In this letter, we consider simultaneous wireless information and power transfer (SWIPT) in multirelay-assisted two-hop relay system, where multiple relay nodes simultaneously assist the transmission ...from source to destination using the concept of distributed space-time coding. Each relay applies power splitting protocol to coordinate the received signal energy for information decoding and energy harvesting. The optimization problems of power splitting ratios at the relays are formulated for both decode-and-forward (DF) and amplify-and-forward (AF) relaying protocols. Efficient algorithms are proposed to find the optimal solutions. Simulations verify the effectiveness of the proposed schemes.
In this paper, we consider relay-assisted simultaneous wireless information and power transfer (SWIPT) for two-hop cooperative transmission, where a half-duplex multiantenna relay adopts ...decode-and-forward relaying strategy for information forwarding. The relay is assumed to be energy-free and needs to harvest energy from the source node. By embedding power splitting (PS) at each relay antenna to coordinate the received energy and information, joint problem of determining PS ratios and power allocation at the multiantenna relay node is formulated to maximize the end-to-end achievable rate. We show that the multiantenna relay is equivalent to a virtual single-antenna relay in such a SWIPT system, and the problem is optimally solved with closed form. To reduce the hardware cost of the PS scheme, we further propose the antenna clustering scheme, where the multiple antennas at the relay are partitioned into two disjoint groups, which are exclusively used for information decoding and energy harvesting, respectively. Optimal clustering algorithm is first proposed but with exponential complexity. Then, a greedy clustering algorithm is introduced with linear complexity and approaches to the optimal performance. Several valuable insights are provided via theoretical analysis and simulation results.
Abstract
Covalent organic frameworks (COFs) have served as a family of porous crystalline molecules for various promising applications. However, controllable synthesis of COFs with uniform morphology ...is paramount yet still remains quite challenging. Herein, we report self-templated synthesis of uniform and unique hollow spheres based on highly conjugated three-dimensional (3D) COFs with diameters of 500–700 nm. A detailed time-dependent study reveals the continuous transformation from initial nano sphere-like particles into uniform hollow spherical structures with Ostwald ripening mechanism. Particularly, the resulting 3D COF (3D-Sp-COF) is prone to transport ions more efficiently and the lithium-ion transference number (
t
+
) of 3D-Sp-COF reaches 0.7, which even overwhelms most typical PEO-based polymer electrolytes. Inspiringly, the hollow spherical structures show enhanced capacitance performance with a specific capacitance of 251 F g
−1
at 0.5 A g
−1
, which compares favorably with the vast majority of two-dimensional COFs and other porous electrode materials.
Due to excellent metal–insulator transition property, vanadium dioxide nanoparticles (VO2 NPs)‐based nanomaterials are extensively studied and applied in various fields, and thus draw safety concerns ...of VO2 NPs exposure through various routes. Herein, the cytotoxicity of VO2 NPs (N‐VO2) and titanium dioxide‐coated VO2 NPs (T‐VO2) to typical human lung cell lines (A549 and BEAS‐2B) was studied by using a series of biological assays. It was found that both VO2 NPs induced a dose‐dependent cytotoxicity, and the two cell lines displayed similar sensitivity to VO2 NPs. Under the same conditions, T‐VO2 NPs showed slightly lower cytotoxicity than N‐VO2 in both cells, indicating the surface coating of titanium dioxide mitigated the toxicity of VO2 NPs. Titanium dioxide coating changed the surface property of VO2 NPs and reduced the vanadium release of particles, and thus helped lowing the toxicity of VO2 NPs. The induced cell viability loss was attributed to apoptosis and proliferation inhibition, which were supported by the assays of apoptosis, mitochondrial membrane damage, caspase‐3 level, and cell cycle arrest. The oxidative stress, i.e., enhanced reactive oxygen species generation and suppressed reduced glutathione , in A549 and BEAS‐2B cells was one of the major mechanisms of the cytotoxicity of VO2 NPs. These findings provide safety guidance for the practical applications of vanadium dioxide‐based materials.
The toxicity of metal–insulator transition materials, a normal monoclinic vanadium dioxide nanoparticle (N‐VO2) and its titanium dioxide‐coated counterpart (T‐VO2), were studied on lung cells. VO2 nanoparticles induced a dose‐dependent cytotoxicity, including apoptosis and proliferation inhibition. The two cell lines displayed similar sensitivity against VO2 NPs, while N‐VO2 was slightly more toxic than T‐VO2. Titanium dioxide coating probably attenuated the cytotoxicity of VO2 NPs, thus supports the development titanium dioxide‐coated VO2 nanoparticles as a safer materials for applications such as intelligent window.
