High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry

A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2 L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a Pb-207-Pb-204 double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28 +/- 21 pg(1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about +/- 1to +/- 10%(1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12 +/- 4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (+/- 2sd) of 700-1500 ppm and 1000-2000ppm were achieved for Pb-207/Pb-206, Pb-208/Pb-206 and Pb-206/Pb-204, Pb-207/Pb-204, Pb-208/Pb-204, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor Pb-204 isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the Pb-206/Pb-204 ratios are well correlated with Pb-207/Pb-206, underlining the significant improvement achieved in the measurement of the minor Pb-204 isotope

Le sentiment de cohérence et le processus physiologique de la naissance: Travail de Bachelor

Cadre de référence : Le respect du processus phyisologique de la naissance est devenu de plus en plus rare dans la société actuelle alors qu’il participe à diminuer de nombreuses morbidités pour la femme et le nouveau-né. Parmi les éléments qui peuvent influencer ce processus naturel, la femme elle-même semble jouer un rôle essentiel. Plus précisément, l’intensité de son sentiment de cohérence (SOC) pourrait influencer le déroulement de sa grossesse, de son accouchement, du post-partum et éventuellent la protéger de certaines complications obstétricales et psychologiques. But : Effectuer une revue de littérature pour déterminer dans quelle mesure un SOC élevé chez la femme enceinte peut favoriser la physiologie de la naissance. Méthode : À travers des bases de données d’articles scientifiques, 5 études récentes (<10 ans) ont été sélectionnées en fonction de leur pertinence avec la question de recherche. Elles ont fait l’objet d’une description, d’une analyse critique et d’une discussion en fonction de cinq thèmes définis. Résultats : Les résultats montrent qu’un SOC prénatal élevé chez la femme enceinte diminuerait significativement le risque d’accouchement par césarienne et qu’un SOC prénatal bas serait significativement corrélé avec un traitement pour menace d’accouchement prématuré (MAP) pendant la grossesse. Concernant la péridurale, son utilisation ne serait pas en lien direct avec le SOC de la femme. Les études montrent des résultats contradictoires sur la relation du SOC avec l’instrumentation et la provocation de l’accouchement. Par ailleurs, le stress perçu par les femmes et la peur de l’accouchement seraient significativement plus bas chez celles qui ont un SOC élevé. Enfin, un SOC prénatal élevé serait associé à une perception positive par la femme de son soutien social mais pas à la satisfaction de l’accouchement. Conclusion : Un SOC élevé chez la femme enceinte pourrait contribuer à favoriser la physiologie de la naissance en influençant de manière positive certains affects liés à des issues non physiologiques. Concernant les issues obstétricales en particulier, il semble que le SOC soit un facteur protecteur de la césarienne et du traitement pour MAP. Néanmoins, d’autres investigations sont encore nécessaires pour démontrer son impact sur différentes interventions médicales telles que la péridurale, l’instrumentation et la provocation de l’accouchement.Background: The respect of the processus of birth physiology has become increasingly rare in actual society, even though it contributes to the decrease in women’s and newborn’s morbidity. Among elements which can influence this natural process, women seem to play a crucial role. In particular, the intensity of her sense of coherence (SOC) could influence the course of the pregnancy, the delivery and the postpartum, and might even prevent obstetrical and psychological complications. Aim: Conduct a literature review to determine to what extent a pregnant woman’s high SOC could promote birth physiology. Methods: Five recent articles (< 10 years old) were selected from a scientific database according to their relevance to the research question. These articles have been described, critically analysed and discussed in relation to five defined topics. Results: Results demonstrate that a high prenatal SOC for pregnant women significantly reduces the risk of caesarean delivery. Results also show that a low prenatal SOC significantly correlates with the treatment for threatened premature birth during pregnancy. SOC does not seem directly related to the use of epidural. Studies indicate contradictory results in regards to the relation between SOC with instrumentation and induction of labour. Furthermore, perceived stress and fear of childbirth (FOC) seem significantly reduced for a patient with a high SOC. Finally, a high prenatal SOC seems connected to a positive perception of social support, but not to the satisfaction of delivery. Conclusion: A high SOC for pregnant women seems to contribute to fostering birth physiology by positively impacting certain emotions related to non-physiological issues. In regards to obstetrical issues in particular, SOC seems to be a protective factor against caesarean births and treatment of threatened premature birth. However, further investigation remains necessary to demonstrate its impact on various medical interventions such as epidural, instrumentation and induction of labour

