60 research outputs found
Population dynamics of Heterorhabditis bacteriophora and Steinernema carpocapsae in in vitro monoxenic solid culture
La présente étude sur la dynamique des populations des nématodes entomopathogènes #Heterorhabditis bacteriophora et #Steinernema carpocapsae en élevage in vitro sur milieu solide montre que la taille de l'inoculum est importante pour optimiser la récolte finale des juvéniles infestants et pour déterminer leur temps de développement. Les plus fortes récoltes sont obtenues pour #H. bacteriophora avec un inoculum de 1 000 000 juvéniles infestants par fiole, ce qui représente dix fois la valeur de l'inoculum optimal pour #S. carpocapsae. Les populations issues des inoculums de valeurs extrêmes (un ou deux contre 1 000 000 juvéniles infestants par fiole) montrent des différences dans la reproduction et le développement des populations entre #H. bacteriophora et #S. carpocapsae. Un inoculum de 10 000 000 juvéniles infestants par fiole provoque un doublement de la population de #H. bacteriophora conduit à une population finale de 25 x 1 000 000 nématodes en 6 semaines. Cependant, il n'a pas été possible d'initier le développement d'une population de #S. carpocapsae$ en inoculant seulement deux juvéniles infestants par fiole. Les résultats de cette étude pourraient être utlisés pour la production en masse de nématodes entomophathogènes, et des recherches futures sur les relations intimes entre valeurs de l'inoculum, développement des populations et population finale de juvéniles infestants de ces nématodes pourraient augmenter l'efficacité de la production commerciale de ces nématodes. (Résumé d'auter
Population development of Heterorhabditis bacteriophora and Steinernema carpocapsae in the larvae of Galleria mellonella
Le développement de populations d'#Heterorhabditis bacteriophaga et #Steinernema carpocapsae dans les larves de #Galleria mellonella$ a été étudié après inoculation avec un ou deux juvéniles infestants, respectivement. Pour les deux nématodes, trois générations d'adultes sont observées et, après trois semaines, une population finale de l'ordre de 150 000 juvéniles infestants par insecte est dénombrée. Cependant, le développement des populations diffère par plusieurs aspects chez ces deux espèces. Les détails du développement dans l'insecte hôte des populations de ces nématodes entomopathogènes les plus couramment utilisés pourraient servir à l'établissement d'un niveau optimal de fécondité, au moins durant la première génération en culture in vitro. (Résumé d'auteur
E´ chelle diagrams and period spacings of g modes in: Doradus stars from four years of Kepler observations
We use photometry from the Kepler Mission to study oscillations in Doradus stars. Some stars show remarkably clear sequences of g modes and we use period ´echelle diagrams to measure period spacings and identifyrotationally split multiplets with ` = 1 and ` = 2.We find small deviations from regular period spacings that arise from the gradient in the chemical composition just outside the convective core. We also find stars for which the period spacing shows a strong linear trend as a function of period, consistent with relatively rapid rotation. Overall, th
Finding non-eclipsing binaries through pulsational phase modulation
We present a method for finding binaries among pulsating stars that were observed by the Kepler Mission. We use entire four-year light curves to accurately mea- sure the frequencies of the strongest pulsation modes, then track the pulsation phases at those frequencies in 10-d segments. This produces a series of time-delay measurements in which binarity is apparent as a periodic modulation whose amplitude gives the projected light travel time across the orbit. Fourier analysis of this time-delay curve provides the pa- rameters of the orbit, including the period, eccentricity, angle of ascending node and time
of periastron passage. Differentiating the time-delay curve yields the full radial-velocity
curve directly from the Kepler photometry, without the need for spectroscopy. We show examples with delta Scuti stars having large numbers of pulsation modes, including one system in which both components of the binary are pulsating. The method is straightfor- ward to automate, thus radial velocity curves can be derived for hundreds of non-eclipsing binary stars from Kepler photometry alone.
