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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Effect of Dispersion Medium Composition and Ionomer Concentration on the Microstructure and Rheology of Fe–N–C Platinum Group Metal-free Catalyst Inks for Polymer Electrolyte Membrane Fuel Cells

In this paper, we present an investigation of the microstructure and rheological behavior of catalyst inks consisting of Fe–N–C platinum group metal-free catalysts and a perfluorosulfonic acid ionomer in a dispersion medium (DM) of water and 1-propanol ( n PA). The effects of the ionomer-to-catalyst (I/C) ratio and weight percentage of water (H 2 O %) in the DM on the ink microstructure were studied. Steady-shear and dynamic-oscillatory-shear rheology, in combination with synchrotron X-ray scattering, was utilized to understand interparticle interactions and the level of agglomeration of the inks. In the absence of the ionomer, the inks were significantly agglomerated, approaching a gel-like microstructure for catalyst concentrations as low as 2 wt %. The effect of H 2 O % in the DM on particle agglomeration was found to vary with particle concentration. In concentrated inks (≥2 wt % catalyst), increasing H 2 O % was found to increase agglomeration because of the hydrophobic nature of the catalysts. In dilute inks (<1 wt % catalyst), the trend was reversed with increasing H 2 O %, suggesting that electrostatic interactions are dominating the behavior. In inks with 5 wt % catalyst, the addition of an ionomer was found to significantly stabilize the catalyst against agglomeration. Maximum stability was observed at 0.35 I/C for all DM H 2 O % studied. At high ionomer concentrations (I/C > 0.35), interesting differences were observed between n PA-rich inks (H 2 O % ≤ 50%) and H 2 O-rich (82% H 2 O) inks. The n PA-rich inks remained predominantly stable—ink viscosity only weakly increased with I/C and the Newtonian behavior was maintained for I/C up to 0.9. In contrast, the H 2 O-rich inks exhibited a significant increase in viscoelasticity with increasing I/C, suggesting flocculation of the catalyst by the ionomer. These differences suggest that the nature of the interactions between the ionomer and catalyst is highly dependent on the H 2 O % in the DM.

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

Ion Conductivity and Correlations in Model Salt-Doped Polymers: Effects of Interaction Strength and Concentration

Correlated anion and cation motion can greatly reduce the overall ion conductivity in electrolytes versus the ideal conductivity calculated based on the diffusion constants alone. Using coarse-grained molecular dynamics simulations, we calculate conductivity and the degree of uncorrelated ion motion in salt-doped homopolymers and block copolymers as a function of concentration and interaction strengths. Calculating conductivity from ion mobility under an applied electric field increases accuracy versus the typical use of fluctuation dissipation relationships in equilibrium simulations. In typical electrolytes, correlation in cation-anion motion is often expected to be reduced at low ion concentrations. Yet, for these polymer electrolytes with strong ion-polymer and ion-ion interactions, we find cation-anion motion is more correlated at lower concentrations when other variables are held constant. We show this phenomenon is related to the slower ion cluster relaxation rate at low concentrations rather than the static spatial state of ion aggregation or the fraction of free ions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Quantitative Measurement of Li-Ion Concentration and Diffusivity in Solid-State Electrolyte

Here, we present a quantitative method to measure the concentration and diffusivity of Li ion in a solid-state electrolyte with nanoscale depth resolution. We designed a standard sample with different depths of trenches and used time-of-flight secondary ion mass spectroscopy, inductively coupled plasma optical emission spectroscopy, three-dimensional (3D) optical microscopy, and electrochemical strain microscopy to obtain effective Li-ion concentration and the corresponding diffusivity as a function of depth. As a result, we verified the dependence of electromechanical strain induced by ionic oscillation on mobile-ion concentration. We also showed the diffusivity change as a function of effective concentration and discussed the difference in diffusivity near the surface and inside the bulk. Our method can be widely used for electromechanical strain in various ionic conductors, rendering our technique universal for quantitative analysis of ionic dynamics at a multiscale.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Suppressing the Shuttle Effects with FeCo/SPAN Cathodes and High-Concentration Electrolytes for High-Performance Lithium–Sulfur Batteries

