NONFARM INVESTORS AND BEEF BREEDING HERDS -- INCENTIVES AND CONSEQUENCES

Livestock Production/Industries,

Critical Review: The Treatment of Syphilis

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Effect of strain on the orbital and magnetic ordering of manganite thin films and their interface with an insulator

We study the effect of uniform uniaxial strain on the ground state electronic configuration of a thin film manganite. Our model Hamiltonian includes the double-exchange, the Jahn-Teller electron-lattice coupling, and the antiferromagnetic superexchange. The strain arises due to the lattice mismatch between an insulating substrate and a manganite which produces a tetragonal distortion. This is included in the model via a modification of the hopping amplitude and the introduction of an energy splitting between the Mn e_g levels. We analyze the bulk properties of half-doped manganites and the electronic reconstruction at the interface between a ferromagnetic and metallic manganite and the insulating substrate. The strain drives an orbital selection modifying the electronic properties and the magnetic ordering of manganites and their interfaces.Comment: 8 pages, 8 figure

Study of Chromium-Frit-Type Coatings for High-Temperature Protection of Molybdenum

The achievement of more compact and efficient power plants for aircraft is dependent, among other factors, on the perfection of heat-resisting materials that are superior to those in current use. Molybdenum is one of the high-melting metals (melting point, 4750 F). It is fairly abundant and also can be worked into many of the shapes required in modern power plants. To permit its widespread use at elevated temperatures, however, some means must first be found to prevent its rapid oxidation. The application of a protective coating is one method that might be used to achieve this goal. In the present work, a number of chromium-frit-type coatings were studied. These were bonded to molybdenum specimens by firing in controlled atmospheres to temperatures in the range of 2400 to 2700 F

Theoretical investigation of magnetoelectric effects in Ba2CoGe2O7

A joint theoretical approach, combining macroscopic symmetry analysis with microscopic methods (density functional theory and model cluster Hamiltonian), is employed to shed light on magnetoelectricity in Ba2CoGe2O7. We show that the recently reported experimental trend of polarization guided by magnetic field can be predicted on the basis of phenomenological Landau theory. From the microscopic side, Ba2CoGe2O7 emerges as a prototype of a class of magnetoelectrics, where the cross coupling between magnetic and dipolar degrees of freedom needs, as main ingredients, the on-site spin-orbit coupling and the spin-dependent O p - Co d hybridization, along with structural constraints related to the noncentrosymmetric structural symmetry and the peculiar configuration of CoO4 tetrahedrons.Comment: 5 pages, 4 figures, submitted for publicatio

Frequencies of infaunal invertebrates related to water content of Chesapeake Bay sediments

The following relationship was investigated for a total of 44 stations, using sequential (linear) multiregression analysis: A = f (D, S a , S., C, M , S , W) where A = the frequency of an infauna! invertebrate species, D : water depth at the station, Sa = per cent sand, Si =percent silt, C = per cent clay, Mz = mean grain size, S o = sediment Sorting Coefficient, and W = water content. Three animals were chosen for the dependent variable: Ensis directus, Nephtys incisa, and Retusa canaliculata. Results of the least-squares search procedure indicate that if the water content is carefully determined this variable always appears as one of the most important, when the independent variables are considered in combinations of two or three at a time. The implication is that water content, a mass property of the sediment that reflects the interrelationships of mean grain size, sorting, grain packing, and mineralogy, is a highly useful environmental variable that should be measured in studies that attempt to establish animal-sediment relationships

Scanning tunneling microscopy simulations of poly(3-dodecylthiophene) chains adsorbed on highly oriented pyrolytic graphite

We report on a novel scheme to perform efficient simulations of Scanning Tunneling Microscopy (STM) of molecules weakly bonded to surfaces. Calculations are based on a tight binding (TB) technique including self-consistency for the molecule to predict STM imaging and spectroscopy. To palliate the lack of self-consistency in the tunneling current calculation, we performed first principles density-functional calculations to extract the geometrical and electronic properties of the system. In this way, we can include, in the TB scheme, the effects of structural relaxation upon adsorption on the electronic structure of the molecule. This approach is applied to the study of regioregular poly(3-dodecylthiophene) (P3DDT) polymer chains adsorbed on highly oriented pyrolytic graphite (HOPG). Results of spectroscopic calculations are discussed and compared with recently obtained experimental datComment: 15 pages plus 5 figures in a tar fil

Origin of electron-hole asymmetry in the scanning tunneling spectrum of Bi2Sr2CaCu2O8+δBi_2Sr_2CaCu_2O_{8+\delta}

We have developed a material specific theoretical framework for modelling scanning tunneling spectroscopy (STS) of high temperature superconducting materials in the normal as well as the superconducting state. Results for $Bi_2Sr_2CaCu_2O_{8+\delta}$ (Bi2212) show clearly that the tunneling process strongly modifies the STS spectrum from the local density of states (LDOS) of the $d_{x^2-y^2}$ orbital of Cu. The dominant tunneling channel to the surface Bi involves the $d_{x^2-y^2}$ orbitals of the four neighbouring Cu atoms. In accord with experimental observations, the computed spectrum displays a remarkable asymmetry between the processes of electron injection and extraction, which arises from contributions of Cu $d_{z^2}$ and other orbitals to the tunneling current.Comment: 5 pages, 4 figures, published in PR

Temperature-dependent resistivity of suspended graphene

In this paper we investigate the electron-phonon contribution to the resistivity of suspended single layer graphene. In-plane as well as flexural phonons are addressed in different temperature regimes. We focus on the intrinsic electron-phonon coupling due to the interaction of electrons with elastic deformations in the graphene membrane. The competition between screened deformation potential vs fictitious gauge field coupling is discussed, together with the role of tension in the suspended flake. In the absence of tension, flexural phonons dominate the phonon contribution to the resistivity at any temperature $T$ with a $T^{5/2}_{}$ and $T^{2}_{}$ dependence at low and high temperatures, respectively. Sample-specific tension suppresses the contribution due to flexural phonons, yielding a linear temperature dependence due to in-plane modes. We compare our results with recent experiments.Comment: 11 pages, 3 figure