Multi-Dimensional Range Querying using a Modification of the Skip Graph

Skip graphs are an application layer-based distributed routing data structure that can be used in a sensor network to facilitate user queries of data collected by the sensor nodes. This research investigates the impact of a proposed modification to the skip graph proposed by Aspnes and Shah. Nodes contained in a standard skip graph are sorted by their key value into successively smaller groups based on random membership vectors computed locally at each node. The proposed modification inverts the node key and membership vector roles, where group membership is computed deterministically and node keys are computed randomly. Both skip graph types are modeled in Java. Range query and node mobility simulations are performed. The number of skip graph levels, total node count, and query precision are varied for query simulations; number of levels and total node count is varied for the mobility simulation. Query performance is measured by the number of skip graph messages used to execute the query while mobility performance is measured by the number of messages transmitted to maintain skip graph coherence. When the number of levels is limited and query precision is low, or when query precision is matched by the number of levels in the skip graph and total network node counts are increased, the modified skip graph transmits fewer messages to execute the query. Furthermore, fewer update messages are needed to fix lost node references due to mobile nodes

Molecular Epidemiology of Eastern Equine Encephalitis Virus, New York

Southern strains are undergoing amplification, perpetuation, and overwintering in New York

Hypoxia Potentiates Glioma-Mediated Immunosuppression

Glioblastoma multiforme (GBM) is a lethal cancer that exerts potent immune suppression. Hypoxia is a predominant feature of GBM, but it is unclear to the degree in which tumor hypoxia contributes to this tumor-mediated immunosuppression. Utilizing GBM associated cancer stem cells (gCSCs) as a treatment resistant population that has been shown to inhibit both innate and adaptive immune responses, we compared immunosuppressive properties under both normoxic and hypoxic conditions. Functional immunosuppression was characterized based on production of immunosuppressive cytokines and chemokines, the inhibition of T cell proliferation and effector responses, induction of FoxP3+ regulatory T cells, effect on macrophage phagocytosis, and skewing to the immunosuppressive M2 phenotype. We found that hypoxia potentiated the gCSC-mediated inhibition of T cell proliferation and activation and especially the induction of FoxP3+T cells, and further inhibited macrophage phagocytosis compared to normoxia condition. These immunosuppressive hypoxic effects were mediated by signal transducer and activator of transcription 3 (STAT3) and its transcriptionally regulated products such as hypoxia inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF). Inhibitors of STAT3 and HIF-1α down modulated the gCSCs' hypoxia-induced immunosuppressive effects. Thus, hypoxia further enhances GBM-mediated immunosuppression, which can be reversed with therapeutic inhibition of STAT3 and HIF-1α and also helps to reconcile the disparate findings that immune therapeutic approaches can be used successfully in model systems but have yet to achieve generalized successful responses in the vast majority of GBM patients by demonstrating the importance of the tumor hypoxic environment

Assessing Standard and Inverted Skip Graphs Using Multi-Dimensional Range Queries and Mobile Nodes

Abstract—The skip graph, an application-layer data structure for routing and indexing, may be used in a sensor network to facilitate queries of the distributed k-dimensional data collected by the nodes, such as their geographic positions. Nodes in a standard skip graph sort keys in layered groups, where group membership is determined by random membership vectors. We propose a skip graph extension that inverts the key and membership vector roles, wherein group membership is based on deterministic z-ordering of k-dimensional data and sorting within groups is based on random keys. This extension retains the structure of a standard skip graph, and can be modified for use in 3-D environments such as unmanned aerial vehicle swarms. Our results indicate this extension reduces the number of nodes contacted relative to the query precision, the volume of the multidimensional space, and the skip graph's height. We discuss our extension’s performance relative to metrics at the application and network layers for static and mobile 2-D networks

Phylogenetic Analysis of North American West Nile Virus Isolates, 2001–2004: Evidence for the Emergence of a Dominant Genotype

The distribution of West Nile virus has expanded in the past 6 years to include the 48 contiguous United States and seven Canadian provinces, as well as Mexico, the Caribbean islands, and Colombia. The suggestion of the emergence of a dominant genetic variant has led to an intensive analysis of isolates made across North America. We have sequenced the premembrane and envelope genes of 74 isolates and the complete genomes of 25 isolates in order to determine if a dominant genotype has arisen and to better understand how the virus has evolved as its distribution has expanded. Phylogenetic analyses revealed the continued presence of genetic variants that group in a temporally and geographically dependent manner and provide evidence that a dominant variant has emerged across much of North America. The implications of these findings are discussed as they relate to transmission and spread of the virus in the Western Hemisphere

Seasonal variation of mercury contamination in Arctic seabirds: A pan-Arctic assessment

Mercury (Hg) is a natural trace element found in high concentrations in top predators, including Arctic seabirds. Most current knowledge about Hg concentrations in Arctic seabirds relates to exposure during the summer breeding period when researchers can easily access seabirds at colonies. However, the few studies focused on winter have shown higher Hg concentrations during the non-breeding period than breeding period in several tissues. Hence, improving knowledge about Hg exposure during the non-breeding period is crucial to understanding the threats and risks encountered by these species year-round. We used feathers of nine migratory alcid species occurring at high latitudes to study bird Hg exposure during both the breeding and non-breeding periods. Overall, Hg concentrations during the non-breeding period were ~3 times higher than during the breeding period. In addition, spatial differences were apparent within and between the Atlantic and Pacific regions. While Hg concentrations during the non-breeding period were ~9 times and ~3 times higher than during the breeding period for the West and East Atlantic respectively, Hg concentrations in the Pacific during the non-breeding period were only ~1.7 times higher than during the breeding period. In addition, individual Hg concentrations during the non-breeding period for most of the seabird colonies were above 5 μg g−1 dry weight (dw), which is considered to be the threshold atwhich deleterious effects are observed, suggesting that some breeding populations might be vulnerable to non-breeding Hg exposure. Since wintering area locations, and migration routes may influence seasonal Hg concentrations, it is crucial to improve our knowledge about spatial ecotoxicology to fully understand the risks associated with Hg contamination in Arctic seabirds. Polar Top predators Metal Seasonal variation FeathersacceptedVersio