589 research outputs found
The function of copulatory plugs in Caenorhabditis remanei: hints for female benefits
<p>Abstract</p> <p>Background</p> <p>Mating plugs that males place onto the female genital tract are generally assumed to prevent remating with other males. Mating plugs are usually explained as a consequence of male-male competition in multiply mating species. Here, we investigated whether mating plugs also have collateral effects on female fitness. These effects are negative when plugging reduces female mating rate below an optimum. However, plugging may also be positive when plugging prevents excessive forced mating and keeps mating rate closer to a females' optimum. Here, we studied these consequences in the gonochoristic nematode <it>Caenorhabditis remanei</it>. We employed a new CO<sub>2</sub>-sedation technique to interrupt matings before or after the production of a plug. We then measured mating rate, attractiveness and offspring number.</p> <p>Results</p> <p>The presence of a mating plug did not affect mating rate or attractiveness to roving males. Instead, females with mating plugs produced more offspring than females without copulatory plugs.</p> <p>Conclusions</p> <p>Our experiment suggests that plugging might have evolved under male-male competition but represents a poor protection against competing males in our experiment. Even if plugging does not reduce mating rate, our results indicate that females may benefit from being plugged in a different sense than remating prevention.</p
Signal yields, energy resolution, and recombination fluctuations in liquid xenon
This work presents an analysis of monoenergetic electronic recoil peaks in
the dark-matter-search and calibration data from the first underground science
run of the Large Underground Xenon (LUX) detector. Liquid xenon charge and
light yields for electronic recoil energies between 5.2 and 661.7 keV are
measured, as well as the energy resolution for the LUX detector at those same
energies. Additionally, there is an interpretation of existing measurements and
descriptions of electron-ion recombination fluctuations in liquid xenon as
limiting cases of a more general liquid xenon re- combination fluctuation
model. Measurements of the standard deviation of these fluctuations at
monoenergetic electronic recoil peaks exhibit a linear dependence on the number
of ions for energy deposits up to 661.7 keV, consistent with previous LUX
measurements between 2-16 keV with H. We highlight similarities in liquid
xenon recombination for electronic and nuclear recoils with a comparison of
recombination fluctuations measured with low-energy calibration data.Comment: 11 pages, 12 figures, 3 table
Planck intermediate results. XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations
We present all-sky modelling of the high resolution Planck, IRAS, and WISE
infrared (IR) observations using the physical dust model presented by Draine
and Li in 2007 (DL). We study the performance and results of this model, and
discuss implications for future dust modelling. The present work extends the DL
dust modelling carried out on nearby galaxies using Herschel and Spitzer data
to Galactic dust emission. We employ the DL dust model to generate maps of the
dust mass surface density, the optical extinction Av, and the starlight
intensity parametrized by Umin. The DL model reproduces the observed spectral
energy distribution (SED) satisfactorily over most of the sky, with small
deviations in the inner Galactic disk and in low ecliptic latitude areas. We
compare the DL optical extinction Av for the diffuse interstellar medium with
optical estimates for 2 10^5 quasi-stellar objects (QSOs) observed in the Sloan
digital sky survey. The DL Av estimates are larger than those determined
towards QSOs by a factor of about 2, which depends on Umin. The DL fitting
parameter Umin, effectively determined by the wavelength where the SED peaks,
appears to trace variations in the far-IR opacity of the dust grains per unit
Av, and not only in the starlight intensity. To circumvent the model
deficiency, we propose an empirical renormalization of the DL Av estimate,
dependent of Umin, which compensates for the systematic differences found with
QSO observations. This renormalization also brings into agreement the DL Av
estimates with those derived for molecular clouds from the near-IR colours of
stars in the 2 micron all sky survey. The DL model and the QSOs data are used
to compress the spectral information in the Planck and IRAS observations for
the diffuse ISM to a family of 20 SEDs normalized per Av, parameterized by
Umin, which may be used to test and empirically calibrate dust models.Comment: Final version that has appeared in A&
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