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At least 1,351 records · Page 75Linked to original sources
PubMed2006

Genetic association between male attractiveness and female differential allocation.

Differential allocation of reproductive effort towards offspring of attractive mates is a form of post-copulatory mate choice. Although differential allocation has been demonstrated in many taxa, its evolutionary implications have received little attention. Theory predicts that mate choice will lead to a positive genetic correlation between female preference and male attractiveness. This prediction has been upheld for pre-copulatory mate choice, but whether such a relationship between male attractiveness and female differential allocation exists has never been tested. Here, we show that both female pre-copulatory mate choice and post-copulatory differential allocation are genetically associated with male attractiveness in house crickets, Acheta domesticus. Daughters of attractive males mated sooner and laid more eggs when paired with larger males. These forms of mate choice are strongest in large females, suggesting that costs decrease with increasing female size. The genetic association between attractiveness and differential allocation suggests potential for differential allocation to become exaggerated by coevolutionary runaway processes in an analogous manner to pre-copulatory choice. Sexual selection is thus likely to be stronger than predicted by pre-copulatory choice alone.

Animals↗
PubMed1999

Stochastic dynamics and a power law for measles variability.

Since the discovery of a power law scaling between the mean and variance of natural populations, this phenomenon has been observed for a variety of species. Here, we show that the same form of power law scaling also occurs in measles case reports in England and Wales. Remarkably this power law holds over four orders of magnitude. We consider how the natural experiment of vaccination affects the slope of the power law. By examining simple generic models, we are able to predict the effects of stochasticity and coupling and we propose a new phenomenon associated with the critical community size.

Demography↗
PubMed2006

Uncertainty estimation by convolution using spatial statistics.

Kriging has proven to be a useful tool in image processing since it behaves, under regular sampling, as a convolution. Convolution kernels obtained with kriging allow noise filtering and include the effects of the random fluctuations of the experimental data and the resolution of the measuring devices. The uncertainty at each location of the image can also be determined using kriging. However, this procedure is slow since, currently, only matrix methods are available. In this work, we compare the way kriging performs the uncertainty estimation with the standard statistical technique for magnitudes without spatial dependence. As a result, we propose a much faster technique, based on the variogram, to determine the uncertainty using a convolutional procedure. We check the validity of this approach by applying it to one-dimensional images obtained in diffractometry and two-dimensional images obtained by shadow moire.

Algorithms↗
PubMed2005

Wavelet-based combined signal filtering and prediction.

We survey a number of applications of the wavelet transform in time series prediction. We show how multiresolution prediction can capture short-range and long-term dependencies with only a few parameters to be estimated. We then develop a new multiresolution methodology for combined noise filtering and prediction, based on an approach which is similar to the Kalman filter. Based on considerable experimental assessment, we demonstrate the powerfulness of this methodology.

Algorithms↗
PubMed2003

Robust deconvolution of high-frequency ultrasound images using higher-order spectral analysis and wavelets.

Deconvolution of high-frequency (30-40 MHz) ultrasonic images of human skin was studied in vivo. Separate one-dimensional (1-D) functions for the axial and lateral profiles were first estimated using higher-order spectral methods. Subsequently, deconvolution was implemented us ing a regularized inverse Wiener filtering of the wavelet and scaling coefficients that were obtained after a wavelet decomposition of the RF signals. Deconvolution was first performed in the axial direction, then in the lateral direction. The methods were applied to data obtained from the skin of 16 volunteers using three different transducers. Significant improvements in both the axial and lateral resolutions were obtained in all the cases. Features such as hair follicles in the dermis and fingerprints on the surface of the finger were more clearly displayed in the processed images compared to the original images. The results indicate that the deconvolution method using higher-order spectral methods and wavelet analysis could significantly improve the quality of high-frequency ultrasonic skin images.

Adult↗
PubMed2000

Negative binomial additive models.

The generalized additive model is extended to handle negative binomial responses. The extension is complicated by the fact that the negative binomial distribution has two parameters and is not in the exponential family. The methodology is applied to data involving DNA adduct counts and smoking variables among ex-smokers with lung cancer. A more detailed investigation is made of the parametric relationship between the number of adducts and years since quitting while retaining a smooth relationship between adducts and the other covariates.

Algorithms↗
PubMed2000

The analysis of group truncated binary data with random effects: injury severity in motor vehicle accidents.

The analysis of group truncated binary data has been previously considered by O'Neill and Barry (1995b, Biometrics 51, 533-541), where the analysis assumed that responses within each group were independent. In this paper, we consider the analysis of such data when there is group-level heterogeneity. A generalized linear mixed model is hypothesized to model the response and maximum likelihood estimates are derived for the truncated case. A score test is derived to test for heterogeneity. Finally, the method is applied to a set of traffic accident data.

