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Search Results: 1 - 10 of 327189 matches for " Evren Süer "
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The effects of aging on fertility in men
Evren Süer,?mer Gülp?nar,?nder Yaman
Turkish Journal of Urology , 2012,
Abstract: The decline in the rate of childbirth observed in older couples gives rise to the question of whether there is a relationship between age and fertility. This question has been studied much more extensively for females than for males, perhaps because of the apparent lack of an age limit for males to have children. Investigating the effects of increased age on male fertility components, such as spermatogenesis, testicular histology and male reproductive histology, may help us understand the inverse relationship between age and birth rate. In this review, we have evaluated the literature regarding the effects of aging on fertility in an effort to determine how male reproductive capacity is affected by old age.
Significance of Tumor Size in Renal Cell Cancer with Perinephric Fat Infiltration: Is TNM Staging System Adequate for Predicting Prognosis?
Evren Süer,Sümer Baltaci,Berk Burgu,?zgü Aydo?du
Urology Journal , 2013,
Abstract: PURPOSE: To evaluate the influence of perinephric fat infiltration and tumor size on survival of patients with renal cell carcinoma (RCC).MATERIALS AND METHODS: We have retrospectively reviewed the records of 338 consecutive patients with pT1-3aN0M0 RCC, including 275 pT1-2 and 63 pT3a tumors, who underwent open partial or radical nephrectomy between 1995 and 2008. Univariate and multivariate analyses were performed in order to evaluate the prognostic factors. RESULTS:Median follow-up period was 36.07 months. Receiver Operating Characteristic curve analysis determined the optimal tumor size cutoff value as 7 cm (Area Under the Curve: 0.65 ± 0.047; 95% Confidence Interval: 0.558 to 0.741). Perinephric fat invasion and Fuhrman grade were independent prognostic factors for disease-specific survival (DSS). In patients with tumor size >7 cm, perinephric fat invasion affected DSS significantly. Tumor size (according to the cutoff value of 7 cm) significantly affected DSS in patients with pT3a disease. According to the TNM 2002 staging system, perinephric fat invasion did not have any significant effect on DSS in patients with tumor size smaller than 4 cm, unlike tumor size of 4 to 7 cm and >7 cm. pT3a tumors larger than 7 cm demonstrated the worst prognosis compared to other groups.CONCLUSION:Perinephric fat invasion was demonstrated as a significant prognostic factor for RCC patients with tumor size >4 cm. Consequently, evaluation of pT3a patients should take tumor size into consideration for better prognostic analysis.
An Overview of Istanbul’s Conservation Sites
?clal D?N?ER,Zeynep ENL?L,Yi?it EVREN
Megaron , 2009,
Abstract: With its 2500 years of historical heritage, Istanbul is situated on a privileged location at the crossroads of two continents. Further to this unique characteristic, the city comprises a wide palette of natural and cultural treasures like the Historic Peninsula, the Golden Horn and the Bosphorus. Since the 1970s, part of that heritage has been listed and is thus under protection. However, since the second half of the past century in particular, Istanbul has become a magnet for investments and individuals, with the result that these heritage sites are now targeted under an ongoing pressure of rapid urban growth and urban regeneration. This report attempts to provide an overview of Turkey’s conservation history, by placing an emphasis on risks in the planning of conservation areas in Istanbul. It is based on a study conducted by the authors in 2005-2006, in which all of Istanbul’s conservation areas were documented, digitalized and transferred into the Strategic Master Plan of Istanbul, prepared to a 1/100,000 scale. This paper provides a spatial and quantitative analysis of the city’s natural, archeological, historical, and urban conservation areas, all of which have been listed since the 1970s - when Turkey’s conservation legislation was expanded beyond the scale of single buildings. It also attempts to shed light on the problematic processes concerning Istanbul’s world heritage sites.
Atrial Septal Aneurysm: A Major Diagnostic Clue for a Patent Foramen Ovale
Amir M. Nia,Natig Gassanov,Evren Caglayan,Fikret Er
The Scientific World Journal , 2010, DOI: 10.1100/tsw.2010.93
Atrial Fibrillation
Natig Gassanov,Evren Caglayan,Firat Duru,Fikret Er
Cardiology Research and Practice , 2013, DOI: 10.1155/2013/142673
Atrial Fibrillation
Natig Gassanov,Evren Caglayan,Firat Duru,Fikret Er
Cardiology Research and Practice , 2013, DOI: 10.1155/2013/142673
The Patterns of High-Level Magnetic Activity Occurring on the Surface of V1285 Aql: The OPEA Model of Flares and DFT Models of Stellar Spots
H. A. Dal,S. Evren
Physics , 2012, DOI: 10.1086/660820
Abstract: Statistically analyzing Johnson UBVR observations of V1285 Aql during the three observing seasons, both activity level and behavior of the star are discussed in respect to obtained results. We also discuss the out-of-flare variation due to rotational modulation. Eighty-three flares were detected in the U-band observations of season 2006 . First, depending on statistical analyses using the independent samples t-test, the flares were divided into two classes as the fast and the slow flares. According to the results of the test, there is a difference of about 73 s between the flare-equivalent durations of slow and fast flares. The difference should be the difference mentioned in the theoretical models. Second, using the one-phase exponential association function, the distribution of the flare-equivalent durations versus the flare total durations was modeled. Analyzing the model, some parameters such as plateau, half-life values, mean average of the flare-equivalent durations, maximum flare rise, and total duration times are derived. The plateau value, which is an indicator of the saturation level of white-light flares, was derived as 2.421{\pm}0.058 s in this model, while half-life is computed as 201 s. Analyses showed that observed maximum value of flare total duration is 4641 s, while observed maximum flare rise time is 1817 s. According to these results, although computed energies of the flares occurring on the surface of V1285 Aql are generally lower than those of other stars, the length of its flaring loop can be higher than those of more active stars.
A New Method for Classifying Flares of UV Ceti Type Stars: Differences Between Slow and Fast Flares
H. A. Dal,S. Evren
Physics , 2012, DOI: 10.1088/0004-6256/140/2/483
Abstract: In this study, a new method is presented to classify flares derived from the photoelectric photometry of UV Ceti type stars. This method is based on statistical analyses using an independent samples t-test. The data used in analyses were obtained from four flare stars observed between 2004 and 2007. The total number of flares obtained in the observations of AD Leo, EV Lac, EQ Peg, and V1054 Oph is 321 in the standard Johnson U band. As a result flares can be separated into two types, slow and fast, depending on the ratio of flare decay time to flare rise time. The ratio is below 3.5 for all slow flares, while it is above 3.5 for all fast flares. Also, according to the independent samples t-test, there is a difference of about 157 s between equivalent durations of slow and fast flares. In addition, there are significant differences between amplitudes and rise times of slow and fast flares.
Rotation Modulations and Distributions of the Flare Occurrence Rates on the Surface of Five UV Ceti Type Stars
H. A. Dal,S. Evren
Physics , 2012, DOI: 10.1093/pasj/63.2.427
Abstract: In this study, we considered stellar spots, stellar flares, and also the relation between these two magnetic proccesses that take place on UV Cet stars. In addition, the hypothesis about slow flares described by Gurzadyan (1986 Ap&SS, 125, 127) was investigated. All of these discussions were based on the results of three years of observations of UV Cet-type stars: AD Leo, EV Lac, V1005 Ori, EQ Peg, and V1054 Oph. First of all, the results show that stellar spot activity occurs on the stellar surface of EV Lac, V1005 Ori, and EQ Peg, while AD Leo does not show any short-term variability and V1054 Oph does not exhibit any variability. We report on new ephemerides for EV Lac, V1005 Ori, and EQ Peg, obtained from time-series analyses. The phases, computed at intervals of 0.10 phase length, where the mean flare occurence rates to obtain maximum amplitude; also, the phases of rotational modulation were compared in order to investigate whether there is any longitudinal relation between stellar flares and spots. Although the results show that flare events are related with spotted areas on stellar surfaces during some of the observing seasons, we did not find any clear correlation among them. Finally, it was tested whether slow flares are fast flares occurring on the opposite side of the stars according to the direction of the observers, as mentioned in a hypothesis developed by Gurzadyan (1986). The flare occurence rates reveal that both slow and fast flares can occur in any rotational phases. The flare occurence rates of both fast and slow flares vary in the same way along the longitudes for all program stars. These results are not expected based on the case mentioned in the hypothesis.
The statistical analyses of flares detected in B band photometry of UV Ceti type stars
H. A. Dal,S. Evren
Physics , 2012, DOI: 10.1016/j.newast.2011.09.008
Abstract: In this study, we present the unpublished flare data collected from 222 flares detected in the B band observations of five stars and the results derived by statistical analysis and modeling of these data. Six basic properties have been found with a statistical analysis method applied to all models and analyses for the flares detected in the B band observation of UV Ceti type stars. We have also compared the U and B bands with the analysis results. This comparison allowed us to evaluate the methods used in the analyses. The analyses provided the following results. (1) The flares were separated into two types, fast and slow flares. (2) The mean values of the equivalent durations of the slow and the fast flares differ by a factor of 16.2 \pm 3.7. (3) Regardless of the total flare duration, the maximum flare energy can reach a different Plateau level for each star. (4) The Plateau values of EV Lac and EQ Peg are higher than the others. (5) The minimum values of the total flare duration increase toward the later spectral types. This value is called the Half-Life value in models. (6) Both the maximum flare rise times and the total flare duration obtained from the observed flares decrease toward the later spectral types.
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