Simultaneously independent control of phase, amplitude, and polarization is pivotal yet challenging for manipulating electromagnetic waves by transmissive metasurfaces. Huygens' metasurface affords a ...high‐efficiency recipe primarily by engineering phase‐only meta‐atoms, restricting itself from realizing unprecedentedly complex functions of the transmission beam. Here, a 3D chirality‐assisted metasurface concept relying on integrated magnetoelectric meta‐atoms is proposed. It empowers the completely decoupled and arbitrary control of phase and amplitude at large incident angles and arbitrary polarizations. This strategy thus facilitates very sophisticated beam manipulations at close‐to‐unity cross‐polarized efficiency via trilayer integrated resonators with mutual twist. The prescribed phase coverage can be determined by geometrical footprints of the unit cell, while the global azimuthal twist unlocks the capability of tuning amplitudes without affecting the phase. The concept and significance of it are validated to implement several proof‐of‐prototype demanding functionalities by thin metasurfaces of λo/12, which generate self‐accelerating diffraction‐free Airy beams, lateral and axial dual focusing, and even specific multiplexed beam shaping, respectively. This finding opens up an alternative way in very fine control of light with minimalist complexity and advanced performance. It can stimulate novel and high‐performance versatile photonic metadevices, thanks to the fully independent control of phase, amplitude, and polarization.
The decoupling of amplitude, phase and polarization is analogous to the mechanical counterpart of three‐gear systems. The traditional dilemma is that tuning of either part will automatically affect the rest. This locks up metasurface functions and thereby limits its potentials. Now the authors' concept unlocks those “gears” such that each could be independently tuned, providing unprecedented access to the flatland of high‐efficiency metasurfaces.
Despite the long discrepancy over their definition, heterogeneity, and functions, mesenchymal stem cells (MSCs) have proved to be a key player in tissue repair and homeostasis. Generally, somatic ...tissue‐derived MSCs (st‐MSCs) are subject to quality variations related to donated samples and biosafety concern for transmission of potential pathogens from the donors. In contrast, human pluripotent stem cells (hPSCs) are unlimited in supply, clear in the biological background, and convenient for quality control, genetic modification, and scale‐up production. We, and others, have shown that hPSCs can differentiate in two dimensions or three dimensions to MSCs (ps‐MSCs) via embryonic (mesoderm and neural crest) or extraembryonic (trophoblast) cell types under serum‐containing or xeno‐free and defined conditions. Compared to st‐MSCs, ps‐MSCs appear less mature, proliferate faster, express lower levels of inflammatory cytokines, and respond less to traditional protocols for st‐MSC differentiation to other cell types, especially adipocytes. Nevertheless, ps‐MSCs are capable of immune modulation and treatment of an increasing number of animal disease models via mitochondria transfer, paracrine, exosomes, and direct differentiation, and can be potentially used as a universal and endless therapy for clinical application. This review summarizes the progress on ps‐MSCs and discusses perspectives and challenges for their potential translation to the clinic. Stem Cells 2019;37:572–581
Mesenchymal stem cells (MSCs) can be derived from somatic tissues (st‐MSCs) such as human bone marrow or human pluripotent stem cell (ps‐MSCs) including induced pluripotent stem cells derived from reprogrammed human somatic cells such as skin fibroblasts and embryonic stem cells derived from human blastocyst. Compared to st‐MSCs, ps‐MSCs possess remarkable advantages in cell supply, quality consistency, and pathogen control.
Hybrid electrocatalysts with excellent electrocatalytic activity for hydrogen reduction are fabricated using an efficient and facile electrochemical route. The electronic and synergistic effects ...between Co(OH)2 and polyaniline (PANI) in the composite structure are the key factors that generate the high electrocatalytic activity and excellent stability. A highly efficient, non‐precious metal‐based flexible electrocatalyst for high‐performance electrocatalysts is shown, which reveals a novel route for the design and synthesis of electrocatalysts.
