Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spatial Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources
PubMed1991

Spatial segregation between populations of ponto-cerebellar neurons: statistical analysis of multivariate spatial interactions.

This study applies terms and methods for describing spatial interactions between multivariate spatial point patterns, which are, to our knowledge, new in neurobiology. We consider two categories of points, type 1 and 2, distributed within a certain reference volume (such as a nucleus of the brainstem or a cortical area). The points may, for example, represent different categories of labelled cells or axonal fields of termination. We say that there is spatial neutrality between points of type 1 and 2 if the types are signed by random labelling. If a mechanism drives the two point categories together, we say that the point patterns are positively associated. Conversely, if a mechanism drives type 1 and 2 points apart, we say that they are segregated. By comparing two cumulative distribution functions of distances between points, we can distinguish neutrality, positive association, and segregation. One function, H12(t), is the cumulative distribution function of the distance t between a pair of randomly selected points of type 1 and 2. The other, H00(t), is the corresponding function for a pair of points randomly selected without reference to type. Plots of the estimated difference between these two functions give an indication of positive association, neutrality, or segregation. A statistical test, based on simulations of random (neutral) distributions, can be used to see whether deviations from neutrality are significant. We apply the analysis described above to a major pathway of the brain, namely the ponto-cerebellar projection. Different types of cells in the pontine nuclei are retrogradely labelled with the fluorescent tracers Rhodamine-B-isothiocyanate, Fluoro-Gold, and Fast Blue. The tracers are injected in adjacent or more distant folia of the cerebellar paraflocculus. The location of the somata of labelled cells are recorded and the total distribution reconstructed in three dimensions and displayed on a dynamic graphics workstation. We ask whether different units (folia) in the paraflocculus receive information from the same population, from two different positively associated populations, or from segregated cell populations. We find a statistically significant tendency for cell populations projecting to adjacent folia to be positively associated, although there are few cells containing multiple labels. Populations of neurons projecting to folia wider apart are significantly segregated. From inspections of the reconstructions, using real-time rotations, we find that the swarms of labelled neurons tend to accumulate in shells or lamellae in the pons. Within the lamellae, the cells are aggregated in clusters and bands with empty holes (containing unlabelled ponto-cerebellar cell bodies, presumably projecting to other cerebellar targets) in between.(ABSTRACT TRUNCATED AT 400 WORDS)

Amidines↗
PubMed2003

The impact of spatial structure on the accuracy of contour maps of small data sets.

Spatial analysis of insect counts provides important information about how insect species respond to the heterogeneity of a given sampling space. Contour mapping is widely used to visualize spatial pest distribution patterns in anthropogenic environments, and in this study we outlined recommendations regarding semivariogram analysis of small data sets (N < 50). Second, we examined how contour maps based upon linear kriging were affected by the spatial structure of the given data set, as error estimation of contour maps appears to have received little attention in the entomological domain. We used weekly trap catches of the warehouse beetle, Trogoderma variabile, and the accuracy assessment was based upon data sets that had either a random spatial structure or were characterized by asymptotic spatial dependence. Asymptotic spatial dependence (typically described with a semivariogram analysis) means that trap catches at locations close to each other are more similar than trap catches at locations further apart. Trap catches were poorly predicted for data sets with a random spatial structure, while there was a significant correlation between observed and predicted trap catches for the spatially rearranged data sets. Therefore, for data sets with a random spatial structure we recommend visualization of the insect counts as scale-sized dots rather than as contour maps.

Animals↗
PubMed2004

A brief visual primer for the mapping of mortality trend data.

Maps are increasingly used to visualize and analyze data, yet the spatial ramifications of data structure are rarely considered. Data are subject to transformations made throughout the research process and then used to map, visualize and conduct spatial analysis. We used mortality data to answer three research questions: Are there spatial patterns to mortality, are these patterns statistically significant, and are they persistent across time? This paper provides differential spatial patterns by implementing six data transformations: standardization, cut-points, class size, color scheme, spatial significance and temporal mapping. We use numerous maps and graphics to illustrate the iterative nature of mortality mapping, and exploit the visual nature of the International Journal of Health Geographics journal on the World Wide Web to present researchers with a series of maps.

Journal Article↗
PubMed2005

Ag-PIE: a GIS-based screening model for assessing agricultural pressures and impacts on water quality on a European scale.

