Emergence of the stochastic resonance in glow discharge plasma

stochastic resonance, glow discharge plasma, excitable medium, absolute mean differenceComment: St

In situ Characterization of Nanoparticles Using Rayleigh Scattering

We report a theoretical analysis showing that Rayleigh scattering could be used to monitor the growth of nanoparticles under arc discharge conditions. We compute the Rayleigh scattering cross sections of the nanoparticles by combining light scattering theory for gas-particle mixtures with calculations of the dynamic electronic polarizability of the nanoparticles. We find that the resolution of the Rayleigh scattering probe is adequate to detect nanoparticles as small as C60 at the expected concentrations of synthesis conditions in the arc periphery. Larger asymmetric nanoparticles would yield brighter signals, making possible to follow the evolution of the growing nanoparticle population from the evolution of the scattered intensity. Observable spectral features include characteristic resonant behaviour, shape-dependent depolarization ratio, and mass-dependent line shape. Direct observation of nanoparticles in the early stages of growth with unobtrusive laser probes should give insight on the particle formation mechanisms and may lead to better-controlled synthesis protocols

An Unusual Case of Tertiary Syphilis Behaving Like Tongue Squamous Cell Carcinoma.

Syphilis may present with a myriad of oral manifestations in the primary, secondary, and tertiary stages, and may be confused with malignancy. Despite a rise in the incidence of syphilis, tertiary syphilis is exceedingly rare. Tertiary syphilis gummas usually affect the hard palate, while tongue involvement is very rare. A 55-year-old male with extensive smoking and alcohol use was referred for malignancy evaluation with an ulcerative mass creating a tongue cleft, and a positron emission tomography scan suggestive for malignancy. Biopsy results demonstrated no carcinoma but histology demonstrated granulomatous inflammation. Further laboratory results demonstrated elevated rapid plasma reagin titers with Treponema pallidum immunoglobulin G antibodies present. The patient was diagnosed with tertiary syphilis, received appropriate antibiotic therapy, and had healing of the tongue with a persistent cleft. Syphilis may mimic many disease processes. As such, it is important to include this disease in the differential of an unusual tongue lesion. An oral lesion may be the first sign of infection

Radiation-induced rotation of small celestial bodies

The rotation was studied of particles in a simulated space environment via a technique known as Laser Particle Levitation. The combination of both a high vacuum and optical laser levitation to negate the effects of Earth's gravity, simulate the space environment. The rotation mechanism under study is known as the 'Windmill Effect,' which is a spin mechanism that suggests that the interaction of the photon field from a star with the surface irregularities of cosmic dust will cause them to spin due to the imbalance in the directionality of the scattered photons which necessitates a non-zero angular momentum. This conclusion is based on the random nature of the orientation of the sites of surface irregularities. The general object is to study the behavior of particles in orbits around the Earth, both natural and man made, as well as interplanetary and circumstellar particles. To meet this objective, an apparatus was constructed which was designed to allow optical levitation in a vacuum

Structure and evolution of strange attractors in non-elastic triangular billiards

We study pinball billiard dynamics in an equilateral triangular table. In such dynamics, collisions with the walls are non-elastic: the outgoing angle with the normal vector to the boundary is a uniform factor $\lambda < 1$ smaller than the incoming angle. This leads to contraction in phase space for the discrete-time dynamics between consecutive collisions, and hence to attractors of zero Lebesgue measure, which are almost always fractal strange attractors with chaotic dynamics, due to the presence of an expansion mechanism. We study the structure of these strange attractors and their evolution as the contraction parameter $\lambda$ is varied. For $\lambda$ in the interval (0, 1/3), we prove rigorously that the attractor has the structure of a Cantor set times an interval, whereas for larger values of $\lambda$ the billiard dynamics gives rise to nonaccessible regions in phase space. For $\lambda$ close to 1, the attractor splits into three transitive components, the basins of attraction of which have fractal basin boundaries.Comment: 12 pages, 10 figures; submitted for publication. One video file available at http://sistemas.fciencias.unam.mx/~dsanders

The Wheeler-DeWitt Quantization Can Solve the Singularity Problem

We study the Wheeler-DeWitt quantum cosmology of a spatially flat Friedmann cosmological model with a massless free scalar field. We compare the consistent histories approach with the de Broglie-Bohm theory when applied to this simple model under two different quantization schemes: the Schr\"odinger-like quantization, which essentially takes the square-root of the resulting Klein-Gordon equation through the restriction to positive frequencies and their associated Newton-Wigner states, or the induced Klein-Gordon quantization, that allows both positive and negative frequencies together. We show that the consistent histories approach can give a precise answer to the question concerning the existence of a quantum bounce if and only if one takes the single frequency approach and within a single family of histories, namely, a family containing histories concerning properties of the quantum system at only two specific moments of time: the infinity past and the infinity future. In that case, as shown by Craig and Singh \cite{CS}, there is no quantum bounce. In any other situation, the question concerning the existence of a quantum bounce has no meaning in the consistent histories approach. On the contrary, we show that if one considers the de Broglie-Bohm theory, there are always states where quantum bounces occur in both quantization schemes. Hence the assertion that the Wheeler-DeWitt quantization does not solve the singularity problem in cosmology is not precise. To address this question, one must specify not only the quantum interpretation adopted but also the quantization scheme chosen.Comment: 13 pages, 1 figur

A Controlled Increase in Dietary Phosphate Elevates BP in Healthy Human Subjects.

Background Despite epidemiologic evidence for increased cardiovascular morbidity and mortality associated with both high dietary and serum phosphate in humans with normal renal function, no controlled phosphate intervention studies of systemic hemodynamics have been reported. Higher serum 25(OH) vitamin D levels are associated with better cardiovascular outcomes, but vitamin D increases intestinal phosphate absorption.Methods We conducted a prospective outpatient study with blinded assessment in 20 young adults with normal renal function randomized to high phosphate (regular diet plus 1 mmol/kg body wt per day of Na as neutral sodium phosphate) or low phosphate (regular diet plus lanthanum, 750 mg thrice/day, plus 0.7 mmol/kg body wt per day of Na as NaCl) for 11 weeks. After 6 weeks, all subjects received vitamin D3 (600,000 U) by intramuscular injection. Outcome parameters were 24-hour ambulatory systolic and diastolic BP (SBP and DBP), pulse rate (PR), biomarkers, and measures of endothelial and arterial function.Results Compared with the low-phosphate diet group, the high-phosphate diet group had a significant increase in mean±SEM fasting plasma phosphate concentration (0.23±0.11 mmol/L); 24-hour SBP and DBP (+4.1; 95% confidence interval [95% CI], 2.1 to 6.1; and +3.2; 95% CI, 1.2 to 5.2 mm Hg, respectively); mean 24-hour PR (+4.0; 95% CI, 2.0 to 6.0 beats/min); and urinary metanephrine and normetanephrine excretion (54; 95% CI, 50 to 70; and 122; 95% CI, 85 to 159 µg/24 hr, respectively). Vitamin D had no effect on any of these parameters. Neither high- nor low-phosphate diet nor vitamin D affected endothelial function or arterial elasticity.Conclusions Increased phosphate intake (controlled for sodium) significantly increases SBP, DBP, and PR in humans with normal renal function, in part, by increasing sympathoadrenergic activity