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Search Results: 1 - 10 of 211813 matches for " Liliana López-Kleine "
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Challenges Analyzing RNA-Seq Gene Expression Data  [PDF]
Liliana López-Kleine, Cristian González-Prieto
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.64053
Abstract: The analysis of messenger Ribonucleic acid obtained through sequencing techniques (RNA-se- quencing) data is very challenging. Once technical difficulties have been sorted, an important choice has to be made during pre-processing: Two different paths can be chosen: Transform RNA- sequencing count data to a continuous variable or continue to work with count data. For each data type, analysis tools have been developed and seem appropriate at first sight, but a deeper analysis of data distribution and structure, are a discussion worth. In this review, open questions regarding RNA-sequencing data nature are discussed and highlighted, indicating important future research topics in statistics that should be addressed for a better analysis of already available and new appearing gene expression data. Moreover, a comparative analysis of RNAseq count and transformed data is presented. This comparison indicates that transforming RNA-seq count data seems appropriate, at least for differential expression detection.
Identification of differentially expressed genes in microarray data in a principal component space
Luis Ospina and Liliana López-Kleine
SpringerPlus , 2013, DOI: 10.1186/2193-1801-2-60
Abstract: Microarray experiments are often conducted in order to compare gene expression between two conditions. Tests to detected mean differential expression of genes between conditions are conducted applying correction for multiple testing. Seldom, relationships between gene expression and microarray conditions are investigated in a multivariate approach. Here we propose determining the relationship between genes and conditions using a Principal Component Analysis (PCA) space and classifying genes to one of two biological conditions based on their position relative to a direction on the PC space representing each condition.
On the Student-t Mixture Inverse Gaussian Modelwith an Application to Protein Production
SANHUEZA,ANTONIO; LEIVA,VíCTOR; LóPEZ-KLEINE,LILIANA;
Revista Colombiana de Estadística , 2011,
Abstract: in this article, we introduce a mixture inverse gaussian (mig) model based on the student-t distribution and apply it to bacterium-based protein production for food industry. this model is mainly useful to describe data that follow positively skewed distributions and accommodate atypical observations in a better way than its classical version. specifically, we present a characterization of the mig-t distribution. in addition, we carry out a hazard analysis of this distribution centered mainly on its hazard rate. furthermore, we discuss the maximum likelihood method, which produces--in this case--robust parameter estimates. moreover, to evaluate the potential influence of atypical observations, we produce a diagnostic analysis for the model. finally, we apply the obtained results to novel bacterium-based protein production data and statistically compare two types of protein producers using the likelihood ratio test based on the mig-t model as an alternative methodology to the procedures available until now. this fact is very important, since the evaluation of protein production using both constructions allows practitioners to choose the most productive one before the bacterial culture is scaled to an industrial level.
