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International audience; The oxidation of tetrahydrofuran (THF) was carried out in a continuously jet-stirred tank reactor (JSR) at a total pressure of 10 atm, in fuel-lean conditions (equivalence ratio = 0.5), an initial fuel mole fraction of 5000 ppm, at a mean residence time of 2 s, and for temperatures ranging from 550 to 620 K. High-resolution mass spectrometry analyses was used to characterize low-temperature oxidation products of THF. MS analyses were performed using atmospheric pressure chemical ionizations in positive and negative modes. Both flow injection analyses and ultra-high-pressure liquid chromatography-MS/MS allowed characterizing a large set of chemicals including hydroperoxides and diols (C 4 H 8 O 3), ketohydroperoxides (C 4 H 6 O 4), and more oxygenated molecules (up to C 4 H 8 O 7) resulting from up to three oxygen molecules addition of on α and β THF radicals. The existence of-OH or-OOH groups in the products was confirmed by hydrogen-deuterium exchange using D 2 O. We detected 24 products with molecular weight of 40-168, not reported in previous studies. Simulations using the latest THF oxidation chemical kinetic reaction mechanism available from the literature were compared to the present measurements of ketohydroperoxides and other products of THF cool flame. The kinetic scheme represented well the present qualitative data.

Elucidating the formation of combustion intermediates is crucial to validate reaction pathways, develop reaction mechanisms and examine kinetic modeling predictions. While high-temperature pyrolysis and oxidation intermediates of alkanes have been thoroughly studied, comprehensive analysis of cool flame intermediates from alkane autoxidation is lacking and challenging due to the complexity of intermediate species produced. In this work, jet-stirred reactor autoxidation of four C10 alkanes: n-decane, 2-methylnonane, 2,7-dimethyloctane, and n-butylcyclohexane, as model compounds of diesel fuel, was investigated from 500 to 630 K using synchrotron vacuum ultraviolet photoionization molecular beam mass spectrometry (SVUV-PIMS). Around 100 intermediates were detected for each fuel. The classes of molecular structures present during the autoxidation of the representative paraffinic functional groups in transport fuels, i.e., n-alkanes, branched alkanes, and cycloalkanes were established and were found to be similar from the oxidation of various alkanes. A theoretical approach was applied to estimate the photoionization cross sections of the intermediates with the same carbon skeleton as the reactants, e.g., alkene, alkenyl keto, cyclic ether, dione, keto-hydroperoxide, diketo-hydroperoxide, and keto-dihydroperoxide. These species are indicators of the first, second, and third O2 addition reactions for the four C10 hydrocarbons, as well as bimolecular reactions involving keto-hydroperoxides. Chemical kinetic models for the oxidation of these four fuels were examined by comparison against mole fraction of the reactants and final products obtained in additional experiments using gas chromatography analysis, as well as the detailed species pool and mole fractions of aforementioned seven types of intermediates measured by SVUV-PIMS. This works reveals that the models in the literature need to be improved, not only the prediction of the fuel reactivity and final products, but also the reaction network to predict the formation of many previous undetected intermediates.

International audience; With the growing interest for biomass-derived fuels the understanding of the combustion chemistry of terpenes becomes of major scientific importance. Terpenes have been proposed as biofuels for aviation because of their high energy density. They usually develop cool flames below 800 K. Very complex processes occur there, with the formation of peroxides intermediates such as ketohydroperoxides and highly oxidized molecules (HOMs) containing both hydroperoxy and carbonyl groups. Such chemicals are relatively unstable and difficult to analyze.We studied the low-temperature oxidation of alpha-pinene, beta-pinene, and limonene (C10H16) in a jet-stirred reactor. The experimental conditions were selected to maximize the production of ketohydroperoxides. We oxidized 5000 ppm of these three terpenes at 1 bar, T = 590 K, an equivalence ratio of 0.5, and at a residence time of 1 s. High-resolution mass spectrometry analyses were performed on solubilized products of terpenes oxidation in cooled acetonitrile. The samples were analyzed using soft HESI electrospray ionization (+/-) and an Orbitrap® mass spectrometer (resolution: 140,000, mass accuracy RO2 QOOH; QOOH + O2 OOQOOH HOOQ’OOH followed by HOOQ’OOH + O2 (HOO)2Q’OO (i) (HOO)2POOH → OH + (HOO)2P=O (i.e., C10H14O5) and (ii) (HOO)2POOH + O2 → (HOO)3POO (HOO)3P’OOH → OH + (HOO)3P=O (i.e., C10H14O7). Fourth oxygen addition yielding C10H14O9 was also observed in the present work. Hydrogen–Deuterium exchange reactions using D2O were used to confirm the presence of –OH groups in the products.

