| 1. |
- Elleby, Björn, et al.
(författare)
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Enhancement of catalytic efficiency by the combination of site-specific mutations in a carbonic anhydrase-related protein
- 2000
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Ingår i: The FEBS Journal, European Journal of Biochemistry. - : Wiley. ; 267:19, s. 5908-15
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Tidskriftsartikel (refereegranskat)abstract
- A single mutation, involving the replacement of an arginine residue with histidine to reconstruct a zinc-binding site, suffices to change a catalytically inactive murine carbonic anhydrase-related protein (CARP) to an active carbonic anhydrase with a CO2-hydration turnover number of 1.2 × 104 s−1. Further mutations, leading to a more ‘carbonic anhydrase-like’ active-site cavity, results in increased activity. A quintuple mutant having His94, Gln92, Val121, Val143, and Thr200 (human carbonic anhydrase I numbering system) shows kcat = 4 × 104 s−1 and kcat/Km = 2 × 107 m−1·s−1, greatly exceeding the corresponding values for carbonic anhydrase isozyme III and approaching those characterizing carbonic anhydrase I. In addition, a buffer change from 50 mm Taps/NaOH to 50 mm 1,2-dimethylimidazole/H2SO4 at pH 9 results in a 14-fold increase in kcat for this quintuple mutant. The CO2-hydrating activity of a double mutant with His94 and Gln92 shows complex pH-dependence, but the other mutants investigated behave as if the activity (kcat/Km) is controlled by the basic form of a single group with pKa near 7.7. In a similar way to human carbonic anhydrase II, the buffer behaves formally as a second substrate in a ping-pong pattern, suggesting that proton transfer between a zinc-bound water molecule and buffer limits the maximal rate of catalysis in both systems at low buffer concentrations. However, the results of isotope-exchange kinetic studies suggest that proton shuttling via His64 is insignificant in the CARP mutant in contrast with carbonic anhydrase II. The replacement of Ile residues with Val in positions 121 or 143 results in measurable 4-nitrophenyl acetate hydrolase activity. The pH–rate profile for this activity has a similar shape to those of carbonic anhydrase I and II. CD spectra of the double mutant with His94 and Gln92 are variable, indicating an equilibrium between a compact form of the protein and a ‘molten globule’-like form. The introduction of Thr200 seems to stabilize the protein.
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| 2. |
- Lundberg, Björn, 1982, et al.
(författare)
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DOC modeling combining kinetics and mass transfer using inert washcoat layers
- 2016
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 191, s. 116-129
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to develop a kinetic and transport model for diesel oxidation catalysts (DOC) with a satisfactory compromise between accuracy and computational demands for robust simulation of transient full-scale operation. Specifically the model accounts for surface concentrations of key species needed to capture transient features for typical lean exhaust conditions. In addition, the model accounts for transport limitations and distinguish them from reaction kinetics as well as apparent NO oxidation inhibition effects due to reactions. To achieve this, lab scale experiments were performed with DOCs with different platinum loadings and three different washcoat configurations of which two had an inert top layer. Both kinetic parameters for a detailed kinetic model and effective diffusivities were optimized for the experimental data using a single channel catalyst model. The experiments showed a clear effect of increased transport resistance for propene and CO and also that NO2 plays an important role as an oxidizing agent for preferentially CO at low temperature (
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| 3. |
- Lundberg, Björn, 1982, et al.
(författare)
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Model-based experimental screening for DOC parameter estimation
- 2015
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Ingår i: Computers and Chemical Engineering. - : Elsevier BV. - 0098-1354. ; 74, s. 144-157
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Tidskriftsartikel (refereegranskat)abstract
- In the current study a parameter estimation method based on data screening by sensitivity analysis is presented. The method applied Multivariate Data Analysis (MVDA) on a large transient data set to select different subsets on which parameters estimation was performed. The subset was continuously updated as the parameter values developed using Principal Component Analysis (PCA) and D-optimal onion design. The measurement data was taken from a Diesel Oxidation Catalyst (DOC) connected to a full scale engine rig and both kinetic and mass transport parameters were estimated. The methodology was compared to a conventional parameter estimation method and it was concluded that the proposed method achieved a 32% lower residual sum of squares but also that it displayed less tendencies to converge to a local minima. The computational time was however significantly longer for the evaluated method.
