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- Naredi, Peter, 1955, et al.
(author)
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Evaluation of blood flow measurements with microspheres and rubidium--an experimental study in rats.
- 1990
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In: International journal of microcirculation, clinical and experimental / sponsored by the European Society for Microcirculation. - 0167-6865. ; 9:4, s. 423-37
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Journal article (peer-reviewed)abstract
- The microsphere method has been widely used for blood flow measurements in normal and tumour tissues. The microsphere method was evaluated for repeated measurements of cardiac output and regional blood flow in anesthetised rats and in anesthetised rats given noradrenalin and thereby having altered haemodynamics with special emphasis on liver blood flow. Comparing the microsphere method with the soluble indicator method (86Rubidium) gave equal cardiac output values. The liver blood flow was lower and the spleen blood flow was higher with the microsphere method. Two microsphere injections at 10 min intervals were performed on anesthetised rats. In one group 817 +/- 10(3) microspheres were injected each time, in a second group 436 +/- 10(3) and in a third noradrenalin was added and then 430 +/- 10(3) microspheres injected twice. There was good reproducibility for cardiac output and for most organ and tissue blood flows between first and second microsphere injection. No influence on arterial liver blood flow was seen. A blood pressure fall and a decreased heart rate was registered after the first injection in the group given 817 x 10(3) spheres. There was also a blood pressure fall in the group given noradrenalin after the first microsphere injection. The microsphere method with two injections of 436 x 10(3) microspheres seems adequate to use in arterial blood flow studies of the liver and simultaneous cardiac output measurements.
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- Sarady, Istvan, et al.
(author)
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Joining of cemented tungsten carbide to tool steel using Nd:YAG-laser and optical fibres
- 1992
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In: Proceedings of the Laser Materials Processing Symposium : ICALEO '92. - Orlando, Fla : Laser institute of America. - 0912035498 ; , s. 529-533
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Conference paper (peer-reviewed)abstract
- The aim of the present work was to produce tools for powder compacting by joining cemented tungsten carbide to high-quality tool steels by laser welding. The conventional method of joining such materials is by brazing or by using adhesives (glue), both of which have disadvantages: low strength and poor positional accuracy. In the case of laser welding, the components were positioned exactly in a jig or fixture, heated to 200-300°C and finally welded by using a pulsed Nd:YAG laser giving a positional accuracy in the order of a few micrometers. The laser beam was optically split and guided by optical fibers to opposite sides of the joint greatly reducing the effect of thermal distortion. The use of optical fibers also result in a smooth energy distribution in the beam spot reducing the risk of crack formation. Compressive fatigue strength of the joined components was determined. Cross-sectioned samples were examined for microstructure, microhardness and the distribution of alloying elements in the joint zone. The weld surface was also examined for evidence of microcracking. The method described can complement conventional and vacuum brazing techniques in certain applications.
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