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Öğe Effects of foliar iron oxide nanoparticles (Fe 3 O 4 ) application on photosynthetic parameters, distribution of mineral elements, magnetic behaviour, and photosynthetic genes in tomato ( Solanum lycopersicum var. cerasiforme) plants(Elsevier France-Editions Scientifiques Medicales Elsevier, 2024) Tombuloglu, Guzin; Tombuloglu, Huseyin; Slimani, Yassine; Almessiere, Munirah A.; Baykal, Abdulhadi; Bostancioglu, Safiye Merve; Kirat, GokhanThis study aims to examine the effect of foliar magnetic iron oxide (Fe 3 O 4 ) nanoparticles (IONP) application on the physiology, photosynthetic parameters, magnetic character, and mineral element distribution of cherry tomatoes ( Solanum lycopersicum var. cerasiforme ). The IONP suspension (500 mg L -1 ) was sprayed once (S1), twice (S2), thrice (S3), and four times (S4) a week on seedlings. Upon 21 days of the treatments, photosynthetic parameters (chlorophyll, carotenoids, photosynthetic yield, electron transport rate) were elucidated. Inductivelycoupled plasma -optical emission spectrometer (ICP-OES) and vibrating sample magnetometer (VSM) were used to determine the mineral elements and abundance of magnetic power in the seedlings. In addition, the RTqPCR method was performed to quantify the expressions of photosystem-related ( PsaC , PsbP6 , and PsbQ ) and ferritin-coding ( Fer-1 and Fer-2 ) genes. Results revealed that the physiological and photosynthetic indices were improved upon S1 treatment. The optimal dosage of IONP spraying enhances chlorophyll, carotenoid, electron transport rate (ETR), and effective photochemical quantum yield of photosystem II (Y(II)) but substantially diminishes non -photochemical quenching (NPQ). However, frequent IONP applications (S2, S3, and S4) caused growth retardation and suppressed the photosynthetic parameters, suggesting a toxic effect of IONP in recurrent treatments. Fer-1 and Fer-2 expressions were strikingly increased by IONP applications, suggesting an attempt to neutralize the excess amount of Fe ions by ferritin. Nevertheless, frequent IONP treatment fluctuated the mineral distribution and caused growth inhibition. Although low -repeat foliar applications of IONP (S1 in this study) may help improve plant growth, consecutive applications (S2, S3, and S4) should be avoided.Öğe Enhancement of magnetic relaxation behavior by texturing in Bi-2212 superconducting rods(Elsevier Sci Ltd, 2016) Ozabaci, Murat; Kizilaslan, Olcay; Kirat, Gokhan; Aksan, Mehmet A.; Madre, Maria A.; Sotelo, Andres; Yakinci, Mehmet E.Time decay of magnetization, known as magnetic relaxation, is crucial for both fundamental and applied point of view in bulk high temperature superconductors (HTS) by setting the limits to the HTS devices stability. Melt-processed Bi2Sr2Ca1Cu2-xGa8+delta rods (Bi-2212, x=0,0.1) were used to study the effect of both grain alignment and substitution on the samples critical current density, relaxation and pinning behavior. The magnetic field has been applied both perpendicular and parallel to the rods growth axis to determine the effect of grain alignment. It has been found that Ga substitution reduces grains orientation and sizes leading to lower magnetic properties. The peaks of the curves, which indicate the temperature dependence of the samples magnetic relaxation rate (S), have been observed in the 7-35 K temperature range. Characteristic pinning energy (U-e/k(B)) of samples was determined using the formalism developed by Maley. The change of pinning energy as a function of magnetization has been found to be exponential between 3 and 60 K, which is in agreement with the collective creep theory. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe GMI-based biosensor for the detection and quantification of doxorubicin anticancer drugs labeled to Fe3O4 superparamagnetic nanoparticles(Elsevier Science Sa, 2024) Kirat, Gokhan; Erdogan, Ali; Aksan, Mehmet AliWe present the results of research on a Co -based giant magnetoimpedance (GMI) biosensor for Fe 3 O 4 -labelled doxorubicin (DOX) anticancer drugs. Co 62 Fe 5 Ni 4 Si 15 B 14 ribbons were used as biosensing material for test solutions containing different concentrations of DOX. The plain ribbon, ribbon +Fe 3 O 4 and ribbon +DOX2 samples exhibited low coercivity ( H c ), high saturation magnetization ( M s ) and low anisotropy ( H k ). The GMI ratio ( Delta Z / Z ) increased from 33% to 38% with the increase of doxorubicin content in the ribbon. It was found that the Delta Z / Z ratio first increased rapidly up to a frequency of -2 MHz, and then decreased slowly as the frequency increased. While the magnetic field dependent Delta Z / Z has a single peak at 1 MHz, it has a double peak at 5 MHz. It was found that the peak height of Delta Z/Z in the ribbons with test solution of 20 ng/ml and 50 ng/ml increased by -3% and -6%, respectively, compared to the ribbon without test solution. Then the Delta Z / Z ratio decreased very rapidly with the increase of the applied external magnetic fields. The frequency -dependent GMI sensitivity ( eta) increased with increasing frequency and reached a maximum value at a critical frequency (-1.6 MHz), after which it decreased. The detection sensitivity of the GMI biosensor ( xi ) increased rapidly with increasing doxorubicin concentration up to -80 ng/ml and then remained almost unchanged. The results show that doxorubicin (DOX +Fe 3 O 4 ), used as an anticancer drug, can be effectively detected even at low concentrations using the GMI based sensors fabricated in this study.