Search results for "multivariate"
showing 10 items of 1520 documents
Extended Granger causality: a new tool to identify the structure of physiological networks.
2015
Granger causality (GC) is a very popular tool for assessing the presence of directional interactions between two time series of a multivariate data set. In its original formulation, GC does not account for zero-lag correlations possibly existing between the observed time series. In the present study we compare the GC with a novel measure, termed extended GC (eGC), able to capture instantaneous causal relationships. We present a two-step procedure for the practical estimation of eGC based on first detecting the existence of zero-lag correlations, and then assigning them to one of the two possible causal directions using pairwise measures of non-Gaussianity. The proposed method was validated …
Treating missing data in a clinical neuropsychological dataset--data imputation.
2001
Missing data frequently reduce the applicability of clinically collected data in research requiring multivariate statistics. In data imputation, missing values are replaced by predicted values obtained from models based on auxiliary information. Our aim was to complete a clinical child neuropsychological data set containing 5.2% of missing observations. This was to be used in research requiring multivariate statistics. We compared four data imputation methods by artificially deleting some data. A real-donor imputation method which preserved the parameter estimates and which predicted the observed values with acceptable accuracy was used to complete the data set. In addressing the lack of st…
Pimonidazole labelling and response to fractionated irradiation of five human squamous cell carcinoma (hSCC) lines in nude mice: The need for a multi…
2006
To investigate the influence on local control after fractionated radiotherapy of hypoxia measured in unirradiated tumours using the hypoxic marker Pimonidazole, using multivariate approaches.Five human squamous cell carcinoma lines (FaDu, UT-SCC-15, UT-SCC-14, XF354, and UT-SCC-5) were transplanted subcutaneously into the right hind-leg of NMRI nude mice. Histological material was collected from 60 unirradiated tumours after injection of Pimonidazole. The relative hypoxic area within the viable tumour area (Pimonidazole hypoxic fraction, pHF) was determined in seven serial 10 microm cross-sections per tumour by fluorescence microscopy and computerized image analysis. Local tumour control wa…
Effects of ambient temperature, humidity, and other meteorological variables on hospital admissions for angina pectoris.
2012
Background: Seasonal peaks in cardiovascular disease incidence have been widely reported, suggesting weather has a role. Design The aim of our study was to determine the influence of climatic variables on angina pectoris hospital admissions. Methods: We correlated the daily number of angina cases admitted to a western Sicilian hospital over a period of 12 years and local weather conditions (temperature, humidity, wind force and direction, precipitation, sunny hours and atmospheric pressure) on a day-to-day basis. A total of 2459 consecutive patients were admitted over the period 1987–1998 (1562 men, 867 women; M/F – 1:8). Results: A seasonal variation was found with a noticeable winter pea…
Comparison of different statistical approaches to evaluate morphometric sperm subpopulations in men.
2016
This study was designed to characterize morphometric sperm subpopulations in normozoospermic men by using different statistical methods and examining their suitability to classify correctly different sperm nuclear morphologies present in human ejaculates. Ejaculates from 21 normozoospermic men were collected for the study. After semen collection and analysis, samples were prepared for morphometric determination. At least 200 spermatozoa per sample were assessed for sperm morphometry by computer-assisted sperm morphometry analysis (CASA-Morph) using fluorescence. Clustering and discriminant procedures were performed to identify sperm subpopulations from the morphometric data obtained. Cluste…
Influence of climatic variables on acute myocardial infarction hospital admissions
2009
BACKGROUND: Seasonal peaks in acute myocardial infarction (AMI) incidence have been widely reported. Weather has been postulated to be one of the elements at the basis of this association. The aim of our study was to determine the influence of seasonal variations and weather on AMI hospital admissions. METHODS: We correlated the daily number of AMI cases admitted to a western Sicily hospital over twelve years and weather conditions on a day-to-day basis. Information on temperature, humidity, wind force and direction, precipitation, sunny hours and atmospheric pressure was obtained from the local Birgi Air Force base. A total of 3918 consecutive patients were admitted with AMI over the perio…
Intravenous bisphosphonate-related osteonecrosis of the jaws: Influence of coadjuvant antineoplastic treatment and study of buccodental condition
2012
Objectives: To determine whether coadjuvant antineoplastic treatment can influence the number and size of bone exposures among patients with intravenous bisphosphonate-related osteonecrosis of the jaws (iBRONJ), and to analyze the buccodental condition of these patients. Material and methods: The study sample comprised 67 patients with iBRONJ, 53 patients without iBRONJ receiving treatment with intravenous bisphosphonates, and 36 healthy subjects. In all three groups, measurements were made of the CAO index and of resting whole saliva and stimulated whole saliva. In the patients with iBRONJ, the size (cm) and number of bone exposures were recorded. The data obtained were subjected to analys…
Noninvasive positive-pressure ventilation in ALS: predictors of tolerance and survival.
2006
Objective: To identify factors associated with tolerance and survival after noninvasive positive-pressure ventilation (NIPPV) and to investigate the influence of NIPPV on lung function in patients with ALS. Methods: NIPPV was offered to 71 patients with ALS in accordance with currently published guidelines. Effects of NIPPV on lung function and factors influencing tolerance and survival after NIPPV were studied. Results: Forty-four patients (61.9%; 95% CI: 50.6 to 73.2) tolerated NIPPV (NIPPV use >= 4 h/day) and 27 (38.1%; 95% CI: 26.8 to 49.4) were intolerant (NIPPV use = 4 h/day) and to the modifications of forced vital capacity decline after treatment initiation. The severity of bulbar i…
Personalized cost-effectiveness of boceprevir-based triple therapy for untreated patients with genotype 1 chronic hepatitis C
2014
Abstract Background We assessed the cost-effectiveness of boceprevir-based triple therapy compared to peginterferon alpha and ribavirin dual therapy in untreated patients with genotype 1 chronic hepatitis C; patients were discriminated according to the combination of baseline plus on-treatment predictors of boceprevir-based triple therapy. Methods Cost-effectiveness analysis performed according to data from the available published literature. The target population was composed of untreated Caucasian patients, aged 50 years, with genotype 1 chronic hepatitis C, and these were evaluated over a lifetime horizon by Markov model. The study was carried out from the perspective of the Italian Nati…
Cotransmission of conduct problems with attention-deficit/hyperactivity disorder: familial evidence for a distinct disorder
2008
Contains fulltext : 69215.pdf (Publisher’s version ) (Closed access) Common disorders of childhood and adolescence are attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD) and conduct disorder (CD). For one to two cases in three diagnosed with ADHD the disorders may be comorbid. However, whether comorbid conduct problems (CP) represents a separate disorder or a severe form of ADHD remains controversial. We investigated familial recurrence patterns of the pure or comorbid condition in families with at least two children and one definite case of DSM-IV ADHDct (combined-type) as part of the International Multicentre ADHD Genetics Study (IMAGE). Using case diagno…