The definitions of these matroids, with a summary of their interesting properties, can be found in the Appendix. Except for P"8 , they were all known to be excluded minors for GF(4)-representability (see Oxley [15, 17]). The matroid P"8 is obtained by relaxing the unique pair of disjoint circuit-hyperplanes of P8 . Ever since Whitney's introductory paper [28] on matroid theory, researchers have...

We prove upper and lower bounds on the size of the largest square grid graph that is a subgraph, minor, or shallow minor of a graph in the form of a larger square grid from which a specified number of vertices have been deleted. Our bounds are tight to within constant factors. We also provide less-tight bounds on analogous problems for higher-dimensional grids.

A minor-closed class of graphs is a set of labelled graphs which is closed under isomorphism and under taking minors. For a minor-closed class G, let gn be the number of graphs in G which have n vertices. The growth constant of G is γ = lim sup(gn/n!) . We study the properties of the set Γ of growth constants of minor-closed classes of graphs. Among other results, we show that Γ does not contai...

the rose sawfly, arge rosae linnaeus, is one of the most destructive pests of rose bushes in the north of iran. nowadays, many attempts have been made to reduce pesticide application by looking for new methods of pest control. a non chemical method for controlling insect pests including a. rosae can be achieved by using genetically engineered plants expressing carbohydrase inhibitors. therefore...

pseudomonas aeruginosa is among the most important pathogens in the nosocomial infections. a genetic mobile element, the integron, is one of the major agents involved in dissemination of multi-drug resistance among gram negative bacteria. during a descriptive study from october 2009 to august 2010, some 130 p. aeruginosa clinical isolates were collected from different wards of three hospitals i...

Thalassemia is a hereditary condition that affects the formation of globin chains. Beta thalassemia characterized by either total loss manufacture (β-thalassemia major) or partial minor). This type inherited anemias found in Mediterranean and Southeast Asian communities. Objective: Assessment parents' knowledge regarding home health care management related to children with β-Thalassemia Major. ...

background :   ampc beta lactamases play a significant role in creating resistance to third generation cephalosporins worldwide. they mostly express on chromosome of enterobacteriaceae especially escherichia coli and cause consequential problem in clinical treatment and lead to failure in diagnosis and phenotypic test recommended by clinical and laboratory standards institute.   methods : total...

background: the potential hazards of exposure to radiation from radon have been of great concern worldwide, as it is associated with an increased risk of lung cancer. radon (222rn) and its progeny are the main sources of radioactivity in the environment. the half-life of 222rn (3.82 days) is long enough for it to diffuse into and build up in homes. 220rn or thoron from the 232th series, and 219...