Vacancy Suppression and Resonant Level Rendering Extraordinary Power Factor in Sn0.99In0.01Te/Tourmaline Composite.

SnTe, as a potential medium-temperature thermoelectric material, reaches a maximum power factor (PF) usually above 750 K, which is not conducive to continuous high-power output in practical applications. In this study, PF is maintained at high values between 18.5 and 25 µW cm-1 K-2 for Sn0.99In0.01Te-x wt% tourmaline samples within the temperature range of 323 to 873 K, driving the highest PFeng of 1.2 W m-1 K-1 and PFave of 22.5 µW cm-1 K-2, over 2.5 times that of pristine SnTe. Such an extraordinary PF is attributed to the synergy of resonant levels and Sn vacancy suppression. Specifically, the Seebeck coefficient increases dramatically, reaching 88 µV K-1 at room temperature. Meanwhile, by Sn vacancy suppression, carrier concentration, and mobility are optimized to ≈1019 cm-3 and 740 cm2 V-1 s-1, respectively. With the tourmaline compositing, Sn vacancies are further suppressed and the thermal conductivity simultaneously decreases, with the minimum lattice thermal conductivity of 0.9 W m-1 K-1. Finally, the zT value ≈0.8 is obtained in the Sn0.99In0.01Te sample. The peak of the power output density reaches 0.89 W cm-2 at a temperature difference of 600 K. Such SnTe alloys with high and "temperature-independent" PF will offer an option for realizing high output power in thermoelectric devices.

High-fat diet effects on contractile performance of isolated mouse soleus and extensor digitorum longus when supplemented with high dose vitamin D.

Evidence suggests vitamin D3 (VD) supplementation can reduce accumulation of adipose tissue and inflammation and promote myogenesis in obese individuals, and thus could mitigate obesity-induced reductions in skeletal muscle (SkM) contractility. However, this is yet to be directly investigated. This study, using the work-loop technique, examined effects of VD (cholecalciferol) supplementation on isolated SkM contractility. Female mice (n = 37) consumed standard low-fat diet (SLD) or high-fat diet (HFD), with or without VD (20,000 IU/kg-1 ) for 12 weeks. Soleus and EDL (n = 8-10 per muscle per group) were isolated and absolute and normalized (to muscle size and body mass) isometric force and power output (PO) were measured, and fatigue resistance determined. Absolute and normalized isometric force and PO of soleus were unaffected by diet (P > 0.087). However, PO normalized to body mass was reduced in HFD groups (P < 0.001). Isometric force of extensor digitorum longus (EDL) was unaffected by diet (P > 0.588). HFD reduced EDL isometric stress (P = 0.048) and absolute and normalized PO (P < 0.031), but there was no effect of VD (P > 0.493). Cumulative work during fatiguing contractions was lower in HFD groups (P < 0.043), but rate of fatigue was unaffected (P > 0.060). This study uniquely demonstrated that high-dose VD had limited effects on SkM contractility and did not offset demonstrated adverse effects of HFD. However, small and moderate effect sizes suggest improvement in EDL muscle performance and animal morphology in HFD VD groups. Given effect sizes observed, coupled with proposed inverted U-shaped dose-effect curve, future investigations are needed to determine dose/duration specific responses to VD, which may culminate in improved function of HFD SkM.

Effects of plasmapheresis frequency on health status and exercise performance in men: A randomized controlled trial.

BACKGROUND AND OBJECTIVES: Most research studies on the effects of repeated plasma donation are observational with different study limitations, resulting in high uncertainty on the link between repeated plasma donation and health consequences. Here, we prospectively investigated the safety of intensive or less intensive plasma donation protocols. MATERIALS AND METHODS: Sixty-three male subjects participated in this randomized controlled trial and were divided into low-frequency (LF, once/month, n = 16), high-frequency (HF, three times/month, n = 16), very high-frequency (VHF, two times/week, n = 16) and a placebo (P, once/month, n = 15) groups. Biochemical, haematological, clinical, physiological and exercise-related data were collected before (D0), after 1½ months (D42) and after 3 months (D84) of donation. RESULTS: In VHF, red blood cells, haemoglobin and haematocrit levels decreased while reticulocyte levels increased from D0 to D84. In both HF and VHF, plasma ferritin levels were lower at D42 and D84 compared to D0. In VHF, plasma levels of albumin, immunoglobulin G (IgG), immunoglobulin A (IgA) and immunoglobulin M (IgM) dropped from D0 to D42 and remained lower at D84 than at D0. In HF, plasma IgG, IgA and IgM were lower at D42, and IgG and IgM were lower at D84, compared to D0. Few adverse events were reported in HF and VHF. Repeated plasma donation had no effect on blood pressure, body composition or exercise performance. CONCLUSION: VHF plasmapheresis may result in a large reduction in ferritin and IgG levels. HF and VHF plasmapheresis may result in little to no difference in other biochemical, haematological, clinical, physiological and exercise-related parameters.

The effect of caffeine chewing gum on muscle performance and fatigue after severe-intensity exercise: isometric vs. dynamic assessments in trained cyclists.

This study investigated the effect of caffeinated chewing gum (GUMCAF) on muscle fatigue (isometric vs. dynamic) after severe-intensity cycling bouts. Fifteen trained male cyclists participated in four visits. Each visit involved two severe-intensity cycling bouts (Δ1 and Δ2) lasting 6 min, separated by a 5-min recovery period. Muscle fatigue was assessed by isometric maximal voluntary knee extension contraction (IMVC) with twitch interpolation technique and dynamically by 7 s all-out cycling sprints. Assessments were performed before GUMCAF (Pre-GUM) and after the cycling bouts (Post-Exercise). GUMCAF and placebo gum (GUMPLA) were administered in a randomized double-blind procedure with participants receiving each gum type (GUMCAF and GUMPLA) during two separate visits. The results showed no significant interaction between gum types and time for the isometric and dynamic measurements (p > 0.05). The percentage change in performance from Pre-GUM to Post-Exercise showed no significant difference between GUMCAF and GUMPLA for either the dynamic-derived TMAX (~ -17.8% and -15.1%, respectively; p = 0.551) or isometric IMVC (~ -12.3% and -17.7%, respectively; p = 0.091) measurements. Moderate to large correlations (r = 0.31-0.51) were found between changes in sprint maximal torque and maximal power output measurements and isometric force, for both gum conditions. GUMCAF was not effective in attenuating muscle force decline triggered by severe-intensity cycling exercises, as measured by both isometric and dynamic methods. The correlations between IMVC and cycling maximal torque and power output suggest caution when interpreting isometric force as a direct measure of fatigue during dynamic cycling exercises.

Machine learning predicts peak oxygen uptake and peak power output for customizing cardiopulmonary exercise testing using non-exercise features.

PURPOSE: Cardiopulmonary exercise testing (CPET) is considered the gold standard for assessing cardiorespiratory fitness. To ensure consistent performance of each test, it is necessary to adapt the power increase of the test protocol to the physical characteristics of each individual. This study aimed to use machine learning models to determine individualized ramp protocols based on non-exercise features. We hypothesized that machine learning models will predict peak oxygen uptake ( V ˙ O2peak) and peak power output (PPO) more accurately than conventional multiple linear regression (MLR). METHODS: The cross-sectional study was conducted with 274 (♀168, ♂106) participants who performed CPET on a cycle ergometer. Machine learning models and multiple linear regression were used to predict V ˙ O2peak and PPO using non-exercise features. The accuracy of the models was compared using criteria such as root mean square error (RMSE). Shapley additive explanation (SHAP) was applied to determine the feature importance. RESULTS: The most accurate machine learning model was the random forest (RMSE: 6.52 ml/kg/min [95% CI 5.21-8.17]) for V ˙ O2peak prediction and the gradient boosting regression (RMSE: 43watts [95% CI 35-52]) for PPO prediction. Compared to the MLR, the machine learning models reduced the RMSE by up to 28% and 22% for prediction of V ˙ O2peak and PPO, respectively. Furthermore, SHAP ranked body composition data such as skeletal muscle mass and extracellular water as the most impactful features. CONCLUSION: Machine learning models predict V ˙ O2peak and PPO more accurately than MLR and can be used to individualize CPET protocols. Features that provide information about the participant's body composition contribute most to the improvement of these predictions. TRIAL REGISTRATION NUMBER: DRKS00031401 (6 March 2023, retrospectively registered).

Effects of different ischemic pressures on bar velocity during the bench press exercise: A randomized crossover trial.

