42 research outputs found
Revisiting stress-corrosion cracking and hydrogen embrittlement in 7xxx-Al alloys at the near-atomic-scale
Tailoring negative pressure by crystal defects: Crack induced hydride formation in Al alloys
Climate change motivates the search for non-carbon-emitting energy generation
and storage solutions. Metal hydrides show promising characteristics for this
purpose. They can be further stabilized by tailoring the negative pressure of
microstructural and structural defects. Using systematic ab initio and
atomistic simulations, we demonstrate that an enhancement in the formation of
hydrides at the negatively pressurized crack tip region is feasible by
increasing the mechanical tensile load on the specimen. The theoretical
predictions have been used to reassess and interpret atom probe tomography
experiments for a high-strength 7XXX-aluminium alloy that show a substantial
enhancement of hydrogen concentration at structural defects near a
stress-corrosion crack tip. These results contain important implications for
enhancing the capability of metals as H-storage materials.Comment: 22 pages, 9 figure
Paraganglioma of the tongue with SDHB gene mutation in a patient with Graves' disease
The authors want to thank Mr. Jose Eduardo Matos (photog-rapher) for his technical assistance.We report a case of an apparently sporadic paraganglioma of the tongue with a germ-line mutation in a female patient with asymptomatic Graves' disease. The tongue is an unusual primary location. Genetic testing is mandatory in all cases. Thyroid gland dysfunction and autoimmune phenomena could be associated with some paragangliomas.S
Patterns of Plant Biomass Partitioning Depend on Nitrogen Source
Nitrogen (N) availability is a strong determinant of plant biomass partitioning, but the role of different N sources in this process is unknown. Plants inhabiting low productivity ecosystems typically partition a large share of total biomass to belowground structures. In these systems, organic N may often dominate plant available N. With increasing productivity, plant biomass partitioning shifts to aboveground structures, along with a shift in available N to inorganic forms of N. We tested the hypothesis that the form of N taken up by plants is an important determinant of plant biomass partitioning by cultivating Arabidopsis thaliana on different N source mixtures. Plants grown on different N mixtures were similar in size, but those supplied with organic N displayed a significantly greater root fraction. 15N labelling suggested that, in this case, a larger share of absorbed organic N was retained in roots and split-root experiments suggested this may depend on a direct incorporation of absorbed amino acid N into roots. These results suggest the form of N acquired affects plant biomass partitioning and adds new information on the interaction between N and biomass partitioning in plants
Methionine Sulfoxides on Prion Protein Helix-3 Switch on the α-Fold Destabilization Required for Conversion
BACKGROUND: The conversion of the cellular prion protein (PrP(C)) into the infectious form (PrP(Sc)) is the key event in prion induced neurodegenerations. This process is believed to involve a multi-step conformational transition from an alpha-helical (PrP(C)) form to a beta-sheet-rich (PrP(Sc)) state. In addition to the conformational difference, PrP(Sc) exhibits as covalent signature the sulfoxidation of M213. To investigate whether such modification may play a role in the misfolding process we have studied the impact of methionine oxidation on the dynamics and energetics of the HuPrP(125-229) alpha-fold. METHODOLOGY/PRINCIPAL FINDINGS: Using molecular dynamics simulation, essential dynamics, correlated motions and signal propagation analysis, we have found that substitution of the sulfur atom of M213 by a sulfoxide group impacts on the stability of the native state increasing the flexibility of regions preceding the site of the modification and perturbing the network of stabilizing interactions. Together, these changes favor the population of alternative states which maybe essential in the productive pathway of the pathogenic conversion. These changes are also observed when the sulfoxidation is placed at M206 and at both, M206 and M213. CONCLUSIONS/SIGNIFICANCE: Our results suggest that the sulfoxidation of Helix-3 methionines might be the switch for triggering the initial alpha-fold destabilization required for the productive pathogenic conversion