Parity-time symmetry in optical microcavity systems

Canonical quantum mechanics postulates Hermitian Hamiltonians to ensure real eigenvalues. Counterintuitively, a non-Hermitian Hamiltonian, satisfying combined parity-time (PT) symmetry, could display entirely real spectra above some phase-transition threshold. This stems from the existence of a parameter in the Hamiltonian governing characteristics features of eigenvalues and eigenfunctions. Varying this parameter causes real eigenvalues to coalesce and become complex conjugate pairs, signaling the occurrence of a nontrivial phase transition and the breakdown of PT symmetry. Such an appealing discovery has aroused extensive theoretical interest in extending canonical quantum theory by including non-Hermitian but PT-symmetric operators in the last two decades. Despite much fundamental theoretical success in the development of PT-symmetric quantum mechanics, an experimental observation of pseudo-Hermiticity remains elusive as these systems with complex potential seem absent in Nature. But nevertheless, the notion of PT symmetry has survived in many other branches of physics including optics, photonics, AMO physics, acoustics, electronic circuits, and material science over the past ten years, where a judicious balance of gain and loss constitutes ingeniously a PT-symmetric system. Here, although we concentrate upon reviewing recent progress on PT symmetry in optical microcavity systems, we also wish to present some new results that may help to accelerate the research in the area. These compound photonic structures with gain and loss provide a powerful platform for testing various theoretical proposals on PT symmetry, and initiate new possibilities for shaping optical beams and pulses beyond conservative structures. Throughout this article there is an effort to clearly present the physical aspects of PT-symmetry in optical microcavity systems, but mathematical formulations are reduced to the indispensable ones. Readers who prefer strict mathematical treatments should resort to the extensive list of references. Despite the rapid progress on the subject, new ideas and applications of PT symmetry using optical microcavities are still expected in the future

Fuzzy analysis of bearing accelerated degradation testing with uncertainty

This paper proposes a novel method of fuzzy analysis for bearing accelerated degradation testing, which extracts degradation index from bearing vibration signals under different accelerated levels and obtains fuzzy failure time based on fuzzy regression model in consideration of uncertainties. Identification of accelerated model is conducted through linear mixture model. The proposed method provides a methodology to do accelerated vibration analysis for rotating machinery products. An industrial application is used to verify its effectiveness

Self-interaction-free density-functional theoretical study of the electronic structure of spherical and vertical quantum dots

This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevB.63.045317.We study the electronic structure and shell-filling effects of both spherical and vertical quantum dots by means of the density functional theory (DFT) with optimized effective potential (OEP) and self-interaction-correction (SIC) recently developed. The OEP/SIC procedure allows the elimination of the spurious self-interaction energy and the construction of accurate single-particle local potential with proper long-range Coulombic behavior. The OEP/SIC equations are discretized and solved accurately and efficiently by the generalized pseudospectral (GPS) method. The highest occupied orbital energy of N-electron quantum dots provides a direct measure of the electron affinity or chemical potential. We apply the OEP/SIC method to the study of the capacitive energy of N-electron spherical dots for N up to 70. The results show the shell and subshell structure pattern and the electron filling pattern follows closely the Hund’s rule. We also consider the effect of including the vertical dimension in the quantum dot study. We perform a detailed study of the shell-filling effect and the angular and radial density distributions of vertical quantum dots. The calculated capacitive energy spectrum is in good agreement with the recent experimental results, providing physical insights regarding the origin of electron shells and the role of electron-electron interaction in quantum dots

NMDA receptor internalization down-regulates NMDA receptor-mediated synaptic responses through the inhibition of remaining (non-internalized) surface NMDA receptors

Cell-surface protein endocytosis is critically involved in the regulation of organismal homeostasis, immune responses, development and neurotransmission [1,2,3,4]. Mechanisms underlying the endocytosis of cell surface proteins have been extensively investigated. However, until very recently no study has reported how non-internalized cell surface proteins may behave following endocytosis of same type of proteins. Here, we highlight findings that regulated NMDA receptor (NMDAR) internalization not only reduces the amount of NMDARs expressed on neuronal surface but also through activating PKD1 pathway phosphorylates and down-regulates remaining (non-internalized) surface NMDARs. This down-regulation of remaining surface NMDARs plays a critical role in the modulation of NMDAR-mediated synaptic responses by NMDAR internalization

