132,385 research outputs found
Wilson, J. R., Panetta, F. D. & Lindgren, C.— Detecting and responding to alien plant incursions. Ecology, Biodiversity and Conservation, Cambridge University Press, Cambridge & New York, 2016
No full textÉrard Chr. Wilson, J. R., Panetta, F. D. & Lindgren, C.— Detecting and responding to alien plant incursions. Ecology, Biodiversity and Conservation, Cambridge University Press, Cambridge & New York, 2016. In: Revue d'Écologie (La Terre et La Vie), tome 72, n°4, 2017. p. 444
Novel strategies for the characterization of cancellous bone morphology: Virtual isolation and analysis
No full textObjectives: The advent of micro-computed tomography (μCT) made cancellous bone more accessible than ever before. Nevertheless, the characterization of cancellous bone is made difficult by its inherent complexity and the difficulties in defining homology across datasets. Here we propose novel virtual methodological approaches to overcome those issues and complement existing methods. Materials and methods: We present a protocol for the isolation of the whole cancellous region within a μCT scanned bone. This method overcomes the subsampling issues and allows studying cancellous bone as a single unit. We test the protocol on a set of primate bones. In addition, we describe a set of morphological indices calculated on the topological skeleton of the cancellous bone: node density, node connectivity, trabecular angle, trabecular tortuosity, and fractal dimension. The usage of the indices is shown on a small comparative sample of primate femoral heads. Results: The isolation protocol proves reliable in isolating cancellous structures from several different bones, regardless of their shape. The indices seem to detect some functional differences, although further testing on comparative samples is needed to clarify their potential for the study of cancellous architecture. Conclusions: The approaches presented overcome some of the difficulties of trabecular bone studies. The methods presented here represent an alternative or supporting method to the existing tools available to address the biomechanics of cancellous bone
Light postcranial skeleton vs heavy skull: a possible deep diving adaptation in beaked whales (Cetacea: Ziphiidae)
No full textA pachyosteosclerotic rostrum is a synapomorphic feature observed in several beaked whales. Four hypotheses have been proposed in the last decades to explain the evolution of this peculiar structure: 1) for favoring deep diving (the ballast hypothesis); 2) for intraspecific fights between adult males; 3) for facilitating sound transmission; 4) for intraspecific sexual display. According to the ballast hypothesis a heavy pachyosteosclerotic rostrum, combined with a light postcranial skeleton, moves the center of mass toward the head of the whale helping to rotate body for vertical diving. To better test this hypothesis, we computed the center of mass of the skeleton of three beaked whales (Hyperoodon ampullatus, Mesoplodon bowdoini, and Ziphius cavirostris) and one dolphin (Delphinus delphis), all kept at the Museo di Storia Naturale, Università di Pisa. Moreover, analyses about the density of the vertebral column and radiodensity of the first thoracic vertebra, first lumbar vertebra, first caudal vertebra and phalanxes were performed. Radiodensity was estimated by means of Computed Tomography (CT) and Micro-CT. Our analyses confirm the significant displacement of the center of mass to the anterior part of the skeleton in beaked whales, with the most notable shift occurring in M. bowdoini, exhibiting the center of mass in correspondencee of the cervical vertebrae. The skeleton of M. bowdoini also exhibits the least dense trabecular bone tissue, both in the vertebral bodies and the phalanx. The common dolphin, on the contrary, shows the posteriormost position of the center of mass and the densest trabecular bone tissue of vertebral bodies. Although this preliminary study seemingly supports the ballast hypothesis, these results should be further strengthened by increasing the number of investigated species and also by analyzing the whole bodies in order to estimate the center of mass of the entire living whales
Estudio del crecimiento tumoral en un modelo Kirschner Panetta con efecto de Interleucina-2
No full textIncluye tablas y graficas.El cáncer es una de las principales causas de muerte en el mundo. La Organización Mundial de la Salud (OMS) define el cáncer como un grupo amplio de enfermedades que pueden afectar cualquier órgano o tejido del cuerpo, también conocidas como tumores malignos o neoplasias malignas. Cada año, el cáncer causa aproximadamente 10 millones de muertes, lo que resulta en un desenlace trágico para muchas familias. Esta situación es provocada por la proliferación descontrolada de células dañadas que pueden diseminarse por todo el cuerpo.
Dada esta realidad, la epidemiología desempeña un papel crucial en el estudio de los diferentes modelos matemáticos propuestos para comprender y combatir el cáncer. La falta de información cuantitativa ha sido un desafío, principalmente debido a las limitaciones en la experimentación con seres humanos. Sin embargo, los modelos matemáticos proporcionan una herramienta valiosa para explorar las dinámicas de la enfermedad y sus posibles tratamientos.
El modelo estudiado en este trabajo es el modelo de Kirschner y Panetta, que se basa en el modelo de Lotka-Volterra. Este sistema de ecuaciones diferenciales es fundamental para el estudio de la dinámica poblacional biológica. El modelo de Kirschner y Panetta considera dos ecuaciones diferenciales ordinarias y ha sido modificado para contribuir al desarrollo de modelos epidemiológicos que se basan en factores determinantes, predicciones y control de factores relacionados con la salud y las enfermedades. Estos modelos también estudian la dinámica y distribución de las enfermedades virales en una población.Introducción. -- 1 Marco referencial. -- 1.1 Antecedentes del problema. -- 1.2 Modelo de lotka-volterra. -- 1.3 Mejoras en los terminos de la ecuacion. -- 1.4 Modelo de kuznetsov y taylor. -- 1.5 Modelo de inmunoterapia del tumor kirschner-panetta. -- 1.6 Puntos fijos. -- 1.7 Estabilidad local de puntos fijos. -- 2 Materiales y métodos. -- 3 Resultados. -- 3.1 Puntos fijos del sistema ce-ct-me. -- 3.2 Estabilidad de los puntos fijos del sistema ce-ct-me. -- 4 Análisis de resultados. -- 5 Conclusiones. – Bibliografía. -- Resumen analitico especializado.Informe final modalidad trabajo de grado como requisito para optar por el título de Licenciado en MatemáticasPregradoLicenciado(a) en Matemática
The potential for skeleton weed
No full textSince its introduction into Australia during the 900s skeleton weed has become one of the most economically significant weeds. Its presence in cereal crops in south-eastern Australia has caused suvere yield reductions and harvesting problems.
Skeleton weed was first found on a Western Australian farm in 963. Since then it has been the subject of an intensive eradication campaign organised by the Agricultural Protection Board and funded by an annual levy on wheat growers. Such campaigns, which rely mainly on volunteer searchers, do not exist in eastern Australia because the weed is so widespread it would be impossible to eradicate.
Studies conducted by the Weed Agronomy research officers, FD Panetta and J Dodd have led to a greater understanding of the biology and porential of skeleton weed in Western Australia. The following article is a sequel to their earlier article in the Journal of Agriculture (Panetta and Dodd 1984) and assesses what influences the establishment and spread of skeleton weed in this State
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
The potential for skeleton weed
No full textSince its introduction into Australia during the 900s skeleton weed has become one of the most economically significant weeds. Its presence in cereal crops in south-eastern Australia has caused suvere yield reductions and harvesting problems.
Skeleton weed was first found on a Western Australian farm in 963. Since then it has been the subject of an intensive eradication campaign organised by the Agricultural Protection Board and funded by an annual levy on wheat growers. Such campaigns, which rely mainly on volunteer searchers, do not exist in eastern Australia because the weed is so widespread it would be impossible to eradicate.
Studies conducted by the Weed Agronomy research officers, FD Panetta and J Dodd have led to a greater understanding of the biology and porential of skeleton weed in Western Australia. The following article is a sequel to their earlier article in the Journal of Agriculture (Panetta and Dodd 1984) and assesses what influences the establishment and spread of skeleton weed in this State
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