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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Calendar-life versus cycle-life aging of lithium-ion cells with silicon-graphite composite electrodes

The use of blended silicon-graphite (Si-Gr) negative electrodes increases the energy density of lithium-ion cells over those containing only graphite (Gr) electrodes. However, volume changes in the Si particles that occur during cycling causes deterioration of the solid-electrolyte interphase (SEI) layer on the particles resulting in further electrolyte reduction that immobilizes Li+ ions and, therefore, capacity fade. Because the volume changes are not expected to occur during a potentiostatic hold (referred to as calendar-life aging), by comparison of cycle-life and calendar-life aged cells one can expect to assess the role of volume changes in the deterioration of cell performance. To this end, cells with Si-Gr and Gr negative electrodes (and Li 1.03 (Ni 0.5 Co 0.2 Mn 0.3 ) 0.97 O 2 containing positive electrodes) were assembled, tested, and compared using cycle-life and calendar-life aging protocols. As expected, the capacity loss of the cycle-life aged cells was higher than that of the calendar-life aged cells. However, the measurable capacity loss for the calendar-life aged cells indicated continued immobilization of Li + ions. Furthermore, electrolytes extracted from the calendar-life aged cells showed more LiPF 6 hydrolysis products than those extracted from the cycle-life aged cells. In conclusion, we discuss possible mechanistic causes for the observed aging behaviors in this article.

25 ENERGY STORAGE↗
DOE OSTI2019

Left ventricular ejection fraction determined with the simulation of a very low-dose CZT-SPECT protocol and an additional count-calibration on planar radionuclide angiographic data

Purpose: To determine whether the left ventricular ejection fractions (EFs), measured on a high-sensitivity CZT single photon emission computed tomography (SPECT)-camera with a 70% reduction in recording times and a prevention of EF overestimation through an additional count-calibration, are concordant with reference EF from planar radionuclide angiography (2D-RNA). Methods: An additional 10-minute CZT-SPECT recording was performed in patients referred to 2D-RNA for cardiomyopathy (n = 23) or chemotherapy monitoring (n = 50) with an in vivo red blood cell labeling with 850 MBq {sup 99m}TcO{sub 4}{sup −}. The EF, obtained from CZT-SPECT with 100% (SPECT100) or 30% (SPECT30) projection times and with a SPECT-count calibration on the 2D-RNA counts of corresponding cavity volumes, were compared to EF from 2D-RNA. Results: Strong and equivalent relationships were documented between the EF from 2D-RNA and the calibrated EF from SPECT100 (y = 0.89x + 6.62; R{sup 2} = 0.87) and SPECT30 (y = 0.87x + 8.40; R{sup 2} = 0.85), and the mean EF from SPECT100 (54% ± 15%) and SPECT30 (53% ± 16%) were close to that from 2D-RNA (55% ± 15%). However, upward shifts in these mean values were documented in the absence of count calibration for both SPECT100 (60% ± 18%) and SPECT30 (60% ± 18%). Conclusion: Left ventricular EF may be determined on a high-sensitivity CZT-camera, a 70% reduction in injected activities, and an additional count-calibration for further enhancing the concordance with 2D-RNA values. [French] French Abstract: Objectif: Déterminer si les fractions d'éjection ventriculaire gauche (EF) mesurées sur une caméra CZT SPECT à haute sensibilité avec une réduction de 70% des temps d'enregistrement et une prévention de la surestimation de l'EF grâce à un étalonnage supplémentaire des coups concordent avec les EF de référence obtenues par angiographie scintigraphique planaire (2D-RNA). Méthodes: Un enregistrement CZT-SPECT supplémentaire de 10 minutes a été réalisé chez les patients référés pour évaluation de cardiomyopathie (n=23) ou suivi de chimiothérapie (n = 50) par angiographie scintigraphique planaire (2D-RNA) au globules rouges marqués avec 850 MBq 99mTcO4-. Les EF, obtenues au moyen d’une caméra CZT-SPECT avec 100% (SPECT100) ou 30% (SPECT30) de temps d’acquisition et avec étalonnage des coups SPECT sur les images 2D-RNA des volumes de cavité correspondants ont été comparés aux EF à partir de 2D-RNA. Résultats: une corrélation significative existe entre les EF obtenues par 2D-RNA et les EF étalonnées obtenues par SPECT100 (y = 0,89x + 6,62; R2 = 0,87) et SPECT30 (y = 0,87x + 8,40; R2 = 0,85). Les EF moyennes de SPECT100 (54 ± 15%) et SPECT30 (53 ± 16%) sont similaires à celles obtenues par 2D-RNA (55 ± 15%). En l'absence d'étalonnage de comptage des études SPECT100 (60 ± 18%) et SPECT30 (60 ± 18%), ces valeurs moyennes d’EF sont généralement plus élevées. Conclusion: La fonction ventriculaire gauche peut être déterminée avec une caméra CZT à haute sensibilité, une réduction des activités injectées et un étalonnage supplémentaire des coups pour améliorer la concordance avec les valeurs obtenues par 2D-RNA. [Spanish] Spanish Abstract: Propósito: Determinar si la fracción de eyección del ventrículo izquierdo, medida con la cámara CZT-SPECT con una reducción del 70% en tiempo de grabación y con la prevención de la sobreestimación mediante una calibración de cuentas adicional, que sea concordante con el valor referencia de fracción de eyección mediante radiografía planar de radionucleidos. (2D-RNA). Métodos: Una grabación adicional de 10 minutos con CZT-SPECT se realizo en pacientes referidos a radiografía planar de radionucleidos (2D-RNA) por miocardiopatías. (n = 23) o para monitorizar las quimioterapias (n = 50) con marcaje de glóbulos rojos con 850 MBq 99m TcO4. La fracción de eyección obtenida por CZT-SPECT con 100% (SPECT100) o 30% (SPECT30) de tiempo de proyección, y con SPECT con calibración de cuentas con el 2D-RNA, los volúmenes de cavidades fueron comparados con fracción de eyección . Relaciones fuertes y equivalentes fueron documentados entre fracción de eyección del 2D-RNA, y la forma calibrada de la fracción de eyección SPECT100 (y = 0.89x + 6.62; R2 = 0.87) y SPECT30 y = 0.87x + 8.40; R2 = 0.85), y la media de fracción de eyección de SPECT100 (54 ± 15%) and SPECT30 (53 ± 16%) fueron cercanos a la de el 2D-RNA (55 ± 15%). Aunque, aumentos en estas medias se documentaron en la ausencia de la calibración de cuentas para SPECT100 (60 ± 18%) y SPECT30 (60 ± 18%). Conclusión: La fracción de eyección del ventrículo izquierdo puede ser determinada con una cámara CZT de alta sensibilidad, una reducción del 70% en actividades inyectadas y la calibración de cuentas adicional para realzar la concordancia con los valores de 2D-RNA. [Chinese] Chinese Abstract: 目的: 以平面放射性核素血管造影 (2D-RNA) 测定左心室射血分数 (EF) 作为参考标准,为确定利用高灵敏度 CZT SPECT 相机在减少 70% 的记录时间, 并结合计数校准防止高估情况下测量的 EF值, 是否与 2D-RNA 测得的 EF 值一致。 方法: 对心肌病 (n = 23) 或化疗监测 (n = 50) 的患者采用体内标记法注射 850 MBq {sup 99m}TcO{sub 4} 标记的红细胞进行 2D-RNA ,随后再采集 10 分钟 CZT-SPECT。 对 CZT-SPECT 100% 投影时间 (SPECT100) 或 30% 投影时间 (SPECT30) 获得的图像进行重建, 并进行计数校准 (对相应容积获得的 2D-RNA 计数通过 SPECT 校准)获得 EF 值, 与 2D-RNA 测定的 EF 的进行比较。 结果: 2D-RNA 测定的 EF 值与 SPECT100 校准后测定的 EF 值 (y = 0.89x + 6.62; R{sup 2} = 0.87) 及 SPECT30 (y = 0.87x + 8.40; R{sup 2} = 0.85) 校准后 EF 值具有高度相关性, 并且 SPECT100 (54 ± 15%) 和 SPECT30 (53 ± 16%) 测定的 EF 平均值与 2D-RNA 测定的 EF 平均值 (55 ± 15%) 非常接近。 但是, 在没有计数校准的情况下, SPECT100 (60 ± 18%) 和 SPECT30 (60 ± 18%) 测定的 EF 平均值会被高估。 结论: 高灵敏度 CZT 相机可在减少 70% 的注射剂量情况下测定左心室 EF 值, 结合计数校准可进一步提高与 2D-RNA测得的 EF 值的一致性。 关键词: 放射性核素血管造影; 血池 SPECT; CZT 相机; 左心室射血分数; 校准曲线。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Structural Characterization of Bimetallic Nanocrystal Electrocatalysts

Late transition metal nanocrystals find applications in heterogeneous catalysis such as plasmon-enhanced catalysis and as electrode materials for fuel cells, a zero-emission and sustainable energy technology. Their commercial viability for automotive transportation has steadily increased in recent years, almost exclusively due to the discovery of more efficient bimetallic nanocatalysts for the oxygen reduction reaction (ORR) at the cathode. Despite improvements to catalyst design, achieving high activity while maintaining durability is essential to further enhance their performance for this and other important applications in catalysis. Electronic effects arising from the generation of metal-metal interfaces, from plasmonic metals, and from lattice distortions, can vastly improve sorption properties at catalytic surfaces, while increasing durability.[1] Multimetallic lattice-strained nanoparticles are thus an interesting opportunity for fundamental research.[2,3] A colloidal synthesis approach is demonstrated to produce AuPd alloy and Pd@Au core-shell nanoicosahedra as catalysts for electro-oxidations. The nanoparticles are characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and large solid angle energy dispersive X-ray spectroscopy (EDS) on an FEI Talos 4-detector STEM/EDS system. Figure 1 shows bright-field (BF) and high-angle annular dark-field (HAADF) ac-STEM images of the alloy and core-shell nanoicosahedra together with EDS line-scans and elemental maps. These structures are unique in that the presence of twin boundaries, alloying, and core-shell morphology could create highly strained surfaces and interfaces. The shell thickness of the core-shell structures observed in HAADF-STEM images is tuned by adjusting the ratio between metal precursors (Figure 2a-f) to produce shells ranging from a few to several monolayers. Specific activity was measured in ethanol electro-oxidation to examine the effect of shell thickness on catalytic activity. A volcano relationship was observed for the core-shell nanoicosahedra having different Pd-shell thicknesses as Pd content is increased (Figure 2g). Durability tests are ongoing for the AuPd system; however, promising ORR materials and morphologies have also been synthesized for a more cost-effective Cu-based system of Cu-CuM (M = Pd, Rh, Pt) core-alloy-shell nanocrystals. The synthesis, characterization, and catalytic behavior of different high-index faceted morphologies of Cu-based materials towards ORR and methanol oxidation catalysis will be discussed, where we show how they exceed the performance of commercial Pd- and Pt- based catalysts. The development of new materials and their characterization is critical to understanding the effects of structure and composition on catalysis. Future efforts are directed at resolving these structures and more industrially relevant fuel cell catalysts in 3D through electron tomography.[4] References: [1] X. Huang, et al., Science 348 (2015) p. 1230. [2] P. Strasser, et al., Nat. Chem. 2 (2010) p. 454. [3] C. Chen, et al., Science 343 (2014) p. 1339. [4] Microscopy performed as part of a user project through ORNL s Center for Nanophase Materials Sciences, which is a U.S. DOE Office of Science User Facility, and instrumentation provided by the U.S. DOE Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities.

Cullen, David A↗
DOE OSTI2019

Acetonitrile contamination in the cathode of proton exchange membrane fuel cells and cell performance recovery

Acetonitrile contamination in an operating cell and performance recovery are investigated in detail by a series of electrochemical characterizations, including constant current operation, electrochemical impedance spectroscopy, cyclic voltammetry, linear scanning voltammetry and chronoamperometry. We demonstrate that 20 ppm of acetonitrile in the air stream causes an approximate 40% reduction in cell performance at 1 A cm -2 ; however, the neat air operation completely restores the single cell. Cell performance degradation and recovery display two distinguishable periods that correspond to the effect of catalyst activity and electrolyte proton conductivity, respectively. The potential effect on acetonitrile contamination is also studied in a non-operating H 2 /N 2 cell. The results indicate that low and high potentials cause a larger proton conductivity effect than a medium potential. Two recovery methods were conducted to restore cell performance after contamination in N 2 at different potentials. The neat air operation completely mitigated the poisoning effect in approximately 5 h regardless of contamination history; however, the N 2 purge and subsequent potential scans, even scanning up to 1.5 V vs hydrogen reference electrode, did not affect the poisoned cell. The liquid water generated in catalyst layers may play an important role during the recovery from acetonitrile contamination in a proton exchange membrane fuel cell.

25 ENERGY STORAGE↗
DOE OSTI2010

Evaluation of PV performance models and their impact on project risk.

Photovoltaic systems are often priced in $/W{sub p}, where Wp refers to the DC power rating of the modules at Standard Test Conditions (1000 W/m{sup 2}, 25 C cell temperature) and $ refers to the installed cost of the system. However, the true value of the system is in the energy it will produce in kWhs, not the power rating. System energy production is a function of the system design and location, the mounting configuration, the power conversion system, and the module technology, as well as the solar resource. Even if all other variables are held constant, the annual energy yield (kWh/kW{sup p}) will vary among module technologies because of differences in response to low-light levels and temperature. Understanding energy yield is a key part of understanding system value. System performance models are used during project development to estimate the expected output of PV systems for a given design and location. Performance modeling is normally done by the system designer/system integrator. Often, an independent engineer will also model system output during a due diligence review of a project. A variety of system performance models are available. The most commonly used modeling tool for project development and due diligence in the United States is probably PVsyst, while those seeking a quick answer to expected energy production may use PVWatts. In this paper, we examine the variation in predicted energy output among modeling tools and users and compare that to measured output.

14 SOLAR ENERGY↗
DOE OSTI2010

CIGS P1, P2, P3 Scribing Processes using a Pulse Programmable Industrial Fiber Laser: Preprint

We describe a novel set of laser processes for the CIGS P1, P2 and P3 scribing steps, the development of which has been enabled by a unique pulse-programmable fiber laser. We find that the unique pulse control properties of this 1064 nm wavelength laser have significant effects on the material removal dynamics of the various film layers in the CIGS material system. In the case of the P2 and P3processes, the shaped pulses create new laser/material interaction effects that permit the material to be cleanly and precisely removed with zero Heat Affected Zone (HAZ) at the edges of the scribe. The new P2 and P3 processes we describe demonstrate the first use of infrared nanosecond laser pulses that eliminate the HAZ and the consequent localized compositional changes in the CIGS absorbermaterial that result in poor shunt resistance. SEM micrographs and EDX compositional scans are presented. For the P1 scribe, we process the bi-layer molybdenum from the film side as well as through the glass substrate. Microscopic inspection and compositional analysis of the scribe lines are not sufficient to determine electrical and optical performance in working PV modules. Therefore, todemonstrate the applicability of the infrared pulse-programmable laser to all three scribing processes for thin-film CIGS, we fabricate small-size multiple-cell monolithically interconnected mini-modules in partnership with the National Renewable Energy Laboratory (Golden, Colorado). A total of four mini-modules are produced, two utilizing all laser scribing, and two with the P2 and P3 stepsmechanically scribed (by a third party) for reference. Mini-module performance data measured at NREL is presented, and we also discuss the commercialization potential of the new single-laser CIGS scribing process. Finally we present a phenomenological model to describe this physics underlying this novel ablation process.

