Magnetoelastic mechanism of spin-reorientation transitions at step-edges

The symmetry-induced magnetic anisotropy due to monoatomic steps at strained Ni films is determined using results of first - principles relativistic full-potential linearized augmented plane wave (FLAPW) calculations and an analogy with the N\'eel model. We show that there is a magnetoelastic anisotropy contribution to the uniaxial magnetic anisotropy energy in the vicinal plane of a stepped surface. In addition to the known spin-direction reorientation transition at a flat Ni/Cu(001) surface, we propose a spin-direction reorientation transition in the vicinal plane for a stepped Ni/Cu surface due to the magnetoelastic anisotropy. We show that with an increase of Ni film thickness, the magnetization in the vicinal plane turns perpendicular to the step edge at a critical thickness calculated to be in the range of 16-24 Ni layers for the Ni/Cu(1,1,13) stepped surface.Comment: Accepted for publication in Phys. Rev.

Absence of stable collinear configurations in Ni(001)ultrathin films: canted domain structure as ground state

Brillouin light scattering (BLS) measurements were performed for (17-120) Angstrom thick Cu/Ni/Cu/Si(001) films. A monotonic dependence of the frequency of the uniform mode on an in-plane magnetic field H was observed both on increasing and on decreasing H in the range (2-14) kOe, suggesting the absence of a metastable collinear perpendicular ground state. Further investigation by magneto-optical vector magnetometry (MOKE-VM) in an unconventional canted-field geometry provided evidence for a domain structure where the magnetization is canted with respect to the perpendicular to the film. Spin wave calculations confirm the absence of stable collinear configurations.Comment: 6 pages, 3 figures (text, appendix and 1 figure added

Dynamics of Excited Electrons in Copper and Ferromagnetic Transition Metals: Theory and Experiment

Both theoretical and experimental results for the dynamics of photoexcited electrons at surfaces of Cu and the ferromagnetic transition metals Fe, Co, and Ni are presented. A model for the dynamics of excited electrons is developed, which is based on the Boltzmann equation and includes effects of photoexcitation, electron-electron scattering, secondary electrons (cascade and Auger electrons), and transport of excited carriers out of the detection region. From this we determine the time-resolved two-photon photoemission (TR-2PPE). Thus a direct comparison of calculated relaxation times with experimental results by means of TR-2PPE becomes possible. The comparison indicates that the magnitudes of the spin-averaged relaxation time \tau and of the ratio \tau_\uparrow/\tau_\downarrow of majority and minority relaxation times for the different ferromagnetic transition metals result not only from density-of-states effects, but also from different Coulomb matrix elements M. Taking M_Fe > M_Cu > M_Ni = M_Co we get reasonable agreement with experiments.Comment: 23 pages, 11 figures, added a figure and an appendix, updated reference

Heart Transplantation in Arrhythmogenic Right Ventricular Dysplasia: Case Reports

Objective. Arrhythmogenic right ventricular dysplasia (ARVD) is a myocardial disease of familiar, origin where the myocardium is replaced by fibrofatty tissue predominantly in the right ventricle. Herein we have presented the clinical courses of 4 patients with ARVD who underwent orthotopic heart transplantation. Patients and Methods. Among 358 adult patients undergoing heart transplantation, 4 (1.1%) displayed ARVD. The main indication for transplantation was the progression to heart failure associated with arrhythmias. All 4 patients displayed rapid, severe courses leading to heart failure with left ventricular involvement and uncontrolled arrhythmias. Results. In all cases the transplantation was performed using a bicaval technique with prophylactic tricuspid valve annuloplasty. One patient developed hyperacute rejection and infection, leading to death on the 7th day after surgery. The other 3 cases showed a good evolution with clinical remission of the symptoms. Pathological study of the explanted hearts confirmed the presence of the disease. Conclusions. ARVD is a serious cardiomyopathy that can develop malignant arrhythmias, severe ventricular dysfunction with right ventricular predominance, and sudden cardiac death. Orthotopic heart transplantation must always be considered in advanced cases of ARVD with malignant arrhythmias or refractory congestive heart failure with or without uncontrolled arrhythmias, because it is the only way to remit the symptoms and the disease

Brazilian capsicum peppers: capsaicinoids content and antioxidant activity

Capsicum peppers are known as a source of capsaicinoids, phenolic compounds and antioxidants. Brazilian Capsicum peppers are important spices used in foods worldwide. However, little information is available on the chemical composition and antioxidant activity of these peppers. RESULTS Capsaicin, dihydrocapsaicin, total phenolic compounds and antioxidant activity were investigated in extracts of three Brazilian peppers: Capsicum frutescens, C. chinense and C. baccatum var. pendulum, in two different harvest years and at two ripening stages. The bioactive compound content was dependent on harvest year, and changes in the concentration profiles were found for capsaicin. Mature fruits of C. chinense harvested in the first year had the highest capsaicin concentration (2.04 mg g−1 fresh pepper), and mature fruits of C. frutescens harvested in the same first year had the highest dihydrocapsaicin content (0.95 mg g−1 fresh pepper). Mature fruits of C. frutescens harvested in the first year showed the major total phenolic compound content (2.46 mg g−1 fresh pepper). The total phenolic compound content was directly related to antioxidant activity. CONCLUSION Our results suggest that phenolic compounds significantly contribute to the antioxidant activity of the investigated peppers. Also, these data add valued novel information that enhances current knowledge of Brazilian pepper fruits98121722