When the sun never sets: diverse activity rhythms under continuous daylight in free-living arctic-breeding birds

Circadian clocks are centrally involved in the regulation of daily behavioural and physiological processes. These clocks are synchronized to the 24-hour day by external cues (Zeitgeber), the most important of which is the light-dark cycle. In polar environments, however, the strength of the Zeitgeber is greatly reduced around the summer and winter solstices (continuous daylight or continuous darkness). How animals time their behaviour under such conditions has rarely been studied in the wild. Using a radio-telemetry-based system, we investigated daily activity rhythms under continuous daylight in Barrow, Alaska, throughout the breeding season in four bird species that differ in mating system and parental behaviour. We find substantial diversity in daily activity rhythms depending on species, sex and breeding stage. Individuals exhibited either robust, entrained 24-hour activity cycles, were continuously active (arrhythmic), or showed “free-running” activity cycles. In semipalmated sandpipers, a shorebird with biparental incubation, we show that the free-running rhythm is synchronized between pair mates. The diversity of diel time-keeping under continuous daylight emphasizes the plasticity of the circadian system and the importance of the social and life-history context. Our results support the idea that circadian behaviour can be adaptively modified to enable species-specific time-keeping under polar conditions

Knowledge Creation through User-Guided Data Mining: A Database Case

This case focuses on learning by applying the four integrating mechanisms of Nonaka\u27s knowledge creation theory: socialization, externalization, combination and internalization. In general, such knowledge creation and internalization (i.e., learning) is critical to database students since they will be expected to apply their specialized database knowledge to a wide variety of business problems, incorporating the various concepts of multiple business disciplines. The case, presented below, depicts a four-phase consulting assignment for each two-student team. In Phase 1, the teams design and implement a reservations database for a small corporate airline, basing their design on a written list of requirements. In Phase 2, each team uses the resulting database to address questions (queries) posed by key managers in the client firm. In Phase 3, each team develops operational and profit improvement recommendations for consideration by the firm\u27s top management. And finally, Phase 4 requires each team to present their recommendations to the client firm\u27s Board of Directors (the rest of the database class), answering any questions and concerns raised by this august board. Taken together, the four phases constitute knowledge creation through user-guided data mining. Since the queries require a variety of functions, subqueries, and cascading views, this case is most suitable as an integrative term project in either an upper-division undergraduate or a graduate level database course

Enhancing Knowledge Integration: An Information System Capstone Project

This database project focuses on learning through knowledge integration; i.e., sharing and applying specialized (database) knowledge within a group, and combining it with other business knowledge to create new knowledge. Specifically, the Tiny Tots, Inc. project described below requires students to design, build, and instantiate a database system for a hypothetical national retail marketing chain. The project also requires the students to test, via queries, several profit improvement hypotheses and, based on their analysis of query results, propose a set of recommendations for improving profits at Tiny Tots. Designing, instantiating, and using a database provides a learning opportunity for students to integrate the basic database techniques (entity-relation diagrams, normalization, scripting, joins, etc.) into a sensible whole and, through teamwork, to diffuse that knowledge throughout the group. Proposing, documenting, and defending their profit improvement recommendations encourages students to integrate their database knowledge with that learned in marketing (price elasticity and supply chain management), accounting (cost accounting and income statement analysis), management (personnel evaluation and compensation analysis), finance (capital budgeting and credit card analysis), and operations management (fraud detection and working capital control). Such knowledge integration is critical to graduating IS students since they will be expected to apply their specialized knowledge to a wide variety of business problems. This project is most suitable in an information systems capstone course or a graduate level database course

The influence of wind-induced compression failures on the mechanical properties of spruce structural timber

Compression failures (CF) are defects in the wood structure in the form of buckled fibres. They are a well-known 'natural' phenomenon in softwood trees exposed to frequent or strong winds, but their influence on the utilisation of timber is still debated. While a reduction of the mechanical properties in bending and tension at the fibre level and in small clear specimens is generally acknowledged, the effect is less obvious with structural timber in the presence of other defects such as knots or grain deviations. In the presented case study a statistically significant reduction of the moduli of rupture and elasticity in bending is observed in a sample of 563 squared timber beams, but the characteristic values of the mechanical properties still exceed the limits for the strength classes of visually graded structural timber (according to the Swiss standard SIA 265). Nevertheless, because of the potential safety risk by the more brittle fracture behaviour, it is recommended to exclude timber with detected CF from use in load bearing structures stressed in tension or bendin

Sub-nanometer free electrons with topological charge

The holographic mask technique is used to create freely moving electrons with quantized angular momentum. With electron optical elements they can be focused to vortices with diameters below the nanometer range. The understanding of these vortex beams is important for many applications. Here we present a theory of focused free electron vortices. The agreement with experimental data is excellent. As an immediate application, fundamental experimental parameters like spherical aberration and partial coherence are determined.Comment: 4 pages, 5 figure

Knowledge Management in Decision Making: Instance-Based Cognitive Mapping

Abstract Knowledge management deals with explicit knowledge and tacit (or implicit