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| 4. |
- Lundberg, Björn, 1982, et al.
(författare)
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New Methodology for Transient Engine Rig Experiments for Efficient Parameter Estimation
- 2013
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 6:4, s. 1995-2003
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Tidskriftsartikel (refereegranskat)abstract
- Introduction The diesel oxidation catalyst (DOC) is a well established technology to reduce CO and hydrocarbon (HC) emissions from diesel engines. Strengthened emission standards have made the importance of the DOC even greater in recent years since it plays an indispensible role in enhancing the performance of diesel particulate filters (DPF) and selective catalytic reduction (SCR) by utilization of NO oxidation to NO2. Therefore correct prediction of the DOC performance is very important for simulations of the entire aftertreatment system. When performing kinetic parameter estimation, laboratory scale experimental data is generally used. In laboratory scale it is possible to use essentially any combination of exhaust gas composition and temperature which makes it possible to estimate parameters over a wide range of conditions. However the applicability of these parameters in full scale models is often limited. Parameter estimation on full scale engine rig experiments on the other hand is limited by the exhaust compositions that are possible for the engine to produce. As a result, the fraction of CO is closely linked to the fraction of hydrocarbons and the fraction of NO is closely linked to the fraction of NO2. When switching between two engine operation points it generally takes several minutes before the properties of the emissions have stabilized. This does not only make the experiments time consuming, but it also complicates the transient modeling of the DOC since the changes in inlet properties are far from ideal step functions. In this study an experimental set-up is presented that makes it possible to change the inlet properties of the DOC without changing engine load point which results in much faster transients. The method also makes it possible to change the fraction of NO2 independently of the NO fraction. Method To achieve more controlled and faster changes in the inlet to the catalyst an extra DOC (DOC1) with the possibility for bypass flow and an SCR with urea injection are mounted before the catalyst. The fraction of exhaust gas flow through DOC1 allows variation in the conversion of HC and CO to CO2 and the conversion of NO to NO2. By injecting different amounts of urea the conversion of NO2 and NO to N2 is controlled. The SCR also makes it possible to obtain an inlet composition to the DOC that contains NO2 but is free of NO. Fast changes in inlet conditions are in other words possible and it is also possible to achieve compositions not achievable by only controlling the operation of the engine. Experiments have been performed at several engine conditions and using catalysts with different noble metal loading, lengths and washcoat thicknesses. To achieve high HC and CO concentrations the engine was tuned to run with late fuel injection. Significance A method to carry out engine rig experiments with a wider range of emission conditions makes it possible to more efficiently retune model parameters for a full-scale catalyst from literature data. This should result in faster model development which is of great importance in exhaust gas aftertreatment.
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| 5. |
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| 6. |
- Lundberg, Björn, 1982, et al.
(författare)
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Parameter Estimation of a DOC from Engine Rig Experiments with a Discretized Catalyst Washcoat Model
- 2014
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 7:2, s. 1093-1112
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Tidskriftsartikel (refereegranskat)abstract
- Parameter tuning was performed against data from a full scale engine rig with a Diesel Oxidation Catalysts (DOC). Several different catalyst configurations were used with varying Pt loading, washcoat thickness and volume. To illustrate the interplay between kinetics and mass transport, engine operating points were chosen with a wide variation in variables (inlet conditions) and both transient and stationary operation was used. A catalyst model was developed where the catalyst washcoat was discretized as tanks in series both radially and axially. Three different model configurations were used for parameter tuning, evaluating three different approaches to modeling of internal transport resistance. It was concluded that for a catalyst model with internal transport resistance the best fit could be achieved if some parameters affecting the internal mass transport were tuned in addition to the kinetic parameters. However it was also shown that a model with negligible internal transport resistance still could obtain a good fit since kinetic parameters could compensate for transport limitations. This highlighted the inherent difficulties using kinetic models with high parameter correlation and also showed the importance of using a kinetic model with a structure that is capable of describing exclusively intrinsic kinetics.
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| 7. |
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| 8. |
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| 9. |
- Edenroth-Cato, Fanny, 1983-, et al.
(författare)
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Biosociality in online interactions : Youths’ positioning of the highly sensitive person category
- 2022
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Ingår i: Young - Nordic Journal of Youth Research. - : SAGE Publications. - 1103-3088 .- 1741-3222. ; 30:1, s. 80-96
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Tidskriftsartikel (refereegranskat)abstract
- This article examines how young people in a Swedish online forum and in blogs engage in discussions of one popularized psychological personality trait, the highly sensitive person (HSP), and how they draw on different positionings in discursive struggles around this category. The material is analysed with concepts from discursivepsychology and post-structuralist theory in order to investigate youths’ interactions.The first is a nuanced positioning, from which youths disclose the weaknesses and strengths of being highly sensitive. Some youths become deeply invested in this kind of positioning, hence forming a HSP subjectivity. This can be opposed using contrasting positionings, which objects to norms of biosociality connected to the HSP. Lastly, there are rather distanced and investigative approaches to the HSP category. We conclude that while young people are negotiating the HSP category, they are establishing an epistemological community.
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| 10. |
- Edenroth Cato, Fanny, 1983-
(författare)
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Det högkänsliga subjektets tillblivelse : Diskursiva praktiker om identitet, förmåga och funktionsvariation
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines discursive practices about the highly sensitive person (HSP) from the perspective of knowledge production, categorization and community formation. In contemporary Sweden it has become increasingly common to talk about oneself in terms of being constituted in a particular way, e.g., as having a brain that functions differently than the average. The HSP often represents a person with exceptional capabilities and vulnerabilities, such as a sensitive nervous system and an empathetic disposition. The HSP discourse shares commonalities with the discourse of disability activism related to neuropsychiatric diagnoses. Namely, that by using specific discursive strategies, communities are being formed. The HSP community works to counteract the negative preconceived notions about high sensitivity, and bring to light the ignorance surrounding the needs of HSPs in society.This compilation thesis consists of a summarizing introduction and three articles. The empirical material covers posts from an online discussion forum for parents, and one aimed at young people, blogs composed by teenage girls, and children’s books written by different types of experts. These discursive arenas are analyzed with concepts from discursive psychology and poststructuralist theory. The results show how psychological and biomedical discourses are producing citizen subjects in relation to governing in specific social contexts. Within a Foucauldian tradition such forms of governance are termed biopolitics and biosociality.The first article examines how the HSP category is transforming notions of good motherhood. It suggests that mothers’ interaction in an online discussion forum reflects the intensive mothering norms of child-centered parenting. Mothers share their therapeutic narratives while highlighting the problems surrounding an incomprehensible social environment and the ordeals of having a guilty conscience. Through the prism of the highly sensitive child, however, motherhood acquires new anticipatory, considerate and susceptible norms, and strategies that constitute a highly sensitive parenting style.The second article studies how young people take different stances in discursive struggles concerning the HSP category online. The article illustrates how youths disclose the weaknesses and strengths of being highly sensitive, as well as objecting to norms of biosociality that are connected to the HSP. According to these findings young people are pioneering a new informed ethics of the self as they perform HSP subjectivity.The third article investigates children’s books that may be used as therapeutic tools aimed at informing and educating both adults and children about girls’ experiences of being HSPs, or of having a neuropsychiatric diagnosis. In these books dis/abilities are often transformed into exceptional capabilities. Through a process of identification, the girl protagonists may come to manage their behavior and emotions according to the premise of the diagnosis, thus, redefining their personhood as ideal citizen subjects.In conclusion, norms of biosociality and biopolitical governance regulate citizens to confess and assert their capabilities and dis/abilities, yet the discursive practices also reflect the construction of social problems and their potential solutions. Citizens appear to struggle to (re)define such problems in an identity political manner in order to (re)produce knowledge on their own terms.
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