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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Initial clinical evaluation of PET-based ion beam therapy monitoring under consideration of organ motion

Purpose: Intrafractional organ motion imposes considerable challenges to scanned ion beam therapy and demands for a thorough verification of the applied treatment. At the Heidelberg Ion-Beam Therapy Center (HIT), the scanned ion beam delivery is verified by means of postirradiation positron-emission-tomography (PET) imaging. This work presents a first clinical evaluation of PET-based treatment monitoring in ion beam therapy under consideration of target motion. Methods: Three patients with mobile liver lesions underwent scanned carbon ion irradiation at HIT and postirradiation PET/CT (x-ray-computed-tomography) imaging with a commercial scanner. Respiratory motion was recorded during irradiation and subsequent image acquisition. This enabled a time-resolved (4D) calculation of the expected irradiation-induced activity pattern and, for one patient where an additional 4D CT was acquired at the PET/CT scanner after treatment, a motion-compensated PET image reconstruction. For the other patients, PET data were reconstructed statically. To verify the treatment, calculated prediction and reconstructed measurement were compared with a focus on the ion beam range. Results: Results in the current three patients suggest that for motion amplitudes in the order of 2 mm there is no benefit from incorporating respiratory motion information into PET-based treatment monitoring. For a target motion in the order of 10 mm, motion-related effects become more severe and a time-resolved modeling of the expected activity distribution can lead to an improved data interpretation if a sufficient number of true coincidences is detected. Benefits from motion-compensated PET image reconstruction could not be shown conclusively at the current stage. Conclusions: The feasibility of clinical PET-based treatment verification under consideration of organ motion has been shown for the first time. Improvements in noise-robust 4D PET image reconstruction are deemed necessary to enhance the clinical potential.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

4D-CT scans reveal reduced magnitude of respiratory liver motion achieved by different abdominal compression plate positions in patients with intrahepatic tumors undergoing helical tomotherapy

Purpose: While abdominal compression (AC) can be used to reduce respiratory liver motion in patients receiving helical tomotherapy for hepatocellular carcinoma, the nature and extent of this effect is not well described. The purpose of this study was to evaluate the changes in magnitude of three-dimensional liver motion with abdominal compression using four-dimensional (4D) computed tomography (CT) images of several plate positions. Methods: From January 2012 to October 2015, 72 patients with intrahepatic carcinoma and divided into four groups underwent 4D-CT scans to assess respiratory liver motion. Of the 72 patients, 19 underwent abdominal compression of the cephalic area between the subxiphoid and umbilicus (group A), 16 underwent abdominal compression of the caudal region between the subxiphoid area and the umbilicus (group B), 11 patients underwent abdominal compression of the caudal umbilicus (group C), and 26 patients remained free breathing (group D). 4D-CT images were sorted into ten-image series, according to the respiratory phase from the end inspiration to the end expiration, and then transferred to treatment planning software. All liver contours were drawn by a single physician and confirmed by a second physician. Liver relative coordinates were automatically generated to calculate the liver respiratory motion in different axial directions to compile the 10 ten contours into a single composite image. Differences in respiratory liver motion were assessed with a one-way analysis of variance test of significance. Results: The average respiratory liver motion in the Y axial direction was 4.53 ± 1.16, 7.56 ± 1.30, 9.95 ± 2.32, and 9.53 ± 2.62 mm in groups A, B, C, and D, respectively, with a significant change among the four groups (p < 0.001). Abdominal compression was most effective in group A (compression plate on the subxiphoid area), with liver displacement being 2.53 ± 0.93, 4.53 ± 1.16, and 2.14 ± 0.92 mm on the X-, Y-, and Z-axes, respectively. There was no significant difference in respiratory liver motion between group C (displacement: 3.23 ± 1.47, 9.95 ± 2.32, and 2.92 ± 1.10 mm on the X-, Y-, and Z-axes, respectively) and group D (displacement: 3.35 ± 1.55, 9.53 ± 2.62, and 3.35 ± 1.73 mm on the X-, Y-, and Z-axes, respectively). Abdominal compression was least effective in group C (compression on caudal umbilicus), with liver motion in this group similar to that of free-breathing patients (group D). Conclusions: 4D-CT scans revealed significant liver motion control via abdominal compression of the subxiphoid area; however, this control of liver motion was not observed with compression of the caudal umbilicus. The authors, therefore, recommend compression of the subxiphoid area in patients undergoing external radiotherapy for intrahepatic carcinoma.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-I-58: Image Quality Comparisons of Different Motion Magnitudes and TR Values in MR-PET

