| 1. |
- Petersson, C. L.M., et al.
(författare)
-
Anisotropic photoemission time delays close to a Fano resonance
- 2018
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Electron correlation and multielectron effects are fundamental interactions that govern many physical and chemical processes in atomic, molecular and solid state systems. The process of autoionization, induced by resonant excitation of electrons into discrete states present in the spectral continuum of atomic and molecular targets, is mediated by electron correlation. Here we investigate the attosecond photoemission dynamics in argon in the 20-40 eV spectral range, in the vicinity of the 3s(-1)np autoionizing resonances. We present measurements of the differential photoionization cross section and extract energy and angle-dependent atomic time delays with an attosecond interferometric method. With the support of a theoretical model, we are able to attribute a large part of the measured time delay anisotropy to the presence of autoionizing resonances, which not only distort the phase of the emitted photoelectron wave packet but also introduce an angular dependence.
|
|
| 2. |
- Agnafors, Marcus, 1977-
(författare)
-
Justice among Us : A Philosophical Analysis of Michael Walzer’s Theory of Justice
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The American philosopher Michael Walzer has been regarded as one of the most influential theorists in the field of distributive justice since the publication of Spheres of Justice in 1983. However, despite the popularity, his theory is often misunderstood or said to suffer from serious shortcomings.The aim of the dissertation is to present and defend a clearer and stronger version of Walzer’s theory of distributive justice. After a brief sketch of Walzer’s early works, in which important concepts were introduced and developed, the mature theory is analysed. By subjecting the key areas of Walzer’s theory to a critical and reconstructive philosophical analysis, a stronger and more detailed account is gained. Important ideas and concepts such as community, consent, interpretation, social meanings, complex equality and minimal morality are discussed, criticised and revised in order to strengthen the theory. In addition, a comparison is made between John Rawls’s method of wide reflective equilibrium and Walzer’s interpretative method; it is argued that the methods of the two philosophers exhibit considerable similarities.
|
|
| 3. |
|
|
| 4. |
- Berg, Marcus, 1973-, et al.
(författare)
-
Higgs diphoton rate enhancement from supersymmetric physics beyond the MSSM
- 2013
-
Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 1550-7998 .- 1550-2368. ; 88:2
-
Tidskriftsartikel (refereegranskat)abstract
- We show that supersymmetric ‘‘new physics’’ beyond the minimal supersymmetric standard model can naturally accommodate a Higgs mass near 126 GeV and enhance the signal rate in the h to gamma gamma channel, while the signal rates in all the other Higgs decay channels coincide with Standard Model expectations, except possibly the h to Z gamma channel. The new physics that corrects the relevant Higgs couplings can be captured by two supersymmetric effective operators. We provide a simple example of an underlying model in which these operators are simultaneously generated. The scale of new physics that generates these operators can be around 5 TeV or larger, and outside the reach of the LHC.
|
|
| 5. |
- Blomberg, Staffan, et al.
(författare)
-
Socialpolitik och socialt arbete
- 2016. - Tredje utgåvan
-
Ingår i: Socialt arbete: En grundbok. - Stockholm : Natur och kultur. - 9789127141490 ; , s. 215-227
-
Bokkapitel (refereegranskat)
|
|
| 6. |
|
|
| 7. |
- Darwish, Essam, et al.
(författare)
-
Touch signaling and thigmomorphogenesis are regulated by complementary CAMTA3- and JA-dependent pathways
- 2022
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:20
-
Tidskriftsartikel (refereegranskat)abstract
- Plants respond to mechanical stimuli to direct their growth and counteract environmental threats. Mechanical stimulation triggers rapid gene expression changes and affects plant appearance (thigmomorphogenesis) and flowering. Previous studies reported the importance of jasmonic acid (JA) in touch signaling. Here, we used reverse genetics to further characterize the molecular mechanisms underlying touch signaling. We show that Piezo mechanosensitive ion channels have no major role in touch-induced gene expression and thigmomorphogenesis. In contrast, the receptor-like kinase Feronia acts as a strong negative regulator of the JA-dependent branch of touch signaling. Last, we show that calmodulin-binding transcriptional activators CAMTA1/2/3 are key regulators of JA-independent touch signaling. CAMTA1/2/3 cooperate to directly bind the promoters and activate gene expression of JA-independent touch marker genes like TCH2 and TCH4. In agreement, camta3 mutants show a near complete loss of thigmomorphogenesis and touch-induced delay of flowering. In conclusion, we have now identified key regulators of two independent touch-signaling pathways.
|
|
| 8. |
- Ehn, Andreas, et al.
(författare)
-
Plasma assisted combustion: Effects of O3 on large scale turbulent combustion studied with laser diagnostics and Large Eddy Simulations
- 2015
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35:3, s. 3487-3495
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Abstract In plasma-assisted combustion, electric energy is added to the flame where the electric energy will be transferred to kinetic energy of the free electrons that, in turn, will modify the combustion chemical kinetics. In order to increase the understanding of this complex process, the influence of one of the products of the altered chemical kinetics, ozone (O3), has been isolated and studied. This paper reports on studies using a low-swirl methane (CH4) air flame at lean conditions with different concentrations of O3 enrichment. The experimental flame diagnostics include Planar Laser Induced Fluorescence (PLIF) imaging of hydroxyl (OH) and formaldehyde (CH2O). The experiments are also modeled using Large Eddy Simulations (LES) with a reaction model based on a skeletal CH4-air reaction mechanism combined with an O3 sub-mechanism to include the presence of O3 in the flame. This reaction mechanism is based on fundamental considerations including reactions between O3 and all other species involved. The experiments reveal an increase in CH2O in the low-swirl flame as small amounts of O3 is supplied to the CH4-air stream upstream of the flame. This increase is well predicted by the LES computations and the relative radical concentration shift is in good agreement with experimental data. Simulations also reveal that the O3 enrichment increase the laminar flame speed, su, with ∼10% and the extinction strain-rate, Ïext, with ∼20%, for 0.57% (by volume) O3. The increase in Ïext enables the O3 seeded flame to burn under more turbulent conditions than would be possible without O3 enrichment. Sensitivity analysis indicates that the increase in Ïext due to O3 enrichment is primarily due to the accelerated chain-branching reactions H 2 + O â OH + H , H 2 O + O â OH + OH and H + O 2 â OH + O . Furthermore, the increase in CH2O observed in both experiments and simulations suggest a significant acceleration of the chain-propagation reaction CH 3 + O â CH 2 O + H .
|
|
| 9. |
- Ehn, Andreas, et al.
(författare)
-
Setup for microwave stimulation of a turbulent low-swirl flame
- 2016
-
Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 49:18
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental setup for microwave stimulation of a turbulent flame is presented. A low-swirl flame is being exposed to continuous microwave irradiation inside an aluminum cavity. The cavity is designed with inlets for laser beams and a viewport for optical access. The aluminum cavity is operated as a resonator where the microwave mode pattern is matched to the position of the flame. Two metal meshes are working as endplates in the resonator, one at the bottom and the other at the top. The lower mesh is located right above the burner nozzle so that the low-swirl flame is able to freely propagate inside the cylinder cavity geometry whereas the upper metal mesh can be tuned to achieve good overlap between the microwave mode pattern and the flame volume. The flow is characterized for operating conditions without microwave irradiation using particle imaging velocimetry (PIV). Microwave absorption is simultaneously monitored with experimental investigations of the flame in terms of exhaust gas temperature, flame chemiluminescence (CL) analysis as well as simultaneous planar laser-induced fluorescence (PLIF) measurements of formaldehyde (CH2O) and hydroxyl radicals (OH). Results are presented for experiments conducted in two different regimes of microwave power. In the high-energy regime the microwave field is strong enough to cause a breakdown in the flame. The breakdown spark develops into a swirl-stabilized plasma due to the continuous microwave stimulation. In the low-energy regime, which is below plasma formation, the flame becomes larger and more stable and it moves upstream closer to the burner nozzle when microwaves are absorbed by the flame. As a result of a larger flame the exhaust gas temperature, flame CL and OH PLIF signals are increased as microwave energy is absorbed by the flame.
|
|
| 10. |
- Ek, Fredrik, et al.
