Comparing Medicare Fee-for-Service Beneficiaries with ESKD who Switched to Medicare Advantage versus Remained in Traditional Medicare.

ABSTRACT: Patients choosing Medicare Advantage vs. Medicare fee-for-service (FFS) differ with respect to race, socioeconomic status, and burden of disease. However, it is unclear whether these differences also occur among patients with kidney failure, who were newly allowed to switch to Medicare Advantage after the 21st Century Cares Act. We used data from the United States Renal Data System (USRDS) to examine differences in characteristics of dialysis patients and kidney transplant recipients who switched from FFS to Medicare Advantage compared with those who stayed with FFS in 2021, the first year such switching was allowed. We used unadjusted and adjusted logistic regression to compare odds of switching among demographic and geographic subgroups. Among 411,513 patients with FFS coverage in 2020, 10.1% switched to Medicare Advantage in 2021. Switchers constituted 12% of the dialysis population and 5% of the kidney transplant population. In the dialysis population, patients of Black race and Hispanic ethnicity were more likely to switch than patients of White race (adjusted OR 1.69, 95% Confidence Interval [CI] 1.64, 1.73 and OR 1.42, 95% CI 1.40, 1.47, respectively), as were patients with dual eligibility for Medicaid (adjusted OR 1.12, 95% CI 1.09, 1.15). Patients living in the South were also more likely to switch to Medicare Advantage than those living in the West (adjusted OR 1.48, 95% CI 1.43, 1.52). Similar differences were observed among kidney transplant recipients. Patients who switched from FFS to Medicare Advantage were disproportionately from historically marginalized groups, including Black, Hispanic, and low income individuals. They were also more likely to live in the South. These differences may threaten the generalizability of USRDS data that relies on FFS insurance claims and suggest that comparisons of outcomes between FFS and MA beneficiaries with kidney failure should be adjusted for key patient characteristics.

Carbon-negative production of acetone and isopropanol by gas fermentation at industrial pilot scale.

Many industrial chemicals that are produced from fossil resources could be manufactured more sustainably through fermentation. Here we describe the development of a carbon-negative fermentation route to producing the industrially important chemicals acetone and isopropanol from abundant, low-cost waste gas feedstocks, such as industrial emissions and syngas. Using a combinatorial pathway library approach, we first mined a historical industrial strain collection for superior enzymes that we used to engineer the autotrophic acetogen Clostridium autoethanogenum. Next, we used omics analysis, kinetic modeling and cell-free prototyping to optimize flux. Finally, we scaled-up our optimized strains for continuous production at rates of up to ~3 g/L/h and ~90% selectivity. Life cycle analysis confirmed a negative carbon footprint for the products. Unlike traditional production processes, which result in release of greenhouse gases, our process fixes carbon. These results show that engineered acetogens enable sustainable, high-efficiency, high-selectivity chemicals production. We expect that our approach can be readily adapted to a wide range of commodity chemicals.

Air Quality and Health Impacts of an Aviation Biofuel Supply Chain Using Forest Residue in the Northwestern United States.

Forest residue is a major potential feedstock for second-generation biofuel; however, little knowledge exists about the environmental impacts of the development and production of biofuel from such a feedstock. Using a high-resolution regional air quality model, we estimate the air quality impacts of a forest residue based aviation biofuel supply chain scenario in the Pacific Northwestern United States. Using two potential supply chain regions, we find that biomass and biofuel hauling activities will add <1% of vehicle miles traveled to existing traffic, but the biorefineries will add significant local sources of NO x and CO. In the biofuel production scenario, the regional average increase in the pollutant concentration is small, but 8-hr maximum summer time O3 can increase by 1-2 ppb and 24-hr average maximum PM2.5 by 2 µg/m3. The alternate scenario of slash pile burning increased the multiday average PM2.5 by 2-5 µg/m3 during a winter simulation. Using BenMAP, a health impact assessment tool, we show that avoiding slash pile burning results in a decrease in premature mortality as well as several other nonfatal and minor health effects. In general, we show that most air quality and health benefits result primarily from avoided slash pile burning emissions.

Simulation of the ozone pretreatment of wheat straw.

Wheat straw is a potential feedstock in biorefinery for sugar production. However, the cellulose, which is the major source of sugar, is protected by lignin. Ozonolysis deconstructs the lignin and makes cellulose accessible to enzymatic digestion. In this study, the change in lignin concentration with different ozonolysis times (0, 1, 2, 3, 5, 7, 10, 15, 20, 30, 60min) was fit to two different kinetic models: one using the model developed by Garcia-Cubero et al. (2012) and another including an outer mass transfer barrier or "cuticle" region where ozone mass transport is reduced in proportion to the mass of unreacted insoluble lignin in the cuticle. The kinetic parameters of two mathematical models for predicting the soluble and insoluble lignin at different pretreatment time were determined. The results showed that parameters derived from the cuticle-based model provided a better fit to experimental results compared to a model without a cuticle layer.

