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    Correction: Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron (International Journal of Metalcasting, (2022), 16, 4, (1836-1848), 10.1007/s40962-021-00723-3)
    (Springer Science and Business Media Deutschland GmbH, 2023) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, Mehmet
    The original online version of this article was revised. The graphical abstract, Fig. 8, Table 4, and miscellaneous values throughout the text were corrected. © 2023, American Foundry Society.
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    Differences in autonomic activity in individuals with optimal, normal, and high-normal blood pressure levels
    (Kare Publ, 2010) Dogru, M. Tolga; Simsek, Vedat; Sahin, Omer; Ozer, Nurtac
    Objectives: We investigated differences in autonomic activity in normotensive individuals having optimal, normal and high-normal blood pressure (BP) levels according to the guidelines of the European Society of Hypertension and European Society of Cardiology (ESH/ESC). Study design: The study included 294 normotensive subjects (135 males, 159 females; age range 16 to 75 years) with similar clinical, morphometric, biochemical, electrocardiographic, and echocardiographic features. The subjects were classified into the following BP groups: group 1 (n=113) with optimal BP (<120/80 mmHg); group 2 (n=104) with normal BP (120-129/80-84 mmHg), and group 3 (n=77) with high-normal BP (130-139/85-89 mmHg). All the subjects underwent 24-hour Holter monitoring to obtain heart rate variability (HRV) parameters of 24-hour, daytime, and nighttime periods. Normalized low (LFn) and high (HFn) frequency powers, and logarithmic (Log) values of HRV parameters were also calculated. Results: On 24-hour Holter monitoring, heart rates were similar in three groups. Compared to group 1 and 2, group 3 exhibited significantly higher LF/HF (p<0.001) and LFn (p=0.001) values, and significantly lower HFn (p=0.001), pNN50 (p=0.001), and rMSSD (p=0.005) values. There were no significant differences between the groups with respect to daytime HRV parameters; however, nighttime LF/HF, LFn, and HFn values were significantly different between the groups. Log LF/HF values obtained during the 24-hour and nighttime periods showed significant differences between group 1 and group 3 (for 24 hours, p<0.001; for night, p=0.001) and between group 2 and group 3 (for 24 hours, p<0.001; for night, p=0.009), but group 1 and group 2 did not differ significantly in this respect (p>0.05). Conclusion: These findings suggest that subjects with high-normal BP have increased sympathetic activity and decreased parasympathetic activity, possibly making them more liable to hypertension.
  • Küçük Resim
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    Effect of Diurnal Blood Pressure on Endothelial Functions in Essential Hypertensive Patients
    (Elsevier Science Inc, 2013) Sahin, Omer; Ebinc, Haksun; Simsek, Vedat; Tulmac, Murat; Dogru, Mehmet Tolga
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  • Küçük Resim
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    Effect of Diurnal Blood Pressure on Myocardial Performance Index and Aortic Elasticity Parameters in Essential Hypertensive Patients
    (Elsevier Science Inc, 2013) Sahin, Omer; Ebinc, Haksun; Simsek, Vedat
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    Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron
    (Springer Science and Business Media Deutschland GmbH, 2022) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, Mehmet
    The present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu–Ni–Mo-alloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 °C for the duration of 15–30–60 min followed by holding in a salt bath at an austempering temperature of 260 °C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. Graphical Abstract: [Figure not available: see fulltext.] © 2021, American Foundry Society.
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    EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON
    (Springer Int Publ Ag, 2022) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat
    The present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu-Ni-Moalloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 degrees C for the duration of 15-30-60 min followed by holding in a salt bath at an austempering temperature of 260 degrees C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. [GRAPHICS] .
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    EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON (vol 16, pg 1836, 2021)
    (Springer Int Publ Ag, 2023) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat
    [Abstract No tAvailable]
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    Investigation and long-term monitoring of the presence of neutralizing antibody in patients with COVID-19 disease of different clinical severity
    (Wiley, 2022) Kaygusuz, Sedat; Korukluoglu, Gulay; Cosgun, Yasemin; Sahin, Omer; Arslan, Ferhat
    Understanding the immune responses elicited by severe acute respiratory syndrome virus (SARS-CoV-2) infection is critical to public health policy and vaccine development and prevention of reinfections for COVID-19. It is important to know the neutralizing capacity of antibodies and to monitor their persistence. Patients with COVID-19 were divided into four groups (severe-critical, moderate, mild, and asymptomatic) according to their clinical severity. Antibodies against SARS-CoV-2 spike viral surface protein were investigated by ELISA method 3 and 9 months after the onset of the disease. Neutralizing antibody (NAb) response was evaluated by microneutralization test. Patients who received at least two doses of COVID-19 vaccine after illness were enrolled. SARS-CoV-2 immunoglobulin G (IgG) and NAb titers were shown to be strongly correlated with disease severity. Anti-SARS-CoV-2 IgG and NAb levels were found to be compatible with each other. After 9 months of follow-up, both IgG and NAb levels continued unabated in individuals who had the disease. In individuals who received at least two doses of the vaccine, these levels increased, except for severe-critical patients. High levels of anti-SARS-CoV-2 IgG are indicative, as it is difficult to investigate NAb in routine laboratories. At the same time, it can be predicted that this period may be much longer if it continues for at least 9 months and is reinforced with vaccination.