Saturation diving | EPFL Graph Search

Saturation diving is diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas used. It is a diving mode that reduces the number of decompressions divers working at great depths must undergo by only decompressing divers once at the end of the diving operation, which may last days to weeks, having them remain under pressure for the whole period. A diver breathing pressurized gas accumulates dissolved inert gas used in the breathing mixture to dilute the nitrogen to a non-toxic level in the tissues, which can cause decompression sickness ("the bends") if permitted to come out of solution within the body tissues; hence, returning to the surface safely requires lengthy decompression so that the inert gases can be eliminated via the lungs. Once the dissolved gases in a diver's tissues reach the saturation point, however, decompression time does not increase with further exposure, as no more inert gas is ac

Chambre sur cours. Unités de logements temporaires pour les Hautes Ecoles lausannoises

Shama Atif

Le projet propose un quartier d'habitations, destiné à la population estudiantine de l'agglomération lausannoise, spécialement rattaché à l'université et à l'école polytechnique. Suivant le développement vers le Nord du site universitaire, il prend place sur la commune de Chavannes-près-Renens, au lieu dit “le taluchet”. Après la lecture de Modèles d'habitats, entre persistances et mutations, une typologie du logement marocain, l'orientation donnée au projet admet certains principes de la maison méditerranéenne. Densité médinale, mitoyenneté maximale, la cour “el wüst el daâr”, comme espace de référence, l'introversion des espaces habités et l'individualisation des entrées aux logements sont autant d'éléments que le projet va tenter d'importer. Sous la forme d'un tissu compact, le projet prend progressivement possession du terrain en forme de cuve le long de la pente. Ce nouveau quartier, composé de diverses pièces autour des cours, admet aussi bien des espaces d'habitations que des espaces communs, collectifs ou publics, intérieurs et extérieurs. Différents types de logements sont développés - du simple studio à l'appartement individuel et de l'appartement en colocation au studio hôtelier - et tentent de répondre à la demande de la population universitaire, une communauté temporaire très diversifiée. Les divers modules d'habitation présentent des gabarits très bas, d'un niveau sur cours. La combinaison de ces modules s'adapte à la pente tout en assurant la continuité des espaces extérieurs-intérieurs. Toutes les cours communiquent entre elles au travers de circulations verticales ou de plain-pied mais se définissent toujours de manière individuelle, multipliant ainsi ambiances, essences végétales et couleurs.

2011

Assessing γ-glutamyl transpeptidase activity in kidney using hyperpolarized γ-Glu-[1-13C]Gly

Arnaud Comment, Steffen Frederic Frank, Rolf Gruetter, Hikari Ananda Infinity Yoshihara

Hyperpolarized γ-Glu-[1-13C]Gly provides a non-invasive means to detect γ-glutamyl transpeptidase (GGT) enzyme activity in vivo with potential for application in functional imaging. Since GGT is most abundant in the proximal tubules of the kidney, and since the properties of γ-Glu-[1-13C]Gly are suitable for in vivo hyperpolarized 13C metabolic analysis, it was proposed as a molecular probe to study kidney function. The aim of the present study is to identify the dose of γ-Glu-[1-13C]Gly that gives high NMR sensitivity in the unsaturated state of the GGT enzyme. Therefore γ-Glu-[1-13C]Gly was polarized with the stable trityl radical OX63 in a custom-designed DNP polarizer (7T, 1.1K) using microwave irradiation at 196.59 GHz and 50 mW. As a first approach to analyze the HP data, method used in [3] was applied. Herein, the reaction rates were calculated by multiplying the kinetic rate constants with the corresponding substrate concentrations, in which the kinetic rate constant is the product of the 13C longitudinal relaxation rate of glycine (~45s) and the ratio of the integrated γ-Glu-[1-13C]Gly and [1-13C]Gly signal amplitude. Benefiting from a narrow spectral linewidth of the hyperpolarized signal (~20 Hz, FWHM), conversion of γ-Glu-[1-13C]Gly to [1-13C]Gly was measurable down to an estimated blood concentration of 32 μM. To address the possibility of substrate saturation of the GGT enzyme in the kidney, different doses of γ-Glu-[1-13C]Gly were administered, corresponding to a blood concentration range of 32 to 500 μM. The variability of the apparent reactions rates between animals is high for all doses of administered γ-Glu-[1-13C]Gly. The rate, however, was proportional with the dose in 7 of 8 rats, and complete saturation of the GGT enzyme cannot be seen in the dosage range tested. This study shows that HP γ-GluGly senses GGT activity with excellent NMR sensitivity and that a broad range of substrate concentrations can be applied to study kidney function. To understand better the distribution of the initial reaction rates and to estimate the dose required to saturate the GGT enzyme, a broader range of substrate doses will be tested, along with simultaneous functional quantification.

2018

Assessing γ-glutamyl transpeptidase activity in kidney using hyperpolarized γ-Glu-[1-13C]Gly

Arnaud Comment, Steffen Frederic Frank, Rolf Gruetter, Hikari Ananda Infinity Yoshihara

2018