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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Paleoenvironmental Interpretations of the Lower Taylor Group, Olympus Range area, southern Victoria Land, Antarctica

Gilmer, Greer Jessie January 2008 (has links)
The Devonian Taylor Group, in the Olympus Range area, southern Victoria Land (SVL), Antarctica, is separated from the basement by a regional nonconformity (Kukri Erosion Surface). A second localized unconformity within the Taylor Group called the Heimdall Erosion Surface separates the New Mountain Sandstone and older units from the younger Altar Mountain Formation. The depositional environment of the New Mountain Sandstone has long been under contention. The New Mountain Sandstone Formation is a predominantly quartzose cross-bedded sandstone. Its newly defined Mt Jason Member is a coarse arkosic small scale cross-bedded pebbly sandstone that grades up section into the rest of the quartzose New Mountain Sandstone with large scale cross beds. The New Mountain Sandstone has been divided into five lithofacies including the Basal Conglomerate Lithofacies, Pebbly Sandstone Lithofacies, Granule Cross-bedded Lithofacies, Pinstripe Cross-bedded Lithofacies and Cross-bedded Sandstone Lithofacies. Deposition was in a shoreface environment with minor coastal aeolian deposition. The environment changed from upper shoreface to lower shoreface up section, forming transgressive to highstand systems tracts. The Heimdall Erosion Surface truncates the Cross-bedded Sandstone Lithofacies and the Pinstripe Cross-bedded Lithofacies and was formed due to relative sea level fall leading to exposure and erosion of underlying sedimentary and basement rocks. It forms a type 1 sequence boundary. The New Mountain Sandstone was partially or totally lithified before erosion as shown by the jagged morphology of the eroded cross beds on the surface. It is not known when cementation of the NMS took place or how much of the formation has been eroded. The Heimdall Erosion Surface and Kukri Erosion Surface converge locally due to erosion on the Heimdall Erosion Surface and relief on the Kukri Erosion Surface. The Heimdall Erosion Surface became a shore platform and the site of deposition as relative sea level rose. The Altar Mountain Formation with its Odin Member is a cross-bedded, massive and bedded feldspathic and quartzose sandstone that fines up section and is deposited on the erosion surface. The Altar Mountain Formation is divided into four lithofacies including the Conglomerate Lithofacies, Trough Cross-bedded Lithofacies, Cross-bedded Bioturbated Lithofacies and Bedded Fine Lithofacies. Deposition was in a shoreface environment, changing up section to an inner shelf environment with minor estuarine/tidal influence near the top of the section forming transgressive to highstand to regressive system tracts. The sedimentary rocks are derived mainly from the Granite Harbour Intrusives and Koettlitz Group, which underlie the sandstones, but were exposed elsewhere in SVL. The sandstone clasts within the Conglomerate Lithofacies could be derived from underlying older Taylor Group rocks or exotic sources from outside the field area. Correlation with data from adjacent areas suggests deposition of the New Mountain Sandstone occurred in a shallow sea that existed from the Olympus Range, southwards into the Asgard Range and included Vashka Crag. The area around Sponsors Peak and to the north was exposed and supplying feldspathic and quartzose sediment and pebbles into the depositional basin. As relative sea level fell due to either tectonic uplift or eustatic processes a large area of southern Victoria Land was exposed including the Olympus and Asgard Ranges and Bull Pass-St Johns Range area. This lead to erosion of the New Mountain Formation and basement rocks. Deposition of the New Mountain Sandstone continued further south shown by the gradational contact between it and the overlying Altar Mountain Formation. Relative sea level rise led to deposition of the Altar Mountain Formation. Shallow seas once more dominated the southern Victoria Land with deltas in the east (in the Bull Pass-St Johns Range area) feeding feldspathic sediment into the depositional basin (Odin Member). Further sea level rise drowned the delta region and a shallow marine to inner shelf environment led to deposition of the rest of the Altar Mountain Formation.
42

Retroarc basin reorganization and aridification during Paleogene uplift of the southern central Andes

Fosdick, J. C., Reat, E. J., Carrapa, B., Ortiz, G., Alvarado, P. M. 03 1900 (has links)
Tectonic development of the Andean Cordillera has profoundly changed the topography, climate, and vegetation patterns of the southern central Andes. The Cenozoic Bermejo Basin in Argentina (30 degrees S) provides a key record of thrust belt kinematics and paleoclimate south of the high-elevation Puna Plateau. Ongoing debate regarding the timing of initiation of upper plate shortening and Andean uplift persists, precluding a thorough understanding of the earlier tectonic and climatic controls on basin evolution. We present new sedimentology, detrital geochronology, sandstone petrography, and subsidence analysis from the Bermejo Basin that reveal siliciclastic-evaporative fluvial and lacustrine environments prior to the main documented phase of Oligocene-Miocene shortening of the Frontal Cordillera and Argentine Precordillera. We report the first radiometric dates from detrital zircons collected in the Cienaga del Rio Huaco Formation, previously mapped as Permian, that constrain a Late Cretaceous (95-93Ma) maximum depositional age. Provenance and paleocurrent data from these strata indicate that detritus was derived from dissected arc and cratonic sources in the north and northeast. Detrital zircon U-Pb ages of 37Ma from the overlying red beds suggest that foredeep sedimentation began by at least the late Eocene. At this time, sediment dispersal shifted from axial southward to transversal eastward from the Andean Arc and Frontal Cordillera. Subsidence analysis of the basin fill is compatible with increasing tectonic deformation beginning in Eocene time, suggesting that a distal foredeep maintained fluvial connectivity to the hinterland during topographic uplift and unroofing of the Frontal Cordillera, prior to Oligocene-Miocene deformation across the Precordillera.
43

Early prehistoric petrology : a case study from Leicestershire

Parker, Matthew John January 2013 (has links)
This research focused on the petrographic analysis of prehistoric ceramics within the East Midlands. Prior assessments have been intermittent and not drawn together by a research-based agenda, with a few notable exceptions. This research uses petrographic analysis to shed light on early prehistoric society within Leicestershire, a county overlooked in comparison to other regions. The aim of this research was to investigate the procurement of raw materials and the subsequent production of Neolithic and early Bronze Age ceramics in Leicestershire, placing the county in its regional context. Petrographic slides from several early prehistoric sites were produced and analysed to determine the presence of any non-local material within the fabric of the ceramics. Existing petrographic data from other sites in the East Midlands were used as a comparative data set to test whether the ceramics from Leicestershire were typical or atypical of the wider production and procurement pattern. The results of the petrographic analysis on the Leicestershire sites indicated that the clay and inclusions were most likely of local origin, with no definitive evidence for non-local inclusions. However, the results from the comparative petrographic data obtained from sites within the wider East Midlands does support the movement of raw materials and/or finished ceramic products within the region. Preferential sources appear to have been continually exploited, both chronologically and geographically. The prime target of the exploitation was the Charnwood Forest area of Leicestershire, with groups from Derbyshire and Nottinghamshire utilising this resource in addition to more local groups within Leicestershire.
44

An architectural approach for reasoning about trust properties

Namiluko, Cornelius January 2012 (has links)
The need for trustworthy system operation has been acknowledged in many circles. However, establishing that a system is trustworthy is a significant challenge. While trusted computing proposes technical mechanisms towards this end, less attention is directed towards providing a basis for trusting such systems. Consequently, it is not clear: (i) how such mechanisms influence the overall trust in a system; (ii) the properties and assumptions upon which trust is based; and (iii) the evidence necessary to reason about these properties. This can be attributed to a number of factors including: (i) the complexity of modern systems; (ii) a lack of consensus on a definition of trust; and (iii) a lack of a systematic approach for identifying and using evidence to reason about trust-related properties. This dissertation presents research towards addressing these challenges. We argue that an architectural approach provides effective abstractions for making trust properties and assumptions explicit and reasoning about a system's ability to satisfy these properties. We propose a framework for identifying, categorising and mapping trust-properties to aspects of a system that could be used to reason about these properties. Guided by this framework, we propose and develop models for representing knowledge about a particular aspect and using it to reason about trust-properties. A semantic model, based on the semantics of Z, is developed to characterise building blocks of trustworthy systems and to demonstrate how the system's constituents determine its trustworthiness. An abstraction model based on formal verification is developed to reason about the impact of the system's construction and configuration on its trustworthiness. Finally, two complementary models for capturing the runtime aspects of the system are developed. A trace-based model enables analysis of runtime evidence in the form of event logs and a provenance-based model captures operations on the system as a provenance graph. The models are validated on a trusted grid architecture, a password manager and a trustworthy collaborative system.
45

