2,718 research outputs found
Contemporaneous Observations of Luminosities and Photometric Amplitudes for M Dwarfs
While many M dwarfs are known to have strong magnetic fields and high levels
of magnetic activity, we are still unsure about the properties of their
starspots and the origin of their magnetic dynamos. Both starspots and
chromospheric heating are generated by the surface magnetic field; they produce
photometric variability and Halpha emission, respectively. Connecting
brightness variations to magnetic activity therefore provides a means to
examine M dwarf magnetism. We survey 30 M dwarfs previously identified as fast
rotating stars (Prot < 10 days). We present time-series optical photometry from
the Transiting Exoplanet Survey Satellite (TESS) and contemporaneous optical
spectra obtained using the Ohio State Multi-Object Spectrograph (OSMOS) on the
2.4m Hiltner telescope at MDM Observatory in Arizona. We measure rotation
periods and photometric amplitudes from TESS light curves using Gaussian
Processes. From the OSMOS spectra, we calculate the equivalent width of Halpha,
and LHalpha/Lbol. We find a weak positive correlation between Halpha luminosity
and the semi-amplitude, Rvar p=0.005_{-0.005}^{+0.075}. We also observe
short-term variability (between 20-45 minutes) in Halpha equivalent widths and
possible enhancement from flares consistent to recent literature.Comment: 19 pages, 9 Figures, 2 Tables, Poster Presented at Cool Stars 21,
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The Factory and the Beehive III: PTFEB132.707+19.810, a Low-Mass Eclipsing Binary in Praesepe Observed by PTF and K2
Theoretical models of stars constitute a fundamental bedrock upon which much
of astrophysics is built, but large swaths of model parameter space remain
uncalibrated by observations. The best calibrators are eclipsing binaries in
clusters, allowing measurement of masses, radii, luminosities, and
temperatures, for stars of known metallicity and age. We present the discovery
and detailed characterization of PTFEB132.707+19.810, a P=6.0 day eclipsing
binary in the Praesepe cluster (~600--800 Myr; [Fe/H]=0.140.04). The
system contains two late-type stars (SpT=M3.50.2;
SpT=M4.30.7) with precise masses (~;
~) and radii (~;
~). Neither star meets the predictions of stellar
evolutionary models. The primary has the expected radius, but is cooler and
less luminous, while the secondary has the expected luminosity, but is cooler
and substantially larger (by 20%). The system is not tidally locked or
circularized. Exploiting a fortuitous 4:5 commensurability between
and , we demonstrate that fitting errors from the unknown spot
configuration only change the inferred radii by <1--2%. We also analyze subsets
of data to test the robustness of radius measurements; the radius sum is more
robust to systematic errors and preferable for model comparisons. We also test
plausible changes in limb darkening, and find corresponding uncertainties of
~1%. Finally, we validate our pipeline using extant data for GU Boo, finding
that our independent results match previous radii to within the mutual
uncertainties (2--3%). We therefore suggest that the substantial discrepancies
are astrophysical; since they are larger than for old field stars, they may be
tied to the intermediate age of PTFEB132.707+19.810.Comment: Accepted to ApJ; 36 pages, 19 figures, 8 tables in two-column AASTEX6
forma
Expression of the p40 isoform of p63 has high specificity for cutaneous sarcomatoid squamous cell carcinoma
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109645/1/cup12387.pd
UNC93B1 Mediates Host Resistance to Infection with Toxoplasma gondii
UNC93B1 associates with Toll-Like Receptor (TLR) 3, TLR7 and TLR9, mediating their translocation from the endoplasmic reticulum to the endolysosome, hence allowing proper activation by nucleic acid ligands. We found that the triple deficient ‘3d’ mice, which lack functional UNC93B1, are hyper-susceptible to infection with Toxoplasma gondii. We established that while mounting a normal systemic pro-inflammatory response, i.e. producing abundant MCP-1, IL-6, TNFα and IFNγ, the 3d mice were unable to control parasite replication. Nevertheless, infection of reciprocal bone marrow chimeras between wild-type and 3d mice with T. gondii demonstrated a primary role of hemopoietic cell lineages in the enhanced susceptibility of UNC93B1 mutant mice. The protective role mediated by UNC93B1 to T. gondii infection was associated with impaired IL-12 responses and delayed IFNγ by spleen cells. Notably, in macrophages infected with T. gondii, UNC93B1 accumulates on the parasitophorous vacuole. Furthermore, upon in vitro infection the rate of tachyzoite replication was enhanced in non-activated macrophages carrying mutant UNC93B1 as compared to wild type gene. Strikingly, the role of UNC93B1 on intracellular parasite growth appears to be independent of TLR function. Altogether, our results reveal a critical role for UNC93B1 on induction of IL-12/IFNγ production as well as autonomous control of Toxoplasma replication by macrophages
HAZMAT. VIII. A Spectroscopic Analysis of the Ultraviolet Evolution of K Stars: Additional Evidence for K Dwarf Rotational Stalling in the First Gigayear
Efforts to discover and characterize habitable zone planets have primarily
focused on Sun-like stars and M dwarfs. K stars, however, provide an appealing
compromise between these two alternatives that has been relatively unexplored.
