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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.

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.

We investigate the optical properties of silicon-vacancy (SiV) and germanium-vacancy (GeV) color centers in nanodiamonds under hydrostatic pressure up to 180 GPa. The nanodiamonds were synthetized by Si or Ge-doped plasma assisted chemical vapor deposition and, for our experiment, pressurized in a diamond anvil cell. Under hydrostatic pressure we observe blue-shifts of the SiV and GeV zero-phonon lines by 17 THz (70 meV) and 78 THz (320 meV), respectively. These measured pressure induced shifts are in good agreement with ab initio calculations that take into account the lattice compression based on the equation of state of diamond and that are extended to the case of the tin-vacancy (SnV) center. This work provides guidance on the use of group-IV-vacancy centers as quantum sensors under extreme pressures that will exploit their specific optical and spin properties induced by their intrinsic inversion-symmetric structure., 7 pages, 4 figures

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.

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.

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.

https://hal.archives-ouvertes.fr/hal-03252301; International audience; Summary In the past, highly productive (hyper)saline and alkaline environments have proved propitious for large accumulation of sedimentary OM that led to the formation of Type I kerogens, such as those of the Green River Formation. A sediment core that covers most of the history of Lake Dziani Dzaha, a hypereutrophic saline, alkaline and mostly anoxic crater lakewhich waspostulatedto be a modern analogue of such environments, has been investigated using several analytical approaches comprising bulk (Rock-Eval and C, N, S elemental analyses), isotopic (δ13,14C, δ15N, δ18O, δ33,34,36S), and sedimentological descriptions. This study revealed that, despite strong environmental changes undergone by the lake since its formation, the conditions prevailing in the lake supported by a continuous high primary production have led to an excellent preservation of OM and to early diagenetic reductive and sulfurization processes which have yielded an exceptionally reduced character of the OM with respect to its short diagenetic history (< 6 ky). The similarities observed between the sediments of Lake Dziani Dzaha and some source rocks associated to Type I kerogens suggest that early diagenetic processes can have a strong and rapid impact on the accumulation of OM in some (semi)closed and highly productive aquatic ecosystems.

https://hal.archives-ouvertes.fr/hal-03252301; International audience

International audience; A harmonic oscillator model is proposed to study the intensification of microwave radiation of an electrically small antenna when surrounded by a subwavelength plasma discharge. This model describes the oscillations of free electrons in a spherical plasma when it is excited by an incident electromagnetic wave. It shows that at resonance, these charge oscillations lead to a significant volume current, and thus to an enhancement of the radiation. Depending on the electron density of the plasma, this radiation enhancement may occur in the microwave range. The proposed model is compared with the Mie scattering theory with perfect agreement when the electrical size ka of the spherical plasma remains smaller than 0.1. Despite its apparent simplicity, this model unveils the main mechanism that stands behind the intensification of microwave radiation by a subwavelength plasma discharge.

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.

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. Via congruent observations in geological samples and pyrolysis experiments, the authors demonstrate that 26-alkylsteranes posited as sponge biomarkers can form during diagenesis of common algal sterols.

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.

International audience; The tribological performances of engine oils have been shown to be enhanced by the synergistic interactions between Mo dithiocarbamates (Mo(DTC)2) with other additives, and notably Zn dithiophosphates (Zn(DTP)2). Being two key components in formulated lubricants, a detailed understanding of the mechanisms involved between these two types of additives is needed to develop engine oils with enhanced friction reduction performances, and improved fuel economy. In this context, we report here the investigation at the molecular level of the interactions between Mo and Zn complexes with DTC and DTP ligands using laboratory experiments. Our analytical approach comprised NMR spectroscopy (1H, 13C, 31P) allowing direct investigation of both homoleptic and heteroleptic Mo and Zn complexes as well as a specifically-developed HPLC-MS method for the investigation of the different DTC species formed during lubricant ageing experiments. The results showed that ligand exchange reactions between Mo(DTP)2 and Zn(DTC)2 complexes strongly favor the migration of the DTC ligands from Zn to Mo, illustrating the higher affinity of Mo for DTC ligands. In the case of binary mixtures involving Mo(DTC)2 and Zn(DTP)2 – a combination of additives frequently used in formulated lubricants – the formation of mixed complexes (Mo(DTC)(DTP)) resulting from ligand exchange reactions could be directly evidenced for the first time by the analytical methods used. These species could account, at least to some extent, for the synergistic effect of Mo(DTC)2 and Zn(DTP)2 on the friction reducing properties of engine oils. However, they were formed in significantly lower proportions than those previously reported in the literature using indirect methods

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.

