945 research outputs found
The Open Navigation Surface Project
Many hydrographic and oceanographic agencies have moved or are moving towards gridded bathymetric products. However, there is no accepted format to allow these grids to be exchanged while maintaining data and metadata integrity. This paper describes the Open Navigation Surface (ONS) Project, which aims to fill this gap. The ONS Project is an open-source software project designed to provide a freely available, portable source-code library to encapsulate gridded bathymetric surfaces with associated uncertainty values. The data file format is called a Bathymetric Attributed Grid (BAG). The BAG is developed and maintained by the ONS Working Group (ONSWG), and the source code is available via the ONS websit
Lineage-Specific Transcriptional Profiles of Symbiodinium spp. Unaltered by Heat Stress in a Coral Host
Dinoflagellates of the genus Symbiodinium form an endosymbiosis with reef building corals, in which photosynthetically derived nutrients comprise the majority of the coral energy budget. An extraordinary amount of functional and genetic diversity is contained within the coral-associated Symbiodinium, with some phylotypes (i.e., genotypic groupings), conferring enhanced stress tolerance to host corals. Recent advances in DNA sequencing technologies have enabled transcriptome-wide profiling of the stress response of the cnidarian coral host; however, a comprehensive understanding of the molecular response to stress of coral-associated Symbiodinium, as well as differences among physiologically susceptible and tolerant types, remains largely unexplored. Here, we examine the transcriptome-wide response to heat stress via RNA-Seq of two types of Symbiodinium, the putatively thermotolerant type D2 and the more susceptible type C3K, resident within the same coral host species, Acropora hyacinthus. Contrary to previous findings with coral hosts, we find no detectable change in gene expression across the dinoflagellate transcriptome after 3 days of elevated thermal exposure, despite physical evidence of symbiosis breakdown. However, hundreds of genes identified as orthologs between the C and D types exhibited significant expression differences within treatments (i.e., attributable solely to type, not heat exposure). These include many genes related to known thermotolerance mechanisms including heat shock proteins and chloroplast membrane components. Additionally, both the between-treatment similarities and between-type differences remained pervasive after 12-18 months of common garden acclimation and in mixed Symbiodinium assemblages within the same coral host colony
Sociology and postcolonialism: another 'missing' revolution?
Sociology is usually represented as having emerged alongside European modernity. The latter is frequently understood as sociology's special object with sociology itself a distinctively modern form of explanation. The period of sociology's disciplinary formation was also the heyday of European colonialism, yet the colonial relationship did not figure in the development of sociological understandings. While the recent emergence of postcolonialism appears to have initiated a reconsideration of understandings of modernity, with the development of theories of multiple modernities, I suggest that this engagement is more an attempt at recuperating the transformative aspect of postcolonialism than engaging with its critiques. In setting out the challenge of postcolonialism to dominant sociological accounts, I also address `missing feminist/queer revolutions', suggesting that by engaging with postcolonialism there is the potential to transform sociological understandings by opening up a dialogue beyond the simple pluralism of identity claims
The Computational Complexity of Generating Random Fractals
In this paper we examine a number of models that generate random fractals.
