608 research outputs found
Detecting and predicting spatial and interannual patterns of temperate forest springtime phenology in the eastern U.S.
We performed a diagnostic analysis of AVHRR-NDVI and gridded, temperature data for the deciduous forests of the eastern U.S., calibrating temperature accumulation model with satellite data for 1982–1993. The model predicts interannual variability in onset date based upon year-to-year changes in springtime temperature. RMS error over the period ranges from 6.9 days in the northern portion of the domain to 10.7 days in the south. The analysis revealed a relationship between temperature accumulation and satellite derived onset date (rank correlation = 0.31–0.62). The required temperature accumulation threshold can be expressed as a function of mean temperature (R2 of 0.90) to facilitate predictive analysis of phenological onset, or when remote sensing data are unavailable
White-light flares on cool stars in the Kepler Quarter 1 Data
We present the results of a search for white light flares on the ~23,000 cool
dwarfs in the Kepler Quarter 1 long cadence data. We have identified 373
flaring stars, some of which flare multiple times during the observation
period. We calculate relative flare energies, flare rates and durations, and
compare these with the quiescent photometric variability of our sample. We find
that M dwarfs tend to flare more frequently but for shorter durations than K
dwarfs, and that they emit more energy relative to their quiescent luminosity
in a given flare than K dwarfs. Stars that are more photometrically variable in
quiescence tend to emit relatively more energy during flares, but variability
is only weakly correlated with flare frequency. We estimate distances for our
sample of flare stars and find that the flaring fraction agrees well with other
observations of flare statistics for stars within 300 pc above the Galactic
Plane. These observations provide a more rounded view of stellar flares by
sampling stars that have not been pre-selected by their activity, and are
informative for understanding the influence of these flares on planetary
habitability.Comment: 42 pages, 10 figures, 2 tables; Accepted for publication in the
Astronomical Journa
Detection of a CMB decrement towards a cluster of mJy radiosources
We present the results of radio, optical and near-infrared observations of
the field of TOC J0233.3+3021, a cluster of milliJansky radiosources from the
TexOx Cluster survey. In an observation of this field with the Ryle Telescope
(RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB)
of Jy on the RT's 0.65 k baseline. Using
optical and infrared imaging with the McDonald 2.7-m Smith Reflector, Calar
Alto 3.5-m telescope and UKIRT, we identify the host galaxies of five of the
radiosources and measure magnitudes of , , .
The CMB decrement is consistent with the Sunyaev-Zel'dovich (SZ) effect of a
massive cluster of galaxies, which if modelled as a spherical King profile of
core radius has a central temperature decrement
of K. The magnitudes and colours of the galaxies are consistent with
those of old ellipticals at . We therefore conclude that TOC
J0233.3+3021 is a massive, high redshift cluster. These observations add to the
growing evidence for a significant population of massive clusters at high
redshift, and demonstrate the effectiveness of combining searches for AGN
`signposts' to clusters with the redshift-independence of the SZ effect.Comment: Six pages; accepted for publication in MNRAS. Version with
full-resolution UV plot available from
http://www.mrao.cam.ac.uk/~garret/MB185.p
Use of the Pill Electrode for Transesophageal Atrial Pacing
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72094/1/j.1540-8159.1985.tb05853.x.pd
Photometric Variability in Kepler Target Stars: The Sun Among Stars -- A First Look
The Kepler mission provides an exciting opportunity to study the lightcurves
of stars with unprecedented precision and continuity of coverage. This is the
first look at a large sample of stars with photometric data of a quality that
has heretofore been only available for our Sun. It provides the first
opportunity to compare the irradiance variations of our Sun to a large cohort
of stars ranging from vary similar to rather different stellar properties, at a
wide variety of ages. Although Kepler data is in an early phase of maturity,
and we only analyze the first month of coverage, it is sufficient to garner the
first meaningful measurements of our Sun's variability in the context of a
large cohort of main sequence stars in the solar neighborhood. We find that
nearly half of the full sample is more active than the active Sun, although
most of them are not more than twice as active. The active fraction is closer
to a third for the stars most similar to the Sun, and rises to well more than
half for stars cooler than mid K spectral types.Comment: 13 pages, 4 figures, accepted to ApJ Letter
Positive practices : solution-focused and narrative therapeutic techniques with children with sexually harmful behaviours
This article explores the use of solution-focused and Narrative Therapeutic approaches with a boy who had sexually harmful behaviours. The paper will highlight the practical challenges of working with someone who is 'problem-saturated' through institutionalisation and who is also subjected to powerful discourses claiming the 'truth' about him. The use of solution-focused and Narrative Therapeutic principles and approaches will be demonstrated in the work described, in a way that allows the reader to reflect on how these may differ from modernist understandings and responses to this behaviour
Planet Hunters: New Kepler planet candidates from analysis of quarter 2
We present new planet candidates identified in NASA Kepler quarter two public
release data by volunteers engaged in the Planet Hunters citizen science
project. The two candidates presented here survive checks for false-positives,
including examination of the pixel offset to constrain the possibility of a
background eclipsing binary. The orbital periods of the planet candidates are
97.46 days (KIC 4552729) and 284.03 (KIC 10005758) days and the modeled planet
radii are 5.3 and 3.8 R_Earth. The latter star has an additional known planet
candidate with a radius of 5.05 R_Earth and a period of 134.49 which was
detected by the Kepler pipeline. The discovery of these candidates illustrates
the value of massively distributed volunteer review of the Kepler database to
recover candidates which were otherwise uncatalogued.Comment: Accepted to A
All Six Planets Known to Orbit Kepler-11 Have Low Densities
The Kepler-11 planetary system contains six transiting planets ranging in
size from 1.8 to 4.2 times the radius of Earth. Five of these planets orbit in
a tightly-packed configuration with periods between 10 and 47 days. We perform
a dynamical analysis of the system based upon transit timing variations
observed in more than three years of \ik photometric data. Stellar parameters
are derived using a combination of spectral classification and constraints on
the star's density derived from transit profiles together with planetary
eccentricity vectors provided by our dynamical study. Combining masses of the
planets relative to the star from our dynamical study and radii of the planets
relative to the star from transit depths together with deduced stellar
properties yields measurements of the radii of all six planets, masses of the
five inner planets, and an upper bound to the mass of the outermost planet,
whose orbital period is 118 days. We find mass-radius combinations for all six
planets that imply that substantial fractions of their volumes are occupied by
constituents that are less dense than rock. The Kepler-11 system contains the
lowest mass exoplanets for which both mass and radius have been measured.Comment: 39 pages, 10 figure
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