| 1. |
- Andreasson, Martin, et al.
(författare)
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Coherence in Synchronizing Power Networks with Distributed Integral Control
- 2017
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Ingår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017. - : IEEE. - 9781509028733 ; , s. 6683-6688
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Konferensbidrag (refereegranskat)abstract
- We consider frequency control of synchronous generator networks and study transient performance under both primary and secondary frequency control. We model random step changes in power loads and evaluate performance in terms of expected deviations from a synchronous frequency over the synchronization transient; what can be thought of as lack of frequency coherence. We compare a standard droop control strategy to two secondary proportional integral (PI) controllers: centralized averaging PI control (CAPI) and distributed averaging PI control (DAPI). We show that the performance of a power system with DAPI control is always superior to that of a CAPI controlled system, which in turn has the same transient performance as standard droop control. Furthermore, for a large class of network graphs, performance scales unfavorably with network size with CAPI and droop control, which is not the case with DAPI control. We discuss optimal tuning of the DAPI controller and describe how internodal alignment of the integral states affects performance. Our results are demonstrated through simulations of the Nordic power grid.
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| 2. |
- Brinkmalm, Gunnar, et al.
(författare)
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A Parallel Reaction Monitoring Mass Spectrometric Method for Analysis of Potential CSF Biomarkers for Alzheimer's Disease.
- 2018
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Ingår i: Proteomics. Clinical applications. - : Wiley. - 1862-8354 .- 1862-8346. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to develop and evaluate a parallel reaction monitoring mass spectrometry (PRM-MS) assay consisting of a panel of potential protein biomarkers in cerebrospinal fluid (CSF).Thirteen proteins were selected based on their association with neurodegenerative diseases and involvement in synaptic function, secretory vesicle function, or innate immune system. CSF samples were digested and two to three peptides per protein were quantified using stable isotope-labeled peptide standards.Coefficients of variation were generally below 15%. Clinical evaluation was performed on a cohort of 10 patients with Alzheimer's disease (AD) and 15 healthy subjects. Investigated proteins of the granin family exhibited the largest difference between the patient groups. Secretogranin-2 (p<0.005) and neurosecretory protein VGF (p<0.001) concentrations were lowered in AD. For chromogranin A, two of three peptides had significantly lowered AD concentrations (p<0.01). The concentrations of the synaptic proteins neurexin-1 and neuronal pentraxin-1, as well as neurofascin were also significantly lowered in AD (p<0.05). The other investigated proteins, β2-microglobulin, cystatin C, amyloid precursor protein, lysozyme C, neurexin-2, neurexin-3, and neurocan core protein, were not significantly altered.PRM-MS of protein panels is a valuable tool to evaluate biomarker candidates for neurodegenerative disorders.
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| 3. |
- Jonsson, Karl
(författare)
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Two Problems in non-linear PDE’s with Phase Transitions
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is in the field of non-linear partial differential equations (PDE), focusing on problems which show some type of phase-transition. A single phase Hele-Shaw flow models a Newtoninan fluid which is being injected in the space between two narrowly separated parallel planes. The time evolution of the space that the fluid occupies can be modelled by a semi-linear PDE. This is a problem within the field of free boundary problems. In the multi-phase problem we consider the time-evolution of a system of phases which interact according to the principle that the joint boundary which emerges when two phases meet is fixed for all future times. The problem is handled by introducing a parameterized equation which is regularized and penalized. The penalization is non-local in time and tracks the history of the system, penalizing the joint support of two different phases in space-time. The main result in the first paper is the existence theory of a weak solution to the parameterized equations in a Bochner space using the implicit function theorem. The family of solutions to the parameterized problem is uniformly bounded allowing us to extract a weakly convergent subsequence for the case when the penalization tends to infinity.The second problem deals with a parameterized highly oscillatory quasi-linear elliptic equation in divergence form. As the regularization parameter tends to zero the equation gets a jump in the conductivity which occur at the level set of a locally periodic function, the obstacle. As the oscillations in the problem data increases the solution to the equation experiences high frequency jumps in the conductivity, resulting in the corresponding solutions showing an effective global behaviour. The global behavior is related to the so called homogenized solution. We show that the parameterized equation has a weak solution in a Sobolev space and derive bounds on the solutions used in the analysis for the case when the regularization is lost. Surprisingly, the limiting problem in this case includes an extra term describing the interaction between the solution and the obstacle, not appearing in the case when obstacle is the zero level-set. The oscillatory nature of the problem makes standard numerical algorithms computationally expensive, since the global domain needs to be resolved on the micro scale. We develop a multi scale method for this problem based on the heterogeneous multiscale method (HMM) framework and using a finite element (FE) approach to capture the macroscopic variations of the solutions at a significantly lower cost. We numerically investigate the effect of the obstacle on the homogenized solution, finding empirical proof that certain choices of obstacles make the limiting problem have a form structurally different from that of the parameterized problem.
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| 4. |
- Olsson, Henrik, 1968-, et al.
(författare)
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Parallel mechanisms of polypyrrole self-discharge in aqueous media
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - 1463-9076 .- 1463-9084. ; 17, s. 11014-11019
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Tidskriftsartikel (refereegranskat)abstract
- In this report we investigate the self-discharge in a positively charged polypyrrole-cellulose composite material in water solution. Rate constants for the self-discharge reaction are determined by potential step methods and their dependence on pH, temperature and applied potential are reported. Based on the results, we propose that two fundamentally different self-discharge mechanisms operate in parallel; one of faradaic origin with a rate constant increasing exponentially with applied potential and one mechanism comprising an initial reaction of the charged polymer with hydroxide ions. The second mechanism dominates at high pH as the rate constant for this reaction increases exponentially with pH whilst the faradaic reaction dominates at low pH. With this report we hope to shed light on the complex and elusive nature of self-discharge in conducting polymers to serve as guidance for the construction of electrical energy storage devices with conducting polymer components.
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| 5. |
- Olsson, Henrik, et al.
(författare)
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Self-discharge in positively charged polypyrrole-cellulose composite electrodes
- 2015
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Ingår i: Electrochemistry communications. - : Elsevier BV. - 1388-2481 .- 1873-1902. ; 50, s. 43-46
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Tidskriftsartikel (refereegranskat)abstract
- Self-discharge is one of the most critical issues to address to allow for industrialization of conducting polymer (CP) based electric energy storage devices. The present work investigates the underlying cause of self-discharge in positively charged polypyrrole (PPy), which is one of the most frequently studied CPs for such devices. The analyzed material is a composite of PPy and cellulose from Cladophora sp. algae forming a free standing paper-like material. From the time dependence of the potential decay as well as from independent spectroelectrochemical investigations the decay was attributed to a kinetically limiting Faradaic reaction, intrinsic to the polymer, forming a reactive intermediate that irreversibly reacts with its surroundings in a kinetically non-limiting following reaction. As such, nucleophilic addition of electrolyte nudeophiles is not found to be rate-determining. These results provide insight into the self-discharge phenomenon in p-doped CPs, and information regarding the potential range in which CPs can operate with insignificant self-discharge.
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| 6. |
- Rezeli, Melinda, et al.
(författare)
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Quantitation of 87 Proteins by nLC-MRM/MS in Human Plasma : Workflow for Large-Scale Analysis of Biobank Samples
- 2017
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Ingår i: Journal of Proteome Research. - : AMER CHEMICAL SOC. - 1535-3893 .- 1535-3907. ; 16:9, s. 3242-3254
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Tidskriftsartikel (refereegranskat)abstract
- A multiple reaction monitoring (MRM) assay was developed for precise quantitation of 87 plasma proteins including the three isoforms of apolipoprotein E (APOE) associated with cardiovascular diseases using nanoscale liquid chromatography separation and stable isotope dilution strategy. The analytical performance of the assay was evaluated and we found an average technical variation of 4.7% in 4-5 orders of magnitude dynamic range (approximate to 0.2 mg/L to 4.5 g/L) from whole plasma digest. Here, we report a complete workflow, including sample processing adapted to 96-well plate format and normalization strategy for large-scale studies. To further investigate the MS-based quantitation the amount of six selected proteins was measured by routinely used clinical chemistry assays as well and the two methods showed excellent correlation with high significance (p-value < 10e-5) for the six proteins, in addition for the cardiovascular predictor factor, APOB: APOA1 ratio (r = 0.969, p-value < 10e-5). Moreover, we utilized the developed assay for screening of biobank samples from patients with myocardial infarction and performed the comparative analysis of patient groups with STEMI (ST- segment elevation myocardial infarction), NSTEMI (non ST- segment elevation myocardial infarction) and type-2 AMI (type-2 myocardial infarction) patients.
