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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A re-examination of the mechanism of whiting events: A new role for diatoms in Fayetteville Green Lake (New York, USA)

Whiting events—the episodic precipitation of fine-grained suspended calcium carbonates in the water column—have been documented across a variety of marine and lacustrine environments. Whitings likely are a major source of carbonate muds, a constituent of limestones, and important archives for geochemical proxies of Earth history. While several biological and physical mechanisms have been proposed to explain the onset of these precipitation events, no consensus has been reached thus far. Fayetteville Green Lake (New York, USA) is a meromictic lake that experiences annual whitings. Materials suspended in the water column collected through the whiting season were characterized using scanning electron microscopy and scanning transmission X-ray microscopy. Whitings in Fayetteville Green Lake are initiated in the spring within the top few meters of the water column, by precipitation of fine amorphous calcium carbonate (ACC) phases nucleating on microbial cells, as well as on abundant extracellular polymeric substances (EPS) frequently associated with centric diatoms. Whiting particles found in the summer consist of 5–7 μm calcite grains forming aggregates with diatoms and EPS. Simple calculations demonstrate that calcite particles continuously grow over several days, then sink quickly through the water column. In the late summer, partial calcium carbonate dissolution is observed deeper in the water column. Settling whiting particles, however, reach the bottom of the lake, where they form a major constituent of the sediment, along with diatom frustules. The role of diatoms and associated EPS acting as nucleation surfaces for calcium carbonates is described for the first time here as a potential mechanism participating in whitings at Fayetteville Green Lake. This mechanism may have been largely overlooked in other whiting events in modern and ancient environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Genomics of turions from the Greater Duckweed reveal its pathways for dormancy and re‐emergence strategy

Summary Over 15 families of aquatic plants are known to use a strategy of developmental switching upon environmental stress to produce dormant propagules called turions. However, few molecular details for turion biology have been elucidated due to the difficulties in isolating high‐quality nucleic acids from this tissue. We successfully developed a new protocol to isolate high‐quality transcripts and carried out RNA‐seq analysis of mature turions from the Greater Duckweed Spirodela polyrhiza . Comparison of turion transcriptomes to that of fronds, the actively growing leaf‐like tissue, were carried out. Bioinformatic analysis of high confidence, differentially expressed transcripts between frond and mature turion tissues revealed major pathways related to stress tolerance, starch and lipid metabolism, and dormancy that are mobilized to reprogram frond meristems for turion differentiation. We identified the key genes that are likely to drive starch and lipid accumulation during turion formation, as well as those in pathways for starch and lipid utilization upon turion germination. Comparison of genome‐wide cytosine methylation levels also revealed evidence for epigenetic changes in the formation of turion tissues. Similarities between turions and seeds provide evidence that key regulators for seed maturation and germination were retooled for their function in turion biology.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Re‐evaluating the energy balance of the many routes of carbon flow through and from photorespiration

Photorespiration is an essential process related to photosynthesis that is initiated following the oxygenation reaction catalyzed by rubisco, the initial enzyme of the Calvin–Benson–Bassham cycle. This reaction produces an inhibitory intermediate that is recycled back into the Calvin–Benson–Bassham cycle by photorespiration which requires the use of energy and the release of a portion of the carbon as CO 2 . The energy use and CO 2 release of canonical photorespiration form a foundation for biochemical models used to describe and predict leaf carbon exchange and energy use (ATP and NAPDH). The ATP and NADPH demand of canonical photorespiration is thought to be different than that of the Calvin–Benson–Bassham cycle, requiring increased flexibility in the ratio of ATP and NADPH from the light reactions. Photorespiration requires many reactions across the chloroplasts, mitochondria and peroxisomes and involves many intermediates. Growing evidence indicates that these intermediates do not all stay in photorespiration as typically assumed and instead feed into other aspects of metabolism and leave as glycine, serine, and methylene‐THF. Here we discuss how alternative flux through and from canonical photorespiration alters the ATP and NADPH requirements of metabolism following rubisco oxygenation using additional derivations of biochemical models of leaf photosynthesis and energetics. Using these new derivations, we determine that the ATP and NADPH demands of photorespiration are highly sensitive to alternative flux in ways that fundamentally changes how photorespiration contributes to the ratio of total ATP and NADPH demand. Specifically, alternative flows of carbon through photorespiration could reduce ATP and NADPH demand ratio to values below what is produced from linear electron transport.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

SU-F-T-214: Re-Thinking the Useful Clinical Beam Energy in Proton Therapy: An Opportunity for Cost Reduction

Purpose: We conducted a retrospective study of the useful clinical proton beam energy based on the beam range data of patients treated over the last 10 years at Massachusetts General Hospital Proton Therapy Center. Methods: Treatment field information were collected for all patients treated over the last 10 years (2005–2015) in the two gantry treatment rooms at MGH. The beam ranges for these fields were retrieved and categorized per treatment site. The 10 prostate patients that required the highest beam range (lateral fields) were selected. For these patients, anterior oblique beams (30–40 degrees) were simulated in a planning system to obtain the required beam ranges including the margins for potential range uncertainties. Results: There were a total of 4033 patients, treated with combined total of 23603 fields. All treatment indications were considered with the exception of ocular tumors generally treated in a fixed beam room. For all non-prostate treatments (21811 fields), only 5 fields for 4 patients (1-pancreas, 1-lumbar chordoma, 2-spine mets) required beam range greater than 25 cm. There were 446 prostate patients (1792 fields), with the required beam range from 22.3 to 29.0 cm; 386 of them had at least one of their lateral beam range greater than 25 cm. For the 10 prostate patients with highest lateral beam ranges (26 to 29 cm), their treatment with anterior oblique beams would drop the beam ranges below 25 cm (17.3 to 18.5 cm). Conclusion: if prostate patients are treated with anterior fields only, the useful maximum beam range is reduced to 25 cm. Thus a proton therapy system with maximum beam energy of 196 MeV is sufficient to treat all tumors sites with very rare exceptions (<0.1%). Designing such PT system would reduce the cost of proton therapy for hospitals and patients and increase the accessibility to the treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-377: Monte Carlo Re-Evaluation of Volumetric-Modulated Arc Plans of Advanced Stage Nasopharygeal Cancers Optimized with Convolution-Superposition Algorithm

Background: Commercial treatment planning system Pinnacle3 (Philips, Fitchburg, WI, USA) employs a convolution-superposition algorithm for volumetric-modulated arc radiotherapy (VMAT) optimization and dose calculation. Study of Monte Carlo (MC) dose recalculation of VMAT plans for advanced-stage nasopharyngeal cancers (NPC) is currently limited. Methods: Twenty-nine VMAT prescribed 70Gy, 60Gy, and 54Gy to the planning target volumes (PTVs) were included. These clinical plans achieved with a CS dose engine on Pinnacle3 v9.0 were recalculated by the Monaco TPS v5.0 (Elekta, Maryland Heights, MO, USA) with a XVMC-based MC dose engine. The MC virtual source model was built using the same measurement beam dataset as for the Pinnacle beam model. All MC recalculation were based on absorbed dose to medium in medium (Dm,m). Differences in dose constraint parameters per our institution protocol (Supplementary Table 1) were analyzed. Results: Only differences in maximum dose to left brachial plexus, left temporal lobe and PTV54Gy were found to be statistically insignificant (p> 0.05). Dosimetric differences of other tumor targets and normal organs are found in supplementary Table 1. Generally, doses outside the PTV in the normal organs are lower with MC than with CS. This is also true in the PTV54-70Gy doses but higher dose in the nasal cavity near the bone interfaces is consistently predicted by MC, possibly due to the increased backscattering of short-range scattered photons and the secondary electrons that is not properly modeled by the CS. The straight shoulders of the PTV dose volume histograms (DVH) initially resulted from the CS optimization are merely preserved after MC recalculation. Conclusion: Significant dosimetric differences in VMAT NPC plans were observed between CS and MC calculations. Adjustments of the planning dose constraints to incorporate the physics differences from conventional CS algorithm should be made when VMAT optimization is carried out directly with MC dose engine.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-626: Intracranial SRS Re-Treatment Without Acquisition of New CT Images

