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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

ONE PLANE FOR ALL: MASSIVE STAR-FORMING AND QUIESCENT GALAXIES LIE ON THE SAME MASS FUNDAMENTAL PLANE AT z ∼ 0 AND z ∼ 0.7

Scaling relations between galaxy structures and dynamics have been studied extensively for early- and late-type galaxies, both in the local universe and at high redshifts. The abundant differences between the properties of disky and elliptical, or star-forming and quiescent, galaxies seem to be characteristic of the local universe; such clear distinctions begin to disintegrate as observations of massive galaxies probe higher redshifts. In this paper we investigate the existence of the mass fundamental plane of all massive galaxies (σ ≳ 100 km s{sup –1}). This work includes local galaxies (0.05 < z < 0.07) from the Sloan Digital Sky Survey, in addition to 31 star-forming and 72 quiescent massive galaxies at intermediate redshift (z ∼ 0.7) with absorption-line kinematics from deep Keck-DEIMOS spectra and structural parameters from Hubble Space Telescope imaging. In two-parameter scaling relations, star-forming and quiescent galaxies differ structurally and dynamically. However, we show that massive star-forming and quiescent galaxies lie on nearly the same mass fundamental plane, or the relationship between stellar mass surface density, stellar velocity dispersion, and effective radius. The scatter in this relation (measured about log σ) is low: 0.072 dex (0.055 dex intrinsic) at z ∼ 0 and 0.10 dex (0.08 dex intrinsic) at z ∼ 0.7. This 3D surface is not unique: virial relations, with or without a dependence on luminosity profile shapes, can connect galaxy structures and stellar dynamics with similar scatter. This result builds on the recent finding that mass fundamental plane has been stable for early-type galaxies since z ∼ 2. As we now find that this also holds for star-forming galaxies to z ∼ 0.7, this implies that these scaling relations of galaxies will be minimally susceptible to progenitor biases owing to the evolving stellar populations, structures, and dynamics of galaxies through cosmic time.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

A numerical evaluation of the ambient air temperature in the Electron-Ion Collider tunnel

The Electron-Ion Collider (EIC) is a next-generation collider-accelerator that may require consistent operating temperature conditions for the beams within the accelerator tunnels to maintain stable operation. Variations in ambient temperature within the tunnel can cause thermal expansion of beampipe and component supports and can negatively affect the tunnel equipment, impacting the stability of the beamline. Modifications will be made to the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) to create the EIC, which necessitates a temperature model that addresses these modifications. To approach this problem, the consistency of temperature changes in different tunnel sections was first evaluated by plotting RHIC tunnel temperature data at various times of the day and year. From this data, a tunnel section was selected and a 2D temperature model was created for RHIC, EIC, and EIC with added cooling configurations. Soil temperature data was analyzed to determine the maximum, average, and mode soil temperatures, which were used as boundary conditions in different temperature scenarios. Computational fluid dynamics modeling was used to create 2D temperature profiles for the configurations. From this model, the predicted temperatures indicate that further analysis is required to validate the boundary conditions and benchmark the current conditions to allow the prediction of the tunnel ambient conditions at EIC. This research can be used as a preliminary model to create an EIC tunnel cooling system that will increase the operational stability of the EIC. As a result of my work this summer, I have become familiar with computational fluid dynamics, including creating fluid dynamic simulations using ANSYS Fluent and related software. I have also learned about the project process required for planning large-scale engineering projects.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Kinetic Properties of Microbial Exoenzymes Vary With Soil Depth but Have Similar Temperature Sensitivities Through the Soil Profile

Current knowledge of the mechanisms driving soil organic matter (SOM) turnover and responses to warming is mainly limited to surface soils, although over 50% of global soil carbon is contained in subsoils. Deep soils have different physicochemical properties, nutrient inputs, and microbiomes, which may harbor distinct functional traits and lead to different SOM dynamics and temperature responses. We hypothesized that kinetic and thermal properties of soil exoenzymes, which mediate SOM depolymerization, vary with soil depth, reflecting microbial adaptation to distinct substrate and temperature regimes. We determined the Michaelis-Menten (MM) kinetics of three ubiquitous enzymes involved in carbon (C), nitrogen (N) and phosphorus (P) acquisition at six soil depths down to 90 cm at a temperate forest, and their temperature sensitivity based on Arrhenius/ Q 10 and Macromolecular Rate Theory (MMRT) models over six temperatures between 4–50°C. Maximal enzyme velocity ( V max ) decreased strongly with depth for all enzymes, both on a dry soil mass and a microbial biomass C basis, whereas their affinities increased, indicating adaptation to lower substrate availability. Surprisingly, microbial biomass-specific catalytic efficiencies also decreased with depth, except for the P-acquiring enzyme, indicating distinct nutrient demands at depth relative to microbial abundance. These results suggested that deep soil microbiomes encode enzymes with intrinsically lower turnover and/or produce less enzymes per cell, reflecting distinct life strategies. The relative kinetics between different enzymes also varied with depth, suggesting an increase in relative P demand with depth, or that phosphatases may be involved in C acquisition. V max and catalytic efficiency increased consistently with temperature for all enzymes, leading to overall higher SOM-decomposition potential, but enzyme temperature sensitivity was similar at all depths and between enzymes, based on both Arrhenius/ Q 10 and MMRT models. In a few cases, however, temperature affected differently the kinetic properties of distinct enzymes at discrete depths, suggesting that it may alter the relative depolymerization of different compounds. We show that soil exoenzyme kinetics may reflect intrinsic traits of microbiomes adapted to distinct soil depths, although their temperature sensitivity is remarkably uniform. These results improve our understanding of critical mechanisms underlying SOM dynamics and responses to changing temperatures through the soil profile.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Monolayer-by-monolayer compositional analysis of InAs/InAsSb superlattices with cross-sectional STM

In this paper, we use cross-sectional scanning tunneling microscopy (STM) to reconstruct the monolayer-by-monolayer composition profile across a representative subset of MBE-grown InAs/InAsSb superlattice layers and find that antimony segregation frustrates the intended compositional discontinuities across both antimonide-on-arsenide and arsenide-on-antimonide heterojunctions. Graded, rather than abrupt, interfaces are formed in either case. We likewise find that the incorporated antimony per superlattice period varies measurably from beginning to end of the multilayer stack. Finally, although the intended antimony discontinuities predict significant discrepancies with respect to the experimentally observed high-resolution x-ray diffraction spectrum, dynamical simulations based on the STM-derived profiles provide an excellent quantitative match to all important aspects of the x-ray data.

36 MATERIALS SCIENCE↗
DOE OSTI2013

ALL SIX PLANETS KNOWN TO ORBIT KEPLER-11 HAVE LOW DENSITIES

The Kepler-11 planetary system contains six transiting planets ranging in size from 1.8 to 4.2 times the radius of Earth. Five of these planets orbit in a tightly packed configuration with periods between 10 and 47 days. We perform a dynamical analysis of the system based upon transit timing variations observed in more than three years of Kepler photometric data. Stellar parameters are derived using a combination of spectral classification and constraints on the star's density derived from transit profiles together with planetary eccentricity vectors provided by our dynamical study. Combining masses of the planets relative to the star from our dynamical study and radii of the planets relative to the star from transit depths together with deduced stellar properties yields measurements of the radii of all six planets, masses of the five inner planets, and an upper bound to the mass of the outermost planet, whose orbital period is 118 days. We find mass-radius combinations for all six planets that imply that substantial fractions of their volumes are occupied by constituents that are less dense than rock. Moreover, we examine the stability of these envelopes against photoevaporation and find that the compositions of at least the inner two planets have likely been significantly sculpted by mass loss. The Kepler-11 system contains the lowest mass exoplanets for which both mass and radius have been measured.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Surface‐Enforced Alignment of Reprogrammable Liquid Crystalline Elastomers

Abstract Liquid crystalline elastomers (LCEs) are stimuli‐responsive materials capable of undergoing large deformations. The thermomechanical response of LCEs is attributable to the coupling of polymer network properties and disruption of order between liquid crystalline mesogens. Complex deformations have been realized in LCEs by either programming the nematic director via surface‐enforced alignment or localized mechanical deformation in materials incorporating dynamic covalent chemistries. Here, the preparation of LCEs via thiol‐Michael addition reaction is reported that are amenable to surface‐enforced alignment. Afforded by the thiol‐Michael addition reaction, dynamic covalent bonds are uniquely incorporated in chemistries subject to surface‐enforce alignment. Accordingly, LCEs prepared with complex director profiles are able to be programmed and reprogrammed by (re)activating the dynamic covalent chemistry to realize distinctive shape transformations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

