| 1. |
- Flores, Olivier, et al.
(author)
-
An evolutionary perspective on leaf economics : phylogenetics of leaf mass per area in vascular plants
- 2014
-
In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:14, s. 2799-2811
-
Journal article (peer-reviewed)abstract
- In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This worldwide leaf economics spectrum consists of a suite of intercorrelated leaf traits, among which leaf mass per area, LMA, is one of the most fundamental as it indicates the cost of leaf construction and light-interception borne by plants. We conducted a broad-scale analysis of the evolutionary history of LMA across a large dataset of 5401 vascular plant species. The phylogenetic signal in LMA displayed low but significant conservatism, that is, leaf economics tended to be more similar among close relatives than expected by chance alone. Models of trait evolution indicated that LMA evolved under weak stabilizing selection. Moreover, results suggest that different optimal phenotypes evolved among large clades within which extremes tended to be selected against. Conservatism in LMA was strongly related to growth form, as were selection intensity and phenotypic evolutionary rates: woody plants showed higher conservatism in relation to stronger stabilizing selection and lower evolutionary rates compared to herbaceous taxa. The evolutionary history of LMA thus paints different evolutionary trajectories of vascular plant species across clades, revealing the coordination of leaf trait evolution with growth forms in response to varying selection regimes.
|
|
| 2. |
- Hollestelle, Antoinette, et al.
(author)
-
No clinical utility of KRAS variant rs61764370 for ovarian or breast cancer
- 2016
-
In: Gynecologic Oncology. - : Elsevier BV. - 0090-8258 .- 1095-6859. ; 141:2, s. 386-401
-
Journal article (peer-reviewed)abstract
- Objective Clinical genetic testing is commercially available for rs61764370, an inherited variant residing in a KRAS 3′ UTR microRNA binding site, based on suggested associations with increased ovarian and breast cancer risk as well as with survival time. However, prior studies, emphasizing particular subgroups, were relatively small. Therefore, we comprehensively evaluated ovarian and breast cancer risks as well as clinical outcome associated with rs61764370. Methods Centralized genotyping and analysis were performed for 140,012 women enrolled in the Ovarian Cancer Association Consortium (15,357 ovarian cancer patients; 30,816 controls), the Breast Cancer Association Consortium (33,530 breast cancer patients; 37,640 controls), and the Consortium of Modifiers of BRCA1 and BRCA2 (14,765 BRCA1 and 7904 BRCA2 mutation carriers). Results We found no association with risk of ovarian cancer (OR = 0.99, 95% CI 0.94-1.04, p = 0.74) or breast cancer (OR = 0.98, 95% CI 0.94-1.01, p = 0.19) and results were consistent among mutation carriers (BRCA1, ovarian cancer HR = 1.09, 95% CI 0.97-1.23, p = 0.14, breast cancer HR = 1.04, 95% CI 0.97-1.12, p = 0.27; BRCA2, ovarian cancer HR = 0.89, 95% CI 0.71-1.13, p = 0.34, breast cancer HR = 1.06, 95% CI 0.94-1.19, p = 0.35). Null results were also obtained for associations with overall survival following ovarian cancer (HR = 0.94, 95% CI 0.83-1.07, p = 0.38), breast cancer (HR = 0.96, 95% CI 0.87-1.06, p = 0.38), and all other previously-reported associations. Conclusions rs61764370 is not associated with risk of ovarian or breast cancer nor with clinical outcome for patients with these cancers. Therefore, genotyping this variant has no clinical utility related to the prediction or management of these cancers.
|
|
| 3. |
- Aardal-Eriksson, Elisabeth, et al.
(author)
-
Iron depletion in blood donors - Have extended erythrocyte and reticulocyte parameters diagnostic utility?
- 2015
-
In: Transfusion and apheresis science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1473-0502 .- 1878-1683. ; 53:1, s. 76-81
-
Journal article (peer-reviewed)abstract
- Background: Blood donation is associated with iron depletion, but donor iron status is not usually investigated, as such tests are cumbersome and costly. It would therefore be desirable to have simple, fast and inexpensive tests that give information on a donors risk of developing iron depletion. In a pilot study we investigated whether novel erythrocyte and reticulocyte parameters can serve this goal. Methods: In regular blood donors extended red cell parameters were measured using the Abbott CELL-DYN Sapphire hematology analyzer and conventional biochemical tests of iron status. Donors were compared with a regionally matched group of non-donating controls. Results: In the controls, the reference ranges of extended RBC parameters were well comparable to published data. Donors had significantly more microcytic RBC than controls (median 0.9 vs 0.6%), lower serum ferritin concentration (median 43 vs 91 mg/L) and higher soluble transferrin receptor/ferritin index (median 1.60 vs 1.27). Overall 18-28% of the donors were iron depleted. Moreover, 3.3% of donors had iron-restricted erythropoiesis. Microcytic RBC and reticulocyte mean cell hemoglobin content predicted iron depletion with 70% and 64% sensitivities and specificities of 72% and 78%, respectively. When combined these two parameters increased the sensitivity to 82%. Conclusions: Our results in Swedish blood donors confirm a high prevalence of iron depletion, despite iron supplementation used by about half of the donors. Microcytic RBC and MCHr appeared to be helpful in identifying iron-depleted donors, who might benefit from iron supplementation. We recommend larger prospective investigations in order to confirm and extend the findings of this pilot study. (C) 2015 Elsevier Ltd. All rights reserved.
|
|
| 4. |
- Abelson, Anna-Karin, et al.
(author)
-
STAT4 Associates with SLE through two independent effects that correlate with gene expression and act additively with IRF5 to increase risk
- 2009
-
In: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 68:11, s. 1746-1753
-
Journal article (peer-reviewed)abstract
- OBJECTIVES: To confirm and define the genetic association of STAT4 and systemic lupus erythematosus, investigate the possibility of correlations with differential splicing and/or expression levels, and genetic interaction with IRF5. METHODS: 30 tag SNPs were genotyped in an independent set of Spanish cases and controls. SNPs surviving correction for multiple tests were genotyped in 5 new sets of cases and controls for replication. STAT4 cDNA was analyzed by 5'-RACE PCR and sequencing. Expression levels were measured by quantitative PCR. RESULTS: In the fine-mapping, four SNPs were significant after correction for multiple testing, with rs3821236 and rs3024866 as the strongest signals, followed by the previously associated rs7574865, and by rs1467199. Association was replicated in all cohorts. After conditional regression analyses, two major independent signals represented by SNPs rs3821236 and rs7574865, remained significant across the sets. These SNPs belong to separate haplotype blocks. High levels of STAT4 expression correlated with SNPs rs3821236, rs3024866 (both in the same haplotype block) and rs7574865 but not with other SNPs. We also detected transcription of alternative tissue-specific exons 1, indicating presence of tissue-specific promoters of potential importance in the expression of STAT4. No interaction with associated SNPs of IRF5 was observed using regression analysis. CONCLUSIONS: These data confirm STAT4 as a susceptibility gene for SLE and suggest the presence of at least two functional variants affecting levels of STAT4. Our results also indicate that both genes STAT4 and IRF5 act additively to increase risk for SLE.
|
|
| 5. |
- Adjei, Evans, et al.
