Experimental and analytical study of a conically diffused flow with a nearly separated boundary layer

Turbulence measurements were obtained in the nearly separated flow in a 13 deg total angle of divergence conical diffuser coupled to a constant area tailpipe. Air at 207 newtons per square centimeter and 308 K provided an inlet velocity of about 51 meters per second at an inlet unit Reynolds number of 63.7 million per meter. Very high longitudinal turbulence intensities accompanied the diffusion process with peak values approaching 40 percent when normalized by the local centerline velocity. Predictions of the pressure recovery coefficient using a mixing length concept were good in the early stages of diffusion. In the latter stages of diffusion satisfactory predictions of the pressure recovery were obtained with an empirical method

No-cloning theorem in thermofield dynamics

We discuss the relation between the no-cloning theorem from quantum information and the doubling procedure used in the formalism of thermofield dynamics (TFD). We also discuss how to apply the no-cloning theorem in the context of thermofield states defined in TFD. Consequences associated to mixed states, von Neumann entropy and thermofield vacuum are also addressed.Comment: 16 pages, 3 figure

Multi-camera Realtime 3D Tracking of Multiple Flying Animals

Automated tracking of animal movement allows analyses that would not otherwise be possible by providing great quantities of data. The additional capability of tracking in realtime - with minimal latency - opens up the experimental possibility of manipulating sensory feedback, thus allowing detailed explorations of the neural basis for control of behavior. Here we describe a new system capable of tracking the position and body orientation of animals such as flies and birds. The system operates with less than 40 msec latency and can track multiple animals simultaneously. To achieve these results, a multi target tracking algorithm was developed based on the Extended Kalman Filter and the Nearest Neighbor Standard Filter data association algorithm. In one implementation, an eleven camera system is capable of tracking three flies simultaneously at 60 frames per second using a gigabit network of nine standard Intel Pentium 4 and Core 2 Duo computers. This manuscript presents the rationale and details of the algorithms employed and shows three implementations of the system. An experiment was performed using the tracking system to measure the effect of visual contrast on the flight speed of Drosophila melanogaster. At low contrasts, speed is more variable and faster on average than at high contrasts. Thus, the system is already a useful tool to study the neurobiology and behavior of freely flying animals. If combined with other techniques, such as `virtual reality'-type computer graphics or genetic manipulation, the tracking system would offer a powerful new way to investigate the biology of flying animals.Comment: pdfTeX using libpoppler 3.141592-1.40.3-2.2 (Web2C 7.5.6), 18 pages with 9 figure

Decoherence in a quantum harmonic oscillator monitored by a Bose-Einstein condensate

We investigate the dynamics of a quantum oscillator, whose evolution is monitored by a Bose-Einstein condensate (BEC) trapped in a symmetric double well potential. It is demonstrated that the oscillator may experience various degrees of decoherence depending on the variable being measured and the state in which the BEC is prepared. These range from a `coherent' regime in which only the variances of the oscillator position and momentum are affected by measurement, to a slow (power law) or rapid (Gaussian) decoherence of the mean values themselves.Comment: 4 pages, 3 figures, lette

Energy Loss from Reconnection with a Vortex Mesh

Experiments in superfluid 4He show that at low temperatures, energy dissipation from moving vortices is many orders of magnitude larger than expected from mutual friction. Here we investigate other mechanisms for energy loss by a computational study of a vortex that moves through and reconnects with a mesh of small vortices pinned to the container wall. We find that such reconnections enhance energy loss from the moving vortex by a factor of up to 100 beyond that with no mesh. The enhancement occurs through two different mechanisms, both involving the Kelvin oscillations generated along the vortex by the reconnections. At relatively high temperatures the Kelvin waves increase the vortex motion, leading to more energy loss through mutual friction. As the temperature decreases, the vortex oscillations generate additional reconnection events between the moving vortex and the wall, which decrease the energy of the moving vortex by transfering portions of its length to the pinned mesh on the wall.Comment: 9 pages, 10 figure

Magnetoconductance switching in an array of oval quantum dots

Employing oval shaped quantum billiards connected by quantum wires as the building blocks of a linear quantum dot array, we calculate the ballistic magnetoconductance in the linear response regime. Optimizing the geometry of the billiards, we aim at a maximal finite- over zero-field ratio of the magnetoconductance. This switching effect arises from a relative phase change of scattering states in the oval quantum dot through the applied magnetic field, which lifts a suppression of the transmission characteristic for a certain range of geometry parameters. It is shown that a sustainable switching ratio is reached for a very low field strength, which is multiplied by connecting only a second dot to the single one. The impact of disorder is addressed in the form of remote impurity scattering, which poses a temperature dependent lower bound for the switching ratio, showing that this effect should be readily observable in experiments.Comment: 11 pages, 8 figure

Formation of long-lived, scarlike modes near avoided resonance crossings in optical microcavities

We study the formation of long-lived states near avoided resonance crossings in open systems. For three different optical microcavities (rectangle, ellipse, and semi-stadium) we provide numerical evidence that these states are localized along periodic rays, resembling scarred states in closed systems. Our results shed light on the morphology of long-lived states in open mesoscopic systems.Comment: 4 pages, 5 figures (in reduced quality), to appear in Phys. Rev. Let

It\u27s Like Deja Vu All Over Again : Williams v. Taylor, Wiggins v. Smith, Rompilla v. Beard and a (Partial) Return to the Guidelines Approach to the Effective Assistance of Counsel

Shoddy lawyering in capital cases is well documented. Many defendants facing the death penalty end up on death row not because of the heinousness of the crime they committed but rather because of the poor quality of trial counsel\u27s performance. Despite the acknowledgment of sometimes shockingly poor representation by academics, litigators and even judges, most post-conviction claims of ineffective assistance of counsel are unsuccessful. Why? The legal standard for adjudicating these allegations which the Court adopted in Strickland v. Washington, which requires a defendant to demonstrate that his lawyer\u27s performance was outside the wide range of competent assistance and that because of the substandard representation there is a reasonable probability that the outcome would have been different, has proven to be very difficult to satisfy. The Supreme Court\u27s recent decisions in Williams v. Taylor, Wiggins v. Smith, and Rompilla v. Beard, however, have provided some reason for optimism. While purporting to operate within the Strickland framework, the Court in all cases held that trial counsel\u27s representation was constitutionally inadequate. In doing so, the Court used the ABA Standards for Criminal Justice as norms for counsel\u27s performance in determining what constituted objectively reasonable representation. This article explores the jurisprudential road to Strickland, and from Strickland to Williams, Wiggins, and Rompilla. It then posits that, viewed through the lens of history, the Court\u27s use of the ABA guidelines is reminiscent of the standard Judge Bazelon articulated thirty years ago in Decoster v. United States which the Court rejected in Strickland. Consciously or subconsciously, the Court has now embraced a variation of the Bazelon\u27s Decoster approach when reviewing ineffective assistance of counsel claims. In all likelihood, this is because the Court concluded that Strickland\u27s vague standard was being misunderstood and misapplied by the state and federal courts in a manner that insulated grossly incompetent representation from judicial review. Thus, the Court used the ABA guidelines to put some flesh on the Strickland skeleton . Finally, the article explores the effect of the Court\u27s decisions on ineffective assistance of counsel claims reviewed by the state and federal courts, concluding that additional reforms are needed if the promise of effective assistance of counsel is to become a reality