334 research outputs found
Clones de batata de sanidad controlada producidos en el Instituto de Patología Vegetal-CIAP-INTA Córdoba
La calidad del material de plantación es uno de los aspectos más importantes para asegurar el éxito de un cultivo de batata. Está dada por dos factores fundamentales: la variedad y la sanidad. La tendencia mundial es el empleo de cultivares precoces de alta productividad, tanto los de pulpa amarilla o anaranjada, ricos en β-carotenos, como los de pulpa morada, con alto contenido de antocianinas que, además, deben estar libres de virus, pues estos patógenos son la principal limitante de la producción cuanti y cualitativamente. Frente a la creciente demanda de material de propagación, el Instituto de Patología Vegetal dependiente del Centro de Investigaciones Agropecuarias (IPAVE-CIAP-INTA) cuenta, al presente, con una colección de genotipos requeridos en las diversas provincias productoras, que fueron «saneados» de virus y de otros patógenos sistémicos a través del cultivo in vitro de meristemas con termoterapia previa, y que recuperaron su pureza varietal. Los mismos son mantenidos por micropropagación in vitro y macropropagación en invernaderos y jaulón antiáfidos. Todos los años se inicia un nuevo ciclo de regeneraciónin vitro, con el fin de disminuir la probabilidad de ocurrencia de variación somaclonal. Actualmente, la institución ofrece a los agricultores y a la agroindustria propágulos de sanidad controlada de los cultivares Arapey INIA, Beauregard, Covington, GEM, Jewel, Morada INTA, Mechada, Boni INTA, Okinawa, Colorado INTA, Sombrerito, Pionera, Bonita, Paraguaya y Famaillá 6, para su distribución en las regiones productoras argentinas, además de tres clones promisorios aún no descriptos, de interés local
Cuantificación de dos potyvirus de batata e interacciones entre ellos y con el crinivirus Sweet potato chlorotic stunt virus (SPCSV)
Todas las regiones de cultivo de batata en Argentina se encuentran afectadas por una grave virosis en la que están involucrados siete virus, entre ellos dos potyvirus: Sweet potato feathery mottle virus (SPFMV), Sweet potato virus G (SPVG) y un crinivirus: SPCSV, con efecto sinérgico, especialmente sobre los potyvirus. Con el fin de estudiar la interacción entre SPFMV y SPVG en infecciones dobles y triples con SPCSV en dos clones de batata y en la indicadora Ipomoea setosa, ambos potyvirus fueron purificados desde I. setosa infectada por injerto y luego se trazaron sendas curvas de concentración viral para su cuantificación en tejidos vegetales mediante DAS-ELISA. Además, se determinó severidad de síntomas y concentración viral a los 15, 21, 30 y 35 desde las infecciones simples, dobles y triples. En ambos casos, las curvas patrón de concentraciónse ajustaron a ecuaciones sigmoideas: [SPFMV]= 〖α*〗^((〖-β*〗^((-γ*A_405))) ); α=0,13 (p<0,0001), β=7,04 (p<0,0001) y γ=1,44 (p<0,0001) y [SPVG]= α⁄(1+ 〖β*〗^((-γ*A_405)) ); α =0,08 (p<0,0001); β=1309,07(p 0,0687); γ=5,36 (p<0,0001). Las mayores concentraciones de virus, en general, ocurrieron en I. setosa, luego en el cv GEM de batata y, por último, en Arapey INIA. Se demostró efecto sinérgico mayor a los 15 días desde la infección con los tres virus en la indicadora, con aumentos de los títulos de SPFMV y de SPVG cercanos a 100 veces. Este hecho no fue notable en Arapey y sí en GEM, con incrementos de concentración de aproximadamente 50 veces a los 35 días de infección y de dos veces a los 21 días, para SPFMV y SPVG, respectivamente. No se evidenció antagonismo entre ambos potyvirus. A los 35 días desde el injerto (infecciones triples), I. setosa y el cv GEM manifestaron síntomas muy severos. Las curvas patrón de concentración constituyen un avance importante en estudios epidemiológicos de virosis de batata en Argentina
Search for Decay
We have searched for the charmless hadronic decay of B0 mesons into two
neutral pions. Using 9.13fb^-1 taken at the Upsilon(4S) with the CLEO detector,
we obtain an improved upper limit for the branching fraction BR(B0-->pi0pi0) <
5.7*10^-6 at the 90% confidence level.Comment: pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Search for Zgamma events with large missing transverse energy in ppbar collisions at sqrt(s)=1.96 TeV
We present the first search for supersymmetry (SUSY) in Zgamma final states
with large missing transverse energy using data corresponding to an integrated
luminosity of 6.2 fb-1 collected with the D0 experiment in ppbar collisions at
sqrt(s)=1.96 TeV. This signature is predicted in gauge-mediated SUSY-breaking
models, where the lightest neutralino is the next-to-lightest supersymmetric
particle (NLSP) and is produced in pairs, possibly through decay from heavier
