Lyapunov exponent in the Vicsek model

The well-known Vicsek model describes the flock dynamics of self-propelled agents. Surprisingly, a direct measure of the chaotic behavior of such systems is missing. Here, we discuss the kinetic phase transition present in Vicsek systems in light of the largest Lyapunov exponent, which is numerically computed by following the dynamical evolution in tangent space. As discontinuities in the neighbors weighting factor hinder the computations, we propose a continuous form of the model. Our results about chaotic regime reinforce the idea that the Lyapunov exponent is also a phase transition indicator.Comment: 7 pages, 16 equations, 6 figure

Caenorhabditis elegans AGXT-1 is a mitochondrial and temperature-adapted ortholog of peroxisomal human AGT1: New insights into between-species divergence in glyoxylate metabolism

In humans, glyoxylate is an intermediary product of metabolism, whose concentration is finely balanced. Mutations in peroxisomal alanine:glyoxylate aminotransferase (hAGT1) cause primary hyperoxaluria type 1 (PH1), which results in glyoxylate accumulation that is converted to toxic oxalate. In contrast, glyoxylate is used by the nematode Caenorhabditis elegans through a glyoxylate cycle to by-pass the decarboxylation steps of the tricarboxylic acid cycle and thus contributing to energy production and gluconeogenesis from stored lipids. To investigate the differences in glyoxylate metabolism between humans and C. elegans and to determine whether the nematode might be a suitable model for PH1, we have characterized here the predicted nematode ortholog of hAGT1 (AGXT-1) and compared its molecular properties with those of the human enzyme. Both enzymes form active PLP-dependent dimers with high specificity towards alanine and glyoxylate, and display similar three-dimensional structures. Interestingly, AGXT-1 shows 5-fold higher activity towards the alanine/glyoxylate pair than hAGT1. Thermal and chemical stability of AGXT-1 is lower than that of hAGT1, suggesting temperature-adaptation of the nematode enzyme linked to the lower optimal growth temperature of C. elegans. Remarkably, in vivo experiments demonstrate the mitochondrial localization of AGXT-1 in contrast to the peroxisomal compartmentalization of hAGT1. Our results support the view that the different glyoxylate metabolism in the nematode is associated with the divergent molecular properties and subcellular localization of the alanine:glyoxylate aminotransferase activity.This work was supported by the Spanish Ministry of Science and Innovation (CSD2009-00088, BIO2012-34937 and SAF2011-23933), the Junta de Andalucia (P11-CTS-7187), and the Oxalosis and Hyperoxaluria Foundation (OHF2012 to B.C.). A.L.P. acknowledges a Ramon y Cajal research contract (RyC2009-04147) from the Spanish Ministry of Science and Innovation and the University of Granada. N. M-T acknowledges a FPI predoctoral fellowship from the Spanish Ministry of Science and Innovation. A.C.C. and N.T. were supported by the grant IOS-1353845 from the National Science Foundation (NSF). N.T. acknowledges the Tetelman Fellowship for International Research on the Sciences awarded by Yale University.Peer Reviewe

Parenting program versus telephone support for Mexican parents of children with acquired brain injury: A blind randomized controlled trial

Introduction: Acquired brain injury (ABI) during childhood typically causes behavior problems in the child and high levels of stress in the family. The aims of this study are: (1) to investigate the effectiveness and feasibility of a parenting intervention in improving behavior and self-regulation in Mexican children with ABI compared to telephone support; (2) to investigate the effectiveness and feasibility of a parenting intervention in improving parenting skills, parent self-efficacy and decreasing parental stress in parents of children with ABI compared to telephone support. Our secondary aims are (1) to explore the impact that parent characteristics have on the intervention outcomes; (2) to investi

Intracerebral infection with dengue-3 virus induces meningoencephalitis and behavioral changes that precede lethality in mice

<p>Abstract</p> <p>Background</p> <p>Dengue, one of the most important arboviral diseases of humans, may cause severe systemic disease. Although dengue virus (DENV) has been considered to be a non-neurotropic virus, dengue infection has been associated recently with a series of neurological syndromes, including encephalitis. In this work, we evaluated behavioral changes and inflammatory parameters in C57BL/6 mice infected with non-adapted dengue virus 3 (DENV-3) genotype I.</p> <p>Methods</p> <p>C57BL/6 mice received 4 × 10³PFU of DENV-3 by an intracranial route. We evaluated the trafficking of leukocytes in brain microvasculature using intravital microscopy, and evaluated chemokine and cytokine profiling by an ELISA test at 3 and 6 days post infection (p.i.). Furthermore, we determined myeloperoxidase activity and immune cell populations, and also performed histopathological analysis and immunostaining for the virus in brain tissue.</p> <p>Results</p> <p>All animals developed signs of encephalitis and died by day 8 p.i. Motor behavior and muscle tone and strength parameters declined at day 7 p.i. We observed increased leukocyte rolling and adhesion in brain microvasculature of infected mice at days 3 and 6 p.i. The infection was followed by significant increases in IFN-γ, TNF-α, CCL2, CCL5, CXCL1, and CXCL2. Histological analysis showed evidence of meningoencephalitis and reactive gliosis. Increased numbers of neutrophils, CD4⁺and CD8⁺T cells were detected in brain of infected animals, notably at day 6 p.i. Cells immunoreactive for anti-NS-3 were visualized throughout the brain.</p> <p>Conclusion</p> <p>Intracerebral infection with non-adapted DENV-3 induces encephalitis and behavioral changes that precede lethality in mice.</p

Previous tuberculosis disease as a risk factor for chronic obstructive pulmonary disease:a cross-sectional analysis of multicountry, population-based studies

Background Risk factors for COPD in high-income settings are well understood; however, less attention has been paid to contributors of COPD in low-income and middle-income countries (LMICs) such as pulmonary tuberculosis. We sought to study the association between previous tuberculosis disease and COPD by using pooled population-based cross-sectional data in 13 geographically diverse, low-resource settings. Methods We pooled six cohorts in 13 different LMIC settings, 6 countries and 3 continents to study the relationship between self-reported previous tuberculosis disease and lung function outcomes including COPD (defined as a postbronchodilator forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) below the lower limit of normal). Multivariable regressions with random effects were used to examine the association between previous tuberculosis disease and lung function outcomes. Results We analysed data for 12 396 participants (median age 54.0 years, 51.5% male); 332 (2.7%) of the participants had previous tuberculosis disease. Overall prevalence of COPD was 8.8% (range 1.7%-15.5% across sites). COPD was four times more common among those with previous tuberculosis disease (25.7% vs 8.3% without previous tuberculosis disease,

Disparities in dietary intake and physical activity patterns across the urbanization divide in the Peruvian Andes.

BACKGROUND: Diet and activity are thought to worsen with urbanization, thereby increasing risk of obesity and chronic diseases. A better understanding of dietary and activity patterns across the urbanization divide may help identify pathways, and therefore intervention targets, leading to the epidemic of overweight seen in low- and middle-income populations. Therefore, we sought to characterize diet and activity in a population-based study of urban and rural residents in Puno, Peru. METHODS: We compared diet and activity in 1005 (503 urban, 502 rural) participants via a lifestyle questionnaire. We then recruited an age- and sex-stratified random sample of 50 (25 urban, 25 rural) participants to further characterize diet and activity. Among these participants, diet composition and macronutrient intake was assessed by three non-consecutive 24-h dietary recalls and physical activity was assessed using Omron JH-720itc pedometers. RESULTS: Among 1005 participants, we found that urban residents consumed protein-rich foods, refined grains, sugary items, and fresh produce more frequently than rural residents. Among the 50 subsample participants, urban dwellers consumed more protein (47 vs. 39 g; p = 0.05), more carbohydrates (280 vs. 220 g; p = 0.03), more sugary foods (98 vs. 48 g, p = 0.02) and had greater dietary diversity (6.4 vs 5.8; p = 0.04). Rural subsample participants consumed more added salt (3.1 vs 1.7 g, p = 0.006) and tended to consume more vegetable oil. As estimated by pedometers, urban subsample participants burned fewer calories per day (191 vs 270 kcal, p = 0.03). CONCLUSIONS: Although urbanization is typically thought to increase consumption of fat, sugar and salt, our 24-h recall results were mixed and showed lower levels of obesity in rural Puno were not necessarily indicative of nutritionally-balanced diets. All subsample participants had relatively traditional lifestyles (low fat intake, limited consumption of processed foods and frequent walking) that may play a role in chronic disease outcomes in this region

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson