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In addition to cross-cultural and environmental stressors, aid workers and missionaries are frequently exposed to trauma. We explored the frequency of traumatic events, their mental health impact, and factors associated with posttraumatic stress in two groups of missionaries, one representing a predominantly stable setting (Europe) and the other an unstable setting (West Africa). The 256 participants completed self-report measures assessing lifetime traumatic events, current posttraumatic stress, depressive and anxiety symptoms, resilience, and functioning. The rate of traumatic events was significantly higher in the unstable setting. More-frequent traumatic events were associated with higher posttraumatic stress. Factors associated with the severity of posttraumatic stress were depression, functional impairment, subjective severity and number of traumatic events, and the level of resilience.

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After an extensive literature survey the experimental thermal-conductivity data for twelve diatomic gases were utilized to produce an accurate and expedient means of predicting values over extensive ranges of temperature and pressure. Plotting values of k* against TR on logarithmic coordinates produced similarities pointing to the existence of corresponding states behavior for this family of substances with the exception of hydrogen. Because hydrogen cannot be included in a correlation generalized for the diatomic gases, it has been eliminated from this study. Based on atmospheric pressure data, ratios of k*/k*,, produced a unique relationship with reduced temperature. To include the effect of pressure, residual thermal conductivities were correlated with density for nitrogen and oxygen, the only substances for which high-pressure data exist. These relationships enabled the determination of the thermal conductivity at the critical point. When the value k, = 8.55 X cal./sec. cm. OK. for nitrogen was used, an extensive reduced thermalconductivity correlation was constructed against reduced temperature for parameters of constant reduced pressure. This chart, extending to reduced pressures of 100 and to reduced temperatures of 85, is recommended for the diatomic gases in their gaseous and liquid states.The developed correlation reproduces experimental nitrogen data to within 1.39%.For the other diatomic gases experimental agreement extends from 1.00 to 3.20%. Such agreement indicates that this correlation is more reliable for the diatomic gases than are other generalized plots presented in the literature.Present technoiogical advances continue to depend upon progress in understanding the fundamentals of mass and energy transfer; consequently, more careful scrutiny of these operations has stimulated an increasing interest in transport properties. An accurate but simple means of predicting coefficients of diffusion, thermal conductivity, and viscosity is needed to meet the demands of 40.

The available experimental density data for hydrogen have been compiled to produce a reduced density correlation for the liquid and gaseous states. This investigation has utilized fifty-seven sources of data, extending from the early studies of Amagat (1880) to the recent contributions of Johnston, Keller, and Friedman (1954).Based on the concept of a reduced density, a correlation for hydrogen has been developed ranging in temperature from the melting point (14OK.) to 3,300"K. and in pressure as high as 2,550 atm. This correlation provides continuity between the liquid and gaseous phases; whereas existing equations of state fail to describe the experimental behavior in the transitional region, particularly near the critical point.Four hundred and eighty-five experimental points covering the entire region were checked to establish the reliability of this correlation, which reproduced the experimental data to within 0.49y0.Present technological practices use generalized reduced-state correlations for the estimation of thermodynamic and transport properties of substances. The validity of this approach has proved satisfactory in the correlation of densities (49), viscosities (7I), thermal conductivities (6'4, 66), and diffusion coefficients (27) ; more intensive investigations indicate that helium and hydrogen do not conform to this generalized pattern. Nelson and Obert (59) also recognize this inconsistency and suggest the use of a quantum parameter for these light gases.To correlate the properties of hydrogen and helium one proposa1 considers adjustment of their critical constants. Newton (60) presents a generalized activitycoefficient chart based on an empirical correction quantity of 8 added to both the critical temperature and critical pressure of hydrogen, helium, and neon. Dodge ($6) utilizes this concept to correlate compressibility factors; Morgen and Childs (57) show that this concept is valid in limited ranges of temperature and pressure. Basing their studies on hydrogen PVT data, Maslan and Littman (52) construct a compressibility chart. Data for the inert gases are fitted to this chart by the application of additive corrections to the critical temperature and pressure of argon, neon, and helium.In viscosity studies Brebach and Thodos (15) present a reduced-state correlation for diatomic gases. To describe properly the behavior of hydrogen with this correlation it was necessary to adjust progressively the critical temperature and pressure.Alternatively equations of state have been used to predict generalized behavior. While such equations are of a generalized form, the constants involved and their use have a specific value for each substance. Reattie and Bridgeman (IS) point out that simple equations of state derived from theoretical considerations are inaccurate for a wide range of temperature and pressure. Furthermore empirical expansion type of equations require a large number of terms for use over a large range; hence they are inconvenient for use in thermodynamic calculations.Owing to the anomalou...