Search Results (253)

The aim of this work is to analyse the effectiveness of the medical use of the Cavitron Ultrasonic Surgical Aspirator (CUSA) in microsurgical treatment of Intramedullary Spinal Cord Tumors (IMSCTs), with a focus on the thermo-mechanical effects on neighbouring tissues to assess any potential damage. Indeed, CUSA emerges as an innovative solution, minimally invasive tumor excision technique, enabling controlled and focused operations. This study employs a Finite Element Analysis (FEA) to simulate the vibratory and thermal interactions occurring during CUSA application. A computational model of a vertebral column segment affected by an IMSCT was developed and analysed using ANSYS 2024 software. The simulations examined strain distribution, heat generation, and temperature propagation within the biological tissues. The FEA results demonstrate that the vibratory-induced strain remains highly localised to the application site, and thermal effects, though measurable, do not exceed the critical safety threshold of 46 °C established in the literature. These findings suggest that CUSA can be safely used within defined operational parameters, provided that energy settings and exposure times are carefully managed to mitigate excessive thermal accumulation. These conclusions contribute to the understanding of the thermo-mechanical interactions in ultrasonic tumour resection and aim to assist medical professionals in optimising surgical protocols. Full article

Abdominal fat necrosis is a dystrophic–necrotic process that is relatively common in dairy cows. It is determined by productive strain (excess fat in the diet), negative energy balance after calving, a lack of physical activity, vitamin E and selenium deficiency, etc. Lipomatous masses are predominantly located in the omentum and mesentery in cattle, potentially causing intestinal obstruction. We report on an outbreak of abdominal fat necrosis that affected 135 of 220 cows and heifers (61.36%); this involved massive fat accumulation in the uterine and salpingian ligaments and severe reproductive disorders (reducing fertility to 20% in cows and 10% in heifers) caused by a hyperenergetic diet (supplementation with saturated fats). A transrectal ultrasound examination of the genital apparatus—both in heifers and in cows in the puerperium—revealed a diffuse pathological hyperechogenicity of the cervical folds, suggesting lipid infiltration, proliferation of the endocervical folds and hyperechogenic lipogranulomas located paracervically or in the uterine ligaments. An ultrasound examination of the ovaries showed the presence of parasalpingial lipogranulomas on the mesovarium, with a uniformly pixelated greasy appearance, that altered the topography of the salpinx, leading to the impossibility of oocyte retrieval. At the histopathological examination, in addition to the necrosis of adipocytes and the subacute–chronic inflammation of the abdominal and retroperitoneal adipose tissue, lipid infiltration of the uterine walls was also observed in the uterine ligaments and lymph nodes. Additionally, lipid infiltration was observed in the wall of the uterine artery. All muscular-type branches of the ovarian artery exhibited subendothelial (subintimal) amyloid deposits, severely reducing their lumen and leading to ischaemia. Amyloidosis was secondary to the systemic inflammatory process triggered by lipid deposition and necrosis. Fertility returned to normal 45–60 days after the exclusion of fat supplements from the diet and their replacement with a vitamin–mineral supplement rich in antioxidants. Full article

This contribution compares various theories dealing with the assessment of dislocation density in metals subjected to different straining levels. The paper examines both substructure development and the evolution of dislocation densities in 1xxx, 5xxx, and 6xxx Al alloys. Barlat’s dislocation model, Kocks–Mecking–Estrin (K-M-E) theory, and Kubin–Estrin (K-E) type modeling approaches were analyzed. The dislocation model parameters were determined from the microindentation profiles for the rolled Al alloys. It was shown that a strong correlation exists between the K-E and K-M-E models, confirming their reliability in describing the relationship between strain, stress, and dislocation density. These numerical approaches effectively capture the evolution of dislocation density with strain, making them suitable for the analysis of the accumulation of stored energy during deformation. The development of substructure during straining was inferred from the microindentation experiments, and the resulting dependencies tended to align with the characteristic curve observed in various metals. Full article

In this study, we found that the deletion of the gene evfG in the type VI secretion system (T6SS) gene cluster significantly affected the motility of porcine extraintestinal pathogenic Escherichia coli (ExPEC) strain PCN033. Furthermore, the bacterial motility assay showed that ΔevfG mutants exhibited reduced motility compared to the parental strain. Transmission electron microscopy (TEM) showed a significant reduction in the number of flagella in the mutant ΔevfG when compared with PCN033. To further explore the reasons why the deletion of evfG affects the motility of PCN033, transcriptomic and metabolomic analyses were conducted. The omics analyses showed that 134 differentially accumulated metabolites and 2236 differentially expressed genes were identified between the mutant ΔevfG and the parental strain PCN033. The metabolome profile and functional annotation analyses indicated that the impaired motility of ΔevfG was connected to the downregulation of the expression levels of genes associated with the energy metabolism pathway and flagellar assembly. Our study provides a new insight into the diminished PCN033 motility induced by evfG deletion. Moreover, the candidate genes and metabolites regulated by the gene evfG in the T6SS, which was involved in the motility of PCN033, were reported in this study. Full article

In the Direct Energy Deposition (DED) process, the deposited material experiences intricate thermo-mechanical processes. Subsequent thermal cycling can trigger Dynamic Recrystallization (DRX) under suitable conditions, with specific strain and temperature parameters facilitating grain refinement and homogenization. While prior research has examined the impact of thermal cycling in continuous wave (CW) lasers on DRX in 316 L stainless steel deposits, this study delves into the effects of pulsed wave (PW) laser thermal cycling on DRX. Here, the thermo-mechanical response to PW cyclic thermal loading is empirically assessed, and the evolution of microstructure, grain morphology, geometric dislocation density (GND), and misorientation map during PW DED of 316 L stainless steel is scrutinized. Findings reveal that DRX is activated between the 8th and 44th thermal cycles, with temperatures fluctuating in the range of 680 K–750 K–640 K and grains evolving within a 5.6%–6.2%–5.2% strain range. After 90 thermal cycles, the grain microstructure undergoes significant alteration. Throughout the thermal cycling, dynamic recovery (DRV) occurs, marked by sub-grain formation and low-angle grain boundaries (LAGBs). Continuous dynamic recrystallization (CDRX) accompanies discontinuous dynamic recrystallization (DDRX), with LAGBs progressively converting into high-angle grain boundaries (HAGBs). Elevated temperatures and accumulated strain drive dislocation movement and entanglement, augmenting GND. The study also probes the influence of frequency and duty cycle on grain microstructure, finding that low pulse frequency spurs CDRX, high pulse frequency favors DRV, and the duty cycle has minimal impact on grain microstructure under PW cyclic thermal load. Full article

p-coumaric acid (p-CA) is one of the main allelochemicals of cultivable Morchella mushrooms. However, its toxicity mechanism has not been elucidated. Therefore, we used physiological and comparative transcriptomic analyses to reveal its toxicity mechanism. The results suggest that the mycelial growth and sclerotial production of M. importuna were promoted under treatment with a low dosage of p-CA (10 μg/mL). The treatment induced moderate reactive oxygen species (ROS) accumulation, with an upregulation of genes associated with antioxidant regulation, energy supply and damage repair. In contrast, oxidative stress induced under treatment with a high dosage of p-CA (50 μg/mL) led to strain ageing. The contents of ROS were significantly increased, along with decreased peroxidase and catalase activity. Moreover, the genes associated with H₂O₂ synthesis were upregulated, while those responsible for H₂O₂ decomposition, non-enzymatic antioxidant components and damage repair were downregulated. Meanwhile, the carbohydrate and lipid metabolic pathways, and the signal transduction and cell division pathways, were impaired. Taken together, moderate stress induced under a low concentration of p-CA promotes the mycelial growth and sclerotial metamorphosis of M. importuna. This study provides new insights into the potential mechanisms of continuous cropping obstacles in the cultivation of morel mushrooms, which is of great importance for the practical aspects of mushroom cultivation. Full article

