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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The Navier-Stokes computer

The Navier-Stokes computer (NSC) has been developed for solving problems in fluid mechanics involving complex flow simulations that require more speed and capacity than provided by current and proposed Class VI supercomputers. The machine is a parallel processing supercomputer with several new architectural elements which can be programmed to address a wide range of problems meeting the following criteria: (1) the problem is numerically intensive, and (2) the code makes use of long vectors. A simulation of two-dimensional nonsteady viscous flows is presented to illustrate the architecture, programming, and some of the capabilities of the NSC.

Nosenchuck, D. M.↗
DOE OSTI2011

Qualitative and Quantitative Assessment of Nuclear Materials Contained in High-Activity Waste Arising from the Operations at the 'SHELTER' Facility

As a result of the nuclear accident at the Chernobyl NPP in 1986, the explosion dispeesed nuclear materials contained in the nuclear fuel of the reactor core over the destroyed facilities at Unit No. 4 and over the territory immediately adjacent to the destroyed unit. The debris was buried under the Cascade Wall. Nuclear materials at the SHELTER can be characterized as spent nuclear fuel, fresh fuel assemblies (including fuel assemblies with damaged geometry and integrity, and individual fuel elements), core fragments of the Chernobyl NPP Unit No. 4, finely-dispersed fuel (powder/dust), uranium and plutonium compounds in water solutions, and lava-like nuclear fuel-containing masses. The new safe confinement (NSC) is a facility designed to enclose the Chernobyl NPP Unit No. 4 destroyed by the accident. Construction of the NSC involves excavating operations, which are continuously monitored including for the level of radiation. The findings of such monitoring at the SHELTER site will allow us to characterize the recovered radioactive waste. When a process material categorized as high activity waste (HAW) is detected the following HLW management operations should be involved: HLW collection; HLW fragmentation (if appropriate); loading HAW into the primary package KT-0.2; loading the primary package filled with HAW into the transportation cask KTZV-0.2; and storing the cask in temporary storage facilities for high-level solid waste. The CDAS system is a system of 3He tubes for neutron coincidence counting, and is designed to measure the percentage ratio of specific nuclear materials in a 200-liter drum containing nuclear material intermixed with a matrix. The CDAS consists of panels with helium counter tubes and a polyethylene moderator. The panels are configured to allow one to position a waste-containing drum and a drum manipulator. The system operates on the ‘add a source’ basis using a small Cf-252 source to identify irregularities in the matrix during an assay. The platform with the source is placed under the measurement chamber. The platform with the source material is moved under the measurement chamber. The design allows one to move the platform with the source in and out, thus moving the drum. The CDAS system and radioactive waste containers have been built. For each drum filled with waste two individual measurements (passive/active) will be made. This paper briefly describes the work carried out to assess qualitatively and quantitatively the nuclear materials contained in high-level waste at the SHELTER facility. These efforts substantially increased nuclear safety and security at the facility.

Cherkas, Dmytro↗
DOE OSTI2016

Test Data Monitor

The National Security Campus (NSC) collects a large amount of test data used The National Security Campus (NSC) collects a large amount of test data used to accept high value and high rigor product. The data has been used historically to support root cause analysis when anomalies are detected in down-stream processes. The opportunity to use the data for predictive failure analysis however, had never been exploited. The primary goal of the Test Data Monitor (TDM) software is to provide automated capabilities to analyze data in near-real-time and report trends that foreshadow actual product failures. To date, the aerospace industry as a whole is challenged at utilizing collected data to the degree that modern technology allows. As a result of the innovation behind TDM, Honeywell is able to monitor millions of data points through a multitude of SPC algorithms continuously and autonomously so that our personnel resources can more efficiently and accurately direct their attention to suspect processes or features. TDM’s capabilities have been recognized by our U.S. Department of Energy National Nuclear Security Administration (NNSA) sponsor for potential use at other sites within the NNSA. This activity supports multiple initiatives including expectations of the NNSA and broader corporate goals that center around data-based quality controls on production.

