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Search Results: 1 - 10 of 1257 matches for " Pawel Olejnik "
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Bifurcations of planar sliding homoclinics
Jan Awrejcewicz,Michal Fe kan,Pawel Olejnik
Mathematical Problems in Engineering , 2006, DOI: 10.1155/mpe/2006/85349
Abstract: We study bifurcations from sliding homoclinic solutions to bounded solutions on ℝ for certain discontinuous planar systems under periodic perturbations. Sufficient conditions are derived for such perturbation problems.
Bifurcations of planar sliding homoclinics
Jan Awrejcewicz,Michal Fe?kan,Pawel Olejnik
Mathematical Problems in Engineering , 2006,
Abstract: We study bifurcations from sliding homoclinic solutions to bounded solutions on for certain discontinuous planar systems under periodic perturbations. Sufficient conditions are derived for such perturbation problems.
Vacuum structure and Casimir scaling in Yang-Mills theories
S. Olejnik
Physics , 2009,
Abstract: The vacuum of Yang-Mills theories can be imagined as a magnetically disordered medium with domain structure, with color magnetic flux in each domain quantized in units corresponding to the gauge group center. This model leads to the prediction of Casimir scaling, i.e. the proportionality of string tensions of potentials (at intermediate distances) between color sources from higher-representations to eigenvalues of the quadratic Casimir operator. I present evidence for Casimir scaling in G(2) lattice gauge theory. I also discuss support for some ingredients of the model from the recently conjectured form of the Yang-Mills ground-state wave-functional.
The Yang-Mills vacuum wave functional thirty-five years later
Stefan Olejnik
Physics , 2015, DOI: 10.1088/1742-6596/631/1/012057
Abstract: The first paper attempting direct calculation of the Yang-Mills vacuum wave functional was published by Greensite in 1979. I review some recent results of the determination of the vacuum wave functional in Monte Carlo simulations of SU(2) lattice gauge theory.
On a complete characterization of a.s. convergence of multiple orthogonal series
Jakub Olejnik
Mathematics , 2011,
Abstract: We present a relation between convergence of multiple and single orthogonal series. This relation implies a complete characterization of all multiple sequences $(a_{n_1...n_d})_{n_1,...,n_d\in\bb N}$ such that for all orthonormal $(\Phi_{n_1...n_d})$ multiple orthogonal series $\sum_{n_1,...,n_d\in\bb N}a_{n_1...n_d}\Phi_{n_1...n_d}$ are a.s.\ convergent.
Casimir scaling in G(2) lattice gauge theory
Liptak, L.;Olejnik, S.
High Energy Physics - Phenomenology , 2008, DOI: 10.1103/PhysRevD.78.074501
Abstract: We computed potentials between static color sources from the six lowest representations of G(2) lattice gauge theory, in numerical simulations with the Wilson action on asymmetric lattices with nonperturbatively estimated values of the bare anisotropy. We present evidence for (approximate) Casimir scaling of the obtained intermediate string tensions. The agreement with the Casimir-scaling prediction improves by increasing the coupling beta in the weak-coupling region above the crossover observed in G(2) gauge theory. The result naturally fits into confinement models with magnetic disorder and vacuum domain structure, but may represent a challenge for other approaches.
Testing the Yang-Mills vacuum wave functional Ansatz in 3+1 dimensions
Greensite, J.;Olejnik, S.
High Energy Physics - Phenomenology , 2013,
Abstract: We proposed a simple Ansatz for the vacuum wave functional (VWF) of SU(2) gauge theory in temporal gauge. In 2+1 dimensions, the Ansatz was shown to be a fairly good approximation to the true VWF of the theory. Relative probabilities of various test configurations in the vacuum can be computed in numerical simulations of lattice-regulated SU(2) gauge theory by the method proposed long ago by Greensite and Iwasaki. We report promising (albeit still preliminary) results of testing the proposed VWF in 3+1 dimensions on various sets of lattice gauge field configurations.
Sulforaphane – a possible agent in prevention and therapy of cancer
Joanna Tomczyk,Anna Olejnik
Post?py Higieny i Medycyny Do?wiadczalnej , 2010,
Abstract: Sulforaphane (SFN) is an isothiocyanate that is naturally present in cruciferous vegetables, with high concentration in broccoli. The results of the most recent studies indicate multi-targeted sulforaphane actions which may contribute to prevention and therapy of cancer. Protective properties of sulforaphane have been observed in every stage of carcinogenesis. The mechanism of protection against the initiation of carcinogenesis by SFN includes modulation of phase I and II xenobiotic-metabolizing enzymes, as well as direct blocking of specific binding sites of carcinogens with the DNA molecule. As a result, sulforaphane inhibits DNA adduct formation, thus reducing the risk of mutations. Further sulforaphane activity is targeted at cancer cells and prevents their expansion due to regulation of proliferation and induction of differentiation or apoptosis. In vitro studies using various types of cancer cells have revealed the ability of SFN to arrest the cell cycle, particularly in G2/M, while SFN at higher concentration is shown to activate apoptotic pathways. The possible SFN anticancer effect in the progression stage of carcinogenesis has been proved by only a few studies, which provide evidence for its antiangiogenic and antimetastatic influence. Additionally, SFN exhibits anti-inflammatory and antibacterial effects relevant to cancer prevention.Apart from the biological activity of SFN, this review also focuses on its bioavailability and tissue distribution as well as individuals’ genetic predispositions as significant factors influencing the potential efficiency of chemoprevention using this compound.
Abrasive Wear Resistance of Cast Iron with Precipitates of Spheroidal VC Carbides
M. Kawalec,E. Olejnik
Archives of Foundry Engineering , 2012,
Abstract: The paper presents the results of abrasive wear resistance tests carried out on high-vanadium cast iron with spheroidal VC carbides. The cast iron of eutectic composition was subjected to spheroidising treatment using magnesium master alloy. The tribological properties were examined for the base cast iron (W), for the cast iron subjected to spheroidising treatment (S) and for the abrasion-resistant steel (SH). Studies have shown that high-vanadium cast iron with both eutectic carbides and spheroidal carbides has the abrasion resistance twice as high as the abrasion-resistant cast steel. The spheroidisation of VC carbides did not change the abrasion resistance compared to the base high-vanadium grade.
A visualization of the eutectic solidification process
E. Olejnik,E. Fra?
Archives of Foundry Engineering , 2007,
Abstract: The study presents a visualization of the sequence of formation of eutectic grains during solidification in volume and directional solidification of model organic materials from the system of salol (faceted phase) - camphor (non-faceted phase) and carbon tetrabromide (non-faceted phase) - hexachloroethane (non-faceted phase). It has been proved that the faceted phase may act as a substrate for nucleation of the non-faceted phase, while the non-faceted phase in a eutectic grain is of polycrystalline character. The directional solidification of non-faceted/non-faceted eutectic enabled disclosing various structural defects, while solidification in volume explained in what way the, so called, halo effect is formed.
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