A High-Throughput Screening System Based on Fluorescence-Activated Cell Sorting for the Directed Evolution of Chitinase A

Chitinases catalyze the degradation of chitin, a polymer of N-acetylglucosamine found in crustacean shells, insect cuticles, and fungal cell walls. There is great interest in the development of improved chitinases to address the environmental burden of chitin waste from the food processing industry as well as the potential medical, agricultural, and industrial uses of partially deacetylated chitin (chitosan) and its products (chito-oligosaccharides). The depolymerization of chitin can be achieved using chemical and physical treatments, but an enzymatic process would be more environmentally friendly and more sustainable. However, chitinases are slow-acting enzymes, limiting their biotechnological exploitation, although this can be overcome by molecular evolution approaches to enhance the features required for specific applications. The two main goals of this study were the development of a high-throughput screening system for chitinase activity (which could be extrapolated to other hydrolytic enzymes), and the deployment of this new method to select improved chitinase variants. We therefore cloned and expressed the Bacillus licheniformis DSM8785 chitinase A (chiA) gene in Escherichia coli BL21 (DE3) cells and generated a mutant library by error-prone PCR. We then developed a screening method based on fluorescence-activated cell sorting (FACS) using the model substrate 4-methylumbelliferyl β-d-N,N′,N″-triacetyl chitotrioside to identify improved enzymes. We prevented cross-talk between emulsion compartments caused by the hydrophobicity of 4-methylumbelliferone, the fluorescent product of the enzymatic reaction, by incorporating cyclodextrins into the aqueous phases. We also addressed the toxicity of long-term chiA expression in E. coli by limiting the reaction time. We identified 12 mutants containing 2–8 mutations per gene resulting in up to twofold higher activity than wild-type ChiA.     

Stable Aqueous Anode-Free Zinc Batteries Enabled by Interfacial Engineering

Anode-free zinc batteries (AFZBs) are proposed as promising energy storage systems due to their high energy density, inherent safety, low cost, and simplified fabrication process. However, rapid capacity fading caused by the side reactions between the in situ formed zinc metal anode and electrolyte hinders their practical applications. To address these issues, aqueous AFZBs enabled by electrolyte engineering to form a stable interphase are designed. By introducing a multifunctional zinc fluoride (ZnF₂) additive into the electrolyte, a stable F-rich interfacial layer is formed. This interfacial layer can not only regulate the growth orientation of zinc crystals, but also serve as an inert protection layer against side reactions such as H₂ generation. Based on these synergy effects, zinc deposition/dissolution with high reversibility (Coulombic efficiency > 99.87%) and stable cycling performance up to 600 h of are achieved in the electrolyte optimized by ZnF₂. With this electrolyte, the cycling life of AFZBs is significantly improved. The work may initiate the research of AFZBs and be useful for the design of high energy, high safety, and low-cost power sources.     

Surface Reconstruction Engineering with Synergistic Effect of Mixed-Salt Passivation Treatment toward Efficient and Stable Perovskite Solar Cells

Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI₂. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.     

通信工程网络安全与对策探讨

分析研究目前通信工程网络安全问题,提出几点解决问题的对策,旨在为提升通信工程网络安全性提供一定的帮助,以此来促使通信工程网络系统安全性的提升。     

Stimuli-Responsive Nanocomposite Hydrogels for Biomedical Applications

The complex tissue-specific physiology that is orchestrated from the nano- to the macroscale, in conjugation with the dynamic biophysical/biochemical stimuli underlying biological processes, has inspired the design of sophisticated hydrogels and nanoparticle systems exhibiting stimuli-responsive features. Recently, hydrogels and nanoparticles have been combined in advanced nanocomposite hybrid platforms expanding their range of biomedical applications. The ease and flexibility of attaining modular nanocomposite hydrogel constructs by selecting different classes of nanomaterials/hydrogels, or tuning nanoparticle-hydrogel physicochemical interactions widely expands the range of attainable properties to levels beyond those of traditional platforms. This review showcases the intrinsic ability of hybrid constructs to react to external or internal/physiological stimuli in the scope of developing sophisticated and intelligent systems with application-oriented features. Moreover, nanoparticle-hydrogel platforms are overviewed in the context of encoding stimuli-responsive cascades that recapitulate signaling interplays present in native biosystems. Collectively, recent breakthroughs in the design of stimuli-responsive nanocomposite hydrogels improve their potential for operating as advanced systems in different biomedical applications that benefit from tailored single or multi-responsiveness.     

