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Bratislava, Slovakia

Kochan D.,FMFI UK | Kochan D.,Nuclear Physics Institute of Czech Republic
Journal of Geometry and Physics

Geometrical formulation of classical mechanics with forces that are not necessarily potential-generated is presented. It is shown that a natural geometrical "playground" for a mechanical system of point particles lacking Lagrangian and/or Hamiltonian description is an odd-dimensional line element contact bundle. Time evolution is governed by certain canonical two-form Ω (an analog of d p ∧ d q - d H ∧ d t), which is constructed purely from forces and the metric tensor entering the kinetic energy of the system. Attempt to "dissipative quantization" in terms of the two-form Ω is proposed. The Feynman path integral over histories of the system is rearranged to a "world-sheet" functional integral. The "umbilical string" surfaces entering the theory connect the classical trajectory of the system and the given Feynman history. In the special case of potential-generated forces, "world-sheet" approach precisely reduces to the standard quantum mechanics. However, a transition probability amplitude expressed in terms of "string functional integral" is applicable (at least academically) when a general dissipative environment is discussed. © 2009 Elsevier B.V. All rights reserved. Source

Maihom T.,University of Innsbruck | Maihom T.,Kasetsart University | Sukuba I.,FMFI UK | Janev R.,Julich Research Center | And 7 more authors.
European Physical Journal D

We report calculated electron impact ionization cross sections (EICSs) for beryllium (Be) and some of its hydrides from the ionization threshold to 1 keV using the Deutsch-Märk (DM) and the Binary-Encounter-Bethe (BEB) formalisms. The positions of the maxima of the DM and BEB cross sections are very close in each case while the DM cross section values at the maxima are consistently higher. Our calculations for Be are in qualitative agreement with results from earlier calculations (convergent close-coupling, R matrix, distorted-wave and plane-wave Born approximation) in the low energy region. For the various beryllium hydrides, we know of no other available data. The maximum cross section values for the various compounds range from 4.0 × 10 -16 to 9.4 × 10-16 cm2 at energies of 44 to 56 eV for the DM cross sections and 3.0 × 10-16 to 5.4 × 10-16 cm2 at energies of 40.5 to 60 eV for the BEB cross sections. © 2013 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source

Safi E.,University of Helsinki | Bjorkas C.,University of Helsinki | Lasa A.,University of Helsinki | Nordlund K.,University of Helsinki | And 2 more authors.
Journal of Nuclear Materials

Abstract Beryllium (Be) is the main plasma-facing material in the present day fusion reactor JET as well as in the upcoming ITER. Thus, the Be erosion plays a key role in predicting the life-time and viability of the reactors. In this work, Be surface erosion and morphology changes due to deuterium (D) irradiation are studied by using molecular dynamics simulations, varying key parameters such as particle flux, surface temperature and impact energy. At low temperatures, the main molecular species among the sputtered particles is BeD due to a low D surface concentration, as the incoming D projectiles cluster beneath the surface. At higher temperatures, the D surface concentration increases and larger species (BeD2, BeD3) dominate the molecular erosion, lowering the BeD to Be ratio. When approaching the Be melting point, D desorbs from the surface, increasing the fraction of Be eroded as BeD. The larger molecules will dissociate as soon as entering the edge plasma, with only a minor contribution to the BeD formation. These findings correlate well with observations at JET. The effect of the incoming D flux on the results is negligible. © 2014 Elsevier B.V. Source

Krajci M.,FMFI UK | Urban J.,FMFI UK | MacH P.,FMFI UK
Journal of Molecular Modeling

The influence of the mechanical strain on the artificial protein L 24 (acetyl-K2-L24-K2-amide) has been studied at the molecular mechanics (MM) level of theory. The effect of the surrounding environment (DPPC molecules) has been observed during the stretching or compressing of the L24. The calculations gave the view on the structural changes occurring during these processes. All calculations were done using the GROMACS code with the ffgmx forcefield enhanced with lipid-protein interaction potentials. [Figure not available: see fulltext.] © 2010 Springer-Verlag. Source

Durina P.,FMFI UK | Stefecka M.,FMFI UK | Roch T.,FMFI UK | Noskovic J.,FMFI UK | And 7 more authors.
Conference Proceedings - The 8th International Conference on Advanced Semiconductor Devices and Microsystems, ASDAM 2010

In this work, the optimalisation of e-beam parameters and the writing strategy have been performed. Various positive and negative e-beam resists have been evaluated for high resolution e-beam lithography and pattern transfer. Both, lift-off method and ion beam etching have been investigated for the pattern transfer into thin Pt and MoC layer on saphire substrate. ©2010 IEEE. Source

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