The Kepler-19 System: A Transiting 2.2 R_⊕ Planet and a Second Planet Detected via Transit Timing Variations

We present the discovery of the Kepler-19 planetary system, which we first identified from a 9.3 day periodic transit signal in the Kepler photometry. From high-resolution spectroscopy of the star, we find a stellar effective temperature T_(eff) = 5541 ± 60 K, a metallicity [Fe/H] = –0.13 ± 0.06, and a surface gravity log(g) = 4.59 ± 0.10. We combine the estimate of T_(eff) and [Fe/H] with an estimate of the stellar density derived from the photometric light curve to deduce a stellar mass of M_*= 0.936 ± 0.040 M_☉ and a stellar radius of R_* = 0.850 ± 0.018 R_☉ (these errors do not include uncertainties in the stellar models). We rule out the possibility that the transits result from an astrophysical false positive by first identifying the subset of stellar blends that reproduce the precise shape of the light curve. Using the additional constraints from the measured color of the system, the absence of a secondary source in the high-resolution spectrum, and the absence of a secondary source in the adaptive optics imaging, we conclude that the planetary scenario is more than three orders of magnitude more likely than a blend. The blend scenario is independently disfavored by the achromaticity of the transit: we measure a transit depth with Spitzer at 4.5 μm of 547^(+113)_(–110) ppm, consistent with the depth measured in the Kepler optical bandpass of 567 ± 6 ppm (corrected for stellar limb darkening). We determine a physical radius of the planet Kepler-19b of R_p = 2.209 ± 0.048 R_⊕; the uncertainty is dominated by uncertainty in the stellar parameters. From radial velocity observations of the star, we find an upper limit on the planet mass of 20.3 M_⊕, corresponding to a maximum density of 10.4 g cm^(–3). We report a significant sinusoidal deviation of the transit times from a predicted linear ephemeris, which we conclude is due to an additional perturbing body in the system. We cannot uniquely determine the orbital parameters of the perturber, as various dynamical mechanisms match the amplitude, period, and shape of the transit timing signal and satisfy the host star's radial velocity limits. However, the perturber in these mechanisms has a period ≾ 160 days and mass ≾ 6 M_(Jup), confirming its planetary nature as Kepler-19c. We place limits on the presence of transits of Kepler-19c in the available Kepler data

Simulation analysis of capacity and scheduling methods in the hospital surgical suite

With health-care costs rising and an aging population, the health-care industry is progressively faced with the problem of growing demand and diminishing reimbursements. Hospital administration is often faced with a lack of quantifiable data regarding surgical suite capacity and the impact of adding new surgical procedures. With the inherent variation in surgery due to unique procedures and patients, accurately measuring maximum capacity in the surgical suite through mathematical models is difficult to do without making simplifying assumptions. Several hospitals calculate their operating room (OR) efficiencies by comparing total OR time available to total surgical time used. This metric fails to account for the required non-value added tasks between surgeries and the balance necessary for patients to arrive at the OR as soon as possible without compromising patient satisfaction. Since surgical suites are the financial engine for many hospitals and the decisions made with regard to the surgical suite can significantly impact a hospital’s success, this thesis develops a methodology through simulation to more accurately define current and potential capacity levels within the surgical suite. Additionally, scheduling policies, which schedule patients based on the variability of their surgical time as well as the implementation of flexible ORs capable of servicing multiple operation genres, are examined for individual and interaction effects with regard to surgical suite capacity, patient waiting times, and resource utilization. Through verification and validation, the model is shown to be an effective tool in representing patient flow and testing policies and procedures within the surgical suite. An application to the surgical suite at Chenango Memorial Hospital (Norwich, NY) illustrates the methodology and potential impacts of this research

Constraints on Evolutionary Timescales for M Dwarf Planets from Dynamical Stability Arguments

The diversity of dynamical conditions among exoplanets is now well established. Yet, the relevance of orbital dynamical timescales to biological evolutionary timescales is poorly understood. Given that even minor orbital changes may place significant pressure on any organisms living on a planet, dynamical sculpting has important implications for the putative evolution of life. In this manuscript, we employ a Monte Carlo framework to investigate how a range of exoplanetary dynamical sculpting timescales affects timescales for biological evolution. We proceed with minimal assumptions for how dynamical sculpting proceeds and the emergence and persistence of life. We focus our investigation on M dwarf stars, the most common exoplanetary hosts in the Milky Way. We assign dynamical statuses, dependent on stellar age, to a suite of planetary systems, varying the rate of dynamical disruption within limits that are consistent with present-day planet demographics. We then simulate the observed yield of planets according to the completeness of NASA's Kepler and TESS missions, and investigate the properties of these samples. With this simplified approach, we find that systems hosting multiple transiting planets ought to have, on average, shorter dynamically-uninterrupted intervals than single-transiting systems. However, depending upon the rate of dynamical sculpting, planets orbiting older stars will exhibit the opposite trend. Even modest constraints on stellar age would help identify "older" stars for which this holds. The degree of these effects varies, dependent upon both the intrinsic dynamical demographics of exoplanets and whether we consider planets detected by NASA's Kepler or TESS missions.Comment: 17 pages, 15 figures, 1 table, submitted to Ap

