114 research outputs found
Adaptive pairs trading strategy performance in Turkish derivatives exchange with the companies listed on Istanbul stock exchange
Due to copyright restrictions, the access to the full text of this article is only available via subscription.We implemented model-driven statistical arbitrage strategies in Turkish equities market. Trading signals are generated by optimized parameters of distance method. When the trade in signal is triggered by the model, market-neutral portfolio is created by long in the synthetic ETF, which is based on constrained least squares regression of selected Istanbul Stock Exchange stocks and short in Turkish Derivatives Exchange (Turkdex) index futures contract. We performed pairs trading strategy based on a comparative mean reversion of asset prices with daily data over the period February 2005 through July 2011 in Istanbul Stock Exchange (ISE) and Turkdex. We constructed a hypothetical ISE30 ETF Index on a daily basis in order to originate pairs trading strategy with Turkdex. Because of the leverage rule of (1–10) index futures contracts, we had to evaluate spot stock pairs formation with futures contracts pairs strategy. The results indicate that applied pairs strategy produced overall returns of 901 per cent during the investment period, whereas naive strategy (buy and hold ISE-30 index) return for the same period was 111 per cent. Similar outperformance was observed in the Sharpe and Sortino ratios
Relationship Between Chronic Obstructive Pulmonary Disease and Severity of Diabetic Retinopathy
The negative effects of chronic obstructive pulmonary disease (COPD) on diabetes mellitus (DM) patients are known. For these reasons, we aimed to investigate the effect of COPD on the severity of diabetic retinopathy (DRP) in patients with DM. Materials and Methods: This prospective cross-sectional study included one-hundred and fifty-six eyes of 156 patients with COPD and DM. Multinomial logistic regression models were applied to evaluate the independent relationships between DRP and COPD, including adjusting for patients’ characteristics. Results: After adjustment for potential confounders, patients with low-level COPD were found to have less PDR and severe PDR. (RRR 0.01 95% CI 0.01-0.03, RRR 0.01 95% CI 0.01-0.08, respectively). Conclusion: The findings suggest an increased risk of DRP severity in patients with severe COPD. Ophthalmologists following these patients should consider the relationship between COPD and DRP
The long outcome in patients with carotico-subclavian bypass surgery for subclavian steal syndrome
OBJECTIVE: In our study we aimed to evaluate long term outcome of carotico-subclavian bypass surgery in patients with subclavian steal syndrome.
MATERIALS and METHODS: We evaluated the patients who underwent caroticosubclavian bypass surgery between the years 1999 and 2011 in our clinic. Total number of patients was 6 (5 female and 1 male). The mean age of the patients was 60.8±2.1 (48- 78). The patients presented with claducatio of upper extremities, headache, dizziness, and differences in arterial pressure between two arms.
RESULTS: There were no complications after the carotico-subclavian bypass surgery. The differences in arterial pressure between the two arms disappeared together with the symptoms after the surgery.
CONCLUSION: Carotico-subclavian bypass surgery is a procedure with low mortality and morbidity rates and good long term outcomes in patients with subclavian steal syndrome
Characteristics of Patients Attending a Cardiology Outpatient Clinic: A Focus on the Turkish Healthcare System
Background and Aim: This study aimed to characterize the clinical and demographic characteristics of patients and to shed light on the Turkish healthcare system.
Materials and Methods: A total of 580 consecutive patients were enrolled in this study. The patient demographic and clinical characteristics and complaints were recorded. Blood samples were taken from the antecubital vein after an overnight fast.
Results: The mean age of the study population was 56.20±15.35 years, 321 (55.3%) of whom were female, 24.8% of whom had diabetes, 55.5% of whom had hypertension, 35.4% of whom had hyperlipidemia, and 24.6% of whom had coronary artery disease (CAD). The major complaints of the patients were chest pain (157, 27.1%), control of their chronic diseases (114, 19.4), prescription of drugs (101, 17.4%), palpitation (63, 10.9%), high blood pressure (46, 7.9%), dyspnea (35, 6.0%), and other complaints (21, 3.6%). Four (0.7%) patients had no complaints, and 39 (6.7%) patients were referred from other clinics for cardiological examination. Compared with men, women more often presented to the cardiology outpatient clinic with complaints of palpitations, whereas men more often presented to the clinic for prescription of drugs. Men had a greater incidence of hyperlipidemia, CAD, and peripheral arterial disease; higher levels of glucose and creatinine; and lower total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol concentrations.
