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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Von Hippel-Lindau (VHL) protein antagonist, VH298, promotes functional activities of tendon-derived stem cells and accelerates healing of entheses in rats by inhibiting ubiquitination of hydroxy-HIF-1α

Enthesis is the region where a tendon attaches to a bone. It is a relatively vulnerable position, and in most cases surgical treatment is required upon rupture. The reconstructed enthesis is usually weaker compared to the original, and is prone to rupture again. Hypoxia-inducible factor-1 α (HIF-1α) is known to be involved in extensive activities in cells. It is inhibited under normoxic conditions, and undergoes two essential processes, hydroxylation and ubiquitination, the latter of which has been largely unexplored. Herein, we measured the levels of HIF-1α and hydroxy-HIF-1α in VH298-treated rat tendon-derived stem cells (TDSCs) by immunoblotting. We also detected the proliferation of TDSCs using CCK-8 assay and the mRNA levels of related genes by quantitative RT-PCR. The TDSCs were observed to be induced and the chondrogenic differentiation related genes were found to be enhanced. We also simulated in-vitro wounding in a scratch test and reconstructed the enthesis in a rat model of Achilles tendon by classical surgery followed by administration of phosphate buffer saline (PBS) injection or VH298 injection. We observed that HIF-1α and hydroxy-HIF-1α levels were increased in VH298-treated TDSCs in a dose- and time-dependent manner. Thirty micromolar VH298 could significantly increase cell proliferation, migration, and expression of collagen-1α, collagen-3α, decorin, tenomodulin, tenascin C genes, and chondrogenic differentiation-related genes, collagen-2α, SRY-box9, aggrecan. VH298-treated enthesis could tolerate more load-to-failure, had a better healing pattern, and activation of HIF signaling pathway. VH298 can thus enhance the functional activities of TDSCs, enhance their chondrogenic differentiation potential, and accelerate enthesis healing by inhibiting the ubiquitination of hydroxy-HIF-1α.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Examining the role of flame topologies and in-cylinder flow fields on cyclic variability in spark-ignited engines using large-eddy simulation

In this work we have studied cycle-to-cycle variation (CCV) in a spark-ignited (SI) engine using large-eddy simulation (LES) in conjunction with the G-equation combustion model. A single cylinder of a four-cylinder port-fueled SI engine was simulated. 49 consecutive full cycles were computed. The operating condition studied in this work is stoichiometric and stable, and represents a load of 16 bar brake mean effective pressure (BMEP), and an engine speed of 2500 revolutions per minute (r/min). The CFD simulation shows good agreement in terms of in-cylinder pressure prediction with respect to the experiments, and is also able to capture the range of CCV observed in experiments. Further, neither the simulation, nor the experiments show any distinguishable pattern in the sequence of high and low cycles. We numerically decoupled the effects of variations in equivalence ratio fields and velocity fields to isolate the effects of differences in the velocity field and differences in the equivalence ratio field on flame development and propagation. Based on this study we inferred that for this engine, under the operating conditions studied, the differences in burn rates can be attributed to the differences in the velocity flow-field in the region around the spark gap during ignition. We then performed an analysis to identify the correlation between peak cylinder pressure (PCP) and flame topologies over all the simulated cycles. We found that high cycles (higher PCP values) are strongly correlated to flatter flame volume shapes (flattened in the piston-to-head direction), and volumes that are more symmetric about the ignition axis. In addition, these kinds of flame volumes were found to correlate well with lower values of prior-to-ignition velocity going from the intake to the exhaust side (mean flow caused by tumble) at the spark, and also higher values of prior-to-ignition velocity in the piston-to-head direction.

CCV↗
NASA NTRS2017

Optimal Control Surface Layout for an Aeroservoelastic Wingbox

This paper demonstrates a technique for locating the optimal control surface layout of an aeroservoelastic Common Research Model wingbox, in the context of maneuver load alleviation and active utter suppression. The combinatorial actuator layout design is solved using ideas borrowed from topology optimization, where the effectiveness of a given control surface is tied to a layout design variable, which varies from zero (the actuator is removed) to one (the actuator is retained). These layout design variables are optimized concurrently with a large number of structural wingbox sizing variables and control surface actuation variables, in order to minimize the sum of structural weight and actuator weight. Results are presented that demonstrate interdependencies between structural sizing patterns and optimal control surface layouts, for both static and dynamic aeroelastic physics.

