2,755 research outputs found

    Competition on MARS? A study of broker-dealer competition in the U.S. municipal auction rate securities market

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    The relationship between competitive bidding in auctions and its impact on price and interest rates has long been of importance for a wide range of market practitioners. Although research has shown that increased competition among broker-dealers and bidders results in lower municipal interest rates, the amount of literature addressing auction rate securities is almost non-existent. The U.S. municipal auction rate securities market (MARS) offers an opportunity to expand the growing but limited empirical analysis of auctions. In particular, researchers can study the impact of market power and competitive search on interest rates using this uniform pricing, multi-unit, frequently repeated dutch auction process. Furthermore, in general, previous cross-sectional models measuring relationships in standard municipal markets are quite static in that they mostly assume some form of dynamic parametric homogeneity. Using a novel empirical approach, i.e., one that doesn't assume the time-constancy of cross-sectional parameters, our research shows that greater underwriter competition and search for potential investors in the form of multiple broker-dealers does indeed lead to lower municipal auction rates. This outcome does not hold for the entire sample life of the security--a result that was captured clearly using our methodology.MARS, municipal auctions, securities, parametric heterogeneity

    SPECIES RECOGNITION IS DRIVING EVOLUTION OF THE ACOUSTIC MATING SYSTEM OF SHIELD BACK KATYDIDS (ORTHOPTERA: TETTIGONIIDAE: AGLAOTHORAX): BEHAVIORAL AND PHYLOGENETIC EVIDENCE

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    Sexual selection and species recognition are two processes that may drive evolution of mating systems and contribute to speciation. Evidence from nature is rare. I asked whether song evolution in shield-back katydids (Aglaothorax) from southern California is consistent with either of these processes. Analysis of male song recordings identified four variable characters, and revealed a song cline in the Transverse Ranges. Of the variable song characters, I estimated female preferences for pulse number and interpulse interval, the former with choice tests on a Y-maze and the latter with no-choice tests on a locomotion compensator. Females of two coexisting Transverse Range species each discriminated against the interpulse intervals of the other. Phylogenetic relationships inferred from nuclear gene fragments were used to reconstruct ancestral distributions and song evolution. Significantly higher rates of song evolution were shown for the species coexisting in response to secondary contact, results consistent with species recognition

    Measuring the Cosmic Equation of State with Counts of Galaxies

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    The classical dN/dz test allows the determination of fundamental cosmological parameters from the evolution of the cosmic volume element. This test is applied by measuring the redshift distribution of a tracer whose evolution in number density is known. In the past, ordinary galaxies have been used as such a tracer; however, in the absence of a complete theory of galaxy formation, that method is fraught with difficulties. In this paper, we propose studying instead the evolution of the apparent abundance of dark matter halos as a function of their circular velocity, observable via the linewidths or rotation speeds of visible galaxies. Upcoming redshift surveys will allow the linewidth distribution of galaxies to be determined at both z~1 and the present day. In the course of studying this test, we have devised a rapid, improved semi-analytic method for calculating the circular velocity distribution of dark halos based upon the analytic mass function of Sheth et al. (1999) and the formation time distribution of Lacey & Cole (1993). We find that if selection effects are well-controlled and minimal external constraints are applied, the planned DEEP Redshift Survey should allow the measurement of the cosmic equation-of-state parameter w to 10% (as little as 3% if Omega_m has been well-determined from other observations). This type of test has the potential also to provide a constraint on any evolution of w such as that predicted by ``tracker'' models.Comment: 4 pages plus 3 embedded figures; version approved by Ap. J. Letters. A greatly improved error analysis has been added, along with a figure showing complementarity to other cosmological test

    Competition on MARS? A study of broker-dealer competition in the U.S. municipal auction rate securities market

    Get PDF
    The relationship between competitive bidding in auctions and its impact on price and interest rates has long been of importance for a wide range of market practitioners. Although research has shown that increased competition among broker-dealers and bidders results in lower municipal interest rates, the amount of literature addressing auction rate securities is almost non-existent. The U.S. municipal auction rate securities market (MARS) offers an opportunity to expand the growing but limited empirical analysis of auctions. In particular, researchers can study the impact of market power and competitive search on interest rates using this uniform pricing, multi-unit, frequently repeated dutch auction process. Furthermore, in general, previous cross-sectional models measuring relationships in standard municipal markets are quite static in that they mostly assume some form of dynamic parametric homogeneity. Using a novel empirical approach, i.e., one that doesn't assume the time-constancy of cross-sectional parameters, our research shows that greater underwriter competition and search for potential investors in the form of multiple broker-dealers does indeed lead to lower municipal auction rates. This outcome does not hold for the entire sample life of the security--a result that was captured clearly using our methodology

