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PubMed1992

Infant mortality and crisis in Mexico.

Data derived from the Encuesta Nacional de Fecundidad y Salud (ENFES) confirm that overall levels of infant mortality in Mexico have been steadily declining. However, a more specific analysis furnishes evidence that this decline has occurred at varying rates within different social groups, reflecting an increase in social inequalities. The analytical strategy used in this article leads to three basic conclusions: (1) the impact of the economic crisis on infant mortality is reflected not in a reversal of the declining trend but an increase in social inequalities; (2) certain variables universally accepted as determinants of infant mortality, such as mother's education, seem nonsignificant for some social sectors; and (3) certain biodemographic characteristics assumed to have a uniform mortality-related behavior vary among sectors, suggesting that even these constants are determined by social factors.

Educational Status↗
PubMed1992

Utilization of maternal health-care services in Peru: the role of women's education.

This article explores the hypothesis that formal education of women influences the use of maternal health-care services in Peru, net of the mother's childhood place of residence, household socioeconomic status and access to health-care services. The findings are consistent with the hypothesis; both cross-sectional and fixed-effects logit models yield quantitatively important and statistically reliable estimates of the positive effect of maternal schooling on the use of prenatal care and delivery assistance. In addition, large differentials were found in the utilization of maternal health-care services by place of residence, suggesting that much greater efforts on the part of the government are required if modern maternal health-care services are to reach women in rural areas.

Adult↗
PubMedDate not supplied

Population concentration: a consideration of density measures and correlates.

"The purpose of the paper is to explore the nature of association of certain external and internal density measures with each other and with a set of selected variables in four states of India. Pearson's Simple Coefficient of Correlations and Stepwise Multiple Regression were used for analysis of data. The results reinforce the notion of a clear distinction between external and internal density measures and their associative factors in India; the two measures of internal density, although highly correlated, were found to have varied relevance to the dependent variables."

Asia↗
PubMed1983

Birthweights in Goroka and Kainantu Hospitals.

Birthweight data for 4474 live, healthy, singleton, full-term births of 2000g or over were analysed. The mean birthweights were 3136 +/- 445g at Goroka, and 3106 +/- 473g at Kainantu. Birthweights varied with sex, region of maternal origin, season and birth order, but not with year. Significant influences on Goroka birthweight values were, in order of importance, birth order, sex and season.

Birth Order↗
PubMed2002

Spatial distribution and sampling plans for Mesoplatys ochroptera (Coleoptera: Chrysomelidae) on sesbania.

With the widespread introduction of the nitrogen-fixing legume sesbania, Sesbania sesban (L.) Merril, in agroforestry systems, the defoliating beetle Mesoplatys ochroptera Stål has become a serious pest of the trees in Africa. To determine within-field and within-plant spatial distribution of M. ochroptera on both seedlings and trees of sesbania, distribution statistics were computed using Iwao's mean crowding regression model. In 1- to 3-mo-old seedlings, the model accounted for 29.8, 32.2, and 61.0% of the variation observed in mean crowding to mean relationships in egg masses, larvae and adults, respectively. The model slopes of the regression were greater than unity for all stages indicating aggregated spatial distribution. Values of the intercept were greater than zero for egg masses, larvae and adults indicating that the basic components of the population are groups of individuals. The highest density (>80%) of mating and feeding adults was found in the upper third of 1- to 2-mo-old seedlings, while most of the egg masses were found in the lower half of seedlings. In trees, >60% of the individuals of all stages were found in the lower third of the foliage canopy, while <10% were found in the upper third. Sampling adults was found to be easier and gave better density estimates of M. ochroptera population than egg masses and larvae. Therefore, sampling plans useful for population studies and decision-making in pest management were developed for adults.

Animals↗
PubMed2001

Two-dimensional versus three-dimensional cell counting: a practical perspective.

