S. Yarman | Istanbul University (original) (raw)

Papers by S. Yarman

In this study, to compress ECG signals, KLT (Karhunen- Loeve Transform) method has been used. The... more In this study, to compress ECG signals, KLT (Karhunen- Loeve Transform) method has been used. The purpose of this method is to perform effective ECG coding by a correlation between the length of frames and the number of vectors of ECG signals.

Journal of Endocrinological Investigation, 2017

ObjectiveData regarding pregnancies in relation to pituitary tumors are limited. The effects of p... more ObjectiveData regarding pregnancies in relation to pituitary tumors are limited. The effects of pregnancy on pituitary adenomas and the effects of adenoma itself (hormonal activity, mass effects and pituitary insufficiency) and/or treatment on the ongoing gestation and developing fetus were evaluated.MethodsThe study was a retrospective study. A questionnaire involving questions regarding medical history before index gestation, history of related pregnancy, result of index gestation and postpartum follow-up of the patients was filled by the investigator in one of the eight Referral Endocrinology Centers from Turkey.ResultsOne hundred and thirteen (83 prolactinoma, 21 acromegaly, 8 NFPA and 1 plurihormonal pituitary adenoma) pregnancies of 87 (60 prolactinoma, 19 acromegaly, 7 NFPA and 1 plurihormonal pituitary adenoma) patients were reviewed. The clinically important pregnancy-related tumor growth of pituitary adenomas was found to be low in previously treated adenomas. Prolactinomas were more likely to increase in size during pregnancy especially if effective prior treatment was lacking. The risk of hypopituitarism is also minimal due to pituitary adenomas during pregnancy. The results of pregnancies did not differ in patients who were on medical treatment or not for prolactinomas and acromegaly during gestation. Neural tube defect and microcephaly associated with maternal cabergoline use; Down syndrome and corpus callosum agenesis associated with maternal bromocriptine use; unilateral congenital cataract, craniosynostosis and microcephaly associated with maternal acromegaly were detected for the first time.ConclusionMedical treatment can be safely done stopped in patients with prolactinoma and acromegaly when pregnancy is confirmed and reinstituted when necessary. Prospective studies may help to determine the effects of medical treatment during gestation on the mother and fetus.

Irish medical journal

The Carney complex is an inherited, autosomal disease of multicentric tumors in many organs. Some... more The Carney complex is an inherited, autosomal disease of multicentric tumors in many organs. Some components of Carney's complex are cardiac myxoma, spotty pigmentation, and endocrine overactivity. Primary pigmented nodular adrenocortical dysplasia (PPNAD) is an exceedingly rare cause of Cushing's syndrome in infants, children, and young adults. PPNAD occurs sporadically or as part of a familial syndrome called Carney's complex. Up to our knowledge, the association of Fallot Tetralogy with Carney's complex has not been previously reported. We presented, a 20-year-old woman, who had been operated for Fallot Tetralogy at the age of 3 years, had Carney's complex, i.e. left atrial myxoma, two facial spotty pigmented areas, and PPNAD.

Journal of Endocrinological Investigation, 2000

Nuclear Medicine Communications, 1997

Hormone Research in Paediatrics, 2007

Insulin-secreting pancreatic tumors and insulin-like growth hormone-secreting non-islet cell tumo... more Insulin-secreting pancreatic tumors and insulin-like growth hormone-secreting non-islet cell tumors can cause hypoglycemia. However, insulin-releasing paraganglioma or pheochromocytoma has almost never been reported. A 67-year-old female patient was admitted to our hospital because of headache, palpitation, perspiration, faintness, frequent sense of hunger and absent-mindedness. These intermittent symptoms had begun approximately a year before admission. On physical examination, she had high blood pressure of 150/90 mm Hg. Hormonal studies demonstrated increased urinary norepinephrine levels, and hyperinsulinemic hypoglycemia was confirmed while the patient was symptomatic. Abdominal MRI revealed a retroperitoneal mass measuring 4.5 cm in the pancreatic region. She was treated with an alpha-blocking agent to control blood pressure preceding the removal of the mass. Histopathological diagnosis was paraganglioma, and immunohistochemically insulin staining in the neoplastic cells was demonstrated. Her blood pressure normalized and hypoglycemia relieved after the operation. The patient did not have recurrence of hypoglycemia after a year of follow-up. Paraganglioma is a rare tumor of the neural crest, and co-secretion of insulin and catecholamines has been reported only by a single case report in the literature. The present patient is another case with this co-secretion.

Endocrine Journal, 2004

We studied the incidence of late-onset congenital adrenal hyperplasia (LOCAH) due to 2l-hydroxyla... more We studied the incidence of late-onset congenital adrenal hyperplasia (LOCAH) due to 2l-hydroxylase (21-OH) deficiency, its molecular genotype expression, and its association with the major histocompatibility complex in 61 women with hirsutism and polycystic ovary. Ultrasound, clinical and hormonal parameters were used to define polycystic ovary syndrome (PCOS). Baseline and ACTH stimulated 17a-hydroxyprogesterone (17-OHP) levels were measured for screening of LOCAH during follicular phase. Forty-one women were diagnosed as having PCOS (67%) and 20 women were diagnosed as having had LOCAH due to 2l-OH deficiency (33%). In LOCAH patients, the most common mutation (Val281-Leu, V281L) was found in 10 patients (7 heterozygous/3 homozygous). The frequency of V281L mutation was found as 32.5% in 20 patients. All patients with the V281L mutation presented HLA-B14 (100%) and six of them presented DR1 (60%), confirming that LOCAH is linked to the histocompatibility complex. Although molecular analysis is a better and more accurate means for an exact and precise definition of LOCAH, it is not routinely available in our country. So, ACTH stimulation test combined with HLA-B14 typing should be more widely utilized in these patients. As a result, LOCAH due to 21-OH deficiency is unexpectedly high in Turkish patients with hirsutism and PCO.

Endocrine, 2011

One form of prolactin (PRL) is macroprolactin with high molecular mass. Many macroprolactinemic p... more One form of prolactin (PRL) is macroprolactin with high molecular mass. Many macroprolactinemic patients have no pituitary adenomas and no clinical symptoms of hyperprolactinemia, it is controversial whether macroprolactinemia is a benign condition that does not need further investigation and treatment. In this study, we aimed to compare macroprolactinemic patients (group I) with the true hyperprolactinemic patients (group II) for the presence of pituitary adenoma. We investigated 161 patients with hyperprolactinemia, whose magnetic resonance imaging records of the pituitary were taken. All patients were questioned for irregular menses, infertility and examined for galactorrhea. Patients were screened for macroprolactinemia by polyethylene glycol precipitation, and a recovery of ≤40% and normal monomeric PRL level was taken as an indication of significant macroprolactinemia. Of 161 patients with hyperprolactinemia, 60 (37.26%) had macroprolactinemia. PRL levels of group II were lower than those of group I (P = 0.011), although monomeric PRL levels of group II were higher than those of group I (P = 0.0005). Of 60 macroprolactinemic patients, 16 (26.7%) had pituitary adenomas. The prevalence of pituitary adenomas was lower in group I, compared with group II (P = 0.0005). No significant differences were found between the prevalences of irregular menses and infertility of group I and II (P = 0.084, P = 0.361). Prevalence of galactorrhea in group I was lower than that in group II (P = 0.048). Prevalence of pituitary adenomas in macroprolactinemic patients is lower compared with the true hyperprolactinemic patients, but may be higher than that found in other recent studies and in the general population.

Electronics Letters, 2010

A new topology for a distributed power amplifier (DPA) is presented to maximise DC-RF conversion ... more A new topology for a distributed power amplifier (DPA) is presented to maximise DC-RF conversion (i.e. for high output power). The topology is featured by vectorially combined current sources when loading power transistors into distributed output and input networks using impedance termination values gathered by device load pull. To the authors' knowledge, the output power achieved in this work is the best for DPAs within the frequency range up to 2 GHz.