Stanford, Bret K.↗
DOE OSTI2014

Probable Causes of the Abnormal Ridge Accompanying the 2013-2014 California Drought: ENSO Precursor and Anthropogenic Warming Footprint

The 2013-14 California drought was accompanied by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer, and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either ENSO or Pacific Decadal Oscillation; instead it is correlated with a type of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased GHG loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-14, the associated drought and its intensity.

anomalous ridge↗
DOE OSTI2025

Insights Into Seismicity Associated With Flexibly Operating Enhanced Geothermal System From Real‐Time Distributed Acoustic Sensing

Enhanced Geothermal Systems (EGS) have the capacity to broaden the accessible resource pool for geothermal power generation. Traditionally viewed as a “baseload” resource, their flexible operation might also enable dispatchable load‐following generation and long‐term energy storage, aligning them with the evolving landscape of decarbonized electricity systems. However, increasing permeability and extracting energy during EGS operations can induce microseismic events; for many prior EGS efforts, some associated seismicity has been observed. While energetically beneficial, the flexibility of EGS operations prompts our inquiry into whether new types of operations will yield previously unseen seismicity patterns. We demonstrate the use of distributed acoustic sensing (DAS) with real‐time edge computing to monitor seismicity during a pilot test of a cyclically operated EGS facility at the Blue Mountain geothermal field. Our focus lies in uncovering seismicity insights from the real‐time microseismic catalog, particularly during load‐following dispatchability tests simulating flexible EGS operation. Here, we find that variations in pore pressure consistently correlate with seismicity, and that controlling pressure cycles during flexible operations appears to constrain microseismic activity during subsequent cycles. The spatio‐temporal evolution of microseismic clouds recorded during cyclic injection cycles fits diffusive models over our available observation period. Additionally, seismicity elevation lags behind pore pressure increases, likely due to pressure diffusion to the fracture system boundary. Through real‐time monitoring, we offer novel insights into seismicity associated with flexibly operating EGS. Our findings suggest that leveraging DAS and edge computing can inform EGS operations and help mitigate induced seismicity.

Chamarczuk, Michal [Rice Univ., Houston, TX (Unite↗
DOE OSTI2018

Cohesive finite element modeling of the delamination of HTPB binder and HMX crystals under tensile loading

Accurately modeling the mechanical behavior of the polymer binders and the degradation of interfaces between binder and crystal is important to science-based understanding of the macro-scale response of polymer bonded explosives. The paper presents a description of relatively a simple bi-crystal HMX-HTPB specimen and associated tensile loading experiment including computed tomography imaging, the pertinent constitutive theory, and details of numerical simulations used to infer the behavior of the material during the delamination process. Within this work, mechanical testing and direct numerical simulation of this relatively simple bi-crystal system enabled reasonable isolation of binder-crystal interface delamination, in which the effects of the complicated thermomechanical response of explosive crystals were minimized. Cohesive finite element modeling of the degradation and delamination of the interface between a modified HTPB binder and HMX crystals was used to reproduce observed results from tensile loading experiments on bi-crystal specimens. Several comparisons are made with experimental measurements in order to identify appropriate constitutive behavior of the binder and appropriate parameters for the cohesive traction-separation behavior of the crystal-binder interface. This research demonstrates the utility of directly modeling the delamination between binder and crystal within crystal-binder-crystal tensile specimen towards characterizing the behavior of these interfaces in a manner amenable to larger scale simulation of polycrystalline PBX materials. One critical aspect of this approach is micro computed tomography imaging conducted during the experiments, which enabled comparison of delamination patterns between the direct numerical simulation and actual specimen. In addition to optimizing the cohesive interface parameters, one important finding from this investigation is that understanding and representing the strain-hardening plasticity of HTPB binder is important within the context of using a cohesive traction-separation model for the delamination of a crystal-binder system.

