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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Building in vitro transcriptional regulatory networks by successively integrating multiple functional circuit modules

The regulation of cellular dynamics and responses to stimuli by genetic regulatory networks suggests how in vitro chemical reaction networks might analogously direct the dynamics of synthetic materials or chemistries. A key step in developing genetic regulatory network analogues capable of this type of sophisticated regulation is the integration of multiple coordinated functions within a single network. In this study, we demonstrate how such functional integration can be achieved using in vitro transcriptional genelet circuits that emulate essential features of cellular genetic regulatory networks. By successively incorporating functional genelet modules into a bistable circuit, we construct an integrated regulatory network that dynamically changes its state in response to upstream stimuli and coordinates the timing of downstream signal expression. We use quantitative models to guide module integration and develop strategies to mitigate undesired interactions between network components that arise as the size of the network increases. This approach could enable the construction of in vitro networks capable of multifaceted chemical and material regulation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

A NEW TOOL FOR IMAGE ANALYSIS BASED ON CHEBYSHEV RATIONAL FUNCTIONS: CHEF FUNCTIONS

We introduce a new approach to the modeling of the light distribution of galaxies, an orthonormal polar basis formed by a combination of Chebyshev rational functions and Fourier polynomials that we call CHEF functions, or CHEFs. We have developed an orthonormalization process to apply this basis to pixelized images, and implemented the method as a Python pipeline. The new basis displays remarkable flexibility, being able to accurately fit all kinds of galaxy shapes, including irregulars, spirals, ellipticals, highly compact, and highly elongated galaxies. It does this while using fewer components than similar methods, as shapelets, and without producing artifacts, due to the efficiency of the rational Chebyshev polynomials to fit quickly decaying functions like galaxy profiles. The method is linear and very stable, and therefore is capable of processing large numbers of galaxies in a fast and automated way. Due to the high quality of the fits in the central parts of the galaxies, and the efficiency of the CHEF basis modeling galaxy profiles up to very large distances, the method provides highly accurate estimates of total galaxy fluxes and ellipticities. Future papers will explore in more detail the application of the method to perform multiband photometry, morphological classification, and weak shear measurements.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

STAR FORMATION: STATISTICAL MEASURE OF THE CORRELATION BETWEEN THE PRESTELLAR CORE MASS FUNCTION AND THE STELLAR INITIAL MASS FUNCTION

We present a simple statistical analysis of recent numerical simulations exploring the correlation between the core mass function (CMF) obtained from the fragmentation of a molecular cloud and the stellar mass function which forms from these collapsing cores. Our analysis shows that the distributions of bound cores and sink particles obtained in the simulations are consistent with the sinks being formed predominantly from their parent core mass reservoir, with a statistical dispersion of the order of one-third of the core mass. Such a characteristic dispersion suggests that the stellar initial mass function (IMF) is relatively tightly correlated to the parent CMF, leading to two similar distributions, as observed. This in turn argues in favor of the IMF being essentially determined at the early stages of core formation and being only weakly affected by the various environmental factors beyond the initial core mass reservoir, at least in the mass range explored in the present study. Accordingly, the final IMF of a star-forming region should be determined reasonably accurately, statistically speaking, from the initial CMF, provided some uniform efficiency factor. The calculations also show that these statistical fluctuations, due to, e.g., variations among the core properties, broaden the low-mass tail of the IMF compared with the parent CMF, providing an explanation for the fact that the latter appears to underestimate the number of 'pre brown dwarf' cores compared with the observationally derived brown dwarf IMF.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Separated response functions in exclusive, forward π ± electroproduction on deuterium

Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q 2 , and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in π⁻ and π⁺ electroproduction are particularly informative. Ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form factor from electroproduction data. Method: Data were acquired with 2.6-5.2 GeV electron beams and the HMS+SOS spectrometers in Jefferson Lab Hall C, at central Q 2 values of 0.6, 1.0, 1.6 GeV 2 at W=1.95 GeV, and Q 2 =2.45 GeV 2 at W=2.22 GeV. There was significant coverage in Φ And ϵ, which allowed separation of σ L,T,LT,TT . Results: σL shows a clear signature of the pion pole, with a sharp rise at small -t. In contrast, σ T is much flatter versus t. The longitudinal/transverse ratios evolve with Q 2 and t, and at the highest Q 2 =2.45 GeV 2 show a slight enhancement for π⁻ Production compared to π⁺. The π⁻/π⁺+ ratio for transverse photons exhibits only a small Q 2 -dependence, following a nearly universal curve with t, with a steep transition to a value of about 0.25, consistent with s-channel quark knockout. The σ TT /σ T ratio also drops rapidly with Q 2 , qualitatively consistent with s-channel helicity conservation. The π⁻/π⁺ ratio for longitudinal photons indicates a small isoscalar contamination at W=1.95 GeV, consistent with what was observed in our earlier determination of the pion form factor at these kinematics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Comparison of the electromagnetic responses of C 12 obtained from the Green's function Monte Carlo and spectral function approaches

