Advanced Search
Now showing items 17921-17930 of 18059
Infirmus: I Love La Paz
(Universidad de Chile, 2005)
Déotte señala que no hay sociedad sin colección de fragmentos y sin un lugar que los albergue: suspensión de objetos, huellas (no están ni ausentes ni presentes) de una arqueología del saber (en el sentido de Foucault, precisará). El fragmento se...
Estudio del comportamiento ambiental de plaguicidas usados en Chile mediante estimaciones computacionales
(Universidad de Chile, 2021)
En las últimas décadas ha empezado a surgir un mayor interés en conocer el comportamiento ambiental de ciertos compuestos orgánicos aprobados para su uso cotidiano, principalmente debido a que se han ido conociendo sus riesgos asociados y el daño...
In recent decades a greater interest has emerged in knowing the environmental behavior of some organic compounds approved for daily use, mainly because their associated risks and the damage they can cause to people’s health and to the environment have become known. Due to the high number of compounds that have been synthesized an experimental analysis results difficult, making the use of computational estimates to evaluate potential persistence, bioaccumulation and transport very useful. The main objective of this study is the estimation of the environmental behavior of pesticides used in Chile, in order to find those that have a potential risk for the environment. The methodology of work consisted on the generation of a database of pesticides authorized by the Servicio Agrícola Ganadero (SAG), the use of the “EPI Suite” program to estimate their distribution coefficients, half-life times and bioaccumulation from their molecular structures, and the use of the “Pov & LRTP Screening Tool” to estimate their overall persistence and transport efficiency in the environment. In addition to this, the P-B-LRT score was obtained, which considers equitably persistence, bioaccumulation and transport. All data were evaluated using as reference the value reported to Polychlorinated Biphenyls (PCB), a chemical group of compounds recognized as Persistent Organic Pollutants, in order to find a list of priority pesticides whose properties exceed that reference value. The results showed that the environmental distribution of pesticides occurs mainly between organic matter and water, where they also had the longest half-life times and potential transport, which could indicate a high mobility in soil and possible leaching to groundwaters. Some pesticides showed a high bioaccumulation, which may be especially important if they are in an aquatic environment. From the analysis a list was obtained of 21 priority pesticides marketed in Chile that present similarities in their structures, which require a more detailed experimental analysis. It is important to consider that these analyses use approximations and are useful to have an idea of the behavior of the compounds, however, they do not consider particular characteristics present in the emission environment....
In recent decades a greater interest has emerged in knowing the environmental behavior of some organic compounds approved for daily use, mainly because their associated risks and the damage they can cause to people’s health and to the environment have become known. Due to the high number of compounds that have been synthesized an experimental analysis results difficult, making the use of computational estimates to evaluate potential persistence, bioaccumulation and transport very useful. The main objective of this study is the estimation of the environmental behavior of pesticides used in Chile, in order to find those that have a potential risk for the environment. The methodology of work consisted on the generation of a database of pesticides authorized by the Servicio Agrícola Ganadero (SAG), the use of the “EPI Suite” program to estimate their distribution coefficients, half-life times and bioaccumulation from their molecular structures, and the use of the “Pov & LRTP Screening Tool” to estimate their overall persistence and transport efficiency in the environment. In addition to this, the P-B-LRT score was obtained, which considers equitably persistence, bioaccumulation and transport. All data were evaluated using as reference the value reported to Polychlorinated Biphenyls (PCB), a chemical group of compounds recognized as Persistent Organic Pollutants, in order to find a list of priority pesticides whose properties exceed that reference value. The results showed that the environmental distribution of pesticides occurs mainly between organic matter and water, where they also had the longest half-life times and potential transport, which could indicate a high mobility in soil and possible leaching to groundwaters. Some pesticides showed a high bioaccumulation, which may be especially important if they are in an aquatic environment. From the analysis a list was obtained of 21 priority pesticides marketed in Chile that present similarities in their structures, which require a more detailed experimental analysis. It is important to consider that these analyses use approximations and are useful to have an idea of the behavior of the compounds, however, they do not consider particular characteristics present in the emission environment....
Propuesta y evaluación de diseño malla de extracción mixta (rectangular-triangular)
(Universidad de Chile, 2021)
El tamaño del LHD es uno de los factores más influyentes en el diseño del diseño minero, principalmente debido a la búsqueda constante de mayores capacidades de producción. Sin embargo, el correcto diseño debe considerar otros aspectos que faciliten...
