| 1. |
- Drews, Anna, et al.
(författare)
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Expression and phylogenetic analyses reveal paralogous lineages of putatively classical and non-classical MHC-I genes in three sparrow species (Passer)
- 2017
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 17:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The Major Histocompatibility Complex (MHC) plays a central role in immunity and has been given considerable attention by evolutionary ecologists due to its associations with fitness-related traits. Songbirds have unusually high numbers of MHC class I (MHC-I) genes, but it is not known whether all are expressed and equally important for immune function. Classical MHC-I genes are highly expressed, polymorphic and present peptides to T-cells whereas non-classical MHC-I genes have lower expression, are more monomorphic and do not present peptides to T-cells. To get a better understanding of the highly duplicated MHC genes in songbirds, we studied gene expression in a phylogenetic framework in three species of sparrows (house sparrow, tree sparrow and Spanish sparrow), using high-throughput sequencing. We hypothesize that sparrows could have classical and non-classical genes, as previously indicated though never tested using gene expression. Results: The phylogenetic analyses reveal two distinct types of MHC-I alleles among the three sparrow species, one with high and one with low level of polymorphism, thus resembling classical and non-classical genes, respectively. All individuals had both types of alleles, but there was copy number variation both within and among the sparrow species. However, the number of highly polymorphic alleles that were expressed did not vary between species, suggesting that the structural genomic variation is counterbalanced by conserved gene expression. Overall, 50% of the MHC-I alleles were expressed in sparrows. Expression of the highly polymorphic alleles was very variable, whereas the alleles with low polymorphism had uniformly low expression. Interestingly, within an individual only one or two alleles from the polymorphic genes were highly expressed, indicating that only a single copy of these is highly expressed. Conclusions: Taken together, the phylogenetic reconstruction and the analyses of expression suggest that sparrows have both classical and non-classical MHC-I genes, and that the evolutionary origin of these genes predate the split of the three investigated sparrow species 7 million years ago. Because only the classical MHC-I genes are involved in antigen presentation, the function of different MHC-I genes should be considered in future ecological and evolutionary studies of MHC-I in sparrows and other songbirds.
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| 2. |
- Ekholm, Kent, et al.
(författare)
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Ethanol-Diesel Fumigation in a Multi-Cylinder Engine
- 2008
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Ingår i: SAE technical paper 2008-01-0033.
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Konferensbidrag (refereegranskat)abstract
- Fumigation was studied in a 12 L six-cylinder heavy-duty engine. Port-injected ethanol was ignited with a small amount of diesel injected into the cylinder. The setup left much freedom for influencing the combustion process, and the aim of this study was to find operation modes that result in a combustion resembling that of a homogeneous charge compression ignition (HCCI) engine with high efficiency and low NOx emissions. Igniting the ethanol-air mixture using direct-injected diesel has attractive properties compared to traditional HCCI operation where the ethanol is ignited by pressure alone. No preheating of the mixture is required, and the amount of diesel injected can be used to control the heat release rate. The two fuel injection systems provide a larger flexibility in extending the HCCI operating range to low and high loads. It was shown that cylinder-to-cylinder variations present a considerable challenge for this type of combustion. By using closed-loop cylinder-individual control based on incylinder pressure sensors, combustion was successfully harmonized between the cylinders. Successful fumigation operation was verified up to 18.4 bar BMEP at a fixed engine speed of 1450 rpm. Two load points (4.6 bar BMEP and 9.2 bar BMEP) were studied in detail. Different diesel injection timings, diesel ratios, and EGR rates were investigated, and comparisons were drawn to pure diesel operation of the same engine. At medium load (9.2 bar BMEP), it was possible to obtain a stable HCCI-like combustion with low NOx emissions (0.1 g/kWh), reasonably high brake efficiency (37 %), and low pressure derivatives (5 bar/CAD). High load operation (18.4 bar BMEP) resulted in low pressure derivatives (5.5 bar/CAD), acceptable brake efficency (36 %), and relatively low NOx emissions (0.34 g/kWh).
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| 3. |
- Ekholm, Kent, et al.
