Validation of a new cycle ergometer.

The purpose of this study was to test the concurrent validity of the ICBE compared to the Monark(®) cycle ergometer by indirect dynamic calibration. 42 men were randomly submitted to 2 maximal stress tests with increments of 50 W at 2-min intervals. One test was performed on the Monark(®) bicycle (834/E) and the other on the ICBE. Cardiovascular, perceived exertion and hemodynamic responses were compared between the 2 bicycles. No differences (p>0.05) were observed in resting heart rate (HR), maximum HR, peak oxygen uptake (VO(2P) L·min(-1) and VO(2P) mL·kg(-1)·min(-1)), and number of stages completed. High correlations (r>0.85) were found between HR and VO (2P). Residual analysis indicated strong agreement between the 2 cycle ergometers in terms of VO(2P) L·min(-1) [-0.36-0.30] and VO(2P) mL·kg(-1)·min(-1) [-4.98-4.46]. Residual dispersion (r=0.25 for both) showed that the mathematical differences in VO(2P) L·min(-1) and VO(2P) mL·kg(-1)·min(-1) between cycle ergometers were independent. The correlation coefficient (r) and coefficient of determination (R(2)) between VO(2P) L·min(-1) (r=0.90; R (2)=0.80) and VO(2P) mL·kg(-1)·min(-1) (r=0.90; R(2)=0.81) obtained for the 2 cycle ergometers were high, whereas the standard error of the estimate was low (0.186 L·min(-1) and 2.56 mL·kg(-1)·min(-1), respectively). The ICBE presents concurrent validity for use in submaximal and maximal cardiopulmonary tests.

A model coupling vibrational and rotational motion for the DNA molecule.

We investigate a mechanical model for the DNA molecule using an extension of the Peyrard and Bishop model. In the present model, there are two chains of oscillators linked by a Morse potential, which represent the hydrogen bonds. The rotational and vibrational motions of each base pair are considered and the coupling for these motions are introduced by a nonlinear combination of them in the Morse potential. In this context, thermodynamics and structural properties are discussed.