Comparison of the craniometric parameters of wild and farm American mink (Mustela vison)

Skulls of 65 American minks from the West Pomeranian Province were examined (farm: n = 33, male: n = 16, female: n = 17; wild: n = 32, male: n = 20, female: n = 12). Craniometric parameters in the number of 24 were determined and measured on each skull. Results were averaged and compared, maintaining the division into sex groups. Males were found to have statistically significant differences between wild and farm animals in 20 parameters; measurements showing no statistically significant differences were: nasal length, postorbital constriction, brain case height and greatest height of the mandibular body. Females were found to have statistically significant differences between wild and farm animals in 6 parameters: condylobasal length, tooth row length, greatest length of the mandible, brain case basis length, postorbital length and palatal length. The percentage conversion of measurements into the greatest length of the skull showed differences in its proportions. Among male skulls, the parameters for which the ratio of differences was more than 2% were palatal length, zygomatic breadth and brain case height. For female skulls, no craniometric parameters showed differences in the skull proportions being greater than 2%. The occurrence of measurable changes in the craniometric parameters between domestic and farm mink populations may indicate that the domestication process is still ongoing and allows distinguishing the population affiliation of an individual specimen.

User-driven design of robot costume for child-robot interactions among children with cognitive impairment

The involvement of arts and psychology elements in robotics research for children with cognitive impairment is still limited. However, the combination of robots, arts, psychology and education in the development of robots could significantly contribute to the improvement of social interaction skills among children with cognitive impairment. In this article, we would like to share our work on building and innovating the costume of LUCA's robot, which incorporating the positive psychological perspectives and arts values for children with cognitive impairment. Our goals are (1) to educate arts students in secondary arts school on the importance of social robot appearance for children with cognitive impairment, and (2) to select the best costume for future child-robot interaction study with children with cognitive impairments

Breaking a chaos-noise-based secure communication scheme

This paper studies the security of a secure communication scheme based on two discrete-time intermittently-chaotic systems synchronized via a common random driving signal. Some security defects of the scheme are revealed: 1) the key space can be remarkably reduced; 2) the decryption is insensitive to the mismatch of the secret key; 3) the key-generation process is insecure against known/chosen-plaintext attacks. The first two defects mean that the scheme is not secure enough against brute-force attacks, and the third one means that an attacker can easily break the cryptosystem by approximately estimating the secret key once he has a chance to access a fragment of the generated keystream. Yet it remains to be clarified if intermittent chaos could be used for designing secure chaotic cryptosystems.Comment: RevTeX4, 11 pages, 15 figure

Investigating slim disk solutions for HLX-1 in ESO 243-49

The hyper luminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the best intermediate mass black hole candidate, displays spectral transitions similar to those observed in Galactic black hole binaries, but with a luminosity 100-1000 times higher. We investigated the X-ray properties of this unique source fitting multi-epoch data collected by Swift, XMM-Newton & Chandra with a disk model computing spectra for a wide range of sub- and super-Eddington accretion rates assuming a non-spinning black hole and a face-on disk (i = 0 deg). Under these assumptions we find that the black hole in HLX-1 is in the intermediate mass range (~2 x 10^4 M_odot) and the accretion flow is in the sub-Eddington regime. The disk radiation efficiency is eta = 0.11 +/-0.03. We also show that the source does follow the L_X ~ T^4 relation for our mass estimate. At the outburst peaks, the source radiates near the Eddington limit. The accretion rate then stays constant around 4 x 10^(-4) M_odot yr^(-1) for several days and then decreases exponentially. Such "plateaus" in the accretion rate could be evidence that enhanced mass transfer rate is the driving outburst mechanism in HLX-1. We also report on the new outburst observed in August 2011 by the Swift-X-ray Telescope. The time of this new outburst further strengthens the ~1 year recurrence timescale.Comment: 24 pages, 10 figures, accepted for publication in Ap

Tunability of the dielectric response of epitaxially strained SrTiO3 from first principles

The effect of in-plane strain on the nonlinear dielectric properties of SrTiO3 epitaxial thin films is calculated using density-functional theory within the local-density approximation. Motivated by recent experiments, the structure, zone-center phonons, and dielectric properties with and without an external electric field are evaluated for several misfit strains within +-3% of the calculated cubic lattice parameter. In these calculations, the in-plane lattice parameters are fixed, and all remaining structural parameters are permitted to relax. The presence of an external bias is treated approximately by applying a force to each ion proportional to the electric field. After obtaining zero-field ground state structures for various strains, the zone-center phonon frequencies and Born effective charges are computed, yielding the zero-field dielectric response. The dielectric response at finite electric field bias is obtained by computing the field dependence of the structure and polarization using an approximate technique. The results are compared with recent experiments and a previous phenomenological theory. The tunability is found to be strongly dependent on the in-plane lattice parameter, showing markedly different behavior for tensile and compressive strains. Our results are expected to be of use for isolating the role of strain in the tunability of real ultrathin epitaxial films.Comment: 11 pages, with postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/ant_srti/index.htm

QPOs in Cataclysmic Variables and in X-ray Binaries

Recent observations, reported by Warner and Woudt, of Dwarf Nova Oscillations (DNOs) exhibiting frequency drift, period doubling, and 1:2:3 harmonic structure, can be understood as disc oscillations that are excited by perturbations at the spin frequency of the white dwarf or of its equatorial layers. Similar quasi-periodic disc oscillations in black hole low-mass X-ray binary (LMXB) transients in a 2:3 frequency ratio show no evidence of frequency drift and correspond to two separate modes of disc oscillation excited by an internal resonance. Just as no effects of general relativity play a role in white dwarf DNOs, no stellar surface or magnetic field effects need be invoked to explain the black hole QPOs.Comment: Revised version. Astronomy & Astrophysics (Letters), in pres

Averaging approach to phase coherence of uncoupled limit-cycle oscillators receiving common random impulses

Populations of uncoupled limit-cycle oscillators receiving common random impulses show various types of phase-coherent states, which are characterized by the distribution of phase differences between pairs of oscillators. We develop a theory to predict the stationary distribution of pairwise phase difference from the phase response curve, which quantitatively encapsulates the oscillator dynamics, via averaging of the Frobenius-Perron equation describing the impulse-driven oscillators. The validity of our theory is confirmed by direct numerical simulations using the FitzHugh-Nagumo neural oscillator receiving common Poisson impulses as an example

A Population of Faint Non-Transient Low Mass Black Hole Binaries

We study the thermal and viscous stability of accretion flows in Low Mass Black Hole Binaries (LMBHBs). We consider a model in which an inner advection-dominated accretion flow (ADAF) is surrounded by a geometrically thin accretion disk, the transition between the two zones occurring at a radius R_tr. In all the known LMBHBs, R_tr appears to be such that the outer disks could suffer from a global thermal-viscous instability. This instability is likely to cause the transient behavior of these systems. However, in most cases, if R_tr were slightly larger than the estimated values, the systems would be globally stable. This suggests that a population of faint persistent LMBHBs with globally stable outer disks could be present in the Galaxy. Such LMBHBs would be hard to detect because they would lack large amplitude outbursts, and because their ADAF zones would have very low radiative efficiencies, making the systems very dim. We present model spectra of such systems covering the optical and X-ray bands.Comment: LateX, 37 pages, 11 figures; Accepted for publication in The Astrophysical Journa

Rare events, escape rates and quasistationarity: some exact formulae

We present a common framework to study decay and exchanges rates in a wide class of dynamical systems. Several applications, ranging form the metric theory of continuons fractions and the Shannon capacity of contrained systems to the decay rate of metastable states, are given