2,770 research outputs found
Desempeño de chorros en flujo cruzado como barrera eólica.
No full textEn el documento presentado se introducen los resultados asociados a los ensayos
de túnel de viento llevados adelante para evaluar el desempeño de chorros en flujo
cruzado como barreras eólicas. Los primeros dos capítulos son dedicados a una revisión bibliográfica. El primer capítulo introduce una revisión cronológica del estudio del chorro en flujo cruzado, y cierra con una descripción de la estructura vorticosa identificada al día de hoy. Por otra parte, el segundo capítulo se aboca a la introducción del estado del arte en la
protección eólica, intercalando el desarrollo de las barreras eólicas con el desarrollo de
conocimiento entorno al confort eólico. El tercer capítulo presenta el orden cronológico de las tareas reportadas en el documento e introduce la motivación en la realización de este trabajo de doctorado. En el capítulo cuatro se presenta la infreaestructura e instrumental utilizado en los ensayos de túnel de viento llevados adelante. Como se evidencia en el documento, los resultados experimentales provienen de dos campañas de medición. La inicial, denominada ”Primer batería de ensayos” fue realizada en Enero del año 2020 y ofreció resultados de dos perfiles verticales de medidas de anemómetro de hilo caliente de dos hilos en el plano de simetría de cuatro modelos de ventiladores inmersos en un flujo cruzado tipo capa límite. Dichos resultados mostraron un desempeño razonable de la variable que caracteriza a la protección eólica, la velocidad relativa (V R). En el capítulo cinco se introduce tanto la configuración experimental como los resultados y las conclusiones alcanzadas al final de dicha campaña. La segunda campaña de medidas, llevada adelante a mediados del año 2022, se introduce en el capítulo 6. En esta se busca ofrecer una descripción más detallada tanto espacialmente como en las relaciones de velocidad (RV ) y el cociente entre el distanciamiento entre chorros y su diámetro (d/D) del fenómeno estudiado. Para eso se realizan ensayos a menor escala geométrica de dos chorros en flujo cruzado. El capítulo comienza presentando la configuración experimental, explicando las decisiones llevadas adelante a la hora de seleccionar las distintas variables que hacen a la medida. Allí se explica el porqué de la grilla seleccionada, el tiempo de muestreo, el área cubierta con los ensayos, y el diámetro de los chorros entre otras cosas. Posteriormente, la sección ”Resultados” presenta las verificaciones realizadas a los resultados de trayectoria, y diversos análisis que se desprenden de las descripciones espaciales alcanzadas. Por un lado, se ahonda en el análisis del flujo medio entorno a los dos chorros, concluyendo sobre el mecanismo mediante el cual se logran zonas de velocidad reducida a sotavento de los chorros. También se procede con el análisis espectral, que ofrece una caracterización de la turbulencia que posteriormente es utilizada para evaluar el efecto de esta sobre los sujetos de protección. El documento cierra con la sección conclusiones. En esta se desarrolla sobre las limitaciones de los ensayos, las conclusiones generadas a partir de los resultados, y las potenciales líneas de trabajo futuras. Se concluye, entre otras cosas, que los chorros en flujo cruzado experimentalmente muestran un desempeño comparable al de algunas barreras eólicas utilizadas. Finalmente se plantea el desarrollo sobre el efecto de la turbulencia en la protección eólica, y se analiza el mecanismo de protección eólica.Comisión académica de posgrado (CAP) a través de sus becas de doctorado
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Understanding Family Planning in San Ignacio, Belize
No full textThis study focuses on women’s decisions and experiences related to family planning in San Ignacio, Belize. The authors sought to identify family planning resources available in San Ignacio, as well as barriers to accessing these resources. Furthermore, this study explored how local barriers affected the use of contraception in San Ignacio. The first author traveled to San Ignacio and carried out four semi-structured interviews and one focus group with local women. She also conducted nine semi-structured interviews with community leaders. Women discussed their own knowledge and use of contraceptive methods, barriers to contraceptive use, the value of planned pregnancies and their pregnancy experiences. Community leaders reported that contraceptive methods were available but also admitted to the existence of perceived barriers to contraceptive use.
Women stated that planned pregnancies were desirable, but often unachievable because of religious beliefs, cultural norms, the opposition of family members, lack of knowledge of contraceptive methods and male partners seeking control over women. Community leaders reported that men are often unsupportive of contraceptive use and that religious groups often seek to discourage contraceptive use. Both women and community leaders stated that in San Ignacio, women are expected to have families and that local religious groups discourage the use of contraception.
