Anderson Localization Triggered by Spin Disorder—With an Application to Eu x Ca1− x B6

The phenomenon of Anderson localization is studied for a class of one-particle Schrödinger operators with random Zeeman interactions. These operators arise as follows: Static spins are placed randomly on the sites of a simple cubic lattice according to a site percolation process with density x and coupled to one another ferromagnetically. Scattering of an electron in a conduction band at these spins is described by a random Zeeman interaction term that originates from indirect exchange. It is shown rigorously that, for positive values of x below the percolation threshold, the spectrum of the one-electron Schrödinger operator near the band edges is dense pure-point, and the corresponding eigenfunctions are exponentially localized. Localization near the band edges persists in a weak external magnetic field, H, but disappears gradually, as H is increased. Our results lead us to predict the phenomenon of colossal (negative) magnetoresistance and the existence of a Mott transition, as H and/or x are increased. Our analysis is motivated directly by experimental results concerning the magnetic alloy Eu x Ca1−x B

The Dichotomy between Property Rules and Liability Rules: Experiences from German Law

Calabresi and Melamed delivered a powerful theory to explain under what conditions it is economically efficient to transfer a property right by voluntary and alternatively by involuntary transactions. In the first instance, the property right should be protected by a property rule or an injunction as well as by criminal law sanctions in order to prevent involuntary transactions altogether. In the second instance, it should be protected only by a liability rule that provides compensation for involuntary transactions. Their theory is normative in the sense that they defend involuntary transactions under one set of conditions and voluntary transactions under another. However, their analysis is also analytical insofar as it predicts an evolutionary pressure on legal norms to encourage voluntary or involuntary transactions if the conditions, which they identified, are met. This article describes two diametrically opposed legal changes in Germany. In nuisance law, the development was from voluntary to involuntary transactions, while in privacy law it was from involuntary to voluntary transactions. We try to make it clear that these developments were triggered by the underlying causes that Calabresi and Melamed identified in their seminal paper on property rules vs. liability rules

Preliminary Results: Effects of Fertilization, Herbicide Application, and Prescribed Burning on Understory Regeneration on Pine Plantations in East Texas

Biodiversity and species rareness are increasingly the focal points for assessment of habitat quality. Managed pine plantations are often viewed as monocultures with little of value beyond their timber crop. The purpose of this study is to assess vegetative biodiversity in the understory of two pine plantations in which different vegetative control mechanisms are being evaluated. Controlled burn, herbicide treatment, and a combination of both are being compared on fertilized and unfertilized plots on two loblolly pine (Pinus taeda) plantations in east Texas. This study will compare species diversity and frequency on untreated and treated plots. One-square meter quadrat samples will be evaluated from 0.04 ha sampling plots within 0.1 ha treatment plots. Species richness will be determined as the number of species in each treatment plot. Shannon Index of Heterogeneity will be determined for each treatment. Comparison of different treatments will be made based on species richness and the Shannon diversity indices. Results for the first growth season after treatment will be presented

Möglichkeiten verstärkter Nord-Süd-Technologiekooperation im Klimaregime: Studie auf Grundlage einer Analyse für das Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit im Rahmen des Projekts Wirtschaftliche Chancen der internationalen Klimapolitik

Dieses Papier gibt einen Überblick über die verschiedenen Formen der Technologiekooperation und prüft ihre Verwendbarkeit für die internationalen post-2012-Klimaverhandlungen. Es plädiert für einen umfassenden Ansatz unter Einbeziehung aller Elemente, also des gemeinsamen RD&D, der gemeinsamen Standardsetzung und der Finanzierung neuer Technologien. Die Vor- und Nachteile eines separaten Technologieprotokolls werden abgewogen - wobei die Nachteile überwiegen. Abschließend wird, unter Verweis auf die Verhandlungen in Bali, die Gründung einer Technologieallianz für Klimaschutz mit den Entwicklungs- und insbesondere den Schwellenländern empfohlen. Dies würde die post-2012-Verhandlungen entscheidend voranbringen, die diplomatische und technologische Zusammenarbeit mit den aufstrebenden Schwellenländern stärken und die Führungsrolle der Europäischen Union in der Klimapolitik - aber nicht nur dort - festigen. -- This paper provides an overview on the different forms of inter-governmental technology cooperation and examines their usefulness for the international climate negotiations post-2012. It advocates a comprehensive approach including all elements, i.e. common research and development, common setting of standards, technology transfer and financing of new technologies. The pros and cons of a separate technology protocol are evaluated: in the end, it is only a second-best option. Finally, taking the negotiations in Bali as a starting point, the paper envisions a technology alliance for climate protection with the developing countries - especially the emerging economies. This would significantly boost the post-2012 negotiations, strengthen diplomatic and technological cooperation and consolidate the European Union's leading role in climate politics - and other policy fields.

Magneto-optical behaviour of EuIn_2P_2

We report results of a magneto-optical investigation of the Zintl-phase compound EuIn$_2$P$_2$. The compound orders magnetically at $T_C$=24 K and exhibits concomitant large magnetoresistance effects. For $T\le$50 K and increasing magnetic fields we observe a transfer of spectral weight in $\sigma_1(\omega)$ from energies above 1 eV into the low-energy metallic component as well as into a mid-infrared signal centered at about 600 cm$^{-1}$. This latter absorption is reminiscent to what has been seen in a large variety of so-called Kondo materials and ascribed to excitations across the hybridization gap. The observed gain of Drude weight upon increasing magnetic field suggests an enhancement of the itinerant charge-carrier concentration due to the increasing magnetization, a phenomenon that was previously observed in other compounds which exhibit colossal magnetoresistive effects.Comment: 13 pages, 4 figure

Longitudinal Assessment of Plasmodium falciparum var Gene Transcription in Naturally Infected Asymptomatic Children in Papua New Guinea

Sequestration and antigenic variation are essential for Plasmodium falciparum survival in vivo contributing to severe pathologic findings and, also, chronic infection. Both are conferred by P. falciparum erythrocyte membrane proteins encoded by ∼60 var genes. To study the dynamics of var gene expression, we conducted a 4-month longitudinal study of semi-immune children from Papua New Guinea. By use of magnetic bead- anchored reverse-transcription polymerase chain reaction analysis performed over 5 var regions, as well as cloning and sequencing, the longitudinal distribution of full-length var transcripts was analyzed. We identified a dynamic picture of var gene expression with rapid switches but with identical var transcripts recurring for up to 10 weeks. The number of var transcripts was correlated to the number of infections, with a mean of 1.7 var transcripts identified per sample and infecting strain. Analysis of 158 different Duffy binding-like 1α sequences confirmed the recombinogenic nature of var genes. This is the first report of the dynamics of var gene expression in chronically infected childre