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Mammographic Features of Hidradenitis Suppurativa  [PDF]
Santo Maimone, Michelle D. McDonough
Open Journal of Radiology (OJRad) , 2012, DOI: 10.4236/ojrad.2012.24023
Abstract: Hidradenitis suppurativa is a chronic suppurative inflammation of the apocrine sweat glands. Axillary, inframammary, intermammary, and peri-areolar apocrine gland involvement may be visualized mammographically. Characteristic lesions tend to be round or oval, lucent, and smooth-bordered, with or without central densities. While diagnosis made purely via mammography is unlikely, having an awareness of this entity may prove useful in patient care in regards to proper utilization of both imaging and consultative resources.
Pancreatic Cancer Imaging: Which Method?
Santo E
JOP Journal of the Pancreas , 2004,
Abstract: Pancreatic cancer is the 10th most common malignancy and the 4th largest cancer killer in adults. Surgery offers the only chance of curing these patients. Complete surgical resection is associated with a 5-year survival rate of between 20 and 30%. The challenge is how to best select those patients for curative surgery. Early studies demonstrated excellent sensitivity of EUS in detecting pancreatic tumors in comparison to CT. Similarly, EUS showed an 85-94% accuracy rate for T staging and 70-80% accuracy rate for N staging. Later studies report on substantially less TN staging accuracy for EUS. Possible explanations and the problem of vascular involvement assessment by EUS will be provided. Considering the role of EUS in M staging and a comparison between EUS, MRI, and positron emission tomography, scanning will be presented. A diagnostic algorithm for the evaluation of patients with a suspected pancreatic mass will be offered, stressing the pivotal role of EUS.
Damage Spreading and Opinion Dynamics on Scale Free Networks
Santo Fortunato
Physics , 2004, DOI: 10.1016/j.physa.2004.09.007
Abstract: We study damage spreading among the opinions of a system of agents, subjected to the dynamics of the Krause-Hegselmann consensus model. The damage consists in a sharp change of the opinion of one or more agents in the initial random opinion configuration, supposedly due to some external factors and/or events. This may help to understand for instance under which conditions special shocking events or targeted propaganda are able to influence the results of elections. For agents lying on the nodes of a Barabasi-Albert network, there is a damage spreading transition at a low value epsilon_d of the confidence bound parameter. Interestingly, we find as well that there is some critical value epsilon_s above which the initial perturbation manages to propagate to all other agents.
Quality functions in community detection
Santo Fortunato
Physics , 2007, DOI: 10.1117/12.726703
Abstract: Community structure represents the local organization of complex networks and the single most important feature to extract functional relationships between nodes. In the last years, the problem of community detection has been reformulated in terms of the optimization of a function, the Newman-Girvan modularity, that is supposed to express the quality of the partitions of a network into communities. Starting from a recent critical survey on modularity optimization, pointing out the existence of a resolution limit that poses severe limits to its applicability, we discuss the general issue of the use of quality functions in community detection. Our main conclusion is that quality functions are useful to compare partitions with the same number of modules, whereas the comparison of partitions with different numbers of modules is not straightforward and may lead to ambiguities.
Community detection in graphs
Santo Fortunato
Physics , 2009, DOI: 10.1016/j.physrep.2009.11.002
Abstract: The modern science of networks has brought significant advances to our understanding of complex systems. One of the most relevant features of graphs representing real systems is community structure, or clustering, i. e. the organization of vertices in clusters, with many edges joining vertices of the same cluster and comparatively few edges joining vertices of different clusters. Such clusters, or communities, can be considered as fairly independent compartments of a graph, playing a similar role like, e. g., the tissues or the organs in the human body. Detecting communities is of great importance in sociology, biology and computer science, disciplines where systems are often represented as graphs. This problem is very hard and not yet satisfactorily solved, despite the huge effort of a large interdisciplinary community of scientists working on it over the past few years. We will attempt a thorough exposition of the topic, from the definition of the main elements of the problem, to the presentation of most methods developed, with a special focus on techniques designed by statistical physicists, from the discussion of crucial issues like the significance of clustering and how methods should be tested and compared against each other, to the description of applications to real networks.
