No Load Research Articles

Estimating marksmanship performance during walking while maintaining weapon aim

Marksmanship performance while moving is a critical skill among tactical athletes due to the high demands of their occupational duties. Qualifications for dynamic marksmanship performance are not standardized across tactical athlete groups, which may limit comprehensive assessment of tactical athlete performance for situational awareness and adaptability to an unpredictable environment. Although static marksmanship performance provides foundational information on skills and level of ability, research is lacking on factors that influence dynamic marksmanship performance to best prepare tactical athletes for duties. The purpose of this study was to identify whether static marksmanship performance, speed of movement, load carriage, and biomechanical factors while ‘shooting on the move’ influenced dynamic marksmanship performance. Twenty-four male tactical athletes (22 active-duty Army Soldiers, two civilian SWAT operators; age: 23.83 ± 5.47 years; height: 1.80 ± 0.08 m; weight: 81.04 ± 7.87 kg) participated; final analyses did not include data from the two civilian operators to maintain sample homogeneity. Tactical athletes completed static and dynamic (‘shoot on the move’) marksmanship tasks under three load conditions: (1) no load (NL), (2) half kit (HK) of 11.34 kg, and (3) full kit (KIT) of 22.68 kg. Dynamic marksmanship was completed under three speed conditions: (1) self-selected slow speed, (2) standard speed, and (3) self-selected fast speed. Hip, knee, and ankle kinematics were collected via wireless inertial measurement units. Spatiotemporal parameters were collected via optical detection system. Marksmanship performance (accuracy) was collected via open-air acoustic target scoring and mean radial error (MRE) was calculated for both static and dynamic marksmanship tasks. Linear mixed-effects models were fit with dynamic MRE as the outcome variable with fixed effects of static MRE, load condition, speed condition, kinematics, and spatiotemporal parameters, adjusting for body mass. Alpha level was set a priori at p ≤ 0.10. The final statistical model included fixed effects of static MRE, load condition, speed condition, and time spent in double limb support. Static MRE (p < 0.01) and time spent in double limb support (p = 0.01) were significant factors. For each 1 cm increase in static MRE there was a 0.66 cm increase in dynamic MRE. For every 1% increase in time spent in double limb support while ‘shooting on the move’ there was a 0.13 cm increase in dynamic MRE. Findings from this study highlight that tactical athletes who have larger static stance MRE and spend a longer time in double limb support during a gait cycle exhibit an increase in MRE during ‘shoot on the move’ trials. Overall, dynamic shooting accuracy is not affected by lower extremity joint angles, load carriage, or speed of movement. Although strong relationships are known between gait speed, load, and lower extremity kinematics, the differences in tactical gait compared to normal gait and multi-task paradigm that likely favors marksmanship accuracy seem to present novel movement characteristics unique to occupational gait. Further investigation is warranted to identify other potential factors that may improve or worsen dynamic marksmanship performance.

