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Öğe Analysis of Polycrystal Acrylamide by Electron Spin Resonance and Thermo-Analytical Methods(WILEY-BLACKWELL, 2011) Usta, Ayhan; Filiz, Ali; Birey, Mehmet; Ozmen, AyhanElectron spin resonance (ESR), thermogravimetry analysis (TGA), and differential thermal analysis (DTA) were performed on acrylamide (C(3)H(5)NO) polycrystal samples. The samples were irradiated at 298 K for 24, 48, 72, and 96 h using (60)Co - gamma source. ESR measurements were carried out between 120 and 450 K. The ESR signals were recorded from the samples exposed to (60)Co - gamma rays for 72 and 96 h. Between 120 and 450 K the spectra changed in a manner roughly. It was detected by means of e.s.r. spectra that unpaired electron took place due to scission of pi bond in the carbon-carbon double bonds in the substance. The produced radiation damage center on the sample was attributed to center dot CH(2)-CH-R Additionally, thermal behavior of the acrylamide samples were investigated by using TGA and DTA methods. It was observed that both irradiated and not irradiated samples decomposed at three steps. (C) 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part A 38A: 102-106, 2011.Öğe Bazı manyetik momente sahip moleküler sistemlerin manyetik rezonans parametrelerinin elektron paramanyetik rezonans ile incelenmesi(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2005-07-01) Usta, Ayhan; Zengin, MehmetBu çalışmada gama ışınlarına tutulan Benzo[c]cinnoline ve 2,4-dinitroklorbenzen tek kristallerinin elektron paramanyetik rezonansı gözlendi ve manyetik alandaki kristallerin farklı doğrultulan için alman spektrumlar analiz edildi. EPR parametreleri bulundu. Benzo[c]cinnoline tek kristalleri 130-450.K sıcaklık aralığında incelendi ve benzo[c]cinnoline kristalinin EPR spektrumunun sıcaklığa bağlı olduğu bulundu.Öğe Bazı monomer ve polimer yapıların elektron paramanyetik rezonans tekniği ile incelenmesi(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2010) Usta, Ayhan; Özmen, Ayhan; Birey, MehmetBu çalışmada, bazı monomer ve polimerlerin 60Co- ? radyasyonuna maruz bırakıldıktan sonra EPR (Elektron Paramanyetik Rezonans) ölçümleri, X-band EPR spektrometresi kullanılarak alındı. Seçilen monomer ve polimer örneklerin gama ışınlarına maruz bırakılarak ve aynı örneklerin ışınlanmadan alınan EPR spektrumları incelendi. Alınan spektrumların analizi sonucunda, incelenen numunelerin EPR parametreleri bulundu. Ayrıca yapılarda bulunan paramagnetik merkezlerin EPR parametrelerinin sıcaklığa (120-450.K) ve manyetik alanın yönüne bağlı olarak değişimi EPR spektrumları yardımıyla ile incelendi.Öğe Determination of free radical on polycrystal of 4,4 '-bis(chloroacetyl)diphenylether: An ESR study(ELSEVIER SCIENCE BV, 2013) Ceylan, Yusuf; Usta, Ayhan; Usta, Keziban; Durmaz, Fatih; Coskun, Ahmet4,4'-Bis(chloroacetyl)diphenylether was synthesized and its polycrystal form was produced. This polycrystal sample was irradiated by gamma rays (Co-60) for 72 h. The ESR method was used to observe formation of free radical on the sample. ESR signal was not recorded from the non-irradiated sample, but the irradiated polycrystal sample exhibited complex ESR spectra. The measurements were carried out in the temperature range of 120-450 K. It was observed that the shape of the spectrum was dependent on the temperature. Two identical radicals were determined on the irradiated sample. Respectively, the spin density, hyperfine, and g values were found to be rho(Ha) = 0.53, rho(Hb) = 0.23, a(Cl) = 1.263 mT, a(Ha) = 1.486 mT, a(Hb) = 0.637 mT, and g(1) = 2.0115 for the Radical rho(Hx) = 0.22, rho(Hy) = 0.14, a(Cl) = 0.905 mT, a(Hx) = 0.615 mT, a(Hy) = 0.391 mT, and g(2) = 2.0383 for the Radical II. (C) 2013 Elsevier B.V. All rights reserved.