Long-term Photometric Analysis of the Active W UMa-type System TU Bootis

We present multi-color light curves for the W UMa-type eclipsing binary TU Boo for two epochs separated by 22 years. An analysis of the O-C diagram indicates the earlier observations took place right in the middle of a major period change, thus allowing for a unique study on mass transfer and period changes in this W UMa-type system. We compute model fits to our light curves, along with the only other published set, using the Wilson-Devinney program, and find temporally correlated changes in the size of the secondary component with anomalies in the O-C diagram. We investigate the cause of these changes and find support for the existence of rapid, large-scale mass transfer between the components. We postulate that this interaction allows them to maintain nearly equal surface temperatures despite having achieved only marginal contact. We also find support for the evolutionary scenario in which TU Boo has undergone a mass ratio reversal in the past due to large-scale mass transfer so that what is presently the secondary component of TU Boo is in an advanced evolutionary state, oversized due to a helium-enriched core, with a total system age of $\geq$ 10 Gyr.Comment: Accepted to AJ, 9 pages of text, 6 Figure

Growth of the adult goldfish eye. II. Increase in retinal cell number

The retinas of adult goldfish, one to four years of age, 4–23 cm in length, were examined with standard paraffin histology to determine if new cells were being added with growth. Retinal cell nuclei were counted and the area of the retina was measured. An analysis of cell densities in various regions throughout the retina showed that the cells are distributed nearly homogeneously. The density (No./mm 2 of retinal surface) of ganglion cells, inner nuclear layer cells and cones decreases with growth, but the density of rods remains constant. Thus the rods account for a larger proportion of the cells in larger retinas. The total number of cells per retina increases: the ganglion cells from 60,000 to 350,000; the inner nuclear layer cells from 1,500,000 to 4,000,000; the cones from 250,000 to 1,400,000; the rods from 1,500,000 to 15,000,000. This increase in the number of retinal neurons implies the formation of even more new synapses, and suggests the adult goldfish retina as a model for both neuro- and synaptogenesis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50001/1/901760303_ftp.pd

Pursuit eye movements in goldfish (Carassius auratus)

Pursuit eye movements made by goldfish were investigated with an optical technique in which the horizontal orientations of both eyes were measured automatically. Moving targets were provided by: 1. (1) a striped drum which rotated about the vertical axis concentrically with the animal's head, and2. (2) tangent screens on either side. Movement seen by either eye alone caused both to move, but the response was greater when both viewed the drum. The angular velocities of the eyes were always less than that of the drum. The ocular velocity depended upon the velocity, area, and contrast of the target, over wide ranges, and upon the state of adaptation and the recent history of the visual system. Evidence is offered supporting the hypothesis that the pursuit movements are controlled by directionally-selective movement-sensitive retinal ganglion cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34131/1/0000415.pd

Absolute visual sensitivity of the goldfish

Absolute visual threshold was measured in dark-adapted goldfish, using classical conditioning of heart and respiration rates. For threshold detection of a 132[deg] diameter stimulus near the peak of the rod pigment's sensitivity, only 1 quantum was incident for every 2000-4000 rods, and 400-830 photoisomerizations were needed for vision. Spectral sensitivity was also determined at absolute threshold, sing respiration rate conditioning. The shape of the function matches the electrophysiologically determined spectral sensitivity of goldfish retinal ganglion cells, but both curves are relatively more sensitive in the long wavelengths than would be predicted on the basis of the rod pigment alone. A dim 703 nm background depressed sensitivity to a 636 nm test light more than to a 532 nm test, proving that another class of photoreceptors is active at absolute threshold. If the other receptors were the red cones, as seems most likely, then only 1 quantum was incident per 220 red cones at their absolute threshold, and photoisomerizations occurred in each of 164 red cones at threshold.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22776/1/0000331.pd