| 1. |
- Boman, Christoffer, et al.
(författare)
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Development of innovative small(micro)-scale biomass-based CHP technologies
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To enhance the overall efficiency of the use of biomass in the energy sector in Europe, the large electricity production potential from small-scale biomass heating systems should be utilised. So far, no technologically sound (in terms of efficiency and reliability) and economically affordable micro- and small-scale biomass CHP technologies are, however, available. Therefore, the present ERA-NET project (MiniBioCHP) aimed at the further development and test of new CHP technologies based on small-scale biomass combustion in the electric capacity range between some W and 100 kW. Within the project, an international consortium consisting of 12 partners from 4 countries, including university institutions, institutes and industry (both engineering and manufacturing), collaborated closely to perform high level R&D on three promising micro/small-scale biomass based CHP technologies which are covering a broad range of applications in the residential heating sector. The Austrian engineering company BIOS, coordinated the international project. The project was based on earlier basic research and development work related to these promising new technologies and aimed at the achievement of a technological level which allows a first (commercial) demonstration after the end of the project. The three CHP concepts included in the MiniBioCHP project were;1. Pellet stoves with a thermoelectric generator (TEG)2. Small-scale biomass boilers (10-30 kWth) with a micro-ORC process3. High temperature heat exchanger (HT-HE) for an externally fired gas turbine (EFGT)The Swedish part of the project was focused on the development of the concept of biomass based EFGT with dedicated R&D activities related to the development of the HT-HE system. The Swedish project consisted of the research partners Umeå University (project leader), Luleå University of Technology, Chalmers University of Technology and RISE Research Institutes of Sweden, together with the industrial partners Enertech AB/Osby Parca and Ecergy. The expertise of the Swedish partners regarding ash related problems, grate boiler combustion and modelling, deposit formation and high temperature corrosion, were combined with the know-how of a Polish partner regarding HT-HE design, construction, testing and optimisation.The HT-HE is the most crucial component in EFGT processes significantly influencing the investment costs, availabilities as well as the efficiencies that can be achieved. With a thermal capacity from several hundred kW up to 2-3 MWth) the CHP technology based on a biomass boiler and an EFGT is suitable for district heating systems, or process heat consumers. The electricity produced by the gas turbine (up to some 100 kWel) can be used to cover the own electricity consumption of a company and/or fed into the grid. Even though the concept of biomass based EFGT has been an interesting alternative for small-scale CHP production for some decades, and R&D activities have been undertaken, tackling both economic and technical aspects, only a few pilot-plants have been in operation and no initiative has so far reached the level of commercial implementation. Thus, the concept of EFGT fed with biomass is still considered to be in a rather early development stage and the main technical challenges are related to alkali deposit induced corrosion and thermal stress of the HT-HE material, turbine design/operation and system integration.Within the present project, a HT-HE prototype aimed for an EFGT system was therefore designed, constructed and successfully tested at flue gas temperatures up to 900°C. Thus, appropriate guidelines for a compact design of the HT-HE and recommendations have been worked out to minimize thermal stresses as well as ash related problems regarding ash deposit formation and high temperature corrosion in a biomass boiler system. Furthermore, different concepts for the overall biomass based EFGT system have been worked out and evaluated. The outcome of the project will hopefully be used in the further development work and form the basis for a first testing and demonstration plant within the coming years.
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| 2. |
- Elliott, Kerryn, et al.
(författare)
-
Elevated pyrimidine dimer formation at distinct genomic bases underlies promoter mutation hotspots in UV-exposed cancers.
- 2018
-
Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- Sequencing of whole cancer genomes has revealed an abundance of recurrent mutations in gene-regulatory promoter regions, in particular in melanoma where strong mutation hotspots are observed adjacent to ETS-family transcription factor (TF) binding sites. While sometimes interpreted as functional driver events, these mutations are commonly believed to be due to locally inhibited DNA repair. Here, we first show that low-dose UV light induces mutations preferably at a known ETS promoter hotspot in cultured cells even in the absence of global or transcription-coupled nucleotide excision repair (NER). Further, by genome-wide mapping of cyclobutane pyrimidine dimers (CPDs) shortly after UV exposure and thus before DNA repair, we find that ETS-related mutation hotspots exhibit strong increases in CPD formation efficacy in a manner consistent with tumor mutation data at the single-base level. Analysis of a large whole genome cohort illustrates the widespread contribution of this effect to recurrent mutations in melanoma. While inhibited NER underlies a general increase in somatic mutation burden in regulatory elements including ETS sites, our data supports that elevated DNA damage formation at specific genomic bases is at the core of the prominent promoter mutation hotspots seen in skin cancers, thus explaining a key phenomenon in whole-genome cancer analyses.
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| 3. |
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| 4. |
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| 5. |
- Alinezhad, Saeid, et al.
(författare)
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Validation of novel biomarkers for prostate cancer progression by the combination of bioinformatics, clinical and functional studies
- 2016
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:5
-
Tidskriftsartikel (refereegranskat)abstract
- The identification and validation of biomarkers for clinical applications remains an important issue for improving diagnostics and therapy in many diseases, including prostate cancer. Gene expression profiles are routinely applied to identify diagnostic and predictive biomarkers or novel targets for cancer. However, only few predictive markers identified in silico have also been validated for clinical, functional or mechanistic relevance in disease progression. In this study, we have used a broad, bioinformatics-based approach to identify such biomarkers across a spectrum of progression stages, including normal and tumor-adjacent, premalignant, primary and late stage lesions. Bioinformatics data mining combined with clinical validation of biomarkers by sensitive, quantitative reverse-transcription PCR (qRT-PCR), followed by functional evaluation of candidate genes in disease-relevant processes, such as cancer cell proliferation, motility and invasion. From 300 initial candidates, eight genes were selected for validation by several layers of data mining and filtering. For clinical validation, differential mRNA expression of selected genes was measured by qRT-PCR in 197 clinical prostate tissue samples including normal prostate, compared against histologically benign and cancerous tissues. Based on the qRT-PCR results, significantly different mRNA expression was confirmed in normal prostate versus malignant PCa samples (for all eight genes), but also in cancer-adjacent tissues, even in the absence of detectable cancer cells, thus pointing to the possibility of pronounced field effects in prostate lesions. For the validation of the functional properties of these genes, and to demonstrate their putative relevance for disease-relevant processes, siRNA knock-down studies were performed in both 2D and 3D organotypic cell culture models. Silencing of three genes (DLX1, PLA2G7 and RHOU) in the prostate cancer cell lines PC3 and VCaP by siRNA resulted in marked growth arrest and cytotoxicity, particularly in 3D organotypic cell culture conditions. In addition, silencing of PLA2G7, RHOU, ACSM1, LAMB1 and CACNA1D also resulted in reduced tumor cell invasion in PC3 organoid cultures. For PLA2G7 and RHOU, the effects of siRNA silencing on proliferation and cell-motility could also be confirmed in 2D monolayer cultures. In conclusion, DLX1 and RHOU showed the strongest potential as useful clinical biomarkers for PCa diagnosis, further validated by their functional roles in PCa progression. These candidates may be useful for more reliable identification of relapses or therapy failures prior to the recurrence local or distant metastases.
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| 6. |
- Alopaeus, Tea, et al.
