| 1. |
- Hademenos, George J, et al.
(författare)
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A Scatter Correction Method for 201-Tl images: A Monte Carlo Investigation
- 1993
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 40:4, s. 1179-1186
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Tidskriftsartikel (refereegranskat)abstract
- Results from the application of a modified dual photopeak window scatter correction method to Monte Carlo simulated Tl-201 emission images are presented. In the Monte Carlo investigation, individual simulations are performed for six radiation emissions of Tl-201. For each emission, point sources of Tl-201 are imaged at various locations in a water-filled elliptical tub phantom using three energy windows. The DPW method is applied to each point source image to estimate the scatter distribution. For point source images in both homogeneous and nonhomogeneous attenuating media, the application of this modified version of DPW results in an approximately sixfold reduction in the scatter fraction and an excellent agreement of the shape of the tails between the estimated scatter distribution and the Monte Carlo-simulated truth. This method is also applied to two views of an extended cardiac distribution within an anthropomorphic phantom, again resulting in at least a sixfold improvement between the scatter estimate and the Monte Carlo-simulated true scatter.
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| 2. |
- Jacquin, Emmanuelle, et al.
(författare)
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Control of sex pheromone biosynthesis in the moth Mamestra brassicae by the pheromone biosynthesis activating neuropeptide
- 1994
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Ingår i: Insect Biochemistry and Molecular Biology. - : Elsevier BV. - 0965-1748. ; 24:2, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- The physiological route for the action of the pheromone biosynthesis activating neuropeptide (PBAN) was determined in Mamestra brassicae (L.) (Lepidoptera:Noctuidae). Removal of the ventral nerve cord including the terminal abdominal ganglia did not affect PBAN stimulation of pheromone production and the biogenic amine octopamine did not stimulate pheromone production in isolated abdomens. PBAN-like activity was found in the hemolymph of intact females in scotophase and not in the hemolymph of decapitated females or females in photophase. Our results suggest that PBAN follows a humoral route to its site of action rather than a neural one after being released from the brain. The hormonal control of the pheromone biosynthetic pathway was investigated using labeled precursors. Our results suggest that PBAN regulates an early step in the pheromone biosynthetic pathway, contrary to a previous report that it stimulates the Δ11-desaturase.
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| 3. |
- Lexell, Jan, et al.
(författare)
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Growth and development of human muscle : a quantitative morphological study of whole vastus lateralis from childhood to adult age
- 1992
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 15:3, s. 404-409
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms underlying the increase in volume of muscle tissue, and the functional development of muscle fibers from childhood through adolescence to adult age, have been studied. Cross sections of autopsied whole vastus lateralis muscle from 22 previously physically healthy males, 5 to 37 years of age, were prepared enzyme histochemically (myofibrillar ATPase) and examined morphometrically. The data obtained on muscle cross-sectional area, size, total number, and proportion of type 1 (slow-twitch) and type 2 (fast-twitch) fibers were analyzed using linear regression techniques. The results show that the increase in muscle cross-sectional area from childhood to adult age is caused by an increase in mean fiber size. This is accompanied by a functional development of the fiber population: the proportion of type 2 fibers increases significantly from the age of 5 (approx. 35%) to the age of 20 (approx. 50%), which, in the absence of any discernible effect on the total number of fibers, is most likely caused by a transformation of type 1 to type 2 fibers.
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