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| 2. |
- Bergström, Gunnar, et al.
(författare)
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Acceptanskriterier för repor och intryck i plaströr Accpetance criteria for scratches and indentations in plastic pipes
- 2009
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Rapport (refereegranskat)abstract
- Development of materials and laying techniques have arisen the question how scratches and indentations in plastics pipes affect the strength and technical lifetime of pipelines. Scratches may occur both in the manufacturing of the pipes, in connection with the installation and subsequent maintenance. The problems in assessing the failure risk from scratches and indentations are similar for pipes used in gas and water distribution and in district heating applications. Therefore, a broad effort to identify the risks in relation to current pipe materials is technically and economically justified. The project has aimed to evaluate the effect of scratches and indentations on the technical lifetime of plastics pipes and to present criteria for maximum allowable depth of scratches and indentations. The study on pressure pipes focused on the conditions for scratched polyethylene pipes to achieve a lifetime of 50 years. It is noted that a scratch damage can not be judged solely on the basis of its depth and sharpness. To assess the impact of the scratch on the serviceability of the pipe, consideration must also be taken to the material from which the pipe was made and the safety factor used in the design. Extensive pressure tests show that pipes made of modern materials can withstand surface scratches to a higher degree than pipes of older materials. For pipes made of modern bimodal PE80 and PE100 materials, scratches up to 10% depth may be accepted without reduction of rated pressure. However, for pipes of older material, a reduction in pressure may be required already at smaller scratches. The study also indicates that for the same relative scratch depth, a greater reduction in pressure is required with increasing pipe dimension. The study on the non pressure pipes shows that the studied polypropylene pipes resist both deep scratches combined with ovalization and large indentations without any cracks penetrating the pipe wall. However, the extent and development of crazing and surface cracking vary with scratch depth, deformation level and material. The test pipes were subjected to extreme conditions very rarely or never occurring in practice. This suggests that small scratches at moderate ovalization and realistic indentations in temperatures around room temperature do not affect the lifetime of the pipes. One objective of the project was to develop a method for the evaluation of the scratch resistance of a pipe. In the proposed test method the force needed to produce a specified scratch is measured. This force is used as a relative measure of the scratch resistance of a pipe material when compared to other materials. In order to assess to what extent a scratch affects the lifetime of the pipe, the depth of the scratch must be estimated with reasonable accuracy. Since the scratch in many cases is found on existing pipelines the method must be suited for field use. To achieve that a simple instrument for scratch depth measurements was made and evaluated.
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| 3. |
- Bergström, Gunnar, et al.
(författare)
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Accpetance criteria for scratches and indentations in plastic pipes
- 2009
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Rapport (refereegranskat)abstract
- Development of materials and laying techniques have arisen the question how scratches and indentations in plastics pipes affect the strength and technical lifetime of pipelines. Scratches may occur both in the manufacturing of the pipes, in connection with the installation and subsequent maintenance. The problems in assessing the failure risk from scratches and indentations are similar for pipes used in gas and water distribution and in district heating applications. Therefore, a broad effort to identify the risks in relation to current pipe materials is technically and economically justified. The project has aimed to evaluate the effect of scratches and indentations on the technical lifetime of plastics pipes and to present criteria for maximum allowable depth of scratches and indentations. The study on pressure pipes focused on the conditions for scratched polyethylene pipes to achieve a lifetime of 50 years. It is noted that a scratch damage can not be judged solely on the basis of its depth and sharpness. To assess the impact of the scratch on the serviceability of the pipe, consideration must also be taken to the material from which the pipe was made and the safety factor used in the design. Extensive pressure tests show that pipes made of modern materials can withstand surface scratches to a higher degree than pipes of older materials. For pipes made of modern bimodal PE80 and PE100 materials, scratches up to 10% depth may be accepted without reduction of rated pressure. However, for pipes of older material, a reduction in pressure may be required already at smaller scratches. The study also indicates that for the same relative scratch depth, a greater reduction in pressure is required with increasing pipe dimension. The study on the non pressure pipes shows that the studied polypropylene pipes resist both deep scratches combined with ovalization and large indentations without any cracks penetrating the pipe wall. However, the extent and development of crazing and surface cracking vary with scratch depth, deformation level and material. The test pipes were subjected to extreme conditions very rarely or never occurring in practice. This suggests that small scratches at moderate ovalization and realistic indentations in temperatures around room temperature do not affect the lifetime of the pipes. One objective of the project was to develop a method for the evaluation of the scratch resistance of a pipe. In the proposed test method the force needed to produce a specified scratch is measured. This force is used as a relative measure of the scratch resistance of a pipe material when compared to other materials. In order to assess to what extent a scratch affects the lifetime of the pipe, the depth of the scratch must be estimated with reasonable accuracy. Since the scratch in many cases is found on existing pipelines the method must be suited for field use. To achieve that a simple instrument for scratch depth measurements was made and evaluated.
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| 4. |
- Bergström, Gunnar, et al.
(författare)
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Does sickness presenteeism have an impact on future general health?
- 2009
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Ingår i: International Archives of Occupational and Environmental Health. - Berlin : Springer. - 0340-0131 .- 1432-1246. ; 82:10, s. 1179-1190
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The primary aim of this prospective study was to investigate whether working despite illness, so called "sickness presenteeism", has an impact on the future general health of two different working populations during a follow-up period of 3 years.METHODS: The study was based on two bodies of data collected at a number of Swedish workplaces from 1999 to 2003. The first material comprised 6,901 employees from the public sector and the second 2,862 subjects from the private sector. A comprehensive survey was issued three times: at baseline, after 18 months and after 3 years. Apart from the explanatory variable sickness presenteeism, several potential confounders were considered. The outcome variable was good/excellent versus fair/poor self-reported health.RESULTS: Sickness presenteeism at baseline was consistently found to heighten the risk of fair/poor health at both the 18-month and 3-year follow ups even after adjusting for the detected confounders.CONCLUSIONS: To the best of the authors' knowledge, this study is the first to show that sickness presenteeism appears to be an independent risk factor for future fair/poor general health.
