| 1. |
- Aleksandrovskii, A. N., et al.
(författare)
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Thermal expansion of single-crystal fullerite C60 at helium temperatures
- 2000
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 26:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2–10 K). At temperatures below ~4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed.
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| 2. |
- Jansson, Roland, 1967-, et al.
(författare)
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Effects of river regulation on river-margin vegetation : A comparison of eight boreal rivers
- 2000
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Ingår i: Ecological Applications. - 1051-0761 .- 1939-5582. ; 10:1, s. 203-224
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Tidskriftsartikel (refereegranskat)abstract
- Regulation and fragmentation by dams belong to the most widespread deliberate impacts of humans on the world's rivers, especially in the Northern Hemisphere. We evaluated the effects of hydroelectric development by comparing the flora of vascular plants in 200-m-long reaches of river margin distributed along eight entire rivers in northern Sweden. Four of these rivers were free-flowing, and four were strongly regulated for hydroelectric purposes. First, we compared species diversity per site between entire free-flowing and regulated rivers. To reduce the effects of natural, between-river variation, we compared adjacent rivers. One regulated river had lower plant species richness and cover than two adjacent free-flowing ones, whereas two other parallel rivers, one regulated and another free-flowing, did not differ significantly. Second, river-margin vegetation responded differently to different types of regulated water-level regimes. Both along run-of-river impoundments, with small but daily water-level fluctuations, and along storage reservoirs, with large fluctuations between low water levels in spring and high levels in late summer and fall, the number of species and their cover per site were lower than along the free-flowing rivers. Regulated but unimpounded reaches were most similar to free-flowing rivers, having lower plant cover per site, but similar numbers of species. For reaches with reduced discharge, evidence was mixed; some variables were lower compared to free-flowing rivers whereas others were not. However, for the last two types of regulation, statistical power was low due to small sample sizes. Third, we classified all plant species according to their dispersal mechanisms and tested whether they respond differently to different types of regulated water-level regimes. Three out of four types of regulation had higher proportions of wind-dispersed species, and two out of four had lower proportions of species without specific mechanisms for dispersal, compared to free-flowing rivers, suggesting that dispersal ability is critical for persistence following regulation. Run-of-river impoundments had higher proportions of long-floating species and species with mechanisms for vegetative dispersal, suggesting that water dispersal may still be important despite fragmentation by dams. Fourth, plant species richness and cover varied with both local factors, such as water-level regime, and regional factors, such as length of the growing season. Presence of clay and silt in the river-margin soil, preregulation position of the contemporary river margin, non-reservoir sites, low altitudes, and long growing seasons were associated with high plant species richness and cover.
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| 3. |
- Wingfors, Håkan, et al.
(författare)
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Multivariate data evaluation of PCB and dioxin profiles in the general population in Sweden and Spain
- 2000
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Ingår i: Chemosphere. - 0045-6535 .- 1879-1298. ; 40:9-11, s. 1083-1088
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Tidskriftsartikel (refereegranskat)abstract
- Thirty-three polychlorinated biphenyls and 20 dioxin-like congeners were determined by GC–MS in blood and adipose tissue samples from two general population groups, one in Spain (n=35) and one in Sweden (n=28). The results were evaluated by multivariate projection (Simca), after normalisation to the most abundant and stable congener in each data set, in order to reveal differences in the “national” congener profiles. The mean values of each population group did not differ significantly. The sum of PCBs in the Spanish was 1450 ng/g and in the Swedish 1310 ng/g. The sum of the dioxin-like compounds in Spain was 1180 pg/g and in Sweden 804 pg/g. The congener profiles differed between the countries. Mainly the higher chlorinated congeners for both the dioxin-like compounds and the PCBs are more dominant in the Spanish group compared to the Swedish.
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| 4. |
- Artursson, Tom, et al.