(författare)
-
Behavioral Analysis of Dopaminergic Activation in Zebrafish and Rats Reveals Similar Phenotypes
- 2016
-
Ingår i: Acs Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 7:5, s. 633-646
-
Tidskriftsartikel (refereegranskat)abstract
- Zebrafish is emerging as a complement to mammals in behavioral studies; however, there is a lack of comparative studies with rodents and humans to establish the zebrafish as a predictive translational model. Here we present a detailed phenotype evaluation of zebrafish larvae, measuring 300-3000 variables and analyzing them using multivariate analysis to identify the most important ones for further evaluations. The dopamine agonist apomorphine has previously been shown to have a complex U-shaped dose response relationship in the variable distance traveled. In this study, we focused on breaking down distance traveled into more detailed behavioral phenotypes for both zebrafish and rats and identified in the multivariate analysis low and high dose phenotypes with characteristic behavioral features. Further analysis of single parameters also identified an increased activity at the lowest concentration indicative of a U-shaped dose response. Apomorphine increased the distance of each swim movement (bout) at both high and low doses, but the underlying behavior of this increase is different; at high dose, both bout duration and frequency increased whereas bout max speed was higher at low dose. Larvae also displayed differences in place preference. The low dose phenotype spent more time in the center, indicative of an anxiolytic effect, while the high-dose phenotype had a wall preference. These dose-dependent effects corroborated findings in a parallel rat study and previous observations in humans. The translational value of pharmacological zebrafish studies was further evaluated by comparing the amino acid sequence of the dopamine receptors (D-1-D-4), between zebrafish, rats and humans. Humans and zebrafish share 100% of the amino acids in the binding site for D-1 and D-3 whereas D-2 and D-4 receptors share 85-95%. Molecular modeling of dopamine D2 and D4 receptors indicated that nonconserved amino acids have limited influence on important ligand receptor interactions.
|
|
| 11. |
- Flink, Henrik, et al.
(författare)
-
Examining the effects of authentic C&R on the reproductive potential of Northern pike
- 2021
-
Ingår i: Fisheries Research. - : Elsevier. - 0165-7836 .- 1872-6763. ; 243
-
Tidskriftsartikel (refereegranskat)abstract
- The practice within recreational fisheries to release captured fish back to the wild, known as catch-and-release (C&R), is an increasingly important strategy to protect fish stocks from overexploitation. However, C&R is a stressor and since animal reproduction is particularly sensitive to stress there is reason to suspect that such a practice induces sublethal fitness consequences. Here, we investigated whether and how C&R fishing influenced the reproductive potential in an anadromous population of Northern pike (Esox lucius). First, female pike were exposed to authentic C&R using rod-and-reel fishing in a coastal foraging habitat prior to the spawning period. Next, we observed the migration to the freshwater spawning habitat and compared both the timing of arrival and maturity stage between C&R-treated and control individuals. Finally, to evaluate effects on the quality and viability of eggs we stripped captured control and recaptured C&R-treated females, measured egg dry mass to assess nutrient content, conducted artificial fertilisations and incubated eggs in a controlled laboratory experiment. We found no evidence of C&R causing alterations in either arrival time, maturity stage, or the quality and viability of fertilised eggs. In combination, our results suggest that long-term effects of C&R-induced stress on key reproductive traits of pike, if any, are minor.
|
|
| 12. |
- Fransén, Erik, 1962-, et al.
(författare)
-
Computational modeling of activity dependent velocity changes in peripheral C-fibers
- 2011
-
Konferensbidrag (refereegranskat)abstract
- Initiation and propagation of action potentials along unmyelinated C-fibers are the first steps of the pain pathway. Propagation velocity and its fiber class-specific activity-dependent slowing (ADS) is intimately linked to fibre excitability. In chronic pain patients, ADS alterations have been suggested to reflect increased excitability, possibly underlying clinical pain. Due to their small diameter, peripheral axons of nociceptors in patients are not accessible for intraaxonal recordings of their ion channel properties. We have therefore constructed a model of a C-fibre to study the relationship between ion channel composition and velocity changes as well as excitability. Ion channels are modeled from data of DRG somata using a Hodgkin-Huxley formalism (Na currents: TTX-sensitive, Nav1.8, Nav1.9, K currents: Kdr, A-type, Kv7.3, non-specific cationic: HCN). Moreover, ion pumps (Na/K-ATPase) and concentrations of intra and extraaxonal sodium and potassium are also included. The geometry and temperature of the fibre represents a section of the superficial branch and the deeper parent and is represented by a multicompartmental structure where each compartment contains passive as well as ion channel and pump elements. Using parameter estimation techniques, we optimized ion channel and pump expression pattern such that basic electrophysiological characteristics of the action potential and its velocity matched the experimental data. Moreover, we have also replicated activity dependent slowing. In ongoing work, we extend optimization to also include recovery cycles. The model will be used to study hypothesis of the relationship between individual ion channel subtypes and axonal excitability related to pain, generating independent information on impact of selective neuronal targets.
|
|
| 13. |
- Fransén, Erik, 1962-, et al.
(författare)
-
Differences in action potential propagation in mechanosensitive and insensitive C-nociceptors - a modeling approach
- 2012
-
Konferensbidrag (refereegranskat)abstract
- C-fibers, unmyelinated afferent axons, convey information from the periphery of the nervous system to the spinal cord. They transmit signals originating from noxious stimulation evoking the sensations of itch and pain in the central nervous system. Different classes of C-fibers are characterized by functional, morphological and biochemical characteristics. In pain studies, a classification into mechano-insensitive (CMi) and mechano responsive fibers (CM) has proven useful as changes in proportions and response characteristics of these fibers have been observed in neuropathy patients (Weidner et al. 1999, 2000; Orstavik 2003, 2010). In this study, using computational modeling of a C-fiber, we have studied the possible contribution of different ion channel subtypes (Na-TTXs, Nav1.8, Nav1.9, Kdr, KA, KM, K(Na), h) as well as the Na/K-ATPase pump to conductive properties of C-fibers. In particular we investigated mechanisms that could generate the fiber-specific differences between CM and CMi fibers with regard to activity dependent slowing (ADS) and recovery cycles (RC). In our study we represent the axon by three cylindrical sections, one representing the peripheral thin end (branch, 2.5 cm), one the central part (parent, 10 cm) and a conical section between these (0.5 cm). In total 730 compartments are used. Temperature is set to 32 degrees C in branch and 37 degrees in parent sections. We represent variable ion concentrations of Na and K intra axonally, periaxonally and extracellularly, from which reversal potentials are calculated. We use ion channel models based on Hodgkin Huxley formalism. An ion pump (Na/K-ATPase) is included. We find that TTX-sensitive Na and Nav1.8 have the strongest influence on action potential conduction velocity as is expected since these are the major components of the rising phase of the action potential. Preliminary observations indicate that a small subset of Na and K currents play a key role in determining differences in activity dependent velocity changes (ADS) in the two fiber classes. We plan to also study contributions from morphological characteristics (superficial branch lengths) to activity dependent differences between the fiber classes (Schmidt et al. 2002). We further intend to investigate candidate ion channels which could play a role in changing the functional characteristics of a CMi fiber to that of a CM fiber. Our studies may provide insights into ionic changes underlying changes in the excitability of C-fibers associated with pain.
|
|
| 14. |
- Granmo, Marcus, et al.
