STRUCTURAL RELAXATION IN AMORPHOUS Fe_<40>Ni_<40>P_<14>B_<6> ALLOY STUDIED BY POSITRON ANNIHILATION AND ELECTRICAL RESISTIVITY MEASUREMENT

The Doppler broadening lineshape of 511 keV γ-ray emitted from positron annihilation, positron lifetime and electrical resistivity of the Fe_Ni_P_B_ amorphous alloy have been measured for the isochronal annealing of 0-500 ℃ temperature range. W-parameter of the Doppler broadening lineshape increased in two stages by annealing below crystallization temperature. These increases appear to be due to the loss of excess free volume in the amorphous alloy. The results indicate that structure of this amorphous alloy relax in two stages and excess free volume losses in the two stage

Apoptosis in Cardiovascular Diseases: Mechanism and Clinical Implications

Apoptosis is a tightly regulated, cell deletion process that plays an important role in various cardiovascular diseases, such as myocardial infarction, reperfusion injury, and heart failure. Since cardiomyocyte loss is the most important determinant of patient morbidity and mortality, fully understanding the regulatory mechanisms of apoptotic signaling is crucial. In fact, the inhibition of cardiac apoptosis holds promise as an effective therapeutic strategy for cardiovascular diseases. Caspase, a critical enzyme in the induction and execution of apoptosis, has been the main potential target for achieving anti-apoptotic therapy. Studies suggest, however, that a caspase-independent pathway may also play an important role in cardiac apoptosis, although the mechanism and potential significance of caspase-independent apoptosis in the heart remain poorly understood. Herein we discuss the role of apoptosis in various cardiovascular diseases, provide an update on current knowledge about the molecular mechanisms that govern apoptosis, and discuss the clinical implications of anti-apoptotic therapies

Structure of dislocations in Al and Fe as studied by positron-annihilation spectroscopy

Positron-lifetime-spectra measurements have been performed on single crystals of Al and polycrystals of Fe deformed under the tensile mode at room temperature and 77 K, respectively. It is shown that the positron-trapping component in Al depends on the number of slip systems activated: The positron lifetime is 215, 220, and 240 ps when single-, double-, and multiple-slip planes are activated, respectively. This dependence is well understood if positrons annihilate at dislocation-associated defects (jogs) with different positron-annihilation characteristics revealing different jog structures. In iron, the positron-lifetime spectra associated with dislocations were found to be independent of the annealing temperature between 110 and 360 K. In this temperature range, screw dislocations should transform into nonscrew dislocations, suggesting that the positrons are not sensitive to the different types of dislocations. These results are interpreted on the basis that positrons annihilate at defects associated with the dislocations rather than at the dislocation lines. © 1992 The American Physical Society.Peer Reviewe

INTERNAL FRICTION AND ACOUSTIC EMISSION DUE TO CHARGE DENSITY WAVES

Much attention has been paid to the charge density waves which are observed in low-densional conductors. The elastic behavior in connection with the formation of charge density waves is reviewed. The change in internal friction due to the formation of charge density wawes is discussed. Results on a few experiments on the acoustic emission due to the formation of charge density waves are presented