Öğe Effect of irradiation on ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate: an ESR study(WILEY-BLACKWELL, 2012) Usta, Ayhan; Birey, Mehmet; Sari, Nursen; Altundas, Aliye; Nartop, DilekEthyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate [C11H15NO2S] was synthesized by the Gewald method. Its single crystals were grown from an alcohol/ethyl acetate solution at 15 degrees C and characterized using IR and 1H-NMR. These single crystals were irradiated for 72h at 298K by a 60Co gamma source with a dose speed of 0.864kGy/h. After irradiation, electron spin resonance (ESR) measurements were carried out to study radiation-induced radicals in the temperature range from 120 to 450K. Additionally, for the single crystal, ESR angular dependencies were measured in the xy, xz and yz planes of the substance. This irradiated single crystal was analyzed based on the ESR spectra. Analysis of the spectra revealed that the radical was formed by a CH bond fission at the carbon end of the substance. It was also observed that the color of the sample changed after irradiation. The hyperfine and g parameters were determined from the experimental spectra. It was inferred from these results that the hyperfine parameters and g value exhibited anisotropic behavior. The average values of these parameters were calculated as follows: g=2.0088, AH1=H2=20.70G, AH3=H4=10.80G, AHa=4.59G, AHb=3.24G and, AN=6.10G. Copyright (c) 2011 John Wiley & Sons, Ltd.Öğe An EPR Study On Cytosine Irradiated(WILEY, 2011) Usta, Ayhan; Vural, Hasibe Cingilli; Usta, Keziban; Aras, Erdal; Ceylan, Yusuf; Ozmen, AyhanIn this study, paramagnetic centers over the cytosine were formed by photolysis then these centers were investigated using EPR method. EPR signals were not recorded from non-irradiated the cytosine, but irradiated polycrystalline exhibited complex EPR spectra. For obtaining of cytosine polycrystalline, novel crystallization method was performed on powder cytosine. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial asetic acid, nitric oxide, percloric acid, glutamic acid, and pH of buffer. Cytosine (C4H5N2O) polycrystalline obtained were irradiated with Co-60 - rays at room temperature for 24 and 72 h. At the sample irradiated for 72 h, the paramagnetic centers were determined between 120 and 450 K by X-band EPR spectrometer. The spectra were found to be dependent slightly on temperature. Two cation radicals were determined in the structure and these were called Radicals I and II. The g and hyperfine constants were found to be a(H2a) = 61 G, a(N2) = 9.39 G, a(N1) = 7.15 G, and g(1) = 2.0026 for the Radical I; a(H3) = 10.57 G, a(H1) = 3 G, a(N3) = 6.72 G, a(N1) = 5.36 G for, and g(2) = 2.0034 the Radical II. Copyright (C) 2010 John Wiley & Sons, Ltd.Öğe An EPR study on irradiated 4-(1,3,5-triazin-2-yloxy)cyclohexanecarbaldehyde single crystal(ELSEVIER SCIENCE BV, 2011) Usta, Ayhan; Ozmen, Ayhan; Birey, MehmetThe single crystals of 4-(1,3,5-triazin-2-yloxy)cyclohexanecarbaldehyde [C(10)H(13)N(3)O(2)] were produced by slow evaporation of a concentrated ethyl acetate solutions. These single crystals were exposed to (60)Co gamma rays with dose speed of 0.980 kGy/h at the room temperature for 48 and 72 h. The free radical of the sample was observed using EPR-X band spectrometer.The EPR spectra were recorded between 120 and 450 K. The sample irradiated for 72 h was rotated in steps of 10 degrees and analysed for different orientations of the crystal in the magnetic field. The hyperfine constants of the sample were found to be anisotropic. The average values of these constants were calculated as following: g = 1.9979, a(H1) = 10.75 G, a(H2) = 2.28 G, and a(N) = 3.83 (C) 2010 Elsevier B.V. All rights reserved.Öğe An EPR study on single crystals of dimethyl-1,3-cyclohexanedione by gamma-rays(TAYLOR & FRANCIS LTD, 2012) Aras, Erdal; Usta, Ayhan; Erturk, Serkan; Asik, BiraySingle crystals of dimethyl-1,3-cyclohexanedione (C8H12O2) were produced by slow evaporation of the concentrated ethyl acetate solutions. These single crystals were exposed to Co-60 gamma-rays with a dose speed of 0.950 kGy/h at room temperature for 24, 48, and 72 h. The free radicals of the samples irradiated for 48 and 72 h were detected using electron paramagnetic resonance (EPR)-X-band spectrometer. EPR measurements were performed between 120 and 300 K. The sample irradiated for 48 h by gamma-rays was rotated in steps of 10 degrees at 298 K. The spectrum parameters were found to be dependent on the temperature. Two radicals were determined in the molecular structure irradiated. These radiation damage centers were called R1 and R2. The average values of g and the hyperfine coupling constants were calculated as follows: a(Ha) = 6.84 G, a(Hb) = 3.60 G, g = 2.0040 for R1, a(H) = 28 G, g = 2.0062 for R2.Öğe IDENTIFICATION OF RADICAL STRUCTURE IN 2,4-DINITROCHLOROBENZENE SINGLE CRYSTAL BY EPR(EDITURA ACAD ROMANE, 2011) Usta, Ayhan; Zengin, Mehmet; Birey, MehmetThe single crystals of the 2,4 dinitrochlorobenzen were grown by slow evaporation of concentrated ethanol solution. Some of these single crystals exposed to Co-60-gamma rays with dose rate of 0.880 kGy/h at room temperature for 48 and 72 h. The EPR spectra were recorded as a function of temperature and orientations of the single crystal in the magnetic field. The single crystal irradiated for 72 h was rotated in steps of 100 in three mutually perpendicular planes in the magnetic field. The ESR temperature measurements were performed between 120 K and 440 K. The spectra recorded were found to be dependent on the temperature and the orientations of the crystal. It was also detected that only a radical structure and color centers were occurred after irradiation. The average values of g and hyperfine coupling constants were calculated as follow: a(Na=Nb)=13.70 G, a(H1=H2)=8.95 G, a(H3)=7.06 G, g=2.0039.Öğe Identification of radical structures on 1-pentamethylbenzyl-3-ethylimidazoliumsilver(I)bromide and 1,3-bis(pentamethylbenzyl)-4,5-dimethylbenzimidazoliumsilver(I)bromide exposed to gamma rays: an EPR study(WILEY, 2016) Ceylan, Yusuf; Usta, Keziban; Kunduracioglu, Ahmet; Usta, Ayhan; Cetinkaya, Bekir1-Pentamethylbenzyl-3-ethylimidazoliumsilver(I)bromide and 1,3-bis(pentamethylbenzyl)-4,5dimethylbenzimidazoliumsilver(I)bromide and their Ag+ complexes were synthesized and their polycrystal forms were produced by recrystallization in dichloromethane/Et2O solvent system. Structural determinations were carried out by H-1 NMR and C-13 NMR with a Varian 400 NMR system using tetramethylsilane as internal standard and CDCl3 as solvent. The disappearance of acidic N-heterocyclic carbene proton showed the formation of Ag(I) complexes. Also, elemental analyses were carried out. Electron paramagnetic resonance (EPR) measurements were performed to determine the formed radical structure on the samples irradiated at the room temperature for 72h by using Co-60-source with dose rate of 0.680kGy. The EPR measurements were carried out in the temperature range of 200K-450K. Identical radicals were determined on the irradiated compounds. It was observed that the shapes of the spectra of the samples were independent of the temperature but, the resonance line intensities changed linearly with the temperature. Also, it was detected that the free radical on the 1-pentamethylbenzyl-3-ethylimidazoliumsilver(I)bromide is not stable compared to that on the 1,3-bis(pentamethylbenzyl)-4,5dimethylbenzimidazoliumsilver(I)bromide. Copyright (c) 2016 John Wiley & Sons, Ltd.