Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.

Aim: To determine whether muscle function is compromised in healthy smokers in comparison with activity-matched non-smokers. Methods: Nine male smokers (aged 22.2 ± 2.5 years: mean ± SD) with a smoking history of 2.5 ± 3.1 pack years, and ten male control participants (25.4 ± 2.9 years) matched for physical activity level participated in this study. Knee extensor strength was measured using isometric maximal voluntary contractions. Voluntary activation of the quadriceps and co-activation of the biceps femoris were determined using interpolated twitches and surface electromyography respectively. The frequency-torque relationship and fatigue resistance were assessed with electrically evoked contractions. A fatigue index was determined as the ratio of final torque to initial torque during a series of isometric contractions (2 min; 30 Hz; 1 s contraction/1 s rest). Quadriceps anatomical cross sectional area was measured with MRI at 50% of femur length. Results: Maximal voluntary contraction torque, quadriceps anatomical cross sectional area, knee extensor torque/quadriceps cross sectional area, activation, co-activation and force-frequency relationship were similar, whereas the fatigue index was 17% lower in smokers than non-smokers. Conclusion: In young men smoking does not significantly affect quadriceps muscle mass and contractile properties, but does reduce fatigue resistance of the quadriceps muscle, which was not attributable to differences in physical activity. © 2007 The Authors

Schadstoffe in der Luftfahrt, Einzelaufgabe Nr. 2227. Experimentelle Untersuchung des Einflusses der Luftfuehrung auf die Zerstaeubungseigenschaften einer Luftzerstaeubungsduese. Bd. 1 Abschlussbericht

In the article experimental results of model airblast atomization nozzles closely related to practical use are presented. They were investigated within a wide range of load for the model fluids water/air. For this the nozzle construction as well as the operation parameters were varied. The air passage, the distribution of air, the air-water ratios and the counterpressure at the nozzle outlet are essential influential parameters investigated. The spray images were visually assessed. Velocity, size and distribution of the droplets were measured by means of phase doppler anemometer (PDA) and taken into account in the assessment of the nozzle. The measurements were conducted under atmospheric as well as under raised pressure at the nozzle outlet. For the measurement with PDA through optical windows rinsing air was applied in some experiments, a fluid coating on the glass surface in others. (orig.)Available from TIB Hannover: F97B423+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Equilibrium attractivity of Krylov-W-methods for nonlinear stiff ODEs

Since implicit integration schemes for differential equations which use Krylov methods for the approximate solution of linear systems depend nonlinearly on the actual solution a classical stability analysis is difficult to perform. A different, weaker property of autonomous dissipative systems y'=f(y) is that the norm parallel f(y(t)) parallel decreases for any solution y(t). This property can also be analysed for W-methods using a Krylov-Arnoldi approximation. We discuss different additional assumptions on f and conditions on the Arnoldi process that imply this kind of attractivity to equilibrium points for the numerical solution. One assumption is general enough to cover quasilinear parabolic problems. (orig.)SIGLEAvailable from TIB Hannover: RR 8708(44) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman