A Markov model for inferring flows in directed contact networks

Directed contact networks (DCNs) are a particularly flexible and convenient class of temporal networks, useful for modeling and analyzing the transfer of discrete quantities in communications, transportation, epidemiology, etc. Transfers modeled by contacts typically underlie flows that associate multiple contacts based on their spatiotemporal relationships. To infer these flows, we introduce a simple inhomogeneous Markov model associated to a DCN and show how it can be effectively used for data reduction and anomaly detection through an example of kernel-level information transfers within a computer.Comment: 12 page

Random walks and search in time-varying networks

The random walk process underlies the description of a large number of real world phenomena. Here we provide the study of random walk processes in time varying networks in the regime of time-scale mixing; i.e. when the network connectivity pattern and the random walk process dynamics are unfolding on the same time scale. We consider a model for time varying networks created from the activity potential of the nodes, and derive solutions of the asymptotic behavior of random walks and the mean first passage time in undirected and directed networks. Our findings show striking differences with respect to the well known results obtained in quenched and annealed networks, emphasizing the effects of dynamical connectivity patterns in the definition of proper strategies for search, retrieval and diffusion processes in time-varying network

Spectral centrality measures in complex networks

Complex networks are characterized by heterogeneous distributions of the degree of nodes, which produce a large diversification of the roles of the nodes within the network. Several centrality measures have been introduced to rank nodes based on their topological importance within a graph. Here we review and compare centrality measures based on spectral properties of graph matrices. We shall focus on PageRank, eigenvector centrality and the hub/authority scores of HITS. We derive simple relations between the measures and the (in)degree of the nodes, in some limits. We also compare the rankings obtained with different centrality measures.Comment: 11 pages, 10 figures, 5 tables. Final version published in Physical Review

Cytokeratin-19 positivity is acquired along cancer progression and does not predict cell origin in rat hepatocarcinogenesis

Although the expression of the stem/progenitor cell marker cytokeratin-19 (CK-19) has been associated with the worst clinical prognosis among all HCC subclasses, it is yet unknown whether its presence in HCC is the result of clonal expansion of hepatic progenitor cells (HPCs) or of de-differentiation of mature hepatocytes towards a progenitor-like cell phenotype. We addressed this question by using two rat models of hepatocarcinogenesis: the Resistant-Hepatocyte (R-H) and the Choline-methionine deficient (CMD) models. Our data indicate that the expression of CK-19 is not the result of a clonal expansion of HPCs (oval cells in rodents), but rather of a further step of preneoplastic hepatocytes towards a less differentiated phenotype and a more aggressive behavior. Indeed, although HCCs were positive for CK-19, very early preneoplastic foci (EPFs) were completely negative for this marker. While a few weeks later the vast majority of preneoplastic nodules remained CK-19 negative, a minority became positive, suggesting that CK-19 expression is the result of de-differentiation of a subset of EPFs, rather than a marker of stem/progenitor cells. Moreover, the gene expression profile of CK-19-negative EPFs clustered together with CK-19-positive nodules, but was clearly distinct from CK-19 negative nodules and oval cells. Conclusion: i) CK-19-positive cells are not involved in the early clonal expansion observed in rat hepatocarcinogenesis; ii) CK-19 expression arises in preneoplastic hepatocyte lesions undergoing malignant transformation; iii) CK-19 positivity in HCCs does not necessarily reflect the cell of origin of the tumor, but rather the plasticity of preneoplastic cells during the tumorigenic proces

Quantifying the effect of temporal resolution on time-varying networks

Time-varying networks describe a wide array of systems whose constituents and interactions evolve over time. They are defined by an ordered stream of interactions between nodes, yet they are often represented in terms of a sequence of static networks, each aggregating all edges and nodes present in a time interval of size Δt. In this work we quantify the impact of an arbitrary Δt on the description of a dynamical process taking place upon a time-varying network. We focus on the elementary random walk, and put forth a simple mathematical framework that well describes the behavior observed on real datasets. The analytical description of the bias introduced by time integrating techniques represents a step forward in the correct characterization of dynamical processes on time-varying graphs

Review of telemedicine use as it expands since the COVID-19 Pandemic

INTRODUCTION: As new technology advances and the world becomes increasingly connected, medical care and physician-patient interactions have changed. Telemedicine, though present in different forms for many decades, has grown, and its use is changing at a faster-than-ever pace. The COVID-19 pandemic highlighted the utility of different telemedicine platforms and has led to an expansion in its capabilities. OBJECTIVES: To explore the evolution of telemedicine, its multiple functions, and how this technology has continued to develop since the COVID-19 pandemic in various medical specialties. METHODS: PubMed was used to assess published studies that either incorporated telehealth resources in their research or evaluated the efficacy of telehealth in different specialties of medicine. Search terms used were “telehealth”, “telemedicine”, and “efficacy”. Additional keywords of “neuropathic pain”, “pulmonology” or “respiratory”, “critical care” or “intensive care”, and “dermatology” were used when exploring specific specialties of pain management, pulmonology, critical care, and dermatology, respectively. Medical specialties assessed were Anesthesiology and Pain Management, Dermatology, Cardiology, Nutrition and Diabetes Management, Pulmonology, Psychiatry, and Critical Care. Studies demonstrating various use of telehealth methods were selected from studies both before 2019 and after 2020 to compare telemedicine capabilities prior to the COVID-19 pandemic to after the COVID-19 crisis. RESULTS: Through this literature analysis, telemedicine has been shown to provide high levels of patient satisfaction, efficacy of treatment, and increased access to medical providers by patients. It was also found that different procedures of telemedicine are more effective in certain specialties than others, requiring the integration of specific technologies depending on the treatment process. Some pre-COVID-19 studies demonstrated that the use of telemedicine was not as effective as in-person care, showing that not all methods of telemedicine are equally effective in all specialties or for all patient-care plans. CONCLUSION: Literature has shown effectiveness in implementation of telemedicine across many specialties in a variety of clinical settings, disease pathologies, and patient-care plans. Although widely established, some studies show unsuccessful use of telehealth technologies. There is a need for further research to find the best tools for each specialty and disease treatment plan so that optimal practices incorporating telemedicine into patient care can be identified. Future studies should also investigate practices to ensure equitable access to telemedicine amongst all patient populations

Whitening Optical Effect of New Chewing Gums

Background: Today, many treatments are available to enhance the color of teeth, but they require a few days to weeks to deliver this effect. Objective: To evaluate the instantaneous optical whitening effect of two new sugar-free chewing gums and one dentifrice of proven efficacy versus one placebo chewing gum. Methods: This was a single-blind, parallel trial. 424 participants entered the study and were randomly allocated to four groups. They received a personal silicone mask with a calibrated hole at one upper incisor to apply a dental colorimeter. The tools tested were chewing-gum containing indigotine (E132-FD&C Blue 2) and spirulina, chewing-gum containing only spirulina, chewing-gum placebo, and dentifrice containing Blue Covarine. Vita® Easyshade scored the tooth color, and the WIO and WID whiteness indexes were calculated. For chewing gums, the color of the teeth was scored before the assumption and after 2’30” of mastication. For dentifrice, participants brushed for 1’30”, then rinsed, and the color was scored before brushing and after 2’30”. Statistical analysis was performed by ANOVA and Tukey post-hoc. Results: The two experimental whitening chewing gums and the dentifrice significantly increased the WIO and the WID indexes from the baselines (p<0.001). Moreover, their effects were statistically greater than those reported for the placebo chewing gum (p<0.05) but not significatively different among them (p=NS). Conclusion: All the tested whitening tools showed an instant optical whitening perception. Further studies are required to assess the intensity of the effect over a prolonged time to meet the people's request for fast whitening tools

Contagion dynamics in time-varying metapopulation networks

The metapopulation framework is adopted in a wide array of disciplines to describe systems of well separated yet connected subpopulations. The subgroups or patches are often represented as nodes in a network whose links represent the migration routes among them. The connections have been so far mostly considered as static, but in general evolve in time. Here we address this case by investigating simple contagion processes on time-varying metapopulation networks. We focus on the SIR process and determine analytically the mobility threshold for the onset of an epidemic spreading in the framework of activity-driven network models. We find profound differences from the case of static networks. The threshold is entirely described by the dynamical parameters defining the average number of instantaneously migrating individuals and does not depend on the properties of the static network representation. Remarkably, the diffusion and contagion processes are slower in time-varying graphs than in their aggregated static counterparts, the mobility threshold being even two orders of magnitude larger in the first case. The presented results confirm the importance of considering the time-varying nature of complex networks

Damage detection via shortest-path network sampling

Large networked systems are constantly exposed to local damages and failures that can alter their functionality. The knowledge of the structure of these systems is, however, often derived through sampling strategies whose effectiveness at damage detection has not been thoroughly investigated so far. Here, we study the performance of shortest-path sampling for damage detection in large-scale networks. We define appropriate metrics to characterize the sampling process before and after the damage, providing statistical estimates for the status of nodes (damaged, not damaged). The proposed methodology is flexible and allows tuning the trade-off between the accuracy of the damage detection and the number of probes used to sample the network. We test and measure the efficiency of our approach considering both synthetic and real networks data. Remarkably, in all of the systems studied, the number of correctly identified damaged nodes exceeds the number of false positives, allowing us to uncover the damage precisely

A large ongoing outbreak of hepatitis A predominantly affecting young males in Lazio, Italy; August 2016 - March 2017

The hepatitis A virus (HAV) is mainly transmitted through the faecal-oral route. In industrialized countries HAV infection generally occurs as either sporadic cases in travelers from endemic areas, local outbreak within closed/semi-closed population and as foodborne community outbreak. Recently, an increasing number of HAV infection clusters have been reported among young men-who-have-sex-with-men (MSM). The Lazio Regional Service for the epidemiology and control for infectious diseases (SeRESMI) has noticed an increase of acute hepatitis A (AHA) since September 2016. Temporal analysis carried out with a discrete Poisson model using surveillance data between January 2016 and March 2017 evidenced an ongoing outbreak of AHA that started at the end of August. Molecular investigation carried out on 130 out of 513 cases AHA reported until March 2017 suggests that this outbreak is mainly supported by an HAV variant which is currently spreading within MSM communities across Europe (VRD_521_2016). The report confirms that AHA is an emerging issue among MSM. In addition through the integration of standard (case based) surveillance with molecular investigation we could discriminate, temporally concomitant but epidemiologically unrelated, clusters due to different HAV variants. As suggested by the WHO, in countries with low HAV circulation, vaccination programmes should be tailored on the local epidemiological patterns to prevent outbreaks among high risk groups and eventual spillover of the infection in the general population