Conclusion: Most patients went directly to outpatient clinics without visiting primary or secondary health centers
Adaptive pairs trading strategy performance in Turkish derivatives exchange with the companies listed on Istanbul stock exchange
Due to copyright restrictions, the access to the full text of this article is only available via subscription.We implemented model-driven statistical arbitrage strategies in Turkish equities market. Trading signals are generated by optimized parameters of distance method. When the trade in signal is triggered by the model, market-neutral portfolio is created by long in the synthetic ETF, which is based on constrained least squares regression of selected Istanbul Stock Exchange stocks and short in Turkish Derivatives Exchange (Turkdex) index futures contract. We performed pairs trading strategy based on a comparative mean reversion of asset prices with daily data over the period February 2005 through July 2011 in Istanbul Stock Exchange (ISE) and Turkdex. We constructed a hypothetical ISE30 ETF Index on a daily basis in order to originate pairs trading strategy with Turkdex. Because of the leverage rule of (1–10) index futures contracts, we had to evaluate spot stock pairs formation with futures contracts pairs strategy. The results indicate that applied pairs strategy produced overall returns of 901 per cent during the investment period, whereas naive strategy (buy and hold ISE-30 index) return for the same period was 111 per cent. Similar outperformance was observed in the Sharpe and Sortino ratios
Laiklik ve anayasa mahkemesi
Bu çalısmanın amacı, Türkiye Cumhuriyeti’nin vazgeçilmez ve
degistirilemez unsurlarından biri olan laiklik ilkesinin anlam ve kapsamını
açıklamak ve Türk Anayasa Mahkemesi’nin laiklik ilkesini ne sekilde ele alıp
kararlarına yansıttıgını ortaya koymaktır.
Çalısmanın ilk bölümde laikligin tanımı ve tarihi gelisimi hakkında bilgi
verildikten sonra, ikinci bölümde laik devletin tanımı yapılmıs ve bu devletin varlıgı
için gerekli sartların neler oldugu ortaya konulmustur. Bu bölümde ayrıca,
Anayasa’da öngörülen zorunlu Din Kültürü ve Ahlak Bilgisi derslerinin ve Diyanet
sleri Baskanlıgı’nın genel idare içerisinde yer almasının laik devlet yapısına
aykırılık olusturup olusturmadıgı degerlendirilmektedir.
Üçüncü bölümde, ülke gündemini sürekli mesgul eden ve sık sık tartısmalar
yasanmasına neden olan türban sorununa Anayasa Mahkemesi’nin yaklasımı
degerlendirilmis, bu degerlendirme sırasında Avrupa nsan Hakları Mahkeme’sinin
türban kararı da ele alınmıstır.
Dördüncü ve son bölümde ise, Anayasa Mahkemesi’nin laik cumhuriyet
ilkesine aykırılık nedeniyle kapattıgı siyasi partiler incelenerek, Mahkeme’nin laiklik
temelli parti kapatma davalarındaki genel tutumu yansıtılmıstır.
Her ülkedeki din ve devlet arası iliskiler ve dolayısıyla laiklik uygulaması
birbirinden farklı olmakta ve laikligin anlamı toplumdan topluma ve zamandan
zamana farklılık göstermektedir. Bununla birlikte laiklik, Türkiye Cumhuriyeti
kuruldugundan beri, bu Cumhuriyet’in en temel ilkelerinden biri olmustur. Anayasa
Mahkemesi de bu temel ilkenin yerlestirilmesi ve korunması konusuna hassasiyetle
yaklasmıs ve bu hassasiyetini konuyla ilgili tüm kararlarına yansıtmıstır
Comprehensive spectral and thermal characterization of oil shales
The heterogeneous nature of oil shale resources associated to the depositional environments, lithology, and organic content make the reserve estimation complex and unpredictable. However, comprehensive laboratory studies on organic rich shale samples collected from different regions can increase the understanding about the organic content of oil shales, interaction of shale with organic matter and injected fluid used during enhanced oil recovery method. This study investigates the characterization of eight different Turkish and American oil shale samples with several spectral methods and a thermal analysis. The main purpose of this study is to characterize the oil shale samples to increase the understanding about the organic content and interaction of shale with organic matter. In this study, we used Thermal Gravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) analysis to estimate organic content of each oil shale sample in air and nitrogen environments. X-Ray Diffraction (XRD) was used to define minerals in oil shale. Fourier Transform Infrared Spectroscopy (FTIR) was used to detect the mineral and kerogen in oil shale before and after the TGA/DSC analysis. Scanning Electron Microscope (SEM) was used to characterize the depositional environment of each oil shale samples. TGA/DSC results verified that oil shale samples have up to 50% of organic matter. XRD and FTIR results helped to identify the organic and inorganic compounds. Effects of minerals and ions were recognized by comparing TGA/DSC curves and FTIR spectra. It was recognized that the more carbonate ion in the oil shale the more increase in weight loss occurred. Diatoms identified from SEM results showed that depositional environments of the some oil shale samples are marine environments. This study provides insight for the reserve estimation of the eight different oil shale samples with comprehensive spectral and thermal characterization
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