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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 OSTI2014

Understanding I/O workload characteristics of a Peta-scale storage system

Understanding workload characteristics is critical for optimizing and improving the performance of current systems and software, and architecting new storage systems based on observed workload patterns. In this paper, we characterize the I/O workloads of scientific applications of one of the world's fastest high performance computing (HPC) storage cluster, Spider, at the Oak Ridge Leadership Computing Facility (OLCF). OLCF flagship petascale simulation platform, Titan, and other large HPC clusters, in total over 250 thousands compute cores, depend on Spider for their I/O needs. We characterize the system utilization, the demands of reads and writes, idle time, storage space utilization, and the distribution of read requests to write requests for the Peta-scale Storage Systems. From this study, we develop synthesized workloads, and we show that the read and write I/O bandwidth usage as well as the inter-arrival time of requests can be modeled as a Pareto distribution. We also study the I/O load imbalance problems using I/O performance data collected from the Spider storage system.

I/O↗
DOE OSTI2025

Performance evaluations of signed and unsigned noisy approximate quantum Fourier arithmetic

The Quantum Fourier Transform (QFT) grants competitive advantages, especially in resource usage and circuit approximation, for performing arithmetic operations on quantum computers, and offers a potential route toward a numerical quantum-computational paradigm. In this paper, we utilize efficient techniques to implement QFT-based integer addition and multiplications. These operations are fundamental to various quantum applications including Shor’s algorithm, weighted-sum optimization problems in data processing and machine learning, and quantum algorithms requiring inner products. We carry out performance evaluations of these implementations based on IBM’s superconducting-qubit architecture using different compatible noise models. We isolate the sensitivity of the component quantum circuits on both one-/two-qubit gate error rates, and the number of the arithmetic operands’ superposed integer states. We analyze performance and identify the most effective approximation depths for unsigned quantum addition and quantum multiplication within the given context. We then perform a similar analysis of signed addition and compare to the unsigned results. We observe significant dependency of the optimal approximation depth on the degree of machine noise and the number of superposed states in certain performance regimes. Finally, we elaborate on the algorithmic challenges—relevant to signed, unsigned, modular and non-modular versions—that could also be applied to current implementations of QFT-based subtraction, division, exponentiation, and their potential tensor extensions. Here, we analyze the performance trends in our results and speculate on possible future developments within this computational paradigm.

Computational models↗
DOE OSTI2016

State Space Truncation with Quantified Errors for Accurate Solutions to Discrete Chemical Master Equation

The discrete chemical master equation (dCME) provides a general framework for studying stochasticity in mesoscopic reaction networks. Since its direct solution rapidly becomes intractable due to the increasing size of the state space, truncation of the state space is necessary for solving most dCMEs. It is therefore important to assess the consequences of state space truncations so errors can be quantified and minimized. Here we describe a novel method for state space truncation. By partitioning a reaction network into multiple molecular equivalence groups (MEGs), we truncate the state space by limiting the total molecular copy numbers in each MEG. We further describe a theoretical framework for analysis of the truncation error in the steady-state probability landscape using reflecting boundaries. By aggregating the state space based on the usage of a MEG and constructing an aggregated Markov process, we show that the truncation error of a MEG can be asymptotically bounded by the probability of states on the reflecting boundary of the MEG. Furthermore, truncating states of an arbitrary MEG will not undermine the estimated error of truncating any other MEGs. We then provide an overall error estimate for networks with multiple MEGs. To rapidly determine the appropriate size of an arbitrary MEG, we also introduce an a priori method to estimate the upper bound of its truncation error. This a priori estimate can be rapidly computed from reaction rates of the network, without the need of costly trial solutions of the dCME. As examples, we show results of applying our methods to the four stochastic networks of (1) the birth and death model, (2) the single gene expression model, (3) the genetic toggle switch model, and (4) the phage lambda bistable epigenetic switch model. We demonstrate how truncation errors and steady-state probability landscapes can be computed using different sizes of the MEG(s) and how the results validate our theories. Overall, the novel state space truncation and error analysis methods developed here can be used to ensure accurate direct solutions to the dCME for a large number of stochastic networks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