The Influence of the Cobalt Content on the Strength Properties of Tungsten Carbide Ceramics under Dynamic Loads

Based on the registration and analysis of the full wave profiles, the Hugoniot elastic limit and spall strength of ceramics based on tungsten carbide with different cobalt content are measured. We also study the influence of the cobalt content on the mechanical characteristics of tungsten carbide such as hardness, fracture strength, Young’s modulus, shear modulus, and sound velocity. It is shown that in the process of spalling, the failure stresses grow and the dynamic elastic limit decreases almost linearly within the scatter of their values with growing cobalt content; moreover, the value of the Hugoniot elastic limit is abruptly practically halved as the cobalt content grows from 0 to 2 wt %.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Thermodynamic approach to the interpretation of self-consistent pressure profiles in a tokamak

The phenomenon of invariable pressure profiles in tokamaks is interpreted in the framework of the thermodynamic approach suggesting that invariable self-consistent states correspond to the minimum of free energy. Solutions qualitatively consistent with the experiment are obtained under the assumption that the mechanism for the formation of self-consistent profiles is directly related to equilibrium diamagnetic currents. The dynamics of the system and specific transport phenomena, such as energy and particle pinching and a decrease in the local density under auxiliary electron cyclotron resonance heating (density pump-out), are analyzed in the vicinity of an equilibrium state characterized by a stable pressure profile. The scaling for the energy confinement time deduced from the transport model agrees qualitatively with the ITER scaling based on the analysis of experimental data obtained in many tokamaks. The possibility of using generalized Tsallis statistics to analyze pressure profiles is considered.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Zeeman spectroscopy as a method for determining the magnetic field distribution in self-magnetic-pinch diodes (invited)

In the self-magnetic-pinch diode, the electron beam, produced through explosive field emission, focuses on the anode surface due to its own magnetic field. This process results in dense plasma formation on the anode surface, consisting primarily of hydrocarbons. Direct measurements of the beam’s current profile are necessary in order to understand the pinch dynamics and to determine x-ray source sizes, which should be minimized in radiographic applications. In this paper, the analysis of the C IV doublet (580.1 and 581.2 nm) line shapes will be discussed. The technique yields estimates of the electron density and electron temperature profiles, and the method can be highly beneficial in providing the current density distribution in such diodes.

Patel, S. G.↗
DOE OSTI2025

Fine‐root dynamics in deeper soils: a critical but overlooked component of ecosystem responses to climate warming

Climate warming is predicted to strongly affect the functioning of terrestrial ecosystems. The plant root system is a critical component of these ecosystems, with fine roots, in particular, playing a key role in plant water and nutrient uptake and transport. In addition, root litter and exudation represent the dominant plant carbon inputs into soil. Consequently, understanding fine‐root responses to warming is essential for predicting how the growth, resilience, and carbon storage of terrestrial ecosystems will respond to future climate change. Despite the growing literature on fine‐root responses to warming, most studies have focused on topsoil (0–30 cm). However, a significant portion of the fine‐root mass occurs below this depth. For instance, c. 40% of fine‐root mass is found below 30 cm in temperate and tropical ecosystems. Due to the importance of fine roots for plants and belowground carbon cycling, focusing solely on surface soils overlooks the critical need for insights into how roots in deeper soil layers (e.g. below 30 cm) respond to warming. We argue that studying the entire soil profile is necessary to comprehensively understand fine‐root dynamics under climate warming and the implications for soil organic carbon cycling, water, and nutrient uptake.

climate warming↗
DOE OSTI2012

Improving N-Glycan Coverage using HPLC-MS with Electrospray Ionization at Subambient Pressure

Human serum glycan profiling with mass spectrometry (MS) has been employed to study several disease conditions and is demonstrating promise for e.g. clinical biomarker discovery. However, the poor glycan ionization efficiency and the large dynamic range of glycan concentrations in human sera hinder comprehensive profiling. In particular, large glycans are problematic because they are present at low concentrations and prone to fragmentation. Here we show that the sub-ambient pressure ionization with nanoelectrospray (SPIN)-MS can expand the serum glycome profile when compared with the conventional atmospheric pressure electrospray ionization (ESI)-MS with a heated capillary inlet. Notably, the ions generated by the SPIN interface were observed at higher charge states for 50% of the annotated glycans. Out of a total of 130 detected glycans, 34 were only detected with the SPIN-MS, resulting in improved coverage of glycan families as well as of glycans with larger numbers of labile monosaccharides.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2014