Accidents, Traffic↗
PubMed2001

Autoregressive spatial smoothing and temporal spline smoothing for mapping rates.

This article proposes generalized additive mixed models for the analysis of geographic and temporal variability of mortality rates. This class of models accommodates random spatial effects and fixed and random temporal components. Spatiotemporal models that use autoregressive local smoothing across the spatial dimension and B-spline smoothing over the temporal dimension are developed. The objective is the identification of temporal treads and the production of a series of smoothed maps from which spatial patterns of mortality risks can be monitored over time. Regions with consistently high rate estimates may be followed for further investigation. The methodology is illustrated by analysis of British Columbia infant mortality data.

Biometry↗
PubMed2001

Matched case-control data analysis with selection bias.

Case-control studies offer a rapid and efficient way to evaluate hypotheses. On the other hand, proper selection of the controls is challenging, and the potential for selection bias is a major weakness. Valid inferences about parameters of interest cannot be drawn if selection bias exists. Furthermore, the selection bias is difficult to evaluate. Even in situations where selection bias can be estimated, few methods are available. In the matched case-control Northern Manhattan Stroke Study (NOMASS), stroke-free controls are sampled in two stages. First, a telephone survey ascertains demographic and exposure status from a large random sample. Then, in an in-person interview, detailed information is collected for the selected controls to be used in a matched case-control study. The telephone survey data provides information about the selection probability and the potential selection bias. In this article, we propose bias-corrected estimators in a case-control study using a joint estimating equation approach. The proposed bias-corrected estimate and its standard error can be easily obtained by standard statistical software.

Bias↗
PubMed1978

Left ventricular function after myocardial infarction: relation between systolic time intervals and quantitative ischaemic ECG changes.

Twentyfour male patients with sustained myocardial infarction (MI) were studied with 12-lead ECG and systolic time intervals (STI) 5 months after the acute episode. From the ECGs were calculated the summed voltages of the R wave (sigma R), the Q wave (sigma Q), and the ST segment deviation (sigma ST). These ischaemic ECG variables were correlated with the STI parameters of left ventricular function: LVETI, PEP and PEP/LVET. Statistically significant regression equations relating the ECG changes to the STI variables were found in anterior MI, for sigma ST in the entire series, but not in inferior MI. Thus a simple and rapid inspection of the resting 12-lead ECG gives an indirect but reliable quantitative estimate of left ventricular function in patients with a sustained myocardial infarction.

Aged↗
PubMed1997

Possible sex-correlated transmission of maternal class I HLA haplotypes.

Forty-seven alleles of class I HLA-AB loci (14 for locus A and 33 for locus B) were identified in 787 participants in two groups of unrelated families. Group I included parents and children typed for bone marrow transplantation. Group II included families typed for renal transplantation. Before statistical evaluation, the A locus alleles were grouped into eight classes according to broad specificity, and the B locus alleles were grouped according to HLA epitopes into two classes. Significant differences in HLA-AB haplotype frequencies were found between male and female offspring. When families with children of both sexes were analysed, the frequencies of maternally inherited HLA-AB haplotypes were found to be significantly different in brothers and sisters. The results suggest the possibility that the transmission of specific AB haplotypes from mother to offspring may be correlated to children's sex. The major histocompatibility complex has been shown to be involved in the expression of H-Y male-specific minor histocompatibility antigens. The possible selection in the transmission of specific maternal HLA-AB haplotypes to male offspring may contribute to the avoidance of maternal cytotoxic reactions toward the male foetus.

Adult↗
PubMed1995

Prospective evaluation of ten methods for estimating creatinine clearance in children with varying degrees of renal dysfunction.

The objective of this study was to evaluate ten methods for calculating creatinine clearance (Clcr) in children with renal dysfunction. The design was a prospective, comparative study using 24-h urinary Clcr as the criterion standard. Twenty-two children (age 7-16 years old) were studied. Urinary Clcr ranged from 0 to 161 ml/min/1.73 m2. Calculated Clcr and 24-h urinary Clcr were evaluated statistically. Linear regression analysis, nominal frequency, and mean relative error were used to rank the methods. Children were stratified based on gender and renal function. None of the methods correlated well when Clcr > 100 ml/min/1.73 m2. Predictive performance deteriorated as Clcr decreased. Simple methods using height and serum creatinine were best. Clcr (ml/min/1.73 m2) = (0.52 x height (cm)/serum creatinine)--3.6 was the best equation for estimating Clcr in our patient population consisting of children over 7 years of age with stable serum creatinine.

Adolescent↗
PubMed1991

The Chiang Mai lactation project: study design and implementation.

