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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Single-Chip T/R Module for 1.2 GHz

A single-chip CMOS-based (complementary-metal-oxide-semiconductorbased) transmit/receive (T/R) module is being developed for L-band radar systems. Previous T/R module implementations required multiple chips employing different technologies (GaAs, Si, and others) combined with off-chip transmission lines and discrete components including circulators. The new design eliminates the bulky circulator, significantly reducing the size and mass of the T/R module. Compared to multi-chip designs, the single-chip CMOS can be implemented with lower cost. These innovations enable cost-effective realization of advanced phased array and synthetic aperture radar systems that require integration of thousands of T/R modules. The circulator is a ferromagnetic device that directs the flow of the RF (radio frequency) power during transmission and reception. During transmission, the circulator delivers the transmitted power from the amplifier to the antenna, while preventing it from damaging the sensitive receiver circuitry. During reception, the circulator directs the energy from the antenna to the low-noise amplifier (LNA) while isolating the output of the power amplifier (PA). In principle, a circulator could be replaced by series transistors acting as electronic switches. However, in practice, the integration of conventional series transistors into a T/R chip introduces significant losses and noise. The prototype single-chip T/R module contains integrated transistor switches, but not connected in series; instead, they are connected in a shunt configuration with resonant circuits (see figure). The shunt/resonant circuit topology not only reduces the losses associated with conventional semiconductor switches but also provides beneficial transformation of impedances for the PA and the LNA. It provides full singlepole/ double-throw switching for the antenna, isolating the LNA from the transmitted signal and isolating the PA from the received signal. During reception, the voltage on control line RX/TX (raised bar) is high, causing the field-effect transistor (FET) switch S1 to be closed, forming a parallel resonant tank circuit L1||C1. This circuit presents high impedance to the left of the antenna, so that the received signal is coupled to the LNA. At the same time, FET switches S2 and S3 are open, so that C2 is removed from the circuit (except for a small parasitic capacitance). The combination of L2 and C3 forms a matching network that transforms the antenna impedance of 50 ohms to a higher value from the perspective of the LNA input terminal. This transformation of impedance improves LNA noise figure by increasing the received voltage delivered to the input transistor. This allows lower transconductance and therefore a smaller transistor, which makes it possible to design the CMOS LNA for low power consumption. During transmission, the voltage on control line RX/TX (raised bar) is low, causing switch S1 to be open. In this configuration, the combination of L1 and C1 transforms the antenna impedance to a lower value from the perspective of the PA. This low impedance is helpful in producing a relatively high output power compatible with the low CMOS operating potential. At the same time, switches S2 and S3 are closed, forming the parallel resonant tank circuit L2||C2. This circuit presents high impedance to the right of the antenna, directing the PA output signal to the antenna and away from the LNA. During this time, S3 presents a short circuit across the LNA input terminals to guarantee that the voltage seen by the LNA is small enough to prevent damage.

Moussessian, Alina↗
NASA NTRS2011

Executive Summary of Ares V: Lunar Capabilities Concept Review Through Phase A-Cycle 3

This Technical Memorandum (TM) was generated as an overall Ares V summary from the Lunar Capabilities Concept Review (LCCR) through Phase A-Cycle 3 (PA-C3) with the intent that it may be coupled with separately published appendices for a more detailed, integrated narrative. The Ares V has evolved from the initial point of departure (POD) 51.00.48 LCCR configuration to the current candidate POD, PA-C3D, and the family of vehicles concept that contains vehicles PA-C3A through H. The logical progression from concept to POD vehicles is summarized in this TM and captures the trade space and performance of each. The family-of-vehicles concept was assessed during PA-C3 and offered flexibility in the path forward with the ability to add options deemed appropriate. A description of each trade space is given in addition to a summary of each Ares V element. The Ares V contributions to a Mars campaign are also highlighted with the goal of introducing Ares V capabilities within the trade space. The assessment of the Ares V vehicle as it pertains to Mars missions remained locked to the architecture presented in Mars Design Reference Authorization 5.0 using the PA-C3D vehicle configuration to assess Mars transfer vehicle options, in-space EDS capabilities, docking adaptor and propellant transfer assessments, and lunar and Mars synergistic potential.

