The interesting physics and potential memory technologies resulting from topologically protected spin textures such as skyrmions, has prompted efforts to discover new material systems that can host these kind of magnetic structures. Here we use the highly tunable magnetic properties of amorphous Fe/Gd multilayer films to explore the magnetic properties that lead to dipole-stabilized skyrmions and skyrmion lattices that form from the competition of dipolar field and exchange energy. Using both real space imaging and reciprocal space scattering techniques we determined the range of material properties and magnetic fields where skyrmions form.Micromagnetic modeling closely matches our observation of small skyrmion features (~50 to 70nm) and suggests these class of skyrmions have a rich domain structure that is Bloch like in the center of the film and more Néel like towards each surface. Our results provide a pathway to engineer the formation and controllability of dipole skyrmion phases in a thin film geometry at different temperatures and magnetic fields.

We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy (PMA) exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

When engineered on scales much smaller than the operating wavelength, metal-semiconductor nanostructures exhibit properties unobtainable in nature. Namely, a uniaxial optical metamaterial described by a hyperbolic dispersion relation can simultaneously behave as a reflective metal and an absorptive or emissive semiconductor for electromagnetic waves with orthogonal linear polarization states. Using an unconventional multilayer architecture, we demonstrate luminescent hyperbolic metasurfaces, wherein distributed semiconducting quantum wells display extreme absorption and emission polarization anisotropy. Through normally incident micro-photoluminescence measurements, we observe absorption anisotropies greater than a factor of 10 and degree-of-linear polarization of emission >0.9. We observe the modification of emission spectra and, by incorporating wavelength-scale gratings, show a controlled reduction of polarization anisotropy. We verify hyperbolic dispersion with numerical simulations that model the metasurface as a composite nanoscale structure and according to the effective medium approximation. Finally, we experimentally demonstrate >350% emission intensity enhancement relative to the bare semiconducting quantum wells.

Background There has been constant speculation about the association between metabolic syndrome (MetS) and colorectal neoplasia (CN); however, the published results are conflicting. The aims of this study are to systematic search, and assess literature to determine the available evidence on the association between these two conditions. Methods Meta-analysis was conducted based on relevant studies identified through a systematic literature review from PubMed, OvidSP and Cochrane database during January 1980 to July 2011. A combined analysis was performed, followed by a subgroup analyses stratified by the study design, type of colorectal lesions and gender. Publication bias was assessed using the Begg’s and Egger’s tests and visual inspection of funnel plot. Results Eighteen studies were included in the final analysis. Overall, MetS was associated with 34% increase in the risk of CN (summary RR - 1.34, 95% CI 1.24–1.44). The association between MetS and CN was found to be statistically significant in separate analysis for both case-control studies (summary RR -1.58, 95% CI 1.44–1.79) and cohort studies (summary RR – 1.21, 95% CI 1.13–1.29). The association remained significant when analyses were restricted by type of colorectal lesions (colorectal cancer: RR – 1.30, 95% CI 1.18–1.43; colorectal adenoma: RR – 1.37, 95% CI 1.26–1.49). Further subgroup analysis by gender showed significant association between MetS and CN in both male and female population. Conclusion Our meta-analysis showed significant association between presence of MetS and CN. These results may help in identifying high risk individuals at early stage that might benefit from targeted CRC screening intervention.