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Geographical Position (geographical + position)
Selected AbstractsSeasonal variation of diagnosis of Type 1 diabetes mellitus in children worldwideDIABETIC MEDICINE, Issue 7 2009E. V. Moltchanova Abstract Aims, To determine if there is a worldwide seasonal pattern in the clinical onset of Type 1 diabetes. Methods, Analysis of the seasonality in diagnosis of Type 1 diabetes was based on the incidence data in 0- to 14-year-old children collected by the World Health Organization Diabetes Mondiale (WHO DiaMond) Project over the period 1990,1999. One hundred and five centres from 53 countries worldwide provided enough data for the seasonality analysis. The incidence seasonality patterns were also determined for age- and sex-specific groups. Results, Forty-two out of 105 centres exhibited significant seasonality in the incidence of Type 1 diabetes (P < 0.05). The existence of significant seasonal patterns correlated with higher level of incidence and of the average yearly counts. The correlation disappeared after adjustment for latitude. Twenty-eight of those centres had peaks in October to January and 33 had troughs in June to August. Two out of the four centres with significant seasonality in the southern hemisphere demonstrated a different pattern with a peak in July to September and a trough in January to March. Conclusions, The seasonality of the incidence of Type 1 diabetes mellitus in children under 15 years of age is a real phenomenon, as was reported previously and as is now demonstrated by this large standardized study. The seasonality pattern appears to be dependent on the geographical position, at least as far as the northern/southern hemisphere dichotomy is concerned. However, more data are needed on the populations living below the 30th parallel north in order to complete the picture. [source] Semiparametric M -quantile regression for estimating the proportion of acidic lakes in 8-digit HUCs of the Northeastern USENVIRONMETRICS, Issue 7 2008Monica Pratesi Abstract Between 1991 and 1995, the Environmental Monitoring and Assessment Program of the US Environmental Protection Agency conducted a survey of lakes in the Northeastern states of the US to determine the ecological condition of these waters. Here, to this end, we want to obtain estimates of the proportion of lakes at (high) risk of acidification or acidified already for each 8-digit hydrologic unit code (HUC) within the region of interest. Sample sizes for the 113 HUCs are very small and 27 HUCs are not even observed. Therefore, small area estimation techniques should be invoked for the estimation of the distribution function of acid neutralizing capacity (ANC) for each HUC. The procedure is based on a semiparametric M -quantile regression model in which ANC depends on elevation and the year of the survey linearly, and on the geographical position of the lake through an unknown smooth bivariate function estimated by low-rank thin plate splines. Copyright © 2008 John Wiley & Sons, Ltd. [source] Ecological relationships between stream communities and spatial scale: implications for designing catchment-level monitoring programmesFRESHWATER BIOLOGY, Issue 5 2007RICHARD K. JOHNSON Summary 1. Stream communities are structured by factors acting over multiple spatial and temporal scales. Identifying what factors are driving spatial patterns in stream communities is a central aim of ecology. 2. Here we used two large European data sets of fish, invertebrates, macrophytes, benthic diatoms and environmental data in two stream groups (lowland and mountain) to determine the importance of variables at different spatial scales (geographical, regional, local) on community structure. 3. Both geographical position and ecoregion were selected first in canonical correspondence analysis (CCA), clearly showing the broad spatial gradients covered in the data set. Secondary predictors (after accounting for spatial and/or ecoregion effects) were similar between stream groups and among the four organism groups. In particular, conductivity and N concentration were strong predictors reflecting catchment land use. 4. Using partial CCA, we assessed the individual importance of the three spatial scales on the community structure of the four organism groups in the two stream groups. The majority of among-site variability (22,29%) was accounted for by local scale variables (e.g. water chemistry and substratum type), with regional and spatial variables accounting 11,13% and 5,6%, respectively. Our findings indicate that the four organism groups are responding similarly to the different levels of spatial scale, implying much redundancy which should be consider when implementing studies of bioassessment. [source] The Crow Corvus corone hybrid zone in southern Denmark and northern GermanyIBIS, Issue 4 2005FREDRIK HAAS In hybrid zones genetically differentiated populations meet and interbreed. As they result from ongoing divergence and potential speciation, such zones provide opportunities to study how different factors affect this process. One well-known avian hybrid zone is that between the Hooded Crow Corvus corone cornix and Carrion Crow C. c. corone, which extends throughout much of Europe. We compare the current position and width of the zone in southern Denmark and northern Germany with that described in detail by Meise in 1928. A GPS technique was used to determine the geographical position of more than 1000 Crows in established pairs in which all individuals were classified as either Carrion, Hooded or hybrid phenotype. The data show that the Carrion Crow has expanded northwards and that this is most pronounced at the eastern side of the study area. Here the hybrid zone has moved around 19 km. However, the width of the zone seems to have remained stable over time. Possible reasons for why the zone may have moved are discussed. [source] The influence of natural conditions on the spatial variation of climate in Lapland, northern FinlandINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2003Andrea Vajda Abstract At high latitudes in Lapland, near the climatological timberline, forestry and other environmental research require detailed