A triple Fano resonance Si-graphene metasurface for multi-channel tunable ultra-narrow band sensing.

In this work, a dielectric metasurface composed of a silicon nanodisk etched with a square hole is proposed. By introducing C4v symmetry breaking, the symmetry-protected bound states in the continuum (SP-BIC) is transformed into a quasi-BIC (Q-BIC), simultaneously inducing triple Fano resonances in the near-infrared light band corresponding to one dipole and two Q-BIC resonances. The characteristics of Q-BIC resonances are elucidated through multipole decomposition and near-field distribution analysis. Subsequently, monolayer graphene is integrated into the Si metasurface. The light field in the composite metasurface can be flexibly modulated by changing the Fermi level of graphene. This modulation enables optimal transmission with an enhancement of up to 252%, while the confined electromagnetic energy experiences a remarkable increase of about 1020%. Simulation results demonstrate that the Si-graphene composite metasurface exhibits a high refractive index sensitivity of 162 nm RIU-1, accompanied by a figure of merit of 170.526 RIU-1. This composite metasurface holds promise as a high-performance sensor in the near-infrared band and has potential for application in the fields of active tunable optical devices and biochemical sensing.

Electromagnetic origin of femtosecond laser-induced periodic surface structures on GaP crystals.

The formations of different types of laser-induced periodic surface structures (LIPSS) on the surface of GaP crystals with different laser fluence are researched in experiments. The transition from the high spatial frequency LIPSS (HSFL) to the low spatial frequency LIPSS (LSFL) occurred as the number of the irradiated laser pulse increased. The finite difference time domain method combined with the holographic ablation model is used to simulate the LIPSS formation under the irradiation of multiple pulses. Different types of ripples are predicted by the electromagnetic approach. Results demonstrate that the electromagnetic origins of HSFL and LSFL are due to the interference of incident field and the scattering field under the multi-pulse irradiation.

Postconditioning With Red-Blue Light Therapy Improves Survival of Random Skin Flaps in a Rat Model.

BACKGROUND: Random skin flap ischemic necrosis is a serious challenge in reconstructive surgery. Photobiomodulation is a noninvasive effective technique to improve microcirculation and neovascularization. Photobiomodulation with red or blue light has been separately proven to partially prevent skin flap necrosis, but the synergistic effect of red and blue light not been elucidated. Our experiment evaluated the impact of postconditioning with red-blue light therapy on the viability of random flaps. METHODS: Thirty Sprague-Dawley male rats (male, 12 weeks) with a cranially based random pattern skin flap (3 × 8 cm) were divided into 3 groups: control group, red light group, and red-blue light group. On postoperative day 7, flap survival was observed and recorded using transparent graph paper, flaps were obtained and stained with hematoxylin and eosin, and microvessel density was measured. Micro-computed tomography was used to measure vascular volume and vascular length. On days 0, 3, and 7 after surgery, blood flow was measured by laser Doppler. To investigate the underlying mechanisms, the amount of nitric oxide (NO) metabolites in the flap tissue was assessed on days 3, 5, and 7 after surgery. RESULTS: The mean percentage of skin flap survival was 59 ± 10% for the control group, 69 ± 7% for the red light group, and 79 ± 9% for the red-blue light group (P < 0.01). The microvessel density was 12.3 ± 1.2/mm2 for the control group, 31.3 ± 1.3/mm2 for the red light group, and 36.5 ± 1.4/mm2 for the red-blue light group (P < 0.01). Both vascular volume and total length in the red-blue light group showed significantly increased compared with the red light and control group (P < 0.01). Blood flow in the red-blue light treated flap showed significantly increased at postsurgery days 3 and 7 compared with the red light and control group (P < 0.01). The level of the NO metabolites was significantly increased in flap tissues belonging to the red-blue light group compared with the other 2 groups (P < 0.01). CONCLUSIONS: This study showed that postconditioning with red-blue light therapy can enhance the survival of random skin flap by improving angiogenesis and NO releasing.

Ultrafast dynamics of the thin surface plasma layer and the periodic ripples formation on GaP crystal irradiated by a single femtosecond laser pulse.