The main objective of this study was to evaluate the effects of different ischemic pressures applied during rest intervals on bar velocity during the bench press exercise. 10 resistance-trained males (age = 23.2 ± 2.7 years; body mass = 83.9 ± 9 kg; body height = 181 ± 5.2 cm; bench press 1 repetition maximum (1RM) = 125 ± 16.4 kg; training experience = 5.4 ± 3.4 years) participated in the study. During 4 experimental sessions, following a randomized crossover design, the subjects performed 5 sets of 3 repetitions of the bench press exercise with a load of 60% 1RM under conditions: with ischemia (50% or 80% of arterial occlusion pressure), with SHAM ischemia (20 mmHg) and without ischemia (control condition). For the ischemic conditions cuffs were applied before each set for 6.5 min and released 30 s before the start of the set as reperfusion (6.5 min ischemia + 0.5 min reperfusion). In the control condition, ischemia was not applied. The two-way repeated measures ANOVA showed no significant condition × set interaction for mean bar velocity (MV; p = 0.17) and peak bar velocity (PV; p = 0.66). There was also no main effect of condition for MV (p = 0.58) and PV (p = 0.61). The results indicate that ischemic or SHAM treatment (6.5 minutes ischemia or SHAM + 30 s reperfusion) does not affect mean and peak bar velocity during the bench press exercise regardless of the applied pressure.

Densification Induced Decoupling of Electrical and Thermal Properties in Free-Standing MWCNT Films for Ultrahigh p- and n-Type Power Factors and Enhanced ZT.

Generating sufficient power from waste heat is one of the most important things for thermoelectric (TE) techniques in numerous practical applications. The output power density of an organic thermoelectric generator (OTEG) is proportional to the power factors (PFs) and the electrical conductivities of organic materials. However, it is still challenging to have high PFs over 1 mW m-1  K-2 in free-standing films together with high electrical conductivities over 1000 S cm-1 . Herein, densifying multi-walled carbon nanotube (MWCNT) films would increase their electrical conductivity dramatically up to over 10 000 S cm-1 with maintained high Seebeck coefficients >60 µV K-1 , thus leading to ultrahigh PFs of 7.25 and 4.34 mW m-1  K-2 for p- and n-type MWCNT films, respectively. In addition, it is interesting to notice that the electrical properties increase faster than the thermal conductivities, resulting in enhanced ZT of 3.6 times in MWCNT films. An OTEG made of compressed MWCNT films is fabricated to demonstrate the heat-to-electricity conversion ability, which exhibits a high areal output power of ∼12 times higher than that made of pristine MWCNT films. This work demonstrates an effective way to high-performance nanowire/nanoparticle-based TE materials such as printable TE materials comprised of nanowires/nanoparticles.

Conversion efficiency of flight power is low, but increases with flight speed in the migratory bat Pipistrellus nathusii.

The efficiency with which flying animals convert metabolic power to mechanical power dictates an individual's flight behaviour and energy requirements. Despite the significance of this parameter, we lack empirical data on conversion efficiency for most species as in vivo measurements are notoriously difficult to obtain. Furthermore, conversion efficiency is often assumed to be constant across flight speeds, even though the components driving flight power are speed-dependent. We show, through direct measurements of metabolic and aerodynamic power, that conversion efficiency in the migratory bat (Pipistrellus nathusii) increases from 7.0 to 10.4% with flight speed. Our findings suggest that peak conversion efficiency in this species occurs near maximum range speed, where the cost of transport is minimized. A meta-analysis of 16 bird and 8 bat species revealed a positive scaling relationship between estimated conversion efficiency and body mass, with no discernible differences between bats and birds. This has profound consequences for modelling flight behaviour as estimates assuming 23% efficiency underestimate metabolic costs for P. nathusii by almost 50% on average (36-62%). Our findings suggest that conversion efficiency may vary around an ecologically relevant optimum speed and provide a crucial baseline for investigating whether this drives variation in conversion efficiency between species.

Evidence for multi-scale power amplification in skeletal muscle.

