Bulunan: 436 Adet 0.001 sn
Koleksiyon [20]
Tam Metin [2]
Yayın Türü [11]
Yazar [20]
Konu Başlıkları [20]
Yayıncı [20]
Yayın Dili [3]
Dergi Adı [20]
Nitroxide-mediated copolymerization of styrene and pentafluorostyrene initiated by polymeric linoleic acid

Allı, Abdulkadir | Allı, Sema | Becer, C. Remzi | Hazer, Baki

Article | 2016 | European Journal of Lipid Science and Technology118 ( 2 ) , pp.279 - 287

Polymeric linoleic asit graft copolymers were synthesized via a nitroxide-mediated radical polymerization (NMRP) method in the presence of 2,2-6,6-tetramethylpiperidinyl-1-oxy (TEMPO). For this purpose, PLina-ox was exposed to polymerization with styrene (Sty) or Sty and pentafluorostyrene (F5Sty) in the presence of TEMPO by NMRP method in order to obtain PLina-g-PSty and PLina-g-PF5Sty-g-PSty graft copolymers with controlled structure and low polydispersity. Chain extension study was evaluated. Principal parameters, such as monomer concentration, initiator concentration, and polymerization time, which effect the polymerization reac . . .tions, were evaluated. The products thus obtained were well characterized by 1H NMR, GPC, and 19F NMR measurements. Practical application: We report for the first time the synthesis of PLina-g-PSty and PLina-g-PSty-g-PF5Sty graft copolymers in the presence of TEMPO. NMRP reactions were performed in the presence of TEMPO in order to obtain graft copolymers with controlled molecular weight and polydispersity. Chain-extension reactions were also successfully carried out because of the activation of TEMPO terminated chain ends of graft copolymers. Pure linoleic acid was auto-oxidized under daylight and air oxygen, yielding peroxidized PLina (PLina-ox). PLina-ox has been used in the polymerization of styrene (Sty) or copolymerization of Sty and pentafluorostyrene (F5Sty). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 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.279 - 287

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

Novel graphene-modified poly(styrene-b-isoprene-b-styrene) enzymatic fuel cell with operation in plant leaves

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

Article | 2016 | Analytical Letters49 ( 14 ) , pp.2322 - 2336

A carboxylated poly(styrene-b-isoprene-b-styrene) triblock copolymer was synthesized for the construction of an enzymatic fuel cell. Glucose oxidase and bilirubin oxidase were chemically immobilized via the carboxylated functional groups of the polymer. The enzymatic fuel cell working electrodes were modified with graphene to accelerate the electron transfer rate of the system. Essential design and operational parameters were carefully optimized for improving the power of the enzymatic fuel cell. A power density of 20 µW cm-2 with only 4 µg of immobilized bilirubin oxidase was generated from 30 mM glucose at 0.72 V. The improved enz . . .ymatic fuel cell was tested in a plant leaf. A power density of 14 nW cm-2 was generated with glucose produced by photosynthesis reactions conducted during 30 min in the leaf. © 2016, Taylor & Francis Group, LLC Daha fazlası Daha az

Evaluation of the protective effect of agmatine against cisplatin nephrotoxicity with 99mTc-DMSA renal scintigraphy and cystatin-C

Salihoglu Y.S. | Elri T. | Gulle K. | Can M. | Aras M. | Ozacmak H.S. | Cabuk M.

Article | 2016 | Renal Failure38 ( 9 ) , pp.1496 - 1502

Background: The aim of the current study was to investigate whether agmatine (AGM) has a protective effect against cisplatin-induced nephrotoxicity. Materials and methods: Thirty-two rats were randomly divided into four groups: (1) Saline (control); (2) Cisplatin (CDDP; 7.5 mg/kg intraperitoneally); (3) Agmatine (AGM; 10 mg/kg intraperitoneally); (4) Cisplatin plus agmatine (CDDP + AGM). Agmatine was given before and two consecutive days after cisplatin injection. All the animals underwent renal scintigraphy with 99mTc-DMSA. The levels of serum creatinine, cystatin C, and blood urea nitrogen (BUN) were measured in addition to examin . . .ation of the tissue samples with light microscopy. Acute renal injury was assessed with biochemical analyses, scintigraphic imaging, and histopathological evaluation. Results: In the cisplatin group, the levels of BUN, creatinine, and cystatin C were significantly higher than that of the controls. Histopathological examination showed remarkable damage of tubular and glomerular structures. Additionally, cisplatin caused markedly decreased renal 99mTc-DMSA uptake. AGM administration improved renal functions. Serum creatinine, BUN, and cystatin C levels had a tendency to normalize and, scintigraphic and histopathological findings showed significantly less evidence of renal toxicity than those observed in animals receiving cisplatin alone. Conclusions: Our data indicate that AGM has a protective effect against cisplatin-induced nephrotoxicity. Therefore, it may improve the therapeutic index of cisplatin. In addition, the early renal damage induced by cisplatin and protective effects of AGM against cisplatin nephrotoxicity was accurately demonstrated with 99mTc-DMSA renal scintigraphy. © 2016 Informa UK Limited, trading as Taylor & Francis Group Daha fazlası Daha az