(author)
-
Regional labour market effects of immigration on low-skilled workers: the case of Sweden 1990–2003
- 2021
-
In: International Journal of Social Economics. - : Emerald Group Publishing Limited. - 0306-8293 .- 1758-6712. ; 48:3, s. 456-476
-
Journal article (peer-reviewed)abstract
- Purpose: The purpose of this paper is to examine the effects of immigration on the labour market outcomes of low-educated natives (i.e. residents without a university diploma). Using the labour market competition theory, which argues that the labour market effects of natives depend on the skill set of immigrants, the paper addresses whether immigrants are complementary to or substitutes for native workers.Design/methodology/approach: Longitudinal matched employer–employee data on Sweden are used to estimate how low-educated natives, in regions experiencing the greatest influx of refugees from the Balkan wars, responded to this supply shock with regard to real wages, employment and job mobility between 1990 and 2003.Findings: First, the analysis shows that low-educated native workers respond to the arrival of immigrants with an increase in real wages. Second, although employment prospects in general worsened for low-skilled workers in most regions, this is not attributable to the regions experiencing the largest supply shock. Third, there are indications that low-skilled natives in immigration-rich regions are more likely to change workplace, particularly in combination with moving upwards in the wage distribution.Originality/value: Rather than seeing an emergence of the commonly perceived displacement mechanism when an economy is subject to a supply shock, the regional findings suggest that high inflows of immigrants tend to induce a mechanism that pulls native workers upwards in the wage distribution. This is important, as the proportion of immigrants is seldom evenly distributed within a nation.
|
|
| 6. |
- Andersson Ersman, Peter, et al.
(author)
-
Integration of Screen Printed Piezoelectric Sensors for Force Impact Sensing in Smart Multifunctional Glass Applications
- 2022
-
In: Advanced Engineering Materials. - : John Wiley & Sons, Ltd. - 1438-1656 .- 1527-2648. ; 24:11
-
Journal article (peer-reviewed)abstract
- Screen printed piezoelectric polyvinylidene fluoride?trifluoro ethylene (PVDF?TrFE)-based sensors laminated between glass panes in the temperature range 80?110?°C are presented. No degradation of the piezoelectric signals is observed for the sensors laminated at 110?°C, despite approaching the Curie temperature of the piezoelectric material. The piezoelectric sensors, here monitoring force impact in smart glass applications, are characterized by using a calibrated impact hammer system and standardized impact situations. Stand-alone piezoelectric sensors and piezoelectric sensors integrated on poly(methyl methacrylate) are also evaluated. The piezoelectric constants obtained from the measurements of the nonintegrated piezoelectric sensors are in good agreement with the literature. The piezoelectric sensor response is measured by using either physical electrical contacts between the piezoelectric sensors and the readout electronics, or wirelessly via both noncontact capacitive coupling and Bluetooth low-energy radio link. The developed sensor concept is finally demonstrated in smart window prototypes, in which integrated piezoelectric sensors are used to detect break-in attempts. Additionally, each prototype includes an electrochromic film to control the light transmittance of the window, a screen printed electrochromic display for status indications and wireless communication with an external server, and a holistic approach of hybrid printed electronic systems targeting smart multifunctional glass applications.
|
|
| 7. |
- Andersson, Therese M. -L., et al.
(author)
-
Estimating the cure proportion of malignant melanoma, an alternative approach to assess long term survival : A population-based study
- 2014
-
In: Cancer Epidemiology. - : Elsevier BV. - 1877-7821 .- 1877-783X. ; 38:1, s. 93-99
-
Journal article (peer-reviewed)abstract
- Objectives: A large proportion of patients with cutaneous malignant melanoma (CMM) do not experience excess mortality due to their disease. This group of patients is referred to as the cure proportion. Few studies have examined the possibility of cure for CMM. The aim of this study was to estimate the cure proportion of patients with CMM in a Swedish population. Methods: We undertook a population-based study of 5850 CMM patients in two Swedish health care regions during 1996-2005. We used flexible parametric cure models to estimate cure proportions and median survival times (MSTs) of uncured by stage, sex, age and anatomical site. Results: Disease stage at diagnosis was the most important factor for the probability of cure, with a cure proportion of approximately 1.0 for stage IA. While the probability of cure decreased with older age, the influence of age was smaller on the MST of uncured. Differences in prognosis between males and females were mainly attributed to differences in cure as opposed to differences in MST of uncured. Conclusions: This population-based study showed approximately 100% cure among stage IA disease. Almost 50% of patients had stage IA disease and the high cure proportion for this large patient group is reassuring.
|
|
| 8. |
|
|
| 9. |
- Anttila, Sara
(author)
-
Power control strategies for renewable energy systems : The inverter's role in future power systems
- 2020
-
Licentiate thesis (other academic/artistic)abstract
- Connecting more non-dispatchable renewable energy sources (RESs) will result in a higher power variability and a lower system inertia when the synchronous generators are replaced by inverter-connected RES. Inverter control can be divided in three categories: grid-following, grid-forming (GFM) and grid-supporting. A literature review of inverter control strategies identifies the GFM control as having an important role in maintaining system stability assuming near 100 % inverter-connected RES. Critical aspects of the inverter control are also identified; the control need to function autonomously, be able to remain connected during transient events and be insensitive to grid topology.Combining various RES is also shown to improve system stability. The combination of RES that has been investigated in most studies is wind, solar and wave power. Wave power is still a young technology compared to solar and wind power. It generates higher power fluctuations over short time periods with a significant difference between average and maximum power. Additionally, wave power parks (WPPs) are often connected via long cables which contribute reactive power to the grid. These challenges has to be considered to maintain system stability and power quality when connecting a WPP to the grid.In a Power Hardware-In-the-Loop study of how a WPP affects the power quality at the point of common coupling (PCC), it is found that the impact is highest for WPPs with fewer generators as the variability is reduced when several generators are excited at different times. Energy storage is also shown to have a significant impact on the power quality at the PCC with reduced flicker, total harmonic distortion and power and voltage variability. A simulation study also shows the positive impact of energy storage on power variability and the role of inverter control in reactive power compensation.
|
|
| 10. |
- Apelfröjd, Senad, et al.
(author)
-
A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University
- 2016
-
In: Energies. - : MDPI AG. - 1996-1073. ; 9:7
-
Research review (peer-reviewed)abstract
- This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of the work done on the 12 kW prototype VAWT in Marsta, Sweden. Several key aspects have been tested and successfully demonstrated at our two experimental research sites. The effort of the VAWT research has been aimed at developing a robust large scale VAWT technology based on an electrical control system with a direct driven energy converter. This approach allows for a simplification where most or all of the control of the turbines can be managed by the electrical converter system, reducing investment cost and need for maintenance. The concept features an H-rotor that is omnidirectional in regards to wind direction, meaning that it can extract energy from all wind directions without the need for a yaw system. The turbine is connected to a direct driven permanent magnet synchronous generator (PMSG), located at ground level, that is specifically developed to control and extract power from the turbine. The research is ongoing and aims for a multi-megawatt VAWT in the near future.
|
|
| 11. |
- Apelfröjd, Senad, et al.
