Path Integral Approach to Strongly Nonlinear Composite

We study strongly nonlinear disordered media using a functional method. We solve exactly the problem of a nonlinear impurity in a linear host and we obtain a Bruggeman-like formula for the effective nonlinear susceptibility. This formula reduces to the usual Bruggeman effective medium approximation in the linear case and has the following features: (i) It reproduces the weak contrast expansion to the second order and (ii) the effective medium exponent near the percolation threshold are $s=1$, $t=1+\kappa$, where $\kappa$ is the nonlinearity exponent. Finally, we give analytical expressions for previously numerically calculated quantities.Comment: 4 pages, 1 figure, to appear in Phys. Rev.

Second-order estimates of the self-consistent type for viscoplastic polycrystals

The ‘second–order’ homogenization procedure of Ponte Castañeda is used to propose new estimates of the self–consistent type for the effective behaviour of viscoplastic polycrystals. This is accomplished by means of appropriately generated estimates of the self–consistent type for the relevant ‘linear thermoelastic comparison composite’, in the homogenization procedure. The resulting nonlinear self–consistent estimates are the only estimates of their type to be exact to second order in the heterogeneity contrast, which, for polycrystals, is determined by the grain anisotropy. In addition, they satisfy the recent bounds of Kohn and Little for two–dimensional power–law polycrystals, which are known to be significantly sharper than the Taylor bound at large grain anisotropy. These two features combined, suggest that the new self–consistent estimates, obtained from the second–order procedure, may be the most accurate to date. Direct comparison with other self–consistent estimates, including the classical incremental and secant estimates, for the special case of power–law creep, appear to corroborate this observation

Second-order estimates of the self-consistent type for viscoplastic polycrystals

The ‘second–order’ homogenization procedure of Ponte Castañeda is used to propose new estimates of the self–consistent type for the effective behaviour of viscoplastic polycrystals. This is accomplished by means of appropriately generated estimates of the self–consistent type for the relevant ‘linear thermoelastic comparison composite’, in the homogenization procedure. The resulting nonlinear self–consistent estimates are the only estimates of their type to be exact to second order in the heterogeneity contrast, which, for polycrystals, is determined by the grain anisotropy. In addition, they satisfy the recent bounds of Kohn and Little for two–dimensional power–law polycrystals, which are known to be significantly sharper than the Taylor bound at large grain anisotropy. These two features combined, suggest that the new self–consistent estimates, obtained from the second–order procedure, may be the most accurate to date. Direct comparison with other self–consistent estimates, including the classical incremental and secant estimates, for the special case of power–law creep, appear to corroborate this observation

Emergence of supersymmetry on the surface of three dimensional topological insulators

We propose two possible experimental realizations of a 2+1 dimensional spacetime supersymmetry at a quantum critical point on the surface of three dimensional topological insulators. The quantum critical point between the semi-metallic state with one Dirac fermion and the s-wave superconducting state on the surface is described by a supersymmetric conformal field theory within $\epsilon$-expansion. We predict the exact voltage dependence of the differential conductance at the supersymmetric critical point.Comment: 8 pages, 2 figures; published versio

Low Dose Thalidomide for Treatment of Resistant Discoid Lupus Erythematosus. A Case Report

Discoid lupus erythematosus (DLE) is a chronic, indolent, disfiguring disease that is characterized by scaly, erythematous, disk-shaped patches and plaques followed by atrophy, scarring and depigmentation. In a small number of patients, it is refractory to standard therapies. In several studies, thalidomide has been reported to be an effective treatment in those cases. The most fearful side effects are teratogenicity and neuropathy. Adequate counseling and vigilance must be given to the patients. We report a 45-year-old Portuguese woman who presented with a 20-year history of severe facial and scalp DLE confirmed by histopathology. For several years, it failed to respond to several therapies, including topical, intralesional and oral corticosteroids, hydroxychloroquine, methotrexate, azathioprine and topical tacrolimus. Thalidomide was initiated at a dosage of 50mg/day and the skin lesions had improved dramatically after three weeks with complete clinical remission. Two months later, the dose was reduced to 50mg, five days per week without disease rebound. The patient´s concomitant medications during the treatment included sunscreen, hydroxycholoroquine, enoxaparin and aspirin to prevent thromboembolic events. Pregnancy testing, routine laboratory and electrocardiography were performed at regular intervals for safety monitoring and the results were within normal limits. Only minor side effects as nausea, constipation and somnolence were noted, however, they improved with dose reduction. Our data confirm that thalidomide therapy is an alternative or adjunctive treatment for patients with severe, chronic DLE that is refractory to standard therapies. In this patient, low-dose thalidomide was an effective treatment with minimal side effects

Efficacy of Narrowband UVB vs. PUVA in Patients with Early-Stage Mycosis Fungoides

INTRODUCTION: Mycosis fungoides (MF) is a non-Hodgkin's T-cell lymphoma of the skin that often begins as limited patches and plaques with slow progression to systemic involvement. Narrowband ultraviolet (UV) B therapy has been proven to be an effective short-term treatment modality for clearing patch-stage MF. The effect of psoralen plus long-wave ultraviolet A (PUVA) in the treatment of patch- and plaque-type MF has also been thoroughly documented. OBJECTIVES: The purpose of this study was to compare the efficacy and safety of narrowband UVB and PUVA in patients with early-stage MF. METHODS: We analysed the response to treatment, relapse-free survival and irradiation dose in 114 patients with histologically confirmed early-stage MF (stage IA, IB and IIA). RESULTS: A total of 95 patients were treated with PUVA (83.3%) and 19 with narrowband UVB (16.7%). With PUVA, 59 patients (62.1%) had a complete response (CR), 24 (25.3%) had a partial response (PR) and 12 (12.6%) had a failed response. Narrowband UVB led to CR in 12 (68.4%) patients, PR in 5 (26.3%) patients and a failed response in 1 (5.3%) patient. There were no differences in terms of time to relapse between patients treated with PUVA and those treated with narrowband UVB (11.5 vs. 14.0 months respectively; P = 0.816). No major adverse reactions were attributed to the treatment. CONCLUSIONS: Our results confirm that phototherapy is a safe, effective and well-tolerated, first-line therapy in patients with early-stage cutaneous T-cell lymphoma, with prolonged disease-free remissions being achieved. It suggests that narrowband UVB is at least as effective as PUVA for treatment of early-stage MF.info:eu-repo/semantics/publishedVersio

Variational estimates for the effective response and field statistics in thermoelastic composites with intra-phase property fluctuations

International audienceIn this work, variational estimates are provided for the macroscopic response, as well as for the first and second moments of the stress and strain fields, in thermoelastic composites with non-uniform distributions of the thermal stress and elastic moduli in the constituent phases. These estimates are obtained in terms of a 'comparison composite' with uniform phase properties depending on the first and second moments of a certain combination of the given intra-phase thermal stresses and modulus field distributions. Under certain hypotheses, these estimates can be shown to lead to upper and lower bounds for the free energy of the composite, which reduce to standard results when the intra-phase fluctuations vanish. An illustrative application is given for rigidly reinforced composites with a non-uniform distribution of the thermal stress in the matrix phase