Yazar "Ozturk, O." seçeneğine göre listele

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    Diverticular disease and posture during defecation : a prospective comparative study
    (Univ Catholique Louvain-Ucl, 2018) Ozturk, O.; Koklu, H.; Akbal, E.; Aksoy, E. K.; Altan, E.; Basar, O.; Yuksel, O.
    Background and study aims : Although several factors are thought to be responsible for the development of colonic diverticulosis the underlying pathogenesis is still obscure and needs clarification. The aim of this study was to determine the prevalence, location and clinical features of CD and especially to detect whether there is an association between CD and postures during defecation. Patients and methods : This prospective study enrolled 757 patients. The subjects were divided into two groups as a diverticulosis group (D group, n:95) and non-diverticulosis group (non-D group, n:662). Results : The median patient age was 54.9 +/- 13.2 years. CD frequency was 12.5% (n:95). The most commonly involved part of the colon was the sigmoid colon (56.8%). Diverticula location was on the left in 45.3% (n:43), on the right in 24.2% (n:23) and on both sides of the colon in 30.5% (n:29). Patients in the D group were older (p<0.001) and were predominantly female (p:0.04). The frequency of sitting during defecation (Western type toilet) was higher in the D group compared to the non-D group (72.2% vs 53.5%; p:0.007). The use-time of a Western-type toilet was longer in the D group compared to the non-D group (p:0.04). In multivariable logistic regression analysis, age and toilet type were independent risk factors for the development of diverticulosis. Conclusion : Sitting during defecation seems to increase the risk of CD.
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    Effect of Planetary Mass on the Orbit of Star-Planet Systems
    (Amer Inst Physics, 2017) Ozturk, O.; Erdem, A.
    Two main parameters, which determine the radial velocity semi-amplitude of the host star in a star-planet system, are the planet mass and the orbital period. In order to examine the effect of planet mass on the radial velocity semi-amplitude, we firstly select sensitive data of spectroscopic orbital solutions of 737 systems, given in the database of exoplanet.org. The selected systems are then categorized into 31 groups according to their orbital periods. For each group, an empirical relation between the radial velocity semi amplitude and the planet mass is obtained. In order to check the accuracy of these empirical relations, the measured and expected values of planet masses are compared.
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    EFFECTS OF ALPHA-BLOCKER AGENTS USED TO TREAT BENIGN PROSTATIC HYPERTROPHY ON ENDOTHELIAL FUNCTIONS AND METABOLIC PARAMETERS
    (Elsevier Ireland Ltd, 2011) Kirilmaz, B.; Dogan, H.; Alan, C.; Saygi, S.; Asgun, H. F.; Celik, H.; Ozturk, O.
    [Anstract Not Available]
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    First Photometric is Study of Two Southern Eclipsing Binaries IS Tel and DW Aps
    (Amer Inst Physics, 2017) Ozer, S.; Surgit, D.; Erdem, A.; Ozturk, O.
    The paper presents the first photometric analysis of two southern eclipsing binary stars, IS Tel and DW Aps. Their V light curves from the All Sky Automated Survey were modelled by using Wilson-Devinney method. The final models give these two Algol-like binary stars as having detached configurations. Absolute parameters of the components of the systems were also estimated.
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    New Photometric Observations of HAT-P-25b and WASP-11b/HAT-P-10b
    (Amer Inst Physics, 2018) Erdem, A.; Ozturk, O.
    We present new photometric follow-up observations of transiting exoplanets HAT-P-25 b and WASP-11b / HAT-P-10b obtained at TUBI. TAK National Observatory, Turkey. The new transit light curves of both systems were analyzed using WinFitter code. Planetary radii of HAT-P25b and WASP-11b/HAT-P-10b were found to be 1.18 +/- 0.11RJ and 1.02 +/- 0.09RJ, respectively. Transit ephemerides were updated and transit timing variation (TTV) analyses were performed using all mid-transit times published in the literature together with ours.
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    Non-conservative mass transfers in Algols
    (Oxford Univ Press, 2014) Erdem, A.; Ozturk, O.
    We applied a revised model for non-conservative mass transfer in semi-detached binaries to 18 Algol-type binaries showing orbital period increase or decrease in their parabolic O-C diagrams. The combined effect of mass transfer and magnetic braking due to stellar wind was considered when interpreting the orbital period changes of these 18 Algols. Mass transfer was found to be the dominant mechanism for the increase in orbital period of 10 Algols (AM Aur, RX Cas, DK Peg, RV Per, WX Sgr, RZ Sct, BS Sct, W Ser, BD Vir, XZ Vul) while magnetic braking appears to be the responsible mechanism for the decrease in that of 8 Algols (FK Aql, S Cnc, RU Cnc, TU Cnc, SX Cas, TW Cas, V548 Cyg, RY Gem). The peculiar behaviour of orbital period changes in three W Ser-type binary systems (W Ser, itself a prototype, RX Cas and SX Cas) is discussed. The empirical linear relation between orbital period (P) and its rate of change (dP/dt) was also revised.
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    On the Classification of Exoplanets according to Safronov Number
    (Amer Inst Physics, 2018) Ozturk, O.; Erdem, A.
    We reexamine the classification of transiting exoplanets proposed by Hansen & Barman (2007) based on equilibrium temperatures and Safronov numbers. We used more sensitive data, namely, photometric and spectroscopic orbital solutions, of 263 well-known planets given in The Exoplanet Data Explorer, while Hansen & Barman (2007) used data on 18 transiting planets. Diagrams of the planet gravity vs. orbital period, planet gravity vs. equilibrium temperature, and Safronov number vs. equilibrium temperature of the 263 transiting planets show that the division of planets into two classes is indistinct.
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    Orbital Periods of Two Algol-Type Binaries: AV Cep and GI Cep
    (Amer Inst Physics, 2018) Apak, B.; Erdem, A.; Ozturk, O.; Gozutok, M. I.; Surgit, D.
    Results are presented of the orbital period analysis of two Algol-type binary stars (AV Cep and GI Cep). All available minima times in the literature together with minima times obtained in this study were used. The orbital period changes were investigated using the O-C method. O-C diagrams of both systems show upward parabolic variations, which indicate that the orbital period of these two systems is increasing secularly. The rate of period increase of AV Cep and GI Cep was calculated to be 0.415 +/- 0.016 s/year and 0.026 +/- 0.009 s/year, respectively. These secular period increases could be explained in terms of mass transfer from the secondary component to the primary component according to the classic Algol scenario.
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    Photometric study of two ? Lyr-type binaries: DD Aqr and RR Lep
    (Elsevier, 2016) Erdem, A.; Ozturk, O.
    This paper presents detailed analysis of photometric observations of two eclipsing binary systems, DD Aqr and RR Lep. The V light curve of the neglected binary star DD Aqr from the All Sky Automated Survey was solved for the first time. The 1982-1987 UBV light curves of RR Lep from Vyas and Abhyankar (1989) were re-analysed. The final solutions give these two beta Lyr-type binary stars as having near contact configurations in which the secondary components almost fill their Roche limiting lobes. Using O-C residuals formed by the updated minima times, orbital period changes of the systems were analysed. The O-C diagram of DD Aqr displays a cyclic variation, while that of RR Lep shows a quasi-sinusoidal variation superimposed on a downward parabolic form. The parabolic variation, which suggests a secular orbital period decrease in RR Lep, was interpreted in terms of the combined effect of mass transfer and loss. The cyclic O-C variations were interpreted in terms of the light travel time effect due to unseen components in these two systems. The absolute parameters of the components of the systems were estimated, and their present evolutionary status is also discussed. (C) 2016 Elsevier B.V. All rights reserved.
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    Photometric Study of Two Neglected Beta Lyr-Type Binaries: V342 Her & V387 Her
    (Amer Inst Physics, 2017) Aktoka, U.; Erdem, A.; Ozturk, O.; Surgit, D.
    In this study, SuperWASP light curves of V342 11cr and V387 Her were analyzed by means of the Wilson Devinney (W-D) code with a Monte Carlo (MC) search method for the first time. The final photometric solutions of these two systems show that while V342 Her has an over contact configuration in which both components overtlows their Roche limiting lobes, V387 Her has a detached configuration. Photometric mass ratios and approximate absolute parameters of the systems are obtained.
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    Re-examining the Light Curves of Kepler-6b, Kepler-8b and Kepler-40b
    (Amer Inst Physics, 2018) Ozturk, O.; Erdem, A.
    We present a fresh analysis of the light curves of Kepler-6, Kepler-8 and Kepler-40 star-planet systems using similar to 3 years of observations by the Kepler space telescope. Transit light curves were solved usingWinFitter code. The proximity effects (ellipticity and reflection effects) and Doppler beaming effect were also examined using the Fourier series method. Mid-transit times of the light curves of the three exoplanets observed during the Kepler mission were recomputed, and transit timing variations for each exoplanet were analyzed.
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    Statistical examination of Orbital Elements affecting Radial Velocity Semi-Amplitude of Host Star in Star-Planet Systems
    (Amer Inst Physics, 2018) Ozturk, O.; Erdem, A.
    Radial velocity semi-amplitude of the host star in a star-planet system is affected by four parameters: the orbital period and mass of the planet, mass of the host star, and orbital eccentricity. Statistical distribution of the orbital elements was examined using sensitive data from the spectroscopic orbital solutions of 737 systems given in the Exoplanet Orbit Database and Exoplanet Data Explorer (exoplanet.org). The orbital element distribution of the exoplanets was plotted in separate diagrams to highlight the basic features of the host star and planet in star-planet systems.
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    SX Aurigae: A close binary at the early stage of contact phase
    (Elsevier Science Bv, 2014) Ozturk, O.; Soydugan, Faruk; Cicek, C.
    This study presents analysis of new multi-band light curves of beta Lyrae-type eclipsing binary SX Aur. Radial velocities of both components of the system were collected from the literature and simultaneous light curve solutions made to determine the properties of the system and absolute elements of its components. The derived masses and radii of the components are M-1 = 11.3 +/- 0.2 M-circle dot, M-2 = 6.9 +/- 0.1 R-1 = 5.32 +/- 0.02 R-circle dot and R-2 = 4.23 +/- 0.03.R-circle dot, while the distance of the system is estimated at 1220 +/- 75 pc. It was found that SX Aur is a shallow-contact binary and thus may be in the stage between beta Lyrae and W UMa-type binaries. From O-C based period analysis of SX Aur, it is seen that the period of the system increases at a rate of 0.0055 s yr(-1). The most plausible physical mechanism for this period variation is non-conservative mass transfer from the secondary to the primary component at a rate of 3.13 x 10(-7) M-circle dot yr(-1). (c) 2014 Elsevier B.V. All rights reserved.