Nonlinear Topological Mechanics in Elliptically Geared Isostatic Metamaterials.

Despite the extensive studies of topological systems, the experimental characterizations of strongly nonlinear topological phases have been lagging. To address this shortcoming, we design and build elliptically geared isostatic metamaterials. Their nonlinear topological transitions can be realized by collective soliton motions, which stem from the transition of nonlinear Berry phase. Endowed by the intrinsic nonlinear topological mechanics, surface polar elasticity and dislocation-bound zero modes can be created or annihilated as the topological polarization reverses orientation. Our approach integrates topological physics with strongly nonlinear mechanics and promises multiphase structures at the micro- and macroscales.

Analysis of optical propagation characteristics of the ultra-long period grating using RCWA.

There have been significant research and analyses on the diffraction efficiency and characteristics of spectral grating with a wavelength-scale period. However, thus far an analysis on a diffraction grating with an ultra-long pitch over several hundred times of the wavelength (>100µm) and a very deep groove over dozens of micrometers has not been performed. We analyzed the diffraction efficiency of these gratings by using the rigorous coupled-wave analysis (RCWA) method and confirmed that the RCWA analytic results correspond well to the actual experimental results on the wide-angle beam-spreading phenomenon. In addition, because a long-period grating with a deep groove results in a small diffraction angle with relatively uniform efficiency, it is possible to convert a point-like distribution to a linear distribution for a short working distance and a discrete distribution for a very long working distance. We believe that a wide-angle line laser with a long grating period can be used in various applications, such as level detectors, precision measurements, multi-point light detecting and ranging (LiDAR) light sources, and security systems.

The Anti-Inflammatory and Skin Barrier Function Recovery Effects of Schisandra chinensis in Mice with Atopic Dermatitis.

Background and Objectives: The fruit of Schisandra chinensis (Turcz.) Baill. is widely used medicinally to treat coughs, asthma, exhaustion, eczema, and pruritus in Northeast Asian countries, including Korea, China, and Japan. This study was designed to investigate the effects of S. chinensis on dermatitis in mice with calcipotriol (MC-903)-induced atopic dermatitis (AD), and its effects on skin barrier dysfunction was also investigated. Materials and Methods: The inhibitory effects of an ethanolic extract of S. chinensis (EESC) on skin lesions, water content, water-holding capacity (WHC), histopathological abnormalities, and inflammatory cytokine and chemokine levels were evaluated in mice with AD induced by MC903. Results: Topical EESC ameliorated skin lesions, reduced skin water content, and increased MC903-induced WHC. EESC also prevented MC-903-induced histopathological abnormalities such as epidermal disruption, hyperkeratosis, spongiotic changes, and immune cell infiltration in inflamed tissue. Moreover, topical EESC reduced MC-903-induced levels of pro-inflammatory cytokines and chemokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-4, IL-6, IL-8, monocyte chemotactic protein (MCP)-1, and thymic stromal lymphopoietin (TSLP). Furthermore, unlike dexamethasone, EESC did not reduce the spleen/body weight ratio. Conclusions: These results suggest that S. chinensis can be used as an alternative to external corticosteroids and that its anti-inflammatory and skin barrier dysfunction-restoring effects are related to the downregulation of pro-inflammatory cytokines and chemokines, such as TNF-α, IL-4, IL-6, IL-8, and TSLP.

Gradient-Index Granular Crystals: From Boomerang Motion to Asymmetric Transmission of Waves.

We present a gradient-index crystal that offers extreme tunability in terms of manipulating the propagation of elastic waves. For small-amplitude excitations, we achieve control over wave transmission depth into the crystal. We numerically and experimentally demonstrate a boomeranglike motion of a wave packet injected into the crystal. For large-amplitude excitations on the same crystal, we invoke nonlinear effects. We numerically and experimentally demonstrate asymmetric wave transmission from two opposite ends of the crystal. Such tunable systems can thus inspire a novel class of designed materials to control linear and nonlinear elastic wave propagation in multiscales.

Demonstration of accelerating and decelerating nonlinear impulse waves in functionally graded granular chains.

We propose a tunable cylinder-based granular system that is functionally graded in its stiffness distribution in space. With no initial compression given to the system, it supports highly nonlinear waves propagating under an impulse excitation. We investigate analytically, numerically and experimentally the ability to accelerate and decelerate the impulse wave without a significant scattering in the space domain. Moreover, the gradient in stiffness results in the scaling of contact forces along the chain. We envision that such tunable systems can be used for manipulating highly nonlinear impulse waves for novel sensing and impact mitigation purposes.This article is part of the theme issue 'Nonlinear energy transfer in dynamical and acoustical systems'.

High refractive index metamaterials using corrugated metallic slots.