2007 18th European Conference on Circuit Theory and Design, 2007

In this paper, gain bandwidth limitations of a regularly processed 0.18 mum Si CMOS FET is invest... more In this paper, gain bandwidth limitations of a regularly processed 0.18 mum Si CMOS FET is investigated over the frequency band of 450 MHz-10 GHz. It is exhibited that 0.18 mum Si CMOS processing technology can safely be utilized to manufacture ultra wideband RF-amplifiers for commercial wireless communication systems placed silicon chips up to X-Band.

Midwest Symposium on Circuits and Systems, 2000

Before this study, we proposed a novel method to represent signals in terms of, so called, "... more Before this study, we proposed a novel method to represent signals in terms of, so called, "Signature Base Functions - SBF" which were extracted from the physical features of the waveform under consideration. SBF were determined in ad-hoc manner, which requires tedious search process, and they were not orthogonal. Furthermore, the optimality of SBF was in question. In this work

2008 International Conference on Recent Advances in Microwave Theory and Applications, 2008

... ACKNOWLEDGEMENT The author greatfuly acknowledes contributions of Kemal Ozanoglu, Onur Uslu, ... more ... ACKNOWLEDGEMENT The author greatfuly acknowledes contributions of Kemal Ozanoglu, Onur Uslu, Dr. Fusun Selcuk and Dr. Ersed Akcasu of Akcasu S/W of Turkey & OEA International Inc., 155 East Main Av., Suite 110, Morgan Hill, CA, 95037, USA.

In this paper, a novel method to compress electroencephalogram (EEG) signal is proposed. The prop... more In this paper, a novel method to compress electroencephalogram (EEG) signal is proposed. The proposed method is based on the generation classified signature and envelope vector sets (CSEVS) by using an effective k-means clustering algorithm. In this work, on a frame basis, any EEG signal is modeled by multiplying three parameters as called the classified signature vector, classified envelope vector, and frame-scaling coefficient. In this case, EEG signal for each frame is described in terms of the two indices R and K of CSEVS and the frame-scaling coefficient. The proposed method is assessed through the use of root-mean-square error (RMSE) and visual inspection measures. The proposed method achieves good compression ratios with low level reconstruction error while preserving diagnostic information in the reconstructed EEG signal.

AEU - International Journal of Electronics and Communications, 2008

A reflectance-based modeling method is presented, to obtain the distributed-element counterpart o... more A reflectance-based modeling method is presented, to obtain the distributed-element counterpart of a lumped-element network, which is described by measured or computed reflectance data at a set of frequencies. Numerical generation of the scattering parameters ...

IEICE Electronics Express, 2013

In this study, balanced and single ended class-E power amplifiers (PAs) were designed and realize... more In this study, balanced and single ended class-E power amplifiers (PAs) were designed and realized for 3.5-3.8 GHz band by using Gallium Nitride high electron mobility transistor (GaN HEMT). Realizations were made on low loss Rogers RT5880 dielectric material which has 0.254 mm thickness and 2.2 dielectric constant. Proposed balanced class-E PA has approximately 20 W (43 dBm) output power with 80% peak power added efficiency (PAE) and shows a very favorable combination of output power, PAE and suppressed even order harmonics compared to the single ended class-E PA prototype.

selected active device is essential to design an RF power amplifier for optimum gain and power ad... more selected active device is essential to design an RF power amplifier for optimum gain and power added efficiency. As they are obtained, these impedances may not be realizable network functions over the desired frequency band to yield the input and the output matching networks for the amplifier. Therefore, in this paper, first, we introduce a new method to test if a given impedance is realizable. Then, a novel “Real Frequency Line Segment Technique” based numerical procedure is introduced to assess the gain-bandwidth limitations of the given source and load impedances, which in turn results in the ultimate RF-power intake/ delivering performance of the amplifier. During the numerical performance assessments process, a robust tool called “Virtual Gain Optimization” is presented. Finally, a new definition called “Power-Performance-Product” is introduced to measure the quality of an active device. Examples are presented to test the realizability of the given source/load pull data and to ...