Microgeographical patterns of schistosomiasis and water contact behavior; examples from Africa and Brazil

This paper examines the results of spatial (microgeographical) water contact/schistosomiasis studies in two African (Egyptian and Kenyan) and one Brazilian communities. All three studies used traditional cartographic and statistical methods but one of them emploeyd also GIS (geographical information systems) tools. The advantage of GIS and their potential role in schistosomiasis control are briefly described. The three cases revealed considerable variation in the spatial distribution of water contact, transmission parameters and infection levels at the household and individual levels. All studies showed considerable variation in the prevalence and intensity of infection between households. They also show a variable influence of distance on water contact behavior associated with type of activity, age, sex, socioeconomic level, perception of water quality, season and availability of water in the home. Water contact behavior and schistosomiasis were evaluated in the Brazilian village of Nova União within the context of water sharing between household and age/sex groups. Recommendations are made for further spatial studies on the transmission and control of schistosomiasis.

Illicit drug profiling, reflection on statistical comparisons

This paper presents reflexions about statistical considerations on illicit drug profiling and more specifically about the calculation of threshold for determining of the seizure are linked or not. The specific case of heroin and cocaine profiling is presented with the necessary details on the target profiling variables (major alkaloids) selected and the analytical method used. Statistical approach to compare illicit drug seizures is also presented with the introduction of different scenarios dealing with different data pre-treatment or transformation of variables.The main aim consists to demonstrate the influence of data pre-treatment on the statistical outputs. A thorough study of the evolution of the true positive rate (TP) and the false positive rate (FP) in heroin and cocaine comparison is then proposed to investigate this specific topic and to demonstrate that there is no universal approach available and that the calculations have to be revaluate for each new specific application.

Comparison of some behavioral and physiological feeding parameters of Triatoma infestans klug, 1834 and Mepraia spinolai porter, 1934, vectors of chagas disease in Chile

There are two vectors of Chagas disease in Chile: Triatoma infestans and Mepraia spinolai. We studied the feeding behavior of these species, looking for differences which could possibly explain the low impact of the latter species on Chagas disease. Both species used thermal cues to locate their feeding source and consumed a similar volume of blood which was inversely related to the body weight before the meal and directly related to the time between meals. The average time between bites were 6.24 and 10.74 days. The average bite of M. spinolai lasted 9.68 min, significantly shorter than the 19.46 min for T. infestans. Furthermore, while T. infestans always defecated on the host, this behavior was observed in M. spinolai in only one case of 27 (3.7%). The delay between the bites and defecation was very long in M. spinolai and short in T. infestans. These differences may affect the reduced efficiency of transmission of Chagas infection by M. spinolai.

Population genetic structure and demography analysis in palinurus elephas populations from atlantic and mediterranean waters

Report for the scientific sojourn at the University of Reading, United Kingdom, from January until May 2008. The main objectives have been firstly to infer population structure and parameters in demographic models using a total of 13 microsatellite loci for genotyping approximately 30 individuals per population in 10 Palinurus elephas populations both from Mediterranean and Atlantic waters. Secondly, developing statistical methods to identify discrepant loci, possibly under selection and implement those methods using the R software environment. It is important to consider that the calculation of the probability distribution of the demographic and mutational parameters for a full genetic data set is numerically difficult for complex demographic history (Stephens 2003). The Approximate Bayesian Computation (ABC), based on summary statistics to infer posterior distributions of variable parameters without explicit likelihood calculations, can surmount this difficulty. This would allow to gather information on different demographic prior values (i.e. effective population sizes, migration rate, microsatellite mutation rate, mutational processes) and assay the sensitivity of inferences to demographic priors by assuming different priors.

Dependence of brain intravoxel incoherent motion perfusion parameters on the cardiac cycle.

Measurement of microvascular perfusion with Intravoxel Incoherent Motion (IVIM) MRI is gaining interest. Yet, the physiological influences on the IVIM perfusion parameters ("pseudo-diffusion" coefficient D*, perfusion fraction f, and flow related parameter fD*) remain insufficiently characterized. In this article, we hypothesize that D* and fD*, which depend on blood speed, should vary during the cardiac cycle. We extended the IVIM model to include time dependence of D* = D*(t), and demonstrate in the healthy human brain that both parameters D* and fD* are significantly larger during systole than diastole, while the diffusion coefficient D and f do not vary significantly. The results non-invasively demonstrate the pulsatility of the brain's microvasculature.

Life cycle and reproductive parameters of Clerada apicicornis signoret (Hemiptera: Lygaeidae) under laboratory conditions

The life cycle of Clerada apicicornis was determined under laboratory conditions. Mean development times in days were: egg 27.2, nymph I 12.5, nymph II 12, nymph III 13.4, nymph IV 16.4, nymph V 26. The life expectancy of adults ranged from 117 to 317 days (mean 196 days). Based on a cohort of 29 females of C. apicicornis, a horizontal life table was constructed. The following predictive parameters were obtained: net rate of reproduction (Ro = 48.31), intrinsic rate of population increase (r m = 0.153), generation time (Tc = 28.20 weeks), and finite rate of population increment (lambda = 1.16). The reproductive value (Vx) for each age class of the cohort females was calculated. The following observed parameters were calculated after mortality in each stage: net rate of reproduction (R'o=13.4), intrinsic rate of population increase (r c' =0.09 ), and finite rate of population increment (lambda' =1.1). The generation time (Tc' =27.4) was estimated using the methods of Laughlin and Bengstron. A vertical life table was elaborated and mortality was described for one generation of the cohort.

