Casimir force between sharp-shaped conductors

Casimir forces between conductors at the sub-micron scale cannot be ignored in the design and operation of micro-electromechanical (MEM) devices. However, these forces depend non-trivially on geometry, and existing formulae and approximations cannot deal with realistic micro-machinery components with sharp edges and tips. Here, we employ a novel approach to electromagnetic scattering, appropriate to perfect conductors with sharp edges and tips, specifically to wedges and cones. The interaction of these objects with a metal plate (and among themselves) is then computed systematically by a multiple-scattering series. For the wedge, we obtain analytical expressions for the interaction with a plate, as functions of opening angle and tilt, which should provide a particularly useful tool for the design of MEMs. Our result for the Casimir interactions between conducting cones and plates applies directly to the force on the tip of a scanning tunneling probe; the unexpectedly large temperature dependence of the force in these configurations should attract immediate experimental interest

The Casimir effect as scattering problem

We show that Casimir-force calculations for a finite number of non-overlapping obstacles can be mapped onto quantum-mechanical billiard-type problems which are characterized by the scattering of a fictitious point particle off the very same obstacles. With the help of a modified Krein trace formula the genuine/finite part of the Casimir energy is determined as the energy-weighted integral over the log-determinant of the multi-scattering matrix of the analog billiard problem. The formalism is self-regulating and inherently shows that the Casimir energy is governed by the infrared end of the multi-scattering phase shifts or spectrum of the fluctuating field. The calculation is exact and in principle applicable for any separation(s) between the obstacles. In practice, it is more suited for large- to medium-range separations. We report especially about the Casimir energy of a fluctuating massless scalar field between two spheres or a sphere and a plate under Dirichlet and Neumann boundary conditions. But the formalism can easily be extended to any number of spheres and/or planes in three or arbitrary dimensions, with a variety of boundary conditions or non-overlapping potentials/non-ideal reflectors.Comment: 14 pages, 2 figures, plenary talk at QFEXT07, Leipzig, September 2007, some typos correcte

Fluctuation induced quantum interactions between compact objects and a plane mirror

The interaction of compact objects with an infinitely extended mirror plane due to quantum fluctuations of a scalar or electromagnetic field that scatters off the objects is studied. The mirror plane is assumed to obey either Dirichlet or Neumann boundary conditions or to be perfectly reflecting. Using the method of images, we generalize a recently developed approach for compact objects in unbounded space [1,2] to show that the Casimir interaction between the objects and the mirror plane can be accurately obtained over a wide range of separations in terms of charge and current fluctuations of the objects and their images. Our general result for the interaction depends only on the scattering matrices of the compact objects. It applies to scalar fields with arbitrary boundary conditions and to the electromagnetic field coupled to dielectric objects. For the experimentally important electromagnetic Casimir interaction between a perfectly conducting sphere and a plane mirror we present the first results that apply at all separations. We obtain both an asymptotic large distance expansion and the two lowest order correction terms to the proximity force approximation. The asymptotic Casimir-Polder potential for an atom and a mirror is generalized to describe the interaction between a dielectric sphere and a mirror, involving higher order multipole polarizabilities that are important at sub-asymptotic distances.Comment: 19 pages, 7 figure

Importance of continued activation of thrombin reflected by fibrinopeptide A to the efficacy of thrombolysis

Factors responsible for initial success or failure of coronary thrombolysis and persistent recanalization or early reocclusion have not been thoroughly elucidated. Both adequate initial clot lysis and preclusion of rethrombosis are required. Failure may reflect clot lysis followed immediately or somewhat later by rethrombosis. To determine whether differences in the intensity and persistence of the activation of thrombin are determinants of success or failure of recanalization, plasma fibrinopeptide A, a fibrinogen product liberated by thrombin, was serially assayed in 19 patients treated with intravenous streptokinase. In patients exhibiting recanalization (n = 9), plasma fibrinopeptide A decreased after administration of streptokinase but before administration of heparin. In patients without initially apparent recanalization, fibrinopeptide A increased, suggesting ongoing thrombosis, and subsequently decreased promptly after heparin. In patients with initial recanalization followed by overt reocclusion the pattern was different. Despite recanalization, fibrinopeptide A continued to rise markedly. Elevations persisted despite administration of heparin. Thus, inhibition of activation of thrombin is associated with successful recanalization. Conversely, persistent activation of thrombin may be a predisposing factor to both apparent initial failure of recanalization and nvprt early reocclusion

