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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on TeP2(N2O7)2 by Materials Project

P2Te(NO6)2(NO)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two nitroxyl molecules and one P2Te(NO6)2 cluster. In the P2Te(NO6)2 cluster, P5+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.47 Å) and one longer (1.60 Å) P–O bond length. N3+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.22 Å) and one longer (1.26 Å) N–O bond length. Te6+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.10 Å) and two longer (2.36 Å) Te–O bond lengths. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one N3+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one N3+ and one Te6+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one P5+ and one O2- atom. The O–O bond length is 1.56 Å. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Te6+ and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Structural and Biophysical Properties of a [4Fe-4S] Ferredoxin-Like Protein from Synechocystis sp. PCC 6803 with a Unique Two Domain Structure

Electron carrier proteins (ECPs), binding iron-sulfur clusters, are vital components within the intricate network of metabolic and photosynthetic reactions. They play a crucial role in the distribution of reducing equivalents. In Synechocystis sp. PCC 6803, the ECP network includes at least nine ferredoxins. Previous research, including global expression analyses and protein binding studies, has offered initial insights into the functional roles of individual ferredoxins within this network. This study primarily focuses on Ferredoxin 9 (slr2059). Through sequence analysis and computational modeling, Ferredoxin 9 emerges as a unique ECP with a distinctive two-domain architecture. It consists of a C-terminal iron-sulfur binding domain and an N-terminal domain with homology to Nil-domain proteins, connected by a structurally rigid 4-amino acid linker. Notably, in contrast to canonical [2Fe-2S] ferredoxins exemplified by PetF (ssl0020), which feature highly acidic surfaces facilitating electron transfer with photosystem I reaction centers, models of Ferredoxin 9 reveal a more neutral to basic protein surface. Using a combination of electron paramagnetic resonance spectroscopy and square-wave voltammetry on heterologously produced Ferredoxin 9, this study demonstrates that the protein coordinates 2x[4Fe-4S]2+/1+ redox-active and magnetically interacting clusters, with measured redox potentials of -420 +/- 9 mV and -516 +/- 10 mV vs SHE. A more in-depth analysis of Fdx9's unique structure and protein sequence suggests that this type of Nil-2[4Fe-4S] multi-domain ferredoxin is well conserved in cyanobacteria, bearing structural similarities to proteins involved in homocysteine synthesis in methanogens.

cyanobacteria↗
DOE OSTI2025

Twisting the Hubbard model into the momentum-mixing Hatsugai–Kohmoto model

The Hubbard model is a standard theoretical tool for studying materials with strong electron–electron interactions, such as cuprate superconductors. Unfortunately, interaction-driven phenomena, such as a transition into the strongly correlated Mott insulator phase, are difficult to treat with established theoretical techniques. However, the exactly solvable Hatsugai–Kohmoto model displays similar Mott physics. In this work we show how the Hatsugai–Kohmoto model can be deformed continuously into the Hubbard model. The trick is to systematically reintroduce all the momentum mixing that the original Hatsugai–Kohmoto model omits. This can be accomplished by grouping n momenta into a cell and hybridizing them, resulting in the momentum-mixing Hatsugai–Kohmoto model. We recover the Bethe ansatz ground-state energy of the one-dimensional Hubbard model to within 1% from only ten mixed momenta. Overall, the convergence scales as 1/n2 as opposed to the inverse linear behaviour of standard finite-cluster techniques. Our results for a square lattice reproduce all the known features from state-of-the-art simulations also with only a few mixed momenta. Consequently, we believe that the momentum-mixing Hatsugai–Kohmoto model offers an alternative tool for strongly correlated quantum matter.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1988

Linear clusters of galaxies - A194

New measurements for 160 redshifts and previous measurements for 108 other redshifts are presented for galaxies within 5 deg of A194. The galaxy distribution in A194 is shown to be inconsistent with a spherically symmetric King model. A mass-to-light ratio is derived using the virial theorem which is lower than the mean for the groups in the CfA redshift survey (Huchra and Geller, 1982; Geller, 1984). A nonparametric test for galaxy-cluster alignment and a Chi-squared test are used to search for alignment of galaxy major axes with the axis of A194. Evidence for neither luminosity segregation nor significant differences in the velocity or surface distributions of galaxies as a function of morphological type is found.

