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  • 2015-2019  (37)
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  • 1
    Online Resource
    Online Resource
    Cham :Springer International Publishing AG,
    Keywords: Polarization (Nuclear physics). ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (414 pages)
    Edition: 2nd ed.
    ISBN: 9783319552163
    Series Statement: Springer Series on Atomic, Optical, and Plasma Physics Series ; v.96
    DDC: 539.757
    Language: English
    Note: Intro -- Foreword to the Second Edition -- Foreword to the First Edition -- Preface to the Second Edition -- Preface to the First Edition -- Acknowledgements -- Contents -- Notation -- Basic Concepts -- 1 Introduction -- 1.1 Motivation -- 1.2 Historical Perspective -- 1.3 Modern Approaches -- References -- 2 Polarized Light -- 2.1 Polarization of Coherent Electromagnetic Radiation -- 2.1.1 Maxwell's Theory of Electromagnetic Radiation -- 2.1.2 The Polarization Ellipse -- 2.1.3 Parameterization of Polarization: Stokes Vectors -- 2.1.4 The Principal Frame -- 2.1.5 The Poincaré Sphere -- 2.2 Electric Dipole Radiation from Atomic Transitions -- 2.2.1 Coordinate Frames, Scattering Amplitudes, and Stokes Parameters -- 2.2.2 Atomic State Parameters, Electron Charge Clouds, and Their Experimental Determination -- 2.2.3 The Incoherent Case with Conservation of Atomic Reflection Symmetry -- 2.2.4 The Incoherent Case Without Conservation of Atomic Reflection Symmetry -- 2.2.5 Summary of Parameterization for P-State Excitation -- 2.2.6 Extension to Coherently Excited Stark Manifolds -- References -- 3 Polarized Electrons -- 3.1 The Dirac Equation -- 3.2 Pure Spin States: State Vector Description -- 3.3 Mixed Spin States: Density Matrix Description -- 3.4 Experimental Determination of Electron Polarization -- References -- 4 Experimental Geometries and Approaches -- 4.1 Integrated Cross Sections and Alignment -- 4.1.1 Schematic Setup for Angle-Integrated Measurements -- 4.1.2 Setups with Results for Electron Impact and Atom Impact Excitation -- 4.2 Differential Cross Sections -- 4.2.1 Schematic Setups for Angle-Differential Measurements -- 4.2.2 A Setup with Results for Electron--Atom Collisions -- 4.2.3 The Magnetic Angle Changer -- 4.2.4 Setups with Results for Electron Impact Ionization -- 4.2.5 A Setup with Results for Atom Impact Excitation. , 4.3 Planar Scattering Symmetry: Alignment and Orientation Parameters -- 4.3.1 Schematic Setups for Coherence and Correlation Analysis -- 4.3.2 Setups with Results for Electron Impact Excitation and De-excitation -- 4.3.3 Setups with Results for Atom Impact Excitation -- 4.4 Generalized STU Parameters for Electron Collisions -- 4.5 Generalized Stokes Parameters for Electron--Atom Collisions -- 4.6 Atom--Atom Collisions with Laser-Prepared Targets -- References -- 5 Density Matrices: Connection Between Experiment and Theory -- 5.1 Motivation -- 5.2 Scattering Amplitudes -- 5.2.1 Scattering Amplitudes in Different Coordinate Frames -- 5.2.2 Symmetry Properties -- 5.2.3 Scattering Amplitudes in the Non-relativistic Limit -- 5.3 Density Matrices -- 5.4 An Explicit Example: Generalized STU Parameters -- 5.4.1 Definition in Terms of Scattering Amplitudes -- 5.4.2 Exact Symmetry Relationships -- 5.4.3 An Approximate Symmetry: The Fine-Structure Effect -- 5.5 Irreducible Tensor Operators and State Multipoles -- 5.5.1 Basic Definitions -- 5.5.2 Coupled Systems -- 5.5.3 Time Evolution of State Multipoles: Quantum Beats -- 5.5.4 Time Integration over Quantum Beats -- 5.6 Stokes Parameters -- 5.7 Atomic and Photon Density Matrices for P-State Excitation -- References -- 6 Computational Methods -- 6.1 Electron Versus Heavy-Particle Impact -- 6.2 Computational Methods for Electron Scattering -- 6.2.1 Potential Scattering -- 6.2.2 Perturbation Approaches -- 6.2.3 The Close-Coupling Expansion -- 6.2.4 Time-Dependent Approaches -- 6.2.5 Recent Developments -- 6.3 Computational Methods for Heavy-Particle Collisions -- 6.3.1 Semi-classical Approaches -- 6.3.2 Classical-Trajectory Monte-Carlo Approach -- 6.4 Visualization of Charge Clouds -- References -- Case Studies -- 7 Electron Impact Excitation -- 7.1 Angle-Integrated Stokes Parameters and Cross Sections. , 7.1.1 Excitation of the (6s6p) States in Hg -- 7.1.2 Excitation of Ions: Cd+(2P3/2) -- 7.1.3 An Unresolved Mystery: Electron Impact Excitation of (4s5s)3S1 in Zn and (6s7s)3S1 in Hg -- 7.2 Angle-Differential Stokes and STU Parameters -- 7.2.1 Electron Impact Excitation of Helium -- 7.2.2 Electron Impact Excitation of Hydrogen, Lithium, and Sodium -- 7.2.3 Electron Impact Excitation of Heavy Noble Gases -- 7.2.4 Electron Impact Excitation of Mercury -- 7.2.5 Elastic Electron Scattering from Cesium -- 7.2.6 Recent Developments in Electron Scattering from Cesium -- 7.3 Conclusions -- References -- 8 Ion and Atom Impact Excitation -- 8.1 Angle-Differential S rightarrow P, D Excitation and Transfer -- 8.1.1 S rightarrow P, D Excitation in Mg+- and Li-Rare-Gas Systems -- 8.1.2 S rightarrow P Transfer Excitation in B3+-He, Ne Collisions -- 8.1.3 S rightarrow P Transfer in Small-Angle H+, Li+-Na(3s) Collisions -- 8.1.4 Vortex Formation in Antiproton-Atomic-Hydrogen Collisions -- 8.2 Angle-Integrated Alignment Studies Using Optically Prepared Targets -- 8.2.1 Alignment Effects in H+, Li+-Na(3p) Collisions -- 8.2.2 Alignment Effects in He2+-Na(3p) Collisions -- 8.3 Angle-Differential Studies Using Optically Prepared Targets -- 8.3.1 Level Populations in H+-Na(3p)rightarrowH(n=2,3)-Na+ Scattering -- 8.3.2 Level Populations in Li+-Na(3p)rightarrowLi(2p)-Na+ Scattering -- 8.3.3 Level Populations in He+ - Na(3p)rightarrowHe(2p)-Na+ Scattering -- 8.4 Angle-Differential Studies Using Optically Prepared -- 8.4.1 H+-Na(3p)rightarrowH (2p)-Na+ Scattering Experiments -- 8.4.2 Li+-Na(3p)rightarrowLi(2p)--Na+ Scattering Experiments -- 8.5 Reaction Microscope Studies: COLTRIMS with Alkali MOTs -- 8.5.1 Li+ Capture from a Na (3s, 3p) MOT -- 8.5.2 Na+ Capture from a Rb (5p) MOT -- References -- 9 Propensity Rules. , 9.1 Orientation for S to P Impact Excitation by Electrons and Positrons -- 9.2 Orientation for S to P Impact Excitation by Protons and Antiprotons -- 9.3 Orientation for Excitation and De-Excitation by Electrons and Positrons -- 9.4 Principal Quantum Number Dependence of Orientation and Alignment Parameters -- 9.5 Spin-Dependent Propensities -- 9.6 Validity Limits of Propensity Rules -- 9.6.1 Electron Impact Excitation of Neon -- 9.6.2 Electron Impact Excitation of He(1s3d)1D -- References -- 10 Impact Ionization -- 10.1 Ionization by Electron Impact -- 10.1.1 Angle-Integrated Studies -- 10.1.2 Angle-Differential Studies -- 10.1.3 Selected Developments Since 2001 -- 10.2 Ionization by Heavy-Particle Impact: Reaction Microscope Studies with Optically Prepared Targets -- 10.3 Ionization with Excitation by Heavy-Particle Impact -- 10.3.1 Angle-Integrated Studies -- 10.3.2 Angle-Differential Studies -- References -- 11 Photo-Driven Processes -- 11.1 Introductory Remarks -- 11.2 Photoionization by Continuous Radiation -- 11.3 Photoionization by Short-Pulse Radiation -- References -- 12 Related Topics and Applications -- 12.1 Spin-Polarized Auger Electrons -- 12.2 Autoionization Anisotropies in Heavy-Particle Collisions -- 12.3 Collisions with Molecules -- 12.3.1 Electron Collisions with Molecules -- 12.3.2 Heavy-Particle Collisions with Molecules -- 12.4 Collisions with Surfaces and Foils -- 12.5 Polarization in Collisional Broadening and Redistribution -- 12.6 Alignment and Orientation Studies at Thermal Energies -- 12.6.1 Alignment Studies Involving an Optically Prepared Atom -- 12.6.2 Alignment and Orientation Studies Involving Two Optically Prepared Atoms -- 12.7 Plasma Polarization Spectroscopy -- 12.8 Spin-Polarized Beams for Nuclear and Particle Physics -- 12.9 Quantum Entanglement and Bell Correlation in Electron-Exchange Collisions. , References -- Selection of Historical Papers (1925-1976) -- 13 Introductory Summaries -- Appendix Further Readings -- Index.