Purpose: The aim of this work is to evaluate the accuracy and sensitivity of a respiratory-triggered MR-PET protocol in detecting four different sized lesions at two different magnitudes of motion, with two different TR values, using a novel PET-MR-CT compatible respiratory motion phantom. Methods: The eight-compartment torso phantom was setup adjacent to the motion stage, which moved four spherical compartments (28, 22, 17, 10 mm diameter) in two separate (1 and 2 cm) linear motion profiles, simulating a 3.5 second respiratory cycle. Scans were acquired on a 3T MR-PET system (Biograph mMR; Siemens Medical Solutions, Germany). MR measurements were taken with: 1) Respiratory-triggered T2-weighted turbo spin echo (BLADE) sequence in coronal orientation, and 2) Real-time balanced steady-state gradient echo sequence (TrueFISP) in coronal and sagittal planes. PET was acquired simultaneously with MR. Sphere geometries and motion profiles were measured and compared with ground truths for T2 BLADE-TSE acquisitions and real time TrueFISP images. PET quantification and geometry measurements were taken using standardized uptake values, voxel intensity plots and were compared with known values, and examined alongside MR-based attenuation maps. Contrast and signal-to-noise ratios were also compared for each of the acquisitions as functions of motion range and TR. Results: Comparison of lesion diameters indicate the respiratory triggered T2 BLADE-TSE was able to maintain geometry within −2 mm for 1 cm motion for both TR values, and within −3.1 mm for TR = 2000 ms at 2 cm motion. Sphere measurements in respiratory triggered PET images were accurate within +/− 5 mm for both ranges of motion for 28, 22, and 17 mm diameter spheres. Conclusion: Hybrid MR-PET systems show promise in imaging lung cancer in non-compliant patients, with their ability to acquire both modalities simultaneously. However, MR-based attenuation maps are still susceptible to motion derived artifacts and pose the potential to affect PET accuracy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-G-JeP1-07: Development of a Programmable Motion Testbed for the Validation of Ultrasound Tracking Algorithms

Purpose: To develop an advanced testbed that combines a 3D motion stage and ultrasound phantom to optimize and validate 2D and 3D tracking algorithms for real-time motion management during radiation therapy. Methods: A Siemens S2000 Ultrasound scanner utilizing a 9L4 transducer was coupled with the Washington University 4D Phantom to simulate patient motion. The transducer was securely fastened to the 3D stage and positioned to image three cylinders of varying contrast in a Gammex 404GS LE phantom. The transducer was placed within a water bath above the phantom in order to maintain sufficient coupling for the entire range of simulated motion. A programmed motion sequence was used to move the transducer during image acquisition and a cine video was acquired for one minute to allow for long sequence tracking. Images were analyzed using a normalized cross-correlation block matching tracking algorithm and compared to the known motion of the transducer relative to the phantom. Results: The setup produced stable ultrasound motion traces consistent with those programmed into the 3D motion stage. The acquired ultrasound images showed minimal artifacts and an image quality that was more than suitable for tracking algorithm verification. Comparisons of a block matching tracking algorithm with the known motion trace for the three features resulted in an average tracking error of 0.59 mm. Conclusion: The high accuracy and programmability of the 4D phantom allows for the acquisition of ultrasound motion sequences that are highly customizable; allowing for focused analysis of some common pitfalls of tracking algorithms such as partial feature occlusion or feature disappearance, among others. The design can easily be modified to adapt to any probe such that the process can be extended to 3D acquisition. Further development of an anatomy specific phantom better resembling true anatomical landmarks could lead to an even more robust validation. This work is partially funded by NIH grant R01CA190298.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TH-CD-207A-12: Impacts of Inter- and Intra-Fractional Organ Motion for High-Risk Prostate Cancer Stereotactic Body Radiation Therapy

