Key Challenges of On-Line Education in Multi-Cultural Context

In meeting the ever-growing educational needs of culturally diverse student populations, universities and colleges still seek to maintain high quality standards, both for in situ and on line education. Despite the latter's reportedly high effectiveness potential, online degree courses tend to have low students' persistence and satisfaction rates. In this pape, r we examine the role that students' and instructors' national cultures play in the way individuals learn at a distance. We argue that students' individual culture dimensions may prove influential in achieving overall learning outcomes. The key complexities for students involve understanding the instructor's role in a socio-constructivist approach, adapting online collaborative learning and acquiring academic skills. These can become crucial barriers to effective online learning. No less a challenge is presented by online distance education for instructors. Academic institutions' managements have high expectations in terms of utilizing up-to-date teaching techniques, enhancing competitive edge and maximizing cost-effectiveness. Thus, the teaching staff is expected to play an increasingly essential role in the new environment. We conclude that instructors have to develop strategies to motivate, support and counsel students with the aim of facilitating the students' on-line learning experience. This implies that teaching staff have to acquire new skills and competences vital for multicultural online education. Robert Kennedy College, whose experience is reflected in this paper, shares much of the issues of other institutions aiming to utilize distance online learning, but has the advantage that it was set up from the start as an online institution. (C) 2017 The Authors. Published by Elsevier Ltd

Spectroscopic and physical parameters of Galactic O-type stars. II. Observational constraints on projected rotational and extra broadening velocities as a function of fundamental parameters and stellar evolution

Rotation is of key importance for the evolution of hot massive stars, however, the rotational velocities of these stars are difficult to determine. Based on our own data for 31 Galactic O stars and incorporating similar data for 86 OB supergiants from the literature, we aim at investigating the properties of rotational and extra line-broadening as a function of stellar parameters and at testing model predictions about the evolution of stellar rotation. Fundamental stellar parameters were determined by means of the code FASTWIND. Projected rotational and extra broadening velocities originate from a combined Ft + GOF method. Model calculations published previously were used to estimate the initial evolutionary masses. The sample O stars with Minit > 50 Msun rotate with less that 26% of their break-up velocity, and they also lack objects with v sin i 35 Msun on the hotter side of the bi-stability jump, the observed and predicted rotational rates agree quite well; for those on the cooler side of the jump, the measured velocities are systematically higher than the predicted ones. In general, the derived extra broadening velocities decrease toward cooler Teff, whilst for later evolutionary phases they appear, at the same v sin i, higher for high-mass stars than for low-mass ones. None of the sample stars shows extra broadening velocities higher than 110 km/s. For the majority of the more massive stars, extra broadening either dominates or is in strong competition with rotation. Conclusions: For OB stars of solar metallicity, extra broadening is important and has to be accounted for in the analysis. When appearing at or close to the zero-age main sequence, most of the single and more massive stars rotate slower than previously thought. Model predictions for the evolution of rotation in hot massive stars may need to be updated.Comment: 15 pages, 10 figures, accepted for publication in A &

The rotation rates of massive stars: How slow are the slow ones?

Context: Rotation plays a key role in the life cycles of stars with masses above 8 Msun. Hence, accurate knowledge of the rotation rates of such massive stars is critical for understanding their properties and for constraining models of their evolution. Aims: This paper investigates the reliability of current methods used to derive projected rotation speeds v sin i from line-broadening signatures in the photospheric spectra of massive stars, focusing on stars that are not rapidly rotating. Methods: We use slowly rotating magnetic O-stars with well-determined rotation periods to test the Fourier transform (FT) and goodness-of-fit (GOF) methods typically used to infer projected rotation rates of massive stars. Results: For our two magnetic test stars with measured rotation periods longer than one year, i.e., with v sin i < 1 km/s, we derive v sin i ~ 40-50 km/s from both the FT and GOF methods. These severe overestimates are most likely caused by an insufficient treatment of the competing broadening mechanisms referred to as microturbulence and macroturbulence. Conclusions: These findings warn us not to rely uncritically on results from current standard techniques to derive projected rotation speeds of massive stars in the presence of significant additional line broadening, at least when v sin i <~ 50 km/s. This may, for example, be crucial for i) determining the statistical distribution of observed rotation rates of massive stars, ii) interpreting the evolutionary status and spin-down histories of rotationally braked B-supergiants, and iii) explaining the deficiency of observed O-stars with spectroscopically inferred v sin i ~ 0 km/s. Further investigations of potential shortcomings of the above techniques are presently under way.Comment: 4 pages, 4 figures, accepted for publication in A&A Letter

Bright OB stars in the Galaxy.II. Wind variability in O supergiants as traced by H-alpha

We investigate the line-profile variability (lpv) of H-alpha for a large sample of O-type supergiants. We used the Temporal Variance Spectrum (TVS) analysis, developed by Fullerton et al 1996 and modified by us to take into account the effects of wind emission. By means of a comparative analysis we put a number of constraints on the properties of the variability as a function of stellar and wind parameters. The results of our analysis show that all the stars in the sample show evidence of significant lpv in H-alpha, mostly dominated by processes in the wind. The variations occur between zero and 0.3 v_inf (i.e., below ~1.5 R_star), in good agreement with the results from similar studies. A comparison between observations and line-profile simulations indicates that for stars with intermediate wind densities the H-alpha variability can be explained by simple models, consisting of coherent or broken shells (blobs) uniformly distributed over the wind volume, with an intrinsic scatter in the maximum density contrast of about a factor of two. For stars at lower and higher wind densities, on the other hand, we found certain inconsistencies between observations and our predictions, most importantly concerning the mean amplitude and the symmetry properties of the TVS. This disagreement might be explained with the presence of coherent large-scale structures, partly confined in a volume close to the star. Interpreted in terms of a variable mass-loss rate, the observed variations of H-alpha indicate changes of 4% with respect to the mean value of M_dot for stars with stronger winds and of 16% for stars with weaker winds. The effect of these variations on the corresponding wind momenta is rather insignificant (<0.16 dex), increasing the local scatter without affecting the Wind Momentum Luminosity Relationship.Comment: 22 pages, 11 figures. Accepted by Astronomy and Astrophysic