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| 7. |
- Sjödin, Henrik, et al.
(författare)
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Principles of niche expansion
- 2018
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 285:1893
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Tidskriftsartikel (refereegranskat)abstract
- Niche expansion is attained by adaptations in two generalized phenotypical traits - niche position and niche width. This gives room for a wide range of conceptual ways of niche filling. The niche variation hypothesis reduces the range by predicting that expansion occurs by increasing variation in niche position, which has been debated on empirical and theoretical grounds as also other options seem possible. Here, we propose a general theory of niche expansion. We review empirical data and show with an eco-evolutionary model how resource diversity and a trade-off in resource acquisition steer niche evolution consistent with observations. We show that the range can be reduced to a discrete set of two orthogonal ways of niche filling, through (1) strict phenotypical differentiation in niche position or (2) strict individual generalization. When individual generalization is costly, niche expansion undergoes a shift from (2) to (1) at a point where the resource diversity becomes sufficiently large. Otherwise, niche expansion always follows (2), consistent with earlier results. We show that this either-or response can operate at both evolutionary and short-term time scales. This reduces the principles of niche expansion under environmental change to a notion of orthogonality, dictated by resource diversity and a resource-acquisition trade-off.
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| 8. |
- Sjödin, Henrik, et al.
(författare)
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Space race functional responses
- 2015
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 282:1801
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Tidskriftsartikel (refereegranskat)abstract
- We derive functional responses under the assumption that predators and prey are engaged in a space race in which prey avoid patches with many predators and predators avoid patches with few or no prey. The resulting functional response models have a simple structure and include functions describing how the emigration of prey and predators depend on interspecific densities. As such, they provide a link between dispersal behaviours and community dynamics. The derived functional response is general but is here modelled in accordance with empirically documented emigration responses. We find that the prey emigration response to predators has stabilizing effects similar to that of the DeAngelis-Beddington functional response, and that the predator emigration response to prey has destabilizing effects similar to that of the Holing type 11 response. A stability criterion describing the net effect of the two emigration responses on a Lotka-Volterra predator-prey system is presented. The winner of the space race (i.e. whether predators or prey are favoured) is determined by the relationship between the slopes of the species' emigration responses. It is predicted that predators win the space race in poor habitats, where predator and prey densities are low, and that prey are more successful in richer habitats.
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| 9. |
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| 10. |
- Sjödin, Simon, et al.
(författare)
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APLP1 as a cerebrospinal fluid biomarker for gamma-secretase modulator treatment
- 2015
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Ingår i: Alzheimers Research & Therapy. - : Springer Science and Business Media LLC. - 1758-9193. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Alzheimer's disease brains are characterized by extracellular plaques containing the aggregated amyloid beta(42) (A beta(42)) peptide and intraneuronal tangles containing hyperphosphorylated tau. A beta(42) is produced by sequential processing of the amyloid precursor protein (APP) by beta-secretase followed by gamma-secretase. Substantial efforts have been put into developing pharmaceuticals preventing the production or increasing the clearance of A beta(42). However, treatments inhibiting gamma- secretase have proven disappointing due to off-target effects. To circumvent these effects, gamma-secretase modulators (GSMs) have been developed, which rather than inhibiting gamma- secretase shift its preference into producing less aggregation-prone shorter A beta peptides. Belonging to the same family of proteins as APP, amyloid-like protein 1 (APLP1) is also a substrate for gamma-secretase. Herein we investigated whether the GSM E2012 affects APLP1 processing in the central nervous system by measuring APLP1 peptide levels in cerebrospinal fluid (CSF) before and after E2012 treatment in dogs. Methods: An in-house monoclonal APLP1 antibody, AP1, was produced and utilized for immunopurification of APLP1 from human and dog CSF in a hybrid immuno-affinity mass spectrometric method. Seven dogs received a single dose of 20 or 80 mg/kg of E2012 in a randomized cross-over design and CSF was collected prior to and 4, 8 and 24 hours after dosing. Results: We have identified 14 CSF APLP1 peptides in humans and 12 CSF APLP1 peptides in dogs. Of these, seven were reproducibly detectable in dogs who received E2012. We found a dose-dependent relative increase of the CSF peptides APLP1 beta 17, 1 beta 18 and 1 beta 28 accompanied with a decrease of 1 beta 25 and 1 beta 27 in response to E2012 treatment. All peptides reverted to baseline over the time of sample collection. Conclusion: We show an in vivo effect of the GSM E2012 on the processing of APLP1 which is measurable in CSF. These data suggest that APLP1 peptides may be used as biomarkers to monitor drug effects of GSMs on gamma-secretase processing in clinical trials. However, this requires further investigation in larger cohorts, including studies in man.
