ABSTRACT
HYPOTHESIS: It is particularly noteworthy to study interfacial tension behavior under pressurized carbon dioxide for supercritical processes such as crystallization or fractionation. For the latter, a liquid phase and a supercritical phase are in contact, and interfacial properties influence mass transfer phenomena and hydrodynamics. Ethanol-water mixture is a good theoretical study case also involved in a wide range of applications. EXPERIMENTAL: Interfacial tensions of ethanol, water and three mixtures, with an ethanol mass fraction from 0.25 to 0.75, under pressurized CO2 were measured for pressures ranging from 0.1 MPa to 15.1 MPa at 313.15 K and 333.15 K. A specific experimental set-up was used for CO2 phase saturation. FINDINGS: This work brings interfacial tension data of five different solutions including water and ethanol in contact with CO2. Effects of pressure, temperature, carbon dioxide density and ethanol mass fraction are discussed regarding the literature. Significant discrepancies are found with previous literature data for ethanol-water mixtures. The "two-step" decrease observed when pressure or density increase is also discussed regarding both the concept of Widom line, and the polar and dispersive contributions of the surface tension of a component. For the first time, fair accurate interfacial tension modeling involving these contributions is addressed.
ABSTRACT
In this study, PDMS13-b-POEGMAx diblock copolymers consisting of a CO2-philic poly(dimethylsiloxane) (PDMS) block connected to a thermosensitive hydrophilic poly(oligoethylene glycol methacrylate) (POEGMA) block were synthesized by reversible addition-fragmentation chain-transfer (RAFT) radical polymerization. Their ability to decrease the water-supercritical CO2 (scCO2) interfacial tension (γ) and to stabilize water-scCO2 emulsions was investigated using an original homemade device developed in the laboratory. This device is able to control the pressure from 1 to 250 bar and the temperature from 40 to 80 °C. It was implemented with 2 visualization windows, a drop tensiometer and a remote optical head for dynamic light scattering (DLS) measurements. These experiments revealed that PDMS-b-POEGMA decreased γ down to 1-2 mN/m and was the most efficient at high pressure (250 bar) and low temperature (40 °C) where PDMS and POEGMA blocks exhibited the highest affinity for their respective phase. The diblock copolymers were shown to stabilize water-scCO2 emulsions. Moreover, the thermosensitive behavior of the POEGMA block in water (with a lower critical solubility temperature around 65 °C) resulted in the formation of temperature-responsive emulsions that could reversibly switch at 100 bar from stable at 40 °C to unstable at 80 °C. These results were rationalized based on the solubility of each individual block of the copolymers in water and scCO2 as a function of temperature and pressure.
ABSTRACT
PURPOSE: To analyse and compare the prevalence of epiretinal membranes (ERMs) obtained using either standard retinal colour images or spectral-domain optical coherence tomography (SD-OCT) in a population-based setting of French elderly subjects. METHODS: Six hundred twenty-four subjects of the Alienor cohort aged 75 years or older underwent both colour fundus imaging and SD-OCT examinations. The ERMs were graded from retinal images and SD-OCT macular scans in a masked fashion. On SD-OCT images, the early ERMs, mature contractile ERMs without foveal modifications and mature contractile ERMs with foveal alterations were distinguished. RESULTS: 610 (97.8%) subjects had gradable SD-OCT examinations, and 511 (81.9%) had gradable fundus images in at least one eye. According to colour photographs, 11.6% of participants had definite ERMs. From SD-OCT images, 52.8% of the subjects had early ERMs, 7.4% had mature ERMs without foveal involvement, and 9.7% had mature ERMs with foveal alterations. Regardless of the imaging method used, the ERMs were more often observed in pseudophakic eyes than in phakic eyes. Comparison of ERM assessment using fundus photographs versus SD-OCT images demonstrated that the specificity of retinal colour images was good (>89.3%), whereas the sensitivity remained low even though it increased with ERM severity on SD-OCT images. CONCLUSIONS: Spectral-domain optical coherence tomography (SD-OCT) examinations have high feasibility in this elderly population and are much more sensitive than standard colour images for ERM assessments, especially in the early stages of the disease. Our results further highlight the need to use SD-OCT instead of colour retinal photographs for the classification of ERMs in epidemiological studies.
