2,102 research outputs found
Facial resemblance between women's partners and brothers
Research on optimal outbreeding describes the greater reproductive success experienced on average by couples who are neither too closely related, nor too genetically dissimilar. How is optimal outbreeding achieved? Faces that subtly resemble family members could present useful cues to a potential reproductive partner with an optimal level of genetic dissimilarity. Here, we present the first empirical data that heterosexual women select partners who resemble their brothers. Raters ranked the facial similarity between a woman's male partner, and that woman's brother compared to foils. In a multilevel ordinal logistic regression that modeled variability in both the stimuli and the raters, there was clear evidence for perceptual similarity in facial photographs of a woman's partner and her brother. That is, although siblings themselves are sexually aversive, sibling resemblance is not. The affective responses of disgust and attraction may be calibrated to distinguish close kin from individuals with some genetic dissimilarity during partner choice
The Dynamics of Radiative Shock Waves: Linear and Nonlinear Evolution
The stability properties of one-dimensional radiative shocks with a power-law
cooling function of the form are the main
subject of this work. The linear analysis originally presented by Chevalier &
Imamura, is thoroughfully reviewed for several values of the cooling index
and higher overtone modes. Consistently with previous results, it is
shown that the spectrum of the linear operator consists in a series of modes
with increasing oscillation frequency. For each mode a critical value of the
cooling index, , can be defined so that modes with are unstable, while modes with
are stable. The perturbative analysis is complemented by several numerical
simulations to follow the time-dependent evolution of the system for different
values of . Particular attention is given to the comparison between
numerical and analytical results (during the early phases of the evolution) and
to the role played by different boundary conditions. It is shown that an
appropriate treatment of the lower boundary yields results that closely follow
the predicted linear behavior. During the nonlinear regime, the shock
oscillations saturate at a finite amplitude and tend to a quasi-periodic cycle.
The modes of oscillations during this phase do not necessarily coincide with
those predicted by linear theory, but may be accounted for by mode-mode
coupling.Comment: 33 pages, 12 figures, accepted for publication on the Astrophysical
Journa
Use of soil moisture information in yield models
There are no author-identified significant results in this report
Theoretical and experimental study of a finite cylindrical antenna in a plasma column
Finite cylindrical antenna in infinite plasma colum
Entropic Upper Bound on Gravitational Binding Energy
We prove that the gravitational binding energy {\Omega} of a self gravitating
system described by a mass density distribution {\rho}(x) admits an upper bound
B[{\rho}(x)] given by a simple function of an appropriate, non-additive
Tsallis' power-law entropic functional Sq evaluated on the density {\rho}. The
density distributions that saturate the entropic bound have the form of
isotropic q-Gaussian distributions. These maximizer distributions correspond to
the Plummer density profile, well known in astrophysics. A heuristic scaling
argument is advanced suggesting that the entropic bound B[{\rho}(x)] is unique,
in the sense that it is unlikely that exhaustive entropic upper bounds not
based on the alluded Sq entropic measure exit. The present findings provide a
new link between the physics of self gravitating systems, on the one hand, and
the statistical formalism associated with non-additive, power-law entropic
measures, on the other hand
Monte Carlo Investigation of Diffusion of Receptors and Ligands that Bind Across Opposing Surfaces
Studies of receptor diffusion on a cell surface show a variety of behaviors, such as diffusive, sub-diffusive, or super-diffusive motion. However, most studies to date focus on receptor molecules diffusing on a single cell surface. We have previously studied receptor diffusion to probe the molecular mechanism of receptor clustering at the cell–cell junction between two opposing cell surfaces. Here, we characterize the diffusion of receptors and ligands that bind to each other across two opposing cell surfaces, as in cell–cell and cell–bilayer interactions. We use a Monte Carlo method, where receptors and ligands are simulated as independent agents that bind and diffuse probabilistically. We vary receptor–ligand binding affinity and plot