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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO2) capture to predict the CO2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive and reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.

Wang, Chao↗
DOE OSTI2017

Manganese-calcium intermixing facilitates heteroepitaxial growth at the 10 1 ¯ 4 calcite-water interface

In situ atomic force microscopy (AFM) measurements were performed to probe surface precipitates that formed on the (10-14) surface of calcite (CaCO3) single crystals following reaction with Mn2+-bearing aqueous solutions with a range of initial concentrations. Three-dimensional epitaxial islands were observed to precipitate and grow on the surfaces and in situ time-sequenced measurements demonstrated that their growth rates were commensurate with those obtained for epitaxial islands formed on calcite crystals reacted with Cd2+-bearing aqueous solutions of the same range in supersaturation with respect to the pure metal carbonate phase. This finding was unexpected as rhodochrosite (MnCO3) and calcite display a 10% lattice mismatch, based on the area of their (10-14) surface unit cells, whereas the lattice mismatch is only 4% for otavite (CdCO3) and calcite. Coatings of varying thicknesses were therefore synthesized by reacting calcite single crystals with calcite-equilibrated aqueous solutions with concentrations of up to 250 µM MnCl2 and analyzed to determine the composition of the surface precipitates. Ex situ X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR), and AFM measurements of the reacted crystals demonstrated the formation of an epitaxial (Mn,Ca)CO3 solid solution with a spatially complex composition atop the calcite surface, whereby the first few nanometers were rich in Ca and the Mn content increased with distance from the original calcite surface, culminating in a topmost region of almost pure MnCO3 for the thickest coatings. These findings explain the measured growth rates (the effective lattice mismatch was much smaller than nominal mismatch) and highlight the strong influence played by the substrate on the composition of surface precipitates in aqueous conditions.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2021

Sectoral and growth rate control on elemental uptake by individual calcite crystals

Heterogeneous distribution of trace elements (impurities) within individual calcite crystals is a phenomenon commonly observed in natural and laboratory systems. Changes in thermodynamic intensive parameters (mostly chemical potential and temperature) cannot always explain the inhomogeneous impurity patterns in calcite crystals and it has been suggested that growth rate and crystallographic orientation may exert strong effects on elemental incorporation into calcite. In addition, there are a number of experimental studies on micro-scale element (E) distribution between non-equivalent pairs of calcite vicinal faces (known as sectoral zoning); however, the variability of partition coefficients (e.g., K E = (E/Ca) calcite /(E/Ca) fluid ) within individual crystals remains undetermined. In this study, we have extended the work on elemental distribution between crystal sectors to evaluation of partition coefficients of trace and minor elements (Li, B, Mg, and Sr) in calcite crystal faces (10–14) and (01-12), whose growth rates were assessed. Growth entrapment model (GEM) and lattice strain theory were applied to explain K E heterogeneity by varying near-surface diffusivity of Mg and Sr and by varying surface enrichment factor for Li, B, Mg, and Sr. Decoupling of sectoral and growth rate effects reveals that sectoral zoning plays a key role in elemental distribution. More specifically, K Li and K B vary by more than one order of magnitude and K Mg varies by a factor of two within individual crystal faces. Strontium sectoral distribution is different from those of Li, B, and Mg and K Sr varies by up to a factor of two. Finally, these behaviors likely reflect different mechanisms of incorporation of Li, B, Mg, and Sr into calcite.

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

Discovering a reaction–diffusion model for Alzheimer’s disease by combining PINNs with symbolic regression

Misfolded tau proteins play a critical role in the progression and pathology of Alzheimer's disease. Recent studies suggest that the spatio-temporal pattern of misfolded tau follows a reaction-diffusion type equation. However, the precise mathematical model and parameters that characterize the progression of misfolded protein across the brain remain incompletely understood. Here, we use deep learning and artificial intelligence to discover a mathematical model for the progression of Alzheimer's disease using longitudinal tau positron emission tomography from the Alzheimer's Disease Neuroimaging Initiative database. Specifically, we integrate physics informed neural networks (PINNs) and symbolic regression to discover a reaction-diffusion type partial differential equation for tau protein misfolding and spreading. First, we demonstrate the potential of our model and parameter discovery on synthetic data. Then, we apply our method to discover the best model and parameters to explain tau imaging data from 46 individuals who are likely to develop Alzheimer's disease and 30 healthy controls. Our symbolic regression discovers different misfolding models f(c) for two groups, with a faster misfolding for the Alzheimer's group, f(c) = 0.23c 3 – 1.34c 2 + 1.11c, than for the healthy control group, f(c) = –c 3 + 0.62c 2 + 0.39c. Our results suggest that PINNs, supplemented by symbolic regression, can discover a reaction-diffusion type model to explain misfolded tau protein concentrations in Alzheimer's disease. Furthermore, we expect our study to be the starting point for a more holistic analysis to provide image-based technologies for early diagnosis, and ideally early treatment of neurodegeneration in Alzheimer's disease and possibly other misfolding-protein based neurodegenerative disorders.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2010

Effects of multi-component diffusion and heat release on laminar diffusion flame liftoff

Numerical simulations were conducted of the liftoff and stabilization phenomena of laminar jet diffusion flames of inert-diluted C{sub 3}H{sub 8} and CH{sub 4} fuels. Both non-reacting and reacting jets were investigated, including multi-component diffusivities and heat release effects (buoyancy and gas expansion). The role of Schmidt number for non-reacting jets was investigated, with no conclusive Schmidt number criterion for liftoff previously arrived at in similarity solutions. The cold-flow simulation for He-diluted CH{sub 4} fuel does not predict flame liftoff; however, adding heat release reaction lead to the prediction of liftoff, which is consistent with experimental observations. Including reaction was also found to improve liftoff height prediction for C{sub 3}H{sub 8} flames, with the flame base location differing from that in the similarity solution - the intersection of the stoichiometric and iso-velocity (equal to 1-D flame speed) is not necessary for flame stabilization (and thus liftoff). Possible mechanisms other than that proposed for similarity solution may better help to explain the stabilization and liftoff phenomena. (author)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

On the reactivity of methylbenzenes

Alkylated aromatic hydrocarbons, including the methylbenzenes, are a major and growing component of liquid transportation fuels. Reactivity (or lack thereof) for the methylbenzenes in combustion systems, measured by octane rating, ignition delay, and laminar flame speed, varies widely with the number and position of methyl substituents. At present this behaviour is not fully understood. This study demonstrates how the low temperature and ignition reactivity of methylbenzenes is controlled by the presence of isolated methyl groups and adjacent methyl pairs (the ortho effect); this allows for the development of octane number correlations. Introduction of an isolated methyl group, adjacent only to CH ring sites, consistently increases the research octane number (RON) by around 26. This phenomenon is explained by the formation of relatively unreactive benzyl free radicals. When an adjacent pair of methyl substituents is present the RON consistently decreases by between 8 and 26, compared to the case when these methyl groups are isolated from each other (this effect generally diminishes with increasing degree of substitution). Research octane numbers for all aromatics with zero to three methyl substituents are accurately described by the empirical relationship RON = 98 + 24.2n{sub m} - 25.8n{sub p}, where n{sub m} is the total number of methyl groups and n{sub p} is the number of contiguous adjacent methyl pairs. The ortho effect is attributed to the unique oxidation chemistry of o-methylbenzyl, o-methylbenzoxyl, and o-methylphenyl type radicals here we provide a preliminary exploration of this chemistry and highlight areas requiring further research. It is shown that the o-methylbenzyl radical can react with two oxygen molecules to form 1,2-diformylbenzene + 2OH + H, a highly chain-branching process. This chemistry is expected to largely explain the two-stage ignition and negative temperature coefficient (NTC) behavior witnessed for polymethylbenzenes with adjacent methyl pairs. Similar chain branching mechanisms exist in the oxidation of o-methylbenzoxyl radicals that also form during o-xylene ignition. (author)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Liquid jet breakup regimes at supercritical pressures

Previously, a theory has been presented that explains how discrete vapor–liquid interfaces become diminished at certain high-pressure conditions in a manner that leads to well known qualitative trends observed from imaging in a variety of experiments. Rather than surface tension forces, transport processes can dominate over relevant ranges of conditions. In this paper, this framework is now generalized to treat a wide range of fuel-oxidizer combinations in a manner consistent with theories of capillary flows and extended corresponding states theory. Different flow conditions and species-specific molecular properties are shown to produce distinct variations of interfacial structures and local free molecular paths. These variations are shown to occur over the operating ranges in a variety of propulsion and power systems. Despite these variations, the generalized analysis reveals that the envelope of flow conditions at which the transition from classical sprays to diffusion-dominated mixing occurs exhibits a characteristic shape for all liquid–gas combinations. As a result, for alkane-oxidizer mixtures, it explains that these conditions shift to higher pressure flow conditions with increasing carbon number and demonstrates that, instead of widely assumed classical spray atomization, diffusion-dominated mixing may occur under relevant high-pressure conditions in many modern devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Understanding fuel anti-knock performances in modern SI engines using fundamental HCCI experiments

Modern spark-ignition (SI) engine technologies have considerably changed in-cylinder conditions under which fuel autoignition and engine knock take place. In this paper, fundamental HCCI engine experiments are proposed as a means for characterizing the impact of these technologies on the knock propensity of different fuels. In particular, the impacts of turbocharging, direct injection (DI), and downspeeding on operation with ethanol and gasoline are investigated to demonstrate this approach. Results reported earlier for ethanol and gasoline on HCCI combustion are revisited with the new perspective of how their autoignition characteristics fit into the anti-knock requirement in modern SI engines. For example, the weak sensitivity to pressure boost demonstrated by ethanol in HCCI autoignition can be used to explain the strong knock resistance of ethanol fuels for turbocharged SI engines. Further, ethanol's high sensitivity to charge temperature makes charge cooling, which can be produced by fuel vaporization via direct injection or by piston expansion via spark-timing retard, very effective for inhibiting knock. On the other hand, gasoline autoignition shows a higher sensitivity to pressure, so only very low pressure boost can be applied before knock occurs. Gasoline also demonstrates low temperature sensitivity, so it is unable to make as effective use of the charge cooling produced by fuel vaporization or spark retard. These arguments comprehensively explain literature results on ethanol's substantially better anti-knock performance over gasoline in modern turbocharged DISI engines. Fundamental HCCI experiments such as these can thus be used as a diagnostic and predictive tool for knock-limited SI engine performance for various fuels. As a result, examples are presented where HCCI experiments are used to identify biofuel compounds with good potential for modern SI-engine applications.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Pressure effects on reactivity and extinction of n -dodecane diffusion cool flame

Low-temperature combustion at high pressure has gained increasing interest owing to the growing demand for clean and efficient propulsion and energy systems. In particular, cool flame structure, extinction limits, and fuel reactivities at high pressure are critical in affecting the engine performance at near-limit conditions. Here, this paper investigates the effects of pressure on the cool flame extinction limit, structure, radical index, reactivity, and oxygen concentration dependence by experiments, analysis, and modeling. A large n-alkane, namely n-dodecane (n C 12 H 26 ), is selected to study its diffusion cool flame dynamics and reactivity in a high-pressure counterflow burner up to 10 atm. The experimental results show that higher pressure increases the cool flame extinction strain rates, and that the pressure-weighted extinction strain rate (aP) is proportional to the square of pressure, P 2 . A scaling analysis explains the relationship between the dependence of flame structure, heat release rate, and pressure-weighted cool flame strain rate on pressure. Furthermore, radical indexes at different pressures are measured by isolating the thermal and transport effects from the chemical contribution to diffusion cool flame extinction. The radical index clearly shows that the low-temperature reactivity increases with pressure. In addition, due to the critical role of multiple oxygen addition reactions in low-temperature chemistry, the relationship between the cool flame extinction limit and the oxygen concentration is explored. It is found that the cool flame extinction limits are proportional to the n th power of the oxygen concentration, [O 2 ] n , and increasing pressure leads to stronger extinction limit dependence (larger n) on the oxygen concentration. The present experiment and detailed kinetic analysis show clearly that increasing pressure promotes the low-temperature chemistry including the oxygen addition reactions, while the scaling analysis explains well the experimental results.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2022

