Segue 2: The Least Massive Galaxy

Segue 2, discovered by Belokurov et al., is a galaxy with a luminosity of only 900 L_☉. We present Keck/DEIMOS spectroscopy of 25 members of Segue 2—a threefold increase in spectroscopic sample size. The velocity dispersion is too small to be measured with our data. The upper limit with 90% (95%) confidence is σ_v < 2.2 (2.6) km s^(–1), the most stringent limit for any galaxy. The corresponding limit on the mass within the three-dimensional half-light radius (46 pc) is M_(1/2) < 1.5 (2.1) × 10^5 M_☉. Segue 2 is the least massive galaxy known. We identify Segue 2 as a galaxy rather than a star cluster based on the wide dispersion in [Fe/H] (from –2.85 to –1.33) among the member stars. The stars' [α/Fe] ratios decline with increasing [Fe/H], indicating that Segue 2 retained Type Ia supernova ejecta despite its presently small mass and that star formation lasted for at least 100 Myr. The mean metallicity, 〈[Fe/H]〉 = -2.22 ± 0.13 (about the same as the Ursa Minor galaxy, 330 times more luminous than Segue 2), is higher than expected from the luminosity-metallicity relation defined by more luminous dwarf galaxy satellites of the Milky Way. Segue 2 may be the barest remnant of a tidally stripped, Ursa Minor-sized galaxy. If so, it is the best example of an ultra-faint dwarf galaxy that came to be ultra-faint through tidal stripping. Alternatively, Segue 2 could have been born in a very low mass dark matter subhalo (v_(max) < 10 km s^(–1)), below the atomic hydrogen cooling limit

Post-hospital medical respite care and hospital readmission of homeless persons

Medical respite programs offer medical, nursing, and other care as well as accommodation for homeless persons discharged from acute hospital stays. They represent a community-based adaptation of urban health systems to the specific needs of homeless persons. This article examines whether post-hospital discharge to a homeless medical respite program was associated with a reduced chance of 90-day readmission compared to other disposition options. Adjusting for imbalances in patient characteristics using propensity scores, respite patients were the only group that was significantly less likely to be readmitted within 90 days compared to those released to Own Care. Respite programs merit attention as a potentially efficacious service for homeless persons leaving the hospital

Safety Recommendations for Evaluation and Surgery of the Head and Neck During the COVID-19 Pandemic

Importance The rapidly expanding novel coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2, has challenged the medical community to an unprecedented degree. Physicians and health care workers are at added risk of exposure and infection during the course of patient care. Because of the rapid spread of this disease through respiratory droplets, health care workers who come in close contact with the upper aerodigestive tract during diagnostic and therapeutic procedures, such as otolaryngologists–head and neck surgeons, are particularly at risk. A set of safety recommendations was created based on a review of the literature and communications with physicians with firsthand knowledge of safety procedures during the COVID-19 pandemic. Observations A high number of health care workers were infected during the first phase of the pandemic in the city of Wuhan, China. Subsequently, by adopting strict safety precautions, other regions were able to achieve high levels of safety for health care workers without jeopardizing the care of patients. The most common procedures related to the examination and treatment of upper aerodigestive tract diseases were reviewed. Each category was reviewed based on the potential risk imposed to health care workers. Specific recommendations were made based on the literature, when available, or consensus best practices. Specific safety recommendations were made for performing tracheostomy in patients with COVID-19. Conclusions and Relevance Preserving a highly skilled health care workforce is a top priority for any community and health care system. Based on the experience of health care systems in Asia and Europe, by following strict safety guidelines, the risk of exposure and infection of health care workers could be greatly reduced while providing high levels of care. The provided recommendations, which may evolve over time, could be used as broad guidance for all health care workers who are involved in the care of patients with COVID-19

BATSE Observations of Gamma-Ray Burst Spectra. IV. Time-Resolved High-Energy Spectroscopy

We report on the temporal behavior of the high-energy power law continuum component of gamma-ray burst spectra with data obtained by the Burst and Transient Source Experiment. We have selected 126 high fluence and high flux bursts from the beginning of the mission up until the present. Much of the data were obtained with the Large Area Detectors, which have nearly all-sky coverage, excellent sensitivity over two decades of energy and moderate energy resolution, ideal for continuum spectra studies of a large sample of bursts at high time resolution. At least 8 spectra from each burst were fitted with a spectral form that consisted of a low-energy power law, a spectral break at middle energies and a high-energy continuum. In most bursts (122), the high-energy continuum was consistent with a power law. The evolution of the fitted high-energy power-law index over the selected spectra for each burst is inconsistent with a constant for 34% of the total sample. The sample distribution of the average value for the index from each burst is fairly narrow, centered on -2.12. A linear trend in time is ruled out for only 20% of the bursts, with hard-to-soft evolution dominating the sample (100 events). The distribution for the total change in the power-law index over the duration of a burst peaks at the value -0.37, and is characterized by a median absolute deviation of 0.39, arguing that a single physical process is involved. We present analyses of the correlation of the power-law index with time, burst intensity and low-energy time evolution. In general, we confirm the general hard-to-soft spectral evolution observed in the low-energy component of the continuum, while presenting evidence that this evolution is different in nature from that of the rest of the continuum.Comment: 30 pages, with 2 tables and 9 figures To appear in The Astrophysical Journal, April 1, 199

A Comparative Study of the ReCell® Device and Autologous Spit-Thickness Meshed Skin Graft in the Treatment of Acute Burn Injuries.

Early excision and autografting are standard care for deeper burns. However, donor sites are a source of significant morbidity. To address this, the ReCell® Autologous Cell Harvesting Device (ReCell) was designed for use at the point-of-care to prepare a noncultured, autologous skin cell suspension (ASCS) capable of epidermal regeneration using minimal donor skin. A prospective study was conducted to evaluate the clinical performance of ReCell vs meshed split-thickness skin grafts (STSG, Control) for the treatment of deep partial-thickness burns. Effectiveness measures were assessed to 1 year for both ASCS and Control treatment sites and donor sites, including the incidence of healing, scarring, and pain. At 4 weeks, 98% of the ASCS-treated sites were healed compared with 100% of the Controls. Pain and assessments of scarring at the treatment sites were reported to be similar between groups. Significant differences were observed between ReCell and Control donor sites. The mean ReCell donor area was approximately 40 times smaller than that of the Control (P &lt; .0001), and after 1 week, significantly more ReCell donor sites were healed than Controls (P = .04). Over the first 16 weeks, patients reported significantly less pain at the ReCell donor sites compared with Controls (P ≤ .05 at each time point). Long-term patients reported higher satisfaction with ReCell donor site outcomes compared with the Controls. This study provides evidence that the treatment of deep partial-thickness burns with ASCS results in comparable healing, with significantly reduced donor site size and pain and improved appearance relative to STSG

Principles for the post-GWAS functional characterisation of risk loci

Several challenges lie ahead in assigning functionality to susceptibility SNPs. For example, most effect sizes are small relative to effects seen in monogenic diseases, with per allele odds ratios usually ranging from 1.15 to 1.3. It is unclear whether current molecular biology methods have enough resolution to differentiate such small effects. Our objective here is therefore to provide a set of recommendations to optimize the allocation of effort and resources in order maximize the chances of elucidating the functional contribution of specific loci to the disease phenotype. It has been estimated that 88% of currently identified disease-associated SNP are intronic or intergenic. Thus, in this paper we will focus our attention on the analysis of non-coding variants and outline a hierarchical approach for post-GWAS functional studies

The Architecture of the GW Ori Young Triple Star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses

We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main sequence hierarchical triple star system GW Ori. A forward-modeling of the ${}^{13}$CO and C${}^{18}$O $J$=2-1 transitions permits a measurement of the total stellar mass in this system, $5.29 \pm 0.09\,M_\odot$, and the circum-triple disk inclination, $137.6 \pm 2.0^\circ$. Optical spectra spanning a 35 year period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a $241.50\pm0.05$ day period; a tertiary companion orbits that inner pair with a $4218\pm50$ day period. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system ($M_\mathrm{A} \approx 2.7\,M_\odot$, $M_\mathrm{B} \approx 1.7\,M_\odot$, $M_\mathrm{C} \approx 0.9\,M_\odot$) and find strong evidence that at least one (and likely both) stellar orbital planes are misaligned with the disk plane by as much as $45^\circ$. A $V$-band light curve spanning 30 years reveals several new $\sim$30 day eclipse events 0.1-0.7~mag in depth and a 0.2 mag sinusoidal oscillation that is clearly phased with the AB-C orbital period. Taken together, these features suggest that the A-B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is $\sim$1 Myr old.Comment: 26 pages, 15 figures, accepted to Ap

