6,076 research outputs found
Noise removal at the rod synapse of mammalian retina
No full textMammalian rods respond to single photons with a hyperpolarization of about 1 mV which is accompanied by continuous noise. Since the mammalian rod bipolar cell collects signals from 20–100 rods, the noise from the converging rods would overwhelm the single-photon signal from one rod at scotopic intensities (starlight) if the bipolar cell summed signals linearly (Baylor et al., 1984). However, it is known that at scotopic intensities the retina preserves single-photon responses (Barlow et al., 1971; Mastronarde, 1983). To explore noise summation in the rod bipolar pathway, we simulated an array of rods synaptically connected to a rod bipolar cell using a compartmental model. The performance of the circuit was evaluated with a discriminator measuring errors in photon detection as false positives and false negatives, which were compared to physiologically and psychophysically measured error rates. When only one rod was connected to the rod bipolar, a Poisson rate of 80 vesicles0s was necessary for reliable transmission of the single-photon signal. When 25 rods converged through a linear synapse the noise caused an unacceptably high false positive rate, even when either dark continuous noise or synaptic noise where completely removed. We propose that a threshold nonlinearity is provided by the mGluR6 receptor in the rod bipolar dendrite (Shiells & Falk, 1994) to yield a synapse with a noise removing mechanism. With the threshold nonlinearity the synapse removed most of the noise. These results suggest that a threshold provided by the mGluR6 receptor in the rod bipolar cell is necessary for proper functioning of the retina at scotopic intensities and that the metabotropic domains in the rod bipolar are distinct. Such a nonlinear threshold could also reduce synaptic noise for cortical circuits in which sparse signals converge. <br/
Rod Murray at Stock Show
No full textRod Murray shows his steer with other particpants at a livestock show at the fairgrounds
The optimal synapse for sparse, binary signals in the rod pathway:Neural Computation
No full textThe sparsity of photons at very low light levels necessitates a nonlinear synaptic transfer function between the rod photoreceptors and the rod-bipolar cells. We examine different ways to characterize the performance of the pathway: the error rate, two variants of the mutual information, and the signal-to-noise ratio. Simulation of the pathway shows that these approaches yield substantially different performance at very low light levels and that maximizing the signal-to-noise ratio yields the best performance when judged from simulated images. The results are compared to recent data.</p
Rod Smith Campaign Sticker
No full textRod Smith 2006 Democrat for Florida Governor campaign sticker. Box 55 Folder 6https://digitalcommons.unf.edu/saffy_images/1073/thumbnail.jp
Rod Smith 2006 circle Sticker
No full textRod Smith 2006 circle campaign sticker. Box 55 Folder 6https://digitalcommons.unf.edu/saffy_images/1075/thumbnail.jp
Rod contributions to color perception: Linear with rod contrast
No full textAbstractAt mesopic light levels, an incremental change in rod activation causes changes in color appearance. In this study, we investigated how rod mediated changes in color perception varied as a function of the magnitude of the rod contrast. Rod-mediated changes in color appearance were assessed by matching them with cone-mediated color changes. A two-channel four-primary colorimeter allowed independent control of the rods and each of the L-, M- and S-cone photoreceptor types. At all light levels, rod contributions to inferred PC, KC and MC pathway mediated vision were linearly related to the rod incremental contrast. This linear relationship could be described by a model based on primate ganglion cell responses with the assumption that rod signals were conveyed via rod–cone gap junctions at mesopic light levels
Rod Mays in a Senior Recital
No full textThis is the program for the senior recital of Rod Mays. Susan Crosby on piano, Russell Hodges on organ, and Tony Hutchins, Rob Potts, Cheryl Smith, and Candace Meredith on trombones accompanied. The recital took place on November 28, 1988, in the Mabee Fine Arts Recital Hall
Rod Smith Democrat for Governor sticker
No full textRod Smith Democrat for Governor sticker. Box 55 Folder 6https://digitalcommons.unf.edu/saffy_images/1074/thumbnail.jp
Multi-trench Fiber for high power laser applications
No full textOptical fibers have realized their immense potential for high power applications in the last decade. However, non-linearity still remains a challenge for power scaling for fiber lasers [1]. A large effective area of the fundamental mode of the optical fiber can increase the threshold of the non-linear effects [2]. However, simply increasing the core size leads to multi-mode operation and hence deteriorates the beam quality. Several novel optical fiber designs have been proposed to offer a large effective area of optical fibers such as Low NA Step index fibers, Photonic Crystal Fibers, Bragg Fibers, etc., while still maintaining single mode operation. Recently, we proposed a novel multi-trench fiber (MTF) design for large effective mode area, as shown by a cross-section schematic and a refractive index profile design in Fig. 1. [3]. This fiber design offers advantages of relatively easy fabrication, splicing, and cleaving. Numerical simulations reveal that the MTF fiber geometry can provide single-mode operation with a core diameter as high as 100µm with an effective area of ~ 10,000µm2 in a rod-type configuration and ~800µm2 in a bend configuration. A 30µm diameter core MTF has been fabricated and the cross-section and measured refractive index profile is shown in Fig. 2. S2 measurement shows ~50dB suppression of higher order modes (HOM) in a one meter length of fiber. Also, an ytterbium-doped single-trench-fiber laser (slope efficiency ~85%) with a 20µm diameter core has been experimentally demonstrated with very high suppression of HOM (~32dB), which was also verified by S2 measurement. The refractive index profile, plot of laser slope efficiency, an output beam profile and a laser output spectrum are shown in Fig. 3
Data set for Thermally-guided Yb-doped fiber-rod amplifier and laser
No full textData set for the paper Smith, C. R., Simakov, N., Hemming, A., & Clarkson, W. A. (2019). Thermally-guided Yb-doped fiber-rod amplifier and laser. Applied Physics B: Lasers and Optics, 125(32), 1-10. DOI: 10.1007/s00340-018-7126-3</span
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