The impact of anisotropic thermal expansion on the isothermal annealing of polycrystalline α -uranium

Although grain growth impacts microstructural evolution in a wide variety of materials systems, the effect of anisotropic thermal expansion on grain boundary mobility and texture evolution has not been widely studied. Anisotropic thermal expansion occurs in multiple non-cubic metals, and the thermomechanical processing behavior of these materials can be better understood with further study into the impact of thermal expansion on grain boundary mobility and texture evolution. In this work, we develop a mesoscale phase field model of grain growth that includes the effect of anisotropic thermal expansion, which is applied to study polycrystalline α-uranium, a highly anisotropic metal. Three-dimensional simulations on polycrystalline a-uranium with and without thermal expansion eigenstrains are performed to study the grain boundary mobility and texture evolution as a function of temperature. A strain-free temperature of 933 K is selected, and the system is studied at within the range of 873 – 933 K at intervals of ten degrees, resulting in increasing thermal eigenstrain with decreasing temperature. We also estimate a grain boundary mobility prefactor and activation energy based on existing experimental data of isothermal annealing of α-uranium. The grain boundary mobility is found to display significant deviation from Arrhenius behavior with the inclusion of thermal expansion eigenstrain as the amount of thermal eigenstrain (and thus elastic strain energy within the system) increases. This result explains an experimentally observed grain boundary mobility deviation from Arrhenius behavior. Furthermore, the texture evolution is affected, such that the grain orientations become less random with increasing thermal eigenstrain, which could explain experimentally observed texture behavior. These results indicate that the effect of thermal expansion should be considered when predicting the thermomechanical processing behavior of α-uranium and other materials with anisotropic thermal expansion.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Benchmarking ADMM in Nonconvex NLPs

Here, we study connections between the alternating direction method of multipliers (ADMM), the classical method of multipliers (MM), and progressive hedging (PH). The connections are used to derive benchmark metrics and strategies to monitor and accelerate convergence and to help explain why ADMM and PH are capable of solving complex nonconvex NLPs. Specifically, we observe that ADMM is an inexact version of MM and approaches its performance when multiple coordination steps are performed. In addition, we use the observation that PH is a specialization of ADMM and borrow Lyapunov function and primal-dual feasibility metrics used in ADMM to explain why PH is capable of solving nonconvex NLPs. This analysis also highlights that specialized PH schemes can be derived to tackle a wider range of stochastic programs and even other problem classes. Our exposition is tutorial in nature and seeks to to motivate algorithmic improvements and new decomposition strategies.

42 ENGINEERING↗
DOE OSTI2012

Spin-Orbit Coupling in Actinide Cations

The limiting case of Russell-Saunders coupling, which leads to a maximum spin alignment for the open shell electrons, usually explains the properties of high spin ionic crystals with transition metals. For actinide compounds, the spin-orbit splitting is large enough to cause a significantly reduced spin alignment. Novel concepts are used to explain the dependence of the spin alignment on the 5f shell occupation. We present evidence that the XPS of ionic actinide materials may provide direct information about the angular momentum coupling within the 5f shell.