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  • 2
    Publication Date: 2019-09-23
    Description: Highlights • Stratigraphic framework over the Miocene-Pliocene boundary at IODP Site U1387. • Abrupt sedimentary changes over the Miocene-Pliocene boundary. • Clear hints for onset of Mediterranean Outflow after the Messinian Salinity Crisis. • Evidence of bottom water currents in contouritic sedimentation and elevated Zr/Al. • Quiet, hemipelagic sediment deposition during the Messinian in the Gulf of Cadiz. Abstract Integrated Ocean Drilling Program (IODP) Expedition 339 cored multiple sites in the Gulf of Cadiz in order to study contourite deposition resulting from Mediterranean Outflow water (MOW). One hole, U1387C, was cored to a depth of 865.6 meters below seafloor (mbsf) with the goal of recovering the Latest Miocene to Pliocene transition in order to evaluate the history of MOW immediately after the end of the Messinian Salinity Crisis. To understand this history, an accurate age model for the succession is needed, but is challenging to construct, because the Miocene-Pliocene boundary is not marked by a clear biostratigraphic event in the Atlantic and coring gaps occur within the recovered stratigraphic record. These limitations are overcome by combining a variety of chronostratigraphic datasets to construct an age-model that fits the currently available age indicators and demonstrates that coring in Hole U1387C did indeed recover the Miocene-Pliocene boundary at around 826 mbsf. This boundary is associated with a distinct and abrupt change in depositional environment. During the latest Messinian, hemipelagic sediments exhibiting precession-induced climate variability were deposited. These are overlain by Pliocene sediments deposited at a much higher sedimentation rate, with much higher and more variable XRF-scanning Zr/Al ratios than the underlying sediment, and that show evidence of winnowing, particle sorting and increasing grain size, which we interpret to be related to the increasing flow of MOW. Pliocene sedimentary cyclicity is clearly visible in both the benthic δ18O record and the Zr/Al data and is probably also precessionally controlled. Two contouritic bigradational sandy-beds are revealed above the third sedimentary cycle of the Pliocene. On the basis of these results, we conclude that sedimentation associated with weak Mediterranean-Atlantic exchange, began in the Gulf of Cadiz virtually at or shortly after the Miocene-Pliocene boundary.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 3
    Publication Date: 2021-04-21
    Description: The stable carbon isotope composition of dissolved inorganic carbon (δ13C-DIC) can be used to quantify fluxes within the carbon system. For example, knowing the δ13C signature of the inorganic carbon pool can help in describing the amount of anthropogenic carbon in the water column. The measurements can also be used for evaluating modeled carbon fluxes, for making basin-wide estimates of anthropogenic carbon, and for studying seasonal and interannual variability or decadal trends in interior ocean biogeochemistry. For all these purposes, it is not only important to have a sufficient amount of data, but these data must also be internally consistent and of high quality. In this study, we present a δ13C-DIC dataset for the North Atlantic which has undergone secondary quality control. The data originate from oceanographic research cruises between 1981 and 2014. During a primary quality control step based on simple range tests, obviously bad data were flagged. In a second quality control step, biases between measurements from different cruises were quantified through a crossover analysis using nearby data of the respective cruises, and values of biased cruises were adjusted in the data product. The crossover analysis was possible for 24 of the 32 cruises in our dataset, and adjustments were applied to 11 cruises. The internal accuracy of this dataset is 0.017 ‰.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2023-02-08
    Description: The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening, and sea ice cover on the Labrador Shelf during the last 6000 years. Our records reveal that the LC underwent three major oceanographic phases from the mid- to late Holocene. From 6.2 to 5.6 ka, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka, possibly associated with the late Holocene thermal maximum. While surface waters on the Labrador Shelf cooled gradually after 3 ka in response to the neoglaciation, Labrador Shelf subsurface or bottom waters show a shift to warmer temperatures after 2.1 ka. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last 2 millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Publication Date: 2022-01-31
    Description: A significant reduction in the Atlantic Meridional Overturning Circulation and rapid northern Hemisphere cooling 8200 years ago have been linked to the final melting of the Laurentide Ice Sheet. Although many studies associated this cold event with the drainage of Lake Agassiz-Ojibway, recent model simulations have shown that the Hudson Bay Ice Saddle collapse would have had much larger effects on the Atlantic Meridional Overturning Circulation than the lake outburst itself. Based on a combination of Mg/Ca and oxygen isotope ratios of benthic foraminifera, this study presents the first direct evidence of a major Labrador shelfwater freshening at 8.5 ka BP, which we associate with the Hudson Bay Ice Saddle collapse. The freshening is preceded by a subsurface warming of the western Labrador Sea, which we link to the strengthening of the West Greenland Current that could concurrently have accelerated the ice saddle collapse in Hudson Bay.
