Structures, origin and evolution of various carbon phases in the ureilite Northwest Africa 4742 compared with laboratory-shocked graphite

International audienceMineralogical structures of carbon phases within the ureilite North West Africa 4742, a recent find, are investigated at various scales by high-resolution transmission electron microscopy (HRTEM), Raman microspectrometry and X-ray diffraction. Ureilites are the most carbon-rich of all meteorites, containing up to 6 wt.% carbon. Diamond, graphite and so-called "amorphous carbon" are typically described, but their crystallographic relationships and respective thermal histories remain poorly constrained. We especially focus on the origin of "amorphous carbon" and graphite, as well as their relationship with diamond. Two aliquots of carbon-bearing material were extracted: the insoluble organic matter (IOM) and the diamond fraction. We also compare the observed structures with those of laboratory-shocked graphite. Polycrystalline diamond aggregates with mean coherent domains of about 40 nm are reported for the first time in a ureilite and TEM demonstrates that all carbon phases are crystallographically related at the nanometre scale. Shock features show that diamond is produced from graphite through a martensitic transition. This observation demonstrates that graphite was present when the shock occurred and is consequently a precursor of diamond. The structure of what is commonly described as the "amorphous carbon" has been identified. It is not completely amorphous but only disordered and consists of nanometre-sized polyaromatic units surrounding the diamond. Comparison with laboratory-shocked graphite, partially transformed into diamond, indicates that the disordered carbon could be the product of diamond post-shock annealing. As diamond is the carrier of noble gases, whereas graphite is noble gas free, graphite cannot be the sole diamond precursor. This implies a multiple-stage history. A first generation of diamond could have been synthesized from a noble gas rich precursor or environment by either a shock or a condensation process. Thermally-induced graphitization of chondritic-like organic matter could have produced the graphite, which was then transformed by shock processes into polycrystalline nanodiamond aggregates. The formation of the disordered carbon occurred by diamond post-shock back-transformation during post-shock heating. The noble gases in the first generation diamond could then be incorporated directly into the disordered carbon during the transformation

Digestive metabolism of glucosinolates: a novel approach using urinary markers for estimating the release of glucosinolate breakdown products in the gastro-intestinal tract of mammals.

Glucosinolates have been implicated as a mediator of the cancer-protective properties of cruciferous vegetables. Enzymatic hydrolysis of glucosinolates by plant or microbial myrosinase yields a range of metabolites including beneficial isothiocyanates. Little is known about the fate of glucosinolates after their ingestion. Using urinary end-products of metabolism as markers, measurement of the production of isothiocyanates in the digestive tract of monogastric animals has been achieved. Initially, a range of isothiocyanates were administered to rats and their excretion as mercapturic acids was quantified. Relative recovery of different isothiocyanates was found to be consistent and predictable, allowing the use of artificial isothiocyanates as recovery standards in subsequent experiments. Subsequently, the relative influence of plant and bacterial myrosinase on isothiocyanate production was quantified in rats. A proportion of 0.80 (s.e.m. 0.076) of benzyl glucosinolate was hydrolysed to isothiocyanate by plant myrosinase. In the presence of both plant and microbial activity,, the proportion of benzyl isothiocyanate release was significantly decreased (0.50 s.e.m. 0.046, p < 0.01) suggesting microbial breakdown of isothiocyanates. The approach, adapted for use with human subjects, showed that the proportions of allyl isothiocyanate measured after ingestion of raw and cooked cabbage were 0.37 (s.e.m. 0.045) and 0.53 (s.e.m. 0.134) respectively in healthy male volunteers. A further experiment with rats established that isothiocyanate uptake in the distal digestive tract was significantly less than in the proximal intestine (0.12 s.e.m. 0.017 and 0.48 s.e.m. 0.029 respectively), suggesting a potential underestimation of isothiocyanate release in the distal digestive tract when using urinary markers. Finally, enhancement of bacterial fermentation by addition of inulin to the diet had little influence on isothiocyanate production in the gut. The findings suggested that the formation of the cancer-protective isothiocyanates was significant in vivo, thereby strengthening the evidence for a beneficial effect of cruciferous vegetables for health. The newly developed method opens up possibilities of concurrently exploring the digestive fate of isothiocyanates and the toxicity of carcinogenic compounds

Characterization of Carbonaceous Materials by Correlated Electron and Optical Microscopy and Raman Microspectroscopy

Carbonaceous materials differ according to their chemical composition (types of heteroatoms), their structure and their microtexture. So, it is interesting to find methods for characterizing them. We choose to correlate data from Raman microspectroscopy, optical microscopy and transmission electron microscopy. First, we use both graphitizable or non-graphitizable reference carbon series of simple chemical composition in order to follow the structural transformation of the carbonaceous materials according to the evolution of these data throughout heat-treatment of these samples. Then, the coals of different ranks are studied. The Raman results are correlated with those from electron microscopy, particularly by plotting, for the graphitizable series, the diameter of the aromatic layers La (determined from lattice fringes and 11 dark-field) versus the specific surface of the Raman band characteristic of the defects centered at about 1350 cm-1 (ratio between surfaces of this band and the whole spectrum). For the coals, the half-maximum width of the band at about 1600 cm-1 has been plotted versus the reflectance. We conclude that the evolution of carbonaceous materials, throughout heat-treatments or natural processes, is possible only because different types of defects are progressively removed. These defects are heteroatoms, tetrahedral carbons, isolated and crosswise basic structural units or BSU (one, two or three stacked in parallel polyaromatic structures, less than 10 A in size) and defects in aromatic layers. The elimination of these defects permits the rearrangement of the BSUs and the establishment of an organization which can possibly reach the triperiodic order according to the series

Duration of systemic antifungal therapy for patients with invasive fungal diseases: A reassessment.

Invasive fungal diseases are associated with significant morbidity and mortality, especially among immunocompromised patients, and often prompt for rapid and aggressive treatment aiming cure. Due to the expanding magnitude of patients burdened by chronic immunosuppression and affected by fungal diseases, the diversity of clinical settings has risen. This often results in prolonged therapy (induction, consolidation and maintenance) associated with potentially severe side effects, and clinicians face the challenging decisions of when and how to stop anti-fungal therapy. Adequate duration of therapy is poorly defined, hampered by the lack of dedicated trials to the question, the heterogeneity of cases (type of fungal pathogen, localization of infection, underlying host conditions) and various confounding factors that may influence the clinical response (e.g. persistence vs recovery of immunosuppression, impact of surgery). In this review, we aim to evaluate the existing data underlying the guidelines and recommendations of treatment duration for the most frequent invasive fungal diseases (cryptococcal meningitis, Pneumocystis pneumonia, invasive aspergillosis, invasive candidiasis and mucormycosis), as well as specific localizations of deep-seated diseases (osteo-articular or central nervous system diseases and endocarditis) and emerging considerations and strategies

Multi-scale simulation of the atomization of a liquid jet in cross-flow in the presence of an acoustic perturbation

International audienceThe reduction of pollutant emissions is currently a major concern in the aerospace sector. Among the proposed solutions, lean combustion appears as an effective technology to reduce the environmental impact. However, this type of technology may also favour the appearance of combustion instabilities. These instabilities, resulting from a thermo-acoustic coupling, can lead to irreversible damage to the combustion chambers.Experimental studies previously conducted at ONERA on a multipoint injector by Apeloig highlighted the importance of atomization on the instabilities loop. Indeed, the fuel vapour concentration near the injection zone has been shown to fluctuate in accordance with the imposed acoustic perturbation. The driving mechanism would then result from a flapping motion of the liquid jets in the multiple injection points, induced by the gas flow oscillations. This would in turn affect the characteristic convective timescales of the fuel, in the form of a spray or even of thin liquid films on the duct walls.In order to characterize this interaction, this work focuses on the unsteady simulation of a round liquid jet in the presence of a transverse gas flow in a rectangular section duct. Following an experimental study, the multi-scale numerical approach for multi-phase flows, implemented in the ONERA CEDRE code, has been tested in presence of an imposed acoustic perturbation. This approach consists of the coupling of three models: a multi-fluid model able to capture the largest scales of the liquid column atomization; a dispersed phase approach for the atomized spray, and a “Shallow Water” approach for wall films. The coupling of these approaches is provided by dedicated atomization and impact models, which ensure liquid transfer between the three models.Simulation results show that the multi-fluid solver is able to correctly capture the largest scales of the liquid jet. The simulated liquid jet trajectories match the experimental ones, as well as their dynamic response to the imposed acoustic perturbation. As the liquid is transferred to the dispersed phase solver, the jet motion deeply affects the spray formation and behaviour. Good agreement was found on the particle resulting mean velocity, but only partial agreement on the phase delay. An important wall deposition has been detected for particular jet positions as well

Melanocortin-1 Receptor, Skin Cancer and Phenotypic Characteristics (M-SKIP) Project: Study Design and Methods for Pooling Results of Genetic Epidemiological Studies

Background: For complex diseases like cancer, pooled-analysis of individual data represents a powerful tool to investigate the joint contribution of genetic, phenotypic and environmental factors to the development of a disease. Pooled-analysis of epidemiological studies has many advantages over meta-analysis, and preliminary results may be obtained faster and with lower costs than with prospective consortia. Design and methods: Based on our experience with the study design of the Melanocortin-1 receptor (MC1R) gene, SKin cancer and Phenotypic characteristics (M-SKIP) project, we describe the most important steps in planning and conducting a pooled-analysis of genetic epidemiological studies. We then present the statistical analysis plan that we are going to apply, giving particular attention to methods of analysis recently proposed to account for between-study heterogeneity and to explore the joint contribution of genetic, phenotypic and environmental factors in the development of a disease. Within the M-SKIP project, data on 10,959 skin cancer cases and 14,785 controls from 31 international investigators were checked for quality and recoded for standardization. We first proposed to fit the aggregated data with random-effects logistic regression models. However, for the M-SKIP project, a two-stage analysis will be preferred to overcome the problem regarding the availability of different study covariates. The joint contribution of MC1R variants and phenotypic characteristics to skin cancer development will be studied via logic regression modeling. Discussion: Methodological guidelines to correctly design and conduct pooled-analyses are needed to facilitate application of such methods, thus providing a better summary of the actual findings on specific fields