4,416 research outputs found
A lower bound on the number of cosmic ray events required to measure source catalogue correlations
Recent analyses of cosmic ray arrival directions have resulted in evidence
for a positive correlation with active galactic nuclei positions that has weak
significance against an isotropic source distribution. In this paper, we
explore the sample size needed to measure a highly statistically significant
correlation to a parent source catalogue. We compare several scenarios for the
directional scattering of ultra-high energy cosmic rays given our current
knowledge of the galactic and intergalactic magnetic fields. We find
significant correlations are possible for a sample of 1000 cosmic ray
protons with energies above 60 EeV.Comment: 23 pages, 9 figure
A Multiparameter, Numerical Stability Analysis of a Standing Cantilever Conveying Fluid
In this paper, we numerically examine the stability of a standing cantilever conveying fluid in a multiparameter space. Based on nonlinear beam theory, our mathematical model turns out to be replete with exciting behavior, some of which was totally unexpected and novel, and some of which confirm our intuition as well as the work of others. The numerical bifurcation results obtained from applying the Library of Continuation Algorithms (LOCA) reveal a plethora of one, two, and higher codimension bifurcations. For a vertical or standing cantilever beam, bifurcations to buckled solutions (via symmetry breaking) and oscillating solutions are detected as a function of gravity and the fluid-structure interaction. The unfolding of these results as a function of the orientation of the beam compared to gravity is also revealed
Memantine for prevention of migraine: a retrospective study of 60 cases.
The objective was to retrospectively characterise the efficacy of memantine as preventive therapy in a series of patients with frequent migraine. Patients in a university headache clinic completed a survey regarding their experience with memantine, and medical records were reviewed. All patients who received memantine as preventive therapy for migraine over a 15-month period were mailed surveys and consent forms for record review. Patients were treated with memantine beginning at a dose of 5 mg/day, increasing if needed by 5 mg/week up to 10 mg twice a day. The majority of patients (36 out of 54) treated with memantine for at least 2 months reported a significant reduction in estimated headache frequency, and improved function. Side effects were uncommon and generally mild. This limited retrospective case review suggests that memantine may be an effective preventive therapy for patients with frequent migraine. A prospective trial is warranted
Two-photon optics of Bessel-Gaussian modes
In this paper we consider geometrical two-photon optics of Bessel-Gaussian
modes generated in spontaneous parametric down-conversion of a Gaussian pump
beam. We provide a general theoretical expression for the orbital angular
momentum (OAM) spectrum and Schmidt number in this basis and show how this may
be varied by control over the radial degree of freedom, a continuous parameter
in Bessel-Gaussian modes. As a test we first implement a back-projection
technique to classically predict, by experiment, the quantum correlations for
Bessel-Gaussian modes produced by three holographic masks, a blazed axicon,
binary axicon and a binary Bessel function. We then proceed to test the theory
on the down-converted photons using the binary Bessel mask. We experimentally
quantify the number of usable OAM modes and confirm the theoretical prediction
of a flattening in the OAM spectrum and a concomitant increase in the OAM
bandwidth. The results have implications for the control of dimensionality in
quantum states.Comment: 8 pages, 10 figure
Obstructive sleep apnea severity affects amyloid burden in cognitively normal elderly a longitudinal study
Recent evidence suggests that Obstructive Sleep Apnea (OSA) may be a risk factor for developing Mild Cognitive Impairment and Alzheimer’s disease. However, how sleep apnea affects longitudinal risk for Alzheimer’s disease is less well understood.Postprint (author's final draft
A Passive Probe for Subsurface Oceans and Liquid Water in Jupiter's Icy Moons
We describe an interferometric reflectometer method for passive detection of
subsurface oceans and liquid water in Jovian icy moons using Jupiter's
decametric radio emission (DAM). The DAM flux density exceeds 3,000 times the
galactic background in the neighborhood of the Jovian icy moons, providing a
signal that could be used for passive radio sounding. An instrument located
between the icy moon and Jupiter could sample the DAM emission along with its
echoes reflected in the ice layer of the target moon. Cross-correlating the
direct emission with the echoes would provide a measurement of the ice shell
thickness along with its dielectric properties. The interferometric
reflectometer provides a simple solution to sub-Jovian radio sounding of ice
shells that is complementary to ice penetrating radar measurements better
suited to measurements in the anti-Jovian hemisphere that shadows Jupiter's
strong decametric emission. The passive nature of this technique also serves as
risk reduction in case of radar transmitter failure. The interferometric
reflectometer could operate with electrically short antennas, thus extending
ice depth measurements to lower frequencies, and potentially providing a deeper
view into the ice shells of Jovian moons.Comment: Submitted to Icaru
Phase transitions, interfacial fluctuations and hidden symmetries for fluids near structured walls
Fluids adsorbed at micro-patterned and geometrically structured substrates can exhibit novel phase transitions and interfacial fluctuation effects distinct from those characteristic of wetting at planar, homogeneous walls. We review recent theoretical progress in this area paying particular attention to filling transitions pertinent to fluid adsorption near wedges, which have highlighted a deep connection between geometrical and contact angles. We show that filling transitions are not only characterized by large scale interfacial fluctuations leading to universal critical singularities but also reveal hidden symmetries with short-ranged critical wetting transitions and properties of dimensional reduction. We propose a non-local interfacial model which fulfills all these properties and throws light on long-standing problems regarding the order of the 3D short-range critical wetting transition
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