SOx storage and release kinetics for ceria-supported Pt

The SOx storage and release kinetics on CeO2 have been studied by lean SOx adsorption and temperature programmed desorption for different pairwise configurations of individual monolith samples, i.e., Pt/CeO2 + SiO2, Pt/SiO2 + CeO2, CeO2 + Pt/SiO2 and CeO2 + SiO2. In the case of sole ceria, SOx adsorption proceeds both via SO2 and SO3 adsorption although the latter channel is kinetically favored. Hence, the rate of SO2 oxidation is crucial for the overall SOx storage kinetics. It is also found that physical contact between Pt and ceria is important for the storage process. This is attributed to efficient transport routes for SOx (surface diffusion and spill-over processes) and/or specific adsorption sites at the platinum–ceria interface. The main route for SOx release is found to be thermal decomposition where the effect of platinum is minor, although an indirect effect cannot be ruled out. Different mechanistic scenarios for SOx adsorption are discussed, which may serve as a guide for future experiments

Circulating protein biomarkers in systemic sclerosis related pulmonary arterial hypertension: a review of published data

Pulmonary arterial hypertension (PAH) develops in 7-12% of patients with systemic sclerosis (SSc) and is associated with a 3 year survival of 52%. Early detection by screening is therefore recommended for all patients with SSc. Historically, screening has been performed using echocardiography and measurement of gas transfer. More recently the DETECT protocol, using a combination of biomarkers (including N-terminal pro-brain natriuretic peptide) and clinical parameters, has been developed. The optimal method of screening for PAH with high sensitivity and specificity is, however, not clear. Protein expression differences between different SSc disease phenotypes have been reported, and include alterations in concentration of NT-proBNP, endoglin, soluble vascular endothelial growth factor receptor 1, placenta growth factor, growth differentiation factor-15, vascular endothelial growth factor alpha, resistin-like molecule beta, and soluble thrombomodulin. This review summarizes the current knowledge of these protein changes in patients with SSc and PAH

Exhaust aftertreatment under lean conditions, regenerable SOx traps and NOx reduction catalysts

The aim of this thesis was to investigate i) potential materials for regenerable SOx traps and ii) the influence of silver distribution within Ag/Al2O3 catalysts on the selective reduction of NOx by hydrocarbons (HC-SCR). Both areas are highly relevant for present and future vehicle aftertreatment technologies for lean exhausts.In the first part, CeO2, Al2O3 and Al2O3:MgO samples, with or without Pt, were prepared and evaluated by flow-reactor measurements for SOx storage and release performance. To facilitate the understanding of the SOx adsorption mechanism, combined diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy and mass spectrometry were employed. In the second part, 2wt% Ag/Al2O3 samples were prepared and calcined at 550, 850 and 950\ub0C, respectively, in order to gain catalysts with different Ag distribution. By flow-reactor measurements, the oxidation of NO and hydrocarbons was investigated and correlated to NOx reduction performance. Moreover, X-ray photoelectron spectroscopy (XPS) was used to study dispersion and redox-properties of the silver species.The results show that Pt/CeO2 samples are efficient SOx adsorbents under normal lean exhaust temperatures, 200-500\ub0C, but also possible to regenerate at 600\ub0C under lean conditions. The SOx adsorption and regeneration properties are improved by increased Pt content at 250\ub0C. DRIFTS analysis reveal that at 250\ub0C, SOx is stored both as surface and bulk sulfates on CeO2 samples and that the presence of Pt increases the rate of bulk sulfate formation. For the Pt/CeO2 sample, both the SOx storage capacity and the rate of bulk sulfate formation are higher at 400\ub0C compared to 250\ub0C. The results from this study indicate the presence of different SOx storage sites on Pt/CeO2 samples, both regenerable and non-regenerable, but the effect of the latter seems here to be minor.The Ag/Al2O3 samples calcined at 550 and 850\ub0C reveal similar HC-SCR performance, while the sample calcined at 950\ub0C show lower NOx reduction capacity but higher activity for HC oxidation. Contrary to the samples calcined at lower temperatures, the latter sample shows ability for oxidation of NO into NO2 in the absence of hydrocarbons. XPS measurements reveal that the high temperature treatment at 950\ub0C resulted in samples with low silver dispersion and Ag species showing less redox-properties compared to the Ag/Al2O3 sample calcined at 550\ub0C

Analys av Styvhetsmätmetoder för Extracellulära Vesiklar

Extracellular vesicles are important players in cell-to-cell communication and have the potential to be used as biomarkers for decease. The mechanical properties of extracellular vesicles is an active field of research, with new methods and models being developed. In this thesis, two samples of extracellular vesicles containing different levels of membrane protein expressions are investigated using atomic force microscopy. Three models for determining stiffness are applied to the samples: the Hertz model, an adhesion angle dependent model, and the modified Canham-Helfrich model. The Hertz model indicated a higher Young’s Modulus for vesicles without membrane proteins, but with large errors. The adhesion angle dependent model did not provide high enough sensitivity to determine any difference in stiffness between the two samples. The modified Canham-Helfrich model indicated a higher bending modulus for the vesicles with membrane proteins. The results highlight the importance of taking several measurements on each vesicle, in contrast to how the method is currently applied in research.Extracellulära vesiklar är essentiella komponenter inom cell-till-cell-kommunikation, och har potentialen att kunna användas som sjukdomsmarkörer. Extracellulära vesiklars mekaniska egenskaper är ett aktivt forskningsfält där nya experimentella metoder och teoretiska modeller är under utveckling. I den här arbetet används atomkraftsmikroskopi för att undersöka de mekaniska egenskaperna av två prover av extracellulära vesiklar med olika mängd membranproteiner. Tre modeller för att utvärdera deras styvhet tillämpas: Hertz-modellen, en adhesionsvinkelberoende modell, och den modifierade Canham-Helfrichmodellen. Hertz-modellen indikerade högre elasticitetsmodul för provet med lägre antal membranprotein, men med stora fel i mätningarna. Den adhesionsvinkelbaserade modellen var inte känslig nog att påvisa några skillnader i styvhet mellan proverna. Den modifierade Canham-Helfrich-modellen indikerade att vesiklarna med membranprotein har högre böjmodul än veiklarna utan membranprotein. Resultaten understryker att det är viktigt att göra flertalet mätningar på varje vesikel, i kontrast mot hur modellen tillämpas i dagsläget