Many animals use a combination of skeletal muscle and elastic structures to amplify power output for fast motions. Among vertebrates, tendons in series with skeletal muscle are often implicated as the primary power-amplifying spring, but muscles contain elastic structures at all levels of organization, from the muscle tendon to the extracellular matrix to elastic proteins within sarcomeres. The present study used ex vivo muscle preparations in combination with high-speed video to quantify power output, as the product of force and velocity, at several levels of muscle organization to determine where power amplification occurs. Dynamic ramp-shortening contractions in isolated frog flexor digitorum superficialis brevis were compared with isotonic power output to identify power amplification within muscle fibers, the muscle belly, free tendon and elements external to the muscle tendon. Energy accounting revealed that artifacts from compliant structures outside of the muscle-tendon unit contributed significant peak instantaneous power. This compliance included deflection of clamped bone that stored and released energy contributing 195.22±33.19 W kg-1 (mean±s.e.m.) to the peak power output. In addition, we found that power detected from within the muscle fascicles for dynamic shortening ramps was 338.78±16.03 W kg-1, or approximately 1.75 times the maximum isotonic power output of 195.23±8.82 W kg-1. Measurements of muscle belly and muscle-tendon unit also demonstrated significant power amplification. These data suggest that intramuscular tissues, as well as bone, have the capacity to store and release energy to amplify whole-muscle power output.

The prognostic role of advanced hemodynamic variables in patients with left ventricular assist devices.

BACKGROUND: Invasive hemodynamic variables obtained from right heart catheterization have been used for risk-stratifying patients with advanced heart failure (HF). However, there is a paucity of data on the prognostic value of invasive hemodynamic variables in patients with left ventricular assist devices (LVAD). We hypothesized that cardiac power output (CPO), cardiac power efficiency (CPE), and left ventricular stroke work index (LVSWI) can serve as prognostic markers in patients with LVADs. METHODS: Baseline hemodynamic data from patients who had LVAD ramp studies at our institution from 4/2014 to 7/2018 were prospectively collected, from which advanced hemodynamic variables (CPO, CPE, and LVSWI) were retrospectively analyzed. Univariate and multivariable analyses were performed for hemocompatibility-related adverse events (HRAE), HF admissions, and mortality. RESULTS: Ninety-one participants (age 61 ± 11 years, 34% women, 40% Black or African American, and 38% ischemic cardiomyopathy) were analyzed. Low CPE was significantly associated with mortality (HR 2.42, 95% CI 1.02-5.74, p = 0.045) in univariate analysis and Kaplan-Meier analysis (p = 0.04). Low LVSWI was significantly associated with mortality (HR 2.13, 95% CI 1.09-4.17, p = 0.03) in univariate analysis and Kaplan-Meier analysis (p = 0.02). CPO was not associated with mortality. CPO, CPE, and LVSWI were not associated with HRAE or HF admissions. CONCLUSIONS: Advanced hemodynamic variables can serve as prognostic indicators for patients with LVADs. Low CPE and LVSWI are prognostic for higher mortality, but no variables were associated with HF admissions or HRAEs.

Force-velocity profiling of elite wheelchair rugby players by manipulating rolling resistance over multiple wheelchair sprints.

This study investigated the effect of increased rolling resistance on wheelchair sprint performance and the concomitant force-velocity characteristics. Thirteen wheelchair rugby (WCR) athletes completed five 15 s wheelchair sprints in their own rugby wheelchair on an instrumented dual-roller wheelchair ergometer. The first sprint was performed against a close to overground resistance and in each of the following sprints, the resistance increased with 80% of that resistance. A repeated-measures ANOVA examined differences between sprints. Subsequently, linear regression analyses examined the individual force-velocity relations and then, individual parabolic power output curves were modeled. Increased rolling resistance led to significantly lower velocities (-36%), higher propulsion forces (+150%) and higher power outputs (+83%). These differences were accompanied by a lower push frequency, higher push time, yet a constant recovery time and contact angle. The modeled linear regressions (R2 = 0.71 ± 0.10) between force and velocity differed a lot in slope and intercept among individual athletes. The peak of the power output parabola (i.e., the optimal velocity) occurred on average at 3.1 ± 0.6 ms-1 . These individual force-velocity profiles can be used for training recommendations or technological changes to better exploit power generation capabilities of the WCR athletes' musculoskeletal system.

Effects of circadian rhythm on anaerobic performance and blood lactate level: a systematic review.

