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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Theoretically Informed Kinetics (ThInK): Establishing a modern C 0 -C 3 mechanism for combustion modeling

In contrast to the adage “Models are to be used, not believed”, combustion kinetics models have been intended to be predictive in nature. Theoretical chemical kinetics is now understood to provide a firm foundation for the reaction parameters, thereby facilitating predictive simulations of chemical reactivity, even in regimes that are poorly characterized by chemical kinetic and/or combustion experiments. In this study, we describe a theory-informed kinetics model (ThInK) for small molecule combustion chemistry (H 2 and C 1 – C 3 species) that is based on the prodigious use of theoretical predictions for reaction rate coefficients, thermochemistry, and transport parameters. The distinct features of this kinetics model, which was developed over the course of several decades, are illustrated through simulations of flame propagation and auto-ignition.

Energy transfer↗
DOE OSTI2017

AHR and CYP1A expression link historical contamination events to modern day developmental effects in the American alligator

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that initiates a transcriptional pathway responsible for the expression of CYP1A subfamily members, key to the metabolism of xenobiotic compounds. Toxic planar halogenated aromatic hydrocarbons, including dioxin and PCBs, are capable of activating the AHR, and while dioxin and PCB inputs into the environment have been dramatically curbed following strict regulatory efforts in the United States, they are still detected in the environment and exposures remain relevant today. Little is known regarding the effects that long-term chronic exposures to dioxin or dioxin-like compounds might have on the development and subsequent health of offspring from exposed individuals, nor is much known regarding AHR expression in reptilians. In this work, we characterize AHR and CYP1A gene expression in embryonic and juvenile specimen of a long-lived, apex predator, the American alligator (Alligator mississippiensis), and investigate variation in gene expression profiles in offspring collected from sites in the southeastern U.S. conveying differential exposures to environmental contaminants. Both age- and tissue-dependent patterning of AHR isoform expression was detected; receptor isoforms are highly expressed in liver, kidney, thyroid, and intestine. We then characterized two downstream transcriptional targets of the AHR, CYP1A1 and CYP1A2, and describe conserved elements of their genomic architecture. When comparisons across different sites were made, hepatic expression of CYP1A2, a direct target of the AHR, was elevated in embryos from a site associated with a dioxin point source and previously characterized PCB contamination. These effects were not persistent, as site-specific variation was absent in juveniles originating from field-collected eggs but reared under lab conditions. Our results illustrate the patterning of AHR gene expression in a long-lived environmental model species, and indicate a potential contemporary influence of historical contamination. This research presents a novel opportunity to link historical contamination events to contemporary effects on critical genetic pathways during embryonic development, and carries significant potential to inform our understanding of potential health effects in wildlife and humans.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2021

Production, fuel properties and combustion testing of an iso-olefins blendstock for modern vehicles

With the increasing pressure to decarbonize the transportation sector, exploring strategies that can reduce emissions from light-duty vehicles (LDV) has become critical. Bioblendstocks that allow for higher engine efficiency and fuel economy could complement vehicle electrification and help reach carbon neutrality by 2050. In this context, the potential of a mixture of iso-olefins as a bioblendstock was investigated for multimode boosted spark-ignition (SI)/advanced compression ignition (ACI) engine operation designed to achieve higher overall vehicle fuel economy. By establishing the relationship between the molecular structure of iso-olefins and research octane number (RON), octane sensitivity (S) (i.e., the difference between RON and motor octane number [MON]), and phi-sensitivity a dimethyl-hexenes rich olefins mixture (DMHROM) was identified as a preferred blendstock for SI/ACI combustion engines. Here, a pathway for DMHROM production from biomass-derived ethanol was developed and scaled up. More than 1 gallon of DMHROM blendstock was produced for fuel properties assessment including engine testing. Measurements in a Cooperative Fuel Research Engine showed that the DMHROM blendstock possesses a RON of 94 and S of 13.5, and blends synergistically. Rapid compression machine tests coupled with single-cylinder gasoline direct injection engine measurements demonstrated the 20 vol.% DMHROM blend has higher phi-sensitivity than an olefin-free gasoline base fuel and a typical California Reformulated Gasoline Blendstock for Oxygenate Blending (CARBOB) gasoline fuel. These results demonstrate the potential of DMHROM for improving gasoline fuel performance and quality for operation under ACI conditions. The effectiveness of the aftertreatment system in mitigating emissions was verified and showed that the pure DMHROM blendstock and 20 vol.% blend would not increase non-methane organic gases, NO x , and carbon monoxide (CO) emissions. The DMHROM blendstock was found to slightly decrease sooting tendency when added to a gasoline-base fuel (i.e., ~6% reduction at 20 vol.% blending level). Oxidation stability and lubricant compatibility were both confirmed for the 20 vol.% blend. Overall, these results demonstrate that dimethyl-hexenes have potential for improving engine efficiency and fuel economy while meeting emissions regulations and ASTM specifications for gasoline fuel.

