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

Article | 2018 | Chaos, Solitons and Fractals114 , pp.164 - 174

In this study, we introduce two hybrid artificial neural network models with particle swarm optimization algorithm to diagnose diabetic retinopathy based on the Video-Oculography signals. The hybrid models use Discrete Wavelet Transform and Hilbert-Huang Transform separately to extract features from the signals. The classification performance of both models is analyzed comparatively. We show that the model based on Hilbert–Huang Transform exhibits better classification performance than the model based on the Discrete Wavelet Transform. © 2018 Elsevier Ltd

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

Proceedings | 2017 | 2016 Medical Technologies National Conference, TIPTEKNO 2016 , pp.164 - 174

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

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Proceedings | 2015 | 2016 MEDICAL TECHNOLOGIES NATIONAL CONFERENCE (TIPTEKNO) , pp.164 - 174

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

Baysal, Veli | Yılmaz, Ergin | Özer, Mahmut

Proceedings | 2014 | 2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings , pp.1958 - 1961

In this paper, the effects of time-periodic coupling on the firing regularity of a scale-free network (SF), consisting of stochastic Hodgkin-Huxley neurons, have been investigated depending on ion channel noise. The effects of both the frequency and the amplitude of periodic coupling on the firing regularity have been tackled, separately. It is seen from the obtained results that the firing (spiking) regularity shows resonance like behavior depending on ion channel noise when the frequency of the periodic coupling equals integer multiple of the sub threshold oscillation frequency of H-H neurons. Additionally, it is determined that t . . .his resonance is maximal at an optimal value of the amplitude of the periodic coupling strength. © 2014 IEEE Daha fazlası Daha az

Çalım, Ali | İleri, Uğur | Uzuntarla, Muhammet | Özer, Mahmut

Proceedings | 2015 | 2015 23rd Signal Processing and Communications Applications Conference, SIU 2015 - Proceedings , pp.2262 - 2265

In this study, the regularity of neuronal firing is investigated. We perform independent simulations to find out effects of synaptic transmission reliability in the background activity on the firing regularity of neurons, using Integrate and Fire (IF) neuron model. The obtained results demonstrate that synaptic transmission reliability changes firing regularity influencing background activity intensity. Moreover, it is investigated how the excitatory and inhibitory synaptic connections effect the regularity of neuronal firing. © 2015 IEEE.

Baysal, Veli | Yılmaz, Ergin

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

In this paper, effects of electromagnetic induction on vibrational resonance phenomenon in a Hodgkin-Huxley neuron are investigated. By stimulating Hodgkin-Huxley neuron with both high-frequency signal and low-frequency weak signal, its weak signal detection capacity have been investigated under electromagnetic induction effect. Obtained results show that electromagnetic induction causes decreasing of the amplitude of vibrational resonance effect emerging depending on the amplitude of high frequency signal. Also, vibrational resonance phenomenon occurs at smaller amplitudes of high frequency signal in Hodgkin-Huxley neuron which is . . .under electromagnetic induction effect. Finally, it is found that the best detection of the weak signal in a Hodgkin-Huxley neuron under electromagnetic induction effect is realized under an optimal electromagnetic current intensity. © 2018 IEEE Daha fazlası Daha az

Erkaymaz, Hande | Orak, I.Muharrem | Özer, Mahmut

Proceedings | 2014 | 2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings , pp.265 - 268

Coding of the organ movements have been seen commonly in the hardware designing which is useful for humanity in scientific researches. 5 sense organs which reveal different data with cellular structures, is the most important focus point. Especially, Eye is known as photosensitive sensor organ of living creature. There is a potential difference between cornea and retina of eye. This potential difference is known as electrooculogram (EOG). Nowadays, EOG signals are commonly used in these hardware designs. Obtained potential differences from EOG signals have been converted coded directional movements. Thus, in this study, 4 basic dire . . .ction movements have been tried to detect with a fuzzy controlled model. It is shown that the fuzzy controlled system as determine the direction can be used successfully. In addition, eye direction movements of squint person are obtained by the system. © 2014 IEEE Daha fazlası Daha az

Ağaoğlu, Şükrüye Nihal | Çalım, Ali | Hövel, Philipp | Özer, Mahmut | Uzuntarla, Muhammet

