Electronic autoradiography of Ba-133 particle emissions; diffusion profiles in granitic rocks

The spatial distribution of barium activity in granitic rocks was measured with two autoradiography techniques; digital autoradiography using phosphor imaging plate technique (Fuji 5100) and filmless electronic autoradiography (i.e. The BeaQuant (TM)), which is based on a gas detector incorporated in a micromesh Parallel Ionization Multiplier (PIM). Rock cubes taken from a diffusion experiment that were in contact with Ba-133 tracer were measured to determine diffusion profiles. In addition, the spatial distribution of Ba-133 in the samples was determined. Polymethyl methacrylate standards for Ba-133 were developed to determine the counting efficiency for electronic autoradiography. Good visual correlation between the two autoradiography methods were obtained in this study. The results of the experiments presented here can be utilized in future studies on the diffusion behavior of barium in granitic rocks.Peer reviewe

Human neural crest cells display molecular and phenotypic hallmarks of stem cells

The fields of both developmental and stem cell biology explore how functionally distinct cell types arise from a self-renewing founder population. Multipotent, proliferative human neural crest cells (hNCC) develop toward the end of the first month of pregnancy. It is assumed that most differentiate after migrating throughout the organism, although in animal models neural crest stem cells reportedly persist in postnatal tissues. Molecular pathways leading over time from an invasive mesenchyme to differentiated progeny such as the dorsal root ganglion, the maxillary bone or the adrenal medulla are altered in many congenital diseases. To identify additional components of such pathways, we derived and maintained self-renewing hNCC lines from pharyngulas. We show that, unlike their animal counterparts, hNCC are able to self-renew ex vivo under feeder-free conditions. While cross species comparisons showed extensive overlap between human, mouse and avian NCC transcriptomes, some molecular cascades are only active in the human cells, correlating with phenotypic differences. Furthermore, we found that the global hNCC molecular profile is highly similar to that of pluripotent embryonic stem cells when compared with other stem cell populations or hNCC derivatives. The pluripotency markers NANOG, POU5F1 and SOX2 are also expressed by hNCC, and a small subset of transcripts can unambiguously identify hNCC among other cell types. The hNCC molecular profile is thus both unique and globally characteristic of uncommitted stem cells

Visceral and subcutaneous fat have different origins and evidence supports a mesothelial source

International audience: Fuelled by the obesity epidemic, there is considerable interest in the developmental origins of white adipose tissue (WAT) and the stem and progenitor cells from which it arises. Whereas increased visceral fat mass is associated with metabolic dysfunction, increased subcutaneous WAT is protective. There are six visceral fat depots: perirenal, gonadal, epicardial, retroperitoneal, omental and mesenteric, and it is a subject of much debate whether these have a common developmental origin and whether this differs from that for subcutaneous WAT. Here we show that all six visceral WAT depots receive a significant contribution from cells expressing Wt1 late in gestation. Conversely, no subcutaneous WAT or brown adipose tissue arises from Wt1-expressing cells. Postnatally, a subset of visceral WAT continues to arise from Wt1-expressing cells, consistent with the finding that Wt1 marks a proportion of cell populations enriched in WAT progenitors. We show that all visceral fat depots have a mesothelial layer like the visceral organs with which they are associated, and provide several lines of evidence that Wt1-expressing mesothelium can produce adipocytes. These results reveal a major ontogenetic difference between visceral and subcutaneous WAT, and pinpoint the lateral plate mesoderm as a major source of visceral WAT. They also support the notion that visceral WAT progenitors are heterogeneous, and suggest that mesothelium is a source of adipocytes

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility.

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings

Clay minerals in uraniferous deposit of Imouraren (Tim Mersoï basin, Niger) : implications on genesis of deposit and on ore treatment process

Les gisements uranifères nigériens sont localisés dans les formations carbonifères et jurassiques du bassin de Tim Mersoï. AREVA est actionnaire de 3 sites miniers de cette région: la SOMAÏR et la COMINAK dans le district d'Arlit, en exploitation depuis 50ans, et IMOURAREN, 80km plus au Sud, dont l'exploitation est programmée pour 2015. La minéralisation du gisement d'Imouraren est comprise dans la formation fluviatile du Tchirézrine 2 (Jurassique), formée de chenaux et de plaines d'inondation. Les faciès de remplissage de chenaux vont des grès grossiers aux grès très fins (cortège détritique : quartz et feldspaths), tandis que les faciès de débordement sont constitués d'analcimolites. La minéralogie secondaire est acquise lors de 2 évènements : 1- la diagenèse, avec formation de minéraux argileux, d'analcime, de quartz et d'albite secondaires, et 2- un épisode de circulations de fluides, qui induit une altération des minéraux détritiques et diagénétiques, la formation de nouvelles phases et le dépôt de l'uranium. Cette altération dessine une zonation minéralogique à l'échelle du gisement.L'hétérogénéité du Tchirézrine 2, tant au niveau des faciès que de la minéralogie, se perçoit lors du traitement du minerai, puisqu'il réagit différemment selon sa provenance, avec parfois des problèmes de récupération de l'U. Des essais de traitement de minerais, ont montré que analcimes et chlorites étaient les deux pénalisants, pour 3 raisons : 1- les piégeages des phases U au sein des analcimes, 2- la dissolution de ces 2 minéraux a tendance à faire sortir des conditions de solubilisation de l'U (pH et Eh) et à former de nombreux sulfates, 3- problèmes de percolation. Une méthode de détection des minerais riches en analcimes, basée sur la spectroscopie infrarouge, a été développée afin d'optimiser les mélanges de minerais et ainsi de réduire les effets néfastes des pénalisants lors du traitement.Nigerian uraniferous deposits are located in carboniferous and jurassic formations of Tim Mersoï basin. AREVA is shareholder of 3 mine sites in this area: SOMAÏR and COMINAK, both in exploitation since 1960’s and IMOURAREN, 80km further South, whose exploitation is planned for 2015. Mineralization of Imouraren deposit is included in the fluvial formation of Tchirezrine 2 (Jurassic), composed of channels and flood plains. Facies of channel infillings range from coarse sandstones to siltstones, while overflow facies are composed of analcimolites.Secondary mineralogy was acquired during 2 stages: 1- diagenesis, with formation of clay minerals, analcime, secondary quartz and albites, and 2- stage of fluids circulations, which induced alteration of detrital and diagenetic minerals, formation of new phases and uranium deposition. A mineralogical zoning, at the scale of deposit resulted from this alteration. The heterogeneity of Tchirezrine 2, at the level of both facies and mineralogy, is also evidenced during ore treatment, as ore reacts differently depending on its source, with sometimes problems of U recovery. Ore treatment tests showed that analcimes and chlorites were both penalizing minerals, because of 1- the sequestration of U-bearing minerals into analcimes, 2- their dissolution which trends to move away from U solubilization conditions (pH and Eh) and to form numerous sulfates, and 3- problems of percolation. A detection method of analcime-rich ores, based on infrared spectroscopy, was developed in order to optimize ore blending and so to reduce negative effects during ore treatment process

Prediction of enthalpies of formation of hydrous sulfates

International audienceA method for the prediction of the enthalpies of formation Delta H-f(o) for minerals of hydrous sulfates is proposed and is decomposed in the following two steps: (1) an evaluation of Delta H-f(o) for anhydrous sulfates based on the differences in the empirical electronegativity parameter Delta O-H= M2+ (c) characterizing the oxygen affinity of the cation M2+; and (2) a prediction of the enthalpy of hydration based on the knowledge of the enthalpy of dissolution for anhydrous sulfates. The enthalpy of formation of sulfate minerals from constituent oxides is correlated to the molar fraction of oxygen atoms bound to each cation and to the difference of the oxygen affinity Delta O-H(=) M2+(c) between any two consecutive cations. The Delta O-H(=) Air (c) value, using a weighing scheme involving the electronegativity of a cation in a given anhydrous sulfate, is assumed to be constant. This value can be calculated by minimizing the difference between the experimental enthalpies and calculated enthalpies of formation of sulfate minerals from constituent oxides. The enthalpy of hydration is closely related to the nature of the cation in the anhydrous salt, to the number of water molecules in the chemical formula and to the enthalpy of dissolution for the anhydrous salt. The results indicate that this prediction method gives an average value within 0.55% of the experimentally measured values for anhydrous sulfates and 0.21% of the enthalpies of hydration or hydrous sulfates. The relationship between Delta O-H(=) M2+ (sulfate), which corresponds to the electronegativity of a cation in a sulfate compound, and known parameter Delta O-H(=) M2+(aq) was determined. These determinations allowed the prediction of the electronegativity of some anhydrous transition metal double sulfate and contributed to the prediction of the enthalpy of formation for any hydrous double sulfate. With a simplified prediction of the entropy of a hydrous sulfate, calculations of Gibbs free energy of formation can be evaluated and contribute to the knowledge of the stability of some hydrous sulfates in different environmental conditions such as temperature or air moiety. Therefore, to check the reliability of the predictive model, stability fields for some hydrous ferric sulfates such as pentahydrate ferric sulfate, lawsonite, komelite, coquimbite, and quenstedtite vs. temperature and relative humidity were studied and compared with experimental measurement

From Bq cm−3 to Bq cm−2 (and conversely)—part 2: useful dataset to apply the conversion to decommissioning operations

Autoradiography technique generally provides an image in cps cm−2, the conversion in Bq g−1 remaining a challenge. The Geant4 tool has been used to establish a conversion procedure based on the estimation of a key parameter, the emission fraction FE. The conversion method was applied on three samples containing 3H, 14C and 238U respectively, allowing then to assess the detection efficiency of a digital radioimager, BeaQuant™. Particular attention was paid to matrix effect of contaminated material that could affect the detection efficiency. This article is coupled with a companion paper, providing support to apply the conversion method to decommissioning investigations

From Bq cm−3 to Bq cm−2 (and conversely)—part 1: a useful conversion for autoradiography

International audienc

Modélisation de la dégradation d’un composant à partir du retour d’expériences

ACLInternational audienc