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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on AgAs(SeF2)3 by Materials Project

AgAs(SeF2)3 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two AgAs(SeF2)3 sheets oriented in the (0, 1, 0) direction. there are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a distorted octahedral geometry to six Se atoms. There are four shorter (2.98 Å) and two longer (3.04 Å) Ag–Se bond lengths. In the second Ag1+ site, Ag1+ is bonded in a 10-coordinate geometry to two equivalent Se and eight F1- atoms. Both Ag–Se bond lengths are 2.74 Å. There are four shorter (2.74 Å) and four longer (3.15 Å) Ag–F bond lengths. As5+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of As–F bond distances ranging from 1.76–1.80 Å. There are two inequivalent Se sites. In the first Se site, Se is bonded in a distorted rectangular see-saw-like geometry to two Ag1+ and two equivalent Se atoms. Both Se–Se bond lengths are 2.40 Å. In the second Se site, Se is bonded in a distorted rectangular see-saw-like geometry to one Ag1+, two Se, and one F1- atom. The Se–Se bond length is 2.36 Å. The Se–F bond length is 3.15 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to one Ag1+, one As5+, and one Se atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Ag1+ and one As5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgAs(S8F3)2 by Materials Project

AgS16AsF6 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four AgS16 clusters and four AsF6 clusters. In each AgS16 cluster, Ag1+ is bonded in a 4-coordinate geometry to four S atoms. There are two shorter (2.72 Å) and two longer (2.81 Å) Ag–S bond lengths. There are eight inequivalent S sites. In the first S site, S is bonded in a water-like geometry to two S atoms. There are one shorter (2.05 Å) and one longer (2.06 Å) S–S bond lengths. In the second S site, S is bonded in a trigonal non-coplanar geometry to one Ag1+ and two S atoms. There are one shorter (2.06 Å) and one longer (2.08 Å) S–S bond lengths. In the third S site, S is bonded in a water-like geometry to two S atoms. The S–S bond length is 2.07 Å. In the fourth S site, S is bonded in a water-like geometry to two S atoms. The S–S bond length is 2.07 Å. In the fifth S site, S is bonded in a water-like geometry to two S atoms. There are one shorter (2.05 Å) and one longer (2.07 Å) S–S bond lengths. In the sixth S site, S is bonded in a water-like geometry to two S atoms. In the seventh S site, S is bonded in a water-like geometry to two S atoms. In the eighth S site, S is bonded in a trigonal non-coplanar geometry to one Ag1+ and two S atoms. In each AsF6 cluster, As5+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of As–F bond distances ranging from 1.77–1.79 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one As5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one As5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgAs(XeF5)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgAs by Materials Project

Ag(As) is beta-prime cadmium gold structured and crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. Ag1+ is bonded to four equivalent Ag1+ and eight equivalent As1- atoms to form AgAg4As8 cuboctahedra that share corners with eight equivalent AsAg8As4 cuboctahedra, corners with ten equivalent AgAg4As8 cuboctahedra, edges with six equivalent AgAg4As8 cuboctahedra, edges with twelve equivalent AsAg8As4 cuboctahedra, faces with eight equivalent AsAg8As4 cuboctahedra, and faces with twelve equivalent AgAg4As8 cuboctahedra. There are two shorter (2.96 Å) and two longer (3.02 Å) Ag–Ag bond lengths. There are four shorter (2.98 Å) and four longer (3.03 Å) Ag–As bond lengths. As1- is bonded to eight equivalent Ag1+ and four equivalent As1- atoms to form distorted AsAg8As4 cuboctahedra that share corners with eight equivalent AgAg4As8 cuboctahedra, corners with ten equivalent AsAg8As4 cuboctahedra, edges with six equivalent AsAg8As4 cuboctahedra, edges with twelve equivalent AgAg4As8 cuboctahedra, faces with eight equivalent AgAg4As8 cuboctahedra, and faces with twelve equivalent AsAg8As4 cuboctahedra. There are two shorter (2.96 Å) and two longer (3.03 Å) As–As bond lengths.

