Killing discarded embryos and the nothing-is-lost principle

A widely held view holds that it is permissible to conduct destructive research on embryos discarded following fertility treatment, but not on embryos especially created for research. One argument in support of this view appeals to the nothing-is-lost principle. It holds that because discarded embryos will die soon in any case, and something good is expected to come out of using them for research, it is presumptively permissible to do so. It is then claimed that no equivalent justification can be adduced in support of destructive research on embryos especially created for research. I argue that, on a standard formulation of the nothing-is-lost principle, this argument fails. I consider whether other plausible variants of the principle render the argument sound and argue that they do not

Precessional switching of thin nanomagnets: analytical study

We study analytically the precessional switching of the magnetization of a thin macrospin. We analyze its response when subjected to an external field along its in-plane hard axis. We derive the exact trajectories of the magnetization. The switching versus non switching behavior is delimited by a bifurcation trajectory, for applied fields equal to half of the effective anisotropy field. A magnetization going through this bifurcation trajectory passes exactly along the hard axis and exhibits a vanishing characteristic frequency at that unstable point, which makes the trajectory noise sensitive. Attempting to approach the related minimal cost in applied field makes the magnetization final state unpredictable. We add finite damping in the model as a perturbative, energy dissipation factor. For a large applied field, the system switches several times back and forth. Several trajectories can be gone through before the system has dissipated enough energy to converge to one attracting equilibrium state. For some moderate fields, the system switches only once by a relaxation dominated precessional switching. We show that the associated switching field increases linearly with the damping parameter. The slope scales with the square root of the effective anisotropy. Our simple concluding expressions are useful to assess the potential application of precessional switching in magnetic random access memories

A conception of genetic parenthood

We seek to develop a plausible conception of genetic parenthood, taking a recent discussion by Heidi Mertes as our point of departure. Mertes considers two conceptions of genetic parenthood—one invoking genetic resemblance, and the other genetic inheritance—and presents counter-examples to both conceptions. We revise Mertes’ second conception so as to avoid these and related counter-examples

Numerical simulation of an array of heaving floating point absorber wave energy converters using OpenFOAM

In this paper we use the CFD toolbox OpenFOAM to perform numerical simulations of multiple floating point absorber Wave Energy Converters (WECs) in a numerical wave basin. The two-phase Navier-Stokes fluid solver is coupled with a motion solver to simulate the wave-induced rigid body heave motion. The key of this paper is to extend numerical simulations of a single WEC unit to multiple WECs and to tackle the issues of modelling individual floating objects close to each other in an array lay-out. The developed numerical model is validated with laboratory experiments for free decay tests and for a regular wave train using two or five WECs in the array. For all the simulations presented, a good agreement is found between the numerical and experimental results for the WECs’ heave motions, the surge forces on the WECs and the perturbed wave field. As a result, our coupled CFD–motion solver proofs to be a suitable and accurate toolbox for the study of wave-structure interaction problems of multiple floating bodies in an array configuration

Towards the numerical simulation of 5 Floating Point Absorber Wave Energy Converters installed in a line array using OpenFOAM

In this paper we use the CFD toolbox OpenFOAM to perform numerical simulations of multiple floating point absorber Wave Energy Converters (WECs) in a numerical wave basin. The two-phase Navier-Stokes fluid solver is coupled with a motion solver to simulate the wave-induced rigid body heave motion. The purpose of this paper is twofold. The first objective is to extend numerical simulations of a single WEC unit to multiple WECs and to tackle the issues of modelling individual floating objects close to each other in an array layout. The second objective aims to include all the physical processes (e.g. friction forces) observed during experimental model tests in the numerical simulations. The achievements are verified by validating the numerical model with laboratory experiments for free decay and regular wave tests using a line array of two and five WECs. For all the simulations presented, a good agreement is found between the numerical and experimental results for the WECs’ heave motions, the surge forces on the WECs and the perturbed wave field. As a result, our coupled CFD–motion solver proves to be a suitable and accurate toolbox for the study of wave-structure interaction problems of WEC arrays.location: Cork, Irelandstatus: publishe