| 1. |
- Almberg, Wah-Sui
(författare)
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Modelling Epidemic Influenza : A Novel Approach
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modellering av dynamiska förlopp i socio-biologiska komplexa system är långt ifrån trivialt. Behovet av fördjupad förståelse av sådana förlopp är många gånger stort. Vi har presenterat ett oortodoxt förslag på hur spridning av influensa i mänsklig population kan beskrivas och simuleras. Traditionellt använder man sig i huvudsak av två typer av modeller. Den ena bygger på matematiska strukturer där dynamiken beskrivs av kontinuerliga differentialförlopp mellan ett fåtal grovt uppdelade sektioner av populationen. Den andra bygger på diskreta förlopp inom visualiserade kontaktnätverk där varje enskild individ i populationen är representerad. Båda dessa metoder har styrkor såväl som svagheter. Bland svagheterna kan man framförallt lyfta fram svårigheterna med att förklara de flesta av influensans observerade epidemiologiska karaktärsdrag. Ett flertal idéer har framlagts för att förklara dessa anomalier. Bland dessa finns en hypotes som trots sin enkelhet skulle kunna förklara en majoritet av de epidemiologiska karaktärsdragen. Problemet med denna hypotes är dock att man inte kunnat hitta empiriska belägg för den. Vi tror att man kan nå närmare en lösning genom att omtolka signifikansen hos denna hypotes och den epidemiologiska karaktäristikan inom ramen för en annorlunda naturvetenskaplig ontologi. Denna omtolkning visar på en informationsbaserad såväl som fysiskt baserad verklighet. Vi menar då inte det traditionella informationsbegreppet som Claude Shannons teoretiserande bygger på, utan David Bohms `aktiva information', där informationen utgör en objektiv aktiv del av naturen, något som existerar oberoende av ett vetande medvetande eller en observatör. Bohm har gett den aktiva informationen en formell struktur i hans teori om det han kallar för `the implicate order'. Tillsammans med Basil Hiley visade han även att kvantmekaniken kan tolkas på ett sådant sätt att aktiv information utgör en fundamental aspekt av teorin, och att den därigenom även förenklas. Baserat på observationer som gjorts och våra resonemang har vi pekat på att en förståelse av epidemiologiska förlopp kanske kan nås genom att använda ett teoretiskt ramverk grundat på aktiv information. I en planerad kommande doktorsavhandling avser vi att presentera en matematisk modell som ytterligare kan underbygga vår hypotes.
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| 2. |
- Arne, Mats, 1954-
(författare)
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Chronic Obstructive Pulmonary Disease : Patients´ Perspectives, Impact of the Disease and Utilization of Spirometry
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to describe subjects with chronic obstructive pulmonary disease (COPD) from different perspectives. Focus was on patients at the time of diagnosis, impact of the disease in comparison to other chronic diseases, factors associated with good health and quality of life (QoL), and diagnostic spirometry in clinical practice. Methods: Qualitative method, grounded theory, was used to analyse patients´ perspectives at the time of diagnosis in a primary care setting (n=10). Public health surveys in the general population were used to compare chronic diseases (n=10,755) and analyse factors associated with health outcomes in COPD (n=1,475). Medical records and spirometry reports, from primary and secondary care, were analysed to assess diagnosis of COPD in clinical practice (n=533). Results: In clinical practice, 70% of patients at the time of diagnosis of COPD lacked spirometry results confirming the diagnosis. Factors related to consequences of smoking, shame and restrictions in physical activity (PA) in particular, were described by patients at the time of diagnosis of COPD. In general subjects with COPD (84%), rheumatoid arthritis (74%) and diabetes mellitus (72%) had an activity level considered too low to maintain good health. In COPD, the most important factor associated with good health and quality of life was a high level of PA. Odds ratios (OR (95%CI)) varied from 1.90 (1.47-2.44) to 7.57 (4.57-12.55) depending on the degree of PA, where subjects with the highest PA level had the best health and QoL. Conclusions: Subjects with COPD need to be diagnosed at an early stage, and health professionals should be aware that feelings of shame could delay patients from seeking care and thus obtaining a diagnosis. The use of spirometry and the diagnostic quality should be emphasised. In patients with COPD greater attention should be directed on increasing the physical activity level, as patients with a low level of physical activity display worse health and quality of life.
