Search Results (99)

In order to innovatively develop high-activity ACE inhibitory peptides from edible fungi, the conditions for a double-enzymatic hydrolysis preparation of ACE inhibitory peptides from Flammulina velutipes were optimized by response surface methodology. After purification by macroporous resin, gel chromatography, and RP-HPLC, a crude peptide fraction was obtained; its ACE inhibition rate was 85.73 ± 0.95% (IC₅₀ = 0.83 ± 0.09 mg/mL). Based on LC-MS/MS sequencing, the four novel peptides, namely, FAGGP, FDGY, FHPGY, and WADP, were screened by computer analysis and molecular docking technology. The four peptides exhibited a binding energy between −9.4 and −10.3 kcal/mol, and formed hydrogen bonds with Tyr523, Ala354, and Glu384 in the S1 pocket, Tyr520 and His353 in the S2 pocket, and His383 in the HEXXH zinc-coordinating motif of ACE, indicating their good affinity with the ACE active site. The IC₅₀ values of the four ACE inhibitory peptides were 29.17, 91.55, 14.79, and 41.27 μM, respectively, suggesting that these peptides could potentially contribute to the development of new antihypertensive products. Full article

This paper aims to assess the influence of cementitious capsules on the hardened properties of concrete, considering several parameters such as the fine fraction (n) of aggregates, capsule size, and capsule dosage. The presence of capsules has been formerly found to disturb packing, which eventually escalates the voids ratio of the inert skeleton. In order to understand the behavior of capsules in various packing structures, two mix design programs were developed, resulting in twenty-three concrete mixtures. The fine fraction of the aggregates was determined to be from 0.2 to 0.8. Both long and short cementitious capsules were used, with dosages of 1 to 7 vol.%. The results show that the incorporation of capsules reduced the compressive strength of concrete, and this reduction varied depending on the fine fraction, capsule dosage, and capsule size. Nevertheless, the optimum fine fraction was found to be 0.4, corresponding to the highest strength and the lowest voids ratio of the aggregate mixtures. In addition, a good bond between the capsule shell and the concrete matrix was showcased, and the embedded capsules broke during compression. Full article

In order to study the strength characteristics of organic-matter-contaminated red soil and the improvement effects of different modifiers, the red soil in the Yulin area was taken as the research object, and triaxial compression tests were carried out to study the effects of different mass fractions (0%, 2%, 4%, 6%, 8%) of organic matter (sodium humate) on the strength characteristics of red soil. Unconfined compressive strength (UCS) tests and scanning electron microscopy (SEM) tests were carried out to study the improvement effects of different amounts of lignin, fly ash, and xanthan gum on organic-matter-contaminated red soil (organic matter content of 8%). The results of the tests showed that the cohesion and internal friction angle of red soil both tended to decrease with the increase in organic matter content. When the organic matter content increased from 0% to 8%, the cohesion of the red soil decreased from 60.98 kPa to 40.07 kPa, a decrease of 34.29%; and the internal friction angle decreased from 17.42° to 7.28°, a decrease of 58.21%. The stress–strain relationship curves of organic-matter-contaminated red soil all show a hardening type. Under different confining pressures, as the organic matter content increased, the shear strength of the red soil decreased continuously. The unconfined compressive strength of organic-matter-contaminated red soil increased with the increase in lignin content, and increased first and then decreased with the increase in fly ash content and xanthan gum content. Through comparative analysis, it was found that the fly ash with a content of 15% had the best improvement effect. The lignin-amended red soil enhanced the connection of soil particles through reinforcement, reduced pores, and improved soil strength. Fly ash improved the acidification reaction, and the hydrates filled the pores and enhanced the soil strength. Xanthan gum improved the red soil by absorbing water and promoting microbial growth, further enhancing the bonding force between soil particles. This study can provide a reference for engineering construction and red soil improvement in red soil areas. Full article

