Search Results (856)

This study evaluated the effect of delay time and storage conditions after airborne-particle abrasion on the shear bond strength between base metal alloys (BMA) and self-adhesive resin cement. It also assessed whether vacuum sealing or re-airborne-particle abrasion could counteract the time-related degradation of bond strength. Sixty BMA specimens were airborne-particle-abraded and divided into six groups (n = 10): immediate bonding; 1-day, 7-day, and 14-day delays; 14-day vacuum-sealed; and 14-day delay with re-airborne-particle abrasion. Resin cement was applied to standardized bond areas, and composite rods were bonded. All specimens were stored in water at 37 °C for 24 h before shear bond strength testing. Failure modes were examined under a stereomicroscope. One-way ANOVA revealed significant differences among groups (p < 0.05). Immediate bonding yielded the highest strength (26.50 ± 2.74 MPa). Bond strength declined with delays, namely, 1-day (21.19 ± 4.94 MPa), 7-day (15.20 ± 4.52 MPa), and 14-day (16.01 ± 4.69 MPa), with no significant difference between the 7- and 14-day groups. Vacuum sealing for 14 days preserved bond strength (25.92 ± 3.94 MPa) comparable to immediate bonding. Re-airborne-particle abrasion restored bond strength (20.66 ± 3.70 MPa). Prolonged delays resulted in 100% adhesive failures, whereas immediate bonding and intervention groups showed 80% adhesive and 20% mixed failures. Delayed bonding after airborne-particle abrasion significantly reduces bond strength due to oxide layer formation on the BMA surface. However, surface sealing might prevent surface oxidation and maintain bonding potential, while re-airborne-particle abrasion can restore bond strength when delays are unavoidable. Clinically, bonding should be performed immediately after airborne-particle abrasion, or appropriate surface management protocols should be implemented to maintain optimal adhesion. Full article

Hydrogels are three-dimensional polymeric networks capable of retaining large amounts of water. Polyvinyl alcohol (PVA)-based hydrogels exhibit autonomous self-healing through reversible physical interactions within the hydrogel matrix, including hydrogen bonding, crystallite formation, and dynamic crosslinking. However, their long self-healing times and low strength limit practical application. Herein, we propose an effective strategy to simultaneously achieve excellent self-repairing and high mechanical strength. The tensile strength of uncut PVA hydrogel was 1.21 MPa; after cutting and rejoining for 12 h at room temperature (RT), it recovered 94% of the original uncut strength. To accelerate self-healing, hydrogels were treated at 40, 50, and 60 °C for 20, 40, and 60 min. Under optimal conditions (60 °C for 60 min), 96% recovery was achieved. Mechanical properties were further improved by silica (Si) nanoparticles of various sizes (~12, ~85, and ~200 nm). Si-loaded hydrogels, particularly ~12 nm, demonstrated increased mechanical properties, reaching a tensile strength of 1.45 MPa and a self-healing recovery of 95% of the uncut hydrogel strength. Ultra-small (~12 nm) Si nanoparticles enhanced the overall mechanical properties by acting as an efficient nucleating agent and did not hinder the existing self-healing mechanism. The developed strategy will pave the way for novel techniques in hydrogel research and will advance applications such as soft robotics and wound dressing. Full article

Aluminum doping can improve the phase stability of metastable compound Sm₂Fe₁₇C_x with a high carbon content (x > 1.5). We investigated the preferential site substitution of Al, chemical bonding, and structural stability in Sm₂(Fe,Al)₁₇C₃ using first-principle calculations. Our results reveal a strong correlation between the preferential substitution of Fe by Al and the atomic site chemical environment, which affects the overall phase stability. Specifically, Al preferentially occupies the 9d site in Sm₂(Fe,Al)₁₇C₃. At the same time, Al prefers the site 6c in its parent phase Sm₂(Fe,Al)₁₇. Partial replacement of Fe with Al leads to a more negative formation energy, indicating enhanced thermodynamic stability. Crystal Orbital Hamilton Population (COHP) and Crystal Orbital Bond Index (COBI) analysis suggest that insertion of carbon weakens the bonding strength of Sm-Fe (18f) and Sm-Fe (18h), resulting in metastability of Sm₂Fe₁₇C_x. Doping Al strengthens Al-Fe, Al-Sm, Sm-Fe (18f, 18h) and Fe–C bonding in Sm₂(Fe,Al)₁₇C₃, as revealed by calculated COHP and COBI. These effects contribute to improved phase stability in the Al-doped 2:17 interstitial compound. Full article

