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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2438-2445 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used the large electric fields at the interface of a Pt(111) electrode and an acetonitrile electrolyte solution to tune the interaction between adsorbed CO and the Pt(111) surface. The electrode potential is varied over a 2.5 Volt range. As the electrode potential is made more positive, the CO vibrational frequency increases and the vibrational lifetime decreases. Over the potential range investigated, the tuning is about 35–40 cm−1 and the lifetime varies from ≈2.1 to ≈1.5 ps. Ab initio calculations performed for CO/Cu(100) predicted the opposite trend for the lifetimes for that system [M. Head-Gordon and J. C. Jully, Chem. Phys. 175, 37 (1993)]. Within an empirical model of nonadiabatic charge transfer [B. N. J. Persson and M. Persson, Solid State Commun. 36, 175 (1980)], our observations can be explained by a decreasing 2π-derived density of states of the Pt/CO complex at the Fermi level. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Glycine max (L.) Merr.] root infection by [Fusarium solani (Mart.) Sacc. F. sp. glycine (Burk.)] (Rfs1), sudden death syndrome (SDS), and soybean cyst nematode (SCN; Heterodera glycines Ichinohe; Rhg4 and rhg1) were previously identified in 'Essex' × 'Forrest'. This study tests the effectiveness of those markers in selecting for disease resistance among recombinant inbred lines from 'Flyer' × 'Hartwig'. A total of 535 among 739 lines were scored by two markers, providing four genotypes. A stratified random sample of 50 lines was evaluated for SDS by F. solani root infection severity at two locations and SCN race 3 index of parasitism in the greenhouse. Selection with BLT65 identified 281 among 671 lines with the genomic region that underlies Rhg4-derived SCN resistance. Selection with Satt038 identified 230 among 613 lines containing the genomic region that underlies resistance to SDS (rfs1) and rfg1-derived SCN resistance. A total of 93 out of 535 lines had genomic regions that underlie resistance to both SDS and SCN in Essex × Forrest. Segregation of both markers was not random (P ≤ 0.05). Infection severity means for genotypes with the Hartwig allele at Satt038 (28-29%) were lower (P = 0.0001, R2 = 28%) than with the Flyer allele (31-42%); irrespective of maturity group. BLT65 was not associated with infection severity. Mean SCN index of parasitism was lower (P ≤ 0.05) only for genotypes carrying the Hartwig allele at both Satt038 and BLT65. Therefore, alleles conferring resistance to SDS and SCN in Essex × Forrest are transferable to other populations.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2017-06-02
    Description: In 2012, NASA’s Curiosity rover landed on Mars to assess its potential as a habitat for past life and investigate the paleoclimate record preserved by sedimentary rocks inside the ~150-kilometer-diameter Gale impact crater. Geological reconstructions from Curiosity rover data have revealed an ancient, habitable lake environment fed by rivers draining into the crater. We synthesize geochemical and mineralogical data from lake-bed mudstones collected during the first 1300 martian solar days of rover operations in Gale. We present evidence for lake redox stratification, established by depth-dependent variations in atmospheric oxidant and dissolved-solute concentrations. Paleoclimate proxy data indicate that a transition from colder to warmer climate conditions is preserved in the stratigraphy. Finally, a late phase of geochemical modification by saline fluids is recognized.
    Keywords: Geochemistry, Geophysics, Online Only, Planetary Science
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2016-06-24
    Description: The presence of potential microbial trace fossils (endolithic microborings) has been well documented in oceanic basaltic pillow lavas, hyaloclastites, tuffs, and transitional subglacial marine lavas in the past 30 yr. Despite their evident abundance in oceanic to subglacial environments, they have not been observed in continental basalts that were not erupted in marine or subglacial settings. To expand the record of putative endolithic microborings in volcanic rocks to nonmarine, continental lacustrine environments, we examined hydrovolcanic pyroclastic deposits in the Fort Rock volcanic field, central Oregon. This study presents the textures, mineralogy, and geochemistry of basaltic tuffs containing possible endolithic microborings comparable in morphology, size, and distribution to those described in earlier oceanic and subglacial basalt studies. We observed a variety of tubular and granular textures that show evidence of biogenic morphologies and behavior, and a primary geological context that expresses their age and syngenicity. Petrographic relationships with secondary phases (chabazite, nontronite, calcite) indicate that the construction of microtunnels occurred in saline, alkaline fluids at temperatures of 25–80 °C. In addition, positive correlations were observed between the extent of aqueous (abiotic) alteration and both the abundance of microtunnels and morphological type. These correlations suggest that microtunnels were more readily formed where there was greater abiotic alteration-fluid flux and that the resulting change in chemical composition of those fluids may have had a direct influence on the formation process or possibly the type of constructing microbe. This work adds to understanding of factors controlling microtunnel formation and is the first account of putative endolithic microborings in a continental lacustrine setting. This new information may also have implications in the search for habitable extraterrestrial environments, such as on Mars.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
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  • 5
    Publication Date: 2011-02-23
    Description: The deep crustal magmatic history of arc volcanoes is obscured by diversity in mantle inputs, modest isotopic contrast between magma and wall-rock, and overprinting processes in the middle and upper crust. To identify and quantify processes in the deep arc crust, we investigated the evolution of the mafic composite North Sister Volcano, the oldest and most mafic of the Three Sisters Volcanic Field of the central Oregon Cascade arc. Here, intra-arc extension limits the degree of magma interaction with the mid- to upper crust and the range in primitive magmas delivered from the mantle is known. North Sister Volcano has produced low-K basaltic andesitic magmas (0·5–0·8 wt % K 2 O) for ~400 kyr during four central-vent eruptive stages and along the late, 11 km long Matthieu Lakes Fissure. Although restricted in bulk composition (53–55 wt % SiO 2 ), North Sister basaltic andesites from different stages cluster into elemental and isotopic groups. Over time, North Sister basaltic andesites generally have decreasing compatible elements, such as Ni (from 112 to 40 ppm), and increasing Al 2 O 3 and TiO 2 . Concurrently, incompatible elements remain the same or decrease (e.g. from 302 to 247 ppm Ba). Isotopic variations at North Sister are small, but systematically progress toward more mantle-like ratios with time; 87 Sr/ 86 Sr decreases (from 0·70369 to 0·70356), and 144 Nd/ 143 Nd increases (from 0·51285 to 0·51292). We present a multi-stage petrological model for the evolution of North Sister magmas to account for: (1) the generation of low-K basaltic andesite; (2) geochemical variations within the eruptive stages; (3) evolution of the magma system over time to more mantle-like compositions. The earliest and most isotopically ‘crust-like’ (highest 87 Sr/ 86 Sr and lowest 143 Nd/ 144 Nd) North Sister magma is consistent with two-component mixing of regionally typical mantle-derived, low-K tholeiites with partial melts of the crust. Crustal melts must be high in SiO 2 and Al 2 O 3 , and most probably result from low-degree melting of plagioclase–clinopyroxene amphibole-bearing gabbro at high pressure. Variations in highly compatible elements within compositional groups (e.g. 60 ppm Ni within a single group) reflect fractionation of plagioclase, olivine, and clinopyroxene and recharge by more primitive basaltic andesite that overprint longer-term variations between groups. To understand the evolution of the North Sister basaltic andesite magmas through time, we use an energy-constrained model that balances assimilation of refractory gabbroic wall-rocks and abundant recharge by mantle-derived low-K tholeiites. These complementary processes allow Sr and Nd isotopic ratios to become more like those of the regional basalts while maintaining high Ni concentrations. Low-K basaltic andesites like those of North Sister Volcano are found along the Oregon Cascade arc and they imply that low-K tholeiitic magmas interact with a refractory mafic underplate along its length. Dominantly basaltic andesite volcanoes are common in arcs and provide insight into the extensive, albeit compositionally cryptic mafic underplating and intraplating that affects arc crust.
    Print ISSN: 0022-3530
    Electronic ISSN: 1460-2415
    Topics: Geosciences
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  • 6
    Publication Date: 2013-01-12
    Description: Palmitoylation, the dynamic post-translational addition of the lipid, palmitate, to proteins by Asp-His-His-Cys-containing palmitoyl acyltransferase (PAT) enzymes, modulates protein function and localization and plays a key role in the nervous system. Huntingtin-interacting protein 14 (HIP14), a well-characterized neuronal PAT, has been implicated in the pathogenesis of Huntington disease (HD), a fatal neurodegenerative disease associated with motor, psychiatric and cognitive symptoms, caused by a CAG expansion in the huntingtin gene ( HTT ). Mice deficient for Hip14 expression develop neuropathological and behavioural features similar to HD, and the catalytic activity of HIP14 is impaired in HD mice, most likely due to the reduced interaction of HIP14 with HTT. Huntingtin-interacting protein 14-like (HIP14L) is a paralog of HIP14, with identical domain structure. Together, HIP14 and HIP14L are the major PATs for HTT. Here, we report the characterization of a Hip14l -deficient mouse model, which develops adult-onset, widespread and progressive neuropathology accompanied by early motor deficits in climbing, impaired motor learning and reduced palmitoylation of a novel HIP14L substrate: SNAP25. Although the phenotype resembles that of the Hip14 –/– mice, a more progressive phenotype, similar to that of the YAC128 transgenic mouse model of HD, is observed. In addition, HIP14L interacts less with mutant HTT than the wild-type protein, suggesting that reduced HIP14L-dependent palmitoylation of neuronal substrates may contribute to the pathogenesis of HD. Thus, both HIP14 and HIP14L may be dysfunctional in the disease.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2014-07-05
    Description: HIP14 is the most highly conserved of 23 human palmitoyl acyltransferases (PATs) that catalyze the post-translational addition of palmitate to proteins, including huntingtin (HTT). HIP14 is dysfunctional in the presence of mutant HTT (mHTT), the causative gene for Huntington disease (HD), and we hypothesize that reduced palmitoylation of HTT and other HIP14 substrates contributes to the pathogenesis of the disease. Here we describe the yeast two-hybrid (Y2H) interactors of HIP14 in the first comprehensive study of interactors of a mammalian PAT. Unexpectedly, we discovered a highly significant overlap between HIP14 interactors and 370 published interactors of HTT, 4-fold greater than for control proteins ( P = 8 x 10 –5 ). Nearly half of the 36 shared interactors are already implicated in HD, supporting a direct link between HIP14 and the disease. The HIP14 Y2H interaction set is significantly enriched for palmitoylated proteins that are candidate substrates. We confirmed that three of them, GPM6A, and the Sprouty domain-containing proteins SPRED1 and SPRED3, are indeed palmitoylated by HIP14; the first enzyme known to palmitoylate these proteins. These novel substrates functions might be affected by reduced palmitoylation in HD. We also show that the vesicular cargo adapter optineurin, an established HTT-binding protein, co-immunoprecipitates with HIP14 but is not palmitoylated. mHTT leads to mislocalization of optineurin and aberrant cargo trafficking. Therefore, it is possible that optineurin regulates trafficking of HIP14 to its substrates. Taken together, our data raise the possibility that defective palmitoylation by HIP14 might be an important mechanism that contributes to the pathogenesis of HD.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 8
    Publication Date: 2019-07-19
    Description: The Mars Science Laboratory rover Curiosity has traversed up section through approximately 100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation unconformably overlies a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Unaltered Stimson sandstone has a basaltic composition similar to the average Mars crustal composition, but is more variable and ranges to lower K and higher Al. Fluids passing through alteration "halos" adjacent to fractures have altered the chemistry and mineralogy of the sandstone. Elemental mass gains and losses in the alteration halos were quantified using immobile element concentrations, i.e., Ti (taus). Alteration halos have elemental gains in Si, Ca, S, and P and large losses in Al, Fe, Mn, Mg, Na, K, Ni, and Zn. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes. The igneous phases were less abundant in the altered sandstone with a lower pyroxene/plagioclase feldspar. Large elemental losses suggest acidic fluids initially removed these elements (Al mobile under acid conditions). Enrichments in Si, Ca, and S suggest secondary fluids (possibly alkaline) passed through these fractures leaving behind X-ray amorphous Si and Ca-sulfates. The mechanism for the large elemental gains in P is unclear. The geochemistry and mineralogy of the altered sandstone suggests a complicated diagenetic history with multiple episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-37384 , AGU Fall Meeting 2016; Dec 12, 2016 - Dec 16, 2016; San Francisco, CA; United States
    Format: application/pdf
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  • 9
    Publication Date: 2019-07-13
    Description: Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.
    Keywords: Exobiology
    Type: GSFC-E-DAA-TN21724 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 343; 6169; 1244734
    Format: text
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  • 10
    Publication Date: 2019-07-13
    Description: The Curiosity Rover landed in a lithologically and geochemically diverse region of Mars. We present a recommended rock classification framework based on terrestrial schemes, and adapted for the imaging and analytical capabilities of MSL as well as for rock types distinctive to Mars (e.g., high Fe sediments). After interpreting rock origin from textures, i.e., sedimentary (clastic, bedded), igneous (porphyritic, glassy), or unknown, the overall classification procedure (Fig 1) involves: (1) the characterization of rock type according to grain size and texture; (2) the assignment of geochemical modifiers according to Figs 3 and 4; and if applicable, in depth study of (3) mineralogy and (4) geologic/stratigraphic context. Sedimentary rock types are assigned by measuring grains in the best available resolution image (Table 1) and classifying according to the coarsest resolvable grains as conglomerate/breccia, (coarse, medium, or fine) sandstone, silt-stone, or mudstone. If grains are not resolvable in MAHLI images, grains in the rock are assumed to be silt sized or smaller than surface dust particles. Rocks with low color contrast contrast between grains (e.g., Dismal Lakes, sol 304) are classified according to minimum size of apparent grains from surface roughness or shadows outlining apparent grains. Igneous rocks are described as intrusive or extrusive depending on crystal size and fabric. Igneous textures may be described as granular, porphyritic, phaneritic, aphyric, or glassy depending on crystal size. Further descriptors may include terms such as vesicular or cumulate textures.
    Keywords: Geophysics
    Type: JSC-CN-32866 , Lunar and Planetary Science Conference; Mar 16, 2015 - Mar 20, 2015; The Woodlands, TX; United States
    Format: application/pdf
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