Search results for " Variability"
showing 10 items of 853 documents
The effects of anthropogenic organic matter inputs on stable carbon and nitrogen isotopes in organisms from different trophic levels in a southern Me…
2005
Stable isotope ratios were used to determine the impact of anthropogenically derived organic matter from onshore and offshore fish farming and a sewage outfall on organisms at different trophic levels (primary producers and consumers) on the south-east coast of Sicily (Italy, Mediterranean). Representative macroalgae and consumers were collected in three sampling locations: "Impact" and two putative "Controls" sited to the north of the impacted location. While delta(13)C values of both organic matter sources and consumers varied little between locations, delta(15)N spatial variability was higher and delta(15)N was shown to be a good descriptor of organic enrichment and uptake of anthropogen…
Heart rate variability and self-control—A meta-analysis
2015
Heart rate variability (HRV) has been suggested as a biological correlate of self-control. Whereas many studies found a relationship between HRV at rest and self-control, effect sizes vary substantially across studies in magnitude and direction. This meta-analysis evaluated the association between HRV at rest and self-control in laboratory tasks, with a particular focus on the identification of moderating factors (task characteristics, methodological aspects of HRV assessment, demographics). Overall, 24 articles with 26 studies and 132 effects (n=2317, mean age=22.44, range 18.4-57.8) were integrated (random effects model with robust variance estimation). We found a positive average effect …
The fate of organic matter sources in coastal environments: a comparison of three Mediterranean lagoons
2008
Trophic processes in coastal lagoons are strongly influenced by freshwater inputs and water exchanges with the sea. In recent years, stable isotope analysis has become a widespread and reliable method for the examination of trophic structure over time and space, also in complex ecosystems such as coastal lagoons. Stable isotopes of carbon and nitrogen were studied in primary producers and consumers to identify organic matter source pools from terrestrial, benthic and pelagic environments and to characterise the trophic structure in three Mediterranean coastal lagoons (Lake Fusaro, the Lake of Sabaudia and Stagnone di Marsala). The results highlighted the negligible importance of terrestrial…
A distributed agro-hydrological model for irrigation water demand assessment
2008
Abstract The actual irrigation water demand in a district in Sicily (Italy) was assessed by the spatially distributed agro-hydrological model SIMODIS (SImulation and Management of On-Demand Irrigation Systems) . For each element with homogeneous crop and soil conditions, in which the considered area can be divided, the model numerically solves the one-dimensional water flow equation with vegetation parameters derived from Earth Observation data. In SIMODIS, the irrigation scheduling is set by means of two parameters: the threshold value of soil water pressure head in the root zone, h m , and the fraction of soil water deficit to be re-filled, Δ . This study investigated the possibility of i…
Genetic structure of Tunisian sheep breeds as inferred from genome-wide SNP markers
2020
Abstract Assessing the status of genetic variability of native sheep breeds could provide important clues for research and policy makers to devise better strategies for the conservation and management of genetic resources. In this study, a genetic investigation of Tunisian sheep breeds using a genome-wide scan of approximately 50,000 SNPs was performed. To reconstruct genetic structure and relationships among four sheep breeds, 40 samples belonging to fat-tailed Barbarine, Queue Fine de l’Ouest, Noire de Thibar and D’Man breeds were genotyped using Illumina Ovine SNP50 BeadChip. Tunisian breeds averaged 96 % polymorphic loci with an expected heterozygosity (He = 0.36). Genetic analysis of r…
Feasibility of Linear Parametric Estimation of Dynamic Information Measures to assess Physiological Stress from Short-Term Cardiovascular Variability
2021
Extensive efforts have been recently devoted to implement fast and reliable algorithms capable of assessing the physiological response of the organism to physiological stress. In this study, we propose the comparison between model-free and linear parametric methods as regards their ability to detect alterations in the dynamics and in the complexity of cardiovascular and respiratory variability evoked by postural and mental stress. Dynamic entropy (DE) and information storage (IS) measures were calculated on three physiological time-series, i.e. heart period, respiratory volume and systolic arterial pressure, on 61 healthy subjects monitored in resting conditions as well as during head-up ti…
Influence of the Madden-Julian Oscillation on Southern African summer rainfall
2007
Rain-causing mechanisms over Southern Africa (south of 15˚S) involve both tropical and temperate dynamics. Most studies focused on the synoptical timescale, while the intraseasonal (20-120 days) variability has more been neglected to date. This study aims at determining whether the dominant mode of intraseasonal variability in the Tropics, namely the Madden-Julian Oscillation (MJO), has a significant impact on Southern African rainfall and associated atmospheric dynamics. The examination of outgoing longwave radiation (OLR) over Southern Africa shows indeed significant intraseasonal fluctuations at the 30-60 day timescale, i.e. in the pe- riods that are typically reminiscent of the MJO. In ord…
Information Decomposition: A Tool to Dissect Cardiovascular and Cardiorespiratory Complexity
2017
This chapter reports some recent developments of information-theoretic concepts applied to the description of coupled dynamical systems, which allow to decompose the entropy of an assigned target system into components reflecting the information stored in the system and the information transferred to it from the other systems, as well as the nature (synergistic or redundant) of the information transferred to the target. The decomposition leads to well-defined measures of information dynamics which in the chapter will be defined theoretically, computed in simulations of linear Gaussian systems and implemented in practice through the application to heart period, arterial pressure and respirat…
Evaluation of the coupled high-resolution atmospheric chemistry model system MECO(n) using in situ and MAX-DOAS NO<sub>2</sub&am…
2021
Abstract. We present high spatial resolution (up to 2.2×2.2 km2) simulations focussed over south-west Germany using the online coupled regional atmospheric chemistry model system MECO(n) (MESSy-fied ECHAM and COSMO models nested n times). Numerical simulation of nitrogen dioxide (NO2) surface volume mixing ratios (VMRs) are compared to in situ measurements from a network with 193 locations including background, traffic-adjacent and industrial stations to investigate the model's performance in simulating the spatial and temporal variability of short-lived chemical species. We show that the use of a high-resolution and up-to-date emission inventory is crucial for reproducing the spatial varia…
Measuring psychosocial stress with heart rate variability-based methods in different health and age groups
2022
Abstract Objective. Autonomic nervous system function and thereby bodily stress and recovery reactions may be assessed by wearable devices measuring heart rate (HR) and its variability (HRV). So far, the validity of HRV-based stress assessments has been mainly studied in healthy populations. In this study, we determined how psychosocial stress affects physiological and psychological stress responses in both young (18–30 years) and middle-aged (45–64 years) healthy individuals as well as in patients with arterial hypertension and/or either prior evidence of prediabetes or type 2 diabetes. We also studied how an HRV-based stress index (Relax-Stress Intensity, RSI) relates to perceived stress …