A New Recycled Al–Si–Mg Alloy for Sustainable Structural Die Casting Applications

The use of secondary aluminum for structural components in the automotive industry is limited by the high Fe contents in recycled alloys which often result in the formation of brittle β-Al 5 FeSi phase which reduces the ductility of aluminum castings. In this study, a new secondary Al-Si-Mg alloy with high Fe content (about 0.44 wt.%) was developed for die casting applications. Based on thermodynamic modeling, manganese was added to obtain a designed Fe-to-Mn ratio of 2 which successfully suppressed the formation of β-Al 5 FeSi phase, by forming α-Al 15 (Fe,Mn) 3 Si 2 phase with rounded or hexagonal morphology. Additionally, a fine needle-like π-Al 8 FeMg 3 Si 2 phase was also formed within the eutectic regions. The new recycled alloy showed comparable mechanical properties in as-cast and heat treated (T5 and T6) conditions to three major primary die cast alloys (≤ 0.2 wt.% Fe) with similar composition. Ductility up to 7.4% from tensile elongation was achieved in as-cast recycled alloy due to the modification and refinement of α-Al 15 (Fe,Mn) 3 Si 2 by Mn and Sr additions. Tensile elongation was further improved to 9.1% after T6 treatment as a result of dissolution of π-Al 8 FeMg 3 Si 2 phase, defragmentation of α-Al 15 (Fe,Mn) 3 Si 2 and the spheroidization of Si phase. This new alloy provides a promising path for increasing usage of recycled aluminum with high Fe content in structural die castings for automotive and other applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Kinetic Modeling of the Silicothermic Reduction of Manganese Oxide from Slag

A model was developed to describe the mixed rate control kinetics in systems with MnO-SiO{sub 2}-CaO-Al{sub 2}O{sub 3} slags and Fe-Si metal droplets. During the reaction of Fe-Si droplets and slag, Mn{sup 2+} transport was found to be part of controlling the system but could not sufficiently describe all initial conditions (chiefly, changes to initial silicon content). The current model describes the kinetics of the stated system and offers answers to the question of rate control; the model has been fitted to nine datasets of varying initial conditions including initial [Si], initial (MnO), initial droplet size, and reaction temperature. The fitted mass transfer coefficients for metal and slag were 2.3 × 10{sup −4} and 6.7 × 10{sup −4} m/s, respectively; these values are constant across the nine datasets. Previous claims about the efficiency of silicon usage in reducing manganese have been modified; it appears that the formation of silica is favored throughout the reaction, but that the formation of a silicon monoxide gas layer on the metal surface dramatically impacts the rate of reaction. As a measure of overall fit of the model, the average of the root-mean-square errors for all datasets is 14 pct. Mass transport in slag is twice as influential on rate control as the metal phase. The simultaneous transport of both Mn{sup 2+} and silicate dimers controls mass transport in the slag. Both [Si] and [Mn] can control from the metal side but are dependent on the initial conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Oxidation Behavior of Copper Concentrate, Gold Concentrate, and Their Mixtures Between 1173 K (900 °C) and 1373 K (1100 °C)

Gold is typically extracted from ores using a cyanidation process. However, environmental regulations and low productivity are the main drawbacks of cyanide usage. Alternative technologies for gold extraction are being studied although development of any new technology necessitates additional investments. In South Korea, recovery of gold and silver is performed by the local copper producer by feeding gold concentrate into a smelter. An integrated copper-making process might be an efficient and feasible alternative for the extraction of precious metals without the use of toxic cyanide. Installed exhaust gas cleaning system of copper smelter would minimize the toxic effects of hazardous elements (arsenic, bismuth, antimony, etc.) contained in gold concentrates. A kinetic and thermodynamic understanding of the effects of gold concentrates on copper metallurgy is necessary for the operation. The effects of various parameters on the oxidation kinetics of sulfides were investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Performance of Functionally Graded Thermoelectric Materials and Devices: A Review

