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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Point-contact Andreev reflection spectroscopy on Bi 2 Se 3 single crystals

In order to study how Andreev reflection (AR) occurs between a superconductor and a three-dimensional topological insulator (TI), we use superconducting Nb tips to perform point-contact AR spectroscopy at 4.2 K on as-grown single crystals of Bi 2 Se 3 . Scanning tunneling spectroscopy and scanning tunneling microscopy are also used to characterize the superconducting tip and both the doping level and surface condition of the TI sample. Furthermore, the point-contact measurements show clear spectral signatures of AR, as well as a depression of zero-bias conductance with decreasing junction impedance. The latter observation can be attributed to interfacial Rashba spin-orbit coupling, and the presence of bulk bands at the Fermi level in our samples suggests that bulk states of Bi2Se3 are involved in the observed AR.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Ceramide-1-phosphate transfer protein enhances lipid transport by disrupting hydrophobic lipid–membrane contacts

Cellular distributions of the sphingolipid ceramide-1-phosphate (C1P) impact essential biological processes. C1P levels are spatiotemporally regulated by ceramide-1-phosphate transfer protein (CPTP), which efficiently shuttles C1P between organelle membranes. Yet, how CPTP rapidly extracts and inserts C1P into a membrane remains unknown. Here, we devise a multiscale simulation approach to elucidate biophysical details of CPTP-mediated C1P transport. We find that CPTP binds a membrane poised to extract and insert C1P and that membrane binding promotes conformational changes in CPTP that facilitate C1P uptake and release. By significantly disrupting a lipid’s local hydrophobic environment in the membrane, CPTP lowers the activation free energy barrier for passive C1P desorption and enhances C1P extraction from the membrane. Upon uptake of C1P, further conformational changes may aid membrane unbinding in a manner reminiscent of the electrostatic switching mechanism used by other lipid transfer proteins. Insertion of C1P into an acceptor membrane, eased by a decrease in membrane order by CPTP, restarts the transfer cycle. Most notably, we provide molecular evidence for CPTP’s ability to catalyze C1P extraction by breaking hydrophobic C1P–membrane contacts with compensatory hydrophobic lipid–protein contacts. Our work, thus, provides biophysical insights into how CPTP efficiently traffics C1P between membranes to maintain sphingolipid homeostasis and, additionally, presents a simulation method aptly suited for uncovering the catalytic mechanisms of other lipid transfer proteins.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Contact-dependent growth inhibition (CDI) systems deploy a large family of polymorphic ionophoric toxins for inter-bacterial competition

Contact-dependent growth inhibition (CDI) is a widespread form of inter-bacterial competition mediated by CdiA effector proteins. CdiA is presented on the inhibitor cell surface and delivers its toxic C-terminal region (CdiA-CT) into neighboring bacteria upon contact. Inhibitor cells also produce CdiI immunity proteins, which neutralize CdiA-CT toxins to prevent auto-inhibition. Here, we describe a diverse group of CDI ionophore toxins that dissipate the transmembrane potential in target bacteria. These CdiA-CT toxins are composed of two distinct domains based on AlphaFold2 modeling. The C-terminal ionophore domains are all predicted to form five-helix bundles capable of spanning the cell membrane. The N-terminal "entry" domains are variable in structure and appear to hijack different integral membrane proteins to promote toxin assembly into the lipid bilayer. The CDI ionophores deployed by E. coli isolates partition into six major groups based on their entry domain structures. Comparative sequence analyses led to the identification of receptor proteins for ionophore toxins from groups 1 & 3 (AcrB), group 2 (SecY) and groups 4 (YciB). Using forward genetic approaches, we identify novel receptors for the group 5 and 6 ionophores. Group 5 exploits homologous putrescine import proteins encoded by puuP and plaP, and group 6 toxins recognize di/tripeptide transporters encoded by paralogous dtpA and dtpB genes. Finally, we find that the ionophore domains exhibit significant intra-group sequence variation, particularly at positions that are predicted to interact with CdiI. Accordingly, the corresponding immunity proteins are also highly polymorphic, typically sharing only ~30% sequence identity with members of the same group. Competition experiments confirm that the immunity proteins are specific for their cognate ionophores and provide no protection against other toxins from the same group. The specificity of this protein interaction network provides a mechanism for self/nonself discrimination between E. coli isolates.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Analysis of mobility data to build contact networks for COVID-19

