogical documents related to the projects). The information was organized and analysed in order to identify differences and similarities in both models. Implications of assessment in PBL and practical recommendation are presented in order to provide more inputs about this topic.Este trabalho foi parcialmente suportado pelos projetos COMPETE-POCI-01-0145-FEDER-007043 e FCT-UID-CEC-00319-2013, de Portugal

ANALYSIS OF BILATERAL ASYMMETRIES BY FLIGHT TIME OF ONE LEG COUNTERMOVEMENT JUMP

Lateral differences concerning the magnitude of strength are frequently found in the lower limbs (LL) and may be related to preference (dominant and non-dominant) and skill performance. For jump tests the lateral differences greater than 15% are considered clinically significant (Noyes et al., 1991). Since Countermovement Jumps (CMJ) on a force platform are an adequate method for the identification of lateral asymmetries (Menzel et al., 2006), the objective was to verify if lateral asymmetries of CMJ performance can also be identified by the flight time of single leg CMJ on a contact mat

Drugs and lifestyle for the treatment and prevention of coronary artery disease: comparative analysis of the scientific basis

In this article, we compare two strategies for atherosclerosis treatment: drugs and healthy lifestyle. Statins are the principal drugs used for the treatment of atherosclerosis. Several secondary prevention studies have demonstrated that statins can significantly reduce cardiovascular events including coronary death, the need for surgical revascularization, stroke, total mortality, as well as fatal and non-fatal myocardial infarction. These results were observed in both men and women, the elderly, smokers and non-smokers, diabetics and hypertensives. Primary prevention studies yielded similar results, although total mortality was not affected. Statins also induce atheroma regression and do not cause cancer. However, many unresolved issues remain, such as partial risk reduction, costs, several potential side effects, and long-term use by young patients. Statins act mainly as lipid-lowering drugs but pleiotropic actions are also present. Healthy lifestyle, on the other hand, is effective and inexpensive and has no harmful effects. Five items are associated with lower cardiac risk: non-smoking, BMI ≤25, regular exercise (30 min/day), healthy diet (fruits, vegetables, low-saturated fat, and 5-30 g alcohol/day). Nevertheless, there are difficulties in implementing these measures both at the individual and population levels. Changes in behavior require multidisciplinary care, including medical, nutritional, and psychological counseling. Participation of the entire society is required for such implementation, i.e., universities, schools, media, government, and medical societies. Although these efforts represent a major challenge, such a task must be faced in order to halt the atherosclerosis epidemic that threatens the world

High coercivity induced by mechanical milling in cobalt ferrite powders

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 treated by mechanical milling with different grinding balls. The cobalt ferrite nanoparticles were prepared using a simple hydrothermal method and annealed at 500oC. The non-milled sample presented coercivity of about 1.9 kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42. After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence ratio MR/MS for these samples increase to 0.49 and 0.51, respectively. To investigate the influence of the microstructure on the magnetic behavior of these samples, we used X-ray powder diffraction (XPD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The XPD analysis by the Williamson-Hall plot was used to estimate the average crystallite size and strain induced by mechanical milling in the samples