We theoretically study a tunable reflective focusing lens, based on graphene metasurface, which consists of rectangle aperture array. Dynamic control of either the focal intensity or focal length for ...terahertz circular polarized waves can be achieved by uniformly tuning the graphene Fermi energy. We demonstrate the graphene apertures with the same geometry; however, spatially varying orientations can only control the focal intensity. To change the focal length, the spatially varying aperture lengths are also required. A comparative study between the metalenses, which generate only geometric or both gradient and geometric phase changes, has shown that the apertures' spatially varying length distribution is the key factor for determining the modulation level, rather than the focal length's modulation range. This kind of metalens provides tunable, high-efficiency, broadband, and wide-angle off-axis focusing, thereby offering great application potential in lightweight and integrated terahertz devices.
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•Cordyceps sinensis polysaccharide (CSP) inhibited the growth of colon cancer cells.•CSP induced apoptosis and autophagy flux blockage in colon cancer cells.•Autophagy inhibition ...increased CSP-induced apoptosis in colon cancer cells.
Cordyceps sinensis is thought to have anti-cancer effects, but its mechanisms remain elusive. In this study, we aimed to investigate the anti-cancer effect of Cordyceps sinensis polysaccharide (CSP) on human colon cancer cell line (HCT116) and its mechanism. Results indicated that CSP significantly inhibited the proliferation of HCT116 cells, increased autophagy and apoptosis, while blocked autophagy flux and lysosome formation. Further experiments showed that CSP decreased the expression of PI3K and phosphorylation level of AKT and mTOR, increased the expression of AMPKa and phosphorylation level of ULK1. In addition, repression of CSP-induced autophagy by bafilomycin (autophagy inhibitor) enhanced apoptosis and cell death of HCT116 cells. Hence, our findings suggested that CSP inhibited the proliferation of HCT116 cells by inducing apoptosis and autophagy flux blockage, which might be achieved through PI3K-AKT-mTOR and AMPK-mTOR-ULK1 signaling. CSP may be a potential therapeutic agent for colon cancer.
In this paper, we present a dual-band metamaterial absorber for graphene surface plasmon resonance at terahertz frequency. We use the finite difference time domain (FDTD) method to study the ...absorption characteristics of the homocentric graphene ring and disk nanostructure. These simulation results show that the change of the geometrical parameters and the substrate thickness of the nanostructure can change the absorption characteristics and the emergence of dual-band absorption peaks. Moreover, we study the field distribution of nanodisks with different radius in detail. By changing the Fermi level of graphene, the wavelength of their absorption peaks can be adjusted flexibly. In addition, the proposed dual-band absorber also shows a good angle tolerance for both TE and TM polarizations. By calculation the surface-filled water (n = 1.332) and 25% aqueous glucose solution (n = 1.372) for the metamaterial absorber, the sensitivities of mode I and mode II are 5.0 μm/RIU and 15.0 μm/RIU. These research results will have broad application prospects for sensing and spatial light modulators.
We present a dual-band metamaterial absorber for graphene surface plasmon resonance at terahertz frequency. We find the nanostructure absorption peak wavelength is flexible and adjustable by changing the graphene Fermi level EF. Display omitted
•The absorption enhancement of the nanostructure can be achieved by changing the geometric parameters.•By changing the Fermi level, the absorption characteristics can be tuned.•As the relaxation time increases, the absorption maximum also increases, while the resonance peak wavelength remains unchanged.•For TM and TE polarizations, the absorbers are insensitive to the incident angle.
The application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) in glycan was limited due to their poor ionization efficiency, compared with ...biomolecules such as proteins and peptides. Aiming to improve the ionization efficiency and simplify preparation procedure simultaneously during MALDI MS analysis, an on-target derivatization method using 3-aminoquinoline (3-AQ)/α-cyano-4-hydroxycinnamic acid (CHCA) as matrix was employed and it was conducted both in the positive and negative ion MALDI TOF MS. Results indicated that after on-target derivatization, the ions generated had substantially improved S/N ratios and sensitivity in the tandem mass spectra. The B/Y− type ions of 3-AQ-labeled glycans could be easily recognized, and cross-ring A− type ions provided additional information to reveal the linkage patterns. Specifically, positive ion mass spectra with protonated adduct as precursor ion produced a simple fragmentation pattern benefited for sequencing and observation of branches. Furthermore, this method was successfully applied in polysaccharides analysis, including arabinoxylan, xylan, arabinogalactan and dextran after enzymatic or acid degradation. This study demonstrated that it was feasible to analyze higher molecular weight polysaccharides by MALDI TOF MS using 3-AQ/CHCA matrix through appropriate hydrolysis, and it allowed much efficient structural interpretation with increased sensitivity and characteristic fragment ions.
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•On-target derivatization using 3-AQ/CHCA increased the ionization efficiency of polysaccharides.•The fragmentation of (A)XOS, malto-oligosaccharides and cyclodextrins in MALDI TOF MS were elucidated.•This method was applied to characterize the polysaccharides after degradation.
Double Fano resonant characteristics are investigated in planar plasmonic structure by embedding a metallic nanorod in symmetric U-shaped split ring resonators, which are caused by a strong interplay ...between a broad bright mode and narrow dark modes. The bright mode is resulted from the nanorod electric dipole resonance while the dark modes originate from the magnetic dipole induced by LC resonances. The overlapped dual Fano resonances can be decomposed to two separate ones by adjusting the coupling length between the nanorod and U-shaped split ring resonators. Fano resonances in the designed structure exhibit high refractive-index sensing sensitivity and figure of merit, which have potential applications in single or double-wavelength sensing in the near-infrared region.
