Linking Signatures of Accretion with Magnetic Field Measurements - Line Profiles are not Significantly Different in Magnetic and Non-Magnetic Herbig Ae/Be Stars

Herbig Ae/Be stars are young, pre-main-sequence stars that sample the transition in structure and evolution between low- and high-mass stars, providing a key test of accretion processes in higher-mass stars. Few Herbig Ae/Be stars have detected magnetic fields, calling into question whether the magnetospheric accretion paradigm developed for low-mass stars can be scaled to higher masses. We present He I 10830 \AA\ line profiles for 64 Herbig Ae/Be stars with a magnetic field measurement in order to test magnetospheric accretion in the physical regime where its efficacy remains uncertain. Of the 5 stars with a magnetic field detection, 1 shows redshifted absorption, indicative of infall, and 2 show blueshifted absorption, tracing mass outflow. The fraction of redshifted and blueshifted absorption profiles in the non-magnetic Herbig Ae/Be stars is remarkably similar, suggesting that the stellar magnetic field does not affect gas kinematics traced by He I 10830 \AA. Line profile morphology does not correlate with the luminosity, rotation rate, mass accretion rate, or disk inclination. Only the detection of a magnetic field and a nearly face-on disk inclination show a correlation (albeit for few sources). This provides further evidence for weaker dipoles and more complex field topologies as stars develop a radiative envelope. The small number of magnetic Herbig Ae/Be stars has already called into question whether magnetospheric accretion can be scaled to higher masses; accretion signatures are not substantially different in magnetic Herbig Ae/Be stars, casting further doubt that they accrete in the same manner as classical T Tauri stars.Comment: accepted to ApJ; 17 pages, 4 figures, 3 table

Synthesis of 3-Farnesyl Salicylic Acid, a Novel Antimicrobial from Piper multiplinervium

Both 3-farnesyl salicylic acid and 3-geranyl salicylic acid were synthesized from 2,6-dibromophenol and showed low levels of antimicrobial activity against E. coli strains

Use of Flow Cytometry and Stable Isotope Analysis to Determine Phytoplankton Uptake of Wastewater Derived Ammonium in a Nutrient-rich River

Anthropogenic alteration of the form and concentration of nitrogen (N) in aquatic ecosystems is widespread. Understanding availability and uptake of different N sources at the base of aquatic food webs is critical to establishment of effective nutrient management programs. Stable isotopes of N (14N,15N) are often used to trace the sources of N fuelling aquatic primary production, but effective use of this approach requires obtaining a reliable isotopic ratio for phytoplankton. In this study, we tested the use of flow cytometry to isolate phytoplankton from bulk particulate organic matter (POM) in a portion of the Sacramento River, California, during river-scale nutrient manipulation experiments that involved halting wastewater discharges high in ammonium (NH4 +). Field samples were collected using a Lagrangian approach, allowing us to measure changes in phytoplankton N source in the presence and absence of wastewater derived NH4 +. Comparison of δ15N-POM and δ15N-phytoplankton (δ15N-PHY) revealed that their δ15N values followed broadly similar trends. However, after 3 days of downstream travel in the presence of wastewater treatment plant (WWTP) effluent, δ15N-POM and δ15N-PHY in the Sacramento River differed by as much as 7‰. Using a stable isotope mixing model approach, we estimated that in the presence of effluent between 40 and 90% of phytoplankton-N was derived from NH4 + after 3 days of downstream transport. An apparent gradual increase over time in the proportion of NH4 + in the phytoplankton N pool suggests that either very low phytoplankton growth rates resulted in an N turnover time that exceeded the travel time sampled during this study, or a portion of the phytoplankton community continued to access nitrate even in the presence of elevated NH4 + concentrations

Umbilical Cord Tissue-Derived Mesenchymal Stem Cells Inhibit T Cell Response to Peptide

