Tracking target and spiral waves.

A new algorithm for analyzing the evolution of patterns of spiral and target waves in large aspect ratio chemical systems is introduced. The algorithm does not depend on finding the spiral tip but locates the center of the pattern by a new concept, called the spiral focus, which is defined by the evolutes of the actual spiral or target wave. With the use of Gaussian smoothing, a robust method is developed that permits the identification of targets and spirals foci independently of the wave profile. Examples of an analysis of long image sequences from experiments with the Belousov-Zhabotinsky reaction catalyzed by ruthenium-tris-bipyridyl are presented. Moving target and spiral foci are found, and the speed and direction of movement of single as well as double spiral foci are investigated. For the experiments analyzed in this paper it is found that the movement of a focus correlates with foci in the immediate neighborhood independently of how they were created. (c) 2002 American Institute of Physics.

Effect of transcutaneous electrical muscle stimulation on postoperative muscle mass and protein synthesis.

In an experimental study, 13 patients undergoing major elective abdominal surgery were given postoperative transcutaneous electrical muscle stimulation (TEMS) to the quadriceps femoris muscle on one leg; the opposite leg served as control. Changes in cross-sectional area (CSA) and muscle protein synthesis were assessed by computed tomography and ribosome analysis of percutaneous muscle biopsies before surgery and on the sixth postoperative day. The percentage of polyribosomes in the ribosome suspension decreased significantly (P < 0.03) after operation in control legs, but not in stimulated legs (P > 0.16). The total concentration of ribosomes decreased significantly in legs treated with TEMS (P < 0.03) but not in control legs (P > 0.16). CSA decreased significantly in both legs. The decrease in polyribosomes and CSA after operation was significantly less in stimulated legs than in controls (P < 0.05). TEMS may be a simple and effective method for improving muscle protein synthesis and muscle mass after abdominal surgery and should be evaluated in other catabolic states with muscle wasting.

The effect of posture on late postoperative oxygenation.

Twelve patients had their arterial oxygen saturation measured pre-operatively and on days 1, 4 and 7 after laparotomy. Measurements were performed in the supine, sitting and standing positions on each day. Arterial oxygen saturation was significantly higher during sitting and standing on days 1 and 4 after operation compared with the supine position (p < 0.05). These results give further evidence for the benefits of patient mobilisation after major surgery.