Plutonium mobility and reactivity in a heterogeneous clay rock barrier accented by synchrotron-based microscopic chemical imaging

The long-term safe disposal of radioactive waste corresponds to a challenging responsibility of present societies. Within deep geological waste disposal concepts, host rocks correspond to the ultimate safety barrier towards the environment. To assess the performance of such barriers over extended time scales, mechanistic information on the interaction between the radiotoxic, long-lived radionuclides like plutonium and the host rock is essential. Chemical imaging based on synchrotron microspectroscopic techniques was used to visualize undisturbed reactive transport patterns of Pu within pristine Opalinus Clay rock material. Pu+V is shown to be progressively reduced along its diffusion path to Pu+IV and Pu+III due to interaction with redox-active clay rock constituents. Experimental results and modeling emphasize the dominant role of electron-transfer reactions determining the mobility of Pu in reactive barrier systems. The effective migration velocity of Pu is controlled by the kinetic rates of the reduction to Pu+IV and Pu+III and the redox capacity of the involved electron donor pools. To advance our predictive capabilities further, an improved understanding of the nature and capacity of redox-active components of the reactive barrier material is fundamental. The findings represent an essential contribution to the evaluation of the long-term safety of potential nuclear waste repositories and have implications regarding the development of effective geological disposal strategies.

Technical description of the radiological safety system for X-ray absorption spectroscopy experiments on radioactive samples at the Rossendorf Beamline

The Rossendorf Beamline at the European Synchrotron Radiation Facility is equipped with a unique radiochemistry experimental station. This dedicated station has been designed to perform environmentally relevant experiments on radionuclides, in particular actinides, using synchrotron based X-ray absorption fine structure spectroscopy. The technical concepts and the layout of this experimental station, where radioactive solids and liquids with activities of up to 185 MBq can be studied, are presented. The radiological safety of experimenters, equipment, and of the environment are ensured by the specially developed radiochemistry safety system. The multibarrier concept, the ventilation and air monitoring systems, the radiological protection system, and special software components for recording and visualisation of the safety status are described in detail.

Impacts of sewage outbursts on seawater reverse osmosis desalination

Sewage outbursts affect coastal environments as seawater is enriched with nutrients, organic matter and microbes, thus can potentially impair seawater reverse osmosis (SWRO) desalination. In this study, we evaluated how municipal sewage outbursts affect SWRO desalination in a pilot-scale system. To this end, feedwater characteristics (i.e., coastal water), the removal efficiency of organic foulants by a dual-media gravity filter, and cartridge micro-filtration were determined daily for 12 days. Permeate water flux was maintained constant during the study, while trans-membrane pressure (TMP) was automatically adjusted and continuously monitored. The results indicate that sewage outbursts caused an immediate (∼1 d) buildup of phyto/bacterioplankton biomass (up to 10-fold), and enhanced activity (maximal 30-fold) followed by an increase in transparent exopolymer particle (TEP) concentrations. After sewage addition, algal biomass was significantly removed by the pretreatment system (72-90%), while a considerable fraction of the bacterial biomass (42-65%) and TEP (53-65%) passed these procedures. The result was a negative impact on the desalination performance reflected by a significant increase (> 10%) in RO-TMP 7.5 d after the sewage addition. Our results indicate on a direct link between sewage outbursts, pretreatment efficiency, and SWRO desalination. Nevertheless, these findings can lead to new avenues for the development of science-based operational protocols to minimize the deleterious effects of abrupt sewage outbursts on SWRO desalination.

FRI0326 PREVALENCE AND IMPACT OF COMORBIDITIES IN AXIAL SPONDYLOARTHRITIS: SYSTEMATIC REVIEW AND META-ANALYSIS

Background:

Comorbidities are common among patients with axial spondyloarthritis (axSpA). The majority of axSpA patients have at least one comorbid medical condition in addition to any extra-articular manifestations [1]. Comorbidity ‘burden’ is associate with poorer function, quality of life and work-related outcomes [2]. They also influence treatment decisions and are key drivers of mortality.

Objectives:

We performed a systematic review and meta-analysis to 1) describe the prevalence of commonly reported comorbidities, 2) compare the prevalence of comorbidities between axSpA and control populations.

