40 research outputs found
Strong asymptotic stability of a compactly coupled system of wave equations
AbstractWe prove the well-posedness and study the strong asymptotic stability of a compactly coupled system of wave equations with a nonlinear feedback acting on one end only
A note on the boundary stabilization of a compactly coupled system of wave equations
AbstractWe obtain decay estimates of the energy of solutions to compactly coupled wave equations with a nonlinear boundary dissipation which is weak as |u′| tends to infinity
Controllability of a viscoelastic plate using one boundary control in displacement or bending
In this paper we consider a viscoelastic plate (linear viscoelasticity of the
Maxwell-Boltzmann type) and we compare its controllability properties with the
(known) controllability of a purely elastic plate (the control acts on the
boundary displacement or bending). By combining operator and moment methods, we
prove that the viscoelastic plate inherits the controllability properties of
the purely elastic plate
Detection of Bioactive Exometabolites Produced by the Filamentous Marine Cyanobacterium Geitlerinema sp.
Marine cyanobacteria are noted for their ability to excrete metabolites with biotic properties. This paper focuses on such exometabolites obtained from the culture of the marine filamentous cyanobacterium Geitlerinema sp. strain, their purification and subsequent analyses. By this means the recoveries of the active compounds, a prerequisite for properly determining their concentration, are quantified here for the first time. We demonstrate a new procedure using Amberlite XAD-1180 resin in combination with the eluent isopropanol for extraction of the culture media and gas chromatography as simplified chemical analysis. This procedure reduced necessary bacteria cultivation time (from 150 to 21 days) at low volumes of culture media (300 mL) required for identification of two selected bioactive compounds: 4,4′-dihydroxybiphenyl and harmane