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

Yilmaz-Savaşkan, Sevil | Abbasoğlu, Rza | Hazer, Baki

Article | 2003 | Journal of Molecular Modeling9 ( 4 ) , pp.230 - 234

The conformational analysis of polynorbornene (PNB) chains was investigated with the AM1, MM2, AMBER and OPLS methods taking into consideration the possibility of binding of norbornene monomers to each other at various positions, i.e. exo-exo, exo-endo, endo-endo. The chain that is formed by connecting exo-endo positions of the monomers has lower torsional barrier energy than those formed with bonds at other positions and has more flexibility. It is determined that the thredisyndiotactic chain formed by exo-endo addition adopts a helix structure and has a coil shape. The disyndiotactic chain formed by connecting norbornene monomers . . .in mixed type has a linear structure. It is found that the repeat unit conformations of thredisyndiotactic and disyndiotactic chains of PNB are TGTG- and (TGTG-)2, respectively Daha fazlası Daha az

Koçer, Halil | Borcaklı, Mehlika | Demirel, Songün | Hazer, Baki

Article | 2003 | Turkish Journal of Chemistry27 ( 3 ) , pp.365 - 373

Poly(3-hydroxy alkanoate)s (PHA)s are bacterial polyesters that have, due to their biodegradability and biocompatibility, attracted considerable industrial interest. All the substrates used in feeding Alcaligenes eutrophus and Pseudomonas oleovorans have been reviewed as far as we know, and some more new substrates or mixtures have been used in PHA production by microorganisms. Alcaligenes eutrophus was fed with 4-pentenoic acid, 2-hydroxy ethyl methacrylate (HEMA), corn oil acids, linseed oil acids and limonene as well as mixtures of acetic acid and glucose or lactose. Either HEMA as a sole carbon source or the mixture of glucose d . . .id not produce polyester; limonene as a sole carbon source gave few dry cells and very few mgl-1 Poly (3-hydroxy butyrate-co-3-hydroxy valerate)(PHBV) containing 5 mol-% of hydroxy valerate (HV) units. Poly(3-hydroxy butyrate), (PHB), was obtained from corn oil acids and the mixture of glucose (15 gl-1) and acetic acid (2.5 gl-1); Poly (3-hydroxy butyrate-co-3-hydroxy valerate) (PHBV) was obtained in moderate yield from 4-pentenoic acid as a sole carbon source and the rest of the substrates above. Pseudomonas oleovorans was fed with linoleic acid, laurel seed oil acids, corn oil acids, laurel leaf oil, rose oil and limonene. Medium chain length polyesters were obtained from linoleic acid, corn oil acids and laurel seed oil acids, but the others did not give any detectable polyester. The polymers obtained were characterized by size exclusion chromatography, 1H and 13C NMR, FT-IR, thermal analysis and fast atom bombardment-mass spectrometer techniques 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

Kargı, Eksal | Altınyazar, Cevat H. | Hosnuter, Mübin | Babuccu, Orhan | Numanoğlu, Gamze | Babuccu, Berfu

Letter | 2003 | PLASTIC AND RECONSTRUCTIVE SURGERY111 ( 4 ) , pp.1562 - 1563

WOS: 000181477700037 PubMed: 12618622

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%.

Yapar, Tuğba | Hazer, Baki

Article | 2003 | Süleyman Demirel Üniversitesi Burdur Eğitim Fakültesi Dergisi4 ( 6 ) , pp.85 - 98

Bu çalışmada kimyasal maddeler konusunda tümevarım ve tümdengelim içerik yaklaşımları karşılaştırılmıştır. Tümevarım içerik sırasında atomun yapısı ve priyodik tablo, kimyasal bağlar, moleküller arası çekim kuvvetleri, sıvı, katı ve gazların özellikleri ve kimyasal maddeler üniteleri sırasıyla işlenirken, tümdengelimde tam tersi bir sırayla üniteler işlenmiştir. Bu araştırma 1999-2000 güz döneminde 74 öğrenci ile yapılmıştır. Bilişsel işlem beceri testi, çoktan seçmeli test ve yazılı sınav kullanılmıştır. Gözlem ve görüşmede yapılmıştır. Veriler MANOVA istatistiği ile analiz edilmiştir. Yazılı sınava göre gruplar arasında anlamlı fa . . .rklar bulunmuştur. Gözlem ve görüşme sonuçları tümevarım içerik sırasının tümdengelime gore öğrenciler üzerinde daha pozitif etkisi olduğunu göstermektedir The comparison of inductive and deductive content sequence of the concept of chemical substances has been studied. Inductive content sequence was ordered in the structure of atom and periodic table, chemical bonding, intermolecular forces and properties of liquids and solids and chemical substances, while deductive content sequence was reverse. This research was applied on 74 freshman students in 1999-2000 spring terms. The students were equally divided in to two groups which one of the group took chemistry course in deductive content sequence and the other group took inductive content sequence. Science process skill test, multiple choice test and essay type test were applied on these students. Observations and interviews with some students were also made during the course. The data obtained from the tests were analyzed with Multivariate analysis of Variance (MANOVA). After the completion of the content sequence, the students who took the course in inductive content sequence, achieved better than students who took the course in deductive content sequence on essay type test results. Additionally gender resulted not significant on dependent variables. Observations and interviews results indicated that inductive content sequence had positive effect on the students Daha fazlası Daha az

Tunaz, Hasan | Park, Youngjin | Büyükgüzel, Kemal | Bedick, Job C. | Aliza, A.R. Nor | Stanley, David W.

Article | 2003 | ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY52 ( 1 ) , pp.1 - 6

Intracellular phospholipase A(2) (PLA(2)) is responsible for releasing arachidonic acid from cellular phospholipids, and is thought to be the first step in eicosanoid biosynthesis. Intracellular PLA(2)s have been characterized in fat body and hemocytes from tobacco hornworms, Manduco sexta. here we show that bacterial challenge stimulated increased PLA(2) activity in isolated hemocyte preparations, relative to control hemocyte preparations that were challenged with water. The increased activity was detected as early as 15 s post-challenge and lasted for at least 1 h. The increased activity depended on a minimum bacterial challenge d . . .ose, and was inhibited in reactions conducted in the presence of oleyoxyethylphosphorylcholine, a site-specific PLA(2) inhibitor. In independent experiments with serum prepared from whole hemolymph, we found no PLA(2) activity was secreted into serum during the first 24 h following bacterial infection. We infer that a hemocytic intracellular PLA(2) activity is increased immediately an infection is detected. The significance of this enzyme lies in its role in launching the biosynthesis of eicosanoids, which mediate cellular immune reactions to bacterial infection Daha fazlası Daha az

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