Fundamental stellar and accretion disc parameters of the eclipsing binary DQ Velorum

To add to the growing collection of well-studied double periodic variables (DPVs) we have carried out the first spectroscopic and photometric analysis of the eclipsing binary DQ Velorum to obtain its main physical stellar and orbital parameters. Combining spectroscopic and photometric observations that cover several orbital cycles allows us to estimate the stellar properties of the binary components and the orbital parameters. We also searched for circumstellar material around the more massive star. We separated DQ Velorum composite spectra and measured radial velocities with an iterative method for double spectroscopic binaries. We obtained the radial velocity curves and calculated the spectroscopic mass ratio. We compared our single-lined spectra with a grid of synthetic spectra and estimated the temperature of the stars. We modeled the V-band light curve with a fitting method based on the simplex algorithm, which includes an accretion disc. To constrain the main stellar parameters we fixed the mass ratio and donor temperature to the values obtained by our spectroscopic analysis. We obtain donor and gainer masses, the radii, and temperatures for the stellar components. We find that DQ Vel is a semi-detached system consisting of a B3V gainer and an A1III donor star plus an extended accretion disc around the gainer. The disc is filling 89% of the gainer Roche lobe and it has a concave shape that is thicker at its edge than at its centre. We find a significant sub-orbital frequency of 0.19 d^{-1} in the residuals of the V-band light curve, which we interpret as a pulsation of an slowly pulsating B-type (SPB) of a gainer star. We also estimate the distance to the binary (3.1 kpc) using the absolute radii, apparent magnitudes, and effective temperatures of the components found in our study.Comment: 12 pages, 13 Postscript figure

Binaries with total eclipses in the LMC: potential targets for spectroscopy

35 Eclipsing binaries presenting unambiguous total eclipses were selected from a subsample of the list of Wyrzykowski et al. (2003). The photometric elements are given for the I curve in DiA photometry, as well as approximate Teff and masses of the components. The interest of these systems is stressed in view of future spectroscopic observations.Comment: 4 pages, 1 figure; poster presented at the conference "Close binaries in the 21st Century: new opportunities and challenges", Syros, 27-30 June 200

Genetic imaging of the association of oxytocin receptor gene (OXTR) polymorphisms with positive maternal parenting

Background: Well-validated models of maternal behavior in small-brain mammals posit a central role of oxytocin in parenting, by reducing stress and enhancing the reward value of social interactions with offspring. In contrast, human studies are only beginning to gain insights into how oxytocin modulates maternal behavior and affiliation. Methods: To explore associations between oxytocin receptor genes and maternal parenting behavior in humans, we conducted a genetic imaging study of women selected to exhibit a wide range of observed parenting when their children were 4-6 years old. Results: In response to child stimuli during functional magnetic resonance imaging (fMRI), hemodynamic responses in brain regions that mediate affect, reward, and social behavior were significantly correlated with observed positive parenting. Furthermore, single nucleotide polymorphisms (SNPs) (rs53576 and rs1042778) in the gene encoding the oxytocin receptor were significantly associated with both positive parenting and hemodynamic responses to child stimuli in orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and hippocampus. Conclusions: These findings contribute to the emerging literature on the role of oxytocin in human social behavior and support the feasibility of tracing biological pathways from genes to neural regions to positive maternal parenting behaviors in humans using genetic imaging methods. © 2014 Michalska, Decety, Liu, Chen, Martz, Jacob, Hipwell, Lee, Chronis-Tuscano, Waldman and Lahey

Unique and universal dew-repellency of nanocones

Surface structuring provides a broad range of water-repellent materials known for their ability to reflect millimetre-sized raindrops. Dispelling water at the considerably reduced scale of fog or dew, however, constitutes a significant challenge, owing to the comparable size of droplets and structures. Nonetheless, a surface comprising nanocones was recently reported to exhibit strong anti-fogging behaviour, unlike pillars of the same size. To elucidate the origin of these differences, we systematically compare families of nanotexture that transition from pillars to sharp cones. Through environmental electron microscopy and modelling, we show that microdroplets condensing on sharp cones adopt a highly non-adhesive state, even at radii as low as 1.5 µm, contrasting with the behaviour on pillars where pinning results in impedance of droplet ejection. We establish the antifogging abilities to be universal over the range of our cone geometries, which speaks to the unique character of the nanocone geometry to repel dew. Truncated cones are finally shown to provide both pinning and a high degree of hydrophobicity, opposing characteristics that lead to a different, yet efficient, mechanism of dew ejection that relies on multiple coalescences

