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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Distant Cluster Hunting: A Comparison of X-Ray and Optical Cluster Detection Techniques and Catalogs from the ROSAT Optical X-Ray Survey - II

We present and analyze the optical and X-ray catalogs of moderate-redshift cluster candidates from the ROSA TOptical X-Ray Survey, or ROXS. The survey covers the sky area contained in the fields of view of 23 deep archival ROSA T PSPC pointings, 4.8 square degrees. The cross-correlated cluster catalogs were con- structed by comparing two independent catalogs extracted from the optical and X-ray bandpasses, using a matched-filter technique for the optical data and a wavelet technique for the X-ray data. We cross-identified cluster candidates in each catalog. As reported in Paper 1, the matched-filter technique found optical counter- parts for at least 60% (26 out of 43) of the X-ray cluster candidates; the estimated redshifts from the matched filter algorithm agree with at least 7 of 1 1 spectroscopic confirmations (Az 5 0.10). The matched filter technique. with an imaging sensitivity of ml N 23, identified approximately 3 times the number of candidates (155 candidates, 142 with a detection confidence >3 u) found in the X-ray survey of nearly the same area. There are 57 X-ray candidates, 43 of which are unobscured by scattered light or bright stars in the optical images. Twenty-six of these have fairly secure optical counterparts. We find that the matched filter algorithm, when applied to images with galaxy flux sensitivities of mI N 23, is fairly well-matched to discovering z 5 1 clusters detected by wavelets in ROSAT PSPC exposures of 8000-60,000 s. The difference in the spurious fractions between the optical and X-ray (30%) and IO%, respectively) cannot account for the difference in source number. In Paper I, we compared the optical and X-ray cluster luminosity functions and we found that the luminosity functions are consistent if the relationship between X-ray and optical luminosities is steep (Lx o( L&f). Here, in Paper 11, we present the cluster catalogs and a numerical simulation of the ROXS. We also present color-magnitude plots for several of the cluster candidates, and examine the prominence of the red sequence in each. We find that the X-ray clusters in our survey do not all have a prominent red sequence. We conclude that while the red sequence may be a distinct feature in the color-magnitude plots for virialized massive clusters, it may be less distinct in lower mass clusters of galaxies at even moderate redshifts. Multiple, complementary methods of selecting and defining clusters may be essential, particularly at high redshift where all methods start to run into completeness limits, incomplete understanding of physical evolution, and projection effects.

Donahue, Megan↗
DOE OSTI2025

A 2D/3D Heterostructure Perovskite Solar Cell with a Phase‐Pure and Pristine 2D Layer

Abstract Interface engineering plays a critical role in advancing the performance of perovskite solar cells. As such, 2D/3D perovskite heterostructures are of particular interest due to their optoelectrical properties and their further potential improvements. However, for conventional solution‐processed 2D perovskites grown on an underlying 3D perovskite, the reaction stoichiometry is normally unbalanced with excess precursors. Moreover, the formed 2D perovskite is impure, leading to unfavorable energy band alignment at the interface. Here a simple method is presented that solves both issues simultaneously. The 2D formation reaction is taken first to completion, fully consuming excess PbI 2 . Then, isopropanol is utilized to remove excess organic ligands, control the 2D perovskite thickness, and obtain a phase‐pure, n = 2, 2D perovskite. The outcome is a pristine (without residual 2D precursors) and phase‐pure 2D perovskite heterostructure with improved surface passivation and charge carrier extraction compared to the conventional solution process. PSCs incorporating this treatment demonstrate a notable improvement in both stability and power conversion efficiency, with negligible hysteresis, compared to the conventional process.

