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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Reconnaissance with JWST of the J-region Asymptotic Giant Branch in Distance Ladder Galaxies: From Irregular Luminosity Functions to Approximation of the Hubble Constant

Abstract We study stars in the J-regions of the asymptotic giant branch (JAGB) of near-infrared color–magnitude diagrams in the maser host NGC 4258 and four hosts of six Type Ia supernovae (SNe Ia): NGC 1448, NGC 1559, NGC 5584, and NGC 5643. These clumps of stars are readily apparent near 1.0 < F150W − F277W < 1.5 andm F150W = 22–25 mag with James Webb Space Telescope NIRCam photometry. Various methods have been proposed to assign an apparent reference magnitude to this recently proposed standard candle, including the mode, median, sigma-clipped mean, or a modeled luminosity function parameter. We test the consistency of these by measuring intrahost variations, finding differences of up to ∼0.2 mag that significantly exceed statistical uncertainties. Brightness differences appear intrinsic, and are further amplified by the nonuniform shape of the JAGB luminosity function, also apparent in the LMC and SMC. We follow a “many methods” approach to measure consistently JAGB magnitudes and distance moduli to the SN Ia host sample calibrated by NGC 4258. We find broad agreement with distance moduli measured from Cepheids, tip of the red giant branch, and Miras. However, the SN host mean distance modulus estimated via the JAGB method necessary to estimateH 0 differs by ∼0.19 mag among the above definitions, the result of different levels of luminosity function asymmetry. The methods yield a full range of 71−78 km s −1 Mpc −1 , i.e., a fiducial result ofH 0 = 74.7 ± 2.1(stat) ± 2.3(sys, ±3.1 if combined in quadrature) km s −1 Mpc −1 , with systematic errors limited by the differences in methods. Future work may seek to standardize and refine this promising tool further, making it more competitive with established distance indicators.

Astronomy & Astrophysics↗
DOE OSTI2020

Benchmarking and parameter sensitivity of physiological and vegetation dynamics using the Functionally Assembled Terrestrial Ecosystem Simulator (FATES) at Barro Colorado Island, Panama

Plant functional traits determine vegetation responses to environmental variation, but variation in trait values is large, even within a single site. Likewise, uncertainty in how these traits map to Earth system feedbacks is large. We use a vegetation demographic model (VDM), the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), to explore parameter sensitivity of model predictions, and comparison to observations, at a tropical forest site: Barro Colorado Island in Panama. We define a single 12-dimensional distribution of plant trait variation, derived primarily from observations in Panama, and define plant functional types (PFTs) as random draws from this distribution. We compare several model ensembles, where individual ensemble members vary only in the plant traits that define PFTs, and separate ensembles differ from each other based on either model structural assumptions or non-trait, ecosystem-level parameters, which include (a) the number of competing PFTs present in any simulation and (b) parameters that govern disturbance and height-based light competition. While single-PFT simulations are roughly consistent with observations of productivity at Barro Colorado Island, increasing the number of competing PFTs strongly shifts model predictions towards higher productivity and biomass forests. Different ecosystem variables show greater sensitivity than others to the number of competing PFTs, with the predictions that are most dominated by large trees, such as biomass, being the most sensitive. Changing disturbance and height-sorting parameters, i.e., the rules of competitive trait filtering, shifts regimes of dominance or coexistence between early- and late-successional PFTs in the model. Increases to the extent or severity of disturbance, or to the degree of determinism in height-based light competition, all act to shift the community towards early-successional PFTs. In turn, these shifts in competitive outcomes alter predictions of ecosystem states and fluxes, with more early-successional-dominated forests having lower biomass. It is thus crucial to differentiate between plant traits, which are under competitive pressure in VDMs, from those model parameters that are not and to better understand the relationships between these two types of model parameters to quantify sources of uncertainty in VDMs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Watershed zonation through hillslope clustering for tractably quantifying above- and below-ground watershed heterogeneity and functions

Abstract. In this study, we develop a watershed zonation approach for characterizing watershed organization and functions in a tractable manner by integrating multiple spatial data layers. We hypothesize that (1) a hillslope is an appropriate unit for capturing the watershed-scale heterogeneity of key bedrock-through-canopy properties and for quantifying the co-variability of these properties representing coupled ecohydrological and biogeochemical interactions, (2) remote sensing data layers and clustering methods can be used to identify watershed hillslope zones having the unique distributions of these properties relative to neighboring parcels, and (3) property suites associated with the identified zones can be used to understand zone-based functions, such as response to early snowmelt or drought and solute exports to the river. We demonstrate this concept using unsupervised clustering methods that synthesize airborne remote sensing data (lidar, hyperspectral, and electromagnetic surveys) along with satellite and streamflow data collected in the East River Watershed, Crested Butte, Colorado, USA. Results show that (1) we can define the scale of hillslopes at which the hillslope-averaged metrics can capture the majority of the overall variability in key properties (such as elevation, net potential annual radiation, and peak snow-water equivalent – SWE), (2) elevation and aspect are independent controls on plant and snow signatures, (3) near-surface bedrock electrical resistivity (top 20 m) and geological structures are significantly correlated with surface topography and plan species distribution, and (4) K-means, hierarchical clustering, and Gaussian mixture clustering methods generate similar zonation patterns across the watershed. Using independently collected data, we show that the identified zones provide information about zone-based watershed functions, including foresummer drought sensitivity and river nitrogen exports. The approach is expected to be applicable to other sites and generally useful for guiding the selection of hillslope-experiment locations and informing model parameterization.

58 GEOSCIENCES↗
DOE OSTI2020

Late-life restoration of mitochondrial function reverses cardiac dysfunction in old mice

Diastolic dysfunction is a prominent feature of cardiac aging in both mice and humans. We show here that 8-week treatment of old mice with the mitochondrial targeted peptide SS-31 (elamipretide) can substantially reverse this deficit. SS-31 normalized the increase in proton leak and reduced mitochondrial ROS in cardiomyocytes from old mice, accompanied by reduced protein oxidation and a shift towards a more reduced protein thiol redox state in old hearts. Improved diastolic function was concordant with increased phosphorylation of cMyBP-C Ser282 but was independent of titin isoform shift. Late-life viral expression of mitochondrial-targeted catalase (mCAT) produced similar functional benefits in old mice and SS-31 did not improve cardiac function of old mCAT mice, implicating normalizing mitochondrial oxidative stress as an overlapping mechanism. These results demonstrate that pre-existing cardiac aging phenotypes can be reversed by targeting mitochondrial dysfunction and implicate mitochondrial energetics and redox signaling as therapeutic targets for cardiac aging.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Innovation of heterochromatin functions drives rapid evolution of essential ZAD-ZNF genes in Drosophila

Contrary to dogma, evolutionarily young and dynamic genes can encode essential functions. We find that evolutionarily dynamic ZAD-ZNF genes, which encode the most abundant class of insect transcription factors, are more likely to encode essential functions in Drosophila melanogaster than ancient, conserved ZAD-ZNF genes. We focus on the Nicknack ZAD-ZNF gene, which is evolutionarily young, poorly retained in Drosophila species, and evolves under strong positive selection. Yet we find that it is necessary for larval development in D. melanogaster. We show that Nicknack encodes a heterochromatin-localizing protein like its paralog Oddjob, also an evolutionarily dynamic yet essential ZAD-ZNF gene. We find that the divergent D. simulans Nicknack protein can still localize to D. melanogaster heterochromatin and rescue viability of female but not male Nicknack-null D. melanogaster. Our findings suggest that innovation for rapidly changing heterochromatin functions might generally explain the essentiality of many evolutionarily dynamic ZAD-ZNF genes in insects.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

High work function MoO2 back contacts for improved solar cell performance

Improved high work function back contacts for solar cells are provided. In one aspect, a method of forming a solar cell includes: forming a completed solar cell having a substrate coated with an electrically conductive material, an absorber disposed on the electrically conductive material, a buffer layer disposed on the absorber, a transparent front contact disposed on the buffer layer, and a metal grid disposed on the transparent front contact; removing the substrate and the electrically conductive material using exfoliation, exposing a backside surface of the solar cell; depositing a high work function material onto the back side surface of the solar cell; and depositing a back contact onto the high work function material. A solar cell formed by the present techniques is also provided. Yield of the exfoliated device can be improved by removing bubbles from adhesive used for exfoliation and/or forming contact pads to access the metal grid.

