Categorization of common sounds by cochlear implanted and normal hearing adults.

Auditory categorization involves grouping of acoustic events along one or more shared perceptual dimensions which can relate to both semantic and physical attributes. This process involves both high level cognitive processes (categorization) and low-level perceptual encoding of the acoustic signal, both of which are affected by the use of a cochlear implant (CI) device. The goal of this study was twofold: I) compare the categorization strategies of CI users and normal hearing listeners (NHL) II) investigate if any characteristics of the raw acoustic signal could explain the results. 16 experienced CI users and 20 NHL were tested using a Free-Sorting Task of 16 common sounds divided into 3 predefined categories of environmental, musical and vocal sounds. Multiple Correspondence Analysis (MCA) and Hierarchical Clustering based on Principal Components (HCPC) show that CI users followed a similar categorization strategy to that of NHL and were able to discriminate between the three different types of sounds. However results for CI users were more varied and showed less inter-participant agreement. Acoustic analysis also highlighted the average pitch salience and average autocorrelation peak as being important for the perception and categorization of the sounds. The results therefore show that on a broad level of categorization CI users may not have as many difficulties as previously thought in discriminating certain kinds of sound; however the perception of individual sounds remains challenging.

n-6 and n-3 polyunsaturated fatty acids differentially modulate oncogenic Ras activation in colonocytes.

Ras proteins are critical regulators of cell function, including growth, differentiation, and apoptosis, with membrane localization of the protein being a prerequisite for malignant transformation. We have recently demonstrated that feeding fish oil, compared with corn oil, decreases colonic Ras membrane localization and reduces tumor formation in rats injected with a colon carcinogen. Because the biological activity of Ras is regulated by posttranslational lipid attachment and its interaction with stimulatory lipids, we investigated whether docosahexaenoic acid (DHA), found in fish oil, compared with linoleic acid (LA), found in corn oil, alters Ras posttranslational processing, activation, and effector protein function in young adult mouse colon cells overexpressing H-ras (YAMC-ras). We show here that the major n-3 polyunsaturated fatty acid (PUFA) constituent of fish oil, DHA, compared with LA (an n-6 PUFA), reduces Ras localization to the plasma membrane without affecting posttranslational lipidation and lowers GTP binding and downstream p42/44(ERK)-dependent signaling. In view of the central role of oncogenic Ras in the development of colon cancer, the finding that n-3 and n-6 PUFA differentially modulate Ras activation may partly explain why dietary fish oil protects against colon cancer development.

Symmetry properties of focused fields.

It is shown that under very general conditions monochromatic scalar wave fields that have a focus in the sense of geometrical optics possess some simple symmetry properties with respect to the focus. Certain well-known but poorly understood symmetry properties of the three-dimensional amplitude distribution and phase distribution in the focal region of a uniform converging spherical wave diffracted at a circular aperture are found to be immediate consequences of our results.

Log-intensity correlations of a laser beam in a turbulent medium.

The log-intensity correlation for any two points in the cross section of a collimated Gaussian laser beam is calculated in the geometrical optics approximation. The log-intensity correlation is found to.be a function of more than the separation distance between the two points. The special case of autocorrelation leads to a result that is identical to that given by Ho if diffraction effects are ignored. The autocorrelation function indicates a new method for determining the inner scale of turbulence and the refractive index structure function coefficient which does not depend upon meteorological measurements of C(N)(2).

Analysis of the interaction of partially polarized light with dielectric plates.

This paper is concerned with a matrix formulation and solution of the interaction of partially polarized light with transparent dielectric plates. Fresnel's equations for transmission and reflection at a dielectric interface are expressed in the form of Mueller-Stokes matrices. These matrices are then applied to (1) transmission and reflection of a light beam by m parallel dielectric plates and (2) multiple reflections within a dielectric plate. It is shown that a diagonalized representation of the Mueller-Stokes polarizing matrix greatly facilitates the calculations.