3,362 research outputs found

    Fetters of Debt, Deposit, or Gold during the Great Depression? The International Propagation of the Banking Crisis of 1931

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    A banking crisis began in Austria in May 1931 and intensified in July, when runs struck banks throughout Germany. In September, the crisis compelled Britain to quit the gold standard. Newly discovered data shows that failure rates rose for banks in New York City, at the center of the United States money market, in July and August 1931, before Britain abandoned the gold standard and before financial outflows compelled the Federal Reserve to raise interest rates. Banks in New York City had large exposures to foreign deposits and German debt. This paper tests to see whether the foreign exposure of money center banks linked the financial crises on the two sides of the Atlantic.

    A case study of black West Indian migrants in urban Canada: The decision to migrate

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    The main purpose of this study is to examine the extent to which traditional models of the migration decision making process adequately account for and describe the decision making process of black West Indian immigrants in Canada. Traditional models of the migration decision making process have suggested that individuals migrate after a rational comparison of place utilities (Wolpert, 1964; Roseman, 1971). These human capital models of migration (De Jong et al, 1981) suggest that individuals, acting in a very rational manner, seek always to maximize their “profits” at an optimum location. However, this study suggests that in the case of the black West Indian migrant potential migrants are not undertaking such an unemotional, calm and rational comparison of place utilities. Rather, it would appear that the decision to migrate is often based on a commonly held notion that migration is the best, inevitable and perhaps only option to be considered by large sections of the population. It would appear that in many cases long before the actual opportunity to migrate presents itself, many black West Indians have already decided that they will eventually leave the Caribbean. The main methodology employed here is a case study of the experiences of five black West Indian immigrants in Canada. Aspects of black West Indians culture such as music, literature and history are also examined to demonstrate the extent to which migration has become a major institution within the Caribbean. The institutionalisation of migration within the Caribbean therefore appears to influence individuals to such a degree that many are loathed to consider any other alternative. Evidence from the case studies appears to confirm the notion that traditional models of migratory behavior have failed to take into account the crucial role of cultural influences in migration decision making. Such a failure ignores a crucial element in any attempt to understand the migration of black West Indians

    Collisional Formation and Modeling of Asteroid Families

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    In the last decade, thanks to the development of sophisticated numerical codes, major breakthroughs have been achieved in our understanding of the formation of asteroid families by catastrophic disruption of large parent bodies. In this review, we describe numerical simulations of asteroid collisions that reproduced the main properties of families, accounting for both the fragmentation of an asteroid at the time of impact and the subsequent gravitational interactions of the generated fragments. The simulations demonstrate that the catastrophic disruption of bodies larger than a few hundred meters in diameter leads to the formation of large aggregates due to gravitational reaccumulation of smaller fragments, which helps explain the presence of large members within asteroid families. Thus, for the first time, numerical simulations successfully reproduced the sizes and ejection velocities of members of representative families. Moreover, the simulations provide constraints on the family dynamical histories and on the possible internal structure of family members and their parent bodies.Comment: Chapter to appear in the (University of Arizona Press) Space Science Series Book: Asteroids I

    Fragment properties at the catastrophic disruption threshold: The effect of the parent body's internal structure

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    Numerical simulations of asteroid break-ups, including both the fragmentation of the parent body and the gravitational interactions between the fragments, have allowed us to reproduce successfully the main properties of asteroid families formed in different regimes of impact energy, starting from a non-porous parent body. In this paper, using the same approach, we concentrate on a single regime of impact energy, the so-called catastrophic threshold usually designated by Q*D, which results in the escape of half of the target's mass. Thanks to our recent implementation of a model of fragmentation of porous materials, we can characterize Q*D for both porous and non-porous targets with a wide range of diameters. We can then analyze the potential influence of porosity on the value of Q*D, and by computing the gravitational phase of the collision in the gravity regime, we can characterize the collisional outcome in terms of the fragment size and ejection speed distributions, which are the main outcome properties used by collisional models to study the evolutions of the different populations of small bodies. We also check the dependency of Q*D on the impact speed of the projectile. In the strength regime, which corresponds to target sizes below a few hundreds of meters, we find that porous targets are more difficult to disrupt than non-porous ones. In the gravity regime, the outcome is controlled purely by gravity and porosity in the case of porous targets. In the case of non-porous targets, the outcome also depends on strength. We then propose some power-law relationships between Q*D and both target's size and impact speed that can be used in collisional evolution models.Comment: 18 pages, 19 Figures. Accepted for publication in Icaru

    Short-term impact of bariatric surgery on best-corrected distance visual acuity and diabetic retinopathy progression

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    The immediate impact of rapid glucose lowering induced by bariatric surgery on diabetic retinopathy (DR) progression remains unclear. We present 3-year changes in the best-corrected visual acuity and DR grade in a retrospective observational study of 32 morbidly obese patients (64 eyes) who underwent Roux-en-Y-gastric bypass surgery. We found that despite overall benefits in vision, there was an initial progression from no retinopathy to background retinopathy in 18.9% and 21.7% at years 1 and 2 respectively. Patients with pre-proliferative DR at baseline were at increased risk of developing sight-threatening DR. We recommend that patients with diabetes undergoing bariatric surgery have a baseline visual acuity, macular optical coherent tomography and diabetic retinopathy grading from wide-field digital imaging to identify those at risk of sight-threatening diabetic retinopathy
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