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

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 Évora (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)

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.

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

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

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