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  • 1
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    Four millennia of vegetation and environmental history above the Hyrcanian forest, northern Iran (2020)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2024-05-30
    Description: Past vegetation, fire, and climate dynamics, as well as human impact, have been reconstructed for the first time in the highlands of the Gilan province in the Alborz mountains (above the Hyrcanian forest) for the last 4,300 cal yrs bp. Multi-proxy analysis, including pollen, spores, non-pollen palynomorphs, charcoal, and geochemical analysis, has been applied to investigate the environmental changes at 2,280 m a.s.l., above the Hyrcanian forest. Dominant steppe vegetation occurred in the study area throughout the recorded period. The formation of the studied mire deposits, as well as vegetation composition, suggest a change to wetter climatic conditions after 4,300 until 1,700 cal yrs bp. Fires were frequent, which may imply long-lasting anthropogenic activities in the area. Less vegetation cover with a marked decrease of the Moisture Index (MI) suggests drier conditions between 1,700 and 1,000 cal yrs bp. A high proportion of Cichorioideae and Amaranthaceae, as well as the reduction of trees, in particular Fagus and Quercus, at lower elevations, indicate human activities such as intense livestock grazing and deforestation. Soil erosion as the result of less vegetation due to dry conditions and/or human activities can be reconstructed from a marked increase of Glomus spores and high values of K and Ti. Since 1,000 cal yrs bp, the increasing MI, as well as the rise of Poaceae and Cyperaceae together with forest recovery, suggest a change to wetter conditions. The occurrence of still frequent Cichorioideae and Plantago lanceolata along with Sordaria reflect continued intense grazing of livestock by humans.
    Description: Deutsche Forschungsgemeinschaft (DE)
    Description: Georg-August-Universität Göttingen (1018)
    Keywords: ddc:561 ; Late Holocene ; Northern Iran ; Multi-proxy studies ; Hyrcanian mountain vegetation ; Climate change ; Human impact
    Language: English
    Type: doc-type:article
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  • 2
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    The inner life of the Atlantic Intertropical Convergence Zone (2023)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2024-05-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The Intertropical Convergence Zone (ITCZ) is a central component of the atmospheric general circulation, but remarkably little is known about the dynamical and thermodynamical structure of the convergence zone itself. This is true even for the structure of the low‐level convergence that gives the ITCZ its name. Following on from the major international field campaigns in the 1960s and 1970s, we performed extensive atmospheric profiling of the Atlantic ITCZ during a ship‐based measurement campaign aboard the research vessel 〈italic toggle="no"〉SONNE〈/italic〉 in summer 2021. Combining data collected during our north–south crossing of the ITCZ with reanalysis data shows the ITCZ to be a meridionally extended region of intense precipitation, with enhanced surface convergence at its edges rather than in the center. Based on the location of these edges, we construct a composite view of the structure of the Atlantic ITCZ. The ITCZ, far from being simply a region of enhanced deep convection, has a rich inner life, that is, a rich dynamical and thermodynamic structure that changes throughout the course of the year, and has a northern edge that differs systematically from the southern edge.〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: Horizon 2020 Framework Programme CONSTRAIN http://dx.doi.org/10.13039/100010661
    Description: https://doi.org/10.5281/ZENODO.7051674
    Description: https://doi.org/10.24381/cds.adbb2d47
    Keywords: ddc:551.5 ; ITCZ ; Atlantic ; convergence ; observations ; reanalysis
    Language: English
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  • 3
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    Mélange Signatures and Low Oxygen Fugacity in Eclogite Xenoliths From the Crust‐Mantle Transition Below a Mesoproterozoic Collision Belt (2024)
    Details
    Publication Date: 2024-05-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Mass transfer across the crust‐mantle boundary is a fundamental process governing planetary differentiation, the evolution of geochemical reservoirs and ore formation, controlled by physicochemical conditions at the crust‐mantle interface. In situ trace‐element, clinopyroxene 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr and garnet Fe〈sup〉3+〈/sup〉/ΣFe of kimberlite‐borne eclogite xenoliths from the deep (∼50 km) crust‐mantle transition below the ca. 1.2–1.0 Ga Namaqua‐Natal Fold Belt (southwestern Kaapvaal craton margin) were determined to elucidate their origin and evolution, and to constrain the oxygen fugacity of this pivotal but largely inaccessible environment. Based on a garnet source signature (NMORB‐normalized Er/Lu > 1) in pristine “gabbroic” eclogites with pronounced positive Eu, Sr, and Pb anomalies, the suite is interpreted as originating as plagioclase‐rich cumulates in oceanic crust from melts generated beneath mature oceanic lithosphere, subsequently subducted during the Namaqua‐Natal orogeny. Enriched eclogites have higher measured 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr in clinopyroxene (up to 0.7054) than gabbroic ones (up to 0.7036), and show increasing bulk‐rock Li, Be and Pb abundances with increasing δ〈sup〉18〈/sup〉O in clinopyroxene, and muted Eu‐Sr‐Pb anomalies. These systematics suggest interaction with a siliceous fluid sourced from seawater‐altered oceanic sediment in a subduction mélange setting. Garnet Fe〈sup〉3+〈/sup〉/ΣFe in deep crustal eclogites is extremely low (0.01–0.04, ±0.01 1〈italic〉σ〈/italic〉), as inherited from the plagioclase‐rich cumulate protolith, and owing to preferred partitioning into clinopyroxene at low temperatures (∼815–1000°C). Average maximum oxygen fugacities (∆logƒO〈sub〉2〈/sub〉(FMQ) = −3.1 ± 1.0 to −0.5 ± 0.7 relative to the Fayalite‐Magnetite‐Quartz buffer) are higher than in deeper‐seated on‐craton eclogite xenoliths, but mostly below sulfate stability, limiting the role of S〈sup〉6+〈/sup〉 species in oxidizing the mantle wedge.〈/p〉
    Description: Plain Language Summary: Subduction zones represent the main interface between Earth's surface and its deep interior. Metamorphic reactions during subduction cause fluid or melt loss from seawater‐altered oceanic crust and sediment, which enriches the overlying mantle, and possibly oxidizes it. This would explain why the mantle sources of subduction zone magmas appear to be more oxidized than in other tectonic settings. However, the details of the mass transfer in this deep environment are difficult to constrain because it is inaccessible. Using rare deep‐seated magmas (kimberlites) as probes of a ca. 1.2 billion year old southern African subduction zone, we investigated eclogite fragments that originated as subducted oceanic crust and were much later plucked from the wallrocks by the ascending magma. These eclogites show elemental and isotopic signatures of interaction with subducted sediments, pointing to mingling processes similar to those observed in modern subduction zones. We also estimated their oxygen fugacity, a measure of the chemical potential of oxygen. We find that sulfur, which has been implicated in mantle oxidation, would have only been stable in these rocks in its reduced form, making even seawater‐altered eclogites sinks rather than sources of oxygen, with implications for the transfer of sulfur‐loving metals across the mantle‐to‐crust‐boundary.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Eclogite xenoliths sampling deep crust‐mantle transition below Namaqua‐Natal Fold Belt have plagioclase‐rich oceanic protoliths〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Enriched xenoliths show signatures of interaction with siliceous, subducted sediment‐derived fluids under shallow fore‐arc conditions〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Fe〈sup〉3+〈/sup〉‐based eclogite oxybarometry with oxygen fugacities below sulfate stability limits the role of S〈sup〉6+〈/sup〉 species in mantle wedge oxidation〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Deutsche Forschungsgemeinschaft
    Description: https://doi.org/10.60520/IEDA/113077
    Keywords: ddc:552.4 ; kimberlite‐borne eclogite xenoliths ; crust‐mantle transition ; subduction zone processes ; redox budget ; metallogeny ; mantle wedge oxidation
    Language: English
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  • 4
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    Kinematics and Convergent Tectonics of the Northwestern South American Plate During the Cenozoic (2023)
    Details
    Publication Date: 2024-05-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The interaction of the northern Nazca and southwestern Caribbean oceanic plates with northwestern South America (NWSA) and the collision of the Panama‐Choco arc (PCA) have significant implications on the evolution of the northern Andes. Based on a quantitative kinematic reconstruction of the Caribbean and Farallon/Farallon‐derived plates, we reconstructed the subducting geometries beneath NWSA and the PCA accretion to the continent. The persistent northeastward migration of the Caribbean plate relative to NWSA in Cenozoic time caused the continuous northward advance of the Farallon‐Caribbean plate boundary, which in turn resulted in its progressive concave trench bending against NWSA. The increasing complexity during the Paleogene included the onset of Caribbean shallow subduction, the PCA approaching the continent, and the forced shallow Farallon subduction that ended in the fragmentation of the Farallon Plate into the Nazca and Cocos plates and the Coiba and Malpelo microplates by the late Oligocene. The convergence tectonics after late Oligocene comprised the accretional process of the PCA to NWSA, which evolved from subduction erosion of the forearc to collisional tectonics by the middle Miocene, as well as changes of convergence angle and slab dip of the Farallon‐derived plates, and the attachment of the Coiba and Malpelo microplates to the Nazca plate around 9 Ma, resulting in a change of convergence directions. During the Pliocene, the Nazca slab broke at 5.5°N, shaping the modern configuration. Overall, the proposed reconstruction is supported by geophysical data and is well correlated with the magmatic and deformation history of the northern Andes.〈/p〉
    Description: Plain Language Summary: The tectonic reconstruction in convergent triple junctions is a particularly challenging task as the relative motion between plates could define highly changing boundaries. Indeed, the resulting interaction between these convergent plates may induce important changes in the disposition of the trenches, and in turn in the three‐dimensional geometry of the subducting plates. Therefore, these highly dynamic conditions throughout geological time may be accommodated by different phases of plate fragmentation and reorganization. These factors could explain the complex spatial‐temporal distribution of subduction‐related magmatism and the different episodes of deformation in the upper plates. This reasoning is validated in the northwestern corner of South America (SA), where the continent has been converging against the Caribbean and Farallon‐derived oceanic plates since Cretaceous time. Additionally, we study the effects of the collision and accretion of the Panama‐Choco arc with SA. To accomplish that, we review the kinematic history of the Farallon/Nazca and Caribbean oceanic plates relative to stable Guiana Craton (SA) and integrate these results with the magmatic and deformation evolution of the northern Andes, which allow us to propose a model of the geometrical evolution of the subducting slabs. The obtained model is additionally constrained by seismological data and published velocity anomalies.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉The tectonics of convergent triple junctions is complicated by the relative plate motion and interaction of the involved plates〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉We propose a model for the kinematic and geometric evolution of the Farallon/Nazca and Caribbean plates throughout the Cenozoic〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉The interaction between the Caribbean, Nazca and South American plates is closely related to the deformation history in the Northern Andes〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Helmholtz‐Zentrum Potsdam‐Deutsches GeoForschungsZentrum GFZ http://dx.doi.org/10.13039/501100010956
    Description: Ecopetrol
    Description: https://doi.org/10.5281/zenodo.7411340
    Description: https://doi.org/10.5281/zenodo.8129751
    Keywords: ddc:551.8 ; plate kinematics ; convergent margins ; slab geometry ; Northern Andean deformation episodes
    Language: English
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  • 5
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    Thermische Eigenschaften von Böden (2024)
    Landesamt für Geologie und Bergbau Rheinland-Pfalz
    Details
    Publication Date: 2024-05-30
    Description: Ob Energiewende, die Gewinnung geothermischer Energie aus dem Boden, der Bau von unterirdischen Stromtrassen oder die Modellierung des Energiehaushalts der Erdoberfläche – die Kenntnisse der physikalisch-thermischen Eigenschaften des oberflächennahen Untergrundes sind von zentraler Bedeutung für zahlreiche Fragestellen der angewandten Bodenkunde. Böden als 3-Phasengemische aus Wasser, Luft und Festsubstanz können erhebliche Unterschiede und Differenzierungen bezüglich der thermischen Eigenschaften aufweisen. Neben dem Wasser- und Lufthaushalt sind Lagerungsdichte, Textur sowie die mineralogische Zusammensetzung entscheidende Einflussfaktoren. Auf Basis dieser Grundlagen wurden von verschiedenen Autoren Modellansätze entwickelt, um thermische Parameter bei unterschiedlichen Feuchtezuständen abzuleiten. Die meisten dieser Ansätze beruhen auf der Auswertung von repräsentativen Bodenproben, die ein möglichst breites Texturspektrum abbilden sollen. Die vorliegende Untersuchung verfolgt einen alternativen Ansatz. Durch Messungen im Routinebetrieb eines bodenphysikalischen Labors wurde ein umfangreicher Datensatz aufgebaut, der Auswertungen nach verschiedenen laboranalytischen sowie boden- und substratsystematischen Aspekten ermöglicht. Auf dieser breiten Datenbasis sollen die thermischen Eigenschaften von Böden bei definierten Randbedingungen noch genauer gefasst werden. Darüber hinaus sollen Grundlagen erarbeitet werden, die es ermöglichen, thermische Kennwerte über die Kenntnis einfacher Feldparameter möglichst präzise abzuschätzen.
