High pressure cell for edge jumping X-ray absorption spectroscopy : Applications to industrial liquid sulfidation of hydrotreatment catalysts

International audienceA new analytical cell to perform liquid sulfidation of HDS catalysts in industrial conditions was developed. It enables the alternate recording of time-resolved Mo and Co K edges X-ray Absorption spectra of bimetallic catalysts under high pressure (30 bar) and temperature (350°C) during the same reaction. Thanks to this cell, a comparative study of the species formed upon gas (1 bar, 15% H 2 S/H 2) and liquid sulfidation (30 bar, H 2 /gas oil/4% DMDS) of a CoMoP/Al 2 O 3 HDS catalyst was carried out, together with a discussion on the evolution of the concentration profiles upon activation. Different Mo and Co-based chemical species are involved during gas and liquid sulfidation. On one hand, in industrial liquid sulfidation, polymolybdate species are transformed into depolymerized oxides, then into an oxysulfide, a MoS x species and finally into MoS 2. On the other hand, gas sulfidation skips the depolymerization process because of the immediate supply of H 2 S at the beginning of the process and proceeds under a stepwise transformation of oxide into oxysulfide, itself into MoS 3 species and finally into MoS 2. Cobalt species under gas sulfidation goes through a CoS 2 intermediate whereas in liquid sulfidation, it is a 4-fold coordinated Co oxide species. Irrespective to the activation route, mixture of Co 9 S 8 and CoMoS is obtained at advanced sulfidation stage (T> 200°C). Graphical Abstract Quick XAS in situ cell Raman Probe H 2 Gas oil + DMDS 350 C 30 bar Synchrotron radiation Co K edge Mo K edge DMDS decomposition CH 4 H 2 S 232 C 284 C 2 Highlights  A high pressure cell has been developed to study the liquid sulfidation of HDS catalyst by X-ray Absorption Spectroscopy  Co and Mo local orders are studied alternatively during the same reaction  The sulfidation mechanism depends on the activation process  The sulfidation of Co and Mo in liquid phase mainly occurs when DMDS is decomposed into H 2 S between 225°C and 350°C. Gas sulfidation starts at room temperature and is completed at 400°

Role of the exchange and correlation potential into calculating the x-ray absorption spectra of half-metallic alloys: the case of Mn and Cu K-edge XANES in Cu2_2MnM (M = Al, Sn, In) Heusler alloys

This work reports a theoretical study of the x-ray absorption near-edge structure spectra at both the Cu and the Mn K-edge in several Cu$_2$MnM (M= Al, Sn and In) Heusler alloys. Our results show that {\it ab-initio} single-channel multiple-scattering calculations are able of reproducing the experimental spectra. Moreover, an extensive discussion is presented concerning the role of the final state potential needed to reproduce the experimental data of these half-metallic alloys. In particular, the effects of the cluster-size and of the exchange and correlation potential needed in reproducing all the experimental XANES features are discussed.Comment: 15 pages, 5 figure

The IKMC web portal: a central point of entry to data and resources from the International Knockout Mouse Consortium

The International Knockout Mouse Consortium (IKMC) aims to mutate all protein-coding genes in the mouse using a combination of gene targeting and gene trapping in mouse embryonic stem (ES) cells and to make the generated resources readily available to the research community. The IKMC database and web portal (www.knockoutmouse.org) serves as the central public web site for IKMC data and facilitates the coordination and prioritization of work within the consortium. Researchers can access up-to-date information on IKMC knockout vectors, ES cells and mice for specific genes, and follow links to the respective repositories from which corresponding IKMC products can be ordered. Researchers can also use the web site to nominate genes for targeting, or to indicate that targeting of a gene should receive high priority. The IKMC database provides data to, and features extensive interconnections with, other community databases

Між Антантою та більшовицькою Росією: основні напрями зовнішньої політики ЗУНР у 1920 – 1923 рр.

Показана реорганізація зовнішньополітичної служби Західно-Української Народної Республіки після еміграції її уряду до Відня, проаналізовано взаємини галицької дипломатії з країнами Антанти, Чехословаччиною, радянськими республіками, Україною і Росією на початку 20-х рр. ХХ ст.The article showed the reorganization of the foreign policy service of the West Ukrainian National Republic after emigration of its government to Vienna, analyzed the relationship between Galician diplomacy with the countries of the Entente, Czechoslovakia, the Soviet republics of Ukraine and Russia in the early 20-ies of XX century

Cohesin Protects Genes against γH2AX Induced by DNA Double-Strand Breaks

Chromatin undergoes major remodeling around DNA double-strand breaks (DSB) to promote repair and DNA damage response (DDR) activation. We recently reported a high-resolution map of γH2AX around multiple breaks on the human genome, using a new cell-based DSB inducible system. In an attempt to further characterize the chromatin landscape induced around DSBs, we now report the profile of SMC3, a subunit of the cohesin complex, previously characterized as required for repair by homologous recombination. We found that recruitment of cohesin is moderate and restricted to the immediate vicinity of DSBs in human cells. In addition, we show that cohesin controls γH2AX distribution within domains. Indeed, as we reported previously for transcription, cohesin binding antagonizes γH2AX spreading. Remarkably, depletion of cohesin leads to an increase of γH2AX at cohesin-bound genes, associated with a decrease in their expression level after DSB induction. We propose that, in agreement with their function in chromosome architecture, cohesin could also help to isolate active genes from some chromatin remodelling and modifications such as the ones that occur when a DSB is detected on the genome

Theoretical investigation of the electronic structure of Fe(II) complexes at spin-state transitions

The electronic structure relevant to low spin (LS)high spin (HS) transitions in Fe(II) coordination compounds with a FeN6 core are studied. The selected [Fe(tz)6]2+(1) (tz=1H-tetrazole), [Fe(bipy)3]2+(2) (bipy=2,2’-bipyridine) and [Fe(terpy)2]2+ (3) (terpy=2,2’:6’,2’’-terpyridine) complexes have been actively studied experimentally, and with their respective mono-, bi-, and tridentate ligands, they constitute a comprehensive set for theoretical case studies. The methods in this work include density functional theory (DFT), time-dependent DFT (TD-DFT) and multiconfigurational second order perturbation theory (CASPT2). We determine the structural parameters as well as the energy splitting of the LS-HS states (ΔEHL) applying the above methods, and comparing their performance. We also determine the potential energy curves representing the ground and low-energy excited singlet, triplet, and quintet d6 states along the mode(s) that connect the LS and HS states. The results indicate that while DFT is well suited for the prediction of structural parameters, an accurate multiconfigurational approach is essential for the quantitative determination of ΔEHL. In addition, a good qualitative agreement is found between the TD-DFT and CASPT2 potential energy curves. Although the TD-DFT results might differ in some respect (in our case, we found a discrepancy at the triplet states), our results suggest that this approach, with due care, is very promising as an alternative for the very expensive CASPT2 method. Finally, the two dimensional (2D) potential energy surfaces above the plane spanned by the two relevant configuration coordinates in [Fe(terpy)2]2+ were computed both at the DFT and CASPT2 levels. These 2D surfaces indicate that the singlet-triplet and triplet-quintet states are separated along different coordinates, i.e. different vibration modes. Our results confirm that in contrast to the case of complexes with mono- and bidentate ligands, the singlet-quintet transitions in [Fe(terpy)2]2+ cannot be described using a single configuration coordinate

Scientific Rationale of Saturn's In Situ Exploration

Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustratedby the exploration of Jupiter, where key measurements such as the determination of the noble gases abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scienti-c goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. In situ exploration of Saturn's atmosphere addresses two broad themes that are discussedthroughout this paper : rst, the formation history of our solar system and second, the processes at play in planetary atmospheres. In this context, we detail the reasons why measurements of Saturn's bulk elemental and isotopiccomposition would place important constraints on the volatile reservoirs in the protosolar nebula. We also show that the in situ measurement of CO (or any other disequilibrium species that is depleted by reaction with water) in Saturn's upper troposphere may help constraining its bulk OH ratio. We compare predictions of Jupiter and Saturn's bulk compositions from different formation scenarios, and highlight the key measurements required to distinguish competing theories to shed light on giant planet formation as a common process in planetary systems with potential applications to mostextrasolar systems. In situ measurements of Saturn's stratospheric and tropospheric dynamics, chemistry and cloud-forming processes will provide access to phenomena unreachable to remote sensing studies. Dierent mission architectures are envisaged, which would benet from strong international collaborations, all based on an entry probe that would descend through Saturn's stratosphere and troposphere under parachute down to a minimum of 10 bars of atmospheric pressure. We rally discuss the science payload required on a Saturn probe to match the measurement requirements

Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko

Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface