Wavelet Features for Recognition of First Episode of Schizophrenia from MRI Brain Images

Machine learning methods are increasingly used in various fields of medicine, contributing to early diagnosis and better quality of care. These outputs are particularly desirable in case of neuropsychiatric disorders, such as schizophrenia, due to the inherent potential for creating a new gold standard in the diagnosis and differentiation of particular disorders. This paper presents a scheme for automated classification from magnetic resonance images based on multiresolution representation in the wavelet domain. Implementation of the proposed algorithm, utilizing support vector machines classifier, is introduced and tested on a dataset containing 104 patients with first episode schizophrenia and healthy volunteers. Optimal parameters of different phases of the algorithm are sought and the quality of classification is estimated by robust cross validation techniques. Values of accuracy, sensitivity and specificity over 71% are achieved

Phase analysis of the cosmic microwave background from an incomplete sky coverage

Phases of the spherical harmonic analysis of full-sky cosmic microwave background (CMB) temperature data contain useful information complementary to the ubiquitous angular power spectrum. In this letter we present a new method of phase analysis on incomplete sky maps. It is based on Fourier phases of equal-latitude pixel rings of the map, which are related to the mean angle of the trigonometric moments from the full-sky phases. They have an advantage for probing regions of interest without tapping polluted Galactic plane area, and can localize non-Gaussian features and departure from statistical isotropy in the CMB.Comment: 5 pages, 3 figures submitted to MNRAS Letters, replaced with minor change

Abelian Duality

We show that on three-dimensional Riemannian manifolds without boundaries and with trivial first real de Rham cohomology group (and in no other dimensions) scalar field theory and Maxwell theory are equivalent: the ratio of the partition functions is given by the Ray-Singer torsion of the manifold. On the level of interaction with external currents, the equivalence persists provided there is a fixed relation between the charges and the currents.Comment: 11 pages, LaTeX, no figures, a reference added, submitted to Phys. Rev.

Novel Symmetry of Non-Einsteinian Gravity in Two Dimensions

The integrability of $R^2$-gravity with torsion in two dimensions is traced to an ultralocal dynamical symmetry of constraints and momenta in Hamiltonian phase space. It may be interpreted as a quadratically deformed $iso(2,1)$-algebra with the deformation consisting of the Casimir operators of the undeformed algebra. The locally conserved quantity encountered in the explicit solution is identified as an element of the centre of this algebra. Specific contractions of the algebra are related to specific limits of the explicit solutions of this model.Comment: 17 pages, TUW-92-04 (LaTeX

Magnetic structure and orbital ordering in BaCoO3 from first-principles calculations

Ab initio calculations using the APW+lo method as implemented in the WIEN2k code have been used to describe the electronic structure of the quasi-one-dimensional system BaCoO3. Both, GGA and LDA+U approximations were employed to study different orbital and magnetic orderings. GGA predicts a metallic ground state whereas LDA+U calculations yield an insulating and ferromagnetic ground state (in a low-spin state) with an alternating orbital ordering along the Co-Co chains, consistent with the available experimental data.Comment: 8 pages, 9 figure

C and S induces changes in the electronic and geometric structure of Pd(533) and Pd(320)

We have performed ab initio electronic structure calculations of C and S adsorption on two vicinal surfaces of Pd with different terrace geometry and width. We find both adsorbates to induce a significant perturbation of the surface electronic and geometric structure of Pd(533) and Pd(320). In particular C adsorbed at the bridge site at the edge of a Pd chain in Pd(320) is found to penetrate the surface to form a sub-surface structure. The adsorption energies show almost linear dependence on the number of adsorbate-metal bonds, and lie in the ranges of 5.31eV to 8.58eV for C and 2.89eV to 5.40eV for S. A strong hybridization between adsorbate and surface electronic states causes a large splitting of the bands leading to a drastic decrease in the local densities of electronic states at the Fermi-level for Pd surface atoms neighboring the adsorbate which may poison catalytic activity of the surface. Comparison of the results for Pd(533) with those obtained earlier for Pd(211) suggests the local character of the impact of the adsorbate on the geometric and electronic structures of Pd surfaces.Comment: 14 pages 9 figs, Accepted J. Phys: Conden

Potential mechanical loss mechanisms in bulk materials for future gravitational wave detectors

Low mechanical loss materials are needed to further decrease thermal noise in upcoming gravitational wave detectors. We present an analysis of the contribution of Akhieser and thermoelastic damping on the experimental results of resonant mechanical loss measurements. The combination of both processes allows the fit of the experimental data of quartz in the low temperature region (10 K to 25 K). A fully anisotropic numerical calculation over a wide temperature range (10 K to 300 K) reveals, that thermoelastic damping is not a dominant noise source in bulk silicon samples. The anisotropic numerical calculation is sucessfully applied to the estimate of thermoelastic noise of an advanced LIGO sized silicon test mass.Comment: 7 pages, 3 figures, submitted to Journal of Physics: Conference Series (AMALDI8

A CLEAN-based Method for Deconvolving Interstellar Pulse Broadening from Radio Pulses

Multipath propagation in the interstellar medium distorts radio pulses, an effect predominant for distant pulsars observed at low frequencies. Typically, broadened pulses are analyzed to determine the amount of propagation-induced pulse broadening, but with little interest in determining the undistorted pulse shapes. In this paper we develop and apply a method that recovers both the intrinsic pulse shape and the pulse broadening function that describes the scattering of an impulse. The method resembles the CLEAN algorithm used in synthesis imaging applications, although we search for the best pulse broadening function, and perform a true deconvolution to recover intrinsic pulse structre. As figures of merit to optimize the deconvolution, we use the positivity and symmetry of the deconvolved result along with the mean square residual and the number of points below a given threshold. Our method makes no prior assumptions about the intrinsic pulse shape and can be used for a range of scattering functions for the interstellar medium. It can therefore be applied to a wider variety of measured pulse shapes and degrees of scattering than the previous approaches. We apply the technique to both simulated data and data from Arecibo observations.Comment: 9 pages, 6 figures, Accepted for publication in the Astrophysical Journa

Weak Scale Superstrings

Recent developments in string duality suggest that the string scale may not be irrevocably tied to the Planck scale. Two explicit but unrealistic examples are described where the ratio of the string scale to the Planck scale is arbitrarily small. Solutions which are more realistic may exist in the intermediate coupling or ``truly strong coupling'' region of the heterotic string. Weak scale superstrings have dramatic experimental consequences for both collider physics and cosmology.Comment: harvmac, 14 pages. References added, 3 typos fixed, Comments added at beginning of section 4 emphasizing flaws of the toy example