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https://hdl.handle.net/20.500.12428/2226

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Zonklayan Çift Sistemler
(Türk Astronomi Derneği, 2020) Soydugan, Esin
Bu çalışmada zonklayan bileşenli çift sistemlerde yapılan zonklama çalışmalarının bilime kazandırdıkları ve çift sistemlerde zonklama çalışmalarının neden önemli olduğu üzerinde durulmuştur. Çanakkale Onsekiz Mart Üniversitesi Gözlemevi'nde sıcak bileşeninde ilk defa $\delta$ Scuti türü ışık değişimi belirlenen bir örten çift sistem IO UMa'nın sıcak bileşenin zonklama doğasını ortaya koymak için zonklayan bileşenin zonklama parametreleri, frekans ve mod değerleri belirlenmiştir. Örnek sistem IO UMa'nın sıcak zonklayan bileşeninin dört frekans değeriyle zonklama yaptığı ve genlik oranları ve evre farklarına göre belirlenen \textit{l} değerine göre çapsal olmayan zonklama gösterdiği bulunmuştur. Yer tabanlı yapılan gözlemler sonucunda elde edilen zonklama parametreleriyle, uydu verileriyle elde edilen zonklama parametrelerinin karşılaştırılması yapılmıştır. Kepler uydusunun zonklama çalışmalarına katkıları üzerinde de durulmuştur.
Tailoring the physical properties of ultrasonically spray pyrolyzed SnS thin films with silver doping
(Springer, 2025) Güneş, İbrahim; Sarıca, Emrah; Bilgin, Vildan; Küçükarslan, Ayşe
In this study, the effects of silver (Ag) doping on the structural, morphological, optical, and electrical properties of tin monosulfide (SnS) thin films were investigated. The films, undoped and doped with 3%, 6%, and 9% Ag, were deposited using the ultrasonic spray pyrolysis (USP) technique at a substrate temperature of 350 degrees C. X-ray diffraction (XRD) analysis confirmed a pi-SnS (cubic) structure with (400) preferred orientation for undoped and <= 6% Ag-doped films, while 9% doping induced amorphization due to severe lattice distortions. Morphological analyses revealed smooth, void-free surfaces, with average roughness increasing from 5.8 nm (undoped) to 19.6 nm (9% doping). Optical measurements showed that the band gap widened from 1.84 eV (undoped) to 2.47 eV (9% Ag-doped), and Urbach energy increased from 190 meV to 600 meV. Hall effect measurements confirmed p-type conductivity for all films. Resistivity ranged from 4.34 x 10(5) Omega cm to 9.48 x 10(5) Omega cm, carrier concentration varied between 2.7 x 10(12) cm(-3) and 5.6 x 10(12) cm(-3), while mobility decreased from 3.3 x 10(1) cm(2)/Vs to 2.0 x 10(1) cm(2)/Vs with increasing Ag doping. These findings demonstrate that Ag doping significantly influences the structural and optoelectronic behavior of SnS thin films, making them promising candidates for thin-film solar cells and optoelectronic applications.
A comprehensive investigation of PtNPs/PEI N-GQDs nanocomposite: DFT modeling, anticancer activity, and biosensing applications
(Springer, 2025) Altınok Güneş, Buket; Kırlangıç, Ömer Faruk; Kılıç, Murat; Ketenoğlu, Didem; Aslan, Ayşenur; Kabaş, Sultan Yağmur; Kabaş, Afşar; Kaya, İsmet; Yıldız, Mustafa
This research focuses on the synthesis and characterization of a novel nanocomposite, PtNPs/PEI N-GQDs, utilizing FTIR, UV-Vis, SEM, TEM, XPS, and XRD techniques. The study investigates the cytotoxic, apoptotic, and antiangiogenic effects of the nanocomposite on OVCAR-3 cells, aiming to understand the interplay between nanomaterials and cancer. Additionally, the electrochemical properties of PtNPs/PEI N-GQDs-modified glassy carbon electrodes (GCE) are explored, emphasizing analyses of HOMO-LUMO energy levels and band gap energy. Density Functional Theory (DFT) analysis results further support these findings by providing insights into the electronic structure and energetics of the nanocomposite. The nanocomposite exhibits promising electrochemical behavior, demonstrating high capacitance and sensitivity in glucose detection through cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Selectivity towards glucose among interfering bioanalytes is highlighted, showcasing potential applications in tumor monitoring and diagnosis. Furthermore, the nanocomposite displays significant toxicity against cancer cells, inducing apoptosis and cell cycle arrest. Antiangiogenic effects are also observed, suggesting potential therapeutic benefits. Overall, these findings underscore the multifunctional properties of the synthesized nanocomposite, offering insights into its potential for cancer therapy and biosensor applications for glucose detection in bodily fluids.
