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PubMed1982

Application of the optical Fourier transform for analysis of the spatial distribution of collagen fibers in normal and osteopetrotic bone tissue.

Optical Fourier analysis was applied for evaluation of the differences between normal and pathologically changed bone tissue. Collagen fibers were used as markers of bone structure. To prove the usefulness of this technique for objective mathematical analysis of these differences the spatial spatial distribution of collagen fiber bundles was evaluated in normal and osteopetrotic bone. The variation in the spatial distribution of collagen fiber bundles in cross sections of femur diaphyses was evaluated quantitatively by optical diffraction three groups of Fatty Orl-op strain rats, i.e. phenotypically normal animals, osteopetrotic (op/op) mutants and op/op-mutants cured by transplantation of normal syngenic bone marrow. The histological sections of decalcified bone were stained with Sirus-Red and then photographed under polarizing microscope. The Sirus-Red staining was used to enhance the natural birefringency of collagen fibers. Diffractograms obtained from microphotographs of selected bone section areas, i.e. outer and inner circumferential lamellae and haversian bone of normal and cured op/op animals as well as whole cortical bone and woven bone filling the medullary cavities in op/op mutants were analysed separately. Diffractograms contain summarized information on the size and relative position of these structures in histological sections. The radial and angular distribution of light energy were evaluated for each diffractogram with an electronic detector. The obtained distributions were described by several sets of parameters concerning the position, level and shape of local maxima and minima. Out of these parameters five with the highest discriminant power were chosen for further mathematical analysis. This analysis was based on the calculation of the position of centroids in the multidimensional space described by the linear functions of the chosen parameters for each of the evaluated bone section areas. The centroids (mean values of discriminant scores of each group) represent the centers of gravity of the analysed groups, while the separation of the centroids tested by the F-test illustrates the differences between the respective groups of selected bone section areas. A high level of separation of centroids was found when osteopetreotic bone was compared with normal one, what means that the spatial distribution, size and interstructural distances between the collagen fiber bundles in bone tissue in these two groups of animals differ markedly. A similar situation was observed when osteopetrotic bone was compared with bone tissue obtained from op/op mutants cured by transplantation of normal syngenic bone marrow. On the other hand, the level of separation of centroids was low when bone tissue of cured op/op mutants was compared with the control one, a finding which corresponds to the less pronounced histological differences between these two groups of animals. Computer-aided classification on single microphotographs of selected bone section areas to the known a priori type of bone tissue was performed...

Animals↗

PubMed2005

Studies of a novel sensor for assessing the spatial distribution of cavitation activity within ultrasonic cleaning vessels.

This paper describes investigations of the spatial distribution of cavitation activity generated within an ultrasonic cleaning vessel, undertaken using a novel cavitation sensor concept. The new sensor monitors high frequency acoustic emissions (>1 MHz) generated by micron-sized bubbles driven into acoustic cavitation by the applied acoustic field. Novel design features of the sensor, including its hollow, cylindrical shape, provide the sensor with spatial resolution, enabling it to associate the megahertz acoustic emissions produced by the cavitating bubbles with specific regions of space within the vessel. The performance of the new sensor has been tested using a 40 kHz ultrasonic cleaner employing four transducers and operating at a nominal electrical power of 140 W under controlled conditions. The results demonstrate the ability of the sensors to identify 'hot-spots' and 'cold-spots' in cavitation activity within the vessel, and show good qualitative agreement with an assessment of the spatial distribution of cavitation determined through erosion monitoring of thin sheets of aluminium foil. The implications of the studies for the development of reliable methods of quantifying the performance of cleaning vessels are discussed in detail.

Journal Article↗

PubMed2006

Effect of action video games on the spatial distribution of visuospatial attention.

The authors investigated the effect of action gaming on the spatial distribution of attention. The authors used the flanker compatibility effect to separately assess center and peripheral attentional resources in gamers versus nongamers. Gamers exhibited an enhancement in attentional resources compared with nongamers, not only in the periphery but also in central vision. The authors then used a target localization task to unambiguously establish that gaming enhances the spatial distribution of visual attention over a wide field of view. Gamers were more accurate than nongamers at all eccentricities tested, and the advantage held even when a concurrent center task was added, ruling out a trade-off between central and peripheral attention. By establishing the causal role of gaming through training studies, the authors demonstrate that action gaming enhances visuospatial attention throughout the visual field.

Adult↗

PubMed1997

Spatial distribution and discharge characteristics of superior colliculus neurons antidromically activated from the omnipause region in monkey.

