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At least 1,333 records · Page 74Linked to original sources
PubMed2004

[Quantitative analysis of landscape patterns at the juncture of Shaanxi, Shanxi and Inner Mongolia, based on remote sensing data--taking Yulin sheet TM image as an example].

Based on the TM image of Yulin sheet and with the help of ERDAS, ARC/INFO and ARC/VIEW software, the landscape of Yulin sheet was classified. Using the spatial pattern analysis software FRAGSTATS of the vector version, a set of landscape indices were calculated at three scale levels of patches, classes and landscape. The results showed that landscape pattern indices could be successfully used in characterizing the spatial pattern of the studied area. However, this study should be further extended to the landscape of the same area in other period to analyze its dynamic change. FRAGSTATS was a good software, but should be improved by adding some indices such as PD2 developed by us.

Ecosystem↗
PubMed1991

Gene expression mediated by cis-acting sequences of the Krüppel gene in response to the Drosophila morphogens bicoid and hunchback.

The initial expression of the gap gene Krüppel (Kr) occurs in a precisely bounded central region of the Drosophila blastoderm embryo. According to genetic analysis, the spatial limits of the Kr expression domain are controlled by the morphogenetic activities of the anterior organizer gene bicoid (bcd) and the anterior gap gene hunchback (hb). Using gene fusion analysis, we assayed for cis-acting sequences of the Kr gene which mediate transcriptional activation and localized gene expression in response to trans-acting factors. A 730 bp Kr control element drives gene expression in place of the endogenous Kr central domain. This cis-acting element, Kr730, is composed of bcd and hb responsive sequences. They map into regions of multiple hb and bcd protein in vitro binding sites. A 142 bp core fragment containing one low affinity hb and five medium to strong bcd protein binding sites drives gene expression in a Kr-like location in the centre of the embryo. Our results show that this fragment represents a target for the redundant activator/repressor system provided by the anterior morphogens bcd and hb.

Animals↗
PubMed2006

Visual area V5/MT remembers "what" but not "where".

Priming for motion direction has been shown to depend upon the functional integrity of extrastriate area V5/MT. Its retinotopic organization and the interactions recently found between motion adaptation and misperceived localization may suggest, for this area, a role for priming of spatial position in addition to the established priming of motion direction. Disruption of V5/MT with repetitive transcranial magnetic stimulation during the intertrial interval had the effect of abolishing priming of motion direction but no effect in priming of spatial position. These effects cannot be explained in terms of perception or task demands but only in terms of the effects of information irrelevant to the correct performance of the task stored over the intertrial interval. We suggest that the attribute of spatial position might be stored in short-term memory either in earlier areas of the motion pathways such as V3 or in higher cortical areas traditionally associated with the analysis of spatial information, for example, posterior parietal cortex or the frontal eye fields.

Adult↗
PubMed2003

Numerical bifurcation analysis of ecosystems in a spatially homogeneous environment.

The dynamics of single populations up to ecosystems, are often described by one or a set of non-linear ordinary differential equations. In this paper we review the use of bifurcation theory to analyse these non-linear dynamical systems. Bifurcation analysis gives regimes in the parameter space with quantitatively different asymptotic dynamic behaviour of the system. In small-scale systems the underlying models for the populations and their interaction are simple Lotka-Volterra models or more elaborated models with more biological detail. The latter ones are more difficult to analyse, especially when the number of populations is large. Therefore for large-scale systems the Lotka-Volterra equations are still popular despite the limited realism. Various approaches are discussed in which the different time-scale of ecological and evolutionary biological processes are considered together.

Animals↗
PubMed2006

A test of the equal environment assumption (EEA) in multivariate twin studies.

In the classic twin design, estimation of genetic and environmental effects is based on the assumption that environmental influences are shared to the same extent by monozygotic and dizygotic twins (equal environment assumption, EEA). We explore the conditions in which the EEA can be tested based on multivariate phenotypic data. We focus on the test whether the correlation between shared environmental factors in dizygotic twins (r(C)) is less than 1. First, model identification was investigated analytically in Maple and Mx. Second, statistical power was examined in Mx. Third, the amount of bias caused by violation of the EEA was evaluated. Finally, applications to empirical data concern spatial ability in adolescents and aggression in children. Bivariate and trivariate models include several instances in which the EEA can be tested. The number of twin pairs that is needed to detect violation of the EEA with a statistical power of .80 (alpha = .05) varied between 508 and 3576 pairs for the situations considered. The bias in parameter estimates, given misspecification, ranged from 5% to 34% for additive genetic effects, and from 4% to 34% for shared environmental effects. Estimates of the nonshared environmental effects were not biased. The EEA was not violated for spatial ability or aggression. Multivariate data provide sufficient information to test the validity of the EEA. The number of twin pairs that is needed is no greater than the number typically available in most twin registries. The analysis of spatial ability and aggression indicated no detectable violation of the EEA.

