Search Results (294)

Recirculating aquaculture systems (RAS) address pollution, disease, and sustainability in commercial fish farming, but marine RAS are limited by biofilter maturation and nitrification. This study investigated the effects of air nanobubbles on water quality, fish growth, and bacterial communities in marine RAS stocked with juvenile Malabar red snapper, barramundi and saline-tolerant hybrid tilapia. Flow cytometry was evaluated as a rapid management tool for non-culturable microbes, finding viable bacterial counts 30–100 times higher than conventional total plate counts. There were no significant differences in fish growth, survival, or Feed Conversion Ratio between groups, likely due to low stocking densities (<20 kg/m³) and high water exchange rates (>100%/hour), indicating low system stress. Air nanobubbles did not significantly increase dissolved oxygen levels. While bacterial abundance in water was consistently higher in nanobubble-treated RAS (RAS-N), tank walls showed less biofilm. RAS-N also exhibited a higher abundance of nitrifying bacteria like Nitrospira and Marinobacter, leading to improved nitrogenous waste breakdown and lower nitrite levels. Future research should investigate nanobubbles’ benefits at higher stocking densities and longer durations to fully assess their impact on intensive aquaculture. Full article

One way to counteract the effects of environmental stresses, including drought, is to use products with growth-promoting properties for plants. Such agents include quercetin, which is known for its antioxidant and photosynthesis-enhancing properties. In the conducted experiment, the influence of the quercetin–copper complex (Q-Cu (II)) treatment, characterized by strong high solubility in water and strong antioxidant properties, was investigated. The pot experiment demonstrated the effect of spraying with Q-Cu (II) solutions (0.01, 0.05 and 0.1%) on wheat plants growing under drought stress conditions. Two treatments of Q-Cu (II) solutions were applied, and chlorophyll content and chlorophyll fluorescence (the maximum quantum yield of photosystem II (PSII) photochemistry (F_v/F_m), the efficiency of the water-splitting complex on the donor side of PSII (F_v/F_o), and the photosynthetic efficiency index (PI)), as well as gas exchange (photosynthetic network intensity (P_N), transpiration rate (E), stomatal conductance (g_s) and intercellular CO₂ concentration (C_i)), were measured 1 and 7 days after each treatment. In addition, antioxidant enzyme activity (catalase (CAT), peroxidase (SOD) and guaiacol peroxidase (GPOX)) and reactive oxygen species (ROS) levels were determined. Drought stress caused a decrease in chlorophyll content, and values of parameters F_v/F_m, F_v/F_o, PI and P_N, E, g_s, C_i, as well as an increase in ROS levels and antioxidant enzyme activity. Exogenous Q-Cu (II) improved photosynthetic indices and modulated redox status in a dose-dependent manner: 0.01–0.05% reduced ROS, whereas 0.1% increased ROS while concomitantly enhancing antioxidant enzyme activities and photosynthetic performance, consistent with ROS-mediated priming. The conducted research indicates the possibility of using Q-Cu (II) as a product to enhance the efficiency of the photosynthetic process under drought stress. Full article

Metal components that undergo ultrasonic cleaning are often stored in rinse water before drying; during this dwell period, surface corrosion can nucleate and grow. Here, we investigate how two easily monitored water-quality parameters—chloride ion concentration (Cl⁻) and chemical oxygen demand (COD), a proxy for residual organic species—govern the initiation and propagation of corrosion on low-carbon steel. After ultrasonic cleaning in five representative cleaning solutions, test coupons were immersed for up to 72 h in the corresponding rinse water and the extent of corrosion was quantified by optical profilometry and mass loss. The surface area covered by corrosion scaled linearly with [Cl⁻] (0–150 mg L⁻¹) and COD (5–120 mg L⁻¹), with correlation coefficients of 0.92 and 0.88, respectively. When both parameters exceeded threshold values of 50 mg L⁻¹ (Cl⁻) and 30 mg L⁻¹ (COD), the corrosion rate doubled relative to the control. A two-step mitigation strategy—ion-exchange pretreatment followed by activated-carbon polishing—reduced Cl⁻ and COD below the thresholds and suppressed corrosion formation by >70%. These findings provide a simple water-quality guideline and a low-cost process retrofit for manufacturers that store steel parts in high-humidity environments. Full article

