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Öğe Adjustable tunneling barrier in bi-based high-Tc cross-whisker junctions(Iop Publishing Ltd, 2015) Kizilaslan, O.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Yakinci, M. E.; Mueller, P.We present a study of cross-whisker junctions with electronically modified tunneling barriers. Cross-whisker junctions were successfully prepared by annealing two crossed Bi-based whisker bars at temperatures of around 840 degrees C. In addition to the artificially produced junction at the interface, intrinsic Josephson junctions in the respective bars of the cross were observed. The artificial junction exhibited reproducible and almost ideal junction characteristics. The tunneling barrier/interface properties were controlled by carrier injection in c-axis direction. Using this process, we were able to reduce the tunneling resistance from 408 Omega to 30 Omega. At the same time, the critical current did rise by a factor of 4. Subsequently, the critical current was doubled while the tunneling resistance stayed constant. We interpret this observation in terms of the counter-play between transparency of the barrier and the carrier concentration of the electrodes. In this sense, we can consider the current injection procedure as an electronic gluing process of the two cross-junction whisker bars.Öğe Enhancement of the critical current of intrinsic Josephson junctions by carrier injection(Iop Publishing Ltd, 2015) Kizilaslan, O.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Mueller, P.We present a study of the doping effect by carrier injection of high-T-c superconducting Bi-based whiskers. The current was injected in the c-axis direction, i.e., perpendicular to the superconducting planes. Superconducting properties were investigated systematically as a function of the doping level. The doping level of one and the same sample was changed by current injection in very small steps from an underdoped state up to a slightly overdoped state. We have observed that T-c versus log (j(c)) exhibits a dome-shaped characteristic, which can be fitted by a parabola. As T-c versus carrier concentration has a parabolic form, too, it can be concluded that the critical current density j(c) increases exponentially with the doping level. The electron-trapping mechanism is interpreted in the framework of Phillips' microscopic theory. In addition, the Joule heating effect in the intrinsic Josephson junction (IJJ) was controlled by carrier injection, and the effect of the non-equilibrium quasiparticle on the I-V curves of the IJJs was also discussed.Öğe Follicular fluid adenosine deamines (ADA), superoxide dismutase and nitric oxide levels in GnRH agonist and antagonist cycles(Oxford Univ Press, 2012) Celik, E.; Celik, O.; Kumbak, B.; Yilmaz, E.; Turkcuoglu, I.; Simsek, Y.; Karaer, A.[Abstract Not Available]Öğe Hydronephrosis of pregnancy associated with torsion of the fallopian tube: a case report(Verduci Publisher, 2011) Simsek, Y.; Ustun, Y.; Kaymak, O.; Akbaba, E.; Danisman, N.; Sirvan, L.Isolated tubal torsion accompanying pregnancy is an extremely rare condition. Preoperative diagnosis is generally difficult; most of the cases can be diagnosed intraoperatively. Here, we reported a 36-week pregnant with a complaint of acute pain in right lower quadrant that emanating to right lomber region. Abdominal utrasonography showed grade 3 hydronephrosis in right kidney, other findings were normal. A cesarean section was carried out and a twisted right tube were diagnosed. Right ovary was normal in appearance. The torsioned tube compressed the right ureter and caused ureteral dilatation. Right salpingectomy was performed. Postoperative follow-up of the patient was uneventful.Öğe The inhibitory effect of Resveratrol on experimental endometriosis via nuclear factor kappa B-independent pathway(Oxford Univ Press, 2012) Simsek, Y.; Celik, O.; Cigremis, Y.; Akgoz, M.; Ozerol, E.; Tanbek, K.; Turhan, U.[Abstract Not Available]Öğe Interlayer tunneling spectroscopy of mixed-phase BSCCO superconducting whiskers(Iop Publishing Ltd, 2016) Kizilaslan, O.; Truccato, M.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Mueller, P.In this work, we present a study on the interlayer tunneling spectroscopy (ITS) of mixed-phase BiSrCaCuO (BSCCO) superconducting whiskers. The tunneling experiments were carried out on the artificial cross-whisker (twist angle of 90 degrees) junctions. A multiple superconducting energy gap in the cross-whisker junctions was observed, which is attributed to the presence of different doping levels of two Bi2Sr2CaCu2O8+delta phases (Bi-2212), rather than two different phases, in the BSCCO whiskers, namely Bi2Sr2CaCu2O8+delta and Bi2Sr2Ca2Cu3O8+delta (Bi-2212 and Bi-2223). The temperature dependence of the energy gaps was discussed in the framework of the BCS T-dependence. On the other hand, the carrier concentration of the cross-whisker junction was changed by the carrier injection process. The effects of the carrier injection on the critical current, I-c, and the ITS of intrinsic Josephson junctions were investigated in details.Öğe Nuclear factor-kappa beta pathway and endometrial cancer: a pilot study(I R O G Canada, Inc, 2017) Yilmaz, E.; Coskun, E. I.; Gul, M.; Sahin, N.; Tuncay, G.; Simsek, Y.Objective: Examination of the role of nuclear factor-kappa beta (NF-kappa B) expression in the etiopathogenesis of endometrial cancer, by means of the immunohistochemical method. Materials and Methods: Patients who applied to participate in the study at the clinic were grouped into three categories: those diagnosed with benign endometrial pathology, those with endometrial hyperplasia, and those with endometrial cancer. NF-kappa B analysis was conducted in the endometrial tissues of the patients' paraffin blocks by means of the immunohistochemical method. For objective assessment purposes, the H score of each patient was calculated. SP SS 15.0 program was employed for statistical analysis. Results: The average H score of the first group, comprising benign endometrial pathologies, was 102.4 +/- 85.9, that of the hyperplasia group was 143.6 +/- 122.4, and that of the cancer group was 276.8 +/- 61.8. The average values of groups 1 and 2 were similar (p = 0.349); however, the third group's average H score was significantly higher (p < 0.001). Conclusion: NF-kappa B, which is a critical mediator in the inflammation process, might be related to the development of premalign and malign endometrial changes.Öğe Predictive value of umbilical artery Doppler for adverse perinatal outcome in patients with HELLP syndrome(Verduci Publisher, 2013) Simsek, Y.; Celen, S.; Simsek, A.; Danisman, N.; Mollamahmutoglu, L.OBJECTIVE: In this study, we aimed to evaluate in a prospective design the importance of pathologic umbilical artery (UA) Doppler findings as a predictive marker for neonatal outcome in patients with HELLP syndrome. PATIENTS AND METHODS: A total of 45 pregnant women at 24-42 weeks of gestation with a diagnosis of HELLP syndrome were included. The study group consisted of 20 patients with abnormal UA Doppler results, and the remaining 25 HELLP syndrome patients with normal UA Doppler results were assigned to the control group. All patients were followed up until delivery, and the neonatal characteristics were compared. RESULTS: Baseline characteristics of the groups were similar. In the study group, gestational week at delivery and infant birth weight were significantly lower (p < 0.05). The rates of significant neonatal morbidity, neonatal mortality, and neonatal intensive care unit (NICU) admission were significantly higher in study group patients (p < 0.05). CONCLUSIONS: UA Doppler abnormalities can be considered predictive of poor neonatal prognosis in patients with HELLP syndrome, as they were significantly related with higher rates of neonatal mortality and significant morbidity.