The application of repetitive strong shock waves to enhance the permeability of coal beds is a frontier research field in recent years. However, the development of cracks in dense coal beds results ...in a multi-scale effect on the porosity of coal rock. The mechanism of permeability enhancement owing to the scale effect of the medium in reservoirs has yet to be elucidated. This study analyzed the patterns of crack development on different scales of coal samples subjected to shock waves. The characteristics of variation of the permeability of coal samples before and after the loading of shock waves were also investigated to establish a quantitative relationship between the number of shocks and permeability. Furthermore, computed tomography (CT) scanning technology was applied to determine the mechanism underlying the internal changes of coal samples after the application of shock waves. The research results demonstrated that, within the impact range of shock waves, coal mass damage, and mechanical fragmentation were clearly apparent. The permeability of coal mass was enhanced after shock waves were applied. This research provides an experimental foundation for the enhancement of coal bed permeability through the application of repetitive strong shock waves.
Based on activity theory, this paper employed data from the 2013, 2015, and 2018 waves of the China Health and Retirement Longitudinal Survey, and adopted Hierarchical Linear Modeling and ...longitudinal mediation analysis to explore the temporal variation characteristics of loneliness and the influence of social participation on loneliness in Chinese Older Adults, as well as the mechanism of them. The study found that loneliness among older adults overall was at a moderate level from 2013 to 2018 and increased over time, which may be related to decreasing social participation from year to year. Decreased social participation was associated with increased loneliness over time (β = -0.060,
< 0.001) and lower social support (β = 0.109,
< 0.001), which was associated with more loneliness (β = -0.098,
< 0.001). In addition, social support played a significant mediating role in the realization of social participation in alleviating loneliness. Social participation can not only directly reduce loneliness, but also reduce loneliness by increasing social support.
Along with the development of information technology and innovation of teaching and learning methods, visual elements, such as images and graphics, being an indispensable method of representing and ...conveying knowledge, have become important components of digital teaching. However, without appropriate design of visual presentation, visual elements cannot authentically improve the efficiency and effectiveness of knowledge communication. The study emphasizes on the necessity of proper visual presentation design in digital foreign language teaching (DFLT) from the perspectives of second language acquisition and other theories, hoping to improve the efficiency of DFLT in modern teaching context.
Sustainable agriculture is a key component of the effort to meet the increased food demand of a rapidly increasing global population. Nano-biotechnology is a promising tool for sustainable ...agriculture. However, rather than acting as nanocarriers, some nanoparticles (NPs) with unique physiochemical properties inherently enhance plant growth and stress tolerance. This biological role of nanoparticles depends on their physiochemical properties, application method (foliar delivery, hydroponics, soil), and the applied concentration. Here we review the effects of the different types, properties, and concentrations of nanoparticles on plant growth and on various abiotic (salinity, drought, heat, high light, and heavy metals) and biotic (pathogens and herbivores) stresses. The ability of nanoparticles to stimulate plant growth by positive effects on seed germination, root or shoot growth, and biomass or grain yield is also considered. The information presented herein will allow researchers within and outside the nano-biotechnology field to better select the appropriate nanoparticles as starting materials in agricultural applications. Ultimately, a shift from testing/utilizing existing nanoparticles to designing specific nanoparticles based on agriculture needs will facilitate the use of nanotechnology in sustainable agriculture.
A wood-inspired aerogel derived from chitosan was obtained by virtue of the unidirectional freezing technology, which allows for anisotropic liquid transport and displays a rather high oil absorption ...capacity of 63 g g−1, together with excellent recyclability via simple hand squeezing.
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•Anisotropic chitosan aerogel was acquired through directional freezing technology.•Displaying superior mechanical performance that allows for fast elastic recovery.•High oil absorption capacity and excellent recyclability via finger squeezing.•Fast oil/water separation (42.1 L g−1 h−1) was achieved by designing a device.
