Auswahl der wissenschaftlichen Literatur zum Thema „Spectre normalisé des REE“

Many rare earth element (REE) deposits have experienced multistage geological enrichment processes resulting in REE bearing mineral assemblages of considerable complexity and variability. Automated scanning electron microscopy (SEM) mineral liberation analysis of such REE ores is confronted by the difficult assignment of energy-dispersive X-ray (EDX) spectra to REE mineral names. To overcome and bypass this problem, a generic and reliable labelling of EDX reference spectra obtained from REE-bearing minerals based on their contents of Si, Ca, F and P in a bulk normalised analysis is proposed. The labelled spectra are then combined into groups of REE-P (~monazite), REE-Ca-Si-P (~britholite), REE-Ca-F (~synchysite) and REE-F (~bastnaesite, parisite, fluocerite). Mixed spectra with low counts for REE from minute REE mineral grains are combined into a separate group. This classification scheme is applied to automated SEM mineral liberation analysis (MLA) data from beneficiation products by comminution and multistage flotation of REE carbonatite ores. Mineral modes, mineral grain size distribution, mineral liberation, mineral locking and mineral grade versus recovery curves based on the analysis of >200,000 particles in a sample can be recognised and interpreted in virtual grain size fractions. The approach as proposed here will allow future process mineralogical studies of REE deposits to be robust and comparable.

Niq Mhlongo's collection of short stories, Soweto, Under the Apricot Tree (2018), does not perhaps immediately present itself as speculative fiction. The collection, however, gives the supernatural world of African indigenous knowledge as much weight in shaping characters' lives and experiences as it does contemporary socio-political realities. It troubles established genre distinctions in that it can be seen as a work simultaneously belonging to magical realism, social realism, and horror. This article contends that it is precisely owing to the work's use of supernatural and uncanny aspects that this collection can be viewed as a form of social or sociological realism, which aims at depicting the peculiar contemporary and subjective (sur)realities of many young black South Africans. It is faithful to the contradictory worlds of tradition and globalisation that many South Africans straddle, as well as to the spectres of colonialism and Apartheid, that impinge on the present in both material and immaterial forms. In many ways the collection stages the difficulty of decolonisation and the subjective spectres and doppeigängers that such a process unleashes. This paper will make use of the work of Sigmund Freud, Avery F. Gordon, Eve Tuck and C. Ree to explore instances of haunting and the uncanny in Mhlongo's collection.

