The Effect of Capital Structure on Profitability: Evidence from the Turkish Manufacturing Companies

Purpose: This study analyses the relationship between capital structure and profitability levels of manufacturing industry companies operating in Türkiye between the years 2006-2020. Methodology: The relationship between capital structure and the profitability of Turkish manufacturing industry companies was analyzed using the standard error estimator proposed by Driscoll and Kraay (1998). In this context, sub-panel data models were created. Findings: The findings showed that capital structure changes (short-term debt, long-term debt, and total debt) in the manufacturing industry are negatively related to both return on assets and return on equity. Originality: It is thought that this study will contribute to the existing literature in terms of better understanding the relationship between the changes in the capital structure decisions of the manufacturing industry companies operating in Türkiye, both their return on assets and their return on equity, taking into account their sub-sectors

Regime changes in monetary policy and the Expectation Hypothesis of the term structure in Turkey

In this study we test the long-run validity of the Expectation Hypothesis of the Term Structure (EHTS) in Turkey by using monthly interest rate series from 2003m1 to 2010m1. The data set is obtained from the bonds and bills market for the government securities in the Istanbul Stock Exchange (ISE). Several results arise from our empirical analysis. First, we find strong evidence that there are stationary combinations of the long and short rates during the sample period. Secondly, when we restrict the cointegrating vectors to be the spread vectors between short and long rates we are not able to reject the restriction if the dynamic specifications of the systems include 2 lags of the interest rates. This result, however, is not robust to the lag length of 4 and 6 if the systems include interest rates with maturities longer than 6 months. Finally, the formal stability test results suggest that the regime change from the implicit to the full-fledged inflation targeting (IT) has no significant effect on the relationship among the interest rates on the short end of the term structure while the structural instability found in the relationship between the short rates and the long rates with maturity longer than 6 months might indicate the effect of the regime shift on this relationship. These results are in line with the conclusions of the literature that argues the EHTS to hold for the short end of the term structure when the focus of the monetary policy is to stabilize the short-term interest rates

Non-sendromik dudak damak yarığı hastalarında multidisipliner tedavi: 2 vaka raporu

Objective: It is intended in this case report to explain the multidisciplinary treatment of 2 non-syndromic cleft lip and palate patients with different approaches, the treatment phases of prosthetic rehabilitation and the results obtained. Case Reports:15-year-old unilateral cleft lip and palate patient and 25-year-old bilateral cleft lip and palate patient was admitted to our clinic with the functional and aesthetic complaints. Orthodontic, surgical and prosthetic treatments were applied Results: With multidisciplinary treatments aesthetic and functional solutions were provided. Aesthetic and functional results were obtained for both cases with fixed restorations. The treatments protocols had no complications. The outcomes were of high quality and brought satisfaction to the patients. Conclusion: Multidisciplinary treatment should be considered in cleft lip and palate patients in order to be able to fully ensure speech and hearing, continuation of occlusion and maxillofacial growth in the normal course and the improvement of physical appearance and psychological state. However, different treatment plans should be considered in its different timing for each case.Amaç: Bu vaka raporunda 2 non-sendromik dudak damak yarıklı vakanın farklı yaklaşımlarla protetik tedavisinin değerlendirilmesi amaçlanmaktadır. Vaka Raporu: 15 yaşında tek taraflı dudak damak yarıklı erkek hasta ve 25 yaşında çift taraflı dudak damak yarıklı kadın hastalarımız kliniğimize estetik ve fonksiyon kaybından dolayı başvurmuşlardır. Ortodontik, cerrahi ve prostodontik yaklaşımlarla hastalara uygulanmıştır. Her iki vakada da sabit protetik restorasyonlar protokolleri uygulanan hastalarımızda herhangi bir komplikasyon gözlemlenmemiştir. Tedaviler yüksek hayat kalitesi ve memnuniyet sağlamıştır. Sonuçlar: Dudak damak yarıklı hastalarda; konuşma, maxillofacial büyümenin normal seyrinde devamı, fiziksel görünüşün arttırılması ve psikolojik durumun düzeltilmesi için multidisipliner yaklaşım gereklidir. zamanlamaları değerlendirilmelidir

Cost-effectiveness of sorafenib for treatment of radioactive iodine (rai)-refractory locally advanced/metastatic differentiated thyroid cancer (dtc) in Turkey

WOS: 000354498503198OBJECTIVES: Sorafenib is the first product approved for treatment of RAI refractory locally advanced/metastatic DTC patients. This study was conducted in order to analyze cost-effectiveness of sorafenib for treatment of patients with RAI refractory locally advanced/metastatic DTC in Turkey. METHODS: A cohort partition model assigning patients to one of three health states according to the proportion of patients who are progression-free, progressed, or dead in each 28-days cycle was adapted to Turkish setting. The incremental cost-effectiveness ratios (ICER) were calculated per quality-adjusted life years (QALYs) and life-years (LYs) gained. Turkish payer’s perspective was taken and time-horizon was set as patient’s lifetime (maximum 30 years). Sorafenib was compared to the best supportive care (BSC) within the model since there are no agents for treatment of patients on this stage of the disease. Essential clinical inputs were derived from DECISION trial and local resource-utilization data were based on expert opinions through an expert panel. Sensitivity of the results was evaluated in terms of key inputs by deterministic oneway and probabilistic sensitivity analyses. All costs were calculated in Turkish Liras (TL) and converted to USD using TL/USD currency rate as 2.2 (mid-2014). RESULTS: Total cost of sorafenib-treated patients is 24,384 USD higher compared to BSC. Besides, sorafenib is associated with increments of 1.29 LYs and 0.80 QALYs compared to BSC. The ICER of sorafenib per LYs and QALYs gained compared to BSC were determined as 18,851 USD and 30,485 USD respectively. One-way sensitivity analysis demonstrated that results are not sensitive to the changes in model inputs and pharmacoeconomic analysis results were validated by probabilistic sensitivity analysis. CONCLUSIONS: Sorafenib is cost-effective for treatment of patients with RAI refractory locally advanced/metastatic DTC compared to BSC with an ICER value below the willingness-to-pay threshold (3-times GDP per capita ─ 32,346 USD) for Turkey

Bir bant içerisinde hareket eden faizlerin modellenmesi.

It is not uncommon to observe interest rates or currencies to move in a band or being subject to an upper and/or lower bound set by national central banks. The Turkish Central Bank is using the interest rate corridor system actively in tandem with the liquidity policy to fine–tune the short rate in the TRY money market. Bond pricing models relying on a single factor use the short rate as the sole determinant of the entire yield curve. It would be a big mistake to ignore the fact that the short rate in Turkey is moving in a corridor, while pricing bonds using the short rate as the single factor. In this work, we try to establish a one factor yield curve model, where the interest rate is modeled as Vasicek process. The closed-form bond price is the main contribution of the novel approach devised in the thesis. Furthermore, mean reversion and normality tests of the time series justifies the usage of Vasicek process as the underlying interest rate modePh.D. - Doctoral Progra

Investigation of the effect of night-day on learning and memory under isoflurane administration in newborn rats

