Search Results (2,694)

Methicillin-resistant Staphylococcus spp. are microorganisms found in dairy products, bovine mastitis, and human infections. The prevalence of resistant strains from this genus in the food chain is increasing, drawing attention to transmission in the community and highlighting the importance of One Health studies. Thus, the aim of this study was to determine the MIC of oxacillin (OXA) and the sanitizers benzalkonium chloride (BAC) and sodium hypochlorite (HP) against isolates of methicillin-resistant Staphylococcus spp., and to evaluate the possible influence of sub-MIC application of these compounds on bacterial cells, in order to observe possible microbial resistance. Ten isolates of methicillin-resistant Staphylococcus spp. (S. epidermidis and S. chromogenes) were used. Among the sanitizers, BAC showed greater efficiency during the pre-inhibition test. Increased resistance to OXA was found in isolates of S. chromogenes and S. epidermidis after sub-MICs of 50% and 90% of OXA, while sub-inhibition of HP favored resistance to OXA. The application of HP and OXA, even at low concentrations, induced a reduction in biofilm production. This study shows that sub-inhibitory sanitizer exposure in Staphylococcus spp. induces antimicrobial resistance phenotypes linked to mutations in regulatory, mobile, and DNA repair genes. These findings suggest that selective pressure promotes resistant variants through genomic plasticity and regulatory activation, supporting the hypothesis that sanitizer residues may drive multidrug resistance emergence, although further functional validation is required. Full article

The rise in the number of cancer cases and the dissemination of strains with multiple drug resistance in the world pose a serious threat to public health care and human well-being. The design and study of new chemotherapeutic agents for cancer and infectious diseases are hot topics in science. Hydrazones, a versatile and diverse class of chemical compounds, gained a lot of attention as a promising base for future drugs. In this paper, we report on the synthesis of eight new gold(III) complexes with hydrazones derived from pyridoxal-5′-phosphate and pyridoxal. The complexes are thoroughly characterized using IR, ¹H, ³¹P NMR, and mass spectroscopy. The cytotoxic effect of twelve various hydrazones derived from pyridoxal 5′-phosphate on both immortalized (HEK293T) and tumor (HCT116) human cell lines was estimated using the MTT assay. In addition, this contribution describes the antibacterial action of complexes of gold(III) and pyridoxal and pyridoxal 5′-phosphate-derived hydrazones, as well as the mixtures of the solutions containing tetrachloroaurate(III) and hydrazones, using the zone of inhibition test. Gold(III) complexes exhibit moderate antibacterial activity against both Gram-positive and Gram-negative bacteria, while free hydrazones show low cytotoxicity and thus could be considered relatively safe for humans. Full article

The combined use of macro-synthetic fibers and traditional steel reinforcement in structural concrete shows promise for enhancing shear behavior, particularly with respect to crack control, ductility, and potentially strength. However, experimental data on such systems remain scarce, especially for elements subjected to pure in-plane shear, where the interaction between fibers and conventional reinforcement is not well understood. This study contributes essential experimental evidence toward addressing this gap. Nine reinforced concrete panels were tested under monotonic in-plane shear, with transverse reinforcement ratios ranging from ρ_v = 0% to 0.91%, and macro-synthetic fiber contents from V_f = 0% to 0.52% by volume. Results showed that fibers were highly effective in reducing crack widths at low reinforcement levels. For specimens with ρ_v = 0.34%, increasing V_f from 0% to 0.52% halved the maximum crack width (from 0.6 mm to 0.3 mm) and reduced the average crack width by 22% (from 0.32 mm to 0.25 mm). Potential ductility improvements were also detected at low reinforcement ratios, with increased shear strain capacities observed as fiber content increased. In contrast, the influence of fibers on shear strength was minimal across all reinforcement levels. These findings highlight the potential of macro-synthetic fibers to enhance the performance of shear-critical elements, particularly in lightly reinforced systems, while also illustrating the need for further experimental and numerical work. The results presented here provide a fundamental dataset that can support future efforts to develop reliable assessment and design approaches accounting for the simultaneous presence of steel reinforcement and synthetic fibers in concrete elements subjected to shear. Full article

Temperature and strain rate play a crucial role in determining the mechanical properties of metals. These critical parameters are typically assessed using the split Hopkinson pressure bar (SHPB) test. However, previous studies have seldom considered the coupled influence of temperature and strain rate on dynamic mechanical behavior, thereby reducing the accuracy of constitutive models. To accurately characterize the dynamic mechanical behavior of 34CrNi3MoA low-alloy steel, a new constitutive model combining temperature and strain rate was developed. Firstly, SHPB experiments under varying temperatures and strain rates were designed to obtain actual stress–strain curves. The results indicate that the mechanical properties of 34CrNi3MoA low-alloy steel are significantly influenced by both temperature and strain rate. True stress has a significant temperature-softening effect within the temperature range of 25 °C to 600 °C, while the flow stress in the yield stage increases with rising strain rate. Secondly, a novel constitutive model was established by integrating a correction function. The model comprises three components: a strain rate-strengthening function influenced by temperature, a temperature-softening function influenced by strain rate, and a strain-hardening correction function accounting for the coupling of temperature and strain rate. Comparing the mean relative error, the new model significantly improves accuracy compared to the original Johnson–Cook (J-C) model. Full article

Potholes are typical scattered distresses on asphalt pavements, severely impairing traffic safety and pedestrian safety due to delayed repair time and secondary distress. Aiming to extend the service life of repaired potholes, this study develops a pothole repair technique characterized by repair materials with superior performance and adhesive materials with high bonding strength. Firstly, the mechanical analysis for repaired potholes was conducted via finite element simulation, and thereafter, corresponding technical measures were derived to prevent the recurrence of distress in repaired potholes. Secondly, according to the material composition of solvent-based cold-mix asphalt (SCMA) and emulsified-based cold-mix asphalt (ECMA), pavement performance testing methods were proposed to test and evaluate their forming strength, high-temperature stability, low-temperature crack resistance, and water stability. On this basis, interlayer shear tests, pull-out tests, and field pothole repair cases with varying repair materials and adhesive materials were conducted, and the interfacial bonding strengths with the old pavement were then compared to optimize the pothole re-pair technique. The results showed that (1) increasing the repair material modulus and interfacial friction coefficient reduces the pressure strain (σ_y) and pressure stress (ε_y), thereby decreasing the risk of secondary dis-tress; (2) ECMA exhibits superior pavement performance, with strength and rutting resistance 49.7%–64.6% higher than SCMA; (3) the combination of ECMA and WER-EA achieves the highest interfacial pull-out and shear strengths, with their values 76.7%–78.2% higher than SCMA+WER-EA); and (4) after 1 year of opening to traffic, potholes repaired with ECMA+WER-EA show minimal thickness loss of 0.2 cm and no aggregate peeling at the edges, thus being recommended as the optimal solution for repairing potholes. This study clarifies the secondary distress mechanism of repaired potholes and provides an optimal repair scheme (ECMA+WER-EA) for engineering applications. Full article

Some common conductive polymers are polyfuran, polyacetylene, polythiophene, and poly-pyrrole. Since their discovery, many researchers have been exploring and evaluating their conductive and electronic properties. Various applications have been developed for conductive materials. Their biocompatibility offers a new alternative for studying and solving complex problems, such as cellular activity, or, more recently, for use as neural implants and as an alternative to spinal cord regenerative tissue. This is particularly true for the use of poly pyrrole. The main obstacle lies in estimating some of the mechanical properties, such as Young’s or shear modulus values for poly pyrrole, since these vary depending on the type of synthesis used. This article outlines a composite methodology for characterizing the elastic modulus according to ASTM D882 and the shear modulus according to E143 standards. It is specifically designed and applied for 3D composite samples involving PLA and PPy, where the PPy was processed by plasma oxidation. As a result, an increase of 360.11 MPa in the modulus of elasticity is observed on samples coated with poly pyrrole. The results are evaluated through a numerical test using COMSOL Multiphysics software 6.2 version, finding a similar behavior in the elastic zone, as indicated by the stress–strain diagram. The statistical analysis yields consistent data for tensile and shear results, with low to moderate variability. Full article

Liquids like water are not expected to produce a thermal change under shear strain or flow (away from extreme conditions). In this study, we reveal experimental conditions for which the conventional athermal hydrodynamic assumption is no longer valid. We highlight the establishment of non-equilibrium hot and cold thermal states occurring when a mesoscopic confined liquid is set in motion. Two stress situations are considered: low-frequency shear stress at large strain amplitude and microfluidic transport (pressure gradient). Two liquids are tested: water and glycerol at room temperature. In confined conditions (submillimeter scale), these liquids exhibit stress-induced thermal waves. We interpret the emergence of non-equilibrium temperatures as a consequence of the solicitation of the mesoscopic liquid elasticity. In analogy with elastic deformation, the mesoscopic volume decreases or increases slightly, which leads to a change in temperature (thermo-mechanical energy conversion). The energy acquired or released is converted to heat or cold, respectively. To account for these non-equilibrium temperatures, the mesoscopic flow is no longer considered as a complete dissipative process but as a way of propagating shear and thus compressive waves. This conclusion is consistent with recent theoretical developments showing that liquids propagate shear elastic waves at small scales. Full article

Poly(3-hydroxybutyrate), P3HB, is a biodegradable polymer produced and stored by different bacterial strains, including Ralstonia eutropha H16. P3HB was used to prepare biocompatible composites modified by nanocellulose. This study aimed to assess selected thermal, mechanical, and biological properties of the obtained nanobiocomposites. Thermal properties, as determined by differential scanning calorimetry measurements, were established. The crystallinity of nanocomposites and polymeric matrix was investigated using DSC analyses. The morphology of the nanocomposites was evaluated using scanning electron microscopy. The Food and Drug Administration and the European Medicines Agency confirmed the immunosafety of the tested nanocomposites and noted they had either no or very low levels of endotoxin contamination. Some mechanical properties of the investigated materials were also measured and are presented here. It was estimated that the addition of 1% by mass of nanocrystalline cellulose to P3HB causes the greatest improvement in the plasticization of the material, characterised by the best processing and utility properties. The processing window of nanobiocomposites was extended by approximately 25 °C in reference to the unfilled poly(3-hydroxybutyrate). Mechanical and thermal tests revealed that the most desirable properties oscillate around the addition of 0.5% and 1% nanocrystalline cellulose by mass in the nanobiocomposites. Biological studies on implant applications have shown that the addition of only 0.5% nanofiller to a nanobiocomposite can be of key importance. Full article

The HIV-1 epidemic continues to challenge global public health, especially in sub-Saharan Africa. The rise in drug-resistant viruses, particularly pan-resistant strains, threatens treatment effectiveness, hindering progress toward UNAIDS viral suppression goals. This is critical in low-to-middle income countries (LMICs) like Zimbabwe, where treatment options and access to drug resistance testing are limited. This cross-sectional study analyzed 102 genotypes from patients with HIV-1 RNA ≥ 1000 copies/mL after at least 6 months on a dolutegravir (DTG)-based ART. HIV-1 genotyping and drug resistance interpretation were performed using the Stanford HIV Drug Resistance Database. Overall, 62% of genotypes harbored at least one drug resistance mutation, with 27% showing integrase strand transfer inhibitor (INSTI)-associated mutations. High-level resistance to DTG and cabotegravir was found in 14% and 23% of integrase sequences, respectively, primarily driven by G118R and E138K/T mutations. Pan-resistance was observed in 18% of complete genotypes, with one case of four class resistance. These results highlight the emergence of INSTI resistance in LMICs. The study underscores the urgent need for enhanced HIV drug resistance testing, continuous surveillance, and strategic optimization of ART regimens in resource-constrained settings to ensure effective HIV management. Full article