Semantic Assistance for Data Utilization and Curation

Becker, Brian J 06 August 2013 (has links)
We propose that most data stores for large organizations are ill-designed for the future, due to limited searchability of the databases. The study of the Semantic Web has been an emerging technology since first proposed by Berners-Lee. New vocabularies have emerged, such as FOAF, Dublin Core, and PROV-O ontologies. These vocabularies, combined, can relate people, places, things, and events. Technologies developed for the Semantic Web, namely the standardized vocabularies for expressing metadata, will make data easier to utilize. We gathered use cases for various data sources, from human resources to big enterprise. Most of our use cases reflect real-world data. We developed a software package for transforming data into these semantic vocabularies, and developed a method of querying via graphical constructs. The development and testing proved itself to be useful. We conclude that data can be preserved or revived through the use of the metadata techniques for the Semantic Web.
46

MPPI: um modelo de procedência para subsidiar processos de integração / MPPI: a provenance model to support data integration processes

Tomazela, Bruno 05 February 2010 (has links)
A procedência dos dados consiste no conjunto de metadados que possibilita identificar as fontes e os processos de transformação aplicados aos dados, desde a criação até o estado atual desses dados. Existem diversas motivações para se incorporar a procedência ao processo de integração, tais como avaliar a qualidade dos dados das fontes heterogêneas, realizar processos de auditoria dos dados e de atribuição de autoria aos proprietários dos dados e reproduzir decisões de integração. Nesta dissertação é proposto o MPPI, um modelo de procedência para subsidiar processos de integração. O modelo enfoca sistemas nos quais as fontes de dados podem ser atualizadas somente pelos seus proprietários, impossibilitando que a integração retifique eventuais conflitos de dados diretamente nessas fontes. O principal requisito do MPPI é que ele ofereça suporte ao tratamento de todas as decisões de integração realizadas em processos anteriores, de forma que essas decisões possam ser reaplicadas automaticamente em processos de integração subsequentes. O modelo MPPI possui quatro características. A primeira delas consiste no mapeamento da procedência dos dados em operações de cópia, edição, inserção e remoção, e no armazenamento dessas operações em um repositório de operações. A segunda característica é o tratamento de operações de sobreposição, por meio da proposta das políticas blind, restrict, undo e redo. A terceira característica consiste na identificação de anomalias decorrentes do fato de que fontes de dados autônomas podem alterar os seus dados entre processos de integração, e na proposta de quatro tipos de validação das operações frente a essas anomalias: validação completa, da origem, do destino, ou nenhuma. A quarta característica consiste na reaplicação de operações, por meio da proposta dos métodos VRS (do inglês Validate and Reapply in Separate) e VRT (do inglês Validate and Reapply in Tandem) e da reordenação segura do repositório, os quais garantem que todas as decisões de integração tomadas pelo usuário em processos de integração anteriores sejam resolvidas automaticamente e da mesma forma em processos de integração subsequentes. A validação do modelo MPPI foi realizada por meio de testes de desempenho que investigaram o tratamento de operações de sobreposição, o método VRT e a reordenação segura, considerando como base as demais características do modelo. Os resultados obtidos mostraram a viabilidade de implementação das políticas propostas para tratamento de operações de sobreposição em sistemas de integração reais. Os resultados também mostraram que o método VRT proporcionou ganhos de desempenho significativos frente à coleta quando o objetivo é restabelecer resultados de processos de integração que já foram executados pelo menos uma vez. O ganho médio de desempenho do método VRT foi de pelo menos 93%. Ademais, os testes também mostraram que reordenar as operações antes da reaplicação pode melhorar ainda mais o desempenho do método VRT / Data provenance is the set of metadata that allows for the identification of sources and transformations applied to data, since its creation to its current state. There are several advantages of incorporating data provenance into data integration processes, such as to estimate data quality and data reliability, to perform data audit, to establish the copyright and ownership of data, and to reproduce data integration decisions. In this master\'s thesis, we propose the MPPI, a novel data provenance model that supports data integration processes. The model focuses on systems in which only owners can update their data sources, i.e., the integration process cannot correct the sources according to integration decisions. The main goal of the MPPI model is to handle decisions taken by the user in previous integration processes, so they can be automatically reapplied in subsequent integration processes. The MPPI model introduces the following properties. It is based on mapping provenance data into operations of copy, edit, insert and remove, which are stored in an operation repository. It also provides four techniques to handle overlapping operations: blind, restrict, undo and redo. Furthermore, it identifies anomalies generated by sources that are updated between two data integration processes and proposes four validation approaches to avoid these anomalies: full validation, source validation, target validation and no validation. Moreover, it introduces two methods that perform the reapplication of operations according to decisions taken by the user, called the VRS (Validate and Reapply in Separate) and the VRT (Validate and Reapply in Tandem) methods, in addition to extending the VRT method with the safe reordering optimization. The MPPI model was validated through performance tests that investigated overlapping operations, the VRT method and the safe reordering optimization. The tests showed that the techniques proposed to handle overlapping operations are feasible to be applied to real integration systems. The results also demonstrated that the VRT method provided significant performance gains over data gathering when the goal is to reestablish previous integration results. The performance gains were of at least 93%. Furthermore, the performance results also showed that reordering the operations before the reapplication process can improve even more the performance of the VRT method
47