42 ENGINEERING↗
DOE OSTI2017

Measuring, Cutting and Sorting Irradiated Control Rods to Limit the Volume of Intermediate Level Long-lived Waste - 17001

During operation, the PWR control rods are either completely extracted (scram or safety rods) or partially inserted in the operating zone of the core (fine control or operating rods). At the nominal rating conditions or close to them, the operating zone is limited to some steps of insertion in the order of a few tens of cm. In fact, only the lower part of the control rods are subjected to a significant neutron flux with an impact on the neutron activation and so on the waste classification (Low Level Short-lived Waste versus Intermediate Level Long-lived Waste). Our calculative as well as experimental experience confirms the significant presence of radionuclides in the control rods, but only in the lower parts. Measuring, cutting and finally sorting control rod scraps can reduce the volume of Intermediate Level Long-lived Waste planned for our storage deposit facility. This paper presents the EDF/DP2D methodologies followed to determine the sort criteria between the Low Level Short-lived Waste versus the Intermediate Level Long-lived Waste zones for the Silver-Indium-Cadmium control rods. The irradiated control rods are stored in cases without their head. Each case can contain several control rods, and the cases are stored under water in the fuel assembly pool. To calculate the radioactive inventories, we have developed a calculation scheme which is composed of a 3-dimensional mapping of the neutron flux, a calculation of the evolution of the isotopic compositions under neutron flux and finally a comparison between calculated and measured values. The main hypotheses of the control rods calculation take into account: - 3-dimensional geometry and 3-dimensional neutron sources distribution, - the isotopic compositions including impurities, - the history of irradiation resulting mainly from the daily power production, the positions of the control rods in the loading patterns and the positions in the axial operating zone. In order to validate the calculations, measurements were made 20 meters under water in the fuel assembly pool. The experimental results show the presence of many gamma emitter radionuclides. Only Ag-108m was retained for validating the calculations. This is due to the fact that silver is considered as the 'standard' chemical element for our control rods and silver produces Ag-108m which is a long-lived gamma emitter radionuclide. The analysis of the calculated results and the measured values allow us to build a simplified physics model for the simulation of the control rods activation. Finally three sort criteria can be proposed: - Without measurement devices, the sorting is based on an empirical sort criterion. Cuttings must then be made on the 2 back-ends of the control rod pins. This option is due to the difficulty in knowing the orientation of the pins in the storage cases. The cutting lines are placed at approximately 1 m from the 2 back-ends of the pins. This approach does not allow a great optimization of the sorting, less than 50% of the length of the control rods can be saved from Intermediate Level Long-lived Waste storage. - With a simple dose rate measurement device, the knowledge of the orientation of the pins in the storage cases allows us to limit cuttings to the lower part of the control rods. Depending on the 'top to tail' cases, between approximately 50% and 75% of the length of the control rods can be saved from Intermediate Level Long-lived Waste storage. - With an accurate measurement device, the sorting can be based on a specific activity of Ag-108m. Over 4400 Bq/g of Ag-108m (corresponding to the Intermediate Level Long-lived Waste limit), the control rod pieces can be considered as a long-lived waste. The measurements must be made over the 2 back-ends of control rod pins to examine the cases of 'top to tail' storage. This approach allows a great optimization of the sorting. Depending on the history of irradiation, more than 75% of the length of the control rods can be saved from Intermediate Level Long-lived Waste storage. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Extraction of Vibration Data with Imaging

To date, the primary sensing technology used to measure the vibration response has been accelerometers and strain gages mounted directly to the structure and using either wired or, more recently, wireless telemetry. Cost issues with these sensors and the associated data acquisition systems typically limit the numbers that are deployed on in situ structures. Although there are a few structures with larger sensing counts that in some cases exceed over 1000 sensors, more typical numbers range from ten to one hundred sensors resulting in low spatial resolution when they are applied to physically large systems. When one considers that nuclear power plant structures usually have complex geometries, material properties, connectivity and boundary conditions, it is clear these current approaches to vibration measurements can only provide limited information about a system’s dynamics response characteristics. As an alternative, many non-contact measurement technologies have emerged, including point wise measurement methods such as Global Positioning System (GPS), microwave interferometry, and laser Doppler vibrometry (LDV), as well as simultaneous full-field measurement methods such as electronic speckle pattern interferometry, holography interferometry, and muon tomography, some of which can provide high spatial resolution measurements. Among these methods, digital video imaging techniques have emerged as a feasible solution for full-field vibration measurements that provide significantly more detailed dynamic response information because every pixel becomes a measurement point. Furthermore, recent advances in image processing and computer vision algorithms have been successfully used to process video data for experimental and operational modal analysis. Such full-field measurements have the potential to significantly improve many current structural assessment procedures including system identification (modal parameter estimation), structural health monitoring, load reconstruction, model validation, and model updating. Furthermore, more recent full-field imaging techniques can be accomplished with relatively low-cost, commercially-available off-the-shelf cameras. However, these measurement procedures have other limitations that must be considered such as the ability to only measure visibly accessible points on a structure and a more limited dynamic range and bandwidth than can be achieved with accelerometers or strain gages.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

