Exploring the impact of high-altitude de-acclimatization on renal function: The roles of oxidative and endoplasmic reticulum stress in rat models.

BACKGROUND: High-altitude de-acclimatization (HADA) significantly impacts physiological functions when individuals acclimatize to high altitudes return to lower altitudes. This study investigates HADA's effects on renal function and structure in rats, focusing on oxidative and endoplasmic reticulum stress as potential mechanisms of renal injury. OBJECTIVE: To elucidate the pathophysiological mechanisms of renal damage in HADA and evaluate the efficacy of antioxidants Vitamin C (Vit C) and tauroursodeoxycholic acid (TUDCA) in mitigating these effects. METHODS: 88 male Sprague-Dawley rats were randomly divided into a control group, a high-altitude (HA) group, a high-altitude de-acclimatization (HADA) group, and a treatment group. The control group was housed in a sea level environment (500 m), while the HA, HADA, and treatment groups were placed in a simulated high-altitude chamber (5000 m) for 90 days. After this period, the HA group completed the modeling phase; the HADA group was further subdivided into four subgroups, each continuing to be housed in a sea level environment for 3, 7, 14, and 30 days, respectively. The treatment group was split into the Vit C group, the TUDCA group, and two placebo groups, receiving medication for 3 consecutive days, once daily upon return to the sea level. The Vit C group received 100 mg/kg Vit C solution via intravenous injection, the TUDCA group received 250 mg/kg TUDCA solution via intraperitoneal injection, and the placebo groups received an equivalent volume of saline similarly. Serum, urine, and kidney tissues were collected immediately after the modeling phase. Renal function and oxidative stress levels were assessed using biochemical and ELISA methods. Renal histopathology was observed with H&E, Masson's trichrome, PAS, and PASM staining. Transmission electron microscopy was used to examine the ultrastructure of glomeruli and filtration barrier. TUNEL staining assessed cortical apoptosis in the kidneys. Metabolomics was employed for differential metabolite screening and pathway enrichment analysis. RESULTS: Compared to the control and HA groups, the HADA 3-day group (HADA-3D) exhibited elevated renal function indicators, significant pathological damage, observable ultrastructural alterations including endoplasmic reticulum expansion and apoptosis. TUNEL-positive cells significantly increased, indicating heightened oxidative stress levels. Various differential metabolites were enriched in pathways related to oxidative and endoplasmic reticulum stress. Early intervention with Vit C and TUDCA markedly alleviated renal injury in HADA rats, significantly reducing the number of apoptotic cells, mitigating endoplasmic reticulum stress, and substantially lowering oxidative stress levels. CONCLUSION: This study elucidates the pivotal roles of oxidative and endoplasmic reticulum stress in the early-stage renal injury in rats undergoing HADA. Early intervention with the Vit C and TUDCA significantly mitigates renal damage caused by HADA. These findings provide insights into the pathophysiological mechanisms of HADA and suggest potential therapeutic strategies for its future management.

Near-perfect absorption of a honeycomb metasurface through QBICs.

All-dielectric high-Q metasurface absorbers based on quasi-bound states in the continuum (QBICs) are essential for optical and photonic devices. However, achieving perfect absorption requires adding back reflectors at the bottom or placing at least four asymmetric elements in each unit of monolayer metasurfaces, which will increase the design complexity. This work proposes a honeycomb structure with units periodically arranged as a hexagonal lattice. Each unit cell is made of two nanopost elements. By only tuning the radius difference of two elements to break the in-plane symmetry, two orthogonal QBIC modes corresponding to toroidal dipole (TD) and electric dipole (ED) modes are excited, respectively. The maximum absorption reaches 92.3% at 955 nm with a Q factor of 1501, breaking the monolayer limit of 50% by the degenerate critical coupling. Our work may provide a promising route for designing high-Q all-dielectric metasurface absorbers applied in ultrafast optoelectronic devices.

Efficient free-space to on-chip coupling of THz-bandwidth pulses for biomolecule fingerprint sensing.