Direct energy conversion using thermoelectric generators (TEGs) is a research area of growing interest because of its potential for increasing energy efficiency. Bulk thermoelectric modules are used widely in industry as Peltier cooling devices. Currently, only bismuth telluride modules are commercially available for power generation. Significant efforts have been put into exploring promising materials and techniques to improve the figure of merit ( zT ) at laboratory scale (5–20 g). A variety of techniques have been investigated to improve the output and useful temperature range for common industrial TEGs made from bulk polycrystalline materials including segmentation, geometric pinning, and property gradients. However, the improvement in zT at device level (500–1000 g and up) is exceptionally limited. In addition, the thermal degradation of TEGs occurs when cracks form due to thermal stresses that arise from transient heat sources, which consequently lead to a decreased lifetime. Functionally graded material (FGM) thermoelectrics in bulk and polycrystalline form have been developed to mitigate some of these issues by improving the temperature bandwidth, current output range, and lifetime. The present work provides a review of functionally graded TEGs, including their manufacturing, usage and current techniques for improving their performance. Furthermore, this article also provides a pathway to additional research and approaches for improving the efficiency and temperature range, as well as reducing the property degradation of bulk polycrystalline TEGs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Corrosion Behavior of Wire Electrical Discharge Machined Surfaces of P91 Steel

The extensive usage of P91 steel in certain reactor components requires its precision fabrication by wire electrical discharge machining (WEDM). The WEDM cut surfaces consist of primarily re-melted and solidified layer (recast layer) of 2-8 µm. The recast layer is a result of fast removal of heat by unaffected metallic substrate and dielectric medium leading to rapid cooling. The WEDM surface is expected to affect the component performance in terms of its corrosion properties. The microstructural changes taking place due to EDM cutting of P91 steel bring about a drastic change in the electrochemical response of surface as compared to that for bulk P91 steel. The surface microstructure is shown to alter the passivation behavior and resistance to localized corrosion. Electrochemical polarization studies were done to evaluate passivation, pitting and intergranular corrosion (IGC) behavior and field emission gun—scanning electron microscopy was used for microstructural characterization of P91 steel surfaces. The passivation behavior for P91 steel WEDM cut surfaces was better than that for diamond polished surface. But pitting corrosion resistance decreased for the P91 steel WEDM surface which is a result of inhomogeneities in the microstructure of recast layer. The IGC resistance though increased due to the decreased grain size in the surface layer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surface and Electrochemical Characteristics of Novel Chromate-Free Mn-V Oxyanion Sealed Tartaric–Sulfuric Acid Anodized Coating

In the present investigation, a novel chromate-free Mn and V oxyanions sealed tartaric–sulfuric acid anodic oxide coating (TSA) was developed on airframe grade aluminum alloy (AA2024). The results obtained from field emission scanning electron microscopy and energy-dispersive x-ray analysis showed effective surface modification of TSA after Mn-V oxyanions sealing (TSAMnVO). Potentiodynamic polarization results showed no significant difference in corrosion current density value (0.01 µA/cm{sup 2}) after 1 h and 336 h of immersion in 3.5% NaCl solution. EIS result exhibited barrier layer resistance (R{sub b}) value of TSAMnVO > 10{sup 6} kΩ cm{sup 2} even after 336 h of immersion in NaCl solution. The 3D profile and Raman analysis showed no significant difference in the topography and composition, respectively, on the surface of TSAMnVO even after 1000 h of salt spray test. TSAMnVO also showed excellent adhesion with aircraft grade epoxy primer as per the ASTM 3359. Tensile and constant amplitude fatigue test results of TSAMnVO exhibited ultimate tensile strength and number of cycles to failure comparable with chromic acid anodization (CAA) process. Hence, the developed novel TSAMnVO coating system eliminates the usage of chromate ions completely in anodization process since it provides comparable corrosion resistance and mechanical properties with CAA.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Therapeutic Potential of DNAzyme Loaded on Chitosan/Cyclodextrin Nanoparticle to Recovery of Chemosensitivity in the MCF-7 Cell Line