(författare)
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Drift correction for gas sensors using multivariate methods
- 2000
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Ingår i: Journal of Chemometrics. - 0886-9383 .- 1099-128X. ; 14:5-6, s. 711-723
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Tidskriftsartikel (refereegranskat)abstract
- Drift is one of the most serious impairments afflicting gas sensors. It can be seen as a gradual change in the sensor response over a long period of time when the external conditions an constant. This paper presents a new simple drift counteraction method based on PCA and PLS. The basic idea is to remove the drift direction component from the measurements. The direction of the drift, p, is calculated from measurements for a reference gas. Projecting the sample gas measurements on this vector gives the score vector t. The drift component tp(T) can then he removed from the sample gas data, which we call component correction (CC). The method is tested on a data set based on a reduced factorial design with four gases and a concentration gradient of hydrogen. It is found that the method works efficiently for both cases. Copyright (C) 2000 John Wiley & Sons, Ltd.
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| 5. |
- Gulliksson, Mårten, et al.
(författare)
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Perturbation identities for regularized Tikhonov inverses and weighted pseudoinverses
- 2000
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Ingår i: Bit: numerical mathematics. - 0006-3835. ; 40:3, s. 513-523
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Tidskriftsartikel (refereegranskat)abstract
- e consider the perturbation analysis of two important problems for solving ill-conditioned or rank-deficient linear least squares problems. The Tikhonov regularized problem is a linear least squares problem with a regularization term balancing the size of the residual against the size of the weighted solution. The weight matrix can be a non-square matrix (usually with fewer rows than columns). The minimum-norm problem is the minimization of the size of the weighted solutions given by the set of solutions to the, possibly rank-deficient, linear least squares problem. It is well known that the solution of the Tikhonov problem tends to the minimum-norm solution as the regularization parameter of the Tikhonov problem tends to zero. Using this fact and the generalized singular value decomposition enable us to make a perturbation analysis of the minimum-norm problem with perturbation results for the Tikhonov problem. From the analysis we attain perturbation identities for Tikhonov inverses and weighted pseudoinverses.
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| 6. |
- Gulliksson, Mårten, et al.
(författare)
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Perturbation theory for generalized and constrained linear least squares
- 2000
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Ingår i: Numerical Linear Algebra with Applications. - 1070-5325. ; 7:4, s. 181-195
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Tidskriftsartikel (refereegranskat)abstract
- The perturbation analysis of weighted and constrained rank-deficient linear least squares is difficult without the use of the augmented system of equations. In this paper a general form of the augmented system is used to get simple perturbation identities and perturbation bounds for the general linear least squares problem both for the full-rank and rank-deficient problem. Perturbation identities for the rank-deficient weighted and constrained case are found as a special case. Interesting perturbation bounds and condition numbers are derived that may be useful when considering the stability of a solution of the rank-deficient general least squares problem. Copyright © 2000 John Wiley & Sons, Ltd.
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| 7. |
- Gulliksson, Mårten, et al.
(författare)
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The use and properties of Tikhonov filter matrices.
- 2000
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Ingår i: SIAM Journal on Matrix Analysis and Applications. - 0895-4798. ; 22:1, s. 276-281
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Tidskriftsartikel (refereegranskat)abstract
- We consider the concept of Tikhonov filter matrices in connection with discrete ill-posed and rank-deficient linear problems. Important properties of the Tikhonov filter matrices are given together with their filtering and regularization effects. We also present new perturbation identities for the Tikhonov regularized linear least squares problem using filter matrices generalizing well-known perturbation identities for the linear least squares problem and pseudoinverses.
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| 8. |
- Kadi, F., et al.
