1,169 research outputs found
Homología persistente de relaciones : del teorema de Dowker al análisis topológico de datos neuronales
No full textEl objetivo principal de esta tesis es estudiar, profundizar y aplicar en problemas reales conexiones entre el Teorema de Dowker y la teoría de Homología Persistente. Exponemos aquí los resultados más significativos del tema, desde las ideas originales desarrolladas por C. Dowker en 1952 para estudiar homología de relaciones, el desarrollo de la teoría de homología persistente para espacios métricos iniciada por Z. Zomorodian y G. Carlsson en 2005 y su conexión con el análisis topológicos lógico de datos, hasta resultados recientes obtenidos por F. Memoli y S. Chowdhury (2018) y por H. Yoon, R. Ghrist y C. Giusti (2023), que conectan ambas teorías. La motivación de nuestro trabajo es analizar desde un punto de vista topológico la actividad neuronal de cierto tipo de neuronas encargadas del sistema de ubicación espacial en mamíferos y, en particular, humanos (grid cells, place cells y head-direction cells). La idea central es utilizar los métodos teóricos desarrollados por H. Yoon, R. Ghrist y C. Giusti para hallar conexiones topológicas originales entre la correlación funcional de la actividad de un conjunto de neuronas en el cerebro, y la dinámica de su actividad en el tiempo a medida que un individuo se mueve en el espacio. Aplicamos los métodos a simulaciones de actividades neuronales desarrolladas por el neurocientífico E. Kropff y su equipo, con quien planeamos una colaboración como resultado de este trabajo.Fil: López Menalled, Lola. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Impact of root fragment dimension, weight, burial depth, and water regime on Cirsium arvense emergence and growth
No full text Sciegienka, J. K., Keren, E. N. and Menalled, F. D. 2011. Impact of root fragment dimension, weight, burial depth, and water regime on Cirsium arvense emergence and growth. Can. J. Plant Sci. 91: 1027–1036. Cirsium arvense is an aggressive, introduced, perennial invasive weed that flourishes in a wide variety of environments including conventional and organic agricultural systems as well as disturbed non-crop habitats. Even though much research has been conducted on the chemical, biological, and cultural management of C. arvense, less information is available on how pre-emergence factors affect its reproductive biology and growth. This research assessed the combined impact of root fragment size, root fragment biomass, burial depth, and water regime (a proxy of water availability) on C. arvenseemergence and growth in fallow conditions. In field experiments, root burial depth was the most important factor determining C. arvenseemergence and growth, with roots at the 10-cm depth having the greatest average emergence (51.2±2.0% in 2007 and 43.5±7.2% in 2008; mean±SEM) compared to roots at the 2 cm (8.9±7.4% in 2007 and 38.1±8.3% in 2008) or 20 cm (12.8±4.0% in 2007 and 17.6±2.7% in 2008) depth. In greenhouse experiments, water regime was the overriding variable determining C. arvense emergence as well as above-ground and below-ground biomass. These results could improve decision-aid models and enhance the efficacy of site-specific C. arvense management practices. </jats:p
Comprehensive behavioral testing in the R6/2 mouse model of Huntington's disease shows no benefit from CoQ10 or minocycline
No full textPrevious studies of the effects of coenzyme Q10 and minocycline on mouse models of Huntington’s disease have produced conflicting results regarding their efficacy in behavioral tests. Using our recently published best practices for husbandry and testing for mouse models of Huntington’s disease, we report that neither coenzyme Q10 nor minocycline had significant beneficial effects on measures of motor function, general health (open field, rotarod, grip strength, rearing-climbing, body weight and survival) in the R6/2 mouse model. The higher doses of minocycline, on the contrary, reduced survival. We were thus unable to confirm the previously reported benefits for these two drugs, and we discuss potential reasons for these discrepancies, such as the effects of husbandry and nutrition
Molecular tools in biological control
No full text1 tab. 43 ref.Las tecnologías moleculares que trabajan con ADN pueden ser de gran ayuda para las personas que trabajan en control biológico. A pesar de esto, son pocos los ecólogos y entomólogos que han incorporado herramientas moleculares en sus programas de investigación. En este trabajo, hacemos una breve introducción a las herramientas moleculares, describimos sus ventajas y desventajas y presentamos ejemplos donde las herramientas moleculares han resuelto problemas. Se concluye que las herramientas moleculares prometen ser una gran ayuda para los investigadores en control biológico y deben ser utilizadas en aquellas situaciones donde no exista una forma más económica o sencilla para responder al problema. Molecular tools that work with DNA may be of great help to those working in biological control. However, few ecologists and entomologists have incorporated molecular tools into their research programs. In this paper, we make a brief introduction to molecular tools, we describe their advantages and disadvantages, and we show examples where molecular tools have solved problems. We conclude that molecular tools can be very helpful in biological control research and should be used whenever a cheaper or simpler way to solve the problem is nonexistent
Herbaceous Filter Strips in Agroecosystems: Implications for Ground Beetle (Coleoptera: Carabidae) Conservation and Invertebrate Weed Seed Predation
No full textA 9.3-ha crop field flanked by two filter strips was selected to: 1) assess carabid beetle activity-density and community composition and 2) assess post-dispersal weed seed predation by invertebrates in these habitats. Over- all during 1997 and 1998, 12,937 carabid beetles comprising 58 species were collected. Greater species richness and activity-density was observed in filter strips than in the field. A multivariate ordination revealed that year of capture and habitat were important variables conditioning carabid beetle communities. While two omnivorous species known to eat weed seeds [Harpalus erraticus (Say), Anisodactylus sanctaecrucis (F.)] dominated the 1997 captures, two carnivorous [Pterostichus melanarius (Ill), Pterostichus permundus (Say)] were predominant in 1998. Two omnivorous species, Harpalus pensylvanicus (DeG) and H. erraticus, were primarily captured in filter strips. Weed seed removal was greater in filter strips than in the field. This study shows that habitat management represents a feasible approach to conserve beneficial organisms in farmlands
Molecular techniques and habitat manipulation approaches for parasitoid conservation in annual cropping systems.
No full textHow biodiversity loss affects society
No full textThe industrialization of agriculture, which has occurred asynchronously in different parts of the world, goes hand in hand with a constant agrobiodiversity decline. The global loss of numerous edible crops and animals, as well as of landraces of still produced species, is not only harming the environmental sustainability of farming systems but has also generated societal consequences. We identify eight fields of consequences of agrobiodiversity loss on society: culture, language, and empirical knowledge; diets and cuisines; health; food environment; societal structures and gender issues; rural life; food security and livelihoods; and resilience of rural communities. We also specify how agrobiodiversity loss impacts society in each of these fields and then provide examples of this impact from as diverse regions as Lake Titicaca in Bolivia, The Pampas of Argentina, the Highlands of Yunnan in China, the Austrian Alps, and Burkina Faso.</p
Interacting agricultural pests and their effect on crop yield: application of a Bayesian decision theory approach to the joint management of Bromus tectorum and Cephus cinctus.
No full textWorldwide, the landscape homogeneity of extensive monocultures that characterizes conventional agriculture has resulted in the development of specialized and interacting multitrophic pest complexes. While integrated pest management emphasizes the need to consider the ecological context where multiple species coexist, management recommendations are often based on single-species tactics. This approach may not provide satisfactory solutions when confronted with the complex interactions occurring between organisms at the same or different trophic levels. Replacement of the single-species management model with more sophisticated, multi-species programs requires an understanding of the direct and indirect interactions occurring between the crop and all categories of pests. We evaluated a modeling framework to make multi-pest management decisions taking into account direct and indirect interactions among species belonging to different trophic levels. We adopted a Bayesian decision theory approach in combination with path analysis to evaluate interactions between Bromus tectorum (downy brome, cheatgrass) and Cephus cinctus (wheat stem sawfly) in wheat (Triticum aestivum) systems. We assessed their joint responses to weed management tactics, seeding rates, and cultivar tolerance to insect stem boring or competition. Our results indicated that C. cinctus oviposition behavior varied as a function of B. tectorum pressure. Crop responses were more readily explained by the joint effects of management tactics on both categories of pests and their interactions than just by the direct impact of any particular management scheme on yield. In accordance, a C. cinctus tolerant variety should be planted at a low seeding rate under high insect pressure. However as B. tectorum levels increase, the C. cinctus tolerant variety should be replaced by a competitive and drought tolerant cultivar at high seeding rates despite C. cinctus infestation. This study exemplifies the necessity of accounting for direct and indirect biological interactions occurring within agroecosystems and propagating this information from the statistical analysis stage to the management stage
Perceptions, Experiences, and Priorities Supporting Agroecosystem Management Decisions Differ among Agricultural Producers, Consultants, and Researchers
No full textThe sustainability of agriculture depends as much on the natural resources required for production as it does on the stakeholders that manage those resources. It is thus essential to understand the variables that influence the decision-making process of agricultural stakeholders to design educational programs, interventions, and policies geared towards their specific needs, a required step to enhance agricultural sustainability. This study employed a survey of multiple-choice and open-ended questions to examine the perceptions, experiences, and priorities that influence management decisions of agricultural stakeholders across Montana, United States. A total of 272 respondents completed a survey, representing five distinct agricultural stakeholder groups: 103 (34.9%) conventional producers, 78 (28.7%) consultants, 37 (13.6%) researchers, 33 (12.1%) organic grain producers, and 21 (7.7%) organic vegetable producers. The results revealed that, while stakeholder groups have distinct perceptions, experiences, and priorities, there were similarities across groups (pseudo-F = 22.92, p = 0.001). Specifically, organic vegetable and organic small-grain producers showed similar responses that were, in turn, divergent from those of conventional producers, researchers, and crop consultants. Conventional small-grain producers and researchers showed overlapping response patterns, while crop consultants formed an isolated group. Six clusters resulting from the classification of the multiple-choice response dataset associated with specific agricultural professions (χ2 = 549.72, p = 0.001). The classification of open-ended questions that assessed agronomic challenges and research needs resulted in six distinctive clusters, with specific associations between clusters and agricultural stakeholder groups (χ2 = 164.41, p = 0.001). These results reinforce the need for agricultural education and programs that address unique and shared experiences, priorities, and concerns of multiple stakeholder groups. This study endorses the call for a paradigm shift from the traditional top-down agricultural extension model to one that accounts for participants’ socio-ecological contexts to facilitate the adoption of sustainable agricultural systems that support environmental and human wellbeing
Evidence for Neuronal Dysfunction in a Mouse Model of Early Stages of Huntington’s Disease
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