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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

SCEDS: protein fragments for molecular replacement in Phaser

Protein fragments suitable for use in molecular replacement can be generated by normal-mode perturbation, analysis of the difference distance matrix of the original versus normal-mode perturbed structures, and SCEDS, a score that measures the sphericity, continuity, equality and density of the resulting fragments. A method is described for generating protein fragments suitable for use as molecular-replacement (MR) template models. The template model for a protein suspected to undergo a conformational change is perturbed along combinations of low-frequency normal modes of the elastic network model. The unperturbed structure is then compared with each perturbed structure in turn and the structurally invariant regions are identified by analysing the difference distance matrix. These fragments are scored with SCEDS, which is a combined measure of the sphericity of the fragments, the continuity of the fragments with respect to the polypeptide chain, the equality in number of atoms in the fragments and the density of C{sup α} atoms in the triaxial ellipsoid of the fragment extents. The fragment divisions with the highest SCEDS are then used as separate template models for MR. Test cases show that where the protein contains fragments that undergo a change in juxtaposition between template model and target, SCEDS can identify fragments that lead to a lower R factor after ten cycles of all-atom refinement with REFMAC5 than the original template structure. The method has been implemented in the software Phaser.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Exploring the speed and performance of molecular replacement with AMPLE using QUARK ab initio protein models

Two ab initio modelling programs solve complementary sets of targets, enhancing the success of AMPLE with small proteins. AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

An integrated mobile system for port security

An integrated mobile system for port security is presented. The system is designed to perform active investigations, by using the tagged neutron inspection technique, of suspect dangerous materials as well as passive measurements of neutrons and gamma rays to search and identify radioactive and special nuclear materials. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Delayed neutron fraction and prompt decay constant measurement in the MINERVE reactor using the PSI instrumentation

The critical decay constant (B/A), delayed neutron fraction (B) and generation time (A) of the Minerve reactor were measured by the Paul Scherrer Institut (PSI) and the Commissariat a l'Energie Atomique (CEA) in September 2014 using the Feynman-alpha and Power Spectral Density neutron noise measurement techniques. Three slightly subcritical configuration were measured using two 1-g {sup 235}U fission chambers. This paper reports on the results obtained by PSI in the near critical configuration (-2g). The most reliable and precise results were obtained with the Cross-Power Spectral Density technique: B = 708.4±9.2 pcm, B/A = 79.0±0.6 s{sup -1} and A 89.7±1.4 micros. Predictions of the same kinetic parameters were obtained with MCNP5-v1.6 and the JEFF-3.1 and ENDF/B-VII.1 nuclear data libraries. On average the predictions for B and B/A overestimate the experimental results by 5% and 11%, respectively. The discrepancy is suspected to come from either a corruption of the data or from the inadequacy of the point kinetic equations to interpret the measurements in the Minerve driven system. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

AlN/SiC MEMS for High-Temperature Applications

The creation of microelectromechanical systems (MEMS) that can operate through elevated temperatures would enable systems diagnostics and controls that are not possible with conventional-off-the-shelf components. The integration of silicon carbide (SiC) with aluminum nitride (AlN) has led to the fabrication of devices that can withstand elevated temperature anneals >935 °C. The results from a piezoelectric micromachined ultrasonic transducer (PMUT) and a microresonator are reported as demonstrations of the fabrication process. Testing the PMUT response before and after annealing at 935 °C led to a change in resonant frequency of less than 1%, which is attributable to a shift in film stress. The response of the microresonator was RF tested in situ up to 500 °C and showed no degradation in its electromechanical coupling coefficient. The resonant frequency decreased with temperature due to the temperature coefficient of Young's modulus, and the quality factor decreased with temperature and remained unrecoverable upon cooling. The degradation in the quality factor is suspected to be a result of oxidation of the titatium nitride (TiN) top electrode, which increases the resistivity and leads to an unrecoverable reduction in the quality factor. As a result, the robust piezoelectric response of AlN at these temperatures show that AlN is a very promising candidate for elevated temperature applications. [2019-0019]