Öğe Improving the Magnetocaloric Performance of NiMnSnB Heusler Alloys with V Substitutions(Springer, 2022) Kirat, GokhanThe effects of V addition on the structural, magnetic, and magnetocaloric properties in Ni49-xVxMn37Sn12B2 (x = 0, 1, 2, and 3) alloys were investigated. XRD analyses performed at room temperature showed that the main sample was in martensite phase, while x = 3 sample was in L2(1) structure which is attributed to austenite phase. The samples exhibited a first-order structural transformation from austenite phase to martensite phase. The martensitic transformation (MT) temperature was reduced by increasing the amount of V. Besides, V doping caused an increase in magnetization. Although antiferromagnetic interactions arising from Mn-Mn couplings were effective at low temperatures, they vanished above the blocking temperature. Magnetic entropy change (Delta S-M) of the samples was estimated using the Maxwell equation from isothermal magnetization curves. An inverse magnetocaloric effect was observed around the MT interval and Delta S-M was significantly improved with increasing V content and applied magnetic field. Maximum refrigerant capacity (RC), which is one of the quality parameters for characterizing a magnetic refrigerant, was determined as 96.7 J/kg for x = 3 samples (Delta H = 5 T).Öğe Investigation of magnetic and electrical properties in the Mo-substituted Ni-Mn-Sb Heusler alloys(Springer, 2023) Ayyildiz, Murat; Kirat, Gokhan; Aksan, Mehmet AliIn this study, Heusler alloys with nominal composition of Ni50-xMoxMn37Sb13+B2 (x = 0, 1, 3, 5, and 7) were synthesized by the arc-melting method. In the samples with low Mo-content, 4O and 10 M phases were obtained, indicating the presence of the martensite phase, while in the samples with high Mo-content, the L21 phase was determined, which is attributed to the austenite structure. The samples showed a two-step transition between T1 and T2 temperatures in the temperature dependent magnetization measurements, which is attributed to a premartensitic transformation. It was observed that the interval T1-T2 decreased with the increase of Mo-content in the system. It was found that there was an increase in magnetization value due to Curie transition around 350 K in x = 0 and x = 1 Mo-substituted samples, but there was no such increase between 5 and 360 K for other samples. It was found that the blocking temperature (TB) was affected by the Mo-substitution. The thermal hysteresis between the M-T curves during cooling and heating indicates a first-order phase transition in the samples. It is evident from both the M-T and rho-T analyses that the MT temperatures shifted to low temperatures as the Mo-content increases. An exchange bias effect was observed in the samples. increment SM with a positive sign was determined for all samples, reaching a maximum value around MT temperature. The maximum increment SM was obtained at a magnetic field of 5 T at 255 K in the x = 3 Mo-substituted sample. Similarly, the highest RC, AHL and RCeff values were also found for the x = 3 Mo-substituted sample.Öğe Investigation of martensitic transformation and magnetoresistance properties of cu-substituted Ni-Mn-Sn-B melt spun ribbons(Elsevier, 2021) Kirat, Gokhan; Aksan, Mehmet AliNi-50-xCu(x)Mn(38)Sn(12) + B3% at (x = 0, 1, 3 and 5) melt spun ribbons have been fabricated by melt spinning technique. Structural, electrical and magnetoresistance properties of the ribbons were investigated in this study. It was identified that the austenite phase with the L2(1) type structure was formed in the ribbons, regardless of composition. Temperature dependence of resistance measurements exhibited the first order martensite transition in the ribbons. The largest negative magnetoresistance (similar to 55%) was obtained at 262 K in the RB1 ribbon. Depending on the Cu-content and magnetic field, a noticeable shift of martensite transition temperature to low temperatures has been clearly observed. From magnetic field dependence of the resistance, it was seen that the resistances dropped sharply with the increase of the applied magnetic field and overlapped near 80 kOe, regardless of temperatures, which strongly indicates the magnetic field-induced martensite-austenite transition.Öğe Investigation on the transport and magnetism properties of the boron-substituted NiMnSb(Springer, 2023) Kilic, Gokhan; Abboosh, Omar; Kirat, Gokhan; Aksan, Mehmet Ali; Aydogdu, Ayse; Aydogdu, YildirimWe fabricated Ni46Mn41Sb13-xBx (x = 0, 1, 2, 3 and 4) (at.