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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Structural, Electrical, and Electromechanical Properties of Inverse Hybrid Perovskites from First-Principles: The Case of (CH 3 NH 3 ) 3 OI

Inverse-hybrid perovskites (IHPs) with large polarization have recently been predicted from first-principles computations. Here, we use one representative from the IHP class of materials, (CH 3 NH 3 ) 3 OI (MA3OI), to propose a route to the first-principles prediction of structural and electrical properties, such as polarization, polarization reversibility, and the associated coercive field for hybrid organic–inorganic perovskites. The route relies on the construction of the polarization reversal path that models experimental measurements. Such a path was found to play an important role in the ground-state search as well as in the identification of competing structural variations. The latter is believed to be the origin of the structural disorder that is characteristic of hybrid organic–inorganic perovskites. The application of such an approach to MA3OI leads to the prediction of several structural variations that are expected to result in a structurally disordered phase above 766 K and of the polar ground state with a polarization of 25.3 μC/cm 2 that is reversible with the application of an electric field. The upper estimate for the coercive field associated with homogeneous polarization reversal is 6.9 GV/m. The piezoelectric constants of MA3OI are predicted to be an order of magnitude smaller in comparison with a prototypical inorganic ferroelectric PbTiO 3 ; however, the low symmetry of the MA3OI structure yields finite values for all components of the piezoelectric tensor. The polarization in MA3OI is tunable by the epitaxial strain (11.5% change under 5% epitaxial strain), although less so as compared with PbTiO 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Throughfall-Reduction Drying Effects on Forest Floor Plant Tissue Biomass (Oi+Oe soil horizons) and Moisture Content in Four Lowland Panamanian Forests

Objectives: Climatic drying is predicted for many tropical forests, yet effects on soil properties across moisture and soil gradients within tropical forests remain poorly characterized, hampering predictions of forest-climate feedbacks. We hypothesized that drying would suppress soil CO2 fluxes (i.e., respiration) in already-drier tropical forests by further reductions in soil moisture, but increases CO2 fluxes in wetter tropical forests by alleviating anaerobiosis and soil saturation. We measured soil CO2 fluxes, soil moisture, soil temperature, and forest floor biomass during wet-dry cycles (2015 – 2022) in four Panamanian forests that vary in rainfall and soil fertility. We also surveyed all tree species and identified to species in 2018 and 2019.Results: We found that soil moisture peaked in the wet season and declined in the dry season. Measured soil CO2 fluxes declined in the dry season and peaked in the early wet season ahead of peak soil moisture, resulting in a lower soil moisture optimum for respiration than previously modeled. Forest floor biomass peaked in the dry season, in contrast. Chronic throughfall exclusion also suppressed soil moisture across the four forests to 20cm depths, and also initially suppressed soil CO2 fluxes across forests. There was sustained suppression of soil CO2 fluxes after four years in the wettest forest only (-28 ± 4% during the dry season), but elevated soil CO2 fluxes in a fertile forest after four years (+75 ± 28% during the late wet season). The unexpected negative drying effect in the wettest, most infertile forest could have resulted from reduced vertical flushing of nutrients into soils, as the drying effect increased with time. Including hydro-nutrient interactions in ecosystem models could improve predictions of tropical forest-climate feedbacks (results presented in Cusack et al. 2023). Datasets included: Datasets included here include .csv and .xls files for forest floor biomass (equivalent to the Oi+Oe soil horizons), and a subset include forest floor biomass moisture content (weight/weight) in the study plots. There is also a .kml file that includes coordinates for all 32 plots included in the study of four forests (n = 4 throughfall reduction and n = 4 control plots per site). No special software is needed to open these files.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Development of a Supercharged Octane Number and a Supercharged Octane Index

