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At the inception of the Apollo Applications Program (later to become Skylab) there was no operational experience with the Apollo EVA System and the Gemini EVA experience had created a concern for the workload to which the crew would be subjected. With a major scientific objective of the program depending upon EVA for data retrieval, strong emphas is was placed upon the EVA system development and validation. This paper will trace the EVA hardware design from initial conceptual development to final flight configuration, identify the major concepts which were considered during design evolution and discuss the reasons for the acceptance or rejection of these concepts. Man/system simulations played a vital part in the decision making process. The types of developmental simulation used will be discussed, as will their role in providing design information. The developmental protocol of interleaving analyses and simulations on an iterative basis provided Skylab with a conservative, flexible and simple FVA system which was effective not only for the nominal mission but for many contingency activities as well.

Results are given of measurements of the conductivity and Hall coefficient of cerium dihydride at 200°C as functions of composition. The conductivity, in agreement with earlier results, decreases with increasing hydrogen‐to‐cerium ratio. The Hall coefficient is positive and increases with hydrogen additions. The results are in agreement with a model in which hydrogen is assumed to be protonic. They are not compatible with the assumption of anionic hydrogen.

The phosphorescence spectra of seven heterocyclic and related conjugated organic compounds in rigid glass solutions (EPA) have been photographed. The compounds are indence, indole, thianaphthene, fluorene, carbazole, dibenzofuran, and dibenzothiopehne. The luminescence is attributed to transitions between the lowest triplet level of each molecule and its ground state. Studies of four other compounds, namely cyclopentadiene, pyrrole, furan, and thiophene, showed that, within the limitations of the experiment, they do not phosphoresce. No evidence of n → π transitions has been found in any of the cases studied. Analyses of the spectra of six of the seven compounds which do phosphoresce are possible on the basis of vibrations known from Raman and infrared measurements. While diffuseness and frequency shifts, due to the different states of aggregation in which measurements are performed, inflict uncertainties in the correlations between phosphorescence and Raman/infrared values, generally very good internal consistencies in the analyses are found. Visual observations of lifetimes for the phosphorescence spectra show that they are in the region between 0.1 and 15 seconds. The lifetimes are usually observed to be in an inverse relationship with the mass of the heaviest atom in each of the molecules, as is to be expected from known spin-orbit interaction effects.

Conductivities of polycrystalline solid samples of cerium hydride and gadolinium hydride were measured over the composition ranges H/Ce=0–2.5 and H/Gd=0–2.13 at room temperature and at elevated temperatures (400°—750°C). Conduction is metallic and the results for the two systems are very similar. The conductivity in the variable composition dihydride phase of each system decreases with increasing hydrogen content and is explained assuming that the hydrogen is anionic, taking its extra electron from the system's conduction band. Measurements of absolute Seebeck coefficients (CeH2.37, —17 μV/°C; GdH2.12, —6 μV/°C) support this model. The measured conductivity curves extrapolate to zero at CeH2.7 and GdH2.3. For the dihydride phases the composition dependencies of the conductivities are used to calculate carrier mobilities. The values obtained are in the range 1 to 10 cm2/V‐sec. The conductivities of compositions H/M=0 to 2 show that the dihydrides can exist with hydrogen‐to‐metal ratios much less than 2.0. Ionic conduction has been found not to be important to the conduction mechanism from the results of a concentration cell measurement.

An error analysis of the flash technique for thermal diffusivity measurements has been made by propagating errors in measured quantities through several data analysis techniques to determine the consequent errors in thermal diffusivity. The effects of extended pulse durations and of heat losses are considered. The results show that for most conditions actually encountered in experiments, relative measurement errors are reflected as relative errors of approximately the same size in the thermal diffusivity.

Summary Three experiments were conducted to determine whether schizonts of E. bovis are appreciably influenced by the immune reaction in calves. Each experiment involved two groups each of four to six calves. Each calf in one group was given an immunizing inoculation of 60,000 to 100,000 oocysts, and after 30 to 35 days each calf in both groups was given a challenging inoculation of 800,000 to 5 million oocysts. One calf in each group was killed on successive days beginning 15 to 17 days after the second inoculation. Numbers of schizonts in the small intestine were estimated by examination with a dissecting microscope and frequency of sexual stages in the cecum and colon was observed in sections. No consistent difference was found in concentration, estimated total number, or size of schizonts in the two groups, although non-immunized calves had a much higher frequency of sexual stages. The results indicate that the schizonts and preceding stages are not appreciably influenced by the immune reaction, so that immunity must chiefly affect the merozoites or sexual stages.