Ultrafast dynamic of thin surface plasma layer plays a crucial role in the formation of periodic surface ripples after laser pulse irradiation. Using the pump-probe imaging technique, a complete scenario of the periodic ripples formation on a GaP surface is demonstrated after being irradiated by single femtosecond laser pulse. The ripples firstly emerge at delay time of several tens of picoseconds, and disappear completely at several hundreds of picoseconds, resulting in a transient overheating solid state ablation crater. It's interesting that new ripples appear and gradually become deep and clear after hundreds of picoseconds. A part of these ripples remain after the ablation crater is solidified. The period of the remained ripples is measured and approximately equal to the periods of the two transient ripples. The thin surface plasma model with multi-layer is introduced to study the formation of periodic ripples. The dynamics of the carrier excitation, carrier and lattice temperature, transient dielectric constant, and other factors are obtained by the two-temperature model and the Drude model. The results show that the periods of electric field distributions at different depths of the plasma layer are the same. The formation of the two transient ripples and the remained ripples are all related to the periodic energy deposition due to the SPP excitation at the air-plasma interface.

An in vitro metabolic system of gut flora and the metabolism of ginsenoside Rg3 and cholic acid.

For orally administered drugs, the metabolism of a drug by the gut flora plays an important role in the bioavailability, activation and disposition of the drug in vivo. However, no in vitro system is currently available to evaluate the metabolism of a drug by the gut flora before the drug is absorbed into the body. This paper presents an in vitro metabolic system in an anaerobic environment that could be used to evaluate the metabolism of an endogenous compound, cholic acid, and a xenobiotic compound, ginsenoside Rg3. We showed that the proliferation of the anaerobic bacteria of the gut content of hamsters produced a similar composition of gut flora in a culture medium for yeast to that in vivo. Incubation of ginsenoside Rg3 and cholic acid in the anaerobic in vitro system efficiently produced the metabolites Rh2 and deoxycholic acid, respectively, similar to those seen in the gut content in vivo. In comparison with in vivo analysis, this anaerobic in vitro metabolic system is convenient, reproducible, economic and animal saving, and can easily be applied to assess the transformation and disposition of a drug before it enters into the circulatory system.

A Generic Strategy to Stabilize Wide Bandgap Perovskites for Efficient Tandem Solar Cells.

Efficient wide bandgap (WBG) perovskite solar cells (PSCs) are essential for fully maximizing the potential of tandem solar cells. However, these cells currently face challenges such as high photovoltage losses and the presence of phase segregation, which impede the attainment of their expected efficiency and stability. Herein, the root cause of halide segregation is investigated, uncovering a close association with the presence of locally aggregated lead iodide (PbI2 ), particularly at the perovskite/C60 interface. Kelvin-probe atomic force microscopy results indicate that the remaining PbI2 at the interface leads to potential electrical differences between the domain surface and boundaries, which drives the formation of halide segregation. By reacting the surface PbI2 residue with ethanediamine dihydroiodide (EDAI2 ) at proper temperature, it is possible to effectively mitigate the phase segregation. By applying this surface reaction strategy in WBG inverted cells, a notable improvement of ≈100 mV is achieved in photovoltage over a wide range of WBG cells (1.67-1.78 eV), resulting in a champion efficiency of 23.1% (certified 22.95%) for 1.67 eV cells and 19.7% (certified 18.81%) for 1.75 eV cells. Furthermore, efficiency of 26.1% is demonstrated in a monolithic all-perovskite tandem cell.

The Cation Distributions of Zn-doped Normal Spinel MgFe2O4 Ferrite and Its Magnetic Properties.