PURPOSE: Circadian rhythm affects maximal short-term performance, and it is an important determinant of the training component. This review aimed to summarise the influence of circadian rhythm on peak and mean power output of muscle, fatigue index, and blood lactate levels. METHODS: English language articles were searched through the following databases: PubMed, Web of Science, Science Direct, and Google Scholar, and pertinent randomized control trials were scrutinized. RESULTS: The search revealed 17,481 articles, and 29 were included in this systematic review based on inclusion and exclusion criteria. Randomized control trials were selected, and the methodological validity of articles was evaluated using the 'Cochrane risk of bias tool'. Findings suggest that outcome variables muscle peak power output (p < 0.0001, Z = 7.22, I2 = 57.42, SMD = - 0.91, 95% confidence interval CI = - 1.16, - 0.67), muscle mean power output (p < 0.0001, Z = 5.66, I2 = 83.85, SMD = - 0.75, 95% CI = - 1.01, - 0.49), and fatigue index (p = 0.02, Z = 2.41, I2 = 2.49, SMD = - 0.39, 95% CI = - 0.72, - 0.07) were higher in the evening while the level of blood lactate was higher in the morning (p = 0.79, Z = 0.27, I2 = 0.73, SMD = - 0.05, 95% CI = - 0.46, - 0.35). CONCLUSION: The results show that diurnal variation affects both peak and mean power output of muscle as well as fatigue index. However, there is no remarkable effect of circadian rhythm on blood lactate level. A major factor attributed to this finding was the variation in the training experience of participants. For an effective training prescription, it is very important to consider the effect of the biological clock on muscle power output since anaerobic exercise performance is discernibly influenced by the time of the day.

Whole-body photobiomodulation improves post-exercise recovery but does not affect performance or physiological response during maximal anaerobic cycling.

This study aims to examine the effects of acute whole-body photobiomodulation (wbPBM), applied pre-exercise, on bouts of anaerobic cycling (Wingate) performances. Forty-eight healthy, active males and females participated in this single-blind, randomized, crossover study. Participants visited the laboratory three times to complete repeat (4 ×) Wingate testing, with one week between each visit. All participants completed baseline testing during their first visit and randomly received either the wbPBM or placebo condition before testing on the second visit, followed by the opposite condition on the third visit. There were no significant condition × time interactions for any variable (peak power, average power, power decrement, lactate, heart rate, ratings of perceived exertion, heart rate variability (HRV), root-mean square of differences between R-R intervals (rMSSD), power in the high-frequency range (HF) average, power in the low-frequency range (LF) average, total power, LF/HF, or power in the very-low-frequency range average). A main condition effect was only noted for heart rate, where peak heart rate was significantly higher for wbPBM (145, 141-148 bpm) than placebo (143, 139-146 bpm; p = 0.006) and baseline testing (143, 140-146; p = 0.049) throughout the entire testing session (i.e., collapsed across all timepoints). Furthermore, HRV (rMSSD) the following morning after testing was significantly higher for the wbPBM session compared to placebo (p = 0.043). There were no differences in perceived recovery (p = 0.713) or stress (p = 0.978) scores between wbPBM and placebo. Implementing 20 min of wbPBM immediately prior to maximal bouts of anaerobic cycling did not improve performance (i.e., power output) or physiological responses (e.g., lactate). However, wbPBM elicited the ability to work at a higher heart rate throughout testing and seemed to enhance recovery through improved HRV the following morning.

Prediction of rowing ergometer performance by technical and core stability parameters.

The purpose of this study was to evaluate the influence of technical and core stability parameters on rowing ergometer performance defined as mean power at the handle. Twenty-four high-level rowers were evaluated at their competitive stroke rate on an instrumented RowPerfect 3 ergometer to determine leg, trunk and arm power output, while trunk and pelvis 3D kinematics were measured. Linear mixed models revealed that mean power at the handle was predicted by the power output of legs, trunk and arms (r2 = 0.99), with trunk power being the best predictor. Time to peak power, work ratio and mean to peak power ratio were relevant technical parameters significantly predicting the different segments' power. In addition, a greater trunk range of motion significantly influenced the power produced by this segment. Accordingly, achieving an earlier peak power together with enhanced work production at the trunk and arm levels, as well as distributing the segments power over the whole drive phase, could serve as recommendations for technical training of rowers on dynamic ergometers in order to produce higher power output. Furthermore, the trunk appears to play a major role as a power producer within the kinetic chain from the legs to the arms.