In order to improve the strength and toughness-matching of metal matrix composites and enhance the mechanical properties of ceramic-reinforced iron matrix composites with a honeycomb architecture, TiCp/H13 steel composites with a honeycomb architecture were successfully prepared using squeeze-infiltration technology, in which the composite region was the honeycomb wall and the steel matrix was the honeycomb core. The effects of the composite-region fraction and TiCp content in the composite region on the compressive mechanical properties of the composites were studied, and the fracture mode and cracking behavior were analyzed. The results show that TiCp was evenly distributed in the composites region, and the interface of TiCp/H13 steel was tightly bonded without obvious defects. With the same TiCp content, the compressive strength of honeycomb-architecture composites first increased and then decreased with the increase in the composite-region volume fraction, and the highest strength was obtained at 50 vol.% of the composite region. The influence factor of the composite-region volume fraction on the strength was −38.3 MPa/%. Meanwhile, the fracture strain of the architecture composites decreased gradually. The influence factor of the composite-region volume fraction on plasticity was −0.25%/%. With the same composite-region fraction, both the compressive strength and plasticity of the composite decreased gradually with the increase in TiCp content (35 vol.%, 50 vol.%, and 65 vol.%). The influence factor of TiCp content on the strength was −21.4 MPa/%, and its influence factor on plasticity was −0.34%/%. The maximum compressive strength (2288.1 MPa) was obtained in the architecture composite with 50 vol.% of the composite region and 35 vol.% of TiCp, and the highest plasticity (25.9%) was obtained for the architecture composite, with 35 vol.% of the composite region and 35 vol.% of TiCp. Compared to those of common ZTA/iron honeycomb-architecture composites, the comprehensive mechanical properties of the TiCp/H13 steel matrix honeycomb-architecture composites were greatly improved. It showed good energy-absorption characteristics during compression. Full article

In this study, an aluminum heating block with two inlets (for the Polylactic acid (PLA) filament and the continuous aramid fiber) was produced and placed onto an extruder, and continuous-aramid-fiber-reinforced PLA composites were fabricated by using the nozzle impregnation method. Layer height values of 0.4 mm, 0.6 mm, and 0.8 mm and hatch spacing values of 0.6 mm, 0.8 mm, and 1.0 mm were used for the investigation of the processing parameters on the properties of composites by differentiating the reinforcement volume fraction. Additionally, atmospheric plasma treatment was used for the surface modification of the reinforcement fiber. The properties of composites reinforced by using surface-modified fibers were also investigated in order to reveal the efficacy of the atmospheric plasma treatment on the properties of composites. The effect of the atmospheric plasma treatment on the fiber properties was investigated by using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Continuous-aramid-fiber-reinforced PLA composites were characterized mechanically by fiber pull-out, tensile, and flexural testing. The fracture surfaces of composites were analyzed by using SEM. The combination of a reduced layer height and a narrower hatch spacing yielded the best mechanical performance, with a tensile strength of 410.25 MPa achieved at a 0.6 mm layer height and a 0.4 mm hatch spacing. This combination minimizes void formation, enhances fiber alignment, and strengthens interlayer adhesion, leading to superior mechanical properties. The FTIR and XPS results showed that atmospheric plasma modification can enhance the interfacial bonding strength by improving the surface morphology and increasing the content of polar groups on the fiber surface. By combining optimized manufacturing conditions with the atmospheric plasma treatment, the mechanical performance of continuous-aramid-fiber-reinforced PLA composites was enhanced. Full article

In order to increase the thermal conductivity of neat epoxy resin and broaden its practical application in high-voltage insulation systems, we have constructed four kinds of epoxy resin nanocomposite models (a neat epoxy resin (EP), a graphene-doped epoxy resin nanocomposite (EP/GR) and hydroxyl- or carboxyl-functionalized graphene-doped epoxy resin nanocomposites (EP/GR-OH or EP/GR-COOH)) to systematically investigate their thermodynamic and electrical properties using molecular dynamics (MD) simulations. Compared with the EP model, carboxyl-functionalized graphene particles enhanced the thermal conductivity of the EP/GR-COOH model by 66.5% and increased its T_g by 26.6 K. Furthermore, the dielectric constant of the EP/GR-COOH model was significantly reduced. To investigate the intrinsic mechanism, the lowest fraction of free volume (13.22%) and the largest number of hydrogen bonds (102.2) in the EP/GR-COOH model were identified as playing essential roles for its excellent thermodynamic properties and favorable electrical performance. The present study provides a molecular-level understanding of the satisfactory thermodynamic and electrical properties of the EP/GR-COOH nanocomposite, which will aid in designing novel epoxy resin nanocomposite materials with high thermal conductivity. Full article

