It is advantageous to construct a dielectric metasurface in silicon due to its compatibility with cost-effective, mature processes for complementary metal-oxide-semiconductor devices. However, ...high-quality crystalline-silicon films are difficult to grow on foreign substrates. In this work, we propose and realize highly efficient structural color filters based on a dielectric metasurface exploiting hydrogenated amorphous silicon (a-Si:H), known to be lossy in the visible regime. The metasurface is comprised of an array of a-Si:H nanodisks embedded in a polymer, providing a homogeneously planarized surface that is crucial for practical applications. The a-Si:H nanodisk element is deemed to individually support an electric dipole (ED) and magnetic dipole (MD) resonance via Mie scattering, thereby leading to wavelength-dependent filtering characteristics. The ED and MD can be precisely identified by observing the resonant field profiles with the assistance of finite-difference time-domain simulations. The completed color filters provide a high transmission of around 90% in the off-resonance band longer than their resonant wavelengths, exhibiting vivid subtractive colors. A wide range of colors can be facilitated by tuning the resonance by adjusting the structural parameters like the period and diameter of the a-Si:H nanodisk. The proposed devices will be actively utilized to implement color displays, imaging devices, and photorealistic color printing.
•Multiple cylinders in FIM work synergistically for hydrokinetic power harnessing.•Peak power conversion efficiency was estimated at 88.6% of the Betz limit.•Power-to-volume density reached 874.7W/m3 ...at flow speed of 1.45m/s.•VIVACE can efficiently harness energy from flows as slow as 0.8m/s, with no upper limit.
Horizontal hydrokinetic energy can be harnessed using Steady Lift Technology (SLT) like turbines or Alternating Lift Technology (ALT) like the VIVACE Converter. Tidal/current turbines with low mechanical losses typically achieve about 30% peak power efficiency, which is equivalent to 50.6% power efficiency over the Betz limit at flow speed nearly 3.0m/s. The majority of flows worldwide are slower than 1.0–1.5m/s. Turbines also require large in-flow spacing resulting in farms of low power-to-volume density. Alternating-lift overcomes these challenges. The purpose of this study is to show that the ALT Converter is a three-dimensional energy absorber that efficiently works in river/ocean currents as slow as 1.0–1.5m/s a range of velocities presently inaccessible to watermills and turbines. This novel converter utilizes flow-induced motions (FIM), which are potentially destructive phenomena for structures, enhances them, and converts hydrokinetic energy to electricity. It was invented in the Marine Renewable Energy Lab (MRELab) and patented through the University of Michigan. MRELab has been studying the effect of passive turbulence control (PTC) to enhance FIMs and to expand their synchronization range for energy harnessing. This study shows that multiple cylinders in proximity can synergistically work and harness more energy than the same number of a single cylinder in isolation. Estimation based on experiments, shows that a 4 PTC-cylinder Converter can achieve 88.6% peak efficiency of the Betz limit at flow speed slower than 1.0m/s and power-to-volume density of 875W/m3 at 1.45m/s. Thus, the Converter can efficiently harness energy from rivers and ocean current as slow as 0.8–1.5m/s, with no upper limit in flow velocity.
Spinal cord injury (SCI) is a life-threatening condition that leads to permanent disability with partial or complete loss of motor, sensory, and autonomic functions. SCI is usually caused by initial ...mechanical insult, followed by a cascade of several neuroinflammation and structural changes. For ameliorating the neuroinflammatory cascades, MSC has been regarded as a therapeutic agent. The animal SCI research has demonstrated that MSC can be a valuable therapeutic agent with several growth factors and cytokines that may induce anti-inflammatory and regenerative effects. However, the therapeutic efficacy of MSCs in animal SCI models is inconsistent, and the optimal method of MSCs remains debatable. Moreover, there are several limitations to developing these therapeutic agents for humans. Therefore, identifying novel agents for regenerative medicine is necessary. Extracellular vesicles are a novel source for regenerative medicine; they possess nucleic acids, functional proteins, and bioactive lipids and perform various functions, including damaged tissue repair, immune response regulation, and reduction of inflammation. MSC-derived exosomes have advantages over MSCs, including small dimensions, low immunogenicity, and no need for additional procedures for culture expansion or delivery. Certain studies have demonstrated that MSC-derived extracellular vesicles (EVs), including exosomes, exhibit outstanding chondroprotective and anti-inflammatory effects. Therefore, we reviewed the principles and patho-mechanisms and summarized the research outcomes of MSCs and MSC-derived EVs for SCI, reported to date.
