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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

AI-Enabled Robotic NDE for Structural Damage Assessment and Repair

The aim of this paper is to develop the concept and a prototype of an intelligent mobile robotic platform that is integrated with nondestructive evaluation (NDE) capabilities for autonomous live inspection and repair. In many industrial environments, such as the application of power plant boiler inspection, human inspectors often have to perform hazardous and challenging tasks. There is a significant chance of injury, considering the confined spaces and limited visibility of the inspection environment and hazards such as pressurization and improper water levels. In order to provide a solution to eliminate these dangers, the concept of a new robotic system was developed and prototyped that is capable of autonomously sweeping the region to be inspected. The robot design contains systematic integration of components from robotics, NDE, and artificial intelligence (AI). A magnetic track system is used to navigate over the vertical steel structures required for examination. While moving across the inspection area, the robot uses an NDE sensor to acquire data for inspection and repair. This paper presents a design of a portable NDE scanning system based on eddy current array probes, which can be customized and installed on various mobile robot platforms. Machine learning methods are applied for semantic segmentation that will simultaneously localize and recognize defects without the need of human intervention. Experiments were conducted that show the NDE and repair capabilities of the system. Improvements in human safety and structural damage prevention, as well as lowering the overall costs of maintenance, are possible through the implementation of this robotic NDE system.

Materials Science↗
NASA NTRS2009

Technology Transfer Challenges: A Case Study of User-Centered Design in NASA's Systems Engineering Culture

The Upper Stage (US) section of the National Aeronautics and Space Administration's (NASA) Ares I rocket will require internal access platforms for maintenance tasks performed by humans inside the vehicle. Tasks will occur during expensive critical path operations at Kennedy Space Center (KSC) including vehicle stacking and launch preparation activities. Platforms must be translated through a small human access hatch, installed in an enclosed worksite environment, support the weight of ground operators and be removed before flight - and their design must minimize additional vehicle mass at attachment points. This paper describes the application of a user-centered conceptual design process and the unique challenges encountered within NASA's systems engineering culture focused on requirements and "heritage hardware". The NASA design team at Marshall Space Flight Center (MSFC) initiated the user-centered design process by studying heritage internal access kits and proposing new design concepts during brainstorming sessions. Simultaneously, they partnered with the Technology Transfer/Innovative Partnerships Program to research inflatable structures and dynamic scaffolding solutions that could enable ground operator access. While this creative, technology-oriented exploration was encouraged by upper management, some design stakeholders consistently opposed ideas utilizing novel, untested equipment. Subsequent collaboration with an engineering consulting firm improved the technical credibility of several options, however, there was continued resistance from team members focused on meeting system requirements with pre-certified hardware. After a six-month idea-generating phase, an intensive six-week effort produced viable design concepts that justified additional vehicle mass while optimizing the human factors of platform installation and use. Although these selected final concepts closely resemble heritage internal access platforms, challenges from the application of the user-centered process provided valuable lessons for improving future collaborative conceptual design efforts.

Quick, Jason↗
NASA NTRS2012

Developments in Atmosphere Revitalization Modeling and Simulation

"NASA's Advanced Exploration Systems (AES) program is pioneering new approaches for rapidly developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit" (NASA 2012). These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must not only blast out of earth's gravity well as during the Apollo moon missions, but also launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by evaluating structured sorbents, seeking more robust pelletized sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach, which is then implemented in a full-scale integrated atmosphere revitalization test. This paper describes the development of atmosphere revitalization models and simulations. A companion paper discusses the hardware design and sorbent screening and characterization effort in support of the Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project within the AES program.

Knox, James C.↗
NASA NTRS2012

Development of Carbon Dioxide Removal Systems for Advanced Exploration Systems

"NASA's Advanced Exploration Systems (AES) program is pioneering new approaches for rapidly developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit" (NASA 2012). These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must not only blast out of earth's gravity well as during the Apollo moon missions, but also launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by seeking more robust pelletized sorbents, evaluating structured sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach, which is then implemented in a full-scale integrated atmosphere revitalization test. This paper describes the carbon dioxide (CO2) removal hardware design and sorbent screening and characterization effort in support of the Atmosphere Resource Recovery and Environmental Monitoring (ARREM) project within the AES program. A companion paper discusses development of atmosphere revitalization models and simulations for this project.