36 MATERIALS SCIENCE↗
NASA NTRS2026

The Operational NASA Anomaly Gas Analyzer and Exploration Follow-Ons

The NASA Anomaly Gas Analyzer (AGA) is the culmination of nearly ten years of advancement of core technology originally developed by Vista Photonics through the Small Business Innovation Research (SBIR) program and expanded using NASA program funding. The AGA is a portable, battery operated, optical gas detection instrument for continuous monitoring of H 2 O, CO 2 , O 2 , CO, NH 3 , HCN, HF, HCl in the spacecraft environment. Real time, in-situ monitored, gas concentrations are communicated at 1 Hz through a built-in display on-orbit and additionally through a serial interface on the ground. The instruments function over the typical range of temperatures and pressures required for the spacecraft environment. A ten-year operational life is targeted. Seven AGA instruments are currently deployed on the International Space Station and two Orion-specific units are manifested for Artemis 2. A variation of the operational AGA is under development for lunar Human Landing Systems. A wider calibrated operating pressure envelope is required in this application. Otherwise, the instruments straightforwardly address lessons learned from the original AGA by improving aspects of thermal control, ruggedness, and ease-of-use. A subset of AGA-developed sensed gases (H 2 O, CO 2 , O 2 ) is the subject of the Primary Constituent Monitor (PCM) development for the Habitation and Logistics Outpost (HALO) destined for lunar orbit. Two PCMs will be installed in HALO as part of the environmental control loop where they will interface with vehicle power and communications. While the basic sensor techniques are unchanged from the AGA, these instruments have been radiation hardened to survive for many years in the harsh target environment. Current development status for these instruments will be presented along with recent developments of a naval submarine variant.

Air Monitoring↗
NASA NTRS2026

The Operational NASA Anomaly Gas Analyzer and Exploration Follow-Ons

The NASA Anomaly Gas Analyzer (AGA) is the culmination of nearly ten years of advancement of core technology originally developed by Vista Photonics through the Small Business Innovation Research (SBIR) program and expanded using NASA program funding. The AGA is a portable, battery operated, optical gas detection instrument for continuous monitoring of H 2 O, CO 2 , O 2 , CO, NH 3 , HCN, HF, HCl in the spacecraft environment. Real time, in-situ monitored, gas concentrations are communicated at 1 Hz through a built-in display on-orbit and additionally through a serial interface on the ground. The instruments function over the typical range of temperatures and pressures required for the spacecraft environment. A ten-year operational life is targeted. Seven AGA instruments are currently deployed on the International Space Station and two Orion-specific units are manifested for Artemis 2. A variation of the operational AGA is under development for lunar Human Landing Systems. A wider calibrated operating pressure envelope is required in this application. Otherwise, the instruments straightforwardly address lessons learned from the original AGA by improving aspects of thermal control, ruggedness, and ease-of-use. A subset of AGA-developed sensed gases (H 2 O, CO 2 , O 2 ) is the subject of the Primary Constituent Monitor (PCM) development for the Habitation and Logistics Outpost (HALO) destined for lunar orbit. Two PCMs will be installed in HALO as part of the environmental control loop where they will interface with vehicle power and communications. While the basic sensor techniques are unchanged from the AGA, these instruments have been radiation hardened to survive for many years in the harsh target environment. Current development status for these instruments will be presented along with recent developments of a naval submarine variant.

ECLSS↗
DOE OSTI2021

Transcription factor FOXC1 positively regulates SFRP1 expression in androgenetic alopecia

Androgenetic alopecia (AGA) is the most common type of hair loss dysfunction. Secreted frizzled related protein 1 (SFRP1) is found to be associated with hair loss, but its role in AGA and the regulation mechanism of its transcription level is unclear. The aim of our study is to explore the expression of SFRP1 in AGA samples and its transcriptional mechanism. Male frontal and occipital scalp hair follicles from AGA patients were collected, and human dermal papilla cells (DPCs) were isolated and cultured. SFRP1 gene was cloned and constructed into recombinant plasmids to perform dual-luciferase reporter assay. Transcription factor binding sites were predicted through the Jaspar website and further confirmed by the chromatin immunoprecipitation (ChIP) assay. Expression of genes in DPCs was determined by immunofluorescence (IF) staining, quantitative real-time PCR (qRT-PCR) and western blotting. Our findings showed that SFRP1 was highly expressed in DPCs of AGA patients. The core promoter region of SFRP1 was from −100 to +50 bp and was found to be positively regulated by forkhead box C1 (FOXC1), a transcription factor related to hair growth, both at mRNA and protein level in DPCs. Our study suggests that FOXC1 plays an important role in regulating SFRP1 transcription, which may provide new insights into the development of therapeutic strategies for the treatment of AGA.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Prediction of crystal structures and motifs in the Fe–Mg–O system at Earth’s core pressures

