Search NASA⌕ Search

SEARCH · Search NASA

Results for “proximity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mutations in the proximal binding site and F-loop of AdeJ confer resistance to efflux pump inhibitors

Multidrug efflux is one of the major mechanisms of antibiotic resistance in gram-negative bacteria. Inhibitors of efflux pumps potentiate the activities of antibiotics, and their discovery could lead to new therapeutic options. The AdeIJK pump in Acinetobacter baumannii is a promising target for efflux pump inhibitors (EPIs) due to its high clinical importance and conservation, and several classes of EPIs targeting this and other A. baumannii efflux transporters have been recently reported. However, the mechanisms of action of these EPIs and their resistance liability remain underexplored. Here, we analyzed the impact of site-specific substitutions in the substrate/EPI translocation path of the inner membrane transporter AdeJ on efflux of substrate antibiotics and fluorescent probes and activities of substituted 4,6-diaminoquinoline EPIs. We found that substitutions in amino acid residues located in the entrance cleft (R701) and the flexible loop (E675) of AdeJ lead to resistance specifically against biphenyl-substituted EPIs, whereas the substitution of F178 in the distal binding pocket increased AdeJ sensitivity to certain naphthyl- and biphenyl-substituted EPIs. No major differences in docking scores and poses of substrates and EPIs were observed between the wild type and corresponding AdeJ variants for any of the mutations considered. This study concludes that substrates and EPIs bound along the translocation path of AdeJ participate in its conformational transitions and can either increase or decrease the rate of transport and therefore the efficiency of EPIs.

Acinetobacter↗
DOE OSTI2025

Ultrafast renormalization of the magnetic continuum in the proximal Kitaev quantum spin liquid H 3 LiIr 2 O 6 by tr-RIXS [Invited]

We present the first circularly polarized non-resonant pump time-resolved resonant inelastic X-ray scattering (tr-RIXS) experiment in H 3 LiIr 2 O 6 , an iridium-based Kitaev system. Our calculations and experimental results are consistent with the modification of the low-energy magnetic excitations in H 3 LiIr 2 O 6 only during illumination by the laser pulse. We discuss these results in a cooperative framework between the Floquet engineering of the exchange interactions and the dynamic renormalization of electron-electron correlations. However, the penetration length mismatch between the X-ray probe and laser pump and the intrinsic complexity of Kitaev magnets prevents us from unequivocally extracting towards which ground state H 3 LiIr 2 O 6 is driven. We outline possible solutions to these challenges for light-driven stabilization and observation of the Kitaev quantum spin liquid limit by RIXS.

Kim, Jungho [Argonne National Laboratory (ANL), Ar↗
DOE OSTI2020

Interfacial Magnetic Skyrmions and Proximity Effects

The goal of this project is to study the fundamental physics of the magnetic skyrmion, an emergent topological spin texture with whirlpool-like spin winding configuration. Distinguishing functionality of the skyrmion can be achieved only when its exotic topological properties are fully understood and control of skyrmions is mastered. In this project, special attention is paid to creation and manipulation of interfacial skyrmions, and skyrmions in confined or hybrid structures. Relevant topics on interfacial magnetism in general are also covered. This project also promotes the skyrmion physics in national laboratories through partnership with the Argonne National Laboratory (ANL).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Imaging the electronic and magnetic structure of topological-superconductor proximity systems (Final Report)

The primary goals of the projects supported by this grant involved developing methods to detect and control electronic states that can aid in the construction of quantum-information devices, including quantum computers. Two types of materials are needed to create these electronic states: superconductors and topological insulators. The interplay of the quantum mechanics of these materials can give rise to elusive states known as Majorana fermions. Majorana Fermions have incredible potential for quantum technology; they can in principle encode quantum information non-locally, and can thus form the basis of especially robust qubits – the basic building blocks of quantum computers. A centerpiece goal of this work was to develop a Majorana detection tool called a Scanning Majorana Microscope. This tool was successfully developed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Focussing Protons from a Kilojoule Laser for Intense Beam Heating Using Proximal Target Structures