Studying the fatigue performance of metallic components and optimizing their design from the perspectives of structure, microstructure, and service conditions has long been a critical research focus. In this study, a comprehensive analysis was conducted on the sealing performance and fatigue behavior of W-shaped metallic sealing rings with varying microstructures. A novel simulation approach is proposed that replaces explicit gradient definitions with temperature conduction to address the issue of stress concentration at interfaces in the finite element modeling of gradient structures. Based on this method, a macroscopic finite element model was developed to simulate the plastic strain accumulation and springback of the sealing ring in service. Then, taking the stress evolution at the trough position of the sealing ring during service as a boundary condition, the evolution of stored-energy density and fatigue life of rings with different microstructures, including both homogeneous and gradient configurations, was quantitatively evaluated. The findings of this work provide valuable insights for the design of structural parameters and the optimization of forming process parameters in high-performance sealing-ring applications. Full article

Photosynthetic organisms such as cyanobacteria have the potential for the sustainable production of complex organic molecules due to their ability to use light as an energy source to fix CO₂ and assimilate inorganic nutrients. Over the past decade, large efforts have been put into the metabolic engineering of cyanobacteria to produce various compounds such as alcohols, isoprenoids, biopolymers, and recombinant proteins. Forskolin is a structurally complex labdane-type diterpenoid with eight chiral carbon atoms and is naturally produced in the root cork of the plant Plectranthus barbatus. Forskolin is a potent cAMP activator indicated as a pharmaceutical for a variety of diseases. In the plant, forskolin biosynthesis from geranylgeranyl diphosphate involves six enzymes: two terpene synthases, three cytochrome P450s, and a single acetyltransferase. In this work, we express all six biosynthetic genes from Plectranthus barbatus in Synechocystis sp. PCC. 6803 and demonstrate heterologous production of this complex diterpenoid in a phototroph cyanobacterium. Forskolin titers reached 25.0 ± 4.4 µg/L and the forskolin was entirely secreted into the media. The forskolin-producing Synechocystis strain and empty vector control were cultivated in a photobioreactor for 8 days. Both strains showed similar chlorophyll a contents, and the forskolin-producing strain reached a slightly higher OD₇₃₀ than the control. Forskolin began accumulating in the supernatant after 4 days and increased over time. These results indicate that forskolin production did not negatively impact cell growth. Full article

Fed-batch cultivation is a widely used strategy for microbial lipid production, offering flexibility in nutrient control and the potential for high lipid productivity. However, optimizing feeding strategies remains a complex challenge, as it depends on multiple factors, including strain-specific metabolism and process limitations. In this study, we developed a computational framework based on dynamic flux balance analysis and small-scale metabolic models to evaluate and optimize lipid production in Rhodosporidium toruloides strains. We proposed equations to estimate both the carbon and energy source mass feed rate ($F_{in}·s_r$) and its concentration in the feed ($s_r$) based on lipid accumulation targets, and defined minimum feeding flow rate ($F_{in}$) according to process duration. We then assessed the impact of these parameters on commonly used bioprocess metrics—lipid yield, titer, productivity, and intracellular accumulation—across wild-type and engineered strains. Our results showed that the selection of $F_{in}·s_r$ was strongly strain-dependent and significantly influenced strain performance. Moreover, for a given $F_{in}·s_r$, the specific values of $s_r$, and the resulting $F_{in}$, had distinct and non-equivalent effects on performance metrics. This methodology enables the rational pre-selection of feeding strategies and strains, improving resource efficiency and reducing the probability of failed experiments. Full article

This study systematically investigated two ecotypes of Ulva prolifera, the dominant species responsible for green tides in the Yellow Sea, classified as Subtype I (strain I08-1) and Subtype II (strain QD-7). Both subtypes produce positively phototactic biflagellate gametes with oval/pear-shaped morphology but exhibit distinct cellular dimensions. Subtype I gametes demonstrated significantly larger cell sizes, with long and short axes measuring 6.55 μm and 4.62 μm, respectively, compared to Subtype II’s dimensions of 6.46 μm (long axis) and 3.03 μm (short axis). Developmental analysis revealed striking morphological divergence at the 6-day germling stage: Subtype I attained an average length of 1301.14 μm, more than doubling Subtype II’s 562.25 μm. Superior growth kinetics were observed in Subtype I, exhibiting enhanced specific growth rates (SGRs) across multiple parameters—main stem length (8.58% vs. 3.55%), primary branch elongation (19.17% vs. 12.59%), main stem width expansion (17.29% vs. 5.00%), and biomass accumulation (41.90% vs. 40.96% fresh weight). Chlorophyll quantification confirmed significantly higher pigment content in Subtype I. Pre-co-culture photosynthetic profiling demonstrated Subtype I’s superior quantum efficiency (α = 0.077 vs. 0.045) with marked differences in regulated energy dissipation (YNPQ) and non-photochemical quenching (NPQ). Post-co-culture physiological adaptation was evident in Subtype II, showing significant elevation of non-regulated energy dissipation quantum yield (YNO) and eventual surpassing of maximum electron transport rate (ETRmax) compared to Subtype I. These findings establish that U. prolifera employs robust photoprotective and thermal adaptation strategies under natural photothermal conditions. Crucially, YNO-based analysis revealed Subtype II’s enhanced high-light protection mechanisms and superior adaptability to intense irradiance environments. This research elucidates ecotype-specific environmental adaptation mechanisms in U. prolifera, providing critical insights for optimizing green tide mitigation strategies and advancing ecological understanding of algal bloom dynamics. Full article

