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Two novel compounds isolated from an amber sample from the Santonian of Piolenc (Vaucluse, SE France) were identified using nuclear magnetic resonance and high-resolution mass spectrometry as sulfurized analogues of diterpenic acids from the isopimaric series originating from ancient conifers possibly related to the Cupressaceae family. These two compounds are members of a diterpenoid series corresponding to early diagenetic transformation products of resin diterpenoids. They were likely formed once plant resin comes into contact with reduced sulfur species originating from bacterial sulfate reduction occurring in anaerobic settings such as mangroves or marshes. They represent the first evidence of sulfurization processes affecting plant resin prior to diagenetic transformation into amber. Given their mode of formation, these compounds may be used as indicators of sulfate-reducing processes in past depositional environments.

Résumé. Fouillé en 2018 dans le cadre du contournement ouest de Strasbourg, le gisement de Berstett Langenberg (site n° 5.6 du projet) a livré sur près de deux hectares plusieurs occupations successives du Néolithique récent à La Tène finale. L’occupation de l’âge du Bronze se caractérise par 43 structures se répartissant quasiment sur toute l’emprise, tandis que les 31 faits du plein Bronze moyen correspondent à une dizaine de fosses, des silos (sept) et des fonds de silos probables (quatre), deux possibles bâtiments excavés, trois fentes et cinq chablis. Aucun plan de bâtiment n’a été repéré, mais des espaces vides entourés de fosses ou silos suggèrent l’emplacement de bâtiments, tout comme les restes de torchis (architecture de terre et de bois). La quantité importante de vestiges céramiques mise au jour (160 récipients), tout comme plusieurs datations radiocarbones ont permis de mieux caractériser la typochronologie des ensembles pour le Bronze D et la transition Bronze C-D. Certains fonds de silos ont livré des vases vraisemblablement déposés entiers. Une série d’analyses biogéochimiques sur les parois internes d’une dizaine de vases ont permis d’identifier des graisses animales, tout comme des restes d’huile végétale (Brassicacées) ou de résine (Pinacée) pour des usages divers. Au-delà de la quantité importante de mobilier céramique exhumée, qui en fait un site de référence pour la fin du Bronze moyen, les autres types de mobiliers exhumés (lithique, faune) permettent de mieux caractériser ce type de site d’habitat encore peu connu dans l’est de la France. Abstract. Excavated in 2018 as part of the western bypass of Strasbourg, the Berstett Langenberg site of nearly two hectares (site no. 5.6 of the project) has revealed occupations dating from the Late Neolithic to the Final La Tène period. The Bronze Age occupation is characterised by 43 features spread over almost the entire area, while the 31 Middle Bronze Age features include ten pits, storage pits (11), two possible excavated buildings, three slits and five windfalls. No buildings were found, but areas devoid of features surrounded by pits suggest the location of buildings, as do the remains of cob (earth and wood architecture). The large quantity of ceramic remains uncovered (160 vessels), as well as several radiocarbon dates have made it possible to better characterise the typochronology of the ensembles for the Bronze D and the transition from Bronze D to Bronze D. Biogeochemical analysis of the inner walls of ten vessels has revealed animal fats, as well as traces of vegetable oil (Brassicaceae) or resin (Pinaceae). In addition to the large quantity of pottery, which makes the site a reference point, other objects unearthed (lithics, fauna) provide supplementary information as to the late Middle Bronze Age settlement for which little is known in eastern France.

The presence of zinc complexes or of oxidative conditions induces dithiocarbamate transfer from methylene-bis(dithiocarbamates) to molybdenum dithiocarbamates via zinc dithiocarbamate species.

A newly-discovered ligand transfer from methylene-bis(dithiocarbamates) to molybdenum dithiocarbamates (MoDTC) leads to MoDTC regeneration and results in enhanced fuel economy upon engine functioning.

International audience; Lynchets correspond to talus slopes that are formed unintentionally at the top of hedgerows by the accumulation of colluvial deposits originating from eroded fields. They may represent highly extended parcellar surfaces, characterized by narrow plots, extending perpendicularly to the slope. The history of these plots and their dating are still largely unknown. Our results deal with a land patch of several hundreds of hectares located at Goldbach-Altenbach, in the Vosges (Haut- Rhin). It could be determined on two cross-sections cutting the lynchets transversally that the parcellar plot was formed ca. 900 AD, after which the place was briefly abandoned during the Thirty Years War. The dating at ca. 900 AD suggests that this parcellar area was installed under the authority of the Murbach Abbey. The whole sector was indeed donated to the Abbey ca. 800 AD. Les rideaux de culture sont des talus qui se forment involontairement à l’amont d’une haie, par accumulation de colluvions érodées dans les champs. Ils peuvent constituer des parcellaires de très grande extension spatiale, caractérisés par des parcelles étroites, allongées perpendiculairement à la pente. L’histoire de ces parcellaires et leur datation sont encore très mal connues. Les résultats présentés ici concernent un parcellaire de plusieurs centaines d’hectares localisé à Goldbach-Altenbach, dans les Vosges haut-rhinoises. Les résultats obtenus sur deux coupes transversales à des rideaux de culture montrent que le parcellaire a été mis en place vers 900 AD, puis que la zone a été brièvement abandonnée pendant la Guerre de Trente Ans. La datation vers 900 AD suggère que ce parcellaire a été mis en place sous l’autorité de l’abbaye de Murbach. L’ensemble de la zone a en effet été donné à cette abbaye vers 800 AD.

