An Introduction to the Inverse Quantum Bound State Problem in One Dimension

A technique to reconstruct one-dimensional, reflectionless potentials and the associated quantum wave functions starting from a finite number of known energy spectra is discussed. The method is demonstrated using spectra that scale like the lowest energy states of standard problems encountered in the undergraduate curriculum such as: the infinite square well, the simple harmonic oscillator, and the one-dimensional hydrogen atom.Comment: 10 pages, 10 figures, Submitted to Am. J. Phys. August 201

An ica algorithm for analyzing multiple data sets

In this paper we derive an independent-component analysis (ICA) method for analyzing two or more data sets simultaneously. Our model permits there to be components individual to the various data sets, and others that are common to all the sets. We explore the assumed time autocorrelation of independent signal components and base our algorithm on prediction analysis. We illustrate the algorithm using a simple image separation example. Our aim is to apply this method to functional brain mapping using functional magnetic resonance imaging (fMRI). 1

A Spatially Robust ICA Algorithm for Multiple fMRI Data Sets

In this paper we derive an independent-component analysis (ICA) method for analyzing two or more data sets simultaneously. Our model extracts independent components common to all data sets and independent data-set-specific components. We use time-delayed autocorrelations to obtain independent signal components and base our algorithm on prediction analysis. We applied this method to functional brain mapping using functional magnetic resonance imaging (fMRI). The results of our 3-subject analysis demonstrate the robustness of the algorithm to the spatial misalignment intrinsic in multiple-subject fMRI data sets. 1

Possible effect of dietary phytase supplementation on broiler sodium requirement.

Projeto/Plano de Ação: 11.11.11.111

Phytase stability during pelleting of broiler feed.

Projeto/Plano de Ação: 11.11.11.111

Selfish Mitochondrial DNA Proliferates and Diversifies in Small, but not Large, Experimental Populations of Caenorhabditis briggsae

Evolutionary interactions across levels of biological organization contribute to a variety of fundamental processes including genome evolution, reproductive mode transitions, species diversification, and extinction. Evolutionary theory predicts that so-called “selfish” genetic elements will proliferate when the host effective population size (Ne) is small, but direct tests of this prediction remain few. We analyzed the evolutionary dynamics of deletion-containing mitochondrial DNA (ΔmtDNA) molecules, previously characterized as selfish elements, in six different natural strains of the nematode Caenorhabditis briggsae allowed to undergo experimental evolution in a range of population sizes (N = 1, 10, 100, and 1,000) for a maximum of 50 generations. Mitochondrial DNA (mtDNA) was analyzed for replicate lineages at each five-generation time point. Ten different ΔmtDNA molecule types were observed and characterized across generations in the experimental populations. Consistent with predictions from evolutionary theory, lab lines evolved in small-population sizes (e.g., nematode N = 1) were more susceptible to accumulation of high levels of preexisting mtDNA compared with those evolved in larger populations. New ΔmtDNA elements were observed to increase in frequency and persist across time points, but almost exclusively at small population sizes. In some cases, mtDNA levels decreased across generations when population size was large (nematode N = 1,000). Different natural strains of C. briggsae varied in their susceptibilities to mtDNA accumulation, owing in part to preexisting compensatory mtDNA alleles in some strains that prevent deletion formation. This analysis directly demonstrates that the evolutionary trajectories of ΔmtDNA elements depend upon the population-genetic environments and molecular-genetic features of their hosts

Interesting magnetic properties of Fe1−x_{1-x}Cox_xSi alloys

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya interaction in the magnetic response of these non-centrosymmetric alloys is discussed.Comment: 11 pages and 3 figure

Structural and electrical transport properties of superconducting Au{0.7}In{0.3} films: A random array of superconductor-normal metal-superconductor (SNS) Josephson junctions

The structural and superconducting properties of Au{0.7}In{0.3} films, grown by interdiffusion of alternating Au and In layers, have been studied. The films were found to consist of a uniform solid solution of Au{0.9}In{0.1}, with excess In precipitated in the form of In-rich grains of various Au-In phases (with distinct atomic compositions), including intermetallic compounds. As the temperature was lowered, these individual grains became superconducting at a particular transition temperature (Tc), determined primarily by the atomic composition of the grain, before a fully superconducting state of zero resistance was established. From the observed onset Tc, it was inferred that up to three different superconducting phases could have formed in these Au{0.7}In{0.3} films, all of which were embedded in a uniform Au{0.9}In{0.1} matrix. Among these phases, the Tc of a particular one, 0.8 K, is higher than any previously reported for the Au-In system. The electrical transport properties were studied down to low temperatures. The transport results were found to be well correlated with those of the structural studies. The present work suggests that Au{0.7}In{0.3} can be modeled as a random array of superconductor-normal metal-superconductor (SNS) Josephson junctions. The effect of disorder and the nature of the superconducting transition in these Au{0.7}In{0.3} films are discussed.Comment: 8 text pages, 10 figures in one separate PDF file, submitted to PR

Microwave-induced control of Free Electron Laser radiation

The dynamical response of a relativistic bunch of electrons injected in a planar magnetic undulator and interacting with a counterpropagating electromagnetic wave is studied. We demonstrate a resonance condition for which the free electron laser (FEL) dynamics is strongly influenced by the presence of the external field. It opens up the possibility of control of short wavelength FEL emission characteristics by changing the parameters of the microwave field without requiring change in the undulator's geometry or configuration. Numerical examples, assuming realistic parameter values analogous to those of the TTF-FEL, currently under development at DESY, are given for possible control of the amplitude or the polarization of the emitted radiation.Comment: 14 pages, 5 figures, accepted for publication in Phys. Rev.