The synthesis and characterization of novel quinone-amine polymers from the reactions of 2,3-dichloro-1,4-naphthoquinone and polyoxypropylenediamines

Ayla-Şahinler, Ayla | Bahar, Hakan | Yavuz, Şenol | Hazer, Baki | İbiş, Cemil

Article | 2016 | Phosphorus, Sulfur and Silicon and the Related Elements191 ( 3 ) , pp.438 - 443

A series of novel N-and N,N'-bis(quinonyl)amines were synthesized from the reactions of 2,3-dichloro-1,4-naphthoquinone (1) and polyoxypropylenediamines. The novel quinone-amine polymers were treated with some thiols in next step and N,S-substituted compounds were obtained. The structures of the novel products were characterized by micro-analysis, 1H NMR, UV-VIS, 13C NMR, and MS. The electrochemical properties of some of the novel amine-quinone polymers derivatives were also investigated by cyclic voltammetry. The number of molecular weight (Mn) of polymer compounds was also determined by Gel Permeation Chromatography (GPC). © 2016 . . .Taylor & Francis Group, LLC Daha fazlası Daha az

Synthesis and characterization of graft copolymers based on polyepichlorohydrin via reversible addition-fragmentation chain transfer polymerization

Öztürk, Temel | Kayğın, Oğuz | Göktaş, Melahat | Hazer, Baki

Article | 2016 | Journal of Macromolecular Science, Part A: Pure and Applied Chemistry53 ( 6 ) , pp.362 - 367

In this study, synthesis of poly(epichlorohydrin-g-methyl methacrylate) graft copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization was reported. For this purpose, epichlorohydrin was polymerized by using HNO3 via cationic ring-opening mechanism. A RAFT macroinitiator (macro-RAFT agent) was obtained by the reaction of potassium ethyl xanthogenate and polyepichlorohydrin. The graft copolymers were synthesized using macro-RAFT agent as initiator and methyl methacrylate as monomer. The synthesis of graft copolymers was conducted by changing the time of polymerization and the amount of monomer-initiator co . . .ncentration that affect the RAFT polymerization. The effects of these parameters on polymerization were evaluated via various analyses. The characterization of the products was determined using 1H-nuclear magnetic resonance (1H-NMR), Fourier-transform infrared spectroscopy, gel-permeation chromatography, thermogravimetric analysis, elemental analysis, and fractional precipitation techniques. The block lengths of the graft copolymers were calculated by using 1H-NMR spectrum. It was observed that the block length could be altered by varying the monomer and initiator concentrations. © 2016 Taylor & Francis Group, LLC Daha fazlası Daha az

Antimicrobial effect of polymer-based silver nanoparticle coated pedicle screws: Experimental research on biofilm inhibition in Rabbits

Hazer, Derya Burcu | Sakar, Mustafa | Dere, Yelda | Altınkanat, Gülşen | Ziyal, M. İbrahim | Hazer, Baki

Article | 2016 | Spine41 ( 6 ) , pp.362 - 367

Study Design. Antimicrobial effect of a novel silverimpregnated pedicle screw in rabbits. Objective. A novel spine implant model was designed to study the antimicrobial effect of a modified Titanium (Ti) pedicle screws with methicillin-resistant Staphylococcus aureus (MRSA) in multiple surgical sites in the lumbar spine of a rabbit. Summary of Background Data. Infection in spinal implant is of great concern. Anti-infection strategies must be tested in relevant animal models that will lead to appropriate clinical studies. Methods. Fourteen New Zealand white rabbits were divided into 2 groups: group 1: infected unmodified Ti screw gro . . .up (n=6), and group 2: infected polyethylene glycol grafted, polypropylene-based silver nanoparticle (PP-g-PEG-Ag) covered Ti screw group (n=6), and 2 rabbits as sterile (sham-operated and control) group. In all groups, left L4-right L6 vertebra levels were exposed and screws were drilled to transverse processes after contamination of burr holes and surrounding tissue with 0.1mL of 106 colony forming units (CFU) MRSA solutions in groups 1 and 2. After 21 days, samples were collected and infection was analyzed via light and scanning electron microscopy and culturing. Silver nanoparticles (Ag-NP) on the screws and tissues were assayed pre and postoperatively. Results. The bacterial colony count for modified-Ti screw group was lower than for unmodified Ti screw (17.2 versus 200 x 103 CFU/mL, P=0.029) with less biofilm formation. There was no difference in duration of surgery among groups and within the surgical sites. Ag-NPs were detected on the screw surface postoperatively. Conclusion. This novel experimental design of implantation in rabbits is easy to apply and resembles human stabilization technique. Modified Ti screws were shown to have antimicrobial effect especially inhibiting the biofilm formation. This anchored Ag NPs that remained after 21st day of implantation shows that it is resistant to tapping forces of the screw. © 2016 Wolters Kluwer Health, Inc. All rights reserved Daha fazlası Daha az

