Agility Measures Related to Game Performance of NCAA Baseball Pitchers

Like most kinetic chains in athletic performance, the baseball pitching motion begins with the muscles of the legs and continues progressively through the torso, shoulders, and arms. Similarities are noted between the baseball pitching motion and the kinetic chain employed in agility tests that involve acceleration, deceleration, and change of direction measures of agility. Purpose: The purpose of this investigation was to determine pre-season agility in NCAA pitchers and to relate these measures to regular season pitching performance. Methods: NCAA Division II pitchers (n=10, age 20.2 ± 1.9 yrs., weight 83.8 ± 10.3 kg, height 1.85 ± 0.48 m) volunteered as study subjects. A previously described laser-timed 60-yd shuttle run (“JJ Shuttle”) provided average speeds for four contiguous agility segments (S1, S2, S3, and S4 of 10, 10, 20, and 20 yds., respectively), as well as Total Shuttle Run (TSR). Statistical measures obtained from regular season games (n=48), including Runs (R), Hits (H), Earned Runs (ER), Base-on-Balls (BB), and Strikeouts (SO), each normalized for innings pitched, provided evidence of game pitching performance. Pearson’s Correlation Coefficient determined the relationship of average agility speeds to pitching performance. Results: Analysis identified significant correlations (p\u3c.05) between S1, S2, and TSR and normalized SO (r=0.77, r=0.73, and r=0.87, respectively); S3 and S4 were insignificant (r=0.42 and r=0.59, respectively). Additionally, a significant correlation (p\u3c.05) was identified between S3 and BB (r=0.67). Conclusion: Results of this study suggest that better agility may lead to selected improvements in game performance in NCAA Division II baseball pitchers

Nonlinear force-free models for the solar corona I. Two active regions with very different structure

With the development of new instrumentation providing measurements of solar photospheric vector magnetic fields, we need to develop our understanding of the effects of current density on coronal magnetic field configurations. The object is to understand the diverse and complex nature of coronal magnetic fields in active regions using a nonlinear force-free model. From the observed photospheric magnetic field we derive the photospheric current density for two active regions: one is a decaying active region with strong currents (AR8151), and the other is a newly emerged active region with weak currents (AR8210). We compare the three-dimensional structure of the magnetic fields for both active region when they are assumed to be either potential or nonlinear force-free. The latter is computed using a Grad-Rubin vector-potential-like numerical scheme. A quantitative comparison is performed in terms of the geometry, the connectivity of field lines, the magnetic energy and the magnetic helicity content. For the old decaying active region the connectivity and geometry of the nonlinear force-free model include strong twist and strong shear and are very different from the potential model. The twisted flux bundles store magnetic energy and magnetic helicity high in the corona (about 50 Mm). The newly emerged active region has a complex topology and the departure from a potential field is small, but the excess magnetic energy is stored in the low corona and is enough to trigger powerful flares.Comment: 11 pages, 11 figure

Subtractive NCE-MRA: Improved background suppression using robust regression-based weighted subtraction.

PURPOSE: To correct the intensity difference of static background signal between bright blood images and dark blood images in subtractive non-contrast-enhanced MR angiography using robust regression, thereby improving static background signal suppression on subtracted angiograms. METHODS: Robust regression (RR), using iteratively reweighted least squares, is used to calculate the regression coefficient of background tissues from a scatter plot showing the voxel intensity of bright blood images versus dark blood images. The weighting function is based on either the Euclidean distance from the estimated regression line or the deviation angle. Results from RR using the deviation angle (RRDA), conventional RR using the Euclidean distance, and ordinary leastsquares regression were compared with reference values determined manually by two observers. Performance was evaluated over studies using different sequences, including 36 thoracic flow-sensitive dephasing data sets, 13 iliac flow-sensitive dephasing data sets, and 26 femoral fresh blood imaging data sets. RESULTS: RR deviation angle achieved robust and accurate performance in all types of images, with small bias, small mean absolute error, and high-correlation coefficients with reference values. Background tissues, such as muscle, veins, and bladder, were suppressed while the vascular signal was preserved. Euclidean distance gave good performance for thoracic and iliac flow-sensitive dephasing, but could not suppress background tissues in femoral fresh blood imaging. Ordinary least squares regression was sensitive to outliers and overestimated regression coefficients in thoracic flow-sensitive dephasing. CONCLUSION: Weighted subtraction using RR was able to acquire the regression coefficients of background signal and improve background suppression of subtractive non-contrast-enhanced MR angiography techniques. RR deviation angle has the most robust and accurate overall performance among three regression methods