One proposed role of the superior colliculus (SC) in oculomotor control is to suppress or excite the activity of brain stem omnipause neurons (OPNs) to initiate or terminate saccades, respectively. Although connections from the SC to the OPNs have been demonstrated, the spatial distribution and discharge characteristics of the projecting neurons from the SC remain unknown. We mapped the spatial distribution of the deeper-layer neurons of the SC by stimulating the region of the OPNs to identify antidromic projections and found that the density of direct projections from the SC to the OPNs was greatest in the most rostral region and decreased gradually for more caudal sites. On the basis of saccade-related discharge characteristics, the antidromically driven neurons were predominantly fixation and buildup neurons. The spatially distributed SC projections to the OPNs and the discharge characteristics of the SC neurons suggest that the direct projections from SC to OPNs are excitatory. Finally, we propose how excitation and disfacilitation from SC activity can contribute to modulation of OPN response and control saccades.

Animals↗

PubMed2003

Effective field sampling for predicting the spatial distribution of reindeer (Rangifer tarandus) with help of the Gibbs sampler.

We describe an approach to estimation of the spatial distribution of reindeer (Rangifer tarandus). Spatial autocorrelation, inherent to the data describing the distribution of wildlife species, contains information that can be utilized to improve the effciency of field inventories. Our data included reindeer fecal pellet counts, satellite imagery and a digital terrain model. We applied ordinary logistic regression, autologistic regression, and the Gibbs sampler to predict spatial distribution of reindeer based on the combined data. A training set was used to compare the outcome for different field sampling designs for each method. Results suggested the possibility to reduce the number of plots by up to 75% with a 15% reduction in prediction accuracy (quality). We also showed that the Gibbs sampler outperformed, in terms of accuracy, the logistic regression. The outcome, however, was dependent on the spectral homogeneity of the area and on the relative position of the sampling design to the elevation curves. Our results justify the incorporation of spatial information when modeling the distribution of reindeer at finer scales (< 1 km).

Animals↗

PubMed2004

Spatial distributions and profiles of atmospheric polycyclic aromatic hydrocarbons in two industrial cities in Japan.

The spatial distribution and concentration profiles of 39 vapor and particulate polycyclic aromatic hydrocarbons (PAHs) have been investigated in two Japanese industrial cities (Fuji and Shimizu; a summer and winter season in each). The concentrations of particulate PAHs in winter tended to be higher than those in the summer, but for vapor PAHs, this was not the case. Significant correlations (p < 0.01) were found between most of the PAH concentrations monitored in winter, suggesting the presence of common emission sources. To identify PAH spatial distributions and emission sources in the area, we created contour maps for PAHs monitored; this indicates that the distinctive local distributions correspond to the emission sources. PAH profiles based on benzo[e]pyrene (BeP) concentration, especially for certain relatively heavy molecular weight PAHs, showed differential behaviors among divided areas related to potential regional emission sources such as paper-making plants, power plants, and traffic. We conclude that the origins of atmospheric PAHs in the surveyed areas were dominated by not only traffic but also by stationary emission sources such as paper-making plants and power plants and that local distributions were dependent on the local wind direction.

Air Movements↗

PubMed2002

Spatial distribution of Plecoptera nymphs in streams of a mountainous area of Central Brazil.

In this paper the spatial distribution of Plecoptera nymphs in the Almas' River basin, Pirenópolis, GO, was studied. Two Surber samples, each comprising 20 sampling units and totalling 2 m2, were taken in each of the 13 stations, one during the rainy season (January 1994) and the second during the dry season (July 1994). In 5 of these stations, monthly samplings were made from June 1993 to July 1994; in these, temperature, velocity, discharge, electrical conductivity and pH were measured. Regional rainfall was also obtained. To ascertain the distribution of nymphs in the habitat, a separate sample was taken. Of the factors considered, the most important affecting the spatial distribution of the stonefly nymphs were altitude, stream order, and anthropic influence. Locally, the genera Anacroneuria and Kempnyia showed clumped distributions, but the data for Gripopteryx and Tupiperla were inconclusive due to low numbers.

Animals↗

PubMed2006

[Spatial distribution of mortality from acute myocardial infarction in Rio de Janeiro, Brazil].

