Loading and relaxation dynamics for a red blood cell

We use mesoscale numerical simulations to investigate the unsteady dynamics of a single red blood cell (RBC) subjected to an external mechanical load. We carry out a detailed comparison between...

Measurement of lower-limb asymmetry in professional rugby league: a technical note describing the use of inertial measurement units

Background Quantifying lower-limb load and asymmetry during team sport match-play may be important for injury prevention and understanding performance. However, current analysis methods of lower-limb symmetry during match-play employ wearable microtechnology that may not be best suited to the task. A popular microtechnology is global positioning systems (GPS), which are torso worn. The torso location, and the summary workload measures calculated by GPS are not suited to the calculation of lower-limb load. Instead, research grade accelerometers placed directly on the lower-limb may provide better load information than GPS. This study proposes a new technique to quantify external mechanical load, and lower-limb asymmetry during on-field team sport play using inertial measurement units. Methods Four professional rugby league players (Age: 23.4 ± 3.1 years; Height: 1.89 ± 0.05 m; Mass: 107.0 ± 12.9 kg) wore two accelerometers, one attached to each foot by the boot laces, during match simulations. Custom Matlab (R2017b, The Mathworks Inc, Natick, MA) code was used to calculate total time, area under the curve (AUC), and percentage of time (%Time) spent in seven acceleration categories (negative to very high, <0 g to >16 g), as well as minimum and maximum acceleration during match simulations. Lower-limb AUC and %Time asymmetry was calculated using the Symmetry Angle Equation, which does not require normalization to a reference leg. Results The range of accelerations experienced across all participants on the left and right sides were 15.68–17.53 g, and 16.18–17.69 g, respectively. Clinically significant asymmetry in AUC and %Time was observed for all but one participant, and only in negative (<0 g) and very high accelerations (>16 g). Clinically significant AUC differences in very high accelerations ranged from 19.10%–26.71%. Clinically significant %Time differences in negative accelerations ranged from 12.65%–25.14%, and in very high accelerations from 18.59%–25.30%. All participants experienced the most AUC at very low accelerations (2–4 g), and the least AUC at very high accelerations (165.00–194.00 AU vs. 0.32–3.59 AU). The %Time results indicated that all participants spent the majority of match-play (73.82–92.06%) in extremely low (0–2 g) to low (4–6 g) acceleration intensities, and the least %Time in very high accelerations (0.01%–0.05%). Discussion A wearable located on the footwear to measure lower-limb load and asymmetry is feasible to use during rugby league match-play. The location of the sensor on the boot is suited to minimize injury risk occurring from impact to the sensor. This technique is able to quantify external mechanical load and detect inter limb asymmetries during match-play at the source of impact and loading, and is therefore likely to be better than current torso based methods. The results of this study may assist in preparing athletes for match-play, and in preventing injury.

Locomotor and Heart Rate Responses of Floaters During Small-Sided Games in Elite Soccer Players: Effect of Pitch Size and Inclusion of Goalkeepers

Purpose: To (1) compare the locomotor and heart rate responses between floaters and regular players during both small and large small-sided games (SSGs) and (2) examine whether the type of game (ie, game simulation [GS] vs possession game [PO]) affects the magnitude of the difference between floaters and regular players. Methods: Data were collected in 41 players belonging to an elite French football team during 3 consecutive seasons (2014–2017). A 5-Hz global positionning system was used to collect all training data, with the Athletic Data Innovation analyzer (v5.4.1.514) used to derive total distance (m), high-speed distance (>14.4 km·h−1, m), and external mechanical load (MechL, a.u.). All SSGs included exclusively 1 floater and were divided into 2 main categories, according to the participation of goalkeepers (GS) or not (PO) and then further divided into small and large (>100 m2per player) SSGs based on the area per player ratio. Results: Locomotor activity and MechL performed were likely-to-most likely lower (moderate to large magnitude) in floaters compared with regular players, whereas differences in heart rate responses were unclear to possibly higher (small) in floaters. The magnitude of the difference in locomotor activity and MechL between floaters and regular players was substantially greater during GS compared with PO. Conclusions: Compared with regular players, floaters present decreased external load (both locomotor and MechL) despite unclear to possibly slightly higher heart rate responses during SSGs. Moreover, the responses of floaters compared with regular players are not consistent across different sizes of SSGs, with greater differences during GS than PO.