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| 5. |
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| 6. |
- Bergström, Gunnar, et al.
(författare)
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A comprehensive workplace intervention and its outcome with regard to lifestyle, health and sick leave : the AHA study
- 2008
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Ingår i: Work. - 1051-9815 .- 1875-9270. ; 31:2, s. 167-180
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Tidskriftsartikel (refereegranskat)abstract
- This study is a prospective multicentre cohort study entitled Work and Health in the Processing and Engineering Industries, the AHA Study (AHA is the Swedish abbreviation for the study). Four large workplaces in Sweden participated during the years from 2000 to 2003. The present report has two objectives: (1) to present a comprehensive occupational health intervention programme and (2) to evaluate this programme with a focus on lifestyle (smoking and exercise), health related quality of life (HRQoL) and sick leave. Interventions were provided on an individual and group level, including evidence-based methods for four health/focus areas (individual level) and a group intervention based on a survey-feedback methodology. The analyses in this report were exclusively employed at an organizational level. The proportion of smokers decreased at three companies and the course of the HRQoL was advantageous at two of the companies as compared to a gainfully employed reference group. A significant decrease in sick leave was revealed at one company, whereas a break in an ascending sick-leave trend appeared at a second company as compared to their respective corporate groups. This comprehensive workplace intervention programme appears to have had positive effects on smoking habits, HRQoL and sick leave.
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| 8. |
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| 9. |
- Lundh, Karin, et al.
(författare)
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Ageing and wear in polymeric child articles
- 2008
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Rapport (refereegranskat)abstract
- Ageing and wear in polymeric child articles This report targets child use and care articles, toys and playground equipment. These products will in this report collectively be referred to as ‘child articles’. It is the authors’ experience that polymers are getting more and more frequent in child articles, probably since they are cheaper and in many ways easier to process than metals. This is not an unwanted development in itself, but the choice of material has to be carefully made since the material properties of polymers vary greatly depending on the type and amount of additives and this can not be assessed visually. In addition they degrade with time due to environmental influence. To verify the properties of a polymer the material has to be tested. One of the challenges with polymers is that they all have a limited lifetime. They degrade over time and might lose almost all their strength, leading to material failure and, in the worst case scenario, accidents. It is a fact that accidents happen due to material failure, although it is hard to trace the true cause in accident statistics. In this report the term ‘ageing’ will be used for chemical degradation of the material structure due to light and/or heat exposure and ‘wear’ refers to mechanical degradation as a result of mechanical stress and contact. The current regulation covers property changes in polymers during the lifetime of a product insufficiently, if at all. Ageing of materials is virtually non-existing in existing child article standards. During its life a product is subjected to all kinds of environmental factors which more or less lead to reduction of function of the product. All products get worn, in one way or another, when used and the surrounding environment affects the material of the product. These effects are greater or lesser depending on usage and the harshness of the surrounding environment, as well as material choice and other qualities of the product. Therefore the material and processing have to be chosen based on the knowledge of the environment in which the product will be used as well as the expected lifetime. This process is called environmental design or environmental engineering. In order to simplify the material selection process when a product is developed, it is recommended to compose a material qualification system for child articles. This system can preferably be based on existing systems from other industries. This study recommends that the requirements and test methods proposed in Chapter 5 are considered when new standards for child articles are being developed or when existing standards are being revised. It is also recommended to perform a risk analysis to identify the hazards of a product.
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| 10. |
- Mandenius, Carl-Fredrik, 1954-, et al.
(författare)
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Monitoring of influenza virus hemagglutinin in process samples using weak affinity ligands and surface plasmon resonance
- 2008
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 623, s. 66-75
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Tidskriftsartikel (refereegranskat)abstract
- Surface plasmon resonance (SPR) was used to screen the interaction between a variety of affinity ligands and hemagglutinin (HA) from human influenza virus, with the aim of identifying low affinity ligands useful for the development of a rapid bioanalytical sensor. Three sialic acid-based structures and four lectins were evaluated as sensor ligands. The sialic acid-based ligands included a natural sialic acid-containing glycoprotein, human α1-acid glycoprotein (α1-AGP), and two synthetic 6′-sialyllactose-conjugates, with varying degree of substitution. The interaction of HA with the four lectin-based ligands, concanavalin A (Con A), wheat germ agglutinin (WGA), Maackia amurensis lectin (MAL), and Sambucus nigra agglutinin (SNA), showed a wide variation of affinity strengths. Affinity and kinetics data were estimated. Strong affinities were observed for Con A, WGA, α1-AGP, and a 6′-sialyllactose-conjugate with a high substitution degree, and low affinities were observed for MAL and a 6′-sialyllactose-conjugate with low substitution. The main objective, to identify a low affinity ligand which could be used for on-line monitoring and product quantification, was met by a 6′-sialyllactose–ovalbumin conjugate that had 0.6 mol ligand per mol carrier protein. The apparent affinity of this ligand was estimated to be 1.5 ± 0.03 μM (KD) on the SPR surface. Vaccine process samples containing HA were analyzed in the range 10–100 μg HA mL−1 and correlated with single-radial immunodiffusion. The coefficient of variation on the same chip was between 0.010 and 0.091.
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