Management of Lumbar Artery Injury Related to Pedicle Screw Insertion

We report on 2 patients who experienced injury to one of their lumbar arteries related to pedicle screw misplacement. In this report, the lumbar pedicle screw holes were made laterally with resultant injury to the lumbar artery. During surgery, arterial bleeding was controlled with pressure and gauze; however, the patients experienced vital shock after surgery. Vital shock ensued and they were rescued by catheter embolization. If patients receiving lumbar instrumentation surgery experience severe anemia or vital shock postoperatively, the surgeon should assume lumbar artery injury as a differential diagnosis

Effects of ferric citrate on intracellular oxidative stress markers after hydrogen peroxide treatment of human U937 monocytes

Phosphate binders, such as iron （III） citrate hydrate （FCH）, are essential medications for hemodialysis patients. Some in vivo studies have demonstrated that FCH prevented induction of oxidative stress in the presence of transferrin. However, how FCH affects iron-related oxidative stress in the absence of transferrin remains unclear. In the current study, we investigated the effects of ferric citrate （FC） on oxidative stress in the absence of transferrin in vitro to address this question. Human U937 monocytes were pretreated with FC, iron （II） chloride tetrahydrate （FeCl2・4H2O）, iron （III） chloride hexahydrate （FeCl3・6H2O）, or saccharated ferric oxide for 24 h and then treated with 10-mM hydrogen peroxide （H2O2） for 30 min. The final Fe concentrations were adjusted to approximately 200µg/dl. Iron concentration, intracellular reactive oxygen species （ROS） levels, and intracellular lipid peroxidation of the cell membrane were measured. After treatment with FC, iron concentration and ROS levels increased. Change in lipid peroxidation after treatment with FC was not observed. However, after treatment with H2O2, no change was observed in the intracellular ROS levels in FC-pretreated cells, whereas lipid peroxidation of the cell membrane was decreased. Despite the high iron concentration in FC-pretreated cells, neither intracellular ROS nor cell membrane lipid peroxidation levels were increased with H2O2 treatment. Their results might represent antioxidative effects of FC. The results of this study may contribute to a better understanding of the effects of oxidative stress in hemodialysis patients treated with FCH

Co thickness dependence of structural and magnetic properties in spin quantum cross devices utilizing stray magnetic fields

We investigate the Co thickness dependence of the structural and magnetic properties of Co thin-film electrodes sandwiched between borate glasses in spin quantum cross (SQC) devices that utilize stray magnetic fields. We also calculate the Co thickness dependence of the stray field between the two edges of Co thin-film electrodes in SQC devices using micromagnetic simulation. The surface roughness of Co thin films with a thickness of less than 20 nm on borate glasses is shown to be as small as 0.18 nm, at the same scanning scale as the Co film thickness, and the squareness of the hysteresis loop is shown to be as large as 0.96-1.0. As a result of the establishment of polishing techniques for Co thin-film electrodes sandwiched between borate glasses, we successfully demonstrate the formation of smooth Co edges and the generation of stray magnetic fields from Co edges. Theoretical calculation reveals that a strong stray field beyond 6 kOe is generated when the Co thickness is greater than 10 nm at a junction gap distance of 5 nm. From these experimental and calculation results, it can be concluded that SQC devices with a Co thickness of 10-20 nm can be expected to function as spin-filter devices

Large magnetocapacitance effect in magnetic tunnel junctions based on Debye-Frohlich model

The frequency dependence of tunneling magnetocapacitance (TMC) in magnetic tunnel junctions (MTJs) is investigated theoretically and experimentally. According to the calculation based on Debye-Frohlich model combined with Julliere formula, the TMC ratio strongly depends on the frequency and it has the maximum peak at a specific frequency. The calculated frequency dependence of TMC is in good agreement with the experimental results obtained in MgO-based MTJs with a tunneling magnetoresistance (TMR) ratio of 108%, which exhibit a large TMC ratio of 155% at room temperature. This calculation also predicts that the TMC ratio can be as large as about 1000% for a spin polarization of 87%, while the TMR ratio is 623% for the same spin polarization. These theoretical and experimental findings provide a deeper understanding on AC spin-dependent transport in the MTJs and will open up wider opportunities for device applications, such as highly sensitive magnetic sensors and impedance-tunable devices

Robustness of Voltage-induced Magnetocapacitance

One of the most important achievements in the field of spintronics is the development of magnetic tunnel junctions (MTJs). MTJs exhibit a large tunneling magnetoresistance (TMR). However, TMR is strongly dependent on biasing voltage, generally, decreasing with applying bias. The rapid decay of TMR was a major deficiency of MTJs. Here we report a new phenomenon at room temperature, in which the tunneling magnetocapacitance (TMC) increases with biasing voltage in an MTJ system based on Co40Fe40B20/Mgo/Co40Fe40B20 . We have observed a maximum TMC value of 102% under appropriate biasing, which is the largest voltage-induced TMC effect ever reported for MTJs. We have found excellent agreement between theory and experiment for the bipolar biasing regions using Debye-Frohlich model combined with quartic barrier approximation and spin-dependent drift-diffusion model. Based on our calculation, we predict that the voltage-induced TMC ratio could reach 1100% in MTJs with a corresponding TMR value of 604%. Our work has provided a new understanding on the voltage-induced AC spin-dependent transport in MTJs. The results reported here may open a novel pathway for spintronics applications, e.g., non-volatile memories and spin logic circuits