1,721,179 research outputs found
La partecipazione associativa è ancora in cerca di autore: le sezioni unite tra progresso e regresso
No full textA Mathematical Study of the Influence of Hypoxia and Acidity on the Evolutionary Dynamics of Cancer
Full text linkHypoxia and acidity act as environmental stressors promoting selection for cancer cells with a more aggressive phenotype. As a result, a deeper theoretical understanding of the spatio-temporal processes that drive the adaptation of tumour cells to hypoxic and acidic microenvironments may open up new avenues of research in oncology and cancer treatment. We present a mathematical model to study the influence of hypoxia and acidity on the evolutionary dynamics of cancer cells in vascularised tumours. The model is formulated as a system of partial integro-differential equations that describe the phenotypic evolution of cancer cells in response to dynamic variations in the spatial distribution of three abiotic factors that are key players in tumour metabolism: oxygen, glucose and lactate. The results of numerical simulations of a calibrated version of the model based on real data recapitulate the eco-evolutionary spatial dynamics of tumour cells and their adaptation to hypoxic and acidic microenvironments. Moreover, such results demonstrate how nonlinear interactions between tumour cells and abiotic factors can lead to the formation of environmental gradients which select for cells with phenotypic characteristics that vary with distance from intra-tumour blood vessels, thus promoting the emergence of intra-tumour phenotypic heterogeneity. Finally, our theoretical findings reconcile the conclusions of earlier studies by showing that the order in which resistance to hypoxia and resistance to acidity arise in tumours depend on the ways in which oxygen and lactate act as environmental stressors in the evolutionary dynamics of cancer cells
Generalized focusing of time-lapse changes with applications to direct current and time-domain induced polarization inversions
Full text linkOften in geophysical monitoring experiments time-lapse inversion models vary too smoothly
with time, owing to the strong imprint of regularization. Several methods have been proposed
for focusing the spatiotemporal changes of the model parameters. In this study, we present two
generalizations of the minimum support norm, which favour compact time-lapse changes and
can be adapted to the specific problem requirements. Inversion results from synthetic direct
current resistivity models that mimic developing plumes show that the focusing scheme significantly improves size, shape and magnitude estimates of the time-lapse changes. Inversions
of the synthetic data also illustrate that the focused inversion gives robust results and that the
focusing settings are easily chosen. Inversions of full-decay time-domain induced polarization
(IP) field data from a CO2 monitoring injection experiment show that the focusing scheme
performs well for field data and inversions for all four Cole–Cole polarization parameters.
Our tests show that the generalized minimum support norms react in an intuitive and predictable
way to the norm settings, implying that they can be used in time-lapse experiments
for obtaining reliable and robust results
A phenotype-structured model to reproduce the avascular growth of a tumor and its interaction with the surrounding environment
Full text linkWe here propose a one-dimensional spatially explicit phenotype-structured model to analyze selected aspects of avascular tumor progression. In particular, our approach distinguishes viable and necrotic cell fractions. The metabolically active part of the disease is, in turn, differentiated according to a continuous trait, that identifies cell variants with different degrees of motility and proliferation potential. A parabolic partial differential equation (PDE) then governs the spatio-temporal evolution of the phenotypic distribution of active cells within the host tissue. In this respect, active tumor agents are allowed to duplicate, move upon haptotactic and pressure stimuli, and eventually undergo necrosis. The mutual influence between the emerging malignancy and its environment (in terms of molecular landscape) is implemented by coupling the evolution law of the viable tumor mass with a parabolic PDE for oxygen kinetics and a differential equation that accounts for local consumption of extracellular matrix (ECM) elements. The resulting numerical realizations reproduce tumor growth and invasion in a number scenarios that differ for cell properties (i.e., individual migratory behavior, duplication, and mutation potential) and environmental conditions (i.e., level of tissue oxygenation and homogeneity in the initial matrix profile). In particular, our simulations show that, in all cases, more mobile cell variants occupy the front edge of the tumor, whereas more proliferative clones are selected at more internal regions. A necrotic core constantly occupies the bulk of the mass due to nutrient deprivation. This work may eventually suggest some biomedical strategies to partially reduce tumor aggressiveness, i.e., to enhance necrosis of malignant tissue and to promote the presence of more proliferative cell phenotypes over more invasive ones
Valutazione di Differenti Quadripoli e Sequenze di Misura per Tomografie Elettriche in Contesti Industriali e Costieri
No full text
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
Advances in Microgeophysics for Engineering and Cultural Heritage
No full textA large number of unconventional investigations have been implemented, tested, and validated in the field of microgeophysics, with the aim being to solve specific diagnostic and/or monitoring problems regarding civil engineering and cultural heritage studies. The investigations were carried out using different tomographic 2D and 3D approaches as well as different energy sources, namely
sonic, ultrasonic and electromagnetic (radar) waves, electric potential fields, and infrared thermography. Many efforts have been made to modify instruments and procedures in order to improve the
resolution of the surveys as well as to greatly reduce the time of the measurements without any loss of information. The main new methodologies here discussed are the sonic imprint, the global tomographic
traveltime, the electrical resistivity tomography, and the control of external films (patinas) grown on stone monuments. The results seem to be very promising and suggest that it is the moment to dedicate
time and effort to this new branch of geophysics, so that these methodologies can be used even more to diagnose, monitor, and safeguard not only engineering buildings and large structures but also ancient monuments and cultural artifacts, like pottery, statues, etc.
Violenza sessuale in famiglia e diritto vivente
No full textL'autore affronta il delicato tema della violenza sessuale in famiglia, soprattutto alla luce di un panorama normativo decisamente inadeguato e delle forti incertezze giurisprudenziali che lo connotano.The author addresses the delicate issue of sexual violence in the family, especially in the light of a an inadequate regulatory landscape and the strong jurisprudential uncertainties that connote it
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