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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Polyatomic interferences on high precision uranium isotope ratio measurements by MC-ICP-MS: Applications to environmental sampling for nuclear safeguards

Modern mass spectrometry and separation techniques have made measurement of major uranium isotope ratios a routine task; however accurate and precise measurement of the minor uranium isotopes remains a challenge as sample size decreases. One particular challenge is the presence of isobaric interferences and their impact on the accuracy of minor isotope 234 U and 236 U measurements. Furthermore, we present techniques used for routine U isotopic analysis of environmental nuclear safeguards samples and evaluate polyatomic interferences that negatively impact accuracy as well as methods to mitigate their impacts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

A multiple ion counter total evaporation (MICTE) method for precise analysis of plutonium by thermal ionization mass spectrometry

This study presents a total evaporation method for the analysis of sub-picogram quantities of Pu, utilizing an array of multiple ion counters. Data from three standards are presented to assess the utility of the technique. An external precision of 1.5% RSD (2σ) was achieved on aliquots approaching 100 fg for the minor 240 Pu isotope. Accurate analysis of <1 femtogram of 240 Pu, is achievable, with an external reproducibility of better than 10% RSD (2σ). Finally, this new technique represents a significant advance in the total evaporation method and will allow routine measurement of femtogram sized Pu samples by thermal ionization mass spectrometry.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

The Most Reliable and Precise Model to Determine Schottky Barrier Height and Photoelectron Yield Spectroscopy

Schottky barrier height (SBH), φ, plays a crucial role in the design of electronic and photo-electronic devices. In order to reckon SBH via internal photoemission (IPE), the technique is through extrapolating square root of IPE yield-and cube root of IPE yield-photon energy plots to zero before this work, this work was motivated by the most reliable and precise model to determine the SBH via IPE. A phenomenological model for connection IPE quantum yield and photon energy has been successfully established based on Fermi–Dirac distribution. The results of experimental observations fitted via the model indicate that the modeled quantum yield agrees well with experimental data. This model emphasizes the threshold of photon energy for calculating SBH, and the SBH of InN/GaN, p-type GaP/p-type Si, Pt/GaP, Au/GaAs, Si/SiO{sub 2} and Cu/SiO{sub 2} were obtained with high reliability after the method had been applied.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Improved Precision and Accuracy of Quantification of Rare Earth Element Abundances via Medium-Resolution LA-ICP-MS

Laser ablation ICP-MS enables streamlined, high-sensitivity measurements of rare earth element (REE) abundances in geological materials. However, many REE isotope mass stations are plagued by isobaric interferences, particularly from diatomic oxides and argides. In this study, we compare REE abundances quantitated from mass spectra collected with low-resolution (m/Δm = 300 at 5% peak height) and medium-resolution (m/Δm = 2500) mass discrimination. A wide array of geological samples was analyzed, including USGS and NIST glasses ranging from mafic to felsic in composition, with NIST 610 employed as the bracketing calibrating reference material. The medium-resolution REE analyses are shown to be significantly more accurate and precise (at the 95% confidence level) than low-resolution analyses, particularly in samples characterized by low (<μg/g levels) REE abundances. A list of preferred mass stations that are least susceptible to isobaric interferences is reported. These findings impact the reliability of REE abundances derived from LA-ICP-MS methods, particularly those relying on mass analyzers that do not offer tuneable mass-resolution and/or collision cell technologies that can reduce oxide and/or argide formation. .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

3D Reconstruction of a High-Energy Diffraction Microscopy Sample Using Multi-modal Serial Sectioning with High-Precision EBSD and Surface Profilometry

High-energy diffraction microscopy (HEDM) combined with in situ mechanical testing is a powerful nondestructive technique for tracking the evolving microstructure within polycrystalline materials during deformation. This technique relies on a sophisticated analysis of X-ray diffraction patterns to produce a three-dimensional reconstruction of grains and other microstructural features within the interrogated volume. However, it is known that HEDM can fail to identify certain microstructural features, particularly smaller grains or twinned regions. Characterization of the identical sample volume using high-resolution surface-specific techniques, particularly electron backscatter diffraction (EBSD), can not only provide additional microstructure information about the interrogated volume but also highlight opportunities for improvement of the HEDM reconstruction algorithms. In this study, a sample fabricated from undeformed “low solvus, high refractory” nickel-based superalloy was scanned using HEDM. The volume interrogated by HEDM was then carefully characterized using a combination of surface-specific techniques, including epi-illumination optical microscopy, zero-tilt secondary and backscattered electron imaging, scanning white light interferometry, and high-precision EBSD. Custom data fusion protocols were developed to integrate and align the microstructure maps captured by these surface-specific techniques and HEDM. The raw and processed data from HEDM and serial sectioning have been made available via the Materials Data Facility (MDF) at https://doi.org/10.18126/4y0p-v604 for further investigation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Experimental and FEM Study of Residual Stresses During Ultra-Precision Turning of Aluminum 2024-T3