During engine tests, it has been observed that the combined use of molybdenum dithiocarbamates (MoDTC) and methylene

International audience; Underwater operations conducted along the southern French coast have unveiled two large, isolated anchors of iron. The largest ever found in the ancient Mediterranean, they reveal that Roman merchantmen moored in Aigues-Mortes Bay. A combination of analyses focusing on the ring, which belonged to one of the two anchors, offered the opportunity to collect data from isolated anchors and to document their production. Radiocarbon analysis, conducted for the first time on this type of object, determined that they were manufactured in the early imperial period. Another key discovery was a layer of fibers found in a concretion from the ring, which revealed rare remnants of ropes impregnated with pitch that could correspond to puddening. The replication of similar analyses on rings belonging to other anchors would provide a better understanding of this crucial component for ancient mooring.

Molybdenum dithiocarbamates (MoDTC) are widely used in automotive industries as lubricant additives to reduce friction and to enhance fuel economy. Sulfur-containing additives such as zinc dithiophosphates (ZnDTP) are proposed to play a key role in the improvement of friction reducing properties of MoDTC in formulated lubricants by facilitating the formation of MoS2 tribofilm at the rubbing contacts. This study focuses on the interactions between MoDTC and ZnDTP under conditions comparable with those prevailing in operating engines. The capacity of ZnDTP to sulfurize MoDTC in solution in a hydrocarbon base oil could be demonstrated. Sulfurized Mo complexes bearing one or two additional sulfur atoms (1S-MoDTC and 2S-MoDTC, respectively) which have replaced the genuine oxygen atom(s) from the MoDTC core were detected and quantified using a specifically developed HPLC-MS analytical method. A possible sulfurization mechanism relying on the higher affinity of phosphorus from ZnDTP for oxygen could be proposed. In parallel, the evolution and molecular transformation of the prepared 2S-MoDTC in hydrocarbon base oil under thermal and thermo-oxidative conditions were followed using HPLC-MS and compared with the evolution of their friction coefficients. 2S-MoDTC complexes were shown to exhibit a better retention of friction reducing capability under oxidative conditions than the "classical" MoDTC, although they did not seem to significantly reduce the friction coefficients of lubricants as compared to the "classical" MoDTC. Therefore, sulfurization of MoDTC by ZnDTP might contribute to delay the progressive consumption of MoDTC and the loss of their friction-reducing efficiency in lubricants under thermo-oxidative conditions.

Summary Four extraction procedures (i.e., Bligh and Dyer, direct acetylation, CH2Cl2/CH3OH extraction and methanolysis) were tested for the recovery of biohopanoids from bacterial cells of a model bacterium (K. xylinus) and yielded similar amounts of bacteriohopanetetrols whatever the procedure used, without significant loss in the aqueous phase in the case of the Bligh and Dyer extraction. In contrast, the recovery of composite bacteriohopanepolyols (cyclitol ether derivatives) was shown to depend on the procedure used, with harsher conditions (i.e., methanolysis and direct acetylation) leading to higher yields. In the case of the Bligh and Dyer extraction, a significant part of the composite biohopanoid pool is lost in the aqueous phase, suggesting that the latter procedure should be avoided if optimal extraction of composite hopanoids is required.

Summary The constitution of Baltic amber, the role of succinic acid and, more generally, of ester bonds in the constitution of macromolecular components of amber has been further investigated by chemical degradation of the solvent insoluble part of Baltic amber using butanolysis (BuOH/HCl). Succinic acid derivatives were the sole compounds released upon butanolysis whereas other compounds which could correspond to the alcohol counterparts of succinates could not be detected by GC-MS. This result indicate that these counterparts are all located on high molecular weight structural moieties. Succinic acid thus plays a key role as cross-linking agent between oligomeric structural moieties based on diterpenoids necessarily bound by at least one non-hydrolysable C-O or C-C bond.

The tribological performances of engine oils have been shown to be enhanced by the synergistic interactions between Mo dithiocarbamates (Mo(DTC)

The absence of unambiguous animal body fossils in rocks older than the late Ediacaran has rendered fossil lipids the most promising tracers of early organismic complexity. Yet much debate surrounds the various potential biological sources of putative metazoan steroids found in Precambrian rocks. Here we show that 26-methylated steranes-hydrocarbon structures currently attributed to the earliest animals-can form via geological alteration of common algal sterols, which carries important implications for palaeo-ecological interpretations and inhibits the use of such unconventional 'sponge' steranes for reconstructing early animal evolution.

A preliminary study of the design of an electrically small plasma-based resonator using a localized surface plasmon resonance (LSPR) above 1 GHz is presented. Such a resonator is intended to be used to develop an electrically small antenna with frequency agility. This resonator consists of a plasma discharge confined in a hemispherical glass shell 3 cm in diameter on a ground plane. From 1 to 1.5 GHz, the plasma electron density required to achieve the LSPR must be between 0. $5\times 10^{11}$ and $1.4\times 10^{11}\mathrm{c}\mathrm{m}^{-3}$. Plasma losses are taken into account in this study and provide information on the required gas pressure. Typically for neon gas, the working pressure must be around 50 mTorr. A practical implementation using a miniature inductively coupled plasma (mICP) source is finally discussed.

International audience; The biomarker distributions of mid-Neoproterozoic sediments (800–717 million yr, Ma) from various locations are characterized by the occurrence, besides cholestane isomers, of a novel series of C28 steranes, whereas classical C-24 alkylated steranes are absent. These unusual C28 steranes, termed cryostanes, seem to be restricted to pre-Snowball Earth sediments. We report their conclusive identification as 26-methyl cholestanes based on comparison of gas chromatographic (GC) behavior and mass spectrum of the last eluting cryostane isomer with those of a 26-methyl 5α(H),14α(H),17α(H),20R-cholestane standard obtained by way of synthesis. Sterols methylated at C-26 seem to be restricted to some demosponges and, based on molecular clock estimates, demosponges may have emerged in the time interval 800–700 Ma. A sponge origin of cryostanes is thereby conceivable, making cryostanes the oldest molecular markers for animals. However, other biological sources need to be explored, including the wide variety of eukaryotic protists.

