EU policy reform simulation based on panel data estimation of on- and off-farm labour supply equations for Dutch dairy farmers

This research focuses on the estimation of labour supply equations for Dutch dairy farmers that are suitable for policy simulations. Data availability leads to the fact that we can not estimate structural labour supply equations. We show how to derive reduced form equations suitable for policy simulations. In this research we use the panel data sample selection estimation approach of Kyriazidou (1997) and Wooldridge (1995) to estimate the off-farm labour supply equation. The two lead to different estimation results and different simulation results based on these.Econometrics, Panel Data, Sample Selection, Labour Supply, CAP Reform, Labor and Human Capital, C23, C24, C51, C53, D13, J22, Q12, Q18,

On- and Off-Farm Labour Supply of Dutch Dairy Farmers: Estimation and Policy Simulations

This research focuses on the effect of decoupled payments on labour supply of Dutch dairy farmers. Data availability leads to the fact that we can not estimate structural labour supply equations. We show how to derive reduced form equations suitable for policy simulations. We use the panel data sample selection estimation approach Wooldridge (1995) to estimate the off-farm labour supply equation. This method is based on Mundlak's (1978) linear panel data estimation approach, which we use to estimate the on-farm labour supply equations. Even though, simulations show a significant negative effect of decoupled payments on labour supply, the economic significance of this effect is very limited.decoupled payments, labour supply, panel data, sample selection, policy simulation, Labor and Human Capital, Livestock Production/Industries, C23, C24, C51, C53, D13, J22, Q12, Q18,

Monitoring the invertebrate benthic fauna in the Dutch sector of the North Sea 1991 - 2005: an overview

In the framework of ‘BIOMON’, a national program for biological monitoring of marine waters, the invertebrate benthic fauna of the Dutch Continental Shelf (DCS) has been monitored from 1991 onwards. The monitoring is based on a boxcore sampling program yearly carried out in spring at 100 stations on the DCS. The aim is to generate a time series that can form a basis to detect possible trends in the development of thefauna in different areas within the DCS. From the very beginnng it became clear that in the fauna of the DCS four clusters could be discerned that are geographically well defined: the Dogger Bank, the Oyster Ground, the southern offshore area and the coastal area. At the community level there were no trendwise changes over the period of monitoring. Species diversity was consistently highest at the Dogger Bank and in the Oyster Ground, on average twice as high as in the southern offshore and coastal areas. Faunal densities were generally the highest in the Oyster Ground. The highest biomass values were found in the coastal area, due to the presence of banks of bivalves (<i>Spisula subtruncata</i> and <i>Ensis americanus</i>). At the species level a few trends were observed: the disappearance of the polychaete <i>Aricidea minuta</i> from the DCS around 2000 and a dip in the densities of the brittle star <i>Amphiura filiformis</i> in the Oyster Ground during the second half of the nineties. A rather strong decrease of silt contents of the sediment in the latter area after 2001 was not reflected in a change in the abundance of one or more common species. A comparison of the monitoring data with data collected in the period 1975 – 1981 appeared to be possible for only a few (mainly mollusc) species in the Oyster Ground, but indicated that the gastropod <i>Turritella communis</i> has strongly decreased since those years whereas there was a significant increase in the abundance of several small bivalve species

The use of digital microfluidics for a silicon photonic sensors platform

status: publishe

The macrobenthic fauna in the Dutch sector of the North Sea in 2002 and a comparison with previous data

