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Scale Dependence (scale + dependence)

Distribution by Scientific Domains

Life Sciences	58%
Physics and Astronomy	29%

Distribution within Life Sciences

Conservation Science	39%

Selected Abstracts

Scale dependence of effective specialization: its analysis and implications for estimates of global insect species richness

DIVERSITY AND DISTRIBUTIONS, Issue 1 2007
Jon C. Gering
ABSTRACT Estimates of global insect species richness are sometimes based on effective specialization, a calculation used to estimate the number of insect species that is restricted to a particular tree species. Yet it is not clear how effective specialization is influenced by spatial scale or characteristics of the insect community itself (e.g. species richness). We investigated scale dependence and community predictors of effective specialization using 15,907 beetles (583 species) collected by insecticide fogging from the crowns of 96 trees (including 32 Quercus trees) located in Ohio and Indiana. Trees were distributed across 24 forest stands (,1 ha) nested within six sites (,10,100 km2) and two ecoregions (> 1000 km2). Using paired-sample randomization tests, we found that effective specialization (fk) exhibited negative scale-dependence in early (May,June 2000) and late (August,September 2000) sampling periods. Our average effective specialization (F) values , those that are comparable to Erwin's (1982) estimates , ranged from 19% to 97%, and increased as spatial scale decreased. We also found that beetle species richness and the number of shared beetle species across host trees were significant and consistent negative predictors of F. This shows that increases in spatial scale, species richness, and the number of trees (and/or tree species) all coincide with decreases in effective specialization. Collectively, our results indicate that estimates of global insect species richness based on effective specialization at a single spatial scale are overestimating the magnitude of global insect species richness. We propose that scale dependence should be promoted to a central concept in the research program on global estimates of species richness. [source]

Scale dependence of diversity measures in a leaf-litter ant assemblage

ECOGRAPHY, Issue 2 2004
Maurice Leponce
A reliable characterization of community diversity and composition, necessary to allow inter-site comparisons and to monitor changes, is especially difficult to reach in speciose invertebrate communities. Spatial components of the sampling design (sampling interval, extent and grain) as well as temporal variations of species density affect the measures of diversity (species richness S, Buzas and Gibson's evenness E and Shannon's heterogeneity H). Our aim was to document the small-scale spatial distribution of leaf litter ants in a subtropical dry forest of the Argentinian Chaco and analyze how the community characterization was best achieved with a minimal sampling effort. The work was based on the recent standardized protocol for collecting ants of the leaf litter ("A.L.L.": 20 samples at intervals of 10 m). To evaluate the consistency of the sampling method in time and space, the selected site was first subject to a preliminary transect, then submitted after a 9-month interval to an 8-fold oversampling campaign (160 samples at interval of 1.25 m). Leaf litter ants were extracted from elementary 1 m2 quadrats with Winkler apparatus. An increase in the number of samples collected increased S and decreased E but did not affect much H. The sampling interval and extent did not affect S and H beyond a distance of 10 m between samples. An increase of the sampling grain had a similar effect on S than a corresponding increase of the number of samples collected, but caused a proportionaly greater increase of H. The density of species m,2 varied twofold after a 9-month interval; the effect on S could only be partially corrected by rarefaction. The measure of species numerical dominance was little affected by the season. A single standardized A.L.L. transect with Winkler samples collected <45% of the species present in the assemblage. All frequent species were included but their relative frequency was not always representative. A log series distribution of species occurrences was oberved. Fisher's , and Shannon's H were the most appropriate diversity indexes. The former was useful to rarefy or abundify S and the latter was robust against sample size effects. Both parametric and Soberón and Llorente extrapolation methods outperformed non-parametric methods and yielded a fair estimate of total species richness along the transect, a minimum value of S for the habitat sampled. [source]

Scale dependence of spatial patterns and cartography on the detection of landscape change: relationships with species' perception

ECOGRAPHY, Issue 4 2002
Susana Suárez-Seoane
This paper analyses how landscape pattern detection changes when different spatial and temporal scales and several levels of detail of the cartography are used to describe a landscape affected by land abandonment in northern Spain. In order to integrate landscape composition and structure at different temporal and spatial scales in the same framework, a multiple correspondence factorial analysis was ran for each typology of landscape units. Annual rates of change and scale dependencies were calculated for each typology from the Euclidean distances in the factorial space. Finally, the potential assessment of habitat utilisation by species with different landscape perception and movement capacity was modelled for the range of typologies. The amount of variance explained by the factorial analysis decreased with the complexity of the typology. Annual rates of change appeared different according to the time span and the detail of the landscape unit typology used. For all typologies, changes were faster during 1983,95, a period characterised by massive land abandonment. However, when the whole period (1956,95) was considered, annual changes were much lower, showing differences between typologies. As a general trend, the variance of the mean annual change decreased with the size of the analysis units. In response to land abandonment, different scale dependencies were found for different levels of detail of the cartography. Coarser typologies are suitable when analysing highly mobile species. However, species with small movement capacity or with a preference for homogeneous habitats perceive more detail in landscape. In this case, a detailed typology is more appropriate. [source]

Scale dependence of the correlation between human population presence and vertebrate and plant species richness

ECOLOGY LETTERS, Issue 1 2007
Marco Pautasso
Abstract Human presence is generally negatively related to species richness locally, but the relationship is positive at coarse scales. An increase in the strength of the latter correlation with increasing study resolution has been documented within studies, but it is not known whether such a scale dependence is present across different studies. We test this with data on the spatial co-occurrence of human beings and the species richness of plants and vertebrates from a continuum of scales. The correlation coefficient between human presence and species richness is positively related to study grain and extent. The correlation turns from positive to negative below a study grain of c. 1 km and below a study extent of c. 10 000 km2. The broad-scale positive correlation between human presence and species richness suggests that people have preferentially settled and generally flourished in areas of high biodiversity and/or have contributed to it with species introductions and habitat diversification. The scale dependency of the correlation between people and biodiversity's presence emphasizes the importance of the preservation of green areas in densely populated regions. [source]