The models are studied using the tools of computational complexity theory from
the perspective of parallel computation. Diffusion limited aggregation and
several widely used algorithms for equilibrating the Ising model are shown to
be highly sequential; it is unlikely they can be simulated efficiently in
parallel. This is in contrast to Mandelbrot percolation that can be simulated
in constant parallel time. Our research helps shed light on the intrinsic
complexity of these models relative to each other and to different growth
processes that have been recently studied using complexity theory. In addition,
the results may serve as a guide to simulation physics.Comment: 28 pages, LATEX, 8 Postscript figures available from
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The Open Navigation Surface Project
Many hydrographic and oceanographic agencies have moved or are moving towards gridded bathymetric products. However, there is no accepted format to allow these grids to be exchanged while maintaining data and metadata integrity. This paper describes the Open Navigation Surface (ONS) Project, which aims to fill this gap. The ONS Project is an open-source software project designed to provide a freely available, portable source-code library to encapsulate gridded bathymetric surfaces with associated uncertainty values. The data file format is called a Bathymetric Attributed Grid (BAG). The BAG is developed and maintained by the ONS Working Group (ONSWG), and the source code is available via the ONS website.Muchas agencies hidrogrĂąficas y oceanogrĂąficas se han orientado o se estĂąn orientando hacia los productos batimĂ©tricos cuadriculados. Sin embargo, no existe un formato aceptado para que estas cuadricuias sean intercambiadas manteniendo la integridad de los datos y los meta datos. Este articulo describe el Proyecto « Superficie de NavegaciĂŽn Abierta » (ONS) cuyo objeto es cubrir este vacio. El proyecto ONS es un proyecto de software de fuente abierta disehado para proveer una biblioteca portĂątil de cĂŽdigo fuente de libre disponibilidad para encapsular superficies batimĂ©tricas cuadriculadas con sus valores de incertidumbre asociados. El formato de archivo de datos es llamado Cuadricula BatimĂ©trica Tributada (BAG). El BAG es desarrollado y mantenido por el Grupo de Trabajo ONS (ONSWG), y el cĂŽdigo fuente es disponible a travĂ©s de sitio web de ONS.De nombreuses agences hydrographiques et ocĂ©anographiques se sont orientĂ©es ou s âorientent actuellement vers les produits bathymĂ©triques quadrillĂ©s. Toutefois, il n'existe pas de format acceptĂ© qui permette Ă ces quadrillages d'ĂȘtre Ă©changĂ©s tout en conservant lâintĂ©gritĂ© des donnĂ©es et des mĂ©tadonnĂ©es. Le prĂ©sent article dĂ©crit le projet ONS (Open Navigation Surface) qui vise Ă combler cette lacune. Le projet ONS est un projet de logiciel libre conçu pour fournir une bibliothĂšque portable de code source Ă libre disponibilitĂ© devant encapsuler des surfaces bathymĂ©triques maillĂ©es avec des valeurs d'incertitude associĂ©es. Le format du fichier des donnĂ©es est appelĂ© Carroyage bathymĂ©trique attribuĂ© (BAG). Le BAG est dĂ©veloppĂ© est tenu Ă jour par le groupe de travail ONS et le code source est disponible sur le site Web ONS
On the Complexity of Query Result Diversification
Query result diversification is a bi-criteria optimization problem for ranking query results. Given a database D, a query Q and a positive integer k, it is to find a set of k tuples from Q(D) such that the tuples are as relevant as possible to the query, and at the same time, as diverse as possible to each other. Subsets of Q(D) are ranked by an objective function defined in terms of relevance and diversity. Query result diversification has found a variety of applications in databases, information retrieval and operations research. This paper studies the complexity of result diversification for relational queries. We identify three problems in connection with query result diversification, to determine whether there exists a set of k tuples that is ranked above a bound with respect to relevance and diversity, to assess the rank of a given k-element set, and to count how many k-element sets are ranked above a given bound. We study these problems for a variety of query languages and for three objective functions. We establish the upper and lower bounds of these problems, all matching, for both combined complexity and data complexity. We also investigate several special settings of these problems, identifying tractable cases. 1
Flow Phase Diagram for the Helium Superfluids
The flow phase diagram for He II and He-B is established and discussed
based on available experimental data and the theory of Volovik [JETP Letters