14 SOLAR ENERGY↗
DOE OSTI2020

Metal-embedded fiber optic sensor packaging and signal demodulation scheme towards high-frequency dynamic measurements in harsh environments

Optical fiber-based sensors are commonly used for industrial monitoring and control processes due to their small size, resistance to electromagnetic interference, and ability to perform a wide variety of high-precision measurements. However, implementing optical fiber sensors in harsh environments is challenging because they are small and fragile. Proper packaging of fiber-optic sensors could extend their use to harsh environments, including at high temperature and under high radiation. Furthermore, conventional fiber optic-based measurement systems often use computationally expensive signal processing algorithms which hinder their use in high-frequency dynamic applications. This work reports on the design of an optical fiber-pressure sensor system based on low-coherence interferometry that uses a metal-embedded optical fiber to provide a robust sensor package. Additionally, a novel phase demodulation scheme is proposed to extract length changes from the deformation of a thin diaphragm within a Fabry–Pérot cavity to measure pressure. The sensor has been tested to ±100 kPa, has a theoretical linear response over a 270 kPa dynamic range (24 dB maximum signal-to-noise ratio), and can resolve pressure transients up to 3910 kPa/s. Sampling at 100 kHz, the present sensor can resolve 2 kPa dynamic pressures at frequencies up to 2 kHz. Faster transients on the order of tens to hundreds of kHz can theoretically be resolved at the expense of decreasing the maximum resolvable amplitude. A methodology for designing a LCI pressure sensor for a given application is outlined based on the limitations imposed by the Nyquist criterion, the diaphragm's resonant frequency, the LCI optoelectronics, and the phase demodulation scheme. The sensor is the first to implement a low-coherence light source and a Fabry–Pérot interferometer designed to provide real-time high-fidelity pressure measurements using a metal-embedded optical fiber. The demonstrated sensor provides a platform for sensing in harsh conditions such as in nuclear and energy applications.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Absolute contrast estimation for soft X-ray photon fluctuation spectroscopy using a variational droplet model

Abstract X-ray photon fluctuation spectroscopy using a two-pulse mode at the Linac Coherent Light Source has great potential for the study of quantum fluctuations in materials as it allows for exploration of low-energy physics. However, the complexity of the data analysis and interpretation still prevent recovering real-time results during an experiment, and can even complicate post-analysis processes. This is particularly true for high-spatial resolution applications using CCDs with small pixels, which can decrease the photon mapping accuracy resulting from the large electron cloud generation at the detector. Droplet algorithms endeavor to restore accurate photon maps, but the results can be altered by their hyper-parameters. We present numerical modeling tools through extensive simulations that mimic previous x-ray photon fluctuation spectroscopy experiments. By modification of a fast droplet algorithm, our results demonstrate how to optimize the precise parameters that lift the intrinsic counting degeneracy impeding accuracy in extracting the speckle contrast. These results allow for an absolute determination of the summed contrast from multi-pulse x-ray speckle diffraction, the modus operandi by which the correlation time for spontaneous fluctuations can be measured.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Crystal structure, magnetism, and specific heat of lightly depleted layered honeycomb oxides, Na$_2$(Ni$_{2-x}$D$_x$)TeO$_6$ ($D$ = Mg, Ga, Co; 0.10 ≤ $x$ ≤ 0.25)

Layered oxides, in which transition metal atoms form a honeycomb lattice, are known for complex magnetic phase diagrams. In this work we study the doped compounds, Na$_2$(Ni$_{2-x}$D$_x$)TeO$_6$, $D$ = Mg, Ga, and Co (0.10 ≤ $x$ ≤ 0.25), to understand how chemical dilution at the nickel site influences the stability of magnetic exchanges within the honeycomb layer of the parent, Na$_2$ Ni$_2$ TeO$_6$. Here, the studied compounds were found to crystallize in $P6_3/mcm$ space group common to P2 type layered oxides. In general, the lattice parameters and the unit cell volume expanded with increased doping. The oxidation states determined from X-ray photoelectron spectroscopy were consistent with bond valence sum estimates, that confirmed the presence of Ni$^{2+}$, Mg$^{2+}$, Ga$^{3+}$, Co$^{2+}$ in our samples. Irrespective of magnetic or non-magnetic doping, the magnetic phase transition temperature ($T_N$) of the doped compounds were reduced from that of Na$_2$ Ni$_2$ TeO$_6$ or Na$_2$ Co$_2$ TeO$_6$, and lay between 21.7 K and 26.8 K. The effective paramagnetic moments extracted from Curie–Weiss analysis were in the range 3.17 μ B to 3.84 μ B and the Weiss temperatures were between $-15$ K and $-25$ K, suggesting antiferromagnetism. Mg- and Ga-doped compounds showed free spin formation, indicated by Curie–Weiss tails in their magnetic susceptibility. Our results suggest emergence of short-range magnetic correlations in Na$_2$(Ni$_{2-x}$D$_x$)TeO$_6$, enhanced due to the depletion of the Ni honeycomb lattice.

75 - CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY A↗
NASA NTRS2006

Multi-Wavelength Dielectrometer (MWD) Sensor For Planetary Subsurface Exploration

NASA's mission to Moon, Mars, and Beyond envisions landing of a light weight measurement platform on the planetary surface. The Multi-Wavelength Dielectrometer (MWD) on-board consists of essential electronics and metallic plates acting as electrodes attached to the body of such platform. An electric signal applied to one of the electrodes acting as a cathode sets up electric field pattern (in the soil medium) between the cathode and other electrodes acting as anodes. The electrodes are swept through multiple wavelengths (1Hz-1MHz) and the electric current drawn by the electrodes is measured at each frequency. The measured current whose amplitude and phase depend upon electrode spacing, dielectric constant of the subsurface soil, and the frequency is then used to estimate electrical properties of the soil. In this paper the MWD sensor that will measure the dielectric properties of Moon/Mars s soil is presented. A procedure to process the MWD measured data for extracting the soil properties is also described. Assuming the subsurface soil structure as multilayer strata having varying electric properties, an electric equivalent circuit of the multiple electrodes configuration placed on a multi-layer soil sample is obtained. The current drawn by the equivalent circuit from the low frequency signal generator is then calculated. By minimizing the difference between the model s estimated current and measured MWD data the electric properties of soil samples are extracted. Experimental and simulated results will be presented to validate the proposed procedure for extracting soil properties.

Deshpande, Manohar↗
DOE OSTI2025

Understanding ERE and iVOC Metrics for Graded CdSeTe Absorbers

PL-based external radiative efficiency (ERE) and implied open-circuit voltage (iVOC) metrics were introduced for thin-film solar absorbers to better understand the voltage deficit and diagnose losses in solar cells. Traditionally, elevated ERE and iVOC measurements are associated with diminished recombination within the solar device, a rationale heavily reliant on the assumption of a uniform bandgap and high carrier mobilities in the absorber. Recently, very low mobilities in CdSeTe absorbers (< 1 cm2/(V.s)) were measured using the light-induced transient grading technique. In this study, we use a detailed numerical model of iVOC to investigate the possible reasons of elevated iVOC in realistic CdSeTe absorbers with a graded Se profile. In particular, we examine how the bandgap nonuniformity and the reduced hole mobility in graded CdSeTe absorbers affect iVOC measurements. We show that high iVOC may result from inflated quasi-Fermi level splitting in the high-Se region in the front part of a CdSeTe absorber with slow hole transport. We reproduce the experimentally reported 360 mV increase in iVOC-VOC gap with reduced doping using a model with sub-1 cm2/(V.s) hole mobility in the high-Se region. Based on our results, we conclude that the iVOC metric (or ERE metric) should not be used as a sole metric of CdSeTe absorber quality. We discuss possible ways to extract useful information from the iVOC-VOC gap by supplementing the front-side illumination measurements with back-side illumination measurements.