Commonly, acquired resistances to anticancer drug are mediated by overexpression of a membrane-associated protein that encode via multi-drug resistance gene-1 (MDR1). Herein, the mRNA-cleaving DNAzyme that targets the mRNA of MDR1 gene in doxorubicin-resistant breast cancer cell line (MCF-7/DR) loaded on the chitosan β-cyclodextrin complexes was used as a tropical agent. Chitosan/β-cyclodextrin complexes were used to deliver DNAzymes into cancer cells. Determination of the physicochemical characteristics of the particles was done by photon correlation spectroscopy and scanning electron microscopy. The encapsulation efficiency of the complexes was tested by using gel retardation assay. Positively charged nanoparticles interacted with DNAzyme that could perform as an efficient DNAzyme transfection system. The rationale usage of this platform is to sensitize MCF-7/DR to doxorubicin by downregulating the drug-resistance gene MDR1. Results demonstrated a downregulation of MDR1 mRNAs in MCF-7/DR/DNZ by real-time PCR, compared to the MCF-7/DR as control. WST1 assay showed the 22-fold decrease in drug resistance on treated cells 24 h after transfection. Results showed the intracellular accumulation of Rh123 increased in the treated cells with DNAzyme. Results suggested a potential platform in association with chemotherapy drug for cancer therapy and indicated extremely efficient at delivery of DNAzyme in restoring chemosensitivity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Comparing datasets of volume servers to illuminate their energy use in data centers

As data centers proliferate, their energy intensity deserves close attention. Always-on operations and growing usage for cloud and other backend processes make servers the fundamental driver of data center energy use. Yet servers’ power draw under real-world conditions is poorly understood. This paper explores characteristics of volume servers that affect energy use, quantifying differences in power draw between higher-performing Standard Performance Evaluation Corporation (SPEC) and ENERGY STAR servers and that of a typical server. First, we establish general characteristics of the US installed base, before reporting hardware configurations from a major online retail website. We then compare idle power across three datasets (one unique to this paper) and explain their differences via the hardware characteristics to which power draw is most sensitive. We find idle server power demand to be significantly higher than benchmarks from ENERGY STAR and the industry-released SPEC database, and SPEC server configurations—and likely their power scaling—to be atypical of volume servers. Next, we examine power draw trends among high-performing servers across their load range to consider whether these trends are representative of volume servers, before inputting average idle power load values into a recent national server energy use model. Lastly, results from two surveys of IT professionals illustrate the incidence of more efficient equipment and operational practices in server rooms/closets. Future work should include server power field measurements in data centers of different sizes, accounting for variations in configurations and setting changes post-purchase, as well as investigating the linkage between time and server energy efficiency.

Fuchs, Heidi (ORCID:0000000300105411)↗
DOE OSTI2021

Timed to save: the added value of accounting for hourly incidence of electricity savings from residential space-conditioning measures

Abstract Previous research has recognized that the value of measures that reduce electricity usage depends upon the timing of the savings generated, but the lack of hourly savings shapes has limited the demonstration of this concept. We develop empirical hourly savings shapes for residential space-conditioning measures from nearly 18,000 efficiency projects in California and show how they combine with the diurnal and seasonal variation in electricity system costs. We find that these measures (cooling replacements; windows, doors, and skylights; and other envelope measures) tend to save electricity when system costs are highest and that the hourly savings account for 1.4–1.5 times as much value as non-time-sensitive estimates of efficiency would predict. We present these impact multipliers for each measure to quantify the additional value revealed by the time-sensitive approach. We show that this additional value is similar in an evolving electricity grid with storage, rather than natural gas generation, as the marginal resource.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

Smart building management vs. intuitive human control—Lessons learnt from an office building in Hungary

