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Thomson JR, Holden PB, Anand P, Edwards NR, Porchier CA, Harris NBW. Tectonic and climatic drivers of Asian monsoon evolution. Nat Commun 2021; 12:4022. [PMID: 34188033 PMCID: PMC8242090 DOI: 10.1038/s41467-021-24244-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 05/26/2021] [Indexed: 11/23/2022] Open
Abstract
Asian Monsoon rainfall supports the livelihood of billions of people, yet the relative importance of different drivers remains an issue of great debate. Here, we present 30 million-year model-based reconstructions of Indian summer monsoon and South East Asian monsoon rainfall at millennial resolution. We show that precession is the dominant direct driver of orbital variability, although variability on obliquity timescales is driven through the ice sheets. Orographic development dominated the evolution of the South East Asian monsoon, but Indian summer monsoon evolution involved a complex mix of contributions from orography (39%), precession (25%), atmospheric CO2 (21%), ice-sheet state (5%) and ocean gateways (5%). Prior to 15 Ma, the Indian summer monsoon was broadly stable, albeit with substantial orbital variability. From 15 Ma to 5 Ma, strengthening was driven by a combination of orography and glaciation, while closure of the Panama gateway provided the prerequisite for the modern Indian summer monsoon state through a strengthened Atlantic meridional overturning circulation.
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Affiliation(s)
| | - Philip B Holden
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK.
| | - Pallavi Anand
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK
| | - Neil R Edwards
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK
- Cambridge Centre for Energy, Environment and Natural Resource Governance, University of Cambridge, Cambridge, UK
| | - Cécile A Porchier
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK
- Department of Geography, University College London, London, UK
| | - Nigel B W Harris
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK
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2
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Morozov G, Sabirov R, Anisimova N. The hidden diversity of the endemic Arctic sponges (Porifera). J NAT HIST 2021. [DOI: 10.1080/00222933.2021.1913256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Grigori Morozov
- Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, Kazan, Russia
| | - Rushan Sabirov
- Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, Kazan, Russia
| | - Natalya Anisimova
- Laboratory of Trophology, Knipovich Polar Research Institute of Marine Fisheries and Oceanography, Murmansk, Russia
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Sen A, Didriksen A, Hourdez S, Svenning MM, Rasmussen TL. Frenulate siboglinids at high Arctic methane seeps and insight into high latitude frenulate distribution. Ecol Evol 2020; 10:1339-1351. [PMID: 32076518 PMCID: PMC7029078 DOI: 10.1002/ece3.5988] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/27/2019] [Accepted: 11/29/2019] [Indexed: 11/08/2022] Open
Abstract
Frenulate species were identified from a high Arctic methane seep area on Vestnesa Ridge, western Svalbard margin (79°N, Fram Strait) based on mitochondrial cytochrome oxidase subunit I (mtCOI). Two species were found: Oligobrachia haakonmosbiensis, and a new, distinct, and undescribed Oligobrachia species. The new species adds to the cryptic Oligobrachia species complex found at high latitude methane seeps in the north Atlantic and the Arctic. However, this species displays a curled tube morphology and light brown coloration that could serve to distinguish it from other members of the complex. A number of single tentacle individuals were recovered which were initially thought to be members of the only unitentaculate genus, Siboglinum. However, sequencing revealed them to be the new species and the single tentacle morphology, in addition to thin, colorless, and ringless tubes indicate that they are juveniles. This is the first known report of juveniles of northern Oligobrachia. Since the juveniles all appeared to be at about the same developmental stage, it is possible that reproduction is either synchronized within the species, or that despite continuous reproduction, settlement, and growth in the sediment only takes place at specific periods. The new find of the well-known species O. haakonmosbiensis extends its range from the Norwegian Sea to high latitudes of the Arctic in the Fram Strait. We suggest bottom currents serve as the main distribution mechanism for high latitude Oligobrachia species and that water depth constitutes a major dispersal barrier. This explains the lack of overlap between the distributions of northern Oligobrachia species despite exposure to similar current regimes. Our results point toward a single speciation event within the Oligobrachia clade, and we suggest that this occurred in the late Neogene, when topographical changes occurred and exchanges between Arctic and North Atlantic water masses and subsequent thermohaline circulation intensified.