International audience; With the growing interest for biomass-derived fuels the understanding of the combustion chemistry of ethers becomes of major scientific importance. Ethers usually develop strong cool flames at relatively low temperatures. Very complex processes occur there, with the formation of peroxidized intermediates such as ketohydroperoxides and highly oxidized molecules. Such chemicals are relatively unstable and difficult to analyze.We studied the low-temperature oxidation of dipropyl ether in a jet-stirred reactor. The experimental conditions were selected to maximize the production of ketohydroperoxides, based on the kinetic model of Serinyel et al. (2019). We oxidized 5000 ppm of dipropyl ether at 1 bar, T = 520–530 K, an equivalence ratio of 0.5, and at a residence time of 1 s. Analyses were performed on solubilized products of dipropyl ether oxidation in cooled acetonitrile. The samples were analyzed using soft HESI electrospray ionization (+/-) and an Orbitrap mass spectrometer (resolution: 140,000, mass accuracy RO2 QOOH; QOOH + O2 OOQOOH HOOQ’OOH followed by HOOQ’OOH + O2 (HOO)2Q’OO (i) (HOO)2POOH → OH + (HOO)2P=O (i.e., C6H12O6) and (ii) (HOO)2POOH + O2 → (HOO)3POO (HOO)3P’OOH → OH + (HOO)3P=O (i.e., C6H12O8).The so-called Korcek mechanism through which ketohydroperoxides are transformed into stable products, namely propanoic acid here, was also observed. Hydrogen–Deuterium exchange reactions using D2O served to confirm the presence of –OH groups in the products.

We report the direct observations of sub-macropulse beam centroid oscillations correlated with higher order modes (HOMs) which were generated by off-axis electron beam steering in TESLA-type superconducting RF cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a photocathode rf gun injecting beam into two separated 9-cell cavities in series with corrector magnets and beam position monitors (BPMs) located before, between, and after them. Oscillations of ~100 kHz in the vertical plane and ~380 kHz in the horizontal plane with up to 600-{\mu}m amplitudes were observed in a 3-MHz micropulse repetition rate beam with charges of 100, 300, 500, and 1000 pC/b. However, the effects were much reduced at 100 pC/b. The measurements were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch array data, imaging cameras, and a framing camera. Calculations reproduced the oscillation frequencies of the phenomena in the vertical case. In principle, these fundamental results may be scaled to cryomodule configurations of major accelerator facilities., Comment: 17 pp

