Impact of the degradation leachate of the polyacrylonitrile-based material UP2W on the retention of Ni(II), Eu(III) and Pu(IV) by cement

The uptake of $^{63}$Ni(II), $^{152}$Eu(III) and $^{242}$Pu(IV) by hardened cement paste (HCP, CEM I) in the degradation stage II (pH ≈ 12.5, [Ca] ≈ 0.02 M) was investigated in the presence of a degradation leachate of UP2W, a polyacrylonitrile-based (PAN) material used as a filter aid in nuclear power plants. The degradation leachate with a concentration of dissolved organic carbon of ∼40 ppm was obtained from the degradation of UP2W in portlandite-buffered solutions for ca. 1100 days. Redox conditions in the Pu systems were buffered with hydroquinone, which defines mildly reducing conditions (pe + pH ≈ 10) where Pu(IV) is the predominant oxidation state. The degradation leachate investigated in this work is moderately sorbed by cement, with distribution ratios (R$_d$) of (0.35 ± 0.15) m$^3$ kg$^{−1}$. These values are 30 to 100 times greater than distribution ratios previously reported for proxy ligands of PAN degradation products, i.e., glutaric acid, α-hydroxyisobutyric acid and 3-hydroxybutyric acid. The presence of the degradation leachate induces a moderate decrease in the uptake of $^{63}$Ni(II), $^{152}$Eu(III) and $^{242}$Pu(IV) by cement, as compared to the sorption in the presence of the proxy ligands. Nevertheless, retention in the presence of the degradation leachate remains high for all investigated radionuclides, with Rd($^{63}$Ni(II)) ≈ 2 m$^3$ kg$^{−1}$, Rd($^{152}$Eu(III)) ≈ 100 m$^3$ kg$^{−1}$ and Rd($^{242}$Pu(IV)) ≈ 30 m$^3$ kg$^{−1}$. These observations possibly reflect that the multiple functionalities (–COOH, –OH, amide groups) expected in the macromolecules (10–15 kDa) present in the degradation leachate, can offer further binding/chelating capabilities compared to the small organic proxy ligands with at most bidentate binding

A Mechanism-Based Explanation of the Institutionalization of Semantic Technologies in the Financial Industry

Part 3: Creating Value through ApplicationsInternational audienceThis paper explains how the financial industry is solving its data, risk management, and associated vocabulary problems using semantic technologies. The paper is the first to examine this phenomenon and to identify the social and institutional mechanisms being applied to socially construct a standard common vocabulary using ontology-based models. This standardized ontology-based common vocabulary will underpin the design of next generation of semantically-enabled information systems (IS) for the financial industry. The mechanisms that are helping institutionalize this common vocabulary are identified using a longitudinal case study, whose embedded units of analysis focus on central agents of change—the Enterprise Data Management Council and the Object Management Group. All this has important implications for society, as it is intended that semantically-enabled IS will, for example, provide stakeholders, such as regulators, with better transparency over systemic risks to national and international financial systems, thereby mitigating or avoiding future financial crises

Solubility of Ca( ii ), Ni( ii ), Nd( iii ) and Pu( iv ) in the presence of proxy ligands for the degradation of polyacrylonitrile in cementitious systems

The solubility of Ca(OH)$_{2}$(cr), β-Ni(OH)$_{2}$(cr), Nd(OH)$_{3}$(s) and PuO$_{2}$(ncr, hyd) was investigated in cement porewater solutions containing glutarate (GTA), α-hydroxyisobutarate (HIBA) and 3-hydroxybutarate (HBA). These ligands were proposed as probable degradation products of UP2W, a polyacrylonitrile-based filter aid used in nuclear power plants. Results obtained in this work are compared with reported solubility data in the presence of iso-saccharinic acid (ISA), a polyhydroxocarboxylic acid resulting from cellulose degradation. None of the investigated proxy ligands shows any significant impact on the solubility of Ca(II), Nd(III) or Pu(IV) in cement porewater solutions. Although the formation of binary complexes M–L (M = Ca(II), Nd(III), An(IV); L = GTA, HIBA, HBA) under acidic conditions is described in the literature, these organic ligands cannot outcompete hydrolysis under hyperalkaline conditions. GTA, HIBA and HBA induce a slight increase in the solubility of β-Ni(OH)$_{2}$(cr) at [L]$_{tot}$ = 0.1 M. This observation supports the formation of stable Ni(II)–GTA, –HIBA and –HBA complexes in hyperalkaline conditions, although the exact stoichiometry of these complexes remains unknown. The comparison of these results with solubility data in the presence of ISA confirms the stronger complexation properties of the latter ligand. Even though HIBA and HBA are carboxylic acids containing one alcohol group, this comparison shows that additional alcohol groups are required to efficiently chelate the metal ion and outcompete hydrolysis. This conclusion is supported by DFT calculations on the Pu(IV)-OH–L systems (L = GTA, HIBA and HBA), which indicate that the complexation with the proxy ligands takes places through the carboxylate group. XRD of selected solid phases after equilibration with proxy ligands at [L]$_{tot}$ = 0.1 M confirms that Ca(II), Ni(II), Nd(III) and Pu(IV) starting solid materials remained mostly unaltered in the course of the experiments. However, the presence of new XRD features suggests the possible formation of secondary phases. These results allow assessment of the effect of the proposed proxy ligands on the solubility of key radionuclides and metal ions in cementitious systems relevant for low and intermediate level waste, and feed into on-going sorption studies evaluating the impact of UP2W degradation products on the uptake of radionuclides by cement

Suicide ideation of individuals in online social networks

Suicide explains the largest number of death tolls among Japanese adolescents in their twenties and thirties. Suicide is also a major cause of death for adolescents in many other countries. Although social isolation has been implicated to influence the tendency to suicidal behavior, the impact of social isolation on suicide in the context of explicit social networks of individuals is scarcely explored. To address this question, we examined a large data set obtained from a social networking service dominant in Japan. The social network is composed of a set of friendship ties between pairs of users created by mutual endorsement. We carried out the logistic regression to identify users' characteristics, both related and unrelated to social networks, which contribute to suicide ideation. We defined suicide ideation of a user as the membership to at least one active user-defined community related to suicide. We found that the number of communities to which a user belongs to, the intransitivity (i.e., paucity of triangles including the user), and the fraction of suicidal neighbors in the social network, contributed the most to suicide ideation in this order. Other characteristics including the age and gender contributed little to suicide ideation. We also found qualitatively the same results for depressive symptoms.Comment: 4 figures, 9 table

Identifying Complex Dynamics in Social Systems: A New Methodological Approach Applied to Study School Segregation

It is widely recognized that segregation processes are often the result of complex nonlinear dynamics. Empirical analyses of complex dynamics are however rare, because there is a lack of appropriate empirical modeling techniques that are capable of capturing complex patterns and nonlinearities. At the same time, we know that many social phenomena display nonlinearities. In this article, we introduce a new modeling tool in order to partly fill this void in the literature. Using data of all secondary schools in Stockholm county during the years 1990 to 2002, we demonstrate how the methodology can be applied to identify complex dynamic patterns like tipping points and multiple phase transitions with respect to segregation. We establish critical thresholds in schools’ ethnic compositions, in general, and in relation to various factors such as school quality and parents’ income, at which the schools are likely to tip and become increasingly segregated