| 1. |
- Andersen, S.J., et al.
(författare)
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Comparison of Engineering Wake Models with CFD Simulations
- 2014
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 524, s. 012161-
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Tidskriftsartikel (refereegranskat)abstract
- The engineering wake models by Jensen [1] and Frandsen et al. [2] are assessed for different scenarios simulated using Large Eddy Simulation and the Actuator Line method implemented in the Navier-Stokes equations. The scenarios include the far wake behind a single wind turbine, a long row of turbines in an atmospheric boundary layer, idealised cases of an infinitely long row of wind turbines and infinite wind farms with three different spacings. Both models include a wake expansion factor, which is calibrated to fit the simulated wake velocities. The analysis highlights physical deficiencies in the ability of the models to universally predict the wake velocities, as the expansion factor can be fitted for a given case, but with not apparent transition between the cases. 1.
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| 2. |
- Sörensen, Jens, et al.
(författare)
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Determination of wind turbine near-wake length based on stability analysis
- 2014
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 524:1
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Tidskriftsartikel (refereegranskat)abstract
- A numerical study on the wake behind a wind turbine is carried out focusing on determining the length of the near-wake based on the instability onset of the trailing tip vortices shed from the turbine blades. The numerical model is based on large-eddy simulations (LES) of the Navier-Stokes equations using the actuator line (ACL) method. The wake is perturbed by applying stochastic or harmonic excitations in the neighborhood of the tips of the blades. The flow field is then analyzed to obtain the stability properties of the tip vortices in the wake of the wind turbine. As a main outcome of the study it is found that the amplification of specific waves (traveling structures) along the tip vortex spirals is responsible for triggering the instability leading to wake breakdown. The presence of unstable modes in the wake is related to the mutual inductance (vortex pairing) instability where there is an out-of-phase displacement of successive helix turns. Furthermore, using the non-dimensional growth rate, it is found that the pairing instability has a universal growth rate equal to π/2. Using this relationship, and the assumption that breakdown to turbulence occurs once a vortex has experienced sufficient growth, we provide an analytical relationship between the turbulence intensity and the stable wake length. The analysis leads to a simple expression for determining the length of the near wake. This expression shows that the near wake length is inversely proportional to thrust, tip speed ratio and the logarithmic of the turbulence intensity.
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| 5. |
- Forghani Targhi, Bita, 1973, et al.
(författare)
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Biochemical Characterization and Storage Stability of Process Waters from Industrial Shrimp Production
- 2021
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:46, s. 30960-30970
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Tidskriftsartikel (refereegranskat)abstract
- Shrimp boiling water (SBW) and shrimp peeling water (SPW), generated during shrimp processing, were characterized in terms of crude composition, volatile compounds, as well as nutritional and potentially toxic elements over a 13 month sampling period. The storage stability of both waters was also evaluated. Results showed that SBW contained on median 14.8 g/L protein and 2.2 g/L total fatty acids with up to 50% comprising eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Astaxanthin esters, which dominated the total astaxanthin, were 2.8 mg/L on median. SPW, on the other hand, contained on median 1.0 g/L of protein, 0.21 g/L of total fatty acids, and 1.2 mg/L astaxanthin esters. For both side-streams, essential amino acids were up to 50% of total amino acids. For SBW and SPW, the most abundant nutritional elements were Na, K, P, Ca, Cu, and Zn. The contents of all potentially toxic elements were below the detection limits, except for As. SBW was more stable at 4 °C compared to SPW as shown, e.g., by thiobarbituric acid reactive substances and relative changes in total volatile basic nitrogen. The extensive compositional mapping of SBW/SPW provides crucial knowledge necessary in the exploitation and value-adding of such side-streams into food or feed products.
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| 6. |
- Leeb, Sarah, 1989-, et al.
(författare)
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The unfolded ß-barrel of SOD1 is in a compact state, stabilised by long-range hydrophobic contacts.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The unfolded state of a globular protein in a physiologically relevant environment is by no means an inert random coil. On the contrary, its structural and dynamic properties are crucial for e.g., protein folding and aggregation. Despite its importance, it has been studied relatively sparsely, which is partly due to its low population which tend to obstruct detailed biophysical characterization. Here, introduction of two destabilizing core mutations allow us to study the unfolded state of the central b-barrel of Superoxide Dismutase 1 under native conditions. In order to structurally characterise the unfolded state, we use high-resolution nuclear magnetic resonance (NMR), including paramagnetic relaxation enhancement, to obtain constraints for the generation of unfolded ensembles. The results show that the unfolded state is more compact than the chemically denatured state of the same protein. This compacted state seems to be stabilised by long-range hydrophobic contacts, out of which many coincide with those found in the native state. We also investigated the previously observed destabilising effect on the unfolded state by a poly-anion, and find that; the interaction does not alter the overall ensemble dimensions, nor the pattern in native-like contacts. On the other hand, addition of the chemical denaturant urea results in a more expanded state. The varying compaction with different co-solutes was validated by pulsed-field gradient NMR diffusion measurements. Unlike helical proteins, b-proteins lack the ability to fulfil hydrogen bonds by local native interactions. This forces specific prerequisites on the collapsed pre-folding state. Here, the compaction is enabled by both native-like and non-native long-range contacts in the unfolded ensemble, and we suggest that the average topology of the collapsed state is determined by the sequence distribution of hydrophobic patches, separated by non-interacting hydrophilic clusters.