Notificaciones por violación a requisitos sanitarios, fitosanitarios y técnicos en exportaciones hortofrutícolas latinoamericanas
(2016-06)
Las exportaciones latinoamericanas de alimentos han aumentado sostenidamente en los últimos años, así como también habrían crecido las exigencias relativas a medidas sanitarias, fitosanitarias y técnicas, sobre todo en sus principales mercados de...
In the past few years Latin American food exports have steadily increased as have the requirements concerning sanitary, phytosanitary and technical measures, especially in its main target markets: the United States of America and the European Union. Failure to comply with these requirements in production puts the access to international markets at risk, particularly affecting the countries of the region as they are net exporters of food products. In this context, the present study aims to describe the current situation of Latin American food exports relative to the fulfilment of sanitary, phytosanitary and technical requirements, and in particular fruit and vegetables. To this end, the following specific objectives were included in this study: a) describe the current situation and recent evolution of Latin American fruit and vegetable exports to the US and the EU, b) describe how the Food Imports Control System operates in both markets, c) analyze the current trends in notifications of horticultural products for violation of the previously mentioned requirements and, d) suggest recommendations according to the information presented in in the previous three points. The results indicate that the country with the largest number of notifications for violation of the U.S. requirements is Mexico by far. However, Guatemala and Peru both show important rejections at border in this market. Altogether, the main violation as notified by the US is the presence of pesticides, and the most affected products were fresh peppers, asparagus, tubers, papayas, berries, grapes, and bananas. On the other hand, the EU gave more notifications to Argentina, Brazil, and the Dominican Republic, mainly for the presence of aflatoxins or other failures relating to inadequate storage and transport conditions, which would have mainly affected shipments of legumes, tubers, and nuts. Finally, I conclude that despite the increase in sanitary, phytosanitary, and technical requirements, a greater number of violation notifications was not observed even though the increased regulations affect a higher percentage of fruit and vegetable shipments from leading regional exporters. However, policies that allow the strengthening of the quality and safety of foods produced must be introduced, especially considering the increased requirements, despite the fact that, generally speaking, the fruit and vegetables of most Latin American do not seem to be perceived as risky....
In the past few years Latin American food exports have steadily increased as have the requirements concerning sanitary, phytosanitary and technical measures, especially in its main target markets: the United States of America and the European Union. Failure to comply with these requirements in production puts the access to international markets at risk, particularly affecting the countries of the region as they are net exporters of food products. In this context, the present study aims to describe the current situation of Latin American food exports relative to the fulfilment of sanitary, phytosanitary and technical requirements, and in particular fruit and vegetables. To this end, the following specific objectives were included in this study: a) describe the current situation and recent evolution of Latin American fruit and vegetable exports to the US and the EU, b) describe how the Food Imports Control System operates in both markets, c) analyze the current trends in notifications of horticultural products for violation of the previously mentioned requirements and, d) suggest recommendations according to the information presented in in the previous three points. The results indicate that the country with the largest number of notifications for violation of the U.S. requirements is Mexico by far. However, Guatemala and Peru both show important rejections at border in this market. Altogether, the main violation as notified by the US is the presence of pesticides, and the most affected products were fresh peppers, asparagus, tubers, papayas, berries, grapes, and bananas. On the other hand, the EU gave more notifications to Argentina, Brazil, and the Dominican Republic, mainly for the presence of aflatoxins or other failures relating to inadequate storage and transport conditions, which would have mainly affected shipments of legumes, tubers, and nuts. Finally, I conclude that despite the increase in sanitary, phytosanitary, and technical requirements, a greater number of violation notifications was not observed even though the increased regulations affect a higher percentage of fruit and vegetable shipments from leading regional exporters. However, policies that allow the strengthening of the quality and safety of foods produced must be introduced, especially considering the increased requirements, despite the fact that, generally speaking, the fruit and vegetables of most Latin American do not seem to be perceived as risky....
Desarrollo de materiales compuesto de polipropileno y nanoestructuras de carbono
(Universidad de Chile, 2014)
La presente tesis doctoral se centra en el desarrollo de compuestos poliméricos de polipropileno (PP) con nanoestructuras de carbono, mediante mezclado en fundido. El interés principal radica en el desarrollo de materiales multifuncionales que...
La nueva norma general anti-elusiva : interpretación administrativa y jurisprudencial
(Universidad de Chile, 2018)
(que
restringen la potestad tributaria en virtud de otros derechos de nivel constitucional que podrían
verse afectados frente a un abuso de esta potestad, como podrían ser el derecho de propiedad
o el de libertad económica)12.
Dada la...
del órgano competente. Así mismo la ley debe definir el hecho imponible y sus elementos; sin embargo, la doctrina aún se encuentra dividida en cuál debe ser el nivel de determinación que debe comprender la ley. Una parte de ella sostiene que todos...
del órgano competente. Así mismo la ley debe definir el hecho imponible y sus elementos; sin embargo, la doctrina aún se encuentra dividida en cuál debe ser el nivel de determinación que debe comprender la ley. Una parte de ella sostiene que todos...
Vitalidad y mortandad léxica de los mapuchismos en el español hablado por los habitantes de la comuna de Teno: a cien años del Diccionario etimológico de Rodolfo Lenz
(Universidad de Chile, 2018)
El propósito principal de este trabajo es investigar la mortandad léxica de los mapuchismos en el español oral de los habitantes de la comuna de Teno. Se pretende establecer si la variable generacional y la variable geográfica se correlacionan con...
Mejoramiento de productividad mediante distribución de instalaciones y reasignación de personal en un área de la planta en empresa textil
(Universidad de Chile, 2012)
a cada trabajo. Se buscó generar mejoras en base a reducción de quiebres de stock y ahorro en desvinculación de personal innecesario. La metodología usada se basó en el estudio de los artículos que transitan por el área y en las distintas tareas por...
Análisis comparativo de los genes involucrados en la supervivencia intracelular de Salmonella enterica serovar Typhimurium en macrófagos murinos y en la ameba Dictyostelium discoideum
(Universidad de Chile, 2017)
Salmonella es un patógeno intracelular capaz de generar cuadros clínicos que incluyen desde una enteritis autolimitada hasta infecciones sistémicas que pueden provocar la muerte del hospedero. Una vez dentro del organismo, la bacteria atraviesa la...
Salmonella is an intracellular pathogen that causes a variety of illnesses ranging from self-limiting gastroenteritis to severe systemic infections that can cause the death of the host. Once inside the organism, these bacteria can cross the epithelial barrier and interact with professional phagocytic cells of the innate immune system, causing a local inflammatory response which culminates in the excretion of the pathogen to the environment. The pathogenicity of Salmonella is associated with its ability to survive in macrophages and dendritic cells, which can act as dissemination vectors inside the host. The molecular mechanisms used for these bacteria to survive and replicate in macrophages have been widely studied. However, no in-depth study has been conducted in order to understand the molecular mechanisms required for Salmonella survival in other stages of its life cycle. For instance, in the environment Salmonella interacts with other phagocytic cells that feed on bacteria and fungus. Among these, the amoebae use similar endocytic and degradation mechanisms to those described in innate immune cells. In this thesis, we aimed to identify a common group of genes required for the intracellular survival of Salmonella Typhimurium in murine macrophages and the amoeba Dictyostelium discoideum. To this end, we performed a high-throughput analysis of mutants under negative selection using different mutant libraries. The identification of mutants unable to survive intracellularly in both phagocytic cells was carried out by deep-sequencing. First, we identified 719 mutants of S. Typhimurium under negative selection in murine macrophages. These mutants included genes encoded in pathogenicity islands conserved in the Salmonella genus, genes involved in transport and biosynthesis of amino acids and carbohydrates, genes encoding regulators associated with response to external signals, genes linked to biosynthesis and modification of lipopolysaccharide (LPS) and genes associated to nutritional and oxidative stress, among other. The comparative analysis between the data of this thesis and data obtained in our laboratory that identified mutants with defects in intracellular survival in D. discoideum, allow us the identification of mutants in 213 genes of S. Typhimurium required to survive intracellularly in both phagocytic cells. Within this group, we found genes encoded in Salmonella pathogenicity islands (SPI-1 and SPI-3), genes involved in iron uptake (iroC, iroN and feoB), genes related with response to starvation and acid pH (spoT and adiY) and genes associated to LPS biosynthesis and modification (waaB, waaI, waaJ, waaL, waaZ, wbaC, wbaK, wbaM, wbaN, wbaD, oafA, wzzfepE and genes in the arn operon), among other. To confirm predictions from our comparative analysis, we choose mutants involved in LPS biosynthesis and evaluated their intracellular survival in both infection models. We demonstrated that mutants ΔwaaL, ΔwzzST and ΔarnBCADTEF are deficient in intracellular survival in murine macrophages and D. discoideum. Hence, a complete LPS containing 16 to 35 AgO units (L-AgO) would be necessary for survival of this pathogen in murine macrophages and D. discoideum. Similarly, a modified LPS containing 4-deoxy-aminoarabinose bound to lipid A would contribute to the intracellular survival of S. Typhimurium in both phagocytic cells. Overall, our results constitute a first step towards understanding the molecular mechanisms exploited by S. Typhimurium in order to survive in strikingly different niches such as mammalians and environmental protozoa...
Salmonella is an intracellular pathogen that causes a variety of illnesses ranging from self-limiting gastroenteritis to severe systemic infections that can cause the death of the host. Once inside the organism, these bacteria can cross the epithelial barrier and interact with professional phagocytic cells of the innate immune system, causing a local inflammatory response which culminates in the excretion of the pathogen to the environment. The pathogenicity of Salmonella is associated with its ability to survive in macrophages and dendritic cells, which can act as dissemination vectors inside the host. The molecular mechanisms used for these bacteria to survive and replicate in macrophages have been widely studied. However, no in-depth study has been conducted in order to understand the molecular mechanisms required for Salmonella survival in other stages of its life cycle. For instance, in the environment Salmonella interacts with other phagocytic cells that feed on bacteria and fungus. Among these, the amoebae use similar endocytic and degradation mechanisms to those described in innate immune cells. In this thesis, we aimed to identify a common group of genes required for the intracellular survival of Salmonella Typhimurium in murine macrophages and the amoeba Dictyostelium discoideum. To this end, we performed a high-throughput analysis of mutants under negative selection using different mutant libraries. The identification of mutants unable to survive intracellularly in both phagocytic cells was carried out by deep-sequencing. First, we identified 719 mutants of S. Typhimurium under negative selection in murine macrophages. These mutants included genes encoded in pathogenicity islands conserved in the Salmonella genus, genes involved in transport and biosynthesis of amino acids and carbohydrates, genes encoding regulators associated with response to external signals, genes linked to biosynthesis and modification of lipopolysaccharide (LPS) and genes associated to nutritional and oxidative stress, among other. The comparative analysis between the data of this thesis and data obtained in our laboratory that identified mutants with defects in intracellular survival in D. discoideum, allow us the identification of mutants in 213 genes of S. Typhimurium required to survive intracellularly in both phagocytic cells. Within this group, we found genes encoded in Salmonella pathogenicity islands (SPI-1 and SPI-3), genes involved in iron uptake (iroC, iroN and feoB), genes related with response to starvation and acid pH (spoT and adiY) and genes associated to LPS biosynthesis and modification (waaB, waaI, waaJ, waaL, waaZ, wbaC, wbaK, wbaM, wbaN, wbaD, oafA, wzzfepE and genes in the arn operon), among other. To confirm predictions from our comparative analysis, we choose mutants involved in LPS biosynthesis and evaluated their intracellular survival in both infection models. We demonstrated that mutants ΔwaaL, ΔwzzST and ΔarnBCADTEF are deficient in intracellular survival in murine macrophages and D. discoideum. Hence, a complete LPS containing 16 to 35 AgO units (L-AgO) would be necessary for survival of this pathogen in murine macrophages and D. discoideum. Similarly, a modified LPS containing 4-deoxy-aminoarabinose bound to lipid A would contribute to the intracellular survival of S. Typhimurium in both phagocytic cells. Overall, our results constitute a first step towards understanding the molecular mechanisms exploited by S. Typhimurium in order to survive in strikingly different niches such as mammalians and environmental protozoa...
Mecánica
(Universidad de Chile, Facultad de Ciencias Físicas y Matemáticas, 2013)
´ıstico depende
de la llamada aceleracio´n de gravedad, g. Al nivel del mar aproximadamente es
g = 9,8 m
s2
.
La atencio´n en el estudio de Meca´nica en una buena parte estara´ dirigida a
describir puntos en movimiento.
z
x
O y Y
X
Z
Figura 1.1: El vector posicio...
frenado en puntos de retorno 107 5.1.3.1. Primer caso: El punto de retorno no corresponde a un ma´ximo de la energ´ıa potencial . . . . . . . . . . . 107 5.1.3.2. Segundo caso: El punto de retorno es un ma´ximo de la energ´ıa potencial...
frenado en puntos de retorno 107 5.1.3.1. Primer caso: El punto de retorno no corresponde a un ma´ximo de la energ´ıa potencial . . . . . . . . . . . 107 5.1.3.2. Segundo caso: El punto de retorno es un ma´ximo de la energ´ıa potencial...