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- Ljungberg, Michael, et al.
(författare)
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Introduction to the Monte Carlo Method
- 1998
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Ingår i: Monte Carlo Calculations in Nuclear Medicine: Applications in Diagnostic Imaging. - 750304790 ; , s. 37-37
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Gustafsson, Agnetha, et al.
(författare)
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Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT
- 1998
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 43:8, s. 2325-2336
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Tidskriftsartikel (refereegranskat)abstract
- SPECT (single photon emission computed tomography) images are distorted by photon attenuation. The effect is complex in the thoracic region due to different tissue densities. This study compares the effect on the image homogeneity of two different methods of attenuation correction in lung SPECT; one pre-processing and one post-processing method. This study also investigates the impact of attenuation correction parameters such as lung contour, body contour, density of the lung tissue and effective attenuation coefficient. The Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing a homogeneous activity distribution in the lung. Homogeneity in reconstructed images was calculated as the coefficient of variation (CV). The isolated effect of the attenuation correction was assessed by normalizing pixel values from the attenuation corrected lung by pixel values from the lung with no attenuation effects. Results show that the CV decreased from 12.8% with no attenuation correction to 4.4% using the post-processing method and true densities in the thoracic region. The impact of variations in the definition of the body contour was found to be marginal while the corresponding effect of variations in the lung contour was substantial
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- Hertz, H.M, et al.
(författare)
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Optically trapped non-linear particles as probes for scanning near-field optical microscopy
- 1995
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Ingår i: Ultramicroscopy. - 0304-3991. ; 57:2-3, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- We use the frequency doubled light from an optically trapped lithium niobate particle for non-intrusive scanning near-field optical microscopy. The detected power from this 50-100 nm diameter probe is currently tens of pW and is expected to approach nW with an improved detection system. The current experimental resolution is approximately 0.5 [mu]m, while the ultimate theoretical resolution is 70-90 nm. An acoustic trap which potentially allows higher resolution imaging is briefly described.
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- Holmström, Henning, et al.
(författare)
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Secondary copper enrichment in tailings at the Laver mine, northern Sweden
- 1999
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Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 38:4, s. 327-342
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Tidskriftsartikel (refereegranskat)abstract
- Field and laboratory studies of the sulphide-bearing tailings at Laver, northern Sweden, show that the present release of metals from the tailings is low, especially with regard to Cu. A large part of the Cu released by sulphide oxidation is enriched in a distinct zone just below the oxidation front. The enrichment zone occurs almost all over the tailings area except in areas with a shallow groundwater table. The Cu enrichment is caused by formation of covellite and adsorption onto mineral surfaces. The transport of Zn, Co, Cd, Ni and S seems to be controlled mainly by adsorption. No secondary zone or secondary minerals containing these metals have been found. Just below the groundwater table, metals are released into solution when the enrichment zone reaches the groundwater due to the low pH. An increased release of metals, especially Cu, can be expected in the future, since the enrichment zone is moving towards the groundwater table.
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