Gasoline knock resistance is characterized by the Research and Motor Octane Number (RON and MON), which are rated on the CFR octane rating engine at naturally aspirated conditions. However, modern automotive downsized boosted spark ignition (SI) engines generally operate at higher cylinder pressures and lower temperatures relative to the RON and MON tests. Using the naturally aspirated RON and MON ratings, the octane index (OI) characterizes the knock resistance of gasolines under boosted operation by linearly extrapolating into boosted “beyond RON” conditions via RON, MON, and a linear regression K factor. Using OI solely based on naturally aspirated RON and MON tests to extrapolate into boosted conditions can lead to significant errors in predicting boosted knock resistance between gasolines due to non-linear changes in autoignition and knocking characteristics with increasing pressure conditions. Here, a new “Supercharged Octane Number” (SON) method was developed on the CFR engine at increased intake pressures, which improved the correlation to boosted knock-limited automotive SI engine data over RON for several surrogate fuels and gasolines, including five “Co-Optima” RON 98 fuels and an E10 regular grade gasoline. Furthermore, the conventional OI was extended to a newly introduced Supercharged Octane Index (OI S ) based on SON and RON, which significantly improved the correlation to fuel knock resistance measurements from modern boosted SI engine knock-limited spark advance tests. This demonstrated the first proof of concept of a SON and OI S to better characterize a fuel’s knock resistance in modern boosted SI engines.

42 ENGINEERING↗
DOE OSTI2021

Octane Index Applicability over the Pressure-Temperature Domain

Modern boosted spark-ignition (SI) engines and emerging advanced compression ignition (ACI) engines operate under conditions that deviate substantially from the conditions of conventional autoignition metrics, namely the research and motor octane numbers (RON and MON). The octane index (OI) is an emerging autoignition metric based on RON and MON which was developed to better describe fuel knock resistance over a broader range of engine conditions. Prior research at Oak Ridge National Laboratory (ORNL) identified that OI performs reasonably well under stoichiometric boosted conditions, but inconsistencies exist in the ability of OI to predict autoignition behavior under ACI strategies. Instead, the autoignition behavior under ACI operation was found to correlate more closely to fuel composition, suggesting fuel chemistry differences that are insensitive to the conditions of the RON and MON tests may become the dominant factor under these high efficiency operating conditions. This investigation builds on earlier work to study autoignition behavior over six pressure-temperature (PT) trajectories that correspond to a wide range of operating conditions, including boosted SI operation, partial fuel stratification (PFS), and spark-assisted compression ignition (SACI). A total of 12 different fuels were investigated, including the Co-Optima core fuels and five fuels that represent refinery-relevant blending streams. It was found that, for the ACI operating modes investigated here, the low temperature reactions dominate reactivity, similar to boosted SI operating conditions because their PT trajectories lay close to the RON trajectory. Additionally, the OI metric was found to adequately predict autoignition resistance over the PT domain, for the ACI conditions investigated here, and for fuels from different chemical families. This finding is in contrast with the prior study using a different type of ACI operation with different thermodynamic conditions, specifically a significantly higher temperature at the start of compression, illustrating that fuel response depends highly on the ACI strategy being used.

02 PETROLEUM↗
DOE OSTI2025

Effect of bisphosphonate treatment on the oim mouse middle ear ossicles' structure, composition and hearing

Hearing loss is common in people with osteogenesis imperfecta (OI or brittle bone disease). Bisphosphonates are commonly used to treat long bone fragility in children with OI. However, its impact on the bone quality of the middle ear ossicles and hearing remains unknown. This study determines whether bisphosphonates treatment itself may contribute to hearing loss in OI by evaluating its effects in the oim/oim mouse model of severe OI having normal auditory function. Specifically, this study reports the effects of alendronate (ALN), a nitrogen-containing bisphosphonate, on ossicle morphology, porosity, and elemental composition in 14-week-old oim/oim mice treated weekly, starting at 2 weeks of age. The ossicles were examined using synchrotron microtomography and X-ray fluorescence microscopy (XFM). Hearing was assessed longitudinally until 26 weeks of age by determining auditory brainstem response (ABR) thresholds in another group of mice also treated weekly starting at 2 weeks of age. ALN treatment further reduces in size the already small oim/oim ossicles, specifically in female mice. Porosity, bone composition, and hearing function, however, were generally not affected by the ALN treatment. Furthermore, ALN does not prevent joint fusions, excessive bone formations, or enlarged joint spaces in WT or oim/oim experimental groups. One ALN-treated oim/oim mouse with a bone formation in the interior of the footplate, and one ALN-treated WT mouse with a fixed footplate had frequency-specific hearing loss. Since footplate abnormalities are not observed in PBS-treated mice in this study, it remains unclear whether ALN fails to prevent these changes or contributes to their development. Future studies should investigate the mechanisms of ossicular abnormalities and bisphosphonates modulatory role in the ossicles.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Materials Data on Hg3BI2(OF2)2 by Materials Project