We report that smart building management and control are adopted nowadays to achieve zero-net energy use in buildings. However, without considering the human dimension, technologies alone do not necessarily guarantee high performance in buildings. An office building was designed and built according to state-of-the-art design and energy management principles in 2008. Despite the expectations of high performance, the owner was facing high utility bills and low user comfort in the building located in Budapest, Hungary. The objective of the project was to evaluate the energy performance and comfort indices of the building, to identify the causes of malfunction and to elaborate a comprehensive energy concept. Firstly, current building conditions and operation parameters were evaluated. Our investigation found that the state-of-the-art building management system was in good conditions but it was operated by building operators and occupants who are not aware of the building management practice. The energy consumption patterns of the building were simulated with energy modelling software. The baseline model was calibrated to annual measured energy consumption, using actual occupant behaviour and presence, based on results of self-reported surveys, occupancy sensors and fan-coil usage data. Realistic occupant behaviour models can capture diversity of occupant behaviour and better represent the real energy use of the building. This way our findings and the effect of our proposed improvements could be more reliable. As part of our final comprehensive energy concept, we proposed intervention measures that would increase indoor thermal comfort and decrease energy consumption of the building. A parametric study was carried out to evaluate and quantify energy, comfort and return on investment of each measure. It was found that in the best case the building could save 23% of annual energy use. Lastly, future work includes the follow-up of: occupant reactions to intervention measures, the realized energy savings, the measurement of occupant satisfaction and behavioural changes.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2025

Integration of a grey-box refrigerated case model in EnergyPlus via Python plugin

Commercial buildings, in particular grocery stores (due mainly to their large refrigeration load), provide opportunities for energy cost reductions. Grocery stores could offer substantial load flexibility to the power grid through participation in demand response programs because of their usage patterns and relatively high energy intensity. This load flexibility could come from modifying the control of heating, ventilation, and air conditioning (HVAC) systems, refrigeration systems, or both. Although estimation of the HVAC system’s load flexibility potential is relatively targeted in the literature, estimating load flexibility of refrigeration systems is nascent and has been a challenge, in part because of the lack of proper simulation tools that capture the dynamics in the refrigeration cases. The existing refrigerated case model within EnergyPlus, a whole building energy simulation program, assumes a constant case temperature throughout the simulation period and does not explicitly model the cycling of the compressor serving the refrigerated case. In addition, it does not encompass modeling of temperatures of the product inside the refrigerated case. This difference between modeled and actual operation can be a barrier to the development of demand control algorithm and accurate analysis of load flexibility potential. In this paper, we present a grey-box model for modeling refrigerated cases in grocery stores, which include medium temperature and low temperature. Four cases are modeled; two are low-temperature closed cases and two are medium-temperature cases with one closed and one open. Data from an experimental facility are used to train and test the models. Results demonstrate the efficacy of the grey-box models in predicting the temperatures. This model is integrated into EnergyPlus to capture the dynamic effects of case temperature on the environment and enhance the calculation of sensible and latent heat exchange with the environment (case credits). These enhancements can be leveraged more broadly to model advanced refrigeration controls such as defrost, develop and test unique algorithms that could affect refrigeration interactions with HVAC, and refine store design for any commercial building with refrigeration.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2022

Synthesis of amorphous Pd-based nanocatalysts for efficient alcoholysis of styrene oxide and electrochemical hydrogen evolution

Amorphous nanomaterials with long-range disordered structures could possess distinct properties and promising applications, especially in catalysis, as compared with their conventional crystalline counterparts. It is imperative to achieve the controlled preparation of amorphous noble metal-based nanomaterials for the exploration of their phase-dependent applications. Here, in this work, we report a facile wet-chemical reduction strategy to synthesize various amorphous multimetallic Pd-based nanomaterials, including PdRu, PdRh, and PdRuRh. The phase-dependent catalytic performances of distinct Pd-based nanomaterials towards diverse catalytic applications have been demonstrated. Specifically, the usage of PdRu nanocatalysts with amorphous and crystalline face-centered cubic (fcc) phases can efficiently switch the ring-opening route of styrene oxide to obtain different products with high selectivity through alcoholysis reaction and hydrogenation reaction, respectively. Moreover, when used as an electrocatalyst for hydrogen evolution reaction (HER), the synthesized amorphous PdRh nanocatalyst exhibits low overpotential and high turnover frequency values, outperforming its crystalline fcc counterpart and most of the reported Pd-based HER electrocatalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Comparative effectiveness of coronary CT angiography vs stress cardiac imaging in patients following hospital admission for chest pain work-up: The Prospective First Evaluation in Chest Pain (PERFECT) Trial

