Cubatic phase for tetrapods

We investigate the phase behavior of tetrapods, hard non-convex bodies formed by 4 rods connected under tetrahedral angles. We predict that, depending on the relative lengths of the rods these particles can form a uniaxial nematic phase, and more surprisingly they can exhibit a cubatic phase, a special case of the biaxial nematic phase. These predictions may be experimentally testable, as experimental realizations of tetrapods have recently become available.Comment: 8 pages ReVTeX 4, including 3 EPS figure

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

Do cylinders exhibit a cubatic phase?

We investigate the possibility that freely rotating cylinders with an aspect ratio $L/D=0.9$ exhibit a cubatic phase similar to the one found for a system of cut-spheres. We present theoretical arguments why a cubatic phase might occur in this particular system. Monte Carlo simulations do not confirm the existence of a cubatic phase for cylinders. However, they do reveal an unexpected phase behavior between the isotropic and crystalline phase.Comment: 24 pages, 12 figures, RevTex (Submitted to J. Chem. Phys.

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

Subsidizing the Adoption of Energy-Saving Technologies: Analyzing the Impact of Uncertainty, Learning and Maturation

As part of the Kyoto Protocol, many countries have committed themselves tosubstantially reduce the emission of greenhouse gases within a politically imposed timeconstraint. Investment subsidies can be an important instrument to stimulate the adoption ofenergy-saving technologies to achieve emission reduction targets. This paper addresses theimpact of adoption subsidies on the amount of energy savings, taking into account endogeneityand uncertainty of technological progress. Neglecting these two characteristics oftechnological progress tends to result in overestimation of the short-run effectiveness ofinvestment subsidies, whereas the effects on long-run effectiveness are ambiguous

Subsidizing the adoption of energy-saving technologies; Analyzing the impact of uncertainty, learning and maturation

As part of the Kyoto Protocol, many countries have committed themselves to substantially reduce the emission of greenhouse gases within a politically imposed time constraint. Investment subsidies can be an important instrument to stimulate the adoption of energy-saving technologies to achieve emission reduction targets. This paper addresses the impact of adoption subsidies on the amount of energy savings, taking into account both the endogenous and uncertain nature of technological progress. Neglecting these two characteristics of technological progress tends to result in overestimation of the short-run effectiveness of investment subsidies, whereas the long-run effects are ambiguous