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Active control of pressure fluctuations in an incompressible turbulent cavity flow
No full textLarge-eddy simulations of incompressible turbulent boundary layer flows over an open cavity are conducted to investigate the effects of wall-normal steady blowing on the suppression of pressure fluctuations on the cavity walls. The length (L) to depth (D) ratio (L/D) of the cavity is 2 and the Reynolds number based on the cavity depth (ReD) is 12,000. Wall-normal steady blowing is imposed through a limited transverse slot in an upstream region of the cavity leading edge while varying the momentum coefficient (C??). As the value of C?? increases, the pressure fluctuations on the cavity walls decrease mostly due to weakened impingement of turbulent vortical structures residing in the shear layer on the aft wall by lifting effects, reaching a maximum reduction of ???7.61% compared to a baseline when C??=0.015. However, as the value of C?? increases further, the pressure fluctuations increase gradually, exceeding that of a baseline when C??>0.05. Because intensified turbulent vortical structures in the shear layer with an increase of C?? lead to strong interactions of small-scale vortices with the cavity walls with an accompanying large motion of the primary recirculation zone within the cavity, additional pressure fluctuations generated on the cavity walls deteriorate the control performance due to the blowing
Directly transforming graphite into iron single atom catalyst for the acidic oxygen reduction reaction
No full textPlatinum group metal (PGM)-free single atom catalysts (SACs) are highly desired to accelerate the sluggish oxygen reduction reaction (ORR) in acidic media, which has a critical role in renewable energy technologies. Herein, we report the direct transformation of commercial graphite into iron (Fe) single atom anchored graphitic flake via a combination of mechanochemical and thermochemical synthesis. By ball milling graphite with zirconium dioxide balls and capsule in the presence of dry ice, the graphite was mechanochemically functionalized and exfoliated into carboxylated graphitic flake (CGF). Subsequent heat-treatment of CGF with nitrogen containing additives formed nitrogenated graphitic flake (NGF) incorporated with Fe single atoms (Fe1NGF). Importantly, the existing Fe impurity in the pristine graphite was converted into value-added product without adding Fe sources. With an ultralow Fe content (0.4 wt%), the as-prepared Fe1NGF exhibited an acidic ORR performance comparable to Pt/C, including ultrahigh mass activity, surpassing the other reported outstanding Fe-based SACs
Patulin alleviates hepatic lipid accumulation by regulating lipogenesis and mitochondrial respiration
No full textAims: The aim of this study is to evaluate the effects of patulin on hepatic lipid metabolism and mitochondrial oxidative function and elucidate the underlying molecular mechanisms.Main methods: The effects of patulin on hepatic lipid accumulation were evaluated in free fatty acid-treated AML12 or HepG2 cells through oil red O staining, triglyceride assay, real-time polymerase chain reaction, and western blotting. Alteration of mitochondrial oxidative capacity by patulin treatment was determined using Seahorse analysis to measure the oxygen consumption rate. Key findings: The increased amounts of lipid droplets induced by free fatty acids were significantly reduced by patulin treatment. Patulin markedly activated the CaMKII/AMP-activated protein kinase (AMPK)/proliferatoractivated receptor-& gamma; coactivator (PGC)-1 & alpha; signaling pathway in hepatocytes, reduced the expression of sterol regulatory element binding protein 1c (SREBP-1c) and lipogenic genes, and increased the expression of genes related to mitochondrial fatty acid oxidation. In addition, patulin treatment enhanced the mitochondrial consumption rate and increased the expression of mitochondrial oxidative phosphorylation proteins in HepG2 hepatocytes. The effects of patulin on anti-lipid accumulation; SREBP-1c, PGC-1 & alpha;, and carnitine palmitoyltransferase 1 expression; and mitochondrial oxidative capacity were significantly prevented by compound C, an AMPK inhibitor.Significance: Patulin is a potent inducer of the AMPK pathway, and AMPK-mediated mitochondrial activation is required for the efficacy of patulin to inhibit hepatic lipid accumulation. This study is the first to report that patulin is a promising bioactive compound that prevents the development and worsening of fatty liver diseases, including non-alcoholic fatty liver disease, by improving mitochondrial quality and lipid metabolism
Metabolic engineering of Escherichia coli for biological production of 1, 3-Butanediol
