Michael John Adams

Supercritical water (SCW) is an effective medium for in-situ shale oil recovery. However, research related to the displacement characteristics of shale oil during SCW flooding (SCWF) has not been conducted in great depth. In the current study, molecular dynamics simulations were performed to investigate the displacement of two- and multi-component hydrocarbons (aromatics, chain alkanes, cycloalkanes, and heavy hydrocarbons) by SCW within various shale nano-slits (calcite, montmorillonite, quartz, organic), thereby systematically demonstrating the key displacement behaviors and revealing the underlying mechanisms governing the displacement performance. The results showed that efficient SCWF exhibited a three-stage pattern: Stage I was a pressure-driven initiation stage, during which the hydrocarbon concentration declined linearly with time; Stage II and Stage III were a partially miscible displacement stage and a diffusion-driven displacement stage, respectively, and the hydrocarbon concentration in these two stages followed an identical exponential decay function. Less effective SCWF involved either Stage I and a fingering-dominated Stage II, or immiscible displacement throughout the process. Each class of hydrocarbon exhibits some common displacement characteristics even in different nano-slits. Under the same operating conditions, in the calcite and organic nano-slits, fingering was dominant compared to miscibility, yielding narrow strip-like and water-in-oil flow patterns with displacement efficiencies of 83.2 and 82.3%, respectively; in the quartz and pretreated montmorillonite nano-slits, miscibility was dominant compared to fingering, yielding cone-like and band-like flow patterns with efficiencies of 92 and 96.9%, respectively. Oil-water miscibility was suppressed in these confined spaces, yet even limited dissolution markedly improved the displacement efficiency. Finally, novel kinetic models for the microscopic displacement of hydrocarbons by SCW were established.

Corneocytes, the fundamental units of the epidermis outer layer, are essential for skin’s barrier function. This study employs Atomic Force Microscopy (AFM) to explore the topographical and biomechanical properties of volar forearm cells. A detailed protocol is presented to eliminate experimental artefacts that have led to variability in reported Young’s moduli. The goal is to create a consistent material model reflecting the elastic and inelastic behaviour of corneocytes. Using standard sharp AFM probes allows for accurate cell topography capture and targeted indentation for mechanical property measurements without changing probes. The methodology for interpreting mechanical data from sharp indenters is also addressed. Results indicate that corneocytes in a dry state exhibit Young’s moduli similar to glassy organic polymers and demonstrate viscoplastic behaviour, described by the Herschel-Bulkley model. These detailed protocols enhance our understanding of skin biomechanics, potentially guiding advancements in biomimetic materials and dermatological studies.

Background: The Stratum Corneum (SC) is the first barrier of the skin. The properties of individual cells are crucial in understanding how the SC at different anatomical regions maintains a healthy mechanical barrier. The aim of the current study is to present a comprehensive description of the maturation and mechanical properties of superficial corneocytes at different anatomical sites in the nominal dry state. Materials and methods: Corneocytes were collected from five anatomical sites: forearm, cheek, neck, sacrum and medial heel of 10 healthy young participants. The surface topography was analysed using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The level of positive‐involucrin cornified envelopes (CEs) and desmoglein‐1 (Dsg1) were used as indirect measures of immature CEs and corneodesmosomes, respectively. In addition, AFM nanoindentation and stress‐relaxation experiments were performed to characterise the mechanical properties. Results: Volar forearm, neck and sacrum corneocytes presented similar topographies (ridges and valleys) and levels of Dsg1 (13–37%). In contrast, cheek cells exhibited circular nano‐objects, while medial heel cells were characterized by villi‐like structures. Additionally, medial heel samples also showed the greatest level of immature CEs (32–56%, p < 0.001) and Dsg1 (59–78%, p < 0.001). A large degree of inter‐subject variability was found for the Young's moduli of the cells (0.19–2.03 GPa), which was correlated with the level of immature CEs at the cheek, neck and sacrum ( p < 0.05). Conclusion: It is concluded that a comprehensive study of the mechanical and maturation properties of corneocytes may be used to understand the barrier functions of the SC at different anatomical sites.