•The iron ore sintering is modeled and simulated based on heat and mass transfer.•The cool rate and melt fraction could be used as an indicator to predict sinter strength and yield.•Increasing coke ...content could improve sinter strength while decrease sinter yield.•The sinter strength and sinter yield could be increased simultaneously by the method of additional heat supplement.
Sinter yield and strength were predicted by the method of numerical simulation in this study. An unsteady two-dimensional mathematical model for the iron ore sintering process was developed by taking most of the significant physical phenomena and chemical reactions into consideration. By employing FLUENT software and C language programming via custom code, numerical simulation was carried out. A sinter pot test was performed and experimental data reasonably agreed with the numerical results, which validated the model. By analyzing temperature profile and melt fraction, parameters including peak temperature, residence time, cooling rate, melt formation heat and melt fraction were analyzed. Relationship between cooling rate and sinter strength was discussed as well as relationship between melt fraction and the yield of product sinter. Results indicated that sinter strength and yield could be predicted by simulation. The effects of different coke contents and additional heat supplement on sinter strength and yield were discussed. Results showed that increasing coke content improves sinter strength. Lower coke content will lead to increasing of under-melted sinter while higher coke content will lead to increasing of over-melted sinter and decreasing of the yield. Additional heat supplement technology can not only enhance sinter strength, but also promote sinter yield significantly.
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•Bacterial community in straw-added soils was less resistant to freeze–thaw cycles.•Changes in bacterial composition was related to ecological trait-based responses.•Freeze-thaw ...cycles promoted bacteria mining more soil C under straw addition.
Crop residues are usually returned into the soil after autumn harvest and maintained throughout the winter and early spring in temperate regions. This agricultural practice may exert important effects on soil microbial communities, consequently changing their compositional and functional stability to freeze–thaw disturbances later in the autumn and early spring. In this study, we examined the effect of straw addition on the composition and function of bacterial communities subjected to different intensities of freeze–thaw cycles in a clay loam soil. Bacterial composition in the control soils varied little after different freeze–thaw cycles. Freeze-thaw cycles, however, significantly changed the bacterial community composition in the straw-amended soils towards a less resistant community that was more vulnerable to freeze–thaw stress. A further analysis showed that straw addition significantly decreased bacterial alpha diversity and shifted soil bacterial community composition to one dominated by copiotrophs. Based on function predictions, the bacterial communities in the straw-amended soils presented superior competitive traits but inferior stress-tolerant and ruderal traits as compared to those in the control soils. Our results suggest that straw addition decreased the resistance of soil bacterial community composition to freeze–thaw disturbances through changes in their physiological and functional traits. These findings implicate that freeze–thaw cycles could exert important consequences on the functioning of agroecosystem when straw is returned into the soil.
Synthesis of macromolecular systems with precise structural and functional control constitutes a fundamental challenge for materials science and engineering. Development of the ability to construct ...complex bio-macromolecular architectures provides a solution to this challenge. The past few years have witnessed the emergence of a new category of peptide-protein chemistry which can covalently stitch together proteinpeptide molecules with high specificity under mild physiological conditions. It has thus inspired the concept of genetically encoded click chemistry （GECC）. As a prototype of GECC, SpyTag/ SpyCatcher chemistry has enabled the precise synthesis ofmacromolecules both in vitro and in vivo, exerting precise control over the fundamental properties of these macromolecules including length, sequence, stereochemistry and topology and leading to the creation of diverse biomaterials for a variety of applications. We thus anticipate a potential toolbox of GECC comprising multiple mutually orthogonal, covalent-bond forming peptide-protein reactive pairs with diverse features, which shall bridge synthetic biology and materials science and open up enormous opportunities for biomaterialsin the future.
Abstract
Developing a step-economical approach for efficient synthesis of
α
,
β
-deuterio aryl ethylamines (
α
,
β
-DAEAs) with high deuterium ratios using an easy-to-handle deuterated source under ...ambient conditions is highly desirable. Here we report a room-temperature one-pot two-step transformation of aryl acetonitriles to
α
,
β
-DAEAs with up to 92% isolated yield and 99%
α
,
β
-deuterium ratios using D
2
O as a deuterium source. The process involves a fast
α
-C − H/C − D exchange and tandem electroreductive deuteration of C ≡ N over an in situ formed low-coordinated Fe nanoparticle cathode. The moderate adsorptions of nitriles/imine intermediates and the promoted formation of active hydrogen (H*) on unsaturated Fe sites facilitate the electroreduction process. In situ Raman confirms co-adsorption of aryl rings and the C ≡ N group on the Fe surface. A proposed H*-addition pathway is confirmed by the detected hydrogen and carbon radicals. Wide substrate scope, parallel synthesis of multiple
α
,
β
-DAEAs, and successful preparation of
α
,
β
-deuterated
Melatonin
and
Komavine
highlight the potential.
Selector devices are indispensable components of large-scale nonvolatile memory and neuromorphic array systems. Besides the conventional silicon transistor, two-terminal ovonic threshold switching ...device with much higher scalability is currently the most industrially favored selector technology. However, current ovonic threshold switching devices rely heavily on intricate control of material stoichiometry and generally suffer from toxic and complex dopants. Here, we report on a selector with a large drive current density of 34 MA cm
and a ~10
high nonlinearity, realized in an environment-friendly and earth-abundant sulfide binary semiconductor, GeS. Both experiments and first-principles calculations reveal Ge pyramid-dominated network and high density of near-valence band trap states in amorphous GeS. The high-drive current capacity is associated with the strong Ge-S covalency and the high nonlinearity could arise from the synergy of the mid-gap traps assisted electronic transition and local Ge-Ge chain growth as well as locally enhanced bond alignment under high electric field.
Abstract
Electrochemical conversion of abundant carbon- and nitrogen-containing small molecules into high-valued organonitrogen compounds is alluring to reducing current dependence on fossil energy. ...Here we report a single-cell electrochemical oxidation approach to transform methanol and ammonia into formamide under ambient conditions over Pt electrocatalyst that provides 74.26% selectivity from methanol to formamide and a Faradaic efficiency of 40.39% at 100 mA cm
−2
current density, gaining an economic advantage over conventional manufacturing based on techno-economic analysis. A 46-h continuous test performed in the flow cell shows no performance decay. The combined results of in situ experiments and theoretical simulations unveil the C–N bond formation mechanism via nucleophilic attack of NH
3
on an aldehyde-like intermediate derived from methanol electrooxidation. This work offers a way to synthesize formamide via C–N coupling and can be extended to substantially synthesize other value-added organonitrogen chemicals (e.g., acetamide, propenamide, formyl methylamine).
Aging is an irreversible physiological process in the human body, and the aging characteristics of the body that accompany this process also lead to many other chronic diseases, such as ...neurodegenerative diseases represented by Alzheimer's disease and Parkinson's disease, cardiovascular diseases, hypertension, obesity, cancer, and so on. The marine environment is highly biodiverse, the natural active products of these organisms constitute a vast treasure trove of marine drugs or drug candidates that play an essential role in disease prevention and treatment, and the active peptide products among them have received special attention because of their unique chemical properties. Therefore, the development of marine peptide compounds as anti-aging drugs is emerging as an important research area. This review highlights the currently available data on marine bioactive peptides with anti-aging potential from 2000 to 2022 by analyzing the prevalent aging mechanisms, critical aging metabolic pathways and well-established multi-omics aging characteristics, as well as grouping different bioactive and biological species lines of peptides from marine organisms and discussing their research modalities and functional characteristics. Active marine peptides is a promising topic to explore and to develop their potential as anti-aging drugs or drug candidates. We expect this review to be instructive for future marine drug development and to reveal new directions for future biopharmaceuticals.
High temperature at grain filling can severely reduce wheat yield. Heat shock factors (Hsfs) are central regulators in heat acclimation. This study investigated the role of TaHsfC2a, a member of the ...monocot‐specific HsfC2 subclass, in the regulation of heat protection genes in Triticum aestivum. Three TaHsfC2a homoeologous genes were highly expressed in wheat grains during grain filling and showed only transient up‐regulation in the leaves by heat stress but were markedly up‐regulated by drought and abscisic acid (ABA) treatment. Overexpression of TaHsfC2a‐B in transgenic wheat resulted in up‐regulation of a suite of heat protection genes (e.g. TaHSP70d and TaGalSyn). Most TaHsfC2a‐B target genes were heat, drought and ABA inducible. Transactivation analysis of two representative targets (TaHSP70d and TaGalSyn) showed that TaHsfC2a‐B activated expression of reporters driven by these target promoters. Promoter mutagenesis analyses revealed that heat shock element is responsible for transactivation by TaHsfC2a‐B and heat/drought induction. TaHsfC2a‐B‐overexpressing wheat showed improved thermotolerance but not dehydration tolerance. Most TaHsfC2a‐B target genes were co‐up‐regulated in developing grains with TaHsfC2a genes. These data suggest that TaHsfC2a‐B is a transcriptional activator of heat protection genes and serves as a proactive mechanism for heat protection in developing wheat grains via the ABA‐mediated regulatory pathway.
The active distribution networks have a tendency to develop towards hybrid AC-DC systems constructed by power electronics, the magnitude and direction of power may change randomly at any time, making ...the usual protection potentially insensitive, raising the negative impacts of single-phase ground (SPG) fault which accounts for the majority of all faults that occurred in medium-voltage (MV) distribution networks in the past. The zero-sequence current in the impedance induced between the lines and ground will pass through the SPG fault branch as fault current. This study transfers the flow path of the zero-sequence current from the SPG fault branch to the power electronic branch connected between the faulty phase and ground involved in the construction of hybrid AC-DC system, thereby limiting SPG fault branch current and reducing fault node potential. This helps to suppress fault arc and provides engineers with safe conditions to clear faulty elements from the SPG fault branch. The power electronic carries this zero-sequence current instead of SPG fault branch and therefore absorb energy from the distribution networks in the same way as SPG fault, but the energy is not lost but routed back to the hybrid AC-DC system for reuse. Simulations and experiments validate the proposal.
Summary
The catalase family of Beauveria bassiana (fungal entomopathogen) consists of catA (spore‐specific), catB (secreted), catP (peroxisomal), catC (cytoplasmic) and catD (secreted ...peroxidase/catalase), which were distinguished in phylogeny and structure and functionally characterized by constructing single‐gene disrupted and rescued mutants for enzymatic and multi‐phenotypic analyses. Total catalase activity decreased 89% and 56% in ΔcatB and ΔcatP, corresponding to the losses of upper and lower active bands gel‐profiled for all catalases respectively, but only 9−12% in other knockout mutants. Compared with wild type and complement mutants sharing similar enzymatic and phenotypic parameters, all knockout mutants showed significant (9−56%) decreases in the antioxidant capability of their conidia (active ingredients of mycoinsecticides), followed by remarkable phenotypic defects associated with the fungal biocontrol potential. These defects included mainly the losses of 40% thermotolerance (45°C) in ΔcatA, 46−48% UV‐B resistance in ΔcatA and ΔcatD, and 33−47% virulence to Spodoptera litura larvae in ΔcatA, ΔcatP and ΔcatD respectively. Moreover, the drastic transcript upregulation of some other catalase genes observed in the normal culture of each knockout mutant revealed functionally complimentary effects among some of the catalase genes, particularly between catB and catC whose knockout mutants displayed little or minor phenotypic changes. However, the five catalase genes functioned redundantly in mediating the fungal tolerance to either hyperosmotic or fungicidal stress. The differentiated roles of five catalases in regulating the B. bassiana virulence and tolerances to oxidative stress, high temperature and UV‐B irradiation provide new insights into fungal adaptation to stressful environment and host invasion.
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