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We investigated the binary Cm-citrate system using time-resolved laser fluorescence spectroscopy (TRLFS), parallel factor analysis (PARAFAC), and quantum chemical calculations. Evidence collectively suggests the stepwise coordination and deprotonation of citrate alcohol groups in Cm-cit complexes with two bound citrate moieties upon increasing pH, which is supported by a bathochromic shift in emission spectra, an observed increase in lifetime measurements, and lower energy minima for citrate alcohol involvement versus hydrolysis of the Cm-citrate species. Our PARAFAC results agree with a 3-component model for the Cm-citrate system and offer pure component decompositions, yielding fraction species across the studied pH range that have a correlated slope = 1 as a function of pH. For the first time, evidence of ternary Ca-Cm-citrate complexes was revealed by TRLFS with increasing calcium concentration at fixed pHm. The formation of these ternary complexes was substantiated with density functional theory (DFT) calculations on simple model systems of the complexes. Shared citrate carboxylate groups between calcium and curium were proposed for all three ternary Ca-Cm-cit complexes based on DFT-determined Ca-O and Cm-O distances. Moreover, we found that the ternary complex with both alcohol groups deprotonated is most stable when it shares both two carboxylate and two alcohol groups between Ca and Cm. The presence of shared functional groups highlights the enhanced stability of these ternary complexes. Additional work is warranted to further constrain the stoichiometry, stability constants and dependence on ionic strength of these complexes for purposes of thermodynamic modeling of repository settings.

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The Japan Atomic Energy Agency (JAEA) has proposed the Solvent Extraction from Liquid waste using Extractants of CHON-type for Transmutation (SELECT) process by solvent extraction as a new separation technology to recover minor actinides (MA) from high-level liquid waste (HLLW) produced by spent fuel reprocessing. The MA separation in the SELECT process comprises the recovery of MA and rare earths (RE) from HLLW, MA/RE separation, and Am/Cm separation. Three highly practical extractants are used in the MA separation. Furthermore, this flow configuration facilitates the preparation of nitric acid concentrations in the aqueous phase. However, the separation factor between Cm and Nd in the MA/RE separation is small (SFCm/Nd = 2.5), requiring many extraction stages for continuous extraction in a mixer settler. Therefore, this study investigated the separation of only Am from an aqueous nitric acid solution containing MA (Am and Cm) and RE using an organic phase mixed with two extractants alkyl diamideamine with 2-ethylhexyl alkyl chains (ADAAM(EH)) and hexa-n-octylnitrilotriacetamide (HONTA) used in the SELECT process. Under high-concentration nitric acid conditions, Am and La, Ce, Pr, Nd (light lanthanides) were extracted in the ADAAM(EH) + HONTA mixed solvent, whereas Cm, medium, and heavy lanthanides, and Y were partitioned in the aqueous phase. Subsequently, only light lanthanides could be back extracted from the ADAAM(EH) + HONTA mixture solvent containing Am and light lanthanides in low nitric acid concentrations. Furthermore, Am could be easily stripped with 0.2 M or 5 M nitric acid. This method does not require the mutual separation of Cm and Nd, which have low separation factors. Am can be efficiently separated by one extraction and two back extractions, reducing the number of steps in the SELECT process.

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Crystalline rock is one of the host rocks considered for a future deep geological repository for highly active radiotoxic nuclear waste. The safety assessment requires reliable information on the retention behavior of minor actinides. In this work, we applied various spatially resolved techniques to investigate the sorption of Curium onto crystalline rock (granite, gneiss) thin sections from Eibenstock, Germany and Bukov, Czech Republic. We combined Raman-microscopy, calibrated autoradiography and µTRLFS (micro-focus time-resolved fluorescence spectroscopy) with vertical scanning interferometry to study in situ the impact of mineralogy and surface roughness on Cm(III) uptake and molecular speciation on the surface. Heterogeneous sorption of Cm(III) on the surface depends primarily on the mineralogy. However, for the same mineral class sorption uptake and strength of Cm(III) increases with growing surface roughness around surface holes or grain boundaries. When competitive sorption between multiple mineral phases occurs, surface roughness becomes the major retention parameter on low sorption uptake minerals. In high surface roughness areas primarily Cm(III) inner-sphere sorption complexation and surface incorporation are prominent and in selected sites formation of stable Cm(III) ternary complexes is observed. Our molecular findings confirm that predictive radionuclide modelling should implement surface roughness as a key parameter in simulations.