Hg3(OI)2BF4 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of four BF4 clusters and two Hg3(OI)2 sheets oriented in the (0, 1, 0) direction. In each BF4 cluster, B is bonded in a tetrahedral geometry to four F atoms. There are a spread of B–F bond distances ranging from 1.38–1.46 Å. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one B atom. In the second F site, F is bonded in a single-bond geometry to one B atom. In the third F site, F is bonded in a single-bond geometry to one B atom. In the fourth F site, F is bonded in a single-bond geometry to one B atom. In each Hg3(OI)2 sheet, there are three inequivalent Hg sites. In the first Hg site, Hg is bonded in a linear geometry to two O atoms. There are one shorter (2.03 Å) and one longer (2.06 Å) Hg–O bond lengths. In the second Hg site, Hg is bonded in a 4-coordinate geometry to two O and two I atoms. There are one shorter (2.15 Å) and one longer (2.30 Å) Hg–O bond lengths. There are one shorter (2.67 Å) and one longer (3.17 Å) Hg–I bond lengths. In the third Hg site, Hg is bonded in a 3-coordinate geometry to two O and one I atom. There are one shorter (2.18 Å) and one longer (2.37 Å) Hg–O bond lengths. The Hg–I bond length is 2.66 Å. There are two inequivalent O sites. In the first O site, O is bonded in a trigonal planar geometry to three Hg atoms. In the second O site, O is bonded in a distorted trigonal non-coplanar geometry to three Hg atoms. There are two inequivalent I sites. In the first I site, I is bonded in a single-bond geometry to one Hg atom. In the second I site, I is bonded in a distorted L-shaped geometry to two Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Role of different organic and inorganic amendments in the biofortification of iodine in Coriandrum sativum crop

Iodine deficiency disorder (IDDs) is one of the most prevailing and common health issues in mountainous communities. An effective way to control the prevalence and emergence of IDDs in remote areas is to use iodized salt. However, recent studies indicated that iodized salt is mostly lost during the cooking process. The current study of iodine biofortification differed from the previous studies in two main aspects: it involved exogenous organic iodine (OI), and inorganic iodine such as potassium iodide (KI), added in the amended soils, which previous studies did not consider. Moreover, the translocation, transformation, and distribution of iodine from soil to plants are poorly understood in amended soil. Thus, identifying an effective management option to enhance iodine (I) bioavailability in nutrient-deficient soils is currently a significant challenge. Therefore, a greenhouse study was conducted to investigate the effects of organic and inorganic soil amendments on the uptake of different iodine sources in coriander crops. Results showed that applying an inorganic iodine source significantly enhanced the iodine edible part of the crop compared to the control ( p < 0.05). The application of soil amendments relatively improved iodine uptake by the coriander crop compared to the control. The highest iodine was found in crop tissues grown in wood ash-amended soil supplemented with KI (291.97 μg kg −1 ). The KI uptake was significantly higher than the OI ( p < 0.05). Compared to OI, a higher translocation factor (0.96) and distribution coefficient (3.51) were found for plants treated with KI. Thus, this study indicates that a suitable soil amendment can be a better option for iodine biofortification and that it can serve as an alternative to iodized salt in preventing IDDs.

Tianyi, Yan↗
DOE OSTI2025

Photocarrier dynamics at the interface between WS 2 and ozone-irradiated graphene

We investigate the photocarrier properties of heterostructures (HSs) formed by WS 2 and ozone-irradiated graphene (OI-graphene), with a focus on the impact of ozone irradiation. Photoluminescence and Raman spectroscopy reveal a pronounced doping effect induced by ozone irradiation on the graphene layer. Transient absorption measurements demonstrate a substantial suppression of charge transfer efficiency across the interface in the presence of ozone molecules. Spatially resolved pump-probe measurements further show a significant reduction in the diffusion coefficient of photocarriers in WS 2 on OI-graphene compared to that of individual WS 2 monolayers. The slower diffusion suggests enhanced spatial separation of electrons and holes in the WS 2 layer, induced by a built-in electric field at the interface. This effect arises from the combined influences of doping and dielectric property changes caused by ozone molecules. These findings highlight the critical influence of ozone irradiation on graphene and HS interfaces, offering valuable insights for the design of future graphene-based two-dimensional HSs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Numerical Investigation of a Central Fuel Property Hypothesis Under Boosted Spark-Ignition Conditions

