PPS-87: a new event oriented solar proton prediction model.

A new event-oriented solar proton prediction model has been developed and implemented at the USAF Space Environment forecast facility. This new model generates predicted solar proton time-intensity profiles for a number of user adjustable energy ranges and is also capable of making predictions for the heavy ion flux. The computer program is designed so a forecaster can select inputs based on the data available in near real-time at the forecast center as the solar flare is occurring. The predicted event amplitude is based on the electromagnetic emission parameters of the solar flare (either microwave or soft X-ray emission) and the solar flare position on the sun. The model also has an update capability where the forecaster can normalize the prediction to actual spacecraft observations of spectral slope and particle flux as the event is occurring in order to more accurately predict the future time-intensity profile of the solar particle flux. Besides containing improvements in the accuracy of the predicted energetic particle event onset time and magnitude, the new model converts the predicted solar particle flux into an expected radiation dose that might be experienced by an astronaut during EVA activities or inside the space shuttle.     

Subcellular components of the amphibian egg: insights provided by gravitational studies.

Most cytoplasmic regions of fertilized amphibian eggs move with respect to the gravity vector in experimentally gravity oriented eggs. The pattern and extent of this movement varies among different batches of eggs. This variation in apparent cytoplasmic viscosity (or, conversely, cytoplasmic mobility) can be correlated with variations in subsequent morphogenesis of experimental, gravitationally manipulated eggs. Therefore, the proper interpretation of gravity experiments with amphibian eggs requires that one understand the subcellular basis for this variation on cytoplasmic mobility. Variation in the packing of the major cytoplasmic organelle, the yolk platelets, or the organization and amount of cytoskeletal components may explain the variation in cytoplasmic mobility. Evidence is presented that the variation in yolk volume density (fraction of total cytoplasmic volume occupied by yolk platelets) does not account for the variation in cytoplasmic mobility in Xenopus laevis eggs. Experimental evidence from cold-shocked inverted eggs indicates that microtubules may be involved in determining cytoplasmic mobility. However, quantitative evidence that the microtubule levels and state of the microtubules (polymerized vs. non-polymerized) in the whole Xenopus laevis egg does not correlate directly with cytoplasmic mobility is presented. The apparent conflict these data represent regarding the role of the cytoskeleton in determining cytoplasmic mobility is discussed.     

On Team Games: A Computational Structural Analysis

Team games are studied here with one performance index for the team as a unit in competition with one common opponent. A structural analysis is presented with the intent to simplify the computation of optimal decision and communication processes. The minimum principle and calculus of variations are used to compute time-optimal and quadratic-optimal trajectories for certain linear "pursuit-evasion" games. A composition method is presented to compute an approximate solution to the two-versus-one problem from the solution to two one-versus-one problems. Help zones of a second pursuer to assist in the "capture" of an evader are derived. The hierarchical command and communication structure for a quadratic linear game of N pursuers and one evader is derived. An approximation is generated which has a convenient ripple or recursive structure.     

Gravitational biology and the mammalian circadian timing system.

Mammals have evolved under the influence of many selective pressures. Two of these pressures have been the static force of gravity and the daily variations in the environment due to the rotation of the earth. It is now clear that each of these pressures has led to specific adaptations which influence how organisms respond to changes in either gravity or daily time cues. However, several unpredicted responses to altered gravitational environments occur within the homeostatic and circadian control systems. These results may be particularly relevant to biological and medical issues related to spaceflight. This paper demonstrates that the homeostatic regulation of rat body temperature, heart rate, and activity become depressed following exposure to a 2 G hyperdynamic field, and recovers within 5-6 days. In addition, the circadian rhythms of these same variables exhibit a depression of rhythm amplitude; however, recovery required a minimum of 7 days.     

Current and potential productivity of wheat for a Controlled Environment Life Support System.