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| 11. |
- Sjödin, Simon, et al.
(författare)
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Endo-lysosomal proteins and ubiquitin CSF concentrations in Alzheimer's and Parkinson's disease
- 2019
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Ingår i: Alzheimer's Research & Therapy. - : Springer Science and Business Media LLC. - 1758-9193. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Increasing evidence implicates dysfunctional proteostasis and the involvement of the autophagic and endo-lysosomal system and the ubiquitin-proteasome system in neurodegenerative diseases. In Alzheimer's disease (AD), there is an accumulation of autophagic vacuoles within the neurons. In Parkinson's disease (PD), susceptibility has been linked to genes encoding proteins involved in autophagy and lysosomal function, as well as mutations causing lysosomal disorders. Furthermore, both diseases are characterized by the accumulation of protein aggregates. Methods Proteins associated with endocytosis, lysosomal function, and the ubiquitin-proteasome system were identified in the cerebrospinal fluid (CSF) and targeted by combining solid-phase extraction and parallel reaction monitoring mass spectrometry. In total, 50 peptides from 18 proteins were quantified in three cross-sectional cohorts including AD (N = 61), PD (N = 21), prodromal AD (N = 10), stable mild cognitive impairment (N = 15), and controls (N = 68). Results A pilot study, including subjects selected based on their AD CSF core biomarker concentrations, showed increased concentrations of several targeted proteins in subjects with core biomarker levels indicating AD pathology compared to controls. Next, in a clinically characterized cohort, lower concentrations in CSF of proteins in PD were found compared to subjects with prodromal AD. Further investigation in an additional clinical study again revealed lower concentrations in CSF of proteins in PD compared to controls and AD. Conclusion In summary, significantly different peptide CSF concentrations were identified from proteins AP2B1, C9, CTSB, CTSF, GM2A, LAMP1, LAMP2, TCN2, and ubiquitin. Proteins found to have altered concentrations in more than one study were AP2B1, CTSB, CTSF, GM2A, LAMP2, and ubiquitin. Interestingly, given the genetic implication of lysosomal function in PD, we did identify the CSF concentrations of CTSB, CTSF, GM2A, and LAMP2 to be altered. However, we also found differences in proteins associated with endocytosis (AP2B1) and the ubiquitin-proteasome system (ubiquitin). No difference in any peptide CSF concentration was found in clinically characterized subjects with AD compared to controls. In conclusion, CSF analyses of subjects with PD suggest a general lysosomal dysfunction, which resonates well with recent genetic findings, while such changes are minor or absent in AD.
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| 12. |
- Sjödin, Simon, et al.
(författare)
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Mass Spectrometric Analysis of Cerebrospinal Fluid Ubiquitin in Alzheimer's Disease and Parkinsonian Disorders
- 2017
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Ingår i: Proteomics - Clinical Applications. - : Wiley. - 1862-8346 .- 1862-8354. ; 11:11-12
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Dysfunctional proteostasis, with decreased protein degradation and an accumulation of ubiquitin into aggregated protein inclusions, is a feature of neurodegenerative diseases. Identifying new potential biomarkers in cerebrospinal fluid (CSF) reflecting this process could contribute important information on pathophysiology. Experimental design: A developed method combining SPE and PRM-MS is employed to monitor the concentration of ubiquitin in CSF from subjects with Alzheimer's disease (AD), Parkinson's disease (PD), and progressive supranuclear palsy (PSP). Four independent cross-sectional studies are conducted, studies 1–4, including controls (n = 86) and participants with AD (n = 60), PD (n = 15), and PSP (n = 11). Results: The method shows a repeatability and intermediate precision not exceeding 6.1 and 7.9%, respectively. The determined LOD is 0.1 nm and the LOQ range between 0.625 and 80 nm. The CSF ubiquitin concentration is 1.2–1.5-fold higher in AD patients compared with controls in the three independent AD-control studies (Study 1, p < 0.001; Study 2, p < 0.001; and Study 3, p = 0.003). In the fourth study, there is no difference in PD or PSP, compared to controls. Conclusion and clinical relevance: CSF ubiquitin may reflect dysfunctional proteostasis in AD. The described method can be used for further exploration of ubiquitin as a potential biomarker in neurodegenerative diseases.
