Ultra Short Period Planets in K2: SuPerPiG Results for Campaigns 0-5

We have analyzed data from Campaigns 0-5 of the K2 mission and report 19 ultra-short-period candidate planets with orbital periods of less than 1 day (nine of which have not been previously reported). Planet candidates range in size from 0.7-16 Earth radii and in orbital period from 4.2 to 23.5 hours. One candidate (EPIC 203533312, Kp=12.5) is among the shortest-period planet candidates discovered to date (P=4.2 hours), and, if confirmed as a planet, must have a density of at least rho=8.9 g/cm^3 in order to not be tidally disrupted. Five candidates have nominal radius values in the sub-Jovian desert (R_P=3-11 R_E and P<=1.5 days) where theoretical models do not favor their long-term stability; the only confirmed planet in this range is in fact thought to be disintegrating (EPIC 201637175). In addition to the planet candidates, we report on four objects which may not be planetary, including one with intermittent transits (EPIC 211152484) and three initially promising candidates that are likely false positives based on characteristics of their light curves and on radial velocity follow-up. A list of 91 suspected eclipsing binaries identified at various stages in our vetting process is also provided. Based on an assessment of our survey's completeness, we estimate an occurrence rate for ultra-short period planets among K2 target stars that is about half that estimated from the Kepler sample, raising questions as to whether K2 systems are intrinsically different from Kepler systems, possibly as a result of their different galactic location.Comment: 13 pages, 8 figures, accepted to AJ on 2016 May 2

Tidal Heating of Extra-Solar Planets

Extra-solar planets close to their host stars have likely undergone significant tidal evolution since the time of their formation. Tides probably dominated their orbital evolution once the dust and gas had cleared away, and as the orbits evolved there was substantial tidal heating within the planets. The tidal heating history of each planet may have contributed significantly to the thermal budget that governed the planet's physical properties, including its radius, which in many cases may be measured by observing transit events. Typically, tidal heating increases as a planet moves inward toward its star and then decreases as its orbit circularizes. Here we compute the plausible heating histories for several planets with measured radii, using the same tidal parameters for the star and planet that had been shown to reconcile the eccentricity distribution of close-in planets with other extra-solar planets. Several planets are discussed, including for example HD 209458 b, which may have undergone substantial tidal heating during the past billion years, perhaps enough to explain its large measured radius. Our models also show that GJ 876 d may have experienced tremendous heating and is probably not a solid, rocky planet. Theoretical models should include the role of tidal heating, which is large, but time-varying.Comment: Accepted for publication to Ap

Toroidal prefactorization algebras associated to holomorphic fibrations and a relationship to vertex algebras

Let $X$ be a complex manifold, $\pi: E \rightarrow X$ a locally trivial holomorphic fibration with fiber $F$, and $\mathfrak{g}$ a Lie algebra with an invariant symmetric form. We associate to this data a holomorphic prefactorization algebra $\mathcal{F}_{\mathfrak{g}, \pi}$ on $X$ in the formalism of Costello-Gwilliam. When $X=\mathbb{C}$, $\mathfrak{g}$ is simple, and $F$ is a smooth affine variety, we extract from $\mathcal{F}_{\mathfrak{g}, \pi}$ a vertex algebra which is a vacuum module for the universal central extension of the Lie algebra $\mathfrak{g} \otimes H^{0}(F, \mathcal{O})[z,z^{-1}]$. As a special case, when $F$ is an algebraic torus $(\mathbb{C}^{*})^n$, we obtain a vertex algebra naturally associated to an $(n+1)$--toroidal algebra, generalizing the affine vacuum module

A study of opposing mixed convection in the GRTS and in downward pipe flows using the FLUENT CFD code

Downward flow opposing mixed convection conditions have been studied using the FLUENT CFD code. This work was comprised of two primary objectives. The first was to study core channel flow reversal susceptibility in the Gas Reactor Test Section (GRTS) at low flow conditions. The second objective was the development of a general stability correlation for opposing mixed convection conditions in downward pipe flows as a function of pipe radius, gas material, inlet velocity and elevated wall temperatures. The traditional criterion that buoyancy forces must be considered in mixed convection flows when the Gr/Re² value is on the order of 1.0 was used to identify low flow conditions in the GRTS when core channel flow reversal may occur. The corresponding GRTS power levels and flowrates were studied using FLUENT. An initial FLUENT model was used to model the solid core GRTS components to obtain the individual coolant channel wall temperatures for each axial level of each coolant channel of the GRTS associated with the low flow conditions susceptible to flow reversal. These coolant channel wall temperatures were then used as boundary conditions in a more refined second FLUENT model containing just the fluid regions of the GRTS that was used to obtain the flow characteristics. It was found that flow reversal did not occur in the GRTS even when the traditional criterion predicted that buoyancy forces could not be neglected. When FLUENT was used to study flow reversal for downward opposing mixed convection as a function of pipe radius, gas material, inlet velocity and elevated wall temperatures, it was found that while the traditional criterion that buoyancy forces must be considered when the Gr/Re² value is on the order of 1.0 is a good estimate, it is insufficient to give a good prediction for when flow reversal occurs. The ability of the flow to reverse was largely dependent on pipe radius and gas material. This thesis presents two correlations, one for pipe radii below 2 cm, and one for pipe radii 2 cm and above, predicting when flow reversal will occur as a function of Grashof and Reynolds numbers