Purpose: We are conducting a clinical trial on stereotactic body radiation therapy (SBRT) for high-risk prostate cancer. Doses to three targets, prostate, intra-prostatic lesion, and pelvic lymph node (PLN) region, are escalated to three different levels via simultaneous integrated boost technique. Inter-/intra-fractional organ motions deteriorate planned dose distribution. This study aims at developing a dose reconstruction system to comprehensively understand the impacts of organ motion in our clinical trial. Methods: A 4D dose reconstruction system has been developed for this study. Using a GPU-based Monte-Carlo dose engine and delivery log file, the system is able to reconstruct dose on static or dynamic anatomy. For prostate and intra-prostatic targets, intra-fractional motion is the main concern. Motion trajectory acquired from Calypso in previously treated SBRT patients were used to perform 4D dose reconstructions. For pelvic target, inter-fractional motion is one concern. Eight patients, each with four cone beam CTs, were used to derive fractional motion. The delivered dose was reconstructed on the deformed anatomy. Dosimetric parameters for delivered dose distributions of the three targets were extracted and compared with planned levels. Results: For prostate intra-fractional motion, the mean 3D motion amplitude during beam delivery ranged from 1.5mm to 5.0mm and the average among all patients was 2.61mm. Inter-fractional motion for the PLN target was more significant. The average amplitude among patients was 4mm with the largest amplitude up to 9.6mm. The D95% deviation from planned level for prostate PTVs and GTVs are on average less than<0.1% and this deviation for intra-prostatic lesion PTVs and GTVs were more prominent. The dose at PLN was significantly affected with D{sub 95}% reduced by up to 44%. Conclusion: Intra-/inter-fractional organ motion is a concern for high-risk prostate SBRT, particularly for the PLN target. Our dose reconstruction approach can also serve as the basis to guide treatment adaptation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Central and Eastern North America Ground-Motion Characterization (NGA-East)

This document is the final project report of the Next Generation Attenuation for Central and Eastern North America (CENA) project (NGA-East). The NGA-East objective was to develop a new ground-motion characterization (GMC) model for the CENA region. The GMC model consists of a set of new ground-motion models (GMMs) for median and standard deviation of ground motions and their associated weights to be used with logic-trees in probabilistic seismic hazard analyses (PSHA). NGA-East is a large multidisciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER), at the University of California. The project has two components: (1) a set of scientific research tasks, and (2) a model-building component following the framework of the “Seismic Senior Hazard Analysis Committee (SSHAC) Level 3” (Budnitz et al. 1997; NRC 2012). Component (2) is built on the scientific results of component (1) of the NGA-East project. This report documents the tasks under component (2) of the project. Under component (1) of NGA-East, several scientific issues were addressed, including: (a) development of a new database of ground motion data recorded in CENA; (b) development of a regionalized ground-motion map for CENA, (c) definition of the reference site condition; (d) simulations of ground motions based on different methodologies; and (e) development of numerous GMMs for CENA. The scientific tasks of NGA-East were all documented as a series of PEER reports. The scope of component (2) of NGA-East was to develop the complete GMC. This component was designed as a SSHAC Level 3 study with the goal of capturing the ground motions’ center, body, and range of the technically defensible interpretations in light of the available data and models. The SSHAC process involves four key tasks: evaluation, integration, formal review by the Participatory Peer Review Panel (PPRP), and documentation (this report). Key tasks documented in this report include review and evaluation of the empirical groundmotion database, the regionalization of ground motions, and screening sets of candidate GMMs. These are followed by the development of new median and standard deviation GMMs, the development of new analyses tools for quantifying the epistemic uncertainty in ground motions, and the documentation of implementation guidelines of the complete GMC for PSHA computations. Appendices include further documentation of the relevant SSHAC process and additional supporting technical documentation of numerous sensitivity analyses results. The PEER reports documenting component (1) of NGA-East are also considered “attachments” to the current report and are all available online on the PEER website (https://peer.berkeley.edu/). The final NGA-East GMC model includes a set of 17 GMMs defined for 24 ground-motion intensity measures, applicable to CENA in the moment magnitude range of 4.0 to 8.2 and covering distances up to 1500 km. Standard deviation models are also provided for site-specific analysis (single-station standard deviation) and for general PSHA applications (ergodic standard deviation). Adjustment factors are provided for consideration of source-depth effects and hanging-wall effects, as well as for hazard computations at sites in the Gulf Coast region.

