58 results on '"Mehmet Koseoglu"'
Search Results
2. Co-occurrence network analysis (CNA) as an alternative tool to assess survey-based research models in hospitality and tourism research
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Mehmet Koseoglu, John Parnell, and Hasan Arici
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co-occurrence network ,multivariate analysis ,methodology ,sample size ,Business ,HF5001-6182 - Abstract
Hospitality and tourism (H&T) researchers employ structural equation modeling (SEM) and other multivariate techniques to test their models with survey data. These approaches assess relationships among constructs and model fit, but they do not highlight the most influential survey items or links among them. Other challenges include method-specific requirements for appropriate data, the best indices to identify optimal models, minimum sample sizes, missing data, and interpreting the results from complex models. Co-occurrence network analysis (CNA) can mitigate these limitations. This study validates CNA in the H&T field with a survey dataset that assesses market strategy, nonmarket strategy (NMS), organizational values, and firm performance. CNA is proposed as a complement to existing multivariate approaches for assessing survey data. The assessment includes nine steps: (1) identify the research purpose and hypothesis, (2) determine the hypothesis-related items to measure, (3) determine the sample, (4) administer the survey, (5) determine the analysis method, (6) test the hypotheses, (7) prepare survey inputs for CNA, (8) employ CNA, and (9) visualize and interpret results. This pathway demonstrates how future research can apply and address CNA’s advantages and limitations.
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- 2022
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3. Plasma leptin values in postmenopausal women with osteoporosis
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Hikmet Kocyigit, Serpil Bal, Ayşenur Atay, Mehmet Koseoglu, and Alev Gurgan
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Bone density ,leptin ,obesity ,postmenopausal osteoporosis ,Biology (General) ,QH301-705.5 - Abstract
Obesity has a protective effect against osteoporosis and this effect has been attributed to a high body fat content. It has been shown that the leptin concentration is higher in obese patients. Leptin, the protein product of obesity gene, is a hormone produced in adipose tissue. Some studies suggest that endogenous leptin might influence bone metabolism in postmenopausal women. In this study, we investigated plasma leptin concentrations in postmenopausal women with osteoporosis and also analyzed the relationship between plasma leptin levels and bone mineral density (BMD) in order to understand the potential role of leptin in maintaining bone mass. Forty-two postmenopausal women with osteoporosis and thirty seven age and BMI-matched healthy postmenopausal women were included in the study. The mean femoral neck BMD value in the patient group was significantly lower than that in the control group (0.691±0.1 g/cm1 and 0.863±0.1 g/cm2, respectively; p0.05). Plasma leptin levels were correlated with BMI in both groups (p
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- 2013
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4. Impact of the HALP Score on Long-Term Mortality among Patients Undergoing EVAR
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Mehmet Altunova, Ali Evsen, Yusuf Demir, Tuğba Aktemur, Onur Erdoğan, Sezgin Atmaca, Mehmet Köseoğlu, Nedim Uzun, Ahmet Anıl Şahin, and Ömer Çelik
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endovascular aortic repair ,halp score ,long-term mortality ,Medicine - Abstract
Introduction: Endovascular aortic repair (EVAR) is commonly used for abdominal aortic aneurysms, but its mortality rate remains high. The hemoglobin, albumin, lymphocyte, and platelet (HALP) score, which measures hemoglobin, albumin, lymphocyte, and platelet levels, provides prognostic value by reflecting the nutritional status and systemic inflammation. This study aimed to explore the relationship between the HALP score upon admission and long-term mortality in patients with EVAR. Methods: Consecutive patients with EVAR at our tertiary center from October 2010 to August 2021 were retrospectively analyzed. HALP scores were calculated using the following formula: hemoglobin (g/L) × albumin (g/L) × lymphocyte count (/L)/platelet count (/L). In-hospital and long-term mortality data were extracted. Receiver operating characteristic curve analysis identified predictors of in-hospital mortality. Multivariate Cox regression analysis was performed to examine determinants of long-term mortality. Results: Among the 162 participants (mean age: 69.4±8.2 years, 90.1% male), the HALP score was the most significant predictor of in-hospital mortality (area under the curve: 0.752, 95% confidence interval: 0.674-0.830; p
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- 2024
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5. The effect of diurnal variation on erythrocyte sedimentation rate
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Alperen Ihtiyar, Muammer Yucel, and Mehmet Koseoglu
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medicine.diagnostic_test ,business.industry ,Biochemistry (medical) ,Clinical Biochemistry ,Diurnal temperature variation ,030204 cardiovascular system & hematology ,Biochemistry ,03 medical and health sciences ,0302 clinical medicine ,Animal science ,030220 oncology & carcinogenesis ,Erythrocyte sedimentation rate ,medicine ,business ,Molecular Biology - Abstract
Objectives It has been known that some laboratory tests showed diurnal variation and were affected by fasting-satiety status. We aimed to examine erythrocyte sedimentation rate (ESR) for both pre-analytical factors. Methods Blood samples from 12 volunteers were taken and studied with the Westergren method. Fasting blood samples taken at 9:00 am were accepted as basal. Samples were taken at 10:00, 11:00, 12:00 were compared with baseline to evaluate fasting-satiety status and samples taken at 12:00, 15:00, 18:00, and 24:00 to evaluate diurnal variation. Results ESR was found to be the lowest at 09:00 and 15:00 (Median=5.5 mm/h). The 10:00, 11:00, and 12:00 results for assessing fasting-satiety status on ESR were not different than the baseline (6.2, 6.0, and 7.8 mm/h, respectively). The rates at 18:00 and 24:00 were not found to be different than the baseline (5.7 and 6.6 mm/h). Conclusions We didn’t find that ESR had diurnal variation, and it wasn’t affected by fasting-satiety status. Although it is known that routine biochemistry tests should be performed from the blood sample taken in the morning in case of starvation, blood sampling can be done for ESR during the day if necessary.