African horse sickness (AHS) is an arthropod-borne, severe equid disease caused by African horse sickness virus (AHSV). AHSV has high mortality and is endemic to sub-Saharan Africa. It has been classified into nine distinct serotypes (AHSV-1 to AHSV-9) based on VP2 immunogenicity. The AHS outbreak in Thailand in 2020, caused by AHSV-1, marked the first occurrence of this disease in Southeast Asia. It posed a substantial threat to the security of the equine industry in the nations across the region. To ensure the emergency reserve for AHS prevention and control, the AHSV strain imported to China from abroad over 60 years ago was characterized in this study. The strain was passaged in mice and then blind-passaged in Vero cells. The plaque purification method was then used to purify the strain and obtain its cell-adapted version, named AHSV/C. Neutralization tests confirmed that the virus belongs to AHSV-1. Whole-genome sequencing revealed that AHSV/C was highly homologous to AHSV-1 isolate 1180, with over 95% homology of major antigenic protein VP2, as compared to other AHSV-1 strains, including the prevalent strain in Thailand. In the mouse models, AHSV/C exhibited no clinical signs or histopathological lesions, suggesting low virulence and safety. This research for the first time characterized the in vitro growth characteristics and viral subtypes of the AHSV in China, determined its complete whole-genome sequence, and evaluated its safety using a mouse model. It provides crucial experimental materials and scientific foundations for the development of diagnostic methods and vaccines against AHSV-1. Full article

Ceratitis capitata (Wiedemann) or medfly is a polyphagous pest of fruit crops worldwide. The Asian-native larval parasitoid Diachasmimorpha longicaudata (Ashmead) is mass-reared at the San Juan Biofactory and is currently released for medfly control in Argentina. Information on parasitoid survival, reproduction, and population growth parameters is critical for optimizing the mass-rearing process and successfully achieving large-scale release. This study provides a first-time insight into the demography of two population lines of D. longicaudata: one mass-reared on medfly larvae of the Vienna-8 temperature-sensitive lethal genetic sexing strain and the other on larvae of the wild biparental medfly strain. The aim was to compare both parasitoid populations to improve mass-rearing quality and to assess performance on medfly in a semi-arid environment, typical of Argentina’s central-western fruit-growing region. Tests were performed under laboratory and non-controlled environmental conditions in semi-field cages during three seasons. Dl_(Cc-bip) females exhibited higher reproductive potential than did Dl_(Cc-tsl) females under lab conditions. However, both Dl_(Cc-bip) and Dl_(Cc-tsl) were found to be similar high-quality females with high population growth rates in warm–temperate seasons, i.e., late spring and summer. Dl_(Cc-bip) females were only able to sustain low reproductive rates in early autumn, a colder season. These results are useful for improving the parasitoid mass production at the San Juan Biofactory and redesigning parasitoid release schedules in Argentina’s irrigated, semi-arid, fruit-growing regions. Full article

Background/Objectives: Malaria remains the most critical parasitic disease globally, responsible for over 600.000 deaths annually. In sub-Saharan Africa, co-infections of Plasmodium falciparum with other pathogens, particularly Staphylococcus aureus, are common in children with severe malaria. Therefore, the design of new compounds targeting both pathogens appears to be an urgent priority. Methods: A small series of hybrid compounds was designed and synthesized by linking the pharmacophore of the antimalarial drug chloroquine with the phenothiazine core. These compounds were tested in vitro against a panel of microbial strains and further analyzed through in silico simulations to predict their physical-chemical properties. Results: Compounds 4b and 5b emerged the most potent candidates of the series, showing a sub-micromolar inhibitory activity on P. falciparum, and a promising micromolar potency on S. aureus alongside with a low toxicity on mammalian cells. Molecular docking followed by molecular dynamics (MD) simulations identified the respiratory membrane NDH-2 enzyme as common target in both pathogens. Conclusions: Both experimental and computational findings provide compelling evidence for the use of the designed compounds in a STOP strategy, i.e., Same-Target-Other-Pathogen, to treat malaria and bacterial infections concurrently. Full article

Isothermal hot compression tests were performed on an Al-4.8Cu-0.25Mg-0.32Mn-0.17Si alloy using a Gleeble-3500 thermomechanical simulator within the temperature range of 350–510 °C and strain rate range of 0.001–10 s⁻¹, achieving a true strain of 0.9. The constitutive equation and hot processing maps were established to predict the flow behavior of the alloy. The hot deformation mechanisms were investigated through microstructural characterization using inverse pole figure (IPF), grain boundary (GB), and grain orientation spread (GOS) analysis. The results demonstrate that both dynamic recovery (DRV) and dynamic recrystallization (DRX) occur during hot deformation. At high lnZ values (high strain rates and low deformation temperatures), discontinuous dynamic recrystallization (DDRX) dominates. Under middle lnZ conditions (low strain rate or high deformation temperature), both continuous dynamic recrystallization (CDRX) and DDRX are the primary mechanisms. Conversely, at low lnZ values (low strain rates and high temperatures), CDRX and geometric dynamic recrystallization (GDRX) become predominant. The DRX process in the Al-Cu-Mg alloy is controlled by the deformation temperature and strain rate. Full article

