Search results for "Linear Models"
showing 10 items of 440 documents
Differential geometric LARS via cyclic coordinate descent method
2012
We address the problem of how to compute the coefficient path implicitly defined by the differential geometric LARS (dgLARS) method in a high-dimensional setting. Although the geometrical theory developed to define the dgLARS method does not need of the definition of a penalty function, we show that it is possible to develop a cyclic coordinate descent algorithm to compute the solution curve in a high-dimensional setting. Simulation studies show that the proposed algorithm is significantly faster than the prediction-corrector algorithm originally developed to compute the dgLARS solution curve.
Can the response to Omalizumab be influenced by treatment duration? A real-life study
2017
Objective It is unknown whether Omalizumab effectiveness changes over the course of time. Our retrospective real-life study tried to analyze whether Omalizumab response may be influenced by treatment duration. Methods 340 severe asthmatics treated with Omalizumab for different periods of time were recruited. They were subdivided into 4 groups according to the Omalizumab treatment length: 60 months. Omalizumab treatment results (FEV1, exacerbations, ACT, SABA use, asthma control levels, medications used e and ICS doses) were compared. Results ACT, exacerbations, GINA control levels, ICS doses and SABA use were similar in all groups with different Omalizumab treatment durations. Using a linea…
Quantification of Listeria monocytogenes in salads by real time quantitative PCR
2005
Abstract A real time quantitative PCR (RTQ-PCR) was carried out purifying DNA extracts of Listeria monocytogenes using a High Pure Listeria Sample Preparation Kit and quantifying in a LightCycler system with hybridisation probes. A standard curve was constructed with serial dilutions. A range linear relationship, from 10 to 10 5 L. monocytogenes colony forming units (CFU), was observed between threshold cycle ( C t ) and logarithmic concentration of the serial dilutions. The assay was linear in a range from 10 to 10 5 L. monocytogenes CFU and the coefficient of determination ( r 2 ) was > 0.98. RTQ-PCR presented an efficiency of > 85%. The accuracy of the PCR-based assay, expressed as % bia…
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…
Effects of escitalopram on the regulation of brain-derived neurotrophic factor and nerve growth factor protein levels in a rat model of chronic stres…
2009
Escitalopram (ES-CIT) is a widely used, highly specific antidepressant. Until now there has been very little evidence on how this drug under pathological conditions affects an important feature within the pathophysiology of stress-related disorders such as depression: the endogenous neurotrophins. By using a well-characterized rat model in which chronic stress induces depressive-like behavior, the levels of neurotrophins brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were determined in representative brain regions and serum using a highly sensitive improved fluorometric two-site ELISA system. There was a significant increase of BDNF in the left and right cortices aft…
Statistical tools and control of internal lubricant content of inhalation grade HPMC capsules during manufacture
2016
The internal lubricant content (ILC) of inhalation grade HPMC capsules is a key factor to ensure good powder release when the patient inhales a medicine from a dry powder inhaler (DPI). Powder release from capsules has been shown to be influenced by the ILC. The characteristics used to measure this are the emitted dose, fine particle fraction and mass median aerodynamic diameter. In addition the ILC level is critical for capsule shell manufacture because it is an essential part of the process that cannot work without it. An experiment has been applied to the manufacture of inhalation capsules with the required ILC. A full factorial model was used to identify the controlling factors and from…
Nonlinear dynamics of interest rate and inflation
2004
According to several empirical studies, US inflation and nominal interest rates, as well as the real interest rate, can be described as unit root processes. These results imply that nominal interest rates and expected inflation do not move one-for-one in the long run, which is not consistent with the theoretical models. In this paper we introduce a nonlinear bivariate mixture autoregressive model that seems to fit quarterly US data (1952 Q1 – 2000 Q2) reasonably well. It is found that the three-month treasury bill rate and inflation share a common nonlinear component that explains a large part of their persistence. The real interest rate is devoid of this component, indicating one-for-one m…
Exploring relationships between drought and epidemic cholera in Africa using generalised linear models
2021
Abstract Background Temperature and precipitation are known to affect Vibrio cholerae outbreaks. Despite this, the impact of drought on outbreaks has been largely understudied. Africa is both drought and cholera prone and more research is needed in Africa to understand cholera dynamics in relation to drought. Methods Here, we analyse a range of environmental and socioeconomic covariates and fit generalised linear models to publicly available national data, to test for associations with several indices of drought and make cholera outbreak projections to 2070 under three scenarios of global change, reflecting varying trajectories of CO2 emissions, socio-economic development, and population gr…
A Critical Review of Statistical Methods for Twin Studies Relating Exposure to Early Life Health Conditions
2021
International audience; When investigating disease etiology, twin data provide a unique opportunity to control for confounding and disentangling the role of the human genome and exposome. However, using appropriate statistical methods is fundamental for exploiting such potential. We aimed to critically review the statistical approaches used in twin studies relating exposure to early life health conditions. We searched PubMed, Scopus, Web of Science, and Embase (2011–2021). We identified 32 studies and nine classes of methods. Five were conditional approaches (within-pair analyses): additive-common-erratic (ACE) models (11 studies), generalized linear mixed models (GLMMs, five studies), gene…
Dual Extrapolation for Sparse Generalized Linear Models
2020
International audience; Generalized Linear Models (GLM) form a wide class of regression and classification models, where prediction is a function of a linear combination of the input variables. For statistical inference in high dimension, sparsity inducing regularizations have proven to be useful while offering statistical guarantees. However, solving the resulting optimization problems can be challenging: even for popular iterative algorithms such as coordinate descent, one needs to loop over a large number of variables. To mitigate this, techniques known as screening rules and working sets diminish the size of the optimization problem at hand, either by progressively removing variables, o…