Amaç: Bu çalışmanın amacı izofluran uygulanan yenidoğan (7 günlük) ratlarda sirkadiyan ritmin öğrenme ve bellek üzerine etkisini araştırmaktır. Yöntem: 42 yenidoğan rat çalışmaya alındı ve rastgele 4 grup oluşturuldu. Grup-1 (n:11) ve Grup-3 (n:11)'e 450 mL cam kavanozlar içerisinde 6 saat süresince %1,5 izofluran uygulandı. Grup-2 (n:10) ve Grup-4 (n:10) 6 saat süresince oda havasında tutuldu (kontrol). Gece grupları (Grup-1 ve Grup-2) 19:00-01:00 saatleri arasında, gündüz grupları (Grup-3 ve Grup-4) 07:00-13:00 saatleri arasında izlendi. İzofluran anestezisinin sona ermesinden iki saat sonra ratlar öğrenme ve bellek testlerinin uygulanacağı zamana dek bakılmak üzere annelerinin yanına alındı. Ratlara 5 hafta sonra öğrenme ve bellek fonsiyonlarının değerlendirilmesi amacıyla Morris Su Tankı testi uygulandı. Verilerin istatistiksel analizi yapıldı. Bulgular: Öğrenme ve bellek deneyleri sonuçları değerlendirildiğinde ilk dört gün uygulanan öğrenme testlerinde platformu bulma süreleri değerlendirildiğinde gruplar arasında fark saptanmadı (p>0,05). Beşinci gün uygulanan probe trial'de hedef kadranda kalış süreleri değerlendirildiğinde gruplar arasında anlamlı fark bulunmadı (p>0,05). Sonuç: İzofluran uygulanan yenidoğan ratlarda sirkadiyan ritmin öğrenme ve bellek fonksiyonlarını etkilemediği saptanmıştır. Anahtar Kelimeler: İzofluran, rat, sirkadiyan ritim, öğrenme ve bellek. Aim: The aim of this study is to evaluate the effect of circadian rhythm on learning and memory in isoflurane administrated newborn (d:7) rats. Material and Methods: 42 newborn rats were involved in this study and randomised to four groups. Group-1 (n:11) and Group-3 (n:11) were received to %1.5 concentration of isoflurane for 6 hours. Group-2 (n:10) and Group-4 (n:10) were exposed to room air for 6 hours (controls). Night groups (Group-1 and Group-2) were studied during between 07:00 pm - 01:00 am and day groups (Group-3 and Group-4) were studied during between 07:00 am -13:00 pm. Two hours after cessation of isoflurane anesthesia rats were carried out to their own mother's sides until learning and memory tests were performed. Five weeks later Morris Water Maze test was performed in order to evaluate learning and memory functions. Results: Learning and memory test results have shown that there was no difference between groups also in platform finding times of initial four days performances (p>0,05). There was no difference in evaluation of standing times on target quadrant in probe trial administration during fifth day (p>0,05). Conclusion: We concluded that circadian rhythm has no effect on memory and learning functions in isoflurane administrated newborn rats. Keywords: Isoflurane, rat, circadian rhythm, learning and memory

Estımatıon Of The Ocean Tıde Loadıng Dısplacements From The Vlbı Observatıons And Valıdatıon Wıth The Global Ocean Tıde Models