Effects of hydrogen plasma treatment on the physical and chemical properties of tin oxide thin films for ambipolar thin-film transistor applications

In this study, we investigated the physical and chemical properties of H₂ plasma-treated tin oxide (SnO_X) thin films, followed by their applications in ambipolar thin-film transistors (TFTs). Finely controlled H₂ implantation was carried out using a reactive-ion-etching system at a radio frequency power of 30 W and under various exposure times. H₂ plasma treatments induced changes in the chemical structures and surface morphologies of the SnO_X thin films, including a partial phase transformation of Sn and SnO to SnO₂. The defects originating from oxygen vacancies (O_Vacs) in the SnO_X thin films were passivated by H via the formation of Sn–H bonds, which decreased the density of subgap states in the SnO_X thin films. The H₂ plasma-treated SnO_X TFTs showed considerably improved ambipolarity and electrical performance. Complementary metal–oxide–semiconductor (CMOS) logic inverters comprising H₂-plasma-treated ambipolar SnO_X TFTs exhibited a maximum gain of 34.5 V/V at a supply voltage of 10 V. The results of this study present the meaningful investigation of H₂ plasma-treated ambipolar SnO_X TFTs that can be used to fabricate CMOS circuits for various applications.     

Ultracompact methane steam reforming reactor based on microwaves susceptible structured catalysts for distributed hydrogen production

Hydrogen is a potential green energy vector. Since the heating of the reforming processes commonly used for its production is obtained by burning hydrocarbons, it has a substantial CO₂ footprint. One of the most critical aspects in the methane steam reforming (MSR) reaction is the heat transfer to the catalytic volume, due to the high heat fluxes required to obtain high methane conversions. Consequently, the reactor has complex geometries, along with the heating medium being characterized by temperatures higher than 1000 °C; expensive construction materials and high reaction volumes are therefore needed, resulting in slow thermal transients. These aspects increase the costs (both operative and fixed) as well as cause a decrease in the whole process efficiency. The heat transfer limitations due to the endothermicity of methane steam reforming reaction could be effectively overcome by microwave (MW) heating. This heating technique, that depends only on the dielectric properties of the materials, can result in an efficient and faster method for transferring heat directly to the catalyst, thus generating the heat directly inside the catalytic volume. In this work, Ni-based catalysts, differing from each other by the Ni loading (7 and 15 wt% with respect to the washcoat) were prepared. The catalysts were characterized by means of several techniques and tested in the MW-assisted methane steam reforming reaction. Furthermore, the energy balance of the entire process was performed to calculate the energy efficiency, making a preliminary evaluation of its feasibility in distributed hydrogen production also possible. The results of the preliminary tests showed that the prepared structured catalysts are very susceptible to the MW radiation, and that in the presence of the MSR reaction, it is possible to make the system reach a temperature of 900 °C. In the same tests, the CH₄ conversion showed a good approach to the thermodynamic equilibrium values starting at temperatures of about 800 °C at a value of gas hourly space velocity (GHSV) of about 5000 h^?1. The energy efficiency of the lab-scale system, calculated as the ratio among the energy absorbed by the system and the energy supplied by the microwaves, was about 50%. Future studies will deal with the microwave reactor optimization, aiming at the increase of the energy efficiency of the system, as well as to obtain a higher CH₄ conversion at lower temperatures and increase the H₂ yield and selectivity.     

