Enhancing Li-Ion Battery Anodes: Synthesis, Characterization, and Electrochemical Performance of Crystalline C60 Nanorods with Controlled Morphology and Phase Transition.

Recently, C60 has emerged as a promising anode material for Li-ion batteries, attracting significant interest due to its excellent lithium storage capacity. The electrochemical performance of C60 as an anode is largely dependent on its internal crystal structure, which is significantly influenced by the synthesis method and corresponding conditions. However, there have been few reports on how the synthesis process affects the crystal structure and Li+ storage capacity of C60. This study used the liquid-liquid interface precipitation method and a low-temperature annealing process to fabricate one-dimensional C60 nanorods (NRs). We thoroughly investigated synthesis conditions, including the growth time, drying temperature, annealing time, and annealing atmosphere. The results demonstrate that these synthesis conditions directly impact the morphology, phase transition, and electrochemical efficiency of pure C60 NRs. Remarkably, the hexagonal close-packed structural C60 NRs-6012h, in a metastable form, exhibits a reversible Li+ storage capacity as an anode material in Li-ion batteries. Furthermore, the face-centered cubic C60 NRs-603001h electrode shows significantly enhanced rate performance and long-cycle stability. A discharge-specific capacity of 603 mAh g-1 was maintained after 2000 cycles at a current density of 2 A g-1. This study elucidates the effect of synthesis conditions on C60 crystals, offering an effective strategy for preparing high-performance C60 anode materials.

Brittle-to-ductile transition and theoretical strength in a metal-organic framework glass.

Metal-organic framework (MOF) glasses, a new type of melt-quenched glass, show great promise to deal with the alleviation of greenhouse effects, energy storage and conversion. However, the mechanical behavior of MOF glasses, which is of critical importance given the need for long-term stability, is not well understood. Using both micro- and nanoscale loadings, we find that pillars of a zeolitic imidazolate framework (ZIF) glass have a compressive strength falling within the theoretical strength limit of ≥E/10, a value which is thought to be unreachable in amorphous materials. Pillars with a diameter larger than 500 nm exhibited brittle failure with deformation mechanisms including shear bands and nearly vertical cracks, while pillars with a diameter below 500 nm could carry large plastic strains of ≥20% in a ductile manner with enhanced strength. We report this room-temperature brittle-to-ductile transition in ZIF-62 glass for the first time and demonstrate that theoretical strength and large ductility can be simultaneously achieved in ZIF-62 glass at the nanoscale. Large-scale molecular dynamics simulations have identified that microstructural densification and atomistic rearrangement, i.e., breaking and reconnection of inter-atomistic bonds, were responsible for the exceptional ductility. The insights gained from this study provide a way to manufacture ultra-strong and ductile MOF glasses and may facilitate their processing toward real-world applications.

Enhanced High-Rate Capability and Long Cycle Stability of FeS@NCG Nanofibers for Sodium-Ion Battery Anodes.

The development of advanced hierarchical anode materials has recently become essential to achieving high-performance sodium-ion batteries. Herein, we developed a facile and cost-effective scheme for synthesizing graphene-wrapped, nitrogen-rich carbon-coated iron sulfide nanofibers (FeS@NCG) as an anode for SIBs. The designed FeS@NCG can provide a significant reversible capacity of 748.5 mAh g-1 at 0.3 A g-1 for 50 cycles and approximately 3.9-fold higher electrochemical performance than its oxide analog (Fe2O3@NCG, 192.7 mAh g-1 at 0.3 A g-1 for 50 cycles). The sulfur- and nitrogen-rich multilayer package structure facilitates efficient suppression of the porous FeS volume expansion during the sodiation process, enabling a long cycle life. The intimate contact between graphene and porous carbon-coated FeS nanofibers offers strong structural barriers associated with charge-transfer pathways during sodium insertion/extraction. It also reduces the dissolution of polysulfides, enabling efficient sodium storage with superior stable kinetics. Furthermore, outstanding capacity retention of 535 mAh g-1 at 5 A g-1 is achieved over 1010 cycles. The FeS@NCG also exhibited a specific capacity of 640 mAh g-1 with a Coulombic efficiency of above 99.8% at 5 A g-1 at 80 °C, indicating its development prospects in high-performance SIB applications.

