Enhanced optical conductivity and many-body effects in strongly-driven photo-excited semi-metallic graphite.

The excitation of quasi-particles near the extrema of the electronic band structure is a gateway to electronic phase transitions in condensed matter. In a many-body system, quasi-particle dynamics are strongly influenced by the electronic single-particle structure and have been extensively studied in the weak optical excitation regime. Yet, under strong optical excitation, where light fields coherently drive carriers, the dynamics of many-body interactions that can lead to new quantum phases remain largely unresolved. Here, we induce such a highly non-equilibrium many-body state through strong optical excitation of charge carriers near the van Hove singularity in graphite. We investigate the system's evolution into a strongly-driven photo-excited state with attosecond soft X-ray core-level spectroscopy. We find an enhancement of the optical conductivity of nearly ten times the quantum conductivity and pinpoint it to carrier excitations in flat bands. This interaction regime is robust against carrier-carrier interaction with coherent optical phonons acting as an attractive force reminiscent of superconductivity. The strongly-driven non-equilibrium state is markedly different from the single-particle structure and macroscopic conductivity and is a consequence of the non-adiabatic many-body state.

Applicability of dermoscopy for evaluation of patients' response to nonablative therapies for the treatment of superficial basal cell carcinoma.

BACKGROUND: Applicability of dermoscopy in evaluation of outcome and monitoring of superficial basal cell carcinoma (sBCC) after nonablative therapies has not been sufficiently assessed. OBJECTIVES: Certain dermoscopic criteria, namely pigmented structures, ulceration and arborizing vessels, have been suggested to predict the presence of residual disease [residual disease-associated dermoscopic criteria (RDADC)]. We aimed to assess this hypothesis. PATIENTS AND METHODS: Lesions exhibiting RDADC 3 months after treatment were biopsied and in the case of histopathological confirmation were excised. Lesions characterized by white/red structureless areas, superficial fine telangiectasias, or lacking any dermoscopic criterion, were monitored for 12 months. RESULTS: At the 3-month evaluation, one or more of the RDADC were detected in 25/98 (25·5%) sBCCs, in which histology confirmed tumour persistence. In 45 (61·6%) of the 73 remaining lesions, dermoscopy showed white/red structureless areas and/or superficial fine telangiectasias. Twenty-eight lacked any dermoscopic criterion of sBCC. The two latter groups entered follow-up. In total, disease recurred in 13 (17·8%) of the 73 lesions. CONCLUSIONS: RDADC accurately predict residual disease. Absence of dermoscopic criteria of sBCC safely predicts complete histopathological clearance. Detection of white/red structureless areas and/or superficial fine telangiectasias warrants close monitoring to recognize early recurrence.

Dermoscopy of discoid lupus erythematosus.

BACKGROUND: Dermoscopy is useful in evaluating skin tumours, but its applicability also extends into the field of inflammatory skin disorders. Discoid lupus erythematosus (DLE) represents the most common subtype of cutaneous lupus erythematosus. While dermoscopy and videodermoscopy have been shown to aid the differentiation of scalp DLE from other causes of scarring alopecia, limited data exist concerning dermoscopic criteria of DLE in other locations, such as the face, trunk and extremities. OBJECTIVE: To describe the dermoscopic criteria observed in a series of patients with DLE located on areas other than the scalp, and to correlate them to the underlying histopathological alterations. METHODS: DLE lesions located on the face, trunk and extremities were dermoscopically and histopathologically examined. Selection of the dermoscopic variables included in the evaluation process was based on data in the available literature on DLE of the scalp and on our preliminary observations. Analysis of data was done with SPSS analysis software. RESULTS: Fifty-five lesions from 37 patients with DLE were included in the study. Perifollicular whitish halo, follicular keratotic plugs and telangiectasias were the most common dermoscopic criteria. Statistical analysis revealed excellent correlation between dermoscopic and histopathological findings. Notably, a time-related alteration of dermoscopic features was observed. CONCLUSIONS: The present study provides new insights into the dermoscopic variability of DLE located on the face, trunk and extremities.

Efficient low dispersion compact plasmonic-photonic coupler.

We report efficient low dispersion light coupling into a silicon waveguide using an antenna consisting of two metallic nanoparticles. We find that strong multiple scattering between the nanoparticles dictates the coupling efficiency. We also explore directional coupling, by using different particles with a relative scattering phase, but find that optimum directionality corresponds to minimum efficiency. A dipole model highlights a subtle interplay between multiple scattering and directionality leading to a compromise allowing up to 30% transmission into a single direction. With a 500 nm bandwidth near infrared telecoms bands, group delay dispersion is sufficiently low to faithfully couple pulses as short as 50 fs.