Ophiocordyceps sinensis is a medicinal fungus with significant nutritional and utilization value. Temperature is a crucial factor influencing its growth, as temperature changes can impact enzyme activity, metabolite content, and gene expression during fungal cultivation. Currently, there are limited reports on the effects of temperature on the quality of fungal fermentation. This study focuses on O. sinensis and conducts temperature stress culture experiments. The results indicate that the optimal culture temperature range is between 18 and 23 °C, with extreme temperatures negatively affecting the morphology, growth rate, sporulation, and antioxidant systems of the strains. Further metabolomic and transcriptomic analyses revealed that differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) were primarily enriched in four metabolic pathways: linoleic acid metabolism, arginine and proline metabolism, and lysine degradation. Many significantly enriched metabolites across various pathways appear to be predominantly regulated by ribosomal and RNA polymerase genes. Furthermore, we cultured O. sinensis mycelium at various temperatures and observed that a significant number of genes and metabolites associated with apoptosis and senescence were expressed at 28 °C. This led to cell damage, excessive energy consumption, and ultimately inhibited mycelial growth. In summary, this study elucidates the response mechanisms of O. sinensis to key metabolic pathways under different temperature growth conditions and explores factors contributing to strain degradation. Full article

Exhaust manifolds accumulate creep and fatigue damage under cyclic thermal loading, leading to localized failure. Understanding a material’s mechanical behavior is crucial for accurate life assessment. This study systematically investigated the low-cycle fatigue (LCF) and creep–fatigue interaction behaviors of medium-silicon molybdenum ductile iron. It was found that QTRSi4Mo exhibited cyclic hardening at room temperature and 400 °C, whereas it exhibited cyclic softening at 600 °C and 700 °C for low-cycle stress–strain responses. During creep–fatigue tests with hold time, variations in the strain amplitude did not alter the hysteresis loop shape or the hardening/softening characteristics of the material. They only induced a slight upward shift in the yield center. Additionally, stress relaxation primarily occurred in the initial phase of the hold period, so the hold duration had little effect on the final stress value. The investigation of creep–fatigue life models highlighted that accurately characterizing the damage induced by stress relaxation during the hold stage is critical for creep damage evaluation. The calculated creep damage results differed greatly from the experimental results of the time fraction model (TF). A combined approach using the strain energy density dissipation model (T-SEDE) and the Ostergren method demonstrated excellent predictive capability for creep–fatigue life. Full article

Aero-engine turbine vanes made from directionally solidified nickel-based superalloys often fail with crack formation from the external wall of cooling channels. Therefore, this study simulates the compressive load on the external wall of the vane and conducts a sequence of creep–fatigue evaluations at 980 °C to investigate the creep–fatigue damage mechanisms of a directionally solidified superalloy and to assess its life. It is found that at low strain ranges, creep damage is dominant, with creep cavities forming inside the specimen and fatigue sources mostly distributed in the specimen interior. As the strain range increases, the damage mechanism transitions from creep-dominated to creep–fatigue coupled damage, with cracks nucleating preferentially on the surface and exhibiting a characteristic of multiple fatigue sources. In the longitudinal (L) specimen, dislocations in multiple orientations of the {111}<110> slip system are activated simultaneously, interacting within the γ channels to form dislocation networks, and dislocations shear through the γ′ phase via antiphase boundary (APB) pairs. In the transverse (T) specimen, stacking intrinsic stacking faults (SISFs) accumulate within the limited {111}<112> slip systems, subsequently forming a dislocation slip band. The modified creep–fatigue life prediction model, incorporating strain energy dissipation and stress relaxation mechanisms, demonstrates an accurate fatigue life prediction under creep–fatigue coupling, with a prediction accuracy within an error band of 1.86 times. Full article

