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In this study, the length scaling for the boundary layer separation induced by two incident shock waves is experimentally and analytically investigated. The experiments are performed in a Mach 2.73 flow. A double-wedge shock generator with two deflection angles ($\alpha _1$ and $\alpha _2$) is employed to generate two incident shock waves. Two deflection angle combinations with an identical total deflection angle are adopted: ($\alpha _1 = 7^\circ$ , $\alpha _2 = 5^\circ$) and ($\alpha _1 = 5^\circ$ , $\alpha _2 = 7^\circ$). For each deflection angle combination, the flow features of the dual-incident shock wave–turbulent boundary layer interactions (dual-ISWTBLIs) under five shock wave distance conditions are examined via schlieren photography, wall-pressure measurements and surface oil-flow visualisation. The experimental results show that the separation point moves downstream with increasing shock wave distance ($d$). For the dual-ISWTBLIs exhibiting a coupling separation state, the upstream interaction length ($L_{int}$) of the separation region approximately linearly decreases with increasing $d$ , and the decrease rate of $L_{int}$ with $d$ increases with the second deflection angle under the condition of an identical total deflection angle. Based on control volume analysis of mass and momentum conservations, the relation between $L_{int}$ and $d$ is analytically determined to be approximately linear for the dual-ISWTBLIs with a coupling separation region, and the slope of the linear relation obtained analytically agrees well with that obtained experimentally. Furthermore, a prediction method for $L_{int}$ of the dual-ISWTBLIs with a coupling separation region is proposed, and the relative error of the predicted $L_{int}$ in comparison with the experimental result is $\sim$ 10 %. [ABSTRACT FROM AUTHOR]

In this study, an atmospheric‐pressure nanosecond impulse discharge initiated above the pyrrole microemulsion surface is applied to polymerize pyrrole and obtain a polypyrrole film. The films obtained under different number of plasma discharge times and duration of argon gas input time are investigated using a field emission scanning electron microscope. Results show that the roughness and thickness of the polypyrrole film can be tuned by controlling discharge times and the gas feed time. Four‐point sheet resistance measurements of the films reflect that those with a smoother and more complete surface have better electrical conductivity. The films are identified as polypyrrole by Fourier‐transform infrared spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectrometry. Also, N2 is a critical factor in polymerizing polypyrrole and the gas–liquid plasma polymerization mechanism, which has three steps, is discussed. [ABSTRACT FROM AUTHOR]

A simple, scalable approach is developed to fabricate a flexible hybrid paper electrode composed of the polyaniline/graphene and the carbon fiber (CF)-reinforced bacterial cellulose. The prepared hybrid paper presents high areal capacitance of 4.145 F cm−2 at 5 mA cm−2 and an extremely low sheet resistance of 29.7 Ω sq.−1. The CF endows the paper electrode remarkable foldability with no mechanical destruction. Even after being repeatedly bent 180° up to 1000 times, the initial capacitance can be retained up to 98%. A fabricated all-solid-state supercapacitor based on the resulting paper electrode has an excellent areal capacitance of 630 mF cm−2 and energy density of 2.8 mWh cm−3. The results confirm that this approach can fabricate the highly foldable and shape-tailorable energy storage devices and may have wide potential applications. [ABSTRACT FROM AUTHOR]

Enriching natural 10 g/100 g β-carotene concentrate further is both meaningful and challenging issue. In this paper, a two-step technique has been reported to boost the concentration of natural β-carotene. Supercritical carbon dioxide (SC-CO 2 ) was utilized to preconcentrate 10 g/100 g β-carotene made from crude palm oil followed with a solvent extraction. In the first step, the β-carotene concentration was preconcentrated to 16.7 g/100 g from 10 g/100 g when pretreating conditions were as follows: extraction temperature 60 °C, extraction pressure 20 MPa, extraction time 3 h, and CO 2 flow rate 22 kg/h, In the second step, the β-carotene was boosted to 58.7 g/100 g from 16.7 g/100 g when the ratio of the preconcentrated sample and n-hexane solvent was 4:200 (g:mL), and the processing temperature was −5 °C. This is attributed to that SC-CO 2 was able selectively to remove the impurities such as oil fraction. Removing impurities enable further purification of the beta-carotene with hexane extraction. The pretreatment of removing oil fraction using supercritical (SC-CO 2 ) plays a vital role in the enrichment of β-carotene from 10 g/100 g β-carotene concentrates to higher content. [ABSTRACT FROM AUTHOR]

