| 1. |
- Farhang, Mehdy, et al.
(författare)
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The trend of radiological severity of hip fractures over a 30 years period : a cohort study
- 2019
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Ingår i: BMC Musculoskeletal Disorders. - : Springer Science and Business Media LLC. - 1471-2474. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Despite advances in operative techniques and preoperative care, proximal femur fractures (PFF) still represent a great public health problem. Displacement and fracture stability have been assumed as important determinants of treatment modality and outcome in such fractures. Purpose of this study was to determine whether the radiological severity of PFF fractures has increased over time.METHODS: In a cohort study, the plain radiographs of all patients with PFF aged over 50 years who were admitted to Umeå University Hospital in 1981/82, 2002 and 2012 were recruited to examine the types of fractures.RESULTS: The ratio of undisplaced to displaced femoral neck (FN) fractures was 30 to 70% in 1981/82, 28 to 72% in 2002 and 25 to 75% in 2012. The ratio of stable to unstable intertrochanteric (IT) fractures was 64 to 36% in 1981/82, 68 to 32% in 2002 and 75 to 25% in 2012. The ratio of simple to comminute subtrochanteric fractures was 35 to 65% in 1981/82, 16 to 84% in 2002 and 12 to 88% in 2012. In both FN and IT fractures we found no statistical difference among these 3 study periods, p = 0.67 and p = 0.40. In subtrochanteric fractures we saw a tendency towards more comminute subtrochanteric fractures (1981/82 to 2012), p = 0.09.CONCLUSIONS: We found no significant increment in the radiological severity of FN and IT over a 30 years' period. However, there was tendency towards an increase in comminute subtrochanteric fractures.
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| 2. |
- Parwal, Arvind, et al.
(författare)
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A comparative analysis of linear and nonlinear control of wave energy converter for a force control application
- 2019
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Ingår i: International Marine Energy Journal. - : European Wave and Tidal Energy Conference. - 2631-5548. ; 2:1, s. 39-50
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Tidskriftsartikel (refereegranskat)abstract
- The aim of wave energy converters (WECs) is to harvest the energy from the ocean waves and convert into electricity. Optimizing the generator output is a vital point of research. A WEC behaves as a nonlinear system in real ocean waves and a control that approximates the behaviour of the system is required. In order to predict the behaviour of WEC, a controller is implemented with an aim to track the referenced trajectory for a force control application of the WEC. A neural model is implemented for the system identification and control of the nonlinear process with a neural nonlinear autoregressive moving average exogenous (NARMAX) model. The neural model updates the weights to reduce the error by using the Levenberg-Marquardt back-propagation algorithm for a single-input-single-output (SISO) nonlinear system. The performance of the system under the proposed scheme is compared to the same system under a PI-controller scheme, where the PI gains have been tuned accordingly, to verify the control capacity of the proposed controller. The results show a good tracking of dq (direct-quadrature) axes currents by regulating the stator currents, and hence a force control is achieved at different positions of the translator. The dynamic performance of the control is verified in a time domain analysis for the displacement of the translator.
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| 3. |
- Parwal, Arvind, et al.
(författare)
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Grid integration and a power quality assessment of a wave-energy park
- 2019
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Ingår i: IET Smart Grid. - UK : Institution of Engineering and Technology (IET). - 2515-2947. ; 2:4, s. 625-634
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a step toward the grid connection of a wave-energy park through an electric power conversion system (EPCS) developed and installed for the wave-energy harvesting in Lysekil, Sweden. The EPCS comprises a rectifier, a DC bus, and an inverter followed by a harmonic filter (HF). The higher- and lower-order harmonics injected by the inverter in a power quality context are investigated. The lower-order voltage harmonics partially distort the voltage-source inverter output grid current. A phase-locked loop-based (PLL) grid-phase tracking is used to attenuate the lower-order harmonics by reflecting the grid harmonics in the inverter output. An expression for the grid-current harmonics as a function of the grid-voltage harmonics has been derived and implemented. A mathematical model is derived to obtain a transfer function for the PLL, and finally, proportional–integral gains are tuned for stable system operation. An HF for mitigating the higher-order harmonics has been implemented. The total harmonic distortion is evaluated experimentally, and the results fulfil the grid-code requirements at various frequencies and harmonic orders.
