...potential between-leg deficits in horizontal force may not be considered during testing due to the bilateral nature of sprinting. ...this study aimed to establish the reliability of unilateral ...tests assessing explosive hip extension and horizontal force production, and their association with sprinting performance. Reliability was established by calculating typical error (TE), coefficient of variation (TE%), interclass correlation coefficient (ICC) and minimal detectable change (MDC). Results Test re-test reliability was good to excellent for the scooter (TE%= 1.7-4.6; ICC= 0.88-0.94), moderate for the isometric hip extension (TE%= 5.6-6.0; ICC = 0.65-0.69) and good for the hamstring switch (TE%= 3.4-4.7; ICC = 0.78 to 0.87) and single hop for distance (TE%= 4.7-5.7; ICC= 0.78-0.86).
The current elasticities of major mantle transition zone minerals and their hydrous counterparts, such as wadsleyite, ringwoodite, and majorite garnet, have the velocity gradients several times lower ...than those of the Earth models. Here we use ultrasonic interferometry technique to measure the sound velocities of wadsleyite (Mg0.91Fe0.09)2SiO4 at pressures up to 14 GPa and room temperature. Compared with previous studies, we have obtained possibly the highest ∂VP/P and ∂KS/P value at transition zone pressure, which are still noticeably lower than the Earth models, such as the preliminary reference Earth model, ak135, iasp91, etc. The results indicate that the VP contrast of “dry” olivine‐wadsleyite transition at 410 km is higher than previous thought, while that of wadsleyite‐ringwoodite transition at 520 km is noticeably low. Using the current and previous data on “dry” and hydrous wadsleyite a water “gradient” model at upper mantle transition zone were proposed and discussed.
Plain Language Summary
Olivine and its high pressure polymorphs (wadsleyite and ringwoodite) are the major components in the Earth's upper mantle and mantle transition zone, which dominant the physical properties of the Earth's mantle. However, using the current pyrolitic model and the measured elasticities (velocities and moduli) of wadsleyite and ringwoodite, one cannot reproduce the observed velocity profiles of the Earth models (e.g., preliminary reference Earth model, ak135). Ultrasonic interferometry technique is a mature technique to measure the compressional and shear wave velocities of polycrystalline aggregates. Using this technique, we obtained the sound velocities and their pressure (depth) dependences of iron‐bearing wadsleyite at pressures up to 14 GPa and room temperature. The results suggest that under dry condition, the seismic velocity contrasts at 410 km discontinuity (olivine‐wadsleyite transition) are higher than previous reported. To match the velocity contrasts at 410 km depth and the high velocity gradients at mantle transition zone, a hydrous transition zone with water “gradient” is proposed based on this study and previous results.
Key Points
Sound velocities of (Mg0.91Fe0.09)2SiO4 Wadsleyite were measured up to 14 GPa at room temperature
Possibly the highest ∂VP/P and KS′ values were obtained, which are still much lower than those of the Earth models
Water content “gradient” was proposed to match the high velocity gradients in the mantle transition zone
The Radial Velocity of OGLE-2015-BLG-0966S Johnson, Samson A; Yee, Jennifer C
Publications of the Astronomical Society of the Pacific,
07/2017, Letnik:
129, Številka:
977
Journal Article
Recenzirano
The distance to the planetary system OGLE-2015-BLG-0966L and the separation between the planet and its host star are ambiguous due to an ambiguity in the distance to the source star. We attempt to ...break this degeneracy by measuring the systemic radial velocity of the source star measured from a spectrum taken while the source was highly magnified. Our measurement of vLSR =54.2 ± 0.3 km s-1 does not definitively resolve the nature of the source, but supports the general conclusion that the source is in the bulge. This work demonstrates that even a low signal-to-noise spectrum has the potential to provide useful information for characterizing microlensing source stars.
(Ti,Mo)(C,N)-25 wt% Ni coatings obtained by spraying an agglomerated and sintered feedstock powder using different high velocity air-fuel (HVAF) and high velocity oxygen-fuel (HVOF) deposition ...processes are comparatively analysed for their sliding, abrasion and impact resistance.
All HVOF-sprayed coatings are particularly dense, with ≈800 HV hardness (tested at 100 gf, 300 gf and 500 gf). In-flight oxidation resulted in some embrittlement, as revealed by scratch tests. In ball-on-disk sliding against an Al2O3 counterpart, they maintained a mild wear regime (wear rates ≤10−6 mm3/(N⋅m)) from room temperature up to 600 °C, with better performance in comparison to Cr3C2–NiCr reference coatings. At room temperature, the Ti(C,N) hard phase limited the abrasive cutting by counterbody asperities. At 400 °C and 600 °C, the coatings developed a thin, protective oxide tribofilm. They also exhibited no interface delamination in cyclic impact tests. However, they suffered higher wear (≈3–5 × 10−3 mm3/(N⋅m)) in high-stress particle abrasion testing, particularly when compared to HVAF-sprayed Cr3C2–NiCr. Gaining improved control over in-flight oxidation of (Ti,Mo)(C,N)–Ni during spraying is probably the key to overcome this limitation.
The HVAF-sprayed (Ti,Mo)(C,N)–Ni coating exhibited severe interlamellar decohesion under all test conditions, as the limited melting degree of the feedstock did not compensate for the intrinsic microstructural inhomogeneity of the powder particles.
