Two-dimensional perturbations in a scalar model for shear banding

We present an analytical study of a toy model for shear banding, without normal stresses, which uses a piecewise linear approximation to the flow curve (shear stress as a function of shear rate). This model exhibits multiple stationary states, one of which is linearly stable against general two-dimensional perturbations. This is in contrast to analogous results for the Johnson-Segalman model, which includes normal stresses, and which has been reported to be linearly unstable for general two-dimensional perturbations. This strongly suggests that the linear instabilities found in the Johnson-Segalman can be attributed to normal stress effects.Comment: 16 pages, 10 figures, to appear in EPJE, available online first, click DOI or http://www.springerlink.com/content/q1q0187385017628

Regular binary thermal lattice-gases

We analyze the power spectrum of a regular binary thermal lattice gas in two dimensions and derive a Landau-Placzek formula, describing the power spectrum in the low-wavelength, low frequency domain, for both the full mixture and a single component in the binary mixture. The theoretical results are compared with simulations performed on this model and show a perfect agreement. The power spectrums are found to be similar in structure as the ones obtained for the continuous theory, in which the central peak is a complicated superposition of entropy and concentration contributions, due to the coupling of the fluctuations in these quantities. Spectra based on the relative difference between both components have in general additional Brillouin peaks as a consequence of the equipartition failure.Comment: 20 pages including 9 figures in RevTex

Gemeenten hebben grote behoefte aan kennis dierenwelzijn : maatschappelijke discussie beperkt zich niet tot intensieve veehouderij

Tachtig procent van het dierenwelzijnsbeleid ligt op het bordje van de gemeente, aldus VVD-wethouder Robert Blom van Alphen aan den Rijn. Terwijl tegelijkertijd bij veel gemeenten kennis hierover ontbreekt. Genoeg reden voor een miniconferentie Gemeentelijk dierenwelzijnsbelei

Driven translocation of a polymer: role of pore friction and crowding

Force-driven translocation of a macromolecule through a nanopore is investigated by taking into account the monomer-pore friction as well as the "crowding" of monomers on the {\it trans} - side of the membrane which counterbalance the driving force acting in the pore. The set of governing differential-algebraic equations for the translocation dynamics is derived and solved numerically. The analysis of this solution shows that the crowding of monomers on the trans side hardly affects the dynamics, but the monomer-pore friction can substantially slow down the translocation process. Moreover, the translocation exponent $\alpha$ in the translocation time - vs. - chain length scaling law, $\tau \propto N^{\alpha}$, becomes smaller when monomer-pore friction coefficient increases. This is most noticeable for relatively strong forces. Our findings may explain the variety of $\alpha$ values which were found in experiments and computer simulations.Comment: 12 page

International trade negotiations and the trans-border movement of people: A review of the literature

We review the international and New Zealand literatures on the two-way interaction between international migration and agreements designed to enhance cross-border trade or investment. Benefits and costs of migration, to the extent that these may feature in trade and migration negotiations, are discussed. While trade and migration can be substitutes in some contexts, they will be complements in other contexts. Liberalisation of services and the movement of people are likely to offer much more significant gains than liberalisation of remaining barriers to goods trade. Significant scope for liberalisation under GATS mode 4 (the movement of natural persons) may remain. However, temporary migration is already promoted on a unilateral and bilateral basis within immigration policy frameworks that may provide greater flexibility than GATS mode 4. With respect to both trade and migration, the more diverse the exchanging countries are, the greater the economic benefits tend to be. However, greater diversity may also imply greater social costs. This paradox of diversity needs to be addressed through appropriate social policies accompanying enhanced temporary and permanent migration

Fruitteler kiest bewust voor korte keten en verbreding

Al elf jaar runnen Annette en Ton Verbeek hun multifunctionele fruitbedrijf. Smaak en smaakbeleving staan er voorop. De omslag van anonieme bulkproductie naar een regionaal ingebed bedrijf verliep zo succesvol, dat het werk hen boven het hoofd dreigde te groeien. Een brand begin januari bracht naast veel ellende ook bezinning: wat willen ze de komende jaren, waar liggen nieuwe kansen voor het bedrijf? Een vernieuwd strategisch plan is bijna klaa

'We zijn nog lang niet klaar met innoveren'

Een geheel nieuw diervriendelijk houderijsysteem hebben ze geïntroduceerd, zodat hun leghennen zich zo natuurlijk mogelijk kunnen gedragen. De stallen staan er, maar het innoveren begint nu pas echt, vinden de pluimveehouders Chris en Marjanne Borren. Allerlei nieuwe kennisvragen doemen op. Waar kunnen ze aankloppen nu het innovatieproject met Wageningen UR is afgerond

Exportkansen op de Franse biologische markt

De markt voor biologische producten groeit in Frankrijk. Dit kan kansen bieden voor de Nederlandse export. Export bestaat al wel, maar is nog beperkt. In een onderzoek is bekeken of en hoe Nederlandse toeleveranciers hun toegang tot de Franse markt kunnen vergroten