For catalysing dioxygen reduction, iron–nitrogen–carbon (Fe–N–C) materials are today the best candidates to replace platinum in proton-exchange membrane fuel cell (PEMFC) cathodes. Despite tremendous ...progress in their activity and site-structure understanding, improved durability is critically needed but challenged by insufficient understanding of their degradation mechanisms during operation. Here, we show that FeN x C y moieties in a representative Fe–N–C catalyst are structurally stable but electrochemically unstable when exposed in an acidic medium to H 2 O 2 , the main oxygen reduction reaction (ORR) byproduct. We reveal that exposure to H 2 O 2 leaves iron-based catalytic sites untouched but decreases their turnover frequency (TOF) via oxidation of the carbon surface, leading to weakened O 2 -binding on iron-based sites. Their TOF is recovered upon electrochemical reduction of the carbon surface, demonstrating the proposed deactivation mechanism. Our results reveal for the first time a hitherto unsuspected key deactivation mechanism during the ORR in an acidic medium. This study identifies the N-doped carbon surface as the Achilles' heel during ORR catalysis in PEMFCs. Observed in acidic but not in alkaline electrolytes, these insights suggest that durable Fe–N–C catalysts are within reach for PEMFCs if rational strategies minimizing the amount of H 2 O 2 or reactive oxygen species (ROS) produced during the ORR are developed.
Meteorin‐like (metrnl) is a recently identified adipomyokine that beneficially affects glucose metabolism; however, its underlying mechanism of action is not completely understood. We here show that ...the level of metrnl increases in vitro under electrical pulse stimulation and in vivo in exercised mice, suggesting that metrnl is secreted during muscle contractions. In addition, metrnl increases glucose uptake via the calcium‐dependent AMPKα2 pathway in skeletal muscle cells and increases the phosphorylation of HDAC5, a transcriptional repressor of GLUT4, in an AMPKα2‐dependent manner. Phosphorylated HDAC5 interacts with 14‐3‐3 proteins and sequesters them in the cytoplasm, resulting in the activation of GLUT4 transcription. An intraperitoneal injection of recombinant metrnl improved glucose tolerance in mice with high‐fat‐diet‐induced obesity or type 2 diabetes, but not in AMPK β1β2 muscle‐specific null mice. Metrnl improves glucose metabolism via AMPKα2 and is a promising therapeutic candidate for glucose‐related diseases such as type 2 diabetes.
We found that metrnl, known as an adipomyokine, is secreted during muscle contractions. Metrnl increases glucose uptake via AMPKα in skeletal muscle cells and increases the phosphorylation of HDAC5 and TBC1D1 in AMPKα‐dependent manner. Recombinant metrnl improves glucose tolerance in mice with obesity or type 2 diabetes. These results suggest that metrnl is a promising therapeutic candidate for diabetes.
Flow Induced Motions (FIMs) of a single, rigid, circular cylinder with end-springs are investigated for Reynolds number 30,000 ≤ Re ≤ 120,000 with mass ratio, damping, and stiffness as parameters. ...Selective roughness is applied to enhance FIM and increase the hydrokinetic energy captured by the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter at higher Reynolds numbers. The second generation of virtual spring-damping system Vck, recently developed in the Marine Renewable Energy Laboratory (MRELab), enables embedded computer-controlled change of viscous-damping and spring-stiffness for fast and precise oscillator modeling. Experimental results for amplitude response, frequency response, energy harvesting, and efficiency are presented and discussed. All experiments were conducted in the Low Turbulence Free Surface Water (LTFSW) Channel of the MRELab of the University of Michigan. The main conclusions are: (1) The oscillator can harness energy from flows as slow as 0.3946 m/s with no upper limit. (2) Increasing the spring stiffness, shifts the VIV synchronization range to higher flow velocities, resulting in reduced gap between VIV and galloping, where the harnessed power drops. (3) In galloping, the harnessed power increases with the mass ratio. (4) Local optima in energy conversion efficiency appear at the beginning of the VIV upper branch and at the beginning of galloping. (5) Local optima in power appear at the end VIV upper branch and at the beginning of galloping.
•The paper experimentally studies the mass ratios, spring stiffness, and damping on power harness of a single circular cylinder with passive turbulence control.•The experiments are base on the Vck, which enables embedded computer-controlled change of viscous-damping and stiffness.•The research exhibits local optima in energy conversion efficiency at the beginning of the VIV upper branch and at the beginning of galloping.•The amplitude and frequency response, power harness, and efficiency, are presented and discussed based on stiffness, damping and mass ratios.•All the experiments are conducted in the TrSL3 (20,000 < Re < 300,000) flow regime.
