Search results for "Linear Model"

An efficient algorithm to estimate the sparse group structure of an high-dimensional generalized linear model

2014

Massive regression is one of the new frontiers of computational statistics. In this paper we propose a generalization of the group least angle regression method based on the differential geometrical structure of a generalized linear model specified by a fixed and known group structure of the predictors. An efficient algorithm is also proposed to compute the proposed solution curve.

Travelling Strings, Beams, Panels, Membranes and Plates

2013

In this chapter, we will introduce in a general manner some of the most common models for axially travelling materials, which will be used in the rest of the book. We will introduce the linear models of travelling strings, panels, and plates. It will be assumed that the material is thin, i.e. its planar dimensions are much larger than its thickness. We will work in the small displacement regime, that is, with linear models approximating the behaviour of the system near the trivial equilibrium. As is well known in the theory of elasticity, this approximation allows for a decoupling of the in-plane and out-of-plane components in the dynamics of the system. We will concentrate on small out-of-…

Noninvasive measurement of intracranial pressure: Is it possible?

2007

BACKGROUND: Some publications suggest a strong correlation between the intracranial pressure and the intraocular pressure. Other studies claim no correlation between these two physiologic variables. Our aim was to study whether the tonometry could be a useful method to evaluate intracranial pressure in patients with suspected intracranial abnormality. METHODS: We evaluated the correlation between the intracranial pressure and the intraocular pressure, the intracranial pressure and the mean arterial pressure, and the intraocular pressure and the mean arterial pressure in 22 patients, initially comatose, who were admitted to our hospital. All patients required the intracranial pressure monito…

The Pursuit of Happiness in Music: Retrieving Valence with Contextual Music Descriptors

2009

In the study of music emotions, Valence is usually referred to as one of the dimensions of the circumplex model of emotions that describes music appraisal of happiness, whose scale goes from sad to happy. Nevertheless, related literature shows that Valence is known as being particularly difficult to be predicted by a computational model. As Valence is a contextual music feature, it is assumed here that its prediction should also require contextual music descriptors in its predicting model. This work describes the usage of eight contextual (also known as higher-level) descriptors, previously developed by us, to calculate happiness in music. Each of these descriptors was independently tested …

Brain atrophy and lesion load in a large population of patients with multiple sclerosis

2005

Objective: To measure white matter (WM) and gray matter (GM) atrophy and lesion load in a large population of patients with multiple sclerosis (MS) using a fully automated, operator-independent, multiparametric segmentation method. Methods: The study population consisted of 597 patients with MS and 104 control subjects. The MRI parameters were abnormal WM fraction (AWM-f), global WM-f (gWM-f), and GM fraction (GM-f). Results: Significant differences between patients with MS and control subjects included higher AWM-f and reduced gWM-f and GM-f. MRI data showed significant differences between patients with relapsing-remitting and secondary progressive forms of MS. Significant correlations bet…

Circulating 25-Hydroxyvitamin D3 in Pregnancy and Infant Neuropsychological Development

2012

OBJECTIVE:To investigate whether circulating 25-hydroxyvitamin D3 [25(OH)D3] concentration in pregnancy is associated with neuropsychological development in infants.METHODS:The Spanish population-based cohort study INfancia y Medio Ambiente Project recruited pregnant women during the first trimester of pregnancy between November 2003 and February 2008. Completed data on 1820 mother-infant pairs were used. Maternal plasma 25(OH)D3 concentration was measured by high-performance liquid chromatography in pregnancy (mean 13.5±2.1 weeks of gestation). Offspring mental and psychomotor scores were assessed by trained psychologists at age 14 months (range, 11–23) by using the Bayley Scales of Infant…

2014

Introduction: Many studies examine gene expression data that has been obtained under the influence of multiple factors, such as genetic background, environmental conditions, or exposure to diseases. The interplay of multiple factors may lead to effect modification and confounding. Higher order linear regression models can account for these effects. We present a new methodology for linear model selection and apply it to microarray data of bone marrow-derived macrophages. This experiment investigates the influence of three variable factors: the genetic background of the mice from which the macrophages were obtained, Yersinia enterocolitica infection (two strains, and a mock control),and treat…

A direct Capillary Liquid Chromatography with electrochemical detection method for determination of phenols in water samples

2010

A fast and direct method based on the use of Capillary Liquid Chromatography (LC) with electrochemical (EC) detection has been described for phenols pollutants in water samples. Concretely, phenol, o-cresol, 2-chlorophenol and bisphenol A have been selected as target analytes. The combination of Capillary LC with EC detection avoided the necessity of preconcentration steps typically used in environmental analysis. The sample injected volume was 2 μL. The achieved detection limits were between 1 and 2 μg/L and the linear dynamic range was up to 50 μg/L for all studied phenols. The precision and uncertainty were satisfactory. The analysis time per sample was 10 min. The proposed procedure has…

Estrogen receptor alpha polymorphism modifies the association between childhood exercise and bone mass: follow-up study.

2007

This follow-up study confirms our previous findings that the ER-α PvuII polymorphism (Pp) modulates the association between exercise and bone mass. The differences in bone properties of girls with consistently low physical activity (LLPA) and consistently high physical activity (HHPA) were evident only in those bearing the heterozygote ER-α genotype (Pp). In particular, areal bone mineral density of the total femur, bone mineral content and areal bone mineral density of the femoral neck, and bone mineral content and cortical thickness of the tibia shaft were significantly (p < .05) lower in the Pp girls with LLPA than in their HHPA counterparts. These findings might partly explain the ge…

Scale dependence of species–area relationships is widespread but generally weak in Palaearctic grasslands

2021

Questions: Species–area relationships (SARs) are fundamental for understanding biodiversity patterns and are generally well described by a power law with a constant exponent z. However, z-values sometimes vary across spatial scales. We asked whether there is a general scale dependence of z-values at fine spatial grains and which potential drivers influence it. Location: Palaearctic biogeographic realm. Methods: We used 6,696 nested-plot series of vascular plants, bryophytes and lichens from the GrassPlot database with two or more grain sizes, ranging from 0.0001 m² to 1,024 m² and covering diverse open habitats. The plots were recorded with two widespread sampling approaches (rooted presenc…