| 1. |
- Hillier, Ladeana W, et al.
(författare)
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Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution
- 2004
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 432:7018, s. 695-716
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Tidskriftsartikel (refereegranskat)abstract
- We present here a draft genome sequence of the red jungle fowl, Gallus gallus. Because the chicken is a modern descendant of the dinosaurs and the first non-mammalian amniote to have its genome sequenced, the draft sequence of its genome--composed of approximately one billion base pairs of sequence and an estimated 20,000-23,000 genes--provides a new perspective on vertebrate genome evolution, while also improving the annotation of mammalian genomes. For example, the evolutionary distance between chicken and human provides high specificity in detecting functional elements, both non-coding and coding. Notably, many conserved non-coding sequences are far from genes and cannot be assigned to defined functional classes. In coding regions the evolutionary dynamics of protein domains and orthologous groups illustrate processes that distinguish the lineages leading to birds and mammals. The distinctive properties of avian microchromosomes, together with the inferred patterns of conserved synteny, provide additional insights into vertebrate chromosome architecture.
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| 2. |
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| 3. |
- Bower, K. N., et al.
(författare)
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ACE-2 HILLCLOUD. An overview of the ACE-2 ground-based cloud experiment
- 2000
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509. ; 52:2, s. 750-778
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Tidskriftsartikel (refereegranskat)abstract
- The ACE-2 HILLCLOUD experiment was carried out on the island of Tenerife in June-July 1997 to investigate the interaction of the boundary layer aerosol with a hill cap cloud forming over a ridge to the north-east of the island. The cloud was used as a natural flow through reactor to investigate the dependence of the cloud microphysics and chemistry on the characteristics of the aerosols and trace gases entering cloud, and to simultaneously study the influence of the physical and chemical processes occurring within the cloud on the size distribution, chemical and hygroscopic properties of the aerosol exiting cloud. 5 major ground base sites were used, measuring trace gases and aerosols upwind and downwind of the cloud, and cloud microphysics and chemistry and interstitial aerosol and gases within the cloud on the hill. 8 intensive measurement periods or runs were undertaken during cloud events, (nocturnally for seven of the eight runs) and were carried out in a wide range of airmass conditions from clean maritime to polluted continental. Polluted air was characterised by higher than average concentrations of ozone (> 50 ppbv), fine and accumulation mode aerosols (> 3000 and > 1500 cm -3 , respectively) and higher aerosol mass loadings. Cloud droplet number concentrations N, increased from 50 cm -3 in background maritime air to > 2500 cm -3 in aged polluted continental air, a concentration much higher than had previously been detected. Surprisingly, N was seen to vary almost linearly with aerosol number across this range. The droplet aerosol analyser (DAA) measured higher droplet numbers than the corrected forward scattering spectrometer probe (FSSP) in the most polluted air, but at other times there was good agreement (FSSP = 0.95 DAA with an r 2 = 0.89 for N < 1200 cm -3 ). Background ammonia gas concentrations were around 0.3 ppbv even in air originating over the ocean, another unexpected but important result for the region. NO 2 was present in background concentrations of typically 15 pptv to 100 pptv and NO 3 . (the nitrate radical) was observed at night throughout. Calculations suggest NO 3 . losses were mainly by reaction with DMS to produce nitric acid. Low concentrations of SO 2 (~30 pptv), HNO 3 and HCl were always present. HNO 3 concentrations were higher in polluted episodes and calculations implied that these exceeded those which could be accounted for by NO 2 oxidation. It is presumed that nitric and hydrochloric acids were present as a result of outgassing from aerosol, the HNO 3 from nitrate rich aerosol transported into the region from upwind of Tenerife, and HCl from sea salt aerosol newly formed at the sea surface. The oxidants hydrogen peroxide and ozone were abundant (i.e., were well in excess over SO 2 throughout the experiment). Occasions of significant aerosol growth following cloud processing were observed, particularly in cleaner cases. Observations and modelling suggested this was due mainly to the take up of nitric acid, hydrochloric acid and ammonia by the smallest activated aerosol particles. On a few occasions a small contribution was made by the in-cloud oxidation of S(IV). The implications of these results from HILLCLOUD for the climatologically more important stratocumulus Marine Boundary Layer (MBL) clouds are considered.
