The challenges in predicting the fatigue life of dissimilar brazed joints and initial finite element results for a tungsten to EUROFER97 steel brazed joint

This paper summarises the challenges in accurately predicting stress states in dissimilar brazed joints and presents initial results from a finite element analysis of a tungsten to EUROFER97 brazed joint. The residual stresses due to joint manufacture are presented and differences in stress distribution due to thermal and mechanical loading highlighted. The results from this analysis correlate well to experimental results from previous research however further validation is required. The challenges in developing fatigue assessment procedures for dissimilar brazed joints are also discussed. These fatigue assessment procedures are introduced and a validation strategy for such procedures is proposed

Observations on the post-mortem investigation of electron beam welds and other micro-structural features of JET Hypervapotrons

A metallurgical post-mortem investigation has been carried out on Mark 1 Hypervapotron elements from the Joint European Tokamak (JET), with the aim of aiding engineers in improving the future design of such high heat flux (HHF) component. Optical and electron microscopy and X-ray techniques have been utilised. Work has predominately focused on the electron beam (EB) welded and vacuum brazed joints of the Hypervapotron. Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) has been used to assess the chemical composition while micro and nano indentation testing has been used to study the hardness profiles of these joints. Poor quality control of the vacuum brazing process resulted in nickel based filler material, contaminating internal surfaces. Variable penetration and entrapped voids in the EB welds suggested weld spiking occurred during the joining process. Details of these findings and a critical assessment of the potential implications are given where appropriate

On the primary structure of polysilenes and polygermenes

Despite the long history and prominence of addition polymerizations in alkene chemistry, addition polymerizations of the heavier main group analogs of alkenes are in their infancy. Herein, the detailed structural and end group analyses of polysilenes (polycarbosilanes) and polygermenes (polycarbogermanes) derived from the anionic polymerization of kinetically-stabilized silenes and germenes, respectively, are reported. The end groups were identified using ESI-TOF mass spectrometry. Careful examination of the C- H HSQC NMR spectra of both polymers confirmed the regular, alternating structure consistent with an addition polymerization with no significant amount of intramolecular rearrangement or back-biting. These results are in contrast to what has been observed during the synthesis of the analogous polyphosphenes. 13

Reproducibility of fluorescent expression from engineered biological constructs in E. coli

We present results of the first large-scale interlaboratory study carried out in synthetic biology, as part of the 2014 and 2015 International Genetically Engineered Machine (iGEM) competitions. Participants at 88 institutions around the world measured fluorescence from three engineered constitutive constructs in E. coli. Few participants were able to measure absolute fluorescence, so data was analyzed in terms of ratios. Precision was strongly related to fluorescent strength, ranging from 1.54-fold standard deviation for the ratio between strong promoters to 5.75-fold for the ratio between the strongest and weakest promoter, and while host strain did not affect expression ratios, choice of instrument did. This result shows that high quantitative precision and reproducibility of results is possible, while at the same time indicating areas needing improved laboratory practices.Peer reviewe