375 research outputs found
LHS6343C: A Transiting Field Brown Dwarf Discovered by the Kepler Mission
We report the discovery of a brown dwarf that transits one member of the M+M
binary system LHS6343AB every 12.71 days. The transits were discovered using
photometric data from the Kelper public data release. The LHS6343 stellar
system was previously identified as a single high-proper-motion M dwarf. We use
high-contrast imaging to resolve the system into two low-mass stars with masses
0.45 Msun and 0.36 Msun, respectively, and a projected separation of 55 arcsec.
High-resolution spectroscopy shows that the more massive component undergoes
Doppler variations consistent with Keplerian motion, with a period equal to the
transit period and an amplitude consistent with a companion mass of M_C = 62.8
+/- 2.3 Mjup. Based on an analysis of the Kepler light curve we estimate the
radius of the companion to be R_C = 0.832 +/- 0.021 Rjup, which is consistent
with theoretical predictions of the radius of a > 1 Gyr brown dwarf.Comment: Our previous analysis neglected the dependence of the scaled
semimajor axis, a/R, on the transit depth. By not correcting a/R for the
third-light contamination, we overestimated the mass of Star A, which led to
an overestimate the mass and radius of the LHS6343
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I owe you: age-related similarities and differences in associative memory for gains and losses
Older adults often experience associative memory impairments but can sometimes remember important information. The current experiments investigate potential age-related similarities and differences associate memory for gains and losses. Younger and older participants were presented with faces and associated dollar amounts, which indicated how much money the person âowedâ the participant, and were later given a cued recall test for the dollar amount. Experiment 1 examined face-dollar amount pairs while Experiment 2 included negative dollar amounts to examine both gains and losses. While younger adults recalled more information relative to older adults, both groups were more accurate in recalling the correct value associated with high value faces compared to lower value faces and remembered gist-information about the values. However, negative values (losses) did not have a strong impact on recall among older adults versus younger adults, illustrating important associative memory differences between younger and older adults
Interactions of Ar(9+) and metastable Ar(8+) with a Si(100) surface at velocities near the image acceleration limit
Auger LMM spectra and preliminary model simulations of Ar(9+) and metastable
Ar(8+) ions interacting with a clean monocrystalline n-doped Si(100) surface
are presented. By varying the experimental parameters, several yet undiscovered
spectroscopic features have been observed providing valuable hints for the
development of an adequate interaction model. On our apparatus the ion beam
energy can be lowered to almost mere image charge attraction. High data
acquisition rates could still be maintained yielding an unprecedented
statistical quality of the Auger spectra.Comment: 34 pages, 11 figures, http://pikp28.uni-muenster.de/~ducree
Measurement of Ï-p Elastic Scattering at 14.15 GeV/c
Results are presented of a wire-spark-chamber spectrometer measurement of the differential cross section for Ï-p elastic scattering at 14.15 GeV/^c. The region covered in the square of the four-momentum transfer, t, is 0.01<-t<0.78 (GeV/c)^2. The cross section is found to obey very nearly a simple exponential t dependence with no evidence of structure. A fit to the data of the form dÏ/dtâexp(bt+ct2) on the range 0.05<-t<0.78 (GeV/c)^2 (i.e., above the region affected by Coulomb scattering) yields b=8.26±0.10 (GeV/c)^2 and c=1.01±0.17 (GeV/c)^-4. Considering the results of previous measurements, bâ11 (GeV/c)^-2 for -t<0.05 (GeV/c)^2, a deviation from the simple exponential near -tâ0.05 (GeV/c)^2 is indicated
Extended Classical Over-Barrier Model for Collisions of Highly Charged Ions with Conducting and Insulating Surfaces
We have extended the classical over-barrier model to simulate the
neutralization dynamics of highly charged ions interacting under grazing
incidence with conducting and insulating surfaces. Our calculations are based
on simple model rates for resonant and Auger transitions. We include effects
caused by the dielectric response of the target and, for insulators, localized
surface charges. Characteristic deviations regarding the charge transfer
processes from conducting and insulating targets to the ion are discussed. We
find good agreement with previously published experimental data for the image
energy gain of a variety of highly charged ions impinging on Au, Al, LiF and KI
crystals.Comment: 32 pages http://pikp28.uni-muenster.de/~ducree
Very Low-Mass Stellar and Substellar Companions to Solar-Like Stars from MARVELS I: A Low Mass Ratio Stellar Companion to TYC 4110-01037-1 in a 79-day Orbit
TYC 4110-01037-1 has a low-mass stellar companion, whose small mass ratio and
short orbital period are atypical amongst solar-like (Teff ~< 6000 K) binary
systems. Our analysis of TYC 4110-01037-1 reveals it to be a moderately aged
(~<5 Gyr) solar-like star having a mass of 1.07 +/- 0.08 MSun and radius of
0.99 +/- 0.18 RSun. We analyze 32 radial velocity measurements from the
SDSS-III MARVELS survey as well as 6 supporting radial velocity measurements
from the SARG spectrograph on the 3.6m TNG telescope obtained over a period of
~2 years. The best Keplerian orbital fit parameters were found to have a period
of 78.994 +/- 0.012 days, an eccentricity of 0.1095 +/- 0.0023, and a
semi-amplitude of 4199 +/- 11 m/s. We determine the minimum companion mass (if
sin i = 1) to be 97.7 +/- 5.8 MJup. The system's companion to host star mass
ratio, >0.087 +/- 0.003, places it at the lowest end of observed values for
short period stellar companions to solar-like (Teff ~< 6000 K) stars. One
possible way to create such a system would be if a triple-component stellar
multiple broke up into a short period, low q binary during the cluster
dispersal phase of its lifetime. A candidate tertiary body has been identified
in the system via single-epoch, high contrast imagery. If this object is
confirmed to be co-moving, we estimate it would be a dM4 star. We present these
results in the context of our larger-scale effort to constrain the statistics
of low mass stellar and brown dwarf companions to FGK-type stars via the
MARVELS survey.Comment: 22 pages; accepted in A
FAK acts as a suppressor of RTK-MAP kinase signalling in Drosophila melanogaster epithelia and human cancer cells
Receptor Tyrosine Kinases (RTKs) and Focal Adhesion Kinase (FAK) regulate multiple signalling pathways, including mitogen-activated protein (MAP) kinase pathway. FAK interacts with several RTKs but little is known about how FAK regulates their downstream signalling. Here we investigated how FAK regulates signalling resulting from the overexpression of the RTKs RET and EGFR. FAK suppressed RTKs signalling in Drosophila melanogaster epithelia by impairing MAPK pathway. This regulation was also observed in MDA-MB-231 human breast cancer cells, suggesting it is a conserved phenomenon in humans. Mechanistically, FAK reduced receptor recycling into the plasma membrane, which resulted in lower MAPK activation. Conversely, increasing the membrane pool of the receptor increased MAPK pathway signalling. FAK is widely considered as a therapeutic target in cancer biology; however, it also has tumour suppressor properties in some contexts. Therefore, the FAK-mediated negative regulation of RTK/MAPK signalling described here may have potential implications in the designing of therapy strategies for RTK-driven tumours
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