%) Heusler alloys using arc melting method and studied the electronic and magnetic properties of the alloys. It was seen that the martensite transformation temperatures shifted to higher temperatures with increasing the B-content in the system. It was found that for x less than 2, the alloys were in the austenite phase at the room temperature. However, when x is larger than 2, the crystal structure changed and a transformation to a martensite phase has occurred at room temperature. There were significant changes in lattice constants by boron substitution, which influenced the electrical and magnetic properties of the alloys. These changes are mainly related to the different atomic radius of Sb and B, which changed the atomic arrangement along a-axis. Hysteresis observed between the heating and cooling M-T curves obviously showed a field-induced martensitic transformation (FIMT) in the alloys. While the characteristic magnetization behavior of NiMnSb system was obtained at high magnetic fields, unstable magnetic behavior was observed at low magnetic fields. The boron substitution caused decrease in magnitude of the saturation magnetization (M-sat).Öğe Magnetocaloric Properties of Ni-Rich Ni50-xCoxMn38Sn12B3 Shape Memory Ribbons(Springer, 2021) Kirat, Gokhan; Kizalaslan, Olcay; Aksan, M. AliThe present study presents the magnetocaloric effect (MCE) properties of Ni-rich Ni50-xCoxMn38Sn12B3 (x = 0, 1, 3, 5) ribbons during both heating and cooling processes. The Co substitution caused an increase of magnetization difference Delta M and hence an improvement of the MCE. An inverse giant magnetocaloric effect (IMCE) and a high effective refrigerant capacity RCeff were observed in the x = 3 ribbons. A high amount of Co (x = 5) content led to an inverse magnetic entropy Delta S-M peak with a wide temperature range. Magnetostructural coupling over a wide temperature range is of great importance for technological purposes. On the other hand, the MCE properties were thermal hysteresis dependent, which has to be considered in the technological applications.Öğe Magnetocaloric Properties of Ni-Rich Ni50-xCoxMn38Sn12B3 Shape Memory Ribbons (vol 34, pg 581, 2021)(Springer, 2021) Kirat, Gokhan; Kizilaslan, Olcay; Aksan, M. Ali[Abstract Not Available]Öğe Magnetoresistance properties of magnetic Ni-Mn-Sn-B shape memory ribbons and magnetic field sensor aspects operating at room temperature(Elsevier Science Bv, 2019) Kirat, Gokhan; Kizilaslan, Olcay; Aksan, M. AliIn this study, the magnetotransport properties of the Ni48.95Mn37.74Sn13.32B3 ribbons prepared by melt-spinning technique were investigated in details. The martensitic-austenite phase transition was obtained between 280 K and 285 K which are near the room temperature. From rho-H measurements, it was found that an anomalous Hall effect at 281, 283 and 285 K between M-s (martensite start temperature) and M-f (martensite finish temperature) temperatures is domianant mechanism. It was seen that a voltage variation of 5 mu V (between 0 and 10 kOe) at a constant current of 1 mA is one of the best values found for the Heusler alloys. The rho-H results revealed that the ribbons showed the magnetic field-induced one-way shape memory effect (SME). High voltage change caused by magnetoresistance was reached at a constant current of 100 mA at 298 K. The results suggest that the Ni-Mn-Sn-B ribbon is a potential candidate to prepare a magnetic field sensor operating at the room temperature.Öğe Thermal and structural characterization of the Bi2-xSmxSr2Ca2Cu3O10+ glass-ceramic system(Wiley Periodicals, Inc, 2017) Kizilaslan, Olcay; Kirat, Gokhan; Aksan, Mehmet AliIn this work, investigations on the crystallization and oxidization kinetics of the Sm substituted BiSrCaCuO glass-ceramic system were performed. It has been shown that the Sm ions changed the glassification properties of the BiSrCaCuO system. While fully glass samples were obtained for low Sm-substitution levels (x=0.2 and x=0.4), the Sm containing particles on the surface have grown especially at high Sm-substitution levels (x>0.6) and glassification problem increased. Nonisothermal crystallization kinetics including activation energy for crystallization, E-a, and Avrami parameter, n, of the samples prepared was investigated using differential thermal analysis (DTA) at four different uniform heating rates. The values of glass transition temperature and crystallization temperature exhibited compositional and heating rate dependence. E-a value of the samples showed an increase with increasing the Sm concentration. The Avrami parameter, n, was found approximately 4.5, suggesting the growth of small particles with an increasing nucleation rate. The calculated values of the oxidization rates and the activation energy for oxygen out-diffusion process, E, indicated that the oxygen deficiencies by the Sm substitution in the unit cell of BiSrCaCuO were formed and more oxygen atoms were absorbed to fill the oxygen deficiencies in the system.