We report on a method for realizing high refractive index metamaterials using corrugated metallic slot structures at terahertz frequencies. The effective refractive index and peak index frequency can be controlled by varying the width of the air gap in the corrugated slot arrays. The phenomenon occurs because of the secondary resonance effect due to the fundamental inductive-capacitive resonance, which generates a red-shift of the fundamental resonance determined by twice the length of the corrugated metallic slots. In addition, multiple gaps in the corrugated slots act as plasmonic hotspots which have the properties of three-dimensional subwavelength confinement due to extremely strong enhancement of the terahertz waves. The versatile characteristics of the structures may have many potential applications in designing compact optical devices incorporating various functionalities and in developing highly sensitive spectroscopic/imaging systems.

Device performance of inverted polymer solar cells with AgSiO(2) nanoparticles in active layer.

Localized surface plasmon mediated polymer solar cells (PSCs) were fabricated using the Ag/SiO(2) nanoparticles (NPs). The inverted PSC structure without poly (3,4-ethylenedioxythiophene) polystyrene sulfonate ( PEDOT: PSS) was prepared due to the efficient insertion of Ag/SiO(2) NPs in the vicinity of active layer, which led to an enhancement in photo-conversion efficiency (PCE). This enhancement mainly comes from the light scattering by the SiO(2) shell and the localized surface plasmon effect by the Ag core, but we also considered the structural issues such as the NP distribution, the swelling of the active layer and of the metal electrode.

Monopole resonators in planar plasmonic metamaterials.

We first present a new phenomenon: the quarter-wavelength resonance of an electromagnetic field in planar plasmonic metamaterials consisting of asymmetrically coupled air-slot arrays, which is essential for a monopole resonator. The anti-nodal electric field intensity of the quarter-wavelength fundamental mode is formed by strong charge concentrations at the sharp metallic edges of the crossing position of the air-slots, and the nodal point of the electric field intensity naturally occurs at the other end of the air-slot. By tuning the structural asymmetry, the quarter-wavelength resonances were successfully split from the half-wavelength resonance, experimentally and numerically.

Insulin signaling and pharmacology in humans and in corals.

Once thought to be a unique capability of the Langerhans islets in the pancreas of mammals, insulin (INS) signaling is now recognized as an evolutionarily ancient function going back to prokaryotes. INS is ubiquitously present not only in humans but also in unicellular eukaryotes, fungi, worms, and Drosophila. Remote homologue identification also supports the presence of INS and INS receptor in corals where the availability of glucose is largely dependent on the photosynthetic activity of the symbiotic algae. The cnidarian animal host of corals operates together with a 20,000-sized microbiome, in direct analogy to the human gut microbiome. In humans, aberrant INS signaling is the hallmark of metabolic disease, and is thought to play a major role in aging, and age-related diseases, such as Alzheimer's disease. We here would like to argue that a broader view of INS beyond its human homeostasis function may help us understand other organisms, and in turn, studying those non-model organisms may enable a novel view of the human INS signaling system. To this end, we here review INS signaling from a new angle, by drawing analogies between humans and corals at the molecular level.

High-frequency imagery to capture coral tissue (Montipora capricornis) response to environmental stress, a pilot study.

Environment stress is a major threat to the existence of coral reefs and has generated a lot of interest in the coral research community. Under the environmental stress, corals can experience tissue loss and/or the breakdown of symbiosis between the cnidarian host and its symbiotic algae causing the coral tissue to appear white as the skeleton can be seen by transparency. Image analysis is a common method used to assess tissue response under the environmental stress. However, the traditional approach is limited by the dynamic nature of the coral-algae symbiosis. Here, we observed coral tissue response in the scleractinian coral, Montipora capricornis, using high frequency image analysis throughout the experiment, as opposed to the typical start/end point assessment method. Color analysis reveals that the process can be divided into five stages with two critical stages according to coral tissue morphology and color ratio. We further explore changes to the morphology of individual polyps by means of the Pearson correlation coefficient and recurrence plots, where the quasi-periodic and nonstationary dynamics can be identified. The recurrence quantification analysis also allows the comparison between the different polyps. Our research provides a detailed visual and mathematical analysis of coral tissue response to environmental stress, which potentially shows universal applicability. Moreover, our approach provides a robust quantitative advancement for improving our insight into a suite of biotic responses in the perspective of coral health evaluation and fate prediction.

Transfer of knowledge from model organisms to evolutionarily distant non-model organisms: The coral Pocillopora damicornis membrane signaling receptome.

