2,533 research outputs found
A system of mobile agents to model social networks
We propose a model of mobile agents to construct social networks, based on a
system of moving particles by keeping track of the collisions during their
permanence in the system. We reproduce not only the degree distribution,
clustering coefficient and shortest path length of a large data base of
empirical friendship networks recently collected, but also some features
related with their community structure. The model is completely characterized
by the collision rate and above a critical collision rate we find the emergence
of a giant cluster in the universality class of two-dimensional percolation.
Moreover, we propose possible schemes to reproduce other networks of particular
social contacts, namely sexual contacts.Comment: Phys. Rev. Lett. (in press
Cadmium removal by Anabaena sp. ATCC 33047 immobilized in polyurethane foam
The nitrogen-fixing cyanobacterium Anabaena sp. ATCC 33047, which generates substantial amounts of exopolysaccharide, was immobilized by entrapment within the reticulate network of polyurethane foam discs. The immobilized Anabaena sp. system has been investigated as a potential biosorbent for the removal of cadmium from aqueous solutions. The results showed that it was a highly fast process, with 80 % of the adsorption taking place in the first 10 min, reaching full equilibrium in about 50 min. Data analysis indicated that the behaviour of the system accurately fits to a monolayer adsorption model (Langmuir isotherm). The maximal biosorption capacity determined for the immobilized Anabaena sp. system was as high as 162 mg Cd (II) per gram dry biomass. The outstanding properties established for immobilized Anabaena sp. in polyurethane foam underline the relevance of such a system as an alternative to current treatments of variety effluents or wastewater contaminated with cadmium.Peer reviewe
Networks based on collisions among mobile agents
We investigate in detail a recent model of colliding mobile agents [Phys.
Rev. Lett.~96, 088702], used as an alternative approach to construct evolving
networks of interactions formed by the collisions governed by suitable
dynamical rules. The system of mobile agents evolves towards a quasi-stationary
state which is, apart small fluctuations, well characterized by the density of
the system and the residence time of the agents. The residence time defines a
collision rate and by varying the collision rate, the system percolates at a
critical value, with the emergence of a giant cluster whose critical exponents
are the ones of two-dimensional percolation. Further, the degree and clustering
coefficient distributions and the average path length show that the network
associated with such a system presents non-trivial features which, depending on
the collision rule, enables one not only to recover the main properties of
standard networks, such as exponential, random and scale-free networks, but
also to obtain other topological structures. Namely, we show a specific example
where the obtained structure has topological features which characterize
accurately the structure and evolution of social networks in different
contexts, ranging from networks of acquaintances to networks of sexual
contacts.Comment: 12 pages, 17 figure
Do humans spread zoonotic enteric bacteria in Antarctica?
Reports of enteric bacteria in Antarctic wildlife have suggested its spread from people to seabirds and seals, but evidence is scarce and fragmentary. We investigated the occurrence of zoonotic enteric bacteria in seabirds across the Antarctic and subantarctic region; for comparison purposes, in addition to seabirds, poultry in a subantarctic island was also sampled. Three findings suggest reverse zoonosis from humans to seabirds: the detection of a zoonotic Salmonella serovar (ser. Enteritidis) and Campylobacter species (e.g. C. jejuni), typical of human infections; the resistance of C. lari isolates to ciprofloxacin and enrofloxacin, antibiotics commonly used in human and veterinary medicine; and most importantly, the presence of C. jejuni genotypes mostly found in humans and domestic animals but rarely or never found in wild birds so far. We also show further spread of zoonotic agents among Antarctic wildlife is facilitated by substantial connectivity among populations of opportunistic seabirds, notably skuas (Stercorarius). Our results highlight the need for even stricter biosecurity measures to limit human impacts in Antarctica.info:eu-repo/semantics/acceptedVersio
A Rapid, Low-Cost, and Scalable Technique for Printing State-of-the-Art Organic Field-Effect Transistors
