Search Results (1,539)

Vascular endothelial growth factor 165 (VEGF₁₆₅) stands out as a pivotal isoform of the VEGF-A protein and is critically involved in various angiogenesis-related diseases. Consequently, it has emerged as a promising target for diagnosing and treating such conditions. Structurally, VEGF₁₆₅ forms a homodimer, and each of its constituting monomers comprises a receptor-binding domain (RBD) and a heparin-binding domain (HBD). These two domains are linked by a flexible linker, and thus the overall structure of VEGF₁₆₅ remains incompletely understood. Aptamers are known as potent drugs that interact with VEGF₁₆₅, and dimeric aptamers that can simultaneously interact with two distant domains are frequently adopted to improve the potency. However, designing such aptamer dimers faces challenges in regard to determining the appropriate length of the linker connecting the two aptamer fragments. To gain insight into this distance information, we here employ biased molecular dynamics (MD) simulations with the umbrella sampling method, with the distance between the two HBDs serving as a reaction coordinate. Our simulations reveal an overall preference for compact conformations with HBD-HBD distances below 3 nm, with the minimum of the potential of mean force located at 1.1 nm. We find that VEGF₁₆₅ with the optimal HBD-HBD distance forms hydrogen bonds with its receptor VEGFR-2 that well match experimentally known key hydrogen bonds. We then try to computationally design aptamer homodimers consisting of two del5-1 aptamers connected by various linker lengths to target VEGF₁₆₅. Collectively, our findings may provide quantitative guidelines for rationally designing high-affinity aptamers for targeting VEGF₁₆₅. Full article

The development of lithium-ion batteries necessitates cathode materials that possess excellent mechanical and thermal properties in addition to electrochemical performance. As a prominent functional ceramic, the properties of spinel LiMn₂O₄ are governed by its atomic-level structure. This study systematically investigates the impact of Ni doping concentration on the mechanical and thermal properties of spinel LiNi_xMn_2−xO₄ via first-principles calculations combined with the bond valence model. The results suggest that when x = 0.25, the LiNi_xMn_2−xO₄ shows excellent mechanical properties, including a high bulk modulus and hardness, due to the favorable ratio of bond valence to bonds length in octahedra. Furthermore, this optimized composition shows a lower thermal expansion coefficient. Additionally, Ni doping concentration has a very minimal influence on the maximum tolerable temperature of the cathode material during rapid heating. Therefore, from the perspective of mechanical and thermal properties, this composition could be beneficial for improving the cycling life of the battery, since comparatively inferior mechanical properties and a higher thermal expansion coefficient make it prone to microcrack formation during charge–discharge cycles. Full article

Cyclic π-conjugated organic species are classical examples of (anti)aromatic compounds. Two key features that characterize their (anti)aromatic behavior are the aromatic stabilization (or destabilization) energy and the degree of bond-length equalization or alternation. Both properties depend strongly on the size of the π-conjugated ring. In small rings, systems with 4n + 2 π electrons exhibit substantial aromatic stabilization and pronounced bond-length equalization, whereas those with 4n π electrons show significant antiaromatic destabilization accompanied by clear bond-length alternation. As the ring size increases, however, the differences in aromatic stabilization energy and bond-length patterns become progressively less distinct. Full article

Taking advantage of the ionic size and mass disorder as component design criteria, three novel high-entropy rare-earth zirconate ceramics, including (Sm_0.2Gd_0.2Dy_0.2Er_0.2Tm_0.2)₂Zr₂O₇, (Gd_0.2Dy_0.2Ho_0.2Er_0.2Tm_0.2)₂Zr₂O₇ and (Gd_0.2Dy_0.2Ho_0.2Er_0.2Yb_0.2)₂Zr₂O₇, with single-phase fluorite structure were successfully synthesized. All compositions exhibited enhanced mechanical properties, with Vickers hardness and fracture toughness increasing as the grain size decreased. (Gd_0.2Dy_0.2Ho_0.2Er_0.2Yb_0.2)₂Zr₂O₇ demonstrated superior mechanical performance, achieving values of 11.41 ± 0.40 GPa and 1.78 ± 0.12 MPa·m^1/2, respectively. The thermal expansion coefficients at 1000 °C ranged from 10.80 × 10⁻⁶ K⁻¹ to 11.39 × 10⁻⁶ K⁻¹, which is proportional to the average ionic bond length. Notably, (Sm_0.2Gd_0.2Dy_0.2Er_0.2Tm_0.2)₂Zr₂O₇ exhibited low room-temperature thermal conductivity (1.58 W·m⁻¹·K⁻¹) due to pronounced size and mass disorder, without compromising structural stiffness. These findings highlight the potential of high-entropy design for advanced thermal barrier coatings. Full article

