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  • 1
    Publication Date: 2021-02-17
    Description: Burial of large quantities of magnetite (Fe(II)Fe(III)2O4) in iron formations (IFs) likely contributed to the protracted oxidation of Earth's surface during the Precambrian Eons. Magnetite can form through a diversity of biological and abiotic pathways and its preservation in IFs may thus be variably interpreted as the result of some combination of these processes. Such interpretations give rise to divergent pictures of the Precambrian Earth system and models for its evolution through time. New knowledge on the contribution of specific magnetite formation pathways is, therefore, needed to accurately tether our conceptual and numerical models to the geologic record. To constrain pathways of magnetite formation under ferruginous conditions, we conducted geochemical and multi-method microspectroscopic analyses on particles obtained from the water columns and sediments of ferruginous lakes Matano and Towuti, in Indonesia. We find that biologically reactive Fe(III) mineral phases are reduced in the anoxic waters of both lakes, causing the formation of primary authigenic magnetite, directly in the water column. This water column magnetite often takes conspicuous framboidal forms, which given the link to microbial Fe(III) reduction, may provide a biological signature on early Earth and by extension, other planetary bodies. The consumption of more biologically reactive forms of Fe(III) and the resulting delivery of primary magnetite to underlying sediments promotes the burial of oxidized equivalents and implies that primary magnetite formation could have been a principal pathway of Fe delivery to IFs. Combined, the removal of Fe from Earth's surface through biologically induced magnetite formation and subsequent burial in IFs, suggests that seawater chemistry and the microbially mediated reactions that cause magnetite formation played key roles in Earth system evolution and in setting the pace for planetary oxidation through the Precambrian Eons.
    Type: info:eu-repo/semantics/article
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  • 2
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/article
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  • 3
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
    Publication Date: 2020-02-12
    Description: Measurements of benthic foraminiferal cadmium:calcium (Cd/Ca) have indicated that the glacial–interglacial change in deep North Pacific phosphate (PO4) concentration was minimal, which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean. Here we present sedimentary redox-sensitive trace metal records from Ocean Drilling Program (ODP) Site 882 (NW subarctic Pacific, water depth 3244 m) to make inferences about changes in deep North Pacific oxygenation – and thus respired carbon storage – over the past 150,000 yr. These observations are complemented with biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep-water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment. Our results suggest that the deep subarctic Pacific water mass was depleted in oxygen during glacial maxima, though it was not anoxic. We reconcile our results with the existing benthic foraminiferal Cd/Ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed, rather than remineralized. This change would have corresponded to an increase in the deep Pacific storage of respired carbon, which would have lowered atmospheric carbon dioxide (CO2) by sequestering CO2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea. The magnitude of change in preformed nutrients suggested by the North Pacific data would have accounted for a majority of the observed decrease in glacial atmospheric pCO2.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 5
    Publication Date: 2021-12-15
    Description: The leaching of lateritic soils can result in drainage waters with high concentrations of Cr(VI). Such Cr(VI)-rich waters have developed in streams that drain lateritic soils in Central Sulawesi Island, Indonesia. Chromium in this lateritic drainage system is removed by reduction of Cr(VI) to Cr(III) through two faucets delivering an FeSO4 solution to the drainage waters. Cr stable isotope compositions from both water and sediment samples along the drainage path were used to evaluate the efficacy of this remediation strategy. Overall, dissolved [Cr(VI)] decreased moving downstream, but there was an increase in [Cr(VI)] after the first faucet that was effectively removed at the second faucet. This intermittent increase in [Cr(VI)] was the likely result of oxidative remobilization of sediment Cr(III) through reaction with Mn oxides. Cr isotope distributions reflect near quantitative reduction associated with the FeSO4 faucets but also reveal that Cr isotope fractionation is imparted due to Cr redox cycling, downstream. During this redox cycling, fractionation appeared to accompany oxidation, with the product Cr(VI) becoming enriched in 53Cr relative to the reactant Cr(III) with an apparent fractionation factor of 0.7 ± 0.3‰. This study suggests that while FeSO4 effectively removes Cr(VI) from the drainage, the presence of Mn oxides can confound attenuation and improvements to Cr(VI) remediation should consider means of preventing the back reaction of Cr(III) with Mn oxides.
    Type: info:eu-repo/semantics/article
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  • 6
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 101 (1979), S. 1625-1626 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 22 (1989), S. 2641-2644 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 28 (1999), S. 453-456 
    ISSN: 1432-2161
    Keywords: Key words Hidradenitis suppurativa ; Acne conglobata ; Arthritis ; Enthesitis ; Hands ; Calcaneus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report the case of a 48-year-old man who presented with an erosive, seronegative, HLA-B27-negative, peripheral polyarthritis, associated with hidradenitis suppurativa of axillae and buttocks. The pertinent literature is reviewed. This paper is the second devoted to this topic in a radiological journal and the first to document erosion of the posterior aspect of the calcaneus.
