Browsing Mühendislik ve Doğa Bilimleri Fakültesi by Author "Pekcan, Önder"
Now showing items 41-60 of 98
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A Fluorescence Study on Swelling of Hydrogels (PAAm) at Various Cross-Linker Contents
Aktas, Demet Kaya; Evingür, Gülşen Akin; Pekcan, Önder (Wiley, 2009)Disk-shaped acrylamide (AAm) gels were prepared from AAm with various NN'-methylenebisacrylamide (Bis) contents as cross-linker in the presence of ammonium persulfate as an initiator by free-radical cross-linking ... -
Fluorescence technique for monitoring swelling of PAAm-kappa-carrageenan gel composites
Evingür, Gülşen Akin; Aktaş, Demet Kaya; Pekcan, Önder (Shaker Publishing, 2009)Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) gels with various content of kappa- carrageenan. Disc shaped composite gels were prepared by free-radical cross/inking ... -
Fractal dimension and phase transition of graphene oxide (GO) doped polyacrylamide
Evingür, Gülşen Akın; Pekcan, Önder (ELSEVIER SCI LTD, 2020)Graphene Oxide (GO)- Polyacrylamide composites prepared between 5 and 50 mu l GO were performed by Fluorescence Spectroscopy. The phase transition performed on the composites was measured by calculating the critical ... -
Fractal Dimensions of kappa-Carrageenan Gels during Gelation and Swelling
Kara, Selim; Arda, Ertan; Pekcan, Önder (Taylor & Francis Inc, 2018)A photon scattering technique for research on the sol-gel and gel-sol transitions in kappa-carrageenan-water systems with various carrageenan contents (CC) was utilized for characterizing the fractal dimensions during ... -
Fractal Features and Structural Morphological Optical Characteristics of Sol-Gel Derived Silica Nanoparticled Thin Films
Uysal, Bengü Özuğur; Pekcan, Önder (Polish Acad Sciences Inst Physics, 2018)Nanostructured silica films using a simple and effective sol-gel spin coating technique were synthesized and the influence of ammonia/sol ratios on the particle size and thickness of this film was investigated. In addition ... -
Gelation electrical conductivity and elasticity of PAM- MWNT
Evingür, Gülşen Akin; Pekcan, Önder (Cambridge Univ Press, 2011)Polyacrylamide- Multiwalled carbonnanotube (PAM- MWNT) composites were prepared via free radical crosslinking copolymerization with different amounts of MWNT varying in the range between 0.1 and 15 wt. %. PAM- MWNT composite ... -
GELATION MECHANISMS
Pekcan, Önder; Kara, Selim (World Scientific Publ Co Pte Ltd, 2012)In this paper, we survey the gelation mechanisms for various polymeric systems which are classified by the type and the strength of the cross-linkages. These are the "irreversible" gels that are cross-linked chemically by ... -
Gelation of PAAm-PVP composites: A fluorescence study
Evingür, Gülşen Akin; Kaygusuz, Hakan; Erim, F. Bedia; Pekcan, Önder (World Scientific, 2014)Hybrid hydrogels are a new class of composite materials. Polyacrylamide (PAAm) hydrogels are mainly produced by free radical crosslinking copolymerization (FCC) of AAm in the presence of N N'-methylene bis (acrylamide) ... -
Group behaviour in physical chemical and biological systems
Saçlıoğlu, Cihan; Pekcan, Önder; Nanjundiah, Vidyanand (Indıan Acad Scıences, 2014)Groups exhibit properties that either are not perceived to exist or perhaps cannot exist at the individual level. Such 'emergent' properties depend on how individuals interact both among themselves and with their surroundings. ... -
In situ steady state fluorescence (SSF) technique to study drying of PAAm hydrogels made of various cross-linker contents
Evingür, Gülşen Akın; Aktas, Demet Kaya; Pekcan, Önder (Elsevier Science, 2009)Drying experiments of polyacrylamide (PAAm) gels were performed using steady-state fluorescence (SSF) spectrometer. Pyranine (P) was introduced as a fluorescence probe and intensity of P from various crosslinker content ... -
