Cerebral vasospasm is a potentially devastating complication in patients with aneurysmal subarachnoid hemorrhage. The purpose of this article is to review the use of computed tomogram (CT) angiography and CT perfusion in the diagnosis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage and also assess their use in guiding treatment decisions. Both techniques are widely used for other indications but their use in cerebral vasospasm has not been well defined. Computed tomogram angiography can directly visualize arterial narrowing and CT perfusion is able to evaluate differences in perfusion parameters after aneurysmal subarachnoid hemorrhage with high sensitivity and specificity. CT perfusion is better at predicting which patients require endovascular treatment.
High dielectric constant, low loss dielectric thin film materials produced by reactive RF sputtering have been investigated for use as capacitor dielectrics in integrated circuits, using oxides of niobium, tantalum, titanium, hafnium, and zirconium and mixtures of these with aluminum oxide. High breakdown fields and low leakage currents are found for the best materials and a reduction in capacitor area of a factor of >3 compared with Si3N4 capacitors of the same value, using a simple production process compatible with semiconductor device manufacturing.
High resistance, low temperature coefficient of resistance (TCR) thin-film resistors have been produced by rf sputtering from compound targets using the Cr–Si–B–SiO2/Al2O3 material system. After postdeposition annealing at 450–550 °C sheet resistances of 20 kΩ/sq and TCR<200 ppm/°C were obtained for films of 40 nm thickness. The effect of changes to the proportions of each component in the mixture was investigated and it was found possible to control resistance and TCR. X-ray photoelectron spectroscopic analysis showed a good correlation between the target and film compositions. X-ray diffraction investigation did not show any crystalline structure in the film either before or after thermal treatment.
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