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The adsorption properties of Pu(IV), Am(III), Cm(III), and U(VI) on desferrioxamine B-immobilized micropolymeric resin (DMPs) and adsorbed species were elucidated using thermodynamic constants and log ß values. This allowed the determination of adsorption characteristics (91, 95, 88, and 97% for Pu(IV), Am(III), Cm(III), and U(VI), respectively) and individual pH-independent adsorption properties. Pu(IV) could be separated from Am(III), Cm(III), and U(VI) at pH 2. The separation of Pu(IV) from Am(III), Cm(III), and U(VI) was achieved by controlling the pH of the solution using a single resin.

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Trivalent actinides such as Cm(III) are able to strongly interact with microbes and especially with bacterial cell walls. However, detailed knowledge of the influence of different cell wall components is somewhat lacking. For this investigation, we studied the formation of aqueous Cm(III) complexes with cell wall components (e.g., lipopolysaccharide, peptidoglycan, and plasma membranes) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). For all systems, two specific Cm(III) complexes with the biomacromolecules were observed as a function of pH. Specifically, Cm(III) was found to bind to phosphate and carboxyl groups present in the structure of the biomacromolecules. Stability constants and luminescence parameters of the specific Cm(III) complexes were determined and are presented. The pH of the surrounding aqueous solution, the plasma membrane concentration, and proteins included in the crude plasma membrane fraction were found to significantly impact the complexation of Cm(III). The Cm(III) luminescence spectra with plasma membranes, cell wall polymers, as well as Gram-negative (Sporomusa sp. MT-2.99 and Pseudomonas fluorescens) and Gram-positive (Paenibacillus sp. MT-2.2) bacteria will be explained by linear combination fitting using the investigated components.

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Microbial communities occurring in reference materials for artificial barriers (e.g., bentonites) in future deep geological repositories of radioactive waste can influence the migration behavior of radionuclides such as curium (CmIII). This study investigates the molecular interactions between CmIII and its inactive analogue europium (EuIII) with the indigenous bentonite bacterium Stenotrophomonas bentonitica at environmentally relevant concentrations. Potentiometric studies showed a remarkably high concentration of phosphates at the bacterial cell wall compared to other bacteria, revealing the great potential of S. bentonitica for metal binding. Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the role of phosphates and carboxylate groups from the cell envelope in the bioassociation of EuIII. Additionally, time-resolved laser-induced fluorescence spectroscopy (TRLFS) identified phosphoryl and carboxyl groups from bacterial envelopes, among other released complexing agents, to be involved in the EuIII and CmIII coordination. The ability of this bacterium to form a biofilm at the surface of bentonites allows them to immobilize trivalent lanthanide and actinides in the environment.

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Trivalent actinides such as Cm(III) are able to occupy natural Ca(II) binding sites in biological systems. For this investigation, we studied the formation of aqueous Cm(III) complexes with S-layer proteins by time-resolved laser-induced fluorescence spectroscopy (TRLFS). S-layer proteins serve as protective biointerfaces in bacteria and archaea against the surrounding solution. Experimental assays were performed at a fixed total concentration of Cm(III) (0.88 µM) using an S-layer protein (5 g/L / 39.6 µM) at varying pH levels (2.0-9.0), as well as several types of S-layer proteins of L. sphaericus JG-A12. Based on resulting luminescence spectra and lifetime data, specific and unspecific binding sites could be distinguished. Notably, specific Cm(III) binding to S-layer proteins was confirmed by the appearance of a sharp emission band at 602.5 nm, combined with a long lifetime of 310 µs. The high affinity of these specific binding sites was also verified using competing EDTA, wherein only a high EDTA concentration (40 µM) could efficiently remove Cm(III) from S-layer proteins.

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To investigate the effective separation of actinides (Ans) from lanthanides (Lns), single-stage batch extraction experiments were performed with a novel extractant, tetradodecyl-1,10-phenanthroline-2,9-diamide (TDdPTDA) with various diluents such as 3-nitrobenzotrifluoride (F-3), nitrobenzene, and n-dodecane for Am, Cm, and Lns. The extraction kinetics with TDdPTDA was rapid enough to perform continuous extraction experiments using mixer-settler extractors. The slopes of the distribution ratio versus the TDdPTDA concentration and the distribution ratio versus the nitric acid concentration were similar for F-3 and nitrobenzene systems, but different from the n-dodecane system. These differences were attributed to the characteristics of the diluents. This study revealed high distribution ratios of Am (DAm) and Cm (DCm) for TDdPTDA, with the high separation factors (SFs) of Am from Lns enough for their separation.