Chapman, G. N. F.↗
DOE OSTI2020

Polyhydrido Copper Nanoclusters with a Hollow Icosahedral Core: [Cu 30 H 18 {E 2 P(OR) 2 } 12 ] (E=S or Se; R= n Pr, i Pr or i Bu)

Although atomically precise polyhydrido copper nanoclusters are of prime interest for a variety of applications, they have so far remained scarce. Here, we describe the synthesis of a dithiophosphate-protected copper(I) hydride-rich nanocluster (NC), [Cu 30 H 18 {S 2 P(O n Pr) 2 } 12 ] ( 1 H ), fully characterized by various spectroscopic methods and single-crystal X-ray diffraction. The X-ray structure of 1 H reveals an unprecedented central Cu 12 hollow icosahedron. Six faces of this icosahedron are capped by Cu 3 triangles, the whole Cu 30 core being wrapped by twelve dithiophosphate ligands and the whole cluster has ideal S 6 symmetry. The locations of the 18 hydrides in 1 H were ascertained by a single-crystal neutron diffraction study. They are composed of three types: capping μ 3 -H, interstitial μ 4 -H (seesaw) and μ 5 -H ligands (square pyramidal), in good agreement with the DFT simulations. The numbers of hydrides and ligand resonances in the 1 H NMR spectrum of 1 H are in line with their coordination environment in the solid state, retaining the S 6 symmetry in solution. Furthermore, two new Se-protected polyhydrido copper nanoclusters, [Cu 30 H 18 {Se 2 P(OR) 2 } 12 ] ( 2 H : R= i Pr 3 H : R= i Bu) were synthesized from their sulfur relative 1 H via ligand displacement reaction and their X-ray structures feature the exceptional case where both the NC shape and size are fully conserved during the course of ligand exchange. DFT and TD-DFT calculations allow understanding the bonding and optical properties of clusters 1 H – 3 H . In addition, the reaction of 1 H with [Pd(PPh 3 ) 2 Cl 2 ] in the presence of terminal alkynes led to the formation of new bimetallic Cu–Pd alloy clusters [PdCu 14 H 2 {S 2 P(O n Pr) 2 } 6 (C≡CR) 6 ] ( 4 : R=Ph; 5 : R = C 6 H 4 F).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1998

The Study of Clusters of Galaxies and Large Scale Structures

The work on the ROSAT Deep Survey has been successfully completed. A number of interesting results have been established within this joint MPE, Cal Tech, JHU, ST Scl, ESO collaboration. First, a very large fraction, 70-80 percent, of the X-ray background has been directly resolved into point sources. We have derived a new log N-log S for X- ray sources and have measured a source density of 970 sources per square degree at a limiting flux level of 10(exp -15)/erg s sq cm (0.5-2.0 keV). Care was taken in these studies to accurately model and measure the effects of sources confusion. This was possible because of our observing strategy which included both deep PSPC and HRI observations. In the last year we initiated work in the design and development of the Next Generation Space Telescope.

Source record↗
DOE OSTI2020

Materials Data on PuN2O11 by Materials Project

(PuO4)2(NO3)4O2 is Cyanogen Chloride-like structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four nitric acid molecules, two water molecules, and two PuO4 clusters. In one of the PuO4 clusters, Pu is bonded in a square co-planar geometry to four equivalent O atoms. There is two shorter (1.80 Å) and two longer (1.81 Å) Pu–O bond length. O is bonded in a single-bond geometry to one Pu atom. In one of the PuO4 clusters, Pu is bonded in a square co-planar geometry to four equivalent O atoms. There is two shorter (1.80 Å) and two longer (1.81 Å) Pu–O bond length. O is bonded in a single-bond geometry to one Pu atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni2N11Cl8 by Materials Project