This contribution is based largely upon the work by Murphy et al. [1], describing the phase-modulation method in detail
Fourier Analysis of Gapped Time Series: Improved Estimates of Solar and Stellar Oscillation Parameters
Quantitative helio- and asteroseismology require very precise measurements of
the frequencies, amplitudes, and lifetimes of the global modes of stellar
oscillation. It is common knowledge that the precision of these measurements
depends on the total length (T), quality, and completeness of the observations.
Except in a few simple cases, the effect of gaps in the data on measurement
precision is poorly understood, in particular in Fourier space where the
convolution of the observable with the observation window introduces
correlations between different frequencies. Here we describe and implement a
rather general method to retrieve maximum likelihood estimates of the
oscillation parameters, taking into account the proper statistics of the
observations. Our fitting method applies in complex Fourier space and exploits
the phase information. We consider both solar-like stochastic oscillations and
long-lived harmonic oscillations, plus random noise. Using numerical
simulations, we demonstrate the existence of cases for which our improved
fitting method is less biased and has a greater precision than when the
frequency correlations are ignored. This is especially true of low
signal-to-noise solar-like oscillations. For example, we discuss a case where
the precision on the mode frequency estimate is increased by a factor of five,
for a duty cycle of 15%. In the case of long-lived sinusoidal oscillations, a
proper treatment of the frequency correlations does not provide any significant
improvement; nevertheless we confirm that the mode frequency can be measured
from gapped data at a much better precision than the 1/T Rayleigh resolution.Comment: Accepted for publication in Solar Physics Topical Issue
"Helioseismology, Asteroseismology, and MHD Connections
An Introduction to Data Analysis in Asteroseismology
A practical guide is presented to some of the main data analysis concepts and
techniques employed contemporarily in the asteroseismic study of stars
exhibiting solar-like oscillations. The subjects of digital signal processing
and spectral analysis are introduced first. These concern the acquisition of
continuous physical signals to be subsequently digitally analyzed. A number of
specific concepts and techniques relevant to asteroseismology are then
presented as we follow the typical workflow of the data analysis process,
namely, the extraction of global asteroseismic parameters and individual mode
parameters (also known as peak-bagging) from the oscillation spectrum.Comment: Lecture presented at the IVth Azores International Advanced School in
Space Sciences on "Asteroseismology and Exoplanets: Listening to the Stars
and Searching for New Worlds" (arXiv:1709.00645), which took place in Horta,
Azores Islands, Portugal in July 201
Accurate fundamental parameters and detailed abundance patterns from spectroscopy of 93 solar-type Kepler targets
We present a detailed spectroscopic study of 93 solar-type stars that are
targets of the NASA/Kepler mission and provide detailed chemical composition of
each target. We find that the overall metallicity is well-represented by Fe
lines. Relative abundances of light elements (CNO) and alpha-elements are
generally higher for low-metallicity stars. Our spectroscopic analysis benefits
from the accurately measured surface gravity from the asteroseismic analysis of
the Kepler light curves. The log g parameter is known to better than 0.03 dex
and is held fixed in the analysis. We compare our Teff determination with a
recent colour calibration of V-K (TYCHO V magnitude minus 2MASS Ks magnitude)
and find very good agreement and a scatter of only 80 K, showing that for other
nearby Kepler targets this index can be used. The asteroseismic log g values
agree very well with the classical determination using Fe1-Fe2 balance,
although we find a small systematic offset of 0.08 dex (asteroseismic log g
values are lower). The abundance patterns of metals, alpha elements, and the
light elements (CNO) show that a simple scaling by [Fe/H] is adequate to
represent the metallicity of the stars, except for the stars with metallicity
below -0.3, where alpha-enhancement becomes important. However, this is only
important for a very small fraction of the Kepler sample. We therefore
recommend that a simple scaling with [Fe/H] be employed in the asteroseismic
analyses of large ensembles of solar-type stars.Comment: MNRAS, in press, 12 page
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