On the genesis of Post constraint in modern electromagnetism

The genesis of the Post constraint is premised on two attributes of modern electromagnetism: (i) its microscopic nature, and (ii) the status of e and b as the primitive electromagnetic fields. This constraint can therefore not arise in EH--electromagnetism, wherein the primitive electromagnetic fields are the macroscopic fields E and H

On electromagnetics of an isotropic chiral medium moving at constant velocity

A medium which is an isotropic chiral medium from the perspective of a co-moving observer is a Faraday chiral medium (FCM) from the perspective of a non-co-moving observer. The Tellegen constitutive relations for this FCM are established. By an extension of the Beltrami field concept, these constitutive relations are exploited to show that planewave propagation is characterized by four generally independent wavenumbers. This FCM can support negative phase velocity at certain translational velocities and with certain wavevectors, even though the corresponding isotropic chiral medium does not. The constitutive relations and Beltrami--like fields are also used to develop a convenient spectral representation of the dyadic Green functions for the FCM

Plane waves with negative phase velocity in Faraday chiral mediums

The propagation of plane waves in a Faraday chiral medium is investigated. Conditions for the phase velocity to be directed opposite to the direction of power flow are derived for propagation in an arbitrary direction; simplified conditions which apply to propagation parallel to the distinguished axis are also established. These negative phase-velocity conditions are explored numerically using a representative Faraday chiral medium, arising from the homogenization of an isotropic chiral medium and a magnetically biased ferrite. It is demonstrated that the phase velocity may be directed opposite to power flow, provided that the gyrotropic parameter of the ferrite component medium is sufficiently large compared with the corresponding nongyrotropic permeability parameters.Comment: accepted for publication in Phys. Rev.

The negative index of refraction demystified

We study electromagnetic wave propagation in mediums in which the effective relative permittivity and the effective relative permeability are allowed to take any value in the upper half of the complex plane. A general condition is derived for the phase velocity to be oppositely directed to the power flow. That extends the recently studied case of propagation in mediums for which the relative permittivity and relative permeability are both simultaneously negative, to include dissipation as well. An illustrative case study demonstrates that in general the spectrum divides into five distinct regions.Comment: 5 pages, 4 figure

Positive-, negative-, and orthogonal-phase-velocity propagation of electromagnetic plane waves in a simply moving medium

Planewave propagation in a simply moving, dielectric-magnetic medium that is isotropic in the co-moving reference frame, is classified into three different categories: positive-, negative-, and orthogonal-phase-velocity (PPV, NPV, and OPV). Calculations from the perspective of an observer located in a non-co-moving reference frame show that, whether the nature of planewave propagation is PPV or NPV (or OPV in the case of nondissipative mediums) depends strongly upon the magnitude and direction of that observer's velocity relative to the medium. PPV propagation is characterized by a positive real wavenumber, NPV propagation by a negative real wavenumber. OPV propagation only occurs for nondissipative mediums, but weakly dissipative mediums can support nearly OPV propagation

On the sensitivity of generic porous optical sensors

A porous material was considered as a platform for optical sensing. It was envisaged that the porous material was infiltrated by a fluid which contains an agent to be sensed. Changes in the optical properties of the infiltrated porous material provide the basis for detection of the agent to be sensed. Using a homogenization approach based on the Bruggeman formalism, wherein the infiltrated porous material was regarded as a homogenized composite material, the sensitivity of such a sensor was investigated. For the case of an isotropic dielectric porous material of relative permittivity $\epsilon^a$ and an isotropic dielectric fluid of relative permittivity $\epsilon^b$, it was found that the sensitivity was maximized when there was a large contrast between $\epsilon^a$ and $\epsilon^b$; the maximum sensitivity was achieved at mid-range values of porosity. Especially high sensitivities may be achieved for $\epsilon^b$ close to unity when $\epsilon^a >> 1$, for example. Furthermore, higher sensitivities may be achieved by incorporating pores which have elongated spheroidal shapes

Neue Wege in der Lehramtsausbildung: Das interdisziplinäre Projekt - Kooperation zwischen Fachwissenschaft, Fachdidaktik und Schulpraxis

In den letzten Jahren wurden die universitären Lehramts-Curricula einer Revision unterzogen und vor allem die fachdidaktischen Anteile vielfach erhöht, sodass insge­samt die berufsvorbildenden Anteile aus Fachdidaktik, Pädagogik und Schulpraxis deutlich zugenommen haben. Dennoch ist die Vernetzung und Integration zwischen Fachinhalten, Fachdidaktik, Pädagogik und Schulpraxis immer noch eher gering. Das im Beitrag vorgestellte interdisziplinäre Projekt an der Naturwissen­schaftlichen Fakultät der Universität Salzburg will einen Beitrag leisten, die Effektivität der Lehramtsaus­bildung zu erhöhen. An Hand des Modells der Didaktischen Rekonstruktion und des Konzepts der naturwissenschaftlichen Grundbildung (Scientific Literacy), das der internationalen PISA-Studie zu Grunde liegt, wird das Konzept der Lehrveranstaltung erläutert und Erfahrungen in der Durchführung dargestellt. 25.02.2007 | Hubert WEIGLHOFER (Salzburg

Curriculumentwicklungen und Organisationsstrukturen im Lehramtsstudium

Der vorliegende Beitrag gibt einen Einblick in die Entwicklungsarbeit zur Erstellung eines kompetenzorientierten Curriculums im Bereich der Lehramtsstudien und stellt die Organisationsstruktur der School of Education an der Universität Salzburg dar. Ausgehend von Rahmenkompetenzstrukturen in den vier Säulen der Lehramtsausbildung werden Kompetenzentwicklungslinien entlang der Bachelor- und Masterphase dargestellt und die Entwicklung hin zu einem Cluster-Verbund wird skizziert. 29.01.2016 | Hubert Weiglhofer (Salzburg