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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ta12MoO33 by Materials Project

Ta12MoO33 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are six inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 octahedra that share corners with four TaO6 octahedra, a cornercorner with one MoO4 tetrahedra, and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 5–31°. There are a spread of Ta–O bond distances ranging from 1.85–2.25 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 octahedra that share corners with four TaO6 octahedra, a cornercorner with one MoO4 tetrahedra, and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 6–30°. There are a spread of Ta–O bond distances ranging from 1.85–2.27 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Ta–O bond distances ranging from 1.92–2.11 Å. In the fourth Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 6–32°. There are a spread of Ta–O bond distances ranging from 1.84–2.31 Å. In the fifth Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 3–33°. There are a spread of Ta–O bond distances ranging from 1.81–2.34 Å. In the sixth Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 3–31°. There are a spread of Ta–O bond distances ranging from 1.85–2.28 Å. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four TaO6 octahedra. The corner-sharing octahedral tilt angles are 45°. There is two shorter (1.79 Å) and two longer (1.80 Å) Mo–O bond length. There are seventeen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the fifth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the sixth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Ta5+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ta5+ and one Mo6+ atom. In the ninth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the tenth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the eleventh O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ta5+ and one Mo6+ atom. In the fourteenth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the sixteenth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the seventeenth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta6Mn2FeO18 by Materials Project

Ta6Mn2FeO18 is beta Vanadium nitride-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are six inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share a cornercorner with one MnO6 octahedra, corners with three equivalent FeO6 octahedra, corners with four TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 40–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.03 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent MnO6 octahedra, corners with two equivalent FeO6 octahedra, corners with four TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.98–2.03 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share a cornercorner with one MnO6 octahedra, corners with three equivalent FeO6 octahedra, corners with four TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.03 Å. In the fourth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four MnO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one MnO6 octahedra. The corner-sharing octahedra tilt angles range from 40–55°. There are three shorter (2.00 Å) and three longer (2.01 Å) Ta–O bond lengths. In the fifth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four MnO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.02 Å. In the sixth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four MnO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.98–2.03 Å. There are three inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 51–54°. There are a spread of Mn–O bond distances ranging from 2.17–2.22 Å. In the second Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with eight TaO6 octahedra and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Mn–O bond distances ranging from 2.17–2.23 Å. In the third Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with eight TaO6 octahedra and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 51–54°. There are two shorter (2.17 Å) and four longer (2.22 Å) Mn–O bond lengths. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Fe–O bond distances ranging from 2.12–2.22 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Ta5+ and one Mn2+ atom. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Mn2+ atom. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ta5+ and one Fe2+ atom. In the fourteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCo4Si by Materials Project

TaCo4Si is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ta is bonded in a 7-coordinate geometry to twelve Co and one Si atom. There are a spread of Ta–Co bond distances ranging from 2.68–2.90 Å. The Ta–Si bond length is 2.67 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Ta and six equivalent Co atoms to form CoTa6Co6 cuboctahedra that share corners with twelve equivalent CoTa3Co6Si3 cuboctahedra, edges with six equivalent CoTa6Co6 cuboctahedra, and faces with twenty CoCo6Si6 cuboctahedra. All Co–Co bond lengths are 2.36 Å. In the second Co site, Co is bonded to six equivalent Co and six equivalent Si atoms to form CoCo6Si6 cuboctahedra that share corners with twelve equivalent CoTa3Co6Si3 cuboctahedra, edges with six equivalent CoCo6Si6 cuboctahedra, and faces with twenty CoTa6Co6 cuboctahedra. All Co–Co bond lengths are 2.28 Å. All Co–Si bond lengths are 2.76 Å. In the third Co site, Co is bonded to three equivalent Ta, six Co, and three equivalent Si atoms to form distorted CoTa3Co6Si3 cuboctahedra that share corners with eighteen CoTa6Co6 cuboctahedra, edges with six equivalent CoTa3Co6Si3 cuboctahedra, and faces with eighteen CoTa6Co6 cuboctahedra. There are two shorter (2.33 Å) and two longer (2.42 Å) Co–Co bond lengths. There are one shorter (2.55 Å) and two longer (2.78 Å) Co–Si bond lengths. Si is bonded in a 1-coordinate geometry to one Ta, twelve Co, and three equivalent Si atoms. All Si–Si bond lengths are 2.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm2Ta2O9 by Materials Project

