Composition variation in Al-based dilute nitride alloys using apertureless scanning near-field optical microscopy.

We use apertureless scanning near-field optical microscopy to study the phase separation in chemical beam epitaxy grown Al0.1Ga0.9NxAs1-x alloys. Pits attributed to nitrogen-clustering observed on the Al0.1Ga0.9NxAs1-x surface grown at 420 °C become larger at higher growth temperatures, and 3D islands appear on the surface at 565 °C. Atomic force microscopy phase measurements reveal a composition difference between the islands and the pits, whereas the sample grown at 420 °C appears to be homogeneous. Confocal Raman spectra show that all the N atoms are bonded to Al instead of Ga. Using apertureless scanning near-field optical microscopy, the luminescence of a gold tip is mapped over the surface of the sample grown at 565 °C. We extract the shift of the tip's surface plasmon resonance and determine the variation in the refractive index between the islands and the pits to be close to 0.2. Numerical simulations of the tip luminescence while in contact with the sample predict a similar variation of ∼0.3 in the refractive indices between AlGaAs islands and AlN pits, a substantially smaller value than the difference in the bulk refractive indices of the two media (∼1.8), which we attribute to a convolution of material distribution in an uneven topography. The excellent agreement between simulation and experiments supports the hypothesis of nitrogen-clustering in the pits.

Association of circulating visfatin concentrations with insulin resistance and low-grade inflammation after dietary energy restriction in Spanish obese non-diabetic women: role of body composition changes.

BACKGROUND AND AIMS: To assess the influence of body composition changes on circulating serum visfatin after following 12 weeks of energy restricted diet intervention. We also examined the possible role of visfatin in glucose metabolism and in obesity-associated low-grade inflammation. METHODS AND RESULTS: A total of 78 obese (BMI 34.0 ± 2.8 kg/m²) women aged 36.7±7 y volunteered to participate in the study. We measured by DXA body fat mass (FM) and lean mass (LM). Fasting serum visfatin, glucose, insulin, adiponectin, leptin, IL-1ß, IL-6, IL-8, TNF-α and CRP concentrations were analyzed before and after the intervention and HOMA and QUIKI indexes were calculated. Mean weight loss 7.7 ± 3.0 kg and HOMA decreased in 24 ± 35%. Serum visfatin concentration change was negatively associated with LM difference (P < 0.05), whereas no significant relationship was observed with FM changes after energy restricted diet intervention. Changes in circulating serum visfatin levels were significantly and inversely associated with HOMA-IR (P < 0.01) and positively with QUICKI index (P < 0.02) after energy restricted diet intervention, regardless of achieved body weight loss. We did not find any significant association between changes in visfatin levels and IL-1ß, IL-6, IL-8, TNF-α and CRP levels after dietary intervention (all P > 0.2). CONCLUSION: Circulating visfatin concentration is associated with sensitivity improvement achieved after energy restricted diet intervention induced weight loss. Furthermore, LM changes could be an influencing factor on visfatin concentrations and consequently, on the improvement of insulin sensitivity after weight loss in obese non-diabetic women. Our findings did not provide any evidence for a role of visfatin increase on low-grade inflammation after weight loss.

Second harmonic generation in AlGaAs photonic wires using low power continuous wave light.

We report modal phase matched (MPM) second harmonic generation (SHG) in high-index contrast AlGaAs sub-micron ridge waveguides, by way of sub-mW continuous wave powers at telecommunication wavelengths. We achieve an experimental normalized conversion efficiency of ~14%/W/cm2, obtained through a careful sub-wavelength design supporting both the phase matching requirement and a significant overlap efficiency. Furthermore, the weak anomalous dispersion, robust fabrication technology and possible geometrical and thermal tuning of the device functionality enable a fully integrated multi-functional chip for several critical areas in telecommunications, including wavelength (time) division multiplexing and quantum entanglement.

Preliminary findings on the role of PLIN1 polymorphisms on body composition and energy metabolism response to energy restriction in obese women.

The aim of the present study was to investigate the association of PLIN1 11482G>A (rs894160) and PLIN1 13041A>G (rs2304795) polymorphisms with body composition, energy and substrate metabolism, and the metabolic response to a 12-week energy-restricted diet in obese women. The study comprised a total of seventy-eight obese (BMI 34·0 (SD 2·8) kg/m(2)) women (age 36·7 (SD 7) years). We measured weight, height and waist circumference before and after a 12-week controlled energy-restricted diet intervention. Body fat mass and lean mass were measured by dual-energy X-ray absorptiometry. RMR and lipid oxidation rate were measured by indirect calorimetry. We also analysed fasting plasma glucose, insulin, cholesterol and leptin. Women carrying the 11482A allele had a lower reduction in waist circumference than non-A allele carriers (3·2 (SD 0·5) v. 4·6 (SD 0·6) %, respectively, P = 0·047; P for gene-diet interaction = 0·064). Moreover, women with the 11482A allele had a higher decrease in lipid oxidation rate than non-A allele carriers (58·9 (SD 6·7) v. 31·3 (SD 8·2) %, respectively, P = 0·012; P for gene-diet interaction = 0·004). There was no interaction effect between the 13041A>G polymorphism and diet-induced changes on the outcome variables (all P>0·1). These results confirm and extend previous findings suggesting that the PLIN1 11482G>A polymorphism plays a modulating role on diet-induced changes in body fat and energy metabolism in obese women.

Optical spatial solitons at the interface between two dissimilar periodic media: theory and experiment.

Discrete spatial solitons traveling along the interface between two dissimilar one-dimensional arrays of waveguides were observed for the first time. Two interface solitons were found theoretically, each one with a peak in a different boundary channel. One evolves into a soliton from a linear mode at an array separation larger than a critical separation where-as the second soliton always exhibits a power threshold. These solitons exhibited different power thresholds which depended on the characteristics of the two lattices. For excitation of single channels near and at the boundary, the evolution behavior with propagation distance indicates that the solitons peaked near and at the interface experience an attractive potential on one side of the boundary, and a repulsive one on the opposite side. The power dependence of the solitons at variable distance from the boundary was found to be quite different on opposite sides of the interface and showed evidence for soliton switching between channels with increasing input power.

Power-dependent switching of nonlinear trapping by local photonic potentials.

We study experimentally and numerically the nonlinear scattering of wave packets by local multisite guiding centers embedded in a continuous dielectric medium as a function of the input power and angle of incidence. The extent of trapping into the linear modes of different sites is manipulated as a function of both the input power and the angle of incidence, demonstrating power-controlled switching of nonlinear trapping by local photonic potentials.

Nonlinear scattering and trapping by local photonic potentials.

We experimentally study the nonlinear scattering by local photonic structures embedded in continuous Kerr media and demonstrate nonlinear trapping in guiding structures and resonant transmission in antiguiding structures. An intuitive physical picture is presented and verified in simulations.