The differentiation and maturation of mesenchymal stem cells (MSCs) to mesodermal and other lineages are known to be controlled by various extrinsic and intrinsic signals. The dysregulation of the ...MSC differentiation balance has been linked to several pathophysiological conditions, including obesity and osteoporosis. Previous research of the molecular mechanisms governing MSC differentiation has mostly focused on transcriptional regulation. However, recent findings are revealing the underrated role of alternative splicing (AS) in MSC differentiation and functions. In this review, we discuss recent progress in elucidating the regulatory roles of AS in MSC differentiation. We catalogue and highlight the key AS events that modulate MSC differentiation to major osteocytes, chondrocytes, and adipocytes, and discuss the regulatory mechanisms by which AS is regulated.
Mesenchymal stem cells (MSCs) are essential cell sources for bone, fat tissues, cartilage, and other connective tissues inside the body and in the test tube. Alternative splicing of pre‐mRNAs, which encode critical determinants of MSC differentiation, regulates the MSC differentiation by specifying cell type‐specific transcriptome or antagonizing the function of the WT protein.
Cylindrical vector vortex beams, a particular class of higher‐order Poincaré sphere beams, are generalized forms of waves carrying orbital angular momentum with inhomogeneous states‐of‐polarization ...on their wavefronts. Conventional methods as well as the more recently proposed segmented/interleaved shared‐aperture metasurfaces for vortex beam generation are either severely limited by bulky optical setups or by restricted channel capacity with low efficiency and mode number. Here, a noninterleaved vortex multiplexing approach is proposed, which utilizes superimposed scattered waves with opposite spin states emanating from all meta‐atoms in a coherent manner, counter‐intuitively enabling ultrahigh‐capacity, high‐efficiency, and flexible generation of massive vortex beams with structured state‐of‐polarization. A series of exemplary prototypes, implemented by sub‐wavelength‐thick metasurfaces, are demonstrated experimentally, achieving kaleidoscopic vector vortex beams. This methodology holds great promise for structured wavefront shaping, vortex generation, and high information‐capacity planar photonics, which may have a profound impact on transformative technological advances in fields including spin‐Hall photonics, optical holography, compressive imaging, electromagnetic communication, and so on.
A noninterleaved vortex multiplexing approach is proposed, which utilizes superimposed scattered waves with opposite spin states emanating from all meta‐atoms on a shared‐aperture metasurface in a coherent manner. This counter‐intuitively enables ultrahigh‐capacity, high‐efficiency, and flexible generation of massive higher‐order Poincaré sphere beams. This methodology may have a profound impact on advances for wavefront sculpturing, electromagnetic communication, planar photonics, etc.
Electromagnetic metasurface cloaks provide an alternative paradigm toward rendering arbitrarily shaped scatterers invisible. Most transformation-optics (TO) cloaks intrinsically need wavelength-scale ...volume/thickness, such that the incoming waves could have enough long paths to interact with structured meta-atoms in the cloak region and consequently restore the wavefront. Other challenges of TO cloaks include the polarization-dependent operation to avoid singular parameters of composite cloaking materials and limitations of canonical geometries, e.g., circular, elliptical, trapezoidal, and triangular shapes. Here, we report for the first time a conformal-skin metasurface carpet cloak, enabling to work under arbitrary states of polarization (SOP) at Poincaré sphere for the incident light and arbitrary conformal platform of the object to be cloaked. By exploiting the foundry three-dimensional (3D) printing techniques to fabricate judiciously designed meta-atoms on the external surface of a conformal object, the spatial distributions of intensity and polarization of its scattered lights can be reconstructed exactly the same as if the scattering wavefront were deflected from a flat ground at any SOP, concealing targets under polarization-scanning detections. Two conformal-skin carpet cloaks working for partial- and full-azimuth plane operation are respectively fabricated on trapezoid and pyramid platforms via 3D printing. Experimental results are in good agreement with numerical simulations and both demonstrate the polarization-insensitive cloaking within a desirable bandwidth. Our approach paves a deterministic and robust step forward to the realization of interfacial, free-form, and full-polarization cloaking for a realistic arbitrary-shape target in real-world applications.
