Collisional Velocities and Rates in Resonant Planetesimal Belts

We consider a belt of small bodies around a star, captured in one of the external or 1:1 mean-motion resonances with a massive perturber. The objects in the belt collide with each other. Combining methods of celestial mechanics and statistical physics, we calculate mean collisional velocities and collisional rates, averaged over the belt. The results are compared to collisional velocities and rates in a similar, but non-resonant belt, as predicted by the particle-in-a-box method. It is found that the effect of the resonant lock on the velocities is rather small, while on the rates more substantial. The collisional rates between objects in an external resonance are by about a factor of two higher than those in a similar belt of objects not locked in a resonance. For Trojans under the same conditions, the collisional rates may be enhanced by up to an order of magnitude. Our results imply, in particular, shorter collisional lifetimes of resonant Kuiper belt objects in the solar system and higher efficiency of dust production by resonant planetesimals in debris disks around other stars.Comment: 31 pages, 11 figures (some of them heavily compressed to fit into arxiv-maximum filesize), accepted for publication at "Celestial Mechanics and Dynamical Astronomy

The Study of the Effects of Surface Dielectric Barrier Discharge Low Temperature Plasma Products on Spring and Winter Wheat Germination

The use of ion-plasma technologies for treatment of seeds of different crop plants is particularly important for regions that exist in environment of risk farming. This is due to the lack of supplies in the treatment, durability, reliability and performance of these technologies. However, the mixed results of studies obtained for different species and varieties of seeds, make it necessary to detail compare the effects of the low-temperature plasma products for different cultures. This paper presents the results of experimental studies of the effects of plasma products of surface dielectric barrier discharge on the germination of spring and winter wheat. It has been shown that irrespective of time and the exposure intensity laboratory germination of spring wheat seeds reduced of 74% in the control group to 52% of the treated seeds, while the germination of wheat seeds is not reduced even at a relatively long exposure (20 min). The modes of treatment (3 min, 2.1-2.4 kV) at which germination of winter wheat seeds increase from 81% in the control group to 87% of the treated seeds have been selected. Resistance of winter wheat seed germination to the product of the discharge plasma can be used to form the conditions for safe suppression of a variety of pathogenic organisms on the surface of seeds

Possible Atmospheric Diversity of Low Mass Exoplanets – Some Central Aspects

Exoplanetary science continues to excite and surprise with its rich diversity. We discuss here some key aspects potentially influencing the range of exoplanetary terrestrial-type atmospheres which could exist in nature. We are motivated by newly emerging observations, refined approaches to address data degeneracies, improved theories for key processes affecting atmospheric evolution and a new generation of atmospheric models which couple physical processes from the deep interior through to the exosphere and consider the planetary-star system as a whole. Using the Solar System as our guide we first summarize the main processes which sculpt atmospheric evolution then discuss their potential interactions in the context of exoplanetary environments. We summarize key uncertainties and consider a diverse range of atmospheric compositions discussing their potential occurrence in an exoplanetary context