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| 3. |
- Zou, Yiming, 1985-
(författare)
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The Effect of Various Dopants on Diamond Growth : A Combined Experimental & Theoretical Approach
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diamond is a unique material with many exceptional properties. It has therefore been proven to be an important material for many applications. Moreover, the introduction of dopant species into the gas phase during the CVD growth process has been shown to strongly influence not only the properties and morphology of diamond, but also the growth rate. The purpose with the theoretical part of the present study has been to support and explain the experimental observations regarding the effect of various dopants (nitrogen, phosphorous, sulphur, and boron) on the diamond growth rate. Commonly observed H-terminated diamond surfaces [(111), (110) and (100)-2×1], were thereby carefully investigated using density functional theory under periodic boundary conditions. Based on the assumption that the hydrogen abstraction reaction is the growth rate-limiting step, both the thermodynamic and kinetic aspects of the diamond growth process were found to be severely affected by various dopants. More specifically, the results showed that nitrogen and phosphorous dopants (positioned within the 2nd, 3rd or 4th carbon layer) will cause an enhancement in the growth rate (as compared with non-doped situations). On the other hand, any growth rate improvement does only occur when positioning boron in the 2nd, and sulphur in the 4th, atomic carbon layer. With boron, and sulphur, positioned within the other atomic carbon layers, the growth rates were observed to decrease. In addition, the main purpose with the experimental part of the present study has been to investigate the effect of one specific dopant precursor (TMB) on the boron-doped diamond growth process. The result has shown that the increasing mass flow of TMB will not affect the mechanism of the HFCVD growth process of boron doped diamond. However, a linear boron carrier concentration in the diamond film vs. mass flow rate of TMB was observed.
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| 4. |
- Böőr, Katalin
(författare)
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Chemical vapor deposition of hard coatings : Development of W(C,N) coatings for cemented carbide and TiN deposition on a CoCrFeNi substrate
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is a constant need for cutting tool material development to be able to machine new materials and improve the metal cutting efficiency. Inserts of indexable cutting tools usually consist of WC-Co cemented carbide (cc) with μm thick layers of ceramic coatings. Chemical vapor deposition (CVD) is a commonly used method for the synthesis of such coatings and this technique was also used in this thesis.The first part of the thesis focuses on a CoCrFeNi substrate, a multi-component alloy previously suggested as an alternative binder phase instead of Co in cc. Titanium nitride (TiN) is typically the first CVD coating layer on cc and therefore the chemical stability of CoCrFeNi in CVD of TiN using TiCl4, N2 and H2 precursors at 850–950 °C was studied. CoCrFeNi was stable in the CVD processes although small amounts of Cr were detected in the grain boundaries and on the top surface of the TiN coating deposited at 950 °C. Thermodynamic calculations were used to explain the experimental observations.In the second part of the thesis W(C,N) coatings were developed by CVD. The motivations behind the CVD of W(C,N) coatings were an expected compressive stress due to a favorable match between the thermal behavior of the coating and that of the cc substrate, and a high coating toughness due to the expected strong metallic character of the coating.A CVD process window was determined for the deposition of columnar hexagonal W(C,N) coatings at a low total pressure as a function of the WF6, CH3CN and H2 precursor partial pressures and the deposition temperature. Electron microscopy, diffraction techniques, spectroscopic methods and ion beam analyses were used to characterize the coatings. Correlations between the microstructure, texture and process parameters were found.The mechanical and tribological performances of the W(C,N) coatings were also investigated. The coatings had a high nanohardness of about 40 GPa and showed indications of a high toughness. The abrasive wear mechanism was primarily micro cutting or plowing. The coatings had good adhesion to the cc substrate.
