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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Can MRI be used to diagnose histologic grade in T1a (< 4 cm) clear cell renal cell carcinomas?

Objective: To assess whether MRI can differentiate low-grade from high-grade T1a cc-RCC. Materials and methods: With IRB approval, 49 consecutive solid < 4 cm cc-RCC (low grade [Grade 1 or 2] N = 38, high grade [Grade 3] N = 11) with pre-operative MRI before nephrectomy were identified between 2013 and 2018. Tumor size, apparent diffusion coefficient (ADC) histogram analysis, enhancement wash-in and wash-out rates, and chemical shift signal intensity index (SI index) were assessed by a blinded radiologist. Subjectively, two blinded Radiologists also assessed for (1) microscopic fat, (2) homogeneity (5-point Likert scale), and (3) ADC signal (relative to renal cortex); discrepancies were resolved by consensus. Outcomes were studied using Chi square, multivariate analysis, logistic regression modeling, and ROC. Inter-observer agreement was assessed using Cohen’s kappa. Results: Tumor size was 24 ± 7 (13–39) mm with no association to grade (p = 0.45). Among quantitative features studied, corticomedullary phase wash-in index (p = 0.015), SI index (p = 0.137), and tenth-centile ADC (p = 0.049) were higher in low-grade tumors. 36.8% (14/38) low-grade tumors versus zero high-grade tumors demonstrated microscopic fat (p = 0.015; Kappa = 0.67). Microscopic fat was specific for low-grade disease (100.0% [71.5–100.0]) with low sensitivity (36.8% [21.8–54.6]). Other subjective features did not differ between groups (p > 0.05). A logistic regression model combining microscopic fat + wash-in index + tenth-centile-ADC yielded area under ROC curve 0.98 (Confidence Intervals 0.94–1.0) with sensitivity/specificity 87.5%/100%. Conclusion: The combination of microscopic fat, higher corticomedullary phase wash-in and higher tenth-centile ADC is highly accurate for diagnosis of low-grade disease among T1a clear cell RCC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Ground State Structure of BaFeO{sub 3}: Density Functional Theory Calculations

Using density functional theory calculations, the ground state structure of BaFeO{sub 3} (BFO) is investigated with local spin density approximation (LSDA). Cubic, tetragonal, orthorhombic, and rhombohedral types BFO are considered to calculate the formation enthalpy. The formation enthalpies reveal that cubic is the most stable structure of BFO. Small energy difference between the cubic and tetragonal suggests a possible tetragonal BFO. Ferromagnetic (FM) and anitiferromagnetic (AFM) coupling between the Fe atoms show that all the striochmetric BFO are FM. The energy difference between FM and AFM shows room temperature ferromagnetism in cubic BFO in agreement with the experimental work. The LSDA-calculated electronic structures are metallic in all studied crystallographic phases of BFO. Calculations including the Hubbard potential U, i.e. LSDA + U, show that all phases of BFO are half-metallic consistent with the integer magnetic moments. The presence of half-metallicity is discussed in terms of electronic band structures of BFO.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic Properties of a Nano-graphene Monolayer with Higher-Order Exchange Interaction Coupling

Using the Monte Carlo simulation, we have studied the phase diagrams and the hysteresis behaviors of a single layer Ising nanographene with next-nearest neighbors coupling J{sub 2} and four-spin interaction J{sub 4} in the presence of a crystal field D and applied magnetic field h. It can emphasize that, for appropriate system parameters, the nanographene can exhibit a new phenomenon manifested in the emergence of an antiferromagnetic phase sandwiched between two ferromagnetic ones. Concerning the hysteresis behavior, the system can present a multiple hysteresis loops.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effects of Forming Pressure on Physicochemical Properties of YBCO Ceramics