The accurate determination of bond lengths is fundamental to understanding molecular geometry and the physicochemical behavior of chemical compounds. However, obtaining these measurements is often challenging, as both experimental techniques and advanced quantum-chemical methods are complex, computationally demanding, and costly to apply across diverse molecular systems. In this work, we present a novel graph-theoretical model for predicting bond lengths in flavonoid molecules based on molecular descriptors derived from atomic and topological parameters. By integrating atomic electronegativity with graph-based descriptors, such as the weighted second-order neighborhood, the proposed model predicts the bond lengths of luteolin with a coefficient of determination of $R^2=0.990$. This approach offers a computationally efficient and highly accurate alternative to conventional experimental and theoretical methods, providing a practical framework for bond length estimation when experimental data are unavailable. Full article

Grouted sleeves are commonly used to connect prefabricated structural components, but construction defects can easily occur after installation, posing potential risks to the structure. This study conducts comparative uniaxial tensile tests on 39 grouted-sleeve specimens in 13 groups—including standard specimens, defective specimens, and specimens repaired with supplementary grouting. The strain distribution patterns under different grouting lengths and loading levels are analyzed to investigate the load-transfer mechanism between reinforcement bars and grouted sleeves, as well as the influence of various supplementary grouting amounts and material strengths on the mechanical performance of defective sleeves. In the uniaxial tensile test of grouted sleeves, with grout strengths of 85 MPa and 100 MPa and HRB400-grade steel bars, when the grouted anchorage length was 4 d, insufficient anchorage length resulted in low bond strength between the grout and the steel bar, leading to bond–slip failure. When the grouted anchorage length reached 6 d, steel bar fracture occurred inside the sleeve. When the total anchorage length formed by two grouting sessions reached 8 d, specimen slippage decreased, showing a trend where the strain growth rate of the sleeve gradually decreased from the grouted end to the anchored end, while the strain growth rate of the steel bar gradually increased. The longer the total anchorage length in the sleeve after grout repair, the stronger its anti-slip capability. The bearing capacity and failure mode of the specimens depend on the strength of the steel bars connected to the grouted sleeves and the strength of the threaded connection ends at the top. Experimental results show that the anchorage length and strength of high-strength grout materials have a significant reinforcing effect on defective sleeves. The ultimate bearing capacity of specimens with anchorage length of 6 d or more is basically the same as that of steel bars. Specimens with a total anchorage length of 8 d show approximately 10%~20% less slippage than those with 6 d. The safe anchorage length for HRB400-grade steel bars in sleeve-grouted connections is 8 d, even though the bearing capacity of grouted sleeves with a 6 d anchorage length already meets the requirements. Bond strength analysis confirms that the critical anchorage length is 4.49 d. When the grouted anchorage length exceeds the critical length, the failure mode of the specimen is steel bar fracture. When the grouted anchorage length is less than the critical length, the failure mode is steel bar slippage. This conclusion aligns closely with experimental results. In engineering practice, the critical anchorage length can be used to predict the failure mode of grouted sleeve specimens. Based on experimental research and theoretical analysis, it is clear that using grout repair to reinforce defective grouted sleeve joints with a safe anchorage length of 8 d is a secure and straightforward strengthening method. Full article