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| 5. |
- Fondell, Mattis, 1984-
(författare)
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Synthesis and Characterisation of Ultra Thin Film Oxides for Energy Applications
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes studies of materials which can be exploited for hydrogen production from water and sunlight. The materials investigated are maghemite (γ-Fe2O3), magnetite (Fe3O4) and especially hematite (α-Fe2O3), which is an iron oxide with most promising properties in this field. Hematite has been deposited using Atomic Layer Deposition (ALD) - a thin-film technique facilitating layer-by-layer growth with excellent thickness control and step coverage. The iron oxides were deposited using bis-cyclopentadienyl iron (Fe(Cp)2) or iron pentacarbonyl (Fe(CO)5) in combination with an O2 precursor. Since it is crucial to have good control of the deposition process, the influence of substrate, process temperature, precursor and carrier gas have been investigated systematically. By careful control of these deposition parameters, three polymorphs of iron oxide could be deposited: hematite (α-Fe2O3), maghemite (γ-Fe2O3) and magnetite (Fe3O4).The deposited materials were characterized using X-ray Diffraction, Raman and UV-VIS Spectroscopy, and Scanning Electron Microscopy. Hard X-ray Photoelectron Spectroscopy (HAXPES) was also used, since it is a non-destructive, chemically specific, surface sensitive technique – the surface sensitivity resulting from the short mean escape depth of the photoelectrons. The depth probed can be controlled by varying the excitation energy; higher photoelectron energies increasing the inelastic mean-free-path in the material.HAXPES studies of atomic diffusion from F-doped SnO2 substrates showed increased doping levels of Sn, Si and F in the deposited films. Diffusion from the substrate was detected at annealing temperatures between 550 °C and 800 °C. Films annealed in air exhibited improved photocatalytic behavior; a photocurrent of 0.23 mA/cm2 was observed for those films, while the as-deposited hematite films showed no photo-activity whatsoever.The optical properties of low-dimensional hematite were studied in a series of ultra-thin films (thicknesses in the 2-70 nm range). The absorption maxima were shifted to higher energies for films thinner than 20 nm, revealing a different electronic structure in thin films.
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| 6. |
- Hedin, Allan, et al.
(författare)
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Corrosion of copper in pure O2-free water?
- 2018
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 137, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Copper exposed to pure, O-2-free water for several months in glass- and metal-contained, well-controlled systems shows no evidence of corrosion, either through hydrogen evolution or through the occurrence of oxidized copper. The results contradict the interpretation of recent experiments where it has been claimed that copper corrodes in pure, O-2-free water far above the very limited extent predicted by established thermodynamic data. Reasons for the different experimental outcomes are discussed. Experimental and theoretical efforts to identify hitherto unknown, potentially corrosion driving species of the Cu-O-H system and studies of copper/water surface reactions are reviewed as background for the present study.
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| 7. |
- Karlsson, Marjam, 1975-
(författare)
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Nano-porous Alumina, a Potential Bone Implant Coating
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes a method of growing a highly adherent nano-porous alumina coating on titanium implant materials, a design which might be useful in hard tissue replacement. Alumina layers were formed by anodisation of aluminium, which had been deposited on titanium and titanium alloys by electron beam evaporation. Mechanical testing showed the coatings’ shear and tensile strength to be ~20MPa and ~10MPa respectively. Human osteoblasts were cultured on purchased membranes, produced in the same way with similar characteristics as the coating mentioned above. Cell viability, proliferation and phenotype were assessed by measuring redox reactions, DNA, tritiated thymidine incorporation and alkaline phosphatase production. Results showed normal osteoblastic growth patterns with increasing cell numbers the first two weeks after which cell growth decreased and alkaline phosphatase production increased, indicating that osteoblastic phenotype was retained on the alumina. Flattened cell morphology with filipodia attached to the pores of the material was seen. Implants frequently trigger inflammatory responses due to accumulation and activation of cells such as polymorphonuclear granulocytes (PMN), also called neutrophils. Activation and morphology of human PMN in response to nano-porous alumina with two pore sizes (20 and 200 nm) was investigated by luminol-amplified chemiluminescence, granule enzyme deposition measurement, optical and scanning electron microscopy. Activation was observed on both membrane types, however less pronounced on the 200 nm alumina. For both membranes a decrease in activation was seen after coating with fibrinogen, collagen I and serum (more pronounced for the two latter). On fibrinogen-coated alumina many flattened cells were observed, indicating frustrated phagocytosis. Finally when culturing osteoblasts on non-coated and collagen-coated membranes (after exposure to PMN) many more cells had established on the protein-coated surface after 24 h. The overall results indicate that it might be possible to produce a novel bone implant coating by anodisation of aluminium deposited on titanium and that this material will support osteoblast adhesion and proliferation. Furthermore neutrophil activation can be suppressed when coating the alumina with collagen I, which is beneficial considering the fact that this protein also is essential for bone formation.
