KINETIC PROPERTIES AND EMG ACTIVITY OF NORMAL AND OVER-SPEED PEDALING IN TRACK SPRINT CYCLISTS: A CASE STUDY

Track sprint cycling requires unique skills. We investigate the pedaling kinetics and muscle coordination of a male track sprinter (170cm, 65kg, peak power 1513W) to see if they differ from that of a non-sprinter, and if the subject’s own technique vary from normal riding to an under-load maximal cadence sprint. Two trials were collected using 3D motion capture technology. EMG signals of 8 leg muscles were recorded. Joint torque and power of each trial were calculated using a subject specific musculoskeletal model, with realistic pedal forces as input to our dynamic simulation. Flexion torque appears at the knee during its extension, different from the non-sprinters. Joint torque and power appears similar for both trials, but 6 of the 8 muscles showed differences in EMG patterns. These findings could potentially benefit the evolvement of training methods

A principled approach to interactive hierarchical non-linear visualization of high-dimensional data

Hierarchical visualization systems are desirable because a single twodimensional visualization plot may not be sufficient to capture all of the interesting aspects of complex high-dimensional data sets. We extend an existing locally linear hierarchical visualization system PhiVis [1] in several directions: (1) we allow for non-linear projection manifolds (the basic building block is the Generative Topographic Mapping – GTM), (2) we introduce a general formulation of hierarchical probabilistic models consisting of local probabilistic models organized in a hierarchical tree, (3) we describe folding patterns of low-dimensional projection manifold in high-dimensional data space by computing and visualizing the manifold’s local directional curvatures. Quantities such as magnification factors [3] and directional curvatures are helpful for understanding the layout of the nonlinear projection manifold in the data space and for further refinement of the hierarchical visualization plot. Like PhiVis, our system is statistically principled and is built interactively in a top-down fashion using the EM algorithm. We demonstrate the visualization system principle of the approach on a complex 12-dimensional data set and mention possible applications in the pharmaceutical industry.Final Accepted Versio

A Parametric Study of Piled Raft Foundation in Clay Subjected to Concentrated Loading

The use of piled raft foundation in building and infrastructure constructions is increasingly popular because of its effectiveness in reducing overall and differential settlements. Parameters influencing the performance of the piled raft foundation need to be comprehended in order to optimize the design of the piled raft system. Most of the current available literature focused on the piled raft foundation subjected to a uniform distributed load in sandy material.  This parametric study aims to provide insights into the performance of the piled raft foundations subjected to concentrated loading in clay. A series of 2D finite element analyses were performed to investigate the influencing parameters affecting the load distribution and settlement behaviour of the piled raft. The results suggested that increases in both pile length and raft thickness, as well as a decrease in pile spacing would reduce the differential settlement of the piled raft. Comparatively, raft thickness was the most significant controlling parameter affecting the differential settlement. The study also revealed the importance of placing the pile nearer to the location of concentrated load as it would yield a more uniform load distribution, and hence a lower differential settlement

Effects of natto extract on endothelial injury in a rat model

Vascular endothelial damage has been found to be associated with thrombus formation, which is considered to be a risk factor for cardiovascular disease. A diet of natto leads to a low prevalence of cardiovascular disease. The aim of the present study was to investigate the effects of natto extract on vascular endothelia damage with exposure to laser irradiation. Endothelial damage both in vitro and in vivo was induced by irradiation of rose bengal using a DPSS green laser. Cell viability was determined by MTS assay, and the intimal thickening was verified by a histological approach. The antioxidant content of natto extract was determined for the free radical scavenging activity. Endothelial cells were injured in the presence of rose bengal irradiated in a dose-dependent manner. Natto extract exhibits high levels of antioxidant activity compared with purified natto kinase. Apoptosis of laser-injured endothelial cells was significantly reduced in the presence of natto extract. Both the natto extract and natto kinase suppressed intimal thickening in rats with endothelial injury. The present findings suggest that natto extract suppresses vessel thickening as a synergic effect attributed to its antioxidant and anti-apoptosis properties

Trickle-Down Technology and Screening of a Durable Goods Monopolist

We show that when it takes time for a durable goods monopolist to make its high-end new technology accessible to low-end market (the trickle-down technology constraint), the monopolist's high-end product might have a higher-than-optimum quality. This result differs from conventional screening models, in which the qualities of non-durable goods supplied by a monopolist never exceed the optimum, and only consumers with the highest valuation consume the efficient quality. In another literature discussing a durable goods monopolist who delays the introduction of low-end product as a marketing strategy, but not due to the trickle-down constraint, the qualities will not exceed the optimum either. Our results show that the trickle-down constraint will make the monopolist chooses a higher-than-optimum quality when the difference of the valuations of high demand and low demand consumers are in certain ranges. The intuition follows Spence (1975): the efficient quality is determined by the marginal cost and the average of all consumers' marginal valuations, while the monopolist chooses quality such that the marginal cost equals the marginal consumer's marginal valuation

Preparation and enhanced electrorheological properties of elastomers filled with rod-shaped TiO2 particles

The morphology of dispersed particles has been proven to have a significant impact on performance of electrorheological (ER) materials, while there is a lack of relevant research on its impact on the properties of electrorheological elastomers (EREs). In this study, the TiO2 particles with spherical, short rod, and long rod shape were fabricated with sol-gel method, and the EREs were prepared with these three kinds of particles as dispersion phase. Particle characterization results show that the rod-shape TiO2 particles with larger average size exhibit a combination of anatase and brookite phase. The viscoelastic properties of three types of EREs under varying strain amplitude and shear frequency were tested. The results indicate that the long rod-shape TiO2 particles filled EREs shows higher storage modulus G′ and higher relative ER effect within the electric field from 0 to 3 kV/mm. The observations indicate the use of rod-shape TiO2 particles in the form of brookite phase may help enhance the ER properties of elastomers. The investigation contributes to the designing, preparation, and application of anisotropic ERE

Loading effects of anterior cervical spine fusion on adjacent segments

AbstractAdjacent segment degeneration typically follows anterior cervical spine fusion. However, the primary cause of adjacent segment degeneration remains unknown. Therefore, in order to identify the loading effects that cause adjacent segment degeneration, this study examined the loading effects to superior segments adjacent to fused bone following anterior cervical spine fusion. The C3–C6 cervical spine segments of 12 sheep were examined. Specimens were divided into the following groups: intact spine (group 1); and C5–C6 segments that were fused via cage-instrumented plate fixation (group 2). Specimens were cycled between 20° flexion and 15° extension with a displacement control of 1°/second. The tested parameters included the range of motion (ROM) of each segment, torque and strain on both the body and inferior articular process at the superior segments (C3–C4) adjacent to the fused bone, and the position of the neutral axis of stress at under 20° flexion and 15° extension. Under flexion and Group 2, torque, ROM, and strain on both the bodies and facets of superior segments adjacent to the fused bone were higher than those of Group 1. Under extension and Group 2, ROM for the fused segment was less than that of Group 1; torque, ROM, and stress on both the bodies and facets of superior segments adjacent to the fused bone were higher than those of Group 1. These analytical results indicate that the muscles and ligaments require greater force to achieve cervical motion than the intact spine following anterior cervical spine fusion. In addition, ROM and stress on the bodies and facets of the joint segments adjacent to the fused bone were significantly increased. Under flexion, the neutral axis of the stress on the adjacent segment moved backward, and the stress on the bodies of the segments adjacent to the fused bone increased. These comparative results indicate that increased stress on the adjacent segments is caused by stress-shielding effects. Furthermore, increased stress and ROM of the adjacent segments after long-term bone fusion may accelerate degeneration in adjacent segment

Evaluation of unilateral cage-instrumented fixation for lumbar spine

<p>Abstract</p> <p>Background</p> <p>To investigate how unilateral cage-instrumented posterior lumbar interbody fusion (PLIF) affects the three-dimensional flexibility in degenerative disc disease by comparing the biomechanical characteristics of unilateral and bilateral cage-instrumented PLIF.</p> <p>Methods</p> <p>Twelve motion segments in sheep lumbar spine specimens were tested for flexion, extension, axial rotation, and lateral bending by nondestructive flexibility test method using a nonconstrained testing apparatus. The specimens were divided into two equal groups. Group 1 received unilateral procedures while group 2 received bilateral procedures. Laminectomy, facectomy, discectomy, cage insertion and transpedicle screw insertion were performed sequentially after testing the intact status. Changes in range of motion (ROM) and neutral zone (NZ) were compared between unilateral and bilateral cage-instrumented PLIF.</p> <p>Results</p> <p>Both ROM and NZ, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF, transpedicle screw insertion procedure did not revealed a significant difference between flexion-extension, lateral bending and axial rotation direction except the ROM in the axial rotation. The bilateral group's ROM (-1.7 ± 0. 8) of axial rotation was decreased significantly after transpedicle screw insertion procedure in comparison with the unilateral group (-0.2 ± 0.1). In the unilateral cage-instrumented PLIF group, the transpedicle screw insertion procedure did not demonstrate a significant difference between right and left side in the lateral bending and axial rotation direction.</p> <p>Conclusions</p> <p>Based on the results of this study, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF have similar stability after transpedicle screw fixation in the sheep spine model. The unilateral approach can substantially reduce exposure requirements. It also offers the biomechanics advantage of construction using anterior column support combined with pedicle screws just as the bilateral cage-instrumented group. The unpleasant effect of couple motion resulting from inherent asymmetry was absent in the unilateral group.</p

An overview of epigenetics and chemoprevention

AbstractIt is now appreciated that both genetic alteration, e.g. mutations, and aberrant epigenetic changes, e.g. DNA methylation, cause cancer. Epigenetic dysregulation is potentially reversible which makes it attractive as targets for cancer prevention. Synthetic drugs targeting enzymes, e.g. DNA methyltransferase and histone deacetylase, that regulate epigenetic patterns are active in clinical settings. In addition, dietary factors have been suggested to have potential to reverse aberrant epigenetic patterns. Uncovering the human epigenome can lead us to better understand the dynamics of DNA methylation in disease progression which can further assist in cancer prevention