Data analysis study and performance evaluation of the scanning laser Doppler system

A simulation program which provided information on theoretically expected vortex spectra, evaluations of potential algorithms, and expected location accuracies for given scan patterns is presented. Field tests using an aircraft engine flow field and aircraft vortices during flyby tests were compared to the results of the simulation. From these studies, a vortex location algorithm was developed which provided vortex location for one or two vortices as a function of time. Results of this algorithm used on data from flyby tests were used to study vortex transport, to evaluate system performance, and to provide suggestions for real-time vortex location algorithms. The results of real-time analysis were compared to those which were expected based on theoretical considerations

Networks of noisy oscillators with correlated degree and frequency dispersion

We investigate how correlations between the diversity of the connectivity of networks and the dynamics at their nodes affect the macroscopic behavior. In particular, we study the synchronization transition of coupled stochastic phase oscillators that represent the node dynamics. Crucially in our work, the variability in the number of connections of the nodes is correlated with the width of the frequency distribution of the oscillators. By numerical simulations on Erd\"os-R\'enyi networks, where the frequencies of the oscillators are Gaussian distributed, we make the counterintuitive observation that an increase in the strength of the correlation is accompanied by an increase in the critical coupling strength for the onset of synchronization. We further observe that the critical coupling can solely depend on the average number of connections or even completely lose its dependence on the network connectivity. Only beyond this state, a weighted mean-field approximation breaks down. If noise is present, the correlations have to be stronger to yield similar observations.Comment: 6 pages, 2 figure

Temporal integration in the neural substrate for brain stimulation reward : duration neglect and the peak-and-end model

There are two competing theories of how organisms evaluate temporally-extended appetitive experiences. The "peak" model states that the most rewarding moment of the experience is recorded into memory, while the "peak-and-end" model asserts that remembered reward value is an averaging of both the "peak" reward and the reward value experienced at the end of the event. Both models also suggest that information about the temporal duration of the experience plays little role in retrospective evaluations ("duration neglect"). The current brain stimulation reward (BSR) studies: (a) tested a mathematical model designed to predict how lever-pressing performance in self-stimulating rats is affected by varying the train duration and pulse frequency, (b) examined how train duration and pulse frequency affect "duration neglect", and (c) compared the "peak" and "peak-and-end" models. Two male rats were chronically implanted with stimulating electrodes aimed at the lateral hypothalamic area. In the first experiment, train duration was held constant while the pulse frequency was varied. In the second experiment, frequency was held constant while the train duration was varied. In the third experiment, constant-frequency trains were compared to trains in which the frequency at the "end" of the train was less rewarding than that of the "peak". The results were consistent with the mathematical model, and allowed for a better understanding of "duration neglect" in BSR. Furthermore, while one subject displayed a lack of a peak-and-end effect, the other rat's results appeared to support the peak-and-end model, although instabilities in performance in the latter rat may have led to a spurious result

Evaluation of brain stimulation reward in rats : heuristics, exemplars, and context-dependency

The current study examined the cognitive heuristics employed by rats evaluating rewarding brain stimulation. Rats implanted with electrodes aimed at the lateral hypothalamus were trained to self-administer brain stimulation. In Experiment 1, one type of stimulation train was presented at a time: some trains were set at a constant frequency, whereas others were composite-frequency trains in which the frequency at the end of the train was set to be lower than in the preceding component. If the "peak" and "end" reward values were used as exemplars in evaluating the stimulation, the weaker end should degrade the overall reward value of the composite trains. However, the performance curves for all trains were overlapping, suggesting that all trains were equally rewarding. A model in which the "peak" exemplar alone is employed, is sufficient to account for these findings. In Experiment 2, constant- and composite-frequency trains were presented simultaneously. Adding a weaker end had no effect on preference, again suggesting that the simple "peak" alone model was sufficient. Experiment 3 was similar to the first experiment, in that constant- and composite-frequency trains were presented one at a time. However, the duration of the weaker, terminal portion of the composite trains was now greater. The performance curves for all trains were again generally overlapping, indicating no consistent preference for any train type. This result is again consistent with the "peak-only" model. The aim of Experiment 4 was to assess whether the "beginning" exemplar played a role in the evaluation of rewarding stimulation. Preliminary results did not support this hypothesis. Lastly, Experiment 5 examined whether duration could serve as an exemplar when the evaluation context was changed. In an earlier experiment involving trains presented one at a time, rats were indifferent to train duration increases once the stimulation exceeded 2-4 s. In Experiment 5, when comparable train durations were presented simultaneously, the longer train was more effective than the shorter trains in 4 out of 7 subjects. The implications of the study findings and future directions are discussed