The graphical presentation of lead isotope data for environmental source apportionment

Lead isotope ratios are widely used to identify original sources of Pb in the environment. Such source apportionment depends on the ability to distinguish potential sources on the basis of their isotopic composition. However, almost all terrestrial Pb is co-linear in some of the plots i.e. &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;208&lt;/sup&gt;Pb versus &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;207&lt;/sup&gt;Pb and &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb versus &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;207&lt;/sup&gt;Pb commonly presented in the literature. These diagrams are unable to distinguish more than two sources of environmental Pb. Linear trends in such plots are an inevitable consequence of the co-linearity of terrestrial leads and should not be taken necessarily to indicate simple binary mixing of sources. A more reliable test for multiple source mixing can be obtained from plots involving &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb, &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb and &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb and therefore requires measurements of the minor &lt;sup&gt;204&lt;/sup&gt;Pb isotope

Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider

Measurements of multi-particle azimuthal correlations (cumulants) for charged particles in p-Pb and Pb-Pb collisions are presented. They help address the question of whether there is evidence for global, flow-like, azimuthal correlations in the p-Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p-Pb collisions. However, when a $|\Delta \eta|$ gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high-multiplicity, indicating the presence of global azimuthal correlations. The Pb-Pb values are higher than the p-Pb values at similar multiplicities. In both systems, the second harmonic four-particle cumulants exhibit a transition from positive to negative values when the multiplicity increases. The negative values allow for a measurement of $v_{2}\{4\}$ to be made, which is found to be higher in Pb-Pb collisions at similar multiplicities. The second harmonic six-particle cumulants are also found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find $v_{2}\{4\} \simeq v_{2}\{6\}\neq 0$ which is indicative of a Bessel-Gaussian function for the $v_{2}$ distribution. For very high-multiplicity Pb-Pb collisions, we observe that the four- and six-particle cumulants become consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and Pb-Pb are measured. These are found to be similar for overlapping multiplicities, when a $|\Delta\eta| > 1.4$ gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87

Electroweak bosons in Pb+Pb and p+Pb collisions from ATLAS

Electroweak boson ($W$, $Z$, $\gamma$) measurements in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV and in $p$+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are presented with the ATLAS detector at the LHC. In Pb+Pb, electroweak boson yields are shown to be independent of centrality. Differential measurements in absolute pseudorapidity are used to investigate nuclear effects to the free-proton parton distribution function (PDF). The distributions lack the experimental precision to unambiguously identify the presence of nuclear modifications. In $p$+Pb, the $Z$ boson cross section is measured as a function of center-of-mass rapidity $y_{Z}^{*}$ and the momentum fraction of the lead-going parton (Bjorken $x_{Pb}$). The distributions are asymmetric and model predictions underestimate the data at large $x_{Pb}$. The overall shape is best described by including nuclear effects. The differential cross section is also measured in different centrality classes and shows evidence of spatially-dependent nuclear PDFs. The $Z$ boson production yields are measured as a function of the mean number of participants using Glauber and Glauber-Gribov color fluctuation models. Binary scaling of the yields is observed utilizing the standard Glauber model after applying a centrality-bias correction.Comment: 4 pages, 7 figures, Proceedings of the 7th International Conference on Hard and Electromagnetic Probes of High Energy Nuclear Collisions (Hard Probes 2015), Montrea

Heavy-flavour decay lepton measurements in pp, p-Pb, and Pb-Pb collisions with ALICE at the LHC

We present the measurements of electrons and muons from the semi-leptonic decays of heavy-flavour hadrons measured in the central and forward rapidity regions with ALICE in pp, Pb-Pb, and p-Pb, collisions at the LHC. The pT-differential production cross section in pp collisions, the elliptic flow in Pb-Pb collisions, and the nuclear modification factor in Pb-Pb and p-Pb collisions are shown. The results are compared to theoretical predictions.Comment: 8 pages, 6 figures, International Conference on the Initial Stages in High-Energy Nuclear Collisions (IS2013