It has previously been reported that a nitric oxide (NO) donor reduces bubble formation from an air dive and that blocking NO production increases bubble formation. The present study was initiated to see whether a short-acting NO donor (glycerol trinitrate, 5 mg/ml; Nycomed Pharma) given immediately before start of decompression would affect the amount of vascular bubbles during and after decompression from a saturation dive in pigs. A total of 14 pigs (Sus scrofa domestica of the strain Norsk landsvin) were randomly divided into an experimental (n = 7) and a control group (n = 7). The pigs were anesthetized with ketamine and alpha-chloralose and compressed in a hyperbaric chamber to 500 kPa (40 m of seawater) in 2 min, and they had 3-h bottom time while breathing nitrox (35 kPa O(2)). The pigs were all decompressed to the surface (100 kPa) at a rate of 200 kPa/h. During decompression, the inspired Po(2) of the breathing gas was kept at 100 kPa. Thirty minutes before decompression, the experimental group received a short-acting NO donor intravenously, while the control group were given equal amounts of saline. The average number of bubbles seen during the observation period decreased from 0.2 to 0.02 bubbles/cm(2) (P < 0.0001) in the experimental group compared with the controls. The present study gives further support to the role of NO in preventing vascular bubble formation after decompression.
The use of inappropriate treadmill inclination might hide training-induced adaptations if the true VO2max is not reached. This study shows that the present test protocol can be used in future studies of exercise on treadmill, when the aim is to measure submaximal and VO2max in pigs.
The main aim of this article is to study and evaluate existing and potential lifting technologies used in deep sea mining. The lifting is an energy intensive operation and can be decisive if a mining operation is feasible or not. An additional goal for this study was to see if it can be rewarding to utilise the potential energy in the returned masses, because the excess material has to be returned to the ocean bottom so that no microorganisms would be released on the ocean surface. After a general study of possible solutions, regulations and existing projects, the technologies further explored in this study include an in-line pump system, a tubular-disc conveyor and a bucket conveyor, all with modifications to suit deep sea mining. To compare different lifting technologies an estimate for power consumption to lift the mined material from 1000 m depth at three different rates, namely 75, 150, 300 tons/hour, is considered. To calculate the power requirements realistic system parameters are considered and internal system resistance are also taken into account. The results show that the power consumption for the tubular and bucket conveyor are almost in the same range, while the pump system requires about two to three times more power than them. This indicates that there are feasible alternatives to hydraulic lifting by adapting existing onshore based technologies for deep sea mining.
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