Exploring the Role of Natural Gas in U.S. Trucking (Revised Version)

The recent emergence of natural gas as an abundant, inexpensive fuel in the United States could prompt a momentous shift in the level of natural gas utilized in the transportation sector. The cost advantage of natural gas vis-à-vis diesel fuel is particularly appealing for vehicles with a high intensity of travel and thus fuel use. Natural gas is already a popular fuel for municipal and fleet vehicles such as transit buses and taxis. In this paper, we investigate the possibility that natural gas could be utilized to provide fuel cost savings, geographic supply diversity and environmental benefits for the heavy-duty trucking sector and whether it can enable a transition to lower carbon transport fuels. We find that a small, cost-effective intervention in markets could support a transition to a commercially sustainable natural gas heavyduty fueling system in the state of California and that this could also advance some of the state’s air quality goals. Our research shows that an initial advanced natural gas fueling system in California could facilitate the expansion to other U.S. states. Such a network would enable a faster transition to renewable natural gas or biogas and waste-to-energy pathways. Stricter efficiency standards for natural gas Class 8 trucks and regulation of methane leakage along the natural gas supply chain would be necessary for natural gas to contribute substantially to California’s climate goals as a trucking fuel. To date, industry has favored less expensive technologies that do not offer the highest level of environmental performance

Parity violating cylindrical shell in the framework of QED

We present calculations of Casimir energy (CE) in a system of quantized electromagnetic (EM) field interacting with an infinite circular cylindrical shell (which we call `the defect'). Interaction is described in the only QFT-consistent way by Chern-Simon action concentrated on the defect, with a single coupling constant $a$. For regularization of UV divergencies of the theory we use % physically motivated Pauli-Villars regularization of the free EM action. The divergencies are extracted as a polynomial in regularization mass $M$, and they renormalize classical part of the surface action. We reveal the dependence of CE on the coupling constant $a$. Corresponding Casimir force is attractive for all values of $a$. For $a\to\infty$ we reproduce the known results for CE for perfectly conducting cylindrical shell first obtained by DeRaad and Milton.Comment: Typos corrected. Some references adde

Design and baseline data from the vanguard of the Comparison of Depression Interventions after Acute Coronary Syndrome (CODIACS) randomized controlled trial

This paper describes the rationale and design of the vanguard for the Comparison of Depression Interventions after Acute Coronary Syndrome (CODIACS), a multicenter, randomized, controlled trial of a patient preference‐based, stepped care protocol for persistent depressive symptoms after acute coronary syndrome (ACS). The overall aim of the vanguard phase was to determine whether the patient-preference, stepped care protocol, which is based on the intervention used in the recent Coronary Psychosocial Evaluation Studies (COPES) trial, was feasible in patients with recent ACS who were recruited from 5 geographically diverse sites. Innovative design features of this trial include randomization to either initial patient-preference of treatment or to a referred care arm in which the primary care provider decided upon care. Additionally, delivery of psychotherapy was accomplished by telephone, or webcam, depending upon patient preference. The vanguard phase provides estimates of eligibility and screening/enrollment ratios, patient acceptance of screening, and retention. In this report, we describe the innovative features and the baseline results of the vanguard phase of CODIACS. The data from this vanguard study will be used to finalize planning for a large, phase III clinical trial designed to evaluate the effect of treatment on depressive symptoms, coronary events, and death

