Wave-like spread of Ebola Zaire

In the past decade the Zaire strain of Ebola virus (ZEBOV) has emerged repeatedly into human populations in central Africa and caused massive die-offs of gorillas and chimpanzees. We tested the view that emergence events are independent and caused by ZEBOV variants that have been long resident at each locality. Phylogenetic analyses place the earliest known outbreak at Yambuku, Democratic Republic of Congo, very near to the root of the ZEBOV tree, suggesting that viruses causing all other known outbreaks evolved from a Yambuku-like virus after 1976. The tendency for earlier outbreaks to be directly ancestral to later outbreaks suggests that outbreaks are epidemiologically linked and may have occurred at the front of an advancing wave. While the ladder-like phylogenetic structure could also bear the signature of positive selection, our statistical power is too weak to reach a conclusion in this regard. Distances among outbreaks indicate a spread rate of about 50 km per year that remains consistent across spatial scales. Viral evolution is clocklike, and sequences show a high level of small-scale spatial structure. Genetic similarity decays with distance at roughly the same rate at all spatial scales. Our analyses suggest that ZEBOV has recently spread across the region rather than being long persistent at each outbreak locality. Controlling the impact of Ebola on wild apes and human populations may be more feasible than previously recognized

Lotus tenuis tolerates combined salinity and waterlogging: maintaining O2 transport to roots and expression of an NHX1-like gene contribute to regulation of Na+ transport

Salinity and waterlogging interact to reduce growth for most crop and pasture species. The combination of these stresses often cause a large increase in the rate of Na+ and Cl− transport to shoots; however, the mechanisms responsible for this are largely unknown. To identify mechanisms contributing to the adverse interaction between salinity and waterlogging, we compared two Lotus species with contrasting tolerances when grown under saline (200 mM NaCl) and O2-deficient (stagnant) treatments. Measurements of radial O2 loss (ROL) under stagnant conditions indicated that more O2 reaches root tips of Lotus tenuis, compared with Lotus corniculatus. Better internal aeration would contribute to maintaining Na+ and Cl− transport processes in roots of L. tenuis exposed to stagnant-plus-NaCl treatments. L. tenuis root Na+ concentrations after stagnant-plus-NaCl treatment (200 mM) were 17% higher than L. corniculatus, with 55% of the total plant Na+ being accumulated in roots, compared with only 39% for L. corniculatus. L. tenuis accumulated more Na+ in roots, presumably in vacuoles, thereby reducing transport to the shoot (25% lower than L. corniculatus). A candidate gene for vacuole Na+ accumulation, an NHX1-like gene, was cloned from L. tenuis and identity established via sequencing and yeast complementation. Transcript levels of NHX1 in L. tenuis roots under stagnant-plus-NaCl treatment were the same as for aerated NaCl, whereas L. corniculatus roots had reduced transcript levels. Enhanced O2 transport to roots enables regulation of Na+ transport processes in L. tenuis roots, contributing to tolerance to combined salinity and waterlogging stresses

Evaluating tag-based information access in image collections

The availability of social tags has greatly enhanced access to information. Tag clouds have emerged as a new "social" way to find and visualize information, providing both one-click access to information and a snapshot of the "aboutness" of a tagged collection. A range of research projects explored and compared different tag artifacts for information access ranging from regular tag clouds to tag hierarchies. At the same time, there is a lack of user studies that compare the effectiveness of different types of tag-based browsing interfaces from the users point of view. This paper contributes to the research on tag-based information access by presenting a controlled user study that compared three types of tag-based interfaces on two recognized types of search tasks - lookup and exploratory search. Our results demonstrate that tag-based browsing interfaces significantly outperform traditional search interfaces in both performance and user satisfaction. At the same time, the differences between the two types of tag-based browsing interfaces explored in our study are not as clear. Copyright 2012 ACM

Spatial rogue waves in photorefractive SBN crystals

We report on the excitation of large-amplitude waves, with a probability of around 1% of total peaks, on a photorefractive SBN crystal by using a simple experimental setup at room temperature. We excite the system using a narrow Gaussian beam and observe different dynamical regimes tailored by the value and time rate of an applied voltage. We identify two main dynamical regimes: a caustic one for energy spreading and a speckling one for peak emergence. Our observations are well described by a two-dimensional Schr\"odinger model with saturable local nonlinearity.Comment: 4 pages, 4 figure

Micromagnetic evaluation of the dissipated heat in cylindrical magnetic nanowires

Magnetic nanowires (NW) are promising candidates for heat generation under AC-field application due to their large shape anisotropy. They may be used for catalysis, hyperthermia or water purification treatments. In the present work we theoretically evaluate the heat dissipated by a single magnetic nanowire, originated from the domain wall dynamics under the action of an AC-field. We compare the Permalloy NWs (which demagnetize via the transverse wall propagation) with the Co fcc NWs whose reversal mode is via a vortex domain wall. The average hysteresis loop areas -which are proportional to the Specific Absorption Rate (SAR)- as a function of the field frequency have a pronounced maximum in the range 200MHz-1GHz. This maximum frequency is smaller in Permalloy than in Co and depends on the nanowire length. A simple model related to the nucleation and propagation time and domain wall velocity (higher for the vortex than for the transverse domain wall) is proposed to explain the non-monotonic SAR dependence on the frequency.Comment: 12 pages, 5 figure

Pullback Attractors for Stochastic Heat Equations in Materials with Memory

We study the asymptotic behaviour of a non-autonomous stochastic reaction-diffusion equation with memory. In fact, we prove the existence of a random pullback attractor for our stochastic parabolic PDE with memory. The randomness enters in our model as an additive Hilbert valued noise. We first prove that the equation generates a random dynamical system (RDS) in an appropriate phase space. Due to the fact that the memory term takes into account the whole past history of the phenomenon, we are not able to prove compactness of the generated RDS, but its asymptotic compactness, ensuring thus the existence of the random pullback attractor

GluR1 links structural and functional plasticity at excitatory synapses

Long-term potentiation (LTP), a cellular model of learning and memory, produces both an enhancement of synaptic function and an increase in the size of the associated dendritic spine. Synaptic insertion of AMPA receptors is known to play an important role in mediating the increase in synaptic strength during LTP, whereas the role of AMPA receptor trafficking in structural changes remains unexplored. Here, we examine how the cell maintains the correlation between spine size and synapse strength during LTP. We found that cells exploit an elegant solution by linking both processes to a single molecule: the AMPA-type glutamate receptor subunit 1 (GluR1). Synaptic insertion of GluR1 is required to permit a stable increase in spine size, both in hippocampal slice cultures and in vivo. Synaptic insertion of GluR1 is not sufficient to drive structural plasticity. Although crucial to the expression of LTP, the ion channel function of GluR1 is not required for the LTP-driven spine size enhancement. Remarkably, a recombinant cytosolic C-terminal fragment (C-tail) of GluR1 is driven to the postsynaptic density after an LTP stimulus, and the synaptic incorporation of this isolated GluR1 C-tail is sufficient to permit spine enlargement even when postsynaptic exocytosis of endogenous GluR1 is blocked. We conclude that during plasticity, synaptic insertion of GluR1 has two functions: the established role of increasing synaptic strength via its ligand-gated ion channel, and a novel role through the structurally stabilizing effect of its C terminus that permits an increase in spine size

Evaluación del comportamiento estructural y de resistencia a la corrosión de armaduras de acero inoxidable austenítico AISI 304 y dúplex AISI 2304 embebidas en morteros de cemento Portland

Se ha evaluado el comportamiento mecánico y estructural de dos aceros inoxidables corrugados, el austenítico EN 1.4301 (AISI 304) y el dúplex EN 1.4362 (AISI 2304), y se han comparado con el tradicional acero al carbono B500SD. El estudio se ha realizado en tres niveles: a nivel de barra, de sección y de pieza. Las diferentes características mecánicas de los aceros inoxidables condicionan el comportamiento a nivel de sección y de pieza estructural. El estudio del comportamiento frente a la corrosión de los dos aceros inoxidables se ha realizado mediante mediciones electroquímicas monitorizando el potencial de corrosión y la resistencia de polarización de armaduras embebidas en probetas de mortero contaminado con diferentes concentraciones de cloruros durante un tiempo de exposición de un año. Ambos aceros inoxidables permanecen en estado pasivo en las probetas para todos los contenidos de cloruros

Existence and Asymptotic Behaviour for Stochastic Heat Equations with Multiplicative Noise in Materials With Memory

The existence and uniqueness of solutions for a stochastic reaction-diffusion equation with infinite delay is proved. Sufficient conditions ensuring stability of the zero solution are provided and a possibility of stabilization by noise of the deterministic counterpart of the model is studied

Proton conductivity of multifunctional metal phosphonate frameworks

Metal phosphonates exhibit attractive characteristics for proton conductivity, such as tunable functionality, chemical and thermal stability and the existence of H-bond networks with acidic protons within their structure.1 In the present work, we examine the relationship between crystal structure and proton conductivity for several metal (mono-, di- and tri-valent) phosphonates containing rigid: (5-(dihydroxyphosphoryl)isophthalic acid, PiPhtA and 2-hydroxyphosphonoacetic acid, HPAA) or flexible: (hexa- or octamethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid, H8HDTMP or H8ODTMP) multifunctional ligands. The crystalline hybrid derivatives prepared show a great structural diversity, from 1D to 3D open-frameworks possessing hydrogen-bonded water molecules and phosphonic and carboxylic acid groups. The rigid 3D framework of Ca-PiPhtA, that exhibits a proton conductivity of 5.7•10-4 S/cm as synthesized, transforms into a layered compound upon exposure to ammonia vapors2 with increased proton conductivity (6.6•10-3 S/cm). The flexible frameworks of magnesium or lanthanide phosphonates, with 1D channels, present conductivities higher than 10-3 S/cm. Their activation energies fall in the range corresponding to a Grotthuss mechanism.3,4 For M(I)-HPAA solids conductivities up to 5.6•10-3 S/cm were measured. References 1. P. Ramaswamy, N.E. Wong, G.K.H. Shimizu, Chem. Soc. Rev. 43 (2014) 5913. 2. M. Bazaga-García, R.M.P. Colodrero, M. Papadaki, P. Garczarek, J. Zoń, P. Olivera-Pastor, E.R. Losilla, L. León-Reina, M.A.G. Aranda, D. Choquesillo-Lazarte, K.D. Demadis, A. Cabeza, J. Amer. Chem. Soc. 136 (2014) 5731. 3. R.M.P. Colodrero, P. Olivera-Pastor, E.R. Losilla, D. Hernández-Alonso, M.A.G. Aranda, L. Leon-Reina, J. Rius, K.D. Demadis, B. Moreau, D. Villemin, M. Palomino, F. Rey, A. Cabeza, Inorg. Chem. 51 (2012) 7689. 4. R.M.P. Colodrero, P. Olivera-Pastor, E.R. Losilla, M.A.G. Aranda, L. Leon-Reina, M. Papadaki, A.C. McKinlay, R.E. Morris, K.D. Demadis, A. Cabeza, Dalton Trans. 41 (2012) 4045.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Junta de Andalucía, Proyecto Excelencia FQM-1656. Ministerio de Economía y Competitividad, MAT2013-41836-