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Article Citation - WoS: 16Citation - Scopus: 15Timing and Spectral Analysis of 2s 1417-624 During Its 2018 Outburst(Oxford University Press, 2022) Serim,M.M.; Özüdoǧru,Ö.C.; Dönmez,Ç.K.; Sahiner,S.; Serim,D.; Baykal,A.; Inam,S.Ç.We investigate timing and spectral characteristics of the transient X-ray pulsar 2S 1417-624 during its 2018 outburst with NICER follow up observations. We describe the spectra with high-energy cut-off and partial covering fraction absorption (PCFA) model and present flux-dependent spectral changes of the source during the 2018 outburst. Utilizing the correlation-mode switching of the spectral model parameters, we confirm the previously reported sub-critical to critical regime transitions and we argue that secondary transition from the gas-dominated to the radiation pressure-dominated disc do not lead us to significant spectral changes below 12 keV. Using the existing accretion theories, we model the spin frequency evolution of 2S 1417-624 and investigate the noise processes of a transient X-ray pulsar for the first time using both polynomial and luminosity-dependent models for the spin frequency evolution. For the first model, the power density spectrum of the torque fluctuations indicate that the source exhibits red noise component (Γ ∼-2) within the time-scales of outburst duration which is typical for disc-fed systems. On the other hand, the noise spectrum tends to be white on longer time-scales with high timing noise level that indicates an ongoing accretion process in between outburst episodes. For the second model, most of the red noise component is eliminated and the noise spectrum is found to be consistent with a white noise structure observed in wind-fed systems. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Article Citation - Scopus: 174Mortality Analysis of Covid-19 Infection in Chronic Kidney Disease, Haemodialysis and Renal Transplant Patients Compared With Patients Without Kidney Disease: a Nationwide Analysis From Turkey(Oxford University Press, 2021) Ozturk,S.; Turgutalp,K.; Arici,M.; Odabas,A.R.; Altiparmak,M.R.; Aydin,Z.; Ates,K.Background. Chronic kidney disease (CKD) and immunosuppression, such as in renal transplantation (RT), stand as one of the established potential risk factors for severe coronavirus disease 2019 (COVID-19). Case morbidity and mortality rates for any type of infection have always been much higher in CKD, haemodialysis (HD) and RT patients than in the general population. A large study comparing COVID-19 outcome in moderate to advanced CKD (Stages 3-5), HD and RT patients with a control group of patients is still lacking. Methods. We conducted a multicentre, retrospective, observational study, involving hospitalized adult patients with COVID-19 from 47 centres in Turkey. Patients with CKD Stages 3-5, chronic HD and RT were compared with patients who had COVID-19 but no kidney disease. Demographics, comorbidities, medications, laboratory tests, COVID-19 treatments and outcome [in-hospital mortality and combined in-hospital outcome mortality or admission to the intensive care unit (ICU)] were compared. Results. A total of 1210 patients were included [median age, 61 (quartile 1-quartile 3 48-71) years, female 551 (45.5%)] composed of four groups: Control (n = 450), HD (n = 390), RT (n = 81) and CKD (n = 289). The ICU admission rate was 266/ 1210 (22.0%). A total of 172/1210 (14.2%) patients died. The ICU admission and in-hospital mortality rates in the CKD group [114/289 (39.4%); 95% confidence interval (CI) 33.9-45.2; and 82/289 (28.4%); 95% CI 23.9-34.5)] were significantly higher than the other groups: HD = 99/390 (25.4%; 95% CI 21.3-29.9; P<0.001) and 63/390 (16.2%; 95% CI 13.0-20.4; P<0.001); RT = 17/81 (21.0%; 95% CI 13.2-30.8; P = 0.002) and 9/81 (11.1%; 95% CI 5.7-19.5; P = 0.001); and control = 36/450 (8.0%; 95% CI 5.8-10.8; P<0.001) and 18/450 (4%; 95% CI 2.5-6.2; P<0.001). Adjusted mortality and adjusted combined outcomes in CKD group and HD groups were significantly higher than the control group [hazard ratio (HR) (95% CI) CKD: 2.88 (1.52- 5.44); P = 0.001; 2.44 (1.35-4.40); P = 0.003; HD: 2.32 (1.21- 4.46); P = 0.011; 2.25 (1.23-4.12); P = 0.008), respectively], but these were