Combining low-level perception with expectations in CHREST

The ability of humans to reliably perceive and recognise objects relies on an interaction between information seen in the visual image and prior expectations. We describe an extension to the CHREST computational model which enables it to learn and combine information from multiple input modalities. Simulations demonstrate the presence of quantitative effects on recognition ability due to cross-modal interactions. Our simulations with CHREST illustrate how expectations can improve classification accuracy, reduce classification time, and enable words to be reconstructed from noisy visual input

Kertesz on Fat Graphs?

The identification of phase transition points, beta_c, with the percolation thresholds of suitably defined clusters of spins has proved immensely fruitful in many areas of statistical mechanics. Some time ago Kertesz suggested that such percolation thresholds for models defined in field might also have measurable physical consequences for regions of the phase diagram below beta_c, giving rise to a ``Kertesz line'' running between beta_c and the bond percolation threshold, beta_p, in the M, beta plane. Although no thermodynamic singularities were associated with this line it could still be divined by looking for a change in the behaviour of high-field series for quantities such as the free energy or magnetisation. Adler and Stauffer did precisely this with some pre-existing series for the regular square lattice and simple cubic lattice Ising models and did, indeed, find evidence for such a change in high-field series around beta_p. Since there is a general dearth of high-field series there has been no other work along these lines. In this paper we use the solution of the Ising model in field on planar random graphs by Boulatov and Kazakov to carry out a similar exercise for the Ising model on random graphs (i.e. coupled to 2D quantum gravity). We generate a high-field series for the Ising model on $\Phi^4$ random graphs and examine its behaviour for evidence of a Kertesz line

Does Micro-CT scanning damage DNA in museum specimens?

X-ray micro-computed tomography and DNA sequencing are useful and increasingly common tools in taxonomy and collections research. Whilst the benefits of each method are continually evaluated and debated individually, how the methods impact each other requires more attention. We compared DNA fragment length and the barcode sequence CO1 in samples throughout a CT-scanning protocol, for a range of X-ray exposures and energies. We found no evidence of DNA damage, but advise caution when using precious or archival material, highlighting the need for further investigations and considering potential areas for research.NatSCA supports open access publication as part of its mission is to promote and support natural science collections. NatSCA uses the Creative Commons Attribution License (CCAL) http://creativecommons.org/licenses/by/2.5/ for all works we publish. Under CCAL authors retain ownership of the copyright for their article, but authors allow anyone to download, reuse, reprint, modify, distribute, and/or copy articles in NatSCA publications, so long as the original authors and source are cited. The attached file is the published version of the article

Two- and three-body problem with Floquet-driven zero-range interactions

We study the two-body scattering problem in the zero-range approximation with a sinusoidally driven scattering length and calculate the relation between the mean value and amplitude of the drive for which the effective scattering amplitude is resonantly enhanced. In this manner we arrive at a family of curves along which the effective scattering length diverges but the nature of the corresponding Floquet-induced resonance changes from narrow to wide. Remarkably, on these curves the driving does not induce heating. In order to study the effect of these resonances on the three-body problem we consider one light and two heavy particles with driven heavy-light interaction in the Born-Oppenheimer approximation and find that the Floquet driving can be used to tune the three-body and inelasticity parameters.Comment: 14 pages, 7 figure

Aerodynamic Parameter Identification of a Venus Lander

An analysis was conducted to identify the parameters of an aerodynamic model for a Venus lander based on experimental free-flight data. The experimental free-flight data were collected in the NASA Langley 20-ft Vertical Spin Tunnel with a 25-percent Froude-scaled model. The experimental data were classified based on the wind tunnel run type: runs where the lander model was unperturbed over the course of the run, and runs were the model was perturbed (principally in pitch, yaw, and roll) by the wind tunnel operator. The perturbations allow for data to be obtained at higher wind angles and rotation rates than those available from the unperturbed data. The model properties and equations of motion were used to determine experimental values for the aerodynamic coefficients. An aerodynamic model was selected using a priori knowledge of axisymmetric blunt entry vehicles. The least squares method was used to estimate the aerodynamic parameters. Three sets of results were obtained from the following data sets: perturbed, unperturbed, and the combination of both. The combined data set was selected for the final set of aerodynamic parameters based on the quality of the results. The identified aerodynamic parameters are consistent with that of the static wind tunnel data. Reconstructions, of experimental data not used in the parameter identification analyses, achieved similar residuals as those with data used to identify the parameters. Simulations of the experimental data, using the identified parameters, indicate that the aerodynamic model used is incapable of replicating the limit cycle oscillations with stochastic peak amplitudes observed during the test

Studies in the Interaction of Heavy Charged Particles With Matter.

In recent years the technology of thin film preparation and the fabrication of gold surface barrier detectors and their associated electronics have become highly developed. This has enabled improved energy loss measurements to be made more conveniently for a large range of absorbers and charged particles. The basic interaction processes of heavy charged particles with matter have been investigated by analysing the energy spectra of charged particles before and after passing through absorbers. Results concerning the variation in energy loss, stopping power and energy straggling are given for alpha particles and fission fragments in various absorbers. Experimental studies of energy straggling have been carried out for Am-241 alpha particles using surface barrier detectors to observe the energy dispersion following transmission through solid absorbers. Energy straggling of the emitted alpha particles increased with increasing absorber thickness in accordance with theory, until the energy spectra of the helium ions entered the capture and loss region, when the trend is reversed and straggling began to decrease with increasing absorber thickness. An explanation of the phenomenon is given by reference to the stopping power of alpha particles as a function of their energy. Similarly measurements have been made of the energy straggling of Cf-252 fission fragments through air and solid films using a heavy ion surface barrier detector. Analysis of the energy spectra of the heavy and light fragments show a decreasing energy straggling with increasing absorber thickness. Again this and other spectra parameters are explained by reference to stopping power data for fission fragments

Aspects of oviposition in the fowl

Each part of the hen's oviduct possesses to some extent, the properties of secretion and. moti- lity. Those secretions of the oviduct which contri bute to egg formation have been studied by several authors but the mechanics of egg formation have so far received little attention. The oviduct may be considered to show two types of movement: relatively slow, propulsive movements by means of which the egg is moved as far as the uterus, and relatively quick, expulsive movements which constitute the process of oviposition. The object of this work is to describe some aspects of the physiology of these latter movements, to suggest possible ways in which they are controlled and to compare them with similar movements observed during mammalian parturition