Measurement of the optical absorption coefficient of a liquid by use of a time-resolved photoacoustic technique.

A time-resolved photoacoustic technique has been applied to the study of dissolved and dispersed absorbers in aqueous systems. The temporal pressure profiles generated from colloidal graphite and glucose solutions were measured, and it was found that the amplitude of the photoacoustic signal of both the glucose and the colloidal graphite solutions increase linearly with concentration and that acoustic signal time delay yields the acoustic velocity. The logarithm of the photoacoustic signal amplitude changes linearly with the time delay, with a slope that is proportional to the product of the acoustic velocity and the optical absorption that can thus be determined.

Advances in photoacoustic noninvasive glucose testing.

We report here on in vitro and in vivo experiments that are intended to explore the feasibility of photoacoustic spectroscopy as a tool for the noninvasive measurement of blood glucose. The in vivo results from oral glucose tests on eight subjects showed good correlation with clinical measurements but indicated that physiological factors and person-to-person variability are important. In vitro measurements showed that the sensitivity of the glucose measurement is unaffected by the presence of common blood analytes but that there can be substantial shifts in baseline values. The results indicate the need for spectroscopic data to develop algorithms for the detection of glucose in the presence of other analytes.

Application of pulsed photoacoustics in water at high pressure.

The application of pulsed photoacoustics to the study of liquids at pressures of up to 350 bars is discussed. The design and development of an in-line sensor for the subsea monitoring of crude oil concentrations in water is reported. Crude oil detection sensitivities at parts per million concentrations were achieved with prototype instrumentation. A comparison of experimental results and a theoretical prediction of the pressure dependence of the pulsed photoacoustic response from water is outlined. The results demonstrate that existing models that describe pulsed photoacoustic generation in liquids are applicable to high-pressure conditions.

Optical fiber interferometry for photoacoustic spectroscopy in liquids.

Optical fiber interferometry was used for measurement of the subnanometer surface and bulk displacements associated with photoacoustic pressure waves in methanol and water. The measurement system is both broadband and noncontacting, giving a pressure sensitivity of 0.1 Pa/ radicalHz.

A multidisciplinary approach to wound care.

An examination of the process by which a health-care team reviewed wound care and produced guidelines for practice.

Introduction and audit of a general practice antibiotic formulary.

A survey of oral antibiotic prescriptions was carried out in a semi-urban general practice. From this a practice formulary was devised. The formulary was put into operation and the results of its introduction were reviewed after 12 months. There was a reduction in antibiotic costs without an increase in the number of patient consultations, home visits or referrals to hospital.

Saliva and blood pethidine concentrations in the mother and the newborn baby.

In a group of mothers who received pethidine intramuscularly during labour, drug concentrations were higher in saliva than in blood and there was a significant correlation (p < 0.001) between saliva and blood concentrations measured between 1 hour and 4 hours 20 minutes after dosage. In newborn babies, the pethidine concentrations detected in pharyngeal aspirates were higher than those in umbilical arterial or umbilical venous blood, but there was no correlation. Pethidine was also detected in the saliva from babies for 48 hours after birth. Furthermore, the appreciably higher levels in breast-fed babies suggest that such babies may receive a dose of pethidine in the milk.