Abstract Fe, Mg, and O are among the most abundant elements in terrestrial planets. While the behavior of the Fe–O, Mg–O, and Fe–Mg binary systems under pressure have been investigated, there are still very few studies of the Fe–Mg–O ternary system at relevant Earth’s core and super-Earth’s mantle pressures. Here, we use the adaptive genetic algorithm (AGA) to study ternary Fe x Mg y O z phases in a wide range of stoichiometries at 200 GPa and 350 GPa. We discovered three dynamically stable phases with stoichiometries FeMg 2 O 4 , Fe 2 MgO 4, and FeMg 3 O 4 with lower enthalpy than any known combination of Fe–Mg–O high-pressure compounds at 350 GPa. With the discovery of these phases, we construct the Fe–Mg–O ternary convex hull. We further clarify the composition- and pressure-dependence of structural motifs with the analysis of the AGA-found stable and metastable structures. Analysis of binary and ternary stable phases suggest that O, Mg, or both could stabilize a BCC iron alloy at inner core pressures.

Wang, Renhai↗
NASA NTRSDate not supplied

Heat Shields for Aerogravity Assist Vehicles Whose Deceleration at Titan Saves Mass for Future Flagship Class Exploration of Enceladus

A mission of great Astrobiological interest is one that would search for life signatures associated with the oceans and geysers of Enceladus [1]. Spilker et al., [2] have shown in a 2009 paper that use of an Aerogravity Assist (AGA) maneuver with a blunt body in Titan’s atmosphere could enable a Flagship Class Mission to Enceladus within reasonable cost ($3 B) and mission duration (14 years). This paper will summarize the 2023 Decadal Survey (DS) Whitepaper by Arnold, et al. [3] that estimated heat shield masses for an AGA vehicle whose deceleration in Titan’s atmosphere saves mass for future missions to explore Enceladus. This study focused on Titan AGA for an Enceladus lander corresponding to mission “E” in the Spilker, et al. paper [2]. The analysis is the first reported for heat shield requirements for an AGA aeroshell that accounts for the convective and radiation heating arising from flight in Titan’s atmosphere.

James O. Arnold↗
NASA NTRS2011

Passive Aerogravity Assisted Trajectories for a Mars Atmospheric Sample Return Mission

A number of studies have demonstrated that aerodynamic lift during a planetary low-altitude atmospheric flyby can increase the V(sub infinity) bending angle and the total delta V achievable from gravity assist. Aero-Gravity Assist (AGA) trajectories of this type require a significantly high spacecraft L/D (lift-to-drag) ratio and a fairly robust closed-loop guidance algorithm capable of providing a desired control authority for level, nearly constant-altitude atmospheric flight. The AGA concept has been described in some previous publications as one of the techniques for Mars and Venus atmospheric sample return mission design strategies. Recent analysis has demonstrated that passive, ballistic (zero-lift) aeropass trajectories could equally satisfy potential future sample return mission objectives and provide quite robust and simple alternatives to a complex guided AGA lifting trajectory design.

sample return missions↗
DOE OSTI2025

Bridging Experiment and Theory to Reveal Compounds in K–Zn(Cd)–Bi Systems

This study investigates the facile hydride synthesis method guided by theoretical predictions to explore the K–T–Bi (T = Zn, Cd) phase spaces. Using an adaptive genetic algorithm (AGA) and density functional theory (DFT), candidate compositions are identified for experimental validation via a facile hydrides route, permitting experimental screening of K–Zn–Bi and “empty” K–Cd–Bi systems. The previously reported KZnBi and KZn 2 Bi 2 are synthesized alongside newly discovered KCdBi and KCd 2 Bi 2 . While the AGA and DFT predict the stability of these compounds, structural predictions align with the experiment only for KZnBi and KZn 2 Bi 2 . Single-crystal X-ray structure refinements confirm that KZnBi and KZn 2 Bi 2 adopt the hexagonal ZrBeSi- and tetragonal ThCr 2 Si 2 -structure types, respectively. KCdBi has tetragonal PbClF-structure type and KCd 2 Bi 2 belongs to the ThCr 2 Si 2 -structure type. A trend based on the ratio of the metal ionic radii allows to rationalize variation in the structure types within the ATBi family (A = Li–Cs), correctly identifying KCdBi as isostructural to NaZnBi. Thermal stability studied by high-temperature powder X-ray diffraction reveals that Zn-containing compounds melt at higher temperatures (821 K for KZn 2 Bi 2 ) than Cd-containing KCd 2 Bi 2 (635 K). This study highlights the efficacy of combining rapid synthesis techniques with predictive modeling, though structural predictions show some limitations in accuracy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

Solar system 'fast mission' trajectories using aerogravity assist

Initial analyses of the aerogravity assist (AGA) delivery technique to solar system targets (and beyond) has been encouraging. Mission opportunities are introduced that do not exist with typical gravity assist trajectories and current launch capabilities. The technique has the most payoff for high-energy missions such as outer planet orbiters and flybys. The goal of this technique is to reduce the flight duration significantly and to eliminate propulsion for orbit insertion. The paper will discuss detailed analyses and parametric studies that consider launch opportunities for missions to the sun, Saturn, Uranus, Neptune, and Pluto using AGA at Venus and Mars.