With the ease of gene sequencing and the technology available to study and manipulate non-model organisms, the extension of the methodological toolbox required to translate our understanding of model organisms to non-model organisms has become an urgent problem. For example, mining of large coral and their symbiont sequence data is a challenge, but also provides an opportunity for understanding functionality and evolution of these and other non-model organisms. Much more information than for any other eukaryotic species is available for humans, especially related to signal transduction and diseases. However, the coral cnidarian host and human have diverged over 700 million years ago and homologies between proteins in the two species are therefore often in the gray zone, or at least often undetectable with traditional BLAST searches. We introduce a two-stage approach to identifying putative coral homologues of human proteins. First, through remote homology detection using Hidden Markov Models, we identify candidate human homologues in the cnidarian genome. However, for many proteins, the human genome alone contains multiple family members with similar or even more divergence in sequence. In the second stage, therefore, we filter the remote homology results based on the functional and structural plausibility of each coral candidate, shortlisting the coral proteins likely to have conserved some of the functions of the human proteins. We demonstrate our approach with a pipeline for mapping membrane receptors in humans to membrane receptors in corals, with specific focus on the stony coral, P. damicornis. More than 1000 human membrane receptors mapped to 335 coral receptors, including 151 G protein coupled receptors (GPCRs). To validate specific sub-families, we chose opsin proteins, representative GPCRs that confer light sensitivity, and Toll-like receptors, representative non-GPCRs, which function in the immune response, and their ability to communicate with microorganisms. Through detailed structure-function analysis of their ligand-binding pockets and downstream signaling cascades, we selected those candidate remote homologues likely to carry out related functions in the corals. This pipeline may prove generally useful for other non-model organisms, such as to support the growing field of synthetic biology.

Localized surface plasmon enhanced quantum efficiency of InGaN/GaN quantum wells by Ag/SiO2 nanoparticles.

Optical properties of InGaN/GaN multi-quantum-well (MQW) structures with a nanolayer of Ag/SiO2 nanoparticle (NP) on top were studied. Modeling and optical absorption (OA) measurements prove that the NPs form localized surface plasmons (LSP) structure with a broad OA band peaked near 440-460 nm and the fringe electric field extending down to about 10 nm into the GaN layer. The presence of this NP LSP electrical field increases the photoluminescence (PL) intensity of the MQW structure by about 70% and markedly decreases the time-resolved PL (TRPL) relaxation time due to the strong coupling of MQW emission to the LSP mode.

Site-specific quantification of bone quality using highly nonlinear solitary waves.

Osteoporosis is a well recognized problem affecting millions of individuals worldwide. The ability to diagnose problems in an effective, efficient, and affordable manner and identify individuals at risk is essential. Site-specific assessment of bone mechanical properties is necessary, not only in the process of fracture risk assessment, but may also be desirable for other applications, such as making intraoperative decisions during spine and joint replacement surgeries. The present study evaluates the use of a one-dimensional granular crystal sensor to measure the elastic properties of bone at selected locations via direct mechanical contact. The granular crystal is composed of a tightly packed chain of particles that interact according to the Hertzian contact law. Such chains represent one of the simplest systems to generate and propagate highly nonlinear acoustic signals in the form of compact solitary waves. First, we investigated the sensitivity of the sensor to known variations in bone density using a synthetic cancellous bone substitute, representing clinical bone quality ranging from healthy to osteoporotic. Once the relationship between the signal response and known bone properties was established, the sensor was used to assess the bone quality of ten human cadaveric specimens. The efficacy and accuracy of the sensor was then investigated by comparing the sensor measurements with the bone mineral density (BMD) obtained using dual-energy x-ray absorptiometry (DEXA). The results indicate that the proposed technique is capable of detecting differences in bone quality. The ability to measure site-specific properties without exposure to radiation has the potential to be further developed for clinical applications.

Leaf-Like Origami with Bistability for Self-Adaptive Grasping Motions.

The leaf-like origami structure is inspired by geometric patterns found in nature, exhibiting unique transitions between open and closed shapes. With a bistable energy landscape, leaf-like origami is able to replicate the autonomous grasping of objects observed in biological systems such as the Venus flytrap. We show uniform grasping motions of the leaf-like origami, as well as various nonuniform grasping motions that arise from its multitransformable nature. Grasping motions can be triggered with high tunability due to the structure's bistable energy landscape. We demonstrate the self-adaptive grasping motion by dropping a target object onto our paper prototype, which does not require an external power source to retain the capture of the object. We also explore the nonuniform grasping motions of the leaf-like structure by selectively controlling the creases, which reveals various unique grasping configurations that can be exploited for versatile, autonomous, and self-adaptive robotic operations.

The Effects of tDCS with NDT on the Improvement of Motor Development in Cerebral Palsy.

