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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on TbMgAg by Materials Project

MgTbAg crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Mg is bonded in a 4-coordinate geometry to six equivalent Tb and four Ag atoms. There are two shorter (3.36 Å) and four longer (3.46 Å) Mg–Tb bond lengths. There are two shorter (2.82 Å) and two longer (2.97 Å) Mg–Ag bond lengths. Tb is bonded in a 5-coordinate geometry to six equivalent Mg and five Ag atoms. There are four shorter (3.12 Å) and one longer (3.18 Å) Tb–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 9-coordinate geometry to six equivalent Mg and three equivalent Tb atoms. In the second Ag site, Ag is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Tb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb3Zn by Materials Project

Tb3Zn is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Tb is bonded to eight equivalent Tb and four equivalent Zn atoms to form distorted TbTb8Zn4 cuboctahedra that share corners with twelve equivalent TbTb8Zn4 cuboctahedra, edges with eight equivalent ZnTb12 cuboctahedra, edges with sixteen equivalent TbTb8Zn4 cuboctahedra, faces with four equivalent ZnTb12 cuboctahedra, and faces with fourteen equivalent TbTb8Zn4 cuboctahedra. All Tb–Tb bond lengths are 3.36 Å. All Tb–Zn bond lengths are 3.36 Å. Zn is bonded to twelve equivalent Tb atoms to form ZnTb12 cuboctahedra that share corners with twelve equivalent ZnTb12 cuboctahedra, edges with twenty-four equivalent TbTb8Zn4 cuboctahedra, faces with six equivalent ZnTb12 cuboctahedra, and faces with twelve equivalent TbTb8Zn4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb2Ce by Materials Project

Tb2Ce is alpha Samarium-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Tb is bonded to nine equivalent Tb and three equivalent Ce atoms to form TbTb9Ce3 cuboctahedra that share corners with six equivalent CeTb6Ce6 cuboctahedra, corners with nine equivalent TbTb9Ce3 cuboctahedra, edges with six equivalent CeTb6Ce6 cuboctahedra, edges with fifteen equivalent TbTb9Ce3 cuboctahedra, faces with seven equivalent CeTb6Ce6 cuboctahedra, and faces with twelve equivalent TbTb9Ce3 cuboctahedra. There are three shorter (3.52 Å) and six longer (3.55 Å) Tb–Tb bond lengths. All Tb–Ce bond lengths are 3.48 Å. Ce is bonded to six equivalent Tb and six equivalent Ce atoms to form CeTb6Ce6 cuboctahedra that share corners with six equivalent CeTb6Ce6 cuboctahedra, corners with twelve equivalent TbTb9Ce3 cuboctahedra, edges with six equivalent CeTb6Ce6 cuboctahedra, edges with twelve equivalent TbTb9Ce3 cuboctahedra, faces with six equivalent CeTb6Ce6 cuboctahedra, and faces with fourteen equivalent TbTb9Ce3 cuboctahedra. All Ce–Ce bond lengths are 3.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbCdPd by Materials Project

TbPdCd crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Tb is bonded in a 11-coordinate geometry to five Pd and six equivalent Cd atoms. There are four shorter (3.04 Å) and one longer (3.12 Å) Tb–Pd bond lengths. There are two shorter (3.24 Å) and four longer (3.36 Å) Tb–Cd bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to three equivalent Tb and six equivalent Cd atoms. All Pd–Cd bond lengths are 2.78 Å. In the second Pd site, Pd is bonded in a 9-coordinate geometry to six equivalent Tb and three equivalent Cd atoms. All Pd–Cd bond lengths are 2.89 Å. Cd is bonded in a 10-coordinate geometry to six equivalent Tb and four Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb2(Ga3Ru)3 by Materials Project

