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The primary structure of Bacillus subtilis 105 kDa 2-oxoglutarate dehydrogenase (E10) was deduced from the nucleotide sequence of the odhA gene and confirmed by N-terminal sequence analysis. The protein is highly homologous to E1o of Azotobacter vinelandii and Escherichia coli and of bakers' yeast cells. The 5' end of the odhAB mRNA was determined and the promoter region for the odhAB operon was localized to a 375 bp DNA fragment. The cellular concentration of the 4.5 kb odhAB transcript was found to be growth stage dependent; its concentration during growth in nutrient sporulation medium decreased abruptly at the end of the exponential growth phase and it was not detectable in early stationary phase. This decrease in the cellular concentration of the transcript is not the result of an increased rate of decay of the full-length odhAB mRNA, suggesting that transcription is down-regulated at the end of the exponential growth phase. The cellular concentration of the odhA and odhB gene products, E1o and dihydrolipoamide transsuccinylase (E2o), remains essentially constant throughout the growth curve in nutrient sporulation medium, indicating that both are rather stable proteins. In exponentially growing cells, glucose in nutrient sporulation medium repressed the cellular concentration of the odhAB mRNA, as well as that of E1o and E2o, about four-fold. This effect is most likely the result of a decreased rate of transcription from the odhAB promoter, since neither the stability nor the 5'-end of the transcript were affected by glucose in the medium. It is concluded that the cellular concentration of the 2-oxoglutarate dehydrogenase multienzyme complex (E1o and E2o) is regulated mainly at the transcriptional level.

Fibre composites are today used as construction material in a growing number of applications. Carbon fibres/epoxy matrix composites are employed in high performance applications as aircrafts where a high stiffness/weight ratio is important. The structures are made of laminates built by stacking thin sheets of the composite with unidirectional ordered fibres. Such laminates are vulnerable to impact damages caused by for example a dropped tool. It is desired to develop computational methods to model such impacts and predict the resulting reduction in the performance. Then accurate models of the mechanical behaviour of the material are needed, models based on measurements not only at quasi-static loading but also at high strain rates. In this thesis two versions of the optical moiré technique are applied to investigate the mechanical behaviour of carbon fibre/epoxy matrix composite laminates. The work is made in co-operation with the Aeronautical Research Institute of Sweden (FFA). With moiré methods the in-plane displacement field on a specimen surface can be measured with high accuracy and with high spatial resolution. Moiré photography is combined with high speed photography to study specimens loaded at high strain rates. Dynamically loaded delamination cracks are studied and numerical finite element models show good agreement to the measured displacement fields. Measurements of the mechanical properties transverse to the fibres show that the composite has a weak dependence of strain rate. Apparent crack speeds of more than 2000 m/s are observed. The dynamic loading is made with a tensile split Hopkinson bar apparatus. Moiré interferometry is used to measure the displacement fields at high magnification. Here mode I loaded delamination cracks and strain concentrations at fibre optics sensors embedded in composites are studied, in both cases at static load. Finite element models have acceptable agreement with the measured results. Godkänd; 1997; 20061124 (haneit)

Godkänd; 1995; 20080330 (ysko)

We have studied the requirements for efficient histone-specific RNA 3' processing in nuclear extract from mammalian tissue culture cells. Processing is strongly impaired by mutations in the pre-mRNA spacer element that reduce the base-pairing potential with U7 RNA. Moreover, by exchanging the hairpin and spacer elements of two differently processed H4 genes, we find that this difference is exclusively due to the spacer element. Finally, processing is inhibited by the addition of competitor RNAs, if these contain a wild-type spacer sequence, but not if their spacer element is mutated. Conversely, the importance of the hairpin for histone RNA 3' processing is highly variable: A hairpin mutant of the H4-12 gene is processed with almost wild-type efficiency in extract from K21 mouse mastocytoma cells but is strongly affected in HeLa cell extract, whereas an identical hairpin mutant of the H4-1 gene is affected in both extracts. The hairpin defect of H4-12-specific RNA in HeLa cells can be overcome by a compensatory mutation that increases the base complementarity to U7 snRNA. Very similar results were also obtained in RNA competition experiments: processing of H4-12-specific RNA can be competed by RNA carrying a wild-type hairpin element in extract from HeLa, but not K21 cells, whereas processing of H4-1-specific RNA can be competed in both extracts. With two additional histone genes we obtained results that were in one case intermediate and in the other similar to those obtained with H4-1. These results suggest that hairpin binding factor(s) can cooperatively support the ability of U7 snRNPs to form an active processing complex, but is(are) not directly involved in the processing mechanism.

In this paper we are returning to the industrial field perspective which again bring to the fore the need for multilevel analyses in order to understand change and stability in industrial sectors. Our purpose is to deepen the understanding of structural change in industrial fields, through emphasizing the interplay between both different units of analysis and the combination of different theoretical approaches.