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Synthesis and characterization of ozonated oil nanoemulsions

Tığlı-Aydın, Rahime Seda | Kazancı, Füsun

Article | 2018 | JAOCS, Journal of the American Oil Chemists' Society95 ( 11 ) , pp.1385 - 1398

In recent years, the use of ozonated oil (ozone enriched oil form) is being increasingly preferred for biomedical applications because of its antibacterial activity. Among most important reasons of this choice is the high molecular affinity of the ozone molecule and intracellular effects of the products of ozone and the unsaturated fatty-acid chemical reactions in cellular signaling systems. The aim of the present study was to synthesize and optimize the ozonated oil nanoemulsion system that would be transferred into the living systems easily, suggesting a promising carrier system for various biomedical applications. By varying form . . .ulation parameters (surfactant-to-oil ratio, surfactant concentration, mixing rate, and surfactant type), nanoemulsions were investigated in terms of mean particle diameters, distributions, and stabilities. Nanoemulsions with high stability and small droplet diameters (212.7 nm) could be produced under optimized conditions with Tween 40 as the surfactant at a 750 rpm mixing rate using the emulsion inversion point (EIP) low-energy method. Spherical and uniformly distributed nanoemulsions were observed by SEM, which also supports mean particle diameter measurements. Fourier-transform infrared spectroscopy (FTIR) and 13C NMR (nuclear magnetic resonance) studies indicated an ozonide structure within the nanoemulsion system, which remained even after 30 days of storage. The antibacterial activity of ozonated oil emulsions against Staphylococcus aureus and Escherichia coli suggests promising applications in the biomedical field. © 2018 AOC Daha fazlası Daha az

Newly designed bioanode for glucose/O2 biofuel cells to generate renewable energy

Korkut, Şeyda | Kılıç, Muhammet Samet | Hazer, Baki

Article | 2019 | Asia-Pacific Journal of Chemical Engineering14 ( 6 ) , pp.1385 - 1398

A copolymer poly(methyl methacrylate-co-vinylferrocene) was synthesized and used for the first time in a biofuel cell design. Bioanaode enzyme glucose oxidase and biocathode enzyme bilirubin oxidase were physically immobilized onto the copolymer-modified electrodes. Characterization studies were conducted by scanning electron microscopy, carbon-13, fourier transform infrared and hydrogen-1 nuclear magnetic resonance, and cyclic voltammograms. The designed biofuel cell was operated with linear sweep voltammetry. The maximum current was at 45°C with 120 µg of polymer amount. An improved power density of 323 µW cm-2 that is higher than . . . other ferrocene-based fuel cells was obtained with 10-mM glucose at 0.4 V with the designed bioanode. © 2019 John Wiley & Sons Ltd Daha fazlası Daha az

Autapse-induced multiple coherence resonance in single neurons and neuronal networks

Yılmaz, Ergin | Özer, Mahmut | Baysal, Veli | Perc, Matjaž

Article | 2016 | Scientific Reports6 , pp.1385 - 1398

We study the effects of electrical and chemical autapse on the temporal coherence or firing regularity of single stochastic Hodgkin-Huxley neurons and scale-free neuronal networks. Also, we study the effects of chemical autapse on the occurrence of spatial synchronization in scale-free neuronal networks. Irrespective of the type of autapse, we observe autaptic time delay induced multiple coherence resonance for appropriately tuned autaptic conductance levels in single neurons. More precisely, we show that in the presence of an electrical autapse, there is an optimal intensity of channel noise inducing the multiple coherence resonanc . . .e, whereas in the presence of chemical autapse the occurrence of multiple coherence resonance is less sensitive to the channel noise intensity. At the network level, we find autaptic time delay induced multiple coherence resonance and synchronization transitions, occurring at approximately the same delay lengths. We show that these two phenomena can arise only at a specific range of the coupling strength, and that they can be observed independently of the average degree of the network. © The Author(s) 2016 Daha fazlası Daha az

Enhancement of pacemaker induced stochastic resonance by an autapse in a scale-free neuronal network

