48,804 research outputs found
Princípios da avaliação de risco ambiental de agrotóxicos.
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Previous issue date: 2006-10-0
Herbicide effects on plant disease.
No full textTo be effective, herbicides they must have strong biological activity against plants. Indirectly through their effects on plants, herbicides can influence almost any process or interaction of the plant, including its susceptibility to plant diseases. In some cases, herbicides also have direct effects on plant pathogens. In this short review, we will discuss both types of effect, and, where possible, provide the mechanism for the effect. We provide a separate section for glyphosate because of the relatively large amount of information on the effects of this very important herbicide on plant diseases and the fact that there have been many seemingly conflicting claims of the effect of glyphosate on diseases in glyphosate-resistant crops (Duke & Cerdeira, 2005). The topic of herbicide effects on plant diseases has been reviewed previously, either as a single topic (e.g., Altman, 1991; Altman & Campbell, 1979; Katan & Eshel, 1973; Levesque et al., 1992) or as part of a more extensive review on secondary effects of pesticides (several of these are in the book by Altman, 1993) or chemical effects on microbial weed biocontrol agents (Hoagland, 1996). There have been no recent reviews of this topic, but a large amount of information has not been generated since the last review of this topic, except in the case of glyphosate
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
No full textThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
Sorção do herbicida 2,4-D em solos brasileiros.
No full textNeste trabalho procurou-se gerar e discutir dados sobre sorção de pesticidas ácidos em solos brasileiros, considerando sua dependência do pH. Amostras de solos foram coletadas em diferentes regiões do Brasil e suas propriedades determinadas (% de argila, % de CO e pH). Valores do coeficiente de sorção do herbicida 2,4-D foram determinados em laboratório usando teste em equilíbrio padrão e cromatografia a líquido de alta eficiência (CLAE). O coeficiente de sorção (Kd) foi estimulado e o coeficiente de sorção normatizado pela fração de carbono orgânico do solo (Koc) calculado para cada solo. Os resultados de Koc variaram entre 21,3 e 306,5 mL/g, sendo que dados de Koc encontrados na literatura internacional estão entre 20 e 60 mL/g. Observou-se tendência de aumento dos valores de Kd em solos com maiores teores de carbono orgânico. No entanto, houve grande variação nos valores de Koc entre solos da mesma classe. Adicionalmente, os efeitos do pH na sorção do 2,4-D foram estudados em Latossolo. Os valores de Kd e Koc diminuíram com o aumento do pH. A sorção do 2,4-D, como composto ácido, é principalmente determinada pela sua dissociação. Entretanto, a dissociação do 2,4-D pode não ser suficiente para explicar a variação em Kd (ou Koc) em função do pH. Parece que a sorção das formas aniônicas de pesticidas ácidos tem sido superestimadas e o efeito da dissociação da matéria orgânica, com mudanças no pH do solo, tem sido subestimada
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Brachiaria plantaginea (Link) Hitchc. as a potential (new) source of shikimic acid. Quantification by NIR and PLS regression.
No full textShikimic acid is a natural compound, precursor of the antiviral Oseltamivir used against influenza A. It is a scarce and expensive chemical, obtained mainly from seeds of shrubs natives in China and Japan. In this study we propose a fast and clean procedure for the quantification of shikimic acid in B. plantaginea, an alternative source of shikimic acid, using NIR spectroscopy combined with PLS regression
Measurement of b-hadron masses
No full textMeasurements of b-hadron masses are performed with the exclusive decay modes B +→J/ψK +, B 0→J/ψK +, B0→J/ψKS0, Bs0→J/ψφ and Λb0→J/ψΛ using an integrated luminosity of 35pb -1 collected in pp collisions at a centre-of-mass energy of 7 TeV by the LHCb experiment. The momentum scale is calibrated with J/ψ→μ +μ - decays and verified to be known to a relative precision of 2 ×10 -4 using other two-body decays. The results are more precise than previous measurements, particularly in the case of the Bs0 and Λb0 masses
Sorption and desorption of Suflafenacil in two soils in the state of São Paulo with different physical and chemical attributes.
No full textResumo: Foi conduzido um estudo para avaliar a sorção e dessorção do herbicida saflufenacil em dois solos do Estado de São Paulo: um Latossolo Vermelho-Amarelo com textura argilosa (LVA-1) e outro com textura média (LVA-2), classificados como argiloso e franco-argiloarenoso, respectivamente, através de isotermas, utilizando o método em batelada. Os solos foram secos ao ar e peneirados em malha de 2 mm. A molécula radiomarcada com 14C foi o saflufenacil, herbicida do grupo das pirimidinadionas. A radioatividade foi determinada por espectrometria de cintilação líquida. Os ensaios foram realizados em sala climatizada (25 ± 2 ºC). Para determinação de sorção e isotermas de sorção, foram empregadas cinco concentrações do saflufenacil (5,0; 2,5; 1,0; 0,5; e 0,05 ?g mL-1), sendo os resultados ajustados à equação de Freundlich, obtendo-se assim os parâmetros de sorção. Na sequência, foram realizadas duas extrações com 0,01 M de CaCl2, determinando-se os parâmetros de dessorção de forma similar à sorção. Os resultados mostraram que a sorção do saflufenacil foi baixa para ambos os solos, sendo maior para o LVA com maior teor de matéria orgânica. Os coeficientes de dessorção foram maiores do que os respectivos coeficientes de sorção, sugerindo a ocorrência de histerese. As isotermas de sorção e dessorção foram classificadas como isotermas tipo C; o índice de histerese mostrou que tanto a sorção como a dessorção ocorreram com igual intensidade. Abstract: A study was conducted to evaluate the sorption and desorption of 14 C herbicide saflufenacil (pyrimidinedione) in two soils in the State of São Paulo, classified as Red Yellow Latosol with clayey texture (LVA-1) and medium texture (LVA-2), using the batch method through isotherms. The soils were air dried and sieved a 2 mm mesh. The radioactivity was determined by liquid scintillation spectrometry in acclimatized room (25 ± 2 °C). Sorption isotherms were conducted for 5 concentrations of saflufenacil (5.0; 2.5; 1.0; 0.5 and 0.05 ?g mL -1 ) and the results were adjusted to the Freundlich equation, thus obtaining the parameters of sorption followed by two extractions with 0.01 M CaCl 2 to determine desorption parameters similarly to sorption. The results showed that saflufenacil sorption was low for both soils studied, being greater for the LVA with higher organic matter content. The desorption coefficients were greater than their sorption coefficients, suggesting the occurrence of hysteresis. The sorption and desorption isotherms (classified as type C isotherms), hysteresis and the t-test between the angular coefficient of the respective isotherms showed that both the sorption and desorption occur with equal intensity
Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+
No full textAn analysis of B+ → K0
Sπ+ and B+ → K0
S K+ decays is performed with the LHCb experiment. The pp
collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass
energies of
√
s = 7 TeV and
√
s = 8 TeV, respectively. The ratio of branching fractions and the
direct CP asymmetries are measured to be B(B+ → K0
S K+
)/B(B+ → K0
Sπ+
) = 0.064 ± 0.009 (stat.) ±
0.004 (syst.), ACP(B+ → K0
Sπ+
) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0
S K+
) =
−0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at
√
s = 7 TeV is used to search for
B+
c
→ K0
S K+ decays and results in the upper limit ( fc · B(B+
c
→ K0
S K+
))/( fu · B(B+ → K0
Sπ+
)) <
5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b
quark
into a B+
c or a B+ meson, respectively
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