14 SOLAR ENERGY↗
DOE OSTI2018

Iridium-Based Nanowires as Highly Active, Oxygen Evolution Reaction Electrocatalysts

Iridium-nickel (Ir-Ni) and iridium-cobalt (Ir-Co) nanowires have been synthesized by galvanic displacement and studied for their potential to increase the performance and durability of electrolysis systems. Performances of Ir-Ni and Ir-Co nanowires for the oxygen evolution reaction (OER) have been measured in rotating disk electrode half-cells and single-cell electrolyzers and compared with commercial baselines and literature references. The nanowire catalysts showed improved mass activity, by more than an order of magnitude compared with commercial Ir nanoparticles in half-cell tests. The nanowire catalysts also showed greatly improved durability, when acid-leached to remove excess Ni and Co. Both Ni and Co templates were found to have similarly positive impacts, although specific differences between the two systems are revealed. In single-cell electrolysis testing, nanowires exceeded the performance of Ir nanoparticles by 4-5 times, suggesting that significant reductions in catalyst loading are possible without compromising performance.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

C5 Benchmark Problem with Discrete Ordinate Radiation Transport Code DENOVO

The C5 benchmark problem proposed by the Organisation for Economic Co-operation and Development/Nuclear Energy Agency was modeled to examine the capabilities of Denovo, a three-dimensional (3-D) parallel discrete ordinates (S{sub N}) radiation transport code, for problems with no spatial homogenization. Denovo uses state-of-the-art numerical methods to obtain accurate solutions to the Boltzmann transport equation. Problems were run in parallel on Jaguar, a high-performance supercomputer located at Oak Ridge National Laboratory. Both the two-dimensional (2-D) and 3-D configurations were analyzed, and the results were compared with the reference MCNP Monte Carlo calculations. For an additional comparison, SCALE/KENO-V.a Monte Carlo solutions were also included. In addition, a sensitivity analysis was performed for the optimal angular quadrature and mesh resolution for both the 2-D and 3-D infinite lattices of UO{sub 2} fuel pin cells. Denovo was verified with the C5 problem. The effective multiplication factors, pin powers, and assembly powers were found to be in good agreement with the reference MCNP and SCALE/KENO-V.a Monte Carlo calculations.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2016

Cyclic performance tests of Sn/MWCNT composite lithium ion battery anodes at different temperatures

In this study tin-multi walled carbon nanotube (Sn-MWCNT) lithium ion battery anodes were produced and their electrochemical galvanostatic charge/discharge tests were conducted at various (25 °C, 35 °C, 50 °C) temperatures to determine the cyclic behaviors of anode at different temperatures. Anodes were produced via vacuum filtration and DC magnetron sputtering technique. Tin was sputtered onto buckypapers to form composite structure of anodes. SEM analysis was conducted to determine morphology of buckypapers and Sn-MWCNT composite anodes. Structural and phase analyses were conducted via X-ray diffraction and Raman Spectroscopy technique. CR2016 coin cells were assembled for electrochemical tests. Cyclic voltammetry test were carried out to determine the reversibility of reactions between anodes and reference electrode between 0.01-2.0 V potential window. Galvanostatic charge/discharge tests were performed to determine cycle performance of anodes at different temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Explicit temperature treatment in Monte Carlo neutron tracking routines - First results

This article discusses the preliminary implementation of the new explicit temperature treatment method to the development version Monte Carlo reactor physics code Serpent 2 and presents the first practical results calculated using the method. The explicit temperature treatment method, as introduced in [1], is a stochastic method for taking the effect of thermal motion into account on-the-fly in a Monte Carlo neutron transport calculation. The method is based on explicit treatment of the motion of target nuclei at collision sites and requires cross sections at 0 K temperature only, regardless of the number of temperatures in the problem geometry. The method includes a novel capability of modelling continuous temperature distributions. Test calculations are performed for two test cases, a PWR pin-cell and a HTGR system. The resulting k{sub eff} and flux spectra are compared to a reference solution calculated using Serpent 1.1.16 with Doppler-broadening rejection correction [2]. The results are in very good agreement with the reference and also the increase in calculation time due to the new method is on acceptable level although not fully insignificant. On the basis of the current study, the explicit treatment method can be considered feasible for practical calculations. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

