Multidisciplinary Digital Publishing Institute (Switzerland)
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Research on Friction and Structural Optimization Design of Segmented Annular Seal
No full textAs a critical sealing component in aero-engines, the segmented annular seal is prone to friction and wear during the running-in stage, which seriously impairs its sealing performance and service life. To address this issue, this study takes the three-petal segmented annular seal made of T482 graphite as the research object, adopting a combined method of high-speed ring-block friction and wear tests and thermal–fluid–solid coupling simulation to investigate its friction and wear mechanisms and optimize its structural design. The results show that the segmented annular seal undergoes more severe friction and wear in the low-speed running-in stage; the wear rate increases with the rise in loading force and decreases with the increase in rotational speed, and the variation trend of surface roughness is consistent with that of the friction coefficient. Frictional heat and wear-induced scratches intensify the deformation and leakage of the seal, thereby leading to the risk of seal failure. Optimizing the depth of radial dynamic pressure grooves can significantly improve the opening performance of the seal, while optimizing the width of axial grooves mainly affects the seal leakage. This research provides a theoretical basis for improving the service life and sealing performance of segmented annular seals in aero-engines
Indoor UAV 3D Localization Using 5G CSI Fingerprinting
No full textFifth-generation (5G) wireless networks have been widely deployed across various applications, including indoor positioning. This paper presents a model for 3D indoor localization of an unmanned aerial vehicle (UAV) using 5G millimeter-wave technology. Wireless InSite software is used to simulate a real-world environment and extract channel state information from multiple 5G next-generation NodeBs (gNBs), which is then used to generate channel frequency response (CFR) images. These images are employed in a fingerprinting method, where a deep convolutional neural network is trained for accurate position prediction. The model is trained across multiple scenarios involving changes in the number of gNBs, receiver positions, and spacing. In all scenarios, the model is tested using a UAV flying along a trajectory at variable speed. It is shown that a mean positioning error (MPE) of 0.36 m in 2D and 0.43 m in 3D is achieved when twelve gNBs with receivers spaced at 0.25 m are used. In addition, the corresponding root mean square error (RMSE) values of 0.32 m (2D) and 0.33 m (3D) further confirm the stability of the localization performance by indicating a low dispersion of positioning errors. This demonstrates that high positioning accuracy is feasible, even when synchronization errors and hardware imperfections exist
Fatty Acids as Prebiotics and Their Role in Antibiofilm Activity
No full textMicrobial biofilms pose significant medical and industrial challenges due to their resistance to conventional antimicrobials, accounting for 40–80% of bacteria in various environments. This resistance primarily results from the extracellular polymeric matrix, a protective network of sugars, proteins, and other molecules produced by bacteria. The matrix restricts antibiotic penetration, facilitates microbial communication, and retains nutrients. Consequently, novel strategies to counteract biofilms are under investigation. Fatty acids have emerged as promising prebiotic agents, defined as substances that stimulate the growth of beneficial bacteria. These compounds can disrupt biofilm structure and increase microbial susceptibility to treatment. Short- and medium-chain fatty acids demonstrate direct antimicrobial activity and can alter microbial community composition, thereby inhibiting biofilm formation in several pathogens, including oral species. For instance, omega-3 fatty acids effectively inhibit Staphylococcus aureus and Pseudomonas aeruginosa biofilms through membrane disruption and quorum sensing (QS) inhibition. Additionally, long-chain fatty acids, particularly omega-3 and omega-6 polyunsaturated fatty acids, exhibit anti-inflammatory and antibacterial properties. This review synthesises current evidence on fatty acids as prebiotics, emphasising their mechanisms of action and therapeutic potential against drug-resistant biofilm-associated infections. Given the increasing prevalence of antimicrobial resistance, unsaturated and essential fatty acids rep-resent promising candidates for innovative biofilm-control strategies
Host-Filtered Blood Nucleic Acids for Pathogen Detection: Shared Background, Sparse Signal, and Methodological Limits
No full textPlasma cell-free RNA (cfRNA) metagenomics is increasingly explored for blood-based pathogen detection, but the structure of the shared background “blood microbiome”, the reproducibility of reported signals, and the practical limits of this approach remain unclear. We performed a critical re-analysis and benchmarking (“stress test”) of host-filtered blood RNA sequencing data from two cohorts: a bacteriologically confirmed tuberculosis (TB) cohort (n = 51) previously used only to derive host cfRNA signatures, and a coronary artery disease (CAD) cohort (n = 16) previously reported to show a CAD-shifted “blood microbiome” enriched for periodontal taxa. Both datasets were processed with a unified pipeline combining stringent human read removal and taxonomic profiling using the latest versions of specialized tools Kraken2 and MetaPhlAn4. Across both cohorts, only a minority of non-host reads were classifiable; under strict host filtering, classified non-host reads comprised 7.3% (5.0–12.0%) in CAD and 21.8% (5.4–31.5%) in TB, still representing only a small fraction of total cfRNA. Classified non-host communities were dominated by recurrent, low-abundance taxa from skin, oral, and environmental lineages, forming a largely shared, low-complexity background in both TB and CAD. Background-derived bacterial signatures showed only modest separation between disease and control groups, with wide intra-group variability. Mycobacterium tuberculosis-assigned reads were detectable in many TB-positive samples but accounted for ≤0.001% of total cfRNA and occurred at similar orders of magnitude in a subset of TB-negative samples, precluding robust discrimination. Phylogeny-aware visualization confirmed that visually “enriched” taxa in TB-positive plasma arose mainly from background-associated clades rather than a distinct pathogen-specific cluster. Collectively, these findings provide a quantitative benchmark of the background-dominated regime and practical limits of plasma cfRNA metagenomics for pathogen detection, highlighting that practical performance is constrained more by a shared, low-complexity background and sparse pathogen-derived fragments than by large disease-specific shifts, underscoring the need for transparent host filtering, explicit background modeling, and integration with targeted or orthogonal assays
Effects of Mixed Fruits and Berries on Ameliorating Gut Microbiota and Hepatic Alterations Induced by Cafeteria Diet
No full textBackground/Objectives: The study investigated the potential of mixed fruits and berries (MFB) as a dietary intervention to mitigate cafeteria (CAF) diet-induced gut microbiome dysbiosis and hepatic dysfunction associated with metabolic syndrome and steatohepatitis (MASH) in an adolescent rat model. Methods: Forty-eight adolescent male Sprague-Dawley rats (n = 3 cages per group (two rats per cage)) were divided into eight experimental groups, where NC received the normal AIN-93G basal diet, PC received the CAF diet and normal AIN-93G basal diet, T1 and T2 received MFB supplementation (3% and 6% levels) without CAF exposure, P1 and P2 received a MFB (3% and 6% levels) supplementation initiated at the onset of CAF feeding, and I1 and I2 received MFB supplementation initiated 2 weeks after CAF feeding. After 6 weeks, cecal 16S rRNA, hepatic histopathology, Oil Red O staining, and metabolic dysfunction-associated steatotic liver disease (MASLD)-related biomarkers (liver enzymes, alanine aminotransferase (ALT), and aspartate aminotransferase (AST)) were analyzed. Results: AST: ALT ratio was the highest in the PC group (3.63, p < 0.05) compared to the MFB groups. Oil Red O staining showed lower hepatic lipid accumulation, and histological analysis demonstrated a marked reduction in portal inflammatory cell infiltration in MFB. Alpha diversity (Simpson Index) decreased in PC (Kruskal–Wallis, p = 0.043). CAF increased Lactobacillus johnsonii (+75%, p < 0.05), while reducing L. murinus and L. intestinalis (~90%, p < 0.05). MFB supplementation restored Bifidobacterium Pseudolongum and increased Akkermansia muciniphila levels in the P2, I1, and I2 groups (~20-fold, p < 0.05). Bacteroides dorei was present in all groups except the PC group. These bacteria presented a positive correlation with key SCFAs. Conclusions: The results from this study indicated that MFB supplementation modulated gut microbiota composition and enhanced SCFA production, thereby strengthening intestinal barrier integrity and reducing gut-derived inflammation. Collectively, these effects attenuated hepatic lipid accumulation and inflammation, highlighting the potential of MFB to restore gut–liver axis homeostasis disrupted by CAF-induced dysbiosis in adolescent rats
Microbial Cell Factories for Phenylethanoid Glycosides: A Review on Engineering Strategies and Perspectives
No full textDue to the neuroprotective and antioxidant properties, phenylethanoid glycosides (PhGs) are valuable plant-derived compounds. Traditional extraction methods are constrained by low yields and limited resources, prompting the integration of synthetic biology and enzyme engineering technologies for sustainable production. This review summarizes the advances in the microbial synthesis of PhGs, emphasizing the elucidation of biosynthetic pathways, enzyme engineering modifications of glycosyltransferases and acyltransferases, and strategies for optimizing microbial cell factories in Escherichia coli and Saccharomyces cerevisiae. Significant advancements encompass the efficient synthesis of verbascoside and echinacoside in S. cerevisiae, as well as the comprehensive elucidation of the echinacoside biosynthetic pathway in Cistanche spp., including the identification of key steps catalyzed by a rhamnosyltransferase, a CYP450 hydroxylase, and a terminal glucosyltransferase that enable pathway reconstruction in S. cerevisiae. We conduct a systematic analysis of methods to address the biosynthetic bottlenecks via protein engineering, including rational design and directed evolution, as well as the metabolic engineering strategies such as precursor enhancement and cofactor recycling. Additionally, we investigate the synthesis of non-natural PhG analogues and the prospective integration with AI-assisted design, emphasizing the significant potential of microbial systems in overcoming the supply challenges for medicine-food homologous ingredients
Leptin, Interleukin 6, and Vascular Endothelial Growth Factor as Potential Predictors of Primary Hypertension in Children and Adolescents with Obesity
No full textThe increasing prevalence of obesity-related primary arterial hypertension (PAH) in the pediatric population emphasizes the need to develop new biomarkers that can aid in clinical practice for prevention or early diagnosis of the cardiovascular disease. The objective of the present study was to evaluate the relationship between selected adipokines, cytokines, and blood pressure (BP) values in children with obesity. A total of 78 children participated in the study: 60 children with obesity (study group) and 18 children with normal weight (control group). Blood pressure was measured according to guidelines. Serum levels of metabolic and inflammatory markers, including leptin, adiponectin, resistin, ghrelin, interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor α (TNF-α), vascular endothelial growth factor (VEGF), and insulin were determined using multiplex immunoassays. Statistical analysis included correlation and ROC tests to identify potential predictors of PAH. The study group had significantly higher systolic and diastolic BP compared to the control group (p < 0.0001). Serum levels of leptin, IL-6, VEGF, insulin, and resistin were increased in the study group. Leptin, IL-6 and resistin correlated positively with BP values (p < 0.05), while ghrelin and adiponectin correlated negatively. ROC analysis identified leptin, IL-6, and VEGF as the most promising biomarkers for predicting PAH. The results confirm the role of adipokines and cytokines in the pathogenesis of PAH. The assessment of adipokine and cytokine profiles complements traditional anthropometric parameters such as BMI in assessing cardiovascular risk. Leptin, IL-6, and VEGF presented the strongest correlation with hypertension, suggesting their potential in future diagnostic and preventive strategies
The Microstructure and Mechanical Properties of a Dissimilar Rotary Friction Welded TC4 Titanium Alloy to 304SS Stainless Steel with Inconel 718 Alloy Interlayer
No full textThis study investigates the microstructure and mechanical properties of a dissimilar joint formed by rotary friction welding, which joins TC4 titanium alloy to 304 stainless steel using an Inconel 718 interlayer. The welding parameters were as follows: a friction time of 9 s, a friction pressure of 160 MPa, an upset time of 2 s, a forging pressure of 250 MPa, and a rotational speed of 1400 rpm. Microstructural analysis revealed the formation of intermetallic compounds (IMCs), including Fe2Ti, Ni3Ti, NiCrFe, FeNi3, Ti2Ni, and FeNi, at the TC4/Inconel 718 interface, while Ni3Ti and FeNi3 IMCs were identified at the Inconel 718/304SS interface. The tensile tests demonstrated that the joint with the Inconel 718 interlayer (TC4/Inconel 718/304SS) achieved an ultimate tensile strength (UTS) of 717.73 MPa and an elongation of 13.05%. In contrast, the direct joint without the interlayer (TC4/304SS) exhibited a lower UTS of 631.58 MPa and a reduced elongation of 7.39%. Therefore, the introduction of the Inconel 718 interlayer significantly improved joint quality, increasing tensile strength by 13.64% and elongation by 76.59%. More importantly, the interlayer effectively inhibited the formation of brittle Ti-Fe intermetallic compounds, which are typically detrimental to joint performance
Preparation of Highly Active Mg-Al-Li-B Alloys via High-Temperature Sintering
No full textBoron is a promising fuel, but its oxide layer impedes combustion. Alloying boron with other high-energy metals can significantly enhance its combustion performance. In this study, we sintered highly reactive lithium-containing Mg-Al-Li-B alloys using magnesium, aluminum–lithium alloy, and boron powder as raw materials. The effects of sintering temperature and holding time on the microstructure were investigated, and the combustion heat value and oxidation resistance of the alloy were tested. Results indicate that sintering temperature significantly influences phase formation: increasing temperature boosts phase content while reducing metallic phases, with 1100 °C identified as the optimal sintering temperature. Holding time had no discernible impact on the phase composition or combustion heat value of the sintered alloy. Alloying enhances material density, thereby increasing volumetric heat value. Thermal oxidation performance tests demonstrate that Li addition significantly lowers the alloy’s oxidation reaction temperature and activation energy, enhancing its reactivity. This high-heat-value, highly reactive alloy holds significant potential for application in pyrotechnics and propellants
