436 research outputs found
Methods of application and dosages of insecticides for Aphis gossypii (Glover) (Hemiptera: Aphididae) in the yellow melon
[PT] - Para aperfeiçoar o manejo fitossanitário de pragas na cultura do melão (Cucumis melo L.), objetivou-se avaliar
os efeitos de formas de aplicação e doses de inseticidas sobre a eficiência de controle químico do pulgão A. gossypii. O
experimento foi realizado em 2010, na cidade de Fortaleza, Ceará, com melão amarelo cultivado em condições de campo.
O delineamento experimental foi em blocos ao acaso, arranjo fatorial 2 x 4, com quatro repetições e parcelas de seis
plantas. Os tratamentos foram duas formas de aplicação (pulverização costal manual e insetigação por gotejamento) e quatro
doses de inseticida (0; 50; 100; 200% da dose recomendada pelo fabricante). Os inseticidas acefato e tiametoxam, testados
separadamente, foram aplicados em manejo de rotação de grupos químicos. A eficiência de controle foi avaliada sete dias
após o uso de cada inseticida. O acefato não apresentou diferença significativa entre as formas de aplicação, atingindo
eficiências de controle de 88,95 e 84,09% com 100 e 200% da dose recomendada, respectivamente. O tiametoxam não
diferiu significativamente quanto às formas de aplicação e doses testadas, apresentando eficiência de 100% em todos os
tratamentos. Atualmente, no Brasil, a utilização de acefato no melão está limitada à aplicação mecanizada devido ao risco de
contaminação. Diante dessa limitação, o controle do pulgão em meloeiro amarelo pode ser realizado via insetigação por gotejo
ou pulverização costal manual, devendo-se empregar, preferencialmente, 100% da dose recomendada de tiametoxam.[EN] In order to perfect the phytosanitary management of pests in the melon crop (Cucumis melo L.), the aim here was to evaluate the effects of different methods of application and dosages of insecticides on the effectiveness of chemical control of the aphid A. gossypii. The experiment was carried out in 2010, in Fortaleza, in the state of Ceara, Brazil, with yellow melon grown under field conditions. The experimental design was of randomised blocks in a 2 x 4 factorial arrangement, with four replications and lots of six plants. Treatments consisted of two methods of application (manual backpack spray and drip insectigation) and four dosages of insecticide (0, 50, 100 and 200% of the dosage recommended by the manufacturer). The insecticides acephate and thiamethoxam, tested separately, were applied in a rotating management of chemical groups. Efficiency of the control was evaluated seven days after the use of each insecticide. The acephate showed no significant difference between the forms of application, reaching control efficiencies of 88.95 and 84.09% with 100 and 200% of the recommended dose respectively. The thiamethoxam did not differ significantly for the application methods and dosages under test, giving 100% efficiency in all treatments. Currently in Brazil the use of acephate in the melon is limited to mechanised application due to the risk of contamination. Because of this limitation, the control of aphids in yellow melon can be carried out via drip insectigation or backsack spray, with preferably 100% of the recommended dose of thiamethoxam.Do Bomfim, G.; Moreira De Azevedo, B.; Viana, TVA.; Manzano Juarez, J.; Vasconcelos, DV. (2015). Formas de aplicação e doses de inseticidas sobre Aphis gossypii (Glover) (Hemiptera: Aphididae) em melão amarelo. Revista Ciencia Agronomica. 46(3):488-496. doi:10.5935/1806-6690.20150030S48849646
Design and installation alternatives of Venturi injectors in drip irrigation
[ES] En la Universitat Politècnica de València, Valencia, España (39°29¿ N; 0°23¿ W; 20 m), ha sido estudiado
el funcionamiento de cuatro prototipos de inyector Venturi y tres formas de instalación distintas. El funcionamiento
se ha analizado bajo diversos parámetros, como pérdidas de carga, relación de caudales y rendimiento. Las formas de
instalación analizadas han sido: sin inyección y con inyección y presiones negativas o positivas en la garganta. Las
presiones se establecieron entre 10 y 40 m.c.a. A partir de los datos experimentales han sido procesados utilizando
técnicas de regresión múltiple y análisis de la varianza. Con ellas, fue posible, a través de la integración de geometrías
en función de los diámetros, caudales y presiones, obtener expresiones para prever la pérdida de carga o el caudal
inyectado. Se pone de manifiesto que la relación de caudales y el rendimiento son mayores cuanto mayor es el diámetro
de la aspiración y empeoran al reducirse el diámetro de la garganta, siendo estas las dimensiones que más condicionan
la inyección. También, puede afirmarse que la pérdida de carga, para un mismo caudal inyectado, es inferior si la
operación se realiza con presiones positivas que con presiones negativas. La relación de caudales o el rendimiento
también proporcionan valores más elevados bajo esta forma de instalación propuesta.[EN] The performance and installation alternatives of four Venturi injector prototypes were studied at Universitat
Politècnica de València, Valencia, Spain (39°29¿ N; 0°23¿ W; 20 m). This device performance was studied under several
parameters such as head loss, relation of flows and injection efficiency. The installation configurations analyzed were:
without the injection of nutrients solution and with the injection either having negative or positive pressure at the Venturi
throat. The inlet pressures were established between 10 and 40 m.w.c. The experimental data has been processed using
multiple stepwise regression techniques and analysis of variance (ANOVA). Moreover, geometry integration versus
diameters, flows and pressures is used to obtain some equations for predicting the head loss and injected flow. The results
of the present study showed that the relation between flows and injection efficiency were better when the diameter of
inlet nutrient line increases and become worse when decreases the diameter of the Venturi throat. Accordingly, these
dimensions become very important in the design prototype and installation configuration. Furthermore, after the analysis
of laboratory experiments it can be concluded that head losses, at the same injected flow, were lower if the injection was
carried out with positive pressures at the throat than in the case of negative pressures. Also in this case, the relationship
between flow rates and injection efficiency leaded to a good performance of the proposed installation.Manzano Juarez, J.; Palau, C.; Moreira De Azevedo, B.; Do Bomfim, G.; Vasconcelos, DV. (2015). Diseño y alternativas en la instalación de inyectores Venturi en riego localizado. Revista Ciencia Agronomica. 46(2):287-298. doi:10.5935/1806-6690.20150008S28729846
Consistency analysis of a nonbirefringent Lorentz-violating planar model
In this work analyze the physical consistency of a nonbirefringent
Lorentz-violating planar model via the analysis of the pole structure of its
Feynman propagators. The nonbirefringent planar model, obtained from the
dimensional reduction of the CPT-even gauge sector of the standard model
extension, is composed of a gauge and a scalar fields, being affected by
Lorentz-violating (LIV) coefficients encoded in the symmetric tensor
. The propagator of the gauge field is explicitly evaluated
and expressed in terms of linear independent symmetric tensors, presenting only
one physical mode. The same holds for the scalar propagator. A consistency
analysis is performed based on the poles of the propagators. The isotropic
parity-even sector is stable, causal and unitary mode for .
On the other hand, the anisotropic sector is stable and unitary but in general
noncausal. Finally, it is shown that this planar model interacting with a
Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
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