Background: Because the frequency of cardiac event rates is low among chest pain patients following either performance of coronary CT angiography (CCTA) or stress testing, there is a need to better assess how these tests influence the central management decisions that follow from cardiac testing. The present study was performed to assess the relative impact of CCTA vs stress testing on medical therapies and downstream resource utilization among patients admitted for the work-up of chest pain. Methods: The admitted patients were randomized in a 1:1 ratio to either cardiac imaging stress test or CCTA. Primary outcomes were time to discharge, change in medication usage, and frequency of downstream testing, cardiac interventions, and cardiovascular re-hospitalizations. We randomized 411 patients, 205 to stress testing, and 206 to CCTA. Results: There were no differences in time to discharge or initiation of new cardiac medications at discharge. At 1 year follow-up, there was no difference in the number of patients who underwent cardiovascular downstream tests in the CCTA vs stress test patients (21% vs 15%, P = .1) or cardiovascular hospitalizations (14% vs 16%, P = .5). However, there was a higher frequency of invasive angiography in the CCTA group (11% vs 2%, P = .001) and percutaneous coronary interventions (6% vs 0%, P < .001). Conclusions: Randomization of hospitalized patients admitted for chest pain work-up to either CCTA or to stress testing resulted in similar discharge times, change in medical therapies at discharge, frequency of downstream noninvasive testing, and repeat hospitalizations. However, a higher frequency of invasive coronary angiography and revascularization procedures were performed in the CCTA arm. (ClinicalTrials.gov number, NCT01604655.)

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Infections in patients using ventricular-assist devices: Comparison of the diagnostic performance of {sup 18}F-FDG PET/CT scan and leucocyte-labeled scintigraphy

