Salihoglu O.,Bilkent University |
Muti A.,Bilkent University |
Kutluer K.,Middle East University of Lebanon |
Tansel T.,Middle East University of Lebanon |
And 3 more authors.
Applied Physics Letters | Year: 2012
In the quest to raise the operating temperature and improve the detectivity of type II superlattice (T2SL) photodetectors, we introduce a design approach that we call the N structure. N structure aims to improve absorption by manipulating electron and hole wavefunctions that are spatially separated in T2SLs, increasing the absorption while decreasing the dark current. In order to engineer the wavefunctions, we introduce a thin AlSb layer between InAs and GaSb layers in the growth direction which also acts as a unipolar electron barrier. Unlike the symmetrical insertion of AlSb into GaSb layers, N design aims to exploit the shifting of the electron and hole wavefunctions under reverse bias. With cutoff wavelength of 4.3 μm at 77 K, temperature dependent dark current and detectivity measurements show that the dark current density is 3.6 × 10 -9 A/cm 2, under zero bias. Photodetector reaches background limited infrared photodetection (BLIP) condition at 125 K with the BLIP detectivity (D + BLIP) of 2.6 × 10 10 Jones under 300 K background and -0.3 V bias voltage. © 2012 American Institute of Physics.
Ozsoy M.G.,Middle East University of Lebanon |
Cicekli I.,Bilkent University |
Alpaslan F.N.,Middle East University of Lebanon
Coling 2010 - 23rd International Conference on Computational Linguistics, Proceedings of the Conference | Year: 2010
Text summarization solves the problem of extracting important information from huge amount of text data. There are various methods in the literature that aim to find out well-formed summaries. One of the most commonly used methods is the Latent Semantic Analysis (LSA). In this paper, different LSA based summarization algorithms are explained and two new LSA based summarization algorithms are proposed. The algorithms are evaluated on Turkish documents, and their performances are compared using their ROUGE-L scores. One of our algorithms produces the best scores.
Ijsselmuiden C.,Council on Health Research for Development |
Ijsselmuiden C.,University of KwaZulu - Natal |
Marais D.L.,Council on Health Research for Development |
Becerra-Posada F.,Council on Health Research for Development |
Ghannem H.,Middle East University of Lebanon
South African Medical Journal | Year: 2012
Building the skills for doing, managing and delivering health research is essential for every country's development. Yet human resources for health research (HRHR) are seldom considered in Africa and elsewhere. Africa's health research capacity has grown considerably, with potential to increase this growth. However, a systemic way of defining, co-ordinating and growing the HRHR needed to support health systems development is missing. Reviewing the status of HRHR in Africa, we assert that it consists of unco-ordinated, small-scale activities, primarily driven from outside Africa. We present examples of ongoing HRHR capacity building initiatives in Africa. There is no overarching framework, strategy or body for African countries to optimise research support and capacity in HRHR. A simple model is presented to help countries plan and strategise for a comprehensive approach to research capacity strengthening. Everyone engaged with global, regional and national research for health enterprises must proactively address human resource planning for health research in Africa. Unless this is made explicit in global and national agendas, Africa will remain only an interested spectator in the decisions, prioritisation, funding allocations, conduct and interpretation, and in the institutional, economic and social benefits of health research, rather than owning and driving its own health research agendas.