Use of contraceptives among women in San Ignacio is thus not solely determined by the availability of contraceptives. Organizations that aim to promote family planning must implement multilevel initiatives that address the needs, desires and perspectives of community members, promote healthy relationships and challenge gender inequitable social norms
Understanding Family Planning in San Ignacio, Belize
No full textThis study focuses on women’s decisions and experiences related to family planning in San Ignacio, Belize. The authors sought to identify family planning resources available in San Ignacio, as well as barriers to accessing these resources. Furthermore, this study explored how local barriers affected the use of contraception in San Ignacio. The first author traveled to San Ignacio and carried out four semi-structured interviews and one focus group with local women. She also conducted nine semi-structured interviews with community leaders. Women discussed their own knowledge and use of contraceptive methods, barriers to contraceptive use, the value of planned pregnancies and their pregnancy experiences. Community leaders reported that contraceptive methods were available but also admitted to the existence of perceived barriers to contraceptive use.
Women stated that planned pregnancies were desirable, but often unachievable because of religious beliefs, cultural norms, the opposition of family members, lack of knowledge of contraceptive methods and male partners seeking control over women. Community leaders reported that men are often unsupportive of contraceptive use and that religious groups often seek to discourage contraceptive use. Both women and community leaders stated that in San Ignacio, women are expected to have families and that local religious groups discourage the use of contraception.
Use of contraceptives among women in San Ignacio is thus not solely determined by the availability of contraceptives. Organizations that aim to promote family planning must implement multilevel initiatives that address the needs, desires and perspectives of community members, promote healthy relationships and challenge gender inequitable social norms
On neutral metacommunity patterns of river basins at different scales of aggregation
No full textNeutral metacommunity models for spatial biodiversity patterns are implemented on river networks acting as ecological corridors at different resolution. Coarse-graining elevation fields (under the constraint of preserving the basin mean elevation) produce a set of reconfigured drainage networks. The hydrologic assumption made implies uniform runoff production such that each link has the same habitat capacity. Despite the universal scaling properties shown by river basins regardless of size, climate, vegetation, or exposed lithology, we find that species richness at local and regional scales exhibits resolution-dependent behavior. In addition, we investigate species-area relationships and rank-abundance patterns. The slopes of the species-area relationships, which are consistent over coarse-graining resolutions, match those found in real landscapes in the case of long-distance dispersal. The rank-abundance patterns are independent of the resolution over a broad range of dispersal length. Our results confirm that strong interactions occur between network structure and the dispersal of species and that under the assumption of neutral dynamics, these interactions produce resolution-dependent biodiversity patterns that diverge from expectations following from universal geomorphic scaling laws. Both in theoretical and in applied ecology studying how patterns change in resolution is relevant for understanding how ecological dynamics work in fragmented landscape and for sampling and biodiversity management campaigns, especially in consideration of climate change
Patterns of vegetation biodiversity: The roles of dispersal directionality and river network structure
No full textThis paper investigates the importance of dispersal directionality and river network structure to biodiversity patterns. Our model results suggest that dispersal directionality plays a crucial role in determining biodiversity patterns, even more so than dispersal rates. Dispersal directionality heterogenizes the spatial distribution of abundance, which results in higher extinction rates of rare species and higher β diversity. It induces a few species with very high abundances at the expense of many species with intermediate abundances, thereby lowering α and γ diversities. The river network structure also increases β diversity, i.e., more heterogeneous ecosystems, in comparison to typical two-dimensional landscapes. We find that the interplay between the dispersal directionality and network topology has important consequences on relative species abundance patterns and the distribution of α diversity. © 2008 Elsevier Ltd. All rights reserved
Generalized reproduction numbers and the prediction of patterns in waterborne disease