Holladay, J. B.↗
NASA NTRS2010

Orion Abort Flight Test

The purpose of NASA's Constellation project is to create the new generation of spacecraft for human flight to the International Space Station in low-earth orbit, the lunar surface, as well as for use in future deep-space exploration. One portion of the Constellation program was the development of the Orion crew exploration vehicle (CEV) to be used in spaceflight. The Orion spacecraft consists of a crew module, service module, space adapter and launch abort system. The crew module was designed to hold as many as six crew members. The Orion crew exploration vehicle is similar in design to the Apollo space capsules, although larger and more massive. The Flight Test Office is the responsible flight test organization for the launch abort system on the Orion crew exploration vehicle. The Flight Test Office originally proposed six tests that would demonstrate the use of the launch abort system. These flight tests were to be performed at the White Sands Missile Range in New Mexico and were similar in nature to the Apollo Little Joe II tests performed in the 1960s. The first flight test of the launch abort system was a pad abort (PA-1), that took place on 6 May 2010 at the White Sands Missile Range in New Mexico. Primary flight test objectives were to demonstrate the capability of the launch abort system to propel the crew module a safe distance away from a launch vehicle during a pad abort, to demonstrate the stability and control characteristics of the vehicle, and to determine the performance of the motors contained within the launch abort system. The focus of the PA-1 flight test was engineering development and data acquisition, not certification. In this presentation, a high level overview of the PA-1 vehicle is given, along with an overview of the Mobile Operations Facility and information on the White Sands tracking sites for radar & optics. Several lessons learned are presented, including detailed information on the lessons learned in the development of wind placards for flight. PA-1 flight data is shown, as well as a comparison of PA-1 flight data to nonlinear simulation Monte Carlo data.

Hayes, Peggy Sue↗
NASA NTRSDate not supplied

Risk Reduction Project in Pad Abort-1 Launch Vehicle Loads & Dynamics

The Pad Abort (PA-1) system includes the Launch Abort System (LAS) and the Command Module (CM). The PA-1 abort flight test will launch from the White Sands Missile Range. Prior to the ignition, the vehicle will be resting, without restraints, on a short support structure. The Launch Abort Motor will ignite and burn for less than 5 seconds before a 20 second coast. Then the LAS will separate from the CM and the CM will descend via parachute to a soil landing. The static firing of the Abort Motor (ST-1) for PA-1 Launch Vehicle resulted in unexpected higher levels that superseded the environment predictions and all the design and test loads of all subassemblies and components. A rapid project was put in place to develop the flight environments, loads and associated uncertainties for the Verification Load Cycle (VLC) of PA-1. An acoustic test and shaker test of the CM were planned and executed in support of the developments of damping and transfer functions. Instead of using the traditional structure-borne envelops, the actual ST-1 pressures and forces were used to develop the internal accelerations. The PA-1 motor was cooled to 60 Deg F using thermal conditioning to reduce the thrust profile. The plumes of the abort motor were studied to determine if the airborne environments would be reduced. The combination of all items, noted above, allowed a reduction in loads for VLC.

Sasan C Armand↗
NASA NTRS2024

Toward a Psychoacoustic Annoyance Model for Urban Air Mobility Vehicle Noise

A psychoacoustic test was performed to obtain annoyance responses to noise from a quadrotor Urban Air Mobility (UAM) vehicle to aid in the development of a model of annoyance to UAM vehicle noise. Previous analysis of that test concluded that a psychoacoustic annoyance (PA) model, including the effects of loudness, sharpness, fluctuation strength and roughness, correlated well with the collected annoyance responses. This motivated the assessment of other PA models available in the literature, as well as the development of a new PA model based on the previously collected annoyance responses to UAM noise. To build the PA model for UAM noise, annoyance ratings to individual sounds and annoyance comparisons between pairs of sounds are first combined into a latent annoyance scale that has a correlation coefficient of 0.98 with the raw responses and that is based on just-noticeable-differences (JNDs) in annoyance. Examples for two sounds that differ in annoyance by 1 JND show when there is 75% agreement about which sound is more annoying. This latent annoyance (JND) scale also gives insight into the interplay of various perceptual components, such as overall loudness, temporal effects and spectral effects. The proposed PA model for UAM noise is fit to the latent annoyance scale, includes the sound quality effects mentioned above, as well as a term for tonality, and offers a step forward in the prediction of annoyance to UAM vehicle noise.