Methods:

A systematic review was performed in September 2019 using Medline, PubMed, Scopus and Web of Science, in accordance with PRISMA guidelines. Studies were included if they reported the prevalence of comorbidities on disease outcomes, and excluded if they focused on a single comorbidity or closely related diseases in one organ system. Two independent reviewers screened titles and abstracts, assessed full-texts for eligibility and extracted data from qualifying studies. Where possible, we performed meta-analyses for comorbidities reported by at least 3 studies using random-effects models. Pooled prevalence estimates were reported as percentages (95% confidence interval, I2statistic for heterogeneity).

Results:

36 studies reported prevalence of of individual comorbidities, amounting to a combined sample size of 119,427 patients. The most prevalent individual comorbidities were hypertension (pooled prevalence 22%), hyperlipidaemia (17%) and obesity (14%) (Figure 1). Eleven studies consistently showed higher prevalence of comorbidities in axSpA than controls (Table 1); odds ratios (OR) were particularly large for depression (pooled OR 1.80) and congestive cardiac failure (OR 1.84). There was significant heterogeneity for the majority of meta-analysis estimates.

Table 1.

Meta-analysis estimates for odds ratios (OR) of comorbidities compared between axSpA and control groups.

Number of studiesPooled OR95% confidence intervalI2, %Hypertension91.581.29 to 1.9298Any cardiovascular disease31.420.999 to 2.0399Any ischaemic heart disease71.511.21 to 1.8787Congestive cardiac failure41.841.25 to 2.7389Stroke61.301.04 to 1.6281Peripheral vascular disease51.471.10 to 1.9683Diabetes81.141.001 to 1.3083Hyperlipidaemia51.181.01 to 1.3994Cancer51.221.01 to 1.4793Depression41.801.45 to 2.2392Figure 1.

Pooled prevalence of individual comorbidities.

Conclusion:

Comorbidities are common in axSpA. Almost all comorbidities examined were more prevalent in axSpA patients than age and sex matched controls, with ≥80% higher odds for congestive cardiac failure and depression. Systematic and repeated assessments should therefore be integrated into routine clinical practice to ensure holistic patient-centred management. Additional studies are needed to validate comorbidities indices for axSpA research.

References:

[1]Zhao SS, Radner H, Siebert S, et al. Comorbidity burden in axial spondyloarthritis: a cluster analysis. Rheumatology. 2019 Oct 1;58(10):1746–54.

[2]Nikiphorou E, Ramiro S, van der Heijde D, et al. Association of Comorbidities in Spondyloarthritis With Poor Function, Work Disability, and Quality of Life: Results From the Assessment of SpondyloArthritis International Society Comorbidities in Spondyloarthritis Study. Arthritis Care Res. 2018 Aug;70(8):1257–62.

Disclosure of Interests:

None declared

Influence of humic acid on neptunium(V) sorption and diffusion in Opalinus Clay

The influence of14C-labeled M42 humic acid (HA) on the interaction between neptunium(V) and natural clay rock (Opalinus Clay (OPA), Switzerland) has been investigated in batch sorption and diffusion experiments under ambient air conditions. The effect of 10 mg/L HA on the diffusion of 8 μM Np(V) in OPA has been investigated in synthetic OPA pore water (pH 7.6, I = 0.4M) for the first time. Batch sorption experiments as a function of solid-to-liquid ratio (4-20 g/L) were performed under same experimental conditions to compare distribution coefficients obtained from both diffusion and sorption experiments. These experiments showed only a slight influence of HA on Np(V) uptake by OPA in both cases and provided comparable distribution coefficients (presence of HA: Kd= 22-32 L/kg, absence of HA: Kd= 30-46 L/kg). As it is known that the interactions of humic substances with actinides depend on various experimental parameters, the effect of HA on Np(V) sorption on 15 g/L OPA was also investigated as a function of pH (6-10) and initial Np concentration (8 μM and 7 pM). A saturated calcite solution was used as a background electrolyte in this case to prevent any dissolution of calcite contained in OPA at low pH. The results showed that the presence of M42 HA increases Np(V) sorption at pH < 7 while lower sorption was obtained above pH 8. Higher sorption at acidic pH can be attributed to strong sorption of HA which increases the number of sorption sites, while sorption decreases at higher pH probably due to formation of soluble ternary neptunium humate carbonate species.

