Propagation of localized surface plasmons in sets of metallic nanocylinders at the exit of subwavelength slits

We analyze, by means of numerical simulations, transmission enhancements through sub- wavelength slits due to the presence of sets of plasmonic nanocylinders, placed near the exit of these apertures. Further, we extend this study to photonic crystals of dipolar plasmonic particles in front of an array of extraordinarily transmitting slits practiced in a metallic slab.Comment: 20 pages, 9 figures. Submitted to Journal of Nanophotonic

Magnetic field evolution and equilibrium configurations in neutron star cores: the effect of ambipolar diffusion

As another step towards understanding the long-term evolution of the magnetic field in neutron stars, we provide the first simulations of ambipolar diffusion in a spherical star. Restricting ourselves to axial symmetry, we consider a charged-particle fluid of protons and electrons carrying the magnetic flux through a motionless, uniform background of neutrons that exerts a collisional drag force on the former. We also ignore the possible impact of beta decays, proton superconductivity, and neutron superfluidity. All initial magnetic field configurations considered are found to evolve on the analytically expected time-scales towards "barotropic equilibria" satisfying the "Grad-Shafranov equation", in which the magnetic force is balanced by the degeneracy pressure gradient, so ambipolar diffusion is choked. These equilibria are so-called "twisted torus" configurations, which include poloidal and toroidal components, the latter restricted to the toroidal volumes in which the poloidal field lines close inside the star. In axial symmetry, they appear to be stable, although they are likely to undergo non-axially symmetric instabilities.Comment: MNRAS, accepte

Minimal AdS-Lorentz supergravity in three-dimensions

The $\mathcal{N}=1$ AdS-Lorentz superalgebra is studied and its relationship to semigroup expansion developed. Using this mathematical tool, the invariant tensors and Casimir operators are found. In terms of these invariants, a three-dimensionnal Chern--Simons supergravity action with AdS-Lorentz symmetry is constructed. The Killing spinors for a BTZ black-hole like solution of the theory are discussed.Comment: 18 pages, matches published versio

In vivo measurement of human brain elasticity using a light aspiration device

The brain deformation that occurs during neurosurgery is a serious issue impacting the patient "safety" as well as the invasiveness of the brain surgery. Model-driven compensation is a realistic and efficient solution to solve this problem. However, a vital issue is the lack of reliable and easily obtainable patient-specific mechanical characteristics of the brain which, according to clinicians' experience, can vary considerably. We designed an aspiration device that is able to meet the very rigorous sterilization and handling process imposed during surgery, and especially neurosurgery. The device, which has no electronic component, is simple, light and can be considered as an ancillary instrument. The deformation of the aspirated tissue is imaged via a mirror using an external camera. This paper describes the experimental setup as well as its use during a specific neurosurgery. The experimental data was used to calibrate a continuous model. We show that we were able to extract an in vivo constitutive law of the brain elasticity: thus for the first time, measurements are carried out per-operatively on the patient, just before the resection of the brain parenchyma. This paper discloses the results of a difficult experiment and provide for the first time in-vivo data on human brain elasticity. The results point out the softness as well as the highly non-linear behavior of the brain tissue.Comment: Medical Image Analysis (2009) accept\'

Coral reef degradation is not correlated with local human population density

The global decline of reef-building corals is understood to be due to a combination of local and global stressors. However, many reef scientists assume that local factors predominate and that isolated reefs, far from human activities, are generally healthier and more resilient. Here we show that coral reef degradation is not correlated with human population density. This suggests that local factors such as fishing and pollution are having minimal effects or that their impacts are masked by global drivers such as ocean warming. Our results also suggest that the effects of local and global stressors are antagonistic, rather than synergistic as widely assumed. These findings indicate that local management alone cannot restore coral populations or increase the resilience of reefs to large-scale impacts. They also highlight the truly global reach of anthropogenic warming and the immediate need for drastic and sustained cuts in carbon emissions

Donor species complement after liver xenotransplantation: The mechanism of protection from hyperacute rejection

Hamster hearts transplanted into stable rat recipients of hamster livers (OLT rats) were hyperacutely rejected after transfer with unaltered rat antihamster hyperimmune serum (HS). This was followed by immediate liver xenograft rejection in 4 of 5 rats. In contrast, simple heat inactivation of the rat HS resulted in prolonged survival of hamster hearts to 25 days without deterioration effect in the liver xenografts. This effect was species-specific because third-party mouse heart grafts in OLT rats were hyperacutely rejected in minutes if either active or heat inactivated antimouse HS was given. In cytotoxicity experiments, the complement in OLT serum produced weak lysis of hamster lymphocytes, while efficiently doing so with mouse cell targets. Because normal hamster serum caused no lysis at all of hamster target cells, the residual low-grade lysis of OLT serum was possibly being mediated by extrahepatic sources of rat C. In conclusion, the homology of C and target cells represents a mechanism of protection that the liver confers to other organs, and that is most easily seen in xenografts but may be allospecifically operational with allografts as well within the limits of MHC restriction. © 1994 by Williams and Wilkins