Habitat Loss and Extinction in the Hotspots of Biodiversity

CONSERVATION BIOLOGY, Issue 4 2002
Thomas M. Brooks
None of these hotspots have more than one-third of their pristine habitat remaining. Historically, they covered 12% of the land's surface, but today their intact habitat covers only 1.4% of the land. As a result of this habitat loss, we expect many of the hotspot endemics to have either become extinct or,because much of the habitat loss is recent,to be threatened with extinction. We used World Conservation Union [ IUCN ] Red Lists to test this expectation. Overall, between one-half and two-thirds of all threatened plants and 57% of all threatened terrestrial vertebrates are hotspot endemics. For birds and mammals, in general, predictions of extinction in the hotspots based on habitat loss match numbers of species independently judged extinct or threatened. In two classes of hotspots the match is not as close. On oceanic islands, habitat loss underestimates extinction because introduced species have driven extinctions beyond those caused by habitat loss on these islands. In large hotspots, conversely, habitat loss overestimates extinction, suggesting scale dependence (this effect is also apparent for plants). For reptiles, amphibians, and plants, many fewer hotspot endemics are considered threatened or extinct than we would expect based on habitat loss. This mismatch is small in temperate hotspots, however, suggesting that many threatened endemic species in the poorly known tropical hotspots have yet to be included on the IUCN Red Lists. We then asked in which hotspots the consequences of further habitat loss (either absolute or given current rates of deforestation) would be most serious. Our results suggest that the Eastern Arc and Coastal Forests of Tanzania-Kenya, Philippines, and Polynesia-Micronesia can least afford to lose more habitat and that, if current deforestation rates continue, the Caribbean, Tropical Andes, Philippines, Mesoamerica, Sundaland, Indo-Burma, Madagascar, and Chocó,Darién,Western Ecuador will lose the most species in the near future. Without urgent conservation intervention, we face mass extinctions in the hotspots. Resumen: Casi la mitad del total de plantas vasculares del mundo y un tercio de los vertebrados terrestres son endémicos en 25 "áreas críticas" para la biodiversidad, cada una de las cuales tiene por lo menos 1500 especies de plantas endémicas. En ninguno de estos sitios permanece más de un tercio de su hábitat prístino. Históricamente, cubrían 12% de la superficie terrestre, pero en la actualidad su hábitat intacto cubre solo 1.4% del terreno. Como resultado de esta pérdida de hábitat esperamos que muchas de las especies endémicas a estos sitios estén extintas o , porque la pérdida de hábitat es reciente , se encuentren amenazadas de extinción. Utilizamos Listas Rojas de UICN para comprobar esta predicción. En general, entre la mitad y dos tercios de las plantas amenazadas y el 57% de los vertebrados terrestres amenazados son endémicos de áreas críticas para la biodiversidad. Para aves y mamíferos en general, las predicciones de extinción en las áreas críticas para la biodiversidad, basadas en la pérdida de hábitat, coinciden con el número de especies consideradas extintas o amenazadas independientemente. En dos clases de áreas críticas para la biodiversidad la coincidencia no es muy grande. En islas oceánicas, la pérdida de hábitat subestima la extinción porque las especies introducidas han causado más extinciones que las producidas por la reducción del hábitat. Por lo contrario, la pérdida de hábitat sobrestima la extinción en áreas críticas para la biodiversidad extensas, lo que sugiere una dependencia de escala (este efecto también es aparente para plantas). Para reptiles, anfibios y plantas mucho menos especies endémicas son consideradas amenazadas o extintas por pérdida de hábitat. Sin embargo, esta discordancia es pequeña en áreas críticas para la biodiversidad en zonas templadas templadas, lo que sugiere que muchas especies endémicas amenazadas en las poco conocidas áreas críticas para la biodiversidad en zonas tropicales aun están por incluirse en las Listas Rojas. Posteriormente nos preguntamos en que áreas críticas para la biodiversidad serían más serias las consecuencias de una mayor pérdida de hábitat (absoluta o con las tasas actuales de deforestación). Nuestros resultados sugieren que el Arco Oriental y los Bosques Costeros de Tanzania/Kenia, Filipinas, Polinesia/Micronesia no pueden soportar mayores pérdidas y que, si continúan las tasas de deforestación actuales, el Caribe, Andes Tropicales, Filipinas, Mesoamérica, Sundaland, Indo-Burma, Madagascar y Chocó/Darién/Ecuador Occidental perderán más especies en el futuro. Sin acciones urgentes de conservación, habrá extinciones masivas en las áreas críticas para la biodiversidad. [source]

BIODIVERSITY RESEARCH: Conserving macroinvertebrate diversity in headwater streams: the importance of knowing the relative contributions of , and , diversity

DIVERSITY AND DISTRIBUTIONS, Issue 5 2010
Amber Clarke
Abstract Aim, We investigated partitioning of aquatic macroinvertebrate diversity in eight headwater streams to determine the relative contributions of , and , diversity to , diversity, and the scale dependence of , and , components. Location, Great Dividing Range, Victoria, Australia. Methods, We used the method of Jost (Ecology, 2007, 88, 2427,2439) to partition , diversity into its , and , components. We undertook the analyses at both reach and catchment scales to explore whether inferences depended on scale of observation. Results, We hypothesized that , diversity would make a large contribution to the , diversity of macroinvertebrates in our dendritic riverine landscape, particularly at the larger spatial scale (among catchments) because of limited dispersal among sites and especially among catchments. However, reaches each had relatively high taxon richness and high , diversity, while , diversity made only a small contribution to , diversity at both the reach and catchment scales. Main conclusions, Dendritic riverine landscapes have been thought to generate high , diversity as a consequence of limited dispersal and high heterogeneity among individual streams, but this may not hold for all headwater stream systems. Here, , diversity was high and , diversity low, with individual headwater stream reaches each containing a large portion of , diversity. Thus, each stream could be considered to have low irreplaceability since losing the option to use one of these sites in a representative reserve network does not greatly diminish the options available for completing the reserve network. Where limited information on individual taxonomic distributions is available, or time and money for modelling approaches are limited, diversity partitioning may provide a useful ,first-cut' for obtaining information about the irreplaceability of individual streams or subcatchments when establishing representative freshwater reserves. [source]

Scale dependence of effective specialization: its analysis and implications for estimates of global insect species richness

Scale dependence of the correlation between human population presence and vertebrate and plant species richness