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| 13. |
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| 14. |
- Sjödin, Åke, et al.
(författare)
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On-Road Emission Performance of Late Model Diesel and Gasoline Vehicles as Measured by Remote Sensing
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A newly developed remote sensing instrument with NO2 and NOX measurement capability was operated in the fall of 2016 over 19 workdays in Gothenburg, Sweden, to measure real driving emissions from a large number light- and heavy-duty vehicles. From more than 30,000 registered vehicle passages, a final QA/QC-reviewed dataset consisting of about 15,000 paired records containing emissions, driving condition and detailed vehicle information data, was used to evaluate the real-world emission performance of in particular Euro 5 and Euro 6 diesel vehicles. More than 9,000 records were of diesel vehicles, of which about 5,500 were of Euro 5 vehicles and about 2,600 of Euro 6 vehicles. The following conclusions were made from the evaluation: - Measurements on more than 6,000 diesel passenger cars reveal that the real driving emissions of NOX from Euro 6 diesel cars on average have been reduced by about 60% from pre-Euro 6 levels, e.g. Euro 5. This may be considered a major breakthrough, since the real-world NOX emissions from diesel passenger cars have been virtually unchanged between Euro 2 and Euro 5, although the NOX emission standard has been significantly lowered from Euro 2 to Euro 5. Still, Euro 6 diesel passenger car real-world NOX emissions are roughly more than 5 times higher than the Euro 6 standard, as well as than the measured average on-road NOX emissions from Euro 6 gasoline passenger cars. - For NOX emissions, an almost identical pattern as for diesel passenger cars was observed for both diesel light-duty commercial vehicles and diesel heavy-duty vehicles (trucks and buses), i.e. virtually no change in real-world emissions between Euro 2 and Euro 5, followed by a major drop in emissions for Euro 6. - Primary NO2 emissions from diesel light-duty vehicles (both PC and LCV) have been reduced from Euro 4 through Euro 6, implying that the emission ratio of NO2 to NOX has also been reduced, but the ratio is still as high as about 25% for both Euro 5 and Euro 6 (compared to about 15% for Euro 2). The opposite pattern exists for heavy-duty vehicles, for which the NO2/NOX-ratio increased from about 10% for Euro 4-5 to ≈35% for Euro 6. - For all categories of diesel vehicles, real-world PM emissions have dropped steadily from Euro 2 through Euro 6 – reductions are in the order of 90% for Euro 6 compared to Euro 2. - For Euro 4, 5 and 6 diesel passenger cars, real-world emissions of both NOX and NO2 increase with decreasing ambient air temperature. The temperature dependence appears to be strongest for Euro 5 cars. At 25-30 degrees C average Euro 5 NOX on-road emissions are around 15 g/kg fuel burned, rising to 20-25 g/kg fuel burned at around 10 degrees C. - Large differences in the on-road NOX emission performance were observed between different makes, models, as well as individual vehicles among Euro 5 and Euro 6 diesel passenger cars. - For the first time, remote sensing measurements were combined with air quality measurements and dispersion calculations in an urban street canyon. Calculated average concentrations of NO2, NOX and PM based on HBEFA 3.2 were comparable with corresponding measured concentrations, but the discrepancy increased with increasing concentrations, with calculated concentrations being lower than measured. The latest version of the HBEFA emission model (version 3.3), launched in May 2017, provided a good match with the remote sensing measurements for both NOX and NO2 as well as exhaust PM, but at the same time tended to lead to an overestimation of street canyon concentrations of NO2 and NOX in dispersion calculations carried out in this study.
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