As a result of the analysis of the measurements of space/satellite geodetic techniques, the defined coordinates of the terrestrial reference frame (TRF) of the earth fixed geodetic control points are estimated. Since the measurement model used for the estimation of the coordinates from the measurement of space/satellite geodesic techniques is not linear, correction estimation is performed to the approximate value of each parameter by linearizing the measurement model before applying the least-squares estimation method. Since the convergence diameter of the least-squares is small, the approximate values should be chosen as close to the exact values as possible. In the Kalman filter, unknown parameters in the first epoch are started with a prediction. The filter moves forward over time until the last epoch is processed. Parameters that are constantly modeled over time are improved in every epoch, and the estimates in the last epoch are the final estimates of these parameters. The approximate values of the station coordinates are obtained as a result of linear velocity correction for each measurement epoch and bringing together some geodynamic position corrections, and the station coordinates a priori values are calculated. According to the magnitude of these geodynamic corrections, respectively; displacements of solid Earth tides, ocean tidal and non-tidal loading, hydrology loading, polar tides, atmospheric tidal and non-tidal loading. The position errors due to the inadequacies of these ocean tide corrections, which are calculated from the ocean tide models for each measurement epoch and brought to each measure, are reflected not only on the station coordinates but also on other parameters with parameter estimation. It is only possible to prevent this situation by developing better ocean tide models. Within the scope of this thesis, International VLBI Service for Geodesy & Astrometry (IVS) daily sessions of VLBI co-located sites (22 stations) homogeneously distributed around the world were analyzed and the position time series of VLBI stations were produced and compared with the values calculated from the ocean tide models for the same epochs. Thus, model inadequacies were revealed for each tidal period. To be compatible with the global ocean models (e.g. FES2014b, GOT4.10c, TPXO9-Atlas), the positive direction in the displacements estimated from VLBI measurements is taken as radial, west and south. Local topocentric coordinates (radial, west, south) time series with 2-hour intervals for each station are taken as a measure again and ocean tide loading semi-diurnal (M2, S2, N2, K2) and diurnal (K1, O1, P1, Q1) tides of amplitudes and Greenwich phase delay components are estimated with using least-squares and Kalman filter. The agreement between the time series of ocean tide displacements from VLBI measurements and global models was examined by statistical methods for each tidal period, and global ocean models and inadequacies due to VLBI measurements were revealed.Uzay/uydu jeodezisi teknikleri ölçülerinin analizi sonucu yer sabit jeodezik kontrol noktalarının yersel referans çatısında (terrestrial reference frame, TRF) tanımlı koordinatları kestirilir. Uzay/uydu jeodezisi teknikleri ölçülerinden koordinatların kestirimi için kullanılan ölçü modeli doğrusal yapıda olmadığı için en-küçük-kareler kestirim yöntemi uygulanmadan önce ölçü modeli doğrusallaştırılarak her bir parametrenin yaklaşık değerine düzeltme kestirimi gerçekleştirilir. En-küçük-karelerin yakınsama çapı küçük olduğu için de yaklaşık değerlerin mümkün olduğu kadar kesin değerlere yakın seçilmesi gerekmektedir. Kalman filtresinde ise ilk epoktaki bilinmeyen parametreler bir tahminle başlatılır. Filtre son epok işlenene kadar zaman içinde ileri gider. Zaman içinde sabit olarak modellenen parametreler, her epokta iyileştirilir ve son epoktaki kestirimler bu parametrelerin nihai tahminleridir. İstasyon koordinatlarının yaklaşık değerleri ise her bir ölçü epoğu için lineer hız düzeltmesi, yanında bir takım jeodinamik konum düzeltmelerinin getirilmesi sonucu elde edilerek parametre kestirimine esas istasyon koordinatları öncül değerleri hesaplanır. Bu jeodinamik düzeltmeler büyüklülerine göre sırasıyla; katı Yer gelgitleri, okyanus gelgit yüklemesi, okyanus gelgitsel olmayan yüklemeleri, hidroloji yüklemesi, kutup gelgitleri, atmosfer gelgitsel ve gelgitsel olmayan yüklemeleri yer değiştirmeleridir. Her bir ölçü epoğu için okyanus gelgit modellerinden hesaplanan ve her bir ölçüye getirilen bu okyanus gelgit düzeltmelerinin yetersizliklerinden kaynaklı konum hataları parametre kestirimi ile sadece istasyon koordinatları değil diğer parametrelere de yansırlar. Bu durumun önüne geçmek ancak daha iyi okyanus gelgit modellerinin geliştirilmesiyle mümkün olabilmektedir. Bu tez çalışması kapsamında, Dünya üzerinde homojen olarak dağılmış VLBI yerleşkelerinin (22 istasyon) Uluslararası VLBI Jeodezi ve Astrometri Servisi (IVS) günlük oturumları analiz edilmiş, VLBI istasyonlarının konum zaman serileri üretilerek aynı epoklar için okyanus gelgit modellerinden hesaplanan değerleri ile karşılaştırılmıştır. Böylece, her bir gelgit periyotu için ayrı ayrı model yetersizlikleri ortaya konmuştur. Global okyanus modelleri (örneğin, FES2014b, GOT4.10c, TPXO9-Atlas) ile uyumlu olması açısından VLBI ölçülerinden kestirilen yer değiştirmelerde pozitif yön radyal, batı ve güney olacak şekilde ele alınmıştır. Her istasyon için 2 saat aralıklı lokal toposentrik koordinatlar (radyal, batı, güney) zaman serileri tekrar ölçü olarak ele alınarak en-küçük-kareler (EKK) ve Kalman filtresi kestirim yöntemleri ile okyanus gelgit yüklemesi yarı-günlük (M2, S2, N2, K2) ve günlük (K1, O1, P1, Q1) gelgitlerin genlik ve Greenwich faz gecikmesi bileşenleri kestirilmiştir. VLBI ölçülerinden ve global modellerden okyanus gelgiti yer değiştirmelerinin zaman serileri arasındaki uyuşum her bir gelgit periyotu için ayrı ayrı istatistiksel yöntemler ile irdelenerek global okyanus modelleri ve VLBI ölçülerine bağlı yetersizlikler ortaya konmuştur

An alternative mean reversion test for interest rates

A number of empirical studies assert that interest rates are governed by unit root processes rejecting any form of reversion to a long term mean by resorting to certain tests, among which the Augmented Dickey Fuller (ADF) is the most widely used one. In this study, we propose an alternative testing methodology that can be applied along with ADF test, in the sense that there are times where it can capture stationarity when the other fails to do so. Moreover, our test has more power than ADF test. As an application to real-data, we consider 10-year US and Turkish T-bond rates