Purpose: Linear accelerator based stereotactic radiosurgery (SRS) for multiple intracranial lesions with frequent surveillance is becoming a popular treatment option. This strategy leads to retreatment with SRS as new lesions arise. Currently, each course of treatment uses magnetic resonance (MR) and computed tomography (CT) images for treatment planning. We propose that new MR images, with course 1 CT images, may be used for future treatment plans with negligible loss of dosimetric accuracy. Methods: Ten patients that received multiple courses of SRS were retrospectively reviewed. The treatment plans and contours from non-initial courses were copied to the initial CTs and recalculated. Doses metrics for the plans calculated on the initial CTs and later CTs were compared. All CT scans were acquired on a Philips CT scanner with a 600 mm field of view and 1 mm slice thickness (Philips Healthcare, Andover, MA). All targets were planned to 20 Gy and calculated in Eclipse V. 13.6 (Varian, Palo Alto, CA) using analytic anisotropic algorithm with 1 mm calculation grid. Results: Sixteen lesions were evaluated. The mean time between courses was 250 +/− 215 days (range 103–979). The mean target volume was 2.0 +/− 2.9 cc (range 0.1–10.1). The average difference in mean target dose between the two calculations was 0.2 +/− 0.3 Gy (range 0.0 – 1.0). The mean conformity index (CI) was 1.28 +/− 0.14 (range 1.07 – 1.82). The average difference in CI was 0.03 +/− 0.16 (range 0.00 – 0.44). Targets volumes < 0.5 cc showed the largest changes in both metrics. Conclusion: Continued treatment based on initial CT images is feasible. Dose calculation on the initial CT for future treatments provides reasonable dosimetric accuracy. Changes in dose metrics are largest for small volumes, and are likely dominated by partial volume effects in target definition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TH-AB-BRA-03: Backscatter Dose Factors Re-Evaluated for Inhomogeneities in the Presence of a 1.5 T Magnetic Field Using the GPUMCD Monte Carlo Algorithm

Purpose: To quantify the backscatter dose factors near the interfaces for clinically relevant high atomic number materials using GPUMCD for the Elekta MRI Linac. Methods: Backscatter dose factors (BSDF) were calculated as the ratio of the dose with and without the presence of the heterogeneity. The BSDF’s were calculated either in the absence or presence of an orthogonal 1.5 T magnetic field. Doses were scored in small voxels of side 1 mm in a water phantom with dimensions of 20×20×20 cm using GPUMCD (Elekta). The minimum uncertainty in dose calculations was kept to 0.5%. A slab of thickness 2 cm, representing the inhomogeneity, was placed inside the phantom with variable position from the surface of the phantom. The slab was filled with either bone, aluminum, titanium, stainless steel, or dental amalgam. The phantom was irradiated using particles sampled from a histogram which represented the true MRI Linac spectrum. Results: With the application of the 1.5 T magnetic field (B-On), all of the BSDF’s were reduced by at least 8% compared to the no magnetic field (B-Off) cases. For the B-Off case, the BSDF decreases exponentially with the upstream distance away from the interface. With B-On, the BSDF decreases exponentially for titanium, SS, and amalgam. However, it remains constant for Aluminum. In the case of bone, the BSDF increases up to a distance of 4 mm away from the interface in the presence of the magnetic field. Conclusion: The BSDF does not depend upon the thickness of the homogeneous material above the inhomogeneity for either the B-Off or B-On cases. For all the materials investigated, the BSDF is lower at the interface for the B-On case. The exponential fall-off of the BSDF away from the interface is not valid for all the materials when the magnetic field is turned ON. Funding support for this research was provided by Elekta.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Deletion of Re -citrate synthase allows for analysis of contributions of tricarboxylic acid cycle directionality to the growth of Heliomicrobium modesticaldum