Geologia isotópica e geocronologia do complexo metamórfico porongos e suíte metamórfica várzea do capivarita, Cinturão Dom Feliciano, Sul do Brasil: i implicações para a evolução do Gondwana em sua margem ocidental

Gruber, Leonardo January 2016 (has links)
Proveniência por métodos isotópicos em duas unidades litodêmicas – o Complexo Metamórfico Porongos (CMP) no domínio central-oriental do Cinturão Dom Feliciano (CDF) e a Suíte Metamórfica Várzea do Capivarita (SMVC), localizada no domínio leste do CDF - apresentou áreas-fonte similares nos dois casos: Os metassedimentos do CMP, na região das Antiformes de Santana da Boa Vista e Serra dos Pedrosas, foram depositados entre 785 e 595 Ma (U-Pb em zircão detrítico por LA-ICP-MS). Apresentam registros de áreas-fonte com predominância de idades de ca. 2.2 – 2.0 Ga, mesmas idades do embasamento da região, o Complexo Encantadas. As assinaturas isotópicas de 207Pb/204Pb X 206Pb/204Pb mostraram pouca relação dos metassedimentos do CMP com áreas-fonte do cráton Rio de La Plata, e εNd variando entre -13 a -6.5, com valores menos negativos para amostras onde foram obtidos zircões com mesma idade do vulcanismo félsico do CMP. Outros registros incluem idades de 1.5-1.4 Ga, cujas assinaturas εHf indicam fontes juvenis, possivelmente relacionadas a um sistema de rifteamento registrado nos Anortositos Capivarita. Na Antiforme Capané, zircões datados em SHRIMP e LA-ICP-MS de rochas metavulcânicas intermediárias a félsicas indicaram idades de 663 ± 2.7 Ma, representando um vulcanismo mais jovem do que aquele encontrado anteriormente no CMP, vinculado à fusão parcial crustal. Novos dados U-Pb em zircão confirmam registro do metavulcanismo de 783.4 ± 3.9 Ma nos metassedimentos, comparáveis a idades obtidas nos Gnaisses Cerro Bori, interpretados como um arco continental de ca. 800 Ma. Zircões detríticos de rochas metassedimentares da SMVC apresentaram registros de ca. 2.2 – 2.0 Ga, além de idades de ca. 1.4 Ga e idade máxima de deposição de 714.3 ± 3.9 Ma, com pico metamórfico registrado em borda metamórfica de zircões com 618 ± 7.3 Ma εHf predominantemente negativas. Mármores apresentaram razões 87Sr/86Sr de 0.70609, o que permite deduzir uma idade de deposição mais antiga que 715 Ma, próximo dos valores encontrados em mármores na região de Arroio Grande. A comparação dos isótopos de Hf com rochas do Cinturão Damara nos crátons Kalahari e Congo, cuja amalgamento junto ao Rio de La Plata deu origem ao Gondwana Ocidental, mostram que existe pouca ou nenhuma relação com áreas-fonte dos metassedimentos do CMP e SMVC no Neoproterozóico. Estes dados levam a dedução de que acresção de terrenos ou microcontinentes com características de embasamento, nesse caso denominado aqui como Embasamento Encantadas, cuja evolução se dá com acresção de um arco continental de idades entre 780 e 660 Ma, é a origem de parte das áreas-fonte do CMP, e possivelmente foi um dos eventos tectônicos que controlaram evolução do terreno ao longo do CMP e SMVC. / Isotopic provenance realized in two lithodemic units – Porongos Metamorphic Complex (PMC), in the central-eastern domain of the Dom Feliciano Belt (DFB) and the Várzea do Capivarita Metamoprhic Suite (VCMS), in the eastern domain of the same belt – presented similar source-areas in both cases: The PMC metasediments, in Santana da Boa Vista and Serra dos Pedrosas Antiforms were deposited between 785 and 595 Ma (LA-ICP-MS detrital zircon U-Pb). Both PMC and VCMS displayed source-areas with ages varying from ca. 2.2 – 2.0 Ga, which is the same age presented in the regional basement, the Encantadas Complex. 