Here, the electromagnetic responses of carbon obtained from the Green's function Monte Carlo and spectral function approaches using the same dynamical input are compared in the kinematical region corresponding to momentum transfer in the range 300–570 MeV. The results of our analysis, aimed at pinning down the limits of applicability of the approximations involved in the two schemes, indicate that the factorization ansatz underlying the spectral function formalism provides remarkably accurate results down to momentum transfer as low as 300 MeV. On the other hand, it appears that at 570 MeV relativistic corrections to the electromagnetic current not included in the Monte Carlo calculations may play a significant role in the transverse channel.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Hanbury-Brown–Twiss correlation functions and radii from event-by-event hydrodynamics

Hanbury-Brown–Twiss correlation functions and radii from event-by-event hydrodynamics (HoTCoffeeh) is a novel computational tool which determines Hanbury-Brown–Twiss (HBT) charged-pion ( π + ) correlation functions and radii for event-by-event hydrodynamics with fluctuating initial conditions in terms of Cooper–Frye integrals, including resonance-decay contributions. Here, we review the basic formalism for computing the HBT correlation functions and radii with resonance-decay contributions included and discuss our implementation of this formalism in the form of HoTCoffeeh. This tool may easily be integrated with other numerical packages [see, e.g., [ Comput. Phys. Commun. 199 , 61 (2016) ]] for the purpose of simulating the evolution of heavy-ion collisions and thereby extracting predictions for heavy-ion observables.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Complexes with mixed primary and secondary cellulose synthases are functional in Arabidopsis thaliana plants

In higher plants, cellulose is synthesized by so-called rosette protein complexes with cellulose synthases (CESAs) as catalytic subunits of the complex. The CESAs are divided into two distinct families, three of which are thought to be specialized for the primary cell wall and three for the secondary cell wall. In this article, the potential of primary and secondary CESAs forming a functional rosette complex has been investigated. The membrane-based yeast two-hybrid and biomolecular fluorescence systems were used to assess the interactions between three primary (CESA1, CESA3, CESA6), and three secondary (CESA4, CESA7, CESA8) Arabidopsis (Arabidopsis thaliana) CESAs. The results showed that all primary CESAs can physically interact both in vitro and in planta with all secondary CESAs. Although CESAs are broadly capable of interacting in pairwise combinations, they are not all able to form functional complexes in planta. Analysis of transgenic lines showed that CESA7 can partially rescue defects in the primary cell wall biosynthesis in a weak cesa3 mutant. Green fluorescent protein-CESA protein fusions revealed that when CESA3 was replaced by CESA7 in the primary rosette, the velocity of the mixed complexes was slightly faster than the native primary complexes. CESA1 in turn can partly rescue defects in secondary cell wall biosynthesis in a cesa8ko mutant, resulting in an increase of cellulose content relative to cesa8ko. These results demonstrate that sufficient parallels exist between the primary and secondary complexes for cross-functionality and open the possibility that mixed complexes of primary and secondary CESAs may occur at particular times.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Operando pair distribution function analysis of nanocrystalline functional materials: the case of TiO 2 -bronze nanocrystals in Li-ion battery electrodes

Structural modelling of operando pair distribution function (PDF) data of complex functional materials can be highly challenging. To aid the understanding of complex operando PDF data, this article demonstrates a toolbox for PDF analysis. The tools include denoising using principal component analysis together with the structureMining , similarityMapping and nmfMapping apps available through the online service `PDF in the cloud' ( PDFitc , https://pdfitc.org/). The toolbox is used for both ex situ and operando PDF data for 3 nm TiO 2 -bronze nanocrystals, which function as the active electrode material in a Li-ion battery. The tools enable structural modelling of the ex situ and operando PDF data, revealing two pristine TiO 2 phases (bronze and anatase) and two lithiated Li x TiO 2 phases (lithiated versions of bronze and anatase), and the phase evolution during galvanostatic cycling is characterized.

