Search Results (661)

The G-function can obtain the formation ground stress information by identifying the fracture closure point after fracturing, but the main fracture closure period of the deep coal seam volume fracture network is long, and the on-site pump stop time is short, and only the branch fracture closure can be observed. In order to explore the relationship between the closure pressure of branch fractures and the horizontal in situ stress, taking the deep coal seam in Daning–Jixian area as the background, the numerical simulation of the pump-stopping pressure drop of a complex fracture network with different complexity and different approximation angles was carried out using a finite element method, and the relationship between the closure pressure corresponding to the fracture closure point and the in situ stress was explored. The results show that when the crack approximation angle is greater than 60°, it can be approximately considered that the closure pressure of the first crack closure point tends to the maximum horizontal in situ stress. Furthermore, the minimum horizontal in situ stress can be obtained by formula conversion. The above-outlined method is applied to the in situ stress prediction of the X well area in Daning–Jixian County. The calculation results are compared with the test fracturing results, and the relative difference is within 5%, which shows that it has good accuracy and feasibility. The research results can provide guidance for the optimization of deep coalbed methane scheme design. Full article

As global demand for renewable energy continues to grow, high-altitude wind energy, characterized by high speed, wide distribution, and strong stability, has emerged as a promising alternative to low-altitude wind energy. Airborne Wind Energy systems (AWEs) are key to harnessing high-altitude wind, and Ground-Generator (Ground-Gen) AWEs are favored for their lower costs and simpler deployment. This study focuses on the umbrella–ladder-type Ground-Gen AWEs, aiming to address the research gap by exploring the influence of canopy permeability on the aerodynamic and structural response characteristics of flexible wind-capturing umbrellas. A single-umbrella model of the high-altitude wind-capturing umbrella was established, and bidirectional fluid–structure interaction (FSI) numerical simulations were conducted using the Arbitrary Lagrangian–Eulerian (ALE) method. Simulations were performed under a 30° angle of attack with two canopy thicknesses (5 × 10⁻⁵ m and 1 × 10⁻⁴ m) and varying permeability (adjusted via viscosity coefficient a and inertial coefficient b). Results showed that higher permeability (smaller a and b) hindered upper canopy inflation, while lower permeability promoted full inflation and more uniform stress distribution. The max/min in-plane shear stress for the model with the lowest permeability (Model F) was approximately 85% lower than that of the model with the highest permeability (Model A). The tension coefficient increased with decreasing permeability. Full inflation resulted in a slightly higher axial load in the upper suspension lines due to the lift force, with a difference of up to 92.3% during slight collapse. This difference becomes significantly more pronounced during severe collapse. Asymmetric flow fields at a 30° attack angle generated a lift force, resulting in higher tension coefficients than those at a 0° attack angle. These findings provide valuable references for the design and optimization of high-altitude wind-capturing umbrellas. Full article

Distinct differences exist between utility tunnels with an irregular cross section and those with a conventional rectangular cross section in terms of construction processes and structural mechanical characteristics. Therefore, based on an ultra-long underground utility tunnel project in China, this study employs the numerical analysis software ABAQUS 2016 to conduct an in-depth investigation into the construction process and mechanical behavior of an irregular cross-section tunnel subjected to fault dislocation activity. The analytical results indicate that utility tunnels with different cross-sectional types exhibit identical failure characteristics when intersected by a ground fissure. Specifically, as the fault dislocation magnitude increases, surface settlement continuously intensifies. The tunnel segment located on the hanging wall undergoes significant settlement deformation, whereas the segment on the footwall remains relatively stable. The tunnel as a whole demonstrates “bending deformation,” which is particularly pronounced at the location of the ground fissure. However, under oblique intersection conditions, the irregular cross-section tunnel generates greater tensile stresses than those generated in orthogonal intersection scenarios. Notably, relatively high tensile stresses concentrate at the junction between the main chamber and the auxiliary chamber. Consequently, segmentation and joint installation measures must be implemented in this area during the structural design phase, and targeted monitoring and reinforcement are essential during construction. Full article