Polyurea (PUR) has been widely used as a protective coating in recent years. In order to complete the understanding of the relationship between PUR microstructure and its energy absorption capabilities, the mechanical and dynamic performance of PURs containing various macrodiol structural units were compared using material characterization techniques and molecular dynamic simulation. The results showed that the PUR polycarbonate diols formed as energy absorbing materials showed high tensile strength, high toughness, and excellent loss factor distribution based on the comparison of stress–strain tensile curves, glass transition temperatures, phase images, and dynamic storage loss modulus. External energy from simple shear deformation was absorbed to convert non-bond energy, in particular, based on fractional free volume, interaction energy, and total energy and hydrogen bond number change from the molecular dynamic simulation. Hydrogen bonds formed between soft segments and hard segments in the PURs have been proven to play a significant role in determining their mechanical and dynamic performance. The mechanical and dynamic properties of PURs characterized and tested using experimental techniques were quantified effectively using molecular dynamic simulation. This is believed to be an innovative theoretical guidance for the structural design of PURs at the molecular level for the optimization of energy absorption capabilities. Full article

Alum, an essential additive in sweet potato vermicelli (SPV) production, is harmful to health. To eliminate the harm to the human body caused by alum in sweet potato vermicelli, and considering the different viscous properties of gliadin fractions, an experiment was performed to replace alum with gliadin fractions to enhance the boiling resistance of SPV in this study. The results showed that the longest boiling-resistant time of fresh SPV extended to 34.31 min when swelling the dough binder at 50 °C for 5 h, adding a 2% complex of ω-gliadin + αβγ-gliadin at a ratio of 1:1, and mixing at 70 °C for 20 min. The result was 95.7% higher than in the control. Starch swelling and freeze–thaw processes could partially replace the role of alum in preparing SPV. The results of FTIR and ¹³C solid-state NMR showed that the esterification reaction of ω-gliadin and αβγ-gliadin and hydrogen bonds between sweet potato starch and gliadin fractions reinforced the boiling resistance of vermicelli. There was no ordered area of starch in the new water-resistant vermicular. The gliadin fractions formed crystal with a diffraction angle of 17.38° (3.25 Å). Long-term cold storage could improve the boiling resistance of fresh sweet potato vermicelli. Additionally, the short-term retrogradation of sweet potato amylose significantly reduces its boiling resistance. The study provides new primary data and theoretical support for the industrial application of alum-free fresh sweet potato vermicelli. Full article

Two rheological Burgers–Faraday models and rheological dynamical systems were created by using two new rheological models: Kelvin–Voigt–Faraday fractional-type model and Maxwell–Faraday fractional-type model. The Burgers–Faraday models described in the paper are new models that examine the dynamical behavior of materials with coupled fields: mechanical stress and strain and the electric field of polarization through the Faraday element. The analysis of the constitutive relation of the fractional order for Burgers–Faraday models is given. Two Burgers–Faraday fractional-type dynamical systems were created under certain approximations. Both rheological Burgers-Faraday dynamic systems have two internal degrees of freedom, which are introduced into the system by each standard light Burgers-Faraday bonding element. It is shown that the sequence of bonding elements in the structure of the standard light Burgers-Faraday bonding element changes the dynamic properties of the rheological dynamic system, so that in one case the system behaves as a fractional-type oscillator, while in the other case, it exhibits a creeping or pulsating behavior under the influence of an external periodic force. These models of rheological dynamic systems can be used to model new natural and synthetic biomaterials that possess both viscoelastic/viscoplastic and piezoelectric properties and have dynamical properties of stress relaxation. Full article

