This article presents the results of CO
2
/brine two-phase flow experiments in rocks at reservoir conditions. X-ray CT scanning is used to determine CO
2
saturation at a fine scale with a resolution ...of a few pore volumes and provide 3D porosity and saturation maps that can be use to correlate CO
2
saturations and rock properties. The study highlights the strong influence of sub-core scale heterogeneities on the spatial distribution of CO
2
at steady state and provides useful relative permeability data on a sample originated from an actual storage site (CO2CRC-Otway project, Victoria, South-West Australia). Two different samples tested, although different in nature, present strong heterogeneities, but differ in the detail of the connectivity of high porosity layers. In both samples, the results of the investigations show that sub-core scale heterogeneities control the sweep efficiency and may cause channeling through the porous medium. In one of the samples, CO
2
saturation appears uncorrelated to porosity close to the outlet end of the core. This observation is understood as a result of the position and the orientation of high porosity layers with respect to the inlet face of the core. Finally, in the operating conditions of the two experiments, the saturation maps demonstrate that gravity does not play a major role since no detectable buoyancy driven flow is observed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Pleomorphic onychomatricoma is a rare condition mimicking malignant neoplasms. Given its rarity, the diagnostic and prognostic criteria of this condition are not well established. The aim of this ...study was to characterize a series of 6 cases of pleomorphic onychomatricoma. In 3 cases the submitting clinical diagnosis was subungual squamous cell carcinoma. For all 6 cases, nail clipping showed typical features of onychomatricoma as a free-edge thickening and pitting of the nail plate with an additional feature of projecting line pattern. Pleomorphic onychomatricoma was diagnosed based on moderate-severe cytological atypia, yet degenerative-appearing with multinucleation or smudged chromatin, no mitotic activity or necrosis, and a Ki67 proliferative index inferior to 5% overall. Other finding s included epithelioid multinucleated cells with deeply eosinophilic cytoplasm mimicking epithelioid malignant cells, overexpression of Ki67 and p53 on atypical cells and diffuse expression of p16. This study describes additional criteria in pleomorphic onychomatricoma, permitting a wider recognition in order to avoid inappropriate treatment.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In philosophy, the problem of solitude has traditionally been either ignored or treated trivially. And when philosophy tackles solitude, it often relies on two unconvincing presuppositions. The first ...is that to be alone one has to put oneself first; the second is that solitude can be both good and bad. What ensues from this two-pronged approach to solitude? Solitary solitude is both sought-after and happy, and lonely solitude both sustained and sad. But once the distinction has been set up, solitude is still not sufficiently described, because neither form of solitude is really solitude. The first one is sheer aloneness, and the second refers to loneliness, far removed from the phenomenon of soloist solitude.
Although proton-exchange membrane fuel cells (PEMFC) are considered as a safe and clean energy technology, aging phenomena of the membrane-electrode assembly (MEA), and more particularly of the ...membrane, still restrict PEMFC lifetime. In this paper, ex-situ accelerated chemical degradation – via Fenton's reagents exposure – of reinforced Nafion™ XL membrane is performed in order to investigate the impact of chemical degradation on membrane structure and properties in comparison with unreinforced Nafion™ NR211 membrane. Results demonstrated that both XL and NR211 membranes undergo chemical decomposition after exposure to Fenton's reagents at different degradation rate. Emissions of two main degradation products released by the Nafion™ membranes were monitored as a function of exposure time, demonstrating the greater stability of the XL membrane compared to the NR211 membrane. However, the impact of chemical degradation on water sorption and water transport properties seems negligible for both membranes. This study aims at providing new insight on chemical degradation of composite Nafion™ XL membrane.