(författare)
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Med de nya svenska klimatmålen i sikte : Gapanalys samt strategier och förutsättningar för att nå etappmålen 2030 med utblick mot 2045
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Under våren 2017 presenterade Naturvårdsverket scenarier för hur växthusgasutsläppen i Sverige skulle kunna utvecklas till 2035. Sedan Naturvårdsverket presenterade scenarierna har ett nytt klimatpolitiskt ramverk för Sverige beslutats av riksdagen med nya klimatmål till 2030, 2040 och 2045. Regeringen har även presenterat ett antal nya styrmedel i budgetpropositionen.Naturvårdsverket ska inom miljömålssystemet löpande och strategiskt analysera och utvärdera styrmedel och åtgärder. Naturvårdsverket har mellan maj och november 2017 gjort en första uppföljning mot de nya klimatmålen. I denna rapport presenteras hur beslutade och planerade styrmedel kan komma att falla ut givet olika antagande. En översiktlig analys av styrmedel görs också.Arbetsgruppens sammansättning har varierat över tid. Sammantaget har följande personer på Naturvårdsverket deltagit i arbetsgruppen: Tea Alopaeus (projektledare), Björn Boström, Mats Björsell, Martin Boije, Joanna Dickinson, Dag Henning, Daniel Engström Stenson, Eva Jernbäcker (projektledare till september), Julien Morel, Miriam Münnich Vass, Karl-Anders Stigzelius, Ulrika Svensson, Per Wollin.Stockholm 29 november 2017Björn RisingerGeneraldirektör
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| 7. |
- Berbyuk, Viktor, 1953, et al.
(författare)
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Ice detection for smart de-icing of wind turbines
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Icing on a wind turbine rotor blade is a problem in the operation of wind turbines in cold climates. Ice detection is a critical process to get a workable cost-effective wind turbine de-icing system. The paper presents the theoretical models, methods, algorithms, principles, and a demonstrator that are the basis for developing a new technique for detecting icing on rotor blades of a wind turbine based on acoustic wave propagation in composite structures. Two methods have been proposed: guided acoustic wave propagation and bulk acoustic wave propagation in composite structures. Analysis of computer simulations and the results of experimental study obtained by using the developed demonstrator in cold climate lab has shown that the integration of the guided acoustic wave propagation and the bulk acoustic wave propagation methods provides an efficient scientific approach to be used for the design of new ice detection system for wind turbines in cold climate regions. In particular, the guided acoustic wave propagation method makes it possible to detect ice and icing area location on the rotor blades. Several criteria (Icing Index, Frequency Factor Index, others) have been proposed for ice detection of composite structures. Bulk acoustic wave propagation method makes it possible to identify the time-varying spatially heterogeneous “landscapes” over the blade surface for each of the following eight ice parameters: thickness, the volumetric bulk density, bulk and shear moduli, stress relaxation time, porosity, and volume and shear viscosities. These data are necessary for smart, energy-efficient de-icing systems. The identification algorithm is computationally efficient and can be implemented in the real-time mode. A LIDAR (Light Detection And Ranging) for the detection of early ice growth on the wind turbine blades has also designed, tested and evaluated in this project. LIDAR uses laser pulses that emit at two different wavelengths and is capable of distinguishing between a thin layer of ice and water covering the turbine blades. The results of the tests that have been carried out in the project are undeniable. LIDAR detects early ice growth by measuring the difference in reflectivity of a surface by using two different laser wavelengths. The limitation of LIDAR is that it cannot be used to determine the amount of ice on the sheet, only if there is ice or not. The obtained results can be used to develop smart de-icing systems for wind turbines operating in cold climates, and can lead to new future products that are sought after by wind power industry. Since the efficient ice detection systems can increase wind turbine profitability, the results contribute to an increased ability to establish multiple wind turbines in cold regions.
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| 8. |
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| 9. |
- Berg, Frenk van den, et al.
(författare)
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Results of the European collaborative project "Product Uniformity Control" to improve the inline sensing of mechanical properties and microstructure of automotive steels
- 2018
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Ingår i: e-Journal of Nondestructive Testing (eJNDT). - 1435-4934. ; 23:8
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Tidskriftsartikel (refereegranskat)abstract
- A European consortium consisting of four major steel manufacturers and ten academic technology institutes has conducted a research and development project, called “Product Uniformity Control“ (PUC) in the period 2013 to 2017. This project aimed to develop and improve non-destructive (inline) measurement techniques to characterise the (uniformity of the) microstructure of steel strip products. In this project, a multitude of strip steel samples from various stages of production have been collected from the four participating steel manufacturers. The samples have been characterised in various ways, namely on their (1) non-destructive measurement parameters using different techniques suited for inline evaluation, (2) fundamental ultrasonic and electromagnetic properties (wave speed, ultrasonic attenuation, magnetisation loops, coercive field), (3) tensile properties (stress-strain curves) and (4) microstructure (by optical micrographs and EBSD images). The correlations between these different characterisations will be addressed. Besides the experimental characterisation, a strong accent has been on modelling activities: during the project, fundamental models have been developed to describe, starting from 2D and 3D microstructures, the ultrasonic and magnetic properties, which are next used as input to sensor models that predict the output of the inline measurement systems. This contribution presents the recent results of experimental work, which underlines the importance of associated modelling studies for the interpretation of the measurement data for the benefit of inline characterisation of the mechanical properties complementary to traditional destructive tensile testing.
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| 10. |
- Björnfot Holmström, Sofia, et al.
(författare)
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MMP-12 and S100s in saliva reflect different aspects of periodontal inflammation
- 2019
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Ingår i: Cytokine. - : Academic Press. - 1043-4666 .- 1096-0023. ; 113, s. 155-161
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Tidskriftsartikel (refereegranskat)abstract
- Matrix metalloproteinase (MMP)-12, S100A8/A9, and S100A12 are involved in innate immune responses. We addressed whether different aspects of oral health and non-disease-related covariates influence their levels in saliva. 436 participants were clinically examined, completed a health questionnaire, and provided stimulated saliva. Salivary levels of MMP-12, S100A8/A9, and S100A12 were determined by enzyme-linked immunosorbent assays. Lower MMP-12 levels were observed in individuals 40-64years old (yo) compared to < 40yo, and higher S100A8/A9 levels were found in individuals > 64yo compared to 40-64yo. Smokers exhibited lower MMP-12 and S100A12 levels compared to non-smokers. All three proteins were elevated in individuals with bleeding on probing (BOP)>20% compared to those with BOP/= 10% gingival pocket depths (PPD)>/=4mm compared to the ones with shallow pockets < 4mm. The extent of alveolar bone loss or presence of manifest caries did not alter any of the markers. MMP-12, S100A8/A9, and S100A12 levels were higher in participants with high periodontal inflammatory burden. All three proteins correlated positively to BOP, PPD, and to several inflammatory mediators. The explanatory variables for MMP-12 in saliva were age, smoking, presence of any tumor, and percentage of PPD>/=4mm. The determinant of salivary S100A8/A9 was percentage of BOP, while S100A12 levels were associated with percentage of BOP and presence of any tumor. Taken together, MMP-12 and the S100/calgranulin levels in saliva reflect different aspects of periodontal inflammation. Smoking and age should be taken into account in further investigation of these proteins as biomarker candidates of periodontal disease.
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| 11. |
- Boström, Anders E, 1951
(författare)
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Scattering by an anisotropic circle
- 2015
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Ingår i: Wave Motion. - : Elsevier BV. - 0165-2125. ; 57, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- The scattering by a circle is considered when the outside medium is isotropic and the inside medium is anisotropic (orthotropic). The problem is a scalar one and is phrased as a scattering problem for elastic waves with polarization out of the plane of the circle (SH wave), but the solution is with minor modifications valid also for scattering of electromagnetic waves. The equation inside the circle is first transformed to polar coordinates and it then explicitly contains the azimuthal angle through trigonometric functions. Making an expansion in a trigonometric series in the azimuthal coordinate then gives a coupled system of ordinary differential equations in the radial coordinate that is solved by power series expansions. With the solution inside the circle complete the scattering problem is solved essentially as in the classical case. Some numerical examples are given showing the influence of anisotropy, and it is noted that the effects of anisotropy are generally strong except at low frequencies where the dominating scattering only depends on the mean stiffness and not on the degree of anisotropy.
