Browsing by Author "Sezgin, A"

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Citation - WoS: 1
On the Decidability of Shared Memory Consistency Verification
(Ieee, 2005) Sezgin, A; Gopalakrishnan, G; 01. Atılım University
We view shared memories as structures which define relations over the set of programs and their executions. An implementation is modeled by a transducer where the relation it realizes is its language. This approach allows us to cast shared memory verification as language inclusion. We show that a specification can be approximated by an infinite hierarchy of finite-state transducers, called the memory model machines. Also, checking whether an execution is generated by a sequentially consistent memory is approached through a constraint satisfaction formulation. It is proved that if a memory implementation generates a non interleaved sequential and unambiguous execution, it necessarily generates one such execution of bounded size. Our paper summarizes the key results from the first author's dissertation, and may help a practitioner understand with clarity what "sequential consistency checking is undecidable" means.
On the Definition of Sequential Consistency
(Elsevier Science Bv, 2005) Sezgin, A; Gopalakrishnan, G; 01. Atılım University
The definition of sequential consistency is compared with an intuitive notion of correctness. That the definition is not strong enough is illustrated through a hypothetical memory system which is clearly incorrect, yet sequentially consistent. It is claimed that the reason for this is the absence of a relation between what actually happens (temporal order) and what seems to happen (logical order). A stronger version of sequential consistency is proposed. (c) 2005 Elsevier B.V. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 2
Our Experience in Cardiac Transplantation in Baskent University
(Elsevier Science inc, 2006) Sezgin, A; Gültekin, B; Özkan, S; Akay, T; Uguz, E; Tokalak, I; Aslamaci, S; Department of Social Sciences for University wide Courses; 02. School of Arts and Sciences; 01. Atılım University
Recently cardiac transplantation has an important place in treatment of end-stage cardiac failure. In Turkey between 2003 and 2005 at 10 centers 64 cardiac transplantations were performed including five at our facility. Herein we have presented our results. All patients were men of mean age 34.2 +/- 10.7 (17 to 44) years. Upon preoperative echocardiography their mean ejection fraction was 18% +/- 3.27% (17% to 23%). Pulmonary vascular resistance was 4.47 wood unit in one patient and in one case, there was Rh incompatibility between donor and recipient. We used HTK solution for protection of donor hearts. Mean ischemia time was 251.2 +/- 62.7 minutes (155 to 314). Mean aortic clamping time was 84 +/- 4.7 minutes (80 to 90). In all patients we performed a biatrial anastomosis technique. Hemofiltration was used to prevent hemodilution during operation. In the postoperative period four patients had acute renal dysfunction; one, a minor cerebrovascular accident; two, reoperated because of bleeding; one, cholestasis; one, temporary atrio-ventricular block; and one, mediastinitis. Mean follow-up time was 15.6 +/- 19.7 months (2 to 50). Neither early nor late mortality has occurred. All patients are in New York Heart Association class I. In all cases we used triple immunosuppressive therapy. In the follow-up period the mean number of cardiac biopsies per patient was 4.2 +/- 3.03 (2 to 8). Two cases had cardiac catheterization. As a complication of cardiac biopsy, pericardial tamponade developed in one patient; in another one we observed a right ventricular aneursym after cardiac biopsy. Cardiac transplantation was performed with low mortality and morbidity rates in end-stage cardiac failure patients with longer life expectancy and higher life quality. Unfortunately in our country, because of difficulties to find donor hearts, cardiac transplantations were small in number. For better results, we need a larger series.