Search results for "multivariate"

Real-time Patterns of Behavior Following Nociceptive Stimulation in Rats

2016

The hot-plate test is employed, in rodents, to assess the analgesic properties of drugs. The surface where the animal is placed is normally maintained at a constant temperature around 50°C or 55°C. For this reason rat’s behavior, once placed on the heated surface, can be observed only for few seconds, and a necessary interruption occurs following an a priori-established cut-off to avoid tissue injuries. Such a narrow time window dampened the assessment of fine behavioral characteristics such as the temporal structure of behavior. In the present paper we demonstrate the possibility to apply a refined multivariate approach, known as T-pattern analysis (TPA), to describe the temporal character…

Comportamiento de las correlaciones producto-momento y tetracórica-policórica en escalas ordinales: un estudio de simulación

2017

El análisis estadístico multivariante de escalas de respuesta tipo Likert, dado su empleo generalizado, resulta un tema controvertido en la comunidad científica, principalmente desde la especificación del problema de la medida. Este trabajo tiene como objeto estudiar cómo afectan diversas condiciones de estas escalas ordinales al cálculo de los coeficientes de correlación producto-momento y tetracórico-policórico. Para ello, se aplica un estudio de simulación en el que se generaron 90 bases de datos con 10 ítems cada una, controlando las siguientes variables: número de categorías de respuesta, distribución simétrica o asimétrica de los datos, tamaño de la muestra y nivel de relación entre l…

A multivariate approach of the factors impacting a small arctic glacier, Austre Lovén-Spitsberg

2015

International audience; Arctic glaciers are good indicators of the ongoing climate change as their dynamics are strongly linked to it. This study is focused on the Austre Lovén glacier, on the Brøgger peninsula in Spitsbergen (Svalbard, 79°N). The aim is to understand how contrasted climate and snow conditions over the course of a year can lead to multiple consequences, sometimes unexpected, on mass balance. In 2014, a negative budget was expected, but data analysis has shown the first positive mass balance in 7 years. The objective here is to (i) identify and qualify the combination of factors affecting an arctic glacier mass balance. Three primary indicators seem to display the greatest i…

Évaluation de l'influence des facteurs climatiques sur le bilan de masse du glacier Austre Loven (Spitsberg, 79°N) par une approche multivariée

2016

Arctic is a region where a quick warming is ongoing. Effects are particularly visible on glaciers of which dynamics is very sensitive to climate change. The goal of this study is to identify and rank the main climatological and nivological factors influencing the mass balance of a small arctic glacier in Svalbard using a statistical approach. To highlight spatial differences, cartography were then used. Results show that positive degree-days play an important role in explaining mass balance contrary to liquid precipitations that had a marginal effect over the studied period (2007-2014). Moreover, years with very different climatic conditions can lead to a similar mass balance.

Sign and rank covariance matrices with applications to multivariate analysis

2002

Some contributions in disease mapping modeling

2020

Disease mapping ha recibido un gran interés durante las tres últimas décadas. Esta área de investigación persigue el estudio de la distribución geográfica de eventos relacionados con la salud, tales como la mortalidad o la incidencia de enfermedades, agregados en unidades geográficas, con el fin de identificar principalmente aquellas localizaciones que presentan un mayor riesgo. La aplicación de métodos estadísticos avanzados para llevar a cabo las estimaciones de los riesgos resulta fundamental para obtener estimaciones precisas y profundizar en el entendimiento de la distribución geográfica de las enfermedades. En esta tesis nos centramos en la aplicación y evaluación de varias propuestas…

A Cross-Cultural Exploratory Study of Health Behaviors and Wellbeing During COVID-19

2021

This study explored the influence of the COVID-19 pandemic on perceived health behaviors; physical activity, sleep, and diet behaviors, alongside associations with wellbeing. Participants were 1,140 individuals residing in the United Kingdom (n = 230), South Korea (n = 204), Finland (n = 171), Philippines (n = 132), Latin America (n = 124), Spain (n = 112), North America (n = 87), and Italy (n = 80). They completed an online survey reporting possible changes in the targeted behaviors as well as perceived changes in their physical and mental health. Multivariate analyses of covariance (MANCOVA) on the final sample (n = 1,131) revealed significant mean differences regarding perceived physical…

Identification of local and allochthonous flint artefacts from the Middle Palaeolithical site ‘Abrigo de la Quebrada’ (Chelva, Valencia, Spain) by ma…

2015

This work summarizes the characterization of flint artefacts from the Middle Palaeolithic site ‘Abrigo de la Quebrada’ (Chelva, Valencia, Spain) and flint geological samples collected in the Chelva area. Additionally, some flint artefacts located outside this geographical zone were also analysed and compared with the samples from the Abrigo de la Quebrada site. Flint samples have been studied using methods of macroscopic description and physicochemical analysis [energy dispersive X-ray fluorescence spectrometry (EDXRF) and X-ray diffraction (XRD)]. Multivariate statistical analysis of the EDXRF data and the determination of the crystalline index of quartz, obtained from the XRD patterns, ar…

Microstructural assessment of rodent behavior in the hole-board experimental assay

2010

The aim of the present methodological article was to assess whether a microstructure of hole-exploratory activity can be demonstrated in rats tested in the hole-board, an experimental assay widely used to study anxiety-related behaviors in rodents. Six never properly described hole exploratory behavioral components were identified: active-dip, static-dip, rapid-dip, circular-sniff, point-sniff and central-sniff. Results, assessed by means of descriptive and multivariate approaches, reveal a complex microstructural organization of these behavioral elements. The hypothesis of an important role of the relationships between point-sniff and head dipping activities, in anxiety-related hole explor…

Prevalence of endodontic infection in patients with Crohn ́s disease and ulcerative colitis

2021

[Background] Previous studies have linked apical periodontitis (AP) to inflammatory bowel disease (IBD). The aim of this study was to compare the prevalence of AP and root canal treatment (RCT) in patients with ulcerative colitis (UC) and Crohn ́s disease (CD).