As social distancing policies and recommendations went into effect in response to COVID-19, people made rapid changes to the places they visit. These changes are clearly seen in mobility data, which records foot traffic using location trackers in cell phones. While mobility data is often used to extract the number of customers that visit a particular business or business type, it is the frequency and duration of concurrent occupancy at those sites that governs transmission. Understanding the way people interact at different locations can help target policies and inform contact tracing and prevention strategies. This paper outlines methods to extract interactions from mobility data and build networks that can be used in epidemiological models. Several measures of interaction are extracted: interactions between people, the cumulative interactions for a single person, and cumulative interactions that occur at particular businesses. Network metrics are computed to identify structural trends which show clear changes based on the timing of stay-at-home orders. Measures of interaction and structural trends in the resulting networks can be used to better understand potential spreading events, the percent of interactions that can be classified as close contacts, and the impact of policy choices to control transmission.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Out-of-reactor test of corrosion and hydrogen pickup in fuel cladding materials in contact with nickel metal - 2016-0038

Increased reactor coolant hydrogen concentration in pressurized water reactors (PWRs) is under consideration for potential benefits in reducing primary water stress corrosion cracking (PWSCC) crack growth rate as well as increasing PWSCC crack initiation time in nickel-based alloys. Potential concerns related to fuel performance include possible increases in hydrogen pickup (HPU) by zirconium based alloys and the enhancement of the pickup through the so-called nickel-window effect. Although the risk of this occurrence may be low, the consequences of increased HPU could be substantial. We examined the impact of dissolved hydrogen (DH) concentrations on Zircaloy-4 corrosion and HPU when the samples are in contact with nickel sources. The work was completed in conjunction with a large project that evaluated the impact of dissolved hydrogen on various fuel cladding and spacer weld specimens of M5{sup R}, ZIRLO{sup R}, Optimized ZIRLO{sup TM}, Low-Tin ZIRLO{sup TM}, Optimized Low-Tin Zircaloy-4, and Zircaloy-2 in either as-received or pre-oxidized conditions for exposures up to 730 days in high-pressure, out-of-reactor autoclave systems operating with a simulated PWR coolant at three different DH concentrations: 30, 100, and 500 cm{sup 3} (cc) H{sub 2}/kg H{sub 2}O. A significant increase in HPU was observed for some Zircaloy-4 specimens in contact with synthetic crud at elevated DH levels. The HPU increased with increasing DH and a metallic nickel fraction in the synthetic crud. The formation of metallic nickel in the synthetic crud samples at elevated DH levels was confirmed. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2011

Thermal And Spectroscopic Analyses Of Next Generation Caustic Side Solvent Extraction Solvent Contacted With 3, 8, And 16 Molar Nitric Acid

A new solvent system referred to as Next Generation Solvent or NGS, has been developed at Oak Ridge National Laboratory for the removal of cesium from alkaline solutions in the Caustic Side Solvent Extraction process. The NGS is proposed for deployment at MCU{sup a} and at the Salt Waste Processing Facility. This work investigated the chemical compatibility between NGS and 16 M, 8 M, and 3 M nitric acid from contact that may occur in handling of analytical samples from MCU or, for 3 M acid, which may occur during contactor cleaning operations at MCU. This work shows that reactions occurred between NGS components and the high molarity nitric acid. Reaction rates are much faster in 8 M and 16 M nitric acid than in 3 M nitric acid. In the case of 16 M and 8 M nitric acid, the nitric acid reacts with the extractant to produce initially organo-nitrate species. The reaction also releases soluble fluorinated alcohols such as tetrafluoropropanol. With longer contact time, the modifier reacts to produce a tarry substance with evolved gases (NO{sub x} and possibly CO). Calorimetric analysis of the reaction product mixtures revealed that the organo-nitrates reaction products are not explosive and will not deflagrate.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Clean Cities Program Contacts (Fact Sheet)

This fact sheet provides contact information for program staff of the U.S. Department of Energy's Clean Cities program, as well as contact information for the nearly 100 local Clean Cities coalitions across the country.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2012

Search for Contact Interactions in the Dimuon Channel in $pp$ Collisions at $\sqrt{s} = 7$ TeV at CMS

