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  • 1
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    Mapping the effectiveness of nature‐based solutions for climate change adaptation (2020)
    Wiley
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    Publication Date: 2020-09-09
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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  • 2
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    Condition, not eyespan, predicts contest outcome in female stalk-eyed flies, Teleopsis dalmanni (2015)
    Wiley
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    Publication Date: 2015-04-10
    Description: In contests among males, body condition is often the key determinant of a successful outcome, with fighting ability signaled by so-called armaments, that is, exaggerated, condition-dependent traits. However, it is not known whether condition and exaggerated traits function in the same way in females. Here, we manipulated adult condition by varying larval nutrition in the stalk-eyed fly, Teleopsis dalmanni , a species in which eyespan is exaggerated in both sexes, and we measured the outcome of contests between females of similar or different body condition and relative eyespan. We found that females in higher condition, with both larger bodies and eyespan, won a higher proportion of encounters when competing against rivals of lower condition. However, when females were of equal condition, neither eyespan nor body length had an effect on the outcome of a contest. An analysis of previously published data revealed a similar pattern in males: individuals with large relative eyespan did not win significantly more encounters when competing with individuals of a similar body size. Contrary to expectations, and to previous findings in males, there was no clear effect of differences in body size or eyespan affecting contest duration in females. Taken together, our findings suggest that although eyespan can provide an honest indicator of condition, large eyespans provide no additional benefit to either sex in intrasexual aggressive encounters; body size is instead the most important factor. Condition determines the outcome of intrasexual competition in female stalk-eyed flies ( Teleopsis dalmanni ). In addition, we find that an exaggerated condition-dependent trait (eyespan), which has previously been thought to be a better predictor of contest outcome in male stalk-eyed flies, does not provide any additional benefit to either sex in intrasexual competition.
    Electronic ISSN: 2045-7758
    Topics: Biology
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  • 3
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    Dy3+-Doped Selenide Chalcogenide Glasses: Influence of Dy3+ Dopant-Additive and Containment (2016)
    Wiley
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    Publication Date: 2016-04-06
    Description: This work reports on process-induced impurities in rare-earth ion: Dy 3+ -doped selenide chalcogenide glasses, which are significant materials for active photonic devices in the mid-infrared region. In particular, the effect of contamination from the silica glass ampoule containment used in chalcogenide glass synthesis is studied. Heat-treating Dy-foil-only, and DyCl 3 -only, separately, within evacuated silica glass ampoules gives direct evidence of silica ampoule corrosion by the rare-earth additives. The presence of [Ga 2 Se 3 ] associated with [Dy] on the silica glass ampoule that has been contact with the chalcogenide glass during glass melting, is reported for the first time. Studies of 0–3000 ppmw Dy 3+ -doped Ge 16.5 As 9 Ga 10 Se 64.5 glasses show that Dy-foil is better than DyCl 3 as the Dy 3+ additive in Ge-As-Ga-Se glass in aspects of avoiding bulk crystallization, improving glass surface quality and lowering optical loss. However, some limited Dy/Si/O related contamination is observed on the surfaces of Dy-foil-doped chalcogenide glasses, as found for DyCl 3 -doped chalcogenide glasses, reported in our previous work. The surface contamination indicates the production of Dy 2 O 3 and/or [≡Si-O-Dy=]-containing particles during chalcogenide glass melting, which are potential light-scattering centers in chalcogenide bulk glass and heterogeneous nucleation agents for α-Ga 2 Se 3 crystals.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
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    The Influence of Dysprosium Addition on the Crystallization Behavior of a Chalcogenide Selenide Glass Close to the Fiber Drawing Temperature (2012)
    Wiley
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    Publication Date: 2012-10-17
    Description: A series of chalcogenide glasses based on Ge 16.5 Ga 3 As 16 Se 64.5 (at.%), doped nominally with 0, 1000, 3000, and 6000 ppmw (by weight) of Dy foil, is prepared by using conventional method: melting inside a sealed silica glass ampoule, which is rocked to homogenize the melt, followed by melt quenching and annealing. Examination of the as-prepared glasses, using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), reveals that dysprosium-rich areas of devitrification have a tendency to form at the surfaces of the prepared chalcogenide glasses which have been adjacent the silica ampoule walls during the final stages of melting, quenching, and annealing; such dysprosium-rich areas of devitrification are not observed using SEM-EDX at the noncontacting-silica-ampoule chalcogenide glass surface nor in the interior of the chalcogenide glass bulk. Samples taken from the interior of the prepared glass boules exhibit an increase in glass transition of up to 9 ± 2°C, and rise in other isoviscous temperatures, with increasing dysprosium content. Extended isothermal heat treatment at the estimated fiber-drawing temperature, followed by quenching to room temperature and analysis using SEM-EDX and X-ray diffraction (XRD), is carried out to investigate the influence of dysprosium addition on crystallization behavior on reheating the chalcogenide glass. Increasing the dysprosium level, surprisingly, appears on the one hand to help to restrain crystallization of the bulk glass on glass reheating, whereas on the other hand, and at the same time, to exacerbate the surface devitrification on glass reheating. The bulk crystallizing phase on reheating the glasses is distorted face-centered cubic α- Ga 2 Se 3 . The same phase was found to grow in the bulk glass during melt cooling of Dy-doped Ge – As – Ga – Se glasses in our earlier work.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
