Generalized model of blockage in particulate flow limited by channel carrying capacity

We investigate stochastic models of particles entering a channel with a random time distribution. When the number of particles present in the channel exceeds a critical value $N$, a blockage occurs and the particle flux is definitively interrupted. By introducing an integral representation of the $n$ particle survival probabilities, we obtain exact expressions for the survival probability, the distribution of the number of particles that pass before failure, the instantaneous flux of exiting particle and their time correlation. We generalize previous results for $N=2$ to an arbitrary distribution of entry times and obtain new, exact solutions for $N=3$ for a Poisson distribution and partial results for $N\ge 4$.Comment: 13 pages, 9 figure

The Effect of Blue Light on Leaf Growth and Plant Development in Two Morphologically Contrasted Perennial Ryegrass Genotypes: Cellular Basis and Ecological Implications

Several major plant responses to competition for light are determined by responses to light signals, in particular to red/far-red ratio (R/FR) and blue light, besides responses mediated through photosynthesis and carbon assimilation (Gautier et al., 1999). These responses to light signals allow plants to react to the presence of neighbours and to anticipate the impact of light competition on photosynthesis. The objective of the study was to evaluate the impact of blue light on leaf growth and its cellular basis, on two short and long leaved populations (FC and FL respectively), which were shown to have different competitive ability (Hazard et al., 1996)

The Icefield Ranges Research Project, 1974

Researchers are braving the Yukon ever earlier in the season for the Icefield Ranges Research Project (IRRP). The first group arrived at the IRRP Kluane Lake base camp (61 N, 138 W) on 15 April 1974 and the last group did not leave until 15 October. The winters of 1974 and 1975 mark the first occasion of the base camp being open year-round for two consecutive years. This innovation made possible as a result of the appointment of Mr. and Mrs. A. Williams as a resident camp-management team, is necessary scientifically because certain meteorological projects have to be conducted on a twelve-month basis, as discussed below. One hundred and four researchers and their assistants, representing nearly twenty universities, government agencies and institutions, made use of the IRRP facilities, and approximately 3,300 man-days of accommodation and subsistence were recorded. A number of improvements were made to the physical facilities; a new 24 ft x 12 ft (7.3 m x 3.7 m) utility building is now under construction, and two small trailer units have been installed by the group from the University of British Columbia as additional laboratory space for animal behavioural studies. The two ski-wheel-equipped Helio Courier aircraft of the Arctic Institute of North America performed a total of 173 hours of project-support flying, and in addition twenty hours of time of a Jet Ranger and a Hughes 400 helicopter was chartered. One of the Institute's aircraft, which was on lease to Trans North Turbo Air Limited and was engaged in commercial and tourist operations, suffered a minor accident during the field season. The largest aircraft ever to land at the base camp, a Canadian Forces Hercules transport, was used in support of the High Altitude Physiology Studies programme. ... Glacier survey project: In 1972 the Institute was awarded funds by the Glaciology Division, Department of the Environment, Ottawa, to undertake an inventory of glaciers in the St. Elias Mountains. This work was continued during 1974 by Messrs, S.G. Collins and R. Ragle. Work on the glacier basins of the Donjek River, Alsek River and Tatshenshini River was completed. To date more than 2,000 glacial features have been mapped and recorded. They concern glacier size, location and description. The Project is scheduled for completion in 1976. An extensive bibliography of the St. Elias Mountains is in preparation also and now contains more than 1,100 entries. Climatological projects: Under the direction of the Camp Manager, Mr. A. Williams, and Mr. R. Lenton of AINA, Montreal, and as part of a proposed long-range plan, two pilot climatological projects were initiated in 1974 on behalf of Environment Canada and Parks Canada. Standard and automatic stations were established in the Kluane National Park adjacent to the Slims River and at the 9,000 ft (2,700 m) Divide Station. The year-round meteorological project at Kluane Lake Base was continued in association with the Atmospheric Environment Service, Whitehorse, Y.T. ..

Efficient Large-scale Trace Checking Using MapReduce

The problem of checking a logged event trace against a temporal logic specification arises in many practical cases. Unfortunately, known algorithms for an expressive logic like MTL (Metric Temporal Logic) do not scale with respect to two crucial dimensions: the length of the trace and the size of the time interval for which logged events must be buffered to check satisfaction of the specification. The former issue can be addressed by distributed and parallel trace checking algorithms that can take advantage of modern cloud computing and programming frameworks like MapReduce. Still, the latter issue remains open with current state-of-the-art approaches. In this paper we address this memory scalability issue by proposing a new semantics for MTL, called lazy semantics. This semantics can evaluate temporal formulae and boolean combinations of temporal-only formulae at any arbitrary time instant. We prove that lazy semantics is more expressive than standard point-based semantics and that it can be used as a basis for a correct parametric decomposition of any MTL formula into an equivalent one with smaller, bounded time intervals. We use lazy semantics to extend our previous distributed trace checking algorithm for MTL. We evaluate the proposed algorithm in terms of memory scalability and time/memory tradeoffs.Comment: 13 pages, 8 figure

Experimental study of granular surface flows via a fast camera: a continuous description

Depth averaged conservation equations are written for granular surface flows. Their application to the study of steady surface flows in a rotating drum allows to find experimentally the constitutive relations needed to close these equations from measurements of the velocity profile in the flowing layer at the center of the drum and from the flowing layer thickness and the static/flowing boundary profiles. The velocity varies linearly with depth, with a gradient independent of both the flowing layer thickness and the static/flowing boundary local slope. The first two closure relations relating the flow rate and the momentum flux to the flowing layer thickness and the slope are then deduced. Measurements of the profile of the flowing layer thickness and the static/flowing boundary in the whole drum explicitly give the last relation concerning the force acting on the flowing layer. Finally, these closure relations are compared to existing continuous models of surface flows.Comment: 20 pages, 11 figures, submitted to Phys. FLuid

Trace checking of Metric Temporal Logic with Aggregating Modalities using MapReduce

Modern complex software systems produce a large amount of execution data, often stored in logs. These logs can be analyzed using trace checking techniques to check whether the system complies with its requirements specifications. Often these specifications express quantitative properties of the system, which include timing constraints as well as higher-level constraints on the occurrences of significant events, expressed using aggregate operators. In this paper we present an algorithm that exploits the MapReduce programming model to check specifications expressed in a metric temporal logic with aggregating modalities, over large execution traces. The algorithm exploits the structure of the formula to parallelize the evaluation, with a significant gain in time. We report on the assessment of the implementation - based on the Hadoop framework - of the proposed algorithm and comment on its scalability.Comment: 16 pages, 6 figures, Extended version of the SEFM 2014 pape

Wigner crystal versus Fermionization for one-dimensional Hubbard models with and without long-range interactions

The ground state properties of Hubbard model with or without long-range interactions in the regime with strongly repulsive on-site interaction are investigated by means of the exact diagonalization method. We show that the appearance of $N$-crests in the density profile of a trapped N-fermion system is a natural result of "fermionization" between antiparallel-spin fermions in the strongly repulsive limit and can not be taken as the only signature of Wigner crystal phase, as the static structure factor does not show any signature of crystallization. On the contrary, both the density distribution and static structure factor of Hubbard model with strong long-range interactions display clear signature of Wigner crystal. Our results indicate the important role of long-range interaction in the formation of Wigner crystal.Comment: 7 pages, 7 figure

Mannose-Specific Lectins from Marine Algae: Diverse Structural Scaffolds Associated to Common Virucidal and Anti-Cancer Properties.

To date, a number of mannose-specific lectins have been isolated and characterized from seaweeds, especially from red algae. In fact, man-specific seaweed lectins consist of different structural scaffolds harboring a single or a few carbohydrate-binding sites which specifically recognize mannose-containing glycans. Depending on the structural scaffold, man-specific seaweed lectins belong to five distinct structurally-related lectin families, namely (1) the griffithsin lectin family (beta-prism I scaffold); (2) the Oscillatoria agardhii agglutinin homolog (OAAH) lectin family (beta-barrel scaffold); (3) the legume lectin-like lectin family (beta-sandwich scaffold); (4) the Galanthus nivalis agglutinin (GNA)-like lectin family (beta-prism II scaffold); and, (5) the MFP2-like lectin family (MFP2-like scaffold). Another algal lectin from Ulva pertusa, has been inferred to the methanol dehydrogenase related lectin family, because it displays a rather different GlcNAc-specificity. In spite of these structural discrepancies, all members from the five lectin families share a common ability to specifically recognize man-containing glycans and, especially, high-mannose type glycans. Because of their mannose-binding specificity, these lectins have been used as valuable tools for deciphering and characterizing the complex mannose-containing glycans from the glycocalyx covering both normal and transformed cells, and as diagnostic tools and therapeutic drugs that specifically recognize the altered high-mannose N-glycans occurring at the surface of various cancer cells. In addition to these anti-cancer properties, man-specific seaweed lectins have been widely used as potent human immunodeficiency virus (HIV-1)-inactivating proteins, due to their capacity to specifically interact with the envelope glycoprotein gp120 and prevent the virion infectivity of HIV-1 towards the host CD4+ T-lymphocyte cells in vitro

Simian immunodeficiency virus infection in wild-caught chimpanzees from Cameroon

Simian immunodeficiency viruses (SIVcpz) infecting chimpanzees (Pan troglodytes) in west central Africa are the closest relatives to all major variants of human immunodeficiency virus type 1 ([HIV-1]; groups M, N and O), and have thus been implicated as the source of the human infections; however, information concerning the prevalence, geographic distribution, and subspecies association of SIVcpz still remains limited. In this study, we tested 71 wild-caught chimpanzees from Cameroon for evidence of SIVcpz infection. Thirty-nine of these were of the central subspecies (Pan troglodytes troglodytes), and 32 were of the Nigerian subspecies (Pan troglodytes vellerosus), as determined by mitochondrial DNA analysis. Serological analysis determined that one P. t. troglodytes ape (CAM13) harbored serum antibodies that cross-reacted strongly with HIV-1 antigens; all other apes were seronegative. To characterize the newly identified virus, 14 partially overlapping viral fragments were amplified from fecal virion RNA and concatenated to yield a complete SIVcpz genome (9,284 bp). Phylogenetic analyses revealed that SIVcpzCAM13 fell well within the radiation of the SIVcpzPtt group of viruses, as part of a clade including all other SIVcpzPtt strains as well as HIV-1 groups M and N. However, SIVcpzCAM13 clustered most closely with SIVcpzGAB1 from Gabon rather than with SIVcpzCAM3 and SIVcpzCAM5 from Cameroon, indicating the existence of divergent SIVcpzPtt lineages within the same geographic region. These data, together with evidence of recombination among ancestral SIVcpzPtt lineages, indicate long-standing endemic infection of central chimpanzees and reaffirm a west central African origin of HIV-1. Whether P. t. vellerosus apes are naturally infected with SIVcpz requires further study