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At least 649 records · Page 36Linked to original sources
PubMed1995

[Homogeneity of the spatial distribution of cancers of the female reproductive tract in Quebec].

Risk factors associated with women's reproductive life and sexual growth do not adequately predict cancer incidence of the breast, uterus and ovary. The heterogeneous worldwide distribution of these cancers could imply that some environmental and cultural risk factors are involved in their cancerogenesis. The few attempts made so far to unravel their spatial structures at a geographic scale facilitating the search for exogenous risk factors have proved inconclusive. This study reports the results of a spatial analysis of the cancer incidence rates for breast, cervix, endometrium and ovary among Community Health Departments (CHD) in Quebec using a spatial autocorrelation method. Correlograms built according to four definitions of the inter-CHDs distance indicate that breast and ovary incidence rates follow quite similar spatial gradients attesting to their etiologic affinity. They also suggest that the spatial distribution of endometrial cancer follows a gradient divergent from that of breast and ovary cancers, and that the CHDs' spatial scale does not suitably describe the distribution of cervical cancer. The demonstration of a structured spatial distribution for breast, endometrium and ovary cancers in Québec strengthen the hypothesis that cultural or environmental risk factors are involved in their etiology. But, the observed disparities in the spatial structure of these cancers imply that their etiologic specificity may be greater than their biologic bond would suggest.

Adolescent↗
PubMed2005

The evolution of a Müllerian mimic in a spatially distributed community.

Strong positive density-dependence should lead to a loss of diversity, but warning-colour and Müllerian mimicry systems show extraordinary levels of diversity. Here, we propose an analytical model to explore the dynamics of two forms of a Müllerian mimic in a heterogeneous environment with two alternative model species. Two connected populations of a dimorphic, chemically defended mimic are allowed to evolve and disperse. The proportions of the respective model species vary spatially. We use a nonlinear approximation of Müller's number-dependent equations to model a situation where the mortality for either form of the mimic decreases hyberbolically when its local density increases. A first non-spatial analysis confirms that the positive density-dependence makes coexistence of mimetic forms unstable in a single isolated patch, but shows that mimicry of the rarer model can be stable once established. The two-patch analysis shows that when models have different abundance in different places, local mimetic diversity in the mimic is maintained only if spatial heterogeneity is strong, or, more interestingly, if the mimic is not too strongly distasteful. Therefore, mildly toxic species can become polymorphic in a wider range of ecological settings. Spatial dynamics thus reveal a region of Müllerian polymorphism separating classical Batesian polymorphism and Müllerian monomorphism along the mimic's palatability spectrum. Such polymorphism-palatability relationship in a spatial environment provides a parsimonious hypothesis accounting for the observed Müllerian polymorphism that does not require quasi-Batesian dynamics. While the stability of coexistence depends on all factors, only the migration rate and strength of selection appear to affect the level of diversity at the polymorphic equilibrium. Local adaptation is predicted in most polymorphic cases. These results are in very good accordance with recent empirical findings on the polymorphic butterflies Heliconius numata and H. cydno.

Adaptation, Physiological↗
PubMed2003

[Study on the application of geographic information system in spatial distribution of hemorrhage fever with renal syndrome in China].

OBJECTIVE: To analyze the spatial distribution of hemorrhagic fever with renal syndrome (HFRS) in China by geographic information system, and to draw up a map on HRFS risk areas. METHODS: A set of database was set up using the information collected and linked to electronic maps of China in a software ArcGIS 8.01 from 41 HFRS surveillance sites during 1995 - 1998. A HFRS spatial distribution model was developed using inverse distance weighted interpolation of ArcGIS's spatial analysis method. The normalized difference vegetation index (NDVI) in each HFRS surveillance site was extracted from SPOT4 satellite vegetation imagery. Correlation analysis was performed through SPSS 10.0 to analyze the association between NDVI and HFRS incidence, HFRS risk areas were mapped under different colors. RESULTS: Spatial distribution model from HFRS surveillance sites showed that HFRS foci mainly presented in the Heilongjiang River drainage, the middle and lower reaches of the Yellow River, the middle and lower reaches of the Yangtze River, and the Jinghang grant Canal-Huaihe River drainage. It was consistent with HFRS distribution map derived from national infectious disease reporting system. Correlation analysis indicated that HFRS incidence rates were significantly associated with NDVI (r = 0.417, P < 0.01). The HFRS risk areas was mapped according to NDVI of each surveillance site. CONCLUSION: It is promising to apply GIS technology in predication of the distribution of HFRS by establishing this prediction model.