First photometric investigation of V517 Cam combined with ground-based and TESS data
(Elsevier, 2025) Alan, Neslihan; Aliçavuş, Fahri; Alpsoy, Mehmet
The observations of eclipsing binary systems are of great importance in astrophysics, as they allow direct measurements of fundamental stellar parameters. By analysing high-quality space-based observations with ground-based photometric data, it becomes possible to detect these fundamental parameters with greater precision using multicolour photometry. Here, we report the first photometric analysis results of the V517 Cam eclipsing binary system by combining the Transiting Exoplanet Survey Satellite ( TESS ) light curve and new CCD observations in BVRI filters, obtained with a 60 cm robotic telescope (T60) at the T & Uuml;B & Idot;TAK National Observatory. By means of photometric analyses, the masses and radii of the primary and secondary stars were carefully determined to be M1 = 1.47 +/- 0.06 M ae, M2 = 0.79 +/- 0.05 M ae, and R1 = 1.43 +/- 0.03 R ae, R2 = 0.75 +/- 0.04 R ae, respectively. Furthermore, the distance to V517 Cam was calculated to be 284 +/- 20 pc. The overall age of the system is estimated to be around 63 +/- 15 Myr. At this age, the primary component stands near the onset of its main-sequence evolution, near the ZAMS, whereas the secondary component remains in the pre-main- sequence evolutionary phase. To better understand the evolutionary status and nature of V517 Cam, the mass ratio and temperature values, obtained with relatively low sensitivity by photometric measurements, need to be confirmed by spectral analysis.
Understanding Primary Charge Separation and Revealing Fermi's Golden Rule in the Heliobacterium Modesticaldum Reaction Center
(Amer Chemical Soc, 2025) Ertürk, Murat; Güneş, Zühra; Aksu, Hüseyin
We investigate the spectroscopic properties and charge transfer (CT) processes in the homodimeric reaction center of Heliobacterium modesticaldum (HbRC), for which we report the first-principles calculation of Fermi's golden rule (FGR) for the first time in the literature. HbRC is the simplest known analogue to other photosystems and consists of the SPP molecule, the adjacent Acc, and key amino acid residues (His537 and Gln458), along with two water molecules. We identify intrapair CT processes within the SPP molecule, which acts as the donor for the simplified model used in this study. We also examine the SPP+Acc- CT processes, where we demonstrate, in agreement with experimental findings, symmetric hole-electron delocalization across both Acc monomers. The calculated forward CT states are lower in energy than the bright states, facilitating electron transfer through a downhill CT reaction pathway. To explore the influence of surrounding molecular pigments on the electronic structure and FGR rate, we use augmented models incorporating nonsymmetrized molecular orientations. Most FGR rates are found to be on the order of picoseconds (ps). All electronic parameters are derived using an optimally tuned screened range-separated hybrid functional within a polarizable continuum model (SRSH-PCM), considering different dielectric constants.
BSN-I: the first in-depth photometric study of seven total-eclipse contact binary systems
(Oxford Univ Press, 2025) Poro, A.; Li, K.; Paki, E.; Baudart, S.; Michel, R.; Wang, L.; Lajus, E. Fernandez; Aliçavuş, Fahri
This is the first in-depth study of seven total-eclipse W Ursae Majoris-type contact binary systems using photometric light curves. The ground-based observations were conducted with four observatories in the Northern and Southern hemispheres. We also used the Transiting Exoplanet Survey Satellite for four target systems. We presented the analysis of orbital period variations of six systems and found that they display parabolic variations. The material transfer rates between the stars of the systems were calculated. Also, the results show that four systems have a long-term increase, while two have a long-term decrease in their orbital periods. We analysed light curves using the PHysics Of Eclipsing BinariEs python code and the Markov chain Monte Carlo algorithm to estimate different parameters of target systems and their uncertainties. Six of the target systems required the addition of a cold or hot star-spot. We estimated absolute parameters using the empirical relationship between the orbital period and the semimajor axis (P-a). According to each component's effective temperature and mass, it was recognized that the studied systems are W subtype. We examined the dynamic stability of two targets, which were low mass ratio contact binary systems. We also showed the evolution of stars in the M-R and M-L diagrams. Finally, we showed that the hotter stars in contact systems have a temperature difference of less than approximate to 400 K compared to the Gaia Data Release 3 temperature report.
