| 1. |
- de Mello, Vanessa D., et al.
(författare)
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Indolepropionic acid and novel lipid metabolites are associated with a lower risk of type 2 diabetes in the Finnish Diabetes Prevention Study
- 2017
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Wide-scale profiling technologies including metabolomics broaden the possibility of novel discoveries related to the pathogenesis of type 2 diabetes (T2D). By applying non-targeted metabolomics approach, we investigated here whether serum metabolite profile predicts T2D in a well-characterized study population with impaired glucose tolerance by examining two groups of individuals who took part in the Finnish Diabetes Prevention Study (DPS); those who either early developed T2D (n = 96) or did not convert to T2D within the 15-year follow-up (n = 104). Several novel metabolites were associated with lower likelihood of developing T2D, including indole and lipid related metabolites. Higher indolepropionic acid was associated with reduced likelihood of T2D in the DPS. Interestingly, in those who remained free of T2D, indolepropionic acid and various lipid species were associated with better insulin secretion and sensitivity, respectively. Furthermore, these metabolites were negatively correlated with low-grade inflammation. We replicated the association between indolepropionic acid and T2D risk in one Finnish and one Swedish population. We suggest that indolepropionic acid, a gut microbiota-produced metabolite, is a potential biomarker for the development of T2D that may mediate its protective effect by preservation of alpha-cell function. Novel lipid metabolites associated with T2D may exert their effects partly through enhancing insulin sensitivity.
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| 2. |
- Häbel, Henrike, 1987, et al.
(författare)
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Colloidal particle aggregation in three dimensions
- 2019
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 275:3, s. 149-158
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal systems are of importance not only for everyday products, but also for the development of new advanced materials. In many applications, it is crucial to understand and control colloidal interaction. In this paper, we study colloidal particle aggregation of silica nanoparticles, where the data are given in a three-dimensional micrograph obtained by high-angle annular dark field scanning transmission electron microscopy tomography. We investigate whether dynamic models for particle aggregation, namely the diffusion limited cluster aggregation and the reaction limited cluster aggregation models, can be used to construct structures present in the scanning transmission electron microscopy data. We compare the experimentally obtained silica aggregate to the simulated postaggregated structures obtained by the dynamic models. In addition, we fit static Gibbs point process models, which are commonly used models for point patterns with interactions, to the silica data. We were able to simulate structures similar to the silica structures by using Gibbs point process models. By fitting Gibbs models to the simulated cluster aggregation patterns, we saw that a smaller probability of aggregation would be needed to construct structures similar to the observed silica particle structure.
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| 3. |
- Kärrholm Peng, Fabian, 1980, et al.
(författare)
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MODELLING INJECTOR FLOW INCLUDING CAVITATION EFFECTS FOR DIESEL APPLICATIONS
- 2007
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Ingår i: ASME Fluids Engineering Conference.
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Konferensbidrag (refereegranskat)abstract
- In this paper, cavitation and pressure parameters measuredin a model diesel injector are compared to data acquired by numericalsimulations using a new code developed for the Open-FOAM platform, which uses a barotropic equation of state togetherwith the homogeneous equilibrium assumption. It is aviscid code, allowing both compressible liquid and vapour tobe modelled. The mass flow and cavitation probabilities obtainedfrom the simulations are compared to data obtained inexperiments performed at AVL’s laboratories, in which the flowthrough an almost two-dimensional nozzle was examined. Theexperimental data used include pressure profiles and cavitationimages. The model proved to be able to predict cavitation probabilities,mass flows, and the occurrence of super-cavitation inthe channel. In addition, it proved to be stable in its dependencyon physical parameters, and grid independent.
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| 4. |
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| 5. |
- Kärrholm Peng, Fabian, 1980, et al.