The standard model fails to explain the variety of observed quark and lepton avors and their masses suggesting that there might exist a more fundamental basis. If quarks and leptons are composite particles made up of more basic constituents, a new physics interaction in the form of a four-fermion contact interaction arises between them. Experimentally the signal is manifest as a deviation from the standard model prediction in the high-mass tail for the invariant mass distribution of the opposite-sign dimuon pairs. The Large Hadron Collider accelerator at the Center for European Nuclear Research is built to explore new physics possibilities from proton-proton collisions occurring at the world's highest center-of-mass energy. This thesis discusses in detail a search strategy for a new physics possibility based on a left-handed current model of contact interactions. Based on 5.3 fb -1 of 2011 data as collected by the Compact Muon Solenoid detector, exclusion lower limits at 95% con dence level are set on the compositeness energy scale , for both destructive and constructive interferences of the new physics with the standard model Drell-Yan process. These limits form the most stringent limits to date and exceed the current published limits signi cantly.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

BISON Investigation of the Effect of the Fuel- Cladding Contact Irregularities on the Peak Cladding Temperature and FCCI Observed in AFC-3A Rodlet 4

The primary objective of this report is to document results of BISON analyses supporting Fuel Cycle Research and Development (FCRD) activities. Specifically, the present report seeks to provide explanation for the microstructural features observed during post irradiation examination of the helium-bonded annular U-10Zr fuel irradiated during the AFC-3A experiment. Post irradiation examination of the AFC-3A rodlet revealed microstructural features indicative of the fuel-cladding chemical interaction (FCCI) at the fuel-cladding interface. Presence of large voids was also observed in the same locations. BISON analyses were performed to examine stress and temperature profiles and to investigate possible correlation between the voids and FCCI. It was found that presence of the large voids lead to a formation of circumferential temperature gradients in the fuel that may have redirected migrating lanthanides to the locations where fuel and cladding are in contact. Resulting localized increase of lanthanide concentration is expected to accelerate FCCI. The results of this work provide important guidance to the post irradiation examination studies. Specifically, the hypothesis of lanthanides being redirected from the voids to the locations where the fuel and the cladding are in contact should be verified by conducting quantitative electron microscopy or Electron Probe Micro-Analyzer (EPMA). The results also highlight the need for computer models capable of simulating lanthanide diffusion in metallic fuel and establish a basis for validation of such models.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Heat Transfer Analysis from laser Energy on Metal Parts in Contact with HE

We consider the heat transfer of laser energy impinging on metal parts that are in contact with high explosives (HE). The intent is to determine the maximum safe illumination level for this configuration, which will assure that the HE is not heated above safety limits by the laser energy. The DOE High Explosives Safety Manual sets an upper limit on the temperature that HE can be heated. However, we will use the limit published by the LANL / Weapons Facilities Operations in WFO-OS-ES-48, which establishes an upper temperature limit of 70°C for metal in contact with HE. This report describes our experimental and analytical study of this problem.

42 ENGINEERING↗
DOE OSTI2015

Parameterized Receptacle-Pin Contact Model

This report describes a simple, quasi-static, closed-form, parameterized model that predicts the contact forces acting between axially-engaging electrical contact receptacles and a pin. This approach is useful for design studies and reduced-order mechanism modeling, where receptacle-pin insertion forces have traditionally been difficult to quantify without high-fidelity (e.g. rigid body dynamics, finite element analysis) simulations. A Matlab implementation of the model is provided and is demonstrated for three receptacle geometries. Results are compared to rigid body dynamics simulations for the first two geometries and experimental insertion force measurements for the third.

42 ENGINEERING↗
DOE OSTI2019

CST Batch Contact Equilibrium Testing of TCCR Tank 10H Batch 1 and 1A Waste Supernate Samples

The Tank Closure Cesium Removal (TCCR) system uses ion exchange columns filled with crystalline silicotitanate media to process radioactive waste solutions for the removal of Cs-137. TCCR currently focuses on dissolving Savannah River Site (SRS) Tank 10H waste (primarily sodium saltcake solids) within the tank followed by at-tank ion exchange column treatment. Equilibrium batch contact tests conducted in the SRNL Shielded Cells laboratory and associated analyses indicated that both the Tank 10H Batch 1 (pre-production) and 1A (production) waste supernates are unique solutions for which CST cesium removal performance is lower than predicted by ZAM modeling. Cesium distribution coefficients (K d ), percent removal, and CST loading data for the TCCR production supernate batch are provided in Table ES-1. ZAM-based cesium loading predictions are compared to the observed loading for the production batch in Figure ES-1, where significantly lower performance was observed than predicted by the model. Even lower cesium loading results (versus ZAM) were observed previously for the in-tank “teabag” batch contact samples.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

