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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Phase Diagram and Critical End Point for Strongly Interacting Quarks

We introduce a method based on chiral susceptibility, which enables one to draw a phase diagram in the chemical-potential-temperature plane for strongly interacting quarks whose interactions are described by any reasonable gap equation, even if the diagrammatic content of the quark-gluon vertex is unknown. We locate a critical end point at ({mu}{sup E},T{sup E}){approx}(1.0,0.9)T{sub c}, where T{sub c} is the critical temperature for chiral-symmetry restoration at {mu}=0, and find that a domain of phase coexistence opens at the critical end point whose area increases as a confinement length scale grows.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Novel Cooperative Interactions and Structural Ordering in H[subscript 2]S-H[subscript 2]

Hydrogen sulfide (H{sub 2}S) and hydrogen (H{sub 2}) crystallize into a 'guest-host' structure at 3.5 GPa and, at the initial formation pressure, the rotationally disordered component molecules exhibit weak van der Waals-type interactions. With increasing pressure, hydrogen bonding develops and strengthens between neighboring H{sub 2}S molecules, reflected in a pronounced drop in S-H vibrational stretching frequency and also observed in first-principles calculations. At 17 GPa, an ordering process occurs where H{sub 2}S molecules orient themselves to maximize hydrogen bonding and H{sub 2} molecules simultaneously occupy a chemically distinct lattice site. Intermolecular forces in the H{sub 2}S+H{sub 2} system may be tuned with pressure from the weak hydrogen-bonding limit to the ordered hydrogen-bonding regime, resulting in a novel clathrate structure stabilized by cooperative interactions.

08 HYDROGEN↗
DOE OSTI2015

Understanding Small-Molecule Interactions in Metal-Organic Frameworks: Coupling Experiment with Theory

Metal-organic frameworks (MOFs) have gained much attention as next generation porous media for various applications, especially gas separations/storage and catalysis. New MOFs are regularly reported; however, to develop better materials in a timely manner for specific applications, the interactions between guest molecules and the internal surface of the framework must first be understood. In this review, we present a combined experimental and theoretical approach that proves essential for the elucidation of small-molecule interactions in a model MOF system known as M 2 (dobdc) (dobdc 4– = 2,5-dioxido-1,4-benzenedicarboxylate; M = Mg, Mn, Fe, Co, Ni, Cu, or Zn), a material whose adsorption properties can be readily tuned via chemical substitution. Here, we additionally show that the study of extensive families like this one can provide a platform to test the efficacy and accuracy of developing computational methodologies in slightly varying chemical environments, a task that is necessary for their evolution into viable, robust tools for screening large numbers of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Crystal Structure of the Receptor Binding Domain of the botulinum C-D Mosiac Neurotoxin Reveals Potential Roles of Lysines 1118 and 1136 in Membrane Interactions

The botulinum neurotoxins (BoNTs) produced by different strains of the bacterium Clostridium botulinum are responsible for the disease botulism and include a group of immunologically distinct serotypes (A, B, E, and F) that are considered to be the most lethal natural proteins known for humans. Two BoNT serotypes, C and D, while rarely associated with human infection, are responsible for deadly botulism outbreaks afflicting animals. Also associated with animal infections is the BoNT C-D mosaic protein (BoNT/CD), a BoNT subtype that is essentially a hybrid of the BoNT/C ({approx}two-third) and BoNT/D ({approx}one-third) serotypes. While the amino acid sequence of the heavy chain receptor binding (HCR) domain of BoNT/CD (BoNT/CD-HCR) is very similar to the corresponding amino acid sequence of BoNT/D, BoNT/CD-HCR binds synaptosome membranes better than BoNT/D-HCR. To obtain structural insights for the different membrane binding properties, the crystal structure of BoNT/CD-HCR (S867-E1280) was determined at 1.56 {angstrom} resolution and compared to previously reported structures for BoNT/D-HCR. Overall, the BoNT/CD-HCR structure is similar to the two sub-domain organization observed for other BoNT HCRs: an N-terminal jellyroll barrel motif and a C-terminal {beta}-trefoil fold. Comparison of the structure of BoNT/CD-HCR with BoNT/D-HCR indicates that K1118 has a similar structural role as the equivalent residue, E1114, in BoNT/D-HCR, while K1136 has a structurally different role than the equivalent residue, G1132, in BoNT/D-HCR. Lysine-1118 forms a salt bridge with E1247 and may enhance membrane interactions by stabilizing the putative membrane binding loop (K1240-N1248). Lysine-1136 is observed on the surface of the protein. A sulfate ion bound to K1136 may mimic a natural interaction with the negatively changed phospholipid membrane surface. Liposome-binding experiments demonstrate that BoNT/CD-HCR binds phosphatidylethanolamine liposomes more tightly than BoNT/D-HCR.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Plumbojarosite Remediation of Soil Affects Lead Speciation and Elemental Interactions in Soil and in Mice Tissues

