Design and performance evaluation of polyvinyl alcohol/polyimide coated optical fibre grating-based humidity sensors.

Optical fibre grating based sensors make a significant contribution to relative humidity measurement for various applications and a number of different designs and sensor configurations have been produced and discussed in the literature. Recent developments have included using sensitive polymers and indeed other materials that experience a variation of their physical and optical properties as a result of the absorption of moisture and which thus creates a modification of the characteristic spectral features of the gratings used. The strain and the effective refractive index of the gratings are affected by the change induced by the polymer and these effects were calibrated against the relative humidity variations that initially induce variations in the polymer layer. In this work, an evaluation is made of the performance characteristics of two different moisture sensitive polymers, i.e., polyimide and polyvinyl alcohol, as the basis of such sensors, while at the same time using different types of fibre gratings i.e., fibre Bragg gratings and long period gratings. Their performance is discussed in light of the operation of similar types of polymer-coated and other grating based sensors reported in the literature.

Risk factors of childhood asthma: a Sri Lankan study.

A case-control study was carried out to evaluate the genetic and environmental risk factors of childhood asthma in a group of Sri Lankan children. Three hundred cases (admitted with symptoms of asthma) and 300 age-matched controls were compared over a period of 23 months commencing in January 1996. Family history of atopy, feeding habits in infancy, bronchiolitis in infancy, passive smoking, exposure to dust and dampness, and exposure to pet animals were studied as risk factors for asthma. The risks associated with social factors were also studied. The risk associated with variables were calculated using the chi-squared test in the bivariate analysis and the forward logistic regression model in the multivariate analysis. Parental asthma, asthma in a sibling and in a relative, parental allergic rhinitis, discontinuation of breastfeeding after 6 months in infancy, bronchiolitis in infancy, living in a dusty environment, and a father with primary education compared to secondary education were independently associated with an increased risk of asthma (p < 0.05). This study reinforces the view that asthma has a multifactorial aetiology. Influence of paternal asthma is more than that of maternal asthma. As a preventive measure continuation of breastfeeding beyond 6 months is important.

Identification from skeletal remains.

The remains of a suspected case of homicide, found to be almost totally skeletal on exhumation, was dug out from a pit in a tract of marshy land in the deep south or Sri Lanka. No clothing or other identifying articles were found with the remains. During exhumation a distinct odour of kerosene oil was observed. Examination revealed that the major part of the skeleton was present, including the skull and lower jaw. Examination of these enabled an opinion to be given on the stature, sex and age of the deceased. The head hair found at exhumation showed evidence of burning. Two groups of injuries were found in the bones. One group was consistent with injuries caused during life and showing the characters of healing and moulding. Although medical records were not available, it was possible to obtain a description of the injuries from the court records as a doctor had given evidence on injuries sustained by the deceased years previously. The other group comprised of injuries that would have caused or contributed to death, or were post-mortem injuries inflicted for purposes of disposal. This case illustrates that personal identification may be established from old healed skeletal injuries.

Agrochemical poisoning in Sri Lanka.

Mortality resulting from agrochemicals met within the Office of the Judicial Medical Officer, Colombo, which is the premier Medico-legal Institute in Sri Lanka, are analysed over a 3-year period and the morbidity and mortality rates of the entire country are examined over a 10-year period. The number of patients admitted to hospitals in Sri Lanka during the period 1975-1983, stood at around 11,000-15,000 each year, with the year 1983 recording 16,649 admissions. The number of deaths during the same period varied from 900 to 1500 each year, while the year 1983 recording 1521 deaths. About 75% of such cases of poisoning were due to self ingestion while accidental and occupational poisoning formed the balance. Principal agricultural districts like Kurunegala, Jaffna, Vavuniya, Nuwara-Eliya and Badulla recorded the highest incidence of poisoning. The mortality figures of the Office of the J.M.O., Colombo, indicated that 4% of all bodies subjected to autopsy were those of agrochemical poisoning. The male/female ratio was 2:1. Seventy-five percent of deaths from agrochemical poisoning were recorded in the 15-39 year age group, while 33% of deaths belonged to the 20-24 age group. One third of cases of agrochemical poisoning were dead on being brought to hospital, while 50% were dead within 2 h and 60% dead within 24 h. Organophosphates accounted for 57.6% of all cases of agrochemical poisoning, while paraquat accounted for 21.2% of cases. Deaths were also reported from what are called safe chemicals like Carbamates and Pyrethrums due to their lethal additives.