In this study, silicon (Si) was doped on a tetrahedral amorphous carbon (ta-C) coating and the tribological characteristics of the resulting Si-doped diamond-like carbon (DLC; a-C:Si:H) were ...investigated against a SUJ2 ball. The Si fraction in the coating was varied from 0 to ~ 20 at.% by increasing the trimethylsilane gas flow rate during filtered cathodic vacuum arc deposition. The coefficient of friction (CoF) showed no obvious change when the Si fraction was less than ~ 7 at.%. However, after Si doping, it significantly decreased when the Si fraction was greater than ~ 8 at.%. The running-in period also decreased to less than 1000 cycles after Si doping. The rapid formation of Si-rich debris and transfer layer led to the fabrication of a low-friction tribofilm, which was induced by the tribochemical reaction with moisture under ambient conditions. When the Si fraction was ~ 17 at.%, the lowest CoF of less than 0.05 was obtained. Further Si doping beyond the critical point led to the destruction of the film because of reduced hardness.
•The study proposes a new design for low-frequency and broadband sound insulation.•Locally resonant structure (LRS) and membrane enhance the sound transmission loss.•LRS- and membrane-induced ...anti-resonance realizes high dynamic effective density.•Effective impedance models are presented to estimate the dynamic effective density.•Soundproofing performance is experimentally verified using SSAM enclosure and plate.
Low-frequency and broadband noise reductions have always been a major industrial concern, as they pose a significant challenge. Although acoustic metamaterials are garnering attention in this field, they cannot simultaneously block low-frequency and broadband noise. Thus, this study developed a synergetic soundproofing acoustic metamaterial (SSAM) comprising a membrane and locally resonant structure (LRS) to realize low-frequency and broadband sound insulation. The SSAM suppresses structure-borne noise by utilizing LRS-induced anti-resonance for low-frequency sound insulation and membrane-induced anti-resonance for broadband sound insulation. The soundproofing mechanism of the proposed design was clarified through the dynamic effective density estimated using two impedance models (apparent and transfer impedances), and its sound insulation performance was validated through sound transmission loss simulations. The experimental sound pressure level results indicate that plate- and enclosure-type SSAMs can provide excellent low-frequency and broadband sound insulation. In the future, SSAMs will serve as a reference for the development of materials with noise-reduction capabilities for soundproofing applications, such as home appliances, vehicles, machinery products, and acoustic walls.
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Water‐borne diseases resulting from pathogen infection are especially challenges in areas with inadequate sanitation and power supply. Here a novel disinfection system is developed for bacterial and ...viral inactivation in water using a self‐powered supercoiling‐mediated rotational triboelectric nanogenerator (S‐TENG) as a power source to drive a new oxidation‐assisted electroporation mechanism. Owing to its rational design, the S‐TENG achieves an ultrafast rotation (≈7500 rpm), therefore it enables a simultaneous nanowire‐enhanced localized electric field and generation of oxidative species resulting in high disinfection performance: >99.9999% microbial inactivation at a high flux of 15 000 L h‐1 m‐2. An integrated S‐TENG‐powered disinfection prototype using an enlarged electrode (area of 50 cm2) achieves complete disinfection when the gravity‐driven natural water flows through the whole system at a high rate (1 L min‐1). This rapid, self‐powered water disinfection method is a potential solution for urgent water disinfection needs during disasters and pandemics, and water disinfection in areas with inadequate power supply.
A self‐powered microbial disinfection system driven by a supercoiling‐mediated rotational triboelectric nanogenerator (S‐TENG) is demonstrated. Enabling an ultrafast rotation (≈7500 rpm), the S‐TENG achieves a simultaneous nanowire‐enhanced localized electric field and oxidative species generation. The integrated prototype enables >99.9999% microbial inactivation when gravity‐driven water flows at a high flux (15 000 L–1 m–2).
•The paper presents soundproofing with a thin membrane.•The membrane is coupled with a host structure and changes the dynamic characteristic of whole structure.•The STL peak is observed at the ...anti-resonance frequency, and the dynamic effective density and acoustic impedance are almost infinite.•The SPL of the enclosure, plate type MAM and vibration displacement of the MAM enclosure exterior wall was measured.•The soundproofing MAM has excellent sound-blocking characteristics.
