A terrestrial laser scanner was used to take four scans of an area of trees, approximately 480 m 2 in area, within a coniferous tree stand situated in Leicestershire, UK. A number of measurements were extracted from the point cloud and compared with field measurements. Automatic stem recognition was achieved for all stems except those at the edge of the study plot. From the locations of detected stems, diameter at breast height (DBH) was measured with two least-squares shape-fitting algorithms and a circular Hough transformation method; the results were then compared with field measurements. The root mean squared error (RMSE) for DBH measurement from the laser scanner was found to be in the range 0.019-0.037 m, using three measures. Stem density (1031 stems ha -1 ) and basal area (73 m 2 ha -1 ) were also measured with reasonable accuracy. Estimation of tree volume was not as successful, in contradiction to previous research, as upper diameters and heights of trees could not be measured. This was probably a result of previous research being focused on low-density forest stands. This study presents an assessment of laser scanning capabilities in a forest environment with high (1000 stems ha -1 ) stand density, and finds automation of the analysis to yield some important tree and stand variables to be very effective.

No abstract

Time course changes in plasma creatine kinase activity during repetitive physical work were studied. Study groups consisted of a control group who performed sedentary administrative work and an experimental group who performed repetitive physical work in a biscuit factory. Venous blood samples were collected on a Monday prior to work and following work on Monday, Tuesday, Wednesday and Thursday and assayed for plasma creatine kinase. A rise in plasma creatine kinase was observed over the four working days and this rise was significantly greater for the experimental group. Despite this rise, creatine kinase values remained within acceptable limits for both groups. These results suggest that mild, repetitive physical work provides sufficient stimulus for creatine kinase release from skeletal muscle. The mechanism underlying the release of creatine kinase cannot be determined from the present study, but it is unlikely that muscle damage was the cause. It is proposed that increased plasma creatine kinase following mild occupational work may be related to increased rates of muscle turnover, stimulated by muscle use, and not be indicative of pathological processes associated with muscular strain and fatigue.