Pulsed electromagnetic energy treatment offers no clinical benefit in reducing the pain of knee osteoarthritis: a systematic review

Background The rehabilitation of knee osteoarthritis often includes electrotherapeutic modalities as well as advice and exercise. One commonly used modality is pulsed electromagnetic field therapy (PEMF). PEMF uses electro magnetically generated fields to promote tissue repair and healing rates. Its equivocal benefit over placebo treatment has been previously suggested however recently a number of randomised controlled trials have been published that have allowed a systematic review to be conducted. Methods A systematic review of the literature from 1966 to 2005 was undertaken. Relevant computerised bibliographic databases were searched and papers reviewed independently by two reviewers for quality using validated criteria for assessment. The key outcomes of pain and functional disability were analysed with weighted and standardised mean differences being calculated. Results Five randomised controlled trials comparing PEMF with placebo were identified. The weighted mean differences of the five papers for improvement in pain and function, were small and their 95% confidence intervals included the null. Conclusion This systematic review provides further evidence that PEMF has little value in the management of knee osteoarthritis. There appears to be clear evidence for the recommendation that PEMF does not significantly reduce the pain of knee osteoarthritis

Political economy of renewable resource federalism

Author Posting. © Ecological Society of America, 2021. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 00 (2021): e2276, doi:10.1002/eap.2276.The authority to manage natural capital often follows political boundaries rather than ecological. This mismatch can lead to unsustainable outcomes, as spillovers from one management area to the next may create adverse incentives for local decision making, even within a single country. At the same time, one‐size‐fits‐all approaches of federal (centralized) authority can fail to respond to state (decentralized) heterogeneity and can result in inefficient economic or detrimental ecological outcomes. Here we utilize a spatially explicit coupled natural–human system model of a fishery to illuminate trade‐offs posed by the choice between federal vs. state control of renewable resources. We solve for the dynamics of fishing effort and fish stocks that result from different approaches to federal management that vary in terms of flexibility. Adapting numerical methods from engineering, we also solve for the open‐loop Nash equilibrium characterizing state management outcomes, where each state anticipates and responds to the choices of the others. We consider traditional federalism questions (state vs. federal management) as well as more contemporary questions about the economic and ecological impacts of shifting regulatory authority from one level to another. The key mechanisms behind the trade‐offs include whether differences in local conditions are driven by biological or economic mechanisms; degree of flexibility embedded in the federal management; the spatial and temporal distribution of economic returns across states; and the status‐quo management type. While simple rules‐of‐thumb are elusive, our analysis reveals the complex political economy dimensions of renewable resource federalism.This work was partially supported through the Ecological Federalism working group of the National Institute for Mathematical and Biological Synthesis, an Institute sponsored by the National Science Foundation through NSF Award (No. DBI‐1300426), with additional support from the Howard H. Baker Jr. Center for Public Policy and The University of Tennessee, Knoxville. M. G. Neubert acknowledges support from the U.S. National Science Foundation (DEB‐1558904) and from the J. Seward Johnson Endowment in support of the Woods Hole Oceanographic Institution’s Marine Policy Center. We would like to thank seminar participants at Oregon State University, Nature Policy Lab at U.C. Davis, and the 2019 Association of Environmental and Resource Economists Summer Conference for valuable comments and suggestions on earlier versions of this research

Sharpening the predictions of big-bang nucleosynthesis

Motivated by the recent measurement of the primeval abundance of deuterium, we re-examine the nuclear inputs to big-bang nucleosynthesis (BBN). Using Monte-Carlo realization of the nuclear cross-section data to directly estimate the theoretical uncertainties for the yields of D, 3-He and 7-Li, we show that previous estimates were a factor of 2 too large. We sharpen the BBN determination of the baryon density based upon deuterium, rho_B = (3.6 +/- 0.4) * 10^{-31} g/cm^3 (Omega_B h^2 = 0.019 +/- 0.0024), which leads to a predicted 4-He abundance, Y_P = 0.246 +/- 0.0014 and a stringent limit to the equivalent number of light neutrino species: N_nu < 3.20 (all at 95% cl). The predicted 7-Li abundance, 7-Li/H = (3.5 + 1.1 - 0.9) * 10^{-10}, is higher than that observed in pop II stars, (1.7 +/- 0.3) * 10^{-10} (both, 95% cl). We identify key reactions and the energies where further work is needed.Comment: 5 pages, 4 figures (epsfig), REVTeX; submitted to Phys. Rev. Let