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  • 1
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    Three-dimensional textural and quantitative analyses of orogenic gold at the nanoscale (2016)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2016-08-23
    Description: Ore textures provide direct clues for tracking ore-forming processes. In this regard, most of our knowledge is generally based on two-dimensional (2-D) image analyses, leaving a considerable gap in comprehending three-dimensional (3-D) in-situ textural settings. Recent advances in lab-based and synchrotron radiation–based X-ray computed microtomography and nanotomography have made it possible to visualize and quantify rock volumes in a 3-D space. In this study, we first analyzed microscale textures in oriented drill cores from the world-class Suurikuusikko orogenic gold deposit of northern Finland using lab-based X-ray computed microtomography. The technique revealed a kinematic history and a number of in-situ 3-D quantitative aspects including size, shape, spatial distribution, and geometrical orientation of arsenopyrite and pyrite in a highly altered host-rock matrix. For 3-D nanotomography, the experimental procedure known as holotomography was adopted. Individual arsenopyrite crystals were separated and scanned with voxel sizes ranging from 50 nm to 150 nm using the X-ray nanoprobe beamline (ID16B) at the European Synchrotron Radiation Facility, France. This ultrahigh-resolution technique illustrated the 3-D distribution of micron- to nanoscale gold inclusions, mostly associated with primary rutile or along secondary microfractures inside arsenopyrite. The workflow, from micro- to nanotomography, outlined in this study offers an indispensable new technique in quantifying and characterizing 3-D textural settings of ores, which is otherwise impossible with conventional 2-D imaging devices. The method can also be highly useful in evaluating the amenability of ores to treatment with different processing options.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 2
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    Design of an {alpha}-L-transfucosidase for the synthesis of fucosylated HMOs (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-03
    Description: Human milk oligosaccharides (HMOs) are recognized as benefiting breast-fed infants in multiple ways. As a result, there is growing interest in the synthesis of HMOs mimicking their natural diversity. Most HMOs are fucosylated oligosaccharides. α- l -Fucosidases catalyze the hydrolysis of α- l -fucose from the non-reducing end of a glucan. They fall into the glycoside hydrolase GH29 and GH95 families. The GH29 family fucosidases display a classic retaining mechanism and are good candidates for transfucosidase activity. We recently demonstrated that the α- l -fucosidase from Thermotoga maritima ( Tm αFuc) from the GH29 family can be evolved into an efficient transfucosidase by directed evolution ( Osanjo et al. 2007 ). In this work, we developed semi-rational approaches to design an α- l -transfucosidase starting with the α- l -fucosidase from commensal bacteria Bifidobacterium longum subsp. infantis ( Bi AfcB, Blon_2336). Efficient fucosylation was obtained with enzyme mutants (L321P- Bi AfcB and F34I/L321P- Bi AfcB) enabling in vitro synthesis of lactodifucotetraose, lacto- N -fucopentaose II, lacto- N -fucopentaose III and lacto- N -difucohexaose I. The enzymes also generated more complex HMOs like fucosylated para -lacto- N -neohexaose (F- p -LNnH) and mono- or difucosylated lacto- N -neohexaose (F-LNnH-I, F-LNnH-II and DF-LNnH). It is worth noting that mutation at these two positions did not result in a strong decrease in the overall activity of the enzyme, which makes these variants interesting candidates for large-scale transfucosylation reactions. For the first time, this work provides an efficient enzymatic method to synthesize the majority of fucosylated HMOs.
    Print ISSN: 0959-6658
    Electronic ISSN: 1460-2423
    Topics: Biology , Medicine
    Published by Oxford University Press
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  • 3
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    Spatial variability in specific discharge and streamwater chemistry during low flows: results from snapshot sampling campaigns in eleven Swiss catchments (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Catchments consist of distinct landforms that affect the storage and release of subsurface water. Certain landforms may be the main contributors to streamflow during extended dry periods and these may vary for different catchments in a given region. We present a unique dataset from snapshot field campaigns during low‐flow conditions in eleven catchments across Switzerland to illustrate this. The catchments differed in size (10 to 110 km2), varied from predominantly agricultural lowlands to Alpine areas, and covered a range of physical characteristics. During each snapshot campaign, we jointly measured streamflow and collected water samples for the analysis of major ions and stable water isotopes. For every sampling location (basin), we determined several landscape characteristics from national geo‐datasets, including drainage area, elevation, slope, flowpath length, dominant land use, and geological and geomorphological characteristics, such as the lithology and fraction of Quaternary deposits. The results demonstrate very large spatial variability in specific low‐flow discharge and water chemistry: neighboring sampling locations could differ significantly in their specific discharge, isotopic composition and ion concentrations, indicating that different sources contribute to streamflow during extended dry periods. However, none of the landscape characteristics that we analyzed could explain the spatial variability in specific discharge or stream water chemistry in multiple catchments. This suggests that local features determine the spatial differences in discharge and water chemistry during low‐flow conditions and that this variability cannot be assessed a priori from available geodata and statistical relations to landscape characteristics. The results furthermore suggest that measurements at the catchment outlet during low‐flow conditions do not reflect the heterogeneity of the different source areas in the catchment that contribute to streamflow.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 4
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    A probabilistic sediment cascade model of sediment transfer in the Illgraben (2014)
    Wiley
    Details
    Publication Date: 2014-01-23