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Affiliation(s)
- Arunima Sen
- CAGE-Centre for Arctic Gas Hydrate, Environment and Climate Department of Geosciences UiT The Arctic University of Norway Tromsø Norway
- Present address: Faculty of Biosciences and Aquaculture Nord University Bodø Norway
| | - Alena Didriksen
- Department of Arctic and Marine Biology UiT The Arctic University of Norway Tromsø Norway
| | - Stéphane Hourdez
- Laboratoire d'écogéochimie des Environnements Benthiques UMR8222 CNRS-Sorbonne Université Banyuls-sur-Mer France
| | - Mette Marianne Svenning
- CAGE-Centre for Arctic Gas Hydrate, Environment and Climate Department of Geosciences UiT The Arctic University of Norway Tromsø Norway
- Department of Arctic and Marine Biology UiT The Arctic University of Norway Tromsø Norway
| | - Tine L Rasmussen
- CAGE-Centre for Arctic Gas Hydrate, Environment and Climate Department of Geosciences UiT The Arctic University of Norway Tromsø Norway
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Hutchinson DK, Coxall HK, OʹRegan M, Nilsson J, Caballero R, de Boer AM. Arctic closure as a trigger for Atlantic overturning at the Eocene-Oligocene Transition. Nat Commun 2019; 10:3797. [PMID: 31439843 PMCID: PMC6706372 DOI: 10.1038/s41467-019-11828-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 08/07/2019] [Indexed: 11/24/2022] Open
Abstract
The Eocene-Oligocene Transition (EOT), approximately 34 Ma ago, marks a period of major global cooling and inception of the Antarctic ice sheet. Proxies of deep circulation suggest a contemporaneous onset or strengthening of the Atlantic meridional overturning circulation (AMOC). Proxy evidence of gradual salinification of the North Atlantic and tectonically driven isolation of the Arctic suggest that closing the Arctic-Atlantic gateway could have triggered the AMOC at the EOT. We demonstrate this trigger of the AMOC using a new paleoclimate model with late Eocene boundary conditions. The control simulation reproduces Eocene observations of low Arctic salinities. Subsequent closure of the Arctic-Atlantic gateway triggers the AMOC by blocking freshwater inflow from the Arctic. Salt advection feedbacks then lead to cessation of overturning in the North Pacific. These circulation changes imply major warming of the North Atlantic Ocean, and simultaneous cooling of the North Pacific, but no interhemispheric change in temperatures. Proxies of deep circulation suggest that the onset or strengthening of the Atlantic meridional overturning circulation occurred at the Eocene-Oligocene Transition. The authors show, using a paleoclimate model of the late Eocene, that a shift from Pacific to Atlantic overturning can be triggered at this time by closing the Arctic–Atlantic gateway.
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Affiliation(s)
- David K Hutchinson
- Department of Geological Sciences, Stockholm University, 10691, Stockholm, Sweden.
| | - Helen K Coxall
- Department of Geological Sciences, Stockholm University, 10691, Stockholm, Sweden
| | - Matt OʹRegan
- Department of Geological Sciences, Stockholm University, 10691, Stockholm, Sweden
| | - Johan Nilsson
- Department of Meteorology, Stockholm University, 10691, Stockholm, Sweden
| | - Rodrigo Caballero
- Department of Meteorology, Stockholm University, 10691, Stockholm, Sweden
| | - Agatha M de Boer
- Department of Geological Sciences, Stockholm University, 10691, Stockholm, Sweden
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5
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Abstract
Understanding how the Atlantic Meridional Overturning Circulation (AMOC) evolved during crucial past geological periods is important in order to decipher the interplay between ocean dynamics and global climate change. Previous research, based on geological proxies, has provided invaluable insights into past AMOC changes. However, the causes of the changes in water mass distributions in the Atlantic during different periods remain mostly elusive. Using a state-of-the-art Earth system model, we show that the bulk of NCW in the deep South Atlantic Ocean below 4000 m migrated from the western basins at 125 ka to the eastern basins at 115 ka, though the AMOC strength is only slightly reduced. These changes are consistent with proxy records, and it is mainly due to more penetration of the AABW at depth at 115 ka, as a result of a larger density of AABW formed at 115 ka. Our results show that depth changes in regional deep water pathways can result in large local changes, while the overall AMOC structure hardly changes. Future research should thus be careful when interpreting single proxy records in terms of large-scale AMOC changes, and considering variability of water-mass distributions on sub-basin scale would give more comprehensive interpretations of sediment records.
