Gravitational quantum states of neutrons in a rough waveguide

A theory of gravitational quantum states of ultracold neutrons in waveguides with absorbing/scattering walls is presented. The theory covers recent experiments in which the ultracold neutrons were beamed between a mirror and a rough scatterer/absorber. The analysis is based on a recently developed theory of quantum transport along random rough walls which is modified in order to include leaky (absorbing) interfaces and, more importantly, the low-amplitude high-aperture roughness. The calculations are focused on a regime when the direct transitions into the continuous spectrum above the absorption threshold dominate the depletion of neutrons from the gravitational states and are more efficient than the processes involving the intermediate states. The theoretical results for the neutron count are sensitive to the correlation radius (lateral size) of surface inhomogeneities and to the ratio of the particle energy to the absorption threshold in a weak roughness limit. The main impediment for observation of the higher gravitational states is the "overhang" of the particle wave functions which can be overcome only by use scatterers with strong roughness. In general, the strong roughness with high amplitude is preferable if one wants just to detect the individual gravitational states, while the strong roughness experiments with small amplitude and high aperture are preferable for the quantitative analysis of the data. We also discuss the ways to further improve the accuracy of calculations and to optimize the experimental regime.Comment: 48 pages, 14 figure

Amphibia: Anura: Hylidae Scarthyla vigilans (Solano 1971): Range Extension and New Country Record for Trinidad, W.I. With Notes on Tadpoles, Habitat, Behaviour and Biogeographical Significance.

We report a range extension and new country record for Scarthyla vigilans in Trinidad, West Indies. The species was previously known only from populations on mainland South America. We include notes on behavior, habitat and tadpole development, and discuss the biogeographical significance of the species’ presence in Trinidad, particularly with respect to consequences for understanding colonization events on this Caribbean island

Microdialysis studies of purine and monoamine release from the central nervous system in vivo

The effects of kainic acid and potassium on the release of endogenous adenosine and its metabolites, inosine, hypoxanthine and xanthine, from the rat hippocampus have been studied by in vivo microdialysis. In the hippocampus of rats anaesthetised with urethane the concentration of extracellular adenosine was estimated to be 0.8muM during the first two hrs after insertion of the dialysis probe. Kainic acid (0.1-25mM) in the perfusate evoked a concentration-dependent release of adenosine with an EC50 of 0.94mM. A 5min pulse of ImM kainic acid in the perfusate, during a sampling period of one hour, increased the 20mul dialysate levels from 3.68 +/- 0.21 to 7.66 +/- 0.82 pmol (mean +/- sem). A second stimulation (S2) 3hrs (hours) after the first stimulation (SI) also induced adenosine release. The S2/S1 ratio was 0.46 +/- 0.02. Kainate- evoked release of adenosine was shown to involve the production of action potentials since TTX (tetrodotoxin) significantly reduced the S2/S1 ratio by 53.85%. The release was reduced by incorporation into the perfusate of CNQX (6-cyano-7-nitroquinoxaline-2,3-dione), a non-NMDA (N-methyl-D-aspartate) receptor antagonist, but not by NMDA receptor blockers, (+)-MK-801 (dizocilpine) or (+/-)-AP-5 ((+/-)-2-amino-5-phosphonopentanoic acid), indicating a non-NMDA receptor mediated process. The kappa agonist, U50 488H (trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneactemide methanesulphonate hydrochloride), significantly reduced the S2/S1 ratio by 55.77%. Release was reduced significantly by 44.23% by ascorbic acid (an antioxidant), 48.08% by glutathione (a scavenger of hydroperoxides) and 71.15% by oxypurinol (a xanthine oxidase inhibitor) indicating the involvement of free radicals in kainate-evoked adenosine release. Neither the adenosine A1 receptor antagonist CPT (8-cyclopentyl-1,3-dimethylxanthine) nor the A1 receptor agonist R-PIA (R(-) N6-(2-phenylisopropyl)adenosine) affected kainate-evoked release of adenosine. This indicates that activation of A1 receptors, by endogenous adenosine or an agonist, does not inhibit kainate-evoked release of adenosine. The present results indicate that kainate-evoked release of adenosine may be mediated by non-NMDA receptor activation, possibly requiring the propagation of action potentials and free radical production

Mode Coupling in Quantized High Quality Films

The effect of coupling of quantized modes on transport and localization in ultrathin films with quantum size effect (QSE) is discussed. The emphasis is on comparison of films with Gaussian, exponential, and power-law long-range behavior of the correlation function of surface, thickness, or bulk fluctuations. For small-size inhomogeneities, the mode coupling is the same for inhomogeneities of all types and the transport coefficients behave in the same way. The mode coupling becomes extremely sensitive to the correlators for large-size inhomogeneities leading to the drastically distinct behavior of the transport coefficients. In high-quality films there is a noticeable difference between the QSE patterns for films with bulk and surface inhomogeneities which explains why the recently predicted new type of QSE with large oscillations of the transport coefficients can be observed mostly in films with surface-driven relaxation. In such films with surface-dominated scattering the higher modes contribute to the transport only as a result of opening of the corresponding mode coupling channels and appear one by one. Mode coupling also explains a much higher transport contribution from the higher modes than it is commonly believed. Possible correlations between the inhomogeneities from the opposite walls provide, because of their oscillating response to the mode quantum numbers, a unique insight into the mode coupling. The presence of inhomogeneities of several sizes leads not to a mechanical mixture of QSE patterns, but to the overall shifting and smoothing of the oscillations. The results can lead to new, non-destructive ways of analysis of the buried interfaces and to study of inhomogeneities on the scales which are inaccessible for scanning techniques