The flow induced motions (FIM) of two rigid circular cylinders, on end linear-springs, in tandem are studied using two-dimensional Unsteady Reynolds-Averaged Navier-Stokes (2-D URANS) simulations ...verified by experimental data. Passive turbulence control (PTC) is being used in the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan to enhance FIM of cylinders in the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter to increase its efficiency and power density in harnessing marine hydrokinetic energy. Simulation is performed using a solver based on the open source CFD tool OpenFOAM, which solves continuum mechanics problems with a finite-volume discretization method. The simulated Reynolds number range for which experiments were conducted in the MRELab is 30,000<Re<105,000, which falls in the TrSL3 regime (Transition in Shear Layer), where the shear layers are fully saturated and consequently lift is high. The amplitude and frequency results are in excellent agreement with experimental data showing the initial and upper branches in VIV, transition from VIV to galloping, and galloping. Vortex structures are studied using high-resolution imaging from the CFD results showing typical 2S structure in the initial branch and both 2P+2S and 2P in the upper branch of VIV. In the galloping branch, amplitudes of 3.5 diameters are reached before the channel stops are hit.
•2-D URANS code developed for two cylinders in FIM and validated experimentally for Reynolds number up to 105,000.•Selectively distributed surface roughness is the key to the agreement between CFD and experiments.•Integral FIM properties are predicted accurately: amplitude, frequency, VIV branches, galloping.•Local flow properties are predicted accurately: vortex structures, shear layer motion.•Coexistence of VIV and galloping driving mechanisms shown in VIV-to-galloping transition.
Tremendous demands for sensitive and reliable label-free biosensors have stimulated intensive research into developing miniaturized radiofrequency resonators for a wide range of biomedical ...applications. Here, we report the development of a robust, reusable radiofrequency resonator based integrated passive device biosensor chip fabricated on a gallium arsenide substrate for the detection of glucose in water-glucose solutions and sera. As a result of the highly concentrated electromagnetic energy between the two divisions of an intertwined spiral inductor coupled with an interdigital capacitor, the proposed glucose biosensor chip exhibits linear detection ranges with high sensitivity at center frequency. This biosensor, which has a sensitivity of up to 199 MHz/mgmL(-1) and a short response time of less than 2 sec, exhibited an ultralow detection limit of 0.033 μM and a reproducibility of 0.61% relative standard deviation. In addition, the quantities derived from the measured S-parameters, such as the propagation constant (γ), impedance (Z), resistance (R), inductance (L), conductance (G) and capacitance (C), enabled the effective multi-dimensional detection of glucose.
This paper presents a robust foreground detection method capable of adapting to different motion speeds in scenes. A key contribution of this paper is the background estimation using a proposed novel ...algorithm, neighbor-based intensity correction (NIC), that identifies and modifies the motion pixels from the difference of the background and the current frame. Concretely, the first frame is considered as an initial background that is updated with the pixel intensity from each new frame based on the examination of neighborhood pixels. These pixels are formed into windows generated from the background and the current frame to identify whether a pixel belongs to the background or the current frame. The intensity modification procedure is based on the comparison of the standard deviation values calculated from two pixel windows. The robustness of the current background is further measured using pixel steadiness as an additional condition for the updating process. Finally, the foreground is detected by the background subtraction scheme with an optimal threshold calculated by the Otsu method. This method is benchmarked on several well-known data sets in the object detection and tracking domain, such as CAVIAR 2004, AVSS 2007, PETS 2009, PETS 2014, and CDNET 2014. We also compare the accuracy of the proposed method with other state-of-the-art methods via standard quantitative metrics under different parameter configurations. In the experiments, NIC approach outperforms several advanced methods on depressing the detected foreground confusions due to light artifact, illumination change, and camera jitter in dynamic scenes.
A single spatial-light-modulator (SLM) full-color holographic 3-D video display based on image and frequency-shift multiplexing (IFSM) is proposed. In the frequency-shift multiplexing (FSM), ...three-color holograms are multiplied with their respective phase factors for shifted-separations of their corresponding frequency-spectrums on the Fourier plane. This FSM process, however, causes three-color images to be reconstructed at the center-shifted locations depending on their multiplied phase factors. Center-shifts of those color images due to the FSM can be balanced out just by generation of three-color holograms whose centers are pre-shifted to the opposite directions to those of the image shifts with the novel-look-up-table (NLUT) based on its shift-invariance property, which is called image-shift multiplexing (ISM). These image and frequency-shifted holograms are then multiplexed into a single color-multiplexed hologram and loaded on the SLM, and from which a full-color 3-D image can be reconstructed on the optical 4-f lens system without any color dispersion just by employing a simple pinhole filter mask. Fourier-optical analysis and experiments with 3-D objects in motion confirm the feasibility of the proposed system.
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