Diffuse pollution of water resources from agricultural sources is a major environmental issue in the European Union, and has been dealt with by specific legislation: the Nitrate Directive of 1991 and the Water Framework Directive of 2000. These attempts to provide a coordinated approach to solving environmental problems require methods and tools for spatial analysis and modelling on a continental scale, with river basins being used as spatial units. This paper presents a screening model (Ag-PIE), developed in a GIS environment, for the assessment of pressures from agricultural land use and the consequent impacts on surface and groundwater. Ag-PIE has been applied at the European scale (EU15), with focus on nitrogen pollution from chemical fertilisers and manure. The model adopts a multi-criteria evaluation procedure applied to spatial data layers which represent the variety of factors affecting the pollution process. The DPSIR (Driving forces, Pressures, State, Impact, Responses) approach is applied to provide the modelling approach with a conceptual framework and to further analyse and communicate results. Ag-PIE is ultimately aimed at providing a tool making use of state-of-the-art geographical databases to support policy-makers at the European level. The scale of reference adopted is the river basin, in particular those that extend across national boundaries. The quality of the results obtained has been assessed against existing related studies and monitoring reports and by means of sensitivity analysis. Conclusions are driven by considering the potential of Ag-PIE in devising policy support and its strengths and weaknesses in view of identifying future research needs.

Agriculture↗
PubMed2006

Masking through averages--intraprovincial heterogeneity in HIV prevalence within the Western Cape.

OBJECTIVE: To measure HIV prevalence at health-district level in the Western Cape (WC) and to compare these findings with those of the National HIV Antenatal Surveys (NHASs). This investigation aimed to estimate the degree of heterogeneity of HIV prevalence within the province in order to inform the design of appropriate and targeted HIV interventions. METHOD: Annual cross-sectional, unlinked district HIV antenatal surveys were implemented in all 25 health districts of the WC for the years 2001 - 2004, concurrently with the NHAS. A stratified proportional sample was drawn for each district, involving all 344 antenatal clinics in the province, and the anonymous screening method as described by the World Health Organization (WHO) was applied. RESULTS: The NHAS revealed a significant increase in HIV prevalence in the WC from 8.6% (95% confidence interval (CI): 5.6 - 11.6) in 2001 to 15.4% (95% CI: 12.5 - 18.2) in 2004. The district-level HIV surveys showed wide variation in HIV prevalence across the health districts, which increased progressively during this period (a range of 0.6 - 22% for the year 2001 increased to 1 - 33% in 2004). Spatial analysis of HIV prevalence by health district for this period also revealed progressive spatial growth of the sub-epidemics, with the highest prevalence observed in districts located in the Cape metropole region. CONCLUSIONS: These concurrent surveys highlight the fact that examining a provincial estimate of HIV prevalence alone has the potential to mask epicentres within the province. This underscores the importance of expanding the surveillance systems to detect heterogeneity sub-provincially, in order to link with local-level planning and resource allocation.

Anonymous Testing↗
PubMed2002

GIS and health care.

GIS and related spatial analysis methods provide a set of tools for describing and understanding the changing spatial organization of health care, for examining its relationship to health outcomes and access, and for exploring how the delivery of health care can be improved. This review discusses recent literature on GIS and health care. It considers the use of GIS in analyzing health care need, access, and utilization; in planning and evaluating service locations; and in spatial decision support for health care delivery. The adoption of GIS by health care researchers and policy-makers will depend on access to integrated spatial data on health services utilization and outcomes and data that cut across human service systems. We also need to understand better the spatial behaviors of health care providers and consumers in the rapidly changing health care landscape and how geographic information affects these dynamic relationships.

Bioterrorism↗
PubMed1979

Visual acuity functions and pattern discrimination in the destriate cat.