Knox, James C.↗
DOE OSTI2026

Activation dynamics of a water-soluble human mu-opioid receptor

The mu-opioid receptor (MOR), a class A G protein-coupled receptor mediates opioid analgesia and remains a central target for pain therapeutics. While crystal structures of MOR exist, they provide limited insight into the receptor’s dynamic conformational landscape underlying function. Here, we engineered a thermostable water-soluble MOR variant (wsMOR) that retains native-like ligand-binding and activation dynamics. This variant enables high-yield production and detailed solution-phase structural studies that are challenging with membrane-embedded MOR, providing a valuable tool for studying receptor activation and aqueous-phase drug screening. Using a combined computational and experimental approach, we performed long-timescale all-atom molecular dynamics simulations together with neutron scattering and single-molecule FRET, revealing a structurally stable receptor with a diverse ensemble of conformations at different temporal resolutions. In the ligand-free state, wsMOR displayed high conformational flexibility, which decreased upon agonist binding, particularly in transmembrane helix 6, a hallmark of G protein-coupled receptor activation. Positive allosteric modulation and G protein binding further stabilized active-like states. These findings highlight wsMOR’s conformational plasticity across picosecond to millisecond timescales and provide a foundation for structure-guided development of next-generation opioid ligands with improved efficacy and safety.

E, Agyemang [University of Tennessee Knoxville]↗
NASA NTRS2023

Estimating the concentration of total suspended solids in inland and coastal waters from Sentinel-2 MSI: A semi-analytical approach

Inland and coastal waters provide key ecosystem services and are closely linked to human well-being. In this study, we propose a semi-analytical method, which can be applied to Sentinel-2 MultiSpectral Instrument (MSI) images to retrieve high spatial-resolution total suspended solids (TSS) concentration in a broad spectrum of aquatic ecosystems ranging from clear to extremely turbid waters. The presented approach has four main steps. First, the remote sensing reflectance ( R rs ) at a band lacking in MSI (620 nm) is estimated through an empirical relationship from R rs at 665 nm. Second, waters are classified into four types (clear, moderately turbid, highly turbid, and extremely turbid). Third, semi-analytical algorithms are used to estimate the particulate backscattering coefficient ( b bp ) at a reference band depending on the water types. Last, TSS is estimated from bbp at the reference band. Validation and comparison of the proposed method with three existing methods are performed using a simulated dataset ( N = 1000), an in situ dataset collected from global inland and coastal waters ( N = 1265) and satellite matchups ( N = 40). Results indicate that the proposed method can improve TSS estimation and provide accurate retrievals of TSS from all three datasets, with a median absolute percentage error (MAPE) of 14.88 %, 31.50 % and 41.69 % respectively. We also present comparisons of TSS mapping between the Sentinel-3 Ocean and Land Colour Instrument (OLCI) and MSI in Lake Kasumigaura, Japan and the Tagus Estuary, Portugal. Results clearly demonstrate the advantages of using MSI for TSS monitoring in small water bodies such as rivers, river mouths and other nearshore waters. MSI can provide more detailed and realistic TSS estimates than OLCI in these water bodies. The proposed TSS estimation method was applied to MSI images to produce TSS time-series in Lake Kasumigaura, which showed good agreements with in situ and OLCI-derived TSS time-series.