Chemistry↗
DOE OSTI2019

Fire affects the taxonomic and functional composition of soil microbial communities, with cascading effects on grassland ecosystem functioning

Fire is a crucial event regulating the structure and functioning of many ecosystems. Yet few studies have focused on how fire affects taxonomic and functional diversities of soil microbial communities, along with changes in plant communities and soil carbon (C) and nitrogen (N) dynamics. Here, we analyze these effects in a grassland ecosystem 9 months after an experimental fire at the Jasper Ridge Global Change Experiment site in California, USA. Fire altered soil microbial communities considerably, with community assembly process analysis showing that environmental selection pressure was higher in burned sites. However, a small subset of highly connected taxa was able to withstand the disturbance. In addition, fire decreased the relative abundances of most functional genes associated with C degradation and N cycling, implicating a slowdown of microbial processes linked to soil C and N dynamics. In contrast, fire stimulated above- and belowground plant growth, likely enhancing plant-microbe competition for soil inorganic N, which was reduced by a factor of about 2. To synthesize those findings, we performed structural equation modeling, which showed that plants but not microbial communities were responsible for significantly higher soil respiration rates in burned sites. Together, our results demonstrate that fire 'reboots' the grassland ecosystem by differentially regulating plant and soil microbial communities, leading to significant changes in soil C and N dynamics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

Measurement of the jet fragmentation function and transverse profile in proton–proton collisions at a center-of-mass energy of 7 TeV with the ATLAS detector

The jet fragmentation function and transverse profile for jets with 25 GeV < p T jet < 500 GeV and |η jet | < 1.2 produced in proton–proton collisions with a center-of-mass energy of 7 TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb –1 . Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. Furthermore, none of these choices reproduce both the transverse profile and fragmentation function over the full kinematic range of the measurement.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Hybrid DFT Functional-Based Static and Molecular Dynamics Studies of Excess Electron in Liquid Ethylene Carbonate

We applied static and dynamic hybrid functional density functional theory (DFT) calculations to study the interactions of one and two excess electrons with ethylene carbonate (EC) liquid and clusters. Optimal structures of (EC) n and (EC) n - clusters devoid of Li + ions, n = 1–6, were obtained. The excess electron was found to be localized on a single EC in all cases, and the EC dimeric radical anion exhibits a reduced barrier associated with the breaking of the ethylene carbon–oxygen covalent bond compared to EC - . In ab initio molecular dynamics (AIMD) simulations of EC - solvated in liquid EC, large fluctuations in the carbonyl carbon–oxygen bond lengths were observed. AIMD simulations of a two-electron attack on EC in EC liquid and on Li metal surfaces yielded products similar to those predicted using nonhybrid DFT functionals, except that CO release did not occur for all attempted initial configurations in the liquid state.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

The Arabidopsis domain of unknown function 1218 (DUF1218) containing proteins, MODIFYING WALL LIGNIN-1 and 2 (At1g31720/MWL-1 and At4g19370/MWL-2) function redundantly to alter secondary cell wall lignin content

DUF1218 is a land plant-specific innovation and has previously been shown to be associated with cell wall biology, vasculature patterning and abiotic/biotic stress response. The Arabidopsis genome encodes 15 members, two of which (At1g31720 and At4g27435) are preferentially expressed in the secondary cell wall depositing inflorescence stems. To further our understanding of the roles of DUF1218-containing proteins in secondary cell wall biology, we functionally characterized At1g31720 (herein referred to as MODIFYING WALL LIGNIN -1 or MWL -1). Since related gene family members may contribute to functional redundancy, we also characterized At4g19370 ( MWL -2), the most closely related gene to MWL -1 in the protein family. Subcellular localization revealed that both Arabidopsis proteins are targeted to the cell periphery. The single T-DNA knockout lines, mwl -1 and mwl -2, and independent overexpression lines showed no significant differences in plant growth or changes in total lignin content relative to wild-type (WT) control plants. However, the double homozygous mutant, mwl -1/ mwl -2, had smaller rosettes with a significant decrease in rosette fresh weight and stem height relative to the WT control at four weeks and six weeks, respectively. Moreover, mwl -1/ mwl -2 showed a significant reduction in total lignin content (by ca. 11% relative to WT) and an increase in syringyl/guaiacyl (S/G) monomer ratio relative to the control plants. Lastly, our study has identified two additional members of the DUF1218 family in Arabidopsis as novel contributors to secondary cell wall biology, specifically lignin biosynthesis, and these proteins appear to function redundantly.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Functional materials and devices by self-assembly

The field of self-assembly has moved far beyond early work, where the focus was primarily the resultant beautiful two- and three-dimensional structures, to a focus on forming materials and devices with important properties either otherwise not available, or only available at great cost. Over the last few years, materials with unprecedented electronic, photonic, energy-storage, and chemical separation functionalities were created with self-assembly, while at the same time, the ability to form even more complex structures in two and three dimensions has only continued to advance. Self-assembly crosscuts all areas of materials. Functional structures have now been realized in polymer, ceramic, metallic, and semiconducting systems, as well as composites containing multiple classes of materials. Finally, as the field of self-assembly continues to advance, the number of highly functional systems will only continue to grow and make increasingly greater impacts in both the consumer and industrial space.

Materials for Devices↗