Abstract:
mutation and recombination processes are involved in the genetic and phenotypic variations of rna viruses, leading to the emergence of new variant strains, and give rise to virus population diversity to be modeled by the host, particularly by the immune system, as occurred with infectious bronchitis virus (ibv) in chickens. the consequence is a continuous emergence of new ibv variants with regard to pathotypes, serotypes, and protectotypes. nucleotide sequencing and subsequent genetic analysis of the s1 and n protein gene sequences provide a fast and accurate method to classify and predict ibv genotype, and a powerful instrument to monitor phylogenetic and epidemiological evolution of ibv variants. despite the use of vaccination programmes, infectious bronchitis has become a serious problem in brazil. thus, a significant number of ibv field variants have been identified circulating in the brazilian commercial poultries between 2000 to 2006 and more recently in argentina. these viruses seem to be indigenous, because they demonstrated a low genetic relatedness with the majority of the reference strains from north america, europe and asia, but were moderately to highly related one to another. in summary, indigenous field ibv variants were evolving and circulating in the field in brazil and argentina, and should be considered as initial candidates for protection against current ibv infectious in chickens. however, in vitro and in vivo studies are needed to determine the pathogenicity and immunogenecity of these new isolates, before defining a new vaccine strain.

Abstract:
A graph G is (d_1,..,d_l)-colorable if the vertex set of G can be partitioned into subsets V_1,..,V_l such that the graph G[V_i] induced by the vertices of V_i has maximum degree at most d_i for all 1 <= i <= l. In this paper, we focus on complexity aspects of such colorings when l=2,3. More precisely, we prove that, for any fixed integers k,j,g with (k,j) distinct form (0,0) and g >= 3, either every planar graph with girth at least g is (k,j)-colorable or it is NP-complete to determine whether a planar graph with girth at least g is (k,j)-colorable. Also, for any fixed integer k, it is NP-complete to determine whether a planar graph that is either (0,0,0)-colorable or non-(k,k,1)-colorable is (0,0,0)-colorable. Additionally, we exhibit non-(3,1)-colorable planar graphs with girth 5 and non-(2,0)-colorable planar graphs with girth 7.

Rapid, sensitive and specific methods are necessary to confirm the diagnosis of outbreaks of avian infectious bronchitis virus (IBV) infection. The amplification of IBV genome by reverse transcription followed by polymerase chain reaction (RT-PCR) has been one of the most used methods for the detection of this virus in clinical samples. To reduce the time and the number of steps in the molecular diagnosis of IBV, we developed a sensitive and rapid detection method based on viral capture by a lectin (Concanavalin A—Con A) in the microplate wells, followed by RT-PCR to amplify the S1 gene. The detection limit of IBV was 10^{3} EID_{50}/ml for the amplification of 5’part of the S1 gene, and 10^{4} EID_{50}/ml for the amplification of full S1 gene. This technique was specific for IBV detection, and no amplified products were detected for other avian viral pathogens (bursal infectious disease virus, avian metapneumovirus and Newcastle disease virus). The MLC-RT-PCR was as sensitive as conventional RT-PCR, and virus isolation method for the detection of IBV in tissue samples collected from experimentally infected birds. The MLC-RT-PCR technique demonstrated a great potential for the rapid and specific diagnosis of IBV.

Abstract:
this study evaluated two enzyme-linked immunosorbent assays (elisa) in the detection of chicken serologic response against salmonella enterica sorotype typhimurium. the assays have used as detecting antigen the soluble bacterial proteins of a non-flagellated strain of salmonella typhimurium (agtm), and antibody conjugated to peroxidase or alkaline phosphatase. according to the results, optimal dilutions of antigen (concentration 5.49 mg/ml) and serum samples in both assays were 1:20,000 and 1:1,000, respectively. in such conditions, the elisa/agtm was able to detect serological response to salmonella typhimurium. cross-reactions to salmonella serotypes gallinarum and pullorum were seen, but not with other serotypes such as enteritidis.

