An analog model for quantum lightcone fluctuations in nonlinear optics

We propose an analog model for quantum gravity effects using nonlinear dielectrics. Fluctuations of the spacetime lightcone are expected in quantum gravity, leading to variations in the flight times of pulses. This effect can also arise in a nonlinear material. We propose a model in which fluctuations of a background electric field, such as that produced by a squeezed photon state, can cause fluctuations in the effective lightcone for probe pulses. This leads to a variation in flight times analogous to that in quantum gravity. We make some numerical estimates which suggest that the effect might be large enough to be observable. © 2012 Elsevier Inc.

Flicker perimetry in healthy subjects: influence of age and gender, learning effect and short-term fluctuation

PURPOSE: To determine the mean critical fusion frequency and the short-term fluctuation, to analyze the influence of age, gender, and the learning effect in healthy subjects undergoing flicker perimetry. METHODS: Study 1 - 95 healthy subjects underwent flicker perimetry once in one eye. Mean critical fusion frequency values were compared between genders, and the influence of age was evaluated using linear regression analysis. Study 2 - 20 healthy subjects underwent flicker perimetry 5 times in one eye. The first 3 sessions were separated by an interval of 1 to 30 days, whereas the last 3 sessions were performed within the same day. The first 3 sessions were used to investigate the presence of a learning effect, whereas the last 3 tests were used to calculate short-term fluctuation. RESULTS: Study 1 - Linear regression analysis demonstrated that mean global, foveal, central, and critical fusion frequency per quadrant significantly decreased with age (p<0.05).There were no statistically significant differences in mean critical fusion frequency values between males and females (p>0.05), with the exception of the central area and inferonasal quadrant (p=0.049 and p=0.011, respectively), where the values were lower in females. Study 2 - Mean global (p=0.014), central (p=0.008), and peripheral (p=0.03) critical fusion frequency were significantly lower in the first session compared to the second and third sessions. The mean global short-term fluctuation was 5.06±1.13 Hz, the mean interindividual and intraindividual variabilities were 11.2±2.8% and 6.4±1.5%, respectively. CONCLUSION: This study suggests that, in healthy subjects, critical fusion frequency decreases with age, that flicker perimetry is associated with a learning effect, and that a moderately high short-term fluctuation is expected.

Aging and fluctuation-dissipation ratio in a nonequilibrium q-state lattice model

A generalized version of the nonequilibrium linear Glauber model with q states in d dimensions is introduced and analyzed. The model is fully symmetric, its dynamics being invariant under all permutations of the q states. Exact expressions for the two-time autocorrelation and response functions on a d-dimensional lattice are obtained. In the stationary regime, the fluctuation-dissipation theorem holds, while in the transient the aging is observed with the fluctuation-dissipation ratio leading to the value predicted for the linear Glauber model.

FLUCTUATION OF THE INITIAL CONDITIONS AND ITS CONSEQUENCES ON SOME OBSERVABLES

We show effects of the event-by-event fluctuation of the initial conditions (IC) in hydrodynamic description of high-energy nuclear collisions on some observables. Such IC produce not only fluctuations in observables but, due to their bumpy structure, several non-trivial effects appear. They enhance production of isotropically distributed high-p(T) particles, making upsilon(2) smaller there. Also, they reduce upsilon(2) in the forward and backward regions where the global matter density is smaller, so where such effects become more efficacious. They may also produce the so-called ridge effect in the two large-p(T) particle correlation.

Comparison of the Salmonella/Microsome Microsuspension Assay with the new Microplate Fluctuation Protocol for Testing the Mutagenicity of Environmental Samples

The objective of this study was to compare the responses of the Salmonella/microsome microsuspension assay with the new microplate fluctuation protocol (MPF) for the evaluation of the mutagenic activity of environmental samples. Organic extracts of total particulate atmospheric air samples, surface waters, and effluents were tested in dose-response experiments. The assays were performed with strain TA98 in the absence and presence of S9 mix. Both protocols produced similar results, despite the fact that the maximum score of the MPF is limited to 48 wells, whereas in the regular plate assay it is possible to count up to 1,500 colonies using an automatic counter. Similar sensitivities based on the lowest dose that resulted in a positive response were obtained for both assays. The MPF procedure is less laborious (e.g., all-liquid format, use of multi-channel pipettors) and allows for automation of the pipetting and dispensing steps, thus, reducing time of the analysis which is particularly important in environmental quality monitoring programs or in effect-directed analysis. The results show that the MPF procedure is a promising tool to test environmental samples for mutagenic activity. Environ. Mol. Mutagen. 51:31-38, 2010. (C) 2009 Wiley-Liss, Inc.

