When BaZrO(3) is doped with Y in 12.5% of Zr sites, density functional theory with the PBE functional predicts octahedral distortions within a cubic phase yielding a greater variety of proton binding sites than undoped BaZrO(3). Proton binding sites, transition states, and normal modes are found and used to calculate transition state theory rate constants. The binding sites are used to represent vertices in a graph. The rate constants connecting binding sites are used to provide weights for graph edges. Vertex and color coding are used to find proton conduction pathways in BaZr(0.875)Y(0.125)O(3). Many similarly probable proton conduction pathways which can be periodically replicated to yield long range proton conduction are found. The average limiting barriers at 600 K for seven step and eight step periodic pathways are 0.29 and 0.30 eV, respectively. Inclusion of a lattice reorganization barrier raises these to 0.42 and 0.33 eV, respectively. The majority of the seven step pathways have an interoctahedral rate limiting step while the majority of the eight step pathways have an intraoctahedral rate limiting step. While the average limiting barrier of the seven step periodic pathway including a lattice reorganization barrier is closer to experiment, how to appropriately weight different length periodic pathways is not clear. Likely, conduction is influenced by combinations of different length pathways. Vertex and color coding provide useful ways of finding the wide variety of long range proton conduction pathways that contribute to long range proton conduction. They complement more traditional serial methods such as molecular dynamics and kinetic Monte Carlo.

Doping orthorhombic SrZrO(3) at 12.5% of the Zr sites with Al(3+) leads to a local squaring of the lattice, while doping with larger Y(3+) increases local octahedral distortions. Proton activation energy barriers and transition state theory prefactors are calculated. The wide range of intra-, inter-, and rotational barriers suggest that a comprehensive pathway analysis is needed to find the limiting conduction barriers. Simple seven to ten step periodic pathways leading to system wide conduction are enumerated using vertex coding. At 900-1300 K, the average limiting barriers to long range conduction are 0.6 and 0.4 eV in Al/SrZrO(3) and Y/SrZrO(3), respectively, in reasonable agreement with the experiment. Path analysis gives the added insight that conduction pathways in Al/SrZrO(3) avoid doped regions, while conduction pathways in Y/SrZrO(3) traverse them.

Purpose of review Hepatitis C (HCV) is the most common cause of viral hepatitis in elderly individuals. This patient population previously experienced suboptimal outcomes with interferon-based regimens. Unfortunately, patients aged 65 years and older were underrepresented in phase 2 and 3 clinical trials with newer direct acting antiviral (DAA) therapies. Since the advent of second-generation DAA in 2013, numerous robust real-world experiences highlighting the efficacy and safety of DAA in the elderly have been published. This review article summarizes the cascade of care for hepatitis C from diagnosis to cure from an evidence-based perspective of the aging population. Recent finding In a large study from the Veterans Affairs Healthcare System, the overall sustained virologic response (SVR) of 15,884 patients treated with DAA regimens was 91.2%. These newer therapies remained highly effective in the subset of patients aged 65 years and older with SVR rates above 90%. A Spanish National Registry reported outcomes in patients ≥ 65 years old treated for HCV with oral DAA regimens over a 2-year period. The overall SVR was 94% in the study of 1252 subjects. Summary Current real-world data imply DAA treatment regimens remain highly effective and safe in elderly patients when compared to the general population.