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Background: The testing of theoretical models with experimental data is an integral part of the scientific method, and a logical place to search for new ways of stimulating scientific productivity. Often experiment/theory comparisons may be viewed as a workflow comprised of well-defined, rote operations distributed over several distinct computers, as exemplified by the way in which predictions from electronic structure theories are evaluated with results from spectroscopic experiments. For workflow's such as this, which may be laborious and time consuming to perform manually, software that could orchestrate the operations and transfer results between computers in a seamless and automated fashion would offer major efficiency gains. Such tools also promise to alter how researchers interact with data outside their field of specialization by, e.g., making raw experimental results more accessible to theorists, and the outputs of theoretical calculations more readily comprehended by experimentalists. Results: An implementation of an automated workflow has been developed for the integrated analysis of data from nuclear magnetic resonance (NMR) experiments and electronic structure calculations. Kepler (Altintas et al. 2004) open source software was used to coordinate the processing and transfer of data at each step of the workflow. This workflow incorporated several open source software components, including electronic structure code to compute NMR parameters, a program to simulate NMR signals, NMR data processing programs, and others. The Kepler software was found to be sufficiently flexible to address several minor implementation challenges without recourse to other software solutions. The automated workflow was demonstrated with data from a 17O NMR study of uranyl salts described previously (Cho et al. in J Chem Phys 132:084501, 2010). Conclusions: The functional implementation of an automated process linking NMR data with electronic structure predictions demonstrates that modern software tools such as Kepler can be used to construct programs that comprehensively manage complex, multi-step scientific workflows spanning several different computers. Automation of the workflow can greatly accelerate the pace of discovery, and allows researchers to focus on the fundamental scientific questions rather than mastery of specialized software and data processing techniques. Future developments that would expand the scope and power of this approach include tools to standardize data and associated metadata formats, and the creation of interactive user interfaces to allow real-time exploration of the effects of program inputs on calculated outputs. [ABSTRACT FROM AUTHOR]

There are large amounts of heavy α-emitters in nuclear waste and nuclear materials inventories stored in various sites around the world. These include plutonium and minor actinides such as americium and curium. In preparation for geological disposal there is consensus that actinides that have been separated from spent nuclear fuel should be immobilized within mineral-based ceramics rather than glass because of their superior aqueous durability and lower risk of accidental criticality. However, in the long term, the α-decay taking place in these ceramics will severely disrupt their crystalline structure and reduce their durability. A fundamental property in predicting cumulative radiation damage is the number of atoms permanently displaced per α-decay. At present, this number is estimated to be 1,000–2,000 atoms/α in zircon. Here we report nuclear magnetic resonance, spin-counting experiments that measure close to 5,000 atoms/α in radiation-damaged natural zircons. New radiological nuclear magnetic resonance measurements on highly radioactive, 239Pu zircon show damage similar to that caused by 238U and 232Th in mineral zircons at the same dose, indicating no significant effect of half-life or loading levels (dose rate). On the basis of these measurements, the initially crystalline structure of a 10 weight per cent 239Pu zircon would be amorphous after only 1,400 years in a geological repository (desired immobilization timescales are of the order of 250,000 years). These measurements establish a basis for assessing the long-term structural durability of actinide-containing ceramics in terms of an atomistic understanding of the fundamental damage event. [ABSTRACT FROM AUTHOR]

Dilute aqueous solutions of the calcium and sodium salts of "α"-D-isosaccharinate (ISA) have been analyzed by [sup 13]C and ¹H NMR spectroscopy. The positions of the six [sup 13]C ISA NMR lines show a pH dependence that can be used to infer that the most acidic proton is the one associated with the carboxylate group, with an average log ko of -3.27 for the reaction H(ISA) &rlarr; H[sup +] + ISA[sup -] in solutions made with the sodium salt. In acidic solutions (pH < 4), NMR signals were found that could be assigned to "α"-D-isosaccharinate-1,4-1actone (ISL), formed from the dehydration of H(ISA). The pH dependence of the H(ISA) [sup 13]C line positions, furthermore, reveals that the deprotonated H(ISA) at neutral to high pH assumes a conformation with the carboxylate anion hydrogen-bonded to the secondary alcohol and the cation (Na[sup +] or Ca[sup 2+]) interacting with the tertiary alcohol. [ABSTRACT FROM AUTHOR]

Isosaccharinate (ISA[sup -]), a degradation product of cellulose codisposed in low-level nuclear wastes, is expected to be one of the dominant complexing ligands for radionuclides, especially tetravalent actinides. This paper presents a comprehensive thermodynamic model for isosaccharinate reactions with Ca(II) and Np(IV). The model is valid for a wide range of pH values (∼2-14), ISA[sup -] concentrations (ranging up to 0.1 m), and ionic strengths (ranging up to 6.54 m), and is based on (1) NMR investigations of HISA(aq) (α-D-isosaccharinic acid) and ISL(aq) [dehydration product of HISA(aq)], and the solubility of Ca(ISA)[sub 2](c) as a function of pH and concentrations of Ca and ISA[sup -]; (2) NpO[sub 2](am) solubility in a wide range of pH values (∼2-14) and total ISA concentrations of 0.0016 and 0.008 m and at fixed pH values of approximately 5 and 12 with total ISA concentrations ranging from 0.0001 to 0.1 m; and (3) solvent extraction of Np-ISA solutions, containing fixed NaClO[sub 4] concentrations ranging from 0.103 to 6.54 m and at fixed pC[sub H+] values ranging from 1.5 to 1.9, with dibenzoylmethane. Pitzer's ion-interaction approach was used to interpret the data. The different aqueous species required to explain these data included HISA(aq), ISL(aq), Ca(ISA)[sup +], Np(OH)[sub 3] (ISA)(aq), Np(OH)[sub 3](ISA)[sup -, sub 2], Np(OH)[sub 4](ISA)[sup -], and Np(OH)[sub 4](ISA)[sup 2-, sub 2]. The values of equilibrium constants for reactions involving these species and determined from these data provided close agreements between the observed and predicted concentrations in all of the systems investigated in this study and those repotted previously. [ABSTRACT FROM AUTHOR]

The development of an aqueous thermodynamic model for polymerized silica species is presented, which is valid for high ionic strengths and high dissolved silica concentration (∼0.1 m) at low temperature (22–25°C). The model is based on the Pitzer equations and has been parameterized from solubility, electromotive force (emf), and nuclear magnetic resonance (NMR) data. The description of the silica speciation reactions at high dissolved silica and basic conditions (pH > 10) required the inclusion of monomeric, dimeric, trimeric (linear, cyclic, and substituted), tetrameric (linear and cyclic), and hexameric (prismatic) species. The standard state equilibrium constants for the formation of these species, as well as the necessary Pitzer ion–interaction parameters to describe the ionic strength dependence of the formation reactions were determined. [ABSTRACT FROM AUTHOR]