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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Diagnostics, Control and Performance Parameters for the BELLA High Repetition Rate Petawatt Class Laser

A laser system producing controllable and stable pulses with high power and ultrashort duration at high repetition rate is a key component of a high energy laser-plasma accelerator (LPA). Precise characterization and control of laser properties are essential to understanding laser-plasma interactions required to build a 10-GeV class LPA. This study discusses the diagnostics, control and performance parameters of a 1 Hz, 1 petawatt (PW) class laser at the Berkeley Lab Laser Accelerator (BELLA) facility. The BELLA PW laser provided up to 46 J on target with a 1% level energy fluctuation and 1.3-μrad pointing stability. The spatial profile was measured and optimized by using a camera, wavefront sensor, and deformable mirror (ILAO system). The focus waist was measured to be r 0 = 53 μm and the fraction of energy within the circular area defined by the first minimum of the diffraction pattern (r = 67 μm) was 0.75. The temporal profile was controlled via the angle of incidence on a stretcher and a compressor, as well as an acousto-optic programmable dispersive. The temporal pulse shape was measured to be about 33 fs in full width at half maximum (WIZZLER and GRENOUILLE diagnostics). In order to accurately evaluate peak intensity, the energy-normalized peak fluence, and energy-normalized peak power were analyzed for the measured spatial and temporal mode profiles, and were found to be 15 kJ/(cm 2 J) with 6% fluctuation (standard deviation) and 25 TW/J with 5% fluctuation for 46-J on-target energy, respectively. This yielded a peak power of 1.2 PW and a peak intensity of 17×10 18 W/cm 2 with 8% fluctuation. A method to model the pulse shape for arbitrary compressor grating distance with high accuracy was developed. The pulse contrast above the amplified spontaneous emission pedestal was measured by SEQUOIA and found to be better than 10 9 . The first order spatiotemporal couplings (STCs) were measured with GRENOUILLE, and a simulation of the pulse's evolution at the vicinity of the target was presented. A maximum pulse front tilt angle of less than 7 mrad was achieved. The reduction of the peak power caused by the first order STCs was estimated to be less than 1%. Finally, the capabilities described in this paper are essential for generation of high quality electron beams.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Experimental Evaluation of Geopolymer, Nano-Modified, and Neat Class H Cement by Using Diametrically Compressive Tests

Abstract Cement is the prime barrier material to maintain zonal isolation during wellbore life-cycle. Different types of the cement have different performances on sealability. The primary objective of this study is evaluation of three types of cement systems, neat Class H, nano-synthetic graphite, and rock-based geopolymer cements, on interfacial bond integrity. Diametrical compressive tests are used on casing–cement–formation systems. Cement performances are tested in a conventional configuration (Berea Sandstone). A universal testing system is utilized to analyze the relationship applied load–axial strain and the digital image correlation (DIC) technique is used to generate the strain field maps. Based on the relationship and DIC results, bond strengths in different cement systems are evaluated. Additionally, microscope images provide insight explanations of the bond from micro-view. Based on the experimental results, failures of all cases initiate and propagate from the casing–cement interface. Then, radial cracks develop through the formation. This is because the mechanical interlocking bonds are formed only at the cement–sandstone interface to enhance the bond strength. The comparison of geopolymer and nano-modified cements with the conventional cement (neat Class H) shows that the unconventional cements have a lower maximum load and higher axial strain before failure of the samples. It indicates that both the two kinds of cements are more ductile than conventional cement and can support more deformation before the initiation of cracks.