Öğe Investigation of irradiated 1H-Benzo[b] pyrrole by ESR, thermal methods and learning algorithm(TAYLOR & FRANCIS LTD, 2016) Algül, Gülay; Ceylan, Yusuf; Usta, Keziban; Aydoğmuş, Hacer Yumurtacı; Usta, Ayhan; Aşık, Biray1H-Benzo[ b] pyrrole samples were irradiated in the air with gamma source at 0.969 kGy per hour at room temperature for 24, 48 and 72 h. After irradiation, electron spin resonance, thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements were immediately carried out on the irradiated and unirradiated samples. The ESR measurements were performed between 320 and 400 K. ESR spectra were recorded from the samples irradiated for 48 and 72 h. The obtained spectra were observed to be dependent on temperature. Two radical-type centres were detected on the sample. Detected radiation-induced radicals were attributed to R-+center dot NH and R=(center dot)CC2H2. The g-values and hyperfine constants were calculated by means of the experimental spectra. It was also determined from TGA spectrum that both the unirradiated and irradiated samples were decomposed at one step with the rising temperature. Moreover, a theoretical study was presented. Success of the machine learning methods was tested. It was found that bagging techniques, which are widely used in the machine learning literature, could optimise prediction accuracy noticeably.Öğe Screening of free radical formation in crystals of guanosine by ESR study(ELSEVIER SCIENCE BV, 2011) Usta, Ayhan; Vural, Hasibe Cingilli; Asik, Biray; Usta, KezibanIn this study, to obtain guanosine polycrystalline, novel crystallization method was performed on powder guanosine material. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial acetic acid, nitric oxide, perchloric acid, glutamic acid, and pH of buffer. Behaviors of the guanosine polycrystal samples exposed to high-energy values were investigated using ESR method. The polycrystal samples were exposed to gamma-rays for 48 and 72 h. ESR signals were not recorded from the non-irradiated sample and the sample irradiated for 48 h, but the polycrystalline sample irradiated for 72 h exhibited complex ESR spectra. ESR measurements were taken on the irradiated sample in temperature range from 300 to 450 K. On the basis of all these measurements dependence temperature, it can be said that the shape of the spectrum was to be dependent on temperature slightly. Hence, we assume that the radical structure occurred was resistance to high temperature. Two radicals were determined in the structure irradiated and these were called radical I and radical II. The g, hyperfine constants, and spin density were found to be rho = 0.96, a(NNH)(N) = 2.7 mT, a(NNH)(N) = 1.155 mT, a(N) = 0.35 ml and g(1) = 2.0093 for the radical 1; a(N) = 4.7 ml and g(2) = 2.0094 for the radical II. (C) 2011 Elsevier B.V. All rights reserved.Öğe X-band EPR study on benzo[c]cinnoline single crystals(TAYLOR & FRANCIS LTD, 2007) Usta, Ayhan; Zengin, Mehmet; Olmez, Oznur; Birey, MehmetThe benzo[c]cinnoline compound has been crystallized in ethanol solution. These crystals have been irradiated with Co-60 gamma-rays at room temperature. The crystals have been investigated by an X-band electron spin resonance (ESR) spectrometer two days after irradiation. Very strong ESR peaks have been observed at the temperatures between 130 and 430 K. However, a line broadening has been observed at 130K. Also analyses found that EPR specra are temperature-dependent and show anisotropic behaviour.