Urban Air Mobility↗
DOE OSTI2024

Distinct Mechanism of Anti-Corrosion and Swelling-Adhesion Modeling of Low-Dimensional Nylon-Fluoropolymer Composite Coatings

Compared to other polymers, composite coatings with fluoropolymers as the matrix have attracted considerable interest due to their mechanical performance, chemical stability, and low surface energy. Herein, we present an anticorrosion mechanism of fluoropolymer composite coatings achieved by dispersing varying amounts of polyamide 12 (PA-12) particles over a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix. The choice of PVDF-HFP as a coating matrix was driven by its superior processability and mechanical properties over Teflon, while PA-12 afforded swelling capacity, preventing electrolyte permeation, and inhibiting matrix stress crack propagation. The corrosion resistance of the coatings was assessed mainly by potentiodynamic polarization and impedance measurements while being immersed in a NaCl solution. Our electrochemical measurement findings showed that 0.75% w/w PA-12 in the PVDF-HFP matrix significantly enhanced corrosion protection even after 21 days of immersion. Microscopy, dielectric spectroscopy, surface analysis, and mechanical testing (American Society for Testing and Materials standards) corroborated the results. PVDF-HFP coatings containing a minimum percolation threshold of 0.75 wt % PA-12 with 1 mil thickness on mild steel exhibited a remarkable increase in resistance and film adhesion, and a notable corrosion rate decrease. Finite element analysis simulation with a bilinear traction-separation law confirmed the swelling mechanism and adhesion behavior. Finally, this study highlights the potential of nylon particle dispersion in PVDF-HFP matrices as a practical approach to developing advanced anticorrosion coatings with promising practical applications in various industries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on PaO3 by Materials Project

PaO3 is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pa is bonded to twelve O atoms to form a mixture of distorted corner, edge, and face-sharing PaO12 cuboctahedra. There are eight shorter (2.40 Å) and four longer (2.60 Å) Pa–O bond lengths. There are two inequivalent O sites. In the first O site, O is bonded to four equivalent Pa atoms to form a mixture of corner and edge-sharing OPa4 tetrahedra. In the second O site, O is bonded in a square co-planar geometry to four equivalent Pa atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PaPd3 by Materials Project

PaPd3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pa is bonded to twelve Pd atoms to form PaPd12 cuboctahedra that share corners with six equivalent PaPd12 cuboctahedra, corners with twelve equivalent PdPa4Pd8 cuboctahedra, edges with eighteen PdPa4Pd8 cuboctahedra, faces with eight equivalent PaPd12 cuboctahedra, and faces with twelve PdPa4Pd8 cuboctahedra. There are six shorter (2.87 Å) and six longer (3.04 Å) Pa–Pd bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded to four equivalent Pa and eight Pd atoms to form distorted PdPa4Pd8 cuboctahedra that share corners with four equivalent PaPd12 cuboctahedra, corners with fourteen PdPa4Pd8 cuboctahedra, edges with six equivalent PaPd12 cuboctahedra, edges with twelve PdPa4Pd8 cuboctahedra, faces with four equivalent PaPd12 cuboctahedra, and faces with sixteen PdPa4Pd8 cuboctahedra. There are a spread of Pd–Pd bond distances ranging from 2.83–3.02 Å. In the second Pd site, Pd is bonded to four equivalent Pa and eight equivalent Pd atoms to form distorted PdPa4Pd8 cuboctahedra that share corners with four equivalent PaPd12 cuboctahedra, corners with fourteen PdPa4Pd8 cuboctahedra, edges with six equivalent PaPd12 cuboctahedra, edges with twelve equivalent PdPa4Pd8 cuboctahedra, faces with four equivalent PaPd12 cuboctahedra, and faces with sixteen PdPa4Pd8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PaPt3 by Materials Project

