Photodissociation de NO

La fluorescence de NO* produit par photodissociation de NO2 a été étudiée en fonction de la longueur d’onde d’excitation dans le domaine 110-140 nm au moyen du rayonnement synchrotron de LURE ACO. Le spectre d’excitation de la fluorescence globale du fragment NO* reproduit le spectre d’absorption de NO2 dans cette région. Les spectres de fluorescence obtenus en excitant N02 dans la bande d’absorption située entre 131 et 125 nm ainsi qu’à 123,6 nm avec la raie de résonance du krypton sont diffus à cause de la superposition des émissions provenant de NO A2Σ+ et B2Π. Deux bandes de fluorescence distinctes ont pu être attribuées aux niveaux NO A (v’ = 2,1). Les mesures de durée de vie de NO Av’ = 1 confirment cette attribution. La population relative de ces deux niveaux est constante dans le domaine 120-130 nm. Un rapport de branchement constant NO A/B = 1 a également pu être évalué dans la même région

The Role Of Crustal Anatexis And Mantle-Derived Magmas In The Genesis Of Synorogenic Hercynian Granites Of The Livradois Area, French Massif Central

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Femtosecond time-resolved photoelectron spectra of ammonia molecules and clusters

The first femtosecond pump-probe photoelectron spectroscopy experiment for neutral clusters is reported. The $\widetilde{A}$ state of ammonia molecules and clusters is excited with 120 fs pulses at 200 nm and probed by ionisation at 267 or 400 nm. Ions and electrons are detected in coincidence. The high repetition rate of the fs laser allows one to reduce the coincidence rate per laser pulse to less than 0.05 per pulse so that photoelectrons and photoions can be correlated unambiguously. The energy flow in the excited neutral cluster states is followed in real time, and the energy content in the ionic clusters can be related to the fragmentation patterns

Photoionization of NaI: inward-outward asymmetry in the wave packet detection

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Shaping the lipid composition of bacterial membranes for membrane protein production

Contains fulltext : 209080.pdf (publisher's version ) (Open Access

Improving the purification of membrane proteins from Escherichia coli C41(DE3)

The overexpression and purification of membrane proteins to high purity and homogeneity is a challenging task. Over time, several strains have been developed that decrease the toxic side-effects and thus result in higher bio mass and protein yield. However, two major contaminants have been identified in membrane protein preparations from E. coli: the outer membrane porin OmpF and AcrB, which is part of a tripartite efflux pump. Both proteins crystallise from low concentrations and diverse conditions, which make them a major problem, especially in membrane protein crystallography. In this study, we present a C41(DE3)-derived expression strains that is depleted of these two proteins

Microbe sample from Escherichia coli

BioSample: SAMN11037806; Sample name: C41 delta ompF delta acrB; SRA: SRS442251

Photoionization of NaI: inward-outward asymmetry in the wave packet detection

The nuclear wave packet in the A state of NaI has been monitored in a pump-probe femtosecond experiment using a resonant two-photon ionization detection scheme. A strong asymmetry depending on the direction of propagation of the wave packet is observed in the ${\rm Na^+}$ ion signal. This phenomenon, well reproduced by a full quantum wave packet calculation, has been assigned to the combination of two effects: i) the motion of the wave packet in the intermediate state of the two-photon probe process, ii) the R-dependence of the photoionization efficiency of this intermediate state

Silicate-carbonate liquid immiscibility: insights from the Crevier alkaline intrusion (Quebec)

International audienceThis contribution explores the petrogenetic relationships between silicate and carbonatitic rocks in the Crevier Alkaline Intrusion (CAI, Québec, Canada). The CAI is located in the Proterozoic Grenville Province and is composed of a suite of undersaturated peralkaline rocks from ijolite to nepheline syenite and carbonatites. Petrogenetic relationships between different undersaturated alkaline igneous rocks, carbonate-bearing and carbonate-free nepheline syenite and carbonatites observed in the CAI suggest that (i) carbonate-bearing and carbonate-free silicate rocks are comagmatic with carbonatite, and that (ii) both silicate and carbonatitic liquids are fractionated from an ijolitic parental magma that has undergone liquid immiscibility. One of the observed facies is characterized by spectacular ocelli of carbonate-bearing nepheline syenite in a matrix of carbonatite. The younger nepheline syenite facies can be divided into two groups based on the presence or absence of magmatic carbonates. Both groups are characterized by the presence of pyrochlore-group minerals that carry the Nb-Ta mineralization.We specifically use accessory minerals such as zircon, pyrochlore and apatite to constrain the temporal and physicochemical parameters of the immiscibility process. By coupling (i) mineral textures, (ii) trace elements, (iii) Ti-in-zircon thermometry, and (iv) oxygen isotope compositions, we have traced the crystallization of zircon before, during and after the immiscibility process. The results allowed us to constrain the minimum temperature of this process at ∼815-865 °C. In addition, two magmatic populations of pyrochlore are identified through their petrographic and geochemical characteristics within the younger nepheline syenite facies. Pyrochlore from the earlier ocelli facies of carbonate-bearing nepheline syenite follow a Nb-Ta differentiation trend, whereas pyrochlore from the younger carbonate-free nepheline syenite follow a more classical Nb-Ti trend. Following the complete immiscibility between the silicate and carbonatitic liquids, the fractionation between Nb and Ta stopped while a new generation of Nb-rich pyrochlore grew, displaying a more classical Nb-Ti fractionation trend and a more constant Nb/Ta ratio in the nepheline syenite