Derated ion thruster design issues

Preliminary activities to develop and refine a lightweight 30 cm engineering model ion thruster are discussed. The approach is to develop a 'derated' ion thruster capable of performing both auxiliary and primary propulsion roles over an input power range of at least 0.5 to 5.0 kilo-W. Design modifications to a baseline thruster to reduce mass and volume are discussed. Performance data over an order of magnitude input power range are presented, with emphasis on the performance impact of engine throttling. Thruster design modifications to optimize performance over specific power envelopes are discussed. Additionally, lifetime estimates based on wear test measurements are made for the operation envelope of the engine

Performance of 10-kW class xenon ion thrusters

Presented are performance data for laboratory and engineering model 30 cm-diameter ion thrusters operated with xenon propellant over a range of input power levels from approximately 2 to 20 kW. Also presented are preliminary performance results obtained from laboratory model 50 cm-diameter cusp- and divergent-field ion thrusters operating with both 30 cm- amd 50 cm-diameter ion optics up to a 20 kW input power. These data include values of discharge chamber propellant and power efficiencies, as well as values of specific impulse, thruster efficiency, thrust and power. The operation of the 30 cm- and 50 cm-diameter ion optics are also discussed

Comparative experiences of two teacher educators: a self study

This paper focuses on the reflections of a less experienced and a veteran teacher educator at a new university and compares and contrasts their experiences of primary teacher education. The paper draws on the power of the narrative to share these experiences through aspects of self-study. Autobiographical research methods were used to elicit reflection on significant events in the teacher educators’ different and individual pasts in order to understand more about effective learning and teaching in their present roles. This process led to an examination of the values that underpinned and continue to underpin practice. The collaborative examination of significant aspects of personal practice has led to renewed confidence and implications for primary teacher education within the University

Memory interference effects in spin glasses

When a spin glass is cooled down, a memory of the cooling process is imprinted in the spin structure. This memory can be disclosed in a continuous heating measurement of the ac-susceptibility. E.g., if a continuous cooling process is intermittently halted during a certain aging time at one or two intermediate temperatures, the trace of the previous stop(s) is recovered when the sample is continuously re-heated [1]. However, heating the sample above the aging temperature, but keeping it below Tg, erases the memory of the thermal history at lower temperatures. We also show that a memory imprinted at a higher temperature can be erased by waiting a long enough time at a lower temperature. Predictions from two complementary spin glass descriptions, a hierarchical phase space model and a real space droplet picture are contested with these memory phenomena and interference effects. [1] K. Jonason, E. Vincent, J. Hammann, J. P. Bouchaud and P. Nordblad, Phys. Rev. Lett. 31, 3243 (1998).Comment: 7 pages, 1 LaTex file + 5 figures in EPS Revised version of June 17, 1999 (minor changes), to appear in EPJ B around November 9

First-principles methodology for quantum transport in multiterminal junctions

We present a generalized approach for computing electron conductance and I-V characteristics in multiterminal junctions from first-principles. Within the framework of Keldysh theory, electron transmission is evaluated employing an O(N) method for electronic-structure calculations. The nonequilibrium Green function for the nonequilibrium electron density of the multiterminal junction is computed self-consistently by solving Poisson equation after applying a realistic bias. We illustrate the suitability of the method on two examples of four-terminal systems, a radialene molecule connected to carbon chains and two crossed carbon chains brought together closer and closer. We describe charge density, potential profile, and transmission of electrons between any two terminals. Finally, we discuss the applicability of this technique to study complex electronic devices.Comment: Will be coming out in JCP soo

Quantum-interference-controlled three-terminal molecular transistors based on a single ring-shaped-molecule connected to graphene nanoribbon electrodes

We study all-carbon-hydrogen molecular transistors where zigzag graphene nanoribbons play the role of three metallic electrodes connected to a ring-shaped 18-annulene molecule. Using the nonequilibrium Green function formalism combined with density functional theory, recently extended to multiterminal devices, we show that the proposed nanostructures exhibit exponentially small transmission when the source and drain electrodes are attached in a configuration that ensures destructive interference of electron paths around the ring. The third electrode, functioning either as an attached infinite-impedance voltage probe or as an "air-bridge" top gate covering half of molecular ring, introduces dephasing that brings the transistor into the "on" state with its transmission in the latter case approaching the maximum limit for a single conducting channel device. The current through the latter device can also be controlled in the far-from-equilibrium regime by applying a gate voltage.Comment: 5 pages, 4 color figures, PDFLaTeX, slightly expanded version of the published PRL articl

Information Costs and Reverse Payment Settlements: Bridging the Gap Between the Courts and the Antitrust Agencies

Reverse payment settlements have attracted increased scrutiny due to the controversial presence of a payment from a brand-name drug company to a generic company that is ostensibly preparing to infringe on the branded company’s patent. The antitrust agencies and the courts settled into an intergovernmental stalemate regarding the appropriate framework of analysis to apply when reviewing antitrust challenges to these settlements. The FTC and DOJ have viewed the deals skeptically as a vehicle for competitors to split monopoly profits, but the lower courts have generally been deferential to what they identified as an exercise of a patent holder’s lawful right to exclude. Much has been written about which side is correct, yet there has been relatively little exploration of the source of the persistent disagreement. Building off of Henry Smith’s property rights theory and the cognitive miser literature from Peter Lee, this Article explains that the long-standing disagreement stems from the judiciary’s application of information-cost-saving rules. Courts adopted a formalistic approach that would almost invariably uphold a reverse payment settlement because they tend to apply bright-line rules when dealing with property rights, and they are prone to adjudicate complex patent and patent-related cases in ways that economize on the costs of information processing. Although the Supreme Court resolved the disagreement by adopting a more information-demanding rule of reason approach in FTC v. Actavis, the cognitive miser phenomenon will continue to affect how courts adjudicate antitrust challenges to reverse-payment settlements

Latitudinal Distribution of Zooplankton in the Southern Ocean with Special Reference to Euphausiids

The oceans are subjected to great variations, in space and time, with regard to their physicochemical and biological features. These changes are more pronounced latitudinally than longitudinally. In order to understand how these changes were reflected in the occurrence and abundance of zooplankton as a whole and the various groups in particular, a series of zooplankton samples were collected during the Third Indian Expedition to Antarctica, from the edge of the pack ice upto 200S along an oblique course between 22°56'E and 56°53'E