13,744 research outputs found
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
Epidermal growth factor (EGF)-like repeats of human tenascin-C as ligands for EGF receptor.
Signaling through growth factor receptors controls such diverse cell functions as proliferation, migration, and differentiation. A critical question has been how the activation of these receptors is regulated. Most, if not all, of the known ligands for these receptors are soluble factors. However, as matrix components are highly tissue-specific and change during development and pathology, it has been suggested that select growth factor receptors might be stimulated by binding to matrix components. Herein, we describe a new class of ligand for the epidermal growth factor (EGF) receptor (EGFR) found within the EGF-like repeats of tenascin-C, an antiadhesive matrix component present during organogenesis, development, and wound repair. Select EGF-like repeats of tenascin-C elicited mitogenesis and EGFR autophosphorylation in an EGFR-dependent manner. Micromolar concentrations of EGF-like repeats induced EGFR autophosphorylation and activated extracellular signal-regulated, mitogen-activated protein kinase to levels comparable to those induced by subsaturating levels of known EGFR ligands. EGFR-dependent adhesion was noted when the ligands were tethered to inert beads, simulating the physiologically relevant presentation of tenascin-C as hexabrachion, and suggesting an increase in avidity similar to that seen for integrin ligands upon surface binding. Specific binding to EGFR was further established by immunofluorescence detection of EGF-like repeats bound to cells and cross-linking of EGFR with the repeats. Both of these interactions were abolished upon competition by EGF and enhanced by dimerization of the EGF-like repeat. Such low affinity behavior would be expected for a matrix-tethered ligand; i.e., a ligand which acts from the matrix, presented continuously to cell surface EGF receptors, because it can neither diffuse away nor be internalized and degraded. These data identify a new class of insoluble growth factor ligands and a novel mode of activation for growth factor receptors
Stochastic Dominance Analysis of Bioenergy Crops as a Production Alternative on an East Tennessee Beef and Crop Farm
This study evaluated prices and incentives for switchgrass stated in a biorefinery’s contract terms that induce switchgrass production on an east Tennessee representative farm when compared with traditional enterprises. The alternate contract terms imitated current subsidies/incentives offered as well as incentives and cost share terms not in the BCAP.switchgrass, contract, risk aversion, net return, Farm Management, Production Economics, Resource /Energy Economics and Policy, Q12,
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
Phase Field Modeling of Fracture and Stress Induced Phase Transitions
We present a continuum theory to describe elastically induced phase
transitions between coherent solid phases. In the limit of vanishing elastic
constants in one of the phases, the model can be used to describe fracture on
the basis of the late stage of the Asaro-Tiller-Grinfeld instability. Starting
from a sharp interface formulation we derive the elastic equations and the
dissipative interface kinetics. We develop a phase field model to simulate
these processes numerically; in the sharp interface limit, it reproduces the
desired equations of motion and boundary conditions. We perform large scale
simulations of fracture processes to eliminate finite-size effects and compare
the results to a recently developed sharp interface method. Details of the
numerical simulations are explained, and the generalization to multiphase
simulations is presented
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
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
A Preliminary Report on Unique Hail and Tornadic Storm Observations in Central Illinois and Eastern Indiana on 3 April 1974
published or submitted for publicationis peer reviewedOpe
Spin-controlled Mott-Hubbard bands in LaMnO_3 probed by optical ellipsometry
Spectral ellipsometry has been used to determine the dielectric function of
an untwinned crystal of LaMnO_3 in the spectral range 0.5-5.6 eV at
temperatures 50 K < T < 300 K. A pronounced redistribution of spectral weight
is found at the Neel temperature T_N = 140 K. The anisotropy of the spectral
weight transfer matches the magnetic ordering pattern. A superexchange model
quantitatively describes spectral weight transfer induced by spin correlations.
This analysis implies that the lowest-energy transitions around 2 eV are
intersite d-d transitions, and that LaMnO_3 is a Mott-Hubbard insulator.Comment: 4 pages, 4 figure
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