Ultra-slow Fatigue Crack Propagation in Metallic Alloys

AbstractThe influence of frequency (20kHz ultrasonic tests and conventional 20 to 35Hz tests) and environment (air and vacuum) on near-threshold fatigue crack propagation of three metallic alloys, Ti-6Al-4V, 2024-T351 and 12% Cr stainless steel is compared experimentally. The effective stress-intensity factor which is considered as the propagation driving force is determined from closure measurements or tests run at high R-ratio. Based on microfractographic observations, the results are discussed in terms of a preexisting model for intrinsic and environmentally assisted fatigue crack propagation

Antibacterial and antioxidant activities of Origanum compactum essential oil

In the present study, essential oil of Origanum compactum was analysed and its chemical composition was identified by gas chromatography coupled to mass spectrometry (GC-MS). Among thirty two assayed constituents, carvacrol (30.53%), thymol (27.50%) and its precursor g-terpinene (18.20%) were found to be the major components. The oil was investigated for its in vitro antibacterial activity against a panel of standard reference strains using well diffusion and broth dilution methods. In solid medium, the oil was found to be remarkably active against all tested strains except Pseudomonas which showed resistance. In liquid medium the Minimum Inhibitory Concentrations (MICs) and Minimum Bactericidal Concentration (MBCs) ranged from 0.0078 to 0.25% (v/v). The antioxidant activity was investigated by three different methods; 1,1-diphenyl-2-picryl-hydrasyl (DPPH) radical scavenging assay, -carotenebleaching test and reducing power. The results of this study revealed evidence that the essential oil of O. compactum possesses a good antioxidant effect with all assays; the antioxidant activity isdependent on the oil concentration and can be attributed to the phenolic compounds present in the oil

Mouse hepatitis virus neurovirulence: evidence of a linkage between S glycoprotein expression and immunopathology.

Differences in disease outcome between the highly neurovirulent MHV-JHM and mildly neurovirulent MHV-A59 have been attributed to variations within the spike (S) glycoprotein. Previously, we found that MHV-JHM neurovirulence was marked by diminished expression of interferon-gamma (IFN-gamma) mRNA and a reduced presence of CD8 T cells in the CNS concomitant with heightened macrophage inflammatory protein (MIP)-1 transcript levels and greater macrophage infiltration relative to MHV-A59 infection. Here, the ability of the S and non-spike genes to regulate these immune responses was evaluated using chimeric viruses. Chimeric viruses WTR13 and S4R22 were made on MHV-A59 variant backgrounds and, respectively, contained the S gene of MHV-A59 and MHV-JHM. Unexpectedly, genes other than S appeared to modulate events critical to viral replication and survival. Unlike unresolving MHV-JHM infections, the clearance of WTR13 and S4R22 infections coincided with strong IFN-gamma transcription and an increase in the number of CD8 T cells infiltrating into the CNS. However, despite the absence of detectable viral titers, approximately 40% of S4R22-infected mice succumbed within 3 weeks, indicating that the enhanced mortality following S4R22 infection was not associated with high viral titers. Instead, similar to the MHV-JHM infection, reduced survival following S4R22 infection was observed in the presence of elevated MIP-1alpha and MIP-1beta mRNA accumulation and enhanced macrophage numbers within infected brains. These observations suggest that the S protein of MHV-JHM influences neurovirulence through the induction of MIP-1alpha- and MIP-1beta-driven macrophage immunopathology

Microbial food web dynamics in response to a Saharan dust event: results from a mesocosm study in the oligotrophic Mediterranean Sea

BiogeosciencesInternational audienceThe significant impact of dust deposition on het-erotrophic bacterial dynamics in the surface oligotrophic ocean has recently been evidenced. Considering the central role of bacteria in the microbial loop, it is likely that dust deposition also affects the structure and the functioning of the whole microbial food web. In the frame of the DUNE project, aiming to estimate the impact of dust deposition on the oligotrophic Mediterranean Sea through mesocosm ex-periments, the main goal of the present paper was to as-sess how two successive dust deposition events affect the dynamics of the microbial food web. The first dust seeding delivered new P and N to the amended mesocosms and re-sulted in a pronounced stimulation of bacterial respiration. It also induced pronounced, but transient, changes in the bac-terial community composition. No significant effects were observed on the abundances of viruses and heterotrophic nanoflagellates. The second dust seeding also delivered new P and N to the amended mesocosms, but the effect on the microbial food web was very different. Bacterial respira-tion remained constant and bacterial abundance decreased. Compositional changes following the second seeding were minor compared to the first one. The decrease in bacterial abundance coincided with an increase in virus abundance, resulting in higher virus : bacteria ratios throughout the sec-ond seeding period. Our study shows that dust deposition to the surface oligotrophic ocean may involve important mod-ifications of the trophic links among the components of the microbial food web with presumed consequences on C and nutrient cycling