Proton beams driven by chirped pulse amplified lasers have multi-picosecond duration and can isochorically and volumetrically heat material samples, potentially providing an approach for creating samples of warm dense matter with conditions not present on Earth. Envisioned on a larger scale, they could heat fusion fuel to achieve ignition. We have shown in an experiment that a kilojoule-class, multi-picosecond short pulse laser is particularly effective for heating materials. The proton beam can be focussed via target design to achieve exceptionally high flux, important for the applications mentioned. The laser irradiated spherically curved diamond-like-carbon targets with intensity 4×10 18 W/cm 2 , producing proton beams with 3MeV slope temperature. A Cu witness foil was positioned behind the curved target, and the gap between was either empty or spanned with a structure. With a structured target, the total emission of Cu Kα fluorescence was increased 18 fold and the emission profile was consistent with a tightly focussed beam. Transverse proton radiography probed the target with ps order temporal and 10 μm spatial resolution, revealing the fast-acting focussing electric field. Complementary particle-in-cell simulations show how the structures funnel protons to the tight focus. The beam of protons and neutralizing electrons induce the bright Kα emission observed and heat the Cu to 100eV.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Safety Hazards of Batteries and Hydrogen Storage Systems in Proximity

This report addresses the safety concerns and mitigations for battery failures and their impact on hydrogen storage systems. Through an analysis of failure modes, this report highlights the risks posed by thermal runaway and chemical emissions caused by batteries. Although rare, battery thermal failure events may prompt the opening of the relief valve on the hydrogen tank. Strategies such as battery management systems, thermal management systems, and multiple thermally activated pressure relief devices can mitigate these risks. Potential simulations and experiments to better quantify the unique risks posed by lithium-ion batteries near tanks are suggested. Improving safety standards will enable integration of batteries and hydrogen storage systems in various energy storage technologies.

08 HYDROGEN↗
DOE OSTI2025

Charge radii measurements of exotic tin isotopes in the proximity of $N=50$ and $N=82$

We report nuclear charge radii for the isotopes $^{104-134}$Sn, measured using two different collinear laser spectroscopy techniques at ISOLDE-CERN. These measurements clarify the archlike trend in charge radii along the isotopic chain and reveal an odd-even staggering that is more pronounced near the $N=50$ and $N=82$ shell closures. The observed local trends are well described by both nuclear density functional theory and valence space in-medium similarity renormalization group calculations. Both theories predict appreciable contributions from beyond-mean-field correlations to the charge radii of the neutron-deficient tin isotopes. The models fall short, however, of reproducing the magnitude of the known $B(E2)$ transition probabilities, highlighting the remaining challenges in achieving a unified description of both ground-state properties and collective phenomena.

FOS: Physical sciences↗
DOE OSTI2021

Method and system for determining a geographical location of an unmanned aerial vehicle flown in proximity to a power grid

A method for determining geolocation of a UAV near a power grid includes detecting, via a transceiver, a carrier signal transmitted from a first grid node to identify the node's fixed geolocation. A response signal may be transmitted from a second grid node in response to the carrier signal to identify a fixed geolocation of the second grid node, or the UAV may process the carrier signal. A processor determines time-of-flight of the carrier signal, e.g., using the response signal, and derives the UAV's geolocation using the time-of-flight. Determining time-of-flight may include referencing a lookup table indexed by time-of-arrival at the transceiver of the modulated carrier and response signals. A timestamp may indicate time-of-transmission of the carrier and response signals, respectively. Deriving geolocation may include subtracting time-of-transmission of the response signal from that of the carrier signal. A system includes the processor and transceiver.