The study provides evidence that the cat is capable of processing visual information of some detail after removal of area 17 and most of area 18. This postoperative discrimination of complex spatial stimuli is not based on the use of such cues as luminance differences or local flux cues. From the deficits which follow extensive lesions of areas 17-18, it appears as though these cortices participate in the detection of fine details. We found a modest increase in the threshold of grating acuity, moderate loss in orientation acuity and extensive deficit in a task requiring topographic alignment of contours (vernier offset). Further evidence for the substantial preservation of spatial vision in the destriate cat is provided by experiments which show that perceptual grouping of rectilinear arrays of figural elements (dots or line segments) into obliquely oriented rows is largely unaffected by the lesion, even when the grouping is initiated by near-threshold proximity cues. Since grouping effects are felt to be involved in the organization of the visual field into the figure-ground dichotomy, these results indicate that the neural mechanisms subserving the initial stage of form perception lie outside of areas 17 and 18. Consistent with the increased acuity thresholds of destriate cats, these animals have deficits in several pattern discriminations that require fine-grained spatial analysis The results suggest that areas 17-18 serve as a high-spatial frequency analyzer, but are not essential to pattern and form recognition.

Animals↗
PubMed2000

Selecting relevant electrode positions for classification tasks based on the electro-encephalogram.

The aim is to describe a general approach to determining important electrode positions when measured electro-encephalogram signals are used for classification. The approach is exemplified in the frame of the brain-computer interface, which crucially depends on the classification of different brain states. To classify two brain states, e.g. planning of movement of right and left index fingers, three different approaches are compared: classification using a physiologically motivated set of four electrodes, a set determined by principal component analysis and electrodes determined by spatial pattern analysis. Spatial pattern analysis enhances the classification rate significantly from 61.3 +/- 1.8% (with four electrodes) to 71.8 +/- 1.4%, whereas the classification rate using principal component analysis is significantly lower (65.2 +/- 1.4%). Most of the 61 electrodes used have no influence on the classification rate, so that, in future experiments, the setup can be simplified drastically to six to eight electrodes without loss of information.

Electrodes↗
PubMed2001

Linkages between FAO agroclimatic data resources and the development of GIS models for control of vector-borne diseases.

The Food and Agriculture Organization (FAO) of the United Nations is the largest specialized UN Agency dealing with agriculture, forestry and fishery, particularly in the developing countries. One of its technical services, placed under the Sustainable Development Department, has the responsibility to provide information on environment and natural resources as related to food and agriculture. It includes, among others, expertise in remote sensing, geographic information systems and agrometeorology, production of global environmental digital datasets, meteorological and remote sensing data collection and analysis at near real-time, development of methodologies, models and tools for data standardization, collection, spatialization, analysis and dissemination, networking and information sharing, development of integrated information management systems. Some experience has also been gained in the use of climatic digital datasets for spatial modeling of crop pests and diseases. The description of mapping the distribution of the Western Corn rootworm (Diabrotica virgifera) in Europe as a function of environmental conditions is presented as well as the global assessment of environmental potential constraints based on processing of digital datasets. A simple spatial interpolation routine is briefly explained.

Animals↗
PubMed2026

CpG hypermethylation and WNT/AP-1 cooperativity define the epigenetic landscape and a clinical subgroup of high-risk pediatric adrenocortical carcinoma.

Pediatric adrenocortical tumors are rare, clinically heterogeneous neoplasms with unpredictable outcomes and limited treatment options. Through integrated multi-omic analysis of 214 pediatric adrenocortical tumors combining DNA methylation profiling, transcriptomics, chromatin accessibility, and spatial deconvolution, we identify four distinct risk groups. A high-risk subgroup is characterized by CpG island hypermethylation, chromosomal instability, and dismal survival. These tumors exhibit transcriptional co-activation of WNT signalling and activator protein-1 transcriptional programs and display balanced admixture of zona glomerulosa and zona fasciculata/reticularis-like cells. Spatial analysis reveals zona glomerulosa cells as WNT signaling hubs driving intercellular crosstalk. Mechanistically, the histone deacetylase inhibitor entinostat reverses promoter methylation, silences activator protein-1 activity, and induces apoptotic reprogramming in tumor models. These findings establish a molecular framework for risk stratification and identify actionable therapeutic vulnerabilities, providing an essential resource for studying this molecularly uncharted pediatric malignancy.

Humans↗
PubMedDate not supplied

Effects of unilateral vascular lesions and gender on visual spatial and auditory verbal attention span.

Unilateral cerebral vascular accidents (CVA) produce dominant hemisphere deficits in language and verbal memory, while nondominant hemisphere lesions often impair visual spatial analysis and visual memory. However, effects of unilateral lesions are less specified for visual spatial and auditory verbal attention span. The present study investigated whether tasks of attention span were sensitive to the effects of unilateral strokes. Left CVA females and males were compared to right CVA females and males on these measures. Age and education were not significantly related to performance Significant gender by stroke laterality interactions were found for the visual spatial attention span tasks. Left CVA females performed significantly worse than the other CVA groups on the visual spatial measures. These results suggest that there may be gender related differences in the effects of unilateral CVA on tasks of attention span.