Neptunium(V) sorption on kaolinite

The sorption behavior of neptunium(V) onto the clay mineral kaolinite was studied in batch experiments under different experimental conditions: [Np(V)]=7 × 10−12–8 × 10−6 M, solid-to-liquid ratio 2–20 g L−1, I=0.1 and 0.01 M NaClO4, pH=6–10, ambient air and Ar atmosphere. The short-lived isotope 239Np (T 1/2=2.36 d) was used instead of 237Np (T 1/2=2.14 × 106 a) to study the sorption behavior of Np(V) at environmentally-relevant concentrations, i.e., 7 × 1012 M Np. In addition, 239Np(V) served as tracer to measure sorption isotherms over six orders of magnitude in Np concentration (4.8 × 10−12–1.0 × 10−4 M). The results show that Np(V) sorption on kaolinite is strongly influenced by pH, CO2, and ionic strength. The sorption of 8 × 10−6 M Np(V) at pH 9.0, and ionic strength of 0.1 M NaClO4 was proportional to the solid-to-liquid ratio of kaolinite in the range of 2–10 g L−1. In the absence of CO2, the Np(V) uptake increased continuously with increasing pH value up to 97% at pH 10. Under ambient CO2, the sorption of Np decreased above pH 8 up to zero at pH 10. An increase of Np(V) concentration from 7 × 10−12 to 8 × 10−6 M resulted in a shift of the sorption pH edge by up to one pH unit to higher pH values. The ionic strength influenced the Np(V) sorption onto kaolinite only in the presence of ambient CO2. Under Ar atmosphere the sorption of Np(V) was independent from ionic strength, indicating the formation of inner-sphere complexes of Np(V) with kaolinite. Time-dependent batch experiments at pH 9.0 under ambient CO2 showed that the sorption of Np(V) on kaolinite is fast and fully reversible over six orders in Np(V) concentration.

Study of the role of sulfur functionalities in humic acids for uranium(VI) complexation

Sulfur containing humic acid model substances have been synthesized to study the role of sulfur functionalities for the complexation behavior of humic acids towards U(VI). Humic acids type M1-S with different sulfur contents (1.9, 3.9, 6.9 wt.%) were synthesized and characterized. The identity of the sulfur species was determined by X-ray photoelectron spectroscopy (XPS). Reduced sulfur species, such as thiols, dialkylsulfides and/or disulfides, were determined as the dominating sulfur functionalities in the used humic acids. The U(VI) complexation of humic acids with different sulfur contents has been studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrashort femtosecond laser pulses (fs-TRLFS) in comparison to a sulfur-free humic acid type M1 (pH 3.80±0.02; I=0.1 M NaClO4; p CO2 =10−3.5 atm). For all studied humic acids, similar complexation constants were determined. However, with increasing sulfur contents of the humic acids (>2 wt.%) an increase of the number of humic acid binding sites for U(VI) was determined which is reflected in increasing U(VI) loading capacities and increasing total humic acid ligand concentrations for U(VI) measured by TRLFS and fs-TRLFS, respectively. This increase of the fraction of humic acid binding sites for U(VI) points to an involvement of reduced sulfur functionalities, such as thiol groups, in the complexation between U(VI) and humic acid. However, for environmentally relevant sulfur contents of humic acids (<2 wt.%) it can be concluded that, compared to oxygen functionalities, especially carboxylic groups, reduced sulfur functionalities play only a subordinate role for the U(VI) complexation by humic acids in the acidic pH range.

EXAFS study on the neptunium(V) complexation by various humic acids under neutral pH conditions

The structure of Np(V) humic acid (HA) complexes at pH 7 was studied by extended X-ray absorption fine structure analysis (EXAFS). For the first time, the influence of phenolic OH groups on the complexation of HA and Np(V) in the neutral pH range was investigated using modified HAs with blocked phenolic OH groups and Bio-Rex70, a cation exchange resin having only carboxyl groups as proton exchanging sites.

The formation of Np(V) humate complexes was verified by near-infrared (NIR) spectroscopy. Axial Np-O bond distances of 1.84–1.85 Å were determined for the studied Np(V) humate complexes and the Np(V)-Bio-Rex70 sorbate. In the equatorial plane Np(V) is surrounded by about 3 oxygen atoms with bond lengths of 2.48–2.49 Å. The comparison of the structural parameters of the Np(V) humates with those of Np(V)-Bio-Rex70 points to the fact that the interaction between HA and Np(V) in the neutral pH range is dominated by carboxylate groups. However, up to now a contribution of phenolic OH groups to the interaction process cannot be excluded completely. The comparison of the obtained structural data for the Np(V) humates to those of Np(V) carboxylates and Np(V) aquo ions reported in the literature indicates that humic acid carboxylate groups predominantly act as monodentate ligands. A differentiation between equatorial coordinated carboxylate groups and water molecules using EXAFS spectroscopy is impossible.

