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We present a simple nonlinear model describing the population dynamics of cancerous, healthy, and effector cells submitted to ionizing radiation. We examine the situations in which intermittently high doses of radiation affect the cells as it occurs in radiotherapy. We characterize the effect of various irradiation parameters, such as the total delivered dose for a given standard dose rate and the number of treatment sessions seeking situations that optimize normal cells survival. In other words, we are interested in enhancing the effectiveness of a radiotherapy treatment by adjusting the temporal pattern of the dose deliverance through an exhaustive dynamical characterization of the system. This includes the study of the parameter planes, the populations’ dynamical behavior going from fixed points to chaotic oscillations, and the basins of attraction. This work leads to counter-intuitive predictions and constitutes a step towards a model of chronomodulated radiotherapy., SCOPUS: ar.j, info:eu-repo/semantics/published

type:Journal Article, The critical current density and flux activation energy of the cuprate superconductor thin films degraded with the increase of x-ray irradiation time. The enlargement of critical current density with the creation of strong pinning sites resulted from the oxygen annealing of the x-ray irradiated films. The electronic state calculation revealed that the oxygen defects could interact with visual light and form color centers in the x-ray irradiated film. The x-ray irradiation process followed by annealing in oxygen provides effective method to control the characteristics of the superconductor thin films., source:http://www.aip.org, source:https://doi.org/10.1063/1.349821

Computer simulation results are reported on transistor design and single-event charge collection modeling of metal-semiconductor field effect transistors (MESFETs) fabricated in the Vitesse H-GaAsIII{reg_sign} process on Low Temperature grown (LT) GaAs epitaxial layers. Tradeoffs in Single Event Upset (SEU) immunity and transistor design are discussed. Effects due to active loads and diffusion barriers are examined.

An introduction to gallium arsenide (GaAs) Pseudo-Complementary MESFET Logic (PCML) circuits is presented. PCML was developed to reduce the sensitivity of high-speed GaAs logic to radiation-induced single event upsets (SEUs). Experiments for testing the single-event upset (SEU) sensitivity of GaAs PCML integrated circuits (ICs) are described. The results of the experiments are analyzed. This new type of high-speed, low-power, GaAs logic provides decreased sensitivity to SEUs compared to more traditional circuit designs such as Directly-Coupled FET Logic (DCFL). PCML is fully compatible with existing GaAs E/D MESFET fabrication processes, such as those commonly used to make DCFL.

The advantages and disadvantages of using gallium arsenide (GaAs) dynamic logic in computers and digital systems are briefly discussed, especially with respect to space applications. A short introduction to the topology and operation of GaAs Two-Phase Dynamic FET Logic (TDFL) circuits is presented. Experiments for testing the SEU sensitivity of GaAs TDFL, using a laser to create charge collection events, are described. Results are used to estimate the heavy-ion, soft error rate for TDFL in a spacecraft in geosynchronous orbit, and the dependence of the SEU sensitivity on clock frequency, clock voltage, and clock phase. Analysis of the data includes a comparison between the SEU sensitivities of TDFL and the more common static form of GaAs logic, Directly Coupled FET Logic (DCFL). This is the first reported SEU testing of GaAs dynamic logic.