Correlated detection of neutral and charged fragments in collision induced fragmentation of molecular clusters

accepté dans International Journal of Mass SpectrometryWe report on collision induced fragmentation of isolated molecular nanosystems studied with an event by event detection technique including the correlated detection of both neutral and charged fragments. This work focuses on the dissociation induced by collisional excitation without ionisation and electron-capture. Two molecular cluster cations are investigated: the collision of protonated hydrogen clusters at 60keV/amu with helium targets and that of protonated water clusters at 8keV with an argon gas. In addition to the molecular evaporation process the dissociation channel leading to the production of the H3+ or H3O+ molecular cations (loss of all the molecules) is observed with an unexpected abundance. The cross section for the production of these cations is observed to increase with the number of molecules in the cluster. Such an increase cannot be associated with the direct collisional excitation of the cation core of the cluster

Polymers of triglycerides generated during heating of fat do not protect linoleic acid from ruminal biohydrogenation

Heating fats often induces a decrease of cis-9, cis-12 C18:2 and cis-9, cis-12, cis-15 C18:3 biohydrogenation (BH) in vivo (Gonthier et al. 2005), in situ (Troegeler-Meynadier et al. 2006) and in vitro (Privé et al. 2010). This is of interest because it could increase polyunsaturated fatty acids (PUFA) content of ruminant products. Temperature and duration of heating of sunflower oil affect ruminal BH of PUFA, in part due to peroxide value (Privé et al., 2010). Our hypothesis was that polymers of triglycerides (TG), formed during heating of TG but not of free FA, could be responsible for partial protection of PUFA from BH

Temperature and duration of heating of sunflower oil affect ruminal biohydrogenation of linoleic acid in vitro

Sunflower oil heated at 110 or 150°C for 1, 3, or 6 h was incubated with ruminal content in order to investigate the effects of temperature and duration of heating of oil on the ruminal biohydrogenation of linoleic acid in vitro. When increased, these 2 parameters acted together to decrease the disappearance of linoleic acid in the media by inhibiting the isomerization of linoleic acid, which led to a decrease in conjugated linoleic acids and trans-C18:1 production. Nevertheless, trans-10 isomer production increased with heating temperature, suggesting an activation of Δ9-isomerization, whereas trans-11 isomer production decreased, traducing an inhibition of Δ12-isomerization. The amount of peroxides generated during heating was correlated with the proportions of biohydrogenation intermediates so that they might explain, at least in part, the observed effects. The effects of heating temperature and duration on ruminal bacteria community was assessed using capillary electrophoresis single-strand conformation polymorphism. Ruminal bacterial population significantly differed according to heating temperature, but was not affected by heating duration. Heating of fat affected ruminal biohydrogenation, at least in part because of oxidative products generated during heating, by altering enzymatic reactions and bacterial population

Charge-Transfer Induced Dissociation in the H+(H2O)3-Ar collisions observed with the COINTOF mass spectrometer

Electron-capture in collisions of singly charged protonated water cluster H+(H2O)3, ions with Ar atoms is studied at the impact energy of 8 keV in the frame of the COrrelated Ion and Neutral fragments Time-Of-Flight, COINTOF, technique. In contrast to methods based only on the detection of the charged fragments, dissociation induced by collisional-excitation and electron-capture induced dissociation can be simultaneously recorded in the present set-up. Time of flight measurement of both neutral and corresponding charged species resulting from the charge-exchange process leads to the direct observation of the dissociation of the neutralized protonated water cluster. Thus, the present COINTOF method provides new valuable insights into the collision processes through the detection of produced neutral fragments. Moreover, it opens new possibilities to measure kinetic energy release also in the dissociation of the produced neutrals, which is our future endeavour in the development of the presented COINTOF set up

Probing the liquid-t-gas like phase transition in a cluster via a caloric curve

IP

Understanding the dual mobility concept for total hip arthroplasty. Investigations on a multiscale analysis-highlighting the role of arthrofibrosis

International audienceIn hip implants, UHMWPE (ultra high molecular weight polyethylene) liner wear is believed to be a key issue affecting the lifetime of the artificial joint. Dual mobility, a THA (total hip arthroplasty) concept where the liner moves inside the metallic shell, has become popular due to its low dislocation rate. To understand the tribological behavior of this particular implant, especially the role of the second mobility, 12 representative explants were selected from a bank of 250 explants. The implants used were Profil® femoral stem and Novae® metallic shell. The external surface, involved in the second mobility, was examined by 3D profilometry, SEM (scanning electron microscopy) and CMM (coordinate measuring machine). This study highlights a correlation between roughness and CMM evolutions and surgical parameters. A particular wear zone and a wear scenario were identified and validated according to the type of metal-back. A metal transfer between the metal back and the liner was isolated. CMM allowed to measure second mobility wear volume at a macroscopic scale. Thus a realistic wear mechanism has been suggested for this specific implant

A novel "Correlated Ion and Neutral Time Of Flight" Method: event-by-event detection of neutral and charged fragments in Collision Induced Dissociation (CID) of mass selected ions

accepté dans Rev. Sci. Instrum.A new mass spectrometric MS-MS method based on Time Of Fight measurements performed on an event-by-event detection technique is presented. This "COrrelated Ion and Neutral Time of Flight (COINTOF)" method allows to explore CID fragmentation processes by directly identifying not only all ions and neutral fragments produced but also their arrival time correlations within each single fragmentation event from a dissociating molecular ion. This constitutes a new step in the characterization of molecular ions. The method will be illustrated here for a prototypical case involving Collision Induced Dissociation (CID) of protonated water clusters H+(H2O)n=1-5 upon collisions with argon atoms

Reply to the comment on direct experimental evidence for a negative heat capacity in the liquid to gas phase transition in hydrogen cluster ions backbending of the caloric curve

IP

Total partial and electron-capture cross sections for ionization of water vapor by 20-150 keV protons

IP