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DOE OSTI2020

Biogenic Iron Sulfide Nanoparticles to Enable Extracellular Electron Uptake in Sulfate‐Reducing Bacteria

Abstract Microbes synthesize cell‐associated nanoparticles (NPs) and utilize their physicochemical properties to produce energy under unfavorable metabolic conditions. Iron sulfide (FeS) NPs are ubiquitous and are predominantly biosynthesized by sulfate‐reducing bacteria (SRB). However, the biological role of FeS NPs in SRB remains understudied. Now, conductive FeS NPs function is demonstrated as an electron conduit enabling Desulfovibrio vulgaris Hildenborough, an SRB strain, to utilize solid‐state electron donors via direct electron uptake. After forming FeS NPs on the cell surface, D. vulgaris initiated current generation coupled with sulfate reduction on electrodes poised at −0.4 V versus standard hydrogen electrode. Single‐cell activity analysis showed that the electron uptake and metabolic rate via FeS NPs in D. vulgaris were about sevenfold higher than those via native cell‐surface proteins in other SRB.

Deng, Xiao↗

DOE OSTI2020

Biogenic Iron Sulfide Nanoparticles to Enable Extracellular Electron Uptake in Sulfate‐Reducing Bacteria

Deng, Xiao↗

DOE OSTI2017

Enzyme-Assisted Extraction and Pb{sup 2+} Biosorption of Polysaccharide from Cordyceps militaris

The enzyme assisted extraction conditions of polysaccharide from Cordyceps militaris mycelia were firstly investigated by kinetics analysis and the optimal operating was found to be: extraction temperature 40 °C; solid-solvent ratio 1:20; extraction pH 4.0; cellulase concentration 2.0%. The polysaccharide extraction yield was 5.99% under these optimized conditions. Furthermore, a fundamental investigation of the biosorption of Pb{sup 2+} from aqueous solution by the C. militaris polysaccharide was performed under batch conditions. The suitable pH (5.0), polysaccharide concentration (0.20 g L{sup −1}), initial Pb{sup 2+} concentration (300 mg L{sup −1}) and contact time (40 min) were outlined to enhance Pb{sup 2+} biosorption from aqueous medium. The Langmuir isotherm model and pseudo first order kinetic model fitted well to the data of Pb{sup 2+} biosorption, suggesting the biosorption of Pb{sup 2+} onto C. militaris polysaccharide was monolayer biosorption and physical adsorption might be the rate-limiting step that controlled the adsorption process. FTIR analysis showed that the main functional groups of C. militaris polysaccharide involved in adsorption process were carbonyl, carboxyl, and hydroxyl groups.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Comparison of pulse shape discrimination performance of stilbene and liquid scintillator under high count-rate active interrogation conditions

Here, we compare the pulse-shape-discrimination performance of a large Stilbene detector, manufactured at the Lawrence Livermore National Laboratory, to a similarly sized liquid scintillator, made by Eljen Technologies, Inc. (type EJ309), under various high-count-rate scenarios, such as can be expected during Active Interrogation of objects using an electric neutron generator for detecting the presence of Special Nuclear Materials and contraband. Pulse Shape Discrimination (PSD) is performed with an extension of previously described wavelet and event fitting algorithms, which are also used to reject pileup events and to correct the energy calibration for event signals clipped during digitization. We find that strong PSD and pileup rejection cuts are required to function in this high-count-rate environment. Whereas the Stilbene detector has intrinsically better pulse-shape discrimination performance, the pulses of events from the liquid scintillator are somewhat narrower, reducing pileup. We use an event fitting cut that provides simultaneous PSD identification and pileup rejection. When applying the same cut to data taken with both detectors, we find that Stilbene has higher event use efficiency by about a factor of two and retains a better gamma rejection ratio compared to EJ309.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2024

Ligand Controls Excited Charge Carrier Dynamics in Metal-Rich CdSe Quantum Dots: Computational Insights

Small metal-rich semiconducting quantum dots (QDs) are promising for solid-state lighting and single-photon emission due to their highly tunable yet narrow emission line widths. Nonetheless, the anionic ligands commonly employed to passivate these QDs exert a substantial influence on the optoelectronic characteristics, primarily owing to strong electron–phonon interactions. In this work, we combine time-domain density functional theory and nonadiabatic molecular dynamics to investigate the excited charge carrier dynamics of Cd 28 Se 17 X 22 QDs (X = HCOO – , OH – , Cl – , and SH – ) at ambient conditions. These chemically distinct but regularly used molecular groups influence the dynamic surface-ligand interfacial interactions in Cd-rich QDs, drastically modifying their vibrational characteristics. The strong electron–phonon coupling leads to substantial transient variations at the band edge states. The strength of these interactions closely depends on the physicochemical characteristics of passivating ligands. Consequently, the ligands largely control the nonradiative recombination rates and emission characteristics in these QDs. Our simulations indicate that Cd 28 Se 17 (OH) 22 has the fastest nonradiative recombination rate due to the strongest electron–phonon interactions. Conversely, QDs passivated with thiolate or chloride exhibit considerably longer carrier lifetimes and suppressed nonradiative processes. The ligand-controlled electron–phonon interactions further give rise to the broadest and narrowest intrinsic optical line widths for OH and Cl-passivated single QDs, respectively. Finally, obtained computational insights lay the groundwork for designing appropriate passivating ligands on metal-rich QDs, making them suitable for a wide range of applications, from blue LEDs to quantum emitters.

36 MATERIALS SCIENCE↗

DOE OSTI2021

A wearable patch for continuous analysis of thermoregulatory sweat at rest

The body naturally and continuously secretes sweat for thermoregulation during sedentary and routine activities at rates that can reflect underlying health conditions, including nerve damage, autonomic and metabolic disorders, and chronic stress. However, low secretion rates and evaporation pose challenges for collecting resting thermoregulatory sweat for non-invasive analysis of body physiology. Here we present wearable patches for continuous sweat monitoring at rest, using microfluidics to combat evaporation and enable selective monitoring of secretion rate. We integrate hydrophilic fillers for rapid sweat uptake into the sensing channel, reducing required sweat accumulation time towards real-time measurement. Along with sweat rate sensors, we integrate electrochemical sensors for pH, Cl - , and levodopa monitoring. We demonstrate patch functionality for dynamic sweat analysis related to routine activities, stress events, hypoglycemia-induced sweating, and Parkinson’s disease. By enabling sweat analysis compatible with sedentary, routine, and daily activities, these patches enable continuous, autonomous monitoring of body physiology at rest.

47 OTHER INSTRUMENTATION↗

DOE OSTI2016

Impact of nuclear mass uncertainties on the r process

Here, nuclear masses play a fundamental role in understanding how the heaviest elements in the Universe are created in the r process. We predict r -process nucleosynthesis yields using neutron capture and photodissociation rates that are based on the nuclear density functional theory. Using six Skyrme energy density functionals based on different optimization protocols, we determine for the first time systematic uncertainty bands—related to mass modeling—for r -process abundances in realistic astrophysical scenarios. We find that features of the underlying microphysics make an imprint on abundances especially in the vicinity of neutron shell closures: Abundance peaks and troughs are reflected in trends of neutron separation energy. Further advances in the nuclear theory and experiments, when linked to observations, will help in the understanding of astrophysical conditions in extreme r -process sites.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Utilisation of flavonoids from Lycium barbarum L. leaves cross‐linked with whey protein for the stabilisation and delivery of β ‐carotene emulsions

Summary Although β ‐carotene is an essential nutrient for the maintenance of human health, it is insoluble in water and extremely unstable, which limits its application. Here, we prepared a stable emulsification system of whey protein (WP)‐ Lycium barbarum L. leaves flavonoids (LBLF) complex as a carrier to load β ‐carotene. The rheological properties, antioxidant properties and stability of emulsion were studied, and the effects of emulsion on the biological retention of β ‐carotene and stability were investigated. The results indicate that, compared with WP, the WP‐LBLF emulsion has smaller particles, a smaller creaming index, and significantly enhanced chemical stability under light and heat treatment conditions. The thiobarbituric acid value of the WP‐LBLF emulsion (0.031 ± 0.016 mg/kg) was dramatically lower than that of the WP emulsion (0.045 ± 0.012 mg/kg) ( P < 0.05). In the simulated gastrointestinal digestion experiment, the retention rate of β ‐carotene was higher in WP‐LBLF emulsion. Additionally, the WP‐LBLF emulsion loaded with β ‐carotene has good salt tolerance and heat stability. In our study, WP‐LBLF was used as an emulsifier to load β ‐carotene emulsion to improve its bioavailability and stability, which provides a new preparation and application method for a complex functional emulsifier.

Fan, Yanli↗

DOE OSTI2023

Rare earth separation in voltage-gated 2D MXene membranes

The separation of rare earth elements (REEs) has historically been a complicated and expensive process, producing significant amounts of pollution. To this end, MXene membranes (MXMs) have attracted researchers' interest. It has been demonstrated that MXMs are capable of separating ions and that it is possible to precisely control the separation rate by applying a voltage to the membrane. Indeed, due to their chemical nature, MXenes show outstanding electrical conductivity. However, the effect of applied voltage on the permeation rate and separation effects of iconic species remains an intriguing area of research. In this work, we demonstrate how applying different voltages (gate voltage) to a MXM affects the permeation rate of various REE ions. Our hypothesis to explain MXMs behavior towards REE is that under negative voltage, the interlayer spacing decreases due to attraction between charged MXene surfaces and intercalated cations, increasing the separation factor between REEs. Under positive voltage, the interlayer spacing increases due to repulsion between the MXene surfaces and intercalated cations. However, we demonstrate relatively poor separation capability for REEs at 1mM starting concentration and 1.0 V applied DC voltage (separation factor ~1-3). This study demonstrates the need for future experiments to observe varied experimental conditions and chemical functionalization to determine whether MXene membranes can be an efficient platform for REE separation.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Material Properties of Zirconium Hydride Phases in Zircaloy-4 Getter Tubes Mapped by Atomic Force Microscopy

Nickel plated Zircaloy-4 tubing (“getter tubing”) is an important functional component in Tritium Producing Burnable Absorber Rods (TBPARs). Getter tubes are used to capture tritium produced during reactor operations and convert it from a gas to a solid by reacting it with Zr to form ZrHx compounds. Previous studies (PNNL-27232, TTP-8-004, and TTP-30710) on forming Zircaloy-4 hydrides demonstrated that hydride concentration gradients formed under prototypic hydriding conditions and that the microstructure of hydrides formed at 350°C is different than those formed at 500°C, a temperature typically used by the Tritium Technology Program (TTP) for getter rate loading experiments. Differences in hydride distribution, microstructure, and phases were characterize using scanning electron microscopy methods. However, the impact of these differences on material properties is not well understood. The goal of this project was to determine whether atomic force microscopy could observe subtle differences in material properties of single domains of hydride phases formed in Zircaloy-4. These properties include surface structure, hardness, thermal conductivity, and magnetic susceptibility.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2026

Lignin Extraction and Condensation as a Function of Temperature, Residence Time, and Solvent System in Flow-through Reactors

Solvolytic extraction of lignin from biomass is a critical step in lignin-first biorefining, including the reductive catalytic fractionation (RCF) process. Key to optimal RCF processing is the ability to rapidly extract lignin from biomass at high delignification extents and transfer the lignin molecules to a catalyst surface in a time frame that minimizes lignin condensation reactions. Here, we use a flow-through reactor to study the effects of temperature (175–250 °C), residence time (9 to 36 min), and solvent composition (methanol and methanol–water) on lignin extraction and condensation. We evaluated three metrics at each condition: total delignification, delignification rate, and extent of condensation, the latter measured by a decrease in monomer yield for batch hydrogenolysis reactions of solvolysis liquor compared to batch RCF reactions. We observe that delignification is predominantly determined by temperature, while residence time dictates the lignin condensation extent. Moreover, the extent of both extraction and condensation increased in the methanol–water solvent system compared to that in the methanol system. Lignin extracted in methanol is stable up to 18-min residence times at or below 225 °C, while a majority of the lignin extracted in methanol–water is condensed with a 9-min residence time at 200 °C. These results can inform reactor designs and solvent selection for lignin-first biorefining processes that aim to physically separate the biomass and catalyst.

