9,050 research outputs found
An examination of some characteristics of Kepler Short and Long Cadence Data
A close comparison of Kepler short- and long-cadence data released prior to
2011 Nov 1 has shown some subtle differences that make the short-cadence data
superior to their long-cadence counterparts. The inevitable results of a faster
sampling rate are present: the short-cadence data provide greater time
resolution for short-lived events like flares, and have a much higher Nyquist
frequency than the long-cadence data; however, they also contain fewer
high-amplitude peaks at low frequency and allow a more precise determination of
pulsation frequencies, amplitudes and phases. The latter observation indicates
that Kepler data are not normally distributed. Moreover, a close inspection of
the Pre-search Data Conditioned (PDC) long-cadence data show residuals that
have increased noise on time-scales important to asteroseismology, but
unimportant to planet searches.Comment: Accepted for publication in MNRAS. 7 pages, 5 figure
Prelude to, and Nature of the Space Photometry Revolution
It is now less than a decade since CoRoT initiated the space photometry
revolution with breakthrough discoveries, and five years since Kepler started a
series of similar advances. I'll set the context for this revolution noting the
status of asteroseismology and exoplanet discovery as it was 15-25 years ago in
order to give perspective on why it is not mere hyperbole to claim CoRoT and
Kepler fostered a revolution in our sciences. Primary events setting up the
revolution will be recounted. I'll continue with noting the major discoveries
in hand, and how asteroseismology and exoplanet studies, and indeed our
approach to doing science, have been forever changed thanks to these
spectacular missions.Comment: Invited review for the CoRoT3-KASC7 Conference: The Space Photometry
Revolution, Toulouse, France, July 2014. 6 page
Brainstem response and state-trait variables
A series of investigations are summarized from a personality research program that have relevance for mental state estimation. Of particular concern are those personality variables that are believed to have either a biological or perceptual basis and their relationship to human task performance and psychophysiology. These variables are among the most robust personality measures and include such dimensions as extraversion-introversion, sensation seeking, and impulsiveness. These dimensions also have the most distinct link to performance and psychophysiology. Through the course of many of these investigations two issues have emerged repeatedly: these personality dimensions appear to mediate mental state, and mental state appears to influence measures of performance or psychophysiology
Variable anodic thermal control coating
A process for providing a thermal control solar stable surface coating for aluminum surfaces adapted to be exposed to solar radiation wherein selected values within the range of 0.10 to 0.72 thermal emittance (epsilon sub tau) and 0.2 to 0.4 solar absorptance (alpha subs) are reproducibly obtained by anodizing the surface area in a chromic acid solution for a selected period of time. The rate voltage and time, along with the parameters of initial epsilon sub tau and alpha subs, temperature of the chromic acid solution, acid concentration of the solution and the material anodized determines the final values of epsilon/tau sub and alpha sub S. 9 Claims, 5 Drawing Figures
Asteroseismic Investigation of Known Planet Hosts in the Kepler Field
In addition to its great potential for characterizing extra-solar planetary
systems the Kepler mission is providing unique data on stellar oscillations. A
key aspect of Kepler asteroseismology is the application to solar-like
oscillations of main-sequence stars. As an example we here consider an initial
analysis of data for three stars in the Kepler field for which planetary
transits were known from ground-based observations. For one of these, HAT-P-7,
we obtain a detailed frequency spectrum and hence strong constraints on the
stellar properties. The remaining two stars show definite evidence for
solar-like oscillations, yielding a preliminary estimate of their mean
densities.Comment: Astrophysical Journal Letters, in the pres
The effect of grass genotype and spring management on the nutritive value of mid-summer ryegrass swards
End of project reportThe objective of this project was to investigate the environmental, morphological and management factors that control reproductive initiation and development in Lolium perenne L. (perennial ryegrass) and their influence on mid-season sward quality. These factors were assessed on eight perennial ryegrass cultivars through spaced plant and plot studies. The first part of this project determined the effects of meteorological conditions and latitude on reproductive initiation and ear emergence of cultivars over two consecutive years. It was concluded that the critical day length requirement for reproductive initiation varies between perennial ryegrass cultivars and is independent of latitude and the normal range of conditions. Using this information a strong correlation (r2 = 0.94) was found between the critical day length for ear initiation and the ten year standardised ear emergence dates of the cultivars. This correlation was sufficiently robust to predict the critical initiation date for any perennial ryegrass cultivar on a UK recommended list or on the EU common catalogue by using their heading dates from the UK Plant Breeders Rights trials at Crossnacreevy. Large variation was observed for secondary initiation and re-heading between cultivars of similar and varying maturity, which is a major factor reducing mid-season sward quality. The propensity for initiation of re-heading was strongly influenced by the severity of defoliation (intense to very lax), but there was also evidence to suggest that critical day length post-solstice, may determine the latest date when further reproductive initiation could occur. Differences in plant growth modes were clearly evident as the sward structure, plant morphology and nutritive compositions differed significantly between cultivars during the mid-season. Defoliation management also significantly affected mid-season sward structure, morphology and nutritive composition. While the effect of defoliation height on the sward physical and chemical compositions was inconclusive, an intensive (30 mm) defoliation resulted in plants returning to a vegetative growth mode earlier compared to a lax (60 mm) defoliation treatment. It was observed that defoliation at a critical growth stage can significantly affect subsequent sward structures. Delaying initial spring defoliation resulted in a greater leaf proportion and swards of greater herbage quality in the plot study. This study, therefore, established the need for more detailed evaluation of cultivars by national testing authorities to allow farmers to select cultivars for grazing use that will optimise animal intake and performance
Influence of testing procedure on evaluation of white clover (Trifolium repens L.)
