| 3551. |
- Åstrand, Håkan, et al.
(författare)
-
Age-related increase in wall stress of the human abdominal aorta : An in vivo study
- 2005
-
Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 42:5, s. 926-931
-
Tidskriftsartikel (refereegranskat)abstract
- Background The regulation of wall stress in the abdominal aorta (AA) of humans might be of specific interest, because the AA is the most common site for aneurysm formation in which wall stress seems to be an important pathophysiological factor. We studied the age-related changes in wall stress of the AA in healthy subjects, with the common carotid artery (CCA) as a comparison. Methods A total of 111 healthy subjects were examined with B-mode ultrasonography to determine the lumen diameter and intima-media thickness (IMT) in the AA and the CCA. Results Aortic IMT was affected by age in men and by both age and lumen diameter in women. Carotid IMT was affected by age and pulse pressure in both men and women. Wall stress was higher in the AA than in the CCA (P < .001), and men had higher wall stress than women in both the AA (P < .001) and the CCA (P < .05). Furthermore, wall stress was constant during life in the CCA of men and women and in the AA of women. In the male aorta, however, wall stress increased with age (P < 0.01). Conclusions Arterial diameters increase with age, and a compensatory thickening of the arterial wall prevents the circumferential wall stress from increasing. However, this compensatory response is insufficient in the male AA and results in an increase in stress with age. These findings might explain the propensity for aneurysms to develop in the AA of men.
|
|
| 3552. |
|
|
| 3553. |
- Åström, Karl Johan, et al.
(författare)
-
Bicycle Dynamics and Control
- 2005
-
Ingår i: Control Systems Magazine. - 0272-1708. ; 25:4, s. 26-47
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the dynamics of bicycles is analyzed from the perspective of control. Models of different complexity are presented, starting with simple ones and ending with more realistic models generated from multibody software. Models that capture essential behavior such as self-stabilization as well as models that demonstrate difficulties with rear wheel steering are considered. Experiences using bicycles in control education along with suggestions for fun and thought-provoking experiments with proven student attraction are presented. Finally, bicycles and clinical programs designed for children with disabilities are described.
|
|
| 3554. |
- Ängquist, Lars, et al.
(författare)
-
Improving the calculation of statistical significance in genome-wide scans
- 2005
-
Ingår i: Biostatistics. - : Oxford University Press (OUP). - 1468-4357 .- 1465-4644. ; 6:4, s. 520-538
-
Tidskriftsartikel (refereegranskat)abstract
- Calculations of the significance of results from linkage analysis can be performed by simulation or by theoretical approximation, with or without the assumption of perfect marker information. Here we concentrate on theoretical approximation. Our starting point is the asymptotic approximation formula presented by Lander and Kruglyak (1995, Nature Genetics, 11, 241-247), incorporating the effect of finite marker spacing as suggested by Feingold et al. (1993, American Journal of Human Genetics, 53, 234-251). We consider two distinct ways in which this formula can be improved. Firstly, we present a formula for calculating the crossover rate rho for a pedigree of general structure. For a pedigree set, these values may then be weighted into an overall crossover rate which can be used as input to the original approximation formula. Secondly, the unadjusted p-value formula is based on the assumption of a Normally distributed nonparametric linkage (NPL) score. This leads to conservative or anticonservative p-values of varying magnitude depending on the pedigree set structure. We adjust for non-Normality by calculating the marginal distribution of the NPL score under the null hypothesis of no linkage with an arbitrarily small error. The NPL score is then transformed to have a marginal standard Normal distribution and the transformed maximal NPL score, together with a slightly corrected value of the overall crossover rate, is inserted into the original formula in order to calculate the p-value. We use pedigrees of seven different structures to compare the performance of our suggested approximation formula to the original approximation formula, with and without skewness correction, and to results found by simulation. We also apply the suggested formula to two real pedigree set structure examples. Our method generally seems to provide improved behavior, especially for pedigree sets which show clear departure from Normality, in relation to the competing approximations.
|
|
| 3555. |
|
|
| 3556. |
- Öborn, Ingrid, et al.
(författare)
-
A systems approach to assess farm-scale nutrient and trace element dynamics: A case study at the Ojebyn dairy farm
- 2005
-
Ingår i: Ambio: a Journal of Human Environment. - 0044-7447 .- 1654-7209. ; 34:4, s. 301-310
-
Tidskriftsartikel (refereegranskat)abstract
- A systems analysis approach was used to assess farmscale nutrient and trace element sustainability by combining full-scale field experiments with specific studies of nutrient release from mineral weathering and trace-element cycling. At the Ojebyn dairy farm in northern Sweden, a farm-scale case study including phosphorus (P), potassium (K), and zinc (Zn) was run to compare organic and conventional agricultural management practices. By combining different element-balance approaches (at farmgate, barn, and field scales) and further adapting these to the FARMFLOW model, we were able to combine mass flows and pools within the subsystems and establish links between subsystems in order to make farm-scale predictions. It was found that internal element flows on the farm are large and that there are farm internal sources (Zn) and loss terms (K). The approaches developed and tested at the Ojebyn farm are promising and considered generally adaptable to any farm.
|
|
| 3557. |
- Öckinger, Erik, et al.
(författare)
-
Is local distribution of the epiphytic lichen Lobaria pulmonaria limited by dispersal capacity or habitat quality?
- 2005
-
Ingår i: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 14:3, s. 759-773
-
Tidskriftsartikel (refereegranskat)abstract
- By surveying and re-surveying 12 forest sites in southern Sweden for the epiphytic lichen Lobaria pulmonaria with a 9-year interval, and measuring tree-related habitat quality variables, we have investigated whether the local distribution of the lichen is limited by poor dispersal capacity or by habitat quality. Dispersal distances were measured indirectly as the distances between colonised trees and the nearest trees occupied by L. pulmonaria in both 1992 and 2001. To compare habitat quality between trees occupied by L. pulmonaria and neighbouring control trees, we recorded tree species and measured age and growth rate of trees, light conditions, bark structure and bryophyte cover. The estimated mean dispersal distance was 35 m, with a recorded maximum of 75 m. Occupied trees were larger and had a larger cover of bryophytes than unoccupied trees of similar size. The results indicate that dispersal capacity probably is the most important factor in limiting the local distribution of L. pulmonaria, but habitat-quality factors may be important on a smaller spatial scale.
|
|
| 3558. |
- Ögren, Magnus, 1977-, et al.
(författare)
-
Solitary waves in elongated clouds of strongly interacting bosons
- 2005
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 72:2
-
Tidskriftsartikel (refereegranskat)abstract
- We examine the propagation of solitary waves in elongated clouds of trapped bosonic atoms as the confinement, the strength of the interatomic interaction, and the atom density are varied. We identify three different physical regimes and develop a general formalism that allows us to interpolate between them. Finally we pay special attention to the transition to the Tonks-Girardeau limit of strongly interacting bosons.
|
|
| 3559. |
- Öhgren, Karin, et al.
(författare)
-
Optimization of steam pretreatment of SO2-impregnated corn stover for fuel ethanol production
- 2005
-
Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 124:1-3, s. 1055-1067
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, corn stover with a dry matter content of 20% was impregnated with SO2 and then steam pretreated for various times at various temperatures. The pretreatment was evaluated by enzymatic hydrolysis of the solid material and analysis of the sugar content in the liquid. The maximum overall yield of glucose, 89% of the theoretical based on the glucan in the raw material, was achieved when the corn stover was pretreated at 200 degrees C for 10 min. The maximum overall yield of, xylose, 78%, was obtained with pretreatment at 190 degrees C for 5 min.
|
|
| 3560. |
|
|