Aggression↗
PubMed2005

Spatial genetic structure of Simarouba amara Aubl. (Simaroubaceae), a dioecious, animal-dispersed Neotropical tree, on Barro Colorado Island, Panama.

Simarouba amara (Simaroubaceae) is a vertebrate-dispersed, insect-pollinated Neotropical tree found in lowland moist forest from upper Mesoamerica to the Amazon basin. We assessed the spatial genetic structure of S. amara within the 50-ha Forest Dynamics Plot on Barro Colorado Island in the Republic of Panama. A total of 300 individuals were genotyped using five microsatellite loci, representing 100 individuals with a dbh>or=10 cm, 100 individuals of 1-10 cm dbh, and 100 individuals of <1 cm dbh. The 200 individuals in the two larger size classes were also genotyped with 155 AFLP loci. Spatial autocorrelation analysis using Moran's Index detected significant genotypic association at the smallest distance classes for 1-10 cm dbh (0-20 m) and >10 cm dbh (0-40 m) size categories. Significant spatial autocorrelations were detected over larger scales (0-140 m) in <1 cm dbh individuals. The relatively weak genetic structure of S. amara, in comparison to other recent studies, may be explained by pollen and seed dispersal over the 50 ha plot, overlapping seed shadows, and postrecruitment mortality.

Demography↗
PubMed2003

GABA is involved in spatial unmasking in the frog auditory midbrain.

Real-world listening situations comprise multiple auditory objects. Sounds originating from different objects are summated at the eardrum. The auditory system therefore must segregate the streams of sounds associated with the different objects. One listening strategy in complex environments is to attend to signals originating from one spatial location. In doing so, signal detection is compromised when a masker is present at close proximity, and detection is improved if the masker is spatially separated from the signal. A recent study has shown that, in frogs, spatial unmasking is more robust at the midbrain than at the periphery, indicating the importance of central mechanisms for this process. In this study, we investigated spatial unmasking patterns of single neurons in the frog inferior colliculus (IC) before and during iontophoretic application of bicuculline, a GABA(A) receptor antagonist. We found that drug application markedly decreased the strength of spatial unmasking such that even large angular separation of signal and masker sources produced only a weak masking release. Under the drug, the strength of spatial unmasking of midbrain neurons approximated that of auditory nerve fibers. These data show that GABAergic interactions in the auditory midbrain play an important role in spatial unmasking. Analysis of the effect of the drug on the direction sensitivity of the units shows that for the majority of IC units, bicuculline degrades binaural processing involved in directional coding, thereby compromising spatial unmasking. For other IC units, however, the decline in the strength of spatial unmasking is attributable to the effects of bicuculline on different central auditory processes.

Acoustic Stimulation↗
PubMedDate not supplied

[The functional role of the retino-tecto-thalamo-cortical system in rats].

After bilateral lesion of the posterior lateral thalamic nucleus in rats, studies been made of motor-feeding reflexes to light stimuli. Using spatial preference technique, it was shown that lesion of this nucleus (representing a part of the retino-tecto-thalamo-cortical system) disturbs differentiation of spatially uncoupled visual stimuli. These data confirm the idea on telencephalization of ancient retino-tectal part of the visual system in evolution and indicate that this part is involved into the analysis of spatial relationships.

Animals↗
PubMed2007

Spatial clustering of endemic Burkitt's lymphoma in high-risk regions of Kenya.

Endemic Burkitt's lymphoma (eBL), the most common childhood cancer in sub-Saharan Africa, occurs at a high incidence in western Kenya, a region that also experiences holoendemic malaria. Holoendemic malaria has been identified as a co-factor in the etiology of this cancer. We hypothesized that eBL may cluster spatially within this region. Medical records for all eBL cases diagnosed from 1999 through 2004 at Nyanza Provincial General Hospital were reviewed for case residential information to examine this hypothesis. Two cluster detection methods, Anselin's Local Moran test for spatial autocorrelation and a spatial scan test statistic, were applied to this residential data to determine whether statistically significant high- and low-risk areas were present in the Province. During the 6-year study period, 272 children were diagnosed with eBL, with an average annual incidence of 2.15 cases per 100,000 children. Using Empirical Bayes smoothed rates, the Local Moran test identified 1 large multi-centered area of low eBL risk (p-values < 0.01) and 2 significant multi-centered clusters of high eBL risk (p-values < 0.001). The spatial scan detected 3 small independent low-risk areas (p-values < 0.02) and 2 high-risk clusters (p-values = 0.001), both similar in location to those identified from the Local Moran analysis. Significant spatial clustering of elevated eBL risk in high-malaria transmission regions and of reduced incidence where malaria is infrequent suggests that malaria plays a role in the complex eBL etiology, but that additional factors are also likely involved.