Local,regional boundary shifts in oribatid mite (Acari: Oribatida) communities: species,area relationships in arboreal habitat islands of a coastal temperate rain forest, Vancouver Island, Canada

JOURNAL OF BIOGEOGRAPHY, Issue 9 2007
Zoë Lindo
Abstract Aim, This study investigates the species,area relationship (SAR) for oribatid mite communities of isolated suspended soil habitats, and compares the shape and slope of the SAR with a nested data set collected over three spatial scales (core, patch and tree level). We investigate whether scale dependence is exhibited in the nested sampling design, use multivariate regression models to elucidate factors affecting richness and abundance patterns, and ask whether the community composition of oribatid mites changes in suspended soil patches of different sizes. Location, Walbran Valley, Vancouver Island, Canada. Methods, A total of 216 core samples were collected from 72 small, medium and large isolated suspended soil habitats in six western redcedar trees in June 2005. The relationship between oribatid species richness and habitat volume was modelled for suspended soil habitat isolates (type 3) and a nested sampling design (type 1) over multiple spatial scales. Nonlinear estimation parameterized linear, power and Weibull function regression models for both SAR designs, and these were assessed for best fit using R2 and Akaike's information criteria (,AIC) values. Factors affecting oribatid mite species richness and standardized abundance (number per g dry weight) were analysed by anova and linear regression models. Results, Sixty-seven species of oribatid mites were identified from 9064 adult specimens. Surface area and moisture content of suspended soils contributed to the variation in species richness, while overall oribatid mite abundance was explained by moisture and depth. A power-law function best described the isolate SAR (S = 3.97 × A0.12, R2 = 0.247, F1,70 = 22.450, P < 0.001), although linear and Weibull functions were also valid models. Oribatid mite species richness in nested samples closely fitted a power-law model (S = 1.96 × A0.39, R2 = 0.854, F1,18 = 2693.6, P < 0.001). The nested SAR constructed over spatial scales of core, patch and tree levels proved to be scale-independent. Main conclusions, Unique microhabitats provided by well developed suspended soil accumulations are a habitat template responsible for the diversity of canopy oribatid mites. Species,area relationships of isolate vs. nested species richness data differed in the rate of accumulation of species with increased area. We suggest that colonization history, stability of suspended soil environments, and structural habitat complexity at local and regional scales are major determinants of arboreal oribatid mite species richness. [source]

The potential of X-ray cluster surveys to constrain primordial non-Gaussianity

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010
B. Sartoris
ABSTRACT We present forecasts for constraints on deviations from Gaussian distribution of primordial density perturbations from future high-sensitivity X-ray surveys of galaxy clusters. Our analysis is based on computing the Fisher matrix for number counts and large-scale power spectrum of clusters. The surveys that we consider have high sensitivity and wide area to detect about 2.5 × 105 extended sources, and to provide reliable measurements of robust mass proxies for about 2 × 104 clusters. Based on the so-called self-calibration approach, and including Planck priors in our analysis, we constrain at once nine cosmological parameters and four nuisance parameters, which define the relation between cluster mass and X-ray flux. Because of the scale dependence of large-scale bias induced by local-shape non-Gaussianity, we find that the power spectrum provides strong constraints on the non-Gaussianity fNL parameter, which complement the stringent constraints on the power spectrum normalization, ,8, from the number counts. To quantify the joint constraints on the two parameters, ,8 and fNL, that specify the timing of structure formation for a fixed background expansion, we define the figure of merit . We find that our surveys constrain deviations from Gaussianity with a precision of ,fNL, 10 at 1, confidence level, with FoMSFT, 39. We point out that constraints on fNL are weakly sensitive to the uncertainties in the knowledge of the nuisance parameters. As an application of non-Gaussian constraints from available data, we analyse the impact of positive skewness on the occurrence of XMMU-J2235, a massive distant cluster recently discovered at z, 1.4. We confirm that in a WMAP -7 Gaussian ,CDM cosmology, within the survey volume, , 5 × 10,3 objects like this are expected to be found. To increase the probability of finding such a cluster by a factor of at least 10, one needs to evade either the available constraints on fNL or on the power-spectrum normalization ,8. [source]

