Search Results (139)

Background: This study examined the impact of amnestic mild cognitive impairment (aMCI) on dynamic changes in cerebrocortical oxygen saturation (ScO₂) and O₂ extraction during acute, moderately intense, normobaric hypoxia and reoxygenation in elderly adults (71 ± 6 years old). Methods: Thirty-two aMCI and thirty-five control subjects participated. Inspired and expired fractions of O₂ and CO₂ (mass spectrometry), arterial O₂ saturation (SaO₂) and prefrontal ScO₂ (near-infrared spectroscopy), heart rate, tidal volume and breathing frequency were monitored while subjects breathed hypoxic air (fractional inspired O₂ 0.10) for 3–5 min (aMCI: 4.5 ± 0.7 min; control: 4.5 ± 0.6 min) and recovered on room air. Values at the pre-hypoxia baseline, the first and last min of hypoxia and the first min of recovery were compared within and between groups using two-factor ANOVA. Results: Despite a similar baseline SaO₂ in aMCI (97.2 ± 1.6%) and control (97.3 ± 1.3%) subjects, prefrontal ScO₂ was lower (p < 0.05) in the aMCI subjects in both the left (67.0 ± 1.7% vs. 69.6 ± 4.5%) and right (66.8 ± 4.6% vs. 69.4 ± 4.1%) hemispheres. Hypoxia similarly decreased SaO₂ and ScO₂ in both groups (last min hypoxia, aMCI vs. control subjects: SaO₂ 76.6 ± 5.3% vs. 77.4 ± 6.1%, left prefrontal ScO₂ 54.0 ± 4.9% vs. 55.2 ± 6.4%, right prefrontal ScO₂ 56.0 ± 4.3% vs. 58.2 ± 4.4%). Upon the resumption of room-air breathing, ScO₂ recovered at similar rates in aMCI and control subjects. Conclusions: Although it produced a greater deoxygenation in the left vs. the right prefrontal cortex, acute, normobaric, moderate hypoxia was well tolerated by elderly adults, even those with aMCI. Dynamic changes in cerebral oxygenation during hypoxia and recovery were unaltered by aMCI. Brief, moderate hypoxia does not impose more intense cerebrocortical oxygen depletion in elderly adults with aMCI, despite pre-hypoxic cerebrocortical oxygenation below that of their non-MCI counterparts. Full article

The article presents the results of research and development work conducted as part of the H2GEO project, aimed at creating a comprehensive technology for the processing of post-mining coal waste heaps. The core of the solution is a mobile density separation system based on a pulsating jig, enabling effective recovery of carbonaceous and mineral fractions. Laboratory experiments assessed the impact of key process parameters—such as sieve slot size, pulsation frequency, and enrichment time—on the efficiency and accuracy of separation for different grain size classes. The most favorable results were obtained using a 2.5 mm screen, a pulsation frequency of 60 min⁻¹, and extended enrichment time, which ensured high-quality separation and low ash content in the carbon-bearing product. The findings supported the design of a new industrial separator (jig) equipped with advanced control systems, facilitating the production of homogeneous fractions suitable for further processing into hydrogen, geopolymers, and construction materials. The proposed solution aligns with circular economy principles, promoting waste reuse, environmental hazard mitigation, and the revitalization of degraded post-industrial areas. Full article