The shuttle effects and the sluggish redox kinetics are two of the main challenges in lithium–sulfur (Li–S) batteries, which significantly reduce the capacity of the batteries and restrict their commercialization. Herein, FeCo/sulfurized polyacrylonitrile (SPAN) is synthesized as a cathode material via the electrospinning technique and a further heat treatment. Synchrotron X-ray absorption spectroscopy confirmed the existence of Fe–S/Fe and Co–S bonds in FeCo/SPAN, which benefit the adsorptive and catalytic activities toward lithium polysulfides (LiPSs). Here, we further investigated the effect of electrolyte concentration in inhibiting the shuttle of LiPSs in Li–S batteries. Small-angle X-ray scattering (SAXS) reveals that more contact ion pairs are formed and fewer free solvent molecules exist with the increase of the electrolyte concentration, which can inhibit the dissolution and shuttle of LiPSs. Finally, the batteries assembled with high-concentration electrolytes (3 M LiTFSI in DOL/DME) exhibit a higher specific capacity retention compared to those assembled with low-concentration electrolytes. This work enriches the route to prepare Li–S batteries with the rational design of cathode materials and electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2025

Assessing Indoor versus Outdoor PM 2.5 Concentrations during the 2025 Los Angeles Fires Using the PurpleAir Sensor Network

In January 2025, a series of fast-moving wildland-urban-interface (WUI) fires swept through the Los Angeles (LA) metropolitan area, causing severe air pollution. While the impacts of WUI fires on outdoor air quality have been extensively studied, indoor exposure remains less understood, despite most people sheltering indoors during WUI fires. Here, this study investigates the spatial and temporal patterns of indoor and outdoor PM 2.5 concentrations across the South Coast Air Basin, with a focus on LA County during the LA fires. Using high-resolution data from co-located indoor and outdoor PurpleAir (PA) sensors, we analyze hourly PM 2.5 levels and indoor/outdoor ratios. Outdoor PM 2.5 concentrations spiked sharply during the fires, reaching unhealthy levels exceeding 130 μg/m 3 , compared to the mean concentration (12 μg/m 3 ) during non-fire hours. Indoor concentrations also increased, though to a lesser extent, peaking around 60 μg/m 3 compared to a mean of 7 μg/m 3 during non-fire hours. This reflects the partial shielding that indoor environments provide from outdoor air pollution. The mean (0.42) and median (0.29) indoor/outdoor PM 2.5 ratios during LA fire hours were lower than the mean (0.93) and median (0.66) ratios during non-fire hours. Indoor/outdoor PM 2.5 ratios across sensors showed a wide distribution, reflecting differences in building characteristics and occupant behavior, such as indoor activities and the use of air purifiers. These findings emphasize the need for guidance and interventions to reduce indoor PM 2.5 exposure and protect public health during extreme WUI fire events.

2025 Los Angeles Fires↗
DOE OSTI2024

Incorporating Diurnal and Meter-Scale Variations of Ambient CO 2 Concentrations in Development of Direct Air Capture Technologies

To be implemented on climate-relevant scales, direct air capture of CO 2 (DAC) will require large capital-intensive facilities and careful attention to cost minimization. In making decisions among potential sites for DAC facilities, all of the factors that will impact process cost and efficiency should be considered. In this paper we focus on a factor that has previously received little attention in the DAC community, namely variations in atmospheric conditions on hourly time scales and length scales of meters. We present data curated from extensive previous studies of biosphere-atmosphere fluxes with observations of CO 2 concentration, temperature, and relative humidity (RH) with hourly resolution from many sites in North America. These include locations where typical diurnal variations in CO 2 concentration during summer months exceeds 150 ppm. These variations are larger than the seasonal variations that exist between averaged CO 2 concentrations in winter and summer, and they are highly correlated with diurnal variations in temperature and RH. Diurnal variations are dependent on the height above ground at which CO 2 concentrations are measured, with smaller variations existing at heights of 10 m or more than at ground level. We illustrate the potential implications of these short-term variations for the operation and optimization of a DAC process with process-level calculations for a specific adsorption-based process using amine-rich adsorbents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Calcite growth rates as a function of aqueous calcium-to-carbonate ratio, saturation index and strontium concentration

