| 11. |
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Qvarford, M, et al.
(författare)
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Photoemission and x-ray absorption study of superconducting and semiconducting Ba1-xKxBiO3 single crystals
- 1996
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 54:9, s. 6700-6707
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Tidskriftsartikel (refereegranskat)abstract
- Semiconducting Ba0.9K0.1BiO3 and superconducting Ba0.6K0.4BiO3 single crystals cleaved in situ have been studied by core level and valence band photoelectron spectroscopy and O K edge x-ray absorption spectroscopy. It was found that the general shape of the valence band spectrum agrees with the shape predicted by band structure calculations, but the intensity near the Fermi level, was lower in the experimental spectrum as compared to the calculated. The O K edge spectra showed that the metallic phase is not related to the presence of doping inducted O 2p holes. This property of Ba1-xKxBiO3 shows that the semiconductor-metal transition of this system is of a different nature than that of the hole doped cuprate high-T-c superconductors. The core level photoemission spectra of the cations showed a small asymmetry for Ba0.9K0.1BiO3. Corresponding spectra for Ba0.6K0.4BiO3 showed a larger asymmetry resulting in a resolved high binding energy shoulder in the Bi 4f spectrum. The origin of this feature is discussed.
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| 16. |
- Alexandersen, V, et al.
(författare)
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Aspects of teeth from archaelogic sites in Sweden and Denmark.
- 1998
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Ingår i: Acta odontologica Scandinavica. - : Informa UK Limited. - 0001-6357 .- 1502-3850. ; 56:1, s. 14-9
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to examine ground sections of primary second molars and permanent first molars from the same jaws. Teeth from 11 individuals were collected from archaeologic sites in Sweden and Denmark. Longitudinal buccolingual sections were examined in a polarization light microscope and in a Philips scanning electron microscope (SEM). The seven teeth from Sweden appeared to have been subjected to environmental influences at their burial site, which had affected both the dentin and the enamel. The teeth from the Danish sites had a normal color, and no disintegration of the dentin was seen. The general morphologic appearance was normal in all primary and permanent teeth. The position of the neonatal line indicated a normal full-term gestational age. The observed accentuated incremental lines in both the primary and permanent enamel suggested periods of dietary changes, possibly related to periods of illness. SEM images of the surface area of the Swedish teeth showed an extremely porous enamel surface with severe changes in the prism structure as an effect of acid penetration. The Danish teeth did not show any marked changes in the enamel.
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| 17. |
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| 18. |
- Aronson, Dag, 1959, et al.
(författare)
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A Shear-Free Turbulent Boundary Layer - Experiments and Modeling
- 1997
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Ingår i: Journal of Fluid Mechanics. ; 338, s. 363-385
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Tidskriftsartikel (refereegranskat)abstract
- The mean shear has a major influence on near-wall turbulence but there are also other important physical processes at work in the turbulence/wall interaction. In order to isolate these, a shear-free boundary layer was studied experimentally. The desired flow conditions were realized by generating decaying grid turbulence with a uniform mean velocity and passing it over a wall moving with the stream speed. It is shown that the initial response of the turbulence field can be well described by the theory of Hunt & Graham (1978). Later, where this theory ceases to give an accurate description, terms of the Reynolds stress transport (RST) equations were measured or estimated by balancing the equations. An important finding is that two different length scales are associated with the near-wall damping of the Reynolds stresses. The wall-normal velocity component is damped over a region extending roughly one macroscale out from the wall. The pressure-strain redistribution that normally would result from the Reynolds stress anisotropy in this region was found to be completely inhibited by the near-wall influence. In a thin region close to the wall the pressure-reflection effects were found to give a pressure-strain that has an effect opposite to the normally expected isotropization. This behaviour is not captured by current models.
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| 19. |
- Aronsson, D., et al.
(författare)
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Shear-free turbulence near a wall
- 1996
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Ingår i: Journal of Fluid Mechanics. - : Cambridge University Press. - 0022-1120 .- 1469-7645. ; 338, s. 363-385
-
Tidskriftsartikel (refereegranskat)abstract
- The mean shear has a major influence on near-wall turbulence but there are also other important physical processes at work in the turbulence/wall interaction. In order to isolate these, a shear-free boundary layer was studied experimentally. The desired flow conditions were realized by generating decaying grid turbulence with a uniform mean velocity and passing it over a wall moving with the stream speed. It is shown that the initial response of the turbulence field can be well described by the theory of Hunt & Graham (1978). Later, where this theory ceases to give an accurate description, terms of the Reynolds stress transport (RST) equations were measured or estimated by balancing the equations. An important finding is that two different length scales are associated with the near-wall damping of the Reynolds stresses. The wall-normal velocity component is damped over a region extending roughly one macroscale out from the wall. The pressure–strain redistribution that normally would result from the Reynolds stress anisotropy in this region was found to be completely inhibited by the near-wall influence. In a thin region close to the wall the pressure–reflection effects were found to give a pressure–strain that has an effect opposite to the normally expected isotropization. This behaviour is not captured by current models.
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| 20. |
- Askebjer, P., et al.
(författare)
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AMANDA : status report from the 1993-94 campaign and optical properties of the South Pole ice
- 1995
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Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 38:1-3, s. 287-292
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Tidskriftsartikel (refereegranskat)abstract
- We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties of the ice in situ. We find that the ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 m, i.e. comparable with the quality of the ultra-pure water used in the IMB and Kamiokande proton-decay and neutrino experiments [1,2] and more than two times longer than the best value reported for laboratory ice [3]. Due to a residual density of air bubbles at these depths, the motion of photons in the medium is randomized. For spherical, smooth bubbles we find that, at 1 km depth, the average distance between collisions is about 25 cm. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated. © 1995 Elsevier Science B.V. All rights reserved.
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