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    Predictive, Miniature Co-Extrusion of Multilayered Glass Fiber-Optic Preforms (2015)
    Wiley
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    Publication Date: 2015-10-04
    Description: A miniature co-extrusion technique, to produce a concentric multilayered glass fiber-optic preform of ~3 mm diameter, is modeled and experimentally demonstrated. A three-dimensional, incompressible, noncavitating, and nonisothermal Computational Fluid Dynamics (CFD) model, similar to one developed in our previous work, is used to predict the dimensions of an alternating four-layer glass stack feed required to produce the desired layer dimensions in a multilayered-glass preform extrudate, using a miniaturized and thus more economical co-extrusion. Strong agreement in the cross-sectional geometrical proportions of the simulated and experimentally obtained preform supports the prowess of the predictive modeling. Nevertheless, some small deviations between the simulated and experimentally obtained dimensions indicate topics for future rheological study. Performing the co-extrusion process under vacuum helps to minimize the inter-layer defects in the multi-layered fiber-optic preform. The miniature co-extrusion potentially removes the need for a postextrusion draw-down prior to fiber drawing, avoiding devitrification issues possible in non-oxide novel glass compositions.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
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    First Identification of Rare-Earth Oxide Nucleation in Chalcogenide Glasses and Implications for Fabrication of Mid-Infrared Active Fibers (2013)
    Wiley
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    Publication Date: 2013-12-13
    Description: Gallium ( Ga ) helps solubilize rare-earth ions in chalcogenide glasses, but has been found to form the dominant crystallizing selenide phase in bulk glass in our previous work. Here, the crystallization behavior is compared of as-annealed 0–3000 ppmw Dy 3+ -doped Ge–As–Ga–Se glasses with different Ga levels: Ge 16.5 As (19− x ) Ga x Se 64.5 (at.%), for x  = 3 and 10, named Ga 3 and Ga 10 glass series, respectively. X-ray diffraction and high-resolution transmission electron microscopy are employed to examine crystals in the bulk of the as-prepared glasses, and the crystalline phase is proved to be the same: Ge-modified, face centered cubic α- Ga 2 Se 3 . Light scattering of polished glass samples is monitored using Fourier transform spectroscopy. When Ga is decreased from 10 to 3 at.%, the bulk crystallization is dramatically reduced and the optical scattering loss decreases. Surface defects, with a rough topology observed for both series of as-prepared chalcogenide glasses, are demonstrated to comprise Dy , Si , and [O]. For the first time, evidence for the proposed nucleation agent Dy 2 O 3 is found inside the bulk of as-prepared glass. This is an important result because rare-earth ions bound in a high phonon–energy oxide local environment are, as a consequence, inactive mid-infrared fluorophores because they undergo preferential nonradiative decay of excited states.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
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    Low gallium‐content, dysprosium III‐doped, Ge–As–Ga–Se chalcogenide glasses for active mid‐infrared fiber optics (2018)
    Wiley
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    Publication Date: 2018
    Description: Abstract A systematic investigation is presented, for the first time, of a 1000 ppmw (parts per million, by weight) Dy3+‐doped Ge–As–Ga–Se chalcogenide glass series, with a fixed low Ga content of 1 atomic% (at. %), suitable for active mid‐infrared fiber optics. Seven glasses constitute the series, which have increasing average coordination number from 2.49 to 2.61, in steps of 0.02, with the GeSe2, As2Se3, and Ga2Se3 stoichiometries kept. Glass formation is confirmed using X‐ray diffraction and differential scanning calorimetry. Fourier transform infrared spectroscopy is reported for the series. Parallel plate viscometry enables prediction of fiber‐drawing temperatures and, with differential thermal analysis, determines the potential for fiber fabrication. X‐ray diffraction of samples after parallel‐plate viscometry shows that Ge25As9Ga1Se65 (at. %) alone, in the glass‐series, devitrifies to form the single‐crystalline phase: monoclinic‐GeSe2; scanning electron microscope imaging suggests that this phase is both surface and bulk grown. Overall, the recommended host glass at. % compositions for doping with rare‐earth ions and drawing to active mid‐infrared fiber are: Ge17.5As18Ga1Se63.5, Ge15As21Ga1Se63, and Ge12.5As24Ga1Se62.5.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 8
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    Compositional dependence of crystallization in Ge-Sb-Se glasses relevant to optical fiber making (2017)