Tb2(RuGa3)3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Tb is bonded in a 11-coordinate geometry to eleven Ga atoms. There are a spread of Tb–Ga bond distances ranging from 3.04–3.18 Å. There are two inequivalent Ru sites. In the first Ru site, Ru is bonded in a 8-coordinate geometry to eight Ga atoms. There are a spread of Ru–Ga bond distances ranging from 2.56–2.63 Å. In the second Ru site, Ru is bonded in a 8-coordinate geometry to eight Ga atoms. There are a spread of Ru–Ga bond distances ranging from 2.59–2.62 Å. There are four inequivalent Ga sites. In the first Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Tb, two equivalent Ru, and six Ga atoms. There are four shorter (2.74 Å) and two longer (2.75 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 3-coordinate geometry to three equivalent Tb, three Ru, and five Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.76–2.98 Å. In the third Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Tb, three Ru, and five Ga atoms. There are one shorter (2.71 Å) and two longer (2.83 Å) Ga–Ga bond lengths. In the fourth Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Tb, two equivalent Ru, and six Ga atoms. The Ga–Ga bond length is 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb9Al5S21 by Materials Project

Tb9Al5S21 crystallizes in the trigonal R3 space group. The structure is three-dimensional. there are six inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded to seven S2- atoms to form distorted TbS7 pentagonal bipyramids that share a cornercorner with one AlS6 octahedra, corners with four TbS7 pentagonal bipyramids, corners with two AlS4 tetrahedra, edges with two TbS7 pentagonal bipyramids, an edgeedge with one AlS4 tetrahedra, and a faceface with one AlS6 octahedra. The corner-sharing octahedral tilt angles are 21°. There are a spread of Tb–S bond distances ranging from 2.77–2.92 Å. In the second Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to eight S2- atoms. There are a spread of Tb–S bond distances ranging from 2.75–3.34 Å. In the third Tb3+ site, Tb3+ is bonded to seven S2- atoms to form distorted TbS7 pentagonal bipyramids that share a cornercorner with one AlS6 octahedra, corners with five TbS7 pentagonal bipyramids, corners with two AlS4 tetrahedra, an edgeedge with one AlS6 octahedra, edges with two TbS7 pentagonal bipyramids, and an edgeedge with one AlS4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Tb–S bond distances ranging from 2.78–2.93 Å. In the fourth Tb3+ site, Tb3+ is bonded to seven S2- atoms to form distorted TbS7 pentagonal bipyramids that share a cornercorner with one AlS6 octahedra, corners with five TbS7 pentagonal bipyramids, corners with two AlS4 tetrahedra, edges with two TbS7 pentagonal bipyramids, an edgeedge with one AlS4 tetrahedra, and a faceface with one AlS6 octahedra. The corner-sharing octahedral tilt angles are 21°. There are a spread of Tb–S bond distances ranging from 2.73–2.98 Å. In the fifth Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to eight S2- atoms. There are a spread of Tb–S bond distances ranging from 2.75–3.33 Å. In the sixth Tb3+ site, Tb3+ is bonded to seven S2- atoms to form distorted TbS7 pentagonal bipyramids that share a cornercorner with one AlS6 octahedra, corners with four TbS7 pentagonal bipyramids, corners with two AlS4 tetrahedra, an edgeedge with one AlS6 octahedra, edges with two TbS7 pentagonal bipyramids, and an edgeedge with one AlS4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Tb–S bond distances ranging from 2.77–2.95 Å. There are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four S2- atoms to form AlS4 tetrahedra that share corners with four TbS7 pentagonal bipyramids and edges with two TbS7 pentagonal bipyramids. There are a spread of Al–S bond distances ranging from 2.23–2.25 Å. In the second Al3+ site, Al3+ is bonded to four S2- atoms to form AlS4 tetrahedra that share corners with four TbS7 pentagonal bipyramids and edges with two TbS7 pentagonal bipyramids. There are a spread of Al–S bond distances ranging from 2.23–2.26 Å. In the third Al3+ site, Al3+ is bonded to six S2- atoms to form AlS6 octahedra that share corners with three equivalent TbS7 pentagonal bipyramids, a