Simulating the Misting of Lubricant in the Piston Assembly of an Automotive Gasoline Engine: The Effect of Viscosity Modifiers and Other Key Lubricant Components

YesThe presence of lubricant droplets in the gas that flows through the piston assembly and crankcase of an internal combustion engine (generically termed oil misting) has important implications for performance, particularly lubricant supply to the upper piston assembly, oil consumption and lubricant degradation. A significant source of these droplets is thought to be oil shearing and blow-through by blow-by gas flows in the piston assembly. An experimental rig was developed to simulate the high velocity gas and lubricant film interactions at a top piston ring gap where the flow conditions are most severe. Flows of lubricant droplets were produced and characterised in terms of the proportion of the oil flow that formed droplets in the gas flow and the size distribution of the droplets produced. Considering various aspects of a commercial automotive crankcase formulation, the effect of lubricant viscosity was found to be particularly important. Of the lubricant additives evaluated, viscosity modifiers were found to have the greatest effect on the tendency to form droplets: Detailed study on a range of viscosity modifiers identified that the influence of their molecular architectures on viscoelasticity was the key mechanism

The Influence of Lubricant Degradation on Measured Piston Ring Film Thickness in a Fired Gasoline Reciprocating Engine

YesA laser induced fluorescence system has been developed to visualise the oil film thickness between the piston ring and cylinder wall of a fired gasoline engine via a small optical window mounted in the cylinder wall. A fluorescent dye was added to the lubricant in the sump to allow the lubricant to fluoresce when absorbing laser radiation. The concentration of the dye did not disturb the lubricant chemistry or its performance. Degraded engine oil samples were used to investigate the influence of lubricant quality on ring pack lubricant film thickness measurements. The results show significant differences in the lubricant film thickness profiles for the ring pack when the lubricant degrades which will affect ring pack friction and ultimately fuel economy

Enteropathogen antibody dynamics and force of infection among children in low-resource settings.

Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG responses to eight enteropathogens (Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica, enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni, norovirus) in cohorts from Haiti, Kenya, and Tanzania. We studied antibody dynamics and force of infection across pathogens and cohorts. Enteropathogens shared common seroepidemiologic features that enabled between-pathogen comparisons of transmission. Overall, exposure was intense: for most pathogens the window of primary infection was <3 years old; for highest transmission pathogens primary infection occurred within the first year. Longitudinal profiles demonstrated significant IgG boosting and waning above seropositivity cutoffs, underscoring the value of longitudinal designs to estimate force of infection. Seroprevalence and force of infection were rank-preserving across pathogens, illustrating the measures provide similar information about transmission heterogeneity. Our findings suggest antibody response can be used to measure population-level transmission of diverse enteropathogens in serologic surveillance

Amniotic fluid volume: Rapid MR-based assessment at 28-32 weeks gestation

Objectives: This work evaluates rapid magnetic resonance projection hydrography (PH) based amniotic fluid volume (AFV) estimates against established routine ultrasound single deepest vertical pocket (SDVP) and amniotic fluid index (AFI) measurements, in utero, at 28-32 weeks gestation. Manual multi-section planimetry (MSP) based measurement of AFV is used as a proxy reference standard. Methods: 35 women with a healthy singleton pregnancy (20-41 years) attending routine antenatal ultrasound were recruited. SDVP and AFI were measured using ultrasound, with same day MRI assessing AFV with PH and MSP. The relationships between the respective techniques were assessed using linear regression analysis and Bland-Altman method comparison statistics. Results: When comparing estimated AFV, a highly significant relationship was observed between PH and the reference standard MSP (R2=0.802, p<0.001). For the US measurements, SDVP measurement related most closely to amniotic fluid volume, (R2=0.470, p<0.001), with AFI demonstrating a weaker relationship (R2=0.208, p=0.007). Conclusion: This study shows that rapid MRI based PH measurement is a better predictor of AFV, relating more closely to our proxy standard than established US techniques. Although larger validation studies across a range of gestational ages are required this approach could form part of MR fetal assessment, particularly where poly or oligohydramnios is suspected.This study was supported by the National Institute of Health Research, Cambridge Biomedical Research Centre. The authors also acknowledge the support of Addenbrooke’s Charitable Trust and thank the participants for their contribution to the study.This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s00330-015-4179-

