On the Mass and Width of the Z-boson and Other Relativistic Quasistable Particles

The ambiguity in the definition for the mass and width of relativistic resonances is discussed, in particular for the case of the Z-boson. This ambiguity can be removed by requiring that a resonance's width $\Gamma$ (defined by a Breit-Wigner lineshape) and lifetime $\tau$ (defined by the exponential law) always and exactly fulfill the relation $\Gamma = \hbar/\tau$. To justify this one needs relativistic Gamow vectors which in turn define the resonance's mass M_R as the real part of the square root $\rm{Re}\sqrt{s_R}$ of the S-matrix pole position s_R. For the Z-boson this means that $M_R \approx M_Z - 26{MeV}$ and $\Gamma_R \approx \Gamma_Z-1.2{MeV}$ where M_Z and $\Gamma_Z$ are the values reported in the particle data tables.Comment: 23 page

Distribution of black flies (Diptera: Simuliidae) in the State of Espírito Santo, Brazil

Entre os anos de 2004 e 2008 foram realizadas coletas de Simuliidae em várias localidades no Estado do Espírito Santo, Brasil. No total, 66 córregos e rios das doze principais bacias hidrográficas do estado foram amostrados. Dezessete espécies foram coletadas, sendo que nove delas representam ocorrências novas para o estado (Simulium pertinax, S. jujuyense, S. rubrithorax, S. subnigrum, S. travassosi, S. spinibranchium, S. hirtipupa, S. lutzianum e S. anamariae), duplicando o número de espécies conhecidas no estado.We conducted a freshwater survey from 2004 to 2008 in several localities of Espírito Santo, Brazil. In total, 66 streams and rivers were sampled in the 12 hydrographic basins of the state. We collected and identified 17 species of which nine represent new records (Simulium pertinax, S. jujuyense, S. rubrithorax, S. subnigrum, S. travassosi, S. spinibranchium, S. hirtipupa, S. lutzianum e S. anamariae). These findings doubled the number of records of black fly species to the State of Espírito Santo, Brazil

Spanning forests and the q-state Potts model in the limit q \to 0

We study the q-state Potts model with nearest-neighbor coupling v=e^{\beta J}-1 in the limit q,v \to 0 with the ratio w = v/q held fixed. Combinatorially, this limit gives rise to the generating polynomial of spanning forests; physically, it provides information about the Potts-model phase diagram in the neighborhood of (q,v) = (0,0). We have studied this model on the square and triangular lattices, using a transfer-matrix approach at both real and complex values of w. For both lattices, we have computed the symbolic transfer matrices for cylindrical strips of widths 2 \le L \le 10, as well as the limiting curves of partition-function zeros in the complex w-plane. For real w, we find two distinct phases separated by a transition point w=w_0, where w_0 = -1/4 (resp. w_0 = -0.1753 \pm 0.0002) for the square (resp. triangular) lattice. For w > w_0 we find a non-critical disordered phase, while for w < w_0 our results are compatible with a massless Berker-Kadanoff phase with conformal charge c = -2 and leading thermal scaling dimension x_{T,1} = 2 (marginal operator). At w = w_0 we find a "first-order critical point": the first derivative of the free energy is discontinuous at w_0, while the correlation length diverges as w \downarrow w_0 (and is infinite at w = w_0). The critical behavior at w = w_0 seems to be the same for both lattices and it differs from that of the Berker-Kadanoff phase: our results suggest that the conformal charge is c = -1, the leading thermal scaling dimension is x_{T,1} = 0, and the critical exponents are \nu = 1/d = 1/2 and \alpha = 1.Comment: 131 pages (LaTeX2e). Includes tex file, three sty files, and 65 Postscript figures. Also included are Mathematica files forests_sq_2-9P.m and forests_tri_2-9P.m. Final journal versio

Enterohemorrhagic Escherichia coli O157: H7 from healthy dairy cattle in Mid-West Brazil: occurrence and molecular characterization

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 represents the major Shiga toxin-producing E. coli (STEC) strain related to large outbreaks and severe diseases such as hemorrhagic colitis (HC) and the potentially lethal hemolytic uremic syndrome (HUS). The aim of this study was to report the occurrence and molecular characterization of O157:H7 isolates obtained by rectal swab from 52 healthy dairy cattle belonging to 21 farms in Mid-West of Brazil. Detection of 16SrRNA, stx1, stx2, rfbO157, fliCh7, eae, ehxA, saa, cnf1, chuA, yjaA and TSPE4.C2 genes was performed by PCR. The isolates were further characterized by serotyping. Two hundred and sixty E. coli isolates were obtained, of which 126 were characterized as STEC. Two isolates from the same cow were identified as serotype O157:H7. Both isolates presented the stx2, eae, ehxA, saa and cnf1 virulence factor genes and the chuA gene in the phylogenetic classification (virulent group D), suggesting that they were clones. The prevalence of O157:H7 was found to be 1.92% (1/52 animals), demonstrating that healthy dairy cattle from farms in the Mid-West of Brazil are an important reservoir for highly pathogenic E. coli O157:H7