The severe charge recombination and the sluggish kinetic for oxygen evolution reaction have largely limited the application of hematite (α‐Fe2O3) for water splitting. Herein, the construction of ...Cu2S/Fe2O3 heterojunction and discover that the formation of covalent SO bonds between Cu2S and Fe2O3 can significantly improve the photoelectrochemical performance and stability for water splitting is reported. Compared with bare Fe2O3, the heterostructure of Cu2S/Fe2O3 endows the resulting electrode with enhanced charge separation and transfer, extended range for light absorption, and reduced charge recombination rate. Additionally, due to the photothermal properties of Cu2S, the heterostructure exhibits locally a higher temperature under illumination, profitable for increasing the rate of oxygen evolution reaction. Consequently, the photocurrent density of the heterostructure is enhanced by 177% to be 1.19 mA cm−2 at 1.23 V versus reversible hydrogen electrode. This work may provide guideline for future in the design and fabrication of highly efficient photoelectrodes for various reactions.
The construction of Cu2S/Fe2O3 heterojunction and the formation of covalent SO bonds between Cu2S and Fe2O3 can significantly improve the performance and stability for photoelectrochemical water splitting. The heterostructure of Cu2S/Fe2O3 endows the resulting electrode with promoted charge separation and transfer, extended light absorption range, and reduced charge recombination rate.
Polyimide (PI) is one of the best engineering plastics with excellent thermal, mechanical, dielectric performance and chemical stability. Among various PI products, film is one of the most dominant ...types. If PI films are to be applied to optical devices and display equipment, it is necessary to improve their optical transparency in the ultraviolet–visible region. However, improving the optical transparency of PI films would affect their thermal performance including thermal and dimensional stability. Therefore, how to balance optical and thermal performance to obtain highly transparent PI films with the best overall performance becomes a focus of current research field. In this review, we categorize transparent PI films into highly transparent PI, transparent PI with high glass transition temperature (Tg) and transparent PI with low coefficient of thermal expansion (CTE) based on their optical and thermal properties. Then, we review research progress in the field of polymer molecular design including synthesis strategies and properties in recent 5 years, to inspire research ideas and elaborate on the possible ways to develop high‐performance, colorless and transparent PI materials.
Building high‐performance colorless and transparent polyimide (PI) films at the molecular level requires balancing the light transmittance, thermal stability, dimensional stability and other properties of PIs. The main strategy is to inhibit the formation of charge transfer complexes intermolecularly and intramolecularly, and to improve the rigidity of the molecule. This review focuses on how to achieve this goal.
Sonodynamic therapy （SDT） is an emerging approach that involves a combination of low-intensity ultrasound and specialized chemical agents known as sonosensitizers. Ultrasound can penetrate deeply ...into tissues and can be focused into a small region of a tumor to activate a sonosensitizer which offers the possibility of non-invasively eradicating solid tumors in a site-directed manner. In this article, we critically reviewed the currently accepted mechanisms of sonodynamic action and summarized the classification of sonosensitizers. At the same time, the breath of evidence from SDT-based studies suggests that SDT is promising for cancer treatment.
Immunotherapy, represented by immune checkpoint inhibitors (ICIs), has greatly improved the clinical efficacy of malignant tumor therapy. ICI-mediated antitumor responses depend on the infiltration ...of T cells capable of recognizing and killing tumor cells. ICIs are not effective in "cold tumors", which are characterized by the lack of T-cell infiltration. To realize the full potential of immunotherapy and solve this obstacle, it is essential to understand the drivers of T-cell infiltration into tumors. We present a critical review of our understanding of the mechanisms underlying "cold tumors", including impaired T-cell priming and deficient T-cell homing to tumor beds. "Hot tumors" with significant T-cell infiltration are associated with better ICI efficacy. In this review, we summarize multiple strategies that promote the transformation of "cold tumors" into "hot tumors" and discuss the mechanisms by which these strategies lead to increased T-cell infiltration. Finally, we discuss the application of nanomaterials to tumor immunotherapy and provide an outlook on the future of this emerging field. The combination of nanomedicines and immunotherapy enhances cross-presentation of tumor antigens and promotes T-cell priming and infiltration. A deeper understanding of these mechanisms opens new possibilities for the development of multiple T cell-based combination therapies to improve ICI effectiveness.
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