Sentinel-2↗
DOE OSTI2023

Energy-Efficient Driving in Connected Corridors via Minimum Principle Control: Vehicle-in-the-Loop Experimental Verification in Mixed Fleets

Connected and automated vehicles (CAVs) can plan and actuate control that explicitly considers performance, system safety, and actuation constraints in a manner more efficient than their human-driven counterparts. In particular, eco-driving is enabled through connected exchange of information from signalized corridors that share their upcoming signal phase and timing (SPaT). This is accomplished in the proposed control approach, which follows first principles to plan a free-flow acceleration-optimal trajectory through green traffic light intervals by Pontryagin's Minimum Principle in a feedback manner. Urban conditions are then imposed from exogeneous traffic comprised of a mixture of human-driven vehicles (HVs) - as well as other CAVs. As such, safe disturbance compensation is achieved by implementing a model predictive controller (MPC) to anticipate and avoid collisions by issuing braking commands as necessary. The control strategy is experimentally vetted through vehicle-in-the-loop (VIL) of a prototype CAV that is embedded into a virtual traffic corridor realized through microsimulation. Up to 36% fuel savings are measured with the proposed control approach over a human-modelled driver, and it was found connectivity in the automation approach improved fuel economy by up to 26% over automation without. Additionally, the passive energy benefits realizable for human drivers when driving behind downstream CAVs are measured, showing up to 22% fuel savings in a HV when driving behind a small penetration of connectivity-enabled automated vehicles.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Optimizing metaproteomics database construction: lessons from a study of the vaginal microbiome

Metaproteomics, a method for untargeted, high-throughput identification of proteins in complex samples, provides functional information about microbial communities and can tie functions to specific taxa. Metaproteomics often generates less data than other omics techniques, but analytical workflows can be improved to increase usable data in metaproteomic outputs. Identification of peptides in the metaproteomic analysis is performed by comparing mass spectra of sample peptides to a reference database of protein sequences. Although these protein databases are an integral part of the metaproteomic analysis, few studies have explored how database composition impacts peptide identification. Here, we used cervicovaginal lavage (CVL) samples from a study of bacterial vaginosis (BV) to compare the performance of databases built using six different strategies. We evaluated broad versus sample-matched databases, as well as databases populated with proteins translated from metagenomic sequencing of the same samples versus sequences from public repositories. Smaller sample-matched databases performed significantly better, driven by the statistical constraints on large databases. Additionally, large databases attributed up to 34% of significant bacterial hits to taxa absent from the sample, as determined orthogonally by 16S rRNA gene sequencing. We also tested a set of hybrid databases which included bacterial proteins from NCBI RefSeq and translated bacterial genes from the samples. These hybrid databases had the best overall performance, identifying 1,068 unique human and 1,418 unique bacterial proteins, ~30% more than a database populated with proteins from typical vaginal bacteria and fungi. Our findings can help guide the optimal identification of proteins while maintaining statistical power for reaching biological conclusions.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2003

Results of Evaluation of Solar Thermal Propulsion

The solar thermal propulsion evaluation reported here relied on prior research for all information on solar thermal propulsion technology and performance. Sources included personal contacts with experts in the field in addition to published reports and papers. Mission performance models were created based on this information in order to estimate performance and mass characteristics of solar thermal propulsion systems. Mission analysis was performed for a set of reference missions to assess the capabilities and benefits of solar thermal propulsion in comparison with alternative in-space propulsion systems such as chemical and electric propulsion. Mission analysis included estimation of delta V requirements as well as payload capabilities for a range of missions. Launch requirements and costs, and integration into launch vehicles, were also considered. The mission set included representative robotic scientific missions, and potential future NASA human missions beyond low Earth orbit. Commercial communications satellite delivery missions were also included, because if STP technology were selected for that application, frequent use is implied and this would help amortize costs for technology advancement and systems development. A C3 Topper mission was defined, calling for a relatively small STP. The application is to augment the launch energy (C3) available from launch vehicles with their built-in upper stages. Payload masses were obtained from references where available. The communications satellite masses represent the range of payload capabilities for the Delta IV Medium and/or Atlas launch vehicle family. Results indicated that STP could improve payload capability over current systems, but that this advantage cannot be realized except in a few cases because of payload fairing volume limitations on current launch vehicles. It was also found that acquiring a more capable (existing) launch vehicle, rather than adding an STP stage, is the most economical in most cases.

Woodcock, Gordon↗
NASA NTRS2001

An Experimental Investigation of Dextrous Robots Using EVA Tools and Interfaces

This investigation of robot capabilities with extravehicular activity (EVA) equipment looks at how improvements in dexterity are enabling robots to perform tasks once thought to be beyond machines. The approach is qualitative, using the Robonaut system at the Johnson Space Center (JSC), performing task trials that offer a quick look at this system's high degree of dexterity and the demands of EVA. Specific EVA tools attempted include tether hooks, power torque tools, and rock scoops, as well as conventional tools like scissors, wire strippers, forceps, and wrenches. More complex EVA equipment was also studied, with more complete tasks that mix tools, EVA hand rails, tethers, tools boxes, PIP pins, and EVA electrical connectors. These task trials have been ongoing over an 18 month period, as the Robonaut system evolved to its current 43 degree of freedom (DOF) configuration, soon to expand to over 50. In each case, the number of teleoperators is reported, with rough numbers of attempts and their experience level, with a subjective difficulty rating assigned to each piece of EVA equipment and function. JSC' s Robonaut system was successful with all attempted EVA hardware, suggesting new options for human and robot teams working together in space.

Ambrose, Robert↗
NASA NTRS1999

Summary of LO2/Ethanol OMS/RCS Technology and Advanced Development 99-2744

NASA is pursuing non-toxic propellant technologies applicable to RLV and Space Shuttle orbital maneuvering system (OMS) and reaction control system (RCS). The primary objectives of making advancements in an OMS/RCS system are improved safety, reliability, and reduced operations and maintenance cost, while meeting basic operational and performance requirements. An OMS/RCS has a high degree of direct interaction with the vehicle and crew and requires subsystem and components that are compatible with integration into the vehicle with regard to external mold-line, power, and thermal control. In July 1997, a Phase I effort for the technology and advanced development of an upgrade of the space shuttle was conducted to define the system architecture, propellant tank, feed system, RCS thrusters, and OMS engine. Phase I of the project ran from July 1997 to October 1998. Phase II is currently being planned for the development and test of full-scale prototype of the system in 1999 and 2000. The choice of pressure-fed liquid oxygen (LO2) and ethanol is the result of numerous trade studies conducted from 1980 to 1996. Liquid oxygen and ethanol are clean burning, high-density propellants that provide a high degree of commonality with other spacecraft subsystems including life support, power, and thermal control, and with future human exploration and development of space missions. The key to this pressure-fed system is the use of subcooled liquid oxygen at 350 psia. In this approach, there is 80 degrees R of subcooling, which means that boil-off will not occur until the temperature has risen 80 R. The sub-cooling results naturally from loading propellants at 163 R, which is the saturation temperature at 14.7 psia, and then pressurizing to 350 psia on the launch pad. Thermal insulation and conditioning techniques are then used to limit the LO2 temperature to 185 R maximum, and maintain the sub-cooling. The other key is the wide temperature range of ethanol, -173 F to +300 F, which can provide heat to gasify liquid oxygen or provide a good coolant.

Curtis, Leslie A.↗
NASA NTRS2000

Effects of Prolonged Centrifugation on Orthostasis

A feasibility study conducted on the Ames 20-G Human Centrifuge examined how well humans can maintain orthostatic tolerance during and after prolonged exposures to hypergravity. Three adult males lived for periods of 22 hours in the centrifuge while it was at rest (1.00 G), and while it rotated at 9.38 RPM to provide 1.25 G-total at the mean radius of 7.62 m. Two participants also experienced 22-hour habitation sessions at 11.46 RPM, which provided 1.50 G-total. Both before and after each habitation session, the participants were given gradual onset rate (GOR) acceleration profiles at 0.067 G/sec to determine their Gz tolerance. In addition, cardiovascular responses were compared while subjects were supine, siting, and standing at various times during the habitation (stand test), and cardiovascular responsiveness was determined using a lower body negative pressure tilt table (LBNPTT) at the beginning of the experiment and after each session. Post-Pre changes in G tolerance were -0.33 (mean) +/- 0.11 (std. error) Gz for habitation at 1.00 G, -0.02 +/- 0.12 Gz for habitation at 1.25 G, and +0.41 +/- 0.13 Gz for habitation at 1.50 G. Performance on the stand test generally improved with duration of habitation in hypergravity. Our results suggest that habitation in a confined chamber at 1.00 G reduces G tolerance and leads to lowered LBNPTT tolerance. Exposure to increased G in the centrifuge leads to enhanced performance on the stand test, and to increased GOR acceleration tolerance, but only when fluid balance is maintained; when motion sickness and negative fluid balance were observed, G tolerance was reduced. The data indicate that enhanced G tolerance can result from prolonged exposure to hypergravity, but that these changes are complex and depend on multiple underlying physiological processes.