In recent years, it has been argued by some neuroanatomists that three-dimensional (3-D) counting approaches must be used in studies of neural systems, so that 'unbiased' counts of neurons can be obtained. By contrast, two-dimensional (2-D) cell-counting methods are said to be 'assumption-based' and to yield inaccurate results. Working from the premise that all scientific methodologies are assumption-based and suffer from inherent biases, the current review considers the relative strengths and weaknesses of 2-D versus 3-D counting approaches. This comparison is from the standpoint of predictive performance with respect to bias, variance and fidelity to the actual spatial arrangements of cells in the tissue under study. When these considerations are taken, together with the human resources that are required in using either methodology, 2-D methods offer more practical alternatives that might even provide more scientifically accurate estimates compared with their 3-D counterparts.

Animals↗
PubMed1997

Analysis of phosphorescence in heterogeneous systems using distributions of quencher concentration.

A continuous distribution approach, instead of the traditional mono- and multiexponential analysis, for determining quencher concentration in a heterogeneous system has been developed. A mathematical model of phosphorescence decay inside a volume with homogeneous concentration of phosphor and heterogeneous concentration of quencher was formulated to obtain pulse-response fitting functions for four different distributions of quencher concentration: rectangular, normal (Gaussian), gamma, and multimodal. The analysis was applied to parameter estimates of a heterogeneous distribution of oxygen tension (PO2) within a volume. Simulated phosphorescence decay data were randomly generated for different distributions and heterogeneity of PO2 inside the excitation/emission volume, consisting of 200 domains, and then fit with equations developed for the four models. Analysis using a monoexponential fit yielded a systematic error (underestimate) in mean PO2 that increased with the degree of heterogeneity. The fitting procedures based on the continuous distribution approach returned more accurate values for parameters of the generated PO2 distribution than did the monoexponential fit. The parameters of the fit (M = mean; sigma = standard deviation) were investigated as a function of signal-to-noise ratio (SNR = maximum signal amplitude/peak-to-peak noise). The best-fit parameter values were stable when SNR > or = 20. All four fitting models returned accurate values of M and sigma for different PO2 distributions. The ability of our procedures to resolve two different heterogeneous compartments was also demonstrated using a bimodal fitting model. An approximate scheme was formulated to allow calculation of the first moments of a spatial distribution of quencher without specifying the distribution. In addition, a procedure for the recovery of a histogram, representing the quencher concentration distribution, was developed and successfully tested.

Light↗
PubMed1995

Age-prevalence and household clustering of Strongyloides stercoralis infection in Jamaica.

The epidemiology of Strongyloides stercoralis was studied in families of clinical (reference) cases and their neighbours at endemic foci in Jamaica. Thirteen foci were studied based on the place of residence of a reference case. For each household of a reference case, the 4 most proximal neighbourhood households (spatial controls) were included in the study. Out of 312 persons contacted 244 were followed up using questionnaires, stool examination and serology. Prevalence of infection based on stool examination was 3.5% and on ELISA 24.2%. Prevalence increased with age but was not related to gender. Reference cases were significantly older than the general study population. The prevalence of infection based on both serology and stool examination was significantly higher in reference than in neighbouring households (the reference cases, themselves, were not included in the analysis). Furthermore, prevalence of infection was highest among persons who shared a bedroom with a reference case and decreased significantly with increasing spatial separation. This is indicative of close contact transmission which has not been previously shown for a geohelminth, but which is common among microparasites.

Adolescent↗
PubMed1992

Assessment of the spatial occurrence of childhood leukaemia mortality using standardized rate ratios with a simple linear Poisson model.

Reports of a suspected cluster of childhood leukaemia cases in West Central Phoenix have led to a number of epidemiological studies in the geographical area. We report here on a death certificate-based mortality study, which indicated an elevated rate ratio of 1.95 during 1966-1986, using the remainder of the Phoenix standard metropolitan statistical area (SMSA) as a comparison region. In the process of analysing the data from this study, a methodology for dealing with denominator variability in a standardized mortality ratio was developed using a simple linear Poisson model. This new approach is seen as being of general use in the analysis of standardized rate ratios (SRR), as well as being particularly appropriate for cluster investigations.

Adolescent↗