Evaluation of hydrogen metabolism by Escherichia coli strains possessing only a single hydrogenase in the genome

The four hydrogenase isozymes; hydrogenase 1 (Hyd-1), hydrogenase 2 (Hyd-2), hydrogenase 3 (Hyd-3) and hydrogenase 4 (Hyd-4) of Escherichia coli have been reported for their crucial functions in the hydrogen metabolism; however, their distinctive roles could not be completely understood. In this study, four ideal hydrogenase operon mutants, Δhyb hyc hyf, Δhya hyc hyf, Δhya hyb hyf, and Δhya hyb hyc, in which only a single hydrogenase is intact in the genome, were constructed as well as one quadruple mutant (Δhya hyb hyc hyf) that all four hydrogenase operons were deleted. First, single operon mutants and single-gene mutants for each hydrogenase showed different hydrogen productivity and growth in the anaerobic fermentation, indicating that bacterial phenotype regarding the hydrogen metabolism via the deletion of each operon is different with that of each single gene. Then, 4 triple hydrogenase operon mutants and one quadruple mutant were investigated to evaluate the hydrogen metabolism (hydrogen production and uptake) using glucose or glycerol as a substrate of hydrogen fermentation. With both the carbon sources, only Hyd-2 and Hyd-3 were able to produce hydrogen. Furthermore, all the hydrogenases showed hydrogen uptake activity. In addition, no hydrogen production and hydrogen uptake were detected in the quadruple mutant which does not have all 4 hydrogenases. Hydrogen production from Hyd-2 and Hyd-3 was further confirmed by complementing their operons in the cloning vector pBR322.     

Improvement of the quality stability of vacuum-packaged fermented fish (Suanyu) stored at room temperature by irradiation and thermal treatments

To evaluate the effects of irradiation and thermal treatments on the quality characteristics of the vacuum-packaged low-salted fermented fish (Suanyu) during 90-day storage, thermal-treated group (TTG), irradiated-treated group (ITG) and non-treated group (CG) were prepared. The results showed that total viable counts reduced by 4.49 and 4.67 log CFU/g after thermal and irradiation treatments, respectively, and no coliforms and pseudomonas growth occurred during storage. Compared with CG, lower levels in L*, springiness, chewiness of TTG and higher levels in L*, b* and chewiness of ITG were detected after 90-day storage. Total biogenic amines content was significantly reduced in ITG compared with CG and TTG (P < 0.05). Both irradiation and thermal treatments have the potential to maintain quality of Suanyu during room storage. Compared with irradiation, thermal treatment could better stabilise the free amino acids and volatile compounds of Suanyu during room storage, but had some negative effects on texture quality.     

Human–Cyber–Physical Systems (HCPSs) in the Context of New-Generation Intelligent Manufacturing

An intelligent manufacturing system is a composite intelligent system comprising humans, cyber systems, and physical systems with the aim of achieving specific manufacturing goals at an optimized level. This kind of intelligent system is called a human–cyber–physical system (HCPS). In terms of technology, HCPSs can both reveal technological principles and form the technological architecture for intelligent manufacturing. It can be concluded that the essence of intelligent manufacturing is to design, construct, and apply HCPSs in various cases and at different levels. With advances in information technology, intelligent manufacturing has passed through the stages of digital manufacturing and digital-networked manufacturing, and is evolving toward new-generation intelligent manufacturing (NGIM). NGIM is characterized by the in-depth integration of new-generation artificial intelligence (AI) technology (i.e., enabling technology) with advanced manufacturing technology (i.e., root technology); it is the core driving force of the new industrial revolution. In this study, the evolutionary footprint of intelligent manufacturing is reviewed from the perspective of HCPSs, and the implications, characteristics, technical frame, and key technologies of HCPSs for NGIM are then discussed in depth. Finally, an outlook of the major challenges of HCPSs for NGIM is proposed.