Slingshot Dynamics for Self Replicating Probes and the Effect on Exploration Timescales

Interstellar probes can carry out slingshot manoeuvres around the stars they visit, gaining a boost in velocity by extracting energy from the star's motion around the Galactic Centre. These maneouvres carry little to no extra energy cost, and in previous work it has been shown that a single Voyager-like probe exploring the galaxy does so 100 times faster when carrying out these slingshots than when navigating purely by powered flight (Forgan et al. 2012). We expand on these results by repeating the experiment with self-replicating probes. The probes explore a box of stars representative of the local Solar neighbourhood, to investigate how self-replication affects exploration timescales when compared with a single non-replicating probe. We explore three different scenarios of probe behaviour: i) standard powered flight to the nearest unvisited star (no slingshot techniques used), ii) flight to the nearest unvisited star using slingshot techniques, and iii) flight to the next unvisited star that will give the maximum velocity boost under a slingshot trajectory. In all three scenarios we find that as expected, using self-replicating probes greatly reduces the exploration time, by up to three orders of magnitude for scenario i) and iii) and two orders of magnitude for ii). The second case (i.e. nearest-star slingshots) remains the most time effective way to explore a population of stars. As the decision-making algorithms for the fleet are simple, unanticipated "race conditions" amongst probes are set up, causing the exploration time of the final stars to become much longer than necessary. From the scaling of the probes' performance with star number, we conclude that a fleet of self-replicating probes can indeed explore the Galaxy in a sufficiently short time to warrant the existence of the Fermi Paradox.Comment: Accepted for publication in the International Journal of Astrobiology, 13 pages, 7 figure

Baseline study of employability related activities in Scottish colleges

In October 2004, the Scottish Funding Council (SFC)'s predecessor bodies, theSFEFC and the SHEFC, publishedLearning to Work(SFC 2004), a discussion paperabout how Scotland's colleges and universities can help to enhance learners'employability. In subsequent dialogue with stakeholders, there was agreement thatemployability should be a specific focus for quality enhancement in the college sectorfrom 2006-07. As a basis for further development, the SFC commissioned this studyto provide information on the range of current activities and practices in Scotland'scolleges which contribute to enhancing employability

Achieving Good Angular Resolution in 3D Arc Diagrams

We study a three-dimensional analogue to the well-known graph visualization approach known as arc diagrams. We provide several algorithms that achieve good angular resolution for 3D arc diagrams, even for cases when the arcs must project to a given 2D straight-line drawing of the input graph. Our methods make use of various graph coloring algorithms, including an algorithm for a new coloring problem, which we call localized edge coloring.Comment: 12 pages, 5 figures; to appear at the 21st International Symposium on Graph Drawing (GD 2013

Robust Buchwald-Hartwig amination enabled by ball-milling

An operationally simple mechanochemical method for the Pd catalysed Buchwald–Hartwig amination of arylhalides with secondary amines has been developed using a Pd PEPPSI catalyst system. The system is demonstrated on 30 substrates and applied in the context of a target synthesis. Furthermore, the performance of the reaction under aerobic conditions has been probed under traditional solution and mechanochemical conditions, the observations are discussed herein

Application of the Observational Method on Crossrail projects

This is the author accepted manuscript. The final version is available from the Federation of Piling Specialists via http://www.fps.org.uk/fps/news/Crossrail%20Programme%20of%20Proceedings%20FINAL.pdfThis paper describes the use of the Observsational Method (OM) on three Crossrail station excavations. Firstly, at Tottenham Court Road, Western Ticket Hall excavation where a code compliant design was started. By the third excavation stage, it was realised that movements were less than predicted and an OM was introduced. This enabled the lowest level of strutting to be eliminated, leading to savings in both programme and costs. Secondly, at Canary Wharf Crossrail Station, an OM approach was envisaged before the start of construction, but was only designed during the final excavation stage when time was available for back-analysis. A saving in costs and programme was achieved. Thirdly, at Moorgate shaft (part of Liverpool St Station) where construction commenced with a standard codecompliant design. A client-led redesign was carried out after installation of the diaphragm wall with an innovative verification process using a proactive OM approach to enable programme savings. When unusual deflection were observed from the shaft east wall due to structural uncertainties and construction activities, the OM and verification process provided a flexible framework within which to reassess ongoing movements and effects on an adjacent tunnel to ensure construction could proceed safely. The case histories described demonstrate the benefit of adopting the OM for excavations in order to achieve savings in time and cost, and to react to unexpected movements during construction. These case histories fit well within a new framework for OM applications developed as part of the CIRIA C760.ARUP, CSI

