The impedance matching to free space in metamaterial perfect absorbers has been believed to involve and rely on magnetic resonant response, with direct evidence provided by the anti-parallel surface ...currents in the metal structures. Here I present a different theoretical interpretation based on interference, which shows that the two layers of metal structures in metamaterial absorbers are linked only by multiple reflections with negligible near-field interactions or magnetic resonances. This is further supported by the out-of-phase surface currents derived at the interfaces of resonator array and ground plane through multiple reflections and superpositions. The theory developed here explains all features observed in narrowband metamaterial absorbers and therefore provides a profound understanding of the underlying physics.
Metamaterials are composed of periodic subwavelength metal/dielectric structures that resonantly couple to the electric and/or magnetic components of the incident electromagnetic fields, exhibiting ...properties that are not found in nature. This class of micro- and nano-structured artificial media have attracted great interest during the past 15 years and yielded ground-breaking electromagnetic and photonic phenomena. However, the high losses and strong dispersion associated with the resonant responses and the use of metallic structures, as well as the difficulty in fabricating the micro- and nanoscale 3D structures, have hindered practical applications of metamaterials. Planar metamaterials with subwavelength thickness, or metasurfaces, consisting of single-layer or few-layer stacks of planar structures, can be readily fabricated using lithography and nanoprinting methods, and the ultrathin thickness in the wave propagation direction can greatly suppress the undesirable losses. Metasurfaces enable a spatially varying optical response (e.g. scattering amplitude, phase, and polarization), mold optical wavefronts into shapes that can be designed at will, and facilitate the integration of functional materials to accomplish active control and greatly enhanced nonlinear response. This paper reviews recent progress in the physics of metasurfaces operating at wavelengths ranging from microwave to visible. We provide an overview of key metasurface concepts such as anomalous reflection and refraction, and introduce metasurfaces based on the Pancharatnam-Berry phase and Huygens' metasurfaces, as well as their use in wavefront shaping and beam forming applications, followed by a discussion of polarization conversion in few-layer metasurfaces and their related properties. An overview of dielectric metasurfaces reveals their ability to realize unique functionalities coupled with Mie resonances and their low ohmic losses. We also describe metasurfaces for wave guidance and radiation control, as well as active and nonlinear metasurfaces. Finally, we conclude by providing our opinions of opportunities and challenges in this rapidly developing research field.
Bismuth tungstate (Bi2WO6) has become a research hotspot due to its potential in photocatalytic energy conversion and environmental purification. Nevertheless, the limited light absorption and fast ...recombination of photogenerated carriers hinder the further improvement of the photocatalytic performance of Bi2WO6. Herein, we provide a systematic review for the recent advances on Bi2WO6-based photocatalysts. It starts with the crystal structure, optical properties and photocatalytic fundamentals of Bi2WO6. Then, we focus on the modification strategies of Bi2WO6 based on morphology control, atomic modulation and composite fabrication for diverse photocatalytic applications, such as organic synthesis, water splitting, CO2 reduction, water treatment, air purification, bacterial inactivation, etc. Finally, some current challenges and future development prospects are proposed. We expect that this review can provide a useful reference and guidance for the development of efficient Bi2WO6 photocatalysts.
This review provides a systematic summary on the recent advances of Bi2WO6-based photocatalysts in fields of energy and environment. More importantly, different modification strategies for improving the photocatalytic activity of Bi2WO6 were discussed.
Polarization is one of the basic properties of electromagnetic waves conveying valuable information in signal transmission and sensitive measurements. Conventional methods for advanced polarization ...control impose demanding requirements on material properties and attain only limited performance. We demonstrated ultrathin, broadband, and highly efficient metamaterial-based terahertz polarization converters that are capable of rotating a linear polarization state into its orthogonal one. On the basis of these results, we created metamaterial structures capable of realizing near-perfect anomalous refraction. Our work opens new opportunities for creating high-performance photonic devices and enables emergent metamaterial functionalities for applications in the technologically difficult terahertz-frequency regime.