Understanding the ultraviolet (UV) environment around such stars is critical to
our understanding of their planets, as the UV can drastically alter the
photochemistry of a planet's atmosphere. Here we present near-UV and far-UV
\textit{Hubble Space Telescope}'s Cosmic Origins Spectrograph observations of
39 K stars at three distinct ages: 40 Myr, 650 Myr, and 5 Gyr. We find
that the K star (0.6 -- 0.8 M) UV flux remains constant beyond 650
Myr before falling off by an order of magnitude by field age. This is distinct
from early M stars (0.3 -- 0.6 M), which begin to decline after only
a few hundred Myr. However, the rotation-UV activity relation for K stars is
nearly identical to that of early M stars. These results may be a consequence
of the spin-down stalling effect recently reported for K dwarfs, in which the
spin-down of K stars halts for over a Gyr when their rotation periods reach
10 d, rather than the continuous spin down that G stars experience.
These results imply that exoplanets orbiting K dwarfs may experience a stronger
UV environment than thought, weakening the case for K stars as hosts of
potential "super-habitable" planets.Comment: 18 pages, 7 figure
Recommended from our members
An Evidence-Based Comparison of Operational Criteria for the Presence of Sarcopenia
Background. Several consensus groups have previously published operational criteria for sarcopenia, incorporating lean mass with strength and/or physical performance. The purpose of this manuscript is to describe the prevalence, agreement, and discrepancies between the Foundation for the National Institutes of Health (FNIH) criteria with other operational definitions for sarcopenia. Methods. The FNIH Sarcopenia Project used data from nine studies including: Age, Gene and Environment Susceptibility-Reykjavik Study; Boston Puerto Rican Health Study; a series of six clinical trials from the University of Connecticut; Framingham Heart Study; Health, Aging, and Body Composition Study; Invecchiare in Chianti; Osteoporotic Fractures in Men Study; Rancho Bernardo Study; and Study of Osteoporotic Fractures. Participants included in these analyses were aged 65 and older and had measures of body mass index, appendicular lean mass, grip strength, and gait speed. Results. The prevalence of sarcopenia and agreement proportions was higher in women than men. The lowest prevalence was observed with the FNIH criteria (1.3% men and 2.3% women) compared with the International Working Group and the European Working Group for Sarcopenia in Older Persons (5.1% and 5.3% in men and 11.8% and 13.3% in women, respectively). The positive percent agreements between the FNIH criteria and other criteria were low, ranging from 7% to 32% in men and 5% to 19% in women. However, the negative percent agreement were high (all >95%). Conclusions. The FNIH criteria result in a more conservative operational definition of sarcopenia, and the prevalence was lower compared with other proposed criteria. Agreement for diagnosing sarcopenia was low, but agreement for ruling out sarcopenia was very high. Consensus on the operational criteria for the diagnosis of sarcopenia is much needed to characterize populations for study and to identify adults for treatment
Salivary molecular spectroscopy : a sustainable, rapid and non-invasive monitoring tool for diabetes mellitus during insulin treatment
Monitoring of blood glucose is an invasive, painful and costly practice in diabetes. Consequently, the search for a more cost-effective (reagent-free), non-invasive and specific diabetes monitoring method is of great interest. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has been used in diagnosis of several diseases, however, applications in the monitoring of diabetic treatment are just beginning to emerge. Here, we used ATR-FTIR spectroscopy to evaluate saliva of non-diabetic (ND), diabetic (D) and insulin-treated diabetic (D+I) rats to identify potential salivary biomarkers related to glucose monitoring. The spectrum of saliva of ND, D and D+I rats displayed several unique vibrational modes and from these, two vibrational modes were pre-validated as potential diagnostic biomarkers by ROC curve analysis with significant correlation with glycemia. Compared to the ND and D+I rats, classification of D rats was achieved with a sensitivity of 100%, and an average specificity of 93.33% and 100% using bands 1452 cm-1 and 836 cm-1, respectively. Moreover, 1452 cm-1 and 836 cm-1 spectral bands proved to be robust spectral biomarkers and highly correlated with glycemia (R2 of 0.801 and 0.788, P < 0.01, respectively). Both PCA-LDA and HCA classifications achieved an accuracy of 95.2%. Spectral salivary biomarkers discovered using univariate and multivariate analysis may provide a novel robust alternative for diabetes monitoring using a non-invasive and green technology
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