Flora fanerogâmica da Serra Negra, Minas Gerais, Brasil

O presente estudo teve como objetivo caracterizar a flora fanerogâmica da região da Serra Negra localizada no sul da Zona da Mata de Minas Gerais, entre os municípios de Lima Duarte, Rio Preto, Santa Bárbara do Monte Verde e Olaria. Embora considerada de importância biológica alta, esta região não possui nenhum registro anterior de dados florísticos, o que levou ao desenvolvimento deste levantamento, durante o período de 2003 a 2010. A vegetação é caracterizada por um mosaico de formações florestais e campestres onde se destacam os campos rupestres e florestas nebulares em altitudes que variam de 1300 a ca. 1700 m. Um total de 1033 espécies foi encontrado, distribuídas em 469 gêneros e 121 famílias sendo as mais representativas Orchidaceae (115 spp.), Asteraceae 54 spp.), Melastomataceae (56 spp.), Myrtaceae (53 spp.), Fabaceae, Poaceae e Rubiaceae (48 spp. cada), Bromeliaceae (43 spp.), Solanaceae (38 spp.) e Piperaceae (33 spp). Novos registros e endemismos para a flora mineira foram encontrados e 58 espécies estão citadas na lista de espécies ameaçadas de Minas Gerais

An annotated list of ornamentals naturally found infected by Brevipalpus mite-transmitted viruses

The first cases of ornamental plants found infected by Brevipalpus transmitted viruses (BTV) were described in the 1990's from the region of Piracicaba, State of São Paulo, Brazil; subsequent cases were from other regions in the country and other American countries. Currently, 37 ornamental plant species (for the sake of simplicity, orchids being considered as a single species), belonging to 18 families of dicotyledons, have been reported hosting BTV. Because of the non systemic type of infection of these viruses, the localized diseases they cause are unimportant usually, but they have the potential to cause economic losses if severe outbreaks of Brevipalpus mite populations occur. Some ornamentals may serve as reservoirs to BTV known to cause serious damage to food crops as Citrus leprosis virus- cytoplasmic type (CiLV-C), passion fruit green spot virus (PFGSV) and Coffee ringspot virus (CoRSV).Os primeiros casos de plantas ornamentais encontradas naturalmente infetadas por vírus transmitidos por Brevipalpus (Acari: Tenuipalpidae) (VTB) foram registrados nos anos 1990 na região de Piracicaba, Estado de São Paulo, e ocorrências subseqüentes foram observadas em várias outras regiões do país e de outros países das Américas. Atualmente acham-se relatadas 37 espécies de ornamentais (para efeito de simplificação, orquídeas foram consideradas como única espécie) pertencentes a 18 famílias botânicas. Pelo fato de causarem apenas infecções localizadas, geralmente nas folhas, VTB em ornamentais não causam preocupações aos produtores, mas potencialmente podem causar perdas econômicas se ocorrerem explosões populacionais do ácaro vetor. Plantas ornamentais podem servir de reservatório de VTB de importância econômica como os vírus da leprose dos citros-tipo citoplasmático (CiLV-C), da mancha verde do maracujá (PFGSV) e da mancha anular do cafeeiro (CoRSV)

Agro-morphological characterization of upland rice accessions

The agro-morphological characterization is fundamental in order to provide information for plant breeding programs. The aim of the present study was to characterize 146 accessions of upland rice (Oryza sativa L.), based on qualitative and quantitative agro-morphological descriptors. The experiment was conducted in Recife, state of Pernambuco, Brazil, using a randomized block design with three replicates. Polymorphism was observed among 12 of 14 qualitative characters evaluated, whereas significant differences (p < 0.05) were observed for 11 of the 14 analysed quantitative traits. Genetic variance was higher than environmental variance and the average inheritability coefficients were above 80 % for all characters, which ensures the predominance of the genetic components in the differences observed among accessions. On the cluster analysis for qualitative traits the accessions were classified in two groups with a total of 18 duplicates, whereas for the quantitative traits three groups were obtained with few subgroups. The principal component analysis for quantitative traits showed great dispersion of the accessions. The most divergent group of accessions included the genotypes Mitsukasane, Mie, Tomoe mochi, Ooba kirishima and Nourin mochi 6, which showed a higher number of spicklets per plant. There is high variability among the rice accessions from the germplasm collection studied, which presents great importance for breeding programs or for genetic studies on this species