Acoustic Cues for Sound Source Distance and Azimuth in Rabbits, a Racquetball and a Rigid Spherical Model

There are numerous studies measuring the transfer functions representing signal transformation between a source and each ear canal, i.e., the head-related transfer functions (HRTFs), for various species. However, only a handful of these address the effects of sound source distance on HRTFs. This is the first study of HRTFs in the rabbit where the emphasis is on the effects of sound source distance and azimuth on HRTFs. With the rabbit placed in an anechoic chamber, we made acoustic measurements with miniature microphones placed deep in each ear canal to a sound source at different positions (10–160 cm distance, ±150° azimuth). The sound was a logarithmically swept broadband chirp. For comparisons, we also obtained the HRTFs from a racquetball and a computational model for a rigid sphere. We found that (1) the spectral shape of the HRTF in each ear changed with sound source location; (2) interaural level difference (ILD) increased with decreasing distance and with increasing frequency. Furthermore, ILDs can be substantial even at low frequencies when distance is close; and (3) interaural time difference (ITD) decreased with decreasing distance and generally increased with decreasing frequency. The observations in the rabbit were reproduced, in general, by those in the racquetball, albeit greater in magnitude in the rabbit. In the sphere model, the results were partly similar and partly different than those in the racquetball and the rabbit. These findings refute the common notions that ILD is negligible at low frequencies and that ITD is constant across frequency. These misconceptions became evident when distance-dependent changes were examined

The known unknowns of anomalous trichromacy

Anomalous trichromacy is the most common minority color vision phenotype, yet the category label obscures a large range of individual differences both in the underlying genetics and in color perception. This review explores both, particularly considering possible reasons for the smaller than expected observed relationship between the spectral sensitivities of anomalous cones and color discrimination. Also considered is the putative process of postreceptoral compensation, where anomalous trichromats may amplify the reduced color signals they receive from their cones to relatively normalize their color vision postreceptorally

Binocular rivalry with isoluminant stimuli visible only via short-wavelength-sensitive cones

To test whether the binocular contour rivalry mechanism is tritanopic, we presented isoluminant, rival stimuli visible only via the short-wavelength-sensitive (S) cones, We stimulated only the S cones with violet gratings superimposed on a bright yellow field that adapted the responses of the middle- and long-wavelength-sensitive (M and L) cones, We found that an S-cone grating presented to one eye rivalled with an orthogonal grating presented to the other, Rivalry persisted over a range of luminances and contrasts of the S-cone stimuli, and was greater than could be accounted for by nonrival fading, The spatial spread of rivalry from S-cone stimuli is similar to that for the same stimuli when visible also to the M and L cones (luminance stimuli). We found that an S-cone stimulus would rival with a luminance stimulus, and exploited this to determine the equivalent luminance contrast of S-cone stimuli by putting them in a rivalry competition with luminance stimuli, For rivalry, the equivalent luminance contrast of isoluminant, S-cone stimuli is much less than their S-cone contrast. The existence of rivalry with isoluminant stimuli, along with earlier evidence that such stimuli can support stereopsis, challenges the view that an achromatic channel alone drives certain higher level functions such as depth perception

Novel copolymers of styrene. 15. Halogen ring-disubstituted propyl 2-cyano-3-phenyl-2-propenoates

Novel halogen ring-disubstituted propyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO2C3H7 (where R is 2-fluoro-5-methyl, 3-iodo-4-methoxy, 5-iodo-2-methoxy, 3,5-dichloro, 3,4-difluoro, 3,5-difluoro, 2-chloro-4-fluoro, 2-chloro-6-fluoro, 3-chloro-2-fluoro, and 3-chloro-4-fluoro) were prepared and copolymerized with styrene. The propenoates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-disubstituted benzaldehydes and propyl cyanoacetate, and characterized by CHN elemental analysis, IR, 1H- and 13C-NMR. All the propenoates were copolymerized with styrene (M1) in solution with radical initiation (ABCN) at 70C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR, GPC, DSC, and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500ºC range with residue (1-3% wt.), which then decomposed in the 500-800ºC range