Nondata-aided channel estimation for OFDM systems with space-frequency transmit diversity

This paper proposes a computationally efficient nondata-aided maximum a posteriori (MAP) channel-estimation algorithm focusing on the space-frequency (SF) transmit diversity orthogonal frequency division multiplexing (OFDM) transmission through frequency-selective channels. The proposed algorithm properly averages out the data sequence and requires a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve (KL) orthogonal expansion and estimates the complex channel parameters of each subcarrier iteratively, using the expectation maximization (EM) method. To further reduce the computational complexity of the proposed MAP algorithm, the optimal truncation property of the KL expansion is exploited. The performance of the MAP channel estimator is studied based on the evaluation of the modified Cramer-Rao bound (CRB). Simulation results confirm the proposed theoretical analysis and illustrate that the proposed algorithm is capable of tracking fast fading and improving overall performance. © 2006 IEEE

Intraband and interband spin-orbit torques in non-centrosymmetric ferromagnets

Intraband and interband contributions to the current-driven spin-orbit torque in magnetic materials lacking inversion symmetry are theoretically studied using Kubo formula. In addition to the current-driven field-like torque ${\bf T}_{\rm FL}= \tau_{\rm FL}{\bf m}\times{\bf u}_{\rm so}$ (${\bf u}_{\rm so}$ being a unit vector determined by the symmetry of the spin-orbit coupling), we explore the intrinsic contribution arising from impurity-independent interband transitions and producing an anti-damping-like torque of the form ${\bf T}_{\rm DL}= \tau_{\rm DL}{\bf m}\times({\bf u}_{\rm so}\times{\bf m})$. Analytical expressions are obtained in the model case of a magnetic Rashba two-dimensional electron gas, while numerical calculations have been performed on a dilute magnetic semiconductor (Ga,Mn)As modeled by the Kohn-Luttinger Hamiltonian exchanged coupled to the Mn moments. Parametric dependences of the different torque components and similarities to the analytical results of the Rashba two-dimensional electron gas in the weak disorder limit are described.Comment: 10 pages, 5 figure

Incommensurate Magnetic Fluctuations in YBa2Cu3O6.6

We use inelastic neutron scattering to demonstrate that at low temperatures, the low frequency magnetic fluctuations in YBa_2Cu_3O_{6.6} ($T_c=62.7$ K) are incommensurate, being found at positions displaced by $\pm\delta$ ($0.057\pm 0.006$ r.l.u.) along the $[\pi,\pi]$ direction from the wave vector $(\pi,\pi)$ associated with the antiferromagnetic order of the parent insulator, YBa_2Cu_3O_{6}. The dynamical susceptibility $\chi''(q,\omega)$ at the incommensurate positions increases on cooling below $T_c$, accompanied by a suppression of magnetic fluctuations at the commensurate points.Comment: 11 pages, Latex, 4 figure

Open issues in probing interiors of solar-like oscillating main sequence stars 1. From the Sun to nearly suns

We review some major, open issues in the current modelling of low and intermediate mass, main sequence stars based on seismological studies. In the present paper, the solar case is discussed together with current problems that are common to the Sun and stars with a structure similar to that of the Sun. Several additional issues specific to main sequence stars other than the Sun are reviewed and illustrated with a few stars observed with CoRoT in a companion paper.Comment: GONG 2010 - SoHO 24, A new era of seismology of the Sun and solar-like stars. To be published in the Journal of Physics: Conference Series (JPCS

Clinical presentations and diagnostic work-up in sarcoidosis: A series of Turkish cases (clinics and diagnosis of sarcoidosis)

Sarcoidosis is an idiopathic granulomatous disease. It usually affects the lung. The diagnosis may be problematic since the known causes of granulomatous inflammation must be excluded. This multicenter study aimed to evaluate the clinical presentations and diagnostic approaches of sarcoidosis. The study protocol was sent via internet, and the participants were asked to send the information (clinical, radiological and diagnostic) on newly diagnosed sarcoidosis cases. 293 patients were enrolled within two years. Pulmonary symptoms were found in 73.3% of the patients, and cough was the most common one (53.2%), followed by dyspnea (40.3%). Constitutional symptoms were occured in half of the patients. The most common one was fatigue (38.6%). The most common physical sign was eritema nodosum (17.1%). The most common chest radiograhical sign was bilateral hilar lymphadenomegaly (78.8%). Staging according to chest X-ray has revealed that most of the patients were in Stage I and Stage II (51.9% and 31.7%, respectively). Sarcoidosis was confirmed histopathologically in 265 (90.4%) patients. Although one-third of the bronchoscopy was revealed normal, mucosal hyperemi (19.8%) and external compression of the bronchial wall (16.8%) were common abnormal findings. The 100% success rate was obtained in mediastinoscopy among the frequently used sampling methods. Transbronchial biopsy was the most frequently used method with 48.8% success rate. Considering sarcoidosis with its most common and also rare findings in the differential diagnosis, organizing the related procedures according to the possibly effected areas, and the expertise of the team would favor multimodality diagnosis

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Russian and German tourist potential and satisfaction in sustainable competitive advantage of Alanya destination

The purpose of the present study is to investigate and compare the potential and the satisfaction levels of Russian and German tourists visiting Alanya in creating a sustainable competitive advantage in Alanya destination. It is a common point that Russian and Germans are two nationalities most frequently visited Alanya, town of Antalya in Turkey. Moreover, every year many Russians and Germans decide to live in Alanya. So we wonder that how global crisis effected Turkish tourism industry, especially Alanya, and Russian and German preferences. The findings from the present study help decision takers to create new marketing strategies for Russian and German tourists. © University of the Aegean