The assessment of lens opacity postmortem and its implication in forensics.

Visual impairment, mostly due to cataracts, has been demonstrated to be an important factor associated with traffic accidents. Although vision screening is standard procedure during licensing in order to prevent motor vehicle accidents, an eye exam is not typically administered after an accident has already occurred. Postmortem assessment of lens opacity in victims of car accidents would provide helpful information for attesting to the liability of the parties in specific accidents, determining the circumstances of the accident, and developing preventive measures for both drivers and pedestrians alike. In this paper, we explore the use of different methods and their limitations for assessing lens opacity postmortem. We discuss the possible use and benefits of a simple, but as-yet untested method: retrobulbar translucency. The method would be based on the recording of shadows formed by opaque regions of the lens while the eye is illuminated from the back with a rigid source of light. The efficacy and objectivity of the method, its reproducibility, and the inter- and intra-observer error should be tested before implementing such a technique to be regularly used to determine lens opacity in cadavers.

FDTD computation of human eye exposure to ultra-wideband electromagnetic pulses.

With an increase in the application of ultra-wideband (UWB) electromagnetic pulses in the communications industry, radar, biotechnology and medicine, comes an interest in UWB exposure safety standards. Despite an increase of the scientific research on bioeffects of exposure to non-ionizing UWB pulses, characterization of those effects is far from complete. A numerical computational approach, such as a finite-difference time domain (FDTD) method, is required to visualize and understand the complexity of broadband electromagnetic interactions. The FDTD method has almost no limits in the description of the geometrical and dispersive properties of the simulated material, it is numerically robust and appropriate for current computer technology. In this paper, a complete calculation of exposure of the human eye to UWB electromagnetic pulses in the frequency range of 3.1-10.6, 22-29 and 57-64 GHz is performed. Computation in this frequency range required a geometrical resolution of the eye of 0.1 mm and an arbitrary precision in the description of its dielectric properties in terms of the Debye model. New results show that the interaction of UWB pulses with the eye tissues exhibits the same properties as the interaction of the continuous electromagnetic waves (CWs) with the frequencies from the pulse's frequency spectrum. It is also shown that under the same exposure conditions the exposure to UWB pulses is from one to many orders of magnitude safer than the exposure to CW.

Exposure of biological material to ultra-wideband electromagnetic pulses: dosimetric implications.

Interest in ultra-wideband (UWB) electromagnetic pulses in the communications industry and various applications in biotechnology and medicine is constantly increasing. While more and more scientific research of bioelectromagnetic phenomena is focusing on bioeffects of exposure to non-ionizing UWB pulses, characterization of those effects is far from complete. In this paper, a synthesis of experimental studies from the point of computational modeling is presented. The complexity of the experiments requires a numerical rather than an analytical approach. Solving Maxwell's equations using a finite-difference time-domain (FDTD) method is a necessary step in visualizing and understanding broadband response. The advantages of this method include having almost no limits in the description of geometrical and dispersive properties of the simulated material, numerical robustness, and appropriateness for the computer technology of today. Some of the results of the computation and their importance in future experimental design are discussed. Improvements in the computational modeling and dielectric material description are suggested. This paper aims at justifying a scientific basis for UWB exposure safety standards relevant for setting the non-ionizing UWB radiation exposure guidelines. The results of this research will be of interest to people who work with electronic devices involving UWB radiation.

Three-dimensional FDTD simulation of biomaterial exposure to electromagnetic nanopulses.

Ultra-wideband (UWB) electromagnetic pulses of nanosecond duration, or nanopulses, have recently been approved by the Federal Communications Commission for a number of different applications. They are also being explored for applications in biotechnology and medicine. The simulation of the propagation of a nanopulse through biological matter, previously performed using a two-dimensional finite-difference time-domain (FDTD) method, has been extended here into a full three-dimensional computation. To account for the UWB frequency range, the geometrical resolution of the exposed sample was 0.25 mm and the dielectric properties of biological matter were accurately described in terms of the Debye model. The results obtained from the three-dimensional computation support the previously obtained results: the electromagnetic field inside a biological tissue depends on the incident pulse rise time and width, with increased importance of the rise time as the conductivity increases; no thermal effects are possible for the low pulse repetition rates, supported by recent experiments. New results show that the dielectric sample exposed to nanopulses behaves as a dielectric resonator. For a sample in a cuvette, we obtained the dominant resonant frequency and the Q-factor of the resonator.

FDTD simulation of exposure of biological material to electromagnetic nanopulses.

Ultra-wideband (UWB) electromagnetic pulses of nanosecond duration, or nanopulses, are of considerable interest to the communications industry and are being explored for various applications in biotechnology and medicine. The propagation of a nanopulse through biological matter has been computed using the finite difference-time domain (FDTD) method. The approach required the reparametrization of existing Cole-Cole model-based descriptions of dielectric properties of biological matter in terms of the Debye model without loss of accuracy. Several tissue types have been considered. Results show that the electromagnetic field inside biological tissue depends on incident pulse rise time and width. Rise time dominates pulse behaviour inside tissue as conductivity increases. It has also been found that the amount of energy deposited by 20 kV m(-1) nanopulses is insufficient to change the temperature of the exposed material for pulse repetition rates of 1 MHz or less, consistent with recent experimental results.