The study analyzes the spatial distribution of mortality from acute myocardial infarction (AMI) in Rio de Janeiro, Brazil. Data from the Mortality Information System refers to the year 2000. Empirical Bayes smoothing technique was used to minimize random variation in mortality coefficients due to the population size in the geographic analytical units. Spatial distribution of AMI mortality in the city of Rio de Janeiro is heterogeneous and displays a pattern associated with a strong socioeconomic gradient. The decreased AMI risk in the West Side of the city fails to reflect the social inequality and limited access to healthcare services observed there. A more likely hypothesis is that the risk of AMI death was underestimated in the West Side, due to the high proportion of ill-defined causes of death in that region. In the rest of the city, the spatial pattern of AMI mortality showed higher values in poorer areas. The various hospitals treating AMI also show a clear pattern in their areas of influence.

Adult↗

PubMed2006

Spatial distribution of lead in human primary teeth as a biomarker of pre- and neonatal lead exposure.

Lead remains one of the most hazardous toxins in our environment. Because the toxic effects of lead are most prominent during early development, it is important to develop a suitable biomarker for lead exposure during the pre- and neonatal periods. In the present study, the spatial distribution of lead was measured in the enamel and dentine of ten human primary teeth using laser ablation-inductively coupled plasma-mass spectrometry. The neonatal line, visualized using confocal laser scanning microscopy, was used to demarcate the pre- and postnatal regions of the sample teeth. Lead levels in pre- and postnatally formed enamel and dentine were compared to blood-lead levels measured at birth and one year of age for four of these participants. Mean dentine-lead levels ranged from 0.17+/-0.02 to 5.60+/-1.79 microg/g, and mean enamel-lead levels ranged from 0.04+/-0.01 to 1.47+/-0.20 microg/g. The results of this preliminary study showed that the spatial distribution of lead in dentine reflected the blood-lead levels. The present study demonstrates a methodology where the spatial distribution of lead in the dentine of human primary teeth may be used to obtain temporal information of environmental lead exposure during the pre- and neonatal periods.

Adolescent↗

PubMed1996

Entomopathogenic nematode (Heterorhabditidae and Steinernematidae) spatial distribution in turfgrass.

Understanding the temporal and spatial distribution of entomopathogenic nematodes is essential for determining the role of these insect parasites in soil communities and ultimately for their use in suppression of pest insect populations. We measured the vertical and horizontal distribution of endemic populations of entomopathogenic nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophora) in turfgrass. Vertical distribution was determined by taking soil cores every 3 h from 05.00 to 23.00 h, over 4 days, and dividing the cores into 8, 1 cm deep sections. Steinernema carpocapsae was recovered primarily near the soil surface: 50% of positive sections were recovered in the thatch or first 1 cm of soil. S. carpocapsae recovery was lower during the middle of the day and none were recovered in the upper section. H. bacteriophora was recovered uniformly throughout the top 8 cm of soil and its vertical distribution did not change over the course of the day. Horizontal distribution was measured as the number of nematodes recovered from cores taken from 12 randomly selected 0.3 x 0.8 m sections from within four 15.3 x 15.3 m plots. Samples were collected biweekly over a 9-month period. H. bacteriophora had a patchier distribution than S. carpocapsae and both nematode species had more patchy distributions then their potential hosts. Our results support the hypothesis that these two species of nematode utilize different foraging strategies; S. carpocapsae primarily a surface adapted ambusher and H. bacteriophora as a cruise forager.

Animals↗

PubMed1991

Spatial distribution of late potentials assessed by signal-averaged body surface mapping.

In order to evaluate the spatial location of late potentials (LPs), we designed a new system for the body surface mapping of signal-averaged, filtered ECG using 45 thoracic unipolar leads (5 X 9 array). Signals from patients with old myocardial infarction (MI, N = 8), arrhythmogenic right ventricular dysplasia (N = 1) and dilated cardiomyopathy (N = 2) were amplified and passed through a digital bandpass filter (60-300Hz). Departure maps, LP isopotential maps, and LP30 area maps were generated and superimposed. The LP30 duration was determined as the section between the filtered QRS endpoints and points 30 msec before. Isopotential maps of the LPs showed distinct positive and negative regions. In 8 cases with MI, the extreme was related to the zones indicated by departure maps, and LP30 area maps also corresponded to the departure areas. Most importantly, the spatial distribution for the LP30 area map was different for each type of disease. In conclusion, body surface LP isopotential maps and LP30 area maps may provide useful information concerning the spatial distribution of LPs.

Arrhythmias, Cardiac↗

PubMed2003

Spatial distribution of the beta2 integrin (CD11b/CD18) and L-selectin (CD62L) adherence receptors on human neutrophils by Conventional Optical Scanning Microscopy (COSM).