This paper discusses the efficiency of ultrasonic-assisted bitumen extraction from bituminous sands of the Beke deposit (Mangistau region, Kazakhstan) using alkaline aqueous solutions. The process parameters, including ultrasonic frequency (22 kHz), power (up to 1500 W), solution pH (>12), and optimal NaOH concentration (1 wt.%) were optimized to achieve a maximum bitumen recovery of 98 wt.% within 8 min. The most effective sand-to-solution mass ratio was determined as 1:2, while the optimal process temperature was 75 °C. The application of ultrasound significantly enhances cavitation and reagent penetration, enabling efficient separation of bitumen with minimal chemical usage. Fourier-transform infrared (FTIR) spectroscopy and GC–MS analyses revealed the presence of aromatic hydrocarbons, paraffinic and naphthenic structures, as well as sulfur- and oxygen-containing functional groups (e.g., sulfoxides, carboxylic acids). These characteristics suggest moderate maturity and a high degree of aromaticity of the organic matter. Despite suitable thermal and compositional properties, the extracted bitumen exhibits a relatively low stiffness and softening point, indicating the need for additional upgrading (e.g., oxidation) prior to use in road construction. Although standard rheological tests (e.g., dynamic shear rhinometry) were not conducted in this study, the penetration and softening point values suggest a relatively soft binder, possibly unsuitable for high-temperature paving applications without modification. Future research will focus on rheological evaluation and oxidative upgrading to meet the ST RK 1373-2013 specification requirements. Full article

The increasing penetration of renewable energy presents substantial challenges to frequency stability, particularly in low-inertia microgrids. This study introduces an agent-based microgrid model that integrates generators, loads, an energy storage system (ESS), and renewable sources, mathematically formalized through the discrete-event system specification (DEVS) to ensure both structural clarity and extensibility. To dynamically simulate power system behavior, the model incorporates multiple control strategies—including ESS scheduling, automatic generation control (AGC), predictive AGC, and grid-forming (GFM) inverter control—each posed as an mathematically defined control problem. Simulations on the IEEE 13-bus system demonstrates that the coordinated operation of ESS, GFM, and the proposed strategies markedly enhances frequency stability, reducing frequency peaks by 1.14, 1.14, and 0.72 Hz, and shortening the average recovery time by 9.05, 0.15, and 2.58 min, respectively. Collectively, the model provides a systematic representation of grid behavior and frequency regulation mechanisms under high renewable penetration, and establishes a rigorous mathematical framework for advancing microgrid research. Full article

Background: Elite athletes are frequently subjected to high-intensity training regimens, which can result in cumulative physical stress, overtraining, and potential health risks. Monitoring autonomic responses to such load is essential for optimizing performance and preventing maladaptation. Objective: The present study aimed to assess changes in autonomic regulation immediately and two hours after training in athletes, using an integrated framework (combining time- and frequency-domain HRV indices with nonlinear and recurrence quantification analysis). It was investigated how repeated assessments over a 4-month period can reveal cumulative effects and identify athletes at risk. Special attention was paid to identifying signs of excessive fatigue, autonomic imbalance, and cardiovascular stress. Methods: Holter ECGs of 12 athletes (mean age 21 ± 2.22 years; males, athletes participating in competitions) over a 4-month period were recorded before, immediately after, and two hours after high-intensity training, with HRV calculated from 5-min segments. Metrics included HRV and recurrent quantitative analysis. Statistical comparisons were made between the pre-, post-, and recovery phases to quantify autonomic changes (repeated-measures ANOVA for comparisons across the three states, paired t-tests for direct two-state contrasts, post hoc analyses with Holm–Bonferroni corrections, and effect size estimates η²). Results: Immediately after training, significant decreases in SDNN (↓ 35%), RMSSD (↓ 40%), and pNN50 (↓ 55%), accompanied by increases in LF/HF (↑ 32%), were observed. DFA α1 and Recurrence Rate increased, indicating reduced complexity and more structured patterns of RR intervals. After two hours of recovery, partial normalization was observed; however, RMSSD (−18% vs. baseline) and HF (−21% vs. baseline) remained suppressed, suggesting incomplete recovery of parasympathetic activity. Indications of overtraining and cardiac risk were found in three athletes. Conclusion: High-intensity training in elite athletes induces pronounced acute autonomic changes and incomplete short-term recovery, potentially increasing fatigue and cardiovascular workload. Longitudinal repeated testing highlights differences between well-adapted, fatigued, and at-risk athletes. These findings highlight the need for individualized recovery strategies and ongoing monitoring to optimize adaptation and minimize the risk of overtraining and health complications. Full article

