bluuebunny/crossref_metadata_2025_split huggingface dataset:
2.5D finite‐difference solution of the acoustic wave equation
Authors: Novais Amélia , Santos Lúcio T. 
Published: June 2005

ABSTRACTThe finite‐difference method applied to the full 3D wave equation is a rather time‐consuming process. However, in the 2.5D case, we can take advantage of the medium symmetry. By taking the Fourier transform with respect to the out‐of‐plane direction (the symmetry axis), the 3D problem can be reduced to a repeated 2D problem. The third dimension is taken into account by a sum over the corresponding wave‐vector component. A criterion for where to end this theoretically infinite sum derives from the stability conditions of the finite‐difference schemes employed. In this way, the computation time of the finite‐difference calculations can be considerably reduced. The quality of the modelling results obtained with this 2.5D finite‐difference scheme is comparable to that obtained using a standard 3D finite‐difference scheme.
Semi‐automatic detection of faults in 3D seismic data
Authors: Tingdahl Kristofer M. , De Rooij Matthijs 
Published: June 2005

ABSTRACTThe semi‐automated detection of objects has been quite successful in detecting various types of seismic object, such as chimneys. The same technique can be applied successfully to detect faults in 3D seismic data. We show that several different attributes – among others, similarity, frequency and curvature, all of which potentially enhance the visibility of faults – can be combined successfully by an artificial neural network. This results in a fault ‘probability’ cube in which faults are more continuous and noise is suppressed compared with single‐attribute cubes. It is believed that the fault‐cube can be improved further by applying image‐processing techniques to enhance the fault prediction.
Analytic expressions for the velocity sensitivity to the elastic moduli for the most general anisotropic media
Authors: Zhou B. , Greenhalgh S.A. 
Published: June 2005

ABSTRACTFor non‐linear kinematic inversion of elastic anisotropy parameters and related investigations of the sensitivity of seismic data, the derivatives of the wavespeed (phase velocity and group velocity) with respect to the individual elastic moduli are required. This paper presents two analytic methods, called the eigenvalue and eigenvector methods, to compute the derivatives of the wavespeeds for wave propagation in a general anisotropic medium, which may be defined by up to 21 density‐normalized elastic moduli. The first method employs a simple and compact form of the eigenvalue (phase velocity) and a general form of the group velocity, and directly yields general expressions of the derivatives for the three wave modes (qP, qS1, qS2). The second method applies simple eigenvector solutions of the three wave modes and leads to other general forms of the derivatives. These analytic formulae show that the derivatives are, in general, functions of the 21 elastic moduli as well as the wave propagation direction, and they reflect the sensitivity of the wavespeeds to the individual elastic moduli. Meanwhile, we give results of numerical investigations with some examples for particular simplified forms of anisotropy. They show that the eigenvalue method is suitable for the qP‐, qS1‐ and qS2‐wave computations and mitigates the singularity problem for the two quasi‐shear waves. The eigenvector method is preferable to the eigenvalue method for the group velocity and the derivative of the phase velocity because it involves simpler expressions and independent computations, but for the derivative of the group velocity the derivative of the eigenvector is required. Both methods tackle the singularity problem and are applicable to any degree of seismic anisotropy for all three wave modes.
Radiation from flexural vibrations of the baseplate and their effect on the accuracy of traveltime measurements
Authors: Lebedev A. , Beresnev I. 
Published: June 2005

