RESUMEN
The detection of trace amount of volatile organic compounds (VOCs) has been covered by tons of researches, which are dedicated to improve the detection limit and insensitivity to humidity. In this work, we have synthesized ZnO@ZIF-71 nanorod arrays (NRAs) equipped with the adsorption effect at metal site that promoted the detection limit of ethanol and acetone, to which also have great selectivity. The gas sensor not only exhibits shorter response/recovery time (53/55% for ethanol, 48/31% for acetone), but also excellent insensitivity to humidity and improved detection limit (10× improved at 21 ppb for ethanol, 4× at 3 ppb for acetone) at low working temperature (150 °C). By the analysis of in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and calculation of density functional theory (DFT), the mechanism of enhanced gas sensing performance from ZnO@ZIF-71 NRAs is proved. It shows ethanol and acetone gas molecules can be adsorbed at the metal sites of ZIF-71. This work provides a new idea to improve the detection limit and humidity-insensitivity of gas sensor toward specific gas molecules.
RESUMEN
OBJECTIVE: To study the risk factors for elevated serum total bile acid (TBA) in preterm infants. METHODS: A retrospective analysis was performed for the clinical data of 216 preterm infants who were admitted to the neonatal intensive care unit. According to the presence or absence of elevated TBA (TBA >24.8 µmol/L), the preterm infants were divided into elevated TBA group with 53 infants and non-elevated TBA group with 163 infants. A univariate analysis and an unconditional multivariate logistic regression analysis were used to investigate the risk factors for elevated TBA. RESULTS: The univariate analysis showed that there were significant differences between the elevated TBA group and the non-elevated TBA group in gestational age at birth, birth weight, proportion of small-for-gestational-age infants, proportion of infants undergoing ventilator-assisted ventilation, fasting time, parenteral nutrition time, and incidence of neonatal respiratory failure and sepsis (P<0.05). The unconditional multivariate logistic regression analysis showed that low birth weight (OR=3.84, 95%CI: 1.53-9.64) and neonatal sepsis (OR=2.56, 95%CI: 1.01-6.47) were independent risk factors for elevated TBA in preterm infants. CONCLUSIONS: Low birth weight and neonatal sepsis may lead to elevated TBA in preterm infants.