4,182 research outputs found
The Kagome Antiferromagnet: A Schwinger-Boson Mean-Field Theory Study
The Heisenberg antiferromagnet on the Kagom\'{e} lattice is studied in the
framework of Schwinger-boson mean-field theory. Two solutions with different
symmetries are presented. One solution gives a conventional quantum state with
order for all spin values. Another gives a gapped spin liquid
state for spin and a mixed state with both and
orders for spin . We emphasize that the mixed
state exhibits two sets of peaks in the static spin structure factor. And for
the case of spin , the gap value we obtained is consistent with the
previous numerical calculations by other means. We also discuss the
thermodynamic quantities such as the specific heat and magnetic susceptibility
at low temperatures and show that our result is in a good agreement with the
Mermin-Wagner theorem.Comment: 9 pages, 5 figure
Toward demonstrating controlled-X operation based on continuous variable four-partite cluster state and quantum teleporters
One-way quantum computation based on measurement and multipartite cluster
entanglement offers the ability to perform a variety of unitary operations only
through different choices of measurement bases. Here we present an experimental
study toward demonstrating the controlled-X operation, a two-mode gate, in
which continuous variable (CV) four-partite cluster states of optical modes are
utilized. Two quantum teleportation elements are used for achieving the gate
operation of the quantum state transformation from input target and control
states to output states. By means of the optical cluster state prepared
off-line, the homodyne detection and electronic feeding forward, the
information carried by the input control state is transformed to the output
target state. The presented scheme of the controlled-X operation based on
teleportation can be implemented nonlocally and deterministically. The
distortion of the quantum information resulting from the imperfect cluster
entanglement is estimated with the fidelity
Experimental generation of 6 dB continuous variable entanglement from a nondegenerate optical parametric amplifier
We experimentally demonstrated that the quantum correlations of amplitude and
phase quadratures between signal and idler beams produced from a non-degenerate
optical parametric amplifier (NOPA) can be significantly improved by using a
mode cleaner in the pump field and reducing the phase fluctuations in phase
locking systems. Based on the two technical improvements the quantum
entanglement measured with a two-mode homodyne detector is enhanced from ~ 4 dB
to ~ 6 dB below the quantum noise limit using the same NOPA and nonlinear
crystal.Comment: 7 pages, 5 figure
Incommensurate Phase of a Triangular Frustrated Heisenberg Model Studied via Schwinger-Boson Mean-Field Theory
We study a triangular frustrated antiferromagnetic Heisenberg model with
nearest-neighbor interaction and third-nearest-neighbor interactions
by means of Schwinger-boson mean-field theory. It is shown that an
incommensurate phase exists in a finite region in the parameter space for an
antiferromagnetic while can be either positive or negtaive. A
detailed solution is presented to disclose the main features of this
incommensurate phase. A gapless dispersion of quasiparticles leads to the
intrinsic -law of specific heat. The local magnetization is
significantly reduced by quantum fluctuations (for S=1 case, a local
magnetization is estimated as ). The magnetic
susceptibility is linear in temperature at low temperatures. We address
possible relevance of these results to the low-temperature properties of
NiGaS. From a careful analysis of the incommensurate spin wave
vector, the interaction parameters for NiGaS are estimated as,
K and K, in order to account for the
experimental data.Comment: 9pages, 3figure
Regulations of the key mediators in inflammation and atherosclerosis by Aspirin in human macrophages
Although its role to prevent secondary cardiovascular complications has been well established, how acetyl salicylic acid (ASA, aspirin) regulates certain key molecules in the atherogenesis is still not known. Considering the role of matrix metalloproteinase-9 (MMP-9) to destabilize the atherosclerotic plaques, the roles of the scavenger receptor class BI (SR-BI) and ATP-binding cassette transporter A1 (ABCA1) to promote cholesterol efflux in the foam cells at the plaques, and the role of NF-κB in the overall inflammation related to the atherosclerosis, we addressed whether these molecules are all related to a common mechanism that may be regulated by acetyl salicylic acid. We investigated the effect of ASA to regulate the expressions and activities of these molecules in THP-1 macrophages. Our results showed that ASA inhibited MMP-9 mRNA expression, and caused the decrease in the MMP-9 activities from the cell culture supernatants. In addition, it inhibited the nuclear translocation of NF-κB p65 subunit, thus the activity of this inflammatory molecule. On the contrary, acetyl salicylic acid induced the expressions of ABCA1 and SR-BI, two molecules known to reduce the progression of atherosclerosis, at both mRNA and protein levels. It also stimulated the cholesterol efflux out of macrophages. These data suggest that acetyl salicylic acid may alleviate symptoms of atherosclerosis by two potential mechanisms: maintaining the plaque stability via inhibiting activities of inflammatory molecules MMP-9 and NF-κB, and increasing the cholesterol efflux through inducing expressions of ABCA1 and SR-BI
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