Assessing risks and benefits of floral supplements in conservation biological control

The use of flowering field margins is often proposed as a method to support biological control in agro-ecosystems. In addition to beneficial insects, many herbivores depend on floral food as well. The indiscriminate use of flowering species in field margins can therefore lead to higher pest numbers. Based on results from field observations and laboratory experiments we assessed risks as well as benefits associated with the provision of nectar plants in field margins, using Brussels sprouts as a model system. Results show that Brussels sprouts bordered by nectar plants suitable for the cabbage white Pieris rapae L., suffered higher infestation levels by this herbivore. In contrast, nectar plants providing accessible nectar for the diamondback moth Plutella xylostella L., did not raise densities of P. xylostella larvae in the Brassica crop. Margins with Anethum graveolens L., selected on the basis of its suitability as nectar plant for parasitoids, significantly increased the number of adult Diadegma semiclausum Hellen in the crop. This didn't translate into enhanced parasitism rates, as parasitism of P. xylostella by D. semiclausum exceeded 65 % in all treatments, irrespective of the plants in the field margin. Our findings emphasize the importance of taking a multitrophic approach when choosing flowering field margin plants for biocontrol or other ecosystem service

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Contains fulltext : 231180.pdf (Publisher’s version ) (Open Access)T. Mertens Boeken voor de eeuwigheid. Middelnederlands geestelijk proza Amsterdam:onbekend ,199

Truncated Autonomy: Neocortical Selves, Reverse Reductionism and End-of-Life Care

In professional guidelines for palliative sedation in end-of life care, a particular notion of conscious life experience is associated with specific cognitivist notion of frontal lobe autonomy. Drawing on Turner and Fauconnier’s work in cognitive linguistics I argue in this chapter that even our most central notions like human subjectivity and autonomy are conceptual blends. This chapter explores the origins and emergence of these concepts and their entailments. It digs deep into the conceptual blending of the ontogenetic development of the individual with the phylogenetic history of life. This hyper-blend of the flesh is contrasted with the hyper-blend of an irreal, non-material deep, inner space that is co-extensive with consciousness and with the rational, operative agent constituting the human subject. The last part of the chapter explores the frictions and problematic entailments of these different hyper-blends for end-of-life care practices concerning brain death, persistent vegetative state and palliative sedation. Despite respect for a patient’s autonomy being first among the principles of medical ethics, cognitivist criteria used in the assessment of a patient’s decision-making competence reduce and constrain (truncate) the patient’s autonomy in a variety of ways in one of the situations in life where it should matter most, in dying

Balance Sheets of Suffering in End-of-Life Care

Drawing on recent work in cognitive linguistics and social studies of knowledge practices, this chapter explores the various ways in which the figure of a balance sheet frames arguments and positions in end-of-life care. Across arguments and positions, there are substantial differences in the kinds of matter that are balanced against each other and the values attributed to them, and which items are allowed as entries on the balance sheet and which are not. A common currency on the balance sheets is human suffering. Comparing Norwegian and Dutch end-of-life care practices, the argument is elaborated by looking at (a) the personal balance sheets of cancer patients, (b) the balance sheets of euthanasia, assisted suicide, and palliative sedation, and (c) the balance sheets that set patient’s right to self-determination up against health professional’s right to conscience. Finally, the different ways in which the balance sheets are operated are considered with regard to their impact on the level of constraints that the different end-of-life care policies put on patients and health professionals, and how these shape the material conditions of our dying

An adaptive-gridding solution method for the 2D unsteady Euler equations

Adaptive grid refinement is a technique to speed up the numerical solution of partial differential equations by starting these calculations on a coarse basic grid and refining this grid only there where the solution requires this, e.g. in areas with large gradients. This technique has already been used often, for both steady and unsteady problems. Here, a simple and efficient adaptive grid technique is proposed for the solution of systems of 2D unsteady hyperbolic conservation laws. The technique is applied to the Euler equations of gasdynamics. Extension to other conservation laws or to 3D is expected to be straightforward. A solution algorithm is presented that refines a rectangular basic grid by splitting coarse cells into four, as often as required, and merging these cells again afterwards. The small cells have a shorter time step too, so the grid is refined in space and time. The grid is adapted to the solution several times per coarse time step, therefore the total number of cells is kept low and a fast solution is ensured. The grid is stored in a simple data structure. All grid data are stored in 1D arrays and the grid geometry is determined with, per cell, five pointers to other cells: one `mother' pointer to the cell from which the cell was split and four `neighbour' pointers. The latter are arranged so, that all cells around the considered cell can be quickly found. To determine where the grid is refined, a refinement criterion is used. Three different refinement criteria are studied: one based on the first spatial derivative of the density, one on the second spatial derivative of the density and one on an estimate of the local truncation error, comparable to Richardson extrapolation. Especially the first-derivative $ho$ criterion gives good results. The algorithm is combined with a simple first-order accurate discretisation of the Euler equations, based on Osher's flux function, and tested. A second-order accurate discretisation of the Euler equations is presented that combines a second-order limited discretisation of the fluxes with the time derivatives of the Richtmyer scheme. This scheme can be easily combined with the adaptive-gridding algorithm. Stability is proved for CFL numbers below 0.25. For cells with different sizes, several interpolation techniques are developed, like the use of virtual cells for flux calculation. The scheme is tested with two standard test cases, the 1D Sod problem and the forward-facing step problem, known from the work of Woodward and Colella. The results show that the second-order scheme is more efficient than the first-order scheme. An accuracy, comparable with solutions on uniform grids is obtained, but with at least five times lower computational costs. Results from a last test problem, the shedding of vortices from a flat plate that is suddenly set into motion, confirm that the method can be used for different flow regimes and that it is very useful in practice for analysis of unsteady flow

Efficient computation of steady water flow with waves

A surface-capturing model for steady water flow is presented. This volume-of-fluid model without reconstruction consists only of conservation laws, hence, it can be solved very efficiently. The model contains a high-accuracy compressive water surface discretization and turbulence; it is solved with a linear multigrid technique and defect correction. Results show that the model is accurate and the solver gives fast convergence