The 7T-MPW-EDDI beamline at BESSY II

The materials science beamline EDDI is operated in the <strong><em>E</em></strong>nergy <strong><em>D</em></strong>ispersive <strong><em>DI</em></strong>ffraction mode and provides hard synchrotron X-rays in an energy range between about 8 … 150 keV for a multitude of experiments reaching from the in-situ study of thin film deposition over the investigation of liquid phase processes to the analysis of the residual stress distribution in complex components and technical parts. For high temperature experiments or measurements under external mechanical load various devices such as heating stations and a tensile/compression load test rig are available. Besides the sample environment for pure diffraction experiments a tomography/radiography setup is provided which allows for combined simultaneous diffraction plus imaging investigations.

Load-Dependent Assembly of the Bacterial Flagellar Motor

ABSTRACTIt is becoming clear that the bacterial flagellar motor output is important not only for bacterial locomotion but also for mediating the transition from liquid to surface living. The output of the flagellar motor changes with the mechanical load placed on it by the external environment: at a higher load, the motor runs more slowly and produces higher torque. Here we show that the number of torque-generating units bound to the flagellar motor also depends on the external mechanical load, with fewer stators at lower loads. Stalled motors contained at least as many stators as rotating motors at high load, indicating that rotation is unnecessary for stator binding. Mutant stators incapable of generating torque could not be detected around the motor. We speculate that a component of the bacterial flagellar motor senses external load and mediates the strength of stator binding to the rest of the motor.IMPORTANCEThe transition between liquid living and surface living is important in the life cycles of many bacteria. In this paper, we describe how the flagellar motor, used by bacteria for locomotion through liquid media and across solid surfaces, is capable of adjusting the number of bound stator units to better suit the external load conditions. By stalling motors using external magnetic fields, we also show that rotation is not required for maintenance of stators around the motor; instead, torque production is the essential factor for motor stability. These new results, in addition to previous data, lead us to hypothesize that the motor stators function as mechanosensors as well as functioning as torque-generating units.

Vibration and Temperature Measuring Experiments on Multilayer Piezoelectric Actuator

In this paper, a kind of Mg, Nb co-doped multilayer piezoelectric ceramic is prepared and a non-contact accurate testing method is introduced. Using Pb(Mg1/3Nb2/3)O3- Pb(Ni1/3Nb2/3)O3- Pb(ZrTi)O3 low temperature co-fired ceramics powder and 90/10 Ag-Pb internal electrodes, the sample is prepared with tape casting processing method and low temperature co-fired technique at 960°C. Based on non-contact method, the piezoelectric constant, butterfly curve, and temperature characters are tested. Experiments show that non-contact method is more accurate for d33 testing. The effect of mechanical load on piezoelectric performance is also investigated. Under external mechanical load, switching polarization (Ps) and remnant polarization (Pr) increase respectively. Mechanical load press is also favorable to dominate the temperature rise of the piezoelectric device.

Intra- and Extrafibrillar Fluid Exchange in the Disc

The mechanical properties of the intervertebral disc are regulated by its biochemical composition. With ageing and degeneration the water content of the disc decreases which highly influences the mechanical properties. The disc is subjected to a combination of elastic, viscous and osmotic forces. Osmotic forces are shown to have a major impact on crack opening and propagation [1] and on cellular responses [2]. In particular, osmosis provides an understanding on why fissures in the degenerating disc are so poorly related to external mechanical load [3].