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- 2020
6. Deep reinforcement learning based flexible preamble allocation for RAN slicing in 5G networks
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Ahmet Melih Gedikli, Mehmet Koseoglu, and Sevil Sen
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Computer Networks and Communications - Published
- 2022
7. Reinforcement Learning based Adaptive Access Class Barring for RAN Slicing
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Ebru Akcapinar Sezer, Mehmet Koseoglu, and Ali Turan
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Network congestion ,Class (computer programming) ,Service (systems architecture) ,Random-access channel ,business.industry ,Computer science ,Quality of service ,Reinforcement learning ,Latency (engineering) ,business ,Bottleneck ,Computer network - Abstract
Machine-to-Machine (M2M) communication is one of the major drivers of 6G networks as M2M traffic might soon surpass Human-to-Human (H2H) traffic. Network slicing is a promising technique for supporting M2M traffic on 6G networks as there is a need to concurrently support varying Quality-of-Service (QoS) requirements of M2M devices. A major bottleneck for M2M traffic is the Random Access Channel (RACH) procedure, which has to be performed for all devices, which results in the same latency for all service types. Due to the event-driven simultaneous access behavior of M2M devices, this procedure can cause severe congestion. Legacy congestion control schemes such as Access Class Barring (ACB) are not adequate to handle the overload in bursty traffic scenarios, which can happen frequently in M2M communications. There is also no clear guideline to adjust ACB parameters dynamically in such situations. Here we propose a multi-rate ACB algorithm using Reinforcement Learning (RL) to tune the barring rates of different service classes. Our priority-based algorithm not only reduces the congestion but also slices the RACH among different service types. Comprehensive simulation results show that our proposed algorithm maximizes the RACH utilization. In the meantime, based on each service priority, it reduces the delays and increases the access probability even when the connection requests exceed the RACH capacity.
- Published
- 2021
8. Random Forest Classification of Finger Movements using Electromyogram (EMG) Signals
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Mehmet Koseoglu, Mucahit Findik, and Seyma Yilmaz
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medicine.diagnostic_test ,InformationSystems_INFORMATIONINTERFACESANDPRESENTATION(e.g.,HCI) ,business.industry ,Computer science ,020208 electrical & electronic engineering ,Feature extraction ,Pattern recognition ,02 engineering and technology ,Electromyography ,Signal ,Random forest ,body regions ,Finger movement ,0202 electrical engineering, electronic engineering, information engineering ,medicine ,020201 artificial intelligence & image processing ,Artificial intelligence ,business - Abstract
One of the fundamental problems in the development of prosthetic fingers is the recognition of finger movements using surface electrocardiogram (EMG) data. Most of the previous studies have proposed the classification of EMG signals using features curated using expert knowledge. We here consider automatic generation and selection of EMG signal features without relying on domain knowledge. We then develop a classification method based on random forests. Our results show that the proposed method achieves 97.5% accuracy. We also present a discussion of the features which are important in distinguishing finger movements.