(författare)
-
Action-based body maps in the spinal cord emerge from a transitory floating organization.
- 2008
-
Ingår i: The Journal of Neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 28:21, s. 5494-5503
-
Tidskriftsartikel (refereegranskat)abstract
- During development primary afferents grow into and establish neuronal connections in the spinal cord, thereby forming the basis for how we perceive sensory information and control our movements. In the somatosensory system, myriads of primary afferents, conveying information from different body locations and sensory modalities, get organized in the dorsal horn of the spinal cord so that spinal multisensory circuits receive topographically ordered information. How this intricate pathfinding is brought about during development is, however, largely unknown. Here we show that a body representation closely related to motor patterns emerges from a transitory floating and plastic organization through profound activity-dependent rewiring, involving both sprouting and elimination of afferent connections, and provide evidence for cross-modality interactions in the alignment of the multisensory input. Thus, far from being inborn and stereotypic, the dorsal horn of the spinal cord now appears to be a highly adaptive brain-body interface.
|
|
| 15. |
- Henriksson, Pontus, et al.
(författare)
-
Body mass index and gestational weight gain in migrant women by birth regions compared with Swedish-born women : A registry linkage study of 0.5 million pregnancies
- 2020
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:10
-
Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Women migrating to high-income countries may have increased risks of adverse pregnancy outcomes as compared with native-born women. However, little is known whether migrant women are more likely to have unhealthy body mass index (BMI) or gestational weight gain (GWG), which is of importance considering the well-established links between unhealthy BMI and GWG with adverse pregnancy outcomes. Hence, the aim of the study was to examine the prevalence and estimate odds ratios (ORs) of underweight and obesity in the first trimester as well as inadequate and excessive GWG across birth regions in migrant (first-generation) and Swedish-born women in a population-based sample of pregnant women in Sweden.METHODS: This population-based study included 535 609 pregnancies from the Swedish Pregnancy Register between the years 2010-2018. This register has a coverage of approximately 90% and includes data on body weight, height, birth country and educational attainment. BMI in the first trimester of pregnancy was classified as underweight, normal weight, overweight and obesity whereas GWG was classified as inadequate, adequate and excessive according to the recommendations from the National Academy of Medicine, USA. BMI and GWG were examined according to 7 birth regions and the 100 individual birth countries. Adjusted ORs of underweight, obesity as well as inadequate or excessive GWG by birth regions were estimated using multinomial logistic regression.RESULTS: There were large disparities in unhealthy BMI and GWG across birth regions. For instance, women born in North Africa and Middle East and Sub-Saharan Africa had 1.40 (95% CI 1.35-1.44) and 2.13 (95% CI 2.03-2.23) higher odds of obesity compared with women born in Sweden. However, women born in Sub-Saharan Africa had also considerably higher odds of underweight (OR, 2.93 [95% CI 2.70-3.18]) and inadequate GWG (OR, 1.97 [95% CI 1.87-2.07]). The limitations of the study include the lack of a validated measure of acculturation and that the study only had data on first-generation migration.CONCLUSIONS: The large differences across the 7 regions and 100 countries highlights the importance of considering birth region and country-specific risks of unhealthy BMI and GWG in first-generation migrant women. Furthermore, inadequate GWG was common among pregnant first-generation migrant women, especially in women born in Sub-Saharan Africa, which demonstrates the need to promote adequate GWG, not only the avoidance of excessive GWG. Thus, our findings also indicate that additional support and interventions may be needed for first-generation migrant women from certain birth regions and countries in order to tackle the observed disparities in unhealthy BMI and GWG. Although further studies are needed, our results are useful for identifying groups of women at increased risk of unhealthy BMI and weight gain during pregnancy.
|
|
| 16. |
- Henriksson, Pontus, et al.
(författare)
-
Self-Rated Health in Migrant and Non-Migrant Women before, during and after Pregnancy : A Population-Based Study of 0.5 Million Pregnancies from the Swedish Pregnancy Register
- 2020
-
Ingår i: Journal of Clinical Medicine. - : MDPI. - 2077-0383. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- Self-rated health is a strong health marker. Migrants have been suggested to have poorer self-rated health than non-migrants (i.e., native-born). However, little is known about whether there are disparities in self-reported health in relation to pregnancy. Therefore, the aim of the current study was to examine the odds of poor self-rated health before, during and after pregnancy in migrant women as compared to women born in Sweden. We utilized population-based data from the Swedish Pregnancy Register containing 0.5 million women born in Sweden (i.e., non-migrant women) and migrant women between 2010 and 2018. Self-rated health was reported on a 5-point scale (from very poor to very good). Very poor and poor health were categorized as poor self-rated health. Logistic regression was utilized to calculate odds ratios (ORs) that were unadjusted and adjusted for covariates (age, parity, educational attainment and body mass index). The results demonstrate disparities in self-rated health across birth regions. In comparison to women born in Sweden, women born in Latin America and the Caribbean, South Asia as well as North Africa and the Middle East had consistently higher odds of poor self-rated health before, during and after pregnancy (ORs ranging from 1.14 to 1.96 in both unadjusted and adjusted models). Although women born in Sub-Saharan Africa did have comparable self-rated health as to women born in Sweden before pregnancy, after accounting for covariates, they had lower odds of poor self-rated health during and after pregnancy (ORs: 0.71 and 0.80 respectively). Therefore, additional measures and support may be needed to tackle disparities in health between migrant and non-migrant women before, during and after pregnancy.
|
|
| 17. |
- Holmberg, Ulrika, 1966, et al.
(författare)
-
Nedslag i konsumtionskulturen
- 2009
-
Ingår i: Sören Holmberg och Lennart Weibull (red.) Svensk höst. Trettiofyra kapitel om politik, medier och samhälle.. - Göteborg : SOM-institutet, Göteborgs universitet. - 9789189673168 ; , s. 77-92
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 18. |
- Hyrenius-Wittsten, Axel, et al.
(författare)
-
De novo activating mutations drive clonal evolution and enhance clonal fitness in KMT2A-rearranged leukemia
- 2018
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Activating signaling mutations are common in acute leukemia with KMT2A (previously MLL) rearrangements (KMT2A-R). These mutations are often subclonal and their biological impact remains unclear. Using a retroviral acute myeloid mouse leukemia model, we demonstrate that FLT3 ITD, FLT3 N676K, and NRAS G12D accelerate KMT2A-MLLT3 leukemia onset. Further, also subclonal FLT3 N676K mutations accelerate disease, possibly by providing stimulatory factors. Herein, we show that one such factor, MIF, promotes survival of mouse KMT2A-MLLT3 leukemia initiating cells. We identify acquired de novo mutations in Braf, Cbl, Kras, and Ptpn11 in KMT2A-MLLT3 leukemia cells that favored clonal expansion. During clonal evolution, we observe serial genetic changes at the Kras G12D locus, consistent with a strong selective advantage of additional Kras G12D . KMT2A-MLLT3 leukemias with signaling mutations enforce Myc and Myb transcriptional modules. Our results provide new insight into the biology of KMT2A-R leukemia with subclonal signaling mutations and highlight the importance of activated signaling as a contributing driver.
|
|
| 19. |
|
|
| 20. |
- Kringhøj, A., et al.
(författare)
-
Anharmonicity of a superconducting qubit with a few-mode Josephson junction
- 2018
-
Ingår i: Physical Review B. - 2469-9950. ; 97:6
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent operation of gate-voltage-controlled hybrid transmon qubits (gatemons) based on semiconductor nanowires was recently demonstrated. Here we experimentally investigate the anharmonicity in epitaxial InAs-Al Josephson junctions, a key parameter for their use as a qubit. Anharmonicity is found to be reduced by roughly a factor of 2 compared to conventional metallic junctions and dependent on gate voltage. Experimental results are consistent with a theoretical model, indicating that Josephson coupling is mediated by a small number of highly transmitting modes in the semiconductor junction.
|
|
| 21. |
|
|
| 22. |
- Lantz, Andreas, et al.
(författare)
-
High-speed imaging of fuel/OH distributions in a gas turbine pilot burner at elevated pressure
- 2011
-
Ingår i: Paper AIAA 2011-986. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
-
Konferensbidrag (refereegranskat)abstract
- Different laser visualization techniques were applied to a pilot burner at elevated pressure using relevant liquid fuels. Special care was spent to investigate the performance of the visualization techniques when using Jet-A as fuel compared to when using Bio-Jet as fuel at gas turbine relevant conditions. The burner, a centrally placed generic injector surrounded by a swirling co-flow, was mounted in a high-pressure combustion test rig with optical access from all four sides. Planar laser-induced fluorescence (PLIF) and Mie scattering was used for visualization of the fuel and OH distributions. For fuel PLIF, two different laser excitation wavelengths, 266 nm and 300 nm, were used to investigate the absorption of the laser sheets by different fuels. The Multi:YAG laser cluster, which can produce eight laser pulses in a rapid burst, and a optical parametric oscillator (OPO) was used for high-speed imaging. Furthermore, three-dimensional measurements of fuel PLIF were performed for the Bio-Jet fuel and the OPO laser was used to capture the flame front and burned gas regions using OH PLIF.
|
|
| 23. |
- Liu, Xin, et al.
(författare)
-
Investigation of turbulent premixed methane/air and hydrogen-enriched methane/air flames in a laboratory-scale gas turbine model combustor
- 2021
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 46:24, s. 13377-13388
-
Tidskriftsartikel (refereegranskat)abstract
- Methane and hydrogen-enriched (25 vol% and 50 vol% H2-enriched CH4) methane/air premixed flames were investigated in a gas turbine model combustor under atmospheric conditions. The flame operability ranges were mapped at different Reynold numbers (Re), showing the dependence on Re and H2 concentrations. The effects of equivalence ratio (Φ), Re, and H2 enrichment on flame structure were examined employing OH-PLIF measurement. For CH4/air cases, the flame was stabilized with an M shape; while for H2-enriched cases, the flame transitions to a П shape above a specific Φ. This transition was observed to influence significantly the flashback limits. The flame shape transition is most likely a result of H2 enrichment, occurring due to the increase in flame speed, higher resistance of the flame to the strain rate, and change in the inner recirculation zone. Flow fields of CH4/air flames were compared between low and high Re cases employing high-speed PIV. The flashback events, led by two mechanisms (combustion-induced vortex breakdown, CIVB, and boundary-layer flashback, BLF), were observed and recorded using high-speed OH chemiluminescence imaging. It was found that the CIVB flashback occurred only for CH4 flames with M shape, whereas the BLF occurs for all H2-enriched flames with П shape.
|
|
| 24. |
- Nair, Monika, 1985-, et al.
(författare)
-
Machine Learning Model for Readmission Prediction of Patients With Heart Failure Based on Electronic Health Records : Protocol for a Quasi-Experimental Study for Impact Assessment
- 2024
-
Ingår i: JMIR Research Protocols. - Toronto, ON : JMIR Publications. - 1929-0748. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Care for patients with heart failure (HF) causes a substantial load on health care systems where a prominent challenge is the elevated rate of readmissions within 30 days following initial discharge. Clinical professionals face high levels of uncertainty and subjectivity in the decision-making process on the optimal timing of discharge. Unwanted hospital stays generate costs and cause stress to patients and potentially have an impact on care outcomes. Recent studies have aimed to mitigate the uncertainty by developing and testing risk assessment tools and predictive models to identify patients at risk of readmission, often using novel methods such as machine learning (ML).Objective: This study aims to investigate how a developed clinical decision support (CDS) tool alters the decision-making processes of health care professionals in the specific context of discharging patients with HF, and if so, in which ways. Additionally, the aim is to capture the experiences of health care practitioners as they engage with the system’s outputs to analyze usability aspects and obtain insights related to future implementation.Methods: A quasi-experimental design with randomized crossover assessment will be conducted with health care professionals on HF patients’ scenarios in a region located in the South of Sweden. In total, 12 physicians and nurses will be randomized into control and test groups. The groups shall be provided with 20 scenarios of purposefully sampled patients. The clinicians will be asked to take decisions on the next action regarding a patient. The test group will be provided with the 10 scenarios containing patient data from electronic health records and an outcome from an ML-based CDS model on the risk level for readmission of the same patients. The control group will have 10 other scenarios without the CDS model output and containing only the patients’ data from electronic medical records. The groups will switch roles for the next 10 scenarios. This study will collect data through interviews and observations. The key outcome measures are decision consistency, decision quality, work efficiency, perceived benefits of using the CDS model, reliability, validity, and confidence in the CDS model outcome, integrability in the routine workflow, ease of use, and intention to use. This study will be carried out in collaboration with Cambio Healthcare Systems.Results: The project is part of the Center for Applied Intelligent Systems Research Health research profile, funded by the Knowledge Foundation (2021-2028). Ethical approval for this study was granted by the Swedish ethical review authority (2022-07287-02). The recruitment process of the clinicians and the patient scenario selection will start in September 2023 and last till March 2024.Conclusions: This study protocol will contribute to the development of future formative evaluation studies to test ML models with clinical professionals. © 2024 JMIR Publications Inc.. All rights reserved.
|
|
| 25. |
- Nilsson, Sten, et al.
(författare)
-
Two-Year Survival Follow-Up of the Randomized, Double-Blind, Placebo-Controlled Phase II Study of Radium-223 Chloride in Patients With Castration-Resistant Prostate Cancer and Bone Metastases
- 2013
-
Ingår i: Clinical Genitourinary Cancer. - : Elsevier. - 1558-7673 .- 1938-0682. ; 11:1, s. 20-26
-
Tidskriftsartikel (refereegranskat)abstract
- In this 24-month follow-up of a phase II study in patients with castration-resistant prostate cancer (CRPC) and bone metastases, radium-223 (4 injections of 50 kBq/kg every 4 weeks [n = 33]) improved median overall survival vs. matching placebo (n = 31) (65.3 vs. 46.4 weeks, respectively; log-rank P = .056), with no long-term safety concerns. Data suggest that treatment of bone disease with radium-223 has survival benefits. less thanbrgreater than less thanbrgreater thanBackground: This phase II randomized, placebo-controlled study was conducted to evaluate efficacy and safety of radium-223 in patients with castration-resistant prostate cancer (CRPC) and painful bone metastases. Twelve-and 18-month survival results were reported previously. Here we report 24-month overall survival (OS) and safety data from the period 12 to 24 months after the first injection of study medication. Methods: Patients with CRPC and bone pain were randomized 1: 1 to receive 4 injections of radium-223 (50 kBq/kg [n = 33]) or placebo (n = 31) after external-beam radiotherapy; each injection was given every 4 weeks. Endpoints for this report were 24-month OS, long-term safety, and treatment-related adverse events (AEs) occurring in the 12- to 24-month period. Results: After 24 months, 10 (30%) patients were alive in the radium-223 group compared with 4 patients (13%) in the placebo group. Patients who received at least 1 dose of study medication had a median OS of 65 weeks in the radium-223 group vs. 46 weeks in the placebo group (log-rank P = .056). The hazard ratio (HR) for OS, adjusted for baseline covariates, was 0.476 (95% confidence interval [CI], 0.258-0.877; Cox regression P = .017). The most frequent cause of death for both arms was disease progression. There were no reports of treatment-related AEs or long-term hematologic toxicity during the 12- to 24-month follow-up. Conclusion: Radium-223 had a highly favorable safety profile, with no evidence of second malignancies at 24-month follow-up. The significant improvement in OS observed in patients receiving radium-223 vs. placebo suggests that treatment of bone disease with radium-223 has survival benefits. Clinical Genitourinary Cancer, Vol. 11, No. 1, 20-6
|
|
| 26. |
- Nogenmyr, Karl-Johan, et al.
