8,377 research outputs found
Valley Carrier Dynamics in Monolayer Molybdenum Disulphide from Helicity Resolved Ultrafast Pump-probe Spectroscopy
We investigate the valley related carrier dynamics in monolayer MoS2 using
helicity resolved non-degenerate ultrafast pump-probe spectroscopy at the
vicinity of the high-symmetry K point under the temperature down to 78 K.
Monolayer MoS2 shows remarkable transient reflection signals, in stark contrast
to bilayer and bulk MoS2 due to the enhancement of many-body effect at reduced
dimensionality. The helicity resolved ultrafast time-resolved result shows that
the valley polarization is preserved for only several ps before scattering
process makes it undistinguishable. We suggest that the dynamical degradation
of valley polarization is attributable primarily to the exciton trapping by
defect states in the exfoliated MoS2 samples. Our experiment and a
tight-binding model analysis also show that the perfect valley CD selectivity
is fairly robust against disorder at the K point, but quickly decays from the
high-symmetry point in the momentum space in the presence of disorder.Comment: 15 pages,Accepted by ACS Nan
Periodic Radio Variability in NRAO 530: Phase Dispersion Minimization Analysis
In this paper, a periodicity analysis of the radio light curves of the blazar
NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved Phase
Dispersion Minimization (PDM) technique. The result, which shows two persistent
periodic components of and years at all three frequencies,
is consistent with the results obtained with the Lomb-Scargle periodogram and
weighted wavelet Z-transform algorithms. The reliability of the derived
periodicities is confirmed by the Monte Carlo numerical simulations which show
a high statistical confidence. (Quasi-)Periodic fluctuations of the radio
luminosity of NRAO 530 might be associated with the oscillations of the
accretion disk triggered by hydrodynamic instabilities of the accreted flow.
\keywords{methods: statistical -- galaxies: active -- galaxies: quasar:
individual: NRAO 530}Comment: 8 pages, 5 figures, accepted by RA
Multiple Parton Scattering in Nuclei: Twist-Four Nuclear Matrix Elements and Off-Forward Parton Distributions
Multiple parton scatterings inside a large nucleus generally involve
higher-twist nuclear parton matrix elements. The gluon bremsstrahlung induced
by multiple scattering depends not only on direct parton matrix elements but
also on momentum-crossed ones, due to the Landau-Pomeranchuk-Migdal
interference effect. We show that both types of twist-four nuclear parton
matrix elements can be factorized approximately into the product of twist-two
nucleon matrix elements in the limit of extremely large nuclei, ,
as assumed in previous studies. Due to the correlative nature of the twist-four
matrix elements under consideration, it is actually the off-forward parton
distributions that appear naturally in this decomposition, rather than the
ordinary diagonal distributions probed in deeply-inelastic scattering. However,
we argue that the difference between these two distribution classes is small in
certain kinematic regimes. In these regions, the twist-four nuclear parton
matrix elements are evaluated numerically and compared to the factorized form
for different nuclear sizes within a schematic model of the two-nucleon
correlation function. The nuclear size dependence is found to be in
the limit of large , as expected. We find that the factorization is
reasonably good when the momentum fraction carried by the gluon field is
moderate. The deviation can be more than a factor of 2, however, for small
gluon momentum fractions, where the gluon distribution is very large.Comment: 23 pages, 7 figures, minor correction
Scale Dependence of Twist-3 Quark-Gluon Operators for Single Spin Asymmetries
We derive the scale dependence of twist-3 quark-gluon operators, or ETQS
matrix elements, at one-loop. These operators are used to factorize transverse
single spin asymmetries, which are studied intensively both in experiment and
theory. The scale dependence of two special cases are particularly interesting.
One is of soft-gluon-pole matrix elements, another is of soft-quark-pole matrix
elements. From our results the evolutions in the two cases can be obtained. A
comparison with existing results of soft-gluon-pole matrix elements is made.Comment: typo in Eq.(10) corrected, references adde
Cerebellar Functional Parcellation Using Sparse Dictionary Learning Clustering
10.3389/fnins.2016.00188Frontiers in neuroscience10188GUSTO (Growing up towards Healthy Outcomes
An Embedding-based Approach to Inconsistency-tolerant Reasoning with Inconsistent Ontologies
Inconsistency handling is an important issue in knowledge management.
Especially in ontology engineering, logical inconsistencies may occur during
ontology construction. A natural way to reason with an inconsistent ontology is
to utilize the maximal consistent subsets of the ontology. However, previous
studies on selecting maximum consistent subsets have rarely considered the
semantics of the axioms, which may result in irrational inference. In this
paper, we propose a novel approach to reasoning with inconsistent ontologies in
description logics based on the embeddings of axioms. We first give a method
for turning axioms into distributed semantic vectors to compute the semantic
connections between the axioms. We then define an embedding-based method for
selecting the maximum consistent subsets and use it to define an
inconsistency-tolerant inference relation. We show the rationality of our
inference relation by considering some logical properties. Finally, we conduct
experiments on several ontologies to evaluate the reasoning power of our
inference relation. The experimental results show that our embedding-based
method can outperform existing inconsistency-tolerant reasoning methods based
on maximal consistent subsets.Comment: 9 pages,1 figur
Nonlinear vibrations of beams with spring and damping delayed feedback control
The primary, subharmonic, and superharmonic resonances of an Euler–Bernoulli beam subjected to harmonic excitations are studied with damping and spring delayed-feedback controllers. By method of multiple scales, the non-linear governing partial differential equation is transformed into linear differential equations directly. Effects of the feedback gains and time-delays on the steady state responses are investigated. The velocity and displacement delayed-feedback controllers are employed to suppress the primary and superharmonic resonances of the forced nonlinear oscillator. The stable vibration regions of the feedback gains and time-delays are worked out based on stablility conditions of the resonances. It is found that proper selection of feedback gains and time-delays can enhance the control performance of beam’s nonlinear vibration. Position of the bifurcation point can be changed or the bifurcation can be eliminated
5,5′,5′′-Triphenyl-2,2′,2′′-[2,4,6-trimethylbenzene-1,3,5-triyltris(methylidenesulfanediyl)]tris(1,3,4-oxadiazole)
In the title compound, C36H30N6O3S3, the phenyl rings are twisted from the attached oxadiazole rings in the three arms by 1.5(2), 2.4 (2) and 25.7 (2)°. The crystal packing exhibits weak intermolecular C—H⋯N interactions
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