Randolph, James E.↗
NASA NTRS2020

Heatshields for Aerogravity Assist Vehicles Whose Deceleration at Titan Saves Mass for Future Flagship Class Exploration of Enceladus

This paper reports the feasibility of using mature heatshield materials for an aerogravity assist (AGA) vehicle whose deceleration in Titan’s atmosphere is a mass-saving enabler for nine different Enceladus missions (T. Spilker et al. 2009). A geometry for the Titan AGA vehicle is recommended as are high-fidelity flow computations on that shape.

James O. Arnold↗
DOE OSTI2023

The microwave spectra of the conformers of $\mathcal{n}$-butyl nitrate

We report the microwave spectrum of n-butyl nitrate was recorded in the 5 to 20 GHz frequency range using broadband chirp and narrowband pulse excitation molecular jet Fourier transform microwave spectrometers. A quantum chemistry structural analysis yielded thirteen stable conformers. Among them, the five most energetically stable conformers were observed in the experimental spectra. The most stable conformer features a butyl chain with an anti-gauche-anti conformation (AGA) where the γ-carbon atom is about 64° out of the nitrate plane. For this conformer, spectra of all 13 C and 15 N minor isotopologues could be measured. The conformer with a straight butyl chain (AAA), and three other conformers (GAA, GGA, and AGG) were also observed. Accurate rotational constants, centrifugal distortion constants, and 14 N nuclear quadrupole coupling constants could be deduced and compared to the theoretical values.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1978

Effects of moisture in infrared thermography of resin matrix composites

Several multiply graphite polyimide composite specimens were examined by real-time infrared thermography in order to study the effects of moisture on their thermograms. Heat was injected from one side and IR emission detected on the opposite side using AGA Thermovision System-680. No differences between the thermograms of dry and water containing specimens were detected for defect-free specimens. However, the presence of trapped water in defective specimens modified the thermographic contrast significantly. It is concluded that: (1) IR thermography can be used to detect moisture in defective composites, and (2) because of the possibility of moisture camouflaging defects, IR thermography for subsurface defect detection should be supplemented by other techniques - such as acoustical imaging and X-radiography.

Singh, J. J.↗
NASA NTRSDate not supplied

Development of a Photoacoustic Formaldehyde Monitor

Key indoor air quality pollutant formaldehyde (H 2 CO) is tracked on International Space Station (ISS) using passive badges returned to the ground periodically for analysis. The process is time-consuming both in preparation and for analysis upon return 6-12 months later. Badges also require precious crew time for deploy, retrieval and stow. As NASA’s focus in space exploration shifts to the Moon and Mars, archival sample return becomes increasingly impractical, so the aim of this project is to develop a highly reliable real-time analyzer for H 2 CO at low concentrations with data downlinked. Potential sources of H 2 CO include materials off gassing, use of formalin as a tissue fixative in biological payloads and overheating of acetal polymers. The Spacecraft Maximum Allowable Concentration (SMAC) for H 2 CO in air is 100 ppb for exposures of 7 days or longer. ISS concentrations of H 2 CO are running only 10 - 30 ppb in the recent several years but have spiked as high as 60 ppb. Gateway real time monitoring requirements for H 2 CO call for a range of 8 - 138 ppb. For this project, a concentration range of 5 - 500 ppb H 2 CO is targeted. The core tunable diode laser spectroscopy (TDLS) technology used for this project was developed by Vista Photonics through the NASA and US Navy Small Business Innovation Research (SBIR) programs. Monitors based on TDLS have been demonstrated on ISS, trialed on a nuclear submarine and are being certified as portable Anomaly Gas Analyzers (AGA) for both ISS and Orion. Initially, direct absorption TDLS was used exclusively in these devices. The H 2 CO target concentration, however, is low ppb, and a longer wavelength is required, so a photoacoustic spectroscopy (PAS) technique was adapted, where the laser excitation is detected by a sensitive microphone vs. a conventional photodetector. This paper will discuss the results of NASA-JSC laboratory testing of a prototype PAS based formaldehyde in air monitor and briefly discuss next steps.

Photoacoustic Formaldehyde Monitor↗