Strindberg, tiden och kulturarvet - en essä om bildningstanken

Teknik och naturvetenskap är kumulativa vetenskaper som kan bygga vidare där föregångarna slutade. Men i humanoria måste var och en börja om från början. Martin Ky/hammar finner denna tanke redan hos Strindberg och reflekterar vidare om bildningens och humanioras villkor och förutsättningar i vår tekniska kultur.Tidskriften Kronos: historia i skola och samhälle gavs ut vid Linköpings univeristet mellan åren 1988-1991.</p

Exhaust aftertreatment under lean conditions, regenerable SOx traps and NOx reduction catalysts

The aim of this thesis was to investigate i) potential materials for regenerable SOx traps and ii) the influence of silver distribution within Ag/Al2O3 catalysts on the selective reduction of NOx by hydrocarbons (HC-SCR). Both areas are highly relevant for present and future vehicle aftertreatment technologies for lean exhausts.In the first part, CeO2, Al2O3 and Al2O3:MgO samples, with or without Pt, were prepared and evaluated by flow-reactor measurements for SOx storage and release performance. To facilitate the understanding of the SOx adsorption mechanism, combined diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy and mass spectrometry were employed. In the second part, 2wt% Ag/Al2O3 samples were prepared and calcined at 550, 850 and 950\ub0C, respectively, in order to gain catalysts with different Ag distribution. By flow-reactor measurements, the oxidation of NO and hydrocarbons was investigated and correlated to NOx reduction performance. Moreover, X-ray photoelectron spectroscopy (XPS) was used to study dispersion and redox-properties of the silver species.The results show that Pt/CeO2 samples are efficient SOx adsorbents under normal lean exhaust temperatures, 200-500\ub0C, but also possible to regenerate at 600\ub0C under lean conditions. The SOx adsorption and regeneration properties are improved by increased Pt content at 250\ub0C. DRIFTS analysis reveal that at 250\ub0C, SOx is stored both as surface and bulk sulfates on CeO2 samples and that the presence of Pt increases the rate of bulk sulfate formation. For the Pt/CeO2 sample, both the SOx storage capacity and the rate of bulk sulfate formation are higher at 400\ub0C compared to 250\ub0C. The results from this study indicate the presence of different SOx storage sites on Pt/CeO2 samples, both regenerable and non-regenerable, but the effect of the latter seems here to be minor.The Ag/Al2O3 samples calcined at 550 and 850\ub0C reveal similar HC-SCR performance, while the sample calcined at 950\ub0C show lower NOx reduction capacity but higher activity for HC oxidation. Contrary to the samples calcined at lower temperatures, the latter sample shows ability for oxidation of NO into NO2 in the absence of hydrocarbons. XPS measurements reveal that the high temperature treatment at 950\ub0C resulted in samples with low silver dispersion and Ag species showing less redox-properties compared to the Ag/Al2O3 sample calcined at 550\ub0C

Analys av Styvhetsmätmetoder för Extracellulära Vesiklar

Extracellular vesicles are important players in cell-to-cell communication and have the potential to be used as biomarkers for decease. The mechanical properties of extracellular vesicles is an active field of research, with new methods and models being developed. In this thesis, two samples of extracellular vesicles containing different levels of membrane protein expressions are investigated using atomic force microscopy. Three models for determining stiffness are applied to the samples: the Hertz model, an adhesion angle dependent model, and the modified Canham-Helfrich model. The Hertz model indicated a higher Young’s Modulus for vesicles without membrane proteins, but with large errors. The adhesion angle dependent model did not provide high enough sensitivity to determine any difference in stiffness between the two samples. The modified Canham-Helfrich model indicated a higher bending modulus for the vesicles with membrane proteins. The results highlight the importance of taking several measurements on each vesicle, in contrast to how the method is currently applied in research.Extracellulära vesiklar är essentiella komponenter inom cell-till-cell-kommunikation, och har potentialen att kunna användas som sjukdomsmarkörer. Extracellulära vesiklars mekaniska egenskaper är ett aktivt forskningsfält där nya experimentella metoder och teoretiska modeller är under utveckling. I den här arbetet används atomkraftsmikroskopi för att undersöka de mekaniska egenskaperna av två prover av extracellulära vesiklar med olika mängd membranproteiner. Tre modeller för att utvärdera deras styvhet tillämpas: Hertz-modellen, en adhesionsvinkelberoende modell, och den modifierade Canham-Helfrichmodellen. Hertz-modellen indikerade högre elasticitetsmodul för provet med lägre antal membranprotein, men med stora fel i mätningarna. Den adhesionsvinkelbaserade modellen var inte känslig nog att påvisa några skillnader i styvhet mellan proverna. Den modifierade Canham-Helfrich-modellen indikerade att vesiklarna med membranprotein har högre böjmodul än veiklarna utan membranprotein. Resultaten understryker att det är viktigt att göra flertalet mätningar på varje vesikel, i kontrast mot hur modellen tillämpas i dagsläget