WoS İndeksli Yayınlar / WoS Indexed Publications
Permanent URI for this collectionhttps://hdl.handle.net/11413/6359
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Browsing WoS İndeksli Yayınlar / WoS Indexed Publications by Publisher "Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA"
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Publication Metadata only Analysis of brain connectivity changes after propofol injection by generalized partial directed coherence(Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA, 2014) Akan, Aydın; Özkan Seyhan, Tülay; GÜRKAN, GÜRAY; 113297; 2918; 25235In this paper we present a method for the analysis of multichannel EEG by using Generalized Partial Directed Coherence (gPDC) to extract cortical connectivity changes under anesthesia. 15 channel EEG data were recorded from female subjects undergoing general anesthesia for gynecological surgery. Multivariate Autoregressive (MAR) modeling was applied to multichannel, bipolar EEG segments of awake and anesthetized states. gPDCs were calculated using the derived MAR model and averaged through EEG alpha frequency band (8-14 Hz) and through a number of data segments. The gPDC calculation was performed for three different sets of bipolar EEG channel pairs each of which mainly represent a specific scalp area. To derive consistency levels of gPDC values, surrogate analysis is also performed. Using paired t-test for 12 patients, we extracted significant gPDC changes between. awake and anesthetized stages for each set. Analysis revealed that during transition from awake to anesthetized stage, gPDCs of central. to parietal directions were suppressed whereas gPDCs of parietal to central directions were increased. The results indicate that the proposed gPDC analysis method can be used to track the changes in brain connectivity and hence to estimate the depth of anesthesia. (C) 2013 Elsevier Inc. All rights reserved.Publication Metadata only Bounded Log-Harmonic Functions with Positive Real Part(Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA, 2013-03-01) Özkan Uçar, Hatice Esra; POLATOĞLU, YAŞAR; 114002; 199370Let H(D) be the linear space of all analytic functions defined on the open unit disc D = {z vertical bar vertical bar z vertical bar < 1}, and let B be the set of all functions w(z) is an element of H(D) such that vertical bar w(z)vertical bar < 1 for all z is an element of D. A log-harmonic mapping is a solution of the non-linear elliptic partial differential equation (f) over bar ((z) over bar) = w(z) ((f) over bar /f) f(z), where w(z) is the second dilatation off and w(z) is an element of B. In the present paper we investigate the set of all log-harmonic mappings R defined on the unit disc D which are of the form R = H(z)<(G(z))over bar>, where H(z) and G(z) are in H(D), H(0) = G(0) = 1, and Re(R) > 0 for all z is an element of D. The class of such functions is denoted by P-LH. (C) 2012 Elsevier Inc. All rights reserved.Publication Metadata only On channel estimation for spatial modulated systems over time-varying channels(Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA, 2015-02) Doğan, Hakan; Panayırcı, Erdal; ACAR, YUSUF; 237377; 10331Spatial Modulation (SM) has been proposed recently for multiple-input multiple-output (MIMO) systems to cope with the interchannel interference and to reduce the detection complexity as compared to the conventional MIMO systems. In SM system, the data symbols are transmitted by a randomly selected active antenna of a MIMO transmitter to the receiver through a wireless channel. The information is carried both by the data symbol from any signal constellation such as M-ary phase shift keying (M-PSK) or M-ary quadrature amplitude modulation (M-QAM), by the index of the selected antenna. The channel estimation is a critical process at the receiver during the coherent detection of the transmitted symbol and the antenna index, randomly selected. Recently, the channel estimation of channel for SM systems has been investigated by the recursive least square (RLS) algorithm for only quasi-static fading channels. In this paper, a novel channel estimation is proposed for SM systems in the presence of rapidly time-varying channels. The Bayesian mean square error (MSE) bound has been derived as a benchmark and the performance of the proposed approaches is studied in terms of MSE and bit-error rate (BER). Computer simulation results have confirmed that the proposed iterative channel estimation technique has significant BER/MSE performance advantages compared with existing channel estimation algorithm proposed earlier in the literature. (C) 2014 Elsevier Inc. All rights reserved.Publication Metadata only Posterior Cramer-Rao Lower Bounds for Dual Kalman estimation(Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA, 2012-01) Akan, Aydın; SAATÇI, ESRA; 112197; 2918We present the Posterior Cramer-Rao Lower Bounds (PCRLB) for the dual Kalman filter estimation where the parameters are assumed to be time-invariant and stationary random variables. Relations between the PCRLB, the states, and the parameters are established and recursions are obtained for finite observation time. As a case study, the closed-form expressions of the PCRLB for a linear lung model, called the Mead respiratory model, are derived. Distribution of the parameters is assumed to be Generalized Gaussian Distribution (GGD) which enabled an investigation of different shape factors. Simulations performed on the signals collected from the human respiratory system yielded encouraging results. It is concluded that the parameter distribution should be chosen as Gaussian to super-Gaussian in order for the PCRLB algorithm to converge. (C) 2011 Elsevier Inc. All rights reserved.Publication Metadata only Solution To N-Dimensional Sturm-Liouville-Like Equations Using Multi-Dimensional Schwarzian(Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA, 2011-12-25) Erkut, Mehmet Hakan; Çağlar, Mert; Borisenok, S. V.; POLATOĞLU, YAŞAR; TR9290; TR108339; TR199370In the present work we produce the solution to the n-dimensional Sturm-Liouville-like equations in R(n). To make it, we define the multi-dimensional Schwarzian derivative of a real-valued function of n variables and show that its basic properties related to its invariance under the action of a group of multi-dimensional Mobius transformations defined in R(n) correspond to a straightforward generalization of those of the one-dimensional Schwarzian. (C) 2011 Elsevier Inc. All rights reserved.Publication Metadata only Tissue-specific transcriptional regulation of seven heavy metal stress-responsive miRNAs and their putative targets in nickel indicator castor bean (R. communis L.) plants(Academic Press inc Elsevier Science, 525 B St, Ste 1900, San Diego, Ca 92101-4495 USA, 2019-04-15) Akdaş, Enes Yağız; ÇELİK, ÖZGER.communis L. has high capability to accumulate nickel which is a trace nutrient for higher plants and also an environmental contaminant causes toxicity related symptoms at higher concentrations. MicroRNAs (miRNAs) are known to be important modulators of responses against heavy metal stress for detoxification of the metal. In this study, we experimentally measured and validated the transcript levels of the seven heavy metal stress response-related miRNAs and the expression levels of target genes in both leaf and root tissues of R. communis L. subjected to three different concentrations of nickel stress via qRT-PCR quantification. The results demonstrated differential regulations of heavy metal stress-responsive miRNAs and their putative targets in both tissues in same stress treatments. This dynamic regulation suggest that regulatory processes differ between the tissues under nickel stress. Our data suggest that, miR838 was the most responsive to the Ni2+ stress. miR398 target gene Cu-Zn/SOD was found to be up-regulated in both root and leaf tissues. The relations between TCP and expression levels of miR159 and miR319 were also found statistically significant exclusive to leaf tissues. In leaf tissue, changes in miR395 level and its putative target genes, sulphate transporter and sulphate adenyltransferase gene were found in relation whereas, only expression level of sulphate transporter represented a statistically significant relation in root tissue. The sharp decrease in transcript levels of 2r3 myb gene at lower nickel dose suggest to investigate the role of r2r3 myb and the all MYB family members in primary and secondary metabolisms against nickel stress.