Sm2Ta2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Sm is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Sm–O bond distances ranging from 2.33–2.60 Å. Ta is bonded to six O atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Ta–O bond distances ranging from 1.90–2.20 Å. There are five inequivalent O sites. In the first O site, O is bonded to two equivalent Sm and two equivalent Ta atoms to form a mixture of distorted corner and edge-sharing OSm2Ta2 trigonal pyramids. In the second O site, O is bonded in a distorted trigonal planar geometry to three equivalent Sm atoms. In the third O site, O is bonded in a linear geometry to two equivalent Ta atoms. In the fourth O site, O is bonded in a distorted T-shaped geometry to one Sm and two equivalent Ta atoms. In the fifth O site, O is bonded in a 4-coordinate geometry to three equivalent Sm and one Ta atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCo4Mo by Materials Project

TaMoCo4 is Hexagonal Laves-derived structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ta is bonded in a 10-coordinate geometry to one Mo and twelve Co atoms. The Ta–Mo bond length is 2.84 Å. There are a spread of Ta–Co bond distances ranging from 2.72–2.85 Å. Mo is bonded in a 1-coordinate geometry to one Ta, three equivalent Mo, and twelve Co atoms. All Mo–Mo bond lengths are 2.86 Å. There are a spread of Mo–Co bond distances ranging from 2.71–2.79 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Mo and six equivalent Co atoms to form CoCo6Mo6 cuboctahedra that share corners with twelve equivalent CoTa3Co6Mo3 cuboctahedra, edges with six equivalent CoCo6Mo6 cuboctahedra, and faces with twenty CoTa6Co6 cuboctahedra. All Co–Co bond lengths are 2.37 Å. In the second Co site, Co is bonded to six equivalent Ta and six equivalent Co atoms to form CoTa6Co6 cuboctahedra that share corners with twelve equivalent CoTa3Co6Mo3 cuboctahedra, edges with six equivalent CoTa6Co6 cuboctahedra, and faces with twenty CoCo6Mo6 cuboctahedra. All Co–Co bond lengths are 2.37 Å. In the third Co site, Co is bonded to three equivalent Ta, three equivalent Mo, and six Co atoms to form CoTa3Co6Mo3 cuboctahedra that share corners with eighteen CoCo6Mo6 cuboctahedra, edges with six equivalent CoTa3Co6Mo3 cuboctahedra, and faces with eighteen CoCo6Mo6 cuboctahedra. There are two shorter (2.33 Å) and two longer (2.39 Å) Co–Co bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2Ta2O9 by Materials Project

La2Ta2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. La is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of La–O bond distances ranging from 2.42–2.65 Å. Ta is bonded to six O atoms to form a mixture of distorted edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–13°. There are a spread of Ta–O bond distances ranging from 1.92–2.22 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted rectangular see-saw-like geometry to two equivalent La and two equivalent Ta atoms. In the second O site, O is bonded in a distorted T-shaped geometry to one La and two equivalent Ta atoms. In the third O site, O is bonded in a linear geometry to two equivalent Ta atoms. In the fourth O site, O is bonded in a 4-coordinate geometry to three equivalent La and one Ta atom. In the fifth O site, O is bonded in a distorted trigonal planar geometry to three equivalent La atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A bi-layer barrier design for 122-type iron-based superconducting wires and tapes

