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- Dahl, P., et al.
(author)
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Densification and properties of zirconia prepared by three different sintering techniques
- 2007
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In: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 33:8, s. 1603-1610
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Journal article (peer-reviewed)abstract
- Densification of nanocrystalline yttria stabilized zirconia (YSZ) powder with 8 mol% Y2O3, prepared by a glycine/nitrate smoldering combustion method, was investigated by spark plasma sintering, hot pressing and conventional sintering. The spark plasma sintering technique was shown to be superior to the other methods giving dense materials (>= 96%) with uniform morphology at lower temperatures and shorter sintering time. The grain size of the materials was 0.21, 0.37 and 12 mu m after spark plasma sintering, hot pressing and conventional sintering, respectively. Total electrical conductivity of the materials showed no clear correlation with the grain size, but the activation energy for spark plasma sintered materials was slightly higher than for materials prepared by the two other densification methods. The hardness, measured by the Vickers indentation method, was found to be independent on grain size while fracture toughness, derived by the indentation method, was slightly decreasing with increasing grain size.
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| 2. |
- Wiik, A, et al.
(author)
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Activation of estrogen response elements is mediated both via estrogen and muscle contractions in rat skeletal muscle myotubes
- 2009
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In: American journal of physiology. Cell physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 296:1, s. C215-C220
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Journal article (peer-reviewed)abstract
- The aim of the present study was to investigate the activation of estrogen response elements (EREs) by estrogen and muscle contractions in rat myotubes in culture and to assess whether the activation is dependent on the estrogen receptors (ERs). In addition, the effect of estrogen and contraction on the mRNA levels of ERα and ERβ was studied to determine the functional consequence of the transactivation. Myoblasts were isolated from rat skeletal muscle and transfected with a vector consisting of sequences of EREs coupled to the gene for luciferase. The transfected myoblasts were then differentiated into myotubes and subjected to either estrogen or electrical stimulation. Activation of the ERE sequence was determined by measurement of luciferase activity. The results show that both ERα and ERβ are expressed in myotubes from rats. Both estrogen stimulation and muscle contraction increased ( P < 0.05) transactivation of the ERE sequence and enhanced ERβ mRNA, whereas ERα was unaffected by estrogen and attenuated ( P < 0.05) by muscle contraction. Use of ER antagonists showed that, whereas the estrogen-induced transactivation is mediated via ERs, the effect of muscle contraction is ER independent. The muscle contraction-induced transactivation of ERE and increase in ERβ mRNA were instead found to be MAP kinase (MAPK) dependent. This study demonstrates for the first time that muscle contractions have a similar functional effect as estrogen in skeletal muscle myotubes, causing ERE activation and an enhancement in ERβ mRNA. However, in contrast to estrogen, the effect is independent of ERs and dependent on MAPK, suggesting activation via the estrogen related receptor (ERR).
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| 3. |
- Wiik, A. C., et al.
(author)
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A population study of a mutation allele associated with cone-rod dystrophy in the standard wire-haired dachshund
- 2009
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In: Animal Genetics. - : Wiley. - 0268-9146 .- 1365-2052. ; 40:4, s. 572-574
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Journal article (peer-reviewed)abstract
- Cone-rod dystrophy in the standard wire-haired dachshund (SWHD) is inherited as a simple autosomal recessive trait and the recently discovered mutation is widespread within the SWHD population in Norway and other Scandinavian countries. The gene frequency was estimated to be 4.8%. On the basis of the assumption that the size of the ancestral haplotype around a mutation is inversely correlated with the number of generations since the mutation arose, we have found that the mutation is of a relatively recent origin. The conserved haplotype was found to be 8 Mb in size and therefore we estimate that the mutation arose roughly eight generations (approximately 37 years) ago. This indicates that the mutation arose after breed separation.
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