Abstract:
Let M be an additive abelian group. A strong oriented coloringof an oriented graph G is a mapping φ from V(G) to M such that (1) φ(u) ≠ φ(v) whenever uv is an arc in G and (2) φ(v) - φ(u) ≠ -(φ(t) - φ(z)) whenever uv and zt are two arcs in G. We say that G has a M-strong-oriented coloring. The strong oriented chromatic number of an oriented graph, denoted by χ s (G), is the minimal order of a group M, such that G has M-strong-oriented coloring. This notion was introduced by Ne et il and Raspaud. In this paper, we pose the following problem: Let i ≥ 4 be an integer. Let G be an oriented planar graph without cycles of lengths 4 to i. Which is the strong oriented chromatic number of G ? Our aim is to determine the impact of triangles on the strong oriented coloring. We give some hints of answers to this problem by proving that: (1) the strong oriented chromatic number of any oriented planar graph without cycles of lengths 4 to 12 is at most 7, and (2) the strong oriented chromatic number of any oriented planar graph without cycles of length 4 or 6 is at most 19.

Abstract:
We prove that for any positive integer $k$, the edges of any graph whose fractional arboricity is at most $k + 1/(3k+2)$ can be decomposed into $k$ forests and a matching.

Abstract:
We give here some new lower bounds on the order of a largest induced forest in planar graphs with girth $4$ and $5$. In particular we prove that a triangle-free planar graph of order $n$ admits an induced forest of order at least $\frac{6n+7}{11}$ , improving the lower bound of Salavatipour [M. R. Salavatipour, Large induced forests in triangle-free planar graphs, Graphs and Combinatorics, 22:113-126, 2006]. We also prove that a planar graph of order $n$ and girth at least $5$ admits an induced forest of order at least $\frac{44n+50}{69}$.

Abstract:
We give here new upper bounds on the size of a smallest feedback vertex set in planar graphs with high girth. In particular, we prove that a planar graph with girth $g$ and size $m$ has a feedback vertex set of size at most $\frac{4m}{3g}$, improving the trivial bound of $\frac{2m}{g}$. We also prove that every $2$-connected graph with maximum degree $3$ and order $n$ has a feedback vertex set of size at most $\frac{n+2}{3}$.

Abstract:
twelve brazilian isolates and one reference vaccine strain of avian infectious bronchitis virus (ibv) were propagated in embryonating chicken eggs. the entire s1 glycoprotein gene of these viruses was analysed by reverse-transcriptase-polymerase chain reaction and restriction fragment length polymorphism (rt-pcr-rflp), using the restriction enzymes haeiii, xcmi and bstyi. the rflp patterns led to the classification of these isolates into five distinct genotypes: a, b, c, d and massachusetts. five of twelve isolates were grouped in massachusetts genotype and the remaining seven viruses were classified into four distinct genotypes: a (2), b (2), c (2) or d (1). such genotyping classification agreed with previous immunological analysis for most of these viruses, highlighting the occurrence of a relevant variability among the ibv strains that are circulating in brazilian commercial poultry flocks.

Abstract:
a semi-nested reverse transcription-polymerase chain reaction (semi-n-rt-pcr) was developed and used to detect the s glycoprotein gene of infectious bronchitis virus (ibv) strains and to discriminate h120 vaccine strain from other strains. viral rna was extracted from the allantoic fluid of chicken embryos and from tissues of chickens experimentally infected with different strains of ibv. amplification and identification of the viral rna was performed using two sets of primers complementary to a region of the s glycoprotein gene in the semi-n-rt-pcr assay. the pair of primers used in the first pcr consisted of universal oligonucleotides flanking a more variable region of s1-s2 gene. the second primer pair was used in the semi-n-rt-pcr and was comprised of one of the primers from the first universal pair together with either another universal internal oligolucleotide or a oligonucleotide sequence specific for the h120 strain of ibv. the universal primers detected all reference ibv strains and field isolates tested herein. the semi-n-rt-pcr had high sensitivity and specificity, and was able to differentiate the h120 vaccine strain from other reference ibv strains; including m41 strain. all tissue samples collected from chickens experimentally infected with h120 or m41 strains were positive in the semi-nested rt-pcr using universal primers, while only the h120-infected tissue samples were amplified by the set of primers containing the h120-oligonucleotide. in conclusion, the ability of semi-n-rt-pcr to detect distinct ibv strains and preliminarily discriminate the vaccine strain (h120) closes a diagnostic gap and offers the opportunity to use comprehensive pcr procedures for the ibv diagnosis.