Evidence for the existence of Tc(IV) – humic substance species by X-ray absorption near-edge spectroscopy

The redox–sensitive fission product technetium–99 has been investigated in systems containing different reducing solid phases (pyrite, magnetite, ironsulphide and Gorleben sand) on the one hand and Gorleben groundwater, which contains a high amount of humic substances, on the other hand. Initially, technetium–99 was added to these systems as pertechnetate (Tc(VII)), which was reduced in presence and absence of humic substances with the aid of the different reducing surfaces (neutral to alkaline pH). Both in absence and presence of humic substances, Tc concentrations were observed which exceeded the TcO2solubility limit, whereby the presence of humic substances had a 100 fold higher Tc concentration compared to its absence. Using the La–precipitation method, it was shown that Tc(IV) inorganic colloids and organic colloids were quantitatively precipitated. It was demonstrated for the first time by a combination of chemical speciation methods (La–precipitation method and gel permeation chromatography) and XANES spectroscopy of the humic substance containing supernatant solutions, that Tc(IV) species were formed in these systems, indicating an association between Tc(IV) and humic substances.

EXAFS and XRD investigations of zeunerite and meta-zeunerite

In this paper EXAFS was used to determine bond lengths in the structures of zeunerite and meta-zeunerite. The atomic distances between heavy and light scatterers observed using EXAFS in meta-zeunerite deviate approximately 0.1 Å from literature data of single-crystal X-ray diffraction measurements. Because this difference is significant higher than the error limits of EXAFS measurements, the complete crystal structure of meta-zeunerite, Cu[UO2AsO4]2·8 H2O, is revised by X-ray structure analysis. The bond length determinations by EXAFS and the revised XRD data agree within the experimental error limits. In this study EXAFS spectroscopy has proven to be an useful tool for determining precise local bond lengths in the environment of heavy atoms. Moreover, the crystal structure of zeunerite, Cu[UO2AsO4]2·12 H2O, hitherto not been described in the literature, was investigated. Reflex broadening effects and intergrowth relationship between zeunerite and meta-zeunerite show that meta-zeunerite grows in nature due to dehydration of zeunerite. The structural transition from zeunerite to meta-zeunerite is connected with a change in the uranyl arsenate layer arrangement and the crystal water content.

Uranyl(VI) carbonate complex formation: Validation of the Ca2UO2(CO3)3(aq.) species

We recently discovered a neutral dicalcium uranyl tricarbonate complex, Ca2UO2(CO3)3(aq.), in uranium mining related waters [1]. We are now reporting a further validation of the stoichiometry and the formation constant of this complex using two analytical approaches with time-resolved laser-induced fluorescence spectroscopy (TRLFS) species detection: i) titration of a non-fluorescent uranyl tricarbonate complex solution with calcium ions, and quantitative determination of the produced fluorescent calcium complex via TRLFS; and ii) variation of the calcium concentration in the complex by competitive calcium complexation with EDTA4-.

Slope analysis of the log (fluorescence intensity)versuslog[Ca2+] with both methods have shown that two calcium ions are bound to form the complex Ca2UO2(CO3)3(aq.). The formation constants determined from the two independent methods are: i) logβ°213=30.45±0.35 and ii) logβ°213=30.77±0.25.

A bathochrome shift of 0.35 nm between the UO2(CO3)34-complex and the Ca2UO2(CO3)3(aq.) complex is observed in the laser-induced photoacoustic spectrum (LIPAS), giving additional evidence for the formation of the calcium uranyl carbonate complex.

EXAFS spectra at the LIIand LIII-edges of uranium in uranyl carbonate solutions with and without calcium do not differ significantly. A somewhat better fit to the EXAFS of the Ca2UO2(CO3)3(aq.) complex is obtained by including the U-Ca shell. From the similarities between the EXAFS of the Ca2UO2(CO3)3(aq.) species in solution and the natural mineral liebigite, we conclude that the calcium atoms are likely to be in the same positions both in the solution complex and in the solid.