Journal Article↗
PubMed2005

[Assessment on ecological security spatial differences of west areas of Liaohe River based on GIS].

Ecological security assessment and early warning research have spatiality; non-linearity; randomicity, it is needed to deal with much spatial information. Spatial analysis and data management are advantages of GIS, it can define distribution trend and spatial relations of environmental factors, and show ecological security pattern graphically. The paper discusses the method of ecological security spatial differences of west areas of Liaohe River based on GIS and ecosystem non-health. First, studying on pressure-state-response (P-S-R) assessment indicators system, investigating in person and gathering information; Second, digitizing the river, applying fuzzy AHP to put weight, quantizing and calculating by fuzzy comparing; Last, establishing grid data-base; expounding spatial differences of ecological security by GIS Interpolate and Assembly.

China↗
PubMed1980

[Polarization method of fluorescence microscopy for the analysis of the spatial organization of cylindrically symmetrical structures].

Basic clue points and applied mathematics of the simplified variant of the theory for the quantitative analysis of spatial macromolecular organization of anisotropic structures with cylindrical symmetry based on emission polarization characteristics are given. Moreover, a graphical method is presented for the effective analysis of the spatial emission anisotropy of multiple-component systems.

Fluorescence↗
PubMed2005

Ecological covariates of Ascaris lumbricoides infection in schoolchildren from rural KwaZulu-Natal, South Africa.

OBJECTIVES: To identify environmental factors that could serve to predict Ascaris lumbricoides infection patterns and thus guide control efforts in the absence of epidemiological information; to assess whether A. lumbricoides infection is positively associated with the soil clay content. METHODS: Information on A. lumbricoides infection and re-infection in a cohort of primary schoolchildren and interview data on their socioeconomic background and behaviour were combined with environmental data using a geographical information system (GIS). Multivariate models served to explore the covariation of environmental and infection patterns adjusted for possible confounders. RESULTS: Prevalence maps and spatial statistics revealed considerable spatial clustering of infection in the small study area. Logistic multivariate regression models showed strong positive associations of infection with vegetation density measured as the normalized difference vegetation index (NDVI) at baseline [odds ratio (OR) for a 10% increase: 1.82; 95% confidence interval (95% CI): 1.24-2.68; P=0.002] and after re-infection (OR: 2.22; 95% CI: 1.71-2.87; P<0.001). We also found a strong negative association of re-infection with the sun exposure of the soil surface as estimated from digital elevation models (OR: 0.78; 95% CI: 0.88; P<0.001). The soil clay content was only moderately positively associated with infection and re-infection. Socioeconomic and behavioural variables, although correlated with A. lumbricoides infection, did not appear to confound the above associations in the demographically homogeneous study area. Spatial analysis of the model residuals suggested that as the models accounted for most of the spatial pattern, the model standard errors should not be affected by spatial clustering. CONCLUSION: NDVI seems to have a high potential for the prediction of A. lumbricoides infection as it was strongly associated with infection patterns in the study area. Further advantages are that NDVI information is easy to use, affordable and available with global coverage.

Aluminum Silicates↗
PubMed2005

Ecologic covariates of hookworm infection and reinfection in rural Kwazulu-natal/south Africa: a geographic information system-based study.

Information on hookworm infection and re-infection in a cohort of primary school children and interview data on their socioeconomic background and behavior were combined with environmental data using a geographic information system (GIS). Multivariate models served to explore the covariation of environmental and infection patterns adjusted for possible confounders. Our aim was to identify environmental factors that might serve to predict infection and thus guide control efforts when epidemiologic information is insufficient. Furthermore, we wanted to establish whether soil type has a genuine influence on hookworm infection. Prevalence maps and spatial statistics showed considerable spatial clustering of infection in the small ( approximately 28 x 16 km) study area. The multivariate logistic regression models showed strong positive associations of infection at baseline (baseline prevalence = 83.2%) with settlement density (odds ratio [OR] = 1.24, 95% confidence interval [CI] = 1.10-1.38) and vegetation density (OR = 1.66, 95% CI = 1.25-2.22) and a strong negative association with the clay content of the soil (OR = 0.67, 95% CI = 0.62-0.73). Similar but weaker correlations were found after re-infection. Socioeconomic status and behavior did not seem to confound these associations. Spatial analysis of the model residuals suggested that because the models accounted for most of the spatial pattern, the model standard errors were not affected by spatial clustering. Our study shows that the pattern of hookworm infection is strongly influenced by several environmental factors. The GIS-aided prediction of areas in need of treatment is therefore a promising tool to guide control efforts when epidemiologic information is insufficient.

