1,867 research outputs found
Quasiparticle interference of C2-symmetric surface states in LaOFeAs parent compound
We present scanning tunneling microscopy studies of the LaOFeAs parent
compound of iron pnictide superconductors. Topographic imaging reveals two
types of atomically flat surfaces, corresponding to the exposed LaO layer and
FeAs layer respectively. On one type of surface, we observe strong standing
wave patterns induced by quasiparticle interference of two-dimensional surface
states. The distribution of scattering wavevectors exhibits pronounced two-fold
symmetry, consistent with the nematic electronic structure found in the
Ca(Fe1-xCox)2As2 parent state.Comment: 13 pages, 4 figure
Projective-anticipating, projective, and projective-lag synchronization of time-delayed chaotic systems on random networks
We study projective-anticipating, projective, and projective-lag
synchronization of time-delayed chaotic systems on random networks. We relax
some limitations of previous work, where projective-anticipating and
projective-lag synchronization can be achieved only on two coupled chaotic
systems. In this paper, we can realize projective-anticipating and
projective-lag synchronization on complex dynamical networks composed by a
large number of interconnected components. At the same time, although previous
work studied projective synchronization on complex dynamical networks, the
dynamics of the nodes are coupled partially linear chaotic systems. In this
paper, the dynamics of the nodes of the complex networks are time-delayed
chaotic systems without the limitation of the partial-linearity. Based on the
Lyapunov stability theory, we suggest a generic method to achieve the
projective-anticipating, projective, and projective-lag synchronization of
time-delayed chaotic systems on random dynamical networks and find both the
existence and sufficient stability conditions. The validity of the proposed
method is demonstrated and verified by examining specific examples using Ikeda
and Mackey-Glass systems on Erdos-Renyi networks.Comment: 14 pages, 6 figure
TRAF5 Is a Downstream Target of MAVS in Antiviral Innate Immune Signaling
The recognition of nucleic acids by the innate immune system during viral infection results in the production of type I interferons and the activation of antiviral immune responses. The RNA helicases RIG-I and MDA-5 recognize distinct types of cytosolic RNA species and signal through the mitochondrial protein MAVS to stimulate the phosphorylation and activation of the transcription factors IRF3 and IRF7, thereby inducing type I interferon expression. Alternatively, the activation of NF-κB leads to proinflammatory cytokine production. The function of MAVS is dependent on both its C-terminal transmembrane (TM) domain and N-terminal caspase recruitment domain (CARD). The TM domain mediates MAVS dimerization in response to viral RNA, allowing the CARD to bind to and activate the downstream effector TRAF3. Notably, dimerization of the MAVS CARD alone is sufficient to activate IRF3, IRF7, and NF-κB. However, TRAF3-deficient cells display only a partial reduction in interferon production in response to RNA virus infection and are not defective in NF-κB activation. Here we find that the related ubiquitin ligase TRAF5 is a downstream target of MAVS that mediates both IRF3 and NF-κB activation. The TM domain of MAVS allows it to dimerize and thereby associate with TRAF5 and induce its ubiquitination in a CARD-dependent manner. Also, NEMO is recruited to the dimerized MAVS CARD domain in a TRAF3 and TRAF5-dependent manner. Thus, our findings reveal a possible function for TRAF5 in mediating the activation of IRF3 and NF-κB downstream of MAVS through the recruitment of NEMO. TRAF5 may be a key molecule in the innate response against viral infection
Fault Mode Probability Factor Based Fault-Tolerant Control for Dissimilar Redundant Actuation System
This paper presents a Fault Mode Probability Factor (FMPF) based Fault-Tolerant Control (FTC) strategy for multiple faults of Dissimilar Redundant Actuation System (DRAS) composed of Hydraulic Actuator (HA) and Electro-Hydrostatic Actuator (EHA). The long-term service and severe working conditions can result in multiple gradual faults which can ultimately degrade the system performance, resulting in the system model drift into the fault state characterized with parameter uncertainty. The paper proposes to address this problem by using the historical statistics of the multiple gradual faults and the proposed FMPF to amend the system model with parameter uncertainty. To balance the system model precision and computation time, a Moving Window (MW) method is used to determine the applied historical statistics. The FMPF based FTC strategy is developed for the amended system model where the system estimation and Linear Quadratic Regulator (LQR) are updated at the end of system sampling period. The simulations of DRAS system subjected to multiple faults have been performed and the results indicate the effectiveness of the proposed approach
Inhibition of EZH2 Promotes Human Embryonic Stem Cell Differentiation into Mesoderm by Reducing H3K27me3.
Mesoderm derived from human embryonic stem cells (hESCs) is a major source of the mesenchymal stem/stromal cells (MSCs) that can differentiate into osteoblasts and chondrocytes for tissue regeneration. While significant progress has been made in understanding of molecular mechanisms of hESC differentiation into mesodermal cells, little is known about epigenetic factors controlling hESC fate toward mesoderm and MSCs. Identifying potential epigenetic factors that control hESC differentiation will undoubtedly lead to advancements in regenerative medicine. Here, we conducted an epigenome-wide analysis of hESCs and MSCs and uncovered that EZH2 was enriched in hESCs and was downregulated significantly in MSCs. The specific EZH2 inhibitor GSK126 directed hESC differentiation toward mesoderm and generated more MSCs by reducing H3K27me3. Our results provide insights into epigenetic landscapes of hESCs and MSCs and suggest that inhibiting EZH2 promotes mesodermal differentiation of hESCs
Spin Fluctuation Induced Linear Magnetoresistance in Ultrathin Superconducting FeSe Films
The discovery of high-temperature superconductivity in FeSe/STO has trigged
great research interest to reveal a range of exotic physical phenomena in this
novel material. Here we present a temperature dependent magnetotransport
measurement for ultrathin FeSe/STO films with different thickness and
protection layers. Remarkably, a surprising linear magnetoresistance (LMR) is
observed around the superconducting transition temperatures but absent
otherwise. The experimental LMR can be reproduced by magnetotransport
calculations based on a model of magnetic field dependent disorder induced by
spin fluctuation. Thus, the observed LMR in coexistence with superconductivity
provides the first magnetotransport signature for spin fluctuation around the
superconducting transition region in ultrathin FeSe/STO films
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