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- Saaf, M, et al.
(författare)
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Growth hormone treatment of osteoporotic postmenopausal women - a one-year placebo-controlled study
- 1999
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Ingår i: European journal of endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 140:5, s. 390-399
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To study the effect of 12 months of growth hormone (GH) treatment on bone markers, bone mineral density (BMD), lean body mass (LBM) and body fat mass (BF) in postmenopausal osteoporotic women. DESIGN: Sixteen patients were randomised to a double-blind randomised placebo-controlled one-year study with daily s.c. injections of GH or placebo. After the first year 14 patients (8 placebo treated, 6 GH treated) were recruited to GH treatment during the second year. All patients were also supplemented with 0.5 g calcium per oral. METHODS: Bone mineral density and body composition were assessed by dual energy X-ray absorptiometry. Biochemical bone markers were analysed by RIA or HPLC techniques. Diurnal GH profiles were performed with continuous venous blood sampling. RESULTS: Sixteen patients started in the placebo-controlled study. In all, twelve patients completed one year and only four patients completed two years of GH treatment. At baseline 3 patients had serum insulin-like growth factor-I (S-IGF-I) levels below -2 S.D. for age. Maximal diurnal GH levels tended to correlate negatively with S-IGF-I (P=0.076). S-IGF-I was unrelated to BMD. Serum IGF-binding protein-1 (S-IGFBP-1) correlated negatively with femoral neck BMD (r=-0.61, P=0.012). The intended GH dose of 0.05U/kg/day or a maximum of 3U/day s.c. was reduced to 0.024+/-0.004U/kg/day, equal to 0.5-2.7U/day due to frequent side effects, and four patients were excluded. After one year of GH treatment BF increased slightly, LBM and BMD in total body and lumbar spine were unchanged but femoral neck BMD had decreased 3.4+/-1.6% (P<0.05). The mean S-IGF-I increase was 32% (range -38-138%). Mean levels of the bone formation markers S-osteocalcin and S-procollagen type I propeptide increased maximally by 88 and 36% respectively after 9-12 months while the bone resorption markers were unchanged. In the placebo-treated group there were no significant alterations. CONCLUSIONS: The effects on S-IGF-I, bone markers and LBM were small although GH-related side effects were common. The reason for this apparent partial resistance to the anabolic effects of GH is not clear but nutritional deficits may be involved. Assessment of the effects of GH on bone mass and fracture rate requires longer study periods than one year.
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- Andersson, Håkan, et al.
(författare)
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Simulation of leakage flow through dynamic sealing gaps in hydraulic percussion units using a co-simulation approach
- 2021
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Ingår i: Simulation (San Diego, Calif.). - : Elsevier B.V.. - 1569-190X .- 1878-1462. ; 111
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a previously developed co-simulation method has been expanded to also simulate the dynamic behaviour of sealing gap regions in hydraulic percussion units. This approach is based on a 1D system model representing the fluid components and a 3D finite element model representing the structural parts of a hydraulic hammer. The sealing gap is a fundamental feature of a percussion unit, where the reciprocating motion of the piston is generated by the valve mechanism of the sealing gap. When the gap is closed it will prevent fluid flow between regions of different pressure levels. However, a small leakage flow through the gap will always occur which size depends on the clearance and the position of the piston. The method proposed here will take the structural motion and deformation into consideration when calculating the leakage flow. The deformed state of the structure is approximated by a cylindrical surface, in a least square manner, and communicated through the co-simulation interface to the fluid simulation module, and then used when calculating the leakage flow. This method aims at a more accurate simulation of the leakage flow that will not only yield a more realistic description of the mechanism on the local level, but also a more accurate estimation of global parameters such as overall performance and efficiency. The results indicate that the simulated leakage flow will decrease when dynamic gaps are used in comparison to static gaps, which is a consequence of the deformed structure that will generate smaller clearances. The leakage flow for the dynamic gaps will even be lower than for the static perfectly concentric case, mainly due to the reduction of clearances. The results also indicate that the dynamic eccentricity does not have a major influence on the leakage flow. The outcome from this study highlights the potentials of the described co-simulation approach for analysing the dynamics of the sealing gaps in a hydraulic percussion unit (i.e. gap heights, eccentricity ratios, etc.) including the evaluation of leakage flows and its impact on the overall performance. © 2021
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| 12. |
- Andersson, Håkan, et al.
(författare)
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Validation of a co-simulation approach for hydraulic percussion units applied to a hydraulic hammer
- 2019
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Ingår i: Advances in Engineering Software. - : ELSEVIER SCI LTD. - 0965-9978 .- 1873-5339. ; 131, s. 102-115
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a previously developed co-simulation approach has been adopted to simulate the responses of an existing hydraulic hammer product. This approach is based on a 1D system model representing the fluid components and a 3D finite element model representing the structural parts of the hydraulic hammer. The simulation model was validated against four experiments with different running conditions. The corresponding set-ups were analysed using the co-simulation method in order to evaluate the overall responses. A parameter study was also performed involving the working pressure and the restrictor diameter, with the objective to validate that a parameter change in the simulation model will affect the input and output power in the same direction as in the experiments. The experimental responses used in the validation were time history data of fluid pressure, component position and acceleration, and structural stresses. The experiments result in high frequency and high amplitude excitations of the hydraulic hammer and thus require a model with a high resolution of the model dynamics. The conclusion of the validation is that the simulation model is able to replicate the experimental responses with high accuracy including the high frequency dynamics. The favourable outcome of the validation makes the described co-simulation approach promising as an efficient tool for a wide range of other applications where short time duration mechanisms need to be studied.
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- Fuks, Kateryna B., et al.
(författare)
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Arterial blood pressure and long-term exposure to traffic-related air pollution : an analysis in the European Study of Cohorts for Air Pollution Effects (ESCAPE)
- 2014
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Ingår i: Journal of Environmental Health Perspectives. - : National Institute of Environmental Health Sciences (NIEHS). - 0091-6765 .- 1552-9924. ; 122:9, s. 896-905
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Forskningsöversikt (refereegranskat)abstract
- BACKGROUND: Long-term exposure to air pollution is hypothesized to elevate arterial blood pressure (BP). The existing evidence is scarce and country-specific. OBJECTIVES: We investigated the cross-sectional association of long-term traffic-related air pollution with BP and prevalent hypertension in European populations. METHODS: Fifteen population-based cohorts, participating in the European Study of Cohorts for Air Pollution Effects (ESCAPE), were analysed. Residential exposure to particulate matter and nitrogen oxides was modelled with land use regression using a uniform protocol. Traffic exposure was assessed with traffic indicator variables. We analysed systolic and diastolic BP in participants medicated and non-medicated with BP lowering medication (BPLM) separately, adjusting for personal and area-level risk factors and environmental noise. Prevalent hypertension was defined as ≥ 140 mmHg systolic, or ≥ 90 mmHg diastolic BP, or intake of BPLM. We combined cohort-specific results using random-effects meta-analysis. RESULTS: In the main meta-analysis of 113,926 participants, traffic load on major roads within 100 m of the residence was associated with increased systolic and diastolic BP in non-medicated participants (0.35 mmHg [95% CI: 0.02-0.68] and 0.22 mmHg [95% CI: 0.04-0.40] per 4,000,000 vehicles × m/day, respectively). The estimated odds ratio for prevalent hypertension was 1.05 [95% CI: 0.99-1.11] per 4,000,000 vehicles × m/day. Modelled air pollutants and BP were not clearly associated. CONCLUSIONS: In this first comprehensive meta-analysis of European population-based cohorts we observed a weak positive association of high residential traffic exposure with BP in non-medicated participants, and an elevated OR for prevalent hypertension. The relationship of modelled air pollutants with BP was inconsistent.
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- Ghandriz, Toheed, et al.
(författare)
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Structural Optimization of Multibody Systems
- 2015
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Ingår i: Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015. - 9788494424403 ; , s. 828-838
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Konferensbidrag (refereegranskat)abstract
- Flexible multibody dynamics (FMD) has found many applications in control, analysis and design of mechanical systems. FMD together with the theory of structural optimization can be used for designing multibody systems with bodies which are lighter, but stronger. Topology optimization of static structures is an active research topic in structural mechanics. However, the extension to the dynamic case is less investigated as one has to face serious numerical difficulties. One way of extending static structural topology optimization to topology optimization of dynamic flexible multibody system with large rotational and transitional motion is investigated in this paper. The optimization can be performed simultaneously on all flexible bodies. The simulation part of optimization is based on an FEM approach together with modal reduction. The resulting nonlinear differential-algebraic systems are solved with the error controlled integrator IDA (Sundials) wrapped into Python environment by Assimulo. A modified formulation of solid isometric material with penalization (SIMP) method is suggested to avoid numerical instabilities and convergence failures of the optimizer. Sensitivity analysis is central in structural optimization. The sensitivities are approximated to circumvent the expensive calculations. The provided examples show that the method is indeed suitable for optimizing a wide range of multibody systems. Standard SIMP method in structural topology optimization suggests stiffness penalization. To overcome the problem of instabilities and mesh distortion in the dynamic case we consider here additionally element mass penalization.
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- Hilding, T., et al.