not significantly different in the RT from in the control group [HR (95% CI) 1.89 (0.76-4.72); P = 0.169; 1.87 (0.81-4.28); P = 0.138, respectively]. Conclusions. Hospitalized COVID-19 patients with CKDs, including Stages 3-5 CKD, HD and RT, have significantly higher mortality than patients without kidney disease. Stages 3-5 CKD patients have an in-hospital mortality rate as much as HD patients, which may be in part because of similar age and comorbidity burden. We were unable to assess if RT patients were or were not at increased risk for in-hospital mortality because of the relatively small sample size of the RT patients in this study. © The Author(s) 2020.Article Glycaemic Control and Complications in Haemodialysis Patients: The TURK-HEMODIAB Study(Oxford University Press, 2026) Gungor, Ozkan; Korucu, Berfu; Oguz, Ebru Gok; Eren, Necmi; Ural, Zeynep; Dheir, Hamad; Arici, MustafaBackground The most common cause of end-stage kidney disease is diabetes mellitus (DM). The most commonly used renal replacement therapy in Turkey and in many countries around the world is haemodialysis (HD). Glycaemia control is important in these populations. In this study we aimed to screen for glycaemic control and complications in a large population of diabetic HD patients in Turkey. Methods A total of 16 043 patients were screened in 253 dialysis centres in Turkey and 5038 diabetic HD patients were included in the study. At participating centres, patients' diabetes history, complications, medications, haemoglobin A1c (HbA1c) and other laboratory data were reviewed and recorded by nephrologists. Results The average age of the patients was 64.0 +/- 11.2 years and 56% were male. The mean HbA1c was 7.4 +/- 1.5%. Patients were divided into three groups according to the HbA1c level (<6.5%, 6.5-8% and >8%). As the HbA1c levels increased, the mean systolic blood pressure and diastolic blood pressure increased significantly. In addition, as the HbA1c levels increased, the number of patients with coronary artery disease, patients undergoing coronary artery bypass graft surgery and the rate of patients with diabetic retinopathy and vision loss increased. Diabetic foot disease and amputation rates were also higher in the group with poor glycaemic control. The number of patients using intensive or mixed insulin was also higher in the group with high HbA1c levels. In ordinal logistic regression analysis, age significantly decreased and higher body mass index slightly increased the risk of a higher HbA1c. Also, the need for a diabetic diet was greater in those with high HbA1c levels. Conclusion Our study highlights that the target values for diabetic HD patients in Turkey are partially compatible with the 2022 Kidney Disease: Improving Global Outcomes guidelines for diabetes management. Nevertheless, more effort and teamwork are needed to improve patient outcomes.Article Citation - WoS: 9Citation - Scopus: 7Pulse Frequency Fluctuations of Persistent Accretion Powered Pulsars(Oxford University Press, 2023) Serim,D.; Serim,M.M.; Baykal,A.In this study, we examine the long-term torque noise fluctuations of persistent X-ray binaries Her X-1, Vela X-1, GX 301-2, Cen X-3, 4U 1538-53, OAO 1657-415, and 4U 1626-67 using the historical pulse frequency measurements provided by CGRO/BATSE and Fermi/GBM. We find that known disc-fed sources exhibit a 1/ω2 red noise component in their power density spectra which is saturated over long time-scales. On the other hand, wind-fed sources form a clear white noise component, and the wind-fed sources with occasional transient disc formation imprint 1/ω type flicker noise. We discuss their long-term timing noise properties based on the models to describe the power density spectrum of pulse frequency derivative fluctuations in terms of monochromatic and coloured noise processes. Furthermore, we investigate the relation between measured timing noise strengths and other independently measured physical parameters. Despite the low number of sample sources, we suggest that the noise strengths of these sources are correlated with their luminosities and uncorrelated with their magnetic field strengths, implying that the dominant noise-generating mechanism is accretion. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
