Improved Bounds on the Phase Transition for the Hard-Core Model in 2-Dimensions

For the hard-core lattice gas model defined on independent sets weighted by an activity $\lambda$, we study the critical activity $\lambda_c(\mathbb{Z}^2)$ for the uniqueness/non-uniqueness threshold on the 2-dimensional integer lattice $\mathbb{Z}^2$. The conjectured value of the critical activity is approximately $3.796$. Until recently, the best lower bound followed from algorithmic results of Weitz (2006). Weitz presented an FPTAS for approximating the partition function for graphs of constant maximum degree $\Delta$ when $\lambda<\lambda_c(\mathbb{T}_\Delta)$ where $\mathbb{T}_\Delta$ is the infinite, regular tree of degree $\Delta$. His result established a certain decay of correlations property called strong spatial mixing (SSM) on $\mathbb{Z}^2$ by proving that SSM holds on its self-avoiding walk tree $T_{\mathrm{saw}}^\sigma(\mathbb{Z}^2)$ where $\sigma=(\sigma_v)_{v\in \mathbb{Z}^2}$ and $\sigma_v$ is an ordering on the neighbors of vertex $v$. As a consequence he obtained that $\lambda_c(\mathbb{Z}^2)\geq\lambda_c( \mathbb{T}_4) = 1.675$. Restrepo et al. (2011) improved Weitz's approach for the particular case of $\mathbb{Z}^2$ and obtained that $\lambda_c(\mathbb{Z}^2)>2.388$. In this paper, we establish an upper bound for this approach, by showing that, for all $\sigma$, SSM does not hold on $T_{\mathrm{saw}}^\sigma(\mathbb{Z}^2)$ when $\lambda>3.4$. We also present a refinement of the approach of Restrepo et al. which improves the lower bound to $\lambda_c(\mathbb{Z}^2)>2.48$.Comment: 19 pages, 1 figure. Polished proofs and examples compared to earlier versio

A Stochastic Approach to Shortcut Bridging in Programmable Matter

In a self-organizing particle system, an abstraction of programmable matter, simple computational elements called particles with limited memory and communication self-organize to solve system-wide problems of movement, coordination, and configuration. In this paper, we consider a stochastic, distributed, local, asynchronous algorithm for "shortcut bridging", in which particles self-assemble bridges over gaps that simultaneously balance minimizing the length and cost of the bridge. Army ants of the genus Eciton have been observed exhibiting a similar behavior in their foraging trails, dynamically adjusting their bridges to satisfy an efficiency trade-off using local interactions. Using techniques from Markov chain analysis, we rigorously analyze our algorithm, show it achieves a near-optimal balance between the competing factors of path length and bridge cost, and prove that it exhibits a dependence on the angle of the gap being "shortcut" similar to that of the ant bridges. We also present simulation results that qualitatively compare our algorithm with the army ant bridging behavior. Our work gives a plausible explanation of how convergence to globally optimal configurations can be achieved via local interactions by simple organisms (e.g., ants) with some limited computational power and access to random bits. The proposed algorithm also demonstrates the robustness of the stochastic approach to algorithms for programmable matter, as it is a surprisingly simple extension of our previous stochastic algorithm for compression.Comment: Published in Proc. of DNA23: DNA Computing and Molecular Programming - 23rd International Conference, 2017. An updated journal version will appear in the DNA23 Special Issue of Natural Computin

Comparing the reliability of networks by spectral analysis

We provide a method for the ranking of the reliability of two networks with the same connectance. Our method is based on the Cheeger constant linking the topological property of a network with its spectrum. We first analyze a set of twisted rings with the same connectance and degree distribution, and obtain the ranking of their reliability using their eigenvalue gaps. The results are generalized to general networks using the method of rewiring. The success of our ranking method is verified numerically for the IEEE57, the Erd\H{o}s-R\'enyi, and the Small-World networks.Comment: 7 pages, 3 figure

Forty years of paleoecology in the Galapagos

The Galapagos Islands provided one of the first lowland paleoecological records from the Neotropics. Since the first cores were raised from the islands in 1966, there has been a substantial increase in knowledge of past systems, and development of the science of paleoclimatology. The study of fossil pollen, diatoms, corals and compound-specific isotopes on the Galapagos has contributed to the maturation of this discipline. As research has moved from questions about ice-age conditions and mean states of the Holocene to past frequency of El Niño Southern Oscillation, the resolution of fossil records has shifted from millennial to sub-decadal. Understanding the vulnerability of the Galapagos to climate change will be enhanced by knowledge of past climate change and responses in the islands

Genera of phytopathogenic fungi: GOPHY 3

This paper represents the third contribution in the Genera of Phytopathogenic Fungi (GOPHY) series. The series provides morphological descriptions, information about the pathology, distribution, hosts and disease symptoms for the treated genera, as well as primary and secondary DNA barcodes for the currently accepted species included in these. This third paper in the GOPHY series treats 21 genera of phytopathogenic fungi and their relatives including: Allophoma, Alternaria, Brunneosphaerella, Elsinoe, Exserohilum, Neosetophoma, Neostagonospora, Nothophoma, Parastagonospora, Phaeosphaeriopsis, Pleiocarpon, Pyrenophora, Ramichloridium, Seifertia, Seiridium, Septoriella, Setophoma, Stagonosporopsis, Stemphylium, Tubakia and Zasmidium. This study includes three new genera, 42 new species, 23 new combinations, four new names, and three typifications of older names