Bosas, Joseph↗
DOE OSTI2020

Applications and Deployment of Neutron Scatter Cameras in Nuclear Safeguards Scenarios

Neutron scatter cameras (NSCs) are a type of directionally sensitive neutron detector that rely on two consecutive neutron scattering events to localize a source of neutrons. NSCs can be used to locate, image, and identify unknown neutron sources or verify the geometry and identity of known sources. Much technical progress has been made in improving NSC designs, but little literature exists exploring the full range of practical application of neutron scatter cameras. This paper seeks to identify scenarios related to nuclear security and non-proliferation where deployment of NSCs may be useful. These situations could include: limited searches for sources during cargo screening, counting nuclear warheads for treaty verification, verification of special nuclear material during inspections, imaging nuclear contamination, imaging nuclear reactor cores, searching for lost sources, and matching neutron images in shipper/receiver or inventory management scenarios. These scenarios are examined with respect to existing NSC designs and proposed designs in terms of usefulness and practicality of deployment when compared to currently used detection systems.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2018

Seasonal patterns of nonstructural carbohydrate reserves in four woody boreal species

Plants store nonstructural carbohydrates (NSCs), such as sugars and starch, to use as carbon and energy sources for daily maintenance and growth needs as well as during times of stress. Allocation of NSCs to storage provides an important physiological strategy associated with future growth and survival, and thus understanding the seasonal patterns of NSC reserves provides insight into how species with different traits (e.g., growth form, leaf habit, wood anatomy) may respond to stress. We characterized the seasonal patterns of NSCs in four woody boreal plant species in Minnesota, USA. Sugar and starch concentrations were measured across the year in the roots and branches of two conifer trees, black spruce ( Picea mariana (Mill.) B.S.P.) and eastern tamarack ( Larix laricina (Du Roi) K. Koch), as well as in the leaves and branches of two evergreen broadleaf shrubs, bog Labrador tea ( Rhododendron groenlandicum (Oeder) Kron & Judd) and leatherleaf ( Chamaedaphne calyculata (L.) Moench). In general, seasonal variation was dominated by changes in starch across all organs and species. While similar seasonal patterns of NSCs were observed in the shrubs, different seasonal patterns were observed between the trees, particularly in the roots. Lastly, our results suggest that species-specific traits likely have consequences for organ-level storage dynamics, which may influence whole-plant growth and survival under global change.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Simulation of flow and mercury transport in Upper East Fork Poplar Creek, Oak Ridge, Tennessee

As a result of nuclear processing activities started back in the 1950s, the environment in the vicinity of the Y-12 National Security Complex (Y-12 NSC) in Oak Ridge, Tennessee, and surrounding watersheds has been contaminated by nearly 1,000 tons of elementary mercury. To comply with the state and federal surface water quality standards, a significant reduction in mercury concentration to parts-per-trillion levels has been proposed. In order to analyze the mercury cycle in the environment and provide forecasting capabilities for the flow and transport of mercury within the Upper East Fork Poplar Creek (UEFPC) watershed, an integrated surface and subsurface flow and transport model has been developed using the hydrodynamic and transport numerical package, MIKE, developed by the Danish Hydraulic Institute. The model has been constructed and calibrated using an extensive collection of historical records (i.e., hydrological data, and mercury concentration measurements in groundwater, soil, and sediment) obtained from the Oak Ridge Environmental Information System database. Daily fluctuations in stream flow, as a result of scattered rainfall, flooding, and flow augmentation, resuspend the contaminated streambed sediments and/or erode the polluted streambank soil and provide a secondary source of mercury to the creek. In order to investigate the significance of sediment-mercury interactions on the fate and transport of mercury within the UEFPC study domain, simulations were performed for two different cases (i.e., with and without consideration of sediment-mercury interactions). Computed total suspended solids and mercury concentrations at the integration point of the creek are compared with the corresponding historical records in both cases. As confirmed by the numerical simulations, a substantial portion of the mercury detected in the river is likely in the form of sediment particle–bound mercury (i.e., mercury particulates).

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

Delivery of cationic polymer-siRNA nanoparticles for gene therapies in neural regeneration

Highlights: Black-Right-Pointing-Pointer Nogo receptor can inhibit growth of injured axons, thus affecting neural regeneration. Black-Right-Pointing-Pointer The delivery of siRNA is crucial to inhibit NgR expression in NSCs. Black-Right-Pointing-Pointer Non-viral vector PEG-PEI condensed siRNA targeting NgR into nanoscale particles. Black-Right-Pointing-Pointer PEG-PEI/siRNA at N/P = 15 displayed high transfection efficiency and low cytotoxicity. Black-Right-Pointing-Pointer PEG-PEI has great potential in carrying siRNA to diminish the gene expression in NSCs. -- Abstract: The therapeutic applications of neural stem cells (NSCs) have potential to promote recovery in many obstinate diseases in central nervous system. Regulation of certain gene expressions using siRNA may have significant influence on the fate of NSC. To achieve the optimum gene silencing effect of siRNA, non-viral vector polyethylene glycol-polyethyleneimine (PEG-PEI) was investigated in the delivery of siRNA to NSCs. The characteristics of PEG-PEI/siRNA polyplexes were detected by scanning electron microscopy (SEM). The effects of nanoparticles on cell viability were measured via CCK-8 assay. In addition, the transfection efficiency was evaluated by fluorescence microscope and flow cytometry, and real-time PCR and Western Blot were employed to detect the gene inhibition effect of siRNA delivered by PEG-PEI. The SEM micrographs showed that PEG-PEI could condense siRNA to form diffuse and spherical nanoparticles. The cytotoxicity of PEG-PEI/siRNA nanocomplexes (N/P = 15) was significantly lower when compared with that of Lipofectamine 2000/siRNA (P < 0.05). Moreover, the highest transfection efficiency of PEG-PEI/siRNA nanoparticles was obtained at an N/P ratio of 15, which was better than that achieved in the transfection using Lipofectamine 2000 (P < 0.05). Finally, the gene knockdown effect of PEG-PEI/siRNA nanoparticles was verified at the levels of mRNA and protein. These results suggest that PEG-PEI may potentially be used as a siRNA delivery vector for neural regeneration therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

The DNA glycosylases OGG1 and NEIL3 influence differentiation potential, proliferation, and senescence-associated signs in neural stem cells

Highlights: Black-Right-Pointing-Pointer DNA glycosylases OGG1 and NEIL3 are required for neural stem cell state. Black-Right-Pointing-Pointer No effect on cell viability by OGG1 or NEIL3 knockdown in neural stem cells. Black-Right-Pointing-Pointer OGG1 or NEIL3 RNA knockdown result in decreased proliferation and differentiation. Black-Right-Pointing-Pointer Increased HP1{gamma} immunoreactivity after NEIL3 knockdown suggests premature senescence. -- Abstract: Embryonic neural stem cells (NSCs) exhibit self-renewal and multipotency as intrinsic characteristics that are key parameters for proper brain development. When cells are challenged by oxidative stress agents the resulting DNA lesions are repaired by DNA glycosylases through the base excision repair (BER) pathway as a means to maintain the fidelity of the genome, and thus, proper cellular characteristics. The functional roles for DNA glycosylases in NSCs have however remained largely unexplored. Here we demonstrate that RNA knockdown of the DNA glycosylases OGG1 and NEIL3 decreased NSC differentiation ability and resulted in decreased expression of both neuronal and astrocytic genes after mitogen withdrawal, as well as the stem cell marker Musashi-1. Furthermore, while cell survival remained unaffected, NEIL3 deficient cells displayed decreased cell proliferation rates along with an increase in HP1{gamma} immunoreactivity, a sign of premature senescence. Our results suggest that DNA glycosylases play multiple roles in governing essential neural stem cell characteristics.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Ubiquitin C-Terminal Hydrolase L1 regulates autophagy by inhibiting autophagosome formation through its deubiquitinating enzyme activity

