Two Particle States and the SS-matrix Elements in Multi-channel Scattering

Using a quantum mechanical model, the exact energy eigenstates for two-particle two-channel scattering are studied in a cubic box with periodic boundary conditions in all three directions. A relation between the exact energy eigenvalue in the box and the two-channel $S$-matrix elements in the continuum is obtained. This result can be viewed as a generalization of the well-known L\"uscher's formula which establishes a similar relation in elastic scattering.Comment: 18 pages, no figures. minor changes compared with previous versio

The Use of Dispersion Relations in the ππ\pi\pi and KKˉK\bar K Coupled-Channel System

Systematic and careful studies are made on the properties of the IJ=00 $\pi\pi$ and $K\bar K$ coupled-channel system, using newly derived dispersion relations between the phase shifts and poles and cuts. The effects of nearby branch point singularities to the determination of the $f_0(980)$ resonance are estimated and and discussed.Comment: 22 pages with 5 eps figures. A numerical bug in previous version is fixed, discussions slightly expanded. No major conclusion is change

A new measurement of K+(e4) decay and the s-wave pi-pi-scattering length a00

A sample of 400000 events from the decay K+->pi+pi-e+nu(e)(K(e4)) has been collected in experiment E865 at the Brookhaven AGS. The analysis of these data yields new measurements of the K(e4) branching ratio (4.11+-0.01+-0.11)*10**(-5)), the s-wave pi-pi scattering length a00=0.228+-0.012+-0.003, and the form factors F, G, and H of the hadronic current and their dependence on the invariant pi-pi mass

Species within the Bemisia tabaci (Hemiptera: Aleyrodidae) Complex in Soybean and Bean Crops in Argentina

The White fly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a cryptic species complex that contains some of the most damaging pests in tropical and subtropical regions. Recent studies suggested that this complex is composed of at least 24 distinct species. We use the approach from these studies to consider the identity of B. tabaci in Argentina. Previous studies have suggested the presence of a B. tabaci presumably indigenous to the Americas and referred to as the BR biotype in Argentina. We placed the entity referred to as the BR biotype within the B. tabaci cryptic species complex using whiteflies collected in soybean and bean crops in northern and central Argentina. The whiteflies were assigned using the mitochondrial cytochrome oxidase (mtCOI) gene. Four unknown haplotypes plus two Argentina sequences from GenBank formed a cluster that was basal to the rest of theNewWorld sequences. These sequences diverged from the consensus sequence across the range of 3.6 to 4.3%. Applying the species assignment rules of recent studies suggests that the individuals from Argentina form a separate species. A unknown haplotype fell within the New World putative species and formed a distinct cluster with haplotypes from Panama. These results suggest that Argentina has two indigenous species belonging to the B. tabaci cryptic species complex. Rather tan using mtCOI sequencing for all B. tabaci collected, a simple random amplifed polymorphic DNApolymerase chain reaction diagnostic was used and tested along with previously published primers designed to work specially with the BR biotype from Brazil. These primers were either unable to distinguish between the two indigenous members of the complex in Argentina or indicated a difference when none was evident on the basis of mtCOI sequence comparison.Fil: Alemandri, V.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; ArgentinaFil: De Barro, P.. No especifíca;Fil: Bejerman, N.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; ArgentinaFil: Argüello Caro, Evangelina Beatriz. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Dumón, A. D.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; ArgentinaFil: Mattio, Maria Fernanda. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Rodríguez, S. M.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; ArgentinaFil: Truol G.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentin

Caenodelphax teapae (Fowler) (Hemiptera: Delphacidae): a new natural vector of the Mal de Río Cuarto virus (MRCV, Fijivirus) in Argentina

El Mal de Río Cuarto virus (MRCV) es el agente causal del mal de Río Cuarto, una de las principales enfermedades del maíz en Argentina. Es transmitido en la naturaleza principalmente por Delphacodes kuscheli (Insecta: Hemiptera). La presencia de otros delfácidos en áreas afectadas por la enfermedad, permite suponer que éstos tendrían un rol en su epidemiología. En prospecciones realizadas entre los años 2003 y 2006 en las provincias de Tucumán y Salta (noroeste argentino), Caenodelphax teapae se destacó por ser una de las especies más abundantes en la vegetación espontánea. El MRCV fue transmitido experimentalmente a trigo a partir de ejemplares naturalmente infectados provenientes de campo en Tucumán. La reacción del virus en las pruebas serológicas realizadas a insectos y plantas infectadas, así como la sintomatología observada en éstas y la presencia de agregados de partículas virales en células floemáticas, confirmaron que C. teapae tuvo la capacidad de transmitir el MRCV a trigo desde poblaciones naturales capturadas en la provincia de Tucumán. Las evidencias demostraron por primera vez que las poblaciones naturales de C. teapae son portadoras del MRCV y que actúan como vectoras del virus con importantes implicancias en la epidemiología del mal de Río Cuarto.Mal de Río Cuarto virus (MRCV) is the causal agent of Mal de Río Cuarto, one of the major diseases of maize in Argentina. It is spread under natural conditions by Delphacodes kuscheli (Insecta: Hemiptera). The presence of other delphacids in areas affected by the disease suggests that they have a role in its epidemiology. In prospective surveys conducted between 2003 and 2006 in the provinces of Tucumán and Salta (northwestern Argentina), Caenodelphax teapae stood out as one of the most abundant species in wild vegetation. The MRCV was experimentally transmitted to wheat through naturally field-infected specimens from Tucumán. The reaction of the virus in serological tests on insects and infected plants as well as the observed symptoms, together with the presence of aggregates of viral particles in phloem cells, confirmed that C. teapae had the ability to transmit the MRCV to wheat from natural populations captured in the province of Tucumán. Evidence showed for the first time that natural populations of C. teapae carry the MRCV and act as vectors of the virus with important implications for the epidemiology of this disease.Facultad de Ciencias Naturales y Muse

QCD Isospin Breaking in Meson Masses, Decay Constants and Quark Mass Ratios

The procedure to calculate masses and matrix-elements in the presence of mixing of the basis states is explained in detail. We then apply this procedure to the two-loop calculation in Chiral Perturbation Theory of pseudoscalar masses and decay constants including quark mass isospin breaking. These results are used to update our analysis of $K_{\ell4}$ done previously and obtain a value of $m_u/m_d$ in addition to values for the low-energy-constants $L_i^r$.Comment: 22 pages, uses axodraw.st

Pyrophagus tigrinus Remes Lenicov & Varela (Hemiptera: Delphacidae), a new vector of the Mal de Río Cuarto virus (MRCV, Fijivirus) under experimental conditions

El Mal de Río Cuarto virus (MRCV), agente causal de la enfermedad más importante del maíz en la Argentina, es transmitido principalmente por Delphacodes kuscheli. La presencia de otros delfácidos en áreas con la virosis, permite suponer que éstos podrían tener un rol en su epidemiología. Pyrophagus tigrinus fue hallada por primera vez en 1997 en Jesús María (Córdoba) sobre cultivos de triticale afectados con el MRCV. El objetivo fue demostrar la capacidad de P. tigrinus para transmitir el MRCV a triticale en condiciones experimentales. Se inició la cría en condiciones controladas y se realizaron transmisiones a triticale, empleando el mismo cereal como fuente de inóculo. Los síntomas observados y el patrón electroforético del dsRNA viral se correspondieron con el del MRCV en transmisiones con D. kuscheli. Se observaron agregados de partículas virales en células floemáticas. La capacidad de P. tigrinus para transmitir el MRCV tiene importantes implicaciones en la epidemiología de esta enfermedad.Mal de Río Cuarto virus (MRCV), causal agent of the most important disease that affects maize in Argentina, is spread under natural conditions by Delphacodes kuscheli. The presence of other delphacid species in areas infected with this virus suggests that those species could have a function in the epidemiology of disease. Pyrophagus tigrinus was first found by chance in 1997 in Jesús María (Córdoba) in triticale crops affected by MRCV. The aim of this work was to demonstrate the capacity of P. tigrinus to transmit the MRCV to triticale under experimental conditions. The culture of P. tigrinus under controlled conditions was initiated and Mentransmissions to triticale using this cereal as source of inoculum were carried out. The symptoms observed and the electrophoretic pattern of viral dsRNA were corresponded with the MRCV using D. kuscheli as vector. Aggregates of MRCV-like particles in phloem tissue cells were also observed. The vector capacity of P. tigrinus has very important implications in the epidemiology of this disease.Facultad de Ciencias Naturales y Muse

Measurements of Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Measurements of transverse energy flow are presented for neutral current deep-inelastic scattering events produced in positron-proton collisions at HERA. The kinematic range covers squared momentum transfers Q^2 from 3.2 to 2,200 GeV^2, the Bjorken scaling variable x from 8.10^{-5} to 0.11 and the hadronic mass W from 66 to 233 GeV. The transverse energy flow is measured in the hadronic centre of mass frame and is studied as a function of Q^2, x, W and pseudorapidity. A comparison is made with QCD based models. The behaviour of the mean transverse energy in the central pseudorapidity region and an interval corresponding to the photon fragmentation region are analysed as a function of Q^2 and W.Comment: 26 pages, 8 figures, submitted to Eur. Phys.