faceface with one AlS6 octahedra, and faces with three equivalent TbS7 pentagonal bipyramids. There are three shorter (2.41 Å) and three longer (2.47 Å) Al–S bond lengths. In the fourth Al3+ site, Al3+ is bonded to six S2- atoms to form AlS6 octahedra that share corners with three equivalent TbS7 pentagonal bipyramids, edges with three equivalent TbS7 pentagonal bipyramids, and a faceface with one AlS6 octahedra. There are three shorter (2.32 Å) and three longer (2.62 Å) Al–S bond lengths. In the fifth Al3+ site, Al3+ is bonded to six S2- atoms to form AlS6 octahedra that share corners with three equivalent TbS7 pentagonal bipyramids, edges with three equivalent TbS7 pentagonal bipyramids, and a faceface with one AlS6 octahedra. There are three shorter (2.32 Å) and three longer (2.63 Å) Al–S bond lengths. In the sixth Al3+ site, Al3+ is bonded to six S2- atoms to form AlS6 octahedra that share corners with three equivalent TbS7 pentagonal bipyramids, a faceface with one AlS6 octahedra, and faces with three equivalent TbS7 pentagonal bipyramids. There are three shorter (2.41 Å) and three longer (2.47 Å) Al–S bond lengths. There are fourteen inequivalent S2- sites. In the first S2- site, S2- is bonded to three Tb3+ and one Al3+ atom to form distorted STb3Al tetrahedra that share corners with three STb3Al2 square pyramids and corners with three STb3Al trigonal pyramids. In the second S2- site, S2- is bonded to three Tb3+ and one Al3+ atom to form distorted STb3Al tetrahedra that share corners with three STb3Al2 square pyramids and corners with three STb3Al trigonal pyramids. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the fourth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the fifth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the sixth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the seventh S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the eighth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the ninth S2- site, S2- is bonded in a 4-coordinate geometry to four Tb3+ and one Al3+ atom. In the tenth S2- site, S2- is bonded to three Tb3+ and two Al3+ atoms to form distorted STb3Al2 square pyramids that share corners with three STb3Al tetrahedra, a cornercorner with one STb3Al trigonal pyramid, edges with two equivalent STb3Al trigonal pyramids, and faces with two equivalent STb3Al2 square pyramids. In the eleventh S2- site, S2- is bonded to three Tb3+ and one Al3+ atom to form distorted STb3Al trigonal pyramids that share a cornercorner with one STb3Al2 square pyramid, corners with three STb3Al tetrahedra, edges with two equivalent STb3Al2 square pyramids, and edges with two equivalent STb3Al trigonal pyramids. In the twelfth S2- site, S2- is bonded to three Tb3+ and two Al3+ atoms to form distorted STb3Al2 square pyramids that share corners with three STb3Al tetrahedra, a cornercorner with one STb3Al trigonal pyramid, edges with two equivalent STb3Al trigonal pyramids, and faces with two equivalent STb3Al2 square pyramids. In the thirteenth S2- site, S2- is bonded to three Tb3+ and one Al3+ atom to form distorted STb3Al trigonal pyramids that share a cornercorner with one STb3Al2 square pyramid, corners with three STb3Al tetrahedra, edges with two equivalent STb3Al2 square pyramids, and edges with two equivalent STb3Al trigonal pyramids. In the fourteenth S2- site, S2- is bonded in a 4-coordinate geometry to four Tb3+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbCoGe2 by Materials Project

TbCoGe2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Tb is bonded in a 10-coordinate geometry to four equivalent Co and ten Ge atoms. All Tb–Co bond lengths are 3.20 Å. There are a spread of Tb–Ge bond distances ranging from 3.12–3.27 Å. Co is bonded in a 5-coordinate geometry to four equivalent Tb and five Ge atoms. There are a spread of Co–Ge bond distances ranging from 2.26–2.38 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 1-coordinate geometry to six equivalent Tb, one Co, and two equivalent Ge atoms. Both Ge–Ge bond lengths are 2.57 Å. In the second Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Tb and four equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb2(Al3Ir)3 by Materials Project

Tb2(IrAl3)3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Tb is bonded in a 11-coordinate geometry to eleven Al atoms. There are a spread of Tb–Al bond distances ranging from 3.05–3.15 Å. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 8-coordinate geometry to eight Al atoms. There are four shorter (2.57 Å) and four longer (2.62 Å) Ir–Al bond lengths. In the second Ir site, Ir is bonded in a 8-coordinate geometry to eight Al atoms. There are a spread of Ir–Al bond distances ranging from 2.56–2.61 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to two equivalent Tb and two equivalent Ir atoms. In the second Al site, Al is bonded in a 3-coordinate geometry to three equivalent Tb, three Ir, and one Al atom. The Al–Al bond length is 2.78 Å. In the third Al site, Al is bonded in a 3-coordinate geometry to two equivalent Tb, three Ir, and five Al atoms. There are one shorter (2.72 Å) and two longer (2.87 Å) Al–Al bond lengths. In the fourth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Tb, two equivalent Ir, and two equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Revealing Site Occupancy in a Complex Oxide: Terbium Iron Garnet

Complex oxide films stabilized by epitaxial growth can exhibit large populations of point defects which have important effects on their properties. The site occupancy of pulsed laser-deposited epitaxial terbium iron garnet (TbIG) films with excess terbium (Tb) is analyzed, in which the terbium:iron (Tb:Fe)ratio is 0.86 compared to the stoichiometric value of 0.6. The magnetic properties of the TbIG are sensitive to site occupancy, exhibiting a higher compensation temperature (by 90 K) and a lower Curie temperature (by 40 K) than the bulk Tb 3 Fe 5 O 12 garnet. Data derived from X-ray core-level spectroscopy, magnetometry, and molecular field coefficient modeling are consistent with occupancy of the dodecahedral sites by Tb 3+ , the octahedral sites by Fe 3+ , Tb 3+ and vacancies, and the tetrahedral sites by Fe 3+ and vacancies. Energy dispersive X-ray spectroscopy in a scanning transmission electron microscope provides direct evidence of Tb Fe antisites. A small fraction of Fe 2+ is present, and oxygen vacancies are inferred to be present to maintain charge neutrality. In conclusion, variation of the site occupancies provides a path to considerable manipulation of the magnetic properties of epitaxial iron garnet films and other complex oxides, which readily accommodate stoichiometries not found in their bulk counterparts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

< c+a > dislocations in {101 - 2} twins in Mg: A kinematic and energetic requirement

Consideration of published TEM and molecular dynamics studies of interactions between matrix dislocations and {101¯2} twin boundaries (TB) in hexagonal close packed metals inspires a hypothesis regarding the formation of dislocations with < c+a > Burgers vectors inside the twins. It was previously reported that when basal < a > dislocations from the matrix are swept by an advancing TB, they are converted into partial dislocations bounding basal I 1 stacking faults (SFs) within the twin. In the present work, we show that this dislocation configuration near TB renders it energetically favorable for a pair of partial dislocations to constrict into a dislocation within the twin. New in situ TEM observations confirm this hypothesis by revealing long < c+a > dislocation dipoles terminated by the TB at one end and by I1 SFs within the twin at the other end. Finally, the resulting near-screw < c+a > dislocation dipoles are observed to be glissile, enabling self-annihilation in some circumstances. Thus, rather than requiring a high energy dislocation pile-up to press two < a > dislocations through a TB into a single < c+a > dislocation, it is demonstrated that < c+a > dislocations naturally form, within {101¯2} twins in Mg, as TB migrates into a matrix, which inevitably contains dislocations with < a > Burgers vectors. Furthermore, these observations help to explain how the twins themselves may subsequently deform and why they may be particularly vulnerable to plastic, shear localization.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Systems biology predicts that fibrosis in tuberculous granulomas may arise through macrophage-to-myofibroblast transformation

