General-purpose and special-purpose visual systems

The information that eyes supply supports a wide variety of functions, from the guidance systems that enable an animal to navigate successfully around the environment, to the detection and identification of predators, prey, and conspecifics. The eyes with which we are most familiar the single-chambered eyes of vertebrates and cephalopod molluscs, and the compound eyes of insects and higher crustaceans allow these animals to perform the full range of visual tasks. These eyes have evidently evolved in conjunction with brains that are capable of subjecting the raw visual information to many different kinds of analysis, depending on the nature of the task that the animal is engaged in. However, not all eyes evolved to provide such comprehensive information. For example, in bivalve molluscs we find eyes of very varied design (pinholes, concave mirrors, and apposition compound eyes) whose only function is to detect approaching predators and thereby allow the animal to protect itself by closing its shell. Thus, there are special-purpose eyes as well as eyes with multiple functions

Partially Ordered Statistics Demapping for Multi-Dimensional Modulation Formats

We propose a very low-complexity and high-performance algorithm for soft-demapping of multi-dimensional modulation formats. We assess its performance over the linear channel for four 8D formats, generated using binary arithmetics. This solution outperforms current algorithms in terms of complexity without loss in performances.Comment: Accepted in the Optical Fiber Communications Conference (OFC) 201

The Operation of the Visual System in Relation to Action

Neurophysiologists studying the visual representation of the world in the parietal lobe generally find that it is based in a gaze-centred (retinotopic) frame. Students of orientation, however, find that the brain also contains a more panoramic egocentric representation that allows appropriate motor actions to take place independent of the orientation of the eyes and head. This representation can operate temporarily without visual input, but is updated from the vestibular system and from other modalities. In this minireview, I shall consider how these two representations are kept aligned with each other, and how they relate to the organisation of motor actions and to the phenomenal world that we see

Fairground rides and spatial updating

A simple experiment with a rotating office chair demonstrates that the extent of counter-rotation we experience when imposed rotation has stopped is the same as the angular inaccuracy of pointing to a previously fixated object. This suggests that our conscious percept of rotation and the updating signal for the egocentric model we use to guide motor actions are closely related

A ‘conversation’ between Frank Land [FL] and Antony Bryant [AB] – : Part 2

Part 1 of the ‘conversation’ offered important insights into a groundbreaking era for computer development – adding further detail to existing writings by Frank Land, the work of the LEO group in general, and extended accounts such as those by Ferry, Hally and Harding. This should have whetted the appetite for readers keen to know more, also prompting others to offer their own accounts. Part 2 moves on to Frank Land’s subsequent activities as one of the founding figures of the Information Systems (IS) Academy, and his ‘Emeritus’ phase

Ways of seeing Visual Ecology Tom Cronin, Sönke Johnsen, Justin Marshall and Eric Warrant (Princeton University Press, Princeton, NJ; 2014) ISBN: 978-1-400853-021

Unknow

Spatial facilitation by a high-performance dragonfly target-detecting neuron

Many animals visualize and track small moving targets at long distances—be they prey, approaching predators or conspecifics. Insects are an excellent model system for investigating the neural mechanisms that have evolved for this challenging task. Specialized small target motion detector (STMD) neurons in the optic lobes of the insect brain respond strongly even when the target size is below the resolution limit of the eye. Many STMDs also respond robustly to small targets against complex stationary or moving backgrounds. We hypothesized that this requires a complex mechanism to avoid breakthrough responses by background features, and yet to adequately amplify the weak signal of tiny targets. We compared responses of dragonfly STMD neurons to small targets that begin moving within the receptive field with responses to targets that approach the same location along longer trajectories. We find that responses along longer trajectories are strongly facilitated by a mechanism that builds up slowly over several hundred milliseconds. This allows the neurons to give sustained responses to continuous target motion, thus providing a possible explanation for their extraordinary sensitivity

Cherenkov and Scintillation Light Separation in Organic Liquid Scintillators

The CHErenkov / Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2g/L of PPO as a fluor (LAB/PPO). This is the first such demonstration for the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338 +/- 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 +/- 3% and 63 +/- 8% for time- and charge-based separation, respectively, with scintillation contamination of 36 +/- 5% and 38 +/- 4%. LAB/PPO data is consistent with a rise time of 0.75 +/- 0.25 ns

A Long Duration Orbital Simulator (LDOS) Utilized in Technical Planning Activities

This paper describes the development and use of a long duration orbital simulator (LDOS). The LDOS capabilities, options, accuracy, and central processing unit (CPU) usage are discussed. The applications described using the LDOS are associated with (a) Manned Space Flight Network (MSFN) support of long duration missions, (b) environmental effects on high earth orbits and (c) long term orbit decay. The appendix depicts the salient portions of the math model