Coupling aspects in the simulation of hydrogen-induced stress-corrosion cracking

AbstractModelling of hydrogen-induced stress-corrosion cracking (HISCC) has to consider coupling effects between the mechanical and the diffusion field quantities. Four main topics are addressed: i) surface kinetics, ii) diffusion, iii) deformation and iv) crack growth. Surface kinetics is realised by a chemisorptions model, hydrogen diffusion is formulated by an enhanced diffusion equation including effects of plastic deformation, deformation rate and hydrostatic pressure, deformation is described by von Mises plasticity, and crack growth is simulated by a cohesive model, where both yield and cohesive strength depend on the hydrogen concentration. The effect of atomic hydrogen on the local yield strength is modelled by the so-called HELP (Hydrogen-Enhanced Localised Plasticity) approach, and the influence on the cohesive strength is taken into account by the so-called HEDE (Hydrogen-Enhanced DEcohesion) model. As the two models predict contrary effects of atomic hydrogen on the material behaviour, namely a decrease of the local yield strength resulting in larger plastic deformations and a reduction of the cohesive strength and energy inducing lower ductility, respectively, the coupling phenomena are studied in detail. The model is verified by comparing experimentally measured and numerically simulated CTOD R-curves of C(T) specimens

Oto-facial syndrome and esophageal atresia, intellectual disability and zygomatic anomalies: expanding the phenotypes associated with EFTUD2 mutations

Background: Mutations in EFTUD2 were proven to cause a very distinct mandibulofacial dysostosis type Guion-Almeida (MFDGA, OMIM #610536). Recently, gross deletions and mutations in EFTUD2 were determined to cause syndromic esophageal atresia (EA), as well. We set forth to find further conditions caused by mutations in the EFTUD2 gene (OMIM *603892). Methods and results: We performed exome sequencing in two familial cases with clinical features overlapping with MFDGA and EA, but which were previously assumed to represent distinct entities, a syndrome with esophageal atresia, hypoplasia of zygomatic complex, microcephaly, cup-shaped ears, congenital heart defect, and intellectual disability in a mother and her two children [AJMG 143A(11):1135-1142, 2007] and a supposedly autosomal recessive oto-facial syndrome with midline malformations in two sisters [AJMG 132(4):398-401, 2005]. While the analysis of our exome data was in progress, a recent publication made EFTUD2 mutations highly likely in these families. This hypothesis could be confirmed with exome as well as with Sanger sequencing. Also, in three further sporadic patients, clinically overlapping to these two families, de novo mutations within EFTUD2 were identified by Sanger sequencing. Our clinical and molecular workup of the patients discloses a broad phenotypic spectrum, and describes for the first time an instance of germline mosaicism for an EFTUD2 mutation. Conclusions: The clinical features of the eight patients described here further broaden the phenotypic spectrum caused by EFTUD2 mutations or deletions. We here show, that it not only includes mandibulofacial dysostosis type Guion-Almeida, which should be reclassified as an acrofacial dysostosis because of thumb anomalies (present in 12/35 or 34% of patients) and syndromic esophageal atresia [JMG 49(12). 737-746, 2012], but also the two new syndromes, namely oto-facial syndrome with midline malformations published by Megarbane et al. [AJMG 132(4): 398-401, 2005] and the syndrome published by Wieczorek et al. [AJMG 143A(11):1135-1142, 2007] The finding of mild phenotypic features in the mother of one family that could have been overlooked and the possibility of germline mosaicism in apparently healthy parents in the other family should be taken into account when counseling such families

Transcription factors relevant to auxin signalling coordinate broad-spectrum metabolic shifts including sulphur metabolism

A systems approach has previously been used to follow the response behaviour of Arabidopsis thaliana plants upon sulphur limitation. A response network was reconstructed from a time series of transcript and metabolite profiles, integrating complex metabolic and transcript data in order to investigate a potential causal relationship. The resulting scale-free network allowed potential transcriptional regulators of sulphur metabolism to be identified. Here, three sulphur-starvation responsive transcription factors, IAA13, IAA28, and ARF-2 (ARF1-Binding Protein), all of which are related to auxin signalling, were selected for further investigation. IAA28 overexpressing and knock-down lines showed no major morphological changes, whereas IAA13- and ARF1-BP-overexpressing plants grew more slowly than the wild type. Steady-state metabolite levels and expression of pathway-relevant genes were monitored under normal and sulphate-depleted conditions. For all lines, changes in transcript and metabolite levels were observed, yet none of these changes could exclusively be linked to sulphur stress. Instead, up- or down-regulation of the transcription factors caused metabolic changes which in turn affected sulphur metabolism. Auxin-relevant transcription factors are thus part of a complex response pattern to nutrient starvation that serve as coordinators of the metabolic shifts driving sulphur homeostasis rather then as direct effectors of the sulphate assimilation pathway. This study provides the first evidence ever presented that correlates auxin-related transcriptional regulators with primary plant metabolism

Microwave instability and energy spread measurement via vertical dispersion bump in PETRA III

The recent measurement of bunch length versus current indicated that the longitudinal impedance (Z/n) is 0.15 Ohm in close agreement with the impedance model [1]. Naïve application of Keil-Schnell criteria predicts that the threshold of microwave instability at 0.25 mA. Since the single bunch intensity is in the range of 0.2 – 2.5 mA depending on the fill pattern of PETRA III, we expect to observe the fill-pattern dependent energy spread according to the theory. However, the 3rd generation light sources comparable to PETRA III often reported the observation which was much greater than the theoretical one. In order to induce the beam size variation we had used skew quadrupoles to generate the dispersion in vertical plane. In particular we made dispersion bump at the undulator sector so that we were able to use the x-ray optics for the precise determination of small vertical beam size. In this paper we report the experimental setup and measurement data with the estimate on the instability threshold. We also report the vertical emittance and energy spread based on the x-ray beam size measurement as well as the rf signal which was excited by the beam at the longitudinal feedback cavity

Contents of cysteine (upper row), γ-glutamylcysteine (GEC; middle row), and glutathione (GSH; lower row) are shown for plants overexpressing , , and , respectively, or down-regulated with respect to

Plants were grown for 10 weeks on soil before thiol extraction. knock-downs are represented by cross-hatched columns, overexpressing lines by white columns, and wild-type (WT) and empty-vector control lines (EV) by black columns. Values are the mean ±SD of three independent experiments. Asterisks indicate that the difference between the wild-type plants and the manipulated transgenic plants was significant using -tests ( ≤0.05).<p><b>Copyright information:</b></p><p>Taken from "Transcription factors relevant to auxin signalling coordinate broad-spectrum metabolic shifts including sulphur metabolism"</p><p></p><p>Journal of Experimental Botany 2008;59(10):2831-2846.</p><p>Published online Jan 2008</p><p>PMCID:PMC2486478.</p><p></p