the molecule-averaged mean square displacement (MSD) of ligand molecules as a function of time. Our results show that MSD plots are qualitatively different for flat and curved interfaces, as well as between the cases of presence and absence of directed transport of receptor–ligand complexes toward a specific location on the interface. Receptor–ligand binding across two opposing surfaces leads to transient sub-diffusive motion at early times provided the interface is flat. This effect is entirely absent if the interface is curved, however, in this instance we observe sub-diffusive motion. In addition, a decrease in the equilibrium value of the MSD occurs as affinity increases, something which is absent for a flat interface. In the presence of directed transport of receptor–ligand complexes, we observe super-diffusive motion at early times for a flat interface. Super-diffusive motion is absent for a curved interface, however, in this case we observe a transient decrease in MSD with time prior to equilibration for high-affinity values
Characterization of AGN from the XMM–Newton Slew Survey
We present optical spectroscopy of candidate active galactic nuclei (AGN) pinpointed by a Swift follow-up campaign on unidentified transients in the XMM-Newton Slew Survey, increasing the completeness of the identifications of AGN in the Survey. Our Swift follow-up campaign identified 17 X-ray Telescope-detected candidate AGN, of which 9 were selected for optical follow-up and a further two were confirmed as AGN elsewhere. Using data obtained at the William Herschel Telescope, Very Large Telescope and New Technology Telescope, we find AGN features in seven of the candidates. We classify six as Seyfert types 1.0-1.5, with broad-line region velocities spanning 2000-12000 km s-1, and identify one as a possible type II AGN, consistent with the lack of a soft band X-ray detection in the Slew Survey. The virial black hole mass estimates for the sample lie between 1 × 108 and 3 × 109 M☉, with one source likely emitting close to its Eddington rate, LBol/LEdd ~ 0.9. We find a wide redshift range 0.08 < z < 0.9 for the nine now confirmed AGN drawn from the unidentified Slew Survey sample. One source remaining unclassified shows outbursts rarely seen before in AGN. We conclude that AGN discovered in this way are consistent with the largely non-varying, Slew-selected, known AGN population. We also find parallels with XMM-Newton Bright Serendipitous Survey AGN selected from pointed observations, and postulate that shallow X-ray surveys select AGN drawn from the same populations that have been characterized in deeper X-ray-selected samples
Swift follow-up of unidentified X-ray sources in the XMM-Newton Slew Survey
We present deep Swift follow-up observations of a sample of 94 unidentified
X-ray sources from the XMM-Newton Slew Survey. The X-ray Telescope on-board
Swift detected 29% of the sample sources; the flux limits for undetected
sources suggests the bulk of the Slew Survey sources are drawn from one or more
transient populations. We report revised X-ray positions for the XRT-detected
sources, with typical uncertainties of 2.9", reducing the number of catalogued
optical matches to just a single source in most cases. We characterise the
sources detected by Swift through their X-ray spectra and variability and via
UVOT photometry and catalogued nIR, optical and radio observations. Six sources
can be associated with known objects and 8 may be associated with unidentified
ROSAT sources within the 3-sigma error radii of our revised X-ray positions. We
find 10 of the 30 XRT-detected sources are clearly stellar in nature, including
one periodic variable star and 2 high proper motion stars. For 11 sources we
propose an AGN classification, among which 4 are detected with BAT and 3 have
redshifts spanning z = 0.2 - 0.9 obtained from the literature or from optical
spectroscopy presented here. The 67 Slew Survey sources we do not detect with
Swift are studied via their characteristics in the Slew Survey and by
comparison with the XRT and BAT detected population. We suggest that these are
mostly if not all extragalactic, though unlikely to be highly absorbed sources
in the X-rays such as Compton thick AGN. A large number of these are highly
variable soft X-ray sources. A small fraction of mainly hard-band detections
may be spurious. This follow-up programme brings us a step further to
completing the identifications of a substantial sample of XMM-Newton Slew
Survey sources, important for understanding the nature of the transient sky and
allowing flux-limited samples to be constructed.Comment: 19 pages, 7 figures. Accepted for publication in MNRA
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