    Type: Article , PeerReviewed
    Format: text
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  • 6
    Publication Date: 2023-03-25
    Description: We present stable hydrogen isotope (dD) and carbon isotope (d13C) of sedimentary terrestrial leaf wax, namely n-alkanes, from marine sediment core SO 188-17286-1 (Bay of Bengal, 19°44.58′N, 89°52.76′E, 1428 m water depth) for the last ~130 kyr. There are four different homologues (n-C27, n-C29, n-C31 and n-C33). The concentration data of each homologues are also present here. Identification and quantification (concentration) of the individual compounds was carried out with an Agilent 6890 Gas Chromatograph (GC) with a flame ionization detector in the Geoscience, University of Kiel. The d13C and dD values of n-alkanes were then analyzed at the Leibniz Laboratory for Radiometric Dating and Stable Isotope Research in Kiel University using an Agilent 6890 GC coupled with a Thermo Finnigan MAT 253 isotope ratio mass (IRMS).
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 7
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    PANGAEA
    In:  Supplement to: Sadatzki, Henrik; Sarnthein, Michael; Andersen, Nils (2015): Changes in monsoon-driven upwelling in the South China Sea over glacial Terminations I and II: a multi-proxy record. International Journal of Earth Sciences, https://doi.org/10.1007/s00531-015-1227-6
    Publication Date: 2023-01-13
    Description: Upwelling intensity in the South China Sea has changed over glacial-interglacial cycles in response to orbital-scale changes in the East Asian Monsoon. Here, we evaluate new multi-proxy records of two sediment cores from the north-eastern South China Sea to uncover millennial-scale changes in winter monsoondriven upwelling over glacial Terminations I and II. On the basis of U/Th-based speleothem chronology, we compare these changes with sediment records of summer monsoondriven upwelling east of South Vietnam. Ocean upwelling is traced by reduced (UK'37-based) temperature and increased nutrient and productivity estimates of sea surface water (d13C on planktic foraminifera, accumulation rates of alkenones, chlorins, and total organic carbon). Accordingly, strong winter upwelling occurred north-west of Luzon (Philippines) during late Marine Isotope Stage 6.2, Heinrich (HS) and Greenland stadials (GS) HS-11, GS-26, GS-25, HS-1, and the Younger Dryas. During these stadials, summer upwelling decreased off South Vietnam and sea surface salinity reached a maximum suggesting a drop in monsoon rains, concurrent with speleothem records of aridity in China. In harmony with a stadial-to-interstadial see-saw pattern, winter upwelling off Luzon in turn was weak during interstadials, in particular those of glacial Terminations I and II, when summer upwelling culminated east of South Vietnam. Most likely, this upwelling terminated widespread deep-water stratification, coeval with the deglacial rise in atmospheric CO2. Yet, a synchronous maximum in precipitation fostered estuarine overturning circulation in the South China Sea, in particular as long as the Borneo Strait was closed when sea level dropped below -40 m.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 8
    Publication Date: 2023-01-30
    Description: The Mozambique Channel is a conduit of trade wind-driven throughflow that is a key component of the Agulhas Current and Agulhas leakage, a flux of warm and salty water from the tropical Indo-Pacific to the Atlantic Ocean. Agulhas leakage is thought to modulate Atlantic meridional overturning circulation variability. Previous studies from the Cape Basin suggest that enhanced Agulhas leakage played an important role in accelerating glacial terminations. The southern African monsoon response to abrupt climate changes associated with meltwater-induced reorganizations of the North Atlantic meridional overturning circulation, and its impact on the Mozambique Channel throughflow and, by extension, on the Agulhas leakage is not well understood. Here we present a high-resolution 26,000 year-long hydroclimate record of northern Madagascar, a core region of the southern hemisphere monsoon domain, and a mixed layer temperature reconstruction using sediment cores collected from the runoff-influenced eastern Mozambique Channel. The record indicates precipitation increases centered at 11.7-12.5 thousand years before present (kyr BP), 14.5-19 kyr BP, 23-24 kyr BP, 25-26 kyr BP. Considering age model uncertainties, this is the first strong evidence for southern African monsoon strengthening in response to meltwater-induced northern high latitude climate instabilities during the Younger Dryas (YD), Heinrich Stadial 1 (HS1), HS2 and the HS-like event prior to HS2, in agreement with the results of transient climate simulations. Furthermore, our study shows a reversal of the mixed layer temperature gradient between the western and eastern Mozambique Channel during Heinrich event 1 (HE1). We posit that the gradient reversal indicates a weakening of the trade wind-driven South Equatorial Current and Mozambique Channel throughflow that likely weakened the Agulhas leakage, potentially creating a feedback that may have contributed to the sustained weakening of the AMOC during HE1 by reducing the amount of heat and salt leakage into the Atlantic.
