High domain wall velocities via spin transfer torque using vertical current injection.

Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm(2). Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching.

The iliac wing sign: an indicator of the presence of bone and/or soft-tissue injury of the pelvis and hips.

PURPOSE: To prospectively evaluate the feasibility of using the "iliac wing sign (IWS)" as an indicator of bone and/or soft-tissue injury of the pelvis and hips on magnetic resonance (MR) imaging. IWS means edema of the iliacus muscle attachment entering the iliac wing that is visualized as a linear high signal intensity on fat-suppressed T2-weighted MR images. METHODS: Consecutive 106 patients who complained of hip pain were enrolled in this study. We evaluated the correlation between IWS and bone and/or soft-tissue injury of the pelvis and hips using Fisher's exact test. Further, performance parameters of sensitivity, specificity, accuracy, the positive predictive value (PPV), and negative predictive value (NPV) of IWS were calculated. RESULTS: Thirty-eight of the 106 (36%) patients had bone and/or soft-tissue injury. Twenty-seven of these 38 (71%) patients with injury showed a positive IWS, while only 11 of 68 (16%) patients without injury showed a positive IWS (p<.0001). IWS, thus, yielded a sensitivity of 71%, specificity of 84%, accuracy of 79%, positive predictive value (PPV) of 71%, and negative predictive value (NPV) of 84%. CONCLUSION: In cases with a positive IWS, the careful interpretation of MR images is needed because injury presence is highly likely, as suggested by the relatively high sensitivity and PPV. IWS absence may mean a low probability of injury because of the high specificity and NPV.

Radiological findings in total colon aganglionosis and allied disorders.

OBJECTIVE: The aim of this study was to review the radiological findings of three cases of total colon aganglionosis (TCA), hypoganglionosis, and immature ganglionosis, and to compare the differences in diagnosis and follow-up of these three disease entities. MATERIALS AND METHODS: Three neonates with neonatal onset of abdominal distension with vomiting were investigated, and the cases were diagnosed as TCA, hypoganglionosis, and immature ganglionosis, respectively. Radiological examination of each neonate was performed during the neonatal period and at follow-up. RESULTS: A plain abdominal radiograph showed massive abdominal bowel gas and multiple air-fluid levels in all cases. Barium enema findings including no transition zone, normal rectosigmoid index, reflux of barium into a dilated ileum, and retention of barium on delayed film were observed in all three cases. In aganglionosis and hypoganglionosis, a normal-sized colon, irregular contraction, shortening of the colon, and lack of redundancy were observed. In immature ganglionosis, microcolon was present but there was no shortening of the colon or loss of redundancy. Barium studies following ileostomy during childhood revealed no efficient peristalsis after the neonatal period in patients with aganglionosis and hypoganglionosis. Conversely, the patient with immature ganglionosis showed maturity of colonic function on barium studies after infancy. CONCLUSION: The clinical and radiological findings of TCA and allied disorders are similar in neonates. Sequential contrast intestinal studies could reveal peristalsis of the colon wall, suggesting maturity of the ganglion cells.