PRINCIPLES OF APPLIED BIOMECHANICS ON THE RACE WALKERS: IMPROVEMENT IN PERFORMANCE WITH A PLANTAR ORTHOSIS

When race walking it is essential to attain and maintain for a period of time the maximal speed with minimal expenditure of energy, in observance of the prescribed standards. To achieve this end, optimizing the physical carriage is indispensable. This may be done in two ways: I) by reducing those force component hat ace employed along directions of application that do no concur with the sense of progression, since they interfere with and disperse part of the energy; and 2) by increasing the vectorial components that have the same direction as the forward movement. The aim of our work was to verify the modifications that are induced by the use of plantar orthoses , as reflected by parameters of biomechanical performance on the race walker: Under standard reference conditions, we studied the kinematics and ground reaction of 10 highly-trained Athletes. With reference to report that confirmed previous study by us and other authors, we verified the modifications induced by the applications of special dynamic plantar orthoses. The ground reaction appeared to be optimized by the use of these orthoses through the following mechanisms: 1) a diminution of the sagittal force components that are opposed to the direction of movemen6 2) a diminution of the transverse edgewise components that are not useful to the progression, and 3) an increase in the reclamation of useful elastic energy stored by the functional unit, the 'musculo-skeletal footwear system”

Determination of gold in alloys via potentiometric titration; an alternative to the fire assay

In this paper we report the results of a deep investigation of gold title in jewellery alloys by means of potentiometric titration. After reviewing the suitable reactions for such purpose we focused on the most profitable one, which involves the use of hexadecylpyridinium chloride (CPC). This cation gives rise to selective and quantitative precipitation of AuCl4 −. We completely revised a method previously proposed by W.S. Selig in the 80's, by improving the sampling preparation and by optimizing the titration steps. Then, the new proposed method was tested on a large number of different alloys, commonly used for goldsmithery purposes. The obtained gold titles were compared with the data achieved by fire assay, giving rise to a very good agreement. At the light of these results, the present method can be rightfully considered a cheaper and "greener" alternative to the traditional one