Banding in the Margins of Basaltic Dykes Indicates Pulsatory Propagation During Emplacement

Basaltic fissure eruptions, which are the most common type of eruption on Earth, are fed by dykes which mediate magma transport through the crust. Dyke propagation processes are important because they determine the geometry of the transport pathway and the nature of any geophysical signals associated with magma ascent. Here, we investigate small‐scale (mm–cm wide) banding features at the margins of dykes in the Teno Massif (Tenerife, Spain) and the Columbia River Basalt Province (CRBP) (USA). Similar marginal bands have been reported for dykes in numerous localities around the world. Dyke margins record valuable information about propagation because they are the first material to solidify against the host rock at the propagating dyke tip. We find that the marginal bands are defined by cyclic variations in phenocryst concentration and vesicularity, and we infer that these cyclic variations in texture are a product of cyclic variations in magma flow rates and pressures within the dyke tip. This indicates that dyke emplacement occurs in pulses, with propagation repeatedly hindered by the rapid cooling and solidification of magma in the narrow dyke tip. Using a 1D conduction model, we estimate the time taken for each band to cool and solidify, which provides a timescale of several minutes to tens of minutes for the pulses. The occurrence of similar bands in various volcanic settings suggests that pulsatory propagation is a common, if not ubiquitous, process associated with dyke emplacement

A 14-Year Empirical Analysis of Undergraduates’ Pre- and Post-Test Scores in Three Introductory Communication Courses: Lessons Learned for Pedagogy and Assessment

Conducting long-term assessment of the impact of students’ participation in introductory communication courses is an important endeavor for enhancing pedagogy and understanding the contribution of communication instruction to the student experience. This 14-year study reports data from a campus-wide assessment program extending from 2004 to 2018. The study analyzed a large sample of undergraduate students’ self-reported pre- and post-test scores on critical variables related to student outcomes in three introductory communication courses. The variables examined were demographic characteristics, self-esteem and communication apprehension in both the public speaking course and the business communication course, and self-esteem and willingness to communicate in the interpersonal communication course. Across the 14-year period, 93% of the results of pre/post comparison scores showed a significant increase in students’ self-perceived levels of self-esteem and willingness to communicate and a significant decrease in communication apprehension (p \u3c .001). The usefulness of the results are discussed. Four general conclusions for engaging in introductory course assessment are outlined, along with specific lessons learned and best practices for consideration by basic course directors and faculty

The Relation Between Halo Shape, Velocity Dispersion and Formation Time

We use dark matter haloes identified in the MareNostrum Universe and galaxy groups identified in the Sloan Data Release 7 galaxy catalogue, to study the relation between halo shape and halo dynamics, parametrizing out the mass of the systems. A strong shape-dynamics, independent of mass, correlation is present in the simulation data, which we find it to be due to different halo formation times. Early formation time haloes are, at the present epoch, more spherical and have higher velocity dispersions than late forming-time haloes. The halo shape-dynamics correlation, albeit weaker, survives the projection in 2D (ie., among projected shape and 1-D velocity dispersion). A similar shape-dynamics correlation, independent of mass, is also found in the SDSS DR7 groups of galaxies and in order to investigate its cause we have tested and used, as a proxy of the group formation time, a concentration parameter. We have found, as in the case of the simulated haloes, that less concentrated groups, corresponding to late formation times, have lower velocity dispersions and higher elongations than groups with higher values of concentration, corresponding to early formation times.Comment: MNRAS in press (10 pages, 10 figures

The interaction of dark matter cusp with the baryon component in disk galaxies

In this paper we examine the effect of the formation and evolution of the disk galaxy on the distribution of dark halo matter. We have made simulations of isolated dark matter (DM) halo and two component (DM + baryons). N-body technique was used for stellar and DM particles and TVD MUSCL scheme for gas-dynamic simulations. The simulations include the processes of star formation, stellar feedback, heating and cooling of the interstellar medium. The results of numerical experiments with high spatial resolution let us to conclude in two main findings. First, accounting of star formation and supernova feedback resolves the so-called problem of cusp in distribution of dark matter predicted by cosmological simulations. Second, the interaction of dark matter with dynamic substructures of stellar and gaseous galactic disk (e.g., spiral waves, bar) has an impact on the shape of the dark halo. In particular, the in-plane distribution of dark matter is more symmetric in runs, where the baryonic component was taken into account.Comment: 7 pages, 6 figure

Transgender and Gender Diverse Community Connection, Help-Seeking, and Mental Health Among Black Transgender Women Who Have Survived Violence: A Mixed-Methods Analysis

Black transgender women are disproportionately affected by violence and poor care-delivery, contributing to poor mental health. Little is known regarding the effect of transgender and gender diverse (TGD) community connection (TCC) on health. This analysis (a) explores relationships between TCC, polyvictimization, and mental health and (b) analyzes how TCC influenced help-seeking following violent experiences among Black transgender women. Mixed-methods data from 19 Black transgender women were analyzed using correlational and thematic content analyses. Findings suggest that TCC is associated with improved help-seeking and mental health among Black transgender women, highlighting a need for longitudinal research to identify approaches for leveraging TCC