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| 12. |
- Boström, Anders E, 1951
(författare)
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Scattering of In-plane Elastic Waves by an Anisotropic Circle
- 2018
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Ingår i: Quarterly Journal of Mechanics and Applied Mathematics. - : Oxford University Press (OUP). - 0033-5614 .- 1464-3855. ; 71:2, s. 139-155
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Tidskriftsartikel (refereegranskat)abstract
- The 2D scattering of in-plane elastic waves by a circle is considered when the surrounding medium is isotropic and the medium inside the circle is anisotropic (orthotropic). The equations inside the circle are transformed to polar coordinates and then depend explicitly on the azimuthal angle through trigonometric functions. Making expansions in trigonometric series in the azimuthal coordinate give a coupled system of ordinary differential equations in the radial coordinate that is solved by power series expansions. With the solution inside the circle complete the scattering problem is solved essentially as in the classical case. The elements of the transition (T) matrix of the circle are given explicitly for low frequencies (long wavelengths). For low frequencies some numerical examples are given showing the strong influence of anisotropy.
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| 13. |
- Boström, Anders E, 1951, et al.
(författare)
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Ultrasonic Attenuation in Polycrystalline Materials in 2D
- 2019
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Ingår i: Journal of Nondestructive Evaluation. - : Springer Science and Business Media LLC. - 1573-4862 .- 0195-9298. ; 38:2
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Tidskriftsartikel (refereegranskat)abstract
- Grains in a polycrystalline material, typically a metal, act as scatterers of ultrasonic waves and thus give rise to attenuation of the waves. Grains have anisotropic stiffness properties, typically orthotropic or cubic. A new approach is proposed to calculate attenuation in a 2D setting starting from the scattering by an anisotropic circle in an isotropic surrounding. This problem has recently been solved, giving explicit, simple expressions for the elements of the transition (T) matrix (which gives the relation between the the incoming and scattered fields) when the circle is small compared to the ultrasonic wavelengths. The T matrix can be used to calculate the total scattering cross section, which in turn can be used to estimate the attenuation in the material. Explicit expressions for the attenuation coefficient for longitudinal and transverse waves are obtained for a cubic material, and contrary to results in the literature these expressions are valid also for strong anisotropy. For the longitudinal attenuation coefficient a comparison with recent FEM results for Inconel 600 gives excellent agreement.
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| 14. |
- Boström, Anders E, 1951
(författare)
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Ultrasonic damping in polycrystalline materials
- 2018
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Ingår i: 12th European Conference on Non-Destructive Testing (ECNDT 2018), Gothenburg 2018, June 11-15 (ECNDT 2018).
-
Konferensbidrag (refereegranskat)abstract
- The grains in a polycrystalline material, typically metals, act as scatterers of ultrasonic waves and thus give rise to attenuation of the waves. The grains have anisotropic stiffness properties, typically orthotropic or cubic. A new approach is proposed to calculate damping in a 2D setting starting from the scattering by an anisotropic circle in an isotropic surrounding. This problem has recently been solved, giving explicit, simple expressions for the elements of the transition (T) matrix (which gives the relation between the the incoming and scattered fields) when the circle is small compared to the ultrasonic wavelengths. The T matrix can be used to calculate the total scattering cross section, which in turn can be used to estimate the damping in the material. Explicit expressions for the damping coefficient for longitudinal and transverse waves are obtained in this way.
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| 15. |
- Boström, Erika, 1975-
(författare)
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Formativ bedömning : en enkel match eller en svår utmaning? Effekter av en kompetensutvecklingssatsning på lärarnas praktik och på elevernas prestationer i matematik
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research reviews have shown that the use of formative assessment in classroom practice can substantially improve student achievement. However, a strong research base about how to support teachers’ implementation of such formative classroom practice is lacking. In this thesis, I investigate the effects of a comprehensive professional development programme (PDP) in formative assessment on teachers’ classroom practice and students’ achievement in mathematics. In addition, I identify reasons for the changes made in the teachers’ formative classroom practice. Fourteen randomly selected year - 7 mathematics teachers participated in the PDP. The teachers’ formative classroom practice before and after attending the programme was analysed and described, and reasons for their change in practice were explored. The effect of the changes in formative classroom practice on students’ mathematics achievement was examined using pre- and post-tests administered to both the intervention group and a control group. A mixed methods approach with classroom observations, teacher interviews, questionnaires and student achievement tests in mathematics was used in the studies included in the thesis.The results show that the teachers used aspects of formative assessment in their classroom practice before the PDP, but that there was plenty of room for development towards a more effective formative assessment practice. Several possibilities for developing the practice were identified. After the PDP the teachers believed in the idea of formative assessment and were motivated to make changes towards a more formative classroom practice. The teachers included new formative assessment activities in their classroom practice, but in different ways and to different degrees. The characteristics of these changes were identified, and also the characteristics of the PDP that the teachers found to be influential for their development of the formative classroom practice. Results also show that the teachers’ motivational beliefs held after the PDP was an explanatory factor for their changes in practice. However, the formative assessment practice the teachers implemented did not have a significant effect on their students’ achievement compared to the control group. In addition, there was no correlation between the number of formative assessment activities implemented by the teachers and their students’ achievement gains. Reasons for these non-effects on student achievement, and for the teachers’ degree and type of implementation of formative assessment in the classroom practice, are discussed in the thesis.
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| 16. |
- Boström, Emil, et al.
(författare)
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Time-resolved spectroscopy at surfaces and adsorbate dynamics : Insights from a model-system approach
- 2016
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 93:19
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a model description of femtosecond laser induced desorption at surfaces. The substrate part of the system is taken into account as a (possibly semi-infinite) linear chain. Here, being especially interested in the early stages of dissociation, we consider a finite-size implementation of the model (i.e., a finite substrate), for which an exact numerical solution is possible. By time-evolving the many-body wave function, and also using results from a time-dependent density functional theory description for electron-nuclear systems, we analyze the competition between several surface-response mechanisms and electronic correlations in the transient and longer time dynamics under the influence of dipole-coupled fields. Our model allows us to explore how coherent multiple-pulse protocols can impact desorption in a variety of prototypical experiments.
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| 17. |
- Boström, Emil Viñas, et al.
(författare)
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Charge Separation in Donor-C60 Complexes with Real-Time Green Functions : The Importance of Nonlocal Correlations
- 2018
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:2, s. 785-792
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Tidskriftsartikel (refereegranskat)abstract
- We use the nonequilibrium Green function (NEGF) method to perform real-time simulations of the ultrafast electron dynamics of photoexcited donor-C60 complexes modeled by a Pariser-Parr-Pople Hamiltonian. The NEGF results are compared to mean-field Hartree-Fock (HF) calculations to disentangle the role of correlations. Initial benchmarking against numerically highly accurate time-dependent density matrix renormalization group calculations verifies the accuracy of NEGF. We then find that charge-transfer (CT) excitons partially decay into charge separated (CS) states if dynamical nonlocal correlation corrections are included. This CS process occurs in ∼10 fs after photoexcitation. In contrast, the probability of exciton recombination is almost 100% in HF simulations. These results are largely unaffected by nuclear vibrations; the latter become however essential whenever level misalignment hinders the CT process. The robust nature of our findings indicates that ultrafast CS driven by correlation-induced decoherence may occur in many organic nanoscale systems, but it will only be correctly predicted by theoretical treatments that include time-nonlocal correlations.
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| 18. |
- Boström, Henrik, et al.
(författare)
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Predicting with Confidence from Survival Data
- 2019
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Ingår i: Conformal and Probabilistic Prediction and Applications. ; , s. 123-141
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Konferensbidrag (refereegranskat)abstract
- Survival modeling concerns predicting whether or not an event will occur before or on a given point in time. In a recent study, the conformal prediction framework was applied to this task, and so-called conformal random survival forest was proposed. It was empirically shown that the error level of this model indeed is very close to the provided confidence level, and also that the error for predicting each outcome, i.e., event or no-event, can be controlled separately by employing a Mondrian approach. The addressed task concerned making predictions for time points as provided by the underlying distribution. However, if one instead is interested in making predictions with respect to some specific time point, the guarantee of the conformal prediction framework no longer holds, as one is effectively considering a sample from another distribution than from which the calibration instances have been drawn. In this study, we propose a modification of the approach for specific time points, which transforms the problem into a binary classification task, thereby allowing the error level to be controlled. The latter is demonstrated by an empirical investigation using both a collection of publicly available datasets and two in-house datasets from a truck manufacturing company.
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| 19. |
- Boström, Jannika E., et al.
(författare)
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The flicker fusion frequency of budgerigars (Melopsittacus undulatus) revisited
- 2017
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Ingår i: Journal of Comparative Physiology A. Sensory, neural, and behavioral physiology. - : SPRINGER. - 0340-7594 .- 1432-1351. ; 203:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- While color vision and spatial resolution have been studied in many bird species, less is known about the temporal aspects of bird vision. High temporal resolution has been described in three species of passerines but it is unknown whether this is specific to passerines, to small actively flying birds, to insectivores or to birds living in bright habitats. Temporal resolution of vision is commonly tested by determining the flicker fusion frequency (FFF), at which the eye can no longer distinguish a flickering light from a constant light of equal intensity at different luminances. Using a food reward, we trained the birds to discriminate a constant light from a flickering light, at four different luminances between 750 and 7500 cd/m(2). The highest FFF found in one bird at 3500 cd/m(2) was 93 Hz. Three birds had higher FFF (82 Hz) at 7500 cd/m(2) than at 3500 cd/m(2). Six human subjects had lower FFF than the birds at 1500 but similar FFF at 750 cd/m(2). These results indicate that high temporal resolution is not a common trait for all small and active birds living in bright light habitats. Whether it is typical for passerines or for insectivorous birds remains to be tested.
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| 20. |
- Boström, Jannika E., et al.
(författare)
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Ultra-Rapid Vision in Birds
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Flying animals need to accurately detect, identify and track fast-moving objects and these behavioral requirements are likely to strongly select for abilities to resolve visual detail in time. However, evidence of highly elevated temporal acuity relative to non-flying animals has so far been confined to insects while it has been missing in birds. With behavioral experiments on three wild passerine species, blue tits, collared and pied flycatchers, we demonstrate temporal acuities of vision far exceeding predictions based on the sizes and metabolic rates of these birds. This implies a history of strong natural selection on temporal resolution. These birds can resolve alternating light-dark cycles at up to 145 Hz (average: 129, 127 and 137, respectively), which is ca. 50 Hz over the highest frequency shown in any other vertebrate. We argue that rapid vision should confer a selective advantage in many bird species that are ecologically similar to the three species examined in our study. Thus, rapid vision may be a more typical avian trait than the famously sharp vision found in birds of prey.
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| 21. |
- Boström, Martina, et al.
(författare)
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A role for endothelial cells in radiation-induced inflammation
- 2018
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 94:3, s. 259-271
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To unravel the role of the vasculature in radiation-induced brain tissue damage.Materials and methods: Postnatal day 14 mice received a single dose of 10Gy cranial irradiation and were sacrificed 6h, 24h or 7 days post-irradiation. Endothelial cells were isolated from the hippocampus and cerebellum using fluorescence-activated cell sorting, followed by cell cycle analysis and gene expression profiling.Results: Flow cytometric analysis revealed that irradiation increased the percentage of endothelial cells, relative to the whole cell population in both the hippocampus and the cerebellum. This change in cell distribution indicates that other cell types are more susceptible to irradiation-induced cell death, compared to endothelial cells. This was supported by data showing that genes involved in endothelial cell-specific apoptosis (e.g. Smpd1) were not induced at any time point investigated but that genes involved in cell-cycle arrest (e.g. Cdkn1a) were upregulated at all investigated time points, indicating endothelial cell repair. Inflammation-related genes, on the other hand, were strongly induced, such as Ccl2, Ccl11 and Il6.Conclusions: We conclude that endothelial cells are relatively resistant to ionizing radiation but that they play an active, hitherto unknown, role in the inflammatory response after irradiation. In the current study, this was shown in both the hippocampus, where neurogenesis and extensive cell death after irradiation occurs, and in the cerebellum, where neurogenesis no longer occurs at this developmental age.
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| 22. |
- Boström, Peter J, et al.
(författare)
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Genomic Predictors of Outcome in Prostate Cancer.
- 2015
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Ingår i: European Urology. - : Elsevier BV. - 1873-7560 .- 0302-2838. ; 68:6, s. 1033-1044
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Forskningsöversikt (refereegranskat)abstract
- Given the highly variable behavior and clinical course of prostate cancer (PCa) and the multiple available treatment options, a personalized approach to oncologic risk stratification is important. Novel genetic approaches offer additional information to improve clinical decision making.
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| 23. |
- Eriksson, Anders I., et al.
(författare)
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Cold and warm electrons at comet 67P/Churyumov-Gerasimenko
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 605
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Tidskriftsartikel (refereegranskat)abstract
- Context. Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. Aims. Our aim is to demonstrate the existence of cold electrons in the inner coma of comet 67P/Churyumov-Gerasimenko and show filamentation of this plasma. Methods. In situ measurements of plasma density, electron temperature and spacecraft potential were carried out by the Rosetta Langmuir probe instrument, LAP. We also performed analytical modelling of the expanding two-temperature electron gas. Results. LAP data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5-10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order -10 V. Conclusions. The warm (5-10 eV) electron population observed throughout the mission is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.
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| 24. |
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| 25. |
- Golub, Mikhail, 1982, et al.
(författare)
-
Modelling of elastic wave propagation through damaged interface via effective spring boundary conditions
- 2018
-
Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 207, s. 375-387
-
Konferensbidrag (refereegranskat)abstract
- The present work deals with the application of spring boundary conditions in order to describe elastic wave propagation in composites with damaged interfaces. Dynamic behaviour of the damaged zone is described by means of a distribution of micro-cracks and introduction of spring boundary conditions, where stresses are proportional to the jump in displacement along the damaged interface and the proportionality factor is the distributed spring stiffness. The stiffness in the spring boundary conditions is determined from the equivalence of the transmission coefficients for these two models. As a result, the normal and tangential components of the spring stiffness tensor depend on the concentration of the defects, their typical size and elastic properties of the contacting materials. The three-dimensional problem with elastic wave scattering by a random or periodic distribution of rectangular microcracks is considered, the latter with a boundary integral equation method. The transmission through the damaged interface with random and periodic distribution of rectangular cracks is compared with a good correspondence giving confidence that the models are appropriate.
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| 26. |
- Golub, M.V., et al.
(författare)
-
Effective spring boundary conditions for a damaged interface between dissimilar media in three-dimensional case
- 2016
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 81, s. 141-150
-
Tidskriftsartikel (refereegranskat)abstract
- Elastic waves in the presence of a damaged interface between two dissimilar elastic media is investigated in the three-dimensional case. The damaged is modeled as a stochastic distribution of equally sized circular cracks which is transformed into a spring boundary condition. First the scattering by a single circular interface crack between two dissimilar half-spaces is investigated and solved explicitly for normally incident waves in the low frequency limit. The transmission by a distribution of cracks is then determined and is transformed into a spring boundary condition, where effective spring stiffnesses are expressed in terms of elastic moduli and damage parameters. A comparison with previous results for a periodic distribution of cracks shows good agreement.
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| 27. |
- Golub, M. V., et al.
