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Results for “MICHELLE”
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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Crystal structure of the potato leafroll virus coat protein and implications for viral assembly
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Probing the local structure of crystalline NaBiO3·XH2O and its acidified derivatives
Not Available
Structural and biochemical analysis of phosphoethanolamine methyltransferase from the pine wilt nematode Bursaphelenchus xylophilus
Abstract not provided
Waste form evaluation for RECl 3 and REO x fission products separated from used electrochemical salt
The work presented here is based off the concept that the rare earth chloride (RECl3) fission products mixture within the used electrorefiner (ER) salt can be selectively removed as RECl3 (not yet demonstrated) or precipitated out as REOCl through oxygen sparging (has been demonstrated). This paper presents data showing the feasibility of immobilizing a mixture of RECl3’s at 10 mass% into a TeO2-PbO glass and it shows that this same mixture of RECl3’s can be oxidized to REOCl at 300°C and then to REOx by 1200°C. When the REOx mixture is heated at temperatures >1200°C, the ratios of REOx’s change. The mixture of REOx was then immobilized in a LABS glass at a high loading of 60 mass%. Both the TeO2-PbO glass and LABS glass systems show good chemical durability. The advantages and disadvantages of tellurite and LABS glasses are compared.
The effect of uranium on bacterial viability and cell surface morphology using atomic force microscopy in the presence of bicarbonate ions
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Strategies of Gammarus pulex L. to cope with arsenic – Results from speciation analyses by IC–ICP-MS and XAS micro-mapping
Abstract not provided
Li + Diffusion in Amorphous and Crystalline Al 2 O 3 for Battery Electrode Coatings
Al 2 O 3 is often applied protectively to lithium-ion battery anode and cathode materials to inhibit surface degradation, suppress dendrite formation, and relieve mechanical stresses. Given the very high intrinsic band gap and diffusion barrier of the material, the mechanism that allows Li diffusion through these coatings is not well understood, and widely varying laboratory results indicate that there may be dependencies on morphology and stoichiometry. Using nudged elastic band calculations and ab initio molecular dynamics, we perform a systematic investigation across Al 2 O 3 structures, both crystalline and amorphous, and at various concentrations of Li + to uncover the optimal parameters for maximally diffusive coatings. We find a correlation between the low proximity of Li + to Al 3+ and the low Li + migration barrier. Although barriers are the lowest in the highly diffusive one-dimensional channels of crystalline θ-Al 2 O 3 , the system is structurally delicate and subject to detrimental distortion as the Li + content is increased. The α-Al 2 O 3 lattice is, conversely, highly stable against distortion at all Li + concentrations but disadvantageous for Li + migration. In amorphous systems, unscreened Li + –Li + Coulomb repulsion and pre-emptive occupation of “trapping sites” combine to lower the energy barriers as a function of increasing concentration. One of our most important findings is that Al-deficient materials can sharply increase Li + movement, and we predict that an amorphous material with a combination of high Li + concentration and Al deficiency would enable highly Li + -conductive protective coatings for electrodes.
Air-Stable Direct Bandgap Perovskite Semiconductors: All-Inorganic Tin-Based Heteroleptic Halides A x SnCl y I z (A = Cs, Rb)
Semiconducting halide perovskites are a group of materials with exciting photoelectronic properties. Compared to the widely studied hybrid organic–inorganic perovskites, the all-inorganic derivatives are less well understood even as they promise high inherent stability. At the moment, such materials are limited due to the fact that there is a very narrow choice of inorganic cations that can stabilize the desirable perovskite structure. Herein we report on the synthesis and characterization of novel all-inorganic tin-based perovskites and perovskitoids that can be stabilized by the heteroleptic coordination of chloride and iodide anions, Cs 2 SnCl 2 I 2 ( 1 ) and Cs 2.38 Rb 1.62 Sn 3 Cl 8 I 2 ( 2 ), consist of two-dimensional (2D) layers of [SnCl 4 I 2 ] 4– octahedra with different connectivity modes. Compound 1 is an n = 1 Ruddlesden–Popper type perovskite adopting the tetragonal archetype structure ( I 4/ mmm space group; a = 5.5905(3) Å, c = 18.8982(13) Å), while compound 2 crystallizes as an orthorhombic modification ( Cmcm space group; a = 5.6730(11) Å, b = 25.973(5) Å, c = 16.587(3) Å) with corrugated layers. The crystal chemistry changes drastically when Cs + is replaced by the smaller Rb + cation which leads to the isolation of the low dimensional compounds Rb 3 SnCl 3 I 2 ( 3a ), Rb 3 SnCl 2.33 I 2.67 ( 3b ) and Rb 7 Sn 4.25 Cl 12 I 3.5 ( 4 ), thus illustrating the importance of the A-cation size in the formation of perovskites. The 2D perovskites show wide band gaps and relatively large resistivities, associated with their chemical stability against the oxidation of Sn 2+ . The chemical stability is coupled with remarkable electronic properties that derive from the perovskite structure. DFT calculations suggest that both compounds are direct band gap semiconductors with large bandwidths, consistently with the experimentally determined band gaps of E g = 2.62 and 2.81 eV for 1 and 2 , respectively. The combination of stability and favorable electronic structure in heteroleptic-halide perovskites presents a new direction toward the realization of functional devices made exclusively from inorganic perovskites.
