The return of the Andromedids meteor shower

The Andromedid meteor shower underwent spectacular outbursts in 1872 and 1885, producing thousands of visual meteors per hour and described as `stars fell like rain' in Chinese records of the time. The shower originates from comet 3D/Biela whose disintegration in the mid-1800's is linked to the outbursts, but the shower has been weak or absent since the late 19th Century. This shower returned in December 2011 with a zenithal hourly rate of approximately 50, the strongest return in over a hundred years. Some 122 probable Andromedid orbits were detected by the Canadian Meteor Orbit Radar. The shower outburst occurred during 2011 Dec 3-5. The radiant at RA +$18\degree$ and Dec +$56\degree$ is typical of the `classical' Andromedids of the early 1800's, whose radiant was actually in Cassiopeia. The orbital elements indicate that the material involved was released before 3D/Biela's breakup prior to 1846. The observed shower in 2011 had a slow geocentric speed (16 km s$^{-1}$) and was comprised of small particles: the mean measured mass from the radar is $\sim5 \times 10^{-7}$ kg corresponding to radii of 0.5 mm at a bulk density of 1000 kg/m$^3$. Numerical simulations of the parent comet indicate that the meteoroids of the 2011 return of the Andromedids shower were primarily ejected during 3D/Biela's 1649 perihelion passage. The orbital characteristics, radiant, timing as well as the absence of large particles in the streamlet are all consistent with simulations. Predictions are made regarding other appearances of the shower in the years 2000-2047 based on our numerical model. We note that the details of the 2011 return can, in principle, be used to better constrain the orbit of 3D/Biela prior to the comets first recorded return in 1772.Comment: submitted to the Astronomical Journal Sep 22 201

The EGNoG Survey: Gas Excitation in Normal Galaxies at z~0.3

As observations of molecular gas in galaxies are pushed to lower star formation rate galaxies at higher redshifts, it is becoming increasingly important to understand the conditions of the gas in these systems to properly infer their molecular gas content. The rotational transitions of the carbon monoxide (CO) molecule provide an excellent probe of the gas excitation conditions in these galaxies. In this paper we present the results from the gas excitation sample of the Evolution of molecular Gas in Normal Galaxies (EGNoG) survey at the Combined Array for Research in Millimeter-wave Astronomy (CARMA). This subset of the full EGNoG sample consists of four galaxies at z~0.3 with star formation rates of 40-65 M_Sun yr^-1 and stellar masses of ~2x10^11 M_Sun. Using the 3 mm and 1 mm bands at CARMA, we observe both the CO(1-0) and CO(3-2) transitions in these four galaxies in order to probe the excitation of the molecular gas. We report robust detections of both lines in three galaxies (and an upper limit on the fourth), with an average line ratio, r_31 = L'_CO(3-2) / L'_CO(1-0), of 0.46 \pm 0.07 (with systematic errors \lesssim 40%), which implies sub-thermal excitation of the CO(3-2) line. We conclude that the excitation of the gas in these massive, highly star-forming galaxies is consistent with normal star-forming galaxies such as local spirals, not starbursting systems like local ultra-luminous infrared galaxies. Since the EGNoG gas excitation sample galaxies are selected from the main sequence of star-forming galaxies, we suggest that this result is applicable to studies of main sequence galaxies at intermediate and high redshifts, supporting the assumptions made in studies that find molecular gas fractions in star forming galaxies at z~1-2 to be an order of magnitude larger than what is observed locally.Comment: Accepted for publication in the Astrophysical Journal, to appear January 2013; 18 pages, 10 figures, 6 table

Combining the Performance Strengths of the Logistic Regression and Neural Network Models: A Medical Outcomes Approach

The assessment of medical outcomes is important in the effort to contain costs, streamline patient management, and codify medical practices. As such, it is necessary to develop predictive models that will make accurate predictions of these outcomes. The neural network methodology has often been shown to perform as well, if not better, than the logistic regression methodology in terms of sample predictive performance. However, the logistic regression method is capable of providing an explanation regarding the relationship(s) between variables. This explanation is often crucial to understanding the clinical underpinnings of the disease process. Given the respective strengths of the methodologies in question, the combined use of a statistical (i.e., logistic regression) and machine learning (i.e., neural network) technology in the classification of medical outcomes is warranted under appropriate conditions. The study discusses these conditions and describes an approach for combining the strengths of the models

Female performance and participation in computer science: a national picture

The change in the English computing curriculum and the shift towards computer science (CS) has been closely observed by other countries. Female participation remains a concern in most jurisdictions, but female attainment in CS is relatively unstudied. Using the English national pupil database, we analysed all exam results (n=5,370,064) for students taking secondary school exams in 2016, focusing on those students taking GCSE CS (n=60,736) contrasting this against ICT (n=67,359). Combining gender with ethnicity and the IDACI poverty indicator, we find that females from the poorest areas were more likely to take CS than those from the richest areas and CS was more popular amongst ethnic minority females than white females. ICT was far more equitable for females and poorer students than CS. CS females typically got better grades than their male peers. However, when controlling for average attainment in other subjects, males got 0.31 of a grade higher. Female relative underperformance in CS was most acute amongst large female cohorts and with girls studying in mixed-gender schools. Girls did significantly better than boys in English when controlling for CS scores, supporting theories around female relative strengths lying outside STEM subjects. The move to introduce CS into the English curriculum and the removal of the ICT qualifications look to be having a negative impact on female participation and attainment in computing. Using the theory of self-efficacy we argue that the shift towards CS might decrease the number of girls choosing further computing qualifications or pursuing computing as a career. Computing curriculum designers and teachers need to carefully consider the inclusive nature of their computing courses

Tests of Two-Body Dirac Equation Wave Functions in the Decays of Quarkonium and Positronium into Two Photons

Two-Body Dirac equations of constraint dynamics provide a covariant framework to investigate the problem of highly relativistic quarks in meson bound states. This formalism eliminates automatically the problems of relative time and energy, leading to a covariant three dimensional formalism with the same number of degrees of freedom as appears in the corresponding nonrelativistic problem. It provides bound state wave equations with the simplicity of the nonrelativistic Schroedinger equation. Here we begin important tests of the relativistic sixteen component wave function solutions obtained in a recent work on meson spectroscopy, extending a method developed previously for positronium decay into two photons. Preliminary to this we examine the positronium decay in the 3P_{0,2} states as well as the 1S_0. The two-gamma quarkonium decays that we investigate are for the \eta_{c}, \eta_{c}^{\prime}, \chi_{c0}, \chi_{c2}, \pi^{0}, \pi_{2}, a_{2}, and f_{2}^{\prime} mesons. Our results for the four charmonium states compare well with those from other quark models and show the particular importance of including all components of the wave function as well as strong and CM energy dependent potential effects on the norm and amplitude. The results for the \pi^{0}, although off the experimental rate by 15%, is much closer than the usual expectations from a potential model. We conclude that the Two-Body Dirac equations lead to wave functions which provide good descriptions of the two-gamma decay amplitude and can be used with some confidence for other purposes.Comment: 79 pages, included new sections on covariant scalar product and added pages on positronium decay for 3P0 and 3P_2 state

Kounis syndrome and hypersensitivity myocarditis – One and the same? Insights from cardiac magnetic resonance imaging

AbstractMyocarditis and acute coronary syndrome are both described in the setting of concurrent hypersensitivity reactions to a variety of allergenic triggers (hypersensitivity myocarditis and Kounis syndrome respectively). Mast cell degranulation is thought to be pivotal in the pathogenesis of both clinical entities. Cardiac magnetic resonance imaging (CMR) has assumed a key role in the assessment of chest pain syndromes, providing a useful non-invasive tool to aid clinical decision-making. Despite increasing availability and uptake of CMR, only a small fraction of published Kounis syndrome cases report CMR findings, and confirmation of myocardial infarction remains elusive. We present a case of presumed Kounis syndrome with comprehensive CMR imaging that provides an insight into why these two well-described clinical entities share many clinical features – perhaps they are one and the same.<Learning objective: Myocarditis and acute coronary syndrome (ACS) in the setting of hypersensitivity reactions share similar clinical characteristics. Endomyocardial biopsies are often not undertaken in this patient group, and differentiation has typically been at the clinicians’ discretion. Cardiac magnetic resonance imaging can provide an insight into the underlying pathogenesis, with currently available evidence suggesting myocarditis is a prerequisite for ACS, rather than being stand-alone clinical entities.

Extended X-ray emission in the IC 2497 - Hanny's Voorwerp system: energy injection in the gas around a fading AGN

We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN. We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN ($L_{\rm bol} \sim 10^{42}-10^{44}$ erg s$^{-1}$). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN (\mbox{E_{\rm bub}} \sim 10^{54} - 10^{55} erg). A possible scenario is that this bubble is inflated by the fading AGN, which after changing accretion state is now in a kinetic mode. Other possibilities are that the bubble has been inflated by the past luminous quasar ($L_{\rm bol} \sim 10^{46}$ erg s$^{-1}$), or that the temperature gradient is an indication of a shock front from a superwind driven by the AGN. We discuss the possible scenarios and the implications for the AGN-host galaxy interaction, as well as an analogy between AGN and X-ray binaries lifecycles. We conclude that the AGN could inject mechanical energy into the host galaxy at the end of its lifecycle, and thus provide a source for mechanical feedback, in a similar way as observed for X-ray binaries.Comment: 9 pages, 5 figures, accepted for publication in MNRA