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| 4. |
- Aspenberg, Per, 1949-, et al.
(författare)
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Artrosskolan : evidensen måste stärkas
- 2018
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Ingår i: Läkartidningen. - : Läkartidningen Förlag AB. - 0023-7205 .- 1652-7518. ; 115
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 5. |
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| 6. |
- Parwal, Arvind, et al.
(författare)
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Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
- 2018
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Ingår i: 2018 5th International Conference on Electric Power and Energy Conversion Systems, EPECS 2018. - 9781538664575
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Konferensbidrag (refereegranskat)abstract
- This paper provides an overview of electric power conversion system installed at the Lysekil research site, located at the west coast of Sweden. The electric power conversion system consists of rectifiers, rectifying the power from the wave energy converters, a DC-link and a grid-tied inverter. The paper focuses on the performance of the inverter and the filter and presents experimental results obtained during the grid integration.
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| 7. |
- Chen, WenChuang, et al.
(författare)
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Numerical modelling of a point-absorbing wave energy converter in irregular and extreme waves
- 2017
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Ingår i: Applied Ocean Research. - : Elsevier BV. - 0141-1187 .- 1879-1549. ; 63, s. 90-105
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Tidskriftsartikel (refereegranskat)abstract
- Based on the Navier-Stokes (RANS) equations, a three-dimensional (3-D) mathematical model for the hydrodynamics and structural dynamics of a floating point-absorbing wave energy converter (WEC) with a stroke control system in irregular and extreme waves is presented. The model is validated by a comparison of the numerical results with the wave tank experiment results of other researchers. The validated model is then utilized to examine the effect of wave height on structure displacements and connection rope tension. In the examined cases, the differences in WEC’s performance exhibited by an inviscid fluid and a viscous fluid can be neglected. Our results also reveal that the differences in behavior predicted by boundary element method (BEM) and the RANS-based method can be significant and vary considerably, depending on wave height.
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| 8. |
- Hulsart Billström, Gry, 1982-
(författare)
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Bone Regeneration with Cell-free Injectable Scaffolds
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bone is a remarkable multifunctional tissue with the ability to regenerate and remodel without generating any scar tissue. However, bone loss due to injury or diseases can be a great challenge and affect the patient significantly. Autologous bone grafting is commonly used throughout the world. Autograft both fills the void and is bone inductive, housing the particular cells that are needed for bone regeneration. However, a regenerative complement to autograft is of great interest as the use of biomaterials loaded with bioactive molecules can avoid donor site morbidity and the problem of a limited volume of material. Two such regenerative products that utilise bone morphogenetic protein (BMP)-7 and -2 have been used for more than a decade clinically. Unfortunately, several side effects have been reported, such as severe swelling due to inflammation and ectopic bone formation. Additionally, the products require open surgery and use of supra physiological doses of the BMPs due to poor localisation and retention of the growth factor. The purpose of this thesis was to harness the strong inductive capacity of the BMP-2 by optimising the carrier of this bioactive protein, thereby minimising the side effects that are associated with the clinical products and facilitating safe and localised bone regeneration. We focused on an injectable hyaluronan-based carrier developed through polymer chemistry at the University of Uppsala. The strategy was to use the body’s own regenerative pathway to stimulate and enhance bone healing in a manner similar to the natural bone-healing process. The hyaluronan-based carrier has a similar composition to the natural extracellular matrix and is degraded by resident enzymes. Earlier studies have shown improved properties when adding hydroxyapatite, a calcium phosphate that constitutes the inorganic part of the bone matrix. In Paper I, the aim was to improve the carrier by adding other forms of calcium phosphate. The results indicated that bone formation was enhanced when using nano-sized hydroxyapatite. In Paper II, we discovered the importance of crushing the material, thus enhancing permeability and enlarging the surface area. We wished to further develop the carrier system, but were lacking an animal model with relatively high throughput, facilitated access, paired data, and we were also committed to the 3Rs of refinement, reduction, and replacement. To meet these challenges, we developed and refined an animal model, and this is described in Paper III. In Paper IV, we sought to further optimise the biomaterial properties of the hydrogel through covalent bonding of bisphosphonates to the hyaluronan hydrogel. This resulted in exceptional retention of the growth factor BMP-2. In Paper V, SPECT/PET/µCT was combined as a tri-modal imaging method to allow visualisation of the biomaterial’s in situ action, in terms of drug retention, osteoblast activity and mineralisation. Finally, in Paper VI the correlation between existing in vitro results with in vivo outcomes was observed for an array of biomaterials. The study identified a surprisingly poor correlation between in vitro and in vivo assessment of biomaterials for osteogenesis.
