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  • 1
    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
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  • 2
    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
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  • 3
    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
    Publication Date: 2017-12-29
    Description: Recent climatic warming and associated glacial retreat may have a large impact on sediment release and transfer in Alpine river basins. Concurrently, the sediment transport capacity of many European Alpine streams is affected by hydropower exploitation, notably where flow is abstracted but the sediment supply downstream is maintained. Here, we investigate the combined effects of climate change and flow abstraction on morphodynamics and sediment transfer in the Borgne River, Switzerland. From photogrammetrically derived historical Digital Elevation Models (DEMs) we find considerable net aggradation of the braided river bed (up to 5 meters) since the onset of flow abstraction in 1963. Reaches responded through bed level steepening which was strongest in the upper most reach. Widespread aggradation however did not commence until the onset of glacier retreat in the late 1980s and the dry and warm years of the early 1990s. Upstream flow intake data shows that this aggradation coincided with an increase in sediment supply, although aggradation accounts for no more than 25% of supplied material. The remainder was transferred through the studied reaches. Estimations of bed load transport capacity indicate that flow abstraction reduces transport capacity by 1-2 orders of magnitude. Whilst residual transport rates vary with morphological evolution, they are in the same order of magnitude as the sediment supply rates, which is why significant transport remains. However, the reduction in transport capacity makes the system more sensitive to short-term (annual) changes in climate-driven hydrological variability and climate-induced changes in intake management and sediment delivery rates.
    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
    Publication Date: 2019
    Description: 〈p〉The human impact on life on Earth has increased sharply since the 1970s, driven by the demands of a growing population with rising average per capita income. Nature is currently supplying more materials than ever before, but this has come at the high cost of unprecedented global declines in the extent and integrity of ecosystems, distinctness of local ecological communities, abundance and number of wild species, and the number of local domesticated varieties. Such changes reduce vital benefits that people receive from nature and threaten the quality of life of future generations. Both the benefits of an expanding economy and the costs of reducing nature’s benefits are unequally distributed. The fabric of life on which we all depend—nature and its contributions to people—is unravelling rapidly. Despite the severity of the threats and lack of enough progress in tackling them to date, opportunities exist to change future trajectories through transformative action. Such action must begin immediately, however, and address the root economic, social, and technological causes of nature’s deterioration.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2016-04-28
    Description: Recent geological studies demonstrate that the Isthmus of Panama emerged some 10 m.y. earlier than previously assumed. Although absent today in Panama, Central American savanna environments likely developed in connection with the onset of Northern Hemisphere glaciations. As is widely recognized, most of the mammals crossing the isthmus since 2.5 Ma lived in savannas. Could climate-induced vegetational changes across Panama explain the delayed migration of mammals, rather than terrestrial connectivity? We investigate the congruence between cross-continental mammal migration and climate change through analysis of fossil data and molecular phylogenies. Evidence from fossil findings shows that the vast majority of mammals crossed between South and North America after ca. 3 Ma. By contrast, dated mammal phylogenies suggest that migration events started somewhat earlier, ca. 4–3 Ma, but allowing for biases toward greater ages of molecular than geologic dating and uncertainties in the former, we consider this age range not to be significantly earlier than 3 Ma. We conclude that savanna-like environments developed in response to the vast Laurentide ice sheet at the first Quaternary glaciation triggered the initiation of the Great American Biotic Interchange in mammals.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 7
    Publication Date: 2017-08-11
    Description: A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.
    Keywords: Geochemistry, Geophysics
    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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  • 8
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2017-06-15
    Description: O’Dea et al . challenged the inference that the Isthmus of Panama has been in place for the last 10 million years or more and from "an exhaustive review and reanalysis of geological, paleontological, and molecular records," they argued for a "formation of the Isthmus of Panama sensu stricto around 2.8 Ma." I review environmental changes since ~5 Ma throughout Earth, and I argue that environmental changes in the Central American-Caribbean region have been part of a concurrent, worldwide phenomenon that requires a global, not local, explanation. Accordingly, evidence of environmental change from the Central American-Caribbean region does not implicate the emergence of the Isthmus of Panama.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 9
    Publication Date: 2016-12-02
    Description: Surface ruptures found east of the high peak of Bukadaban that formed during the 2001 Kunlun earthquake reveal a minor northeast–southwest-trending graben, across which oblique approximately east–west extension occurred. Scarps along the southeast flank of the graben indicate vertical components of slip of 3–4 m, and left steps in the trace suggest a component of left-lateral slip. Scarps on the northwest flank show vertical components of only ~1.5??m; east–west-trending ridges in the flanking footwall and hanging wall imply north–south shortening and therefore also a component of left-lateral slip. These observations corroborate the inference made by others that Bukadaban, though 〉6000??m high, lies within or adjacent to an active pull-apart basin between two major strike-slip segments oriented ~N100°E.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 10
    Publication Date: 2015-11-18
    Description: An application of a simple hydrological model to likely climatic conditions of Lake Sambhar provides tighter bounds on the range of increased precipitation seen during the early- to mid-Holocene than those inferred from paleoclimatic proxies. To examine past lake levels, we developed a simple lake model, based on hydrological principles of a watershed balance between precipitation, evaporation, and runoff from the watershed to calculate daily depth and volume. Calculations reveal that early- to mid-Holocene rainfall was most likely in a range of 40–65% greater than present levels, resulting in lake depths of ~6–8 m. This estimate incorporates all major sources of uncertainty into the lake model, but it is likely that the value of mid-Holocene precipitation lies in the lower part of the 40–65% range. Additionally, a 40–65% greater precipitation could have led to greater interannual variability in lake levels, which may account for the lack of clear shorelines. We find, however, that it is unlikely that Lake Sambhar filled to its maximum depth of 21 m above the present-day lakebed during this period due both to the much greater precipitation than today required to maintain a lake of such depth (greater than double present-day precipitation) and to the lack of current evidence (no shorelines and little vegetation). We also find that differences between mid-Holocene and present-day winter insolation alone have virtually no effect on average annual lake depths.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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