ON THE STUDENT-T MIXTURE INVERSE GAUSSIAN MODEL WITH AN APPLICATION TO PROTEIN PRODUCTION SOBRE EL MODELO GAUSSIANO INVERSO MEZCLADO T-STUDENT Y UNA APLICACIóN A PRODUCCIóN DE PROTEíNAS
Sanhueza Antonio,Leiva Víctor,López-Kleine Liliana
Revista Colombiana de Estadística , 2011,
Abstract: In this article, we introduce a mixture inverse Gaussian (MIG) model based on the Student-t distribution and apply it to bacterium-based protein production for food industry. This model is mainly useful to describe data that follow positively skewed distributions and accommodate atypical observations in a better way than its classical version. Specifically, we present a characterization of the MIG-t distribution. In addition, we carry out a hazard analysis of this distribution centered mainly on its hazard rate. Furthermore, we discuss the maximum likelihood method, which produces–in this case–robust parameter estimates. Moreover, to evaluate the potential influence of atypical observations, we produce a diagnostic analysis for the model. Finally, we apply the obtained results to novel bacterium-based protein production data and statistically compare two types of protein producers using the likelihood ratio test based on the MIG-t model as an alternative methodology to the procedures available until now. This fact is very important, since the evaluation of protein production using both constructions allows practitioners to choose the most productive one before the bacterial culture is scaled to an industrial level. En este artículo, introducimos un modelo Gaussiano inverso (MIG) mezclado basado en la distribución t-Student y lo aplicamos a la producción de proteínas basada en bacterias para la industria de alimentos. Este modelo es especialmente útil para describir datos que siguen una distribución con sesgo positivo ya que permite acomodar observaciones atípicas de mejor forma que su versión clásica. Específicamente, presentamos una caracterización de la distribución MIG-t y realizamos un análisis de confiabilidad de esta distribución centrado principalmente en la tasa de fallas. También, discutimos el método de verosimilitud máxima, el cual proporciona en este caso estimaciones robustas de los parámetros del modelo. Con el fin de evaluar la influencia potencial de observaciones atípicas, proponemos un análisis de diagnóstico para la distribución. Finalmente, aplicamos los resultados obtenidos al análisis de datos nuevos de producción de proteína basada en bacterias utilizada en la industria de alimentos y comparamos estadísticamente dos tipos de bacterias productoras usando la prueba de razón de verosimilitudes basada en el modelo MIG-t como una metodología alternativa a los procedimientos disponibles a la fecha. Este punto es muy importante, ya que la evaluación de producción de proteínas usando dos construcciones distintas permite a los investigador
EVALUACIóN PRELIMINAR DE LA CALIDAD DE LA ESCORRENTíA PLUVIAL SOBRE TEJADOS PARA SU POSIBLE APROVECHAMIENTO EN ZONAS PERIURBANAS DE BOGOTá PRELIMINARY ASSESSMENT OF ROOF RUNOFF RAIN WATER QUALITY FOR POTENTIAL HARVESTING IN BOGOTA’S PERI-URBAN AREAS
Andrés Torres,Sandra Méndez-Fajardo,Liliana López-Kleine,Valentina Marín
Revista U.D.C.A Actualidad & Divulgación Científica , 2011,
Abstract: En Colombia, varias comunidades, cuyo acceso al servicio de agua potable es limitado o precario, recolectan aguas lluvias para diferentes usos domésticos. Este artículo presenta los resultados de análisis de calidad de aguas lluvias de escorrentía sobre tejados, en barrios de Kennedy (Bogotá) y del municipio de Soacha (Cundinamarca), con miras a evaluar su adaptabilidad para satisfacer usos domésticos, en dichas comunidades. De acuerdo a los resultados obtenidos, el agua muestreada no es apta para ninguno de los usos de las comunidades estudiadas, debido principalmente a altos valores de turbiedad y altas concentraciones de Sólidos Suspendidos Totales, Demanda Bioquímica de Oxígeno a los cinco días y metales pesados; sin embargo, se detectó una alta variabilidad espacial y temporal de los resultados, así como en función de los materiales de los techos de las casas. En algunos casos y condiciones especiales, el agua lluvia de escorrentía sobre tejados, se podría adaptar para ser utilizada como fuente alternativa para satisfacer algunos usos domésticos. In Colombia, several communities with limited or precarious access to potable water services collect rain water for different domestic uses. This paper presents results of the quality analysis of runoff rainwater on roofs in Kennedy (Bogotá) and Soacha (Cundinamarca) in order to evaluate their adaptability to satisfy domestic uses in these districts. Based on the results obtained, it can be conclude that the sampled water is not suitable for none of the possible domestic uses in these communities. This is due to high values of turbidity and high concentrations of Total Suspended Solids, Biochemical Oxygen Demand and heavy metals. Nevertheless, high spatial and temporal variability was detected, as well as variability in function of the roof material. In some of the analyzed samples, the runoff water of the roofs could be adapted as an alternative for domestic uses.
