Sub-wavelength visualization of near-field scattering mode of plasmonic nano-cavity in the far-field

Spatial visualization of mode distribution of light scattering from plasmonic nanostructures is of vital importance for understanding the scattering mechanism and applications based on these plasmonic nanostructures. A long unanswered question in how the spatial information of scattered light from a single plasmonic nanostructure can be recovered in the far-field, under the constraints of the diffraction limit of the detection or imaging optical system. In this paper, we reported a theoretical model on retrieving local spatial information of scattered light by plasmonic nanostructures in a far-field optical imaging system. In the far-field parametric sin δ images, singularity points corresponding to near-field hot spots of the edge mode and the gap mode were resolved for gold ring and split rings with subwavelength diameters and feature sizes. The experimental results were verified with Finite Difference Time Domain (FDTD) simulation in the near-field and far-field, for the edge mode and the gap mode at 566 nm and 534 nm, respectively. In sin δ image of split-ring, two singularity points associated with near-field hot spots were visualized and resolved with the characteristic size of 90 and 100 nm, which is far below the diffraction limit. The reported results indicate the feasibility of characterizing the spatial distribution of scattering light in the far-field and with sub-wavelength resolution for single plasmonic nanostructures with sub-wavelength feature sizes

Self-trapping of polarons with off-diagonal coupling

A variational polaron wave function pioneered by Toyozawa is utilized to elucidate exciton-phonon correlations in a generalized Holstein Hamiltonian in the simultaneous presence of diagonal and off-diagonal exciton-phonon couplings. We show that a simple analysis of quantum entanglement between excitonic and phononic degrees of freedom allows one to effectively characterize both the small- and large-polaron regimes as well as the crossover in between.Published versio

Size-Dependent Optical Properties of Aluminum Nanoparticles: From Classical to Quantum Description

The absorption spectra of a series of tetrahedral-shaped aluminum nanoparticles (ANPs) with side lengths ranging from <i>L</i> = 1.4 to 141.4 nm have been calculated. The size-dependent evolution of structures and spectra has been demonstrated. The plasmon resonance of ANPs is highly sensitive to the particle size and spans a wide spectral region from ultraviolet to visible. As <i>L</i> increases from 70 to 141 nm, an apparent spectral red shift is still observed, although their spectral line shapes do not change much. For the small clusters Al_<i>n</i> with <i>n</i> ≤ 560 (or with <i>L</i> ≤ 3.68 nm), their absorption spectra have been calculated by both the real-time time-dependent density functional theory (RT-TDDFT) scheme and the finite difference time domain (FDTD) classical electrodynamics method, whereas for the larger nanoparticles, their absorption spectra have only been calculated by the FDTD method. Al_<i>n</i> with <i>n</i> ≤ 560 has two main absorption bands attributed to two kinds of localized surface plasmon resonance modes, vertexes and edges, revealed by the corresponding induced electron densities. RT-TDDFT and FDTD approaches produce obvious spectral differences, and RT-TDDFT predicts more intensive low-energy absorption bands and broader high-energy bands than FDTD. The effect of geometrical relaxation on the absorption spectra of small clusters is visible, which tends to blue shift and broaden the spectra. The smaller the cluster, the larger is the geometrical change

Hydrogen Sulfide Up-Regulates the Expression of ATP-Binding Cassette Transporter A1 via Promoting Nuclear Translocation of PPARα

ATP binding cassette transporter A1 (ABCA1) plays a key role in atherogenesis. Hydrogen sulfide (H2S), a gasotransmitter, has been reported to play an anti-atherosclerotic role. However, the underlying mechanisms are largely unknown. In this study we examined whether and how H2S regulates ABCA1 expression. The effect of H2S on ABCA1 expression and lipid metabolism were assessed in vitro by cultured human hepatoma cell line HepG2, and in vivo by ApoE−/− mice with a high-cholesterol diet. NaHS (an exogenous H2S donor) treatment significantly increased the expression of ABCA1, ApoA1, and ApoA2 and ameliorated intracellular lipid accumulation in HepG2 cells. Depletion of the endogenous H2S generator cystathionine γ-lyase (CSE) by small RNA interference (siRNA) significantly decreased the expression of ABCA1 and resulted in the accumulation of lipids in HepG2 cells. In vivo NaHS treatment significantly reduced the serum levels of total cholesterol (TC), triglycerides (TG), and low-density lipoproteins (LDL), diminished atherosclerotic plaque size, and increased hepatic ABCA1 expression in fat-fed ApoE−/− mice. Further study revealed that NaHS upregulated ABCA1 expression by promoting peroxisome proliferator-activated receptor α (PPARα) nuclear translocation. H2S up-regulates the expression of ABCA1 by promoting the nuclear translocation of PPARα, providing a fundamental mechanism for the anti-atherogenic activity of H2S. H2S may be a promising potential drug candidate for the treatment of atherosclerosis