(author)
-
Evaluation of Harmonic Content from a Tap Transformer Based Grid Connection System for Wind Power
- 2013
-
In: Journal of Renewable Energy. - : Hindawi Publishing Corporation. - 2314-4386 .- 2314-4394. ; 2013, s. 8-
-
Journal article (peer-reviewed)abstract
- Simulations done in MATLAB/Simulink together with experiments conducted at the Ångströms laboratory are used to evaluate and discuss the total harmonic distortion (THD) and total demand distortion (TDD) of a tap transformer based grid connection system. The grid connection topology can be used with different turbine and generator topologies and is here applied on a vertical axis wind turbine (VAWT) with a permanent magnet synchronous generator (PMSG) and its operational scheme. The full variable-speed wind conversion system consists of a diode rectifier, DC link, IGBT inverter, LCL-filter, and tap transformer. The full variable-speed operation is enabled by the use of the different step-up ratios of the tap transformer. In the laboratory study, a full experimental setup of the system was used, a clone of the on-site PMSG driven by a motor was used, and the grid was replaced with a resistive load. With a resistive load, grid harmonics and possible unbalances are removed. The results show a TDD and THD below 5% for the full operating range and harmonic values within the limits set up by IEEE-519. Furthermore, a change in tap, going to a lower step-up ratio, results in a reduction in both THD and TDD for the same output power.
|
|
| 12. |
- Apelfröjd, Senad
(author)
-
Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems
- 2016
-
Doctoral thesis (other academic/artistic)abstract
- Renewable energy is harnessed from continuously replenishing natural processes. Some commonly known are sunlight, water, wind, tides, geothermal heat and various forms of biomass. The focus on renewable energy has over the past few decades intensified greatly. This thesis contributes to the research on developing renewable energy technologies, within the wind power, wave power and marine current power projects at the division of Electricity, Uppsala University. In this thesis grid connection of permanent magnet generator based renewable energy sources is evaluated.A tap transformer based grid connection system has been constructed and experimentally evaluated for a vertical axis wind turbine. Full range variable speed operation of the turbine is enabled by using the different step-up ratios of a tap transformer. This removes the need for a DC/DC step or an active rectifier on the generator side of the full frequency converter and thereby reduces system complexity. Experiments and simulations of the system for variable speed operation are done and efficiency and harmonic content are evaluated. The work presented in the thesis has also contributed to the design, construction and evaluation of a full-scale offshore marine substation for wave power intended to grid connect a farm of wave energy converters. The function of the marine substation has been experimentally tested and the substation is ready for deployment. Results from the system verification are presented. Special focus is on the transformer losses and transformer in-rush currents.A control and grid connection system for a vertical axis marine current energy converter has been designed and constructed. The grid connection is done with a back-to-back 2L-3L system with a three level cascaded H-bridge converter grid side. The system has been tested in the laboratory and is ready to be installed at the experimental site. Results from the laboratory testing of the system are presented.
|
|
| 13. |
- Apelfröjd, Senad, et al.
(author)
-
Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
- 2012
-
In: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012.
-
Conference paper (peer-reviewed)abstract
- In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.
|
|
| 14. |
- Apelfröjd, Senad, et al.
(author)
-
System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power
- 2014
-
In: Scientific World Journal. - : Hindawi Limited. - 1537-744X .- 2356-6140. ; , s. 784295-
-
Journal article (peer-reviewed)abstract
- Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.
|
|
| 15. |
- Arvidsson, Sandra, 1986-, et al.
(author)
-
Enlarged cross-sectional area in peripheral nerves in Swedish patients with hereditary V30M transthyretin amyloidosis
- 2023
-
In: Annals of Medicine. - : Taylor & Francis Group. - 0785-3890 .- 1365-2060. ; 55:2
-
Journal article (peer-reviewed)abstract
- Introduction: In hereditary transthyretin amyloidosis (ATTRv), two different fibrillar forms causing the amyloid deposition, have been identified, displaying substantially cardiac or neuropathic symptoms. Neuropathic symptoms are more frequent in early-onset patients, whereas late-onset patients, besides cardiac symptoms, seem to develop carpal tunnel syndrome, more often. With ultrasonography (US) of peripheral nerves, it is possible to distinguish structural changes, and enlarged cross-sectional area (CSA). The main purpose of this study was, for the first time, to elucidate US of peripheral nerves in Swedish ATTRv patients at an early stage of the disease, and to evaluate possible early enlarged CSA.Material and methods: This prospective study included first visit data of 13 patients, aged 30–88 years, of which 11 with late-onset age. All had a positive V30M mutation. Eight men and six women (aged 28–74 years) served as controls.Results: Significantly enlarged CSA was seen in ATTRv patients for the tibial nerve at the ankle (p =.001), the sural nerve (p <.001), the peroneal nerve at the popliteal fossa (p =.003), and the ulnar nerve at the middle upper arm (p =.007).Conclusion: US of peripheral nerves could be a valuable tool in disease evaluation and could facilitate monitoring of disease progression.
|
|
| 16. |
- Augier, Gaëlle, et al.
(author)
-
Wistar rats choose alcohol over social interaction in a discrete-choice model
- 2023
-
In: Neuropsychopharmacology. - : SPRINGERNATURE. - 0893-133X .- 1740-634X. ; 48, s. 1098-1107
-
Journal article (peer-reviewed)abstract
- Animal models of substance use disorders have been criticized for their limited translation. One important factor behind seeking and taking that has so far been largely overlooked is the availability of alternative non-drug rewards. We recently reported that only about 15% of outbred Wistar rats will choose alcohol over a sweet solution of saccharin. It was also shown using a novel operant model of choice of drugs over social rewards that social interaction consistently attenuates self-administration and incubation of craving for stimulants and opioids. Whether this is also true for alcohol and choice of alcohol over a sweet reward translates to social rewards is currently unknown. We therefore evaluated choice between alcohol and a social reward in different experimental settings in both male and female Wistar rats. We found, in contrast to prior work that employed discrete choice of drugs vs. social reward, that rats almost exclusively prefer alcohol over social interaction, irrespective of the nature of the social partner (cagemate vs. novel rat), the length of interaction, housing conditions and sex. Alcohol choice was reduced when the response requirement for alcohol was increased. However, rats persisted in choosing alcohol, even when the effort required to obtain it was 10-16 times higher (for females and males respectively) than the one for the social reward. Altogether, these results indicate that the social choice model may not generalize to alcohol, pointing to the possibility that specific interactions between alcohol and social reward, not seen when a sweet solution is used as an alternative to the drug, may play a crucial role in alcohol vs. social choice experiments.
|
|
| 17. |
|
|
| 18. |
- Bayati, Zahra, 1958, et al.