3D reconstruction of carbon nanotube networks from neutron scattering experiments

Structure reconstruction from statistical descriptors, such as scattering data obtained using x-rays or neutrons, is essential in understanding various properties of nanocomposites. Scattering based reconstruction can provide a realistic model, over various length scales, that can be used for numerical simulations. In this study, 3D reconstruction of a highly loaded carbon nanotube (CNT)-conducting polymer system based on small and ultra-small angle neutron scattering (SANS and USANS, respectively) data was performed. These light-weight and flexible materials have recently shown great promise for high-performance thermoelectric energy conversion, and their further improvement requires a thorough understanding of their structure-property relationships. The first step in achieving such understanding is to generate models that contain the hierarchy of CNT networks over nano and micron scales. The studied system is a single walled carbon nanotube (SWCNT)/poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS). SANS and USANS patterns of the different samples containing 10, 30, and 50 wt% SWCNTs were measured. These curves were then utilized to calculate statistical two-point correlation functions of the nanostructure. These functions along with the geometrical information extracted from SANS data and scanning electron microscopy images were used to reconstruct a representative volume element (RVE) nanostructure. Generated RVEs can be used for simulations of various mechanical and physical properties. This work, therefore, introduces a framework for the reconstruction of 3D RVEs of high volume faction nanocomposites containing high aspect ratio fillers from scattering experiments.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Cold plasma finite element wave model for helicon waves

Helicon waves have been recently proposed as an off-axis current drive actuator due to their expected high current drive efficiency in the mid-radius region in high beta tokamaks. This current drive efficiency has mostly been calculated ignoring the effects of the plasma in the scrape-off-layer (SOL) in the modeling. The net core current drive efficiency will decrease if helicon power is lost to the SOL. Previous efforts to estimate the loss of helicon power in the SOL have used the hot plasma code AORSA. The large computational cost of AORSA prevents large parametric scans, so to further the understanding of helicon power loss in the SOL, a reduced finite element, full wave plasma model with effective collision frequency for collisional and Landau damping has been developed to study the helicon wave power lost to the SOL. It will be shown that the reduced finite element model (FEM) can reproduce the magnitude and trends of helicon |E| field patterns and power loss in the SOL of the hot plasma AORSA model. The reduced FEM provides significant advantages over AORSA in reducing the computational time and memory requirements, and in simulating arbitrary tokamak vessel geometry. Parametric scans of antenna parallel refractive index, antenna location, minimum SOL density, SOL density gradient, and vacuum vessel geometry will be carried out to determine the dependencies of the helicon power lost to the SOL as a function of important parameters. Subsequently, the helicon cutoff density is shown to be an important quantity in determining helicon power lost to the SOL. Furthermore, losses due to antenna loading and wave accessibility are also observed at different antenna and plasma parameters.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2019

How Does Water Delivery System Design Impact the Microbial Load of Salad Crops?

In a microgravity setting, such as the environment aboard the International Space Station (ISS), an ideal plant water delivery system is one that can grow edible crops with minimal resource consumption and minimal risk to crew members. There are also concerns associated with the ability to control fluid escape and biofilm formation resulting in potential dangers to systems, crops, or crewmembers. To identify an appropriate system, candidate systems were assembled and operated under simulated ISS environmental conditions (T,CO2,and RH) with red romaine lettuce (Lactuca sativa cultivar 'Outredgeous') as a model crop. Fluid reservoirs and randomly selected planting sites were sampled every seven days until maturity at which point edible plant biomass and root samples were also taken. Heterotrophic bacteria and fungi growth patterns throughout each planting cycle were determined by plate counts on appropriate agar media. The candidate systems were compared to a classic hydroponics system as a control and harvested crops were compared to controls as well as Veggie-grown and market produce. Plants harvested from candidate systems yielded lower average heterotrophic bacteria and fungi per gram of plant mass levels when compared to market and Veggie samples as well as those from the control system. Additional studies to evaluate the system sanitation regimen as well as testing additional crops should be considered to aid in the selection of an ideal system.