This article proposes an end-to-end learnt lossy image compression approach, which is built on top of the deep nerual network (DNN)-based variational auto-encoder (VAE) structure with Non-Local ...Attention optimization and Improved Context modeling (NLAIC). Our NLAIC 1) embeds non-local network operations as non-linear transforms in both main and hyper coders for deriving respective latent features and hyperpriors by exploiting both local and global correlations, 2) applies attention mechanism to generate implicit masks that are used to weigh the features for adaptive bit allocation, and 3) implements the improved conditional entropy modeling of latent features using joint 3D convolutional neural network (CNN)-based autoregressive contexts and hyperpriors. Towards the practical application, additional enhancements are also introduced to speed up the computational processing (e.g., parallel 3D CNN-based context prediction), decrease the memory consumption (e.g., sparse non-local processing) and reduce the implementation complexity (e.g., a unified model for variable rates without re-training). The proposed model outperforms existing learnt and conventional (e.g., BPG, JPEG2000, JPEG) image compression methods, on both Kodak and Tecnick datasets with the state-of-the-art compression efficiency, for both PSNR and MS-SSIM quality measurements. We have made all materials publicly accessible at https://njuvision.github.io/NIC for reproducible research.
Higher education can play a crucial role in shaping one’s social identity, and a diploma from a prestigious institution has a positive effect on a person’s social status. However, the expansion of ...college enrollment in 1999 in China weakened the capacity of a college diploma to confer on graduates a distinct identity as someone of high standing. For youth from rural backgrounds, higher education was once the most important channel for upward social mobility. As the social value of a college diploma has declined, most college graduates from rural backgrounds have been assigned a new identity: the “new urban poor” (NUP). This article discusses the construction and characteristics of the NUP identity in China, using evidence from television series.
The lineage transition between epithelium and mesenchyme is a process known as epithelial–mesenchymal transition (EMT), by which polarized epithelial cells lose their adhesion property and obtain ...mesenchymal cell phenotypes. EMT is a biological process that is often involved in embryogenesis and diseases, such as cancer invasion and metastasis. The EMT and the reverse process, mesenchymal–epithelial transition (MET), also play important roles in stem cell differentiation and de‐differentiation (or reprogramming). In this review, we will discuss current research progress of EMT in embryonic development, cellular differentiation and reprogramming, and cancer progression, all of which are representative models for researches of stem cell biology in normal and in diseases. Understanding of EMT and MET may help to identify specific markers to distinguish normal stem cells from cancer stem cells in future.
In this review, we discuss current research progress of EMT in embryonic development, cellular differentiation and reprogramming, and cancer progression, all of which are representative models for researches of stem cell biology in normals and in diseases.
Tamoxifen is the most commonly used endocrine therapy for patients with hormone receptor (HR)-positive breast cancer. Despite its initial therapeutic efficacy, many patients eventually develop drug ...resistance, which remains a serious clinical challenge. To investigate roles of circular RNAs (circRNAs) in tamoxifen resistance, a tamoxifen-resistant MCF-7 cell line was established and screened for its circRNA expression profile by RNA sequencing. hsa_circ_0025202, a circRNA that was significantly downregulated, was selected for further investigation. Using a large cohort of clinical specimens, we found that hsa_circ_0025202 exhibited low expression in cancer tissues and was negatively correlated with lymphatic metastasis and histological grade. Gain- and loss-of-function assays indicated that hsa_circ_0025202 could inhibit cell proliferation, colony formation, and migration and increase cell apoptosis and sensitivity to tamoxifen. Bioinformatics and luciferase reporter assays verified that hsa_circ_0025202 could act as a miRNA sponge for miR-182-5p and further regulate the expression and activity of FOXO3a. Functional studies revealed that tumor inhibition and tamoxifen sensitization effects of hsa_circ_0025202 were achieved via the miR-182-5p/FOXO3a axis. Moreover, in vivo experiments confirmed that hsa_circ_0025202 could suppress tumor growth and enhance tamoxifen efficacy. Taken together, hsa_circ_0025202 served an anti-oncogenic role in HR-positive breast cancer, and it could be exploited as a novel marker for tamoxifen-resistant breast cancer.