Moore, Andrew J.↗
DOE OSTI2023

Nitric oxide delivery and heme-assisted S-nitrosation by the bedbug nitrophorin

Here, nitrophorins are heme proteins used by blood feeding insects to deliver nitric oxide (NO) to a victim, leading to vasodilation and antiplatelet activity. Cimex lectularius (bedbug) nitrophorin (cNP) accomplishes this with a cysteine ligated ferric (Fe(III)) heme. In the acidic environment of the insect's salivary glands, NO binds tightly to cNP. During a blood meal, cNP-NO is delivered to the feeding site where dilution and increased pH lead to NO release. In a previous study, cNP was shown to not only bind heme, but to also nitrosate the proximal cysteine, leading to Cys-NO (SNO) formation. SNO formation requires oxidation of the proximal cysteine, which was proposed to be metal-assisted through accompanying reduction of ferric heme and formation of Fe(II)-NO. Here, we report the 1.6 Å crystal structure of cNP first chemically reduced and then exposed to NO, and show that Fe(II)-NO is formed but SNO is not, supporting a metal-assisted SNO formation mechanism. Crystallographic and spectroscopic studies of mutated cNP show that steric crowding of the proximal site inhibits SNO formation while a sterically relaxed proximal site enhances SNO formation, providing insight into specificity for this poorly understood modification. Experiments examining the pH dependence for NO implicate direct protonation of the proximal cysteine as the underlying mechanism. At lower pH, thiol heme ligation predominates, leading to a smaller trans effect and 60-fold enhanced NO affinity (K d = 70 nM). Unexpectedly, we find that thiol formation interferes with SNO formation, suggesting cNP-SNO is unlikely to form in the insect salivary glands.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Lifetime risk of suicide among survivors of the atomic bombings of Japan

Abstract Aims The long-term physical health effects of the atomic bombings of Hiroshima and Nagasaki are well characterised, but the psychological effects remain unclear. Therefore, we sought to determine whether measures of exposure severity, as indirect measures of psychological trauma arising from exposure to the atomic bombings, are associated with suicide mortality among atomic bomb survivors. Methods The Life Span Study is a prospective cohort study of 93 741 Japanese atomic bomb survivors who were located within 10 km of the hypocentre in Hiroshima or Nagasaki at the time of the bombings in 1945, and 26 579 residents of Hiroshima and Nagasaki who were not in either city at the time of the bombings, matched to survivors on city, sex and age. Measures of exposure severity included: proximity to the hypocentre, type of shielding between the survivor and the blast and self-reported occurrence of acute radiation and thermal injuries. Date of death was obtained from the Japanese National Family Registry system. Cause of death was obtained from death certificates. Adjusted hazard ratios (HRs) were estimated from Cox regression models overall and stratified by sex and age. Results During the 60-year follow-up period (1950–2009), 1150 suicide deaths were recorded among 120 231 participants (23.6 per 100 000 person-years): 510 among 70 092 women (17.2 per 100 000 person-years) and 640 among 50 139 men (33.6 per 100 000 person-years). Overall, there was no association of proximity, type of shielding or the occurrence of acute injuries with suicide mortality. Among those <25 years of age at the time of the bombings, increased suicide risk was observed for survivors outside v . shielded inside any structure (HR: 1.24; 95% confidence interval (CI): 1.03, 1.48; interaction p = 0.054) and for those who reported flash burns (HR: 1.32; 95% CI: 1.00, 1.73; interaction p = 0.025). Sex-stratified analyses indicated that these associations were limited to men. Among women, closer proximity to the hypocentre was associated with a non-significant increase in suicide risk, with a positive association between proximity and suicide risk observed among women <15 years of age (HR: 1.09 per km; 95% CI: 1.00, 1.18; interaction p = 0.067). Conclusions Proximity to the hypocentre, shielding and acute injury presence do not generally appear to influence suicide mortality among atomic bomb survivors. However, heterogeneity may exist by age and sex, with younger survivors potentially more sensitive to psychological trauma. Coupled with other studies, our results suggest the importance of long-term monitoring of mental health among young populations exposed to catastrophic events or mass trauma.

Psychiatry↗