Mean Maximum Speed Research Articles

Propagation of a Realistic Magnetar Jet through a Binary Neutron Star Merger Medium and Implications for Short Gamma-Ray Bursts

The origin of short gamma-ray bursts is associated with outflows powered by the remnant of a binary neutron star merger. This remnant can be either a black hole or a highly magnetized, fast-spinning neutron star, also known as a magnetar. Here we present the results of two relativistic magnetohydrodynamical simulations aimed at investigating the large-scale dynamics and propagation of magnetar collimated outflows through the medium surrounding the remnant. The first simulation evolves a realistic jet by injecting external simulation data, while the second evolves an analytical model jet with similar properties for comparison. We find that both outflows remain collimated and successfully emerge through the static medium surrounding the remnant. However, they fail to attain relativistic velocities and only reach a mean maximum speed of ∼0.7c for the realistic jet and ∼0.6c for the analytical jet. We also find that the realistic jet has a much more complex structure. The lack of highly relativistic speeds, which makes these jets unsuitable as short gamma-ray burst sources, is due to numerical limitations and is not general to all possible magnetar outflows. A jet like the one we study, however, could give rise to or augment a blue kilonova component. In addition, it would make the propagation of a relativistic jet easier, should one be launched after the neutron star collapses into a black hole.

The introduction of the six-again rule has increased acceleration intensity across all positions in the National Rugby League competition

ABSTRACT The impact of the six-again rule change on the movement of National Rugby League (NRL) athletes was examined. Player Global Navigation Satellite System (GNSS) data (10 Hz) was collected from 42 athletes who competed in 56 matches across the 2019 to 2021 NRL seasons. Maximal mean speed (m·min−1) and acceleration (m·s−2) were established across a 10 s to 10-min duration via raw GNSS files, with subsequent intercept (mean estimates) and slope values determined via power law analysis. The distributions of match distance (m) and impulse (kN·s−1) were established during ball-in-play time. To determine the significance between positions and seasons under different rules, linear mixed models were used. Effects were described using standardised effect sizes (ES) with 90% confidence limits (CL). Acceleration intercepts (power law-derived) across all positions were substantially greater (>0.6 SD) following the introduction of the six-again rule in the 2020 (mean ± SD; 1.02 ± 0.10 m·s−2) and 2021 seasons (1.05 ± 0.08 m·s−2) compared to the 2019 season (0.91 ± 0.07 m·s−2). Mean acceleration during ball-in-play time was greater in 2020 (ES; 90% CL = 0.75; ± 0.32) compared to 2019. The acceleration requirements of rugby league increased across all positional groups following the modification in NRL competition rules. Practitioners should tailor training programs for athletes to reflect the increased acceleration intensity found under the revised competition format.

Increased Corneal Endothelial Cell Migration in Fuchs Endothelial Corneal Dystrophy: A Live Cell Imaging Study

PurposeTo investigate if corneal endothelial cells (CECs) in Fuchs endothelial corneal dystrophy (FECD) have altered cellular migration compared with normal controls.DesignComparative analysis.MaterialsDescemet’s membrane and CECs derived from patients with FECD undergoing endothelial keratoplasty or normal cadaveric donors.MethodsEx vivo specimens were used for live cell imaging and generation of immortalized cell lines. Live imaging was performed on FECD and normal CECs and on ex vivo specimens transfected with green fluorescent protein. Migration speeds were determined as a function of cellular density using automated cell tracking. Ex vivo specimens were classified as either FECD or normal low cell density (nonconfluent) or high cell density (confluent). Scratch assay was performed on CECs seeded at high confluence to determine migration speed. Genetic analysis from blood samples or CECs was performed to detect a CTG repeat expansion in the TCF4 gene.Main Outcome MeasuresMean cell migration speed.ResultsFuchs endothelial corneal dystrophy CECs in low cell density areas displayed increased mean speed (0.391 ± 0.005 μm/minute vs. 0.364 ± 0.005 μm/minute; P < 0.001) and mean maximum speed (0.961 ± 0.010 μm/minute vs. 0.787 ± 0.011 μm/minute; P < 0.001) compared with normal CECs, and increased mean maximum speed (0.778 ± 0.014 μm/minute vs. 0.680 ± 0.011 μm/minute; P < 0.001) in high cell density areas ex vivo. Similarly, FECD CECs displayed increased mean speed compared with normal CECs (1.958 ± 0.020 μm/minute vs. 2.227 ± 0.021 μm/minute vs. 1.567 ± 0.019 μm/minute; P < 0.001) under nonconfluent conditions in vitro. Moreover, FECD CECs also displayed increased mean speed compared with normal CECs under high confluent conditions as detected by scratch assay (37.2 ± 1.1% vs. 44.3 ± 4.1% vs. 70.7 ± 5.2%; P < 0.001). Morphologic analysis showed that FECD CECs displayed an increased fibroblastic phenotype as detected by filamentous-actin labeling.ConclusionsFuchs endothelial corneal dystrophy CECs demonstrated increased migration speed compared with normal CECs. Further investigation into the mechanisms of heightened cell migration in FECD is needed and may provide insight into its pathogenesis, as well as having implications on descemetorhexis without endothelial keratoplasty.