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| 8. |
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| 9. |
- Öhman, Sebastian, 1991-
(författare)
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Reaching Kinetic Selectivities : In Pursuing Novel Ternary Oxide Coatings, and Beyond
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Kinetically driven synthesis pathways have the potential to allow new ways to develop materials and phases with much-improved properties. This particularly concerns metastable and multicomponent phases that require a selective kinetic targeting during the synthesis to circumvent the formation of thermodynamically stable products. Thin film deposition techniques, including chemical vapour deposition (CVD), can offer this selectivity. However, conventional CVD relies heavily on halide-based precursors, which are corrosive, toxic, and typically require high deposition temperatures. Moreover, the significant variations in their displayed vapour pressures, reaction routes, and reaction rates impede their chemical compatibilities, thus limiting the prospects of making novel multicomponent coatings, especially mixed-metal ones. Therefore, there is a need to find new types of precursors that may mitigate the drawbacks of halides, which also can strengthen CVD as a technique for both existing and future-emerging technologies.In light of this, this thesis explores the simultaneous use of metal-organic precursors in synthesising and designing novel chemically vapour-deposited coatings. The ternary Al2TiO5 phase, renowned for its good refractory properties and low-to-negative thermal expansion, has been synthesised, which is typically challenging by other approaches. By combining aluminium and titanium isopropoxide in an in-house built CVD reactor, a selective targeting of the phase can be made that avoids stable binary phase formations. The role of local coordination in the phase formations is expressed by discovering unconventional phases in the Al–Ti–O system, such as Al6Ti2O13 and Al16Ti5O34. All coatings were amorphous as-deposited and readily crystallised at lower temperatures than those typically suggested by pseudobinary phase diagrams. In situ X-ray diffraction studies revealed that the crystallisation process was predominantly nucleation-controlled rather than governed by diffusion. The diminishing role of diffusion was also corroborated by subsequent studies using additional in situ analytical techniques, including hard X-ray photoelectron spectroscopy (HAXPES), Rutherford backscattering spectrometry (RBS), and heating in a transmission electron microscope (TEM). Combined, these techniques show that the amorphous-to-crystalline transformation occurs through a displacive (diffusionless) transformation. Based on the results, it can be inferred that short-range structural displacements by oxygen are essentially required to spur nucleation and subsequent crystallisation. Performed theoretical calculations and molecular dynamics simulations support this notion, which also highlights the potential involvement of oxygen vacancies during the crystallisation and co-formation of Al6Ti2O13 and Al16Ti5O34 beyond Al2TiO5.The coherent results of this thesis emphasise situations where kinetics – rather than thermodynamics – may control the phase selection and microstructural evolution of CVD coatings. It is proposed that the findings of this doctoral work may contribute to expanding the capabilities of CVD as a technique and the rational synthesis of inorganic materials in general, especially in terms of new functional oxides.
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| 10. |
- Öhman, Sebastian, 1991-, et al.
(författare)
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Selective kinetic growth and role of local coordination in forming Al2TiO5-based coatings at lower temperatures
- 2021
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Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 2:17, s. 5737-5751
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Tidskriftsartikel (refereegranskat)abstract
- Negative thermal expansion is an elusive property found among certain materials, whose potential applications have remained limited due to the many challenges faced in their synthesis. Herein, we report the successful formation of aluminium titanate-based coatings (Al2TiO5), a material renowned for its low-to-negative thermal expansion, by the co-deposition of aluminium-isopropoxide and titanium-isopropoxide in a hot-wall chemical vapour deposition instrument. While coatings grown at 450 °C were amorphous as-deposited, a short-range order into the Al2TiO5-phase was found and analysed by using Raman spectroscopy. Upon subsequent annealing at 700 °C for 3 hours, crystalline coatings were achieved without forming any binary phases. The selective synthesis of the Al2TiO5 phase is ascribed to the precursors’ inherent chemical similarities, resulting in a kinetic targeting of this phase and a short-range homogeneity, entailing its preferred crystallisation. The role of local coordination is expressed by demonstrating the formation of intergrowth phases ascribed to lower coordinating interstices in the compound. Both the formation and crystallisation temperatures reported herein, as well as the timescales needed for the synthesises, are considerably lower than any conventional adopted solid-state techniques used so far to attain the Al2TiO5 phase.
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