Bagus, Paul S↗
DOE OSTI2014

Compensatory mitigation and screening rules in environmental impact assessment

Concerns about the effectiveness of environmental impact assessment (EIA) have prompted proposals to improve its performance by limiting the discretion of decision-makers in screening. To investigate whether such proposals are likely to generate the desired results, we conducted an evaluation of the screening process under the Australian government's EIA regime from its introduction on 16 July 2000 to 30 June 2013 (study period). Almost 1 in 5 ‘particular manner’ decisions—a type of screening decision under the regime—were found to be unlawful. The extent of non-compliance is explained on the basis of convenience. The department was required to assess a large number of projects under tight timeframes and with limited resources, while being pressured by proponents to allow their projects to bypass EIA. These pressures resulted in the development of an informal custom whereby the formal compensatory mitigation restrictions were frequently ignored. The results highlight the relative significance of formal and informal institutions in EIA. Formal EIA rules typically provide a mere outline of the process. The informal institutions adopted by administrators often have a greater influence on how the process operates and what it achieves. - Highlights: • Concerns about the effectiveness of environmental impact assessment (EIA) have prompted proposals to improve its performance by limiting the discretion of decision-makers in screening. • To investigate whether such proposals are likely to generate the desired results, we conducted an evaluation of the Australian government's screening process, looking at the extent of compliance with a formal prohibition on the consideration of compensatory mitigation. • Almost 1 in 5 ‘particular manner’ decisions – a type of screening decision under the regime – were found to be unlawful (with a 95% confidence interval of between 1:4 and 1:7) because of a failure to abide by the compensatory mitigation restrictions. For urban development actions, the ratio between lawful and unlawful particular manner decisions was worse than 1:1. • The extent of non-compliance is explained on the basis of convenience. Budget and interest group pressures resulted in the development of an informal custom whereby the formal compensatory mitigation restrictions were ignored. • The results highlight the relative significance of formal and informal institutions in EIA. Formal EIA rules typically provide a mere outline of the process. The informal institutions adopted by administrators often have a greater influence on how the process operates and what it achieves.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

A review of uncertainty research in impact assessment

This paper examines uncertainty research in Impact Assessment (IA) and the focus of attention of the IA scholarly literature. We do so by first exploring ‘outside’ the IA literature, identifying three main themes of uncertainty research, and then apply these themes to examine the focus of scholarly research on uncertainty ‘inside’ IA. Based on a search of the database Scopus, we identified 134 journal papers published between 1970 and 2013 that address uncertainty in IA, 75% of which were published since 2005. We found that 90% of IA research addressing uncertainty focused on uncertainty in the practice of IA, including uncertainty in impact predictions, models and managing environmental impacts. Notwithstanding early guidance on uncertainty treatment in IA from the 1980s, we found no common, underlying conceptual framework that was guiding research on uncertainty in IA practice. Considerably less attention, only 9% of papers, focused on uncertainty communication, disclosure and decision-making under uncertain conditions, the majority of which focused on the need to disclose uncertainties as opposed to providing guidance on how to do so and effectively use that information to inform decisions. Finally, research focused on theory building for explaining human behavior with respect to uncertainty avoidance constituted only 1% of the IA published literature. We suggest the need for further conceptual framework development for researchers focused on identifying and addressing uncertainty in IA practice; the need for guidance on how best to communicate uncertainties in practice, versus criticizing practitioners for not doing so; research that explores how best to interpret and use disclosures about uncertainty when making decisions about project approvals, and the implications of doing so; and academic theory building and exploring the utility of existing theories to better understand and explain uncertainty avoidance behavior in IA. - Highlights: • We identified three main themes of uncertainty research in 134 papers from the scholarly literature. • The majority of research has focused on better methods for managing uncertainty in predictions. • Uncertainty disclosure is demanded of practitioners, but there is little guidance on how to do so. • There is limited theoretical explanation as to why uncertainty is avoided or not disclosed. • Conceptual, practical and theoretical guidance are required for IA uncertainty consideration.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

No evidence of a threshold in traffic volume affecting road-kill mortality at a large spatio-temporal scale

Previous studies have found that the relationship between wildlife road mortality and traffic volume follows a threshold effect on low traffic volume roads. We aimed at evaluating the response of several species to increasing traffic intensity on highways over a large geographic area and temporal period. We used data of four terrestrial vertebrate species with different biological and ecological features known by their high road-kill rates: the barn owl (Tyto alba), hedgehog (Erinaceus europaeus), red fox (Vulpes vulpes) and European rabbit (Oryctolagus cuniculus). Additionally, we checked whether road-kill likelihood varies when traffic patterns depart from the average. We used annual average daily traffic (AADT) and road-kill records observed along 1000 km of highways in Portugal over seven consecutive years (2003–2009). We fitted candidate models using Generalized Linear Models with a binomial distribution through a sample unit of 1 km segments to describe the effect of traffic on the probability of finding at least one victim in each segment during the study. We also assigned for each road-kill record the traffic of that day and the AADT on that year to test for differences using Paired Student's t-test. Mortality risk declined significantly with traffic volume but varied among species: the probability of finding road-killed red foxes and rabbits occurs up to moderate traffic volumes (< 20,000 AADT) whereas barn owls and hedgehogs occurred up to higher traffic volumes (40,000 AADT). Perception of risk may explain differences in responses towards high traffic highway segments. Road-kill rates did not vary significantly when traffic intensity departed from the average. In summary, we did not find evidence of traffic thresholds for the analysed species and traffic intensities. We suggest mitigation measures to reduce mortality be applied in particular on low traffic roads (< 5000 AADT) while additional measures to reduce barrier effects should take into account species-specific behavioural traits. - Highlights: • Traffic and road-kills were analysed along 1000 km of highways over seven years. • Mortality risk declined significantly with traffic volume. • Perception of risk may explain different responses towards high traffic sections. • Reducing barrier effects should take into account species behavioural traits.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

