3 research outputs found

    Adjustable Functionalization of Hyper-Cross-Linked Polymers of Intrinsic Microporosity for Enhanced CO2 Adsorption and Selectivity over N2 and CH4

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    In this paper, we report the design, synthesis, and characterization of a series of hyper-cross-linked polymers of intrinsic microporosity (PIMs), with high CO2 uptake and good CO2/N2 and CO2/CH4 selectivity, which makes them competitive for carbon capture and biogas upgrading. The starting hydrocarbon polymers’ backbones were functionalized with groups such as −NO2, −NH2, and −HSO3, with the aim of tuning their adsorption selectivity toward CO2 over nitrogen and methane. This led to a significant improvement in the performance in the potential separation of these gases. All polymers were characterized via Fourier transform infrared (FTIR) spectroscopy and 13C solid-state NMR to confirm their molecular structures and isothermal gas adsorption to assess their porosity, pore size distribution, and selectivity. The insertion of the functional groups resulted in an overall decrease in the porosity of the starting polymers, which was compensated with an improvement in the final CO2 uptake and selectivity over the chosen gases. The best uptakes were achieved with the sulfonated polymers, which reached up to 298 mg g–1 (6.77 mmol g–1), whereas the best CO2/N2 selectivities were recorded by the aminated polymers, which reached 26.5. Regarding CH4, the most interesting selectivities over CO2 were also obtained with the aminated PIMs, with values up to 8.6. The reason for the improvements was ascribed to a synergetic contribution of porosity, choice of the functional group, and optimal isosteric heat of adsorption of the materials

    Transcatheter Aortic Valve Replacement in Low-Population Density Areas Assessing Healthcare Access for Older Adults With Severe Aortic Stenosis

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    Background: Restricting transcatheter aortic valve replacement (TAVR) to centers based on volume thresholds alone can potentially create unintended disparities in healthcare access. We aimed to compare the influence of population density in state of Florida in regard to access to TAVR, TAVR utilization rates, and in-hospital mortality. Methods and Results: From 2011 to 2016, we used data from the Agency for Health Care Administration to calculate travel time and distance for each TAVR patient by comparing their home address to their TAVR facility ZIP code. Travel time and distance, TAVR rates, and mortality were compared across categories of low to high population density (population per square miles of land). Of the 6531 patients included, the mean (SD) age was 82 (9) years, 43% were female and 91% were White. Patients residing in the lowest category (<50/square miles) were younger, more likely to be men, and less likely to be a racial minority. Those residing in the lowest category density faced a longer unadjusted driving distances and times to their TAVR center (mean extra distance [miles]=43.5 [95% CI, 35.6–51.4]; P <0.001; mean extra time (minutes)=45.6 [95% CI, 38.3–52.9], P <0.001). This association persisted regardless of the methods used to determine population density. Excluding uninhabitable land, there was a 7-fold difference in TAVR utilization rates in the lowest versus highest population density regions (7 versus 45 per 100 000, P -for-pairwise-comparisons <0.001) and increase in TAVR in-hospital mortality (adjusted OR, 6.13 [95% CI, 1.97–19.1]; P <0.001). Conclusions: Older patients living in rural counties in Florida face (1) significantly longer travel distances and times for TAVR, (2) lower TAVR utilization rates, and (3) higher adjusted TAVR mortality. These findings suggest that there are trade-offs between access to TAVR, its rate of utilization, and procedural mortality, all of which are important considerations when defining institutional and operator requirements for TAVR across the country