Animals↗
PubMed2025

An integrated multiscale air quality modelling framework for industrial park pollution: Linking local emissions to regional transport.

Capturing the spatiotemporal distribution of pollutants in industrial parks remains challenging for regional air quality models because of their coarse resolution (3 km), resulting in uncertainties in local emission quantification. To address this, we developed the Integrated Multiscale Air Quality Modelling System for Industry (IAQMS-Industry), coupling the regional Nested Air Quality Prediction Modelling System (NAQPMS) with a city-scale chemical transport model. This framework integrates point-source locations and Gaussian plume dispersion to simulate particulate matter with a diameter smaller than 2.5 micrometres (PM2.5) at 100 m resolution. Applied to the Beijing Yi Zhuang and Tangshan industrial parks and evaluated against observations. The coupled model achieved a normalized mean bias (NMB) ranging from 3.1 % to 6.2 %, improving upon NAQPMS (-16.9 % to -7.7 %). Spatial analysis revealed that coarse regional grids underestimated the PM2.5&#x200b; concentrations at industrial sites by smoothing gradients, whereas IAQMS-Industry successfully resolved spatial patterns. Industrial point emissions accounted for 22.9 %-26.4 % of PM2.5 in the coupled model, which was significantly greater than the regional model estimates of 1.6 %-13.7 %. These findings indicate that regional models overestimate pollutant dispersion processes in industrial parks while underestimating local industrial impacts. By explicitly resolving point-source dynamics and linking them to regional transport, IAQMS-Industry provides a robust tool for designing targeted emission controls in industrial cities and balancing local air quality improvements with minimized regional pollution outflow. This study underscores the necessity of multiscale modelling for accurate source apportionment and informed environmental governance in industrial zones.

Air Pollution↗
PubMed2005

Disease mapping and risk assessment in veterinary parasitology: some case studies.

Disease mapping and risk assessment are important tasks in the area of medical and veterinary epidemiology. The development of methods for mapping diseases has progressed considerably in recent years. Geographical Information Systems (GIS), Remote Sensing (RS), and Spatial Analysis represent new tools for the study of epidemiology, and their application to parasitology has become more and more advanced, in particular to study the spatial and temporal patterns of diseases. The present review highlights the usefulness of GIS and RS in veterinary parasitology in order to better know the epidemiology of parasite organisms, causing either snail/arthropod borne diseases or direct transmissible diseases, mostly in small areas with a strong impact by man. It demonstrates the potential of these technologies to serve as effective tools for: data capture, mapping and analysis for the development of descriptive parasitological maps; studying the environmental features that influence the distribution of parasites; predicting parasite occurrence/seasonality based on their environmental requirements and as decision support for disease intervention; and surveillance and monitoring of animal diseases.

Animals↗
PubMed2000

Template mixture models for direct cortical electrical interference data.

This paper introduces a statistical approach for high-level spatial analysis when there is little prior information about the shape or location of the region of interest in the underlying image and limited spatial resolution of the available data. Our work was motivated by a functional brain mapping technique called direct cortical electrical interference (DCEI) that gives binary observations at multiple sites throughout the brain. We estimate an underlying, binary spatial response function using a mixture of an unknown number of simple geometrical shapes (e.g. circles) with unknown centers and sizes to be estimated. Inference is made using reversible jump Markov chain Monte Carlo. The approach is illustrated with simulated examples and a real example with DCEI data.

Journal Article↗
PubMed2003

Shell shape of the land snail Cornu aspersum in North Africa: unexpected evidence of a phylogeographical splitting.

