Radiation tolerance for the osmotic fractionation of erythrocytes as radiacoes como agente sensibilizante da fragilidade osmotica dos eritrocitos
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Azevedo, N. L. C.↗
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Spatial distributions of Tribrachidium, Rugoconites, and Obamus from the Ediacara Member (Rawnsley Quartzite), South Australia
The spatial distribution of in situ sessile organisms, including those from the fossil record, provides information about life histories, such as possible dispersal and/or settlement mechanisms, and how taxa interact with one another and their local environments. At Nilpena Ediacara National Park (NENP), South Australia, the exquisite preservation and excavation of 33 fossiliferous bedding planes from the Ediacara Member of the Rawnsley Quartzite reveals in situ communities of the Ediacara Biota. Here, the spatial distributions of three relatively common taxa, Tribrachidium, Rugoconites, and Obamus, occurring on excavated surfaces were analyzed using spatial point pattern analysis. Tribrachidium have a variable spatial distribution, implying that settlement or post-settlement conditions/preferences had an effect on populations. Rugoconites display aggregation, possibly related to their reproductive methods in combination with settlement location availability at the time of dispersal and/or settlement. Additionally, post-settlement environmental controls could have affected Rugoconites on other surfaces, resulting in lower populations and densities. Both Tribrachidium and Rugoconites also commonly occur as individuals or in low numbers on a number of beds, thus constraining possible reproductive strategies and environmental/substrate preferences. The distribution of Obamus is consistent with selective settlement, aggregating near conspecifics and on substrates of mature microbial mat. This dispersal process is the first example of substrate-selective dispersal among the Ediacara Biota, thus making Obamus similar to numerous modern sessile invertebrates with similar dispersal and settlement strategies. Resumen La distribución espacial de los organismos sésiles in situ, incluyendo los del registro fósil, brinda información sobre las historias de vida, tal como los posibles mecanismos de dispersión y/o asentamiento, y sobre cómo los taxones interactúan entre sí y entre sus entornos locales. En el Parque Nacional Nilpena Ediacara (NENP), Australia Meridional, la excelente preservación y excavación de 33 planos de lecho fosilífero del Miembro Ediacara de la Cuarcita Rawnsley revela comunidades in situ de la biota ediacárica. En este estudio analizamos las distribuciones espaciales de tres taxones relativamente comunes, Tribrachidium, Rugoconites y Obamus, que se encuentran en superficies excavadas mediante el análisis de patrones de puntos espaciales. Tribrachidium tiene una distribución espacial variable, lo que implica que las condiciones/preferencias durante o después del asentamiento tuvieron un efecto en las poblaciones. Rugoconites muestran agregación, posiblemente relacionado con sus métodos reproductivos en combinación con la disponibilidad de lugares de asentamiento en el momento de la dispersión y/o asentamiento. Además, los controles ambientales posteriormente al asentamiento podrían estar afectando a Rugoconites en otras superficies, lo que resultaría en poblaciones y densidades más bajas. Tanto Tribrachidium como Rugoconites ocurren como individuos en varios lechos, restringiendo las posibles estrategias reproductivas y las preferencias ambientales/de sustrato. La distribución de Obamus es consistente con un asentamiento selectivo, agregando cerca de sus congéneres y sobre sustratos de tapete microbiano maduro. Este proceso de dispersión es el primer ejemplo de dispersión selectiva de sustrato entre la biota ediacárica, lo que hace que Obamus sea similar a numerosos invertebrados sésiles modernos con estrategias similares de dispersión y asentamiento.
Phillip C. Boan↗
Pilot and Controller Evaluations of Separation Function Allocation in Air Traffic Management
Two human-in-the-loop simulation experiments were conducted in coordinated fashion to investigate the allocation of separation assurance functions between ground and air and between humans and automation. The experiments modeled a mixed-operations concept in which aircraft receiving ground-based separation services shared the airspace with aircraft providing their own separation service (i.e., self-separation). Ground-based separation was provided by air traffic controllers without automation tools, with tools, or by ground-based automation with controllers in a managing role. Airborne self-separation was provided by airline pilots using self-separation automation enabled by airborne surveillance technology. The two experiments, one pilot-focused and the other controller-focused, addressed selected key issues of mixed operations, assuming the starting point of current-day operations and modeling an emergence of NextGen technologies and procedures. In the controller-focused experiment, the impact of mixed operations on controller performance was assessed at four stages of NextGen implementation. In the pilot-focused experiment, the limits to which pilots with automation tools could take full responsibility for separation from ground-controlled aircraft were tested. Results indicate that the presence of self-separating aircraft had little impact on the controllers' ability to provide separation services for ground-controlled aircraft. Overall performance was best in the most automated environment in which all aircraft were data communications equipped, ground-based separation was highly automated, and self-separating aircraft had access to trajectory intent information for all aircraft. In this environment, safe, efficient, and highly acceptable operations could be achieved for twice today's peak airspace throughput. In less automated environments, reduced trajectory intent exchange and manual air traffic control limited the safely achievable airspace throughput and negatively impacted the maneuver efficiency of self-separating aircraft through high-density airspace. In a test of scripted conflicts with ground-managed aircraft, flight crews of self-separating aircraft prevented separation loss in all conflicts with detection time greater than one minute. In debrief, pilots indicated a preference for at least five minute's alerting notice and trajectory intent information on all aircraft. When intent information on ground-managed aircraft was available, self-separating aircraft benefited from fewer conflict alerts and fewer required deviations from trajectory-based operations.
Wing, David↗