Determining the exact occupation sites of the doping ions in spinel ferrites is vital for tailoring and improving their magnetic properties. In this study, the distribution and occupation sites of cations in MgFe2O4 and Zn-doped MgFe2O4 ferrite are imaged by Cs-STEM. The experimental STEM images along [001], [011] and [111] orientations suggest that the divalent Mg2+ cations occupy all A sites, and the trivalent Fe3+ cations occupy all B sites in MgFe2O4 ferrite prepared by electrospinning, which is consistent with the normal spinel structure. We further clarify that the preferred sites of dopant Zn2+ ions are Fe3+ crystallographic sites in the Zn-doped MgFe2O4 ferrite nanofibers. Magnetic measurements show that Zn doping affects the spin states of the Fe3+, and the Fe3+-O2--Fe3+ super-exchange interaction leads to enhancements in the magnetization and reduction in the Curie temperature. Our work should contribute a significant step toward eventually realizing the practical application of doped spinel ferrites.

Comparative study on high-pressure physical properties of monoclinic MgCO3 and Mg2CO4.

The physical properties of Mg-carbonate at high temperature and pressure are crucial for understanding the deep carbon cycle. Here, we use first-principles calculations to study the physical properties of MgCO3-C2/m and Mg2CO4-P21/c under high pressure. The research shows that the structure and equation of state of MgCO3-C2/m are in good agreement with the experimental results, and the phase transition pressure of Mg2CO4 from pnma to P21/c structure is 44.66 GPa. By comparing the elastic properties, seismic properties and anisotropy of MgCO3-C2/m and Mg2CO4-P21/c, it is found that the elastic modulus and sound velocity of Mg2CO4-P21/c are smaller than those of MgCO3-C2/m, while the anisotropy is larger than that of MgCO3-C2/m. These results indicate that Mg2CO4-P21/c exists in the deep mantle and may be the main reason why carbonate cannot be detected. The minimum thermal conductivity of MgCO3-C2/m and Mg2CO4-P21/c is the largest in the [010] direction and the smallest in the [001] direction. The thermodynamic properties of MgCO3-C2/m and Mg2CO4-P21/c are predicted using the quasi-harmonic approximation (QHA) method.

Synergistic Effects of Photobiomodulation Therapy with Combined Wavelength on Diabetic Wound Healing In Vitro and In Vivo.

Objective: The difficulty in chronic diabetic wound healing remains the focus of clinical research. Photobiomodulation therapy (PBMT) with different wavelengths could exert different effects on wound healing, but the effects of combined red and blue light (BL) remained unclear. Methods: Diabetic rat wound model and diabetic wounded endothelial cell model were established to observe possible effects of PBMT using combined wavelengths for wound healing. Cells and animals were separated into four groups exposed to red and/or BL. Cell viability, apoptosis, and migration, as well as the expression level of nitric oxide (NO), vascular endothelial growth factor, interleukin-6, and tumor necrosis factor-α were measured in vitro. Diabetic rats were evaluated for wound closure rates, collagen deposition, inflammation intensity, and density of neovascularization after light irradiation. Results: PBMT using combined wavelengths significantly sped up the healing process with increasing angiogenesis density, collagen deposition, and alleviating inflammation in vivo. Moreover, combined wavelength irradiation promoted cell proliferation and migration, and NO production, as well as reduced reactive oxygen species and inflammation in vitro. Conclusions: PBMT using combined wavelengths performed a synergistic effect for promoting diabetic wound healing and would be helpful to explore a more efficient pattern toward chronic wound healing.

Ultrasensitive electrochemical determination of phosphate in water by using hydrophilic TiO2 modified glassy carbon electrodes.

In this paper, ultrasensitive electrochemical determination of phosphate in water is achieved by using hydrophilic TiO2 modified glassy carbon electrodes for the first time. The differential pulse voltammetry (DPV) method is proposed to measure phosphate in water as pulse techniques offer higher sensitivity compared with the conventional cyclic voltammetry (CV) method. Hydrophilic TiO2 films were obtained upon ultraviolet (UV) illumination after TiO2 precursor emulsions were coated on the surfaces of glassy carbon electrodes, and used for phosphate determination. Contact angle measurements (around 23.4°) proved the good hydrophilicity of the TiO2 modified surface upon UV illumination. A detection limit of 0.1 µg L-1 is obtained, and a linear relationship (R2 = 0.99) between the phosphate concentration (ranging from 0.1 µg L-1 to 1 µg L-1) and the peak current was observed.