Adolescent↗
PubMed2006

Advancing insights into methods for studying environment-health relationships: a multidisciplinary approach to understanding Legionnaires' disease.

Recent years have witnessed important advances in the analysis of spatially referenced health data. This paper uses GIS and point pattern modelling to address previously unanswered questions regarding the spatial epidemiology of Legionnaires' disease. We demonstrate a distance effect for proximity of residence to cooling towers; mixed support for a directional effect; and some evidence relating to multiple sources. In uncovering complex conceptual and technical problems in the spatial modelling of infection risk we also extended the limits of existing point pattern techniques. We advocate further multidisciplinary research to advance methodological developments for understanding spatial environment-health relationships.

Air Conditioning↗
PubMed2003

Spatial relative risk mapping of pseudorabies-seropositive pig herds in an animal-dense region.

This paper describes a new approach for spatial relative risk mapping as a tool for geographical risk assessment. The spatial epidemiological analysis is based on geographically referenced data about pseudorabies (Aujeszky's disease) virus infections at farm level in a region of high animal density in Germany at the beginning of the national eradication project. On the basis of serological findings 186 farms were classified as positive out of a total of 482 investigated farms listed in veterinary administrative registers. Geographical cluster analysis was used to identify two areas of high risk (RR = 2.4 and 3.3). Non-parametric density estimation was used to estimate the proportion of infected farms per square kilometre. Furthermore, the spatial relative risk function was approximated through the prevalence ratio defined by the ratio of the local prevalence and the overall prevalence of the farms outside the cluster regions. The corresponding approximated relative risk map indicates and quantifies a clear spatial pattern of disease frequency.

Animals↗
PubMed1992

Three-dimensional reconstruction and stereometric analysis of Langerhans cells in mouse epidermis.

In the presented studies stereometric analysis and spatial reconstruction was performed on two Langerhans cell (LC) types. One was free of LC-I and the other contained LC-II Birbeck granules in the perinuclear space. The presented stereometric analysis demonstrated significant differences between the so-distinguished two cell types. Differences were observed not only in the number and distribution of Birbeck's granules but also in the areas of smooth and rough endoplasmic reticulum, in the area of vesicles surrounding Golgi apparatus, in the volume of cisterns of the apparatus, and in the ratio of cell nucleus area to its volume. Differences noted between the two cell types were of quantitative character. They might result from different stages of differentiation of the cells from their precursors in the epidermis or from distinct functional stages of the cells.

Animals↗
PubMed1991

[Socioecological determinants of the risk of accidents in young pedestrians].

We studied all traffic accidents to pedestrians under age 15 which occurred on the Island of Montreal during an eighteen months period. Data were collected from eleven hospitals and completed with accident police records. A spatial quadrat analysis, a Comparative Accident Index, and a comparative analysis of the means of different socio-ecological variables between high and low risk accident areas revealed interesting patterns. The location of traffic accidents is not random but rather presents a particular spatial structure. High risk zones are characterized by dense population, fast-moving traffic, and the absence of parks. Accidents often take place on two-way streets, far from traffic lights, on dry surfaces, in good weather, and with good visibility. The socio-economic status of the victim's family as measured by education, income, and unemployment, tends to be low. More boys than girls are victims. Children are often injured while getting out of a car or crossing unconventionally.

Accidents, Traffic↗
PubMed2004

The anatomy of spatial neglect based on voxelwise statistical analysis: a study of 140 patients.

A major challenge for any anatomical study of spatial neglect in neurological patients is that human lesions vary tremendously in extent and location between individuals. Approaches to this problem used in previous studies were to focus on subgroups of patients that are more homogeneous either with respect to the branch territory affected by the stroke or with respect to existing additional neurological symptoms (e.g. additional visual field defects). It could be argued that such strategies might bias the conclusions on the critical substrate associated with spatial neglect. The present study thus addressed the high variability inherent in naturally occurring lesions by using an unselected, but very large sample size and by comparing a neglect group with a non-neglect group using voxelwise statistical testing. We investigated an unselected 7 year sample of 140 consecutively admitted patients with right hemisphere strokes. Seventy-eight had spatial neglect, 62 did not show the disorder. The incidence of visual field defects was comparable in both groups. For assessing lesion location, in a first step, we used conventional lesion density plots together with subtraction analysis. Moreover, due to the large size of the sample voxelwise statistical testing was possible to objectively estimate which brain regions are more frequently compromised in neglect patients relative to patients without neglect. The results demonstrate that the right superior temporal cortex, the insula and subcortically putamen and caudate nucleus are the neural structures damaged significantly more often in patients with spatial neglect.