In this study, a polyvinyl alcohol/polyethylene glycol/hydroxypropyltrimethyl ammonium chloride chitosan (PVA/PEG/HACC) ternary composite hydrogel was synthesized using electron-beam radiation. The materials were thoroughly characterized via Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, Brunauer–Emmett–Teller analysis, gelation fraction tests, and swelling rate tests. Systematic adsorption experiments revealed that the rate of adsorption of calf thymus DNA (ctDNA) by the PVA/PEG/HACC hydrogel reached 89%. The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetic model. This process was mainly characterized by monolayer chemical adsorption, with intraparticle diffusion playing a crucial role. In addition, the process was spontaneous, with higher temperatures enhancing adsorption. The possible adsorption mechanisms included electrostatic interactions, hydrogen bonding, and van der Waals forces. The maximum ctDNA desorption rate was 81.67%. The adsorption rate remained at 71.39% after five adsorption–desorption cycles. The bioactivity of the PVA/PEG/HACC hydrogel was validated by antibacterial, cytotoxicity, and apoptosis tests. The results of this study demonstrated the crucial application potential of adsorbent materials in DNA adsorption and biomedical applications. Full article

The dextrinization of potato starch was performed using a sophisticated single-mode microwave reactor with temperature and pressure control using 10 cycles of heating with stirring between cycles. Microwave power from 150 to 250 W, a cycle time from 15 to 25 s, and two types of vessels with different internal diameters (12 and 24 mm) and therefore different thicknesses of the heated starch layer were used in order to estimate the impact of vessel size used for microwave dextrinization. The characteristics of resistant dextrins (RD) including solubility in water, total dietary fiber (TDF) content, color parameters, the share of various glycosidic bonds, and pasting and rheological properties were carried out. The applied conditions allowed us to obtain RDs with water solubility up to 74% at 20 °C, as well as TDF content up to 47%, with a predominance of low-molecular-weight soluble fiber fraction, with increased content of non-starch glycosidic bonds, negligible viscosity, and a slightly beige color. The geometry of the reaction vessel influenced the properties of dextrins obtained under the same heating power, time, and repetition amounts. Among the conditions used, the most favorable conditions were heating 10 times for 20 s at 200 W in a 10 mL vessel and the least favorable were 15 s cycles. Full article

Hydrogel features can be designed and optimized using different crosslinking agents to meet specific requirements. In this regard, the present work investigates the physico-chemical features of cellulose-based hydrogels, designed by using different epoxy crosslinkers from the same glycidyl family, namely epichlorohydrin (ECH), 1,4-butanediol diglycidyl ether (BDDE), and trimethylolpropane triglycidyl ether (TMPTGE). The effect of the crosslinker’s structure (from simple to branched) and functionality (mono-, bi- and tri-epoxy groups) on the hydrogels’ features was studied. The performances of the hydrogels were investigated through the gel fraction, as well as by ATR-FTIR, DVS, SEM, DSC, and TG analyses. Also, the swelling and rheological behaviors of the hydrogels were examined. The advantages and limitations of each approach were discussed and a strong correlation between the crosslinker structure and the hydrogel properties was established. The formation of new ether bonds was evidenced by ATR-FTIR spectroscopy. It was emphasized that the pore size is directly influenced by the crosslinker type, namely, it decreases with the increasing number of epoxy groups from the crosslinker molecule, i.e., from 46 ± 11.1 µm (hydrogel CE, with ECH) to 12.3 ± 2.5 µm (hydrogel CB, with BDDE) and 6.7 ± 1.5 µm (hydrogel CT, with TMPTGE). The rheological behavior is consistent with the swelling data and hydrogel morphology, such as CE with the highest Q_max and the largest pore size being relatively more elastic than CB and CT. Instead, the denser matrices obtained by using crosslinkers with more complex structures have better thermal stability. The experimental results highlight the possibility of using a specific crosslinking agent, with a defined structure and functionality, in order to establish the main characteristics of hydrogels and, implicitly, to design them for a certain field of application. Full article

