An R Package for a General Class of Inverse Gaussian Distributions

The inverse Gaussian distribution is a positively skewed probability model that has received great attention in the last 20 years. Recently, a family that generalizes this model called inverse Gaussian type distributions has been developed. The new R package named ig has been designed to analyze data from inverse Gaussian type distributions. This package contains basic probabilistic functions, lifetime indicators and a random number generator from this model. Also, parameter estimates and diagnostics analysis can be obtained using likelihood methods by means of this package. In addition, goodness-of-fit methods are implemented in order to detect the suitability of the model to the data. The capabilities and features of the ig package are illustrated using simulated and real data sets. Furthermore, some new results related to the inverse Gaussian type distribution are also obtained. Moreover, a simulation study is conducted for evaluating the estimation method implemented in the ig package.

An R Package for a General Class of Inverse Gaussian Distributions

The inverse Gaussian distribution is a positively skewed probability model that has received great attention in the last 20 years. Recently, a family that generalizes this model called inverse Gaussian type distributions has been developed. The new R package named ig has been designed to analyze data from inverse Gaussian type distributions. This package contains basic probabilistic functions, lifetime indicators and a random number generator from this model. Also, parameter estimates and diagnostics analysis can be obtained using likelihood methods by means of this package. In addition, goodness-of-fit methods are implemented in order to detect the suitability of the model to the data. The capabilities and features of the ig package are illustrated using simulated and real data sets. Furthermore, some new results related to the inverse Gaussian type distribution are also obtained. Moreover, a simulation study is conducted for evaluating the estimation method implemented in the ig package

Estimation in the Birnbaum-Saunders distribution based on scale-mixture of normals and the EM-algorithm

Scale mixtures of normal (SMN) distributions are used for modeling symmetric data. Members of this family have appealing properties such as robust estimates, easy number generation, and efficient computation of the ML estimates via the EM-algorithm. The Birnbaum-Saunders (BS) distribution is a positively skewed model that is related to the normal distribution and has received considerable attention. We introduce a type of BS distributions based on SMN models, produce a lifetime analysis, develop the EM-algorithm for ML estimation of parameters, and illustrate the obtained results with real data showing the robustness of the estimation procedure.Peer Reviewe

La Regulación del Transporte de Carga en Santiago: Características, Evaluación y Propuestas

This paper is an assessment of freight transport regulation in Santiago. We conclude that most regulations restrict quantities and access. Moreover, agents perceive them as erratic and uncertain. We argue that these restrictions are not only costly but aExternal effects, urban highways, management vs. Policy, road pricing, urban freight trasport

Estimation in the Birnbaum-Saunders distribution based on scale-mixture of normals and the EM-algorithm

Scale mixtures of normal (SMN) distributions are used for modeling symmetric data. Members of this family have appealing properties such as robust estimates, easy number generation, and efficient computation of the ML estimates via the EM-algorithm. The Birnbaum-Saunders (BS) distribution is a positively skewed model that is related to the normal distribution and has received considerable attention. We introduce a type of BS distributions based on SMN models, produce a lifetime analysis, develop the EM-algorithm for ML estimation of parameters, and illustrate the obtained results with real data showing the robustness of the estimation procedure

Risk factor correlates of platelet and leukocyte markers assessed by flow cytometry in a population-based sample

Background—Platelet and leukocyte products are involved in atherothrombosis. However, the determinants of of platelet and leukocyte markers assessed by flow cytometry have not been documented in a population-based sample. Methods and results—We performed flow cytometry on blood from participants (n=1,894) in the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study. Cellular aggregates and multiple platelet and leukocyte markers, such as myeloperoxidase in granulocytes and toll-like receptor-4, CD14, and CD45 in monocytes, were quantified. Their cross-sectional associations with demographic and risk factors were assessed using multiple linear regression. Mean values of most cellular markers and aggregates were considerably higher in blacks than whites (p<0.01). There were some differences in cellular markers between men and women, but little association with age. LDL-cholesterol was associated positively with several markers (toll-like receptor-4 and myeloperoxidase in granulocytes and CD162 in lymphocytes). Lipid lowering therapy tended to show opposite associations. Smokers had much higher granulocyte myeloperoxidase than nonsmokers. However, most other correlations between risk factors and cellular markers were nonsignificant. Conclusions—Race/ethnicity, sex, and to a lesser degree LDL-cholesterol and lipid-lowering therapy, but few other risk factors, were correlated with markers of cellular activation in this population-based study

Estudio prospectivo de anticuerpos Antifosfolipido-Proteinas, en pacientes portadores de insuficiencia renal cronica en Hemodialisis

