Search results for "Statistical"
showing 10 items of 4960 documents
Uncertainty quantification in simulations of epidemics using polynomial chaos.
2012
Mathematical models based on ordinary differential equations are a useful tool to study the processes involved in epidemiology. Many models consider that the parameters are deterministic variables. But in practice, the transmission parameters present large variability and it is not possible to determine them exactly, and it is necessary to introduce randomness. In this paper, we present an application of the polynomial chaos approach to epidemiological mathematical models based on ordinary differential equations with random coefficients. Taking into account the variability of the transmission parameters of the model, this approach allows us to obtain an auxiliary system of differential equa…
Early detection of Toxoplasma infection by molecular monitoring of Toxoplasma gondii in peripheral blood samples after allogeneic stem cell transplan…
2004
International audience; Background. Isolated case reports have shown that recipients of allogeneic hematopoietic stem cell transplants ( HSCTs) who develop toxoplasmosis may have circulating Toxoplasma gondii DNA in peripheral blood before the onset of clinical symptoms. Methods. We prospectively studied 106 T. gondii - seropositive adult recipients of HSCTs for the incidence of reactivation of toxoplasmosis in the first 6 months after transplantation. Toxoplasmosis infection ( TI) was defined by a positive result of polymerase chain reaction ( PCR) of peripheral blood specimens, whereas toxoplasmosis disease ( TD) was defined as an invasive infection. Results. The incidence of TI was 16% (…
Surrogate data approaches to assess the significance of directed coherence: Application to EEG activity propagation
2009
This paper addresses the topic of evaluating the significance of frequency domain measures of causal coupling in multivariate time series through generation of surrogate data. The considered approaches are the traditional Fourier Transform (FT) algorithm and a new causal FT (CFT) algorithm for surrogate data generation. Both algorithms preserve the FT modulus of the original series; differences are in the phase relationships, that are completely destroyed for FT surrogates and imposed after switching off the link over the considered causal direction for CFT surrogates. The ability of the algorithms to assess causality in the frequency domain was tested using the directed coherence as discri…
Mixed predictability and cross-validation to assess non-linear Granger causality in short cardiovascular variability series
2006
A method to evaluate the direction and strength of causal interactions in bivariate cardiovascular and cardiorespiratory series is presented. The method is based on quantifying self and mixed predictability of the two series using nearest-neighbour local linear approximation. It returns two causal coupling indexes measuring the relative improvement in predictability along direct and reverse directions, and a directionality index indicating the preferential direction of interaction. The method was implemented through a cross-validation approach that allowed quantification of directionality without constraining the embedding of the series, and fully exploited the available data to maximise th…
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…
Types of Adult Attention-Deficit/Hyperactivity Disorder: A Replication Analysis.
2019
OBJECTIVE Research supports the importance of emotional symptoms in adults with attention-deficit/hyperactivity disorder (ADHD), which are not reflected in the DSM-5 or ICD-10 criteria. The Wender-Reimherr Adult Attention Deficit Disorder Scale (WRAADDS) assesses these symptoms, plus inattention, hyperactivity, and impulsivity. This scale allowed us to divide adult ADHD into 2 subtypes in a 2015 publication: ADHD inattentive presentation and ADHD emotional dysregulation presentation. The present study refines this observation using a larger, more diverse sample. METHODS Eight double-blind adult ADHD clinical trials (encompassing 1,490 subjects) were selected because they included assessment…
Accuracy of the water-siphon test associated to barium study in a high prevalence gastro-oesophageal reflux disease population: a novel statistical a…
2010
Abstract RATIONALE, AIMS AND OBJECTIVES: Gastro-oesophageal reflux disease (GORD) is 'a condition which develops when the reflux of gastric content causes troublesome symptoms or complications'. Instrumental diagnostic tests generally used for GORD are 24-hour pH-metry and upper gastrointestinal (GI) endoscopy but barium study associated with provocative manoeuvres such as the water-siphon test (WST), has also been used for GORD. The aim of this paper was to estimate the accuracy of several tests in patients with GORD in a tertiary care setting, focusing on WST, which is rapid and non-invasive, simple to perform and well-tolerated by patients. METHOD: A total of 172 consecutive patients, sy…
Monocular versus binocular pupillometry.
2004
Purpose To quantify differences between monocular and binocular pupil size measurement under scotopic and mesopic conditions. Setting Department of Ophthalmology, Johannes Gutenberg-University, and Department of Medical Biometry, Epidemiology and Informatics, University of Mainz, Mainz, Germany. Methods Computerized dynamic pupillometry (P2000 SA, Procyon Instruments Ltd.) was used at 3 illumination levels: scotopic at 0.03 lux, mesopic low at 0.82 lux, and mesopic high at 6.4 lux. One hundred forty eyes of 70 healthy volunteers without ocular pathology were examined. The subjects were divided into 2 groups. In the first group, the pupil diameter was measured binocularly first. In the secon…
Depth of alveolar bone dehiscences in relation to gingival recessions.
1984
Dehiscence depths were measured in vivo during surgical treatment of 113 teeth with gingival recession in 27 subjects. The average dehiscence depth determined was 5.43 mm with an average recession depth of 2.67 mm. Statistical evidence of a correlation between recession depth and dehiscence depth (average distance between lowest point of recession and dehiscence = 2.8 mm) leaves 16 affected teeth (n = 113) with a distance of 4 mm or more (up to a maximum of 7.5 mm) between the gingival margin and the alveolar crest (facial) unaccounted for. The significance of these deviations from mean values in the etiology and prognosis of recessions is discussed.
Oral and dental health status in patients with eating disorders in Madrid, Spain
2019
Background The aim of the present study was to describe and compare the oral and dental health status of two groups, one diagnosed with eating disorders (EDs), and another group without this pathology, assessing the following oral manifestations: dental alterations, periodontal disorders, soft tissue disorders, non-stimulated salivary flow, and oral pH. Material and Methods This comparative transversal epidemiological study included 179 participants, of whom 59 were diagnosed with EDs (Eating Disorder Group: EDG) and 120 had no antecedents of EDs (No Eating Disorder Group: NEDG). All patients fulfilled the following inclusion criteria: women aged over 18 years, diagnosed with an ED by a spe…