Wide bandwidth THz pulses can be used to record the distinctive spectral fingerprints related to the vibrational or rotational modes of polycrystalline biomolecules, and can be used to resolve the time-dependent dynamics of such systems. Waveguides, owing to their tight spatial confinement of the electromagnetic fields and the longer interaction distance, are promising platforms with which to study small volumes of such systems. The efficient input of sub-ps THz pulses into waveguides is challenging owing to the wide bandwidth of the THz signal. Here, we propose a sensing chip comprised of a pair of back-to-back Vivaldi antennas feeding into, and out from, a 90° bent slotline waveguide to overcome this problem. The effective operating bandwidth of the sensing chip ranges from 0.2 to 1.15 THz, and the free-space to on-chip coupling efficiency is as high as 51% at 0.44 THz. Over the entire band, the THz signal is ∼42 dB above the noise level at room temperature, with a peak of ∼73 dB above the noise. In order to demonstrate the use of the chip, we have measured the characteristic fingerprint of α-lactose monohydrate, and its sharp absorption peak at ∼0.53 THz was successfully observed, demonstrating the promise of our technique. The chip has the merits of efficient in-plane coupling, ultra-wide bandwidth, ease-of-integration, and simple fabrication. It has the potential for large-scale manufacture, and can be a strong candidate for integration into other THz light-matter interaction platforms.

Optical analogy for temporal diffraction in tight-binding lattice.

The wave propagating through the temporal boundary has attracted considerable attention in the past few years because of the potential applications of time-varying systems in the optics community. However, temporal diffraction of light remains to be investigated, because free space is non-dispersive. Here, we theoretically provide the analytical expressions for the temporal diffraction contributions of electron waves across the temporal boundary between the free space and a dispersive medium. With the help of coupled waveguide arrays, temporal diffraction is analogously observed by the optical platform. The optical analogy results confirm the theoretical predictions of the temporal diffraction wave at the temporal boundary. By changing the permittivity of the waveguides, implying the coupling coefficient is modified, the temporal diffraction angle is tuned. Our analysis and observations of temporal diffraction of dispersive media have great potential in time-varying physics, signal processing, and photonics communications.

Lorentzian dispersive antireflection temporal coatings with multiple time durations.

As the temporal counterparts of traditional antireflection coatings, antireflection temporal coatings (ATCs) provide a novel approach to eliminate reflections by employing two-step temporal modulations. The interval between these two temporal modulation steps is called the time duration of the ATC. In this Letter, we explore ATCs utilizing Lorentzian dispersive media through an extended temporal transfer matrix method, and we discover that they exhibit diverse time durations and offer the potential for enhanced transmission. On one hand, the Lorentzian dispersive ATC can function as a temporal quarter-wave impedance transformer, similar to nondispersive ATCs. In this scenario, the time durations are consistently shorter than those of nondispersive ATCs, gradually converging to a constant value as the dielectric constant of the output layer approaches infinity. On the other hand, by finely tuning the parameters of the Lorentzian dispersive temporal coating, reflections can also be accidentally eliminated, which is not achievable with nondispersive temporal coatings. Consequently, Lorentzian dispersive ATCs offer additional time durations compared with nondispersive ATCs. Furthermore, Lorentzian dispersive ATCs with different time durations lead to distinct transmission characteristics. In certain cases, they can even enhance transmissions, a feat unattainable for nondispersive ATCs. These Lorentzian dispersive ATCs are feasible in the gigahertz and even terahertz regimes.

Carbon nanocoils decorated with scale-like mesoporous NiO nanosheets for ultrasensitive room temperature ppb-level NO2 sensing.

Although NO2 detection based on metal oxide semiconductors (MOSs) has received continuous attention, the sensing properties of MOSs still need to be further improved for practical application. Carbon nanocoils (CNCs) exhibit excellent physicochemical properties due to their unique polycrystalline amorphous structure and helical morphology. Herein, CNCs composited with NiO nanosheets were developed for room temperature NO2 sensing, in which highly dispersed mesoporous NiO nanosheets on CNCs was achieved with extremely higher sensitivity. Due to a large number of exposed active sites and the efficient conductive network of CNCs, this particular scale-like nanocomposite exhibits a nearly 8 times higher response to 60 ppm NO2 than bare NiO nanosheets at room temperature, outperforming the majority of previously reported NO2 sensors at room temperature. Moreover, the nanocomposite-based gas sensor has a detection concentration limit of 60.3 ppb, which is advantageous for the sensing of NO2 at low concentrations. We believe that this work will provide the direction for the research and development of highly sensitive smart sensors, as well as encourage further investigation of multifunctional sensing applications utilizing CNCs as the primary frame support material.

Parental presence during induction of anesthesia in children undergoing tonsillectomy and adenoidectomy.

OBJECTIVE: To investigate the effect of parental presence during induction of anesthesia (PPIA) in relieving preoperative anxiety of children undergoing tonsillectomy and adenoidectomy. METHODS: One hundred and sixty children undergoing tonsillectomy and adenoidectomy were divided into the control group and the trial group. The control group received routine nursing in the operation room, while anesthesia was induced in the trial group children in the presence of their parents as part of the routine nursing. The differences in heart rate and mean dynamic pressure during pre-operative visit and anesthesia induction between the two groups were observed and recorded. The Modified Yale Preoperative Anxiety Scale (m-YPAS) and the Induction Compliance Checklist (ICC) were scored. The anxiety status of the children and their family members in the two groups was scored at different times, and the psychological stress of anesthesiologists during anesthesia induction was scored by a visual analogue scale. The differences in each index between the two groups were compared. Operation time and costs in-hospital were also compared. RESULTS: Compared with the control group, the heart rate and blood pressure scores as well as the ICC in the trial group were lower than those in the control group (P < 0.01). On comparing the scores of m-YPAS between the two groups, we observed that the scores of the children in the trial group were lower than those in the control group before entering the induction room and anesthesia induction (P < 0.01). There was no statistical difference between the scores of the children in the trial group and the control group on the day of operation and on the way to the operating room (P > 0.05). The nursing satisfaction scores of the family members in the trial group were significantly superior to those in the control group (P < 0.01). The scores of the visual analogue scale for psychological pressure of anesthesiologists during anesthesia induction were higher in the trial group than in the control group (P < 0.05). The operation time and costs in study group were both significantly higher than those of control group (P < 0.05). CONCLUSION: PPIA can significantly reduce preoperative anxiety and surgical physiological stress response in children undergoing tonsillectomy and adenoidectomy, and it is worth being encouraged.

[Correlation between rhizosphere environment and content of medicinal components of Arnebia euchroma].

This study aimed to explore the correlation between rhizosphere soil microorganisms of wild Arnebia euchroma and the content of medicinal components to provide guidance for the selection of the ecological planting base. The total DNA of rhizosphere soil microorganisms of wild A. euchroma was extracted, and the microbial community structure of rhizosphere soil microorganisms was analyzed by IlluminaMiseq high-throughput sequencing technology. The content of total hydroxynaphthoquinone pigment and ß,ß'-dimethylacrylalkannin in medicinal materials was determined by high-performance liquid chromatography(HPLC). The physicochemical pro-perties of rhizosphere soil of wild A. euchroma in main producing areas were determined, and the correlation of soil microbial abundance with index component content and soil physicochemical properties was analyzed by SPSS software. The results showed that the species composition of rhizosphere fungi and bacteria in A. euchroma from different habitats was similar at the phylum and genus levels, but their relative abundance, richness index(Chao1), and community diversity(Simpson) index were different. Correlation analysis showed that the content of available phosphorus in soil was positively correlated with the content of total hydroxynaphthoquinone pigment and ß,ß'-dimethylacrylalkannin, and the abundance of five fungal genera such as Solicoccozyma and six bacterial genera such as Pseudo-nocardia and Bradyrhizobium was positively correlated with the content of medicinal components in medicinal materials. The abundance of Bradyrhizobium was significantly positively correlated with the content of ß,ß'-dimethylacrylalkanin. The abundance of fungi such as Archaeorhizomyces was significantly positively correlated with the content of available phosphorus in rhizosphere soil, and Bradyrhizobium was significantly negatively correlated with soil pH. Therefore, the abundance of fungi and bacteria in the rhizosphere of A. euchroma has a certain correlation with the medicinal components and the physicochemical properties of the rhizosphere soil, which can provide a scientific basis for the selection of ecological planting bases in the later stage.

Detection of Matrix Metalloproteinase-1 in Human Saliva Based on a Pregnancy Test Strip Platform.

Matrix metalloproteinase (MMP) is closely correlated with tumorigenesis and progression. Establishing a low-cost, simple, rapid, and sensitive method for its detection is highly desired for the broad-spectrum screening of oral cancer. Herein, we combine the MMP-specific cleavage ability with magnetic separation technology and a commercial test strip to construct a sensitive biosensor to detect MMP-1 conveniently for the first time. The method involves two DNA probes, peptide-DNA1 and hCG-DNA2, where DNA1 and DNA2 are complementary sequences, and the peptide labeled with biotin can bind streptavidin-modified magnetic nanoparticles stably. The human chorionic gonadotropin (hCG) is the target of the pregnancy test strip. The cleavage reaction mediated by MMP-1 releases peptide-DNA1 and the hybridized hCG-DNA2 into the solution, and the hCG probe in the solution can develop color on the test strip for the determination of MMP-1 after magnetic separation. This method utilizes the high specificity of MMP-1's proteolytic cleavage and the high sensitivity of the test strip to the target probe, achieving a sensitive detection of MMP-1 with a visual detection limit of 65.5 pg/mL. The method shows better anti-interference and sensitivity than the enzyme-linked immunosorbent assay in the application of a biological sample matrix, suggesting its great potential for clinical diagnosis, especially for broad-spectrum oral cancer screening.