Throughput Maximization for UAV-Enabled Relaying in Wireless Powered Communication Networks.

This paper investigates mobile relaying in wireless powered communication networks (WPCN), where an unmanned aerial vehicle (UAV) is employed to help information delivery from multiple sources to destination with communication channels severely blocked. The sources are low-power without energy supply. To support information transmission, the UAV acts as a hybrid access point (AP) to provide wireless power transfer (WPT) and information reception for sources. We set the issue of system throughput maximization as the optimization problem. On the one hand, the system is subject to the information causality constraint due to the dependent processes of information reception and transmission for the UAV. On the other hand, the sources are constrained by a so-called neutrality constraints due to the dependent processes of energy harvesting and energy consumption. In addition, we take account of the access delay issue of all ground nodes. Specifically, two paradigms of delay-tolerant case and delay-sensitive case are presented. However, the formulated problem including optimizations for time slot scheduling, power allocation and UAV trajectory is non-convex and thus is difficult to obtain its optimal solution. To tackle this problem, we apply the successive convex approximation (SCA) technique and propose an iterative algorithm by which a suboptimal solution can be achieved. Simulation results validate our proposed design, and show that the obtained suboptimal solution is high-quality, as compared to benchmark scheme.

Heterostructured SnS/TiO2@C hollow nanospheres for superior lithium and sodium storage.

Tin(ii) sulfide (SnS) is considered to be one of the most promising anode materials for lithium/sodium ion batteries (LIBs/SIBs) due to its high theoretical capacity and low-cost. However, its practical applications are severely impeded by its low electrical conductivity and large volume change upon cycling. Herein, we demonstrate a high-performance SnS/TiO2 encapsulated by a carbon shell (SnS/TiO2@C) synthesized by facile coprecipitation and annealing treatment. The exterior carbon coating can not only improve the conductivity, but also effectively relieve volume variation to maintain the structural integrity during cycling. Significantly, the internal SnS/TiO2 heterostructure formed a built-in electric field to provide favorable driving force for ion transfer. Consequently, the synthesized SnS/TiO2@C delivered a reversible capacity of 672.4 mA h g-1 at 0.5 A g-1 after 100 cycles for lithium storage and 331.2 mA h g-1 at 0.2 A g-1 after 200 cycles for sodium storage. Meanwhile, ultra-long lifespans of 3000 cycles at 5.0 A g-1 with a capacity of 394.5 mA h g-1 for LIBs and 750 cycles at 5.0 A g-1 with a capacity of 295 mA h g-1 for SIBs were achieved. The electrochemical reaction mechanisms of the SnS/TiO2@C electrode have been investigated by in situ XRD, ex situ XRD, and ex situ HRTEM. Our work may offer further understanding of the hierarchical structure to boost the electrochemical properties of the electrode materials.

MicroRNA-223 Ameliorates Nonalcoholic Steatohepatitis and Cancer by Targeting Multiple Inflammatory and Oncogenic Genes in Hepatocytes.

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of diseases ranging from simple steatosis to more severe forms of liver injury including nonalcoholic steatohepatitis (NASH), fibrosis, and hepatocellular carcinoma (HCC). In humans, only 20%-40% of patients with fatty liver progress to NASH, and mice fed a high-fat diet (HFD) develop fatty liver but are resistant to NASH development. To understand how simple steatosis progresses to NASH, we examined hepatic expression of anti-inflammatory microRNA-223 (miR-223) and found that this miRNA was highly elevated in hepatocytes in HFD-fed mice and in human NASH samples. Genetic deletion of miR-223 induced a full spectrum of NAFLD in long-term HFD-fed mice including steatosis, inflammation, fibrosis, and HCC. Furthermore, microarray analyses revealed that, compared to wild-type mice, HFD-fed miR-223 knockout (miR-223KO) mice had greater hepatic expression of many inflammatory genes and cancer-related genes, including (C-X-C motif) chemokine 10 (Cxcl10) and transcriptional coactivator with PDZ-binding motif (Taz), two well-known factors that promote NASH development. In vitro experiments demonstrated that Cxcl10 and Taz are two downstream targets of miR-223 and that overexpression of miR-223 reduced their expression in cultured hepatocytes. Hepatic levels of miR-223, CXCL10, and TAZ mRNA were elevated in human NASH samples, which positively correlated with hepatic levels of several miR-223 targeted genes as well as several proinflammatory, cancer-related, and fibrogenic genes. Conclusion: HFD-fed miR-223KO mice develop a full spectrum of NAFLD, representing a clinically relevant mouse NAFLD model; miR-223 plays a key role in controlling steatosis-to-NASH progression by inhibiting hepatic Cxcl10 and Taz expression and may be a therapeutic target for the treatment of NASH.

Minimum-Throughput Maximization for Multi-UAV-Enabled Wireless-Powered Communication Networks.

This paper considers a wireless-powered communication network (WPCN) system that uses multiple unmanned aerial vehicles (UAVs). Ground users (GUs) first harvest energy from a mobile wireless energy transfer (WET) UAV then use the energy to power their information transmission to a data gatherer (DG) UAV. We aim to maximize the minimum throughput for all GUs by jointly optimizing UAV trajectories, and the resource allocation of ET UAV and GUs. Because of the non-convexity of the formulated problem, we propose an alternating optimization algorithm, applying successive convex optimization techniques to solve the problem; the UAV trajectories and resource allocation are alternately optimized in each iteration. Numerical results show the efficiency of the proposed algorithm in different scenarios.

Coordination Polymers-Derived Three-Dimensional Hierarchical CoFe2O4 Hollow Spheres as High-Performance Lithium Ion Storage.

Hierarchical CoFe2O4 (CFO) hollow spheres were successfully synthesized via solvothermal method and calcination treatment. The obtained CFO completely inherited the hollow structure and spherical morphology of its precursor of cobalt-based ferrocenyl coordination polymers (Co-Fc-CPs). The three-dimensional (3D) porous hierarchical hollow structure can not only promote the permeation of electrolyte and shorten the lithium-ion transfer distance but also provide a cushion for the volume change during insertion/extraction of lithium ions. To improve the electrochemical properties, the CFO was combined with two forms of carbonaceous materials to controllably obtain 3D CoFe2O4@C (CFO@C) and CoFe2O4@reduced graphene oxide (CFO@rGO) composites. Compared with bare CFO and CFO@C, CFO@rGO exhibited a superior electrochemical performance, achieving a high specific capacity of 933.1 mA h g-1 at a current density of 100 mA g-1 after 100 cycles and showing an outstanding cycling life with a capacity of 615.6 mA h g-1 at 1000 mA g-1 after 600 cycles. In situ X-ray diffraction technique was applied to investigate the lithium storage mechanism during discharge/charge processes. This work provides a new approach to prepare hierarchical hollow bimetallic oxides composites for lithium-ion anode materials.

A Weighted Two-Level Bregman Method with Dictionary Updating for Nonconvex MR Image Reconstruction.

Nonconvex optimization has shown that it needs substantially fewer measurements than l 1 minimization for exact recovery under fixed transform/overcomplete dictionary. In this work, two efficient numerical algorithms which are unified by the method named weighted two-level Bregman method with dictionary updating (WTBMDU) are proposed for solving lp optimization under the dictionary learning model and subjecting the fidelity to the partial measurements. By incorporating the iteratively reweighted norm into the two-level Bregman iteration method with dictionary updating scheme (TBMDU), the modified alternating direction method (ADM) solves the model of pursuing the approximated lp -norm penalty efficiently. Specifically, the algorithms converge after a relatively small number of iterations, under the formulation of iteratively reweighted l 1 and l 2 minimization. Experimental results on MR image simulations and real MR data, under a variety of sampling trajectories and acceleration factors, consistently demonstrate that the proposed method can efficiently reconstruct MR images from highly undersampled k-space data and presents advantages over the current state-of-the-art reconstruction approaches, in terms of higher PSNR and lower HFEN values.