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Flexible and mechanically robust gas sensors are the key technologies for wearable and implantable electronics. Herein, the authors demonstrate the high-performance, flexible nitrogen dioxide (NO2) chemiresistors using a series of n-type conjugated polymers (CPs: PNDIT2/IM-x) and a polymer dopant (poly(ethyleneimine), PEI). Imine double bonds (C = N) are incorporated into the backbones of the CPs with different imine contents (x) to facilitate strong and selective interactions with NO2. The PEI provides doping stability, enhanced electrical conductivity, and flexibility. As a result, the NO2 sensors with PNDIT2/IM-0.1 and PEI (1:1 by weight ratio) exhibit outstanding sensing performances, such as excellent sensitivity (𝚫R/Rb = 240%@1 ppm), ultralow detection limit (0.1 ppm), high selectivity (𝚫R/Rb < 8%@1 ppm of interfering analytes), and high stability, thereby outperforming other state-of-the-art CP-based chemiresistors. Furthermore, the thin film of PNDIT2/IM-0.1 and PEI blend is stretchable and mechanically robust, providing excellent flexibility to the NO2 sensors. Our study contributes to the rational design of high-performance flexible gas sensors. [ABSTRACT FROM AUTHOR]

Although p-type semiconductors exhibit highly selective and stable chemiresistive gas sensing performances compared to conventional n-type semiconductors, their low sensitivity had long impeded their practical development. In this work, we developed highly porous Co 3 O 4 /CoMoO 4 heterostructure nanosheets (NSs) with enhanced sensitivity and superior stability toward acetone gas through a facile solution-based approach with Mo-impregnated Co-based metal-organic frameworks as the starting material. The spontaneous formation of a large number of p-p heterojunctions at the Co 3 O 4 -CoMoO 4 interface would facilitate the adsorption of oxygen and acetone molecules, as verified by density functional theory calculations. Consequently, experimental results showed that the Co 3 O 4 /CoMoO 4 NSs have a greatly enhanced response of 8.5 toward 5 ppm acetone, which is 7.1 times higher than that of pure Co 3 O 4 NS, without involving any noble metal catalysts. Moreover, the limit of detection of the Co 3 O 4 /CoMoO 4 NSs was as low as 10 ppb. Altogether, we propose that our synthetic approach for the engineering of p-p heterojunctions is an effective strategy for the future development of highly practical and sensitive gas sensors based on p-type semiconductors.

The purpose of this study was to determine whether the introduction of diagnosis-related groups (DRGs) shifted the medical services from inpatient to outpatient settings. Using a difference-in-difference analysis, the changes in length of stay, outpatient visit days within 30 days before hospitalization, and outpatient visit days within 30 days after hospital discharge were evaluated. The length of stay was reduced after the DRG policy, consistent with previous studies. Outpatient visit days within 30 days before a hospital admission increased significantly after the policy change. In addition, outpatient visit days within 30 days after a hospital discharge increased in all the medical institutions excluding hospitals. The study findings are consistent with the expectation that providers respond to changes in the payment system to protect or enhance their economic interests. Health care providers in Korea responded to the DRG policy by reducing the intensity of inpatient treatment and transferring costs to outpatient settings.

Hospitalization rates for ambulatory care sensitive conditions (ACSCs) can indicate the accessibility of a community's primary care. We examined regional variation in ACSC hospitalization rates and identified associated factors. ACSC hospitalization rates in the 232 districts in 2013 ranged from 4.08 to 101.53 per 1000 adults. Spatial analysis showed that none of the 24 highest rate districts were located near Seoul, whereas 80% of the 45 lowest rate districts were, suggesting health care inequality between people living near Seoul and in other areas. Regression analysis showed significantly higher ACSC hospitalization rates in districts with higher elderly (β = 0.94) and low-income populations (β = 2.25), more remote areas (β = 0.29), and more hospital beds (β = 0.03). The number of primary care clinics was negatively associated with ACSC hospitalization (β = -1.37). For these variables, geographically weighted regression analysis provided local regression coefficients, useful for developing region-specific strategies to reduce ACSC hospitalization.