Tunable bilayer dielectric metasurface via stacking magnetic mirrors.

Functional tunability, environmental adaptability, and easy fabrication are highly desired properties in metasurfaces. Here we provide a tunable bilayer metasurface composed of two stacked identical dielectric magnetic mirrors. The magnetic mirrors are excited by the interaction between the interference of multipoles of each cylinder and the lattice resonance of the periodic array, which exhibits nonlocal electric field enhancement near the interface and high reflection. We achieve the reversible conversion between high reflection and high transmission by manipulating the interlayer coupling near the interface between the two magnetic mirrors. Controlling the interlayer spacing leads to the controllable interlayer coupling and scattering of meta-atom. The magnetic mirror effect boosts the interlayer coupling when the interlayer spacing is small. Furthermore, the high transmission of the bilayer metasurface has good robustness due to the meta-atom with interlayer coupling can maintain scattering suppression against positional perturbation. This work provides a straightforward method to design tunable metasurface and sheds new light on high-performance optical switches applied in communication and sensing.

Optical Bound States in Continuum in MoS2-Based Metasurface for Directional Light Emission.

High quality factor (Q-factor) and strong field localization in nanostructures is a newly emerged direction in nanophotonics. The bound states in the continuum (BIC) have been investigated in nanoparticles with infinite Q-factor. We report BIC in molybdenum disulfide (MoS2) based Mie nanoresonator suspended in air. The ultrathin nanodisk supports symmetry protected BIC, and the quasi-BIC (q-BIC) are exploited by breaking the symmetry of the structure. The strongly localized modes in our MoS2-based nanodisk sustain a similar magnetic field profile before and after symmetry breaking, unlike what has been previously reported in silicon-based structures. Strong directional emission is observed in BIC regime from a hybrid configuration with a resonator placed on the stacked metal-dielectric layers, which transform BIC to q-BIC and exploit highly directional light. The structure persists emission with small variations in normalized intensity at distorted symmetry. The giant Q-factor in q-BIC is highly desired for biosensing and optical filters.

[The distribution of Mas-related G protein-coupled receptor A in cerebrospinal fluid-contacting nucleus of normal rats and its up-regulation in neuropathic pain].

This study was aimed to observe the distribution of Mas-related G protein-coupled receptor A (MrgA) in cerebrospinal fluid (CSF)-contacting nucleus of normal rats and its expression in neuropathic pain, and to provide morphological evidence for CSF-contacting nucleus to participate in neuropathic pain. The model of neuropathic pain with chronic constriction injury (CCI) of the sciatic nerve was made in Sprague-Dawley rats. The thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were measured. The expressions of MrgA in the CSF-contacting nucleus were examined by double labeling with immunofluorescent staining. The results showed that on the 5th, 7th, 10th and 14th days, the values of MWT and TWL in CCI group were all lower than those in sham group (P < 0.05). MrgA was found to be distributed in CSF-contacting nucleus of normal rats; and the expression was markedly up-regulated in rats at the peak of neuropathic pain. Our data suggest that CSF-contacting nucleus may participate in neuropathic pain through the MrgA-mediated signaling pathway.

Silencing linc00662 inhibits cell proliferation and colony formation of lung cancer cells via regulating the miR-145-5p-PAFAH1B2 axis.

Lung cancer is the most common cause of cancer-related death in the world. Long non-coding RNAs (lncRNAs) are longer than 200 nucleotide transcripts, and are not translated into protein. The lncRNA linc00662 is overexpressed in lung cancer; however, its role in lung cancer is still unknown. In our study, by analyzing the TCGA data, we found that linc00662 was overexpressed in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). We knocked-down the expression of linc00662 using siRNA, and found that silencing linc00662 significantly inhibited the proliferation and colony formation of the lung cancer cell lines A549 and H460. We also found that knockdown of linc00662 increased the expression of the microRNA miR-145-5p and decreased the expression of the platelet-activating factor acetylhydrolase IB subunit beta (PAFAH1B2) gene. We further show that linc00662 binds with miR-145-5p, and that miR-145-5p binds to the 3'UTR of PAFAH1B2. miR-145-5p negatively regulates PAFAH1B2 both at the mRNA and the protein level. Loss of miR-145-5p abolished the inhibitory effects of silencing linc00662 on the proliferation and colony formation of A549 and H460 cells. These findings indicate that linc00662 functions as an oncogene by acting as a competing endogenous RNA (ceRNA) and sponges and regulates miR-145-5p in lung cancer, and thus may provide a potential target for treating lung cancer.

