The Law and Policy of Civil Rights: A Tactical Perspective for Educators

This article is presented to share with fellow professional teacher-scholars the preparation of a freshly-formulated teaching project. The aim of this project is to provide a classroom public policy study program wherein students debate policy issues in a carefully structured and professional fashion. This structure encompasses hands-on study of actually-litigated minority set-aside/affirmative action controversies before the U.S. Supreme Court, with every student always utilizing the primary documents (the litigants\u27 briefs) used by the Supreme Court Justices themselves. These briefs provide readymade resources fueling policy debate on either side of each case

A method for the visual detection of holes in thin polymeric films

Back-lighting polymeric film with polarized light from a polarizing plate and viewing it through a second plate cross-polarized to the back-lighting provides visual contrast between the flaw and the transparent film

The epiphyllous habit in the hepatic genus Frullania

We report for the first time 11 species of Frullania growing as epiphylls in New Zealand, New Caledonia, and Colombia . Also listed are 29 Frullania species that have previously been recorded growing as epiphylls in other regions of the world. The highest diversity of Frullania epiphyllous species are in the floristic regions of New Zealand, New Caledonia, Macraonesia, and Madagascar. Frullania epiphylls range in altitude from sea-level to 2500m and can be categorised into facultative or accidental epiphylls. The number of Frullania species currently recorded growing as epiphylls will no doubt increase as more revisions of the genus in different floristic regions take place. This number may also increase if botanists were to explore leaf surfaces as a potential substrate for Frullania species, in addition to bark and rock habitats that have traditionally been described as microhabitats for the genus

Determining topological order from a local ground state correlation function

Topological insulators are physically distinguishable from normal insulators only near edges and defects, while in the bulk there is no clear signature to their topological order. In this work we show that the Z index of topological insulators and the Z index of the integer quantum Hall effect manifest themselves locally. We do so by providing an algorithm for determining these indices from a local equal time ground-state correlation function at any convenient boundary conditions. Our procedure is unaffected by the presence of disorder and can be naturally generalized to include weak interactions. The locality of these topological indices implies bulk-edge correspondence theorem.Comment: 7 pages, 3 figures. Major changes: the paper was divided into sections, the locality of the order in 3D topological insulators is also discusse

Parametric resonance of a two-dimensional electron gas under bichromatic irradiation

In an ultrahigh mobility 2D electron gas, even a weak nonparabolicity of the electron dispersion, by violating Kohn's theorem, can have a drastic effect on dc magnetotransport under ac drive. We study theoretically the manifestation of this effect in the dc response to the combined action of two driving ac-fields (bichromatic irradiation). Compared to the case of monochromatic irradiation, which is currently intensively studied both experimentally and theoretically, the presence of a second microwave source provides additional insight into the properties of an ac-driven 2D electron gas. In particular, we find that nonparabolicity, being the simplest cause for a violation of Kohn's theorem, gives rise to new qualitative effects specific to bichromatic irradiation. Namely, when the frequencies $\omega_1$ and $\omega_2$ are well away from the cyclotron frequency, $\omega_c$, our simple classical considerations demonstrate that the system becomes parametrically unstable with respect to fluctuations with frequency $(\omega_1+\omega_2)/2$. As an additional effect of nonparabolicity, this parametric instability can manifest itself in the dc properties of the system. This happens when $\omega_1$, $\omega_2$ and $\omega_c$ are related as 3:1:2, respectively. Even for weak detuning between $\omega_1$ and $\omega_2$, the effect of the bichromatic irradiation on the dc response in the presence of nonparabolicity can differ dramatically from the monochromatic case. In particular, the equations of motion can acquire multistable solutions. As a result, the diagonal dc-conductivity can assume several stable negative values at the same magnetic field.Comment: 11 pages, 10 figure

Spitzer White Dwarf Planet Limits

We present preliminary limits on the presence of planets around white dwarf stars using the IRAC photometer on the Spitzer space telescope. Planets emit strongly in the mid-infrared which allows their presence to be detected as an excess at these wavelengths. We place limits of $5 M_J$ for 8 stars assuming ages of $1 Gyr$, and $10 M_J$ for 23 stars.We describe our survey, present our results and comment on approaches to improve our methodology.Comment: 4 pages, 3 figures, to appear in Proceedings of 15th European White Dwarf Worksho

Magnetospherically-trapped dust and a possible model for the unusual transits at WD 1145+017

The rapidly evolving dust and gas extinction observed towards WD 1145+017 has opened a real-time window onto the mechanisms for destruction-accretion of planetary bodies onto white dwarf stars, and has served to underline the importance of considering the dynamics of dust particles around such objects. Here it is argued that the interaction between (charged) dust grains and the stellar magnetic field is an important ingredient in understanding the physical distribution of infrared emitting particles in the vicinity of such white dwarfs. These ideas are used to suggest a possible model for WD 1145+017 in which the unusual transit shapes are caused by opaque clouds of dust trapped in the stellar magnetosphere. The model can account for the observed transit periodicities if the stellar rotation is near 4.5 h, as the clouds of trapped dust are then located near or within the co-rotation radius. The model requires the surface magnetic field to be at least around some tens of kG. In contrast to the eccentric orbits expected for large planetesimals undergoing tidal disintegration, the orbits of magnetospherically-trapped dust clouds are essentially circular, consistent with the observations.Comment: 5 pages, accepted to MNRAS Letter