Spin-valley phase diagram of the two-dimensional metal-insulator transition

Using symmetry breaking strain to tune the valley occupation of a two-dimensional (2D) electron system in an AlAs quantum well, together with an applied in-plane magnetic field to tune the spin polarization, we independently control the system's valley and spin degrees of freedom and map out a spin-valley phase diagram for the 2D metal-insulator transition. The insulating phase occurs in the quadrant where the system is both spin- and valley-polarized. This observation establishes the equivalent roles of spin and valley degrees of freedom in the 2D metal-insulator transition.Comment: 4 pages, 2 figure

The Association of Serum Sialic Acid with Carotid Intima-Media Thickness and Anthropometric and Metabolic Parameters in Obese Children and Adolescents

Background: Sialic acid (SA) has been shown to be a strong predictor of cardiovascular mortality in adults. No study in children regarding the association of SA with cardiovascular risks exists in the literature. Aim: We aimed to investigate the association of SA with anthropometric and metabolic parameters and its correlation with metabolic syndrome (MS) and carotid intima-media thickness (IMT) in obese children. Methods: A total of 154 obese children were included in the study (74 females, 80 males; mean age 11.3 ± 2.6 years). Anthropometric measurements including body fat percentage (BFP) were recorded. Fasting lipids and SA levels were measured. The carotid IMT was evaluated with ultrasonography. Results: We found a significant correlation between serum total SA (TSA) levels and BFP (r = 0.25, p = 0.01 in the whole group; r = 0.43, p = 0.00 in girls). The group with BFP ≥95th percentile had higher TSA levels than the group with BFP <95th percentile (p = 0.04). TSA and carotid IMT were weakly correlated (r = 0.20, p = 0.01), but the significance was lost after correcting for BFP. No correlations were found between TSA and other anthropometric measurements. TSA did not correlate with serum fasting glucose, lipids, insulin or homeostasis model assessment-insulin resistance. TSA levels were not different between children with or without MS. Conclusion: Serum TSA levels are significantly correlated with BFP in obese children. Copyright © 2011 S. Karger AG, Basel