NiCl4NiNCl4(N2)5 crystallizes in the orthorhombic Pmmm space group. The structure is one-dimensional and consists of four ammonia molecules; two triazane molecules; one NiCl4 cluster; and one NiNCl4 ribbon oriented in the (1, 0, 0) direction. In the NiCl4 cluster, Ni+2.50+ is bonded in a square co-planar geometry to four equivalent Cl1- atoms. All Ni–Cl bond lengths are 2.20 Å. Cl1- is bonded in a single-bond geometry to one Ni+2.50+ atom. In the NiNCl4 ribbon, Ni+2.50+ is bonded in a distorted square co-planar geometry to four equivalent Cl1- atoms. All Ni–Cl bond lengths are 2.27 Å. N+0.27+ is bonded in a square co-planar geometry to four equivalent Cl1- atoms. All N–Cl bond lengths are 2.14 Å. Cl1- is bonded in an L-shaped geometry to one Ni+2.50+ and one N+0.27+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Percolation technique for galaxy clustering

We study percolation in mass and galaxy distributions obtained in 3D simulations of the CDM, C + HDM, and the power law (n = -1) models in the Omega = 1 universe. Percolation statistics is used here as a quantitative measure of the degree to which a mass or galaxy distribution is of a filamentary or cellular type. The very fast code used calculates the statistics of clusters along with the direct detection of percolation. We found that the two parameters mu(infinity), characterizing the size of the largest cluster, and mu-squared, characterizing the weighted mean size of all clusters excluding the largest one, are extremely useful for evaluating the percolation threshold. An advantage of using these parameters is their low sensitivity to boundary effects. We show that both the CDM and the C + HDM models are extremely filamentary both in mass and galaxy distribution. The percolation thresholds for the mass distributions are determined.

Klypin, Anatoly↗
DOE OSTI2020

Materials Data on H16PdC4S4(N4Cl)2 by Materials Project

PdC4H16(N2S)4Cl2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight hydrochloric acid molecules and four PdC4H16(N2S)4 clusters. In each PdC4H16(N2S)4 cluster, Pd2+ is bonded in a square co-planar geometry to four S2- atoms. There are two shorter (2.37 Å) and two longer (2.38 Å) Pd–S bond lengths. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.74 Å. In the second C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.74 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the third N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom. In the second S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2003

A Fast Implementation of the ISOCLUS Algorithm

Unsupervised clustering is a fundamental tool in numerous image processing and remote sensing applications. For example, unsupervised clustering is often used to obtain vegetation maps of an area of interest. This approach is useful when reliable training data are either scarce or expensive, and when relatively little a priori information about the data is available. Unsupervised clustering methods play a significant role in the pursuit of unsupervised classification. One of the most popular and widely used clustering schemes for remote sensing applications is the ISOCLUS algorithm, which is based on the ISODATA method. The algorithm is given a set of n data points (or samples) in d-dimensional space, an integer k indicating the initial number of clusters, and a number of additional parameters. The general goal is to compute a set of cluster centers in d-space. Although there is no specific optimization criterion, the algorithm is similar in spirit to the well known k-means clustering method in which the objective is to minimize the average squared distance of each point to its nearest center, called the average distortion. One significant feature of ISOCLUS over k-means is that clusters may be merged or split, and so the final number of clusters may be different from the number k supplied as part of the input. This algorithm will be described in later in this paper. The ISOCLUS algorithm can run very slowly, particularly on large data sets. Given its wide use in remote sensing, its efficient computation is an important goal. We have developed a fast implementation of the ISOCLUS algorithm. Our improvement is based on a recent acceleration to the k-means algorithm, the filtering algorithm, by Kanungo et al.. They showed that, by storing the data in a kd-tree, it was possible to significantly reduce the running time of k-means. We have adapted this method for the ISOCLUS algorithm. For technical reasons, which are explained later, it is necessary to make a minor modification to the ISOCLUS specification. We provide empirical evidence, on both synthetic and Landsat image data sets, that our algorithm's performance is essentially the same as that of ISOCLUS, but with significantly lower running times. We show that our algorithm runs from 3 to 30 times faster than a straightforward implementation of ISOCLUS. Our adaptation of the filtering algorithm involves the efficient computation of a number of cluster statistics that are needed for ISOCLUS, but not for k-means.

