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PubMedDate not supplied

Steam-sterilizable, fluorescence lifetime-based sensing film for dissolved carbon dioxide.

An autoclavable sensing film was developed for monitoring dissolved CO2. The sensing film, based on fluorescence resonance energy transfer (FRET), consisted of a fluorescent donor, an acceptor, and a quaternary ammonium hydroxide, which were doped in a two-component silicone film. As no aqueous solution was used in the sensing film matrix, the sensing film was unaffected by osmotic pressure. Fluorescence lifetime was selected as the sensing parameter, and measured in frequency domain using phase fluorometry. Upon exposure to 20% CO2-saturated water, a 43 degrees increase in phase angle was observed at 100 MHz. The process was fully reversible when the sensing film was exposed to nitrogen-saturated water. The estimated response and recovery times for 90% signal change were 1 min (for a step change from 0 to 6.7% CO2-saturated water) and 1.5 min (for a step change from 6.7 to 3.3% CO2-saturated water). When used for on-line monitoring of dissolved CO2 produced by a culture of Escherichia coli, the sensing film showed a similar trend to that obtained from off-line measurements using a wet chemistry analyzer.

Carbon Dioxide↗
PubMed2000

Comparison of oil recovered from tea tree leaf by ethanol extraction and steam distillation.

Two methods for the determination of oil and oil major components from tea tree (Melaleuca alternifolia) leaf are quantitatively compared. A microwave assisted ethanol extraction and a 2-h hydrodistillation technique were used on both dry and fresh leaf from a low and a high oil concentration tree. There was no significant difference between dry and fresh leaf. The distillation technique recovered 88% and 82% of the extractable oil for the low and high concentration material, respectively. For both samples this distilled oil was composed of lower absolute amounts of sesquiterpenoids and marginally lower amounts of monoterpenoids. Extending the distillation to 6 h increased the sesquiterpenoid recovery but this resulted in a reduction in both the absolute and relative amounts of the oxygenated monoterpenoids, terpinen-4-ol and 1,8-cineole.

Chromatography, Gas↗
PubMed1999

The effect of steam sterilisation at 134 degrees C on light intensity provided by fibrelight Macintosh laryngoscopes.

We studied the repeated effect of sterilisation on light intensity in laryngoscopes from Penlon, Riester, Heine (two different blades), Medicon and Upsher. Light intensity was measured by a light meter using two methods. Measurements were performed before the decontamination procedure was carried out and subsequently after each series of 25 procedures until a total of 200 cycles was reached. Using method 1 (and 2), the reduction in light intensity after 200 cycles was 100% (100%; no light emitted), 37% (13%), 75% (69%), 79% (60%), 37% (14%) and 63% (55%) for each blade, respectively.

Equipment Failure↗
PubMed1998

Biological indicators for steam sterilization: characterization of a rapid biological indicator utilizing Bacillus stearothermophilus spore-associated alpha-glucosidase enzyme.

The alpha-glucosidase enzyme was isolated from vegetative cells and spores of Bacillus stearothermophilus, ATCC 7953. Spore-associated enzyme had a molecular weight of approximately 92,700, a temperature optimum of 60 degrees C, and a pH optimum of 7.0-7.5. The enzyme in crude aqueous spore extract was stable for 30 min up to a temperature of 65 degrees C, above which the enzyme was rapidly denatured. The optimal pH for stability of the enzyme was approximately 7.2. The alpha-glucosidase in crude vegetative cell extract had similar characteristics to the spore-associated enzyme but its molecular weight was 86,700. The vegetative cell and spore-associated enzymes were cross-reactive. The enzymes are postulated to derive from a single gene product, which undergoes modification to produce the spore-associated form. The location of alpha-glucosidase in the spore coats (outside the spore protoplast) is consistent with the location of most enzymes involved in activation, germination and outgrowth.

Animals↗