Iron-based superconducting wires and tapes hold great promise for high-field magnet applications. A promising design for 122-type wires and tapes based on the powder-in-tube method is using silver and copper double-layer sheaths. For this design a heat treatment temperature below ~ 779 °C is required to prevent Ag-Cu liquid formation. However, this may be below the optimal heat treatment temperature for the critical current density, and still cannot prevent Ag-Cu interdiffusion occurring in the solid state. In this work we propose adding a niobium or tantalum or vanadium (or their alloys) barrier layer between the Ag and Cu to solve the Ag-Cu interdiffusion issue, given that the group-VB metals (vanadium, niobium, tantalum) are relatively inert to both Ag and Cu. To investigate the effectiveness of this design, BaFe 1.84 Co 0.16 As 2 wires and tapes with Ag/Cu and Ag/Ta/Cu sheaths, as well as Ba 0.6 K 0.4 Fe 2 As 2 wires and tapes with Ag/Cu and Ag/Nb/Cu sheaths, were fabricated. It was found that both the Ta and Nb layers kept integral after wire drawing, but after a large flat-rolling reduction the Ta layer broke while the Nb layer kept integral. In the tapes with Ag/Cu sheaths (without the Ta or Nb layer) Cu diffused through the Ag layer and into the powder cores during 740 °C heat treatment, while in the tapes with Ag/Nb/Cu sheaths the Nb layer effectively blocked Ag-Cu interdiffusion even at 900 °C. Further, this work demonstrates that Ta is a suitable barrier material for 122-type wires, while Nb is suitable for both wires and tapes. In this design using Ag/Nb (or Ta)/Cu sheaths, we can regard the outer Cu as the conductor matrix while the Ag and Nb (or Ta) serve as two layers of barriers that suppress reactions between the components. Thus, we call this design a “bi-layer barrier” design for 122-type wires and tapes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Discrepant trends in global land-surface and air temperatures controlled by vegetation biophysical feedbacks

Satellite-based land surface temperature (Ts) with continuous global coverage is increasingly used as a complementary measure for air temperature (Ta), yet whether they observe similar temporal trends remains unknown. Here, we systematically analyzed the trend of the difference between satellite-based Ts and station-based Ta (Ts–Ta) over 2003–2022. We found the global land warming rate inffered from Ts was on average 42.6% slower than that from Ta (Ts–Ta trend: -0.011 °C yr -1 , p = 0.06) during daytime of summer. This slower Ts-based warming was attributed to recent Earth greening, which effectively cooled canopy surface through enhancing evapotranspiration and turbulent heat transfer. However, Ts showed faster warming than Ta during summer nighttime (0.015 °C yr -1 , p < 0.01), winter daytime (0.0069 °C yr -1 , p = 0.08) and winter nighttime (0.0042 °C yr -1 , p = 0.16), when vegetation activity is limited by temperature and solar radiation. Our results indicate potential biases in assessments of atmospheric warming and the vegetation-air temperature feedbacks using satellite-observed surface temperature proxies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Antitoxin control of optimal transcriptional repression in the atypical HigB–HigA toxin–antitoxin system from Proteus vulgaris

Abstract Bacterial toxin–antitoxin (TA) pairs transcriptionally autoregulate their expression via a repression/derepression mechanism in response to changing environmental conditions. The structural diversity of TA systems influences the mechanisms of transcriptional regulation. Here, we define the molecular mechanism for the plasmid-encoded HigB–HigA TA pair originally identified in a post-operative infection with antibiotic-resistant Proteus vulgaris. We determine DNA binding and promoter activity by the HigB–HigA complex supported by structural biology and molecular dynamics simulations of an elusive DNA operator–TA repressor complex. To define the optimal oligomeric TA repressor–DNA operator complex required for derepression, we engineered a dedicated trimeric HigB–HigA2 complex that represses transcription more than 26-fold as compared to the tetrameric HigB2–HigA2. These results expand the known diversity of how the HigB–HigA TA family is autoregulated.