This article details the solid-state synthesis of high-temperature superconducting YBa{sub 2}Cu{sub 3}O{sub 7−x}. Tests were carried out on samples formed at different pressures (200, 400, 600 and 800 MPa) before being annealed under pure oxygen. The X-ray diffraction method showed that, regardless of the forming pressure, the samples contain about 97 wt.% of Y-123 phase. SEM images showed a polycrystalline structure of samples of similar grain size and number of pores (intergranular spaces). The values of critical temperatures (T{sub c0}), determined from magnetoresistance measurements, are about 91.5 K for all samples, and the T{sub c0} temperatures do not depend on sample-forming pressure. Magnetoresistance measurements have shown that samples formed with higher pressures exhibit smaller changes in T{sub c0} and superconducting transition width ΔT due to the influence of the H{sub DC} magnetic field, than the samples formed with lower pressures. Values of specific resistance determined by the use of van der Pauw method at 300 K is about 2 mΩcm for all samples. The critical temperatures (T cintra) of grains and critical current densities at 77 K were determined from AC magnetic susceptibility measurements, and they are about 91.6 K and 400 A cm{sup −2}, respectively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Nd Substitution on Properties of Multiferroic Bismuth Ferrite Synthesized by Sol-Gel Auto-combustion Method

In this work, pure and Nd-doped bismuth ferrite nanocrystals with the general formula of Bi{sub 1−x}Nd{sub x}FeO{sub 3} (x = 0, 0.05, 0.1, 0.15, 0.2) were synthesized via the sol-gel auto-combustion method at two different calcination temperatures (550 and 650{sup ∘}C). Phase analysis and investigating structural, thermal, and magnetic properties and measuring the size of nanoparticles have been done by using X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG/DTA), and vibrating sample magnetometry (VSM). For undoped BiFeO{sub 3} (BFO), increasing calcination temperature will increase the average size of nanocrystals. On the other hand, the average size of nanoparticles is decreased by increasing the concentration of neodymium in the structure of BFO. By entering neodymium to the structure of bismuth ferrite at the calcination temperature of 550{sup ∘}C, the ferromagnetic properties decline. However, at 650{sup ∘}C, ferromagnetic properties are improved which is due to a fall in the number of Fe{sup 2+} ions. In this case, by decreasing the Fe{sup 2+} ions, remanent and saturation magnetization increase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

The Effects of an Applied Transverse Field in a Graphene-Like Ising Bilayer Film with Nonequivalent Planes

Using the effective field theory with correlations, we have studied the phase diagrams and the thermal variations of total magnetization (m{sub T}) in a graphene-like Ising bilayer film with nonequivalent planes, consisting of two A (spin-1/2) and B (spin-1) planes with an applied transverse field in the B plane. We have investigated the effects of an applied transverse field and the interplane exchange interaction on the magnetic properties. Many interesting behaviors, such as various types of m{sub T} curves and the re-entrant phenomena, have been obtained, depending on the selections of physical parameters.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Structural-Phase States of Fe–Cu and Fe–Ag Bimetallic Particles Produced by Electric Explosion of Two Wires

X-ray phase analysis, transmission electron microscopy, and X-ray microanalysis were used to examine the structural-phase states of Fe–Cu and Fe–Ag bimetallic nanoparticles. The nanoparticles were obtained by the electric explosion of two twisted metal wires in argon atmosphere. It was demonstrated that the nanoparticles have the structure of Janus particles. Presence of the Janus particle structure in the samples indicates formation of binary melt under conditions of combined electric explosion of two wires. Phases based on supersaturated solid solutions were not found in the examined samples. The data obtained allow arguing that it is possible to achieve uniform mixing of the two-wire explosion products under the described experiment conditions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Quantitative Phase Analysis of Plasma-Treated High-Silica Materials

The paper presents the X-ray diffraction (XRD) analysis of the crystal structure of SiO{sub 2} in two modifications, namely quartzite and quartz sand before and after plasma treatment. Plasma treatment enables the raw material to melt and evaporate after which the material quenches and condenses to form nanoparticles. The Rietveld refinement method is used to identify the lattice parameters of SiO{sub 2} phases. It is found that after plasma treatment SiO{sub 2} oxides are in the amorphous state, which are modeled within the microcanonical ensemble. Experiments show that amorphous phases are stable, and model X-ray reflection intensities approximate the experimental XRD patterns with fine precision. Within the modeling, full information is obtained for SiO{sub 2} crystalline and amorphous phases, which includes atom arrangement, structural parameters, atomic population of silicon and oxygen atoms in lattice sites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Mechanism of Na{sub 2}SO{sub 4} Promoting Nickel Extraction from Sulfide Concentrates by Sulfation Roasting–Water Leaching