14 SOLAR ENERGY↗
DOE OSTI2020

Cell-based composite materials with programmed structures and functions

The present invention is directed to the use of silicic acid to transform biological materials, including cellular architecture into inorganic materials to provide biocomposites (nanomaterials) with stabilized structure and function. In the present invention, there has been discovered a means to stabilize the structure and function of biological materials, including cells, biomolecules, peptides, proteins (especially including enzymes), lipids, lipid vesicles, polysaccharides, cytoskeletal filaments, tissue and organs with silicic acid such that these materials may be used as biocomposites. In many instances, these materials retain their original biological activity and may be used in harsh conditions which would otherwise destroy the integrity of the biological material. In certain instances, these biomaterials may be storage stable for long periods of time and reconstituted after storage to return the biological material back to its original form. In addition, by exposing an entire cell to form CSCs, the CSCs may function to provide a unique system to study enzymes or a cascade of enzymes which are otherwise unavailable.

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

Recent Experiences Calculating g-functions for Use in Simulation of Ground Heat Exchangers

Temperature response functions, known as g-functions, are a computationally efficient method for simulating ground heat exchangers (GHEs), used with ground-source heat pump (GSHP) systems, either as part of a whole-building energy simulation or as part of a dedicated ground heat exchanger design tool. In fact, at present, they are the only feasible way to simulate a ground-source heat pump system in a whole-building energy simulation. This paper summarizes recent developments in the field and recent experience using a new open-source g-function calculation tool known as pygfunction (Cimmino 2018a, 2018b). This experience includes accuracy, computation time, memory requirements and sensitivity to boundary conditions. With larger ground heat exchangers, e.g. in excess of 100 boreholes, the computational time and memory requirements can create challenges.

Spitler, Jeffery↗
DOE OSTI2021

Click-chemistry compatible structures, click-chemistry functionalized structures, and materials and methods for making the same

According to several embodiments, a composition of matter includes: a three-dimensional structure comprising photo polymerized molecules. At least some of the photo polymerized molecules further comprise one or more protected click-chemistry compatible functional groups; and at least portions of one or more surfaces of the three-dimensional structure are functionalized with one or more of the protected click-chemistry compatible functional groups.

Campbell, Patrick↗
DOE OSTI2021

High work function MoO2 back contacts for improved solar cell performance

Improved high work function back contacts for solar cells are provided. In one aspect, a method of forming a solar cell includes: forming a completed solar cell having a substrate coated with an electrically conductive material, an absorber disposed on the electrically conductive material, a buffer layer disposed on the absorber, a transparent front contact disposed on the buffer layer, and a metal grid disposed on the transparent front contact; removing the substrate and the electrically conductive material using exfoliation, exposing a backside surface of the solar cell; depositing a high work function material onto the back side surface of the solar cell; and depositing a back contact onto the high work function material. A solar cell formed by the present techniques is also provided. Yield of the exfoliated device can be improved by removing bubbles from adhesive used for exfoliation and/or forming contact pads to access the metal grid.

Antunez, Priscilla D.↗
DOE OSTI2021

Higher-order $\beta$-functions in the Standard Model and beyond

In this contribution we consider the recent computation of the gauge coupling $\beta$-function at four loops and the Yukawa matrix $\beta$-function at three loops in the most general, renormalizable and four-dimensional quantum field theory. Furthermore, we discuss ambiguities and divergences arising in Yukawa matrix $\beta$-functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Click-chemistry compatible structures, click-chemistry functionalized structures, and materials and methods for making the same

According to several embodiments, a composition of matter includes: a three-dimensional structure comprising photo polymerized molecules. At least some of the photo polymerized molecules further comprise one or more protected click-chemistry compatible functional groups; and at least portions of one or more surfaces of the three-dimensional structure are functionalized with one or more of the protected click-chemistry compatible functional groups. An additive manufacturing resin suitable for fabricating a click-chemistry compatible composition of matter includes: a photo polymerizable compound; and a click-chemistry compatible compound. A method of forming an additive manufacturing resin suitable for fabricating a click-chemistry compatible composition of matter includes: reacting a compound comprising a terminal alkyne group or a terminal azide group with a protecting reagent to form a protected reactive diluent precursor, reacting the precursor with a compound to form a protected reactive diluent; and mixing the protected reactive diluent with a photo polymerizable compound.

Campbell, Patrick↗
DOE OSTI2023

Mitigating Green&#x27;s function Monte Carlo signal-to-noise problems using contour deformations

The Green's function Monte Carlo (GFMC) method provides accurate solutions to the nuclear many-body problem and predicts properties of light nuclei starting from realistic two- and three-body interactions. Controlling the GFMC fermion-sign problem is crucial, as the signal-to-noise ratio decreases exponentially with Euclidean time, requiring significant computing resources. Inspired by similar scenarios in lattice quantum field theory and spin systems, in this work, we employ integration contour deformations to improve the GFMC signal-to-noise ratio. Machine learning techniques are used to select optimal contours with minimal variance from parameterized families of deformations. As a proof of principle, we consider the deuteron binding energies and Euclidean density response functions. We only observe mild signal-to-noise improvement for the binding energy case. On the other hand, we achieve an order of magnitude reduction of the variance for Euclidean density response functions, paving the way for computing electron- and neutrino-nucleus cross-sections of larger nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Functional soft materials and methods of making and using thereof

Disclosed are functional materials for use in additive manufacturing (AM). The functional material can comprise an elastomeric composition (e.g., a silicone composite) for use in, for example, direct ink writing. The elastomeric composition can include and elastomeric resin, and a magnetic nanorod filler dispersed within the elastomeric resin. Nanorod characteristics (e.g., length, diameter, aspect ratio) can be selected to create 3D-printed constructs with desired mechanical properties along different axes. Furthermore, since nickel nanorods are ferromagnetic, the spatial distribution and orientation of nanorods within the continuous phase can be controlled with an external magnetic field. This level of control over the nanostructure of the material system offers another degree of freedom in the design of functional parts and components with anisotropic properties. Magnetic fields can be used to remotely sense compression of the constructs, or alternatively, control the stiffness of these materials.

Berkland, Cory↗
DOE OSTI2023

Functionalized porous organic polymers as uranium nano-traps for efficient uranium extraction

Compositions are provided for efficient uranium extraction, for example from wastewater, seawater, or other water sources. The compositions can include a functionalized porous organic polymer functionalized with one or more uranium binding moieties, e.g. having a plurality of amidoxime or amidrazone groups covalently attached thereto. The compositions can include covalent organic frameworks, porous aromatic frameworks, and various porous organic polymers, especially those having a hierarchical pore size distribution over a range of pore sizes. The compositions can have functional groups such as amidoxime or an amidrazone covalently attached thereto. The hierarchical pore size distribution can be determined based upon at least 60% of the pore sizes in the range of pore sizes having a pore volume of at least 0.01 cm 3 g −1 in the pore size distribution at 77 K. Methods of making the compositions and methods of using the compositions are also provided.

Ma, Shengqian↗
DOE OSTI2024

Logistic function as a characteristic of multipactor development

Simulations of multipacting with or without space charge effect bring out a different behavior of particle number growth, namely, the exponential growth of particle number in the simulations without space charge effect and the saturation of particle number (or collision and emission currents) when space charge is considered. That creates a certain confusion in evaluation and comparison of overall danger of multipactor between the approaches. On the other hand, both growth rate and total multipactor current loading at saturation are important for multipactor barriers evaluation. It was noticed and then verified that the logistic function, widely used in chemistry, biology, and ecosystem study, reproduces the particle number growth curves remarkably well. The function contains the parameters, which can be interpreted as particle number growth rate and multipactor current saturation level, so both become correlated and obtained simultaneously in one run. In this work it is shown how the logistic function can be used for characterization of the multipactor barriers and how it can be used for possible reduction of simulation time in the simulations with space charge effect.

Romanov, Gennady↗
DOE OSTI2024

Functional soft materials and methods of making and using thereof

Disclosed are functional materials for use in additive manufacturing (AM). The functional material can comprise an elastomeric composition (e.g., a silicone composite) for use in, for example, direct ink writing. The elastomeric composition can include an elastomeric resin, and a magnetic nanorod filler dispersed within the elastomeric resin. Nanorod characteristics (e.g., length, diameter, aspect ratio) can be selected to create 3D-printed constructs with desired mechanical properties along different axes. Furthermore, since nickel nanorods are ferromagnetic, the spatial distribution and orientation of nanorods within the continuous phase can be controlled with an external magnetic field. This level of control over the nanostructure of the material system offers another degree of freedom in the design of functional parts and components with anisotropic properties. Magnetic fields can be used to remotely sense compression of the constructs, or alternatively, control the stiffness of these materials.

Berkland, Cory↗