THE INFLUENCE OF SAND SURFACE ON THE KINEMATICS OF VOLLEYBALL SPIKE JUMPS

Several types of sports, like soccer, European handball, and volleyball have expanded their classical fields of activity from indoor surfaces made of wood or synthetic and outdoor turf to sand surfaces. Previous studies reported differences in both body mechanics and energy demands during several types of movement on sand or similar compliant surfaces compared to hard surfaces. Therefore, we investigated the differences in kinematics during spike jumps performed on indoor or sand surface (Tilp et al., 2008)

The Corrosion Behavior of Electroless Ni-P-SiC and Ni-Sn-P-SiC Nano-Composite Coating

Abstract: Electroless nickel (EN) and EN composite with SiC and Sn-SiC were deposited by chemical deposition. The microstructure analysis was conducted with scanning electron microscopy, Thin film indicated that the presence of SiC particles did not affect the microstructure of the Ni-P alloy matrix when annealing temperature was below 400°C. EDAX (Energy dispersive x-ray analysis) technique have been applied in order to investigate the chemical composition and indicated that linear relation between SiC concentrations and SiC content. Microhardness of electroless Ni-Sn-P deposite, Ni-P-SiC composite and Ni-Sn-P-SiC composite were studied. Microhardness reached to the maximum value after heating to 400ºC for 1h. Microhardness follow the sequence Ni-P-SiC > Ni-Sn-P-SiC > Ni-P > Ni-Sn-P. Finally, the corrosion resistance of different SiC content and constant concentration of SnCl2 was studied in different corrosive solutions (1M H2SO4 and 3.5% NaCl solution)

Coherent diffractive imaging of microtubules using an X-ray laser

X-ray free electron lasers (XFELs) create new possibilities for structural studies of biological objects that extend beyond what is possible with synchrotron radiation. Serial femtosecond crystallography has allowed high-resolution structures to be determined from micro-meter sized crystals, whereas single particle coherent X-ray imaging requires development to extend the resolution beyond a few tens of nanometers. Here we describe an intermediate approach: the XFEL imaging of biological assemblies with helical symmetry. We collected X-ray scattering images from samples of microtubules injected across an XFEL beam using a liquid microjet, sorted these images into class averages, merged these data into a diffraction pattern extending to 2 nm resolution, and reconstructed these data into a projection image of the microtubule. Details such as the 4 nm tubulin monomer became visible in this reconstruction. These results illustrate the potential of single-molecule X-ray imaging of biological assembles with helical symmetry at room temperature

Flow-aligned, single-shot fiber diffraction using a femtosecond X-ray free-electron laser

A major goal for X-ray free-electron laser (XFEL) based science is to elucidate structures of biological molecules without the need for crystals. Filament systems may provide some of the first single macromolecular structures elucidated by XFEL radiation, since they contain one-dimensional translational symmetry and thereby occupy the diffraction intensity region between the extremes of crystals and single molecules. Here, we demonstrate flow alignment of as few as 100 filaments (Escherichia coli pili, F-actin, and amyloid fibrils), which when intersected by femtosecond X-ray pulses result in diffraction patterns similar to those obtained from classical fiber diffraction studies. We also determine that F-actin can be flow-aligned to a disorientation of approximately 5 degrees. Using this XFEL-based technique, we determine that gelsolin amyloids are comprised of stacked β-strands running perpendicular to the filament axis, and that a range of order from fibrillar to crystalline is discernable for individual α-synuclein amyloids

Ultrasound as a tool to study muscle\u2013tendon functions during locomotion: A systematic review of applications

Movement science investigating muscle and tendon functions during locomotion utilizes commercial ultrasound imagers built for medical applications. These limit biomechanics research due to their form factor, range of view, and spatio-temporal resolution. This review systematically investigates the technical aspects of applying ultrasound as a research tool to investigate human and animal locomotion. It provides an overview on the ultrasound systems used and of their operating parameters. We present measured fascicle velocities and discuss the results with respect to operating frame rates during recording. Furthermore, we derive why muscle and tendon functions should be recorded with a frame rate of at least 150 Hz and a range of view of 250 mm. Moreover, we analyze why and how the development of better ultrasound observation devices at the hierarchical level of muscles and tendons can support biomechanics research. Additionally, we present recent technological advances and their possible application. We provide a list of recommendations for the development of a more advanced ultrasound sensor system class targeting biomechanical applications. Looking to the future, mobile, ultrafast ultrasound hardware technologies create immense opportunities to expand the existing knowledge of human and animal movement

Human fascicle strain behavior during twitch using ultrafast ultrasound

There is recent experimental evidence that sarcomere strain behavior is highly heterogeneous across and between muscle structures. Hence, considering the hierarchical architecture of muscles, also the behavior of all acting muscle substructures is effected. However, typical investigations are limited to ex-vivo experiments or pose serious limitations for in-vivo studies. In this work, we investigate in-vivo length changes in human muscle fascicles by means of non-invasive ultrafast ultrasound. To this end, we employ a research ultrasound system and a linear array transducer to image, in plane-wave mode, medial gastrocnemius muscles during electrically-stimulated contractions. The ultrasound-based approach presented in this study allows to measure strain distributions within muscle fascicles during contractions, where the sub-fascicle structures exhibit heterogeneous behaviors