La traçabilité géographique des produits alimentaires à l'aide de marqueurs chimiques est un défi important pour garantir la qualité et l'authenticité des aliments. Le comportement des Eléments de Terres Rares (REE) a été identifié comme un possible outil pour l'identification géographique des aliments. Dans cette thèse, le comportement des REE dans le système Sol-Vitis vinifera L. a été exploré en utilisant une approche géochimique. L'objectif est de comprendre si le spectre normalisé des REE (REE*) peut être un outil pour retracer l'origine géographique des aliments. Nous nous sommes concentrés sur des plantes cultivées sur des substrats enrichis et non enrichis en REE, en nous demandant si les enrichissements en REE du sol influencent la croissance de Vitis vinifera L et l'accumulation des REE dans les organes de la plante. Nous avons trouvé que l'enrichissement en REE du sol n'influence ni la masse de la plante ni l'accumulation de REE dans les feuilles, ce qui implique que les sols pollués par les REE ne devraient pas influencer significativement la quantité des REE trouvée dans le produit alimentaire de Vitis vinifera L. Nous démontrons que les REE* des organes de la plante sont capables de tracer les conditions d'enrichissement du sol en discriminant les conditions environnementales de la croissance de Vitis vinifera L. Puisque les REE* peuvent être utilisés pour différencier les plantes de différents sols de croissance, nous proposons que les REE* sont un marqueur potentiel pour identifier le substrat de croissance de Vitis vinifera L. Par conséquent, nous proposons que les REE sont un outil potentiel pour évaluer la qualité et la sécurité d'autres écosystèmes
The geographic traceability of food products through the use of chemical markers is an important challenge to ensure quality and authenticity of food. In recent years, the behaviour of Rare Earth Elements (REE) has been identified as possible tool for food geographical identification based on their known capability of tracing pedo-genetic and petro-genetic processes. In this thesis, the behaviour of REE in the Soil/Vitis vinifera L. system has been explored using a geochemical approach. The goal is to understand if the normalized pattern of REE (REE*) can be a useful tool to trace the geographical origin of food. We focused on plants grown in both greenhouse and field using REE enriched and non-enriched substrates wondering if REE soil enrichments influence the growth of Vitis vinifera L. and the REE accumulation in plant organs. We found that the stress generated by REE enriched soil does not influence neither the plant mass nor the REE accumulation in leaves implying that REE polluted soils should not influence the amount of REE found in Vitis vinifera L food-products. We have, also, demonstrated that that the REE* in plant organs t trace enriched soil substrates discriminating plants from different soils of growth. This work allows to propose that REE* as potential marker for identifying the substrate where Vitis vinifera L. growth. Finally, discrimination of substrate enrichments suggests that REE* is a potential tool for quality and safety of other ecosystems. Our experimental investigation improves our knowledge on REE uptake in soil-Vitis vinifera L. system, highlighting the potential use of REE as biogeochemical tracers of environmental conditions
La tracciabilità geografica dei prodotti alimentari, attraverso l'uso di traccianti chimici, è una sfida importante per garantire la qualità e l'autenticità degli alimenti. Negli ultimi anni, il comportamento degli Elementi delle Terre Rare (REE) è stato identificato come possibile strumento per l'identificazione geografica degli alimenti, sulla base della nota proprietà di tracciare i processi pedo-genetici e petro-genetici. In questa tesi, il comportamento dei REE nel sistema Suolo/Vitis vinifera L. è stato esplorato utilizzando un approccio geochimico. L'obiettivo è capire se il modello normalizzato di REE (REE*) può essere uno strumento utile per tracciare l'origine geografica degli alimenti. Le REE possono essere accumulate nelle piante mantenendo la loro distribuzione nel passaggio dal suolo alle foglie o ai frutti, anche se le foglie possono incorporare i metalli lisciviati dalle particelle di polvere atmosferica in particolari condizioni ambientali. Tuttavia, il meccanismo di trasferimento di REE dal suolo alle piante è poco conosciuto. Ci siamo concentrati su piante cresciute sia in serra che in campo usando substrati arricchiti e non arricchiti di REE chiedendoci se gli arricchimenti del suolo di REE influenzassero la crescita di Vitis vinifera L. e l'accumulo di REE negli organi della pianta, testando l'uso di REE* come discriminatore di piccole quantità di REE nel suolo. Inoltre, abbiamo valutato il ruolo giocato dallo xylema nel trasferimento di REE e il possibile impatto fisiologico nella Vitis vinifera L. Abbiamo trovato che lo stress generato dal suolo arricchito di REE non influenza né la massa della pianta né l'accumulo di REE nelle foglie e abbiamo dimostrato che le REE* negli organi della pianta sono in grado di tracciare le condizioni del suolo arricchito discriminando le condizioni ambientali di crescita della Vitis vinifera L. Poiché REE* può essere usato per differenziare le piante da diversi terreni di crescita, proponiamo che l'uso di REE* sia un potenziale marcatore per identificare il substrato di crescita di Vitis vinifera L. Dal nostro lavoro si possono dedurre importanti implicazioni dal punto di vista ambientale. Poiché la quantità iniziale di REE nei substrati non influenza la quantità accumulata nelle foglie, eventuali suoli inquinati da REE non dovrebbero influenzare significativamente la quantità di REE trovata nei prodotti alimentari di Vitis vinifera L. Infine, la capacità di discriminare degli arricchimenti del substrato suggerisce che REE* può essere uno strumento potenziale per valutare la qualità e la sicurezza di altri ecosistemi. La nostra indagine sperimentale migliora le nostre conoscenze sull'assorbimento di REE nel sistema Suolo/Vitis vinifera L. evidenziando il potenziale uso di REE come traccianti biogeochimici delle condizioni ambientali

The geographic traceability of food products through the use of chemical markers is an important challenge to ensure quality and authenticity of food. In recent years, the behaviour of Rare Earth Elements (REE) has been identified as possible tool for food geographical identification based on their known capability of tracing pedo-genetic and petro-genetic processes. In this thesis, the behaviour of REE in the Soil/Vitis vinifera L. system has been explored using a geochemical approach. The goal is to understand if the normalized pattern of REE (REE*) can be a useful tool to trace the geographical origin of food. REE may be accumulated in plants keeping their distribution in passing from soil to leaves or fruits. However, the mechanism of soil/plant REE transfer is poorly known, even if leaves may incorporate metals leached from atmospheric dust particles in particular environmental conditions. We focused on plants grown in both greenhouse and field using REE enriched and non-enriched substrates wondering if REE soil enrichments influence the growth of Vitis vinifera L. and the REE accumulation in plant organs testing the use of REE* as discriminator of small amounts of REE in the soil. We, also, have evaluated the role of xylem-sap in the transfer of REE transfer and the possible physiological impact in Vitis vinifera L. We found that the stress generated by REE enriched soil does not influence neither the plant mass nor the REE accumulation in leaves and demonstrated that the REE* in plant organs traces enriched soil substrates discriminating plants from different soils of growth. This work allows to propose that REE* as potential marker for identifying the substrate where Vitis vinifera L. grows. This work yields, also, important consequences from environmental perspective: since the REE amount in the substrates does not influence the amount accumulated in leaves REE polluted soils should not influence the amount of REE found in Vitis vinifera L food-products. Finally, discrimination of substrate enrichments suggests that REE* is a potential tool for quality and safety of other ecosystems. Our experimental investigation improves our knowledge on REE uptake in soil-Vitis vinifera L. system, highlighting the potential use of REE as biogeochemical tracers of environmental conditions.

Previously we reported the development and validation of a technique of estimating the spectral sensitivities of the middle-wavelength sensitive (MWS) and long-wavelength sensitive (LWS) cones that relies on the use of transient adaptation conditions. The spectral sensitivity for detecting 17-Hz flicker is measured during the first 500 ms following a change of background color from deep-red to blue for LWS cone isolation or vice versa for MWS cone isolation. In this paper, we report the final analysis of the MWS and LWS cone spectral sensitivities obtained in two protanopes, four deuteranopes and eleven normals.