Dataset Information

Measurements of the Relationship Between Microstructure, pH, and the Streaming and Zeta Potentials of Sandstones.

ABSTRACT: A large number (1253) of high-quality streaming potential coefficient ( Csp) measurements have been carried out on Berea, Boise, Fontainebleau, and Lochaline sandstones (the latter two including both detrital and authigenic overgrowth forms), as a function of pore fluid salinity ( Cf) and rock microstructure. All samples were saturated with fully equilibrated aqueous solutions of NaCl (10 -5 and 4.5 mol/dm 3) upon which accurate measurements of their electrical conductivity and pH were taken. These Csp measurements represent about a fivefold increase in streaming potential data available in the literature, are consistent with the pre-existing 266 measurements, and have lower experimental uncertainties. The Csp measurements follow a pH-sensitive power law behaviour with respect to Cf at medium salinities ( Csp=-1.44×10-9Cf-1.127 , units: V/Pa and mol/dm 3) and show the effect of rock microstructure on the low salinity Csp clearly, producing a smaller decrease in Csp per decade reduction in Cf for samples with (i) lower porosity, (ii) larger cementation exponents, (iii) smaller grain sizes (and hence pore and pore throat sizes), and (iv) larger surface conduction. The Csp measurements include 313 made at Cf>1 mol/dm 3 , which confirm the limiting high salinity Csp behaviour noted by Vinogradov et al., which has been ascribed to the attainment of maximum charge density in the electrical double layer occurring when the Debye length approximates to the size of the hydrated metal ion. The zeta potential ( ? ) was calculated from each Csp measurement. It was found that ? is highly sensitive to pH but not sensitive to rock microstructure. It exhibits a pH-dependent logarithmic behaviour with respect to Cf at low to medium salinities ( ?=0.01133log10Cf+0.003505 , units: V and mol/dm 3) and a limiting zeta potential (zeta potential offset) at high salinities of ?o=-17.36±5.11 mV in the pH range 6-8, which is also pH dependent. The sensitivity of both Csp and ? to pH and of Csp to rock microstructure indicates that Csp and ? measurements can only be interpreted together with accurate and equilibrated measurements of pore fluid conductivity and pH and supporting microstructural and surface conduction measurements for each sample.

SUBMITTER: Walker E

PROVIDER: S-EPMC6954024 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Measurements of the Relationship Between Microstructure, pH, and the Streaming and Zeta Potentials of Sandstones.

Walker E E Glover P W J PWJ

Transport in porous media 20171113 1

A large number (1253) of high-quality streaming potential coefficient ( C sp ) measurements have been carried out on Berea, Boise, Fontainebleau, and Lochaline sandstones (the latter two including both detrital and authigenic overgrowth forms), as a function of pore fluid salinity ( C f ) and rock microstructure. All samples were saturated with fully equilibrated aqueous solutions of NaCl (10 - 5 and 4.5 mol/dm 3 ) upon which accurate measurements of their electrical conductivity an ...[more]

PMID: 31983794

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Project description:Subjective cognitive decline (SCD) is a perceived cognitive change prior to objective cognitive deficits, and although it is associated with Alzheimer's disease (AD) pathology, it likely results from multiple underlying pathologies. We investigated the association of white matter microstructure to SCD as a sensitive and early marker of cognitive decline and quantified the contribution of white matter microstructure separate from amyloidosis. Vanderbilt Memory & Aging Project participants with diffusion MRI data and a 45-item measure of SCD were included [n = 236, 137 cognitively unimpaired (CU), 99 with mild cognitive impairment (MCI), 73 ± 7 years, 37% female]. A subset of participants (64 CU, 40 MCI) underwent a fasting lumbar puncture for quantification of cerebrospinal fluid (CSF) amyloid-β(CSF Aβ42), total tau (CSF t-tau), and phosphorylated tau (CSF p-tau). Diffusion MRI data was post-processed using the free-water (FW) elimination technique, which allowed quantification of extracellular (FW) and intracellular compartment (fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity) microstructure. Microstructural values were quantified within 11 cognitive-related white matter tracts, including medial temporal lobe, frontal transcallosal, and fronto-parietal tracts using a region of interest approach. General linear modeling related each tract to SCD scores adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile scores, APOE ε4 carrier status, diagnosis, Geriatric Depression Scale scores, hippocampal volume, and total white matter volume. Competitive models were analyzed to determine if white matter microstructural values have a unique role in SCD scores separate from CSF Aβ42. FW-corrected radial diffusivity (RDT) was related to SCD scores in 8 tracts: cingulum bundle, inferior longitudinal fasciculus, as well as inferior frontal gyrus (IFG) pars opercularis, IFG orbitalis, IFG pars triangularis, tapetum, medial frontal gyrus, and middle frontal gyrus transcallosal tracts. While CSF Aβ42 was related to SCD scores in our cohort (Radj2 = 39.03%; β = -0.231; p = 0.020), competitive models revealed that fornix and IFG pars triangularis transcallosal tract RDT contributed unique variance to SCD scores beyond CSF Aβ42 (Radj2 = 44.35% and Radj2 = 43.09%, respectively), with several other tract measures demonstrating nominal significance. All tracts which demonstrated nominal significance (in addition to covariates) were input into a backwards stepwise regression analysis. ILF RDT, fornix RDT, and UF FW were best associated with SCD scores (Radj2 = 46.69%; p = 6.37 × 10-12). Ultimately, we found that medial temporal lobe and frontal transcallosal tract microstructure is an important driver of SCD scores independent of early amyloid deposition. Our results highlight the potential importance of abnormal white matter diffusivity as an early contributor to cognitive decline. These results also highlight the value of incorporating multiple biomarkers to help disentangle the mechanistic heterogeneity of SCD as an early stage of cognitive decline.

Dataset Information

Measurements of the Relationship Between Microstructure, pH, and the Streaming and Zeta Potentials of Sandstones.

Publications

Measurements of the Relationship Between Microstructure, pH, and the Streaming and Zeta Potentials of Sandstones.

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