PaPt3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pa is bonded to twelve Pt atoms to form PaPt12 cuboctahedra that share corners with six equivalent PaPt12 cuboctahedra, corners with twelve equivalent PtPa4Pt8 cuboctahedra, edges with eighteen PtPa4Pt8 cuboctahedra, faces with eight equivalent PaPt12 cuboctahedra, and faces with twelve PtPa4Pt8 cuboctahedra. There are six shorter (2.89 Å) and six longer (3.05 Å) Pa–Pt bond lengths. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded to four equivalent Pa and eight Pt atoms to form distorted PtPa4Pt8 cuboctahedra that share corners with four equivalent PaPt12 cuboctahedra, corners with fourteen PtPa4Pt8 cuboctahedra, edges with six equivalent PaPt12 cuboctahedra, edges with twelve PtPa4Pt8 cuboctahedra, faces with four equivalent PaPt12 cuboctahedra, and faces with sixteen PtPa4Pt8 cuboctahedra. There are a spread of Pt–Pt bond distances ranging from 2.86–3.03 Å. In the second Pt site, Pt is bonded to four equivalent Pa and eight equivalent Pt atoms to form distorted PtPa4Pt8 cuboctahedra that share corners with four equivalent PaPt12 cuboctahedra, corners with fourteen PtPa4Pt8 cuboctahedra, edges with six equivalent PaPt12 cuboctahedra, edges with twelve equivalent PtPa4Pt8 cuboctahedra, faces with four equivalent PaPt12 cuboctahedra, and faces with sixteen PtPa4Pt8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PaBi3 by Materials Project

PaBi3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pa is bonded to twelve Bi atoms to form PaBi12 cuboctahedra that share corners with four equivalent PaBi12 cuboctahedra, edges with eight equivalent PaBi12 cuboctahedra, edges with sixteen equivalent BiPa4Bi8 cuboctahedra, faces with four equivalent PaBi12 cuboctahedra, and faces with eight equivalent BiPa4Bi8 cuboctahedra. There are four shorter (3.28 Å) and eight longer (3.59 Å) Pa–Bi bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded to four equivalent Pa and eight Bi atoms to form distorted BiPa4Bi8 cuboctahedra that share corners with twelve equivalent BiPa4Bi8 cuboctahedra, edges with eight equivalent PaBi12 cuboctahedra, edges with eight equivalent BiPa4Bi8 cuboctahedra, faces with four equivalent PaBi12 cuboctahedra, and faces with ten equivalent BiPa4Bi8 cuboctahedra. There are four shorter (3.28 Å) and four longer (3.59 Å) Bi–Bi bond lengths. In the second Bi site, Bi is bonded in a square co-planar geometry to four equivalent Pa and eight equivalent Bi atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PaFe3 by Materials Project

PaFe3 is Uranium Silicide structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Pa is bonded to twelve Fe atoms to form PaFe12 cuboctahedra that share corners with twelve equivalent PaFe12 cuboctahedra, edges with twenty-four FePa4Fe8 cuboctahedra, faces with six equivalent PaFe12 cuboctahedra, and faces with twelve FePa4Fe8 cuboctahedra. All Pa–Fe bond lengths are 2.72 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to four equivalent Pa and eight equivalent Fe atoms to form FePa4Fe8 cuboctahedra that share corners with twelve equivalent FePa4Fe8 cuboctahedra, edges with eight equivalent PaFe12 cuboctahedra, edges with sixteen equivalent FePa4Fe8 cuboctahedra, faces with four equivalent PaFe12 cuboctahedra, and faces with fourteen FePa4Fe8 cuboctahedra. All Fe–Fe bond lengths are 2.72 Å. In the second Fe site, Fe is bonded to four equivalent Pa and eight Fe atoms to form FePa4Fe8 cuboctahedra that share corners with twelve equivalent FePa4Fe8 cuboctahedra, edges with eight equivalent PaFe12 cuboctahedra, edges with sixteen FePa4Fe8 cuboctahedra, faces with four equivalent PaFe12 cuboctahedra, and faces with fourteen FePa4Fe8 cuboctahedra. All Fe–Fe bond lengths are 2.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pm3Pa by Materials Project