Impact of leptin or melatonin on Sema4D overexpression-related bone metabolism

PurposeThe current study aims to investigate the regulatory impact of leptin or melatonin on bone metabolism as well as the underlying mechanism in conjunction with Sema4D (monoclonal antibody to semaphorin 4D).MethodsRats were used to create the osteoporosis model utilizing the OVX (OVariectomize) technique. Rat tibial specimens from each side were collected for three-dimensional reconstruction and Micro-CT scanning examination. The Hematoxylin-osinstaining (HE) staining technique was used to determine the pathological condition of bone tissues. The ELISA (Enzyme-Linked Immunosorbent Assay) assay was used to measure the amount of estradiol present in the serum. In the current study, there were six groups: control, OVX, OVX + NL (no load group), OVX + Sema4D, OVX + Sema4D + leptin, and OVX + Sema4D + MT (melatonin). Rats were given injections of the Sema4D or leptin overexpressing vectors via the tail vein in accordance with the aforementioned classification. By using a high-resolution micro-CT technology, 3D bone structure was discovered. The activity of tartrate-resistant acid phosphatase-5b (TRAP-5b) and bone-derived alkaline phosphatase (BALP) in serum was assessed using an ELISA. The number of osteoclasts in the metaphysis of the upper tibia was determined using TRAP (tartrate-resistant acid phosphatase) staining. Immunohistochemistry was used to find leptin and bone morphogenetic protein-2 (BMP-2) expressions in bone tissue.ResultsThe BV/TV (Bone volume/Tissue volume), Tb.N (Trabecular number), BMD (Bone Mineral Density), and BMC (Bone Mineral Content) levels were significantly higher in the OVX + Sema4D + leptin and OVX + Sema4D + MT groups compared to OVX + NL, while Tb.Sp (Trabecular separation) levels were significantly lower. In contrast to the OVX group, the bone trabeculae in the OVX + Sema4D + leptin and OVX + Sema4D + MT groups had a relatively complete structure and tended to be organized closely. The amount of bone trabeculae grew drastically, whereas the proportion of TRAP-positive osteoclasts declined dramatically. BMP-2 and leptin were also elevated, while BALP and TRAP-5b activity was reduced.ConclusionLeptin or melatonin improved Sema4d's role in trabecular bone microstructure, bone production, and repairment of trabecular bone loss in osteoporosis rats.

Effect of long-distance load marching on physiological responses at desert environment

AIM: The present study was undertaken to examine the effect of long-distance load marching on the physiological responses, walking efficiency, and mobility of soldiers at sandy desert environment. METHODS: A total of nine physically fit soldiers (age, 30.00 [SE 0.9] years; height, 175.56 [SE 1.18] cm; and weight, 77.83 [SE 1.37] kg) volunteered for long-distance (6 km) load marching by self-selected speed when carrying 22 kg (28.27% of body weight [BW]) load and no load (NL). Heart rate (HR), respiratory frequency (RF), and core body temperature (CBT) were recorded. Relative workload (RWL) and Physiological Cost Index (PCI) were calculated to assess the work intensity and mobility. RESULTS: It was observed that HR (P = 0.01), RWL (P = 0.01), and PCI (P = 0.01) were significantly increased by 23.79, 39.71, and 77.73%, respectively, and mobility was significantly reduced (P = 0.01) by 18.56% during marching with 22 kg load as compared to NL. CONCLUSION: It may be that marching without external load at speed of 4.85 ± 0.54 km/h should not be continued for more than 2 h, whereas marching with load of 28.27% of BW at speed of 3.95 ± 0.55 km/h should be restricted to maximum 30 min. This combination of load, speed, and duration provides information about soldiers' routine load carriage tasks, which may help in optimizing the load carriage task to reduce the chances of cumulative carriage-related injuries and, therefore, may contribute to improved soldiers' operational readiness and mobility.

Tensile Bond Strength and Marginal Integrity of a Self-adhering and a Self-etch Adhesive Flowable Composite after Artificial Thermomechanical Aging.

This study aims to compare the self-etch adhesive (SEA) and self-adhesive flowable composite (SAF) concerning tensile bond strength (TBS) and marginal integrity by microleakage (µ LK) test in deciduous molars after artificial thermomechanical aging. 120 extracted primary molars were collected. Sixty teeth were mounted for testing TBS. Teeth were restored using SAF (n = 30) and SEA-conventional flowable (CF) composite (n = 30) and subjected to artificial thermal aging. Half the teeth (n = 15) from each material were subjected to mechanical loading (SEA-TBS-L and SAF-TBS-L). The specimens with no-load (NL) served as control (SEA-TBS-NL and SAF-TBS-NL). Class V cavity prepared and restored with SAF (n = 30) and SEA-CF (n = 30) to test µ LK after thermal aging. The subgroups were as same as the TBS based on with or without mechanical loading (SEA-µ LK-L, SEA-µ LK-NL, SAF-µ LK-L, SAF-µ LK-L; n = 15 each). µ LK was determined by employing the dye immersion technique. Concerning TBS, there is a significant difference between SEA and SAF with load or no load. Concerning µ LK, there is a significant difference between the materials under loading and no difference was found when not mechanically loaded. Also, concerning both TBS and µ LK, a significant difference was observed between the load and no-load subgroups within each material. SAF exhibited higher TBS than the SEA. Mechanical loading not only adversely affected the TBS but also increased the µLK of the compared materials. Restoring the primary teeth with SAF not only shortens the laborious operatory time but also yields good clinical serviceability with the good bond strength and minimal µ LK, thus preventing premature loss of teeth and consequential malocclusion. Kamatchi M, Ajay R, Gawthaman M, et al. Tensile Bond Strength and Marginal Integrity of a Self-adhering and a Self-etch Adhesive Flowable Composite after Artificial Thermomechanical Aging. Int J Clin Pediatr Dent 2022;15(2):204-209.