(författare)
-
TRANSMISSION OF ELASTIC WAVES THROUGH AN INTERFACE BETWEEN DISSIMILAR MEDIA WITH RANDOM AND PERIODIC DISTRIBUTIONS OF STRIP-LIKE MICRO-CRACKS
- 2018
-
Ingår i: Materials Physics and Mechanics. - 1605-8119 .- 1605-2730. ; 37:1, s. 52-59
-
Tidskriftsartikel (refereegranskat)abstract
- The present work investigates wave propagation through a damaged interface between two elastic media. Dynamic behaviour of the deterioration or damage of an interface is described using a random distribution of strip-like micro-cracks of different sizes, a periodic array of strip-like cracks or via a distributed spring model. The wave-field scattered by cracks is calculated using a boundary integral equation method. The spring model assumes introduction of the spring boundary conditions, where stresses are proportional to the displacement jump with the proportionality given by the spring stiffness. Components of the spring stiffness matrix are defined in terms of the concentration of the defects, their typical size and the elastic properties of the contacting materials. Numerical analysis of reflection and transmission for the considered models of the damaged interface is provided.
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| 28. |
- Grönstedt, Helena, et al.
(författare)
-
A study protocol of Older Person's Exercise and Nutrition Study (OPEN) - a sit-to-stand activity combined with oral protein supplement - effects on physical function and independence : a cluster randomized clinical trial
- 2018
-
Ingår i: BMC Geriatrics. - : BIOMED CENTRAL LTD. - 1471-2318. ; 18
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Poor nutrition and age per see add to the development of sarcopenia, i.e. loss of muscle mass and strength, which contributes to increased risk of impaired activities of daily living (ADL) and reduced independence. Protein deficiency plays an important role in the development of sarcopenia. In order to increase the muscle mass protein intake should be combined with physical exercise. A daily physical activity, the sit-to-stand exercise, has been proven to decrease older persons' dependence in ADL. Our study aims to evaluate the effects of the sit-to-stand exercise in combination with a protein-rich nutritional supplement, on physical function and independence in frail nursing home residents. The resident's perceptions and experiences of the intervention and the staff's experiences of supporting the resident to complete the intervention will also be explored.Methods: The study is a two-arm cluster-randomized controlled trial which will be performed in nursing homes at two municipalities in Sweden. We will recruit 120 residents, age 75 or older and able to stand up from a seated position. Residents (n = 60) randomized to the intervention group will perform the sit-to-stand exercise at four occasions daily and will be offered a protein-rich oral supplement, twice a day. The intervention period will last for 12 weeks and measures of physical function, nutritional status, quality of life and health economy will be performed at baseline and at 12-weeks follow-up. The primary outcome will be the number of chair rises performed in 30 s. The control group will receive standard care. Data will be analysed by intention-to-treat analysis and with mixed effect models. During the last part of the intervention period individual interviews with the residents, on the topic of feasibility with the OPEN concept will be held. Likewise, focus-group-interviews with staff will be performed.Discussion: The residents' physical and mental health could be expected to improve. Even the work situation for staff could be positively affected. One innovative feature of the OPEN study is the simple intervention consisting of a basic daily activity that can be performed by several nursing home residents with the support of existing staff and available resources.
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| 29. |
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| 30. |
- Johansson, Ulf, et al.
(författare)
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Venn predictors for well-calibrated probability estimation trees
- 2018
-
Ingår i: 7th Symposium on Conformal and Probabilistic Prediction and Applications. ; , s. 3-14, s. 3-14
-
Konferensbidrag (refereegranskat)abstract
- Successful use of probabilistic classification requires well-calibrated probability estimates, i.e., the predicted class probabilities must correspond to the true probabilities. The standard solution is to employ an additional step, transforming the outputs from a classifier into probability estimates. In this paper, Venn predictors are compared to Platt scaling and isotonic regression, for the purpose of producing well-calibrated probabilistic predictions from decision trees. The empirical investigation, using 22 publicly available datasets, showed that the probability estimates from the Venn predictor were extremely well-calibrated. In fact, in a direct comparison using the accepted reliability metric, the Venn predictor estimates were the most exact on every data set.
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| 31. |
- Kreisel, Katrin, 1991, et al.
(författare)
-
DNA polymerase η contributes to genome-wide lagging strand synthesis.
- 2019
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Ingår i: Nucleic acids research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 47:5, s. 2425-2435
-
Tidskriftsartikel (refereegranskat)abstract
- DNA polymerase η (pol η) is best known for its ability to bypass UV-induced thymine-thymine (T-T) dimers and other bulky DNA lesions, but pol ηalso has other cellular roles. Here, we present evidence that pol η competes with DNA polymerases α and δfor the synthesis of the lagging strand genome-wide, where it also shows a preference for T-T in the DNA template. Moreover, we found that the C-terminus of pol η,which contains a PCNA-Interacting Protein motif is required for pol ηto function in lagging strand synthesis. Finally, we provide evidence that a pol η dependent signature is also found to be lagging strand specific in patients with skin cancer. Taken together, these findings provide insight into the physiological role of DNA synthesis by pol η and have implications for our understanding of how our genome is replicated to avoid mutagenesis, genome instability and cancer.
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| 32. |
- Larsson, Lars, 1984, et al.
(författare)
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Integral Equation Method for Evaluation of Eddy-Current Impedance of a Rectangular, Near Surface Crack Inside a Cylindrical Hole
- 2016
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Ingår i: Journal of Nondestructive Evaluation. - : Springer Science and Business Media LLC. - 1573-4862 .- 0195-9298. ; 35:2
-
Tidskriftsartikel (refereegranskat)abstract
- An integral equation method for solving the eddy-current nondestructive evaluation problem of a flat, rectangular, near surface crack inside of a cylindrical hole in a conducting material is presented. The method involves expanding the Green’s tensor, the incoming field, and the jump in electric potential over the crack in suitable basis functions. Here, plane waves, cylindrical waves, and basis functions related to the Chebyshev polynomials, are used. The way of discretization in this method leads to a formulation where the scattering is defined by a scattering matrix, independent of the incoming field. This presents an advantage, when conducting numerical simulations, since the scattering matrix does not have to be recalculated for every probe position. The numerical calculations are straightforward to perform and model predictions are compared with finite element results.
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| 33. |
- Lira-Junior, Ronaldo, et al.
(författare)
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Colony stimulating factor-1 in saliva in relation to age, smoking, and oral and systemic diseases
- 2017
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Colony stimulating factor (CSF)-1 is a growth factor that stimulates the survival, proliferation and differentiation of mononuclear phagocytes, which has been implicated in several inflammatory diseases. This study evaluated the possible influence of age, sex, smoking, periodontitis, caries, and several systemic conditions on salivary levels of CSF-1. Four-hundred and forty-one individuals were enrolled in this study. All participants answered a health questionnaire and underwent a comprehensive oral examination. Stimulated saliva was collected and CSF-1 levels were analysed by enzyme-linked immunosorbent assay. Salivary levels of CSF-1 were significantly increased in participants over 64 years old and in non-smoking individuals, whereas no difference was observed between men and women. Individuals having periodontitis and manifest caries had significantly higher levels of CSF-1. Participants with muscle and joint disease exhibited increased CSF-1 levels as compared to those without. Age, smoking, percentage of pockets >= 4 mm, number of manifest caries lesions, and presence of tumor were associated with CSF-1 levels. Salivary levels of CSF-1 are associated with age, smoking, periodontitis, manifest caries, and the presence of muscle and joint diseases and tumors. CSF-1 might be a promising biomarker candidate in saliva of both local and systemic conditions that needs further investigation.
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| 34. |
- Lira-Junior, Ronaldo, et al.
(författare)
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Salivary microbial profiles in relation to age, periodontal, and systemic diseases
- 2018
-
Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 13:3
-
Tidskriftsartikel (refereegranskat)abstract
- Background Analysis of saliva is emerging as a promising tool to diagnose and monitor diseases which makes determination of the salivary microbial profile in different scenarios essential. Objective To evaluate the effects of age, periodontal disease, sex, smoking, and medical conditions on the salivary microbial profile. Design A randomly selected sample of 441 individuals was enrolled (51% women; mean age 48.5 +/- 16.8). Participants answered a health questionnaire and underwent an oral examination. Stimulated saliva was collected and the counts of 41 bacteria were determined by checkerboard DNA-DNA hybridization. Results Elderly participants (>64 years old) presented a significant increase in 24 out of 41 bacterial species compared to adults (<= 64 years old). Eubacterium nodatum, Porphyromonas gingivalis, and Tannerella forsythia were significantly higher in participants with generalized bone loss compared to without. Males and non-smokers had higher bacteria counts in saliva. Individuals having mental disorders or muscle and joint diseases showed significantly altered microbial profiles whereas small or no differences were found for subjects with high blood pressure, heart disease, previous heart surgery, bowel disease, tumors, or diabetes. Conclusion Age, periodontal status, sex, smoking, and certain medical conditions namely, mental disorders and muscle and joint diseases, might affect the microbial profile in saliva.
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| 35. |
- Lönnermark, Anders, et al.
(författare)
-
Brandsäkerhet vid lagring av avfallsbränslen
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med detta projekt har varit att ge ökad kunskap kring olika förekommande brandrisker och råd om hur dessa kan reduceras med olika åtgärder, primärt baserat på praktiska erfarenheter från genomfört säkerhetsarbete samt uppkomna bränder ute i olika anläggningar. Målet är att de samlade kunskaperna och erfarenheterna kan komma till nytta för hela branschen, övriga berörda intressenter och myndigheter och på sikt ligga till grund för t.ex. framtida branschrekommendationer.Projektet kan delas in metodmässigt i; statistik, workshoppar samt analys av anläggningsspecifik information.Analysen av insatsstatistik från Myndigheten för samhällsskydd och beredskap (MSB) pekar på att det inträffar i storleksordningen 60–70 bränder årligen i avfallsanläggningar och att brandorsaken i de flesta fall är självantändning eller okänd anledning. Tittar man på "brand ej i byggnad" med relevanta bränder för avfallsanläggningar så ser man en svagt ökande trend i antal bränder 2012–2015. De vanligaste materialfraktionerna som enligt statistik från MSB är kopplade till bränder i avfallsanläggningar är sopor, kompost, fluff, papper, trädgårdsavfall, däckgranulat, annat, skrot, återvinningscontainrar. Även en del av flisbränderna kan vara relaterade till RT-trä.Från avfallsindustrins sida ansågs bark, returträ, flisat material och GROT (grenar och toppar) kunna ge problem med självuppvärmning. Även krossning av avfall angavs som ett generellt problem av flera deltagare.Många incidenter och bränder anses bero på felsorterat eller feldeklarerat avfall och kontrollen av inkommande gods är därför väldigt viktig. Det är också viktigt att kommunicera uppströms i leveranskedjan för att öka chanserna att komma tillrätta med problemen. Många deltagare identifierade batterier (speciellt litiumbatterier) som ett växande problem.Hanteringen av förorenat släckvatten varierar mycket. Man påpekar att samma krav över hela landet vore bra. Man önskar tydligare riktlinjer för släckvattenanalyser, kunskap om vad vattnet kan innehålla och information om reningsmetoder för släckvatten.Det påpekas att det finns många standarder och normer att förhålla sig till så det vore därför bra att ha en lägsta nivå av krav som bestäms i samarbete med branschen som man kan förhålla sig till och någon form av vägledning från myndigheterna för göra hanteringen mer lik över riket.Diskussionerna under workshopparna och tillsammans med projektets referensgrupp har lett fram till 33 rekommendationer uppdelade på olika områden. För varje rekommendation ges i rapporten ytterligare förklaringar. Dessa rekommendationer kan ligga till grund för framtida riktlinjer.
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| 36. |
- Mårsell, Erik, et al.
(författare)
-
Spatial Control of Multiphoton Electron Excitations in InAs Nanowires by Varying Crystal Phase and Light Polarization
- 2018
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:2, s. 907-915
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the control of multiphoton electron excitations in InAs nanowires (NWs) by altering the crystal structure and the light polarization. Using few-cycle, near-infrared laser pulses from an optical parametric chirped-pulse amplification system, we induce multiphoton electron excitations in InAs nanowires with controlled wurtzite (WZ) and zincblende (ZB) segments. With a photoemission electron microscope, we show that we can selectively induce multiphoton electron emission from WZ or ZB segments of the same wire by varying the light polarization. Developing ab initio GW calculations of first to third order multiphoton excitations and using finite-difference time-domain simulations, we explain the experimental findings: While the electric-field enhancement due to the semiconductor/vacuum interface has a similar effect for all NW segments, the second and third order multiphoton transitions in the band structure of WZ InAs are highly anisotropic in contrast to ZB InAs. As the crystal phase of NWs can be precisely and reliably tailored, our findings open up for new semiconductor optoelectronics with controllable nanoscale emission of electrons through vacuum or dielectric barriers.
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| 37. |
- Näzelius, Ida-Linn, et al.
(författare)
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Fuel Indices for Estimation of Slagging of Phosphorus-Poor Biomass in Fixed Bed Combustion
- 2017
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 31:1, s. 904-915
-
Tidskriftsartikel (refereegranskat)abstract
- The market for solid biofuels will grow rapidly during the coming years and there will be a great demand for raw materials. This will force the existing fuel base to also cover wooden materials of lower qualities as well as agricultural raw materials and residues, which often show unfavorable ash melting temperatures. This may lead to combustion related problems. Thus, for the utilization of lower quality fuels, it is important to be able to predict potential fuel ash related problems such as slagging. In light of this, the first objective of the present paper was to evaluate the applicability of previously defined indices for slagging of biomass fuels (phosphorus-poor) in fixed bed combustion. The evaluation showed that none of the previously suggested indices in the literature are suitable for qualitative (nor quantitative) prediction of slagging during fixed bed combustion of P-poor biomass fuels. Hence, a second objective was to develop improved novel fuel indices that can be applied to estimate the slagging of phosphorus-poor biomass in fixed bed combustion. The novel fuel indices give a qualitative prediction of the slagging tendency in biomass fixed bed combustion but still needs additional work to further extend the compositional range as well as to fine-tune the indices’ boundaries.
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| 38. |
- Ocheng, Francis, et al.
(författare)
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Essential Oils from Ugandan Medicinal Plants : In Vitro Cytotoxicity and Effects on IL-1 beta-Induced Proinflammatory Mediators by Human Gingival Fibroblasts
- 2016
-
Ingår i: Evidence-based Complementary and Alternative Medicine. - : Hindawi Publishing Corporation. - 1741-427X .- 1741-4288.
-
Tidskriftsartikel (refereegranskat)abstract
- The study investigated cytotoxicity of essential oils from four medicinal plants (Bidens pilosa, Ocimum gratissimum, Cymbopogon nardus, and Zanthoxylum chalybeum) on human gingival fibroblasts and their effects on proinflammatory mediators' secretion. Cytotoxicity of essential oils was investigated using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Effects of essential oils at subcytotoxicity concentrations on interleukin-(IL-) 6, IL-8, and prostaglandin E-2 (PGE(2)) secretions by gingival fibroblasts treated with IL-1 beta (300 pg/mL) were evaluated by ELISA and EIA. IC50 values of the essential oils ranged from 26 mu g/mL to 50 mu g/mL. Baseline and IL-1 beta-induced secretion of PGE(2) was inhibited by treatment with essential oil from O. gratissimum. Essential oils from B. pilosa and C. nardus had synergistic effects with IL-1 beta on PGE(2) seceretion. In conclusion, the study suggests that essential oil from O. gratissimum decreases gingival fibroblasts secretion of PGE(2), while essential oils from B. pilosa and C. nardus increase PGE(2) secretion. Essential oil from Z. chalybeum was the most cytotoxic, while oil from C. nardus was the least cytotoxic. Although the clinical significance of these findings remains to be determined, it may be suggested that essential oil from O. gratissimum, applied at subcytotoxicity concentrations, could reduce the participation of gingival fibroblasts in the gingival inflammation and tissue destruction associated with periodontitis.
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| 39. |
- Okhovat, Reza, 1984, et al.
(författare)
-
Dynamic equations for an isotropic spherical shell using power series method and surface differential operators
- 2015
-
Ingår i: Conference Proceedings of the Society for Experimental Mechanics Series. - Cham : Springer International Publishing. - 2191-5644 .- 2191-5652. - 9783319069883 ; 6, s. 29-36
-
Konferensbidrag (refereegranskat)abstract
- Dynamic equations for an isotropic spherical shell are derived by using a series expansion technique. The displacement field is split into a scalar (radial) part and a vector (tangential) part. Surface differential operators are introduced to decrease the length of the shell equations. The starting point is a power series expansion of the displacement components in the thickness coordinate relative to the mid-surface of the shell. By using the expansions of the displacement components, the three-dimensional elastodynamic equations yield a set of recursion relations among the expansion functions that can be used to eliminate all but the four of lowest order and to express higher order expansion functions in terms of these of lowest orders. Applying the boundary conditions on the surfaces of the spherical shell and eliminating all but the four lowest order expansion functions give the shell equations as a power series in the shell thickness. After lengthy manipulations, the final four shell equations are obtained in a more compact form which can be represented explicitly in terms of the surface differential operators. The method is believed to be asymptotically correct to any order. The eigenfrequencies are compared to exact three-dimensional theory and membrane theory.
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| 40. |
- Okhovat, Reza, 1984, et al.
(författare)
-
Dynamic equations for an isotropic spherical shell using the power series method and surface differential operators
- 2017
-
Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 393, s. 415-424
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic equations for an isotropic spherical shell are derived by using a series expansion technique. The displacement field is split into a scalar (radial) part and a vector (tangential) part. Surface differential operators are introduced to decrease the length of all equations. The starting point is a power series expansion of the displacement components in the thickness coordinate relative to the mid-surface of the shell. By using the expansions of the displacement components, the three-dimensional elastodynamic equations yield a set of recursion relations among the expansion functions that can be Used to eliminate all but the four of lowest order and to express higher order expansion functions in terms of those of lowest orders. Applying the boundary conditions on the surfaces of the spherical shell and eliminating all but the four lowest order expansion functions give the shell equations as a power series in the shell thickness. After lengthy manipulations, the final four shell equations are obtained in a relatively compact form which are given to second order in shell thickness explicitly. The eigenfrequencies are compared to exact three-dimensional theory with excellent agreement and to membrane theory.
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| 41. |
- Okhovat, Reza, 1984, et al.
(författare)
-
Dynamic equations for an orthotropic cylindrical shell
- 2018
-
Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223. ; 184, s. 1197-1203
-
Tidskriftsartikel (refereegranskat)abstract
- A hierarchy of dynamic shell equations is derived for an orthotropic cylindrical shell. The displacement components are expanded into power series in the thickness coordinate and the three-dimensional elastodynamic equations then yield a set of recursion relations among the expansion functions that can be used to eliminate all but the six lowest-order functions. Applying the boundary conditions on the surfaces of the shell and eliminating all but the six lowest-order expansion functions give the shell equations as a power series in the shell thickness. In principle, these six differential equations can be truncated to any order. Numerical examples showing eigenfrequencies for a ring and for a simply supported shell show the convergence of the method to the 3D solution, and a comparison with previous investigations is also made. Finally, the exact 3D solution is given for a simply supported transversely isotropic shell of arbitrary thickness.
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| 42. |
- Piotrowska, Patrycja, et al.
(författare)
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Waste gypsum bpard and ash related problems during combustion of biomass : Part 1 : fluidized bed
- 2015
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 29:2, s. 877-893
-
Tidskriftsartikel (refereegranskat)abstract
- This paper is the first in a series of two describing the use of waste gypsum boards as an additive during combustion of biomass. This paper is focusing on experiments performed in a bench-scale bubbling fluidized-bed reactor (5 kW). Three biomass fuels were used; i.e. wheat straw (WS), reed canary grass (RC), and spruce bark (SB), with and without addition of shredded waste gypsum board (SWGB). The objective of this work was to determine the effect of SWGB addition on biomass ash transformation reactions during fluidized bed combustion. The combustion was carried out in a bed of quartz sand at 800 °C or 700 °C for 8 hours. After the combustion stage a controlled fluidized-bed agglomeration test was carried out to determine the defluidization temperature. During combustion experiments outlet gas composition was continuously measured by means of FT-IR. At the same place in the flue gas channel particulate matter (PM) was collected with a 13-stage Dekati low-pressure impactor. Bottom and cyclone fly ash samples were collected after the combustion tests. In addition, during the combustion tests a 6-hour deposit sample was collected with an air-cooled (430 °C) probe. All ash samples were analyzed by means of scanning electron microscope combined with energy dispersive X-ray spectrometer (SEM-EDS) for elemental composition and with X-ray powder diffractometer (XRD) for the detection of crystalline phases. Decomposition of CaSO4 originating from SWGB was mainly observed during combustion of reed canary grass at 800 °C. The decomposition was observed as doubled SO2 emissions. No significant increase of SO2 during combustion of SB and WS was observed. However, the interaction of SWGB particles with WS and SB ash forming matter, mainly potassium containing compounds, led to the formation of K2Ca2(SO4)3
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| 43. |
- Rebbling, Anders, 1980-
(författare)
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Application of fuel design to mitigate ash-related problems during combustion of biomass
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The energy supply of today is, through the use of fossil energy carriers,contributing to increased net emissions of greenhouse gases. This hasseveral negative effects on our environment and our climate. In order toreduce the impact of this, and possibly to reverse some of the effects, allrenewable energy sources must be used. Biomass is the renewable energycarrier that has the greatest potential to reduce net greenhouse gasemissions, but the transition from fossil fuels to biofuels is challenging.The combustion of biomass is associated with various technical andenvironmental problems such as slagging, corrosion, and emissions ofparticles, soot, or harmful chemical compounds. Most of these problemsare linked to ash chemical reactions involving alkali metals. Therefore, toreduce the risk of operational and environmental problems, it is importantto understand and control the ash transformation reactions involvingalkali metals.The research presented in this thesis has focused on the development oftools, such as models and indices, for predicting the behaviour of variousbiofuels during combustion, and on the development of the concept of fueldesign and implementation of the same during industrial combustion ofbiomass. The development of easy-to-use tools for predicting problematicash behaviour is crucial in order to make it possible to increase the use ofbiomass as an alternative to fossil fuels. The tools presented here are basedon theoretical and empirical knowledge and can be used to predictchallenges concerning the fuel ash composition and to propose relevantfuel design measures.The purpose of fuel design, as used here, is to broaden the fuel feedstockand to increase the usability of biomass in the global energy system. Thisis achieved through measures to change the ash chemical composition inorder to enhance beneficial properties, or reduce problematic properties,via the use of additives or blending of two or more different fuels.The present thesis extends the foundation of knowledge regarding fuel ashtransformation reactions and their implications for operational problemsthrough in-depth laboratory studies and analyses. Furthermore, thefeasibility of applying this extended knowledge in the medium and largescaleindustrial combustion of biomass is demonstrated and validated. More specifically, a slagging index has been developed using the results ofseveral years of combustion experiments. Fuel designs based on the indexwas demonstrated during normal operation in local and district heatingplants. Furthermore, a model was developed for predicting slaggingproblems that take into account both the chemical composition of the fueland the burner technology.Several studies have also been performed on different fuel designs basedon the same foundation as the index and the model. Additives to supply forexample calcium and sulphur, as well as the clay kaolin, have been used toreduce both technical and environmental problems.The conclusion is that fuel design, based on ash chemistry, is a possiblepath for increased fuel flexibility and a broader feedstock for bioenergy.
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| 44. |
- Rebbling, Anders, 1980-, et al.