Aims: The present study evaluated the acute morning effect of melatonin supplementation (5 mg) on cardiometabolic responses. Methods: For this purpose, 12 physically active men (22.1 ± 1.3 years; 1.7 ± 01 m; 74.7 ± 12.1 kg; 24.3 ± 2.7 m/kg²; VO₂max: 46.9 ± 2.3 mL/kg/min; 17.3 ± 5.2%F) were measured in a double-blind crossover protocol, where participants were measured before, during, and after a high-intensity interval exercise (HIIE) protocol [4 × 4 min at 95% of maximum heart rate (HRmax) with a 3 min interval at 60–70% of HRmax] followed by 30 min of recovery. At rest, the following variables were measured: HR, systolic blood pressure (SBP), diastolic blood pressure (DBP), lactate, and maximum oxygen consumption (VO₂max). At the end of each stage and interval, VO₂, respiratory exchange ratio (RER), and HR were measured. During recovery, VO₂, VCO₂, RER, SBP, DBP, and HR were measured. Results: Melatonin significantly enhanced recovery metabolism, as evidenced by increased VO₂ at Interval 3 (+2.2 mL/kg/min, p = 0.03, d = 0.69) and 5 min postexercise (+2.4 mL/kg/min, p = 0.02, d = 0.81). The RER was higher during Sprint 4 (+0.08, p = 0.01, d = 0.84), indicating greater carbohydrate reliance. Cardiovascular recovery was also improved, with a reduced HR at 30 min (−5 bpm, p = 0.04, d = 0.66) and lower SBP at 15 min (−8 mmHg, p = 0.02, d = 0.75). Lactate concentration at 30 min was lower with melatonin (−0.7 mmol/L, p = 0.03, d = 0.72). No significant effects were observed at rest or during early exercise. Conclusions: Acute morning melatonin intake may amplify metabolic responses to HIIE while facilitating cardiometabolic recovery. This dual-phase action may benefit athletes aiming to optimize energy expenditure, fat metabolism, and recovery during early-day training. Full article

CrossFit performance is influenced by physiological, neuromuscular, and perceptual factors, yet the extent to which these determinants vary by sex or training experience in standardized CrossFit Workouts of the Day (WODs) remains unclear. This study examined whether variables such as lactate accumulation, oxygen uptake dynamics, jump performance loss, and ventilatory responses relate differently to performance when stratified by sex and expertise. Fifteen trained athletes (eight males, seven females; overall mean age 27.7 ± 4.6 years) took part. Assessments included body composition, squat (SJ) and countermovement jumps (CMJ), and maximal oxygen consumption [VO₂max]. On a separate day, they performed Fran (21-15-9 thrusters and pull-ups, Rx or scaled) The prescribed (‘Rx’) version used standardized barbell loads (43 kg for men, 29 kg for women), while the scaled version involved reduced loads or pull-up modifications. Respiratory gas exchange and heart rate were continuously monitored, while blood lactate and jump performance were measured pre- and post-WOD. Workout completion time [s] was the primary outcome. Correlation heatmaps explored associations in the overall sample and by sex and expertise. Mean completion time was 422.1 ± 173.2 s (range: 200–840). Faster performance correlated with higher ventilatory responses [ΔVe, r = −0.60, p = 0.018], greater mean VO₂ (r = −0.62, p = 0.014), superior jump power [CMJ pre, r = −0.65, p = 0.009], and higher post-WOD lactate [r = −0.54, p = 0.036]. Sex-stratified analyses showed that males relied on ventilatory efficiency and neuromuscular power, whereas females were more constrained by performance loss and higher resting perceived exertion (RPE). Experts depended on ventilatory and neuromuscular efficiency, while initiates showed stronger associations with decrements in jump performance and higher RPE. These findings highlight subgroup-specific performance profiles and reinforce the need for tailored training strategies in CrossFit athletes. Full article

Background: After a warm-up and before the start of sports competition, athletes often take a break. During this break, the effects of the warm-up (e.g., capillary vasodilation) may diminish. The aim of this study was to compare cardiorespiratory responses during high-intensity physical exercise, either preceded or not preceded by post-warm-up breathing, using an additional respiratory dead space volume mask (ARDSv). Methods: The study included 20 trained cyclists. Each participant completed two 3 min tests at an intensity of 110% of their maximal power, determined during a progressive test. A standardised warm-up preceded each 3 min test. Following the warm-up, there was an 8 min passive rest period. During this break, participants either breathed using ARDSv or breathed normally (non-ARDSv). The volume of the ARDSv mask was 1000 mL. Cardiorespiratory parameters were measured during the tests, including mean: oxygen uptake (VO₂av), respiratory exchange ratio (RERav), respiratory rate (RRav), tidal volume (TVav), stroke volume (SVav), and rating of perceived exertion (RPE). Results: VO₂peak was higher in participants breathing using ARDSv compared to non-ARDSv (4.22 ± 0.40 [CI: 4.03–4.41] vs. 3.98 ± 0.42 [CI: 3.79–4.18]; p = 0.002; t = 3.56; d = 0.585). Additionally, RERav (1.08 ± 0.06 [CI: 1.06–1.11] vs. 1.13 ± 0.06 [CI: 1.11–1.16]; p = 0.008; t = 2.96; d = 0.833) and RPE (18.0 ± 1.7 [CI: 17.3–18.8] vs. 18.9 ± 1.1 [CI: 18.4–19.4]; p = 0.009; Z = 2.61; r = 0.583) were lower in participants breathing using ARDSv compared to non-ARDSv. Conclusions: Breathing using ARDSv between warm-up and high-intensity exercise increases oxygen uptake and reduces perceived exertion, likely through peripheral mechanisms. These effects suggest practical applications in competitive sports and provide directions for further mechanistic research. Full article

Background: Exercise duration at maximum oxygen uptake ($\dot{\mathrm{V}}$O₂max) appears to be influenced not only by metabolic factors but also by the interplay between brain dynamics and ventilatory regulation. This study examined how cortical activity, assessed via electroencephalography (EEG), relates to performance and acute fatigue regulation during a constant-load cycling test. We hypothesized that oscillatory activity in the theta, alpha, and beta bands would be associated with ventilatory coordination and endurance capacity. Methods: Thirty trained participants performed a cycling test to exhaustion at 90% maximal aerobic power. EEG and gas exchange were continuously recorded; ratings of perceived exertion were assessed immediately after exhaustion. Results: Beta power was negatively correlated with time spent at $\dot{\mathrm{V}}$O₂max (r = −0.542, p = 0.002). Theta and Alpha power alone showed no direct associations with endurance, but EEG–metabolic ratios revealed significant correlations. Specifically, the time to reach $\dot{\mathrm{V}}$O₂max correlated with Alpha/$\dot{\mathrm{V}}$O₂ (p < 0.001), Alpha/$\dot{\mathrm{V}}$CO₂ (p < 0.001), and Beta/$\dot{\mathrm{V}}$CO₂ (p = 0.002). The time spent at $\dot{\mathrm{V}}$O₂max correlated with Theta/$\dot{\mathrm{V}}$O₂ (p = 0.002) and Theta/$\dot{\mathrm{V}}$CO₂ (p < 0.001). The time-to-exhaustion was correlated with Theta/$\dot{\mathrm{V}}$CO₂ (p < 0.001) and Alpha/$\dot{\mathrm{V}}$CO₂ (p < 0.001). Conclusions: These findings indicate that cortical oscillations were associated with different aspects of acute fatigue regulation. Beta activity was associated with fatigue-related neural strain, whereas Theta and Alpha bands, when normalized to metabolic load, were consistent with a role in ventilatory coordination and motor control. EEG–metabolic ratios may provide exploratory indicators of brain–metabolism interplay during high-intensity exercise and could help guide future brain-body interactions in endurance performance. Full article

