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Ohne Zusammenfassung     

Peripheral O2 diffusion does not affect V(O2)on-kinetics in isolated insitu canine muscle

To test the hypothesis that muscle O2 uptake (V(O2)) on-kinetics is limited, at least in part, by peripheral O2 diffusion, we determined the V(O2) on-kinetics in 1) normoxia (Control); 2) hyperoxic gas breathing (Hyperoxia); and 3) hyperoxia and the administration of a drug (RSR-13, Allos Therapeutics), which right-shifts the Hb-O2 dissociation curve (Hyperoxia+RSR-13). The study was conducted in isolated canine gastrocnemius muscles (n = 5) during transitions from rest to 3 min of electrically stimulated isometric tetanic contractions (200-ms trains, 50 Hz; 1 contraction/2 s; 60-70% peak V(O2)). In all conditions, before and during contractions, muscle was pump perfused with constantly elevated blood flow (Q), at a level measured at steady state during contractions in preliminary trials with spontaneous Q x Adenosine was infused intra-arterially to prevent inordinate pressure increases with the elevated Q x Q was measured continuously, arterial and popliteal venous O2 concentrations were determined at rest and at 5- to 7-s intervals during contractions, and V(O2) was calculated as Q x arteriovenous O2 content difference. PO2 at 50% HbO2 saturation (P50) was calculated. Mean capillary PO2 (Pc(O2)) was estimated by numerical integration. P50 was higher in Hyperoxia+RSR-13 [40 +/- 1 (SE) Torr] than in Control and in Hyperoxia (31 +/- 1 Torr). After 15 s of contractions, Pc(O2) was higher in Hyperoxia (97 +/- 9 Torr) vs. Control (53 +/- 3 Torr) and in Hyperoxia+RSR-13 (197 +/- 39 Torr) vs. Hyperoxia. The time to reach 63% of the difference between baseline and steady-state V(O2) during contractions was 24.7 +/- 2.7 s in Control, 26.3 +/- 0.8 s in Hyperoxia, and 24.7 +/- 1.1 s in Hyperoxia+RSR-13 (not significant). Enhancement of peripheral O2 diffusion (obtained by increased PcO2 at constant O2 delivery) during the rest-to-contraction (60-70% of peak V(O2)) transition did not affect muscle V(O2) on- kinetics.     

Properties of tin/plasma polymer nanocomposites

Thin composite layers (tin in plasma polymer matrix) were prepared in a stainless steel vacuum chamber. An RF powered magnetron with tin target was used to excite the discharge and to activate the monomer species (n-hexane). The gas mixture introduced comprised Ar and n-hexane vapours. The properties of the films and chemical composition were characterized by AFM (surface morphology), TEM and Electron tomography (bulk structure characterization), XPS and FTIR spectroscopy (chemical composition analyses). Current-voltage characteristics were measured to examine the electrical properties of the layers and their dependence on the deposition parameters.     

Verfahren zur selbsttätigen Chlorierung für die Ermittlung der oxydischen Einschlüsse in einem Chrom-Nickel-Stahl mit rd. 18% Cr und 8% Ni

Übersicht über das Schrifttum. Beschreibung und Arbeitsweise des Gerätes. Erprobung an Rückständen aus einem Stahl mit 0,10% C, 17,5% Cr, 1,6% Mo, 14,0% Ni, 0,7% Nb, 0,26% Ti und 0,3% W. Verhalten von Eisenoxyd und Manganoxyd bei längerer Chlorierungsdauer. Anwendung auf Stähle mit 18% Cr und 8% Ni sowie 18% Cr und 10% Ni, mit und ohne Molybdän, Niob und Titan, die zum Teil unter Argon, im Vakuum und im Elektronenstrahlofen umgeschmolzen waren.     

Bioenergetics of contracting skeletal muscle after partial reduction of blood flow

The purpose of this study was to examine the bioenergetics and regulation of O2 uptake (VO2) and force production in contracting muscle when blood flow was moderately reduced during a steady-state contractile period. Canine gastrocnemius muscle (n = 5) was isolated, and 3-min stimulation periods of isometric, tetanic contractions were elicited sequentially at rates of 0.25, 0.33, and 0.5 contractions/s (Hz) immediately followed by a reduction of blood flow [ischemic (I) condition] to 46 +/- 3% of the value obtained at 0.5 Hz with normal blood flow. The VO2 of the contracting muscle was significantly (P < 0.05) reduced during the I condition [6.5 +/- 0.8 (SE) ml . 100 g-1 . min-1] compared with the same stimulation frequency with normal flow (11.2 +/- 1.5 ml . 100 g-1 . min-1), as was the tension-time index (79 +/- 12 vs. 123 +/- 22 N . g-1 . min-1, respectively). The ratio of VO2 to tension-time index remained constant throughout all contraction periods. Muscle phosphocreatine concentration, ATP concentration, and lactate efflux were not significantly different during the I condition compared with the 0. 5-Hz condition with normal blood flow. However, at comparable rates of VO2 and tension-time index, muscle phosphocreatine concentration and ATP concentration were significantly less during the I condition compared with normal-flow conditions. These results demonstrate that, in this highly oxidative muscle, the normal balance of O2 supply to force output was maintained during moderate ischemia by downregulation of force production. In addition, 1) the minimal disruption in intracellular homeostasis after the initiation of ischemia was likely a result of steady-state metabolic conditions having already been activated, and 2) the difference in intracellular conditions at comparable rates of VO2 and tension-time index between the normal flow and I condition may have been due to altered intracellular O2 tension.     

An analysis of social interaction between novice older adults when learning gesture-based skills through simple digital games

Universal Access in the Information Society - This paper reports three exploratory empirical studies with older adults that had little or no prior experience with interactive technologies. The...