Quantum mechanics of spin transfer in coupled electron-spin chains

The manner in which spin-polarized electrons interact with a magnetized thin film is currently described by a semi-classical approach. This in turn provides our present understanding of the spin transfer, or spin torque phenomenon. However, spin is an intrinsically quantum mechanical quantity. Here, we make the first strides towards a fully quantum mechanical description of spin transfer through spin currents interacting with a Heisenberg-coupled spin chain. Because of quantum entanglement, this requires a formalism based on the density matrix approach. Our description illustrates how individual spins in the chain time-evolve as a result of spin transfer.Comment: 4 pages, 3 (colour) figure

Pseudogap and incommensurate magnetic fluctuations in YBa_2Cu_3O_{6. 6}

Unpolarized inelastic neutron scattering is used to study the temperature and wave vector dependence of the dynamical magnetic susceptibility, $\chi''(q,\omega)$, of a well characterized single crystal $YBa_2Cu_3O_{6.6}$ ($T_c=62.7$ K). We find that a pseudogap opens in the spin fluctuation spectrum at temperatures well above $T_c$. We speculate that the appearance of the low frequency incommensurate fluctuations is associated with the opening of the pseudogap. To within the error of the measurements, a gap in the spin fluctuation spectrum is found in the superconducting state.Comment: 6 pages, 3 ps figs, Proceedings of ICNS, Physica B, to be publishe

Asymmetric Analysis Of Okun’s Law: The Case For Turkey

This paper revisits Okun’s law under an asymmetric approach for Turkey applying structural threshold regression model that allows for endogeneity of the threshold variable that separates the dataset into low and high regime periods according to economic growth. Moreover, the theory is investigated taking subcategories of unemployment rate into account, such as age, education and gender. Empirical findings suggest that only the overall unemployment rate and female unemployment rate reflect significantly negative impacts in both periods. During deep recessions, unemployment rates are more responsive to economic growth. In order to consider nonlinearities, Kourtellos et al. (2016) structural threshold regression (STR) model is employed. STR model estimates the threshold parameter and it is not known which observation belongs to which regime. In addition to the threshold variable, the model allows the regressors to be endogeneous. This methodology also allows for regime-specific heteroskedasticity

Charge Fluctuations in YBa2Cu3O6+x Superconductors

Striped phases in which spin and charge separate into different regions in the material have been proposed to account for the unusual properties of the high-$T_c$ cuprate superconductors. The driving force for a striped phase is the charge distribution, which self-organizes itself into linear regions. In the highest $T_c$ materials such regions are not static but fluctuate in time. Neutrons, having no charge, can not directly observe these fluctuations but they can be observed indirectly by their effect on the phonons. Neutron scattering measurements have been made using a specialized technique to study the phonon line shapes in four crystals with oxygen doping levels varying from highly underdoped to optimal doping. It is shown that fluctuating charge stripes exist over the whole doping range, and become visible below temperatures somewhat higher than the pseudogap temperature.Comment: 10 pages, 4 figures,Proceedings of Third International Conference on Theories, Discoveries, and Applications of Superconductors, to be published in Physica

European Union as a global security actor: common security and defence policy and its challenges in the 2011 Libya crisis and 2014 Ukraine conflict

Focusing on how to explain the problems in creating a sustainable common security and defence mechanism for the EU, this research explores a causal mechanism based on the institutional gridlock, member states’ preferences, and the characteristics of the EU strategic culture, and their reflections in the context of two specific policy issues (2011 Libya crisis and 2014 Ukraine conflict). It observes that three factors play an equally and simultaneously important role. Nevertheless, its empirical findings (e.g., the absence of an operational headquarters, military capacities, the issue of applying to EU institutions, local ownership, and political will) suggest considering other related factors in explaining the problem. For example, the main problem in institutional gridlock is the coordination problem of EU institutions. So, studies should focus on that, and the EU institutions integrated actions with member states. In addition, although case studies provide strong evidence, the member states' preferences should be analysed multi-dimensionally. Indeed, the research findings do not conclude that national preferences replace CSDP decisions or that CSDP actors affect member states through socialisation. Therefore, ongoing studies should focus on alternative explanations for socialisation. Finally, the research details the characteristics of EU strategic culture, stating that it should be studied from a holistic perspective, perhaps independently. Doing so makes an essential contribution to the EU strategic culture debates. Overall, this research produces more accurate explanations about the functioning of defence and security policies and the reasons for forming specific results in the EU and contributes to the existing literature by presenting alternative suggestions.Security and Global Affair

Breast cancer with diabetes insipidus

Diabetes insipidus (DI) is a rare clinical condition, which is usually caused by neurohypophyseal or pituitary stalk infiltration in cancer patients. Case report: we present a 62-year old metastatic breast cancer woman with DI. She admitted to the hospital because of nausea, vomiting, polyuria and polydipsia, while she was on no cytotoxic medication. She had no electrolyte imbalance except mild hypernatremia. The CT scan of the brain yielded a suspicious area in pituitary gland. A pituitary stalk metastasis was found on magnetic resonance imaging (MRI) of pituitary. Water deprivation test was compatible with DI. A clinical response to nasal vasopressin was achieved. Conclusions: Cancer patients who have symptoms such as nausea, vomiting, polyuria and polydipsia while they are not on chemotherapy should be evaluated for not only metabolic complications like hypercalcemia but also posterior pituitary or stalk metastasis MRI could be the choice of imaging for pituitary metastasis.Несахарный диабет (DI) — редкое клиническое состояние, вызываемое инфильтрацией нейрогипофизарной ножки или ножки гипофиза у онкологических больных. Описание случая: в исследовании рассмотрен случай выявления DI у 62-летней женщины, у которой был выявлен рак молочной железы с наличием метастазов. Она поступила в больницу с симптомами тошноты, рвоты, полиурии и полидипсии, хотя не проходила курса химиотерапии. У больной не выявлено дисбаланса электролитов, кроме небольшой гипернатриемии. Компьютерная томография мозга показала подозрительную область в мозговом придатке. На магнитно-резонансном изображении выявлен метастаз в ножке гипофиза. Обезвоживание также соответствовало диагнозу DI. Получен клинический ответ на назальный вазопрессин. Выводы: онкологические больные с симптомами тошноты, рвоты, полиурии и полидипсии, не проходящие курса химиотерапии, должны быть обследованы не только на предмет метаболических осложнений, таких как гиперкальциемия, но и на возможное наличие метастазов в ножке и задней части гипофиза с помощью магнитно-резонансного изображения. Ключевые слова: рак, несахарный диабет, метастаз в гипофизе