- Published
- 2020
9. Pricing-Based Load Control of M2M Traffic for the LTE-A Random Access Channel
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Mehmet Koseoglu
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Engineering ,business.industry ,05 social sciences ,050801 communication & media studies ,020206 networking & telecommunications ,Context (language use) ,Throughput ,02 engineering and technology ,LTE Advanced ,Base station ,0508 media and communications ,Random-access channel ,Dynamic pricing ,0202 electrical engineering, electronic engineering, information engineering ,Revenue ,Wireless ,Electrical and Electronic Engineering ,business ,Computer network - Abstract
Existing cellular infrastructures have to be revisited for emerging machine-to-machine (M2M) traffic as semi-synchronized M2M arrivals may create a significant congestion resulting in a high access delay. In such a case, there is a strong need for service differentiation, since the delay requirements of IoT applications may vary greatly from delay-tolerant metering applications to security applications with stringent requirements. This problem has been receiving significant interest from the research community in the context of the LTE-A random access channel. Most studies, however, consider load control schemes with few fixed service classes, which can provide limited service differentiation. We propose an alternative scheme where the load is controlled by the price announced by the base station. The proposed method controls the load effectively and provides negligible delay for messages with the highest priority. It also enables low-cost wireless access to delay-tolerant messages by generating most of the revenue from high-priority messages. We derive pricing-based load control schemes for throughput and revenue maximization, and present the relationship between delay, revenue, and cost in both schemes. Our results suggest that dynamic pricing is a promising solution for major problems associated with cellular M2M traffic.
- Published
- 2017
10. Learning to Take Good Pictures of People with a Robot Photographer
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Akansel Cosgun, Rhys Newbury, Mehmet Koseoglu, and Tom Drummond
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FOS: Computer and information sciences ,Artificial neural network ,Computer science ,business.industry ,media_common.quotation_subject ,020207 software engineering ,02 engineering and technology ,Convolutional neural network ,Expression (mathematics) ,Computer Science - Robotics ,Face (geometry) ,0202 electrical engineering, electronic engineering, information engineering ,Robot ,020201 artificial intelligence & image processing ,Computer vision ,Quality (business) ,Artificial intelligence ,Line (text file) ,business ,Robotics (cs.RO) ,media_common - Abstract
We present a robotic system capable of navigating autonomously by following a line and taking good quality pictures of people. When a group of people are detected, the robot rotates towards them and then back to line while continuously taking pictures from different angles. Each picture is processed in the cloud where its quality is estimated in a two-stage algorithm. First, features such as the face orientation and likelihood of facial emotions are input to a fully connected neural network to assign a quality score to each face. Second, a representation is extracted by abstracting faces from the image and it is input to a to Convolutional Neural Network (CNN) to classify the quality of the overall picture. We collected a dataset in which a picture was labeled as good quality if subjects are well-positioned in the image and oriented towards the camera with a pleasant expression. Our approach detected the quality of pictures with 78.4% accuracy in this dataset and received a better mean user rating (3.71/5) than a heuristic method that uses photographic composition procedures in a study where 97 human judges rated each picture. A statistical analysis against the state-of-the-art verified the quality of the resulting pictures.
- Published
- 2019
11. Deep reinforcement learning based energy beamforming for powering sensor networks
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Mani Srivastava, Mehmet Koseoglu, Anders Ahlén, and Ayca Ozcelikkale
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Beamforming ,Signal processing ,Artificial neural network ,Computer science ,05 social sciences ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,050801 communication & media studies ,020206 networking & telecommunications ,Signalbehandling ,02 engineering and technology ,Electrical Engineering, Electronic Engineering, Information Engineering ,Transmitter power output ,System model ,0508 media and communications ,Signal Processing ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Computer Science::Networking and Internet Architecture ,Reinforcement learning ,ComputerSystemsOrganization_SPECIAL-PURPOSEANDAPPLICATION-BASEDSYSTEMS ,Elektroteknik och elektronik ,Energy harvesting ,Wireless sensor network - Abstract
We focus on a wireless sensor network powered with an energy beacon, where sensors send their measurements to the sink using the harvested energy. The aim of the system is to estimate an unknown signal over the area of interest as accurately as possible. We investigate optimal energy beamforming at the energy beacon and optimal transmit power allocation at the sensors under non-linear energy harvesting models. We use a deep reinforcement learning (RL) based approach where multi-layer neural networks are utilized. We illustrate how RL can approach the optimum performance without explicitly forming a system model, but suffers from slow convergence. We also quantify the importance of the number of antennas at the energy beamformer and the number of sensors.
