| 1. |
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| 2. |
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| 3. |
- Andersson, Niklas, 1970, et al.
(författare)
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Pharmacological treatment of osteopenia induced by gastrectomy or ovariectomy in young female rats.
- 2004
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Ingår i: Acta orthopaedica Scandinavica. - : Medical Journals Sweden AB. - 0001-6470 .- 1651-1964. ; 75:2, s. 201-9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Both gastrectomy (GX) and ovariectomy (OVX) induce osteopenia in man and experimental animals. The present study addresses the question--can alendronate, estrogen or parathyroid hormone (PTH) be used to treat established GX- or OVX -evoked osteopenia? METHODS: Rats were GX-, OVX- or SHAM-operated 8 weeks before starting the treatment with drugs. Each group was then treated for 8 weeks with 50 microg/kg/day alendronate, 10 microg/kg/day estrogen or 75 microg/kg/day PTH(1-84); n = 8 rats/group. Peripheral Quantitative Computed Tomography (pQCT) was used to measure trabecular bone mineral density (BMD) and various cortical bone parameters. RESULTS: At killing, 16 weeks after surgery, GX and OVX rats had a greatly reduced trabecular BMD in the metaphysis of the distal femur (GX -44% and OVX -55%). Alendronate increased the trabecular BMD by 44% in GX rats and by 64% in OVX rats, while PTH increased it by 51% and 115%, respectively. However, estrogen increased the trabecular BMD in GX rats (35%), but not in OVX rats (15%, not significant). Cortical bone parameters were adversely (but moderately) affected by GX, but not by OVX or by treatment with the three drugs. INTERPRETATION: Alendronate, estrogen and PTH restored the trabecular bone loss in rats with an established GX-evoked osteopenia. In contrast, alendronate and PTH, but not estrogen, restored the trabecular bone loss after OVX. Hence, the mechanism underlying GX-evoked bone loss differs from that underlying OVX-evoked bone loss. The ability of alendronate, estrogen and PTH to reverse the GX-evoked osteopenia in the rat may be of clinical interest when dealing with bone loss in humans after GX.
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| 4. |
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| 5. |
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| 6. |
- Eckert, Jörn, et al.
(författare)
-
Einleitung
- 2004
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Ingår i: Juristische Fakultäten und Juristenausbildung im Ostseeraum: zweiter Rechtshistorikertag im Ostseeraum = Law faculties and legal education in the Baltic sea area: second Conference in Legal History in the Baltic Sea Area. - Uppsala : Kungl. Gustav Adolfs akademien för svensk folkkultur. - 9185190756 ; , s. 13-15, s. 9-12, s. 1-13, s. -357
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
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| 8. |
- Kilbo Edlund, Karl, et al.
(författare)
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Occupational particle exposure and chronic kidney disease: a cohort study in Swedish construction workers.
- 2024
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Ingår i: Journal of Occupational and Environmental Medicine. - : BMJ Publishing Group Ltd. - 1351-0711 .- 1470-7926. ; 81:5, s. 238-243
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Tidskriftsartikel (refereegranskat)abstract
- Increasing epidemiological and experimental evidence suggests that particle exposure is an environmental risk factor for chronic kidney disease (CKD). However, only a few case-control studies have investigated this association in an occupational setting. Hence, our objective was to investigate associations between particle exposure and CKD in a large cohort of Swedish construction workers.We performed a retrospective cohort study in the Swedish Construction Workers' Cohort, recruited 1971-1993 (n=286089). A job-exposure matrix was used to identify workers exposed to nine different particulate exposures, which were combined into three main categories (inorganic dust and fumes, wood dust and fibres). Incident CKD and start of renal replacement therapy (RRT) were obtained from validated national registries until 2021 and analysed using adjusted Cox proportional hazards models.Exposure to inorganic dust and fumes was associated with an increased risk of CKD and RRT during working age (adjusted HR for CKD at age <65 years 1.15, 95%CI 1.05 to 1.26). The elevated risk did not persist after retirement age. Exposure to cement dust, concrete dust and diesel exhaust was associated with CKD. Elevated HRs were also found for quartz dust and welding fumes.Workers exposed to inorganic particles seem to be at elevated risk of CKD and RRT. Our results are in line with previous evidence of renal effects of ambient air pollution and warrant further efforts to reduce occupational and ambient particle exposure.
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| 9. |
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| 10. |
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| 11. |
- Neitzel, R. L., et al.
(författare)
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Development of a Job Exposure Matrix for Noise in the Swedish Soft Tissue Paper Industry
- 2018
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Ingår i: Annals of Work Exposures and Health. - : Oxford University Press (OUP). - 2398-7308 .- 2398-7316. ; 62:2, s. 195-209
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Noise exposure is a common occupational hazard, but has not been sufficiently characterized in paper mills. We developed a job-exposure matrix (JEM) for noise exposure for use in estimating exposures among Swedish soft tissue paper mill workers.& para;& para;Methods: We used a combination of area and personal dosimetry noise exposure measurements made at four soft tissue paper mills by industry and research staff between 1977 and 2013 to estimate noise exposures by department, location, and job title. We then utilized these estimates, in conjunction with information on process and facility changes and use of hearing protection collected via focus groups, to create a seven-category, semi-quantitative JEM for all departments, locations, and job titles spanning the years 1940-2010.& para;& para;Results: The results of the 1157 area and personal dosimetry noise measurements indicated that noise levels have generally declined in Swedish paper mills over time, though these changes have been neither uniform nor monotonic within or across the four mills. Focus group results indicated that use of hearing protection has generally increased over time. The noise JEM totals 1917 cells, with each cell representing a unique combination of operation, job title, and single year. We estimated that -50% of workers at the four mills assessed were exposed at or above the Swedish 8-h average noise exposure limit of an 85 dBA at the conclusion of the study period in 2010.& para;& para;Conclusions: Our results highlight the continuing need for hearing loss prevention and noise control efforts at these and similar mills, and the completed JEM now represents a tool for use in epidemiological studies of noise-related health outcomes.
