Nanoparticle collection efficiency of capillary pore membrane filters.

The surface and overall collection efficiencies of capillary pore membrane filters were measured for sub-micrometer particles. Collection efficiencies were derived from the surface loadings of particles on filters measured by scanning electron microscopy and from airborne particle concentrations measured with a scanning mobility particle sizer. Tests used filters with nominal pore diameters of 0.4 and 0.8 µm and face velocities of 3.7 and 18.4 cm/s. Surface collection efficiencies were below 100% for particles smaller than 316 nm and below 55% for particles smaller than 100 nm. Overall collection efficiencies reached as low as 45% for 70 nm particles. For nanoparticles, collection efficiencies overall were substantially higher than those to the filter surface, indicating that deposition occurs to a large extent inside the filter pores. These results underscore the need to account for surface collection efficiency when deriving airborne concentrations from microscopic analysis of nanoparticles on capillary pore membrane filters.

Solid acids as fuel cell electrolytes.

Fuel cells are attractive alternatives to combustion engines for electrical power generation because of their very high efficiencies and low pollution levels. Polymer electrolyte membrane fuel cells are generally considered to be the most viable approach for mobile applications. However, these membranes require humid operating conditions, which limit the temperature of operation to less than 100 degrees C; they are also permeable to methanol and hydrogen, which lowers fuel efficiency. Solid, inorganic, acid compounds (or simply, solid acids) such as CsHSO4 and Rb3H(SeO4)2 have been widely studied because of their high proton conductivities and phase-transition behaviour. For fuel-cell applications they offer the advantages of anhydrous proton transport and high-temperature stability (up to 250 degrees C). Until now, however, solid acids have not been considered viable fuel-cell electrolyte alternatives owing to their solubility in water and extreme ductility at raised temperatures (above approximately 125 degrees C). Here we show that a cell made of a CsHSO4 electrolyte membrane (about 1.5 mm thick) operating at 150-160 degrees C in a H2/O2 configuration exhibits promising electrochemical performances: open circuit voltages of 1.11 V and current densities of 44 mA cm-2 at short circuit. Moreover, the solid-acid properties were not affected by exposure to humid atmospheres. Although these initial results show promise for applications, the use of solid acids in fuel cells will require the development of fabrication techniques to reduce electrolyte thickness, and an assessment of possible sulphur reduction following prolonged exposure to hydrogen.

Effect of intramuscular intraoperative pain medication on narcotic usage after laparoscopic cholecystectomy.

The purpose of this randomized, double-blind, clinical trial was to determine whether intraoperative, intramuscular (IM) injections of meperidine or ketorolac would improve postoperative pain relief in patients undergoing elective laparoscopic cholecystectomy. A total of 125 patients were entered into five study groups: 1) (N = 23) control placebo; 2) (N = 31) meperidine 100 mg IM intraoperative preprocedure; 3) (N = 20) meperidine 100 mg IM intraoperative postprocedure; 4) (N = 25) ketorolac tromethamine 60 mg IM intraoperative preprocedure; 5) (N = 26) ketorolac tromethamine 60 mg IM postprocedure. All groups were analyzed by comparing the amount of pain medication received in the recovery room, the time until first oral pain medication was requested, the overall amount of pain medication used in the first 24 hours, the percent requiring IM medication, and the pain score ratings from each group. There was decreased pain medication usage in the recovery room in all groups compared to control (P < 0.05). Group 4 had a longer painfree interval than meperidine groups or control. Both Groups 4 and 5 had decreased postoperative narcotic usage. Finally, the analogue pain scores showed that both ketorolac groups had significantly less postoperative pain compared to control, whereas the meperidine groups showed no improvement in postoperative pain relief. Intraoperative ketorolac given preprocedure or postprocedure significantly improved postoperative pain management and facilitated the transition to oral pain medication.

Clinical experience with three-in-one admixtures administered peripherally.

The purpose of this report was to describe the tolerance of hyperosmolar nutritionally complete solutions infused peripherally, as a bridge to enteral therapy in the surgical patient. Solutions providing approximately 40% of calories as carbohydrates were administered to 23 surgical patients with the fats, amino acids, and dextrose mixed in one container. Final osmolarity, when measured directly with additives, ranged from 1200-1350 mOsm/L. Approximately 85% of the patients had acceptable tolerance to this new technique. The patient tolerance of the high osmolar admixture in peripheral veins might be attributed to the buffering and dilution effect of the IV fats in combination with the higher pH of the amino acid solutions and the addition of heparin to the admixture. Strong support for this technique was voiced by experienced nutritional support physicians and hospital personnel for use in surgical patients who have immediate short-term needs.