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Abstract: An effective technique for numerical simulation, using the Monte Carlo technique, of the kinetics of relativistic runaway electron (RE) avalanche and its bremsstrahlung in a dense gas in the external electric field, based on successive generations of REs multiplied due to electron impact, and bremsstrahlung, which is the source of the next RE generation, has been developed. This technique is especially effective at low overvoltages (δ) relative to a relativistic minimum of the drag force (218 keV m−1 atm−1). It has been indicated that the characteristic time of avalanche enhancement is slightly smaller than the time obtained during the previous studies. The numerical simulation of an avalanche in the air has been performed for δ = 1.5. It has been indicated that the processes of secondary RE generation by bremsstrahlung substantially contribute to the rate of avalanche development. In spite of participation of photons, avalanche is concentrated in a relatively small volume, with ∼1% of electrons outside this volume, which indicates that the feedback mechanism in the development of ascending atmospheric discharges is actual.

Summary Dehydration of the desert iguana,Dipsosaurus dorsalis, resulted in a progressive elevation in the magnitude of the skin temperature necessary to elicit thermal panting (i.e., the panting threshold). Panting threshold increased from 43.4±0.8 °C at 100% initial body weight (IBW) to 45.4±1.2 °C at 90% IBW to 45.7±0.9 °C at 80% IBW. Plasma osmolality showed no significant change with dehydration to 80% IBW. Changes in plasma osmolality, whether induced by NaCl or non-ionic sucrose loading, had a significant impact on panting threshold. Increasing plasma osmolality resulted in an elevation of panting threshold while decreasing plasma osmolality resulted in lower panting thresholds. Decreasing body fluid volume by exsanguination of 1 ml whole blood/100 g body weight resulted in a mean increase in panting threshold by 0.7±0.2 °C. Volume loading with 160 mM NaCl (approximately isosmotic) had no significant effect on panting threshold. These data suggest that plasma osmolality and decreases in body fluid volume may be potent modulators of panting threshold during periods of water deprivation. However, at least in desert iguanas, increases in plasma osmolality would not appear to be an important factor in the elevation of panting threshold during dehydration to 80% IBW.

We have carried out a phenomenological analysis of the latest deep virtual Compton scattering experimental data based on the generalized parton distribution formalism. This allows us to extract the dependence of the spatial size of the proton on the quark's longitudinal momentum. This results in the first continuous two-dimensional momentum-space image and tomography of the proton based on experimental data. [ABSTRACT FROM AUTHOR]

Our contribution to this symposium is a review of recent models and experimental cdata on oxygen homeostasis in vertebrates with normal intracardiac shunts; i.e., amphibians and reptiles. We focus on the interactions among hemoglobin function, body temperature regulation, and cardiovascular shunts under normal conditions (i.e., breathing fresh air at or near sea level) and during external hypoxia (e.g., altitude, burrows) and internal hypoxia (e.g., anemia, hemorrhage). Mathematical models and experimental data suggest that animals with venous admixture from cardiovascular shunts will show biphasic arterial and mixed venous Po2 responses to warming; i.e., first increasing and then, as the dissociation curve shifts too far to the right, decreasing. This has implications for many physiological functions including oxygen consumption by tissues, control of breathing, as well as preferred body temperature and its regulation. We present some of the recent experiments that have explored these implications.