This complex influences considerably the speciation of uranium in the pH region from 6 to 10 in calcium-rich uranium-mining-related waters.

EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces

Uranium(VI) complex formation at vegetative cells and spores of Bacillus cereus and Bacillus sphaericus was studied using uranium L II-edge and L III-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. A comparison of the measured equatorial U-O distances and other EXAFS structural parameters of uranyl species formed at the Bacillus strains with those of the uranyl structure family indicates that the uranium is predominantly bound as uranyl complexes with phosphoryl residues.

Characterization of U(VI)-Acidithiobacillus ferrooxidans complexes using EXAFS, transmission electron microscopy, and energy-dispersive X-ray analysis

We used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) analysis to conduct molecular scale studies on U(VI) interaction with three recently described eco-types of Acidithiobacillus ferrooxidans. On the basis of the information obtained by using these methods, we concluded that uranyl phosphate complexes were formed by the cells of the three eco-types studied. The uranium accumulated by A. ferrooxidans cells was located mainly within the extracellular polysaccharides, and on the cell wall. Smaller amounts were also observed in the cytoplasm.

Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution

The complex formation in the binary uranium(VI)-glycolate, -α-hydoxyisobutyrate, -α-aminoisobutyrate systems in 1.0 M NaClO4 medium was studied by means of UV-vis, TRLFS, and EXAFS. An increase in absorption and a red shift of the spectra, 5 nm compared to the free UO2 2+, indicate a complex formation between UO2 2+ and α-substituted carboxylic acids already at pH 2. 1:1 complexes dominate the uranyl speciation in the glycolate, α-hydoxyisobutyrate, and α-aminoisobutyrate system at pH 2 and 3, respectively. At higher ligand concentrations a 1:2 complex between UO2 2+ and α-aminoisobutyric acid was observed. There is a very strong quenching of the U(VI) fluorescence in theuranyl–α-hydroxycarboxylate systems that can be quantitatively described by the Stern–Volmer equation. As a result of the strong quenching it is not possible to detect fluorescence spectra for these complexes using TRLFS. The UO2 2+(aq) concentration calculated from the Stern–Volmer equation was used to determine equilibrium constants which are in good agreement with those obtained by potentiometry and NMR spectroscopy. No quenching was observed in the α-aminoisobutyrate system and their fluorescence spectra could be deconvoluted into components for the different species present. The following stability constants result from our TRLFS experiments: a) for the glycolate system log β UO₂(HOCH₂COO)⁺=2.52±0.20, b) for the α-hydroxyisobutyrate system log β UO₂[HOC(CH₃)₂COO]⁺=3.40±0.21, and c) for the α-aminoisobutyrate system logβUO₂[NH₃C(CH₃)₂COO]²⁺=1.30±0.10 and log β UO₂[NH₃C(CH₃)₂COO]₂²⁺=2.07±0.25. An increase of the fluorescence intensity connected with a red shift of the fluorescence emission spectra was observed in the system uranyl–α-aminoisobutyric acid. Fluorescence lifetimes and spectra were obtained for UO2 2+, UO2[NH3C(CH3)2COO]2+, and UO2[NH3C(CH3)2COO]2 2+. Uranium L III-edge EXAFS measurements yielded an U-Oeq distance of 2.40 to 2.43 Å in the pH range from 2 to 4 in the α-hydroxyisobutyrate system showing a dominant bidentate coordination via the oxygens of the carboxylic group. Slightly shorter U-Oeq distances of 2.40 to 2.38 Å and no evidence for U-C distances around 2.90 Å in the glycolate system in this pH range may indicate a monodentate coordinated ligand via one oxygen from the carboxylic group. The decrease in the U-Oeq distance of the equatorial oxygens in both systems to 2.36-2.37 Å at pH values ≥5 is a strong indication for the formation of a chelate complex due to the deprotonation of the α-OH-group of the ligand. In the glycolate system in the pH range 5.5 to 11, the EXAFS spectrum showed evidence of U-U interaction at 3.81 Å indicating the formation of dimeric species.