(författare)
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The effects of different training programs on the trapezius muscle of women with work-related neck and shoulder myalgia
- 2000
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Ingår i: Acta Neuropathologica. - Berlin : Springer Berlin/Heidelberg. - 0001-6322 .- 1432-0533. ; 100:3, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine the effects of training on the structural characteristics of the trapezius muscle in women with work-related trapezius myalgia. Muscle biopsies were taken before and after 10 weeks of three different training programs (strength, endurance and coordination). Enzyme-immunohistochemical analysis was performed to assess muscle fibre types, fibre area, capillary supply and cytochrome c oxidase (COX) activity. There was an increase in the proportion of type LIA fibres in strength trained group (P < 0.05). Strength training elicited a preferential increase in the area of type II fibres (P < 0.05); both strength and endurance programs induced an increase in the number of capillaries around type I and IIA muscle fibres. Finally, all training programs induced a decrease in the proportion of COX-negative fibres. In conclusion, the trapezius muscle of women with neck and shoulder myalgia is characterised by a great potential of adaptation to physical exercise over a period of 10 weeks. The significant changes in the number of capillaries and the specific changes induced by training at the level of muscle fibres might well explain the improvement of muscle function.
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| 9. |
- Mincheva-Nilsson, Lucia, et al.
(författare)
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gammadelta T cells of human early pregnancy decidua : evidence for cytotoxic potency.
- 2000
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Ingår i: International Immunology. - : Oxford University Press (OUP). - 0953-8178 .- 1460-2377. ; 12:5, s. 585-96
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Tidskriftsartikel (refereegranskat)abstract
- The immune compromise in decidua allows a semiallogeneic fetus to survive without impairing the ability of the maternal immune system to fight infections. Cytotoxic mechanisms are likely to be important in this compromise. Using RT-PCR, immunoflow cytometry and immunoelectron microscopy, the cytotoxic potential of isolated human decidual gammadelta T cells was studied. mRNA for perforin (Pf), granzymes A and B, granulysin and Fas ligand (FasL) was simultaneously expressed in decidual gammadelta T cells. Pf and FasL were not expressed on the cell surface. However, the cells constitutively synthesized Pf and stored it in cytolytic granules. Within the granules Pf mainly resided in the granule core formed by Pf-containing microvesicles. Ultrastructurally, three groups of Pf-containing granules were distinguished. They probably represent different stages of granule maturation in a process where Pf-containing microvesicles first attach to the core cortex and then are translocated across the cortex into the core. Presynthesized FasL was also stored in the core and microvesicles of the cytolytic granules. Upon degranulation by ionomycin/Ca(2+) treatment, FasL was rapidly translocated to the cell surface, demonstrating that its surface expression was not controlled by de novo biosynthesis. Thus decidual gammadelta T cells appear to perform Pf- and FasL-mediated cytotoxicity utilizing a common secretory mechanism based on cytolytic granule exocytosis. The first cytochemical visualization of lipids in the cytolytic granules is provided. These intragranular lipids probably wrap up the core and participate in packaging of the cytotoxic proteins as well as in the killing process. An ultrastructural model of a cytolytic granule is presented.
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| 10. |
- Persson, Mats, 1954-, et al.
(författare)
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Development and maintenance of guideline-based decision support for pharmacological treatment of hypertension
- 2000
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Ingår i: Computer Methods and Programs in Biomedicine. - : Elsevier. - 0169-2607 .- 1872-7565. ; 61:3, s. 209-219
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Tidskriftsartikel (refereegranskat)abstract
- The objective was to build a computer-based decision support system (DSS), which could apply the formal rules embedded in guidelines regarding pharmacological treatment of hypertension. The aim was also to test VISUAL BASIC as a development tool for DSS's in health care. From the Swedish guidelines for treatment of hypertension, the most widely accepted and scientifically best proved treatment strategies were chosen and implemented as rules. A DSS that is capable of applying the evidence-based rules extracted from guidelines regarding drug treatment of hypertension, to any patient's medical profile, was constructed. The output consists of a recommendation regarding preferred generic drug class and also a written report, reflecting decision steps provided by the rule-base and inference engine. We also provide methods for formalising an implementable language of guidelines. A mainstream programming language like VISUAL BASIC can be an alternative when building complicated decision support systems. A logic formal notation can facilitate communication between the expert and the programmer. The program is a stand-alone product independent of computerized medical records and thereby easy to install and maintain.
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