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| 4. |
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| 5. |
- Li, Jian-Liang, et al.
(författare)
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A genome scan for modifiers of age at onset in Huntington disease : The HD MAPS study.
- 2003
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 73:3, s. 682-7
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Tidskriftsartikel (refereegranskat)abstract
- Huntington disease (HD) is caused by the expansion of a CAG repeat within the coding region of a novel gene on 4p16.3. Although the variation in age at onset is partly explained by the size of the expanded repeat, the unexplained variation in age at onset is strongly heritable (h2=0.56), which suggests that other genes modify the age at onset of HD. To identify these modifier loci, we performed a 10-cM density genomewide scan in 629 affected sibling pairs (295 pedigrees and 695 individuals), using ages at onset adjusted for the expanded and normal CAG repeat sizes. Because all those studied were HD affected, estimates of allele sharing identical by descent at and around the HD locus were adjusted by a positionally weighted method to correct for the increased allele sharing at 4p. Suggestive evidence for linkage was found at 4p16 (LOD=1.93), 6p21-23 (LOD=2.29), and 6q24-26 (LOD=2.28), which may be useful for investigation of genes that modify age at onset of HD.
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| 6. |
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| 7. |
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| 8. |
- Djoussé, Luc, et al.
(författare)
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Evidence for a modifier of onset age in Huntington disease linked to the HD gene in 4p16.
- 2004
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Ingår i: Neurogenetics. - : Springer Science and Business Media LLC. - 1364-6745 .- 1364-6753. ; 5:2, s. 109-14
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Tidskriftsartikel (refereegranskat)abstract
- Huntington disease (HD) is a neurodegenerative disorder caused by the abnormal expansion of CAG repeats in the HD gene on chromosome 4p16.3. A recent genome scan for genetic modifiers of age at onset of motor symptoms (AO) in HD suggests that one modifier may reside in the region close to the HD gene itself. We used data from 535 HD participants of the New England Huntington cohort and the HD MAPS cohort to assess whether AO was influenced by any of the three markers in the 4p16 region: MSX1 (Drosophila homeo box homologue 1, formerly known as homeo box 7, HOX7), Delta2642 (within the HD coding sequence), and BJ56 ( D4S127). Suggestive evidence for an association was seen between MSX1 alleles and AO, after adjustment for normal CAG repeat, expanded repeat, and their product term (model P value 0.079). Of the variance of AO that was not accounted for by HD and normal CAG repeats, 0.8% could be attributed to the MSX1 genotype. Individuals with MSX1 genotype 3/3 tended to have younger AO. No association was found between Delta2642 (P=0.44) and BJ56 (P=0.73) and AO. This study supports previous studies suggesting that there may be a significant genetic modifier for AO in HD in the 4p16 region. Furthermore, the modifier may be present on both HD and normal chromosomes bearing the 3 allele of the MSX1 marker.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Pace, Michael L., et al.
(författare)
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Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs
- 2004
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 427:6971, s. 240-243
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent influences on population dynamics, predator-prey relationships and ecosystem processes(1). For example, exogenous inputs provide resources that may enhance consumer abundance beyond levels supported by within-system primary production(2). Exogenous fluxes of organic carbon to ecosystems are often large, but this material is recalcitrant and difficult to assimilate, in contrast to endogenously produced organic matter, which is used more easily(3,4). Here we show, by the experimental manipulation of dissolved inorganic C-13 in two lakes, that internal primary production is insufficient to support the food webs of these ecosystems. Additions of NaH (CO3)-C-13 enriched the C-13 content of dissolved inorganic carbon, particulate organic carbon, zooplankton and fish. Dynamics of C-13 indicate that 40-55% of particulate organic carbon and 22-50% of zooplankton carbon are derived from terrestrial sources, showing that there is significant subsidy of these ecosystems by organic carbon produced outside their boundaries.
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| 14. |
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| 15. |
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| 16. |
- Aspholm-Hurtig, Marina, et al.
(författare)
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Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin.
- 2004
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 305:5683, s. 519-22
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Tidskriftsartikel (refereegranskat)abstract
- Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations.
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| 17. |
- Carpten, JD, et al.
(författare)
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HRPT2, encoding parafibromin, is mutated in hyperparathyroidism-jaw tumor syndrome
- 2002
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 32:4, s. 676-680
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Tidskriftsartikel (refereegranskat)abstract
- We report here the identification of a gene associated with the hyperparathyroidism-jaw tumor (HPT-JT) syndrome. A single locus associated with HPT-JT (HRPT2) was previously mapped to chromosomal region 1q25-q32. We refined this region to a critical interval of 12 cM by genotyping in 26 affected kindreds. Using a positional candidate approach, we identified thirteen different heterozygous, germline, inactivating mutations in a single gene in fourteen families with HPT-JT. The proposed role of HRPT2 as a tumor suppressor was supported by mutation screening in 48 parathyroid adenomas with cystic features, which identified three somatic inactivating mutations, all located in exon 1. None of these mutations were detected in normal controls, and all were predicted to cause deficient or impaired protein function. HRPT2 is a ubiquitously expressed, evolutionarily conserved gene encoding a predicted protein of 531 amino acids, for which we propose the name parafibromin. Our findings suggest that HRPT2 is a tumor-suppressor gene, the inactivation of which is directly involved in predisposition to HPT-JT and in development of some sporadic parathyroid tumors.
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| 18. |
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| 19. |
- Godl, Klaus, et al.
(författare)
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The N terminus of the MUC2 mucin forms trimers that are held together within a trypsin-resistant core fragment.
- 2002
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Ingår i: The Journal of biological chemistry. - 0021-9258 .- 1083-351X. ; 277:49, s. 47248-56
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Tidskriftsartikel (refereegranskat)abstract
- The N terminus of the human MUC2 mucin (amino acids 1-1397) has been expressed as a recombinant tagged protein in Chinese hamster ovary cells. The intracellular form was found to be an endoglycosidase H-sensitive monomer, whereas the secreted form was an oligomer that gave monomers upon disulfide bond reduction. The secreted MUC2 N terminus contained a trypsin-resistant core fragment. Edman sequencing and mass spectrometry of the peptides obtained localized this core fragment to the C-terminal end of the recombinant protein. This core retained its oligomeric nature with an apparent mass of approximately 240 kDa. Upon reduction, peptides of approximately 85 kDa were found, suggesting that the N terminus forms trimers. This interpretation was also supported by gel electrophoresis and gel filtration of the intact MUC2 N terminus. Electron microscopy revealed three globular domains each linked via an extended and flexible region to a central part in a trefoil-like manner. Immunostaining with gold-labeled antibodies localized the N-terminal end to the three globular structures, and the antibodies directed against the Myc and green fluorescent protein tags attached at the C terminus localized these to the stalk side of the central trefoil. The N terminus of the MUC2 mucin is thus assembled into trimers that contain proteolytically stable parts, suggesting that MUC2 can only be partly degraded by intestinal proteases and thus is able to maintain a mucin network protecting the intestine.
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| 20. |
- Golriz, Mohammad R., et al.
(författare)
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Mass transport inside a flowing electrolyte direct methanol fuel cell
- 2004
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Ingår i: ASME 2004 2nd International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL 2004. - : American Society of Mechanical Engineers (ASME). - 0791841650 - 9780791841655 ; , s. 107-112
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Konferensbidrag (refereegranskat)abstract
- In this work, analytical mass transfer models are developed for two different types of Direct Methanol Fuel Cells (DMFCs). One type is a conventional assembly with a proton exchange membrane (PEM) and the other utilizes a flowing electrolyte in addition to a PEM to reduce methanol crossover. These models are used to predict methanol crossover behaviour that is a major issue affecting the efficiencies of PEM-DMFCs. It is shown that using flowing electrolyte DMFCs can lead to a significant decrease in methanol crossover with a corresponding increase in electrical efficiency of the cell. Combined with the experiments carried out in a previous work, the simulation showed significant efficiency improvements when using a flowing electrolyte DMFC compared to a traditional PEM assembly.
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| 21. |
- Gröbner, Gerhard, et al.
(författare)
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Observations of light-induced structural changes of retinal within rhodopsin
- 2000
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 405, s. 810-3
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Tidskriftsartikel (refereegranskat)abstract
- Photo-isomerization of the 11-cis retinal chromophore activates the mammalian light-receptor rhodopsin1, a representative member of a major superfamily of transmembrane G-protein-coupled receptor proteins (GPCRs) responsible for many cell signal communication pathways. Although low-resolution (5 Å) electron microscopy studies2, 3 confirm a seven transmembrane helix bundle as a principal structural component of rhodopsin, the structure of the retinal within this helical bundle is not known in detail. Such information is essential for any theoretical or functional understanding of one of the fastest occurring photoactivation processes in nature, as well as the general mechanism behind GPCR activation4, 5, 6. Here we determine the three-dimensional structure of 11-cis retinal bound to bovine rhodopsin in the ground state at atomic level using a new high-resolution solid-state NMR method7. Significant structural changes are observed in the retinal following activation by light to the photo-activated MI state of rhodopsin giving the all-trans isomer of the chromophore. These changes are linked directly to the activation of the receptor, providing an insight into the activation mechanism of this class of receptors at a molecular level.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Helgesson, Johan, et al.
(författare)
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Finite Size scaling and the nuclear liquid-gas phase transition
- 2003
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Konferensbidrag (refereegranskat)abstract
- Recent analyses of multifragmentation data in terms of Fisher's model have led to the estimate of the coexistence curve of finite nuclear matter as well as of the location of the critical point. In order to extrapolate those results to infinite nuclear matter, finite size effects have to be taken into account. Guided by the finite size behavior of the three-dimensional Ising model, we propose a modified Fisher Droplet model expression that incorporates surface and correlation length effects.
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Jonsson, Ulf J., et al.
(författare)
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Design of seal cavities in refrigeration compressors
- 2000
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Ingår i: Proceedings of the 2000 International Compressor Engineering Conference at Purdue : July 25 - 28, 2000, Purdue University, West Lafayette, Indiana, USA. ; , s. 193-200
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Konferensbidrag (refereegranskat)
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| 30. |
- Karpman, Diana, et al.
(författare)
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Antibodies to intimin and Escherichia coli secreted proteins A and B in patients with enterohemorrhagic Escherichia coli infections
- 2002
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Ingår i: Pediatric Nephrology. - : Springer Science and Business Media LLC. - 1432-198X .- 0931-041X. ; 17:3, s. 201-211
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Tidskriftsartikel (refereegranskat)abstract
- Enterohemorrhagic Escherichia coli produce an attaching and effacing lesion upon adhering to the intestinal epithelium. Bacterial factors involved in this histopathology include the intimin adhesin and E. coli secreted proteins (Esps) A and B. In this study we investigated the serum antibody responses to recombinant E. coli O157:H7 intimin, EspA, and EspB by immuno-blotting. Canadian patients with O157:H7 infection (n=10), Swedish patients with 0157:H7 (n=21), non-O157 (n=18), or infection from which the serotype was not available (n=3), and asymptomatic household members (n=25) were studied and compared with Canadian (n=20) and Swedish controls (n=52). In Canadian patients, IgG antibodies to intimin, EspA, and EspB were analyzed, in Swedish patients and their household members I-A, IgG, and IgM antibodies to EspA and EspB were studied. Patients and household members mounted an antibody response to the antigens. Significantly more patients developed an acute response to EspB compared with controls (P<0.01 Canadian patients, P<0.0001 Swedish patients). EspB IgA, IgG, and IgM had a specificity of 100%, 86%, and 86%, positive predictive value of 100%, 83%, and 81%, and sensitivity of 57%, 69%, and 63%, respectively, and appear to be an appropriate assay for the detection of EHEC infection. In cases of hemolytic uremic syndrome or hemorrhagic colitis this assay may be useful when a fecal strain has not been isolated, or in epidemics of non-O157 infection.