No full textThe production of 1,3-butanediol (1,3-BDO) from glucose was investigated using Escherichia coli as the host organism. A pathway was engineered by overexpressing genes phaA (acetyl-CoA acetyltransferase), phaB (acetoacetyl-CoA reductase), bld (CoA-acylating aldehyde dehydrogenase), and yqhD (alcohol dehydrogenase). The expression levels of these genes were optimized to improve 1,3-BDO production and pathways that compete with 1,3-BDO synthesis were disrupted. Culture conditions were also optimized, including the C: N ratio, aeration, induction time, temperature, and supplementation of amino acids, resulting in a strain that could produce 1,3BDO at 257 mM in 36 h, with a yield of 0.51 mol/mol in a fed-batch bioreactor experiment. To the best of our knowledge, this is the highest titer of 1,3-BDO production ever reported using biological methods, and our findings provide a promising strategy for the development of microbial cell factories for the sustainable synthesis of other acetyl-CoA-derived chemicals
Beyond Catalysts: Exploring Systematic Approaches and Alternative Electron Sources in Electrolysis
No full textExperimental and computational investigations of the abnormal slow dissociation behavior of CH4 hydrate in the presence of Poly (N-vinylcaprolactam)
No full textIn this study, the dissociation behavior of CH4 hydrate in the absence and presence of poly(N-vinylcaprolactam) (PVCap) was closely investigated using a combination of experimental techniques, including in-situ Raman spectroscopy and high-pressure micro-differential scanning calorimetry (HP & mu;-DSC), and molecular dynamics (MD) simulations. The experimental results clearly demonstrated that CH4 hydrate dissociated more slowly and in two steps in the presence of PVCap. The MD simulations revealed that this slow and two-step dissociation was mainly due to the adsorption of PVCap onto the hydrate surface, which hindered the mass transfer of CH4 from the hydrate into the solution. The high viscosity and steric hindrance of PVCap also impeded the formation and growth of CH4 bubbles during the hydrate dissociation, contributing to the slower dissociation of CH4 hydrate in the PVCap solution. The broad and asymmetric shape of the last endothermic peak observed via HP & mu;-DSC was caused by the adsorption of PVCap during CH4 hydrate dissociation. The findings of this study provide valuable insights into the precise mechanism of hydrate dissociation in the presence of kinetic hydrate inhibitors
Infinitely many solutions to Kirchhoff double phase problems with variable exponents
No full textIn this work we deal with elliptic equations driven by the variable exponent double phase operator with a Kirchhoff term and a right-hand side that is just locally defined in terms of very mild assumptions. Based on an abstract critical point result of Kajikiya (2005) and recent a priori bounds for generalized double phase problems by the authors (Ho and Winkert, 2022), we prove the existence of a sequence of nontrivial solutions whose L & INFIN;-norms converge to zero. & COPY; 2023 Elsevier Ltd. All rights reserved
Aesthetic and efficient perovskite/Si tandem solar cells using luminescent down-shifting textured anti-reflection films
No full textPerovskite-based tandem cells are emerging as new photovoltaic (PV) cells with a high efficiency that exceeds the efficiency limit of single-junction cells. Building-integrated PVs that require high efficiency are attractive, but aesthetics play key roles in these urban applications. One of the most challenging problems with respect to aesthetic PV cells is the efficiency loss due to color tuning. Here, we demonstrate for the first time lossless full-color tunable PV cells based on the use of textured luminescent down-shifting (LDS) films with LDS dyes with ultraviolet-selective absorption. The LDS anti-reflection (AR) films improve the perovskite/Si tandem cell efficiency by reducing the loss of parasitic UV absorption of the layers above the perovskite film due to LDS effect and the loss due to cell reflection due to the textured surface. Therefore, color tuning with LDS AR films can be used to produce highly aesthetic and efficient PV cells for urban applications
Compact and modular bioprobe: Integrating SpyCatcher/SpyTag recombinant proteins with zwitterionic polymer-coated quantum dots
No full textThe development of quantum dot (QD)-based modular bioprobe that has a compact size and enable a facile conjugation of various biofunctional groups is in high demand. To address this, we surface engineered QDs with zwitterion polymer ligands to have an inherent compact size and derivatized them sequentially with the recombinant proteins SpyCatcher/SpyTag (SC/ST) to use their protein ligation system. SC/ST spontaneously form one complex through the isopeptide bond between them. SC-conjugated QDs (QD???SC) were used as base building blocks. Then, ST???biomolecules were added for modular biofunctionalization. We synthesized compact sized (???15 nm) QD???SC???ST???affibody (antibody-mimicking small protein for tumor detection) conjugates, which showed successful cell-receptor targeting. The target cell-receptor could be easily tuned by changing the type of ST-affibody. We also demonstrated that anti-human-chorionic-gonadotropin mouse IgG1 antibodies can be labeled on the QD surface by mixing QD???SC with the ST???MG1Nb (mouse-IgG1-specific protein). The immunoassay performance of the antibody-labeled QDs was evaluated using a pregnancy test kit, displaying equivalent detection sensitivity to a commercially available kit. This study proposed an innovative strategy for QD biofunctionalization in a modular manner, which can be expanded to a diverse range of colloidal particle derivatization