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•Ex-situ chemical degradation of Nafion™ XL and NR211 membranes is analyzed.•Degradation products suggest a polymer decomposition by unzipping reaction.•Chemical degradation has no significant impact on water sorption and diffusion.•XL membrane is more enduring against radical attack than unreinforced NR211.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Through a tight collaboration between chemical engineers, polymer scientists, and electrochemists, we address the degradation mechanisms of membrane electrode assemblies (MEAs) during proton exchange ...membrane fuel cell (PEMFC) operation in real life (industrial stacks). A special attention is paid to the heterogeneous nature of the aging and performances degradation in view of the hardware geometry of the stack and MEA. Macroscopically, the MEA is not fuelled evenly by the bipolar plates and severe degradations occur during start‐up and shut‐down events in the region that remains/becomes transiently starved in hydrogen. Such transients are dramatic to the cathode catalyst layer, especially for the carbon substrate supporting the Pt‐based nanoparticles. Another level of heterogeneity is observed between the channel and land areas of the cathode catalyst layer. The degradation of Pt3Co/C nanocrystallites employed at the cathode cannot be avoided in stationary operation either. In addition to the electrochemical Ostwald ripening and to crystallite migration, these nanomaterials undergo severe corrosion of their high surface area carbon support. The mother Pt3Co/C nanocrystallites are continuously depleted in Co, generating Co2+ cations that pollute the ionomer and depreciate the performance of the cathode. Such cationic pollution has also a negative effect on the physicochemical properties of the proton‐exchange membrane (proton conductivity and resistance to fracture), eventually leading to hole formation. These defects were localized with the help of an infrared camera. The mechanical fracture‐resistance of various perfluorosulfonated membranes further demonstrated that polytetrafluoroethylene‐reinforced membranes better resist hole formation, due to their high resistance to crack initiation and propagation. WIREs Energy Environ 2014, 3:540–560. doi: 10.1002/wene.113
This article is categorized under:
Fuel Cells and Hydrogen > Science and Materials
Fuel Cells and Hydrogen > Systems and Infrastructure
Energy Research & Innovation > Science and Materials
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
► We performed sorption and transport measurements in Nafion 115 and 212. ► We provide the community with a comprehensive set of experimental data. ► If the membrane is dried its water uptake ...decreases due to shrinkage of its structure. ► The proton conductivity and water self-diffusion coefficient are also reduced. ► The water uptake of Nafion 115 and 212 decreases with the measuring temperature.
We carried out systematic sorption, proton conductivity and water diffusion measurements in commercial Nafion N115 and Nafion NRE212 membranes. Because of the high dispersion of data in the literature, our primary objective was to gather a comprehensive set of experimental measurements and compare them with published results. Our simple, reproducible, experimental protocol allowed us to measure these important membrane properties over a wide range of experimental conditions. The membrane samples were heat-treated at different temperatures and the effect of thermal history on water sorption capacity and transport properties was investigated. We show that water uptake, proton conductivity and water self-diffusion coefficient decrease with increasing drying temperature. As a consequence, these variations must systematically be taken into account when comparing literature values to each other. The effect of temperature on sorption has also been investigated. The measurements show that the water sorption capacity of heat-treated (60
°C during 24
h) N115 and NRE212 membranes measured in vapor phase decreases with temperature while it increases in liquid phase. In membranes that were not heat-treated, however, the sorption in liquid water is independent of temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report a QENS study of the molecular motions in a perfluorinated ionomer membrane, Nafion, under increasing hydration levels from almost dry to fully saturated. Combined experiments performed on ...time-of-flight and backscattering spectrometers have been used to investigate the picosecond to the nanosecond dynamic behavior of water. The experimental spectra have been simulated over the whole Q range from 0.34 to 2.25 Å-1 by a single theoretical model taking into account the localized motions within confining domains, the microscopic features of the elementary jump process, and the long-range diffusion mechanism. The diffusion in a restricted geometry with ill-defined boundaries has been described by Gaussian statistics, contrary to the popular diffusion inside an impermeable sphere model where the boundaries are well defined. Evaluation of the spectra reveals the existence of two populations of protons in Nafion at all hydrations that are nonexchangeable on the nanosecond time-scale. A first population of three protons per ionic group is involved in a slow jump mechanism on characteristic length-scales of 2 to 4 Å and typical times ranging from 500 to 150 ps when increasing the water content in the membrane. This slow population, already present in the dried state, is presumably composed of the protons of the hydronium ions. The second fast population is composed of the additional hydrating water molecule protons. Between low hydration (3 H2O/SO3 -) and saturation (17.5 H2O/SO3 -), these protons are involved in a faster localized motion on roughly the same length scale, i.e., in the same water droplet as the hydronium ion. Long-range diffusion of these protons between neighboring domains of restricted motions is observed, even at very low hydration. As the number of water molecules in the membrane increases, a general finding is that the characteristic sizes increase and the characteristic times decrease, approaching asymptotic values at saturation. This is further reflected by the behavior of the local diffusion coefficient (inside a droplet) and the long-range diffusion coefficient (from one droplet to another) that vary, respectively, from 0.45 to 2 (10-5 cm2/s), and 0.1 to 0.58 (10-5 cm2/s), for λ ∼ 3 to 17.5. Overall, a molecular scenario for the proton motions among the different hydration steps has been proposed on the basis of the quantification of the dynamics on different length scales and time scales: below 10 H2O/SO3 - the hydration protons diffuse faster and faster in ionic clusters of growing size. Above this first hydration regime, the asymptotic upper limit with increased hydration is reached: the water molecules locally display a bulk-like behavior within the hydrophilic domains. The long-range diffusion appears to be correlated to the enhancement of hydronium mobility with water loading. These findings, that qualitatively confirm the results of a previous similar study, bring a significant improvement to the description of the experimental data and new quantitative information concerning the nature of the molecular motions in hydrated Nafion.