This study examines the role of psychological factors on Greek K-12 teachers’ perceptions of the European Union (EU) and their readiness to integrate EU-related content into class-room practice. Grounded in self-determination theory and burnout literature, it focuses on the role of personality traits, psychological needs, self-efficacy, and mental health. A sample of 171 teachers (M_age = 47.67, SD = 8.61) completed validated instruments assessing EU perceptions, Big Five traits, psychological need satisfaction and frustration, well-being, self-efficacy, and symptoms of depression, anxiety, stress, and burnout. Confirmatory factor analysis supported the factorial validity of the instruments, along with proper indices for assessing their internal consistency. Cluster analysis identified three distinct teacher profiles: Skeptically Exhausted, Realistically Cautious, and Optimistically Engaged. These groups differed significantly in burnout, self-efficacy, and openness to EU programs. Teachers with high well-being and self-efficacy demonstrated stronger readiness to adopt EU-related pedagogy, while those experiencing elevated burnout reported low institutional trust and limited involvement. These findings highlight the psychological heterogeneity of the teaching workforce and suggest that differentiated, context-sensitive policy interventions are essential for fostering inclusive readiness for European initiatives. Enhancing teacher well-being and strengthening professional development pathways may serve as strategic entry points for promoting meaningful and sustainable EU integration in school curricula. Full article

Shallow-buried, closely spaced tunnels under bias loading often encounter stability challenges due to excavation-induced interaction effects. These effects are particularly significant in the middle rock pillar zone. To evaluate the influence of face lag distance on tunnel stability, the Georgia No. 1 Tunnel was selected as a case study. Numerical simulations and field monitoring were combined to analyze the deformation and stress evolution under different face lag distances. The analysis focused on ground surface settlement, vault displacement, and tunnel clearance convergence. The results indicate that ground surface settlement decreases notably as the face lag distance increases. When the face lag distance increased from 0.5 D to 2.0 D, the maximum settlement decreased by about 11.9%, with the absolute maximum measured value of approximately 3.48 mm. Stress concentration occurred mainly within 15 m behind the excavation face, suggesting that a face lag distance exceeding this range can effectively mitigate tunnel interaction effects. The biased tunnel side experienced greater vault settlement and convergence, requiring closer monitoring. An insufficient face lag distance amplifies deformation superposition, whereas an excessive one causes additional horizontal fluctuations. For the geological and structural conditions of the Georgia No. 1 Tunnel, a face lag distance of approximately 2.0 D provides an optimal balance between stability, safety, and construction efficiency. These findings offer practical guidance for the design and safe construction of shallow-buried twin tunnels under bias loading. Full article

The evaluation of the fracturing effect of coalbed methane (CBM) wells is crucial for the efficient development of CBM reservoirs. Currently, studies focusing on the evaluation of the hydraulic fracture stimulation effect of coal seams and the integrated analysis of “drilling-fracturing-monitoring” are relatively insufficient. Therefore, this paper takes three drainage and production wells in the coalbed methane block on the northwest wing of the Xiangxia anticline in the Bijie Experimental Zone of Guizhou Province as the research objects. In view of the complex geological characteristics of this area, such as multiple and thin coal seams, high gas content, and high stress and low permeability, the paper systematically summarizes the results of drilling and fracturing engineering practices of the three drainage and production wells in the area, including the application of key technologies such as a two-stage wellbore structure and the “bentonite slurry + low-solid-phase polymer drilling fluid” system to ensure wellbore stability, low-solid-phase polymer drilling fluid for wellbore protection, and staged temporary plugging fracturing. On this basis, a study on microseismic signal acquisition and tomographic energy inversion based on a ground dense array was carried out, achieving four-dimensional dynamic imaging and quantitative interpretation of the fracturing fractures. The results show that the fracturing fractures of the three drainage and production wells all extend along the direction of the maximum horizontal principal stress, with azimuths concentrated between 88° and 91°, which is highly consistent with the results of the in situ stress calculation from the previous drilling engineering. The overall heterogeneity of the reservoir leads to the asymmetric distribution of fractures, with the transformation intensity on the east side generally higher than that on the west side, and the maximum stress deformation influence radius reaching 150 m. The overall transformation effect of each well is good, with the effective transformation volume ratio of fracturing all exceeding 75%, and most of the target coal seams are covered by the fracture network, significantly improving the fracture connectivity. From the perspective of the transformed planar area per unit fluid volume, although there are numerical differences among the three wells, they are all within the effective transformation range. This study shows that microseismic fracture monitoring technology can provide a key basis for the optimization of fracturing technology and the evaluation of the production increase effect, and offers a solution to the problem of evaluating the hydraulic fracture stimulation effect of coal seams. Full article