44 p.Los Anticuerpos Antifosfolípidos (aFL-P) son un grupo heterogéneo de anticuerpos que se asocian a trombosis, trombocitopenia y abortos espontáneos a repetición. Los pacientes portadores de Insuficiencia Renal Crónica en Hemodiálisis presentan trombosis de la Fístula arterio-venosa (FAV) y cero grado de trombocitopenia. El mecanismo de generación de estos fenómenos en los pacientes en Hemodiálisis no están muy claros del todo. Este estudio comprende 77 pacientes portadores IRCr en HD de tres centros de la región del Maule. Se realizaron ensayos para pesquizar Anticuerpos Anticardiolipina (aCL) y Antifosfatidilserina (aFS) (IgG, -M, -A) por ELISA de fase sólida. Trece (16.8%) de los 77 pacientes presentaron algun tipo de aFL-P independiente del isotipo. El isotipo mas frecuente en aCL es IgG y para aFS es IgA, siendo aFS los que se encontraron en la mayoría de los pacientes con aFL-P. Solo un paciente presento aCL y aFS, solamente dos (16.6%) pacientes en el grupo de los trasplantados presentaron aFL-P. Los resultados nos permiten concluir que la prevalencia de aFL-P en pacientes con IRCr en HD fue de 16.8% y no se observo asociación entre la presencia de aFL-P con trombosis de la FAV, ni con trombocitopenia

Factores exógenos: Incidencia en el rendimiento académico

The purpose of this article is to determine the factors that negatively affect the performance of the students of the Military School for the achievement of their academic goals and objectives of the institute, despite the existence of a system of caution of academic progression aimed at avoiding the academic failures and voluntary defections of these. The paradigm from which the article was focused corresponds to a qualitative and quantitative study to complement the tools and techniques of information collection, the design is especially suitable for the study of educational contexts as the case of the Military School and is a descriptive study in which the theoretical contrast is carried out with an academic reality of the area under study. The conclusions obtained indicate what are the factors that affect the academic performance of the students of the Military School, the recommendations through proposals to address them and their respective implications.El presente artículo tiene por objetivo determinar los factores que inciden negativamente en el rendimiento de los alumnos de la Escuela Militar para el logro de sus metas y objetivos académicos del instituto, pese a la existencia de un sistema de cautela de la progresión académica orientado a evitar los fracasos académicos y deserciones voluntarias de estos. El paradigma desde el cual se enfocó el artículo corresponde a un estudio cualitativo y cuantitativo por complementar las herramientas y técnicas de recolección de información, el diseño es, especialmente, apto para el estudio de contextos educativos como el caso de la Escuela Militar y es un estudio descriptivo en el cual se realiza la contrastación teórica con una realidad académica del área en estudio. Las conclusiones obtenidas señalan cuales son los factores que afectan el rendimiento académico de los alumnos de la Escuela Militar, las recomendaciones a través de proposiciones para enfrentarlos y sus respectivas implicaciones

Percepcion empresarial de los factores que limitan el aumento de las exportaciones de las empresas de la provincia de Talca

77 p.El propósito de nuestra investigación es determinar la percepción de los empresarios de las empresas exportadoras de la provincia de Talca acerca de los factores que limitan el aumento de las exportaciones. Con este fin fue aplicado un cuestionario, que se realizó sobre la base de un modelo confeccionado con información proveniente de textos teóricos. Este provee de todas las variables claves en el proceso de exportación, y fue contrastado con la opinión de los empresarios a cargo de las 20 empresas exportadoras encuestadas. Este tamaño corresponde a todas las empresas que pudieron ser encuestas del total de 31 empresas identificadas (que fueron obtenidas sobre la base de restricciones de exportaciones anuales sobre US$ 15.000 (F.O. B.)). Los resultados del estudio arrojan que las variables que mas limitan las exportaciones son Ias variables económicas, seguida de la capacidad de gestión estratégica. Por otra parte, las que menos influyen, a juicio de los empresarios, son las relaciones exteriores, la condición financiera y las políticas de promoción de exportaciones. En cuanto a las variables especificas, la que mas frena las exportaciones, a juicio de los empresarios, es el tipo de cambio real, seguida de las medidas proteccionistas del país de destino, los aranceles de los países de destino y la información sobre disposiciones legales del país de destino. Por otro lado, el conocimiento de fuentes de financiamiento para exportadores, las misiones gubernamentales, los acuerdos con universidades e institutos tecnológicos, el sistema de telecomunicación actual y los actuales mecanismo