ABSTRACTWe analyse the problem of radiation of seismic waves by a vibroseis source when the baseplate is subject to flexure. A theoretical model is proposed to account for baseplate flexure, generalizing the well‐known model of the vibroseis source of Sallas and Weber, which was developed for a rigid plate. Using the model proposed, we analyse the effect of flexure on the properties of seismic waves. We show that the flexure does not contribute to the far‐field and mainly affects the readings of the reference accelerometer that is used to measure the force applied to the ground; these readings generally become dependent on the location of the sensor on the plate. For muddy and sandy soils, the effect of flexure on baseplate‐acceleration measurements is nonetheless pronounced at the high end of the vibroseis frequency band only (∼100 Hz), and is negligible at all frequencies for stiffer soils. The corresponding phase lags introduced by the flexural vibrations at high frequencies lead to errors in the traveltime measurements (through the cross‐correlation function) of up to 0.6 ms for muddy soils and less for denser soils. We show the existence of an optimal position of the reference sensor on the baseplate and also propose a general method of eliminating the phase lag due to the baseplate flexure in acceleration measurements.
Structure and genetic diversity inColliguaja odoriferaMol. (Euphorbiaceae), a shrub subjected to Pleisto‐Holocenic natural perturbations in a mediterranean South American region
Authors: Bull‐Hereñu Kester , Martínez Enrique A. , Squeo Francisco A. 
Published: June 2005

AbstractAim Colliguaja odoriferaMol., a Euphorbiaceous shrub of central Chile, inhabits the matorral formation, growing at low altitudes on both Andean and coastal mountain range slopes. In the recent geological past, this region was subjected to climatic changes and geological disturbances that most probably caused population shrinkages on the Andean mountain slopes. This study tested the hypothesis that under such a scenario, existing populations should show lower genetic diversity in the Andean than in the coastal areas; these coastal populations being the potential source populations for recolonization.Location The study was carried out in central Chile by comparing the genetic diversity between the Andean and coastal areas, each represented by five localities distributed from 32°30′ S to 34° S.Methods Genetic diversity was estimated by DNA analysis using 18 dominant multilocus Random Amplified Polymorphic DNA (RAPD) loci, characterizing 73 genetic phenotypes.Results The comparison of the two matorral areas showed that Andean populations ofC. odoriferahave a subset of the genetic diversity found in the coastal populations. Andean populations also show a consistently lower genetic diversity, lower genetic distances and higher genetic structure, coincident with expectations based on the Pleisto‐Holocenic perturbation regime.Main conclusions This first genetic analysis for South American mediterranean populations confirms the findings of previous floristic and palynological studies that identified refuge zones in the coastal mountain range of central Chile, a situation analogous with that occurring during periods of inter‐glacial northward migration in Southern Europe.
Development of individual recognition of female southern elephant seals, Mirounga leonina, from Punta Norte Península Valdés, applying principal components analysis
Authors: Caiafa Cesar F. , Proto Araceli N. , Vergani Daniel , Stanganelli Zulma 
Published: June 2005

AbstractAim  The development of software able to provide individual recognition of southern elephant seals, as a tool to study colonies. This analysis was performed within a framework of studies concerning environmental dispersion produced by the El Niño Southern Oscillation effect in the Southern Ocean Ecosystem.Location  Digital photographs of reproductive female elephant seals were taken at Punta Norte (Península Valdés, Patagonia; 42°05′ S, 63°45′ W) during the 2002 breeding season (August to November). The data set under analysis is composed of 96 elephant seal images for a population of 56 individuals.Method  Identification of specimens was carried out using digital pictures taken with a digital video camera, and processed through the ‘Eigenfaces’ method, which is based on principal components analysis. Special care was taken to control possible variations among images of the same individual, like distance, angle, light intensity, etc. To deal with these variations, an initial alignment procedure is proposed to have all images framed; in addition an initial histogram equalization was used which attenuates any potential variation in light intensity. The software was developed in IDL5.5 language.Results  A complete set of empirical results is displayed showing the potential effectiveness of this technique. Individual recognition and pertinence to different population subsets (harems) tests have been carried out. A principal result of this work is that all 96 elephant seal images (representing 56 individuals) were correctly identified.Conclusion  The Eigenfaces method can be used successfully for identification of elephant seals. With the appropriate preparatory treatment of images, high performance results can be expected.
Aboriginal fire management in south‐eastern Australia: aims and frequency
Authors: Gott Beth 
Published: June 2005