The influence of actor capacities on EIA system performance in low and middle income countries —Cases from Georgia and Ghana

In this paper, we aim to better understand the factors that contribute to the substantive performance of EIA systems in low and middle income countries. Substantive performance is defined as the extent to which the EIA process contributes to the EIA objectives for the long term, namely environmental protection or, even more ambitious, sustainable development. We have therefore developed a conceptual model in which we focus on the key actors in the EIA system, the proponent and the EIA authority and their level of ownership as a key capacity to measure their performance, and we distinguish procedural performance and some contextual factors. This conceptual model is then verified and refined for the EIA phase and the EIA follow-up phase (permitting, monitoring and enforcement) by means of 12 case studies from Ghana (four cases) and Georgia (eight cases), both lower–middle income countries. We observe that in most cases the level of substantive performance increases during the EIA phase but drops during the EIA follow-up phase, and as a result only five out of 12 operational cases are in compliance with permit conditions or national environmental standards. We conclude, firstly that ownership of the proponent is the most important factor explaining the level of substantive performance; the higher the proponent's level of ownership the higher the level of substantive performance. The influence of the EIA authority on substantive performance is limited. Secondly, the influence of procedural performance on substantive performance seems less important than expected in the EIA phase but more important during the EIA follow-up phase. In order to improve substantive performance we learned two lessons. Firstly, increasing the proponent's level of ownership seems obvious, but direct change is probably difficult. However, where international finance institutes are involved they can increase ownership. Despite the limited influence of the EIA authority, a proactive strategy of, for example, working together with international finance institutes has a slightly larger influence than a reactive strategy. - Highlights: • Ownership of the proponent is the most important factor explaining the level of substantive performance. • The influence of the EIA authority on substantive performance is limited. • The influence of procedural performance on substantive performance seems less important than expected in the EIA phase but more important during the EIA follow-up phase.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Microbial influences on hormesis, oncogenesis, and therapy: A review of the literature

Utilization of environmental stimuli for growth is the main factor contributing to the evolution of prokaryotes and eukaryotes, independently and mutualistically. Epigenetics describes an organism’s ability to vary expression of certain genes based on their environmental stimuli. The diverse degree of dose-dependent responses based on their variances in expressed genetic profiles makes it difficult to ascertain whether hormesis or oncogenesis has or is occurring. In the medical field this is shown where survival curves used in determining radiotherapeutic doses have substantial uncertainties, some as large as 50% (Barendsen, 1990). Many in-vitro radiobiological studies have been limited by not taking into consideration the innate presence of microbes in biological systems, which have either grown symbiotically or pathogenically. Present in-vitro studies neglect to take into consideration the varied responses that commensal and opportunistic pathogens will have when exposed to the same stimuli and how such responses could act as stimuli for their macro/microenvironment. As a result many theories such as radiation carcinogenesis explain microscopic events but fail to describe macroscopic events (Cohen, 1995). As such, this review shows how microorganisms have the ability to perturb risks of cancer and enhance hormesis after irradiation. It will also look at bacterial significance in the microenvironment of the tumor before and during treatment. In addition, bacterial systemic communication after irradiation and the host’s immune responses to infection could explain many of the phenomena associated with bystander effects. Therefore, the present literature review considers the paradigms of hormesis and oncogenesis in order to find a rationale that ties them all together. This relationship was thus characterized to be the microbiome.

54 ENVIRONMENTAL SCIENCES↗