ABSTRACT Heliomicrobium modesticaldum,a phototrophic member of the phylum Firmicutes and family Clostridiales, possesses most of the enzymes specific to the reductive tricarboxylic acid (rTCA) cycle, except for the key enzyme, ATP-citrate lyase. It is thought to utilize a split TCA cycle when growing on pyruvate as a carbon source, in which the oxidative TCA (oTCA) direction generates most of the 2-ketoglutarate, but some can be produced in the reductive direction. Although a typicalSi-citrate synthase gene is not found in the genome, it was suggested that gene HM1_2993, annotated as homocitrate synthase, actually encodesRe-citrate synthase, which would function as the initial enzyme of the oTCA cycle. We deleted this gene to test this hypothesis and, if true, see what effect severing access to the oTCA cycle would have on this organism. The endogenous CRISPR-Cas system was used to replace the open reading frame with a selectable marker. The deletion mutants could grow on pyruvate but were unable to grow phototrophically on acetate + CO 2 as carbon source. Growth on acetate could be rescued by the addition of different electron sources (formate or ascorbate), suggesting that the oTCA cycle is used to oxidize acetate to generate electrons required to drive the carboxylation of acetyl-CoA. The deletion mutants were capable of growing in acetate minimal media without additional organic supplements beyond formate, demonstrating that the rTCA cycle can be employed to support sufficient 2-ketoglutarate production in this organism, unlike citrate synthase mutants in several chemoheterotrophic organisms utilizing the oTCA cycle. IMPORTANCE Heliobacteria are a unique group of phototrophic bacteria that are obligate anaerobes and possess a rudimentary system to use light as a source of energy. They do not make oxygen or fix carbon dioxide. Here, we explore their fundamental carbon metabolism to understand the role and operation of the central TCA cycle. This work shows both the role and operation of this cycle under different growth modes and explains how these organisms can obtain electrons to drive their biosynthetic metabolism. This foundational knowledge will be crucial in the future when attempts are made to use this organism as a platform for oxygen-sensitive synthesis of compounds in an anaerobe that can use light as its energy source.

Biotechnology & Applied Microbiology↗
DOE OSTI2016

Magnetic noise as the cause of the spontaneous magnetization reversal of RE–TM–B permanent magnets

The relation between the macroscopic spontaneous magnetization reversal (magnetic viscosity) of (NdDySm)(FeCo)B alloys and the spectral characteristics of magnetic noise, which is caused by the random microscopic processes of thermally activated domain wall motion in a potential landscape with uniformly distributed potential barrier heights, is found.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Sodium Intercalation of Graphene Films on Re(101̄0)

It is shown that during low-temperature (300–500 K) intercalation of sodium atoms into thin multilayer graphene and graphite films on rhenium the first graphene layer plays the role of a trap to which atoms coming on the surface diffuse through a graphite film. The intercalation phase of the interlayer space in the graphite bulk is actively filled at a sodium atoms concentration under the first graphene layer close to the maximum possible (2 ± 0.5) × 10{sup 14} cm{sup –2}. This phase capacity is proportional to the graphite film thickness that can be varied in this work from one graphene layer to ~50 atomic layers. The diffusion energy E{sub d} of Na atoms through the graphite film was estimated to be E{sub d} ≈ 1.4 eV.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Cookie-Jar: An Adaptive Re-configurable Framework for Wireless Network Infrastructures

5G advancements like Massive Multiple Input Multiple Output (MIMO) bring high capacity and low latency, but also intensify interference challenges. Static and dynamic coordination techniques address this, often at the cost of increased power draw. We introduce Cookie-Jar (CJ), an interference coordination (IC) framework using reinforcement learning for multi-goal optimization. By dynamically adjusting network, power, and topology parameters based on real-time conditions, CJ improves Signal to Noise and Interference Ratio (SINR) while minimizing power consumption. Simulated 5G experiments showcase CJ's potential, achieving a 15% SINR improvement with near-identical power draw compared to existing methods.

Network↗
DOE OSTI2025

What to Support When You’re Compressing

Over the last nearly 20 years, lossy compression has become an essential aspect of HPC applications’ data pipelines, allowing them to overcome limitations in storage capacity and bandwidth and, in some cases, increase computational throughput and capacity. However, with the adoption of lossy compression comes the requirement to assess and control the impact lossy compression has on scientific outcomes. In this work, we take a major step forward in describing the state of practice and by characterizing workloads. We examine applications’ needs and compressors’ capabilities across 9 different supercomputing application domains. We present 24 takeaways that provide best practices for applications, operational impacts for facilities achieving compressed data, and gaps in application needs not addressed by production compressors that point towards opportunities for future compression research.

Error-Bounded Lossy Compression↗