One-step synthesis of triarm block copolymers by simultaneous atom transfer radical and ring-opening polymerization

Öztürk, Temel | Yavuz, Mahmut | Göktaş, Melahat | Hazer, Baki

Article | 2016 | Polymer Bulletin73 ( 6 ) , pp.1497 - 1513

One-step synthesis of poly(MMA-b-CL) triarm block copolymers was carried out by atom transfer radical polymerization of methyl methacrylate (MMA) and ring-opening polymerization of ?-caprolactone (CL) using 3-chloro-1,2-propanediol trifunctional initiator. The triarm block copolymers comprising one poly-MMA arm and two poly-CL arms were synthesized by changing some polymerization conditions such as monomer/initiator concentration, polymerization time. The effect of the reactions conditions on the polydispersity and molecular weights was also investigated. The block lengths of the block copolymers were calculated by using 1H-nuclear . . .magnetic resonance (1H-NMR) spectrum. It was observed that the block length could be altered by varying the monomer and initiator concentrations. The characterization of the products was achieved by using 1H-NMR, Fourier-transform infrared spectroscopy, gel-permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and fractional precipitation techniques. © 2015, Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

Simultaneous localization and mapping of mines with unmanned aerial vehicle [Insansiz Hava Araci ile Maden Ocaginin Es Zamanli Konum Belirleme ve Haritalandirilmasi]

Altan, Aytaç | Bayraktar, Köksal | Hacıoğlu, Rıfat

Proceedings | 2016 | 2016 24th Signal Processing and Communication Application Conference, SIU 2016 - Proceedings , pp.1433 - 1436

In this stuidy, the position information from ultrasound sensors on UAV related to floor gallery mine passed through the filter, it is aimed to control the position of simultaneously creating the optimum environmental map. The simultaneous in galleries made mapping, mine the data of air to the designated central monitoring system with real-time location information is transmitted to the ventilation system, which is intended to more effectively work in the mines. The gallery maps which simultaneous location and mapping information obtained by UAV Extended Kalman Filter algorithms processed were obtained experimentally. © 2016 IEEE.

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

Electrochemical, continuous-flow determination of p-benzoquinone on a gold nanoparticles poly(propylene-co-imidazole) modified gold electrode

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

Article | 2016 | Instrumentation Science and Technology44 ( 6 ) , pp.614 - 628

A novel continuous flow biosensor based on gold nanoparticles and poly(propylene-co-imidazole) was developed for the online determination of p-benzoquinone. The amperometric response was measured as a function of p-benzoquinone concentration at an applied potential of -50 mV. The hydrogen peroxide concentration was optimized and fixed at 1 mM in samples. The mass transfer resistance of the copolymer film was minimized, and the flow cell was regenerated quickly at 1 mL/min. The resulting device provided good analytical performance based on a linear dynamic range from 5–100 µM, a short response time of 3 s, a detection limit of 3.3 µM . . ., excellent repeatability with a relative standard deviation of 0.82%, long-term stability of 95% after four weeks, and an accuracy of 105%. The gold nanoparticles enhanced the electron transfer rate on the electrode. The apparent Michaelis-Menten constant was 4 mM, showing that the enzyme retained catalytic specificity and provided high activity for p-benzoquinone. © 2016, Taylor & Francis Daha fazlası Daha az

Comparison of the efficiencies of buffers containing ankaferd and chitosan on hemostasis in an experimental rat model with femoral artery bleeding

Abacıoğlu, Serkan | Aydın, Kemal | Büyükcam, Fatih | Kaya, Ural | Işık, Bahattin | Karakılıç, Muhammed Evvah

Article | 2016 | TURKISH JOURNAL OF HEMATOLOGY33 ( 1 ) , pp.48 - 52

Objective: In the first assessment of trauma patients with major vascular injuries, we need effective and rapid-acting homeostatic materials. In this study we compare the efficiencies of Ankaferd Blood Stopper (R) and a chitosan linear polymer (Celox (R)) in an experimental rat model with femoral artery bleeding. Materials and Methods: Thirty male Wistar albino rats weighing 200250 g were divided into 3 groups: control, Ankaferd, and chitosan. The femoral artery and vein were visualized and bleeding was started by an incision. The bleeding time was recorded and categorized as 'bleeding stopped at the second minute', 'bleeding stoppe . . .d at the fourth minute', and 'unsuccessful' if bleeding continued after the fourth minute. Results: In the control group, 60% of the bleeding did not stop. In the first 4 min in the Ankaferd group, the bleeding stopped in all rats; only in 1 of the rats in the chitosan group did the bleeding not stop. In stopping the bleeding in the first 4 min, Ankaferd was similar to chitosan but better than the control group; the chitosan group was similar to the control, but the p-value was close to significance. Conclusion: For major arterial bleeding, the main treatment is surgical bleeding control, but outside of the hospital we can use buffers containing Ankaferd and chitosan on the bleeding region. The results of this study should be supported with larger studies. Furthermore, in our study, healthy rats were used. New studies are needed to evaluate the results of hypovolemic and hypotensive cases with major artery bleeding Daha fazlası Daha az

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