Biochemistry & Molecular Biology↗
DOE OSTI2022

2021 Results for Avian Monitoring of Inorganic and Organic Element Concentrations in Passerine Eggs and Nestlings Collected from Technical Area 16 Burn Grounds, Technical Area 36 Minie, and Technical Area 39 Point 6 at Los Alamos National Laboratory (Rev. 2)

In 2021, non-viable avian eggs and one nestling were opportunistically collected at Los Alamos National Laboratory (LANL) near open detonation sites located at Technical Area (TA) 16 burn grounds and TA-36 Minie. Similar to previous years, nestboxes were monitored at TA-39 Point 6, however, no avian samples were available for opportunistic collection. Samples were evaluated for inorganic elements (mostly metals), dioxins, and furans. One ash-throated flycatcher (Myiarchus cinerascens) egg sample was collected from TA-16 burn grounds. One ash-throated flycatcher and one mountain bluebird (Sialia currucoides) egg sample and one deceased western bluebird (Sialia mexicana) nestling sample were collected from TA-36 Minie. Concentrations of inorganic elements observed in this study were compared with the regional statistical reference level (RSRL) which is the upper-level bounds of background concentrations (mean + three standard deviations = 99% confidence interval). Several inorganic elements were not detected in avian eggs. Most inorganic elements detected were below the RSRL and all were the lowest observable adverse effect level (LOAEL), when available. The nestling collected from TA-36 did not contain detectable concentrations of dioxin or furan congeners. These data suggest that inorganic and organic element concentrations in eggs and nestlings are not of ecological concern. More data are needed to make a robust assessment and to evaluate trends over time.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

A Dynamically Distinct Stellar Population in the Leading Arm of the Sagittarius Stream

We present a chemical and dynamical analysis of the leading arm (LA) and trailing arm (TA) of the Sagittarius (Sgr) stream, as well as for the Sgr dwarf galaxy core (SC), using red giant branch, main-sequence, and RR Lyrae stars from large spectroscopic survey data. The different chemical properties among the LA, TA, and SC generally agree with recent studies and can be understood by a radial metallicity gradient established in the progenitor of the Sgr dwarf, followed by preferential stellar stripping from the outer part of the Sgr progenitor. One striking finding is a relatively larger fraction of low-eccentricity stars (e < 0.4) in the LA than in the TA and SC. The TA and SC exhibit very similar distributions. Considering that a tidal tail stripped off from a dwarf galaxy maintains the orbital properties of its progenitor, we expect that the e-distribution of the LA should be similar to that of the TA and SC. Thus, the disparate behavior of the e-distribution of the LA is of particular interest. Following the analysis of Vasiliev et al., we attempt to explain the different e-distribution by introducing a time-dependent perturbation of the Milky Way by the Large Magellanic Cloud's (LMC) gravitational pull, resulting in substantial evolution of the angular momentum of the LA stars to produce the low-e stars. In addition, we confirm from RR Lyrae stars with high eccentricity (e > 0.6) that the TA stars farther away from the SC are also affected by disturbances from the LMC.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1983

Mechanics of conducting a task analysis

Task analysis (TA) which is a set of analytical procedures used to describe human work in terms of tasks is discussed. The method of TA was derived from various techniques of methods analysis of the industrial engineers. The topic of TA is organized around the following main areas: (1) a detailed discussion of what a TA is; (2) the uses of TA; (3) evaluation of the TA procedure and an assessment of the procedure's worth.

Rappold, V.↗
NASA NTRS2001

Circadian force and EMG activity in hindlimb muscles of rhesus monkeys

Continuous intramuscular electromyograms (EMGs) were recorded from the soleus (Sol), medial gastrocnemius (MG), tibialis anterior (TA), and vastus lateralis (VL) muscles of Rhesus during normal cage activity throughout 24-h periods and also during treadmill locomotion. Daily levels of MG tendon force and EMG activity were obtained from five monkeys with partial datasets from three other animals. Activity levels correlated with the light-dark cycle with peak activities in most muscles occurring between 08:00 and 10:00. The lowest levels of activity generally occurred between 22:00 and 02:00. Daily EMG integrals ranged from 19 mV/s in one TA muscle to 3339 mV/s in one Sol muscle: average values were 1245 (Sol), 90 (MG), 65 (TA), and 209 (VL) mV/s. The average Sol EMG amplitude per 24-h period was 14 microV, compared with 246 microV for a short burst of locomotion. Mean EMG amplitudes for the Sol, MG, TA, and VL during active periods were 102, 18, 20, and 33 microV, respectively. EMG amplitudes that approximated recruitment of all fibers within a muscle occurred for 5-40 s/day in all muscles. The duration of daily activation was greatest in the Sol [151 +/- 45 (SE) min] and shortest in the TA (61 +/- 19 min). The results show that even a "postural" muscle such as the Sol was active for only approximately 9% of the day, whereas less active muscles were active for approximately 4% of the day. MG tendon forces were generally very low, consistent with the MG EMG data but occasionally reached levels close to estimates of the maximum force generating potential of the muscle. The Sol and TA activities were mutually exclusive, except at very low levels, suggesting very little coactivation of these antagonistic muscles. In contrast, the MG activity usually accompanied Sol activity suggesting that the MG was rarely used in the absence of Sol activation. The results clearly demonstrate a wide range of activation levels among muscles of the same animal as well as among different animals during normal cage activity.