Aluminum 2024-T3 is commonly used in ultra-precision turning. In this study, the residual stresses of aluminum 2024-T3 were investigated by the finite element method (FEM) and a series of cutting experiments. The effects of depth of cut, cutting speed, rake angle and tool edge radius on the residual stresses were discussed by FEM. Moreover, an orthogonal simulation experiment was also conducted. The order of the strong-to-weak sequence of factors on residual stresses in cutting direction is the rake angle, tool edge radius, depth of cut and cutting speed. The cutting experiments were conducted and the surface residual stresses in the cutting direction were measured by X-ray diffraction. The experimental results showed that increasing cutting speed and decreasing tool edge radius can reduce the surface residual stresses.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Local quantum uncertainty guarantees the measurement precision for two coupled two-level systems in non-Markovian environment

Quantum Fisher information (QFI) is an important feature for the precision of quantum parameter estimation based on the quantum Cramér–Rao inequality. When the quantum state satisfies the von Neumann–Landau equation, the local quantum uncertainty (LQU), as a kind of quantum correlation, present in a bipartite mixed state guarantees a lower bound on QFI in the optimal phase estimation protocol (Girolami et al., 2013). However, in the open quantum systems, there is not an explicit relation between LQU and QFI generally. In this paper, we study the relation between LQU and QFI in open systems which is composed of two interacting two-level systems coupled to independent non-Markovian environments with the entangled initial state embedded by a phase parameter θ. The analytical calculations show that the QFI does not depend on the phase parameter θ, and its decay can be restrained through enhancing the coupling strength or non-Markovianity. Meanwhile, the LQU is related to the phase parameter θ and shows plentiful phenomena. In particular, we find that the LQU can well bound the QFI when the coupling between the two systems is switched off or the initial state is Bell state.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Precision measurement of relative γ-ray intensities from the decay of 61Cu

A discrepancy, well outside reported uncertainties, has been observed between the accepted and measured values of the intensity ratio of the two strongest γ-ray following 61 Cu β + decay. This discrepancy has significant impact since the nat Ni(d,x) 61 Cu reaction has historically been one of only a few IAEA recommendations for use as a deuteron flux monitor and a considerable number of published cross sections measured in ratio to that beam monitor cross section may depend on the choice of either the first or second strongest ray in those calculations. To determine the magnitude of this error most precisely, over a hundred separate measurements of the 283 keV to 656 keV γ-ray emission ratio were collected from seven experiments and a variety of detectors and detection geometries. A weighted average of all these measurements indicates an error in the value listed in the Nuclear Data Sheets of 11% in either the primary or second-highest intensity γ-ray of 61 Cu, potentially introducing an 11% error in 61 Cu production cross section measurements, cross sections using nickel activation as a deuteron beam current monitor, or in dose rates when 61 Cu is used in nuclear medicine. General agreement with the Data Sheets with ten other intensity ratios suggests the most probable error is in the secondary (656 keV) emission, which accordingly should be updated from 10.8% to 9.69%.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Analysis of the cyanobacterial amino acid metabolism with a precise genome-scale metabolic reconstruction of Anabaena sp. UTEX 2576

Filamentous cyanobacteria such as Anabaena sp. UTEX 2576 (a.k.a., Nostoc sp. PCC 7120) are a sustainable platform for commodity and specialty chemical production. Anabaena is a model cyanobacterium adopted to study production of nitrogen-containing metabolites useful for chemical, cosmetic, and pharmaceutical industries. Therefore, a precise description of the Anabaena metabolic network is desired to analyze their amino-acid metabolism and elucidate potential applications of these cyanobacteria as host organisms for biotechnological production. Secondary metabolite production depends on the metabolic availability of amino acids. We provide new insight on the biotechnological utilization of Anabaena after predicting phycocyanobilin and amino-acid production rates, using a genome-scale metabolic model (iDN1004). This metabolic reconstruction is a highly comprehensive representation of the global metabolism of Anabaena, which also contains experimental biomass equations and constraints under photoautotrophic and photodiazotrophic growth. Modelling results ranked proteinogenic amino acids based on predicted metabolic fluxes through amino-acid producing reactions. From these, l-aspartate, glycine, l-serine, l-valine, l-alanine, l-threonine, and l-leucine were selected as the best branching points to conduct metabolic engineering, where l-aspartate, l-serine, l-valine and glycine serve as potential precursors of the secondary metabolites Schizokinen (a siderophore), Sphingosine (a ceramide), Lyngbyatoxin A (an alkaloid), and Shinorine (a sunscreen).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

The catalytic behavior of precisely synthesized Pt–Pd bimetallic catalysts for use as diesel oxidation catalysts

The demands of stricter diesel engine emission regulations have created challenges for current exhaust systems. With advances in low-temperature internal combustion engines and their operations, advances must also be made in vehicle exhaust catalysts. Most current diesel oxidation catalysts use heavy amounts of precious group metals (PGMs) for hydrocarbon (HC), CO, and NO oxidation. These catalysts are expensive and are most often synthesized with poor bimetallic interaction and dispersion. In this paper, the goal was to study the effect of aging on diesel emission abatement of Pt–Pd bimetallic nanoparticles precisely prepared with different morphologies: well dispersed core–shell vs. well dispersed homogeneously alloyed vs. poorly dispersed, poorly alloyed particles. Alumina and silica supports were studied. Particle morphology and dispersion were analyzed before and after hydrothermal treatments by XRD, EDX, and STEM. Reactivity as a function of aging was measured in simulated diesel engine exhaust. While carefully controlled bimetallic catalyst nanoparticle structure has a profound influence on initial or low temperature catalytic activity, the differences in behavior disappear with higher temperature aging as thermodynamic equilibrium is achieved. The metallic character of Pt-rich alumina-supported catalysts is such that behavior rather closely follows the Pt–Pd metal phase diagram. Nanoparticles disparately composed as well-dispersed core–shell (via seq-SEA), well-dispersed homogeneously alloyed (via co-SEA), and poorly dispersed, poorly alloyed (via co-DI) end up as well alloyed, large particles of almost the same size and activity. With Pd-rich systems, the oxidation of Pd also figures into the equilibrium, such that Pd-rich oxide phases appear in the high temperature forms along with alloyed metal cores. Finally, the small differences in activity after high temperature aging can be attributed to the synthesis methods, sequential SEA and co-DI which give rise, after aging, to a bimetallic surface enriched in Pd.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Precision measurement of relative permittivity of aluminum oxide for a high power resonant waveguide window with low return loss

An iterative method of estimating permittivity and window thickness with high precision is developed for half wavelength resonant waveguide windows for use in a lower hybrid launcher for DIII-D. The high Q factor of half-wavelength windows results in extreme sensitivity of return loss on small deviations in permittivity. Permittivity and loss tangent measurements of Morgan AL-995 99.5% aluminum oxide ceramic using a waveguide resonant cavity per ASTM D2520-13 determine variation of permittivity with frequency. Measurement of window resonant frequency in conjunction with the slope of permittivity from waveguide cavity measurements determine required thickness of a resonant window within 5 MHz of the desired resonant frequency. Methods to improve measurement accuracy of resonant peaks on a vector network analyzer are discussed. A sensitivity study to dimensional variations in window or sample rod geometry, and shift in resonant frequency due to RF heating of the window material is conducted.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Precision masses for studies of the astrophysical r process

Half of the elements heavier than iron (Z > 26) are thought to be created through the astrophysical r process, whereby nuclides are produced via a rapid series of nuclear reactions that are postulated to occur in high temperature and neutron density environments such as supernovae or merging neutron stars. The nucleosynthetic path that describes the sequence of reactions through the chart of nuclides strongly depends on the neutron-separation energies of the nuclei. Until recently, however, almost all of these neutron-rich nuclei were not within reach of accelerator facilities, and therefore simulations of the r process had to rely on mass models for input into the calculations. Now, with the advent of facilities such as CARIBU at Argonne National Laboratory, the masses of many nuclides along the r-process path can be determined precisely with Penning trap mass spectrometers coupled to these facilities. More than 70 nuclides have been measured with the Canadian Penning Trap mass spectrometer alone in the past year, which overlap and complement results from other Penning trap mass spectrometers, and first calculations with these new masses suggest the timescale of the r process through the tin isotopes is delayed much more strongly than mass models would suggest.

Clark, Jason↗
DOE OSTI2012

On-Line Use of Three-Dimensional Marker Trajectory Estimation From Cone-Beam Computed Tomography Projections for Precise Setup in Radiotherapy for Targets With Respiratory Motion

Purpose: To develop and evaluate accurate and objective on-line patient setup based on a novel semiautomatic technique in which three-dimensional marker trajectories were estimated from two-dimensional cone-beam computed tomography (CBCT) projections. Methods and Materials: Seven treatment courses of stereotactic body radiotherapy for liver tumors were delivered in 21 fractions in total to 6 patients by a linear accelerator. Each patient had two to three gold markers implanted close to the tumors. Before treatment, a CBCT scan with approximately 675 two-dimensional projections was acquired during a full gantry rotation. The marker positions were segmented in each projection. From this, the three-dimensional marker trajectories were estimated using a probability based method. The required couch shifts for patient setup were calculated from the mean marker positions along the trajectories. A motion phantom moving with known tumor trajectories was used to examine the accuracy of the method. Trajectory-based setup was retrospectively used off-line for the first five treatment courses (15 fractions) and on-line for the last two treatment courses (6 fractions). Automatic marker segmentation was compared with manual segmentation. The trajectory-based setup was compared with setup based on conventional CBCT guidance on the markers (first 15 fractions). Results: Phantom measurements showed that trajectory-based estimation of the mean marker position was accurate within 0.3 mm. The on-line trajectory-based patient setup was performed within approximately 5 minutes. The automatic marker segmentation agreed with manual segmentation within 0.36 {+-} 0.50 pixels (mean {+-} SD; pixel size, 0.26 mm in isocenter). The accuracy of conventional volumetric CBCT guidance was compromised by motion smearing ({<=}21 mm) that induced an absolute three-dimensional setup error of 1.6 {+-} 0.9 mm (maximum, 3.2) relative to trajectory-based setup. Conclusions: The first on-line clinical use of trajectory estimation from CBCT projections for precise setup in stereotactic body radiotherapy was demonstrated. Uncertainty in the conventional CBCT-based setup procedure was eliminated with the new method.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Precision Hypofractionated Radiation Therapy in Poor Performing Patients With Non-Small Cell Lung Cancer: Phase 1 Dose Escalation Trial

Purpose: Treatment regimens for locally advanced non-small cell lung cancer (NSCLC) give suboptimal clinical outcomes. Technological advancements such as radiation therapy, the backbone of most treatment regimens, may enable more potent and effective therapies. The objective of this study was to escalate radiation therapy to a tumoricidal hypofractionated dose without exceeding the maximally tolerated dose (MTD) in patients with locally advanced NSCLC. Methods and Materials: Patients with stage II to IV or recurrent NSCLC and Eastern Cooperative Oncology Group performance status of 2 or greater and not candidates for surgical resection, stereotactic radiation, or concurrent chemoradiation were eligible. Highly conformal radiation therapy was given to treat intrathoracic disease in 15 fractions to a total of 50, 55, or 60 Gy. Results: Fifty-five patients were enrolled: 15 at the 50-Gy, 21 at the 55-Gy, and 19 at the 60-Gy dose levels. A 90-day follow-up was completed in each group without exceeding the MTD. With a median follow-up of 12.5 months, there were 93 grade ≥3 adverse events (AEs), including 39 deaths, although most AEs were considered related to factors other than radiation therapy. One patient from the 55- and 60-Gy dose groups developed grade ≥3 esophagitis, and 5, 4, and 4 patients in the respective dose groups experienced grade ≥3 dyspnea, but only 2 of these AEs were considered likely related to therapy. There was no association between fraction size and toxicity (P=.24). The median overall survival was 6 months with no significant differences between dose levels (P=.59). Conclusions: Precision hypofractionated radiation therapy consisting of 60 Gy in 15 fractions for locally advanced NSCLC is generally well tolerated. This treatment regimen could provide patients with poor performance status a potent alternative to chemoradiation. This study has implications for the cost effectiveness of lung cancer therapy. Additional studies of long-term safety and efficacy of this therapy are warranted.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

The Quest for Evidence for Proton Therapy: Model-Based Approach and Precision Medicine