    Description: research
    Keywords: ddc:631.436 ; Bodenphysik ; Wärmeleitfähigkeit ; Rheinland-Pfalz
    Language: German
    Type: doc-type:book , publishedVersion
    Format: 56
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  • 6
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    Fifty years after deep‐ploughing: Effects on yield, roots, nutrient stocks and soil structure (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-05-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Deep‐ploughing far beyond the common depth of 30 cm was used more than 50 years ago in Northern Germany with the aim to break root‐restricting layers and thereby improve access to subsoil water and nutrient resources. We hypothesized that effects of this earlier intervention on soil properties and yields prevailed after 50 years. Hence, we sampled two sandy soils and one silty soil (Cambisols and a Luvisol) of which half of the field had been deep‐ploughed 50 years ago (soils then re‐classified as Treposols). The adjacent other half was not deep‐ploughed and thus served as the control. At all the three sites, both deep‐ploughed and control parts were then conventionally managed over the last 50 years. We assessed yields during the dry year 2019 and additionally in 2020, and rooting intensity at the year of sampling (2019), as well as changes in soil structure, carbon and nutrient stocks in that year. We found that deep‐ploughing improved yields in the dry spell of 2019 at the sandy sites, which was supported by a more general pattern of higher NDVI indices in deep‐ploughed parts for the period from 2016 to 2021 across varying weather conditions. Subsoil stocks of soil organic carbon and total plant‐available phosphorus were enhanced by 21%–199% in the different sites. Root biomass in the subsoil was reduced due to deep‐ploughing at the silty site and was increased or unaffected at the sandy sites. Overall, the effects of deep‐ploughing were site‐specific, with reduced bulk density in the buried topsoil stripes in the subsoil of the sandy sites, but with elevated subsoil density in the silty site. Hence, even 50 years after deep‐ploughing, changes in soil properties are still detectable, although effect size differed among sites.〈/p〉
    Description: BonaRes http://dx.doi.org/10.13039/501100022576
    Keywords: ddc:631.4 ; aggregates ; carbon sequestration ; deep‐ploughing ; macronutrients ; subsoil ; Treposol
    Language: English
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  • 7
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    Northern Hemisphere Summer Insolation and Ice Volume Driven Variations in Hydrological Environment in Southwest China (2023)
    Details
    Publication Date: 2024-05-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The interpretation of stalagmite δ〈sup〉18〈/sup〉O in terms of reflecting Asian summer monsoon (ASM) precipitation is still elusive. Here, we present high‐resolution stalagmite trace element ratios (X/Ca, X = Mg, Sr, Ba) records from southwest China covering 116.09 to 4.07 ka BP. δ〈sup〉18〈/sup〉O, δ〈sup〉13〈/sup〉C, and X/Ca values exhibit clear precessional cycles, with δ〈sup〉18〈/sup〉O values reflecting ASM circulation/intensity, while X/Ca ratios capture local precipitation or evapotranspiration variations. Our results show that Northern Hemisphere summer insolation (NHSI) is the main driver of ASM intensity and precipitation phase variation, but global ice volume modulates the response magnitude of summer precipitation to insolation. During the Last Glacial Maximum, high ice volumes caused significant monsoon precipitation to decrease. In contrast to modern observations of the tripolar distribution of precipitation in China, our record is consistent with paleo‐precipitation records in southern and northern China.〈/p〉