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| 12. |
- Neitzel, Richard L, et al.
(författare)
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Dust Exposures in Swedish Soft Tissue Paper Mills.
- 2022
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Ingår i: Annals of work exposures and health. - : Oxford University Press (OUP). - 2398-7316 .- 2398-7308. ; 66:1, s. 14-26
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Tidskriftsartikel (refereegranskat)abstract
- Paper dust has previously been linked to adverse health effects. However, a comprehensive dataset of paper dust exposures does not appear to have been published previously. Our study was intended to address this need by describing a large dataset of measurements made in Swedish soft tissue paper mills.We compiled personal and area total dust exposure measurements collected from a range of operations by our research staff at four soft tissue paper mills in Sweden. We also compiled measurements made by the occupational health staff at each mill and the Swedish Work Environment Authority. We analyzed these measurements to describe patterns and trends in exposures and used mixed-effects regression models to identify measurement characteristics that predicted exposure levels.We compiled 1578 measurements from 1971 to 2009, of which 1026 (65%) were personal samples. Statistically significant differences were found between measurements made by research, mill, and Swedish Work Environment Authority staff, as well as between personal and area measurements. The measurement data suggest that, beginning in the 1980s, exposures declined at three of the four mills, but that overexposures were still common at the end of the period. Papermaking and converting operations had the highest observed dust exposures. One mill had significantly lower exposures than the others. Type of measurement (personal versus area) and source of measurement (research staff, company, or regulatory agency) were not significant predictors of measured total dust exposure after controlling for mill, operation, and time.Our analysis of measured paper dust exposures may be useful for historical and contemporary exposure assessment in our own and other epidemiological studies. We have identified specific characteristics (i.e. papermaking operations and mill) and time trends that are important data features to consider, and documented continuing overexposure situations. Our results highlight the ongoing need for application of exposure controls to reduce paper dust exposures in the soft tissue paper industry.
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| 13. |
- Olin, Anna-Carin, 1960, et al.
(författare)
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Prevalence of asthma and exhaled nitric oxide are increased in bleachery workers exposed to ozone.
- 2004
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Ingår i: The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology. - 0903-1936. ; 23:1, s. 87-92
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the present study were to determine whether exposure to high peaks of ozone resulted in an increased prevalence of asthma or respiratory symptoms among bleachery workers and whether nitric oxide (NO) was elevated in the exhaled air of these workers. Bleachery workers (n=228) from three Swedish pulp mills who had been exposed to ozone, together with 63 unexposed control subjects, were investigated by means of spirometry, Phadiatop, exhaled and nasal NO and answers to a questionnaire concerning respiratory symptoms and exposure. Exposure to an ozone peak that gave rise to respiratory symptoms was defined as a "gassing". Bleachery workers reporting four or more gassings involving ozone had an increased prevalence of adult-onset asthma, wheeze, and current asthma symptoms. They also had a higher median concentration of exhaled NO in comparison with those who reported no such gassings (19.2 versus 15.7 parts per billion). No such associations were found in respect of nasal NO. The results from this study show that bleachery workers who have been repeatedly exposed to ozone gassings have an increased prevalence of adult-onset asthma. The results also indicate exhaled nitric oxide may be a marker of airway inflammation in bleachery workers who have been exposed to high peaks of ozone.
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| 14. |
- Aalberg, Laura, et al.
(författare)
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Development of a harmonised method for the profiling of amphetamines : I. Synthesis of standards and compilation of analytical data
- 2005
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Ingår i: Forensic Science International. - : Elsevier BV. - 0379-0738 .- 1872-6283. ; 149:2-3, s. 219-229
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Tidskriftsartikel (refereegranskat)abstract
- Reference material was synthesised for 21 substances that are frequently present as synthetic impurities, i.e. by-products, in illicitly produced amphetamine. Each of these substances is a typical by-product for at least one of the three approaches most often used to synthesise amphetamine, namely, the Leuckart, the reductive amination of benzyl methyl ketone, and the nitrostyrene routes. A large body of data on the substances was recorded, including the following: mass spectra, ultraviolet spectra, Fourier transform infrared spectra, infrared spectra in gas phase, and 1H NMR and 13C NMR spectra. © 2004 Elsevier Ireland Ltd. All rights reserved.
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| 15. |
- Abrahamsen, R., et al.
(författare)
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Association of respiratory symptoms and asthma with occupational exposures: findings from a population-based cross-sectional survey in Telemark, Norway
- 2017
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Ingår i: Bmj Open. - : BMJ. - 2044-6055. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The aim of this study was to estimate the prevalence of respiratory symptoms and physiciandiagnosed asthma and assess the impact of current occupational exposure. Design: Cross-sectional analyses of the prevalence of self-reported respiratory health and association with current occupational exposure in a random sample of the general population in Telemark County, Norway. Settings: In 2013, a self-administered questionnaire was mailed to a random sample of the general population, aged 16-50, in Telemark, Norway. The overall response rate was 33%, comprising 16 099 responders. Outcome measures: The prevalence for respiratory symptoms and asthma, and OR of respiratory symptoms and asthma for occupational groups and exposures were calculated. Occupational exposures were assessed using self-reported exposure and an asthma-specific job-exposure matrix (JEM). Results: The prevalence of physician-diagnosed asthma was 11.5%. For the occupational groups, the category with agriculture/fishery workers and craft/related trade workers was associated with wheezing and asthma attack in the past 12 months, showing OR 1.3 (1.1 to 1.6) and 1.9 (1.2 to 2.8), respectively. The group including technicians and associated professionals was also associated with wheezing OR 1.2 (1.0 to 1.3) and asthma attack OR 1.4 (1.1 to 1.9). The JEM data show that exposure to flour was associated with wheezing OR 3.2 (1.4 to 7.3) and woken with dyspnoea OR 3.5 (1.3 to 9.5), whereas exposures to diisocyanates, welding/soldering fumes and exposure to vehicle/motor exhaust were associated with dyspnoea OR 2.9 (1.5 to 5.7), 3.2 (1.6 to 6.4) and 1.4 (1.0 to 1.8), respectively. Conclusions: The observed prevalence of physiciandiagnosed asthma was 11.5%. The 'manual' occupations were associated with respiratory symptoms. Occupational exposure to flour, diisocyanates, welding/soldering fumes and vehicle/motor exhaust was associated with respiratory symptoms in the past 12 months and use of asthma medication. However, prospective data are needed to confirm the observed associations.
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| 16. |
- Aftab, Ahmad, 1979-, et al.
(författare)
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A stiffness modeling methodology for simulation-driven design of haptic devices
- 2014
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Ingår i: Engineering with Computers. - : Springer Science and Business Media LLC. - 0177-0667 .- 1435-5663. ; 30:1, s. 125-141
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Tidskriftsartikel (refereegranskat)abstract
- Efficient development and engineering of high performing interactive devices, such as haptic robots for surgical training benefits from model-based and simulation-driven design. The complexity of the design space and the multi-domain and multi-physics character of the behavior of such a product ask for a systematic methodology for creating and validating compact and computationally efficient simulation models to be used in the design process. Modeling the quasi-static stiffness is an important first step before optimizing the mechanical structure, engineering the control system, and performing hardware in the loop tests. The stiffness depends not only on the stiffness of the links, but also on the contact stiffness in each joint. A fine-granular Finite element method (FEM) model, which is the most straightforward approach, cannot, due to the model size and simulation complexity, efficiently be used to address such tasks. In this work, a new methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device is proposed, which considers the stiffness of actuation systems, flexible links and passive joints. For the modeling of passive joints, a hertzian contact model is introduced for both spherical and universal joints, and a simply supported beam model for universal joints. The validation process is presented as a systematic guideline to evaluate the stiffness parameters both using parametric FEM modeling and physical experiments. Preloading has been used to consider the clearances and possible assembling errors during manufacturing. A modified JP Merlet kinematic structure is used to exemplify the modeling and validation methodology.
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| 17. |
- Aftab, Ahmad, 1979-, et al.
(författare)
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Kinematics and Dynamics of a novel 6-DoF TAU Haptic Device
- 2011
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Ingår i: Proceedings of the 2011 IEEE International Conference on MechatronicsInternational Conference on Mechatronics, April 13-15, 2011, Istanbul, Turkey. - : IEEE conference proceedings. - 9781612849829 ; , s. 719-724
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Konferensbidrag (refereegranskat)abstract
- This paper presents the kinematics and dynamics modeling of a novel hybrid kinematic concept, i.e. the TAU haptic device. This new concept was obtained from the modification of TAU-2 structure proposed by Khan et al. First a kinematic model for inverse and forward kinematics was developed and analyzed. Then an algorithm to solve the close form inverse dynamics is presented using Lagrangian formulation. Numerical simulation was carried out to examine the validity of the approach and accuracy of the technique employed. A trigonometric helical trajectory of 5th order spline was developed in Cartesian space for each degree of freedom of the moving platform in order to verify and simulate the inverse dynamics; the motion of the platform is such that the tool centre point remains on this trajectory while its orientation is changing constantly in roll, pitch and yaw.
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| 18. |
- Aftab, Ahmad, 1979-
(författare)
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Model-based design of haptic devices
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efficient engineering design and development of high precision and reliable surgical simulators, like haptic devices for surgical training benefits from model-based and simulation driven design. The complexity of the design space, multi-domains, multicriteria requirements and multi-physics character of the behavior of such a product ask for a model based systematic approach for creating and validating compact and computationally efficient simulation models to be used for the design process.The research presented in this thesis describes a model-based design approach towards the design of haptic devices for simulation of surgical procedures, in case of hard tissues such as bone or teeth milling. The proposed approach is applied to a new haptic device based on TAU configuration.The main contributions of this thesis are: Development and verification of kinematic and dynamic models of the TAU haptic device. Multi-objective optimization (MOO) approach for optimum design of the TAU haptic device by optimizing kinematic performance indices, like workspace volume, kinematic isotropy and torque requirement of actuators. A methodology for creating an analytical and compact model of the quasi-static stiffness of haptic devices, which considers the stiffness of; actuation system;flexible links and passive joints.
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| 19. |
- Aghapour, Sajad, et al.
(författare)
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Helicity, spin, and infra-zilch of light : A Lorentz covariant formulation
- 2021
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Ingår i: Annals of Physics. - : Elsevier BV. - 0003-4916 .- 1096-035X. ; 431
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel conserved Lorentz covariant tensor, termed the helicity tensor, is introduced in Maxwell theory. The conservation of the helicity tensor expresses the conservation laws contained in the helicity array, introduced by Cameron et al. (2012), including helicity, spin, as well as the spin-flux or infra zilch. The Lorentz covariance of the helicity tensor is in contrast to previous formulations of the helicity hierarchy of conservation laws, which required the non-Lorentz covariant transverse gauge. The helicity tensor is shown to arise as a Noether current for a variational symmetry of a duality-symmetric Lagrangian for Maxwell theory. This symmetry transformation generalizes the duality symmetry and includes the symmetry underlying the conservation of the spin part of the angular momentum.
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| 20. |
- Aghapour, Sajad, et al.
(författare)
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The zilch electromagnetic conservation law revisited
- 2020
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Ingår i: Journal of Mathematical Physics. - : AIP Publishing. - 0022-2488 .- 1089-7658. ; 61:12
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the zilch conservation law arises as the Noether current corresponding to a variational symmetry of a duality-symmetric Maxwell Lagrangian. The action of the corresponding symmetry generator on the duality-symmetric Lagrangian, while non-vanishing, is a total divergence as required by the Noether theory. The variational nature of the zilch conservation law was previously known only for some of the components of the zilch tensor, notably the optical chirality. By contrast, our analysis is fully covariant and is, therefore, valid for all components of the zilch tensor. The analysis is presented here for both the real and complex versions of duality-symmetric Maxwell Lagrangians.
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| 21. |
- Ahmad, Aftab, et al.
(författare)
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A comparative study of friction estimation and compensation using extended, iterated, hybrid, and unscented kalman filters
- 2013
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Ingår i: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - 2013. - : ASME Press. - 9780791855966
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Konferensbidrag (refereegranskat)abstract
- Transparency is a key performance evaluation criterion for haptic devices, which describes how realistically the haptic force/torque feedback is mimicked from a virtual environment or in case of master-slave haptic device. Transparency in haptic devices is affected by disturbance forces like friction between moving parts. An accurate estimate of friction forces for observer based compensation requires estimation techniques, which are computationally efficient and gives reduced error between measured and estimated friction. In this work different estimation techniques based on Kalman filter, such as Extended Kalman filter (EKF), Iterated Extended Kalman filter (IEKF), Hybrid extended Kalman filter (HEKF) and Unscented Kalman filter (UKF) are investigated with the purpose to find which estimation technique that gives the most efficient and realistic compensation using online estimation. The friction observer is based on a newly developed friction smooth generalized Maxwell slip model (S-GMS). Each studied estimation technique is demonstrated by numerical and experimental simulation of sinusoidal position tracking experiments. The performances of the system are quantified with the normalized root mean-square error (NRMSE) and the computation time. The results from comparative analyses suggest that friction estimation and compensation based on Iterated Extended Kalman filter both gives a reduced tracking error and computational advantages compared to EKF, HEKF, UKF, as well as with no friction compensation.
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| 22. |
- Ahmad, Aftab, et al.
(författare)
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A deterministic and probabilistic approach for robust optimal design of a 6-DOF haptic device
- 2014
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Ingår i: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference--2013. - : ASME Press. - 9780791855898 ; , s. V03BT03A032-
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Konferensbidrag (refereegranskat)abstract
- This work suggests a two-stage approach for robust optimal design of 6-DOF haptic devices based on a sequence of deterministic and probabilistic analyses with a multi-objective genetic algorithm and the Monte-Carlo method. The presented model-based design robust optimization approach consider simultaneously the kinematic, dynamic, and kinetostatic characteristics of the device in both a constant and a dexterous workspace in order to find a set of optimal design parameter values for structural configuration and dimensioning. Design evaluation is carried out based on local and global indices, like workspace volume, quasi-static torque requirements for the actuators, kinematic isotropy, dynamic isotropy, stiffness isotropy, and natural frequencies of the device. These indices were defined based on focused kinematic, dynamic, and stiffness models. A novel procedure to evaluate local indices at a singularity-free point in the dexterous workspace is presented. The deterministic optimization approach neglects the effects from variations of design variables, e.g. due to tolerances. A Monte-Carlo simulation was carried out to obtain the response variation of the design indices when independent design parameters are simultaneously regarded as uncertain variables. It has been observed that numerical evaluation of performance indices depends of the type of workspace used during optimization. To verify the effectiveness of the proposed procedure, the performance indices were evaluated and compared in constant orientation and in dexterous workspace.
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| 23. |
- Ahmad, Aftab, et al.
(författare)
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A model-based and simulation driven design approach for haptic devices
- 2013
-
Ingår i: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference--2013. - : ASME Press. - 9780791855867 ; , s. V02BT02A014-
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Konferensbidrag (refereegranskat)abstract
- The output from a design process of high precision and reliable haptic devices for surgical training like bones and teeth is a complex design. The complexity is largely due to the multi-criteria and conflicting character of the functional requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, and high transparency. The requirements are a basis for generating design concepts. The concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, and friction models. The design process can benefit from a model-based and simulation driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a complete realization of the system. Such an approach is presented and evaluated through a test case where a haptic device, based on a Stewart platform, has been designed and realized. It can be concluded, based on simulation and experimental results that the performance of this optimally designed haptic device satisfies the stated user requirements. This indicates that the methodology can support the development of an optimal haptic device. However, more test cases are needed to further verify the presented methodology.
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| 24. |
- Ahmad, Aftab, et al.
(författare)
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A model-based and simulation-driven methodology for design of haptic devices
- 2014
-
Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 24:7, s. 805-818
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Tidskriftsartikel (refereegranskat)abstract
- High precision and reliable haptic devices are highly complex products. The complexity that has to be carefully treated in the design process is largely due to the multi-criteria and conflicting character of the functional and performance requirements. These requirements include high stiffness, large work-space, high manipulability, small inertia, low friction, high transparency, as well as cost constraints. The requirements are a basis for creating and assessing design concepts. Concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, friction, and control models. The design process can benefit from a model-based and simulation-driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized. Such an approach is presented, put in context of the V-model, and evaluated through a test case where a haptic device, based on a Stewart platform, is designed and realized. It can be concluded, based on simulation and experimental results that the performance of this deterministically optimized haptic device satisfies the stated user requirements. Experiences from this case indicate that the methodology is capable of supporting effective and efficient development of high performing haptic devices. However, more test cases are needed to further validate the presented methodology.
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| 25. |
- Ahmad, Aftab, 1979-, et al.
(författare)
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An approach to stiffness analysis methodology for haptic devices
- 2011
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Ingår i: 2011 3rd International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT). - : IEEE conference proceedings. - 9781457706820 ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- In this work a new methodology is proposed to model the static stiffness of a haptic device. This methodology can be used for other parallel, serial and hybrid manipulators. The stiffness model considers the stiffness of; actuation system; flexible links and passive joints. For the modeling of the passive joints a Hertzian contact model is introduced for both spherical and universal joints and a simply supported beam model for universal joints. For validation of the stiffness model a modified JP Merlet kinematic structure has been used as a test case. A parametric Ansys FEM model was developed for this test case and used to validate the resulting stiffness model. The findings in this paper can provide an additional index to use for multi-objective structural optimization to find an optimum compromise between a lightweight design and the stiffness performance for high precision motion within a larger workspace.
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| 26. |
- Ahmad, Aftab, et al.
(författare)
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An Optimization Approach Toward a Robust Design of Six Degrees of Freedom Haptic Devices
- 2015
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Ingår i: Journal of mechanical design (1990). - : ASME International. - 1050-0472 .- 1528-9001. ; 137:4
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents an optimization approach for the robust design of six degrees of freedom (DOF) haptic devices. Our objective is to find the optimal values for a set of design parameters that maximize the kinematic, dynamic, and kinetostatic performances of a 6-DOF haptic device while minimizing its sensitivity to variations in manufacturing tolerances. Because performance indices differ in magnitude, the formulation of an objective function for multicriteria performance requirements is complex. A new approach based on Monte Carlo simulation (MCS) was used to find the extreme values (minimum and maximum) of the performance indices to enable normalization of these indices. The optimization approach presented here is formulated as a methodology in which a hybrid design-optimization approach, combining genetic algorithm (GA) and MCS, is first used. This new approach can find the numerical values of the design parameters that are both optimal and robust (i.e., less sensitive to variation and thus to uncertainties in the design parameters). In the following step, with design optimization, a set of optimum tolerances is determined that minimizes manufacturing cost and also satisfies the allowed variations in the performance indices. The presented approach can thus enable the designer to evaluate trade-offs between allowed performance variations and tolerances cost.
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| 27. |
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| 28. |
- Ahmad, Aftab, 1979-
(författare)
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Effective development of haptic devices using a model-based and simulation-driven design approach
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Virtual reality (VR)-based surgical simulators using haptic devices can increase the effectiveness of surgical training for surgeons when performing surgical procedures in hard tissues such as bones or teeth milling. The realism of virtual surgery through a surgical simulator depends largely on the precision and reliability of the haptic device, which reflects the interaction with the virtual model. The quality of perceptiveness (sensation, force/torque) depends on the design of the haptic device, which presents a complex design space due to its multi-criteria and conflicting character of functional and performance requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, high transparency, and cost constraints.This thesis proposes a design methodology to improve the realism of force/torque feedback from the VR-based surgical simulator while fulfilling end-user requirements.The main contributions of this thesis are:1. The development of a model-based and simulation-driven design methodology, where one starts from an abstract, top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized.2. A methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device, which considers the stiffness of actuation systems, flexible links and passive joints.3. A robust design optimization approach to find the optimal numerical values for a set of design parameters to maximize the kinematic, dynamic and kinetostatic performances of a 6-degrees of freedom (DOF) haptic device, while minimizing its sensitivity to variations in manufacturing tolerances and cost, and also satisfying the allowed variations in the performance indices.4. A cost-effective approach for force/torque feedback control using force/torque estimated through a recursive least squares estimation.5. A model-based control strategy to increase transparency and fidelity of force/torque feedback from the device by compensating for the natural dynamics of the device, friction in joints, gravity of platform, and elastic deformations.
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| 29. |
- Ahmad, Aftab, et al.
(författare)
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Evaluation of friction models for haptic devices
- 2013
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Konferensbidrag (refereegranskat)abstract
- In this work different friction models are evaluated to determine how well these models are suited for performance simulation and control of a 6-DOF haptic device. The studied models include, Dahl model, LuGre model, Generalized Maxwell slip model (GMS), smooth Generalized Maxwell slip model (S-GMS) and Differential Algebraic Multistate (DAM) friction model. These models are evaluated both numerically and experimentally with an existing 6-DOF haptic device that is based on a Stewart platform. In order to evaluate how well these models compensate friction, a model-based feedback friction compensation strategy along with a PID controller were used for position fracking accuracy The accuracies of the friction compensation models are examined separately for both low-velocity and high-velocity motions of the system. To evaluate these models, we use criteria based on fidelity to predict realistic friction phenomena, easiness to implement, computational efficiency and easiness to estimate the model parameters. Experimental results show that friction compensated with GMS, S-GMS and DAA4 models give better accuracy in terms of standard deviation, Root Mean Squared Error, and maximum error between a reference and measured trajectory. Based on the criteria of fidelity, ease of implementation and ease to estimate model parameters, the S-GMS model, which represents a smooth transition between sliding and pre-sliding regime through an analytical set of differential equations, is suggested.
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| 30. |
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| 31. |
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| 32. |
- Alestig, Kjell, 1931, et al.
(författare)
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Ceftazidime and renal function.
- 1984
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Ingår i: The Journal of antimicrobial chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 13:2, s. 177-81
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Tidskriftsartikel (refereegranskat)abstract
- Glomerular filtration rate (GFR) as measured by 51Chrome-EDTA clearance, decreased with a mean of 10 ml/min during therapy with ceftazidime 2 g bid in 16 patients with initial GFR of 30 to 110 ml/min. A significant increase in the excretion of urinary alanine aminopeptidase was also found. In another three patients with initial GFR of 17-22 ml/min increases in serum creatinine during therapy were noted. These observations indicate that ceftazidime should be used with caution in patients with impaired renal function and not be combined with nephrotoxic drugs until the safety of such combinations has been studied.
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| 33. |
- Andersson, Anders, et al.
(författare)
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Describing fish passage in a river confluence with telemetry and CFD
- 2016
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Konferensbidrag (refereegranskat)abstract
- The confluence between hydropower tailrace and the old river bed in Stornorrfors in the river Umeälven in the northern part of Sweden has shown to be the largest obstacle for upstream migrating salmon and sea trout during the migrating season. Fish are attracted to the high flow rate from the tailrace and will not migrate upstream in the old river bed being the passage to the fishway leading past the hydropower dam. By triangulating the movements of radio tagged fish using eight antennas in the confluence, it is here possible to describe the individual fish tracks left by radio tagged fish during the migrating season. These tracks are then compared with three-dimensional Computational Fluid Dynamics (CFD) simulations of the confluence. By simulating the most common combinations of turbine flow and spill flow in the old river bed it is then possible to find correlations between individual fish movements and flow parameters such as velocity, turbulence intensity or vorticity for different flow combinations. It was previously assumed that fish had trouble locating the old river bed, the results of the triangulation however shows that most fish finds the old river bed within a few days but does not chose to migrate until several days (or weeks) later. The main issue to be solved is therefore not how to attract the fish to the old river bed but rather how to create favorable conditions in the old river bed so that migrating fish are more inclined to take that path upstream.
