137 research outputs found
Annual Report Town of Bowdoinham Maine 2013
Perceptual processes play an important role in motor learning. While it is evident that visual information greatly contributes to learning new movements, much less is known about provision of prescriptive proprioceptive information. Here, we investigated whether passive (proprioceptively-based) movement training was comparable to active training for learning a new bimanual task. Three groups practiced a bimanual coordination pattern with a 1∶2 frequency ratio and a 90° phase offset between both wrists with Lissajous feedback over the course of four days: 1) passive training; 2) active training; 3) no training (control). Retention findings revealed that passive as compared to active training resulted in equally successful acquisition of the frequency ratio but active training was more effective for acquisition of the new relative phasing between the limbs in the presence of augmented visual feedback. However, when this feedback was removed, performance of the new relative phase deteriorated in both groups whereas the frequency ratio was better preserved. The superiority of active over passive training in the presence of augmented feedback is hypothesized to result from active involvement in processes of error detection/correction and planning.status: publishe
Beta Cephei stars in the ASAS-3 data. I. Long-term variations of periods and amplitudes
We analysed V-filter ASAS-3 photometry of 41 known Beta Cephei-type stars.
The ASAS-3 photometry was combined with the archival data, if available, to
determine long-term stability of periods and amplitudes of excited modes. We
detected amplitude changes in three Beta Cephei stars, BW Cru, V836 Cen, and
V348 Nor. Period changes were found in KK Vel and V836 Cen. Our analysis shows
that intrinsic period changes are more common among multiperiodic stars,
apparently because they are caused by some kind of mode interaction. In
addition, we found new modes for seven stars, and for ten others we provide new
solutions or remove ambiguities in the detected frequencies. One candidate
hybrid Beta Cephei/SPB star, HD133823, is discovered.Comment: 22 pages, 11 figures, accepted for publication in A&
CoRoT's view of newly discovered B-star pulsators: results for 358 candidate B pulsators from the initial run's exoplanet field data
We search for new variable B-type pulsators in the CoRoT data assembled
primarily for planet detection, as part of CoRoT's Additional Programme. We aim
to explore the properties of newly discovered B-type pulsators from the
uninterrupted CoRoT space-based photometry and to compare them with known
members of the Beta Cep and slowly pulsating B star (SPB) classes. We developed
automated data analysis tools that include algorithms for jump correction,
light-curve detrending, frequency detection, frequency combination search, and
for frequency and period spacing searches. Besides numerous new, classical,
slowly pulsating B stars, we find evidence for a new class of low-amplitude
B-type pulsators between the SPB and Delta Sct instability strips, with a very
broad range of frequencies and low amplitudes, as well as several slowly
pulsating B stars with residual excess power at frequencies typically a factor
three above their expected g-mode frequencies. The frequency data we obtained
for numerous new B-type pulsators represent an appropriate starting point for
further theoretical analyses of these stars, once their effective temperature,
gravity, rotation velocity, and abundances will be derived spectroscopically in
the framework of an ongoing FLAMES survey at the VLT.Comment: 22 pages, 30 figures, accepted for publication in A&
A spectroscopic study of southern (candidate) gamma Doradus stars. I. Time series analysis
We present results of a spectroscopic study of 37 southern (candidate) gamma
Doradus stars based on echelle spectra. The observed spectra were
cross-correlated with the standard template spectrum of an F0-type star for an
easier detection of binary and intrinsic variations. We identified 15 objects
as spectroscopic binaries, including 7 new ones, and another 3 objects are
binary suspects. At least 12 objects show composite spectra. We could determine
the orbital parameters for 9 binaries, of which 4 turn out to be ellipsoidal
variables. For 6 binaries, we estimated the expected time-base of the orbital
variations. Clear profile variations are observed for 17 objects, pointing
towards stellar pulsation. For 8 of them, we have evidence that the main
spectroscopic and photometric periods coincide. Our results, in combination
with prior knowledge from the literature, lead to the classification of 10
objects as new bona-fide gamma Doradus stars, 1 object as new bona-fide delta
Scuti star, and 8 objects as constant stars. Finally, we determined the
projected rotational velocity with two independent methods. The resulting vsini
values range from 3 to 135 km/s. For the bona-fide gamma Doradus stars, the
majority has vsini below 60 km/s.Comment: 13 pages (+ 10 pages online material), 10 (+16) figures. Accepted for
publication by A&
Long-term photometric monitoring with the Mercator telescope. Frequencies and multicolour amplitudes of Doradus stars
Gamma Doradus stars are excellent targets for asteroseismology since the
gravity modes present in these stars probe the deep stellar interiors. Mode
identification will improve the knowledge of these stars considerably. A
selected group of Gamma Doradus stars and some candidates were observed with
the Mercator telescope to find and/or confirm the periodicities in the light
variations and to derive reliable amplitude ratios in different pass bands. A
frequency analysis was performed on all new data obtained in the Geneva
photometric system. In order to have more reliable and accurate frequencies,
the new data were combined with similar data from the literature and with
Hipparcos observations. A set of frequencies that minimized the the residuals
in a harmonic fit was searched for while allowing means and amplitudes to vary
from one observation set to another. Frequencies and amplitudes in the
photometric passbands of the Geneva system are given for 21 Gamma Doradus
stars. We report the discovery of HD 74504 as a newly found Gamma Doradus star.