In nature, many brittle materials contain natural defects such as microcracks or joints, for example, rocks. Under water-saturated conditions, the strength of defective materials undergoes varying degrees of attenuation, leading to material failure and even structural instability in engineering contexts. Moreover, the deformation and failure of defective brittle materials are essentially the result of the accumulation and dissipation of energy. Studying the energy evolution of defective brittle materials under load is more conducive to reflecting the intrinsic characteristics of strength changes and overall failure of brittle materials under external loading. Natural defective brittle rock materials were firstly water saturated and triaxial compression tests were performed to determine the mechanical properties of water-saturated materials. The energy evolution patterns of water-saturated materials under varying confining pressures were also obtained. Using the discrete element method, the macro- and micro-failure characteristics of water-saturated materials were investigated, revealing the mesoscopic mechanisms of deformation and failure evolution in these materials. The results indicate that confining pressure significantly enhances the peak compressive strength and elastic modulus of water-saturated defective materials. When the confining pressure increased from 0 MPa to 20 MPa, the peak strength and elastic modulus of the water-saturated materials increased by 126.8% and 91.9%, respectively. Confining pressure restricts the radial deformation of water-saturated materials and dominates the failure mode. As confining pressure increases, the failure mode transitions from tensile splitting (at 0 MPa confining pressure) to shear failure (at confining pressures ≥ 10 MPa), with the failure plane angle gradually decreasing as confining pressure rises. Confining pressure significantly alters the energy storage–release mechanism of water-saturated defective brittle materials. At peak load, the total energy, elastic energy, and dissipated energy increased by 347%, 321%, and 1028%, respectively. The ratio of elastic energy storage to peak strain ratio shows a positive correlation, and the elastic storage ratio of water-saturated defective brittle materials under confining pressure is always higher than that without confining pressure. When the strain ratio exceeds 0.94, a negative correlation between confining pressure and the rate of elastic storage ratio is observed. From the perspective of mesoscopic fracture evolution in water-saturated defective brittle materials, the crack propagation path shifts from the periphery to the center of the material, and the fracture angle decreases linearly from 89° to 58° as confining pressure increases. The dominant direction of crack development is concentrated within the 45–135° range. The findings elucidate the mechanisms by which water saturation and confining pressure influence the strength degradation of natural defective brittle materials from both mesoscopic and energy perspectives, providing theoretical support for the stability control of related engineering structures. Full article

The instability and collapse of surrounding rock in mine goaf areas often lead to the destabilization of geological structures, surface subsidence, and mining safety accidents. To investigate the evolutionary mechanisms and precursor characteristics of rock instability and failure processes, uniaxial loading and cyclic loading–unloading tests were conducted on red sandstone using a rock mechanics loading system. These experiments aimed to explore the mechanical behavior of the rock and the development process of internal fractures. The characteristics of infrasonic signals generated during red sandstone fracturing and the laws governing damage evolution were analyzed with an infrasonic acquisition system. The research results indicate that the infrasonic signal activity generated by rock under loading conditions can be characterized by three distinct stages, namely the relative stability period, the active period, and the pre-failure precursor period. Prior to peak strength, a substantial number of infrasonic signals are generated in rocks with significant activity; this characteristic is independent of the loading path but dependent on the stress magnitude. The variation in cumulative infrasonic energy reflects the accumulation of damage in rock specimens during the loading process, and as damage accumulates, the stress–strain curve exhibits hysteresis effects and nonlinear increases, accompanied by a rapid rise in infrasonic energy. By analyzing the characteristics of infrasonic parameters and characterizing the damage and its evolutionary features in red sandstone based on infrasonic energy, the internal crack damage evolution process in rocks can be effectively characterized. This approach provides theoretical foundations and technical support for early warning and monitoring prior to rock failure. Full article