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| 34. |
- Andersson, Anders G., et al.
(författare)
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A numerical study of the location and function of the entrance of a fishway in a regulated river
- 2010
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Ingår i: 8th International Symposium on ECOHYDRAULICS. ; , s. 277-284
-
Konferensbidrag (refereegranskat)abstract
- Simulation driven design with Computational Fluid Dynamics has been used to evaluate the flow downstream a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations and the tailrace jet from the turbines is stronger in the simulations. The simulations are however considered to capture the important features of the flow in a way that makes them viable for attraction water simulations. A fishway entrance was included in the simulations and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.
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| 35. |
- Andersson, Anders G., et al.
(författare)
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A study of the location of the entrance of a fishway in a regulated river with CFD and ADCP
- 2012
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Ingår i: Modelling and Simulation in Engineering. - : Hindawi Limited. - 1687-5591 .- 1687-5605. ; 2012
-
Tidskriftsartikel (refereegranskat)abstract
- Simulation-driven design with computational fluid dynamics has been used to evaluate the flow downstream of a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed, and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations, and the tailrace jet from the turbines is stronger in the simulations. A fishway entrance was included in the simulations, and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed for further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.
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| 36. |
- Andersson, Andreas, 1980-
(författare)
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Utmattningsanalys av järnvägsbroar : En fallstudie av stålbroarna mellan Stockholm Central och Söder Mälarstrand, baserat på teoretiska analyser och töjningsmätningar
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Föreliggande avhandling omfattar en fallstudie av utmattningsrisken för järnvägsbroarna mellan Stockholm Central och Söder Mälarstrand. Ett stort antal utmattningssprickor i broarna över Söderström och Söder Mälarstrand har sedan länge varit kända. I samband med en bärighetsutredning av sträckan har ett stort antal anslutningspunkter i samtliga broar identifierats som kritiska avseende utmattningsrisk. Sträckan är den mest trafikerade i Sverige och de förenklade beräkningsmetoder som anges i Banverkets föreskrift för bärighetsberäkningar är i vissa fall inte tillämpliga. De formella bärighetsberäkningarna har visat på flerfaldiga överskridanden i utnyttjandegrad gällande utmattning. I de punkter som beräkningarna visar störst risk för utmattning har inga sprickor påträffats, trots omfattande förbandsbesiktningar. Beräkningarna baseras på typiserade spänningskollektiv och givet antal spänningsväxlingar, oberoende av den aktuella trafikmängden. Enligt bärighetsnormen ges möjlighet att beakta den verkliga trafikmängden baserat på historiskt bruttotonnage och typiserade trafiklaster. Dessa beräkningar har utförts och visar på ännu större risk för utmattning, jämfört med den förenklade metoden. I syfte att på ett ännu mer nyanserat sätt uppskatta utmattningsrisken har en metod använts, baserat på uppskattning av den faktiska trafikmängden och dess fördelningar. Beräkningarna baseras på trafikdata tillgänglig från Banverket. Metoden är tillämplig på andra järnvägsbroar på andra sträckor. Utöver teoretiska beräkningar har töjningsmätningar utförts. Under 2006 utförde dåvarande Carl Bro AB töjningsmätningar på bro över Söder Mälarstrand och viadukt söder om Söder Mälarstrand, avseende några enskilda tågöverfarter. Under 2008 utförde KTH Brobyggnad omfattande töjningsmätningar på bro över Söderström, avseende all trafik under en månads tid.
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| 37. |
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| 38. |
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| 39. |
- Andersson, Britta, 1979-
(författare)
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Manipulation of potassium ion fluxes to induce apoptosis in lung cancer cells
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Apoptosis is a special form of cell death that if non-functional may lead to diseases such as cancer. A reduction of the intracellular potassium ion (K+) content is necessary for activating enzymes important for the execution of apoptosis. Pharmacological modulation of K+ fluxes to reduce intracellular K+ in cancer cells might therefore force the cells into apoptosis and decrease tumour cell mass. Human malignant pleural mesothelioma (MPM) is a form of cancer often caused by asbestos exposure. Although asbestos has been banned in the Western World, the incidence of MPM is expected to increase. Cisplatin is the first-line chemotherapy for MPM, but acquired resistance to the drug is a clinical problem. This thesis is mainly based on work with the human malignant pleural mesothelioma cell line (P31 wt) and a cisplatin-resistant sub-line (P31 res). The aim was to first characterize K+ fluxes in P31 wt and P31 res cells, and then manipulate them in order to reduce intracellular K+ and induce apoptosis with K+ manipulation alone or in combination with cisplatin. Characterization of K+ fluxes in P31 wt cells showed that: 1) ouabain, a digitalis-like drug, and specific blocker of the Na+, K+, ATPase pump, effectively inhibited K+ uptake, 2) bumetanide, a diuretic, and an inhibitor of the Na+, K+, 2Cl-¬-cotransporter, had a transient effect on K+ uptake, and 3) the antifungal drug amphotericin B stimulated K+ efflux. In order to determine intracellular K+ content, the potassium-binding fluorescent probe PBFI-AM was used in a 96-well plate assay. After a 3-h incubation with ouabain, with or without bumetanide, combined with amphotericin B, the intracellular K+ content was reduced in P31 wt cells but not in P31 res cells. Ouabain induced apoptosis in both P31 wt and P31 res cells. P31 res cells were sensitized to cisplatin by ouabain, since 10 mg/L cisplatin in combination with ouabain induced about the same percentage of apoptotic cells as 40 mg/L cisplatin. Apoptosis was executed via caspase-3 activation in both P31 wt and P31 res cells. Amphotericin B enhanced ouabain-induced apoptosis in P31 wt cells via caspase-9 activation, with increased caspase-3 activation and DNA fragmentation as consequences. Ouabain-induced apoptosis in P31 res cells was executed via increased expression of pro-apoptotic Bak. The combination of cisplatin with ouabain and amphotericin B was stressful to both P31 wt and P31 res cells, since SAPK/JNK a known factor in stress-induced apoptosis was activated. In conclusion, K+ flux manipulation with clinical used drugs can induce apoptosis per se and also enhance cisplatin-induced apoptosis in P31 wt and P31 res cells.