A growing scientific interest in bioactive compounds from sea cucumbers is contributing to a broader recognition even in regions where their consumption is not common. This study evaluated the biological potential of a Holothuria forskali extract obtained through different extraction methods, including water extraction, ethanol–water extraction, and enzymatic hydrolysis. The hydrolysate (H), rich in low-molecular-weight peptides, yielded the highest antioxidant (30.6 ± 0.6 mg VitC Eq/g sample for ABTS and 10.7 ± 0.1 mg GAEs/g sample for Folin-reactive substances) and ACE-inhibitory (82.6%) activities. Based on these results, the hydrolysate was selected for encapsulation in two nanostructured delivery systems for comparative purposes: chitosan nanoparticles (NPs) and rapeseed lecithin liposomes (LPs). Both nanostructures were characterized in terms of size, ζ-potential, and polydispersity and subjected to simulated in vitro gastrointestinal digestion (GIDv) to assess their stability and mucoadhesive properties. After digestion, antioxidant activity increased in both systems, particularly in liposomes. Although encapsulation initially reduced ACE-inhibitory activity, gastrointestinal digestion restored or enhanced it, especially in liposomal formulations (≈37% inhibition). The mucoadhesive potential of the nanostructures after DGIv, focusing on their interactions with mucin, was assessed. Liposomal digests significantly increased viscosity in the presence of mucin, while chitosan nanoparticles decreased it, suggesting the formation of soluble complexes with reduced hydrodynamic volume. Electrostatic and hydrogen bonding interactions between chitosan and mucin were particularly evident in the NPH formulation. The rheological synergism parameter (Δη) revealed more negative values for NPs and NPHs, indicating stronger mucoadhesive interactions compared to controls and suggesting their suitability for mucosal delivery. These findings support the use of H. forskali hydrolysates as a source of functional bioactive compounds and highlight the potential of chitosan-based nanocarriers for enhancing their stability, bioaccessibility, and mucoadhesive properties in functional food or nutraceutical applications. Full article

Amorphous hydrogenated germanium–carbon alloys (Ge_1−xC_x:H) were synthesized by X-ray-activated Chemical Vapor Deposition and investigated to evaluate the effects of annealing on their structure, composition, and properties given the limited information available on their behavior at high temperatures. Thermogravimetric and elemental analyses showed that the materials are stable up to 573 K; above this temperature, the carbon and hydrogen content progressively decrease, favoring structural reorganization. XRPD and Raman analyses demonstrate that the as-deposited films are fully amorphous, while annealing promotes the progressive formation of crystalline Ge. This crystallization occurs heterogeneously through the nucleation of small “islands” embedded within the sample matrix. Optical measurements reveal a narrowing of the band gap with increasing annealing temperature and time. The weak contribution of sp²-carbon observed in some Raman spectra indicates that band gap reduction is mainly governed by the overall composition and the variation of germanium hydrogen bonding configuration, rather than by graphitization. The study also notes that the parameter B^1/2 does not follow a regular trend due to the complex nature of the material’s microstructural evolution during annealing. These results provide a comprehensive picture of the annealing-driven transformations in Ge–C:H alloys relevant for the design of thermally stable optoelectronic materials. Full article

The nutritional value of a diet and its bioavailability in fish depend on three primary capacities: (a) ingestion, (b) digestion, and (c) absorption. Among these, digestive capacity, defined here as the total enzyme activity available to hydrolyze the bonds of dietary macromolecules to obtain hydrolysis products that are ultimately converted into absorbable micromolecular units, establishes the upper limit for the bioaccessibility of nutrients. To clarify usage and measurement, we conducted a systematic SCOPUS survey (January 2020–June 2024; 62 relevant articles). Most studies either omit a clear definition of digestive capacity or conflate it with digestive organ morphology or isolated enzyme activities. We compared indicators and assay conditions (substrate type, pH, temperature, and expression of units), revealing significant inter-study variability. Based on this synthesis, we propose four operational definitions: (a) Extract Theoretical Volume (ETV)—calculated volume of extract, considering both the solvent volume (SV) used for tissue homogenization and the tissue’s water content; (b) digestive capacity (U)—the total catalytic activity present in the digestive tract at the moment of sampling, where 1 U is the amount of enzyme catalyzing the formation of 1 µmol of product per minute under species-specific physiological pH, ionic strength, and temperature, with the total activity expressed as U fish⁻¹, U organ⁻¹, or U g⁻¹ fish or U g⁻¹ organ, enabling direct comparisons across studies; (c) Digestive Processing (DP)—the total number of bonds hydrolyzed during a given digestion time, whether instantaneous or over a defined period; and (d) Digestive Processing Index (DPI, U-min or U-h), which integrates digestive capacity over time. This framework provides a harmonized checklist for assay standardization and advances comparative studies in fish digestive physiology. Full article

This study quantifies the effects of freeze–thaw (FT) cycling and dynamic water scouring, and establishes links between mesoscale pore evolution and macroscale strength degradation in cement-stabilized macadam (CSM) bases. The objective is to provide quantitative indicators for durability design and non-destructive evaluation of CSM bases. First, laboratory tests were conducted to simulate alpine service conditions: CSM cylindrical specimens (Ø150 × 150 mm) with 4.5% cement content, cured for 28 days, were exposed to 0, 5, or 20 FT cycles (−18 °C for 16 h ↔ +25 °C for 8 h), followed by dynamic water scouring (0.5 MPa, 10 Hz) for 15, 30, or 60 min. Second, the resulting damage was tracked at two scales. Acoustic emission (AE) sensors monitored internal damage during subsequent splitting tests, while industrial computed tomography (CT) was used to scan selected specimens and quantify porosity, pore number, and average pore diameter. Third, gray relational analysis correlated pore structure parameters with strength loss. The results indicate that under 30 min of scouring, increasing FT cycles from 0 to 20 increased mass loss from 0.33% to 1.27% and reduced splitting strength by 28.8%. AE cumulative ringing count and energy decreased by 97.9% and 98.4%, respectively, indicating severe internal degradation. CT scans revealed porosity and pore count increased monotonically with FT cycles, while average pore diameter decreased (dominated by microcrack formation). Frost-heave pressure and cyclic suction enlarged edge pores and interconnected internal voids, accelerating erosion of cement paste. FT cycles compromise the cement–aggregate interfacial bond, thereby predisposing the matrix to accelerated deterioration under dynamic scouring; the ensuing evolution of pore structure emerges as the pivotal mechanism governing strength degradation. Average pore diameter exhibited the strongest correlation with splitting strength (r = 0.763), and its change was the primary driver of strength loss (r = 0.774). These findings facilitate optimizing cement dosage, validating non-destructive evaluation models for in-service base courses, and erosion durability of road base materials in permafrost regions. Full article

Gelatin microparticles (GMPs) can load functional active substances, but they tend to redissolve in high-temperature aqueous solutions during food processing. In this study, a new loading system adapted to food processing and digestive environments was constructed through the crosslinking of tea polyphenols (TP) on GMPs. The effects of pH, temperature, and crosslinking time on the methylene blue (MB) retention rate in crosslinked gelatin microparticles (cGMPs) were investigated, resulting in optimized crosslinking conditions. Compared with GMPs, the surface of cGMPs was denser and smoother. ATR-FTIR results showed that the N–H groups were involved in the formation of hydrogen bonds during the crosslinking process. The crosslinking effect of TP significantly disrupted the triple-helical structure of gelatin. The melting temperature ($T_m$) of cGMPs is 147.79 °C, which is significantly higher than that of GMPs (87.11 °C), indicating a marked improvement in thermal stability. In high-temperature aqueous solutions, Folic acid-loaded cGMPs (FA-cGMPs) maintained morphological integrity for 2 h (at 40 °C) and 0.5 h (at 60 °C). In vitro digestion simulations revealed excellent sustained-release characteristics of FA-cGMPs, with a release rate of only 4.91% in simulated gastric fluid and 88.13% in simulated intestinal fluid. This study provides an ideal carrier with food processing stability and intestinal-targeted release capabilities for functional active substances. Full article