Mesenchymal stem cells (MSC) have been shown to possess immunomodulatory properties that highlight their potential as a cellular therapy for autoimmune disease. We propose to examine the in vitro potential of stem cells derived from umbilical cord tissue to suppress the effector functions of human auto-reactive T cells. While the mechanism(s) of suppression of T cell function are not fully understood, it has been hypothesized that MSC-derived immunosuppressive soluble factors and cell-to-cell contact are important. We developed an in vitro culture assay to assess the effects of umbilical cord derived MSC (TC-MSC) on T cell function. Various doses of low-passage TC-MSCs were adhered to collagen-coated 96 well plates or in the lower chamber wells of transwell plates. HLA-matched EBV transformed B cells were pulsed +/- with appropriate autoantigenic peptide and cultured with adherent MSC or in the upper transwell chambers with the appropriate T cell clone. After 48 hours, cells were stained for CD4 and stained intracellularly for IFN-γ and analyzed by flow cytometry. We observed decreased T cell effector function with MSC co-culture and this was partially restored by separation of MSC and T cell+B cell+peptide in the transwell. We examined if prostaglandin E2 derived from the MSC also contributed to decreased T cell effector function. The inclusion of a COX-2 inhibitor in the culture system led to partially restored T cell effector function. We conclude that TC-MSC-derived soluble factor(s) and TC-MSC:T cell contact both contribute to the TC-MSC’s immunosuppressive effects. Primary TC-MSC isolates (with no prior cell culture) will also be tested in this system to determine if they possess similar immunosuppressive effects as adherent, cultured TC-MSC. These studies will pinpoint the functional mechanisms of the TC-MSC immunomodulatory properties on T cell effector function and may suggest avenues of enhancing MSC function in the treatment of autoimmune disease

Demographics of the M-star Multiple Population in the Orion Nebula Cluster

We present updated results constraining multiplicity demographics for the stellar population of the Orion Nebula Cluster (ONC, a high-mass, high-density star-forming region), across primary masses 0.08-0.7M$_{\odot}$. Our study utilizes archival Hubble Space Telescope data obtained with the Advanced Camera for Surveys using multiple filters (GO-10246). Previous multiplicity surveys in low-mass, low-density associations like Taurus identify an excess of companions to low-mass stars roughly twice that of the Galactic field and find the mass ratio distribution consistent with the field. Previously, we found the companion frequency to low-mass stars in the ONC is consistent with the Galactic field over mass ratios=0.6-1.0 and projected separations=30-160au, without placing constraints on the mass ratio distribution. In this study, we investigate the companion population of the ONC with a double point-spread function (PSF) fitting algorithm sensitive to separations larger than 10au (0.025") using empirical PSF models. We identified 44 companions (14 new), and with a Bayesian analysis, estimate the companion frequency to low-mass stars in the ONC =0.13$^{+0.05}_{-0.03}$ and the power law fit index to the mass ratio distribution =2.08$^{+1.03}_{-0.85}$ over all mass ratios and projected separations of 10-200au. We find the companion frequency in the ONC is consistent with the Galactic field population, likely from high transient stellar density states, and a probability of 0.002 that it is consistent with that of Taurus. We also find the ONC mass ratio distribution is consistent with the field and Taurus, potentially indicative of its primordial nature, a direct outcome of the star formation process.Comment: 23 pages, 11 figures, Accepted to ApJ Nov. 3, 202

ZODIACAL EXOPLANETS IN TIME (ZEIT). III. A SHORT-PERIOD PLANET ORBITING A PRE-MAIN-SEQUENCE STAR IN THE UPPER SCORPIUS OB ASSOCIATION