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Andersson, Daniel, et al.
(författare)
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M-Sequence UWB Radar for Industrial Applications
- 2010
-
Ingår i: Program of GigaHertz Symposium 2010, March 9-10, at Lund University.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Ultra Wideband Radar has the potential of dramatically improving the control and surveillance of industrial processes in confined areas. An example is the application of UWB radar for surveillance of furnaces for heath treatment of steel billets developed by Radarbolaget in Gävle. In our installation at AB Sandvik Materials Technology, we have shown that by using a non-destructive UWB Radar technique it is possible to visualize in real-time the ongoing process inside the furnace behind a 0.5 m thick ceramic wall. Since the operating temperature inside the furnace is 1200 °C, there is today no other known method capable of visualizing the process for the operator of the furnace. The system is therefore designed to sustain high temperatures and powerful electromagnetic disturbances while performing measurement with wide dynamics and high stability. The design of this radar is based on the idea of transmitting a continuous m-sequence and then detecting the correlated impulse response (see figure below). The wide bandwidth is a requirement for obtaining high spatial accuracy and resolution but puts further requirements on the design of the antennas and the electronics. Our results show that with this technique it is possible to determine the deformation of the steel billets inside the furnace with an accuracy of less than 5 mm. The radar system is also able to detect deformations in the furnace wall The m-sequence radar has many advantages over other UWB radar technologies since it e.g. does not require many analogue components. Its performance is a result of the choice of code length, sampling rate and averaging. However, the resolution is still limited by the impulse response of the analogue antenna (ringing). In this paper system parameters that affect the overall performance of an m-sequence radar are reviewed and means of enhancing its performance are discussed.
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| 44. |
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| 45. |
- Andersson, Eva, 1955, et al.
(författare)
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A case-referent study of cancer mortality among sulfate mill workers in Sweden.
- 2001
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Ingår i: Occupational and environmental medicine. - 1351-0711. ; 58:5, s. 321-4
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate whether workers in Swedish sulfate mills have an increased risk of death from certain malignancies that have previously been linked to the pulping process. METHODS: Subjects of the study (n=2480) were men aged 40-75 at death during 1960-89 in the parishes surrounding four sulfate mills. Exposure assessment was based on information from the personnel files in the mills- 35% of the subjects were recognised there, and work categories were created. RESULTS: Among all sulfate mill workers, the odds ratio (OR) (90% confidence interval (90% CI)) for death from lung cancer was 1.6 (1.1 to 2.3), pleural mesotheliomas 9.5 (1.9 to 48), brain tumours 2.6 (1.2 to 5.3), and liver or biliary tract cancer 2.3 (1.0 to 5.2). There was an increased mortality from leukaemia among workers in the soda recovery plant (5.9 (2.6 to 13)) and bleaching plant and digester house (2.8 (1.0 to 7.5)). CONCLUSIONS: Sulfate mill workers were at increased risk of dying from lung cancer and pleural mesotheliomas, probably due to exposure to asbestos. Increased risks of brain tumours and cancers of the liver or biliary tract were also found but the aetiology is not obvious.
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| 46. |
- Andersson, Eva, 1955, et al.
(författare)
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Adult-onset asthma and wheeze among irritant-exposed bleachery workers.
- 2003
-
Ingår i: American journal of industrial medicine. - : Wiley. - 0271-3586. ; 43:5, s. 532-538
-
Tidskriftsartikel (refereegranskat)abstract
- Background Whether new-onset asthma is associated with irritant exposure is unclear. The aim was to investigate if occupational exposure to irritant gases, especially repeated peak exposure (gassings), increased the risk of obstructive airways disease. Methods Data on airway symptoms and exposure among bleachery (n=101) and paper department workers (n=314) were collected by a questionnaire. Incidence rates and hazard ratios (HR) (Cox regression) were calculated. Non-responders were interviewed by telephone. Results The incidence rate for adult-onset physician-diagnosed asthma among bleachery workers reporting gassings giving rise to respiratory symptoms was 7.6/103 person-years and for those without gassings 2.2/103 person-years, compared to 1.0/103 person-years for paper workers. In a Cox regression model for asthma (n=12), stratified for sex, HR for gassings were 5.6 (95% confidence intervals (CI) 1.6–20), for hay fever 3.0 (95% CI 0.8–11), and for ever smoking 0.7 (95% CI 0.2–2.4). The same model for adult-onset wheeze gave HR of 5.2 (95% CI 2.2–12), 1.7 (95% CI 0.6–5.4), and 1.1 (95% CI 0.5–2.7), respectively. Conclusions Repeated peak exposure to irritant gases, here studied as gassings in the pulp industry, increased the risk for both adult-onset asthma and wheeze.
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| 47. |
- Andersson, Eva, 1955, et al.
