Measurements of zeta potential for improved understanding of controlled salinity waterflooding

Improved oil recovery (IOR) processes increase the efficiency of oil extraction from subsurface reservoirs. Controlled salinity waterflooding (CSW) is an IOR process where brine of a specific ionic composition is injected into a reservoir. However, CSW does not always yield IOR and the underlying mechanism(s) responsible remain unclear. It is generally accepted that successful CSW is associated with a shift to a more water-wet state. The wetting state is thought to be controlled by the zeta potential, a measure of the electrical potential, at the mineral and oil interfaces. This thesis explores how modifying the brine composition changes the zeta potential of these interfaces and impacts wettability in sandstones and carbonates. This is primarily done by streaming potential measurements (SPM) of natural, intact rock cores at conditions relevant to CSW. Results are discussed with specific focus on their application to CSW. Under fully water saturated conditions, the zeta potential of carbonates becomes more negative with reduction of the divalent cations Ca2+ and Mg2+. Sandstones exhibit more complex behaviour; however, the bulk clay content appears to be an important control. Following wettability alteration with crude oil, the zeta potential of carbonate samples became more positive or negative with increasing oil-wetness. The direction of change is interpreted to represent the polarity of the oil-brine zeta potential. During CSW, if the injection brine yields a mineral-brine zeta potential polarity that is the same as the oil-brine zeta potential, then IOR is observed. Determining the polarity of the oil-brine zeta potential appears critical in controlling CSW but directly measuring this under relevant conditions is challenging using conventional methods. A theoretical pore network model was developed which allows for prediction of the oil-brine zeta potential under such conditions. The model predicts that this was positive in most of the carbonate experiments. However, previous literature data from conventional methods suggest positive values are rare. Therefore, a new method to directly measure the oil-brine zeta potential was also developed. Strongly oil-wet substrates were prepared using natural porous media and coated with crude oil. The zeta potential of these substrates reflects the oil-brine zeta potential. These results show Ca2+ is a key control, however, most of the data were negative, conflicting with prior results. There is an apparent difference between the zeta potential of the ‘pristine’ oil-brine interface and that of the ‘in-situ’ oil-brine interface present in the subsurface; the latter of which appears critical in controlling CSW. Understanding the in-situ oil-brine zeta potential contributes to better design and optimisation of CSW processes to maximise oil recovery.Open Acces

Mechanical stress and deformation analyses of pressurized cylindrical shells based on a higher-order modeling

In this research, mechanical stress, static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented. The kinematic relations are developed based on higher-order sinusoidal shear deformation theory. Thickness stretching formulation is accounted for more accurate analysis. The total transverse deflection is divided into bending, shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction. The axisymmetric formulations are derived through principle of virtual work. A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions. To explore effect of thickness stretching model on the static results, a comparison between the present results with the available results of literature is presented. As an important output, effect of micro-scale parameter is studied on the static stress and strain distributio

Molecular Response in One-Photon Absorption via Natural Thermal Light vs Pulsed Laser Excitation

Photoinduced biological processes occur via one photon absorption in natural light, which is weak, CW and incoherent, but are often studied in the laboratory using pulsed coherent light. Here we compare the response of a molecule to these two very different sources within a quantized radiation field picture. The latter is shown to induce coherent time evolution in the molecule, whereas the former does not. As a result, the coherent time dependence observed in the laboratory experiments will not be relevant to the natural biological process. Emphasis is placed on resolving confusions regarding this issue that are shown to arise from aspects of quantum measurement and from a lack of appreciation of the proper description of the absorbed photon.Comment: Revised (now published) manuscript: Replaces ArXiv:1109.002

Sports review: A content analysis of the International Review for the Sociology of Sport, the Journal of Sport and Social Issues and the Sociology of Sport Journal across 25 years

The International Review for the Sociology of Sport, the Journal of Sport and Social Issues and Sociology of Sport Journal have individually and collectively been subject to a systematic content analysis. By focusing on substantive research papers published in these three journals over a 25-year time period it is possible to identify the topics that have featured within the sociology of sport. The purpose of the study was to identify the dominant themes, sports, countries, methodological frameworks and theoretical perspectives that have appeared in the research papers published in these three journals. Using the terms, identified by the author(s), that appear in the paper’s title, abstract and/or listed as a key word, subject term or geographical term, a baseline is established to reflect on the development of the sub-discipline as represented by the content of these three journals. It is suggested that the findings illustrate what many of the more experienced practitioners in the field may have felt subjectively. On the basis of this systematic, empirical study it is now possible to identify those areas have received extensive coverage and those which are under-researched within the sociology of sport. The findings are used to inform a discussion of the role of academic journals and the recent contributions made by Michael Silk, David Andrews, Michael Atkinson and Dominic Malcolm on the past, present and future of the ‘sociology of sport’

Impact of SARS-CoV-2 on elective surgical volume in Tuscany: effects on local planning and resource prioritization

No abstract availabl

Quantum transport in quantum networks and photosynthetic complexes at the steady state

Recently, several works have analysed the efficiency of photosynthetic complexes in a transient scenario and how that efficiency is affected by environmental noise. Here, following a quantum master equation approach, we study the energy and excitation transport in fully connected networks both in general and in the particular case of the Fenna-Matthew-Olson complex. The analysis is carried out for the steady state of the system where the excitation energy is constantly "flowing" through the system. Steady state transport scenarios are particularly relevant if the evolution of the quantum system is not conditioned on the arrival of individual excitations. By adding dephasing to the system, we analyse the possibility of noise-enhancement of the quantum transport.Comment: 10 pages, single column, 6 figures. Accepted for publication in Plos On

Measurement of charged particle yields from therapeutic beams in view of the design of an innovative hadrontherapy dose monitor

Particle Therapy (PT) is an emerging technique, which makes use of charged particles to efficiently cure different kinds of solid tumors. The high precision in the hadrons dose deposition requires an accurate monitoring to prevent the risk of under-dosage of the cancer region or of over-dosage of healthy tissues. Monitoring techniques are currently being developed and are based on the detection of particles produced by the beam interaction into the target, in particular: charged particles, result of target and/or projectile fragmentation, prompt photons coming from nucleus de-excitation and back-to-back γ s, produced in the positron annihilation from β + emitters created in the beam interaction with the target. It has been showed that the hadron beam dose release peak can be spatially correlated with the emission pattern of these secondary particles. Here we report about secondary particles production (charged fragments and prompt γ s) performed at different beam and energies that have a particular relevance for PT applications: 12C beam of 80 MeV/u at LNS, 12C beam 220 MeV/u at GSI, and 12C, 4He, 16O beams with energy in the 50–300 MeV/u range at HIT. Finally, a project for a multimodal dose-monitor device exploiting the prompt photons and charged particles emission will be presented

Fabrication of photothermally active poly(vinyl alcohol) films with gold nanostars for antibacterial applications.

The unique photothermal properties of non-spherical gold nanoparticles under near-infrared (NIR) irradiation find broad application in nanotechnology and nanomedicine. The combination of their plasmonic features with widely used biocompatible poly(vinyl alcohol) (PVA) films can lead to novel hybrid polymeric materials with tunable photothermal properties and a wide range of applications. In this study, thin PVA films containing highly photothermally efficient gold nanostars (GNSs) were fabricated and their properties were studied. The resulting films displayed good mechanical properties and a pronounced photothermal effect under NIR irradiation. The local photothermal effect triggered by NIR irradiation of the PVA-GNS films is highly efficient at killing bacteria, therefore providing an opportunity to develop new types of protective antibacterial films and coatings

Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and Rural Africa

peer reviewe