Öğe Removal of uterine fibroids during cesarean section: a difficult therapeutic decision(I R O G Canada, Inc, 2012) Simsek, Y.; Celen, S.; Danisman, N.; Mollamahmutoglu, L.Purpose of investigation: Myoma excision during cesarean delivery has traditionally been discouraged, however controversy persists among studies of myomectomy being performed during cesarean section. In this study, medical records of patients who underwent cesarean section our institution were evaluated retrospectively. Methods: A total of 70 cases of cesarean myomectomy done during this period were included (group 1) and compared with the patients who underwent cesarean section alone (group 2). Results: Mean surgical time of the myomectomy group was 58.1 +/- 23 minutes which was significantly increased (p < 0.01). Mean postoperative hemoglobin value was 9.6 +/- 1.5 in the myomectomy group and 10.8 +/- 1.01 in controls (p = 0.01). Length of hospital stay was significantly longer in the myomectomy group (p < 0.05). Conclusion: This study shows that myomectomy during cesarean section is a feasible procedure without any serious complications. The procedure is related with increased blood loss that does not require blood transfusion.Öğe Severe preeclampsia and fetal virilization in a spontaneous singleton pregnancy complicated by hyperreactio luteinalis(Verduci Publisher, 2012) Simsek, Y.; Celen, S.; Ustun, Y.; Danisman, N.; Bayramoglu, H.Background: Hyperreactio luteinalis is a rare condition that stems from theca cell hyperplasia in the ovaries due to a high level of human chorionic gonadotropin during gestation. It occurs commonly in pregnant patients with trophoblastic disease, occasionally in multiple pregnancies, and rarely in normal singleton pregnancy. Case Report: A 24-year-old pregnant woman, G3 P0, who was admitted to the Perinatology Clinic with increasing findings of virilization during pregnancy was presented. The patient had bilaterally enlarged multicystic ovaries on sonographic examination and elevated serum androgen levels She was managed conservatively until 38th week of gestation as a presumptive diagnosis of hyperreactio luteinalis. Elevated blood pressure and prominent proteinuria were detected during the follow-up of the patient and labor was induced. She underwent an emergency caesarean delivery because of fetal distress. During caesarean section, ovarian biopsies were taken and a histopathological diagnosis of hyperreactio luteinalis was determined. The female fetus also presented virilization. Conclusion: Although infrequent, hyperreactio luteinalis with both maternal and fetal virilization can occur in women with spontaneous singleton pregnancies. The clinical manifestations in such women may be complicated by severe preeclampsia.Öğe Spontaneous resolution of fetal dural sinus thrombosis following term delivery of a live infant(Wiley-Blackwell, 2012) Simsek, Y.; Oztanir, N.; Sigirci, A.; Celik, E.; Yilmaz, E.; Celik, O.; Onal, C.[Abstract Not Available]Öğe Therapeutic efficiency of atosiban, an oxytocin receptor antagonist in the treatment of experimental endometriosis(Oxford Univ Press, 2011) Simsek, Y.; Celik, O.; Yilmaz, E.; Karaer, A.; Koc, O.; Aydin, N. E.[Abstract Not Available]Öğe XPD and XRCC1 gene polymorphism in patients with normal and abnormal cervical cytology by pap smear(Verduci Publisher, 2012) Yilmaz, E.; Celik, O.; Celik, E.; Turkcuoglu, I.; Simsek, Y.; Karaer, A.; Otlu, B.AIM: The purpose of the present study was to identify the role of abnormalities in DNA repair pathways by measuring the XPD and XRCC1 gene polymorphisms. MATERIALS AND METHODS: Thirty-five patients with abnormal cervical cytology (study group) and 10 women with normal cytology (control group) were included in the study. The polymorphisms of XRCC1 Arg194Trp, XRCC1 Arg399Gln and XPD Lys751Gln genes were investigated from the blood samples. RESULTS: There was no statistically significant difference in allele frequencies of XPD gene among the groups (p = 0.097), while XRCC1R399Q gene polymorphism was strikingly more frequent in the study group than that of control cases (p = 0.029). The prevalence of XRCC1R194W gene polymorphism on the other hand, was similar between the groups (p = 0.579). CONCLUSIONS: Patients with abnormal and normal cervical cytology have similar XPD gene polymorphism. However, the frequency of gene polymorphism in XRCC1 Arg 399 Gln codon was significantly higher in abnormal cervical cytology group.