Yılmaz, Ergin | Baysal, Veli | Perc, Matjaž | Özer, Mahmut

Article | 2016 | Science China Technological Sciences59 ( 3 ) , pp.364 - 370

An autapse is an unusual synapse that occurs between the axon and the soma of the same neuron. Mathematically, it can be described as a self-delayed feedback loop that is defined by a specific time-delay and the so-called autaptic coupling strength. Recently, the role and function of autapses within the nervous system has been studied extensively. Here, we extend the scope of theoretical research by investigating the effects of an autapse on the transmission of a weak localized pacemaker activity in a scale-free neuronal network. Our results reveal that by mediating the spiking activity of the pacemaker neuron, an autapse increases . . .the propagation of its rhythm across the whole network, if only the autaptic time delay and the autaptic coupling strength are properly adjusted. We show that the autapse-induced enhancement of the transmission of pacemaker activity occurs only when the autaptic time delay is close to an integer multiple of the intrinsic oscillation time of the neurons that form the network. In particular, we demonstrate the emergence of multiple resonances involving the weak signal, the intrinsic oscillations, and the time scale that is dictated by the autapse. Interestingly, we also show that the enhancement of the pacemaker rhythm across the network is the strongest if the degree of the pacemaker neuron is lowest. This is because the dissipation of the localized rhythm is contained to the few directly linked neurons, and only afterwards, through the secondary neurons, it propagates further. If the pacemaker neuron has a high degree, then its rhythm is simply too weak to excite all the neighboring neurons, and propagation therefore fails. © 2016, Science China Press and Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

Osteogenic activities of polymeric soybean oil-g-polystyrene membranes

Tığlı-Aydın, Rahime Seda | Hazer, Baki | Acar, Merve | Gümüşderelioğlu, Menemşe

Article | 2013 | Polymer Bulletin70 ( 7 ) , pp.2065 - 2082

A novel biocompatible copolymer membrane was synthesized and characterized for use in guided bone regeneration using polymeric soybean oil-g-polystyrene (PSO-g-PS) graft copolymer which was successfully obtained by free radical polymerization of styrene initiated by PSO peroxide as a macroinitiator at 80 C. Osteoblastic cellular activities of MC3T3-E1 cells on PSO-g-PS membranes with different soybean oil composition (PSO-g-PS1, PSO-g-PS2, and PSO-g-PS3) were evaluated. Nuclear magnetic resonance (1H NMR) spectra showed that PSO inclusion (mol%) was found to be 27, 69, and 51 % for PSO-g-PS1, PSO-g-PS2, and PSO-g-PS3 membranes, resp . . .ectively. Superior biocompatibility of the PSO-g-PS membranes was determined compared to polystyrene tissue culture plates (TCPS) as positive control. Cell proliferation was enhanced on PSO-g-PS2 and PSO-g-PS3 membranes compared to PSO-g-PS1 membranes (p < 0.001), and a statistically significant higher ALP value of MC3T3-E1 cells on PSO-g-PS2 membranes (p < 0.05) suggested that proliferation and differentiation of preosteoblastic on PSO-g-PS membranes were enhanced with regard to soybean oil content within the membranes. Thus, the present study suggests that PSO-g-PS2 membranes, which showed a favorable biological environment for the preosteoblastic cells, can be well suited for bone tissue engineering applications. © 2013 Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

Enhancement of temporal coherence via time-periodic coupling strength in a scale-free network of stochastic Hodgkin-Huxley neurons

Yılmaz, Ergin | Baysal, Veli | Özer, Mahmut

Article | 2015 | Physics Letters, Section A: General, Atomic and Solid State Physics379 ( 26-27 ) , pp.1594 - 1599

We investigate the effects of time-periodic coupling strength on the temporal coherence or firing regularity of a scale-free network consisting of stochastic Hodgkin-Huxley (H-H) neurons. The temporal coherence exhibits a resonance-like behavior depending on the cell size or the channel noise intensity. The best temporal coherence requires an optimal channel noise intensity, and this coherence can be significantly increased by time-periodic coupling strength when its frequency matches the integer multiples of the intrinsic subthreshold oscillation frequency of H-H neuron. Particularly, we find the multiple-coherence resonance depend . . .ing on frequency of time-periodic coupling strength at the optimal noise intensity. We also obtain a resonance-like dependence of temporal coherence on the amplitude of time-periodic coupling strength. Additionally, we investigate the effects of average degree on the temporal coherence and find that the temporal coherence exhibits a resonance-like behavior with respect to the network average degree, indicating that the best regularity requires an optimal average degree. © 2015 Elsevier B.V. All rights reserved Daha fazlası Daha az

