Sparse covariance estimation in heterogeneous samples

Standard Gaussian graphical models (GGMs) implicitly assume that the conditional independence among variables is common to all observations in the sample. However, in practice, observations are usually collected form heterogeneous populations where such assumption is not satisfied, leading in turn to nonlinear relationships among variables. To tackle these problems we explore mixtures of GGMs; in particular, we consider both infinite mixture models of GGMs and infinite hidden Markov models with GGM emission distributions. Such models allow us to divide a heterogeneous population into homogenous groups, with each cluster having its own conditional independence structure. The main advantage of considering infinite mixtures is that they allow us easily to estimate the number of number of subpopulations in the sample. As an illustration, we study the trends in exchange rate fluctuations in the pre-Euro era. This example demonstrates that the models are very flexible while providing extremely interesting interesting insights into real-life applications

Innovación tecnológica en el proceso de producción de alimentos en la fábrica “la Matagalpa”, municipio de Matagalpa, año 2013

El presente trabajo expone un estudio realizado en la fábrica “La Matagalpa” sobre el proceso de producción de alimentos “Encurtidos a base de vegetales” con el objetivo de conocer las etapas de su producción, para determinar las principales dificultades que se encuentran en el proceso y proponer técnicas de innovación que ayuden a la empresa a mejorar su proceso. Este trabajo se enfoca en el estudio del proceso de producción que realizan en la empresa, teniendo como fundamentos para nuestro estudio, la calidad y productividad de la empresa, para esto es necesario identificar los elementos del sistema, las normas de higiene, la capacidad y disposición de los operarios en las gestiones a realizar dentro del proceso productivo. Actualmente la empresa cuenta con procesos manuales y cuenta con ayuda de pequeñas maquinarias para la elaboración de los distintos procesos, las instalaciones de la empresa podrían mejorar para brindar una mejor condición e higiene laboral, sin embargo el producto cumple con los requerimientos higiénicos exigidos. La empresa, a pesar de contar con cierto material, equipo y conocimientos necesarios para la producción de encurtidos, aún no ha adquirido una nueva cultura de calidad, productividad e innovación contínua en lo que se elabora, ente esto surgen aspectos que obstaculizan la calidad, la productividad y el éxito de la empresa. Entre estos el más influyente, la indisposición de sus directivos en la inversión, para generarles nuevos conocimientos a sus operarios a través de capacitaciones y la falta de actitud de los operarios hacia la mejora contínua. Existen distintos factores que puede afectar todo el proceso productivo, por ello se recomienda tomar en cuenta los distintos aspectos mencionados en la guía de recomendaciones los cuales están basados en las dificultades encontradas en la empresa y podría ser de ayuda para búsqueda de la calidad, productividad y el éxito de la empres

Removal of Carbamazepine from Drinking Water

Due to the increasing prevalence of prescription medication over the past few decades, pharmaceuticals have accumulated in various water sources. This has become a public health concern because many pharmaceuticals have limited research on the effects of chronic low-level exposure. According to the World’s Health Organization (WHO), traces of pharmaceuticals products have been reported in different water sources such as surface waters, wastewater, groundwater, and drinking water.[1] One pharmaceutical of interest that has been detected in water sources is carbamazepine. Carbamazepine (CBZ) is a common pharmaceutical prescribed for the treatment of seizure disorders, neuropathic pain, and various psychological disorders. It’s mechanism of action is “sodium channel blocking,” which is the impairment of conduction of sodium ions in sodium channels. This, in effect, reduces nervous-system conductivity in key areas related to the treated disorders mentioned above.[2] Carbamazepine is also not easily biodegradable and current conventional treatment methods in some drinking water and wastewater facilities do not adequately remove carbamazepine and other pharmaceuticals from treated water. While carbamazepine is not federally regulated by the Environmental Protection Agency (EPA) under the Safe Water Drinking Act (SWDA) at this time, it does have the potential for producing adverse health effects in humans. Therefore, being proactive in finding ways to remove carbamazepine and compounds like it should be encouraged. The Carbamaza-Clean team designed a bench scale unit as well as an in-home treatment system using granular activated carbon (GAC) to effectively remove carbamazepine from water. GAC was chosen for this design because it is inexpensive and does not create by-products that are harmful to human health. Several experiments were conducted to determine the efficiency of the removal of carbamazepine using two different GACs: coconut shell GAC (CSGAC) and bituminous coal GAC (BGAC). A packed bed column was constructed to determine if both carbons could reduce the concentration of carbamazepine from 1 ppm to 1 ppb or lower. The CSGAC packed bed was able to lower the concentration below 1 ppb at a packed bed length of 4.4 ft, while the BGAC only required half that (2.2 ft). Both carbons can remove carbamazepine to the desired concentration; however, the costs vary. An economic analysis was performed to determine the costs of the carbons. The CSGAC system would cost $990 for the first year and$589.68 for each following year. The BGAC system would cost $639 for the first two years, and then$200 every two years following the initial capital investment