Optical forces on a cylinder induced by surface waves and the conservation of the canonical momentum of light.

Based on rigorous derivations using the electromagnetic energy-momentum tensor, we established a generic relationship between the longitudinal optical force (along the surface wave propagating direction) on a cylinder induced by surface waves and the energy flux of each surface mode supported on the interface between air and a lossless substrate possessing continuous translational symmetry along the longitudinal direction. The longitudinal optical force is completely attributed to the canonical momentum of light. Our theory is valid for generic types of surface waves and lays the theoretical foundation for the research and applications of optical manipulations by surface waves.

Refractive index sensing and switching of leaky states in a metasurface.

We theoretically propose leaky states in an electro-optic (EO)-based all-dielectric metasurface. The EO substrate tunes leaky modes to the desired wave band with changes in applied voltage (Vapp). For refractive index (RI) sensing, the highest figure-of-merit (FoM) in this work is 9166, quality factor (Q-factor) is 1.7450e4, sensitivity is 407 nm/RIU (in RI range of 1.00-1.03), minimum detectable RI is 1.0542e-4, and relative sensitivity is 9.94e-4V-1. The structure sustains the figure and line shape of leaky modes, high Q-factor, and FoM at different Vapp and EO-coefficients. Our FoM and Q-factor are high, and the minimum detectable RI is smaller than previously reported. The giant Q-factor is promising for optical filters, modulation, and slow-light device applications.

Distinct effects of asthma and COPD comorbidity on disease expression and outcome in patients with COVID-19.

BACKGROUND: The impacts of chronic airway diseases on coronavirus disease 2019 (COVID-19) are far from understood. OBJECTIVE: To explore the influence of asthma and chronic obstructive pulmonary disease (COPD) comorbidity on disease expression and outcomes, and the potential underlying mechanisms in COVID-19 patients. METHODS: A total of 961 hospitalized COVID-19 patients with a definite clinical outcome (death or discharge) were retrospectively enrolled. Demographic and clinical information were extracted from the medical records. Lung tissue sections from patients suffering from lung cancer were used for immunohistochemistry study of angiotensin-converting enzyme II (ACE2) expression. BEAS-2B cell line was stimulated with various cytokines. RESULTS: In this cohort, 21 subjects (2.2%) had COPD and 22 (2.3%) had asthma. After adjusting for confounding factors, COPD patients had higher risk of developing severe illness (OR: 23.433; 95% CI 1.525-360.135; P < .01) and acute respiratory distress syndrome (OR: 19.762; 95% CI 1.461-267.369; P = .025) than asthmatics. COPD patients, particularly those with severe COVID-19, had lower counts of CD4+ T and CD8+ T cells and B cells and higher levels of TNF-α, IL-2 receptor, IL-10, IL-8, and IL-6 than asthmatics. COPD patients had increased, whereas asthmatics had decreased ACE2 protein expression in lower airways, compared with that in control subjects without asthma and COPD. IL-4 and IL-13 downregulated, but TNF-α, IL-12, and IL-17A upregulated ACE2 expression in BEAS-2B cells. CONCLUSION: Patients with asthma and COPD likely have different risk of severe COVID-19, which may be associated with different ACE2 expression.

Polymer dependent acoustic mode coupling and Hooke's law spring constants in stacked gold nanoplates.

Metal nanoparticles are excellent acoustic resonators and their vibrational spectroscopy has been widely investigated. However, the coupling between vibrational modes of different nanoparticles is less explored. For example, how the intervening medium affects the coupling strength is not known. Here, we investigate how different polymers affect coupling in Au nanoplate-polymer-Au nanoplate sandwich structures. The coupling between the breathing modes of the Au nanoplates was measured using single-particle pump-probe spectroscopy, and the polymer dependent coupling strength was determined experimentally. Analysis of the acoustic mode coupling gives the effective spring constant for the polymers. A relative motion mode was also observed for the stacked Au nanoplates. The frequency of this mode is strongly correlated with the coupling constant for the breathing modes. The breathing mode coupling and relative motion mode were analyzed using a coupled oscillator model. This model shows that both these effects can be described using the same spring constant for the polymer. Finally, we present a new type of mass balance using the strongly coupled resonators. We show that the resonators have a mass detection limit of a few femtograms. We envision that further understanding of the vibrational coupling in acoustic resonators will improve the coupling strength and expand their potential applications.

