SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
AlP is Wurtzite structured and crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Al3+ is bonded to four equivalent P3- atoms to form corner-sharing AlP4 tetrahedra. There are three shorter (2.38 Å) and one longer (2.39 Å) Al–P bond lengths. P3- is bonded to four equivalent Al3+ atoms to form corner-sharing PAl4 tetrahedra.
New light particles produced in supernovae can lead to additional energy loss and a consequent deficit in neutrino production in conflict with the neutrinos observed from Supernova 1987A (SN1987A). Contrary to the majority of previous SN1987A studies, we examine the impact of Z' bosons, axions, and axion-like particles (ALPs) interacting with the muons produced in SN1987A. For the first time, we find constraints on generic Z' bosons coupled to muons, and apply our results to particle models including gauged $L_μ –L_τ$ number, U(1)$_{L_μ–L_τ}$, and gauged B – L number, U(1)$_{B–L}$. We constrain Z' bosons with masses up to about 250 – 500 MeV, and down to about 10 –9 in Z'-muon coupling. We also extend previous work on axion-muon couplings by examining the importance of loop-level interactions, as well as performing calculations over a wider range of axion masses. We constrain muon-coupled axions from arbitrarily low masses up to about 200 – 500 MeV, with bounds extending down to axion-muon couplings of approximately 10 –8 GeV –1 . We conclude that supernovae broadly provide a sensitive probe of new lightly-coupled particles interacting with muons.
Fluids generated from subducted slabs participate in the cycling of deep carbon in the crust and upper mantle. In these fluids, aqueous carbon species vary in oxidation state between +IV and -IV depending on whether the fluids are oxidizing or reducing, respectively. Most studies of subduction-zone fluids have focused on oxidized carbon species. However, recent studies of natural samples have demonstrated the occurrence of deep, reducing fluids, generated in both subducted oceanic upper mantle and crustal rocks. CH 4 -H 2 -rich fluid inclusions in subducted carbonated serpentinites have demonstrated the existence of abiotic, immiscible, hydrocarbon fluids at upper mantle conditions. To investigate the formation of such immiscible hydrocarbon fluids during the evolution of subducted carbonated serpentinites, we used equilibrium constants from the Deep Earth Water model to carry out predictive chemical mass transfer modeling to simulate the alteration reactions. A novel feature of the models was the inclusion of an immiscible hydrocarbon fluid containing six components (CH 4,f , C 2 H 6,f , C 3 H 8,f , isoC 4 H 10,f , CO 2,f , H 2,f ). This feature enabled prediction of the formation of a separate immiscible fluid in equilibrium with aqueous species and minerals. We developed a predictive reaction path model of invasive H 2,f reacting with carbonated serpentinites and interstitial aqueous fluids for comparison with the natural samples from the Lanzo Massif, western Italian Alps. Over a range of temperatures and pressures, immiscible hydrocarbon fluids formed in association with altered mineral assemblages. Reaction progress caused the transformation of carbonated serpentinites and the formation of clinopyroxene, brucite, graphite, and hydrocarbon fluids, along with changes of pH, logfO 2 , and aqueous species. CH 4,f was the most abundant hydrocarbon species in all the models. The overall results at 2.0 GPa and 400 to 450 °C were consistent with the natural samples from the Lanzo Massif. Interestingly, large amounts of H 2 O formed due to oxidation of H 2 . More hydrocarbons and H 2 O formed in models with lower fluid/rock mass ratios or with more reactant H 2 . Models at different pressure and temperature conditions showed similar results with some variation in the relative stabilities of aragonite, graphite and olivine solid solution, and associated differences in mineral sequences, hydrocarbon fluids, values of aqueous species, and the final log fO 2 and pH. As a result, our models strongly support the laboratory and field evidence that reduction of carbonated serpentinites by infiltrating H 2 fluids can cause the formation of immiscible, abiotic hydrocarbon fluids in subduction zones.
Axion-photon conversion is a prime mechanism to detect axion-like particles that share a coupling to the photon. We point out that in the vicinity of neutron stars with strong magnetic fields, magnetars, the effective photon mass receives comparable but opposite contributions from free electrons and the radiation field. This leads to an energy-dependent resonance condition for conversion that can be met for arbitrary light axions and leveraged when using systems with detected radio component. Using the magnetar SGR J1745-2900 as an exemplary source, we demonstrate that sensitivity to |g aγ | ~ 10 -12 GeV -1 or better can be gained for m a ≲ 10 -6 eV, with the potential to improve current constraints on the axion-photon coupling by more than one order of magnitude over a broad mass range. With growing insights into the physical conditions of magnetospheres of magnetars, the method hosts the potential to become a serious competitor to future experiments such as ALPS-II and IAXO in the search for axion-like particles.
This report presents an exploration of sensitivity estimates for multiple prominent proposed techniques to search for axion-like particles (ALPs). The sensitivities are plotted over particle mass ($m_a$) and coupling ($g_{aγγ}$) parameter space. Explorations include variation over detector type, integration time, background cosmology, and size of the apparatus.
AlPO4(H2O)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four equivalent PO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.88–1.98 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 28–42°. There is two shorter (1.54 Å) and two longer (1.56 Å) P–O bond length. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.67 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.64 Å) H–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Al3+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Al3+ and two H1+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Al3+, one P5+, and one H1+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Al3+, one P5+, and one H1+ atom.
AlPO4H2 is High (Orthorhombic) Tridymite-derived structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of eight hydrogen molecules and one AlPO4 framework. In the AlPO4 framework, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent PO4 tetrahedra. There is two shorter (1.75 Å) and two longer (1.76 Å) Al–O bond length. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four equivalent AlO4 tetrahedra. There is two shorter (1.53 Å) and two longer (1.54 Å) P–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one Al3+ and one P5+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Al3+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom.
Not Available
Not Available
The hallmark of the eukaryotic cell is the complex endomembrane system that compartmentalizes cellular functions. Transport into and out of the nucleus occurs through the nuclear pore complex (NPC). The heptameric Nup84 or Y complex is an essential scaffolding component of the NPC. Here we report two nanobody-bound structures: the full-length Nup84-Nup133 C-terminal domain complex and the Nup133 N-terminal domain, both from S. cerevisiae. Together with previously published structures, this work enables the structural description of the entire 575 kDa Y complex from one species. The structure of Nup84-Nup133CTD details the high flexibility of this dimeric unit of the Y complex. Further, the Nup133NTD contains a structurally conserved amphipathic lipid packing sensor motif, confirmed by liposome interaction studies. The presented structures reveal important details about the function of the Y complex that affect our understanding of NPC structure and assembly.
Not Available
Not Available
Not Available
Not Available
One major hurdle for understanding earthquake mechanics are observational limitations. Important phenomena like strain localisation, fault dilation, and fault healing are readily studied in rock mechanical laboratory experiments and with numerical models. At the scale of natural earthquakes, however, these phenomena are often unresolvable, even by state-of-the-art observatories. To overcome this limitation, we are currently building the Earthquake Physics Testbed at the Bedretto Underground Laboratory for Geosciences and Geoenergies (BedrettoLab), an experimental testbed where we can activate an extensively instrumented natural fault zone via hydraulic stimulation. The goal of the Fault Activation and Earthquake Rupture (FEAR) project is to induce earthquakes of up to Mw~1.0 on this exceptionally well characterised and instrumented fault zone. Here we summarize the main scientific goals and current FEAR project status, and present first results from conducted experiments. We discuss how this large-scale experimental approach may allow us to tackle both fundamental science as well as practical questions on earthquake physics, induced seismicity and seismic hazard.
Explore the source record for details and available documents.