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

Yıldırım, Yılmaz | Hughes, Ronald

Article | 2003 | Process Safety and Environmental Protection: Transactions of the Institution of Chemical Engineers, Part B81 ( 4 ) , pp.257 - 261

In this investigation, the preparation and gas selectivity characteristics of an 'ultrafine' composite ceramic membrane are reported. A dip-coating technique was used to prepare a thin selective membrane on a commercially available ceramic macroporous filter (SCT, France). The permeabilities of H2, N2 and CO2 were measured at temperatures of 25-470°C and average pressures of 1-2 bar. The separation of CO2/N2 binary mixtures was also performed. The separation factors for CO2 were found to be higher than that of the Knudsen separation mechanism at room and high temperature. The potential applications of these membranes to CO2 separati . . .on at these temperatures are discussed on the basis of measured selectivity values 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

Özer, Mahmut | Erdem, Rıza

Article | 2003 | NeuroReport14 ( 7 ) , pp.1071 - 1073

A voltage-gated ion channel is fundamental in generation and propagation of electrical signals in the excitable membranes. Dynamics of (in)activation gates of the ion channel is modeled by first-order kinetics. The equilibrium value function is crucial in the kinetics of the (in)activation gates for fitting experimental data. We present a new methodology to define the equilibrium value function based on the lowest approximation of the cluster variation method and the static properties in the molecular field approximation. The methodology allows for exploration of the gating dynamics. © 2003 Lippincott Williams & Wilkins.

Yıldırım, Yılmaz | Bayramoğlu, Mahmut | Hasıloğlu, Samet

Article | 2003 | Fresenius Environmental Bulletin12 ( 10 ) , pp.1173 - 1179

Air pollution continues to be a major problem in many countries. Mathematical models are useful in relating emissions to air quality under a variety of meteorological conditions and source emission concentrations over an urban area. Meanwhile, the forecasting capability of sophisticated models is limited to very large and complex terrains. In this study, an adaptive neuro-fuzzy logic method has been developed to estimate the impact of meteorological factors on SO2 pollution levels. The model satisfactorily forecasts the trends of SO2 concentration levels with a performance between 78-90%.

Özer, Mahmut

Other | 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