A conserved but plant-specific CDK-mediated regulation of DNA replication protein A2 in the precise control of stomatal terminal division

The R2R3-MYB transcription factor FOUR LIPS (FLP) controls the stomatal terminal division through transcriptional repression of the cell cycle genes CYCLIN-DEPENDENT KINASE (CDK) B1s (CDKB1s), CDKA; 1, and CYCLIN A2s (CYCA2s). We mutagenized the weak mutant allele flp-1 seeds with ethylmethane sulfonate and screened out a flp-1 suppressor 1 (fsp1) that suppressed the flp-1 stomatal cluster phenotype. FSP1 encodes RPA2a subunit of Replication Protein A (RPA) complexes that play important roles in DNA replication, recombination, and repair. Here, we show that FSP1/RPA2a functions together with CDKB1s and CYCA2s in restricting stomatal precursor proliferation, ensuring the stomatal terminal division and maintaining a normal guard-cell size and DNA content. Furthermore, we provide direct evidence for the existence of an evolutionarily conserved, but plant-specific, CDK-mediated RPA regulatory pathway. Serine-11 and Serine-21 at the N terminus of RPA2a are CDK phosphorylation target residues. The expression of the phosphorylation-mimic variant RPA2a(S11,21/D) partially complemented the defective cell division and DNA damage hypersensitivity in cdkb1;1 1;2 mutants. Thus, our study provides a mechanistic understanding of the CDK-mediated phosphorylation of RPA in the precise control of cell cycle and DNA repair in plants

Fuzzy reliability prediction of rotating machinery product with accelerated testing data

For machinery product experienced several operating conditions, this paper proposes a framework of fuzzy reliability analysis of machinery accelerated testing. Due to the non-stationary of the vibration signals, a Gaussian mixture model (GMM) method is introduced to obtain the degradation index through calculating the overlap between current feature set and the historical baseline set. The features in four domains are extracted. Considered that the uncertainties exit in feature extraction and health assessment, a fuzzy regression model is used to describe the degradation path at each operating condition and compute fuzzy quasi time to failures (q-TTFs). Meanwhile, the relationship between q-TTFs and environmental variables are identified by a linear model, through which the fuzzy reliability analysis can be conducted with the most appropriate lifetime distribution. An industrial application is used to verify the effectiveness of the proposed framework and the results have confirmed a good consistency with the true values

Polysaccharides from the Medicinal Mushroom Cordyceps taii Show Antioxidant and Immunoenhancing Activities in a D-Galactose-Induced Aging Mouse Model

Cordyceps taii, an edible medicinal mushroom native to south China, is recognized as an unparalleled resource of healthy foods and drug discovery. In the present study, the antioxidant pharmacological properties of C. taii were systematically investigated. In vitro assays revealed the scavenging activities of the aqueous extract and polysaccharides of C. taii against various free radicals, that is, 1,1-diphenyl-2-picrylhydrazyl radical, hydroxyl radical, and superoxide anion radical. The EC50 values for superoxide anion-free radical ranged from 2.04 mg/mL to 2.49 mg/mL, which was at least 2.6-fold stronger than that of antioxidant thiourea. The polysaccharides also significantly enhanced the antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase) and markedly decreased the malondialdehyde production of lipid peroxidation in a D-galactose-induced aging mouse model. Interestingly, the immune function of the administration group was significantly boosted compared with the D-galactose-induced aging model group. Therefore, the C. taii polysaccharides possessed potent antioxidant activity closely associated with immune function enhancement and free radical scavenging. These findings suggest that the polysaccharides are a promising source of natural antioxidants and antiaging drugs. Consequently, a preliminary chemical investigation was performed using gas chromatography-mass spectroscopy and revealed that the polysaccharides studied were mainly composed of glucose, mannose, and galactose. Fourier-transform infrared spectra also showed characteristic polysaccharide absorption bands