Predicting solute partitioning in lipid bilayers: Free energies and partition coefficients from molecular dynamics simulations and COSMOmic

Quantitative predictions of biomembrane/water partition coefficients are important, as they are a key property in pharmaceutical applications and toxicological studies. Molecular dynamics (MD) simulations are used to calculate free energy profiles for different solutes in lipid bilayers. How to calculate partition coefficients from these profiles is discussed in detail and different definitions of partition coefficients are compared. Importantly, it is shown that the calculated coefficients are in quantitative agreement with experimental results. Furthermore, we compare free energy profiles from MD simulations to profiles obtained by the recent method COSMOmic, which is an extension of the conductor-like screening model for realistic solvation to micelles and biomembranes. The free energy profiles from these molecular methods are in good agreement. Additionally, solute orientations calculated with MD and COSMOmic are compared and again a good agreement is found. Four different solutes are investigated in detail: 4-ethylphenol, propanol, 5-phenylvaleric acid, and dibenz[a,h]anthracene, whereby the latter belongs to the class of polycyclic aromatic hydrocarbons. The convergence of the free energy profiles from biased MD simulations is discussed and the results are shown to be comparable to equilibrium MD simulations. For 5-phenylvaleric acid the influence of the carboxyl group dihedral angle on free energy profiles is analyzed with MD simulations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

The mond external field effect on the dynamics of the globular clusters: general considerations and application to NGC 2419

In this paper, we investigate the external field effect in the context of the MOdified Newtonian Dynamics (MOND) on the surface brightness and velocity dispersion profiles of globular clusters (GCs). Using N-MODY, which is an N-body simulation code with a MOND potential solver, we show that the general effect of the external field for diffuse clusters, which obey MOND in most of their parts, is that it pushes the dynamics toward the Newtonian regime. On the other hand, for more compact clusters, which are essentially Newtonian in their inner parts, the external field is effective mainly in the outer parts of compact clusters. As a case study, we then choose the remote Galactic GC NGC 2419. By varying the cluster mass, half-light radius, and mass-to-light ratio, we aim to find a model that will reproduce the observational data most effectively, using N-MODY. We find that even if we take the Galactic external field into account, a Newtonian Plummer sphere represents the observational data better than MOND to an order of magnitude in terms of the total χ{sup 2} of surface brightness and velocity dispersion.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

The Splashback Feature around DES Galaxy Clusters: Galaxy Density and Weak Lensing Profiles

Splashback refers to the process of matter that is accreting onto a dark matter halo reaching its first orbital apocenter and turning around in its orbit. The clustercentric radius at which this process occurs, r sp, defines a halo boundary that is connected to the dynamics of the cluster. A rapid decline in the halo profile is expected near r sp. We measure the galaxy number density and weak lensing mass profiles around redMaPPer galaxy clusters in the first-year Dark Energy Survey (DES) data. For a cluster sample with mean M 200m mass ≈2.5 × 10 14 M ⊙ , we find strong evidence of a splashback-like steepening of the galaxy density profile and measure r sp = 1.13 ± 0.07 h –1 Mpc, consistent with the earlier Sloan Digital Sky Survey measurements of More et al. and Baxter et al. Moreover, our weak lensing measurement demonstrates for the first time the existence of a splashback-like steepening of the matter profile of galaxy clusters. We measure r sp = 1.34 ± 0.21 h –1 Mpc from the weak lensing data, in good agreement with our galaxy density measurements. For different cluster and galaxy samples, we find that, consistent with ΛCDM simulations, r sp scales with R 200m and does not evolve with redshift over the redshift range of 0.3–0.6. We also find that potential systematic effects associated with the redMaPPer algorithm may impact the location of r sp . In conclusion, we discuss the progress needed to understand the systematic uncertainties and fully exploit forthcoming data from DES and future surveys, emphasizing the importance of more realistic mock catalogs and independent cluster samples.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

