Backwards is the way forward: feedback in the cortical hierarchy predicts the expected future

Clark offers a powerful description of the brain as a prediction machine, which offers progress on two distinct levels. First, on an abstract conceptual level, it provides a unifying framework for perception, action, and cognition (including subdivisions such as attention, expectation, and imagination). Second, hierarchical prediction offers progress on a concrete descriptive level for testing and constraining conceptual elements and mechanisms of predictive coding models (estimation of predictions, prediction errors, and internal models)

Decoding face categories in diagnostic subregions of primary visual cortex

Higher visual areas in the occipitotemporal cortex contain discrete regions for face processing, but it remains unclear if V1 is modulated by top-down influences during face discrimination, and if this is widespread throughout V1 or localized to retinotopic regions processing task-relevant facial features. Employing functional magnetic resonance imaging (fMRI), we mapped the cortical representation of two feature locations that modulate higher visual areas during categorical judgements – the eyes and mouth. Subjects were presented with happy and fearful faces, and we measured the fMRI signal of V1 regions processing the eyes and mouth whilst subjects engaged in gender and expression categorization tasks. In a univariate analysis, we used a region-of-interest-based general linear model approach to reveal changes in activation within these regions as a function of task. We then trained a linear pattern classifier to classify facial expression or gender on the basis of V1 data from ‘eye’ and ‘mouth’ regions, and from the remaining non-diagnostic V1 region. Using multivariate techniques, we show that V1 activity discriminates face categories both in local ‘diagnostic’ and widespread ‘non-diagnostic’ cortical subregions. This indicates that V1 might receive the processed outcome of complex facial feature analysis from other cortical (i.e. fusiform face area, occipital face area) or subcortical areas (amygdala)

The laboratory diagnosis of typhoid fever

An outline of the methods used at the goverment pathological laboratory, Cape Tow

On the nullification of threshold amplitudes

The nullification of threshold amplitudes is considered within the conventional framework of quantum field theory. The relevant Ward identities for the reduced theory are derived both on path-integral and diagrammatic levels. They are then used to prove the vanishing of tree-graph threshold amplitudes.Comment: 16 page

Arctic Ice Islands

Contains an account of the discovery of two groups of "ice islands" evidently originating on the north coast of Ellesmere Island. Their size, shape and surface structure, as well as tracking the drift of the large ice islands by planes and radar, are discussed by Major Koenig (from U.S.A.F. "Ptarmigan" and other flights), and by Squadron-Leader Greenaway (from Canadian flights and air photographs). Extensive documentation is presented (by Miss Dunbar) of 19th-20th century explorers' references to, and observations of such "islands". The probability of their origin from shelf ice and the character of the ice shelf of Northern Ellesmere is presented (by Mr. Hattersley-Smith). Special consideration is given to three very large islands (identified as T1 T2 T3), their discovery, positions and movement, description, seasonal changes, etc.; with additional data on smaller "islands," arranged according to the areas of their presence. From the air the "floating islands" are easily distinguishable from pack ice by their large size, homogenous appearance, very regular, characteristically patterned surface, and a fixed shape suggesting great thickness and hardness. Bibliography (about 40 items)

Gravitational waves from coalescing binaries: detection strategies and Monte Carlo estimation of parameters

The paper deals with issues pertaining the detection of gravitational waves from coalescing binaries. We introduce the application of differential geometry to the problem of optimal detection of the `chirp signal'. We have also carried out extensive Monte Carlo simulations to understand the errors in the estimation of parameters of the binary system. We find that the errors are much more than those predicted by the covariance matrix even at a high SNR of 10-15. We also introduce the idea of using the instant of coalescence rather than the time of arrival to determine the direction to the source.Comment: 28 pages, REVTEX, 12 figures (bundled via uufiles command along with this paper) submitted to Phys. Rev.

Proof of the Hyperplane Zeros Conjecture of Lagarias and Wang

We prove that a real analytic subset of a torus group that is contained in its image under an expanding endomorphism is a finite union of translates of closed subgroups. This confirms the hyperplane zeros conjecture of Lagarias and Wang for real analytic varieties. Our proof uses real analytic geometry, topological dynamics and Fourier analysis.Comment: 25 page

Charged Grains In Saturn's F-Ring: Interaction With Saturn's Magnetic Field

Saturn's dynamic F-Ring still presents a challenge for understanding and explaining the kinematic processes that lead to the changing structure visible in our observations of this ring. This study examines the effect of Saturn's magnetic field on the dynamics of micron-sized grains that may become electrically charged due to interaction with plasma in Saturn's rigidly corotating magnetosphere. The numerical model calculates the dynamics of charged dust grains and includes forces due to Saturn's gravitational field, the plasma polarization electric field, a third order harmonic expansion of Saturn's magnetic field, and the F Ring's Shepherding moons, Prometheus and Pandora.Comment: 6 pages, PDF, to be published in Advances in Space Researc

Thermodynamics and kinetics of boundary friction

A deterministic theory describing the behavior of an ultrathin lubricant film between two atomically-smooth solid surfaces is proposed. For the description of lubricant state the parameter of excess volume arising due to chaotization of solid medium structure in the course of melting is introduced. Thermodynamic and shear melting is described consistently. Dependences of friction force on temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon surfaces are analyzed. Within the framework of a simple tribological model the stick-slip mode of friction, when the lubricant periodically melts and solidifies, is described. The obtained results are qualitatively compared with the experimental data.Comment: 14 pages, 6 figures, 33 reference