25,594 research outputs found
Fish tracking technology development. Phase 1 project definition desk study
The document reports on Phase 1 of a definition study to appraise the options to develop fish tracking equipment, in particular tags and data logging systems in order to improve the efficiency of the Environment Agency's tracking studies and to obtain a greater understanding of fish
biology.
Covered in this report are radio telemetry, audio telemetry, High Resolution Position Fixing, data storage and archival tags and other fish tracking systems such as biosonics
Atmospheric and surface compositional studies of Mercury and the moon
The atmosphere of the Moon and Mercury will be studied by means of high resolution spectroscopy of sodium and potassium resonance line emissions. The variation of metal vapor abundances with time, and with location will be measured with a view to understanding the origin and evolution of these elements in the atmospheres of the Moon and Mercury. Infrared spectroscopic measurements will be made of Mercury to determine the surface mineralogy, predicated on the availability of the Kuiper Airborne Observatory and infrared charge coupled device (CCD). During the past year, an excellent series of measurements were completed of the spatial distribution of sodium on Mercury. Sodium was found to be concentrated at the polar regions, and to be displaced towards the terminator by solar radiation pressure. Sodium and potassium were discovered in the atmosphere of the Moon. The ratio of sodium to potassium approximates that of the lunar regolith. Thermal infrared measurements of Mercury showed that the Christiansen peak was located shortwards of 8 micrometer, which indicates an acidic mineralogy
Revised estimates for ozone reduction by shuttle operation
Previous calculations by five different modeling groups of the effect of space shuttle operations on the ozone layer yielded an estimate of 0.2 percent ozone reduction for the Northern Hemisphere at 60 launches per year. Since these calculations were made, the accepted rate constant for the reaction between hydroperoxyl and nitric oxide to yield hydroxyl and nitrogen dioxide, HO2 + NO yields OH + NO2, was revised upward by more than an order of magnitude, with a resultant increase in the predicted ozone reduction for chlorofluoromethanes by a factor of approximately 2. New calculations of the shuttle effect were made with use of the new rate constant data, again by five different modeling groups. The new value of the shuttle effect on the ozone layer was found to be 0.25 percent. The increase resulting from the revised rate constant is considerably less for space shuttle operations than for chlorofluoromethane production, because the new rate constant also increases the calculated rate of downward transport of shuttle exhaust products out of the stratosphere
Key factor for hastening the strategic issue diagnosis process: a within organisational model
Previous research on Strategic Issue Diagnosis (SID) had focused on the complexity and novelty associated with the decision-making process in a turbulent environment. What had not been previously addressed in the extant literature is the requirement for speed inherent within the SID process, especially that is related to the gathering of information and facts through an organisation’s environmental scanning procedures. Since proactive management techniques, nimble processes, and systems that allow an organisation to be responsive and build rapid decision-making capabilities are important determinants of success in a turbulent environment, the element of speed associated with SID is an important factor. Our paper identifi es a series of propositions focusing att ention
on elements of the environmental scanning processes and management hierarchies that are intended to counteract the recursiveness and redundancy inherent in SID systems and ultimately hasten the strategic decision-making process
Fish tracking technology development. Phases 1 and 2, project definition desk study and equipment
The document reports on the major findings from a definition study to appraise the options to develop fish tracking equipment, in particular tags and data logging systems, in order to improve the effeciency of the Agency tracking studies and to obtain a greater understanding of fish biology. The definition study was in two parts. The first, Phase 1, collated and evaluated all the known tracking systems that may be suitable for studies of fish which are either produced commercially or have been constructed for specific in-house studies. Phase 2 was an evaluation of all the tracking equipment considered to merit further investigation in Phase 1. The deficiencies between existing and required technologies to improve the efficiency of Agency's tracking studies and to obtain a greater understanding of fish biology are also identified
Topological Superconductivity and Majorana Fermions in Metallic Surface-States
Heavy metals, such as Au, Ag, and Pb, often have sharp surface states that
are split by strong Rashba spin-orbit coupling. The strong spin-orbit coupling
and two-dimensional nature of these surface states make them ideal platforms
for realizing topological superconductivity and Majorana fermions. In this
paper, we further develop a proposal to realize Majorana fermions at the ends
of quasi-one-dimensional metallic wires. We show how superconductivity can be
induced on the metallic surface states by a combination of proximity effect,
disorder, and interactions. Applying a magnetic field along the wire can drive
the wire into a topologically non-trivial state with Majorana end-states.
Unlike the case of a perpendicular field, where the chemical potential must be
fined tuned near the Rashba-band crossing, the parallel field allows one to
realize Majoranas for arbitrarily large chemical potential. We then show that,
despite the presence of a large carrier density from the bulk metal, it is
still possible to effectively control the chemical potential of the surface
states by gating. The simplest version of our proposal, which involves only an
Au(111) film deposited on a conventional superconductor, should be readily
realizable.Comment: 9 Pages, 6 Figure
A versatile all-channel stimulator for electrode arrays, with real-time control
Over the last few decades, technology to record through ever increasing numbers of electrodes has become available to electrophysiologists. For the study of distributed neural processing, however, the ability to stimulate through equal numbers of electrodes, and thus to attain bidirectional communication, is of paramount importance. Here, we present a stimulation system for multi-electrode arrays which interfaces with existing commercial recording hardware, and allows stimulation through any electrode in the array, with rapid switching between channels. The system is controlled through real-time Linux, making it extremely flexible: stimulation sequences can be constructed on-the-fly, and arbitrary stimulus waveforms can be used if desired. A key feature of this design is that it can be readily and inexpensively reproduced in other labs, since it interfaces to standard PC parallel ports and uses only off-the-shelf components. Moreover, adaptation for use with in vivo multi-electrode probes would be straightforward. In combination with our freely available data-acquisition software, MeaBench, this system can provide feedback stimulation in response to recorded action potentials within 15 ms
Engineering a p+ip Superconductor: Comparison of Topological Insulator and Rashba Spin-Orbit Coupled Materials
We compare topological insulator materials and Rashba coupled surfaces as
candidates for engineering p+ip superconductivity. Specifically, in each type
of material we examine 1) the limitations to inducing superconductivity by
proximity to an ordinary s-wave superconductor, and 2) the robustness of the
resulting superconductivity against disorder. We find that topological
insulators have strong advantages in both regards: there are no fundamental
barriers to inducing superconductivity, and the induced superconductivity is
immune to disorder. In contrast, for Rashba coupled quantum wires or surface
states, the the achievable gap from induced superconductivity is limited unless
the Rashba coupling is large. Furthermore, for small Rashba coupling the
induced superconductivity is strongly susceptible to disorder. These features
pose serious difficulties for realizing p+ip superconductors in semiconductor
materials due to their weak spin-orbit coupling, and suggest the need to seek
alternatives. Some candidate materials are discussed.Comment: 10 pages, 4 Figures; Changes for v2: References added, Includes an
expanded discussion of surface vs bulk disorder (see Sec. IVc. and Appendix
A
Recommended from our members
HEA/JISC Open Educational Resources case study: pedagogical development from OER practice: research ethics OER: can they be 'radically repurposed and remixed'?
This case study provides guidance on discovering, reusing and repurposing of Open Educational Resources (OER). It is presented within the context of research ethics OER for higher education learning and teaching and, together with the OER guidance, provides examples of OER found for this subject area
- …