Reliability and Validity of Maximal Mean and Critical Speed and Metabolic Power in Australian Youth Soccer Players.

The reliability and validity of maximal mean speed (MMS), maximal mean metabolic power (MMPmet), critical speed (CS) and critical metabolic power (CPmet) were examined throughout the 2016-2017 soccer National Youth League competitions. Global positioning system (GPS) data were collected from 20 sub-elite soccer players during a battery of maximal running tests and four home matches. A symmetric moving average algorithm was applied to the instantaneous velocity data using specific time windows (1, 5, 10, 60, 300 and 600 s) and peak values were identified. Additionally, CS and CP¬met values calculated from match data were compared to CS and CPmet values determined from previously validated field tests to assess the validity of match values. Intra-class correlation (one-way random absolute agreement) scores ranged from 0.577 to 0.902 for speed, and from 0.701 to 0.863 for metabolic power values. Coefficients of variation (CV) ranged from good to moderate for speed (4-6%) and metabolic power (4-8%). Only CS and CPmet values were significantly correlated (r = 0.842; 0.700) and not statistically different (p = 0.066; 0.271) to values obtained in a shuttle-running critical test. While the present findings identified match-derived MMS, MMPmet, CS and CPmet to be reliable, only CS and CPmet derived from match play were validated to a CS field test that required changes in speed and direction rather than continuous running. This suggests that both maximal mean and critical speed and metabolic power analyses could be alternatives to absolute distance and speed in the assessment of match running performance during competitive matches.

Comparing Maximal Mean and Critical Speed and Metabolic Powers in Elite and Sub-elite Soccer.

The quantification of maximal mean speed (MMS), maximal mean metabolic power (MMPmet), critical speed (CS) and critical metabolic power (CPmet) was conducted over full A-League (elite) and National Premier League (NPL; sub-elite) seasons. Comparisons were made between levels of soccer competition and playing positions (i. e. centre backs, full backs, central midfielders, wide midfielders and strikers). A symmetric moving average algorithm was applied to the GPS raw data using specific time windows (i. e. 1, 5, 10, 60, 300 and 600 s) and maximal values were obtained. Additionally, these maximal values were used to derive estimates of CS and CPmet. Maximal mean values, particularly during smaller time windows (i. e. 1 and 5 s), were greater in A-League match play. Only MMPmet1 was identified as being consistently different between competitions (P=<0.001-0.049) in all playing positions. Significance was only observed in CS (P=0.005) and CPmet (P=0.005) of centre backs between competitions. Centre backs were identified as the least energy demanding playing position. The present findings suggests that both maximal mean and critical analyses are suitable alternatives to common absolute distance and speed assessments of match running performance during competitive matches.

A Reduction in Match-to-match Variability Using Maximal Mean Analyses in Sub-elite Soccer.

The match-to-match variability of external loads in National Premier League soccer competition was determined. Global positioning systems (GPS) data were collected from 20 sub-elite soccer players over 2-10 matches from a single season. Match data were collected from during one season. Twenty-six matches were recorded and 10 were utilised within final match-to-match analysis based on stringent data selection criteria. A symmetric moving average algorithm was applied to GPS data over specific time windows (1, 5, 10, 60, 300 and 600 s), and maximal speed and metabolic power values then calculated at each time interval during each match. Match-to-match coefficients of variation (CV) were greatest for sprint-speed running distance (36.3-43.6%) when comparing 2 vs. 10 matches. CVs for maximal mean speed (4.9-7.0%) and metabolic power (4.4-9.6%) ranged from good to moderate. As the variability of absolute high-speed distance values are greater, and therefore less reliable, their use as indicators of performance is reduced, suggesting that maximal mean analyses could be used as an alternative in the assessment of match running performance during competitive matches.