14 SOLAR ENERGY↗
NASA NTRS1989

Polyamine binding to proteins in oat and Petunia protoplasts

Previous work (A Apelbaum et al. [1988] Plant Physiol 88: 996-998) has demonstrated binding of labeled spermidine (Spd) to a developmentally regulated 18 kilodalton protein in tobacco tissue cultures derived from thin surface layer explants. To assess the general importance of such Spd-protein complexes, we attempted bulk isolation from protoplasts of Petunia and oat (Avena sativa). In Petunia, as in tobacco, fed radioactive Spd is bound to protein, but in oat, Spd is first converted to 1,3,-diaminopropane (DAP), probably by polyamine oxidase action. In oat, binding of DAP to protein depends on age of donor leaf and conditions of illumination and temperature, and the extraction of the DAP-protein complex depends upon buffer and pH. The yield of the DAP-protein complex was maximized by extraction of frozen-thawed protoplasts with a pH 8.8 carbonate buffer containing SDS. Its molecular size, based on Sephacryl column fractionation of ammonium sulfate precipitated material, exceeded 45 kilodaltons. Bound Spd or DAP can be released from their complexes by the action of Pronase, but not DNAse, RNAse, or strong salt solutions, indicating covalent attachment to protein.

NASA Discipline Plant Biology↗
DOE OSTI2026

A STUDY OF SHORT-RANGE CORRELATED PAIR FORMATION MECHANISMS

Short-Range Correlations (SRCs) refers to pairs of nucleons that are temporary high density fluctuations with high relative momenta and lower center-of-mass momenta com pared to the nuclear Fermi momentum (kF). SRCs account for 20–25% of the nucleons in medium to heavy nuclei, make up essentially all nucleons with momentum greater than kF, and contribute most of the kinetic energy carried by nucleons in nuclei. The existing semi-inclusive and exclusive measurements only cover a handful of light nu clei or heavy elements. This does not allow for a systematic study of the dependence of SRC pairs on nuclear mass and proton-neutron asymmetry. It also does not allow for insights into SRC pairing mechanisms. Therefore, we systematically studied the individual probabilities for finding SRC protons in symmetric and neutron-rich asymmetric nuclei d, 9Be, 10B, 11B, 12C, 40Ca, 48Ca, 54Fe, and 197Au. We measured the (e,e'p) reaction in kinematics dominated by scattering off mean-field nucleons (k = kF) and nucleons in SRC pairs (k = kF) at the Thomas Jefferson National Accelerator Facility (JLab) in Hall C of the Continuous Electron Beam Accelerator Facility (CEBAF) in the Fall of 2022. The measured results were used to determine the SRC pairing probabilities for protons to examine how pairing depends on nuclear mass, proton-neutron asymmetry, and nuclear shell structure. The extracted cross-section ratios were also compared to theoretical calculations. We found that SRC pair formation depends more on the nuclear shell structure with sharp increases locally within the general trend of a slower increase with larger A. We also found that intra-shell pairing has a much larger influence than inter-shell pairing. Comparisons to theory suggest that angular momentum selection rules are important to SRC pair formation and can provide new constraints for new theoretical models.

Swan, Noah [Old Dominion Univ., Norfolk, VA (Unite↗
DOE OSTI2020

Mapping Vegetation at Species Level with High-Resolution Multispectral and Lidar Data Over a Large Spatial Area: A Case Study with Kudzu