We confirm and characterize a close-in (${P}_{{\rm{orb}}}$ = 5.425 days), super-Neptune sized (${5.04}_{-0.37}^{+0.34}$ ${R}_{\oplus }$) planet transiting K2-33 (2MASS J16101473-1919095), a late-type (M3) pre-main-sequence (11 Myr old) star in the Upper Scorpius subgroup of the Scorpius–Centaurus OB association. The host star has the kinematics of a member of the Upper Scorpius OB association, and its spectrum contains lithium absorption, an unambiguous sign of youth ($\lt 20$ Myr) in late-type dwarfs. We combine photometry from K2 and the ground-based MEarth project to refine the planet's properties and constrain the host star's density. We determine K2-33's bolometric flux and effective temperature from moderate-resolution spectra. By utilizing isochrones that include the effects of magnetic fields, we derive a precise radius (6%–7%) and mass (16%) for the host star, and a stellar age consistent with the established value for Upper Scorpius. Follow-up high-resolution imaging and Doppler spectroscopy confirm that the transiting object is not a stellar companion or a background eclipsing binary blended with the target. The shape of the transit, the constancy of the transit depth and periodicity over 1.5 yr, and the independence with wavelength rule out stellar variability or a dust cloud or debris disk partially occulting the star as the source of the signal; we conclude that it must instead be planetary in origin. The existence of K2-33b suggests that close-in planets can form in situ or migrate within ~10 Myr, e.g., via interactions with a disk, and that long-timescale dynamical migration such as by Lidov–Kozai or planet–planet scattering is not responsible for all short-period planets

How to Constrain Your M Dwarf. II. The Mass–Luminosity–Metallicity Relation from 0.075 to 0.70 Solar Masse

The mass-luminosity relation for late-type stars has long been a critical tool for estimating stellar masses. However, there is growing need for both a higher-precision relation and a better understanding of systematic effects (e.g., metallicity). Here we present an empirical relationship between Mks and mass spanning $0.075M_\odot<M<0.70M_\odot$. The relation is derived from 62 nearby binaries, whose orbits we determine using a combination of Keck/NIRC2 imaging, archival adaptive optics data, and literature astrometry. From their orbital parameters, we determine the total mass of each system, with a precision better than 1% in the best cases. We use these total masses, in combination with resolved Ks magnitudes and system parallaxes, to calibrate the mass-Mks relation. The result can be used to determine masses of single stars with a precision of 2-3%, which we confirm by a comparison to dynamical masses from the literature. The precision is limited by scatter around the best-fit relation beyond mass uncertainties, perhaps driven by intrinsic variation in the mass-Mks relation or underestimated measurement errors. We find the effect of [Fe/H] on the mass-Mks relation is likely negligible for metallicities in the Solar neighborhood (0.0+/-2.2% change in mass per dex change in [Fe/H]). This weak effect is consistent with predictions from the Dartmouth Stellar Evolution Database, but inconsistent with those from MESA Isochrones and Stellar Tracks. A sample of binaries with a wider range of abundances will be required to discern the importance of metallicity in extreme populations (e.g., in the Galactic Halo or thick disk).Comment: Published in ApJ/AAS Journals. Comments welcome. Code for computing mass posteriors from Ks+distance at https://github.com/awmann/M_-M_K

Prospecting in ultracool dwarfs : Measuring the metallicities of mid- and late-m dwarfs

© 2014. The American Astronomical Society. All rights reserved.Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. The low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R ∼ 2000) K-band (≃ 2.2 μm) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early-M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early-M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to ∼0.07 dex for M4.5-M9.5 dwarfs with -0.58 <[Fe/H] <+0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolved binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.Peer reviewe

Association between adrenergic receptor genotypes and beta-blocker dose in heart failure patients: analysis from the HF-ACTION DNA substudy

Beta-blockers reduce morbidity and mortality in chronic heart failure (HF) patients with reduced ejection fraction. However, there is heterogeneity in the response to these drugs, perhaps due to genetic variations in the β1-adrenergic receptor (ADRβ1). We examined whether the Arg389Gly polymorphism in ADRβ1 interacts with the dose requirements of beta-blockers in patients with systolic HF