Casimir forces between cylinders and plates

We study collective interaction effects that result from the change of free quantum electrodynamic field fluctuations by one- and two-dimensional perfect metal structures. The Casimir interactions in geometries containing plates and cylinders is explicitly computed using partial wave expansions of constrained path integrals. We generalize previously obtained results and provide a more detailed description of the technical aspects of the approach \cite{Emig06}. We find that the interactions involving cylinders have a weak logarithmic dependence on the cylinder radius, reflecting that one-dimensional perturbations are marginally relevant in 4D space-time. For geometries containing two cylinders and one or two plates, we confirm a previously found non-monotonic dependence of the interaction on the object's separations which does not follow from pair-wise summation of two-body forces. Qualitatively, this effect is explained in terms of fluctuating charges and currents and their mirror images

Centralized, Stepped, Patient Preference–Based Treatment for Patients With Post–Acute Coronary Syndrome Depression

IMPORTANCE: Controversy remains about whether depression can be successfully managed after acute coronary syndrome (ACS) and the costs and benefits of doing so. OBJECTIVE: To determine the effects of providing post-ACS depression care on depressive symptoms and health care costs. DESIGN: Multicenter randomized controlled trial. SETTING: Patients were recruited from 2 private and 5 academic ambulatory centers across the United States. PARTICIPANTS: A total of 150 patients with elevated depressive symptoms (Beck Depression Inventory [BDI] score ≥10) 2 to 6 months after an ACS, recruited between March 18, 2010, and January 9, 2012. INTERVENTIONS: Patients were randomized to 6 months of centralized depression care (patient preference for problem-solving treatment given via telephone or the Internet, pharmacotherapy, both, or neither), stepped every 6 to 8 weeks (active treatment group; n = 73), or to locally determined depression care after physician notification about the patient's depressive symptoms (usual care group; n = 77). MAIN OUTCOME MEASURES: Change in depressive symptoms during 6 months and total health care costs. RESULTS: Depressive symptoms decreased significantly more in the active treatment group than in the usual care group (differential change between groups, -3.5 BDI points; 95% CI, -6.1 to -0.7; P = .01). Although mental health care estimated costs were higher for active treatment than for usual care, overall health care estimated costs were not significantly different (difference adjusting for confounding, -$325; 95$2639 to $1989; P = .78). CONCLUSIONS: For patients with post-ACS depression, active treatment had a substantial beneficial effect on depressive symptoms. This kind of depression care is feasible, effective, and may be cost-neutral within 6 months; therefore, it should be tested in a large phase 3 pragmatic trial. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01032018

The radial velocity dispersion profile of the Galactic halo: constraining the density profile of the dark halo of the Milky Way

We have compiled a new sample of 240 halo objects with accurate distance and radial velocity measurements, including globular clusters, satellite galaxies, field blue horizontal branch (FHB) stars and red giant stars from the Spaghetti survey. The new data lead to a significant increase in the number of known objects for Galactocentric radii beyond 50 kpc, which allows a reliable determination of the radial velocity dispersion profile out to very large distances. The radial velocity dispersion shows an almost constant value of 120 km s −1 out to 30 kpc and then continuously declines down to 50 km s −1 at about 120 kpc. This fall-off puts important constraints on the density profile and total mass of the dark matter halo of the Milky Way. For a constant velocity anisotropy, the isothermal profile is ruled out, while both a dark halo following a truncated flat (TF) model of mass 1.2 +1.8 −0.5 × 10 12  M ⊙ and a Navarro, Frenk & White (NFW) profile of mass 0.8 +1.2 −0.2 × 10 12  M ⊙ and c = 18 are consistent with the data. The significant increase in the number of tracers combined with the large extent of the region probed by these has allowed a more precise determination of the Milky Way mass in comparison to previous works. We also show how different assumptions for the velocity anisotropy affect the performance of the mass models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73086/1/j.1365-2966.2005.09367.x.pd