Anti-ferrodistortive Nanodomains in PMN Relaxor

Temperature dependent studies of the 1/2(hk0) superlattice reflections \alpha spots by synchrotron x-ray scattering measurements were performed in (PMN) and (PMN-xPT) with Ti doping x<0.32 single crystals. Separation of the \alpha spots from the underlying diffuse scattering background allowed studying them as separate entities for the first time. Structure factor calculations have shown that alpha spots constitute the presence of a new kind of anti-ferrodistortive nanoregions (AFR) in the form of fluctuations produced by anti-parallel short-range correlated Pb^2+ displacements. AFR appear to be different and unrelated to the chemical nanodomains (CND) and ferroelectric polar nanoregions (PNR). Simultaneous presence of AFR and PNR can explain relaxor behavior as a result of competition between randomly occurring ferroelectric and anti-ferroelectric fluctuations. Temperature dependence of the \alpha spots in PMN showed a direct correlation with the freezing phase transition near Tf~220 K.Comment: 10 pages, 7 figures, Conference-Fundamental Physics of Ferroelectrics 200

Detecting the Lee-Yang zeros of a high-spin system by the evolution of probe spin

Recently in paper [Peng et al., Phys. Rev. Lett. 114, 010601 (2015)] the experimental observation of the Lee-Yang zeros of an Ising-type spin-1/2 bath, by measuring the coherence of a probe spin, was reported. We generalize this problem to the case of an arbitrary high-spin bath. Namely, we consider the evolution of a probe arbitrary spin which interacts with bath composed by N arbitrary spins. As a result, the connection between the observed values of the probe spin, such as magnetization and susceptibility, and the Lee-Yang zeros is found. We apply these results to some models, namely, a triangle spin cluster, the Ising model with a long-range interaction and the 1D Ising model with nearest-neighbor interaction. Also we propose the implementation of these models on real physical systems.Comment: 13 pages, 6 figure

Quantum brachistochrone problem for spin-1 in a magnetic field

We study quantum brachistochrone problem for the spin-1 system in a magnetic field of a constant absolute value. Such system gives us a possibility to examine in detail the statement of papers [A. Carlini {\it et al.}, Phys. Rev. Lett. {\bf 96}, 060503 (2006), D. C. Brody, D. W. Hook, J. Phys. A {\bf 39}, L167, (2006)] that {\it the state vectors realizing the evolution with the minimal time of passage evolve along the subspace spanned by the initial and final state vectors.} Using explicit example we show the existence of quantum brachistochrone with minimal possible time, but the state vector of which, during the evolution {\em leaves} the subspace spanned by the initial and final state vectors. This is the result of the choice of more constrained Hamiltonian then assumed in the general quantum brachistochrone problem, but what is worth noting, despite that such evolution is more complicated it is still time optimal. This might be important for experiment, where general Hamiltonian with the all allowed parameters is difficult to implement, but constrained one depending on magnetic field can be realized. However for pre-constrained Hamiltonian not all final states are accessible. Present result does not contradict general statement of the quantum brachistochrone problem, but gives new insight how time optimal passage can be realized.Comment: 7 pages, no figure

System for testing drainage devices for output intraocular fluid in glaucoma

Основною причиною розвитку глаукоми стає неконтрольована зміна витоку внутрішньоочної рідини через трабекулярну мережу[1], що при патології призводить до підвищення внутрішньоочного тиску (ВОТ) та ураження очного нерва [2]. Імплантація дренажних пристроїв зазвичай виконується після попередніх невдалих лікувань та є останнім шансом пацієнта зберегти зір [3]. Тому виникає необхідність перевірити параметри тиску при якому відбувається виведення внутрішньоочної рідини імплантатом перед вживленням в око людини, та покращити підбір, або виявити відхилення параметрів виведення внутрішньоочної рідини в імплантаті. Пропонується тестова система контролю і налаштування параметрів дренажних пристроїв що нормалізують виведення внутрішньоочної рідини при глаукомі, до значень внутрішньоочного тиску в діапазоні 9 – 21 мм рт. ст.Implantation of drainage devices is usually performed after previous unsuccessful treatments and is the last chance for the patient to save vision. This work introduces the test system for monitoring and adjusting the parameters of drainage devices for normalize the output of the intraocular fluid in glaucoma eye, for normal values of intraocular pressure 9 – 21 mm Hg