Memarsadeghi, Nargess↗
DOE OSTI2024

Cryogenic Photoelectron Spectroscopic and Theoretical Study of the Electronic and Geometric Structures of Undercoordinated Osmium Chloride Anions OsCl n – ( n = 3–5)

A series of anionic transition metal halides OsCl n - (n=3–5) have been investigated using a newly developed, home-constructed, cryogenic anion cluster photoelectron spectroscopy. Here, the target anionic species are generated through collision-induced dissociation in a two-stage ion funnel. The measured vertical detachment energies (VDEs) are 3.48 eV, 4.54 eV, and 4.81 eV for n = 3, 4, and 5, respectively. Density functional theory calculations at the B3LYP-D3(BJ)//aug-cc-pVTZ (-pp) level predict the lowest energy structures of OsCl n - (n = 3–5) to be a quintet triangle, quartet square, and quintet square-based pyramid, respectively. The CCSD(T)-calculated VDEs and corresponding adiabatic detachment energies (ADEs) agree well with our experimental measurements. Analysis of the corresponding frontier molecular orbitals (FMOs) and charge density differences suggests that the d-orbitals of the transition metal Os play a primary role in the single-photon detachment processes, and the detached electrons originating from different molecular orbitals are distinguishable.

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

Materials Data on CuN6(ClO4)3 by Materials Project

(CuN4)2N2(N(O4Cl)2)2(ClO4)2 crystallizes in the tetragonal P-42_1m space group. The structure is two-dimensional and consists of two ammonia molecules; two nsc1302 molecules; two ClO4 clusters; and one N(O4Cl)2 sheet oriented in the (0, 0, 1) direction. In each ClO4 cluster, there are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.49 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.44 Å. Cl1- is bonded in a tetrahedral geometry to four O2- atoms. In the N(O4Cl)2 sheet, N+4.33+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All N–O bond lengths are 2.23 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.43 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.45 Å. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one N+4.33+ and one Cl1- atom. The O–Cl bond length is 1.50 Å. Cl1- is bonded in a tetrahedral geometry to four O2- atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Discovery of Activities via Statistical Clustering of Fixation Patterns

Human behavior often consists of a series of distinct activities, each characterized by a unique pattern of interaction with the visual environment. This is true even in a restricted domain, such as a piloting an aircraft, where activities with distinct visual signatures might be things like communicating, navigating, and monitoring. We propose a novel analysis method for gaze-tracking data, to perform blind discovery of these hypothetical activities. The method is in some respects similar to recurrence analysis, but here we compare not individual fixations, but groups of fixations aggregated over a fixed time interval. The duration of this interval is a parameter that we will refer to as delta. We assume that the environment has been divided into a set of N different areas-of-interest (AOIs). For a given interval of time of duration delta, we compute the proportion of time spent fixating each AOI, resulting in an N-dimensional vector. These proportions can be converted to integer counts by multiplying by delta divided by the average fixation duration (another parameter that we fix at 280 milliseconds). We compare different intervals by computing the chi-square statistic. The p-value associated with the statistic is the likelihood of observing the data under the hypothesis that the data in the two intervals were generated by a single process with a single set of probabilities governing the fixation of each AOI. The method has been applied to approximately 100 hours of eye movement data collected from pilots in a high-fidelity B747 flight simulator, and the results have been compared to synthetic data in which the each activity is represented as first-order Markov process with random probabilities assigned to the AOIs. Randomly-generated synthetic activities can require thousands of fixations to be discriminated with statistical significance, while the human data can be clustered using averaging windows of some 10's of seconds, suggesting that the actual activities are much more narrowly focused than random Markov models.