Using in situ atomic force microscopy, the growth rates of the obtuse and acute step orientations on the calcite surface were measured at two saturation indices as a function of the aqueous calcium-to-carbonate ratio and aqueous strontium concentration. The amount of strontium required to inhibit growth was found to correlate with the aqueous calcium concentration, but did not correlate with carbonate. This suggests that strontium inhibits attachment of calcium ions to the reactive sites on the calcite surface. Strontium/calcium cation exchange selectivity coefficients for those sites, Kex, of 1.09 0.09 and 1.44 0.19 are estimated for the obtuse and acute step orientations, respectively. The implication of this finding is that to avoid poisoning calcite growth, the concentration of calcium should be higher than the quotient of the strontium concentration and Kex, regardless of saturation state. Additionally, analytical models of nucleation and propagation of steps are expanded from previous work to capture growth rates of these steps at multiple saturation indices and the effect of strontium. This work will have broader implications for naturally occurring or engineered calcite growth, such as to sequester subsurface strontium contamination.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Analytical Platform To Characterize Dopant Solution Concentrations, Charge Carrier Densities in Films and Interfaces, and Physical Diffusion in Polymers Utilizing Remote Field-Effect Transistors

Characterizing doping effects in a conductive polymer and physical diffusion in a passive polymer were performed using a remote-gate field-effect transistor (RG FET) detection system that was able to measure the electrical potential perturbation of a polymer film coupled to the gate of a silicon FET. Poly(3-hexylthiophene) (P3HT) film doped using various concentrations of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) solutions imposed additional positive potentials on the P3HT RG, resulting in a lower threshold voltage ($V_{th}$) on the n-channel silicon FET. Changes in $V_{th}$ were related to the induced hole concentrations and hole mobility in P3HT films by using our $V_{th}$ shifting model for the RG FET. We discovered that the electron-donating P3HT and even inorganic materials, indium tin oxide and gold, showed similar electrical potential perturbations dependent on the concentration of F4TCNQ in overlying solutions as the dopant radical anions maximally covered the surfaces. This suggests that there are limited electroactive sites for F4TCNQ binding on electron donor surfaces which results in a similar number of positive charges in film materials forming dipoles with the F4TCNQ radical counteranions. The effect of electron acceptors such as 7,7,8,8-tetracyanoquinodimethane and tetracyanoethylene was compared with that of F4TCNQ in terms of $V_{th}$ shift using our analytical tool, with differences attributed to acceptor size and reduction potential. Meanwhile, this FET analysis tool offered a means of monitoring the physical diffusion of small molecules, exemplified by F4TCNQ, in the passive polymer polystyrene, driven by concentration gradients. The technique allows for nondestructive, nonspectroscopic, ambient characterization of electron donor-acceptor interactions at surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Atomic detail brownian dynamics simulations of concentrated protein solutions with a mean field treatment of hydrodynamic interactions.

High macromolecular concentrations are a distinguishing feature of living organisms. Understanding how the high concentration of solutes affects the dynamic properties of biological macromolecules is fundamental for the comprehension of biological processes in living systems. In this paper, we describe the implementation of mean field models of translational and rotational hydrodynamic interactions into an atomically detailed many-protein brownian dynamics simulation method. Concentrated solutions (30-40% volume fraction) of myoglobin, hemoglobin A, and sickle cell hemoglobin S were simulated, and static structure factors, oligomer formation, and translational and rotational self-diffusion coefficients were computed. Good agreement of computed properties with available experimental data was obtained. The results show the importance of both solvent mediated interactions and weak protein-protein interactions for accurately describing the dynamics and the association properties of concentrated protein solutions. Specifically, they show a qualitative difference in the translational and rotational dynamics of the systems studied. Although the translational diffusion coefficient is controlled by macromolecular shape and hydrodynamic interactions, the rotational diffusion coefficient is affected by macromolecular shape, direct intermolecular interactions, and both translational and rotational hydrodynamic interactions.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2012

