Balans van de leefomgeving 2010

Deze veelomvattende studie geeft de ontwikkelingen op het gebied van onder meer klimaat, lucht en energie; verstedelijking, bereikbaarheid en milieu; landelijk gebied (met landbouw, natuur, recreatie, water, landschap) en biodiversiteit. Veel gegevens kwamen tot stand via de inzet van Wageningen UR. Deze eerste Balans van de Leefomgeving evalueert het rijksbeleid voor de fysieke leefomgeving in Nederland en geeft aan in hoeverre de beleidsdoelen voor milieu, natuur en ruimte worden gehaald. Waar dat niet het geval is, analyseren we de oorzaken. Tevens gaan we na of het beleid samenhangend is, waar ongewenste neveneffecten optreden en wat handelingsopties zijn om beleidstekorten weg te werken. De kwaliteit van de leefomgeving is de laatste twintig jaar sterk verbeterd, mede dankzij het gevoerde overheidsbeleid. Lucht en oppervlaktewater zijn schoner geworden, de steden zijn aantrekkelijker om te wonen en de natuur krijgt meer ruimte. Tegenover dit goede nieuws staat dat er op het gebied van de leefomgeving nog grote problemen overblijven, zoals de reeds merkbare klimaatverandering, de afnemende biodiversiteit en de teruglopende bereikbaarheid, vooral van de Randstad. Om het tij te keren zijn gerichte beleidsmaatregelen nodig. Dit zal een belangrijke opgave zijn voor het nieuwe kabinet

IRREGULARITIES IN THE YRAST LINE OF 156Er

The variation of the moment of inertia vs the rotational frequency has been investigated at high spin values using the141Pr(19F, 4nγ) 156Er reaction. In addition to the backbending at I = 12 ħ, a second one has been found at I = 26 ħ. Calculations performed by the Warsaw group with the HFB cranking model suggest a probable neutron effect

Surface rearrangement at complex adsorbate-substrate interfaces

On the basis of the information theory approach we propose a novel statistical scheme for analyzing the evolution of coupled adsorbate-substrate systems, in which the substrate undergoes the adsorbate-induced transformations. A relation between the substrate morphology and the adsorbate thermodynamic state is established. This allows one to estimate the surface structure in terms of incomplete experimental information and the one concerning the adsorbate thermodynamic response to the structural modifications.Comment: 5 pages, 3 figure

Chaotic scalar fields as models for dark energy

We consider stochastically quantized self-interacting scalar fields as suitable models to generate dark energy in the universe. Second quantization effects lead to new and unexpected phenomena is the self interaction strength is strong. The stochastically quantized dynamics can degenerate to a chaotic dynamics conjugated to a Bernoulli shift in fictitious time, and the right amount of vacuum energy density can be generated without fine tuning. It is numerically observed that the scalar field dynamics distinguishes fundamental parameters such as the electroweak and strong coupling constants as corresponding to local minima in the dark energy landscape. Chaotic fields can offer possible solutions to the cosmological coincidence problem, as well as to the problem of uniqueness of vacua.Comment: 30 pages, 3 figures. Replaced by final version accepted by Phys. Rev.

An integrated approach to modelling the fluid-structure interaction of a collapsible tube

The well known collapsible tube experiment was conducted to obtain flow, pressure and materials property data for steady state conditions. These were then used as the boundary conditions for a fully coupled fluid-structure interaction (FSI) model using a propriety computer code, LS-DYNA. The shape profiles for the tube were also recorded. In order to obtain similar collapse modes to the experiment, it was necessary to model the tube flat, and then inflate it into a circular profile, leaving residual stresses in the walls. The profile shape then agreed well with the experimental ones. Two departures from the physical properties were required to reduce computer time to an acceptable level. One of these was the lowering of the speed of sound by two orders of magnitude which, due to the low velocities involved, still left the mach number below 0.2. The other was to increase the thickness of the tube to prevent the numerical collapse of elements. A compensation for this was made by lowering the Young's modulus for the tube material. Overall the results are qualitatively good. They give an indication of the power of the current FSI algorithms and the need to combine experiment and computer models in order to maximise the information that can be extracted both in terms of quantity and quality

Comparisons of Supergranule Characteristics During the Solar Minima of Cycles 22/23 and 23/24

Supergranulation is a component of solar convection that manifests itself on the photosphere as a cellular network of around 35 Mm across, with a turnover lifetime of 1-2 days. It is strongly linked to the structure of the magnetic field. The horizontal, divergent flows within supergranule cells carry local field lines to the cell boundaries, while the rotational properties of supergranule upflows may contribute to the restoration of the poloidal field as part of the dynamo mechanism that controls the solar cycle. The solar minimum at the transition from cycle 23 to 24 was notable for its low level of activity and its extended length. It is of interest to study whether the convective phenomena that influences the solar magnetic field during this time differed in character to periods of previous minima. This study investigates three characteristics (velocity components, sizes and lifetimes) of solar supergranulation. Comparisons of these characteristics are made between the minima of cycles 22/23 and 23/24 using MDI Doppler data from 1996 and 2008, respectively. It is found that whereas the lifetimes are equal during both epochs (around 18 h), the sizes are larger in 1996 (35.9 +/- 0.3 Mm) than in 2008 (35.0 +/- 0.3 Mm), while the dominant horizontal velocity flows are weaker (139 +/- 1 m/s in 1996; 141 +/- 1 m/s in 2008). Although numerical differences are seen, they are not conclusive proof of the most recent minimum being inherently unusual.Comment: 22 pages, 5 figures. Solar Physics, in pres