In this report the results are presented of a macrobenthos survey on the Dutch Continental Shelf (DCS), carried out in spring 2001. The survey forms part of the 'Biological monitoring programme of marine waters' (MON*BIOLOGIE, generally referred to as 'BIOMON') which was initiated by the National Institute for Coastal and Marine Management (RIKZ). The purpose of the programme is to obtain insight into the year-to-year variations of the macrobenthic assemblages and to detect trend-like changes, that possibly indicate anthropogenic influences on the marine environment (e.g. eutrophication, pollution, beam-trawl fishery). Within the framework of this project fieldwork is carried out every year in spring. In 2001 the 100 BIOMON stations were sampled in the period between February 27 and April 4. On the basis of the results collected in 2001 and previous years an analysis is made of the trends and fluctuations of some selected species and of basic community attributes over the period 1986-2001. The community attributes studied were the diversity, abundance and biomass of the total macrofauna and of the 4 major taxonomic groups. Temporal variation or trends were investigated separately for each of the four subareas in the DCS i.e. the Coastal, Offshore areas, Dogger Bank and Oyster Ground.The conclusions of this study can be summarized as follows:1. The sediment composition in the four subareas was quite similar to that found in previous years. Also at most of the individual stations the median grain size and silt content of the sediment had hardly changed. There were only three stations with strong year to year differences in sediment composition. At the stations OFF 2 and OFF 6 the median grain size strongly fluctuated and at station OYS 8 the silt content. lt is suggested that these stations are situated at a sharp local gradient.2. At the community level, there were only a few slight changes compared to preceding years. In the offshore area and in the coastal area there seemed to be a tendency for increased diversity. This was not due to increased species richness but to a more even distribution in the abundance of the various species. With respect to the share of the different taxonomic groups to the total biomass, a decrease has been observed in previous years in molluscs, particularly at the Dogger Bank and in the Oyster Ground. This decrease has come to an end in 2001 and turned into an increase. Since molluscs also increased numerically, the increase in biomass is caused by higher densities rather than by a larger size of the animals.3. At the Dogger Bank a few species showed a remarkable decrease. The polychaete <i>Nephtys cirrosa</i> shows a decrease from 2000 onwards, the sand star <i>Acrocnida brachiata</i> and the bivalve <i>Mysella bidentata</i> from 1999 and the polychaete <i>Aricidea minuta</i> decreased in 1997 and has no longer been found since 1999. On the other hand the population density of the gastropod <i>Euspira nitida</i> (formerly called <i>Natica alderi</i>) had recovered from a dip in the period 1998-2000. The occurrence of <i>Ensis phaxoides</i> is new for the Dogger Bank. Further, living specimens of the bivalve <i>Gouldia minima</i> and the gastropod <i>Turbonilla pusilla</i> have not been found on the DCS before.4. In the Oyster Ground the decreasing trend that has been observed in previous years in the brittle star <i>Amphiura filiformis</i> and the polychaete <i>Nephtys hombergii</i> had turned into au increase in 2001. However, densities of <i>A. filiformis</i> were still low at the Frisian Front. There was a number of species that have not been found before during the BIOMON programma. The occurrence of the polychaete <i>Nephtys assimilis</i> is new for the Oyster Ground. The records of the polychaete <i>Sabella penicillus</i>, the bivalves <i>Montacuta tenella</i> and <i>Gari costulata</i> and the gastropods <i>Turbonilla pusilla</i> and <i>Roxania utriculus</i> are probably new to the DCS.5. In the offshore area, a slightly increasing trend that has been observed in the sea urchin <i>Echinocardium cordatum</i> in the preceding years has come to an end in 2001. In contrast, the gastropod <i>Euspira nitida</i> showed a recovery of populations from 2000 onwards. Station OFF 33 that in 2000 had shown a rich fauna that was clearly different from the other stations in the offshore area was still rich in 2001, but the fauna composition did not show 'exotic' elements.6. In the Coastal area there seemed to be a recovery of the populations of the gastropod <i>Euspira nitida</i>. After an 8 year period of very low densities the species returned at 5 stations, albeit in low numbers. The bivalve <i>Tellina fabula</i> also showed a steady increase, after a dip in the second half of the nineties. At stations where banks of <i>Spisula subtruncata</i> or <i>Ensis americanus</i> occurred, biomass values were very high

Predicting crystal structures: the Parrinello-Rahman method revisited

By suitably adapting a recent approach [A. Laio and M. Parrinello, PNAS, 99, 12562 (2002)] we develop a powerful molecular dynamics method for the study of pressure-induced structural transformations. We use the edges of the simulation cell as collective variables. In the space of these variables we define a metadynamics that drives the system away from the local minimum towards a new crystal structure. In contrast to the Parrinello-Rahman method our approach shows no hysteresis and crystal structure transformations can occur at the equilibrium pressure. We illustrate the power of the method by studying the pressure-induced diamond to simple hexagonal phase transition in a model of silicon.Comment: 5 pages, 2 Postscript figures, submitte

ASM-Clust: classifying functionally diverse protein families using alignment score matrices

Rapid advances in sequencing technology have resulted in the availability of genomes from organisms across the tree of life. Accurately interpreting the function of proteins in these genomes is a major challenge, as annotation transfer based on homology frequently results in misannotation and error propagation. This challenge is especially pressing for organisms whose genomes are directly obtained from environmental samples, as interpretation of their physiology and ecology is often based solely on the genome sequence. For complex protein (super)families containing a large number of sequences, classification can be used to determine whether annotation transfer is appropriate, or whether experimental evidence for function is lacking. Here we present a novel computational approach for de novo classification of large protein (super)families, based on clustering an alignment score matrix obtained by aligning all sequences in the family to a small subset of the data. We evaluate our approach on the enolase family in the Structure Function Linkage Database