In this article, an ecological composite based on a neat polylactide with 50 and 75% degrees of coffee particles and eggshells as an infill and organic filler, was developed. It has been shown that the content of fillers used reduced the mechanical properties, increasing the possibility of environmental degradation and accelerating the biodegradation process. During the additive production of polylactide with 10% of coffee grounds as a filler, it was possible to reduce the additive manufacturing temperature, which reduced the process time, energy costs, carbon dioxide emissions and the amount of polymer that may affect the environment. The structure of polylactide enriched with hen eggshells is characterized by roan and irregular shapes, which can cause a high tendency to form a concentration of cracks in these areas. Based on the results obtained from the stress relaxation test, the Zener model was used to describe a creep model of the produced ecological composites. The polymer composition of coffee grounds and eggshells shows a tendency to creep faster than pure polylactide and with different degrees of infill. Voids reduce the strength of composite materials, which increases the creep potential of samples with incomplete degrees of infill. Full article

Long-term spaceflight induces multisystem stress, including cardiovascular deconditioning, skeletal muscle atrophy, immune suppression, and neuro-ocular syndromes. Current countermeasures reduce symptoms but cannot replicate the synergistic resilience needed for extended missions or critical illness. Hibernating animals, specifically brown bears (Ursus arctos), survive prolonged immobility, starvation, and bradycardia without resultant pathology. This review incorporates adaptations observed in bears and certain torpid species, including reversible insulin resistance, suppression of muscle atrophy genes MuRF1 and Atrogin-1, and maintenance of the heart despite seasonal production decline. The thirteen-lined ground squirrels (Ictidomys tridecemlineatus) maintain retinal structure and synaptic stability throughout torpor, avoiding neuro-ocular complications despite prolonged inactivity. Mechanisms span from RBM3-dependent synaptic maintenance, titin isoform remodeling under the control of RBM20, mTOR and FOXO pathway regulation, remodeled hydrogen sulfide metabolism, and microbiome-mediated nitrogen salvage. These adaptations are different from human adaptation to microgravity and disuse and offer translational candidates for synthetic torpor, probiotic engineering, neuroprotection, and protein-sparing therapy. Hibernators are not passive stress subjects; they perform coordinated anticipatory responses in multiple organs. Comparing these systems in large and small hibernators, we aim to uncover a biologically realistic path to human resilience. These findings guide a shift from reactive, pharmacological measures for preserving human health during space flight, intensive care, and extreme environments towards proactive, biologically initiated measures. Full article

Salinity is one of the major problems limiting plant growth, development, survival, yield, and quality. Climate change and increasing salinity levels force a concentration on sustainable production systems. Therefore, this study aimed to determine the effects of different doses of gibberellic acid (GA₃) (0, 150, and 300 mg/L) and salicylic acid (SA) (0, 0.25, and 0.50 mM) priming on some morphological and antioxidant enzyme activities of silage maize (Zea mays L.) seedlings exposed to salinity stress. Four different NaCl (0, 75, 150, and 225 mM) concentrations as salt stress and three different doses of both SA and GA₃ were investigated. The data obtained were subjected to analysis of variance according to a randomized complete block design using a factorial experimental design with four replications per treatment in 3 L pots. The results showed that GA₃ and SA priming had statistically significant effects on all investigated traits under different salt concentrations (except water content). Findings revealed that shoot, root, and leaf development, as well as antioxidant enzymes, were suppressed by salinity stress. The silage maize plant was statistically significantly affected starting from the lowest dose of 75 mM, depending on salt concentrations. Increasing salt concentrations negatively affected above-ground and below-ground parameters. However, SA and GA₃ treatments had positive impacts on all examined traits. SA and GA₃ priming treatments emerged as important strategies supporting root and shoot growth under saline conditions, thereby strengthening plant adaptation. The best results were obtained in groups exposed to 75 mM salt stress, where 300 mg/L GA3 was applied, and in groups without salt stress, where the same GA3 dose was applied. It was concluded that GA₃ priming treatments, in particular, were more effective than SA treatments, alleviating salt stress and positively contributing to plant development. Full article

