1,721 research outputs found

    My Three Cats and the Apocalypse

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    Essays on the influence of experience and environment on behavior

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    This dissertation explores how experience and environment impact behavior. In the first chapter, I provide behavioral foundations for a model of taste uncertainty with endogenous learning through consumption. In this setting, uncertainty is over an unobservable, subjective state space. Preference over lottery-menu pairs is sufficient to identify the state space and the learning process. In this model, the agent is viewed as if he learns the utility of an object upon its consumption. This information is used to improve choice from the follow-on menu. This implies a trade-off between consumption value and information leading to experimentation. I provide a behavioral definition of experimentation. While the literature focuses on identifying subjective states through a demand for flexibility, I show that experimentation also (partially) identifies taste uncertainty. The second chapter explores the potential for social networks to affect decisions of political leaders. To this end we construct a database linking European royal kinship networks, monarchies, and wars to study the effect of family ties on conflict. To establish causality, we exploit decreases in connection caused by apolitical deaths of network important individuals. These deaths are associated with substantial increases in the frequency and duration of war. We provide evidence that these deaths affect conflict only through changing the kinship network. Over our period of interest, the percentage of European monarchs with kinship ties increased threefold. Together, these findings help explain the well-documented decrease in European war frequency. The final chapter builds on the robust finding from the psychology literature that the co-presentation of products causes consumers to associate them. Associated products are evaluated more similarly. Supposing that agents behave according to this evidence, I axiomatically derive a tractable utility model of this association effect. In an application, I study a two-product monopolist that can strategically choose whether or not to offer his products under the same brand. I demonstrate that psychological association can provide strict incentives for either brand extension or brand differentiation depending on the distribution of product valuations in the market. Appropriate branding strategies allow firms to extract more surplus from consumers when psychological association is present

    Magnificent Constructions: The Role of Environment on the Stellar Mass Growth of Massive Galaxies

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    To understand how the present day universe came to be, we must understand how the massive structures in which we live formed and evolved over the preceding billions of years. Constraining how galaxies grow are the most massive galaxies, called brightest cluster galaxies (BCGs). These luminous and diffuse elliptical galaxies inhabit relaxed positions within their host cluster\u27s gravitational potentials and provide a look at the high mass extreme of galaxy evolution. The relaxed structure, old stellar populations, and central location within the cluster indicate a high redshift formation scenario, however, star-forming BCGs have been observed at much more recent epochs. Addressing this evolutionary complexity, my dissertation consists of four studies to investigate the growth rates of BCGs over several epochs, and how they relate to the growth of the general galaxy population. In my first paper, I present a multiwavelength (far-ultraviolet to far-infrared) study of BCG star formation rates and stellar masses from 0.2 \u3c z \u3c 0.7 (Cooke et al. 2016), selected from the CLASH and SGAS surveys. I find that in-situ star formation in my sample is consistent with overall quiescence, and star-forming BCGs remain very rare. In my second paper (Cooke et al. 2018), my sample\u27s redshift range is expanded to z ~ 1 with the addition of massive BCGs (M_Stellar \u3e 10^11 M_Solar) from galaxy clusters available in the COSMOS X-ray Group Catalog. I find that star formation is roughly constant in our sample of high mass BCGs from 0.3 \u3c z \u3c 1.0, with a possible decrease at lower redshifts. We also find a growth rate of ~1% yr^-1, inconsistent with portions of the literature that find an order of magnitude higher growth from infrared selected samples. My third paper (Cooke et al. 2019) identifies BCG progenitors out to z ~ 3 using cumulative comoving number density tracks from the Illustris Project. We identify three phases of growth, limiting the star-formation dominated epoch to z \u3e 2.25. Finally, my fourth paper (Cooke et al. in preparation) places the preceding results in context by measuring the correlation between star formation rate and stellar mass for all galaxies above the COSMOS mass completeness limit from 0 \u3c z \u3c 3.5

    The effects of postactivation potentiation on sprint and jump performance of male academy soccer players.

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    The purpose of this investigation was to evaluate the postactivation potentiation (PAP) effects of both dynamic and isometric maximum voluntary contractions (MVCs) on sprint and jump performance and establish whether PAP methods could be used effectively in warm up protocols for soccer players. Twelve male soccer players performed 4 warm up protocols in a cross-over, randomized, and counterbalanced design. In addition to a control warm up, subjects performed deadlift (5 repetitions at 5 repetitions maximum), tuck jump (5 repetitions), and isometric MVC knee extensions (3 repetitions for 3 s) as PAP treatments in an otherwise identical warm up protocol. After each treatment, the subjects underwent 3 10 m and 20 m sprints 4, 5, and 6 minutes post-warm up and 3 vertical jumps (VJ) at 7, 8, and 9 minutes post-warm up. Repeated measures analysis of variance showed no significant differences in the first 10 m (p = 0.258) and 20 m (p = 0.253) sprint and VJ (p = 0.703) performance and the average 10 m (p = 0.215), 20 m (p = 0.388), and VJ (p = 0.529) performance between conditions. There were also no significant differences in performance responses between the strongest and weakest subjects, but large variations in individual responses were found between the subjects. The findings suggest that there was no significant group PAP effect on sprint and jump performance after dynamic and isometric MVCs compared with a control warm up protocol. However, the large variation in individual responses (-7.1% to +8.2%) suggests PAP should be considered on an individual basis. Factors such as method, volume, load, recovery, and interindividual variability of PAP must be considered in the practical application of PAP and the rigorous research design of future studies to evaluate the potential for performance enhancement

    A Network of Thrones: Kinship and Conflict in Europe, 1495–1918

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    We construct a database linking European royal kinship networks, monarchies, and wars to study the effect of family ties on conflict. To establish causality, we exploit decreases in connection caused by apolitical deaths of rulers\u27 mutual relatives. These deaths are associated with substantial increases in the frequency and duration of war. We provide evidence that these deaths affect conflict only through changing the kinship network. Over our period of interest, the percentage of European monarchs with kinship ties increased threefold. Together, these findings help explain the well-documented decrease in European war frequency

    Physiological correlates of performance in international-standard squash players

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    Tactical, technical and fitness factors are important for success in elite squash. While tactical and endurance fitness aspects have been explored, altered demands that have resulted from rule changes and absence of specific tests of high-intensity exercise capabilities have prevented identification of elements of fitness that correlate with performance in elite-standard players. Accordingly, the purpose of this study was to investigate relationships between test scores and player rank in such players. With institutional ethics approval, 31 players from the England Squash performance programme participated (11 women and 20 men, mean±SD body mass 62.4±5.5 kg and 73.1±7.5 kg respectively). After habituation, participants completed countermovement and drop-jump tests, squash-specific tests of change-of-direction speed and multiple-sprint ability and the multistage fitness test in one test session. Short recoveries were allowed between tests. World rank at the time of testing was obtained from the Professional Squash Association website. In men, change-of-direction speed (??=?0.59, p?=?0.02, n?=?14) multiple-sprint ability (??=?0.78, p<0.01, n?=?13) and fastest sprint from the multiple-sprint test (??=?0.86, p<0.01, n?=?13) correlated with world rank. In women, only fastest repetition from the multiple-sprint test correlated with world rank (??=?0.65, p?=?0.04, n?=?10). Measures of high-intensity exercise capability correlated with world rank in elite-standard men and women players. Endurance capability did not relate to rank in either the men or women. The results suggest that high-intensity, variable-direction exercise capabilities are important for success in elite squash

    Upper boundary condition for asteroseismological modelling of solar-type stars

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    ix, 67 leaves : col. ill. ; 29 cm.Includes abstract.Includes bibliographical references (leaves 65-67).We present a grid of line blanketed spherical LTE model atmospheres and high resolution extinction spectra for use in interpolating an accurate outer boundary condition for asteroseismology calculations at arbitrary T[subscript eff] and log g. We investigate the accuracy of four interpolation methods by interpolating within our grid to solar values of T[subscript eff] and log g and comparing the results to an exact solar model. We test the impact of the resolution of our grid on the accuracy of the interpolations by performing linear interpolations within our grid at different sampling rates in T[subscript eff] and log g. We test whether interpolating k[subscript R] within our grid and computing T[subcript R] or calculating T[subscript R] for each model and interpolating it directly produces more accurate results. We also present a NLTE exact solar model and compare the boundary condition resulting from it to those of the LTE exact model

    Correlated X-ray and Optical Variability in Mkn 509

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    We present results of a 3 year monitoring campaign of the Seyfert 1 galaxy Markarian 509, using X-ray data from the Rossi X-ray Timing Explorer (RXTE) and optical data taken by the SMARTS consortium. Both light curves show significant variations, and are strongly correlated with the optical flux leading the X-ray flux by 15 days. The X-ray power spectrum shows a steep high-frequency slope of -2.0, breaking to a slope of -1.0 at at timescale of 34 days. The lag from optical to X-ray emission is most likely caused by variations in the accretion disk propagating inward.Comment: 13 pages, 3 figures. Accepted for publication in the Astrophysical Journa

    A self-insulating, high-power, microwave source

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    We present first predictions for the performance of a novel, mildly relativistic (500keV, 2kA), X-band Cherenkov oscillator, nominally a variant of the backward-wave oscillator. The source operates with no externally-applied magnetic insulation, relying only on the self-fields of the electron beam for propagation. This significantly reduces the overall energy requirements for operation, along with the complexity; conventional (magnetically insulated) sources of this type typically require magnetic field strengths of 1 – 2T for efficient beam propagation, translating to a relatively large solenoid and associated power-supply. By eliminating this factor, the overall-efficiency of the source is tightly coupled to the conversion-efficiency between the beam and the wave. Conversion efficiencies in excess of 30% have been predicted for the source, when driven by a high-quality electron beam; the parameters of which were determined via numerical modelling of the electron gun. A tolerance study of variation in the beam parameters shows the efficiency remains better than ∼25% over the variation in critical control parameters expected in experiment, with clean excitation of the intended TM01 operating mode achieved at a stable output frequency of ~9.4GHz. The resonant frequency of the source was found to be insensitive to variation in the electron energy over an extended range (400-600keV)
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