Sadi G.,Karamanoglu Mehmetbey University |
Kartal D.I.,Middle East University of Lebanon |
Guray T.,Middle East University of Lebanon
Turkish Journal of Biochemistry | Year: 2013
Objective: Increased oxidative stress is now related with the pathogenesis and the chronic complications associated with the disease, diabetes mellitus. While roles of oxidative stress in diabetic complications are widely studied, the molecular mechanisms playing role in the regulations of detoxification enzymes in the presence of antioxidants have not been clearly established because of the complexity of the pathways. Methods: Diabetes was induced by single dose streptozotocin application and rats were treated with 50mg/kg antioxidants DL-α-lipoic acid (LA), vitamin C (VC) and combination of both for three weeks. Lipid peroxidation, protein oxidation and reduced glutathione levels were measured and Glutathione S-Transferase Mu (GST-Mu) isozyme activity was determined by using enzyme specific substrate. mRNA and protein expressions were evaluated by RT-PCR and western blot methods respectively. Results: In diabetic animals the products of lipid peroxidation and protein oxidation reactions were all found to be elevated significantly (p<0.05) and supplementing the animals either individually or in combination with two powerful antioxidants restored this effect. GST-Mu activities were also significantly decreased in diabetic group compared to controls and RT-PCR and Western blot analysis results showed that this decrease in activity is regulated at the level of gene expression, as both mRNA and protein expressions were suppressed. All antioxidant treatments did not reverse the effect of diabetes at the gene expression level and interestingly protein expressions were further suppressed indicating a post-translational regulation by antioxidants. Conclusion: Presence of oxidative stress and the effects of antioxidants in diabetic rats were confirmed and it was found that diabetes leads to GST-Mu to be down regulated at mRNA expression levels. Future post-translational modification studies will help to determine the mechanism or combination of mechanisms underlying the damaging effects of oxidative stress observed in streptozotocin induced diabetic rats. © TurkJBiochem.com.
Gur C.H.,Middle East University of Lebanon
RILEM Bookseries | Year: 2012
Optimization and control of the microstructure is vital for improving performance and service life of the steel components. Development of non-destructive techniques for microstructure characterization has been a challenging task for many years. Magnetic Barkhausen Noise method is a non-destructive evaluation technique with high potential for characterization of steels. This paper summarizes the related studies performed at METU. © RILEM 2013.
Selcuk G.,ASELSAN Inc. |
Koc S.S.,Middle East University of Lebanon
8th European Conference on Antennas and Propagation, EuCAP 2014 | Year: 2014
Solution of surface scattering problems with electric field integral equation (EFIE) requires careful treatment of singularities introduced by the 3D dyadic Green's function when source and observation points are close to each other or coincide. One may either consult to divergence conforming basis and testing functions to reduce the order of singularity or directly deal with singularities via analytical singularity extraction methods. The latter method is a not commonly used although it enables use of less complicated pulse-like basis functions and no attempt is done to apply it in time domain. In this study a new time domain formulation for EFIE is obtained. Self-cell contribution is evaluated by efficient treatment of hypersingular integrals and close cell contribution is evaluated by increasing the number of quadrature points and applying interpolation. Explicit marching on in time (MOT) scheme along with new formulation is applied to solve transient scattering from perfect electric conductor (PEC) surfaces. Agreement with analytical results is obtained. © 2014 European Association on Antennas and Propagation.
Filik T.,Anadolu University |
Tuncer T.E.,Middle East University of Lebanon
Multidimensional Systems and Signal Processing | Year: 2016
In this paper, two dimensional (2-D) direction-of-arrival (DOA) estimation problem in case of unknown mutual coupling and multipath signals is investigated for antenna arrays. A new technique is proposed which uses a special array structure consisting of parallel uniform linear array (PULA). PULA structure is complemented with auxiliary antennas in order to have a structured mutual coupling matrix (MCM). MCM has a symmetric banded Toeplitz structure which allows the application of the ESPRIT algorithm for 2-D paired DOA estimation. The advantage of the PULA structure is exploited by dividing it into overlapping linear sub-arrays (triplets) and spatial smoothing is employed to mitigate multipath signals. Closed form expressions are presented for search-free, paired and unambiguous 2-D DOA estimation. Two algorithms PULA-1 and PULA-2 are proposed to effectively solve the problem. Several simulations are done and the accuracy of the proposed solution is shown. © 2014, Springer Science+Business Media New York.
