Rotating gravitational lenses: a kinematic approach

This paper uses the Kerr geodesic equations for massless particles to derive an acceleration vector in both Boyer-Lindquist and Cartesian coordinates. As a special case, the Schwarzschild acceleration due to a non-rotating mass has a particularly simple and elegant form in Cartesian coordinates. Using forward integration, these equations are used to plot the caustic pattern due to a system consisting of a rotating point mass with a smaller non-rotating planet. Additionally, first and second order approximations to the paths are identified, which allows for fast approximations of paths, deflection angles and travel-time delays.Comment: 18 pages, 8 figure

Considerate constructors scheme : Glenfarg water treatment works

The project to modify Glenfarg Water Treatment Works by Scottish Water, working in conjunction with its partners Black and Veatch Ltd. and Scottish Water Solutions, received a gold award and ‘the ultimate accolade’ of ‘The Most Considerate Site 2009’ at the considerate constructors scheme (CCS) awards. Although previous projects undertaken by Scottish Water have achieved high considerate constructor scores, Glenfarg exceeded previous projects’ standards. This level of performance was delivered across the eight categories of the scheme: considerate, environment, cleanliness, good neighbour, respectful, safe responsible and accountable. The steps the project team took under each of these categories to deliver the project are reviewed in this article. The article also outlines some of the challenges the project team faced while delivering such a high level of performance. Furthermore, the article makes particular reference to ‘soft’ management skills and the development of a project organisational culture that emphasised pride and passion through engagement of the workforce. Overall, the article presents valuable insights into how performing beyond the CCS requirements remains a dynamic and ongoing activity for all parties involved with the scheme

Defining Canada’s Extended Continental Shelves

Article 76 of the United Nations Convention on the Law of the Sea provides a process to delineate Canada’s continental shelf where it extends beyond 200 nautical miles. After ratification of the Convention in 2003, Canada started a program to acquire and analyze the scientific data required for a submission to the Commission on the limits of the continental shelf. This submission will assist Canada in defining the outer limits of its continental shelf, thereby determining, with precision, the area where Canada may exercise its sovereign rights over natural resources. This paper outlines the scope of that program and summarizes the scientific activities to date. Data collection along the Atlantic margin was completed according to plan and the data are presently being analyzed. Data collection in the Arctic has been challenging because of ice and weather conditions, and several innovative solutions were implemented to collect seismic and bathymetry data using ice-breakers and large ice camps. The narrow Pacific margin provides no clear prospects for an extended continental shelf. Overall, the program is on schedule to meet the December 2013 deadline for submission to the Commission. SOMMAIRE L’article 76 de la Convention des Nations Unies sur le droit de la mer comporte une procédure permettant de définir l’étendue du plateau continental canadien au-delà des 200 miles nautiques. Après ratification de la Convention en 2003, le Canada a lancé un programme d’acquisition et d’analyse des données scientifiques exigées par la Commission pour définir les limites du plateau continental. Le dépôt de ces données aidera le Canada à définir les limites extérieures de son plateau continental, et donc, de déter-miner précisément le territoire où il pourra exercer des droits souverains sur les ressources naturelles. Le présent article décrit ce programme et résume les activités scientifiques réalisées à ce jour. Le long du plateau continental de l’Atlantique la collecte des données s’est terminée comme prévu et leur analyse est en cours. Dans l’Arctique, la collecte des données n’a pas été facile en raison de la glace et les conditions météorologiques, et plusieurs solutions innovantes ont dues être mises en œuvre afin de recueillir des données sismiques et bathymétriques, comme l’utilisation de brise-glaces et le recours à de grands camps de glace. Sur la côte du Pacifique, l'étroitesse du plateau continental exclu toutes possibilités d'extension évidemment. En gros, le programme se déroule comme prévu, et la date limite du décembre 2013 pour soumission du dossier à la Commission devrait être respectée

The Importance of Computing Education Research

Interest in computer science is growing. As a result, computer science (CS) and related departments are experiencing an explosive increase in undergraduate enrollments and unprecedented demand from other disciplines for learning computing. According to the 2014 CRA Taulbee Survey, the number of undergraduates declaring a computing major at Ph.D. granting departments in the US has increased 60% from 2011-2014 and the number of degrees granted has increased by 34% from 2008-2013. However, this growth is not limited to higher education. New York City, San Francisco and Oakland public schools will soon be offering computer science to all students at all schools from preschool to 12th grade, although it will be an elective for high school students. This unprecedented demand means that CS departments are likely to teach not only more students in the coming decades, but more diverse students, with more varied backgrounds, motivations, preparations, and abilities. This growth is an unparalleled opportunity to expand the reach of computing education. However, this growth is also a unique research challenge, as we know very little about how best to teach our current students, let alone the students soon to arrive. The burgeoning field of Computing Education Research (CER) is positioned to address this challenge by answering research questions such as, how should we teach computer science, from programming to advanced principles, to a broader and more diverse audience? We argue that computer science departments should lead the way in establishing CER as a foundational research area of computer science, discovering the best ways to teach CS, and inventing the best technologies with which to teach it. This white paper provides a snapshot of the current state of CER and makes actionable recommendations for academic leaders to grow CER as a successful research area in their departments.Comment: A Computing Community Consortium (CCC) white paper, 12 page

BCS 100 Module 3: Northern Environments

The landscapes of the Circumpolar North have been shaped by the interplay of physical, chemical and biological processes operating over many millennia or many millions of years. Many of the physical features and processes found in the Circumpolar North are unique to this part of the earth. The flora and fauna of the northern regions are unique because the environments they inhabit are extreme and finely balanced. This module provides a brief introduction to the physical and biological features and processes of the Arctic and Subarctic regions and highlights the significant factors that influence those features and processes

Faculty Brass Quintet

Center for the Performing Arts Tuesday Evening October 15, 2002 8:00p.m

Topologically controlled multiskyrmions in photonic gradient-index lenses

Skyrmions are topologically protected quasiparticles, originally studied in condensed-matter systems and recently in photonics, with great potential in ultra-high-capacity information storage. Despite the recent attention, most optical solutions require complex and expensive systems yet produce limited topologies. Here we demonstrate an extended family of quasiparticles beyond normal skyrmions, which are controlled in confined photonic gradient-index media, extending to higher-order members such as multiskyrmions and multimerons, with increasingly complex topologies. We introduce new topological numbers to describe these complex photonic quasiparticles and propose how this new zoology of particles could be used in future high-capacity information transfer. Our compact creation system lends integrated and programmable solutions of complex particle textures, with potential impacts on both photonic and condensed-matter systems for revolutionizing topological informatics and logic devices

The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0

[1] The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of Arctic undersea features. IBCAO Version 3.0 represents the largest improvement since 1999 taking advantage of new data sets collected by the circum-Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO Version 1.0 (2.5 km) and Version 2.0 (2.0 km). The area covered by multibeam surveys has increased from ∼6% in Version 2.0 to ∼11% in Version 3.0

Predicting impacts of chemicals from organisms to ecosystem service delivery: A case study of endocrine disruptor effects on trout

We demonstrate how mechanistic modeling can be used to predict whether and how biological responses to chemicals at (sub)organismal levels in model species (i.e., what we typically measure) translate into impacts on ecosystem service delivery (i.e., what we care about). We consider a hypothetical case study of two species of trout, brown trout (Salmo trutta; BT) and greenback cutthroat trout (Oncorhynchus clarkii stomias; GCT). These hypothetical populations live in a high-altitude river system and are exposed to human-derived estrogen (17α‑ethinyl estradiol, EE2), which is the bioactive estrogen in many contraceptives. We use the individual based model in STREAM to explore how seasonally varying concentrations of EE2 could influence male spawning and sperm quality. Resulting impacts on trout recruitment and the consequences of such for anglers and for the continued viability of populations of GCT (the state fish of Colorado) are explored. in STREAM incorporates seasonally varying river flow and temperature, fishing pressure, the influence of EE2 on species-specific demography, and inter-specific competition. The model facilitates quantitative exploration of the relative importance of endocrine disruption and inter-species competition on trout population dynamics. Simulations predicted constant EE2 loading to have more impacts on GCT than BT. However, increasing removal of BT by anglers can enhance the persistence of GCT and offset some of the negative effects of EE2. We demonstrate how models that quantitatively link impacts of chemicals and other stressors on individual survival, growth, and reproduction to consequences for populations and ecosystem service delivery, can be coupled with ecosystem service valuation. The approach facilitates interpretation of toxicity data in an ecological context and gives beneficiaries of ecosystem services amore explicit role in management decisions. Although challenges remain, this type of approach may be particularly helpful for site-specific risk assessments and those in which trade offs and synergies among ecosystem services need to be considered