42 ENGINEERING↗
DOE OSTI2012

Materials characterisation with the associated particle technique

Since the last past years, the Nuclear Measurement Laboratory of CEA Cadarache, France, together with Partners from European and National projects, has been studying the application of fast neutron interrogation with the Associated Particle Technique for material identification in different areas of homeland and maritime security, and for the characterisation of the materials constituting radioactive waste. Fast 14 MeV neutrons are produced from the H-3(H-2,n)alpha fusion reaction in a sealed tube neutron generator embedding an alpha detector. The alpha particle is used to tag neutron direction and emission time, thus allowing the electronic selection of neutron-induced gamma spectra in the voxels of interest. Gamma rays emitted by tagged neutron interactions on the present nuclei (C, O, N, Fe, Al, Si, Cl, etc.) are recorded with spectroscopic detectors and analysed to determine elemental proportions, thus allowing material identification. Investigations have been conducted for the detection of explosives, illicit drugs and contraband materials in cargo containers, for the inspection of objects lying on the sea floor suspected to contain explosives like mines, bombs, torpedoes, etc., for the recognition of an improvised chemical device, and for material identification in radioactive waste packages. Recently the detection of special nuclear materials is being investigated using time correlation analysis between induced fission particles, instead of gamma-ray spectroscopy. The paper presents an overview of these studies and last results. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Evaluating Synthetic Smart Meter Locations For Communication System Modeling

An important part of good communication models for smart grid applications, particularly when wireless protocols are used, is the location information of the nodes. We’ve developed metrics to assist in evaluating whether a given model with such information is representative of feeders found in the world. These metrics are applied to a set of feeder models with known good location information for the smart meter locations and compared to a set of feeder models with similar location information that is not expected to be representative of real-world feeders. The comparison reveals that the suspect models do not pass statistical tests utilizing the developed metrics, providing initial validation of the analysis technique.

smart meter, feeder model, GridLAB-D↗
DOE OSTI2018

Identifying Reverse-Bias Breakdown Sites in CuInxGa(1-x)Se2

CIGS mini-modules are stressed under reverse bias, resembling partial shading conditions, to predict and characterize where failure occurs. Partial shading can cause permanent damage in the form of 'wormlike' defects on thin-film modules due to thermal runaway. We use electroluminescence (EL) imaging and dark lock-in thermography (DLIT) to supplement current-voltage curves when reverse-bias breakdown occurs on various CIGS minimodules. For better understanding of how these defects originate and propagate, we have implemented a current-limited, reverse-bias stressing technique. This allowed for DLIT-based detection and detailed study of the region where breakdown initiates before thermal runaway leads to permanent damage. A correlation between suspected defect sites and actual breakdown has been determined using this method.

14 SOLAR ENERGY↗
DOE OSTI2025

Comparison of Nb 3 Sn Insulation Systems With as Received and De-Sized Glass

Epoxy cracking has been the main suspected contributor to training in Nb 3 Sn magnets for some time, as it leads to energy release and magnet quenching. Cracking in a superconducting composite can occur from several modes, and the likelihood of these modes is not well understood. Failure has been observed between insulation systems and the superconducting cable itself rather than within the cable or insulation. To target the behavior at the interface, samples have been fabricated and tested for Mode I fracture toughness in an adapted version of ASTM D5528. This work seeks to better characterize the fracture toughness of this interface to better understand how to model and design insulation systems.

Krave, Steven T. [Fermilab] (ORCID:000000021752145↗
DOE OSTI2016

Adaptive Visual Sort and Summary of Micrographic Images of Nanoparticles for Forensic Analysis

Forensic analysis of nanoparticles is often conducted through the collection and identifi- cation of electron microscopy images to determine the origin of suspected nuclear material. Each image is carefully studied by experts for classification of materials based on texture, shape, and size. Manually inspecting large image datasets takes enormous amounts of time. However, automatic classification of large image datasets is a challenging problem due to the complexity involved in choosing image features, the lack of training data available for effective machine learning methods, and the availability of user interfaces to parse through images. Therefore, a significant need exists for automated and semi-automated methods to help analysts perform accurate image classification in large image datasets. We present INStINCt, our Intelligent Signature Canvas, as a framework for quickly organizing image data in a web based canvas framework. Images are partitioned using small sets of example images, chosen by users, and presented in an optimal layout based on features derived from convolutional neural networks.

active canvas↗
DOE OSTI2017

Scheduled Sequential Compressed Spectrum Sensing for Wideband Cognitive Radios

The support for high data rate applications with the cognitive radio technology necessitates wideband spectrum sensing. However, it is costly to apply long-term wideband sensing and is especially difficult in the presence of uncertainty, such as high noise, interference, outliers, and channel fading. In this paper, we propose scheduling of sequential compressed spectrum sensing which jointly exploits compressed sensing (CS) and sequential periodic detection techniques to achieve more accurate and timely wideband sensing. Instead of invoking CS to reconstruct the signal in each period, our proposed scheme performs backward grouped-compressed-data sequential probability ratio test (backward GCD-SPRT) using compressed data samples in sequential detection, while CS recovery is only pursued when needed. This method on one hand significantly reduces the CS recovery overhead, and on the other takes advantage of sequential detection to improve the sensing quality. Furthermore, we propose (a) an in-depth sensing scheme to accelerate sensing decision-making when a change in channel status is suspected, (b) a block-sparse CS reconstruction algorithm to exploit the block sparsity properties of wide spectrum, and (c) a set of schemes to fuse results from the recovered spectrum signals to further improve the overall sensing accuracy. Finally, extensive performance evaluation results show that our proposed schemes can significantly outperform peer schemes under sufficiently low SNR settings.

