Discrete sarcomere length distribution in skeletal muscle.

We analyzed the microstructure in the first-order laser diffraction line from both resting and tetanically contracting single twitch fibers from frog anterior tibial muscle to see if the distribution of sarcomere lengths is continuous or discrete. Measuring the distance between adjacent microstructural elements lying parallel, we plotted a histogram of the corresponding differences of sarcomere length. The histograms obtained both from resting and contracting fibers had a prominent peak at approximately 12-14 nm. The result suggests that the sarcomere length distribution may be discrete with unit separation of approximately 12-14-nm sarcomere length

Numerical Simulation of Flow over an Axisymmetric body in Free Flight

Flow field around a projectile after thrust has been stopped and in inertia flight is studied numerically by a finite difference scheme. This study aims at clarifying the mechanism of free flight, which is generated and developed by rotation of body and gravity. Among two types of projectiles concerned a three-dimensional flow around the slender body, such as aircraft body, rocket .causes drastic variation with high angle of attack and has considerable influence on the aerodynamic behavior. The flow over a paraboloidal-nose cylinder at pitching rotation is considered with inertia translating motion and the flow symmetry assumption . Another example is a oblate spheroid, and in these examples the initial condition is the flow at steady \u91flight\u92. In present numerical study coordinate system fixed on the body ,with non-inertial frame of reference, which yields additional terms in Navier Stokes equation. The dual-time pseudo compressibility code is applied for incompressible flow. The Newton\u92s 2nd law is used with the balance of aerodynamic force and gravity together with angular momentum equation. For the slender body the initial incidence angle is horizontal or 40deg. For the spheroid the initial motion is set either upwardi: counter to gravity-direction or downward one. For Reynolds numbers lower than 10000, the behavior of flow field and varying incidence angle will be discussed as well asthe trajectory of body

Measurement of laser absorptivity for operating parameters characteristic of laser drilling regime

Publisher version : http://iopscience.iop.org/0022-3727/41/15/155502/Laser drilling in the percussion regime is commonly used in the aircraft industry to drill sub-millimetre holes in metallic targets. Characteristic laser intensities in the range of 10 MW cm−2 are typically employed for drilling metallic targets. With these intensities the temperature of the irradiated matter is above the vaporization temperature and the drilling process is led by hydrodynamic effects. Although the main physical processes involved are identified, this process is not correctly understood or completely controlled. A major characteristic coefficient of laser–matter interaction for this regime, which is the absorptivity of the laser on the irradiated surface, is still unknown, because of the perturbing effects due to laser beam geometrical trapping inside the drilled hole. So, by using time resolved experiments, this study deals with the direct measurement of the variation of the intrinsic absorption of aluminium, nickel and steel materials, as a function of the incident laser intensity up to 20 MW cm−2. We observe that for this incident intensity, the absorptivity can reach up to 80%. This very high and unexpected value is discussed by considering the microscopic behaviour of the heated matter near the vapour–liquid interface that undergoes possible Rayleigh–Taylor instability or volume absorptio