(författare)
-
A Comparative Study of LES Turbulent Combustion Models Applied to a Low Swirl Lean Premixed Burner
- 2008
-
Ingår i: AIAA 2008-513. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
-
Konferensbidrag (refereegranskat)abstract
- In this study we compare two types of Large Eddy Simulation (LES) turbulent combustion models with experimental data for a low swirl stabilized turbulent lean premixed flame. Such flames are a great challenge to numerical simulations since they are unsteady and sensitive to boundary conditions, and details of the experimental set-up. The two classes of LES turbulent combustion models considered are the flamelet and finite rate chemistry models. Individual models of each category may be very different, but in the former the flame is considered infinitely thin, whereas in the latter the chemical kinetics and the diffusion governs the flame behavior. As representative of the flamelet models we here use a G-equation model, and as representative of the finite rate chemistry models we use the thickened flame model and the partially stirred reactor model. Predictions are being compared with measurement data for an atmospheric low-swirl methane/air flame. The experimental measurement data include data from stereoscopic PIV, filtered Rayleigh scattering and acetone LIF, providing information about the velocity, temperature and fuel distribution. All LES show reasonable agreement with the experimental data, predicting a lifted weakly swirling, flame oscillating back and forth just above the rim of the burner. A more detailed comparison of the predictions with the experimental data show that best quantitative agreement is obtained by one of the finite rate chemistry models, whereas the best qualitative comparison is obtained by the flamelet model. Causes for the difference in qualitative and quantitative behavior are elaborated on in the concluding remarks section.
|
|
| 27. |
|
|
| 28. |
- Nogenmyr, Karl-Johan, et al.
(författare)
-
Large Eddy Simulation and Experiments of Stratified Lean Premixed Methane/Air Turbulent Flames
- 2007
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 31:1, s. 1467-1475
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a joint large eddy simulation and laser diagnostic investigation of premixed turbulent low swirl flames. A lean premixed methane/air mixture, of the equivalence ratio 0.60-0.66, is injected from a 50 mm diameter low swirl burner to a low speed co-flowing air at room temperature and pressure. The level-set G-equation is employed to simulate the inner layer flame front. Flamelet chemistry is used to determine the flame properties in the reactive zones. Mixing and heat transfer in the post-flame zone down-stream are modeled using transport equations. In addition to large eddy simulation, simultaneous 2-D laser induced fluorescence of OH and 2-D particle image velocimetry are used to characterize the basic flame structure. Laser Doppler velocimetry is employed to further analyze the flow velocity along the central axis above the burner, and 2-D filtered Rayleigh scattering is used to measure the temperature field in the lower part of the flame. A bowl-shaped, highly wrinkled turbulent flame is stabilized at a position about one-half diameter above the burner. The flame consists of two distinct parts; around the burner axis, a premixed flame with uniform mixture fraction is stabilized in the low speed flow region induced by the inflow swirl; off the axis of the burner, a stratified lean premixed flame is found in the shear layer of the flow field. Flame holes (local extinction) owing to overly lean mixtures are observed in the off-axis lean stratified part of the flame. A unified level-set G-equation is developed to model the flame holes. The basic flow and flame structure from the model simulations are compared to the laser diagnostic measurements; the height of flame stabilization (lift-off height), the mean temperature profile, and the mean axial and radial velocity components together with rms velocity components are in fairly good agreement with measurement data. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 29. |
|
|
| 30. |
- Nogenmyr, Karl-Johan, et al.
(författare)
-
Structure and stabilization mechanism of a stratified premixed low swirl flame
- 2011
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 33, s. 1567-1574
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents numerical and experimental investigations of the structure and stabilization of a low swirl turbulent stratified lean premixed methane/air flame. Large-eddy simulations are performed using a two-scalar flamelet model based on mixture fraction for predicting the stratification in the fuel/air mixture and a level-set G-function for tracking the flame. Measurements are carried out with LDV for velocity field and simultaneous PLIF of OH radicals and fuel tracer acetone to identify the structures of the flame. The leading edge flame front is observed to exhibit large-scale flame front wrinkling with a particular W-shaped front frequently occurring. This structure is formed due to the interaction of flame front with the large-scale flow motion in the inner low speed zone and the outer high-speed shear-layer of the burner. The W-structures are formed and destroyed periodically at 15 Hz. The flame stabilization is shown to be dictated by the large-scale vortex rings in the shear-layer. This flame stabilization mechanism is rather different from that found in typical bluff-body stabilized flames and high-swirl flames. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 31. |
- Nogenmyr, Karl-Johan, et al.
(författare)
-
Structure and stabilization mechanism of a stratified premixed low swirl flame
- 2010
-
Ingår i: 33rd International Symposium on Combustion.
-
Konferensbidrag (refereegranskat)abstract
- Simultaneous OH-, fuel- planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements were performed in turbulent low-swirl stratified premixed flames. Acetone was used as a fuel tracer and seeded in to the lean premixed methane/air flow. A laser at 283 nm was used for both the fuel-, and OH-PLIF measurements. For PIV two Nd:YAG lasers operating at 532 nm were used. The combined PIV/PLIF images revealed e.g. the fuel distribution, entrainment of ambient air, mixing with the air/fuel stream and the resulting stratification in thetrailing edge of the flame. Furthermore, the combined PLIF images visualized the preheat layer (> 1000K) and flame front location. Pockets of unburnt reactants were occasionally detected above the local flame front as a result from the flame wrinkling and following flame pinching. From the simultaneous PIV data flame-flow interaction was investigated including the large-scale vortex structures continuously created in the outer shear layer and its influence on the flame stabilization.
|
|
| 32. |
- Omrane, Alaa, et al.
(författare)
-
Simultaneous 2D flow velocity and gas temperature measurements using thermographic phosphors
- 2008
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 92:1, s. 99-102
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper a new approach for simultaneous 2D velocity and temperature measurements using phosphoric particles is presented. The phosphoric particles respond to the temperature changes in the flow while acting as tracers for velocity mapping. The temperature sensitive particles were seeded into a heated flow and were excited by a pulsed UV laser. The subsequent red shifted emission was detected and analyzed to infer temperature using calibration procedures for lifetime and emission spectra against temperature. The diameter of the temperature sensitive particles, usually in the range of 1-10 mu m, makes them useful for velocity measurements using particle image velocimetry (PIV). As such, simultaneous measurement of temperature and flow velocity of a gaseous flow were performed and presented.