Mouth Rinsing and Ingestion of Unpleasant Salty or Bitter Solutions Does Not Improve Cycling Sprint Performance in Trained Cyclists.

The purpose of this study was to investigate the influence of mouth rinsing and ingesting unpleasant salty or bitter solutions on cycling sprint performance and knee extensor force characteristics. Eleven male and one female trained cyclists (age: 34 ± 9 years, maximal oxygen uptake 56.9 ± 3.9 ml·kg-1·min-1) completed a ramp test and familiarization followed by four experimental trials. In each trial, participants completed an all-out 30-s cycling sprint with knee extensor maximal voluntary contractions before and immediately after the sprint. In a randomized, counterbalanced, cross-over order, the four main trials were: a no solution control condition, water, salty (5.8%), or bitter (2 mM quinine) solutions that were mouth rinsed (10 s) and ingested immediately before the cycling sprint. There were no significant differences between conditions in mean power (mean ± SD, no solution: 822 ± 115 W, water: 818 ± 108 W, salt: 832 ± 111 W, bitter: 818 ± 105 W); peak power (no solution: 1,184 ± 205 W, water: 1,177 ± 207 W, salt: 1,195 ± 210 W, bitter: 1,184 ± 209 W); or fatigue index (no solution: 51.5% ± 5.7%, water: 50.8% ± 7.0%, salt: 51.1% ± 5.9%, bitter: 51.2% ± 7.1%) during the sprint. Maximal force and impulse declined postexercise; however, there were no significant differences between conditions in knee extensor force characteristics. The present data do not support the use of unpleasant salty or bitter solutions as an ergogenic aid to improve sprint exercise performance.

Concurrent Validity and Reliability of Two Portable Powermeters (Power2Max vs. PowerTap) to Measure Different Types of Efforts in Cycling.

The purpose was to assess the concurrent validity and reliability of two portable powermeters (PowerTap vs. Power2Max) in different types of cycling efforts. Ten cyclists performed two submaximal, one incremental maximal and two supramaximal sprint tests on an ergometer, while pedaling power and cadence were registered by both powermeters and a cadence sensor (GarminGSC10). During the submaximal and incremental maximal tests, significant correlations were found for power and cadence data (r = 0.992-0.997 and 0.996-0.998, respectively, p < 0.001), with a slight power underestimation by PowerTap (0.7-1.8%, p < 0.01) and a high reliability of both powermeters (p < 0.001) for measurement of power (ICC = 0.926 and 0.936, respectively) and cadence (ICC = 0.969 and 0.970, respectively). However, during the supramaximal sprint test, their agreement to measure power and cadence was weak (r = 0.850 and -0.253, p < 0.05) due to the low reliability of the cadence measurements (ICC between 0.496 and 0.736, and 0.574 and 0.664, respectively; p < 0.05) in contrast to the high reliability of the cadence sensor (ICC = 0.987-0.994). In conclusion, both powermeters are valid and reliable for measuring power and cadence during continuous cycling efforts (~100-450 W), but questionable during sprint efforts (>500 W), where they are affected by the gear ratio used (PowerTap) and by their low accuracy in cadence recording (PowerTap and Power2Max).

Review of Zinc Oxide Piezoelectric Nanogenerators: Piezoelectric Properties, Composite Structures and Power Output.

Lead-containing piezoelectric materials typically show the highest energy conversion efficiencies, but due to their toxicity they will be limited in future applications. In their bulk form, the piezoelectric properties of lead-free piezoelectric materials are significantly lower than lead-containing materials. However, the piezoelectric properties of lead-free piezoelectric materials at the nano scale can be significantly larger than the bulk scale. This review looks at the suitability of ZnO nanostructures as candidate lead-free piezoelectric materials for use in piezoelectric nanogenerators (PENGs) based on their piezoelectric properties. Of the papers reviewed, Neodymium-doped ZnO nanorods (NRs) have a comparable piezoelectric strain constant to bulk lead-based piezoelectric materials and hence are good candidates for PENGs. Piezoelectric energy harvesters typically have low power outputs and an improvement in their power density is needed. This review systematically reviews the different composite structures of ZnO PENGs to determine the effect of composite structure on power output. State-of-the-art techniques to increase the power output of PENGs are presented. Of the PENGs reviewed, the highest power output belonged to a vertically aligned ZnO nanowire (NWs) PENG (1-3 nanowire composite) with a power output of 45.87 µW/cm2 under finger tapping. Future directions of research and challenges are discussed.