NASA Discipline Musculoskeletal↗
NASA NTRS1998

Localized infusion of IGF-I results in skeletal muscle hypertrophy in rats

Insulin-like growth factor I (IGF-I) peptide levels have been shown to increase in overloaded skeletal muscles (G. R. Adams and F. Haddad. J. Appl. Physiol. 81: 2509-2516, 1996). In that study, the increase in IGF-I was found to precede measurable increases in muscle protein and was correlated with an increase in muscle DNA content. The present study was undertaken to test the hypothesis that direct IGF-I infusion would result in an increase in muscle DNA as well as in various measurements of muscle size. Either 0.9% saline or nonsystemic doses of IGF-I were infused directly into a non-weight-bearing muscle of rats, the tibialis anterior (TA), via a fenestrated catheter attached to a subcutaneous miniosmotic pump. Saline infusion had no effect on the mass, protein content, or DNA content of TA muscles. Local IGF-I infusion had no effect on body or heart weight. The absolute weight of the infused TA muscles was approximately 9% greater (P < 0.05) than that of the contralateral TA muscles. IGF-I infusion resulted in significant increases in the total protein and DNA content of TA muscles (P < 0.05). As a result of these coordinated changes, the DNA-to-protein ratio of the hypertrophied TA was similar to that of the contralateral muscles. These results suggest that IGF-I may be acting to directly stimulate processes such as protein synthesis and satellite cell proliferation, which result in skeletal muscle hypertrophy.

Non-NASA Center↗
NASA NTRS2007

Triamcinolone Acetonide Selectively Inhibits Angiogenesis in Small Blood Vessels and Decreases Vessel Diameter within the Vascular Tree

The steroid triamcinolone acetonide (TA) is a potent anti-angiogenesis drug used to treat retinal vascular diseases that include diabetic retinopathy, vascular occlusions and choroidal neovascularization. To quantify the effects of TA on branching morphology within the angiogenic microvascular tree of the chorioallantoic membrane (CAM) of quail embryos. Increasing concentrations of TA (0-16 ng/ml) were applied topically on embryonic day 7 (E7) to the chorioallantoic membrane (CAM) of quail embryos cultured in Petri dishes, and incubated for an additional 24 or 48 hours until fixation. Binary (black/white) microscopic images of arterial end points were quantified by VESGEN software (for Generational Analysis of Vessel Branching) to obtain major vascular parameters that include vessel diameter (Dv), fractal dimension (Df), tortuosity (Tv) and densities of vessel area, length, number and branch point (Av, Lv, Nv and Brv). For assessment of specific changes in vascular morphology induced by TA, the VESGEN software automatically segmented the vascular tree into branching generations (G1...G10) according to changes in vessel diameter and branching. Vessel density decreased significantly up to 34% as the function of increasing concentration of TA according to Av, Lv, Brv, Nv and Df. TA selectively inhibited the growth of new, small vessels, because Lv decreased from 13.14plus or minus 0.61 cm/cm2 for controls to 8.012 plus or minus 0.82 cm/cm2 at 16 ng TA/ml in smaller branching generations (G7-G10), and for Nv from 473.83 plus or minus 29.85 cm(-)2 to 302.32 plus or minus 33.09 cm-()2. In contrast, vessel diameter (Dv) decreased throughout the vascular tree (G1-G10).