|
|
| 33. |
- Petersson, Marcus, 1983-
(författare)
-
Beyond AMPA and NMDA: Slow synaptic mGlu/TRPC currents : Implications for dendritic integration
- 2010
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to understand how the brain functions, under normal as well as pathological conditions, it is important to study the mechanisms underlying information integration. Depending on the nature of an input arriving at a synapse, different strategies may be used by the neuron to integrate and respond to the input. Naturally, if a short train of high-frequency synaptic input arrives, it may be beneficial for the neuron to be equipped with a fast mechanism that is highly sensitive to inputs on a short time scale. If, on the contrary, inputs arriving with low frequency are to be processed, it may be necessary for the neuron to possess slow mechanisms of integration. For example, in certain working memory tasks (e. g. delay-match-to-sample), sensory inputs may arrive separated by silent intervals in the range of seconds, and the subject should respond if the current input is identical to the preceeding input. It has been suggested that single neurons, due to intrinsic mechanisms outlasting the duration of input, may be able to perform such calculations. In this work, I have studied a mechanism thought to be particularly important in supporting the integration of low-frequency synaptic inputs. It is mediated by a cascade of events that starts with activation of group I metabotropic glutamate receptors (mGlu1/5), and ends with a membrane depolarization caused by a current that is mediated by canonical transient receptor potential (TRPC) ion channels. This current, denoted ITRPC, is the focus of this thesis. A specific objective of this thesis is to study the role of ITRPC in the integration of synaptic inputs arriving at a low frequency, < 10 Hz. Our hypothesis is that, in contrast to the well-studied, rapidly decaying AMPA and NMDA currents, ITRPC is well-suited for supporting temporal summation of such synaptic input. The reason for choosing this range of frequencies is that neurons often communicate with signals (spikes) around 8 Hz, as shown by single-unit recordings in behaving animals. This is true for several regions of the brain, including the entorhinal cortex (EC) which is known to play a key role in producing working memory function and enabling long-term memory formation in the hippocampus. Although there is strong evidence suggesting that ITRPC is important for neuronal communication, I have not encountered a systematic study of how this current contributes to synaptic integration. Since it is difficult to directly measure the electrical activity in dendritic branches using experimental techniques, I use computational modeling for this purpose. I implemented the components necessary for studying ITRPC, including a detailed model of extrasynaptic glutamate concentration, mGlu1/5 dynamics and the TRPC channel itself. I tuned the model to replicate electrophysiological in vitro data from pyramidal neurons of the rodent EC, provided by our experimental collaborator. Since we were interested in the role of ITRPC in temporal summation, a specific aim was to study how its decay time constant (τdecay) is affected by synaptic stimulus parameters. The hypothesis described above is supported by our simulation results, as we show that synaptic inputs arriving at frequencies as low as 3 - 4 Hz can be effectively summed. We also show that τdecay increases with increasing stimulus duration and frequency, and that it is linearly dependent on the maximal glutamate concentration. Under some circumstances it was problematic to directly measure τdecay, and we then used a pair-pulse paradigm to get an indirect estimate of τdecay. I am not aware of any computational model work taking into account the synaptically evoked ITRPC current, prior to the current study, and believe that it is the first of its kind. We suggest that ITRPC is important for slow synaptic integration, not only in the EC, but in several cortical and subcortical regions that contain mGlu1/5 and TRPC subunits, such as the prefrontal cortex. I will argue that this is further supported by studies using pharmacological blockers as well as studies on genetically modified animals.
|
|
| 34. |
|
|
| 35. |
- Petersson, Marcus, 1983-
(författare)
-
Dendritic and axonal ion channels supporting neuronal integration : From pyramidal neurons to peripheral nociceptors
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The nervous system, including the brain, is a complex network with billions of complex neurons. Ion channels mediate the electrical signals that neurons use to integrate input and produce appropriate output, and could thus be thought of as key instruments in the neuronal orchestra. In the field of neuroscience we are not only curious about how our brains work, but also strive to characterize and develop treatments for neural disorders, in which the neuronal harmony is distorted. By modulating ion channel activity (pharmacologically or otherwise) it might be possible to effectively restore neuronal harmony in patients with various types of neural (including channelopathic) disorders. However, this exciting strategy is impeded by the gaps in our understanding of ion channels and neurons, so more research is required. Thus, the aim of this thesis is to improve the understanding of how specific ion channel types contribute to shaping neuronal dynamics, and in particular, neuronal integration, excitability and memory. For this purpose I have used computational modeling, an approach which has recently emerged as an excellent tool for understanding dynamically complex neurophysiological phenomena.In the first of two projects leading to this thesis, I studied how neurons in the brain, and in particular their dendritic structures, are able to integrate synaptic inputs arriving at low frequencies, in a behaviorally relevant range of ~8 Hz. Based on recent experimental data on synaptic transient receptor potential channels (TRPC), metabotropic glutamate receptor (mGluR) dynamics and glutamate decay times, I developed a novel model of the ion channel current ITRPC, the importance of which is clear but largely neglected due to an insufficient understanding of its activation mechanisms. We found that ITRPC, which is activated both synaptically (via mGluR) and intrinsically (via Ca2+) and has a long decay time constant (τdecay), is better suited than the classical rapidly decaying currents (IAMPA and INMDA) in supporting low-frequency temporal summation. It was further concluded that τdecay varies with stimulus duration and frequency, is linearly dependent on the maximal glutamate concentration, and might require a pair-pulse protocol to be properly assessed.In a follow-up study I investigated small-amplitude (a few mV) long-lasting (a few seconds) depolarizations in pyramidal neurons of the hippocampal cortex, a brain region important for memory and spatial navigation. In addition to confirming a previous hypothesis that these depolarizations involve an interplay of ITRPC and voltage-gated calcium channels, I showed that they are generated in distal dendrites, are intrinsically stable to weak excitatory and inhibitory synaptic input, and require spatial and temporal summation to occur. I further concluded that the existence of multiple stable states cannot be ruled out, and that, in spite of their small somatic amplitudes, these depolarizations may strongly modulate the probability of action potential generation.In the second project I studied the axonal mechanisms of unmyelinated peripheral (cutaneous) pain-sensing neurons (referred to as C-fiber nociceptors), which are involved in chronic pain. To my knowledge, the C-fiber model we developed for this purpose is unique in at least three ways, since it is multicompartmental, tuned from human microneurography (in vivo) data, and since it includes several biologically realistic ion channels, Na+/K+ concentration dynamics, a Na-K-pump, morphology and temperature dependence. Based on simulations aimed at elucidating the mechanisms underlying two clinically relevant phenomena, activity-dependent slowing (ADS) and recovery cycles (RC), we found an unexpected support for the involvement of intracellular Na+ in ADS and extracellular K+ in RC. We also found that the two major Na+ channels (NaV1.7 and NaV1.8) have opposite effects on RC. Furthermore, I showed that the differences between mechano-sensitive and mechano-insensitive C-fiber types might reside in differing ion channel densities.To conclude, the work of this thesis provides key insights into neuronal mechanisms with relevance for memory, pain and neural disorders, and at the same time demonstrates the advantage of using computational modeling as a tool for understanding and discovering fundamental properties of central and peripheral neurons.
|
|
| 36. |
- Petersson, Marcus E., et al.
(författare)
-
Differential Axonal Conduction Patterns of Mechano-Sensitive and Mechano-Insensitive Nociceptors - A Combined Experimental and Modelling Study
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:8, s. e103556-
-
Tidskriftsartikel (refereegranskat)abstract
- Cutaneous pain sensations are mediated largely by C-nociceptors consisting of both mechano-sensitive (CM) and mechano-insensitive (CMi) fibres that can be distinguished from one another according to their characteristic axonal properties. In healthy skin and relative to CMi fibres, CM fibres show a higher initial conduction velocity, less activity-dependent conduction velocity slowing, and less prominent post-spike supernormality. However, after sensitization with nerve growth factor, the electrical signature of CMi fibres changes towards a profile similar to that of CM fibres. Here we take a combined experimental and modelling approach to examine the molecular basis of such alterations to the excitation thresholds. Changes in electrical activation thresholds and activity-dependent slowing were examined in vivo using single-fibre recordings of CM and CMi fibres in domestic pigs following NGF application. Using computational modelling, we investigated which axonal mechanisms contribute most to the electrophysiological differences between the fibre classes. Simulations of axonal conduction suggest that the differences between CMi and CM fibres are strongly influenced by the densities of the delayed rectifier potassium channel (Kdr), the voltage-gated sodium channels Na(V)1.7 and Na(V)1.8, and the Na+/K+-ATPase. Specifically, the CM fibre profile required less K-dr and Na(V)1.8 in combination with more Na(V)1.7 and Na+/ K(+)AT-Pase. The difference between CM and CMi fibres is thus likely to reflect a relative rather than an absolute difference in protein expression. In support of this, it was possible to replicate the experimental reduction of the ADS pattern of CMi nociceptors towards a CM-like pattern following intradermal injection of nerve growth factor by decreasing the contribution of Kdr (by 50%), increasing the Na+/K+-ATPase (by 10%), and reducing the branch length from 2 cm to 1 cm. The findings highlight key molecules that potentially contribute to the NGF-induced switch in nociceptors phenotype, in particular NaV1.7 which has already been identified clinically as a principal contributor to chronic pain states such as inherited erythromelalgia.
|
|
| 37. |
- Petersson, Marcus E., 1983-, et al.