Aerogels that derived from biomass have long been attractive as absorbents for oil clean-up. However, it remains a significant challenge to prepare fully bio-based oil absorbents that combines fast oil/water separation capacity, adequate mechanical robustness and easy recyclability through green and facile strategy. Inspired by the fascinating structure of wood, here we report a highly porous and anisotropic bio-based aerogel by taking advantage of the directional freezing technology, followed by a freeze-drying and silylation process. Due to the directional growth of ice crystals along the vertical direction, a special spring like morphology was obtained, which is mainly composed of well aligned low-tortuosity channels that seamlessly connected to bottom layer. Superior mechanical properties that allow for high mechanical compressing and fast elastic recovery were consequently acquired. Moreover, the silylated CS aerogel displays a rather high oil absorption capacity of 63 g g−1, together with excellent recyclability via simple hand squeezing. By virtue of such hierarchical morphology, a device that could continuously separate oil from water was successfully designed. Given the natural abundance of raw material as well as the easy processability, this work would lay solid foundation for further fabrication of bio-based oil absorbents toward low-cost, high-performance and large-scale commodities.
Inspired by the electrostatic interaction between the oppositely charged ions, here we report the fabrication of a series of MXene-filled polymeric films possessing superior EMI shielding ...performance, accompanied with excellent in-plane TC, as well as distinguished Joule heating performance that allows for fast deicing.
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•Fabricating CS/MXene alternating layered films via LBL strategy.•Successful construction of continuous electrical/thermal conductive channel.•Absorption dominant (92%) EMI shielding with SSEt of 10, 650 dB cm2 g−1.•Excellent anisotropic thermal management capacity.•Distinguished Joule heating performance that allows for rapid deicing.
Polymeric composites that feature both highly efficient EMI shielding and rapid heat dissipation have long been attractive, but it remains a significant challenge to fulfill such goals by virtue of lower film thickness and less filler. Inspired by the electrostatic interaction between oppositely charged chitosan (CS) solution and transition metal carbide (MXene) slurry, here we report a series of CS/MXene alternating layered films by taking advantage of layer by layer assembly strategy. The resultant 35-μm thick CS/MXene multilayer film presents a maximum EMI SE of 40.8 dB, a high specific EMI SE (SSEt) of 10, 650 dB cm2 g−1, together with superior thermal conductivity (6.3 W m−1 K−1) and excellent Joule heating capacity. Thus, this research opens up a new horizon for achieving satisfying EMI shielding and heat dissipation capacity, which will further benefit the development of MXene‑based composite materials in next-generation electrical devices.
Silica nanoparticles (SiO2-NPs) are promising in nanoenabled agriculture due to their large surface area and biocompatible properties. Understanding the fundamental interaction between SiO2-NPs and ...plants is important for their sustainable use. Here, 3 week-old pakchoi (Brassica chinensis L.) plants were sprayed with SiO2-NPs every 3 days for 15 days (5 mg of SiO2-NPs per plant), after which the phenotypes, biochemical properties, and molecular responses of the plants were evaluated. The changes in rhizosphere metabolites were characterized by gas chromatography–mass spectrometry (GC–MS)-based metabolomics, and the response of soil microorganisms to the SiO2-NPs were characterized by high-throughput bacterial 16S rRNA and fungal internal transcribed spacer (ITS) gene sequencing. The results showed that the SiO2-NP spray had no adverse effects on photosynthesis of pakchoi plants nor on their biomass. However, the rhizosphere metabolite profile was remarkably altered upon foliar exposure to SiO2-NPs. Significant increases in the relative abundance of several metabolites, including sugars and sugar alcohols (1.3–9.3-fold), fatty acids (1.5–18.0-fold), and small organic acids (1.5–66.9-fold), and significant decreases in the amino acid levels (60–100%) indicated the altered carbon and nitrogen pool in the rhizosphere. Although the community structure was unchanged, several bacterial (Rhodobacteraceae and Paenibacillus) and fungal (Chaetomium) genera in the rhizosphere involved in carbon and nitrogen cycles were increased. Our results provide novel insights into the environmental effects of SiO2-NPs and point out that foliar application of NPs can alter the soil metabolite profile.