Biodegradable poly(ε-caprolactone)-based graft copolymers via poly(linoleic acid): In vitro enzymatic evaluation

Allı, Sema | Tığlı-Aydın, Rahime Seda | Allı, Abdülkadir | Hazer, Baki

Article | 2015 | JAOCS, Journal of the American Oil Chemists' Society92 ( 3 ) , pp.449 - 458

Well-defined graft copolymers based on poly(?-caprolactone) (PCL) via poly(linoleic acid) (PLina), are derived from soybean oil. Poly(linoleic acid)-g-poly(?-caprolactone) (PLina-g-PCL) and poly(linoleic acid)-g-poly(styrene)-g-poly(?-caprolactone) (PLina-g-PSt-g-PCL) were synthesized by ring-opening polymerization of ?-caprolactone initiated by PLina and one-pot synthesis of graft copolymers, and by ring-opening polymerization and free radical polymerization by using PLina, respectively. PLina-g-PCL, PLina-g-PSt-g-PCL3, and PLina-g-PSt-g-PCL4 copolymers containing 96.97, 75.04 and 80.34 mol% CL, respectively, have been investigated . . . regarding their enzymatic degradation properties in the presence of Pseudomonas lipase. In terms of weight loss, after 1 month, 51.5% of PLina-g-PCL, 18.8% of PLina-g-PSt-g-PCL3, and 38.4% of PLina-g-PSt-g-PCL4 were degraded, leaving remaining copolymers with molecular weights of 16,140, 83,220 and 70,600 Da, respectively. Introducing the PLina unit into the copolymers greatly decreased the degradation rate. The molar ratio of [CL]/[Lina] dramatically decreased, from 21.3 to 8.4, after 30 days of incubation. Moreover, reduced PCL content in PLina-g-PSt-g-PCL copolymers decreased the degradation rate, probably due to the PSt enrichment within the structure, which blocks lipase contact with PCL units. Thus, copolymerization of PCL with PLina and PSt units leads to a controllable degradation profile, which encourages the use of these polymers as promising biomaterials for tissue engineering applications. © AOCS 2015 Daha fazlası Daha az

Vibrational resonance in a heterogeneous scale free network of neurons

Uzuntarla, Muhammet | Yılmaz, Ergin | Wagemakers, Alexandre | Özer, Mahmut

Article | 2015 | Communications in Nonlinear Science and Numerical Simulation22 ( 01.Mar ) , pp.367 - 374

Vibrational resonance (VR) is a phenomenon whereby the response of some dynamical systems to a weak low-frequency signal can be maximized with the assistance of an optimal intensity of another high-frequency signal. In this paper, we study the VR in a heterogeneous neural system having a complex network topology. We consider a scale-free network of neurons where the heterogeneity is in the intrinsic excitability of the individual neurons. It is shown that emergence of VR in heterogeneous neuron population requires less energy than a homogeneous population. We also find that electrical coupling strength among neurons plays a key role . . . in determining the weak signal processing capacity of the heterogeneous population. Lastly, we investigate the influence of interneuronal link density on the VR and demonstrate that the energy needed to obtain the resonance grows with the increase in average degree. © 2014 Elsevier B.V Daha fazlası Daha az

Delayed feedback and detection of weak periodic signals in a stochastic Hodgkin-Huxley neuron

Yılmaz, Ergin | Özer, Mahmut

Article | 2015 | Physica A: Statistical Mechanics and its Applications421 , pp.455 - 462

We study the effect of the delayed feedback loop on the weak periodic signal detection performance of a stochastic Hodgkin-Huxley neuron. We consider an electrical autapse characterized by its coupling strength and delay time. The stochastic Hodgkin-Huxley neuron exhibits subthreshold oscillations, and thus has an intrinsic time scale with the subthreshold oscillations. Therefore, we investigate the interplay of the subthreshold oscillations, coupling strength and delay time on the weak periodic signal detection. Results indicate that the delayed feedback either enhances or suppresses the weak signal detection depending on its param . . .eters, when compared to that without the feedback. The delayed feedback augments the weak periodic signal detection for the optimal values of the intrinsic noise and the coupling strength when the delay time is close to the integer multiples of the period of the intrinsic oscillations, due to the multiple resonance among the weak signal, the intrinsic oscillations, and the delayed feedback. We analyze the interspike interval histograms and show that the delayed feedback enhances or suppresses the weak periodic signal detection by increasing or decreasing the phase locking (synchronization) between the spiking and the weak periodic signal. We also show that an optimal phase locking is obtained when the delay time is close to the period of the intrinsic oscillations, leading a single dominant time scale in the spike trains. © 2014 Elsevier B.V. All rights reserved Daha fazlası Daha az

