ABSTRACT
We investigated adsorption of N2 on stoichiometric and O-rich IrO2(110) surfaces using temperature programmed desorption (TPD) experiments and density functional theory (DFT) calculations. TPD shows that N2 desorbs predominantly from the stoichiometric-IrO2(110) surface in a well-defined peak at 270 K for N2 coverages below about 0.5 ML and that a shoulder centered near 235 K develops in the N2 TPD traces as the coverage approaches saturation, indicating that adsorbed N2 molecules destabilize at high N2 coverages. Experiments of N2 adsorption onto O-rich IrO2(110) surfaces provide evidence that N2 adsorbs exclusively on the coordinatively unsaturated Ir atoms (Ircus) of the surface and that pre-adsorbed O-atoms ("on-top" oxygen) stabilize adsorbed N2 molecules, causing the main N2 TPD peak to shift toward higher temperature with increasing oxygen coverages. Consistent with prior results, our DFT calculations predict that an N2 molecule preferentially adsorbs into an upright configuration on an Ircus atom of the IrO2(110) surface and achieves a binding energy of about 100 kJ/mol. The computed binding energy agrees well with our experimental estimate of â¼90 kJ/mol for low N2 coverages on stoichiometric IrO2(110). The DFT calculations also quantitatively reproduce the observed stabilization of N2 by co-adsorption on-top O-atoms and predict the destabilization of N2 on IrO2(110) as the N2 adlayer becomes crowded at high coverages.
ABSTRACT
The frequency of postanesthesia side effects and times to reach "benchmarks" in the recovery process for IV preinduction doses of 20 micrograms/kg butorphanol, 40 micrograms/kg butorphanol, or a 2 micrograms/kg dose of fentanyl were compared in a double-blinded study involving ambulatory surgical patients. The authors hypothesized that all drugs would perform equally well in all study areas. Sixty ASA physical status I and II women undergoing laparoscopic tubal sterilization were randomly assigned to one of three groups: Group I (n = 20) received 20 micrograms/kg butorphanol as a preinduction agent; Group II (n = 20) received 40 micrograms/kg butorphanol; Group III (n = 20) received 2 micrograms/kg fentanyl. Anesthesia management for all groups was the same. Statistically significant variance was found in time to discharge-ready status and duration of nausea (p less than 0.05) between 40 micrograms/kg butorphanol and 2 micrograms/kg fentanyl, but no significant difference was found between 20 micrograms/kg butorphanol and 2 micrograms/kg fentanyl in these areas. Statistically significant variance was found in duration of dizziness and time to obtain a 10 on the Aldrete Post Anesthesia Recovery Score (APARS) between 40 micrograms/kg butorphanol and 20 micrograms/kg butorphanol and 40 micrograms/kg butorphanol and 2 micrograms/kg fentanyl. From the study, 20 micrograms/kg butorphanol appears to be as suitable as 2 micrograms/kg fentanyl for use as a preinduction narcotic analgesic, whereas 40 micrograms/kg butorphanol appears to be unsuitable due to increased duration of nausea, dizziness, and time to score 10 on APARS and reach discharge-ready status.