(författare)
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Three-Dimensional Simulation of Diesel Spray Ignition and Flame Lift-Off Using OpenFOAM and KIVA-3V CFD Codes
- 2008
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional simulations of ignition and combustion of a dieselspray were conducted. The primary goal of the work was to compare twodifferent CFD codes: OpenFOAM, an object-oriented C++ based code, andKIVA-3V. The spray is modelled by the Eulerian-Lagrangian approach inboth codes, with several common submodels. Some important sub-modelsimplemented include \emph{inter alia} aKelvin-Helmholtz/Rayleigh-Taylor (KH/RT) model for spray break-up, animproved spray collision model, and a Partially Stirred Reactor (PaSR)model for turbulence-chemistry interaction. Both CFD codes solve thechemical reaction equations in a fully coupled manner. A cubic-shaped Cartesianmesh was used in the KIVA-3V simulations, while a polyhedral meshincluding a combination of hexagonal and prism-shaped cells wasconstructed for the OpenFOAM computations.The effects of high EGR and ambient temperature on the ignition and flamelift-off processes of a diesel spray were investigated. Sandia experimentsconducted in a high-pressure and high-temperature constant-volume vessel werechosen for the simulations and validations. A single spray was injected intothe vessel, and EGR was mimicked by reducing the oxygen concentration. Thediesel reference fuel (n-heptane) was considered. For the study, a medium-sizemechanism involving 83 species and 338 reactions was employed. The mechanismwas validated using the CHEMKIN II package and the reaction rate constantswere adjusted on the basis of measurements of auto-ignition delays ofn-heptane/air mixtures in shock-tube experiments (with equivalence ratiosranging from 0.2 to 0.4 at 50 bar, and from 0.5 to 2.0 at 13.5 bar and 41.0bar), laminar flame speeds (1 atm and 3 atm), and flame structure inburner-stabilized premixed flames (1 atm).The simulations demonstrate that both CFD codes are capable of spray ignitionand combustion studies, though both show stronggrid-dependence. The numerical results show that the ignition delay,flame lift-off and combustion temperature of the spray are stronglyinfluenced by EGR and ambient gas temperature. These predictions arein agreement with measurements. Nevertheless, differences are observedbetween the results predicted by OpenFOAM and those from KIVA-3V, forexample, the flame predicted by the former is thinner and longer than that by thelatter, which requires further investigation.
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| 6. |
- Magnusson, Alf, 1958, et al.
(författare)
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A Comparison of Experiments and Numerical Calculations of Diesel Sprays
- 2004
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Ingår i: VAFSEP. ; , s. 42-47
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Validation of diesel spray behaviour is a necessity when simulating direct injected diesel combustion engines. A problem is that model fuels instead of standard diesel often must be used in both experiments and spray calculations. Therefore a study was carried out where atwo-component model fuel (IDEA-fuel) was used both in calculations and in experiments using different optical methods. Penetration and evaporation of a two-component model fuel were calculated using the FOAM C++ CFD library which allows for multi-component treatment of the liquid. The experiments were carried out in the high-pressure, high temperature spray rig at Chalmers. The injection pressure were altered between 700 and 1350 bar and injected through a single-hole nozzle with a diameter of 0.19 mm. The opticalmethods used were Mie-scattering/LIF, Schlieren/Shadowgraph and direct photography capturing the size and shape of the sprays. Also Phase Doppler Anemometry which measures droplet size and velocity in the periphery of the spray was used.The results show that the model used underestimates spray penetration and droplet size. A comparison of the measurement results indicates that by combining the methods one can achieve a good understanding of the spray characteristics.
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| 7. |
- Nordin, Elise, 1985, et al.