Receptors such as CD62L and CD11b/CD18, are transmembrane glycoproteins which regulate leukocyte adhesive phenotype. Flow cytometry (FCM) makes it possible to assess a characterization of the cell activation level by receptor quantifying, but that technique does not integrate other factors of adherence regulation, such as spatial distribution and molecular conformation. Our study consisted in exploring the main adherence receptors on Polymorphonuclear Neutrophils (PMN) that were simultaneously analyzed by FCM and Conventional Optical Scanning Microscopy (COSM). FCM analysis showed that TNFalpha induce a decrease in CD62L expression and an increase in beta2 integrins. COSM analysis distinguished three stages of cellular distribution of CD11b/CD18 within resting PMN: most of them (about 80%) had homogeneous distribution (heterogeneous spots distributed over the entire cell surface), for 10-15% of the cells, there was a crown distribution around the widest cell diameter and in less that 10% of them receptor distribution was polarized. CD62L was in the form of heterogeneous spots distributed in a circle on the surface on non-stimulated PMN. PMN stimulation by TNFalpha was associated to a randomized clustering involving both selectin and beta2 integrin. Three-dimensional analysis elicited data not shown by quantitative cytometry. For a single averaged value of the density determined by FMC, various spatial distributions of adherence receptors are found on the surface of non-stimulated PMN. The characterization of the leukocyte adhesive phenotype has to integrate adherence receptors density as well as their spatial distribution.

CD18 Antigens↗

PubMed2006

Spatial distribution of foot-and-mouth disease in Pakistan estimated using imperfect data.

We estimated the spatial distribution of foot-and-mouth disease (FMD) in Pakistan; we used a probability co-kriging model and the number of FMD outbreaks reported between 1996 and 2000 by Pakistan to the Office International des Epizooties. We used a k-Bessel model and small-ruminant and human densities as surrogate covariates for the population at risk and for livestock markets and movements, respectively. Compared to no or only one covariate, the co-kriging model with both densities provided the best fit to independently obtained data on the spatial distribution of virus isolations (P=0.57). The estimated probability of an FMD outbreak per 25km(2) cell ranged from 0.017 to 0.812, with the maximum relative probability of 47.8 (0.812/0.017). Areas with the highest relative probability of having an FMD outbreak were located in the Punjab region; this is a major animal-production area located along a traditional international animal-trade route.

Animals↗

PubMed1988

Postnatal development of cat hind limb motoneurons. I: Changes in length, branching structure, and spatial distribution of dendrites of cat triceps surae motoneurons.

The postnatal development of length, branching structure, and spatial distribution of dendrites of triceps surae motoneurons, intracellularly stained with horseradish peroxidase, was studied from birth up to 44-46 days of postnatal (d.p.n.) age in kittens and compared with corresponding data from adult cats. The number of dendrites of a triceps surae motoneuron was about 12, and the arborization of each dendrite generated an average of 12-15 terminal branches. There was no net change in the number of dendrites of a neuron or in the degree of branching of the dendrites despite the occurrence of both a transient remodeling of the dendritic branching structure and changes of the spatial distribution of the dendritic branches during postnatal development. The perisomatic territory in the transverse plane occupied by the dendritic branches of a motoneuron increased in parallel with the overall growth of the spinal cord. Thus, the relative size of the dendritic territory in this plane was kept almost constant, whereas dendritic branches projecting in the rostrocaudal direction grew much faster than the spinal cord and also became more numerous. At birth the rostro-caudal dendritic span of individual motoneurons bridged 1:6 to 1:5 of the L7 spinal cord segment length; this figure was 1:3 at 22-24 d.p.n. Hence, in this direction, the growing dendritic branches invaded novel dendritic territories. The change in dendritic branch length from birth to 6 weeks of age corresponded to an average growth rate of 2 to 4 microns per dendritic branch and day, which implies that the total increase in length of the dendrites of a neuron could amount to 1 mm/day. The increase in branch length did not occur in a uniform or random manner; instead, it followed a spatiotemporal pattern with three phases: From birth to 22-24 d.p.n., growth was particularly prominent in greater than or equal to 3rd order preterminal and 2nd through 6th order terminal branches. From 22-24 to 44-46 d.p.n., a large increase in branch length confined to terminal branches of greater than or equal to 3rd branch orders was observed. As indicated by topological analysis, this length increase was probably due in part to a resorption of peripheral dendritic branches during this stage of development. From 44-46 d.p.n. to maturity, the increase of dendritic branch length was restricted to preterminal branches of low (less than or equal to 4th) branch order.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2006

[Spatial distribution of Aedes albopictus in the southern area of Mato Grosso do Sul State, Brazil].