58 GEOSCIENCES↗
NASA NTRS1994

Assessment of Psychophysiological Responses During Motion Sickness Testing

The purpose of this investigation is to evaluate a methodology designed to accurately trace the temporal progression of motion sickness and space motion sickness symptoms. With this method, subjects continuously monitor their own motion sickness symptoms during exposure to a provocative stimulus as symptoms occur, in contrast to previous methods during which subjects report symptoms verbally at discrete time intervals. This method not only is comparable to previous methods in the type of symptoms that subjects report, but subjects report symptoms more frequently. Frequent reporting of motion sickness symptoms allows researchers to detail the waxing and waning of motion sickness symptoms for each individual. Previous research has shown that physiological responses to motion sickness stimuli are characterized by unique individual differences in response patterns. By improving our assessment of motion sickness symptoms with continuous monitoring of symptoms, the relationship between specific physiological responses and sickness levels can be more accurately determined for each individual. Results from this study show significant positive relationships between skin conductance levels and symptom levels for ten individuals; a significant positive relationship between temperature and symptom levels for 5 of 10 individuals; and both positive and negative relationships between respiration, heart rate, blood volume pulse and symptom levels. Continuous monitoring of motion sickness symptoms can be used to more accurately assess motion sickness to aid in the evaluation of countermeasures. In addition, recognition of the onset of symptoms that are strongly related to specific physiological responses could be used as cues to initiate procedures (e.g., Autogenic Feedback Training) to prevent the development of severe motion sickness symptoms.

Stoud, Cynthia S.↗
NASA NTRS2005

Quantifying Exact Motions Along Lineaments on Europa

Evaluating the precise motions along lineaments on the surface of Jupiter's icy moon, Europa, is a valuable tool for interpreting the development and history of lineaments of various morphologies. Such morphologies include strike-slip faults, dilational bands, ridges, and convergence zones. However, the exact mode of origin and kinematic behavior of these various lineaments are not obvious based on morphology alone. In fact, the apparent motions implied by displaced crosscut features can provide misleading indications of true motions along lineaments. Identifying the precise motions (combinations of sliding and opening/closing) is critical to the accurate characterization and interpretation of each of these lineament types. Lineaments of interest (i.e., those having displaced relatively older features in some manner) are identified on Galileo spacecraft images and measurements are made of the total offset, the separation, and relative orientations of crosscut features with respect to the lineament of interest. Specifically, by using these measured quantities and a series of trigonometric equations, the precise motions (i.e., dilation, convergence, strike-slip, or a combination of strike-slip and dilation or convergence) can be determined. These measurements are, however, limited by the resolution of the available images. This study focuses on motion analysis techniques for Europan lineaments and the precise characterization of fault-orthogonal and/or strike-slip motion along lineaments of varying morphologies. We highlight potential pitfalls of cursory analyses of motion indicators. For example, lineaments with obvious lateral offsets have typically been identified simply as strike-slip faults. This assumption may actually be incorrect, as fault-orthogonal motions may contribute to apparent lateral displacements (offsets or separations). Also, variability in the amount of fault motion along the trace length should theoretically be identifiable using the outlined technique. Strike-slip faults on Europa have conventionally been presumed to have a constant slip magnitude along their lengths; however, we posit that variable distributions of slip may be common, as is typical along terrestrial strike-slip faults.