According to the mass law, a dense and thick soundproofing material is generally used to block low-frequency sounds. However, lightweight thin soundproofing materials in the form of metamaterials can also be implemented with high sound transmission loss. In this study, we present a soundproofing comprising a thin membrane coupled with an ultralight membrane-type acoustic metamaterial (MAM). Owing to the vibration in the membrane, the structure-borne acoustic radiation of the soundproofing can be easily tuned, making broadband sound insulation possible. The anti-resonance generated by the membrane and thin plate surface minimizes the response of the radiating surface to the acoustic load. Thus, the dynamic effective density and acoustic impedance become extremely high, whereas the normal displacement of the radiating surface is almost zero. We numerically and experimentally demonstrated an open-field test for a plate-type and an enclosure-type of soundproofing MAM. In addition, the vibration displacement of the MAM enclosure exterior wall is measured using laser Doppler vibrometer. The results show that the soundproofing MAM exhibits excellent sound-blocking characteristics at multiple anti-resonance frequencies compared to homogeneous materials of the same weight. We expect that its simple construction can be used in noise-insulation applications in acoustic enclosures, automobile insulation, walls, and engine rooms.
and other related species of
are the major sources of the bis-benzylisoquinoline alkaloids tetrandrine (TET), fangchinoline (FAN), and cepharanthine (CEP). Although the pharmacological properties of ...these compounds include anticancer and anti-inflammatory activities, the antiviral effects of these compounds against human coronavirus (HCoV) remain unclear. Hence, the aims of the current study were to assess the antiviral activities of TET, FAN, and CEP and to elucidate the underlying mechanisms in HCoV-OC43-infected MRC-5 human lung cells. These compounds significantly inhibited virus-induced cell death at the early stage of virus infection. TET, FAN, and CEP treatment dramatically suppressed the replication of HCoV-OC43 as well as inhibited viral S and N protein expression. The virus-induced host response was reduced by compound treatment as compared with the vehicle control. Taken together, these findings demonstrate that TET, FAN, and CEP are potential natural antiviral agents for the prevention and treatment of HCoV-OC43 infection.
Cerebral ischemia causes tissue death owing to occlusion of the cerebral blood vessels, and cerebral ischemia activates mitogen-activated protein kinase (MAPK) and induces secretion of ...pro-inflammatory cytokines. Adenosine A2A receptor agonist, polydeoxyribonucleotide (PDRN), suppresses the secretion of pro-inflammatory cytokines and exhibits anti-inflammatory effect. In the current study, the therapeutic effect of PDRN on cerebral ischemia was evaluated using gerbils. For the induction of cerebral ischemia, the common carotid arteries were exposed, and then aneurysm clips were used to occlude the common carotid arteries bilaterally for 7 minutes. In the PDRN-treated groups, the gerbils were injected intraperitoneally with 0.3 mL of saline containing 8 mg/kg PDRN, per a day for 7 days following cerebral ischemia induction. In order to confirm the participation of the adenosine A2A receptor in the effects mediated by PDRN, 8 mg/kg 7-dimethyl-1-propargylxanthine (DMPX), adenosine A2A receptor antagonist, was treated with PDRN. In the current study, induction of ischemia enhanced the levels of pro-inflammatory cytokines and increased phosphorylation of MAPK signaling factors in the hippocampus and basolateral amygdala. However, treatment with PDRN ameliorated short-term memory impairment by suppressing the production of pro-inflammatory cytokines and inactivation of MAPK signaling factors in cerebral ischemia. Furthermore, PDRN treatment enhanced the concentration of cyclic adenosine-3,5'-monophosphate (cAMP) as well as phosphorylation of cAMP response element-binding protein (p-CREB). Co-treatment of DMPX and PDRN attenuated the therapeutic effect of PDRN on cerebral ischemia. Based on these findings, PDRN may be developed as the primary treatment in cerebral ischemia.
A robust strategy is developed for preparing light-responsive block copolymer (BCP) particles in which shape and color can be actively controlled with high spatial and temporal resolution. The key to ...achieving light-responsive shape transitions of BCP particles is the design and synthesis of surfactants containing light-active groups (i.e., nitrobenzyl esters and coumarin esters) that modulate the amphiphilicity and interfacial activity of the surfactants in response to light of a specific wavelength. These light-induced changes in surfactant structure modify the surface and wetting properties of BCP particles, affording both shape and morphological transitions of the particles, for example from spheres with an onion-like inner morphology to prolate or oblate ellipsoids with axially stacked nanostructures. In particular, wavelength-selective shape transformation of the BCP particles can be achieved with a mixture of two light-active surfactants that respond to different wavelengths of light (i.e., 254 and 420 nm). Through the use of light-emitting, photoresponsive surfactants, light-induced changes in both color and shape are further demonstrated. Finally, to demonstrate the potential of the light-triggered shape control of BCP particles in patterning features with microscale resolution, the shape-switchable BCP particles are successfully integrated into a patterned, free-standing hydrogel film, which can be used as a portable, high-resolution display.