PaPm3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pa is bonded to twelve Pm atoms to form PaPm12 cuboctahedra that share corners with four equivalent PaPm12 cuboctahedra, corners with eight equivalent PmPm8Pa4 cuboctahedra, edges with eight equivalent PaPm12 cuboctahedra, edges with sixteen equivalent PmPm8Pa4 cuboctahedra, faces with four equivalent PaPm12 cuboctahedra, and faces with fourteen PmPm8Pa4 cuboctahedra. There are four shorter (3.52 Å) and eight longer (3.55 Å) Pa–Pm bond lengths. There are two inequivalent Pm sites. In the first Pm site, Pm is bonded to four equivalent Pa and eight Pm atoms to form PmPm8Pa4 cuboctahedra that share corners with twelve equivalent PmPm8Pa4 cuboctahedra, edges with eight equivalent PaPm12 cuboctahedra, edges with sixteen PmPm8Pa4 cuboctahedra, faces with four equivalent PaPm12 cuboctahedra, and faces with fourteen PmPm8Pa4 cuboctahedra. There are four shorter (3.52 Å) and four longer (3.55 Å) Pm–Pm bond lengths. In the second Pm site, Pm is bonded to four equivalent Pa and eight equivalent Pm atoms to form distorted PmPm8Pa4 cuboctahedra that share corners with four equivalent PmPm8Pa4 cuboctahedra, corners with eight equivalent PaPm12 cuboctahedra, edges with twenty-four PmPm8Pa4 cuboctahedra, faces with six equivalent PaPm12 cuboctahedra, and faces with twelve PmPm8Pa4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd3Pa by Materials Project

PaNd3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pa is bonded to twelve Nd atoms to form PaNd12 cuboctahedra that share corners with four equivalent PaNd12 cuboctahedra, corners with eight equivalent NdNd8Pa4 cuboctahedra, edges with eight equivalent PaNd12 cuboctahedra, edges with sixteen equivalent NdNd8Pa4 cuboctahedra, faces with four equivalent PaNd12 cuboctahedra, and faces with fourteen NdNd8Pa4 cuboctahedra. There are four shorter (3.54 Å) and eight longer (3.57 Å) Pa–Nd bond lengths. There are two inequivalent Nd sites. In the first Nd site, Nd is bonded to four equivalent Pa and eight Nd atoms to form NdNd8Pa4 cuboctahedra that share corners with twelve equivalent NdNd8Pa4 cuboctahedra, edges with eight equivalent PaNd12 cuboctahedra, edges with sixteen NdNd8Pa4 cuboctahedra, faces with four equivalent PaNd12 cuboctahedra, and faces with fourteen NdNd8Pa4 cuboctahedra. There are four shorter (3.54 Å) and four longer (3.57 Å) Nd–Nd bond lengths. In the second Nd site, Nd is bonded to four equivalent Pa and eight equivalent Nd atoms to form distorted NdNd8Pa4 cuboctahedra that share corners with four equivalent NdNd8Pa4 cuboctahedra, corners with eight equivalent PaNd12 cuboctahedra, edges with twenty-four NdNd8Pa4 cuboctahedra, faces with six equivalent PaNd12 cuboctahedra, and faces with twelve NdNd8Pa4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Report Series: Finding of Effect and Mitigation Documentation for Building 23-W10, Mercury, Area 23, Nevada National Security Site, Nye County, Nevada