Energetic evaluation of phenol wastewater treatment by reverse electrodialysis reactor using different anodes.

Efficient electrode materials are essential to convert salinity gradient energy into oxidative degradation energy and electrical energy by reverse electrodialysis reactor (REDR). In this context, comparative experiments of REDR using different anodes (Ti/IrO2-RuO2, Ti/PbO2 and Ti/Ti4O7) were conducted. The effects of output current and electrode rinse solution (ERS) flowrate on mineralization efficiency and energy output were discussed. Results demonstrated that the COD removal rate(ηCOD) rose almost linearly with output current and ERS flowrate when using Ti/Ti4O7 anode, but excessive operating conditions caused a slow increase or even decrease of ηCOD when using Ti/IrO2-RuO2 or Ti/PbO2 anodes. The order of electrode system potential loss (Eele) for the three anodes was Ti/Ti4O7> Ti/PbO2> Ti/IrO2-RuO2. High Eele was beneficial to ηCOD but had a negative effect on the net output power (Pnet) of REDR. Regardless of the applied anodes, increasing the current and decreasing the ERS flowrate was detrimental to Pnet due to higher Eele. Based on these findings, four energy efficiency parameters were defined to evaluate energy recovery from multiple perspectives by linking energy output with mineralization capacity. They were electrode efficiency (ηele), energy efficiency (EE), general current efficiency (GCE) and energy consumption (EC), respectively. Results showed that REDR with Ti/Ti4O7 anodes and suitable operating conditions achieved the optimal energy indicators and mineralization efficiency, which provided an efficient and economical option for wastewater treatment and energy recovery.

Analysis of the Maximum Efficiency and the Maximum Net Power as Objective Functions for Organic Rankine Cycles Optimization.

Maximum efficiency and maximum net power output are some of the most important goals to reach the optimal conditions of organic Rankine cycles. This work compares two objective functions, the maximum efficiency function, ß, and the maximum net power output function, ω. The van der Waals and PC-SAFT equations of state are used to calculate the qualitative and quantitative behavior, respectively. The analysis is performed for a set of eight working fluids, considering hydrocarbons and fourth-generation refrigerants. The results show that the two objective functions and the maximum entropy point are excellent references for describing the optimal organic Rankine cycle conditions. These references enable attaining a zone where the optimal operating conditions of an organic Rankine cycle can be found for any working fluid. This zone corresponds to a temperature range determined by the boiler outlet temperature obtained by the maximum efficiency function, maximum net power output function, and maximum entropy point. This zone is named the optimal temperature range of the boiler in this work.

Analysis of velocity- and power-load relationships of the free-weight back-squat and hexagonal bar deadlift exercises.

The aim of this study was to analyse the load-velocity and load-power relationships in the free-weight back-squat (BSQ) and hexagonal bar deadlift (HBD) exercises. Twenty-five (n = 25) resistance-trained men (age = 23.7 ± 2.8 years) performed a progressive load test at maximal intended velocity to determine their BSQ and HBD one-repetition maximum (1RM). Mean propulsive velocity (MPV) during the concentric phase of the lift was recorded through a linear encoder. Load-velocity and load-power relationships were analysed by fitting linear regression and the second-order polynomial, respectively, to the data. Maximum strength (1RM), MPV (30-80% 1RM), and power output (30-90% 1RM) were higher for HBD compared to BSQ exercise (p < 0.05). A very strong relationship between MPV and relative intensity was found for both BSQ (R2 = 0.963) and HBD (R2 = 0.967) exercises. The load that maximizes power output (Pmax) was 64.6 ± 2.9% (BSQ) and 59.6 ± 1.1% (HBD) 1RM. There was a range of loads at which power output was not different than Pmax (BSQ: 40-80% 1RM; HBD: 50-70% 1RM). In conclusion, the load-velocity and load-power relationships might assist strength and conditioning coaches to monitor and prescribe exercise intensity in the BSQ and HBD exercises using the velocity-based training approach.