The Chiang Mai lactation project is a longitudinal field study of human lactation carried out among northern Thai women living in the Sanpatong area of Chiang Mai Province. Its aim was to measure the volume and composition of breast milk transferred from mothers to their infants in the first year postpartum, and to relate it to predictors of milk production, and to the growth of the child. Breast milk and supplementary food intake, and nursing patterns, were recorded over two consecutive 24-hour periods six times during the first year. Samples of breast milk and of supplementary foods were analysed for energy and protein. Supplementary foods were also analysed for bacterial contamination. The growth of the child was measured, and health assessed using a combination of health diaries and examination by a physician. Recruitment to the study was excellent. After recruitment, two subjects left the study area, but otherwise only two dropped out, so complete sets of data covering these variables are available for 58 of the 62 recruited subjects.

Body Weight↗
PubMed1994

Past obstetric history of the mother and its association with low birthweight of a subsequent child: a population based study.

A total population sample of 7286 multigravidae from the Greek National Perinatal Survey (April 1983) was used to determine the association between maternal obstetric history and low birthweight of the subsequent singleton delivery. Significant associations were found with previous early and late fetal losses (miscarriages, induced abortions, stillbirths) and history of haemorrhage during a prior pregnancy. It was found that mothers who had experienced miscarriage(s), induced abortion(s) or stillbirth(s) had relative risks (RRs) of 1.65, 1.81 and 3.59 respectively compared with mothers without any fetal loss. The risk increased substantially with the increasing number of losses and reached 8.83 for the small group of mothers who had experienced all three kinds of fetal loss. For mothers with a history of bleeding in a previous pregnancy the risk was double that of mothers without such a history. The results above were changed only slightly when the significant socio-economic characteristics of the family were taken into account.

Abortion, Spontaneous↗
PubMed1987

Is disordered folate metabolism the basis for the genetic predisposition to neural tube defects?

Vitamin levels were measured in twenty women under 35 years of age with a history of two or more neural tube defect pregnancies. Each index case was compared with a female control matched for age, obstetric history and social class. The mean concentration of red cell folate in the subjects was 178 ng/ml, significantly lower than the mean of 268 ng/ml for the control group (P = 0.005). Red cell folate levels showed a linear relationship with the number of neural tube defect pregnancies, the levels being lowest in women who had had three or four affected offspring. There was no significant difference in serum folate; plasma or white cell vitamin C; plasma vitamin A; thiamine, riboflavine or pyridoxine status; serum vitamin B12; plasma vitamin E; total protein, albumin, transferrin, magnesium, copper or zinc. Diet was assessed by a questionnaire. The dietary intakes of total folate and other vitamins except vitamin A were lower in the subjects than the controls but none of the differences were statistically significant. Regression analysis showed a difference between subjects and controls in the relationship of red cell folate to dietary folate. This study demonstrates an association between susceptibility to offspring with neural tube defects and depressed red cell folate levels which cannot be entirely attributed to a lower dietary intake of folate. It is postulated that one factor predisposing to the occurrence of neural tube defects may be an inherited disorder of folate metabolism.

Adult↗
PubMed2006

Independent effects of socioeconomic status and place of residence on the incidence of childhood type 1 diabetes in Western Australia.

OBJECTIVE: To analyze the incidence of type 1 diabetes in 0- to 14-year olds in Western Australia, from 1985 to 2002, by region and socioeconomic status. METHODS: Primary case ascertainment was from the prospective population-based Western Australian Diabetes Register, and secondary case ascertainment was from the Western Australian Hospital Morbidity Data System. The address at diagnosis was used to categorize cases into urban, rural and remote areas and into five socioeconomic groups using the Index of Relative Socioeconomic Disadvantage. Denominator data were obtained from the Australian Bureau of Statistics. Poisson regression was used to analyze the incidence rates by area and socioeconomic status. RESULTS: There were a total of 1143 cases (904 urban, 190 rural and 49 remote). Case ascertainment was estimated to be 99.8% complete. The mean annual age-standardized incidence from 1985 to 2002 was 18.1 per 100,000 person years in urban (95% CI: 16.3-19.9), 14.3 per 100,000 in rural (95% CI: 11.4-7.3) and 8.0 per 100,000 in remote areas (95% CI: 5.8-10.3). The incidence was significantly higher in urban compared with rural (rate ratio 1.27, p = 0.001) and remote (rate ratio 2.28, p < 0.001) areas. The incidence increased with higher socioeconomic status. The incidence in the highest socioeconomic group was 56% greater than the lowest socioeconomic group (rate ratio 1.56, p < 0.001). These differences in incidence by socioeconomic status and region were independent of each other. CONCLUSIONS: Higher socioeconomic status and residence in the urban area are independently associated with an increased risk of childhood type 1 diabetes in Western Australia.

Adolescent↗