2,967 research outputs found
Competition on MARS? A study of broker-dealer competition in the U.S. municipal auction rate securities market
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
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The Potosi Mita under Hapsburg administration : the seventeenth century.
The mita was a draft Indian labor system that Viceroy Francisco de Toledo developed in 1573 for the silver industry at Potos(\u27)i (in colonial Upper Peru; current-day Bolivia). For a brief period the mita served, in combination with the introduction of amalgamation technology, stockpiles of previously unrefinable ore and a large capital investment by the mine and mill owners (azogueros) to cause a boom in production. By 1600, however, the stockpiles of ore had been exhausted and the boom had given way to decreasing levels of silver production at Potos(\u27)i. The Indians who were serving in the mita (mitayos) had become more important to the industry, because they were now the principal means of obtaining ore, but their condition had deteriorated. As their own profits fell, the Indians began to flee from Potos(\u27)i and from the provinces that were subject to the mita. Their migration, which was caused by tribute requirements and other labor obligations as well, disrupted the social, economic and political order that the Spanish were trying to impose upon the Indians. Their method of resisting the invaders was passive, but the Indians were neither conquered nor submissive victims of the mita. The group that was caught between the continuing demand for mitayos at Potos(\u27)i and the decreasing number of Indians in the provinces was the caciques (Indian nobles). They were the key to the entire system, because they delivered the Indians to the mines and the mills. At first the caciques were able to meet their quotas by abridging the legal restrictions on the recruitment of the mitayos. But in the early seventeenth century they found themselves fined for the growing number of Indians that they were unable to deliver, and a new form of mita service was founded: service in silver, ostensibly to hire substitutes. By 1630, between one-third and one-half of the total delivery of mitayos to Potos(\u27)i was made in money. The azogueros used some of the silver they received from the caciques for operating funds, rather than to hire laborers. The mita therefore became a capital subsidy as well as forced labor system. The Hapsburg government of colonial Peru opposed the new form of mita service because it was an unauthorized arrangement between the azogueros and the caciques to which it was not a party. The crown\u27s ability to counter the de facto mita was restricted, however, by its isolation in Spain, by the time that was consumed by trans-Atlantic correspondence and by its own bureaucracy. The viceroys who were stationed in Lima were plagued by similar problems, and they depended upon the President of the Audiencia de Charcas and the Corregidor de Potos(\u27)i to administer the mita on a daily basis. A constant interplay of personal and professional jealousies among these officials, the viceroy\u27s reluctance to innovate and the contradictory orders that were issued from Lima and Madrid complicated the government\u27s efforts to reform the mita to the point of near-total ineffectiveness. In 1670, the Viceroy Conde de Lemos determined that the system could not be purged of the azogueros\u27 misuse of mita service in silver and the other abuses that stemmed from it, and he proposed that the system be abolished. The crown was reluctant to accept the loss of revenue that such an act would have entailed, and instead it ordered a total reformation of the mita. That program was executed during the 1680s, under the Viceroy Duque de la Palata. It too failed, because it was based on an untenable premise: that the Toledan mita could be re-established despite 110 years of economic, political and demographic change in Peru
SPECIES RECOGNITION IS DRIVING EVOLUTION OF THE ACOUSTIC MATING SYSTEM OF SHIELD BACK KATYDIDS (ORTHOPTERA: TETTIGONIIDAE: AGLAOTHORAX): BEHAVIORAL AND PHYLOGENETIC EVIDENCE
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
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
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
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
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
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
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
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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