Consumer-Directed Health Insurance vs. Managed Care: Analysis of Health Care Utilization and Expenditure Incurred by Employees in a Rural Area

Consumer-Directed Health Plans (CDHPs) are proposed as an option to control healthcare costs. No research has addressed their applicability in rural settings. This study analyzes three years (2003–2005) of healthcare expenditure and utilization incurred by two employers and a national carrier providing data from a rural state, Kentucky. The study included two measures of expenditures (health care and prescription drugs) and three measures of utilization (physician visits, hospital admissions, and hospital inpatient days). In general, the CDHP successfully controlled the growth of medical costs. These findings suggest that CDHPs may be a viable alternative benefit structure for rural employers

Basalts erupted along the Tongan fore-arc during subduction initiation: evidence from geochronology of dredged rocks from the Tonga fore-arc and trench

A wide variety of different rock types were dredged from the Tonga fore arc and trench between 8000 and 3000 m water depths by the 1996 Boomerang voyage. 40Ar-39Ar whole rock and U-Pb zircon dating suggest that these fore arc rocks were erupted episodically from the Cretaceous to the Pliocene (102 to 2 Ma). The geochemistry suggests that MOR-type basalts and dolerites were erupted in the Cretaceous, that island arc tholeiites were erupted in the Eocene and that back arc basin and island arc tholeiite and boninite were erupted episodically after this time. The ages generally become younger northward suggesting that fore arc crust was created in the south at around 48–52 Ma and was extended northward between 35 and 28 Ma, between 9 and 15 Ma and continuing to the present-day. The episodic formation of the fore arc crust suggested by this data is very different to existing models for fore arc formation based on the Bonin-Marianas arc. The Bonin-Marianas based models postulate that the basaltic fore arc rocks were created between 52 and 49 Ma at the beginning of subduction above a rapidly foundering west-dipping slab. Instead a model where the 52 Ma basalts that are presently in a fore arc position were created in the arc-back arc transition behind the 57–35 Ma Loyalty-Three Kings arc and placed into a fore arc setting after arc reversal following the start of collision with New Caledonia is proposed for the oldest rocks in Tonga. This is followed by growth of the fore arc northward with continued eruption of back arc and boninitic magmas after that time

The regulation of television sports broadcasting: a comparative analysis

Based on seven different sports broadcasting markets (Australia, Brazil, Italy, India, South Africa, United Kingdom and the United States), this article provides a comparative analysis of the regulation of television sports broadcasting. The article examines how contrasting perspectives on television and sport – economic and sociocultural – have been reflected in two main approaches to the regulation of sports broadcasting, namely competition law and major events legislation. The results of this analysis suggest that in many cases, the balance between commerce and culture in sports broadcasting has shifted too far in favour of the commercial interests of dominant pay-TV operators and sports organisations. Here, the case is made for the pursuit of an approach to sports broadcasting regulation that seeks to balance the commercial priorities of broadcasters and sports organisations with the wider sociocultural benefits citizens gain from freeto- air sports broadcasting

One-pot multistep mechanochemical synthesis of fluorinated pyrazolones

Solventless mechanochemical synthesis represents a technique with improved sustainability metrics compared to solvent-based processes. Herein, we describe a methodical process to run one solventless reaction directly into another through multistep mechanochemistry, effectively amplifying the solvent savings. The approach has to consider the solid form of the materials and compatibility of any auxiliary used. This has culminated in the development of a two-step, one-jar protocol for heterocycle formation and subsequent fluorination that has been successfully applied across a range of substrates, resulting in 12 difluorinated pyrazolones in moderate to excellent yields