LONGITUDINAL FACE CRACK PREDICTION WITH THERMO-MECHANICAL MODELS OF THIN SLABS IN FUNNEL MOULDS

This paper investigates longitudinal depressions and cracks in steel continuous-cast in funnel moulds usinga finite-element model to simulate thermo-mechanical behavior of the solidifying shell in the thin-slab castermould at the Corus Direct Sheet Plant (DSP) in IJmuiden, The Netherlands. The commercial code ABAQUS[1] is used to study the effect of the funnel shape on the stresses developed within a two-dimensional sectionthrough the shell while it moves through the mould. The model first simulates heat transfer, based on heatflux profiles found from extensive plant measurements of mould heat removal and thermocouples embedded inthe mould wall. It incorporates the drop in heat flux due to local gap formation. The temperature solution isinput to the mechanical model which incorporates grade-dependent elastic-viscoplastic constitutive behavior,ferrostatic pressure, taper, mould-wall oscillations, and contact with the profiled mould wall. The results arevalidated with plant measurements, including a breakout shell, and crack statistics. The model is applied tostudy the effects of increasing casting speed and funnel design in order to avoid longitudinal cracks

Housekeeping genes for quantitative expression studies in the three-spined stickleback Gasterosteus aculeatus

Background During the last years the quantification of immune response under immunological challenges, e.g. parasitation, has been a major focus of research. In this context, the expression of immune response genes in teleost fish has been surveyed for scientific and commercial purposes. Despite the fact that it was shown in teleostei and other taxa that the gene for beta-actin is not the most stably expressed housekeeping gene (HKG), depending on the tissue and experimental treatment, the gene has been us Results To establish a reliable method for the measurement of immune gene expression in Gasterosteus aculeatus, sequences from the now available genome database and an EST library of the same species were used to select oligonucleotide primers for HKG, in order to perform quantitative reverse-transcription (RT) PCR. The expression stability of ten candidate reference genes was evaluated in three different tissues, and in five parasite treatment groups, using the three algorithms BestKeeper, geNorm and N Conclusion As they were the most stably expressed genes in all tissues examined, we suggest using the genes for the L13a ribosomal binding protein and ubiquitin as alternative or additional reference genes in expression analysis in Gasterosteus aculeatus.

Divergence in Sex Steroid Hormone Signaling between Sympatric Species of Japanese Threespine Stickleback

Sex steroids mediate the expression of sexually dimorphic or sex-specific traits that are important both for mate choice within species and for behavioral isolation between species. We investigated divergence in sex steroid signaling between two sympatric species of threespine stickleback (Gasterosteus aculeatus): the Japan Sea form and the Pacific Ocean form. These sympatric forms diverge in both male display traits and female mate choice behaviors, which together contribute to asymmetric behavioral isolation in sympatry. Here, we found that plasma levels of testosterone and 17β-estradiol differed between spawning females of the two sympatric forms. Transcript levels of follicle-stimulating hormone-β (FSHβ) gene were also higher in the pituitary gland of spawning Japan Sea females than in the pituitary gland of spawning Pacific Ocean females. By contrast, none of the sex steroids examined were significantly different between nesting males of the two forms. However, combining the plasma sex steroid data with testis transcriptome data suggested that the efficiency of the conversion of testosterone into 11-ketotestosterone has likely diverged between forms. Within forms, plasma testosterone levels in males were significantly correlated with male body size, a trait important for female mate choice in the two sympatric species. These results demonstrate that substantial divergence in sex steroid signaling can occur between incipient sympatric species. We suggest that investigation of the genetic and ecological mechanisms underlying divergence in hormonal signaling between incipient sympatric species will provide a better understanding of the mechanisms of speciation in animals