Collective firing regularity of a scale-free Hodgkin-Huxley neuronal network in response to a subthreshold signal

Yılmaz, Ergin | Özer, Mahmut

Article | 2013 | Physics Letters, Section A: General, Atomic and Solid State Physics377 ( 18 ) , pp.1301 - 1307

We consider a scale-free network of stochastic HH neurons driven by a subthreshold periodic stimulus and investigate how the collective spiking regularity or the collective temporal coherence changes with the stimulus frequency, the intrinsic noise (or the cell size), the network average degree and the coupling strength. We show that the best temporal coherence is obtained for a certain level of the intrinsic noise when the frequencies of the external stimulus and the subthreshold oscillations of the network elements match. We also find that the collective regularity exhibits a resonance-like behavior depending on both the coupling . . .strength and the network average degree at the optimal values of the stimulus frequency and the cell size, indicating that the best temporal coherence also requires an optimal coupling strength and an optimal average degree of the connectivity. © 2013 Elsevier B.V Daha fazlası Daha az

Comprehensive and quantitative profiling of lipid molecular species by LC-ESI-MS/MS of four native species from semiarid Patagonian Monte

Cenzano, Ana M. | Arslan, İdris

Article | 2020 | Plant Physiology and Biochemistry146 , pp.447 - 456

The maintenance of lipid and fatty acids unsaturated composition has been described as one of the mechanisms associated to drought tolerance, but research about the lipid profile in native plants of semiarid environment is still limited. The primary objective was to study whether lipid profiles correlates with drought resistance strategies (tolerant or avoidant) of two life forms (shrubs and grasses). The lipid classes and molecular species of green leaves of Larrea divaricata and Lycium chilense shrubs and Pappostipa speciosa and Poa ligularis grasses were determined using LC–ESI-MS/MS. The soil water content was very low during sp . . .ring and leaf relative water content was between 47 and 74% in the four species. Lipid profiling was different between both life forms. The prevalent compounds were digalactosyldiacylglycerol (DGDG), monogalactosyldiacylglycerol (MGDG) and phosphatidic acid (PA). The lipid signature shows that L. divaricata adjust its lipid composition to tolerate drought, increasing the content of: a) total lipids and total phospholipids, b) structural phospholipids (36:4 and 36:2-PC, phosphatidylcholine; 36:4-PE, phosphatidylethanolamine), c) chloroplast and mitochondria lipids (32:1 and 32:0-PG, phosphatidylglycerol; 34:3, 36:6 and 36:3-DGDG), d) signaling lipids (34:3, 34:2 and 36:5-PA and PI, phosphatidylinositol), and e) polyunsaturated fatty acids (PUFAs, 18:3 and 18:2) and long chain polyunsaturated fatty acids (LC-PUFAs, in 40:2 and 42:2-PS, phosphatidylserine). This membrane lipid composition contributes to membrane stabilization as metabolic-functional strategy for drought tolerance in the Patagonian Monte. In addition, the 18:3 present in lipids of both grasses could be incorporated to lamb fed based on pastures and result healthy for human dietary. © 201 Daha fazlası Daha az

Effects of subthreshold excitation characteristics on vibrational resonance in weighted scale-free network

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

Proceedings | 2017 | 2017 25th Signal Processing and Communications Applications Conference, SIU 2017 , pp.447 - 456

In this paper, the phenomena of Vibrational Resonance is investigated in an excitable system which consists of FitzHugh-Nagumo neurons with electrical coupling. Weak signal detection performance of excitable system is examined in scale-free network (unweighted or weighted) topology. The simulation results show that; weighting the scale-free network, average connectivity degree, amplitude and frequency of weak signal play an active role to determine the data carrying performance of neurons based on Vibrational Resonance. It is determined that, the amount of required energy for creating resonance peaks of excitable system is decreased . . . significantly by choosing the correct value of weight control parameter in a weighted network especially. © 2017 IEEE Daha fazlası Daha az

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