The role of defects in Fe(II) – goethite electron transfer
Despite accumulating experimental evidence for Fe(II)-Fe(III) oxide electron transfer, computational chemical calculations suggest that oxidation of sorbed Fe(II) is not energetically feasible unless defects are present. Here we used isotope specific 57Fe Mössbauer spectroscopy to investigate whether Fe(II)-goethite electron transfer is influenced by defects. Specifically, we heated the mineral to try to anneal the goethite surface and ground goethite to try to create defects. We found that heating goethite results in less oxidation of sorbed Fe(II) by goethite. When goethite was re-ground after heating, electron transfer was partially restored. X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) of heated and ground goethite confirm that heating and grinding alter the surface structure of the goethite. We propose that the heating process annealed the surface and decreased the number of sites where electron transfer could occur. Our experimental findings suggest that surface defects play an important role in Fe(II)-goethite electron transfer as suggested by computational calculations. Our finding that defects influence heterogeneous Fe(II)-goethite electron transfer has important implications for Fe(II) driven recrystallization of Fe oxides, as well as X and Y.
Canting of the Magnetic Moments on the Octahedral Site of an Iron Oxide Garnet in Response to Diamagnetic Cation Substitution
Using neutron powder diffraction and magnetic susceptibility measurements, we report on the preparation and characterization of the temperature- and field-dependent properties of CaY2ZrFe4O12, a composition closely related to the high-temperature ferrimagnet Y3Fe5O12. By diluting the concentration of paramagnetic ions on the octahedral sublattice of the garnet structure, we find temperature-dependent canting of the magnetic moments. This reflects the importance of the octahedral sublattice in mediating the magnetic interactions between the tetrahedral sites and offers insight into a large number of competing magnetic interactions in the garnet structure.
Discovery of MK-4688: an Efficient Inhibitor of the HDM2?p53 Protein?Protein Interaction
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Discovery of Potent, Selective, and Peripherally Restricted Pan-Trk Kinase Inhibitors for the Treatment of Pain
Abstract not provided
Uncovering the Local Magnesium Environment in the Metal–Organic Framework Mg 2 (dobpdc) Using 25 Mg NMR Spectroscopy
The incorporation of N,N'-dimethylethylenediamine into an expanded MOF-74 framework has yielded a material (mmen-Mg2(dobpdc)) exhibiting “step-shaped” CO2 adsorption isotherms. The coordination of mmen at the Mg open metal center is essential for the unique cooperative adsorption mechanism elucidated for this material. Despite its importance for carbon capture, there is as yet no experimental structure determination available for the underlying metal– organic framework Mg2(dobpdc). Our 25Mg solid-state NMR data unravel the local Mg environments in several Mg2(dobpdc) samples, unambiguously confirming the formation of fivecoordinate Mg centers in the activated material and six-coordinate Mg centers in the solvent- or diamine-loaded samples, such as mmen-Mg2(dobpdc). A fraction of the Mg centers are locally disordered due to the framework deformation accompanied by the guest distributions and dynamics.
Acetic Acid Adsorption and Reactions on Ni(110)
Acetic acid adsorption and reactions at multiple surface coverage values on Ni(110) were studied with temperature-programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS) at 90–500 K. The experimental measurements were interpreted with density functional theory (DFT) calculations that provided information on adsorbate geometries, energies, and vibrational modes. Below the monolayer saturation coverage of 0.36 ML at 90 K, acetic acid adsorbs mostly molecularly. Above this coverage, a physisorbed layer is formed with dimers and catemers, without detectable monomers. Dimers and catemers desorb as molecular acetic acid at 157 and 172 K, respectively. Between 90 and 200 K, the O–H bond in acetic acid breaks to form bridge-bonded bidentate acetate that becomes the dominant surface species. Desorption-limited hydrogen evolution is observed at 265 K. However, even after the acetate formation, acetic acid desorbs molecularly at 200–300 K due to recombination. Minor surface species observed at 200 K, acetyls or acetates with a carbonyl group, decompose below 350 K and generate adsorbed carbon monoxide. At 350 K, the surface likely undergoes restructuring, the extent of which increases with acetic acid coverage. The initial dominant bridge-bonded bidentate acetate species formed below 200 K remain on the surface, but they now mostly adsorb on the restructured sites. Here, the acetates and all other remaining hydrocarbon species decompose simultaneously at 425 K in a narrow temperature range with concurrent evolution of hydrogen, carbon monoxide, and carbon dioxide. Above 425 K, only carbon remains on the surface.