Energy & Fuels↗
DOE OSTI2012

Correction factors for A1SL ionization chamber dosimetry in TomoTherapy: Machine-specific, plan-class, and clinical fields

Purpose: Recently, an international working group on nonstandard fields presented a new formalism for ionization chamber reference dosimetry of small and nonstandard fields [Alfonso et al., Med. Phys. 35, 5179-5186 (2008)] which has been adopted by AAPM TG-148. This work presents an experimental determination of the correction factors for reference dosimetry with an Exradin A1SL thimble ionization chamber in a TomoTherapy unit, focusing on: (i) machine-specific reference field, (ii) plan-class-specific reference field, and (iii) two clinical treatments. Methods: Ionization chamber measurements were performed in the TomoTherapy unit for intermediate (machine-specific and plan-class-specific) calibration fields, based on the reference conditions defined by AAPM TG-148, and two clinical treatments (lung and head-and-neck). Alanine reference dosimetry was employed to determine absorbed dose to water at the point of interest for the fields under investigation. The corresponding chamber correction factors were calculated from alanine to ionization chamber measurements ratios. Results: Two different methods of determining the beam quality correction factor k{sub Q,Q{sub 0}} for the A1SL ionization chamber in this TomoTherapy unit, where reference conditions for conventional beam quality determination cannot be met, result in consistent values. The observed values of overall correction factors obtained for intermediate and clinical fields are consistently around 0.98 with a typical expanded relative uncertainty of 2% (k = 2), which when considered make such correction factors compatible with unity. However, all of them are systematically lower than unity, which is shown to be significant when a hypothesis test assuming a t-student distribution is performed (p=1.8x10{sup -2}). Correction factors k{sub Q{sub c{sub l{sub i{sub n,Q{sub p{sub c{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub p}{sub c}{sub s}{sub r}}}}}}}}}} and k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}}, which are needed for the computation of field factors for relative dosimetry of clinical beams, have been found to be very close to unity for two clinical treatments. Conclusions: The results indicate that the helical field deliveries in this study (including two clinical fields) do not introduce changes on the ion chamber correction factors for dosimetry. For those two specific clinical cases, ratios of chamber readings accurately represent field output factors. The values observed here for intermediate calibration fields are in agreement with previously published data based on alanine dosimetry but differ from values recently reported obtained via radiochromic dosimetry.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Correction factors for ionization chamber dosimetry in CyberKnife: Machine-specific, plan-class, and clinical fields

Purpose: The aim of this work is the application of the formalism for ionization chamber reference dosimetry of small and nonstandard fields [R. Alfonso, P. Andreo, R. Capote, M. S. Huq, W. Kilby, P. Kjaell, T. R. Mackie, H. Palmans, K. Rosser, J. Seuntjens, W. Ullrich, and S. Vatnitsky, 'A new formalism for reference dosimetry of small and nonstandard fields,' Med. Phys. 35, 5179-5186 (2008)] to the CyberKnife robotic radiosurgery system. Correction factors for intermediate calibration fields, a machine-specific reference field (msr) and two plan-class specific reference fields (pcsr), have been studied. Furthermore, the applicability of the new formalism to clinical dosimetry has been analyzed through the investigation of two clinical treatments. Methods: PTW31014 and Scanditronix-Wellhofer CC13 ionization chamber measurements were performed for the fields under investigation. Absorbed dose to water was determined using alanine reference dosimetry, and experimental correction factors were calculated from alanine to ionization chamber readings ratios. In addition, correction factors were calculated for the intermediate calibration fields and one of the clinical treatment fields using the Monte Carlo method and these were compared with the experimental values. Results: Overall correction factors deviating from unity by approximately 2% were obtained from both measurements and simulations, with values below and above unity for the studied intermediate calibration fields and clinical fields for the ionization chambers under consideration. Monte Carlo simulations yielded correction factors comparable with those obtained from measurements for the machine-specific reference field, although differences from 1% to 3.3% were observed between measured and calculated correction factors for the composite intermediate calibration fields. Dose distribution inhomogeneities are thought to be responsible for such discrepancies. Conclusions: The differences found between overall correction factors associated with the proposed intermediate calibration fields and the clinical fields under investigation show that depending on the clinical field and the detector used, either a machine-specific reference field or a plan-class specific reference field is more representative for the clinical field. Given the experimental and numerical uncertainties and the small number of clinical fields considered in this study the significance of these observations is limited and it remains unclear for the CyberKnife if there would be a significant gain in using a pcsr field rather than a msr field as reference field for relative dosimetry.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

