Dancing with the Stars: Formation of the Fomalhaut triple system and its effect on the debris disks

Fomalhaut is a triple system, with all components widely separated (~1E5 au). Such widely separated binaries are thought to form during cluster dissolution, but that process is unlikely to form such a triple system. We explore an alternative scenario, where A and C form as a tighter binary from a single molecular cloud core (with semimajor axis ~1E4 au), and B is captured during cluster dispersal. We use N-body simulations augmented with the Galactic tidal forces to show that such a system naturally evolves into a Fomalhaut-like system in about half of cases, on a timescale compatible with the age of Fomalhaut. From initial non-interacting orbits, Galactic tides drive cycles in B's eccentricity that lead to a close encounter with C. After several close encounters, typically lasting tens of millions of years, one of the stars is ejected. The Fomalhaut-like case with both components at large separations is almost invariably a precursor to the ejection of one component, most commonly Fomalhaut C. By including circumstellar debris in a subset of the simulations, we also show that such an evolution usually does not disrupt the coherently eccentric debris disk around Fomalhaut A, and in some cases can even produce such a disk. We also find that the final eccentricity of the disk around A and the disk around C are correlated, which may indicate that the dynamics of the three stars stirred C's disk, explaining its unusual brightness.Comment: Accepted to MNRA

India in 2014:Decisive National Elections

The much anticipated general election produced a majority for the Bharatiya Janata Party under the leadership of Narendra Modi. The new administration is setting out an agenda for governing. The economy showed some signs of improvement, business confidence is returning, but economic growth has yet to return to earlier high levels.</jats:p

The drums of the southern TRB

This dissertation examines the clay drums found in the Neolithic contexts of the southern Trichterrandbecher culture (TRB).Chapter 1 introduces the subject and provides basic definitions.Chapter 2 reviews the archaeological literature of the southern TRB, including typological, stratigraphic and dating concerns, followed by a survey of the settlement, economic and burial evidence.Chapter 3 reviews the classifications of the drums and proposes a revised version, based on the vessel form, the decoration and the archaeological context.In Chapter 4 we review the comparative analysis of the decoration and vessel form with a view to understanding their origins.Chapter 5 summarises the anthropological and archaeological literature on the subject of shamanism, and shamanistic practices, reviewing the concept of altered states of consciousness and providing definitions of the terms "trance", "ecstasy", "shamanism" and "possession". Then we discuss the neurological evidence of shamanism and brain structure, and explain the technical terminology. The chapter then proceeds to examine the methods of inducing changes in consciousness, specifically the use of auditory driving and imagery cultivation, finishing with a look at the evidence of European shamanisms.Chapter 6 examines the validity of applying a shamanistic approach using the comparison with entoptic imagery.Chapter 7 summarises the investigation, and after sifting the evidence draws conclusions on the interpretation of the Neolithic drums, the plausibility of shamanistic approaches and the nature of music in human culture

A model for rolling swarms of locusts

We construct an individual-based kinematic model of rolling migratory locust swarms. The model incorporates social interactions, gravity, wind, and the effect of the impenetrable boundary formed by the ground. We study the model using numerical simulations and tools from statistical mechanics, namely the notion of H-stability. For a free-space swarm (no wind and gravity), as the number of locusts increases, it approaches a crystalline lattice of fixed density if it is H-stable, and in contrast becomes ever more dense if it is catastrophic. Numerical simulations suggest that whether or not a swarm rolls depends on the statistical mechanical properties of the corresponding free-space swarm. For a swarm that is H-stable in free space, gravity causes the group to land and form a crystalline lattice. Wind, in turn, smears the swarm out along the ground until all individuals are stationary. In contrast, for a swarm that is catastrophic in free space, gravity causes the group to land and form a bubble-like shape. In the presence of wind, the swarm migrates with a rolling motion similar to natural locust swarms. The rolling structure is similar to that observed by biologists, and includes a takeoff zone, a landing zone, and a stationary zone where grounded locusts can rest and feed.Comment: 18 pages, 11 figure

The AIADMK’s re-election conceals the nuances of a highly competitive campaign in Tamil Nadu

Last week the AIADMK held off a strong challenge from the DMK to win a consecutive term in office for the first time since 1984. Andrew Wyatt and C. Manikandan discuss the battle between to two regional parties, which featured material promises, debates on alcohol prohibition and a subtle restructuring to the party elites. This post forms part of a series of posts on the 2016 Legislative Assembly Elections. Click here to read more

Adhesion Lithography Peel Tool Design

This document describes the adhesion lithography peel tool, designed for the automation of the final step of the adhesion lithography process

Adhesion lithography for large-area patterning of asymmetric nanogap electrodes

As the resolution of devices in the electronics industry has hit the nanoscale, device fabrication costs have rapidly increased. Whilst commercial technologies such as electron-beam lithography are able to define nanoscale features, they are costly and unsuitable for large area electronics. Research is now focusing on fabrication techniques that can pattern features on the nanoscale on flexible substrates, over large areas without incurring these high costs, such as adhesion lithography (a-Lith). A-Lith is a large-scale fabrication technique for producing planar asymmetric nanogap electrodes [1]. Devices have been created with gap width:length aspect ratios \u3e100000. The technique can be carried out in air and at ambient temperature making it ideal for the field of plastic electronics [2]. The a-Lith technique relies on a self-assembled monolayer (SAM) molecule selectively coating a prepatterned metal (M1) which then changes the adhesion forces. A second metal (M2) is then deposited over the top and can be specifically patterned when peeled using an adhesive due to its reduced adhesion on M1 relative to elsewhere. M2 only remains in the areas where there is no M1 (in the areas where it directly contacts the substrate). Where M2 fractures at the edge of M1, a nanogap (≈10 nm) is formed between the two metals [1]. A-Lith has shown improved device performance across many areas of device electronics as the ability to pattern electrodes side-by-side largely eliminates parasitic capacitances. Such electrodes have been utilized in device applications including high responsivity photodiodes [3], nano organic light emitting diodes [4], memristors [2] and high speed diodes [5]. This fabrication technique was previously only successfully carried out with Al, Au and Ti as M1, and Al and Au as M2, with the Al and Au (with an Al adhesion layer) thermally evaporated. In this work, a-Lith has been successful executed with a variety of materials sputtered including Cu, Ni, Ti, Mo, Cr and Al as M1. M2 is shown to be successful with Al, Ni, Cu and Cr. This has allowed for further devices applications to be explored including devices utilizing 2D materials. References [1] D. J. Beesley et al., “Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography.” Nat. Commun., vol. 5, (2014), p. 3933. [2] J. Semple et al., “Large-area plastic nanogap electronics enabled by adhesion lithography,” npj Flex. Electron., vol. 18, (2018). [3] G. Wyatt-Moon, et al., “Deep Ultraviolet Copper(I) Thiocyanate (CuSCN) Photodetectors Based on Coplanar Nanogap Electrodes Fabricated via Adhesion Lithography,” ACS Appl. Mater. Interfaces, vol. 9, (2017), p. 41965. [4] G. Wyatt-Moon, et al., “Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith),” J. Phys. Mater, vol. 1, (2018). [5] J. Semple et al., “Radio Frequency Coplanar ZnO Schottky Nanodiodes Processed from Solution on Plastic Substrates,” Small, vol. 12, (2016), p. 1993