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- Blomström, Per, et al.
(författare)
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Pre- and intraoperative identification of multiple accessory pathways. Experience of 19 pathways in 9 patients
- 1989
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Ingår i: Cardiology. - : S. Karger AG. - 0008-6312 .- 1421-9751. ; 76:1, s. 42-52
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Tidskriftsartikel (refereegranskat)abstract
- The pre- and intraoperative electrophysiological studies in 9 patients with two or more accessory pathways are described. The presence of multiple accessory pathways was clinically suspected in only 2 patients. During the preoperative electrophysiological study two accessory pathways were identified in 7 patients and a single pathway in 2 patients. At operation, additionally three accessory pathways were identified in 3 patients. One out of two pathways, found preoperatively, could not be confirmed in 1 patient. It is concluded that the clinical or preoperative electrophysiological evidence of only one accessory pathway should not distract one's attention from considering multiple accessory pathways in patients presenting only one type of tachycardia.
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| 2. |
- Ekström, Thommy, et al.
(författare)
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Dense single-phase β-sialon ceramics by glass-encapsulated hot isostatic pressing
- 1989
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Ingår i: Journal of Materials Science. - 0022-2461. ; 24:5, s. 1853-1861
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Tidskriftsartikel (refereegranskat)abstract
- Single phase-sialon ceramics, Si6–z Al z O z N8–z , have been prepared from carefully balanced powder mixtures, also taking account of any excess oxygen in the starting materials. Sintering powder compacts in a nitrogen atmosphere (0.1 MPa) at 1800° C or higher transforms the starting mixture into a-sialon solid solution atz-values up to about 4.3, but the sintered material has an open porosity. Addition of 1 wt% Y2O3 to the starting mix improved the sintering behaviour somewhat and the density of the sintered compacts reached 95% of the theoretical value. By glass-encapsulated hot isostatic pressing at 1825° C, however, sintered materials of virtually theoretical density could be obtained, with or without the 1 wt% Y2O3 addition. These latter samples have been studied by X-ray diffraction and electron microscopy, and their hardness and indentation fracture toughness have been measured. It was found that the maximum extension of the-sialon phase composition at 1825° C and 200 MPa pressure is slightly below 4,z 3.85 and about 4.1 at atmospheric pressure, and that the hexagonal unit cell parameters are linear functions of thez-value. The single-phase-sialon ceramics had no residual glassy grain-boundary phase. The grain shape was equi-axed and the grain size increased from about 1m at lowz-values to 5m at highz-values. At lowz-values the hardness at a 98 N load was 1700 and the fracture toughness 3, whereas an increase inz above 1 caused both the hardness and fracture toughness to decrease significantly. Addition of 1 wt % Y2O3 to the starting mix prior to the HIP-sintering gave rise to a small amount of amorphous intergranular phase, changes in grain size and shape, a clear increase in fracture toughness and a moderate decrease in hardness.
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| 3. |
- Ekström, Thommy, et al.
(författare)
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Mixed α- and β-(Si-Al-O-N) Materials with Yttria and Neodymia Additions
- 1988
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 105/106, s. 161-168
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Tidskriftsartikel (refereegranskat)abstract
- A number of ceramic materials have been fabricated on a semipilot plant scale at different overall compositions in the (Y, Nd)---Al---O---N system at 177°C. Constant molar amounts of oxide mixtures of Y2O3: Nd2O3 in the ratios 100:0, 75:25, 50:50, 25:75 or 0:100 have been added. Dense materials were obtained for all compositions except those corresponding to mixed α- and β-(Si---Al---O---N) with higher α-(Si---Al---O---N) contents and high Nd2O3 contents. At the preparation temperature used in this study, the formation of an α-(Nd---Si---Al---O---N) seems prohibited and, thus, with increasing Nd2O3 content the amount of α-(Si---Al---O---N) decreased. The Nd2O3 added mainly formed crystalline intergranular phases such as the N-melilite phase, which increased in amount with increasing Nd2O3 in the starting mix. Hardness and indentation fracture toughness measurements were made and are discussed in relation to the phase composition and the microstructure. Some of the high Nd2O3 content Si---Al---O---N materials have as high fracture toughness values as the pure Y2O3 Si---Al---O---N materials do.
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| 5. |
- Brechensbauer Brandin, Madeleine, et al.
(författare)
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Centralen : Studier i området kring Stockholms Centralstation
- 1989
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Rapport (populärvet., debatt m.m.)abstract
- Denna skrift handlar om Centralen i Stockholm och dess närmaste omgivningar, Centralplan, T-centralen, Vasagatan och Klarabergsgatan. Den är resultatet av Arkitekturskolans arbete läsåret 1983- 84 och innehåller förutom en rad projekt också historiska utblickar och samtidskritiska resonemang. En stor del av innehållet redovisades redan våren 1984 - det skedde genom en utställning på Arkitekturmuseet och en preliminär publikation. Materialet har sedan svällt ut med innehållsrika uppsatser om Centralen, om äldre och nyare insatser för att förena konst och arkitektur och om den föga kända, ännu obebyggda Blekholmen.
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