In the present work, a central fuel property hypothesis (CFPH), which states that fuel properties are sufficient to provide an indication of a fuel’s performance irrespective of its chemical composition, was numerically investigated. In particular, the objective of the study was to determine whether Research Octane Number (RON) and Motor Octane Number (MON), as fuel properties, are sufficient to describe a fuel’s knock-limited performance under boosted spark-ignition (SI) conditions within the framework of CFPH. To this end, four TPRF-bioblendstock surrogates having different compositions but matched RON (=98) and MON (=90), were first generated using a non-linear regression model based on artificial neural network (ANN). Additionally, three unconventional bioblendstocks were included in the analysis: di-isobutylene (DIB), isobutanol, and Anisole. Skeletal reaction mechanisms were generated for the TPRF-DIB, TPRF-isobutanol, and TPRF-anisole blends from a detailed kinetic mechanism. Thereafter, numerical simulations were performed for the fuel surrogates using the skeletal mechanisms and a virtual cooperative fuel research (CFR) engine model, under a representative boosted operating condition. In the computational fluid dynamics (CFD) model, the G-equation approach was employed to track the turbulent flame front and the well-stirred reactor model combined with the multi-zone binning strategy was used to capture auto-ignition in the end-gas. In addition, laminar flame speed (LFS) was tabulated for each blend as a function of pressure, temperature, and equivalence ratio a priori, and the lookup tables were used to prescribe laminar flame speed as an input to the G-equation model. Parametric spark timing sweeps were performed for each fuel blend to determine the corresponding knock-limited spark advance (KLSA) and 50% burn point (CA50) at the respective KLSA timing. It was observed that despite same RON, MON, and engine operating conditions, the TPRF-anisole blend exhibited markedly different knock-limited performance from the other three blends. This deviation from the octane index (OI) expectation was shown to be caused by differences in laminar flame speed. However, it was found that relatively large fuel-specific differences in LFS (>20%) would have to be present to cause any appreciable deviation from the OI framework. Otherwise, RON and MON would still be robust enough to predict a fuel’s knock-limited performance.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on Sr2Cu(IO)2 by Materials Project

Sr2Cu(OI)2 crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of two Sr2Cu(OI)2 sheets oriented in the (0, 0, 1) direction. Sr2+ is bonded in a 8-coordinate geometry to four equivalent O2- and four equivalent I1- atoms. All Sr–O bond lengths are 2.64 Å. All Sr–I bond lengths are 3.37 Å. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- and two equivalent I1- atoms. All Cu–O bond lengths are 2.03 Å. Both Cu–I bond lengths are 3.44 Å. O2- is bonded to four equivalent Sr2+ and two equivalent Cu2+ atoms to form a mixture of edge, face, and corner-sharing OSr4Cu2 octahedra. The corner-sharing octahedral tilt angles are 0°. I1- is bonded in a 5-coordinate geometry to four equivalent Sr2+ and one Cu2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ReC2(IO)2 by Materials Project

ReC2(OI)2 crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three ReC2(OI)2 clusters. there are two inequivalent Re6+ sites. In the first Re6+ site, Re6+ is bonded to three equivalent C and three equivalent I1- atoms to form distorted face-sharing ReC3I3 octahedra. All Re–C bond lengths are 1.91 Å. All Re–I bond lengths are 2.85 Å. In the second Re6+ site, Re6+ is bonded to six equivalent I1- atoms to form face-sharing ReI6 octahedra. All Re–I bond lengths are 2.74 Å. C is bonded in a linear geometry to one Re6+ and one O2- atom. The C–O bond length is 1.17 Å. O2- is bonded in a single-bond geometry to one C atom. I1- is bonded in a distorted L-shaped geometry to two Re6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaBi2(IO)2 by Materials Project

BaBi2(OI)2 crystallizes in the tetragonal I-4m2 space group. The structure is two-dimensional and consists of two BaBi2(OI)2 sheets oriented in the (0, 0, 1) direction. Ba2+ is bonded to four equivalent O2- atoms to form distorted corner-sharing BaO4 tetrahedra. All Ba–O bond lengths are 2.61 Å. Bi2+ is bonded in a distorted water-like geometry to two equivalent O2- and four equivalent I1- atoms. Both Bi–O bond lengths are 2.46 Å. All Bi–I bond lengths are 3.38 Å. O2- is bonded in a rectangular see-saw-like geometry to two equivalent Ba2+ and two equivalent Bi2+ atoms. I1- is bonded in a 12-coordinate geometry to four equivalent Bi2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaBi2(IO)2 by Materials Project