EVALUACIóN PRELIMINAR DE LA CALIDAD DE LA ESCORRENTíA PLUVIAL SOBRE TEJADOS PARA SU POSIBLE APROVECHAMIENTO EN ZONAS PERIURBANAS DE BOGOTá
Torres,Andrés; Méndez-Fajardo,Sandra; López-Kleine,Liliana; Marín,Valentina; González,Jorge Andrés; Suárez,Juan Camilo; Pinzón,Julián David; Ruiz,Alejandra;
Revista U.D.C.A Actualidad & Divulgación Científica , 2011,
Abstract: in colombia, several communities with limited or precarious access to potable water services collect rain water for different domestic uses. this paper presents results of the quality analysis of runoff rainwater on roofs in kennedy (bogotá) and soacha (cundinamarca) in order to evaluate their adaptability to satisfy domestic uses in these districts. based on the results obtained, it can be conclude that the sampled water is not suitable for none of the possible domestic uses in these communities. this is due to high values of turbidity and high concentrations of total suspended solids, biochemical oxygen demand and heavy metals. nevertheless, high spatial and temporal variability was detected, as well as variability in function of the roof material. in some of the analyzed samples, the runoff water of the roofs could be adapted as an alternative for domestic uses.
Identification of Global Gene Expression Shifts Using Microarray Data from Different Biological Conditions  [PDF]
José Rafael Tovar Cuevas, Liliana López Kleine, José Alejandro Ordo?ez
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.55038
Abstract: Gene expression data have been very useful during the past two decades for the detection of differentially expressed genes when two (or more) biological conditions are compared. Studies seeking for differentially expressed genes are based on testing gene by gene for a mean differential expression between two conditions. Nevertheless, the global shift in gene expression when taking into account all genes present on a microarray experiment, has not yet been investigated and could provide different information on genes that could be affected by the condition under research. Such a global approach would help identifying a gene expression threshold, characteristic of a certain condition and therefore could be used for diagnosis together with the list of differentially expressed genes detected by classical methods. Moreover, characterizing genes below or above such a threshold could give new insights into the molecular mechanisms implicated functionally in each condition. Here, we present a simple methodology, based on heuristics, gene filtering, variable transformation and descriptive statistics in order to identify such global gene expression shifts and the characteristic threshold so the same can be applied by any professional that works with expression gene data and not only by statisticians. Our procedure is illustrated on a real gene expression data set comparing pathogen inoculated tomatoes with non-inoculated tomatoes. This methodology can be used for the identification of the threshold values when we have continuous variable data sets from two populations with overlapped distributional forms (histograms) in most of their percentiles.
Redistritación electoral en México: logros pasados y retos futuros
López Levi, Liliana;
Investigaciones geográficas , 2006,
Abstract: electoral redistricting in mexico has been an important step in the so called transition to democracy. the solutions implemented in the last decade have been positive for electoral institutions, as well as a mean to promote dialogue between political actors. however, according to population dynamics, the problem should be issued periodically. the abovementioned allows a reflexion on the path followed, particularly on the criteria adopted. this article has the aim to analyze mexican achievements and challenges and makes a proposal intended to contribute in this political and geographical task.
Fortificaciones habitacionales en México: De la violencia dominante a la violencia dominadora
López Levi, Liliana;
Argumentos (México, D.F.) , 2011,
Abstract: one of the main problems in mexico, which has increased considerably during the last years, is public insecurity and violence. the fear that it creates, produces certain imaginaries, which are symbolically reflected in different urban spaces, of which, i emphasize on the case of gated communities, where developers have made a successful use of the situation to sell fortified residence. the analysis of the production of closed living space is based on the theory of urban imaginaries and it is used to point out the way that violence becomes a dominating force that reduces the quality of citizenship of mexico city's inhabitants.
Rese a de "Decentralization in Mexico", en Reforma Municipal to Solidaridad to Nuevo Federalismo" de Victoria E. Rodríguez
Liliana López Levi
Política y cultura , 1999,
Abstract:
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