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Infestações do ácaro Calepitrimerus vitis foram verificadas nas últimas safras nos parreirais do Sul do Brasil, entre os meses de dezembro e março. A espécie ataca somente videira e provoca deformações nas folhas, queda prematura e até mesmo atraso no desenvolvimento das plantas. A eliminação de restos de poda durante o inverno é importante esttratégia de controle, porque nesse período as fêmeas ficam alojadas nas reentrâncias dos ramos e no interior das brácteas das gemas

The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Nucleon

The Gerasimov-Drell-Hearn sum rule is one of several dispersive sum rules that connect the Compton scattering amplitudes to the inclusive photoproduction cross sections of the target under investigation. Being based on such universal principles as causality, unitarity, and gauge invariance, these sum rules provide a unique testing ground to study the internal degrees of freedom that hold the system together. The present article reviews these sum rules for the spin-dependent cross sections of the nucleon by presenting an overview of recent experiments and theoretical approaches. The generalization from real to virtual photons provides a microscope of variable resolution: At small virtuality of the photon, the data sample information about the long range phenomena, which are described by effective degrees of freedom (Goldstone bosons and collective resonances), whereas the primary degrees of freedom (quarks and gluons) become visible at the larger virtualities. Through a rich body of new data and several theoretical developments, a unified picture of virtual Compton scattering emerges, which ranges from coherent to incoherent processes, and from the generalized spin polarizabilities on the low-energy side to higher twist effects in deep inelastic lepton scattering.Comment: 32 pages, 19 figures, review articl

Acarinose da videira no Rio Grande do Sul.

bitstream/item/48495/1/Circular-Tecnica-85.pd

Compton Scattering by the Proton using a Large-Acceptance Arrangement

Compton scattering by the proton has been measured using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The new data are interpreted in terms of dispersion theory based on the SAID-SM99K parameterization of photo-meson amplitudes. It is found that two-pion exchange in the t-channel is needed for a description of the data in the second resonance region. The data are well represented if this channel is modeled by a single pole with mass parameter m(sigma)=600 MeV. The asymptotic part of the spin dependent amplitude is found to be well represented by pi-0-exchange in the t-channel. A backward spin-polarizability of gamma(pi)=(-37.1+-0.6(stat+syst)+-3.0(model))x10^{-4}fm^4 has been determined from data of the first resonance region below 455 MeV. This value is in a good agreement with predictions of dispersion relations and chiral pertubation theory. From a subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to a E2/M1 multipole ratio of the p-to-Delta radiative transition of EMR(340 MeV)=(-1.7+-0.4(stat+syst)+-0.2(model))%. It was found that this number is dependent on the parameterization of photo-meson amplitudes. With the MAID2K parameterization an E2/M1 multipole ratio of EMR(340 MeV)=(-2.0+-0.4(stat+syst)+-0.2(model))% is obtained

π\piNN coupling and two-pion photoproduction on the nucleon

Effects of non-resonant photoproductions arising from two different $\pi NN$ couplings are investigated in the $\gamma N\to\pi\pi N$ reaction. We find that the pseudoscalar (PS) $\pi NN$ coupling is generally preferable to the pseudovector (PV) $\pi NN$ coupling and particularly the total cross sections are successfully described by the model with the PS $\pi NN$ coupling. In order to see the difference between the two couplings, we also show the results of invariant mass spectra and helicity-dependent cross sections in various isospin channels calculated with the PS and PV couplings.Comment: 35 pages, 11 figures, minor changes and version to be published in Phys.Rev.

Predição do consumo de matéria seca de cabras leiteiras durante a gestação.

Resumo: O período da gestação é caracterizado por importantes mudanças fisiológicas no corpo materno tais como a diminuição da ingestão de alimento no último terço de gestação em fêmeas com gestação de múltiplos fetos. O objetivo desse estudo foi desenvolver modelos para predizer a ingestão de matéria seca (IMS) em cabras durante gestação simples e gemelar. Parar este estudo, foram usadas 1820 observações de IMS, obtidos diariamente a partir de sete cabras com gestação gemelar e seis cabras com gestação simples a partir do primeiro dia até os 140 dias de gestação. A IMS diária foi ajustada em três modelos não lineares, os quais foram avaliados através do critério de informação Bayesiana (BIC) como um indicador de melhor ajuste do modelo aos dados. O modelo que melhor se ajustou aos dados foi o modelo quadrático, com valor de BIC de 11549. Os interceptos e coeficientes de regressões do modelo quadrático utilizado para predição do IMS diário foram diferentes entre gestação simples e gemelar (P< 0.01). Comparado as cabras com gestação simples, as cabras com gestação gemelar tiveram maior decréscimo na IMS durante a gestação. Esse decréscimo na IMS em fêmeas com gestação gemelar se deve principalmente a mudanças hormonais e a maior compressão ruminal causada pelo maior tamanho de seus úteros grávidos. Os modelos desenvolvidos nesse estudo devem de ser considerados no manejo nutricional de cabras leiteiras durante a gestação. [Prediction of dry matter intake of dairy goats during pregnancy]. Abstract: The pregnancy is characterized by important physiological changes in maternal body such as a decrease on feed intake in the last third of pregnancy mainly in pregnancy of multiples fetuses. The objective of this study was to develop a model to predict the dry matter intake (DMI) of dairy goats carrying single and twin fetuses throughout pregnancy. For this study it was used a total of 1820 individual records of DMI from seven goats carrying twins and six goats carrying single fetuses. The DMI was daily recorded from the first up to 140 days of pregnancy. The daily DMI as a proportion of the average BW was fitted to tree non-linear models which were evaluated considering the Bayesian information criterion (BIC) value as an indicator how well the model fit the data. The best model fitting the data was the quadratic model with had BIC value of 11549. The intercepts and the slopes of the quadratic models used to predict the daily DMI were different between litter sizes (P < 0.01). Goats carrying twin fetuses showed a greater decrease in the DMI during pregnancy compared to goats carrying single fetus. The decrease of feed intake in females carrying twins may be mainly related to hormonal changes and a greatest rumen compression due to the biggest size of the gravid uterus. The models developed in this study may be relevant in the adoption of nutritional management of dairy goats during the pregnancy

Subthreshold rho^0 photoproduction on 3He

A large reduction of the rho^0 mass in the nuclear medium is reported, inferred from dipion photoproduction spectra in the 1 GeV region, for the reaction 3He(gamma,pi+ pi-)X with a 10% duty factor tagged-photon beam and the TAGX multi-particle spectrometer. The energy range covered (800 < E(gamma) < 1120 MeV) lies mostly below the free rho^0 production threshold, a region which is believed sensitive to modifications of light vector-meson properties at nuclear-matter densities. The rho^0 masses extracted from the MC fitting of the data, m*(rho^0) = 642 +/- 40, 669 +/- 32, and 682 +/- 56 MeV/c^2 for E(gamma) in the 800-880, 880-960, and 960-1040 MeV regions respectively, are independently corroborated by a measured, assumption-free, kinematical observable. This mass shift, far exceeding current mean-field driven theoretical predictions, may be suggestive of rho^0 decay within the range of the nucleonic field.Comment: 40 pages, 13 figures, submitted to Phys. Rev.

Photoproduction of scalar mesons on protons and nuclei

We study the photoproduction of scalar mesons close to the threshold of f_0(980) and a_0(980) using a unitary chiral model. Peaks for both resonances show up in the invariant mass distributions of pairs of pseudoscalar mesons. A discussion is made on the photoproduction of these resonances in nuclei, which can shed light on their nature, a subject of continuous debate.Comment: 25 pages, 9 figures, accepted for publication in Phys Rev