Entry and return times for semi-flows

Determination of room entry times for radiation therapists after routine 15 MV photon treatments

Background: Radiation therapy  uses high-energy radiation to kill cancer cells. Photoneutron contamination and induced radioactivity of high energy therapeutic photon beams are considered as the main source of occupational exposure to radiation therapists who works with linear accelerators operating above 10 MV. Materials and Methods: The gamma dose rates were measured after termination of...

Return Probabilities for Stochastic Fluid Flows

Convergence of Logarithmic Return Times

Foreword The last nine months of my study were dedicated to writing this master thesis. After having determined that I wanted it to be based on the course of Ergodic Theory, that I took in the first semester of the academic year 2003/2004, Karma Dajani suggested the subject of repetitions in number expansions. The subject interested me right from the start. Since in general writing my master th...

Continuous symmetry reduction and return maps for high-dimensional flows

We present two continuous symmetry reduction methods for reducing highdimensional dissipative flows to local return maps. In the Hilbert polynomial basis approach, the equivariant dynamics is rewritten in terms of invariant coordinates. In the method of moving frames (or method of slices) the state space is sliced locally in such a way that each group orbit of symmetry-equivalent points is repr...

Entry Costs , Intermediation , and Capital Flows ¤

In this paper, we reexamine the question “Why doesn’t capital ‡ow from rich to poor countries?” posed, most recently, by Lucas (1990). We build a simple contracting framework where costly intermediation together with an adverse selection problem have quantitatively important e¤ects on capital ‡ows. When intermediation costs are ignored, the model behaves much like the neoclassical model in term...