Bending and Breathing Modes of the Galactic Disk

We explore the hypothesis that a passing satellite or dark matter subhalo has excited coherent oscillations of the Milky Way's stellar disk in the direction perpendicular to the Galactic midplane. This work is motivated by recent observations of spatially dependent bulk vertical motions within ~ kpc of the Sun. A satellite can transfer a fraction of its orbital energy to the disk stars as it plunges through the Galactic midplane thereby heating and thickening the disk. Bulk motions arise during the early stages of such an event when the disk is still in an unrelaxed state. We present simple toy-model calculations and simulations of disk-satellite interactions, which show that the response of the disk depends on the relative velocity of the satellite. When the component of the satellite's velocity perpendicular to the disk is small compared with that of the stars, the perturbation is predominantly a bending mode. Conversely, breathing and higher order modes are excited when the vertical velocity of the satellite is larger than that of the stars. We argue that the compression and rarefaction motions seen in three different surveys are in fact breathing mode perturbations of the Galactic disk.Comment: 12 pages, 12 figure

Metabolic abnormalities in advanced pancreatic cancer and their modulation by an eicosapentaenoic acid-based preparation

A combination of a nutritional supplement and eicosapentaenoic acid was given to patients with advanced pancreatic cancer to assess its effect on the ongoing cachectic process. The administration of a fish oil-enriched nutritional supplement providing 2g eicosapentaenoic acid and around 600kcal per day resulted in a significant change in the metabolic disposition of patients with advanced pancreatic cancer. Consumption of the supplement resulted in a reversal of weight loss and a gain in lean body mass in association with a reversal of negative nitrogen balance. Performance status and appetite improved. Production of interleukin-6 was reduced and the acute phase protein response stabilised, insulin concentration increased and proteolysis inducing factor excretion fell. These changes were associated with a rise in energy intake, a fall in relative resting energy expenditure and a normalisation of the metabolic response to feeding and substrate utilisation. The increase in acute phase protein synthesis with feeding was abolished after the administration of the fish oil-enriched nutritional supplement. The progressive nutritional and functional deterioration of advanced pancreatic cancer patients thus seems to be associated with broadly pro-inflammatory metabolic mediators and a progressive acute phase protein response. This deterioration may in part be resistant to conventional nutritional supplementation because of further stimulation of acute phase protein production by feeding. The provision of a fish oil-enriched nutritional supplement normalises the metabolic milieu, stabilises the acute phase protein response and abolishes the stimulation of acute phase protein production by feeding. One explanation to account for the effects observed after intervention would be that it to allows dietary amino acids to be used for lean tissue anabolism with the consequent potential for quality of life and survival benefit

Choosing How to Choose: Self-Stable Majority Rules and Constitutions

Constitutional arrangements affect the decisions made by a society. We study how this effect leads to preferences of citizens over constitutions; and ultimately how this has a feedback that determines which constitutions can survive in a given society. Constitutions are stylized here, to consist of a voting rule for ordinary business and possibly different voting rule for making changes to the constitution. We deffine an equilibrium notion for constitutions, called self-stability, whereby under the rules of a self-stable constitution, the society would not vote to change the constitution. We argue that only self-stable constitutions will endure. We prove that self-stable constitutions always exist, but that most constitutions (even very prominent ones) may not be self-stable for some societies. We show that constitutions where the voting rule used to amend the constitution is the same as the voting rule used for ordinary business are dangerously simplistic, and there are (many) societies for which no such constitution is self-stable rule. We conclude with a characterization of the set of self-stable constitutions that use majority rule for ordinary business.

Phosphorylation of the Arp2 subunit relieves auto-inhibitory interactions for Arp2/3 complex activation.

Actin filament assembly by the actin-related protein (Arp) 2/3 complex is necessary to build many cellular structures, including lamellipodia at the leading edge of motile cells and phagocytic cups, and to move endosomes and intracellular pathogens. The crucial role of the Arp2/3 complex in cellular processes requires precise spatiotemporal regulation of its activity. While binding of nucleation-promoting factors (NPFs) has long been considered essential to Arp2/3 complex activity, we recently showed that phosphorylation of the Arp2 subunit is also necessary for Arp2/3 complex activation. Using molecular dynamics simulations and biochemical assays with recombinant Arp2/3 complex, we now show how phosphorylation of Arp2 induces conformational changes permitting activation. The simulations suggest that phosphorylation causes reorientation of Arp2 relative to Arp3 by destabilizing a network of salt-bridge interactions at the interface of the Arp2, Arp3, and ARPC4 subunits. Simulations also suggest a gain-of-function ARPC4 mutant that we show experimentally to have substantial activity in the absence of NPFs. We propose a model in which a network of auto-inhibitory salt-bridge interactions holds the Arp2 subunit in an inactive orientation. These auto-inhibitory interactions are destabilized upon phosphorylation of Arp2, allowing Arp2 to reorient to an activation-competent state