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This work describes the molecular characterization of the interaction mechanism of a bentonite yeast isolate, Rhodotorula mucilaginosa BII-R8, with curium(III) as representative of trivalent actinides and europium(III) used as inactive analogue of Cm(III). A multidisciplinary approach combining spectroscopy, microscopy and flow cytometry was applied. Time-Resolved Laser Induced Fluorescence Spectroscopy (TRLFS) analyses demonstrated that the biosorption of Cm(III) is a reversible and pH-dependent process for R. mucilaginosa BII-R8 cells. Two Cm(III)-R. mucilaginosa BII-R8 species were identified having emission maxima at 599.6 and 601.5 nm. They were assigned to Cm(III) species bound to phosphoryl and carboxyl sites from the yeast cell, respectively. Phosphate groups were involved in the sorption of this actinide, as demonstrated by the Eu(III)-phosphate accumulates at the cell membrane shown by microscopy. In addition, cell viability and metabolic potential were assessed to determine the negative effect of Eu(III) in the yeast cells. The results obtained in this work showed that the interaction of Cm(III) with the yeast R. mucilaginosa BII-R8 cells at circumneutral and alkaline pH values will make this radionuclide more mobile to reach the biosphere. Therefore, geochemical conditions in the bentonite engineering barrier need to be carefully adjusted for the safe deep geological disposal of radioactive wastes.

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In addition to geological, geochemical, and geophysical aspects, also, microbial aspects have to be taken into account when considering the final storage of high-level radioactive waste in a deep geological repository. Rock salt is a potential host rock formation for such a repository. One indigenous microorganism, that is, common in rock salt, is the halophilic archaeon Halobacterium noricense DSM15987T, which was used in our study to investigate its interactions with the trivalent actinide curium and its inactive analogue europium as a function of time and concentration. Time-resolved laser-induced fluorescence spectroscopy was applied to characterize formed species in the micromolar europium concentration range. An extended evaluation of the data with parallel factor analysis revealed the association of Eu(III) to a phosphate compound released by the cells (F2/F1 ratio, 2.50) and a solid phosphate species (F2/F1 ratio, 1.80). The association with an aqueous phosphate species and a solid phosphate species was proven with site-selective TRLFS. Experiments with Cm(III) in the nanomolar concentration range showed a time- and pCH+-dependent species distribution. These species were characterized by red-shifted emission maxima, 600-602 nm, in comparison to the free Cm(III) aqueous ion, 593.8 nm. After 24 h, 40% of the luminescence intensity was measured on the cells corresponding to 0.18 µg Cm(III)/gDBM. Our results demonstrate that Halobacterium noricense DSM15987T interacts with Eu(III) by the formation of phosphate species, whereas for Cm(III), a complexation with carboxylic functional groups was also observed.

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High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.

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The interaction of trivalent Cm and Eu with the aluminum hydroxide bayerite (ß-Al(OH)3) and the aluminum oxide corundum (α-Al2O3) was investigated by batch sorption experiments and time resolved laser fluorescence spectroscopy (TRLFS). The experimental methods for both polymorphs show similar pH dependent sorption behavior at trace metal ion concentrations (∼10(-7) M), i.e. similar Eu sorption edges and nearly identical Cm speciation between pH=3 and 13. In this pH range the Cm aquo ion as well as the Cm(III) surface species surface⋯Cm(OH)x(H2O)(5-x) (x=0, 1, 2) can be distinguished by TRLFS. The similar sorption data point to a (surface) transformation of the thermodynamically unstable Al2O3 surface into bayerite, in agreement with the similar isoelectric points obtained for both minerals (pH(IEP)=8.6-8.8). The pH dependent surface charge is most likely due to the protonation/deprotonation of singly coordinated Al-OH surface groups, prevailing on the edge planes of the rod-like bayerite crystals and the surface of the colloidal Al2O3 particles. These surface groups are also believed to act as ligands for lanthanide/actinide(III) surface complexation. In contrast to the similar sorption behavior at trace metal ion concentrations, discrepancies are observed at higher Eu levels. While similar sorption edges occur up to 7×10(-7) M Eu for corundum, the pH edge on bayerite is gradually shifted to higher pH values in this Eu concentration range. The latter behavior may be related either to the existence of multiple sorption sites with different sorption affinities, or to the influence of an additional amorphous Al-phase, forming in the course of the bayerite synthesis.

