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- Blomqvist, Lars, 1962-
(författare)
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Laminated Veneer Products : Shape Stability and Effect of Enhanced Formability on Bond-Line Strength
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns two aspects of the manufacture of laminated veneer products (LVPs). The first aspect is related to the possible improvement of the shape stability of LVPs, and the second has its starting point in the modification of the veneer for enhanced formability as well as the question of whether and how these modifications affect the bond-line strength.LVPs are veneers bonded with adhesive into predetermined shapes, mostly for the production of furniture and interior fittings. Since any deviation from the intended shape is a problem for both manufacturer and customer, various studies have sought to evaluate the influence of different materials and process parameters on shape stability. Parameters studied have included wood species (beech and birch), an adhesive system based on urea formaldehyde, the adhesive distribution on the veneer, climate, moisture content and fibre orientations of the veneers, as well as the orientation of the individual veneers in a multiply.Manufacturers of LVPs must consider some basic facts about wood in orders adequately to provide shape-stable LVPs to customers. Wood emits and absorbs moisture in relation to the surrounding climate, and this can lead to shrinkage and swelling. Such moisture induced movements differ in the wood’s different directions, and the magnitude is specific for the species. A thorough understanding of this is the basis for achieving shape-stable LVPs.Symmetry is defined in this thesis such that the veneer properties are balanced in the laminate. This means that opposite veneers on either side of the centre veneer have similar characteristic. An LVP will become distorted if the veneers are asymmetrically oriented before the press. Deviation from the desired shape can be small immediately after the pressing, but it may increase significantly with moisture content (MC) variations. Asymmetry may result when veneers with different fibre orientations are included in the laminate or when the veneers are placed asymmetrically. It may also occur if veneers with different MCs are bonded together asymmetrically. One aggravating factor is that the lathe checks that are introduced when the veneers are peeled or sliced from the log affect the shape stability. In 3-ply crosswise-oriented plywood, the veneer surfaces on which the lathe checks occur should be oriented in the same way for high shape stability.Based on existing knowledge, the production of shape-stable LVPs requires that the veneers are conditioned to a uniform MC and sorted with regard to fibre orientation and the side with lathe checks before bonding. End-user climates should govern the MC of the veneers and the moisture added with the adhesive during the process. Straight-grain veneers and symmetry should always be the goal.Moulding can cause stretching, i.e. strain, of the veneers depending on the curvature of the mould. To prevent the veneers from rupture, there are various ways to strengthen the veneers particularly in the transverse direction in which the veneer is weakest. However, tests have shown that these pre-treatments of veneers for enhanced formability can prevent the adhesive from penetrating the wood surface. It is therefore important to confirm that the pre-treatment does not affect the bond-line strength.
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| 2. |
- Blomqvist, Maria, et al.
(författare)
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Chlamydophila psittaci in birds of prey, Sweden
- 2012
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Ingår i: Infection Ecology & Epidemiology. - : Informa UK Limited. - 2000-8686 .- 2000-8686. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Background: Chlamydia psittaci is an intracellular bacterium primarily causing respiratory diseases in birds but may also be transmitted to other animals, including humans. The prevalence of the pathogen in wild birds in Sweden is largely unknown.Methods: DNA was extracted from cloacae swabs and screened for C. psittaci by using a 23S rRNA gene PCR assay. Partial 16S rRNA and ompA gene fragments were sequence determined and phylogenies were analysed by the neighbour-joining method.Results and conclusion: The C. psittaci prevalence was 1.3% in 319 Peregrine Falcons and White-tailed Sea Eagles, vulnerable top-predators in Sweden. 16S rRNA and ompA gene analysis showed that novel Chlamydia species, as well as novel C. psittaci strains, are to be found among wild birds.
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| 3. |
- Årestedt, Kristofer, et al.
(författare)
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Social support and its association with health-related quality of life among older patients with chronic heart failure
- 2013
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Ingår i: European Journal of Cardiovascular Nursing. - : Elsevier / SAGE Publications (UK and US). - 1474-5151 .- 1873-1953. ; 12:1, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- Background: Social support is generally known to influence health-related quality of life (HRQoL), but this association is not well explored among older patients with chronic heart failure. less thanbrgreater than less thanbrgreater thanAims: (1) To describe social support in older patients with chronic heart failure in relation to gender. (2) To investigate if age, gender, cohabitation, perceived financial situation, and disease severity are associated with social support. (3) To investigate if social support is associated with HRQoL after controlling for age, gender, and disease severity. less thanbrgreater than less thanbrgreater thanMethods: Data were collected in a sample of 349 patients (andgt;= 65 years) with chronic heart failure. Patients HRQoL was measured with the Minnesota Living with Heart Failure Questionnaire and the Short Form-12 Health Survey Questionnaire. The Interview Schedule for Social Interaction measured social support. Data were analysed with descriptive statistics, repeated-measure ANOVA, and multiple linear regression analyses with robust standard errors. less thanbrgreater than less thanbrgreater thanResults: Social support was generally rated high, although being a man, living alone, perceiving a problematic financial situation, and high disease severity (NYHA) were associated with lower levels of social support. Age was not associated with social support. Social support was generally associated with HRQoL, in particular the emotional dimensions. less thanbrgreater than less thanbrgreater thanConclusion: Taking social support into account when caring for older patients with heart failure can be of importance for improving or maintaining HRQoL.
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