TU-G-BRD-08: In-Vivo EPID Dosimetry: Quantifying the Detectability of Four Classes of Errors

Purpose: EPID dosimetry is an emerging method for treatment verification and QA. Given that the in-vivo EPID technique is in clinical use at some centers, we investigate the sensitivity and specificity for detecting different classes of errors. We assess the impact of these errors using dose volume histogram endpoints. Though data exist for EPID dosimetry performed pre-treatment, this is the first study quantifying its effectiveness when used during patient treatment (in-vivo). Methods: We analyzed 17 patients; EPID images of the exit dose were acquired and used to reconstruct the planar dose at isocenter. This dose was compared to the TPS dose using a 3%/3mm gamma criteria. To simulate errors, modifications were made to treatment plans using four possible classes of error: 1) patient misalignment, 2) changes in patient body habitus, 3) machine output changes and 4) MLC misalignments. Each error was applied with varying magnitudes. To assess the detectability of the error, the area under a ROC curve (AUC) was analyzed. The AUC was compared to changes in D99 of the PTV introduced by the simulated error. Results: For systematic changes in the MLC leaves, changes in the machine output and patient habitus, the AUC varied from 0.78–0.97 scaling with the magnitude of the error. The optimal gamma threshold as determined by the ROC curve varied between 84–92%. There was little diagnostic power in detecting random MLC leaf errors and patient shifts (AUC 0.52–0.74). Some errors with weak detectability had large changes in D99. Conclusion: These data demonstrate the ability of EPID-based in-vivo dosimetry in detecting variations in patient habitus and errors related to machine parameters such as systematic MLC misalignments and machine output changes. There was no correlation found between the detectability of the error using the gamma pass rate, ROC analysis and the impact on the dose volume histogram. Funded by grant R18HS022244 from AHRQ.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Fermi establishes classical novae as a distinct class of gamma-ray sources

A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter from a low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in γ rays and stood in contrast to the first γ-ray detected nova V407 Cygni 2010, which belongs to a rare class of symbiotic binary systems. Despite likely differences in the compositions and masses of their white dwarf progenitors, the three classical novae are similarly characterized as soft spectrum transient γ-ray sources detected over 2-3 week durations. The γ-ray detections point to unexpected high-energy particle acceleration processes linked to the mass ejection from thermonuclear explosions in an unanticipated class of Galactic γ-ray sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

An antibody class with a common CDRH3 motif broadly neutralizes sarbecoviruses

The devastation caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made clear the importance of pandemic preparedness. To address future zoonotic outbreaks due to related viruses in the sarbecovirus subgenus, we identified a human monoclonal antibody, 10-40, that neutralized or bound all sarbecoviruses tested in vitro and protected against SARS-CoV-2 and SARS-CoV in vivo. Comparative studies with other receptor-binding domain (RBD)–directed antibodies showed 10-40 to have the greatest breadth against sarbecoviruses, suggesting that 10-40 is a promising agent for pandemic preparedness. Moreover, structural analyses on 10-40 and similar antibodies not only defined an epitope cluster in the inner face of the RBD that is well conserved among sarbecoviruses but also uncovered a distinct antibody class with a common CDRH3 motif. Our analyses also suggested that elicitation of this class of antibodies may not be overly difficult, an observation that bodes well for the development of a pan-sarbecovirus vaccine.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D β-Lactamases