supersymmetric particles. The NLSP can decay either to a Z boson or a photon
and an associated gravitino that escapes detection. We exclude this model at
the 95% C.L. for SUSY breaking scales of Lambda < 87 TeV, corresponding to
neutralino masses of < 151 GeV.Comment: submitted to Phys. Rev. Let
Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production
We present measurements of lepton (l) angular distributions in ttbar -> W+ b
W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a
center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using
data corresponding to an integrated luminosity of 5.4fb^-1, collected with the
D0 detector at the Fermilab Collider, we find that the angular distributions of
l- relative to anti-protons and l+ relative to protons are in agreement with
each other. Combining the two distributions and correcting for detector
acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat)
+- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted)
= (4.7 +- 0.1)%. This result is further combined with the measurement based on
the analysis of the l+jets final state to obtain A^l_FB = (11.8 +- 3.2)%.
Furthermore, we present a first study of the top-quark polarization.Comment: submitted versio
Journal Staff
We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar < 1.0 and transverse momenta 30 < p(T)(gamma) < 200 GeV. The b-quark jets are required to have p(T)(jet) > 15 GeVand vertical bar y(jet)vertical bar < 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators
A search for charged massive long-lived particles
We report on a search for charged massive long-lived particles (CMLLPs),
based on 5.2 fb of integrated luminosity collected with the D0 detector
at the Fermilab Tevatron collider. We search for events in which one
or more particles are reconstructed as muons but have speed and ionization
energy loss inconsistent with muons produced in beam collisions.
CMLLPs are predicted in several theories of physics beyond the standard model.
We exclude pair-produced long-lived gaugino-like charginos below 267 GeV and
higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar
top quarks with mass below 285 GeV.Comment: submitted to Phys. Rev. Letter
Zgamma production and limits on anomalous ZZgamma and Zgammagamma couplings in ppbar collisions at sqrt(s)=1.96 TeV
We present a measurement of ppbar->Zgamma->ll+gamma (l = e, mu) production
with a data sample corresponding to an integrated luminosity of 6.2 fb^{-1}
collected by the D0 detector at the Fermilab Tevatron ppbar Collider. The
results of the electron and muon channels are combined, and we measure the
total production cross section and the differential cross section
dsigma/dp_T^gamma, where p_T^gamma is the momentum of the photon in the plane
transverse to the beamline. The results obtained are consistent with the
standard model predictions from next-to-leading order calculations. We use the
transverse momentum spectrum of the photon to place limits on anomalous ZZgamma
and Zgammagamma couplings
Search for associated production in collisions at
This report describes a search for associated production of and Higgs
bosons based on data corresponding to an integrated luminosity of collected with the D0 detector at the Fermilab
Tevatron Collider. Events containing a
candidate (with corresponding to or ) are selected in
association with two or three reconstructed jets. One or two of the jets are
required to be consistent with having evolved from a quark. A multivariate
discriminant technique is used to improve the separation of signal and
backgrounds. Expected and observed upper limits are obtained for the product of
the production cross section and branching ratios and reported in terms of
ratios relative to the prediction of the standard model as a function of the
mass of the Higgs boson (). The observed and expected 95% C.L. upper
limits obtained for an assumed are, respectively, factors
of 4.5 and 4.8 larger than the value predicted by the standard model.Comment: 25 pages, 14 figure
Search for first generation leptoquark pair production in the electron + missing energy + jets final state
We present a search for the pair production of first generation scalar
leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4
fb collected with the D0 detector at the Fermilab Tevatron Collider in
ppbar collisions at TeV. In the channel , where q, q' are u or d quarks, no significant excess
of data over background is observed, and we set a 95% C.L. lower limit of 326
GeV on the leptoquark mass, assuming equal probabilities of leptoquark decays
to eq and .Comment: 7 pages, 6 figures, submitted to PRD-R
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