An experimental study of laminarization induced by acceleration and curvature

The Generation IV Very High Temperature Reactor (VHTR) design is being actively studied in various countries for application due to its inherent passive safe design, higher thermal efficiencies, and proposed capability of providing high temperature process heat. The pebble bed core is one of two core designs used in gas reactors. In the pebble bed core there are mechanisms present which can cause the flow to laminarize, thus reducing its heat transfer effectiveness. Wind tunnel experiments were conducted using Particle Image Velocimetry (PIV) to investigate boundary layer laminarization due to flow acceleration and convex curvature effects. The flow was subject to acceleration and curvature both separately and together and the flow behavior characterized with velocity flow profiles, mean boundary layer parameters, and turbulence quantities. Laminarization was identified and the influence of acceleration and curvature was characterized

Respiratory effect of beta-blockers in people with asthma and cardiovascular disease:population-based nested case control study

Background: Cardiovascular disease (CVD) is a common comorbidity in people with asthma. However, safety concerns have caused heterogeneity in clinical guideline recommendations over the use of cardioselective beta-blockers in people with asthma and CVD, partly because risk in the general population has been poorly quantified. The aim of this study was to measure the risk of asthma exacerbations with beta-blockers prescribed to a general population with asthma and CVD.Methods: Linked data from the UK Clinical Practice Research Datalink was used to perform nested case-control studies among people with asthma and CVD matched on age, gender and calendar time. Adjusted incidence rate ratios (IRR) were calculated for the association between oral beta-blocker use and moderate asthma exacerbations (rescue oral steroids) or severe asthma exacerbations (hospitalisation or death) using conditional logistic regression.Results: The cohort consisted of 35502 people identified with active asthma and CVD, of which 14.1% and 1.2% were prescribed cardioselective and non-selective beta-blockers respectively during follow-up. Cardioselective beta-blocker use was not associated with a significantly increased risk of moderate or severe asthma exacerbations. Consistent results were obtained following sensitivity analyses and a self-controlled case series approach. In contrast, non-selective beta-blockers were associated with a significantly increased risk of moderate asthma exacerbations when initiated at low to moderate doses (IRR 5.16, 95%CI 1.83-14.54, p=0.002), and both moderate and severe exacerbations when prescribed chronically at high dose (IRR 2.68, 95%CI 1.08-6.64, p=0.033 and IRR 12.11, 95%CI 1.02-144.11, p=0.048 respectively).Conclusions: Cardioselective beta-blockers prescribed to people with asthma and CVD were not associated with a significantly increased risk of moderate or severe asthma exacerbations and potentially could be used more widely when strongly indicated

The Kaposi's sarcoma-associated herpesvirus ORF57 protein and its multiple roles in mRNA biogenesis

Post-transcriptional events which regulate mRNA biogenesis are fundamental to the control of gene expression. A nascent mRNA is therefore steered through multimeric RNA–protein complexes that mediate its capping, splicing, polyadenylation, nuclear export, and ultimately its translation. Kaposi’s sarcoma-associated herpesvirus (KSHV) mRNA transport and accumulation protein, or ORF57, is a functionally conserved protein found in all herpesviruses which plays a pivotal role in enhancing viral gene expression at a post-transcriptional level. As such, ORF57 has been implicated in multiple steps of RNA biogenesis, including augmenting viral splicing, protecting viral RNAs from degradation to enhancing viral mRNA nuclear export and translation. In this review, we highlight the multiple roles of KSHV ORF57 in regulating the post-transcriptional events which are fundamental to the control of virus gene expression

Spatial and vertical distribution of mercury in upland forest soils across the northeastern United States

Assessing current Hg pools in forest soils of the northeastern U.S. is important for monitoring changes in Hg cycling. The forest floor, upper and lower mineral horizons were sampled at 17 long-term upland forest sites across the northeastern U.S. in 2011. Forest floor Hg concentration was similar across the study region (274 +/- 13 mu g kg(-1)) while Hg amount at northern sites (39 +/- g ha(-1)) was significantly greater than at western sites (11 +/- 4 g ha(-1)). Forest floor Hg was correlated with soil organic matter, soil pH, latitude and mean annual precipitation and these variables explained approximately 70% of the variability when multiple regressed. Mercury concentration and amount in the lower mineral soil was correlated with Fe, soil organic matter and latitude, corresponding with Bs horizons of Spodosols (Podzols). Our analysis shows the importance of regional and soil properties on Hg accumulation in forest soils. (C) 2013 Elsevier Ltd. All rights reserved