Class D carbapenemases are enzymes of the utmost clinical importance due to their ability to confer resistance to the last-resort carbapenem antibiotics. We investigated the role of the conserved hydrophobic bridge in the carbapenemase activity of OXA-23, the major carbapenemase of the important pathogen Acinetobacter baumannii . We show that substitution of the bridge residue Phe110 affects resistance to meropenem and doripenem and has little effect on MICs of imipenem. The opposite effect was observed upon substitution of the other bridge residue Met221. Complete disruption of the bridge by the F110A/M221A substitution resulted in a significant loss of affinity for doripenem and meropenem and to a lesser extent for imipenem, which is reflected in the reduced MICs of these antibiotics. In the wild-type OXA-23, the pyrrolidine ring of the meropenem tail forms a hydrophobic interaction with Phe110 of the bridge. Similar interactions would ensue with ring-containing doripenem but not with imipenem, which lacks this ring. Our structural studies showed that this interaction with the meropenem tail is missing in the F110A/M221A mutant. These data explain why disruption of the interaction between the enzyme and the carbapenem substrate impacts the affinity and MICs of meropenem and doripenem to a larger degree than those of imipenem. Our structures also show that the bridge directs the acylated carbapenem into a specific tautomeric conformation. Furthermore, it is not this conformation but rather the stabilizing interaction between the tail of the antibiotic and the hydrophobic bridge that contributes to the carbapenemase activity of class D β-lactamases.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Resistance to oxyimino-cephalosporins conferred by an alternative mechanism of hydrolysis by the Acinetobacter -derived cephalosporinase-33 (ADC-33), a class C β-lactamase present in carbapenem-resistant Acinetobacter baumannii (CR Ab )

ABSTRACT Antimicrobial resistance inAcinetobacter baumanniiis partly mediated by chromosomal class C β-lactamases, theAcinetobacter-derived cephalosporinases (ADCs). Recently, a growing number of emerging variants were described, expanding this threat. Consistent with other β-lactamases, one of the main areas of variance exists in the Ω-loop region near the site of cephalosporin binding. Interestingly, a common alanine duplication (Adup) is found in this region. Herein, we studied specific Adup variants expressed in a uniformEscherichia coligenetic background that demonstrated high-level resistance to multiple oxyimino-cephalosporins. For ceftolozane and ceftazidime, the Adup ADCs significantly increased levels of resistance (minimum inhibitory concentration [MIC] ≥ 512 µg/mL and MIC ≥ 1,024 µg/mL, respectively). These observations were consistent with the increasedk cat /K M for ceftazidime. For cefiderocol, three Adup variants exhibited increased MICs and increasedk cat /K M for this compound. Timed electrospray ionization mass spectrometry demonstrated stable cephalosporin:ADC adducts with ADC-30 (non-Adup), but not with ADC-33 (Adup), consistent with turnover. The X-ray crystal structure of Adup variant ADC-33 in complex with ceftazidime was determined (1.57 Å resolution) and suggests that increased turnover is facilitated by conformational changes (shift in Tyr221 and orientation of the oxyimino portion of the R1 side chain) and repositioning of water in the active site. These changes appear to favor substrate-assisted catalysis as an alternative mechanism to base-assisted catalysis. These studies also provide unprecedented insight into the mechanism underlying oxyimino-cephalosporin hydrolysis by expanded-spectrum ADC β-lactamases and possibly other class C β-lactamases, which is of critical importance to future drug design. IMPORTANCE The characterization of emergingAcinetobacter-derived cephalosporinase (ADC) variants is necessary to understand the increasing resistance to β-lactam antibiotics inAcinetobacterspp. In this study, cefiderocol retains effectiveness against ADC variants with and without an Ω-loop alanine duplication (Adup). However, the presence of the Adup appears to introduce loop flexibility and structural alterations resulting in increased resistance and steady-state turnover of larger cephalosporins. Further characterization provides unprecedented insight into the mechanism of cephalosporin hydrolysis by ADC β-lactamases and supports a concomitant increase in ADC structural flexibility and cephalosporin affinity that leads to more efficient hydrolysis. In addition, the crystal structure of ADC-33 in complex with ceftazidime is consistent with a substrate-assisted catalysis mechanism. The structural differences in the ADC-33 active site leading to ceftazidime catalysis provide a better understanding of β-lactamase Adup variants and open important opportunities for future drug design and development.

