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Blast-induced damage
Published in Xia-Ting Feng, Rock Mechanics and Engineering, 2017
These authors applied the one-dimensional hydrodynamic theory of detonation to estimate peak dynamic pressure on the blasthole walls that exerted a fully coupled charge. It was assumed that the gases expanded isentropically and behaved polytropially and that rock behavior was defined by a shock equation of state. Using regression, they then related the dynamic pressure to a set of parameters that roughly represented the detonation pressure and the impedance contrast Z (the rock mass/explosive impedance ratio). Ouchterlony included the effect of charge decoupling in the results of Liu & Katsabanis, obtaining an equation that can be expressed in general form as: PΦ/2=PbZa where a is a constant. Applying detonation theory and the hypothesis of isentropic gas expansion, the following relationships are obtained between Pb, explosion pressure (Pe) and detonation pressure (Pcj): Pcj=ρeDe2γ+1;Pe=Pcj(γγ+1)γ;Pb=Pefcγ1 where De is detonation velocity, γ is the isentropic expansion factor of the gaseous products in the state of detonation (assumed to remain constant until the gases return to the initial explosive density ρe), γ1 is the average isentropic expansion factor of the gases from ρe to their final expanded state in the borehole, f is the coupling factor and c is a constant usually set to 2 for elongated charges.
An in vitro model to assess effects of a desensitising agent on bacterial biofilm formation
Published in Acta Biomaterialia Odontologica Scandinavica, 2019
Jamie Coulter, Nicholas S. Jakubovics, Philip M. Preshaw, Matthew J. German
Dentine hypersensitivity occurs when a tooth with exposed dentine interprets relatively innocuous stimuli as noxious [1]. One explanation for dentine hypersensitivity is the hydrodynamic theory; this stipulates that a stimulus causes movement of fluid within dentine tubules resulting in nerve depolarisation and a painful stimulus. Thus, dentine tubules exposed to temperature changes or air pressure could result in fluid movement and pain [2]. Some treatments such as the desensitising agents added to dentifrices focus upon blocking or occluding the dentinal tubules in an attempt to reduce sensitivity. One product which works via this mechanism is calcium sodium phosphosilicate (CSPS). This forms a layer of carbonated hydroxyapatite crystals on dentine when in contact with an aqueous environment [3]. CSPS occludes significantly more dentine tubules and decreases dentine permeability significantly more than other control toothpastes [4,5].