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Now showing items 97 - 112 of 138

  • Effect of boron containing materials on flammability and thermal degradation of polyamide-6 composites containing melamine cyanurate

    Dogan, Mehmet   Yilmaz, Aysen   Bayramli, Erdal  

    Three different boron containing materials, zinc borate (ZnB), borophosphate (BPO(4)), and boron and silicon containing oligomer (BSi), were used to improve the flame retardancy of melamine cyanurate (MC) in a polyamide-6 (PA-6) matrix. The combustion and thermal degradation characteristics were investigated using limiting oxygen index (LOI), UL-94 standard, thermogravimetric analysis-Fourier transform infrared spectroscopy (TGA-FTIR), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM). All the three boron compounds showed no synergistic effect with MC, and only BPO(4) at high loadings showed comparable LOI values by increasing the dripping rate. For ZnB and BSi glassy film and char formation decreases the dripping rate and sublimation of melamine and give rise to low LOI. According to TGA-FTIR results, addition of boron compounds does not alter the gaseous product distribution of both MC and PA-6. The addition of boron compounds affects flame retardancy through physical means. It was noted from the TGA data that boron compounds reduced the decomposition temperature of both MC and PA-6, also affecting the flame retardancy negatively by premature degradation of MC at low temperatures. Copyright (C) 2009 John Wiley & Sons, Ltd.
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  • American Missionaries and the Middle East: Foundational Encountersby Mehmet Ali Doğan; Heather J. Sharkey

    Review by: Hans-Lukas Kieser  

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  • The effects of POSS particles on the flame retardancy of intumescent polypropylene composites and the structure-property relationship

    Turgut, Gizem   Dogan, Mehmet   Tayfun, Umit   Ozkoc, Guralp  

    In the current study, the effects of four different POSS nanoparticles on the flame retardant properties of intumescent PP were investigated through mass-loss calorimetry (MLC), limiting oxygen index (LOI) test and UL-94 ratings. In addition, the structure-property relationship was enlightened via thermal, morphological and mechanical tests. The four different POSS types, namely aminopropyl isobutyl-POSS (A-POSS), octaphenyl-POSS (OP-POSS), octaammonium-POSS (OA-POSS) and trissulfonic acid propyl-POSS (TS-POSS), were used. The ratio of ammonium polyphosphate (APP) to pentaerythritol (PER) was kept constant and the POSS content was varied as 0.5%, 1% and 3%. The MLC, LOI and UL-94 tests revealed that the addition of POSS particles had adjuvant on the flame retardant properties of PP/IFR system. All POSS nanoparticles showed their highest adjuvant effect at the lowest concentration of 0.5 wt%. The highest UL-94 rating and the highest LOI values were achieved in the presence of OA-POSS and TS-POSS. The ceramic layer formation was monitored using scanning electron microscopy (SEM) and FTIR on the char residues. The thermal properties of PP/IFR/POSS composites were obtained via differential scanning calorimeter and thermo-gravimetric analysis. The inline melt flow properties were observed via vertical force measurements. The fracture morphology was investigated using SEM. Mechanical tests showed that the yield strengths of the composites were lower than that of pristine PP; in contrast, the elongation at break and the impact strength of composites enhanced in A-POSS and TS-POSS based composites.
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  • Diastolic heart failure in elderly: The prognostic factors and interventions regarding heart failure with preserved ejection fraction

    Acikel, Sadik   Akdemir, Ramazan   Kilic, Harun   Yesilay, Asuman Bicer   Dogan, Mehmet   Cagirci, Goksel  

    Heart failure with a preserved ejection fraction is more common in elderly. Common comorbidities may have an impact on management of heart failure with preserved ejection fraction. The prognosis in more recent studies has been shown to be essentially similar to heart failure with reduced ejection fraction. Unlike heart failure with reduced ejection fraction for which many medications have been demonstrated to improve morbidity and mortality, no treatment has yet been shown to reduce morbidity and mortality in heart failure with preserved ejection fraction. Therefore, current treatment recommendations are aimed at symptomatic management as well as management of concomitant comorbidities. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
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  • Native aortic coarctation stenting in adults and adolescents: early and mid-term results of an adult interventional cardiology team

    Akdemir, Ramazan   Gunduz, Huseyin   Murat, Sani   Kilic, Harun   Yeter, Ekrem   Agac, Mustafa Tarik   Acar, Zeydin   Kaya, Yuksel   Dogan, Mehmet   Vatan, Mehmet Bulent   Cakar, Mehmet Akif   Erdem, Ali Fuat  

