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

A Dialectical Basis for Software Development Tool Building

We identify typical problems in the interactions of people with current software-based systems. In particular we observe the need to expend significant on-going effort to adapt these systems to reflect changes in the world about them, the need for people to adapt their working practices to fit in with these systems, and the inflexibility of these systems when faced with unusual circumstances or the need for change. We believe that these problems follow, at least in part, from these systems being developed and evolved using mechanisms each based on one Inquiry System only. This basis leads to assumptions being embedded in the mechanisms’ analysis outputs, and in system designs and implementations. We suggest that the problems noted may be mitigated by the use of a dialectical approach to Inquiry System selection for software development, based on the work of Hegel, which places in opposition different models of a situation based on different Inquiry Systems. We claim that such a mechanism has the potential to make explicit some of the assumptions which would otherwise be embedded implicitly in the delivered system without being questioned. We outline a research programme intended to test this hypothesis, and suggest other research directions

Phytase stability during pelleting of broiler feed.

Projeto/Plano de Ação: 11.11.11.111

Possible effect of dietary phytase supplementation on broiler sodium requirement.

Projeto/Plano de Ação: 11.11.11.111

The celebrity entrepreneur on television: profile, politics and power

This article examines the rise of the ‘celebrity entrepreneur’ on television through the emergence of the ‘business entertainment format’ and considers the ways in which regular television exposure can be converted into political influence. Within television studies there has been a preoccupation in recent years with how lifestyle and reality formats work to transform ‘ordinary’ people into celebrities. As a result, the contribution of vocationally skilled business professionals to factual entertainment programming has gone almost unnoticed. This article draws on interviews with key media industry professionals and begins by looking at the construction of entrepreneurs as different types of television personalities and how discourses of work, skill and knowledge function in business shows. It then outlines how entrepreneurs can utilize their newly acquired televisual skills to cultivate a wider media profile and secure various forms of political access and influence. Integral to this is the centrality of public relations and media management agencies in shaping media discourses and developing the individual as a ‘brand identity’ that can be used to endorse a range of products or ideas. This has led to policy makers and politicians attempting to mobilize the media profile of celebrity entrepreneurs to reach out and connect with the public on business and enterprise-related issues

Doping a semiconductor to create an unconventional metal

Landau Fermi liquid theory, with its pivotal assertion that electrons in metals can be simply understood as independent particles with effective masses replacing the free electron mass, has been astonishingly successful. This is true despite the Coulomb interactions an electron experiences from the host crystal lattice, its defects, and the other ~1022/cm3 electrons. An important extension to the theory accounts for the behaviour of doped semiconductors1,2. Because little in the vast literature on materials contradicts Fermi liquid theory and its extensions, exceptions have attracted great attention, and they include the high temperature superconductors3, silicon-based field effect transistors which host two-dimensional metals4, and certain rare earth compounds at the threshold of magnetism5-8. The origin of the non-Fermi liquid behaviour in all of these systems remains controversial. Here we report that an entirely different and exceedingly simple class of materials - doped small gap semiconductors near a metal-insulator transition - can also display a non-Fermi liquid state. Remarkably, a modest magnetic field functions as a switch which restores the ordinary disordered Fermi liquid. Our data suggest that we have finally found a physical realization of the only mathematically rigourous route to a non-Fermi liquid, namely the 'undercompensated Kondo effect', where there are too few mobile electrons to compensate for the spins of unpaired electrons localized on impurity atoms9-12.Comment: 17 pages 4 figures supplemental information included with 2 figure

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.