Ultrasonically sprayed cobalt oxide thin films: Enhancing of some physical properties by nickel doping
(Elsevier B.V., 2021) Kuş, Esra; Küçükkarslan, Ayşe; Demirselçuk, Barbaros; Sarıca, Emrah; Akyüz, İdris; Bilgin, Vildan
In this study, the effect of Ni doping (3, 6, 9 at%) on structural, optical, electrical and magnetic properties of Co3O4 films was reported. Films were grown at 300 ± 5 °C substrate temperature via ultrasonic spray pyrolysis (USP) technique. The structural analyses showed that undoped and Ni (3%) doped films exhibit an amorphous structure. Ni doping at higher ratios caused the films to have improved crystallinity. Optical band gap values the films were found to be between 2.03 and 2.08 eV with an additional sub-band corresponding to energies varying between 1.35 and 1.46 eV. The electrical conductivity values of the films increased significantly depending on the Ni doping. The hysteresis curves of the films showed that the films have weak ferromagnetic properties. Ni doping significantly improved the structural and electrical properties of Co3O4 films making them suitable materials for technological applications.
New photometric analysis of hot Jupiter: WASP-135b
(Elsevier B.V., 2021) Öztürk, Oğuz; Erdem, Ahmet
We report photometric follow-up observations of WASP-135b obtained using the 1.23-m telescope at Calar Alto Observatory and 1.00-m telescope at TÜBİTAK National Observatory during the 2017 and 2018 observational seasons. Eight new transit light curves of WASP-135b were analyzed with JKTEBOP code. The ratio of the planet radius to radius of host star, fractional radius of host star, and orbital inclination of WASP-135b were found to be 0.138 ± 0.002, 0.181 ± 0.008 and 82.44 ± 0.64 degrees, respectively. Planetary radius of WASP-135b was derived from transit parameters to be 1.075 ± 0.150 RJ. The transit ephemeris of WASP-135b was also updated using the maximum likelihood method (MLM). 165 well-known hot Jupiters (HJs) were selected from the Exoplanet Data Explorer database and the classification of these HJs together with WASP-135b, based on their equilibrium temperatures and Safronov numbers, is discussed.
Einstein-Rosen universe with scalar field in f(R,T) theories
(Elsevier B.V., 2021) Taṣer, Dog̃ukan; Dog̃ru, Melis Ulu
Non-static Einstein–Rosen universe with scalar field is examined via two different selection of f(R,T) models. Firstly, we analyzed Einstein–Rosen universe with scalar field in f(R,T)=R+2f(T) model. Then, we constructed field equations for f(R,T)=f1(R)+f2(R)f3(T) model, as well. For both models, exact solutions of field equations have been attained without considering any approximation or restriction. Whether scalar field corresponds to phantom and/or quintessence scalar field are investigated for each models.
Sol-gel derived ZnO:Sn thin films and fabrication of n-ZnO:Sn/p-Si heterostructure
(Elsevier B.V., 2021) Sarıca, Emrah; Güneş, İbrahim; Akyüz, İdris; Bilgin, Vildan; Ertürk, Kadir
In this work ZnO:Sn thin films were deposited onto glass and p-Si substrates by spin coating of prepared sols which contains different amounts of Zn(CH3COO)2·2H2O and SnCl2 (0, 5, 10 and 15%). Physical properties of ZnO films were examined as a function of SnCl2 in prepared sols. In addition to that, heterostructure examinations were also carried out by depositing all films on p-Si substrates as well. XRD studies revealed that all films have c-axis orientation with crystallite sizes between 38 and 47 nm. AFM and SEM images showed that morphology of the films remarkably deteriorated with the increase in amount of SnCl2 in sol. Optical transmittance and absorbance spectra showed that films have high transmittance and low absorbance in the visible region. Besides, optical band gap increased from 3.27 eV to 3.37 eV. Additional band gap energies were determined for 10% and 15% Sn doped ZnO films. Room temperature photoluminescence spectra for all films were deconvoluted for the evaluation of all emission bands and it was noted that incorporation of SnCl2 into sol led to enhancement of UV-blue emission bands and caused emission bands related to oxygen vacancies to diminish. Four-point-probe measurements revealed that electrical resistivity of ZnO:Sn films increased from 3.20 × 100 Ωcm to 2.82 × 104 Ωcm and diode ideality factor of Ag/ZnO:Sn/p-Si/Au heterostructure was calculated to be in the range of 2.14–4.59 while zero-bias barrier height is in the range of 0.63–0.78 eV.