Birch bark tar, an organic material frequently encountered during archaeological excavations, has been identified from its lipid composition on the cracks of a ceramic dated to the late Neolithic. Lipids of this black substance were dominated by a characteristic triterpenoid assemblage of lupane-related triterpenoids from birch bark, together with their thermal degradation products formed during preparation of the tar. Among the latter, four main series of unusual triterpenoid esters have been detected and were postulated to correspond to esters of Δ 2-betulin and Δ2-dihydrobetulin based on their mass spectra and hydrolysis experiments. Their conclusive identification has been achieved by synthesis of reference compounds. These compounds most likely originate from the esterification between triterpenoid alcohols related to betulin and fatty acids from suberin formed upon heating of birch bark tar. They could be considered as markers of intense heating during birch bark tar preparation using the “single pot” procedure.

The widely distributed aromatic di- and triterpenoids from higher plants occurring in sediments are formed by diagenetic microbial processes affecting their precursor plant lipids. These compounds and their stable isotopic composition (δ13C and δ2H) have the potential to be used for palaeoenvironmental and palaeoclimatic studies. In the present study, the isotopic composition of di- and triterpenoids aromatized to different extents has been measured to specifically examine the isotopic effects associated with the aromatization reaction. To overcome the possibility of multiple higher plant sources, as is generally the case with sedimentary lipids, the δ13C and δ2H values of aromatized di- and triterpenoids from lipid extracts recovered from conifer and angiosperm buried wood have been determined, allowing an unambiguous substrate/product relationship along the aromatization pathway to be assured. The results show that the δ13C compositions of both di- and triterpenes do not seem to be significantly affected by progressive aromatization, whereas the situation is different for δ2H values. In the case of diterpenoids related to abietic acid, a significant increase of the δ2H values by up to 86‰ with ongoing aromatization was measured. This is in contrast to what is expected for dehydrogenated compounds which should be globally more 2H-depleted than their precursor molecules (e.g., biosynthesized unsaturated fatty acids vs. their saturated precursors). This 2H enrichment of aromatized diterpenoids could indicate that they represent only minor residual intermediates, the majority having been further degraded by processes favoring the degradation of the 1H-containing substrates and having a moderately pronounced 12C/13C selectivity. With triterpenoids, preservation of the δ2H values was observed whatever the nature and extent of the aromatization process considered, which may be related to enzymatic reactions showing a limited influence on the hydrogen stable isotopic composition of the aromatized compounds.

International audience; Plant exudates have been extensively used in the past for different applications related to their olfactory, physical or medical properties. Their identification in archaeological samples relies, notably, on the characterisation of chemotaxonomic molecular markers but is often hampered by the severe alteration of their typical genuine molecular signature due to ageing. Among these exudates, those recovered from Styrax, Liquidambar and Myroxylon tree species – defined as balsams – have been exploited in the past for their pleasant scent and medical properties. They are characterised by a large variety of aromatic compounds, especially of the cinnamate and benzoate series, which can be used to assess their botanical source. These compound series may, however, be subject to alteration over time during exposure to environmental conditions in the case of archaeological material. As a result, their reliability as chemotaxonomic markers to characterise and discriminate archaeological balsams is problematic and questionable. We have, therefore, carried out a comparative analysis of various extant balsams (Styrax officinalis, S. paralleloneurum, S. tonkinensis, Liquidambar styraciflua, L. orientalis and Myroxylon balsamum var. pereirae) using gas chromatography–mass spectrometry to search for more solid lipid markers. The results revealed that a distinction between styrax, liquidambars, Peru and Tolu balsams is possible based on the distribution of pentacyclic triterpenes. The predominance of uncommon 6‑oxygenated derivatives of oleanolic acid among triterpenoids could be specifically related to styrax resins. Liquidambar gums were characterised by the predominance of oleanonic acid together with uncommon 3-epi oleanolic and ursolic acids, whereas Peru balsam was rich in cinnamic and benzoic acids, but devoid of triterpenoids. Thanks to the high specificity of some of these triterpenes, already known for their low volatility and robustness towards alteration processes, they should be considered as reliable molecular tools for the unambiguous identification of archaeological balsams. In addition to archaeological applications, these triterpenic markers might also find an application for the detection of counterfeit balsams.