Mapping vegetation species is critical to facilitate related quantitative assessment, and mapping invasive plants is important to enhance monitoring and management activities. Integrating high-resolution multispectral remote-sensing (RS) images and lidar (light detection and ranging) point clouds can provide robust features for vegetation mapping. However, using multiple sources of high-resolution RS data for vegetation mapping on a large spatial scale can be both computationally and sampling intensive. Here, we designed a two-step classification workflow to potentially decrease computational cost and sampling effort and to increase classification accuracy by integrating multispectral and lidar data in order to derive spectral, textural, and structural features for mapping target vegetation species. We used this workflow to classify kudzu, an aggressive invasive vine, in the entire Knox County (1362 km2) of Tennessee (U.S.). Object-based image analysis was conducted in the workflow. The first-step classification used 320 kudzu samples and extensive, coarsely labeled samples (based on national land cover) to generate an overprediction map of kudzu using random forest (RF). For the second step, 350 samples were randomly extracted from the overpredicted kudzu and labeled manually for the final prediction using RF and support vector machine (SVM). Computationally intensive features were only used for the second-step classification. SVM had constantly better accuracy than RF, and the producer’s accuracy, user’s accuracy, and Kappa for the SVM model on kudzu were 0.94, 0.96, and 0.90, respectively. SVM predicted 1010 kudzu patches covering 1.29 km2 in Knox County. We found the sample size of kudzu used for algorithm training impacted the accuracy and number of kudzu predicted. The proposed workflow could also improve sampling efficiency and specificity. Our workflow had much higher accuracy than the traditional method conducted in this research, and could be easily implemented to map kudzu in other regions as well as map other vegetation species.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

The Near-infrared Spectrum of the Nuclear Star Cluster: Looking below the Tip of the Iceberg, and Comparisons with Extragalactic Nuclei

Long-slit near-infrared (NIR) spectra of the Galactic nuclear star cluster (NSC) are discussed. The spectra sample the major axis of the NSC out to its half-light radius. The absorption spectrum of the central regions of the NSC is averaged over angular scales of tens of arc seconds in order to sample globular cluster-like total luminosities, and the results are compared with model spectra. The equivalent widths of Na i2.21 μm and Ca 2.26 μm outside of the center of the NSC, where light from nuclear bulge stars contributes a large fraction to the total flux, are consistent with solar chemical mixtures. In contrast, the equivalent widths of Na i2.21 μm and Ca i2.26 μm near the center of the NSC are larger than expected from models with solar chemical mixtures, even after light from the brightest evolved stars is removed. The depths of spectroscopic features changing along the major axis of the NSC are consistent with imaging studies that have found evidence of population gradients in the NSC. That Na i2.21 μm and Ca i2.26 μm are deeper than predicted for solar chemical mixtures over a range of evolutionary states is consistent with previous studies that find that the majority of stars near the center of the NSC formed from material that had nonsolar chemical mixtures. The depths of the Na i2.21 μm and Ca i2.26 μm features in the central regions of the NSC are comparable to those in the nuclear spectrum of the early-type Virgo disk galaxy NGC 4491, and are deeper than in the central spectra of NGC 253 and 7793. A spectrum of nebular emission and the youngest stars near the galactic center is also extracted. The equivalent widths of emission features in the extracted NIR spectrum are similar to those in the nuclear spectrum of NGC 253, and it is argued that this agreement is best achieved if the current episode of star formation near the center of the NSC has been in progress for at least a few megayears.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2019

The 3D Printing of Polyimide Aerogels

Polyimide aerogels are a nanoporous material made by extracting the liquid portion of a wet gel and replacing it with air, while still maintaining the porous solid internal architecture. This results in a material with extremely low densities, low thermal conductivities, high internal surfaces areas, and low dielectric constants. Currently, complex aerogel forms are not possible, since they require molds in order to be shaped. To overcome this challenge, we are attempting to use various additive manufacturing techniques to produce complex architectures. Three different approaches are being studied to accomplish this. One is to print using a viscous wet gel and have the structure solidify at the end of the print, another is to use a mixing tip, where a less viscous gel and the final chemical that causes gelation will be mixed as it is printing, allowing it to gel layer by layer, and the third is to use a UV curable aerogel with a UV light following behind to solidify the gel as it prints. To have these approaches be successful, the printing parameters and the aerogel's chemical formulation need to be optimized. The more harmonious these two factors can be made, the more defined and complex the resulting structure can be. Preliminary results show that 3D printing polyimide aerogels are a viable option, but further optimization must occur for reliable printing.

