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Santa Cruz de Tenerife, Spain

The University of San Fernando de La Laguna, also known as the ULL is situated in San Cristóbal de La Laguna, on the island of Tenerife. It is the oldest university in the Canary Islands. It has four campuses: Central, Anchieta, Guajara, and Santa Cruz de Tenerife. Wikipedia.

Cajal-Retzius (CR) cells are the most significant source of reelin, an extracellular matrix glycoprotein essential for cortical development. Strategically located in the marginal zone, CR cells control radial migration and laminar positioning of pyramidal neurons of the cortical plate. They degenerate and undergo cell death when cortical migration is completed. In human cortex development, reelin-expressing CR cells are already present in the early preplate, and continue to increase in number after the appearance of the cortical plate. In the course of the first half of gestation, the reelin signal in the marginal zone undergoes a huge amplification in parallel with the growth of the cortical plate and the expansion of the cortical surface. A significant source of CR cells is the cortical hem, a putative signalling centre at the interface of the prospective hippocampus and the choroid plexus. Hem-derived CR cells co-express reelin and p73, a transcription factor of the p53-family. They form the predominant CR cell population of the human neocortex. Characteristically, CR cells express the anti-apoptotic isoform DeltaNp73 which may be responsible for the protracted lifespan of human CR cells and the morphological differentiation of their axonal plexus. This dense fibre plexus, absent in lower mammals, amplifies the reelin-signal and establishes a physical boundary between the cortical plate and the marginal zone. In this review, we analyze the multiple sources of reelin/p73 positive CR cells at the interface of various telencephalic centres and the choroid plexus of the lateral ventricles. Additional populations of CR cells may derive from the thalamic eminence in the ventral thalamus and from the strionuclear neuroepithelium, or 'amygdalar hem'. Comparative studies in a variety of species indicate that the cortical hem is the main origin of CR cells destined for the neocortex, and is most highly developed in the human brain. The close association between cortical hem and choroid plexus suggests a concerted role in the evolutionary increase of CR cells, amplification of the reelin signal in the marginal zone, and cortical expansion. © 2010 The Author. Journal of Anatomy © 2010 Anatomical Society of Great Britain and Ireland. Source

Gimeno Garca A.Z.,University of La Laguna
Gastroenterology Research and Practice | Year: 2012

Colorectal cancer (CRC) is a major health problem worldwide. Although population-based CRC screening is strongly recommended in average-risk population, compliance rates are still far from the desirable rates. High levels of screening uptake are necessary for the success of any screening program. Therefore, the investigation of factors influencing participation is crucial prior to design and launches a population-based organized screening campaign. Several studies have identified screening behaviour factors related to potential participants, providers, or health care system. These influencing factors can also be classified in non-modifiable (i.e., demographic factors, education, health insurance, or income) and modifiable factors (i.e., knowledge about CRC and screening, patient and provider attitudes or structural barriers for screening). Modifiable determinants are of great interest as they are plausible targets for interventions. Interventions at different levels (patient, providers or health care system) have been tested across the studies with different results. This paper analyzes factors related to CRC screening behaviour and potential interventions designed to improve screening uptake. Copyright © 2012 Antonio Z. Gimeno Garca. Source

Buchan A.,University of Tennessee at Knoxville | LeCleir G.R.,University of Tennessee at Knoxville | Gulvik C.A.,Georgia Institute of Technology | Gonzalez J.M.,University of La Laguna
Nature reviews. Microbiology | Year: 2014

Marine phytoplankton blooms are annual spring events that sustain active and diverse bloom-associated bacterial populations. Blooms vary considerably in terms of eukaryotic species composition and environmental conditions, but a limited number of heterotrophic bacterial lineages - primarily members of the Flavobacteriia, Alphaproteobacteria and Gammaproteobacteria - dominate these communities. In this Review, we discuss the central role that these bacteria have in transforming phytoplankton-derived organic matter and thus in biogeochemical nutrient cycling. On the basis of selected field and laboratory-based studies of flavobacteria and roseobacters, distinct metabolic strategies are emerging for these archetypal phytoplankton-associated taxa, which provide insights into the underlying mechanisms that dictate their behaviours during blooms. Source