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  • 10
    ISSN: 1432-2323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Sur 258 patients opérés pour hyperparathyroïdie secondaire (HPT II) entre 1971 et 1988, 33 ont eu une ou plusieurs réinterventions pour HPT II persistante ou récidivante. Ces réinterventions n'ont été suivie ni d'une mortalité ni d'une morbidité significative. Après parathyroïdectomie incomplète (25 cas), 15 patients ont été réopérés. Douze d'entre eux avaient déjà été opérés dans un autre établissement. Trois patients sont morts pour des causes sans rapport avec leur HPT II. Les 12 autres patients sont guéris. Après parathyroïdectomie subtotale réussie (79 cas), 2 patients (2.5%) ont eu une récidive, respectivement 5 et 6 ans plus tard. Actuellement les 2 patients sont guéris. Après parathyroïdectomie totale avec autotransplantation (152 cas), 16 patients (10.5%) ont dû être réopérés á cause des greffons. Le délai moyen avant la réintervention fut de 2 1/2 ans. Une hypertrophie des fragments greffés fut observés dans 4 cas (2.6%) mais 2 seulement de ces 4 patients ont été guéris après ablation des greffons. Chez 5 patients du tissu parathyroïdien résiduel ou une glande surnuméraire au cou ou dans le médiastin ont été suspectés, mais ceci n'a pas été confirmé: un patient a été à nouveau cervicotomisé sans succès, un autre refuse toujours la réopération, et 3 sont morts. Chez 6 autres patients la récidive était discutable et l'HPT II n'a pas été confirmée. Quant aux 3 derniers patients, le diagnostic était incorrect et une intoxication à l'aluminium fut démontre utérieurement. Les résultats d'une réintervention pour HPT II persistante ou récidivante dépendent avant tout d'un bon diagnostic. Après parathyroïdectomie subtotale réussie, les réinterventions sont rares et simples. Après parathyroïdectomie totale et transplantation, on ne doit pas oublier que les récidives peuvent survenir sur les greffons et/ou sur le tissu résiduel au cou ou au médiastin.
    Abstract: Resumen Entre 258 pacientes operados por hiperparatiroidismo secundario (HPT II) entre 1971 y 1988, un total de 33 tenían historia de una o más reoperaciones por HPT II persistente o recurrente. Estas operaciones no produjeron mortalidad ni morbilidad significativa. De 25 pacientes con paratiroidectomía inadecuada, 15 pacientes fueron reoperados. Doce habían sido operados inicialmente en otra institución. Tres murieron por causas no relacionadas con su HIPT II; los otros 12 pacientes se encuentran libres de enfermedad. De 79 pacientes sometidos a paratiroidectomía subtotal exitosa, 2 (2.5%) tuvieron recurrencia a los 5 y 6 años, respectivamente. Actualmente los 2 están libres de enfermedad. De 152 pacientes sometidos a paratiroidectomía con autotrasplante, 16 (10.5%) requirieron reoperaciones sobre los injertos. El promedio del intervalo a la reoperación fue de 2 1/2 años. Se observó hipertrofia de los fragmentos injertados en 4 casos (2.6%), pero sólo 2 fueron curados con la remoción de los injertos. Se sospechó la presencia de tejido paratiroideo residual o de una glándula supernumeraria ubicada en el cuello o en el mediastino en 5 casos, pero ésto no pudo ser confirmado puesto que uno ya había sido reoperado sobre el cuello sin éxito, otro aún rehusa operación, y 3 han muerto. En otros 6 pacientes, la recurrencia apareció dudosa y el HPT II no pudo ser confirmado. El diagnóstico fue incorrecto en los últimos 3 pacientes, y en ellos se comprobó, más tarde, intoxicación por aluminio. Los resultados de la reoperación por HPT II dependen, en primer lugar, de un diagnóstico correcto. Después de paratiroidectomia total y trasplante, debe tenerse en cuenta que las recurrencias pueden presentarse en el trasplante y/o el tejido residual en el cuello o el mediastino.
    Notes: Abstract Among 258 patients operated on for secondary hyperparathyroidism (HPT II) from 1971 to 1988, a total of 33 had one or more reoperations for persistent or recurrent HPT II. These reoperations did not induce any mortality or significant morbidity. After inadequate parathyroidectomy (25 cases), 15 patients were reoperated. Twelve of these had undergone initial surgery at another institution. Three patients died of causes unrelated to their HPT II. The other 12 patients are disease-free. After successful subtotal parathyroidectomy (79 cases), 2 patients (2.5%) had a recurrence 5 and 6 years later, respectively. Currently, the 2 patients remain disease-free. After total parathyroidectomy with autotransplantation (152 cases), 16 patients (10.5%) had reoperations on the grafts. The mean time before reoperation was 2 1/2 years. Hypertrophy of grafted fragments was observed in 4 cases (2.6%), but only 2 of these 4 patients were cured by removal of the grafts. Residual parathyroid tissue or a supernumerary gland in the neck or the mediastinum was suspected in 5 patients, but this could not be confirmed because one had already been reoperated on in the neck without success, another still refuses reoperation, and 3 died. In 6 other patients, the recurrence was debatable and HPT II was not confirmed. In the last 3 patients, the diagnosis was incorrect and aluminium intoxication was proved later. Results of reoperations for persistent or recurrent HPT II depend, first, on a correct diagnosis. After Successful subtotal parathyroidectomy, reoperations are rare and simple. After total parathyroidectomy and transplantation, it must be kept in mind that recurrences can occur on the grafts and/or on residual tissue in the neck or mediastinum.
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