On the Weights of Nations: Assigning Voting Weights in a Heterogenous Union

Consider a voting procedure where countries, states, or districts comprising a union each elect representatives who then participate in later votes at the union level on their behalf. The countries, provinces, and states may vary in their populations and composition. If we wish to maximize the total expected utility of all agents in the union, how to weight the votes of the representatives of the different countries, states or districts at the union level? We provide a simple characterization of the efficient voting rule in terms of the weights assigned to different districts and the voting threshold (how large a qualified majority is needed to induce change versus the status quo). Next, in the context of a model of the correlation structure of agents preferences, we analyze how voting weights relate to the population size of a country. We then analyze the voting weights in Council of the European Union under the Nice Treaty and the recently proposed constitution, and contrast them under different versions of our model.

Insecticide resistance in the currant-lettuce aphid, Nasonovia ribisnigri

Available from British Library Document Supply Centre- DSC:DXN059679 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

13kW Advanced Electric Propulsion Flight System Development and Qualification

The next phase of robotic and human deep space exploration missions requires high performance, high power solar electric propulsion systems for large-scale science missions and cargo transportation. Aerojet Rocketdyne's Advanced Electric Propulsion System (AEPS) program is completing development and qualification of a 13kW flight EP system to support NASA exploration. The first use of the AEPS is planned for the NASA Power & Propulsion Element, which is the first element of NASA's cis-lunar Gateway. The flight AEPS system includes a magnetically shielded long-life Hall thruster, power processing unit (PPU), and xenon flow controller (XFC). The Hall thruster, originally developed and demonstrated by NASA's Glenn Research Center and the Jet Propulsion Laboratory, operates at input powers up to 13.3kW while providing a specific impulse over 2600s at an input voltage of 600V. The power processor is designed to accommodate an input voltage range of 95 to 140V, consistent with operation beyond the orbit of Mars. The integrated system is continuously throttleable between 3 and 13.3kW. The program has completed testing of the Technology Development Units and is progressing into the Engineering Development Unit test phase and the final design phase to Critical Design Review (CDR). This paper will present the high power AEPS system capabilities, overall program and design status and the latest test results for the 13kW flight system development as well as the plans for the development and qualification effort of the EP string

Deployable Antenna for CubeSat

This project is a proof-of-concept ground model of a large deployable antenna designed for the small space requirements of CubeSats. This small deployment module is designed to fit a 2 m by 1 m reflective antenna inside a storage volume of with the dimensions 20 cm by 20 cm x 40 cm. The reflector will be deployed to a parabolic shape with the goal of modeling the reflector necessary for high frequency communication. Because this module is designed as a proof-of-concept for the deployable parabolic reflector specifically, no electrical components will be incorporated and will just focus on the deployment mechanism and will not be space grade. Because this module is designed as a first iteration, it has the potential to be built upon and improved by other groups in the future

Shooting the President: The Depiction of the American Presidency on Film and Television from John F. Kennedy to Josiah Bartlet

This thesis – Shooting the President: Screen Depictions of the American Presidency from John F. Kennedy to Josiah Bartlet – examines the depiction of the presidency in American film and television from 1960 until the present day. In this study I explore the relationships between the presidency and Hollywood, particularly in the context of genre structures. I examine the constructions of specific presidential mythologies based on the real presidencies of Kennedy, Nixon and Clinton and the construction of fictional presidencies in the television series The West Wing. In four sets of case studies, I will chart the changing significance of each president through different genres, looking particularly at how each presidential mythology is affected by the anxieties and fashions of the contemporary political and social world. I also examine the ways in which the appearance of presidentiality is created within each text by various means including set design, the choice of actor, the use of dialogue and the framing of particular characters. The aims of my thesis are to demonstrate how a telegenic style of politics formed during and after the Kennedy presidency can be seen to be both represented and enhanced in genre films and television series. I chart the relationship of this new mediated style of presidency through my case studies as it faces challenges such as Watergate, Clinton’s sex scandals and the terrorist attacks of September 11 2001. Finally, I aim to demonstrate through a close reading of the latter seasons of The West Wing how the American public can be seen to be prepared by its popular media for the success of the first black president, Barack Obama

A Cryogenic Fluid System Simulation in Support of Integrated Systems Health Management

Simulations serve as important tools throughout the design and operation of engineering systems. In the context of sys-tems health management, simulations serve many uses. For one, the underlying physical models can be used by model-based health management tools to develop diagnostic and prognostic models. These simulations should incorporate both nominal and faulty behavior with the ability to inject various faults into the system. Such simulations can there-fore be used for operator training, for both nominal and faulty situations, as well as for developing and prototyping health management algorithms. In this paper, we describe a methodology for building such simulations. We discuss the design decisions and tools used to build a simulation of a cryogenic fluid test bed, and how it serves as a core technology for systems health management development and maturation