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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Energetic neutral atoms measured by the interstellar boundary explorer (IBEX): Evidence for multiple heliosheath populations

Energetic neutral atoms (ENAs) observed by the Interstellar Boundary Explorer (IBEX) provide powerful diagnostics about the origin of the progenitor ion populations and the physical mechanisms responsible for their production. In this paper, we extend the work of Desai et al. and Fuselier et al. and combine and compare ENA spectra from the first 3 yr of observations by the IBEX-Hi and -Lo ENA imagers along the lines-of-sight (LOSs) from the inner heliosphere through to the locations of Voyager 1 and 2 with results from an updated physics-based model of the three-dimensional heliosphere and its constituent ion populations. Our results show that (1) IBEX ENA fluxes and spectra above ∼0.7 keV measured along the LOSs of the Voyagers are consistent with several models in which the parent pickup ion (PUI) populations originate in the inner heliosheath, and (2) a significant fraction of lower energy ENAs between ∼0.1-0.5 keV may originate from interstellar neutral gas charge-exchanging with a non-thermalized (hot) population of PUIs in the outer heliosheath beyond the heliopause. We discuss the implications of ENAs observed by IBEX originating from distinct parent populations as well as from two distinct locations in the heliospheric interface. These results indicate that ENA spectral measurements at various energies can be used to remotely probe distinct physical processes operating in vastly different regions of the distant heliosphere.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Multiple-view, multiple-selection visualization of simulation geometry in CMS

Fireworks, the event-display program of CMS, was extended with an advanced geometry visualization package. ROOT's TGeo geometry is used as internal representation, shared among several geometry views. Each view is represented by a GUI list-tree widget, implemented as a flat vector to allow for fast searching, selection, and filtering by material type, node name, and shape type. Display of logical and physical volumes is supported. Color, transparency, and visibility flags can be modified for each node or for a selection of nodes. Further operations, like opening of a new view or changing of the root node, can be performed via a context menu. Node selection and graphical properties determined by the list-tree view can be visualized in any 3D graphics view of Fireworks. As each 3D view can display any number of geometry views, a user is free to combine different geometry-view selections within the same 3D view. Node-selection by proximity to a given point is possible. A visual clipping box can be set for each geometry view to limit geometry drawing into a specified region. Visualization of geometric overlaps, as detected by TGeo, is also supported. The geometry visualization package is used for detailed inspection and display of simulation geometry with or without the event data. It also serves as a tool for geometry debugging and inspection, facilitating development of geometries for CMS detector upgrades and for SLHC.

Bauerdick, L. A.T.↗
DOE OSTI2023

Multiple highly expressed phospho enol pyruvate carboxylase genes have divergent enzyme kinetic properties in two C4 grasses

Abstract Background and Aims Phosphoenolpyruvate (PEP) carboxylase (PEPC) catalyses the irreversible carboxylation of PEP with bicarbonate to produce oxaloacetate. This reaction powers the carbon-concentrating mechanism (CCM) in plants that perform C4 photosynthesis. This CCM is generally driven by a single PEPC gene product that is highly expressed in the cytosol of mesophyll cells. We found two C4 grasses, Panicum miliaceum and Echinochloa colona, that each have two highly expressed PEPC genes. We characterized the kinetic properties of the two most abundant PEPCs in E. colona and P. miliaceum to better understand how the enzyme’s amino acid structure influences its function. Methods Coding sequences of the two most abundant PEPC proteins in E. colona and P. miliaceum were synthesized by GenScript and were inserted into bacteria expression plasmids. Point mutations resulting in substitutions at conserved amino acid residues (e.g. N-terminal serine and residue 890) were created via site-directed PCR mutagenesis. The kinetic properties of semi-purified plant PEPCs from Escherichia coli were analysed using membrane-inlet mass spectrometry and a spectrophotometric enzyme-coupled reaction. Key Results The two most abundant P. miliaceum PEPCs (PmPPC1 and PmPPC2) have similar sequence identities (>95 %), and as a result had similar kinetic properties. The two most abundant E. colona PEPCs (EcPPC1 and EcPPC2) had identities of ~78 % and had significantly different kinetic properties. The PmPPCs and EcPPCs had different responses to allosteric inhibitors and activators, and substitutions at the conserved N-terminal serine and residue 890 resulted in significantly altered responses to allosteric regulators. Conclusions The two, significantly expressed C4Ppc genes in P. miliaceum were probably the result of genomes combining from two closely related C4Panicum species. We found natural variation in PEPC’s sensitivity to allosteric inhibition that seems to bypass the conserved 890 residue, suggesting alternative evolutionary pathways for increased malate tolerance and other kinetic properties.

DiMario, Robert J. (ORCID:0000000250566868)↗
DOE OSTI2017

Multiple superconducting states induced by pressure in Mo 3 Sb 7

Tuning competing ordering mechanisms with hydrostatic pressure in the 4 d intermetallic compound Mo 3 Sb 7 reveals an intricate interplay of structure, magnetism, and superconductivity. Synchrotron x-ray diffraction and magnetic susceptibility measurements, both employing diamond anvil cell technologies, link a first-order structural phase transition to a doubling of the superconducting transition temperature. In contrast to the spin-dimer picture for Mo 3 Sb 7 , we deduce from x-ray absorption near-edge structure and dc magnetization measurements at ambient pressure that Mo 3 Sb 7 should possess only very small, itinerant magnetic moments. As a result, the pressure evolution of the superconducting transition temperature strongly suggests its enhancement is due to a difference in the phonon density-of-states with changed crystal symmetry.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Transitions from order to disorder in multiple dark and multiple dark-bright soliton atomic clouds

We have performed a systematic study quantifying the variation of solitary wave behavior from that of an ordered cloud resembling a “crystalline” configuration to that of a disordered state that can be characterized as a soliton “gas.” As our illustrative examples, we use both one-component, as well as two-component, one-dimensional atomic gases very close to zero temperature, where in the presence of repulsive interatomic interactions and of a parabolic trap, a cloud of dark (dark-bright) solitons can form in the one- (two-) component system. We corroborate our findings through three distinct types of approaches, namely a Gross-Pitaevskii type of partial differential equation, particle-based ordinary differential equations describing the soliton dynamical system, and Monte Carlo simulations for the particle system. In addition, we define an “empirical” order parameter to characterize the order of the soliton lattices and study how this changes as a function of the strength of the “thermally” (i.e., kinetically) induced perturbations. As may be anticipated by the one-dimensional nature of our system, the transition from order to disorder is gradual without, apparently, a genuine phase transition ensuing in the intermediate regime.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Search for new T' particles in final states with large jet multiplicities and missing transverse energy in pp collisions at √s=1.96 TeV

We present a search for a new particle T decaying to a top quark via T = t + X, where X goes undetected. We use a data sample corresponding to 5.7 fb -1 of integrated luminosity of pp collisions with √s = 1.96 TeV, collected at Fermilab Tevatron by the CDF II detector. Our search for pair production of T' is focused on the hadronic decay channel, pp = TT= tt+XX=bqqbqq + XX. We interpret our results in terms of a model where T is an exotic fourth generation quark and X is a dark matter particle. The data are consistent with standard model expectations. We set a limit on the generic production of TT = tt =+ XX, excluding the fourth generation exotic quarks T at 95% confidence level up to m T = 400 GeV/c 2 for m X ≤ 70 GeV/c 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