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- Holst, Anders, et al.
(författare)
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Heat transfer augmentation in an oscillating flow
- 2002
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Ingår i: American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD. - 0272-5673. ; 372:2, s. 89-93
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Konferensbidrag (refereegranskat)abstract
- For combustors a heat transfer augmentation of two to five times higher than expected has been reported. Experiments, where the temperature profile in the tail pipe of the pulse combustor has been measured, give no indication why the heat transfer should be augmented. The objective is to study the heat transfer of an oscillating flow between two parallel plates. A set of governing equations is formulated from first principles. Analytical solutions can then be obtained for both the velocity and temperature fields for the special flow considered. The heat conduction vector can so be determined and the heat transfer at the plates over one cycle is found to be dependent of the frequency of the oscillations as well as the phase difference between the pressure and temperature oscillations. From the analysis it is found that for certain intervals of the phase difference and the frequency of the oscillations an augmented heat transfer can be found. This means that an augmented heating (or cooling) process can be arranged in a steady flow by superimposing oscillations.
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- Mårtensson, Olof, et al.
(författare)
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Effects of fermented, ropy, non-dairy, oat-based products on serum lipids and the faecal excretion of cholesterol and short chain fatty acids in germfree and conventional rats
- 2002
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Ingår i: Nutrition Research. - 0271-5317. ; 22:12, s. 1461-1473
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Tidskriftsartikel (refereegranskat)abstract
- Three fermented, ropy, non-dairy, oat-based products were evaluated for their effect on serum lipids, faecal cholesterol and faecal short chain fatty. acids in germfree and conventional rats. Three different exopolysaccharide (EPS) producing lactic acid bacteria strains were used to ferment the non-dairy oat-base (Adavena(R) G40) (Ceba Foods AB, Lund; Sweden). Two commercial non-dairy products based on oats (Mill Milk(TM)) (Ceba Foods AB, Lund, Sweden) and rice (Rice Dream(R)) (Imagine Foods, London, UK) were used as non-ropy and unfermented controls. All the standardized feeds were sterilized before being fed to the animals. Adult, germfree-and conventional AGUS rats, were fed the above sterile diets ad libitum for 21 days. Blood samples and faecal samples were collected and the animals' weight gain was monitored throughout the study. No significant change in serum lipids or faecal excretion of cholesterol was observed between the groups on the different diets. A difference in faecal SCFA pattern was observed in conventional rats fed on the oat-based diets in comparison. to the group fed on the rice-based diet. More evidence is needed to support the effect of fermented, ropy, oat-based products and their potential effect on serum lipids, faecal cholesterol/coprostanol levels and amounts of short chain fatty acids.
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- Wicher, K. B., et al.
(författare)
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Deletion of a cytotoxic, N-terminal putative signal peptide results in a significant increase in production yields in Escherichia coli and improved specific activity of Cel12A from Rhodothermus marinus
- 2001
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 55:5, s. 578-584
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Tidskriftsartikel (refereegranskat)abstract
- The thermostable cellulase Cel12A from Rhodothermus marinus was produced at extremely low levels when expressed in Escherichia coli and was cytotoxic to the cells. In addition, severe aggregation occurred when moderately high concentrations of the enzyme were heat-treated at 65°C, the growth optimum of R. marinus. Sequence analysis revealed that the catalytic module of this enzyme is preceded by a typical linker sequence and a highly hydrophobic putative signal peptide. Two deletion mutants lacking this hydrophobic region were cloned and successfully expressed in E. coli. These results indicated that the N-terminal putative signal peptide was responsible for the toxicity of the full-length enzyme in the host organism. This was further corroborated by cloning and expressing the hydrophobic N-terminal domain in E. coli, which resulted in extensive cell lysis. The deletion mutants, made up of either the catalytic module of Cel12A or the catalytic module and the putative linker sequence, were characterised and their properties compared to those of the full-length enzyme. The specific activity of the mutants was approximately threefold higher than that of the full-length enzyme. Both mutant proteins were highly thermostable, with half-lives exceeding 2 h at 90°C and unfolding temperatures up to 103°C.
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