A Comparison of Grassland Management Systems for Beef Cattle Using Self-Contained Farmlets: Effects of Contrasting Nitrogen Inputs and Management Strategies on the Farm Economy

The financial implications of manipulating nitrogen (N) inputs and management strategies for beef production systems were assessed. One-hectare grassland farmlets were grazed to a target sward height by beef steers; herbage surplus to grazing requirements was cut for silage. Three systems were compared: ‘CN’, conventional mineral N application to a grass monoculture and broadcast slurry; ‘TN’, tactical mineral N application at fortnightly intervals to a grass monoculture with slurry injection and the early housing of cattle; ‘GC’, a mixed grass/white clover sward with no mineral N addition and slurry injection. Comparisons were made on two contrasting soil types: a freely-draining sandy loam (site 1) and a poorly drained clay (site 2). Financial budgets for 1999-2000 show that estimated gross profit margins (gross outputs minus variable costs), after deducting contractor’s charges for sward preparation and fertiliser spreading, were highest for treatment CN at both sites Î(€1552, €1356 and €1461 ha-1 for site 1 and €1562, €1281 and €1287 ha-1 for site 2, for treatments CN, TN and GC, respectively). Treatment TN was penalised by increased costs associated with an extended housed period and the need to purchase additional silage for winter feeding which cost €242 ha-1 at site 1 and €250 ha-1 at site 2. Savings in N fertiliser for TN in comparison with CN (€44 ha-1 at site 1 and €39 ha-1 at site 2) were more than offset by the increased costs of fortnightly fertiliser applications (€54 ha-1 at site 1 and €46 ha-1 at site 2). Treatment GC benefited from zero costs for the purchase and spreading of mineral N fertiliser but was penalised by increased variation in forage DM production which resulted in a shortfall in winter fodder requirements with a replacement cost of €250 at site 1 and €435 at site 2. The best overall economic performance after the allocation of all possible relevant costs (variable, fixed and capital) in terms of the relative net profit margin, was for GC at site 1 and for CN at site 2 (-€1358, -€2399 and -€1304 ha-1 at site 1 and -€1122, -€2810 and - €1380 ha-1 at site 2, for CN, TN and GC, respectively). The opportunity costs of reducing N surpluses at the gross profit margin level (after contractor’s charges) for treatments TN and GC over treatment CN were calculated at €2.29 kg-1 N surplus for TN and €0.67 kg-1 N surplus for GC at site 1, with corresponding values of €4.91 and €1.57 at site 2.Farmlets, Systems, Beef cattle, Nitrogen, Slurry, Animal production, Economics, UK, Farm Management,

Quantum cosmological perfect fluid model and its classical analogue

The quantization of gravity coupled to a perfect fluid model leads to a Schr\"odinger-like equation, where the matter variable plays the role of time. The wave function can be determined, in the flat case, for an arbitrary barotropic equation of state $p = \alpha\rho$; solutions can also be found for the radiative non-flat case. The wave packets are constructed, from which the expectation value for the scale factor is determined. The quantum scenarios reveal a bouncing Universe, free from singularity. We show that such quantum cosmological perfect fluid models admit a universal classical analogue, represented by the addition, to the ordinary classical model, of a repulsive stiff matter fluid. The meaning of the existence of this universal classical analogue is discussed. The quantum cosmological perfect fluid model is, for a flat spatial section, formally equivalent to a free particle in ordinary quantum mechanics, for any value of $\alpha$, while the radiative non-flat case is equivalent to the harmonic oscillator. The repulsive fluid needed to reproduce the quantum results is the same in both cases.Comment: Latex file, 13 page

An extension of the coupled-cluster method: A variational formalism

A general quantum many-body theory in configuration space is developed by extending the traditional coupled cluter method (CCM) to a variational formalism. Two independent sets of distribution functions are introduced to evaluate the Hamiltonian expectation. An algebraic technique for calculating these distribution functions via two self-consistent sets of equations is given. By comparing with the traditional CCM and with Arponen's extension, it is shown that the former is equivalent to a linear approximation to one set of distribution functions and the later is equivalent to a random-phase approximation to it. In additional to these two approximations, other higher-order approximation schemes within the new formalism are also discussed. As a demonstration, we apply this technique to a quantum antiferromagnetic spin model.Comment: 15 pages. Submitted to Phys. Rev.

Unofficial trade when states are weak: the case of cross-border commerce in the Horn of Africa

This paper addresses informal cross-border trade in the Horn of Africa, with an emphasis on the Somalia borderlands. It will be shown that despite the collapse of a government in 1991, Somalia’s unofficial exports of cattle to Kenya have grown considerably during the past 13 years.Qoraalkani wuxuu ka hadlayaa ganacsiga ka gudbo xuduudaha Geeska Afrika. Gaar ahaan markii uu dhacay taliskii militeriga waxaa aad u sii kordhay xoolixii soomaaliyeed ee loo suuq geynaayay Kenya.Questo documento è dedicato al commercio transnazionale informale nel Corno D'Africa, con particolare attenzione ai confini della Somalia. Si dimostra che nonostante la caduta del governo nel 1991, le esportazioni di bestiame non ufficiali somale in Kenya sono aumentate considerevolmente durante gli ultimi 13 anni

Assessing the adaptation of arable farmers to climate change using DEA and bio-economic modelling

The objective of this article is to assess the impact of climate change on arable farming systems in Flevoland (the Netherlands) and to explore the adoption of different adaptation strategies. Data Envelopment Analysis (DEA) is applied that uses empirical data from individual farms to identify “best” current farm practices and derive relationships regarding current farm managemen