Searching for R-Parity Violation at Run-II of the Tevatron

We present an outlook for possible discovery of supersymmetry with broken R-parity at Run II of the Tevatron. We first present a review of the literature and an update of the experimental bounds. In turn we then discuss the following processes: 1. Resonant slepton production followed by R-parity violating decay, (a) via $LQD^c$ and (b) via $LLE^c$. 2. How to distinguish resonant slepton production from $Z'$ or $W'$ production. 3. Resonant slepton production followed by the decay to neutralino LSP, which decays via $LQD^c$. 4. Resonant stop production followed by the decay to a chargino, which cascades to the neutralino LSP. 5. Gluino pair production followed by the cascade decay to charm squarks which decay directly via $L_1Q_2D^c_1$. 6. Squark pair production followed by the cascade decay to the neutralino LSP which decays via $L_1Q_2D^c_1$. 7. MSSM pair production followed by the cascade decay to the LSP which decays (a) via $LLE^c$, (b) via $LQD^c$, and (c) via $U^cD^cD^c$, respectively. 8. Top quark and top squark decays in spontaneous R-parity violation.Comment: 39 pages, 51 figures, LaTex, reqires aipproc2.sty and axodraw.sty. To be published in the Physics at Run II Workshop: Supersymmetry/Higgs. Text has been edited by H. Dreiner. Author list on front page has been correcte

Megaprojetos de infraestrutura territorial em face da vulnerabilidade urbana regional-sub-Regional. O Caso do Departamento de Antioquia

The main objective of this paper is to address the impact of mega infrastructure projects on the planning and management of the territory in accordance with its vulnerability. As a methodology, it describes, from the point of view of social transaction costs, the infrastructure, order and territorial planning, which allow to orientate the components that are required so that the mega-projects cohere the diffuse conditions derived from the physical space of the territory. As main contributions, the management of mega-projects from the point of view of territorial ordering, planning and ecological dependence, must pass to the scenario of the applied and masterly chair, through the research and proposal foundation as a line of work.El escrito tiene como principal objetivo el abordaje de la incidencia de los megaproyectos de infraestructura en el ordenamiento y la planeación conforme a la vulnerabilidad territorial. Como metodología, describe desde la óptica de los costos sociales de transacción, la infraestructura, ordenamiento y planeación territorial, que permiten orientar los componentes que se requieren para que los megaproyectos cohesionen las condiciones difusas derivadas de lo físico espacial del territorio. Como principales aportes resalta la gestión de los megaproyectos desde el ordenamiento, la planeación y la dependencia ecológica territorial, deben pasar al escenario de la cátedra aplicada y magistral, a través, de la fundamentación investigativa y propositiva como línea de trabajo.L'objectif principal de ce document est d'aborder l'impact des mégaprojets d'infrastructure sur la planification et la gestion en fonction de la vulnérabilité du territoire. En tant que méthodologie, elle décrit, sous l'angle des coûts de transaction sociaux, les infrastructures, la planification et l'aménagement du territoire, qui permettent d'orienter les composantes nécessaires aux mégaprojets pour mettre en cohérence les conditions diffuses issues de l'espace physique du territoire. Comme contributions principales, la gestion des méga-projets du point de vue de l'ordonnancement territorial, de la planification et de la dépendance écologique, doit passer au scénario de la chaire appliquée et magistrale, à travers la fondation de recherche et de proposition comme ligne de travail.Oprincipal objetivo deste trabalho é abordar o impacto dos megaprojetos de infra-estrutura no planejamento e gestão de acordo com a vulnerabilidade territorial. Como metodologia, descreve, do ponto de vista dos custos de transação social, infra-estrutura, planejamento e ordenação territorial, que permitem orientar os componentes necessários para que os megaprojetos coexistam as condições difusas derivadas do espaço físico do território. Como principais contribuições, a gestão de megaprojetos do ponto de vista da ordenação territorial, planejamento e dependência ecológica, deve passar para o cenário da cadeira aplicada e magistral, através da pesquisa e da fundamentação da proposta como uma linha de trabalho

Respuesta productiva de gallinas semipesadas inducidas al descanso ovárico en diferentes edades

RESUMEN Objetivo. Evaluar el efecto de la inducción al descanso ovárico (DO) a diferentes edades sobre la respuesta productiva en aves semipesadas productoras de huevo comercial. Materiales y método. Se usaron 840 aves de la línea Hy Line Brown con 64 semanas de edad, distribuidas en 10 tratamientos, consistentes en tres edades (65, 70 y 75 semanas) con la aplicación de tres períodos de ayuno (5, 10 y 15 días) y un control (sin DO). El análisis estadístico utilizó un modelo completamente aleatorizado, anidado, efecto fijo y balanceado. Se evaluó consumo de calcio durante el ayuno (g/ave/día), consumo de alimento (g/ave/día), porcentaje de producción, peso del huevo (g), conversión por masa de huevo y huevos por ave alojada (HAA). Resultados. La edad presentó efecto significativo (p<0.05) sobre las variables consumo de alimento, día del primer huevo postmuda, días sin producción, día postmuda de retorno al 50% de producción, peso del huevo, número de huevos, masa huevos, conversión y porcentaje de producción (p<0.01). Al comparar con el control, el tratamiento 75-5 presentó efecto significativo (p<0.05) para las variables: consumo de alimento, número de huevos promedio, masa huevos y conversión. Conclusiones. Las aves con mayor período de ayuno presentaron mayor período improductivo postmuda, grandes pérdidas de peso y alto consumo de alimento, lo que genera alta conversión e ineficiencia productiva. En comparación con reportes de literatura sobre DO en aves livianas, las aves semipesadas llegan al cese de producción en menos días y su período improductivo es menor