Cohen, Malcolm M..↗
NASA NTRS2019

Streamlining Pre-Launch Support for Missions with Highly Variable Trajectories

As the Goddard Space Flight Center's (GSFC) Flight Dynamics Facility (FDF) continues to ensure mission success in support of Human Space Flight (HSF) and Launch Vehicle (LV) missions, it continues to improve on different areas of mission support. The FDF processes numerous different types of trajectory profiles, and, for each trajectory, the FDF provides multiple acquisition data vectors to the Space Network (SN) White Sands Complex (WSC) for further processing and uplinking to the SN's Tracking and Data Relay Satellites (TDRSs), tracking the vehicle and maintaining communications throughout required support. Some trajectories target a specific orbit plane through Right Ascension of the Ascending Node (RAAN), or yaw, steering, which can yield to high variability across the launch window. Because of this, there can be a large number of trajectory profiles to process and generate acquisition data for that ensure TDRS is accurately pointing to the launch vehicle. Processing many trajectory profiles by FDF and WSC increases the complexity and level of effort associated with support. FDF employs a legacy boundary on the range difference between trajectories, which determines the number of discrete trajectory cases required to maintain communication with TDRS over the full launch window. An analysis was performed to determine a new boundary, taking into consideration current support requirements. The results show the boundary can be expanded beyond the currently employed legacy value without an impact on communication. In doing so, the number of trajectory profiles processed can be reduced, reducing the complexity and level of effort required, with no impact to mission safety.

Flight Operations↗
NASA NTRS2024

Transfer of NASA Technology to the DoD: Mitigating Motion Sickness with Autogenic Feedback Training Exercise

Motion sickness poses a significant safety risk, particularly in the context of aviation. Given its prevalence among aviators and its detrimental impact on performance, researchers have attempted to identify effective mitigation strategies for motion sickness. Currently, many of the existing interventions are pharmacological, and while effective, they present a problem due to their associated adverse side effects. The primary goals of the current research were 1) demonstrate the value of the application of Autogenic-Feedback Training Exercise (AFTE), a physiological training program developed by NASA to mitigate the impact of operational stressors such as motion sickness and spatial disorientation on human physiology and performance and 2) evaluate a new enhanced version of AFTE training software and demonstrate the ability to apply it remotely and train other personnel to administer it. AFTE combines principles of autogenic therapy, and biofeedback in training individuals to control their physiological reactions through a series of relaxation and arousal exercises. This study included twenty-six participants, 17 men and 9 women. On day 1 participants were tested in a rotating chair (pre-test) to determine their motion sickness tolerance (measured as minutes of rotation); days 2-5 consisted of four AFTE training sessions, each 30-min. in duration for a total of 2 hours; and on day 6 the participants were re-tested in the rotating chair. Results revealed a significant increase in motion sickness tolerance with AFTE on the post-test when compared to pre-test, participants had significantly lower symptom diagnostic scores post-test, and there was no significant gender effect. In addressing the first goal it was concluded that the modified 2-hour version of AFTE significantly improved motion sickness tolerance with participants experiencing fewer symptoms. A second goal of this research was to refine and transfer a NASA technology, software and methods for applications within DOD by training other personnel to administer AFTE. A comparison of NASA and NAMRU-D trainers on AFTE outcome for improving participants’ motion sickness tolerance revealed no significant difference indicating the successful transfer of methods to DOD. In addition, remote AFTE training of military aviators at distant sites was feasible. A third goal was to identify individual patterns of interoceptive abilities and related autonomic metrics able to predict stress response and training outcome. These data included measures of personality traits obtained from questionnaires and specific autonomic measures (e.g., heart rate variability) collected by NAMRU-D investigators. These results will be reported in a separate paper.