As a more environmentally friendly and energy-efficient route, the sulfation roasting–water leaching technique has been developed for highly effective extraction of non-ferrous metals from nickel sulfide concentrate in the presence of a Na{sub 2}SO{sub 4} additive. The effects of several important roasting parameters—the roasting temperature, the addition of Na{sub 2}SO{sub 4}, the holding time, and the heating rate in particular—have been investigated. The results suggest that about 90 pct Ni, 92 pct Co, 95 pct Cu, and < 1 pct Fe can be leached from the calcine roasted under the optimum conditions. Furthermore, the behavior and mechanism of the Na{sub 2}SO{sub 4} additive in the roasting process have been well addressed by detailed characterization of the roasted product and leaching residue using quantitative phase analysis (QPA) and energy dispersive spectroscopy (EDS) mapping. The Na{sub 2}SO{sub 4} additive was observed to play a noticeable role in promoting the sulfation degree of valuable metals by forming liquid phases [Na{sub 2}Me(SO{sub 4}){sub 2}] at the outermost layer, which can create a suitable dynamic environment for sulfation. Thus, addition of Na{sub 2}SO{sub 4} might be conducive to an alternative metallurgical process involving complex sulfide ores.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effect of Cerium Oxide on Morphologies and Electrochemical Properties of Ni-W-P Coating on AZ91D Magnesium

AZ91D magnesium alloy substrate was first pretreated in a phosphoric acid to obtain a phosphate coating, and then, the electroless ternary Ni-W-P coating was deposited using a sulfate nickel bath. The morphologies of the Ni-W-P coating were observed by using scanning electron microscope, the deposition rate of the coating was examined with the method of gravimetric analysis, and the phase analysis was identified by x-ray diffractometer. Electrochemical property was tested by means of an electrochemical analyzer. The results indicated that the addition of an optimum concentration of CeO{sub 2} (cerium oxide) particles could evidently improve the deposition rate and the stability of the plating bath. However, it acted as an inhibiting effect as the concentration of CeO{sub 2} particles exceeded to 8 mg/L in the sulfate nickel bath. The results also revealed that the morphology of Ni-W-P coating became more smooth, compact and uniform with the increase in the concentrations of CeO{sub 2} particles in the bath, but the corrosion resistance decreased due to the precipitation of crystal phases (Ni{sub 3}P, Ni{sub 4}W, etc.) after heat treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Wear Behavior of Vanadium and V-Ti-Ta Alloys under Reciprocating Sliding Conditions

Vanadium and newly developed V-Ti-Ta alloys have been systematically investigated for wear characteristics using ball-on-flat reciprocative sliding experiments. These materials have been tested at different sliding conditions (load and frequency) against hardened steel (AFBMA Grade 10) ball as counter-body. Coefficient of friction, wear volume and specific wear rate were measured and evaluated. Friction coefficient of vanadium and its alloys increases with increase in applied load irrespective of sliding frequencies. Wear rate decreases with increase in alloying content. Among the investigated compositions, V-4Ti-7Ta alloy exhibited superior wear performance having a least wear rate of 3.06 × 10{sup −6} mm{sup 3}/Nm, which is three times lower as compared with unalloyed vanadium when tested at 5 N and 5 Hz conditions. Addition of Ti and Ta strengthens the vanadium matrix by solid solution and contributes to enhanced wear resistance of the material without affecting the friction coefficient values. The major phases identified in the wear track regions were V{sub 2}O{sub 5} and Fe{sub 0.11}V{sub 2}O{sub 5.15}. Microstructural investigation reveals the predominant presence of adhesive wear regions at higher loads (15 N).

36 MATERIALS SCIENCE↗
DOE OSTI2017

Review of cardiovascular imaging in the journal of nuclear cardiology in 2016: Part 2 of 2—myocardial perfusion imaging

In 2016, the Journal of Nuclear Cardiology published many high-quality articles. Similar to previous years, we will summarize here a selection of the articles that were published in the Journal in 2016 to provide a concise review of the main advancements that have recently occurred in the field. In the first article of this two-part series we focused on publications dealing with positron emission tomography, computed tomography, and magnetic resonance. This review will place emphasis on myocardial perfusion imaging using single-photon emission-computed tomography summarizing advances in the field including in diagnosis, prognosis, and appropriate use.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Interactions between myocardial sympathetic denervation and left ventricular mechanical dyssynchrony: A CZT analysis

Background: A correlation between left ventricular (LV) dyssynchrony (LVD) and impaired myocardial sympathetic tone has been hypothesized. We sought to assess the interactions between regional LV sympathetic innervation, perfusion, and mechanical dyssynchrony. Methods: Eighty-three patients underwent evaluation of LV perfusion and sympathetic innervation on {sup 99m}Tc-tetrofosmin/{sup 123}I-metaiodobenzylguanidine ({sup 123}I-MIBG) imaging. The summed rest score and summed {sup 123}I-MIBG score (SS-MIBG) were computed. The extent of “innervation/perfusion” mismatch was defined as the number of denervated LV segments with relatively preserved perfusion. LVD was evaluated on phase analysis and the wall with latest mechanical activation identified. Results: LVD was revealed in 36 (43%) patients. Patients with LVD had more abnormal values of SRS (21 ± 9 vs 10 ± 8, P < 0.001) and SS-MIBG (29 ± 9 vs 17 ± 11, P < 0.001) than those without LVD. The presence of LVD also clustered with a higher burden of “innervation/perfusion” mismatch (P = 0.019). On per-wall analysis, LV walls with delayed mechanical activation showed a higher burden of “innervation/perfusion” mismatch (2.3 ± 1.4 segments) than normally contracting walls (1.3 ± 1.2 segments; P < 0.001). On multivariate analysis, the extent of “innervation/perfusion” mismatch was the only predictor of delayed mechanical activation (P = 0.029). Conclusions: Patients with LVD show an elevated burden of “innervation/perfusion” mismatch that is concentrated at the level of the most dyssynchronous walls.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Left ventricular mechanical dyssynchrony assessment in long-standing type II diabetes mellitus patients with normal gated SPECT-MPI

Background: Assessment of left ventricular mechanical dyssynchrony (LVMD) using phase analysis of gated SPECT-MPI is well established. However, there is little information about the influence of diabetes mellitus on phase analysis. The present work was to evaluate the LVMD in longstanding type II diabetes mellitus (DM) patients with normal gated SPECT-MPI. Methods: Retrospective analysis of 146 (86 type II diabetics for > 5 years’ duration and 60 nondiabetics) consecutive patients with normal gated SPECT-MPI and adequate LVEF was done. Sixty age- and sex-matched nondiabetic served as control. LVMD was determined from the cutoff values (> mean + 2 SD) observed for phase standard deviation (PSD) and phase bandwidth (PBW) from the control subjects. Multivariate logistic regression analysis was applied to assess the correlation between various confounding factors. Results: LVMD was detected in 24 (28%) diabetic patients with the pre-defined cut-off values for PSD (> 10.8) and PBW (> 35.6) derived from the controls. Hyperlipidemia, overweight/obesity, duration of DM and its long-term complications were independently associated with LVMD, with long-term complications being the highest risk factor (OR 28.00; P < .001). Conclusion: The evolution time of the patients with type II diabetes mellitus affects the left ventricular mechanical synchrony.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2026

Exploring the tempering behaviour of additively manufactured high-alloy tool steel using synchrotron X-ray and neutron techniques

Post-processing heat treatment provides a critical pathway toward the commercialisation of additively manufactured (AM) S390 high-speed steel, which is a representative high-alloy tool steel employed in precision manufacturing, offering up to 1.5 times longer tool life and over 20% higher cutting speeds compared to conventional grades. In this study, the phase evolution of AM S390 steel during heat treatment, with particular emphasis on carbide precipitation behaviour, was systematically investigated using a combination of synchrotron X-ray and neutron techniques. The metastable M2C carbides were found to dissolve during austenitisation, while the stable primary carbides MC and M6C experienced coarsening with an average size increase of about 60 nm after just 2 min of tempering. Moreover, the austenite lattice parameters reduced from 3.618 to 3.608 Å within the first 10 min of tempering, suggesting carbon depletion in the steel matrix was likely associated with the formation of secondary carbides. This interpretation was substantiated by small-angle scattering results, which revealed the presence of nanoscale precipitates with a volume fraction of 3.1% after 60 min of tempering. These microstructural evolutions collectively accounted for the observed peak hardness of 921 HV. Furthermore, a comparative analysis of synchrotron and neutron small-angle scattering data highlighted the complementary strengths of each technique, offering critical insight into their suitability for characterising nanoscale features in AM high-alloy steels.

Synchrotron X-ray diffraction↗