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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Mapping microhabitats of lignocellulose decomposition by a microbial consortium

The leaf-cutter ant fungal garden ecosystem is a naturally evolved model system for efficient plant biomass degradation. Degradation processes mediated by the symbiotic fungus Leucoagaricus gongylophorus are difficult to characterize due to dynamic metabolisms and spatial complexity of the system. Herein, we performed microscale imaging across 12-µm-thick adjacent sections of Atta cephalotes fungal gardens and applied a metabolome-informed proteome imaging approach to map lignin degradation. This approach combines two spatial multiomics mass spectrometry modalities that enabled us to visualize colocalized metabolites and proteins across and through the fungal garden. Spatially profiled metabolites revealed an accumulation of lignin-related products, outlining morphologically unique lignin microhabitats. Metaproteomic analyses of these microhabitats revealed carbohydrate-degrading enzymes, indicating a prominent fungal role in lignocellulose decomposition. Integration of metabolome-informed proteome imaging data provides a comprehensive view of underlying biological pathways to inform our understanding of metabolic fungal pathways in plant matter degradation within the micrometer-scale environment.

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

Nanoparticle Tracking to Probe Transport in Porous Media

From the granular and fractured subsurface environment to highly engineered polymer membranes used in pharmaceutical purification, porous materials are ubiquitous in nature and industrial applications. In particular, porous media are used extensively in processes including water treatment, pharmaceutical sterilization, food/beverage processing and heterogeneous catalysis, where hindered mass transport is either essential to the process or a necessary, but undesirable limitation. Unfortunately, there are currently no universal models capable of predicting mass transport based on a description of the porous material because real porous materials are complex, and because many coupled dynamic mechanisms (e.g. adsorption, steric effects, hydrodynamic effects, electrostatic interactions, etc.) give rise to the observed macroscopic transport phenomena. While classical techniques, like nuclear magnetic resonance and dynamic light scattering, provide useful information about mass transport in porous media at the ensemble level, they provide limited insight into the microscopic mechanisms that give rise to complex phenomena such as anomalous diffusion, hindered pore-space accessibility, and unexpected retention under flow, among many others. To address this issue, we have developed refractive index matching imaging systems, combined with single-particle tracking methods, allowing the direct visualization of single particle motion within a variety of porous materials. Here, we summarize our recent efforts to advance the understanding of nanoparticle transport in porous media using single-particle tracking methods in both fundamental and applied scenarios. First, we describe the basic principles for two-dimensional and three-dimensional single-particle tracking in porous materials. Then, we describe concrete examples of nanoparticle transport in porous materials from two perspectives: (1) understanding fundamental elementary particle transport processes in porous media, including pore accessibility and cavity escape, which limit transport in porous media; (2) facilitating applications in industrial processes, e.g. by understanding the mechanisms of particle fouling and remobilization in filtration membranes. Finally, we provide an outlook of opportunities associated with investigating other types of mass transport in confined environments using single-particle tracking methods, including electrophoretic and self-propelled motion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Tracking Restoration And Closure (TRAC): Status Update on Story Maps for Communicating Site Cleanup and Closure Status - 19033

The U.S. Department of Energy (DOE) Office of Environmental Management (EM) initiated the development of a customized, web-based mapping tool for communicating technical information on groundwater plumes at sites within the EM complex. Although the online tool was initially conceived to be a simple conversion of a paper report on contaminant plume sizes, remedial approaches, and regulatory status, it has advanced to providing specific information on cleanup status and site closure. The story maps provide robust geospatial visualization of plumes at DOE sites, as well as explanatory text, photographs, and video for an entire site, or for a management unit within the site. This collection of story maps is called TRAC (Tracking Restoration And Closure), and not only communicates information for each individual site, but also summarizes pertinent metrics on cleanup and remaining contaminants across all EM sites. TRAC is focused on communicating cleanup status, technical challenges, and needs for site closure, with a key challenge of transforming data into relevant, easily understood information. Although DOE managers are the target audience, the story maps can also be used to contribute to public understanding of groundwater cleanup progress at EM sites. Unlike the data access tools maintained at some EM sites (e.g., Hanford, Portsmouth, and Paducah), TRAC is neither a portal for data downloads, nor a tool for performing data analytics. Rather, the goal of TRAC is to provide relevant information on cleanup progress and closure that is consistent across all sites, allowing the user to view summary information across all sites, or examine information relevant to a particular site. This information sharing is needed to maintain open communications with interested parties and communicate efforts that ensure long-term protection of human health and the environment. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Limited effect of anthropogenic nitrogen oxides on secondary organic aerosol formation

Globally, secondary organic aerosol (SOA) is mostly formed from emissions of biogenic volatile organic compounds (VOCs) by vegetation, but it can be modified by human activities as demonstrated in recent research. Specifically, nitrogen oxides (NO x = NO + NO 2 ) have been shown to play a critical role in the chemical formation of low volatility compounds. We have updated the SOA scheme in the global NCAR (National Center for Atmospheric Research) Community Atmospheric Model version 4 with chemistry (CAM4-chem) by implementing a 4-product volatility basis set (VBS) scheme, including NO x -dependent SOA yields and aging parameterizations. Small differences are found for the no-aging VBS and 2-product schemes; large increases in SOA production and the SOA-to-OA ratio are found for the aging scheme. The predicted organic aerosol amounts capture both the magnitude and distribution of US surface annual mean measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network by 50 %, and the simulated vertical profiles are within a factor of 2 compared to aerosol mass spectrometer (AMS) measurements from 13 aircraft-based field campaigns across different regions and seasons. We then perform sensitivity experiments to examine how the SOA loading responds to a 50 % reduction in anthropogenic nitric oxide (NO) emissions in different regions. We find limited SOA reductions of 0.9–5.6, 6.4–12.0 and 0.9–2.8 % for global, southeast US and Amazon NO x perturbations, respectively. The fact that SOA formation is almost unaffected by changes in NO x can be largely attributed to a limited shift in chemical regime, to buffering in chemical pathways (low- and high-NO x pathways, O 3 versus NO 3 -initiated oxidation) and to offsetting tendencies in the biogenic versus anthropogenic SOA responses.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Phase compatibilities of YBa2Cu3O(9-delta) type structure in quintenary systems Y-Ba-Cu-O-X (impurity)

Electrical transport properties of the oxidic high T(sub c) superconductors are significantly affected by the presence of minor amounts of various elements adventing as impurities, e.g., from the chemical environment during manufacturing. YBa2Cu3O(9-delta) is prone to an extinction of the superconductivity on (partial) substitution of all four elemental components. E.g., Pr (for Y), La (for Ba), Zn (for Cu) or peroxygroup (for O) substituents will alter some of the superconductivity preconditions, like mixed valence state in Cu3O7/O(9-delta) network or structural distortion of the network. Although various pseudoternary chemical equilibrium phase diagrams of the Y(O)-Ba(O)-Cu(O) system now are available, no consensus is generally shown, however, this is partly due to lack of compatible definitions of the equilibrium conditions. Less information is available about the phase compatibilities in the appropriate quaternary phase diagram (including oxygen) and virtually no information exists about any pentenary phase diagrams (including one impurity). Unfortunately, complexity of such systems, stemming both from number of quaternary or pentenary compounds and from visualizing the five-component phase system, limits this presentation to more or less close surroundings of the YBa2Cu3O(9-delta) type phase in appropriate pseudoquaternary or pseudopseudoternary diagrams, involving Y-Ba-Cu and O, O-CO2, alkaline metals, Mg and alkaline earths, and Sc and most of the 3-d and 4-f elements. The systems were investigated by means of x ray diffraction, neutron diffraction and chemical analytical methods on samples prepared by sol-gel technique from citrates. The superconductivity was characterized by measuring the diamagnetic susceptibility by SQUID.

Karen, P.↗
DOE OSTI2022

Facet-selective etching trajectories of individual semiconductor nanocrystals

The size and shape of semiconductor nanocrystals govern their optical and electronic properties. Liquid cell transmission electron microscopy (LCTEM) is an emerging tool that can directly visualize nanoscale chemical transformations and therefore inform the precise synthesis of nanostructures with desired functions. However, it remains difficult to controllably investigate the reactions of semiconductor nanocrystals with LCTEM, because of the highly reactive environment formed by radiolysis of liquid. Here, we harness the radiolysis processes and report the single-particle etching trajectories of prototypical semiconductor nanomaterials with well-defined crystalline facets. Lead selenide nanocubes represent an isotropic structure that retains the cubic shape during etching via a layer-by-layer mechanism. The anisotropic arrow-shaped cadmium selenide nanorods have polar facets terminated by either cadmium or selenium atoms, and the transformation trajectory is driven by etching the selenium-terminated facets. LCTEM trajectories reveal how nanoscale shape transformations of semiconductors are governed by the reactivity of specific facets in liquid environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

2D IR Microscopy—Technology for Visualizing Chemical Dynamics in Heterogeneous Environments (Final Technical Report)

The primary focus of this project was the design, prototype, and demonstration of a 2D IR microscope. The start date of this project was July 15, 2016 and the project end date was July 14, 2022. In the early years of this project our team designed, prototyped, and completely integrated a homebuilt microscope head with our high-repetition rate 2D IR spectrometer. Once in place our research team focused on characterizing the 2D IR microscope and using it to investigate model systems relevant to energy technologies. As part of this process, we identified two initial chemical systems to use to further develop 2D IR imaging modalities. The first chemical system developed was a room temperature ionic liquid (RTIL) electrolyte system and the second chemical system was a mixture of carbonates and salts developed as a battery electrolyte system. The completion of this project resulted in the full characterization of chemical dynamics in a bulk RTIL system and the demonstration of 2D IR imaging across the RTIL cast as a microdroplet in silicon oil. In addition, we explored the liquid structures and dynamics of organic carbonate mixtures from the vantage point of the vibrational probe, methyl thiocyanate. By the end of the project, we had moved toward in-depth studies of the organic carbonate mixtures.

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

Electrostatic Barriers to Nanoparticle Accessibility of a Porous Matrix

Translocation from one cavity to another through a narrow constriction (i.e., a “hole”) represents the fundamental elementary process underlying hindered mass transport of nanoparticles and macromolecules within many natural and synthetic porous materials, including intracellular environments. This process is complex and may be influenced by long-range (e.g., electrostatic) particle–wall interactions, transient adsorption/desorption, surface diffusion, and hydrodynamic effects. In this study, we used a three-dimensional (3D) tracking method to explicitly visualize the process of nanoparticle diffusion within periodic porous nanostructures, where electrostatic interactions were mediated via ionic strength. The effects of electrostatic interactions on nanoparticle transport were surprisingly large. For example, an increase in the Debye length of only a few nanometers (in a material with a hole diameter of ~100 nm) increased the mean cavity escape time 3-fold. A combination of computational and experimental analyses indicated that this hindered cavity escape was due to an electrostatic energy barrier in the region of the hole, which was quantitatively explained using DLVO theory. These findings explicitly demonstrate that the cavity escape process was barrier-limited and dominated by electrostatic effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Visualizing the NIOSH Pocket Guide: Open-source web application for accessing and exploring the NIOSH Pocket Guide to Chemical Hazards

The NIOSH Pocket Guide to Chemical Hazards is a trusted resource that displays key information for a collection of chemicals commonly encountered in the workplace. Entries contain chemical structures—occupational exposure limit information ranging from limits based on full-shift time-weighted averages to acute limits such as short-term exposure limits and immediately dangerous to life or health values, as well as a variety of other data such as chemical-physical properties and symptoms of exposure. The NIOSH Pocket Guide (NPG) is available as a printed, hardcopy book, a PDF version, an electronic database, and a downloadable application for mobile phones. All formats of the NIOSH Pocket Guide allow users to access the data for each chemical separately, however, the guide does not support data analytics or visualization across chemicals. This project reformatted existing data in the NPG to make it searchable and compatible with exploration and analysis using a web application. The resulting application allows users to investigate the relationships between occupational exposure limits, the range and distribution of occupational exposure limits, and the specialized sorting of chemicals by health endpoint or to summarize information of particular interest. These tasks would have previously required manual extraction of the data and analysis. The usability of this application was evaluated among industrial hygienists and researchers and while the existing application seems most relevant to researchers, the open-source code and data are amenable to modification by users to increase customization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Perfect Crystals: microgravity capillary counterdiffusion crystallization of human manganese superoxide dismutase for neutron crystallography

The NASA mission Perfect Crystals used the microgravity environment on the International Space Station (ISS) to grow crystals of human manganese superoxide dismutase (MnSOD)—an oxidoreductase critical for mitochondrial vitality and human health. The mission’s overarching aim is to perform neutron protein crystallography (NPC) on MnSOD to directly visualize proton positions and derive a chemical understanding of the concerted proton electron transfers performed by the enzyme. Large crystals that are perfect enough to diffract neutrons to sufficient resolution are essential for NPC. This combination, large and perfect, is hard to achieve on Earth due to gravity-induced convective mixing. Capillary counterdiffusion methods were developed that provided a gradient of conditions for crystal growth along with a built-in time delay that prevented premature crystallization before stowage on the ISS. Here, we report a highly successful and versatile crystallization system to grow a plethora of crystals for high-resolution NPC.

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

A Multi-modal Approach to Understanding Degradation of Organic Photovoltaic Materials

State-of-the-art organic photovoltaic (OPV) materials are composed of complex, chemically diverse polymeric and molecular structures that form highly intricate solid-state interactions, collectively yielding exceptional tunability in performance and aesthetics. These properties are especially attractive for semitransparent power-generating windows or shades in living environments, greenhouses, or other architectural integrations. However, before such a future is realized, a broader and deeper understanding of property stability must be acquired. Stability during operating and environmental conditions is critical, namely, material color steadfastness, optoelectronic performance retention, morphological rigidity, and chemical robustness. To date, no single investigation encompasses all four distinct, yet interconnected, metrics. Here, we present a multimodal strategy that captures a dynamic and interconnected evolution of each property during the course of an accelerated photobleaching experiment. We demonstrate this approach across relevant length scales (from molecular to visual macroscale) using X-ray photoelectron spectroscopy, grazing-incidence X-ray scattering, microwave conductivity, and time-dependent photobleaching spectroscopies for two high-performance semitransparent OPV blends—PDPP4T:PC 60 BM and PDPP4T:IEICO-4F, with comparisons to the stabilities of the individual components. We present direct evidence that specific molecular acceptor (fullerene vs nonfullerene) designs and the resulting donor–acceptor interactions lead to distinctly different mechanistic routes that ultimately arrive at what is termed “OPV degradation.” We directly observe a chemical oxidation of the cyano endcaps of the IEICO-4F that coincides with a morphological change and large loss in photoconductivity while the fullerene acceptor-containing blend demonstrates a significantly greater fraction of oxygen uptake but retains 55% of the photoconductivity. Finally, this experimental roadmap provides meaningful guidance for future high-throughput, multimodal studies, benchmarking the sensitivity of the different analytical techniques for assessing stability in printable active layers, independent of complete device architectures.

14 SOLAR ENERGY↗
DOE OSTI2022

Structure of a dimeric photosystem II complex from a cyanobacterium acclimated to far-red light

Photosystem II (PSII) is the water-splitting enzyme central to oxygenic photosynthesis. To drive water oxidation, light is harvested by accessory pigments, mostly chlorophyll (Chl) a molecules, which absorb visible light (400–700 nm). Some cyanobacteria facultatively acclimate to shaded environments by altering their photosynthetic machinery to additionally absorb far-red light (FRL, 700–800 nm), a process termed far-red light photoacclimation or FaRLiP. During far-red light photoacclimation, FRL-PSII is assembled with FRL-specific isoforms of the subunits PsbA, PsbB, PsbC, PsbD, and PsbH, and some Chl-binding sites contain Chls d or f instead of the usual Chl a. The structure of an apo-FRL-PSII monomer lacking the FRL-specific PsbH subunit has previously been determined, but visualization of the dimeric complex has remained elusive. Here, we report the cryo-EM structure of a dimeric FRL–PSII complex. The site assignments for Chls d and f are consistent with those assigned in the previous apo-FRL-PSII monomeric structure. All sites that bind Chl d or Chl f at high occupancy exhibit a FRL-specific interaction of the formyl moiety of the Chl d or Chl f with the protein environment, which in some cases involves a phenylalanine sidechain. The structure retains the FRL-specific PsbH2 subunit, which appears to alter the energetic landscape of FRL-PSII, redirecting energy transfer from the phycobiliprotein complex to a Chl f molecule bound by PsbB2 that acts as a bridge for energy transfer to the electron transfer chain. Collectively, these observations extend our previous understanding of the structure-function relationship that allows PSII to function using lower energy FRL.

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

Controlling thermoelectric transport via native defects in the diamond-like semiconductors Cu 2 HgGeTe 4 and Hg 2 GeTe 4

Diamond like semiconductors (DLS) have emerged as candidates for thermoelectric energy conversion. Towards understanding and optimizing performance, we present a comprehensive investigation of the electronic properties of two DLS phases, quaternary Cu 2 HgGeTe 4 and related ordered vacancy compound Hg 2 GeTe 4 , including thermodynamic stability, defect chemistry, and transport properties. To establish the thermodynamic link between the related but distinct phases, the stability region for both is visualized in chemical potential space. In spite of their similar structure and bonding, we show that the two materials exhibit reciprocal behaviors for dopability. Cu 2 HgGeTe 4 is degenerately p-type in all environments despite its wide stability region, due to the presence of low-energy acceptor defects V Cu and Cu Hg and is resistant to extrinsic n-type doping. Meanwhile Hg 2 GeTe 4 has a narrow stability region and intrinsic behavior due to the relatively high formation energy of native defects, but presents an opportunity for bi-polar doping. While these two compounds have similar structure, bonding, and chemical constituents, the reciprocal nature of their dopability emerges from significant differences in band edge positions. A Brouwer band diagram approach is utilized to visualize the role of native defects on carrier concentrations, dopability, and transport properties. Here this study elucidates the doping asymmetry between two solid-solution forming DLS phases Cu 2 HgGeTe 4 and Hg 2 GeTe 4 by revealing the defect chemistry of each compound, and suggests design strategies for defect engineering of DLS phases.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Warning Signs of Potential Black Swan Outbreaks in Infectious Disease

Black swan events in infectious disease describe rare but devastatingly large outbreaks. While experts are skeptical that such events are predictable, it might be possible to identify the warning signs of a black swan event. Specifically, following the initiation of an outbreak, key differentiating features could serve as alerts. Such features could be derived from meta-analyses of large outbreaks for multiple infectious diseases. We hypothesized there may be common features among the pathogen, environment, and host epidemiological triad that characterize an infectious disease black swan event. Using Los Alamos National Laboratory’s tool, Analytics for Investigation of Disease Outbreaks, we investigated historical disease outbreak information and anomalous events for several infectious diseases. By studying 32 different infectious diseases and global outbreaks, we observed that in the past 20–30 years, there have been potential black swan events in the majority of infectious diseases analyzed. Importantly, these potential black swan events cannot be attributed to the first introduction of the disease to a susceptible host population. This paper describes our observations and perspectives and illustrates the value of broad analysis of data across the infectious disease realm, providing insights that may not be possible when we focus on singular infectious agents or diseases. Data analytics could be developed to warn health authorities at the beginning of an outbreak of an impending black swan event. Such tools could complement traditional epidemiological modeling to help forecast future large outbreaks and facilitate timely warning and effective, targeted resource allocation for mitigation efforts.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Spatial and Temporal Variations in Characteristic Ratios of Elemental Carbon to Carbon Monoxide and Nitrogen Oxides across the United States

Here, a ratio-based method is used to characterize anthropogenic elemental carbon (EC a ) using in situ measurements and emissions of carbon monoxide (CO) and nitrogen oxides (NO x ). We use long-term records of ground-based measurements from the U.S. Environmental Protection Agency (EPA) Air Quality System and Interagency Monitoring of Protected Visual Environments to assess the patterns in anthropogenic combustion ratios (ΔEC a /ΔCO and ΔEC a /ΔNO x ) across the U.S. Petroleum Administration for Defense Districts (PADD) regions for the years 2000-2015. We investigate the change in these ratios between the periods 2000-2007 and 2008-2015. Overall, ΔEC a /ΔCO ratios increase by 0.7-82% and ΔEC a /ΔNO x by 6.8-104% across the East and West PADD regions. The urban West showed the largest increase relative to other regions. This is mainly attributed to a 13-23% increase in ΔEC a during the winter and fall seasons and significant reductions in urban ΔNO x (except in winter). We also find that emission ratios derived from the EPA's National Emission Inventory (NEI) overestimate (underestimate) the increase in the observed enhancement ratios in the East (West). Analyses of changes in NEI emissions in the West reveal (a) smaller reductions in NEI emissions for NO x from the off-road sector and (b) an increase in PM 2.5 (particulate matter 2.5 μm or less in diameter) emissions from commercial/residential combustion and smaller reductions in nonroad emissions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Visualizing Light-Induced Microstrain and Phase Transition in Lead-Free Perovskites Using Time-Resolved X-Ray Diffraction