Highlights: • UCHL1 interacts with LC3 and inhibits autophagosome formation. • UCHL1 Parkinson mutant I93 M abolishes to suppress autophagosome formation. • UCHL1 inhibitors LDN-57444 and NSC632839 promote autophagosome formation in cells. Ubiquitination modification has been shown to play a key role in autophagy. Increasing studies reported the involvement of de-ubiquitinating enzymes (DUBs) in autophagy pathway. To systematically search how DUBs manipulate autophagy, we utilized a double fluorescence tagged LC3 stable HeLa cell line, and did a genome wide screen of 55 human DUBs which is about 60% coverage of the DUB family. We found a bunch of DUBs have impact on autophagy by either changing the LC3 puncta formation or the autophagy flux. One of them, Ubiquitin C-Terminal Hydrolase L1 (UCHL1) correlated to Parkinson's disease, strongly affects autophagy by inhibiting autophagosome formation. We found UCHL1 overexpression inhibits LC3 puncta formation and is dependent on its DUB activity. Knockdown of UCHL1 significantly promotes LC3 puncta formation. Further study revealed that UCHL1 may affect autophagy by interacting with LC3 but not other autophagy related proteins. Interestingly, a Parkinson's disease related mutant UCHL1 I93 M defects its DUB activity and can no longer inhibit autophagosome formation. We further screened 22 commercially available DUB inhibitors and found two potent UCHL1 inhibitors LDN-57444 (LDN) and NSC632839 (NSC), when treating cells, both strongly induce LC3 puncta formation. Taken together, our results indicated a new insight into the manner in which DUB regulates autophagy and provided potential drugs for the Parkinson's disease.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Identification of small molecule inhibitors of botulinum neurotoxin serotype E via footprint similarity

Botulinum neurotoxins (BoNT) are among the most poisonous substances known, and of the 7 serotypes (A–G) identified thus far at least 4 can cause death in humans. Here, the goal of this work was identification of inhibitors that specifically target the light chain catalytic site of the highly pathogenic but lesser-studied E serotype (BoNT/E). Large-scale computational screening, employing the program DOCK, was used to perform atomic-level docking of 1.4 million small molecules to prioritize those making favorable interactions with the BoNT/E site. In particular, ‘footprint similarity’ (FPS) scoring was used to identify compounds that could potentially mimic features on the known substrate tetrapeptide RIME. Among 92 compounds purchased and experimentally tested, compound C562-1101 emerged as the most promising hit with an apparent IC 50 value three-fold more potent than that of the first reported BoNT/E small molecule inhibitor NSC-77053. Additional analysis showed the predicted binding pose of C562-1101 was geometrically and energetically stable over an ensemble of structures generated by molecular dynamic simulations and that many of the intended interactions seen with RIME were maintained. Finally, several analogs were also computationally designed and predicted to have further molecular mimicry thereby demonstrating the potential utility of footprint-based scoring protocols to help guide hit refinement.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

A NEA review on innovative structural materials solutions, including advanced manufacturing processes for nuclear applications based on technology readiness assessment

