Seminář se koná každé úterý v 10:40 v posluchárně ÚTF MFF UK
v 10. patře katedrové budovy v Tróji, V Holešovičách 2, Praha 8
Radiation can be recently sensitively controlled both in time and energy. Chemistry can benefit from the advancement in physics and use light to control matter. In my talk, I will focus on molecular simulations of the chemical processes initiated by the interaction of photons with molecules. Photochemical processes are usually associated with photons in the UV, visible and sometimes also in the IR range. Photochemical simulations describing the processes in this range have significantly advanced in the last decade. I will briefly describe the techniques typically used in the field, emphasizing particularly the role of solvent environment. The field of X-ray initiated photodynamics is much more complicated and much less developed. In fact, dynamical processes initiated by X-ray photons are so far not typically considered as part of photochemistry as the amount of energy deposited into the system is way too large for defined chemical changes. On the other hand, X-ray photons allow us to excite/ionize specific atoms. Here, I will present our recent findings on new processes which we have identified in solvated systems upon X-ray exposure. In this context, I will also discuss new liquid state spectroscopies using tunable X-radiation and allowing us to investigate X-ray initiated processes.
Changes in climate influence the distribution of ice and water over the Earth's surface, which, in turn influence the climate itself. Ice accumulation or ablation followed by changes in sea level induce glacial-isostatic adjustment of the solid Earth. Conversely, the solid-Earth deformation influences a rise and fall of sea level. Moreover, the redistribution of ice and water and changes in the mass distribution in the Earth's interior are capable to induce perturbations in the rotation of the Earth, both in direction and magnitude of the rotation vector. A wander of the rotation axis, in turn, induces variations in the centrifugal potential and, subsequently, variations in the sea level. All this means that the determination of sea level variations coupled with polar wander due to changes in ice's water mass load is a complex geophysical and mathematical problem.
The theory and modelling of glacial isostatic adjustment have been rapidly developing since the launch of the GRACE satellite gravity mission in 2002. The lecture presents an overview what has been achieved in the theory and data assimilation on a precise modelling and prediction of glacial isostatic adjustment.
Examples of solar flares in UV and radio observations are shown. The standard model of solar flares is explained. Then we present processes in solar flares and their simulations in magnetohydrodynamic and particle-in-cell models. Maps of waves and oscillations based on the broadband radio spectrum are added. A role of thermal fronts in solar flares is mentioned. Finally, a question of solar superflares is shortly discussed.
Jiří Horáček Jiří Bičák