activity analysis↗
DOE OSTI2020

Materials Data on CoAu(BrN)6 by Materials Project

AuBr4Co(NBr)2(N2)2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four nitrogen molecules, two AuBr4 clusters, and two Co(NBr)2 clusters. In each AuBr4 cluster, Au5+ is bonded in a square co-planar geometry to four Br1- atoms. There are two shorter (2.48 Å) and two longer (2.52 Å) Au–Br bond lengths. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a single-bond geometry to one Au5+ atom. In the second Br1- site, Br1- is bonded in a distorted single-bond geometry to one Au5+ atom. In each Co(NBr)2 cluster, Co3+ is bonded in a linear geometry to two equivalent N+0.33- atoms. Both Co–N bond lengths are 1.66 Å. N+0.33- is bonded in a distorted single-bond geometry to one Co3+ and one Br1- atom. The N–Br bond length is 1.77 Å. Br1- is bonded in a distorted single-bond geometry to one N+0.33- atom.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Optical signatures of high-redshift galaxy clusters

We combine an N-body and gasdynamic simulation of structure formation with an updated population synthesis code to explore the expected optical characteristics of a high-redshift cluster of galaxies. We examine a poor (2 keV) cluster formed in a biased, cold dark matter cosmology and employ simple, but plausible, threshold criteria to convert gas into stars. At z = 2, the forming cluster appears as a linear chain of very blue (g-r approximately equals 0) galaxies, with 15 objects brighter than r = 25 within a 1 square arcmin field of view. After 2 Gyr of evolution, the cluster viewed at z = 1 displays both freshly infalling blue galaxies and red galaxies robbed of recent accretion by interaction with the hot intracluster medium. The range in G-R colors is approximately 3 mag at z = 1, with the reddest objects lying at sites of highest galaxy density. We suggest that red, high-redshift galaxies lie in the cores of forming clusters and that their existence indicates the presence of a hot intracluster medium at redshifts z approximately equals 2. The simulated cluster viewed at z = 2 has several characteristics similar to the collection of faint, blue objects identified by Dressler et al. in a deep Hubble Space Telescope observation. The similarities provide some support for the interpretation of this collection as a high-redshift cluster of galaxies.

Evrard, August E.↗
NASA NTRS1996

Kinetics of Diffusional Droplet Growth in a Liquid/Liquid Two-Phase System

We address the problem of diffusional interactions in a finite sized cluster of spherical particles for volume fractions, V(sub v) in the range 0-0.01. We determined the quasi-static monopole diffusion solution for n particles distributed at random in a continuous matrix. A global mass conservation condition is employed, obviating the need for any external boundary condition. The numerical results provide the instantaneous (snapshot) growth or shrinkage rate of each particle, precluding the need for extensive time-dependent computations. The close connection between these snapshot results and the coarsegrained kinetic constants are discussed. A square-root dependence of the deviations of the rate constants from their zero volume fraction value is found for the higher V(sub v) investigated. This behavior is consistent with predictions from diffusion Debye-Huckel screening theory. By contrast, a cube-root dependence, reported in earlier numerical studies, is found for the lower V(sub v) investigated. The roll-over region of the volume fraction where the two asymptotics merge depends on the number of particles, n, alone. A theoretical estimate for the roll-over point predicts that the corresponding V(sub v) varies as n(sup -2), in good agreement with the numerical results.

Glicksman, M. E.↗
DOE OSTI2021

From hard spheres to hard-core spins

A system of hard spheres exhibits physics that is controlled only by their density. This comes about because the interaction energy is either infinite or zero, so all allowed configurations have exactly the same energy. The low-density phase is liquid, while the high-density phase is crystalline, an example of “order by disorder” as it is driven purely by entropic considerations. Here we study a family of hard spin models, which we call hard-core spin models, where we replace the translational degrees of freedom of hard spheres with the orientational degrees of freedom of lattice spins. Their hard-core interaction serves analogously to divide configurations of the many spin system into allowed and disallowed sectors. We present detailed results on the square lattice in d = 2 for a set of models with $\mathbb{Z}_n$ symmetry, which generalize Potts models, and their U(1) limits, for ferromagnetic and antiferromagnetic senses of the interaction, which we refer to as exclusion and inclusion models. As the exclusion and inclusion angles are varied, we find a Kosterlitz-Thouless phase transition between a disordered phase and an ordered phase with quasi-long-ranged order, which is the form order by disorder takes in these systems. These results follow from a set of height representations, an ergodic cluster algorithm, and transfer matrix calculations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