Development of innovative steels and thermo-mechanical treatments for DEMO high operating temperature blanket options

Among the options currently taken into account for the realization of the first DEMO reactor there are the "helium-cooled" and the "dual coolant" breeding blanket. Therefore the high temperature (650 °C) behavior of the proposed innovative martensitic alloys should be improved, namely the frame of the hereby reported activities is the development of martensitic alloys more resistant to creep, suitable to tolerate such a high operating temperature. In order to improve the high temperature mechanical properties, concerning the alloy design strategies, two alternative routes are proposed; the effect of Nitrogen and Tungsten increase are taken into account as well as the addition of carbo-nitride forming elements, like Vanadium, combined with the "ausforming" thermo-mechanical treatments. Two alloys have been designed and a special thermo-mechanical treatment on Eurofer 97-2 is proposed. The "ausforming" treatment, consisting in a sort of hot-working at a lower temperature with respect to the austenitization one after the austenitization stage, is aimed at the achievement of a beneficial dislocation "pinning" at high temperature due to carbide precipitation. Generally the improvement of tensile properties is associated to the hardening of the steel due to dislocation network and precipitation effects. This hardening is accompanied by a DBTT increase to markedly higher values with respect to Standard Eurofer. The proposed materials should be, in any case, at least room temperature ductile in order to undergo safe manufacturing and assembling processes. Therefore the issue of the DBTT increase has been taken into account by tuning the tempering temperature adequately. The two variations from chemical composition of Eurofer 97 have been casted and the thermo-mechanical treatments have been selected by means of SEM and hardness measurements to tune grain size and precipitation of carbides. The outcomes of the preliminary mechanical characterization (tensile, creep and impact tests) will be discussed in this paper. Keywords: EUROFER 97, RAFM steels, Thermo-mechanical treatment, Ausforming, Tensile, Creep, Charp

Environmental stress affects the expression of a carotenoid-based sexual trait in male zebra finches.

Abiotic factors including thermal stress are suggested to exert constrains on sexual ornaments through trade-offs between sexual displays and physiological functions related to self-maintenance. Given the health properties of carotenoid pigments, carotenoid-based ornaments offer a relevant context in which to investigate the effect of environmental stress, such as ambient temperature, on the production and maintenance of secondary sexual traits and, also, to explore the proximate mechanisms shaping their expression. In this study, we exposed male zebra finches (Taeniopygia guttata) to environmental stress by exposing them to two temperature regimes (6 and 26 degrees C) over a 4 week period. Simultaneously, half of the males in each temperature group were supplemented with carotenoids, whereas the other half were not. The expression of a carotenoid-based sexual trait (bill colour) and the amount of circulating carotenoids were assessed before and at the end of the experiment. Carotenoid-supplemented males developed a redder bill, but the effect of supplementation was reduced under cold exposure. However, we found evidence that birds facing a cold stress were carotenoid limited, since supplemented males developed redder bills than the non-supplemented ones. Interestingly, while cold-exposed and non-supplemented males developed duller bills, they circulated a higher amount of carotenoids at the end of the experiment compared to the pre-experimental values. Together, these results suggest that ambient temperature might contribute to the modulation of the expression of carotenoid-based ornaments. Our findings suggest that carotenoids are a limiting resource under cold exposure and that they might be prioritized for self-maintenance at the expense of the ornament. The physiological functions related to self-maintenance that might have benefited from carotenoid saving are discussed

An experimental manipulation of life-history trajectories and resistance to oxidative stress.

Optimal investment into life-history traits depends on the environmental conditions that organisms are likely to experience during their life. Evolutionary theory tells us that optimal investment in reproduction versus maintenance is likely to shape the pattern of age-associated decline in performance, also known as aging. The currency that is traded against different vital functions is, however, still debated. Here, we took advantage of a phenotypic manipulation of individual quality in early life to explore (1) long-term consequences on life-history trajectories, and (2) the possible physiological mechanism underlying the life-history adjustments. We manipulated phenotypic quality of a cohort of captive zebra finches (Taeniopygia guttata) by assigning breeding pairs to either an enlarged or a reduced brood. Nestlings raised in enlarged broods were in poorer condition than nestlings raised in reduced broods. Interestingly, the effect of environmental conditions experienced during early life extended to the age at first reproduction. Birds from enlarged broods delayed reproduction. Birds that delayed reproduction produced less offspring but lived longer, although neither fecundity nor longevity were directly affected by the experimental brood size. Using the framework of the life-table response experiment modeling, we also explored the effect of early environmental condition on population growth rate and aging. Birds raised in reduced broods tended to have a higher population growth rate, and a steeper decrease of reproductive value with age than birds reared in enlarged broods. Metabolic resources necessary to fight off the damaging effect of reactive oxygen species (ROS) could be the mechanism underlying the observed results, as (1) birds that engaged in a higher number of breeding events had a weaker red blood cell resistance to oxidative stress, (2) red blood cell resistance to oxidative stress predicted short-term mortality (but not longevity), and (3) was related with a parabolic function to age. Overall, these results highlight that early condition can have long-term effects on life-history trajectories by affecting key life-history traits such as age at first reproduction, and suggest that the trade-off between reproduction and self-maintenance might be mediated by the cumulative deleterious effect of ROS

Eco‐evolutionary dynamics in response to selection on life‐history

Understanding the consequences of environmental change on ecological and evolutionary dynamics is inherently problematic because of the complex interplay between them. Using invertebrates in microcosms, we characterise phenotypic, population and evolutionary dynamics before, during and after exposure to a novel environment and harvesting over 20 generations. We demonstrate an evolved change in life-history traits (the age- and size-at-maturity, and survival to maturity) in response to selection caused by environmental change (wild to laboratory) and to harvesting (juvenile or adult). Life-history evolution, which drives changes in population growth rate and thus population dynamics, includes an increase in age-to-maturity of 76% (from 12.5 to 22 days) in the unharvested populations as they adapt to the new environment. Evolutionary responses to harvesting are outweighed by the response to environmental change (~ 1.4 vs. 4% change in age-at-maturity per generation). The adaptive response to environmental change converts a negative population growth trajectory into a positive one: an example of evolutionary rescue. © 2013 John Wiley & Sons Ltd/CNRS

An experimental test of the dose-dependent effect of carotenoids and immune activation on sexual signals and antioxidant activity.

Carotenoid-based sexual traits are thought to be reliable indicators of male quality because they might be scarce and therefore might indicate the ability of males to gather high-quality food and because they are involved in important physiological functions (as immune enhancers and antioxidants). We performed an experiment where male and female zebra finches (Taeniopygia guttata) were provided with increasing carotenoid doses in the drinking water during 4 weeks (bill color of this species is a carotenoid-based sexual signal). Simultaneously, birds were split into two groups: one receiving weekly injections of Escherichia coli lipopolysaccharide in order to activate the immune system, the other being injected with the same volume of phosphate buffered saline. We assessed how carotenoid availability and immune activation affected the amount of circulating plasma carotenoids, the beak color, and the antioxidant defenses (assessed as the resistance of red blood cells to a controlled free radical attack). Carotenoid availability affected the amount of circulating carotenoids and beak color; both variables reached a plateau at the highest carotenoid doses. Immune activation diverted carotenoids from plasma, and this in turn affected the expression of the sexual trait. Finally, we found a positive correlation between the change in circulating carotenoids and antioxidant defenses. These results support the idea that carotenoids have important physiological properties that ensure the honesty of carotenoid-based sexual traits

Glutamine versus Ammonia Utilization in the NAD Synthetase Family

NAD is a ubiquitous and essential metabolic redox cofactor which also functions as a substrate in certain regulatory pathways. The last step of NAD synthesis is the ATP-dependent amidation of deamido-NAD by NAD synthetase (NADS). Members of the NADS family are present in nearly all species across the three kingdoms of Life. In eukaryotic NADS, the core synthetase domain is fused with a nitrilase-like glutaminase domain supplying ammonia for the reaction. This two-domain NADS arrangement enabling the utilization of glutamine as nitrogen donor is also present in various bacterial lineages. However, many other bacterial members of NADS family do not contain a glutaminase domain, and they can utilize only ammonia (but not glutamine) in vitro. A single-domain NADS is also characteristic for nearly all Archaea, and its dependence on ammonia was demonstrated here for the representative enzyme from Methanocaldococcus jannaschi. However, a question about the actual in vivo nitrogen donor for single-domain members of the NADS family remained open: Is it glutamine hydrolyzed by a committed (but yet unknown) glutaminase subunit, as in most ATP-dependent amidotransferases, or free ammonia as in glutamine synthetase? Here we addressed this dilemma by combining evolutionary analysis of the NADS family with experimental characterization of two representative bacterial systems: a two-subunit NADS from Thermus thermophilus and a single-domain NADS from Salmonella typhimurium providing evidence that ammonia (and not glutamine) is the physiological substrate of a typical single-domain NADS. The latter represents the most likely ancestral form of NADS. The ability to utilize glutamine appears to have evolved via recruitment of a glutaminase subunit followed by domain fusion in an early branch of Bacteria. Further evolution of the NADS family included lineage-specific loss of one of the two alternative forms and horizontal gene transfer events. Lastly, we identified NADS structural elements associated with glutamine-utilizing capabilities

Identification of withania somnifera-silybum marianum-trigonella foenum-graecum formulation as a nutritional supplement to contrast muscle atrophy and sarcopenia

Background: Muscle atrophy, i.e., the loss of skeletal muscle mass and function, is an unresolved problem associated with aging (sarcopenia) and several pathological conditions. The im-balance between myofibrillary protein breakdown (especially the adult isoforms of myosin heavy chain, MyHC) and synthesis, and the reduction of muscle regenerative potential are main causes of muscle atrophy. Methods: Starting from one-hundred dried hydroalcoholic extracts of medical plants, we identified those able to contrast the reduction of C2C12 myotube diameter in well-characterized in vitro models mimicking muscle atrophy associated to inflammatory states, glucocorticoid treatment or nutrient deprivation. Based on their ability to rescue type II MyHC (MyHC-II) expression in atrophying conditions, six extracts with different phytochemical profiles were selected, mixed in groups of three, and tested on atrophic myotubes. The molecular mechanism underpinning the effects of the most efficacious formulation, and its efficacy on myotubes obtained from muscle biopsies of young and sarcopenic subjects were also investigated. Results: We identified WST (Withania som-nifera, Silybum marianum, Trigonella foenum-graecum) formulation as extremely efficacious in protecting C2C12 myotubes against MyHC-II degradation by stimulating Akt (protein kinase B)-dependent protein synthesis and p38 MAPK (p38 mitogen-activated protein kinase)/myogenin-dependent myoblast differentiation. WST sustains trophism in C2C12 and young myotubes, and rescues the size, developmental MyHC expression and myoblast fusion in sarcopenic myotubes. Conclusion: WST strongly counteracts muscle atrophy associated to different conditions in vitro. The future validation in vivo of our results might lead to the use of WST as a food supplement to sustain muscle mass in diffuse atrophying conditions, and to reverse the age-related functional decline of human muscles, thus improving people quality of life and reducing social and health-care costs

Association of oily fish intake, sex, age, BMI and APOE genotype with plasma long-chain n-3 fatty acid composition

n-3 Fatty acids are associated with better cardiovascular and cognitive health. However, the concentration of EPA, DPA and DHA in different plasma lipid pools differs and factors influencing this heterogeneity are poorly understood. Our aim was to evaluate the association of oily fish intake, sex, age, BMI and APOE genotype with concentrations of EPA, DPA and DHA in plasma phosphatidylcholine (PC), NEFA, cholesteryl esters (CE) and TAG. Healthy adults (148 male, 158 female, age 20–71 years) were recruited according to APOE genotype, sex and age. The fatty acid composition was determined by GC. Oily fish intake was positively associated with EPA in PC, CE and TAG, DPA in TAG, and DHA in all fractions (P≤0·008). There was a positive association between age and EPA in PC, CE and TAG, DPA in NEFA and CE, and DHA in PC and CE (P≤0·034). DPA was higher in TAG in males than females (P<0·001). There was a positive association between BMI and DPA and DHA in TAG (P<0·006 and 0·02, respectively). APOE genotype×sex interactions were observed: the APOE4 allele associated with higher EPA in males (P=0·002), and there was also evidence for higher DPA and DHA (P≤0·032). In conclusion, EPA, DPA and DHA in plasma lipids are associated with oily fish intake, sex, age, BMI and APOE genotype. Such insights may be used to better understand the link between plasma fatty acid profiles and dietary exposure and may influence intake recommendations across population subgroups