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The effect of sustained Gz acceleration ("high G") upon endocrine function has been investigated in man using a human centrifuge. Five male volunteers were exposed to accelerations of up to 6Gz for one minute without G protection. No effect of acceleration was observed on the peripheral blood levels of growth hormone, prolactin, thyrotropin and the gonadotrophins. In contrast, cortisol levels increased in a "dose-related" manner following acceleration i.e. the higher the acceleration, the greater the response. The unusual specificity of these endocrine changes is discussed. In a second experiment on the same subjects exposed to 6Gz for one minute, the modification of this cortisol response by two methods of G protection, the anti-G suit and the reclined seat, was investigated. Noradrenaline, adrenaline and arginine vasopressin were also measured and shown to increase rapidly after acceleration. These endocrine changes were all reduced by the anti-G suit but reductions were not clearly observed with seat reclination until an angle of 80° from the vertical was reached. The mechanisms underlying the release of these hormones are discussed in terms of the circulatory disturbances produced by acceleration. Finally, the endocrine effects of positive pressure breathing (PPB), with and without counterpressure (CP) have been compared with the use of an anti-G suit alone in subjects exposed to +6Gz for one minute. Arterial oxygen saturation (SaO[2]) was monitored continuously by ear oximetry. SAO[2] fell during +Gz acceleration with only anti-G suit protection but this was ameliorated significantly by PPB. Further benefit was obtained with CP. No differences in endocrine responses were observed between these three conditions which suggested that hypoxia was not the stimulus for hormonal responses to high G. This assertion was confirmed by the failure of hypoxia, induced by breathing a gas mixture of low oxygen content, to induce hormonal changes in the subjects.

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Earth’s biosphere is sustained by its biological diversity, which forms an intricate network of biological, physical and chemical pathways. This network has many fail-safe redundant func-tions including buffer stocks of inert biomass, huge amounts of water and the large volume of gases in the atmosphere. By contrast, manmade habitats for human space exploration are closed ecosystems that represent only a trivial fraction of Earth’s biosphere. The employment of bio-regenerative processes complemented with physical-chemical tech-nologies is thought to have numerous advantages from the perspective of redundancy and reducing resupply mass for the sustained human presence in space or on other planetary surfaces. However, the combination of bio-regenerative processes, such as plant cultivation, with physical-chemical processes to form hybrid life support systems is challenging. Such systems are a concert of many interdependencies and interacting feedback loops, which are difficult to operate in a desired range of set points. Furthermore, the complexity of such sys-tems makes them vulnerable to perturbations. Applying system dynamics modelling to study hybrid life support systems is a promising ap-proach. System dynamics is a methodology used to study the dynamic behavior of complex systems and how such systems can be defended against, or made to benefit from, the per-turbations that fall upon them. This thesis describes the development of a system dynamics model to run exploratory simulations, which can lead to new insights into the complex behav-ior of hybrid life support systems. An improved understanding of the overall system behavior also helps to develop sustainable, reliable and resilient life support architectures for future human space exploration. A set of simulations with a hybrid life support system integrated into a Mars habitat has been executed and the results show a strong impact of space greenhouses on the life support sys-tem behavior and the different matter flows. It is also evident from the simulation results that a hybrid life support system can recover from a perturbation event in most cases without a fatal mission end. Recycling urine to produce a plant nutrient solution is a novel approach in further closing loops in space life support systems. Within this thesis, a number of experiments have been executed in order to determine the effectiveness of a urine-derived nutrient solution com-pared to a standard reference solution. The results show that in principle plants can be grown with a nutrient solution made of human urine, but that the yield is lower compared to the reference solution. However, the urine-derived solution might be tuned by adding small amounts of additional nutrients to remove the imbalance of certain elements. This way the nutrient salts supplied from Earth could be reduced.

Disputes between patients and providers regarding life-sustaining medical treatment (LSMT) are universal across all U.S. states, yet policies regarding these disputes differ significantly. This dissertation determines that all 50 states have advance directive laws that protect a patient’s right to refuse LSMT even when a healthcare provider objects, yet only some states have policies that protect the patient’s right to choose to continue LSMT when a healthcare provider objects (a dispute known as medical futility). Some states have pro-patient laws that protect the patient’s right to make the final decision, while other states have enacted pro-provider medical futility policies that explicitly grant the provider authority to remove LSMT against the patient’s wishes. Finally, in one state, the law delegates the final decision to a third-party: institutional healthcare ethics committees. This dissertation studies the innovation and adoption of these 17 state medical futility policies, examining the theory that values determine both whether the state adopts a medical futility policy as well as what type of medical futility policy a state will adopt- as the policy actors that represent these values: policy entrepreneurs and interest groups. A comparative case study of successful third-party policy adoption in Texas contrasted against a failed effort in Idaho could not affirm the necessity of policy entrepreneurs for policy adoption but did affirm the necessity of interest group consensus and the role of values. Furthermore, quantitative analysis failed to offer statistically-significant evidence of value indicators, but did suggest that government ideology and political party affiliation may potentially become indicators of the type of medical futility policy that states choose to adopt.

Thesis (Ph. D.)--University of Oklahoma, 1994. / Includes bibliographical references (leaves 110-129).