Design of EM-artifact-free earphone based on the photoacoustic effect
(Elsevier GmbH, 2021) Muşdal, Bengi Derya; Kurt, Mustafa
Electromagnetic interactions between conventional earphones and the electroencephalography (EEG) electrodes used for analyzing brain waves give rise to efficiency problems in neurophysiological studies of auditory perception. Currently used speakers and headphones are electromagnetic devices based on strong magnets. In spite of intensive use of such systems, there has been no effective way to eliminate the electromagnetic artifacts produced by such audio transmitting devices to date. The ability for transferring audible sounds without the use of electromagnetic devices that can affect the EEG signal would open up many innovative possibilities in Audio Technologies. Audible sound transfer over long distances is possible by the photoacoustic effect. In such studies, the modulated optical signal can be converted into an audible signal arising from the absorption of the light energy of relevant molecules. In this study, we propose an earphone based on the photoacoustic effect, and calculated the dB SPL (Sound Pressure Level) values for a spherical cell filled with olive pomace. By the use of the method of Diebold and Westervelt, we theoretically calculated the sound pressure levels for our cell and determined a 60 dB SPL at a sound frequency of 1000 Hz for our preliminary earphone design.
Improvement of electrical characteristics of SnSe/Si heterostructure by integration of Si nanowires
(Elsevier B.V., 2021) Coşkun, Emre; Güllü, H. H.; Emir, C.; Parlak, M.
In this study, the effects of the nanowire geometry on Si wafer substrate were investigated for the SnSe/Si-nanowire heterojunction device and the obtained results were compared with the one fabricated on planar Si surface. Nanowires on Si surface were produced by metal-assisted etching method and the SnSe film layer was deposited by thermal evaporation technique. On both Si and glass surfaces, deposited film shows polycrystalline and single SnSe phase. From optical transmission measurements, optical band gap of this film was determined as 1.36 eV in a good agreement with the literature. All SnSe/Si heterostructures were found in a p-n diode behavior and the ideality factor and series resistance values were calculated as 2.40, 547 Ω, and 3.71, 1.57 × 103 Ω, for SnSe/Si-nanowire and SnSe/Si heterojunctions, respectively. As a result, an improvement in device characteristics concerning the planar Si structure was found by utilizing Si nanowire structure.
Electronic Spectra of C60Films Using Screened Range Separated Hybrid Functionals
(American Chemical Society, 2021) Chakravarty, Chandrima; Aksu, Hüseyin; Maiti, Buddhadev; Dunietz, Barry D.
We study computationally the electronic spectra of C60thin films using the recently developed density functional theory (DFT) framework combining a screened range separated hybrid (SRSH) functional with a polarizable continuum model (PCM). The SRSH-PCM approach achieves excellent correspondence between the frontier orbital’s energy levels and the ionization potential and electron affinity of the molecular systemat the condensed phaseand consequently leads to high quality electronic excitation energies when used in time-dependent DFT calculations. Our calculated excited states reproduce the experimentally main reported spectral peaks at the 3.6-4.6 eV energy range and when addressing excitonic effects also reproduce the red-shifted spectral feature. Notably, we analyze the low-lying peak at 2.7 eV and associate it to an excitonic state.
Construction of One-Range Addition Theorems for Noninteger Slater Functions Using Self-Friction Exponential Type Orbitals and Polynomials
(Maik Nauka/Interperiodica/Springer, 2020) Guseinov, İsrafil İsa; Mamedov, B. A.; Çopuroğlu, E.
The addition theorems of Slater type orbitals (STOs) presented in literature are generally complicated to theoretically examine the electronic structure of atoms and molecules. The computational deficiencies in use of these theorems arise from the separation of integral variables. In this work, to eliminate these calculation efforts, a large number of independent one-range addition theorems for chi-noninteger Slater type orbitals (chi-NISTOs) in terms of chi-integer STOs (chi-ISTOs) is presented by using complete orthogonal basis sets of L-(pi*)-self-friction (SF) polynomials (L-(pi*)-SFPs), psi((pi*))-SF exponential type orbitals (psi((pi*))-SFETOs), L-(alpha*)-modified SFPs (L-(alpha*)-MSFPs), and psi((alpha*))-modified SFETOs (psi((alpha*))-MSFETOs) introduced by one of the authors. Here, pl(*) = 2l + 2 - alpha* and alpha* are the integer or noninteger (alpha* = alpha -infinity < alpha <= 2) or noninteger (alpha* not equal alpha, -infinity < 3) SF quantum numbers based on the Lorentz damping theory. The expansion coefficients of series for the one-range addition theorems are expressed through the analytical relations for the overlap integrals of chi-NISTOs with the same screening parameters. As an application, the calculations of overlap integrals with the different screening constants of (chi)-NISTOs are performed.
Plasma Copolymerization of Thiophene and Pyrrole
(IEEE-Inst Electrical Electronics Engineers Inc, 2011) Göktas, Hilal; Güneş, Taylan; Atalay, Betül; Er, Ali Oğuz; Kaya, İsmet
The copolymerization of thiophene and pyrrole thin films synthesized by using a double discharge technique which has a fast filamentary discharge formed from the superposition of an ordinary low-pressure dc glow discharge and a high-current pulsed one is presented. Quartz glass substrates were coated at a pressure of 0.8 mbar and 19-kV pulsed and 2-kV dc potentials. The analysis of functional groups by FTIR spectrometry showed that the molecular structure of the copolymerized thin films with the filamentary discharge part almost preserves the conventional polymeric structure.
Correction to: Evaluation of incomplete gamma functions using downward recursion and analytical relations
(Springer, 2025) Guseinov, İsrafil İsa; Mamedov, B. A.
Domain wall solutions with quark matter in higher dimensional space-times
(Amer Inst Physics, 2007) Aktaş, Can; Yılmaz, İhsan; Baysal, Hüsnü; Aygün, Melis; Demirel, Canan
In this paper, we have examined quark matter in the perfect form attached to domain walls in the higher dimensional spherical symmetric space-time admitting one-parameter group of conformal motions. For this purpose, we have solved Einstein's field equations for higher dimensional spherical symmetric space-time via conformal motions. Also, we have discussed the features of the obtained solutions.
Polyfluorene Thin Films Synthesized by a Novel Plasma Polymerization Method
(Springer, 2012) Göktaş, Hilal; Mansuroğlu, Doğan; Atalay, Betül; Bilikmen, Sinan; Kaya, İsmet
The synthesis of polyfluorene (PF) thin films by simultaneously superposing a continuous and pulsed discharge and the characterizations of these samples are presented. The double discharge plasma system is constructed by superposing two discharges; namely, a low pressure dc glow one and a high current pulsed one. The fluorene monomer in powder form was vaporized in the system at argon plasma without any modification, at 0.5 mbar operating pressure. The structure of the thin films was investigated via XPS, UV-visible, FTIR, XRD and SEM. The FTIR and the UV-visible results revealed that the fluorene structure was retained at the produced samples. Semi-conducting behavior was established, and upon the iodine doping, the optical energy band gap (E-g) dropped down from 3.7 to 2.4 eV. The morphology of the synthesized PF thin films was amorphous, with granular structures of different sizes depending on the location of the substrate.
Strange quark matter solutions for Marder's universe in f (R, T) gravity with Λ
(Springer, 2016) Aygün, Sezgin; Aktaş, Can; Yılmaz, İhsan
In this paper, we investigate homogeneous cylindrically symmetric Marder's universe in the presence of strange quark matter (SQM) source in f (R, T) gravity with cosmological constant Lambda. For this aim we have used the anisotropy feature (sigma(x)(x)/theta) of Marder type universe and equation of state (EoS) strange quark matter to obtain solutions in two classes f (R, T) gravity (Harko et al. in Phys. Rev. D 84:024020, 2011). Finally, some physical and kinematical properties are discussed.
Quark and strange quark matter solutions for higher dimensional FRW universe in Lyra geometry
(Springer Heidelberg, 2015) Aygün, Sezgin; Çağlar, Halife; Taşer, Doğukan; Aktaş, Can
In this study, we have investigated the higher dimensional flat Friedmann-Robertson-Walker (FRW) universe for a cloud of string with perfect fluid attached quark and strange quark matter (SQM) in Lyra geometry. Generalized (n + 2) dimensional flat FRW universe solutions have been achieved with the aid of equation of states (EOS) and deceleration parameter (q). From the field equations, we have obtained that the cloud of string with perfect fluid does not survive. Since the string tension density vanishes (lambda = 0) for this model, as a result, the cloud of string with perfect-fluid-attached quark and strange quark matter energy-momentum tensor is automatically transformed into a perfect-fluid-attached quark and strange quark matter energy-momentum tensor. Also, our solutions agree with Halford's study. beta(2) behaves like a cosmological constant. When t -> infinity the pressure of quark matter and the density go to zero, then, the quark matter transforms into another matter with time. Also our quark matter solutions are in agreement with the present idea.

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