US food regulatory agencies have adopted a preference for researchers and testing labs to use ‘acid-adapted challenge cultures’ when performing inoculated validation studies of food processes that involve acidic treatments to accustom the cultures to acidic pH so that they will not be easily affected during processing. We evaluated acid adaptation in regard to the processing of South African style air-dried beef, notably biltong and droëwors, using a mixture of five serovars of Salmonella as well as a unique serovar isolated from dried beef (Salmonella Typhimurium 1,4,[5],12:i:-). Acid adaptation was obtained by growing cultures in tryptic soy (TS) broth containing 1% glucose. Non-adapted cultures were obtained by growth in TS broth without glucose or in TS broth with 1% glucose but buffered with 0.2 M phosphate buffer. Processes included biltong (dried solid beef) and droëwors (ground, sausage-style). Each trial was performed twice and triplicate samples were examined at each sampling point (i.e., n = 6). Statistical analysis was applied using analysis of variance (ANOVA) or one-way repeated measures (RM-ANOVA) and the Holm–Sidak test for pairwise multiple comparisons to determine significant differences (p < 0.05). We observed that in all processes examined (eight trials), treatments using acid-adapted cultures were more sensitive to the biltong and droëwors processes, giving greater reductions (5.3-log reduction) than when non-adapted cultures were used (3.8-log reduction). Acid adaptation leads to stressed conditions in Salmonella resulting in sensitization to the multiple hurdles found in biltong and droëwors processing (acid/vinegar, salt, desiccation). Based on our data, the use of non-adapted Salmonella cultures to achieve desired challenge culture process lethality could result in more robust processing conditions and a greater level of safety in these products as intended by US regulatory guidance. Full article

Potato is an important crop in the world and is rich in various nutrients. Common tetraploid potato is not tolerant of low temperatures and frost. Low-temperature stress severely affects the growth above-ground and the yield underground in potato. The BBX genes play an important role in the plant response to low-temperature stress. However, the molecular mechanism underlying the potato StBBX genes involved in cold stress response remains unclear. In the present study, 30 StBBX genes were identified in potato and divided into five groups. A total of 10 motifs and 10 cis-acting elements were obtained in all BBX proteins. All StBBX genes contained light responsive elements in the promoter, of which nine StBBX genes harbored low-temperature responsive elements. In total, 15 pairs of StBBX genes were identified in duplicated genomic regions. The gene expression patterns of all StBBXs were assessed in different tissues by transcriptome data. The qRT-PCR analysis indicated that six StBBX genes were significantly induced in response to cold stress. Subcellular localization suggested that the StBBX17 protein was localized in the nucleus. Compared with wild type (WT), the cold tolerance in StBBX17 overexpression lines was dramatically increased. After cold treatment, the StBBX17 overexpression lines displayed a less injured area of leaves and lower electrolyte leakage compared with the WT plants, demonstrating StBBX17 positively regulated cold tolerances in potato. These results indicate that StBBX genes have important functions under cold stress, providing a theoretical reference for the breeding of cold-resistant potato. Full article

This study aimed to valorize Codium sp. and Osmundea sp. as functional ingredients for European seabass diets. For this purpose, triplicate groups of 25 fish (20.6 g) were fed, during 8 weeks, one of seven diets: the control (CTR), 5% of Codium and Osmundea ground (diets CO and OS, respectively), 5% of Codium and Osmundea ground and autoclaved (diets COA and OSA, respectively), and 0.5% of Codium and Osmundea polysaccharide extracts (diets COP and OSP, respectively). The same diets were used for a digestibility trial. Fish fed the CO diet presented lower growth and an apparent digestibility coefficient (ADC) for dry matter and protein compared to fish fed the CTR and OS diets. Diet COA counteracted these negative effects. No differences were observed in feed intake, feed efficiency, and lipid ADC. Antioxidant enzyme activities and distal intestine histomorphology, an indicator of gut health, were not affected. The expression of interleukin-1β and interleukin-6 increased in fish fed the COP diet. In conclusion, the processing methods counteracted the negative effects of raw Codium, enhancing its value as a dietary ingredient, while its polysaccharides showed immunomodulatory potential that could be valuable during stress or disease periods. These findings support the valorization of these algae for aquafeeds, with Osmundea being safely included at 5% without processing. Full article

The stability of the mine pillar is a key issue related to the safe mining underground. Reinforcing the mine pillar is an important method to improve its stability. To reveal the reinforcement effect and mechanism of concrete-encased mine pillars, laboratory tests and field engineering application studies were conducted. Four groups of tests were carried out considering different sample sizes, rock strengths, encasing material strengths, and encasing layer thicknesses. The results demonstrated that mortar-encased rock specimens exhibited significant improvements in peak stress and axial peak strain. The reinforcement effectiveness was inversely proportional to the specimen’s height-to-diameter ratio and rock strength, while directly proportional to the wrapping material strength and layer thickness. Orthogonal range analysis revealed the sensitivity ranking of influencing factors as follows: encasing thickness > specimen height-to-diameter ratio > encasing material strength > rock strength. After encasing, the failure mode transitioned from integral failure to fragmented failure, with encased specimens demonstrating enhanced energy absorption capacity and bearing capacity. Increasing encasing strength and thickness induced a tendency towards plastic deformation failure. The encased rock-specimen system can be regarded as a parallel composite structure of rock and mortar layer. This configuration not only increases the bearing capacity of the mortar layer but also significantly enhances the rock’s intrinsic bearing capacity through confining pressure provided by the encasing material, which grows substantially with improvements in encasing material strength and thickness. Field applications in mines demonstrated that concrete-encased reinforcement of key area pillars can effectively control overall ground pressure in mining operations. The research results of this paper indicated that the reinforcement of mine pillars by concrete wrapping can enhance the stability of mine pillars and provide a new idea for improving the safety of mines. Full article

Microgravity exposure during spaceflight has been linked to cognitive impairments, including deficits in attention, executive function, and spatial memory. Both space missions and ground-based analogs—such as head-down bed rest, dry immersion, and hindlimb unloading—consistently demonstrate that altered gravity disrupts brain structure and neural plasticity. Neuroimaging data reveal significant changes in brain morphology, functional connectivity, and cerebrospinal fluid dynamics. At the cellular level, simulated microgravity impairs synaptic plasticity, alters dendritic spine architecture, and compromises neurotransmitter release. These changes are accompanied by dysregulation of neuroendocrine signaling, decreased expression of neurotrophic factors, and activation of oxidative stress and neuroinflammatory pathways. Molecular and omics-level analyses further point to mitochondrial dysfunction and disruptions in key signaling cascades governing synaptic integrity, energy metabolism, and neuronal survival. Despite these advances, discrepancies across studies—due to differences in models, durations, and endpoints—limit mechanistic clarity and translational relevance. Human data remain scarce, emphasizing the need for standardized, longitudinal, and multimodal investigations. This review provides an integrated synthesis of current evidence on the cognitive and neurobiological effects of microgravity, spanning behavioral, structural, cellular, and molecular domains. By identifying consistent patterns and unresolved questions, we highlight critical targets for future research and the development of effective neuroprotective strategies for long-duration space missions. Full article

Maintaining physiologically controlled conditions during the transport of biological experiments remains a long-standing but under-addressed challenge in spaceflight operations. Pre-launch thermal or mechanical stress induce artefacts that compromise the interpretation of biological responses to space conditions. Existing transport systems are limited to basic heating of small sample containers and lack the capability to power and protect full experimental hardware during mission-critical phases. A modular transport incubator was developed and validated that combines active thermal regulation, battery-buffered power management, and mechanical protection in a compact, field-deployable platform. It enables autonomous environmental conditioning of complex biological payloads and continuous operation of integrated scientific instruments during ground-based transport and recovery. Validation included controlled experiments under sub-zero ambient temperatures, demonstrating rapid warm-up, stable thermal regulation, and uninterrupted autonomous performance. A steady-state finite difference thermal model was experimentally validated across 21 boundary conditions, enabling predictive power requirement estimation for mission planning. Field deployments during multiple MAPHEUS^® sounding rocket campaigns confirmed functional robustness under wind, snow, and airborne recovery scenarios. The system closes a critical infrastructure gap in spaceflight logistics. Its validated performance, modular architecture, and proven operational readiness establish it as an enabling platform for standardized, reproducible ground handling of biological payloads and experiment hardware. Full article