(author)
-
Nytt centrum mot rasism får fel vetenskaplig inriktning
- 2015
-
In: Göteborgs Posten. - 1103-9345. ; :2015-06-14
-
Journal article (pop. science, debate, etc.)abstract
- När rasism ska förstås som något som kan lösas genom att lära ut tolerans undergrävs förtroendet för regeringens satsning. Dessutom saknas det etnisk/rasifierad mångfald bland forskargruppen.
|
|
| 19. |
- Benter, Sandra, et al.
(author)
-
Tuneable 2D surface Bismuth incorporation on InAs nanosheets
- 2023
-
In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 15:21, s. 9551-9559
-
Journal article (peer-reviewed)abstract
- The chemical bonding at the interface between compound semiconductors and metals is central in determining electronic and optical properties. In this study, new opportunities for controlling this are presented for nanostructures. We investigate Bi adsorption on 2D wurtzite InAs (1120) nanosheets and find that temperature-controlled Bi incorporation in either anionic- or cationic-like bonding is possible in the easily accesible range between room temperature and 400 degrees C. This separation could not be achieved for ordinary zinc blende InAs(110) surfaces. As the crystal structures of the two surfaces have identical nearest neighbour configurations, this indicates that overall geometric differences can significantly alter the adsorption and incorporation. Ab initio theoretical modelling confirms observed adsorption results, but indicate that both the formation energies as well as kinetic barriers contributes to the observed temperature dependent behaviour. Further, we find that the Bi adsorption rate can differ by at least 2.5 times between the two InAs surfaces while being negligible for standard Si substrates under similar deposition conditions. This, in combination with the observed interface control, provides an excellent opportunity for tuneable Bi integration on 2D InAs nanostructures on standard Si substrates.
|
|
| 20. |
|
|
| 21. |
- Bonow, Sandra, et al.
(author)
-
Consequences of specialized breeding in the Swedish Warmblood horse population
- 2023
-
In: Journal of Animal Breeding and Genetics. - : Wiley. - 0931-2668 .- 1439-0388. ; 140, s. 79-91
-
Journal article (peer-reviewed)abstract
- In many European warmblood studbooks, clear specialization toward either jumping or dressage horses is evident. The Swedish Warmblood (SWB) is also undergoing such specialization, creating a possible need for separate breeding programs and a discipline-specific Young Horse Test (YHT). This study investigated how far specialization of the SWB breed has proceeded and the potential consequences. Individuals in a population of 122,054 SWB horses born between 1980 and 2020 were categorized according to pedigree as jumping (J), dressage (D), allround (AR), or thoroughbred (Th). Data on 8,713 J horses and 6,477 D horses assessed for eight traits in YHT 1999-2020 were used to estimate genetic parameters within and between J and D horses and between different periods. Future scenarios in which young horses are assessed for either jumping or dressage traits at YHT were also analyzed. More than 80% of horses born in 1980-1985 were found to be AR horses, while 92% of horses born in 2016-2020 belonged to a specialized category. The average relationship within J or D category was found to increase during the past decade, whereas the relationship between these categories decreased. Heritability estimates for gait traits were 0.42-0.56 for D horses and 0.25-0.38 for J horses. For jumping traits, heritability estimates were 0.17-0.26 for J horses and 0.10-0.18 for D horses. Genetic correlations between corresponding traits assessed in J and D horses were within the range 0.48-0.81, with a tendency to be lower in the late study period. In the future scenarios, heritability and genetic variance both decreased for traits that were not assessed in all horses, indicating that estimation of breeding value and genetic progress for these traits could be affected by a specialized YHT. However, ranking of sires based on estimated breeding values (EBVs) and accuracy of EBVs was only slightly altered for discipline-specific traits. With continued specialization in SWB, specialization of the YHT should thus be considered.
|
|
| 22. |
|
|
| 23. |
- Broadaway, K Alaine, et al.
(author)
-
Loci for insulin processing and secretion provide insight into type 2 diabetes risk.
- 2023
-
In: American Journal of Human Genetics. - : Elsevier. - 0002-9297 .- 1537-6605. ; 110:2, s. 284-299
-
Journal article (peer-reviewed)abstract
- Insulin secretion is critical for glucose homeostasis, and increased levels of the precursor proinsulin relative to insulin indicate pancreatic islet beta-cell stress and insufficient insulin secretory capacity in the setting of insulin resistance. We conducted meta-analyses of genome-wide association results for fasting proinsulin from 16 European-ancestry studies in 45,861 individuals. We found 36 independent signals at 30 loci (p value < 5 × 10-8), which validated 12 previously reported loci for proinsulin and ten additional loci previously identified for another glycemic trait. Half of the alleles associated with higher proinsulin showed higher rather than lower effects on glucose levels, corresponding to different mechanisms. Proinsulin loci included genes that affect prohormone convertases, beta-cell dysfunction, vesicle trafficking, beta-cell transcriptional regulation, and lysosomes/autophagy processes. We colocalized 11 proinsulin signals with islet expression quantitative trait locus (eQTL) data, suggesting candidate genes, including ARSG, WIPI1, SLC7A14, and SIX3. The NKX6-3/ANK1 proinsulin signal colocalized with a T2D signal and an adipose ANK1 eQTL signal but not the islet NKX6-3 eQTL. Signals were enriched for islet enhancers, and we showed a plausible islet regulatory mechanism for the lead signal in the MADD locus. These results show how detailed genetic studies of an intermediate phenotype can elucidate mechanisms that may predispose one to disease.
|
|
| 24. |
|
|
| 25. |
- Bülow, Fredrik, et al.
(author)
-
No-load core loss prediction of PM generator at low electrical frequency
- 2012
-
In: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 43, s. 389-392
-
Journal article (peer-reviewed)abstract
- A method for measurement of frequency dependent electromagnetic core loss of a permanent magnet generator is presented. Core loss of a PM generator is measured at electrical frequencies ranging from 4 to 14 Hz. Core loss in the same interval is simulated using the finite element method and frequency domain loss separation. The specific loss is both extrapolated from specific loss at 50 Hz and measured directly at 4, 8, 12 and 16 Hz. Core loss simulations based on extrapolated specific loss are 38–53% smaller than measured loss. Core loss simulations based on specific loss measured at 4, 8, 12 and 16 Hz are 19–23% smaller than measured loss.
|
|
| 26. |
- Callaghan, Terry, et al.
(author)
-
Multi-Decadal Changes in Tundra Environments and Ecosystems : Synthesis of the International Polar Year-Back to the Future Project (IPY-BTF)
- 2011
-
In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:6, s. 705-716
-
Journal article (peer-reviewed)abstract
- Understanding the responses of tundra systemsto global change has global implications. Most tundraregions lack sustained environmental monitoring and oneof the only ways to document multi-decadal change is toresample historic research sites. The International PolarYear (IPY) provided a unique opportunity for such researchthrough the Back to the Future (BTF) project (IPY project#512). This article synthesizes the results from 13 paperswithin this Ambio Special Issue. Abiotic changes includeglacial recession in the Altai Mountains, Russia; increasedsnow depth and hardness, permafrost warming, andincreased growing season length in sub-arctic Sweden;drying of ponds in Greenland; increased nutrient availabilityin Alaskan tundra ponds, and warming at mostlocations studied. Biotic changes ranged from relativelyminor plant community change at two sites in Greenland tomoderate change in the Yukon, and to dramatic increasesin shrub and tree density on Herschel Island, and in subarcticSweden. The population of geese tripled at one sitein northeast Greenland where biomass in non-grazed plotsdoubled. A model parameterized using results from a BTFstudy forecasts substantial declines in all snowbeds andincreases in shrub tundra on Niwot Ridge, Colorado overthe next century. In general, results support and provideimproved capacities for validating experimental manipulation,remote sensing, and modeling studies.
|
|
| 27. |
- Carlos-Pinedo, Sandra, et al.
(author)
-
Methane yield from SS-AD : Experiences to learn by a full spectrum analysis at laboratory-, pilot- and full-scale
- 2019
-
In: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 127
-
Research review (peer-reviewed)abstract
- Solid-state anaerobic digestion (SS-AD) takes place when solid content of the substrate is higher than 15%. Some advantages of this technology have been recognized as e.g., less required water added to raw feedstock and consequently minimized digester size and cost, higher volumetric organic loading rates (OLR) that may lead to higher efficiency methane yield and better acceptance of a wide range of feedstocks. However, scientific studies of SS-AD at pilot- and full-scale are very few and difficulties have been reported in operating SS-AD, especially when the system undergoes a scale-up, where methane production is the purpose. As a result, this review gives a summary of scientific studies for SS-AD processes at laboratory-, pilot- and full-scale, where a great diversity of substrate composition, reactor design and operational parameters have been categorized, and their performances in terms of methane yield have been analyzed. This, in turn, helps to identify that factors affecting methane yields at different scales arise mainly from operational conditions as well as the characteristic of feedstocks. This review even contributes to suggest several strategies for improvement of methane yield at full-scale.
|
|
| 28. |
- Carlos-Pinedo, Sandra
(author)
-
Renewable Energy and Nutrient Valorization from Anaerobic Digestion : Resource-Efficient Solutions
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- This thesis presents a comprehensive analysis aimed at understanding process performance, methane yield, and key influencing factors within the context of solid-state anaerobic digestion (SS-AD). SS-AD is used to treat organic material with high solids content, which can be challenging to address by alternative methods. The investigation involves modelling and simulation exploring mass and energy balances and the associated environmental implications. To achieve this, a waste management tool, ORganic WAste REsearch (ORWARE) was adapted and validated to suit the unique parameters of SS-AD operating under a plug-flow reactor configuration, representing a specific case study. The search of an optimal feedstock mix that enhances the digestion process and energy performance is highlighted. Findings suggest that feedstock selection significantly affects methane yield in SS-AD systems, and optimizing substrate mixtures can enhance process efficiency. Key considerations include biodegradability and lignocellulosic content. Operational parameters, such as temperature variations, impact the results from the model, while responsiveness of hydraulic retention time and organic loading rate remains limited. A further comparison between a liquid anaerobic digestion (L-AD) vs SS-AD is made, despite similar methane yields, SS-AD outperforms due to higher energy turnover. Additionally, effective management of digestate nutrients is crucial for its biofertilizer use. Beyond the biogas system, the thesis explores interconnected relationships between SS-AD inputs and outputs and their subsequent use as resources for a hydroponic greenhouse production system. The examination of system interconnections and their broader implications emphasizes the importance of comprehensive assessments when integrating biogas systems beyond their conventional applications.
|
|
| 29. |
- Carlos-Pinedo, Sandra, et al.
(author)
-
Study of the digestion process at a full-scale solid-state biogas plant by using ORWARE : Model modification and implementation
- 2020
-
In: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 107, s. 133-142
-
Journal article (peer-reviewed)abstract
- The configuration of the reactor influences the digestion process and thus the product yields; other factors such as the rate of biogas production or biogas loss also affect the process specifically with high solid configuration. With these in mind, the ORganic WAste REsearch (ORWARE) anaerobic digestion sub-model was modified to be able to study solid-state anaerobic digestion (SS-AD) (using plug-flow reactor). The simulation results from the updated model agreed with the operational data with respect to methane yield, digestate yield and energy turnover. The model was found to be sensitive to changes in feedstock composition but to a lesser extent to changes in process temperature and retention time. By applying the model on several cases of liquid anaerobic digestion (L-AD), it was noticed that L-AD at mesophilic condition with 25 retention days seemed to be superior to other cases of L-AD with regard to energy turnover. However, even if similar methane production were observed for L-AD and SS-AD, the model suggested higher energy turnover for the case of SS-AD at thermophilic condition, being 10% more in average in comparison with cases of L-AD.
|
|
| 30. |
|
|
| 31. |
- Carpman, Nicole
(author)
-
Marine Current Resource Assessment : Measurements and Characterization
- 2015
-
Licentiate thesis (other academic/artistic)abstract
- The increasing interest in converting energy from renewable resources into electricity has led to an increase in research covering the field of marine current energy, mainly concerning tidal currents and in-stream tidal turbines. Tides have the advantage of being predictable decades ahead. However, the tidal resource is intermittent and experiences local variations that affect the power output from a conversion system. The variability is mainly due to four aspects: the tidal regime, the tidal cycle, bathymetry at the site and weather effects. Each potential site is unique, the velocity flow field at tidal sites is highly influenced by local bathymetry and turbulence. Hence, characterizing the resource requires careful investigations and providing high quality velocity data from measurement surveys is of great importance. In this thesis, measurements of flow velocities have been performed at three kinds of sites.A tidal site has been investigated for its resource potential in one of all of the numerous fjords in Norway. Measurements have been performed to map the spatial and temporal variability of the resource. Results show that currents in the order of 2 m/s are present in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus have potential for in-stream energy conversion. A model is proposed that predicts peak current speed from information on tidal range at the site. A corresponding model can be set up and implemented at other similar sites affected by tides, i.e. fjord inlets connecting the ocean to a fjord or a basin.A river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydrokinetic power plant nearby, making the site suitable for experiments on the performance of the vertical axis turbine in its natural environment. The turbine has been run in uniform flow and measurements have been performed to characterize the extent of the wake.An ocean current site was a target of investigation for its potential for providing utilizable renewable energy. A measurement campaign was conducted, mapping the flow both spatially and temporally. However, the site was shown to not be suitable for energy conversion using present technique.