In this report a novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

14 SOLAR ENERGY↗
DOE OSTI2011

Investigation of Path Dependence in Commercial Li-ion Cells Chosen for PHEV Duty Cycle Protocols (paper)

Path dependence is emerging as a premier issue of how electrochemical cells age in conditions that are diverse and variable in the time domain. For example, lithium-ion cells in a vehicle configuration will experience a variable combination of usage and rest periods over a range of temperature and state of charge (SOC). This is complicated by the fact that some aging can actually become worse (or better) when a lithium-ion cell is idle for extended periods under calendar-life (calL) aging, as opposed to cycle-life (cycL) conditions where the cell is used within a predictable schedule. The purpose of this study is to bridge the gap between highly idealized and controlled laboratory test conditions and actual field conditions regarding PHEV applications, so that field-type aging mechanisms can be mimicked and quantified in a repeatable laboratory setting. The main parameters are the magnitude and frequency of the thermal cycling, looking at isothermal, mild, and severe scenarios. To date, little is known about Li-ion aging effects caused by thermal cycling superimposed onto electrochemical cycling, and related path dependence. This scenario is representative of what Li-ion batteries will experience in vehicle service, where upon the typical start of a HEV/PHEV, the batteries will be cool or cold, will gradually warm up to normal temperature and operate there for a time, then will cool down after the vehicle is turned off. Such thermal cycling will occur thousands of times during the projected life of a HEV/PHEV battery pack. We propose to quantify the effects of thermal cycling on Li-ion batteries using a representative chemistry that is commercially available. The secondary Li-ion cells used in this study are of the 18650 configuration, have a nominal capacity rating of 1.9 Ah, and consist of a {LiMn2O4 + LiMn(1/3)Ni(1/3)Co(1/3)O2} cathode and a graphite anode. Electrochemical cycling is based on PHEV-relevant cycle-life protocols that are a combination of charge depleting (CD) and charge sustaining (CS) modes discussed in the Battery Test Manual for Plug-in Hybrid Electric Vehicles (INL, March 2008, rev0). A realistic duty cycle will involve both CD and CS modes, the proportion of each defined by the severity of the power demands. We assume that the cells will start each cycling day at 90% SOC, and that they will not be allowed to go below 35% SOC, with operation around 70% SOC being a nominal condition. The 35, 70, and 90% SOC conditions are also being used to define critical aspects of the related reference performance test (RPT) for this investigation. There are three primary components to the RPT, all assessed at room temperature: (A) static and residual capacity (SRC) over a matrix of current, (B) kinetics and pulse performance testing (PPT) over current for SOCs of interest, and (C) EIS for SOCs of interest. The RPT is performed on all cells every 30 day test interval, as well as a pulse-per-day to provide a quick diagnostic snapshot. Where feasible, we utilize various elements of Diagnostic Testing (DT) to characterize performance of the cells and to gain mechanistic-level knowledge regarding both performance features and limitations. We will present the rationale behind the experimental design, early data, and discuss the fundamental tools used to elucidate performance degradation mechanisms.

25 ENERGY STORAGE↗
DOE OSTI2022

Achieving robust somatic mutation detection with deep learning models derived from reference data sets of a cancer sample

Accurate detection of somatic mutations is challenging but critical in understanding cancer formation, progression, and treatment. We recently proposed NeuSomatic, the first deep convolutional neural network-based somatic mutation detection approach, and demonstrated performance advantages on in silico data. In this study, we use the first comprehensive and well-characterized somatic reference data sets from the SEQC2 consortium to investigate best practices for using a deep learning framework in cancer mutation detection. Using the high-confidence somatic mutations established for a cancer cell line by the consortium, we identify the best strategy for building robust models on multiple data sets derived from samples representing real scenarios, for example, a model trained on a combination of real and spike-in mutations had the highest average performance. The strategy identified in our study achieved high robustness across multiple sequencing technologies for fresh and FFPE DNA input, varying tumor/normal purities, and different coverages, with significant superiority over conventional detection approaches in general, as well as in challenging situations such as low coverage, low variant allele frequency, DNA damage, and difficult genomic regions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Evaluation of Photodiode and Thermopile Pyranometers for Photovoltaic Applications: Preprint

Accurately determining PV module performance in the field requires measurement of solar irradiance reaching the PV panel at a high level of accuracy and known uncertainty. Silicon detectors used in various solar energy measuring instruments including reference cells are potentially an attractive choice for multiple reasons that include faster responsivity than thermopile detectors, cheaper cost and lower maintenance. The main drawback though is the fact that the silicon detectors are only spectrally responsive in a narrow part of the solar spectrum. Therefore, to determine broadband solar irradiance a calibration factor that converts the narrowband response to broadband is required. Normally this calibration factor is a single number determined under standard conditions but then used for various scenarios including varying air-mass, panel orientation and atmospheric conditions. This would not have been an issue if all wavelengths that form the broadband spectrum responded uniformly to atmospheric constituents. Unfortunately the scattering and absorption signature varies widely across wavelengths and the calibration factor computed under certain test conditions is not appropriate for other conditions. This paper lays out the issues that will arise from the use of silicon detectors for PV performance measurement in the field. We also present a comparison of simultaneous spectral and broadband measurements from silicon and thermopile detectors and estimated measurement errors when using silicon devices for both array performance and resource assessment.

14 SOLAR ENERGY↗
DOE OSTI2012

Enhanced U(VI) release from autunite mineral by aerobic Arthrobacter sp. in the presence of aqueous bicarbonate

The bacterial effect on U(VI) release from the autunite mineral (Ca[(UO2)(PO4)]2·3H2O) was investigated to provide a more comprehensive understanding of the important microbiological processes affecting autunite stability within subsurface bicarbonate-bearing environments. Experiments were performed in a culture of the Arthrobacter oxydans G975 strain, herein referred to as G975, a soil bacterium previously isolated from Hanford Site soil. 91 mg of autunite powder and 50 mL of phosphorous-limiting sterile media were amended with bicarbonate (ranging between 1 and 10 mM) in glass reactor bottles and inoculated with the G975 strain after the dissolution of autunite was at steady state. SEM observations indicated that G975 formed a biofilm on the autunite surface and penetrated the mineral cleavages. The mineral surface colonization by bacteria tended to increase concomitantly with bicarbonate concentrations. Additionally, a sterile cultureware with inserts was used in non-contact dissolution experiments where autunite and bacteria cells were kept separately. The data suggest that G975 bacteria is able to enhance the release of U(VI) from autunite without direct contact with the mineral. In the presence of bicarbonate, the damage to bacterial cells caused by U(VI) toxicity was reduced, yielding similar values for total organic carbon (TOC) degradation and cell density compared to U(VI)-free controls. The presence of active bacterial cells greatly enhanced the release of U(VI) from autunite in bicarbonate-amended media.

42 ENGINEERING↗
DOE OSTI2020

Effects of composition and pressure on electronic states of iron in bridgmanite

Electronic states of iron in the lower mantle's dominant mineral, (Mg,Fe,Al)(Fe,Al,Si)O 3 bridgmanite, control physical properties of the mantle including density, elasticity, and electrical and thermal conductivity. However, the determination of electronic states of iron has been controversial, in part due to different interpretations of Mössbauer spectroscopy results used to identify spin state, valence state, and site occupancy of iron. We applied energy-domain Mössbauer spectroscopy to a set of four bridgmanite samples spanning a wide range of compositions: 10–50% Fe/total cations, 0–25% Al/total cations, 12–100% Fe 3+ /total Fe. Measurements performed in the diamond-anvil cell at pressures up to 76 GPa below and above the high to low spin transition in Fe 3+ provide a Mössbauer reference library for bridgmanite and demonstrate the effects of pressure and composition on electronic states of iron. Results indicate that although the spin transition in Fe 3+ in the bridgmanite B-site occurs as predicted, it does not strongly affect the observed quadrupole splitting of 1.4 mm/s, and only decreases center shift for this site to 0 mm/s at ~70 GPa. Thus center shift can easily distinguish Fe 3+ from Fe 2+ at high pressure, which exhibits two distinct Mössbauer sites with center shift ~1 mm/s and quadrupole splitting 2.4–3.1 and 3.9 mm/s at ~70 GPa. Correct quantification of Fe 3+ /total Fe in bridgmanite is required to constrain the effects of composition and redox states in experimental measurements of seismic properties of bridgmanite. Furthermore, in Fe-rich, mixed-valence bridgmanite at deep-mantle-relevant pressures, up to ~20% of the Fe may be a Fe 2.5+ charge transfer component, which should enhance electrical and thermal conductivity in Fe-rich heterogeneities at the base of Earth's mantle.

58 GEOSCIENCES↗
DOE OSTI2016

COLLISIONLESS ELECTRON–ION SHOCKS IN RELATIVISTIC UNMAGNETIZED JET–AMBIENT INTERACTIONS: NON-THERMAL ELECTRON INJECTION BY DOUBLE LAYER

The course of non-thermal electron ejection in relativistic unmagnetized electron–ion shocks is investigated by performing self-consistent particle-in-cell simulations. The shocks are excited through the injection of a relativistic jet into ambient plasma, leading to two distinct shocks (referred to as the trailing shock and leading shock) and a contact discontinuity. The Weibel-like instabilities heat the electrons up to approximately half of the ion kinetic energy. The double layers formed in the trailing and leading edges then accelerate the electrons up to the ion kinetic energy. The electron distribution function in the leading edge shows a clear, non-thermal power-law tail which contains ∼1% of electrons and ∼8% of the electron energy. Its power-law index is −2.6. The acceleration efficiency is ∼23% by number and ∼50% by energy, and the power-law index is −1.8 for the electron distribution function in the trailing edge. The effect of the dimensionality is examined by comparing the results of three-dimensional simulations with those of two-dimensional simulations. The comparison demonstrates that electron acceleration is more efficient in two dimensions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SU-E-I-84: Accuracy Comparison of Multi-Modality Image-Based Volumes of Rodent Solid Tumors Using In-Air Micro-CT Image Volume

Purpose: Tumor volume is considered as a better predictor for therapy response monitoring and tumor staging over Response Evaluation Criteria In Solid Tumors (RECIST) or World Health Organization (WHO) criteria. In this study, the accuracy of subcutaneous rodent tumor volumes using preclinical magnetic resonance imaging (MRI), micro-computed tomography (micro-CT) and ultrasound (US) equipment and with an external caliper was compared using in-air micro-CT image volume of excised tumors determined as reference tumor volume in our prior study. Methods: MR, US and micro-CT images of subcutaneous SCC4 head and neck tumor xenografts were acquired 4, 6, 9, 11 and 13 days after tumor cell inoculation. Before MR and US scans, caliper measurements were made. After tumors were excised, in-air micro-CT imaging and ex vivo caliper measurements were performed. Tumor volumes were calculated using formula V = (π/6)*a*b*c where a, b and c are the maximum diameters in three perpendicular dimensions determined by the three image modalities and caliper, and compared with reference tumor volume by linear regression analysis as well as Bland-Altman plots. A one-way Analysis of Variance (ANOVA) test was also performed to compare volumes among caliper measurements. Results: The correlation coefficients (R2) of the regression lines for tumor volumes measured by the three imaging modalities and caliper were 0.9939, 0.9669, 0.9806, 0.9274, 0.9619 and 0.9819 for MRI, US and micro-CT, caliperbeforeMRI, caliperbeforeUS and ex vivo caliper respectively. In Bland-Altman plots, the average of tumor volume difference from reference tumor volume (bias) was significant for caliper and micro- CT, but not for MRI and US. Comparison of caliper measurements showed a significant difference (p < 0.05). Conclusion: Using the in-air micro-CT image volume, tumor volume measured by MRI was the most accurate among the three imaging modalities. In vivo caliper volume measurements showed unreliability while ex vivo caliper measurements reduced errors.

60 APPLIED LIFE SCIENCES↗