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    • Polyharmonic hypersurfaces into pseudo-Riemannian space forms
    Authors: V., Branding; S., Montaldo; C., Oniciuc;  Advisor: -;  Co-Author: - (2022)

    In this paper, we shall assume that the ambient manifold is a pseudo-Riemannian space form Nm+1t(c) of dimension m+1 and index t (m≥2 and 1≤t≤m). We shall study hypersurfaces Mmt′ which are polyharmonic of order r (briefly, r-harmonic), where r≥3 and either t′=t or t′=t−1. Let A denote the shape operator of Mmt′. Under the assumptions that Mmt′ is CMC and TrA2 is a constant, we shall obtain the general condition which determines that Mmt′ is r-harmonic.
    • Surface tension behavior of superspreading and non-superspreading trisiloxane surfactants
    Authors: Séforah Carolina Marques, Silva; Tatiana, Gambaryan-Roisman; Joachim, Venzmer;  Advisor: -;  Co-Author: - (2023)

    One parameter frequently considered to be relevant for superspreading of trisiloxane surfactants is surface tension kinetics. In the scientific literature, some experimental results reported for trisiloxane surfactants are in contradiction with fundamental concepts of surfactant monomer diffusion. Therefore, maximum bubble pressure tensiometry has been used to determine dynamic surface tension (DST) of two types of trisiloxane surfactants: superspreader and non-superspreader. Results show that both surfactants behave similarly at concentrations below critical micelle concentration (CMC), as expected. The CMC curves, as determined by drop shape analysis, confirmed that the more hydrophilic non-superspreader has a higher CMC as compared to the more hydrophobic superspreader.