1,657 research outputs found
Uranium distribution as a proxy for basin-scale fluid flow in distributive fluvial systems
This work was supported by the Fluvial Systems Research Group sponsors BG Group, BP, Chevron, ConocoPhilips, and Total. We thank reviews from Martin Stokes, an anonymous reviewer and Editor Stuart Jones.Peer reviewedPostprin
Quantification of a distributive fluvial system; the Salt Wash DFS of the Morrison Formation, SW USA
Peer reviewedPostprin
Adsorbed 3d transition metal atoms and clusters on Au(111):Signatures derived from one electron calculations
The spectroscopic characteristics of systems with adsorbed d impurities on
noble metal surfaces should depend on the number and geometric arrangement of
the adsorbed atoms and also on their d band filling. Recent experiments using
scanning tunneling microscopy have probed the electronic structure of all 3d
transition metal impurities and also of Co dimers adsorbed on Au(111),
providing a rich variety of results. In this contribution we correlate those
experimental results with ab-initio calculations and try to establish necessary
conditions for observing a Kondo resonance when using the single impurity
Anderson model. We find that the relevant orbitals at the STM tip position,
when it is on top of an impurity, are the dThe spectroscopic characteristics of
systems with adsorbed d impurities on noble metal surfaces should depend on the
number and geometric arrangement of the adsorbed atoms and also on their d band
filling. Recent experiments using scanning tunneling microscopy have probed the
electronic structure of all 3d transition metal impurities and also of Co
dimers adsorbed on Au(111), providing a rich variety of results. In this
contribution we correlate those experimental results with ab-initio
calculations and try to establish necessary conditions for observing a Kondo
resonance when using the single impurity Anderson model. We find that the
relevant orbitals at the STM tip position, when it is on top of an impurity,
are the d orbitals with m=0 and that the energy of these levels with respect to
the Fermi energy determines the possibility of observing a spectroscopic
feature due to the impurity. orbitals with m=0 and that the energy of these
levels with respect to the Fermi energy determines the possibility of observing
a spectroscopic feature due to the impurity
Controls on the apex location of large deltas
Acknowledgements and Funding We would like to acknowledge the sponsors of the Fluvial Systems Research Group consortium BP, BG, Chevron, ConocoPhillips and Total. We would like to thank A. Felicia for image generation and database management.Peer reviewedPublisher PD
Impurities, Quantum Interference and Quantum Phase Transitions in s-wave superconductors
We study the effects of quantum interference in impurity structures
consisting of two or three magnetic impurities that are located on the surface
of an s-wave superconductor. By using a self-consistent Bogoliubov-de Gennes
formalism, we show that quantum interference leads to characteristic signatures
not only in the local density of states (LDOS), but also in the spatial form of
the superconducting order parameter. We demonstrate that the signatures of
quantum interference in the LDOS are qualitatively, and to a large extent
quantitatively unaffected by the suppression of the superconducting order
parameter near impurities, which illustrates the robustness of quantum
interference phenomena. Moreover, we show that by changing the interimpurity
distance, or the impurities' scattering strength, the s-wave superconductor can
be tuned through a series of first order quantum phase transitions in which the
spin polarization of its ground state changes. In contrast to the single
impurity case, this transition is not necessarily accompanied by a -phase
shift of the order parameter, and can in certain cases even lead to its
enhancement. Our results demonstrate that the superconductor's LDOS, its spin
state, and the spatial form of the superconducting order parameter are
determined by a subtle interplay between the relative positions of the
impurities and their scattering strength
Vertical trends within the prograding Salt Wash distributive fluvial system, SW USA
This work has been supported by the Fluvial Systems Research Group Consortium Phase 1, supported by BG, Chevron, Conoco Philips and Total. Discussions with John Howell on prograding sequences are greatly appreciated. The authors would also like to thank Anna Kulikova, Guy Prince, Kelsey McNamara and Karen Oud for assistance in the ļ¬eld. We thank reviewer Brian Willis, an anonymous reviewer and Editor Sebastien Castelltort for constructive comments that improved this manuscript.Peer reviewedPostprin
Highly neurotic never-depressed students have negative biases in information processing
BACKGROUND: Cognitive theories associate depression with negative biases in information processing. Although negatively biased cognitions are well documented in depressed patients and to some extent in recovered patients, it remains unclear whether these abnormalities are present before the first depressive episode. METHOD: High neuroticism (N) is a well-recognized risk factor for depression. The current study therefore compared different aspects of emotional processing in 33 high-N never-depressed and 32 low-N matched volunteers. Awakening salivary cortisol, which is often elevated in severely depressed patients, was measured to explore the neurobiological substrate of neuroticism. RESULTS: High-N volunteers showed increased processing of negative and/or decreased processing of positive information in emotional categorization and memory, facial expression recognition and emotion-potentiated startle (EPS), in the absence of global memory or executive deficits. By contrast, there was no evidence for effects of neuroticism on attentional bias (as measured with the dot-probe task), over-general autobiographical memory, or awakening cortisol levels. CONCLUSIONS: These results suggest that certain negative processing biases precede depression rather than arising as a result of depressive experience per se and as such could in part mediate the vulnerability of high-N subjects to depression. Longitudinal studies are required to confirm that such cognitive vulnerabilities predict subsequent depression in individual subjects
Theory of STM Spectroscopy of Kondo Ions on Metal Surfaces
The conduction electron density of states nearby a single magnetic impurity,
as measured recently by scanning tunneling microscopy (STM), is calculated. It
is shown that the Kondo effect induces a narrow Fano resonance as an intrinsic
feature in the conduction electron density of states. The line shape varies
with the distance between STM tip and impurity, in qualitative agreement with
experiments, and is sensitive to details of the band structure. For a Co
impurity the experimentally observed width and shift of the Kondo resonance are
in accordance with those obtained from a combination of band structure and
strongly correlated calculations.Comment: 5 pages, 4 figures, presented at the NATO Advanced Research Workshop
on "Size Dependent Magnetic Scattering", Pecs, Hungary, May 28 - June 1, 200
- ā¦