A note on uniform power connectivity in the SINR model

In this paper we study the connectivity problem for wireless networks under the Signal to Interference plus Noise Ratio (SINR) model. Given a set of radio transmitters distributed in some area, we seek to build a directed strongly connected communication graph, and compute an edge coloring of this graph such that the transmitter-receiver pairs in each color class can communicate simultaneously. Depending on the interference model, more or less colors, corresponding to the number of frequencies or time slots, are necessary. We consider the SINR model that compares the received power of a signal at a receiver to the sum of the strength of other signals plus ambient noise . The strength of a signal is assumed to fade polynomially with the distance from the sender, depending on the so-called path-loss exponent $\alpha$. We show that, when all transmitters use the same power, the number of colors needed is constant in one-dimensional grids if $\alpha>1$ as well as in two-dimensional grids if $\alpha>2$. For smaller path-loss exponents and two-dimensional grids we prove upper and lower bounds in the order of $\mathcal{O}(\log n)$ and $\Omega(\log n/\log\log n)$ for $\alpha=2$ and $\Theta(n^{2/\alpha-1})$ for $\alpha<2$ respectively. If nodes are distributed uniformly at random on the interval $[0,1]$, a \emph{regular} coloring of $\mathcal{O}(\log n)$ colors guarantees connectivity, while $\Omega(\log \log n)$ colors are required for any coloring.Comment: 13 page

Artificial inoculation on plants and banana leaf pieces with Mycosphaerella spp., responsible for Sigatoka leaf spot diseases

Ce protocole vise (i) à analyser la nature des interactions hôtes-parasites (résistance ou sensibilité), (ii) à étudier la variabilité de la pathogénicité de différentes populations pathogènes (intra/interspécifiques) quant à leur virulence et leur agressivité mesurées à partir d''inoculation artificielle avec Mycosphaerella fijiensis ou Mycosphaerella musicola sur des plants et des morceaux de feuille de bananier. Le principe, les principaux avantages, le matériel végétal de départ et le temps nécessaire de la méthode sont présentés. Matériel et méthodes. Le matériel de laboratoire nécessaire et le détail des seize étapes de réalisation du protocole (préparation de l'inoculum conidial, inoculation artificielle sur des plants de bananier, et inoculation artificielle sur des morceaux de feuille de bananier) sont décrits. Des problèmes potentiels sont évoqués. Résultats. Des symptômes-types de la maladie sont obtenus après inoculation artificielle (Résumé d'auteur

Growth, Structure and Properties of Epitaxial Thin Films of First Principles Predicted Multiferroic Bi2FeCrO6

We report the structural and physical properties of epitaxial Bi2FeCrO6 thin films on epitaxial SrRuO3 grown on (100)-oriented SrTiO3 substrates by pulsed laser ablation. The 300 nm thick films exhibit both ferroelectricity and magnetism at room temperature with a maximum dielectric polarization of 2.8 microC/cm2 at Emax = 82 kV/cm and a saturated magnetization of 20 emu/cc (corresponding to ~ 0.26 Bohr magneton per rhombohedral unit cell), with coercive fields below 100 Oe. Our results confirm the predictions made using ab-initio calculations about the existence of multiferroic properties in Bi2FeCrO6.Comment: Manuscript accepted for publication in Applied Physics Letters (in press). The paper consists of 1619 words, 13 references and 3 figure

Dual Stimuli Response Frequency and Stimulus Choice of the African Clawed Frog, Xenopus laevis, when presented with two stimuli

This preliminary study examines responses of African Clawed Frogs to simultaneous presentation of two stimuli. Frogs were tested in a round arena with water 4 cm deep. Four stimulus rods driven via computer-controlled stepper motors were concealed in a screen suspended above the water. These rods could present a lateral line stimulus, a visual stimulus, or a combination of both. Overall, reactions and no reactions were evenly distributed--51.1% and 48.9%, respectively. Frogs responded more frequently to rostral than caudal stimuli (chi-squared 20.8, df=11, p \u3c 0.04). Frogs reacted more to stimuli between -90° and 90°. Turn angle depended linearly on stimulus angle (e.g., Turn angle = 0.44 + 0.64 x Stimulus angle; pslope \u3c 0.0001; R2adj = 69.5%). (The distributions of stimulus angles appear slightly skewed as often the same stimulus rod was retested after the frog responded and partially oriented towards it, prompting a second test with smaller angles.) Two stimuli did not elicit more responses than one stimuli (P=0.25). The frogs’ choice of stimulus depended primarily on stimulus proximity and angle, not stimulus type. When presented with two stimuli, the frog chose the nearer stimulus and the more rostral stimulus (p \u3c 0.0001). The largest factor in predicting the frog’s choice of stimuli seems to be the linear distance from the stimuli to the frog.https://engagedscholarship.csuohio.edu/u_poster_2015/1009/thumbnail.jp