The productivity of higher plants is determined by the incident photosynthetic photon flux (PPF) and the efficiency of the following four physiological processes: absorption of PPF by photosynthetic tissue, carbon fixation (photosynthesis), carbon use (respiration), and carbon partitioning (harvest index). These constituent processes are analyzed to determine theoretical and potentially achievable productivity. The effects of optimal environmental and cultural factors on each of these four factors is also analyzed. Results indicate that an increase in the percentage of absorbed photons is responsible for most of the improvement in wheat yields in an optimal controlled environment. Several trials confirm that there is an almost linear increase in wheat yields with increasing PPF. An integrated PPF of 150 mol m-2 d-1 (2.5 times summer sunlight) has produced 60 g m-2 d-1 of grain. Apparently, yield would continue to increase with even higher PPF's. Energy efficiency increased with PPF to about 600 micromoles m-2 s-1, then slowly decreased. We are now seeking to improve efficiency at intermediate PPF levels (1000 micromoles m-2 s-1) before further exploring potential productivity. At intermediate and equal integrated daily PPF levels, photoperiod had little effect on yield per day or energy efficiency. Decreasing temperature from 23 degrees to 17 degrees increased yield per day by 20% but increased the life cycle from 62 to 89 days. We hope to achieve both high productivity and energy efficiency.     

Mammalian cell cultivation in space.

Equipment used in space for the cultivation of mammalian cells does not meet the usual standard of earth bound bioreactors. Thus, the development of a space worthy bioreactor is mandatory for two reasons: First, to investigate the effect on single cells of the space environment in general and microgravity conditions in particular, and second, to provide researchers on long term missions and the Space Station with cell material. However, expertise for this venture is not at hand. A small and simple device for animal cell culture experiments aboard Spacelab (Dynamic Cell Culture System; DCCS) was developed. It provides 2 cell culture chambers, one is operated as a batch system, the other one as a perfusion system. The cell chambers have a volume of 200 microliters. Medium exchange is achieved with an automatic osmotic pump. The system is neither mechanically stirred nor equipped with sensors. Oxygen for cell growth is provided by a gas chamber that is adjacent to the cell chambers. The oxygen gradient produced by the growing cells serves to maintain the oxygen influx by diffusion. Hamster kidney cells growing on microcarriers were used to test the biological performance of the DCCS. On ground tests suggest that this system is feasible.     

Ultrastructural and growth indices of Chlorella culture in multicomponent aquatic systems under space flight conditions.

Submicroscopic organization of Chlorella cells cultivated under space flight conditions in three-component aquatic system has been studied. Comparison of the experimental cells with that of the controls revealed certain rearrangements of cell organelles particularly, a reduction in the amount of reserve polysaccharides in chloroplasts, increase of cell vacuolization and mitochondrion volume, complication configuration of plasmalemma evaginations and invaginations, and also disturbances in the process of cytokinesis. More over an increase in the number of Chlorella cells infected by bacteria was shown in the experimental variant. No considerable differences were established in the growth characteristics of the experimental and control populations. A comparative cytological analysis revealed general regularities of organelles in Chlorella cells cultivated under space flight condition in the uni- and multicomponent systems.     

The Future of UAS: Standards, Regulations, and Operational Experiences [Workshop Report]

The outcomes of "the future of UAS: standards, regulations and operational experiences" workshop, held on the 7 -8 December 2006, in Brisbane, Queensland, Australia. The goal of the workshop was to identify recent international activities in the unmanned airborne systems (UAS) airspace integration problem. The workshop attracted a broad cross-section of the UAS community, including: airspace and safety regulators, developers, operators, and researchers. The three themes of discussion were: progress in the development of standards and regulations; lessons learnt from recent operations; and advances in new technologies. This summarises the activities of the workshop and explores the important outcomes and trends as perceived by these authors.     

High LET-induced H2AX phosphorylation around the Bragg curve.

We investigated the spatial distribution of the induction of the phosphorylated form of the histone protein H2AX (gamma-H2AX), known to be activated by DSBs. Following irradiation of human fibroblast cells with 600 MeV/nucleon silicon and 600 MeV/nucleon iron ions we observed the formation of gamma-H2AX aggregates in the shape of streaks stretching over several micrometers in an x/y plane. Polyethylene shielding was used to achieve a Bragg curve distribution with beam geometry parallel to the monolayer of cells. We present data that highlights the formation of immunofluorescent gamma-H2AX tracks showing the ion trajectories across the Bragg peak of irradiated human fibroblast cells. Qualitative analyses of these distributions indicated potentially increased clustering of DNA damage before the Bragg peak, enhanced gamma-H2AX distribution at the peak, and provided visual evidence of high-linear energy transfer particle traversal of cells beyond the Bragg peak in agreement with one-dimensional transport approximations. Spatial assessment of gamma-H2AX fluorescence may provide direct insights into DNA damage across the Bragg curve for high charge and energy ions including the biological consequences of shielding and possible contributors to bystander effects.