Background: The usage of left-ventricular-assist device (LVAD) is increasing in patients presenting with advanced heart failure. However, device-related infections are a challenge to recognize and to treat, with an important morbidity and mortality rate. The role of nuclear medicine imaging remains not well established for LVAD infections. The present study compared the accuracy of positron emission tomography/computed tomography with {sup 18}F-fludeoxyglucose ({sup 18}F-FDG PET/CT) and radiolabeled leucocyte scintigraphy for the diagnosis of infections in patients supported with a continuous-flow LVAD. Methods: From a prospectively maintained database, we retrospectively analyzed the diagnostic performance of radiolabeled leucocyte scintigraphy and {sup 18}F-FDG PET/CT in 24 patients who had a LVAD with a suspected device-related infection. Both examinations were routinely performed in all patients. Infection was assessed by the International Society for Heart and Lung Transplantation criteria. Results: Twenty-four patients were included: 15 had a specific VAD infection (5 cardiac-LVAD and 10 driveline), 6 had a VAD-related infection, while 3 patients had a non-VAD-related infection. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 95.2%, 66.7%, 95.2%, 66.7%, and 91.6%, respectively, for {sup 18}F-FDG-PET; and 71.4%, 100%, 100%, 33.3%, and 75%, respectively, for leucocyte scintigraphy. {sup 18}F-FDG PET/CT showed significantly higher sensitivity (P = 0.01) than leucocyte scintigraphy. Conclusion: {sup 18}F-FDG PET/CT and radiolabeled leucocyte scintigraphy single-photon emission computed tomography carry high performance in the diagnostic of LVAD infections. {sup 18}F-FDG PET/CT shows significantly higher sensitivity and could be proposed as first-line nuclear medicine procedure. [French] French Abstract: Contexte: L’utilisation du dispositif d’assistance ventriculaire gauche (DAVG) est en utilisation croissante chez les patients avec insuffisance cardiaque avancée. Cependant, les infections liées au dispositif sont un défi à reconnaître et à traiter en raison d’ un taux de morbidité et de mortalité important. Le rôle de l’imagerie de médecine nucléaire n’est pas encore bien établi pour les infections secondaires au DAVG. La présente étude compare la précision de la tomographie par émission de positrons / tomodensitométrie au 18F-fluorodéoxyglucose (18F-FDG TEP/TDM) et la scintigraphie leucocytaire radio-marquée pour le diagnostic d’infections chez des patients porteurs par un DAVG à flux continu. Méthodes: A partir d’une base de données complétée de manière prospective nous avons analysé rétrospectivement les performances diagnostiques de la scintigraphie leucocytaire radio-marquée et de la TEP / TDM au 18F-FDG chez 24 patients ayant un DAVG avec une infection suspectée liée à l’appareillage. Les deux types d’examens scintigraphiques ont été systématiquement réalisé chez tous les patients. Le diagnostic d’infection fut établi selon les critères ISHLT. Résultats: Parmi les 24 patients inclus, 15 avaient une infection spécifique de l’appareillage AVG (5 au niveau de la pompe et/ou canule d’insertion myocardique) et 10 au niveau du driveline, 6 avaient une infection indirectement liée à l’appareillage AVG, tandis que 3 patients avaient une infection non liée au DAVG. La sensibilité, la spécificité, la valeur prédictive positive, la valeur prédictive négative et la précision étaient de 95,2%, 66,7%, 95,2%, 66,7% et 91,6%, respectivement, pour le 18F-FDG-PET et 71,4%, 100%, 100%, 33,3 %, et 75%, respectivement, pour la scintigraphie leucocytaire. La TEP / TDM au 18F-FDG a montré une sensitivité significativement plus élevée (p = 0,01) que la scintigraphie leucocytaire. Conclusion: 18F-FDG TEP/TDM et scintigraphie leucocytaire radio-marquée SPECT s’avèrent très efficaces pour le diagnostic des infections à DVAG. La TEP/TDM au 18F-FDG montre une sensibilité significativement plus élevée et pourrait être proposée en tant que la procédure de médecine nucléaire de premier choix. [Spanish] Spanish Abstract: Antecedentes: El uso de dispositivos de asistencia ventricular izquierda (DAVI) está incrementando en pacientes con insuficiencia cardiaca avanzada. Sin embargo, las infecciones relacionadas al dispositivo representan un reto diagnóstico y de tratamiento, con una importante tasa de morbilidad y mortalidad. El papel de los estudios de imagen de medicina nuclear en las infecciones de DAVI no se ha establecido claramente. El presente estudio comparó la precisión de la tomografía por emisión de positrones/tomografía computada con {sup 18}F-fluorodesoxiglucosa ({sup 18}F-FDG PET/CT) y la gammagrafía con leucocitos marcados para el diagnóstico de infecciones en pacientes utilizando un DAVI de flujo continuo. Métodos: Desde una base de datos obtenida de manera prospectiva, analizamos de manera retrospectiva el rendimiento diagnóstico de la gammagrafía de leucocitos marcados y del {sup 18}F-FDG PET/CT en 24 pacientes quienes tenían un DAVI con sospecha de infección relacionada al dispositivo. Ambos estudios fueron realizados rutinariamente en todos los pacientes. Se determinó la presencia de infección mediante los criterios de la ISHTL. Resultados: Se incluyeron veinticuatro pacientes, de los cuales 15 tuvieron una infección específica de DAV (5 con infecciones DAVI, y 10 con infección del driveline), 6 tuvieron una infección relacionada al DAV, y 3 pacientes tuvieron una infección no relacionada al DAV. La sensibilidad, especificidad, valor predictivo positivo, valor predictivo negativo y precisión diagnóstica fueron 95.2%, 66.7%, 95.2%, 66.7% y 91.6%, respectivamente para {sup 18}F-FDG PET/CT, y 71.4%, 100%, 100%, 33.3% y 75%, respectivamente para la gammagrafía de leucocitos marcados. El {sup 18}F-FDG PET/CT mostró una significativa mayor sensibilidad (p=0.01) que la gammagrafía con leucocitos marcados. Conclusión: El {sup 18}F-FDG PET/CT y la gammagrafía de leucocitos marcados tienen un alto desempeño en el diagnóstico de infecciones de DAVI. El {sup 18}F-FDG PET/CT muestra una significativa mayor sensibilidad y podría ser propuesto como el procedimiento de medicina nuclear de primera línea. [Chinese] Chinese Abstract: 背景: 左心室辅助装置 (LVAD) 越来越多的应用于重度心力衰竭患者。然而, 设备相关的感染有着重要的发病率和死亡率, 并且对其诊断和治疗均是一项挑战。对于 LVAD 相关感染, 核医学影像可扮演的角色一直没有完善。本研究针对装备有连续流式 LVAD 的感染病人,对比了 {sup 18}F-FDG PET/CT 造影术和放射性标记白细胞闪烁扫描法对感染诊断的准确性。 方法: 从一个前瞻性的数据库, 入选了24名疑似设备感染的 LVAD 病人, 并回顾性的分析了放射性标记白细胞闪烁扫描法和 {sup 18}F-FDG PET/CT 的诊断表现。所有病人都常规进行了上述两种检查。利用 ISHLT 标准对感染情况进行评估。 结果: 在入选的 24 名病人中, 15 名有明确的 VAD 感染 (5 名心脏的 LVAD 和 10 名动力传动系统装置), 6 名有 VAD 相关的感染,另外3名有 VAD 无关的感染。对于 {sup 18}F-FDG PET/CT 诊断方法,其敏感性,特异性,阳性预测值,阴性预测值和准确率分别为: 95.2%, 66.7%, 95.2%, 66.7%, 和 91.6%; 而对于白细胞闪烁扫描诊断方法, 其敏感性, 特异性, 阳性预测值,阴性预测值和准确率分别为: 71.4%, 100%, 100%, 33.3% 和 75%。相比于白细胞闪烁扫描, {sup 18}F-FDG PET/CT 明显展现出较高的敏感性 (p=0.01)。 结论: {sup 18}F-FDG PET/CT 和白细胞闪烁扫描 SPECT 对于 LVAD 感染的诊断具有很好的表现。{sup 18}F-FDG PET/CT 展现出较高的敏感性,可以作为核医学的首要检查。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Street context of various demographic groups in their daily mobility