According to the records from the Civil Court in Homs, where only 30% of the reported cases in the district were related to the countryside when 60% of the population lived in the rural areas, the author studies the practice/application of rural law and of the Civil Code by the users (civil servants, notables, farmers, land owners…) and how they adaptated to the new Ottoman bureaucratic authorities. In the administrative sub-district of Homs, the recording of trivial stories, and minor disputes dealt with in court reveal both the roles and implications of each actor in the implementation of the tenure, as well as the lability of laws, legal concepts and land tenure. The analysis of each story highlights the language, the multiple terms for ownership or lease of litigants and the different degrees of understanding law and customs. At the local level and with minute details of the litigations at the court in the late nineteenth century, a time that was characterized by the application of Ottoman institutional reforms (Tanẓīmāt), this paper suggests to observe the Ottoman land reform through the eyes of a local user in Wilāyat Sūriyya., En se fondant sur les comptes rendus d'audience issus des registres du tribunal civil de Homs, où seuls 30% des cas sont relatifs à la campagne alors que 60% de la population est rurale, cet article analyse la pratique du droit par les usagers (fonctionnaires, notables, paysans, propriétaires) et leur adaptation aux nouvelles instances bureaucratiques ottomanes. Dans la subdivision administrative de Homs, les histoires anodines, les litiges mineurs débattus auprès de la cour révèlent tant les rôles et implications de chacun des acteurs dans la mise en place du régime foncier que la labilité des lois et des notions juridiques et foncières. L'analyse au fil de l'anecdote met en valeur les registres de langue, les multiples titres de propriété ou de location des parties plaidantes ainsi que les nuances d'entendement des lois et coutumes. À l'échelle locale et avec les détails infimes des recours en justice, durant la fin du xix e siècle caractérisée par l'application des réformes institutionnelles ottomanes (Tanẓīmāt), cet article propose d'observer la réforme ottomane foncière à la lunette d'usagers locaux de la Wilāyat Sūriyya.

The historian in front of the conflict: Homs and the uprising. Until 2011, when the revolutionary sparkle was lit in Homs (Syria), it was a place considered being insignificant or forgotten by most people. Its revolutionary effervescence transformed the city – until then without any major historical events – to an emblematic city and the apocalyptic images of the events were accessed/used by the media and by the local stakeholders thanks to social media. In this context, facing these brutal actions, the role and position of the historian needs to be reconsidered. It forces him/her to review his/her understanding of the past, of his/her choice of source material and their interpretation of them. With the transformation of the field of study into a " battlefield " , the concept of tangible and intangible heritage is renewed. Be it abandoned., En 2011, l'effervescence révolutionnaire au coeur de Homs (Syrie), localité méconnue voire oubliée de la plupart des contemporains, transforme cette ville-sans événements historiques majeurs-en une ville phare dont les images apocalyptiques sont drainées par les médias et par les acteurs locaux grâce aux réseaux sociaux. Dans ce contexte, la position et le rôle de l'historien face à une actualité brutale est interrogée. Ici, l'historien revient sur sa compréhension du passé, son choix des sources et de leurs interprétations. Avec la métamorphose du terrain d'étude en « champ de bataille », la conception du patrimoine matériel et immatériel se renouvèle. Vieilles pierres à l'état d'abandon, expressions désuètes ou encore rituels populaires oubliés, les Homsiotes redécouvrent leur ville et se réapproprient leur patrimoine. Dans ce chaos, l'historien peut-il encore s'abstraire de l'événementiel, de l'émotionnel. Le récit de la Homs ottomane écrit en 2007 doit-il être réécrit ?

International audience

International audience; La plupart des villes du Moyen-Orient ont entretenu et, pour certaines, entretiennent encore, en leurs murs ou à leur périphérie immédiate, des jardins maraîchers ou des vergers : ceux d'Alep ou de Tripoli, mis à mal ou anéantis par l'urbanisation, ceux des villes de la vallée de l'Oronte, encore relativement préservés, ceux de Damas, vaste oasis désormais malmenée par la croissance urbaine, ceux des villes de Mésopotamie ou encore, beaucoup plus au sud, les jardins clos de la vieille ville de Sanaa. Alimentés à partir de puits, de sources ou d'un cours d'eau, bénéficiant de systèmes d'irrigation anciens et relativement sophistiqués, entretenues et exploitées par des jardiniers le plus souvent citadins, ces terres hautement productives ont longtemps assuré une grande part des besoins en fruits et légumes des villes de Homs et de Hama en Syrie centrale, tout en participant, avec les marchés et la vieille ville, d'un mode de vie proprement citadine

International audience; Thierry Boissière étudie le monde social des jardins urbains de l'Oronte, dont il nous restitue les systèmes techniques, la structure et l'organisation socioprofessionnelles, les liens étroits avec la ville ainsi que l'évolution depuis une cinquantaine d'années

International audience

International audience

International audience