Removal of Hot Saturns in Mass-Radius Plane by Runaway Mass Loss

The hot Saturn population exhibits a boundary in mass-radius space, such that no planets are observed at a density less than $\sim$0.1 g cm$^{-3}$. Yet, planet interior structure models can readily construct such objects as the natural result of radius inflation. Here, we investigate the role XUV-driven mass-loss plays in sculpting the density boundary by constructing interior structure models that include radius inflation, photoevaporative mass loss and a simple prescription of Roche lobe overflow. We demonstrate that planets puffier than $\sim$0.1 g cm$^{-3}$ experience a runaway mass loss caused by adiabatic radius expansion as the gas layer is stripped away, providing a good explanation of the observed edge in mass-radius space. The process is also visible in the radius-period and mass-period spaces, though smaller, high-bulk-metallicity planets can still survive at short periods, preserving a partial record of the population distribution at formation.Comment: 10 pages, 5 figures, submitted to ApJ Letter

FIB-TEM Investigations of Fe-NI-Sulfides in the CI Chondrites Alais and Orgueil

The CI chondrites are primitive meteorites with bulk compositions matching the solar photosphere for all but the lightest elements. They have been extensively aqueously altered, and are composed primarily of fine-grained phyllosilicate matrix material which is host to carbonates, sulfates, sulfides, and minor amounts of olivine and pyroxene. The alteration, while extensive, is heterogeneous. For example, CI-chondrite cubanite and carbonate grains differ on mm to sub-mm scales, demonstrating multiple aqueous episodes. CI-chondrite variability is also evidenced by degree of brecciation, abundance and size of coarse-grained phyllosilicates, olivine and pyroxene abundance, as well as Ni-content and size of sulfide grains. Our previous work revealed Orgueil sulfide grains with variable Ni-contents, metal:S ratios, crystal structures and textures. We continue to explore the variability of CI-chondrite pyrrhotite (Po, (FeNi)1-xS) and pentlandite (Pn, (Fe,Ni)9S8) grains. We investigate the microstructure of sulfides within and among CI-chondrite meteorites in order to place constraints on the conditions under which they formed

Self-Similar Magnetocentrifugal Disk Winds with Cylindrical Asymptotics

We construct a two-parameter family of models for self-collimated, radially self-similar magnetized outflows from accretion disks. A flow at zero initial poloidal speed leaves the surface of a rotating disk and is accelerated and redirected toward the pole by helical magnetic fields threading the disk. At large distances from the disk, the flow streamlines asymptote to wrap around the surfaces of nested cylinders. In constrast to previous disk wind modeling, we have explicitly implemented the cylindrical asymptotic boundary condition to examine the consequences for flow dynamics. The solutions are characterized by the logarithmic gradient of the magnetic field strength and the ratios between the footpoint radius R_0 and asymptotic radius R_1 of streamlines; the Alfven radius must be found as an eigenvalue. Cylindrical solutions require the magnetic field to drop less steeply than 1/R. We find that the asymptotic poloidal speed on any streamline is typically just a few tenths of the Kepler speed at the corresponding disk footpoint. The asymptotic toroidal Alfven speed is, however, a few times the footpoint Kepler speed. We discuss the implications of the models for interpretations of observed optical jets and molecular outflows from young stellar systems. We suggest that the difficulty of achieving strong collimation in vector velocity simultaneously with a final speed comparable to the disk rotation rate argues against isolated jets and in favor of models with broader winds.Comment: 39 pages, Latex (uses AAS Latex macros), 6 eps figures, postscript preprint with embedded figures available from http://www.astro.umd.edu/~ostriker/professional/publications.html , to appear in ApJ 9/1/9

Suppression of Gravitational Structure Formation by Cosmological Accretion Heating

As increasingly precise information about the spectrum of the cosmic microwave background fluctuations is gathered with balloon and satellite experiments, interest has grown in foreground sources of opacity affecting these observations. One potentially important source is electron scattering produced by a post-recombination luminosity source, which would significantly attenuate the higher harmonics in the spectrum. If such an ionization source exists, then it would also heat the universe, hence increasing the Jeans mass and suppressing early gravitational structure formation. Here we consider the effects of such heating. We concentrate on one type of ionization source: luminosity generated by accretion onto primordial compact objects. We show that if such objects generate enough luminosity to affect the CMB power spectrum, then they would produce enough heat to prevent the formation of 1 sigma collapsed objects until redshifts of about 5, significantly less than the redshift at which baryonic collapse could otherwise occur. Such processes would leave signatures detectable by upcoming instruments such as NGST, SIRTF, and SWIFT.Comment: 17 pages including 3 figures, accepted by Ap