Microbiology↗
DOE OSTI2017

Curative Treatment of Severe Gram-Negative Bacterial Infections by a New Class of Antibiotics Targeting LpxC

ABSTRACT The infectious diseases caused by multidrug-resistant bacteria pose serious threats to humankind. It has been suggested that an antibiotic targeting LpxC of the lipid A biosynthetic pathway in Gram-negative bacteria is a promising strategy for curing Gram-negative bacterial infections. However, experimental proof of this concept is lacking. Here, we describe our discovery and characterization of a biphenylacetylene-based inhibitor of LpxC, an essential enzyme in the biosynthesis of the lipid A component of the outer membrane of Gram-negative bacteria. The compound LPC-069 has no known adverse effects in mice and is effective in vitro against a broad panel of Gram-negative clinical isolates, including several multiresistant and extremely drug-resistant strains involved in nosocomial infections. Furthermore, LPC-069 is curative in a murine model of one of the most severe human diseases, bubonic plague, which is caused by the Gram-negative bacterium Yersinia pestis . Our results demonstrate the safety and efficacy of LpxC inhibitors as a new class of antibiotic against fatal infections caused by extremely virulent pathogens. The present findings also highlight the potential of LpxC inhibitors for clinical development as therapeutics for infections caused by multidrug-resistant bacteria. IMPORTANCE The rapid spread of antimicrobial resistance among Gram-negative bacilli highlights the urgent need for new antibiotics. Here, we describe a new class of antibiotics lacking cross-resistance with conventional antibiotics. The compounds inhibit LpxC, a key enzyme in the lipid A biosynthetic pathway in Gram-negative bacteria, and are active in vitro against a broad panel of clinical isolates of Gram-negative bacilli involved in nosocomial and community infections. The present study also constitutes the first demonstration of the curative treatment of bubonic plague by a novel, broad-spectrum antibiotic targeting LpxC. Hence, the data highlight the therapeutic potential of LpxC inhibitors against a wide variety of Gram-negative bacterial infections, including the most severe ones caused by Y. pestis and by multidrug-resistant and extensively drug-resistant carbapenemase-producing strains.

Lemaître, Nadine↗
DOE OSTI2025

A protective and broadly binding antibody class engages the influenza virus hemagglutinin head at its stem interface

ABSTRACT Influenza infection and vaccination impart strain-specific immunity that protects against neither seasonal antigenic variants nor the next pandemic. However, antibodies directed to conserved sites can confer broad protection. Here, we identify and characterize a class of human antibodies that engage a previously undescribed, conserved epitope on the influenza hemagglutinin (HA) protein. Prototype antibody S8V1-157 binds at the normally occluded interface between the HA head and stem. Antibodies to this HA head–stem interface epitope are non-neutralizingin vitrobut protect against lethal influenza infection in mice. These antibodies bind to most influenza A subtypes and seasonal human variants, and are present at low frequencies in the memory B cell populations of multiple human donors. Vaccines designed to elicit these antibodies might contribute to “universal” influenza immunity. IMPORTANCE Antibodies to the influenza virus hemagglutinin (HA) protein confer the strongest protection against infection. Human antibodies elicited by infection and/or vaccination fail to protect against antigenically novel animal, pandemic, or human seasonal viruses. Improved vaccines are needed. We identify a novel class of antibodies that bind most divergent HA subtypes and all seasonal human HA antigenic variants tested. These antibodies confer protection from lethal influenza challenge in animal models. The corresponding epitope on the HA head is occluded by its interaction with the stem and is inaccessible in the well-resolved prefusion state. The immunogenicity of this head–stem interface indicates that poorly understood conformations of HA presenting widely conserved surfaces are explored in biochemical, cell-based, andin vivoassays. Head–stem interface antibodies warrant further investigation as an avenue to improve influenza vaccines and therapeutics.

