Exceptional cavity quantum electrodynamics

An open quantum system operated at the spectral singularities where dimensionality reduces, known as exceptional points (EPs), demonstrates distinguishing behavior from the Hermitian counterpart. Based on the recently proposed microcavity with exceptional surface (ES), we report and explain the peculiar quantum dynamics in atom-photon interaction associated with EPs: cavity transparency, decoherence suppression beyond the limitation of Jaynes-Cummings (JC) system, and the population trapping of lossy cavity. An analytical description of the local density of states (LDOS) for ES microcavity is derived from an equivalent cavity quantum electrodynamics (QED) model, which goes beyond the single-excitation approximation and allows exploring the quantum effects of EPs on multiphoton process by parametrizing the extended cascaded quantum master equation. It reveals that a square Lorentzian term in LDOS induced by second-order EPs interferes with the linear Lorentzian profile, giving rise to cavity transparency for atom with special transition frequency in the weak coupling regime. This additional contribution from EPs also breaks the limit on dissipation rate of JC system bounded by bare components, resulting in the decoherence suppression with anomalously small decay rate of the Rabi oscillation and the long-time dynamics. Remarkably, we find that the cavity population can be partially trapped at EPs, achieved by forming a bound dressed state in the limiting case of vanishing atom decay. Our work unveils the exotic phenomena unique to EPs in cavity QED systems, which opens the door for controlling light-matter interaction at the quantum level through non-Hermiticity, and holds great potential in building high-performance quantum-optics devices.Comment: 11 pages, 6 figure

Imaging of the Space-time Structure of a Vortex Generator in Supersonic Flow

AbstractThe fine space-time structure of a vortex generator (VG) in supersonic flow is studied with the nanoparticle-based planar laser scattering (NPLS) method in a quiet supersonic wind tunnel. The fine coherent structure at the symmetrical plane of the flow field around the VG is imaged with NPLS. The spatial structure and temporal evolution characteristics of the vortical structure are analyzed, which demonstrate periodic evolution and similar geometry, and the characteristics of rapid movement and slow change. Because the NPLS system yields the flow images at high temporal and spatial resolutions, from these images the position of a large scale structure can be extracted precisely. The position and velocity of the large scale structures can be evaluated with edge detection and correlation algorithms. The shocklet structures induced by vortices are imaged, from which the generation and development of shocklets are discussed in this paper

The Inhibitory Effect of Lysophosphatidylcholine on Proangiogenesis of Human CD34+ Cells Derived Endothelial Progenitor Cells

Increasing evidence reveals that lysophosphatidylcholine (LPC) is closely related to endothelial dysfunction. The present study aimed to investigate the mechanism of LPC in inhibiting the proangiogenesis and vascular inflammation of human endothelial progenitor cells (EPCs) derived from CD34+ cells. The early EPCs were derived from CD34+ hematopoietic stem cells whose purity was identified using flow cytometry analysis. The surface markers (CD34, KDR, CD31; VE-cadherin, vWF, eNOS) of EPCs were examined by flow cytometry analysis and immunofluorescence. RT-qPCR was used to detect the mRNA expression of inflammatory cytokines (CCL2, IL-8, CCL4) and genes associated with angiogenesis (VEGF, ANG-1, ANG-2) in early EPCs after treatment of LPC (10 μg/ml) or phosphatidylcholine (PC, 10 μg/ml, control). The angiogenesis of human umbilical vein endothelial cells (HUVECs) incubated with the supernatants of early EPCs was detected by a tube formation assay. The mRNA and protein levels of key factors on the PKC pathway (phosphorylated PKC, TGF-β1) were measured by RT-qPCR and western blot. The localization of PKC-β1 in EPCs was determined by immunofluorescence staining. We found that LPC suppressed the expression of CCL2, CCL4, ANG-1, ANG-2, promoted IL-8 expression and had no significant effects on VEGF expression in EPCs. EPCs promoted the angiogenesis of HUVECs, which was significantly inhibited by LPC treatment. Moreover, LPC was demonstrated to promote the activation of the PKC signaling pathway in EPCs. In conclusion, LPC inhibits proangiogenesis of human endothelial progenitor cells derived from CD34+ hematopoietic stem cells

Structural state scale-dependent physical characteristics and endurance of cermet composite for cutting metal

A structural-phase state developed on the surface of a TiC/Ni-Cr-Al cermet alloy under superfast heating and cooling produced by pulse electron beam melting has been presented. The effect of the surface's structural state multimodality on the temperature dependencies of thefriction and endurance of the cermet tool in cutting metal has been investigated. The high-energy flux treatment of subsurface layers by electron beam pulses in argon-containing gas discharge plasma serves to improve the endurance of metal cutting tools manifold (by a factor of 6), to reduce the friction via precipitation of secondary 200 nm carbides in binder interlayers. It is possible to improve the cermet tool endurance for cutting metal by a factor of 10-12 by irradiating the cermet in a reactive nitrogen-containing atmosphere with the ensuingprecipitation of nanosize 50 nm AlN particles in the binder interlayers