(författare)
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Effects of FODMAPs and Gluten on Gut Microbiota and Their Association with the Metabolome in Irritable Bowel Syndrome: A Double-Blind, Randomized, Cross-Over Intervention Study
- 2023
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Ingår i: Nutrients. - : MDPI AG. - 2072-6643 .- 2072-6643. ; 15:13
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Tidskriftsartikel (refereegranskat)abstract
- Background: A mechanistic understanding of the effects of dietary treatment in irritable bowel syndrome (IBS) is lacking. Our aim was therefore to investigate how fermentable oligo- di-, monosaccharides, and polyols (FODMAPs) and gluten affected gut microbiota and circulating metabolite profiles, as well as to investigate potential links between gut microbiota, metabolites, and IBS symptoms. Methods: We used data from a double-blind, randomized, crossover study with week-long provocations of FODMAPs, gluten, and placebo in participants with IBS. To study the effects of the provocations on fecal microbiota, fecal and plasma short-chain fatty acids, the untargeted plasma metabolome, and IBS symptoms, we used Random Forest, linear mixed model and Spearman correlation analysis. Results: FODMAPs increased fecal saccharolytic bacteria, plasma phenolic-derived metabolites, 3-indolepropionate, and decreased isobutyrate and bile acids. Gluten decreased fecal isovalerate and altered carnitine derivatives, CoA, and fatty acids in plasma. For FODMAPs, modest correlations were observed between microbiota and phenolic-derived metabolites and 3-indolepropionate, previously associated with improved metabolic health, and reduced inflammation. Correlations between molecular data and IBS symptoms were weak. Conclusions: FODMAPs, but not gluten, altered microbiota composition and correlated with phenolic-derived metabolites and 3-indolepropionate, with only weak associations with IBS symptoms. Thus, the minor effect of FODMAPs on IBS symptoms must be weighed against the effect on microbiota and metabolites related to positive health factors.
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| 8. |
- Nordin, P. A. Niklas, 1968
(författare)
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Complex Chemistry Modeling of Diesel Spray Combustion
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis illustrates the application of computational fluid dynamics (CFD) to turbulent reactive two-phase flows in piston engines. The focus of the thesis lies on numerical simulations of spray combustion phenomena with an emphasis on the modeling of turbulence/chemistry interaction effects using a detailed chemistry approach. The turbulence/chemistry interaction model accounts for the effects of turbulent micro-mixing on the chemical reaction rates. The models have been implemented in the {\bf KIVA3-V} code and successfully applied to spray combustion analysis in a constant volume and a DI Diesel engine. The limitations and difficulties of representing the spray in a Lagrangian fashion are also adressed. Three different liquid fuels have been used in the simulations: n-heptane, methanol and dimethyl ether (DME). Detailed and reduced chemical mechanisms have been developed and validated for all these fuels and reasonable agreement between experimental data and numerical simulations has been obtained.
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| 9. |
- Nordstierna, Lars, 1976, et al.
(författare)
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Comparison of release behaviour from microcapsules and microspheres
- 2010
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Ingår i: Progress in Organic Coatings. - : Elsevier BV. - 0300-9440. ; 69:1, s. 49-51
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Tidskriftsartikel (refereegranskat)abstract
- The plasticizing effect of core oil in the polymer shell of core shell particles, so-called microcapsules, was here examined. The study involved release measurements of 4-nitroanisole into aqueous solution from two types of microparticles. In the first study, a microcapsule with PMMA shell and hexadecane core was examined. The second type of particle was a homogeneous PMMA microsphere containing no oil. Experimental data were compared to models that describe release by a diffusion mechanism out from core shell particles as well as homogeneous spherical particles. Results clearly show that the alkane oil has a plasticizing effect on the PMMA shell, thereby generating a faster release of 4-nitroanisole. In both types of microparticles, the diffusion coefficients of 4-nitroanisole could be determined. The findings increase our understanding of important parameters in the microcapsule design with regard to tuning the release behaviour. Using microparticles, the ambition is to prolong the protection of paint and other coatings against fouling.
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| 10. |
- Sundell, Gustav, 1985, et al.
(författare)
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Direct observation of hydrogen and deuterium in oxide grain boundaries in corroded Zirconium alloys
- 2015
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 90, s. 1-4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Atom probe tomography has been used to the study the distribution of hydrogen and deuterium in the oxide scale of two common zirconium alloys after autoclave testing in H2O and D2O, respectively. Comparison between hydrogen and deuterium in the mass spectra allows for separation of hydrogen as a corrosion product from adsorbed H2 gas from the vacuum chamber. Enrichment of hydrogen and deuterium, as OH+ and OD+, was observed in grain boundaries. The grain boundaries were identified through segregation of iron. This lends experimental support to existing theories for the mechanism of hydrogen pick-up in zirconium alloys.
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