No full textUnderstanding, predicting, and controlling outbreaks of waterborne diseases are crucial goals of public health policies, but pose challenging problems because infection patterns are influenced by spatial structure and temporal asynchrony. Although explicit spatial modeling is made possible by widespread data mapping of hydrology, transportation infrastructure, population distribution, and sanitation, the precise condition underwhich awaterborne disease epidemic can start in a spatially explicit setting is still lacking. Here we show that the requirement that all the local reproduction numbers R 0 be larger than unity is neither necessary nor sufficient for outbreaks to occur when local settlements are connected by networks of primary and secondary infection mechanisms. To determine onset conditions, we derive general analytical expressions for a reproduction matrix G0, explicitly accounting for spatial distributions of human settlements and pathogen transmission via hydrological and human mobility networks. At disease onset, a generalized reproduction number Λ0 (the dominant eigenvalue of G0) must be larger than unity.We also show that geographical outbreak patterns in complex environments are linked to the dominant eigenvector and to spectral properties of G0. Tests against data and computations for the 2010 Haiti and 2000 KwaZulu-Natal cholera outbreaks, as well as against computations for metapopulation networks, demonstrate that eigenvectors of G0 provide a synthetic and effective tool for predicting the disease course in space and time. Networked connectivity models, describing the interplay between hydrology, epidemiology, and social behavior sustaining human mobility, thus prove to be key tools for emergency management of waterborne infections
RIVER NETWORKS AS ECOLOGICAL CORRIDORS: A COMPLEX SYSTEMS PERSPECTIVE FOR INTEGRATING HYDROLOGIC, GEOMORPHOLOGICAL AND ECOLOGIC DYNAMICS
No full textThis paper synthesizes recent works at the interface of hydrology, geomorphology, and ecology under an integrated framework of analysis with an aim for a general theory. It addresses a wide range of related topics, including biodiversity of freshwater fish in river networks and vegetation along riparian systems, how river networks affected historic spreading of human populations, and how they influence the spreading of water-borne diseases. Given the commonalities among various dendritic structures and despite the variety and complexity of the ecosystems involved, we present here an integrated line of research addressing the above and related topics through a unique, coherent ecohydrological thread and similar mathematical methods. Metacommunity and individual-based models are studied in the context of hydrochory, population, and species migrations and the spreading of infections of water-borne diseases along the ecological corridors of river basins. A general theory emerges on the effects of dendritic geometries on the ecological processes and dynamics operating on river basins that will establish a new significant scientific branch. Insights provided by such a theory will lend themselves to issues of great practical importance such as integration of riparian systems into large-scale resource management, spatial strategies to minimize loss of freshwater biodiversity, and effective prevention campaigns against water-borne diseases
Intratumoral delivery of immunotherapy - Act locally, think globally
No full textImmune mechanisms have evolved to cope with local entry of microbes acting in a confined fashion but eventually inducing systemic immune memory. Indeed, in situ delivery of a number of agents into tumors can mimic in the malignant tissue the phenomena that control intracellular infection leading to the killing of infected cells. Vascular endothelium activation and lymphocyte attraction, together with dendritic cell–mediated cross-priming, are the key elements. Intratumoral therapy with pathogen-associated molecular patterns or recombinant viruses is being tested in the clinic. Cell therapies can be also delivered intratumorally, including infusion of autologous dendritic cells and even tumor-reactive T lymphocytes. Intralesional virotherapy with an HSV vector expressing GM-CSF has been recently approved by the Food and Drug Administration for the treatment of unresectable melanoma. Immunomodulatory monoclonal Abs have also been successfully applied intratumorally in animal models. Local delivery means less systemic toxicity while focusing the immune response on the malignancy and the affected draining lymph nodes
Neutral metacommunity models predict fish diversity patterns in Mississippi-Missouri basin
No full textRiver networks, seen as ecological corridors featuring connected and hierarchical dendritic landscapes for animals and plants, present unique challenges and opportunities for testing biogeographical theories and macroecological laws(1). Although local and basin- scale differences in riverine fish diversity have been analysed as functions of energy availability and habitat heterogeneity(2), scale- dependent environmental conditions(3) and river discharge(4,5), a model that predicts a comprehensive set of system-wide diversity patterns has been hard to find. Here we show that fish diversity patterns throughout the Mississippi - Missouri River System are well described by a neutral metacommunity model coupled with an appropriate habitat capacity distribution and dispersal kernel. River network structure acts as an effective template for characterizing spatial attributes of fish biodiversity. We show that estimates of average dispersal behaviour and habitat capacities, objectively calculated from average runoff production, yield reliable predictions of large- scale spatial biodiversity patterns in riverine systems. The success of the neutral theory in two- dimensional forest ecosystems(6-8) and here in dendritic riverine ecosystems suggests the possible application of neutral metacommunity models in a diverse suite of ecosystems. This framework offers direct linkage from large- scale forcing, such as global climate change, to biodiversity patterns
Awards Presented at the Spring Meeting: Sixteenth Presentation: James B. Macelwane Award to Ignacio Rodriguez-Iturbe in Recognition of Significant Contributions to the Geophysical Sciences by a Young Scientist of Outstanding Ability
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