Nosel, Theresa↗
DOE OSTI2026

Spatiotemporal and Statistical Mapping of Transition Metal Equilibria in Alkaline Media

Transition metal dissolution and redeposition (D/R) kinetics in alkaline media play a critical role in various chemical and electrochemical processes. Competitive reaction kinetics between different transition metals can modulate individual metal behavior in these processes. To date, these phenomena have remained largely unmeasured, and even when captured, they are difficult to statistically characterize due to their dynamic nature, simultaneous occurrence, and spatially heterogeneous nature. Here, in this study, we develop a statistical analysis framework based on in situ and operando X-ray fluorescence microscopy (XFM) to investigate the relative D/R kinetics of multiple transition metals in alkaline media. By employing statistical analysis, we quantify the spatial distribution of D/R species and assess the rate at which the system reaches equilibrium under varying reaction conditions. We show that pH does not simply change the rate of dissolution and redeposition, but reorganizes the cross-element kinetic correlations among Ni, Fe, and Mn and accelerates the spatial equilibration of D/R events, as quantified through correlation analysis, reaction-rate estimation, probability function distributions, and texture-based monitoring statistics. Additionally, we demonstrate how modifying the solvent environment can influence D/R kinetics, providing a pathway for tuning materials synthesis and process optimization. Our study offers valuable insights into the complex interplay between different transition metals and provides a reliable statistical framework for spatial analysis of diverse imaging data sets, enabling deeper extraction of latent information across multiple modalities.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Critical role of oxide anchoring groups in organic electron transport layers for perovskite solar cell stability

Charge transport layers (CTLs) play a critical role in the performance and long-term stability of perovskite solar cells (PSCs) by facilitating efficient charge extraction and providing interfacial stabilization. For organic CTLs, different functional groups have been designed to modulate the interactions with the substrate. Anchoring groups are used to establish strong adhesion to transparent conductive oxides (TCOs) but are not routinely incorporated in organic CTL design. In this study, we investigate the influence of anchoring groups in organic electron transport layers (ETLs) on PSC performance and stability by synthesizing and evaluating two naphthalene diimide (NDI)-based ETLs: NDI-(PhPA) 2 , functionalized with polar phenyl phosphonic acid (PhPA) groups, and NDI-(PhBr) 2 , modified with nonpolar bromophenyl (PhBr) groups. X-ray photoelectron spectroscopy confirms that PhPA functionalization leads to NDIs anchored onto fluorine-doped tin oxide (FTO) following chemical bath deposition, while NDI-(PhBr) 2 shows no detectable surface presence after deposition. We show that NDI-(PhPA) 2 deposits as a thin film on FTO, exhibiting strong adhesion, high solvent resistance, and enhanced light and thermal stability, achieving a maximum device efficiency of 14.3%. Stability assessments conducted under continuous illumination at 25 °C for 200 hours and at 65 °C for 100 hours demonstrate performance on par with TiO 2 -based ETLs. In contrast, NDI-(PhBr) 2 , which lacks strong anchoring interactions, fails to adhere to the FTO surface, resulting in a rapid decrease in efficiency over a few hours, comparable to devices without an ETL. These findings highlight the importance of anchoring groups in organic CTLs for achieving long-term PSC stability under operational conditions.

Kim, Sanggyun [Georgia Institute of Technology, At↗
NASA NTRS2007

Multiple-Parameter, Low-False-Alarm Fire-Detection Systems

Fire-detection systems incorporating multiple sensors that measure multiple parameters are being developed for use in storage depots, cargo bays of ships and aircraft, and other locations not amenable to frequent, direct visual inspection. These systems are intended to improve upon conventional smoke detectors, now used in such locations, that reliably detect fires but also frequently generate false alarms: for example, conventional smoke detectors based on the blockage of light by smoke particles are also affected by dust particles and water droplets and, thus, are often susceptible to false alarms. In contrast, by utilizing multiple parameters associated with fires, i.e. not only obscuration by smoke particles but also concentrations of multiple chemical species that are commonly generated in combustion, false alarms can be significantly decreased while still detecting fires as reliably as older smoke-detector systems do. The present development includes fabrication of sensors that have, variously, micrometer- or nanometer-sized features so that such multiple sensors can be integrated into arrays that have sizes, weights, and power demands smaller than those of older macroscopic sensors. The sensors include resistors, electrochemical cells, and Schottky diodes that exhibit different sensitivities to the various airborne chemicals of interest. In a system of this type, the sensor readings are digitized and processed by advanced signal-processing hardware and software to extract such chemical indications of fires as abnormally high concentrations of CO and CO2, possibly in combination with H2 and/or hydrocarbons. The system also includes a microelectromechanical systems (MEMS)-based particle detector and classifier device to increase the reliability of measurements of chemical species and particulates. In parallel research, software for modeling the evolution of a fire within an aircraft cargo bay has been developed. The model implemented in the software can describe the concentrations of chemical species and of particulate matter as functions of time. A system of the present developmental type and a conventional fire detector were tested under both fire and false-alarm conditions in a Federal Aviation Administration cargo-compartment- testing facility. Both systems consistently detected fires. However, the conventional fire detector consistently generated false alarms, whereas the developmental system did not generate any false alarms.

Hunter, Gary W.↗
NASA NTRS2005

Fluorescent Approaches to High Throughput Crystallography

X-ray crystallography remains the primary method for determining the structure of macromolecules. The first requirement is to have crystals, and obtaining them is often the rate-limiting step. The numbers of crystallization trials that are set up for any one protein for structural genomics, and the rate at which they are being set up, now overwhelm the ability for strictly human analysis of the results. Automated analysis methods are now being implemented with varying degrees of success, but these typically cannot reliably extract intermediate results. By covalently modifying a subpopulation, 51%, of a macromolecule solution with a fluorescent probe, the labeled material will add to a growing crystal as a microheterogeneous growth unit. Labeling procedures can be readily incorporated into the final stages of purification. The covalently attached probe will concentrate in the crystal relative to the solution, and under fluorescent illumination the crystals show up as bright objects against a dark background. As crystalline packing is more dense than amorphous precipitate, the fluorescence intensity can be used as a guide in distinguishing different types of precipitated phases, even in the absence of obvious crystalline features, widening the available potential lead conditions in the absence of clear hits. Non-protein structures, such as salt crystals, will not incorporate the probe and will not show up under fluorescent illumination. Also, brightly fluorescent crystals are readily found against less fluorescent precipitated phases, which under white light illumination may serve to obscure the crystals. Automated image analysis to find crystals should be greatly facilitated, without having to first define crystallization drop boundaries and by having the protein or protein structures all that show up. The trace fluorescently labeled crystals will also emit with sufficient intensity to aid in the automation of crystal alignment using relatively low cost optics, further increasing throughput at synchrotrons. This presentation will focus on the methodology for fluorescent labeling, the crystallization results, and the effects of the trace labeling on the crystal quality.

Pusey, Marc L.↗
DOE OSTI2025

Identification of the Liquid Argon Scattering Experimental Discrepancies Using Simulation

Scintillation light analysis in liquid argon based neutrino detectors is restrained in capability due to uncertainty in fundamental constants critical to the analysis process. One such property is the Rayleigh scattering length of liquid argon. In the fall of 2023, the TallBo cryostat, located in the Proton Assembly Building at Fermilab, was used to study the scattering length of liquid argon in the Liquid Argon Scattering (LArS) experiment. Due to systematic errors unknown during measurement analysis, LArS’s measurements were quite uncertain. By simulating the LArS experiment, we found that the downturn in detector count rate as a function of liquid argon height at low heights was caused by a misplaced photo multiplier. With concentrated effort, we may be able to successfully correct this effect by understanding the relationship between the specified Rayleigh scattering length and the measured attenuation length. With this information and further progression in analysis, we may be able to extract corrected measurements from the LArS data and attain a tangible experimental measurement of the scattering length of liquid argon.

Breaux, Auto D. [Tulane U.; Fermilab]↗