Bayesian optimal reconstruction of the primordial power spectrum

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009
M. Bridges
ABSTRACT The form of the primordial power spectrum has the potential to differentiate strongly between competing models of perturbation generation in the early universe and so is of considerable importance. The recent release of five years of Wilkinson Microwave Anisotropy Probe observations have confirmed the general picture of the primordial power spectrum as deviating slightly from scale invariance with a spectral tilt parameter of ns, 0.96. None the less, many attempts have been made to isolate further features such as breaks and cut-offs using a variety of methods, some employing more than ,10 varying parameters. In this paper, we apply the robust technique of the Bayesian model selection to reconstruct the optimal degree of structure in the spectrum. We model the spectrum simply and generically as piecewise linear in ln k between ,nodes' in k space whose amplitudes are allowed to vary. The number of nodes and their k -space positions are chosen by the Bayesian evidence so that we can identify both the complexity and location of any detected features. Our optimal reconstruction contains, perhaps, surprisingly few features, the data preferring just three nodes. This reconstruction allows for a degree of scale dependence of the tilt with the ,turn-over' scale occurring around k, 0.016 Mpc,1. More structure is penalized by the evidence as overfitting the data, so there is currently little point in attempting reconstructions that are more complex. [source]

Clustering of luminous red galaxies , II.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009
Small-scale redshift-space distortions
ABSTRACT This is the second paper of a series where we study the clustering of luminous red galaxies (LRG) in the recent spectroscopic Sloan Digital Sky Survey (SDSS) data release, DR6, which has 75 000 LRG covering over 1 Gpc3 h,3 for 0.15 < z < 0.47. Here, we focus on modelling redshift-space distortions in ,(,, ,), the two-point correlation in separate line-of-sight and perpendicular directions, at small scales and in the line-of-sight. We show that a simple Kaiser model for the anisotropic two-point correlation function in redshift space, convolved with a distribution of random peculiar velocities with an exponential form, can describe well the correlation of LRG on all scales. We show that to describe with accuracy the so-called ,fingers-of-God' (FOG) elongations in the radial direction, it is necessary to model the scale dependence of both bias b and the pairwise rms peculiar velocity ,12 with the distance. We show how both quantities can be inferred from the ,(,, ,) data. From r, 10 Mpc h,1 to r, 1 Mpc h,1, both the bias and ,12 are shown to increase by a factor of 2: from b= 2 to 4 and from ,12= 400 to 800 km s,1. The latter is in good agreement, within a 5 per cent accuracy in the recovered velocities, with direct velocity measurements in dark matter simulations with ,m= 0.25 and ,8= 0.85. [source]

Scale-dependent galaxy bias in the Sloan Digital Sky Survey as a function of luminosity and colour

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009
James G. Cresswell
ABSTRACT It has been known for a long time that the clustering of galaxies changes as a function of galaxy type. This galaxy bias acts as a hindrance to the extraction of cosmological information from the galaxy power spectrum or correlation function. Theoretical arguments show that a change in the amplitude of the clustering between galaxies and mass on large scales is unavoidable, but cosmological information can be easily extracted from the shape of the power spectrum or correlation function if this bias is independent of scale. Scale-dependent bias is generally small on large scales, k < 0.1 h Mpc,1, but on smaller scales can affect the recovery of ,mh from the measured shape of the clustering signal, and have a small effect on the Baryon Acoustic Oscillations. In this paper, we investigate the transition from scale-independent to scale-dependent galaxy bias as a function of galaxy population. We use the Sloan Digital Sky Survey Data Release 5 sample to fit various models, which attempt to parametrize the turn-off from scale-independent behaviour. For blue galaxies, we find that the strength of the turn-off is strongly dependent on galaxy luminosity, with stronger scale-dependent bias on larger scales for more luminous galaxies. For red galaxies, the scale dependence is a weaker function of luminosity. Such trends need to be modelled in order to optimally extract the information available in future surveys, and can help with the design of such surveys. [source]

Analysis of scale dependence of quantitative precipitation forecast verification: A case-study over the Mackenzie river basin