207Pb/204Pb X 206Pb/204Pb isotopic signatures displayed little resemblance between CMP metasediments and possible source-areas in the Rio de La Plata Craton, and εNd varied between -13 to -6.5, with less negative values in samples were where obtained zircons with the same age of felsic volcanism in the PMC. Others records included ages from 1.5 to 1.4 Ga, with εHf signatures indicating juvenile sources, possibly related to a rifting system recorde in the Capivarita Anorthosite. In the Capané Antiform, SHRIMP and LA-ICP-MS U-Pb zircon ages from felsic to intermediary metavolcanic rocks displayed 663 ± 2.7 Ma, which is a younger record than the previously obtained in the PMC, and can be related to partial crustal fusion. Also new U-Pb detrital zircon ages confirm the record of the metavolcanics of 783.4 ± 3.9 Ma in the metasediments, comparable to the ages obtained in the Cerro Bori orthogneisses, interpreted as a continental arc of ca. 800 Ma. Metasedimentary rocks of VCMS displayed zircons with ca. 2.2-2.0 Ga, besides ages of ca. 1.4 Ga and maximum depositional age of 714.3 ± 3.9 Ma, with metamorpich peak recorded in metamorphic rims of 618 ± 7.3 Ma and negative εHf signatures. Marbles presented 87Sr/86Sr ratios of 0.70609, which can be deducted as an older than 715 Ma depositional age, near values obtained to Arroio Grande marbles. Comparison of Hf signatures with rocks from Damara Belt of Kalahari and Congo Cratons, whose assembly with Rio de La Plata to form West Gondwana in Neoproterozoic, displayed little to no relationship with the source-areas of PMC and VCMS metasediments I in the Neoproterozoic. This indicates that terrain or a microcontinent accretion with basement features, in this case the Encantadas Basement, whose evolution underwent accretion in a continental arc between 780 to 660 Ma, it’s the source to part of the PMC , and possible was one of the tectonic events that controlled terrain evolution in the PMC and VCMS.
48

Geochemical sourcing of granite ground stone tools from Belize

Tibbits, Tawny Lynn Bailey 01 May 2016 (has links)
Portable X-ray fluorescence (pXRF) provides a new alternative to destructive methods of raw material characterization, such as X-ray fluorescence (XRF), neutron activation analysis (NAA), and traditional thin section petrography, although its effectiveness on coarse-grained materials, such as granite, has been questioned. This project addressed this question by determining the effectiveness of pXRF in characterizing granites from Belize and in sourcing granite ground stone tools from Maya sites in Belize. Geochemical fingerprints were defined for three potential source areas (granite plutons in the Maya Mountains of Belize) using outcrop samples. Samples were analyzed using pXRF, XRF, electron microprobe (EMPA), and thin section analyses. PXRF data from archaeological collections of granite ground stone tools from sites in Belize were then compared to the pluton geochemical signatures. There were two principle results of this research. First, analyses indicated that pXRF can accurately characterize the geochemistry of granites from Belize on a suite of elements. Second, this research demonstrated that the Maya of Belize exploited multiple granite outcrops and participated in different kinds of exchange networks to acquire granite, sometimes acquiring stone from the nearest outcrops and sometimes not. While Mountain Pine Ridge was the dominant source outcrop that was exploited, Cockscomb Basin and Hummingbird Ridge granites were also quarried or scavenged. Sometimes the closest source was used, as is the case at Alabama, who exploited the locally available Cockscomb Basin granite. Through this study it appears that the nearest pluton was not always used. Instead Mountain Pine Ridge granite tools were imported from a greater distance, implying that there were additional factors, such as economic partners and changing political powers, which lead to Mountain Pine Ridge granite being the most pervasive in most archaeological collections within Belize.
49

Predicting the Geographic Origin of Heroin by Multivariate Analysis of Elemental Composition and Strontium Isotope Ratios

DeBord, Joshua S 12 June 2018 (has links)
The goal of this research was to aid in the fight against the heroin and opioid epidemic by developing new methodology for heroin provenance determination and forensic sample comparison. Over 400 illicit heroin powder samples were analyzed using quadrupole and high-resolution inductively-coupled plasma mass spectrometry (Q-ICP-MS and HR-ICP-MS) in order to measure and identify elemental contaminants useful for associating heroin samples of common origin and differentiating heroin of different geographic origins. Additionally, 198 heroin samples were analyzed by multi-collector ICP-MS (MC-ICP-MS) to measure radiogenic strontium isotope ratios (87Sr/86Sr) with high-precision for heroin provenance determination, for the first time. Supervised discriminant analysis models were constructed to predict heroin origin using elemental composition. The model was able to correctly associate 88% of the samples to their region of origin. When 87Sr/86Sr data were combined with Q-ICP-MS elemental data, the correct association of heroin samples improved to ≥90% for all groups with an average of 93% correct classification. For forensic sample comparisons, quantitative elemental data (11 elements measured) from 120 samples, 30 from each of the four regions, were compared in order to assess the rate of discrimination (5400 total comparisons). Using a match criterion of ±3 standard deviations about the mean, only 14 of the 5400 possible comparison pairs were not discriminated resulting in a discrimination rate of 99.7%. For determining the rate of correct associations, 3 replicates of 24 duplicate samples were prepared and analyzed on separate days. Only 1 of the 24 correct pairs were not associated for a correct association rate of 95.8%. New methods for provenance determination and sample comparison are expected to be incredibly useful to intelligence agencies and law enforcement working to reduce the proliferation of heroin.
50

Sequence Stratigraphy and Detrital Zircon Provenance of the Eureka Quartzite in South-Central Nevada and Eastern California

Workman, Benjamin David 2012 May 1900 (has links)
The Middle-Late Ordovician Eureka Quartzite in south-central Nevada and eastern California is a supermature quartz arenite that was deposited along the Lower Paleozoic western passive margin of Laurentia. Measured section descriptions and facies stacking patterns indicate that the Eureka Quartzite represents a 3rd-order sequence and contains three ~2-4 m.y. sequences and many small parasequences. Detrital zircon analysis of eight samples from the base and top of four locations contains three main populations of ~1.8-2.0 Ga, ~2.6-2.8 Ga, and ~2.0-2.3 Ga, and a smaller infrequent population of ~1.6-1.8 Ga grains. These peaks are interpreted to represent sediment sourced from exposed proximal basement to the east, likely from the Yavapai and Mazatzal Provinces (~1.6-1.7 Ga), the Trans-Hudson Orogen (~1.8-1.9 Ga), Paleoproterozoic crusts (~2.0-2.3 Ga), and underlying or proximal Archean (~2.6-2.8 Ga) sources. Sediment likely was transported to the shoreline and across Archean basement by rivers draining the Transcontinental Arch. Long-shore currents played an important role in deposition and likely account for the similarity of Middle-Late Ordovician, supermature, quartz arenite deposits on western Laurentia. Although the Peace River Arch likely provided some sediment for the Eureka Quartzite, it is apparent its provenance was mostly Trans-Hudson Orogen and Archean basement. Temporal and spatial provenance changes are inferred from probability-density plots of the detrital zircon analyses to indicate sea-level changes covered or exposed possible sediment sources during deposition.

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