Spin state transition in LaCoO3 by variational cluster approximation

The variational cluster approximation is applied to the calculation of thermodynamical quantities and single-particle spectra of LaCoO3. Trial self-energies and the numerical value of the Luttinger-Ward functional are obtained by exact diagonalization of a CoO6 cluster. The VCA correctly predicts LaCoO3 as a paramagnetic insulator and a gradual and relatively smooth increase of the occupation of high-spin Co3+ ions causes the temperature dependence of entropy and magnetic susceptibility. The single particle spectral function agrees well with experiment, the experimentally observed temperature dependence of photoelectron spectra is reproduced satisfactorily. Remaining discrepancies with experiment highlight the importance of spin orbit coupling and local lattice relaxation.Comment: Revtex file with 10 eps figure

Kondo resonance line-shape of magnetic adatoms on decoupling layers

The zero-bias resonance in the dI/dV tunneling spectrum recorded using a scanning tunneling microscope above a spin-1/2 magnetic adatom (such as Ti) adsorbed on a decoupling layer on metal surface can be accurately fitted using the universal spectral function of the Kondo impurity model both at zero field and at finite external magnetic field. Excellent agreement is found both for the asymptotic low-energy part and for the high-energy logarithmic tails of the Kondo resonance. For finite magnetic field, the nonlinear fitting procedure consists in repeatedly solving the impurity model for different Zeeman energies in order to obtain accurate spectral functions which are compared with the experimental dI/dV curves. The experimental results at zero field are sufficiently restraining to enable an unprecedented reliability in the determination of the Kondo temperature, while at finite fields the results are more ambiguous and two different interpretations are proposed

Correlated band structure of NiO, CoO and MnO by variational cluster approximation

The variational cluster approximation proposed by Potthoff is applied to the calculation of the single-particle spectral function of the transition metal oxides MnO, CoO and NiO. Trial self-energies and the numerical value of the Luttinger-Ward functional are obtained by exact diagonalization of a TMO6-cluster. The single-particle parameters of this cluster serve as variational parameters to construct a stationary point of the grand potential of the lattice system. The stationary point is found by a crossover procedure which allows to go continuously from an array of disconnected clusters to the lattice system. The self-energy is found to contain irrelevant degrees of freedom which have marginal impact on the grand potential and which need to be excluded to obtain meaningful results. The obtained spectral functions are in good agreement with experimental data.Comment: 14 pages, 17 figure

On the Interface Between LENS® Deposited Stainless Steel 304L Repair Geometry and Cast or Machined Components

Laser Engineered Net Shaping™ (LENS®) is being evaluated for use as a metal component repair/modification process. A component of the evaluation is to better understand the characteristics of the interface between LENS deposited material and the substrate on which it is deposited. A processing and metallurgical evaluation was made on LENS processed material fabricated for component qualification tests. A process parameter evaluation was used to determine optimum build parameters and these parameters were used in the fabrication of tensile test specimens to study the characteristics of the interface between LENS deposited material and several types of substrates. Analyses of the interface included mechanical properties, microstructure, and metallurgical integrity. Test samples were determined for a variety of geometric configurations associated with interfaces between LENS deposited material and both wrought base material or previously deposited LENS material. Thirteen different interface configurations were fabricated for evaluation representing a spectrum of deposition conditions from complete part build, to hybrid substrate-LENS builds, to repair builds for damaged or re-designed housings. Good mechanical properties and full density were observed for all configurations. When tested to failure, fracture occurred by ductile microvoid coalescence. The repair and hybrid interfaces showed the same metallurgical integrity as, and had properties similar to, monolithic LENS deposits.Mechanical Engineerin

Spectroscopy on two coupled flux qubits

We have performed spectroscopy measurements on two coupled flux qubits. The qubits are coupled inductively, which results in a $\sigma_1^z\sigma_2^z$ interaction. By applying microwave radiation, we observe resonances due to transitions from the ground state to the first two excited states. From the position of these resonances as a function of the magnetic field applied we observe the coupling of the qubits. The coupling strength agrees well with calculations of the mutual inductance

How agricultural cooperatives are taxed

"Many Missouri farmers are members of locally owned or regional agricultural cooperatives. Cooperatives are unique in that the owners are also the patrons of the business. The cooperative's purpose is to provide marketing or supply services to its farmer-owners. Farmers act collectively in this manner to get better terms of trade for their products and to provide themselves services and supplies at cost. Cooperatives often implement the cooperative principle of "service at cost" by refunding earnings to patrons."--First page.J. Brian Griffith and C. Brice Ratchford (Department of Agricultural Economics University of Missouri--Columbia )New 4/86/6

Highly-functionalised difluorinated cyclohexane polyols via the Diels–Alder reaction : regiochemical control via the phenylsulfonyl group

A difluorinated dienophile underwent cycloaddition reactions with a range of furans to afford cycloadducts whichcould be processed regio- and stereoselectively via episulfonium ions, generated by the reaction between their alkenyl groups and phenylsulfenyl chloride. The oxabicyclic products were oxidised to the phenylsulfonyl level and ring opened via E1CB or reductive desulfonative pathways to afford, ultimately, difluorinated cyclohexene or cyclohexane polyols

A handbook for rose growers

Although the current wave of popularity enjoyed by the rose began in the nineteenth century under the sponsorship of the Empress Josephine of France, the rose has been a cherished inhabitant of gardens since earliest times. In this respect it shares the esteem of gardeners with the lily and violet. However, unlike those flowers, its popularity has never waned. Its close association with mankind has led to its inclusion in the customs, languages and cultures of the peoples of the western world. In tribute to its beauty the Greeks gave it the title “Queen of Flowers”—a title which it well deserves if we are to credit the many attempts to grow it in the myriad climates and soils of the earth. The genus Rosa is widely distributed over the north temperate zone. In a plant group whose members are adapted to the many different climates of this broad geographical area, it would be strange indeed if there were not at least one rose which would flourish in almost any given climatic condition. Because the climate of Iowa and its neighboring states is rigorous and highly changeable, certain handicaps are presented to the rose grower living in this area. However, it is possible to select rose varieties that may be grown with a minimum of care in locations suitable for other sun-loving plants. The experienced gardener will carefully study the requirements of his particular situation before choosing the roses to grow in his garden

Basics of Missouri agricultural cooperatives

"In 1983, 105 locally owned agricultural cooperatives operated in Missouri. But although they strongly support the idea of cooperatives, farmers may not fully understand their role in the cooperative or the unique features of cooperatives. They have many questions about members' rights and director and cooperator responsibilities."--First page.J. Brian Griffith and C. Brice Ratchford (Department of Agricultural Economics, University of Missouri--Columbia)New 3/86/6