Regulatory Taking: A Contract Approach

This Article begins by defining the parameters of the fifth amendment\u27s taking clause. The Article then reviews the various tests used in determining whether governmental action constitutes a taking, and discusses the recent Supreme Court decisions within the framework of case law as it has evolved since the Court\u27s 1922 landmark decision, Pennsylvania Coal Co. v. Mahon. Finally, the Article suggests a formula based on well-established contract principles for analyzing the impact of land use regulation on private property interests

Realization of La2MnVO6: Search for half-metallic antiferromagnetism?

Single-phase polycrystalline La2MnVO6 samples were synthesized by arc melting and characterized by X-ray diffraction, magnetization and resistivity measurements. We find that the compound has cubic (space group), partly ordered double perovskite structure. The sample exhibits ferrimagnetic behavior and variable-range hopping conductivity. We conclude based on the magnetic properties that both Mn and V ions are trivalent; moreover, the Mn3+ ions are in a high-spin state, which is the reason that the compound is not a half-metallic antiferromagnet.Comment: 15 pages, 6 figure

Minimal charge gap in the ionic Hubbard model

We study the ionic Hubbard model at temperature T=0 within the mean-field approximation, and show that the charge gap does not close completely at the ionic-band insulator to antiferromagnetic insulator transition, contrary to previous expectations. Furthermore, we find an intermediate phase for on-site repulsions $U>U_c$ for different lattices, and calculate the phase diagram for the ionic Hubbard model with alternating U, corresponding to a Cu-O lattice.Comment: 5 pages with 7 figures; minor correction

Spin-dependent transport in metal/semiconductor tunnel junctions

This paper describes a model as well as experiments on spin-polarized tunnelling with the aid of optical spin orientation. This involves tunnel junctions between a magnetic material and gallium arsenide (GaAs), where the latter is optically excited with circularly polarized light in order to generate spin-polarized carriers. A transport model is presented that takes account of carrier capture in the semiconductor surface states, and describes the semiconductor surface in terms of a spin-dependent energy distribution function. The so-called surface spin-splitting can be calculated from the balance of the polarized electron and hole flow in the semiconductor subsurface region, the polarized tunnelling current across the tunnel barrier between the magnetic material and the semiconductor surface, and the spin relaxation at the semiconductor surface. Measurements are presented of the circular-polarization-dependent photocurrent (the so-called helicity asymmetry) in thin-film tunnel junctions of Co/Al2O3/GaAs. In the absence of a tunnel barrier, the helicity asymmetry is caused by magneto-optical effects (magnetic circular dichroism). In the case where a tunnel barrier is present, the data cannot be explained by magneto-optical effects alone; the deviations provide evidence that spin-polarized tunnelling due to optical spin orientation occurs. In Co/τ-MnAl/AlAs/GaAs junctions no deviations from the magneto-optical effects are observed, most probably due to the weak spin polarization of τ-MnAl along the tunnelling direction; the latter is corroborated by bandstructure calculations. Finally, the application of photoexcited GaAs for spin-polarized tunnelling in a scanning tunnelling microscope is discussed.

Bipolar Magnetic Semiconductors: A New Class of Spintronics Materials

Electrical control of spin polarization is very desirable in spintronics, since electric field can be easily applied locally in contrast with magnetic field. Here, we propose a new concept of bipolar magnetic semiconductor (BMS) in which completely spin-polarized currents with reversible spin polarization can be created and controlled simply by applying a gate voltage. This is a result of the unique electronic structure of BMS, where the valence and conduction bands possess opposite spin polarization when approaching the Fermi level. Our band structure and spin-polarized electronic transport calculations on semi-hydrogenated single-walled carbon nanotubes confirm the existence of BMS materials and demonstrate the electrical control of spin-polarization in them.Comment: 20 pages, 6 figures, accepted by Nanoscal

Half-metallic antiferromagnets in thiospinels

We have theoretically designed the half-metallic (HM) antiferromagnets (AFMs) in thiospinel systems, $\rm Mn(CrV)S_{4}$ and $\rm Fe_{0.5}Cu_{0.5}(V_{0.5}Ti_{1.5})S_{4}$, based on the electronic structure studies in the local-spin-density approximation (LSDA). We have also explored electronic and magnetic properties of parent spinel compounds of the above systems; $\rm CuV_{2}S_{4}$ and $\rm CuTi_{2}S_{4}$ are found to be HM ferromagnets in their cubic spinel structures, while $\rm MnCr_{2}S_{4}$ is a ferrimagnetic insulator. We have discussed the feasibility of material synthesis of HM-AFM thiospinel systems.Comment: 4 pages, 5 figure

Half-metallic Antiferromagnet BaCrFeAs2

First-principles calculations and a tight-binding analysis predict that the iron-pnictide BaCrFeAs2 is a promising candidate for half-metallic material with fully-compensated magnetization. The transition-metal ions Cr and Fe prefer the three-dimensional intervening lattice, which yields the antiferromagnetic order of spin orientations. Due to the difference between Cr and Fe in the electronegativity, a band gap is opened at the Fermi level in the spin channel in which Fe provides the majority carriers. The selective hybridization between 3d orbitals of Cr and As:4p states due to the peculiar lattice structure of the iron-pnictide is shown to be crucial for the novel properties.Comment: added reference

