Search Results (73)

This paper presents a theoretical model of a thin, penny-shaped piezoelectric actuator bonded to an isotropic thermo-elastic substrate under coupled electrical-thermal-diffusive loading. The problem is assumed to be axisymmetric, and the peeling stress of the film is neglected in accordance with membrane theory, yielding a simplified equilibrium equation for the piezoelectric film. By employing potential theory and the Hankel transform technique, the surface strain of the substrate is analytically derived. Under the assumption of perfect bonding, a governing integral equation is established in terms of interfacial shear stress. The solution to this integral equation is obtained numerically using orthotropic Chebyshev polynomials. The derived results include the interfacial shear stress, stress intensity factors, as well as the radial and hoop stresses within the system. Finite element analysis is conducted to validate the theoretical predictions. Furthermore, parametric studies elucidate the influence of material mismatch and actuator geometry on the mechanical response. The findings demonstrate that, the performance of the piezoelectric actuator can be optimized through judicious control of the applied electrical-thermal-diffusive loads and careful selection of material and geometric parameters. This work provides valuable insights for the design and optimization of piezoelectric actuator structures in practical engineering applications. Full article

In this study, a new, patented form of a water-soluble cannabidiol (CBD) complex was synthesised and tested. The formation of the complex is based on the interactions, presumably through hydrogen bonding, between cannabidiol and glucosamine, the latter contributing significantly to the increased hydrophilicity. The complex was characterised by chromatography, thermal analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and permeability tests. This complex has a substantially higher water solubility than normal CBD. Permeability tests indicate that it has almost five times lower permeability through lipophilic membranes and less than half the membrane mass retention of conventional CBD. At the same time, its equilibrium concentration is almost four times higher than that of normal CBD. These results suggest that this new form of CBD is a promising candidate for future biological and clinical studies, as it offers improved bioavailability and biodistribution. Full article

Citral, an organic compound found in lemongrass (Cymbopogon citratus) oil and Litsea cubeba essential oil, has been reported to exhibit notable antifungal activity against Magnaporthe oryzae (M. oryzae), the pathogen of rice blast, which causes significant economic losses in rice production. However, the role of citral in inducing oxidative stress related to antifungal ability and its underlying regulatory networks in M. oryzae remain unclear. In this study, we investigated the oxidative effects of citral on M. oryzae and conducted transcriptomic and widely targeted metabolomic (WTM) analyses on the mycelia. The results showed that citral induced superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) activities but reduced glutathione S-transferase (GST) activity with 25% maximal effective concentration (EC₂₅) and 75% maximal effective concentration (EC₇₅). Importantly, citral at EC₇₅ reduced the activities of mitochondrial respiratory chain complex I, complex III and ATP content, while increasing the activity of mitochondrial respiratory chain complex II. In addition, citral triggered a burst of reactive oxygen species (ROS) and a loss of mitochondrial membrane potential (MMP) through the observation of fluorescence. Furthermore, RNA-seq analysis and metabolomics analysis identified a total of 466 differentially expression genes (DEGs) and 32 differential metabolites (DAMs) after the mycelia were treated with citral. The following multi-omics analysis revealed that the metabolic pathways centered on AsA, GSH and melatonin were obviously suppressed by citral, indicating a disrupted redox equilibrium in the cell. These findings provide further evidences supporting the antifungal activity of citral and offer new insights into the response of M. oryzae under oxidative stress induced by citral. Full article

This article investigates the boundary value problem for an extended stationary system of Nernst–Planck–Poisson equations, corresponding to a mathematical model of the influence of changes in the equilibrium coefficient on the transport of ions of a binary salt in the diffusion layer. Dimensionless variables were introduced using characteristic parameter values. As a result, a dimensionless boundary value problem was obtained, which is singularly perturbed, containing a small parameter in the derivative of the Poisson equation and, additionally, another regular small parameter. A similarity theory was developed: trivial and non-trivial similarity criteria and their physical meaning were determined, which allowed for the identification of general properties of the solutions. A numerical investigation of the boundary value problem was conducted using the finite element method. With an increase in the initial solution concentration, the value of the small parameter entering singularly decreases, reaching values on the order of 10⁻¹² and below, leading to computational difficulties that prevent a comprehensive analysis of the influence of changes in the equilibrium coefficient on salt ion transport. In this regard, an analytical solution to the problem was constructed, based on dividing the solution domain into several subdomains (regions of electroneutrality, extended space charge region, quasi-equilibrium region, recombination region, intermediate layer), in each of which the problem is solved differently, followed by matching these solutions. Verification of the analytical solution was carried out by comparing it with the numerical solution. The advantage of the obtained analytical solution is the possibility of a comprehensive analysis of the influence of the dissociation/recombination reaction of water molecules on salt ion transport over a wide range of real changes in the concentration and composition of the electrolyte solution and other input parameters. This boundary value problem serves as a benchmark for constructing asymptotic solutions for other singularly perturbed boundary value problems in membrane electrochemistry. Full article

Background: Alterations in the adrenergic system have been associated with the pathophysiology of Alzheimer’s disease (AD). A novel α_1A-adrenergic receptor (AR)-positive allosteric modulator (PAM), CCF219B, has been shown to outperform donepezil with rescue of AD cognition/memory deficits with a reduction in amyloid biomarkers and without cardiovascular side effects. Initial pharmacological analysis in transfected cell lines revealed a signal bias with increased efficacy (but not potency) of cAMP signaling and ligand selectivity for norepinephrine (NE). As most GPCR allosteric modulators change the potency of agonists, we hypothesized and now report that CCF219B induced additional aspects of its allosteric interactions with NE that may provide mechanistic insight. Methods: Using Rat-1 fibroblasts stably transfected with α_1A-AR, we determined the activation profile of pERK and p38 messengers by CCF219B in the presence of NE. Using membranes prepared from the stably transfected fibroblasts or from the brain of WT mice or the AD mouse model, hAPP(lon), equilibrium or kinetic radioligand-binding analyses were performed. Results: We identified p-ERK1/2 but not p38 as an additional signal pathway that is potentiated by CCF219B in the presence of NE. An analysis of binding studies of CCF219B in membranes derived from the brains of WT or hAPP(lon) mice revealed profiles that were time-dependent and resulted in an increase in α_1A-AR expression that was unaltered in the presence of cycloheximide or when performed at 37 °C. hAPP(lon) mice displayed a reduction in α_1A-AR-binding sites that were rescued upon prolonged incubation with CCF219B but also displayed a compensatory increase in α_1B/D-AR subtype expression. Binding kinetics reveal that CCF219B can decrease the association rate of ³H-NE but only in the presence of GTP. The association rate increased for the radiolabeled antagonist, ¹²⁵I-HEAT. There were no changes in the dissociation rate of either radiolabel. Conclusions: CCF219B affects the association but not the dissociation rate of NE and explains its ability to increase the active state of the receptor by promoting a pre-coupled conformation, consistent with increasing efficacy but not potency. Potentiation of pERK may contribute to CCF219B’s ability to confer neuroprotection and be pro-cognitive in AD. CCF219B’s ability to increase the expression of α_1A-AR provides a positive feedback loop and strengthens the hypothesis that α₁-AR subtypes may be involved in AD etiology and/or progression. Full article

Valsa mali (V. mali) is a necrotrophic fungus responsible for apple Valsa canker, which significantly diminishes apple production yields and quality in China. Our serendipitous findings revealed that genistein significantly inhibits the mycelial growth of V. mali, with an inhibition rate reaching 42.36 ± 3.22% at a concentration of 10 µg/mL. Scanning electron microscopy analysis revealed that genistein caused significant changes in the structure of V. mali, including mycelial contraction, distortion, deformity, collapse, and irregular protrusions. Transmission electron microscopy analysis revealed leakage of cellular contents, blurred cell walls, ruptured membranes, and organelle abnormalities. Genistein has been shown to increase reactive oxygen species levels in V. mali mycelia, as demonstrated by 2′,7′-dichlorofluorescin diacetate staining. This increase was associated with a decrease in superoxide dismutase activity alongside increases in catalase and peroxidase activities. These changes collectively disrupted the oxidative equilibrium, leading to the induction of oxidative stress. The transcriptomic analysis revealed 13 genes enriched in this process, linked to unsaturated fatty acid biosynthesis (three downregulated DEGs), saturated fatty acid biosynthesis (three upregulated and six downregulated DEGs), and fatty acid metabolism (four upregulated and nine downregulated DEGs). Additionally, the downregulated DEGs VMIG_07417 and VMIG_08675, which are linked to ergosterol biosynthesis, indicate possible changes in membrane composition. In conjunction with the qRT-PCR results, it is hypothesized that genistein exerts an antifungal effect on V. mali through ROS-mediated lipid peroxidation. This finding has the potential to contribute to the development of novel biological control agents for industrial crops. Full article