Four-Meter Gait Speed: Normative Values and Reliability Determined for Adults Participating in the NIH Toolbox Study

ObjectivesTo establish reference values and determine test-retest reliability for usual and maximal 4-meter gait speed. DesignCross-sectional observational study. SettingOffices in 10 geographically dispersed cities in the United States. ParticipantsMen and women (N=1320), aged 18 to 85 years, enrolled in the National Institutes of Health Toolbox norming study. InterventionNot applicable. Main Outcome MeasuresSpecifically used were data from men and women who were timed over 4 meters (after a static start) while walking at their usual and maximum speeds. Norms for usual and maximum gait speed were derived using data from 1320 participants. Test-retest reliability for 164 participants was described using paired t tests, intraclass correlation coefficients (ICCs), and minimal detectable changes (MDCs). ResultsMean usual speed was 1.12 meters per second, whereas mean maximum speed was 1.61 meters per second. As a general linear model showed 4-meter gait speed to differ significantly according to gait condition (speed), sex, and age group; estimates of normal were calculated accordingly. The usual speed of 80- to 85-year-old women was lowest at 0.95 meters per second; the maximum speed of 18- to 29-year-old men was highest at 1.85 meters per second. Test-retest measures did not differ significantly, but the ICCs were only fair and the MDCs were high. ConclusionsNormative reference values provided herein may be helpful in interpreting measurements of 4-meter gait speed obtained from adult men and women. The limited reliability of the gait speed measurements, however, limits their usefulness in making judgments regarding change.

Linear and Nonlinear Prediction Models Show Comparable Precision for Maximal Mean Speed in a 4x1000 m Field Test

Abstract Maximal oxygen uptake (VO2max) is one of the most distinguished parameters in endurance sports and plays an important role, for instance, in predicting endurance performance. Different models have been used to estimate VO2max or performance based on VO2max. These models can use linear or nonlinear approaches for modeling endurance performance. The aim of this study was to estimate VO2max in healthy adults based on the Queens College Step Test (QCST) as well as the Shuttle Run Test (SRT) and to use these values for linear and nonlinear models in order to predict the performance in a maximal 1000 m run (i.e. the speed in an incremental 4×1000 m Field Test (FT)). 53 female subjects participated in these three tests (QCST, SRT, FT). Maximal oxygen uptake values from QCST and SRT were used as (a) predictor variables in a multiple linear regression (MLR) model and as (b) input variables in a multilayer perceptron (MLP) after scaling in preprocessing. Model output was speed [km·h−1] in a maximal 1000 m run. Maximal oxygen uptake values estimated from QCST (40.8 ± 3.5 ml·kg−1·min−1) and SRT (46.7 ± 4.5 ml·kg−1·min−1) were significantly correlated (r = 0.38, p &lt; 0.01) and maximal mean speed in the FT was 12.8 ± 1.6 km·h−1. Root mean squared error (RMSE) of the cross validated MLR model was 0.89 km·h−1 while it was 0.95 km·h−1 for MLP. Results showed that the accuracy of the applied MLP was comparable to the MLR, but did not outperform the linear approach.

Effect of Tinospora cordifolia on physical and cardiovascular performance induced by physical stress in healthy human volunteers

Introduction:In Ayurveda Tinospora cordifolia (Willd.) Miers., has been used for its Rasayana, Deepana, Jwaranashana, Tridosha Shamaka properties. It is an immunomodulator, useful in stress, hyperlipidemia, pyrexia. T. cordifolia was evaluated for adaptogenic activity in healthy volunteers during exercise.Aims:The primary objective of this study was to evaluate the effect of T. cordifolia on physical performance, and secondary objectives were to evaluate muscle power, maximal oxygen consumption, and sympathetic activity in comparison with placebo when subjected to physical stress.Materials and Methods:A total of thirty participants were randomly assigned into three groups (n = 10 each) namely placebo, TC 150 and TC 300. Placebo group received maize starch capsule, TC 150 and TC 300 received 150 mg and 300 mg, respectively of T. cordifolia aqueous extract in capsule form once daily in the morning for 28 days. The assessment was performed at baseline visit, day 14 and 28. Physical stressors were cycle ergometer exercise, Jammer's hand-held dynamometer, and cold pressor tests. Physical performance evaluated was maximum distance and speed, oxygen consumption (VO2 max), and hand grip strength. Cardiovascular response was assessed by multiple heart rate (HR) and blood pressure (BP) measurements during each test.Results:On day 28, TC 150 mg group showed a significant increase in mean maximum speed compared to placebo. On day 14 and 28, TC 300 mg group showed a significant decrease in mean systolic BP (SBP) and HR on fixed workload exercise compared to placebo. There was significant increasing dose effect of both TC groups on SBP on day 14 and 28 and on HR on day 28 only. On day 14 and 28, TC 300 mg showed a significant decrease in mean HR on the cold pressor test, compared to placebo.Conclusion:T. cordifolia improved physical performance and suppressed over activation of the sympathetic nervous system showing its adaptogenic property.