Transport, optical and electronic properties of the half metal CrO2

The electronic structure of CrO_2 is critically discussed in terms of the relation of existing experimental data and well converged LSDA and GGA calculations of the electronic structure and transport properties of this half metal magnet, with a particular emphasis on optical properties. We find only moderate manifestations of many body effects. Renormalization of the density of states is not large and is in the typical for transition metals range. We find substantial deviations from Drude behavior in the far-infrared optical conductivity. These appear because of the unusually low energy of interband optical transitions. The calculated mass renormalization is found to be rather sensitive to the exchange-correlation functional used and varies from 10% (LSDA) to 90% (GGA), using the latest specific heat data. We also find that dressing of the electrons by spin fluctuations, because of their high energy, renormalizes the interband optical transition at as high as 4 eV by about 20%. Although we find no clear indications of strong correlations of the Hubbard type, strong electron-magnon scattering related to the half metallic band structure is present and this leads to a nontrivial temperature dependence of the resistivity and some renormalization of the electron spectra.Comment: 9 Revtex 2 column pages, including 8 postscript figures. Two more figures are included in the submission that are not embedded in the paper, representing DOS and bandstructure of the paramagnetic CrO

Half-metallic antiferromagnets in double perovskites: LaAVRuO6_6 (A=Ca, Sr, and Ba)

Based on the theoretical exploration of electronic structures, we propose that the ordered double perovskites LaAVRuO$_6$ and LaVO$_3$/ARuO$_3$ (001) superlattice (A = Ca, Sr and Ba) are strong candidates for half-metallic (HM) antiferromagnets (AFMs). %LaAVRuO$_6$ and LaVO$_3$/ARuO$_3$ have the %100% spin polarizations at the Fermi level but with zero %total magnetic moments. We have shown that the HM-AFM nature in LaAVRuO$_6$ is very robust regardless of (i) divalent ion replacement at A-sites, (ii) oxygen site relaxation, (iii) the inclusion of the Coulomb correlation, and (iv) cation disorder. A type of the double exchange interaction is expected to be responsible for the half-metallicity and the antiferromagnetism in these systems.Comment: 4 pages, 4 figure

Bronnen van antibioticaresistentie in het milieu en mogelijke maatregelen

Het RIVM heeft in samenwerking met andere instituten onderzocht hoeveel resistente bacteriën via afvalwater in het Nederlandse oppervlaktewater terechtkomen. Afvalwater is, naast mest, de belangrijkste bron waardoor antibioticaresistente bacteriën in het milieu belanden. In 60 tot 100% van het onderzochte afvalwater zitten bijzonder resistente micro-organismen(BMRO), zoals ESBL-producerende E. coli en carbapenemresistente Enterobacteriaceae. Daarnaast zijn resten van antibiotica in het afvalwater gevonden. Mensen kunnen aan resistente bacteriën in het milieu worden blootgesteld, bijvoorbeeld als zij in contact komen met water waarop gezuiverd afvalwater wordt geloosd. Vooralsnog is het onduidelijk hoe groot de bijdrage van deze blootstelling is ten opzichte van andere blootstellingsroutes, en wat de gevolgen daarvan voor de volksgezondheid zijn. Daarvoor wordt aanvullend onderzoek aanbevolen. Duidelijk is wel dat mensen naast blootstelling via het milieu, ook door andere bronnen kunnen worden blootgesteld aan antibioticaresistente bacteriën, bijvoorbeeld tijdens reizen naar landen in Azië of Zuid-Amerika. Door de huidige behandeling van afvalwater nemen de concentraties van antibioticaresistente bacteriën af. Er bestaan aanvullende zuiveringstechnieken voor afvalwater die het aantal antibioticaresistente bacteriën in het oppervlaktewater nog verder kunnen verminderen. Ook de concentraties van resistente bacteriën in mest kunnen door aanvullende zuiveringstechnieken verminderd worden.In collaboration with other institu tions , RIVM investigated how many resistant bacteria enter Dutch surface water s from waste water treatment plants. Next to manure, waste water is the main source of resistant bacteria in the environment. Resistant bacteria of particular public health concern, including ESBL -producing E. coli and carbapenem resistant Enterobacteriace ae, have been found in 60 -100% of all investigated waste water samples. Antibiotics themselves have also been found in waste water. Human exposure to resistant bacteria is possible, for example, upon contact with surface water which receives waste water treatment plant effluent. So far, the contribution of this exposure to the total exposure to resistant bacteria is unknown, as are the effects of this exposure on public health. Additional research is therefore recommended. Humans can also be exposed to resistant bacteria via other routes, such as travel to Asian or Latin American. The current treatment of waste water reduces the concen trations of resistant bacteria. Advanced techniques are available which can decrease the amounts of resistant bacteria further. Options for the reduction of resistant bacteria also exist for the treatment of manure