Finding the Pion in the Chiral Random Matrix Vacuum

The existence of a Goldstone boson is demonstrated in chiral random matrix theory. After determining the effective coupling and calculating the scalar and pseudoscalar propagators, a random phase approximation summation reveals the massless pion and massive sigma modes expected whenever chiral symmetry is spontaneously broken.Comment: 3 pages, 1 figure, revte

Radiation Reaction fields for an accelerated dipole for scalar and electromagnetic radiation

The radiation reaction fields are calculated for an accelerated changing dipole in scalar and electromagnetic radiation fields. The acceleration reaction is shown to alter the damping of a time varying dipole in the EM case, but not the scalar case. In the EM case, the dipole radiation reaction field can exert a force on an accelerated monopole charge associated with the accelerated dipole. The radiation reaction of an accelerated charge does not exert a torque on an accelerated magnetic dipole, but an accelerated dipole does exert a force on the charge. The technique used is that originally developed by Penrose for non-singular fields and extended by the author for an accelerated monopole charge.Comment: 11 page

Scaling Symmetries of Scatterers of Classical Zero-Point Radiation

Classical radiation equilibrium (the blackbody problem) is investigated by the use of an analogy. Scaling symmetries are noted for systems of classical charged particles moving in circular orbits in central potentials V(r)=-k/r^n when the particles are held in uniform circular motion against radiative collapse by a circularly polarized incident plane wave. Only in the case of a Coulomb potential n=1 with fixed charge e is there a unique scale-invariant spectrum of radiation versus frequency (analogous to zero-point radiation) obtained from the stable scattering arrangement. These results suggest that non-electromagnetic potentials are not appropriate for discussions of classical radiation equilibrium.Comment: 13 page

Electron tunneling time measured by photoluminescence excitation correlation spectroscopy

The tunneling time for electrons to escape from the lowest quasibound state in the quantum wells of GaAs/AlAs/GaAs/AlAs/GaAs double-barrier heterostructures with barriers between 16 and 62 Å has been measured at 80 K using photoluminescence excitation correlation spectroscopy. The decay time for samples with barrier thicknesses from 16 Å (≈12 ps) to 34 Å(≈800 ps) depends exponentially on barrier thickness, in good agreement with calculations of electron tunneling time derived from the energy width of the resonance. Electron and heavy hole carrier densities are observed to decay at the same rate, indicating a coupling between the two decay processes

Turbulence characteristics of swirling flowfields

The time mean and turbulence properties of a confined swirling jet using the six orientation, single hot wire technique were obtained. The effect of swirl on a confined, expanding jet is to reduce the size of the corner recirculation zone and generate a central recirculation zone followed by a precessing vortex core. The effect of introducing a contraction nozzle of area ratio four, located two test section diameters downstream of the inlet, is to dramatically reduce the size and shape of the central recirculation zone for the swirling flows considered. The shear stresses are found to increase by an order of magnitude in the region of the contraction nozzle because of large radial gradients of axial velocity. Reduction of the expansion ratio to D/o = 1 causes the time mean flow field to be homogeneous throughout the entire test section with the tangential velocity dominating in the swirling cases. No recirculation zones were observed for these particular flows. Turbulence levels and dissipation rates were found to be low except in the entrance regions and in areas of acceleration in the swirling flow cases

"Quantum Interference with Slits" Revisited

Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his calculation as if no approximations are employed. We show that he implicitly makes the same approximations found in classical treatments of interference and that no new physics has been introduced. At the same time, some of the quantum mechanical arguments Marcella gives are, at best, misleading.Comment: 11 pages, 3 figure

Ethane steam reforming over a platinum/alumina catalyst: effect of sulphur poisoning

In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity

On the physical meaning of the Unruh effect

We present simple arguments that detectors moving with constant acceleration (even acceleration for a finite time) should detect particles. The effect is seen to be universal. Moreover, detectors undergoing linear acceleration and uniform, circular motion both detect particles for the same physical reason. We show that if one uses a circularly orbiting electron in a constant external magnetic field as the Unruh--DeWitt detector, then the Unruh effect physically coincides with the experimentally verified Sokolov--Ternov effect.Comment: 7 pages, 0 figures references added, small changes in text. To be published JETP Lett

Responses of women to orthostatic and exercise stresses

The results are presented from a special physiological study of women at the Johnson Space Center in 1976 to 1977. Its purpose was to establish a large (98 subjects) database from normal working women. The data sets are medical historical, clinical, anthropometric, and stress response statistics useful for establishing medical criteria for selecting women astronauts. Stressors were lower body negative pressure and static standing (both orthostatic) and treadmill exercise (ergometric). Data shown are original individual values with analyses and subsets, and statistical summaries and correlations relating to human responses to microgravity. Similarities appear between the characteristics of women in this study and those of women astronauts currently flying in Shuttle crews

A closed form for the electrostatic interaction between two rod-like charged objects

We have calculated the electrostatic interaction between two rod-like charged objects with arbitrary orientations in three dimensions. we obtained a closed form formula expressing the interaction energy in terms of the separation distance between the centers of the two rod-like objects, $r$, their lengths (denoted by $2l_1$ and $2l_2$), and their relative orientations (indicated by $\theta$ and $\phi$). When the objects have the same length ($2l_1=2l_2=l$), for particular values of separations, i.e for $r\leq0.8 l$, two types of minimum are appeared in the interaction energy with respect to $\theta$. By employing the closed form formula and introducing a scaled temperature $t$, we have also studied the thermodynamic properties of a one dimensional system of rod-like charged objects. For different separation distances, the dependence of the specific heat of the system to the scaled temperature has been studied. It is found that for $r<0.8 l$, the specific heat has a maximum.Comment: 10 pages, 9 figures, 1 table, Accepted by J. Phys.: Condens. Matte