Cardiorespiratory responses of load carriage in female and male soldiers

PurposeTo investigate the effect of sex and load carriage on cardiorespiratory responses to high intensity exercise in male and female soldiers. MethodsSoldiers (9 women, 9 men) performed a graded treadmill test until exhaustion with no load (NL) and combat-gear with body armor (CG). Cohen's d effect sizes, paired t-tests and ANOVA were used to study differences between conditions. A mixed linear regression model analyzed the relationship between heart rate (HR) and oxygen uptake (V̇O2) with load and between sexes. ResultsWearing CG resulted in, for both sexes, a decreased time to exhaustion (−11 min), lower V̇O2peak (L/min) ES = 0.56; VO2peak (mL//kg/min) ES = 2.44, both p < 0.001, a net decrease in minute ventilation (ES = 3.53) and no change in HRmax. No sex-difference were present except for absolute V̇O2peak. The VO2 and HR relationship showed a cardiorespiratory reduction wearing CG vs. NL. Added load was equal between sexes, although female soldiers' CG relative to body mass was higher (25%) than male soldiers’ (20%), p < 0.01. ConclusionWearing CG reduces soldiers’ cardiorespiratory capacity and exercise performance level, although the reduction cannot be explained solely based on the added load of CG, instead CG seems to restrict the capacity to fully ventilate. No sex differences were found in relative cardiorespiratory responses to wearing CG compared to NL.

Changes in Plantar Pressure Levels Generated Using Military Backpack During Standing Position: An Experimental Study

Introduction: The feet are one the main anatomical site affected by injuries arising from load carriage tasks and can negatively affect the soldier mobility reducing the operational capability of an entire military troops. Objective: Identify the changes in the plantar pressure distribution during standing position carrying a military backpack with 15 kg, 20 kg, 25 kg, and no-load (NL) always comparing with control group; and examining if the combat boots contribute to decreasing the plantar pressure. Methods: Twenty-four active-duty male military (26.4±5.6 years; 171.5±3.6 cm; 75.2±6.0 kg) were evaluated in standing posture using an insole baropodometry system wearing a military backpack. The Kruskal-Wallis test was used to check for differences and the Dunnett post hoc test to determine which groups were different from the control (p≤0.05). Results: Data showed a significant decrease in plantar pressure in the forefoot no loaded when we compare barefoot (control = 54.02±19.56 kPa) versus wearing combat boots (35.30±13.00 kPa). With loads there was a significative increase in the plantar pressure only in the rearfoot (control = 74.18±3.80 kPa vs 15 Kg = 89.19±15.49 kPa, 20 Kg = 102.81±15.01 kPa, 25 Kg = 94.20±26.60 kPa). Conclusion: Rearfoot is most affected by the load and boot promoted a significant decrease of plantar pressure in the forefoot in the NL group. Midfoot does not change the plantar pressure. This information can help to minimize the soldier's discomfort.

