Nonlinear oscillatory mixing in the generalized Landau scenario

We present a set of phase-space portraits illustrating the extraordinary oscillatory possibilities of the dynamical systems through the so-called generalized Landau scenario. In its simplest form the scenario develops in N dimensions around a saddle-node pair of fixed points experiencing successive Hopf bifurcations up to exhausting their stable manifolds and generating N-1 different limit cycles. The oscillation modes associated with these cycles extend over a wide phase-space region by mixing ones within the others and by affecting both the transient trajectories and the periodic orbits themselves. A mathematical theory covering the mode-mixing mechanisms is lacking, and our aim is to provide an overview of their main qualitative features in order to stimulate research on it.Peer ReviewedPostprint (author's final draft

N-dimensional dynamical systems exploiting instabilities in full

We report experimental and numerical results showing how certain N-dimensional dynamical systems are able to exhibit complex time evolutions based on the nonlinear combination of N-1 oscillation modes. The experiments have been done with a family of thermo-optical systems of effective dynamical dimension varying from 1 to 6. The corresponding mathematical model is an N-dimensional vector field based on a scalar-valued nonlinear function of a single variable that is a linear combination of all the dynamic variables. We show how the complex evolutions appear associated with the occurrence of successive Hopf bifurcations in a saddle-node pair of fixed points up to exhaust their instability capabilities in N dimensions. For this reason the observed phenomenon is denoted as the full instability behavior of the dynamical system. The process through which the attractor responsible for the observed time evolution is formed may be rather complex and difficult to characterize. Nevertheless, the well-organized structure of the time signals suggests some generic mechanism of nonlinear mode mixing that we associate with the cluster of invariant sets emerging from the pair of fixed points and with the influence of the neighboring saddle sets on the flow nearby the attractor. The generation of invariant tori is likely during the full instability development and the global process may be considered as a generalized Landau scenario for the emergence of irregular and complex behavior through the nonlinear superposition of oscillatory motion

Nutritional quality of Vidal grass (Bothriochloa saccharoides) under dry tropical conditions

P?ginas 51-55Recurso Electr?nicoEste articulo contiene informaci?n acerca del pasto Vidal (Botriochloa saccharoides), gram?nea poco estudiada y que posee grandes cualidades a nivel nutricional y productivo tanto en monocultivo como en asociaci?n con especies arb?reas. Durante el desarrollo de esta investigaci?n se evaluaron las caracter?sticas de calidad nutricional del pasto Vidal durante sus diferentes etapas fenol?gicas (germinaci?n, vegetativa, reproductiva y senescencia). Para ello se estableci? una parcela en la granja ?CURDN? (Centro Universitario Regional del Norte del Tolima) ubicada en el municipio de Armero Guayabal. El ensayo fue desarrollado con el objetivo de determinar las caracter?sticas nutricionales m?s relevantes durante el desarrollo del ciclo del pasto Vidal. Seg?n los resultados obtenidos el pasto Botriochloa saccharoides present? un ciclo fenol?gico de 137 d?as, tiempo en el cual se observaron las fases de germinaci?n, prefloraci?n, floraci?n y senescencia a los 37, 91, 114 y 128 d?as respectivamente. El tiempo ideal para el primer pastoreo es aproximadamente a los 91 d?as etapa en la cual el pasto est? en estado de prefloraci?n con una PC de 5,24%; DIVMS 54,21%; 45,8% de FDA y 8,3% de lignina.ABSTRACT. This article contains information about Vidal grass (Botriochloa saccharoides) , which has been little studied although it has good nutritional and productive qualities as much in single-crop farming as in association with arboreal species. Throughout this project, the Characteristics of nutritional quality of Vidal grass were evaluated during their different stages of development (germination, vegetative, reproductive and senescence,). Then, an experimental plot was sown in the ?CURDN? farm (Centro Universitario Regional del Norte del Tolima), located in the municipality of Armero - Guayabal. According to the results obtained, the Botriochloa saccharoides grass presented a cycle of 137 days. The germination, vegetative, reproductive and senescence phases could be observed at the 37th , 91st , 114th and 128th days, respectively. The ideal time for the first harvest is immediately after the first stage is over (91 days), stage in which the grass has a CP of 5,24%; DMIVD 54,21%; 72,1% of ADF and 8,3% lignin

FGF23-klotho axis as predictive factors of fractures in type 2 diabetics with early chronic kidney disease

Background: The aim of our study was to evaluate the relevance of FGF23-klotho axis in the predisposition for bone fractures in type 2 diabetic patients with early chronic kidney disease. Methods: In a prospective study we included 126 type 2 diabetic patients with CKD stages 2-3 (from 2010 to 2017). We used descriptive statistics, ANOVA and chi-square test. Our population was divided into two groups according to the occurrence of a bone fracture event or not, and the groups were compared considering several biological and laboratorial parameters. We employed a multiple regression model to identify risk factors for bone fracture events and hazard ratios (HR) were calculated using a backward stepwise likelihood ratio (LR) Cox regression. Results: Patients with a fracture event displayed higher levels of FGF-23, Phosphorus, PTH, TNF-alpha, OxLDL, HOMA-IR, calcium x phosphorus product and ACR and lower levels of Osteocalcin, alpha-Klotho, 25(OH)D3 and eGFR compared with patients without a fracture event (p < 0.001). The number of patients with a fracture event was higher than expected within inclining CKD stages (chi 2, p = 0.06). The occurrence of fracture and the levels of TNF-alpha, klotho, 25(OH)D3 and OxLDL were found to predict patient entry into RRT (p < 0.05). Age, osteocalcin, alpha-Klotho and FGF-23 independently influenced the occurrence of bone fracture (p < 0.05). Conclusions: alpha-Klotho and FGF-23 levels may have a good clinical use as biomarkers to predict the occurrence of fracture events. (C) 2019 Elsevier Inc. All rights reserved.info:eu-repo/semantics/publishedVersio

