High-Performance Multifunctional Carbon Fibrous Sponges Derived from Pitch.

3D carbon-based porous sponges are recognized for significant potential in oil absorption and electromagnetic interference (EMI). However, their widespread application is hindered by a common compromise between high performance and affordability of mass production. Herein, a novel approach is introduced that involves laser-assisted micro-zone heating melt-blown spinning (LMHMS) to address this challenge by creating pitch-based submicron carbon fibers (PSCFs) sponge with 3D interconnected structures. These structures bestow the resulting sponge exceptional characteristics including low density (≈20 mg cm-3), high porosity (≈99%), remarkable compressibility (80% maximum strain), and superior conductivity (≈628 S m-1). The resultant PSCF sponges realize an oil/organic solvent sorption capacity over 56 g/g and possess remarkable regenerated ability. In addition to their effectiveness in cleaning up oil/organic solvent spills, they also demonstrated strong electromagnetic shielding capabilities, with a total shielding effectiveness (SE) exceeding 60 dB across the X-band GHz range. In virtue of extreme lightweight of ≈20 mg cm-3, the specific SE of the PSCF sponge reaches as high as ≈1466 dB cm3 g-1, surpassing the performance of numerous carbon-based porous structures. Thus, the unique blend of properties renders these sponges promising for transforming strategies in addressing oil/organic solvent contaminations and providing effective protection against EMI.

Large-scale assembly of isotropic nanofiber aerogels based on columnar-equiaxed crystal transition.

Ice-templating technology holds great potential to construct industrial porous materials from nanometers to the macroscopic scale for tailoring thermal, electronic, or acoustic transport. Herein, we describe a general ice-templating technology through freezing the material on a rotating cryogenic drum surface, crushing it, and then re-casting the nanofiber slurry. Through decoupling the ice nucleation and growth processes, we achieved the columnar-equiaxed crystal transition in the freezing procedure. The highly random stacking and integrating of equiaxed ice crystals can organize nanofibers into thousands of repeating microscale units with a tortuous channel topology. Owing to the spatially well-defined isotropic structure, the obtained Al2O3·SiO2 nanofiber aerogels exhibit ultralow thermal conductivity, superelasticity, good damage tolerance, and fatigue resistance. These features, together with their natural stability up to 1200 °C, make them highly robust for thermal insulation under extreme thermomechanical environments. Cascading thermal runaway propagation in a high-capacity lithium-ion battery module consisting of LiNi0.8Co0.1Mn0.1O2 cathode, with ultrahigh thermal shock power of 215 kW, can be completely prevented by a thin nanofiber aerogel layer. These findings not only establish a general production route for nanomaterial assemblies that is conventionally challenging, but also demonstrate a high-energy-density battery module configuration with a high safety standard that is critical for practical applications.

Highly Efficient Thermo-Acoustic Insulating Aerogels Enabled by Resonant Cavity Engineering.

Lightweight, flexible, and noncombustible thermo-acoustic insulating (TAI) materials have great potential in vehicles, cold-chain transportation, and aerospace engineering, where weight and space savings are critical. However, the TAI capabilities of many commodities are hindered by the lack of diverse and reasonable resonant cavities with broadband and highly efficient acoustic responsiveness. This study demonstrates a layer-by-layer freeze-casting method for superelastic cellular aerogel construction from varied nanofibers and ice particulates with widely distributed resonant cavities from 0.5 to 300 µm. The method enabled the cumulative freezing of the nanofiber solution from one side to the other side, resulting in vertical pore channels with random holes across the entire freezing distance. The formed cellular networks of stable hinged ternary nanofiber membranes, functionalized as ultrathin nanofiber drums, exhibit strong resonances and efficiently dissipate sound waves in a broad frequency range. A high noise reduction coefficient of 0.65 at a frequency range of 63-6300 Hz and a low thermal conductivity of 0.026 W m-1 K-1 at room temperature was obtained. This work presents the bottom-up fabrication of high-performance TAI aerogels that are beneficial for practical energy-saving devices and buildings and broadband acoustic absorption applications.

Processing Nomex Nanofibers by Ionic Solution Blow-Spinning for Efficient High-Temperature Exhausts Treatment.

Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrinsically high chemical stability, superior mechanical performance, and excellent high-temperature resistance. However, the mass production of hard-to-dissolve nanofibers still remains a critical challenge. A simple, scalable, and low-cost ionic solution blow-spinning method has herein been provided for the large-scale preparation of hard-to-dissolve Nomex polymeric nanofibers with an average diameter of nearly 100 nm. After rapidly dissolving Nomex microfibers in the lithium chloride/dimethylacetamide (LiCl/DMAc) solution system, the conductive solution can be stably and conductivity-independently processed into nanofibers. The method optimizes electrospinning and avoids spinnability degradation and potential safety hazards caused by high electrical conductivity. Owing to nanofibrous structure and high dipole moment, Nomex nanofibrous filters show a stable high filtration efficiency of 99.92% for PM0.3 with a low areal density of 4.6 g m-2, as well as a low-pressure drop of 189.47 Pa. Moreover, the flame-retardant filter can work at 250 °C and 280 °C for a long and short time without shrinking or burning, respectively, exhibiting a high filtration efficiency of 99.50% for PM0.3-10.0. The outstanding properties and low cost enable the efficient capture of PM from various high-temperature exhausts, making Nomex nanofibrous membrane an even more ideal industrial-grade air filter than polypropylene, polytetrafluoroethylene, polyimide, and ceramic nanofibrous filters. Graphical abstract: Hard-to-dissolve nanofibers provide alternatives for high-efficiency and low-resistant air filtration but are limited by the universality and economics of fabrication methods. A scalable and efficient ionic solution blow-spinning strategy has herein been proposed in preparing hard-to-dissolve nanofibrous filters. Supplementary Information: The online version contains supplementary material available at 10.1007/s42765-022-00231-x.

Thermal-Switchable, Trifunctional Ceramic-Hydrogel Nanocomposites Enable Full-Lifecycle Security in Practical Battery Systems.

Thermal runaway (TR) failures of large-format lithium-ion battery systems related to fires and explosions have become a growing concern. Here, we design a smart ceramic-hydrogel nanocomposite that provides integrated thermal management, cooling, and fire insulation functionalities and enables full-lifecycle security. The glass-ceramic nanobelt sponges exhibit high mechanical flexibility with 80% reversible compressibility and high fatigue resistance, which can firmly couple with the polymer-nanoparticle hydrogels and form thermal-switchable nanocomposites. In the operating mode, the high enthalpy of the nanocomposites enables efficient thermal management, thereby preventing local temperature spikes and overheating under extremely fast charging conditions. In the case of mechanical or thermal abuse, the stored water can be immediately released, leaving behind a highly flexible ceramic matrix with low thermal conductivity (42 mW m-1 K-1 at 200 °C) and high-temperature resistance (up to 1300 °C), thus effectively cooling the TR battery and alleviating the devastating TR propagation. The versatility, self-adaptivity, environmental friendliness, and manufacturing scalability make this material highly attractive for practical safety assurance applications.

Design of Optimum Portfolio Scheme Based on Improved NSGA-II Algorithm.

In the financial industry, it is of great significance to study the multiobjective portfolio optimization for obtaining a reasonable investment strategy. This paper designs the financial portfolio scheme based on the multiobjective optimization algorithm that is based on the framework of the NSGA-II algorithm. In order to introduce convergence information, aiming at the actual problem of the portfolio, the mixed individual coding mechanism with asset information expands the application of the multiobjective evolutionary algorithm in portfolio optimization. The portfolio scheme obtained is effective, which is helpful to improve the decision-making efficiency of financial investors and enriches the application of modern financial theory.

Design, synthesis, and biological evaluation of novel 7-deazapurine nucleoside derivatives as potential anti-dengue virus agents.

Dengue fever, caused by four distinct serotypes of dengue virus (DENV-1 to -4), has become the fastest spreading human infectious disease in recent years. Despite extensive efforts, there is no specific antiviral treatment approved for dengue until now. Nucleoside inhibitors represent an actively pursued area to develop small-molecule anti-dengue virus agents. In this study, we designed and synthesized a series of 7-deazapurine nucleoside derivatives and evaluated their anti-DENV activity. Our design strategy and structure activity relationship studies revealed 6e as the most potent inhibitor (EC50 = 2.081 ± 1.102 µM) of DENV replication. 6e suppressed RNA levels and DENV E protein expression, without causing any apparent cytotoxicity in A549 and HepG2 cells (CC50 = 150.06 ± 11.42 µM, SI = 72.11 in A549 cells, and CC50 = 146.47 ± 11.05 µM and SI = 63.7 in HepG2 cells). In addition, 6e showed similar inhibition potency against four serotypes of DENV, suggesting that it restrains some evolutionarily conserved targets essential for DENV replication. We conceive that 6e may serve as a promising lead compound for anti-DENV drug development.

Synthesis and Evaluation of 2'-Deoxy-2'-Spirodiflurocyclopropyl Nucleoside Analogs.

The preparation of 2'-deoxy-2'-siprodifluorocyclopropany-lnucleoside analogs has been achieved from α-d-glucose in several steps. The key step in the synthesis was the introduction of the difluorocyclopropane through a difluorocarbene type reaction at the 2'-position. Then, a series of novel 2'-deoxy-2'-spirodifluorocyclopropanyl nucleoside analogs were synthesized using the Vorbrüggen method. All the synthesized nucleosides were characterized and subsequently evaluated against hepatitis C and influenza A virus strains in vitro.

Regulation of proinflammatory genes by the circulating microRNA hsa-miR-939.

Circulating microRNAs are beneficial biomarkers because of their stability and dysregulation in diseases. Here we sought to determine the role of miR-939, a miRNA downregulated in patients with complex regional pain syndrome (CRPS). Hsa-miR-939 is predicted to target several proinflammatory genes, including IL-6, VEGFA, TNFα, NFκB2, and nitric oxide synthase 2 (NOS2A). Binding of miR-939 to the 3' untranslated region of these genes was confirmed by reporter assay. Overexpression of miR-939 in vitro resulted in reduction of IL-6, NOS2A and NFκB2 mRNAs, IL-6, VEGFA, and NOS2 proteins and NFκB activation. We observed a significant decrease in the NOS substrate l-arginine in plasma from CRPS patients, suggesting reduced miR-939 levels may contribute to an increase in endogenous NOS2A levels and NO, and thereby to pain and inflammation. Pathway analysis showed that miR-939 represents a critical regulatory node in a network of inflammatory mediators. Collectively, our data suggest that miR-939 may regulate multiple proinflammatory genes and that downregulation of miR-939 in CRPS patients may increase expression of these genes, resulting in amplification of the inflammatory pain signal transduction cascade. Circulating miRNAs may function as crucial signaling nodes, and small changes in miRNA levels may influence target gene expression and thus disease.

Effects of aging on the structural, mechanical, and thermal properties of the silicone rubber current transformer insulation bushing for a 500 kV substation.

In order to analyze the cracking and aging reason of the silicone rubber current transformer (CT) insulation bushing used for 8 years from a 500 kV alternating current substation, characteristics including Fourier transform infrared (FTIR) spectroscopy, mechanical properties analysis, hardness, and thermo gravimetric analysis have been carried out. The FTIR results indicated that the external surface of the silicone rubber CT insulation bushing suffered from more serious aging than the internal part, fracture of side chain Si-C bond was much more than the backbone. Mechanical properties and thermal stability results illustrated that the main aging reasons were the breakage of side chain Si-C bond and the excessive cross-linking reaction of the backbone. This study can provide valuable basis for evaluating degradation mechanism and aging state of the silicone rubber insulation bushing in electric power field.

Design, synthesis, and in vitro biological evaluation of novel 6-methyl-7-substituted-7-deaza purine nucleoside analogs as anti-influenza A agents.

Among many subtypes of influenza A viruses, influenza A(H1N1) and A(H3N2) subtypes are currently circulating among humans (WHO report 2014-15). Therapeutically, the emergence of viral resistance to currently available drugs (adamantanes and neuraminidase inhibitors) has heightened alarms for developing novel drugs that could address diverse targets in the viral replication cycle in order to improve treatment outcomes. To this regard, the design and synthesis of nucleoside analog inhibitors as potential anti-influenza A agents is a very active field of research nowadays. In this study, we designed and synthesized a series of hitherto unknown 6-methyl-7-substituted-7-deaza purine nucleoside analogs, and evaluated for their biological activities against influenza A virus strains, H1N1 and H3N2. From the viral inhibition assay, we identified some effective compounds, among which, compounds 5x (IC50 = 5.88 µM and 6.95 µM for H1N1 and H3N2, respectively) and 5z (IC50 = 3.95 µM and 3.61 µM for H1N1 and H3N2, respectively) demonstrated potent anti-influenza A activity. On the basis of selectivity index, we conceive that compound 5x may serve as a chemical probe of interest for further lead optimization studies with a general aim of developing novel and effective anti-influenza A virus agents.