Free monopoles have fascinated and eluded researchers since their prediction by Dirac 1 in 1931. In spin ice, the bulk frustrated magnet, local ordering principles known as ice rules-two-in/two-out for four spins arranged in a tetrahedron-minimize magnetic charge. Remarkably, recent work 2-5 shows that mobile excitations, termed 'monopole defects', emerge when the ice rules break down 2 . Using a cobalt honeycomb nanostructure we study the two-dimensional planar analogue called kagome or artificial spin ice. Here we show direct images of kagome monopole defects and the flow of magnetic charge using magnetic force microscopy. We find the local magnetic charge distribution at each vertex of the honeycomb pins the magnetic charge carriers, and opposite charges hop in opposite directions in an applied field. The parameters that enter the problem of creating and imaging monopole defects can be mapped onto a simple model that requires only the ice-rule violation energy and distribution of switching fields of the individual bars of a cobalt honeycomb lattice. As we demonstrate, it is the exquisite interplay between these energy scales in the cobalt nanostructure that leads to our experimental observations.The dipolar interactions of a given spin with all of its nearest neighbours cannot be satisfied on a triangular lattice, resulting in a frustrated magnetic state with strong correlations and a local ordering principle, but no long-range order. Owing to its equivalence to the electrical charge distribution in water ice 6 , the materials are known as 'spin ices' and the local ordering scheme as the 'ice rules'. Spin-ice materials such as Dy 2 Ti 2 O 7 have been subject to an intense research effort 7,8 and frustrated magnetism has evolved into a deeply interdisciplinary field, providing model systems for complex biological problems and a mathematical basis for the neural network algorithm from the Sherrington-Kirkpatrick model 9 .A powerful way to understand spin ice is to consider the magnetic dipole as a positive and negative magnetic charge (±q) separated by one lattice spacing. The ice rule can then be described as the local minimization at each lattice site i of the total magnetic charge (Q i, = q i ). Predictions suggest that the magnetic properties can be fractionalized, with mobile excitations carrying magnetic charge, rather than spin, and their interactions being described by a magnetic Coulomb's law 2 (equation (1))where V 0 is the self-energy and r ij is the separation. Although these topological excitations are confined to the dipole lattice, and they are compatible with Maxwell's equations 10 , their free magnetic charge character has led to the nomenclature magnetic Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK. *e-mail: W.Branford@imperial.ac.uk.monopole defects. Recent studies 3-5,10 in rare-earth pyrochlores strongly suggest that monopole defects exist in bulk spin ice 10 .Creating an odd number of intersecting dipoles, as in 'kagome spin ice' 11 , is interesting becaus...

A set of exploratory studies and mental model interviews was conducted in order to characterize public understanding of climate change. In general, respondents regarded global warming as both bad and highly likely. Many believed that warming has already occurred. They tended to confuse stratospheric omne depletion with the greenhouse effect and weather with climate. Automobile use, heat and emissions from industrial processes, aerosol spray cans, and pollution in general were frequently perceived as primary causes of global warming. Additionally, the "greenhouse effect" was often interpreted literally as the cause of a hot and steamy climate. The effects attributed to climate change often included increased skin cancer and changed agricultural yields. The mitigation and control strategies proposed by interviewees typically focused on general pollution control, with few specific links to carbon dioxide and energy use. Respondents appeared to be relatively unfamiliar with such regulatory developments as the ban on CFCS for nonessential uses. These beliefs must be considered by those designing risk communications or presenting climaterelated policies to the public.

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Recent research has revealed a pattern of choice characterized as a diversification bias: If people make combined choices of quantities of goods for future consumption, they choose more variety than if they make separate choices immediately preceding consumption. This phenomenon is explored in a series of experiments in which the researchers first eliminated several hypotheses that held that the discrepancy between combined and separate choice can be explained by traditional accounts of utility maximization. On the basis of results of further experiments, it was concluded that the diversification bias is largely attributable to 2 mechanisms: time contraction, which is the tendency to compress time intervals and treat long intervals as if they were short, and choice bracketing, which is the tendency to treat choices that are framed together differently from those that are framed apart. The researchers describe how the findings can be applied in the domains of marketing and consumer education.

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It is commonly assumed that people make intertemporal choices by "discounting" the value of delayed outcomes, assigning discounted values independently to all options, and comparing the discounted values. We identify a class of anomalies to this assumption of alternative-based discounting, which collectively shows that options are not treated independently but rather comparatively: The time difference, or interval, between the options sometimes counts more and sometimes counts less if it is taken as a whole than if it is divided into shorter subintervals (superadditivity and subadditivity, respectively), and whether the interval counts more or less depends on the money difference, or compensation, involved (inseparability). We develop a model that replaces alternative-based discounting with attribute-based tradeoffs. In our model, people make intertemporal choices by weighing how much more they will receive or pay if they wait longer against how much longer the wait will be, or, conversely, how much less they will receive or pay if they do not wait longer against how much shorter the wait will be. This model, called the tradeoff model, accommodates, in a psychologically plausible way, all anomalies that the discounting approach can and cannot address.Keywords: intertemporal choice, delay discounting, alternative-based choice, tradeoffs, attribute-based choice Intertemporal choices involve tradeoffs between costs and benefits that occur at different points in time (Loewenstein & Elster, 1992;Loewenstein, Read, & Baumeister, 2003). These include choices such as taking a job now or getting an education and having a chance at a better job later, and spending money now or saving it and having more to spend later. Most intensively investigated, however, are much more elementary choices between smaller-sooner and larger-later amounts of money, such as receiving $100 now or $150 in 3 months. It is commonly assumed that people make intertemporal choices by "discounting" the value of delayed outcomes, assigning discounted values to the options, and then comparing these discounted values. For this choice, they would compare the value of $100 now with the discounted value of $150 in 3 months. We argue that this does not accurately describe the psychology of intertemporal tradeoffs.Discounting models belong to the broad class of alternativebased choice models, in which the options are independently assigned an overall value, these values are compared, and the option with the highest value is chosen. Alternative-based choice models can be contrasted with attribute-based ones (Payne, Bettman, & Johnson, 1988), in which the options are directly compared along their attributes, and the option favored by these comparisons is chosen.1 Alternative-based discounting models can accommodate much of what we know about intertemporal choice, but there remains evidence, reviewed and strengthened in this article, that can only be addressed by an attribute-based choice model. In this article, we develop such a model, called the tradeoff mod...

(2005) 'Four score and seven years from now : the date/delay e ect in temporal discounting.', Management science., 51 (9). pp. 1326-1335. Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. W e describe a new anomaly in intertemporal choice-the "date/delay effect": discount rates that are imputed when time is described using calendar dates (e.g., on October 17) are markedly lower than those revealed when future outcomes are described in terms of the corresponding delay (e.g., in six months). Date descriptions not only reduce discount rates, but also affect the implied shape of the discount function: When inferred from intertemporal choices between options referenced by calendar dates, the discount function appears markedly less hyperbolic. We discuss potential psychological bases of the date/delay effect, its implications, and other modes of temporal reference.

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