RESUMO
Chemisorbed oxygen acts a crucial role in the redox reaction of semiconductor gas sensors, and which is of great significance for improving gas sensing performance. In this study, an oxygen-plasma-assisted technology is presented to enhance the chemisorbed oxygen for improving the formaldehyde sensing performance of SnO2electropun fiber. An inductively coupled plasma device was used for oxygen plasma treatment of SnO2electrospun fibers. The surface of SnO2electrospun fibers was bombarded with high-energy oxygen plasma for facilitating the chemisorption of electronegative oxygen molecules on the SnO2(110) surface to obtain an oxygen-rich structure. Oxygen-plasma-assisted SnO2electrospun fibers exhibited excellent formaldehyde sensing performance. The formaldehyde adsorption mechanism of oxygen-rich SnO2was investigated using density functional theory. After oxygen plasma modification, the adsorption energy and the charge transfer number of formaldehyde to SnO2were increased significantly. And an unoccupied electronic state appeared in the SnO2band structure, which could enhance the formaldehyde adsorption ability of SnO2. The gas sensing test revealed that plasma-treated SnO2electrospun fibers exhibited excellent gas sensing properties to formaldehyde, low operating temperature, high response sensitivity, and considerable cross-selectivity. Thus, plasma modification is a simple and effective method to improve the gas sensing performance of sensors.
RESUMO
OBJECTIVE: To assess the feasibility, safety, and effectiveness of early rapid icy normal saline infusion to attain mild hypothermia in cardiac arrest patients. METHODS: A single-center prospective randomized controlled trial was conducted. From March 2011 to October 2013, patients who had recovery of spontaneous circulation (ROSC) after cardiopulmonary resuscitation (CPR) in Beijing Daxing District People's Hospital were randomly divided into two groups. In icy normal saline group, patients received a rapid infusion of 1 000 mL of 4 centigrade normal saline intravenously to attain a mild hypothermia. In the control group, the patients were treated with ice bag on head, and axillary temperature was monitored. For all patients, rectal temperature was measured and recorded immediately and 1 hour later. The occurrence of pulmonary edema on initial chest X-ray at 6 hours, occurrence of tremor within 48 hours, ventricular fibrillation recurring within 48 hours, and consciousness or death within 14 days were recorded. RESULTS: A total of 45 patients were enrolled, including 23 patients in icy normal saline group and 22 in control group. The patients in icy normal saline group had a rectal temperature descended from (36.7 ± 0.9) centigrade to (34.9 ± 0.7) centigrade 1 hour later, while the patients in control group had a rectal temperature risen from (36.5 ± 1.0) centigrade to (37.9 ± 0.9) centigrade 1 hour later. There was significant difference in rectal temperature between two groups (t=2.228, P=0.031). The number of patients who successfully awaken within 14 days in ice normal saline group was significantly larger than that in control group (13 cases vs. 7 cases, χ² = 65.710, P=0.021). There was no statistical difference in the occurrence of acute pulmonary edema (4 cases vs. 6 cases), tremor (2 cases vs. 0 case), ventricular fibrillation recurrence (4 cases vs. 5 cases) and death within 14 days(11 cases vs. 12 cases, all P>0.05). CONCLUSIONS: The study shows that early rapid i.v. infusion of 4 centigrade normal saline is feasible, safe and effective for cerebral resuscitation.