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IJS, KILJ, NUK, PNG, UL, UM
PFSA-based reinforced membranes are used today as the benchmark material for the electrolyte in PEMFCs. Although greatly improved relatively to their unreinforced version, they still suffer from ...aging and degradation during fuel cell (FC) operation. In this study we first performed proton NMR to characterize the different water populations in the pristine Nafion XL reinforced membrane. Then we used proton and fluorine NMR, FTIR and sorption measurements in order to qualitatively observe the differences induced in the membrane's chemical structure and properties by long term FC operation. Proton NMR is seen to be an adapted tool to quickly measure a signature that is correlated to the degradation state while FTIR can serve as a local probe of the chemical structure.
Demographic and epidemiological transitions are changing the age structure of the population and the most common diseases. Non-communicable respiratory diseases are an increasing problem at both ends ...of the age range in low-income and middle-income countries. In children, who represent a large proportion of the total population, the increasing problem of asthma is a strain on health services. Improved survival of the older population is increasing the proportion of morbidity and mortality attributable to chronic lung diseases. Health services in low-resource countries are poorly adapted to treating chronic diseases. Designed to respond episodically to acute disease, almost all historical investment has focused on infectious diseases. Crucial to the successful management of chronic diseases is an infrastructure designed to support pro-active management, providing not only an accurate diagnosis, but also a secure supply of cost effective drugs at an affordable price. The absence of such an infrastructure in many countries and the market failure that makes drugs generally more expensive in low-resource regions means that many people with chronic non-communicable lung diseases are not given effective treatment. This has damaging economic consequences. The common causes of poor lung health in low-income countries are not the same as those in richer countries, and there is a need to study why they are so common and how best to manage them.
Some authors have suggested that the fibroblasts of the nail mesenchyme (onychofibroblasts) can be distinguished from skin fibroblasts by their high expression of CD10. My 2015 study documented the ...presence of a relatively sparse CD34 + /CD10 + dendritic subpopulation in the dermis and hypodermis of the matrix. For some time now, my hypothesis has been that these interstitial dendritic mesenchymal cells of the matrix correspond to telocytes. Telocytes have been described as peculiar interstitial dendritic cells present in the mesenchymal tissue of numerous organs, including the skin, but their presence and characteristics in the nail unit have not been explored. This study was undertaken to more comprehensively investigate the existence and characteristics of nail telocytes. A series of 20 normal adult nail units were examined with a combination of morphological and immunohistochemical analyses. The matrix dermis contained a sparse subpopulation of CD34 + /CD10 + elongated telocytes with a higher density in the lunular region and, at this distal level, a change in their immunohistochemical profile, resulting in a progressive loss of CD34 expression. The matrix hypodermis showed CD34 + /CD10 + telocytes in their classical elongated aspect, which acquired, especially in the distal fibromyxoid area of the thumb, an oval to round morphology with multiple intracytoplasmic vacuoles. The characteristic dynamic immunophenotypic profile of the dermal telocytes with a progressive distal loss of the defining molecule CD34 was equally observed in the distal hypodermis. The nail bed dermis was thick with a dense fibrous connective tissue. A reticular network of CD34 - /CD10 + telocytes was present in the superficial dermis of the proximal nail bed. The mesenchymal cells of the deep part of the proximal nail bed dermis and the entire distal nail bed dermis were CD34 - /CD10 - . The adult nail mesenchyme is composed of 3 microanatomically distinct regions. Only the thumb has a distal hypodermis rich in mucinous material. The population of telocytes is relatively sparse compared with the fibroblastic population of the entire nail mesenchyme. The concept of onychodermis/onychofibroblasts is not valid. Nail telocytes have a dynamic immunohistochemical profile depending on whether they are located proximally or distally. The CD34 + /CD10 + profile correlates with the onychogenic epithelial region, while the CD34 - /CD10 + profile correlates with a spatial rearrangement of the nail epidermal bed.
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