biorefining↗

NASA NTRS1980

Advanced methods for preparation and characterization of infrared detector materials

Mercury cadmium telluride crystals were prepared by the Bridgman method with a wide range of crystal growth rates and temperature gradients adequate to prevent constitutional supercooling under diffusion-limited, steady state, growth conditions. The longitudinal compositional gradients for different growth conditions and alloy compositions were calculated and compared with experimental data to develop a quantitative model of the crystal growth kinetics for the Hg(i-x)CdxTe alloys, and measurements were performed to ascertain the effect of growth conditions on radial compositional gradients. The pseudobinary HgTe-CdTe constitutional phase diagram was determined by precision differential thermal analysis measurements and used to calculate the segregation coefficient of Cd as a function of x and interface temperature. Computer algorithms specific to Hg(1-x)CdxTe were developed for calculations of the charge carrier concentrations, charge carrier mobilities, Hall coefficient, optical absorptance, and Fermi energy as functions of x, temperature, ionized donor and acceptor concentrations, and neutral defect concentrations.

Lehoczky, S. L.↗

NASA NTRS1985

Slip-boundary equations for multicomponent nonequilibrium airflow

Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low Reynolds number, high-altitude flight regime of a space vehicle. These are obtained from closed-form solutions of the mass, momentum, and energy flux equations by using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent airflow, includes the finite-rare surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities have been obtained in a form which can readily be employed in flow-field computations. A consistent set of equations is provided for multicomponent and binary mixtures and single-species gas. An expression is also provided for the finite-rate species-concentration boundary condition for a multicomponent mixture in the absence of slip.

Gupta, R. N.↗

NASA NTRS2004

Quantum Scattering Study of Ro-Vibrational Excitations in N+N(sub 2) Collisions under Re-entry Conditions

A three-dimensional time-dependent quantum dynamics approach using a recently developed ab initio potential energy surface is applied to study ro-vibrational excitation in N+N2 exchange scattering for collision energies in the range 2.1- 3.2 eV. State-to-state integral exchange cross sections are examined to determine the distribution of excited rotational states of N(sub 2). The results demonstrate that highly-excited rotational states are produced by exchange scattering and furthermore, that the maximum value of (Delta)j increases rapidly with increasing collision energies. Integral exchange cross sections and exchange rate constants for excitation to the lower (upsilon = 0-3) vibrational energy levels are presented as a function of the collision energy. Excited-vibrational-state distributions for temperatures at 2,000 K and 10,000 K are included.

Wang, Dunyou↗

NASA NTRS1998

Constitutive Theory Developed for Monolithic Ceramic Materials

With the increasing use of advanced ceramic materials in high-temperature structural applications such as advanced heat engine components, the need arises to accurately predict thermomechanical behavior that is inherently time-dependent and that is hereditary in the sense that the current behavior depends not only on current conditions but also on the material's thermomechanical history. Most current analytical life prediction methods for both subcritical crack growth and creep models use elastic stress fields to predict the time-dependent reliability response of components subjected to elevated service temperatures. Inelastic response at high temperatures has been well documented in the materials science literature for these material systems, but this issue has been ignored by the engineering design community. From a design engineer's perspective, it is imperative to emphasize that accurate predictions of time-dependent reliability demand accurate stress field information. Ceramic materials exhibit different time-dependent behavior in tension and compression. Thus, inelastic deformation models for ceramics must be constructed in a fashion that admits both sensitivity to hydrostatic stress and differing behavior in tension and compression. A number of constitutive theories for materials that exhibit sensitivity to the hydrostatic component of stress have been proposed that characterize deformation using time-independent classical plasticity as a foundation. However, none of these theories allow different behavior in tension and compression. In addition, these theories are somewhat lacking in that they are unable to capture the creep, relaxation, and rate-sensitive phenomena exhibited by ceramic materials at high temperatures. The objective of this effort at the NASA Lewis Research Center has been to formulate a macroscopic continuum theory that captures these time-dependent phenomena. Specifically, the effort has focused on inelastic deformation behavior associated with these service conditions by developing a multiaxial viscoplastic constitutive model that accounts for time-dependent hereditary material deformation (such as creep and stress relaxation) in monolithic structural ceramics. Using continuum principles of engineering mechanics, we derived the complete viscoplastic theory from a scalar dissipative potential function.

