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There is continuing interest, by health professionals and individuals, in the composition of mainstream tobacco smoke. Regular official surveys of tar, nicotine and carbon monoxide yields are from time to time supplemented by special surveys of specific components. In this study, gas chromatography-mass spectrometry was used to identify and quantify benzene and certain other volatile compounds of interest in the mainstream smoke of 26 cigarette brands on the UK market and of smoke from hand rolled tobacco. Validation of the method adopted demonstrated the ability to identify and to measure reliably the yields of benzene and seven other compounds: toluene, ethylbenzene, m/p-xylene, o-xylene, styrene, isoprene and acrylonitrile. Yields of these analytes were ranked and compared with the tar yields of the brands. In general terms, brands yielding < or = 3 mg of tar yielded proportionately more of the vapour phase analytes than did brands yielding > 3 mg of tar per cigarette. For many of the higher tar brands the yield of vapour phase analyte was approximately proportional to the tar yield. Smoking cigarettes with an average yield of 50 micron of benzene per cigarette has been compared with the occupational maximum exposure limit (16 mg m-3) concentration and with US studies on the home environment. Smoking the majority of brands examined could contribute significantly to the population exposure of benzene and the other volatile organic compounds considered in this study.

Apparatus has been built to explore the practical feasibility of using automatic control with electrical stimulation of paralysed legs to restore function. The experiments are performed with paraplegics with the aim of achieving a realistic postural task: to see whether the body may be maintained upright by stimulation of the plantarflexors when the other joints are braced. Significantly, the intact upper body, under natural control of the brain, cannot interfere with the automatic control. The "Wobbler" apparatus allows measurement of the ankle muscle properties in isometric conditions or in sinusoidal motion. Using the biomechanical properties of the body, which are also measured, controllers for stabilising the body can be designed. Controllers can be dynamically tested, imitating anterior-posterior sway, while the body is held upright, before "actual standing" is attempted.

Since 1972, regular six-monthly surveys of cigarettes on sale in the UK have determined the yields of tar, nicotine and carbon monoxide in mainstream smoke. During 1983-1990, a series of special studies investigated the yields of a range of additional analytes and their inter-relationships with the routinely monitored components. The results for total cyanide (as hydrogen cyanide), total aldehydes (including acetaldehyde), acrolein, formaldehyde and nitrogen monoxide are summarized, and the full data for six low-molecular weight phenols and three polycyclic aromatic hydrocarbons (PAHs) are reported. It is concluded that with the exception of nitrogen monoxide, which is strongly dependent upon the type of tobacco, and the delivery of some phenols and PAHs, which may be affected to a minor extent by the design of cigarette, the three routinely monitored smoke components provide an adequate guide to the yields of the other analytes examined, across the range of manufactured cigarettes available in the UK in the 1980s.

A microcomputer was used to analyse uterine activity during spontaneous labour in 30 nulliparous and 30 parous patients. The intrauterine mean active pressure (MAP) in the nulliparous group was 1.51 kPa (SD 0.45) in the first stage and 2.71 kPa (SD 0.77) in the second stage. For the parous group, the MAP in the first stage was 1.22 kPa (SD 0.37) and in the second stage was 2.92 kPa (SD 0.98). A significant parity difference in MAP and contraction frequency was observed in the first stage but not in the second stage. Epidural analgesia did not appear to influence uterine activity in the first stage but was associated with a lower MAP, contraction frequency and intensity in the second stage. During the first stage, MAP increased by 21% in nulliparas and by 39% in multiparas. The rise in MAP was mainly due to an increase in contraction frequency.

A system has been devised to monitor the movements of the finger made by patients after a tendon repair. A small transducer was used attached to the nail. The results were analysed by computer. The fingers moved much less than expected in spite of instruction.

The Laboratory of the Government Chemist examines most of the drugs that have been seized at the point of entry into the United Kingdom of Great Britain and Northern Ireland and has developed analytical methods for their rapid identification in the field and for more exact analysis and quantitation in the Laboratory. These methods are described for the major types of drugs encountered. Many seizures are examined in greater detail in order to compare samples and to correlate origin with physical and chemical appearance. Information on the procedures necessary to undertake this aspect of work is also presented.

An improved system of units is proposed for evaluating the contractile activity of the myometrium. Mean active pressure (in kPa) provides the best overall measure of contractility. This measure is broadly compatible with studies quoting 'uterine activity integral' in kPa s per 15 min, but may be applied to any period of time. Units are suggested for measuring the amplitude, frequency and duration of contractions. It is shown that these are independent variables, and that mean active pressure is the numerical product of these three components.

In order to develop a control system for electrical stimulation of paralysed muscle and improve muscle resistance to fatigue, it is useful to investigate the possibilities of simulating the control systems of the normal body. One way is the periodic shifting of stimulation from one muscle to another. This technique is called sequential stimulation and allows sufficient rest time for each muscle to reduce fatigue and consequently prolong muscle strength. It can also be seen to improve the muscle recovery time. In the following study, the muscles rectus femoris, vastus lateralis and vastus medialis were used to keep the knee locked and extended during stimulation. Several experiments were carried out using a three-channel computer controlled stimulator. The results for three-phase sequential stimulation (33% duty cycle per muscle) were most effective and significantly improved the muscle fatigue characteristics.

A hybrid functional electrical stimulation (FES) orthosis is described, comprising a rigid ankle-foot brace, a multi-channel FES stimulator with surface electrodes, body mounted sensors, a 'rule-based' controller and an electro-cutaneous display for supplementary sensory feedback. The mechanical brace provides stability, without FES activation of muscles, for standing postures normally adopted by patients. This avoids inducing muscle fatigue during prolonged upright activity. However, stability is conditional upon the position of the ground reaction vector (GRV) relative to the knee joint. The finite state FES controller reacts automatically to destabilizing shifts of the GRV by stimulating appropriate anti-gravity musculature to brace the leg. The FES system also features a control mode to initiate and terminate flexion of the leg during forward progression. A simple mode of supplementary sensory feedback was used during the laboratory standing tests to assist the patient in maintaining a set posture. Preliminary results of laboratory tests for two spinal cord injured subjects are presented.