Impact of Environmental Parameters on Marathon Running Performance

PurposeThe objectives of this study were to describe the distribution of all runners' performances in the largest marathons worldwide and to determine which environmental parameters have the maximal impact.MethodsWe analysed the results of six European (Paris, London, Berlin) and American (Boston, Chicago, New York) marathon races from 2001 to 2010 through 1,791,972 participants' performances (all finishers per year and race). Four environmental factors were gathered for each of the 60 races: temperature (°C), humidity (%), dew point (°C), and the atmospheric pressure at sea level (hPA); as well as the concentrations of four atmospheric pollutants: NO2 – SO2 – O3 and PM10 (μg.m−3).ResultsAll performances per year and race are normally distributed with distribution parameters (mean and standard deviation) that differ according to environmental factors. Air temperature and performance are significantly correlated through a quadratic model. The optimal temperatures for maximal mean speed of all runners vary depending on the performance level. When temperature increases above these optima, running speed decreases and withdrawal rates increase. Ozone also impacts performance but its effect might be linked to temperature. The other environmental parameters do not have any significant impact.ConclusionsThe large amount of data analyzed and the model developed in this study highlight the major influence of air temperature above all other climatic parameter on human running capacity and adaptation to race conditions.

Observations of the velocity profile of a fast and deep oceanic density current constrained in a gully

The southwestern side of the Wyville Thomson Ridge transports cold Faroe‐Shetland Channel Bottom Water in a narrow cascade from a depth of 500 m down to 1700 m. An upward looking acoustic Doppler current profiler located at a depth of 1200 m measured its currents to a height of 500 m for 6 months. The westward flowing deep density current (mean thickness 343 m) extended well above the bottom Ekman layer (of order 20 m) and had a profile with a bullet nose shape that had a peak velocity at a height that was about of its thickness. The mean maximum speed was about 60 cm s−1, although there was significant variability in velocity with 90% of the variance explained by mode 1 that had a similar bullet nose shape. From the downstream momentum balance it is estimated that the vertical eddy viscosity in the overflow was of order 0.5 m2 s−1 through most of its depth but somewhat larger near the interface. A full description of the velocity profile requires an opposing surface slope and current, with zero net pressure gradient within the overflow. The transverse circulation (mean speed ∼3 cm s−1) had southward flows at the interface and seabed and a return flow at middepth. This circulation is driven by imbalances between Coriolis forcing from the downstream current and the transverse pressure gradient. Its overturning scales suggest a bulk eddy viscosity of order 2 m2 s−1 and may indicate a feedback between the downstream and transverse currents.

Manual wheelchair pushrim dynamics in people with multiple sclerosis

Fay BT, Boninger ML, Fitzgerald SG, Souza AL, Cooper RA, Koontz AM. Manual wheelchair pushrim dynamics in people with multiple sclerosis. Arch Phys Med Rehabil 2004;85:935–42. Objectives To define differences in pushrim dynamics during manual wheelchair propulsion by users with multiple sclerosis (MS) relative to 2 control groups of subjects with spinal cord injury (SCI) and no disability (ND) and to investigate changes in propulsion biomechanics at different speeds and with fatigue. Design Case-control. Setting Biomechanics laboratory. Participants A convenience sample of 42 people, 8 women and 6 men per group. Interventions Not applicable. Main outcome measures The propulsion pattern, mean maximum speed, percentage of time in push and recovery phases, push angle, push frequency, mean maximum resultant pushrim force, mean work and push cycle, and hand-to-pushrim coupling and decoupling effects. Results The MS groups tended to use an arcing propulsion pattern more than did the control groups ( Pmax=.003). The MS group pushed at a lower mean maximum velocity ( v) when allowed to choose the speed of propulsion ( v MS, .67±.20m/s; v SCI, 1.10±0.23m/s; P=.001), when asked to push at 1m/s ( v MS, .91±.26m/s; v SCI, 1.12±0.11m/s; v ND, 1.05±0.13m/s; P=.010), and were unable to maintain a self-selected speed during a 5-minute trial (Δ v MS, .15±.02m/s; Δ v ND, .03±.06m/s; P<.001). The MS group spent a higher proportion of time in the push phase of propulsion ( Pmax=.001). In general, the MS group had smaller push angles, but push frequencies similar to the controls. Statistically adjusted MS group pushrim forces and work per push measures varied depending on context, but in all trials the MS group displayed a braking effect when grasping and releasing the pushrim. The MS group had declines in most measures when pushing at a self-selected speed for 5 minutes. In all trials, the MS group was more likely to display asymmetry between right and left sides in biomechanic parameters. Conclusions Manual wheelchair users with MS have difficulty grasping and releasing the pushrim and maintaining speed during a fatigue trial. This likely leads to a slow self-selected speed of propulsion that may not be functional. Clinicians should remember these results when prescribing manual wheelchairs for people with MS.

