A Sobolev Poincar\'e type inequality for integral varifolds

In this work a local inequality is provided which bounds the distance of an integral varifold from a multivalued plane (height) by its tilt and mean curvature. The bounds obtained for the exponents of the Lebesgue spaces involved are shown to be sharp.Comment: v1: 27 pages, no figures; v2: replaced citations of the author's dissertation by proofs, material of sections 1 and 3 reorganised, slightly more general results in section 2, some remarks, some discussion and some references added, 40 pages, no figure

Bonding of brackets using a caries-protective adhesive patch

OBJECTIVES: The purpose of this study was to assess the shear bond strength (SBS) of metal brackets when placed with a caries protective adhesive patch. METHODS: Forty stainless steel brackets (Ormco) were bonded to 40 bovine enamel samples according to the following conditioning/bonding procedures using a resin-based orthodontic luting material (Heliosit Orthodontic, N=10 per group): (A) 35% phosphoric acid (30s), rinse and dry; (B) as in A but additional placement of a prototype adhesive patch (Ivoclar Vivadent) using a bonding agent (Heliobond); (C) application of a two-step self-etch adhesive (AdheSE); (D) as in C but additional patch placement. Samples were stored at 37 degrees C for 24h. SBS was measured with a universal testing machine with a crosshead speed of 0.5mm/min and the adhesive remnant index (ARI) was determined under a stereomicroscope (16x). RESULTS: Mean SBS (standard deviation) values were as follows: (A) 16.6 (6.4)MPa; (B) 12.2 (5.8); (C) 12.9 (5.0); and (D) 10.5 (4.7). Analysis of variance followed by Bonferroni correction revealed no statistically significant differences. In 2 (B) and 4 (D) specimens, complete retention of the adhesive patch was observed. CONCLUSIONS: All treatment groups showed adequate bond strength values. The adhesive patch could therefore be applied in combination with orthodontic brackets and seal the enamel adjacent to the bracket

Isotropic-Nematic Transition in Liquid-Crystalline Elastomers

In liquid-crystalline elastomers, the nematic order parameter and the induced strain vary smoothly across the isotropic-nematic transition, without the expected first-order discontinuity. To investigate this smooth variation, we measure the strain as a function of temperature over a range of applied stress, for elastomers crosslinked in the nematic and isotropic phases, and analyze the results using a variation on Landau theory. This analysis shows that the smooth variation arises from quenched disorder in the elastomer, combined with the effects of applied stress and internal stress.Comment: 4 pages, including 4 postscript figures, uses REVTeX

Magnetic moment of welded HTS samples: dependence on the current flowing through the welds

We present a method to calculate the magnetic moments of the high-temperature superconducting (HTS) samples which consist of a few welded HTS parts. The approach is generalized for the samples of various geometrical shapes and an arbitrary number of welds. The obtained relations between the sample moment and the density of critical current, which flows through the welds, allow to use the magnetization loops for a quantitative characterization of the weld quality in a wide range of temperatures and/or magnetic fields.Comment: RevTeX4, 4 pages, 2 figures. Submitted to Supercond. Sci. Techno

Soft and non-soft structural transitions in disordered nematic networks

Properties of disordered nematic elastomers and gels are theoretically investigated with emphasis on the roles of non-local elastic interactions and crosslinking conditions. Networks originally crosslinked in the isotropic phase lose their long-range orientational order by the action of quenched random stresses, which we incorporate into the affine-deformation model of nematic rubber elasticity. We present a detailed picture of mechanical quasi-Goldstone modes, which accounts for an almost completely soft polydomain-monodomain (P-M) transition under strain as well as a ``four-leaf clover'' pattern in depolarized light scattering intensity. Dynamical relaxation of the domain structure is studied using a simple model. The peak wavenumber of the structure factor obeys a power-law-type slow kinetics and goes to zero in true mechanical equilibrium. The effect of quenched disorder on director fluctuation in the monodomain state is analyzed. The random frozen contribution to the fluctuation amplitude dominates the thermal one, at long wavelengths and near the P-M transition threshold. We also study networks obtained by crosslinking polydomain nematic polymer melts. The memory of initial director configuration acts as correlated and strong quenched disorder, which renders the P-M transition non-soft. The spatial distribution of the elastic free energy is strongly dehomogenized by external strain, in contrast to the case of isotropically crosslinked networks.Comment: 19 pages, 15 EPS figure

Magneto - transport characterization of Dy123 monodomain superconductors

The following report considers textured materials of the DyBa2Cu3O7 type seeded with a Nd123 seed as initiator. They are grown with an excess 20% Dy211 phase on a Dy2O3 substrate. We report chemical characterizations, electrical resistivity, thermoelectric power and thermal conductivity over a broad temperature range as a function of an applied magnetic field up to 6 T. We show that specific features appear on the magneto thermal transport properties different in these materials from those found in single crystals and polycrystalline samples. We propose that two vortex regimes can be distinguished in the mixed phase, - due to the intrinsic microstructure. We calculate the viscosity, entropy and figure of merit of the samples.Comment: 18 pages, with 8 figures; 4 color figuresx missing (much memory needed

Trueness of CAD/CAM digitization with a desktop scanner – an in vitro study

Desktop scanners are devices for digitization of conventional impressions or gypsum casts by indirect Computer-Aided Design/Computer-Assisted Manufacturing (CAD/CAM) in dentistry. The purpose of this in vitro study was: 1, to investigate whether virtual models produced by the extraoral scanner have the same trueness as sectioned casts; and 2, to assess if digitization with an extraoral scanner influences the surface information

Nonsmooth analysis of doubly nonlinear evolution equations

In this paper we analyze a broad class of abstract doubly nonlinear evolution equations in Banach spaces, driven by nonsmooth and nonconvex energies. We provide some general sufficient conditions, on the dissipation potential and the energy functional,for existence of solutions to the related Cauchy problem. We prove our main existence result by passing to the limit in a time-discretization scheme with variational techniques. Finally, we discuss an application to a material model in finite-strain elasticity.Comment: 45 page