Background/Objectives: Respiratory impairment is the leading cause of morbidity and mortality in participants with spinal cord injury (SCI). Cervical SCI (cSCI) severely compromises respiratory function due to paralysis and weakness of the respiratory muscles. Recent evidence suggests that transcutaneous electrical spinal cord stimulation (tSCS) may enhance motor strength and promote functional recovery. Therefore, cervical tSCS, applied at cervical segments, holds potential as a therapeutic strategy to improve respiratory function in participants with cervical SCI. Methods: This randomized controlled trial with a partial crossover design included participants with both complete and incomplete cSCI. Neurological assessments were used, as well as tests to evaluate pulmonary function maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), and spirometric measurements. These assessments were conducted at baseline and after the last session. The experimental group received tSCS at the C3–C4 and C6–C7 cervical spinal levels, delivered at a frequency of 30 Hz during occupational therapy. The control group underwent identical occupational therapy sessions without stimulation. Each session lasted 30 min and was conducted over eight days. Results: Fifteen participants with cSCI received tSCS, while 11 cSCI participants were included in the control group. Seven participants took part in both groups. Only the tSCS group showed significant improvements in MIP, MEP, and forced vital capacity (p < 0.05), while no significant changes were observed in the control group. Conclusions: tSCS applied at the cervical segments can promote respiratory function following cervical SCI. This approach may support neuroplasticity and help reduce long-term respiratory complications in participants with cervical SCI. However, to confirm these effects, long-term stimulation protocols and follow-up studies in larger SCI populations are required. Full article

The superiority of Variable Resistance Training (VRT) over traditional Constant Resistance Training (CRT) for enhancing lower-limb performance is debated, with previous meta-analyses limited by aggregating disparate exercises. This systematic review and meta-analysis, the first to focus exclusively on the squat, compared the acute and long-term effects of VRT versus CRT on maximal strength and explosive power. Following PRISMA guidelines, 20 studies were analyzed (literature search up to 15 June 2025), with Hedges’ g used for effect size (ES) calculation. Results demonstrated VRT’s superiority for both acute (ES = 0.34) and long-term adaptations. Acutely, effects peaked with an 8–12 min recovery (ES = 0.43). Long-term, VRT produced greater gains in maximal strength (ES = 0.31) and explosive power (ES = 0.17). Subgroup analyses on maximal strength revealed that elastic bands were highly effective (ES = 0.67), particularly in trained individuals (ES = 0.35), males (ES = 0.41), within cycles < 8 weeks (ES = 0.44), and at frequencies of ≤2 sessions/week (ES = 0.45). For explosive power, chains were most effective (ES = 0.37), significantly improving jumping performance but not sprinting. In conclusion, VRT is a more effective modality for squat training; optimal programs should utilize elastic bands for strength and chains for power, with strength-focused blocks being short-term (<8 weeks) and lower-frequency (≤2 sessions/week) for trained individuals. Full article

Antibiotic contaminants such as tetracycline (TC) from agricultural production have become widely distributed and persistently accumulated in aquatic environments (rivers, lakes, and oceans), posing severe threats to ecological security and human health. This study developed a modified rice-straw-derived biochar through NaOH activation and ball-milling-assisted Fe₃O₄ loading, which simultaneously enhanced TC adsorption capacity and enabled magnetic recovery. The Box–Behnken design (BBD) response surface methodology was employed to optimize three key preparation parameters: ball-milling time (A, 39.95 min), frequency (B, 57.23 Hz), and Fe₃O₄/biochar mass ratio (C, 2.85:1), with TC adsorption capacity as the response value. The modified biochar was systematically characterized using SEM, BET, FTIR, XRD, and XPS, while adsorption mechanisms were elucidated through kinetic studies, isotherm analyses, and pH-dependent experiments. The results demonstrate that modification via ball-milling with Fe₃O₄ loading significantly enhanced the biochar’s tetracycline adsorption capacity. The maximum adsorption capacity of the modified biochar reached 102.875 mg/g, representing a 114.85% increase from the initial value of 47.882 mg/g observed for the pristine biochar. Furthermore, the modified biochar exhibited excellent stability, maintaining robust adsorption performance across a wide pH range. The primary adsorption mechanisms involved metal coordination complexation, supplemented by hydrogen bonding, π-π interactions, and pore filling. Full article