(författare)
-
Cohort mortality study of Swedish pulp and paper mill workers-nonmalignant diseases
- 2007
-
Ingår i: Scandinavian Journal of Work, Environment and Health. - : Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 33:6, s. 470-478
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives The aim of this study was to determine mortality among pulp and paper mill workers according to the main mill pulping process, department, and gender, particular reference being given to diseases of the circulatory and respiratory systems.Methods The cohort of 18 163 men and 2 291 women employed between 1939 and 1999 and with >1 year of employment was followed for mortality from 1952 to 2001 (acute myocardial infarction from 1969). Standardized mortality ratios (SMR) with 95% confidence intervals (95% CI) were estimated by comparing the observed number of deaths with the expected number for the entire Swedish population. Exposure was assessed from personnel files in the mills. Data from an exposure measurement database are also presented.Results There were 5898 deaths in the cohort. Total mortality had an SMR of 1.02 (95% CI 0.98–1.06) for the men in the sulfate mills and an SMR of 0.93 (95% CI 0.90–0.97) for the men in the sulfite mills. Mortality from acute myocardial infarction was increased among the men in both the sulfate and sulfite mills [SMR 1.22 (95% CI 1.12–1.32) and SMR 1.11 (95% CI 1.02–1.21), respectively] and by department in sulfate pulping (SMR 1.29, 95% CI 1.07–1.54), paper production (SMR 1.26, 95% CI 1.06–1.49), and maintenance (SMR 1.16, 95% CI 1.02–1.30). Mortality from cerebrovascular disease, diabetes mellitus, and nonmalignant respiratory diseases was not increased.Conclusions Death from acute myocardial infarction, but not cerebrovascular diseases, was increased in this cohort and was probably related to a combination of different occupational exposures (eg, dust, sulfur compounds, shift work, and noise).
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| 48. |
- Andersson, Eva, 1955, et al.
(författare)
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Gliomas among men employed in the Swedish pulp and paper industry.
- 2002
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Ingår i: Scandinavian journal of work, environment & health. - 0355-3140. ; 28:5, s. 333-40
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: This study investigated whether previous findings of an increased risk of gliomas among workers in some pulp and paper mills could be confirmed for all Swedish pulp and paper mill workers and whether the increase could be attributed to certain occupational groups. METHODS: The study was based on the Swedish Cancer Environment Register, which links the incidence of cancer from 1971 to 1990 and the 1960 and 1970 census data on codes of occupation and industry for the whole population. Standardized incidence ratios (SIR) were used to estimate the risks for men in different occupations in pulp (N = 28,142) and paper (N = 39,169) mills in 1960, 1970 or both years as compared with those of all gainfully employed men in Sweden. RESULTS: Maintenance workers employed in pulp or paper mills in 1960, 1970 or both years, as well aspulp workers, showed an increased incidence of gliomas in 1971-1990 [SIR 1.5, 95% confidence interval (95% CI) 1.1-2.1 and SIR 1.5,95% CI 1.0-2.2, respectively], whereas the incidence among process workers in paper mills was lower than expected (SIR 0.6, 95% CI 0.3-0.9). Taken together, all employed men in the pulp mill industry had an increased incidence of gliomas (SIR 1.3, 95% CI 1.0-1.7). CONCLUSIONS: Pulp mill workers, but not paper mill workers, were found to have more gliomas in 1971-1990 than expected. There was an increased risk of gliomas among maintenance workers in both pulp and paper mills. Few risk factors for brain tumors are recognized, and the causes of the increase are not obvious.
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| 49. |
- Andersson, Eva, 1955, et al.
(författare)
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Incidence of asthma among workers exposed to sulfur dioxide and other irritant gases
- 2006
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Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 0903-1936 .- 1399-3003. ; 27:4, s. 720-5.
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate whether repeated peak exposure (gassings) to sulphur dioxide (SO2) and other irritant gases increases the risk of new-onset asthma. A questionnaire was sent to 4,112 sulphite workers, of whom 1,919 completed the questionnaire and 396 completed the short-form questionnaire, which was sent out as a last reminder. A sample of 130 nonrespondents completed a telephone interview using the short-form questionnaire. The incidence of adult-onset, physician-diagnosed asthma during employment duration was analysed in relation to exposure to SO2 and gassings giving rise to respiratory symptoms. Incidence rates, as well as incidence rate ratios with 95% confidence interval (CI), were calculated. Further Cox regression models were used allowing assessment of hazard ratios (HR) stratified for sex and adjusted for atopy, smoking habits and age. The incidence rate for asthma among sulphite mill workers reporting gassings of SO2 was 6.2 out of 1,000 person-yrs, compared with 1.9 out of 1,000 person-yrs among subjects unexposed to SO2 and any gassings (HR (95% CI) 4.0 (2.1-7.7)). Among males reporting gassings to SO2, the HR (95% CI) for asthma was 5.8 (2.6-13) compared with unexposed males. In conclusion, repeated peak exposure to sulphur dioxide increased the incidence of asthma during work in sulphite pulp mills, which supports the hypothesis of irritant-induced asthma.
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| 50. |
- Andersson, Eva, 1955, et al.
(författare)
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Incidence of chronic bronchitis in a cohort of pulp mill workers with repeated gassings to sulphur dioxide and other irritant gases
- 2013
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Ingår i: Environmental Health. - : BioMed Central (BMC). - 1476-069X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Occupational exposure to irritants is associated with chronic bronchitis. The aim of this study was to elucidate whether repeated peak exposures with respiratory symptoms, gassings, to sulphur dioxide (SO2) and other irritant gases could increase the risk of chronic bronchitis.METHODS: The study population comprised 3,060 Swedish pulp mill workers (84% males) from a cohort study, who completed a comprehensive questionnaire with items on chronic bronchitis symptoms, smoking habit, occupational history, and specific exposures, including gassings. 2,037 have worked in sulphite mills. Incidence rates and hazard ratios (HRs) for the observation period, 1970-2000, in relation to exposure and the frequency of repeated gassings to SO2 and other irritant gases were calculated.RESULTS: The incidence rate for chronic bronchitis among workers with repeated gassings was 3.5/1,000 person-years compared with 1.5/1,000 person-years among unexposed workers (HR 2.1, 95% confidence interval (CI) 1.4-3.1). The risk was even higher in the subgroup with frequent gassings (HR 3.2, 95% CI 2.0-5.2), particularly among never-smokers (HR 8.7, 95% CI 3.5-22).CONCLUSIONS: Repeated gassings to irritant gases increased the incidence of chronic bronchitis in our study population during and after work in pulp mills, supporting the hypothesis that occupational exposures to irritants negatively affect the airways. These results underscore the importance of preventive actions in this work environment.
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