Classification of the Hydraulic Behavior Along the No-Load Curve of Francis Turbines

Abstract For hydraulic turbines, no-load (NL) is considered a homogeneous family of operating conditions, although the literature exposes a wide variety of flow structures depending on many factors. A better understanding of the flow structures developed during NL operation is necessary, since they generate pressure fluctuations in the turbine causing significant fatigue damage and reducing the life expectancy of the machines. Hydraulic turbines at model scale show that behavioral trends can be identified for NL conditions. This paper presents a classification of NL operating conditions following the swirl level at the runner outlet. The main tendencies linking the cavitation level to the runner speed and the discharge for operating points along NL curves of different turbines are also detailed. To study the NL conditions, data from 26 Francis turbines, measured between 2007 and 2020 at the laboratory of Andritz Hydro Canada Inc., are analyzed. This study demonstrates that NL operating conditions exhibit flow features very similar to those at regular operation with similar runner outlet swirl. The runner acceleration or deceleration with cavitation is related to the flow topology at the runner outlet.

Effects of additional load at different heights on gait initiation: A statistical parametric mapping of center of pressure and center of mass behavior.

The purpose of this study was to investigate the effects of different vertical positions of an asymmetrical load on the anticipatory postural adjustments phase of gait initiation. Sixty-eight college students (32 males, 36 females; age: 23.65 ± 3.21 years old; weight: 69.98 ± 8.15 kg; height: 1.74 ± 0.08 m) were enrolled in the study. Ground reaction forces and moments were collected using two force platforms. The participants completed three trials under each of the following random conditions: no-load (NL), waist uniformly distributed load (WUD), shoulder uniformly distributed load (SUD), waist stance foot load (WST), shoulder stance foot load (SST), waist swing foot load (WSW), and shoulder swing foot load (SSW). The paired Hotelling's T-square test was used to compare the experimental conditions. The center of pressure (COP) time series were significantly different for the SUD vs. NL, SST vs. NL, WST vs. NL, and WSW vs. NL comparisons. Significant differences in COP time series were observed for all comparisons between waist vs. shoulder conditions. Overall, these differences were greater when the load was positioned at the shoulders. For the center of mass (COM) time series, significant differences were found for the WUD vs. NL and WSW vs. NL conditions. However, no differences were observed with the load positioned at the shoulders. In conclusion, only asymmetrical loading at the waist produced significant differences, and the higher the extra load, the greater the effects on COP behavior. By contrast, only minor changes were observed in COM behavior, suggesting that the changes in COP (the controller) behavior are adjustments to maintain the COM (controlled object) unaltered.

Acute effects of Running Anaerobic-based Sprint Test with different loads in amateur Rugby Union players

The aim of this study was to compare the acute effects of the Running Anaerobic-based Sprint Test (RAST) with different loads in physiologic and neuromuscular parameters. 12 amateur rugby union players performed the RAST, with heart rate (HR) and blood lactate concentration ([LAC]) measurements pre, post and 5 min post RAST, squat jump (SJ), countermovement jump (CMJ), 10 m (S10) and 20 m (S20) sprints pre and post RAST. These procedures were carried out during three sessions, randomly performed in different conditions: no load (NL), load with 13% (L13) or 25% (L25) of body mass. Between loads, peak power in RAST and mean power were statistically different, with lower in L25 condition. Between moments, significant differences were observed with decrease in HR, increase in [LAC] for pre, post and 5 min post, respectively, and performance decrease in CMJ and S10, without load vs moment interaction. In addition, between loads, with exception of power produced in RAST, no significant differences were observed for any variable. Therefore, despite the differences in power production during RAST, it is concluded that RAST performed with or without loads of either 13 or 25% of body mass induces similar acute effects in both physiologic and neuromuscular parameters. Le but de cet article était de comparer les effets aigus du test Sprint basé sur anaérobie (RAST) avec différentes charges de paramètres physiologiques et neuromusculaires. Douze joueurs amateurs de rugby à XV ont effectué le RAST, avec des mesures de la fréquence cardiaque (HR) et de la concentration en lactate sanguin ([LAC]) avant, après et 5 minutes après le RAST, squat jump (SJ), contre-mouvement (CMJ), 10 m (S10) et 20 m (S20) sprints avant et après RAST. Ces procédures ont été réalisées au cours de trois séances, effectuées au hasard dans différentes conditions : sans charge (NL), charge avec 13 % (L13) ou 25 % (L25) de masse corporelle. Entre les charges, la puissance de pointe dans RAST et la puissance moyenne étaient statistiquement différentes, avec une condition inférieure à L25. Entre les moments, des différences significatives ont été observées avec une diminution de la FC, une augmentation de [LAC] pour le pré, le post et le post 5 min, respectivement, et une diminution des performances en CMJ et S10, sans interaction charge/moment. De plus, entre les charges, à l’exception de la puissance produite dans RAST, aucune différence significative n’a été observée pour aucune variable. Par conséquent, malgré les différences de production d’énergie pendant le RAST, il est conclu que le RAST effectué avec ou sans charges de 13 ou 25 % de la masse corporelle induit des effets aigus similaires dans les paramètres physiologiques et neuromusculaires.