Curry, Aaron B.↗
DOE OSTI2016

Positive low cloud and dust feedbacks amplify tropical North Atlantic Multidecadal Oscillation

Abstract The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to the appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.

58 GEOSCIENCES↗
DOE OSTI2024

Electric Vehicle Charging Demand in the Chicago Metropolitan Area through 2030

This report outlines the collaborative efforts between Argonne National Laboratory and Exelon in advancing the Agent-Based Transportation Energy Analysis Model (ATEAM). Aligning with ComEd’s beneficial electrification plan, this study developed eight scenarios to access the temporal and spatial distribution of charging load and demand stemming from the widespread adoption of battery electric vehicles (BEV) adoption, augmented public charging infrastructure deployment, and increased multi-unit dwelling (MUD) charging availability. Enhancements to the ATEAM model encompassed the simulation of multiple days of travel behavior, estimation of total public charging infrastructure needs, user interface refinements, and output tracking at both vehicle and charging station levels. The total electricity consumption for residential and public charging to support over 800,000 BEVs in Chicago in 2029 is projected at approximately 10.2 GWh. Enhanced MUD home charging accessibility (70%) amplifies the home charging load in the study area by 1.5% compared to the baseline scenario (10%). The widespread adoption of BEVs reduces peak charging loads, owing to their inclusion across households with diverse income levels, thus fostering a more dispersed charging activity pattern. However, widespread BEV adoption increases the peak home charging load in areas with lower median household incomes, reflecting a higher BEV concentration in these locales and, subsequently, heightened peak charging demands. In the Widespread BEV adoption scenario, fewer census tracts exhibit elevated peak loads for combined home and public charging, indicating a more even distribution of charging demand across the study area. Predominantly, peak loads for combined charging—both home and public— occur between 2 p.m. and 10 p.m. across all scenarios, encompassing the majority of census tracts.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS2012

Analysis of Ares Crew Launch Vehicle Transonic Alternating Flow Phenomenon

A transonic wind tunnel test of the Ares I-X Rigid Buffet Model (RBM) identified a Mach number regime where unusually large buffet loads are present. A subsequent investigation identified the cause of these loads to be an alternating flow phenomenon at the Crew Module-Service Module junction. The conical design of the Ares I-X Crew Module and the cylindrical design of the Service Module exposes the vehicle to unsteady pressure loads due to the sudden transition between a subsonic separated and a supersonic attached flow about the cone-cylinder junction as the local flow randomly fluctuates back and forth between the two flow states. These fluctuations produce a square-wave like pattern in the pressure time histories resulting in large amplitude, impulsive buffet loads. Subsequent testing of the Ares I RBM found much lower buffet loads since the evolved Ares I design includes an ogive fairing that covers the Crew Module-Service Module junction, thereby making the vehicle less susceptible to the onset of alternating flow. An analysis of the alternating flow separation and attachment phenomenon indicates that the phenomenon is most severe at low angles of attack and exacerbated by the presence of vehicle protuberances. A launch vehicle may experience either a single or, at most, a few impulsive loads since it is constantly accelerating during ascent rather than dwelling at constant flow conditions in a wind tunnel. A comparison of a windtunnel- test-data-derived impulsive load to flight-test-data-derived load indicates a significant over-prediction in the magnitude and duration of the buffet load. I. Introduction One

Sekula, Martin K.↗
NASA NTRS1988

Effect of field-aligned potential drop in a global magnetosphere-ionosphere coupling model

Effects of field-aligned potential drops on the magnetosphere-ionosphere coupling in a steady state are studied on a global ionospheric scale. It is shown that a constant-current generator can support a larger field-aligned potential drop than a constant voltage generator under similar conditions. The magnetospheric convection pattern is distorted more in the constant current generator case than in the constant voltage generator case. The main difference between a constant current generator and a constant voltage generator is found to lie in their ability to adjust the vorticity of the magnetospheric convection. The results show that a constant current generator allows the vorticity of the magnetospheric convection to adjust so that the field-aligned current can be kept constant under the loading influence of the field-aligned potential. On the other hand, a constant voltage generator by definition cannot adjust the vorticity of the magnetospheric convection to maintain the field-aligned current under the loading influence of the field-aligned potential.