The design of a quad-band (18, 28, 38, and 48 GHz) feed horn is presented. Corrugations are used for a good polarization purity at the higher frequencies. At the lower frequency, they act as a smooth wall and the horn profile is tuned to achieve a high aperture efficiency.

International audience; Deciphering the role of sulfur in biogeochemical cycles strongly relies on its stable isotope composition, which ultimately depends on the ability to quantitatively recover different sulfur species from geological samples. For decades most studies have been restricted to the 34S/32S composition of bulk samples, using simple methods based on the analysis of SO2 released by sample combustion combined to mass spectrometry. The wet chemistry procedures required to selectively extract specific sulfur species were generally avoided due to their tediousness and inefficiency for some complex matrices, especially when targeting organic sulfur. With the recent advent of multi-isotope studies (investigating the minor sulfur stable isotopes 33S and 36S) which rely either on the analysis of sulfur as SF6, or on the use of secondary ion or multi-collector inductively coupled plasma mass spectrometry, wet chemistry-based preparation procedures were brought back to the stage with a renewed interest in developing procedures better adapted to the investigation of specific sulfur species. Here we propose a new stepwise chemical procedure for the quantitative recovery and multi-isotope analysis of organic sulfur from both solvent soluble (total lipid extract) and insoluble (kerogen) fractions, based on a wet oxidation by sodium hypochlorite. This procedure also allows the multi-isotope analysis of inorganic sulfur species (elemental sulfur, sulfates and sulfides) in the same sample. Its application to different well-known petroleum source rocks and to an oil demonstrates its relevance for disentangling the interactions between the different sulfur pools and for shedding new light on the sulfur biogeochemical cycle.

International audience

A recent article (Said-Ahmad, W., Amrani, A., Aizenshtat, Z., 2013. The action of elemental sulfur plus water on 1-octene at low temperatures. Organic Geochemistry 59, 82–86) is commented on in this discussion. Radical mechanisms proposed by Said-Ahmad et al. (2013) for the formation of sulfurized and oxidized organic compounds in experiments involving elemental sulfur and 1-octene under aqueous conditions, aimed at investigating the interaction of organic matter and sulfur compounds under geological conditions, are not compatible with their experimental results and other studies. In addition, results from the experiments aimed at demonstrating the role of HO radicals in the formation of oxidized organic compounds were incorrectly interpreted by the authors. In this discussion, alternative mechanisms for the formation of the sulfurized and oxygenated products reported by Said-Ahmad et al. (2013) are proposed.

The skilled work of the Roman carpenter (lignarius or tignarius faber) was essential to the construction of domestic and public buildings, creation of machines and structures for military purposes, and overcoming natural features. Composed in the 1st century bce, Vitruvius’s ten-book illustrated commentary on Roman architecture and architectural techniques, De architectura, comprises the primary textual evidence for the architectural techniques employed by Roman carpenters and engineers. In his various books, Vitruvius discusses the characteristics of different types of wood (supplemented by descriptions in Pliny’s Natural History); machines used on work sites, such as hoists and hydraulic machines; and covering frameworks for houses and the larger spans of basilicas and other massive public structures. For the latter, Roman carpenters devised the triangulated truss, a complex construction corroborated by surviving visual evidence. Archaeological evidence fills many gaps in Vitruvius’s coverage of practical carpentry methods and provides the only extant evidence for woodcutting and finishing implements, such as felling axes and handsaws. Houses at Pompeii and Herculaneum preserve traces of key carpentry techniques: timber framing, stairways, and load-bearing ceiling frameworks. The carpenter’s expertise also extended to shipbuilding and construction of strategic wooden bridges, most notably those erected during military campaigns under Caesar and later Trajan.

The greatest mass extinction on Earth occurred 252 million years ago during the latest Permian. Complete biotic recovery, characterized by a return to pre-extinction diversity levels, took an extraordinarily long time (ca. 5 × 10 6 yr), probably because harsh conditions developed repeatedly during the Early Triassic. Here, we show the recurrence of euxinic conditions during the Early Triassic and the development of especially severe such conditions during the late Early Triassic, just prior to full biotic recovery from the mass extinction. Dibenzothiophenes and carotenoids accumulated in upper Lower Triassic sediments from South China, located on the western margin of the Paleotethys Ocean. Among these, chlorobactane, a biomarker for green-pigmented green sulfur bacteria, and okenane, a biomarker for purple sulfur photosynthetic bacteria, were identified in upper Early Triassic samples. Both compounds were detected in limestone (micrite) and we therefore infer that planktonic green and purple sulfur bacteria were the sources of these carotenoids, and that their presence indicates photic zone euxinia at the time of deposition. Concentrations of redox sensitive elements (M, V, and U), relative to that of Al, and the U/Th ratio, progressively increased during the late Early Triassic. The euxinic conditions represented by the carotenoids and the elements were likely caused by a combination of locally shallow restricted conditions and global environmental oscillations, such as those related to global warming, during the late Early Triassic. The presence of these biomarkers, together with the increase in the abundance of redox sensitive elements relative to Al and the U/Th, suggests that euxinic conditions could be one of the causes for the delayed recovery of marine communities in the Paleotethys Ocean after the latest Permian mass extinction event.

Euphorbia species are characterized by a net of laticifers producing large amounts of triterpenes. These hydrocarbon-like metabolites can be converted into fuel by the methods of the oil industry. Euphorbia lathyris is easily grown at an industrial scale. In an attempt to increase its triterpene production, the metabolic pathways leading to isoprenoid were investigated by incorporation of 13C labeled glucose and mevalonate and 2H labeled deoxyxylulose as well as by natural abundance isotope ratio GC-MS. Latex triterpenes are exclusively synthesized via the mevalonate (MVA) pathway: this may orient future search for improving the triterpene production in E. lathyris. Phytosterols and their precursors are mainly derived from MVA pathway with a slight contribution of the methylerythritol phosphate (MEP) pathway, whereas phytol is issued from MEP pathway with a minor contribution of the MVA pathway: this is in accordance with the metabolic cross-talk between cytosolic and plastidial compartments in plants. In addition, hopenol B behaved differently from the other latex triterpenes. Its 13C isotope abundance after incorporation of 13C labeled glucose and its natural abundance &delta, 2H signature clearly differed from those of the other latex triterpenes indicating another metabolic origin and suggesting that it may be synthesized by an endophytic fungus.

Terpenoid biomarkers with high chemotaxonomic value, which can be used for the identification of an angiosperm input to sedimentary organic matter are desirable for studies devoted to the reconstitution of past environmental change. There is also a need, in the framework of archaeometric investigations, for reliable biomarkers to allow wood species determination from archaeological remains. In this context, we report the analysis of the triterpene content of buried wood and bark from oak, alder and birch, and comparison with that of the corresponding fresh material. Identification of new biomarkers led us to elucidate the diagenetic transformations undergone by triterpenoids in buried wood. A large set of triterpenoid biomarkers characterized by the presence of an oxygenated functionality in ring A at C-2 only could be exclusively evidenced in buried oak wood. An overall diagenetic pathway leading from the predominant polyfunctionalized triterpenoids in fresh oak wood (oxygenated functionalities at C-2/C-3/C-19/C-23/C-24/C-28) via numerous C-2 and C-2,C-3 functionalized intermediates to C-2 oxygenated aromatic triterpenoids is proposed. The evolution of the triterpenoid assemblage with respect to the level of diagenetic alteration could be followed. In contrast, the predominant triterpenoids in fresh alder and birch are common C-3 functionalized compounds. Their degradation follows the classical degradation/aromatization pathways reported for C-3 oxygenated triterpenes, ring A degradation appearing to represent only a minor process. In addition, the formation of phenolic triterpenoids, which have only been reported from brown coal, was observed.

Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility +/- 3-4 degrees C when translated to temperature) but a large spread in BIT measurements (reproducibility +/- 0.41 on a scale of 0-1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0 degrees C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the true (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar-based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar-based, BIT values.

International audience; Nitrogen-vacancy (NV) color centers in nanodiamonds are highly promising for bioimaging and sensing. However, resolving individual NV centers within nanodiamond particles and the controlled addressing and readout of their spin state has remained a major challenge. Spatially stochastic super-resolution techniques cannot provide this capability in principle, whereas coordinate-controlled super-resolution imaging methods, like stimulated emission depletion (STED) microscopy, have been predicted to fail in nanodiamonds. Here we show that, contrary to these predictions, STED can resolve single NV centers in 40–250 nm sized nanodiamonds with a resolution of ≈10 nm. Even multiple adjacent NVs located in single nanodiamonds can be imaged individually down to relative distances of ≈15 nm. Far-field optical super-resolution of NVs inside nanodiamonds is highly relevant for bioimaging applications of these fluorescent nanolabels. The targeted addressing and readout of individual NV– spins inside nanodiamonds by STED should also be of high significance for quantum sensing and information applications.

Maleimides (transformation products of chlorophylls and bacteriochlorophylls) were studied in recent sediments from the Swiss lake Rotsee and the Romanian Black Sea Shelf to investigate chlorophyll degradation, the role of oxygen in maleimide formation, and to identify their sources. Naturally occurring maleimides (i.e. “free” maleimides) and maleimides obtained after chromic acid oxidation of sediment extracts (i.e. “bound” maleimides) were analysed. 2-Methyl-maleimide (Me,H maleimide), 2,3-dimethyl-maleimide (Me,Me maleimide), 2-methyl-3-vinyl-maleimide (Me,vinyl maleimide), 2-methyl-3-ethyl-maleimide (Me,Et maleimide) and traces of 2-methyl-3- iso -butyl-maleimide (Me, i -Bu maleimide) occurred naturally in the sediment with a large predominance of the Me,Et homologue. Tetrapyrrolic pigments related to chlorophylls were the main source of maleimides, although variable contributions of other sources such as cytochromes and/or phycobilins cannot be completely ruled out. The predominant Me,Et maleimide and Me,vinyl maleimide most likely originate mainly from chlorophyll a related pigments. The same holds for Me,H maleimide, which might be formed following degradation of ring E from the tetrapyrrolic nucleus. Alternatively, Me,H maleimide and Me,Me maleimides might be formed by a recently discovered transformation pathway involving the oxidation of vinylic chlorophyll substituents and the formation of an aldehyde intermediate. 2-Methyl-3- n -propyl-maleimide (Me, n -Pr maleimide) and Me, i -Bu maleimide arising from bacteriochlorophyll related pigments traced the presence of phototrophic sulfur bacteria (Chlorobi), indicating photic zone euxinic and anoxic conditions in Rotsee during the last 150 years and throughout the Black Sea history, including the limnic phase of the Black Sea (Unit 3). Some other minor maleimides with specific alkylation pattern also originate from bacteriochlorophylls, while the source of others could not be identified. Free maleimides were mainly formed in the sediment in the absence of oxygen. Novel maleimide degradation indices are proposed to estimate the degree of OM degradation (OM freshness/degradability). These proxies are applicable on longer timescales than e.g. the chlorin index.

The article entitled “Ozonation of triterpenoids: Implications for early diagenesis of biomarkers in oxic environments” (Tay, K.S., Rahman, N.A., Abas, M.R.B, Simoneit, B.R.T., 2013. Organic Geochemistry 57, 34–40) deals with an investigation of the early diagenetic transformations undergone by higher plant triterpenoids under oxic conditions by means of laboratory experiments involving various triterpenes in the presence of ozone. Several aspects of the publication by Tay et al. (2013) are questionable, and are discussed in detail here. These comprise (i) the analytical procedure (based mainly on gas chromatography–mass spectrometry, GC–MS) used for the investigation of reaction mixtures likely to contain thermally labile (poly)oxygenated triterpenoids, (ii) the proposed mechanisms involving the hydroxyl radical as the key oxidizing species, (iii) the interpretation of mass spectra of the products and the structural assignments therefrom, and (iv) the geochemical relevance of the experiments with respect to non-biological oxidative alteration undergone by higher plant triterpenes in sediments.

Samples of young, outer surfaces of brucite-carbonate deposits from the ultramafic-hosted Lost City hydrothermal field were analyzed for DNA and lipid biomarker distributions and for carbon and hydrogen stable isotope compositions of the lipids. Methane-cycling archaeal communities, notably the Lost City Methanosarcinales (LCMS) phylotype, are specifically addressed. Lost City is unlike all other hydrothermal systems known to date and is characterized by metal- and CO2 -poor, high pH fluids with high H2 and CH4 contents resulting from serpentinization processes at depth. The archaeal fraction of the microbial community varies widely within the Lost City chimneys, from 1-81% and covaries with concentrations of hydrogen within the fluids. Archaeal lipids include isoprenoid glycerol di- and tetraethers and C25 and C30 isoprenoid hydrocarbons (pentamethylicosane derivatives - PMIs - and squalenoids). In particular, unsaturated PMIs and squalenoids, attributed to the LCMS archaea, were identified for the first time in the carbonate deposits at Lost City and probably record processes exclusively occurring at the surface of the chimneys. The carbon isotope compositions of PMIs and squalenoids are remarkably heterogeneous across samples and show highly (13) C-enriched signatures reaching δ(13) C values of up to +24.6‰. Unlike other environments in which similar structural and isotopic lipid heterogeneity has been observed and attributed to diversity in the archaeal assemblage, the lipids here appear to be synthesized solely by the LCMS. Some of the variations in lipid isotope signatures may, in part, be due to unusual isotopic fractionation during biosynthesis under extreme conditions. However, we argue that the diversity in archaeal abundances, lipid structure and carbon isotope composition rather reflects the ability of the LCMS archaeal biofilms to adapt to chemical gradients in the hydrothermal chimneys and possibly to perform either methanotrophy or methanogenesis using dissolved inorganic carbon, methane or formate as a function of the prevailing environmental conditions.

An improved calculation technique allowing the radar cross section computation of electrically large targets is presented in this paper. It is based on a hybridization technique combining the Geometrical Optics (GO) and the Physical Optics (PO) techniques. The GO technique takes high order interactions into account while the PO technique allows to get rid of caustics problems. The Physical Theory of Diffraction (PTD) is also implemented, in order to improve the accuracy and take into account the wedges diffraction of the target. This hybrid technique is well suited to compute the backscattered field from wind turbines illuminated by meteorological radars.

We report here a novel reductive coupling reaction of conjugated, non- or poorly enolizable aldehydes induced by H(2) S and operative in aqueous solutions under prebiotically relevant conditions. This reaction leads from retinal to β-carotene, and from benzylic aldehydes to the corresponding diarylethylenes. This novel reaction also opens a new potentially prebiotic pathway leading from glyoxylic acid to various compounds that are involved in the reductive tricarboxylic acid cycle. This C--C bond forming reaction of prebiotic interest might have been operative, notably, in the sulfide-rich environments of hydrothermal vents, which have been postulated as possible sites for the first steps of organic chemical evolution.

This article deals with the impact of ionospheric electron density inhomogeneities on the functionality of global navigation satellite systems emphasizing positioning errors. The scintillation characteristics of transmitted signals have been obtained using data gathered in measurement campaigns. The effects on a standard receiver are then presented. Positioning errors due to scintillations were shown to be greater than 10 meters in the worst case.

Laboratory experiments carried out under plausible prebiotic conditions (under conditions that might have occurred at primitive deep-sea hydrothermal vents) in water and involving constituents that occur in the vicinity of submarine hydrothermal vents (e.g., CO, H(2)S, NiS) have disclosed an iterative Ni-catalyzed pathway of C-C bond formation. This pathway leads from CO to various organic molecules that comprise, notably, thiols, alkylmono- and disulfides, carboxylic acids, and related thioesters containing up to four carbon atoms. Furthermore, similar experiments with organic compounds containing various functionalities, such as thiols, carboxylic acids, thioesters, and alcohols, gave clues to the mechanisms of this novel synthetic process in which reduced metal species, in particular Ni(0), appear to be the key catalysts. Moreover, the formation of aldehydes (and ketones) as labile intermediates via a hydroformylation-related process proved to be at the core of the chain elongation process. Since this process can potentially lead to organic compounds with any chain length, it could have played a significant role in the prebiotic formation of lipidic amphiphilic molecules such as fatty acids, potential precursors of membrane constituents.

The total lipid extracts (TLEs) from a series of 13 soil surface samples from sites covered by a stable vegetation for at least 150 years and located in the Vosges Massif (France) have been investigated in order to establish a molecular reference for soil surface horizons. The TLEs are dominated by plant n-alkyl lipids with distributions (homologue predominance) clearly discriminant with regard to the vegetation cover. Higher plant terpenoids, present in varying relative abundances, allow distinction between soils from grassland and oak, fir and beech forests to be made. Furthermore, the occurrence of some specific terpenoids seems to be restricted to a particular vegetation cover, so they may therefore be used as diagnostic markers for tracing back past vegetation in ancient soils.

The hypothesis of a low temperature natural “vulcanization” process as a potential mechanism for the formation of insoluble bitumen and H2S in reservoirs which have not undergone biodegradation, high thermal stress, or thermochemical sulfate reduction (TSR) has been investigated using laboratory simulation experiments. The experiments, involving elemental sulfur (32S and 34S), a low maturity oil and water at 200 °C in sealed gold tubes, clearly showed that elemental sulfur is able to induce the formation of H2S, polar compounds (resins and asphaltenes) and insoluble bitumen most likely by way of sulfur cross-linking processes. Specific organic sulfur compounds (thiophenes, dithiophenes and thienothiophenes) formed by the reaction of sulfur and hydrocarbons may be potential markers of such a process, but remain to be detected in natural samples.

In order to confirm the tentative structure of a dithiane sulfide with a bicyclic squalene hydrocarbon skeleton representing the predominant alkyl sulfide in Shell Beach samples from the Monterey Formation (Miocene, CA) and also occurring in various immature sulphur-rich sediments [Schouten, S., Sinninghe Damste, J.S., de Leeuw, J.W., 1995. A novel triterpenoid carbon skeleton in immature sulphur-rich sediments. Geochimica et Cosmochimica Acta 59, 953–958], synthesis of a reference compound bearing two thiochromane moieties has been carried out. The product was obtained as a diastereomeric mixture appearing in the form of five peaks (partly) resolved in gas chromatography (GC). This is in sharp contrast with the geochemical compound, which appears as a single broad peak in GC. Co-elution experiments showed that none of the peaks from the synthetic mixture coelute in GC with that of the geochemical sulfide. Furthermore, the different synthetic isomers have identical mass spectra, which are clearly distinct from that of the naturally-occurring compound. The results unambiguously indicate that the natural compound is not the dithiane triterpenoid originally envisaged. Instead, we propose that the compound has a structure of a bicyclic squalene derivative bearing two “S-spiro”-type moieties as is the case for other sulfides related to regular polycyclic polyprenoids and hopanoids in Monterey sediments.

A sulfide with a bicyclic squalene hydrocarbon skeleton present in sediments from various depositional settings and of different geological age has been identified by synthesis of a reference compound. In contrast to previous expectations [cf. Schouten, S., Sinninghe Damste, J.S., de Leeuw, J.W., 1995. A novel triterpenoid carbon skeleton in immature sulphur-rich sediments. Geochimica et Cosmochimica Acta 59, 953–958; Gug, S., Schaeffer, P., Adam, P., Klein, S., Motsch, E., Albrecht, P., 2009. Identification of a sulfide derivative with a bicyclic hydrocarbon skeleton related to squalene. Part I: Synthesis of a dithiane triterpenoid. Organic Geochemistry 40, 876–884.], this sulfide bears two “S-spiro type“ thiolane moities, but not the two thiochromane moieties originally envisaged. The synthesis resulted in the formation of a complex isomeric mixture of compounds, all co-eluting in gas chromatography (GC) in the form of one broad peak, as is the case with the geochemical compound. The spiro-type sulfide was formed by intramolecular sulfurization of a polyunsaturated bicyclic squalene derivative of unknown biological origin. The presence of this sulfide in a number of Triassic to Miocene marine sediments from various and contrasting depositional settings (upwelling environments, shallow continental platforms, lagoonal sub-basins, hypersaline environments), all characterized by strongly anoxic conditions, but with or without photic zone anoxia, indicates that the microorganisms biosynthesizing the precursor bicyclic squalene occupy diverse ecological niches.

The sulfur isotopic composition (δ34S) of petroleum is believed to be affected mainly by sulfur incorporation reactions into the sedimentary organic matter during the early diagenesis. However, secondary processes could affect the original δ34S of oil under the effect of thermal maturity or of the microbial activity of biodegraded reservoirs. In this study, the different processes that may affect the δ34S of in-reservoir oils were assessed based on the sulfur content and isotopes of a series of oil and core samples coming from various reservoirs of the Lower Cretaceous Mannville Group, Western Canada Sedimentary Basin (WCSB). Based on the molecular study, these samples appear to have reached various levels of maturity and biodegradation, ranging from 0 to 6.5 on the biodegradation scale of Peters and Moldowan. In addition, mixing of organic matter coming from different source rocks was identified based on the comparison with extensive correlation studies performed in the WCSB. Investigation of the δ34S shows a trend that seems a priori correlated to the level of biodegradation. However, a careful interpretation of molecular and sulfur isotope data leads to the conclusion that the observed δ34S variations have rather to be ascribed to contributions of oils generated by various source rocks. Alternatively, variations of δ34S could neither be related to maturity differences nor to kinetic effects during organic sulfur compounds biodegradation. In the case of some specific core samples showing a common origin based on biomarker study, δ34S variations might not be related to different sources but to secondary sulfur incorporation/exchange processes occurring within the reservoir. These processes would involve reduced sulfur species from bacterial sulfate reduction formed in situ or migrated into Mannville reservoirs. This hypothesis is supported by laboratory experiments showing sulfur exchange/incorporation under plausible conditions for shallow reservoirs.

32,35-Anhydrobacteriohopanetetrol (anhydroBHT) is a functionalized hopanoid of unknown origin found recently in a wide range of sediments. Acidic treatment of cells of the bacterium Zymomonas mobilis and of bacteriohopanetetrol (BHT) led to the formation of anhydroBHTs in the form of an epimeric mixture. These laboratory experiments indicate that sedimentary anhydrobacteriohopanepolyols likely correspond to diagenetic transformation products of bacteriohopanepolyols formed by intramolecular acid catalyzed cyclization of the hopanoid side chain, rather than being biogenic products.