42 ENGINEERING↗
DOE OSTI2017

A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements

An extension of the point kinetics model is developed in this paper to describe the neutron multiplicity response of a bare uranium object under interrogation by an associated particle imaging deuterium-tritium (D-T) measurement system. This extended model is used to estimate the total neutron multiplication of the uranium. Both MCNPX-PoliMi simulations and data from active interrogation measurements of highly enriched and depleted uranium geometries are used to evaluate the potential of this method and to identify the sources of systematic error. The detection efficiency correction for measured coincidence response is identified as a large source of systematic error. If the detection process is not considered, results suggest that the method can estimate total multiplication to within 13% of the simulated value. Values for multiplicity constants in the point kinetics equations are sensitive to enrichment due to (n, xn) interactions by D-T neutrons and can introduce another significant source of systematic bias. This can theoretically be corrected if isotopic composition is known a priori. Finally, the spatial dependence of multiplication is also suspected of introducing further systematic bias for high multiplication uranium objects.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Thermal neutron-induced single-event upsets in microcontrollers containing boron-10

Single-event upsets (SEUs) were measured in thermal neutron-irradiated microcontrollers with 65-nm node and 130-nm node SRAMs. The suspected upset mechanism is charge deposition from the energetic byproducts of 10 B thermal neutron capture. Although elemental analysis confirmed that both microcontrollers contain 10 B, only the 65-nm node microcontroller exhibited a strong response to thermal neutrons. Monte Carlo simulations were performed to investigate the effects of 11 B enrichment on thermal neutron-induced SEUs in a 65-nm SRAM node when boron is present in the p -type well, p -type source and drain, or tungsten plug. Simulations indicate that the byproducts of 10 B(n,α) 7 Li reactions are capable of generating sufficient charge to upset a 65-nm SRAM. Finally, the highest amount of charge deposition from 10 B(n,α) 7 Li reaction byproducts occurs when natural boron is used to dope the p -type source and drain regions. Simulations also show that the SEU cross section is non-negligible when 11 B-enriched boron is used for doping.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Asymmetric Dual Sensor Latency in Distributed Control

Considerable geographical separation between various phasor measurement unit sensor suites used in the wide-area damping control architecture results in time delays with varying steady-state and stochastic components. The consequences of asymmetric latent sensors used in a standard feedback configuration are presented, indicating that asymmetry of the delay provides not only a previously suspected modification to the argument of the loop transmission function, but also a potentially substantial impact on its modulus. Under particular delay configurations, the controller may experience the introduction of varying crossovers in the loop transmission, resulting in a shifting of control bandwidth and previously unconsidered (in)stability characteristics (e.g., alteration of relative stability margins). With consideration to the theoretical results provided, the optimal sensor location based on delay characteristics is provided. Finally, results of the study indicate that it is most frequently best practice to act on the most current sample in the feedback channel, rather than wait for precise time alignment of the delayed sensor.

42 ENGINEERING↗
DOE OSTI2014

VAST Challenge 2014: The Kronos Incident

The 2014 IEEE Visual Analytics Science and Technology (VAST) Challenge presented researchers with a single fictitious scenario: the disappearance of staff members of the GASTech oil and gas company on location on the island of Kronos. A group named the Protectors of Kronos (POK) was the prime suspect in the disappearance. Three mini-challenges and a grand challenge were offered. Mini-challenge 1 included multiple types of text data for participants to provide a timeline of key events and characterize the POK, mini-challenge 2 focused on individuals’ movement and financial data for participants to provide patterns of daily life, and mini-challenge 3 featured real-time streaming social media and emergency service data for participants to provide hostage and kidnapper information. The grand challenge asked the participants to integrate results and generate a synopsis of events. The VAST Challenge received 73 submissions from 13 countries

visual analytics, visualization, evaluation, VAST ↗
DOE OSTI2015

Identification and analysis of the bacterial endosymbiont specialized for production of the chemotherapeutic natural product ET-743