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PICOS model-based case teaching of medical information retrieval curium is of benefit to stimulate the EBM thinking of students. The necessity of PICOS model-based case teaching of medical information retrieval curi-um was thus described, with its design, case analysis, retrieval methods, applicability and implementation studied and illustrated by examples.

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The photophysical properties, solution thermodynamics, and in vivo complex stabilities of Cm(III) complexes formed with multidentate hydroxypyridinonate ligands, 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO), are reported. Both chelators were investigated for their ability to act as antenna chromophores for Cm(III), leading to highly sensitized luminescence emission of the metal upon complexation, with long lifetimes (383 and 196 µs for 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO), respectively) and remarkable quantum yields (45 % and 16 %, respectively) in aqueous solution. The bright emission peaks were used to probe the electronic structure of the 5f complexes and gain insight into ligand field effects; they were also exploited to determine the high (and proton-independent) stabilities of the corresponding Cm(III) complexes (log ß110 = 21.8(4) for 3,4,3-LI(1,2-HOPO) and log ß120 = 24.5(5) for 5-LIO(Me-3,2-HOPO)). The in vivo complex stability for both ligands was assessed by using (248) Cm as a tracer in a rodent model, which provided a direct comparison with the in vitro thermodynamic results and demonstrated the great potential of 3,4,3-LI(1,2-HOPO) as a therapeutic Cm(III) decontamination agent.

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The reactions of trivalent lanthanides and actinides with molten boric acid in high chloride concentrations result in the formation of M4[B16O26(OH)4(H2O)3Cl4] (M = Sm, Eu, Gd, Pu, Am, Cm, Cf). This cubic structure type is remarkably complex and displays both chirality and polarity. The polymeric borate network forms helical features that are linked via two different types of nine-coordinate f-element environments. The f-f transitions are unusually intense and result in dark coloration of these compounds with actinides.

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Plutonium uranium mixed oxide (MOX) fuels are being used in commercial nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regards to their environment and the coolant. In this work the study of the local occurrence, speciation and next-neighbour environment of curium (Cm) in the (Pu,U)O2 lattice within an irradiated (60 MW d kg(-1) average burn-up) MOX sample was performed employing micro-x-ray fluorescence (µ-XRF) and micro-x-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Cm (≈ 0.7 wt% in the rim and ≈ 0.03 wt% in the centre) are determined from the experimental data gained for the irradiated fuel material examined in its centre and peripheral (rim) zones of the fuel. Curium occurrence is also reduced from the centre (hot) to the periphery (colder) because of the condensation of these volatile oxides. In the irradiated sample Cm builds up as Cm(3+) species (>90%) within a [CmO8](13-) or [CmO7](11-) coordination environment and no (<10%) Cm(IV) can be detected in the rim zone. Curium dioxide is reduced because of the redox buffering activity of the uranium dioxide matrix and of its thermodynamic instability.

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BACKGROUND: Previous studies examining the pharmacodynamic effects of succinylcholine(SCC) on subsequent doses of nondepolarizing muscle relaxants showed potentiation with resultant prolonged respiratory depression or no interaction at all. The interaction between SCC and mivacurium especially has not been investigated in animal and other clinical studies. METHODS: The pharmacodynamic effects of SCC on mivacurium-induced neuromuscular blockade and its reversal were investigated in 10 cats of either sex using the anterior tibialis muscle-sciatic nerve preparation. RESULTS: There was no significant difference at the onset of mivacurium neummuscular blockade between the control group(1.81+/-0.48 min) and SCC-pretreated group(1.86+/-1.04 min). However the duration of action of mivacurium neuromuscular blockade was significantly longer in the SCC-pretreated group(33.08+/-19.13 min) than that of the control group(10.65+/-2.45 min). In the control group recovery indices(RI) were 2.35+/-1.01 min and 0.68+/-0.30 min at spontaneous recovery and antagonism with neostigmine, respectively and in the SCC-pretreated group they were 6.88+/-2.42 min and 1.90+/-0.64 min. RI were significantly shortened by antagonism with neostigmine whether or not SCC was pretreated. In the SCC-pretreated group, RI were significantly longer than in the control group at spontaneous recovery and antagonism with neostigmine. But the maximal recovery and antagonism effect were 100% in all cases. There was no sigriificant difference in the train-of-four ratios measured after antagonism with neostigmine between the control group(0.91+/-0.01) and the SCC-pretreated group(0.93+/-0.06). CONCLUSIONS: The prior administration of SCC prolonged the duration of mivacurium-induced neuromuscular blockade and delayed recovery but had no influence in antagonism with neostigmine in cats.

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