Fernandez A.J.,University of La Laguna
IEEE Transactions on Reliability | Year: 2014

Optimal sampling inspection plans for defects per unit with fixed acceptance numbers and limiting quality levels are developed to provide the appropriate protection to customers when the number of nonconformities per sampled item follows a Poisson distribution. The best inspection scheme assures the customer, who has to judge the quality of the submitted material, that a supplier's lot is released only when there is conclusive evidence that it is satisfactory. The underlying integer nonlinear programming problem is formulated and solved in the frequentist setting, and a practically exact approximation to the minimum sample size is presented. Because there is often no reason to assume that the process average is constant, the classical perspective is then extended to those situations in which there is substantial prior information on the supplier's process. A family of generalized truncated gamma models and several restricted maximum entropy distributions satisfying typical constraints are adopted to describe the stochastic fluctuations in the process average. Optimal defects-per-unit acceptance plans are determined by solving the corresponding constrained minimization problems. Lower and upper bounds on the required sample size are deduced in closed-forms. A general procedure based on Taylor series expansions of the operating characteristic function around the mean quality level of the rejectable lots is proposed to derive an explicit, accurate, easily computable approximation to the smallest sample size that provides the required average customer protection. This procedure greatly simplifies the determination of optimal plans from defect or failure count data and prior knowledge, and also requires little prior information, namely the prior mean and variance of the quality level of the rejectable lots, which could be estimated from past data and expert opinions. The suggested methodology is applied to the manufacturing of paper and glass for illustrative purposes. Our approach allows the practitioners to incorporate into the quality analysis a reduced parameter space for the process average. Furthermore, the proposed sampling plans are reasonably insensitive to small disturbances in the prior knowledge on the process average, and the effective use of the available information on the supplier's process provides a more realistic assessment of the actual customer protection, as well as considerable savings in testing time and sample size. © 2014 IEEE. Source

Ritter A.,University of La Laguna | Munoz-Carpena R.,University of Florida
Journal of Hydrology | Year: 2013

Success in the use of computer models for simulating environmental variables and processes requires objective model calibration and verification procedures. Several methods for quantifying the goodness-of-fit of observations against model-calculated values have been proposed but none of them is free of limitations and are often ambiguous. When a single indicator is used it may lead to incorrect verification of the model. Instead, a combination of graphical results, absolute value error statistics (i.e. root mean square error), and normalized goodness-of-fit statistics (i.e. Nash-Sutcliffe Efficiency coefficient, NSE) is currently recommended. Interpretation of NSE values is often subjective, and may be biased by the magnitude and number of data points, data outliers and repeated data. The statistical significance of the performance statistics is an aspect generally ignored that helps in reducing subjectivity in the proper interpretation of the model performance. In this work, approximated probability distributions for two common indicators (NSE and root mean square error) are derived with bootstrapping (block bootstrapping when dealing with time series), followed by bias corrected and accelerated calculation of confidence intervals. Hypothesis testing of the indicators exceeding threshold values is proposed in a unified framework for statistically accepting or rejecting the model performance. It is illustrated how model performance is not linearly related with NSE, which is critical for its proper interpretation. Additionally, the sensitivity of the indicators to model bias, outliers and repeated data is evaluated. The potential of the difference between root mean square error and mean absolute error for detecting outliers is explored, showing that this may be considered a necessary but not a sufficient condition of outlier presence. The usefulness of the approach for the evaluation of model performance is illustrated with case studies including those with similar goodness-of-fit indicators but distinct statistical interpretation, and others to analyze the effects of outliers, model bias and repeated data. This work does not intend to dictate rules on model goodness-of-fit assessment. It aims to provide modelers with improved, less subjective and practical model evaluation guidance and tools. © 2012 Elsevier B.V. Source

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