Lead (Pb) contamination of soils is of global concern due to the devastating impacts of Pb exposure in children. Because early-life exposure to Pb has long-lasting health effects, reducing exposure in children is a critical public health goal that has intensified research on the conversion of soil Pb to low bioavailability phases. Recently, plumbojarosite (PLJ) conversion of highly available soil Pb was found to decrease Pb relative bioavailability (RBA <10%). However, there is sparse information concerning interactions between Pb and other elements when contaminated soil, pre- and post-remediation, is ingested and moves through the gastrointestinal tract (GIT). Addressing this may inform drivers of effective chemical remediation strategies. In this study, we utilize bulk and micro-focused Pb X-ray absorption spectroscopy to probe elemental interactions and Pb speciation in mouse diet, cecum, and feces samples following ingestion of contaminated soils pre- and post-PLJ treatment. RBA of treated soils was less than 1% with PLJ phases transiting the GIT with little absorption. In contrast, Pb associated with organics was predominantly found in the cecum. These results are consistent with transit of insoluble PLJ to feces following ingestion. The expanded understanding of Pb interactions during GIT transit complements our knowledge of elemental interactions with Pb that occur at higher levels of biological organization.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Study of double parton interactions in diphoton + dijet events in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV

We use a sample of diphoton+dijet events to measure the effective cross section of double parton interactions, which characterizes the area containing the interacting partons in proton-antiproton collisions, and find it to be σeff=19.3±1.4(stat)±7.8(syst) mb. The sample was collected by the D0 detector at the Fermilab Tevatron collider in pp¯ collisions at s=1.96 TeV and corresponds to an integrated luminosity of 8.7 fb-1.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Active to Sterile Neutrino Mixing Limits from Neutral-Current Interactions in MINOS

Results are reported from a search for active to sterile neutrino oscillations in the MINOS long-baseline experiment, based on the observation of neutral-current neutrino interactions, from an exposure to the NuMI neutrino beam of 7.07x10{sup 20} protons on target. A total of 802 neutral-current event candidates is observed in the Far Detector, compared to an expected number of 754{+-}28(stat){+-}37(syst) for oscillations among three active flavors. The fraction f{sub s} of disappearing {nu}{sub {mu}} that may transition to {nu}{sub s} is found to be less than 22% at the 90% C.L.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Spatially adaptive stochastic methods for fluid–structure interactions subject to thermal fluctuations in domains with complex geometries

We develop stochastic mixed finite element methods for spatially adaptive simulations of fluid–structure interactions when subject to thermal fluctuations. To account for thermal fluctuations, we introduce a discrete fluctuation–dissipation balance condition to develop compatible stochastic driving fields for our discretization. We perform analysis that shows our condition is sufficient to ensure results consistent with statistical mechanics. We show the Gibbs–Boltzmann distribution is invariant under the stochastic dynamics of the semi-discretization. To generate efficiently the required stochastic driving fields, we develop a Gibbs sampler based on iterative methods and multigrid to generate fields with O(N) computational complexity. Our stochastic methods provide an alternative to uniform discretizations on periodic domains that rely on Fast Fourier Transforms. To demonstrate in practice our stochastic computational methods, we investigate within channel geometries having internal obstacles and no-slip walls how the mobility/diffusivity of particles depends on location. Our methods extend the applicability of fluctuating hydrodynamic approaches by allowing for spatially adaptive resolution of the mechanics and for domains that have complex geometries relevant in many applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS low ionization Threshold Experiment

The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Results are presented from the second CDMSlite run with an exposure of 70 kg day, which reached an energy threshold for electron recoils as low as 56 eV. A fiducialization cut reduces backgrounds below those previously reported by CDMSlite.

New Results, Low-Mass, Mazzive Particles, CDMS Low↗