Estimation of PM Machine Efficiency Maps From Limited Data

This article investigates the accuracy of the estimation of efficiency maps for permanent magnet (PM) machines using the stator resistance, d - and q -axis flux-linkages versus the corresponding axis current and the iron loss versus the speed characteristic. The ultimate goal is to apply this approach to the experimental measurements, but this article performs initial investigation using only the finite-element (FE) data. Detailed FE data for 50-kW surface PM (SPM) and interior PM (IPM) machines are used to determine the “actual” or exact efficiency map and, hence, the accuracy of using approximations. This article examines the effect on the torque–speed capability curve when ignoring cross-saturation effects. It also examines the modeling of the variation of iron losses as a function of load in the constant torque and power regions. A novel approach based on scaling the no-load (NL) losses as a function of load is proposed and shown to give promising results. FE results from two other machines are also provided, which show good correspondence.

Knee joint kinematics of the pendulum test in children with and without Down syndrome

BackgroundThe Wartenberg pendulum test is a common clinical test that is used to measure stiffness about the knee in persons with and without disabilities such as cerebral palsy and Down syndrome (DS). Adults and adolescents with DS show fewer number of swing cycles and a lower relaxation index than healthy controls. However, it is not clear if children with DS show a similar trend compared to typically developing (TD) children. Research questionWas the knee joint kinematics different between children with and without DS during the pendulum test? MethodsThirteen children with DS and 13 TD children participated in this study. There were two load conditions: no load (NL) and with ankle load (AL) equal to 2 % of the subject’s body weight. Five trials of a pendulum test were collected for each condition. ResultsThe DS group showed a smaller first flexion excursion, a lower relaxation index, lower mean and peak velocities and accelerations during the first and second flexion and extension, and greater variability of acceleration during the first flexion than the TD group across both load conditions. This suggests that the DS group may have greater stiffness of the knee than the TD group to compensate for joint instability. SignificanceThe pendulum test appears to be a valid test to evaluate the passive stiffness of the knee in children with DS. The lower relaxation index in children with DS suggests that larger bursts of quadriceps may be activated during a pendulum test, particularly in the first flexion excursion, to assure the knee joint stability.

Influence of mini-screw diameter and loading conditions on static and dynamic assessments of bone-implant contact: An animal study.

