3,114 research outputs found
Elastic contact to a coated half-space - Effective elastic modulus and real penetration
A new approach to the contact to coated elastic materials is presented. A
relatively simple numerical algorithm based on an exact integral formulation of
the elastic contact of an axisymmetric indenter to a coated substrate is
detailed. It provides contact force and penetration as a function of the
contact radius. Computations were carried out for substrate to layer moduli
ratios ranging from 0.01 to 100 and various indenter shapes. Computed
equivalent moduli showed good agreement with the Gao model for mismatch ratios
ranging from 0.5 to 2. Beyond this range, substantial effects of inhomogeneous
strain istribution are evidenced. An empirical function is proposed to fit the
equivalent modulus. More importantly, if the indenter is not flat-ended, the
simple relation between contact radius and penetration valid for homogeneous
substrates breaks down. If neglected, this phenomenon leads to significant
errors in the evaluation of the contact radius in depth-sensing indentation on
coated substrates with large elastic modulus mismatch
Environment of compact extragalactic radio sources
We have studied the interrelation of young AGN with their hosts. The objects
of study are the young and powerful GPS and CSS radio sources. Due to their
small size, GPS and CSS sources are excellent probes of this relation.
Furhthermore, their young age allows us to compare them to the larger, old
radio sources and establish a time-line evolution of this relation. Combining
imaging and spectroscopy at UV, optical and radio wavelengths we find evidence
of strong interaction between the host and the radio source. The presence and
expansion of the radio source clearly affects the properties and evolution of
the host. Furthermore, the radio source and host significantly affect each
other's evolution. We describe our results and how these interactions take
place.Comment: 6 pages. To appear in "Highlights of Spanisg astrophysics IV.
Proceedings of the VII scientific meeting of the Spanish Astronomical
Society". Editors: F. Figueras, J.M. Girart, M.Hernanz, C. Jordi. Springe
Are forgiving people less likely to experience cognitive dissonance?
People differ in the degree to which they are able and willing to forgive themselves after they have committed a transgression against another person (Thompson et al., 2005). The purpose of the current study was to see if individuals with lower levels of dispositional forgiveness would experience more attitude change toward a boring task than those who have higher levels of dispositional forgiveness, as a result of cognitive dissonance being induced. Participants completed a boring task that involved moving beads back and forth on an abacus, and then were either asked or told to mislead the next participant by telling them that the task was enjoyable in order to induce cognitive dissonance in the participant. They were then asked to complete a questionnaire designed to measure their attitudes toward the abacus task. It was predicted that the participants with lower levels of dispositional forgiveness would end with more positive attitudes toward the abacus task than those with higher levels of dispositional forgiveness. The study did not yield any statistically significant results. The limitations of the study will be discussed
Interlaced Dynamical Decoupling and Coherent Operation of a Singlet-Triplet Qubit
We experimentally demonstrate coherence recovery of singlet-triplet
superpositions by interlacing qubit rotations between Carr-Purcell (CP) echo
sequences. We then compare performance of Hahn, CP, concatenated dynamical
decoupling (CDD) and Uhrig dynamical decoupling (UDD) for singlet recovery. In
the present case, where gate noise and drift combined with spatially varying
hyperfine coupling contribute significantly to dephasing, and pulses have
limited bandwidth, CP and CDD yield comparable results, with T2 ~ 80
microseconds.Comment: related papers at http://marcuslab.harvard.ed
Rapid Single-Shot Measurement of a Singlet-Triplet Qubit
We report repeated single-shot measurements of the two-electron spin state in
a GaAs double quantum dot. The readout scheme allows measurement with fidelity
above 90% with a 7 microsecond cycle time. Hyperfine-induced precession between
singlet and triplet states of the two-electron system are directly observed, as
nuclear Overhauser fields are quasi-static on the time scale of the measurement
cycle. Repeated measurements on millisecond to second time scales reveal
evolution of the nuclear environment.Comment: supplemental material at
http://marcuslab.harvard.edu/papers/single_shot_sup.pd
On the comparison of stable and unstable P-completion
In this note we show that a p-complete nilpotent space X has a p-complete suspension spectrum if and only if its homotopy groups pi X-* are bounded p-torsion. In contrast, if pi X-* is not all bounded p-torsion, we locate uncountable rational vector spaces in the integral homology and in the stable homotopy groups of X. To prove this, we establish a homological criterion for p-completeness of connective spectra. Moreover, we illustrate our results by studying the stable homotopy groups of K(Z(p), n) via Goodwillie calculus
Hyperfine-mediated gate-driven electron spin resonance
An all-electrical spin resonance effect in a GaAs few-electron double quantum
dot is investigated experimentally and theoretically. The magnetic field
dependence and absence of associated Rabi oscillations are consistent with a
novel hyperfine mechanism. The resonant frequency is sensitive to the
instantaneous hyperfine effective field, and the effect can be used to detect
and create sizable nuclear polarizations. A device incorporating a micromagnet
exhibits a magnetic field difference between dots, allowing electrons in either
dot to be addressed selectively.Comment: related papers available at http://marcuslab.harvard.ed
Many-body effects on Cr(001) surfaces: An LDA+DMFT study
The electronic structure of the Cr(001) surface with its sharp resonance at
the Fermi level is a subject of controversial debate of many experimental and
theoretical works. To date, it is unclear whether the origin of this resonance
is an orbital Kondo or an electron-phonon coupling effect. We have combined ab
initio density functional calculations with dynamical mean-field simulations to
calculate the orbitally resolved spectral function of the Cr(001) surface. The
calculated orbital character and shape of the spectrum is in agreement with
data from (inverse) photoemission experiments. We find that dynamic electron
correlations crucially influence the surface electronic structure and lead to a
low energy resonance in the and orbitals. Our results
help to reconvene controversial experimental results from (I)PES and STM
measurements.Comment: 8 pages, 5 figure
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