Finding of Effect: The U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Field Office (NNSA/NFO) plans to demolish Building 23-W10 in Mercury (Nevada State Historic Preservation Office [SHPO] Resource No. B15228), which is on the Nevada National Security Site (NNSS) in Nye County, Nevada (Figure 1). The purpose of the undertaking is related to the modernization of Mercury for future mission needs. The NNSA/NFO will implement this undertaking in accordance with the Programmatic Agreement between the National Nuclear Security Administration Nevada Field Office and the Nevada State Historic Preservation Officer Regarding Modernization and Operational Maintenance of the Nevada National Security Site, at Mercury in Nye County, Nevada, hereafter referred to as the Mercury PA. Building 23-W10, a supply warehouse, was installed in Mercury in 1962 (NNSS GIS Database) and served as a support facility for nuclear testing throughout much of the Cold War. It was likely produced during World War II (WWII) and previously installed at Camp Desert Rock. The town of Mercury and the immediate surrounding area have been formally determined eligible for listing in the National Register of Historic Places (National Register, NRHP) as the Mercury Historic District (MHD, SHPO Resource #D230) under Criteria A and C for their importance in supporting nuclear testing and scientific research from 1951 through 1992. Building 23-W10 was identified as a contributing element to the MHD in a 2018 architectural survey of the district (Reno et al. 2018) and recorded on a Nevada Architectural Resource Assessment (ARA) form (Reno et al. 2017). Building 23-W10 was also identified in Appendix C of the Mercury PA as a Category II contributing element. Category II properties are those that have several representatives in the MHD, such as warehouses, but may possess different engineering or architectural characteristics that distinguish them from other classes of similar elements. Building 23-W10 is a historic property for the purposes of compliance with Section 106 of the National Historic Preservation Act (NHPA) and subject to the stipulations of the Mercury PA. Mitigation: The purpose of this letter report is to support the mitigation of the demolition of Building 23-W10 (Nevada State Historic Preservation Office [SHPO] Resource No. B15228) in the Mercury Historic District (MHD, SHPO Resource #D230) at the Nevada National Security Site (NNSS) in Nye County, Nevada. The warehouse is considered contributing to the significance of the district both for its historic importance in relation to nuclear testing under Criterion A and as a part of the distinctive design and construction of the district under Criterion C. This submission is intended to comply with the stipulations in the Programmatic Agreement between the National Nuclear Security Administration Nevada Field Office and the Nevada State Historic Preservation Officer Regarding Modernization and Operational Maintenance of the Nevada National Security Site, at Mercury in Nye County, Nevada, hereafter referred to as the Mercury PA.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Report Series: Finding of Effect and Mitigation Documentation for Building 23-153, Mercury, Area 23, Nevada National Security Site, Nye County, Nevada

Finding of Effect: The U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Field Office (NNSA/NFO) plans to demolish Building 23-153, the Mechanical Calibration Laboratory (Calibration Lab), in Mercury (Nevada State Historic Preservation Office [SHPO] Resource No. B15271), which is on the Nevada National Security Site (NNSS) in Nye County, Nevada. The purpose of the undertaking is related to the modernization of Mercury for future mission needs. The NNSA/NFO will implement this undertaking in accordance with the Programmatic Agreement between the National Nuclear Security Administration Nevada Field Office and the Nevada State Historic Preservation Officer Regarding Modernization and Operational Maintenance of the Nevada National Security Site, at Mercury in Nye County, Nevada, hereafter referred to as the Mercury PA. Building 23-153 was constructed in Mercury in 1982 as the Mechanical Calibration Laboratory and served as a support facility for nuclear testing throughout the last decade of the Cold War. The town of Mercury and the immediate surrounding area have been formally determined eligible for listing in the National Register of Historic Places (NRHP) as the Mercury Historic District (MHD, SHPO Resource No. D230) under Criteria A and C for their importance in supporting nuclear testing and scientific research from 1951 through 1992. Building 23-153 was identified as a contributing element to the MHD in a 2018 architectural survey of the district (Reno et al. 2018) and recorded on a Nevada Architectural Resource Assessment (ARA) form (Reno et al. 2017). Building 23-153 was also identified in Appendix C of the Mercury PA as a Category II contributing element. Category II properties are those that have several representatives in the MHD but may possess different engineering or architectural characteristics that distinguish them from other classes of similar elements. Building 23-153 is a historic property for the purposes of compliance with Section 106 of the National Historic Preservation Act (NHPA) and subject to the stipulations of the Mercury PA. Mitigation: The purpose of this letter report is to submit documentation related to the mitigation of the demolition of Building 23-153, the Mechanical Calibration Laboratory (Calibration Lab, Nevada State Historic Preservation Office [SHPO] Resource No. B15271), in the Mercury Historic District (MHD, SHPO Resource No. D230) at the Nevada National Security Site (NNSS) in Nye County, Nevada. The Calibration Lab is considered contributing to the significance of the district both for its historic importance in relation to nuclear testing under Criterion A and as a part of the distinctive design and construction of the district under Criterion C. This submission is intended to comply with the stipulations in the Programmatic Agreement between the National Nuclear Security Administration Nevada Field Office and the Nevada State Historic Preservation Officer Regarding Modernization and Operational Maintenance of the Nevada National Security Site, at Mercury in Nye County, Nevada, hereafter referred to as the Mercury PA.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Results from a controlled depleted uranium metal casting experiment designed to investigate nuclear Forensic Radiochronometry Signatures

