MR image reconstruction from under-sampled measurements using local and global sparse representations

This work presented a new model by enforcing both local and global sparsity, which captures both the patch-level and global sparse structures of the anatomical images. Using a model split approach, the image reconstruction quality can be iteratively further improved. Our simulation results demonstrate that, the proposed method outperform those existing methods using only the patch-level or global sparse structure

A new operando surface restructuring pathway via ion-pairing of catalyst and electrolyte for water oxidation

The highly efficient and stable electrolysis needs the rational control of the catalytically active interface during the reactions. Here we report a new operando surface restructuring pathway activated by pairing catalyst and electrolyte ions. Using SrCoO3-δ-based perovskites as model catalysts, we unveil the critical role of matching the catalyst properties with the electrolyte conditions in modulating catalyst ion leaching and steering surface restructuring processes toward efficient oxygen evolution reaction catalysis in both pH-neutral and alkaline electrolytes. Our results regarding multiple perovskites show that the catalyst ion leaching is controlled by catalyst ion solubility and anions of the electrolyte. Only when the electrolyte cations are smaller than catalyst's leaching cations, the formation of an outer amorphous shell can be triggered via backfilling electrolyte cations into the cationic vacancy at the catalyst surface under electrochemical polarization. Consequently, the current density of reconstructed SrCoO3-δ is increased by 21 folds compared to the pristine SrCoO3-δ at 1.75 V vs. reversible hydrogen electrode and outperforms the benchmark IrO2 by 2.1 folds and most state-of-the-art electrocatalysts in the pH-neutral electrolyte. Our work could be a starting point to rationally control the electrocatalyst surface restructuring via matching the compositional chemistry of the catalyst with the electrolyte properties

Online dynamic cardiac imaging based on the elastic-net model

Purpose: The purpose of this work was to develop an online dynamic cardiac MRI model to reconstruct image frames from partial acquisition of the Cartesian k-space data, which utilizes structural knowledge of consecutive image frames. Materials and methods: Using an elastic-net model, the proposed algorithm reconstructs dynamic images using both L and L norm operations. The L norm enforces the sparsity of the frame difference, while the L norm with motion-adaptive weights catches the internal structure of frame differences. Unlike other online methods such as the Kalman filter (KF) technique, the new model requires no assumption of Gaussian noise, and can faithfully reconstruct the dynamic images within a compressive sensing framework. Results: The proposed method was evaluated using simulated dynamic phantoms with 40 frames of images (128 × 128) and a cardiac MRI cine of 25 frames (256 × 256). Both results showed that the new model offered a better performance than the online KF method in depicting simulated phantom and cardiac dynamics. Conclusion: It is concluded that the proposed imaging model can be used to capture a large variety of objects in motion from highly under-sampled k-space data, and being particularly useful for improving temporal resolution of cardiac MRI

Gas diffusion electrodes (GDEs) for electrochemical reduction of carbon dioxide, carbon monoxide, and dinitrogen to value-added products: a review

Electrochemical reduction of gaseous feeds such as CO2, CO, and N2 holds promise for sustainable energy and chemical production. Practical application of this technology is impeded by slow mass transport of the sparingly soluble gases to conventional planar electrodes. Gas diffusion electrodes (GDEs) maintain a high gas concentration in the vicinity of the catalyst and improve mass transport, thereby resulting in current densities higher by orders of magnitude. However, gaseous feeds cause changes to the GDE environment, and specific features are required to efficiently tune the product selectivity and improve reaction stability. Herein, with a comprehensive review of the challenges and advances in GDE development for various electrocatalytic reactions, we intend to complement the body of material-focused reviews. This review outlines GDE fundamentals and highlights key advantages of GDE over conventional electrodes. Through critical discussion about steps in GDE fabrication, and specific shortcomings and remedial strategies for various electrochemical applications, this review discusses connections, unique design criteria, and potential opportunities for gas-fed reactions and desired products. Finally, priorities for future studies are suggested, to support the advancement and scale-up of GDE-based electrochemical technologies

Orientated growth of copper-based MOF for acetylene storage

Manipulating crystal growth of metal-organic frameworks (MOFs) has great potential in achieving unique properties for adsorption, separation and catalysis applications. For the first time, we used Mg/Al layered double hydroxide (LDH) nanosheets as modulators to tune the growth orientation of HKUST-1 without either pore blockage or crystallinity degradation. Through the introduction of LDH during hydrothermal process, HKUST-1 crystal shape transfers from octahedron with fully exposed {1 1 1} facets to tetrakaidecahedron with both {1 0 0} and {1 1 1} facets. The exposure of {1 0 0} facet with large pore size facilitates the activation of MOF, thereby providing more open metal sites. As a result, the micropore volume and BET surface area increase remarkably from 0.75 cm3/g to 1.01 cm3/g and 2255m2/g to 3001m2/g, respectively. The tetrakaidecahedral HKUST-1 exhibits high acetylene uptake of 275 cm3 (STP)/g at 298 K and 1 atm, which is the highest value ever reported to the best of our knowledge

