8,609 research outputs found
Impact on the Higgs Production Cross Section and Decay Branching Fractions of Heavy Quarks and Leptons in a Fourth Generation Model
In a fourth generation model with heavy quarks, the production cross section
of the Higgs boson in the gluon-gluon fusion process is significantly increased
due to additional quark loops. In a similar way, the partial decay width of the
decay channels and is modified.
These changes and their impact on the Higgs search are discussed.Comment: 9 pages, 6 figures, minor changes with a few more references adde
Adaptive recurrence quantum entanglement distillation for two-Kraus-operator channels
Quantum entanglement serves as a valuable resource for many important quantum
operations. A pair of entangled qubits can be shared between two agents by
first preparing a maximally entangled qubit pair at one agent, and then sending
one of the qubits to the other agent through a quantum channel. In this
process, the deterioration of entanglement is inevitable since the noise
inherent in the channel contaminates the qubit. To address this challenge,
various quantum entanglement distillation (QED) algorithms have been developed.
Among them, recurrence algorithms have advantages in terms of implementability
and robustness. However, the efficiency of recurrence QED algorithms has not
been investigated thoroughly in the literature. This paper put forth two
recurrence QED algorithms that adapt to the quantum channel to tackle the
efficiency issue. The proposed algorithms have guaranteed convergence for
quantum channels with two Kraus operators, which include phase-damping and
amplitude-damping channels. Analytical results show that the convergence speed
of these algorithms is improved from linear to quadratic and one of the
algorithms achieves the optimal speed. Numerical results confirm that the
proposed algorithms significantly improve the efficiency of QED
Generalized Interference Alignment --- Part I: Theoretical Framework
Interference alignment (IA) has attracted enormous research interest as it
achieves optimal capacity scaling with respect to signal to noise ratio on
interference networks. IA has also recently emerged as an effective tool in
engineering interference for secrecy protection on wireless wiretap networks.
However, despite the numerous works dedicated to IA, two of its fundamental
issues, i.e., feasibility conditions and transceiver design, are not completely
addressed in the literature. In this two part paper, a generalised interference
alignment (GIA) technique is proposed to enhance the IA's capability in secrecy
protection. A theoretical framework is established to analyze the two
fundamental issues of GIA in Part I and then the performance of GIA in
large-scale stochastic networks is characterized to illustrate how GIA benefits
secrecy protection in Part II. The theoretical framework for GIA adopts
methodologies from algebraic geometry, determines the necessary and sufficient
feasibility conditions of GIA, and generates a set of algorithms that can solve
the GIA problem. This framework sets up a foundation for the development and
implementation of GIA.Comment: Minor Revision at IEEE Transactions on Signal Processin
Mechanisms of dysregulation of low-density lipoprotein receptor expression in vascular smooth muscle cells by inflammatory cytokines
Objective - Although inflammation is a recognized feature of atherosclerosis, the impact of inflammation on cellular cholesterol homeostasis is unclear. This study focuses on the molecular mechanisms by which inflammatory cytokines disrupt low-density lipoprotein (LDL) receptor regulation.Methods and Results - IL-1 beta enhanced transformation of vascular smooth muscle cells into foam cells by increasing uptake of unmodified LDL via LDL receptors and by enhancing cholesterol esterification as demonstrated by Oil Red O staining and direct assay of intracellular cholesterol concentrations. In the absence of IL-1 beta, a high concentration of LDL decreased LDL receptor promoter activity, mRNA synthesis and protein expression. However, IL-1 beta enhanced LDL receptor expression, overriding the suppression usually induced by a high concentration of LDL and inappropriately increasing LDL uptake. Exposure to IL-1 beta also caused overexpression of the sterol regulatory element binding protein ( SREBP) cleavage-activating protein ( SCAP), and enhanced its translocation from the endoplasmic reticulum to the Golgi, where it is known to cleave SREBP, thereby enhancing LDL receptor gene expression.Conclusions - These observations demonstrate that IL-1 beta disrupts cholesterol-mediated LDL receptor feedback regulation, permitting intracellular accumulation of unmodified LDL and causing foam cell formation. The implication of these findings is that inflammatory cytokines may contribute to intracellular LDL accumulation without previous modification of the lipoprotein
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Simulation of turbulent lifted methane jet flames: Effects of air-dilution and transient flame propagation
Turbulent lifted methane jet flames with various air-dilution levels and a range
of inlet velocities are simulated. A partially premixed combustion model based
on premixed flamelets with presumed joint Probability Density Function (PDF) is
used. The joint PDF is obtained using a copula to include the statistical correlation
between mixture fraction, Z, and progress variable, c. The non-premixed combustion
effect is included using a simple algebraic model. Both steady and unsteady
RANS simulations are performed. The steady simulations show that the computed
lift-off heights agree well with measured values for a wide range of jet velocities
and air-dilution level. Both of the Z-c correlation and non-premixed combustion
effects are found to be important to get the correct lift-off height. Their individual
and combined effects are analysed systematically. The unsteady RANS results
indicate that multi-stage flame development, namely the initial expansion, flame
brush development, its propagation and final stabilisation, is captured reasonably
well in simulations. The various stages of temporal evolution of the flame brush edge is captured well and the agreement with experimental measurements is good.The supports of Cambridge Overseas Trust and China Scholarship Council are
acknowledged by ZC. SR and NS acknowledge the support of MHI, Takasago,
Japan.This is the accepted manuscript. The final version will be available from Elsevier at: http://www.sciencedirect.com/science/article/pii/S001021801400279X
Measurement of the c-axis optical reflectance of AFeAs (A=Ba, Sr) single crystals: Evidence of different mechanisms for the formation of two energy gaps
We present the c-axis optical reflectance measurement on single crystals of
BaFeAs and SrFeAs, the parent compounds of FeAs based
superconductors. Different from the ab-plane optical response where two
distinct energy gaps were observed in the SDW state, only the smaller energy
gap could be seen clearly for \textbf{E}c-axis. The very pronounced
energy gap structure seen at a higher energy scale for
\textbf{E}ab-plane is almost invisible. We propose a novel picture
for the band structure evolution across the SDW transition and suggest
different driving mechanisms for the formation of the two energy gaps.Comment: 4 page
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