Mental Health of Parents and Life Satisfaction of Children: A Within-Family Analysis of Intergenerational Transmission of Well-Being

This paper addresses the extent to which there is an intergenerational transmission of mental health and subjective well-being within families. Specifically it asks whether parents’ own mental distress influences their child’s life satisfaction, and vice versa. Whilst the evidence on daily contagion of stress and strain between members of the same family is substantial, the evidence on the transmission between parental distress and children’s well-being over a longer period of time is sparse. We tested this idea by examining the within-family transmission of mental distress from parent to child’s life satisfaction, and vice versa, using rich longitudinal data on 1,175 British youths. Results show that parental distress at year t-1 is an important determinant of child’s life satisfaction in the current year. This is true for boys and girls, although boys do not appear to be affected by maternal distress levels. The results also indicated that the child’s own life satisfaction is related with their father’s distress levels in the following year, regardless of the gender of the child. Finally, we examined whether the underlying transmission correlation is due to shared social environment, empathic reactions, or transmission via parent-child interaction

Influence of baryons on the orbital structure of dark matter haloes

We explore the dynamical signatures imprinted by baryons on dark matter haloes during the formation process using the OverWhelmingly Large Simulations (OWLS), a set of state-of-the-art high-resolution cosmological hydrodynamical simulations. We present a detailed study of the effects of the implemented feedback prescriptions on the orbits of dark matter particles, stellar particles and subhaloes, analysing runs with no feedback, with stellar feedback and with feedback from supermassive black holes. We focus on the central regions (0.25 r_{200}) of haloes with virial masses ~ 6 x 10^{13} (~ 7 x 10^{11}) Msun/h at z = 0(2). We also investigate how the orbital content (relative fractions of the different orbital types) of these haloes depends on several key parameters such as their mass, redshift and dynamical state. The results of spectral analyses of the orbital content of these simulations are compared, and the change in fraction of box, tube and irregular orbits is quantified. Box orbits are found to dominate the orbital structure of dark matter haloes in cosmological simulations. There is a strong anticorrelation between the fraction of box orbits and the central baryon fraction. While radiative cooling acts to reduce the fraction of box orbits, strong feedback implementations result in a similar orbital distribution to that of the dark matter only case. The orbital content described by the stellar particles is found to be remarkably similar to that drawn from the orbits of dark matter particles, suggesting that either they have forgotten their dynamical history, or that subhaloes bringing in stars are not biased significantly with respect to the main distribution. The orbital content of the subhaloes is in broad agreement with that seen in the outer regions of the particle distributions.Comment: 18 pages, 13 figures, 3 tables. Accepted for publication in MNRA

Astronomical X-Ray Optics Using Mono-Crystalline Silicon: High Resolution, Light Weight, and Low Cost

X-ray astronomy critically depends on X-ray optics. The capability of an X-ray telescope is largelydetermined by the point-spread function (PSF) and the photon-collection area of its mirrors, the same astelescopes in other wavelength bands. Since an X-ray telescope must be operated above the atmosphere inspace and that X-rays reflect only at grazing incidence, X-ray mirrors must be both lightweight and thin, bothof which add significant technical and engineering challenge to making an X-ray telescope. In this paper wereport our effort at NASA Goddard Space Flight Center (GSFC) of developing an approach to making an Xraymirror assembly that can be significantly better than the mirror assembly currently flying on the ChandraX-ray Observatory in each of the three aspects: PSF, effective area per unit mass, and production cost per uniteffective area. Our approach is based on the precision polishing of mono-crystalline silicon to fabricate thinand lightweight X-ray mirrors of the highest figure quality and micro-roughness, therefore, having thepotential of achieving diffraction-limited X-ray optics. When successfully developed, this approach will makeimplementable in the 2020s and 2030s many X-ray astronomical missions that are currently on the drawingboard, including sounding rocket flights such as OGRE, Explorer class missions such as STAR-X andFORCE, Probe class missions such as AXIS, TAP, and HEX-P, as well as large missions such as Lynx

How to Educate Entrepreneurs?

Entrepreneurship education has two purposes: To improve students’ entrepreneurial skills and to provide impetus to those suited to entrepreneurship while discouraging the rest. While entrepreneurship education helps students to make a vocational decision its effects may conflict for those not suited to entrepreneurship. This study shows that vocational and the skill formation effects of entrepreneurship education can be identified empirically by drawing on the Theory of Planned Behavior. This is embedded in a structural equation model which we estimate and test using a robust 2SLS estimator. We find that the attitudinal factors posited by the Theory of Planned Behavior are positively correlated with students’ entrepreneurial intentions. While conflicting effects of vocational and skill directed course content are observed in some individuals, overall these types of content are complements. This finding contradicts previous results in the literature. We reconcile the conflicting findings and discuss implications for the design of entrepreneurship courses