Vetter, J. C.↗
NASA NTRS2010

Human Perception of Ambiguous Inertial Motion Cues

Human daily activities on Earth involve motions that elicit both tilt and translation components of the head (i.e. gazing and locomotion). With otolith cues alone, tilt and translation can be ambiguous since both motions can potentially displace the otolithic membrane by the same magnitude and direction. Transitions between gravity environments (i.e. Earth, microgravity and lunar) have demonstrated to alter the functions of the vestibular system and exacerbate the ambiguity between tilt and translational motion cues. Symptoms of motion sickness and spatial disorientation can impair human performances during critical mission phases. Specifically, Space Shuttle landing records show that particular cases of tilt-translation illusions have impaired the performance of seasoned commanders. This sensorimotor condition is one of many operational risks that may have dire implications on future human space exploration missions. The neural strategy with which the human central nervous system distinguishes ambiguous inertial motion cues remains the subject of intense research. A prevailing theory in the neuroscience field proposes that the human brain is able to formulate a neural internal model of ambiguous motion cues such that tilt and translation components can be perceptually decomposed in order to elicit the appropriate bodily response. The present work uses this theory, known as the GIF resolution hypothesis, as the framework for experimental hypothesis. Specifically, two novel motion paradigms are employed to validate the neural capacity of ambiguous inertial motion decomposition in ground-based human subjects. The experimental setup involves the Tilt-Translation Sled at Neuroscience Laboratory of NASA JSC. This two degree-of-freedom motion system is able to tilt subjects in the pitch plane and translate the subject along the fore-aft axis. Perception data will be gathered through subject verbal reports. Preliminary analysis of perceptual data does not indicate that the GIF resolution hypothesis is completely valid for non-rotational periodic motions. Additionally, human perception of translation is impaired without visual or spatial reference. The performance of ground-base subjects in estimating tilt after brief training is comparable with that of crewmembers without training.

Zhang, Guan-Lu↗
DOE OSTI2010

Prostate Intrafraction Motion Assessed by Simultaneous kV Fluoroscopy at MV Delivery II: Adaptive Strategies

Purpose: To investigate potential benefits of adaptive strategies for managing prostate intrafractional uncertainties when interfraction motion is corrected online. Methods and Materials: Prostate intrafraction motion was measured using kV fluoroscopy during MV delivery for 571 fractions from 30 hypofractionated radiotherapy patients. We evaluated trending over treatment course using analysis of variance statistics, and we evaluated the ability to correct patient-specific systematic error and apply patient-specific statistical margins after 2 to 15 fractions to compensate 90% of motion. We also evaluated the ability to classify patients into small- and large-motion subgroups based on the first 2 to 20 fractions using discriminant analysis. Results: No time trend was observed over treatment course, and intrafraction motion was patient specific (p < 0.0001). Systematic error in the first week correlated well with that in subsequent weeks, with correlation coefficients of 0.53, 0.50, and 0.41 in right-left (RL), anterior-posterior (AP), and superior-inferior (SI), respectively. After 5 fractions, the adaptive strategy resulted in average margin reductions of 0.3, 0.7, and 0.7 mm in RL, AP, and SI, respectively, with margins ranging from 1 to 3.2 mm in RL, 2 to 7.0 mm in AP, and 2 to 6.6 mm in SI. By contrast, population margins to include the same percentage of motion were 1.7, 4.0, and 4.1 mm. After 2 and 5 fractions, patients were classified into small- and large-motion groups with {approx}77% and {approx}83% accuracy. Conclusions: Adaptive strategies are feasible and beneficial for intrafraction motion management in prostate cancer online image guidance. Patients may be classified into large- and small-motion groups in early fractions using discriminant analysis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

Relationship Between Diseased Lung Tissues on Computed Tomography and Motion of Fiducial Marker Near Lung Cancer

Purpose: For lung cancer patients with poor pulmonary function because of emphysema or fibrosis, it is important to predict the amplitude of internal tumor motion to minimize the irradiation of the functioning lung tissue before undergoing stereotactic body radiotherapy. Methods and Materials: Two board-certified diagnostic radiologists independently assessed the degree of pulmonary emphysema and fibrosis on computed tomography scans in 71 patients with peripheral lung tumors before real-time tumor-tracking radiotherapy. The relationships between the computed tomography findings of the lung parenchyma and the motion of the fiducial marker near the lung tumor were investigated. Of the 71 patients, 30 had normal pulmonary function, and 29 had obstructive pulmonary dysfunction (forced expiratory volume in 1 s/forced vital capacity ratio of <70%), 6 patients had constrictive dysfunction (percentage of vital capacity <80%), and 16 had mixed dysfunction. Results: The upper region was associated with smaller tumor motion, as expected (p = .0004), and the presence of fibrosis (p = .088) and pleural tumor contact (p = .086) were weakly associated with tumor motion. The presence of fibrotic changes in the lung tissue was associated with smaller tumor motion in the upper region (p <.05) but not in the lower region. The findings of emphysema and pulmonary function tests were not associated with tumor motion. Conclusion: Tumors in the upper lung region with fibrotic changes have smaller motion than those in the upper region of the lungs without fibrotic changes. The tumor motion in the lower lung region was not significantly different between patients with and without lung fibrosis. Emphysema was not associated with the amplitude of tumor motion.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

Intrafractional Target Motions and Uncertainties of Treatment Setup Reference Systems in Accelerated Partial Breast Irradiation

Purpose: This study investigated the magnitude of intrafractional motion and level of accuracy of various setup strategies in accelerated partial breast irradiation (APBI) using three-dimensional conformal external beam radiotherapy. Methods and Materials: At lumpectomy, gold fiducial markers were strategically sutured to the surrounding walls of the cavity. Weekly fluoroscopy imaging was conducted at treatment to investigate the respiration-induced target motions. Daily pre- and post-RT kV imaging was performed, and images were matched to digitally reconstructed radiographs based on bony anatomy and fiducial markers, respectively, to determine the intrafractional motion magnitudes over the course of treatment. The positioning differences of the laser tattoo- and the bony anatomy-based setups compared with those of the marker-based setup (benchmark) were also determined. The study included 21 patients. Results: Although lung exhibited significant motion, the average marker motion amplitude on the fluoroscopic image was about 1 mm. Over a typical treatment time period, average intrafractional motion magnitude was 4.2 mm and 2.6 mm based on the marker and bony anatomy matching, respectively. The bony anatomy- and laser tattoo-based interfractional setup errors, with respect to the fiducial marker-based setup, were 7.1 and 9.0 mm, respectively. Conclusions: Respiration has limited effects on the target motion during APBI. Bony anatomy-based treatment setup improves the accuracy relative to that of the laser tattoo-based setup approach. Since fiducial markers are sutured directly to the surgical cavity, the marker-based approach can further improve the interfractional setup accuracy. On average, a seroma cavity exhibits intrafractional motion of more than 4 mm, a magnitude that is larger than that which is otherwise derived based on bony anatomy matching. A seroma-specific marker-based approach has the potential to improve treatment accuracy by taking the true inter- and intrafractional motions into consideration.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Quasars with large proper motions: A selection from the LQAC-5 catalogue combined with Gaia EDR3: Focusing on astrometric and photometric properties

Thanks to the cross-identification between the Gaia EDR3 (E-Data Release 3) catalogue and the quasars’ compiled catalogue LQAC-5 (Large Quasar Astrometric Catalogue-5), accurate astrometric parameters as well as photometric measurements were available for a set of 416 113 quasars. After analysing the astrometric and photometric properties of these quasars, we concentrate our study on objects characterized by significant proper motion, which contradicts the postulate that they are fixed in the celestial sphere. We derived statistical properties of the positions, parallaxes, and proper motions of the quasars cross-matched with Gaia EDR3. We carried out a specific investigation of quasars with a proper motion larger than 10 mas yr -1 , and used colour-colour diagrams in mid-infrared to discriminate these quasars from stellar contamination. We discuss, in detail, a few cases where the abnormal proper motion could be caused by misidentifications. We note that 43% of LQAC-5 quasars were not detected by Gaia EDR3, mainly because of the cut-off magnitude at G = 21. The comparison between r(G) (Gaia) and r (SDSS) shows a normal distribution. The normalized distributions of parallaxes and proper motions are identical to that of the Gaia CRF2, as well as the distribution of the G BP -G RP colour index. We have identified 937 LQAC-5 objects (0.27% of the sample) with Gaia EDR3 proper motion which is significant at the 5σ level. We have clearly shown that below z = 0.35, the integrated magnitude G(r) obtained from SDSS spectra is smaller than G (Gaia), leading to the statement that the quasars are generally resolved under this threshold, which should lead to a bad determination of proper motion. Moreover, to discriminate quasars from stellar contamination, we have plotted them in a mid-infrared colour–colour diagram. Finally, we have made a final selection of 41 objects with μ > 10 mas yr -1 , satisfying drastic constraints, which makes them potential candidates for considering their proper motion as real. In this paper we carried out a complete analysis of the quasars of the LQAC-5 which were cross-identified with Gaia EDR3 ; this serves as an alternative and complementary study with respect to Gaia CRF2, involving a different population of quasars. We selected a set of 41 quasars with a proper motion exceeding 10 mas yr -1 , which can be considered as very high for objects which are a priori fixed in the celestial sphere.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Atomic motion from the mean square displacement in a monatomic liquid