Investigation of Drying of Poly(N-isoproplacrylamide-co-acrylamide) by Fluorescence Technique
Evingür, Gülşen Akin; Pekcan, Önder (Wiley-Blackwell, 2013)The steady-state fluorescence technique was performed on drying of various molar percentages of poly(N-isopropylacrylamide-co- acrylamide) [poly(NIPA-co-AAc)] to elucidate the mechanism of temperature-induced phase separation ... -
Investigation of PSt-MWCNT concentration on epoxyacrylate photopolymerization and conductivity of polymer films
Doğruyol, Zekeriya; Temel, Gökhan; Doğruyol, Sevnur Keskin; Pekcan, Önder; Arsu, Nergis (Elsevier Science SA, 2013)Photopolymerization kinetics and conductivity changes of epoxyacrylate composites for various loading modified PSt-MWCNT weight fractions changing from 0.0025 to 0.2 wt.% were evaluated by performing photo differential ... -
Kinetic models for the dynamical behavior of polyacrylamide (PAAm)-kappa-carrageenan (kappa C) composite gels
Evingür, Gülşen Akın; Pekcan, Önder (Springer, 2015)A fluorescence method was employed for studying the drying and swelling of PAAm-kappa C composite gels which were formed from acrylamide (AAm) and N N'- methylenebisacrylamide (BIS) with various kappa-carrageenan (kappa ... -
A mathematical characterization of the gel point in sol-gel transition
Bilge, Ayşe Hümeyra; Pekcan, Önder (IOP Publishing Ltd, 2015)We model the sol-gel transition in terms of Susceptible-Infected-Removed (SIR) and Susceptible-Exposed-Infected-Removed (SEIR) models and compare with experimental results. We show, numerically, that the "gel point" described ... -
Mathematical Characterization of Thermo-reversible Phase Transitions of Agarose Gels
Öğrenci, Arif Selçuk; Pekcan, Önder; Kara, Selim; Bilge, Ayşe Hümeyra (Taylor & Francis Inc, 2018)The thermal phase transition temperatures of high (HMP) and low melting point (LMP) agarose gels were investigated by using UV-vis spectroscopy techniques. Transmitted light intensities from the gel samples with different ... -
A MATHEMATICAL DESCRIPTION OF THE CRITICAL POINT IN PHASE TRANSITIONS
Bilge, Ayşe Hümeyra; Pekcan, Önder (World Scientific Publ Co Pte Ltd, 2013)Let y(x) be a smooth sigmoidal curve, y((n)) be its nth derivative and {x(m,i)} and {x(a,i)}, i = 1, 2, ... , be the set of points where respectively the derivatives of odd and even order reach their extreme values. We ... -
Mathematical models for phase transitions in biogels
Bilge, Ayşe Hümeyra; Öğrenci, Arif Selçuk; Pekcan, Önder (World Scientific Publ Co Pte Ltd, 2019)It has been shown that reversible and irreversible phase transitions of biogels can be represented by epidemic models. The irreversible chemical sol-gel transitions are modeled by the Susceptible-Exposed-Infected-Removed ... -
Measurement of oxygen diffusion in PS/PNIPAM films using fluorescence quenching
Yargı, Önder; Pekcan, Önder; Uğur, Şaziye (Taylor & Francis Ltd, 2015)The diffusion of oxygen into pyrene labelled polystyrene (PS) latex/poly(N-isopropylacrylamide) (PNIPAM) composite films (PS/PNIPAM) was studied based on PS content with the use of fluorescence quenching method. Fluorescence ... -
Mechanical properties of graphene oxide-polyacrylamide composites before and after swelling in water
Evingür, Gülşen Akin; Pekcan, Önder (Springer, 2018)Polyacrylamide (PAAm) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering but their poor mechanical and water-retention properties have hindered their development. Graphene ... -
Modelling of Swelling by the Fluorescence Technique in Kappa Carrageenan Gels
Tari, Özlem; Pekcan, Önder (Amer Inst Physics, 2011)Kappa (-kappa) carrageenan gels prepared with various carrageenan concentrations in pure water were completely dried and then swelled in water vapor. Steady state fluorescence measurements were performed using a spectrometer ...