    Anaxipha hyalicetra sp. n. (Gryllidae, Trigonidiinae), a new sword-tailed cricket species from Arizona

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    A new Anaxipha species is described from a locality in southeastern Arizona adjacent to the border with Mexico. The species is unique among the North American fauna by virtue of the broad tegmina, distinctive male genitalia, and calling song phrased in an irregular chirp with a variable pulse train rate. The possibility that the behavioral repertoire of this species includes aggressive song as well as calling song is discussed

    Rapid Transfer of Abstract Rules to Novel Contexts in Human Lateral Prefrontal Cortex

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    Flexible, adaptive behavior is thought to rely on abstract rule representations within lateral prefrontal cortex (LPFC), yet it remains unclear how these representations provide such flexibility. We recently demonstrated that humans can learn complex novel tasks in seconds. Here we hypothesized that this impressive mental flexibility may be possible due to rapid transfer of practiced rule representations within LPFC to novel task contexts. We tested this hypothesis using functional MRI and multivariate pattern analysis, classifying LPFC activity patterns across 64 tasks. Classifiers trained to identify abstract rules based on practiced task activity patterns successfully generalized to novel tasks. This suggests humans can transfer practiced rule representations within LPFC to rapidly learn new tasks, facilitating cognitive performance in novel circumstances

    A Conceptual Model for Navigating a Career Path in Medical School Leadership

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    There is a paucity of literature providing guidance to physicians hoping to attain a position as a medical school dean. Realizing this gap, the Society for Academic Emergency Medicine (SAEM) Faculty Development Committee organized an educational session focused on offering faculty guidance for obtaining a position in medical school leadership. The session involved panelists who are nationally known leaders in medical school administration and was successfully presented at the SAEM 2018 annual meeting in Indianapolis, Indiana. Knowledge and perspective gained both during this session and through literature review was analyzed using a conceptual thinking skills framework. This process offered insights that promoted the development of a conceptual model informed by current evidence and expert insight and rooted in educational, economic, and cognitive theory. This model provides a step‐by‐step guide detailing a process that physicians can use to create a plan for professional development that is informed, thoughtful, and individualized to their own needs to optimize their future chances of advancing to a career in medical school leadership.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146843/1/aet210212.pd

    Hydrodynamics of cold atomic gases in the limit of weak nonlinearity, dispersion and dissipation

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    Dynamics of interacting cold atomic gases have recently become a focus of both experimental and theoretical studies. Often cold atom systems show hydrodynamic behavior and support the propagation of nonlinear dispersive waves. Although this propagation depends on many details of the system, a great insight can be obtained in the rather universal limit of weak nonlinearity, dispersion and dissipation (WNDD). In this limit, using a reductive perturbation method we map some of the hydrodynamic models relevant to cold atoms to well known chiral one-dimensional equations such as KdV, Burgers, KdV-Burgers, and Benjamin-Ono equations. These equations have been thoroughly studied in literature. The mapping gives us a simple way to make estimates for original hydrodynamic equations and to study the interplay between nonlinearity, dissipation and dispersion which are the hallmarks of nonlinear hydrodynamics.Comment: 18 pages, 3 figures, 1 tabl

    Severity of Depression Predicts Remission Rates Using Transcranial Magnetic Stimulation

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    Background: Multiple factors likely impact response and remission rates in the treatment of depression with repetitive transcranial magnetic stimulation (rTMS). Notably the role of symptom severity in outcomes with rTMS is poorly understood.Objective/Hypothesis: This study investigated the predictors of achieving remission in patients suffering from depression who receive ≥3 rTMS treatments per week. Methods: Available data on 41 patients treated at Walter Reed National Military Medical Center from 2009 to 2014 were included for analysis. Patients received a range of pulse sequences from 3,000 to 5,000 with left sided or bilateral coil placement. Primary outcome measures were total score on the Patient Health Questionnaire (PHQ-9) or the Quick Inventory of Depressive Symptomatology—Self Rated (QIDS-SR). Remission was defined as a total score less than five, and response was defined as a 50% decrease in the total score on both outcome metrics. Outcomes in patients diagnosed as suffering from mild or moderate depression were compared to those suffering from severe depression. Results: Of the 41 patients receiving treatment, 16 reached remission by the end of treatment. Remission rate was associated with the initial severity of depression, with patients with mild or moderate depression reaching remission at a significantly higher rate than those with severe depression. Total number of rTMS sessions or length of treatment were not predictors of remission. Conclusion: Patients with a baseline level of depression characterized as mild or moderate had significantly better outcomes following rTMS compared to patients with severe depression
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