Chromium complexes with triamidoamine derivatives bearing bulky substituents at the terminal positions of the ligands, tris(2-(3-pentylamino)ethyl)amine (H₃L^Pen) and tris(2-dicyclohexylmethylaminoethyl)amine (H₃L^Cy), are prepared: [{Cr(L^Pen)}₂(μ-N₂)] (1), [{CrK(L^Pen)(μ-N₂)(Et₂O)}₂] (2), [CrCl(L^Pen)] (3), [Cr(L^Cy)] (4), [CrK(L^Cy)(μ-N₂)(18-crown-6)(THF)] (5(THF)), and [CrCl(L^Cy)] (6). The preparation of these complexes is confirmed by X-ray diffraction analysis. Complexes 1, 2, and 5(THF) have coordinated dinitrogen molecules, with N–N bond lengths of 1.185(3), 1.174(9), and 1.162(3) Å, respectively. These lengths are significantly elongated compared to that of a free dinitrogen molecule (1.10 Å), indicating that the N₂ ligands are activated. The ν(¹⁴N–¹⁴N) values of 1, 2, and 5(THF) are 1715 cm⁻¹ for 1 (Raman, in solution), 1787, 1743 cm⁻¹ for 2 (IR, in solid), and 1824 cm⁻¹ for 5(THF) (IR, in solid), respectively. These values are markedly smaller than free nitrogen (2331 cm⁻¹), confirming that the dinitrogen is interacting with the metal ions and is activated. The structures of 2 and 5(THF) in solution are also studied by ¹H NMR and solution IR spectroscopies. ¹H NMR spectra of these complexes reveal that the peaks of 2 and 5(THF) are observed in the diamagnetic region, whereas those for the other complexes (1, 3, 4, and 6) exhibit paramagnetic shifts. The reactions of these complexes with K[C₁₀H₈] and HOTf under N₂ in THF yield hydrazine and a small amount of ammonia; however, they are not catalytic. The ¹H NMR and IR spectra of the products obtained by reacting 1 or 3 with reductant K in THF under N₂ atmosphere indicate that 2 is formed based on spectral agreement. Similarly, upon examining for 4 or 6, it is confirmed that a species similar to 5(THF) is generated. Full article

In this study, hydroxyapatite was synthesized using a microwave-assisted hydrothermal method. Calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O) and ammonium phosphate ((NH₄)₂HPO₄) served as precursors in a pH 10 ammonium hydroxide (NH₄OH) solution. Polyvinylpyrrolidone (PVP) was employed as a surfactant at varying concentrations of 0 (M0), 0.1% (M1), 0.2% (M2), and 0.3%wt (M3) to control particle size and morphology. The synthesized samples were characterized using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The addition of PVP during synthesis resulted in Ca/P ratios ranging from 0.93 to 1.37, and promoted predominantly rod-like morphologies. Samples M1 and M3 exhibited average diameters of 11.23–104.24 nm and lengths of 47.21–222.32 nm. XRD analysis confirmed the presence of both hexagonal and monoclinic phases, with crystallite sizes varying from 18.66 to 22.49 nm. FTIR spectra of sample M1 revealed an elongation at 3432 cm⁻¹ corresponding to OH⁻ groups, indicative of water absorption within the material structure. Vibrational bands at 2950–2300, 1090, and 975 cm⁻¹, attributed to C–H bonds in PVP were also identified. These findings highlight the influence of PVP concentration on the structural and morphological properties of hydroxyapatite, providing insights into its potential applications in various fields. Full article

Defective graphene has emerged as a promising strategy to enhance electrochemical performance of pristine graphene (p-Gr) as anodes in lithium-ion batteries (LIBs). Herein, we perform a comprehensive first-principles study based on density functional theory (DFT) to systematically investigate the Li adsorption, charge transfer, and diffusion behaviors of p-Gr and defective graphene (d-Gr) with single vacancy (SV Gr) and double vacancy (DV5-8-5 Gr) defects, aiming to clarify the mechanism by which defects modulate Li storage performance. Structural optimization reveals that SV Gr undergoes notable out-of-plane distortion after Li adsorption, while DV5-8-5 Gr retains planar geometry but exhibits more significant C-C bond length variations compared to p-Gr. Binding energy results confirm that defects enhance Li adsorption stability, with DV5-8-5 Gr showing the strongest Li–graphene interaction, followed by SV Gr and p-Gr. Bader charge analysis and charge density difference plots further validate that defects enhance charge transfer from Li ions to graphene. Using the nudged elastic band (NEB) method, we find that defects reduce Li diffusion barriers: DV5-8-5 Gr exhibits a lower barrier than p-Gr. Our findings demonstrate that DV5-8-5 Gr exhibits the most favorable Li storage performance, providing a robust theoretical basis for designing high-performance graphene anodes for next-generation LIBs. Full article