Cardiopulmonary exercise testing (CPET) is recommended as part of routine care in people with congenital heart disease. A significant difference has been observed in many CPET parameters, depending on the ergometer and exercise protocol used. The aim of this study is to investigate such differences in Fontan patients. All Fontan patients (<40 years old, NYHA class I/I–II) underwent two consecutive CPETs on different ergometers (treadmill with ramped Bruce protocol versus cycle ergometer with ramp protocol) within less than 12 months. The exclusion criterion was the presence of significant clinical/anthropometric changes between the two tests. Anthropometric, surgical, clinical, electrocardiogram (ECG) and CPET data were collected. 47 subjects were enrolled (25 males, mean age 16.4 at first test). Peak heart rate (HR) tended to be higher on the treadmill (p = 0.05 as % of predicted, p = 0.062 in absolute value). Peak oxygen consumption (VO₂) (mL/min, mL/kg/min, and % of predicted) was significantly higher on the treadmill (p < 0.01), as well the VO₂ at the ventilatory anaerobic threshold (VAT) and the peak oxygen pulse. A different kinetics of the oxygen pulse wave was observed in the same patient comparing the two testing modalities. Maximal respiratory-exchange-ratio values (>1.1) were reached more frequently on the cycle ergometer (p < 0.001). The minute ventilation–carbon dioxide output slope (VE/VCO₂ slope) was not different between the two tests (p = 0.400). Many parameters of CPET may differ depending on the ergometer used. These should be considered in clinical evaluation of Fontan patients and when exercise is to be prescribed. Full article

Background: Sickle cell disease (SCD) is a hereditary hemoglobinopathy associated with life-threatening complications such as acute chest syndrome (ACS), which may necessitate extracorporeal membrane oxygenation (ECMO) in refractory cases. Despite growing use, ECMO in SCD remains challenging due to risks of hemolysis, thrombosis, and anticoagulation complications. This systematic review consolidates existing evidence on ECMO outcomes in SCD, focusing on indications, complications, and survival. Methods: A systematic search of MEDLINE, Cochrane CENTRAL, and Google Scholar was conducted up to January 2025, identifying case reports/series on ECMO use in SCD. Studies reporting venovenous (VV) or venoarterial (VA) ECMO for acute cardiopulmonary failure were included. Data on demographics, laboratory findings, management, and outcomes were extracted. Quality assessment was performed using the Joanna Briggs Institute checklist. Results: Sixteen case reports (23 patients) were included. Most patients were female (65.2%), with ACS (47.8%) and pulmonary embolism (13.0%) as common ECMO indications. VV-ECMO (69.6% of cases) was primarily used for respiratory failure, with a 69% survival rate, while VA-ECMO (30.4%) had a 29% survival rate, often due to cardiogenic shock or cardiac arrest. Complications included hemorrhage (26.1%), neurological injury (21.7%), and thrombosis (13.0%). Exchange transfusion was frequently employed (43.5%), with post-ECMO echocardiography showing improved right ventricular function in survivors. Conclusions: VV-ECMO demonstrates favorable outcomes in SCD-related respiratory failure, whereas VA-ECMO carries higher mortality risks. Careful patient selection, anticoagulation management, and multidisciplinary coordination are essential. Larger prospective studies are needed to refine ECMO utilization in this high-risk population. Full article

Microbiological and biogeochemical investigation of the bottom sediments of semiclosed basins was carried out at the Kislaya Guba tidal power station (Barents Sea) and in Kanda Bay (White Sea). Suppressed tidal water mixing is known to affect the hydrological regime of isolated basins, resulting in the development of oxygen-free sediments. The upper sediments of the studied bays were shown to contain higher concentrations of sulfide and methane, with increased rates of sulfate reduction, methanogenesis, and methane oxidation. The relative abundance of truly marine microorganisms decreased, while microorganisms common in anoxic sediments of meromictic basins developed. The indicator microorganisms with increased relative abundance were archaea of the genera Methanoregula and Methanosaeta. Bacteria of the class Chlorobia, Chloroflexi of the family Anaerolineaceae, and Rhodoferax-related bacteria were indicators of the stagnant seawater. Members of the genus Woeseia were counter-indicators, occurring only in marine water. In our opinion, under reasonably regulated water exchange via the dams, the ecosystems of the Kanda and Kislaya Guba bays may retain the characteristics of marine bays. Otherwise, the studied bays may become stratified basins with anoxic near-bottom water, harboring microbial communities similar to those inhabiting meromictic basins. Full article

