Quantitative Biology

1711 Submissions

[3] viXra:1711.0456 [pdf] submitted on 2017-11-27 09:00:14

On the Importance of the Dynamic Measurement of the Pupil Size

Authors: Vicent Sanchis-Jurado, Álvaro Pons, Santiago García-Lázaro
Comments: 8 Pages.

In this pilot study we analyse the pupil fluctuations of the right eye of two subjects during forty-five seconds while keeping constant the viewing distance and the room illumination. Measurements were taken with an infrared eye-tracker working at 250 Hz. The results were for subject A a median diameter of 2.913 mm with a maximum diameter of 3.313 mm and a minimum diameter of 2.66 mm, for subject B the median diameter was 4.39 mm with a maximum of 5.23 mm and a minimum of 3.26 mm. For both subjects the distribution of the pupil diameter did not follow a normal distribution, this was determined with the Lilliefors test, the p-values were 0.0251 for subject A and 0.001 for subject B. In conclusion, even in constant conditions of illumination and viewing distance the pupil cannot be considered to remain constant and its diameter varies not following a normal distribution.
Category: Quantitative Biology

[2] viXra:1711.0444 [pdf] submitted on 2017-11-28 07:34:24

Effect of Fixation Target on the Contrast Sensitivity in the Foveal and Parafoveal Area

Authors: Vicent Sanchis-Jurado, Sophie Triantaphillidou, Edward Fry, Álvaro Pons
Comments: 12 pages, 4 figures, 1 table

Purpose To determine the influence on the contrast sensitivity when the stimulus contains a fixation target in two retinal locations, foveal and parafoveal. Methods Four young adults with 0.0 logMar acuity participated in this study. The stimulus was based on vertical sinusoidal gratings masked by a circular (for foveal area) or a ring (for parafoveal area). To increase the luminance resolution of the display a bit-stealing technique was used. Four different sets of stimuli were generated, two for exploring the foveal sensitivity and two for the parafoveal area. The difference between the sets designed for the same area was the presence, or absence, of a fixation target (a white cross) in the centre of the stimulus. A modified staircase method was implemented. Results The results show a drop in the contrast sensitivity when the fixation target was present on the stimulus for frequencies smaller than 4 cycles per degree. Conclusions The presence of fixation targets diminishes the contrast sensitivity for low to mid frequencies over different concentric areas of the retina. This could be due to the fixational eye movements, different patterns of eye movements were found using an eyetracker. The relationship between the sensitivity in the foveal area and the parafoveal agrees with those reported by other authors using different designs confirming that the new stimulus design is suitable to measure the contrast sensitivity outside the foveal area.
Category: Quantitative Biology

[1] viXra:1711.0300 [pdf] submitted on 2017-11-13 11:25:35

Rotationally Symmetric Structures of the C-ring of Escherichia Coli

Authors: Herbert Weidner
Comments: 5 Pages.

The C-ring of a motor contains either 34 or 44 copies of FliM but only about 26 copies of FliG. In addition, the amount of FliMs is influenced both by the direction of rotation and by the number of CheY-P signal molecules in the cytoplasm. The rotationally symmetrical model described here combines all known properties.
Category: Quantitative Biology