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Search Results: 1 - 10 of 167 matches for " Ertugrul COLAK "
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Comparison of Generalized Estimating Equations' Performance in Clustered Binary Observations
Ertugrul COLAK,Kazim OZDAMAR
Trakya Universitesi Tip Fakultesi Dergisi , 2007,
Abstract: Objectives: The objective of this study is to compare the performance of generalized estimating equations (GEE) for analysis of clustered binary observations under varying group and observation numbers according to intraclass correlation coefficients (ICC).Materials and Methods: The comparison of GEE performance was made by using bias of parameter estimations through computer simulations under varying group sizes, ICC, number of clusters, and number of observations per cluster. Simulations were performed in SAS 9.0 by using Monte Carlo simulation method. Analyses were made with SAS GENMOD procedure.Results: When intraclass correlation coefficient was low (ICC<0.10), there was no significant difference in parameter estimation and their biases and it was observed that GEE gave reliable, consistent and unbiased estimations. However, when ICC increased (ICC>0.10), it was found that the parameter estimations were significantly biased. On the condition that total sample size is fixed; it was observed that, even though the general sample size was constant in all groups while the number of groups was decreasing, when the number of observations per cluster increased, parameter estimations and their biases weren't affected significantly and the effective factor in parameter estimation was ICC.Conclusion: Because GEE method uses population averaged logistic regression approach, it cannot explain the changes and correlations in clusters completely. The use of GEE method is inconvenient particularly for data sets which have ICC greater than 0.10.
Di Hekimli inde Topikal Florür Uygulama Metotlar
Ertugrul Ercan,Serdar Baglar,Hakan Colak
Cumhuriyet Dental Journal , 2011, DOI: 10.7126/cdj.2012.693
Abstract: ocuklarda ve yeti kinlerde di ürü ünün nlenmesi modern di hekimli i prati inin en nemli niteli idir. Di hekimleri taraf ndan di ürü ünün nlenmesi amac yla ok say da koruyucu di hekimli i program geli tirilmi olmas na kar n muhtemelen bunlardan hi biri florun uygun kullan m kadar nemli de ildir. Di hekimleri hastalar n optimal flor al m n sa lamak i in e itli se enekleri vard r. Bu makalede, di hekimli i prati inde hem profesyonel hem de bireysel uygulanan farkl topikal florür uygulama metotlar n derlenmesi ama lanm t r
Glaucoma after Penetrating Keratoplasty: Incidence, Risk Factors, and Management
Nilgun Yildirim,Huseyin Gursoy,Afsun Sahin,Ahmet Ozer,Ertugrul Colak
Journal of Ophthalmology , 2011, DOI: 10.1155/2011/951294
Abstract: Purpose. To report the incidence and risk factors for postkeratoplasty glaucoma (PKG), as well as its management. Subjects and Methods. 122 eyes, (43% with pseudophakic and aphakic bullous keratopathy (PABK)) which underwent penetrating keratoplasty (PK), were analyzed. Results. The rate of PKG development was 34% within 39 months of follow-up. PABK, corneal perforations, keratitis, and previous high intraocular pressure (PHIOP) were high risk factors for PKG. Glaucoma was controlled medically in 62% of PKG cases. Surgery (Ex-PRESS shunt in 63%) and diode laser cyclophotocoagulation were applied in others (38%). The rate of postoperative complications and graft survival was similar in eyes with and without PKG. Conclusion. PHIOP, preoperative diagnoses other than keratoconus, and corneal dystrophies were highly associated with PKG. Ex-PRESS shunts were effective in refractory PKG. If glaucoma is controlled, it is possible to obtain similar rates of graft survival and postoperative complications in eyes with and without PKG.
ki Farkl Restoratif Materyalin S n f V Kavitelerdeki Mikros z nt ya Etkisi
Serdar Baglar,Mehmet Dalli,Hakan Colak,Ertugrul Ercan
Cumhuriyet Dental Journal , 2011, DOI: 10.7126/cdj.2012.688
Abstract: Ama : Bu al man n amac s n f V kavitelerde bir kompozit rezin ile bir yüksek viskoziteli cam iyonomer siman n mikros z nt lar n n in vitro artlarda de erlendirilmesidir. Gere ve Y ntem: Bu al mada 30 adet ürüksüz insan üst premolar di i kullan ld . Her di in bukkal yüzeylerine mine-sement s n r ndan 1 mm a a da olacak ekilde standardize edilmi S n f V kaviteler haz rland . Di ler her biri 15 di ten olu an rastgele 2 gruba ayr ld . Haz rlanan kaviteler birinci grupta bir kompozit rezinle (S3 Bond / Clearfil Esthetic; Kuraray, Tokyo, Japonya), ikinci grupta bir yüksek viskoziteli cam ionomer (Fuji IX GP; GC, Tokyo, Japonya) ile dolduruldu. Restoratif maddeler bir LED (Elipar Freelight; 3M ESPE, Seefeld, Germany) k kayna kullan larak polimerize edildi. Bütün rnekler 24 saat distile su i erisinde bekletildi ve 1 dakika kalacak ekilde 5 ve 55°C termal siklus i lemi 10000 kez uyguland . Di ler restorasyonlar n 1 mm evresi hari t rnak cilas ile kapland . 24 saat %1’lik metilen mavisi solüsyonunda bekletildi. Daha sonra di ler y kan p, bukkolingual y nde dikey olarak kesilerek x15 büyütmede stereomikroskop ile de erlendirildi. Elde edilen veriler Kruskal Wallis ve Whitney U testleriyle de erlendirildi. Bulgular: Deney gruplar aras nda istatistiksel bir farkl l k bulunamad (p>0.05). Grup 1’de servikal ve oklüzal mikros z nt de erleri aras nda istatistiksel olarak anlaml l k bulundu ( p<0.05 ). Grup 2’ de ise servikal ve oklüzal skorlarda fark bulunmad . Sonu : Kullan lan her iki restoratif materyal, s n f V kavitelerde mikros z nt de erlendirmesinde ba ar l bulunmu tur.
Glaucoma after Penetrating Keratoplasty: Incidence, Risk Factors, and Management
Nilgun Yildirim,Huseyin Gursoy,Afsun Sahin,Ahmet Ozer,Ertugrul Colak
Journal of Ophthalmology , 2011, DOI: 10.1155/2011/951294
Abstract: Purpose. To report the incidence and risk factors for postkeratoplasty glaucoma (PKG), as well as its management. Subjects and Methods. 122 eyes, (43% with pseudophakic and aphakic bullous keratopathy (PABK)) which underwent penetrating keratoplasty (PK), were analyzed. Results. The rate of PKG development was 34% within 39 months of follow-up. PABK, corneal perforations, keratitis, and previous high intraocular pressure (PHIOP) were high risk factors for PKG. Glaucoma was controlled medically in 62% of PKG cases. Surgery (Ex-PRESS shunt in 63%) and diode laser cyclophotocoagulation were applied in others (38%). The rate of postoperative complications and graft survival was similar in eyes with and without PKG. Conclusion. PHIOP, preoperative diagnoses other than keratoconus, and corneal dystrophies were highly associated with PKG. Ex-PRESS shunts were effective in refractory PKG. If glaucoma is controlled, it is possible to obtain similar rates of graft survival and postoperative complications in eyes with and without PKG. 1. Introduction There are many corneal transplantation techniques such as deep anterior lamellar keratoplasty and Descemet’s stripping endothelial keratoplasty with many advantages over penetrating keratoplasty (PK), but PK is still the most common type of corneal transplant performed [1]. The leading indications for PK are keratoconus, bullous keratopathy (BK), corneal scars due to previous intraocular surgeries, infections, or trauma, corneal dystrophies, and graft failure [2]. In developing countries, corneal scars due to herpes simplex virus, presumed bacterial infections, or traumatic insults are more frequent indications for PK than the noninflammatory conditions such as keratoconus and corneal dystrophies [3]. The success of PK depends on many preoperative, intraoperative, and postoperative factors, including the health of the donor cornea, the indication for PK, suture techniques preferred, the quality of postoperative management, and the presence of high intraocular pressure (IOP) [1]. Postkeratoplasty glaucoma (PKG) is one of the challenging issues important for the survival of the graft. The incidence of PKG has been reported to range between 9% and 35% [4–9]. It has been reported to be one of the most serious complications following PK and the second leading cause of graft failure after graft rejection [10, 11]. Its diagnosis and management are much more difficult than the glaucoma cases with their own corneas [12]. The aims of our study were to report the incidence and risk factors for PKG and its management. 2.
Serum Amyloid A, Procalcitonin, Tumor Necrosis Factor-, and Interleukin-1 Levels in Neonatal Late-Onset Sepsis
Birsen Ucar,Bilal Yildiz,M. Arif Aksit,Coskun Yarar,Omer Colak,Yildiz Akbay,Ertugrul Colak
Mediators of Inflammation , 2008, DOI: 10.1155/2008/737141
Abstract: Background. Sepsis is an important cause of mortality in newborns. However, a single reliable marker is not available for the diagnosis of neonatal late-onset sepsis (NLS). The aim of this study is to evaluate the value of serum amyloid A (SAA) and procalcitonin (PCT) in the diagnosis and follow-up of NLS. Methods. 36 septic and healthy newborns were included in the study. However, SAA, PCT, TNF-, IL-1, and CRP were serially measured on days 0, 4, and 8 in the patients and once in the controls. Töllner's sepsis score (TSS) was calculated for each patient. Results. CRP, PCT, and TNF- levels in septic neonates at each study day were significantly higher than in the controls (=.001). SAA and IL-1 levels did not differ from healthy neonates. The sensitivity and specificity were 86.8% and 97.2% for PCT, 83.3% and 80.6% for TNF-, 75% and 44.4% for SAA on day 0. Conclusion. Present study suggests that CRP seems to be the most helpful indicator and PCT and TNF- may be useful markers for the early diagnosis of NLS. However, SAA, IL-1, and TSS are not reliable markers for the diagnosis and follow-up of NLS.
Comparison of Semiparametric, Parametric, and Nonparametric ROC Analysis for Continuous Diagnostic Tests Using a Simulation Study and Acute Coronary Syndrome Data
Ertugrul Colak,Fezan Mutlu,Cengiz Bal,Setenay Oner,Kazim Ozdamar,Bulent Gok,Yuksel Cavusoglu
Computational and Mathematical Methods in Medicine , 2012, DOI: 10.1155/2012/698320
Abstract: We aimed to compare the performance of three different individual ROC methods (one from each of the broad categories of parametric, nonparametric and semiparametric analysis) for assessing continuous diagnostic tests: the binormal method as a parametric method, an empirical approach as a nonparametric method, and a semiparametric method using generalized linear models (GLM). We performed a simulation study with various sample sizes under normal, skewed, and monotone distributions. In the simulations, we used estimates of the ROC curve parameters and , estimates of the area under the curve (AUC), the standard errors and root mean square errors (RMSEs) of these estimates, and the 95% AUC confidence intervals for comparison. The three methodologies were also applied to an acute coronary syndrome dataset in which serum myoglobin levels were used as a biomarker for detecting acute coronary syndrome. The simulation and application studies suggest that the semiparametric ROC analysis using GLM is a reliable method when the distributions of the diagnostic test results are skewed and that it provides a smooth ROC curve for obtaining a unique cutoff value. A sample size of 50 is sufficient for applying the semiparametric ROC method.
Temperature profiles of Agaricus bisporus in composting stages and effects of different composts formulas and casing materials on yield
Mehmet Colak
African Journal of Biotechnology , 2004,
Abstract: Three compost formulas using different activator materials were prepared for Agaricus bisporus cultivation. A locally available casing material known as peat of Bolu district and its different combinations with perlite were used. Temperature profiles of all mixtures during composting were measured at every composting stages at various depth in order to determine the compostability level of substrates. Compost temparature steadily increased until the 10th day of composting and maximum temperatures were recorded at the second turning stage of composting. The highest yield of (5124.1 g/kg) was recorded by wheat straw mixed with pigeon manure (formula number II) with the peat as casing material mixed with perlite (80:20 in volume). The most appropriate casing materials was appeared to be the peat of Bolu district mixed with perlite (80:20; in volume) for all of compost materials. Key Words: Composting, Agaricus bisporus, compost temperature, casing material, yield. African Journal of Biotechnology Vol.3(9) 2004: 456-462
Importance of Superoxide Dismutase in Distinguishing of Apodemus flavicollis and Apodemus sylvaticus (Mammalia: Rodentia) in Thrace
Reyhan Colak
Pakistan Journal of Biological Sciences , 2006,
Abstract: Specimens of Apodemus flavicollis, Apodemus sylvaticus and Apodemus agrarius in Thrace were analyzed based on superoxide dismutase (SOD). Sod fixed for A alleles in A. flavicollis, B alleles in A. sylvaticus and C alleles in A. agrarius in Turkish Thrace and very clearly separated two sibling species A. flavicollis and A. sylvaticus along with A. agrarius.
Case 2
Errol Colak
University of Toronto Medical Journal , 2002, DOI: 10.5015/utmj.v80i1.847
Abstract:
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