343 research outputs found
Exoplanetary atmosphere target selection in the era of comparative planetology
The large number of new planets expected from wide-area transit surveys means
that follow-up transmission spectroscopy studies of their atmospheres will be
limited by the availability of telescope assets. We argue that telescopes
covering a broad range of apertures will be required, with even 1m-class
instruments providing a potentially important contribution. Survey strategies
that employ automated target selection will enable robust population studies.
As part of such a strategy, we propose a decision metric to pair the best
target to the most suitable telescope, and demonstrate its effectiveness even
when only primary transit observables are available. Transmission spectroscopy
target selection need not therefore be impeded by the bottle-neck of requiring
prior follow-up observations to determine the planet mass. The decision metric
can be easily deployed within a distributed heterogeneous network of telescopes
equipped to undertake either broadband photometry or spectroscopy. We show how
the metric can be used either to optimise the observing strategy for a given
telescope (e.g. choice of filter) or to enable the selection of the best
telescope to optimise the overall sample size. Our decision metric can also
provide the basis for a selection function to help evaluate the statistical
completeness of follow-up transmission spectroscopy datasets. Finally, we
validate our metric by comparing its ranked set of targets against lists of
planets that have had their atmospheres successfully probed, and against some
existing prioritised exoplanet lists.Comment: 20 pages, 16 figures, 3 tables. Revision 3, accepted by MNRAS.
Improvements include always using planetary masses where available and
reliable, treatment for sky backgrounds and out-of-transit noise and a use
case for defocused photometr
Is the Large Magellanic Cloud a Large Microlensing Cloud?
An expression is provided for the self-lensing optical depth of the thin LMC
disk surrounded by a shroud of stars at larger scale heights. The formula is
written in terms of the vertical velocity dispersion of the thin disk
population. If tidal forcing causes 1-5 % of the disk mass to have a height
larger than 6 kpc and 10-15 % to have a height above 3 kpc, then the
self-lensing optical depth of the LMC is , which is
within the observational uncertainties. The shroud may be composed of bright
stars provided they are not in stellar hydrodynamical equilibrium.
Alternatively, the shroud may be built from low mass stars or compact objects,
though then the self-lensing optical depths are overestimates of the true
optical depth by a factor of roughly 3. The distributions of timescales of the
events and their spatial variation across the face of the LMC disk offer
possibilities of identifying the dominant lens population. In propitious
circumstances, an experiment lifetime of less than 5 years is sufficient to
decide between the competing claims of Milky Way halos and LMC lenses. However,
LMC disks can sometimes mimic the microlensing properties of Galactic halos for
many years and then decades of survey work are needed. In this case
observations of parallax or binary caustic events offer the best hope for
current experiments to deduce the lens population. The difficult models to
distinguish are Milky Way halos in which the lens fraction is low (< 10 %) and
fattened LMC disks composed of lenses with a typical mass of low luminosity
stars or greater. A next-generation wide-area microlensing survey, such as the
proposed ``SuperMACHO'' experiment, will be able to distinguish even these
difficult models with just a year or two of data.Comment: 25 pages, 4 figures, The Astrophysical Journal (in press
Theory of pixel lensing towards M31 I: the density contribution and mass of MACHOs
POINT-AGAPE is an Anglo-French collaboration which is employing the Isaac
Newton Telescope (INT) to conduct a pixel-lensing survey towards M31. In this
paper we investigate what we can learn from pixel-lensing observables about the
MACHO mass and fractional contribution in M31 and the Galaxy for the case of
spherically-symmetric near-isothermal haloes. We employ detailed pixel-lensing
simulations which include many of the factors which affect the observables. For
a maximum MACHO halo we predict an event rate in V of up to 100 per season for
M31 and 40 per season for the Galaxy. However, the Einstein radius crossing
time is generally not measurable and the observed full-width half-maximum
duration provides only a weak tracer of lens mass. Nonetheless, we find that
the near-far asymmetry in the spatial distribution of M31 MACHOs provides
significant information on their mass and density contribution. We present a
likelihood estimator for measuring the fractional contribution and mass of both
M31 and Galaxy MACHOs which permits an unbiased determination to be made of
MACHO parameters, even from data-sets strongly contaminated by variable stars.
If M31 does not have a significant population of MACHOs in the mass range
0.001-1 Solar masses strong limits will result from the first season of INT
observations. Simulations based on currently favoured density and mass values
indicate that, after three seasons, the M31 MACHO parameters should be
constrained to within a factor four uncertainty in halo fraction and an order
of magnitude uncertainty in mass (90% confidence). Interesting constraints on
Galaxy MACHOs may also be possible. For a campaign lasting ten years,
comparable to the lifetime of current LMC surveys, reliable estimates of MACHO
parameters in both galaxies should be possible. (Abridged)Comment: 21 pages, 14 figures. Submitted to MNRA
PHYTOCHEMICAL SCREENING AND ANALYSIS POLYPHENOLIC ANTIOXIDANT ACTIVITY OF METHANOLIC EXTRACT OF WHITE DRAGON FRUIT (Hylocereus undatus)
White dragon fruit is a well known and widely used herbal
medicine, especially in Asia, which contains several interesting
bioactive constituents and possesses health promoting properties.
The aim of this study was to analyze for the bioactive
compounds, evaluate total phenolic contents and antioxidant
capacities of methanolic extract of white dragon fruit. The
antioxidant activity was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity assay. Total
phenolic content were determined by Folin-Ciocalteu method.
Phytochemical screening of the white dragon fruit showed
the presence of triterpenoid, alkaloid, flavonoid and saponin.