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron sublineages BA.2.12.1, BA.4 and BA.5 exhibit higher transmissibility than the BA.2 lineage
1
. The receptor binding and ...immune-evasion capability of these recently emerged variants require immediate investigation. Here, coupled with structural comparisons of the spike proteins, we show that BA.2.12.1, BA.4 and BA.5 (BA.4 and BA.5 are hereafter referred collectively to as BA.4/BA.5) exhibit similar binding affinities to BA.2 for the angiotensin-converting enzyme 2 (ACE2) receptor. Of note, BA.2.12.1 and BA.4/BA.5 display increased evasion of neutralizing antibodies compared with BA.2 against plasma from triple-vaccinated individuals or from individuals who developed a BA.1 infection after vaccination. To delineate the underlying antibody-evasion mechanism, we determined the escape mutation profiles
2
, epitope distribution
3
and Omicron-neutralization efficiency of 1,640 neutralizing antibodies directed against the receptor-binding domain of the viral spike protein, including 614 antibodies isolated from people who had recovered from BA.1 infection. BA.1 infection after vaccination predominantly recalls humoral immune memory directed against ancestral (hereafter referred to as wild-type (WT)) SARS-CoV-2 spike protein. The resulting elicited antibodies could neutralize both WT SARS-CoV-2 and BA.1 and are enriched on epitopes on spike that do not bind ACE2. However, most of these cross-reactive neutralizing antibodies are evaded by spike mutants L452Q, L452R and F486V. BA.1 infection can also induce new clones of BA.1-specific antibodies that potently neutralize BA.1. Nevertheless, these neutralizing antibodies are largely evaded by BA.2 and BA.4/BA.5 owing to D405N and F486V mutations, and react weakly to pre-Omicron variants, exhibiting narrow neutralization breadths. The therapeutic neutralizing antibodies bebtelovimab
4
and cilgavimab
5
can effectively neutralize BA.2.12.1 and BA.4/BA.5, whereas the S371F, D405N and R408S mutations undermine most broadly sarbecovirus-neutralizing antibodies. Together, our results indicate that Omicron may evolve mutations to evade the humoral immunity elicited by BA.1 infection, suggesting that BA.1-derived vaccine boosters may not achieve broad-spectrum protection against new Omicron variants.
In this study an innovative parameterized water-bomb wheel modeling method based on recursive solving are introduced, significantly reducing the modeling workload compared to traditional methods. A ...multi-link supporting structure is designed upon the foundation of the water-bomb wheel model. The effectiveness of the supporting structure is verified through simulations and experiments. For robots equipped with this water-bomb wheel featuring the multi-link support, base on the kinematic model of multi-link structure, a mapping algorithm that incorporates parameterized kinematic solutions and IMU-fused parameterized odometry is proposed. Based on this algorithm, SLAM and autonomous navigation experiments are carried out in simulation environment and real environment respectively. Compared with the traditional algorithm, this algorithm the precision of SLAM is enhanced, achieving high-precision SLAM and autonomous navigation with a robot error rate below 5%.
A novel water-compatible fenitrothion imprinted polymer was prepared on Au nanoparticles (AuNPs) by click chemistry and reversible addition–fragmentation chain transfer (RAFT) precipitation ...polymerization (RAFTPP). The RAFT chain-transfer agent was synthesized on the surface of AuNPs using click chemistry, then an imprinted polymer with hydrophilic polymer brushes was prepared on the RAFT chain-transfer agent modified AuNPs by RAFTPP, mediated by hydrophilic polyethylene glycol macromolecular cochain-transfer agent. The obtained molecularly imprinted material showed improved accessibility to fenitrothion and recognition property in water medium. When the material was immobilized on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of fenitrothion, the resulting electrochemical sensor presented linear response in the range of 0.01−5μM, with a sensitivity of 6.1μA/μMmm2. The low limit of detection was 8nM (S/N=3). The sensor was successfully applied to the determination of real samples and the recovery for standard added was 95−108%.
•A hydrophilic surface-imprinted polymer based sensor was fabricated for fenitrothion.•RAFT chain-transfer agent modified AuNPs were prepared by click chemistry.•Hydrophilic fenitrothion imprinted polymer on AuNPs was prepared by RAFTPP.•The sensor showed high selective and sensitive response to fenitrothion.
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