Child↗
PubMed1997

Fibre type grouping in porcine masseter and soleus muscles assessed by the enclosed fibre type concept. A statistical and computational analysis.

Muscle function is determined not only by the frequency of slow (type I) and fast (type II) fibres but also the spatial fibre type organization. During ageing as well as in muscle disorders, divergencies from the normal pattern may occur and are expressed as 'fibre-type grouping'. To elucidate whether intramuscular differences in spatial fibre type arrangements may underlie the functional heterogeneity of the porcine masseter, the arrangements of intrafascicular type I and type II fibres were assessed in terms of the number of enclosed fibres in whole fascicles. The intrafascicular proportions of edge- and centrally located type I and type II fibres were investigated. Two hundred and forty-two porcine masseter fascicles (six masseters) and 63 pig soleus fascicles (five soleus muscles) were investigated by ATP-ase histochemistry. All fascicles were from 11 domestic pigs (1 year, 70-90 kg body weight, all female). Sixty-nine to 90% of the total fibres were type II fibres in the porcine masseter (P < 0.01). In four of five soleus muscles the type II fibre population was dominant. No enclosed type I fibres could be identified in the porcine masseter muscles. This was in contrast to the finding of 1270 enclosed type II fibres. Five enclosed type I fibres (two soleus) and 361 enclosed type II fibres were identified in the pig soleus. The spatial analysis indicated that the fibre type arrangements in the porcine masseter muscles were not homogeneous. No biopsies with random type II fibre organization were identified. Furthermore, half the number of biopsies showed type I fibre segregation. These data suggest that the porcine masseter cannot be considered as having one homogeneous structural identity.

Adenosine Triphosphatases↗
PubMed1998

A distinct low-level mechanism for interaural timing analysis in human hearing.

The detection of phase or timing differences, and amplitude differences between the two ears are cues for the spatial analysis of sound by humans. Previous physiological and anatomical studies of animals suggest that phase and amplitude differences between the ears may depend on different pathways, though human psychophysical studies suggest that interaural phase and amplitude differences between the two ears may be coded in the same way. Here we describe detailed psychophysical analysis of a subject with multiple sclerosis affecting the brain stem. He has a complete deficit in the detection of phase between the ears with preserved detection of interaural amplitude. The results prove that a distinct mechanism exists in humans for interaural phase detection.

Acoustic Stimulation↗
PubMed2004

Spatial patterns of infant mortality in Mali: the effect of malaria endemicity.

A spatial analysis was carried out to identify factors related to geographic differences in infant mortality risk in Mali by linking data from two spatially structured databases: the Demographic and Health Surveys of 1995-1996 and the Mapping Malaria Risk in Africa database for Mali. Socioeconomic factors measured directly at the individual level and site-specific malaria prevalence predicted for the Demographic and Health Surveys' locations by a spatial model fitted to the Mapping Malaria Risk in Africa database were examined as possible risk factors. The analysis was carried out by fitting a Bayesian hierarchical geostatistical logistic model to infant mortality risk, by Markov chain Monte Carlo simulation. It confirmed that mother's education, birth order and interval, infant's sex, residence, and mother's age at infant's birth had a strong impact on infant mortality risk in Mali. The residual spatial pattern of infant mortality showed a clear relation to well-known foci of malaria transmission, especially the inland delta of the Niger River. No effect of estimated parasite prevalence could be demonstrated. Possible explanations include confounding by unmeasured covariates and sparsity of the source malaria data. Spatial statistical models of malaria prevalence are useful for indicating approximate levels of endemicity over wide areas and, hence, for guiding intervention strategies. However, at points very remote from those sampled, it is important to consider prediction error.

Adult↗