30,617 research outputs found
Weight function for the quantum affine algebra
We give a precise expression for the universal weight function of the quantum
affine algebra . The calculations use the technique of
projecting products of Drinfeld currents on the intersections of Borel
subalgebras.Comment: 28 page
Angle-resolved photoemission studies of the superconducting gap symmetry in Fe-based superconductors
The superconducting gap is the fundamental parameter that characterizes the
superconducting state, and its symmetry is a direct consequence of the
mechanism responsible for Cooper pairing. Here we discuss about angle-resolved
photoemission spectroscopy measurements of the superconducting gap in the
Fe-based high-temperature superconductors. We show that the superconducting gap
is Fermi surface dependent and nodeless with small anisotropy, or more
precisely, a function of momentum. We show that while this observation is
inconsistent with weak coupling approaches for superconductivity in these
materials, it is well supported by strong coupling models and global
superconducting gaps. We also suggest that the strong anisotropies measured by
other probes sensitive to the residual density of states are not related to the
pairing interaction itself, but rather emerge naturally from the smaller
lifetime of the superconducting Cooper pairs that is a direct consequence of
the momentum dependent interband scattering inherent to these materials.Comment: 7 pages, 5 figure
Characterization of a Reductively-Activated Elimination Pathway Relevant to the Biological Chemistry of the Kinamycins and Lomaiviticins
The lomaiviticins (1 and 2) and kinamycins (3–5) are bacterial metabolites with potent antimicrobial and antiproliferative activities. Herein we establish that 1–5 are capable of generating electrophilic acylfulvene intermediates (6) under mildly reducing conditions. These acylfulvenes 6 are formed by a multistep process comprising two-electron reduction and loss of dinitrogen to form an ortho-quinone methide, followed by elimination. Based on these studies, the structure of the product formed from 1 in DNA-cleavage assays is proposed (26). We also show that the bis(hydroxynaphthoquinone) substructures of the lomaiviticins activate the metabolites toward reduction. Finally, based on COMPARE and time-dependent cell response profiling analyses, we show that kinamycin C (4) and the monomeric lomaiviticin aglycon (24) operate by a mechanism of action that is distinct from simple diazofluorenes, such as 23
Recurrent Coronal Jets Induced by Repetitively Accumulated Electric Currents
Three extreme-ultraviolet (EUV) jets recurred in about one hour on 2010
September 17 in the following magnetic polarity of active region 11106. The EUV
jets were observed by the Atmospheric Imaging Assembly (AIA) on board the Solar
Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board
SDO measured the vector magnetic field, from which we derive the magnetic flux
evolution, the photospheric velocity field, and the vertical electric current
evolution. The magnetic configuration before the jets is derived by the
nonlinear force-free field (NLFFF) extrapolation.
We derive that the jets are above a pair of parasitic magnetic bipoles which
are continuously driven by photospheric diverging flows. The interaction drove
the build up of electric currents that we indeed observed as elongated patterns
at the photospheric level. For the first time, the high temporal cadence of HMI
allows to follow the evolution of such small currents. In the jet region, we
found that the integrated absolute current peaks repetitively in phase with the
171 A flux evolution. The current build up and its decay are both fast, about
10 minutes each, and the current maximum precedes the 171 A by also about 10
minutes. Then, HMI temporal cadence is marginally fast enough to detect such
changes.
The photospheric current pattern of the jets is found associated to the
quasi-separatrix layers deduced from the magnetic extrapolation. From previous
theoretical results, the observed diverging flows are expected to build
continuously such currents. We conclude that magnetic reconnection occurs
periodically, in the current layer created between the emerging bipoles and the
large scale active region field. It induced the observed recurrent coronal jets
and the decrease of the vertical electric current magnitude.Comment: 10 pages, 7 figures, accepted for publication in A&
Large exchange bias after zero-field cooling from an unmagnetized state
Exchange bias (EB) is usually observed in systems with interface between
different magnetic phases after field cooling. Here we report an unusual
phenomenon in which a large EB can be observed in Ni-Mn-In bulk alloys after
zero-field cooling from an unmagnetized state. We propose this is related to
the newly formed interface between different magnetic phases during the initial
magnetization process. The magnetic unidirectional anisotropy, which is the
origin of EB effect, can be created isothermally below the blocking
temperature.Comment: including supplementary information, Accepted by Physical Review
Letter
Heavy Quark diffusion from lattice QCD spectral functions
We analyze the low frequency part of charmonium spectral functions on large
lattices close to the continuum limit in the temperature region as well as for . We present evidence for the
existence of a transport peak above and its absence below . The
heavy quark diffusion constant is then estimated using the Kubo formula. As
part of the calculation we also determine the temperature dependence of the
signature for the charmonium bound state in the spectral function and discuss
the fate of charmonium states in the hot medium.Comment: 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28,
2011, Annecy, Franc
Zero-Shot Deep Domain Adaptation
Domain adaptation is an important tool to transfer knowledge about a task
(e.g. classification) learned in a source domain to a second, or target domain.