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Affiliation(s)
- Yiming Luo
- Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Allegaten 70, 5007, Bergen, Norway.
| | - Jerry Tjiputra
- Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway
| | - Chuncheng Guo
- Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway
| | - Zhongshi Zhang
- Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway
| | - Jörg Lippold
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120, Heidelberg, Germany
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Stärz M, Jokat W, Knorr G, Lohmann G. Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge. Nat Commun 2017; 8:15681. [PMID: 28580952 PMCID: PMC5465373 DOI: 10.1038/ncomms15681] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Accepted: 04/19/2017] [Indexed: 11/30/2022] Open
Abstract
High latitude ocean gateway changes are thought to play a key role in Cenozoic climate evolution. However, the underlying ocean dynamics are poorly understood. Here we use a fully coupled atmosphere-ocean model to investigate the effect of ocean gateway formation that is associated with the subsidence of the Greenland–Scotland Ridge. We find a threshold in sill depth (∼50 m) that is linked to the influence of wind mixing. Sill depth changes within the wind mixed layer establish lagoonal and estuarine conditions with limited exchange across the sill resulting in brackish or even fresher Arctic conditions. Close to the threshold the ocean regime is highly sensitive to changes in atmospheric CO2 and the associated modulation in the hydrological cycle. For larger sill depths a bi-directional flow regime across the ridge develops, providing a baseline for the final step towards the establishment of a modern prototype North Atlantic-Arctic water exchange. During the Cenozoic the Arctic Ocean change from a restricted freshwater regime towards more saline modern ocean conditions is supposedly driven by the subsidence of the Greenland-Scotland Ridge. Here, the authors derive a threshold for this shift, constrained by the characteristic depth of wind mixing.
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Affiliation(s)
- Michael Stärz
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
| | - Wilfried Jokat
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
| | - Gregor Knorr
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
| | - Gerrit Lohmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
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7
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The emergence of modern sea ice cover in the Arctic Ocean. Nat Commun 2014; 5:5608. [DOI: 10.1038/ncomms6608] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/20/2014] [Indexed: 11/09/2022] Open
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van Kempen MML, Smolders AJP, Lamers LPM, Roelofs JGM. Micro-halocline enabled nutrient recycling may explain extreme Azolla event in the Eocene Arctic Ocean. PLoS One 2012; 7:e50159. [PMID: 23166833 PMCID: PMC3500341 DOI: 10.1371/journal.pone.0050159] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 10/22/2012] [Indexed: 11/29/2022] Open
Abstract
In order to understand the physicochemical mechanisms that could explain the massive growth of Azolla arctica in the Eocene Arctic Ocean, we carried out a laboratory experiment in which we studied the interacting effects of rain and wind on the development of salinity stratification, both in the presence and in the absence of a dense Azolla cover. Additionally, we carried out a mesocosm experiment to get a better understanding of the nutrient cycling within and beneath a dense Azolla cover in both freshwater and brackish water environments. Here we show that Azolla is able to create a windproof, small-scale salinity gradient in brackish waters, which allows for efficient recycling of nutrients. We suggest that this mechanism ensures the maintenance of a large standing biomass in which additional input of nutrients ultimately result in a further expansion of an Azolla cover. As such, it may not only explain the extent of the Azolla event during the Eocene, but also the absence of intact vegetative Azolla remains and the relatively low burial efficiency of organic carbon during this interval.
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Affiliation(s)
- Monique M L van Kempen
- Department of Aquatic Ecology and Environmental Biology, Faculty of Science, Institute for Water and Wetland Research, Radboud University, Nijmegen, The Netherlands.
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Abstract
There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points.
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Affiliation(s)
- Timothy M Lenton
- College of Life and Environmental Sciences, Hatherly Laboratories, University of Exeter, Exeter EX4 4PS, UK.
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Speelman EN, Van Kempen MML, Barke J, Brinkhuis H, Reichart GJ, Smolders AJP, Roelofs JGM, Sangiorgi F, de Leeuw JW, Lotter AF, Sinninghe Damsté JS. The Eocene Arctic Azolla bloom: environmental conditions, productivity and carbon drawdown. GEOBIOLOGY 2009; 7:155-70. [PMID: 19323694 DOI: 10.1111/j.1472-4669.2009.00195.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Enormous quantities of the free-floating freshwater fern Azolla grew and reproduced in situ in the Arctic Ocean during the middle Eocene, as was demonstrated by microscopic analysis of microlaminated sediments recovered from the Lomonosov Ridge during Integrated Ocean Drilling Program (IODP) Expedition 302. The timing of the Azolla phase (approximately 48.5 Ma) coincides with the earliest signs of onset of the transition from a greenhouse towards the modern icehouse Earth. The sustained growth of Azolla, currently ranking among the fastest growing plants on Earth, in a major anoxic oceanic basin may have contributed to decreasing atmospheric pCO2 levels via burial of Azolla-derived organic matter. The consequences of these enormous Azolla blooms for regional and global nutrient and carbon cycles are still largely unknown. Cultivation experiments have been set up to investigate the influence of elevated pCO2 on Azolla growth, showing a marked increase in Azolla productivity under elevated (760 and 1910 ppm) pCO2 conditions. The combined results of organic carbon, sulphur, nitrogen content and 15N and 13C measurements of sediments from the Azolla interval illustrate the potential contribution of nitrogen fixation in a euxinic stratified Eocene Arctic. Flux calculations were used to quantitatively reconstruct the potential storage of carbon (0.9-3.5 10(18) gC) in the Arctic during the Azolla interval. It is estimated that storing 0.9 10(18) to 3.5 10(18) g carbon would result in a 55 to 470 ppm drawdown of pCO2 under Eocene conditions, indicating that the Arctic Azolla blooms may have had a significant effect on global atmospheric pCO2 levels through enhanced burial of organic matter.
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Affiliation(s)
- E N Speelman
- Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands.
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Matthiessen J, Knies J, Vogt C, Stein R. Pliocene palaeoceanography of the Arctic Ocean and subarctic seas. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:21-48. [PMID: 18926969 DOI: 10.1098/rsta.2008.0203] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The Pliocene is important in the geological evolution of the high northern latitudes. It marks the transition from restricted local- to extensive regional-scale glaciations on the circum-Arctic continents between 3.6 and 2.4Ma. Since the Arctic Ocean is an almost land-locked basin, tectonic activity and sea-level fluctuations controlled the geometry of ocean gateways and continental drainage systems, and exerted a major influence on the formation of continental ice sheets, the distribution of river run-off, and the circulation and water mass characteristics in the Arctic Ocean. The effect of a water mass exchange restricted to the Bering and Fram Straits on the oceanography is unknown, but modelling experiments suggest that this must have influenced the Atlantic meridional overturning circulation. Cold conditions associated with perennial sea-ice cover might have prevailed in the central Arctic Ocean throughout the Pliocene, whereas colder periods alternated with warmer seasonally ice-free periods in the marginal areas. The most pronounced oceanographic change occurred in the Mid-Pliocene when the circulation through the Bering Strait reversed and low-salinity waters increasingly flowed from the North Pacific into the Arctic Ocean. The excess freshwater supply might have facilitated sea-ice formation and contributed to a decrease in the Atlantic overturning circulation.
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Affiliation(s)
- Jens Matthiessen
- Alfred Wegener Institute for Polar and Marine Research, 27515 Bremerhaven, Germany.
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Haywood AM, Dowsett HJ, Valdes PJ, Lunt DJ, Francis JE, Sellwood BW. Introduction. Pliocene climate, processes and problems. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:3-17. [PMID: 18852089 DOI: 10.1098/rsta.2008.0205] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Climate predictions produced by numerical climate models, often referred to as general circulation models (GCMs), suggest that by the end of the twenty-first century global mean annual surface air temperatures will increase by 1.1-6.4 degrees C. Trace gas records from ice cores indicate that atmospheric concentrations of CO2 are already higher than at any time during the last 650000 years. In the next 50 years, atmospheric CO2 concentrations are expected to reach a level not encountered since an epoch of time known as the Pliocene. Uniformitarianism is a key principle of geological science, but can the past also be a guide to the future? To what extent does an examination of the Pliocene geological record enable us to successfully understand and interpret this guide? How reliable are the 'retrodictions' of Pliocene climates produced by GCMs and what does this tell us about the accuracy of model predictions for the future? These questions provide the scientific rationale for this Theme Issue.
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Affiliation(s)
- Alan M Haywood
- School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
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Knutz P. Chapter 24 Palaeoceanographic Significance of Contourite Drifts. DEVELOPMENTS IN SEDIMENTOLOGY 2008. [DOI: 10.1016/s0070-4571(08)10024-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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