This report demonstrates a novel circular RNA, named hsa_circ_0025202, which is downregulated in tamoxifen-resistant breast cancer cells. hsa_circ_0025202 was identified as a tumor suppressor, and it could improve tamoxifen sensitivity through regulating the miR-182-5p/FOXO3a axis, suggesting it could be a potential therapeutic target and marker for patients with hormone receptor-positive breast cancer.
Abstract
Occupational noise-induced hearing loss (ONIHL) is the most prevalent occupational disease in the world. The goal of this study was to review the epidemiology, pathogenesis, and preventive ...measures of ONIHL among workers and provide evidence for the implementation of control measures. Literature studies were identified from the MEDLINE, PubMed, Embase, Web of Science, and Google Scholar using the search terms “noise-induced hearing loss” “prevalence”, “pathogenesis”, and “preventive measures”. The articles reviewed in this report were limited from 2000 to 2020. Articles that were not published in the English language, manuscripts without an abstract, and opinion articles were excluded. After a preliminary screening, all of the articles were reviewed and synthesized to provide an overview of the current status of ONIHL among workers. The mechanism of ONIHL among workers is a complex interaction between environmental and host factors (both genetic and acquired factors). The outcomes of noise exposure are different among individual subjects. Clinical trials are currently underway to evaluate the treatment effect of antioxidants on ONIHL. Noise exposure may contribute to temporary or permanent threshold shifts; however, even temporary threshold shifts may predispose an individual to eventual permanent hearing loss. Noise prevention programs are an important preventive measure in reducing the morbidity of ONIHL among workers.
ETHNOPHARMACOLOGICAL RELEVANCEAloe barbadensis Mill. (Aloe vera), is a homology of medicine and food plant, widely applied in functional food, cosmetics, and medicine. Aloe vera whole leaf extract, ...one of the most popular traditional Chinese medicines (TCMs), is mainly used in China to treat functional constipation.AIM OF THE STUDYTo elucidate the active constituents of Aloe vera for treating functional constipation.MATERIALS AND METHODSPrototype constituents and metabolites in rat plasma and excreta after oral administration of Aloe vera whole leaf extract were identified by UPLC-Q-TOF/MS, and the pharmacokinetics (PK) properties of its key anti-constipation constituents speculated by network pharmacology were investigated via the established UFLC-MS/MS method.RESULTSA total of 13 prototype constituents and 56 metabolites were identified in rat plasma, urine, and feces after oral administration of Aloe vera. Among them, aloesin, aloenin, aloin B, aloin A, and aloe-emodin were intimately connected to the core targets of constipation in network pharmacology analysis, and recognized as major anti-constipation constituents in Aloe vera. The validated quantitative method of the six active constituents in rat plasma exhibited good linearity, and lower limits of quantification (0.64-1.95 ng/mL). Aloin A, aloin B, aloeresin D and aloe-emodin exhibited better absorption and slower elimination rate, whereas the others, including aloesin and aloenin showed fast absorption and elimination in rat plasma after oral administration of Aloe vera. Aloin A and its isomer aloin B present similar Tmax and t1/2 but different AUC and Cmax values, indicating different relative bioavailability. The results suggested that aloin A, aloin B and aloe-emodin may be key constituents of Aloe vera for the treatment of constipation, and the other constituents including aloeresin D also contribute to its anti-constipation.CONCLUSIONSThis study will benefit understanding the contributions of those constituents for the anti-constipation effect of Aloe vera and also provide valuable information for its application in functional food development and clinics.
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