autonomic nervous system↗
DOE OSTI2022

Accelerating Scientific Workflows on HPC Platforms with In Situ Processing

Scientific workflows drive most modern large-scale science breakthroughs by allowing scientists to define their computations as a set of jobs executed in a given order based on their data dependencies. Workflow management systems (WMSs) have become key to automating scientific workflows-executing computational jobs and orchestrating data transfers between those jobs running on complex high-performance computing (HPC) platforms. Traditionally, WMSs use files to communicate between jobs: a job writes out files that are read by other jobs. However, HPC machines face a growing gap between their storage and compute capabilities. To address that concern, the scientific community has adopted a new approach called in situ, which bypasses costly parallel filesystem I/O operations with faster in-memory or in-network communications. When using in situ approaches, communication and computations can be interleaved. In this work, we leverage the Decaf in situ dataflow framework to accelerate task-based scientific workflows managed by the Pegasus WMS, by replacing file communications with faster MPI messaging. We propose a new execution engine that uses Decaf to manage communications within a sub-workflow (i.e., set of jobs) to optimize inter-job communications. We consider two workflows in this study: (i) a synthetic workflow that benchmarks and compares file- and MPI-based communication; and (ii) a realistic bioinformatics workflow that computes mu-tational overlaps in the human genome. Experiments show that in situ communication can improve the bioinformatics workflow execution time by 22% to 30% compared with file communication. Our results motivate further opportunities and challenges for bridging traditional WMSs with in situ frameworks.

Decaf↗
DOE OSTI2022

Interpreting machine learning prediction of fire emissions and comparison with FireMIP process-based models

Annual burned areas in the United States have increased 2-fold during the past decades. With more large fires resulting in more emissions of fine particulate matter, an accurate prediction of fire emissions is critical for quantifying the impacts of fires on air quality, human health, and climate. This study aims to construct a machine learning (ML) model with game-theory interpretation to predict monthly fire emissions over the contiguous US (CONUS) and to understand the controlling factors of fire emissions. The optimized ML model is used to diagnose the process-based models in the Fire Modeling Intercomparison Project (FireMIP) to inform future development. Results show promising performance for the ML model, Community Land Model (CLM), and Joint UK Land Environment Simulator-Interactive Fire And Emission Algorithm For Natural Environments (JULES-INFERNO) in reproducing the spatial distributions, seasonality, and interannual variability of fire emissions over the CONUS. Regional analysis shows that only the ML model and CLM simulate the realistic interannual variability of fire emissions for most of the subregions (r >0.95 for ML and r =0.14~0.70 for CLM), except for Mediterranean California, where all the models perform poorly (r =0.74 for ML and r <0.30 for the FireMIP models). Regarding seasonality, most models capture the peak emission in July over the western US. However, all models except for the ML model fail to reproduce the bimodal peaks in July and October over Mediterranean California, which may be explained by the smaller wind speeds of the atmospheric forcing data during Santa Ana wind events and limitations in model parameterizations for capturing the effects of Santa Ana winds on fire activity. Furthermore, most models struggle to capture the spring peak in emissions in the southeastern US, probably due to underrepresentation of human effects and the influences of winter dryness on fires in the models. As for extreme events, both the ML model and CLM successfully reproduce the frequency map of extreme emission occurrence but overestimate the number of months with extremely large fire emissions. Comparing the fire PM 2.5 emissions from the ML model with process-based fire models highlights their strengths and uncertainties for regional analysis and prediction and provides useful insights into future directions for model improvements.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2003

Comparison of left ventricular diastolic function in obstructive hypertrophic cardiomyopathy in patients undergoing percutaneous septal alcohol ablation versus surgical myotomy/myectomy

