Discovering the underlying structures present in large real world graphs is a fundamental scientific problem. In this paper we show that a graph's clique tree can be used to extract a hyperedge replacement grammar. If we store an ordering from the extraction process, the extracted graph grammar is guaranteed to generate an isomorphic copy of the original graph. Or, a stochastic application of the graph grammar rules can be used to quickly create random graphs. In experiments on large real world networks, we show that random graphs, generated from extracted graph grammars, exhibit a wide range of properties that are very similar to the original graphs. In addition to graph properties like degree or eigenvector centrality, what a graph "looks like" ultimately depends on small details in local graph substructures that are difficult to define at a global level. We show that our generative graph model is able to preserve these local substructures when generating new graphs and performs well on new and difficult tests of model robustness.

In this paper, we present a meta-analysis of several Web content extraction algorithms, and make recommendations for the future of content extraction on the Web. First, we find that nearly all Web content extractors do not consider a very large, and growing, portion of modernWeb pages. Second, it is well understood that wrapper induction extractors tend to break as theWeb changes; ; heuristic/ feature engineering extractors were thought to be immune to a Web site's evolution, but we find that this is not the case: heuristic content extractor performance also tends to degrade over time due to the evolution of Web site forms and practices. We conclude with recommendations for future work that address these and other findings.

Un método rápido, sensible y preciso por Cromatografía Líquida de Alta Resolución fue desarrollado y validado para la determinación de los niveles de N-3-metoxibencil-linoleamida en cerebro de ratas Sprague Dawley. Durante la preparación de la muestra se usó acetonitrilo como solvente de extracción y N-bencil-palmitamida como estándar interno. El analito se separó en una columna Chromolith® Performance con elución isocrática de acetonitrilo-agua ultrapura (80:20, v/v) a 1.0 mL/min y a 40°C. La detección se realizó utilizando un detector de arreglo de diodos a una longitud de onda de 205 nm. La selectividad del método se confirmó por la ausencia de interferentes endógenos. El método desarrollado se usó para construir curvas de calibración lineales en el rango de concentración de 250 y 10 000 ng/mL, (R2 ≥ 0.9900). Usando 500 μg de homogeneizado de cerebro, el límite inferior de cuantificación validado fue de 250.0 ng/mL. La exactitud y precisión intra e inter-día estuvieron dentro del 15% de las concentraciones nominales. Asimismo, el analito y su estándar interno demostraron ser estables durante el almacenamiento, la preparación de muestra y el análisis cromatográfico.