    Description: Plain Language Summary: While it is well known that global changes have led to variations in the intensity and spatial distribution of Asian monsoon precipitation, the mechanisms behind this are not well understood. Paleoclimate records are essential for revealing the drivers behind monsoon variation. However, speleothem records from the Asian monsoon region rarely provide direct information on the amount of rainfall. Here we report on multiple indicator data sets from a stalagmite in southwestern China. It could help explore the variation of monsoon precipitation over the last ∼100,000 years. We find that the increase/decrease of Northern Hemisphere summer insolation controls the increase/decrease of Asian summer monsoon rainfall. In addition, global ice volume moderates the magnitude of rainfall response to insolation, and precipitation decreases significantly during high ice volume periods. Based on the present paleo‐precipitation records evidence, the existence of the spatial pattern of increasing/decreasing rainfall in central China corresponding to decreasing/increasing rainfall in northern and southern China remains ambiguous on the orbital scales, although the feature has been captured by some of the model simulations.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Stalagmite trace elements are indicators of regional hydrological environmental variations in Southwestern China〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Northern Hemisphere summer insolation and global ice volume modulate the phase and amplitude variations of regional hydrological environment〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉The meridional tripolar spatial pattern of precipitation in monsoon region in China on the orbital scale remains ambiguous〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: German Science Grant
    Description: Structure and Innovation Fund of the Region of Baden Württemberg
    Description: China Scholarship Council http://dx.doi.org/10.13039/501100004543
    Description: National Nature Science Foundation of China
    Description: Yunnan Fundamental Research Projects
    Description: Young and Middle‐age Academic and Technical Leader in Yunnan Province
    Description: https://doi.org/10.5281/zenodo.10072475
    Keywords: ddc:551 ; stalagmite ; trace elements ; Asian summer monsoon ; Northern Hemisphere summer insolation ; global ice volume ; regional hydrological environment
    Language: English
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  • 8
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    On the Along‐Slope Heat Loss of the Boundary Current in the Eastern Arctic Ocean (2021)
    In:  EPIC3Journal of Geophysical Research: Oceans, 126(2), ISSN: 2169-9275
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    Publication Date: 2024-05-30
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Effects of bottom‐up factors on growth and toxin content of a harmful algae bloom dinoflagellate (2024)
    Wiley
    In:  EPIC3Limnology and Oceanography, Wiley, ISSN: 0024-3590
    Details
    Publication Date: 2024-05-30
    Description: The toxin-producing dinoflagellate Alexandrium pseudogonyaulax has become increasingly abundant in northern European waters, replacing other Alexandrium species. A. pseudogonyaulax produces goniodomins and lytic substances, which can be cytotoxic toward other organisms, including fish, but we still know little about the environmental conditions influencing its growth and toxicity. Here, we investigated the impacts of different nitrogen sources and light intensities, common bottom-up drivers of bloom formation, on the growth and toxin content of three A. pseudogonyaulax strains isolated from the Danish Limfjord. While the growth rates were significantly influenced by nitrogen source and light intensity, the intracellular toxin contents only showed strong differences between the exponential and stationary growth phases. Moreover, the photophysiological response of A. pseudogonyaulax showed little variation across varying light intensities, while light-harvesting pigments were significantly more abundant under low light conditions. This study additionally highlights considerable physiological variability between strains, emphasizing the importance of conducting laboratory experiments with several algal strains. A high physiological plasticity toward changing abiotic parameters points to a long-term establishment of A. pseudogonyaulax in northern European waters.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
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    Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream – CORRIGENDUM (2023)
    Cambridge University Press (CUP)
    In:  EPIC3Annals of Glaciology, Cambridge University Press (CUP), pp. 1-1, ISSN: 0260-3055
    Details
    Publication Date: 2024-05-30
    Repository Name: EPIC Alfred Wegener Institut
    Type: Other , notRev
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