(författare)
-
Low-frequency summation of synaptically activated transient receptor potential channel-mediated depolarizations
- 2011
-
Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 34:4, s. 578-593
-
Tidskriftsartikel (refereegranskat)abstract
- Neurons sum their input by spatial and temporal integration. Temporally, presynaptic firing rates are converted to dendritic membrane depolarizations by postsynaptic receptors and ion channels. In several regions of the brain, including higher association areas, the majority of firing rates are low. For rates below 20 Hz, the ionotropic receptors alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and N-methyl-d-aspartate (NMDA) receptor will not produce effective temporal summation. We hypothesized that depolarization mediated by transient receptor potential (TRP) channels activated by metabotropic glutamate receptors would be more effective, owing to their slow kinetics. On the basis of voltage-clamp and current-clamp recordings from a rat slice preparation, we constructed a computational model of the TRP channel and its intracellular activation pathway, including the metabotropic glutamate receptor. We show that synaptic input frequencies down to 3-4 Hz and inputs consisting of as few as three to five pulses can be effectively summed. We further show that the time constant of integration increases with increasing stimulation frequency and duration. We suggest that the temporal summation characteristics of TRP channels may be important at distal dendritic arbors, where spatial summation is limited by the number of concurrently active synapses. It may be particularly important in regions characterized by low and irregular rates.
|
|
| 38. |
|
|
| 39. |
|
|
| 40. |
|
|
| 41. |
- Petersson, Marcus, 1983-, et al.
(författare)
-
Long-lasting small-amplitude TRP-mediated dendritic depolarizations in CA1 pyramidal neurons are intrinsically stable and originate from distal tuft regions
- 2012
-
Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 36:7, s. 2917-2925
-
Tidskriftsartikel (refereegranskat)abstract
- In several regions of the nervous system, neurons display bi- or multistable intrinsic properties. Such stable states may be subthreshold and long-lasting, and can appear as a sustained afterdepolarization. In hippocampal CA1 pyramidal neurons, small-amplitude (1 mV) long-lasting (seconds) afterdepolarizations have been reported and are thought to depend on calcium-activated nonselective (CAN) currents recently identified as transient receptor potential (TRP) channels. Continuing our previous experimental and computational work on synaptically metabotropic glutamate receptor (mGluR)-activated TRP currents, we here explore small-amplitude long-lasting depolarizations in a detailed multicompartmental model of a CA1 pyramidal neuron. We confirm a previous hypothesis suggesting that the depolarization results from an interplay of TRP and voltage-gated calcium channels, and contribute to the understanding of the depolarization in several ways. Specifically, we show that: (i) the long-lasting depolarization may be intrinsically stable to weak excitatory and inhibitory input, (ii) the phenomenon is essentially located in distal apical dendrites, (iii) induction is facilitated if simultaneous input arrives at several dendritic branches, and if calcium- and/or mGluR-evoked signals undergo summation, suggesting that both spatial and temporal synaptic summation might be required for the depolarization to occur and (iv) we also show that the integration of inputs to oblique dendrites is strongly modulated by the presence of small-amplitude long-lasting depolarizations in distal tuft dendrites. To conclude, we suggest that small-amplitude long-lasting dendritic depolarizations may contribute to sustaining neural information during behavioural tasks in cases where information is separated in time, as in trace conditioning and delay tasks.
|
|
| 42. |
- Petersson, Per, et al.
(författare)
-
An imaging system for monitoring receptive field dynamics
- 2001
-
Ingår i: Journal of Neuroscience Methods. - 1872-678X. ; 104:2, s. 123-131
-
Tidskriftsartikel (refereegranskat)abstract
- The paper describes a computerized method, termed receptive field imaging (RFI), for the rapid mapping of multiple receptive fields and their respective sensitivity distributions. RFI uses random stimulation of multiple sites, in combination with an averaging procedure, to extract the relative contribution from each of the stimulated sites. Automated multi-electrode stimulation and recording, with spike detection and counting, are performed on-line by the RFI programme. Direct user interpretation of receptive field changes is made possible by a user-friendly graphic interface. A series of imaging experiments was carried out to evaluate the functional capacity of the system. RFI was tested on the receptive fields in the nociceptive withdrawal reflex (NWR) system in the rat. RFI replicates the results obtained with conventional methods and allows the display of receptive field dynamics induced by topical spinal cord application of morphine and naloxone on a minute-to-minute time scale. Data variance was estimated, and proved to be small enough to yield a stable representation of the receptive field, thereby achieving a high sensitivity in dynamic imaging experiments. The large number of stimulation and registration sites that can be monitored in parallel permits detailed network analysis of synaptic sets, corresponding to 'connection weights' between individual neurones.
|
|
| 43. |
- Petersson, Per, et al.
(författare)
-
Properties of an adult spinal sensorimotor circuit shaped through early postnatal experience.
- 2004
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 92:1, s. 280-288
-
Tidskriftsartikel (refereegranskat)abstract
- During development, information about the three-dimensional shape and mechanical properties of the body is laid down in the synaptic connectivity of sensorimotor systems through adaptive mechanisms. This functional adaptation occurs through alteration of connection properties. Here, we characterize the differences between strong and weak connections in the nociceptive withdrawal reflex in adult decerebrate spinal rats, representing the preserved end product of the developmental adaptation process. Stronger excitatory reflex connections from the skin onto a muscle had relatively higher gain in their input-output relations, shorter onset latencies ( up to similar to 150 ms) and lower trial-to-trial variability in relation to response amplitude (SD similar to mean(1/2)) than weaker pathways. Although inhibitory and excitatory nociceptive receptive fields of a muscle overlap to some degree, the results indicate that the inhibitory input is not a major determinant of the gain distribution within the excitatory receptive field and vice versa. The N-methyl-D-aspartate ( NMDA) receptor antagonist, D-2-amino-5-phosphonovalerate (0.1 - 1 mug), applied topically on the spinal cord reduced the gain, whereas the response amplitude was mainly reduced by an absolute number by the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor antagonist, 6-nitro-7-sulfamoylbenzo(f) quinoxaline-2,3- dione ( 1 - 10 mug). The results indicate that NMDA receptors have a critical role in gain regulation in the nociceptive withdrawal reflex system. It is suggested that after normal postnatal experience-dependent adaptation, the number of connections from a given skin site onto the reflex encoding interneurons is a major determinant of the difference in gain.
|
|
| 44. |
- Petersson, Per, et al.
(författare)
-
Simultaneous PIV, OH- and fuel-PLIF measurements in a low swirl stratified turbulent lean premixed flame
- 2011
-
Ingår i: Proceedings of the 5th European Combustion Meeting.
-
Konferensbidrag (refereegranskat)abstract
- Simultaneous OH-, fuel- planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV)measurements were performed in turbulent low-swirl stratified premixed flames. The combined PIV/PLIF images revealed e.g. the fuel distribution, entrainment of ambient air, mixing with the air/fuel stream and the resulting stratification in the trailing edge of the flame. Flame-flow interaction was also investigated including the large-scale vortex structures continuously created in the outer shear layer and its influence on the flame stabilization.
|
|
| 45. |
- Petersson, Per, et al.
(författare)
-
Simultaneous PIV/PH-PLIF, Rayleigh thermometry/OH-PLIF and stereo PIV measurements in a low-swirl-flame
- 2007
-
Ingår i: Applied Optics. - 2155-3165. ; 46:19, s. 3928-3936
-
Tidskriftsartikel (refereegranskat)abstract
- The diagnostic techniques for simultaneous velocity and relative OH distribution, simultaneous temperature and relative OH distribution, and three component velocity mapping are described. The data extracted from the measurements include statistical moments for inflow fluid dynamics, temperature, conditional velocities, and scalar flux. The work is a first step in the development of a detailed large eddy simulation (LES) validation database for a turbulent, premixed flame. The low-swirl burner used in this investigation has many of the necessary attributes for LES model validation, including a simplified interior geometry; it operates well into the thin reaction zone for turbulent premixed flames, and flame stabilization is based entirely on the flow field and not on hardware or pilot flames.
|
|
| 46. |
- Pettersson-Rimgard, Belinda, et al.
(författare)
-
Ultrafast Interligand Electron Transfer in cis-[Ru(4,4’-dicarboxylate-2,2’-bipyridine)2(NCS)2]4- and Implications for Electron Injection Limitations in Dye Sensitized Solar Cells
- 2018
-
Ingår i: Chemical Science. - : RSC Publishing. - 2041-6520 .- 2041-6539. ; 9:41, s. 7958-7967
-
Tidskriftsartikel (refereegranskat)abstract
- Interligand electron transfer (ILET) of the lowest metal-to-ligand charge transfer (MLCT) state of N712 (cis-[Ru(dcb)2(NCS)2]4−, where dcb = 4,4′-dicarboxylate-2,2′-bipyridine) in a deuterated acetonitrile solution has been studied by means of femtosecond transient absorption anisotropy in the mid-IR. Time-independent B3LYP density functional calculations were performed to assign vibrational bands and determine their respective transition dipole moments. The transient absorption spectral band at 1327 cm−1, assigned to a symmetric carboxylate stretch, showed significant anisotropy. A rapid anisotropy increase (τ1 ≈ 2 ps) was tentatively assigned to vibrational and solvent relaxation, considering the excess energy available after the excited singlet–triplet conversion. Thereafter, the anisotropy decayed to zero with a time constant τ2 ≈ 240 ps, which was assigned to the rotational correlation time of the complex in deuterated acetonitrile. No other distinctive changes to the anisotropy were observed and the amplitude of the slow component at time zero agrees well with that predicted for a random mixture of MLCT localization on either of the two dcb ligands. The results therefore suggest that MLCT randomization over the two dcb ligands occurs on the sub-ps time scale. This is much faster than proposed by previous reports on the related N3 complex [Benkö et al., J. Phys. Chem. B, 2004, 108, 2862, and Waterland et al., J. Phys. Chem. A, 2001, 105, 4019], but in agreement with that found by Wallin and co-workers [J. Phys. Chem. A, 2005, 109, 4697] for the [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) complex. This suggests that electron injection from the excited dye into TiO2 in dye-sensitized solar cells is not limited by ILET.
|
|
| 47. |
- Soliman, Amira, 1980-, et al.
(författare)
-
Interdisciplinary Human-Centered AI for Hospital Readmission Prediction of Heart Failure Patients
- 2023
-
Ingår i: Caring is sharing - exploiting the value in data for health and innovation. - Amsterdam : IOS Press. - 9781643683881 ; , s. 556-560
-
Konferensbidrag (refereegranskat)abstract
- The evolution of clinical decision support (CDS) tools has been improved by usage of new technologies, yet there is an increased need to develop user-friendly, evidence-based, and expert-curated CDS solutions. In this paper, we show with a use-case how interdisciplinary expertise can be combined to develop CDS tool for hospital readmission prediction of heart failure patients. We also discuss how to make the tool integrated in clinical workflow by understanding end-user needs and have clinicians-in-the-loop during the different development stages. © 2023 European Federation for Medical Informatics (EFMI) and IOS Press.
|
|
| 48. |
- Tigerholm, Jenny, 1981-, et al.
(författare)
-
C-Fiber Recovery Cycle Supernormality Depends on Ion Concentration and Ion Channel Permeability
- 2015
-
Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 108:5, s. 1057-1071
-
Tidskriftsartikel (refereegranskat)abstract
- Following each action potential, C-fiber nociceptors undergo cyclical changes in excitability, including a period of superexcitability, before recovering their basal excitability state. The increase in superexcitability during this recovery cycle depends upon their immediate firing history of the axon, but also determines the instantaneous firing frequency that encodes pain intensity. To explore the mechanistic underpinnings of the recovery cycle phenomenon a biophysical model of a C-fiber has been developed. The model represents the spatial extent of the axon including its passive properties as well as ion channels and the Na/K-ATPase ion pump. Ionic concentrations were represented inside and outside the membrane. The model was able to replicate the typical transitions in excitability from subnormal to supernormal observed empirically following a conducted action potential. In the model, supernormality depended on the degree of conduction slowing which in turn depends upon the frequency of stimulation, in accordance with experimental findings. In particular, we show that activity-dependent conduction slowing is produced by the accumulation of intraaxonal sodium. We further show that the supernormal phase results from a reduced potassium current K-dr as a result of accumulation of periaxonal potassium in concert with a reduced influx of sodium through Na(v)1.7 relative to Na(v)1.8 current. This theoretical prediction was supported by data from an in vitro preparation of small rat dorsal root ganglion somata showing a reduction in the magnitude of tetrodotoxin-sensitive relative to tetrodotoxin - resistant whole cell current. Furthermore, our studies provide support for the role of depolarization in supernormality, as previously suggested, but we suggest that the basic mechanism depends on changes in ionic concentrations inside and outside the axon. The understanding of the mechanisms underlying repetitive discharges in recovery cycles may provide insight into mechanisms of spontaneous activity, which recently has been shown to correlate to a perceived level of pain.
|
|
| 49. |
- Tigerholm, Jenny, et al.
(författare)
-
Modeling activity-dependent changes of axonal spike conduction in primary afferent C-nociceptors
- 2014
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 111:9, s. 1721-1735
-
Tidskriftsartikel (refereegranskat)abstract
- Action potential initiation and conduction along peripheral axons is a dynamic process that displays pronounced activity dependence. In patients with neuropathic pain, differences in the modulation of axonal conduction velocity by activity suggest that this property may provide insight into some of the pathomechanisms. To date, direct recordings of axonal membrane potential have been hampered by the small diameter of the fibers. We have therefore adopted an alternative approach to examine the basis of activity-dependent changes in axonal conduction by constructing a comprehensive mathematical model of human cutaneous C-fibers. Our model reproduced axonal spike propagation at a velocity of 0.69 m/s commensurate with recordings from human C-nociceptors. Activity-dependent slowing (ADS) of axonal propagation velocity was adequately simulated by the model. Interestingly, the property most readily associated with ADS was an increase in the concentration of intra-axonal sodium. This affected the driving potential of sodium currents, thereby producing latency changes comparable to those observed for experimental ADS. The model also adequately reproduced post-action potential excitability changes (i.e., recovery cycles) observed in vivo. We performed a series of control experiments replicating blockade of particular ion channels as well as changing temperature and extracellular ion concentrations. In the absence of direct experimental approaches, the model allows specific hypotheses to be formulated regarding the mechanisms underlying activity-dependent changes in C-fiber conduction. Because ADS might functionally act as a negative feedback to limit trains of nociceptor activity, we envisage that identifying its mechanisms may also direct efforts aimed at alleviating neuronal hyperexcitability in pain patients.
|
|
| 50. |
|
|
