Meridional x-ray diffraction diagrams, recorded with high angular resolution, from muscles contracting at the plateau of isometric tension show that the myosin diffraction orders are clusters of peaks. These clusters are due to pronounced interference effects between the myosin diffracting units on either side of the M-line. A theoretical analysis based on the polarity of the myosin (and actin) filaments shows that it is possible to extract phase information from which the axial disposition of the myosin heads can be determined. The results show that each head in a crown pair has a distinct structural disposition. It appears that only one of the heads in the pair stereospecifically interacts with the thin filament at any one time.

The effects of plasma processing conditions on the microstructural properties of silicon powders are presented. Hydrogenated nanophase silicon powden were preparedming low-pressure and low-temperature square wave modulated RF plasma (1 3.56 MHz) using pure Silane gas. Plasma parameters such as pressure, RF power, plasma modulation frequency, and gas flow rate were varied.In situ analysis by quadrupoiar mass spectroscopy and ex situ analysis of the silicon powders by Fourier transform infrared spectroscopy ( F m ) and thermal desorption spectrometry of hydrogen were performed. The thermal desorption spectrometry results show the fundamental differences behveen the concentrations of hydrogen weakly and strongly bonded in silicon powders as compared to amorphous silicon iiims. Tie mi R anaiysis aiso deiermined ine microstructurai characteristics of powders and hence their volume/surface ratio. This parameter was determined from the balance of Pi probahilities of having one of the HjS[-Si4_j bond arrangements in the powder particles. These results reveal an increase In hydrogen content and a reduction in volume/suriace ratio as the modulation frequency of RF power Increases. in consequence, higher compactness of silicon powders is associated with long particle residence times inside the plasma as a result of ion bombardment TEM analysis indicated a considerable dispersion of particle size and some degree of structure of the silicon powder characterized by intergrain linkage. We point out the dominant presence of hydrogen on the particle surfaces (external voids), which may cause the high reactivity of grains, increasing the degree of intergrain linkage.

No abstract

No abstract