(författare)
-
Understanding reactivity using fuel design - phosphorus vs kaolin in combustion of stem wood
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The fate of various ash-forming elements determine how well a fuel will perform in a given thermochemical energy conversion process. In order understand ash-related process problems it is particularly important in which compounds alkali metal ions, for biomass this primarily means K+ and Na+, are bonded. Their low charge and relatively large ionic radii leads to poor bond strengths in compounds where they provide the only Lewis acid component, i.e. electron acceptor. This can be remedied by trying to bond alkali metal ions to stronger, predominantly molecular Lewis bases which is the case in for instance arkanite, K2SO4 – the targeted reaction product when (NH4)2SO4 is added in the flue gas to reduce KCl formation. Another approach is to bond alkali in bottom or bed ash, by including Lewis base forming elements such as phosphorus or the additive kaolin which is dominated by kaolinite. This route attempts to promote formation of high-temperature melting compounds with at least one alkali metal ion per phosphate or other starting molecule.While the understanding of how phosphorus reacts in combustion process is increasing it is valuable to understand how it will react in presence of other elements or molecules that play an important role for alkali capture. This will be of interest in situations where the base fuels may be combusted with addition of sulphur or kaolin, for instance. If the base fuels has a high concentration of phosphorus the amount of additive may need to be adjusted according to what phosphates will form, and if they will form even in the presence of the amending additives. Using the inherent composition of the fuel to decide suitable strategies for additive choice or possibly co-combustion is a key component of fuel design.The aim of this study is to investigate the relative Lewis base potential for capture of alkali metal ions between phosphates and kaolin. This is made by adding highly available phosphorus in the form of di-ammonium hydrogen phosphate, (NH4)2HPO4, and kaolin, a mineral where kaolinite is the main constituent for capturing alkali to the fuel blend. The fuel chosen is stem wood where the amount of Lewis acid forming elements greatly surpass that of Lewis base forming elements found in the ash forming matter.
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| 45. |
- Rebbling, Anders, et al.
(författare)
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Waste Gypsum Board and Ash-Related Problems during Combustion of Biomass : 2. Fixed Bed
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:12, s. 10705-10713
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Tidskriftsartikel (refereegranskat)abstract
- This paper is the second of two describing the use of shredded waste gypsum board (SWGB) as an additive during combustion of biomass. The focus of this paper is to determine whether SWGB can be used as a fuel additive providing CaO and SO2/SO3 for mitigation of ash-related operational problems during combustion of biomass and waste derived fuels in grate fired fixed bed applications. The former study in this series was performed in a fluidized bed and thus allow for comparison of results. Gypsum may decompose at elevated temperatures and forms solid CaO and gaseous SO2/SO3 which have been shown to reduce problems with slagging on the fixed bed and alkali chloride deposit formation. Three different biomasses, spruce bark (SB), reed canary grass (RG), and wheat straw (WS), were combusted with and without addition of SWGB in a residential pellet burner (20 kWth). Waste derived fuel with and without the addition of SWGB was combusted in a large scale grate-fired boiler (25 MWth). The amount of added SWGB varied between 1 and 4 wt %. Ash, slag, and particulate matter (PM) were sampled and subsequently analyzed with scanning electron microscopy/ energy dispersive spectroscopy and X-ray diffraction. Decomposition of CaSO4 originating from SWGB was observed as elevated SO2 emissions in both the large scale and small scale facilities and significantly higher than was observed in the fluidized bed study. Slag formation was significantly reduced due to formation of calcium-silicates in small scale application, but no conclusive observations regarding calcium reactivity could be made in the large scale application. In the small scale study the formation of K2SO4 was favored over KCl in PM, while in the large scale study K3Na(SO4)2 and K2Zn2(SO4)3 increased. It is concluded that SWGB can be used as a source of CaO and SO2/SO3 to mitigate slag formation on the grate and chloride-induced high temperature corrosion and that fixed bed applications are likely more suitable than bubbling fluidized beds when using SWGB as an additive.
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| 46. |
- Rubenson, Jacob, 1985, et al.
(författare)
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Modelling of Ultrasonic Bulk Wave Scattering by an Axial Crack in a Pipe
- 2017
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Ingår i: Journal of Nondestructive Evaluation. - : Springer Science and Business Media LLC. - 1573-4862 .- 0195-9298. ; 36:2, s. Article no 19 -
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Tidskriftsartikel (refereegranskat)abstract
- Modelling of ultrasonic bulk wave scattering by an internal, infinitely long, axial crack in a thick-walled pipe is considered. The problem is formulated as a hypersingular integral equation for the crack-opening displacement (COD), the hypersingularity arises in the Green’s tensor. The COD is expanded in Chebyshev functions which have the correct square-root singularity along the crack edges, thereby regularizing the integral equation. To discretize the integral equation it is likewise projected onto the same Chebyshev functions. A model of an ultrasonic rectangular vertically polarized shear wave contact probe is developed, and the signal response is calculated using a reciprocity argument. Some numerical examples demonstrate the possible application of the method, in particular investigating the importance of the pipe curvature.
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| 47. |
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| 48. |
- Shoja, Siavash, 1982, et al.
(författare)
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COMPUTATIONAL MODELLING OF GUIDED WAVE PROPAGATION FOR ICE DETECTION ON COMPOSITE MATERIALS
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Guided waves are an efficient non-destructive tool in inspection and fault detection of elongated structures. Due to the special characteristics of composite materials, study of guided wave propagation in them has been an interest. Icing condition is a well-known problem in wind turbine industry and in this work application of guided wave propagation for ice detection on composite materials is studied.A 3D shell model is developed in which ice is placed on the plate by changing the properties of specific elements in the icing region. The excitation is applied to the middle of one side of the plate with a low angle of inclination and the centre frequencies varying from 3 kHz to 7 kHz. The signal is received in 24 nodes equally distributed on the plate known as the measurement nodes. The model with a patch of ice is validated using a 3D solid model in which ice is placed as a second solid layer. Comparison shows the model can be simplified using this method without significant change in the results.The Baseline Signal Stretch with the mode decomposition method is applied to the model for temperature variations. Effects of ice accretion on a composite plate is studied in time, frequency and wavenumber domains. In each case post-processing approaches are introduced for this specific application. Moreover, icing index is introduced which is sensitive to accumulated ice on the plate.The model is calibrated and final results are validated using an experimental work which is performed in a cold climate lab.Using the model and introduced criteria both thickness and location of ice on the plate are identified. All the results show that application of guided waves is a promising and accurate tool in ice detection on composite plates.
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| 49. |
- Shoja, Siavash, 1982, et al.
(författare)
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Delamination detection in composite laminates using low frequency guided waves: Numerical simulations
- 2018
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Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223. ; 203, s. 826-834
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to find an efficient way of finite element modelling of guided wave propagation in composite laminates to detect delaminations. A novel approach is proposed to model delaminations by locally reducing the stiffness and it is implemented in a finite element shell model. The approach is verified by comparing the results with the results of two existing approaches. Results show that the stiffness reduction approach gives reasonable accuracy for the primary wave modes and improvement in simulation time. Moreover, it is shown that new convergence criteria should be considered to simulate the guided wave propagation. Additionally, the Pearson correlation coefficient is introduced as a good criterion for delamination detection in such problems. All the conclusions are made when simulations are performed in the low frequency range and can be used to study guided wave propagation in large composite structures such as wind turbine blades.
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| 50. |
- Shoja, Siavash, 1982, et al.
(författare)
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Effects of Delamination on Guided Wave Propagation in Laminated Composite Beams - Numerical Simulation
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this study, three methods are used to model guided wave propagation in composite laminate including delamination. First, the model is created using 3D solid elements and delamination is applied between the plies. Next, composite laminate is modelled by homogenizing the material properties into a single layer with 3D shell elements. Delamination is applied using duplicate node method (DNM) and stiffness reduction method (SRM). The three models are compared by comparing the wave pattern, time signal and wave velocity. Results show SRM can be used as the most efficient method with reasonable accuracy to model wave propagation in large and complicated structures.
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