Spin-torque-induced dynamics at fine-split frequencies in nano-oscillators with two stacked vortices.

The gyrotropic rotation around the equilibrium position constitutes the fundamental excitation of magnetic vortices in nanostructures. The frequency of this mode varies with material and sample geometry, but is independent of the vortex handedness and its core direction. Here, we demonstrate that this degeneracy is lifted in a spin-torque oscillator containing two vortices stacked on top of each other. When driven by spin-polarized currents, such devices exhibit a set of dynamic modes with discretely split frequencies, each corresponding to a specific combination of vorticities and relative core polarities. The fine splitting occurs even in the absence of external fields, demonstrating that such devices can function as zero-field, multi-channel, nano-oscillators for communication technologies. It also facilitates the detection of the relative core polarization and allows for the eight non-degenerate configurations to be distinguished electrically, which may enable the design of multi-state memory devices based on double-vortex nanopillars.

[The stress interview after acute myocardial infarct]. / Stressové interview po akutním infarktu myokardu.

Patients suffering from myocardial infarction (MI) form the high risk group. Residual ischemia, impaired left ventricular function and dysrhythmias are life endangering. Sudden death is more frequent in this group than in the one of patients with CHD. Therefore before discharge from the hospital we applied to the patients after MI series of noninvasive methods to disclose ventricular dysrhythmias. 136 patients after MI, mean age 56 (36-74), were examined. From those 90 patients underwent early exercise test and stress interview--application of common and specific mental stress. Holter ambulatory monitoring was applied to 18 post MI patients and echocardiography to 23 ones. A control group constituted 20 apparently healthy men, mean age 54 (44-64), which underwent exercise test and stress interview too. We have shown the incidence of ventricular dysrhythmias is always significantly higher (p < 0.01) in the post IM group than in the healthy one at exercise test and stress interview. The incidence in the post MI group is 49.4% at specific stress, 38.2% at common stress and 34.5% at exercise test. Significantly higher is the incidence at specific stress than at common stress or early exercises test, respectively (p < 0.05). Patients with dysrhythmias at both mental stresses have significantly lower exercise performance and workload at exercise test narrow correlation with disclosure at Holter monitoring is observed. Stress interview aids identification of risk group of post MI patients with serious ventricular dysrhythmias and demonstrates importance of psychotherapeutic care after MI. This method of mental stressing completes noninvasive test s and it is good way to II. phase of rehabilitation after myocardial infarction.