Children Order Statistical Bulletin 2005 (PDF 278 KB)

Statistical information based on the Children Order returns for NI up to 31st March 2005

Statistical evaluation of the influence of writing postures on on-line signatures. Study of the impact of time.

The aim of this study is to investigate the influence of unusual writing positions on a person's signature, in comparison to a standard writing position. Ten writers were asked to sign their signature six times, in each of four different writing positions, including the standard one. In order to take into consideration the effect of the day-to-day variation, this same process was repeated over 12 sessions, giving a total of 288 signatures per subject. The signatures were collected simultaneously in an off-line and on-line acquisition mode, using an interactive tablet and a ballpoint pen. Unidimensional variables (height to width ratio; time with or without in air displacement) and time-dependent variables (pressure; X and Y coordinates; altitude and azimuth angles) were extracted from each signature. For the unidimensional variables, the position effect was assessed through ANOVA and Dunnett contrast tests. Concerning the time-dependent variables, the signatures were compared by using dynamic time warping, and the position effect was evaluated through classification by linear discriminant analysis. Both of these variables provided similar results: no general tendency regarding the position factor could be highlighted. The influence of the position factor varies according to the subject as well as the variable studied. The impact of the session factor was shown to cover the impact that could be ascribed to the writing position factor. Indeed, the day-to-day variation has a greater effect than the position factor on the studied signature variables. The results of this study suggest guidelines for best practice in the area of signature comparisons and demonstrate the importance of a signature collection procedure covering an adequate number of sampling sessions, with a sufficient number of samples per session.

Health and Social Care in Northern Ireland: A statistical Profile

2002 edition

MAMOT: hidden Markov modeling tool.

Hidden Markov models (HMMs) are probabilistic models that are well adapted to many tasks in bioinformatics, for example, for predicting the occurrence of specific motifs in biological sequences. MAMOT is a command-line program for Unix-like operating systems, including MacOS X, that we developed to allow scientists to apply HMMs more easily in their research. One can define the architecture and initial parameters of the model in a text file and then use MAMOT for parameter optimization on example data, decoding (like predicting motif occurrence in sequences) and the production of stochastic sequences generated according to the probabilistic model. Two examples for which models are provided are coiled-coil domains in protein sequences and protein binding sites in DNA. A wealth of useful features include the use of pseudocounts, state tying and fixing of selected parameters in learning, and the inclusion of prior probabilities in decoding. AVAILABILITY: MAMOT is implemented in C++, and is distributed under the GNU General Public Licence (GPL). The software, documentation, and example model files can be found at http://bcf.isb-sib.ch/mamot

Statistical tests for scaling in the inter-event times of earthquakes in California

We explore in depth the validity of a recently proposed scaling law for earthquake inter-event time distributions in the case of the Southern California, using the waveform cross-correlation catalog of Shearer et al. Two statistical tests are used: on the one hand, the standard two-sample Kolmogorov-Smirnov test is in agreement with the scaling of the distributions. On the other hand, the one-sample Kolmogorov-Smirnov statistic complemented with Monte Carlo simulation of the inter-event times, as done by Clauset et al., supports the validity of the gamma distribution as a simple model of the scaling function appearing on the scaling law, for rescaled inter-event times above 0.01, except for the largest data set (magnitude greater than 2). A discussion of these results is provided.

Morphometric study of Schistosoma mansoni adult worms recovered from undernourished infected mice

Some unfavourable effects of malnutrition of the host on Schistosoma mansoni worm biology and structure have been reported based upon brigthfield microscopy. This paper aims to study by morphometric techniques, some morphological parameters in male and female adult worms recovered from undernourished albino mice in comparison with parasites recovered from well-fed infected mice. Undernourished animals were fed a multideficient and essentially low protein diet (RBD diet) and compared to well-fed control mice fed with the commercial diet NUVILAB. Seventy-five days post-infection with 80 cercarie (BL strain) animals were sacrificed. All adult worms were fixed in 10% formalin and stained with carmine chloride. One hundred male and 60 female specimens from each group (undernourished and control) were examined using an image system analysis Leica Quantimet 500C and the Sigma Scan Measurement System. The following morphometrical parameters were studied: body length and width, oral and ventral suckers, number and area of testicular lobes, length and width of ovary and uterine egg. For statistical analysis, the Student's t test for unpaired samples was applied. Significant differences (p < 0.05) were detected in body length and width, in parameters of suckers, uterine egg width, ovary length and area of testicular lobes, with lower values for specimens from undernourished mice. The nutritional status of the host has negative influence on S. mansoni adult worms, probably through unavailability of essential nutrients to the parasites.

Parameters affecting cellular invasion and escape from the parasitophorous vacuole by different infective forms of Trypanosoma cruzi

In this study we have examined certain aspects of the process of cell invasion and parasitophorous vacuole escape by metacyclic trypomastigotes and extracellular amastigote forms of Trypanosoma cruzi (G strain). Using Vero (and HeLa) cells as targets, we detected differences in the kinetics of vacuole escape by the two forms. Alcalinization of intercellular pH influenced both invasion as well as the escape from the parasitophorous vacuole by metacyclic trypomastigotes, but not the escape kinetics of extracellular amastigotes. We used sialic acid mutants as target cells and observed that the deficiency of this molecule facilitated the escape of both infective forms. Hemolysin activity was only detected in extracellular amastigotes and neither form presented detectable transialidase activity. Invasion of extracellular amastigotes and trypomastigotes in Vero cells was affected in different ways by drugs that interfere with host cell Ca2+ mobilization. These results are in line with previous results that indicate that metacyclic trypomastigotes and extracellular amastigote forms utilize mechanisms with particular features to invade host cells and to escape from their parasitophorous vacuoles.