Purpose: Reducing dose to normal tissues is the advantage of protons versus photons. We aimed to describe a method for translating this reduction into a clinically relevant benefit. Methods and Materials: Dutch scientific and health care governance bodies have recently issued landmark reports regarding generation of relevant evidence for new technologies in health care including proton therapy. An approach based on normal tissue complication probability (NTCP) models has been adopted to select patients who are most likely to experience fewer (serious) adverse events achievable by state-of-the-art proton treatment. Results: By analogy with biologically targeted therapies, the technology needs to be tested in enriched cohorts of patients exhibiting the decisive predictive marker: difference in normal tissue dosimetric signatures between proton and photon treatment plans. Expected clinical benefit is then estimated by virtue of multifactorial NTCP models. In this sense, high-tech radiation therapy falls under precision medicine. As a consequence, randomizing nonenriched populations between photons and protons is predictably inefficient and likely to produce confusing results. Conclusions: Validating NTCP models in appropriately composed cohorts treated with protons should be the primary research agenda leading to urgently needed evidence for proton therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Phase 1/2 Study of the Addition of Cisplatin to Adjuvant Chemotherapy With Image Guided High-Precision Radiation Therapy for Completely Resected Gastric Cancer

Purpose: Locoregional recurrence is common after surgery for gastric cancer. Adjuvant therapy improves outcomes but with toxicity. This phase 1/2 study investigated infusional 5-fluorouracil (5-FU) in combination with biweekly cisplatin delivered concurrently with image guided high-precision radiation therapy. Methods and Materials: Eligible patients had completely resected stage IB to IV (Union for International Cancer Control TNM 6th edition) nonmetastatic gastric adenocarcinoma. Treatment constituted 12 weeks of infusional 5-FU (200 mg/m{sup 2}/day) with cisplatin added in a standard 3 + 3 dose escalation protocol (0, 20, 30, and 40 mg/m{sup 2}) during weeks 1, 3, 5, and 7, and an additional week 9 dose in the final cohort. Radiation therapy (45 Gy in 25 fractions) was delivered during weeks 3 to 7. Maximum tolerated dose (MTD) was determined in phase 1 and confirmed in phase 2. Results: Among the 55 patients (median age, 54 years; range 28-77 years; 55% male), the median follow-up time was 3.0 years (range, 0.3-5.3 years). Five patients in phase 1 experienced dose-limiting toxicity, and MTD was determined as 4 cycles of 40 mg/m{sup 2} cisplatin. Twenty-seven patients were treated at MTD. Acute grade 3 to 4 toxicity rate was 37.0% at MTD and 29.1% across all dose levels. No treatment-related deaths occurred. Fourteen patients experienced recurrent disease. The 2-year overall survival (OS) and relapse-free survival were 85% and 74%, respectively. Median OS has not been reached. Quality of life (QOL) was impaired during treatment, but most scores recovered by 4 weeks. Conclusion: Cisplatin can be safely delivered with 5-FU–based chemoradiation therapy. Acute toxicity was acceptable, and patient-reported QOL showed the regimen was tolerable. Outcomes are encouraging and justify further study of this regimen.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Personalising Prostate Radiotherapy in the Era of Precision Medicine: A Review

Prostate cancer continues to be the most commonly diagnosed cancer among Canadian men. The introduction of routine screening and advanced treatment options have allowed for a decrease in prostate cancer-related mortality, but outcomes following treatment continue to vary widely. In addition, the overtreatment of indolent prostate cancers causes unnecessary treatment toxicities and burdens health care systems. Accurate identification of patients who should undergo aggressive treatment, and those which should be managed more conservatively, needs to be implemented. More tumour and patient information is needed to stratify patients into low-, intermediate-, and high-risk groups to guide treatment options. This paper reviews the current literature on personalised prostate cancer management, including targeting tumour hypoxia, genomic and radiomic prognosticators, and radiobiological tumour targeting. A review of the current applications and future directions for the use of big data in radiation therapy is also presented. Prostate cancer management has a lot to gain from the implementation of personalised medicine into practice. Using specific tumour and patient characteristics to personalise prostate radiotherapy in the era of precision medicine will improve survival, decrease unnecessary toxicities, and minimise the heterogeneity of outcomes following treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Precision current regulator for NMR electromagnets

When using electromagnets or non-persistent superconducting magnets, the field stability can be directly proportional to the current stability. We present in this report a simple design for a current regulator based upon a high-precision, dc-dc fluxgate transformer. The output current and NMR frequency are stabilized by about a factor of 50, over times of order one hour. The method can be applied to essentially any current supply.

59 BASIC BIOLOGICAL SCIENCES↗