Anatomical and molecular characters used to differentiate populations of the land snail Cornu aspersum (Helix aspersa) exhibit, in the western Mediterranean, definite and concordant patterns of correlation with geography. Scenarios involving Pliocene geological changes and postglacial expansion during the Pleistocene were proposed in previous studies to account for the establishment of this geographical structure. In the present work, we have performed a spatial analysis of variation in shell morphometrics, after the partitioning of the overall variation into size and shape components by means of a principal component-based approach (Cadima and Jolliffe, 1996). In order to know if the same historical events have also structured shell variation, the analysis includes all the populations from North Africa which were investigated for anatomical and molecular surveys. Contrary to shell size, which shows a significant spatial heterogeneity essentially related to environmental pressures, variation in shell shape components splits the populations according to a geographical pattern reflective of hypotheses suggested for molecular markers and genital anatomy. This implies that the selective forces often invoked to explain spatial changes in shell shape are not the deciding factors in the present case. Moreover, within each of the two geographical clusters defined, Mantel correlograms show that the similarity between populations declines according to an isolation by distance model. Because of the different allometric relationships between shell size and genitalia measurements in Western and Eastern entities of North Africa, mechanical constraints, possibly leading to a precopulatory isolation in the contact zone, are involved.

Africa, Northern↗
PubMed1980

[Complex spatial evaluation of the electromotive force of the heart in persons with healthy hearts].

A complex spatial analysis of the electromotive cardiac force was performed to 150 subjects with intact hearts, aged from 20 to 55. The extend, direction and rate of the change in the direction and extend of 10, 20, 30, 40, 50, -30, -20, -10 and maximum spatial vectors were analysed. The results were processed according to the method of variation analysis, presented in diagrams and tables. The results obtained, which do not contradict those found in literature, show that the methods applied (graphic and automatic) could successfully be applied in practice and the data obtained--serve as standards for the work with the same apparatuses (Hellige EG-22 with an appliance, constructed and produced in Bulgaria.

Adult↗
PubMed2006

An image analysis of the spatial distribution of perivascular mast cells in human melanoma.

A mutual spatial and functional relationship occurs between mast cells (MCs) and endothelial cells and the density of MCs is highly correlated with the extent of tumor angiogenesis. The aim of this study was to investigate the pattern of MCs around the blood vessels in melanoma samples by means of an approach derived from spatial statistics, based on the analysis of the distribution of the distances of MCs from vessels to objectively establish if the two structures (MCs and vessels) are distributed independently over the studied area or if they displayed any kind of spatial association. Results showed that a higher number of vessels and MCs can be observed in melanoma as compared with samples from common acquired nevi (control group). The percent of area covered by vessel profiles was significantly higher in the melanoma group than the control group and the MC density was also significantly different; the melanoma group showing a number of MCs per unit area twice as high as the number measured in the control group. Furthermore, in the melanoma group, MCs were closer to each other and to the vessels. In fact, both the mean distance from vessels and the mean distance from the nearest cell profile were significantly lower than in the control group. This close association between MCs and the endothelium does not necessarily imply a participation of MCs in angiogenic processes, but might rather indicate that MCs are involved in the maintenance reaction necessary for the long lasting functional integrity of the endothelium.

Adult↗
PubMed1997

An experimental investigation of the spray issued from a pMDI using laser diagnostic techniques.

This research was concerned with the experimental investigation of the spray issued from a pressurised metered-dose inhaler (pMDI) using laser diagnostic techniques and has been motivated by the urgent need to find suitable replacements to the environmentally destructive CFC propellants currently used in the device. The experimental work was conducted using phase-Doppler particle analysis (PDPA), a single particle light scattering technique that provides the simultaneous measurement of drop size, velocity, and concentration, yielding the most detailed temporal and spatial analysis of the pMDI spray to date. Three formulations were studied to compare the performance of an "ozone-friendly" hydrofluoroalkane propellant against that of a traditional CFC propellant mixture and a commercially available CFC formulation containing drug and surfactant. The PDPA analysis was complemented by a visual investigation of the near-orifice flow field using copper laserstrobe microcinematography to obtain information on the primary atomization process of the pMDI. This work was conducted in parallel with the theoretical investigation of the spray issued from a pMDI.

Aerosol Propellants↗
PubMedDate not supplied

[The occurrence of Echinococcus multilocularis in red foxes in lower Saxony: identification of a high risk area by spatial epidemiological cluster analysis].

There is considerable interest in the spatial distribution of Echinococcus multilocularis in red foxes (Vulpes vulpes L.), because this parasite causes the zoonoses of alveolar echinococcosis which is potentially of high fatality rate. High risk areas are known from France, Switzerland and the Swabian Alb in Germany for a long time. In this work, the spatial scan statistic is introduced as an instrument for identification and localisation of high risk areas, so called disease clusters in spatial epidemiology. The use of the spatial scan statistic along with data about the distribution of the parasite in 5365 red foxes in Lower Saxony, that were collected during 1991 to 1997, led to the identification of another high risk area. The relative risk for this disease cluster is approximated by RR = 5.03 (CI0.95(RR) = [4.27; 6.58]) for the period of 1991 to 1994 and by RR = 4.45 (CI0.95(RR) = [3.53; 5.59]) for the period of 1994 to 1997, respectively.

Animals↗
PubMed2006

Spatial distribution pattern of oviposition in the mosquito Aedes aegypti in relation to urbanization in Buenos Aires: southern fringe bionomics of an introduced vector.

The distribution of Aedes aegypti (L) (Diptera: Culicidae) oviposition in Buenos Aires City is spatially heterogeneous. Oviposition activity was monitored for a year with a grid of 279 traps at 850-m intervals that were serviced weekly. Geostatistics were used for the spatial analysis and generalized linear regression to model oviposition as a function of demographic and environmental variables. The proportion of weeks infested and the total number of eggs showed spatial continuity and were higher in areas that had higher densities of houses and were closer to industrial sites; they were lower in areas with higher human populations or higher densities of flats. When all sites were considered, the spatial structure showed a strong trend, but after regression, the residuals presented lower spatial dependence. When only infested sites were considered, the oviposition variables were spatially autocorrelated and the regression residuals showed little or no spatial dependence. The spatial pattern of Ae. aegypti oviposition in a highly urbanized city such as Buenos Aires seems to be related to the urbanization gradient. These urban environments might present different resource availability or continuity between patches of resources.

Aedes↗
PubMed1999

Transitions and inequalities in acute myocardial infarction mortality in New South Wales, 1969-94.

OBJECTIVE: To chart the transition in myocardial infarction mortality in NSW between 1969 and 1994 and to determine whether spatial, marital and occupational status differentials increased over time, despite overall mortality decline. METHOD: The study was undertaken in NSW for the 25-year period from 1969 when mortality from ischaemic heart disease declined. The demographic and spatial analysis involved descriptive epidemiology and utilised the unit list mortality files of the Australian Bureau of Statistics which are based on detailed death certificate information. RESULTS: Spatial, marital and occupational status differentials in myocardial infarction mortality increased over time, more especially variations by occupational status, inland/metropolitan differences, and married/divorced or widowed variation. Spatial variations in mortality were not simply the result of occupational status differences as mortality from white collar groups was also elevated in inland areas. Spatial variation in mortality was not diluted due to the impact of immigration. CONCLUSIONS: Particular subgroups of people remained at risk and it is likely that differential access to ambulance services and travel time contribute, more particularly in inland rural areas. IMPLICATIONS: Groups at risk need to be more precisely targeted for preventative measures and public health initiatives, with particular implications for groups in inland rural areas, the Hunter Region, and outer lower income areas of Sydney.

Adult↗
PubMed1998

Cognitive decline unlike normal aging is associated with alterations of EEG temporo-spatial characteristics.

The diagnosis of beginning dementia is based mainly on neuropsychological testing. Several measures of EEG spectral composition, coherence and complexity (correlation dimension) have been shown to correspond to cognitive function. Only a few studies have evaluated EEG changes in normal aging, and no quantitative study has addressed changes in EEG during cognitive tasks in demented elderly. In this study the quantitative descriptors of EEGs from 31 demented or cognitively impaired elderly persons, 30 healthy elderly (mean age 69 years) and 35 young controls (mean age 31 years) were compared. The EEGs were recorded during two resting conditions (eyes closed and eyes opened) and two tasks (mental arithmetics and a lexical decision). The goal of the study was to evaluate which temporal and spatial EEG descriptors change with cognitive decline and with normal aging, respectively. Cognitive categories (unimpaired, impaired, demented) were based on Structured Interview for the Diagnosis of Dementia of Alzheimer Type (SIDAM) scores. The EEGs were analysed using adaptive segmentation of continuous EEG, which quantifies the succession of distinct stable topographic voltage patterns (EEG microstates). The main findings were a significant increase in the number of ultra-short EEG microstates and, independently, a reduction in the average duration of EEG microstates in the cognitively impaired and demented patients. In addition, cognitive impairment was associated with a reduction or loss of EEG reactivity normally observed when the resting states with closed and with opened eyes are compared. No alterations in temporal or spatial EEG descriptors were found in normal aging. Cognitive tasks did not add to information already obtained during the resting states. The reduction in EEG microstate duration correlated with loss of cognitive function. Temporo-spatial analysis of EEG therefore is a useful indicator of cortical dysfunction in dementia, correlating with the degree of cognitive impairment. Normal aging seems not to be accompanied by changes in temporo-spatial EEG patterns. The data suggest that fragmentation of the electrophysiological processes underlies cognitive dysfunction in Alzheimer's disease.

Adult↗
PubMed2005

Image acquisition with immersion objective lenses using electrons emitted with several tenths of an electron volt energies: towards high spatial resolution ESCA analysis.

This study aims to evaluate the spatial resolution achievable with photoelectrons in order to perform localised UPS or XPS analyses on various heterogeneous samples. This investigation is intentionally restricted to direct image acquisition by immersion objective lenses, involving electrons ejected with initial energies of several tenths of an electron-volt. In order to characterise the contribution of all optical elements, analytical investigations were associated to numerical simulations based on SIMION 7 software. The acquisition of high-quality images implies a simultaneous reduction in spherical and chromatic aberrations by a narrow aperture stop placed at the output pupil of the objective. With such limitations in useful emission angles, it is shown that monochromatic electron beams build images with a resolution of about 1 nm, especially for the acceleration bias mode where the focussing electrode is biased at a positive high voltage. Even energy dispersed electron beams, limited by a 4 eV band pass spectrometer, can produce images convenient for highly localised ESCA analyses (resolution 3 nm), where the objective lens is associated with an aperture stop of 30 microm in diameter without using acceleration voltages above 5000 V.

Journal Article↗
PubMed2001

Differential expression of XET-related genes in the leaf elongation zone of F. pratensis.

Festuca pratensis Huds. is a forage grass with the ability to withstand harsh climatic conditions. However, its potential agronomic use is limited by its poor competitive ability, which can be traced to limitations in leaf growth. In order to characterize this process and to identify genes which might function as markers for leaf growth, three XET-related genes in the leaf elongation zone (LEZ) of F. pratensis are reported. A detailed expression analysis is presented of the three genes in two F. pratensis genotypes with contrasting leaf growth characteristics grown under two nitrogen levels. By means of a detailed spatial analysis of growth and XET encoding transcript pattern along the LEZ, a specific correlation is shown between FpXET1 expression and tissue elongation that is maintained under the different growth conditions, while the two other XETs expressed in the LEZ show different transcript dynamics. Tissue localization of FpXET1 and FpXET2 transcripts indicate an accumulation throughout young tissue, which is consistent with the encoded proteins playing roles in cell wall modification processes during growth. It is proposed that FpXET1 is a potential marker for tissue elongation and leaf growth in F. pratensis.

Amino Acid Sequence↗
PubMed2001

Disease map reconstruction.

The analysis of the geographical distribution of disease incidence or prevalence is now of considerable importance for public health workers and epidemiologists alike. Important disease variations often have a spatial expression and so spatial analysis methods are an important additional tool in this connection. In this tutorial I have aimed to highlight the main issues relating to the analysis of disease where the goal is the reduction in noise in a disease map. This area is sometimes simply called disease mapping. A number of modelling approaches to disease mapping are considered and a case study highlighting the methods advocated is also included.

Bayes Theorem↗
PubMed1985

Cross correlation studies in primate motor cortex: event related correlation.

Simultaneous extracellular unit recordings were made from each cell of 237 pairs in two awake monkeys, during a voluntary reaching movement of the forelimb. The cells were located in contralateral precentral cortex and functionally coupled to single forelimb joints, as indicated by intracortical microstimulation and passive sensory stimulation. Cross correlation analysis showed that 72 of these pairs exhibited significant event-related correlation over periods of up to 780 ms, comparable to and coincident with the forelimb movement. Spatial analysis showed that such correlation extended across contiguous portions of all four forelimb joint zones of precentral cortex, over distances up to 3.5 mm. No preferred direction of correlation was observed. The data confirm the previously described nested organization of the forelimb area of precentral cortex. Findings are discussed in terms of mechanisms by which columns of neurons in motor cortex participate in the reaching movement.

Animals↗