Both percutaneous transcoronary alcohol septal reduction (ASR) and surgical myectomy are effective treatments to relieve left ventricular (LV) outflow tract obstruction in obstructive hypertrophic cardiomyopathy (HC). LV diastolic function was assessed by echocardiography in 57 patients with obstructive HC at baseline and 5 +/- 4 months after ASR (n = 37) or surgical myectomy (n = 20). LV outflow tract pressure gradient decreased from 65 +/- 40 to 23 +/- 21 mm Hg (p <0.01) after treatment. The ratio of the early-to-late peak diastolic LV inflow velocities, and the ratio of the early peak diastolic LV inflow velocity to the lateral mitral annulus early diastolic velocity determined by tissue Doppler imaging significantly decreased after the procedures (1.6 +/- 1.7 vs 1.0 +/- 0.7 and 15 +/- 8 vs 11 +/- 5, respectively), whereas LV inflow propagation velocity significantly increased (60 +/- 24 vs 71 +/- 36 cm/s). Left atrial size decreased from 29 +/- 7 to 25 +/- 6 cm(2) (p <0.05). Patients had a significant improvement in New York Heart Association functional class and in exercise performance. When comparing ASR with myectomy, no difference was found in the degree of change in any parameter of diastolic function. Thus, diastolic function indexes obtained by echocardiography changed after septal reduction interventions in patients with obstructive HC; this change was similar to that after surgical myectomy and ASR.

Non-NASA Center↗
NASA NTRS2001

Effects of afternoon "siesta" naps on sleep, alertness, performance, and circadian rhythms in the elderly

STUDY OBJECTIVES: To determine the effects of a 90-minute afternoon nap regimen on nocturnal sleep, circadian rhythms, and evening alertness and performance levels in the healthy elderly. DESIGN AND SETTING: Nine healthy elderly subjects (4m, 5f, age range 74y-87y) each experienced both nap and no-nap conditions in two studies each lasting 17 days (14 at home, 3 in the laboratory). In the nap condition a 90-minute nap was enforced between 13:30 and 15:00 every day, in the no-nap condition daytime napping was prohibited, and activity encouraged in the 13:30-15:00 interval. The order of the two conditions was counterbalanced. PARTICIPANTS: N/A INTERVENTIONS: N/A MEASUREMENTS: Diary measures, pencil and paper alertness tests, and wrist actigraphy were used at home. In the 72 hour laboratory studies, these measures were augmented by polysomnographic sleep recording, continuous rectal temperature measurement, a daily evening single trial of a Multiple Sleep Latency Test (MSLT), and computerized tests of mood, activation and performance efficiency. RESULTS: By the second week in the "at home" study, an average of 58 minutes of sleep was reported per siesta nap; in the laboratory, polysomnography confirmed an average of 57 minutes of sleep per nap. When nap and no-nap conditions were compared, mixed effects on nocturnal sleep were observed. Diary measures indicated no significant difference in nocturnal sleep duration, but a significant increase (of 38 mins.) in 24-hour Total Sleep Time (TST) when nocturnal sleeps and naps were added together (p<0.025). The laboratory study revealed a decrease of 2.4% in nocturnal sleep efficiency in the nap condition (p<0.025), a reduction of nocturnal Total Sleep Time (TST) by 48 mins. in the nap condition (p<0.001) which resulted primarily from significantly earlier waketimes (p<0.005), but no reliable effects on Wake After Sleep Onset (WASO), delta sleep measures, or percent stages 1 & 2. Unlike the diary study, the laboratory study yielded no overall increase in 24-hour TST consequent upon the siesta nap regimen. The only measure of evening alertness or performance to show an improvement was sleep latency in a single-trial evening MSLT (nap: 15.6 mins., no nap: 11.5 mins., p<0.005). No significant change in circadian rhythm parameters was observed. CONCLUSIONS: Healthy seniors were able to adopt a napping regimen involving a 90-minute siesta nap each day between 13:30 and 15:00, achieving about one hour of actual sleep per nap. There were some negative consequences for nocturnal sleep in terms of reduced sleep efficiency and earlier waketimes, but also some positive consequences for objective evening performance and (in the diary study) 24-hour sleep totals. Subjective alertness measures and performance measures showed no reliable effects and circadian phase parameters appeared unchanged.

Non-NASA Center↗