Browsing by Author "Kahraman, N"

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    The Contribution of Motivational Beliefs to Students' Metacognitive Strategy Use
    Kahraman, N; Sungur, S
    This study aimed at investigating how well elementary students' self-efficacy and achievement goals (mastery approach, mastery avoidance, performance approach, and performance avoidance goals) predict their metacognitive strategy use in science. For the specified purpose, Achievement Goal Questionnaire and Motivated Strategies for Learning Questionnaire were administered to 115 elementary school students. Results showed that the elementary students who feel self-efficacious in science and study for the reasons of learning and understanding (mastery approach goals) the course material tend to use metacognitive strategies at higher levels. In line with the findings, specific suggestions were made for science teachers to help development of adaptive motivational beliefs and effective strategy use.
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    Exergy analysis of a combined RO, NF, and EDR desalination plant
    Kahraman, N; Cengel, YA; Wood, B; Cerci, Y
    A brackish water desalination plant in California that incorporates RO, NF, and EDR units was analyzed thermodynamically using actual plant operation data. Exergy flow rates were evaluated throughout the plant, and the exergy flow diagrams were prepared. The rates of exergy destruction and their percentage are indicated on the diagram so that the locations of highest exergy destruction can easily be identified. The analysis shows that most exergy destruction occurs in the pump/motor and the separation units. The fraction of exergy destruction in the pump/motor units is 39.7% for the RO unit, 23.6% for the NF unit, and 54.1% for the EDR unit. Therefore, using high-efficiency pumps and motors equipped with VFD drives can reduce the cost of desalination significantly. The plant was determined to have a Second Law efficiency of 8.0% for the RO unit, 9.7% for the NF unit, and 6.3% for the EDR unit, which are very low. This indicates that there are major opportunities in the plant to improve thermodynamic performance by reducing exergy destruction and thus the amount of electrical energy supplied, making the operation of the plant more cost effective.
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    Preoperative Oral Pentoxifylline for Management of Cytokine Reactions in Cardiac Surgery
    Iskesen, I; Kurdal, AT; Kahraman, N; Cerrahoglu, M; Sirin, BH
    Background: Cardiopulmonary bypass may lead to many inflammatory responses that may cause myocardial dysfunction after open heart surgery. We aimed to investigate the effect of preoperative pentoxifylline treatment to reduce the occurrence of cardiopulmonary bypass-induced inflammatory response. Methods: In a prospective, randomized study, 40 patients undergoing coronary artery bypass graft surgery received either pentoxifylline (study group, n = 21) or not (control group, n = 19). Pretreatment with pentoxifylline (800 mg/day orally) was started 5 days before the operation. Blood samples for measurements of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8 from the arterial line, and venous blood samples for creatine kinase (CK) and CK isoenzyme fraction MB (CK-MB) were taken in both groups at 5 different time points. Hemodynamic parameters were measured with the thermodilution technique. Results: TNF-alpha, IL-6, and IL-8 plasma levels increased in both groups after cardiopulmonary bypass, with a greater increase in the control group (P < .05). There were no significant differences between the groups for the values of CK-MB and hemodynamic parameters. Conclusions: We conclude that pretreatment with oral pentoxifylline before cardiac surgery inhibits proinflammatory cytokine release caused by cardiopulmonary bypass and has some beneficial effects in protecting the myocardium during the cardioplegic arrest period in open-heart surgery, without affecting postoperative hemodynamics.
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    Unusual location of hydatid cyst: the posterior leaflet of tricuspid valve
    Kurdal, AT; Kahraman, N; Iskesen, I; Sirin, BH
    Hydatid Cyst disease involves the heart in 0.02-2% of the cases. It can appear with symptoms very similar to coronary artery disease, cardiac valvular disease and pericarditis. We present a case of hydatid cyst that was located on the posterior tricuspid leaflet and that caused tricuspid regurgitation in 37 year old female patient who has gone through hydatid cyst excision from the bilateral lungs with median sternotomy 2 years ago. In addition to the right atrial and ventricular dilatation, second degree tricuspid regurgitation and significant pulmonary hypertension was found. The 2x2 cm smooth surfaced mass was resected from the posterior leaflet of the tricuspid valve and the defect was closed with suture with the aid of cardiopulmonary bypass. The patient followed with long term albendazole treatment. Cardiac echinococcosis should be kept in mind in some patients throughout their lift with a history of previous hydatid cyst disease. Surgical excision without rupture is the treatment of choice for cardiac hydatid cyst, with following medical therapy in order to prevent recurrence.