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 620 2006
Olivier Bousquet
Abstract Six-hour rainfall accumulations derived from radar observations collected during a 3-day summertime precipitation event over central Alberta (Canada) are used to assess the performance of a regional Canadian numerical weather prediction system for quantitative precipitation forecast verification. We show that radar data provide a simple and efficient way to significantly reduce model phase errors associated with misplacement of predicted precipitation patterns. Using wavelet analysis, we determine that the limiting spatial scale of predictability of the model is about six times its grid resolution for 6 h accumulated fields. The use of longer accumulation periods is shown to smooth out forecast errors that may have resulted from slight phase or time shift errors but does not change the limiting scale of predictability. The scale decomposition of the mean-square forecast error also reveals that scales which cannot be accurately reproduced by the model account for about 20% of the total error. Using classical continuous and categorical scores, we show that significantly better model performance can be achieved by smoothing out wavelengths that cannot be predicted. Copyright © 2006 Royal Meteorological Society [source]

Functional renormalization group approach to the BCS-BEC crossover

ANNALEN DER PHYSIK, Issue 9 2010
S. Diehl
Abstract The phase transition to superfluidity and the BCS-BEC crossover for an ultracold gas of fermionic atoms is discussed within a functional renormalization group approach. Non-perturbative flow equations, based on an exact renormalization group equation, describe the scale dependence of the flowing or average action. They interpolate continuously from the microphysics at atomic or molecular distance scales to the macroscopic physics at much larger length scales, as given by the interparticle distance, the correlation length, or the size of the experimental probe. We discuss the phase diagram as a function of the scattering length and the temperature and compute the gap, the correlation length and the scattering length for molecules. Close to the critical temperature, we find the expected universal behavior. Our approach allows for a description of the few-body physics (scattering and molecular binding) and the many-body physics within the same formalism. [source]

Local adaptation in a plant herbivore interaction depends on the spatial scale

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009
RODRIGO COGNI
Local adaptation has central importance in the understanding of co-evolution, maintenance of sexual reproduction, and speciation. We investigated local adaptation in the alkaloid-bearing legume Crotalaria pallida and its seed predator, the arctiid moth Utetheisa ornatrix, at different spatial scales. When we studied three populations from south-east Brazil (150 km apart), we did not find evidence of local adaptation, although we did find interpopulational differences in herbivore performance, and a significant interaction between herbivore sex and plant population. These results indicate that both moth and plant populations are differentiated at the regional scale. In a comparison of populations from Brazil and Florida, the herbivore showed local adaptation to its host plant; for both moth populations, the pupae were heavier when the larvae ate the sympatric than the allopatric host population. We discuss the scale dependence of our results and the possible causes for the lack of local adaptation at the regional scale, even in the presence of plant and moth differentiation. The results obtained demonstrate the importance of studying co-evolution and local adaptation at different geographical scales. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 494,502. [source]

Analyzing characteristic length scales in biofilm structures

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009
K. Milferstedt
Abstract The quantification of biofilm structure based on image analysis requires a statistical measure like representative elemental areas (REA) to determine the necessary size of biofilm area to be imaged. In this study, REAs for biofilm structure were calculated for the descriptors Gray level and Correlation (COR) derived from a spatial gray level dependence matrix analysis (SGLDM). An important difference between these two descriptors is their response to structural features at different spatial scales. Gray level is a scale-independent descriptor, whereas COR is scale-dependent. For scale-independent descriptors, the size of the individual images is not relevant when determining REAs. This is in contrast to scale-dependent descriptors for which REAs can only be determined when the area of each image covers the range of structural variability of the biofilm. We used COR to analyze scale dependence of structural heterogeneity at different length scales. A characteristic length of 400 µm in biofilm images provides structural information relevant for mass transport phenomena in biofilms. Overall REAs for gray level and COR were on average 3.4 mm2. The scale-dependent descriptor COR could not in all cases accurately be determined from combining individual image analysis results,even when the combined area resulted in the REA. Microscope and camera specifications define the upper and lower limit of detectable characteristic length that can be extracted from images and should therefore be considered in the experimental design when choosing an imaging technique. Biotechnol. Bioeng. 2009;102: 368,379. © 2008 Wiley Periodicals, Inc. [source]