Wellbore stability is a crucial factor affecting the safe exploitation of offshore natural gas hydrates. As a sustainable energy source, natural gas hydrate has significant reserves, high energy density, and low environmental impact, making it an important candidate for alternative energy. Although research on the stability of screen pipes during horizontal-well hydrate production is currently limited, its importance in sustainable energy extraction is growing. This study therefore considers the effects of hydrate phase change, gas–water seepage, energy and mass exchange, reservoir deformation, and screen pipe influence and develops a coupled thermal–fluid–solid–chemical field model for horizontal-well natural gas hydrate production. The model results were validated using experimental data and standard test cases from the literature. The results obtained by applying this model in COMSOL Multiphysics 6.1 showed that the errors in all simulations were less than 2%, with errors of 12% and 6% observed at effective stresses of 0.5 MPa and 3 MPa, respectively. The simulation results indicate that the presence of the screen pipe in the hydrate reservoir exerts little effect on the decomposition of gas hydrates, but it effectively mitigates stress concentration in the near-wellbore region, redistributing the effective stress and significantly reducing the instability risk of the hydrate reservoir. Furthermore, the distribution of mechanical parameters around the screen pipe is uneven, with maximum values of equivalent Mises stress, volumetric strain, and displacement generally occurring on the inner side of the screen pipe in the horizontal crustal stress direction, making plastic instability most likely to occur in this area. With other basic parameters held constant, the maximum equivalent Mises stress and the instability area within the screen increase with the rise in the production pressure drop and wellbore size, and the decrease in screen pipe thickness. The results of this study lay the foundation for wellbore instability control in the production of offshore natural gas hydrates via depressurization. The study provides new insights into sustainable energy extraction, as improving wellbore stability during the extraction process can enhance resource utilization, reduce environmental impact, and promote sustainable development in energy exploitation. Full article

Cracking is a critical distress that reduces an asphalt pavement’s service life, and fiber reinforcement is an effective strategy to enhance anti-cracking capacity. However, the effects of fiber type, morphology, and length on key cracking modes remain insufficiently understood, limiting rational fiber selection in practice. This study systematically evaluated the influence of four representative fiber types on the anti-cracking performance of Stone Mastic Asphalt (SMA) mixture, combining mechanical testing and microstructural analysis. The fibers included lignin fiber (LF); polyester fiber (PF); chopped basalt fiber (CBF) with lengths of 3 mm, 6 mm, 9 mm; and flocculent basalt fiber (FBF). Key mechanical tests assessed specific cracking behaviors: three-point bending (low-temperature cracking), indirect tensile (tensile cracking), pre-cracked semi-circular bending (crack propagation), overlay (reflective cracking), and four-point bending (fatigue resistance) tests. A scanning electron microscopy (SEM) test characterized fiber morphology and fiber–asphalt interface interactions, revealing microstructural mechanisms underlying performance improvements. The results showed that all fibers improved anti-cracking performance, but their efficacy varied with fiber type, appearance, and length. PF exhibited the best low-temperature cracking resistance, with a 26.8% increase in bending strength and a 16.6% increase in maximum bending strain. For tensile and crack propagation resistance, 6 mm CBF and FBF outperformed the other fibers, with fracture energy increases of up to 53.2% (6 mm CBF) and CT_index improvements of 72.8% (FBF). FBF optimized reflective cracking resistance, increasing the loading cycles by 48.0%, while 6 mm CBF achieved the most significant fatigue life improvement (36.9%) by balancing rigidity and deformation. Additionally, SEM analysis confirmed that effective fiber dispersion and strong fiber–asphalt bonding were critical for enhancing stress transfer and inhibiting crack initiation/propagation. These findings provide quantitative insights into the relationship between fiber characteristics (type, morphology, length) and anti-cracking performance, offering practical guidance for rational fiber selection to improve pavement durability. Full article