Rechterlijke toetsing van bestuurlijk gedrag: binnen het vennootschapsrecht van Nederland en Delaware

In deze studie staat centraal de vraag hoe – kort gezegd – de rechter binnen het Nederlandse vennootschapsrecht op systematische(r) wijze het bestuurlijk gedrag in de context van gevoerd ondernemingsbeleid kan toetsen. Daarbij richt de analyse zich op het frequent toegepaste enquêterecht en bestuurdersaansprakelijkheid in de zin van art. 2:9 BW (dat ziet op persoonlijke aansprakelijkheid van de bestuurder(s) jegens de vennootschap wegens 'onbehoorlijke taakvervulling'). Aan rechterlijke toetsing van bestuurlijk gedrag in de context van gevoerd ondernemingsbeleid zitten diverse haken en ogen, die in het eerste hoofdstuk in kaart worden gebracht. Daarbij wordt ook ingegaan op de ratio van beperkte rechterlijke toetsing van bestuurlijk gedrag en de wijze waarop daaraan invulling wordt gegeven binnen het Nederlandse vennootschapsrecht. Vervolgens wordt ter inspiratie in hoofdstukken 2-4 bezien hoe binnen het vennootschapsrecht van Delaware rekening wordt gehouden met voornoemde haken en ogen. Daarbij speelt de rechtsfiguur business judgment rule, een begrenzer van de rechterlijke toetsingsvrijheid, een voorname rol. Een kernaspect van deze rechtsfiguur is dat de rechter het gedrag van het ondernemende bestuur in beginsel niet op redelijkheid/billijkheid mag toetsen. Zo streng voor het bestuur mag de rechter niet zijn, tenzij het bestuur bijvoorbeeld geraakt wordt door een dusdanig persoonlijk – niet aan het belang van de vennootschap parallel lopend – belang dat het risico van belangenvermenging ten detrimente van de vennootschap aanwezig is. Binnen het Nederlandse vennootschapsrecht wordt vaak het vage begrip 'marginale' toetsing gebruikt, waarmee in wezen wordt gedoeld op een – inhoudelijke – redelijkheidstoets. Milder dan dat toetst de rechter het bestuurlijk gedrag doorgaans niet, ook niet wanneer de tegenstrijdig belang problematiek niet speelt. In hoofdstuk 5 wordt de blik weer gericht op het Nederlandse vennootschapsrecht en worden – de verhouding tussen – de kernbegrippen als gehanteerd binnen het enquêterecht geanalyseerd: 'wanbeleid', 'onjuist beleid' en 'gegronde redenen om aan een juist beleid te twijfelen'. In hoofdstukken 6-7 wordt vervolgens – op basis van de bevindingen in hoofdstukken 1-5 – een nuancering bepleit van de wijze waarop de Ondernemingskamer in enquêteprocedures bestuurlijk gedrag dient te toetsen, waarbij de Nederlandse variant van de business judgment rule als in deze studie voorgestaan een belangrijke rol speelt. Daarbij wordt een werkmethode uiteengezet die de Ondernemingskamer handvatten biedt bij de toetsing van gedrag van het ondernemende bestuur. Nadat de werkmethode is toegepast op een zestal enquêtebeschikkingen van de Ondernemingskamer wordt deze, inclusief de Nederlandse variant van de business judgment rule, ten slotte ingepast in de systematiek van art. 2:9 BW.Op de volledige tekst van dit proefschrift rust een embargo van 12 maanden. Van dit proefschrift is tevens een handelseditie verschenen in de serie Uitgaven vanwege het Instituut voor Ondernemingsrecht, Rijksuniversiteit Groningen, nr. 59, onder ISBN 978 90 13 04772 1, Kluwer, 2007

Efficient updating of node importance in dynamic real-life networks

The analysis of real-life networks, such as the internet, biometrical networks, and social networks, is challenged by the constantly changing structure of these networks. Typically, such networks consist of multiple weakly connected subcomponents and efficiently updating the importance of network nodes, as captured by the ergodic projector of a random walk on these networks, is a challenging task. In this paper, new approximations are introduced that allow to efficiently update the ergodic projector of Markov multi-chains. Properties such as convergence and error bounds for approximations are established. The numerical applicability is illustrated with a real-life social network example

Non-ergodic Jackson Networks with Infinite Supply - Local Stabilization and Local Equilibrium Analysis

Classical Jackson networks are a well established tool for the analysis of complex systems. In this paper we analyze Jackson networks with the additional features that (i) nodes may have an in nite supply of low priority work and (ii) nodes may be unstable in the sense that the queue length at these nodes grows beyond any bound. We provide the limiting distribution of the queue length distribution at stable nodes, which turns out to be of product-form. A key step in establishing this result is the development of a new algorithm based on adjusted trac equations for detecting instable nodes. Our results complement the results known in the literature for the sub-cases of Jackson networks with either innite supply nodes or unstable nodes by providing an analysis of the signicantly more challenging case of networks with both types of nonstandard nodes present. Building on our product-form results, we provide closed-form solutions for common customer and system oriented performance measures

Adapting agriculture in 2050 in Flevoland; perspectives from stakeholders

Although recently more research has gone into farm level studies, little attention has been given to the variety of responses of farmers, considering their characteristics, objectives and the socio-economic, technological and political contexts (Reidsma et al, 2010). In the Agri-Adapt project we focus on farm level adaptation within an agricultural region considering the socio-economic context of 2050