{\bf{78}} (2003) 553]. The effective temperature - dependent but scale -
independent Reynolds number , where
and are the mutual friction parameters and the superfluid Reynolds
number characterizing the circulation of the superfluid component in units of
the circulation quantum are used as the dynamic parameters. In particular, the
flow diagram allows identification of experimentally observed turbulent states
I and II in counterflowing He II with the turbulent regimes suggested by
Volovik.Comment: 2 figure
The inhibitor of differentiation-2 promotes synovial fibroblast-dependent osteoclastogenesis in rheumatoid arthritis
Objectives:
Despite indirect evidence suggesting that low oxygen levels might occur in the rheumatoid arthritis (RA) synovium, direct proof of the presence of hypoxia in the arthritic synovium as well as the relevance of low oxygen levels for joint destruction is lacking. The aim of this study was to analyse the distribution of hypoxia in arthritic joints and to evaluate the molecular effects of the hypoxic environment on the phenotype of RA synovial fibroblasts (SF).<p></p>
Methods:
The hypoxia marker EF-5 was applied in mice with the collagen-induced arthritis (CIA). Expression profile analysis with hypoxic and normoxic SF was performed using subtractive hybridization and microarray. The expression of the inhibitor of differentiation-2 (Id-2), CD68 (macrophage marker) and prolyl hydroxylase (fibroblast marker) was evaluated by immunohistochemistry on synovial tissues from RA, osteoarthritis patients and CIA mice. To evaluate the function of Id-2 in SF, cells were transfected with the pcDNA3.1 containing cDNA for Id-2 or Id-2-specific siRNA or mock controls. The expression of Id-2 and genes regulated by Id-2 in transfected SF was evaluated by SYBR Green real-time PCR and western blot. SF stably transfected with Id-2 were cocultured with bone marrow cells in a transwell system. The expression of the receptor activator of NF-ÎșB ligand (RANKL) and osteoprotegerin were measured by real-time PCR. The development of osteoclasts was evaluated by visualization of the activity of tartrate-resistant acid phosphatase.<p></p>
Results:
Using the hypoxia marker EF-5 we found that in mice with CIA, synovial cells invading bone and cartilage are exposed to reduced oxygen levels. Expression profile studies identified Id-2 as being upregulated under low oxygen conditions. In addition, IL-1beta stimulation increased the expression of Id-2 in these cells. Histological studies of RA synovium and CIA synovium showed strong expression of Id-2 in SF at sites of synovial invasion into bone. Overproduction of Id-2 in SF by stable transfection triggered the expression of several genes promoting osteoclastogenesis, including BMP-2, PTHrP, Wnt5a and vascular endothelial growth factor. Conversely, the suppression of endogenous Id-2 led to the downregulation of the expression of these molecules. Consistent with these findings coculture of Id-2 transfected SF with bone marrow cells increased the expression of the osteoclast differentiation factor RANKL, and decreased the expression of the osteoclast inhibitory factor osteoprotegerin in bone marrow stromal cells, which was followed by an increase in the number of osteoclasts.<p></p>
Conclusion:
Taken together, our data provide evidence that hypoxia is present at sites of synovial invasion in RA and that Id-2 induced by hypoxia contributes at these sites to joint destruction by promoting SF-dependent osteoclastogenesis
The Complexity of Computing Minimal Unidirectional Covering Sets
Given a binary dominance relation on a set of alternatives, a common thread
in the social sciences is to identify subsets of alternatives that satisfy
certain notions of stability. Examples can be found in areas as diverse as
voting theory, game theory, and argumentation theory. Brandt and Fischer [BF08]
proved that it is NP-hard to decide whether an alternative is contained in some
inclusion-minimal upward or downward covering set. For both problems, we raise
this lower bound to the Theta_{2}^{p} level of the polynomial hierarchy and
provide a Sigma_{2}^{p} upper bound. Relatedly, we show that a variety of other
natural problems regarding minimal or minimum-size covering sets are hard or
complete for either of NP, coNP, and Theta_{2}^{p}. An important consequence of
our results is that neither minimal upward nor minimal downward covering sets
(even when guaranteed to exist) can be computed in polynomial time unless P=NP.
This sharply contrasts with Brandt and Fischer's result that minimal
bidirectional covering sets (i.e., sets that are both minimal upward and
minimal downward covering sets) are polynomial-time computable.Comment: 27 pages, 7 figure
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