Numerical investigations of escape panic of confined pedestrians have revealed interesting dynamical features such as pedestrian arch formation around an exit, disruptive interference, self-organized queuing, and scale-free behavior. However, these predictions have remained unverified because escape panic experiments with real systems are difficult to perform. For mice escaping out of a water pool, we found that for a critical sampling rate the escape behavior exhibits the predicted features even at short observation times. The mice escaped via an exit in bursts of different sizes that obey exponential and (truncated) power-law distributions depending on exit width. Oversampling or undersampling the mouse escape rate prevents the observation of the predicted features. Real systems are normally subject to unavoidable constraints arising from occupancy rate, pedestrian exhaustion, and nonrigidity of pedestrian bodies. The effect of these constraints on the dynamics of real escape panic is also studied.social behavior ͉ structures in complex systems ͉ dynamics of social systems S earches of disaster databases § would readily show that the escape panic of confined pedestrians is costly in terms of fatalities and property loss. Despite the huge toll inflicted by these incidents to society, the dynamics of escape panic are not completely understood because studies have been largely confined to numerical simulations that revealed a number of interesting dynamical features such as pedestrian arch formation around an exit, herding, and interference between arches in multiple-exit rooms (1). Recently, additional features such as disruptive interference, self-organized queuing, and scale-free escape dynamics (2) were found. Experiments in genuine escape panic are difficult, especially with humans because of possible ethical and even legal concerns.This work addresses the behavior of panicking groups and how it is influenced by the architecture of the space in which they are confined. It determines whether the dynamical features predicted earlier in numerical experiments are observed in a group of real biological (nonrigid) agents undergoing escape panic. Experimental results from mice escaping out of a water pool show that for a critical sampling interval their escape behavior agrees with the numerically predicted exponential and powerlaw frequency distributions of the exit burst size even for short time durations. Oversampling or undersampling of the mouse escape rate prevents the observation of the predicted features.Escape panic could happen in different confinement sizes, from a rioting crowd in a packed stadium to stunned customers in a smoke-filled bar. It is characterized by strong contact interactions between selfish individuals that quickly gives rise to herding, stampede, and clogging (3-7). Escape panic is simulated by solving a set of coupled differential equations (1,8) or by the cellular automata (CA) technique (2) where the movement of confined pedestrians is tracked over time. Both approaches yield consiste...

The imaging properties of a scanning optical system that incorporates an axicon are presented. Beamshape characteristics including the axial distribution of the J(0) beam and its control and aberration effects arising from off-axis illumination are experimentally studied. These parameters are relevant when the axicon is used in an imaging system operating in the beam-scanning mode. The J(0) pattern produced by a blazed axicon transmittance grating is also presented.

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Acute hepatopancreatic necrosis disease (AHPND) has recently emerged as a serious disease of cultured shrimp. It has also been described as early mortality syndrome (EMS) due to mass mortalities occurring within 20 to 30 d after stocking of ponds with postlarvae. Here, Penaeus vannamei and Penaeus monodon from shrimp farms in the Philippines were examined for the toxin-producing strain of Vibrio parahaemolyticus due to AHPND-like symptoms occurring in marketable size shrimp. In the P. vannamei, histology revealed typical AHPND pathology, such as sloughing of undifferentiated cells in the hepatopancreatic tubule epithelium. Analysis using the IQ2000 AHPND/EMS Toxin 1 PCR test generated 218 bp and 432 bp amplicons confirmative of the toxin-producing strain of V. parahaemolyticus among shrimp sampled from 8 of 9 ponds. In the P. monodon, histology revealed massive sloughing of undifferentiated cells of the hepatopancreatic tubule epithelium in the absence of basophilic bacterial cells. PCR testing generated the 2 amplicons confirmatory for AHPND among shrimp sampled from 5 of 7 ponds. This study confirms the presence of AHPND in P. vannamei and P. monodon farmed in the Philippines and suggests that the disease can also impact late-stage juvenile shrimp.

The behavior of two-photon fluorescence imaging through a scattering medium is analyzed by use of the Monte Carlo technique. The axial and transverse distributions of the excitation photons in the focused Gaussian beam are derived for both isotropic and anisotropic scatterers at different numerical apertures and at various ratios of the scattering depth with the mean free path. The two-photon fluorescence profiles of the sample are determined from the square of the normalized excitation intensity distributions. For the same lens aperture and scattering medium, two-photon fluorescence imaging offers a sharper and less aberrated axial response than that of single-photon confocal fluorescence imaging. The contrast in the corresponding transverse fluorescence profile is also significantly higher. Also presented are results comparing the effects of isotropic and anisotropic scattering media in confocal reflection imaging. The convergence properties of the Monte Carlo simulation are also discussed.