EXAFS structural analysis of aqueous uranium(VI) complexes with lignin degradation products

Uranium LIII-edge extended X-ray absorption fine structure (EXAFS) analysis was carried out on aqueous uranium(VI) complexes with monomeric intermediates of the natural wood-degradation process such as protocatechuic acid (3,4-dihydroxybenzoic acid), catechol (2-hydroxyphenol), pyrogallol (1,2,3-trihydroxybenzol), and vanillic acid (4-hydroxy-3-methoxybenzoic acid). The structural parameters of the 1:1 complexes with protocatechuic acid and vanillic acid in weakly acidic solution indicate that the carboxylic group coordinates the uranyl cation in a bidentate mode in the equatorial plane. Based on the identical structural parameters observed for protocatechuic acid, catechol and pyrogallol in alkaline media, we conclude that the coordination with uranium occurs via the neighboring OH groups of the phenols under formation of a five-membered ring.

Structure of uranium sorption complexes at montmorillonite edge sites

Extended X-ray absorption fine structure (EXAFS) spectroscopy at the uranium LIII-edge was used for determining the structural environment of aqueous uranyl sorbed onto montmorillonite. The study reveals that uranyl uptake at pH ∼5-∼7 and at an initial uranyl concentration of 5×10−5M takes place at amphoteric surface hydroxyl sites as inner-sphere complex. The measured bond distances between uranium and the equatorial oxygen atoms are in the range of 2.34 Å and 2.37 Å indicating an inner-sphere coordination. At ∼3.4 Å the presence of a U-Al backscattering pair was determined. This backscattering pair indicates that the binding of the uranyl unit to amphoteric surface hydroxyl sites occurs preferred as a bidentate inner-sphere complex on aluminol groups.

EXAFS analyses of technetium(I) carbonyl complexes – stability studies in solutions

EXAFS analyses were successfully used to determine the structure of Re and Tc carbonyl thioether complexes in solid and liquid samples. In connection with chromatographic and mass spectrometric methods the behaviour of Tc carbonyl dithioether complexes in aqueous solution was studied. It was found that complexes containing a bidentate thioether ligand are able to react with water by exchange of the chloride ion, which results in the formation of a cationic complex. As expected, the exchange proceeds faster at the n.c.a. level because of concentration differences.

Neptunium(IV) complexation by humic substances studied by X-ray absorption fine structure spectroscopy

We studied the coordination environment of neptunium(IV) in complexes with various natural and synthetic humic and fulvic acids at pH 1 by X-ray absorption fine structure (XAFS) spectroscopy. The results were compared to those obtained for the interaction of neptunium(IV) with Bio-Rex70, a cation exchange resin having solely carboxylic groups as metal binding functional groups. In both neptunium humate complexes and neptunium Bio-Rex70 sorbates, Np4+is surrounded by about 10 oxygen atoms at an average distance of 2.36±0.02 Å. This verifies that the carboxylic groups are the main complexing sites of the humic substances responsible for binding neptunium(IV) in the acidic pH range. The data suggest a predominant monodentate coordination of the carboxylate groups to neptunium(IV) ions.

The hydrolysis of dioxouranium(VI) investigated using EXAFS and17O-NMR

The structure of dioxouranium(VI) as a function of pH at different (CH3)4N-OH concentrations has been investigated with the aid of U LIII-edge EXAFS. Polynuclear hydroxo species were identified by an U-U interaction at 3.808Å at pH = 4.1. The precipitate formed at pH = 7 has a schoepite like structure. In solution at high pH [0.5 M (CH3)4N-OH], the EXAFS data are consistent with the formation of a monomeric four coordinated uranium(VI) hydroxide complex UO2(OH)42-of octahedral geometry. The first shell contains two O atoms with a U=O distance of 1.830Å, and four O atoms were identified at a U-O distance of 2.265Å.

In strong alkaline solutions [>1 M (CH3)4N)-OH],17O-NMR spectra indicate the presence of two species, presumably UO2(OH)42-and UO2(OH)53-, the latter in low concentration, which are in rapid equilibrium with one another at 268 K in aqueous solution.

