Canonical Quantization of Spherically Symmetric Dust Collapse

Quantum gravity effects are likely to play a crucial role in determining the outcome of gravitational collapse during its final stages. In this contribution we will outline a canonical quantization of the LeMaitre-Tolman-Bondi models, which describe the collapse of spherical, inhomogeneous, non-rotating dust. Although there are many models of gravitational collapse, this particular class of models stands out for its simplicity and the fact that both black holes and naked singularity end states may be realized on the classical level, depending on the initial conditions. We will obtain the appropriate Wheeler-DeWitt equation and then solve it exactly, after regularization on a spatial lattice. The solutions describe Hawking radiation and provide an elegant microcanonical description of black hole entropy, but they raise other questions, most importantly concerning the nature of gravity's fundamental degrees of freedom.Comment: 19 pages no figures. Contribution to a festschrift in honor of Joshua N. Goldber

Role of hexagonal boron nitride in protecting ferromagnetic nanostructures from oxidation

Ferromagnetic contacts are widely used to inject spin polarized currents into non-magnetic materials such as semiconductors or 2-dimensional materials like graphene. In these systems, oxidation of the ferromagnetic materials poses an intrinsic limitation on device performance. Here we investigate the role of ex-situ transferred chemical vapour deposited hexagonal boron nitride (hBN) as an oxidation barrier for nanostructured cobalt and permalloy electrodes. The chemical state of the ferromagnets was investigated using X-ray photoemission electron microscopy owing to its high sensitivity and lateral resolution. We have compared the oxide thickness formed on ferromagnetic nanostructures covered by hBN to uncovered reference structures. Our results show that hBN reduces the oxidation rate of ferromagnetic nanostructures suggesting that it could be used as an ultra-thin protection layer in future spintronic devices.Comment: 7 pages, 6 figure

The Quantum Stress-Tensor in Self-Similar Spherical Dust Collapse

We calculate the quantum stress tensor for a massless scalar field in the 2-d self-similar spherical dust collapse model which admits a naked singularity. We find that the outgoing radiation flux diverges on the Cauchy horizon. This may have two consequences. The resultant back reaction may prevent the naked singularity from forming, thus preserving cosmic censorship through quantum effects. The divergent flux may lead to an observable signature differentiating naked singularities from black holes in astrophysical observations.Comment: Latex File, 19 page

The Eastward Enlargement of the Eurozone: Trade and FDI

Trade and FDI, Economic Integration

Magnetic anisotropy modulation of magnetite in Fe3O4/BaTiO3(100) epitaxial structures

Temperature dependent magnetometry and transport measurements on epitaxial Fe3O4 films grown on BaTiO3(100) single crystals by molecular beam epitaxy show a series of discontinuities, that are due to changes in the magnetic anisotropy induced by strain in the different crystal phases of BaTiO3. The magnetite film is under tensile strain at room temperature, which is ascribed to the lattice expansion of BaTiO3 at the cubic to tetragonal transition, indicating that the magnetite film is relaxed at the growth temperature. From the magnetization versus temperature curves, the variation in the magnetic anisotropy is determined and compared with the magnetoelastic anisotropies. These results demonstrate the possibility of using the piezoelectric response of BaTiO3 to modulate the magnetic anisotropy of magnetite films.Comment: 4 pages, 4 figure

NEONATAL RESPIRATORY DISTRESS ... A CASE FOR OPHTHALMOLOGY?

Introdução: O dacriocistocelo congénito é uma obstrução rara do canal lacrimo-nasal no recém-nascido, que pode dar sintomatologia precoce. A fisiologia deve-se à obstrução proximal e distal do canal lacrimo-nasal. A apresentação clínica é variada e inclui formações quísticas, infetadas ou não, dificuldade na amamentação ou respiratória. A apresentação clássica é uma massa quística de coloração azulada, abaixo do epicanto interno. O diagnóstico correto implica exames complementares. A intervenção terapêutica está dependente da evolução clínica. O prognóstico é bom e geralmente não tem sequelas futuras. Caso clínico: As autoras apresentam o caso de um recém nascido, internado por dificuldade respiratória de início no segundo dia de vida. Ao exame objetivo tinha sinais de dificuldade respiratória e lesão circinada de aspeto semelhante a hematoma no canto interno do olho esquerdo. Nesta localização houve desenvolvimento posterior de formação quística com sinais inflamatórios, com diagnóstico inicial de dacriocistite. Após realização de tomografia computorizada das órbitas mostrou tratar-se de um dacriocistocelo. Conclusão: A dificuldade respiratória pode mesmo ser um caso oftalmológico