2,486 research outputs found

    Rational Expectations Voting in Agent-based Models: An Application to Tax Ceilings

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    This paper introduces rational expectations voting into an agentbased model of collective choice. Our model is unique because it generates sophisticated forecasts of endogenous policy outcomes by computationally sampling the space of exogenous random variables. Together these forecasts generate a common prior, a joint distribution of all random variables as a function of the set of policy choices, which agents use to select the policy that maximizes their expected utility. We apply our simulated rational expectations methodology by using administrative data on property taxes from two U.S. cities to investigate how observed levels of (plausibly exogenous) tax-payment uncertainty affect collective choice. Specifically, we show that, for sophisticated risk-averse or loss-averse voters, higher levels of tax-payment uncertainty generate majority support for a binding constraint on collective choice

    Mechanisms of change during group metacognitive therapy for repetitive negative thinking in primary and non-primary generalized anxiety disorder

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    © 2015 Elsevier Ltd. Repetitive negative thinking (RNT) is a transdiagnostic process that serves to maintain emotional disorders. Metacognitive theory suggests that positive and negative metacognitive beliefs guide the selection of RNT as a coping strategy which, in turn, increases psychological distress. The aim of this study was to test the indirect effect of metacognitive beliefs on psychological distress via RNT. Patients (N=52) with primary and non-primary generalized anxiety disorder attended a brief, six-week group metacognitive therapy program and completed measures of metacognitive beliefs, RNT, and symptoms at the first and final treatment sessions, and at a one-month follow-up. Prospective indirect effects models found that negative metacognitive beliefs (but not positive metacognitive beliefs) had a significant indirect effect on psychological distress via RNT. As predicted by metacognitive theory, targeting negative metacognitions in treatment appears to reduce RNT and, in turn, emotional distress. Further research using alternative measures at multiple time points during therapy is required to determine whether the absence of a relationship with positive metacognitive beliefs in this study was a consequence of (a) psychometric issues, (b) these beliefs only being relevant to a subgroup of patients, or (c) a lack of awareness early in treatment

    Single unit responses recorded from the first order neuron of the pigeon auditory system

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    Intracochlear recordings from the first order neurons in the eighth nerve of the pigeon were made with microelectrodes. The basic response characteristics of the single units were similar to those recorded from mammalian first order auditory neurons with the following exceptions: units responding solely to `sweep frequencies' were found and one unit was found for which the rate of discharge decreased with increased intensity. Suppression of spontaneous activity during tonal stimulation was found within the response curve of the unit and for frequencies beyond the boundaries of the response curve. In addition, suppression of spontaneous activity was found after the termination of the tone. The amount of suppression and the recovery process varied considerably from unit to unit. The controlling variables were intensity and duration of the stimulus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21841/1/0000244.pd

    Fluid-Induced Propulsion of Rigid Particles in Wormlike Micellar Solutions

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    In the absence of inertia, a reciprocal swimmer achieves no net motion in a viscous Newtonian fluid. Here, we investigate the ability of a reciprocally actuated particle to translate through a complex fluid that possesses a network using tracking methods and birefringence imaging. A geometrically polar particle, a rod with a bead on one end, is reciprocally rotated using magnetic fields. The particle is immersed in a wormlike micellar (WLM) solution that is known to be susceptible to the formation of shear bands and other localized structures due to shear-induced remodeling of its microstructure. Results show that the nonlinearities present in this WLM solution break time-reversal symmetry under certain conditions, and enable propulsion of an artificial "swimmer." We find three regimes dependent on the Deborah number (De): net motion towards the bead-end of the particle at low De, net motion towards the rod-end of the particle at intermediate De, and no appreciable propulsion at high De. At low De, where the particle time-scale is longer then the fluid relaxation time, we believe that propulsion is caused by an imbalance in the fluid first normal stress differences between the two ends of the particle (bead and rod). At De~1, however, we observe the emergence of a region of network anisotropy near the rod using birefringence imaging. This anisotropy suggests alignment of the micellar network, which is "locked in" due to the shorter time-scale of the particle relative to the fluid

    Group metacognitive therapy for repetitive negative thinking in primary and non-primary generalized anxiety disorder: An effectiveness trial

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    Background Generalized anxiety disorder (GAD) is a common and highly comorbid anxiety disorder characterized by repetitive negative thinking (RNT). Treatment trials tend to exclude individuals with non-primary GAD, despite this being a common presentation in real world clinics. RNT is also associated with multiple emotional disorders, suggesting that it should be targeted regardless of the primary disorder. This study evaluated the acceptability and effectiveness of brief group metacognitive therapy (MCT) for primary or non-primary GAD within a community clinic. Methods Patients referred to a specialist community clinic attended six, two-hour weekly sessions plus a one-month follow-up (N=52). Measures of metacognitive beliefs, RNT, symptoms, positive and negative affect, and quality of life were completed at the first, last, and follow-up sessions. Results Attrition was low and large intent-to-treat effects were observed on most outcomes, particularly for negative metacognitive beliefs and RNT. Treatment gains increased further to follow-up. Benchmarking comparisons demonstrated that outcomes compared favorably to longer disorder-specific protocols for primary GAD. Limitations No control group or independent assessment of protocol adherence. Conclusions Brief metacognitive therapy is an acceptable and powerful treatment for patients with primary or non-primary GAD

    The tonotopic organization of the auditory thalamus of the squirrel monkey (Saimiri sciureus)

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    Single unit responses were recorded from the auditory thalamus of anesthetized squirrel monkeys. The microelectrode penetrations had an orientation perpendicular to the sagittal plane. The small cell division is tonotopically organized. The cells in the most lateral aspect of this division have their `best frequencies' (BFs) in the low frequency range with a progressive shift in the BF toward the higher frequencies the further medially the sampling progressed. Dorsal to and extending ventromedially are large cells which are darkly stained. In addition there is a bulbous extension more ventrally of large cells less dense and perhaps less darkly stained. The large cells in these subdivisions did not always discharge spontaneously nor were they always responsive to tones. In the dorsal group, there is an initial low to high sequence of BF followed by one or more reversals in BF. Within the border region between the small cell division and both the ventromedial extension and bulbous extension of the large cells there starts a reversal, a high-to-low sequence which occurs within a comparatively short distance. Beyond the initial reversal, in both subdivisions, there are one or two additional reversals of BF.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22426/1/0000876.pd

    Magnetour: Surfing Planetary Systems on Electromagnetic and Multi-Body Gravity Fields

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    In this NIAC Phase One study, we propose a new mission concept, named Magnetour, to facilitate the exploration of outer planet systems and address both power and propulsion challenges. Our approach would enable a single spacecraft to orbit and travel between multiple moons of an outer planet, with no propellant required. Our approach would enable a single spacecraft to orbit and travel between multiple moons of an outer planet, with no propellant nor onboard power source required. To achieve this free-lunch _Grand Tour', we exploit the unexplored combination of magnetic and multi-body gravitational fields of planetary systems, with a unique focus on using a bare tether for power and propulsion. The main objective of the study is to develop this conceptually novel mission architecture, explore its design space, and investigate its feasibility and applicability to enhance the exploration of planetary systems within a 10-year timeframe. Propellantless propulsion technology offers enormous potential to transform the way NASA conducts outer planet missions. We hope to demonstrate that our free-lunch tour concept can replace heavy, costly, traditional chemical-based missions and can open up a new variety of trajectories around outer planets. Leveraging the powerful magnetic and multi-body gravity fields of planetary systems to travel freely among planetary moons would allow for long-term missions and provide unique scientific capabilities and flagship-class science for a fraction of the mass and cost of traditional concepts. New mission design techniques are needed to fully exploit the potential of this new concept.This final report contains the results and findings of the Phase One study, and is organized as follows. First, an overview of the Magnetour mission concept is presented. Then, the research methodology adopted for this Phase One study is described, followed by a brief outline of the main findings and their correspondence with the original Phase One task plan. Next, an overview of the environment of outer planets is provided, including magnetosphere, radiation belt and planetary moons. Then performance of electrodynamic tethers is assessed, as well as other electromagnetic systems. A method to exploit multi-body dynamics is given next. These analyses allow us to carry out a Jovian mission design to gain insight in the benefits of Magnetour. In addition, a spacecraft configuration is presented that fully incorporates the tether in the design. Finally technology roadmap considerations are discussed

    Bose-Einstein condensates in standing waves: The cubic nonlinear Schroedinger equation with a periodic potential

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    We present a new family of stationary solutions to the cubic nonlinear Schroedinger equation with a Jacobian elliptic function potential. In the limit of a sinusoidal potential our solutions model a dilute gas Bose-Einstein condensate trapped in a standing light wave. Provided the ratio of the height of the variations of the condensate to its DC offset is small enough, both trivial phase and nontrivial phase solutions are shown to be stable. Numerical simulations suggest such stationary states are experimentally observable.Comment: 4 pages, 4 figure

    Rice Fertilizer Recommendations.

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