We constructed phase diagrams of conformationally asymmetric diblock copolymer A-B melts using the polymer self-consistent field (SCF) calculations of both the dissipative particle dynamics chain (DPDC) model (i.e., compressible melts of discrete Gaussian chains with the DPD non-bonded potential) and the “standard” model (i.e., incompressible melts of continuous Gaussian chains with the Dirac δ-function non-bonded potential) in the χN-ε plane, where χN and ε characterize, respectively, the repulsion and conformational asymmetry between the A and B blocks, at the A-block volume fraction f = 0.2 and 0.3. Consistent with previous SCF calculations of the “standard” model, σ and A15 are the only stable Frank–Kasper (FK) phases among the five FK (i.e., σ, A15, C14, C15 and Z) phases considered. The stability of σ and A15 is due to their delicate balance between the energetic and entropic contributions to the Helmholtz free energy per chain of the system, which, within our parameter range, increases in the order of σ/A15, Z, and C14/C15. While in general the SCF phase diagrams of these two models are qualitatively consistent, A15 is not stable for the DPDC model at the copolymer chain length N = 10 and f = 0.3; any differences in the SCF phase diagrams are solely due to the differences between these two models. Full article

In the FCC conversion of heavy petroleum fractions as atmospheric residues, the main challenge for refiners to achieve the quantity and quality of various commercial products depends essentially on the catalyst used in the process. A deep characterization of the catalyst at different steps of the process (fresh, regenerated, and spent catalyst) was investigated to study the catalyst’s behavior including the physicochemical evolution, the deactivation factor, and kinetic–thermodynamic parameters. All samples were characterized using various spectroscopy methods such as N₂ adsorption–desorption, UV-visible spectroscopy, Raman spectroscopy, LECO carbon analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), nuclear magnetic resonance spectroscopy (NMR¹³C) analysis, and thermogravimetric analysis. The results of the N₂ adsorption–desorption, UV-vis, Raman, LECO carbon, and SEM imaging showed that the main causes of catalyst deactivation and coking were the deposition of carbon species that covered the active sites and clogged the pores, and the attrition factor due to thermal conditions and poisonous metals. The XRD and XRF results showed the catalyst’s physicochemical evolution during the process and the different interlinks between catalyst and feedstock (Nickel, Vanadium, Sulfur, and Iron) elements which should be responsible for the coking and catalyst attrition factor. It has been found that, in addition to the temperature, the residence time of the catalyst in the process also influences catalyst structure transformation. NMR¹³C analysis revealed that polyaromatic hydrocarbon is the main component in the deposited coke of the spent catalyst. The pyridine-FTIR indicates that the catalyst thermal treatment has an influence on its Brønsted and Lewis acid sites and the distribution of the products. Thermogravimetric analysis showed that the order of catalyst mass loss was fresh > regenerated > spent catalyst due to the progressive losses of the hydroxyl bonds (OH) and the structure change along the catalyst thermal treatment. Moreover, the kinetic and thermodynamic parameters showed that all zones are non-spontaneous endothermic reactions. Full article

The changes in the secondary structure of individual gluten protein fractions (gliadin and glutenin) caused by the supplementation of model dough with eight phenolic acids were analysed. Gliadins and glutenins were extracted from gluten samples obtained from overmixed dough. The changes in the gliadin secondary structure depended on the amount of phenolic acid added to the dough. Higher acid concentrations (0.1% and 0.2%) led to a significant reduction in the amount of α-helices and to the formation of aggregates, non-ordered secondary structures, and antiparallel β-sheets. After the addition of acids at a lower concentration (0.05%), the disaggregation of pseudo-β-sheet structures and the formation of β-turns, hydrogen-bonded β-turns, and antiparallel β-sheets were detected. In the case of glutenin, most of the phenolic acids induced the formation of intermolecular hydrogen bonds between the polypeptide chains, leading to glutenin aggregation. When phenolic acids were added at a concentration of 0.05%, the process of protein folding and regular secondary structure formation was also observed. In this system, antiparallel β-sheets and β-turns were created at the expense of pseudo-β-sheets. Full article