    Description: We present a probabilistic sediment cascade model to simulate sediment transfer in a mountain basin (Illgraben, Switzerland) where sediment is produced by hillslope landslides and rockfalls and exported out of the basin by debris flows and floods. The model conceptualizes the fluvial system as a spatially lumped cascade of connected reservoirs representing hillslope and channel storages where sediment goes through cycles of storage and remobilization by surface runoff. The model includes all relevant hydrological processes that lead to runoff formation in an Alpine basin, such as precipitation, snow accumulation, snow melt, evapotranspiration, and soil water storage. Although the processes of sediment transfer and debris flow generation are described in a simplified manner, the model produces complex sediment discharge behavior which is driven by the availability of sediment and antecedent wetness conditions (system memory) as well as the triggering potential (climatic forcing). The observed probability distribution of debris flow volumes and their seasonality in 2000-2009 are reproduced. The stochasticity of hillslope sediment input is important for reproducing realistic sediment storage variability, although many details of the hillslope landslide triggering procedures are filtered out by the sediment transfer system. The model allows us to explicitly quantify the division into transport and supply-limited sediment discharge events. We show that debris flows may be generated for a wide range of rainfall intensities because of variable antecedent basin wetness and snowmelt contribution to runoff, which helps to understand the limitations of methods based on a single rainfall threshold for debris flow initiation in Alpine basins.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    On basal-prismatic twinning interfaces in magnesium (2014)
    Institute of Physics (IOP)
    Details
    Publication Date: 2014-08-09
    Description: The existence of basal-prismatic interfaces and their roles in twinning of hexagonal materials have recently attracted appreciable attention of scientific community. In this paper, we utilize molecular statics to investigate the formation of basal-prismatic facets in the ##IMG## [http://ej.iop.org/images/1757-899X/63/1/012134/mse14_63_012034.jpg] {10bar12} twin boundary of magnesium. This interface is shown to be the consequence of a collective motion and interaction of twinning disconnections. By analyzing volume deformations caused by the migration of a single basal-prismatic interface, we show that the passage of this interface distorts the material equivalently to twinning shear.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 6
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    Earthquakes. Himalayan seismic hazard (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-08-25
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bilham, R -- Gaur, V K -- Molnar, P -- New York, N.Y. -- Science. 2001 Aug 24;293(5534):1442-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences and the Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA. bilham@colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11520972" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Continuous deformation versus faulting through the continental lithosphere of new zealand (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-10-16
    Description: Seismic anisotropy and P-wave delays in New Zealand imply widespread deformation in the underlying mantle, not slip on a narrow fault zone, which is characteristic of plate boundaries in oceanic regions. Large magnitudes of shear-wave splitting and orientations of fast polarization parallel to the Alpine fault show that pervasive simple shear of the mantle lithosphere has accommodated the cumulative strike-slip plate motion. Variations in P-wave residuals across the Southern Alps rule out underthrusting of one slab of mantle lithosphere beneath another but permit continuous deformation of lithosphere shortened by about 100 kilometers since 6 to 7 million years ago.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Molnar -- Anderson -- Audoine -- Eberhart-Phillips -- Gledhill -- Klosko -- McEvilly -- Okaya -- Savage -- Stern -- Wu -- New York, N.Y. -- Science. 1999 Oct 15;286(5439):516-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Quaternary Research Center and Geophysics Program, University of Washington, Seattle, WA, 98195-1360, USA, and Department of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, US.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10521344" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Comment on "Slip-rate measurements on the Karakorum Fault may imply secular variations in fault motion" (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-08-27
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brown, Erik T -- Molnar, Peter -- Bourles, Didier L -- New York, N.Y. -- Science. 2005 Aug 26;309(5739):1326; author reply 1326.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Large Lakes Observatory and, Department of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, USA. etbrown@d.umn.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16123287" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Thinning and flow of Tibetan crust constrained by seismic anisotropy (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-07-13
    Description: Intermediate-period Rayleigh and Love waves propagating across Tibet indicate marked radial anisotropy within the middle-to-lower crust, consistent with a thinning of the middle crust by about 30%. The anisotropy is largest in the western part of the plateau, where moment tensors of earthquakes indicate active crustal thinning. The preferred orientation of mica crystals resulting from the crustal thinning can account for the observed anisotropy. The middle-to-lower crust of Tibet appears to have thinned more than the upper crust, consistent with deformation of a mechanically weak layer that flows as if confined to a channel.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shapiro, Nikolai M -- Ritzwoller, Michael H -- Molnar, Peter -- Levin, Vadim -- New York, N.Y. -- Science. 2004 Jul 9;305(5681):233-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Imaging the Earth's Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO 80309, USA. nshapiro@ciei.colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15247475" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Jack oliver (1923-2011) (2011)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2011-02-11
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Molnar, Peter -- England -- Nature. 2011 Feb 10;470(7333):176. doi: 10.1038/470176a.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences at the University of Colorado in Boulder, Colorado 80309, USA. peter.molnar@colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21307924" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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