Disjoint Paired-Dominating sets in Cubic Graphs

A paired-dominating set of a graph G is a dominating set D with the additional requirement that the induced subgraph G[D] contains a perfect matching. We prove that the vertex set of every claw-free cubic graph can be partitioned into two paired-dominating sets

Hitting all Maximal Independent Sets of a Bipartite Graph

We prove that given a bipartite graph G with vertex set V and an integer k, deciding whether there exists a subset of V of size k hitting all maximal independent sets of G is complete for the class Sigma_2^P.Comment: v3: minor chang

Inhibition of virus replication and symptom expression by reactive oxygen species in tobacco infected with Tobacco mosaic virus

In spite of the enormous information from research on genetics of plant disease resistance, the question still remains unresolved: what is directly inhibiting or killing pathogens and suppressing symptoms in resistant plants? This is particularly true for resistance to viral infections. Here we show that externally applied reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) or ROS-producing (O2·−[superoxide] and H2O2) chemical systems infiltrated into tobacco leaves 2 hours after inoculation suppress replication of Tobacco mosaicvirus (TMV) in the susceptible Samsun (nn) cultivar. This was determined by a biological and a real-time PCR method. Infiltration of leaves of the resistant Xanthi (NN) cultivar with the ROS-producing chemicals and H2O2 significantly suppressed local necrotic lesions (i.e. the hypersensitive response) after inoculation of tobacco leaves with TMV. Accordingly, an early accumulation or external application of ROS, such as O2·− and H2O2, in tobacco may contribute to the development of resistance to TMV infection

Kv1.3 potassium channels are localized in the immunological synapse formed between cytotoxic and target cells

Membrane proteins of cytotoxic T cells specifically reorganize to form an immunological synapse (IS) on interaction with their specific target. In this paper, we investigated the redistribution of Kv1.3 channels, which are the dominant voltage-gated potassium channels, in the plasma membrane of allogen-activated human cytotoxic T lymphocytes (CTLs) on interacting with their specific target cells. Kv1.3 channels bearing a FLAG epitope were expressed in the CTLs and the cell-surface distribution of fluorescently labeled ion channels was determined from confocal laser-scanning microscopy images. FLAG epitope-tagged Kv1.3 channels showed a patchy distribution in CTLs not engaged with target cells, whereas the channels were accumulated in the IS formed between CTLs and specific target lymphocytes. Localization of Kv1.3 channels in the IS might open an unrevealed possibility in the regulation of ion channel activity by signaling molecules accumulated in the IS

List coloring in the absence of a linear forest.

The k-Coloring problem is to decide whether a graph can be colored with at most k colors such that no two adjacent vertices receive the same color. The List k -Coloring problem requires in addition that every vertex u must receive a color from some given set L(u) ⊆ {1,…,k}. Let P n denote the path on n vertices, and G + H and rH the disjoint union of two graphs G and H and r copies of H, respectively. For any two fixed integers k and r, we show that List k -Coloring can be solved in polynomial time for graphs with no induced rP 1 + P 5, hereby extending the result of Hoàng, Kamiński, Lozin, Sawada and Shu for graphs with no induced P 5. Our result is tight; we prove that for any graph H that is a supergraph of P 1 + P 5 with at least 5 edges, already List 5-Coloring is NP-complete for graphs with no induced H. We also show that List k -Coloring is fixed parameter tractable in k + r on graphs with no induced rP 1 + P 2, and that k-Coloring restricted to such graphs allows a polynomial kernel when parameterized by k. Finally, we show that List k -Coloring is fixed parameter tractable in k for graphs with no induced P 1 + P 3