TRUST-EABM Contact Thermal Conductance (CTC) Report

(U) Single Feature Testbeds to Reduce Uncertainty in Simulations and Tests [3] provided an overview for the need of experiments, with accompanying models and simulations, specifically designed to reduce uncertainties and build confidence in complex testing and analysis applications. The Contact Thermal Conductance (CTC) testbed is a joint effort between W-13 (formerly E-13) and MST-8. The objective of this study was to design a testbed, with accompanying finite element models, to quantify, reduce, and propagate measurement uncertainties in contact thermal conductance measurements between two mating components in WR-like thermal environments. The knowledge gained through this simplified experiment would educate more complex assessments and interaction conditions with WR-like materials and geometries.

42 ENGINEERING↗
DOE OSTI2022

Development of a Novel Electrical Characterization Technique for Measuring Hidden Joint Contacts in Weapons Cavities (LDRD Final Report 218470)

This report summarizes research performed in the context of a REHEDS LDRD project that explores methods for measuring electrical properties of vessel joints. These properties, which include contact points and associated contact resistance, are “hidden” in the sense that they are not apparent from a computer-assisted design (CAD) description or visual inspection. As is demonstrated herein, the impact of this project is the development of electromagnetic near-field scanning capabilities that allow weapon cavity joints to be characterized with high spatial and/or temporal resolution. Such scans provide insight on the hidden electrical properties of the joint, allowing more detailed and accurate models of joints to be developed, and ultimately providing higher fidelity shielding effectiveness (SE) predictions. The capability to perform high-resolution temporal scanning of joints under vibration is also explored, using a multitone probing concept, allowing time-varying properties of joints to be characterized and the associated modulation to SE to be quantified.

42 ENGINEERING↗
DOE OSTI2023

Bringing high-efficiency silicon solar cells with heterojunction contacts to market with a new, versatile deposition technique

Silicon heterojunction (SHJ) and tunnel-oxide-passivated-contacts (TOPCon) solar cells are the future for silicon technology after passivated-emitter-and-rear-contact (PERC) cells. However, the tool costs (CapEx) for SHJ (TOPCon) make the cell lines more than 2 (1.5) times of the cost of the PERC, which hinders the wide adoption these new technologies despite higher efficiencies. A common challenge for both cell types is that the passivation layers are sensitive to sputter damage. Furthermore, for TOPCon cells, it is desirable to have an inline (instead of batch) process for tunnel oxide and polysilicon to maximize the throughput and thus reduce the operation cost.

14 SOLAR ENERGY↗
DOE OSTI2020

Commercial Off-the-Shelf Flexible Contact Stress Sensor System: Design Thinking and Systems Engineering Assignment

NNSA has a need to measure the contact stress over long-term durations with minimal impact on the element of interest. The sensor and package should have a small footprint, thin, flexible, modular, and preferably commercially available. There exists an opportunity to leverage expertise within LLNL in sensor development to provide a minimally invasive contact stress sensing solution for NNSA and potentially external customers.

42 ENGINEERING↗
DOE OSTI2024

Non-contact Real-time Target Health Monitor

Targets are an essential part of many accelerator-based experiments, yet their constant radiation exposure eventually affects their internal structure and, consequently, their properties. Current methods typically involve either direct contact with the target or complete removal of the system, which may not be the most efficient for assessing radiation damage. For this reason, a system has been proposed that will monitor a target s radiation damage without the need for direct contact or removal. This sensor will achieve this by measuring the reflectivity of S- and P-polarized waves, which are expected to change measurably due to radiation-induced alterations. As is commonly done, smaller-scale tests were performed to ensure that the necessary equipment was functioning correctly. Once all equipment is tested, the next step will be to perform reflectivity measurements using a tungsten sample, a material often used in targets. Longer-term work will involve scaling up the system and implementing higher-energy beams. This sensor will enable a more comprehensive study of radiation damage in materials and is being considered for projects such as Mu2e, Mu2e-II, LBNF, AMF, and muon colliders.

Agosto Reyes, Alanice↗