Our study provides the first extensive multicolour database for the
understanding of gravity modes in F-type stars.Comment: Electronic tables (5 to 25) not included in this versio
Beta Cephei stars in the ASAS-3 data. II. 103 new Beta Cephei stars and a discussion of low-frequency modes
We analysed ASAS-3 photometry of bright early-type stars with the goal of
finding new Beta Cephei stars. We were particularly interested in stars that
would be good for seismic analysis, i.e., stars that (i) have a large number of
excited modes, (ii) show rotationally split modes, (iii) are components of
eclipsing binary systems, (iv) have low-frequency modes, that is, are hybrid
Beta Cephei/SPB stars. Our study was made with a homogeneous sample of over
4100 stars having MK spectral type B5 or earlier. For these stars, the ASAS-3
photometry was analysed by means of a Fourier periodogram. We have discovered
103 Beta Cephei stars, nearly doubling the number of previously known stars of
this type. Among these stars, four are components of eclipsing binaries, seven
have modes equidistant or nearly equidistant in frequency. In addition, we
found five Beta Cephei stars that show low-frequency periodic variations, very
likely due to pulsations. We therefore regard them as candidate hybrid Beta
Cephei/SPB pulsators. All these stars are potentially very useful for seismic
modeling. Moreover, we found Beta Cephei-type pulsations in three late O-type
stars and fast period changes in one, HD 168050.Comment: 30 pages, 26 figures, accepted for publication in Astronomy &
Astrophysic
A computational method for the identification of dengue, zika and chikungunya virus species and genotypes
In recent years, an increasing number of outbreaks of Dengue, Chikungunya and Zika viruses have been reported in Asia and the Americas. Monitoring virus genotype diversity is crucial to understand the emergence and spread of outbreaks, both aspects that are vital to develop effective prevention and treatment strategies. Hence, we developed an efficient method to classify virus sequences with respect to their species and sub-species (i.e. serotype and/or genotype). This tool provides an easy-to-use software implementation of this new method and was validated on a large dataset assessing the classification performance with respect to whole-genome sequences and partial-genome sequences.publishersversionpublishe
Catalog of Galactic Beta Cephei Stars
We present an extensive and up-to-date catalog of Galactic Beta Cephei stars.
This catalog is intended to give a comprehensive overview of observational
characteristics of all known Beta Cephei stars. 93 stars could be confirmed to
be Beta Cephei stars. For some stars we re-analyzed published data or conducted
our own analyses. 61 stars were rejected from the final Beta Cephei list, and
77 stars are suspected to be Beta Cephei stars. A list of critically selected
pulsation frequencies for confirmed Beta Cephei stars is also presented. We
analyze the Beta Cephei stars as a group, such as the distributions of their
spectral types, projected rotational velocities, radial velocities, pulsation
periods, and Galactic coordinates. We confirm that the majority of these stars
are multiperiodic pulsators. We show that, besides two exceptions, the Beta
Cephei stars with high pulsation amplitudes are slow rotators. We construct a
theoretical HR diagram that suggests that almost all 93 Beta Cephei stars are
MS objects. We discuss the observational boundaries of Beta Cephei pulsation
and their physical parameters. We corroborate that the excited pulsation modes
are near to the radial fundamental mode in frequency and we show that the mass
distribution of the stars peaks at 12 solar masses. We point out that the
theoretical instability strip of the Beta Cephei stars is filled neither at the
cool nor at the hot end and attempt to explain this observation
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