Experimental and theoretical study of instantaneous piston assembly friction in a gasoline engine

ABSTRACT A piston assembly friction model has been developed to predict the individual performance of compression rings, the oil control ring and the piston skirt. Validation of this model has been undertaken by comparing the predicted results with the experimental measurements of piston assembly friction in a gasoline engine under fired conditions using the IMEP (indicated mean effective pressure) method. The experimental results for an SAE 0W20 without friction modifier were compared with the predictions. The predicted results correlate very well with the measurements, especially at higher lubricant inlet temperatures. Piston skirt friction was predicted using both a simple concentric piston / cylinder model and a more realistic but computationally intensive method incorporating piston secondary motion. The results clearly indicate that the latter more realistic method is required to achieve satisfactory correlation with the measured data

Thin-film and marginal lubrication of PolyEtherKetone-steel sliding contacts at high temperature and high speed

YesPolyEtherKetone (PEK) is a suitable material for tribological systems which specifically require the properties of high chemical resistance, low component weight, seizure resistance under starved lubrication conditions and operation at higher temperatures than many other engineering polymers can survive. PEK is used with a liquid lubricant at high temperatures and velocities to reduce friction and also to control unstable friction and wear, particularly in the region of the material’s glass transition temperature, Tg. Intermittent and marginal lubrication using representative high temperature synthetic lubricants was applied to high speed, high temperature PEK/steel sliding contacts to determine the effectiveness of lubrication under these conditions. Variations in the stability of the thin lubricant films were observed, particularly under different load conditions. Under low load conditions, the lubricant polarity and the related ability to form a film in the contact was important. Under high load conditions, the thermal stability of the lubricant became more important in retaining stability in the friction and wear mechanisms. Whilst not ideal practice, marginal lubrication of PEK-steel sliding contacts can be achieved by selection of an appropriate lubricant, even in the glass transition region of PEK.Innovate UK Knowledge Transfer Partnership (KTP) grant, No. 8092

Quantitative BOLD imaging at 3T: Temporal changes in hepatocellular carcinoma and fibrosis following oxygen challenge.

PURPOSE: To evaluate the utility of oxygen challenge and report on temporal changes in blood oxygenation level-dependent (BOLD) contrast in normal liver, hepatocellular carcinoma (HCC) and background fibrosis. MATERIALS AND METHODS: Eleven volunteers (nine male and two female, mean age 33.5, range 27-41 years) and 10 patients (nine male and one female, mean age 68.9, range 56-87 years) with hepatocellular carcinoma on a background of diffuse liver disease were recruited. Imaging was performed on a 3T system using a multiphase, multiecho, fast gradient echo sequence. Oxygen was administered via a Hudson mask after 2 minutes of free-breathing. Paired t-tests were performed to determine if the mean pre- and post-O2 differences were statistically significant. RESULTS: In patients with liver fibrosis (n = 8) the change in T2* following O2 administration was elevated (0.88 ± 0.582 msec, range 0.03-1.69 msec) and the difference was significant (P = 0.004). The magnitude of the BOLD response in patients with HCC (n = 10) was larger, however the response was more variable (1.07 ± 1.458 msec, range -0.93-3.26 msec), and the difference was borderline significant (P = 0.046). The BOLD response in the volunteer cohort was not significant (P = 0.121, 0.59 ± 1.162 msec, range -0.81-2.44 msec). CONCLUSION: This work demonstrates that the BOLD response following oxygen challenge within cirrhotic liver is consistent with a breakdown in vascular autoregulatory mechanisms. Similarly, the elevated BOLD response within HCC is consistent with the abnormal capillary vasculature within tumors and the arterialization of the blood supply. Our results suggest that oxygen challenge may prove a viable BOLD contrast mechanism in the liver. J. Magn. Reson. Imaging 2016;44:739-744.This study was supported by the Addenbrooke’s Charitable Trust, Cambridge’s Experimental Cancer Medicine Centre and a NIHR comprehensive Biomedical Research Centre award to Cambridge University Hospitals NHS Foundation Trust in partnership with the University of Cambridge.This is the final version of the article. It first appeared from Wiley via https://doi.org/10.1002/jmri.2518