BaBi2(OI)2 crystallizes in the tetragonal I4mm space group. The structure is two-dimensional and consists of two BaBi2(OI)2 sheets oriented in the (0, 0, 1) direction. Ba2+ is bonded to five I1- atoms to form BaI5 square pyramids that share corners with four equivalent BaI5 square pyramids, corners with four equivalent BiIO4 square pyramids, and edges with four equivalent BaI5 square pyramids. There are one shorter (3.12 Å) and four longer (3.47 Å) Ba–I bond lengths. There are two inequivalent Bi2+ sites. In the first Bi2+ site, Bi2+ is bonded to four equivalent O2- and one I1- atom to form distorted BiIO4 square pyramids that share corners with four equivalent BaI5 square pyramids and corners with four equivalent BiIO4 square pyramids. All Bi–O bond lengths are 2.44 Å. The Bi–I bond length is 3.42 Å. In the second Bi2+ site, Bi2+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Bi–O bond lengths are 2.50 Å. O2- is bonded in a rectangular see-saw-like geometry to four Bi2+ atoms. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded in a single-bond geometry to one Ba2+ atom. In the second I1- site, I1- is bonded to four equivalent Ba2+ and one Bi2+ atom to form a mixture of distorted edge and corner-sharing IBa4Bi square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn3Sb2(IO)4 by Materials Project

Mn3Sb2(OI)4 crystallizes in the orthorhombic Cmce space group. The structure is two-dimensional and consists of two Mn3Sb2(OI)4 sheets oriented in the (0, 1, 0) direction. there are two inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded in a distorted linear geometry to two equivalent O2- and four I1- atoms. Both Mn–O bond lengths are 2.06 Å. There are two shorter (2.97 Å) and two longer (3.05 Å) Mn–I bond lengths. In the second Mn2+ site, Mn2+ is bonded in a distorted bent 150 degrees geometry to two equivalent O2- and four I1- atoms. Both Mn–O bond lengths are 2.07 Å. There are two shorter (2.93 Å) and two longer (3.35 Å) Mn–I bond lengths. Sb3+ is bonded in a 3-coordinate geometry to three O2- atoms. There are one shorter (1.98 Å) and two longer (2.06 Å) Sb–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mn2+ and two equivalent Sb3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Mn2+ and one Sb3+ atom. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded in a 1-coordinate geometry to three Mn2+ atoms. In the second I1- site, I1- is bonded in a 3-coordinate geometry to three Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PtC4S2(IO)2 by Materials Project

PtC4S2(OI)2 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of one PtC4S2(OI)2 ribbon oriented in the (0, 1, 0) direction. Pt2+ is bonded in a square co-planar geometry to two equivalent S2- and two equivalent I1- atoms. Both Pt–S bond lengths are 2.22 Å. Both Pt–I bond lengths are 2.65 Å. There are two inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a bent 150 degrees geometry to one C2+ and one S2- atom. The C–C bond length is 1.29 Å. The C–S bond length is 1.60 Å. In the second C2+ site, C2+ is bonded in a single-bond geometry to one C2+ atom. S2- is bonded in a distorted trigonal planar geometry to one Pt2+, one C2+, and one O2- atom. The S–O bond length is 1.46 Å. O2- is bonded in a single-bond geometry to one S2- and one I1- atom. The O–I bond length is 3.68 Å. I1- is bonded in a distorted bent 120 degrees geometry to one Pt2+ and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Improving tide-estuary representation in MPAS-Ocean (Final Report)

