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[en] Current diagnostic tools for the assessment of lung function are limited by global measurements or the need for radioactive tracers. Ideally, these tools should allow quantitative, regional distinct analyses without exposure to radiation. The current paper presents oxygen-enhanced functional MRI for assessment of lung ventilation. First applied in humans in 1996, a considerable amount of experience is now available on 1.5T scanners. The generation of quantitative T1-maps shows a high clinical potential. Low-field MR scanners, which are mostly open-designed, are especially interesting for functional lung imaging. The open design has advantages in respect to patient comfort by lower noise production and easy access to the patients and the costs are lower (no need for helium cooling). Lower signal-to-noise ratios can be overcome by changing the relaxation times. New navigator techniques allow further compensations. This article focuses on the presentation of low-field scanners and the application of T1 and T2* maps is described for healthy volunteers and first patients. (orig.)
[de]Heutige Verfahren zur Lungenfunktionsuntersuchung erlauben nur globale Analysen oder sind auf die Anwendung radioaktiver Tracer angewiesen. Wuenschenswert waeren jedoch quantitative, regional aufgeloeste Techniken ohne jegliche Strahlenexposition. Der vorliegende Artikel stellt die sauerstoffverstaerkte MR-Lungenfunktionsventilationsmessung vor. Erstmalig 1996 am Menschen eingesetzt, liegen bereits zahlreiche Erfahrungen mit 1,5-Tesla-Systemen vor. Dabei erwies sich insbesondere die quantitative T1-Bildgebung als zukunftsfaehiges Verfahren. Besonders attraktiv fuer die funktionelle Lungenbildgebung sind so genannte offene Niederfeld-MR-Systeme. Vorteile sind die Patientenfreundlichkeit des Systems, insbesondere fuer die Untersuchung von Kindern und Jugendlichen, niedrige Kosten durch Verzicht auf Heliumkuehlung und die deutlich geringere Geraeuschentwicklung. Geringere Signal-zu-Rausch-Verhaeltnisse koennen durch veraenderte Relaxationszeiten ausgeglichen werden. Neuere Navigationstechniken ermoeglichen weitere Kompensationen. Der vorliegende Artikel fokussiert auf die Darstellung der Niederfeld-Lungen-MRT und stellt T1- wie auch T2*-Messungen an Probanden und ersten Patienten vor. (orig.)
[en] Remarkable enhancement of the electrical conductivity and electrocatalytic activity is demonstrated as a result of the transformation of crystal structure between Sr2Mn2O6 and CaSrMn2O6. The structure of Sr2Mn2O6 is known to consist of dimeric units of face-sharing MnO6 octahedra. Whereas, CaSrMn2O6 contains individual octahedra, connected to each other through corner-sharing. Herein we show that the changes in the crystal structure result in significant improvement of the electrical conductivity, by five orders of magnitude, for CaSrMn2O6, compared to Sr2Mn2O6. Variable temperature conductivity studies from 25–800 °C indicate semiconducting properties for both compounds, where the enhanced conductivity of CaSrMn2O6 persists in the entire temperature range. The electrocatalytic activity of both compounds toward oxygen evolution reaction (OER) has also been investigated, indicating superior OER activity of CaSrMn2O6 compared to Sr2Mn2O6. A pronounced improvement in the onset potential and kinetics of OER is observed for CaSrMn2O6. These studies demonstrate an important correlation between crystal structure, electrical conductivity and electrocatalytic properties.
Graphic abstractRemarkable enhancement of the electrical conductivity and electrocatalytic activity is demonstrated as a result of the transformation of crystal structure between Sr2Mn2O6 and CaSrMn2O6. .
[en] Mammalian cells cultured in vitro were used to study the radiobiological characteristics of neutron beams generated by 43 MeV protons on beryllium or 25 MeV deuterons on beryllium. For an unfiltered beam of neutrons generated by 43 MeV p+→Be the relative biological effectiveness was found to be 8-12% higher at a depth of 2 cm than at a depth of 12 cm due to the presence of a large component of low-energy neutrons. The addition of a hydrogenous filter 4 cm thick preferentially removed the low-energy neutrons from the beam and, as a result, the neutron RBE was independent of depth. There was no significant difference in the oxygen enhancement ratio between the filtered neutrons produced by 43 Mev p+ → Be and neutrons produced by 25 MeV d+ → Be; for both beams the OER value was about 1.6. (author)
[en] The present report summarizes the results of a new series of biological intercomparisons of neutron therapy beams using mammalian cells cultured in vitro. Experiment design was based upon two important considerations: (a) It is a characteristic of cell culture experiments that variations within an experiment are much smaller than those between experiments. Consequently, neutron facilities were intercompared in pairs, within a given experiment, using cells from a common culture irradiated on the same day. (b) A standardized treatment fixture was used at all facilities, constructed of lucite, with space for 6 tissue culture flasks, and provision for an ionization chamber to be inserted into the jig to determine the dose received at the position occupied by the cells. Full build-up was ensured because the cells were overlaid with 2 cm of tissue culture medium. A substantial international effort to achieve compatible dosimetry was mounted by the physicists at the various installations engaged in neutron therapy, as a consequence of which there is agreement to within +-1.5% for dose measurements in air. The use of the standard treatment fixture was an attempt to extend the compatible dosimetry to a practical set-up for the irradiation of cell cultures
[en] The physico chemical study of oxygen effect and the part played by excitation energy are described. The case of a model molecule of biological interest: tryptophan and its N-acetyl derivative, is given
[fr]Etude physicochimique de l'effet oxygene et mise en evidence du role de l'energie d'excitation. Cas d'une molecule modele d'interet biologique: le tryptophane et son derive N-acetyle