A sex-adjusted and age-adjusted genome screen for nested alcohol dependence diagnoses

Alcohol dependence is a complex disorder with a substantial genetic contribution to susceptibility. The Collaborative Study on the Genetics of Alcoholism is a multi-site study whose purpose is to detect, localize, and characterize genes contributing to this susceptibility. Previous linkage analyses of the trait of alcohol dependence in Collaborative Study on the Genetics of Alcoholism have used affected sib-pair methods with a dichotomous phenotype definition. In contrast, the analysis in this paper uses a sex-adjusted and age-adjusted multiple threshold liability model. The use of such a model, in that it includes unaffected as well as as affected subjects and in that it utilizes the differential severity of a diagnosis scale, should heuristically be more powerful than a straight affected sib-pair analysis. Three regions of interest are found on chromosome 1 (lod 5.17), chromosome 4 (lod 3.46), and chromosome 8 (lod 4.31). The region on chromosome 1 near the marker D1S532 is in the region previously reported as linked to alcohol dependence and correlated phenotypes in this dataset. The region on chromosome 4 near the alcohol dehydrogenase gene cluster has been reported to be linked to alcohol dependence in other studies, as well as to the alcohol consumption phenotype 'Maximum Number of Drinks in a 24-Hour Period' in this dataset. The region on chromosome 8 near the marker D8S1988 is homologous to a section of rat chromosome 5 to which an alcohol consumption phenotype has been linked.

Complexation of uranium(VI) with protocatechuic acid-application of iterative transformation factor analysis to EXAFS spectroscopy

The speciation of 1 mM uranium(VI) in carbonate-free aqueous solutions of 50 mM protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid) was studied in the pH range of 4.0 to 6.8 using EXAFS spectroscopy. The uranium L(III)-edge EXAFS spectra were analyzed using a newly developed computer algorithm for iterative transformation factor analysis (FA). Two structural different uranium(VI) complexes were observed. The speciation in the pH range of 4.0 to 4.8 is dominated by a 1:2 or 1:3 uranium(VI)/PCA complex with bidentate coordination of the carboxyl group to the uranium(VI) moiety. Already at pH 4.6 significant amounts of a second species are formed. This uranium(VI) species contains two PCA ligands that are bound to the uranium via their neighboring phenolic hydroxyl groups under formation of five-member rings.

Linkage mapping of quantitative trait loci in humans: an overview

In this article, we provide an overview of the different statistical procedures that have been developed for linkage mapping of quantitative trait loci. We outline the model assumptions, the data requirements and the underlying tests for linkage for the different methods.

Molecular and atomic analysis of uranium complexes formed by three eco-types of Acidithiobacillus ferrooxidans

A combination of EXAFS, transmission electron microscopy and energy-dispersive X-ray was used to conduct a molecular and atomic analysis of the uranium complexes formed by Acidithiobacillus ferrooxidans. The results demonstrate that this bacterium accumulates uranium as phosphate compounds. We suggest that at toxic levels when the uranium enters the bacterial cells, A. ferrooxidans can detoxify and efflux this metal by a process in which its polyphosphate bodies are involved.

Markov chain Monte Carlo linkage analysis of complex quantitative phenotypes

We report a Markov chain Monte Carlo analysis of the five simulated quantitative traits in Genetic Analysis Workshop 12 using the Loki software. Our objectives were to determine the efficacy of the Markov chain Monte Carlo method and to test a new scoring technique. Our initial blind analysis, on replicate 42 (the "best replicate") successfully detected four out of the five disease loci and found no false positives. A power analysis shows that the software could usually detect 4 of the 10 trait/gene combinations at an empirical point-wise p-value of 1.5 x 10(-4).

Comparison of 3190 alcohol-dependent individuals with and without suicide attempts

INTRODUCTION

Suicidal behaviors are often seen in alcohol-dependent individuals. The aim of this study is to identify and confirm risk factors for suicide attempts in a large, family-based sample of alcoholics.

METHODS

Semistructured, detailed interviews were administered to 3190 alcohol-dependent individuals as part of the Collaborative Study on the Genetics of Alcoholism (COGA). Information about suicidal behavior, socioeconomic characteristics, psychiatric comorbidity, substance use disorders, and characteristics of alcohol dependence were obtained from alcohol-dependent probands, controls, and their relatives.

RESULTS

As determined by both univariate comparison and multivariate logistic regression analysis, alcohol-dependent individuals with a history of suicide attempts were found to have a significantly more severe course of alcohol dependence and a higher prevalence of both independent and substance-induced psychiatric disorders and other substance dependence. First-degree relatives of subjects with suicide attempts showed a significantly higher rate of suicide attempts, even after controlling for additional relevant diagnoses.

CONCLUSION

These results support the hypothesis that alcohol-dependent individuals with a history of suicide attempts are more severely impaired. Screening and subsequent treatment of alcohol use disorder, psychiatric comorbidity, and substance use disorders among alcoholics may be crucial in preventing suicide attempts and completions.