The dependence of ice microphysics on aerosol concentration in arctic mixed-phase stratus clouds during ISDAC and M-PACE

Cloud and aerosol data acquired by the National Research Council of Canada (NRC) Convair-580 aircraft in, above, and below single-layer arctic stratocumulus cloud during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 were used to test three aerosol indirect effects hypothesized to act in mixed-phase clouds: the riming indirect effect, the glaciation indirect effect, and the cold second indirect effect. The data showed a correlation of R= 0.75 between liquid drop number concentration, Nliq, inside cloud and ambient aerosol number concentration NPCASP below cloud. This, combined with increasing liquid water content LWC with height above cloud base and the nearly constant profile of Nliq, suggested that liquid drops were nucleated from aerosol at cloud base. No strong evidence of a riming indirect effect was observed, but a strong correlation of R = 0.69 between ice crystal number concentration Ni and NPCASP above cloud was noted. Increases in ice nuclei (IN) concentration with NPCASP above cloud combined with the subadiabatic LWC profiles suggest possible mixing of IN from cloud top consistent with the glaciation indirect effect. The higher Nice and lower effective radius rel for the more polluted ISDAC cases compared to data collected in cleaner single-layer stratocumulus conditions during the Mixed-Phase Arctic Cloud Experiment is consistent with the operation of the cold second indirect effect. However, more data in a wider variety of meteorological and surface conditions, with greater variations in aerosol forcing, are required to identify the dominant aerosol forcing mechanisms in mixed-phase arctic clouds.

58 GEOSCIENCES↗
DOE OSTI2020

Effects of Low-Carbon Energy Adoption on Airborne Particulate Matter Concentrations With Feedbacks to Future Climate Over California

California plans to reduce emissions of long-lived greenhouse gases (GHGs) through adoption of new energy systems that will also lower concentrations of short-lived absorbing soot contained in airborne particulate matter (PM). Here we examine the direct and indirect effects of reduced PM concentrations under a low-carbon energy (GHG-Step) scenario on radiative forcing in California. Simulations were carried out using the source-oriented WRF/Chem (SOWC) model with 12 km spatial resolution for the year 2054. Furthermore, the avoided aerosol emissions due to technology advances in the GHG-Step scenario reduce ground level PM concentrations by ~8.85% over land compared to the Business-as-Usual (BAU) scenario, but changes to meteorological parameters are more modest. Top-of-atmospheric forcing predicted by the SOWC model increased by 0.15 W m -2 , surface temperature warmed by 0.001 K, and planetary boundary layer height (PBLH) increased by 2.20 cm in the GHG-Step scenario compared to the BAU scenario. PM climate feedbacks are small because the significant changes in ground level PM concentrations associated with the GHG-Step scenario are limited to the first few hundred meters of the atmosphere, with little change for the majority of the vertical column above that level. As an order-of-magnitude comparison, the long-term effects of global reductions in GHG emissions (RCP8.5–RCP4.5) lowered average surface temperature over the California study domain by approximately 0.76 K. The effects of long-lived climate pollutants such as CO 2 are much stronger than the effects of short-lived climate pollutants such as PM soot over California in the year 2054.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Three-Dimensional Free Gas Flow Focuses Basin-Wide Microbial Methane to Concentrated Methane Hydrate Reservoirs in Geological System

Here, we present a systematic model that links the generation, migration, phase partitioning, and accumulation of methane into a closed loop as the sediment is deposited from the seafloor and buried through the base of hydrate stability zone (BHSZ). In our model, methane is generated by biodegradation of organic carbon in muds. Hydrate does not form and methane is not trapped until a coarse-grained layer is deposited, because the small pores prevent hydrate formation in muds. Instead, methane diffuses into sands/silts where methane solidifies into hydrate. As hydrate-bearing sands/silts pass through the BHSZ during sediment burial, methane hydrate dissociates, and releases free gas. The released and the newly generated free gas below the BHSZ concentrates into a vertical/dipping zone with low capillary entry pressure and high permeability and flows upward driven its buoyancy. When free gas reaches the hydrate stability zone (HSZ), capillary forces drive free gas to flow laterally, preferentially enter sands/silts, feed hydrate growth, and elevate hydrate saturation. With three-dimensional focused free gas flow, microbial methane that is generated from a much larger fetch area of the entire basin, both above and below the BHSZ, is concentrated into coarse-grained layers at structural closures for hydrate formation. Our model illustrates how geological evolution, microbial methane generation, and gas flow by buoyancy couple to generate concentrated hydrate deposits in geological system. These insights can be used to explore for high-concentration methane hydrate and are important for understanding the methane budget and carbon cycle under the seafloor.

58 GEOSCIENCES↗
DOE OSTI2024

Climate, Hydrology, and Nutrients Control the Seasonality of Si Concentrations in Rivers

Abstract The seasonal behavior of fluvial dissolved silica (DSi) concentrations, termedDSi regime, mediates the timing of DSi delivery to downstream waters and thus governs river biogeochemical function and aquatic community condition. Previous work identified five distinct DSi regimes across rivers spanning the Northern Hemisphere, with many rivers exhibiting multiple DSi regimes over time. Several potential drivers of DSi regime behavior have been identified at small scales, including climate, land cover, and lithology, and yet the large‐scale spatiotemporal controls on DSi regimes have not been identified. We evaluate the role of environmental variables on the behavior of DSi regimes in nearly 200 rivers across the Northern Hemisphere using random forest models. Our models aim to elucidate the controls that give rise to (a) average DSi regime behavior, (b) interannual variability in DSi regime behavior (i.e., Annual DSi regime), and (c) controls on DSi regime shape (i.e., minimum and maximum DSi concentrations). Average DSi regime behavior across the period of record was classified accurately 59% of the time, whereas Annual DSi regime behavior was classified accurately 80% of the time. Climate and primary productivity variables were important in predicting Average DSi regime behavior, whereas climate and hydrologic variables were important in predicting Annual DSi regime behavior. Median nitrogen and phosphorus concentrations were important drivers of minimum and maximum DSi concentrations, indicating that these macronutrients may be important for seasonal DSi drawdown and rebound. Our findings demonstrate that fluctuations in climate, hydrology, and nutrient availability of rivers shape the temporal availability of fluvial DSi.

Environmental Sciences & Ecology↗
DOE OSTI2023

River thorium concentrations can record bedrock fracture processes including some triggered by distant seismic events

Fractures are integral to the hydrology and geochemistry of watersheds, but our understanding of fracture dynamics is very limited because of the challenge of monitoring the subsurface. Here we provide evidence that long-term, high-frequency measurements of the river concentration of the ultra-trace element thorium (Th) can provide a signature of bedrock fracture processes spanning neighboring watersheds in Colorado. River Th concentrations show abrupt (subdaily) excursions and biexponential decay with approximately 1-day and 1-week time constants, concentration patterns that are distinct from all other solutes except beryllium and arsenic. The patterns are uncorrelated with daily precipitation records or seasonal trends in atmospheric deposition. Groundwater Th analyses are consistent with bedrock release and dilution upon mixing with river water. Most Th excursions have no seismic signatures that are detectable 50 km from the site, suggesting the Th concentrations can reveal aseismic fracture or fault events. We find, however, a weak statistical correlation between Th and seismic motion caused by distant earthquakes, possibly the first chemical signature of dynamic earthquake triggering, a phenomenon previously identified only through geophysical methods.

58 GEOSCIENCES↗
DOE OSTI2024

Exponential concentration in quantum kernel methods

Kernel methods in Quantum Machine Learning (QML) have recently gained significant attention as a potential candidate for achieving a quantum advantage in data analysis. Among other attractive properties, when training a kernel-based model one is guaranteed to find the optimal model’s parameters due to the convexity of the training landscape. However, this is based on the assumption that the quantum kernel can be efficiently obtained from quantum hardware. In this work we study the performance of quantum kernel models from the perspective of the resources needed to accurately estimate kernel values. We show that, under certain conditions, values of quantum kernels over different input data can be exponentially concentrated (in the number of qubits) towards some fixed value. Thus on training with a polynomial number of measurements, one ends up with a trivial model where the predictions on unseen inputs are independent of the input data. We identify four sources that can lead to concentration including expressivity of data embedding, global measurements, entanglement and noise. For each source, an associated concentration bound of quantum kernels is analytically derived. Lastly, we show that when dealing with classical data, training a parametrized data embedding with a kernel alignment method is also susceptible to exponential concentration. Our results are verified through numerical simulations for several QML tasks. Altogether, we provide guidelines indicating that certain features should be avoided to ensure the efficient evaluation of quantum kernels and so the performance of quantum kernel methods.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Localized high-concentration electrolytes get more localized through micelle-like structures

Liquid electrolytes in batteries are typically treated as macroscopically homogeneous ionic transport media despite having a complex chemical composition and atomistic solvation structures, leaving a knowledge gap of the microstructural characteristics. Here, we reveal a unique micelle-like structure in a localized high-concentration electrolyte, in which the solvent acts as a surfactant between an insoluble salt in a diluent. The miscibility of the solvent with the diluent and simultaneous solubility of the salt results in a micelle-like structure with a smeared interface and an increased salt concentration at the centre of the salt–solvent clusters that extends the salt solubility. These intermingling miscibility effects have temperature dependencies, wherein a typical localized high-concentration electrolyte peaks in localized cluster salt concentration near room temperature and is used to form a stable solid–electrolyte interphase on a Li metal anode. Importantly, these findings serve as a guide to predicting a stable ternary phase diagram and connecting the electrolyte microstructure with electrolyte formulation and formation protocols of solid–electrolyte interphases for enhanced battery cyclability.

25 ENERGY STORAGE↗
DOE OSTI2023

Two decades of fumigation data from the Soybean Free Air Concentration Enrichment facility

Abstract The Soybean Free Air Concentration Enrichment (SoyFACE) facility is the longest running open-air carbon dioxide and ozone enrichment facility in the world. For over two decades, soybean, maize, and other crops have been exposed to the elevated carbon dioxide and ozone concentrations anticipated for late this century. The facility, located in East Central Illinois, USA, exposes crops to different atmospheric concentrations in replicated octagonal ~280 m 2 Free Air Concentration Enrichment (FACE) treatment plots. Each FACE plot is paired with an untreated control (ambient) plot. The experiment provides important ground truth data for predicting future crop productivity. Fumigation data from SoyFACE were collected every four seconds throughout each growing season for over two decades. Here, we organize, quality control, and collate 20 years of data to facilitate trend analysis and crop modeling efforts. This paper provides the rationale for and a description of the SoyFACE experiments, along with a summary of the fumigation data and collation process, weather and ambient data collection procedures, and explanations of air pollution metrics and calculations.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

A multi-modal sweat sensing patch for cross-verification of sweat rate, total ionic charge, and Na + concentration

Sweat sensors introduced in recent years have targeted a variety of sweat features and biomarkers for non-invasive health monitoring. Amongst these targets, reliable monitoring of sweat rate is crucial due to its modulation of sweat analyte concentrations and its intrinsic significance to numerous medical and physiological health conditions. In this paper, we present a sweat rate sensor structure comprising of electrodes with interdigitated fingers in a microfluidic channel. Each time the accumulating sweat impinges on an electrode finger, the sensor reports a jump in admittance that can be simply and efficiently counted to estimate sweat rate, overcoming selectivity limitations of previously reported sweat rate sensors. We further integrate an impedimetric sensor for measuring total ionic charge concentration and an electrochemical Na + sensor, together creating a multi-modal system for analyzing fluid and electrolyte secretion. We demonstrate how low analyte diffusion rates through this microfluidic device allow for multi-purpose sensor function, including utilizing the sweat rate sensor signal to corroborate total ionic sensor measurements. This cross-verification capability ensures data integrity in real time, satisfying a vital consideration for personalized healthcare technologies. We use the presented patch for continuous analysis of sweat rate, total ionic charge concentration, and Na + concentration during exercise, while demonstrating how multi-modal cross-verification brings new trust to sensor readings.

47 OTHER INSTRUMENTATION↗