Two-dimensional transition metal dichalcogenides (TMDCs) present extraordinary nonlinearities and direct bandgaps at the K and K′ valleys. These valleys can be optically manipulated through, for ...example, plasmon–valley-exciton coupling with spin-dependent photoluminescence. However, the weak coherence between the pumping and emission makes exploring nonlinear valleytronic devices based on TMDCs challenging. Here, we show that a synthetic metasurface, which entangles the phase and spin of light, can simultaneously enhance and manipulate nonlinear valley-locked chiral emission in monolayer tungsten disulfide (WS2) at room temperature. The second-harmonic valley photons, accessed and coherently pumped by light, with a spin-related geometric phase imparted by a gold (Au) metasurface, are separated and routed to predetermined directions in free space. In addition, the nonlinear photons with the same spin as the incident light are steered owing to the critical spin–valley-locked nonlinear selection rule of WS2 in our designed metasurface. Our synthetic TMDC–metasurface interface may facilitate advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices.By entangling the phase and spin of light, a synthetic metasurface is shown to be able to coherently manipulate the valley-exciton-locked chiral emission in monolayer tungsten disulfide at room temperature. The findings will be of benefit to advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices.
Recently, deep learning-based techniques have shown great power in image inpainting especially dealing with squared holes. However, they fail to generate plausible results inside the missing regions ...for irregular and large holes as there is a lack of understanding between missing regions and existing counterparts. To overcome this limitation, we combine two non-local mechanisms including a contextual attention module (CAM) and an implicit diversified Markov random fields (ID-MRF) loss with a multi-scale architecture which uses several dense fusion blocks (DFB) based on the dense combination of dilated convolution to guide the generative network to restore discontinuous and continuous large masked areas. To prevent color discrepancies and grid-like artifacts, we apply the ID-MRF loss to improve the visual appearance by comparing similarities of long-distance feature patches. To further capture the long-term relationship of different regions in large missing regions, we introduce the CAM. Although CAM has the ability to create plausible results via reconstructing refined features, it depends on initial predicted results. Hence, we employ the DFB to obtain larger and more effective receptive fields, which benefits to predict more precise and fine-grained information for CAM. Extensive experiments on two widely-used datasets demonstrate that our proposed framework significantly outperforms the state-of-the-art approaches both in quantity and quality.
Chiral secondary alcohols play an important role in pharmaceutical, agrochemical, and chemical industries. In recent years, impressive steps forward have been achieved towards biocatalytic ketone ...reduction as a green and useful access to enantiopure alcohols. An increasing number of novel and robust enzymes are now accessible as a result of the ongoing progress in genomics, screening and evolution technologies, while process engineering provides further success in areas of biocatalytic reduction in meeting synthetic challenges. The versatile platform of these techniques and strategies offers the possibility to apply high substrate loading and thus to overcome the limitation of low volumetric productivity of usual enzymatic processes which is the bottleneck for their practical application. In addition, the integration of bioreduction with other enzymatic or chemical steps allows the efficient synthesis of more complex chiral products.
We propose a high-gain transmitting lens antenna by employing layered phase-gradient metasurface (MS). The MS is engineered to focus the propagating plane wave to a point with high efficiency. An ...X-band patch antenna is placed at the focal point of the MS as a feed source, and then the quasi-spherical wave emitted by the source is transformed to plane wave. Due to the successful conversion of quasi-spherical wave to plane wave, the beam width of the patch antenna has been decreased 66° and the gain has been enhanced 11.6 dB. The proposed lens antenna not only opens up a new route for the applications of phase-gradient MS in microwave band, but also affords an alternative for high-gain antenna.
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