Flow of temporal network properties under local aggregation and time shuffling: a tool for characterizing, comparing and classifying temporal networks

Although many tools have been developed and employed to characterize temporal networks, the issue of how to compare them remains largely open. It depends indeed on what features are considered as relevant, and on the way the differences in these features are quantified. In this paper, we propose to characterize temporal networks through their behaviour under general transformations that are local in time: (i) a local time shuffling, which destroys correlations at time scales smaller than a given scale $b$, while preserving large time scales, and (ii) a local temporal aggregation on time windows of length $n$. By varying $b$ and $n$, we obtain a flow of temporal networks, and flows of observable values, which encode the phenomenology of the temporal network on multiple time scales. We use a symbolic approach to summarize these flows into labels (strings of characters) describing their trends. These labels can then be used to compare temporal networks, validate models, or identify groups of networks with similar labels. Our procedure can be applied to any temporal network and with an arbitrary set of observables, and we illustrate it on an ensemble of data sets describing face-to-face interactions in various contexts, including both empirical and synthetic data

From temporal network data to the dynamics of social relationships

Networks are well-established representations of social systems, and temporal networks are widely used to study their dynamics. Temporal network data often consist in a succession of static networks over consecutive time windows whose length, however, is arbitrary, not necessarily corresponding to any intrinsic timescale of the system. Moreover, the resulting view of social network evolution is unsatisfactory: short time windows contain little information, whereas aggregating over large time windows blurs the dynamics. Going from a temporal network to a meaningful evolving representation of a social network therefore remains a challenge. Here we introduce a framework to that purpose: transforming temporal network data into an evolving weighted network where the weights of the links between individuals are updated at every interaction. Most importantly, this transformation takes into account the interdependence of social relationships due to the finite attention capacities of individuals: each interaction between two individuals not only reinforces their mutual relationship but also weakens their relationships with others. We study a concrete example of such a transformation and apply it to several data sets of social interactions. Using temporal contact data collected in schools, we show how our framework highlights specificities in their structure and temporal organization. We then introduce a synthetic perturbation into a data set of interactions in a group of baboons to show that it is possible to detect a perturbation in a social group on a wide range of timescales and parameters. Our framework brings new perspectives to the analysis of temporal social networks

Modeling framework unifying contact and social networks

International audienceTemporal networks of face-to-face interactions between individuals are useful proxies of the dynamics of social systems on fast time scales. Several empirical statistical properties of these networks have been shown to be robust across a large variety of contexts. In order to better grasp the role of various mechanisms of social interactions in the emergence of these properties, models in which schematic implementations of such mechanisms can be carried out have proven useful. Here, we put forward a new framework to model temporal networks of human interactions, based on the idea of a co-evolution and feedback between (i) an observed network of instantaneous interactions and (ii) an underlying unobserved social bond network: social bonds partially drive interaction opportunities, and in turn are reinforced by interactions and weakened or even removed by the lack of interactions. Through this co-evolution, we also integrate in the model well-known mechanisms such as triadic closure, but also the impact of shared social context and non-intentional (casual) interactions, with several tunable parameters. We then propose a method to compare the statistical properties of each version of the model with empirical face-to-face interaction data sets, to determine which sets of mechanisms lead to realistic social temporal networks within this modeling framework

Should Human Factors/Ergonomics Go to Therapy?

One does not have to look far to see the increasing role of human factors/ergonomics (HF/E

Effect of pasteurization on human milk digestion as simulated in an in vitro dynamic system

Human milk is the ideal food for infant nutrition and optimal growth. This is especially true for preterm neonates that are preferentially fed donor milk when their own mother milk is not available. For sanitary reasons, donor milk is pasteurized. This may have structural and biochemical consequences on the maternal milk emulsion and affect digestive kinetics. This has been rarely investigated. Thus that was the aim of our study. Mature human milk was collected over 2 days and stored at +4°C. Half of it was digested as is (fresh milk). The other half was frozen (-20°C, 5 weeks) and pasteurized (62.5°C, 30 min) prior digestion. An in vitro dynamic system was used to simulate the gastric and intestinal digestion phases of a 1-month old newborn. Structural changes of digested samples were evaluated by confocal microscopy and laser light scattering. Proteolysis and lipolysis were monitored over 180 min. Hydrolysis kinetics were followed by SDS-PAGE and Thin-Layer Chromatography methods, followed by densitometry for semi-quantitative estimations. Pasteurization impacted the emulsion structure by increasing the protein susceptibility to acid aggregation especially on the milk fat globule membrane (Fig. 1). In the gastric compartment, we observed a faster hydrolysis of caseins (κ, β) and lactoferrin in pasteurized milk than in fresh milk (X 2 at 30 min). At 120 min, virtually all proteins were digested in pasteurized milk, whereas approximately 55% of proteins were undigested in fresh milk. In the intestinal phase, most proteins were digested during the first 30 min. Lactoferrin was more resistant in fresh milk than in pasteurized milk. Similarly, lipids were digested faster in pasteurized than in fresh milk, but to a lesser extent than proteins. These results demonstrate that pasteurization increases the rate of proteolysis and lipolysis. The physiologic and metabolic impacts remain unknown, especially in newborns exclusively fed pasteurized milk