|
|
| 32. |
- Carpman, Nicole
(author)
-
Resource characterization and variability studies for marine current power
- 2017
-
Doctoral thesis (other academic/artistic)abstract
- Producing electricity from marine renewable resources is a research area that develops continuously. The field of tidal energy is on the edge to progress from the prototype stage to the commercial stage. However, tidal resource characterization, and the effect of tidal turbines on the flow, is still an ongoing research area in which this thesis aims to contribute.In this thesis, measurements of flow velocities have been performed at three kinds of sites. Firstly, a tidal site has been investigated for its resource potential in a fjord in Norway. Measurements have been performed with an acoustic Doppler current profiler to map the spatial and temporal characteristics of the flow. Results show that currents are in the order of 2 m/s in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus has potential for in-stream energy conversion. Secondly, a river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydro power plant, making the site suitable for experiments on the performance of the vertical axis turbine in a natural environment. The turbine was run in steady discharge flows and measurements were performed to characterize the extent of the wake. Lastly, at an ocean current site, the effect that transiting ferries may have on submerged devices was investigated. Measurements were conducted with two sonar systems to obtain an underwater view of the wake caused by a propeller and a water jet thruster respectively.Furthermore, the variability of the intermittent renewable sources wind, solar, wave and tidal energy was investigated for the Nordic countries. All of the sources have distinctly different variability features, which is advantageous when combining power generated from them and introducing it on the electricity grid. Tidal variability is mainly due to four aspects: the tidal regime, the tidal cycle, local bathymetry causing turbulence, asymmetries etc. and weather effects. Models of power output from the four sources was set up and combined in different energy mixes for a “highly renewable” and a “fully renewable” scenario. By separating the resulting power time series into different frequency bands (long-, mid-, mid/short-, and short-term components) it was possible to minimize the variability on different time scales. It was concluded that a wise combination of intermittent renewable sources may lower the variability on short and long time scales, but increase the variability on mid and mid/short time scales.The tidal power variability in Norway was then investigated separately. The predictability of tidal currents has great advantages when planning electricity availability from tidal farms. However, the continuously varying tide from maximum power output to minimum output several times per day increases the demand for backup power or storage. The phase shift between tidal sites introduces a smoothing effect on hourly basis but the tidal cycle, with spring and neap tide simultaneously in large areas, will inevitably affect the power availability.
|
|
| 33. |
- Crochiquia, Alice, 1990-, et al.
(author)
-
A perceptual and acoustic study of dubbed voices in an animated film
- 2022
-
In: Proceedings of the 11th International Conference on Speech Prosody. - : The International Speech Communication Association (ISCA). ; , s. 565-569
-
Conference paper (peer-reviewed)abstract
- Listeners rely on speech vocal cues to judge speakers’ age, size, personality, and other paralinguistic and extralinguistic features. These judgements are often based on vocal stereotypes which may be universally or culturally determined. This study examines how physical, psychological, social, and vocal features are perceived by listeners and which acoustic features may influence their judgements. An experiment integrating a perceptual test and acoustic measurements was performed. The corpus consisted of speech utterances produced by five animated film characters, dubbed in Brazilian Portuguese. The stimuli were judged by 77 Brazilian Portuguese native speakers, 46 women and 31 men, aged 20 to 50. The acoustic analysis was performed automatically. Acoustic measures included mean f0, f0 baseline, spectral emphasis and H1-H2. For inter-rater agreement analysis, Cronbach's Alpha was chosen. The results indicated close agreements among judges for all characters. Overall scores obtained for all characters were above .90. In interpreting the results, the influence sound symbolism codes may have on listeners’ judgments and the factors influencing vocal stereotypes have been considered. The discussion of the acoustic and perceptual analysis results takes into consideration if voice actors adapt their voices to fit the characters or otherwise are cast because of their natural voice characteristics
|
|
| 34. |
- Crochiquia, Alice, et al.
(author)
-
A phonetic study of Zootopia characters’ voices inBrazilian Portuguese dubbing : the role of stereotypes
- 2020
-
In: DELTA. - 0102-4450 .- 1678-460X. ; 36:3
-
Journal article (peer-reviewed)abstract
- This work comprises an experimental investigation approach of expressive speech that integrates methodological procedures of perceptual and acoustic analyses. As the object of this work, we have focused on voice quality and vocal dynamics. Speech samples from the four main personality-distinct characters in the animated feature film “Zootopia” dubbed by Brazilian voice actors have been analysed. Due to the expressive function of voice quality, we have posed the following question: what types of voice quality and vocal dynamics settings were used by the voice actors in the Brazilian dubbing of “Zootopia” to compose the vocal profiles of the characters? Perceptual evaluation of the 54 speech stimuli was performed using the Vocal Profile Analysis protocol (Laver & Mackenzie Beck, 2007). Acoustic measures were automatically extracted using the Expression Evaluator script (Barbosa, 2008) for PRAAT. The profiles for each of the four characters were composed based on the psychological traits described in the film script. The results of the acoustic analysis, the perceptual analysis of voice quality and vocal dynamics settings were correlated using the MFA (Multiple Factor Analysis) method in the R environment based on 40 variables (quantitative and qualitative) and it turned out that the speech stimuli were distributed in 6 clusters according to the variables analysed. The quantitative variables that presented the highest correlation percentage were: Standard Deviation of f0 Derivative, Standard Deviation of Spectral Tilt, f0 Median. The qualitative variables that presented the highest correlation percentage were: Lowered Larynx, Lip Rounding, Breathy Voice and Minimised Pitch Range. The research has presented evidence in favor of the symbolic use of phonic matter and contributions to the understanding of how vocal stereotypes are established.
|
|
| 35. |
- Crochiquia, Alice, 1990-, et al.
(author)
-
Animated character profiles : The role of voice and lexical content
- 2023
-
In: Proceedings of the 20<sup>th</sup> International Congress of Phonetic Sciences, Prague 2023. - Prague. ; , s. 466-470
-
Conference paper (peer-reviewed)abstract
- Our study examines the attribution of physical and psychosocial features to the characters of a dubbed animated film by comparing the results of a listening test experiment with the results of a reading test experiment. The aim of this study was to investigate the potential influence of lexical content on the perceptual evaluation of speaker characteristics. In the listening test, respondents were asked to listen to audio samples of dubbed dialogues in the film produced by voice actors and rate the characters on fourteen bipolar continuous scales. The task in the reading test was the same, except for the stimuli, which were transcriptions of the audio files. Results from both tests are congruent, as the character profiles based on the perception scores from each test are nearly identical for all characters. Differences are mainly due to the degree judgement scores are amplified by the characters' voice quality profiles.
|
|
| 36. |
- D. Silva, Marcelo, 1995-, et al.
(author)
-
On the Mitigation of Leakage Flux in Spoke Type Permanent Magnet Synchronous Machines
- 2022
-
In: 2022 International Conference on Electrical Machines (ICEM). - : IEEE. - 9781665414333 - 9781665414326 ; , s. 302-308
-
Conference paper (peer-reviewed)abstract
- The use of rare-earth elements in permanent magnets rises economic, environmental and supply-chain related concerns. Instead, ferrite magnets have been researched as an alternative. The magnetic flux concentration capacity of the Spoke Type Permanent Magnet Synchronous Motor (PMSM) and the low magnetic remanence of the ferrite magnet make them complementary strategies towards the desirable performance. However, if restricted to conventional manufacturing processes and materials, the mechanical design is a challenging step of the development of these machines. This paper explores how mechanical constraints impact electromagnetic performance. To access the interdependency of the performance and the mechanical constraints, finite element analyses are done both in the mechanical and electromagnetic domain. The results show that the mechanical constraints have an impact on the performance, although it is possible to reduce it by adapting the design to the electromagnetic and mechanical properties of the electrical steel.
|
|
| 37. |
- de Santiago, Juan, et al.
(author)
-
Electrical Motor Drivelines in Commercial All Electric Vehicles : a Review
- 2012
-
In: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 61:2, s. 475-484
-
Journal article (peer-reviewed)abstract
- This paper presents a critical review of the drivelines in all Electric Vehicles (EVs). The motor topologies that are the best candidates to be used in EVs are presented. The advantages and disadvantages of each electric motor type are discussed from a system perspective. A survey of the electric motors used in commercial EVs is presented. The survey shows that car manufacturers are very conservative when it comes to introducing new technologies. Most of the EV’s in the market mount a single induction or permanent magnet motor with a traditional mechanic driveline with a differential. The study illustrates that comparisons between the different motors are made difficult by the large number of parameters and the lack of a recommended test scheme. The authors propose that a standardized drive cycle is used to test and compare motors.
|
|
| 38. |
- Deglaire, Paul, et al.
(author)
-
Experimental results from a 12 kW vertical axis wind turbine with a direct driven PM synchronous generator
- 2007
-
Conference paper (other academic/artistic)abstract
- Experimental results from a three bladed vertical axis wind turbine with a direct driven PM synchronous generatorare presented. The H-rotor turbine, independent of wind direction, does not require any yaw mechanism.Furthermore, the variable speed, stall regulated turbine does not require pitch mechanism. The specifically designeddirectly driven generator eliminates the need for a gearbox. All electrical equipment, including generator, are placedon the ground. This reduces the weight that has to be supported by the structure and simplifies maintenance. Thus, theoverall strength of this concept is simplicity.The H-rotor has five meter long blades that are tapered at the tips. The aerodynamic torque is transferred to thegenerator via a 5.4 meter long drive shaft supported by a tower. A universal joint connects the drive shaft to thegenerator shaft, cancelling any transverse bending moments from the turbine on the generator. The generator acts as amotor to start up the turbine using a separate auxiliary winding. The turbine has a swept area of 30 m2 and is rated at12 kW in 12 m/s winds for 127 rpm.The turbine has been placed on a site where the wind resources have been extensively documented. The wind datarecord is more then ten years and includes data from various heights giving an accurate wind mapping of the area.The experimental aerodynamic power curve in turbulent wind conditions is presented. Considering the highlyturbulent wind conditions and the small size of the wind turbine these results are encouraging.
|
|
| 39. |
|
|
| 40. |
- Dyachuk, Eduard, 1988-
(author)
-
Aerodynamics of Vertical Axis Wind Turbines : Development of Simulation Tools and Experiments
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- This thesis combines measurements with the development of simulation tools for vertical axis wind turbines (VAWT). Numerical models of aerodynamic blade forces are developed and validated against experiments. The studies were made on VAWTs which were operated at open sites. Significant progress within the modeling of aerodynamics of VAWTs has been achieved by the development of new simulation tools and by conducting experimental studies. An existing dynamic stall model was investigated and further modified for the conditions of the VAWT operation. This model was coupled with a streamtube model and assessed against blade force measurements from a VAWT with curved blades, operated by Sandia National Laboratories. The comparison has shown that the accuracy of the streamtube model has been improved compared to its previous versions. The dynamic stall model was further modified by coupling it with a free vortex model. The new model has become less dependent on empirical constants and has shown an improved accuracy. Unique blade force measurements on a 12 kW VAWT were conducted. The turbine was operated north of Uppsala. Load cells were used to measure the forces on the turbine. A comprehensive analysis of the measurement accuracy has been performed and the major error sources have been identified.The measured aerodynamic normal force has been presented and analyzed for a wide range of operational conditions including dynamic stall, nominal operation and the region of high flow expansion. The improved vortex model has been validated against the data from the new measurements. The model agrees quite well with the experiments for the regions of nominal operation and high flow expansion. Although it does not reproduce all measurements in great detail, it is suggested that the presented vortex model can be used for preliminary estimations of blade forces due to its high computational speed and reasonable accuracy.
|
|
| 41. |
- Edling, Lars, et al.
(author)
-
Celiac disease and giardiasis : a case report
- 2012
-
In: European Journal of Gastroenterology and Hepathology. - : Lippincott Williams & Wilkins. - 0954-691X .- 1473-5687. ; 24:8, s. 984-987
-
Journal article (peer-reviewed)abstract
- When investigating a patient with suspected celiac disease (CD), several other conditions must be considered, including potential infection with Giardia lamblia. Although giardiasis is rare, its histopathological and serological picture may resemble that of CD. We report the case of a young man with diabetes mellitus and a family history of CD referred to our hospital because of diarrhoea and weight loss. Investigation showed, among other factors, partial villous atrophy in duodenal biopsies and elevated immunoglobulin A antitissue transglutaminase antibodies. The patient was diagnosed with CD and recommended a gluten-free diet. At the same time, faecal tests were conducted, indicating the presence of G. lamblia. The patient was treated and improved, even after discontinuing the gluten-free diet. Subsequent follow-up after 6 months showed total regression of mucosal histopathology and a normal antitissue transglutaminase antibodies level. Eur J Gastroenterol Hepatol 24:984-987 (c) 2012 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.
|
|
| 42. |
|
|
| 43. |
- Eklund, Petter, 1989-, et al.
(author)
-
A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator
- 2014
-
In: Machines. - Basel, Switzerland : Multidisciplinary Digital Publishing Institute. - 2075-1702.
-
Journal article (peer-reviewed)abstract
- The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage.
|
|
| 44. |
- Eklund, Petter, 1989-, et al.
(author)
-
Air Gap Magnetic Flux Density Variations due to Manufacturing Tolerances in a Permanent Magnet Synchronous Generator
- 2016
-
In: 2016 XXII INTERNATIONAL CONFERENCE ON ELECTRICAL MACHINES (ICEM). - : IEEE. - 9781509025381 ; , s. 93-99
-
Conference paper (peer-reviewed)abstract
- The impact of manufacturing tolerances on the performance of a permanent magnet synchronous generator is investigated. A generator with a flux concentrating spoke-type rotor, with ferrite permanent magnets, is used in the investigation. Measurements of the air gap magnetic flux density, the air gap length, as well as the magnetization and size of the permanent magnets have been performed. Correlations are calculated and causalities are discussed. It is found that the permanent magnets used are below tolerance in remanent magnetic flux density, that the air gap length is smaller than specified, and that the resulting air gap magnetic flux density is lower than specified. From the results it can be concluded that the design should be made with tolerances in mind and that quality control of parts, especially of PM magnetization, is important for machine performance.
