1,378 research outputs found
Recommended from our members
Family relations, love relationships, attachment, and their influence on people\u27s conceptions of love.
Eclipse radius measurements
Methods for predicting the path edges and reducing observations of total solar eclipses for determining variations of the solar radius are described. Analyzed observations of the 1925 January eclipse show a 0.7 (arc second) decrease in the solar radius during the past fifty years
Using Lens lamottei to transfer anthracnose resistance to lentil varieties
Non-Peer ReviewedAnthracnose is a serious fungal disease of lentil that can cause severe yield loss. It is now widespread in Saskatchewan and can be devastating in years with warm wet weather. Producers are limited to controlling this disease by crop rotation, foliar spray or development of varieties with resistance to anthracnose. Pathology research shows that we have two major strains of lentil anthracnose. Varieties like CDC Robin have resistance to one of the strains, but after exhaustive screening of cultivated lentil germplasm, no resistance was found to the second strain of anthracnose. One of the newly discovered wild species of lentil, Lens lamottei, has recently been discovered to have resistance to a combination of both strains of anthracnose when grown under field conditions in an inoculated disease nursery. The objective of this project is to determine if L. lamottei can be by crossed with L. culinaris in order to transfer anthracnose resistance into lentil varieties
On Structural Parameterizations of Hitting Set: Hitting Paths in Graphs Using 2-SAT
Hitting Set is a classic problem in combinatorial optimization. Its input
consists of a set system F over a finite universe U and an integer t; the
question is whether there is a set of t elements that intersects every set in
F. The Hitting Set problem parameterized by the size of the solution is a
well-known W[2]-complete problem in parameterized complexity theory. In this
paper we investigate the complexity of Hitting Set under various structural
parameterizations of the input. Our starting point is the folklore result that
Hitting Set is polynomial-time solvable if there is a tree T on vertex set U
such that the sets in F induce connected subtrees of T. We consider the case
that there is a treelike graph with vertex set U such that the sets in F induce
connected subgraphs; the parameter of the problem is a measure of how treelike
the graph is. Our main positive result is an algorithm that, given a graph G
with cyclomatic number k, a collection P of simple paths in G, and an integer
t, determines in time 2^{5k} (|G| +|P|)^O(1) whether there is a vertex set of
size t that hits all paths in P. It is based on a connection to the 2-SAT
problem in multiple valued logic. For other parameterizations we derive
W[1]-hardness and para-NP-completeness results.Comment: Presented at the 41st International Workshop on Graph-Theoretic
Concepts in Computer Science, WG 2015. (The statement of Lemma 4 was
corrected in this update.
On vertex coloring without monochromatic triangles
We study a certain relaxation of the classic vertex coloring problem, namely,
a coloring of vertices of undirected, simple graphs, such that there are no
monochromatic triangles. We give the first classification of the problem in
terms of classic and parametrized algorithms. Several computational complexity
results are also presented, which improve on the previous results found in the
literature. We propose the new structural parameter for undirected, simple
graphs -- the triangle-free chromatic number . We bound by
other known structural parameters. We also present two classes of graphs with
interesting coloring properties, that play pivotal role in proving useful
observation about our problem. We give/ask several conjectures/questions
throughout this paper to encourage new research in the area of graph coloring.Comment: Extended abstrac
INTEGRATION OF SCALE INSECTS (HEMIPTERA: COCCIDAE) IN THE SOUTH-EAST ASIAN ANT-PLANT (CREMATOGASTER (FORMICIDAE)- MACARANGA (EUPHORBIACEAE)) SYSTEM.
INTEGRATION OF SCALE INSECTS (HEMIPTERA: COCCIDAE) IN THE SOUTH-EAST ASIAN ANT-PLANT (CREMATOGASTER (FORMICIDAE)-MACARANGA (EUPHORBIACEAE)) SYSTEM. The coccid colonisers of myrmecophytic Macaranga were tested for their trophic integration into the mutualistic Crematogaster-Macaranga ant-plant system. Honeydew secretion by these mostly endophytic scale insects was observed in Coccus caviramicolus Morrison, C. penangensis Morrison, C. secretus Morrison, C. tumuliferus Morrison, C. tumuliferus var. C.84 and in two other Macaranga coccid species. However, the use of coccids as protein-rich food by ants under normal and starvation conditions was not observed. Key words: trophobiosis, ant nutrition, Myzolecaniinae, survival, dumping areas, C. macarangae, food-bodies, Pseudococcidae, Malaysia, Macaranga bancana, M. hypoleuca, M. hullettii, M. winkleri, M. triloba
Expanding the expressive power of Monadic Second-Order logic on restricted graph classes
We combine integer linear programming and recent advances in Monadic
Second-Order model checking to obtain two new algorithmic meta-theorems for
graphs of bounded vertex-cover. The first shows that cardMSO1, an extension of
the well-known Monadic Second-Order logic by the addition of cardinality
constraints, can be solved in FPT time parameterized by vertex cover. The
second meta-theorem shows that the MSO partitioning problems introduced by Rao
can also be solved in FPT time with the same parameter. The significance of our
contribution stems from the fact that these formalisms can describe problems
which are W[1]-hard and even NP-hard on graphs of bounded tree-width.
Additionally, our algorithms have only an elementary dependence on the
parameter and formula. We also show that both results are easily extended from
vertex cover to neighborhood diversity.Comment: Accepted for IWOCA 201
Light Activation of an Innate Olfactory Avoidance Response in Drosophila
How specific sensory stimuli evoke specific behaviors is a fundamental problem in neurobiology. In Drosophila, most odorants elicit attraction or avoidance depending on their concentration, as well as their identity [1]. Such odorants, moreover, typically activate combinations of glomeruli in the antennal lobe of the brain 2, 3 and 4, complicating the dissection of the circuits translating odor recognition into behavior. Carbon dioxide (CO_2), in contrast, elicits avoidance over a wide range of concentrations 5 and 6 and activates only a single glomerulus, V [5]. The V glomerulus receives projections from olfactory receptor neurons (ORNs) that coexpress two GPCRs, Gr21a and Gr63a, that together comprise a CO_2 receptor 7, 8 and 9. These CO_2-sensitive ORNs, located in the ab1 sensilla of the antenna, are called ab1c neurons [10]. Genetic silencing of ab1c neurons indicates that they are necessary for CO_2-avoidance behavior [5]. Whether activation of these neurons alone is sufficient to elicit this behavior, or whether CO_2 avoidance requires additional inputs (e.g., from the respiratory system), remains unclear. Here, we show that artificial stimulation of ab1c neurons with light (normally attractive to flies) elicits the avoidance behavior typical of CO_2. Thus, avoidance behavior appears hardwired into the olfactory circuitry that detects CO_2 in Drosophila
Revisiting strategies for breeding anthracnose resistance in lentil: the case with wild species
Non-Peer ReviewedBreeders at the Crop Development Centre (CDC) have up to now only used germplasm resources available in the cultivated lentil to develop new varieties with resistance to diseases. Based on recent studies, the available cultivated germplasm does not offer sufficient genetic variation for resistance to anthracnose and ascochyta diseases. Lentil crop is attacked by two major diseases (anthracnose and ascochyta) that can cause 100% loss in the worst scenarios. Since anthracnose is only a major lentil disease in North America, no work has been done to improve resistance to this disease elsewhere. Wild species of many crops are known to carry many disease resistance genes lacking in the cultivated crop. We began the search for anthracnose resistance in the six wild species of lentil (world collection), of which two can be easily crossed with the cultivated type. Two strains of anthracnose (race 1 and race 2) with varying degrees of virulence were reported. The 2002 field data suggested that some of the Lens ervoides and Lens lamottei accessions exhibited no lesions at all when exposed to the combination of the two anthracnose strains. The cultivated types that show resistance to the less virulent strain were severely affected by anthracnose. In the greenhouse study the wild species were inoculated with the two strains separately and results indicate that no accession is immune to the more virulent type. However, some of the L. ervoides and L. lamottei
accessions had good resistance compared to their cultivated counterparts. As a long term strategy, the lentil breeding program at CDC, University of Saskatchewan has a goal of fully utilizing the available resistance sources. However, these two species cannot be easily crossed with the cultivated types using the conventional/manual crossing techniques. A tissue culture procedure involving embryo rescue is used to facilitate crossing. We have been able to successfully rescue some embryos from crosses with Lens ervoides. The hybrid plants produce some fertile seeds which will be evaluated for resistance to both anthracnose and ascochyta. The selected resistant lines will then be backcrossed to the adopted backgrounds in order to deploy resistance genes
- …