The Cop Number of the One-Cop-Moves Game on Planar Graphs

Cops and robbers is a vertex-pursuit game played on graphs. In the classical cops-and-robbers game, a set of cops and a robber occupy the vertices of the graph and move alternately along the graph's edges with perfect information about each other's positions. If a cop eventually occupies the same vertex as the robber, then the cops win; the robber wins if she can indefinitely evade capture. Aigner and Frommer established that in every connected planar graph, three cops are sufficient to capture a single robber. In this paper, we consider a recently studied variant of the cops-and-robbers game, alternately called the one-active-cop game, one-cop-moves game or the lazy-cops-and-robbers game, where at most one cop can move during any round. We show that Aigner and Frommer's result does not generalise to this game variant by constructing a connected planar graph on which a robber can indefinitely evade three cops in the one-cop-moves game. This answers a question recently raised by Sullivan, Townsend and Werzanski.Comment: 32 page

The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites

No abstract available

Toppling Numbers of Complete and Random Graphs

We study a two-person game played on graphs based on the widely studied chip-firing game. Players Max and Min alternately place chips on the vertices of a graph. When a vertex accumulates as many chips as its degree, it fires, sending one chip to each neighbour; this may in turn cause other vertices to fire. The game ends when vertices continue firing forever. Min seeks to minimize the number of chips played during the game, while Max seeks to maximize it. When both players play optimally, the length of the game is the toppling number of a graph G, and is denoted by t(G). By considering strategies for both players and investigating the evolution of the game with differential equations, we provide asymptotic bounds on the toppling number of the complete graph. In particular, we prove that for sufficiently large n 0.596400n2 \u3c t(Kn) \u3c 0.637152n2. Using a fractional version of the game, we couple the toppling numbers of complete graphs and the binomial random graph G(n,p). It is shown that for pn ≥ n2 / √ log n asymptotically almost surely t(G(n,p)) = (1+o(1))pt(Kn)

Meiotic Arrest Compromises Pollen Fertility in an Interspecific Hybrid Between \u3cem\u3eBrachiaria Ruziziensis\u3c/em\u3e X \u3cem\u3eBrachiaria Decumbens\u3c/em\u3e (Gramineae)

Disruptions in meiosis, development of the free microspores, microspore mitosis, pollen differentiation or anthesis can result in male-sterile plants (Glover et al., 1998). An understanding of the meiotic process is pivotal to work on reproduction, fertility, genetics and breeding in plants, with serious implications in crop production (Armstrong & Jones, 2003). Some African species of Brachiaria are the most important for pastures in the American tropics due to good adaptation and production. Artificial hybridization is underway in Embrapa to improve production, quality and insect resistance (Valle & Miles, 2001). For a cultivar to be successfully adopted good seed production and pollen viability are required. This paper reports on meiotic abnormalities impairing pollen fertility in a hybrid between B. ruziziensis x B. decumbens

Analysis of Genomic Affinity Between \u3cem\u3eBrachiaria Ruziziensis\u3c/em\u3e and \u3cem\u3eB. Brizantha\u3c/em\u3e Through Meiotic Behaviour

Genetic divergence between polyploid hybrids is displayed in chromosome pairing and in the rate of chromosome elimination due to differences in cell cycle between the two combined genomes (Sundberg et al. 1991). In Brachiaria, a genus of African grasses reaching continental proportions as a tropical pasture in Latin America, genome analysis has never been performed. The majority of accessions in this genus is polyploid and apomictic, which restricts breeding. The relative ease of obtaining fertile interspecific hybrids once ploidy barriers are overcome (Pereira et al. 2001) confirms the phylogenetic proximity among B. ruziziensis, B. decumbens and B. brizantha. Hybrids were synthesised using sexual artificial 4x as the female genitor and natural apomictic 4x as the pollen donors. Genome affinity is a pre-requisite for chosen genitors to produce fertile hybrids and plenty of viable seed to assure adoption of the new cultivar. Microsporogenesis of a hybrid between B. ruziziensis and B. brizantha is described in this paper, focusing on the behaviour of both genomes

A simple method for the quantitative analysis of tyrosol by hplc in liquid Czapek Cultures from endophytic fungi

Tyrosol is a possible quorum sensing molecule in endophytic fungi. High-performance liquid chromatography (HPLC) coupled with diode array detector (DAD) was used for the analysis of tyrosol in liquid Czapek fungal cultures. The optimized conditions were gradient mobile phase, in linear mode, consisting initially of acetonitrile/water (1:9 v/v) and increasing up to acetonitrile (100%) in 30 minutes at a flow rate of 1 mL min-1. The column used was a ZORBAX® ODS (250 × 4.6 mm, 5 μm) at 25 ºC. Liquid-liquid extraction of 0.5 mL medium (pH 7.0) with ethyl acetate and injection of 20 μL after solvent evaporation under air flow gave good results. Some validation parameters obtained were: linearity 0.0125-5.0 μg mL-1 medium (r = 0.9967), quantification limit of 0.0125 μg mL-1 medium, %CV (precision) and %E (accuracy) bellow 15% and recovery around 80%. Therefore, the developed method presented satisfactory validation parameters and it was efficient for the analysis of tyrosol in Czapek medium.O tirosol é provavelmente uma molécula sinalizadora em fungos endofíticos. A análise do tirosol em cultura líquida Czapek de fungo endofítico foi realizada através de cromatografia líquida de alta eficiência acoplada a detector por arranjo de diodos. As análises foram obtidas em sistema de fase móvel utilizando gradiente, modo linear, iniciando em acetonitrila/água (1:9 v/v) e terminando em acetonitrila 100% em 30 minutos com vazão de 1 mL min-1. Coluna analítica ZORBAX® ODS (250 × 4,6 mm, 5 μm) à 25 ºC foi utilizada. Extração líquido-líquido de 0,5 mL do meio (pH 7,0) com acetato de etila e injeção de 20 μL após concentração do solvente sob ar comprimido originou bons resultados. Os parâmetros validados foram: linearidade 0,0125-5,0 μg mL-1 (r = 0,9967), limite de quantificação 0,0125 μg mL-1 obtidos pela média das análises; %CV (precisão) e %E (exatidão) com valores abaixo de 15% e recuperação de cerca de 80%. Além disso, o método desenvolvido apresentou valores de validação satisfatórios demonstrando eficiência na análise do tirosol em meio líquido Czapek.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPES

Otimização do método de extração de DNA de Magnaporthe oryzae de trigo.

bitstream/item/114990/1/2014-Comunicado-tecnico-online-343.pd