A Dynamic Model of Interactions of Ca^(2+), Calmodulin, and Catalytic Subunits of Ca^(2+)/Calmodulin-Dependent Protein Kinase II

During the acquisition of memories, influx of Ca^(2+) into the postsynaptic spine through the pores of activated N-methyl-D-aspartate-type glutamate receptors triggers processes that change the strength of excitatory synapses. The pattern of Ca^(2+) influx during the first few seconds of activity is interpreted within the Ca^(2+)-dependent signaling network such that synaptic strength is eventually either potentiated or depressed. Many of the critical signaling enzymes that control synaptic plasticity, including Ca^(2+)/calmodulin-dependent protein kinase II (CaMKII), are regulated by calmodulin, a small protein that can bind up to 4 Ca^(2+) ions. As a first step toward clarifying how the Ca^(2+)-signaling network decides between potentiation or depression, we have created a kinetic model of the interactions of Ca^(2+), calmodulin, and CaMKII that represents our best understanding of the dynamics of these interactions under conditions that resemble those in a postsynaptic spine. We constrained parameters of the model from data in the literature, or from our own measurements, and then predicted time courses of activation and autophosphorylation of CaMKII under a variety of conditions. Simulations showed that species of calmodulin with fewer than four bound Ca^(2+) play a significant role in activation of CaMKII in the physiological regime, supporting the notion that processing ofCa^(2+) signals in a spine involves competition among target enzymes for binding to unsaturated species of CaM in an environment in which the concentration of Ca^(2+) is fluctuating rapidly. Indeed, we showed that dependence of activation on the frequency of Ca^(2+) transients arises from the kinetics of interaction of fluctuating Ca^(2+) with calmodulin/CaMKII complexes. We used parameter sensitivity analysis to identify which parameters will be most beneficial to measure more carefully to improve the accuracy of predictions. This model provides a quantitative base from which to build more complex dynamic models of postsynaptic signal transduction during learning

Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens

We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged. © 2013 Lombardo et al

Loss of AMP-activated protein kinase alpha 2 subunit in mouse beta-cells impairs glucose-stimulated insulin secretion and inhibits their sensitivity to hypoglycaemia

AMPK (AMP-activated protein kinase) signalling plays a key role in whole-body energy homoeostasis, although its precise role in pancreatic β-cell function remains unclear. In the present stusy, we therefore investigated whether AMPK plays a critical function in β-cell glucose sensing and is required for the maintenance of normal glucose homoeostasis. Mice lacking AMPKα2 in β-cells and a population of hypothalamic neurons (RIPCreα2KO mice) and RIPCreα2KO mice lacking AMPKα1 (α1KORIPCreα2KO) globally were assessed for whole-body glucose homoeostasis and insulin secretion. Isolated pancreatic islets from these mice were assessed for glucose-stimulated insulin secretion and gene expression changes. Cultured β-cells were examined electrophysiologically for their electrical responsiveness to hypoglycaemia. RIPCreα2KO mice exhibited glucose intolerance and impaired GSIS (glucose-stimulated insulin secretion) and this was exacerbated in α1KORIPCreα2KO mice. Reduced glucose concentrations failed to completely suppress insulin secretion in islets from RIPCreα2KO and α1KORIPCreα2KO mice, and conversely GSIS was impaired. β-Cells lacking AMPKα2 or expressing a kinase-dead AMPKα2 failed to hyperpolarize in response to low glucose, although KATP (ATP-sensitive potassium) channel function was intact. We could detect no alteration of GLUT2 (glucose transporter 2), glucose uptake or glucokinase that could explain this glucose insensitivity. UCP2 (uncoupling protein 2) expression was reduced in RIPCreα2KO islets and the UCP2 inhibitor genipin suppressed low-glucose-mediated wild-type mouse β-cell hyperpolarization, mimicking the effect of AMPKα2 loss. These results show that AMPKα2 activity is necessary to maintain normal pancreatic β-cell glucose sensing, possibly by maintaining high β-cell levels of UCP2

The pH Dependent Interaction between Nicotine and Simulated Pulmonary Surfactant Monolayers with Associated Molecular Modelling

Pulmonary surfactant is an endogenous material that lines and stabilises the alveolar air-liquid interface. Respiratory mechanics can be compromised by exposure to environmental toxins such as cigarette vapour, which contains nicotine. This study aims to determine the influence of nicotine on the activity of simulated lung surfactant at pH 7 and pH 9. In all cases, the addition of nicotine to the test zone caused deviation in surfactant film performance. Importantly, the maximum surface pressure was reduced for each system. Computational modelling was applied to assess key interactions between each species, with the Gaussian 09 software platform used to calculate electrostatic potential surfaces. Modelling data confirmed either nicotine penetration into the two-dimensional structure or interfacial / electrostatic interactions across the underside. The results obtained from this study suggest that nicotine can impair the ability of pulmonary surfactant to reduce the surface tension term, which can increase the work of breathing. When extrapolated to gross lung function alveolar collapse and respiratory disease (e.g. chronic airway obstruction) may result. The delivery of nicotine to the (deep) lung can cause a deterioration in lung function and lead to reduced quality of life

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns