Search Results (16,472)

Background: Frailty is a multifactorial condition that significantly impacts older adults’ health and independence, which can be mitigated through training. This study examined the effects of a 12-week progressive strength training (PST) program on frailty status and short-term autonomic compensatory responses during postural transitions. Methods: Eight older adults (60–79 years) classified as pre-frail or frail according to the frailty index (FI) participated in a 12-week PST program. Time and frequency-domain heart rate variability (HRV) in the supine position, cardiac parasympathetic modulation (CPM) determined from the HR 30:15 ratio (longest RR interval around the 30th heartbeat divided by the shortest RR interval around the 15th heartbeat after standing), and cardiac baroreceptor gain (CBG) assessed as the ratio of heart rate change to systolic blood pressure drop (ΔHR/ΔSBP) at 30, 60, 180, and 420 s after standing were assessed at pre-test, 8 weeks and 12 weeks (autonomic function outcomes). Physical activity levels (PAL), handgrip strength (HGS), and gait speed (GS) were assessed, and orthostatic intolerance (OI) symptoms were self-reported at pre-test, 8 weeks, and 12 weeks. Results: After 12 weeks of PST, FI scores decreased from 0.18 to 0.04 (78% reduction). PAL, HGS, and GS improved by 152%, 13%, and 11%, respectively. Three of eight participants reported OI symptoms at pre-test, with no reported symptoms at week 12. Despite this, PST did not enhance short-term autonomic responses. Conclusions: PST counteracted frailty and improved physical and muscular function but did not enhance indices of short-term autonomic regulation in frail older people. Full article

Domestically developed wheat breeding plot combine harvesters in China currently utilize cyclone separation self-cleaning systems. However, these systems struggle to meet the agronomic requirement of zero wheat grain residue. Seed mixing caused by residual grains can compromise the accuracy of entire breeding field trials. This study focused on the structural design of a cyclone separation self-cleaning system based on high self-cleaning agronomic requirements. Research was conducted on the key structural and operational parameters of the cyclone separator and the negative-pressure centrifugal fan, preliminarily determining the ranges for critical parameters such as the diameter of the cylindrical section of the separator wall, the dust outlet diameter, and the rotational speed of the negative-pressure centrifugal fan. A test bench for the cyclone separation self-cleaning system of wheat breeding plot combine harvesters was designed and developed. Through single-factor experiments and Box–Behnken design optimization, the effects of key parameters on system performance were investigated. The optimal parameter combination—cylindrical section diameter of 614 mm, dust outlet diameter of 290 mm, and fan speed of 1495 r/min—achieved a self-cleaning rate of 100%, self-cleaning time ≤12 s, loss rate of 1.70%, and impurity rate of 0.16%, fully meeting the requirements for high-quality, rapid, and effective separation and self-cleaning operations. Full article

To reveal the cumulative damage mechanism of surrounding rock with initial damage under cyclic blasting loads during tunnel reconstruction and expansion, this study combines theoretical modeling, split Hopkinson pressure bar (SHPB) tests, and three-dimensional numerical simulation. First, based on the Z-W-T model framework, a dynamic damage constitutive model capable of uniformly describing the coupling effects of initial damage and dynamic disturbance is constructed by introducing a damage evolution equation based on the Weibull distribution and an initial damage variable D₀. Second, SHPB impact tests are conducted on sandstone specimens with different D₀ values under various strain rates to obtain their dynamic mechanical responses. The model parameters are calibrated and its validity is verified. Finally, the validated model is implemented in ABAQUS via a user material subroutine to establish a 3D finite element model of the tunnel reconstruction and expansion, and a numerical test with seven cyclic blasting events is performed. The results show that the dynamic compressive strength of the surrounding rock increases significantly with increasing strain rate, but D₀ has a clear weakening effect, which is amplified under high strain rates. Numerical simulation reveals that the damage in the surrounding rock accumulates nonlinearly with the number of blasts. The incremental expansion of the damage zone after the first blast is 1.51 m, decreasing to 0.03 m by the seventh blast, indicating a successively diminishing incremental expansion per blast. This reflects the saturation characteristics of damage accumulation and the diminishing driving effect of subsequent blasts due to energy dissipation and compaction within the already-damaged zone. The study provides key theoretical and analytical tools for evaluating the long-term stability of surrounding rock with initial damage under cyclic blasting. Full article

Microchannel liquid cooling technology, characterized by high heat-transfer efficiency, represents an effective solution for thermal management in high heat-flux density electronic devices. Existing research has mainly focused on optimizing the structural design of microchannel heat sinks, while neglecting the specific effects of inlet manifold configurations on their heat transfer and flow performance. To obtain more systematic data on microchannel heat transfer performance and internal velocity distribution, this study designed microchannels with single-inlet and triple-inlet configurations. A microchannel cooling performance testing platform was established, and visualization experiments of the internal flow field in straight microchannels were conducted using a particle image velocimetry (PIV) system. The velocity distribution uniformity and heat transfer performance were compared between single-inlet and triple-inlet microchannels with varying channel spacings. The results show that under the same flow conditions, the triple-inlet splitter structure yields a more uniform flow distribution, a lower peak temperature for the heat source chip, and improved heat transfer performance, with its pressure drop reduced to 11.1–26.6% of that of the single-inlet configuration. Furthermore, smaller channel spacings yield improved heat-transfer efficiency in microchannels. Full article

Titanium aluminide intermetallics have gained considerable attention as high-temperature structural materials for aerospace applications, but are susceptible to “titanium fire” under extreme service conditions. The role of Al elements on the combustion behavior of titanium aluminide intermetallics remains not fully understood. Herein, the influence of Al content on the ignition critical condition and burning rate of Ti_1−xAl_x alloys was investigated by using promoted ignition combustion (PIC) tests under oxygen-enriched atmosphere. Results indicated that the critical oxygen pressure of Ti_1−xAl_x alloys increases from 0.11 MPa to 0.23 MPa, and the ignition temperature under oxygen pressure of 0.41 MPa increases from 1059.5 ± 4.8 K to 1120.4 ± 2.5 K as Al content increases from 20 at% to 70 at%. However, the combustion rate increases from 11.85 ± 0.13 mm·s⁻¹ to 14.05 ± 0.09 mm·s⁻¹ as Al content increases from 20 at% to 70 at%. Moreover, the activation energy for ignition increases from 105.44 kJ·mol⁻¹ to 153.04 kJ·mol⁻¹ as Al content increases from 20 at% to 70 at%. According to the microstructure analysis after combustion, the influence of Al content on the ignition activation energy and burning rate is attributed to multiple factors involving bonding energy, melting temperature, and heat release. Full article

Exercise stress testing remains one of the most widely used and cost-effective diagnostic tools in clinical cardiology. Beyond the traditional evaluation of induced ischemia, it provides valuable information on functional capacity, blood pressure response and arrhythmic behavior during exercise. In particular, the test plays a crucial role in assessing and interpreting exercise-induced arrhythmias, including tachyarrhythmias, such as premature ventricular beats (PVBs) and bradyarrhythmias, as well as corroborating the suspicion of some ion channel diseases. The usefulness of exercise testing is also highlighted in patients with devices, where it can help evaluate their function and exercise adaptation, as well as in specific conduction disorders, such as Wolff–Parkinson–White syndrome. This practical guide summarizes the key aspects of performing and interpreting the exercise stress test, focusing on hemodynamic and arrhythmic findings and their clinical implications, and includes several illustrative clinical cases. Full article

Polytetrafluoroethylene (PTFE) is attractive for high-frequency communications but adheres very poorly to other materials due to its very low surface energy. Conventionally, surface treatments of PTFE are used to increase the polarity of the PTFE surface and enable bonding to materials with increased surface free energy. However, surface treatments are difficult to scale, can damage surfaces, and often lack reproducibility. Therefore, developing a material that can make PTFE adhere well to other materials without surface treatment is highly desirable. In this study, we aimed to develop a new material with strong adhesion to PTFE. We synthesized three polymer gels from dodecyl acrylate (DA) and 2-(dimethylamino) ethyl acrylate (DMAE): the homopolymer gels PDEAE and PDA, and the copolymer gel P(DEAE-co-DA). The copolymer gel P(DEAE-co-DA) exhibited high pressure-sensitive adhesion to PTFE, recording the highest adhesive strength (F = 430.0 N/m) and the highest peel energy (G = 713.4 J/m²) compared to the homopolymer gels PDEAE and PDA. Mechanical testing showed PDEAE had the greatest strength and toughness, PDA balanced stiffness and extensibility, and P(DEAE-co-DA) was the most flexible and extensible. The P(DEAE-co-DA) with the smoothest surface (Sz ≈ 0.176 µm) showed the highest F and G, implying that surface roughness did not contribute significantly to the interfacial adhesion between the gels and the PTFE. Based on the surface free energy ${\sigma }_s$ and work of adhesion $W_a$ values, the adhesive strength to PTFE was predicted to be PDEAE > P(DEAE-co-DA) > PDA, but the measured G in peel tests contradicted this, indicating that the gels’ viscoelastic deformation and energy dissipation dominate the measured F and G. The frequency-dependent viscoelastic data and relaxation times τ and activation energies $E_a$ suggested optimal adhesion requires a balance of adhesion (mobility for energy dissipation (short τ, low $E_a$)) and sufficient cohesion (high G′). P(DEAE-co-DA) achieved this balance, explaining its high measured F and G. With precise control of polymer chain mobility, the adhesion of P(DEAE-co-DA) gels can likely be improved further. Future work will employ block copolymerization and monomer-ratio control to tune molecular motion and enhance adhesion to PTFE. Full article

Background/Objectives: This study investigated whether serum 25-hydroxyvitamin D (25(OH)D) modifies the association between meeting WHO aerobic physical activity guidelines and cardiometabolic risk clustering among rural older adults in South Korea. Methods: This cross-sectional study analyzed 2023 Korea National Health and Nutrition Examination Survey (KNHANES) data for rural-dwelling adults aged ≥65 years with complete data (n = 441). Cardiometabolic risk clustering (CMRC) was defined as the presence of ≥3 of five risk factors (abdominal obesity, elevated blood pressure, low HDL-cholesterol, elevated triglycerides, and hyperglycemia). Exposures were continuous serum 25-hydroxyvitamin D (25(OH)D) and adherence to the WHO aerobic physical activity guidelines (yes/no). Multivariable logistic regression models tested the 25(OH)D × physical activity interaction, adjusting for sex, age (≥75 vs. <75 years), education, household income, smoking status, alcohol use, and obesity (BMI ≥ 25 kg/m²). Conditional effects of physical activity were estimated at the 16th, 50th, and 84th percentiles of 25(OH)D. Results: A significant interaction between 25(OH)D and physical activity was observed (OR = 0.91, 95% CI: 0.85–0.97; p = 0.005). Physical activity was not associated with CMRC at low 25(OH)D (16th percentile, 17.08 ng/mL; OR = 1.64, 95% CI: 0.78–3.47), but it was associated with lower odds of CMRC at high 25(OH)D (84th percentile, 36.98 ng/mL; OR = 0.25, 95% CI: 0.10–0.62). Conclusions: Vitamin D status modified the association between aerobic physical activity and cardiometabolic risk clustering among rural older adults. Integrated prevention strategies addressing both physical activity and vitamin D insufficiency may be valuable in rural aging populations. Full article

During a vehicle’s approach to a stop, significant longitudinal impact and pitch oscillations occur due to the decrease in vehicle speed and the substantial nonlinearity of the electro-hydraulic braking (EHB) system. To balance comfort and control accuracy at the end of braking, this paper proposes a comfort braking control strategy based on deceleration evolution characteristics. This method utilizes the adjustable pressure characteristics of the EHB system to construct an adaptive PI (proportional-integral) controller based on fuzzy rules, achieving a smooth transition between normal braking and comfort braking without mode switching. Simultaneously, target deceleration planning is introduced to gradually reduce the vehicle’s deceleration during the approach to a stop. Simulation and real-vehicle test results show that at initial speeds of 36 km/h, 40 km/h, and 44 km/h, the longitudinal deceleration impact amplitude is reduced by approximately 3.8%, 16.7%, and 11.7%, respectively. At 4 s, the vehicle pitch angle is reduced by 3.4%, 3.4%, and 3.8%, respectively. Meanwhile, the average braking distance change is less than 0.05%, and the maximum braking distance change is less than 0.1%. The results demonstrate that this strategy effectively improves braking comfort during the vehicle’s start-stop phase without compromising braking performance. Full article

With the development of manufacturing towards stricter precision requirements and increasingly complex geometric shapes, dimensional accuracy has become a key factor affecting precision engineering components used in many industries. Effective cooling and lubrication methods have always been a meaningful way to improve the surface quality of cutting materials. Minimum-quantity lubrication technology mixes compressed air with cutting fluid, produces a spray at ambient temperature, and guides these droplets to the cutting area under the action of high-pressure air to promote penetration into the contact area between the tool, workpiece, and chip. Minimum-quantity lubrication can be used to increase cutting speed, cool workpieces, improve workpiece quality, and significantly reduce the pollution caused by cutting fluid to the environment. However, minimum-quantity lubrication technology still cannot meet the requirements of sustainable machining in cutting processes. A test device platform for milling 6030 aluminum alloy with minimal quantity lubrication was established, and different cooling methods were used to analyze the effect on surface roughness. The spindle speed n, feed rate f, and cutting depth a_p are selected as optimization variables, with surface roughness as the optimization objective. Single-factor experiments were conducted to determine the optimal range for these variables. Subsequently, a model was constructed using the response surface methodology and solved using Design-Expert software. The interaction effects of spindle speed, feed rate, and depth of cut on surface roughness were analyzed. Additionally, genetic algorithms were employed to optimize cutting process parameters for the best combination. The results demonstrated that by combining Response Surface Methodology (RSM)and genetic algorithms, when the spindle speed n was 2520 r/min, the feed rate f was 48 mm/min, and the depth of cut a_p was 0.08 mm, the actual surface roughness after milling reached 0.148 µm, representing a 74.57% reduction compared to the initial surface roughness. This research method provides a theoretical foundation and technical support for optimizing minimal quantity lubrication (MQL) cutting processes. Full article

Mg-Zn-Ca bulk metallic glasses (BMGs) have attracted significant attention in the field of biodegradable metallic biomaterials due to their desirable in vivo degradability and high strength. However, their relatively high brittleness limits further practical applications. In this work, porous Fe skeleton-reinforced Mg-Zn-Ca bulk metallic glass composites (BMGCs) were fabricated by pressure infiltration using porous Fe skeleton as the toughening phase and Mg₆₆Zn₃₀Ca₃Sr₁ alloy as the matrix. It was found that electroless copper plating improved the interfacial wettability between molten Mg and Fe, as well as the infiltration-forming capability of the BMGCs. Quasi-static compression tests showed that the BMGC exhibited a compressive strength of 500 MPa, a plastic strain of 0.2%, and a yield strength of 420 MPa, representing a significant improvement over the matrix BMG alloy. The fracture surface displayed a vein-like pattern, indicating a noticeable transition from brittle to ductile fracture behavior. Thus, the porous Fe skeleton-reinforced Mg-Zn-Ca BMGC shows promise as a potential biodegradable biomedical material. Moreover, the preparation route presented here offers a new perspective for developing degradable Mg-Zn-Ca-based BMGCs. Full article

Background: To evaluate the effects of preoperative topical ripasudil, a Rho-associated protein kinase (ROCK) inhibitor, on Schlemm’s canal (SC) morphology in patients with primary open-angle glaucoma (POAG). Methods: This study included 95 SC specimens obtained during trabeculectomy from 95 patients with POAG. Based on preoperative treatment, patients were divided into two groups: ripasudil (–) group (n = 68) receiving four topical medications [FP receptor agonist, β-blocker, carbonic anhydrase inhibitor (CAI), and α₂ agonist], and ripasudil (+) group (n = 27) receiving the same four medications plus ripasudil. SC morphology parameters were assessed in thrombomodulin (TBM)-stained sections, including length parameters [TBM-positive/negative and opened/closed SC lengths] and area parameters [TBM-positive/negative and opened SC areas]. Between-group comparisons were performed using unpaired t-tests, and multiple regression analysis was conducted to adjust for age, gender, preoperative intraocular pressure (IOP), and oral CAI use. Results: The ripasudil (+) group had significantly longer total SC length (TSC: 302.5 µm) than the ripasudil (–) group (273.0 µm, p = 0.023). Among area parameters, the ripasudil (+) group showed significantly larger opened SC area (OSC-A: 2689 µm² vs. 1881 µm², p = 0.008) and TBM-negative opened SC area (NOSC-A: 716 µm² vs. 305 µm², p = 0.001), whereas TBM-positive opened SC area (POSC-A) was not significantly different between groups (2001 µm² vs. 1575 µm², p = 0.096). After multivariate adjustment, ripasudil use remained significantly associated with longer TSC (p = 0.011) and larger OSC-A (p = 0.014) and NOSC-A (p = 0.001). Conclusions: Preoperative use of topical ripasudil was associated with preservation of SC lumen morphology, particularly in regions lacking SC endothelium. These findings provide a theoretical basis for therapeutic strategies employing ROCK inhibitors to maintain SC morphology and function. Full article

Impure rock salt is increasingly used as a host medium for underground hydrogen and compressed air energy storage in China; however, its permeability evolution under stress remains insufficiently constrained. This study presents a systematic experimental and modeling investigation of the permeability behavior of impure rock salt from the Pingdingshan (Henan) and Yunying (Hubei) salt mines. Nineteen cylindrical specimens were subjected to full-process triaxial permeability testing, including initial measurements, hydrostatic damage recovery, and staged deviatoric loading. A hydrostatic recovery stage (15 h at 40 MPa) was applied to reduce coring- and machining-induced micro-damage, resulting in a permeability reduction in one to three orders of magnitude. After recovery, the initial permeability decreases nonlinearly with increasing effective stress and converges to approximately 10⁻²¹ m² at stress levels corresponding to in situ burial depths. During deviatoric loading, permeability exhibits a two-stage response: a rapid increase associated with early damage and microcrack initiation, followed by saturation once the dilatant volumetric strain exceeds approximately 1–2%. Impurity content influences both the magnitude and evolution of permeability by modifying the initial pore structure and damage development; however, the response is non-monotonic and region-dependent due to differences in dominant impurity mineralogy. Based on the experimental results, a semi-theoretical permeability model incorporating effective stress, dilatant strain, and impurity content was developed. The model reproduces the observed permeability evolution under different confining pressures with good agreement, providing a practical framework for evaluating the hydraulic integrity of impure rock salt in underground energy storage applications. Full article

The paper presents the results of a study of linear wear of gas-flame and ion-plasma coatings of KNA-82 seals with an yttrium content of 0.5%, used in gas turbine engine assemblies, during physical modeling of their thermomechanical loading on small-sized samples. Tribotechnical tests were carried out in four stages, simulating the operating conditions of real gas turbine engines—from the first start-up with running-in of the coating cut-in areas to reaching a steady state with their service properties formed. The surface of the coatings was in contact with the ridges of triangular-shaped plates without heating (20 °C), at average heating (350–470 °C), after holding the samples at 1100 °C and average heating of 410–460 °C, and after grinding off the worn layer that had worn out after holding the samples at 1100 °C at average heating of 320–440 °C. Trends in the change in the linear ear of coatings and the formation of friction tracks caused by the uneven manifestation of the physical and mechanical properties of coatings, which are unevenly distributed throughout their body, were determined. It was found that both coatings tend to stabilize the wear process at certain mechanical pressures in the friction contact zone and only in the temperature range from 20 °C to 400 °C. These pressures range from 4 MPa to 6.7 MPa for gas-flame coatings and from 3 MPa to 4.2 MPa for ion-plasma coatings. It has been determined that within the depth range of 30–100 μm, the wear resistance (as assessed by linear wear) of ion-plasma coatings is higher than that of gas-flame coatings. This predetermines the fact that in the event of a catastrophic collision between the coatings and a blade, the geometry of the damage to the surface of the gas-flame coating will be greater than that of the ion-plasma coating. In the event of damage exceeding 75–100 μm in depth, both coatings become inoperable, since their wear characteristics are no longer maintained. This is indicated by a rapid decrease in their wear resistance under step loading. Moreover, the gas-flame coating is more prone to catastrophic failure than the ion-plasma coating. Full article

Background: Energy metabolism progressively deteriorates from a healthy state to non-alcoholic fatty liver disease (NAFLD), and circulating lipopolysaccharide (LPS) may contribute to this process. However, previous studies have analyzed healthy individuals and NAFLD patients together, leaving stage-specific associations unclear. Whether LPS and its surrogate marker, lipopolysaccharide-binding protein (LBP), show similar relationships during NAFLD development also remains unknown. This study evaluated the associations between plasma LPS and LBP concentrations with clinical parameters in healthy individuals and NAFLD patients. Methods: We conducted a cross-sectional study of 31 healthy individuals (median age [IQR]: 31 (26–43) years) and 31 NAFLD patients (59 (54–70) years). Plasma LPS and LBP concentrations and clinical parameters were measured. Correlations were assessed using Spearman’s rank analysis, followed by multivariate regression adjusting for age, sex, and BMI. Results: Plasma LPS and LBP concentrations were significantly higher in NAFLD patients compared to healthy individuals. Additionally, in the univariate regression analysis for all study participants, plasma LPS concentrations were correlated with obesity, blood pressure, liver function, lipid metabolism, and glucose metabolism. Plasma LBP concentrations were also correlated with age, obesity, blood pressure, liver function, lipid metabolism, glucose metabolism, and inflammatory cytokines. In healthy individuals, LPS correlated positively with triglycerides (TG), remaining significant after adjustment and exclusion of participants with any clinical test values outside the normal range. This association was not observed in NAFLD patients. Plasma LBP did not correlate with TG in either group; however, it was inversely associated with hepatic fat fraction in NAFLD patients, although this association was attenuated after adjusting for alanine aminotransferase. Conclusions: Plasma LPS correlates with TG even in clinically healthy individuals, suggesting LPS may influence lipid metabolism before NAFLD onset. Full article