Due to the failure of traditional oscillation mechanism based on an acoustic wave feedback loop and the supersonic spillage at the duct entrance, the unstart flow pattern of hypersonic inlets is quite different from that of traditional supersonic inlets. What's more, the hypersonic inlet unstart is more harmful, more closely coupled with the combustor, and has more demand for real-time control. Therefore, it should be drawn more attention in the development of hypersonic technology. In this paper, the main progress of the hypersonic inlet unstart is reviewed from its characteristics, classification, detection and control methods. The remaining problems are also analyzed and some issues for future study are suggested. [ABSTRACT FROM AUTHOR]

In order to operate efficiently in various operating conditions, a turbine-based combined cycle engine (TBCC) variable nozzle is proposed to adjust the area of the nozzle throat and the exit simultaneously. The performances of the nozzle at static condition and at different freestream Mach numbers are analyzed. Results show that the design has a preferable static performance and the thrust ratios are 0. 90, 0. 97 and 0. 98 in typical states. After the introduction of the external flow, the freestream can suppress the overexpansion of the exhaust flow effectively at the low Mach number condition (Ma = 0. 8), so the thrust coefficient is enhanced by 6.7%. In the high Mach number conditions (Ma = 2. 8,4. 0), though the flow pattern of the nozzle downstream is apparently affected by the external flow, the pressure distribution of the central body and the internal flow path is hardly affected. Therefore, there is no change in the thrust ratios which stay at 0. 97 and 0. 98, respectively. [ABSTRACT FROM AUTHOR]

The intricate balance among cost, output, and quality has substantially hindered the practical application of graphene within the downstream industry chain. Here we present a scalable and green supercritical CO 2 -assisted mechano-exfoliation (SCME) process that omits the use of organic solvents and oxidants throughout the production lifecycle, including exfoliation, separation, and purification. The SCME process achieves graphene powder space-time yields exceeding 40 kg/(m³·day) at laboratory (0.06-0.2 kg) and pilot scales ( > 4 kg), with resultant free-standing films showing conductivities up to 5.26 × 10⁵ S/m. Further kinetic investigations propose general guidelines for grinding-assisted exfoliation: (1) the macroscopic optimizing ability of mechanotechnics for mass transfer frequency and stress distribution and (2) the microscopic multiplication ability of exfoliation medium for shear-delamination. The comprehensive techno-economic analysis also underscores the economic viability of the SCME process for large-scale production., (© 2024. The Author(s).)

Small RNA (sRNA)-mediated RNA interference (RNAi) is a sequence-specific gene silencing mechanism that modulates gene expression in eukaryotes. As core molecules of RNAi, various sRNAs are encoded in the plant genome or derived from invading RNA molecules, and their biogenesis depends on distinct genetic pathways. Transitive small interfering RNAs (siRNAs), which are sRNAs produced from double-strand RNA (dsRNA) in a process that depends on RNA-dependent RNA polymerases (RDRs), can amplify and spread silencing signals to additional transcripts, thereby enabling a phenomenon termed "transitive RNAi". Members of this class of siRNAs function in various biological processes ranging from development to stress adaptation. In Arabidopsis thaliana , two RDRs participate in the generation of transitive siRNAs, acting cooperatively with various siRNA generation-related factors, such as the RNA-induced silencing complex (RISC) and aberrant RNAs. Transitive siRNAs are produced in diverse subcellular locations and structures under the control of various mechanisms, highlighting the intricacies of their biogenesis and functions. In this review, we discuss recent advances in understanding the molecular events of transitive siRNA biogenesis and its regulation, with a particular focus on factors involved in RDR recruitment. We aim to provide a comprehensive description of the generalized mechanism governing the biogenesis of transitive siRNAs. Additionally, we present an overview of the diverse biological functions of these siRNAs and raise some pressing questions in this area for further investigation.

Laccases are enzymes belonging to the group of multi-copper oxidases. These enzymes are widely distributed in insects, plants, fungi and bacteria. In general, laccases can oxidize an exceptionally high number of substrates, so they have broad applications in textile, pulp, food and the degradation of lignin. However, low yield, low activity and thermo-instability of laccase in nature limit the application of laccase. High efficient heterologous expression of the protein is an effective way for solving this problem. Here, we summarize the research advances of heterologous expression of eukaryote-origin laccases. We focus on the overexpression of eukaryote-origin laccases using different expression system and the method for improving the production yield and enzyme activity in yeast cells. Information provided in this review would be helpful for researchers in the field.