| 1. |
- Ravinet, Mark, 1986, et al.
(author)
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Unique mitochondrial DNA lineages in Irish stickleback populations: cryptic refugium or rapid recolonization?
- 2014
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:12, s. 2488-2504
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Journal article (peer-reviewed)abstract
- Repeated recolonization of freshwater environments following Pleistocene glaciations has played a major role in the evolution and adaptation of anadromous taxa. Located at the western fringe of Europe, Ireland and Britain were likely recolonized rapidly by anadromous fishes from the North Atlantic following the last glacial maximum (LGM). While the presence of unique mitochondrial haplotypes in Ireland suggests that a cryptic northern refugium may have played a role in recolonization, no explicit test of this hypothesis has been conducted. The three-spined stickleback is native and ubiquitous to aquatic ecosystems throughout Ireland, making it an excellent model species with which to examine the biogeographical history of anadromous fishes in the region. We used mitochondrial and microsatellite markers to examine the presence of divergent evolutionary lineages and to assess broad-scale patterns of geographical clustering among postglacially isolated populations. Our results confirm that Ireland is a region of secondary contact for divergent mitochondrial lineages and that endemic haplotypes occur in populations in Central and Southern Ireland. To test whether a putative Irish lineage arose from a cryptic Irish refugium, we used approximate Bayesian computation (ABC). However, we found no support for this hypothesis. Instead, the Irish lineage likely diverged from the European lineage as a result of postglacial isolation of freshwater populations by rising sea levels. These findings emphasize the need to rigorously test biogeographical hypothesis and contribute further evidence that postglacial processes may have shaped genetic diversity in temperate fauna.
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| 2. |
- Good, Lars, 1953-
(author)
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Anterior cruciate ligament reconstruction : Anatomic and biomechanical considerations of graft placement and fixation
- 1993
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Doctoral thesis (other academic/artistic)abstract
- This study, comprising 7 separate papers, is concerned with the mechanical causes of graft failure after intraarticular reconstruction of the anterior cruciate ligament (ACL). The study is predominantly experimental in design, but a clinical follow-up is also included to test a causal hypothesis of secondary graft elongation.Fixations of synthetic ACL substitutes with ligament staples had low security and the maximum tolerance loads were in parity with forces generated during daily activities, while screw fixations of looped ligaments had higher load to failure than a normal ACL.A stenosis, caused by osteophyte formation, was found at the intercondylar notch less than 2 years after an ACL tear, strongly suggesting impingement and wear as a possible mechanism of ACL substitute failure. The intercondylar notch was also found to be narrowed in patients with an acute tear of the ACL compared to a normal control group, thus implying causality.A standardized technique of graft placement, using a guide to aid bone drilling, was found more accurate and reproducible in achieving desired graft insertions compared to freehand drilling. This was evaluated by a new method for detennining the graft insertion locations on the femur and tibia, using a ratio related to the sagittal depth of the condyles.The ability to restore knee kinematics from an ACL deficient state, was evaluated for a drill guided graft route and an over-the-top route. The only effect of both methods, using a dacron graft tensioned in full extension, was restoring or partially restoring the increased anterior -posterior translation.A good in vitro and in vivo correlation was found between the patterns of change in dynamic fixation distance, as measured intraoperatively with an isometer, and tension in the fixed ACL substitute. The isometry measurement could not predict the magnitude of the frnal tension due to the biological variability in soft tissue compliance.Sagittal knee stability was measured at regular intervals for 2 years on patients who had an intraarticular ACL reconstruction with a patellar tendon substitute. Increasing anterior-posterior displacement was found for all patients as a group, and more for patients with an anterior femoralligament insertion location.A standardized treatment including aided bone drilling, notch plasty, isometry measurement, and restricted postoperative rehabilitation is recommended.
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| 3. |
- Juhlin, Greger
(author)
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Development and Application of Laser Diagnostics for Studies of Phenomena Related to IC Engine Combustion
- 2003
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Doctoral thesis (other academic/artistic)abstract
- Various laser diagnostic techniques have been developed and demonstrated for engine, or engine-related measurements. The experimental work is presented in Chapter 3 and in Papers I-VII. In Chapter 3, imaging of soot in a running compression-ignition (CI) is described. Four different approaches were applied with the aim of investigating the applicability of these approaches in a running engine. In Paper I, Planar Laser-Induced Fluorescence (PLIF) was applied in a running spark ignition (SI) engine for measurements of the fuel concentration and homogeneity in the vicinity of the spark gap prior to ignition. The aim was to find out how the fuel distribution influences the cycle-to-cycle variations of the engine. In Paper II, PLIF of water was applied in a running engine to investigate the influence of residual gases in the vicinity of the spark gap prior to ignition. In Paper III is reported a basic investigation of the potential of PLIF for the study of water as a marker for residual gas in engines. Special care was taken in studying the effects of a focused laser beam in combination with a two-photon transition which arises in the excitation of water at 248 nm. In Paper IV is described how a combination of PLIF and spontaneous Raman scattering can be used for simultaneous imaging of vapour and liquid phase water. In Paper V, the application of PLIF to investigate the emissions of hydrocarbons in the exhaust of small two-stroke engines is described. Cycle-resolved, 2D measurements were conducted in order to find out when, during the stroke, the hydrocarbons are emitted. Cycle-resolved spectral measurements gave information on the species emitted at different crank angle positions. In Paper VI is demonstrated how phosphor thermometry can be applied to measure the temperature of a falling water droplet. Finally, in Paper VII, phosphor thermometry was applied to perform two-dimensional surface temperature measurements in a running optically accessible engine.
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| 4. |
- Rodriguez-Rojas, F., et al.
(author)
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Oxidation behaviour of pressureless liquid-phase-sintered α-SiC with additions of 5Al2O3 + 3RE2O3 (RE = La, Nd, Y, Er, Tm, or Yb)
- 2010
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In: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 30:15, s. 3209-3217
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Journal article (peer-reviewed)abstract
- The oxidation behaviour of pressureless liquid-phase-sintered (PLPS) α-SiC was investigated as a function of the sintering additives of 5Al2O3 + 3RE2O3 (RE = La, Nd, Y, Er, Tm, or Yb) by thermogravimetry experiments in oxygen at 1075–1400 °C for up to 22 h. It was found that the oxidation is in all cases passive and protective, with kinetics governed by the arctan-rate law. This is because the PLPS SiC ceramics develop oxide scales having no cracks or open porosity and accordingly prevent the parent material from direct contact with oxygen. In addition, these oxide scales crystallize gradually during the exposure to the oxidizing atmosphere with the attendant reduction in the amorphous cross-section available for oxygen diffusion. It was also found that the rate-limiting mechanism of the oxidation is outward diffusion of RE3+ cations from the intergranular phase into the oxide scale, and that the activation energy of the oxidation increases with increasing size of the RE3+ cation. It was also observed that the oxidation of PLPS SiC increases with increasing size of the RE3+ cation, an effect that is especially marked for cation sizes above 0.9 Å because the oxidation rate becomes several orders of magnitude faster. This trend is attributable to the oxide scales being more crystalline, and containing crystals that are more refractory and amorphous residual phases that are more viscous as the size of the RE3+ cation decreases. Finally, implications for the design of PLPS SiC ceramics with superior oxidation resistance are discussed.
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| 5. |
- Szabo, Attila
(author)
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Matematikundervisning för begåvade elever – en forskningsöversikt
- 2017
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In: Nordisk matematikkdidaktikk, NOMAD. - 1104-2176. ; 22:1, s. 21-44
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Research review (other academic/artistic)abstract
- Artikeln redovisar de huvudsakliga pedagogiska och organisatoriska metoder relaterade till begåvade elevers matematikundervisning som fokuseras i forskningslitteraturen – även könsskillnader, motivation och matematiskt begåvade elevers sociala situation i klassrummet diskuteras. Översikten visar att det finns åtgärder – t.ex. frivillig acceleration i ämnet där undervisningen är anpassad till elevens förkunskaper och kapacitet eller arbete med utmanande uppgifter i prestationshomogena grupper – som antas ha goda effekter på begåvade elevers kunskapsutveckling i matematik. Analysen visar också att det kan uppfattas som problematiskt att vara begåvad i matematik samt att begåvade flickor upplever vissa aspekter av matematikundervisningen annorlunda jämfört med motsvarande grupp pojkar.
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| 6. |
- Szabo, Attila, 1965-
(author)
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Matematiska förmågors interaktion och det matematiska minnets roll vid lösning av matematiska problem
- 2013
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Licentiate thesis (other academic/artistic)abstract
- The thesis deals with the interaction of mathematical abilities and the mathematical memory's role in problem-solving. To examine those phenomena, I analyzed the expression of mathematical abilities for high achieving students from upper secondary school. The study shows that the mathematical memory accounts for a relatively small proportion of time of the problem-solving process and that the mathematical memory emerges mainly during the initial phase of the process. Although the mathematical memory accounts for a small percentage of the time of the problem-solving process, the mathematical memory has a decisive role for the choice of problem-solving methods, because the students choose their solution methods in the initial phase of their problem-solving activity. The study shows that the choice of problem-solving method has significant consequences for the students' problem-solving activity; if the chosen methods did not lead to the desired outcome, so the students found it very difficult to change their initially chosen problem-solving methods. The study also shows that students who use general problem-solving methods perform better than students who use numerical methods.
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| 7. |
- Staffas, Louise, et al.
(author)
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Alternative sources for products competing with forest based biofuel, a pre-study
- 2013
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Reports (other academic/artistic)abstract
- Skogsråvara används idag till olika ändamål, som till exempel pappersprodukter av olika slag, sågade trävaror och energi – huvudsakligen i form av fasta bränslen. Det finns även en viss produktion av drivmedel, men inte i så stor skala som förväntas i framtiden. Utvecklingen av sådan tillverkning är intensiv och biobaserade drivmedel eftersträvas och premieras med bland annat styrmedel och politiska mål. Biomassa är en förnyelsebar resurs och som sådan mycket intressant för många användningsområden, som till exempel nya material och flytande och gasformiga bränslen och drivmedel. Framställningen av biodrivmedel kommer med all sannolikhet att öka under de kommande åren – i synnerhet som Sverige har ett mål om en fossiloberoende fordonsflotta till år 2030. Skogen ska, förutom att vara råvara till ovanstående typer av produkter, också tillgodose behoven av de så kallade ekosystemtjänsterna, som till exempel biodiversitet, fiske, jakt, rekreation och bärplockning som därmed också konkurrerar om denna råvara. Idag har Sverige en netto-tillväxt av skog, vilket, åtminstone teoretiskt, ger utrymme för ökat uttag av skogsbiomassa i Sverige och därmed en ökad tillverkning av produkter därav. Tillgången på skogsbiomassa är dock inte obegränsad eftersom tillväxten måste vara lika med, eller större, än uttaget. Därför måste skogsbiomassa betraktas som en begränsad resurs och dess användning bör vara sådan att den ger maximal fördel jämfört med användning av fossila resurser. Det medför att LCA och andra utvärderingar av miljömässiga konsekvenser av en produkt från skogsbiomassa bör inkludera alternativa råvaror för produkter som konkurrerar om samma råvara. Denna förstudie omfattar en beskrivning av svenskt skogsbruk och sambandet mellan olika kvaliteter av skogsbiomassa, en workshop (vid vilken konkurrensen om skogsbiomassa diskuterades med experter i ämnet), en teoretisk diskussion om indirekta effekter och biomasse-potentialer, samt två fallstudier i vilka de teroetiska resonemangen appliceras. Traditionella utvärderingar av produkters miljöbelastning inkluderar inte begränsning av tillgång på råvara eller konkurrens om densamma, vilket, bland annat för produktionen av bioetanol har befunnits ha stor betydelse. Samma sak gäller även för andra produkter från skogsbiomassa. Den huvudsakliga slutsatsen av studien är att alternativa råvaror för produkter som konkurrerar om skogsråvaran måste inkluderas när miljöbelastningen av en skogsråvarubaserad produkt analyseras. Detta är mycket komplext eftersom indirekta effekter är svåra att förutse och beror på många faktorer, som exempelvis marknadslägen, styrmedel och politiska mål. Icke desto mindre är frågan viktig för att utvecklingen av biobaserade råvaror ska bidra till en så minskad miljöbelastning som möjligt jämfört med de fossilbaserade motsvarigheterna.
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| 8. |
- Lee, Ki-ahm, et al.
(author)
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Highly oscillating thin obstacles
- 2013
-
In: Advances in Mathematics. - : Elsevier BV. - 0001-8708 .- 1090-2082. ; 237, s. 286-315
-
Journal article (peer-reviewed)abstract
- The focus of this paper is on a thin obstacle problem where the obstacle is defined on the intersection between a hyper-plane Gamma in R-n and a periodic perforation T-epsilon of R-n, depending on a small parameters epsilon > 0. As epsilon -> 0, it is crucial to estimate the frequency of intersections and to determine this number locally. This is done using strong tools from uniform distribution. By employing classical estimates for the discrepancy of sequences of type {k alpha}(k=1)(infinity), alpha is an element of R, we are able to extract rather precise information about the set Gamma boolean AND T-epsilon. As epsilon -> 0, we determine the limit u of the solution u(epsilon) to the obstacle problem in the perforated domain, in terms of a limit equation it solves. We obtain the typical "strange term" behavior for the limit problem, but with a different constant taking into account the contribution of all different intersections, that we call the averaged capacity. Our result depends on the normal direction of the plane, but holds for a.e. normal on the unit sphere in R-n.
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| 9. |
- Mushtaq, Naveed, et al.
(author)
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Tuning the Energy Band Structure at Interfaces of the SrFe0.75Ti0.25O3-delta-Sm0.25Ce0.75O2-delta Heterostructure for Fast Ionic Transport
- 2019
-
In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 11:42, s. 38737-38745
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Journal article (peer-reviewed)abstract
- Interface engineering holds huge potential for enabling exceptional physical properties in heterostructure materials via tuning properties at the atomic level. In this study, a heterostructure built by a new redox stable semiconductor SrFe0.75Ti0.25O3-delta (SFT) and an ionic conductor Sm0.25Ce0.75O2 (SDC) is reported. The SFT-SDC heterostructure exhibits a high ionic conductivity >0.1 S/cm at 520 degrees C, which is 1 order of magnitude higher than that of bulk SDC. When it was applied into the fuel cell, the SFT-SDC can realize favorable electrolyte functionality and result in an excellent power density of 920 mW cm(-2) at 520 degrees C. The prepared SFT-SDC heterostructure materials possess both electronic and ionic conduction, where electron states modulate local electrical field to facilitate ion transport. Further investigations to calculate the structure and electronic structure/state of SFT and SDC are done using density functional theory (DFT). It is found that the reconstruction of the energy band at interfaces is responsible for such enhanced ionic conductivity and cell power output. The current study about the perovskite-based heterostructure presents a novel strategy for developing advanced ceramic fuel cells.
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