Electrofishing in streams of low water conductivity but high biodiversity value: Challenges, limits and perspectives

International audienceElectrofishing in streams of low water conductivity has technical limitations leading to the widespread use of poison fishing. In theory, provided a high enough voltage gradient can be created in water, electrofishing should be possible in all but the lowest of conductivities (<10 µS/cm). Using custom‐made equipment delivering up to 1,500 V DC, tests were carried out in French Guiana on 27 streams with water conductivity as low as 16 µS/cm. Approximately 5,800 fish of 93 species were captured, with an electrofishing mortality rate of 1.83%. Poison treatments were used within enclosed sections to assess how efficient multiple pass electrofishing removal is when assessing species richness and population number. The Chao II estimator on 2 electrofishing passes gave the best results for species richness, but rare species can elude electrofishing. Estimates of total fish abundance (i.e. all species pooled) were possible with the use of depletion models. Capture efficiencies by species were highly biased, however, and abundance could be underestimated for the most difficult species to catch. These results show that with the right equipment and settings, electrofishing can be an efficient alternative to poison fishing surveys in small tropical streams of low water conductivity but high biodiversity valu

Effect of pasteurization on human milk digestion as simulated in an in vitro dynamic system

Human milk is the ideal food for infant nutrition and optimal growth. This is especially true for preterm neonates that are preferentially fed donor milk when their own mother milk is not available. For sanitary reasons, donor milk is pasteurized. This may have structural and biochemical consequences on the maternal milk emulsion and affect digestive kinetics. This has been rarely investigated. Thus that was the aim of our study. Mature human milk was collected over 2 days and stored at +4°C. Half of it was digested as is (fresh milk). The other half was frozen (-20°C, 5 weeks) and pasteurized (62.5°C, 30 min) prior digestion. An in vitro dynamic system was used to simulate the gastric and intestinal digestion phases of a 1-month old newborn. Structural changes of digested samples were evaluated by confocal microscopy and laser light scattering. Proteolysis and lipolysis were monitored over 180 min. Hydrolysis kinetics were followed by SDS-PAGE and Thin-Layer Chromatography methods, followed by densitometry for semi-quantitative estimations. Pasteurization impacted the emulsion structure by increasing the protein susceptibility to acid aggregation especially on the milk fat globule membrane (Fig. 1). In the gastric compartment, we observed a faster hydrolysis of caseins (κ, β) and lactoferrin in pasteurized milk than in fresh milk (X 2 at 30 min). At 120 min, virtually all proteins were digested in pasteurized milk, whereas approximately 55% of proteins were undigested in fresh milk. In the intestinal phase, most proteins were digested during the first 30 min. Lactoferrin was more resistant in fresh milk than in pasteurized milk. Similarly, lipids were digested faster in pasteurized than in fresh milk, but to a lesser extent than proteins. These results demonstrate that pasteurization increases the rate of proteolysis and lipolysis. The physiologic and metabolic impacts remain unknown, especially in newborns exclusively fed pasteurized milk

Effect of pasteurization on human milk digestion as simulated in an in vitro dynamic system

Human milk is the ideal food for infant nutrition and optimal growth. This is especially true for preterm neonates that are preferentially fed donor milk when their own mother milk is not available. For sanitary reasons, donor milk is pasteurized. This may have structural and biochemical consequences on the maternal milk emulsion and affect digestive kinetics. This has been rarely investigated. Thus that was the aim of our study. Mature human milk was collected over 2 days and stored at +4°C. Half of it was digested as is (fresh milk). The other half was frozen (-20°C, 5 weeks) and pasteurized (62.5°C, 30 min) prior digestion. An in vitro dynamic system was used to simulate the gastric and intestinal digestion phases of a 1-month old newborn. Structural changes of digested samples were evaluated by confocal microscopy and laser light scattering. Proteolysis and lipolysis were monitored over 180 min. Hydrolysis kinetics were followed by SDS-PAGE and Thin-Layer Chromatography methods, followed by densitometry for semi-quantitative estimations. Pasteurization impacted the emulsion structure by increasing the protein susceptibility to acid aggregation especially on the milk fat globule membrane (Fig. 1). In the gastric compartment, we observed a faster hydrolysis of caseins (κ, β) and lactoferrin in pasteurized milk than in fresh milk (X 2 at 30 min). At 120 min, virtually all proteins were digested in pasteurized milk, whereas approximately 55% of proteins were undigested in fresh milk. In the intestinal phase, most proteins were digested during the first 30 min. Lactoferrin was more resistant in fresh milk than in pasteurized milk. Similarly, lipids were digested faster in pasteurized than in fresh milk, but to a lesser extent than proteins. These results demonstrate that pasteurization increases the rate of proteolysis and lipolysis. The physiologic and metabolic impacts remain unknown, especially in newborns exclusively fed pasteurized milk