The Nuclear Energy Agency (NEA) Expert Group on Innovative Structural Materials (EGISM) was established in 2008 under the guidance of the Nuclear Science Committee (NSC). Its objectives are to conduct joint and comparative studies to support the development, selection and characterisation of innovative structural materials that can be implemented in advanced nuclear fuel cycles, under long service lifetime and extreme conditions, such as high temperature, high dose/dose rate and corrosive chemical environments. In this context of growing interest and initiatives, the EGISM initiated at the beginning of 2018 an activity among its members to: Identify, in a non-exhaustive way, the currently existing programs on innovative materials and fabrication processes in NEA member countries and China; Establish a first cartography of the activities that are underway on these topics and identify common subjects and thematic; Propose a Technology Readiness Level scale to estimate the maturity of both innovative materials and fabrication processes; Carry out a reflection on what the enablers are to quickly climb this TRL scale, as well as the obstacles, in order to identify solutions to overcome them. This paper first gives definitions shared between the EGISM members on what are considered as advanced structural materials solutions. Next, some international initiatives for the accelerated development of high performance materials are presented both in non-nuclear and nuclear fields. Then, the methodology adopted for technology readiness assessment is explained. A non-exhaustive synthesis of the projects identified among the EGISM members on innovative structural materials and advanced manufacturing solutions such as additive manufacturing is presented. The TRL level of these projects is evaluated. A focus is also made on some of these projects to illustrate and explain the TRLs chosen as well as highlighting enablers or obstacles identified to climbing up the TRL scale.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Perfluorooctane sulfonate induces neuronal and oligodendrocytic differentiation in neural stem cells and alters the expression of PPARγ in vitro and in vivo

Perfluorinated compounds are ubiquitous chemicals of major concern for their potential adverse effects on the human population. We have used primary rat embryonic neural stem cells (NSCs) to study the effects of perfluorooctane sulfonate (PFOS) on the process of NSC spontaneous differentiation. Upon removal of basic fibroblast growth factor, NSCs were exposed to nanomolar concentrations of PFOS for 48 h, and then allowed to differentiate for additional 5 days. Exposure to 25 or 50 nM concentration resulted in a lower number of proliferating cells and a higher number of neurite-bearing TuJ1-positive cells, indicating an increase in neuronal differentiation. Exposure to 50 nM also significantly increased the number of CNPase-positive cells, pointing to facilitation of oligodendrocytic differentiation. PPAR genes have been shown to be involved in PFOS toxicity. By q-PCR we detected an upregulation of PPARγ with no changes in PPARα or PPARδ genes. One of the downstream targets of PPARs, the mitochondrial uncoupling protein 2 (UCP2) was also upregulated. The number of TuJ1- and CNPase-positive cells increased after exposure to PPARγ agonist rosiglitazone (RGZ, 3 μM) and decreased after pre-incubation with the PPARγ antagonist GW9662 (5 μM). RGZ also upregulated the expression of PPARγ and UCP2 genes. Meanwhile GW9662 abolished the UCP2 upregulation and decreased Ca{sup 2+} activity induced by PFOS. Interestingly, a significantly higher expression of PPARγ and UCP3 genes was also detected in mouse neonatal brain after prenatal exposure to PFOS. These data suggest that PPARγ plays a role in the alteration of spontaneous differentiation of NSCs induced by nanomolar concentrations of PFOS. - Highlights: • PFOS decreases proliferation of neural stem cells (NSCs). • PFOS induces neuronal and oligodendrocytic differentiation in NSCs. • PFOS alters expression of PPARγ and UCP2 in vitro. • PFOS alters expression of PPARγ and UCP3 in vivo. • Block of PPARγ by the selective antagonist GW9662 abolishes the effects of PFOS.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Activation of Aurora A kinase through the FGF1/FGFR signaling axis sustains the stem cell characteristics of glioblastoma cells

