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Complexation of europium( iii ) with exopolysaccharides from a marine bacterium envisaged as luminescent probe in a theranostic approach
No full textInternational audienceExopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties in osteosarcoma (bone tumor). These EPSs could be employed as new drug deliverysystems for therapeutic uses. They may represent a new class of ligands to be combined in a theranosticapproach with fluorescent metals, such as Eu(III), to serve as imaging probe. The goal of this work was toinvestigate the feasibility of such coupling by time-resolved laser-induced fluorescence spectroscopy(TRLFS). Since these EPSs are polyelectrolytes their conformation could affect the complexation properties.Thus, viscosimetric measurements were performed as a function of their concentration as well asthe background electrolyte concentration. Polysaccharides conformation exhibited a lower hydrodynamicvolume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexationwith metal for high concentration but no change was evidenced when increasing europiumconcentration. Two sites of complexation of Eu(III) were evidenced by TRLFS in heparin, whereas only onesite was evidenced in two modified EPSs produced from Alteromonas infernus
Elliptic Flow of Electrons from Beauty-Hadron Decays in Pb-Pb Collisions at = 5.02 TeV
No full textInternational audienceThe elliptic flow of electrons from beauty hadron decays at midrapidity (|y|<0.8) is measured in Pb-Pb collisions at sNN=5.02 TeV with the ALICE detector at the LHC. The azimuthal distribution of the particles produced in the collisions can be parametrized with a Fourier expansion, in which the second harmonic coefficient represents the elliptic flow, v2. The v2 coefficient of electrons from beauty hadron decays is measured for the first time in the transverse momentum (pT) range 1.3–6 GeV/c in the centrality class 30%–50%. The measurement of electrons from beauty-hadron decays exploits their larger mean proper decay length cτ≈500 μm compared to that of charm hadrons and most of the other background sources. The v2 of electrons from beauty hadron decays at midrapidity is found to be positive with a significance of 3.75 σ. The results provide insights into the degree of thermalization of beauty quarks in the medium. A model assuming full thermalization of beauty quarks is strongly disfavored by the measurement at high pT, but is in agreement with the results at low pT. Transport models including substantial interactions of beauty quarks with an expanding strongly interacting medium describe the measurement within uncertainties
Cumulants of the chiral order parameter at lower RHIC energies
No full textInternational audienceWe study cumulants of the chiral order parameter as function of beam energy as a possible signal for the presence of a critical end point and first-order phase transition in the QCD phase diagram. We model the expansion of a heavy-ion collision by a fluid dynamic expansion coupled to the explicit propagation of the chiral order parameter sigma via a Langevin equation. We evolve the medium until a parametrized freeze-out condition is met where we calculate event-by-event fluctuations and cumulants of sigma which are expected to follow the trend of net-proton number cumulants. We emphasize the role of a nonequilibrium first-order phase transition: The presence of an unstable phase causes the well-known bending of the trajectories in the space of temperature and baryochemical potential. For these cases at lower beam energies, the system crosses the freeze-out line more than once, allowing us to calculate a range of cumulants for each initial condition which are overall enhanced for the second hit of the freeze-out line. We thus find not only the critical end point but also the phase transition of the underlying model clearly reflected in the cumulants. The impact of volume fluctuations is demonstrated to play a measurable role for fluid dynamical evolutions that last significantly long
Search for inelastic scattering of WIMP dark matter in XENON1T
No full textInternational audienceWe report the results of a search for the inelastic scattering of weakly interacting massive particles (WIMPs) in the XENON1T dark matter experiment. Scattering off Xe129 is the most sensitive probe of inelastic WIMP interactions, with a signature of a 39.6 keV deexcitation photon detected simultaneously with the nuclear recoil. Using an exposure of 0.83 tonne-years, we find no evidence of inelastic WIMP scattering with a significance of more than 2σ. A profile-likelihood ratio analysis is used to set upper limits on the cross section of WIMP-nucleus interactions. We exclude new parameter space for WIMPs heavier than 100 GeV/c2, with the strongest upper limit of 3.3×10-39 cm2 for 130 GeV/c2 WIMPs at 90% confidence level
Delocalized relativistic effects, from the viewpoint of halogen bonding
No full textInternational audienceThe ability of organic and inorganic compounds bearing both iodine and astatine atoms to form halogen-bond interactions is theoretically investigated. Upon inclusion of the relativistic spin–orbit interaction, the I-mediated halogen bonds are more affected than the At-mediated ones in many cases. This unusual outcome is disconnected from the behavior of iodine's electrons. The significant decrease of astatine electronegativity with the spin–orbit coupling triggers a redistribution of the electron density, which propagates relativistic effects toward the distant iodine atom. This mechanism can be controlled by introducing suitable substituents and, in particular, strengthened by taking advantage of electron-withdrawing inductive and mesomeric effects. Noticeable relativistic effects can actually be transferred to light atoms properties, e.g., the halogen-bond basicity of bridgehead carbon atoms doubled in propellane derivatives
La radiochimie théorique comme composante essentielle de la radiochimie moléculaire: De l’interprétation à la prédiction des expériences
No full textInternational audienceMolecular radiochemistry is being developed for different fields of application, such as fundamental chemistry, environment, nuclear safety, and even health. Electronic structure and/or molecular dynamics calculations allow a detailed understanding of the underlying physico-chemical phenomena, and are most often added to experimental data. This article presents recent examples from the French scientific community to show the issues and difficulties of the theoretical studies, as well as the main challenges for the coming years.La radiochimie moléculaire se développe pour différents champs d’application, tels que la chimie fondamentale, l’environnement, la sûreté nucléaire ou encore la santé. Les calculs de structures électroniques ou de dynamique moléculaire permettent une compréhension fine des phénomènes physico-chimiques sous-jacents et s’ajoutent le plus souvent aux données expérimentales. Cet article présente des exemples récents de la communauté scientifique française, afin de montrer les enjeux et difficultés des études théoriques, ainsi que les principaux verrous à lever pour les prochaines années
Solubility of monoclinic and yttrium stabilized cubic ZrO: Solution and surface thermodynamics guiding ultra-trace analytics in aqueous phase
No full textInternational audienceThe high stability of zirconium dioxide in aqueous environments is known and demonstrated, and this property is strongly used in nuclear industry to ensure the long term storage of wastes. However, only upper limits of its aqueous solubility are known reliably and lower limits linked to very well crystallized ZrO 2 are much less assessed. Indeed, the low dissolution rate of zirconia makes the solubility measurements a challenging task. To overcome, high S/V ratios of nanoparticles zirconia were used. This work also improved the sensitivity of analytical techniques (HR ICP-MS) and methodologies, and a reliable experimental procedure was developed to measure zirconium (quantification limit ≈10 −11 mol∙L −1 ). New Zr(IV) dioxide solubility data at pH between 0 and 2 were obtained approaching solubility from under-saturated conditions in (Na,H)Cl and (Na,H)ClO 4 medium. Two crystalline nanoparticle structures were compared: monoclinic and yttrium stabilized cubic zirconia. Very low solubility was measured for monoclinic phase between pH 1.5 and 2: between (1.8±1.2) × 10 −10 mol∙L −1 at pH 2 and (2.3±1.0) × 10 −10 mol∙L −1 at pH 1.5. The cubic zirconia showed higher solubility. Integrating the effect of ionic strength, particle size and aqueous speciation, solubility constants of log Ks0 = (-8.43±0.69) for the monoclinic nanoparticles and log Ks0 = (-7.12±0.35) for the yttrium stabilized cubic nanoparticles were obtained. High-resolution techniques (HR-TEM, SAXS and STEM-HAADF) were also used to assess the evolution of morphology and surface before, during and at equilibrium. Analysis of these results shows that the morphology and surface of nanoparticles in the raw state and after reaching equilibrium in (Na,H)Cl and (Na,H)ClO 4 medium are similar
First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV
No full textInternational audienceThe first measurement of the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV is presented. This result, together with previous HERA γp data and γ–Pb measurements from ALICE, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe+Xe→ρ0+Xe+Xe process, measured at midrapidity through the decay channel ρ0→π+π−, is found to be dσ/dy=131.5±5.6(stat.)−16.9+17.5(syst.) mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on A of cross section for the coherent ρ0 photoproduction at a centre-of-mass energy per nucleon of the γA system of WγA,n=65 GeV is found to be consistent with a power-law behaviour σ(γA→ρ0A)∝Aα with a slope α=0.96±0.02(syst.). This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit
Installation, Use and Follow-Up of an Emittance-Meter at the Arronax Cyclotron 70XP
No full textInternational audienceThe 70 MeV cyclotron group of the Arronax GIP (Interest Public Group), France, foresees to increase its beam intensity on target. For this, several beam studies are being performed in the various sections of the accelerator including the injection. Thus, an Allison-type emittance-meter has been installed in this section above the cyclotron and downstream a quadrupole triplet. Installation and the first results of a campaign of measurements are presented including high intensity runs, up to 1 mA for 40 keV H⁻ ions. The emittance-meter is expected to be used with several accelerators throughout the world. Therefore, a strategy on the follow-up of the activation of sample materials used in the equipment is being established and is described in the paper
Extraction of giant Dzyaloshinskii–Moriya interaction from ab initio calculations: First-order spin–orbit coupling model and methodological study
No full textInternational audienceThe Dzyaloshinskii–Moriya interaction is expected to be at the origin of interesting magnetic properties, such as multiferroicity, skyrmionic states, and exotic spin orders. Despite this, its theoretical determination is far from being established, neither from the point of view of ab initio methodologies nor from that of the extraction technique to be used afterward. Recently, a very efficient way to increase its amplitude has been demonstrated near the first-order spin–orbit coupling regime. Within the first-order regime, the anisotropic spin Hamiltonian involving the Dzyaloshinskii–Moriya operator becomes inappropriate. Nevertheless, in order to approach this regime and identify the spin Hamiltonian limitations, it is necessary to characterize the underlying physics. To this end, we have developed a simple electronic and spin–orbit model describing the first-order regime and used ab initio calculations to conduct a thorough methodological study