Structural characterization of lignin: a potential source of antioxidants guaiacol and 4-vinylguaiacol.

The structure of lignin obtained from the ozone and soaking aqueous ammonia pretreatment of wheat straw has been characterized utilizing chemical analytical methods in order to reveal its antioxidant characteristics, including attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), pyrolysis/tetramethylammonium hydroxide-gas chromatography/mass spectrometry (Py/TMAH-GC/MS), gel permeation chromatography (GPC), ultra violet-visible spectroscopy (UV-vis), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant evaluation assay. The results demonstrated that the isolated lignin is a ρ-hydroxyphenyl- guaiacyl-syringyl (H-G-S) lignin, with S/G ratio of 0.35 and significant amounts of phenol 2-methoxy (guaiacol) and phenol 2-methoxy-4-vinyl (4-vinylguaiacol). The Py-GC/MS and Py/TMAH-GC/MS pyrograms indicated that the major units in this lignin are derived from hydroxycinnamic acids. The GPC results revealed the molecular weight of the lignin was considerably low and also the FTIR analysis showed that the lignin possessed hydroxyl and methoxy functional groups; the factors led to the extracted lignin having a comparable antioxidant activity to that of currently used commercial antioxidants. The UV-vis and DPPH antioxidant assay results suggested a percentage of inhibition of the DPPH radicals in the following order: guaiacol (103.6 ± 1.36)>butylated hydroxytoluene (103.3 ± 1)>ferulic acid (102.6 ± 0.79)>pretreated lignin (86.9 ± 0.34).

Structural modification of lignin and characterization of pretreated wheat straw by ozonation.

Ozonolysis is potentially an effective method for pretreating lignocellulosic biomass to improve the production of fermentable sugars via enzymatic hydrolysis. Further understanding of the ozonolysis process and identifying specific lignin structural changes are crucial for improving the pretreatment process. Investigation into pretreatment of wheat straw using ozonolysisis is reported in this paper, with special emphasis on selective modification/degradation of lignin subunits. The ozonolysis was performed for 2 h with less than 60 mesh particles in order to achieve maximum lignin oxidation. The results showed that the lignin structure was significantly modified under these conditions, leading to higher sugar recovery of more than 50% which increased from 13.11% to 63.17% corresponding to the control and ozone treated samples, respectively. Moisture content was found to be an important parameter for improving sugar recovery. Ninety percent (w/w) moisture produced the highest sugar recovery. The concentration of acid soluble lignin in the ozone treated sample increased from 4% to 11% after 2 h treatment. NMR analysis revealed that the S2/6 and G2 lignin units in the wheat straw were most prone to oxidation by ozone as the concentration of aromatic units decreased while the carboxylic acids became more abundant. The experimental data suggest the degradation of ß-O-4 moieties and aromatic ring opening in lignin subunits. The pyrolysis-gas chromatography/mass spectrometry results revealed that the rate of lignin unit degradation was in the following order: syringyl > guaiacyl > p-hydroxyphenyl. Long ozone exposure resulted in few condensed lignin structure formation. In addition, the formation of condensed units during this process increased the activation energy from ASTM-E, 259.74 kJ/mol; Friedman-E, 270.08 kJ/mol to ASTM-E, 509.29 kJ/mol; Friedman-E, 462.17 kJ/mol. The results provide new information in overcoming lignin barrier for lignocellulose utilization.

Structural and thermal characterization of wheat straw pretreated with aqueous ammonia soaking.

Production of renewable fuels and chemicals from lignocellulosic feedstocks requires an efficient pretreatment technology to allow ready access of polysaccharides for cellulolytic enzymes during saccharification. The effect of pretreatment on wheat straw through a low-temperature and low-pressure soaking aqueous ammonia (SAA) process was investigated in this study using Fourier transform infrared (FTIR), pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS), solid and liquid state nuclear magnetic resonance (NMR), and thermogravimetry/differential thermogravimetry (TG/DTG) to demonstrate the changes in lignin, hemicellulose, and cellulose structure. After treatment of 60 mesh wheat straw particles for 60 h with 28-30% ammonium hydroxide (1:10 solid/liquid) at 50 °C, sugar recovery increased from 14% (untreated) to 67% (SAA treated). The FTIR study revealed a substantial decrease in absorbance of lignin peaks. Solid and liquid state NMR showed minimal lignin structural changes with significant compositional changes. Activation energy of control and pretreated wheat straw was calculated according to the Friedman and ASTM methods and found to be decreased for SAA-treated wheat straw, from 259 to 223 kJ/mol. The SAA treatment was shown to remove significant amounts of lignin without strongly affecting lignin functional groups or structure.