Search results for "Variability"
showing 10 items of 904 documents
20th century droughts in southern Africa: spatial and temporal variability, teleconnections with oceanic and atmospheric conditions
2001
Southern African rainfall does not show any trend to desiccation during the 20th century. However, the subcontinent experienced particularly severe droughts in the 1980s and at the beginning of the 1990s and the magnitude of the interannual summer rainfall variability shows significant changes. Modifications of the intensity and spatial extension of droughts is associated with changes in ocean–atmosphere teleconnection patterns. This paper focuses mostly on the well-documented 1950–1988 period and on late summer season (January–March). A principal component analysis on southern African rainfall highlights modifications of the rainfall variability magnitude. The 1970–1988 period had more var…
Spatial and temporal temperature trends on the Yunnan Plateau (Southwest China) during 1961-2004
2010
Monthly mean (TEM), maximum (Tmax) and minimum (Tmin) surface air temperatures at 119 meteorological stations on the Yunnan Plateau (YP, Southwest China) were analysed for temporal trends and spatial variation patterns during the period 1961–2004. Linear trend analyses revealed that annual temperature over the YP increased at a rate of 0.3 °C/decade during the period 1961–2004, while warming trend of 0.33 °C/decade and 0.26 °C/decade was observed for winter and summer temperatures, respectively. Warming trends of nighttime minimum temperature are more pronounced than those of daytime maximum temperature, especially during winter season. Consequently, a decreasing trend of diurnal temperatur…
Carbon Stocks in Peri-Urban Areas: A Case Study of Remote Sensing Capabilities
2014
Peri-urban areas are the extension of cities into contiguous areas, where households and farms coexist. Carbon stocks (CSs) assessment, a concept here extended to urban features, has not yet been studied in depth over peri-urban areas due to uncertainties in such CSs quantification, level of detail required about construction materials, and the high spatial variability of those stocks. Remote sensing (RS)-based techniques have been successfully utilized in urban areas for assessing phenomena such as soil sealing, sprawl patterns, and dynamics of surface imperviousness, especially focusing on land cover classification at high to medium spatial scales. Over the floodplain study area of Emilia…
Impaired circadian heart rate variability in Parkinson’s disease: a time-domain analysis in ambulatory setting
2020
Abstract Background Heart rate variability (HRV) decreases in Parkinson’s disease (PD) and it can be considered a marker for cardiovascular dysautonomia. The purpose of this pilot study is to evaluate long-term time-domain analysis of HRV of PD patients and compare the results with those of matched healthy individuals. Methods Idiopathic PD patients without comorbidity impairing HRV, and age-matched healthy individuals were recruited in a pilot study. A long-term time domain analysis of HRV using 24-h ambulatory ECG was performed. Results Overall, 18 PD patients fulfilling inclusion criteria completed the evaluation (mean age was 55.6 ± 8.8, disease duration: 5.0 ± 4.7). Mean SCOPA-AUT scor…
Heart rate variability changes at 2400 m altitude predicts acute mountain sickness on further ascent at 3000-4300 m altitudes
2012
Objective: If the body fails to acclimatize at high altitude, acute mountain sickness (AMS) may result. For the early detection of AMS, changes in cardiac autonomic function measured by heart rate variability (HRV) may be more sensitive than clinical symptoms alone. The purpose of this study was to ascertain if the changes in HRV during ascent are related to AMS. Methods: We followed Lake Louise Score (LLS), arterial oxygen saturation at rest (R-SpO2) and exercise (Ex-SpO2) and HRV parameters daily in 36 different healthy climbers ascending from 2400 m to 6300 m altitudes during five different expeditions. Results: After an ascent to 2400 m, root mean square successive differences, high-fre…
Effects of anxiety during mental arithmetic stress on heart rate variability in healthy subjects
2011
Aim: Anxiety may cause an increased risk of myocardial infarction by reductions in heart rate variability (HRV). However, no data exists on the effect of anxiety on a standard mental test of HRV. The aim of this study was to evaluate the association between anxiety elicited by mental stress and HRV. Methods: Effect of anxiety in the actual state (A-State) and in everyday life (A-Trait) has been assessed in 13 healthy subjects and its association to low (LF) and high-frequency (HF) of HRV during mental arithmetic stress has been tested through correlation analysis. Results: A significant increase from baseline through arithmetic stress was observed in the LF component (LF(nu) from 56.87 ± 4.…
Predictability decomposition detects the impairment of brain-heart dynamical networks during sleep disorders and their recovery with treatment
2016
This work introduces a framework to study the network formed by the autonomic component of heart rate variability (cardiac process η ) and the amplitude of the different electroencephalographic waves (brain processes δ , θ , α , σ , β ) during sleep. The framework exploits multivariate linear models to decompose the predictability of any given target process into measures of self-, causal and interaction predictability reflecting respectively the information retained in the process and related to its physiological complexity, the information transferred from the other source processes, and the information modified during the transfer according to redundant or synergistic interaction betwee…
Genetic variability of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) populations from Latin America is associated with variations in susceptib…
2006
ABSTRACT Bacillus thuringiensis strains isolated from Latin American soil samples that showed toxicity against three Spodoptera frugiperda populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and cry gene content. We found that the different S. frugiperda populations display different susceptibilities to the selected B. thuringiensis strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the …
High Genetic Variability for Resistance to Bacillus thuringiensis Toxins in a Single Population of Diamondback Moth
2001
ABSTRACT The long-term benefit of insecticidal products based on Cry toxins, either in sprays or as transgenic crops, is threatened by the development of resistance by target pests. The models used to predict evolution of resistance to Cry toxins most often are monogenic models in which two alleles are used. Moreover, the high-dose/refuge strategy recommended for implementation with transgenic crops relies on the assumption that the resistance allele is recessive. Using selection experiments, we demonstrated the occurrence in a laboratory colony of diamondback moth of two different genes (either allelic or nonallelic) that confer resistance to Cry1Ab. At the concentration tested, resistance…
A statistical model for predicting the inter-annual variability of birch pollen abundance in Northern and North-Eastern Europe
2018
The paper suggests a methodology for predicting next-year seasonal pollen index (SPI, a sum of daily-mean pollen concentrations) over large regions and demonstrates its performance for birch in Northern and North-Eastern Europe. A statistical model is constructed using meteorological, geophysical and biological characteristics of the previous year). A cluster analysis of multi-annual data of European Aeroallergen Network (EAN) revealed several large regions in Europe, where the observed SPI exhibits similar patterns of the multi-annual variability. We built the model for the northern cluster of stations, which covers Finland, Sweden, Baltic States, part of Belarus, and, probably, Russia and…