16,091 research outputs found
Possibility of S=1 spin liquids with fermionic spinons on triangular lattices
In this paper we generalize the fermionic representation for spins to
arbitrary spins. Within a mean field theory we obtain several spin liquid
states for spin antiferromagnets on triangular lattices, including
gapless f-wave spin liquid and topologically nontrivial spin liquid.
After considering different competing orders, we construct a phase diagram for
the -- model. The application to recently discovered material
is discussed.Comment: 5 pages, 3 figure
Fermionic theory for quantum antiferromagnets with spin S > 1/2
The fermion representation for S = 1/2 spins is generalized to spins with
arbitrary magnitudes. The symmetry properties of the representation is analyzed
where we find that the particle-hole symmetry in the spinon Hilbert space of S
=1/2 fermion representation is absent for S > 1/2. As a result, different path
integral representations and mean field theories can be formulated for spin
models. In particular, we construct a Lagrangian with restored particle-hole
symmetry, and apply the corresponding mean field theory to one dimensional (1D)
S = 1 and S = 3/2 antiferromagnetic Heisenberg models, with results that agree
with Haldane's conjecture. For a S = 1 open chain, we show that Majorana
fermion edge states exist in our mean field theory. The generalization to spins
with arbitrary magnitude S is discussed. Our approach can be applied to higher
dimensional spin systems. As an example, we study the geometrically frustrated
S = 1 AFM on triangular lattice. Two spin liquids with different pairing
symmetries are discussed: the gapped px + ipy-wave spin liquid and the gapless
f-wave spin liquid. We compare our mean field result with the experiment on
NiGa2S4, which remains disordered at low temperature and was proposed to be in
a spin liquid state. Our fermionic mean field theory provide a framework to
study S > 1/2 spin liquids with fermionic spinon excitations.Comment: 16 pages, 4 figure
Optimal Online Transmission Policy for Energy-Constrained Wireless-Powered Communication Networks
This work considers the design of online transmission policy in a
wireless-powered communication system with a given energy budget. The system
design objective is to maximize the long-term throughput of the system
exploiting the energy storage capability at the wireless-powered node. We
formulate the design problem as a constrained Markov decision process (CMDP)
problem and obtain the optimal policy of transmit power and time allocation in
each fading block via the Lagrangian approach. To investigate the system
performance in different scenarios, numerical simulations are conducted with
various system parameters. Our simulation results show that the optimal policy
significantly outperforms a myopic policy which only maximizes the throughput
in the current fading block. Moreover, the optimal allocation of transmit power
and time is shown to be insensitive to the change of modulation and coding
schemes, which facilitates its practical implementation.Comment: 7 pages, accepted by ICC 2019. An extended version of this paper is
accepted by IEEE TW
Sex significantly influences transduction of murine liver by recombinant adeno-associated viral vectors through an androgen-dependent pathway.
A systematic evaluation of the influence of sex on transduction by recombinant adeno-associated viral vector (rAAV) indicated that transgene expression after liver-targeted delivery of vector particles was between 5- to 13-fold higher in male mice compared with female mice, irrespective of the proviral promoter or cDNA and mouse strain. Molecular analysis revealed that the rAAV genome was stably retained in male liver at levels that were 7-fold higher than those observed in females. Further, the sex difference in transduction was observed with AAV-2- and AAV-5-based vectors, which use distinct receptor complexes for infection. In concordance with the differences in AAV transduction, gel shift analysis with nuclear extracts derived from the liver of mice and humans revealed substantially higher binding of host nuclear protein to the rep-binding site (RBS) of AAV inverted terminal repeat (ITR) in males compared with females. Transduction efficiency and binding of nuclear protein to RBS was dramatically reduced in male mice by castration. In contrast, although oophorectomy did not significantly influence rAAV transduction, administration of 5alpha dihydrotestosterone, prior to gene transfer, increased stable hepatocyte gene transfer in females to levels observed in male mice, implying that androgens significantly influence hepatocyte gene transfer. Interestingly, sex did not have a significant effect on AAV gene transfer into nonhepatic tissue, indicating that there are distinct tissue- and sex-specific differences in the mechanisms responsible for efficient transduction with this vector. These results have significant implications for gene therapy of autosomal and acquired disorders affecting the liver
Electro-osmotic flow through a thin channel with gradually varying wall potential and hydrodynamic slippage
The lubrication approximation is applied to electro-osmotic flow through a thin parallel-plate channel under the combined effect of charge and hydrodynamic slippage modulation on the walls. The walls are periodically patterned for the charge and slip distributions, with a wavelength much longer than the channel height. It is shown that the phase of the wall patterns will play a significant role in determining the section-averaged velocity as well as the local convection pattern, both quantitatively and qualitatively. The effect of the phase on the flow will be dramatically different, depending on whether the electric field is applied along or perpendicular to the varying direction of the patterns. The possibility of generating a net flow in a direction perpendicular to the applied field is demonstrated. © 2012 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.postprin
Quantum impurity in the bulk of topological insulator
We investigate physical properties of an Anderson impurity embedded in the
bulk of a topological insulator. The slave-boson mean-field approximation is
used to account for the strong electron correlation at the impurity. Different
from the results of a quantum impurity on the surface of a topological
insulator, we find for the band-inverted case, a Kondo resonant peak and in-gap
bound states can be produced simultaneously. However, only one type of them
appears for the normal case. It is shown that the mixed-valence regime is much
broader in the band-inverted case, while it shrinks to a very narrow regime in
the normal case. Furthermore, a self-screening of the Kondo effect may appear
when the interaction between the bound-state spin and impurity spin is taken
into account.Comment: 11 pages, 8 figure
- …