1,720,960 research outputs found
Epigenetic and geometrical characterisation of cancer cell populations: A personalised-medicine oriented mathematical study of tumour evolutionary dynamics and therapies
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
A hybrid modeling environment to describe aggregates of cells heterogeneous for genotype and behavior with possible phenotypic transitions
Full text linkBiological systems are typically composed of cells heterogeneous for genotype and phenotype, the latter being time-evolving in response to internal or external stimuli. In order to take these aspects into account, we here propose a modeling framework in which a discrete structuring variable distinguishes cells according to their genotype while a specific mathematical representation (i.e., individual/pointwise vs. collective/density-based) is assigned to each individual on the basis of its phenotypic hallmarks. A coherent procedure is then set to reproduce mechanisms of phenotypic plasticity: based on the definition of a bubble function, which gives the spatial distribution of the mass of a single cell, it possibly accounts the role played by stochasticity and environmental conditions. The proposed modeling environment is then enriched with the inclusion of further cell behavior, such as migratory dynamics and duplication/apoptotic processes, as well as with chemical kinetics. The resulting multiscale hybrid approach is finally applied to the scenario of a heterogeneous tumor aggregate cultured in vitro
Hypoxia-resistance heterogeneity in tumours: the impact of geometrical characterization of environmental niches and evolutionary trade-offs. A mathematical approach
Full text linkIn the study of cancer evolution and therapeutic strategies, scientific
evidence shows that a key dynamics lies in the tumor-environment interaction.
In particular, oxygen concentration plays a central role in the determination
of the phenotypic heterogeneity of cancer cell populations, whose qualitative
and geometric characteristics are predominant factors in the occurrence of
relapses and failure of eradication. We propose a mathematical model able to
describe the eco-evolutionary spatial dynamics of tumour cells in their
adaptation to hypoxic microenvironments. As a main novelty with respect to the
existing literature, we combine a phenotypic indicator reflecting the
experimentally-observed metabolic trade-off between the hypoxia-resistance
ability and the proliferative potential with a 2d geometric domain, without the
constraint of radial symmetry. The model is settled in the mathematical
framework of phenotype-structured population dynamics and it is formulated in
terms of systems of coupled non-linear integro-differential equations. The
computational outcomes demonstrate that hypoxia-induced selection results in a
geometric characterization of phenotypic-defined tumour niches that impact on
tumour aggressiveness and invasive ability. Furthermore, results show how the
knowledge of environmental characteristics provides a predictive advantage on
tumour mass development in terms of size, shape, and composition
Hypoxia-related radiotherapy resistance in tumours: treatment efficacy investigation in an eco-evolutionary perspective
Full text linkIn the study of therapeutic strategies for the treatment of cancer,
eco-evolutionary dynamics are of particular interest, since characteristics of
the tumour population, interaction with the environment and effects of the
treatment, influence the geometric and epigenetic characterization of the
tumour with direct consequences on the efficacy of the therapy and possible
relapses. In particular, when considering radiotherapy, oxygen concentration
plays a central role both in determining the effectiveness of the treatment and
the selective pressure due to hypoxia. We propose a mathematical model, settled
in the framework of epigenetically-structured population dynamics and
formulated in terms of systems of coupled non-linear integro-differential
equations, that aims to catch these phenomena and to provide a predictive tool
for the tumour mass evolution and therapeutic effects. The outcomes of the
simulations show how the model is able to explain the impact of environmental
selection and therapies on the evolution of the mass, motivating observed
dynamics such as relapses and therapeutic failures. Furthermore it offers a
first hint for the development of therapies which can be adapted to overcome
problems of resistance and relapses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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