The overarching goal of this research is to produce a skill-assessed tide-estuary representation, including BGC (biogeochemistry) components of the ecosystem, into the MPAS-O global climate modeling system. Specifically, in the original proposal we proposed one-way nesting, into global MPAS-O, of a high-resolution model for TES (tidal and estuary systems) including the coupling of the BGC components. We have completed the proposed tasks during the past 4 years. Specifically, after extensive consultation with the MPAS-O group during the first year, we have decided to go beyond the original proposal and to two-way nest SCHISM into MPAS-O. As a result, SCHISM-CoSiNE (with CoSiNE being the BGC model) is now fully integrated into MPAS-O as a subroutine (more precisely, an analysis member) and can be invoked as MPAS-O is running with two-way exchange of information between the TES and global models (with proper spatial interpolation done on the fly). As originally proposed, we have also developed the new finite-volume (FV) model MPAS-OI (aka ELCIRC-sub) for TES. We have conducted several tests using the coupled MPAS-SCHISM- CoSiNE model and also MPAS-OI for Columbia River, San Francisco Bay and Chesapeake Bay. Four journal publications have been produced so far as the result of the project and 1 is under review (cf. Publication section). With these achievements, we will be ready to conduct fully coupled simulations of TES and global ocean anywhere, as soon as some missing capabilities in MPAS-O (e.g. tides, improved ability to handle the boundary conditions, and streamlining of the global BGC model) are worked out. The significance of the outcome of this project cannot be overstated. It marks the first time, as far as we know, that a global climate model is tightly coupled to a bona fide nearshore and terrestrial model (SCHISM system); in fact SCHISM is the first bona fide compound flooding model that seamlessly covers the coastal ocean, estuaries, rivers and watersheds (Ye et al. 2020; Zhang et al. 2020). The coupled model will reduce the errors and uncertainties of the MPAS-O global climate model system. It also complements and extends on-going E3SM project, as the latter seeks in the long-term to include components required to simulate impacts of sea-level change and storm surge on coastal regions, including wave models and focusing resolution in coastal and storm-track regions, as an important component of the Cryosphere-ocean system. Note that a spectral wave model (the unstructured-grid version of Wave Watch III, aka Wind Wave Model) is already incorporated inside the SCHISM system and is therefore directly accessible in the coupled system.

58 GEOSCIENCES↗
DOE OSTI2022

Comparative Genomics Applied to Systematically Assess Pathogenicity Potential in Shiga Toxin-Producing Escherichia coli O145:H28

Shiga toxin-producing Escherichia coli (STEC) O145:H28 can cause severe disease in humans and is a predominant serotype in STEC O145 environmental isolates. Here, comparative genomics was applied to a set of clinical and environmental strains to systematically evaluate the pathogenicity potential in environmental strains. While the core genes-based tree separated all O145:H28 strains from the non O145:H28 reference strains, it failed to segregate environmental strains from the clinical. In contrast, the accessory genes-based tree placed all clinical strains in the same clade regardless of their genotypes or serotypes, apart from the environmental strains. Loss-of-function mutations were common in the virulence genes examined, with a high frequency in genes related to adherence, autotransporters, and the type three secretion system. Distinct differences in pathogenicity islands LEE, OI-122, and OI-57, the acid fitness island, and the tellurite resistance island were detected between the O145:H28 and reference strains. A great amount of genetic variation was detected in O145:H28, which was mainly attributed to deletions, insertions, and gene acquisition at several chromosomal “hot spots”. Finally, our study demonstrated a distinct virulence gene repertoire among the STEC O145:H28 strains originating from the same geographical region and revealed unforeseen contributions of loss-of-function mutations to virulence evolution and genetic diversification in STEC.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

On the mechanism of radiation and thermal-induced degradation of the insulation cables in nuclear power plants-the presence of long-lived polyenyl C-centered radicals

Radiolytically and thermally produced long-lived polyenyl C-centered radicals in the nuclear power plants’ insulation cables are detected and measured after more than 45 months of aging since the irradiation and the thermal treatment. Electron Paramagnetic Resonance (EPR) results of the irradiated Cross-linked Polyethylene (XLPE) and Ethylene Propylene Rubber (EthProRu), used as primary insulation materials at Nuclear Power Plants (NPP), clearly demonstrate the presence of polyenyl radicals along with allyl and peroxyl radicals. The yields of these free radicals are dose-rate dependent. EPR results also show the presence of the long-lived polyenyl along with allyl and peroxyl free radicals in the thermally treated XLPE, and EthProRu. These free radicals can cause a major failure in the performance of these cables in NPPs. Besides, the results showed the enhancement in the oxidation reactions due to the migration of copper ions from the conductor to the bulk of the insulation. Further, this study also shows that the oxidation index (OI) and Elongation at Break (EAB) increases and decreases respectively at higher doses and temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