The applicability of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the quantification of 13C enrichment of proteinogenic amino acids in metabolic tracer experiments was evaluated. Measurement of the 13C enrichment of proteinogenic amino acids from cell hydrolyzates of Corynebacterium glutamicum growing on different mixtures containing between 0.5 and 10% [1-13C]glucose shows the significance of kinetic isotope effects in metabolic flux studies at low degree of labeling. We developed a method to calculate the 13C enrichment. The approach to correct for these effects in metabolic flux studies using delta13C measurement by GC-C-IRMS uses two parallel experiments applying substrate with natural abundance and 13C-enriched tracer substrate, respectively. The fractional enrichment obtained in natural substrate is subtracted from that of the enriched one. Tracer studies with C. glutamicum resulted in a statistically identical relative fractional enrichment of 13C in proteinogenic amino acids over the whole range of applied concentrations of [1-13C]glucose. The current findings indicate a great potential of GC-C-IRMS for labeling quantification in 13C metabolic flux analysis with low labeling degree of tracer substrate directly in larger scale bioreactors.

Thermochemical sulfate reduction (TSR) is usually associated with significant sour gas (H 2 S) generation and calcite precipitation in deep and hot carbonate reservoirs as a result of reaction between sulfate minerals (primarily anhydrite) and petroleum fluids at elevated temperature (beginning at ∼110-140°C). Thermal enhanced oil recovery (TEOR) techniques are widely applied during production to increase heavy oil recovery in mature fields by lowering oil viscosity. The reservoir rock may reach high temperature (150 °C < T< 300 °C) during steam and hot water flooding for secondary oil recovery that induces TSR. Experimental (pyrolysis in gold tubes) and numerical (0D fluid-rock interaction numerical model: ArXim) simulations were undertaken with a simple petroleum system assimilated to n-alkane model compounds in the presence of sulfate to assess the feasibility of "induced TSR" and to tentatively estimate the sulfur risk in terms of H 2 S and organosulfur compound (OSC) formation during steam and hot water stimulated enhanced recovery operations. The oxidation of organic matter (by reaction with both S° and sulfate) can be easily reproduced under laboratory conditions, as confirmed by the presence of organic sulfur in the soluble and insoluble residue. For the experiments performed in the presence of sulfate, higher amounts of H 2 S, polar compounds and organic residue are produced, and aromatic fractions are enriched in condensed aromatics (sulfur-containing and non-sulfur-containing). Although sulfate reduction from 3% to 5% is deduced from a sulfur balance calculation, no secondary carbonate is detected using X-ray diffraction (XRD). Numerical simulations suggest no limiting thermodynamic factor for the precipitation of carbonate under our experimental conditions and indicate the replacement of sulfate by carbonate. According to numerical data, the lack of carbonate can be explained by its slow growth and/or high energy barrier of nucleation and/or insufficient residence time in laboratory experiments.

International audience; We describe a new method for detecting and localizing multiple objects in an image using context aware deep neural networks. Common architectures either proceed locally per pixel-wise sliding-windows, or globally by predicting object localizations for a full image. We improve on this by training a semi-local model to detect and localize objects inside a large image region, which covers an object or a part of it. Context knowledge is integrated, combining multiple predictions for different regions through a spatial context layer modeled as an LSTM network.The proposed method is applied to a complex problem in historical document image analysis, where we show that is capable of robustly detecting text lines in the images from the ANDAR-TL competition. Experiments indicate that the model can cope with difficult situations and reach the state of the art in Vision such as other deep models.

We describe the structural elucidation of four novel series of hopanoid sulfides bearing a thiane or a thiolane ring fused to the pentacyclic hopanoid skeleton and the partial identification of an additional spiro-type hopanoid sulfide series which occurs in various immature sulfur-rich sediments and crude oils. These novel diagenetic hopanoid derivatives have been identified either by isolation of one member of the series, followed either by nuclear magnetic resonance (NMR) structural characterization, by synthesis of a reference compound or by deuterium labelling experiments. Location of the C–S bonds between the C-30 or C-31 positions from the side chain and the C-16, C-17, C-20 or C-21 positions in rings D or E of the polycyclic hopanoid skeleton likely indicates that intramolecular sulfurization occurred on precursor molecules functionalized at C-17 and C-21, such as hop-17(21)-ene derivatives, but also, for some of them, at C-16 or C-20. The predominance of one series over the others is variable within the different samples. Their occurrence in a wide variety of sediments and crude oils of different maturity and ranging in age from Triassic to Upper Miocene suggests that the precursor molecules which underwent sulfurization are relatively widespread and that the sulfurization processes involved in their formation are operative during early diagenesis.

A novel series of sedimentary aromatic lycopane derivatives, cyclolycopatrienes, has been found in an outcrop sample from the Messel oil shale. The predominant monoaromatic compound 4 from this hydrocarbon series has been isolated using reversed phase HPLC and its structure determined using 1D and 2D 1H NMR spectroscopy, as well as from identification of the RuO4 degradation products. From examination of its structure, related to that of lycopane, and from its stable carbon isotopic composition, this compound and related isomers can be considered as new proxies for Botryococcus braunii race L in sediments deposited under freshwater and/or brackish conditions.

