Diffusion Thermopower at Even Denominator Fractions

We compute the electron diffusion thermopower at compressible Quantum Hall states corresponding to even denominator fractions in the framework of the composite fermion approach. It is shown that the deviation from the linear low temperature behavior of the termopower is dominated by the logarithmic temperature corrections to the conductivity and not to the thermoelectric coefficient, although such terms are present in both quantities. The enhanced magnitude of this effect compared to the zero field case may allow its observation with the existing experimental techniques.Comment: Latex, 12 pages, Nordita repor

Dural ectasia in adolescent idiopathic scoliosis: quantitative assessment on magnetic resonance imaging

To our knowledge, the assessment of dural sac diameters in patients with adolescent idiopathic scoliosis (AIS) is not reported in the literature. The aim of this study was to find out if, dural ectasia occurs more frequently among patients with AIS, to define cut-off values for dural sac ratio and test the validity of such values. A total of 126 spine MRIs (79 patients with AIS and 47 control subjects) were included in this retrospective analysis (age range 7–25 years, 62% were females). Dural sac diameter (DSD) and vertebral body diameter (VBD) were estimated and dural sac ratio (DSR = DSD/VBD) was calculated at T5 and L3. DSR at T5 and L3 were 0.69 ± 0.12, and 0.52 ± 0.10, respectively, in patients with AIS compared with 0.62 ± 0.11, and 0.44 ± 0.07, respectively, in controls (P = 0.001 at T5 and <0.001 at L3). Our estimated cut-off values for DSR were 0.84 and 0.58 at T5 and L3, respectively. This resulted in 100% sensitivity compared with 74% when using the cut-off values proposed by Oosterhof et al. No statistically significant association was found between the occurrence of dural sac enlargement in patients with AIS and the severity of scoliotic deformity, the apical vertebral rotation, epidural fat thickness, occurrence of pain, neurological deficit, atypical scoliosis or rapid curve progression. Females were affected more frequently than males. As dural sac enlargement means thinning of the pedicles, we believe that the findings of this study have important clinical implications on the preoperative workup of AIS