150 research outputs found
Geoscientific process monitoring with positron emission tomography (GeoPET)
Transport processes in geomaterials can be observed with input–output
experiments, which yield no direct information on the impact of
heterogeneities, or they can be assessed by model simulations based on
structural imaging using µ-CT. Positron emission tomography (PET)
provides an alternative experimental observation method which directly and
quantitatively yields the spatio-temporal distribution of tracer
concentration. Process observation with PET benefits from its extremely high
sensitivity together with a resolution that is acceptable in relation to
standard drill core sizes. We strongly recommend applying high-resolution PET
scanners in order to achieve a resolution on the order of 1 mm.
We discuss the particularities of PET applications in geoscientific
experiments (GeoPET), which essentially are due to high material density.
Although PET is rather insensitive to matrix effects, mass attenuation and
Compton scattering have to be corrected thoroughly in order to derive
quantitative values.
Examples of process monitoring of advection and diffusion processes with
GeoPET illustrate the procedure and the experimental conditions, as
well as the benefits and limits of the method
Analysis of concentration response curves to describe and compare tha antimicrobial activity anof model cationic alpha-helical peptides.
To assess and compare different model Leu-Lys-containing cationic α-helical peptides, their antimicrobial activities were tested against Escherichia coli as target organism over a broad peptide concentration range. The natural cationic α-helical peptides magainin 2 and PGLa and the cyclic cationic peptide gramicidin S were also tested between comparison. The dose-response curves differed widely for these peptides, making it difficult to rank them into an activity order over the whole concentration range. We therefore compared five different inhibition parameters from dose-response curves: I
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