information about the spatial variation of climate. In this study, the influence of local geographical factors on the climate in northern Finland (Lapland), as well as the applicability of the kriging interpolation method in the case of detailed spatial resolution, were examined. The spatial analysis of mean, maximum, minimum temperatures, length of the frost-free season, degree-days and daily range was made using a 1 km × 1 km resolution. The time period used was 1971,2000. We studied whether taking account of external forcing, such as lake coverage and altitude, would improve the accuracy of spatial interpolation of climatological parameters. The geographical factors of coordinates, elevation, lakes and sea influence on the regional features of the climate were examined. According to the results of this study, only geographical position and local relief have a significant influence on regional climate in Lapland. The effect of lakes and sea seems to be secondary. Copyright © 2003 Royal Meteorological Society [source] Fish assemblages of the Casiquiare River, a corridor and zoogeographical filter for dispersal between the Orinoco and Amazon basinsJOURNAL OF BIOGEOGRAPHY, Issue 9 2008Kirk O. Winemiller Abstract Aim, The aim of this study was to determine whether the Casiquiare River functions as a free dispersal corridor or as a partial barrier (i.e. filter) for the interchange of fish species of the Orinoco and Negro/Amazon basins using species assemblage patterns according to geographical location and environmental features. Location, The Casiquiare, Upper Orinoco and Upper Negro rivers in southern Venezuela, South America. Methods, Our study was based on an analysis of species presence/absence data and environmental information (11 habitat characteristics) collected by the authors and colleagues between the years 1984 and 1999. The data set consisted of 269 sampled sites and 452 fish species (> 50,000 specimens). A wide range of habitat types was included in the samples, and the collection sites were located at various points along the entire length of the Casiquiare main channel, at multiple sites on its tributary streams, as well as at various nearby sites outside the Casiquiare drainage, within the Upper Orinoco and Upper Rio Negro river systems. Most specimens and field data used in this analysis are archived in the Museo de Ciencias Naturales in Guanare, Venezuela. We performed canonical correspondence analysis (CCA) based on species presence/absence using two versions of the data set: one that eliminated sites having < 5 species and species occurring at < 5 sites; and another that eliminated sites having < 10 species and species occurring at < 10 sites. Cluster analysis was performed on sites based on species assemblage similarity, and a separate analysis was performed on species based on CCA loadings. Results, The CCA results for the two versions of the data set were qualitatively the same. The dominant environmental axis contrasted assemblages and sites associated with blackwater vs. clearwater conditions. Longitudinal position on the Casiquiare River was correlated (r2 = 0.33) with CCA axis-1 scores, reflecting clearwater conditions nearer to its origin (bifurcation of the Orinoco) and blackwater conditions nearer to its mouth (junction with the Rio Negro). The second CCA axis was most strongly associated with habitat size and structural complexity. Species associations derived from the unweighted pair-group average clustering method and pair-wise squared Euclidean distances calculated from species loadings on CCA axes 1 and 2 showed seven ecological groupings. Cluster analysis of species assemblages according to watershed revealed a stronger influence of local environmental conditions than of geographical proximity. Main conclusions, Fish assemblage composition is more consistently associated with local environmental conditions than with geographical position within the river drainages. Nonetheless, the results support the hypothesis that the mainstem Casiquiare represents a hydrochemical gradient between clearwaters at its origin and blackwaters at its mouth, and as such appears to function as a semi-permeable barrier (environmental filter) to dispersal and faunal exchanges between the partially vicariant fish faunas of the Upper Orinoco and Upper Negro rivers. [source] Determinants of inselberg floras in arid Nama Karoo landscapesJOURNAL OF BIOGEOGRAPHY, Issue 10 2001Antje Burke Aim This study investigated the relationship between inselberg floras in floristic and functional terms and their correlation with environmental variables at macro-scale and landscape level. Location Four inselberg landscapes in Namibia's arid Nama Karoo in southern Africa were selected. Methods Plant surveys were undertaken over a 3-year period and species composition, growth form and dispersal spectra were used as measures for floristic and functional composition. Canonical correspondence analysis (CCA) was employed as the main tool to explain the perceived patterns. Results Regarding floristic affinities, inselberg floras formed distinct groups per study area and thus geographical position, with strong correlations between inselbergs within a particular study area. Neither growth form nor dispersal spectra closely resembled the pattern that emerged in the ordination of floristic composition. The influence of geographical position lessened when functional rather than floristic measures were introduced in the analysis. Main conclusions (1) On landscape and macro-scale, floristic composition of inselberg floras was largely determined by geographical position, geology, elevation, habitat diversity, rock outcrop in the surrounding and surface area of inselbergs. (2) Environmental variables operating at landscape level had greater influence on functional composition than on floristic composition. (3) Stochastic variables were more important in shaping the flora of these arid Nama Karoo inselbergs than deterministic processes such as niche relations and competition. [source] Foliomena Fauna (Brachiopoda) from the Upper Ordovician of SardiniaPALAEONTOLOGY, Issue 2 2002E. Villas The late Ordovician brachiopod assemblage from Sardinia is one of the