V-T theory is constructed in the many-body Hamiltonian formulation, and is being developed as a novel approach to liquid dynamics theory. In this theory the liquid atomic motion consists of two contributions, normal mode vibrations in a single representative potential energy valley, and transits, which carry the system across boundaries between valleys. The mean square displacement time correlation function (the MSD) is a direct measure of the atomic motion, and our goal is to determine if the V-T formalism can produce a physically sensible account of this motion. We employ molecular dynamics (MD) data for a system representing liquid Na, and find the motion evolves in three successive time intervals: on the first 'vibrational' interval, the vibrational motion alone gives a highly accurate account of the MD data; on the second 'crossover' interval, the vibrational MSD saturates to a constant while the transit motion builds up from zero; on the third 'random walk' interval, the transit motion produces a purely diffusive random walk of the vibrational equilibrium positions. Furthermore, this motional evolution agrees with, and adds refinement to, the MSD atomic motion as described by current liquid dynamics theories.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

TREAT Fuel Motion Summary Report. SETH A-E Experiments

In support of the Accident Tolerant Fuels program, experiment devices are being developed to enable transient testing of pressurized water reactor (PWR) type fuel specimens. In fiscal year 2019 several fueled tests were conducted in the Transient Reactor Test Facility (TREAT) using the Separate Effects Test Holder (SETH). Five different SETH capsules (SETH A-E) were assembled, each holding a 10-pellet rodlet with 4.9% enriched, commercially-produced fresh UO2 pellets in zirconium alloy cladding with pellet dimensions having typical PWR radial dimensions and a total pellet stack length measuring 10.16 cm. The rodlet’s length allows the specimen to be axially positioned in the center of the core with minimal flux variation over the height of the rodlet. The fuel motion monitoring system (FMMS) is located on the north side of the TREAT reactor. Having direct line-of-sight of the core enables the FMMS to collect spatially-resolved data for fast neutrons generated due to fission occurring in experiment specimens. The FMMS contains 360 channels that make up a 10 (horizontal) by 36 (vertical) array of viewing slots; for the SETH A-E test series 96 proton-recoil scintillator (PRS) detectors were installed in the system. The fast neutrons are detected in the PRS detectors from light produced by the recoil of protons interacting with ZnS(Ag) grains in each detector's scintillator button. This report focuses on the FMMS data captured in the SETH A-E experiments, with multiple transients varying in reactivity addition and length. The first three experiments had a total reactor energy of 101 MJ each and were critical in understanding the FMMS field of view, lead shielding, and other TREAT data acquisition systems. SETH-B2 and C had a reactivity addition of almost double the previous transients and served as a demonstration of the detector array behavior under increased reactor energy. The final two SETH experiments (D and E) were aimed at reaching cladding melting temperatures with a reactor energy over 500 MJ for each test. In preparation for the higher energy transients, the FMMS lead shielding was reduced to 0.5 inches from the 6 inches used in SETH A-C. This was expected to saturate the detectors at the peak of the transient in exchange for higher sensitivity at lower energies after the peak, when the motion was expected. SETH-D was clipped at approximately 3 seconds, which was too early for the FMMS to capture any rodlet motion. SETH-E had the same reactivity addition as SETH-D but the transient time was extended to 18 seconds. The FMMS captured the downward motion of the rodlet in SETH-E as the count rate significantly changed for the detectors viewing the specimen. Snapshots taken throughout the transient helped identify the approximate time at which the motion initiated. Further analysis of the individual detector data captured on a per-millisecond time basis resulted in a determination that the approximate time for the onset of the downward motion was 2.84 ± 0.02 seconds. Neutron radiographs confirmed that downward motion occurred for SETH-D and SETH-E. Motion in SETH-D could also have been captured by the FMMS if the transient time had been longer for SETH-D. Ultimately, these final two tests served to demonstrate the FMMS's ability to track fuel motion during transient experiments at TREAT.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

