Search results for "VARIABILITY"
showing 10 items of 904 documents
Carbon use efficiency variability from MODIS data
2017
[EN] Carbon use efficiency (CUE) describes how efficiently plants incorporate the carbon fixed during photosynthesis into biomass gain and can be calculated as the ratio between net primary production (NPP) and gross primary production (GPP). In this work, annual CUE has been obtained from annual GPP and NPP MODIS products for the peninsular Spain study area throughout eight years. CUE is spatially and temporally analyzed in terms of the vegetation type and annual precipitation and annual average air temperature. Results show that dense vegetation areas with moderate to high levels of precipitation present lower CUE values, whereas more arid areas present the highest CUE values. However, th…
Typology of pentad circulation anomalies over the Eastern Africa - Western Indian Ocean region, and their relationship with rainfall
2005
International audience; The aim of this study was to classify the most frequently observed atmospheric circula- tion anomaly patterns in eastern Africa and the adjacent Indian Ocean. As an example of the useful- ness of such a classification, the second objective was to test whether these patterns account for intraseasonal rainfall anomalies in the region. A partitioning algorithm, known as dynamical cluster analysis, was therefore applied to the zonal (U)and meridional (V)components of the wind anom- alies, obtained from the NCEP-NCAR Reanalysis R-2 at the pentad (5 d) timescale. The 3 geopoten- tial levels 850, 700 and 200 hPa were combined. Focus is on the transition seasons (March to Ma…
Hydrology is reflected in the functioning and community composition of methanotrophs in the littoral wetland of a boreal lake
2010
In lake ecosystems a major proportion of methane (CH4) emissions originate from the littoral zone, which can have a great spatial variability in hydrology, soil quality and vegetation. Hitherto, spatial heterogeneity and the effects it has on functioning and diversity of methanotrophs in littoral wetlands have been poorly understood. A diagnostic microarray based on the particulate methane monooxygenase gene coupled with geostatistics was used to analyse spatial patterns of methanotrophs in the littoral wetland of a eutrophic boreal lake (Lake Kevaton, Eastern Finland). The wetland had a hydrology gradient with a mean water table varying from −8 to −25 cm. The wettest area, comprising the h…
Genetic and morphological differentiation ofDikerogammarusinvaders and their invasion history in Central Europe
2002
SUMMARY 1. Biological invasions often involve close taxonomic relatives either as native/invader pairs or as invader/invader pairs. Precise identification and differentiation of species is therefore of paramount importance to reconstruct the invasion history. Genetic studies are indispensable in the case of morphologically conservative taxonomic groups. 2. We analysed the Pontocaspian freshwater amphipods Dikerogammarus that have successfully invaded the benthos of large Central European rivers. Taxonomic uncertainties were clarified by phylogenetic analyses of mitochondrial 16S and COI genes. The three-way partitioning of allozyme genotypes in a syntopic population further corroborated the…
Information Decomposition in Bivariate Systems: Theory and Application to Cardiorespiratory Dynamics
2015
In the framework of information dynamics, the temporal evolution of coupled systems can be studied by decomposing the predictive information about an assigned target system into amounts quantifying the information stored inside the system and the information transferred to it. While information storage and transfer are computed through the known self-entropy (SE) and transfer entropy (TE), an alternative decomposition evidences the so-called cross entropy (CE) and conditional SE (cSE), quantifying the cross information and internal information of the target system, respectively. This study presents a thorough evaluation of SE, TE, CE and cSE as quantities related to the causal statistical s…
Distinctive body perception mechanisms in high versus low symptom reporters: A neurophysiological model for medically-unexplained symptoms.
2020
Abstract Objective The neurophysiological processes involved in the generation of medically-unexplained symptoms (MUS) remain unclear. This study tested three assumptions of the perception-filter model contributing to MUS: (I.) increased bodily signal strength (II.) decreased filter function, (III.) increased perception. Methods In this cross-sectional, observational study, trait MUS were assessed by a web-based survey (N = 486). The upper and lower decile were identified as extreme groups of high (HSR; n = 29; 26 women; Mage = 26.0 years) and low symptom reporters (LSR; n = 29; 21 women; Mage = 28.4 years). Mean heart rate (HR) and heart rate variability (HRV), and cortisol awakening respo…
Statistical upscaling of ecosystem CO2 fluxes across the terrestrial tundra and boreal domain: Regional patterns and uncertainties
2021
The regional variability in tundra and boreal carbon dioxide (CO2) fluxes can be high, complicating efforts to quantify sink-source patterns across the entire region. Statistical models are increasingly used to predict (i.e., upscale) CO2 fluxes across large spatial domains, but the reliability of different modeling techniques, each with different specifications and assumptions, has not been assessed in detail. Here, we compile eddy covariance and chamber measurements of annual and growing season CO2 fluxes of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem exchange (NEE) during 1990–2015 from 148 terrestrial high-latitude (i.e., tundra and boreal) sites to a…
Sampling and repeatability in the evaluation of hepatitis C virus genetic variability.
2003
Among the experimental techniques available to study the genetic variability of RNA virus populations, the most informative involve reverse transcription (RT), amplification, cloning and sequencing. The effects of several aspects of these techniques on the estimation of genetic variability in a virus population were analysed. Hepatitis C virus populations from four patients were examined. For each patient, ten series of data derived from independent PCR amplifications of a single RT reaction were obtained. The sample size of each data set was 10 sequences (in nine series) and 100 sequences (in one series). An additional data set derived from an independent RT reaction (about 10 sequences) p…
Heterogeneity of volatile sources along the Halmahera arc, Indonesia
2021
co-auteur étranger; International audience; The parallel Halmahera and Sangihe arcs in eastern Indonesia are sites of active arc-arc collision of considerable interest in developing understanding of the geodynamics and geochemistry of subduction zones. Owing to the comparative remoteness of the region, few ground-based studies of the volcanoes have been undertaken. Here, we report and integrate gas measurements and (isotope) geochemical analyses of lava samples for Dukono, Ibu, Gamkonora, Gamalama, and Makian volcanoes of the Halmahera arc. Summing gas fluxes for all five volcanoes indicates arcscale emission budgets for H 2 O, CO 2 , SO 2 , H 2 S, and H 2 of 96300±27000, 2093±450, 944±400,…
THE EFFECTS OF MATING SYSTEM AND GENETIC VARIABILITY ON SUSCEPTIBILITY TO TREMATODE PARASITES IN A FRESHWATER SNAIL, LYMNAEA STAGNALIS
2004
The amount and distribution of genetic variability in host populations can have significant effects on the outcome of host-parasite interactions. We studied the effect of mating system and genetic variability on susceptibility of Lymnaea stagnalis snails to trematode parasites. Mating system of snails from eight populations differing in the amount of genetic variability was manipulated, and self- and cross-fertilized offspring were exposed to naturally occurring trematode parasites in a controlled lake experiment. Susceptibility of snails varied between populations, but mating-system treatment did not have a significant effect. Heterozygosity of snails was negatively correlated with the pro…