27 research outputs found

    Neutron diffraction, magnetization and ESR studies of pseudocubic Nd(0.75)Ba(0.25)MnO3 and its unusual critical behavior above Tc

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    Results of structural neutron diffraction study, magnetization and ESR measure-ments are presented for insulating Nd0.75Ba0.25MnO3, Tc = 129 K. The crystal structure is refined in the range 4.2-300 K. The compound is found to exhibit the Jahn-Teller (JT) transition at 250 K. The field cooled (FC) magnetization data are in a reasonable agreement with the predictions for a 3D isotropic ferromagnet above Tc. However, these measurements reveal a difference between the FC and zero FC data in the paramagnetic region. ESR results are also in a correspondence with behavior of a cubic ferromagnet above T* = 143 K. It is shown that an anisotropic exchange coupling of the Mn and Nd magnetic moments can give a substantial contribution in ESR linewidth masking its critical enhan-cement. The different temperature treatments of the sample reveal a temperature hysteresis of the ESR spectra below T* indicating an anomalous response in the paramagnetic region. The study of phase transition in this manganite suggests change in its character from the second to first order at T*. The conventional free energy including the magnetization and magnetic field is not found to describe the first order transition. This suggests that the charge, orbital and JT phonon degrees of freedom, in addition to magnetization, may be the critical variables, the unusual character of the transition being determined by their coupling. Unconventional critical behavior is attributed to orbital liquid metallic phase that coexists with the initial orbital ordered phase below T*.Comment: 18 pages, 5 figures, submitted to Phys. Rev.

    Hall effect for neutrons scattered by an A

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    USE OF THE RADIAL ARTERY IN CORONARY SURGERY IN PATIENTS WITH MULTIVESSEL LESIONS OF THE CORONARY ARTERIES

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    Aim. To analyze literature data on the methods and methods of using the radial artery as an arterial graft for coronary artery bypass grafting in patients with multivessel coronary artery disease. Results. The literature data on ways and methods of arterial revascularization with the use of the radial artery in patients with multivessel coronary artery disease were reviewed and analyzed. Conclusions. Complete arterial revascularization with the use of the radial artery in patients with multivessel lesion of the coronary bed is a promising direction of coronary surgery and enables to achieve better long-term results

    EXPERIENCE OF LARGE SAPHENOUS VEIN HARVESTING BY METHOD OF "SKIN BRIDGES" IN AORTO-CORONARY ARTERY BYPASS SURGERY

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    Background. This article focuses on the experience of great saphenous vein (GSV) harvesting by the method of "skin bridges" in operations of coronary artery bypass grafting (CABG). Objective. To show the possibility of using minimally invasive GSV harvesting in CABG operations. Material and methods. We applied the two methods of BPV harvesting in patients with ischemic heart disease (standard and open method of "skin bridges"). Results. Comparative evaluation of these methods enables to make a preliminary judgment about their advantages and disadvantages. The results obtained were compared with those of other clinics in endoscopic vein harvesting (EVH). Conclusions. A method of "skin bridges" harvesting in the hands of a competent surgeon is comparable to the EE way of vein harvesting
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