In the last few years exciting advances have been achieved in developing printing techniques for organic semiconductors, and impressive mobility values have been reported for the resulting organic field-effect transistors (OFETs). However, not all these techniques are scalable and some of them require additional crystallization steps. This study reports on the fabrication of OFETs employing blends of four benchmark organic semiconductors with polystyrene and demonstrates that applying the same formulation and experimental conditions for printing them, highly reproducible and uniform crystalline films exhibiting high OFET performance are successfully achieved. It is noted that the mobility values achieved here are not the highest reported for the studied materials; however, they are state-of-the-art values and could be regarded as exceptional considering the low cost and fast speed of the fabrication process involved here.This work was mainly funded by the ERC StG 2012 306826 e GAMES and ERC PoC 2014 640120 LAB TECH projects. The authors also thank the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER BBN), the DGI (Spain) project BE WELL CTQ2013 40480 R, the Generalitat de Catalunya (2014 SGR 17) and the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV 2015 0496). The authors would like to thank the ICTS "NANBIOSIS", more specifically to the Nanotechnology Platform, unit of CIBER BBN at the Institute for Bioengineering of Catalonia (IBEC) for their assistance in ToF SIMS analyses. I. T. acknowledges FPU fellowship from the Ministery and the Materials Science PhD Program of Universitat Autònoma de Barcelona. F. G. D. P. thanks Universidad TĂ©cnica de Ambato and SecretarĂa de EducaciĂłn Superior, Ciencia, TecnologĂa e InnovaciĂłn for funding through a doctoral scholarship “Convocatoria abierta 2010”.Peer reviewe
Cancer, Warts, or Asymptomatic Infections: Clinical Presentation Matches Codon Usage Preferences in Human Papillomaviruses
Viruses rely completely on the hosts' machinery for translation of viral transcripts. However, for most viruses infecting humans, codon usage preferences (CUPrefs) do not match those of the host. Human papillomaviruses (HPVs) are a showcase to tackle this paradox: they present a large genotypic diversity and a broad range of phenotypic presentations, from asymptomatic infections to productive lesions and cancer. By applying phylogenetic inference and dimensionality reduction methods, we demonstrate first that genes in HPVs are poorly adapted to the average human CUPrefs, the only exception being capsid genes in viruses causing productive lesions. Phylogenetic relationships between HPVs explained only a small proportion of CUPrefs variation. Instead, the most important explanatory factor for viral CUPrefs was infection phenotype, as orthologous genes in viruses with similar clinical presentation displayed similar CUPrefs. Moreover, viral genes with similar spatiotemporal expression patterns also showed similar CUPrefs. Our results suggest that CUPrefs in HPVs reflect either variations in the mutation bias or differential selection pressures depending on the clinical presentation and expression timing. We propose that poor viral CUPrefs may be central to a trade-off between strong viral gene expression and the potential for eliciting protective immune response
Detection of Maternal and Fetal Stress from the Electrocardiogram with Self-Supervised Representation Learning
In the pregnant mother and her fetus, chronic prenatal stress results in
entrainment of the fetal heartbeat by the maternal heartbeat, quantified by the
fetal stress index (FSI). Deep learning (DL) is capable of pattern detection in
complex medical data with high accuracy in noisy real-life environments, but
little is known about DL's utility in non-invasive biometric monitoring during
pregnancy. A recently established self-supervised learning (SSL) approach to DL
provides emotional recognition from electrocardiogram (ECG). We hypothesized
that SSL will identify chronically stressed mother-fetus dyads from the raw
maternal abdominal electrocardiograms (aECG), containing fetal and maternal
ECG. Chronically stressed mothers and controls matched at enrolment at 32 weeks
of gestation were studied. We validated the chronic stress exposure by
psychological inventory, maternal hair cortisol and FSI. We tested two variants
of SSL architecture, one trained on the generic ECG features for emotional
recognition obtained from public datasets and another transfer-learned on a
subset of our data. Our DL models accurately detect the chronic stress exposure
group (AUROC=0.982+/-0.002), the individual psychological stress score
(R2=0.943+/-0.009) and FSI at 34 weeks of gestation (R2=0.946+/-0.013), as well
as the maternal hair cortisol at birth reflecting chronic stress exposure
(0.931+/-0.006). The best performance was achieved with the DL model trained on
the public dataset and using maternal ECG alone. The present DL approach
provides a novel source of physiological insights into complex multi-modal
relationships between different regulatory systems exposed to chronic stress.
The final DL model can be deployed in low-cost regular ECG biosensors as a
simple, ubiquitous early stress detection and monitoring tool during pregnancy.
This discovery should enable early behavioral interventions.Comment: ClinicalTrials.gov registration number: NCT03389178. Code repo:
https://code.engineering.queensu.ca/17ps21/ssl-ecg-v
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