The goal was to compare static versus dynamic bone-implant interface histology of mini-screws and to evaluate its relation to diameter and load. Canine animal model. Custom-machined, titanium alloy (Ti6AI4V) mini-screws (n=70) of 1.60, 2.00, 3.00 and 3.75mm diameter were placed into edentulous sites in five skeletally mature beagle dogs. Using a split-mouth design, no load (NL) was applied to one side while a 2N load (L) was applied by calibrated coil springs on the other side. Intravenous bone labels were administered 21 and 7days prior to sacrifice. Dogs were euthanized 90days after screw placement. Bone sections were analysed under bright-field and epifluorescent light. The region of interest was defined as the bone within the threads of the screws. The following parameters were quantified: (a) Static-bone volume/tissue volume (BV/TV %) and bone-implant contact (BIC, %); (b) Dynamic-labelled bone/bone volume (LB/BV, %), and dynamic BIC (DBIC, %). BV/TV ranged from 71.2% to 85.0% of the screw surface. BIC ranged from 45.7% to 55.4% of the screw surface and was not affected by diameter (P=0.66). In contrast, the percentage of DBIC did not vary with the applied load (P=0.41); however, it correlated significantly with the diameter of the screw (P=0.001). The percentage of DBIC that is actively remodelling increases with increasing diameter of the screw. Dynamic histomorphometry is more sensitive to detecting changes in bone-implant contact when compared to static measurements.

Assessment of tractor noise level during spraying operation while using a tractor mounted aero blast sprayer

Tractor noise consists of engine noise, exhaust, intake fan and mechanical noise created by combustion, gears, cams, bearings and pumps, etc. Its noise spectra cover the entire audible range from 20 Hz to 20 kHz.The severity associated with noisy tractor may be annoying to varying degrees, lack of concentration, fatigue, rhythm disturbance and damage to hearing. In this paper noise of the tractor (John Deere (5103)) at the operator’s ear level and for bystander position was measured during no load (NL) and spraying operation using an areo blast sprayer at different engine speeds. The results showed that noise level during spraying operation higher than during NL condition. It is found that the effect of engine speed was significant at the 5 percent level of significance. It is observed that noise at a tractor operator’s ear level during spraying operation using an areo blast sprayer was higher than the permissible level (85 dB (A)) which was given by Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH).

Effect of wearing positions of load on the dynamic balance during gait.

The study aim to analyze the influence on dynamic stability relative to positions carrying with weight during gait, for which experiment participated with healthful adult males (n=9), were performed under three-dimensional (3D) conditions of no load (NL), right of trunk (RT), and front of trunk (FT). The kinematic and kinetic conclusions obtained from 3D cinematography and ground reaction force system were as follows; 1-step time elapsed showed longest in NL of all, and maximum velocity of RT showed slower than NL and FT, which resulted in significant level at (P<0.05) respectively. While NL showed slower average velocity than RT and FT, RT showed larger incline angle (extrapolated center of mass θ) than NL and FT, which resulted in significant level at (P<0.01) respectively. Also FT showed larger peak vertical force than NL and RT, which resulted in significant level at (P<0.001). Because gait pattern is regarded it as a success when fulfilled both forward propulsive force and dynamic stability, we may ensure that each other active strategy for securement and performance in a situation carrying with 20 kg of the same weight in forward and lateral plane was mobilized. However, participants in pathological gait such as leg injury, and exercise rehabilitation during walking should avoid carrying loads bag to ensure dynamic stability.

Evaluation of peri-implant bone metabolism under immediate loading using high-resolution Na18F-PET.

This study aimed to examine the influence of immediate loading on the dynamic changes of bone metabolism around dental implants using a high-resolution semiconductor sodium 18F-fluoride (Na18F)-PET. Tibiae of 12 adult male rats were divided into 4 groups: immediate loading (IL), no loading (NL), bone defect (BD), and control (CTR). For the IL group, a 4.0-N load was applied continuously by two closed-coil springs attached between two implants in tibia. Each rat received an intravenous injection of Na18F and was scanned by high-resolution Na18F-PET at day 1 and then at weeks 1, 2, 3, 4, 5, 6, and 8 after surgery. Bone metabolism around the implant was evaluated by standardized uptake value (SUV), which indicates the outcome of Na18F accumulation. CT scanning was also performed, and PET and CT images were superposed to determine the anatomical orientation in PET images. Bone metabolism peaked at 7days after surgery and then gradually decreased in all three test groups (IL, NL, and BD). SUVs of all three test groups were significantly higher than the baseline at 1, 2, 3, and 4weeks after surgery, with SUVs in the IL group returning to baseline levels earlier than those in the NL and BD groups. Fluorine integrates preferentially with the initial low-calcified bone; thus, our results suggest that immediate loading promotes the calcification of the bone tissue in the early stage on peri-implant bone formation. Na18F-PET allows for an estimate of bone metabolism change around the implant.

