TY - GEN A1 - Dettmann, Sophie A1 - Huittinen, Nina Maria A1 - Jahn, Nicolas A1 - Kretzschmar, Jerome A1 - Kumke, Michael A1 - Kutyma, Tamara A1 - Lohmann, Janik A1 - Reich, Tobias A1 - Schmeide, Katja A1 - Azzam, Salim Shams Aldin A1 - Spittler, Leon A1 - Stietz, Janina T1 - Influence of gluconate on the retention of Eu(III), Am(III), Th(IV), Pu(IV), and U(VI) by C-S-H (C/S = 0.8) T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The retention of actinides in different oxidation states (An(X), X = III, IV, VI) by a calcium-silicate-hydrate (C-S-H) phase with a Ca/Si (C/S) ratio of 0.8 was investigated in the presence of gluconate (GLU). The actinides considered were Am(III), Th(IV), Pu(IV), and U(VI). Eu(III) was investigated as chemical analogue for Am(III) and Cm(III). In addition to the ternary systems An(X)/GLU/C-S-H, also binary systems An(X)/C-S-H, GLU/C-S-H, and An(X)/GLU were studied. Complementary analytical techniques were applied to address the different specific aspects of the binary and ternary systems. Time-resolved laser-induced luminescence spectroscopy (TRLFS) was applied in combination with parallel factor analysis (PARAFAC) to identify retained species and to monitor species-selective sorption kinetics. ¹³C and ²⁹Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to determine the bulk structure and the composition of the C-S-H surface, respectively, in the absence and presence of GLU. The interaction of Th(IV) with GLU in different electrolytes was studied by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS). The influence of GLU on An(X) retention was investigated for a large concentration range up to 10⁻² M. The results showed that GLU had little to no effect on the overall An(X) retention by C-S-H with C/S of 0.8, regardless of the oxidation state of the actinides. For Eu(III), the TRLFS investigations additionally implied the formation of a Eu(III)-bearing precipitate with dissolved constituents of the C-S-H phase, which becomes structurally altered by the presence of GLU. For U(VI) sorption on the C-S-H phase, only a small influence of GLU could be established in the luminescence spectroscopic investigations, and no precipitation of U(VI)-containing secondary phases could be identified. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1318 KW - actinide, organic ligand, sorption, cementitious material, concrete, luminescence KW - organic ligand KW - sorption KW - cementitious material KW - concrete KW - luminescence Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-588455 SN - 1866-8372 IS - 1318 ER - TY - JOUR A1 - Dettmann, Sophie A1 - Huittinen, Nina Maria A1 - Nicolas, Jahn A1 - Kretzschmar, Jerome A1 - Kumke, Michael A1 - Kutyma, Tamara A1 - Lohmann, Janik A1 - Reich, Tobias A1 - Schmeide, Katja A1 - Azzam, Salim Shams Aldin A1 - Spittler, Leon A1 - Stietz, Janina T1 - Influence of gluconate on the retention of Eu(III), Am(III), Th(IV), Pu(IV), and U(VI) by C-S-H (C/S = 0.8) JF - Frontiers in Nuclear Engineering N2 - The retention of actinides in different oxidation states (An(X), X = III, IV, VI) by a calcium-silicate-hydrate (C-S-H) phase with a Ca/Si (C/S) ratio of 0.8 was investigated in the presence of gluconate (GLU). The actinides considered were Am(III), Th(IV), Pu(IV), and U(VI). Eu(III) was investigated as chemical analogue for Am(III) and Cm(III). In addition to the ternary systems An(X)/GLU/C-S-H, also binary systems An(X)/C-S-H, GLU/C-S-H, and An(X)/GLU were studied. Complementary analytical techniques were applied to address the different specific aspects of the binary and ternary systems. Time-resolved laser-induced luminescence spectroscopy (TRLFS) was applied in combination with parallel factor analysis (PARAFAC) to identify retained species and to monitor species-selective sorption kinetics. ¹³C and ²⁹Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to determine the bulk structure and the composition of the C-S-H surface, respectively, in the absence and presence of GLU. The interaction of Th(IV) with GLU in different electrolytes was studied by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS). The influence of GLU on An(X) retention was investigated for a large concentration range up to 10⁻² M. The results showed that GLU had little to no effect on the overall An(X) retention by C-S-H with C/S of 0.8, regardless of the oxidation state of the actinides. For Eu(III), the TRLFS investigations additionally implied the formation of a Eu(III)-bearing precipitate with dissolved constituents of the C-S-H phase, which becomes structurally altered by the presence of GLU. For U(VI) sorption on the C-S-H phase, only a small influence of GLU could be established in the luminescence spectroscopic investigations, and no precipitation of U(VI)-containing secondary phases could be identified. KW - actinide KW - organic ligand KW - sorption KW - cementitious material KW - concrete KW - luminescence Y1 - 2023 U6 - https://doi.org/10.3389/fnuen.2023.1124856 SN - 2813-3412 VL - 2 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Reich, Karin A1 - Ette, Ottmar A1 - Ren, Haiyan A1 - Kraft, Tobias A1 - Beck, Hanno A1 - Krumpel, Andreas ED - Ette, Ottmar ED - Knobloch, Eberhard T1 - HiN : Alexander von Humboldt im Netz N2 - -Karin Reich: Der Humboldt’sche Magnetische Verein im historischen Kontext -Ottmar Ette, Haiyan REN: Exploring China in Alexander von Humboldt: The Humboldt Center for Transdisciplinary Studies (HCTS), Changsha -Tobias Kraft: Humanist, Wissenschaftler, Akteur? Alexander von Humboldts Rolle im Jahrhundert der Massensklaverei -Hanno Beck: Ein Ehrenbürger der Erde. A. von Humboldt und seine Bedeutung -Andreas Krumpel: Ein deutscher Philosoph in Lateinamerika. Nachruf auf Heinz Krumpel T3 - HiN : Alexander von Humboldt im Netz ; International Review for Humboldtian Studies - 46 KW - Humboldt Center for Transdisciplinary Studies KW - Changsha KW - Sklaverei KW - Kuba KW - Haiti KW - Sklavenhandel KW - Abolition KW - Essai politique sur l'île de Cuba KW - Essai politique sur le royaume de la Nouvelle-Espagne KW - Amerikanische Reisetagebücher KW - Societas meteorologica Palatina KW - Humboldtscher Magnetischer Verein KW - Göttinger Magnetischer Verein KW - Gauß KW - allgemeine Theorie des Erdmagnetismus KW - biographische Skizze KW - Johann Wolfgang von Goethe KW - Heinz Krumpel Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-588808 SN - 2568-3543 SN - 1617-5239 VL - XXIV IS - 46 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Ruipérez-Valiente, José A. A1 - Staubitz, Thomas A1 - Jenner, Matt A1 - Halawa, Sherif A1 - Zhang, Jiayin A1 - Despujol, Ignacio A1 - Maldonado-Mahauad, Jorge A1 - Montoro, German A1 - Peffer, Melanie A1 - Rohloff, Tobias A1 - Lane, Jenny A1 - Turro, Carlos A1 - Li, Xitong A1 - Pérez-Sanagustín, Mar A1 - Reich, Justin T1 - Large scale analytics of global and regional MOOC providers: Differences in learners' demographics, preferences, and perceptions JF - Computers & education N2 - Massive Open Online Courses (MOOCs) remarkably attracted global media attention, but the spotlight has been concentrated on a handful of English-language providers. While Coursera, edX, Udacity, and FutureLearn received most of the attention and scrutiny, an entirely new ecosystem of local MOOC providers was growing in parallel. This ecosystem is harder to study than the major players: they are spread around the world, have less staff devoted to maintaining research data, and operate in multiple languages with university and corporate regional partners. To better understand how online learning opportunities are expanding through this regional MOOC ecosystem, we created a research partnership among 15 different MOOC providers from nine countries. We gathered data from over eight million learners in six thousand MOOCs, and we conducted a large-scale survey with more than 10 thousand participants. From our analysis, we argue that these regional providers may be better positioned to meet the goals of expanding access to higher education in their regions than the better-known global providers. To make this claim we highlight three trends: first, regional providers attract a larger local population with more inclusive demographic profiles; second, students predominantly choose their courses based on topical interest, and regional providers do a better job at catering to those needs; and third, many students feel more at ease learning from institutions they already know and have references from. Our work raises the importance of local education in the global MOOC ecosystem, while calling for additional research and conversations across the diversity of MOOC providers. KW - Learning analytics KW - Educational data mining KW - Massive open online courses KW - Large scale analytics KW - Cultural factors KW - Equity KW - Distance learning Y1 - 2022 U6 - https://doi.org/10.1016/j.compedu.2021.104426 SN - 0360-1315 SN - 1873-782X VL - 180 PB - Elsevier CY - Oxford ER -