Background/Objectives: Cast walkers (CWs) are often prescribed to offload diabetic foot ulcers (DFUs). However, their mass, the degree of ankle immobilization and the limb length discrepancy they induce may increase the energetic demands of walking, contributing to lower adherence and poorer healing. The purpose of this study was to evaluate the effects of different commercially available CW options on the metabolic costs and perceived exertion of walking, and on related spatiotemporal kinematics, in healthy young participants as an initial step to understanding factors that impact adherence in patients with DFUs. Methods: Participants walked on an instrumented treadmill at a standardized speed for six minutes under five footwear conditions: (1) athletic shoes only (control); (2) ankle-high CW on the dominant limb with athletic shoe on the contralateral limb; (3) condition two with an external lift on the athletic shoe; (4 and 5) conditions two and three with a knee-high CW. Condition 1 was performed first, after which the CW conditions were randomized. During all conditions, a portable calorimeter recorded gas exchange on a breath-by-breath basis. The metabolic cost of transport (MCoT) was quantified as the mean oxygen consumed per meter walked per kilogram body mass, after accounting for standing. After walking, participants reported perceived exertion using the Borg Rating of Perceived Exertion scale (RPE). From the treadmill data, we extracted the mean step width (SW) as well as absolute values for symmetry indices (SIs) for step length (SL) and step time (ST), all of which have associations with MCoT. For each outcome, linear mixed models compared each CW condition with the control and tested for effects of CW height (ankle-high vs. knee-high) and of the lift. Results: A total of 14 healthy young adults without diabetes participated. MCoT, RPE and SW were significantly higher for all CW conditions compared to the control, with less consistent results for asymmetry measures. MCoT was not significantly different across CW height or lift condition although an unexpected interaction between limb and CW height n was observed; MCoT was lower in the knee-high CW with vs. without a lift but did not change in the ankle-high CW based on lift status. Similarly, neither SW nor SIs changed in expected fashions across conditions. In contrast, RPE was significantly lower using the ankle- vs. knee-high CW and when using a lift vs no lift, with no significant interaction. Conclusions: Although metabolic costs were unaffected by CW design changes, which may reflect the absence of anticipated changes in kinematics that impact MCoT, perceived exertion was reduced through such changes. Unanticipated biomechanical changes may reflect a complex interaction among a number of competing factors that dictate behavior and MCoT. The differing results in perception of exertion and metabolic costs might be due to participants’ perceived exertion being sensitive to the collective impact of interacting biomechanical factors, including those not quantified in this study. Future work should seek to directly evaluate the impact of CW design changes in patients with DFU and the relationship to adherence. Full article

This study presents a machine learning-enhanced optimization framework for proton exchange membrane fuel cell (PEMFC), designed to address critical challenges in dynamic load adaptation and thermal management for automotive applications. A high-fidelity model of a 65-cell stack (45 V, 133.5 A, 6 kW) is developed in MATLAB/Simulink, integrating four core subsystems: PID-controlled fuel delivery, humidity-regulated air supply, an electrochemical-thermal stack model (incorporating Nernst voltage and activation, ohmic, and concentration losses), and a 97.2–efficient SiC MOSFET-based DC/DC boost converter. The framework employs the NSGA-II algorithm to optimize key operational parameters—membrane hydration (λ = 12–14), cathode stoichiometry (λO₂ = 1.5–3.0), and cooling flow rate (0.5–2.0 L/min)—to balance efficiency, voltage stability, and dynamic performance. The optimized model achieves a 38% reduction in model-data discrepancies (RMSE < 5.3%) compared to experimental data from the Toyota Mirai, and demonstrates a 22% improvement in dynamic response, recovering from 0 to 100% load steps within 50 ms with a voltage deviation of less than 0.15 V. Peak performance includes 77.5% oxygen utilization at 250 L/min air flow (1.1236 V/cell) and 99.89% hydrogen utilization at a nominal voltage of 48.3 V, yielding a peak power of 8112 W at 55% stack efficiency. Furthermore, fuzzy-PID control of fuel ramping (50–85 L/min in 3.5 s) and thermal management (ΔT < 1.5 °C via 1.0–1.5 L/min cooling) reduces computational overhead by 29% in the resulting digital twin platform. The framework demonstrates compliance with ISO 14687-2 and SAE J2574 standards, offering a scalable and efficient solution for next-generation fuel cell electric vehicle (FCEV) aligned with global decarbonization targets, including the EU’s 2035 CO₂ neutrality mandate. Full article

Chronic respiratory diseases claim nearly four million lives annually, making them the third leading cause of death worldwide. Extracorporeal membrane oxygenation (ECMO) is often the last line of support for patients with severe lung failure. Still, its performance is limited by an incomplete understanding of gas exchange in hollow fiber membrane (HFM) oxygenators. Computational fluid dynamics (CFD) has become a robust oxygenator design and optimization tool. However, most models oversimplify O₂ and CO₂ transport by ignoring their physiological coupling, instead relying on fixed saturation curves or constant-content assumptions. For the first time, this study introduces a novel physiologically informed CFD model that integrates the Bohr and Haldane effects to capture the coupled transport of oxygen and carbon dioxide as functions of local pH, temperature, and gas partial pressures. The model is validated against in vitro experimental data from the literature and assessed against established CFD models. The proposed CFD model achieved excellent agreement with experiments across blood flow rates (100–500 $\mathrm{mL}/\min$ ), with relative errors below 5% for oxygen and 10–15% for carbon dioxide transfer. These results surpassed the accuracy of all existing CFD approaches, demonstrating that a carefully formulated single-phase model combined with physiologically informed diffusivities can outperform more complex multiphase simulations. This work provides a computationally efficient and physiologically realistic framework for oxygenator optimization, potentially accelerating device development, reducing reliance on costly in vitro testing, and enabling patient-specific simulations. Full article

Trail running involves constant changes in terrain and slope, complicating the accurate assessment of energy expenditure during performance. This study aimed to examine the relationship between running power output (RPO), oxygen consumption (VO₂), carbon dioxide production (VCO₂), and energy expenditure per minute (EE_min) across positive and negative slopes in trained trail runners under standardized laboratory conditions. Fifteen male trail runners performed five randomized 5 min treadmill runs at 70% of VO₂ maximal speed on −7%, −5%, 0%, +5%, and +7% slopes. VO₂, VCO₂, EE_min, respiratory exchange ratio (RQ), heart rate (HR), and RPO were recorded. Statistical analysis included Shapiro–Wilk tests for normality, repeated-measures ANOVA to compare variables across slopes, and Spearman or Pearson correlations between RPO and physiological variables. Moderate to strong positive correlations were found between RPO and VO₂ (Rho = 0.80–0.84, p < 0.001) and between RPO and EE_min (Rho= 0.74–0.87, p < 0.01) across all conditions. These findings suggest that RPO measured via a wearable device may reflect changes in energy expenditure and supports the integration of wearable power metrics into training and nutritional strategies for trail running. However, further studies in female athletes, outdoor settings, extreme slopes, and altitude conditions are needed to confirm the generalizability of these results. Full article

Background: Maintaining thermal homeostasis is a basic function of the human body. This homeostasis depends largely on the body’s nutritional status and other conditions related to it. Aim: The present study investigated the impact of 8 days of water-only fasting (8DW-F) on selected features of thermal homeostasis, taking into account somatic, metabolic, and circulatory changes in middle-aged men. Methods: A total of 13 healthy men took part in the experiment. Volunteers were examined twice: after a mixed diet (C) and after using 8DW-F. At baseline, the following were recorded: body mass (BM), body fat (FM), fat-free mass (FFM), and total water (TBW), along with basal metabolic rate (BMR) and body surface area (BSA). Then, after 30 min of sitting under thermoneutral conditions, the following measurements were taken: eardrum temperature (Ti), skin temperatures (Tsk), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), oxygen uptake (VO₂), and respiratory exchange ratio (RER). The following were then calculated: average body (MTB) and skin temperature (MTsk), resting metabolic rate (RMR), body to skin temperature gradient (g), and whole-body thermal conductivity (C). Results: The results showed that 8DW-F cause a significant reduction in most somatic variables as well as SBP and BMR (p < 0.001), RMR (p < 0.05) with no changes in Ti, MTsk, MTB, or C and g (p = 0.09). There were also significant correlations between Δ MTB × Δ BMR (p < 0.05) and Δ RMR × Δ VO₂ (p < 0.001). Moreover, changes in the C range correlated with Δ RMR (p < 0.005) and Δ DBP (p < 0.05). Conclusions: 8DW-F reduced resting metabolic heat production in the studied men, but sufficient heat conservation ensured that thermal homeostasis was maintained under thermally neutral conditions. Full article