Due to the topological charge-independent doughnut spatial structure as well as the association of orbital angular momentums, perfect vortex beams promise significant advances in fiber communication, ...optical manipulation and quantum optics. Inspired by the development of planar photonics, several plasmonic and dielectric metasurfaces have been constructed to generate perfect vortex beams, instead of conventional bulky configuration. However, owing to the intrinsic Ohmic losses and interband electron transitions in materials, these metasurface-based vortex beam generators only work at optical frequencies up to the visible range. Herein, using silicon nitride nanopillars as high-efficiency half-wave plates, broadband and high-performance metasurfaces are designed and demonstrated numerically to directly produce perfect vortex beams in the ultraviolet region, by combining the phase profiles of spiral phase plate, axicon and Fourier transformation lens based on geometric phase. The conversion efficiency of the metasurface is up to 86.6% at the design wavelength. Moreover, the influence of several control parameters on perfect vortex beam structures is discussed. We believe that this ultraviolet dielectric generator of perfect vortex beams will find many significant applications, such as high-resolution spectroscopy, optical tweezer and on-chip communication.
Due to the helical phase profile as well as the topological charge-independent doughnut spatial structure, perfect vortex beams have attract attentions in fiber communications and particle ...manipulations. However, for some advanced applications such as optical cage and optical microfluidic sorting and acceleration, it is more meaningful to generate asymmetric optical vortex fields such as elliptic perfect optical vortex (EPOV) beams. Herein we utilize silicon nitride nanopillars, functioning as half-wave plates, to construct high-efficiency geometric phase metasurfaces for the generation of EPOV beams with the integer and fractional topological charges in the ultraviolet range. By adjusting scaling factor, the shape of beams can be freely changed from circle to ellipse. In addition, multi-channel EPOV beams with arbitrary shape and different topological charges are produced with the help of the superposition principle of phase in Fourier space. We envision that this ultraviolet metasurface-based generator of EPOV beams can be used for manipulation of microscopic particle along an ellipse with acceleration and for the generation OAM-entangled photons.
•Efficient dielectric metasurfaces for the generation of elliptic perfect optical vortex (EPOV) beams.•Shape of EPOV beams can be freely changed from circle to ellipse by changing scaling factor.•Multi-channel EPOV beams with arbitrary shape and different topological charges are produced.
Acrylamide (ACR) generated in carbohydrate-rich foods during thermal processing has been demonstrated to exhibit hepatotoxicity. As one of the most consumed flavonoids with diet, quercetin (QCT) ...possesses the ability to protect against ACR-induced toxicity, albeit its mechanism is unclear. Herein, we discovered that QCT alleviated ACR-induced elevated levels of reactive oxygen species (ROS), AST, and ALT in mice. RNA-seq analysis revealed that QCT reversed the ferroptosis signaling pathway upregulated by ACR. Subsequently, experiments indicated that QCT inhibited ACR-induced ferroptosis through the reduction of oxidative stress. With autophagy inhibitor chloroquine, we further confirmed that QCT suppressed ACR-induced ferroptosis by inhibiting oxidative stress-driven autophagy. Additionally, QCT specifically reacted with autophagic cargo receptor NCOA4, blocked the degradation of iron storage protein FTH1, and eventually downregulated the intracellular iron levels and the consequent ferroptosis. Collectively, our results presented a unique approach to alleviate ACR-induced liver injury by targeting ferroptosis with QCT.
Solar energy as an inexhaustible source of clean energy has attracted more and more attention. As an important way to collect source of energy, solar absorber is widely reported and studied. However, ...how to efficiently absorb the solar energy in the solar radiation range is a long-term perplexing problem. In this work, we propose a new type of broadband solar energy absorber based on monolayer molybdenum disulfide (MoS2). Tungsten (W) elliptical arrays are introduced into the structure to enhance its absorption. By exciting local surface plasmon resonance (LSPR) between monolayer MoS2 and tungsten elliptical arrays, ultra-broadband solar energy absorber with high absorption rate is obtained. Theoretical calculation by a finite-difference time-domain method (FDTD) shows that absorption with a bandwidth of 1750 nm from about 280 nm to 2030 nm has been achieved. The peak values of resonance wavelength at 1275 nm and 1885 nm are both greater than 99%. Our absorber also has good polarization independence and incidence insensitivity, which provides a theoretical basis for its work in the actual solar environment and possibilities for its application in other solar devices. The inspiration for proposed absorber can also be applied to other transition-metal dichalcogenides (TMDCs).
We propose a broadband solar energy absorber based on monolayer molybdenum disulfide (MoS2) using tungsten (W) elliptical arrays. We find that the solar energy absorption efficiency is high and the operating region is extremely wide due to the combination of monolayer MoS2 and W elliptical arrays. Display omitted
•The absorption efficiency can be effectively improved by combining MoS2 and W elliptical arrays.•Our absorber has good operating band, polarization independence and incidence insensitivity.•The proposed nanostructure can be used for other TMDCs materials.
A novel planar plasmonic metamaterial for electromagnetically induced transparency and slow light characteristic is presented in this paper, which consists of nanoring and nanorod compound ...structures. Two bright modes in the metamaterial are induced by the electric dipole resonance inside nanoring and nanorod, respectively. The coupling between two bright modes introduces transparency window and large group index. By adjusting the geometric parameters of metamaterial structure, the transmittance of EIT window at 385 THz is about 60%, and the corresponding group index and Q factor can reach up to 1.2 × 10³ and 97, respectively, which has an important application in slow-light device, active plasmonic switch, SERS and optical sensing.
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