(författare)
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Study of gasification reaction of cokes excavated from pilot blast furnace
- 2004
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Ingår i: SCANMET II. - Luleå : MEFOS. - 9163149109 ; , s. 467-478
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Konferensbidrag (refereegranskat)abstract
- Fundamental understanding of coke reactions with gas, metal and slag phases is essential for ensuring smooth operation and optimisation of coke performance in existing and advanced blast furnace process, and is dictated by coke properties and blast furnace process conditions. In this study, coke samples excavated from LKAB's Experimental Blast Furnace (EBF) at MEFOS in Luleå, Sweden were collected. The centreline quenched coke samples from different zones of this EBF were used to observe the influence of in-furnace reactions on the evolution of coke properties and their associations with CO2 reactivity. Carbon structure of coke was found to increasingly ordered, silicon and iron concentration in the coke samples decreased, while alkali concentration particularly potassium and sodium were found to increase as the coke descended towards lower part of the EBF. Both isothermal and non-isothermal reactivity based on TGA measurements showed that coke reactivity towards CO2 is increased as coke descends towards cohesive zone despite increasing order of carbon structures. Increased reactivity of cokes at lower parts of EBF was related to alkali enrichments of cokes. The study further shows that increased alkali components in cokes have a strong impact on CO2 gasification in EBF such that influence of coke graphitisation could be compensated by catalytic influence of alkalis. To further assist with development of understanding of reactivity of coke, gasification studies were also conducted in a fixed bed reactor at 900ºC using a series of cokes made from Australian coals (varying in rank, maceral and mineral matter). The CO2 reactivity of cokes in a fixed bed reactor was also found to be strongly influenced by the coke minerals compared to carbon structure. Further studies are required to provide a critical insight into the influence of key parameters such as coke graphitisation and mineral reactions on coke gasification particularly at higher temperatures.
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- Korek, Michal J., et al.
(författare)
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Traffic-related air pollution exposure and incidence of stroke in four cohorts from Stockholm
- 2015
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Ingår i: Journal of Exposure Science and Environmental Epidemiology. - : Springer Science and Business Media LLC. - 1559-0631 .- 1559-064X. ; 25:5, s. 517-523
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the risk of stroke related to long-term ambient air pollution exposure, in particular the role of various exposure time windows, using four cohorts from Stockholm County, Sweden. In total, 22,587 individuals were recruited from 1992 to 2004 and followed until 2011. Yearly air pollution levels resulting from local road traffic emissions were assessed at participant residences using dispersion models for particulate matter (PM10) and nitrogen oxides (NOX). Cohort-specific hazard ratios were estimated for time-weighted air pollution exposure during different time windows and the incidence of stroke, adjusted for common risk factors, and then meta-analysed. Overall, 868 subjects suffered a non-fatal or fatal stroke during 238,731 person-years of follow-up. An increment of 20 mu g/m(3) in estimated annual mean of road-traffic related NOX exposure at recruitment was associated with a hazard ratio of 1.16 (95% Cl 0.83-1.61), with evidence of heterogeneity between the cohorts. For PM10, an increment of 10 mu g/m(3) corresponded to a hazard ratio of 1.14(95% Cl 0.68-1.90). Time-window analyses did not reveal any clear induction-latency pattern. In conclusion, we found suggestive evidence of an association between long-term exposure to NOX and PM10 from local traffic and stroke at comparatively low levels of air pollution.
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- Schierbeck, S., et al.
(författare)
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Simulation and education National coverage of out-of-hospital cardiac arrests using automated external defibrillator-equipped drones-A geographical information system analysis
- 2021
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Ingår i: Resuscitation. - : Elsevier BV. - 0300-9572 .- 1873-1570. ; 163, s. 136-145
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Tidskriftsartikel (refereegranskat)abstract
- Background: Early defibrillation is essential for increasing the chance of survival in out-of-hospital-cardiac-arrest (OHCA). Automated external defibrillator (AED)-equipped drones have a substantial potential to shorten times to defibrillation in OHCA patients. However, optimal locations for drone deployment are unknown. Our aims were to find areas of high incidence of OHCA on a national level for placement of AED-drones, and to quantify the number of drones needed to reach 50, 80, 90 and 100% of the target population within eight minutes. Methods: This is a retrospective observational study of OHCAs reported to the Swedish Registry for Cardiopulmonary Resuscitation between 2010-2018. Spatial analyses of optimal drone placement were performed using geographical information system (GIS)-analyses covering high-incidence areas (>100 OHCAs in 2010-2018) and response times. Results: 39,246 OHCAs were included. To reach all OHCAs in high-incidence areas with AEDs delivered by drone or ambulance within eight minutes, 61 drone systems would be needed, resulting in overall OHCA coverage of 58.2%, and median timesaving of 05:01 (min:sec) [IQR 03:22-06:19]. To reach 50% of the historically reported OHCAs in <8 min, 21 drone systems would be needed; for 80%, 366; for 90%, 784, and for 100%, 2408. Conclusions: At a national level, GIS-analyses can identify high incidence areas of OHCA and serve as tools to quantify the need of AED-equipped drones. Use of only a small number of drone systems can increase national coverage of OHCA substantially. Prospective real-life studies are needed to evaluate theoretically optimized suggestions for drone placement.
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