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Interpolation with restrictions -- role of the boundary conditions and individual restrictions
Valášek, Jan ; Sváček, P.
The contribution deals with the remeshing procedure between two computational finite element meshes. The remeshing represented by the interpolation of an approximate solution onto a new mesh is needed in many applications like e.g. in aeroacoustics, here we are particularly interested in the numerical flow simulation of a gradual channel collapse connected with a~severe deterioration of the computational mesh quality. Since the classical Lagrangian projection from one mesh to another is a dissipative method not respecting conservation laws, a conservative interpolation method introducing constraints is described. The constraints have form of Lagrange multipliers enforcing conservation of desired flow quantities, like e.g. total fluid mass, flow kinetic energy or flow potential energy. Then the interpolation problem turns into an error minimization problem, such that the resulting quantities of proposed interpolation satisfy these physical properties while staying as close as possible to the results of Lagrangian interpolation in the L2 norm. The proposed interpolation scheme does not impose any restrictions on mesh generation process and it has a relatively low computational cost. The implementation details are discussed and test cases are shown.
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The Influence of Different Geometries of Human Vocal Tract Model on Resonant Frequencies
Valášek, Jan ; Sváček, Petr ; Horáček, Jaromír
This paper presents the transfer function approach in order to determine the acoustic resonant frequencies of a human vocal tract model. The transfer function is introduced here as an acoustic pressure ratio between input amplitude at glottis position and output amplitude at mouth opening given by the solution of Helmholtz equation. This equation is numerically approximated by finite element method. The influence of different boundary conditions are studied and also different locations of excitation and microphone. Four different vocal tract geometries motivated by vocal tract geometry for vowel [u:] are investigated. Its acoustic resonance frequencies in range 100 - 2500 Hz are computed and compared with published results. Further, the transient acoustic computation with different acoustic analogies are performed. The frequency spectra of Lighthill analogy, acoustic wave equation and perturbed convective wave equation are compared, where the vocal tract model with best frequency agreement with published results was chosen. The dominant frequencies correspond with predicted frequencies of transfer function approach.\n
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A potential role of DAXX in cell cycle arrest and cellular senescence
Valášek, Ján ; Hanzlíková, Hana (advisor) ; Vopálenský, Václav (referee)
Death domain-associated protein 6 (DAXX) is a multifunctional protein involved in diverse cellular processes. It acts as a histone chaperone or regulator of transcription and apoptosis, in which is its role quite controversial. DAXX also participates in regulation of cell DNA damage response (DDR). DAXX co-creates and stabilizes complex with Mdm2, which negatively regulates the stability of p53, an important tumor suppressor, which is a part of signalling node in the DDR. If DNA damage is not lethal for the cell and unables it to proliferate, the irreversible state of cell cycle called cellular senescence takes place. Under physiological conditions, induction of senescence can prevent the development of tumorigenesis. Therefore, the description of mechanisms involved in the induction of senescence has potential clinical significance. In my thesis, I aimed to determine changes in the level of DAXX protein in senescent cells and to characterize the manner of its regulation. In tumor cells MCF-7 and primary BJ fibroblasts, I observed decrease in DAXX protein level and its regulation. I tested the hypothesis according to which an increase in DAXX level before DNA damage canprevent induction of cellular senescence, or increase in its expression during senescence can cause recovery of cell proliferation....
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Artificial lipid membranes and the properties of the membrane proteins.
Valášek, Ján ; Fišer, Radovan (advisor) ; Vopálenský, Václav (referee)
Cell membrane and membrane proteins play fundamental roles in cell life. Cells use transporters and ion channels to interact with the environment and maintain cellular homeostasis. Therefore, their understanding and characterization are important area of basic and applied research. Large size of the cell and membrane protein insolubility make hamper their study and requires more sophisticated approaches, e.g. for the research of individual channels and transporters. This work seeks to create a simple overview of the most used methods for creating artificial lipid membranes. They are LB film, DIB, BLM and SLB. They can be examined by applying lipid bilayer and individual proteins. The work also outlines the procedure for the preparation, use and benefits of different approaches and briefly describes the membrane proteins, biological membranes and conventional methods for their study.
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