Janosik, Lesley A.↗

NASA NTRS2005

Optic Flow Dominates Visual Scene Polarity in Causing Adaptive Modification of Locomotor Trajectory

Locomotion and posture are influenced and controlled by vestibular, visual and somatosensory information. Optic flow and scene polarity are two characteristics of a visual scene that have been identified as being critical in how they affect perceived body orientation and self-motion. The goal of this study was to determine the role of optic flow and visual scene polarity on adaptive modification in locomotor trajectory. Two computer-generated virtual reality scenes were shown to subjects during 20 minutes of treadmill walking. One scene was a highly polarized scene while the other was composed of objects displayed in a non-polarized fashion. Both virtual scenes depicted constant rate self-motion equivalent to walking counterclockwise around the perimeter of a room. Subjects performed Stepping Tests blindfolded before and after scene exposure to assess adaptive changes in locomotor trajectory. Subjects showed a significant difference in heading direction, between pre and post adaptation stepping tests, when exposed to either scene during treadmill walking. However, there was no significant difference in the subjects heading direction between the two visual scene polarity conditions. Therefore, it was inferred from these data that optic flow has a greater role than visual polarity in influencing adaptive locomotor function.

Nomura, Y.↗

NASA NTRS2005

Optic Flow Dominates Visual Scene Polarity in Causing Adaptive Modification of Locomotor Trajectory

Nomura, Y.↗

NASA NTRS2004

Effects of Vestibular Loss on Orthostatic Responses to Tilts in the Pitch Plane

The purpose of this study was to determine the extent to which vestibular loss might impair orthostatic responses to passive tilts in the pitch plane in human subjects. Data were obtained from six subjects having chronic bilateral vestibular loss and six healthy individuals matched for age, gender, and body mass index. Vestibular loss was assessed with a comprehensive battery including dynamic posturography, vestibulo-ocular and optokinetic reflexes, vestibular evoked myogenic potentials, and ocular counterrolling. Head up tilt tests were conducted using a motorized two-axis table that allowed subjects to be tilted in the pitch plane from either a supine or prone body orientation at a slow rate (8 deg/s). The sessions consisted of three tilts, each consisting of20 min rest in a horizontal position, tilt to 80 deg upright for 10 min, and then return to the horizontal position for 5 min. The tilts were performed in darkness (supine and prone) or in light (supine only). Background music was used to mask auditory orientation cues. Autonomic measurements included beat-to-beat recordings of blood pressure (Finapres), heart rate (ECG), cerebral blood flow velocity in the middle cerebral artery (transcranial Doppler), end tidal CO2, respiratory rate and volume (Respritrace), and stroke volume (impedance cardiography). For both patients and control subjects, cerebral blood flow appeared to exhibit the most rapid adjustment following transient changes in posture. Outside of a greater cerebral hypoperfusion in patients during the later stages of tilt, responses did not differ dramatically between the vestibular loss and control subjects, or between tilts performed in light and dark room conditions. Thus, with the 'exception of cerebrovascular regulation, we conclude that orthostatic responses during slow postural tilts are not substantially impaired in humans following chronic loss of vestibular function, a result that might reflect compensation by nonvisual graviceptor inputs (e.g., somatosensory) or other circulatory reflex mechanisms.

Wood, Scott J.↗