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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.

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At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Security vulnerabilities of connected vehicle streams and their impact on cooperative driving

Autonomous vehicles capable of navigating unpredictable real-world environments with little human feedback are a reality today. Such systems rely heavily on onboard sensors such as cameras, radar/LIDAR, and GPS as well as capabilities such as 3G/4G connectivity and V2V/V2I communication to make real-time maneuvering decisions. Autonomous vehicle control imposes very strict requirements on the security of the communication channels used by the vehicle to exchange information as well as the control logic that performs complex driving tasks such as adapting vehicle velocity or changing lanes. This research presents a first look at the effects of security attacks on the communication channel as well as sensor tampering of a connected vehicle stream equipped to achieve CACC. Our simulation results show that an insider attack can cause significant instability in the CACC vehicle stream. We also outline how different countermeasures, such as downgrading to ACC mode, could potentially be used to improve the security and safety of the connected vehicle streams.

42 ENGINEERING↗
DOE OSTI2021

Stochastic Gradient-Based Distributed Bayesian Estimation in Cooperative Sensor Networks

Distributed Bayesian inference provides a full quantification of uncertainty offering numerous advantages over point estimates that autonomous sensor networks are able to exploit. However, fully-decentralized Bayesian inference often requires large communication overheads and low network latency, resources that are not typically available in practical applications. In this paper, we propose a decentralized Bayesian inference approach based on stochastic gradient Langevin dynamics, which produces full posterior distributions at each of the nodes with significantly lower communication overhead. We provide analytical results on convergence of the proposed distributed algorithm to the centralized posterior, under typical network constraints. Finally, we also provide extensive simulation results to demonstrate the validity of the proposed approach.

42 ENGINEERING↗
DOE OSTI2016

Cooperation between two periplasmic copper chaperones is required for full activity of the cbb 3 -type cytochrome c oxidase and copper homeostasis in Rhodobacter capsulatus

Copper (Cu) is an essential micronutrient that functions as a cofactor in several important enzymes, like respiratory heme-copper oxygen reductases. Yet, Cu is also toxic and therefore cells engage a highly coordinated Cu uptake and delivery system to prevent the accumulation of toxic Cu concentrations. In the current work we analyzed Cu delivery to the cbb 3 -type cytochrome c oxidase ( cbb 3 -Cox) of Rhodobacter capsulatus . We identified the PCu A C-like periplasmic chaperone PccA and analyzed its contribution to cbb 3 -Cox assembly. Our data demonstrate that PccA is a Cu-binding protein with a preference for Cu(I), which is required for efficient cbb 3 -Cox assembly, in particular at low Cu concentrations. By using in vivo and in vitro crosslinking we show that PccA forms a complex with the Sco1-homologue SenC. This complex is stabilized in the absence of the cbb 3 -Cox specific assembly factors CcoGHIS. In cells lacking SenC, the cytoplasmic Cu content is significantly increased, but the simultaneous absence of PccA prevents this Cu accumulation. Lastly, these data demonstrate that the interplay between PccA and SenC is not only required for Cu delivery during cbb 3 -Cox assembly, but that it also regulates Cu homeostasis in R. capsulatus .

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Citrus FRIGIDA cooperates with its interaction partner dehydrin to regulate drought tolerance

SUMMARY Drought is a major environmental stress that severely affects plant growth and crop productivity. FRIGIDA ( FRI ) is a key regulator of flowering time and drought tolerance in model plants. However, little is known regarding its functions in woody plants, including citrus. Thus, we explored the functional role of the citrus FRI ortholog ( CiFRI ) under drought. Drought treatment induced CiFRI expression. CiFRI overexpression enhanced drought tolerance in transgenic Arabidopsis and citrus, while CiFRI suppression increased drought susceptibility in citrus. Moreover, transcriptomic profiling under drought conditions suggested that CiFRI overexpression altered the expression of numerous genes involved in the stress response, hormone biosynthesis, and signal transduction. Mechanistic studies revealed that citrus dehydrin likely protects CiFRI from stress‐induced degradation, thereby enhancing plant drought tolerance. In addition, a citrus brassinazole‐resistant (BZR) transcription factor family member ( CiBZR1 ) directly binds to the CiFRI promoter to activate its expression under drought conditions. CiBZR1 also enhanced drought tolerance in transgenic Arabidopsis and citrus. These findings further our understanding of the molecular mechanisms underlying the CiFRI ‐mediated drought stress response in citrus.

