Spatial Distribution Of Damage Research Articles

Acoustic trauma in the guinea pig cochlea: Early changes in ultrastructure and neural threshold

Scanning microscopy was used to examine guinea pig cochleas for structural damage immediately after exposure to a pure tone ranging from 96 to 129 dB SPL. Functional changes to the cochlear neural sensitivity were assessed using the N 1 audiogram. Principal findings were: (1) The order of damge to receptor cells with increasing sound intensity was OHC1, then IHC, then OHC2 and OHC3. (2) The spatial distribution of damage to OHC1 and IHC differed with IHC tending to show damage mainly in the vicinity of the exposure frequency location and OHC1 damage spreading basalward of this point. (3) N 1 threshold losses spread progressively to lower frequencies as exposure intensity increased. This was accompanied by an apical spread of damage to the receptor cells.

UPS and LEED studies of GaAs (110) and (111) As surfaces

By comparison of LEED intensity–voltage data on GaAs (110) surfaces prepared by cleaving and by chemical etch followed by sputter annealing, we find the surfaces to be essentially the same in atomic geometry within the limits of experimental error. However, we find that important distinctions can be made between (110) surfaces prepared by these two methods when Fermi-energy pinning and UPS data are considered. In this regard, we show that Fermi-energy pinning is a particularly sensitive indicator of the degree of surface perfection and that the UPS data gives valuable information about the degree of perfection achieved by the different surface preparation techniques used. As an example of this, we show differences in the spatial distribution of damage on sputter-annealed and heat-cleaned surfaces which are seen by UPS. The sputtered surface is extremely imperfect prior to annealing. Finally, we find no evidence for intrinsic filled surface states in the band gap on the (111) As surface when prepared by heat cleaning or sputter annealing.

Influence of Radiation Damage on Hyperfine-Interaction Measurements after Implantation in Metals

We report electron microscopy experiments showing that the spatial distribution of damage produced in metals by implanted ions is generally quite different from that of the ions themselves. We discuss how this affects hyperfine-interaction measurements.

Techniques for Examining Void Distribution in Ion Bombarded Metals

Ion bombardment is a convenient and economical means for simulating the damage produced in metals due to fast neutron irradiation. Unlike that produced by neutrons, however, the damage caused by ion bombardment is not homogeneously distributed throughout the volume of the metal since ions penetrate metallic specimens only a short distance. Moreover, the number of displaced atoms is a sensitive function of the kinetic energy of the bombarding ions as well as the depth within the target material (specimen). Therefore materials which have been subjected to ion bombardment require careful analysis of the spatial distribution of the damage before meaningful inferences can be made.The experimental material for this study was Type-304 stainless steel sheet, approximately 100 μm thick, which was bombarded in a cyclotron with 12 MeV deuterons. Irradiation time and temperature were the principal variables. Because of the small size of the voids produced and the shallow damage zone, techniques of transmission electron microscopy (TEM) are most commonly used for void examination. In the present work we compare two alternative approaches to the problem of characterizing the spatial distribution of damage within such specimens.