Simulation of mechanical resistive loading on an optimal respiratory control model with added dead space and CO2 breathing

• Simulation of how resistive loading affects the respiratory control is presented. • Behavior of optimal chemical–mechanical respiratory control model is simulated. • Respiratory signals under dead space loadings and CO 2 inhalation are optimized. • Comparisons of the respiratory control behavior were performed under various loading effects. To investigate how respiratory resistive loading affects the behavior of optimal chemical–mechanical respiratory control, respiratory signals and breathing pattern were optimized under various dead space loadings (0, 0.4, and 0.8 L) and CO 2 inhalation concentrations (0%, 3%, and 5%). The optimal respiratory control model, which has been studied earlier, was characterized to include a description of the neuromuscular drive P ( t ) as the control output and accurately derive the waveshapes of instantaneous airflow V ˙ ( t ) , lung volume V ( t ) profiles, and breathing pattern, including total and alveolar ventilation, breathing frequency, tidal volume, inspiratory and expiratory duration, duty cycle, and arterial CO 2 pressure. Simulations were performed under various respiratory resistive loads: no load (NL), inspiratory resistive load (IRL), expiratory resistive load (ERL), and continuous resistive load (CRL). The simulation results provide an extended view of breathing pattern and the respiratory signals of neural muscular driving pressure, airflow, and lung volume for rest and various specific cases with external dead space loading and/or CO 2 inhalation. The results showed that an IRL generally resulted in a higher amplitude of P ( t ) and V ( t ), with more convex upward pressure waveshapes, a prolonged inspiratory duration, and a higher duty cycle ( T I / T ≈ 0.55–0.56 at Rest, ≈ 0.54∼0.68 in Case 1, and ≈0.61∼0.69 in Case 3 during resistive loading) for the waveforms. In comparison to the resting state, an abrupt fall occurred at the beginning of the expiratory phases of P ( t ) and the peak flows ( V ˙ peak ≈ −5, −5.5, and −7 L/min in Cases 1, 2, and 3, correspondingly) in the expiratory phase were significantly boosted with ERL during CO 2 inhalation (Case 1_3%, 5%), and EDS loadings (Case 2_EDS = 0.4, 0.8), or a combination of both (Case 3_5% and EDS = 0.4). CRL in all cases exhibited greater rises in amplitude for pressure and lung volume in comparison to IRL and ERL; nevertheless, it also appeared not to have a substantial influence on the waveshapes of airflow, except in the case of a higher concentration of CO 2 inhalation.

Phase coherence of auditory steady-state response reflects the amount of cognitive workload in a modified N-back task

The auditory steady-state response (ASSR) is an oscillatory brain activity evoked by repetitive auditory stimuli. Previous studies have reported that the power and phase locking index (PLI) of ASSR could be modulated by the degree of workload. However, those studies used different physical stimuli for tasks of differing difficulty, and the effect of the internal workload itself has not been clearly understood. In this study, we employed the modified N-back task as a visual working memory task in order to vary the degree of difficulty while keeping the physical stimulus constant. The experiment consisted of four types of tasks: No-Load (NL), 1-back, 2-back, and 3-back tasks. The auditory stimulus was a 40Hz click sound to induce ASSR. Sixteen healthy subjects participated in the present study and magnetoencephalogram responses were recorded using a 148-channel magnetometer system. The hit rate decreased and the reaction time increased according to the task difficulty. Grand averaged phase coherence activities showed the 40Hz ASSR reductions accompanying an increase in the task difficulty even with the identical external stimuli. In particular, the phase coherence activities in 3-back task were significantly lower than that in the NL and 1-back tasks. Our results suggest that the ASSR can be a useful indicator for the amount of workload in the brain.

