Development and parametric evaluation of the prototype 2 and 3 flash evaporators

Development of the Prototype 2 and 3 flash evaporator heat sinks which vaporize an expendable fluid to cool a heat transport fluid loop is reported. The units utilize Freon 21 as the heat transport fluid and water as the expendable fluid to meet the projected performance requirements of the space shuttle for both on-orbit and ascent/reentry operations. The evaporant is pulse-sprayed by on-off control onto heat transfer surfaces containing the transport fluid and exhausted to the vacuum environment through fixed area exhaust ducts

Shatter cones: Diagnostic impact signatures

Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures)

Radiator design system computer programs

Minimum weight space radiator subsystems which can operate over heat load ranges wider than the capabilities of current subsystems are investigated according to projected trends of future long duration space vehicles. Special consideration is given to maximum heat rejection requirements of the low temperature radiators needed for environmental control systems. The set of radiator design programs that have resulted from this investigation are presented in order to provide the analyst with a capability to generate optimum weight radiator panels or sets of panels from practical design considerations, including transient performance. Modifications are also provided for existing programs to improve capability and user convenience

Threshold effects for two pathogens spreading on a network

Diseases spread through host populations over the networks of contacts between individuals, and a number of results about this process have been derived in recent years by exploiting connections between epidemic processes and bond percolation on networks. Here we investigate the case of two pathogens in a single population, which has been the subject of recent interest among epidemiologists. We demonstrate that two pathogens competing for the same hosts can both spread through a population only for intermediate values of the bond occupation probability that lie above the classic epidemic threshold and below a second higher value, which we call the coexistence threshold, corresponding to a distinct topological phase transition in networked systems.Comment: 5 pages, 2 figure

Locomotion in Parkinson's disease: neuronal coupling of upper and lower limbs

Quadrupedal limb coordination during human walking was recently shown to be upregulated during obstacle stepping. An anticipatory activity of coupled cervico-thoraco-lumbar interneuronal circuits is followed by an appropriate executory activation of leg and arm muscles during task performance. This mechanism was studied in subjects with Parkinson's disease and age-matched controls walking on a treadmill with a randomly approaching obstacle. Spinal reflex (SR) responses, evoked by tibial nerve stimulation during mid-stance, were present in all arm and leg muscles investigated. They were larger before execution of obstacle avoidance compared with normal steps in both subject groups. The performance of obstacle stepping was slightly worse in Parkinson's disease than in control subjects. The anticipatory SR in the arm muscles prior to normal and obstacle steps was larger in Parkinson's disease compared with age-matched subjects, but smaller in the tibialis anterior. The arm and leg muscle activation was stronger during obstacle compared with normal swing but did not differ between Parkinson's disease and age-matched subjects. These observations indicate that quadrupedal limb coordination is basically preserved in Parkinson's disease subjects. Our data are consistent with the proposal that in Parkinson's disease subjects the enhanced anticipatory spinal neuronal activity (reflected in the SR) in the arm muscles is required to achieve an appropriate muscle activation for the automatic control of body equilibrium during the performance of the task. In the tibialis anterior the SR is attenuated presumably because of a stronger voluntary (i.e. cortical) control of leg movement

Lucky, Competent, or Just a Cheat? Interactive Effects of Honesty-Humility and Moral Cues on Cheating Behavior.

Despite substantial research on cheating, how and when individual predispositions figure into cheating behavior remains unclear. In Study 1, we investigated to what extent Honesty-Humility predicted cheating behavior. As expected, individuals high on Honesty-Humility were less likely to cheat than were individuals low on this trait. In Study 2, integrating arguments from personality research about traits with arguments from behavioral ethics about moral primes, we examined how Honesty-Humility and situational primes interacted to affect cheating. We found an interaction indicating that individuals high on Honesty-Humility consistently did not cheat much across situational primes, whereas individuals low on Honesty-Humility cheated more when exposed to immoral primes than when exposed to moral primes. Our research invites reflection about the interplay of individual differences in Honesty-Humility and situational cues in predicting cheating, including the design of anti-cheating systems and the context in which these person and situation factors interact

Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment

Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified

Leadership process models: A review and synthesis

In organizational research, studying "processes" is important for uncovering and understanding the underlying causal mechanisms in a predictor-mediator-outcome logic. Processes answer "how" and "why" questions and provide more complete explanations about phenomena. Our focus in this review is on studies of leadership processes, which we systematically analyze to report on the state-of-the science. In doing so, we present a two-dimensional target-centric taxonomy to integrate previous research: The taxonomy distinguishes the target's level (i.e., individual follower, team, organizational, and extra-organizational) as well as the type of leadership processes that affect either the target's development or leverage of resources. Our review indicates that the predominantly studied leadership "meta" process model looks at the effect of leader traits or behaviors on performance-related outcomes through cognitive, affective, or behavioral leveraging factors. This "meta" model points to several important and understudied processes including a leader's influence on the target's development or work context. We also identify two largely overlooked yet critical issues for leadership process research: Modeling the role of time and that of multiple processes through which leadership effects manifest themselves in organizations. Using our taxonomy, we provide several reflection points that can guide the development of genuine and thoughtful leadership process theories. We conclude by urging future leadership process research to embrace multi-process, multi-level, and time-sensitive models