A model of the reflection distribution in the vacuum ultra violet region

A reflection model with three components, a specular spike, a specular lobe and a diffuse lobe is discussed. This model was successfully applied to describe reflection of xenon scintillation light (175 nm) by PTFE and other fluoropolymers and can be used for Monte Carlo simulation and analysis of scintillation detectors. The measured data favors a Trowbridge-Reitz distribution function of ellipsoidal micro-surfaces. The intensity of the coherent reflection increases with increasing angle of incidence, as expected, since the surface appears smoother at grazing angles. The total reflectance obtained for PTFE is about 70% for VUV light at normal incidence in vacuum and estimated to be up to 100% in contact with liquid xenon

The Effect of Random Surface Inhomogeneities on Microresonator Spectral Properties: Theory and Modeling at Millimeter Wave Range

The influence of random surface inhomogeneities on spectral properties of open microresonators is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields the method of eigen-mode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering which is the highly responsible for non-dissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object we use dielectric disc resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigen-frequencies and the Q-factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data.Comment: 17+ pages, 5 figure

Seismic topographic scattering in the context of GW detector site selection

In this paper, we present a calculation of seismic scattering from irregular surface topography in the Born approximation. Based on US-wide topographic data, we investigate topographic scattering at specific sites to demonstrate its impact on Newtonian-noise estimation and subtraction for future gravitational-wave detectors. We find that topographic scattering at a comparatively flat site in Oregon would not pose any problems, whereas scattering at a second site in Montana leads to significant broadening of wave amplitudes in wavenumber space that would make Newtonian-noise subtraction very challenging. Therefore, it is shown that topographic scattering should be included as criterion in the site-selection process of future low-frequency gravitational-wave detectors.Comment: 16 pages, 7 figure

Attitudes to and Understanding of Risk of Acquisition of HIV Over Time: Design and Methods for an Internet-based Prospective Cohort Study Among UK Men Who Have Sex With Men (the AURAH2 Study)

Background: The annual number of new HIV infections among men who have sex with men (MSM) has risen in the UK and, of those HIV positive, the proportion undiagnosed is high. The prospective AURAH2 study aims to assess factors associated with HIV acquisition among MSM in the UK, and to investigate changes over time within individuals in sexual behaviour and HIV-testing practices. / Methods/Design: AURAH2 is a prospective study among MSM without diagnosed HIV, aiming to recruit up to 1000 sexually active MSM attending sexual health clinics in London and Brighton. Participants complete an initial paper-based questionnaire, followed by four monthly online follow-up questionnaires collecting socio-demographic, health and behavioural data, including sexual behaviour, recreational and other drug use, HIV testing practices and Pre-Exposure Prophylaxis use, over a planned three year period. / Discussion: The results from AURAH2 study will provide an important insight into established and emerging risk behaviours that may be associated with acquisition of HIV in MSM, in the UK, changes over time within individuals in sexual behaviour, and inform on HIV testing practices. This data will be crucial to inform future HIV prevention strategies

Surfaces roughness effects on the transmission of Gaussian beams by anisotropic parallel plates

Influence of the plate surfaces roughness in precise ellipsometry experiments is studied. The realistic case of a Gaussian laser beam crossing a uniaxial platelet is considered. Expression for the transmittance is determined using the first order perturbation theory. In this frame, it is shown that interference takes place between the specular transmitted beam and the scattered field. This effect is due to the angular distribution of the Gaussian beam and is of first order in the roughness over wavelength ratio. As an application, a numerical simulation of the effects of quartz roughness surfaces at normal incidence is provided. The interference term is found to be strongly connected to the random nature of the surface roughness.Comment: 18 pages, Journal of Physics D: Applied Physics, volume 36, issue 21, pages 2697 - 270

A new application of reduced Rayleigh equations to electromagnetic wave scattering by two-dimensional randomly rough surfaces

The small perturbations method has been extensively used for waves scattering by rough surfaces. The standard method developped by Rice is difficult to apply when we consider second and third order of scattered fields as a function of the surface height. Calculations can be greatly simplified with the use of reduced Rayleigh equations, because one of the unknown fields can be eliminated. We derive a new set of four reduced equations for the scattering amplitudes, which are applied to the cases of a rough conducting surface, and to a slab where one of the boundary is a rough surface. As in the one-dimensional case, numerical simulations show the appearance of enhanced backscattering for these structures.Comment: RevTeX 4 style, 38 pages, 16 figures, added references and comments on the satellites peak