Challenges in Dynamic Pressure and Stress Predictions at No-Load Operation in Hydraulic Turbines

Some of the potentially most damaging continuous operating conditions for hydraulic turbines are the no-load (NL) conditions. At NL conditions the flow passes through the turbine without power generation, but with non-negligible flow rate, and therefore all the potential energy in the flow has to be dissipated. This takes place through a mechanism where the runner channels are partially pumping, thus generating large scale unsteady vortex structures which, by their nature, break down into smaller and smaller vortices until energy dissipation occurs at the smallest scales. This type of flow, dominated by its turbulent character, is inherently difficult to simulate by means of numerical methods since turbulence model and numerical dissipation have a major influence. The resulting dynamic loads on the runner are largely of stochastic nature, exciting a broad band of frequencies and thus, almost always interact with at least one deformation mode. The presented investigations are aimed at predicting the effect of the unsteady NL pressure loads on the fatigue life of a Francis turbine runner. A combination of computational fluid dynamics (CFD) and finite element analysis (FEA) methods has been employed. The results from transient CFD simulations are presented. Comparison of the results with prototype strain gauge measurements at no load conditions shows that the stochastic nature and the approximate range of the dynamic stresses can be predicted.

Region Specific Response of Intervertebral Disc Cells to Complex Dynamic Loading: An Organ Culture Study Using a Dynamic Torsion-Compression Bioreactor

The spine is routinely subjected to repetitive complex loading consisting of axial compression, torsion, flexion and extension. Mechanical loading is one of the important causes of spinal diseases, including disc herniation and disc degeneration. It is known that static and dynamic compression can lead to progressive disc degeneration, but little is known about the mechanobiology of the disc subjected to combined dynamic compression and torsion. Therefore, the purpose of this study was to compare the mechanobiology of the intervertebral disc when subjected to combined dynamic compression and axial torsion or pure dynamic compression or axial torsion using organ culture. We applied four different loading modalities [1. control: no loading (NL), 2. cyclic compression (CC), 3. cyclic torsion (CT), and 4. combined cyclic compression and torsion (CCT)] on bovine caudal disc explants using our custom made dynamic loading bioreactor for disc organ culture. Loads were applied for 8 h/day and continued for 14 days, all at a physiological magnitude and frequency. Our results provided strong evidence that complex loading induced a stronger degree of disc degeneration compared to one degree of freedom loading. In the CCT group, less than 10% nucleus pulposus (NP) cells survived the 14 days of loading, while cell viabilities were maintained above 70% in the NP of all the other three groups and in the annulus fibrosus (AF) of all the groups. Gene expression analysis revealed a strong up-regulation in matrix genes and matrix remodeling genes in the AF of the CCT group. Cell apoptotic activity and glycosaminoglycan content were also quantified but there were no statistically significant differences found. Cell morphology in the NP of the CCT was changed, as shown by histological evaluation. Our results stress the importance of complex loading on the initiation and progression of disc degeneration.

Improving the Testing of Power Generation Modules and Resulting Performance Projections

The traditional way of testing power generation modules and projecting their performance may be prone to overestimation of capabilities. Frequently, an assumption is made that the no-load (NL) voltage measured during testing can simply be employed as the default V NL in all subsequent calculations using data taken under load. In reality, while current is flowing, wattage due to the Peltier effect creates temperature drops across interface materials. These significantly diminish the ΔT across the thermoelectric material and attenuate the Seebeck voltage. Therefore, for each level of load current, there is a different V NL that corresponds to the associated ΔT. Each of these distinctive V NL levels should be used for calculations relative to its associated operational point. With the proper equipment and use of curve fits, it is possible to test and project in a manner which can more closely approximate the true performance characteristics of power generation devices.