345 research outputs found
Strong-majority bootstrap percolation on regular graphs with low dissemination threshold
International audienceConsider the following model of strong-majority bootstrap percolation on a graph. Let r ≥ 1 be some integer, and p ∈ [0, 1]. Initially, every vertex is active with probability p, independently from all other vertices. Then, at every step of the process, each vertex v of degree deg(v) becomes active if at least (deg(v) + r)/2 of its neighbours are active. Given any arbitrarily small p > 0 and any integer r, we construct a family of d = d(p, r)-regular graphs such that with high probability all vertices become active in the end. In particular, the case r = 1 answers a question and disproves a conjecture of Rapaport, Suchan, Todinca and Verstraëte [38]
Thermodynamics of percolation in interacting systems
Interacting systems can be studied as the networks where nodes are system
units and edges denote correlated interactions. Although percolation on network
is a unified way to model the emergence and propagation of correlated
behaviours, it remains unknown how the dynamics characterized by percolation is
related to the thermodynamics of phase transitions. It is non-trivial to
formalize thermodynamics for most complex systems, not to mention calculating
thermodynamic quantities and verifying scaling relations during percolation. In
this work, we develop a formalism to quantify the thermodynamics of percolation
in interacting systems, which is rooted in a discovery that percolation
transition is a process for the system to lose the freedom degrees associated
with ground state configurations. We derive asymptotic formulas to accurately
calculate entropy and specific heat under our framework, which enables us to
detect phase transitions and demonstrate the Rushbrooke equality (i.e.,
) in six representative complex systems (e.g.,
Bernoulli and bootstrap percolation, classical and quantum synchronization,
non-linear oscillations with damping, and cellular morphogenesis). These
results suggest the general applicability of our framework in analyzing diverse
interacting systems and percolation processes
Cancer therapeutic potential of combinatorial immuno- and vaso-modulatory interventions
Currently, most of the basic mechanisms governing tumor-immune system
interactions, in combination with modulations of tumor-associated vasculature,
are far from being completely understood. Here, we propose a mathematical model
of vascularized tumor growth, where the main novelty is the modeling of the
interplay between functional tumor vasculature and effector cell recruitment
dynamics. Parameters are calibrated on the basis of different in vivo
immunocompromised Rag1-/- and wild-type (WT) BALB/c murine tumor growth
experiments. The model analysis supports that tumor vasculature normalization
can be a plausible and effective strategy to treat cancer when combined with
appropriate immuno-stimulations. We find that improved levels of functional
tumor vasculature, potentially mediated by normalization or stress alleviation
strategies, can provide beneficial outcomes in terms of tumor burden reduction
and growth control. Normalization of tumor blood vessels opens a therapeutic
window of opportunity to augment the antitumor immune responses, as well as to
reduce the intratumoral immunosuppression and induced-hypoxia due to vascular
abnormalities. The potential success of normalizing tumor-associated
vasculature closely depends on the effector cell recruitment dynamics and tumor
sizes. Furthermore, an arbitrary increase of initial effector cell
concentration does not necessarily imply a better tumor control. We evidence
the existence of an optimal concentration range of effector cells for tumor
shrinkage. Based on these findings, we suggest a theory-driven therapeutic
proposal that optimally combines immuno- and vaso-modulatory interventions
Diffuse and Localized Functional Dysconnectivity in Schizophrenia: a Bootstrapped Top-Down Approach
Schizophrenia (SZ) is a brain disorder leading to detached mind's normally
integrated processes. Hence, the exploration of the symptoms in relation to
functional connectivity (FC) had great relevance in the field. FC can be
investigated on different levels, going from global features to single edges
between regions, revealing diffuse and localized dysconnection patterns. In
this context, SZ is characterized by a diverse global integration with reduced
connectivity in specific areas of the Default Mode Network (DMN). However, the
assessment of FC presents various sources of uncertainty. This study proposes a
multi-level approach for more robust group-comparison. FC between 74 AAL brain
areas of 15 healthy controls (HC) and 12 SZ subjects were used. Multi-level
analyses and graph topological indexes evaluation were carried out by the
previously published SPIDER-NET tool. Robustness was augmented by bootstrapped
(BOOT) data and the stability was evaluated by removing one (RST1) or two
subjects (RST2). The DMN subgraph was evaluated, toegether with overall local
indexes and connection weights to enhance common activations/deactivations. At
a global level, expected trends were found. The robustness assessment tests
highlighted more stable results for BOOT compared to the direct data testing.
Conversely, significant results were found in the analysis at lower levels. The
DMN highlighted reduced connectivity and strength as well as increased
deactivation in the SZ group. At local level, 13 areas were found to be
significantly different (), highlighting a greater divergence in the
frontal lobe. These results were confirmed analyzing the negative edges,
suggesting inverted connectivity between prefronto-temporal areas. In
conclusion, multi-level analysis supported by BOOT is highly recommended,
especially when diffuse and localized dysconnections must be investigated in
limited samples.Comment: 28 pages, 8 figure
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