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At least 631 records · Page 35

Chandra Detection of a Parsec Scale Wind in the Broad Line Radio Galaxy 3C 382

We present unambiguous evidence for a parsec scale wind in the Broad-Line Radio Galaxy (BLRG) 3C 382, the first radio-loud AGN whereby an outflow has been measured with X-ray grating spectroscopy. A 118 ks Chandra grating (HETG) observation of 3C 382 has revealed the presence of several high ionization absorption lines in the soft X-ray band, from Fe, Ne, Mg and Si. The absorption lines are blue-shifted with respect to the systemic velocity of 3C 382 by -840+/-60 km/s and are resolved by Chandra with a velocity width of sigma = 340+/-70 km/s. The outflow appears to originate from a single zone of gas of column density N(sub H) = 1.3 x 10(exp 21)/sq cm and ionization parameter log(E/erg/cm/s) = 2.45. From the above measurements we calculate that the outflow is observed on parsec scales, within the likely range from 10-1000 pc, i.e., consistent with an origin in the Narrow Line Region. Finally we also discuss the possibility of a much faster (0.1c) outflow component, based on a blue-shifted iron K(alpha) emission line in the Suzaku observation of 3C 382, which could have an origin in an accretion disk wind.

Reeves, J. N.↗

Understanding the Reactivity of Lunar Dust for Future Lunar Missions

Fluorescence and EPR can be used to measure the reactivity of lunar soil. Lunar soil is highly activated by grinding. Reactivity is dependent upon soil maturity and locale. Maturity is based on the amount of nanophase iron (np-Fe) in a soil relative to the total iron (FeO). Lunar soil activity ia a direct function of the amount of np-Fe present. Reactive soil can be "deactivated" by humid atmosphere.

Wallace, W. T.↗

Theoretical and numerical difficulties in 3-D vector potential methods in finite element magnetostatic computations

This paper describes the results of application of three well known 3D magnetic vector potential (MVP) based finite element formulations for computation of magnetostatic fields in electrical devices. The three methods were identically applied to three practical examples, the first of which contains only one medium (free space), while the second and third examples contained a mix of free space and iron. The first of these methods is based on the unconstrained curl-curl of the MVP, while the second and third methods are predicated upon constraining the divergence of the MVP 10 zero (Coulomb's Gauge). It was found that the two latter methods cease to give useful and meaningful results when the global solution region contains a mix of media of high and low permeabilities. Furthermore, it was found that their results do not achieve the intended zero constraint on the divergence of the MVP.

Demerdash, N. A.↗

Flow synthesis of iron oxide nanoparticles: using multiple precursor additions to improve size control

Controlling the size of iron oxide nanoparticles while maintaining uniformity in flow-based synthesis systems has been a great challenge in nanoparticle synthesis. Using an extended LaMer mechanism, we improve both the size and shape uniformity as compared to a conventional flow synthesis. The key to this approach is the injection of additional Fe precursor during the flow reaction, providing extra precursor during the growth process leading to a size focusing step. This approach has also allowed for the systematic variation of the nanoparticle size produced in the flow reaction. This work represent a new synthetic concept for improving the size uniformity of iron oxide nanoparticles in flow-based synthesis and has potential for application across a wide range of nanoparticle systems.

36 MATERIALS SCIENCE↗

Mechanisms and heterogeneity of in situ mineral processing by the marine nitrogen fixer Trichodesmium revealed by single-colony metaproteomics

The keystone marine nitrogen fixer Trichodesmium thrives in high-dust environments. While laboratory investigations have observed that Trichodesmium colonies can access the essential nutrient iron from dust particles, less clear are the biochemical strategies underlying particle–colony interactions in nature. Here we demonstrate that Trichodesmium colonies engage with mineral particles in the wild with distinct molecular responses. We encountered particle-laden Trichodesmium colonies at a sampling location in the Southern Caribbean Sea; microscopy and synchrotron-based imaging then demonstrated heterogeneous associations with iron oxide and iron-silicate minerals. Metaproteomic analysis of individual colonies by a new low-biomass approach revealed responses in biogeochemically relevant proteins including photosynthesis proteins and metalloproteins containing iron, nickel, copper, and zinc. The iron-storage protein ferritin was particularly enriched implying accumulation of mineral-derived iron, and multiple iron acquisition pathways including Fe(II), Fe(III), and Fe-siderophore transporters were engaged. While the particles provided key trace metals such as iron and nickel, there was also evidence that Trichodesmium was altering its strategy to confront increased superoxide production and metal exposure. Chemotaxis regulators also responded to mineral presence suggesting involvement in particle entrainment. These molecular responses are fundamental to Trichodesmium’s ecological success and global biogeochemical impact, and may contribute to the leaching of particulate trace metals with implications for global iron and carbon cycling.