Temporal integration in the neural substrate for brain stimulation reward : duration neglect and the peak-and-end model

There are two competing theories of how organisms evaluate temporally-extended appetitive experiences. The "peak" model states that the most rewarding moment of the experience is recorded into memory, while the "peak-and-end" model asserts that remembered reward value is an averaging of both the "peak" reward and the reward value experienced at the end of the event. Both models also suggest that information about the temporal duration of the experience plays little role in retrospective evaluations ("duration neglect"). The current brain stimulation reward (BSR) studies: (a) tested a mathematical model designed to predict how lever-pressing performance in self-stimulating rats is affected by varying the train duration and pulse frequency, (b) examined how train duration and pulse frequency affect "duration neglect", and (c) compared the "peak" and "peak-and-end" models. Two male rats were chronically implanted with stimulating electrodes aimed at the lateral hypothalamic area. In the first experiment, train duration was held constant while the pulse frequency was varied. In the second experiment, frequency was held constant while the train duration was varied. In the third experiment, constant-frequency trains were compared to trains in which the frequency at the "end" of the train was less rewarding than that of the "peak". The results were consistent with the mathematical model, and allowed for a better understanding of "duration neglect" in BSR. Furthermore, while one subject displayed a lack of a peak-and-end effect, the other rat's results appeared to support the peak-and-end model, although instabilities in performance in the latter rat may have led to a spurious result

Knotted solutions for linear and nonlinear theories: Electromagnetism and fluid dynamics

We examine knotted solutions, the most simple of which is the “Hopfion”, from the point of view of relations between electromagnetism and ideal fluid dynamics. A map between fluid dynamics and electromagnetism works for initial conditions or for linear perturbations, allowing us to find new knotted fluid solutions. Knotted solutions are also found to be solutions of nonlinear generalizations of electromagnetism, and of quantum-corrected actions for electromagnetism coupled to other modes. For null configurations, electromagnetism can be described as a null pressureless fluid, for which we can find solutions from the knotted solutions of electromagnetism. We also map them to solutions of Euler's equations, obtained from a type of nonrelativistic reduction of the relativistic fluid equations

Focused laser Doppler velocimeter

A system for remotely measuring velocities present in discrete volumes of air is described. A CO2 laser beam is focused by a telescope at such a volume, a focal volume, and within the focusable range, near field, of the telescope. The back scatter, or reflected light, principally from the focal volume, passes back through the telescope and is frequency compared with the original frequency of the laser, and the difference frequency or frequencies represent particle velocities in that focal volume

Polynomials, Riemann surfaces, and reconstructing missing-energy events

We consider the problem of reconstructing energies, momenta, and masses in collider events with missing energy, along with the complications introduced by combinatorial ambiguities and measurement errors. Typically, one reconstructs more than one value and we show how the wrong values may be correlated with the right ones. The problem has a natural formulation in terms of the theory of Riemann surfaces. We discuss examples including top quark decays in the Standard Model (relevant for top quark mass measurements and tests of spin correlation), cascade decays in models of new physics containing dark matter candidates, decays of third-generation leptoquarks in composite models of electroweak symmetry breaking, and Higgs boson decay into two tau leptons.Comment: 28 pages, 6 figures; version accepted for publication, with discussion of Higgs to tau tau deca