A large-scale analysis of bioinformatics code on GitHub

In recent years, the explosion of genomic data and bioinformatic tools has been accompanied by a growing conversation around reproducibility of results and usability of software. However, the actual state of the body of bioinformatics software remains largely unknown. Here, the purpose of this paper is to investigate the state of source code in the bioinformatics community, specifically looking at relationships between code properties, development activity, developer communities, and software impact. To investigate these issues, we curated a list of 1,720 bioinformatics repositories on GitHub through their mention in peer-reviewed bioinformatics articles. Additionally, we included 23 high-profile repositories identified by their popularity in an online bioinformatics forum. We analyzed repository metadata, source code, development activity, and team dynamics using data made available publicly through the GitHub API, as well as article metadata. We found key relationships within our dataset, including: certain scientific topics are associated with more active code development and higher community interest in the repository; most of the code in the main dataset is written in dynamically typed languages, while most of the code in the high-profile set is statically typed; developer team size is associated with community engagement and high-profile repositories have larger teams; the proportion of female contributors decreases for high-profile repositories and with seniority level in author lists; and, multiple measures of project impact are associated with the simple variable of whether the code was modified at all after paper publication. In addition to providing the first large-scale analysis of bioinformatics code to our knowledge, our work will enable future analysis through publicly available data, code, and methods.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Parallel pumping of magnons in inhomogeneous spin textures probed through NV spin relaxometry

We combine micromagnetic simulations and nitrogen-vacancy (NV) defect center spin relaxometry measurements to study magnon modes in inhomogeneous spin textures. A thin, micrometer-scale ferromagnetic disk is magnetized in a vortex state in which the magnetization curls around a central core. Micromagnetic simulations show that at zero applied field, the magnetization dynamics of the disk consist of a low frequency gyrotropic mode and higher frequency azimuthal magnon modes, all far detuned from the NV spin transition frequencies. An in-plane static magnetic field breaks the azimuthal symmetry of the vortex state, resulting in the magnon modes transforming in frequency and spatial profile as the field increases. Experimentally, we probe the dynamics of vortex magnetization as a function of applied in-plane static field and ac driving frequency by optically monitoring a nearby NV defect center spin. At certain values of the applied magnetic field, we observe enhanced spin relaxation when driving at twice the frequency of the NV ground state spin transition in optically detected magnetic resonance measurements. We attribute this effect to parallel pumping of a magnon mode in the disk producing magnons at half the excitation frequency. Micromagnetic simulations support this finding, showing spatial and spectral overlap of a confined magnon mode and an NV spin transition, with sufficient interaction strength to explain the observed signal.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Regulation-Structured Dynamic Metabolic Model Provides a Potential Mechanism for Delayed Enzyme Response in Denitrification Process

In a recent study of denitrification dynamics in hyporheic zone sediments, we observed a significant time lag (up to several days) in enzymatic response to the changes in substrate concentration. To explore an underlying mechanism and understand the interactive dynamics between enzymes and nutrients, we developed a trait-based model that associates a community’s traits with functional enzymes, instead of typically used species guilds (or functional guilds). This enzyme-based formulation allows to collectively describe biogeochemical functions of microbial communities without directly parameterizing the dynamics of species guilds, therefore being scalable to complex communities. As a key component of modeling, we accounted for microbial regulation occurring through transcriptional and translational processes, the dynamics of which was parameterized based on the temporal profiles of enzyme concentrations measured using a new signature peptide-based method. The simulation results using the resulting model showed several days of a time lag in enzymatic responses as observed in experiments. Further, the model showed that the delayed enzymatic reactions could be primarily controlled by transcriptional responses and that the dynamics of transcripts and enzymes are closely correlated. The developed model can serve as a useful tool for predicting biogeochemical processes in natural environments, either independently or through integration with hydrologic flow simulators.

trait-based modeling↗
DOE OSTI2015

Core-halo limit and internal dynamics of high intensity beams

The dynamics of high-intensity beams largely depends on their internal space charge forces. These forces are responsible of non-linear coupling, emittance growth, and halo generation. They contribute to shape the beam density profile. As a consequence, an analysis of this profile can be a precious indicator capable of revealing the internal dynamics of the beam. This paper recalls the precise core-halo limit determination proposed earlier, then studies its behavior through a wide range of beam profiles, and finally shows its relevance as an indicator of the limit separating the two space charge field regimes of the core and the halo.

43 PARTICLE ACCELERATORS↗