Formaldehyde is a toxic gas commonly found in industrial emissions, and ZnO is widely used for its detection due to its excellent gas-sensing properties. Most studies focus on non-polar or low-index ZnO surfaces, whereas investigations on high-index polar surfaces remain limited. In this work, density functional theory (DFT) was employed to study CH₂O adsorption on the ZnO [$10\overline{11}$] surface. By exploring various coverages, adsorption sites, and unit cell dimensions, ten stable configurations were identified. A maximum adsorption energy of −2.19 eV/CH₂O on configuration S1 was obtained, surpassing reported low-index surfaces. Strong adsorption originated from dual unsaturated Zn bonds, which promoted C–C formation between CH₂O molecules and induced synergistic Zn–O bonding. Adsorption further led to sp³-like hybridization and O 2p/Zn 3d orbital interactions, significantly narrowing the band gap. Electron redistribution, as evidenced by charge density analysis, revealed strong electronic modulation. This work clarifies the microscopic mechanism of ZnO high-index surfaces, offering insights for optimizing gas-sensing materials. Full article

The compound 3-((benzyloxy)carbonyl)bicyclo[1.1.1]pentane-1-carboxylic acid was successfully synthesized. High-quality crystals were obtained, and its X-ray structure was solved and refined by Hirshfeld atom refinement using custom aspherical scattering factors with the Olex2/NoSphereA2 package. Hydrogen bonding interactions lead to head-to-head carboxylic acid dimer formation. A positional disorder for the bridging H-atom was detected and modeled to two parts in a 0.85:0.15 ratio. Detailed comparison with a neutron diffraction study of benzoic acid at the same temperature (100 K) demonstrates that the E–H-bond distances in the title compound are in excellent agreement (differing less than 1%) and the displacement ellipsoids volumes to the model are also in excellent agreement to the neutron diffraction structure. Moreover, both the variation in refined disorder occupancy and differences in C=O and C–O lengths of the disordered carboxylic acids in the two structures track well with their dimer O···O separations. This is longer by 0.023 Å in the structure of the title compound than in that of benzoic acid. A database search was conducted and used for comparison of the title compound to other high-quality structures of bicyclo[1.1.1]pentane-containing species. Full article

In this study, first-principles calculations were employed to systematically investigate the interaction mechanisms between (18-crown-6) potassium (18C6-K⁺) and six typical defect sites on the SnO₂ (110) surface, including Sn_i + Sn_O, O_i + O_Sn, V_O + Sn_i, V_Sn + Sn_O, V_Sn + Sn_i, and Sn_i. Six intrinsic or complex defects universally coexist on the SnO₂ surface, and the defect states they introduced allow for precise tuning of material performance. The results demonstrated that the 18C6-K⁺ molecule can stably adsorb on all six defect sites and significantly increase defect formation energies, indicating its thermodynamic capability to suppress defect generation. A subsequent density of states (DOS) analysis revealed that the 18C6-K⁺ molecule exhibits strong defect passivation effects at Sn_i + Sn_O, V_O + Sn_i, V_Sn + Sn_i, and Sn_i sites, and partially mitigated the electronic disturbances induced by O_i + O_Sn and V_Sn + Sn_O defects. Furthermore, the incorporation of 18C6-K⁺ has been shown to reduce the electronic effective mass of defective systems, thereby enhancing surface carrier transport. A subsequent charge density difference (CDD) analysis revealed that the 18C6-K⁺ molecule forms Sn-ether and O-ether interactions through its ether bonds (C-O-C) with surface Sn and O atoms, inducing interfacial electronic reconstruction and charge transfer. The Bader charge analysis revealed that the H, C, and O atoms in 18C6-K⁺ lose electrons, whereas the Sn or O atoms at the surface defect sites gain electrons. This outcome is consistent with the CDD analysis and quantitatively confirms the extent of electron transfer from 18C6-K⁺ to the SnO₂ defect regions. These interactions effectively passivate defect states, thereby enhancing interfacial stability. The present study offers theoretical guidance and design insights for the development of molecular passivation strategies in SnO₂-based optoelectronic devices. Full article

Shape memory polymer composites (SMPCs) are an intelligent class of materials capable of self-actuation, offering promising applications in diverse stimuli-responsive material systems. This study developed epoxy-based SMPCs reinforced with carbon–aramid fibers at a 15:85 ratio, with their glass transition temperature (T_g) tailored by incorporating 5 wt.% (SMPC-5) and 10 wt.% (SMPC-10) polyethylene glycol (PEG-600). Dynamic mechanical analysis (DMA) confirmed that PEG addition effectively reduced the T_g from 89.79 °C in the neat composite (SMPC-P) to 70.28 °C in SMPC-5 and 59.34 °C in SMPC-10. Incorporating 5 wt.% PEG enhanced storage and loss moduli, whereas excessive plasticization at 10 wt.% reduced stiffness. Infrared spectroscopy analysis revealed shifts and increased intensities in hydroxyl (OH), aliphatic C-H, and carbonyl (C=O) groups, indicating enhanced intermolecular interactions and bond formation. Tensile testing showed that the carbon–aramid filler significantly improved tensile strength and stiffness, with SMPC-10 achieving the highest tensile strength (233.59 MPa) and SMPC-5 the highest Young’s modulus (14.081 GPa). These results highlight the complementary role of carbon–aramid reinforcement and PEG plasticization in tuning thermomechanical behavior, providing baseline insights for designing SMPCs with tailored actuation and reliable structural performance. Full article

In this study, we report the synthesis of three new derivatives of betulinic acid, a pentacyclic triterpenoid known for its antitumor activity. These derivatives were synthesized via amide bond formation at the C-28 position using 3-[(Ethylimino)methylidene]amino-N,N-dimethylpropan-1-amine (EDC)/Hydroxybenzotriazole (HOBt) activation and various amines as nucleophiles. The synthesized compounds were characterized by nuclear magnetic resonance (NMR) techniques, including proton (¹H), carbon-13 (¹³C), COSY, HSQC, and DEPT, as well as ultraviolet–visible (UV-VIS) spectroscopy, Fourier-transform infrared (IR) and elemental analysis. This work highlights the potential of semi-synthetic modification of betulinic acid to enhance anticancer properties while addressing challenges in solubility and bioavailability. Further structural optimization and formulation studies are warranted to improve drug-like properties and therapeutic applicability. Full article

This work presents an innovative approach to enhancing the performance of concrete with reclaimed asphalt pavement (RAP) aggregates using titanium dioxide (TiO₂) nanoparticles. Traditional limestone coarse aggregates were partially replaced with 30% and 50% RAP aggregates; a subset of mixtures containing RAP aggregates was treated with TiO₂ nanoparticles. The rheological, mechanical, and long-term properties of concrete, along with changes in its chemical composition following the addition of RAP and TiO₂, were evaluated. Results revealed that using 30% and 50% RAP in concrete mixtures reduced their compressive strength by 18% and 27%, respectively. However, using TiO₂ in those mixtures enhanced their compressive strength by 8.7% and 6.3%. Moreover, concrete with 50% RAP exhibited an 85% increase in water absorption (the highest among all mixtures) compared to the control. TiO₂ treatment was most beneficial in the 30% RAP mixture, reducing its water absorption by 32.5% compared to its untreated counterpart. Additionally, the 30% RAP mixture treated with TiO₂ showed the highest resistance to sulfates among modified mixtures, as its compressive strength decreased by 10.4% compared to a decrease of 23% in the strength of the untreated 30% RAP mixture. Statistical analysis using single-factor ANOVA showed that integrating RAP aggregates with or without the presence of TiO₂ particles would significantly affect the concrete properties in terms of their population means. The t-test analysis, on the other hand, proved sufficient evidence that the mean values of the 30% RAP mixture treated with TiO₂ would not differ significantly from the control in terms of its slump and water absorption properties. The chemical structure analysis revealed an increase in the Si-O-Si and Si-O functional groups when using TiO₂ in RAP mixtures, suggesting improved hydration activity and accelerated C-S-H formation in the treated RAP mixtures. Moreover, distinct C-H peaks were witnessed in concrete with untreated RAP aggregates, resulting from the aged asphalt coating on the RAP, which weakened the bond between the RAP and the cementitious matrix. Full article

Crystal molecular structure of 3-(anthracen-2′-yl)-ortho-carborane was determined by single crystal X-ray diffraction study at 100 K. The asymmetric cell unit contains two enantiomeric pairs of molecules, in one of which the intramolecular dihydrogen bond CH...HB is formed with the participation of the C(1)H hydrogen of the anthracene substituent, and in the other with the participation of the C(3)H hydrogen. In all molecules, the polycyclic aromatic and carborane fragments are rotated relative to each other in such a way that the C-C bond of the ortho-carborane cage is approximately parallel to the plane of the aromatic substituent. According to quantum chemical calculations, the minimum energy corresponds to the formation of an intramolecular dihydrogen bond C(1)H...HB(4/7), whereas the C(3)H...HB(4/7) bond is formed rather as a result of intermolecular interactions in the crystal lattice. Full article