|
|
| 45. |
- Eklund, Petter, 1989-
(author)
-
Design of Rare Earth Free Permanent Magnet Generators
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- Low speed permanent magnet (PM) synchronous generators (SGs) are commonly used in renewable energy. Rare earth (RE) PMs such as neodymium-iron-boron are a popular choice due to their high performance. In 2011 supply and cost issues were added to the previously existing environmental concerns regarding REPM raw materials as the world's major producer China imposed export restrictions. This thesis aims to investigate and propose design solutions for PMSGs that do not use REPMs. Two approaches are used: to design generators using the cheaper and more abundant ferrite PM materials, and to investigate how properties of new PM materials influence SG design.A ferrite PM rotor is designed to replace a REPM rotor in an experimental 12 kW wind power generator. The new design employs a flux concentrating spoke type rotor to achieve performance similar to the old REPM rotor while using ferrite PMs. The ferrite PM rotor design is built. The air gap length, magnetic flux density in the air gap, PM remanence, and voltage at both load and no load are measured. The generator has lower no load voltage than expected, which is mainly explained by lower than specified remanence of the ferrite PMs in the prototype. With the measured remanence inserted into the calculations some discrepancy remains. It is found that the discrepancy can be explained by the magnetic leakage flux in the end regions of the spoke type rotor, which is not modeled in the two dimensional simulations used for the design calculations.To investigate the influence of PM material properties three different PM rotor topologies are optimized for torque production using PM materials described by their remanence, recoil permeability, and demagnetization resistance. Demagnetization is considered using currents determined by a novel, winding design independent short circuit model. It is found that the spoke type rotor gives the highest torque of the three rotor topologies for low remanence materials as long as the PMs have sufficient demagnetization resistance. For high remanence materials the surface mounted PM rotor can give higher torque if the demagnetization resistance is high, but otherwise a capped PM rotor gives higher torque.
|
|
| 46. |
- Eklund, Petter, 1989-, et al.
(author)
-
Experimental Evaluation of a Rare Earth-Free Permanent Magnet Generator
- 2021
-
In: IEEE Transactions on Energy Conversion. - Piscataway : Institute of Electrical and Electronics Engineers (IEEE). - 1558-0059 .- 0885-8969. ; 36:1, s. 3-10
-
Journal article (peer-reviewed)abstract
- Low speed, high torque machines are used in wind turbines where the turbine rotor is directly connected to the generator. A permanent magnet synchronous generator using high-energy rare-earth permanent magnets (PMs) is one common choice for this application, but rare-earth PMs have supply insecurities and cost risks. A rare-earth free 32-pole PM generator, using ferrite PMs in a spoke-type rotor, for use in a 12 kW experimental wind turbine is built and tested. Voltages and currents at load and no load are measured, as well as the magnetic field in the end regions of the machine. The generator can deliver the required power at nominal speed and has low harmonic content in the output. The electrical measurements are compared to two-dimensional finite element design calculations and the experimental results are lower than expected from simulations. The measured voltage is lower than expected, requiring a higher current than calculated for the rated power. Three-dimensional magnetic field simulations show that there are leakage flux paths in the end-regions that the two-dimensional design calculations overlook, explaining the discrepancy between simulations and measurements.
|
|
| 47. |
- Eklund, Petter, 1989-, et al.
(author)
-
Magnetic End LeakageFlux in a Spoke Type Rotor Permanent Magnet SynchronousGenerator
- 2017
-
Conference paper (other academic/artistic)abstract
- The spoke type rotor can be used to obtain magnetic flux concentration in permanent magnet machines. This allows the air gap magnetic flux density to exceed the remanent flux density of the permanent magnets but gives problems with leakage fluxes in the magnetic circuit. The end leakage flux of one spoke type permanent magnet rotor design is studied through measurements and finite element simulations. The measurements are performed in the end regions of a 12 kW prototype generator for a vertical axis wind turbine. The simulations are made using three dimensional finite elements to calculate the magnetic field distribution in the end regions of the machine. Also two dimensional finite element simulations are performed and the impact of the two dimensional approximation is studied. It is found that the magnetic leakage flux in the end regions of the machine is equal to about 20 % of the flux in the permanent magnets. The overestimation of the performance by the two dimensional approximation is quantified and a curve-fitted expression for its behavior is suggested.
|
|
| 48. |
- Eklund, Petter, 1989-
(author)
-
Rare Earth Metal–Free Permanent Magnet Generators
- 2016
-
Licentiate thesis (other academic/artistic)abstract
- Permanent magnet (PM) synchronous generators (SGs) are used in renewable energy production. The preferred PM material is neodymium-iron-boron (NdFeB), which has very high performance and, until recently, low cost. In recent years there has emerged a cost and supply insecurity in NdFeB PMs due to export restrictions imposed by China, where the majority of the raw materials are produced. In this thesis various methods of avoiding the use of PM materials based on NdFeB, or other rare earth metals, are investigated.One approach is the use of the cheap and abundant ferrite PM. A ferrite PM rotor intended to be interchangeable with an NdFeB PM rotor is designed and built. Some initial investigation of the performance of the new rotor, and how this relates to manufacturing tolerances, is also made.Another approach is to make parameter studies in anticipation of new PM materials. A study of how three different rotor topologies perform with different PM materials, described by their remanence and recoil permeability, is made. The rotor topologies are: a spoke type PM rotor, a surface mounted PM rotor and a capped PM rotor.It is concluded that a viable replacement rotor can be designed using ferrite PMs. The new rotor will be heavier and mechanically more complex, and give slightly lower output voltage. Losses in the machine will increase slightly. A study is made on the impact of manufacturing tolerances on the performance of the resulting rotor.The different rotor topologies work best with different PM material properties. The surface mounted PM and capped PM rotors require higher remanence for good performance; the spoke type PM rotor works well with larger amounts of low remanence material. The recoil permeability should be low for the surface mounted and high for the capped PM rotor.
|
|
| 49. |
- Eklund, Petter, 1989-, et al.
(author)
-
The influence of permanent magnet material properties on generator rotor design
- 2019
-
In: Energies. - : MDPI AG. - 1996-1073. ; 12:7
-
Journal article (peer-reviewed)abstract
- Due to the price and supply insecurities for rare earth metal-based permanent magnet (PM) materials, a search for new PM materials is ongoing. The properties of a new PM material are not known yet, but a span of likely parameters can be studied. This paper presents an investigation on how the remanence and recoil permeability of a PM material affect its usefulness in a low speed, multi-pole, and PM synchronous generator. Demagnetisation is also considered. The investigation is carried out by constrained optimisation of three different rotor topologies for maximum torque production for different PM material parameters and a fixed PM maximum energy. The rotor topologies used are surface mounted PM rotor, spoke type PM rotor and an interior PM rotor with radially magnetised PMs. The three different rotor topologies have their best performance for different kinds of materials. The spoke type PM rotor is the best at utilising low remanence materials as long as they are sufficiently resistant to demagnetisation. The surface mounted PM rotor works best with very demagnetisation resistant PM materials with a high remanence, while the radial interior PM rotor is preferable for high remanence materials with low demagnetisation resistance.
|
|
| 50. |
|
|