IDENTIFICATION OF THE STATE OF A WET SPOUTED BED THROUGH TIME-FREQUENCY ANALYSIS OF PRESSURE FLUCTUATION TIME SERIES

The feasibility of detecting instability in wet spouted beds via pressure fluctuation (PF) time-series analyses was investigated. Experiments were carried out in a cylindrical Plexiglas column of diameter 150 mm with a conical base of internal angle 60 degrees, an inlet orifice diameter of 25 mm and glass beads of diameter 2.4 mm. Transducers at several axial positions measured PF time series with incremental addition of aqueous sucrose solutions of different concentrations. Liquid addition affected the spouted bed dynamics, causing irregular spouting, increased voidage in the annulus, increased fountain height, irregular annulus height, channelling, agglomeration, and adhesion of particles to the column walls. Autocorrelations indicated the appearance of periodicities in the PF signals with increasing sucrose addition. Dominant peaks in power-spectral density developed at low frequencies with changing system dynamics. The results indicate that PF signals furnish relevant information on system dynamics, useful for monitoring and control of spouted bed operations such as particle coating and drying of paste-like materials.

Effect of cold wire inclination on temperature fluctuation measurements in a heated jet

Hot-wire anemometers at low operating currents are used as fast response resistance thermometers for the study of heated turbulent flows. Simultaneous measurement of temperature and velocity is generally performed with multi-wire arrays. In order to give good spatial resolution a new layout has been tested which uses an inclined temperature wire positioned parallel to the nearest inclined velocity wire. This leads to an asymmetric wire arrangement relative to the mean flow direction. As expected, a reduction in thermal interference from the velocity wires results when compared with an array containing a temperature wire placed normal to the flow. However, measurement of higher order moments of fluctuating quantities in an axisymmetric jet shows considerable distortion of radial distributions which is traced to alteration of the temperature field sensed by the temperature wire. When inclined velocity sensitive wires contain a temperature component, the latter may be affected by the same phenomenon.

Ecology of sandflies (Diptera: Psychodidae) in a restricted focus of cutaneous leishmaniasis in Northern Venezuela: III. Seasonal fluctuation

A one year-long study (March 1979-March 1980) was carried out at San Esteban, an endemic focus of cutaneous leishmaniasis in Northern Venezuela, with the aim of observing the seasonal fluctuation of the local phlebotomine sandflies species. The influence of climatic factors (temperature, relative humidity and rainfall) on population dynamics was analyzed in three collecting sites - a house, a peridomestic area and a sylvatic region. Among anthropophilic species, L. panamensis behaved as a wetseason species, the mean minimum relative humidity being the critical factor influencing the total number of individuals. When the population density of this fly decreased, it was successfully replaced by L. ovallesi, a dry-season species. On the other hand, seasonal variations of L. gomezi were more strongly affected by the temperature.

Ecology of sandflies Diptera: Psychodidae) in a restricted focus of cutaneous leishmaniasis in Northern Venezuela: IV. Sandfly monthly fluctuation and leishmaniasis incidence relationship

An attempt has been made to correlate the monthly incidence of human leishmaniasis with the temporal distribution of sandfly species at San Esteban, Northern Venezuela. Upon statistical analysis, the seasonal fluctuation of L. ovallesi population correlated strongly with the human disease, while the dynamics of L. panamensis, generally believed to be the vector in the Central area of the country, showed only a very weak correlation. These findings support the hypothesis that L. panamensis might not be the main or unique species responsible for the transmission in this area and that L. ovallesi and additionally L. olmeca bicolor might be involved in the epidemiology of the disease.

Long-term fluctuation of relative afferent pupillary defect in subjects with normal visual function.

PURPOSE: To determine whether the relative afferent pupillary defect (RAPD) remains constant over time in normal subjects. METHODS: Seventeen normal subjects were tested with infrared pupillography and automated perimetry in four sessions over 3 years. The changes in RAPD and visual field asymmetry between testing sessions were compared. RESULTS: The range of RAPD was 0.0 to 0.3 log unit, and the difference in the mean deviation between the eyes on automated static perimetry was 0 to 3 dB. Eight subjects repeatedly had an RAPD in the same eye. There was no correlation between the RAPD and the visual field asymmetry at the same visit. Changes in the magnitude of the RAPD between any two sessions were typically small (median, 0.08 log unit; 25th percentile, 0.04 log unit; 75th percentile, 0.15 log unit). CONCLUSIONS: Some normal subjects may show a persistent but small RAPD in the absence of detectable pathologic disease. Therefore, an isolated RAPD in the range of 0.3 log unit that is not associated with any other significant historical or clinical finding should probably be considered benign.