Özer, Mahmut

Makale | 2004 | Iranian Journal of Science and Technology, Transaction B: Engineering28 ( 3 B ) , pp.351 - 358

In this study, the time-course of the recovery from inactivation of molluscan ionic currents is examined. Molluscan voltage-gated ionic currents are described in Hodgkin-Huxley-like equations. The peak value function of the recovering conductance is derived from the mathematical equivalent of an experimental procedure of the recovery process in a general form by including the number of inactivation gates. Then the curves of the recovery and its approximation for the molluscan ionic currents are obtained. It is shown that recovering conductance of molluscan ionic currents is asymptotically exponential. © Shiraz University.

İşler, Yalçın | Ekmekçi, N.Hakan | Özer, Mahmut

Makale | 2006 | Pamukkale Üniversitesi Mühendislik Fakültesi Mühendislik Bilimleri Dergisi12 ( 1 ) , pp.97 - 104

Bu çalışmada, kablo teoremine dayalı pasif dentrit elektriksel özelliklerinin benzetimi için geliştirilen bir yazılım tanıtılmaktadır. Üzerinden sinaptik bilgi taşman dentritler, sinir hücresinin yüzey alanı bakımından en büyük bileşenidir. Dentritik nöronlar için kablo teoremi, sürekli pasif dentrit ağaç yapısı içinde akım-gerilim ilişkilerini modellemektedir. Pasif kablo ve dentritlerle ilgili iyi bir yaklaşıklık olan ve uyarılabilir membranlar için önemli bir referans olan kablo teoremi kısaca özetlenmektedir. Önerilen yazılım, kullanıcı tarafından tanımlanan dentrit ağaç yapısını oluşturmak için kullanılabilmektedir. Kullanıcı, . . .yazılımı kullanarak modeli detaylı olarak tanımlayabilmekte, oluşturduğu dentrit ağacını görüntüleyebilmekte ve dentrit ağacının temel elektriksel özelliklerini inceleyebilmektedir. In this study, a software is introduced for simulating the electrical properties of passive dendrite based on the cable theory. Dendrites along which the synaptic information is conveyed are the largest component of a neuron in surface area. The Cable theory for dendritic neurons addresses to current-voltage relations in a continuous passive dendritic tree. It is briefly summarized that the cable theory related to passive cables and dendrites, which is a useful approximation and an important reference for excitable cases. The proposed software can be used to construct user-defined dendritic tree model. The user can define the model in detail, display the constructed dendritic tree, and examine the basic electrical properties of the dendritic tree Daha fazlası Daha az

Özer, Mahmut | Erdem, Rıza

Makale | 2004 | Physica A: Statistical Mechanics and its Applications331 ( 01.Feb ) , pp.51 - 60

Dynamics of voltage-gated ion channels in the excitable cell membranes is formulated by the path probability method of nonequilibrium statistical physics and approaches of the system toward the steady or equilibrium states are presented. For a single-particle noninteractive two-state model, a first-order rate equation or dynamic equation is derived by introducing the path probability rate coefficients which satisfy the detailed balancing relation. Using known parameters for the batrachotoxin (BTX)-modified sodium channels in giand squid axon as an example, the rate equation is solved and voltage dependence of the time constant (?) a . . .nd its temperature effect are investigated. An increase in voltage caused a shift in ? towards shorter durations while increasing temperature caused a shift in time distribution towards longer durations. Results are compared with the kinetic model for the squid axon BTX-modified sodium channels by the cut-open axon technique and a very good agreement is found. © 2003 Elsevier B.V. All rights reserved Daha fazlası Daha az

Özer, Mahmut

Diğer | 2003 | Pamukkale Üniversitesi Mühendislik Fakültesi Mühendislik Bilimleri Dergisi9 ( 3 ) , pp.349 - 356

Bu makalede, iyonik kanal aktivasyon ve inaktivasyon kapılarının dinamik davranışı için yol ihtimaliyet yöntemine dayalı olarak elde edilen alternatif denklemler sunulmaktadır. Gerilim-kapılı iyonik kanalın dinamik davranışı, geleneksel Hodgkin-Huxley (H-H) matematiksel biçimciliği ile modellenmektedir. Bu modelde kanal iletkenliği, aktivasyon ve inaktivasyon kapılarına göre tanımlanmaktadır. Aktivasyon ve inaktivasyon kapılarının dinamiği, kapı değişkenine ve membran potansiyeline bağlı birinci dereceden diferansiyel denklemlerle modellenmektedir. Bu çalışmada sunulan yeni yaklaşımda, aktivasyon ve inaktivasyon kapısının dinamik da . . .vranışı, istatistik fizikte yaygın olarak kullanılan yol ihtimaliyet yöntemi kullanılarak iç enerji ve membran potansiyeline bağlı birinci dereceden diferansiyel denklemlerle modellenmektedir. Yeni model, H-H modelinde açıkça kullanılan zaman sabiti ve sürekli-hal değerlerini de gerektirmemektedir. Sayısal sonuçlar önerilen yöntemin geçerliliğini göstermektedir. In this paper, alternative equations for dynamics of ionic channel activation and inactivation gates are proposed based on the path probability method. Dynamic behavior of a voltage-gated ionic channel is modeled by the conventional Hodgkin-Huxley (H-H) mathematical formalism. In that model, conductance of the channel is defined in terms of activation and inactivation gates. Dynamics of the activation and inactivation gates is modeled by first-order differential equations dependent on the gate variable and the membrane potential. In the new approach proposed in this study, dynamic behavior of activation and inactivation gates is modeled by a first-order differential equation dependent on internal energy and membrane potential by using the path probability method which is widely used in statistical physics. The new model doesn't require the time constant and steady-state values which are used explicitly in the H-H model. The numerical results show validity of the proposed method Daha fazlası Daha az

Uzun, Rukiye | Özer, Mahmut

Bildiri | 2015 | 2015 23RD SIGNAL PROCESSING AND COMMUNICATIONS APPLICATIONS CONFERENCE (SIU) , pp.1191 - 1199

We investigate the first-spike response latency dynamics of a single Hodgkin-Huxley neuron model with a tunable intensity of intrinsic noise and fraction of blocked voltage-gated sodium and potassium ion channels embedded in biological membranes. In contrast to previous studies, we consider a biophysically realistic neuron model which contains stochastic ion channels. We show that potassium ion channels play a key role than sodium ion channels on the appearance of the noise delayed decay (NDD) effect in the first-spike timing.

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Bildiri | 2015 | 2016 MEDICAL TECHNOLOGIES NATIONAL CONFERENCE (TIPTEKNO) , pp.1191 - 1199

In this paper, the effects of autapse (a kind of synapse formed between the axon or soma of a neuron and its own dendrite) on the transmission of weak signal are investigated in scale-free neuronal networks. In the study, we consider that each neuron in the network has an autapse modelled as chemical synapse. Besides, a subthreshold signal are injected to all neurons in the network. When obtained results are analyzed, it is seen that the autaptic conductance has a threshold value. According to this threshold, the effects of autapse on the transmission of weak signal are evaluated within two categories. When conductance of autapse is . . . less than this threshold value, autapses with proper autaptic time delay values slightly increase the transmission of weak signal. When autaptic conductance is bigger than the threshold value, autapses with proper autaptic time deley values prominently block the transmission of weak signal Daha fazlası Daha az

Erkan, Yasemin | Özer, Mahmut | Yılmaz, Ergin

Bildiri | 2017 | 2017 MEDICAL TECHNOLOGIES NATIONAL CONGRESS (TIPTEKNO) , pp.1191 - 1199

Astrocytes are star-shaped glia cells and the most common cell type in the human brain with neurons. Astrocytes fulfill many functions in human brain. Providing support to the cells of the blood-brain barrier, balancing the extracellular ion concentration, supplying nutrients to the nerve tissue, and controlling the development of nerve cells are some of these tasks. In this study, the effects of calcium (Ca') ion concentration oscillations occuring in astrocytes on the neuron firing dynamics are investigated. When the obtained results are examined, it is observed that the production rate of insole 1,4,5-triphosphate (IP3), which is . . . an agent that triggers calcium release from the resoruces in astrocytes, and the degradation time of that within the cell are important effects on the spike production dynamics of the neuron in contact with astrocyte. It is determined that neurons without any stimulation continue to produce spikes through calcium oscillations in the astrocytes, at high IP3 production rates and longer IP3 degradation times Daha fazlası Daha az

Özdinç, Tuğba Özge | Hacıoğlu, Rıfat

Bildiri | 2007 | 2007 IEEE 15TH SIGNAL PROCESSING AND COMMUNICATIONS APPLICATIONS, VOLS 1-3 , pp.1191 - 1199

Acoustic echo in voice transmission systems severely degrades the speech quality and the speech intelligibility of speech signal due to it is formed through picking up sounds from the loudspeaker by speaker microphone. The dynamic strucure of the acoustic echo system contains cascade connection of an electro-acoustic static nonlinear system and a dynamic linear system. Hence linear models can not be successful solution to echo problem. In this paper, acoustic echo problem is mentioned and an algorithm that adapts the parameters of nonlinear Hammerstein system (cascade connection of a static nonlinearity and a dynamic linear system) . . .is suggested Daha fazlası Daha az

Emir, Ahmet | Saraç, Zehra

Bildiri | 2009 | 2009 IEEE 17TH SIGNAL PROCESSING AND COMMUNICATIONS APPLICATIONS CONFERENCE, VOLS 1 AND 2 , pp.1191 - 1199

This paper proposes the use of single sideband modulation technique with Gaussian and band pass fillers for the analysis of the thermal lens fringe to obtain the map of the refractive index change. Maps of the refractive index and phase change are achieved by using single side band modulation technique with Gaussian and band pass filters. Consequently it is seen that single side band modulation technique with Gaussian filter shows more accurate results.

Öztürk, Ertan | Yılmaz, Ergin

Makale | 2009 | Telecommunication Systems42 ( 03.Apr ) , pp.213 - 222

In this paper, we first investigate the power spectral densities (PSD) of bipolar modulated Direct Sequence Ultra Wide Band (DS-UWB) signals using various pulse shapes under the FCC UWB emission mask. Considered pulse shapes are the first five derivatives of the Gauss pulse (p 1 , p 2 , p 3 , p 4 and p 5 ), the first four orthogonal modified Hermite waveforms, and Daubechies wavelets (db-q). It is observed in the PSD results that p 4 and p 5 Gauss pulses, the Daubechies (db-q) for q>4 comply with the FCC UWB rule by selecting proper values for the pulse duration. Then, we derive the pulse shape dependent probability of error expr . . .ession for bipolar DS-UWB signals over the standard UWB channel. The five pulse shapes (p 4 , p 5 , db-5, db-6 and db-7) complying with the FCC emission mask are numerically compared by using the derived probability of error expression over the CM1 model of the Standard UWB channel. Results reveal that the Daubechies have better performance than those of the two Gauss pulses. © 2009 Springer Science+Business Media, LLC Daha fazlası Daha az

Karasu, Seçkin | Altan, Aytaç | Saraç, Zehra | Hacıoğlu, Rıfat

Bildiri | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017 , pp.213 - 222

In this study, the wind speed prediction model is created that gives a minimum error for different hidden layer neuron numbers and delay step numbers. Using the one-minute time series, the prediction of the next wind speed is performed with the NAR neural network model. The predicted values of wind speed obtained are compared with predicted values of wind speed obtained with filter methods. For different window functions and lengths, wind speed prediction is made using filters with different weight coefficients. For the number of hidden layer neurons is 14 and the number of delay steps is 10, MAE, MSE and RMSE values are calculated . . .as 0.0315, 0.0019, 0.0445, respectively, with NAR neural network. It is seen that the proposed method for the wind speed dataset has a higher prediction performance than thefilter methods. © 2017 IEEE Daha fazlası Daha az

Onur, Tuğba Özge | Carlson, Johan E. | Svanström, Erika | Hacıoğlu, Rıfat

Makale | 2017 | Erzincan Üniversitesi Fen Bilimleri Enstitüsü Dergisi10 ( 1 ) , pp.138 - 147

Elastik dalgalar, sadece gaz ve sıvılarda değil aynı zamanda katılarda da yayılırlar. Katılar, sıvı ve gazlarda olmayan form elastisitesine sahip olduğundan, katıların elastik özellikleri farklıdır. Bu nedenle, sadece boylamsal dalgalar değil aynı zamanda diğer dalgalar da katılarda yayılabilir. Katı içinde yayılan dalgalar kullanılarak hedefin konumu hakkında bilgi edinilebilir. Bu çalışmada ince düzlemlerde tek transdüktör kullanılarak ultrasonik dalga yayılımının modellenmesi yapılarak, uyarlamalı algoritma ile hedef uzaklığı kestirilmektedir. Elde edilen sonuçlarda, modellenen dalga yayılımında ultrasonik dalganın hızı ile birli . . .kte zaman gecikmesi uyartım noktasının sensöre olan uzaklığı ile ilintili olduğu için, uyarlamalı algoritma ile darbe cevabı başlangıç noktası belirlenerek hedef konumunun tespit edilebildiği görülmektedir. Elastic waves propagate not only in gases and liquids but also in solids. The elastic properties of solids are different since they have form elasticity which liquids and gases don't have. Because of this reason, not only longitudinal waves but also other waves can propagate in solids. Waves propagating in solids can be used to get information about target location. In this paper, modelling of ultrasonic wave propagation in thin plates is investigated by using a single transducer and target distance is estimated with adaptive algorithm. According to the obtained results, it can be seen that target location can be estimated by detecting the starting point of the impulse response with adaptive algorithm since the delay along with the velocity of ultrasound wave in the modelled wave propagation is related to the distance between the excitation point and sensor Daha fazlası Daha az