OBJECTIVE: To investigate the spatial distribution of Aedes albopictus population to provide input for developing sampling plans and supporting decision making on the control of this vector in field sampling. METHODS: A study was carried out in an urban area that has a vestige of primary vegetation, 20 km away from Dourados, Midwestern Brazil. Ten samplings were conducted between January 28, 2003 and April 9, 2003, using ovitraps which were monitored once a week, and distributed in a fixed sample area with 10 collection points for each sampling 300 m away from each other. Aggregation indexes were calculated and adjusted to the following theoretical frequency distribution: negative binomial, positive binomial and Poisson's. RESULTS: The sample variance was higher than the sampling mean, resulting in mean-variance indexes above the unit (32.066, 29.410, 14.444, 58.840, 56.042, 111.262, 70.140, 50.701, 93.221 and 8.481). Morisita's index was also statistically above the unit in all samplings (6.275, 3.947, 1.484, 3.725, 3.014, 5.450, 3.214, 3.886, 3.954 and 5.810), and K parameter ranged 0 and 8 (0.174, 0.309, 1.867, 0.332, 0.449, 0.203, 0.408, 0.314, 0.306 and 0.200). The Chi-square test for adjustment to the negative binomial distribution, positive binomial distribution, and Poisson's distribution was not statistically significant. CONCLUSIONS: Ae. albopictus population in the studied municipality showed an aggregated standard spatial distribution. This means that when individual vectors are found in a certain site, it is likely that other vectors can be found in the proximities, recommending insecticide spraying for vector control in this site without requiring sampling other sites in this same locality.

Aedes↗

PubMed1993

The spatial distribution of attention following an exogenous cue.

Three target-discrimination experiments were conducted to explore the spatial distribution of covert visual attention following an exogenous cue. On each trial, a brief peripheral onset was followed by a target stimulus in an otherwise empty visual field at one of eight (Experiment 1) or one of four (Experiments 2 and 3) possible locations centered at the fixation point. The spatial relation between the cue and the target was manipulated. The main results were that (1) performance was better at the cued location than at another nearby location in the same visual quadrant; (2) performance was not affected by the major horizontal and vertical visual meridians; and (3) performance was affected by the spatial distance between the cued and target locations. Together, the results suggest that the spatial distribution of exogenously oriented attention can be most easily integrated with a simple gradient model.

Adult↗

PubMed2004

Modelling the spatial distribution of ammonia emissions from seabirds in the UK.

Knowledge of the sources and distribution of ammonia (NH3) emissions underpins our understanding of the nitrogen budget. Research has focused on quantifying NH3 emissions from anthropogenic sources, whilst those from natural sources have received little attention internationally. Seabirds excrete large quantities of nitrogen, making seabird colonies a major natural source of NH3. Ammonia emissions from each UK seabird species were estimated and combined with population distribution data to model their spatial distribution. Total NH3 emissions from UK seabirds were estimated at 2.7 kt per year. Seabird emissions are concentrated in remote parts of the UK where anthropogenic emissions are small, so that seabirds often represent the main source of NH3 emissions in these areas. Seabird NH3 emissions were found to have increased by 34% since the 1970s. This corresponds to population changes which may be influenced by human activities, showing that even this natural source can be anthropogenically modified.

Agriculture↗

PubMed2006

Assessing sites contaminated with unexploded ordnance: statistical modeling of ordnance spatial distribution.

More than 40,000 km2 of former military land in the United States are contaminated with unexploded ordnance (UXO). Cleanup costs are estimated to total as much as 140 billion dollars. The amount of contaminated acreage and total costs are likely to increase as the U.S. Department of Defense (DOD) follows through on recently announced plans to close an additional 22 domestic military bases. The U.S. Environmental Protection Agency(EPA) and DOD disagree on how these sites should be characterized to assess their risks and plan for cleanup. As a result, much potentially valuable land remains idle while remediation decisions are pending. One of the sources of disagreement is how the locations of UXO should be characterized, given that the exact spatial distribution of UXO is unknown in advance of cleanup. In this paper, we propose and test a new model to represent the spatial distribution of UXO. Unlike existing DOD models, the new model accounts for the tendency of UXO to cluster, presumably around targets at which soldiers aimed during training. We fit the cluster model to geographic data on UXO locations at two former military installations and show that it describes key characteristics of the data more accuratelythan the existing DOD model. We discuss how the choice of a UXO spatial distribution model could affect important decisions about cleaning up and reusing UXO-affected property.

Environmental Monitoring↗