Bupleurum chinense Polysaccharide Improves LPS-Induced Senescence of RAW264.7 Cells by Regulating the NF-κB Signaling Pathway

Macrophages are important inflammatory cells that play a vital role in inflamm-aging. Bupleurum chinense polysaccharide (BCP), an effective component of the Bupleurum chinense herb, exerts multiple beneficial pharmacological effects, such as improving immunity and antioxidant activity. However, the effects of BCP on macrophage-aging and inflamm-aging are yet to be established. In this study, we examined the effects of BCP on proliferation, inflammatory cytokines, β-galactosidase (SA-β-gal), senescence-associated heterochromatin foci (SAHF), reactive oxygen species (ROS), mitochondrial membrane potential, p53, p16, and p65/NF-κB signaling proteins in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. BCP significantly inhibited production of interleukin-1α (IL-1α), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), reduced the expression of SA-β-gal and formation of SAHF, as well as ROS level, and stabilized the mitochondrial membrane potential in RAW264.7 cells stimulated with LPS. Furthermore, BCP inhibited the expression of aging-related genes, p53 and p16, suppressed phosphorylation of p65 protein, and enhanced the expression of I-κBα protein through the NF-κB signaling pathway in LPS-stimulated RAW264.7 cells. Accordingly, we conclude that BCP effectively suppresses inflamm-aging by reducing inflammatory cytokine levels and oxidative stress production following activation of the NF-κB signaling pathway in RAW264.7 cells stimulated with LPS. Our collective findings support the utility of BCP as a novel pharmaceutical agent with potential anti-inflamm-aging effects

Fine-tuning the coordinatively unsaturated metal sites of metal–organic frameworks by plasma engraving for enhanced electrocatalytic activity

Metal-organic frameworks (MOFs) have recently emerged as promising electrocatalysts because of their atomically dispersed metal sites and porous structures. The active sites of MOF catalysts largely exist as coordinatively unsaturated metal sites (CUMSs). In this study, facile microwave-induced plasma engraving is applied to fine-tune the CUMSs of cobalt-based MOF (Co-MOF-74) without destroying its phase integrity by controlling the plasma-engraving species, intensity, and duration. The electrochemical activity of the engraved MOF is found to be quantitatively correlated to the coordination geometry of the metal centers corresponding to CUMSs. Specifically, the hydrogen plasma-engraved Co-MOF-74 shows an enhanced catalytic activity of oxygen evolution reaction, which exhibits a low overpotential (337 mV at 15 mA cm), high turnover frequency (0.0219 s), and large mass activity (54.3 A g). The developed CUMS control strategy and the revealed CUMSs activity correlation can inspire the further microstructure tuning of MOFs for various applications

Ultrathin iron-cobalt oxides nanosheets with abundant oxygen vacancies for oxygen evolution reaction

Electrochemical water splitting is a promising method for storing light/electrical energy in the form of H2 fuel; however, it is limited by the sluggish anodic oxygen evolution reaction (OER). To improve the accessibility of H2 production, it is necessary to develop an efficient OER catalyst with large surface area, abundant active sites, and good stability, through a low-cost fabrication route. Herein, a facile solution reduction method using NaBH4 as a reductant is developed to prepare iron-cobalt oxide nanosheets (FexCoy-ONSs) with a large specific surface area (up to 261.1 m2 g−1), ultrathin thickness (1.2 nm), and, importantly, abundant oxygen vacancies. The mass activity of Fe1Co1-ONS measured at an overpotential of 350 mV reaches up to 54.9 A g−1, while its Tafel slope is 36.8 mV dec−1; both of which are superior to those of commercial RuO2, crystalline Fe1Co1-ONP, and most reported OER catalysts. The excellent OER catalytic activity of Fe1Co1-ONS can be attributed to its specific structure, e.g., ultrathin nanosheets that could facilitate mass diffusion/transport of OH− ions and provide more active sites for OER catalysis, and oxygen vacancies that could improve electronic conductivity and facilitate adsorption of H2O onto nearby Co3+ sites