Financial Crises and Macro-Prudential Policies

Stochastic general equilibrium models of small open economies with occasionally binding financial frictions are capable of mimicking both the business cycles and the crisis events associated with the sudden stop in access to credit markets (Mendoza, 2010). In this paper we study the inefficiencies associated with borrowing decisions in a two-sector small open production economy. We find that this economy is much more likely to display "under-borrowing" rather than "over-borrowing" in normal times. As a result, macro-prudential policies (i.e. Tobin taxes or economy-wide controls on capital inflows) are costly in welfare terms in our economy. Moreover, we show that macro-prudential policies aimed at minimizing the probability of the crisis event might be welfare-reducing in production economies. Our analysis shows that there is a much larger scope for welfare gains from policy interventions during financial crises. That is to say that, within our modeling approach, ex post or crisis-management policies dominate ex ante or macro-prudential ones.Capital controls, crises, financial frictions, macro prudential policies, bailouts,overborrowing

Revisiting Overborrowing and its Policy Implications

This paper analyzes quantitatively the extent to which there is overborrowing (i.e., inefficient borrowing) in a business cycle model for emerging market economies with production and an occasionally binding credit constraint. The main finding of the analysis is that overborrowing is not a robust feature of this class of model economies: it depends on the structure of the economy and its parametrization. Specifically, we find underborrowing in a production economy with our baseline calibration, but overborrowing with more impatient agents and more volatile shocks. Endowment economies display overborrowing regardless of parameter values, but they do not allow for policy intervention when the constraint binds (in crisis times). Quantitatively, the welfare gains from implementing the constrained efficient allocation are always larger near crisis times than in normal

Late-Time Convection in the Collapse of a 23 Solar Mass Star

The results of a 3-dimensional SNSPH simulation of the core collapse of a 23 solar mass star are presented. This simulation did not launch an explosion until over 600ms after collapse, allowing an ideal opportunity to study the evolution and structure of the convection below the accretion shock to late times. This late-time convection allows us to study several of the recent claims in the literature about the role of convection: is it dominated by an l=1 mode driven by vortical-acoustic (or other) instability, does it produce strong neutron star kicks, and, finally, is it the key to a new explosion mechanism? The convective region buffets the neutron star, imparting a 150-200 km/s kick. Because the l=1 mode does not dominate the convection, the neutron star does not achieve large (>450 km/s) velocities. Finally, the neutron star in this simulation moves, but does not develop strong oscillations, the energy source for a recently proposed supernova engine. We discuss the implications these results have on supernovae, hypernovae (and gamma-ray bursts), and stellar-massed black holes.Comment: 31 pages (including 13 figures), submitted to Ap

Age-related declines and disease-associated variation in immune cell telomere length in a wild mammal

publication-status: Publishedtypes: Article© 2014 Beirne et al.The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files.This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Immunosenescence, the deterioration of immune system capability with age, may play a key role in mediating age-related declines in whole-organism performance, but the mechanisms that underpin immunosenescence are poorly understood. Biomedical research on humans and laboratory models has documented age and disease related declines in the telomere lengths of leukocytes (‘immune cells’), stimulating interest their having a potentially general role in the emergence of immunosenescent phenotypes. However, it is unknown whether such observations generalise to the immune cell populations of wild vertebrates living under ecologically realistic conditions. Here we examine longitudinal changes in the mean telomere lengths of immune cells in wild European badgers (Meles meles). Our findings provide the first evidence of within-individual age-related declines in immune cell telomere lengths in a wild vertebrate. That the rate of age-related decline in telomere length appears to be steeper within individuals than at the overall population level raises the possibility that individuals with short immune cell telomeres and/or higher rates of immune cell telomere attrition may be selectively lost from this population. We also report evidence suggestive of associations between immune cell telomere length and bovine tuberculosis infection status, with individuals detected at the most advanced stage of infection tending to have shorter immune cell telomeres than disease positive individuals. While male European badgers are larger and show higher rates of annual mortality than females, we found no evidence of a sex difference in either mean telomere length or the average rate of within-individual telomere attrition with age. Our findings lend support to the view that age-related declines in the telomere lengths of immune cells may provide one potentially general mechanism underpinning age-related declines in immunocompetence in natural populations.Biotechnology and Biological Sciences Research Council (BBSRC)The Food and Environmental Research Agency (FERA

Mean shear flows generated by nonlinear resonant Alfven waves

In the context of resonant absorption, nonlinearity has two different manifestations. The first is the reduction in amplitude of perturbations around the resonant point (wave energy absorption). The second is the generation of mean shear flows outside the dissipative layer surrounding the resonant point. Ruderman et al. [Phys. Plasmas 4, 75 (1997)] studied both these effects at the slow resonance in isotropic plasmas. Clack et al. [Astron. Astrophys. 494}, 317 (2009)] investigated nonlinearity at the Alfven resonance, however, they did not include the generation of mean shear flow. In this present paper, we investigate the mean shear flow, analytically, and study its properties. We find that the flow generated is parallel to the magnetic surfaces and has a characteristic velocity proportional to $\epsilon^{1/2}$, where $\epsilon$ is the dimensionless amplitude of perturbations far away from the resonance. This is, qualitatively, similar to the flow generated at the slow resonance. The jumps in the derivatives of the parallel and perpendicular components of mean shear flow across the dissipative layer are derived. We estimate the generated mean shear flow to be of the order of $10{\rm kms}^{-1}$ in both the solar upper chromosphere and solar corona, however, this value strongly depends on the choice of boundary conditions. It is proposed that the generated mean shear flow can produce a Kelvin--Helmholtz instability at the dissipative layer which can create turbulent motions. This instability would be an additional effect, as a Kelvin--Helmholtz instability may already exist due to the velocity field of the resonant Alfven waves. This flow can also be superimposed onto existing large scale motions in the solar upper atmosphere.Comment: 11 page

