982 research outputs found
WISE J072003.20-084651.2: An Old and Active M9.5 + T5 Spectral Binary 6 pc from the Sun
[Abridged] We report observations of the recently discovered, nearby late-M
dwarf WISE J072003.20-084651.2. Astrometric measurements obtained with TRAPPIST
improve the distance measurement to 6.01.0 pc and confirm the low
tangential velocity (3.50.6 km/s) reported by Scholz. Low-resolution
optical spectroscopy indicates a spectral type of M9.5 and prominent H
emission ( = -4.680.06), but no evidence of subsolar
metallicity or Li I absorption. Near-infrared spectroscopy reveals subtle
peculiarities indicating the presence of a T5 binary companion, and
high-resolution laser guide star adaptive optics imaging reveals a faint
(H = 4.1) candidate source 0"14 (0.8 AU) from the primary. We measure a
stable radial velocity of +83.80.3 km/s, indicative of old disk kinematics
and consistent with the angular separation of the possible companion. We
measure a projected rotational velocity of v sin i = 8.00.5 km/s, and find
evidence of low-level variability (~1.5%) in a 13-day TRAPPIST lightcurve, but
cannot robustly constrain the rotational period. We also observe episodic
changes in brightness (1-2%) and occasional flare bursts (4-8%) with a 0.8%
duty cycle, and order-of-magnitude variations in H line strength.
Combined, these observations reveal WISE J0720-0846 to be an old, very low-mass
binary whose components straddle the hydrogen burning minimum mass, and whose
primary is a relatively rapid rotator and magnetically active. It is one of
only two known binaries among late M dwarfs within 10 pc of the Sun, both
harboring a mid T-type brown dwarf companion. While this specific configuration
is rare (1.4% probability), roughly 25% of binary companions to late-type M
dwarfs in the local population are likely low-temperature T or Y brown dwarfs.Comment: 18 pages, 23 figures; accepted for publication in A
Extensive hydrogen supersaturations in the western South Atlantic Ocean suggest substantial underestimation of nitrogen fixation
The nitrogen cycle is fundamental to Earth's biogeochemistry. Yet major uncertainties of quantification remain, particularly regarding the global oceanic nitrogen fixation rate. Hydrogen is produced during nitrogen fixation and will become supersaturated in surface waters if there is net release from diazotrophs. Ocean surveys of hydrogen supersaturation thus have the potential to illustrate the spatial and temporal distribution of nitrogen fixation, and to guide the far more onerous but quantitative methods for measuring it. Here we present the first transect of high resolution measurements of hydrogen supersaturations in surface waters along a meridional 10,000 km cruise track through the Atlantic. We compare measured saturations with published measurements of nitrogen fixation rates and also with model-derived values. If the primary source of excess hydrogen is nitrogen fixation and has a hydrogen release ratio similar to Trichodesmium, our hydrogen measurements would point to similar rates of fixation in the North and South Atlantic, roughly consistent with modelled fixation rates but not with measured rates, which are lower in the south. Possible explanations would include any substantial nitrogen fixation by newly discovered diazotrophs, particularly any having a hydrogen release ratio similar to or exceeding that of Trichodesmium; under-sampling of nitrogen fixation south of the equator related to excessive focus on Trichodesmium; and methodological shortcomings of nitrogen fixation techniques that cause a bias towards colonial diazotrophs relative to unicellular forms. Alternatively our data are affected by an unknown hydrogen source that is greater in the southern half of the cruise track than the northern
Osteohistological variation in growth marks and osteocyte lacunar density in a theropod dinosaur (Coelurosauria: ornithomimidae)
Highly selective CO2 vs. N2 adsorption in the cavity of a molecular coordination cage
Two M8L12 cubic coordination cages, as desolvated crystalline powders, preferentially adsorb CO2 over N2 with ideal selectivity CO2/N2 constants of 49 and 30 at 298 K. A binding site for CO2 is suggested by crystallographic location of CS2 within the cage cavity at an electropositive hydrogen-bond donor site, potentially explaining the high CO2/N2 selectivity compared to other materials with this level of porosity
Threats to the operational use of situational judgment tests in the college admission process
IN-SYNC. V. Stellar kinematics and dynamics in the Orion A Molecular Cloud
The kinematics and dynamics of young stellar populations enable us to test
theories of star formation. With this aim, we continue our analysis of the
SDSS-III/APOGEE IN-SYNC survey, a high resolution near infrared spectroscopic
survey of young clusters. We focus on the Orion A star-forming region, for
which IN-SYNC obtained spectra of stars. In Paper IV we used these
data to study the young stellar population. Here we study the kinematic
properties through radial velocities (). The young stellar population
remains kinematically associated with the molecular gas, following a
gradient along filament. However, near the center
of the region, the distribution is slightly blueshifted and asymmetric;
we suggest that this population, which is older, is slightly in foreground. We
find evidence for kinematic subclustering, detecting statistically significant
groupings of co-located stars with coherent motions. These are mostly in the
lower-density regions of the cloud, while the ONC radial velocities are
smoothly distributed, consistent with it being an older, more dynamically
evolved cluster. The velocity dispersion varies along the filament.
The ONC appears virialized, or just slightly supervirial, consistent with an
old dynamical age. Here there is also some evidence for on-going expansion,
from a --extinction correlation. In the southern filament, is
-- times larger than virial in the L1641N region, where we infer a
superposition along the line of sight of stellar sub-populations, detached from
the gas. On the contrary, decreases towards L1641S, where the
population is again in agreement with a virial state.Comment: 14 pages, 13 figures, ApJ accepte
Keratinocyte growth factor for the treatment of the acute respiratory distress syndrome (KARE): a randomised, double-blind, placebo-controlled phase 2 trial
<p>(<b>A</b>) Immunofluorescence signal for dystrophin is significantly reduced in the SSI heart (bottom left panel) compared with the immunofluorescent signal in the SHAM heart (upper left panel), and the SHAM+ALLN (upper right panel) and SSI+ALLN (bottom right panel) myocardium. (<b>B</b>) Protein levels of dystrophin in the SHAM, SSI, SHAM+ALLN and SSI+ALLN hearts were measured 24 h after the CLP procedure and were expressed in arbitrary units (AUs). α-Tubulin was used to determine equivalent loading conditions. The results (n = 6 per group) are representative of three different experiments. Scale bars indicate 50 μm.</p
Total Parenteral Nutrition in Patients Following Pancreaticoduodenectomy: Lessons from 1184 Patients
Poster presented at Sigma XI Student Research Day at Thomas Jefferson University.
Background:
Total parenteral nutrition (TPN) has historically been used conservatively in the management of patients after pancreaticoduodenectomy (PD).
In this study, we evaluate the indications for and outcomes associated with TPN use in a high-volume pancreatic surgery center.https://jdc.jefferson.edu/surgeryposters/1007/thumbnail.jp
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