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

Antiferromagnetic spin chain behavior and a transition to 3D magnetic order in Cu(D,L-alanine)2: Roles of H-bonds

We study the spin chain behavior, a transition to 3D magnetic order and the magnitudes of the exchange interactions for the metal-amino acid complex Cu(D,L-alanine)2.H2O, a model compound to investigate exchange couplings supported by chemical paths characteristic of biomolecules. Thermal and magnetic data were obtained as a function of temperature (T) and magnetic field (B0). The magnetic contribution to the specific heat, measured between 0.48 and 30 K, displays above 1.8 K a 1D spin-chain behavior that can be fitted with an intrachain antiferromagnetic (AFM) exchange coupling constant 2J0 = (-2.12 $\pm$ 0.08) cm$^{-1}$, between neighbor coppers at 4.49 {\AA} along chains connected by non-covalent and H-bonds. We also observe a narrow specific heat peak at 0.89 K indicating a phase transition to a 3D magnetically ordered phase. Magnetization curves at fixed T = 2, 4 and 7 K with B0 between 0 and 9 T, and at T between 2 and 300 K with several fixed values of B0 were globally fitted by an intrachain AFM exchange coupling constant 2J0 = (-2.27 $\pm$ 0.02) cm$^{-1}$ and g = 2.091 $\pm$ 0.005. Interchain interactions J1 between coppers in neighbor chains connected through long chemical paths with total length of 9.51 {\AA} are estimated within the range 0.1 < |2J1| < 0.4 cm$^{-1}$, covering the predictions of various approximations. We analyze the magnitudes of 2J0 and 2J1 in terms of the structure of the corresponding chemical paths. The main contribution in supporting the intrachain interaction is assigned to H-bonds while the interchain interactions are supported by paths containing H-bonds and carboxylate bridges, with the role of the H-bonds being predominant. We compare the obtained intrachain coupling with studies of compounds showing similar behavior and discuss the validity of the approximations allowing to calculate the interchain interactions.Comment: 10 pages, 4 figure

Efeito da vitamina C no ganho de peso e em parâmetros hematológicos de tambaqui.

O objetivo deste trabalho foi avaliar o efeito da suplementação dietária com ácido L-ascórbico (vitamina C) no ganho de peso e em parâmetros hematológicos de juvenis de tambaqui, Colossoma macropomum

Kahoot! and socrative in higher education: a comparative study

Technology brings new challenges and opportunities to higher education institutions, as it can promote learner-centered activities. Mobile devices such as smartphones are very popular among students and can easily engage them and promote motivation and active learning. In this study, we investigate Tourism undergraduate students’ perceptions on the use of mobile technology in the classroom, specifically two quiz makers in a comparative perspective: Kahoot! and Socrative. The purpose of this two-stage study is to identify and meet students’ preferences, so as to design activities that can truly promote learning. The participants are Mathematics and English students from a Portuguese higher education institution. At the first stage, in a preliminary survey, 33 students have identified their quiz preferences and most of them (87,88%) selected Socrative as their favourite quiz maker. At the second stage, students were also inquired about their general perceptions and preferred features, such as collaborative mode, competition mode, self-paced mode or immediate feedback. Similar studies have shown that these tools can promote engagement, motivation, concentration and learning. Therefore, we hope to contribute to a better understanding of how technology can improve the learning process.info:eu-repo/semantics/publishedVersio

Student receptiveness to Kahoot! in higher education

The use of technology in higher education has been increasing in the past few years and new online tools have emerged for very different purposes. Kahoot! is an example of a platform that can be used for reviewing content and motivating students for learning. Our research is based on data from a quantitative survey conducted in the previous school year and the participants were 86 undergraduate students from a Portuguese higher education institution. The preliminary results of the survey showed that students are very receptive to this tool and highly recommend it, as it promotes motivation. Other studies have shown that higher education students are usually receptive to web tools and consider technology can positively impact learning. To better understand students’ responses to the platform, in this study we aim at analysing the results according to area of study and investigating new correlations between variables, specifically (i) gender vs receptiveness to Kahoot!, (ii) gender vs recommendation of its use and (iii) technology readiness vs receptiveness to Kahoot!.info:eu-repo/semantics/publishedVersio

Assessing students' engagement levels during lockdown: a survey in tourism degrees

In early 2020, the crisis of a new virus and a pandemic context took the world by storm. All sectors of society were affected: health, economics,… and education was no exception, with all levels suspending face-to-face classes, which were replaced by online activities. In view of this situation, several doubts and uncertainties emerged among educators, but one question stood out: how to proceed with teaching activities in the online format without compromising the commitment and engagement of the students? Within this context, the teachers involved in this study sought to adapt the activities and teaching materials to the exclusive use of technology and promoted asynchronous tasks, which could be developed independently by the students. In order to understand how the profound changes in Higher Education were experienced by students, a quantitative survey was conducted. The participants in the study are undergraduate students from a Portuguese Higher Education institution attending the curricular units of Statistical Analysis and English.info:eu-repo/semantics/publishedVersio

Enhancing students’ motivation with Kahoot!: a case study in English and mathematics

In the last few decades, technology has advanced in multiple fields, including Education. Some of its benefits include improving student performance and motivation, fostering active learning and tracking student progress. As a "new learning generation" is around, profound changes to the role and function of both teachers and students are particularly vital, so active, cooperative and participative methodologies of learning must be privileged. Given that most higher education students are technology savvy and very receptive to the integration of Web 2.0 tools in class, the teachers involved in this study began using Kahoot! in their classes as an alternative teaching methodology. The participants in the study are undergraduate students from a Portuguese higher education institution and encompassed the curricular units of Statistical Analysis and English. The aim of the study is to investigate students’ perceptions of how Kahoot! can be used as a tool for testing new vocabulary, reviewing class content or designing warm-up activities. A quantitative survey is being conducted to gather information about students’ insights on the use of Kahoot!. Similar studies have shown that students are generally receptive to the use of this tool and find it useful to increase their motivation.info:eu-repo/semantics/publishedVersio

Toxicidade aguda do paration metílico para tambaqui (Colossoma macropomum).

O objetivo deste trabalho foi determinar a toxicidade aguda do paration metílico para o tambaqui