Direct synthesis of mesoporous silica containing cobalt: A new strategy using a cobalt soap as a co-template

A novel approach to incorporate transition metals into porous structures is presented, which makes use of a cobalt soap in combination with the templating agent C16TMABr. An ordered mesoporous silica MCM-41 type material doped with Co is obtained after removal of the organic part by calcination. The a unit cell parameter of the cobalt containing mesoporous matrices is larger than that of pure MCM-41 and increases with the amount of cobalt present in the sample as well as the diameter of the pores. This is not observed when e.g. cobalt acetate is employed instead of the metal soap. The procedure presented establishes a new route for the incorporation of a transition metal into MCM-41 together with a tuning of the porous structure

‘Stick that knife in me’: Shane Meadows’ children

This article brings Shane Meadows’ Dead Man's Shoes (2004) into dialogue with the history of the depiction of the child on film. Exploring Meadows’ work for its complex investment in the figure of the child on screen, it traces the limits of the liberal ideology of the child in his cinema and the structures of feeling mobilised by its uses – at once aesthetic and sociological – of technologies of vision

Analog of Magnetoelectric Effect in High-Tc Granular Superconductors

We propose the existence of an electric-field induced nonlinear magnetization in a weakly coupled granular superconductor due to time-parity violation. As the field increases the induced magnetization passes from para- to dia-magnetic behavior. We discuss conditions under which this effect could be experimentally measured in high-temperature superconductors.Comment: REVTEX (epsf style), 1 PS figure; to appear in Europhysics Letter

Geometric optics and instability for semi-classical Schrodinger equations

We prove some instability phenomena for semi-classical (linear or) nonlinear Schrodinger equations. For some perturbations of the data, we show that for very small times, we can neglect the Laplacian, and the mechanism is the same as for the corresponding ordinary differential equation. Our approach allows smaller perturbations of the data, where the instability occurs for times such that the problem cannot be reduced to the study of an o.d.e.Comment: 22 pages. Corollary 1.7 adde

Limiting Carleman weights and anisotropic inverse problems

In this article we consider the anisotropic Calderon problem and related inverse problems. The approach is based on limiting Carleman weights, introduced in Kenig-Sjoestrand-Uhlmann (Ann. of Math. 2007) in the Euclidean case. We characterize those Riemannian manifolds which admit limiting Carleman weights, and give a complex geometrical optics construction for a class of such manifolds. This is used to prove uniqueness results for anisotropic inverse problems, via the attenuated geodesic X-ray transform. Earlier results in dimension $n \geq 3$ were restricted to real-analytic metrics.Comment: 58 page

Nonlinear Seebeck Effect in a Model Granular Superconductor

The change of the Josephson supercurrent density of a weakly-connected granular superconductor in response to externally applied arbitrary thermal gradient dT/dx (nonlinear Seebeck effect) is considered within a model of 3D Josephson junction arrays. For dT/dx>(dT/dx)_c, where (dT/dx)_c is estimated to be of the order of 10^4 K/m for YBCO ceramics with an average grain's size of 10 microns, the weak-links-dominated thermopower S (Seebeck coefficient) is predicted to become strongly dT/dx-dependent.Comment: REVTEX, no figure

Resonance-free Region in scattering by a strictly convex obstacle

We prove the existence of a resonance free region in scattering by a strictly convex obstacle with the Robin boundary condition. More precisely, we show that the scattering resonances lie below a cubic curve which is the same as in the case of the Neumann boundary condition. This generalizes earlier results on cubic poles free regions obtained for the Dirichlet boundary condition.Comment: 29 pages, 2 figure

Scattering frequencies and Gervey 3 singularities

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46619/1/222_2005_Article_BF01389032.pd

Nucleation of Stable Superconductivity in YBCO-Films

By means of the linear dynamic conductivity, inductively measured on epitaxial films between 30mHz and 30 MHz, the transition line $T_g (B)$ to generic superconductivity is studied in fields between B=0 and 19T. It follows closely the melting line $T_m (B)$ described recently in terms of a blowout of thermal vortex loops in clean materials. The critical exponents of the correlation length and time near $T_g (B)$, however, seem to be dominated by some intrinsic disorder. Columnar defects produced by heavy-ion irradiation up to field-equivalent-doses of $B_{\phi} = 10T$ lead to a disappointing reduction of $T_g (B \to 0)$ while for $B>B_{\phi}$ the generic line of the pristine film is recovered. These novel results are also discussed in terms of a loop-driven destruction of generic superconductivity.Comment: 11 pages including 7 EPS figures, accepted for publication in the Proceedings of the Spring Meeting of the German Physical Society, Muenster 1999,Festkoerperprobleme/Advances in Solid State Physics 199