[Comprehensive analysis of components in Chinese medicines derived from Apocynum venetum and Poacynum pictum in Xinjiang based on HPLC fingerprint and chemometrics].

This study established high-performance liquid chromatography(HPLC) fingerprints of Chinese medicines derived from Apocynum venetum and Poacynum pictum in Xinjiang and explored their composition differences with the combination of content determination, similarity analysis, cluster analysis and principal component analysis. The HPLC conditions included Phenomenex Kinetex C_(18) column(4.6 mm ×100 mm, 2.6 µm), acetonitrile-0.01% trifluoroacetic acid aqueous solution as mobile phase, gradient elution, flow rate of 0.6 mL·min~(-1), detection wavelength of 281 nm and column temperature of 25 ℃. The content of chlorogenic acid, quercetin-3-O-sophoroside, rutin, hyperin, isoquercitrin, trifolin and astragalin was determined in 31 batches of medicinal materials, and fingerprint research and chemometric analysis were performed with Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine(Version 2004 A) and SPSS 21.0. In the Chinese Pharmacopoeia 2020, the quality of Apocyni Veneti Folium is controlled by character identification, microscopic identification, thin layer chromatography identification and quantitative determination of hyperin. There were 21 common peaks of A. venetum and P. pictum in the HPLC fingerprints, 5 of which were identified as chlorogenic acid, hyperin, isoquercitrin, trifolin and astragalin, with their content also determined. Except for 3 batches of medicinal materials, the similarity of other 28 batches was higher than 0.83, indicating good similarity. Two categories were formed in the cluster analysis based on content determination, which showed that some differences existed in similarities between different regions of Xinjiang. The medicinal materials were ranked by quality with principal component analysis, and the results indicated that the top 15 all came from northern Xinjiang. The quality difference of A. venetum and P. pictum had a correlation with the place of origin. This study provides a reference for the analysis and evaluation of A. venetum and P. pictum from different habitats and the selection of introduction and cultivation areas.

Tunable perfect magnetic mirrors and retroreflectors in terahertz band.

A magnetic mirror operating in the terahertz band is designed based on the functional reflective metasurface, which is simply constructed by a one-dimensional periodic lithium tantalate micro cylindrical rod array on a Teflon substrate coated with a metal layer at the bottom and reflects the incoming electric field with a zero-phase change. Magnetic dipole resonance of the micro cylindrical rods excited in the metasurface is attributed to the perfect magnetic mirror at the frequency of 0.286 THz with the reflectivity of R = 0.98 for a normal incident electromagnetic wave. By real-time varying the direction from normal (0) to 28.45 degrees and the frequency from 0.286 to 0.382 THz of the incident wave, the metasurface can still behave as a perfect magnetic mirror with the reflectivity as high as 0.99. Most interestingly, in this case, the metasurface possesses the property of a retroreflector that the reflected wave returns along the direction of the incident wave, which is consistent with the grating equation. The tunable perfect magnetic mirror effect and the retroreflector property may provide ways in novel photonic devices and sensing applications.

Substrate integrated Bragg waveguide: an octave-bandwidth single-mode hybrid transmission line for millimeter-wave applications.

We demonstrate an air-core single-mode hollow hybrid waveguide that uses Bragg reflector structures in place of the vertical metal walls of the standard rectangular waveguide or via holes of the so-called substrate integrated waveguide. The high-order modes in the waveguide are substantially suppressed by a modal-filtering effect, making the waveguide operate in the fundamental mode over more than one octave. Numerical simulations show that the propagation loss of the proposed waveguide can be lower than that of classic hollow metallic rectangular waveguides at terahertz frequencies, benefiting from a significant reduction in Ohmic loss. To facilitate fabrication and characterization, a proof-of-concept 20 to 45 GHz waveguide is demonstrated, which verifies the properties and advantages of the proposed waveguide. A zero group-velocity dispersion point is observed at near the middle of the operating band, which is ideal for reducing signal distortion. This work offers a step towards a hybrid transmission-line medium that can be used in a variety of functional components for multilayer integration and broadband applications.