Kinematic and kinetic analyses of novice running in dress shoes and running shoes.

The purpose of the study was to investigate how novice runners adjust their lower extremities in heel-toe running while they wear dress shoes and running shoes. Ten novice male runners repeatedly ran across a force plate at 4 m/s in each type of shoes. Joint kinematics and kinetics, vertical ground reaction force, and utilized coefficient of friction during the stance phase were quantified. The results obtained showed no differences in impact peaks, stance time, stride length and joint kinematics. However, dorsiflexion moment was significantly greater with dress shoes (407 Nm) compared to that with running shoes (304 Nm; p<0.05). Compared to the runners in running shoes (0.23), the runners in dress shoes (0.20) achieved a significantly lower utilized coefficient of friction ( p<0.05). When running in dress shoes, novice runners tended to use better a dorsiflexion moment than when running in running shoes. This adaptation appears to minimize the chances of slipping at the moment of heel strike.

Quantitative analysis of single bacterial chemotaxis using a linear concentration gradient microchannel.

A microfluidic device to quantify bacterial chemotaxis has been proposed, which generates a linear concentration gradient of chemoattractant in the main channel only by convective and molecular diffusion, and which enables the bacteria to enter the main channel in a single file by hydrodynamic focusing technique. The trajectory of each bacterium in response to the concentration gradient of chemoattractant is photographed by a CCD camera and its velocity is acquired by a simple PTV (Particle Tracking Velocimetry) algorithm. An advantage of this assay is to measure the velocity of a single bacterium and to quantify the degree of chemotaxis by analyzing the frequency of velocities concurrently. Thus, the parameter characterizing the motility of wild-type Escherichia coli strain RP437 in response to various concentration gradients of L-aspartate is obtained in such a manner that the degree of bacterial chemotaxis is quantified on the basis of a newly proposed Migration Index.

Quantification of the cell-substratum contact and cell lift-off under different intra/extracellular conditions.

Analyses of images of the cell-to-substratum region of contact have been carried out by the means of total internal reflection fluorescence (TIRF) microscopy during both the formation and the dissolution of cellular contacts. The evolutions of the cellular contacts are visualized during the adhesion process under normal and virus-infected intracellular conditions, and during the lift-off process under various toxicities of the extracellular medium fluid. Then, propositions are developed for quantifying the cell viabilities by estimating the increase in the area of contact for the adhesion process and by specifying the maximum intensity of the TIRF image for the lift-off process.