Fibroblast growth factor 1 (FGF1) binds and activates FGF receptors, thereby regulating cell proliferation and neurogenesis. Human FGF1 gene 1B promoter (−540 to +31)-driven SV40 T antigen has been shown to result in tumorigenesis in the brains of transgenic mice. FGF1B promoter (−540 to +31)-driven green fluorescent protein (F1BGFP) has also been used in isolating neural stem cells (NSCs) with self-renewal and multipotency from developing and adult mouse brains. In this study, we provide six lines of evidence to demonstrate that FGF1/FGFR signaling is implicated in the expression of Aurora A (AurA) and the activation of its kinase domain (Thr288 phosphorylation) in the maintenance of glioblastoma (GBM) cells and NSCs. First, treatment of FGF1 increases AurA expression in human GBM cell lines. Second, using fluorescence-activated cell sorting, we observed that F1BGFP reporter facilitates the isolation of F1BGFP(+) GBM cells with higher expression levels of FGFR and AurA. Third, both FGFR inhibitor (SU5402) and AurA inhibitor (VX680) could down-regulate F1BGFP-dependent AurA activity. Fourth, inhibition of AurA activity by two different AurA inhibitors (VX680 and valproic acid) not only reduced neurosphere formation but also induced neuronal differentiation of F1BGFP(+) GBM cells. Fifth, flow cytometric analyses demonstrated that F1BGFP(+) GBM cells possessed different NSC cell surface markers. Finally, inhibition of AurA by VX680 reduced the neurosphere formation of different types of NSCs. Our results show that activation of AurA kinase through FGF1/FGFR signaling axis sustains the stem cell characteristics of GBM cells. Implications: This study identified a novel mechanism for the malignancy of GBM, which could be a potential therapeutic target for GBM. - Highlights: • We report that FGF1 treatment can stimulate AurA kinase expression in human GBM cells. • FGF1/FGFR signaling is involved in the activation of AurA kinase. • FGF1 sustains the self-renewal of human GBM cells and embryonic stem cells via AurA activation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Identification and Structure–Activity Relationships of Novel Compounds that Potentiate the Activities of Antibiotics in Escherichia coli

In Gram-negative bacteria, efflux pumps are able to prevent effective cellular concentrations from being achieved for a number of antibiotics. Small molecule adjuvants that act as efflux pump inhibitors (EPIs) have the potential to reinvigorate existing antibiotics that are currently ineffective due to efflux mechanisms. Through a combination of rigorous experimental screening and in silico virtual screening, we recently identified novel classes of EPIs that interact with the membrane fusion protein AcrA, a critical component of the AcrAB-TolC efflux pump in Escherichia coli. In this paper, we present initial optimization efforts and structure–activity relationships around one of those previously described hits, NSC 60339 (1). Finally, from these efforts we identified two compounds, SLUPP-225 (17h) and SLUPP-417 (17o), which demonstrate favorable properties as potential EPIs in E. coli cells including the ability to penetrate the outer membrane, improved inhibition of efflux relative to 1, and potentiation of the activity of novobiocin and erythromycin.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

HIGH-CONTRAST STELLAR OBSERVATIONS WITHIN THE DIFFRACTION LIMIT AT THE PALOMAR HALE TELESCOPE

We report on high-accuracy high-resolution (<20 mas) stellar observations obtained with the Palomar Fiber Nuller (PFN), a near-infrared ({approx_equal}2.2 {mu}m) interferometric coronagraph installed at the Palomar Hale telescope. The PFN uses destructive interference between two elliptical (3 m Multiplication-Sign 1.5 m) sub-apertures of the primary to reach high dynamic range inside the diffraction limit of the full telescope. In order to validate the PFN's instrumental approach and its data reduction strategy, based on the newly developed 'Null Self-Calibration' (NSC) method, we observed a sample of eight well-characterized bright giants and supergiants. The quantity measured is the source astrophysical null depth, or equivalently the object's visibility at the PFN 3.2 m interferometric baseline. For the bare stars {alpha} Boo, {alpha} Her, {beta} And, and {alpha} Aur, PFN measurements are in excellent agreement with previous stellar photosphere measurements from long baseline interferometry. For the mass-losing stars {beta} Peg, {alpha} Ori, {rho} Per, and {chi} Cyg, circumstellar emission and/or asymmetries are detected. Overall, these early observations demonstrate the PFN's ability to measure astrophysical null depths below 10{sup -2} (limited by stellar diameters), with 1 {sigma} uncertainties as low as a few 10{sup -4}. Such visibility accuracy is unmatched at this spatial resolution in the near-infrared and translates into a contrast better than 10{sup -3} within the diffraction limit. With further improvements anticipated in 2011/2012, a state-of-the-art infrared science camera and a new extreme adaptive optics system, the PFN should provide a unique tool for the detection of hot debris disks and young self-luminous sub-stellar companions in the immediate vicinity of nearby stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

AMUSE-Field. II. Nucleation of early-type galaxies in the field versus cluster environment

The optical light profiles of nearby early-type galaxies are known to exhibit a smooth transition from nuclear light deficits to nuclear light excesses with decreasing galaxy mass, with as much as 80% of the galaxies with stellar masses below 10{sup 10} M {sub ☉} hosting a massive nuclear star cluster (NSC). At the same time, while all massive galaxies are thought to harbor nuclear supermassive black holes (SMBHs), observational evidence for SMBHs is slim at the low end of the mass function. Here, we explore the environmental dependence of the nucleation fraction by comparing two homogeneous samples of nearby field versus cluster early-type galaxies with uniform Hubble Space Telescope (HST) coverage. Existing Chandra X-ray Telescope data for both samples yield complementary information on low-level accretion onto nuclear SMBHs. Specifically, we report on dual-band (F475W and F850LP) Advanced Camera for Surveys (ACS) imaging data for 28 out of the 103 field early-type galaxies that compose the AMUSE-Field Chandra survey, and compare our results against the companion HST and Chandra surveys for a sample of 100 Virgo Cluster early-types (ACS Virgo Cluster and AMUSE-Virgo surveys, respectively). We model the two-dimensional light profiles of the field targets to identify and characterize NSCs, and find a field nucleation fraction of 26%{sub −11%}{sup +17%} (at the 1σ level), consistent with the measured Virgo nucleation fraction across a comparable mass distribution (30%{sub −12%}{sup +17%}). Coupled with the Chandra result that SMBH activity is higher for the field, our findings indicate that, since the last epoch of star formation, the funneling of gas to the nuclear regions has been inhibited more effectively for Virgo galaxies, arguably via ram pressure stripping.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Photometric calibration in u -band using blue halo stars

ABSTRACT We develop a method to calibrate u-band photometry based on the observed colour of blue Galactic halo stars. The Galactic halo stars belong to an old stellar population of the Milky Way and have relatively low metallicity. The ‘blue tip’ of the halo population – the main sequence turn-off (MSTO) stars – is known to have a relatively uniform intrinsic edge u-g colour with only slow spatial variation. In SDSS data, the observed variation is correlated with Galactic Latitude, which we attribute to contamination by higher metallicity disc stars and fit with an empirical curve. This curve can then be used to calibrate u-band imaging if g-band imaging of matching depth is available. Our approach can be applied to single-field observations at |b| > 30°, and removes the need for standard star observations or overlap with calibrated u-band imaging. We include in our method the calibration of g-band data with ATLAS-Refcat2. We test our approach on stars in KiDS DR 4, ATLAS DR 4, and DECam imaging from the NOIRLab Source Catalog (NSC DR2), and compare our calibration with SDSS. For this process, we use synthetic magnitudes to derive the colour equations between these data sets, in order to improve zero-point accuracy. We find an improvement for all data sets, reaching a zero-point precision of 0.016 mag for KiDS (compared to the original 0.033 mag), 0.020 mag for ATLAS (originally 0.027 mag), and 0.016 mag for DECam (originally 0.041 mag). Thus, this method alone reaches the goal of 0.02 mag photometric precision in u-band for the Rubin Observatory’s Legacy Survey of Space and Time (LSST).

79 ASTRONOMY AND ASTROPHYSICS↗