    Wiley
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    Publication Date: 2017-09-06
    Description: For fiber-optic mid-infrared bio- and chemical-sensing, Ge-Sb-Se glass optical fibers are more attractive than Ge-As-Se because of: (i) lowered toxicity and (ii) lower phonon energy and hence transmission to longer wavelengths, with potential to reach the spectral ‘fingerprint region’ for molecular sensing. There is little previous work on Ge-Sb-Se fibers. Here, fibers are fabricated from two glass compositions in the Ge x Sb 10 Se 90-x atomic (at.) % series. Both glass compositions are of similar mean-coordination-number, lying in the overconstrained region, yet of different chemical composition: stoichiometric Ge 25 Sb 10 Se 65 at. % and non-stoichiometric Ge 20 Sb 10 Se 70 at. %. Thermal analysis on bulk glasses has previously shown that the former exhibited the maximum glass stability of the series. However, during fiber-drawing of Ge 25 Sb 10 Se 65 at. %, the preform tip is found to undergo surface-devitrification to monoclinic GeSe 2 alone, the primary phase, no matter if the preform is an annealed, as-melted rod or annealed, extruded rod. The heating rate of the preform-tip to the fiber-drawing temperature is estimated to be up to ~ 100 °C min −1 to ~ 490 °C. Lower heating rates of 10 °C min −1 using thermal analysis, in contrast, encourage crystallization of both Sb 2 Se 3 and GeSe 2 . The non-stoichiometric: Ge 20 Sb 10 Se 70 at. % composition drew successfully to low optical loss fiber, no matter whether the preform was an annealed, as-melted rod or annealed, extruded rod. This article is protected by copyright. All rights reserved.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
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    Holocene carbon dynamics at the forest – steppe ecotone of southern Siberia (2016)
    Wiley
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    Publication Date: 2016-12-10
    Description: The forest – steppe ecotone in southern Siberia is highly sensitive to climate change; global warming is expected to push the ecotone northwards, at the same time resulting in degradation of the underlying permafrost. To gain a deeper understanding of long-term forest – steppe carbon dynamics, we use a highly-resolved, multiproxy, palaeolimnological approach, based on sediment records from Lake Baikal. We reconstruct proxies that are relevant to understanding carbon dynamics including carbon mass accumulation rates (CMAR; g C m −2 yr −1 ) and isotope composition of organic matter ( δ 13 C TOC ). Forest – steppe dynamics were reconstructed using pollen, and diatom records provided measures of primary production from near- and off-shore communities. We used a Generalized Additive Model (GAM) to identify significant change points in temporal series, and by applying generalised linear least-squares regression modelling to components of the multiproxy data, we address: (1) what factors influence carbon dynamics during early Holocene warming and late Holocene cooling?; (2) how did carbon dynamics respond to abrupt sub-Milankovitch scale events?; and (3) what is the Holocene carbon storage budget for Lake Baikal. CMAR values range between 2.8 – 12.5 g C m −2 yr −1 . Peak burial rates (and greatest variability) occurred during the early Holocene, associated with melting permafrost and retreating glaciers, while lowest burial rates occurred during the neoglacial. Significant shifts in carbon dynamics at 10.3, 4.1 and 2.8 kyr BP, provide compelling evidence for the sensitivity of the region to sub-Milankovitch drivers of climate change. We estimate that 1.03 Pg C were buried in Lake Baikal sediments during the Holocene, almost one quarter of which was buried during the early Holocene alone. Combined, our results highlight the importance of understanding the close linkages between carbon cycling and hydrological processes, not just temperatures, in southern Siberian environments. This article is protected by copyright. All rights reserved.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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  • 10
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    Co-Extrusion of Multilayer Glass Fiber-Optic Preforms: Prediction of Layer Dimensions in the Extrudate (2012)
    Wiley
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    Publication Date: 2012-11-22
    Description: A three-dimensional, incompressible and noncavitating model of a glass-stack coextrusion process, under isothermal and non-isothermal conditions is numerically simulated by means of computational fluid dynamics. A dynamic mesh approach is taken in a domain-subdomain type setup to simulate the transient steps in the steady-velocity phase of the experimental co-extrusion. The multiphase setup consists of a glass-stack which is composed of different glass compositions. Experimentally measured glass properties, such as the temperature coefficient of the viscosity of the supercooled glass melts are used to define the flow behavior of the glasses in the starting stack when extruded. The modeled extrudate is numerically verified for transient and spatial errors, leading to the choice of a suitable mesh. Excellent agreement is found between modeling and experiment when plotting the core/cladding dimensions of a step-index extruded fiber-optic preform along the length of the preform. This approach can identify the stable part of the preform, in terms of constant core/cladding layer geometry, obviating costly and time-consuming experimental iteration. Also, the modeling allows prediction of the starting glass-stack dimensions for a specified fiber design.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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