Fady R.I.,Middle East University of Lebanon
Proceedings of the Annual Hawaii International Conference on System Sciences | Year: 2013
In this research, approaches to e-business in the maritime sector in Egypt were examined. The organizational strategic view, the evolution of ebusiness in terms of an analysis of business functions, and the consideration of some stage models of the evolution were explored. The research method combines a case study approach with the use of process modeling tools and ebusiness evolution stage model. These tools were applied to Alexandria, Egypt's largest, long established and Government-run port. The process architecture modeling method used was Ould's Riva method. In this study, possibilities for achieving higher stages of e-business in Alexandria port were reexamined using a combination of three methods: Ould's improvement diagnosis; Davenport's analysis of information technology; and Earl's six stage model of e- business development. Adherence of the top management to the port's strategic view is a key success factor to the transformation and improvement of the organizational processes, including process automation. © 2012 IEEE.
Tezcan O.,Middle East University of Lebanon |
Gunduz U.,Middle East University of Lebanon
Biomedicine and Pharmacotherapy | Year: 2014
Chemotherapy is one of the well-known treatments in cancer therapy. The effectiveness of chemotherapy is limited by several factors one of which is the emergence of multidrug resistance (MDR). One of the major mechanisms of MDR is the activity of several ATP binding cassette (ABC) transporters that pump drugs out of the cells. Doxorubicin intercalates and inhibits DNA replication; it is a powerful chemotherapeutic agent. However, it causes development of MDR in tumor cells. Vimentin is a type III intermediate filament protein that is expressed frequently in epithelial carcinomas correlating with invasiveness and also poor prognosis of cancer. There are several studies that have shown the connection between expression level of vimentin and invasiveness of tumor cells. In this study, MCF-7 cell line which is a model for human mammary carcinoma, and a doxorubicin resistant subline (MCF-7/Dox) were used. The resistant subline was previously obtained by stepwise selection in our laboratory. In the resistant cells, high levels of vimentin expression were observed. The main purpose of this study was to investigate changes in invasive and migration characteristics of MCF-7/Dox cell line, after transient silencing of vimentin gene by specific siRNA. © 2014 Elsevier Masson SAS.
Alpsoy A.,Middle East University of Lebanon |
Yasa S.,Middle East University of Lebanon |
Gunduz U.,Middle East University of Lebanon
Biomedicine and Pharmacotherapy | Year: 2014
Purpose: Acquired or intrinsic drug resistance is one of the major handicaps in the success of chemotherapy. Etoposide is a topoisomerase II poison widely used in chemotherapy. Similar to other topoisomerase inhibitors and DNA damaging agents, resistance to etoposide may arise as a result of alterations in target expression and activity, increased drug efflux and alterations in DNA damage response mechanisms. Here, we tested the involvement of such mechanisms in etoposide-resistant MCF-7 breast cancer cells. Methods: Relative etoposide resistance was determined by XTT cell proliferation assay. For gene expression analysis, total RNA was extracted from each cell line and gene expression was quantified by real-time PCR following reverse transcription. Topoisomerase II activities of each cell line were compared by using in vitro topoisomerase II activity assay. Results: Etoposide-resistant sublines MCF-7/1E and MCF-7/4E are 2.6- and 4.6-fold more resistant to etoposide compared to parental cell line MCF-7/S. TOP2A, the gene encoding the topoisomerase II alpha, is significantly downregulated in drug resistant sublines while topoisomerase II activity seemed similar among cell lines. MRP1, which encodes an etoposide efflux pump, is significantly upregulated in etoposide-resistant sublines. Two DNA damage response proteins TOPBP1 and EDD were found to be downregulated in etoposide-resistant sublines. Conclusions: This study sheds light into the etoposide resistance in breast cancer by investigating previously proposed and novel factors that may have a role in development or progression of etoposide resistance which can be considered as diagnostic markers and therapy targets. © 2014 Elsevier Masson SAS.