    Background: Stent implantation has evolved as an important therapeutic strategy for aortic coarctation. Aim: This study aimed to present the experience of aortic coarctation stenting using the Cheatham-Platinum stent by an Adult Interventional Cardiology Team. Material and methods: The data of 11 patients (ages were between 15 to 58 years) who underwent aortic coarctation stent implantation between 2008 and 2011 for moderate to severe native aortic coarctation were retrospectively collected. Results: Average systolic blood pressure was 175 +/- 35 mm Hg, and mean diastolic blood pressure was 115 +/- 15 mm Hg. Pressure gradient proximal and distal to aortic coarctation was 55.5 +/- 17.7 before the stenting. The invasive gradient decreased below 10 mm Hg in all patients. There were no complications except in one patient whose subclavian artery was occluded without any clinical finding. One patient had a totally occluded lesion, needing perforation for acquired interruption using a 0.35 inch hydrophilic wire under the supporting balloon. There was no aneurysm or restenosis at follow-up. Left ventricular functions completely recovered within 1 month in all patients. Conclusions: Stenting using the Cheatham-Platinum stent, either covered or bare, is safe in moderate to severe native aortic coarctation and provides an excellent transcoarctation gradient and clinical hypertension and left ventricular functional relief in adult patients.
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  • Is the presence of left atrial diverticulum associated with recurrence in patients undergoing catheter ablation for atrial fibrillation?

    Demir, Gültekin Günhan   Güneş, Hacı Murat   Seker, Mehmet   Savur, Ümeyir   Güler, Gamze Babur   Güler, Ekrem   Dogan, Mehmet   Erol, Cengiz   Kılıçaslan, Fethi  

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  • Native aortic coarctation stenting in adults and adolescents: early and mid-term results of an adult interventional cardiology team

    Akdemir, Ramazan   Gunduz, Huseyin   Murat, Sani   Kilic, Harun   Yeter, Ekrem   Tarik Agaç, Mustafa   Acar, Zeydin   Kaya, Yuksel   Dogan, Mehmet   Vatan, Mehmet Bulent   Cakar, Mehmet Akif   Erdem, Ali Fuat  

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  • eComment. The combined use of clinical pretest probability and brain natriuretic peptide in predicting the risk of atrial fibrillation

    Dogan, Mehmet   Kucuk, Ugur   Uz, Omer  

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  • Effect of reperfusion therapy on index of myocardial performance in acute myocardial infarction: thrombolytics versus primary angioplasty

    Karakurt, Ozlem   Kilic, Harun   Yesilay, Asuman B.   Dogan, Mehmet   Cagirci, Goksel   Acikel, Sadik   Akdemir, Nermin  

    It is known that primary angioplasty is more effective than thrombolytic therapy for the treatment of ST-segment elevation acute myocardial infarction. The aim of the present study is to compare the effects of the two strategies on the left ventricular functions using the Tei index (a combined myocardial performance index). Of 81 patients (11 female, mean age 52.7 +/- 11.9 years, and 70 male, mean age 54.8 +/- 11.5 years) matching the selection criteria, 41 patients were treated by primary percutaneous transluminal coronary angioplasty and stenting (group A, 41 patients) and 40 patients were treated by thrombolytic agents (streptokinase) (group B, 40 patients). All patients underwent a complete two-dimensional transthoracic echocardiographic and Doppler study in the left lateral decubitus position from multiple windows. There was no significant difference between the two groups in isovolumetric contraction time and ejection time. Isovolumetric relaxation time was 95.2 +/- 18.4 in group A and 116.2 +/- 28.1 in group B (P = 0.001) and the Tei index was 0.51 +/- 0.12 in group A and 0.59 +/- 0.16 in group B (P = 0.019). Isovolumetric relaxation time and Tei index were significantly higher in group B. Primary angioplasty is superior to thrombolytic therapy as assessed by the Tei index even in the first 3 h, with no apparent change in systolic function.
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  • Achilles tendon of descending aorta: intimal tear distal to the left subclavian artery and anterograde dissection of descending aorta.