Microbiology↗
DOE OSTI2024

Multivariate Testing of Sampling Techniques to Address Class Imbalance in Building Use Type Classification

This study addresses the challenges inherent in building use type classification, particularly focusing on the issue of class imbalance in the training datasets for machine learning classifiers. We comprehensively analyze the efficacy of various class-balancing sampling techniques. Employing Monte Carlo simulations and Bayesian optimization, we evaluated the performance of multiple sampling methods, including Random Oversampling, Random Undersampling, SMOTE, Borderline-SMOTE, and ADASYN, across a dataset encompassing nine southeastern coastal states of the United States. Our findings reveal that simple random over- and undersampling techniques outperform more sophisticated methods. Additionally, we show inherent value in creating an imbalance in training data to effectively train a machine learning classifier for distinguishing between residential and nonresidential buildings. This study provides valuable guidance for future research on building use type classification research and lays essential groundwork for developing attribute-rich building stock datasets.

Adams, Daniel↗
DOE OSTI2026

Scalable Federated Learning for Scientific Foundation Models on Leadership-Class Systems

Federated learning (FL) at leadership-class HPC systems remains largely unexplored, despite growing interest in deploying federated workflows on modern HPC systems. This paper provides the first system-level empirical characterization of federated fine-tuning of pretrained foundation models on an exascale supercomputer under a multi-node deployment. Using up to 96 concurrent FL clients deployed across Frontier nodes, we study the impact of client scale, model size, data heterogeneity, partial participation, and differential privacy on runtime, communication overhead, and convergence stability. Our results show that pretrained transformer models remain robust to heterogeneity, client dropout, and privacy noise, while system efficiency degrades rapidly with scale as synchronizat and orchestration dominate runtime. We further demonstrate that system-aware execution strategies, including intra-node aggregation and early aggregation, significantly reduce wall-clock time without degrading model quality. These findings establish a practical performance baseline and inform the design of communication-efficient FL systems on leadership-class HPC platforms.

Kotevska, Olivera [ORNL] (ORCID:0000000316772243)↗
DOE OSTI2018

PRISM Class Library

The PRISM Class Library (PRISM.dll) is a collection of routines used by many of the software tools that support the Proteomics Research Information and Management System (PRISM) at PNNL. Although written for use by PRISM tools, the methods in the PRISM class library are general utility methods, and are not dependent on any PNNL resources.

Monroe, Matthew↗
DOE OSTI2024

Discovery of BBO-8520, a First-In-Class Direct and Covalent Dual Inhibitor of GTP-Bound (ON) and GDP-Bound (OFF) KRASG12C

Abstract Approved inhibitors of KRASG12C prevent oncogenic activation by sequestering the inactive, GDP-bound (OFF) form rather than directly binding and inhibiting the active, GTP-bound (ON) form. This approach provides no direct target coverage of the active protein. Expectedly, adaptive resistance to KRASG12C (OFF)-only inhibitors is observed in association with increased expression and activity of KRASG12C(ON). To provide optimal KRASG12C target coverage, we have developed BBO-8520, a first-in-class, direct dual inhibitor of KRASG12C(ON) and (OFF) forms. BBO-8520 binds in the Switch-II/Helix3 pocket, covalently modifies the target cysteine, and disables effector binding to KRASG12C(ON). BBO-8520 exhibits potent signaling inhibition in growth factor–activated states, in which current (OFF)-only inhibitors demonstrate little measurable activity. In vivo, BBO-8520 demonstrates rapid target engagement and inhibition of signaling, resulting in durable tumor regression in multiple models, including those resistant to KRASG12C(OFF)-only inhibitors. BBO-8520 is in phase 1 clinical trials in patients with KRASG12C non–small cell lung cancer. Significance: BBO-8520 is a first-in-class direct, small molecule covalent dual inhibitor that engages KRASG12C in the active (ON) and inactive (OFF) conformations. BBO-8520 represents a novel mechanism of action that allows for optimal target coverage and delays the emergence of adaptive resistance seen with (OFF)-only inhibitors in the clinic. See related commentary by Zhou and Westover, p. 455

