PubMed Health⌕ Search

Biomedical subjects

V de Silva

Publications and source records attributed to V de Silva.

8 recordsLinked to original sources

A global geometric framework for nonlinear dimensionality reduction.

Scientists working with large volumes of high-dimensional data, such as global climate patterns, stellar spectra, or human gene distributions, regularly confront the problem of dimensionality reduction: finding meaningful low-dimensional structures hidden in their high-dimensional observations. The human brain confronts the same problem in everyday perception, extracting from its high-dimensional sensory inputs-30,000 auditory nerve fibers or 10(6) optic nerve fibers-a manageably small number of perceptually relevant features. Here we describe an approach to solving dimensionality reduction problems that uses easily measured local metric information to learn the underlying global geometry of a data set. Unlike classical techniques such as principal component analysis (PCA) and multidimensional scaling (MDS), our approach is capable of discovering the nonlinear degrees of freedom that underlie complex natural observations, such as human handwriting or images of a face under different viewing conditions. In contrast to previous algorithms for nonlinear dimensionality reduction, ours efficiently computes a globally optimal solution, and, for an important class of data manifolds, is guaranteed to converge asymptotically to the true structure.

Algorithms↗

Permanent neonatal diabetes mellitus: clinical presentation and epidemiology in Oman.

AIM: To estimate the accurate incidence and prevalence of permanent neonatal diabetes mellitus, and to determine the clinical profile of this condition in the Sultanate of Oman. METHODS: All children diagnosed as having permanent neonatal diabetes mellitus between 1991 and 1995 in Oman were included in the study. RESULTS: The mean incidence was 2.2 per 100 000 live births/year and the prevalence among under 5s during 1995 was 2.0/100 000. Intrauterine growth retardation was noted in all (mean birthweight 1.86 kg), and diabetic ketoacidosis (mean plasma glucose 34.4 (SD 8.7) mmol/l, mean pH 7.17 (SD 0.09) in 80%. Hypertriglyceridaemia (mean serum triglyceride 19.06 (6.13) mmol/) was constant. No infant had clinical or immunological evidence of congenital viral infections. None had C-peptide excretion or circulating islet cell antibody during diagnosis or follow up. The other important features were parental consanguinity in all, HLA DR3/DR4 association in 80%, development of autoimmune hypothyroidism in one and observation of autoimmune disorders (insulin dependent diabetes mellitus and Hashimoto's thyroiditis) in family members. CONCLUSIONS: These findings strongly suggest an immune mediated aetiology for diabetes mellitus. The reported incidence of permanent insulin dependent neonatal diabetes mellitus in Oman is the highest in the world.

Consanguinity↗

Potential acceptors of Norplant implants in comparison with recently sterilized women in Sri Lanka.

This paper analyzes data from a population-based survey fielded in Sri Lanka, which showed that almost half of the women interested in using Norplant contraceptive subdermal implants were actually those who wanted to limit childbearing, a pattern also found in international Norplant clinical studies. A comparison between recently sterilized women and professed limiters of potential Norplant users showed the limiters to be socio-economically and demographically a significantly different group of women from those sterilized. Among several variables analyzed, the most important factor distinguishing the two groups was their relative economic status. Further comparison of the limiters with professed spacers interested in using Norplant showed that the spacers were yet another distinct category of women, the most important characteristic distinguishing between the two groups being the total number of living children. The preliminary results suggest that the Norplant implants system is not necessarily a substitute for sterilization; it appears potentially a popular method among those who want no more children but are not ready to accept sterilization. These findings that the potential Norplant implant users represent different gradients of women in the population have implications for provider counseling and user satisfaction as well as continuation.

Adolescent↗

Contraceptive method change among rural Sri Lankan women.

Patterns of contraceptive method change and their association with reproductive motivation and contraceptive failure are examined using data from a 1986 survey of family planning behaviour of rural Sinhalese married women aged 15-44 in seventeen districts of Sri Lanka. A notable degree of rationality in contraceptive method changes occurs with family formation. The attempt to control unwanted fertility leads to more efficacious use of contraception, including traditional methods. Some methodological improvements to the analysis of contraceptive switching are indicated. Implications of the findings for programmatic emphasis on permanent versus non-permanent modern methods are discussed.

Adolescent↗

Permanent neonatal diabetes mellitus: epidemiology, mode of presentation, pathogenesis and growth.

Permanent neonatal diabetes mellitus (PNIDDM) is a rare form of IDDM with unclear etiology and pathogenesis. We determined the incidence and prevalence rates and studied the clinical and biochemical features of PNIDDM in the Sultanate of Oman. The mean incidence rate during the study period from January 1989 to December 1994 was 1.788 +/- 0.82 per 100,000 live births per year. At the end of December 1994 the prevalence rate was 2.4 per 100,000 children below the age of 5 years. They constituted 41.6% of all cases of IDDM in this age group. Diarrhoea, fever, lethargy, poor feeding and failure to thrive were the most common presenting symptoms. Dehydration and tachypnoea were the most common signs. All patients who developed IDDM during the neonatal period had intrauterine growth retardation and 4.5 presented with diabetic ketoacidosis (plasma glucose 37 +/- 9 mmol/L, pH 7.12 +/- 0.1). Hypertriglyceridemia was a constant feature (19.4 +/- 4.8 mmol/L). They were products of consanguineous marriage with significantly high prevalence of IDDM and NIDDM in their family members. None of the infants had clinical or immunological evidence of congenital viral infection. Three of the five children had HLA-DR2, the diabetes resistance alleles. C-peptide secretion was absent during and after metabolic control of hyperglycemia in all the studied infants and none had circulating islet cell antibody at presentation or during the first year after diagnosis. Despite marked growth retardation at birth, there was a significant improvement of growth after initiating insulin therapy. Four of the 5 patients had normal developmental milestones, one had mild developmental delay following a severe and prolonged attack of hypoglycemia. None of the patients had exocrine pancreatic deficiency. In summary, the very high rate of parental consanguinity, occurrence in both sexes and in two siblings in the same family, absence of islet cell antibodies and the presence of HLA-DR2 loci in 3/5 of patients suggest that PNIDDM is a different disease process to standard IDDM in childhood and an autosomal recessive mode of transmission.

Autoantibodies↗

Satisfied IUD acceptors as family planning motivators in Sri Lanka.

In this study, government midwives were teamed with currently satisfied IUD acceptors to strengthen field motivational and recruitment efforts. The objective was to increase the number of new IUD acceptors. In the experimental study areas, a total of 3,019 new IUD acceptors were recruited. Time series regression analysis revealed a significant difference between the experimental and comparison areas that was over and above what might be expected on the basis of the past history of differences between these two areas. These and other findings suggest that teaming currently satisfied acceptors with government field-workers can have a substantial impact on the recruitment of new family planning users.

Consumer Behavior↗