09 BIOMASS FUELS↗
DOE OSTI2023

Chromium isotopes in an acidic fluvial system: Implications for modern and ancient Cr isotope records

Chromium is an important redox-active element, with significant Cr isotope fractionations driven by redox transformations in the natural environment and quantified through laboratory experiments. Recent work has demonstrated that non-redox-driven transformations can also produce small variations in Cr isotopes, but the role of these processes in controlling environmental Cr isotope variations remains unclear. The highly acidic but biologically diverse acid rock drainage system in Río Tinto, Spain (and affiliated rivers) provides a unique opportunity to examine how non-redox-related processes can substantially affect the isotopic composition of Cr in a natural system. Our results suggest that under conditions where Cr redox transformations are obviated, Cr cycling is largely controlled by formation of Fe-oxyhydroxides and Fe-hydroxysulfates, Cr adsorption, and Cr speciation, with little apparent Cr isotope fractionation between source materials, waters, and sediments. Moderate Cr isotope shifts, however, may be the result of non-redox processes, including adsorption to organic ligands and potentially biological uptake. These results add to a growing body of evidence for the importance of non-redox transformations in contributing to environmental Cr isotope variations, with implications for the use of chromium isotopes in studies of sedimentary Cr isotope records. In particular, this study is a validation of the potential for sulfide weathering in the Proterozoic to deliver relatively unfractionated Cr isotopes to the ocean, despite rising and sustained high oxygen levels.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

The Modern Role of Radiation Therapy in Treating Advanced-Stage Retinoblastoma: Long-Term Outcomes and Racial Differences

Purpose/Objective(s): To evaluate the effects of various patient characteristics and radiation therapy treatment variables on outcomes in advanced-stage retinoblastoma. Methods and Materials: This was a retrospective review of 41 eyes of 30 patients treated with external beam radiation therapy between June 1, 1992, and March 31, 2012, with a median follow-up time of 133 months (11 years). Outcome measures included overall survival, progression-free survival, local control, eye preservation rate, and toxicity. Results: Over 90% of the eyes were stage V. Definitive external beam radiation therapy (EBRT) was delivered in 43.9% of eyes, adjuvant EBRT in 22% of eyes, and second-line/salvage EBRT in 34.1% of eyes. A relative lens sparing (RLS) technique was used in 68.3% of eyes and modified lens sparing (MLS) in 24.4% of eyes. Three eyes were treated with other techniques. Doses ≥45 Gy were used in 68.3% of eyes. Chemotherapy was a component of treatment in 53.7% of eyes. The 10-year overall survival was 87.7%, progression-free survival was 80.5%, and local control was 87.8%. White patients had significantly better overall survival than did African-American patients in univariate analysis (hazard ratio 0.09; 95% confidence interval 0.01-0.84; P=.035). Toxicity was seen in 68.3% of eyes, including 24.3% with isolated acute dermatitis. Conclusions: External beam radiation therapy continues to be an effective treatment modality for advanced retinoblastoma, achieving excellent long-term local control and survival with low rates of treatment-related toxicity and secondary malignancy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Management of Nodular Lymphocyte Predominant Hodgkin Lymphoma in the Modern Era

Purpose: To analyze treatment outcomes for nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) at a single institution. Patients and Methods: Patients with newly diagnosed NLPHL between 1996 and 2013 were reviewed retrospectively. Patients treated before 1996 were excluded because the majority received extended field radiation therapy (RT) alone. Results: Fifty-five patients (22 ≤ 21 years old) were identified. The median follow-up time was 6.8 years. Among 37 patients with limited-stage (I-II) disease, treatments included involved field RT at a median dose of 36 Gy (n=9), rituximab monotherapy (n=9), observation (n=3), and response-adaptive therapy (n=16), in which the RT dose was reduced from 25.5 Gy to 15 Gy or was eliminated based on interim imaging after chemotherapy. The 5-year progression-free survival (PFS) was 76.4% (95% confidence interval [CI], 63.1-92.4). Nine patients experienced progression, including 5 receiving rituximab, 2 undergoing observation, and 2 receiving response-adaptive therapy. Rituximab was associated with an inferior PFS compared with RT alone (P=.02). The difference in PFS between response-adaptive therapy and RT alone was not statistically significant (P=.39). Among 18 patients with advanced-stage (III-IV) disease, treatments included chemotherapy alone (n=3), combined modality therapy (CMT) (n=2), response-adaptive therapy (n=2), rituximab (n=7), and observation (n=4). The 5-year PFS was 29.9% (CI, 13.3-67.4). Twelve patients experienced progression, including 1 receiving chemotherapy, 1 receiving CMT, 6 receiving rituximab, and 4 undergoing observation. There was no significant PFS difference between rituximab and non-rituximab therapies (P=.19) within the caveat of small sample sizes. In the entire cohort, 9 patients (3 with limited disease, 6 with advanced disease) experienced large cell transformation (LCT). Seven patients died; of those, 5 died with LCT. Conclusions: For limited disease, response-adaptive therapy demonstrated comparable outcomes with RT alone. Rituximab monotherapy resulted in inferior outcomes for limited disease and a high relapse rate for advanced disease.

62 RADIOLOGY AND NUCLEAR MEDICINE↗