Mycobacterium tuberculosis (Mtb) infection causes tuberculosis (TB), a disease characterized by development of granulomas. Granulomas consist of activated immune cells that cluster together to limit bacterial growth and restrict dissemination. Control of the TB epidemic has been limited by lengthy drug regimens, antibiotic resistance, and lack of a robustly efficacious vaccine. Fibrosis commonly occurs during treatment and is associated with both positive and negative disease outcomes in TB but little is known about the processes that initiate fibrosis in granulomas. Human and nonhuman primate granulomas undergoing fibrosis can have spindle-shaped macrophages with fibroblast-like morphologies suggesting a relationship between macrophages, fibroblasts, and granuloma fibrosis. This relationship has been difficult to investigate because of the limited availability of human pathology samples, the time scale involved in human TB, and overlap between fibroblast and myeloid cell markers in tissues. To better understand the origins of fibrosis in TB, we used a computational model of TB granuloma biology to identify factors that drive fibrosis over the course of local disease progression. We validated the model with granulomas from nonhuman primates to delineate myeloid cells and lung-resident fibroblasts. Our results suggest that peripheral granuloma fibrosis, which is commonly observed, can arise through macrophage-to-myofibroblast transformation (MMT). Further, we hypothesize that MMT is induced in M1 macrophages through a sequential combination of inflammatory and anti-inflammatory signaling in granuloma macrophages. We predict that MMT may be a mechanism underlying granuloma-associated fibrosis and warrants further investigation into myeloid cells as drivers of fibrotic disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Nutritional markers and proteome in patients undergoing treatment for pulmonary tuberculosis differ by geographic region

Contemporary phase 2 TB disease treatment clinical trials have found that microbiologic treatment responses differ between African versus non-African regions, the reasons for which remain unclear. Understanding host and disease phenotypes that may vary by region is important for optimizing curative treatments. We characterized clinical features and the serum proteome of phase 2 TB clinical trial participants undergoing treatment for smear positive, culture-confirmed TB, comparing host serum protein expression in clinical trial participants enrolled in African and Non-African regions. Serum samples were collected from 289 participants enrolled in the Centers for Disease Control and Prevention TBTC Study 29 (NCT00694629) at time of enrollment and at the end of the intensive phase (after 40 doses of TB treatment). After a peptide level proteome analysis utilizing a unique liquid chromatography IM-MS platform (LC-IM-MS) and subsequent statistical analysis, a total of 183 core proteins demonstrated significant differences at both baseline and at week 8 timepoints between participants enrolled from African and non-African regions. The majority of the differentially expressed proteins were upregulated in participants from the African region, and included acute phase proteins, mediators of inflammation, as well as coagulation and complement pathways. Downregulated proteins in the African population were primarily linked to nutritional status and lipid metabolism pathways. We have identified differentially expressed nutrition and lipid pathway proteins by geographic region in TB patients undergoing treatment for pulmonary tuberculosis, which appear to be associated with differential treatment responses. Future TB clinical trials should collect expanded measures of nutritional status and further evaluate the relationship between nutrition and microbiologic treatment response.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1998