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| 31. |
- Kullander, Klas, et al.
(författare)
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Role of EphA4 and EphrinB3 in local neuronal circuits that control walking
- 2003
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 299:5614, s. 1889-1892
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Tidskriftsartikel (refereegranskat)abstract
- Local circuits in the spinal cord that generate locomotion are termed central pattern generators (CPGs). These provide coordinated bilateral control over the normal limb alternation that underlies walking. The molecules that organize the mammalian CPG are unknown. Isolated spinal cords from mice lacking either the EphA4 receptor or its ligand ephrinB3 have lost left-right limb alternation and instead exhibit synchrony. We identified EphA4-positive neurons as an excitatory component of the locomotor CPG. Our study shows that dramatic locomotor changes can occur as a consequence of local genetic rewiring and identifies genes required for the development of normal locomotor behavior.
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| 32. |
- Kumar, Sunil J., et al.
(författare)
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A simple method for synthesis of organotin species to investigate extraction procedures in sediments by isotope dilution-gas chromatography-inductively coupled plasma mass spectrometry : Part 2. Phenyltin species
- 2004
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Ingår i: Journal of Analytical Atomic Spectrometry. - London : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 19:3, s. 368-372
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Tidskriftsartikel (refereegranskat)abstract
- A rapid method for the synthesis of phenyltin species based on the phenylation of tin iodide was developed and a standard of 124Sn, enriched monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT) was produced. Isotope enriched species were added to and equilibrated with the certified reference material BCR 646 to evaluate different extraction procedures currently in use for the determination of organic tin species in sediments. Samples were measured by gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS) with species specific isotope dilution (SSID) calibration. For TPhT measurement results agreed with the certified values for extraction methods using tropolone in diethyl ether alone or in the presence of NaCl and HCl as well as with 50% HBr. However, with 50% HBr, concentrations obtained for DPhT and MPhT were above the upper limit (2) of the certification. The stability of phenyltin species was studied by comparing their signal magnitudes in spike solutions generated directly after derivatisation with those obtained after applying the extraction–derivatisation procedures. Degradation of phenyltin species was matrix dependent and appeared for most of the extraction methods investigated. For water standards and BCR 646, extraction with methanol combined with dichloromethane or methanol combined with acetic acid gave no degradation when applied with less than 20 min ultrasonication. Extraction efficiencies for these two methods were however low for the BCR 646 matrix, in particular for DPhT and MPhT.
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| 33. |
- Kuo, Jer-Lai, et al.
(författare)
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On the use of graph invariants for efficiently generating hydrogen bond topologies and predicting physical properties of water clusters and ice
- 2001
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 114:6, s. 2527-2540
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Tidskriftsartikel (refereegranskat)abstract
- Water clusters and some phases of ice are characterized by many isomers with similar oxygen positions, but which differ in direction of hydrogen bonds. A relationship between physical properties, like energy or magnitude of the dipole moment, and hydrogen bond arrangements has long been conjectured. The topology of the hydrogen bond network can be summarized by oriented graphs. Since scalar physical properties like the energy are invariant to symmetry operations, graphical invariants are the proper features of the hydrogen bond network which can be used to discover the correlation with physical properties. We demonstrate how graph invariants are generated and illustrate some of their formal properties. It is shown that invariants can be used to change the enumeration of symmetry-distinct hydrogen bond topologies, nominally a task whose computational cost scales like N2, where N is the number of configurations, into an N ln N process. The utility of graph invariants is confirmed by considering two water clusters, the (H2O)6 cage and (H2O)20 dodecahedron, which, respectively, possess 27 and 30 026 symmetry-distinct hydrogen bond topologies associated with roughly the same oxygen atom arrangements. Physical properties of these clusters are successfully fit to a handful of graph invariants. Using a small number of isomers as a training set, the energy of other isomers of the (H2O)20 dodecahedron can even be estimated well enough to locate phase transitions. Some preliminary results for unit cells of ice-Ih are given to illustrate the application of our results to periodic systems.
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| 34. |
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| 35. |
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| 36. |
- Levander, Fredrik, et al.
(författare)
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Automated methods for improved protein identification by peptide mass fingerprinting
- 2004
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Ingår i: Proteomics. - Weinheim : Wiley. - 1615-9861 .- 1615-9853. ; 4:9, s. 2594-2601
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Tidskriftsartikel (refereegranskat)abstract
- In order to maximize protein identification by peptide mass fingerprinting noise peaks must be removed from spectra and recalibration is often required. The preprocessing of the spectra before database searching is essential but is time-consuming. Nevertheless, the optimal database search parameters often vary over a batch of samples. For high-throughput protein identification, these factors should be set automatically, with no or little human intervention. In the present work automated batch filtering and recalibration using a statistical filter is described. The filter is combined with multiple data searches that are performed automatically. We show that, using several hundred protein digests, protein identification rates could be more than doubled, compared to standard database searching. Furthermore, automated large-scale in-gel digestion of proteins with endoproteinase LysC, and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis, followed by subsequent trypsin digestion and MALDI-TOF analysis were performed. Several proteins could be identified only after digestion with one of the enzymes, and some less significant protein identifications were confirmed after digestion with the other enzyme. The results indicate that identification of especially small and low-abundance proteins could be significantly improved after sequential digestions with two enzymes.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
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| 41. |
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| 42. |
- Peng, Hong, 1970-
(författare)
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Spark Plasma Sintering of Si3N4-based Ceramics : Sintering mechanism-Tailoring microstructure-Evaluationg properties
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spark Plasma Sintering (SPS) is a promising rapid consolidation technique that allows a better understanding and manipulating of sintering kinetics and therefore makes it possible to obtain Si3N4-based ceramics with tailored microstructures, consisting of grains with either equiaxed or elongated morphology. The presence of an extra liquid phase is necessary for forming tough interlocking microstructures in Yb/Y-stabilised α-sialon by HP. The liquid is introduced by a new method, namely by increasing the O/N ratio in the general formula RExSi12-(3x+n)Al3x+nOnN16-n while keeping the cation ratios of RE, Si and Al constant. Monophasic α-sialon ceramics with tailored microstructures, consisting of either fine equiaxed or elongated grains, have been obtained by using SPS, whether or not such an extra liquid phase is involved. The three processes, namely densification, phase transformation and grain growth, which usually occur simultaneously during conventional HP consolidation of Si3N4-based ceramics, have been precisely followed and separately investigated in the SPS process.The enhanced densification is attributed to the non-equilibrium nature of the liquid phase formed during heating. The dominating mechanism during densification is the enhanced grain boundary sliding accompanied by diffusion- and/or reaction-controlled processes. The rapid grain growth is ascribed to a dynamic ripening mechanism based on the formation of a liquid phase that is grossly out of equilibrium, which in turn generates an extra chemical driving force for mass transfer. Monophasic α-sialon ceramics with interlocking microstructures exhibit improved damage tolerance. Y/Yb- stabilised monophasic α-sialon ceramics containing approximately 3 vol% liquid with refined interlocking microstructures have excellent thermal-shock resistance, comparable to the best β-sialon ceramics with 20 vol% additional liquid phase prepared by HP. The obtained sialon ceramics with fine-grained microstructure show formidably improved superplasticity in the presence of an electric field. The compressive strain rate reaches the order of 10-2 s-1 at temperatures above 1500oC, that is, two orders of magnitude higher than that has been realised so far by any other conventional approaches. The high deformation rate recorded in this work opens up possibilities for making ceramic components with complex shapes through super-plastic forming.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Sigfrid, Louise A., et al.
