On the validity of the “thin” and “thick” double-layer assumptions when calculating streaming currents in porous media

We find that the thin double layer assumption, in which the thickness of the electrical diffuse layer is assumed small compared to the radius of curvature of a pore or throat, is valid in a capillary tubes model so long as the capillary radius is >200 times the double layer thickness, while the thick double layer assumption, in which the diffuse layer is assumed to extend across the entire pore or throat, is valid so long as the capillary radius is >6 times smaller than the double layer thickness. At low surface charge density (0.5 M) the validity criteria are less stringent. Our results suggest that the thin double layer assumption is valid in sandstones at low specific surface charge (<10 mC· m -2), but may not be valid in sandstones of moderate- to small pore-throat size at higher surface charge if the brine concentration is low (<0.001 M). The thick double layer assumption is likely to be valid in mudstones at low brine concentration (<0.1 M) and surface charge (<10 mC· m -2), but at higher surface charge, it is likely to be valid only at low brine concentration (<0.003 M). Consequently, neither assumption may be valid in mudstones saturated with natural brines. Copyright © 2012 Matthew D. Jackson and Eli Leinov

A Case Report of Multiple Aseptic Facial and Spinal Abscesses in a 45-Year-Old with Inflammatory Bowel Disease

INTRODUCTION Sterile abscess syndrome is a rarely described entity that is often associated with auto-inflammatory disorders. Although clinically similar to septic abscesses, sterile abscesses are known to be unaffected by antibiotic regimens and instead highly sensitive to steroids. The association of sterile abscesses with inflammatory bowel disease has been well-described. The majority of sterile abscess syndromes described in the literature are intraabdominal abscesses related to a primary gastrointestinal inflammatory disease. We describe a unique case of extra-abdominal sterile abscess syndrome associated with inflammatory bowel disease presenting as facial and paraspinal lesions

Zeta potential of intact natural limestone: Impact of potential-determining ions Ca, Mg and SO4

We report measurements of the zeta potential on intact limestone samples obtained using the streaming potential method (SPM), supplemented by the more ubiquitous electrophoretic mobility method (EPM). The effect of the potential-determining ions (PDI) Ca, Mg and SO4, and the total ionic strength controlled by NaCl concentration, is investigated over the range typical of natural brines. We find that the zeta potential varies identically and linearly with calcium and magnesium concentration expressed as pCa or pMg. The zeta potential also varies linearly with pSO4. The sensitivity of the zeta potential to PDI concentration, and the IEP expressed as pCa or pMg, both decrease with increasing NaCl concentration. We report considerably lower values of IEP than most previous studies, and the first observed IEP expressed as pMg. The sensitivity of the zeta potential to PDI concentration is lower when measured using the SPM compared to the EPM, owing to the differing location of the shear plane at which the zeta potential is defined. SPM measurements are more appropriate in natural porous samples because they reflect the mineral surfaces that predominantly interact with the adjacent fluids. We demonstrate that special cleaning procedures are required to return samples to a pristine zeta potential after exposure to PDIs. We apply our results to an engineering process: the use of modified injection brine composition to increase oil recovery from carbonate reservoirs. We find a correlation between an increasingly negative zeta potential and increased oil recovery

NICU Poster - 2019

NICU Poster - 2019https://scholarlycommons.libraryinfo.bhs.org/research_education/1006/thumbnail.jp

Breaking down barriers to eye care for Indigenous people: A new scheme for delivery of eye care in Victoria

This report describes the implementation of and outcomes from a new spectacle subsidy scheme and de-centralised care options for Aboriginal and Torres Strait Islander peoples in Victoria, Australia. The Victorian Aboriginal Spectacle Subsidy Scheme (VASSS) commenced in 2010, as an additional subsidy to the long-established Victorian Eyecare Service (VES). The Victorian Aboriginal Spectacle Subsidy Scheme aimed to improve access to and uptake of affordable spectacles and eye examinations by Indigenous Victorians. The scheme is overseen by a committee convened by the Victorian Government's Department of Health and Human Services and includes eye-health stakeholders from the Aboriginal community and government, not-for-profit, university and Aboriginal communities. Key features of the Victorian Aboriginal Spectacle Subsidy Scheme include reduced and certain patient co-payments of $10, expanded spectacle frame range, broadened eligibility and community participation in service design and implementation. We describe the services implemented by the Australian College of Optometry (ACO) in Victoria and their impact on access to eye-care services. In 2014, optometric services were available at 36 service sites across Victoria, including 21 Aboriginal Health Services (AHS) sites. Patient services have increased from 400 services per year in 2009, to 1,800 services provided in 2014. During the first three years of the Victorian Aboriginal Spectacle Subsidy Scheme program (2010 to 2013), 4,200 pairs of glasses (1,400 pairs per year) were provided. Further funding to 2016/17 will lift the number of glasses to be delivered to 6,600 pairs (1,650 per year). This compares to population projected needs of 2,400 pairs per year. Overcoming the barriers to using eye-care services by Indigenous people can be difficult and resource intensive; however the Victorian Aboriginal Spectacle Subsidy Scheme provides an example of positive outcomes achieved through carefully designed and targeted approaches that engender sector and stakeholder support. Sustained support for the Victorian Aboriginal Spectacle Subsidy Scheme at a level that meets population needs is an ongoing challenge

Effective flow properties of heterolithic, cross-bedded tidal sandstones: Part 1. Surface-based modeling

Tidal heterolithic sandstones are commonly characterized by millimeter- to centimeter-scale intercalations of mudstone and sandstone. Consequently, their effective flow properties are poorly predicted by (1) data that do not sample a representative volume or (2) models that fail to capture the complex three-dimensional architecture of sandstone and mudstone layers. We present a modeling approach in which surfaces are used to represent all geologic heterogeneities that control the spatial distribution of reservoir rock properties (surface-based modeling). The workflow uses template surfaces to represent heterogeneities classified by geometry instead of length scale. The topology of the template surfaces is described mathematically by a small number of geometric input parameters, and models are constructed stochastically. The methodology has been applied to generate generic, three-dimensional minimodels (9 m3 volume) of cross-bedded heterolithic sandstones representing trough and tabular cross-bedding with differing proportions of sandstone and mudstone, using conditioning data from two outcrop analogs from a tide-dominated deltaic deposit. The minimodels capture the cross-stratified architectures observed in outcrop and are suitable for flow simulation, allowing computation of effective permeability values for use in larger-scale models. We show that mudstone drapes in cross-bedded heterolithic sandstones significantly reduce effective permeability and also impart permeability anisotropy in the horizontal as well as vertical flow directions. The workflow can be used with subsurface data, supplemented by outcrop analog observations, to generate effective permeability values to be derived for use in larger-scale reservoir models. The methodology could be applied to the characterization and modeling of heterogeneities in other types of sandstone reservoirs