AbstractAim  To examine the purpose of burning by Aborigines of south‐eastern Australia.Location  South‐eastern Australia.Methods  A survey of the ethnography and ecology relating to Aboriginal fire.Results  Ecologists have only recently acknowledged the past history of Aboriginal burning. Its purpose was to maximise plant and animal food resources.Main Conclusions  The seasonal timing and frequency of Aboriginal burning is embedded in various ecosystems.
Environmental determinants of vascular plant species richness in the Austrian Alps
Authors: Moser Dietmar , Dullinger Stefan , Englisch Thorsten , Niklfeld Harald , Plutzar Christoph , Sauberer Norbert , Zechmeister Harald Gustav , Grabherr Georg 
Published: June 2005

AbstractAim  To test predictions of different large‐scale biodiversity hypotheses by analysing species richness patterns of vascular plants in the Austrian Alps.Location  The Austrian part of the Alps (c. 53,500 km2).Methods  Within the floristic inventory of Central Europe the Austrian part of the Alps were systematically mapped for vascular plants. Data collection was based on a rectangular grid of 5 × 3 arc minutes (34–35 km2). Emerging species richness patterns were correlated with several environmental factors using generalized linear models. Primary environmental variables like temperature, precipitation and evapotranspiration were used to test climate‐related hypotheses of species richness. Additionally, spatial and temporal variations in climatic conditions were considered. Bedrock geology, particularly the amount of calcareous substrates, the proximity to rivers and lakes and secondary variables like topographic, edaphic and land‐use heterogeneity were used as additional predictors. Model results were evaluated by correlating modelled and observed species numbers.Results  Our final multiple regression model explains c. 50% of the variance in species richness patterns. Model evaluation results in a correlation coefficient of 0.64 between modelled and observed species numbers in an independent test data set. Climatic variables like temperature and potential evapotranspiration (PET) proved to be by far the most important predictors. In general, variables indicating climatic favourableness like the maxima of temperature and PET performed better than those indicating stress, like the respective minima. Bedrock mineralogy, especially the amount of calcareous substrate, had some additional explanatory power but was less influential than suggested by comparable studies. The amount of precipitation does not have any effect on species richness regionally. Among the descriptors of heterogeneity, edaphic and land‐use heterogeneity are more closely correlated with species numbers than topographic heterogeneity.Main conclusions  The results support energy‐driven processes as primary determinants of vascular plant species richness in temperate mountains. Stressful conditions obviously decrease species numbers, but presence of favourable habitats has higher predictive power in the context of species richness modelling. The importance of precipitation for driving global species diversity patterns is not necessarily reflected regionally. Annual range of temperature, an indicator of short‐term climatic stability, proved to be of minor importance for the determination of regional species richness patterns. In general, our study suggests environmental heterogeneity to be of rather low predictive value for species richness patterns regionally. However, it may gain importance at more local scales.
Global distribution of the European species of the lichen genus Melanelia Essl.
Authors: Otte Volker , Esslinger Theodore L. , Litterski Birgit 
Published: June 2005

AbstractAim  The global distribution of the European species of Melanelia Essl. (Lichenes: Parmeliaceae) was investigated in order to understand their distribution patterns against the background of ecogeographical and historical factors.Location  The location of the study is global, with a local emphasis on Europe.Methods  Geographical distribution and ecology of the species were investigated on the basis of herbarium studies and data from the literature as well as field observations. Distribution maps were created with ArcView GIS. The distribution patterns are expressed as three‐dimensional ‘areal formulas’, regarding zonal distribution, altitudinal range and oceanicity, using a previously described method. The observed distribution patterns are discussed on the basis of their analogies with vascular plants and with respect to the ecogeographical vs. historical factors reflected by them.Results  With the exception of one species that is endemic to Europe, all species studied occur in both northern continents. A number of species have tropical‐alpine outposts, and two species occur also in extratropical zones of the southern hemisphere. Arctic and boreal distributions are circumpolar, while in the southern holarctic zones an affinity to the western sides of both northern continents is frequent.Main conclusions  The distribution patterns appear to be mainly determined by contemporary ecogeographical factors. Most species probably have largely filled their potential distribution, at least within the Holarctic. Thus, the geographical origin and dispersal history of a species cannot reliably be reconstructed; they can be dissimilar in different species with similar distributions.
Body size, biomic specialization and range size of African large mammals
Authors: Fernández Manuel Hernández , Vrba Elisabeth S. 
Published: June 2005

AbstractAim The goal of this paper is to examine the relationships between body size, biomic specialization and range size in the African large mammals, which are defined as all the African species corresponding to the orders Primates, Carnivora, Proboscidea, Perissodactyla, Hyracoidea, Tubulidentata, Artiodactyla and Pholidota.Location The study used the large mammal assemblage from Africa.Methods The degree of biomic specialization of African large mammals is investigated using the biomic specialization index (BSI) for each mammal species, based on the number of biomes it inhabits. Range size for each species is measured as the latitudinal extent of the geographical distribution of the species. We have analysed our data using both conventional cross‐species analyses and phylogenetically independent contrasts.Results There is a polygonal relationship between species biomic specialization and body size. While small and large species are biomic specialists, medium‐sized species are distributed along the whole range of biomic specialization. The latitudinal extent–body size relationship is approximately triangular. Small‐bodied species may have either large or small ranges, whereas large‐bodied ones have only large ranges. A positive correlation between latitudinal extent and biomic specialization is evident, although their relationship is better described as triangular.Main conclusions We found a polygonal relationship between species biomic specialization and body size, which agrees with previous arguments that small‐bodied species have more limited dispersal and, therefore, they may come to occupy a lesser proportion of their potential inhabitable biomes. On the other hand, large‐bodied species are constrained to inhabit biomes with a high productivity. A polygonal relationship between species latitudinal extent and body size in African large mammals agrees with previous studies of the relationship between range size and body size in other continents. The independent study of the macroecological pattern in biomic specialization highlights different factors that influence the body size–range size relationship. Although body size is usually implicated as a correlate of both specialization and geographical range size in large mammals, much of the variation in these variables cannot be attributed to size differences but to biome specific factors such as productivity, area, history, etc.
Global patterns of plant diversity and floristic knowledge
Authors: Kier Gerold , Mutke Jens , Dinerstein Eric , Ricketts Taylor H. , Küper Wolfgang , Kreft Holger , Barthlott Wilhelm 
Published: June 2005

AbstractAims  We present the first global map of vascular plant species richness by ecoregion and compare these results with the published literature on global priorities for plant conservation. In so doing, we assess the state of floristic knowledge across ecoregions as described in floras, checklists, and other published documents and pinpoint geographical gaps in our understanding of the global vascular plant flora. Finally, we explore the relationships between plant species richness by ecoregion and our knowledge of the flora, and between plant richness and the human footprint – a spatially explicit measure of the loss and degradation of natural habitats and ecosystems as a result of human activities.Location  Global.Methods  Richness estimates for the 867 terrestrial ecoregions of the world were derived from published richness data of c. 1800 geographical units. We applied one of four methods to assess richness, depending on data quality. These included collation and interpretation of published data, use of species–area curves to extrapolate richness, use of taxon‐based data, and estimates derived from other ecoregions within the same biome.Results  The highest estimate of plant species richness is in the Borneo lowlands ecoregion (10,000 species) followed by nine ecoregions located in Central and South America with ≥ 8000 species; all are found within the Tropical and Subtropical Moist Broadleaf Forests biome. Among the 51 ecoregions with ≥ 5000 species, only five are located in temperate regions. For 43% of the 867 ecoregions, data quality was considered good or moderate. Among biomes, adequate data are especially lacking for flooded grasslands and flooded savannas. We found a significant correlation between species richness and data quality for only a few biomes, and, in all of these cases, our results indicated that species‐rich ecoregions are better studied than those poor in vascular plants. Similarly, only in a few biomes did we find significant correlations between species richness and the human footprint, all of which were positive.Main conclusions  The work presented here sets the stage for comparisons of degree of concordance of plant species richness with plant endemism and vertebrate species richness: important analyses for a comprehensive global biodiversity strategy. We suggest: (1) that current global plant conservation strategies be reviewed to check if they cover the most outstanding examples of regions from each of the world's major biomes, even if these examples are species‐poor compared with other biomes; (2) that flooded grasslands and flooded savannas should become a global priority in collecting and compiling richness data for vascular plants; and (3) that future studies which rely upon species–area calculations do not use a uniform parameter value but instead use values derived separately for subregions.
Historical biogeography and phylogeny of monachine seals (Pinnipedia: Phocidae) based on mitochondrial and nuclear DNA data
Authors: Fyler C. A. , Reeder T. W. , Berta A. , Antonelis G. , Aguilar A. , Androukaki E. 
Published: June 2005