GSA’s Commercial Marketplaces Initiative: Opening Amazon and Other Private Marketplaces To Direct Purchases By Government Users

The U.S. General Services Administration (GSA) opened a new chapter in public procurement by awarding three contracts—to Amazon Business, Overstock.com, and Fisher Scientific—that will allow federal users to buy directly from online electronic marketplaces, with sales anticipated to total $6 billion annually. This proof-of-concept effort, dubbed the “commercial platforms” initiative by GSA, marks a radical departure from traditional procurement practices because it will allow individual Government users (not necessarily procurement officials) to make “micro-purchases” (generally up to$10,000) using Government purchase cards. By removing the federal procurement system as an intermediary in the purchasing process, and in essence outsourcing the selection of available sources to private providers of electronic platforms, GSA’s initiative has both reshaped procurement and potentially redrawn a marketplace. This paper reviews the purpose and history of GSA’s commercial platforms initiative, which began with a mandate from Congress to explore electronic commerce options and evolved through long exchanges with industry, users, and other stakeholders. In assessing the reasons for the initiative, the paper notes a longstanding concern (framed by principles of agency theory) that users’ needs were not being met by the traditional procurement system. The paper discusses GSA’s decision to steer the initiative to existing commercial platforms and reviews key elements of the solicitation used to frame the “no-cost” contracts with the online marketplaces. Because Amazon Business was by far the most prominent of the awardees—indeed, Amazon had played an ongoing role in pressing for the procurement—and vendors may want to sell through the commercial platforms to reach federal customers, this paper focuses on Amazon Business’ procedures in discussing how vendors might join the commercial platforms. The paper concludes with a series of Guidelines that vendors and other market participants might use, as they enter this new corner of the federal marketplace

The Environments around Long-Duration Gamma-Ray Burst Progenitors

Gamma-ray burst (GRB) afterglow observations have allowed us to significantly constrain the engines producing these energetic explosions. Te redshift and position information provided by these afterglows have already allowed us to limit the progenitors of GRBs to only a few models. The afterglows may also provide another observation that can place further constraints on the GRB progenitor: measurements telling us about the environments surrounding GRBs. Current analyses of GRB afterglows suggest that roughly half of long-duration gamma-ray bursts occur in surroundings with density profiles that are uniform. We study the constraints placed by this observation on both the classic ``collapsar'' massive star progenitor and its relative, the ``helium-merger'' progenitor. We study several aspects of wind mass-loss and find that our modifications to the standard Wolf-Rayet mass-loss paradigm are not sufficient to produce constant density profiles. Although this does not rule out the standard ``collapsar'' progenitor, it does suggest a deficiency with this model. We then focus on the He-merger models and find that such progenitors can fit this particular constraint well. We show how detailed observations can not only determine the correct progenitor for GRBs, but also allow us to study binary evolution physics.Comment: 44 pages including 11 figure

Extreme morning chronotypes are often familial and not exceedingly rare: the estimated prevalence of advanced sleep phase, familial advanced sleep phase, and advanced sleep-wake phase disorder in a sleep clinic population.

Study objectivesReport the first prevalence estimates of advanced sleep phase (ASP), familial advanced sleep phase (FASP), and advanced sleep-wake phase disorder (ASWPD). This can guide clinicians on the utility of screening for extreme chronotypes both for clinical decision-making and to flag prospective participants in the study of the genetics and biology of FASP.MethodsData on morning or evening sleep schedule preference (chronotype) were collected from 2422 new patients presenting to a North American sleep center over 9.8 years. FASP was determined using a severity criterion that has previously identified dominant circadian mutations in humans. All patients were personally seen and evaluated by one of the authors (C.R.J.).ResultsOur results demonstrate an ASP prevalence of 0.33%, an FASP prevalence of 0.21%, and an ASWPD prevalence of at least 0.04%. Most cases of young-onset ASP were familial.ConclusionsAmong patients presenting to a sleep clinic, conservatively 1 out of every 300 patients will have ASP, 1 out of every 475 will have FASP, and 1 out of every 2500 will have ASWPD. This supports obtaining a routine circadian history and, for those with extreme chronotypes, obtaining a family history of circadian preference. This can optimize treatment for evening sleepiness and early morning awakening and lead to additional circadian gene discovery. We hope these findings will lead to improved treatment options for a wide range of sleep and medical disorders in the future

Real time unmanned aerial vehicle tracking of fast moving small target on ground

In order to solve problems of occlusion and fast motion of small targets in UAV (Unmanned Aerial Vehicle) target tracking , an adaptive algorithm which fuses the improved color histogram tracking response and the correlation filter tracking response based on multi-channel HOG features is proposed to realize small target tracking with high accuracy. The state judgment index is used to determine whether the target is in a fast motion or an occlusion state. In the fast motion state, the search area is enlarged, and the color optimal model which suppresses the suspected area is used for rough detection. Then, re-detection in the location of multiple peaks in the rough detection response is carried out using the correlation filter to accurately locate the target. In an occlusion state, the model stops updating, the search area is expanded, and the current color model is used for rough detection. Then, re-detection in the place of multiple peaks in the rough detection response is carried out using the correlation filter to accurately locate the target. Experimental results show that the proposed method can track small targets accurately. The frame rate of the proposed method is 40.23 frames/second, indicating usable real-time performance