Joint Survey Processing. II. Stellar Proper Motions in the COSMOS Field from Hubble Space Telescope ACS and Subaru Telescope HSC Observations

We analyze stellar proper motions in the COSMOS field to assess the presence of bulk motions. At bright magnitudes (G-band 18.5–20.76 AB), we use the proper motions of 1010 stars in the Gaia DR2 catalog. At the faint end, we compute proper motions of 11,519 pointlike objects at i-band magnitudes 19–25 AB using Hubble ACS and Subaru HSC data, which span two epochs about 11 yr apart. In order to measure these proper motions with unprecedented accuracy at faint magnitudes, we developed a foundational set of astrometric tools that will be required for joint survey processing of data from the next generation of optical/infrared surveys. The astrometric grids of Hubble ACS and Subaru HSC mosaics were corrected at the catalog level using proper motion–propagated and parallax-corrected Gaia DR2 sources. These astrometric corrections were verified using compact extragalactic sources. Upon comparison of our measured proper motions with Gaia DR2, we estimate the uncertainties in our measurements to be ~2–3 mas yr –1 axis –1 , down to 25.5 AB mag. We correct proper motions for the mean motion of the Sun, and we find that late-type main-sequence stars predominantly in the thin disk in the COSMOS field have space velocities mainly toward the Galactic center. We detect candidate high-velocity (≥220 km s –1 ) stars, six of them at ~0.4–6 kpc, from the Gaia sample, and five of them at ~20 kpc, from the faint star HSC and ACS sample. The sources from the faint star sample may be candidate halo members of the Sangarius stream.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

Integration of speed signals in the direction of motion

Speed discrimination tasks were used to examine the spatial and temporal characteristics of the integration mechanism involved when signals are extended in the direction of motion. We varied the aspect ratio of a signal patch whose speed differed from the background, while holding the area of the signal patch constant, so that the signal patch could be either extended in the direction of motion or extended orthogonal to the direction of motion. Speed discrimination thresholds decreased dramatically as the signal patch was extended in the direction of motion. The spatial and temporal integration regions were larger than would be expected if the integration mechanism were a low-level motion detector. The mechanism was tuned for direction of motion. The data are discussed with reference to two alternative integration mechanisms: a low-level detector that is elongated in the direction of motion and a higher level integration mechanism characterized by cooperative or facilitatory interactions between low-level detectors tuned to the same direction of motion. Our data are consistent with a second-level, direction-specific process that integrates the responses of low-level motion detectors.

NASA Discipline Space Human Factors↗
NASA NTRS2000

Autogenic-feedback training exercise is superior to promethazine for control of motion sickness symptoms

Motion sickness symptoms affect approximately 50% of the crew during space travel and are commonly treated with intramuscular injections of promethazine. The purpose of this paper is to compare the effectiveness of three treatments for motion sickness: intramuscular injections (i.m.) of promethazine, a physiological training method (autogenic-feedback training exercise [AFTE]), and a no-treatment control. An earlier study tested the effects of promethazine on cognitive and psychomotor performance and motion sickness tolerance in a rotating chair. For the present paper, motion sickness tolerance, symptom reports, and physiological responses of these subjects were compared to matched subjects selected from an existing database who received either AFTE or no treatment. Three groups of 11 men, between the ages of 33 and 40 years, were matched on the number of rotations tolerated during their initial rotating-chair motion sickness test. The motion sickness test procedures and the 7-day interval between tests were the same for all subjects. The drug group was tested under four treatment conditions: baseline (no injections), a 25 mg dose of promethazine, a 50 mg dose of promethazine, and a placebo of sterile saline. AFTE subjects were given four 30-minute AFTE sessions before their second, third, and fourth motion sickness tests (6 hours total). The no-treatment control subjects were only given the four rotating-chair tests. Motion sickness tolerance was significantly increased after 4 hours of AFTE when compared to either 25 mg (p < 0.00003) or 50 mg (p < 0.00001) of promethazine. The control and promethazine groups did not differ. AFTE subjects reported fewer or no symptoms at higher rotational velocities than subjects in the control or promethazine groups. The primary physiological effect of promethazine was an inhibition of skin conductance level. The AFTE group showed significantly less heart rate and skin conductance variability during motion sickness tests administered after training.

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