Kan, J. R.↗
DOE OSTI2014

Occupancy schedules learning process through a data mining framework

Building occupancy is a paramount factor in building energy simulations. Specifically, lighting, plug loads, HVAC equipment utilization, fresh air requirements and internal heat gain or loss greatly depends on the level of occupancy within a building. Developing the appropriate methodologies to describe and reproduce the intricate network responsible for human-building interactions are needed. Extrapolation of patterns from big data streams is a powerful analysis technique which will allow for a better understanding of energy usage in buildings. A three-step data mining framework is applied to discover occupancy patterns in office spaces. First, a data set of 16 offices with 10 minute interval occupancy data, over a two year period is mined through a decision tree model which predicts the occupancy presence. Then a rule induction algorithm is used to learn a pruned set of rules on the results from the decision tree model. Finally, a cluster analysis is employed in order to obtain consistent patterns of occupancy schedules. Furthermore, the identified occupancy rules and schedules are representative as four archetypal working profiles that can be used as input to current building energy modeling programs, such as EnergyPlus or IDA-ICE, to investigate impact of occupant presence on design, operation and energy use in office buildings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1982

CDTI: Crew Function Assessment

Man machine interaction often requires the operator to perform a sterotyped scan of instruments to monitor and/or control a system. Situations in which this type of behavior exists, such as instrument flight, scan pattern has been shown to be altered by imposition of simultaneous verbal tasks. The relationship between pilot visual scan of instruments and mental workload was described. A verbal loading task of varying difficulty caused pilots to stare at the primary instrument as the difficulty increased and to shed looks at instruments of less importance. The verbal loading task affected rank ordering of scanning sequences. The behavior of pilots with widely varying skill levels suggested that these effects occur most strongly at lower skill levels and are less apparent at high skill levels. Graphical interpretation of the hypothetical relationship between skill, workload, and performance is introduced and modeling results are presented to support this interpretation.

Tole, J. R.↗
NASA NTRS2012

Plasticity of Neurovestibular Systems Following Micro- and Hyper-Gravity Exposure and Readaptation to Earth's 1G

The gravity-sensing organs sense the sum of inertial force due to head translation and head orientation relative to gravity. Normally gravity is constant, and yet the neural sensors show remarkable plasticity. When the force of gravity changes, such as in spaceflight or during centrifugation, the neurovestibular system responds by regulating its neural output, and this response is similar for the vertebrate utricular nerve afferents and for the statocyst hair cell in invertebrates. First, we examine the response of utricular afferents in toadfish following exposure to G on two orbital missions (STS-90 and 95). Within the first day after landing, magnitude of neural response to an applied acceleration was significantly elevated, and re-adaptation back to control values occurred within approximately 30 hours. Time course of return to normal approximately parallels the decrease in vestibular disorientation in astronauts following return. Next, we use well-controlled hyper-G experiments in the vertebrate model to address: If G leads to adaptation and subsequent re-adaptation neural processes, does the transfer from 1G to hyper-G impart the opposite effects and do the effects accompanying transfer from the hyper-G back to the 1G conditions resemble as an analog the transfer from 1G to the microG Results show a biphasic pattern in reaction to 3G exposures: an initial sensitivity up-regulation (3- and 4-day) followed by a significant decrease after longer exposure. Return to control values is on the order of 4-8 days. Utricular sensitivity is strongly regulated up or down by gravity load and the duration of exposure. Interestingly, we found no correlation of response and hair cell synaptic body counts despite the large gain difference between 4- and 16-Day subjects. Lastly, we examine responses of statocyst receptors in land snail following exposure to G on two unmanned Russian Orbital missions (Foton M-2 and -3). Here, we have the ability to measure the output directly from the hair cells. Similar to afferents in vertebrates the hair cells increased their response sensitivity to vestibular stimulation. Two major pieces of information are needed: the precise vertebrate hair cell response to altered gravity and the impact of longer duration exposures on sensory plasticity.

Boyle, Richard D.↗