133,984 research outputs found
Estimating the epidemic risk using non-uniformly sampled contact data
Many datasets describing contacts in a population suffer from incompleteness
due to population sampling and underreporting of contacts. Data-driven
simulations of spreading processes using such incomplete data lead to an
underestimation of the epidemic risk, and it is therefore important to devise
methods to correct this bias. We focus here on a non-uniform sampling of the
contacts between individuals, aimed at mimicking the results of diaries or
surveys, and consider as case studies two datasets collected in different
contexts. We show that using surrogate data built using a method developed in
the case of uniform population sampling yields an improvement with respect to
the use of the sampled data but is strongly limited by the underestimation of
the link density in the sampled network. We put forward a second method to
build surrogate data that assumes knowledge of the density of links within one
of the groups forming the population. We show that it gives very good results
when the population is strongly structured, and discuss its limitations in the
case of a population with a weaker group structure. These limitations highlight
the interest of measurements using wearable sensors able to yield accurate
information on the structure and durations of contacts
Uncovering distinct protein-network topologies in heterogeneous cell populations
Background: Cell biology research is fundamentally limited by the number of intracellular components, particularly proteins, that can be co-measured in the same cell. Therefore, cell-to-cell heterogeneity in unmeasured proteins can lead to completely different observed relations between the same measured proteins. Attempts to infer such relations in a heterogeneous cell population can yield uninformative average relations if only one underlying biochemical network is assumed. To address this, we developed a method that recursively couples an iterative unmixing process with a Bayesian analysis of each unmixed subpopulation. Results: Our approach enables to identify the number of distinct cell subpopulations, unmix their corresponding observations and resolve the network structure of each subpopulation. Using simulations of the MAPK pathway upon EGF and NGF stimulations we assess the performance of the method. We demonstrate that the presented method can identify better than clustering approaches the number of subpopulations within a mixture of observations, thus resolving correctly the statistical relations between the proteins. Conclusions: Coupling the unmixing of multiplexed observations with the inference of statistical relations between the measured parameters is essential for the success of both of these processes. Here we present a conceptual and algorithmic solution to achieve such coupling and hence to analyze data obtained from a natural mixture of cell populations. As the technologies and necessity for multiplexed measurements are rising in the systems biology era, this work addresses an important current challenge in the analysis of the derived data.Fil: Wieczorek, Jakob. Universitat Dortmund; AlemaniaFil: Malik Sheriff, Rahuman S.. Institut Max Planck fur Molekulare Physiologie; Alemania. Imperial College London; Reino Unido. European Bioinformatics Institute. European Molecular Biology Laboratory; Reino UnidoFil: Fermin, Yessica. Universitat Dortmund; AlemaniaFil: Grecco, Hernan Edgardo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de FÃsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FÃsica de Buenos Aires; Argentina. Institut Max Planck fur Molekulare Physiologie; AlemaniaFil: Zamir, Eli. Institut Max Planck fur Molekulare Physiologie; AlemaniaFil: Ickstadt, Katja. Universitat Dortmund; Alemani
Epidemic risk from friendship network data: an equivalence with a non-uniform sampling of contact networks
Contacts between individuals play an important role in determining how
infectious diseases spread. Various methods to gather data on such contacts
co-exist, from surveys to wearable sensors. Comparisons of data obtained by
different methods in the same context are however scarce, in particular with
respect to their use in data-driven models of spreading processes. Here, we use
a combined data set describing contacts registered by sensors and friendship
relations in the same population to address this issue in a case study. We
investigate if the use of the friendship network is equivalent to a sampling
procedure performed on the sensor contact network with respect to the outcome
of simulations of spreading processes: such an equivalence might indeed give
hints on ways to compensate for the incompleteness of contact data deduced from
surveys. We show that this is indeed the case for these data, for a
specifically designed sampling procedure, in which respondents report their
neighbors with a probability depending on their contact time. We study the
impact of this specific sampling procedure on several data sets, discuss
limitations of our approach and its possible applications in the use of data
sets of various origins in data-driven simulations of epidemic processes
Spectral convergence in tapping and physiological fluctuations: coupling and independence of 1/f noise in the central and autonomic nervous systems.
When humans perform a response task or timing task repeatedly, fluctuations in measures of timing from one action to the next exhibit long-range correlations known as 1/f noise. The origins of 1/f noise in timing have been debated for over 20 years, with one common explanation serving as a default: humans are composed of physiological processes throughout the brain and body that operate over a wide range of timescales, and these processes combine to be expressed as a general source of 1/f noise. To test this explanation, the present study investigated the coupling vs. independence of 1/f noise in timing deviations, key-press durations, pupil dilations, and heartbeat intervals while tapping to an audiovisual metronome. All four dependent measures exhibited clear 1/f noise, regardless of whether tapping was synchronized or syncopated. 1/f spectra for timing deviations were found to match those for key-press durations on an individual basis, and 1/f spectra for pupil dilations matched those in heartbeat intervals. Results indicate a complex, multiscale relationship among 1/f noises arising from common sources, such as those arising from timing functions vs. those arising from autonomic nervous system (ANS) functions. Results also provide further evidence against the default hypothesis that 1/f noise in human timing is just the additive combination of processes throughout the brain and body. Our findings are better accommodated by theories of complexity matching that begin to formalize multiscale coordination as a foundation of human behavior
Elasticity sampling links thermodynamics to metabolic control
Metabolic networks can be turned into kinetic models in a predefined steady
state by sampling the reaction elasticities in this state. Elasticities for
many reversible rate laws can be computed from the reaction Gibbs free
energies, which are determined by the state, and from physically unconstrained
saturation values. Starting from a network structure with allosteric regulation
and consistent metabolic fluxes and concentrations, one can sample the
elasticities, compute the control coefficients, and reconstruct a kinetic model
with consistent reversible rate laws. Some of the model variables are manually
chosen, fitted to data, or optimised, while the others are computed from them.
The resulting model ensemble allows for probabilistic predictions, for
instance, about possible dynamic behaviour. By adding more data or tighter
constraints, the predictions can be made more precise. Model variants differing
in network structure, flux distributions, thermodynamic forces, regulation, or
rate laws can be realised by different model ensembles and compared by
significance tests. The thermodynamic forces have specific effects on flux
control, on the synergisms between enzymes, and on the emergence and
propagation of metabolite fluctuations. Large kinetic models could help to
simulate global metabolic dynamics and to predict the effects of enzyme
inhibition, differential expression, genetic modifications, and their
combinations on metabolic fluxes. MATLAB code for elasticity sampling is freely
available
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