Özer, Mahmut

Proceedings | 2003 | Mathematical and Computational Applications8 ( 1-3 ) , pp.71 - 78

In this study, phase-plane analysis is carried out for a simplified model of Purkinje cell dendrite in terms of voltage-gated ionic channels involved. State variables, nullclines and equilibrium points of the model are determined, and effects of ionic channel conductance and injected current on the shape of nullclines and the equilibrium points are investigated. In this study, phase-plane analysis is carried out for a simplified model of Purkinje cell dendrite in terms of voltage-gated ionic channels involved. State variables, nullclines and equilibrium points of the model are determined, and effects of ionic channel conductance and . . . injected current on the shape of nullclines and the equilibrium points are investigated Daha fazlası Daha az

Öztürk, Ertan | Özer, Mahmut

Proceedings | 2005 | Proceedings of the IEEE 13th Signal Processing and Communications Applications Conference, SIU 20052005 , pp.147 - 150

Voltage-gated ion channels in neuronal membrane show random fluctuations between different conformational states. These fluctuations give rise to channel noise current. This channel noise current is of great importance in the determination single-channel properties of voltage-gated ion channels. In this study, single-channel currents of potassium and sodium channels in Wang-Buzsaki neuronal model are examined, and their single-channel conductances and total sodium and potassium channel numbers in the membrane are computed by using non-stationary noise analysis. © 2005 IEEE.

Kaya, Ceren | Erkaymaz, Okan | Ayar, Orhan | Özer, Mahmut

Proceedings | 2018 | 26th IEEE Signal Processing and Communications Applications Conference, SIU 2018 , pp.1 - 4

Refractive disorders are common health problems in the community and they are the most important cause of visual impairment. In this study, it was aimed to classify the individuals who have hypermetropia and myopia refractive disorders or not. For this, horizontal and vertical Electrooculogram (EOG) signal data from the right and left eyes of the individuals were used. The performance of the data was investigated by using Logistic Regression (LR), Naive Bayes (NB), Random Forest (RF) and REP Tree (RT) data mining methods. According to the obtained results, REP Tree method has shown the most successful classification performance to d . . .etect hypermetropia and myopia refractive disorders from Electrooculogram (EOG) signals. © 2018 IEEE Daha fazlası Daha az

Özer, Mahmut

Proceedings | 2003 | Chinese Journal of Physics41 ( 2 ) , pp.206 - 218

The dynamics of a voltage-gated ionic channel is modeled by the conventional Hodgkin-Huxley mathematical formalism. In that formalism, the dynamics of the ionic channel activation and inactivation gates is modeled by a first-order differential equation dependent on the gate variable and the membrane potential. In this study a method, which combines statistical equilibrium theory and the thermodynamics of irreversible processes, is proposed for the study of the relaxation phenomena in the activation and inactivation gates of ionic channels present in the excitable membranes of neurons. In order to study the relaxation phenomena, the . . .assumption is made that the activation and inactivation gate order parameters can be treated as fluxes and forces, in the sense of Onsager's theory of irreversible thermodynamics. The kinetic equations are solved by using the Runge-Kutta method, in order to study the relaxation of the order parameters. It is found that the kinetic equations are characterized by two relaxation times. The kinetic coefficients that relate the fluxes to the forces are determined. Furthermore, it is shown that the obtained relaxation times have the same results as those obtained by using the Hodgkin-Huxley model. These results therefore indicate the validity of the proposed approach Daha fazlası Daha az

Ekmekçi N. Hakan | Özer, Mahmut

Proceedings | 2005 | Proceedings of the IEEE 13th Signal Processing and Communications Applications Conference, SIU 20052005 , pp.143 - 146

Voltage-gated ion channels are of great importance in the generation and propagation of electrical signals in the excitable membranes. In this study, we introduce the stochastic version of the Hodgkin-Huxley formalism and investigate the effect of channel noise on neuronal dynamic behaviors based on a model with the Gaussian noise. We show that the channel noise may result in a spiking activity for subthreshold stimulus, and that the firing dynamics follows more regular patterns when the membrane patch becomes smaller. It is also shown that the stochastic model converges to the deterministic model for very large membrane patches and . . . the neurons can encode subthreshold stimuli by considering the channel noise. © 2005 IEEE Daha fazlası Daha az

Kaya, Ceren | Erkaymaz, Okan | Ayar, Orhan | Özer, Mahmut

Proceedings | 2017 | 2017 Medical Technologies National Conference, TIPTEKNO 20172017-January , pp.1 - 4

'Diabetes Mellitus (Diabetes)' is a disease based on insulin hormone disorders secreted from the pancreas gland. Clinical findings find out that diabetes causes some diseases in vital organs. 'Diabetic Retinopathy' is one of the most common eye diseases based on diabetes, and it is the leading cause of visual loss resulting from structural changes in the retinal vessels. Recent researches show that signals from vital organs can be used to diagnose diseases in the literature. In this study, the features of horizontal and vertical Video-Oculography (VOG) signals from right and left eye are used to classify non-proliferative and prolif . . .erative diabetic retinopathy disease. 25 statistical features are obtained using discrete wavelet transform with VOG signals from 24 subjects. Feature selection is performed using C4.5 decision tree algorithm from 25 features obtained. The statistical features obtained from C4.5 decision tree and discrete wavelet transform are applied as input to artificial neural networks and the classification performance of the 'Diabetic Retinopathy' disease are compared according to these two methods. Our results show that feature selection by C4.5 decision tree algorithm (96.87%) provides better classification performance than feature extraction with discrete wavelet transform (93.75%). © 2017 IEEE Daha fazlası Daha az

Erkan, Yasemin | Özer, Mahmut | Yılmaz, Ergin

Proceedings | 2017 | 2017 MEDICAL TECHNOLOGIES NATIONAL CONGRESS (TIPTEKNO) , pp.1 - 4

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

Narin, Ali | İşler, Yalçın | Özer, Mahmut

Proceedings | 2018 | Proceedings - 2018 Innovations in Intelligent Systems and Applications Conference, ASYU 2018 , pp.1 - 4

The heart is very important to pump in a healthy way, but any disease that can occur in the heart has vital preventive measures. One of the most important of these diseases is Atrial Fibrillation (AF). This disease is a disturbance caused by excitations that occur outside of the sinoatrial node that occurs in the atrium of the heart. Paroxysmal Atrial Fibrillation (PAF) is the first stage of AF. Early prediction of this disease prevents the disease from passing to the other heavier stages. In this study, it was aimed to develop a warning system that warns PAF patients before an attack begins. Starting from the PAF, 99 pieces of data . . . consisting of 10 parts in 5 minutes were used. Time domain measurements and poincare plot measurements were obtained over the data. the features that best distinguish the classes have been determined by choosing a feature with a genetic algorithm. As a result, PAF can be predicted up to 7.5 minutes before the attack occurs using the selected features. © 2018 IEEE Daha fazlası Daha az

Orhan, Umut | Hekim, Mahmut | Özer, Mahmut

Proceedings | 2010 | 2010 15th National Biomedical Engineering Meeting, BIYOMUT2010 , pp.1 - 4

Electroencephalogram (EEG) recording systems have been frequently used as the sources of information in diagnosis of epilepsy by several researchers. In this study, rearranged EEG signals were classified by Multilayer Perceptron Neural Network (MLPNN) model. Used data consists of five groups (A, B, C, D, and E) each containing 100 EEG segments. In this study, center points with equal interval were selected on amplitude axis of each EEG segment. EEG signals were rearranged by way of that each amplitude value was shifted to the center point closest to itself. Equal width discretization (EWD) method was used for rearrangement process. . . .Wavelet coefficients of each segment of EEG signals were computed by using discrete wavelet transform (DWT). The mean, the standard deviation and the entropy of these coefficients was used as the inputs of MLPNN model. The model was protected from the overfitting by cross validation. Two different classification experiments were implemented by the same MLPNN model: 1) the classification of healthy volunteers, epilepsy patients during seizure and epilepsy patients during a seizure-free interval, 2) the classification of epilepsy patients during seizure and seizure-free interval. MLPNN model classified EEG signals with the accuracy of 99.60% in first experiment and 100% in second experiment. It is observed that MLPNN classification of EEG signals after rearrangement in amplitude axis provides better results. ©2010 IEEE Daha fazlası Daha az

Kaya, Ceren | Erkaymaz, Okan | Ayar, Orhan | Özer, Mahmut

Proceedings | 2017 | 2016 Medical Technologies National Conference, TIPTEKNO 2016 , pp.1 - 4

The insulin hormone secreted from the pancreas gland in the body is not present in sufficient amount, or because they do not fit, which is defined as the elevation of blood glucose 'Diabetes Mellitus (Diabetes)'. 'Diabetic Retinopathy' is the most common in diabetes-related eye diseases. It had done damages in the retina that detect light on behind the eye as a result of changes in the arteries that is one of the reasons that makes blindness (loss of vision) in people. In this study, horizontal and vertical Video-Oculography (VOG) signals captured by using internal tracking camera in Metrovision MonPackOne Electrooculography device. . . . In order to filter the noise from the signals, the wavelet transform method was used. Obtained signals have shown that the signals of diabetic retinopathy patients have higher amplitude and irregular characteristic than the signals obtained from healthy groups. In both groups, significant Daubechies-6 wavelet coefficients (A6-D6) gave better results than Daubechies-4 wavelet coefficients (A4-D4). Obtained data as a result of using wavelet transform sheds light on feature extraction and classification in proposed future works. © 2016 IEEE Daha fazlası Daha az

Fesli, Uğur | Bayır, Raif | Özer, Mahmut

Proceedings | 2009 | ELECO 2009 - 6th International Conference on Electrical and Electronics Engineering , pp.1 - 4

In parallel to developing technology, demand for more energy makes us seek new energy sources. The most important application field of this search is renewable energy resources. Wind and solar energy have being popular ones owing to abundant, ease of availability and convertibility to the electric energy. This work covers realization of a hybrid renewable energy system for a domestic application, which runs under a microcontroller to utilize the solar and wind power. This project is implemented in accordance with available lineelectricity. Batteries in the system are charged by either wind power via a small alternator or solar power . . . via an MPPT Module. System control relies mainly on microcontroller. Power resources and loads in the system are monitored and controlled In real time Daha fazlası Daha az