Nudging or Fudging: The World Development Report 2015

The 2015 World Development Report, Mind Society and Behaviour (World Bank, 2015), seeks a redesign of development policy on the basis of insights emerging from behavioural economics. This paper offers a critical assessment of the Report across four dimensions. First, it situates the Report within the broader and evolving knowledge role of the Bank. Second, the paper locates the Report in the context of the evolution of economics as a discipline and how this informs the evolution of the Bank’s development economics. Third, the Report is critically assessed for its narrow take on behavioural economics itself. Finally, the practical significance of the promotion of behavioural economics is considered through reference to its use in interventions in health in general and in response to HIV/AIDS in particular. It is argued that the Report suggests a dramatic and flawed reduction of what development is about, in that it foregoes any analysis of the structural problems facing developing countries and fails to propose major reforms to tackle these

Magneto-Optical Spectrum Analyzer

We present a method for the investigation of gigahertz magnetization dynamics of single magnetic nano elements. By combining a frequency domain approach with a micro focus Kerr effect detection, a high sensitivity to magnetization dynamics with submicron spatial resolution is achieved. It allows spectra of single nanostructures to be recorded. Results on the uniform precession in soft magnetic platelets are presented.Comment: 5 pages, 7 figure

Adaptively time stepping the stochastic Landau-Lifshitz-Gilbert equation at nonzero temperature: implementation and validation in MuMax3

Thermal fluctuations play an increasingly important role in micromagnetic research relevant for various biomedical and other technological applications. Until now, it was deemed necessary to use a time stepping algorithm with a fixed time step in order to perform micromagnetic simulations at nonzero temperatures. However, Berkov and Gorn have shown that the drift term which generally appears when solving stochastic differential equations can only influence the length of the magnetization. This quantity is however fixed in the case of the stochastic Landau-Lifshitz-Gilbert equation. In this paper, we exploit this fact to straightforwardly extend existing high order solvers with an adaptive time stepping algorithm. We implemented the presented methods in the freely available GPU-accelerated micromagnetic software package MuMax3 and used it to extensively validate the presented methods. Next to the advantage of having control over the error tolerance, we report a twenty fold speedup without a loss of accuracy, when using the presented methods as compared to the hereto best practice of using Heun's solver with a small fixed time step.Comment: 9 pages, 9 figure

Study of the pitch change of carbon coils during their growth

AbstractIn the present paper, carbon coils (CCs) were prepared by CVD. Their morphology, particularly pitch changes of the carbon coils prepared in different conditions were observed. It was found that the carbon source flow plays an important role in carbon coil growth and its morphology evolution. The appropriate atmosphere and flow rate is beneficial to the steady reactivity of catalyst particles. As such each carbon coil can grow well and have an exact growth rate. When the carbon supply is sufficient, the CCs exhibit close spiral and small coil diameter. When carbon supply decreases, small carbon supply leads to large pitch and coil diameter. CCs can be synthesized with different coil pitch under different carbon supply. This may be of great significance for the controllable preparation of carbon coil and its application

Thermodynamically self-consistent non-stochastic micromagnetic model for the ferromagnetic state

In this work, a self-consistent thermodynamic approach to micromagnetism is presented. The magnetic degrees of freedom are modeled using the Landau-Lifshitz-Baryakhtar theory, that separates the different contributions to the magnetic damping, and thereby allows them to be coupled to the electron and phonon systems in a self-consistent way. We show that this model can quantitatively reproduce ultrafast magnetization dynamics in Nickel.Comment: 5 pages, 3 figure

Magnetization structure of a Bloch point singularity

Switching of magnetic vortex cores involves a topological transition characterized by the presence of a magnetization singularity, a point where the magnetization vanishes (Bloch point). We analytically derive the shape of the Bloch point that is an extremum of the free energy with exchange, dipole and the Landau terms for the determination of the local value of the magnetization modulus.Comment: 4 pages, 2 figure

Chiral symmetry breaking of magnetic vortices by sample roughness

Finite-element micromagnetic simulations are employed to study the chiral symmetry breaking of magnetic vortices, caused by the surface roughness of thin-film magnetic structures. An asymmetry between vortices with different core polarizations has been experimentally observed for square-shaped platelets. E.g., the threshold fields for vortex core switching were found to differ for core up and down. This asymmetry was however not expected for these symmetrically-shaped structures, where both core polarizations should behave symmetrically. Three-dimensional finite element simulations are employed to show that a small surface roughness can break the symmetry between vortex cores pointing up and down. A relatively small sample roughness is found sufficient to reproduce the experimentally observed asymmetries. It arises from the lack of mirror-symmetry of the rough thin-film structures, which causes vortices with different handedness to exhibit asymmetric dynamics

Is Kapton * Really That Simple?

Age momentum correlation experiments in kapton has revealed the existence of two positron states corresponding to the trapping of positrons on the partially negatively charged O and/or N sites in the polymer chain. A young age broadening of the annihilation line shape is also observed and is attributed to the annihilation in flight of the positrons