Background: This study aimed to examine changes in heart rate variability (HRV) across three match-related time points (pre-match, during the match, and post-match) and to explore whether these physiological responses differed between winners and losers in competitive padel. Methods: Twelve matches were analyzed, involving 11 high-level Finnish padel players ranked within the national top 24. HRV was recorded before, during, and immediately after each match, with each measurement lasting a minimum of five min. Time-domain (e.g., SDNN, RMSSD, pNN50), frequency-domain (e.g., LF, HF), and non-linear (e.g., SD1, SD2) HRV metrics were extracted for analysis. All matches took place in Tampere, Finland, under controlled conditions. Results: Results revealed significant intra-match fluctuations in HRV across all domains. Moreover, losing players exhibited consistently higher relative heart rate during the match, suggesting greater physiological strain. Conclusions: This study contributes novel evidence on the dynamic nature of autonomic responses in padel and supports the integration of HRV monitoring in performance and recovery management protocols for high-level athletes. Full article

The in situ emulsification synergistic self-profile control system has wide application prospects for efficient development on offshore oil reservoirs. During water flooding in Bohai heavy oil reservoirs, random emulsification occurs with superimposed Jamin effects. Effectively utilizing this phenomenon can enhance the efficient development of offshore oilfields. This study addresses the challenges hindering water flooding development in offshore oilfields by investigating the emulsification mechanism and key influencing factors based on oil–water emulsion characteristics, thereby proposing a novel in situ emulsification flooding method. Based on a fundamental analysis of oil–water properties, key factors affecting emulsion stability were examined. Core flooding experiments clarified the impact of spontaneous oil–water emulsification on water flooding recovery. Two-dimensional T1–T2 NMR spectroscopy was employed to detect pure fluid components, innovating the method for distinguishing oil–water distribution during flooding and revealing the characteristics of in situ emulsification interactions. The results indicate that emulsions formed between crude oil and formation water under varying rheometer rotational speeds (500–2500 r/min), water cuts (30–80%), and emulsification temperatures (40–85 °C) are all water-in-oil (W/O) type. Emulsion viscosity exhibits a positive correlation with shear rate, with droplet sizes primarily ranging between 2 and 7 μm and a viscosity amplification factor up to 25.8. Emulsion stability deteriorates with increasing water cut and temperature. Prolonged shearing initially increases viscosity until stabilization. In low-permeability cores, spontaneous oil–water emulsification occurs, yielding a recovery factor of only 30%. For medium- and high-permeability cores (water cuts of 80% and 50%, respectively), recovery factors increased by 9.7% and 12%. The in situ generation of micron-scale emulsions in porous media achieved a recovery factor of approximately 50%, demonstrating significantly enhanced oil recovery (EOR) potential. During emulsification flooding, the system emulsifies oil at pore walls, intensifying water–wall interactions and stripping wall-adhered oil, leading to increased T2 signal intensity and reduced relaxation time. Oil–wall interactions and collision frequencies are lower than those of water, which appears in high-relaxation regions (T1/T2 > 5). The two-dimensional NMR spectrum clearly distinguishes oil and water distributions. Full article

