Evaluation of the undersea habitats - Tektite II,Hydro-Lab,and Edalhab - for scientific saturation diving programs

Summary 1. The assessment of three undersea habitats — Tektite, Hydro-Lab and Edalhab — is based primarily upon the experience of the authors during a total of 62 man-days under saturation diving conditions while conducting biological research programs.2. A number of desirable and undesirable features were found in each habitat system; none of the individual systems included all of the desirable features.3. The paper discusses advantages and disadvantages of various features of the habitats including work and living areas, support equipment and techniques, operations and safety. The authors offer their experiences and suggestions to contribute to improvement of habitats and undersea diving operations.

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Bewertung der Unterwasser-Habitate Tektite II, Hydro-Lab und Edalhab für Programme des wissenschaftlichen Sättigungstauchens

Kurzfassung Eine kritische Bewertung der 3 Unterwasserlaboratorien Tektite II, Hydro-Lab und Edalhab wird auf Grund der praktischen Erfahrungen vorgenommen, die während eines längeren bemannten Einsatzes unter Sättigungsbedingungen im Rahmen eines biologischen Forschungsprogrammes in den USA gewonnen wurden. Keines der erprobten Unterwasser-Systeme erfüllte alle Erwartungen. Alle Habitate wiesen sowohl zufriedenstellende als auch mangelhafte Eigenschaften auf, die ausführlich diskutiert werden. Unter Berücksichtigung der bisher gemachten Erfahrungen werden zahlreiche Anregungen zur Verbesserung von Unterwasserlaboratorien und Empfehlungen für Taucheinsätze mitgeteilt.

     

Characteristics of the Photosystem II reaction centre. II. Electron donors

The properties of Photosystem II electron donation were investigated by EPR spectrometry at cryogenic temperatures. Using preparations from mutants which lacked Photosystem I, the main electron donor through the Photosystem II reaction centre to the quinone-iron acceptor was shown to be the component termed Signal II. A radical of 10 G line width observed as an electron donor at cryogenic temperatures under some conditions probably arises through modification of the normal pathway of electron donation. High-potential cytochrome b-559 was not observed on the main pathway of electron donation. Two types of PS II centres with identical EPR components but different electron-transport kinetics were identified, together with anomalies between preparations in the amount of Signal II compared to the quinone-iron acceptor. Results of experiments using cells from mutants of Scenedesmus obliquus confirm the involvement of the Signal II component, manganese and high-potential cytochrome b-559 in the physiological process leading to oxygen evolution.