Introduction

What are the strategies, modalities and aspirations of island-based, stateless nationalist and regionalist parties in the twenty-first century? Political independence is now easier to achieve, even by the smallest of territories; yet, it is not so likely to be pursued with any vigour by the world's various persisting sub-national (and mainly island) jurisdictions. Theirs is a pursuit of different expressions of sub-national autonomy, stopping short of independence. And yet, a number of independence referenda are scheduled, including one looming in Scotland in autumn 2014

Ramsey interferometry with an atom laser

We present results on a free-space atom interferometer operating on the first order magnetically insensitive |F=1,mF=0> -> |F=2,mF=0> transition of Bose-condensed 87Rb atoms. A pulsed atom laser is output-coupled from a Bose-Einstein condensate and propagates through a sequence of two internal state beam splitters, realized via coherent Raman transitions between the two interfering states. We observe Ramsey fringes with a visibility close to 100% and determine the current and the potentially achievable interferometric phase sensitivity. This system is well suited to testing recent proposals for generating and detecting squeezed atomic states.Comment: published version, 8 pages, 3 figure

A different appetite for sovereignty? Independence movements in subnational island jurisdictions

Local autonomy in a subnational jurisdiction is more likely to be gained, secured or enhanced where there are palpable movements or political parties agitating for independence in these smaller territories. A closer look at the fortunes, operations and dynamics of independence parties from subnational island jurisdictions can offer some interesting insights on the appetite for sovereignty and independence, but also the lack thereof, in the twenty-first century.peer-reviewe

Kinematics of Spiral Arm Streaming in M51

We use CO and H alpha velocity fields to study the gas kinematics in the spiral arms and interarms of M51 (NGC 5194), and fit the 2D velocity field to estimate the radial and tangential velocity components as a function of spiral phase (arm distance). We find large radial and tangential streaming velocities, which are qualitatively consistent with the predictions of density wave theory and support the existence of shocks. The streaming motions are complex, varying significantly across the galaxy as well as along and between arms. Aberrations in the velocity field indicate that the disk is not coplanar, perhaps as far in as 20\arcsec\ (800 pc) from the center. Velocity profile fits from CO and H alpha are typically similar, suggesting that most of the H alpha emission originates from regions of recent star formation. We also explore vortensity and mass conservation conditions. Vortensity conservation, which does not require a steady state, is empirically verified. The velocity and density profiles show large and varying mass fluxes, which are inconsistent with a steady flow for a single dominant global spiral mode. We thus conclude that the spiral arms cannot be in a quasi-steady state in any rotating frame, and/or that out of plane motions may be significant.Comment: 50 pages, including 20 figures; Accepted for publication in ApJ. PDF version with high resolution figures available at http://www.astro.umd.edu/~shetty/Research

Real-Time Identification of Serious Infection in Geriatric Patients Using Clinical Information System Surveillance

To develop and characterize an automated syndromic surveillance mechanism for early identification of older emergency department (ED) patients with possible life-threatening infection. DESIGN : Prospective, consecutive-enrollment, single-site observational study. SETTING : A large university medical center with an annual ED census of 75,273. PARTICIPANTS : Patients aged 70 and older admitted to the ED and having two or more systemic inflammatory response syndrome (SIRS) criteria during their ED stay. MEASUREMENTS : A search algorithm was developed to screen the census of the ED through its clinical information system. A study coordinator confirmed all patients electronically identified as having a probable infectious explanation for their visit. RESULTS : Infection accounted for 28% of ED and 34% of final hospital diagnoses. Identification using the software tool alone carried a 1.63 relative risk of infection (95% confidence interval CI=1.09–2.44) compared with other ED patients sufficiently ill to require admission. Follow-up confirmation by a study coordinator increased the risk to 3.06 (95% CI=2.11–4.44). The sensitivity of the strategy overall was modest (14%), but patients identified were likely to have an infectious diagnosis (specificity=98%). The most common SIRS criterion triggering the electronic notification was the combination of tachycardia and tachypnea. CONCLUSION : A simple clinical informatics algorithm can detect infection in elderly patients in real time with high specificity. The utility of this tool for research and clinical care may be substantial.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66036/1/j.1532-5415.2008.02094.x.pd

Day of Archaeology 2011–2017: Global Community, Public Engagement, and Digital Practice.

The Day of Archaeology (http://www.dayofarchaeology.com) was a volunteer-led international archaeological blogging event that ran from 2011 to 2017. The project asked people who define themselves as archaeologists to submit one or more blog posts about their working day on a chosen day in June or July. This article explores the history of the Day of Archaeology project and the practicalities of running a large-scale collaborative blogging project, before examining some of the topics covered in the posts. An assessment of the impact of the project follows. Overall, we hope in this work to answer some of the basic questions regarding this type of collaborative, online, global engagement – what we did, who we reached, what they talked about – and also to provide some insights for any other similar initiatives that may follow us in the future