Introduction: The monitoring of autonomic nervous balance during childhood remains underexplored. However, heart rate variability (HRV) is widely recognized as a biomarker of health risk across the lifespan. Juvenile idiopathic arthritis (JIA), a group of chronic inflammatory joint disorders, is associated with persistent inflammation and pain, both of which contribute to increased cardiovascular risk, commonly linked to reduced HRV. Among HRV parameters, very-low frequency (VLF) components have been associated with physiological recovery processes. This study aimed to assess HRV during sleep in patients with JIA. Methods: We studied 10 patients with JIA and 10 age-, gender-, and Tanner stage-matched healthy controls. All participants underwent polysomnographic monitoring following an adaptation night in the sleep laboratory. HRV was analyzed using standard time and frequency domain measures over 5 min epochs across all sleep stages. Frequency components were classified into low- and high-frequency bands, and time domain measures included the standard deviation of the beat-to-beat intervals. Group differences in HRV parameters were assessed using nonparametric tests for independent samples, with a significance level set at p < 0.05. Results: JIA exhibited greater sleep disruption than controls, including reduced NREM sleep, longer total sleep time, and increased wake time after sleep onset. HRV analyses in both time and frequency domains revealed significant differences between groups across all stages of sleep. In JIA patients, the standard deviation of the normal-to-normal interval during slow wave sleep (SWS) and total power across all sleep stages (p < 0.05) was reduced. In JIA patients, the standard deviation of the normal-to-normal interval during slow wave sleep and total power across all sleep stages were significantly reduced (p < 0.05). VLF power was also significantly lower in JIA patients across all sleep stages (p = 0.002), with pronounced reductions during N2 and SWS (p = 0.03 and p = 0.02, respectively). A group effect was observed for total power across all stages, mirroring the VLF findings. Additionally, group differences were detected in LF/HF ratio analyses, although values during N2, SWS, and REM sleep did not differ significantly between groups. Notably, the number of affected joints showed a moderate positive correlation with the parasympathetic HRV parameter. Conclusions: Patients with JIA exhibited sleep disruption and alterations in cardiovascular autonomic functioning during sleep. Reduced HRV across all sleep stages in these patients suggests underlying autonomic nervous dysfunction. Addressing sleep disturbances in patients with chronic pain may serve as an effective strategy for managing their cardiovascular risk. Full article

Currently, research on the modification mechanisms of activated rubber/SBS (styrene–butadiene–styrene) composites and the microscopic processes involved remains limited. To investigate the impact of the rubber activation treatment combined with SBS modifier on asphalt modification, this study employs composite-modified asphalt formulations using either a conventional mix or activated rubber in conjunction with SBS. Infrared spectroscopy (IR) and scanning electron microscopy (SEM) were utilized to analyze the chemical components and microscopic morphology of the composite-modified asphalt following activation treatment. Microscopic analysis revealed that the asphalt stirred for 20 min has a characteristic peak with a wave number of 966 cm⁻¹, while the characteristic peak with a wave number of 700 cm⁻¹ is not obvious. That is, the asphalt sample contains the polybutadiene component and a reduced amount of the polystyrene component. Therefore, it can be inferred that the asphalt sample only contains activated rubber, along with less SBS modifier content. Traditional rubber undergoes significant expansion reactions during the mixing stage, but there are difficulties in degradation, which leave large particles and reduce the proportions of the lightweight asphalt components. However, active rubber and SBS mainly expand and degrade more completely during the shear stage, forming many micro-volume particles in asphalt. Additionally, frequency scanning and multiple creep recovery tests were conducted to evaluate the high-temperature rheological properties of the asphalt. The results indicate that activated rubber, doped at 20%, and SBS, doped at 2%, significantly enhance the high-temperature rheological properties of the composite-modified asphalt compared to base asphalt, exhibiting a 417.16% increase in the complex modulus at 64 °C and 1 Hz. Furthermore, these modifiers interact synergistically to improve modification efficiency. Full article

Introduction: Pediatric heart transplantation (HTX) remains the only therapeutic option for end-stage heart failure not amenable to conventional surgical or catheter interventions. We reviewed our pediatric HTX outcomes according to primary diagnosis. Patients and Methods: Sixty-two patients underwent HTX between 01/2007 and 12/2022. Patients were divided into congenital heart disease (CHD, n = 20) and cardiomyopathy (CMP, n = 42) groups. All potential variables relevant to patient recovery and long-term survival with endpoints of retransplantation or death were analyzed. Results: CHD patients underwent HTX after significantly more multiple major cardiac surgeries per patient (2.5 [0–5]) than CMP patients (0.5 [0–2], p < 0.01), without notable allosensitization. Post-HTX recovery was longer in CHD (mean mechanical ventilation 7 vs. 3 days, p = 0.001), likely due to longer surgical time (468 vs. 375 min, p = 0.037). There were no significant differences in the frequency of rejections between the two groups (4/20 vs. 9/42). Midterm survival was slightly better (85/70% p = NS) in CMP (median follow-up 44.5 [0–177] months). Conclusion: Our study confirmed good short- and long-term outcomes of pediatric HTX in both CMP and CHD. The longer postoperative recovery in CHD did not lead to higher mortality. No higher pretransplant hypersensitization was observed, possibly explaining the lack of difference in the number and severity of rejections. Full article

Objectives: Interval block resistance training (IBRT) and circuit resistance training (CRT) are periodization models aimed at enhancing neuromuscular and metabolic adaptations. This study aims to evaluate the effects of a 12-week IBRT program compared to CRT on body composition, muscle strength, speed, functional capacity, and autonomic recovery in young Chilean adults. Methods: A randomized, parallel, double-blind study was conducted with 30 participants assigned to IBRT (n = 15) or CRT (n = 15). Assessments included body mass index (BMI), waist circumference, right-hand grip strength, the running anaerobic sprint test (RAST), the 6 min walk test (6 MWT), and heart rate variability (HRV) indices: low-frequency to high-frequency ratio (LF/HF) and root mean square of successive differences (RMSSD, a time-domain HRV metric reflecting parasympathetic activity). Statistical analyses included t-tests and ANCOVA. Results: Groups were similar in age (IBRT: 25.2 ± 3.19; CRT: 23.27 ± 3.69, p = 0.14) and BMI (IBRT: 21.56 ± 2.22; CRT: 22.36 ± 1.70 kg/m², p = 0.40). Both groups improved significantly in waist circumference (IBRT: −1.85%; CRT: −2.37%), grip strength (IBRT: +5.47%; CRT: +4.02%), RAST (IBRT: −2.67%; CRT: −1.04%), 6 MWT (IBRT: +4.53%; CRT: +2.17%), LF/HF (IBRT: −11.43%; CRT: −5.11%), and RMSSD (IBRT: +5.36%; CRT: +3.81%) (all p ≤ 0.01). IBRT produced significantly greater gains in 6 MWT (B = 19.51, 95% CI: 0.79 to 38.23, p = 0.04). Conclusions: Both IBRT and CRT effectively improved body composition, muscle strength, speed, functional capacity, and autonomic recovery. However, IBRT demonstrated a superior effect on aerobic capacity. Full article

In this study, ultrasonic excitation was employed for filter cloth cleaning, with the aim of predicting optimal cleaning conditions and monitoring the efficiency and performance of the cloth under various cleaning parameters. A clogged filter cloth of uniform size (Φ0.11 m) was secured in a prepared cleaning apparatus, and cleaning experiments were conducted by varying the following operational conditions: time (2, 5, 10 min), frequency (34, 76, 120 kHz), and power output (100, 200, 300 W). Through these experiments, this study sought to investigate the cleaning capacity and efficiency of each condition and to evaluate the effectiveness of ultrasonic cleaning. The morphology of the filter cloths before and after cleaning was examined through SEM imaging, and the weight content of the filter cloths was measured before and after the cleaning experiments to incorporate these values into the cleaning efficiency assessment. Additionally, air permeability measurements were taken to predict the impact of permeability on cleaning performance, which was statistically analyzed based on a predictive model’s equation. The experimental results showed that the maximum recovery rate of air permeability for clogged filter cloths was approximately 28.6%. Using Response Surface Methodology (RSM), the air permeability recovery rate and weight reduction rate were 19.8% and 5.8%, respectively, under conditions of 5.2 min, 34 kHz, and 300 W. It is anticipated that the utilization of the filter press cleaning device will enable data acquisition through repeated experiments and that this device can be used in filter cloth management and operational techniques. Full article