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| 7. |
- Nielsen, Steffen, et al.
(författare)
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Differential gene expression in primary fibroblasts induced by proton and cobalt-60 beam irradiation
- 2017
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 56:11, s. 1406-1412
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Proton beam therapy delivers a more conformal dose distribution than conventional radiotherapy, thus improving normal tissue sparring. Increasing linear energy transfer (LET) along the proton track increases the relative biological effectiveness (RBE) near the distal edge of the Spread-out Bragg peak (SOBP). The severity of normal tissue side effects following photon beam radiotherapy vary considerably between patients.Aim: The dual study aim was to identify gene expression patterns specific to radiation type and proton beam position, and to assess whether individual radiation sensitivity influences gene expression levels in fibroblast cultures irradiated in vitro.Methods: The study includes 30 primary fibroblast cell cultures from patients previously classified as either radiosensitive or radioresistant. Cells were irradiated at three different positions in the proton beam profile: entrance, mid-SOBP and at the SOBP distal edge. Dose was delivered in three fractions × 3.5 Gy(RBE) (RBE 1.1). Cobalt-60 (Co-60) irradiation was used as reference. Real-time qPCR was performed to determine gene expression levels for 17 genes associated with inflammation response, fibrosis and angiogenesis.Results: Differences in median gene expression levels were observed for multiple genes such as IL6, IL8 and CXCL12. Median IL6 expression was 30%, 24% and 47% lower in entrance, mid-SOBP and SOBP distal edge groups than in Co-60 irradiated cells. No genes were found to be oppositely regulated by different radiation qualities. Radiosensitive patient samples had the strongest regulation of gene expression; irrespective of radiation type.Conclusions: Our findings indicate that the increased LET at the SOBP distal edge position did not generally lead to increased transcriptive response in primary fibroblast cultures. Inflammatory factors were generally less extensively upregulated by proton irradiation compared with Co-60 photon irradiation. These effects may possibly influence the development of normal tissue damage in patients treated with proton beam therapy.
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| 8. |
- Singers Sørensen, Brita, et al.
(författare)
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Relative biological effectiveness (RBE) and distal edge effects of proton radiation on early damage in vivo
- 2017
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 56:11, s. 1387-1391
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The aim of the present study was to examine the RBE for early damage in an in vivo mouse model, and the effect of the increased linear energy transfer (LET) towards the distal edge of the spread-out Bragg peak (SOBP).Method: The lower part of the right hind limb of CDF1 mice was irradiated with single fractions of either 6 MV photons, 240 kV photons or scanning beam protons and graded doses were applied. For the proton irradiation, the leg was either placed in the middle of a 30-mm SOBP, or to assess the effect in different positions, irradiated in 4 mm intervals from the middle of the SOBP to behind the distal dose fall-off. Irradiations were performed with the same dose plan at all positions, corresponding to a dose of 31.25 Gy in the middle of the SOBP. Endpoint of the study was early skin damage of the foot, assessed by a mouse foot skin scoring system.Results: The MDD50 values with 95% confidence intervals were 36.1 (34.2–38.1) Gy for protons in the middle of the SOBP for score 3.5. For 6 MV photons, it was 35.9 (34.5–37.5) Gy and 32.6 (30.7–34.7) Gy for 240 kV photons for score 3.5. The corresponding RBE was 1.00 (0.94–1.05), relative to 6 MV photons and 0.9 (0.85–0.97) relative to 240 kV photons. In the mice group positioned at the SOBP distal dose fall-off, 25% of the mice developed early skin damage compared with 0–8% in other groups. LETd,z = 1 was 8.4 keV/μm at the distal dose fall-off and the physical dose delivered was 7% lower than in the central SOBP position, where LETd,z =1 was 3.3 keV/μm.Conclusions: Although there is a need to expand the current study to be able to calculate an exact enhancement ratio, an enhanced biological effect in vivo for early skin damage in the distal edge was demonstrated.
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| 9. |
- Andersen, S. J., et al.
(författare)
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Quantifying variability of Large Eddy Simulations of very large wind farms
- 2015
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Ingår i: Wake Conference 2015. - : IOP Publishing. ; , s. 012027-
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Konferensbidrag (refereegranskat)abstract
- Large Eddy Simulations are inherently dynamic as the largest scales are resolved and the smallest scales are modeled temporally. This raises challenges for simulations including very large scales such as atmospheric flows, which require very long simulation times. Simple averages fail at capturing these dynamics and potentially yield misleading interpretations concerning the capabilities of different models when tested in blind tests or in benchmarking exercises such as Wakebench, where results from different flow models are compared. This article will present results from very large wind farm simulations using Actuator Disc (AD) and Line (AL) models for two different turbine spacings with turbulent inflow. The results of each numerical flow model include a certain variability, and it will be examined if different models result in comparable probability distributions.
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