    Keywords: Agulhas Leakage; marine sediments; Mozambique Channel; Mozambique Channel throughflow; oxygen isotope data; SST
    Type: Dataset
    Format: application/zip, 5 datasets
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  • 9
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    PANGAEA
    In:  Supplement to: Lübbers, Julia; Kuhnt, Wolfgang; Holbourn, Ann E; Bolton, Clara T; Gray, Emmeline; Usui, Yoichi; Kochhann, Karlos Guilherme Diemer; Beil, Sebastian; Andersen, Nils (2019): The Middle to Late Miocene "Carbonate Crash" in the Equatorial Indian Ocean. Paleoceanography and Paleoclimatology, 34(5), 813-832, https://doi.org/10.1029/2018PA003482
    Publication Date: 2023-02-24
    Description: We integrate benthic foraminiferal stable isotopes, X-ray fluorescence elemental ratios, and carbonate accumulation estimates in a continuous sedimentary archive recovered at International Ocean Discovery Program Site U1443 (Ninetyeast Ridge, Indian Ocean) to reconstruct changes in carbonate deposition and climate evolution over the interval 13.5 to 8.2 million years ago. Declining carbonate percentages together with a marked decrease in carbonate accumulation rates after ~13.2 Ma signal the onset of a prolonged episode of reduced carbonate deposition. This extended phase, which lasted until ~8.7 Ma, coincides with the middle to late Miocene Carbonate Crash, originally identified in the eastern equatorial Pacific Ocean and the Caribbean Sea. Inter-ocean comparison reveals that intense carbonate impoverishment at Site U1443 (~11.5 to ~10 Ma) coincides with prolonged episodes of reduced carbonate deposition in all major tropical ocean basins. This implies that global changes in the intensity of chemical weathering and riverine input of calcium and carbonate ions into the ocean reservoir were instrumental in driving the Carbonate Crash. An increase in U1443 Log(Ba/Ti) together with a change in sediment color from red to green indicate a rise in organic export flux to the sea floor after ~11.2 Ma, which predates the global onset of the Biogenic Bloom. This early rise in export flux from biological production may have been linked to increased advection of nutrients and intensification of upper ocean mixing, associated with changes in the seasonality and intensity of the Indian Monsoon.
    Keywords: Carbonate Crash; Indian Ocean; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; stable carbon isotopes; stable oxygen isotopes; XRF
    Type: Dataset
    Format: application/zip, 6 datasets
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  • 10
    Publication Date: 2023-06-27
    Keywords: AGE; Age, 14C; Age, uncertainty; Agulhas Leakage; Calendar age; Calendar age, error to older; Calendar age, error to younger; Core; Date/Time of event; DEPTH, sediment/rock; Event label; GIK16163-2; GIK16164-2; GIK16166-2; Gravity corer (Kiel type); Laboratory code/label; Latitude of event; Longitude of event; M75/3; M75/3_143-2; M75/3_144-2; M75/3_146-2; marine sediments; Meteor (1986); Mozambique Channel; Mozambique Channel throughflow; oxygen isotope data; Sample material; SL; SST
    Type: Dataset
    Format: text/tab-separated-values, 217 data points
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