Reciprocity and Reflection in Community-based Study Abroad Courses in Rural Costa Rica

This manuscript will examine two high-impact practices in academia, community-based learning, and study abroad. The authors discuss the benefits of both practices and how pairing the two can benefit not only future educators but future leaders. This model provides students with the opportunity to become more globally competent through their time in another culture. Throughout this immersion, college students taught English in the context of reading, mathematics, science, or social studies. Critical and analytical reflection was a significant aspect of their college course. At the conclusion of their community-based study abroad course, students were asked to synthesize a final report referencing earlier reflections. Experiences both positive and negative are shared to provide a realistic picture of how college students might maneuver the dual role of student and community provider

End-of-life care and dementia

In the UK, research continues to confirm that people with certain chronic illnesses, such as chronic lung disease and cardiac failure, represent the ‘disadvantaged dying’ compared to those with terminal cancer. But what is the situation for people dying with advanced dementia and what is the experience of their carers? Practical guidance for clinicians is scarce. In Standard 7 of the National Service Framework for Older People, which covers mental health, there is mention neither of how care should be provided nor of how patient choice should be ensured for people with dementia at the end of life. In the UK, 5% of the population aged 65 and over and 20% of those aged 80 and over have dementia similar prevalence figures are found in the USA. Current predictions suggest that the number of people with dementia will increase by 40% by 2026 and will double by 2050. The increased demand for end-of-life care for people with dementia will be associated with major social and economic costs, but what is the current standard of such care? How can the quality be improved? And how should future services be configured to cope with this increasing need? In this paper, we review current knowledge around end-of-life care in dementia, discuss the clinical challenges and ethical dilemmas presented to carers, consider the difficulties in delivering such care and suggest practical approaches to improve the quality of such care

THE KEPLER DICHOTOMY IN PLANETARY DISKS: LINKING KEPLER OBSERVABLES TO SIMULATIONS OF LATE-STAGE PLANET FORMATION

NASA's Kepler Mission uncovered a wealth of planetary systems, many with planets on short-period orbits. These short-period systems reside around 50% of Sun-like stars and are similarly prevalent around M dwarfs. Their formation and subsequent evolution is the subject of active debate. In this paper, we simulate late-stage, in situ planet formation across a grid of planetesimal disks with varying surface density profiles and total mass. We compare simulation results with observable characteristics of the Kepler sample. We identify mixture models with different primordial planetesimal disk properties that self-consistently recover the multiplicity, radius, period and period ratio, and duration ratio distributions of the Kepler planets. We draw three main conclusions. (1) We favor a "frozen-in" narrative for systems of short-period planets, in which they are stable over long timescales, as opposed to metastable. (2) The "Kepler dichotomy," an observed phenomenon of the Kepler sample wherein the architectures of planetary systems appear to either vary significantly or have multiple modes, can naturally be explained by formation within planetesimal disks with varying surface density profiles. Finally, (3) we quantify the nature of the "Kepler dichotomy" for both GK stars and M dwarfs, and find that it varies with stellar type. While the mode of planet formation that accounts for high multiplicity systems occurs in 24% ± 7% of planetary systems orbiting GK stars, it occurs in 63% ± 16% of planetary systems orbiting M dwarfs.United States. National Aeronautics and Space Administration (NASA grant NNX12AC01G)Massachusetts Institute of Technology (Torres Fellowship for Exoplanet Research)

Signatures of impact-driven atmospheric loss in large ensembles of exoplanets

The results of large-scale exoplanet transit surveys indicate that the distribution of small planet radii is likely sculpted by atmospheric loss. Several possible physical mechanisms exist for this loss of primordial atmospheres, each of which produces a different set of observational signatures. In this study, we investigate the impact-driven mode of atmosphere loss via N-body simulations. We compare the results from giant impacts, at a demographic level, to results from another commonly-invoked method of atmosphere loss: photoevaporation. Applying two different loss prescriptions to the same sets of planets, we then examine the resulting distributions of planets with retained primordial atmospheres. As a result of this comparison, we identify two new pathways toward discerning the dominant atmospheric loss mechanism at work. Both of these pathways involve using transit multiplicity as a diagnostic, in examining the results of follow-up atmospheric and radial velocity surveys.Comment: 17 pages, 10 figures, Submitted to Ap