Article | 2019 | Neurocomputing325 , pp.59 - 66

We investigate the phenomenon of vibrational resonance (VR) in neural populations, whereby weak low-frequency signals below the excitability threshold can be detected with the help of additional high-frequency driving. The considered dynamical elements consist of excitable FitzHugh–Nagumo neurons connected by electrical gap junctions and chemical synapses. The VR performance of these populations is studied in unweighted and weighted scale-free networks. We find that although the characteristic network features – coupling strength and average degree – do not dramatically affect the signal detection quality in unweighted electrically . . .coupled neural populations, they have a strong influence on the required energy level of the high-frequency driving force. On the other hand, we observe that unweighted chemically coupled populations exhibit the opposite behavior, and the VR performance is significantly affected by these network features whereas the required energy remains on a comparable level. Furthermore, we show that the observed VR performance for unweighted networks can be either enhanced or worsened by degree-dependent coupling weights depending on the amount of heterogeneity. © 2018 Elsevier B.V Daha fazlası Daha az

Aydın, R. Seda Tığlı | Akyol, Elvan | Hazer, Baki

Article | 2017 | JAOCS, Journal of the American Oil Chemists' Society94 ( 3 ) , pp.413 - 424

Due to the great interest in oil-based polymers, which are prepared from renewable resources, different forms and amounts of soybean oil-based PLA films were prepared and evaluated for their potential usage as a medical biomaterial. Soybean oil, epoxidized soybean oil and auto-oxidized soybean oil were blended with PLA and PLA/oil films with appropriate oil amounts [2, 7, 14 and 20% (w/w)] were obtained by solvent casting. Thermal stability and plasticization effect were determined by adjusting oil amounts and type. Epoxidized soybean oil blended films showed the smallest increase in elongation breaks (13–20%) and the highest decrea . . .se in thermal decomposition temperatures (364–327 °C) compared to other oil blended films. In vitro quantitative and qualitative cytotoxicity results showed no reactivity (grade 0) for the L929 cells treated with 14% (w/w) oil blended PLA films. In vivo irritation and implantation tests concluded that 14% (w/w) oil blended PLA films were non-irritant. No erythema, no oedema reactions, no traumatic necrosis and foreign debris were observed. Thus, along with superior biocompatibility, PLA/oil films can replace petroleum-based products for several biomedical uses. © 2017, AOCS Daha fazlası Daha az

Aydın Tığlı, R. Seda | Akyol, Elvan | Hazer, Baki

Article | 2018 | Journal of Polymers and the Environment26 ( 3 ) , pp.1262 - 1271

Controlling the degradation parameters is one of the main challenges of preparing appropriate biomaterials for biomedical applications. In this study, the effect of soybean oil inclusion on hydrolytic degradation of polylactic acid (PLA) was investigated both in vitro and in vivo. PLA/oil membranes were prepared by using polymeric soybean oil (PSO), epoxidized soybean oil and soybean oil (SOYA) with their varied concentrations. Degradation of membranes was performed in vitro for 8 weeks period and in vivo for 4 weeks period. Weight loss, changes in molecular weight, thermal properties and morphological changes were studied during de . . .gradation. SOYA blended PLA membranes show the lowest degradation rates by bulk degradation after 4 weeks in vitro, followed by surface erosion for the first week. Approximately twofold high percentage weight losses of all membranes were obtained after 4 weeks of degradation in vivo in comparison with in vitro data. The significant weight loss, molecular weight loss and thermal property change for PSO blended membranes were determined during in vivo degradation which highlights the increase of degradation rate by bulk degradation. Drastic morphological changes were observed on surface of degraded membranes in vivo with large pores, cracks, fissures and large cavities. © 2017, Springer Science+Business Media New York Daha fazlası Daha az

Ağaoğlu, Şükrüye Nihal | Özer, Mahmut | Çalım, Ali | Uzuntarla, Muhammet

Proceedings | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017 , pp.1262 - 1271

In the phenomenon of vibrational resonance, the excitable system is under the influence of two periodic forces: a low-frequency (signal), a high-frequency (carrier). In this study, the effects of synaptic time delay on the vibrational resonance were investigated in two coupled FitzHugh-Nagumo neurons with electrical or chemical coupling. It is seen that, for both types of coupling by appropriate choice of synaptic time delay can be had a curative effect to transmission between two neurons at certain values of synaptic conductivity. © 2017 IEEE.