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

Sulfur is a key element of biogeochemical cycles, being both an essential component of living cells and involved in major geological processes. Its four stable isotopes (32S, 34S, 33S, 36S, in order of abundance) are subject to equilibrium and kinetic fractionations, which can be used as tracers to understand sulfur cycling processes. Multi-isotope studies noticeably revealed mass-independent fractionation processes of 33S and 36S, enlightening previously unknown specific organic or inorganic (bio)(geo)chemical mechanisms. Though the analytical procedures for the determination of S-multi-isotope compositions, which requires a quantitative extraction and purification of sulfur, are well-known for mineral sulfur species, the existing procedures for the extraction of organic sulfur are either restricted to specific species or technically restrictive. Here we propose a new chemical procedure for the quantitative recovery of organic sulfur in the form of Ag2S, for multi-isotope analysis, which is also compatible with the multi-isotope analysis of inorganic sulfur species from the same samples. This procedure is based on a standard sequence of reductive attacks specific of mineral sulfur species and was validated on various samples including fresh sediments, source rocks and oils.

International audience; Organic residue analysis has been undertaken on an organic material found on a necklace with a pendant unearthed from a necropolis dated to the Early Iron Age (800-475 BC) and located in Eckwersheim (NE France). The molecular composition of the substance, which was investigated using gas chromatography coupled to mass spectrometry, points towards an adhesive used to stick two bronze half-spheres to form a pendant. The predominance of triterpenoids from the lupane series led to the identification of the adhesive as a birch bark tar and constitutes a rare example of the use of such a material in jewellery in the past

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.

International audience; Brain diseases such as autism and Alzheimer's disease (each inflicting >1% of the world population) involve a large network of genes displaying subtle changes in their expression. Abnormalities in intraneuronal transport have been linked to genetic risk factors found in patients, suggesting the relevance of measuring this key biological process. However, current techniques are not sensitive enough to detect minor abnormalities. Here we report a sensitive method to measure the changes in intraneuronal transport induced by brain-disease-related genetic risk factors using fluorescent nanodiamonds (FNDs). We show that the high brightness, photostability and absence of cytotoxicity allow FNDs to be tracked inside the branches of dissociated neurons with a spatial resolution of 12 nm and a temporal resolution of 50 ms. As proof of principle, we applied the FND tracking assay on two transgenic mouse lines that mimic the slight changes in protein concentration (∼30%) found in the brains of patients. In both cases, we show that the FND assay is sufficiently sensitive to detect these changes.

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.

Molecular and isotopic investigation of lipids from soils filling several structures from an archaeological site located at Obernai (Alsace, NE France) has revealed the presence of miliacin, a triterpenoid marker from Panicum miliaceum (broomcorn millet), indicating that this cereal was cultivated at the site. The concentration profiles of miliacin within silos and its detection in other archaeological structures (e.g., Gaulish pit) suggest that miliacin did not originate from cereals stored in the silos but rather came from remains of millet from cultivated soils which filled the silos after they were abandoned. Furthermore, the 14C age of miliacin isolated from a silo of the Second Iron Age was shown to be considerably older (Bronze Age) than the structure itself, revealing that the soil filling the silo therefore archived the molecular signature from past millet cropping, predating the digging of the silo. Thus, radiocarbon dating of the isolated miliacin allowed the timing of millet cropping to be determined, showing that it was established during the Bronze Age and the Roman Gaul period at Obernai. This is the first evidence of millet cultivation in Alsace dating back to the Bronze Age, bringing new perspectives on agricultural practices and past dietary practice in Eastern France. The combination of molecular studies and radiocarbon dating of individual lipids highlights the potential of hollow structures like silos and pits to act as “pedological traps”, recording information on past vegetation cover or agricultural practices from the surface horizons of surrounding soils that filled these structures after abandonment.

International audience; Organic substances from three jars found at Abydos in the tombs of Kings from the two first Egyptian dynasties (3100–2700 BCE) were investigated using gas chromatography–mass spectrometry in order to assess their biological origin, use and mode of preparation. The organic material was found to correspond to essential oils from conifers severely altered/oxidized. A predominant contribution from Cedrus libani was determined from the identification of sesquiterpenoid derivatives of the himachalene series which constitute new molecular tools for the identification of ancient oils made from real cedars. The presence of cuparene-related terpenoids suggests an additional contribution of members from the Cupressaceae family (junipers, cypresses). The genuine substances were most likely prepared in the Levant since neither C. libani nor junipers or cypresses are native from Egypt. Despite obvious analogies with “cedrium” used for embalming during later periods, their use as ingredients for embalming remains uncertain because true embalming only began in Egypt after 2500 BCE. Instead, it is proposed that these substances have been used as cosmetics, medicinal substances or for cultual purposes. The predominance of low molecular weight sesquiterpenoids and the absence of typical markers for wood tars indicate that the substances have possibly been prepared by steam-distillation of odoriferous plant material rather than by pyrolysis. Our study gives clues to the controversy concerning the composition of “cedrium”, indicating that it most likely originates from mixed true cedar and junipers or cypresses, and not exclusively from real cedar vs. juniper oil.

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.

International audience; Resinous material from conifers from the Pinaceae family is frequently found in an archaeological context. The material was used, notably, as waterproofing agent, as adhesive or for the caulking of boats. Two main types of material can be distinguished: resin, the exudate of conifer trees, and wood tar obtained by dry distillation of wood. Molecular investigation of such material aims, notably, at developing new molecular tools for the determination of the biological and geographical origin or of the manufacturing techniques, and for the discrimination between resin and wood tar. In this context, we report the identification by synthesis of alkyl guaiacyl dehydroabietates, which occur in a series of recent and archaeological conifer wood tar samples from shipwrecks and Gallo-Roman tar preparation sites. They most likely result from the reaction of dehydroabietic acid and alkyl guaiacols, the latter being typical wood pyrolysis products formed during the preparation of wood tar. Alkyl guaiacyl dehydroabietates are therefore proposed to be specific molecular markers for conifer wood tar, allowing a clear molecular distinction between this material and resin to be made. They are also more resistant to the alteration undergone by archaeological samples than other compounds previously proposed as markers of conifer wood tar such as anhydrosugars or alkyl guaiacols.

International audience; Our graduate engineering school in Information and Communication Technology offers different academic programmes ranging from Masters of Engineering to PhD. One programme is dedicated to apprenticeships with around 40 students per year. Each student alternates equally between the school and a company over a three year period. The companies vary from small and medium size to large ones such as IT operators. All these companies require that the students are able to work in the complex and fast-changing environment of the digital industry. To this end, we have developed project based learning where students are placed in practical situations close to those they will experience in their future career. In particular, during a final-year project, we require that our students perform a technical and economic study involving constraints which can vary during the project. The students work in large teams (around 15 students) and improve skills such as agility, project management and team-working.These skills are relatively removed from standard academic and technical skills but they are essential for a career in engineering. As teachers, we provide tools to help organize, schedule and manage teamwork in a fast-changing environment. During the first two years, students have academic lectures on risk management, customer requirement analysis, schedule management and communication basics. Although the students spend many training periods in companies, they usually practice only basic project management. During their final year, we aim to boost their skills by introducing the complexity of the industrial world into academic activities. We stress team work, self-organization, conflict management and uncertainty. Even though, as teachers, we of course verify that they eventually master these topics to a high level, students must also perform a self-assessment and discuss this assessment with their teachers. Over the last 3 years, we have analysed the students' point of view on their skills improvement. This allows us, firstly, to adapt the course in order to continually improve student skills. However, we also have to make sure that the students are aware of their skills increase so that they apply this new knowledge with more confidence in the company environment. Our method is based on a quantitative analysis of the answers to a poll on the self-assessment of skills. The same poll was filled in by a hundred students over three years, before and after the complex project activity. We focused the analysis on three main issues: project management tools, team-working and agility. For each question, the students had to individually rate their capacity on a 5-level scale: from "No knowledge" to "Mastery of complex projects". We observe a strong increase in the self-assessed level in these skills. The "Mastery of complex project" which was claimed by only 20% of the students before the activity reaches 50 % after the project. The other students shifted from "No knowledge" to "Mastery of simple projects". Furthermore, agility is assessed as the most boosted skill. Why? Throughout the project, professors aim to put the students in situations which are different to those generally occurring in an academic environment. Moreover, students certainly have more difficulties to assess this skill when compared to the others. Indeed, the students have many written and factual feedbacks from the teachers all along the project so that they moderate their self-assessment about project management tools and team-working. To go further, we aim to involve the student's partner companies in the skill assessment of our students before and after their final project which concludes their apprenticeship. This will give us a more complete skill assessment from the three stakeholders of this programme: students, teachers and companies.