Multiple GISS AGCM Hindcasts and MSU Versions of 1979-1998

Multiple realizations of the 1979-1998 time period have been simulated by the Goddard Institute for Space Studies Atmospheric General Circulation Model (GISS AGCM) to explore its responsiveness to accumulated forcings, particularly over sensitive agricultural regions. A microwave radiative transfer postprocessor has produced the AGCM's lower tropospheric, tropospheric and lower stratospheric brightness temperature (Tb) time series for correlations with the various Microwave Sounding Unit (MSU) time series available. MSU maps of monthly means and anomalies were also used to assess the AGCM's mean annual cycle and regional variability. Seven realizations by the AGCM were forced by observed sea surface temperatures (sst) through 1992 to gather rough standard deviations associated with internal model variability. Subsequent runs hindcast January 1979 through April 1998 with an accumulation of forcings: observed ssts, greenhouse gases, stratospheric volcanic aerosols. stratospheric and tropospheric ozone and tropospheric sulfate and black carbon aerosols. The goal of narrowing gaps between AGCM and MSU time series was complicated by MSU time series, by Tb simulation concerns and by unforced climatic variability in the AGCM and in the real world. Lower stratospheric Tb correlations between the AGCM and MSU for 1979-1998 reached as high as 0.91 +/-0.16 globally with sst, greenhouse gases, volcanic aerosol, stratospheric ozone forcings and tropospheric aerosols. Mid-tropospheric Tb correlations reached as high as 0.66 +/-.04 globally and 0.84 +/-.02 in the tropics. Oceanic lower tropospheric Tb correlations similarly reached 0.61 +/-.06 globally and 0.79 +/-.02 in the tropics. Of the sensitive agricultural areas considered, Nordeste in northeastern Brazil was simulated best with mid-tropospheric Tb correlations up to 0.75 +/- .03. The two other agricultural regions, in Africa and in the northern mid-latitudes, suffered from higher levels of non-sst variability. Zimbabwe had a maximum mid-tropospheric correlation of 0.54 +/- 0.11 while the U.S. Cornbelt had only 0.25 +/- .10. Precipitation and surface temperature performance are also examined over these regions. Correlations of MSU and AGCM time series mostly improved with addition of explicit atmospheric forcings in zonal bands but not in agricultural regional bins each encompassing only six AGCM gridcells.

Shah, Kathryn Pierce↗
NASA NTRS2013

Uncertainty Quantification of GEOS-5 L-band Radiative Transfer Model Parameters Using Bayesian Inference and SMOS Observations

Uncertainties in L-band (1.4 GHz) radiative transfer modeling (RTM) affect the simulation of brightness temperatures (Tb) over land and the inversion of satellite-observed Tb into soil moisture retrievals. In particular, accurate estimates of the microwave soil roughness, vegetation opacity and scattering albedo for large-scale applications are difficult to obtain from field studies and often lack an uncertainty estimate. Here, a Markov Chain Monte Carlo (MCMC) simulation method is used to determine satellite-scale estimates of RTM parameters and their posterior uncertainty by minimizing the misfit between long-term averages and standard deviations of simulated and observed Tb at a range of incidence angles, at horizontal and vertical polarization, and for morning and evening overpasses. Tb simulations are generated with the Goddard Earth Observing System (GEOS-5) and confronted with Tb observations from the Soil Moisture Ocean Salinity (SMOS) mission. The MCMC algorithm suggests that the relative uncertainty of the RTM parameter estimates is typically less than 25 of the maximum a posteriori density (MAP) parameter value. Furthermore, the actual root-mean-square-differences in long-term Tb averages and standard deviations are found consistent with the respective estimated total simulation and observation error standard deviations of m3.1K and s2.4K. It is also shown that the MAP parameter values estimated through MCMC simulation are in close agreement with those obtained with Particle Swarm Optimization (PSO).