Background: To improve the solubility and permeability of Sparfloxacin (SPX) and enhance its antimicrobial activity in vitro, two unreported pharmaceutical crystalline salts were synthesized and characterized in this paper. One is a hydrated crystal of Sparfloxacin with Pimelic acid (PIA), another is a hydrated crystal of Sparfloxacin with Azelaic acid (AZA), namely, SPX-PIA-H₂O (2C₁₉H₂₃F₂N₄O₃·C₇H₁₀O₄·2H₂O) and SPX-AZA-H₂O (4C₁₉H₂₃F₂N₄O₃·2C₉H₁₄O₄·5H₂O). Methods: The structure and purity of two crystalline salts were analyzed using solid-state characterization methods such as single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and infrared spectroscopy. Additionally, the interaction characteristics between two crystal salt molecules were examined by constructing Hirshfeld surfaces and mapping specific real-space functions through Hirshfeld surface analysis. The solubility under physiological conditions, diffusivity across simulated biological membranes, and in vitro antibacterial activity against specific bacterial strains of two crystalline salts were evaluated using established assays, including minimum inhibitory concentration (MIC) tests. Results: Single-crystal X-ray diffraction and Hirshfeld surface analysis indicate that SPX forms stable crystal structures with PIA through charge-assisted hydrogen bonds N1-H1e···O10 (1.721 Å, 173.24°), N5-H5a···O11 (1.861 Å, 169.38°), and with AZA through charge-assisted hydrogen bonds N5-H5B···O8 (1.810 Å, 154.55°), N4-H4B···O6 (1.806 Å, 174.97°). The binding sites of two crystalline salts were at the nitrogen atoms on the piperazine ring of SPX. Compared with SPX, the equilibrium solubility of the two crystalline salts was improved by 1.17 and 0.33 times, respectively, and the permeability of the two crystalline salts was increased by 26.6% and 121.9%, respectively. In addition, SPX-AZA-H₂O has much higher antibacterial activity on Pseudomonas aeruginosa and Bacillus subtilis than SPX. Conclusions: This research yielded the successful synthesis of two crystalline salts of Sparfloxacin (SPX), significantly improving its solubility and diffusivity, and bolstering its antibacterial efficacy against targeted bacterial species. These breakthroughs set the stage for innovative advancements in the realm of antimicrobial drug development. Full article

The manuscript presents research focusing on the adsorption and emulsion properties of starch hydrolysates modified through acetylation, oxidation, and cross-linking. The techniques used in this study included measurements of equilibrium surface tension (du Noüy ring) dynamic surface tension (drop shape analysis), and the preparation and evaluation of emulsion stability (TURBISCAN). The surface activity of the acetylated starch hydrolysates is affected by the degree of acetylation. The acetylated starch 0.02Ac-H exhibited higher surface activity than the more highly substituted derivative 0.1Ac-H. Furthermore, it was shown that the surface activity of the components increased as the acetylated oxidized starch underwent hydrolysis. The fractions collected after 180 min using a membrane with a low separation capability (8 kDa) revealed the highest capacity for reducing surface tension. In binary systems consisting of starch derivatives and surfactants, synergistic effects in reducing surface tension were particularly noticeable in systems containing ionic surfactants. The addition of a cationic surfactant to the modified starch hydrolysate solution (1:6 mol/mol) resulted in a significantly more efficient saturation of the air/water interface. This study demonstrated that emulsions stabilized with modified starch hydrolysates remained stable over time, even when these hydrolysates constituted up to 60% of the emulsifier mixture. Full article

To solve the problem of heavy metal hexavalent chromium (Cr(VI)) pollution in water bodies, this study was carried out to prepare nitrogen-doped porous carbon by using bamboo shoots as the raw material and KHCO₃ as the activator, which has a good ability to remove Cr(VI) from water bodies. The prepared N-doped carbon materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscopy (SEM). The results showed that the prepared carbon material had hierarchical pore structures and abundant functional groups, which is conducive to the adsorption of Cr(VI). The effects of various factors on the adsorption performance of Cr(VI), such as the carbon materials prepared under different conditions, the pH of the initial solution, the concentration of the initial solution, and the contact time between the carbon and Cr(VI), were explored. The results showed that the bamboo shoot-based nitrogen-doped carbon materials, especially BSNC-800 (prepared at 800 °C with a mass ratio of KHCO₃ to bamboo shoot of 4:1), performed well in removing Cr(VI) from a water solution. The maximum adsorption of Cr(VI) by BSNC-800 under equilibrium conditions was 385.8 mg g⁻¹ (conditions: at the pH of 2 with the initial concentration of 400 mg L⁻¹). The adsorption kinetics and isotherms were analyzed, and the adsorption mechanism was discussed. It can be found that the adsorption of Cr(VI) by BSNC-800 fits better with the Langmuir isotherm model and the pseudo-second-order kinetic model. The adsorption mechanism between the Cr(VI)-containing solution and BSNC-800 was controlled by membrane diffusion and chemisorption. The results broaden the ways of utilizing biomass resources as precursors of carbon materials, which is significant and helpful for applying biomass carbon materials as adsorbents for wastewater treatment. Full article

This study investigated the use of chicken egg white (CEW) waste immobilized on weak acidic nanofiber membranes for removing the anionic acid orange 7 (AO7) dye in batch and continuous flow modes. Different experiments were conducted to evaluate the effectiveness of CEW-modified nanofiber membranes for AO7 removal, focusing on CEW immobilization conditions, adsorption kinetics, and thermodynamics. The CEW-modified nanofiber membrane (namely NM-COOH-CEW) exhibited a maximum AO7 adsorption capacity of 589.11 mg/g within approximately 30 min. The Freundlich isotherm model best represented the equilibrium adsorption data, while the adsorption kinetics followed a pseudo-second-order rate model. Breakthrough curve analysis using the Thomas model and the bed depth service time (BDST) model showed that the BDST model accurately described the curve, with an error percentage under 5%. To investigate AO7 elution efficiency, different concentrations of organic solvents or salts were tested as eluents. The NM-COOH-CEW nanofiber membrane exhibited promising performance as an effective adsorbent for removing AO7 dye from contaminated water. Full article

Dialysis membranes are not hemocompatible with human blood, as the patients are suffering from the blood–membrane interactions’ side effects. Zwitterionic structures have shown improved hemocompatibility; however, their complicated synthesis hinders their commercialization. The goal of the study is to achieve fast functionalization for carboxybetaine and sulfobetaine zwitterionic immobilization on PES membranes while comparing the stability and the targeted hemocompatibility. The chemical modification approach is based on an aminolysis reaction. Characterization, computational simulations, and clinical analysis were conducted to study the modified membranes. Atomic force microscopy (AFM) patterns showed a lower mean roughness for carboxybetaine-modified (6.3 nm) and sulfobetaine-modified (7.7 nm) membranes compared to the neat membrane (52.61 nm). The pore size of the membranes was reduced from values above 50 nm for the neat PES to values between 2 and 50 nm for zwitterionized membranes, using Brunauer–Emmett–Teller (BET) analysis. More hydrophilic surfaces led to a growth equilibrium water content (EWC) of nearly 6% for carboxybetaine and 10% for sulfobetaine-modified membranes. Differential scanning calorimetry (DSC) measurements were 12% and 16% stable water for carboxybetaine- and sulfobetaine-modified membranes, respectively. Sulfobetaine membranes showed better compatibility with blood with respect to C5a, IL-1a, and IL-6 biomarkers. Aminolysis-based zwitterionization was found to be suitable for the improvement of hemodialysis membranes. The approach introduced in this paper could be used to modify the current dialysis membranes with minimal change in the production facilities. Full article