Held, Noelle A.↗

Use of near infrared correlation spectroscopy for quantitation of surface iron, absorbed water and stored electronic energy in a suite of Mars soil analog materials

A number of questions concerning the surface mineralogy and the history of water on Mars remain unresolved using the Viking analyses and Earth-based telescopic data. Identification and quantitation of iron-bearing clays on Mars would elucidate these outstanding issues. Near infrared correlation analysis, a method typically applied to qualitative and quantitative analysis of individual constituents of multicomponent mixtures, is adapted here to selection of distinctive features of a small, highly homologous series of Fe/Ca-exchanged montmorillonites and several kalinites. Independently determined measures of surface iron, relative humidity and stored electronic energy were used as constituent data for linear regression of the constituent vs. reflectance data throughout the spectral region 0.68 to 2.5 micrometers. High correlations were found in appropriate regions for all three constituents, though that with stored energy is still considered tenuous. Quantitation was improved using 1st and 2nd derivative spectra. High resolution data over a broad spectral range would be required to quantitatively identify iron-bearing clays by remotely sensed reflectance.

Coyne, Lelia M.↗

Architecture, catalysis and regulation of methylthio-alkane reductase for bacterial sulfur acquisition from volatile organic compounds

Bacteria utilize methylthio-alkane reductase (MAR) to acquire sulfur from volatile organic sulfur compounds. Reductive cleavage of methylthio-ethanol and dimethylsulfide liberates methanethiol for methionine synthesis and concomitantly releases ethylene and methane, respectively. Here we show that the native MAR of Rhodospirillum rubrum is a two-component system composed of a MarH ATP-dependent reductase and a MarDK catalytic core, whose architecture parallels nitrogenase. MarS complexes with MarDK to downregulate MAR activity during cellular sulfate influx, based on chromatographic and activity analyses. MarDK possesses complex metallocofactors resembling, but not identical to, nitrogenase P- and iron-only M-clusters, designated as mar1 and mar2 clusters based on metal, spectroscopic and mutagenesis analyses. They exhibit electronic features similar to the iron-only nitrogenase under turnover and, remarkably, are matured by MarB or nitrogenase NifB, resulting in maturase-dependent activity profiles. Altogether, this suggests a broader scope of reactivity, mechanisms and regulation in microbial metabolism for the nitrogenase-like family of enzymes than previously considered.

09 BIOMASS FUELS↗

Iron crystals in lunar breccias

Many of the vugs in the highly recrystallized breccias from Apollos 14, 15, and 16 contain euhedral iron crystals. Three populations have been recognized based on crystal habit. In the first group the trapezohedron predominates and the cube faces are smaller. The second group is characterized by the cube as the dominant form; trapezohedron and tetrahexahedron faces are smaller and about equally developed. The dominant habit of the third group is the octahedron with smaller but equally developed cube and dodecahedron faces. Iron has been mobilized and redistributed in a vapor phase. The euhedral crystals, the abundant growth steps, and the open network of substrate crystals clearly support the concept of growth from a vapor-phase.

Clanton, U. S.↗

Dislocation loop bias and void swelling in irradiated α-iron from mesoscale and atomistic simulations

Abstract Dislocation loops are ubiquitous in irradiated materials, and dislocation loop bias plays a critical role in void swelling. However, due to complicated interactions between dislocation loops and point defects, it is challenging to evaluate the bias factors of dislocation loops. Here, we determine the bias of sessile < 100 > loops in α-iron using a recently developed atomistic approach based on the lifetime of point defects. We establish a mechanistic understanding of the loop interaction based on the diffusion tendency of point defects near the loop core region. Mobile self-interstitial atoms tend to be absorbed from the edge of the loop, and a trapping region perpendicular to the habit plane of the loop exists. The dislocation loop bias is found to be substantially lower than those of straight dislocations in α-iron and should be included in swelling rate estimates. With the obtained sink strength and bias values, agreement is achieved with experimental results for both absolute values and temperature dependence.

Yu, Ziang↗

Asteroid size distribution - Implications for the origin of stony-iron and iron meteorites

The diameter-frequency distribution of large asteroids is analyzed, based on polarimetric and radiometric albedo data. The population of carbonaceous objects shows a high degree of fragmentation. But a class of apparently stony-iron asteroids shows a relative excess frequency between diameters of 100 to 200 km. It is proposed that the latter objects are predominantly metallic cores of a group of chemically differentiated planetesimals all of which (except Vesta) have suffered catastrophic collisions. Collision frequencies in the asteroid belt may have been much greater than previously supposed.

Chapman, C. R.↗

Midwest Nuclear-based Net-Zero Carbon Steelmaking Demonstration

Globally, the iron and steel industry accounts for around a quarter of GHG emissions from the manufacturing sector , which is about 7% of the 33 gigatonnes (Gt) of global CO 2 emissions . Thus, globally, the steel industry is a 2-3 Gt CO 2 per year emissions challenge. The steel industry is important to the U.S. economy with output equal to $0.5 trillion and domestic production capacity is critical to national defense, infrastructure, energy production, and transportation. President Biden’s executive order on climate identifies actions and policies to put the Nation on a path to achieve net-zero carbon emissions, economy-wide, by no later than 2050. To achieve this, deep carbon reductions in the power, transportation, buildings and capital-intensive industrial manufacturing segments such as steel, cement and chemicals need to be addressed. In its recent “Accelerating Decarbonization of the U.S. Energy System” report , the National Academy of Sciences (NAS) stated that, “while technology exists to decarbonize all parts of the energy system, some sectors remain at precommercial or first-of-a-kind demonstration stages and require significant improvement in cost and performance to become commercially viable.” The NAS goes on to state that these hard to decarbonize sectors include “aviation, shipping, and industrial subsectors such as steel, cement, and chemicals manufacturing .” The Administration has proposed a timeline to decarbonize energy, transportation and then industry and manufacturing. From a life-cycle approach, decarbonizing steel and other large industrial inputs are necessary to decarbonize transformations in energy and transportation. DOE’s TRI-Lab Consortium’s Integrated Energy Systems (IES) program is a collaboration amongst DOE’s three applied energy laboratories: the National Energy Technology Laboratory; National Renewable Energy Laboratory and Idaho National Laboratory. The IES approach looks at more tightly integrating low-carbon nuclear energy, renewable electricity, energy storage, load/demand balancing, and biomass (including plastics and other wastes) with one or more industrial processes that utilize heat and/or power from these clean and waste energy sources to produce a low-carbon commodity-scale product.

08 HYDROGEN↗

Utilizing Ionic Liquids to Enable the Future of Closed-Loop Life Support Technology

Current oxygen recovery technology onboard the International Space Station only recovers approximately 50% of the oxygen from metabolic carbon dioxide, thus requiring resupply mass in order to sustain life onboard. Future long duration manned missions will require maximum oxygen recovery in order to reduce resupply mass. Complete recovery of oxygen can be achieved through Bosch technology. The challenge with this technology is that the solid carbon produced during the process results in undesired catalyst resupply mass. Although there have been several approaches to solve this challenge, in order to totally eliminate the need for resupply only one potential process has been identified. This process is a fully-regenerable Ionic Liquid (IL)-based Bosch system that employs in situ resources. In 2016, efforts were made that proved the feasibility of an IL-based Bosch system. ILs were used to electroplate iron onto a copper substrate and to regenerate the iron by extracting the iron from the copper substrate and product carbon. In 2017, efforts were initiated to scale the proposed technology. Here we report the results of those efforts as well as an IL-based Bosch system concept and basic reactor design.

Brown, Brittany R.↗

A "Mesosiderite" Rock from Northern Siberia, Russia: Not a Meteorite

A possible mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by: (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence of high-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from mesosiderites.

Treiman, Allan H.↗

Magnetostrictive Ultrasonic Waveguide Transducer for In-Pile Thermometry

Real-time and reliable temperature measurement on nuclear fuels is crucial for the safe operation of existing pressurized-water reactors and future advanced nuclear reactors. Magnetostrictive materials deform when subjected to a magnetic field or exhibit magnetization variation when stressed. Here, based on these properties, this study prototyped an ultrasonic thermometer (UT) consisting of a magnetostrictive waveguide, a dc coil providing appropriate magnetic biasing, and an ac coil generating an acoustic impulse and detecting the resulting acoustic echoes. By tracking the time of flight between the excitation pulse and the echoes, the UT can potentially detect nuclear fuel cladding temperature from a long distance. In this study, magnetostrictive iron–gallium alloys, or Galfenol, were selected as the waveguide due to their large magnetostriction, superior temperature survivability, excellent radiation resilience, and high mechanical robustness. A multiphysics finite-element model considering electrical, magnetic, and mechanical dynamics in the magnetostrictive UT was then developed. The model exhibited an error of 0.24% in time-of-flight simulation and, therefore, enabled computer-aided design and guided signal processing. Between room temperature and 120 °C, the new Galfenol-based UT exhibits a linear sensitivity of 162.8×10 ₋6 °C ₋1 , which is 51.7% higher than a previous magnetostrictive UT based on iron–cobalt–vanadium alloys.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Symmetry-Breaking Design of an Organic Iron Complex Catholyte for a Long Cyclability Aqueous Organic Redox Flow Battery

The limited availability of a high-performance catholyte has hindered development of aqueous organic redox flow batteries (AORFB) that are environmentally benign, have tunable structures, and are safer than their traditional transition metal ion-based counterparts for large-scale energy storage. In this paper, a symmetry-breaking design of iron complexes with 2,2’-bipyridine-4,4’-dicarboxylic (Dcbpy) acid and cyanide ligands is described. By introducing two ligands to the metal center, the complex compounds (M4[FeII(Dcbpy)2(CN)2], M = Na, K) exhibited 4.2 times higher solubility (1.22 M, 33 Ah/L) and a 50% increase in potential compared with the widely used ferrocyanide. The symmetry-breaking, iron complex catholyte-based AORFBs were demonstrated at a concentration near the solubility limit (1.02 M Na4[FeII(Dcbpy)2(CN)2]) with a 1:1 catholyte:anolyte electron ratio. The AORFBs achieved a cell voltage of 1.2 V and a demonstrated energy density of 12.5 Wh/L. This symmetry-breaking design paves the way for development of metal complexes for high-energy-density AORFBs.

Li, Xiang↗

Detectability of crystalline ferric and ferrous minerals on Mars

Telescopic and spacecraft spectroscopic and geochemical data have been used to constrain the surface mineralogy of Mars and to yield clues about past and present Mars surface weathering/alteration scenarios. Based primarily on their visible to near-IR reflectance properties, several terrestrial iron-bearing minerals have been either identified on Mars or proposed as Mars spectral analogs. Among these are crystalline hematite, pyroxenes, as well as poorly crystalline materials like nonophase hematite and palagonite. Other iron-bearing minerals include nontronite, magnetite, jarosite, and goethite and the have been proposed as Mars surface constituents based on Viking Lander measurements or geochemical modeling. If present on Mars, these materials likely appear as spectral mixtures at the coarse spatial resolution of remotely sensed data. The detectability of any of these components must be evaluated relative to the other components with which they occur. The primary goal of this study is to determine how much of any given mineral would have to be present for it to be detectable in remotely-sensed data. Here, the detectability of iron-bearing minerals was evaluated using detection threshold analysis (DTA), an analytical technique based on spectral mixture analysis.

Sabol, Donald E., Jr.↗

Stable, Efficient Iron Electrodeposition via Anion-Directed Control of Fe(II) Coordination

Traditional steelmaking processes consume about 7% of the world’s energy supply, with reduction of iron oxides into iron via blast furnaces representing the most energy-demanding and capital-intensive step. To economize and modularize iron reduction processes, we aim to develop an electrodeposition technique to reduce aqueous iron ions to metallic iron. However, the hydrogen reduction reaction (HER) occurs at a more positive standard reduction potential than the iron reduction reaction. In addition, aqueous Fe(II) cations easily precipitate at mildly acidic conditions (pH ≥ 3), which limits the deposition efficiency and degrades deposit quality. To address these challenges, we first search for anions that have intermediate coordination strength with Fe(II) based on the hard-soft acid-base theory, trading a slightly more negative Fe(II) reduction potential for a considerably broader pH stability range. We select citrate with predicted intermediate coordination strength, in combination with more weakly coordinating anions (e.g., SO 4 2- , Cl - ) to control the coordination structure of Fe 2+ for improved electrolyte stability and electrodeposition behavior. We find that citrate coordination stabilizes Fe 2+ -based electrolytes at higher pH conditions (4.8–5.5), significantly extending their shelf life while also suppressing HER during Fe electrodeposition by orders of magnitude. To measure Faradaic efficiencies (FE), we developed a straightforward, titration-based methodology to quantify the amount of deposited iron regardless of the rate of concurrent HER. Although coordination between citrate and Fe 2+ decreases the reduction potential of Fe(II), high FE (≥98%) was achieved at 10 mA cm -2 . FE and achievable deposition rates are tunable by both concentration and the ratio of Fe 2+ to citrate. In all cases, Raman spectroscopy and X-ray diffraction (XRD) reveal that iron deposition in citrate-containing electrolytes suppresses iron oxide/hydroxide precipitation, in contrast to deposits generated in citrate-free electrolytes. Altogether, this work demonstrates that citrate-mediated anion coordination enables high-purity iron electrodeposition with increased FE, high current density, and improved electrolyte stability. This multi-anion coordination strategy provides a versatile framework for designing stable electrolyte and efficient metal electrodeposition.

coordination↗

Chemical and Microstructural Changes in Metallic and Ceramic Materials Exposed to Venusian Surface Conditions

The chemical and microstructural behavior of steels (304, 310, 316, and 1018), nickel-based alloys (beta-NiAl, G30, and 625), gold, coatings (4YSZ, SilcoNert(TradeMark) 1040 (SilcoTek Co.), Dursan(TradeMark) (SilcoTek Co.), and porcelain), and bulk ceramics (alpha-Al2O3, fused quartz, beta-SiC, and alpha-Si3N4) were probed after exposure to supercritical fluid with temperature, pressure, and composition mimicking the Venus lower atmosphere. Exposures were carried out in the Glenn Extreme Environments Rig (GEER) chamber with the Venusian gas mixture (96.5% CO2, 3.5% N2, 30 ppm H2O, 150 ppm SO2, 28 ppm CO, 15 ppm OCS, 3 ppm H2S, 0.5 ppm HCl, and 5 ppb HF) at 92 bar (1330 psi) and 467 C (873 F) for durations of 10 and 42 days. An additional 21-day exposure was done to stainless steel uncoated and coated with SilcoNert(TradeMark) and Dursan(TradeMark). Samples were characterized before and after the experiment by gravimetric analysis, X-ray diffraction, X-ray photoelectron and Auger electron spectroscopies, and cross section electron microscopy analysis. All steels exposed for 10 and 42 days formed double-layered scales consisting mainly of metal (Cr, Fe, Ni) oxides and sulfides showing different chemistry, microstructure, and crystalline phases. The alloys G30 and 625 formed double-layered scales consisting mainly of nickel sulfides. After 10 days, the beta-NiAl exhibited no detectable scale, suggesting only a very thin film was formed. The 304 and 316 stainless steels coated with 4YSZ that were exposed for 10 and 42 days exhibited no significant oxidation. Steel 1018 coated with 4YSZ exhibited a corrosion scale of iron and/or chromium oxide formed at the base of the alloy. The 304 steel coated with porcelain did not exhibit corrosion, although the coating exhibited recession. SilcoNert(TradeMark) exposed for 10 and 42 days exhibited recession, although no oxidation was found to occur at the base of the alloy. Stainless steel 316 coated with Dursan(TradeMark)  exhibited corrosion at the base of the alloy. All ceramics tested showed no clear evidence of reaction. The weight-gain-per-area performance of the materials exposed in the GEER for 10 and 42 days are reported from the lowest to the highest weight gain per area as follows: gold did not exhibit any weight change; nickel-based alloys: beta- NiAl < G30 < 625; steels: 304 < 310 < 316 < 1018; ceramics: considering the experimental uncertainties, no weight change was observed for all ceramics of this work (alpha-Al2O3, Si3N4, SiC, and amorphous SiO2).

Costa, Gustavo C. C.↗