Wideband-Efficient SOI Uniform Subwavelength Grating Couplers by Effective-Index and Leakage-Factor Matching at Multiple Wavelengths

By improving both effective-index (EI) matching and leakage-factor (LF) matching at multiple wavelengths, a method to achieve a wideband-efficient uniform subwavelength grating coupler (SWGC) has been theoretically demonstrated. First, the root-mean-square-error between the grating EI and ideal EI (RMSE-EI) and root-mean-square-error between the grating LF and ideal LF (RMSE-LF) are adopted to weigh EI and LF matching at multiple wavelengths. It is found that when the RMSE-EI decreases and keeping RMSE-LF almost constant, the coupling bandwidth of the uniform SWGC could be substantially increased. Moreover, when RMSE-LF of the uniform SWGC decreases while RMSE-EI remains almost constant, the overall integral coupling efficiency (ICE) within the band from 1525 nm to 1575 nm is enhanced. Furthermore, by simultaneously enhancing both EI matching and LF matching at three wavelengths, a 1-dB bandwidth of 53.7 nm and ICE of 22.31 is obtained in an optimized SOI uniform SWGC. Using the proposed multi-wavelength optimizing methodology, even more efficient wideband couplers could be expected by adopting more optimization accounting for more structural parameters in the future

TXNIP inhibition in the treatment of type 2 diabetes mellitus: design, synthesis, and biological evaluation of quinazoline derivatives

AbstractThioredoxin interacting protein (TXNIP) is a potential drug target for type 2 diabetes mellitus (T2DM) treatment. A series of quinazoline derivatives were designed, synthesised, and evaluated to inhibit TXNIP expression and protect from palmitate (PA)-induced β cell injury. In vitro cell viability assay showed that compounds D-2 and C-1 could effectively protect β cell from PA-induced apoptosis, and subsequent results showed that these two compounds decreased TXNIP expression by accelerating its protein degradation. Mechanistically, compounds D-2 and C-1 reduced intracellular reactive oxygen species (ROS) production and modulated TXNIP-NLRP3 inflammasome signalling, and thus alleviating oxidative stress injury and inflammatory response under PA insult. Besides, these two compounds were predicted to possess better drug-likeness properties using SwissADME. The present study showed that compounds D-2 and C-1, especially compound D-2, were potent pancreatic β cell protective agents to inhibit TXNIP expression and might serve as promising lead candidates for the treatment of T2DM

TXNIP aggravates cardiac fibrosis and dysfunction after myocardial infarction in mice by enhancing the TGFB1/Smad3 pathway and promoting NLRP3 inflammasome activation

Myocardial infarction (MI) results in high mortality. The size of fibrotic scar tissue following MI is an independent predictor of MI outcomes. Thioredoxin-interacting protein (TXNIP) is involved in various fibrotic diseases. Its role in post-MI cardiac fibrosis, however, remains poorly understood. In the present study, we investigate the biological role of TXNIP in post-MI cardiac fibrosis and the underlying mechanism using mouse MI models of the wild-type (WT), Txnip-knockout (Txnip-KO) type and Txnip-knock-in (Txnip-KI) type. After MI, the animals present with significantly upregulated TXNIP levels, and their fibrotic areas are remarkably expanded with noticeably impaired cardiac function. These changes are further aggravated under Txnip-KI conditions but are ameliorated in Txnip-KO animals. MI also leads to increased protein levels of the fibrosis indices Collagen I, Collagen III, actin alpha 2 (ACTA2), and connective tissue growth factor (CTGF). The Txnip-KI group exhibits the highest levels of these proteins, while the lowest levels are observed in the Txnip-KO mice. Furthermore, Txnip-KI significantly upregulates the levels of transforming growth factor (TGF)B1, p-Smad3, NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), Cleaved Caspase-1, and interleukin (IL)1B after MI, but these effects are markedly offset by Txnip-KO. In addition, after MI, the Smad7 level significantly decreases, particularly in the Txnip-KI mice. TXNIP may aggravate the progression of post-MI fibrosis and cardiac dysfunction by activating the NLRP3 inflammasome, followed by IL1B generation and then the enhancement of the TGFB1/Smad3 pathway. As such, TXNIP might serve as a novel potential therapeutic target for the treatment of post-MI cardiac fibrosis