•HVOF (Ti,Mo)(C,N)–Ni exhibited better sliding wear resistance than Cr3C2–NiCr up to 600 °C.•HVOF (Ti,Mo)(C,N)–Ni is not sensitive to the p × V factor over a tested range of 1–25 MPa × m/s.•Oxide inclusion and ensuing brittleness worsened the resistance of HVOF coatings to high-stress particles' abrasion.•The coatings did not delaminate under cyclic impact conditions.•The HVAF coating is less homogeneous and weaker because the Ni matrix did not melt under the chosen deposition conditions.
Objectives:
Supraphysiologic forces placed on the glenohumeral joint during pitching leads to a high incidence of bicipital-labral pathology in competitive pitchers. Heavy debate in operative ...management between biceps tenodesis, labral repair, and debridement warrants further study in the role of the biceps during pitching. The purpose of this study was to evaluate the recruitment of the long and short heads of the biceps utilizing electromyographic evaluation and correlate activity with pitch velocity.
Methods:
Seventeen healthy, competitive, pitchers were recruited and consented to pitch in a controlled laboratory setting, under electromyographic observation. Surface electromyography (sEMG) was performed via electrodes placed on either head of the biceps, deltoid, infraspinatus, and latissimus dorsi, band pass filtered between 10-500 Hz and sampled at a rate of 1500 Hz during the pitching motion. sEMG was normalized to maximal volumetric isometric contraction (MVIC) via manual muscle testing (MMT). Pitch velocity was measured using a Speedster III radar gun, and then correlated to sEMG readings.
Results:
Average age of recruited subjects was 19.8 ± 1.4 years old. Average number of years pitched was 10.3 ± 3.6 years. Fourteen players reported their highest level of play was college, while two reported semi-professional, and one reported high-school. Average pitch velocity from included pitches was 70.6 ± 4.0 (range: 61 - 79). sEMG signals were interpreted in three modalities: median signal, integral sum of all signals, and time spent (ms) above 10% MVIC. Pitch velocity did not correlate to any sEMG analysis (p>0.05) by bivariate linear regression. Coefficient of variation was greater between pitchers than within pitchers. Greater than 80% of pitchers demonstrated statistically different activation of the long head of biceps muscle (LHBM) versus short head of biceps muscle (SHBM) (Figure 1). Three players had significantly greater short head activation, while 12 players had significantly greater long head activation.
Conclusion:
The long and short heads of the biceps are consistently activated during pitching, suggested they have a role during the late cocking and deceleration phase of pitching, although not correlated to ball acceleration. Preferential recruitment of either long or short head biceps suggest variability in fast ball pitching styles, that warrant further research for clinical implications.
Figure 1.
Electromyography time series data demonstrating LHBM dominant pitcher subject 9 (Blue) in comparison to SHBM dominant pitcher subject 10 (Yellow)
Aiming at the problem that lack of the measured sound velocity profile (SVP) leads to the unreliable underwater positioning solution, this paper proposed an efficient underwater positioning method by ...the self-constraint conditions of water depth and sound velocity gradient. To construct the depth constraint condition, the sound propagation distance error model is deduced by acoustic ray tracing, and the sound vertical propagation error model related to the incident angle and sound velocity error is given firstly. By fitting the vertical propagation error model, the reference depth is solved, and the vertical propagation distances between the transducer and the underwater control points of all observation epochs are gotten. Then with the solved vertical distance of each epoch and the sound velocity gradient from neighbor SVPs as the constraint conditions, the SVP is retrieved by the simulated annealing (SA) algorithm. With the retrieved SVP, the underwater positioning can be performed when the measured SVP is absent. The proposed method was verified by an experiment in the 3000 m depth water area of the South China Sea. The results achieved 2.07 m/s of standard deviation of the SVP inversion, centimeter-level horizontal positioning accuracy and 0.54 m of vertical positioning accuracy under the circumstance of lack of SVP measurement.
Purpose
Benchmarking of flow and perfusion MR techniques on standardized phantoms can facilitate the use of advanced angiography and perfusion‐mapping techniques across multiple sites, field ...strength, and vendors. Here, MRA and perfusion mapping by arterial spin labeling (ASL) using Fourier transform (FT)–based velocity‐selective saturation and inversion pulse trains were evaluated on a commercial perfusion phantom.
Methods
The FT velocity‐selective saturation–based MRA and FT velocity‐selective inversion–based ASL perfusion imaging were compared with time‐of‐flight and pseudo‐continuous ASL at 3 T on the perfusion phantom at two controlled flow rates, 175 mL/min and 350 mL/min. Velocity‐selective MRA (VSMRA) and velocity‐selective ASL (VSASL) were each performed with three velocity‐encoding directions: foot–head, left–right, and oblique 45°. The contrast‐to‐noise ratio for MRA scans and perfusion‐weighted signal, as well as labeling efficiency for ASL methods, were quantified.
Results
On this phantom with feeding tubes having only vertical and transverse flow directions, VSMRA and VSASL exhibited the dependence of velocity‐encoding directions. The foot–head‐encoded VSMRA and VSASL generated similar signal contrasts as time of flight and pseudo‐continuous ASL for the two flow rates, respectively. The oblique 45°–encoded VSMRA yielded more uniform contrast‐to‐noise ratio across slices than foot–head and left–right‐encoded VSMRA scans. The oblique 45°–encoded VSASL elevated labeling efficiency from 0.22‐0.68 to 0.82‐0.90 through more uniform labeling of the entire feeding tubes.
Conclusion
Both FT velocity‐selective saturation–based VSMRA and FT velocity‐selective inversion–based VSASL were characterized on a commercial perfusion phantom. Careful selection of velocity‐encoding directions along the major vessels is recommended for their applications in various organs.
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