Current approaches assume that task-relevant target-domain data is available
during training. We demonstrate how to perform domain adaptation when no such
task-relevant target-domain data is available. To tackle this issue, we propose
zero-shot deep domain adaptation (ZDDA), which uses privileged information from
task-irrelevant dual-domain pairs. ZDDA learns a source-domain representation
which is not only tailored for the task of interest but also close to the
target-domain representation. Therefore, the source-domain task of interest
solution (e.g. a classifier for classification tasks) which is jointly trained
with the source-domain representation can be applicable to both the source and
target representations. Using the MNIST, Fashion-MNIST, NIST, EMNIST, and SUN
RGB-D datasets, we show that ZDDA can perform domain adaptation in
classification tasks without access to task-relevant target-domain training
data. We also extend ZDDA to perform sensor fusion in the SUN RGB-D scene
classification task by simulating task-relevant target-domain representations
with task-relevant source-domain data. To the best of our knowledge, ZDDA is
the first domain adaptation and sensor fusion method which requires no
task-relevant target-domain data. The underlying principle is not particular to
computer vision data, but should be extensible to other domains.Comment: This paper is accepted to the European Conference on Computer Vision
(ECCV), 201
Critical frontier for the Potts and percolation models on triangular-type and kagome-type lattices II: Numerical analysis
In a recent paper (arXiv:0911.2514), one of us (FYW) considered the Potts
model and bond and site percolation on two general classes of two-dimensional
lattices, the triangular-type and kagome-type lattices, and obtained
closed-form expressions for the critical frontier with applications to various
lattice models. For the triangular-type lattices Wu's result is exact, and for
the kagome-type lattices Wu's expression is under a homogeneity assumption. The
purpose of the present paper is two-fold: First, an essential step in Wu's
analysis is the derivation of lattice-dependent constants for various
lattice models, a process which can be tedious. We present here a derivation of
these constants for subnet networks using a computer algorithm. Secondly, by
means of a finite-size scaling analysis based on numerical transfer matrix
calculations, we deduce critical properties and critical thresholds of various
models and assess the accuracy of the homogeneity assumption. Specifically, we
analyze the -state Potts model and the bond percolation on the 3-12 and
kagome-type subnet lattices , , for which the
exact solution is not known. To calibrate the accuracy of the finite-size
procedure, we apply the same numerical analysis to models for which the exact
critical frontiers are known. The comparison of numerical and exact results
shows that our numerical determination of critical thresholds is accurate to 7
or 8 significant digits. This in turn infers that the homogeneity assumption
determines critical frontiers with an accuracy of 5 decimal places or higher.
Finally, we also obtained the exact percolation thresholds for site percolation
on kagome-type subnet lattices for .Comment: 31 pages,8 figure
Chaotic to ordered state transition of cathode-sheath instabilities in DC glow discharge plasmas
Transition from chaotic to ordered state has been observed during the initial
stage of a discharge in a cylindrical dc glow discharge plasma. Initially it
shows a chaotic behavior but increasing the discharge voltage changes the
characteristics of the discharge glow and shows a period substraction of order
7 period 5 period 3 period 1 period i.e. the system goes to
single mode through odd cycle subtraction. On further increasing the discharge
voltage, the system goes through period doubling, like 1 period 2 period
4 period. On further increasing the voltage, the system goes to stable
state without having any oscillations.Comment: chathode-sheath, instabilities, chaos, period-subtraction,
bifurcation, dc-discharg
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