Dynamics of a classical Hall system driven by a time-dependent Aharonov--Bohm flux

We study the dynamics of a classical particle moving in a punctured plane under the influence of a strong homogeneous magnetic field, an electrical background, and driven by a time-dependent singular flux tube through the hole. We exhibit a striking classical (de)localization effect: in the far past the trajectories are spirals around a bound center; the particle moves inward towards the flux tube loosing kinetic energy. After hitting the puncture it becomes ``conducting'': the motion is a cycloid around a center whose drift is outgoing, orthogonal to the electric field, diffusive, and without energy loss

A constant of quantum motion in two dimensions in crossed magnetic and electric fields

We consider the quantum dynamics of a single particle in the plane under the influence of a constant perpendicular magnetic and a crossed electric potential field. For a class of smooth and small potentials we construct a non-trivial invariant of motion. Do to so we proof that the Hamiltonian is unitarily equivalent to an effective Hamiltonian which commutes with the observable of kinetic energy.Comment: 18 pages, 2 figures; the title was changed and several typos corrected; to appear in J. Phys. A: Math. Theor. 43 (2010

Detection of gaps in the spatial coverage of coral reef monitoring projects in the US Caribbean and Gulf of Mexico

As part of the US Coral Reef Task Force\u27s National Program to Map, Assess, Inventory, and Monitor US Coral Reef Ecosystems, a comprehensive survey of projects/programs monitoring coral reef ecosystems and related habitats (i.e., seagrass beds and mangroves) in the US Caribbean and Pacific was undertaken. Information was gathered on a total of 296 monitoring and assessment projects conducted since 1990 in the US Caribbean and the Gulf of Mexico. Substantial gaps in monitoring coverage of US coral reef ecosystems were revealed through geographic information system (GIS) analysis of survey metadata. Although southern Florida contains approximately two-thirds of all marine monitoring projects found in the US Caribbean and Gulf of Mexico, we were unable to identify any ongoing projects that monitor coral reefs along Florida\u27s western coast and off of the Florida Middle Grounds. Additionally, Florida is covered by approximately 1 900 km2 of mangroves, yet there were only four ongoing projects that monitor this ecosystem, leaving gaps in coverage in the Lower and Middle Keys and along the eastern and western coasts. The Flower Garden Banks National Marine Sanctuary, located offshore of the Texas/Louisiana border, has an integral long-term monitoring program, but lacks a monitoring project that gathers long-term, quantitative data on reef fish abundance and certain water quality parameters. Numerous coral reef monitoring projects in Puerto Rico are concentrated on the island\u27s southwestern coast surrounding La Parguera, while far fewer monitoring projects are conducted along the northern and southeastern coasts and around Vieques Island. In the US Virgin Islands, the paucity of monitoring projects in large areas of St. Croix and St. Thomas contrasts with monitoring activity in three marine protected areas (MPAs), where 66% of the US Virgin Islands\u27 coral reef monitoring sites were found. Only a series of assessments have been conducted at Navassa, a small, uninhabited island located 55 km west of Haiti and 137 km northeast of Jamaica. In order to better understand changes in coral reef communities and to produce a series of biennial reports on the status of US coral reef ecosystems, the National Oceanic and Atmospheric Administration (NOAA) is developing a national coral reef monitoring network. This network has already begun to fill some of these gaps in monitoring coverage through issuing cooperative grants to states and territories to build long-term monitoring capacity

On the Way to Health

Information technology (IT) has fundamentally changed the way we work, bank, and communicate. Its impact on health care and health research, however, has been limited by the lack of a comprehensive infrastructure to connect patients, providers, and researchers. As we learn more about how to address the unhealthy behaviors that underlie many chronic conditions, researchers are seeking IT solutions to connect to patients in scalable ways. This Issue Brief describes the development and use of a new web-based IT platform, Way to Health, to deliver and evaluate behavioral interventions to improve health

What Business are We In? The Emergence of Health as the Business of Health Care

On January 19, 2012, after 131 years of operation, the Eastman Kodak Company filed for Chapter 11 protection in U.S. bankruptcy court. No doubt some people were surprised by this filing, because they grew up at a time when bright yellow boxes of film accompanied every family vacation and celebration. Those who were paying more attention offered many explanations for the bankruptcy. Central among them was that Kodak was late to recognize that it was not in the film and camera business: it was in the imaging business. With the advent of digital imaging, Kodak was outpaced by other companies that could better achieve consumer goals

Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network

The coupled plate interface of subduction zones—commonly called the seismogenic zone—has been recognized as the origin of fatal earthquakes. A subset of the after-shock series of the great Antofagasta thrust-type event (1995 July 30; Mw= 8.0) has been used to study the extent of the seismogenic zone in northern Chile. To achieve reliable and precise hypocentre locations we applied the concept of the minimum 1-D model, which incorporates iterative simultaneous inversion of velocity and hypocentre parameters. The minimum 1-D model is complemented by station corrections which are influenced by near-surface velocity heterogeneity and by the individual station elevations. By relocating mine blasts, which were not included in the inversion, we obtain absolute location errors of 1 km in epicentre and 2 km in focal depth. A study of the resolution parameters ALE and DSPR documents the importance of offshore stations on location accuracy for offshore events. Based on precisely determined hypo-centres we calculate a depth of 46 km for the lower limit of the seismogenic zone, which is in good agreement with previous studies for this area. For the upper limit we found a depth of 20 km. Our results of an aseismic zone between the upper limit of the seismogenic zone and the surface correlates with a detachment zone proposed by other studies; the results are also in agreement with thermal studies for the Antofagasta forearc regio

Incentives in Health: Different Prescriptions for Physicians and Patients

Financial incentives abound in health care. They are found in the ways physicians are paid and in the ways health insurance coverage, co-payments, and deductibles are structured for patients. The effects of these incentives are often understood through conventional economic principles, with the assumption that individuals are self-interest maximizers who respond directly to changes in incentives. In contrast, behavioral economics imports insights from psychology and recognizes that individuals often do not respond to incentives as rationally as they might. In some cases, individuals lack information, but in others, they just seem to act contrary to their own known interests, for example, when they overeat, fail to take medication, or neglect to wear seat belts

Assessing Value in Health Care Programs

Many health care services provided in the United States are of low value, meaning that the cost of providing those services is high relative to the health care benefit they confer. In some cases, the care provided may have no value or even, on average, may be harmful. Examples of low- or negative-value services include unnecessary surgery or diagnostic imaging that will not change management. Given estimates that 30% of the $2.5 trillion the United States spends on health care services each year may provide little benefit,1 there is a widespread eagerness to enhance the ratio of benefits to costs