Metal halide perovskites have emerged as promising materials for optoelectronic applications in the last decade. A large amount of effort has been made to investigate the interplay between the crystalline lattice and photoexcited charge carriers as it is vital to their optoelectronic performance. Among them, ultrafast laser spectroscopy has been intensively utilized to explore the charge carrier dynamics of perovskites, from which the local structural information can only be extracted indirectly. Here, we have applied a time-resolved X-ray diffraction technique to investigate the structural dynamics of prototypical two-dimensional lead-free halide perovskite Cs 3 Bi 2 Br 9 nanoparticles across temporal scales from 80 ps to microseconds. We observed a quick recoverable (a few ns) photoinduced microstrain up to 0.15% and a long existing lattice expansion (~a few hundred nanoseconds) at mild laser fluence. Once the laser flux exceeds 1.4 mJ/cm 2 , the microstrain saturates and the crystalline phase partially transfers into a disordered phase. This photoinduced transient structural change can recover within the nanosecond time scale. Furthermore, these results indicate that photoexcitation of charge carriers couples with lattice distortion, which fundamentally affects the dielectric environment and charge carrier transport.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Flexible visualization of a 3rd party Intrusion Prevention (Security) tool: A use case with the ELK stack

A difficult aspect of cyber security is the ability to achieve automated real time intrusion prevention across various sets of systems. To this extent, several companies are offering comprehensive solutions that leverage an "accuracy of scale" and moving much of the intelligence and detection on the Cloud, relying on an ever-growing set of data and analytics to increase decision accuracy. Often, they provide tools to visualize the decision workflows in attack prevention (as well as tune the algorithm) but those solutions are not always practical as companies see the problem as "global" that is, from a unified Cyber-security standpoint. However, a key to a successful Cyber-security program is transparency and trust: from an experimental team viewpoint, this specifically means having the ability to immediately see what and from where, who has been blocked and being able to inform the community in case of a revoked access without the need for filing a "ticket" (that may eventually be answered) – in other words, rapid response to their user-base is essential but solutions targeting "sub-groups" in an organization are not often available. We have come up with a versatile solution leveraging the ELK stack (Elasticsearch, Logstash, & Kibana) and an IPS (Intrusion Prevention System) based WAF (Web Application Firewall) from Signal Sciences. Signal Science allows the streaming of detailed logs in a Logstash format suitable for custom solutions for visualization. By combining these two tools, we have strengthened our security posture and enabled individual experiments to monitor their own traffic. Specifically, the IPS WAF provides unique data such as country of origin, protocol, response code, source IP, and paths accessed. In this contribution, we will show how we engineered a visualization solution so experiment groups could access a dashboard with predefined graphs but also, where they can create individual customizable dashboards used to display blocked traffic and troubleshoot latency issues. We will discuss the details and procedures for developing and configuring these tools and how it benefits cyber security postures across our scientific based environment.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Direct Observation of the Growth of Au-Pd Core-Shell Nanoparticles Using in situ Low-Dose Liquid Cell STEM imaging

Bimetallic core-shell nanoparticles are widely used as catalysts in several industrial reactions, with core-shell structures permitting facile surface modification and allowing increased stability and durability, and cost-effectiveness of the catalysts. We report, for the first time, on observing the early stages of the formation of Au-Pd core-shell bimetallic nanoparticles via the seed-mediated growth in the presence of reducing agent, while employing the low-dose scanning transmission electron microscopy imaging with the fluid cell in situ. Use of the continuous flow in situ fluid cell platform allows for delivery of reagent solutions and generation of near-native reaction environment in the reaction chamber, and permits direct visualization of the early stages of formation of Au-Pd core-shell structures at low dose rate (0.1 e - /(Å 2 s)) in the presence of ascorbic acid. No core-shell structures were detected in the absence of reducing agent at the electron dose of 32.6 e - /Å 2 . While the core-shell structures formed in situ under the low-dose imaging closely resemble those obtained in solution synthesis, the reaction kinetics in the fluid cell is affected by the radiolysis of liquid reagents induced by electron beam, altering the rate-determining reaction steps. The enhanced reduction of Pd ions leads to initial rapid growth of the nascent Pd shell along the <111> direction at the Au interface, followed by a slower rearrangement of the outer Pd layer. The latter becomes the rate-determining step in the in situ reaction and appears to follow the oriented attachment-like movement to yield a remodeled, compact and stable Au-Pd core-shell nanostructure. Our findings highlight the differences between the two reaction pathways and aid in understanding the mechanism of formation of the core-shell nanostructure in situ.

36 MATERIALS SCIENCE↗