The accurate interpretation of uranium metal 230 Th/ 234 U and 231 Pa/ 235 U radiochronometry model ages requires an understanding of how uranium parent nuclides and decay progeny ( 230 Th and 231 Pa) behave during uranium metal casting. In order to directly measure the spatial distribution of 230 Th and 231 Pa in uranium metal before and after vacuum induction melting (VIM), Los Alamos National Laboratory identified uranium metal feedstock, characterized the metal feedstock, conducted a controlled casting experiment of an approximately 120 kg uranium metal rod, and characterized the cast metal. Herein this study presents radiochronometry results and quantified 230 Th and 231 Pa VIM separation factors from bulk uranium.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Hydrogen Bonding Stiffens Peptide Amphiphile Supramolecular Filaments by Aza-Glycine Residues

Peptide amphiphiles (PAs) are a class of molecules comprised of short amino acid sequences conjugated to hydrophobic moieties that may exhibit self-assembly in water into supramolecular structures. Here, we investigate here how mechanical properties of hydrogels formed by PA supramolecular nanofibers are affected by hydrogen bond densities within their internal structure by substituting glycine for aza-glycine (azaG) residues. We found that increasing the number of PA molecules that contain azaG up to 5 mol% in PA supramolecular nanofibers increases their persistence length fivefold and decreases their diffusion coefficients as measured by fluorescence recovery after photobleaching. When these PAs are used to create hydrogels, their bulk storage modulus (G') was found to increase as azaG PA content in the supramolecular assemblies increases up to a value of 10 mol% and beyond this value a decrease was observed, likely due to diminished levels of nanofiber entanglement in the hydrogels as a direct result of increased supramolecular rigidity. Interestingly, we found that the bioactivity of the scaffolds toward dopaminergic neurons derived from induced pluripotent stem cells can be enhanced directly by persistence length independently of storage modulus. We hypothesize that this is due to interactions between the cells and the extracellular environment across different size scales: from filopodia adhering to individual nanofiber bundles to cell adhesion sites that interact with the hydrogel as a bulk substrate. Fine tuning of hydrogen bond density in self-assembling peptide biomaterials such as PAs provides an approach to control nanoscale stiffness as part of an overall strategy to optimize bioactivity in these supramolecular systems. supramolecular biomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fouling behavior of zwitterionic membranes compared to polyamide membranes

Membrane fouling remains a critical bottleneck for reverse osmosis (RO) desalination, driving energy consumption and reducing membrane lifetime. Here, we employ all-atom molecular dynamics simulations to investigate the antifouling behavior of random zwitterionic amphiphilic copolymer (r-ZAC) membranes composed of sulfobetaine methacrylate (SBMA) and allyl methacrylate (AMA), benchmarked against conventional polyamide (PA) RO membranes. Structural and dynamical analyses—including radial distribution functions, coordination numbers, tetrahedral order parameters, vector orientation, and residence-time correlation functions—reveal that r-ZAC surfaces sustain tightly bound, long-lived hydration layers with preserved tetrahedrality and anisotropic water orientation, in sharp contrast to the weak and disordered hydration of PA. Steered molecular dynamics simulations demonstrate that r-ZAC membranes impose substantial free-energy barriers to foulant approach (alginate ≈ 90 kcal/mol, sucrose ≈ 35 kcal/mol, humic acid ≈ 15 kcal/mol), whereas PA membranes exhibit negligible barriers (< 1 kcal/mol) and thermodynamically favorable adsorption. Detailed foulant–surface interaction analyses show that zwitterionic hydration and electrostatic heterogeneity in r-ZAC suppress adhesion, except in the case of amphiphilic humic acid, which exploits multiple binding modes. Together, these results establish molecular-level design principles for antifouling membranes: the combination of zwitterionic hydration, structured interfacial water, and controlled amphiphilic balance in r-ZAC membranes provides superior resistance to organic fouling relative to PA.

Cross-linked polyamide↗