Digital Politics: Mobilization, Engagement, and Participation

The article provides insights into the driving forces that underpin new forms of political participation. Digital technologies offer opportunities for engaging in a wide range of civicallyoriented activities, each of which can contribute to deeper democratic engagement. Conventional acts of political participation are argued to be driven primarily by intrinsic motivations relating to self-efficacy and empowerment with participants feeling they can have influence over decision makers. Little research explores whether similar motivations drive participation in less conventional acts, as well as whether mobilisation attempts via social media by peers or political organisations mediate those motivations. Drawing on data from a survey among a representative sample of the UK electorate, we find the offline and online spheres of agency remain fairly distinct. Intrinsic and extrinsic motivations both matter but extrinsic motivations have the strongest explanatory power independent of the sphere of activity. The mediating effect of mobilisation tactics has a minimal effect on extrinsic motivations, online or offline, but online intrinsic motivations lose their explanatory power. As intrinsic factors offer little explanatory power some forms of online political participation may lack meaning to the individual. Rather, these non-conventional acts result from reward seeking and are more likely to be encouraged by non-governmental campaigning organizations suggesting social media users are most likely to perform simple acts in support of non-contentious causes

The 2003-4 multisite photometric campaign for the Beta Cephei and eclipsing star 16 (EN) Lacertae with an Appendix on 2 Andromedae, the variable comparison star

A multisite photometric campaign for the Beta Cephei and eclipsing variable 16 Lacertae is reported. 749 h of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with ten telescopes during 185 nights. After removing the pulsation contribution, an attempt was made to solve the resulting eclipse light curve by means of the computer program EBOP. Although a unique solution was not obtained, the range of solutions could be constrained by comparing computed positions of the secondary component in the Hertzsprung-Russell diagram with evolutionary tracks. For three high-amplitude pulsation modes, the uvy and the Geneva UBG amplitude ratios are derived and compared with the theoretical ones for spherical-harmonic degrees l <= 4. The highest degree, l = 4, is shown to be incompatible with the observations. One mode is found to be radial, one is l = 1, while in the remaining case l = 2 or 3. The present multisite observations are combined with the archival photometry in order to investigate the long-term variation of the amplitudes and phases of the three high-amplitude pulsation modes. The radial mode shows a non-sinusoidal variation on a time-scale of 73 yr. The l = 1 mode is a triplet with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and 29.1 yr. The amplitude and phase of the l = 2 or 3 mode vary on time-scales of 380.5 d and 43 yr. The light variation of 2 And, one of the comparison stars, is discussed in the Appendix.Comment: 18 pages, 19 figures, accepted for publication in MNRA

What drives political participation? Motivations and Mobilization in a Digital Age

The article provides insights into the driving forces that underpin new forms of political participation. Digital technologies offer opportunities for engaging in a wide range of civically-oriented activities, whether liking or sharing political content, joining online political communities or joining discussions, each can contribute to deeper democratic engagement and, for the individual, act as a pathway towards further civic participation. Conventional acts of political participation, demonstrating, petitioning and voting, are argued to be driven primarily by intrinsic motivations relating to self-efficacy and empowerment as the individual feels they can have influence over decision makers. Little research explores whether similar motivations drive participation in less conventional acts, as well as whether mobilisation attempts via social media by peers or political organisations mediate those motivations. Drawing on data from a survey among a representative sample of the UK electorate, we find the offline and online spheres of agency as still fairly distinct. Intrinsic and extrinsic motivations both matter but extrinsic motivations, following norms of behaviour within networks and supporting the activities of peers, have the strongest explanatory power independent of the sphere of activity. The mediating effect of mobilisation tactics has a minimal effect on extrinsic motivations, online or offline, but online intrinsic motivations lose their explanatory power. This finding suggests online political acts are carried out due to mobilisation, although as intrinsic factors offer little explanatory power these acts may lack meaning to the individual. We also found that campaign organisations are the most powerful mobilisers perhaps suggesting social media users are most likely to perform simple acts in support of non-contentious causes