The Krause-Hegselmann Consensus Model with Discrete Opinions
Santo Fortunato
Physics , 2004, DOI: 10.1142/S0129183104006479
Abstract: The consensus model of Krause and Hegselmann can be naturally extended to the case in which opinions are integer instead of real numbers. Our algorithm is much faster than the original version and thus more suitable for applications. For the case of a society in which everybody can talk to everybody else, we find that the chance to reach consensus is much higher as compared to other models; if the number of possible opinions Q<=7, in fact, consensus is always reached, which might explain the stability of political coalitions with more than three or four parties. For Q>7 the number S of surviving opinions is approximately the same independently of the size N of the population, as long as Q
Cluster Percolation and Critical Behaviour in Spin Models and SU(N) Gauge Theories
Santo Fortunato
Physics , 2002, DOI: 10.1088/0305-4470/36/15/304
Abstract: The critical behaviour of several spin models can be simply described as percolation of some suitably defined clusters, or droplets: the onset of the geometrical transition coincides with the critical point and the percolation exponents are equal to the thermal exponents. It is still unknown whether, given a model, one can define at all the droplets. In the cases where this is possible, the droplet definition depends in general on the specific model at study and can be quite involved. We propose here a simple general definition for the droplets: they are clusters obtained by joining nearest-neighbour spins of the same sign with some bond probability p_B, which is the minimal probability that still allows the existence of a percolating cluster at the critical temperature T_c. By means of lattice Monte Carlo simulations we find that this definition indeed satisfies the conditions required for the droplets, for many classical spin models, discrete and continuous, both in two and in three dimensions. In particular, our prescription allows to describe exactly the confinement-deconfinement transition of SU(N) gauge theories as Polyakov loop percolation.
Site Percolation and Phase Transitions in Two Dimensions
Santo Fortunato
Physics , 2002, DOI: 10.1103/PhysRevB.66.054107
Abstract: The properties of the pure-site clusters of spin models, i.e. the clusters which are obtained by joining nearest-neighbour spins of the same sign, are here investigated. In the Ising model in two dimensions it is known that such clusters undergo a percolation transition exactly at the critical point. We show that this result is valid for a wide class of bidimensional systems undergoing a continuous magnetization transition. We provide numerical evidence for discrete as well as for continuous spin models, including SU(N) lattice gauge theories. The critical percolation exponents do not coincide with the ones of the thermal transition, but they are the same for models belonging to the same universality class.
Universality of the Threshold for Complete Consensus for the Opinion Dynamics of Deffuant et al
Santo Fortunato
Physics , 2004, DOI: 10.1142/S0129183104006728
Abstract: In the compromise model of Deffuant et al., opinions are real numbers between 0 and 1 and two agents are compatible if the difference of their opinions is smaller than the confidence bound parameter \epsilon. The opinions of a randomly chosen pair of compatible agents get closer to each other. We provide strong numerical evidence that the threshold value of \epsilon above which all agents share the same opinion in the final configuration is 1/2, independently of the underlying social topology.
The Sznajd Consensus Model with Continuous Opinions
Santo Fortunato
Physics , 2004, DOI: 10.1142/S0129183105006917
Abstract: In the consensus model of Sznajd, opinions are integers and a randomly chosen pair of neighbouring agents with the same opinion forces all their neighbours to share that opinion. We propose a simple extension of the model to continuous opinions, based on the criterion of bounded confidence which is at the basis of other popular consensus models. Here the opinion s is a real number between 0 and 1, and a parameter \epsilon is introduced such that two agents are compatible if their opinions differ from each other by less than \epsilon. If two neighbouring agents are compatible, they take the mean s_m of their opinions and try to impose this value to their neighbours. We find that if all neighbours take the average opinion s_m the system reaches complete consensus for any value of the confidence bound \epsilon. We propose as well a weaker prescription for the dynamics and discuss the corresponding results.
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