Ecteinascidin 743 (ET-743, Yondelis) is a clinically approved chemotherapeutic natural product isolated from the Caribbean mangrove tunicate Ecteinascidia turbinata . Researchers have long suspected that a microorganism may be the true producer of the anti-cancer drug, but its genome has remained elusive due to our inability to culture the bacterium in the laboratory using standard techniques. Here, we sequenced and assembled the complete genome of the ET-743 producer, Candidatus Endoecteinascidia frumentensis, directly from metagenomic DNA isolated from the tunicate. Analysis of the ~631 kb microbial genome revealed strong evidence of an endosymbiotic lifestyle and extreme genome reduction. Phylogenetic analysis suggested that the producer of the anti-cancer drug is taxonomically distinct from other sequenced microorganisms and could represent a new family of Gammaproteobacteria. The complete genome has also greatly expanded our understanding of ET-743 production and revealed new biosynthetic genes dispersed across more than 173 kb of the small genome. The gene cluster’s architecture and its preservation demonstrate that the drug is likely essential to the interactions of the microorganism with its mangrove tunicate host. In conclusion, taken together, these studies elucidate the lifestyle of a unique, and pharmaceutically-important microorganism and highlight the wide diversity of bacteria capable of making potent natural products.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Antibody dynamics to SARS‐CoV‐2 in asymptomatic COVID‐19 infections

Abstract Background The missing asymptomatic COVID‐19 infections have been overlooked because of the imperfect sensitivity of the nucleic acid testing (NAT). Globally understanding the humoral immunity in asymptomatic carriers will provide scientific knowledge for developing serological tests, improving early identification, and implementing more rational control strategies against the pandemic. Measure Utilizing both NAT and commercial kits for serum IgM and IgG antibodies, we extensively screened 11 766 epidemiologically suspected individuals on enrollment and 63 asymptomatic individuals were detected and recruited. Sixty‐three healthy individuals and 51 mild patients without any preexisting conditions were set as controls. Serum IgM and IgG profiles were further probed using a SARS‐CoV‐2 proteome microarray, and neutralizing antibody was detected by a pseudotyped virus neutralization assay system. The dynamics of antibodies were analyzed with exposure time or symptoms onset. Results A combination test of NAT and serological testing for IgM antibody discovered 55.5% of the total of 63 asymptomatic infections, which significantly raises the detection sensitivity when compared with the NAT alone (19%). Serum proteome microarray analysis demonstrated that asymptomatics mainly produced IgM and IgG antibodies against S1 and N proteins out of 20 proteins of SARS‐CoV‐2. Different from strong and persistent N‐specific antibodies, S1‐specific IgM responses, which evolved in asymptomatic individuals as early as the seventh day after exposure, peaked on days from 17 days to 25 days, and then disappeared in two months, might be used as an early diagnostic biomarker. 11.8% (6/51) mild patients and 38.1% (24/63) asymptomatic individuals did not produce neutralizing antibody. In particular, neutralizing antibody in asymptomatics gradually vanished in two months. Conclusion Our findings might have important implications for the definition of asymptomatic COVID‐19 infections, diagnosis, serological survey, public health, and immunization strategies.

Lei, Qing↗
DOE OSTI2022

Clinical practice gaps and challenges in non‐alcoholic steatohepatitis care: An international physician needs assessment

Abstract Background and aims Even as several pharmacological treatments for non‐alcoholic steatohepatitis (NASH) are in development, the incidence of NASH is increasing on an international scale. We aim to assess clinical practice gaps and challenges of hepatologists and endocrinologists when managing patients with NASH in four countries (Germany/Italy/United Kingdom/United States) to inform educational interventions. Methods A sequential mixed‐method design was used: qualitative semi‐structured interviews followed by quantitative online surveys. Participants were hepatologists and endocrinologists practising in one of the targeted countries. Interview data underwent thematic analysis and survey data were analysed with chi‐square and Kruskal‐Wallis tests. Results Most interviewees ( n = 24) and surveyed participants (89% of n = 224) agreed that primary care must be involved in screening for NASH, yet many faced challenges involving and collaborating with them. Endocrinologists reported low knowledge of which blood markers to use when suspecting NASH (56%), when to order an MRI (65%) or ultrasound/FibroScan® (46%), and reported sub‐optimal skills interpreting alanine aminotransferase (ALT, 37%) and aspartate aminotransferase (AST, 38%) blood marker test results, causing difficulty during diagnosis. Participants believed that more evidence is needed for upcoming therapeutic agents; yet, they reported sub‐optimal knowledge of eligibility criteria for clinical trials. Knowledge and skill gaps when managing comorbidities, as well as skill gaps facilitating patient lifestyle changes were reported. Conclusions Educational interventions are needed to address the knowledge and skill gaps identified and to develop strategies to optimize patient care, which include implementing relevant care pathways, encouraging referrals and testing, and multidisciplinary collaboration, as suggested by the recent Global Consensus statement on NAFLD.

Lazure, Patrice↗