Glued laminated timber (glulam) is increasingly adopted as a sustainable structural material; however, its performance under bending can be limited by brittle tensile failures and variability caused by natural defects. This study examines the flexural behavior of glulam beams strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. A four-point bending experimental program was carried out on glulam beams with varying CFRP bonded lengths, including unreinforced control beams. The results demonstrate that CFRP reinforcement enhanced load–carrying capacity by up to 48%, increased stiffness, and shifted failure modes from brittle tension–side ruptures to more favorable compression–controlled mechanisms. A nonlinear finite element (FE) model was developed using DIANA software 10.5 to simulate the structural response of both unreinforced and CFRP–strengthened beams. The numerical model accurately reproduced the experimental load–deflection behavior, stress redistribution, and failure trends, with deviations in ultimate load prediction generally within ±16% across all reinforcement configurations. The simulations further revealed the critical influence of CFRP bonded length on stress transfer efficiency and failure mode transition, mimicking experimental observations. By integrating experimental findings with numerical simulations and simplified analytical predictions, the study demonstrates that reinforcement length and bond activation govern the effectiveness of CFRP strengthening. The proposed combined methodology provides a reliable framework for evaluating and designing CFRP strengthened glulam beams. Full article

This study examines the torsional behavior of an additively manufactured bushing featuring a unique topology, which includes a flexible gyroid core and rigid inner and outer sleeves. The bushing is designed and fabricated using two materials: thermoplastic polyurethane (TPU) and polylactic acid (PLA), which are interpenetrated in successive layers throughout the bushing’s thickness. First, tensile mechanical tests are conducted on both materials with different infill patterns. The 45/135 infill proves to be the most suitable, providing good stiffness, strength, ductility, and data reproducibility. Additionally, the effectiveness of the interlocking created between the two materials through the printing process is evaluated by testing different overlap lengths. With an overlap of 2 mm, the extrusion process remains unaffected, minimizing voids and defects while ensuring strong interlayer bonding. Next, the designed bushing is subjected to torsional loading under both single and repetitive angular rotations, and its response is measured in terms of torque. The aim of this study is to evaluate the suitability of TPU and PLA materials for developing a design intended for dynamic mechanical environments, serving as a proof of concept. The quasi-static results indicate the presence of local damages and a viscoelastic response of the bushing during twisting, while also demonstrating its strong ability to withstand significant angles of rotation. Quasi-static results indicate local damage and the bushing’s viscoelastic response during twisting, as well as its ability to withstand significant angles of rotation. Full article

The embedded through-section (ETS) technique is a promising method for fiber-reinforced polymer (FRP)-strengthening reinforced concrete (RC) structures, offering higher bond resistance and reduced surface preparation compared to externally bonded or near-surface mounted FRP systems. A common failure in ETS applications is debonding at the FRP bar-to-concrete interface. However, current design standards often assume uniform bond stress and lack predictive models that account for debonding propagation and its effect on load capacity. Furthermore, a detailed analysis of interfacial stress development, including debonding initiation and progression along varying bond lengths, remains limited. To address these gaps, this study introduces an analytical model that describes the complete debonding process in ETS FRP bar-to-concrete joints, incorporating both long and short bond lengths and frictional effects. Based on a trilinear cohesive material law (CML), closed-form expressions are deduced for the load–slip response, maximum load, interfacial shear stress and strain distribution along the FRP bar. The proposed model is validated experimentally through pull-out tests on glass FRP (GFRP) bars adhesively bonded to concrete with different strength grades. The results show that the analytical predictions agree well with both the self-conducted experimental data for short joints and existing test results for long joints given in the literature. Therefore, the developed design-oriented solution enables accurate evaluation of the actual contribution of ETS FRP reinforcement to RC members by explicitly modeling debonding behavior. This provides a rigorous and mechanics-based tool for performance-based design of ETS FRP-to-concrete joints, addressing a critical gap in the future refinement of current design standards. Full article