AbstractAim To determine the origin and diversification of monachine seals using a phylogenetic framework.Methods Molecular sequence data from three mitochondrial genes (cytb, ND1 and 12S), and one nuclear marker (an intron from theα‐lactalbumin gene) were examined from all extant species of monachine seals. Maximum likelihood and partitioned Bayesian inference were used to analyse separate and combined (mitochondrial + nuclear) data sets. Divergence times were estimated from the resultant phylogeny using nonparametric rate smoothing as implemented by the program r8s.Results Mirounga,Monachusand the Lobodontini form three well‐supported clades within a monophyletic Monachinae. Lobodontini + Miroungaform a clade sister toMonachus. Molecular divergence dates indicate that the first split within the Monachinae (Lobodontini + Miroungaclade andMonachus) occurred between 11.8 and 13.8 Ma andMirounga,Monachusand the Lobodontini originated 2.7–3.4, 9.1–10.8 and 10.0–11.6 Ma, respectively.Main conclusions Two main clades exist within Monachinae,Monachusand Lobodontini + Mirounga.Monachus, a warm water clade, originated in the North Atlantic and maintained the temperate water affinities of their ancestors as they diversified in the subtropic regions of the Northern Hemisphere. The cold‐water clade, Lobodontini + Mirounga, dispersed southward to the cooler climates of the Southern Hemisphere. The Lobodontini continued south until reaching the Antarctic region where they diversified into the present‐day fauna.Miroungashows an anti‐tropical distribution either reflective of a once cosmopolitan range that was separated by warming waters in the tropics or of transequatorial dispersal.
Lichenological evidence for the recognition of inland rain forests in western North America
Authors: Goward Trevor , Spribille Toby 
Published: June 2005

AbstractAim  The coastal temperate rain forests of north‐western North America are internationally renowned as the archetypal expression of the temperate rain forest biome. Less well documented is the existence of somewhat similar forests 500–700 km inland on the windward slopes of the Columbia and Rocky Mountains. Here we attempt to show that these inland ‘wetbelt’ forests warrant rain forest status.Location  North‐western North America.Methods  We use tree‐dwelling macrolichens to assess the degree of environmental congruence between the coastal temperate rain forests and their inland counterparts.Results  We report three key findings: (1) 40% of oceanic, epiphytic macrolichens found in Pacific coastal rain forests occur also in inland regions; (2) epiphytic species richness decreases with decreasing latitude, such that roughly 70% of disjunct oceanic species are restricted to regions north of 51° N; and (3) the southward decline in lichen diversity is correlated with a parallel decrease in summer precipitation, but not with mean annual precipitation.Main conclusions  These observations are consistent with the recognition of an inland rain forest formation between 50 and 54° N. Inland rain forests represent a small, biologically significant ecosystem whose continued fragmentation and conversion to tree plantations warrant close scrutiny.