424 research outputs found
Field weed population models: a review of approaches and application domains
We evaluated models of weed population dynamics based on an analysis of their assumptions, biological rationale, flexibility, documentation, accessibility, demand for parameter estimation and documented validity. We arrived at general recommendations regarding which modelling approach should be applied in order to address different application domains
Free-riding and team performance in project education
This article derives lessons from the quality approach for further developing the organizational sustainability approach. Taking a responsibility perspective on organizational sustainability, four issues emerge that need to be resolved, i.e. what is the responsibility?, what is the responsibility area?, who is involved in determining responsibilities and area?, and, in what way is the organization able to take care of these responsibilities?. The article explores in what way the quality approach has been dealing with these issues, which is the basis for some lessons for the sustainability approach. An important lesson is that the who is involved question should be leading. The stakeholder who is willing to pay for sustainability dominates answering the other three issues. With respect to the accounting practices, sustainability programmes could be inspired by the same need for protective and accountable behaviour as quality programmes, if the well-known negative aspects are minimized.
Worden plantenziekten ten onrechte buiten het debat over klimaatverandering gehouden? : verslag van een conferentie over klimaatverandering en het optreden en beheer van plantenziekten
Van 10-12 november 2011 werd in Ăvora (Portugal), voorafgaand aan het EFPP-Congres, een conferentie gehouden over de gevolgen van klimaatverandering voor de ontwikkeling en beheersing van plantenziekten. Op de conferentie kwam een drietal kernvragen aan de orde. Leidt klimaatverandering tot een toename in ziektedruk? Speelt gewasbescherming mogelijk een rol bij het verminderen van klimaatverandering (mitigatie)? Welke maatregelen stellen ons in staat om de invloed van klimaatverandering op het optreden van plantenziekten te ondervangen (adaptatie)
Purity-bounded uncertainty relations in multidimensional space -- generalized purity
Uncertainty relations for mixed quantum states (precisely, purity-bounded
position-momentum relations, developed by Bastiaans and then by Man'ko and
Dodonov) are studied in general multi-dimensional case. An expression for
family of mixed states at the lower bound of uncertainty relation is obtained.
It is shown, that in case of entropy-bounded uncertainty relations, lower-bound
state is thermal, and a transition from one-dimensional problem to
multi-dimensional one is trivial. Results of numerical calculation of the
relation lower bound for different types of generalized purity are presented.
Analytical expressions for general purity-bounded relations for highly mixed
states are obtained.Comment: 12 pages, 2 figures. draft version, to appear in J. Phys. A Partially
based on a poster "Multidimensional uncertainty relations for states with
given generalized purity" presented on X Intl. Conf. on Quantum Optics'2004
(Minsk, Belarus, May 30 -- June 3, 2004) More actual report is to be
presented on ICSSUR-2005, Besan\c{c}on, France and on EQEC'05, Munich. V. 5:
amended article after referees' remark
Ratio between virtual and visual lesion size as a measure to describe reduction in leaf photosynthesis of rice due to leaf blast.
Understanding yield reduction in rice due to leaf blast
The study described in this thesis focuses on a quantitative understanding of the effect of leaf blast on growth and production of a rice crop, based on insight in the physiological processes underlying damage. For this purpose, experimental research was conducted at two levels of integration: plant and crop. Research was first conducted at the plant level and focused on the effects of the disease on photosynthesis and respiration. To determine the consequences of these physiological disturbances for crop growth and production, submodels for the effects of leaf blast on photosynthesis and respiration were constructed and introduced in a mechanistic model for crop growth. Experimental research at the crop level was used to validate and improve the extended crop growth model. At the same time the model was used to analyse the results of the field experiments. This interaction resulted in a better understanding of yield reduction in rice due to leaf blast and in a model that can be used to estimate yield reduction due to leaf blast for various epidemics under variable environmental conditions
Effects of leaf blast on growth and production of a rice crop. 1. Determining the mechanism of yield reduction.
Food security under attack: Africa's struggle against parasitic weeds
Parasitic weeds invade around 1.34 million hectares of rainfed rice areas in Africa causing damages estimated at USD 200 million
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