Search results for " Variability"
showing 10 items of 853 documents
Time-Varying Surrogate Data to Assess Nonlinearity in Nonstationary Time Series: Application to Heart Rate Variability
2009
We propose a method to extend to time-varying (TV) systems the procedure for generating typical surrogate time series, in order to test the presence of nonlinear dynamics in potentially nonstationary signals. The method is based on fitting a TV autoregressive (AR) model to the original series and then regressing the model coefficients with random replacements of the model residuals to generate TV AR surrogate series. The proposed surrogate series were used in combination with a TV sample entropy (SE) discriminating statistic to assess nonlinearity in both simulated and experimental time series, in comparison with traditional time-invariant (TIV) surrogates combined with the TIV SE discrimin…
Assessing Causality in normal and impaired short-term cardiovascular regulation via nonlinear prediction methods
2009
We investigated the ability of mutual nonlinear prediction methods to assess causal interactions in short-term cardiovascular variability during normal and impaired conditions. Directional interactions between heart period (RR interval of the ECG) and systolic arterial pressure (SAP) short-term variability series were quantified as the cross-predictability (CP) of one series given the other, and as the predictability improvement (PI) yielded by the inclusion of samples of one series into the prediction of the other series. Nonlinear prediction was performed through global approximation (GA), approximation with locally constant models (LA0) and approximation with locally linear models (LA1) …
Sympathetic activity at rest and motor brain areas: FDG-PET study.
2008
Although recent studies identified brain areas which are involved in short term activation of the sympathetic nervous system, little is known about brain mechanisms which generate the individual variability of basal autonomic activity. In this fluorodeoxyglucose positron emission tomography study (FDG-PET), we aimed to identify brain regions, which covary with function parameters of the autonomic nervous system at rest. Therefore, FDG-PET (Siemens, Germany) was performed twice in 14 healthy resting subjects (7 m, 7 f; mean age 29.5 years) while different parameters of autonomic function were assessed simultaneously: Blood pressure, heart rate, power spectra of heart rate variability (HF/LF …
Effects of a HIIT Protocol on Cardiovascular Risk Factors in a Type 1 Diabetes Mellitus Population
2021
Cardiovascular complications are important causes of morbidity and mortality of Type 1 Diabetes Mellitus (T1DM) people. Regular exercise is strongly recommended to these patients due to its preventive action against this type of disease. However, a large percentage of patients with T1DM people present a sedentary behavior, mainly, because of the fear of a post-exercise hypoglycemia event and lack of time. High-intensity interval training (HIIT) is an efficient and safe methodology since it prevents hypoglycemia and does not require much time, which are the main barriers for this population to doing exercise and increasing physical conditioning. Nineteen sedentary adults (37 ± 6.5 years) wit…
AEROgui: A graphical user interface for the optical properties of aerosols
2014
Atmospheric aerosols have an uncertain effect on climate and serious impacts on human health. The uncertainty in the aerosols' role on climate has several sources. First, aerosols have great spatial and temporal variability. The spatial variability arises from the fact that aerosols emitted in a certain place can travel thousands of kilometers, swept by the winds to modify the destination region's climate. The spatial variability also means that aerosols are inhomogeneously distributed in the vertical direction, which can lead to a differential effect on the energy balance depending on the aerosols' altitude. On the other hand, aerosols experience physical and chemical transformations in th…
Climate variability and agriculture in Italy: a stochastic frontier analysis at the regional level
2020
In the next future, climate change effects will represent a challenge for Europe and the Mediterranean area. These will have to cope with a rapid increase in climate variability. Although many economic sectors may be affected, agriculture is the most susceptible as climate heavily affects crop production trends, yield variability and the availability of areas suitable for cultivation. Using the stochastic frontier approach, the aim of this work is to analyse the impacts of climate variability on Italian regional technical efficiency in the agricultural sector for a period spanning from 2000 to 2009. Considering that technical inefficiency could be influenced by two main annual meteorologica…
Mycotoxin Profile and Phylogeny of Pathogenic Alternaria Species Isolated from Symptomatic Tomato Plants in Lebanon
2021
The tomato is one of the most consumed agri-food products in Lebanon. Several fungal pathogens, including Alternaria species, can infect tomato plants during the whole growing cycle. Alternaria infections cause severe production and economic losses in field and during storage. In addition, Alternaria species represent a serious toxicological risk since they are able to produce a wide range of mycotoxins, associated with different toxic activities on human and animal health. Several Alternaria species were detected on tomatoes, among which the most important are A. solani, A. alternata, and A. arborescens. A set of 49 Alternaria strains isolated from leaves and stems of diseased tomato plant…
Within-visit BP variability, cardiovascular risk factors, and BP control in central and eastern Europe: findings from the BP-CARE study.
2015
INTRODUCTION AND OBJECTIVE Blood pressure variability (BPV) within 24 h or between visits has been found to represent an independent risk factor for cardiovascular disease. The present study was aimed at determining whether a clinical significance can be given also to the BP variations occurring within a single clinical visit. METHODS BPV was quantified as coefficient of variation and as standard deviation (SD) of the mean of three systolic SBP values within a visit in the context of a large-cross subclinical survey (BP-CARE) of treated hypertensive patients living in Eastern European countries. The study population was divided into coefficient of variation and SD quartiles and for each qua…
Distribution of clay minerals in Early Jurassic Peritethyan seas: palaeoclimatic significance inferred from multiproxy comparisons.
2009
13 pages; International audience; A set of published, unpublished, and new clay mineral data from 60 European and Mediterranean localities allows us to test the reliability of clay minerals as palaeoclimatic proxies for the Pliensbachian–Toarcian period (Early Jurassic) by reconstructing spatial and temporal variations of detrital fluxes at the ammonite biochronozone resolution. In order to discuss their palaeoclimatic meaning, a compilation of low-latitude belemnite δ18O, δ13C, Mg/Ca, and 87Sr/86Sr values is presented for the first time for the whole Pliensbachian– Toarcian period. Once diagenetic and authigenic biases have been identified and ruled out, kaolinite content variation is cons…
Gene-diet interaction in plasma lipid response to plant sterols and stanols: A review of clinical trials
2021
Abstract Plant sterols and stanols (PS) are well known for their cholesterol-lowering effect by reducing intestinal absorption of cholesterol. However, genetic factors modulate the low-density lipoprotein cholesterol (LDL-C) response to PS therapy. This review examines clinical trials evaluating the impact of the main genes associated with response of plasma lipid concentrations to PS intake: APOE, CYP7A1, ABCG5/G8, NPC1L1, CETP, APOA4/A5, SCARBI, HMGCR, PPARα, LIPC, MTHFR and LPA. Evidence indicates that carriers of mutant allele of the CYP7A1 c. −204 A > C variant experience a greater plasma cholesterol reduction after PS intake, although there is discrepancy for the rest of genetic varia…