An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation

Bibliography: p. 243-248.An intensive photometric study in the Johnson B band of ten β Cephei stars in the open cluster NGC 3293 is presented. High sampling rates of the stars' light curves allow the identification of many formerly unknown pulsation frequencies in these stars, by means of Fourier periodogram analysis. All of the stars are found to be multiperiodic, with up to five frequencies identified for individual stars. Physical parameters of the stars are determined from previous photometric results in the literature. These parameters are used to make a comparison of the observed frequencies with theoretical predictions, including the effects of rotation. The results imply a preference for first and second overtone quadrupole (l=2) pulsation in these stars, while a weak relationship between stellar mass and pulsation overtone is identified. One of the stars is identified as a member of an eclipsing binary system, only the second β Cephei star to be identified as such. Physical parameters of the system are determined. The effects of rapid rotation (specifically, the distortion of the stellar profile from a perfect sphere) on alternative methods of pulsation mode identification are investigated for a model β Cephei star. Ratios between light and velocity amplitudes show extreme differences between rotationally distorted and undistorted models, but these ratios show high sensitivity to other parameters as well. Thermally broadened spectral line profiles are calculated for the same model, for modes with l = 0 to 4 and equatorial rotation velocities up to 400 km/s. Neglect of rotational distortion is shown to lead to underestimation of true equatorial rotation velocities by as much as 253. This result confirms that observed B stars are probably rotating at break-up velocities. In summary, various aspects of the behaviour of the β Cephei stars in NGC 3293 in particular, and of β Cephei stars in general, including rapid rotators, are illuminated and augmented by this study

Hunting Starstuff: Searching for Calcium-Aluminum-Rich Inclusions in Cometary Dust

NASA’s Stardust mission (1999 - 2006) returned physical samples of the particles ejected by the comet 81P/Wild 2, collected in ultralight and extremely low density aerogel. These samples have been extensively analyzed using X-Ray Fluorescence (XRF), among other techniques, to determine the elemental, chemical and mineralogical composition of Wild 2. Because comets are thought to be formed in the icy outer regions of the solar system, billions of years ago, the Stardust data gives us details of the composition of the ancient solar system and its subsequent evolution. One of the surprises to come out of the data is the presence of Calcium-aluminum-rich inclusions (CAIs). CAIs are composed of exotic minerals that form at very high temperatures, in stark contrast to the icy conditions beyond the orbit of Neptune. To date, only a small handful of CAIs have been found in Wild 2. My summer research has been to organize some of the Stardust XRF data into a “datamine-able” format, in order to search more efficiently for the presence of additional CAI

The influence of flow maldistribution on the performance of inhomogeneous parallel plate heat exhangers

The heat transfer performance of inhomogeneous parallel plate heat exchangers in transient operation is investigated using an established model. A performance parameter, denoted the Nusselt-scaling factor, is used as benchmark and calculated using a well-established single blow technique. A sample of 50 random stacks having equal average channel thicknesses with 20 channels each are used to provide a statistical base. The standard deviation of the stacks is varied as are the flow rate (Reynolds number) and the thermal conductivity of the solid heat exchanger material. It is found that the heat transfer performance of inhomogeneous stacks of parallel plates may be reduced significantly due to the maldistribution of the fluid flow compared to the ideal homogeneous case. The individual channels experience different flow velocities and this further induces an inter-channel thermal cross tal

Church Attendance and Religious Experience : Differential Associations to Well-Being for Norwegian Women and Men?

Previous studies have shown that gender may moderate the relationship between religiousness and mental health in most countries, but few studies have been conducted in Norway and Denmark. This study examined gender differences in religious experiences and church attendance as predictors of existential well-being among 295 women and 233 men from the general Norwegian population. Analyses showed that the structural equation models for women and men did not differ significantly on the global level. The models for women and men, however, showed different patterns. Among men, church attendance and negative religious experiences predicted existential well-being; among women, positive and negative religious experiences were related to existential well-being, but church attendance was not. The present findings suggest that men may benefit more from active religiousness, whereas women may benefit more from affective religiousness. Comparing these results with research in other cultural contexts, we find that different operationalizations of church attendance yield the same types of patterns across cultural contexts. Consequently, the benefits of religiousness may be similar for women and men irrespective of cultural context.© The Author(s) 2015 This article is distributed under the terms of the Creative Commons Attribution 3.0 License (http://www.creativecommons.org/licenses/by/3.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/en-us/nam/open-access-at-sage)

The effect of flow maldistribution in heterogeneous parallel-plate active magnetic regenerators

The heat transfer properties and performance of parallel-plate active magnetic regenerators (AMRs) with heterogeneous plate spacing are investigated using detailed models previously published. Bulk heat transfer characteristics in the regenerator are predicted as a function of variation in plate spacing. The results are quantified through a Nusselt number scaling factor that is applied in a detailed 1D AMR model. In this way, the impact of flow maldistribution due to heterogeneous parallel plate stacks on AMR performance is systematically investigated. It is concluded that parallel-plate stacks having a standard deviation greater than about 5% on their plate spacing are severely penalized in terms of both cooling power and achievable temperature span due to the inhomogeneity of the stacks