    Acikel, Sadik   Dilli, Alper   Sari, Munevver   Keyik, Bahri   Kilic, Harun   Dogan, Mehmet   Yeter, Ekrem  

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  • Direct and indirect methods for the determination of vitamin K(3) using differential pulse polarography and application to pharmaceuticals

    Somer, Gueler   Dogan, Mehmet  

    Two methods for the determination of vitamin K(3) have been developed. Vitamin K(3) in its oxidized form is determined by direct and indirect methods. Its standard solution was prepared by the indirect method using Ti(III) as reducing agent. For this purpose vitamin K(3) (menadion) in a clinical injection solution, which is in its hydroquinone form in the presence of sulfite, is oxidized with oxygen. In 0.2 M HAc and 0.02 M HCl electrolyte vitamin K(3) and Ti(IV) have reduction peaks at -0.58 V at -0.82 V respectively. The reaction between Ti(III) and vitamin takes place quantitatively in a medium of 0.2 M HAc and 0.002 M HCl. After the reduction. the reaction product Ti(IV) is followed from its polarographic peak at about -0.82 V. The most important result in this work is that, with this method vitamin K(3) can be standardized and after standardization this solution can be used for the direct determination in routine analysis with a very simple and fast method, using only the peak at -0.71 V in 0.2 M HAc medium. Both direct and indirect methods have been used for the determination of Vitamin K(3) in a clinical injection solution. The limit of quantification (LOQ) was 1.5 x 10(-6) M and in both methods the detection limit found was 7 x 10(-7) M. (C) 2008 Elsevier B.V. All rights reserved.
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  • Association between Her2/neu status in colorectal carcinoma and clinicopathological features: aretrospective study using whole - tissue sections.

    Kilicarslan, Aydan   Dogan, Hayriye Tatli   Sungu, Nuran   Dogan, Mehmet   Yalcin, Abdussamet   Dede, Didem Sener  

    The human epidermal growth factor receptor 2 (Her2/neu) signal pathway plays asignificant role in theoccurance ofvarious solid tumor types. Therate ofHer2/neu in colorectal carcinoma (CRC) is not clearly elucidated. In this study, we discuss theassociation between Her2/neu overexpression and clinicopathological parameters in CRC. Her2/neu immunohistochemical (IHC) staining was performed on whole sections offormalin fixed paraffin embedded tumor tissues of100 CRC resections. Cases with score 3+ and score 2+ expressions were further evaluated by silver in-situ hybridization (ISH) for theexistence ofHer2/neu gene amplification. Her2/neu membranous overexpression was observed in 12 ofthe100 cases (6 cases with ascore 3+ and 6 cases with ascore 2+) and 6 ofthese were heterogenous. There were 10 cases with Her2/neu amplification (6/6 score 3+, 4/6 score 2+). Strong cytoplasmic staining was observed in 5 cases. Membranous scores were either 3+ or 2+ in 3 ofthese 5 cases. Moreover, there was Her2/neu amplification in 2 ofthese 3 cases. Her2/neu amplification status and overexpression was not related to clinicopathological parameters and overall survival. More clear results can be obtained from studies with Her2/neu IHC and ISH test on whole sections.=20
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  • Ferroelectric ZrO 2 Monolayers as Buffer Layers between SrTiO 3 and Si

    Dogan, Mehmet   Ismail-Beigi, Sohrab  

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  • Book Review: Mehmet Ali Dogan, Heather J. Sharkey (eds.) American Missionaries and the Middle East: Foundational Encounters

    Singh   D. E.  

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  • Book Review: Mehmet Ali Dogan, Heather J. Sharkey (eds.) American Missionaries and the Middle East: Foundational Encounters

    Singh, D. E.  

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  • Matrix elimination method for the determination of precious metals in ores using electrothermal atomic absorption spectrometry RID C-4287-2011

    Salih, Bekir   Celikbicak, Omur   Doker, Serhat   Dogan, Mehmet  

    Poly(N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using Co-60 gamma source in the ternary mixture of NHMMA-ATU-H2O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimination of inorganic matrices such as different transition and heavy metal ions, and anions was performed by adjusting the solution pH to 0.5 that was the selective adsorption pH of the precious metal ions. Desorption of the precious metal ions was performed by using 0.8 M thiourea in 3 M HCl as the most efficient desorbing agent with recovery values more than 95%. In the desorption medium, thiourea effect on the atomic signal was eliminated by selecting proper pyrolysis and atomization temperatures for all precious metal ions. Precision and the accuracy of the results were improved in the graphite fumace-atomic absorption spectrometer (GFAAS) measurements by applying the developed matrix elimination method performing the adsorption at pH 0.5. Pre-concentration factors of the studied precious metal ions were found to be at least 1000-fold. Detection limits of the precious metal ions were found to be less than 10 ng L-1 of the all studied precious metal ions by using the proposed pre-concentration method. Determination of trace levels of the precious metals in the sea-water, anode slime, geological samples and photographic fixer solutions were performed using GFAAS clearly after applying the adsorption-desorption cycle onto the poly(NHMMA-UTU) hydrogels. (c) 2007 Published by Elsevier B.V.
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