Mechano-chemical interface processes with application to rock weathering

The object of this thesis is to study the coupling of chemical and physical processes during rock weathering. Stresses which are produced due to chemical reactions can lead to fracture propagation which in turn increases the transport of reactants and the reactive surface area, and this coupling can therefore control overall rate of weathering. It is shown that weathering induced expansion can drive a hierarchical fracture process where originally intact rock is broken into progressively smaller blocks. Studies are also made on the micrometer scale in order to gain a more fundamental understanding both of fracture propagation and reaction induced stresses. It was found experimentally that the local chemistry has a profound effect on the velocity of fracture propagation in single crystals of calcite when stresses are applied slowly. This is related to the interaction between the mineral surface and water. Experiments on the so-called force of crystallisation showed that the process in which a crystal growing from a supersaturated solution can push on a neighbouring wall is more complex than previously assumed. This has implications for the understanding of how stresses evolve when crystals grow in a porous material

Volume changes in solids induced by chemical alteration

It is a fundamental issue in material science to understand the mechanical effects of chemical alterations. Often the replacement of one chemical component by another in a solid induces local volume changes. Experiments on chemical alteration in “model” materials reveal an intricate dynamics of elastic stress build-up, fracturing and creation of porosity. In that way permeability is increased and provides a positive feedback on the process rate. Important examples from geology are presented

Public-private collaboration : innovation in the health sector : a qualitative study of health app providers' encounters with regulatory requirements and an immature market

Bakgrunn: Helse- og omsorgstjenesten står overfor mange utfordringer i tiden som kommer, og innføring av digital teknologi anses som en viktig forutsetning for å imøtekomme disse. Bruken av helseapper er økende blant befolkningen, og dette har vært et uregulert landskap med stor risiko for både innbyggere og myndigheter. Gjennom prosjektet “Tryggere helseapper”, skal myndighetene i samarbeid med fem helseapp-leverandører utvikle et evalueringsrammeverk, som både sikrer innbyggere trygge og effektive apper, og samtidig tilrettelegge for god næringsutvikling og skape et hjemmemarked for helseapp-leverandører. Hensikt: Formålet med denne studien er å undersøke hvordan et offentlig-privat samarbeid kan bidra til verdiskapning i helsesektoren, og hvorvidt de regulatoriske kravene setter føringer for innovasjonskraften hos helseapp-leverandører. Følgelig vil vi besvare problemstillingen: «Hvordan har norske helsemyndigheter i samarbeid med private aktører fremmet innovasjon og implementering av helseapper i helsesektoren, og hvilke innvirkninger har regulatoriske føringer hatt for prosessen?» Metode: Dette er en kvalitativ studie, der vi ved bruk av eksplorerende design har fremskaffet empiri gjennom en fenomenologisk tilnærming. Metodetriangulering gjennom deltagende observasjon og individuelle semistrukturerte intervju legger grunnlaget for datainnsamlingen. Totalt 14 individuelle dybdeintervju er gjennomført med helseapp-leverandører, helsemyndigheter og en helseklynge, hvilket legger grunnlaget for oppgavens besvarelse. Funn og implikasjoner: Studien avdekker at helseapp-leverandører opplever stor usikkerhet knyttet til kommersialisering og etterlevelse av de regulatoriske kravene. Tryggere helseapper og evalueringsrammeverket er med på å øke forutsigbarheten og markedspotensialet for leverandørene. Økt samhandling mellom aktørene i sektoren, anerkjennelse av leverandørenes finansielle situasjon, etablering av en råd- og veiledningstjeneste og økt fokus på interoperabilitet er likevel forbedringsområder studiens funn kaster lys over.Background: The health sector faces many future challenges, and the introduction of digital technology is considered an important prerequisite for meeting these. The use of health apps is increasing among the population, and this has been an unregulated area with great risk for both consumers and health authorities. Through the project Tryggere helseapper (Safer health apps), the health authorities have collaborated with five health app providers to develop an evaluation framework, which ensures secure and efficient apps. Furthermore, it will facilitate good business development and create a domestic market for health app providers. Purpose:The purpose of this study is to investigate how public-private collaborations can contribute to value creation in the health sector, and whether the regulatory requirements influence the process of innovation for health app providers. Consequently, we will answer the question: “How have the health authorities, in collaboration with providers, promoted innovation and implementation of health apps in the health sector, and what impact do regulatory guidelines have on this process?” Method: A qualitative design was used, where 14 in-depth interviews were collected. With an exploratory research design and through a phenomenological approach, empirical data were obtained. The data was collected through participatory observation and individual semistructured interviews with informants from the health authorities, health app providers and a health innovation cluster. Findings and implications: The study reveals that health providers experience considerable uncertainty related to commercialisation and compliance with the regulatory requirements. Tryggere helseapper and the evaluation framework increased predictability and market potential for providers. However, some areas of improvement are improved collaboration between organizations in the sector, recognition of the providers financial situation, establishment of an advisory and guidance service and increased focus on interoperability.M-E

The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

Chemically activated processes of subcritical cracking in calcite control the time-dependent strength of this mineral, which is a major constituent of the Earth's brittle upper crust. Here experimental data on subcritical crack growth are acquired with a double torsion apparatus to characterize the influence of fluid pH (range 5–7.5) and ionic strength and species (Na2SO4, NaCl, MgSO4, and MgCl2) on the propagation of microcracks in calcite single crystals. The effect of different ions on crack healing has also been investigated by decreasing the load on the crack for durations up to 30 min and allowing it to relax and close. All solutions were saturated with CaCO3. The crack velocities reached during the experiments are in the range 10−9–10−2 m/s and cover the range of subcritical to close to dynamic rupture propagation velocities. Results show that for calcite saturated solutions, the energy necessary to fracture calcite is independent of pH. As a consequence, the effects of fluid salinity, measured through its ionic strength, or the variation of water activity have stronger effects on subcritical crack propagation in calcite than pH. Consequently, when considering the geological sequestration of CO2 into carbonate reservoirs, the decrease of pH within the range of 5–7.5 due to CO2 dissolution into water should not significantly alter the rate of fracturing of calcite. Increase in salinity caused by drying may lead to further reduction in cracking and consequently a decrease in brittle creep. The healing of cracks is found to vary with the specific ions present

An experimental study of the carbonation of serpentinite and partially serpentinised peridotites

In situ sequestration of CO2 in mantle peridotites has been proposed as a method to alleviate the amount of anthropogenic CO2 in the atmosphere. This study presents the results of 8-month long laboratory fluid-rock experiments on representative mantle rocks from the Oman-United Arab Emirates ophiolite to investigate this process. Small core samples (3 cm long) were reacted in wet supercritical CO2 and CO2-saturated brine at 100 bar and 70◦C. The extent of carbonate formation, and hence the degree of carbon sequestration, varied greatly depending on rock type, with serpentinite (lizardite-dominated) exhibiting the highest capacity, manifested by the precipitation of magnesite MgCO3 and ferroan magnesite (Mg,Fe)CO3. The carbonate precipitation occurred predominantly on the surface of the core and subordinately within cross-cutting fractures. The extent of the CO2 reactions appeared to be principally controlled by the chemical and mineralogical composition of the rock, as well as the rock texture, with all these factors influencing the extent and rate of mineral dissolution and release of Mg and Fe for subsequent reaction with the CO2. It was calculated that ≈0.7 g of CO2 was captured by reacting ≈23 g of serpentinite, determined by the mass of magnesite formed. This equates to ≈30 kg CO2 per ton of host rock, equivalent to ≈3% carbonation in half a year. However, recycling of carbonate present in veins within the original rock sample could mean that the overall amount is around 2%. The increased reactivity of serpentinite was associated with preferential dissolution of more reactive types of serpentine minerals and brucite that were mainly present in the cross-cutting veins. The bulk of the serpentinite rock was little affected. This study, using relatively short term experiments, suggests that serpentinite might be a good host rock for CO2 sequestration, although long term experiments might prove that dunite and harzburgite could be as effective in an engineered system of CCSM. Wet scCO2 proved to be chemically more aggressive than CO2-saturated brine and its ingress along fractures and grain boundaries resulted in greater host rock dissolution and subsequent carbonate precipitation

Porosity and permeability development in compacting chalks during flooding of nonequilibrium brines: Insights from long-term experiment

We report the complete chemical alteration of a Liège outcrop chalk core resulting from a 1072 flow-through experiment performed during mechanical compaction at 130°C. Chemical rock-fluid interactions alter the volumetric strain, porosity, and permeability in a nontrivial way. The porosity reduced only from 41.32% to 40.14%, even though the plug compacted more than 25%. We present a novel analysis of the experimental data, which demonstrates that the geochemical alteration does not conserve the volume of the solids, and therefore, the strain is partitioned additively into a pore volume and solid volume component. At stresses beyond yield, the observed deformation can be explained by grain reorganization reducing the pore space between grains and solid volume changes fromthe rock-fluid interactions. Themechanical and chemical effects are discussed in relation to the observed permeability development.publishedVersio