Xu, Yuan‐Yuan↗
DOE OSTI2021

Discovery of segmented Fermi surface induced by Cooper pair momentum

Imaging a peculiar Fermi surface Running a current through a superconductor can cause the superconducting gap to close on a section of the Fermi surface. However, observing this segmented Fermi surface directly is tricky. To do so, Zhu et al . worked with a thin film of the topological insulator bismuth telluride placed on top of superconducting niobium diselenide. A small applied magnetic field caused a screening current, which in turn led to a segmented Fermi surface in the topological insulator layer. Using a scanning tunneling microscope, the researchers were able to map out this Fermi surface. —JS

Science & Technology - Other Topics↗
DOE OSTI2019

Structural Basis for Cooperative Binding of EBNA1 to the Epstein-Barr Virus Dyad Symmetry Minimal Origin of Replication

Epstein-Barr virus is associated with several human malignancies, including nasopharyngeal carcinoma, gastric cancer, and lymphoma. Latently infected cells carry a circularized EBV episome where the origin of replication (oriP) is comprised of two elements: the family of repeats (FR) and dyad symmetry (DS). The viral protein Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) binds to FR and DS to promote EBV episome maintenance and DNA replication during latent infection in proliferating cells. EBNA1 binding to the DS constitutes a minimal origin of DNA replication. Here we report the crystal structure of two EBNA1 DNA-binding domain dimers bound to a DS half-site. This structure shows that the DNA is smoothly bent, allowing for stabilizing interactions between the dimers. The dimer-dimer interface requires an intricate hydrogen bonding network involving residues R491 and D581. When this interface is disrupted, we note loss of stable dimer-dimer complex formation on the DNA, compromised oriP-containing plasmid replication in cells, and impaired recruitment of the MCM3 complex to the oriP. Surface conservation analysis reveals that these residues are part of a larger conserved surface that may be critical for recruitment of replication machinery to the oriP. Our results reveal a new region of EBNA1 critical for its activity and one that may be exploited by targeted small molecules to treat EBV-associated disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Backward-Diode Heterostructure Based on a Zinc-Oxide Nanoarray Formed by Pulsed Electrodeposition and a Cooper-Iodide Film Grown by the SILAR Method

A heterostructure promising for designing a backward diode is formed from a zinc-oxide nanorod array and a nanostructured copper-iodide film. The effect of modes of successive ionic layer adsorption and reaction (SILAR) deposition and the subsequent iodization of CuI films on smooth glass, mica, and fluorine-doped tin oxide (FTO) substrates and on the surface of electrodeposited nanostructured zinc-oxide arrays on the film structure and electrical and optical properties is investigated. A connection between the observed variations in the structure and properties of this material and intrinsic and iodination-induced point defects is established. It is found that the cause and condition for creating a backward-diode heterostructure based on a zinc-oxide nanoarray formed by pulsed electrodeposition and a copper-iodide film grown by the SILAR method is the formation of a p{sup +}-CuI degenerate semiconductor by the excessive iodination of layers of this nanostructured material through its developed surface. The n-ZnO/p{sup +}-CuI barrier heterostructure, which is fabricated for the first time, has the I–V characteristic of a backward diode, the curvature factor of which (γ = 12 V{sup –1}) confirms its high Q factor.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Phoenix Dust Storm (PHX-DUST) Scale: A Cooperatively Developed Dust Storm Scale for Phoenix, Arizona

Using extensive localized meteorological and air quality data for central Arizona from 2010 to 2023, we create a postevent dust storm scale for use by the primary stakeholders in central Arizona for the Phoenix metropolitan area called the Phoenix Dust Storm (PHX-DUST) scale. To ensure usability across a wide spectrum of users, a core concept was to “keep it simple.” The PHX-DUST scale is based on (i) maximum dust concentration for particulate matter (PM10) across the network in micrograms per cubic meter which determines category, e.g., “category 5 (the highest observed category)” and category 4; (ii) the number of network monitors achieving dust concentrations above a threshold of 500 μg m−3 (categorized as “widespread” or “isolated,” as measures of spatial extent); (iii) a duration parameter (which determines “long duration” or “short duration”); and (iv) a measure of wind speed over the affected area (maximum wind gust recorded over the network, which may not be the maximum wind of the storm). Using this index for the 189 dust storms impacting the Phoenix metropolitan area for the period 2010–23, the most severe dust storm occurred on 5 July 2011 and is classified as a “Category 5, Widespread, Long-Duration High-Gust” event. This initial attempt at defining the PHX-DUST scale holds valuable applications for research, education, and applied analyses. It demonstrates that a consortium of interested groups can effectively work to create products benefiting the weather community and general public. Here, the PHX-DUST scale can also serve as a foundational framework for application in other regions where dust storms pose a threat to the well-being of populations, infrastructure, and ecosystems.

Atmosphere↗