Effect of pasteurization on human milk digestion as simulated in an in vitro dynamic system

Human milk is the ideal food for infant nutrition and optimal growth. This is especially true for preterm neonates that are preferentially fed donor milk when their own mother milk is not available. For sanitary reasons, donor milk is pasteurized. This may have structural and biochemical consequences on the maternal milk emulsion and affect digestive kinetics. This has been rarely investigated. Thus that was the aim of our study. Mature human milk was collected over 2 days and stored at +4°C. Half of it was digested as is (fresh milk). The other half was frozen (-20°C, 5 weeks) and pasteurized (62.5°C, 30 min) prior digestion. An in vitro dynamic system was used to simulate the gastric and intestinal digestion phases of a 1-month old newborn. Structural changes of digested samples were evaluated by confocal microscopy and laser light scattering. Proteolysis and lipolysis were monitored over 180 min. Hydrolysis kinetics were followed by SDS-PAGE and Thin-Layer Chromatography methods, followed by densitometry for semi-quantitative estimations. Pasteurization impacted the emulsion structure by increasing the protein susceptibility to acid aggregation especially on the milk fat globule membrane (Fig. 1). In the gastric compartment, we observed a faster hydrolysis of caseins (κ, β) and lactoferrin in pasteurized milk than in fresh milk (X 2 at 30 min). At 120 min, virtually all proteins were digested in pasteurized milk, whereas approximately 55% of proteins were undigested in fresh milk. In the intestinal phase, most proteins were digested during the first 30 min. Lactoferrin was more resistant in fresh milk than in pasteurized milk. Similarly, lipids were digested faster in pasteurized than in fresh milk, but to a lesser extent than proteins. These results demonstrate that pasteurization increases the rate of proteolysis and lipolysis. The physiologic and metabolic impacts remain unknown, especially in newborns exclusively fed pasteurized milk

Validation and comparison of simple noninvasive indexes for predicting liver fibrosis in HIV-HCV-coinfected patients: ANRS CO3 Aquitaine cohort.: Non invasive fibrosis indexes in HIV-HCV coinfected patients

International audienceBACKGROUND: Although an increasing number of noninvasive fibrosis markers are available in HCV-monoinfected patients, data on the performance of these tests in HIV-HCV-coinfected patients are lacking. OBJECTIVE: To assess the diagnostic performance for predicting hepatic fibrosis stage of four simple and inexpensive noninvasive indexes (FIB-4, APRI, Forns, and platelet count) in HIV-HCV-coinfected patients. METHODS: Two hundred consecutive HIV-HCV-coinfected patients from the ANRS-CO3 Aquitaine cohort who underwent liver biopsy were studied. Fibrosis stage was assessed according to Metavir scoring system by a single pathologist unaware of the data of the patients. Diagnostic performances were assessed by measuring the areas under the receiver operating characteristic curves (AUROC) and the percentage of patients correctly identified (PCI). RESULTS: For predicting significant fibrosis (F > or = 2), APRI, Forns index, and FIB-4 had AUROCS of 0.77, 0.75, and 0.79, with 39%, 25%, and 70% of PCI, respectively. For predicting severe fibrosis (F > or = 3), FIB-4 had AUROC of 0.77 with 56% of PCI. For predicting cirrhosis (F4), FIB-4, APRI, and platelet count had AUROCs of 0.80, 0.79, and 0.78, with 59%, 60%, and 76% of PCI, respectively. Overall, diagnostic performances of the different indexes did not differ significantly for both significant fibrosis and cirrhosis. CONCLUSION: The use of these noninvasive indexes could save liver biopsies in up to 56-76% of cases for the prediction of severe fibrosis-cirrhosis. However, given the high percentage of misclassified cases for significant fibrosis, such indexes do not appear currently suitable for use in clinical practice in HIV-HCV-coinfected patients