Luca Giuggioli

Diffusion and home range parameters for rodents: Peromyscus maniculatus in New Mexico

We analyze data from a long-term field project in New Mexico, consisting of repeated sessions of mark-recaptures of Peromyscus maniculatus (Rodentia: Muridae), the host and reservoir of Sin Nombre virus (Bunyaviridae: Hantavirus). The displacements of the recaptured animals provide a means to study their movement from a statistical point of view. We extract two parameters from the data with the help of a simple model: the diffusion constant of the rodents, and the size of their home range. The short time behavior shows the motion to be approximately diffusive and the diffusion constant to be 470 � 50 m 2 /day. The long time behavior provides an estimation of the diameter of the rodent home ranges, with an average value of 100 � 25 m. As in previous investigations directed at Zygodontomys brevicauda observations in Panama, we use a box model for home range estimation. We also use a harmonic model in the present investigation to study the sensitivity of the conclusions to the model used and find that both models lead to similar estimates.

Effects of finite probing windows on the interpretation of the multifractal properties of random walks

We investigate the general problem of how the finiteness of a probing window for measurements of the movements of a random walker can lead to spurious detection of multifractality as well as to incorrect values of Hurst exponents, and propose a method for correcting for these effects. We also study the case in which the roaming region of the walker is itself of limited extent, when a nonlinear interplay occurs between the roaming area and the window size. In the context of animal movements, we describe briefly an application of these ideas to mark-recapture observations in a mouse population, of interest to the important topic of the spread of the Hantavirus epidemic.

Quasi-one-dimensional waves in rodent populations in heterogeneous habitats: A consequence of elevational gradients on spatio-temporal dynamics

Wave propagation can be clearly discerned in data collected on mouse populations in the Cibola National Forest (New Mexico, USA) related to seasonal changes. During an exploration of the construction of a methodology for investigations of the spread of the Hantavirus epidemic in mice we have built a system of interacting reaction diffusion equations of the Fisher-Kolmogorov-Petrovskii-Piskunov type. Although that approach has met with clear success recently in explaining Hantavirus refugia and other spatiotemporal correlations, we have discovered that certain observed features of the wave propagation observed in the data we mention are impossible to explain unless modifications are made. However, we have found that it is possible to provide a tentative explanation/description of the observations on the basis of an assumed Allee effect proposed to exist in the dynamics. Such incorporation of the Allee effect has been found useful in several of our recent investigations both of population dynamics and pattern formation and appears to be natural to the observed system. We report on our investigation of the observations with our extended theory.

UV filaments:great potential for long distance waveguides in air

We report studies on UV filaments regarding length, energy, spectrum, and conductivity. They show no energy loss in form of conical emission and their high conductivity makes them excellent candidates for waveguides in air.

Tests of laser-induced discharge of high DC voltage using high power femtosecond UV pulses

Pulses of 500 fs or greater duration and several tens of millijoules at 248 nm are used to trigger discharges in air. We will discuss the influence of beam geometry, the minimum field strength that can be triggered, and the electrical discharge guiding properties. The latest measurements have concentrated on DC discharges in air at up to 200 kV. Thanks to a new technique of background free, single shot interferometry, 2D snapshots of the evolving plasma can be recorded. This will lead to further insight about the dynamics involved in the discharge process. The existing laser system is costly and difficult to use in the field. We will show however that similar performance can be achieved with a solid state laser and frequency conversion by nonlinear optics. Such a compact system can be tuned to cover the wavelength range from 240 nm to 350 nm.

Pulse stretching in an alexandrite laser

Summary form only given. The idea of using an energy limiting process such as two photon absorption to increase the pulse duration of Q-switched lasers is not recent. We demonstrate that by using this idea it is possible to achieve pulse stretching on the order of microseconds in a Q-switched alexandrite laser (750 nm) using ZnSe as the two photon absorber.