Oncology↗
DOE OSTI2020

Conserving Land–Atmosphere Synthesis Suite (CLASS)

Accurate estimates of terrestrial water and energy cycle components are needed to better understand climate processes and improve models’ ability to simulate future change. Various observational estimates are available for the individual budget terms; however, these typically show inconsistencies when combined in a budget. In this work, a Conserving Land–Atmosphere Synthesis Suite (CLASS) of estimates of simultaneously balanced surface water and energy budget components is developed. Individual CLASS variable datasets, where possible, 1) combine a range of existing variable product estimates, and hence overcome the limitations of estimates from a single source; 2) are observationally constrained with in situ measurements; 3) have uncertainty estimates that are consistent with their agreement with in situ observations; and 4) are consistent with each other by being able to solve the water and energy budgets simultaneously. First, available datasets of a budget variable are merged by implementing a weighting method that accounts both for the ability of datasets to match in situ measurements and the error covariance between datasets. Then, the budget terms are adjusted by applying an objective variational data assimilation technique (DAT) that enforces the simultaneous closure of the surface water and energy budgets linked through the equivalence of evapotranspiration and latent heat. Comparing component estimates before and after applying the DAT against in situ measurements of energy fluxes and streamflow showed that modified estimates agree better with in situ observations across various metrics, but also revealed some inconsistencies between water budget terms in June over the higher latitudes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Does class matter? Understanding differential pandemic recovery via a building typology

This study investigates the recovery of building-level footfall from the COVID-19 pandemic using privacy-preserving mobile devices-based footfall data within 60 downtown areas in the USA and Canada. Using clustering, we identify five distinct building typologies based on their characteristics, including rent, quality and recovery rates. The results reveal significant variation of recovery rates by building features. We find negative relationships with footfall recovery for both the percentage of office and remote work tenants and building quality. In contrast, buildings with traditional work tenants and retail functions achieve higher recovery rates. We also test the ‘flight to quality’ hypothesis via on our typology results. High-quality office buildings (Class A+) continue to have high rents but experience low physical footfall recovery, which suggests that this class is not as resilient as portrayed. The findings thus suggest the importance of considering both economic and footfall resilience in evaluating the performance of office buildings.

Covid-19↗
DOE OSTI2021

Gene co-expression network analysis in zebrafish reveals chemical class specific modules

Zebrafish is a popular animal model used for high-throughput screening of chemical hazards, however, investigations of transcriptomic mechanisms of toxicity are still needed. Here, our goal was to identify genes and biological pathways that Aryl Hydrocarbon Receptor 2 (AHR2) Activators and flame retardant chemicals (FRCs) alter in developing zebrafish. Taking advantage of a compendium of phenotypically-anchored RNA sequencing data collected from 48-h post fertilization (hpf) zebrafish, we inferred a co-expression network that grouped genes based on their transcriptional response. Genes responding to the FRCs and AHR2 Activators localized to distinct regions of the network, with FRCs inducing a broader response related to neurobehavior. AHR2 Activators centered in one region related to chemical stress responses. We also discovered several highly co-expressed genes in this module, including cyp1a, and we subsequently show that these genes are definitively within the AHR2 signaling pathway. Systematic removal of the two chemical types from the data, and analysis of network changes identified neurogenesis associated with FRCs, and regulation of vascular development associated with both chemical classes. We also identified highly connected genes responding specifically to each class that are potential biomarkers of exposure. Overall, we created the first zebrafish chemical-specific gene co-expression network illuminating how chemicals alter the transcriptome relative to each other. In addition to our conclusions regarding FRCs and AHR2 Activators, our network can be leveraged by other studies investigating chemical mechanisms of toxicity.

59 BASIC BIOLOGICAL SCIENCES↗