youngest members of the deep-water Foliomena fauna and is characterized by the following core taxa: Christiania, Cyclospira, Dedzetina and Foliomena. The fauna also contains Epitomyonia, Leangella, Glyptorthis and Skenidioides, which are more typical of shallower-water environments during the late Ordovician but occupied deeper-water niches during the Silurian following the termination of the Foliomena fauna. The suprafamilial placement of the family Chrustenoporidae is discussed and the new species Dedzetina serpaglii and Leangella (Leangella) fecunda are established. In common with many mid-Ashgill Foliomena faunas the Sardinian assemblage shows significant differences from other faunal developments of this type, reflecting its geographical position and shallower water conditions than those of the classic early Ashgill Foliomena faunas. The brachiopods occur with abundant trilobites belonging to a variant of the cyclopygid fauna. The faunas developed on part of a complex of microcontinents derived from peri-Gondwana during the Ordovician. [source] Gender and chain migration: the case of ArubaPOPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 2 2010Haime Croes Abstract Family reunification and family formation form a substantial part of chain migration, as most countries accept this form of settlement on the basis of humanitarian commitment to protecting families. Yet this does not mean that all migrants are treated equally in allowing them to bring over family members. Whether people are allocated this statutory right depends on their social and economic position. Women might be ,triply disadvantaged' as migrant women are often in more marginal jobs, from a different ethnicity, and have a harder time in acquiring these statutory rights. In this contribution we test this gender hypothesis using data from Aruba. Aruba provides an interesting case because the rapid development of the tourist-driven economy has given rise to enormous labour shortages across the various sectors of the economy, and it is now among the ten countries in the world with the highest net immigration rate. Due to its geographical position the island has recruited labour migrants from both Latin and North America and also from Europe. Dutch nationals receive preferential treatment as Aruba is a country within the Kingdom of the Netherlands. This diversity in immigration allows for an analysis of the social, ethnic, economic and legal determinants of family reunification. The results show that women have a disadvantaged position with respect to each of these determinants. On top of that a separate gender effect remains, indicating that it is harder for women migrants to bring over their spouses and children from their home country. Copyright © 2009 John Wiley & Sons, Ltd. [source] East-Central Europe's changing energy landscapes: a place for geographyAREA, Issue 4 2009Stefan Bouzarovski Energy developments in the post-Communist states of Eastern and Central Europe (ECE) have a major impact on global energy security and sustainability, thanks to this region's key geographical position between the energy-exporting states of the former Soviet Union, on the one hand, and the energy-importing states of Western and Southern Europe, on the other. At the same time, post-socialist reforms of energy industries in this region provide unique insights into the complex relations of power, economic transformation and spatial inequality that govern energy production and consumption. This paper therefore aims to provide an initial look at some of the theoretical and policy issues that underpin the emergent ,geographies' of energy reform in ECE, as well as their embeddedness in relations of power stemming from organisational, infrastructural and economic inequalities in the region. It employs an analysis of local news reports, policy papers and statistical data to examine the intricate institutional networks and spatial formations that have governed the energy transformation process. In broader terms, the paper aims to emphasise the important role that human geography can play in making sense of the territorial differences and frictions that have emerged during the post-socialist reform process, while challenging the idea of a ,neat' neoliberal transition from a centrally planned to a market-based mode of energy regulation. [source] Tree Diversity, Forest Structure and Productivity along Altitudinal and Topographical Gradients in a Species-Rich Ecuadorian Montane Rain ForestBIOTROPICA, Issue 2 2010Jürgen Homeier ABSTRACT We studied the spatial heterogeneity of tree diversity, and of forest structure and productivity in a highly diverse tropical mountain area in southern Ecuador with the aim of understanding the causes of the large variation in these parameters. Two major environmental gradients, elevation and topography, representing a broad range of climatic and edaphic site conditions, were analyzed. We found the highest species richness of trees in valleys <2100 m. Valleys showed highest values of basal area, leaf area index and tree basal area increment as well. Tree diversity also increased from ridges to valleys, while canopy openness decreased. Significant relationships existed between tree diversity and soil parameters (pH, total contents of Mg, K, Ca, N and P), and between diversity and the spatial variability of pH and Ca and Mg contents suggesting a dependence of tree diversity on both absolute levels and on the small-scale heterogeneity of soil nutrient availability. Tree diversity and basal area increment were positively correlated, partly because both are similarly affected by soil conditions. We conclude that the extraordinarily high tree species richness in the area is primarily caused by three factors: (1) the existence of steep altitudinal and topographic gradients in a rather limited area creating a small-scale mosaic of edaphically different habitats; (2) the intermingling of Amazonian lowland plant species, that reach their upper distribution limits, and of montane forest species; and (3) the geographical position of the study area between the humid eastern Andean slope and the dry interandean forests of South Ecuador. [source] | ||||||||||||||||