High-strength steel (HSS) members with welded sections exhibit a notably lower residual compressive stress ratio compared with common mild steel (CMS) members. Despite this difference, current codes often generalize the findings from CMS members to HSS members, and the previous unified residual stress models are generally conservative. This study focuses on the membrane residual stress distribution in Q690 steel welded box sections. By leveraging experimental results, the influence of section sizes and welding parameters on membrane residual stress was delved into. A larger plate size correlates with a decrease in the residual compressive stress across the section, with a more pronounced reduction observed in adjacent plates. Additionally, augmenting the number of welding passes tends to diminish residual stresses across the section. Results showed that membrane residual stress adhered to the section’s self-equilibrium, while the self-equilibrium in the plates was not a uniform pattern. A reliable residual stress simulation method for Q690 steel welded box sections was established using a three-dimensional thermal–elastic–plastic finite element model (3DTEFEM) grounded in experimental data. This method served as the cornerstone for parameter analysis in this study and set the stage for subsequent research. As a result, an accurate unified residual stress model for Q690 steel welded box sections was derived. Full article

Electrochemical impedance and chronopotentiometric measurements with Na⁺-selective solvent polymeric (PVC) membranes containing a neutral ionophore and a cation exchanger revealed low-frequency resistance, which is ascribed to Na⁺ ion transfer across the interface between the membrane and aqueous solution. The attribution is based on the observed regular dependence of this resistance on the concentration of Na⁺ in solutions. The respective values of the exchange current densities were found to be significantly larger than the currents flowing through ion-selective electrodes (ISEs) during an analysis in non-zero-current mode. This fact suggests that the interfacial electrochemical equilibrium is not violated by the current flow and implies that the Nernst equation can be applied to interpret the data obtained in non-zero-current mode, e.g., constant potential coulometry. Full article

Capitellacin is the β-hairpin membrane-active cationic antimicrobial peptide from the marine polychaeta Capitella teleta. Capitellacin exhibits antibacterial activity, including against drug-resistant strains. To gain insight into the mechanism of capitellacin action, we investigated the structure of the peptide in the membrane-mimicking environment of dodecylphosphocholine (DPC) micelles using high-resolution NMR spectroscopy. In DPC solution, two structural forms of capitellacin were observed: a monomeric β-hairpin was in equilibrium with a dimer formed by the antiparallel association of the N-terminal β-strands and stabilized by intermonomer hydrogen bonds and Van der Waals interactions. The thermodynamics of the enthalpy-driven dimerization process was studied by varying the temperature and molar ratios of the peptide to detergent. Cooling the peptide/detergent system promoted capitellacin dimerization. Paramagnetic relaxation enhancement induced by lipid-soluble 12-doxylstearate showed that monomeric and dimeric capitellacin interacted with the surface of the micelle and did not penetrate into the micelle interior, which is consistent with the “carpet” mode of membrane activity. An analysis of the known structures of β-hairpin AMP dimers showed that their dimerization in a membrane-like environment occurs through the association of polar or weakly hydrophobic surfaces. A comparative analysis of the physicochemical properties of β-hairpin AMPs revealed that dimer stability and hemolytic activity are positively correlated with surface hydrophobicity. An additional positive correlation was observed between hemolytic activity and AMP charge. The data obtained allowed for the provision of a more accurate description of the mechanism of the oligomerization of β-structural peptides in biological membranes. Full article

In this study, we investigated toroidal shell wrinkling in free hydroforming. We specifically focused on toroidal shells with a regular hexagonal cross-section. Membrane theory was used to examine the distribution of stress and yield load in both preform and toroidal shells. The wrinkling moment was then predicted using an empirical formula of shell buckling. In addition, the wrinkling state was investigated using a general statics method, and the free hydroforming of toroidal shells was simulated using the Riks method. Subsequently, nonlinear buckling and equilibrium paths were analyzed. A toroidal preform was manufactured, and free hydroforming experiments were conducted. Overall, the experimental results confirmed the accuracy of the theoretical predictions and numerical simulations. This indicates that the prediction method used in the study was effective. We also found that wrinkling occurs during hydroforming in the inner region of toroidal shells due to compressive stress. Consequently, we improved the structure of the toroidal shells and performed analytical calculations and numerical simulations for the analysis. Our results indicate that wrinkling can be eliminated by increasing the number of segments on the inner side of toroidal preforms, thereby improving the quality of toroidal shells. Full article