7,509 research outputs found

    Prominence and consumer search

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    This paper examines the implications of “prominence” in search markets. We model prominence by supposing that the prominent firm will be sampled first by all consumers. If there are no systematic quality differences among firms, we find that the prominent firm will charge a lower price than its non-prominent rivals. The impact of making a firm prominent is that it will typically lead to higher industry profit but lower consumer surplus and welfare. The model is extended by introducing heterogeneous product qualities, in which case the firm with the highest-quality product has the greatest incentive to become prominent, and making it prominent will boost industry profit, consumer surplus and welfare

    Portable electrophoresis apparatus using minimum electrolyte

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    An electrophoresis unit for use in conducting electrophoretic analysis of specimens is described. The unit includes a sealable container in which a substrate mounted specimen is suspended in an electrolytic vapor. A heating unit is employed to heat a supply of electrolyte to produce the vapor. The substrate is suspended within the container by being attached between a pair of clips which also serve as electrodes to which a direct current power source may be connected

    The Lives of Stars: Insights From the TGAS-RAVE-LAMOST Dataset

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    In this paper we investigate how the chemical and kinematic properties of stars vary as a function of age. Using data from a variety of photometric, astrometric and spectroscopic surveys, we calculate the ages, phase space information and orbits for \sim125,000 stars covering a wide range of stellar parameters. We find indications that the inner regions of the disk reached high levels of enrichment early, while the outer regions were more substantially enriched in intermediate and recent epochs. We consider these enrichment histories through comparison of the ages of stars, their metallicities, and kinematic properties, such as their angular momentum in the solar neighborhood (which is a proxy for orbital radius). We calculate rates at which the velocity dispersions evolve, investigate the Oort constants for different aged populations (finding a slightly negative VC/R\partial V_{C} / \partial R and VR/R\partial V_{R} / \partial R for all ages, being most negative for the oldest stars), as well as examine the behavior of the velocity vertex deviation angle as a function of age (which we find to fall from \sim15 degrees for the 2 Gyr aged population to \sim6 degrees at around 6.5 Gyr of age, after which it remains unchanged). We find evidence for stellar churning, and find that the churned stars have a slightly younger age distribution than the rest of the data.Comment: 18 Pages, 14 Figures, Accepted Ap

    WISDOM: history and early demise - was it inevitable?

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    In 1989, the UK Medical Research Council (MRC) agreed that, if feasible, a randomized controlled trial to assess the long-term risks and benefits of hormone replacement therapy (HRT) was a priority. Feasibility work began in 1990 and demonstrated that a large-scale multicenter trial was possible. An application for funding for a main trial was submitted to MRC in 1993 and, after extensive review, funding was released in late 1996. Set-up work for the trial - the Women's International Study of long Duration Oestrogen after Menopause (WISDOM) - began in 1997 with recruitment in 1999. In October 2002, following the early discontinuation of one arm of the US Women's Health Initiative HRT trial, the MRC decided to stop the WISDOM trial. This article, by the principal UK investigators of WISDOM, sets out the background and history of the trial

    Intermittent type silica gel adsorption refrigerator Patent

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    Intermittent type silica gel adsorption refrigerator for providing temperature control for spacecraft component

    Adaptive Multicast of Multi-Layered Video: Rate-Based and Credit-Based Approaches

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    Network architectures that can efficiently transport high quality, multicast video are rapidly becoming a basic requirement of emerging multimedia applications. The main problem complicating multicast video transport is variation in network bandwidth constraints. An attractive solution to this problem is to use an adaptive, multi-layered video encoding mechanism. In this paper, we consider two such mechanisms for the support of video multicast; one is a rate-based mechanism that relies on explicit rate congestion feedback from the network, and the other is a credit-based mechanism that relies on hop-by-hop congestion feedback. The responsiveness, bandwidth utilization, scalability and fairness of the two mechanisms are evaluated through simulations. Results suggest that while the two mechanisms exhibit performance trade-offs, both are capable of providing a high quality video service in the presence of varying bandwidth constraints.Comment: 11 page

    Quantised vortices and mutual friction in relativistic superfluids

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    We consider the detailed dynamics of an array of quantised superfluid vortices in the framework of general relativity, as required for quantitative modelling of realistic neutron star cores. Our model builds on the variational approach to relativistic (multi-) fluid dynamics, where the vorticity plays a central role. The description provides a natural extension of, and as it happens a better insight into, existing Newtonian models. In particular, we account for the mutual friction associated with scattering of a second "normal" component in the mixture off of the superfluid vortices.Comment: 9 pages, RevTe

    Flow modifying device

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    A swirler for a gas turbine engine combustor is disclosed for simultaneously controlling combustor flow rate, swirl angle, residence time and fuel-air ratio to provide three regimes of operation. A first regime is provided in which fuel-air ratio is less than stoichiometric, NOx is produced at one level, and combustor flow rate is high. In a second regime, fuel-air ratio is nearly stoichiometric, NOx production is less than that of the first regime, and combustor flow rate is low. In a third regime, used for example at highoff, fuel-air ratio is greater than stoichiometric and the combustor flow rate is less than in either of the other regimes