Safe and long cycle life electrode materials for lithium‐ion batteries are significantly important to meet the increasing demands of rechargeable batteries. Niobium pentoxide (Nb2O5) is one of the ...highly promising candidates for stable electrodes due to its safety and minimal volume expansion. Nevertheless, pulverization and low conductivity of Nb2O5 have remained as inherent challenges for its practical use as viable electrodes. A highly facile method is proposed to improve the overall cycle retention of Nb2O5 microparticles by ammonia (NH3) gas‐driven nitridation. After nitridation, an ultrathin surficial layer (2 nm) is formed on the Nb2O5, acting as a bifunctional nanolayer that allows facile lithium (Li)‐ion transport (10–100 times higher Li diffusivity compared with pristine Nb2O5 microparticles) and further prevents the pulverization of Nb2O5. With the subsequent decoration of silver (Ag) nanoparticles (NPs), the low electric conductivity of nitridated Nb2O5 is also significantly improved. Cycle retention is greatly improved for nitridated Nb2O5 (96.7%) compared with Nb2O5 (64.7%) for 500 cycles. Ag‐decorated, nitridated Nb2O5 microparticles and nitridated Nb2O5 microparticles exhibit ultrastable cycling for 3000 cycles at high current density (3000 mA g−1), which highlights the importance of the surficial nanolayer in improving overall electrochemical performances, in addition to conductive NPs.
A surficial bifunctional nanolayer is adopted on Nb2O5 microparticles by a simple nitridation process, where it results in higher ionic transport and further prevents the pulverizaton of Nb2O5. Upon decoration of Ag nanoparticles, electric conductivity of Nb2O5 is further improved, resulting in ultralong cycle retention at high current density (3000 mA g−1).
We report the structure, mechanical properties, thermal stability, and durability of Si/SiC/ta-C composite (Si-ta-C) coatings fabricated using simultaneous filtered cathodic vacuum arc deposition and ...direct current unbalanced magnetron sputtering. Si concentration of 1.25-6.04 at.% was achieved by increasing the unbalanced magnetron sputtering power from 25 to 175 W. Si addition provided functionality to the coating, such as heat resistance, while retaining the high hardness of ta-C coatings. The Si-ta-C coatings were stable up to 600 °C regardless of the Si content, while the coating containing 3.85 at.% Si was stable up to 700 °C. The friction behavior and mechanical properties were dependent on the coating film before and after annealing at 100-200 °C; however, annealing at 300-400 °C decreased disk wear and increased counterpart wear due to an increase in film hardness on account of an endothermic reaction that increased the number of Si-C bonds. This indicates that the basic hardness characteristics of the ta-C coating and the high-temperature structural change of the Si-ta-C coating are important for ensuring high-temperature durability. These characteristics were verified through the low coefficient of friction and wear rate of the 1.25 at.% Si-ta-C coating after annealing at 500 °C.
This study examined the tribological behavior of a ta-C coating fabricated at a substrate bias of −100 V via filtered cathodic vacuum arc (FCVA) deposition. Defects in the ta-C coating were ...categorized as droplets, pores, and spikes, considering the morphological, structural, and mechanical properties of the ta-C surface. A friction test was conducted at 170 °C in ambient air using a ball-on-disk tribometer. The friction coefficient was 0.08 during the steady state and the wear rate was 4.3 × 10−6 mm3/Nm. To explain the friction and wear behavior, the morphological and structural properties of the defects in the designated area were compared among different sliding cycles.
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•Defects in the ta-C coating fabricated by FCVA were classified as droplets, pores, and spikes•Clarified effect of each defects on tribological behavior at high temperature at 170 °C•Spike and droplet have a shape of convex whereas pore is in the form of concave.•Spikes having similar properties of matrix of ta-C remain on the ta-C surface even after high-temperature friction test.•Spikes and droplet prevent tribolayer formation on Si3N4 ball in running-in region and steady state, respectively.
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