MCMC↗
NASA NTRS2017

Intercalibration of AMSR2 NASA Team 2 Algorithm Sea Ice Concentrations with AMSR-E Slow Rotation Data

Sea ice estimates from AMSR2 are intercalibrated with AMSR-E fields through a two-step process. First, slow rotation 2 r/min AMSR-E data is used to derive regression equations from colocated pairs of AMSR2 and AMSR-E brightness temperatures (Tb s). The regression equations are used to modify AMSR2 Tb s into AMSR-E equivalent Tb s that are then input into the NASA Team 2 (NT2) sea ice concentration algorithm used for the AMSR-E standard products. The regressed Tb s result in changes in sea ice concentration of a few percent compared to using the original un-regressed AMSR2 Tb s. Next, sea ice estimates from the F17 SSMIS sensor are used as a bridge to compare AMSR-E total sea ice extent estimates in 2010 with AMSR2 total sea ice extent estimates in 2013. Based on this comparison, a further adjustment is made to a weather filter threshold used in the NT2 algorithm to minimize the total extent bias between AMSR2 and AMSR-E using a double-differencing approach. The adjustments reduced apparent bias with AMSR-E from 200 000 km2 for the original unmodified AMSR2 Tb s to –700 and 4700 km2 for the Arctic and Antarctic, respectively. These differences are within the range of previous passive microwave sea ice intercalibrations. The adjusted AMSR2 sea ice fields provide a nearly 15-year time series of sea ice change; depending on the lifetime of AMSR2 and possible follow on sensors, AMSR2 has the potential to be part of a multidecadal record of sea ice change.

remote sensing↗
NASA NTRS2022

L-Band Microwave Satellite Data and Model Simulations Over the Dry Chaco to Estimate Soil Moisture, Soil Temperature, Vegetation and Soil Salinity

The Dry Chaco in South America is a semi-arid ecoregion prone to dryland salinization. In this region, we investigated coarse-scale surface soil moisture (SM), soil temperature, soil salinity and vegetation, using L-band microwave brightness temperature (TB) observations and retrievals from the Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) satellite missions, Catchment Land Surface Model (CLSM) simulations, and in situ measurements within 26 sampled satellite pixels. Across these 26 sampled pixels, the satellite-based SM outperformed CLSM SM compared to field data, and forward L-band TB simulations derived from in situ SM and temperature performed better than those derived from CLSM estimates relative to SMOS TB observations. The surface salinity for the sampled pixels was on average only 4 mg/g and only locally influenced the TB simulations, when including salinity in the dielectric mixing model of the forward radiative transfer model (RTM) simulations. To explore the potential of retrieving salinity together with other RTM parameters to optimize TB simulations over the entire Dry Chaco, the RTM was inverted using 10 years of multi-angular SMOS TB data and constraints of CLSM SM and temperature. However, the latter modeled SM was not sufficiently accurate and factors such as open surface water were missing in the background constraints, so that the salinity retrievals effectively represented a bulk correction of the dielectric constant, rather than salinity per se. However, the retrieval of vegetation, scattering albedo and surface roughness resulted in realistic values.

L-Band↗
DOE OSTI2020

Materials Data on TbGaPd by Materials Project

TbPdGa crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Tb is bonded in a 1-coordinate geometry to five equivalent Pd and six equivalent Ga atoms. There are a spread of Tb–Pd bond distances ranging from 2.92–3.16 Å. There are a spread of Tb–Ga bond distances ranging from 3.11–3.24 Å. Pd is bonded in a 9-coordinate geometry to five equivalent Tb and four equivalent Ga atoms. There are three shorter (2.62 Å) and one longer (2.76 Å) Pd–Ga bond lengths. Ga is bonded in a 10-coordinate geometry to six equivalent Tb and four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbAl7Au3 by Materials Project

TbAu3Al7 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Tb is bonded in a 6-coordinate geometry to six equivalent Au and twelve equivalent Al atoms. All Tb–Au bond lengths are 3.26 Å. There are six shorter (3.32 Å) and six longer (3.38 Å) Tb–Al bond lengths. Au is bonded in a 9-coordinate geometry to two equivalent Tb and seven Al atoms. There are a spread of Au–Al bond distances ranging from 2.59–2.67 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a distorted trigonal planar geometry to two equivalent Tb and three equivalent Au atoms. In the second Al site, Al is bonded in a trigonal planar geometry to three equivalent Au atoms.

36 MATERIALS SCIENCE↗