(författare)
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Antioxidant enzyme activity and mRNA expression in islets of Langerhans from the BB/S rat model of type 1 diabetes and an insulin-producing cell line
- 2004
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Ingår i: Journal of Molecular Medicine. - : Springer. - 0946-2716 .- 1432-1440. ; 82:5, s. 325-335
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Tidskriftsartikel (refereegranskat)abstract
- It has been proposed that low activities of antioxidant enzymes in pancreatic beta cells may increase their susceptibility to autoimmune attack. We have therefore used the spontaneously diabetic BB/S rat model of type 1 diabetes to compare islet catalase and superoxide dismutase activities in diabetes-prone and diabetes-resistant animals. In parallel studies, we employed the RINm5F beta cell line as a model system (previously validated) to investigate whether regulation of antioxidant enzyme activity by inflammatory mediators (cytokines, nitric oxide) occurs at the gene or protein expression level. Diabetes-prone rat islets had high insulin content at the age used (58–65 days) but showed increased amounts of DNA damage when subjected to cytokine or hydrogen peroxide treatments. There was clear evidence of oxidative damage in freshly isolated rat islets from diabetes-prone animals and significantly lower catalase and superoxide dismutase activities than in islets from age-matched diabetes-resistant BB/S and control Wistar rats. The mRNA expression of antioxidant enzymes in islets from diabetes-prone and diabetes-resistant BB/S rats and in RINm5F cells, treated with a combination of cytokines or a nitric oxide donor, DETA-NO, was analysed semi-quantitatively by real time PCR. The mRNA expression of catalase was lower, whereas MnSOD expression was higher, in diabetes-prone compared to diabetes-resistant BB/S rat islets, suggesting regulation at the level of gene expression as well as of the activities of these enzymes in diabetes. The protein expression of catalase, CuZnSOD and MnSOD was assessed by Western blotting and found to be unchanged in DETA-NO treated cells. Protein expression of MnSOD was increased by cytokines in RINm5F cells whereas the expression of CuZnSOD was slightly decreased and the level of catalase protein was unchanged. We conclude that there are some changes, mostly upregulation, in protein expression but no decreases in the mRNA expression of catalase, CuZnSOD or MnSOD enzymes in beta cells treated with either cytokines or DETA-NO. The lower antioxidant enzyme activities observed in islets from diabetes-prone BB/S rats could be a factor in the development of disease and in susceptibility to DNA damage in vitro and could reflect islet alterations prior to immune attack or inherent differences in the islets of diabetes-prone animals, but are not likely to result from cytokine or nitric oxide exposure in vivo at that stage.
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| 47. |
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| 48. |
- Szita, S., Fazakerley, A.N., Carter, P.J., James, A.M., Travnicek, P., Watson, G., André, M., Ericsson, A. and Torkar, K.
(författare)
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Cluster PEACE observations of electrons of spacecraft.
- 2001
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Ingår i: Annales Geophysicae. ; 19, s. 1721-1730
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Tidskriftsartikel (refereegranskat)abstract
- The two PEACE (Plasma Electron And Current Experiment) sensors onboard each Cluster spacecraft sample the electron velocity distribution across the full 4 ¡ solid angle and the energy range 0.7eV to 26keV with a time resolution of 4 sec-onds. We present h
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| 49. |
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| 50. |
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