In this paper, a review is presented on computational methods for the prediction of Radar Cross-Sections (RCS) and antenna–platform interactions. In a first part the techniques for RCS computations are considered. A list of frequency and time domain solvers for the Maxwell's equations are given with their performances in memory requirements and run-time. Boundary Elements Methods, Finite Difference Time Domain Methods, Finite Elements—Finite Volume Methods, Hybridization and Factorization Techniques, are reviewed. The exceptional performances of the Fast Multipole Method compared to those of the classical Moment Method are especially highlighted. We have also made mention of some recent research work on numerical techniques conducted in France. Asymptotic methods are mainly discussed in the second part of this article devoted to antenna–platform interactions. After a brief description of the historical evolution of Geometrical Theory of Diffraction tools for antenna analysis and design, the advantages and drawbacks of different techniques for generating the geometry and searching the rays are discussed. Then a list of unsolved problems and lines of future research on asymptotic techniques are presented together with an example of a computer code founded on the Uniform Theory of Diffraction. In the conclusion some new research topics such as higher order finite elements defined on surfaces represented by B-Splines and macro-basis functions containing information on the phase or derived from analytical or asymptotic solutions are briefly introduced. To cite this article: F. Molinet et al., C. R. Physique 6 (2005).

The effects of weathering on the organic matter within a narrow sediment interval from surficial to 10 m depth belonging to the Lower Toarcian shales of the Paris basin, were studied at a molecular level. Among the compositional changes observed, the most striking feature is a severe breakdown of the metalloporphyrins (Ni and VO) at the surface, as evidenced by quantitative data. In addition, this degradation of the geoporphyrins is accompanied by substantial modification of their composition with preferential degradation of porphyrins with exocyclic rings over polyalkylporphyrins. These quantitative and qualitative changes are thought to result from exposure of the sediment to weathering conditions. More specifically, abiotic oxidation is likely to be the main weathering process responsible for this superficial alteration of the sedimentary porphyrins. This is particularly suggested by oxidation experiments carried out on a mixture of sedimentary nickel and vanadyl porphyrins where oxidation of the former complexes occurs at a faster rate. Thus, geoporphyrins may be used as molecular indicators to evaluate the degree of oxidation of weathered geological samples containing this kind of molecule.

The desulfurization of fuels (for example,diese loil) is a major concern of the petroleum industry worldwide because of the consequences for human health and the environment of high levels of sulfur dioxide emissions. In this context, a major problem encountered in refineries is the elimination of organosulfur components resistant to hydrodesulfurization processes. Although it has been shown that a substantial fraction of the organic sulfur compounds remaining after hydrodesulfurization is composed of mono-andpolyalkylated dibenzothiophenes (mainly 4,6-dialkyldibenzothiophenes),[1] the lack of knowledge concerning the structures of residual highly resistant organic sulfur compounds still appears to be the greatest handicap in progressing towards higher degrees of hydrodesulfurization.We report here the identification of a series of novel, terpenoid-derived, non-dibenzothiophenic polycyclic sulfides from highly desulfurized diesel oils. These 1,1,4a,6-tetramethyl-9-alkyl-1,2,3,4,4a,9b-hexahydrodibenzothiophenes1(9-alkylHDBT) were isolated from the aromatic fraction after oxidation to the corresponding sulfones 2 (9alkyl-HDBTO2).[2–4] The 9-ethyl homologue was unambiguously identified by mass spectrometry and NMR studies.

The reduction of allylic thiols to alkenes by hydrogen sulfide in aqueous solutions, a novel reaction that may explain reduction processes widely occurring in natural environments, has been discovered. Its mechanism has been studied and suggested to follow an S(RN)1-like pathway involving radical intermediates undergoing 1,4 hydrogen shifts. [reaction: see text]

C30 tetracyclic polyprenoids (TPP) are most prominently observed in samples derived from low salinity, i.e. fresh to brackish lacustrine environments, and are generally present in low levels in samples derived from saline, i.e., marine and saline lacustrine, environments. A near-shore facies of the Chonta Formation, Peru, that has no marine palynomorphs but abundant Chlorococcalean (Green) algal nonmarine palynomorphs, has high levels of TPP, suggesting Green algae (or Chlorophyta) are a possible source for the TPP compounds. The ratio between a C30 TPP compound and 27-norcholestanes is useful for assessing this nonmarine algal input. Moderate elevations of TPP, above what is common in marine derived samples, were found in ostensibly marine source rocks and oils from certain basins of western and northern South America (Middle Magdalena, Colombia; Maracaibo, Venezuela; and Trinidad basins). This is likely due to transport from the nonmarine to the marine environment because of an influx of fresh water into the near-shore marine environment. Alternatively, oils from these basins may have inputs from near-shore shallow marine algae with chemistry similar to that found in lacustrine settings. The TPP ratio, in conjunction with other environmental indicators such as 4-methyl steranes or hopane/sterane ratio, is useful for differentiating marine and nonmarine influences in pre-salt oils and source rocks of West Africa. The TPP ratio, used with other environmental indicators (gammacerane, C29 steranes, C30 steranes) and age diagnostic biomarkers (dinosteranes, 4-methylsteranes), can be useful in differentiating among nonmarine source facies. For example, in the Turpan-Hami basin, China, Permian saline lacustrine and Jurassic lacustrine deltaic facies can be discriminated.

Although perfectly transparent specimens are imaged faster with light-sheet microscopy, less transparent samples are often imaged with two-photon microscopy leveraging its robustness to scattering; however, at the price of increased acquisition times. Clearing methods that are capable of rendering strongly scattering samples such as brain tissue perfectly transparent specimens are often complex, costly, and time intensive, even though for many applications a slightly lower level of tissue transparency is sufficient and easily achieved with simpler and faster methods. Here, we present a microscope type that has been geared toward the imaging of semicleared tissue by combining multispot two-photon excitation with rolling shutter wide-field detection to image deep and fast inside semicleared mouse brain. We present a theoretical and experimental evaluation of the point spread function and contrast as a function of shutter size. Finally, we demonstrate microscope performance in fixed brain slices by imaging dendritic spines up to 400-μm deep.