We investigated the effects of transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) with neurodevelopmental treatment (NDT) on the improvement of motor development and reduction of spasticity in children with cerebral palsy (CP). Twenty-four children with CP were allocated to two groups: the tDCS + NDT group and the only NDT group, done 3 times per week for 5 weeks. The Gross Motor Function Measurement (GMFM-88) and Box and Block Test (BBT) were used to assess changes in motor development, and the Modified Ashworth Scale (MAS) was used to evaluate changes in spasticity. All measurements were carried out at 3 time points: baseline, post-intervention, and 1 month follow-up. We found improvements in the GMFM-88 total scores and in each individual GMFM-88 dimension scores, favoring the tDCS + NDT group over the only NDT group. The BBT scores improved only in the tDCS + NDT group. In addition, the MAS scores reduced in the hemibody with significant motor impairment only in the tDCS + NDT group. The present findings suggest that tDCS combined with NDT can be considered a promising intervention for children with CP, as it can enhance motor development and reduce spasticity in this population.

Light-to-Hydrogen Improvement Based on Three-Factored Au@CeO2/Gr Hierarchical Photocatalysts.

Recently, various attempts have been made for light-to-fuels conversion, often with limited performance. Herein we report active and lasting three-factored hierarchical photocatalysts consisting of plasmon Au, ceria semiconductor, and graphene conductor for hydrogen production. The Au@CeO2/Gr2.0 entity (graphene outer shell thickness of 2.0 nm) under visible-light irradiation exhibits a colossal achievement (8.0 µmol mgcat-1 h-1), which is 2.2- and 14.3-fold higher than those of binary Au@CeO2 and free-standing CeO2 species, outperforming the currently available catalysts. Yet, it delivers a high maximum quantum yield efficiency of 38.4% at an incident wavelength of 560 nm. These improvements are unambiguously attributed to three indispensable effects: (1) the plasmon resonant energy is light-excited and transferred to produce hot electrons localizing near the surface of Au@CeO2, where (2) the high-surface-area Gr conductive shell will capture them to direct hydrogen evolution reactions, and (3) the active graphene hybridized on the defect-rich surface of Au@CeO2 favorably adsorbs hydrogen atoms, which all bring up thorough insight into the working of a ternary Au@CeO2/Gr catalyst system in terms of light-to-hydrogen conversion.

Three-dimensional subwavelength confinement of terahertz electromagnetic surface modes in a coupled slit structure.

We report on the three-dimensional subwavelength confinement of the electromagnetic waves at a coupled metallic slit structure beyond diffraction limit in terahertz region. Lateral confinement behavior, leading to the three-dimensional confinement, is caused by a strong funneling effect of the light which occurs at the intersection of slits with a sharp metal geometry. Tunability of the resonant frequency and the position of the light confinement is achieved by controlling the slit length and the position of the intersection of slits, respectively.

Photonic network laser.

We demonstrated lasing in two-dimensional trivalent network structures with short-range order. Despite the lack of translational and rotational symmetries, such structures possess a large isotropic photonic bandgap. Different from those of a photonic crystal, the band-edge modes are spatially localized and have high quality factor.

Control of lasing in biomimetic structures with short-range order.

We demonstrate lasing in photonic amorphous structures that mimic the isotropic nanostructures which produce noniridescent color in nature. Our experimental and numerical studies reveal that lasing becomes most efficient at certain frequencies, due to enhanced optical confinement by short-range order. The optimal lasing frequency can be tuned by adjusting the structure factor. This work shows that lasing in nanostructures may be effectively improved and manipulated by short-range order.

Digital image processing to detect subtle motion in stony coral.

Coral reef ecosystems support significant biological activities and harbor huge diversity, but they are facing a severe crisis driven by anthropogenic activities and climate change. An important behavioral trait of the coral holobiont is coral motion, which may play an essential role in feeding, competition, reproduction, and thus survival and fitness. Therefore, characterizing coral behavior through motion analysis will aid our understanding of basic biological and physical coral functions. However, tissue motion in the stony scleractinian corals that contribute most to coral reef construction are subtle and may be imperceptible to both the human eye and commonly used imaging techniques. Here we propose and apply a systematic approach to quantify and visualize subtle coral motion across a series of light and dark cycles in the scleractinian coral Montipora capricornis. We use digital image correlation and optical flow techniques to quantify and characterize minute coral motions under different light conditions. In addition, as a visualization tool, motion magnification algorithm magnifies coral motions in different frequencies, which explicitly displays the distinctive dynamic modes of coral movement. Specifically, our assessment of displacement, strain, optical flow, and mode shape quantify coral motion under different light conditions, and they all show that M. capricornis exhibits more active motions at night compared to day. Our approach provides an unprecedented insight into micro-scale coral movement and behavior through macro-scale digital imaging, thus offering a useful empirical toolset for the coral research community.