In Vitro Antibacterial Activity of Essential Oils against Streptococcus pyogenes

Streptococcus pyogenes plays an important role in the pathogenesis of tonsillitis. The present study was conducted to evaluate the in vitro antibacterial activities of 18 essential oils chemotypes from aromatic medicinal plants against S. pyogenes. Antibacterial activity of essential oils was investigated using disc diffusion method. Minimum Inhibitory Concentration of essential oils showing an important antibacterial activity was measured using broth dilution method. Out of 18 essential oils tested, 14 showed antibacterial activity against S. pyogenes. Among them Cinnamomum verum, Cymbopogon citratus, Thymus vulgaris CT thymol, Origanum compactum, and Satureja montana essential oils exhibited significant antibacterial activity. The in vitro results reported here suggest that, for patients suffering from bacterial throat infections, if aromatherapy is used, these essential oils, considered as potential antimicrobial agents, should be preferred

Proba-3: ESA’s Small Satellites Precise Formation Flying Mission to Study the Sun’s Inner Corona as Never Before

This paper showcases ESA’s Proba-3 mission as a demonstration of how small satellites, in combination with formation flying technology, can achieve relevant scientific goals and perform scientific measurements not possible otherwise, all within a tight cost and programmatic context. The study of the Sun inner corona down to 1.1 solar radius can only be performed by creating in space artificial eclipses with a large distance between a Coronograph instrument and an occulting disk, much bigger than the size of any spacecraft that can fit within a launcher. Proba-3 will achieve these enhanced scientific observations by controlling two small satellites (~1.5 m cubes in the 200-300kg range) as a 150 m long ‘large virtually rigid structure’ by maintaining millimetre and arc second relative precision. In effect the paired satellites will fly as a giant virtual satellite creating an ‘externally occulted’ coronagraph, in which a satellite imager is shielded from glaring sunlight by an occulting disk on the other satellite, forming an artificial eclipse. Precise station keeping for Coronagraphy will be kept for 6 consecutive hours within each 20 hour orbit for a minimum total of 1000 hours of scientific observations over the 2 years of mission lifetime. This will be achieved autonomously, without relying on the ground for active control of the formation. In addition, Proba-3 will practically demonstrate formation flying technologies enabling other future science missions: station-keeping at different relative distances (from 25 m up to 250 m); approaching and separating in precise formation without losing millimetre precision; the capability to repoint the formation as a virtual rigid body away from the Sun and the combination of station keeping, resizing and re-targeting manoeuvres. Proba-3 is at full speed in the assembly, integration and verification phase, with the aim of launching Proba-3 in two years’ time. The paper describes the overall Proba-3 mission concept and detailed design, the different challenges that were overcome in spacecraft design, formation flying metrology and control, and the need to implement novel verification and operation approaches to achieve the world’s first precise formation flying mission

Modélisation sous Abaqus de la fermeture de fissures courtes dans un acier inoxydable 304L

La connaissance précise du comportement d'une fissure courte est nécessaire pour comprendre la propagation des fissures de faïençage thermique dans les structures nucléaires. La présente étude porte sur l'influence, sur les cinétiques de propagation, de la fermeture induite par plasticité. Une approche numérique sous Abaqus, en 3D, avec un front de fissure droit ou courbe permet de retrouver des résultats expérimentaux mettant en évidence des vitesses de propagation supérieures pour des fissures courtes

Effect of HLA-matching recipients to donor non-inherited maternal antigens on outcomes after mismatched umbilical cord blood transplantation for hematologic malignancy

peer reviewe

Abundance of a chlorophyll a precursor and the oxidation product hydroxychlorophyll a during seasonal phytoplankton community progression in the Western English Channel

This study presents the first in-situ measurements of the chlorophyll a oxidation product, hydroxychlorophyll a as well as the chlorophyll a precursor, chlorophyll aP276 conducted over an annual cycle. Chlorophyll a oxidation products, such as hydroxychlorophyll a may be associated with the decline of algal populations and can act as an initial step in the degradation of chlorophyll a into products which can be found in the geochemical record, important for studying past climate change events. Here, hydroxychlorophyll a and chlorophyll aP276 were measured at the long-term monitoring station L4, Western Channel Observatory (UK, www.westernchannelobservatory.org) over an annual cycle (2012). Weekly measurements of phytoplankton species composition and abundance enabled detailed analysis of possible sources of hydroxychlorophyll a. Dinoflagellates, 2 diatom species, the prymnesiophyte Phaeocystis spp. and the coccolithophorid Emiliania huxleyi were all associated with hydroxychlorophyll a occurrence. However, during alternate peaks in abundance of the diatoms, no association with hydroxychlorophyll a occurred, indicating that the oxidation of chlorophyll a was dependant not only on species but also on additional factors such as the mode of mortality, growth limiting factor (i.e. nutrient concentration) or phenotypic plasticity. Surface sediment samples contained 10 times more hydroxychlorophyll a (relative to chlorophyll a) than pelagic particulate samples, indicating that more chlorophyll a oxidation occurred during sedimentation or at the sediment-water interface, than in the pelagic environment. In addition, chlorophyll aP276 correlated with chl-a concentration, thus supporting its assignment as a chl-a precursor