Adult↗
PubMed2002

Potential of cathodoluminescence (CL) microscopy and spectroscopy for the analysis of minerals and materials.

The present study summarizes results of cathodoluminescence (CL) microscopy and spectroscopy applied to minerals and materials. CL can be used both in a purely descriptive way to detect and distinguish different minerals or mineral generations by their variable CL colours or as an effective method for spatially resolved analysis of point defects in solids by spectral CL measurements. The cathodoluminescence emission is in all cases either related to lattice defects (e.g. electron defects on broken bonds, vacancies or radiation induced defects) and/or to trace activator ions such as REE(2+/3+), Fe(3+), Cr(3+), Al(3+), Mn(2+), Pb(2+), Cu(2+), Sn(2+) or uranyl groups. CL spectroscopy is an outstanding method to characterize the degree of purity of materials or to detect trace elements in natural and synthetic minerals. In this way, alterations, diffusion of trace elements or formation of new phases are successfully detectable even in the case of materials with heterogeneous texture and high contents of non-crystalline phases.

Journal Article↗
PubMed1980

The spatial distribution of depressive illness in Plymouth.

Diagnostic and demographic data were collected from all 2,298 psychiatric hospital admissions for affective illnesses from private households in the City of Plymouth for the six-year period 1970-1975 inclusive. Intercorrelations of diagnostic subtypes were performed, together with a multiple regression analysis against spatial and ecological data from the 1971 Census. Rate differences were related to the geographic structure of Plymouth. With psychotic illnesses, ecological correlations were low for male and female first admissions and for male readmissions. However, important correlations relating to socio-economic status, housing tenure and structure, population instability, and other sociodemographic features emerged in varying degrees of specificity for reactive and neurotic illness in males, and for all readmissions in females, largely irrespective of diagnostic subtype. Explanations for the processes underlying these patterns are offered in terms of population structure, particularly the differing vulnerability of age and marital status groups, the referral and diagnostic process, social and physical stresses in the lower socioeconomic groups, and urban drift.

Adult↗
PubMed2026

Full-length single-cell spatial transcriptomics reveals spatial and cell-type-specific transcript isoforms in the primate brain.

The primate brain exhibits complex RNA alternative splicing heterogeneity crucial for functional complexity, yet systematic spatial isoform characterization has been lacking. We developed Fullscope-seq, a full-length single-molecule large field-of-view spatial transcriptomics sequencing method at single-cell resolution, based on programmed concatenation cDNA for multiple long-read sequencing platforms. Applying Fullscope-seq to the macaque brain, we uncovered thousands of genes exhibiting differential transcript usage (DTU) across cortical layers, cell types and brain regions. Fullscope-seq resolved hundreds of major isoform switches across distinct brain regions and identified DTUs between superficial and deep cortical layers. Cortical layer-specific DTUs showed cell-composition dependence, whereas regional DTUs were regulated according to both cellular composition and spatial contexts. These isoform variations showed substantial enrichment for neuropsychiatric disorder-associated genes and were conserved across platforms and species. Our study establishes a scalable framework for spatial isoform analysis and provides a resource for understanding transcriptomic diversity in complex tissues.

Animals↗
PubMed2003

Characterization of nitrifying granules produced in an aerobic upflow fluidized bed reactor.

Since nitrification is the rate-determining step in the biological nitrogen removal from wastewater, many research studies have been conducted on the immobilization of nitrifying bacteria. In this research, granulation of nitrifying bacteria in an aerobic upflow fluidized bed (AUFB) reactor in a nitrification process for inorganic wastewater containing 500 g/m(3) of NH(4)(+)-N was investigated. It was observed that spherical, pseudocubic and elliptical granules with a diameter of 346 microm were produced at the bottom of the reactor after 300 days. Denaturing gradient gel electrophoresis analysis revealed that Nitrosomonas-like bacteria were the dominant ammonia-oxidizing species in the granules. Many colonies of Nitrosomonas-like bacteria were found in the outer part of the granules based on the spatial distribution analysis by fluorescence in situ hybridization. By stepwise reduction of the hydraulic retention time, the ammonia removal rate of the AUFB reactor containing these nitrifying granules finally reached 1.5 kg-N/m(3)/day. Results suggested that the use of granules realizes the retention of a large amount of nitrifying bacteria in the reactor, which guarantees a highly efficient nitrification.

Ammonia↗