peer-reviewedThis study examined data sets derived from the white clover cultivar evaluation
programmes of AFBI (N. Ireland), and DAFF (Republic of Ireland) to determine
whether elite performing genotypes are identifiable, independent of test procedure and
leaf size factors. Genetic variation in yield and persistency, independent of the leaf size
continuum effect, was observed. Identification of elite cultivars by breeders or testers
therefore required readjustment of assessment standards to account for the mostly curvilinear
relationships between performance and leaf size. The different testing procedures,
involving cutting or grazing at different heights, frequencies and nitrogen rates
changed the relative performances between the cultivars, making it difficult to predict
performance potential beyond specific test conditions. The underlying causes for these
changes in rankings was considered, including sensitivity to season and location, the
antagonistic affects of defoliation pressure and companion grass competition, the independence
of different seasonal profiles and the probable role of other morphological
characteristics. In is concluded that testing authorities must calculate the management
by leaf size relationships to adjust pass/fail standards if elite performing cultivars are
to be correctly indentified
Video signal processing system uses gated current mode switches to perform high speed multiplication and digital-to-analog conversion
Video signal processor uses special-purpose integrated circuits with nonsaturating current mode switching to accept texture and color information from a digital computer in a visual spaceflight simulator and to combine these, for display on color CRT with analog information concerning fading
Photometric Oscillations of Low Luminosity Red Giant Stars
I present details of the variations of several hundred red giant stars on
time scales of a few hours to a few days from Hubble Space Telescope (HST)
observations of a low-extinction galactic bulge sample from an intensive seven
day campaign. Variations in the red giants are shown to be a strong function of
position within the color-magnitude diagram (CMD) in accord with general
expectations from theory. Amplitudes are greater for stars with larger radii,
whether this results from higher luminosity at the same effective temperature
or lower temperature at a fixed apparent magnitude. Likewise, characteristic
time scales for the variations increase to the upper right in a CMD as does the
ratio of amplitudes measured at 606 nm compared to 814 nm. Characteristic
variation time scales are well matched by low-order radial pulsation modes. The
effective sample discussed here extends from about two magnitudes above the
bulge turnoff at which red giant radii are ~7 R/R_{\odot} at 5,000 K with
typical amplitudes of ~0.5 mmag to ~40 R/R_{\odot} at 4,000 K with amplitudes
of ~3.5 mmag. Variability characteristics are quite similar at any given
position in the CMD, and at levels in the CMD where oscillations are easily
detected nearly all red giants show such. If these variations represent
oscillations with sufficient lifetimes to derive accurate mode frequencies more
extensive observations, e.g. as should soon be provided by the Kepler Mission},
would provide a rich asteroseismic return.Comment: 36 pages, 12 figures, 7 tables; accepted for publication in A
Solar-like oscillations in a metal-poor globular cluster with the HST
We present analyses of variability in the red giant stars in the metal-poor
globular cluster NGC6397, based on data obtained with the Hubble Space
Telescope. We use an non-standard data reduction approach to turn a 23-day
observing run originally aimed at imaging the white dwarf population, into
time-series photometry of the cluster's highly saturated red giant stars. With
this technique we obtain noise levels in the final power spectra down to 50
parts per million, which allows us to search for low amplitude solar-like
oscillations. We compare the observed excess power seen in the power spectra
with estimates of the typical frequency range, frequency spacing and amplitude
from scaling the solar oscillations. We see evidence that the detected
variability is consistent with solar-like oscillations in at least one and
perhaps up to four stars. With metallicities two orders of magnitude lower than
of the Sun, these stars present so far the best evidence of solar-like
oscillations in such a low metallicity environment.Comment: 7 pages, 6 figures, accepted by Ap
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