The extract exhibited strong antioxidant activity with IC50 of
193 μg/mL, and total phenolic content of 246 μg/mL in 1 Kg dry
extract
Gamma ray astronomy and baryonic dark matter
Recently, Dixon et al. have re-analyzed the EGRET data, finding a
statistically significant diffuse -ray emission from the galactic halo.
We show that this emission can naturally be explained within a
previously-proposed model for baryonic dark matter, in which -rays are
produced through the interaction of high-energy cosmic-ray protons with cold
clouds clumped into dark clusters - these dark clusters supposedly
populate the outer galactic halo and can show up in microlensing observations.
Our estimate for the halo -ray flux turns out to be in remarkably good
agreement with the discovery by Dixon et al. We also address future prospects
to test our predictions.Comment: 9 pages, 1 figure included, to appear in ApJ 510, L103 (1999
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Genome-Wide CRISPR Screen Reveals Autophagy Disruption as the Convergence Mechanism That Regulates the NRF2 Transcription Factor
The nuclear factor (erythroid 2)-like 2 (NRF2 or NFE2L2) transcription factor regulates the expression of many genes that are critical in maintaining cellular homeostasis. Its deregulation has been implicated in many diseases, including cancer and metabolic and neurodegenerative diseases. While several mechanisms by which NRF2 can be activated have gradually been identified over time, a more complete regulatory network of NRF2 is still lacking. Here we show through a genome-wide clustered regularly interspaced short palindromic repeat (CRISPR) screen that a total of 273 genes, when knocked out, will lead to sustained NRF2 activation. Pathway analysis revealed a significant overrepresentation of genes (18 of the 273 genes) involved in autophagy. Molecular validation of a subset of the enriched genes identified 8 high-confidence genes that negatively regulate NRF2 activity irrespective of cell type: ATG12, ATG7, GOSR1, IFT172, NRXN2, RAB6A, VPS37A, and the well-known negative regulator of NRF2, KEAP1 Of these, ATG12, ATG7, KEAP1, and VPS37A are known to be involved in autophagic processes. Our results present a comprehensive list of NRF2 negative regulators and reveal an intimate link between autophagy and NRF2 regulation.National Institute of Environmental Health Sciences [R21ES027920]; National Science Foundation Graduate Research Fellowship Program [DGE-1746060]; [R01CA226920]; [R01DK109555]; [R01ES026845]; [P42ES004940]; [P30ES006694]6 month embargo; accepted manuscript posted online 22 April 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
EUCLID : Dark Universe Probe and Microlensing planet Hunter
There is a remarkable synergy between requirements for Dark Energy probes by
cosmic shear measurements and planet hunting by microlensing. Employing weak
and strong gravitational lensing to trace and detect the distribution of matter
on cosmic and Galactic scales, but as well as to the very small scales of
exoplanets is a unique meeting point from cosmology to exoplanets. It will use
gravity as the tool to explore the full range of masses not accessible by any
other means. EUCLID is a 1.2m telescope with optical and IR wide field imagers
and slitless spectroscopy, proposed to ESA Cosmic Vision to probe for Dark
Energy, Baryonic acoustic oscillation, galaxy evolution, and an exoplanet hunt
via microlensing. A 3 months microlensing program will already efficiently
probe for planets down to the mass of Mars at the snow line, for free floating
terrestrial or gaseous planets and habitable super Earth. A 12+ months survey
would give a census on habitable Earth planets around solar like stars. This is
the perfect complement to the statistics that will be provided by the KEPLER
satellite, and these missions combined will provide a full census of extrasolar
planets from hot, warm, habitable, frozen to free floating.Comment: 6 pages 3 figures, invited talk in Pathways towards habitable
planets, Barcelona, Sept 200
Reliability of the Myotonometer for Assessment of Posterior Shoulder Tightness
BACKGROUND/PURPOSE: The Myotonometer® is an electronic tissue compliance meter that has been used to quantify the compliance of soft tissues. The Myotonometer® may be a valuable tool to measure the effectiveness of interventions commonly used to increase tissue compliance in individuals with posterior shoulder tightness (PST). Limited data exist on reliability and responsiveness of the Myotonometer® for assessment of soft tissues about the shoulder; therefore, the purpose of this study is to determine the intra- and inter-session reliability and responsiveness of the Myotonometer® in measuring tissue compliance of the posterior shoulder musculature in asymptomatic subjects with PST.
METHODS: Fifteen asymptomatic subjects with unilateral shoulder range of motion deficits attended two measurement sessions to assess the compliance of the tissues overlying the posterior deltoid, infraspinatus, and teres musculature. Analyses of reliability and responsiveness were conducted using intra-class correlation coefficients (ICCs) and the determination of minimal detectible change (MDC).
RESULTS: Intra-session ICC values ranged from 0.69 to 0.91 for all muscles with MDC never exceeding 1.0 mm. Inter-session ICC values were best for the posterior deltoid, which averaged 0.82, compared to the infraspinatus and the teres complex, which averaged 0.42 and 0.5 respectively. Inter-session MDC ranged from 0.55 to 1.20 mm across all muscles.
CONCLUSIONS: Clinicians can reliably detect relatively small changes in tissue compliance within a single treatment session utilizing the Myotonometer®. The Myotonometer® can reliably detect changes between sessions for tissues overlying the posterior deltoid; however, observed change in the infraspinatus and teres musculature must be above 1 mm to achieve meaningful change and account for decreased inter-session reliability.
LEVEL OF EVIDENCE: 3
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