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| 9. |
- Sjökvist, Linnea, et al.
(författare)
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Calculating Buoy Response for a Wave Energy Converter - a Comparsion Between Two Computational Methods and Experimental Results
- 2017
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Ingår i: Theoretical and Applied Mechanics Letters. - : Elsevier BV. - 2095-0349. ; 7:3, s. 164-168
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Tidskriftsartikel (refereegranskat)abstract
- When designing a wave power plant, reliable and fast simulation tools are required. Computational fluid dynamics (CFD) software provides high accuracy but with a very high computational cost, and in operational, moderate sea states, linear potential flow theories may be sufficient to model the hydrodynamics. In this paper, a model is built in COMSOL Multiphysics to solve for the hydrodynamic parameters of a point-absorbing wave energy device. The results are compared with a linear model where the hydrodynamical parameters are computed using WAMIT, and to experimental results from the Lysekil research site. The agreement with experimental data is good for both numerical models.
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| 10. |
- Unneby, Anna, et al.
(författare)
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Femoral nerve block in a representative sample of elderly people with hip fracture : a randomised controlled trial
- 2017
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Ingår i: Injury. - : ELSEVIER SCI LTD. - 0020-1383 .- 1879-0267. ; 48:7, s. 1542-1549
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The number of elderly people with hip fracture and dementia is increasing, and many of these patients suffer from pain. Opioids are difficult to adjust and side effects are common, especially with increased age and among patients with dementia. Preoperative femoral nerve block is an alternative pain treatment. Aim: To investigate whether preoperative femoral nerve block reduced acute pain and opioid use after hip fracture among elderly patients, including those with dementia. Patients and methods: In this randomised controlled trial involving patients aged >= 70 years with hip fracture (trochanteric and cervical), including those with dementia, we compared femoral nerve block with conventional pain management, with opioid use if required. The primary outcome was preoperative pain, measured at five timepoints using a visual analogue scale (VAS). Preoperative opioid consumption was also registered. Results: The study sample comprised 266 patients admitted consecutively to the Orthopaedic Ward. The mean age was 84.1 (+/- 6.9) years, 64% of participants were women, 44% lived in residential care facilities, and 120 (45.1%) had dementia diagnoses. Patients receiving femoral nerve block had significantly lower self-rated pain scores from baseline to 12 h after admission than did controls. Self-rated and proxy VAS pain scores decreased significantly in these patients from baseline to 12 h compared with controls (p < 0.001 and p = 0.003, respectively). Patients receiving femoral nerve block required less opioids than did controls, overall (2.3 +/- 4.0 vs. 5.7 +/- 5.2 mg, p < 0.001) and in the subgroup with dementia (2.1 +/- 3.3 vs. 5.8 +/- 5.0 mg, p < 0.001). Conclusion: Patients with hip fracture, including those with dementia, who received femoral nerve block had lower pain scores and required less opioids before surgery compared with those receiving conventional pain management. Femoral nerve block seems to be a feasible pain treatment for elderly people, including those with dementia.
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