Blood gas changes during incremental and sprint exercise

We investigated and compared arterial blood gas and ventilatory changes during rapid acceleration sprint and during incremental treadmill exercise. Seven clinically normal racehorses completed standardised incremental exercise tests and rapid acceleration tests at speeds calculated to elicit 115% VO2max. Arterial oxygen tension decreased (P < 0.001) between 15 s (mean +/- s.d. 103.8 +/- 14.3 mmHg) and 30 s (85.0 +/- 7.7 mmHg) after the onset of rapid acceleration exercise, but did not change significantly during the remainder of the sprint. This was accompanied by an increase in PaCO2 of 5.9 mmHg (P < 0.05). Despite reductions in SaO2 during exercise, CaO2 did not change due to increases in haemoglobin concentration. Heart rate increased rapidly (P < 0.001) during the first 15 s of exercise and thereafter remained constant. The mean maximum speed during the incremental test (11.4 +/- 0.5 m/s) was not significantly different to the speed calculated to elicit 115% VO2max during the sprint test (12.2 +/- 0.8 m/s). The mean peak HR and Hb during the sprint test were significantly less than during the incremental test. However, there were no significant differences in the maximum or minimum values achieved for other variables. We conclude that rapid acceleration exercise is accompanied by rapid changes in blood gas variables, reaching steady state within 45 s. Blood gas responses during the simpler incremental test describe maximal changes during high-intensity sprint exercise.

Tauroursodeoxycholic acid enhances phagocytosis of the cultured rat Kupffer cell.

Ursodeoxycholic acid is used in the treatment of acute and chronic intrahepatic cholestasis because it ameliorates cholestasis and protects hepatocytes. However, few studies have examined the effect of bile acids on the function of Kupffer cells. The effect of various bile acids on cultured rat Kupffer cells was studied in terms of phagocytic activity in response to latex particles and morphological alterations. Video-enhanced differential interference contrast microscopy was used. Taurochenodeoxycholic acid and taurodeoxycholic acid reduced the number of latex particles incorporated into Kupffer cells, but taurocholic and tauroursodeoxycholic acids enhanced phagocytosis of latex particles. Inhibition of phagocytosis by taurochenodeoxycholic acid or taurodeoxycholic acid was essentially dose dependent. Tauroursodeoxycholic acid also enhanced phagocytosis by Kupffer cells in which phagocytosis had been reduced by pretreatment with taurochenodeoxycholic acid or taurodeoxycholic acid. Incorporated latex particles had a distinct translocation speed of 0.084+/-0.024 microm/s (mean maximum speed+/-SD); the speed was in the same range with tauroursodeoxycholic acid treatment. Tauroursodeoxycholic acid induced a 56% expansion of cytoplasm, associated with increased ruffling and movement of intracellular organelles. These observations suggest that tauroursodeoxycholic acid enhances membrane trafficking without changing translocation speed.

The Jackass Penguin (Spheniscus demersus) as a pelagic predator

The Jackass Penguin (Spheniscus demersus) as a pelagic predator

Air calorics: a technique and results.

A major problem with air calorics appears to be one of technique. A pilot study led to the design of irrigating tips which allow consistant air presentation and simultaneous measurements of irrigating temperature at the delivery orifice (adding a second sensor). Preset temperatures of 24 C and 50 C in our system yielded air equilibration mean temperatures of 27.4 C and 45 C at the delivery orifice during testing. A normal study was carried out at these temperatures with an air flow of six liters per minute for 60 seconds. The range of caloric responses, mean maximum speed, and standard deviation are comparable to values previously reported with water stimulations. Statistical testing indicated no difference between ears for either warm or cold. Also, there was no significant difference for warm versus cold responses. We have performed over 2000 clinical examinations that incorporate this technique with satisfactory results and remarkable acceptance by the patients. The normal or "standard" probe size has been found to be adequate for the majority of the clinic population.