McKay, Terri L.↗
NASA NTRS2008

Chromium and Tantalum Site Substitution Patterns in Ni3Al (L1(sub 2))gamma(prime)- Precipitates

The site substitution behavior of Cr and Ta in the Ni3Al (Ll2)-type gamma'-precipitates of a Ni-Al-Cr-Ta alloy is investigated by atom-probe tomography (APT) and first-principles calculations. Measurements of the gamma'-phase composition by APT suggest that Al, Cr, and Ta share the Al sublattice sites of the gamma'-precipitates. The calculated substitutional energies of the solute atoms at the Ni and Al sublattice sites indicate that Ta has a strong preference for the Al sites, while Cr has a weak Al site preference. Furthermore, Ta is shown to replace Cr at the Al sublattice sites of the gamma'-precipitates, altering the elemental phase partitioning behavior of the Ni-Al-Cr-Ta alloy.

Booth-Morrison, Christopher↗
NASA NTRS2015

Use of a Tantalum Liner to Reduce Bore Erosion and Increase Muzzle Velocity in Two-Stage Light Gas Guns

Muzzle velocities and gun erosion predicted by earlier numerical simulations of two stage light gas guns with steel gun tubes were in good agreement with experimental values. In a subsequent study, simulations of high performance shots were repeated with rhenium (Re) gun tubes. Large increases in muzzle velocity (2 - 4 km/sec) were predicted for Re tubes. In addition, the hydrogen-produced gun tube erosion was, in general, predicted to be zero with Re tubes. Tantalum (Ta) has some mechanical properties superior to those of Re. Tantalum has a lower modulus of elasticity than Re for better force transmission from the refractory metal liner to an underlying thick wall steel tube. Tantalum also has greater ductility than Re for better survivability during severe stress/strain cycles. Also, tantalum has been used as a coating or liner in military powder guns with encouraging results. Tantalum has, however, somewhat inferior thermal properties to those of rhenium, with a lower melting point and lower density and thermal conductivity. The present study was undertaken to see to what degree the muzzle velocity gains of rhenium gun tubes (over steel tubes) could be achieved with tantalum gun tubes. Nine high performance shots were modeled with a new version of our CFD gun code for steel, rhenium and tantalum gun tubes. For all except the highest velocity shot, the results with Ta tubes were nearly identical with those for Re tubes. Even for the highest velocity shot, the muzzle velocity gain over a steel tube using Ta was 82% of the gain obtained using Re. Thus, the somewhat inferior thermal properties of Ta (when compared to those of Re) translate into only very slightly poorer overall muzzle velocity performance. When this fact is combined with the superior mechanical properties of Ta and the encouraging performance of Ta liners/coatings in military powder guns, tantalum is to be preferred over Re as a liner/coating material for two stage light gas guns to increase muzzle velocity and reduce bore erosion.

Launchers↗
DOE OSTI2026

Tantalum alloy–based resonators for quantum information systems

Utilizing tantalum (Ta) in superconducting circuits has led to significant improvements, such as high qubit lifetime (T 1 ) and quality factors in both qubits and resonators, suggesting that material optimization plays an important role in the development of superconducting circuits. Thus we here explore superconducting gap engineering in Ta-based devices as a powerful strategy for expanding the range of suitable host materials. By alloying 20 atomic percent (at.%) hafnium into Ta thin films, we achieve a superconducting transition temperature (T c ) of 6.09 K as observed in direct current (DC) transport measurements, reflecting an increase in the superconducting gap. We systematically vary deposition conditions to control film orientation and transport properties of Ta-Hf alloy thin films. We then confirm the enhancement in T c via microwave measurements at millikelvin temperatures. We verify the ~40 increase in T c relative to bare Ta devices, while the loss contributions from two-level systems and quasi-particles remain unchanged in the low temperature regime. These findings emphasize the promise of material engineering in superconducting circuits and point to many potential material candidates for further exploration.

Ta-Hf alloy thin films↗