Amphiphilic dendrimers represent a promising class of nanoscale building blocks for functional materials, yet their conformational behavior, solvation, and interfacial activity remain incompletely understood. In this work, we employ atomistic molecular dynamics simulations to investigate G2–G4 carbosilane dendrimers functionalized with ethylene glycol terminal groups of two lengths—R1 (one ethylene glycol unit) and R3 (three units)—in water, toluene, and at fluid interfaces (water–toluene and water–air). Both types of dendrimers adopt compact, nearly spherical conformations in water but swell significantly (~83% in volume for G4) in toluene, a good solvent for the hydrophobic core. At the water–toluene interface, the dendrimers remain fully solvated in the toluene phase and show no surface activity. In contrast, at the water–air interface, they adsorb and adopt a mildly anisotropic, biconvex conformation, with a modest deformation. The total number of hydrogen bonds is reduced by ~50% compared to bulk water. Notably, the R3 dendrimers form more hydrogen bonds overall due to their higher oxygen content, which may contribute to the enhanced stability of their monolayers observed experimentally. These results demonstrate how dendrimer generation as well as terminal group length and hydrophilicity finely tune dendrimer conformation, hydration, and interfacial behavior, which are key factors for applications in nanocarriers, interfacial engineering, and self-assembled materials. The validated simulation protocol provides a robust foundation for future studies of multi-dendrimer systems and monolayer formation. Full article

In this study, the changes in the DNA native conformation induced by pH changes in the alkaline and acidic regions were examined. It was shown by the methods of low gradient viscometry and flow birefringence that protonation and deprotonation of nitrogen bases inside the double helix cause a change in the persistent length of DNA. The pK values shift with the change in the ionic strength of the solution (NaCl concentration). The additional charges appearing on the DNA bases are not shielded by counterions from the solution. The increase and decrease in the volume of the DNA coil in solution resulting from protonation and deprotonation of base pairs, respectively, are mainly determined by changes in the persistent length of the macromolecule. The stability of the double-helical conformation of DNA ensures the steadiness of the equilibrium rigidity of this macromolecule. The emergence of charges on the bases, resulting from DNA protonation or deprotonation, weakens and even disrupts the hydrogen bonds between complementary bases. However, at the first stage, this occurs without altering the stacking interactions of base pairs, as reflected in the absorption spectra of DNA and in the stability of the DNA persistent length at different pH levels. Full article

Lignin is one of the primary biomass resources in nature; however, its highly stable structure makes it difficult to degrade and utilise. As efficient decomposers of lignocellulosic biomass, termites rely on their gut microbiota for digestion. Consequently, termite guts harbour abundant and specialized lignin-degrading microorganisms. In this study, we isolated a bacterium from the termite gut and identified it as Bacillus cereus BC-8. The laccase activity of B. cereus BC-8 reached the maximum of 87.8 U/L at 72 h, and the lignin degradation rate reached 33.66% within 7 days. Furthermore, we analyzed the structural changes in lignin after treatment with this bacterial strain. Field emission scanning electron microscopy observations revealed that the surface structural integrity of lignin was significantly disrupted after treatment. Fourier transform infrared spectroscopy analysis indicated that B. cereus BC-8 affected the side chains and aromatic skeleton structures of lignin. Thermogravimetric analysis further revealed that B. cereus BC-8 disrupted the primary inter-unit β-O-4 ether bonds of lignin. Whole-genome sequencing of B. cereus BC-8 revealed a genome length of 5,374,773 bp and a GC content of 35.34%. Functional gene annotation revealed that the B. cereus BC-8 genome contains genes encoding various lignin-degrading enzymes (laccase, cytochrome P450, and vanillin oxidase) and their auxiliary factors, along with the phenylalanine and benzoic acid metabolic pathways, which are associated with lignin degradation. In conclusion, B. cereus BC-8 can break down the side chains, aromatic skeletons, and β-O-4 ether bonds of lignin molecules, demonstrating excellent lignin degradation ability. At the molecular level, this study elucidates the key genes and metabolic pathways related to lignin degradation in the genome of B. cereus BC-8. Full article