(författare)
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Ethanol-Diesel Fumigation in a Multi-Cylinder Engine
- 2009
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Ingår i: SAE International Journal of Fuels and Lubricants. - 1946-3952. ; 1:1, s. 26-36
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Tidskriftsartikel (refereegranskat)abstract
- Fumigation was studied in a 12 L six-cylinder heavy-duty engine. Port-injected ethanol was ignited with a small amount of diesel injected into the cylinder. The setup left much freedom for influencing the combustion process, and the aim of this study was to find operation modes that result in a combustion resembling that of a homogeneous charge compression ignition (HCCI) engine with high efficiency and low NOx emissions. Igniting the ethanol-air mixture using direct-injected diesel has attractive properties compared to traditional HCCI operation where the ethanol is ignited by pressure alone. No preheating of the mixture is required, and the amount of diesel injected can be used to control the heat release rate. The two fuel injection systems provide a larger flexibility in extending the HCCI operating range to low and high loads. It was shown that cylinder-to-cylinder variations present a challenge for this type of combustion. By using closed-loop cylinder-individual control of pressure derivatives and IMEP with the amounts of fuels injected, combustion was successfully harmonized between the cylinders. Successful fumigation operation was verified up to 18.4 bar BMEP at a fixed engine speed of 1450 rpm. Two load points (4.6 bar BMEP and 9.2 bar BMEP) were studied in detail. Different diesel injection timings, diesel ratios, and EGR rates were investigated, and comparisons were drawn to pure diesel operation of the same engine. At medium load (9.2 bar BMEP), it was possible to obtain a stable HCCI-like combustion with low NOx emissions (0.1 g/kWh), reasonably high brake efficiency (38 %), and low pressure derivatives (5 bar/CAD). High load operation (18.4 bar BMEP) resulted in low pressure derivatives (5.5 bar/CAD), acceptable brake efficency (38 %), and relatively low NOx emissions (0.34 g/kWh).
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| 4. |
- Gonzalez, Francisco, et al.
(författare)
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Odorant receptor phylogeny confirms conserved channels for sex pheromone and host plant signals in tortricid moths
- 2020
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 10:14, s. 7334-7348
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Tidskriftsartikel (refereegranskat)abstract
- The search for mates and food is mediated by volatile chemicals. Insects sense food odorants and sex pheromones through odorant receptors (ORs) and pheromone receptors (PRs), which are expressed in olfactory sensory neurons. Molecular phylogenetics of ORs, informed by behavioral and functional data, generates sound hypotheses for the identification of semiochemicals driving olfactory behavior. Studying orthologous receptors and their ligands across taxa affords insights into the role of chemical communication in reproductive isolation and phylogenetic divergence. The female sex pheromone of green budworm mothHedya nubiferana(Lepidoptera, Totricidae) is a blend of two unsaturated acetates, only a blend of both elicits male attraction. Females produce in addition codlemone, which is the sex pheromone of another tortricid, codling mothCydia pomonella. Codlemone also attracts green budworm moth males. Concomitantly, green budworm and codling moth males are attracted to the host plant volatile pear ester. A congruent behavioral response to the same pheromone and plant volatile in two tortricid species suggests co-occurrence of dedicated olfactory channels. In codling moth, one PR is tuned to both compounds, the sex pheromone codlemone and the plant volatile pear ester. Our phylogenetic analysis finds that green budworm moth expresses an orthologous PR gene. Shared ancestry, and high levels of amino acid identity and sequence similarity, in codling and green budworm moth PRs offer an explanation for parallel attraction of both species to the same compounds. A conserved olfactory channel for a sex pheromone and a host plant volatile substantiates the alliance of social and habitat signals in insect chemical communication. Field attraction assays confirm that in silico investigations of ORs afford powerful predictions for an efficient identification of behavior-modifying semiochemicals, for an improved understanding of the mechanisms of host plant attraction in insect herbivores and for the further development of sustainable insect control.
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| 5. |
- Hansson, Bengt, et al.
(författare)
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Contrasting results from GWAS and QTL mapping on wing length in great reed warblers
- 2018
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Ingår i: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 18:4, s. 867-876
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Tidskriftsartikel (refereegranskat)abstract
- A major goal in evolutionary biology is to understand the genetic basis of adaptive traits. In migratory birds, wing morphology is such a trait. Our previous work on the great reed warbler (Acrocephalus arundinaceus) shows that wing length is highly heritable and under sexually antagonistic selection. Moreover, a quantitative trait locus (QTL) mapping analysis detected a pronounced QTL for wing length on chromosome 2, suggesting that wing morphology is partly controlled by genes with large effects. Here, we re-evaluate the genetic basis of wing length in great reed warblers using a genomewide association study (GWAS) approach based on restriction site-associated DNA sequencing (RADseq) data. We use GWAS models that account for relatedness between individuals and include covariates (sex, age and tarsus length). The resulting association landscape was flat with no peaks on chromosome 2 or elsewhere, which is in line with expectations for polygenic traits. Analysis of the distribution of p-values did not reveal biases, and the inflation factor was low. Effect sizes were however not uniformly distributed on some chromosomes, and the Z chromosome had weaker associations than autosomes. The level of linkage disequilibrium (LD) in the population decayed to background levels within c. 1 kbp. There could be several reasons to why our QTL study and GWAS gave contrasting results including differences in how associations are modelled (cosegregation in pedigree vs. LD associations), how covariates are accounted for in the models, type of marker used (multi- vs. biallelic), difference in power or a combination of these. Our study highlights that the genetic architecture even of highly heritable traits is difficult to characterize in wild populations.
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| 6. |
- Henningsson, Maria, et al.
(författare)
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Closed-Loop Control of Combustion Phasing in an HCCI Engine Using VVA and Variable EGR
- 2007. - 10
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Ingår i: 5th IFAC Symposium on Advances in Automotive Control. ; 40, s. 501-506
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Konferensbidrag (refereegranskat)abstract
- A homogeneous charge compression ignition (HCCI) engine requires closed-loop control of combustion phasing for reliable operation. Variable valve actuation (VVA) has previously been shown to enable cycle-to-cycle, cylinder-individual control with high precision, but suffers from a narrow operating range. Adding variable exhaust gas recirculation (EGR) to the closed-loop control structure can extend the operating range. A mid-ranging control structure is presented here for combined VVA and EGR actuations in a multi-cylinder engine. The control structure is simple to implement and preserves the fast, cylinder-individual, and precise actuation of the VVA system while extending the operating range. Experimental results verify the performance of the control structure.
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| 7. |
- Henningsson, Maria, et al.
(författare)
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Dynamic Mapping of Diesel Engine through System identification
- 2012
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Ingår i: Identification for Automotive Systems. - London : Springer London. - 0170-8643. ; LNCIS 418, s. 223-239
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Konferensbidrag (refereegranskat)abstract
- From a control design point of view, modern diesel engines are dynamic, nonlinear, MIMO systems. This paper presents a method to find low-complexity black-box dynamic models suitable for model predictive control (MPC) of NOx and soot emissions based on on-line emissions measurements. A four-input-five-output representation of the engine is considered, with fuel injection timing, fuel injection duration, exhaust gas recirculation (EGR) and variable geometry turbo (VGT) valve positions as inputs, and indicated mean effective pressure, combustion phasing, peak pressure derivative, NOx emissions, and soot emissions as outputs. Experimental data were collected on a six-cylinder heavy-duty engine at 30 operating points. The identification procedure starts by identifying local linear models at each operating point. To reduce the number of dynamic models necessary to describe the engine dynamics, Wiener models are introduced and a clustering algorithm is proposed. A resulting set of two to five dynamic models is shown to be able to predict all outputs at all operating points with good accuracy.
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| 8. |
- Henningsson, Maria, et al.
(författare)
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Dynamic Mapping of Diesel Engine through System Identification
- 2010
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Ingår i: Proceedings of the 2010 American Control Conference. - 2378-5861 .- 0743-1619. - 9781424474264 - 9781424474271 ; , s. 3015-3020
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Konferensbidrag (refereegranskat)abstract
- From a control design point of view, modern diesel engines are dynamic, nonlinear, MIMO systems. This paper presents a method to find low-complexity black-box dynamic models suitable for model predictive control (MPC) of NOx and soot emissions based on on-line emissions measurements. A four-input-five-output representation of the engine is considered, with fuel injection timing, fuel injection duration, exhaust gas recirculation (EGR) and variable geometry turbo (VGT) valve positions as inputs, and indicated mean effective pressure, combustion phasing, peak pressure derivative, NOx emissions, and soot emissions as outputs. Experimental data were collected on a six-cylinder heavy-duty engine at 30 operating points. The identification procedure starts by identifying local linear models at each operating point. To reduce the number of dynamic models necessary to describe the engine dynamics, Wiener models are introduced and a clustering algorithm is proposed. A resulting set of two to five dynamic models is shown to be able to predict all outputs at all operating points with good accuracy.
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| 9. |
- Henningsson, Maria, et al.
(författare)
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LQG Control for Minimization of Emissions in a Diesel Engine
- 2008
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Ingår i: 2008 IEEE International Conference on Control Applications, Vol1 and 2. - 1085-1992. - 9781424422227 ; , s. 303-308
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Konferensbidrag (refereegranskat)abstract
- The problem of minimizing emissions of NO. and soot in a diesel engine using fuel injection timings and exhaust gas recirculation (EGR) valve position in a low-pressure EGR system as control variables is addressed. Two feedback variables are computed from in-cylinder pressure sensor data, the crank angle degree of 50 % fuel burnt, and the ignition delay. Empirical maps of NO, and soot according to the feedback variables form the basis of a quadratic cost function in the feedback variables which is minimized by LQG control. For a multi-cylinder engine, the number of control variables will be less than the number of output variables to be controlled, and the consequences of this setup for the LQG controller is addressed. Experimental results verify the performance of the controller at a fixed operating point of a six-cylinder heavy-duty engine.
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| 10. |
- Henningsson, Maria, et al.
(författare)
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Multiple-Input Multiple-Output Model Predictive Control of a Diesel Engine
- 2010
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. ; 43:7, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- Traditionally, diesel engine control has had to rely on indirect feedback variables and empirical open-loop maps because direct measurements of the variables representing high-level objectives, such as emissions, have not been available in production engines. With new sensors being developed, the opportunity opens to design the controller directly based on high-level objectives. In this paper, we propose to use model predictive control as a systematic way to go directly from high-level specifications to a control algorithm. The controller uses four actuator variables and five measured variables and is based on a model obtained through system identification. Experimental results on a six-cylinder heavy-duty engine around a fixed operating point demonstrate the potential of the control scheme.
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