1,046 research outputs found
Effects of growth conditions on postharvest Botrytis infection in Gerbera - a nursery comparison
Botrytis cinerea is one of the main postharvest problems in gerbera cut flowers. There are clear differences among growers in the percentage of flowers showing symptoms of Botrytis infection after harvest. Because the factors causing these differences are uncertain, cultivation parameters of twelve different growers were followed and a nursery comparison was carried out. Gerbera flowers ‘Dino’ were sampled twelve times; six times in autumn 2006 and six times in spring of 2007. At the nurseries climate (air temperature, relative humidity, light intensity and CO2 concentration) was logged, and plant density, plant age and other characteristics were monitored. Before each harvest Botrytis spores were trapped in the greenhouses and counted. After sampling, flowers were treated according to a standard transport simulation. Thereafter Botrytis infection was monitored, and statistical analyses were performed on the effect of the pre-harvest conditions on Botrytis infection in the postharvest stage. Clear influence of the spore level in the greenhouse was observed. When a sufficient number of spores were present in the greenhouse environment, the humidity level and the intensity and duration of irradiation had the strongest influence on infection. In general, factors those lead to a dry microclimate such as the use of ventilators, the use of supplemental lighting and a low plant density were related with a lower number of lesions on gerbera petals in the postharvest phase
QCD Radiative Correction to Zero Recoil Sum Rules for Heavy Flavor Transitions in the Small Velocity Limit.
We consider the small velocity sum rules for heavy flavour semileptonic
transitions that are used to estimate the zero recoil values of semileptonic
heavy flavour form factors. We analyze the complete O() radiative
correction to these sum rules. The corrections are universal and influence all
"model-independent" bounds previously derived for semileptonic form factors at
zero recoil.Comment: 13 pages, LaTeX, 3 figures
Two -loop radiative corrections to the Higgs decay width for large Higgs boson masses
This note is devoted to the calculation of the two-loop
radiative corrections to the Higgs decay width for large
values of the Higgs boson mass within the Minimal Standard Model.
The use of the Equivalence Theorem makes it possible to reduce the problem to
the consideration of the physical Higgs boson field and the Goldstone bosons
. We present analytical results for the various two- and
three-particle absorptive parts of two-loop contributions, using dispersive
techniques, analytic results for all but one of the dispersive contributions.
The typical size of the correction is percent for a Higgs boson
mass of order .Comment: 21 pages, 7 uuencoded figure
Sturing kasklimaat op basis van modellering van Botrytis
Schade aan kasgewassen door Botrytisaantasting (smet) is één van de belangrijkste knelpunten in de kasteelt. Te hoge luchtvochtigheid en lokale koude plekken met condensvorming zijn de belangrijkste oorzaken van smet. Het instellen van een droog kasklimaat kost veel energie, maar door het gebruik van een waarschuwings- of sturingsmodel is het mogelijk om naast het vermijden van besmetting straks ook energiewinst te behalen ten opzichte van telen zonder model. Met verklarende computermodellen kunnen plantengroei, -kwaliteit en schimmelinfectie berekend worden. De modellen kunnen Botrytis helpen voorkomen door de juiste klimaatinstellingen en de inrichting van de kas
Exclusive semileptonic and nonleptonic decays of the Bc meson
We study exclusive nonleptonic and semileptonic decays of the Bc-meson within
a relativistic constituent quark model previously developed by us. For the
nonleptonic decays we use the factorizing approximation. We update our model
parameters by using new experimental data for the mass and the lifetime of the
Bc meson and the leptonic decay constants of the D-meson. We calculate the
branching ratios for a large set of exclusive nonleptonic and semileptonic
decays of the meson and compare our results with the results of other
studies. As a guide for further experimental exploration we provide explicit
formulas for the full angular decay distributions in the cascade decays Bc^- =>
J/psi(=> l^+l^-) + rho^-(=> pi^- pi^0) and Bc^- => J/psi(=> l^+l^-) +
W^-(off-shell)(=> l^- + nubar).Comment: 19 pages, 2 figure
Helicity Analysis of Semileptonic Hyperon Decays Including Lepton Mass Effects
Using the helicity method we derive complete formulas for the joint angular
decay distributions occurring in semileptonic hyperon decays including lepton
mass and polarization effects. Compared to the traditional covariant
calculation the helicity method allows one to organize the calculation of the
angular decay distributions in a very compact and efficient way. In the
helicity method the angular analysis is of cascade type, i.e. each decay in the
decay chain is analyzed in the respective rest system of that particle. Such an
approach is ideally suited as input for a Monte Carlo event generation program.
As a specific example we take the decay () followed by the nonleptonic decay for which we show a few examples of decay distributions which are
generated from a Monte Carlo program based on the formulas presented in this
paper. All the results of this paper are also applicable to the semileptonic
and nonleptonic decays of ground state charm and bottom baryons, and to the
decays of the top quark.Comment: Published version. 40 pages, 11 figures included in the text. Typos
corrected, comments added, references added and update
\Omb \rightarrow \Omc , \Omc ^* $ transitions: Model-independent bounds on invariant form factors
In this note we report some model-independent bounds involving transition
form factors for \Omb \rightarrow \Omc and \Omb \rightarrow \Omc ^* and
the nonperturbative matrix elements of the \Omb system. They are derived by
using operator product expansion (OPE) in Heavy Quark Effective Theory .Comment: Latex, 7 page
CP Violation and the Width
We discuss the effect of CP-violating , and
couplings on the width . The
presence of such couplings leads in a natural way to an increase of this width
relative to the prediction of the standard model. Various strategies of a
direct search for such CP-violating couplings by using CP-odd observables are
outlined. The number of bosons required to obtain significant information
on the couplings in this way is well within the reach of present LEP
experiments.Comment: 18 pages, LaTeX, no figure
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