Abstract We present an urban science framework to characterize phone users’ exposure to different street context types based on network science, geographical information systems (GIS), daily individual trajectories, and street imagery. We consider street context as the inferred usage of the street, based on its buildings and construction, categorized in nine possible labels. The labels define whether the street is residential, commercial or downtown, throughway or not, and other special categories. We apply the analysis to the City of Boston, considering daily trajectories synthetically generated with a model based on call detail records (CDR) and images from Google Street View. Images are categorized both manually and using artificial intelligence (AI). We focus on the city’s four main racial/ethnic demographic groups (White, Black, Hispanic and Asian), aiming to characterize the differences in what these groups of people see during their daily activities. Based on daily trajectories, we reconstruct most common paths over the street network. We use street demand (number of times a street is included in a trajectory) to detect each group’s most relevant streets and regions. Based on their street demand, we measure the street context distribution for each group. The inclusion of images allows us to quantitatively measure the prevalence of each context and points to qualitative differences on where that context takes place. Other AI methodologies can further exploit these differences. This approach presents the building blocks to further studies that relate mobile devices’ dynamic records with the differences in urban exposure by demographic groups. The addition of AI-based image analysis to street demand can power up the capabilities of urban planning methodologies, compare multiple cities under a unified framework, and reduce the crudeness of GIS-only mobility analysis. Shortening the gap between big data-driven analysis and traditional human classification analysis can help build smarter and more equal cities while reducing the efforts necessary to study a city’s characteristics.

Salgado, Ariel (ORCID:0000000177015372)↗