- Published
- 2019
12. Evaluation of YouTube Videos Quality of Pediatric Cardiac Surgery Anesthesia
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Eyüp Murat Kanber and Mehmet Köseoğlu
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cardiac surgery anesthesia ,discern ,global quality score ,pediatric ,youtube ,Medicine - Abstract
Introduction:To evaluate the quality of YouTube videos on pediatric cardiac surgery anesthesia (PCSA).Methods:The keywords including, “PCSA”, “pediatric cardiac surgery”, and “pediatric anesthesia” were browsed on YouTube between January 1st, 2023 and January 10th, 2023. Video characteristics were recorded. The modified DISCERN instrument, the Global Quality Score (GQS), and the Patient Education Materials Assessment Tool (PEMAT) were used to evaluate the quality of the videos. The videos were divided into two groups as professionals (doctor, nurse, hospital, etc.) and non-professional (patient, non-health institutions, etc.) according to the upload source.Results:A total 82 of the videos were included in the study. Fifty-six (68.3%) videos were uploaded by professional sources and 26 (31.7%) were by non-professional sources. Statistically, the average like of the videos uploaded by professional sources were significantly higher (64.0 and 29.0, p=0.005). The average number of comments on professionally sourced videos was 46.0, and it was 30.0 for non-professional videos (p=0.015). The GQS was 3.7±1.0 for professional videos and 2.2±0.8 for non-professional videos (p=0.001). The Modified DISCERN score was found to be significantly higher in the professional videos (p=0.001). The PEMAT score was above 70% in 50 (89.3%) videos in the professional video group and 12 (46.1%) videos in the non-professional video group (p=0.001).Conclusion:Our findings revealed that professional videos about PCSA had significantly higher “likes” number and comments rate and YouTube videos about PCSA, which were shared by professional healthcare providers had significantly higher modified DISCERN score, GQS, and PEMAT score.
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- 2023
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13. Evaluation of Postprandial Total Antioxidant Activity in Normal and Overweight Individuals
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Aysenur Atay, Fatma Demet Arslan, Yasemin Akçay, Eser Yıldırım Sözmen, Yavuz Yigit, Mehmet Koseoglu, and Ege Üniversitesi
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medicine.medical_specialty ,obesity ,Antioxidant ,Total Antioxidant Activity ,business.industry ,medicine.medical_treatment ,lcsh:R ,Postprandiyal Period ,lcsh:Medicine ,Postprandial period ,antioxidant effect ,General Medicine ,Overweight ,Antioxidant capacity ,Postprandial ,Endocrinology ,Internal medicine ,Medicine ,medicine.symptom ,business - Abstract
WOS: 000396415800012, Aim: Postprandial changes acutely alter some mechanisms in body. There are many studies showing blood oxidative status changes after food intake and supplementation. The aim of the present study was to evaluate the effects of a standardized meal on serum total antioxidant activity (TAA) in normal weight and overweight individuals. Material and Method: Fourteen normal weight and twelve overweight individuals were given a standardized meal in the morning after an overnight fast. Serum TAA, glucose, total cholesterol, HDL cholesterol, LDL cholesterol and triglyceride concentrations were measured at baseline, 3rd hour and 6th hour after the meal in both groups. Results: In both normal and overweight groups, the difference between baseline and 3rd hour was significant for TAA. The TAA of the overweight group was also significantly lower than the TAA of the normal weight group at 3rd hour. However, there was no significant correlation between lipid parameters and TAA levels. Discussion: The present study shows that postprandial oxidative stress occurs more prominently in overweight individuals than in normal weight individuals. Postprandial changes acutely induce oxidative stress and impair the natural antioxidant defense mechanism. It should be noted that consuming foods with antioxidants in order to avoid various diseases and complications is useful, particularly in obese subjects.
- Published
- 2016
14. Kidney Injury Molecule Levels in Type 2 Diabetes Mellitus
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Metin Demir, Ozgur Aslan, and Mehmet Koseoglu
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Adult ,Male ,Microbiology (medical) ,medicine.medical_specialty ,Urinary system ,Clinical Biochemistry ,Blood Pressure ,Enzyme-Linked Immunosorbent Assay ,030209 endocrinology & metabolism ,Urine ,030204 cardiovascular system & hematology ,Positive correlation ,Gastroenterology ,Statistics, Nonparametric ,Diabetic nephropathy ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Internal medicine ,Albuminuria ,Humans ,Immunology and Allergy ,Medicine ,Hepatitis A Virus Cellular Receptor 1 ,Research Articles ,Aged ,Creatinine ,business.industry ,Biochemistry (medical) ,Public Health, Environmental and Occupational Health ,Albumin ,Type 2 Diabetes Mellitus ,Hematology ,Middle Aged ,medicine.disease ,Medical Laboratory Technology ,Kidney injury molecule ,Endocrinology ,Diabetes Mellitus, Type 2 ,chemistry ,Female ,Kidney Diseases ,business - Abstract
Background This study was designed to determine the diagnostic role of urinary kidney injury molecule (KIM)-1 levels in renal damage in patients with type 2 diabetes mellitus according to the urinary albumin/creatinine ratio. Methods Patients with type 2 diabetes mellitus admitted to different polyclinics in our hospital enrolled in the study and were subdivided into three groups according to albumin/creatinine ratio – normalbuminuric (n: 20); microalbuminuric (n: 20); albuminuric (n: 18) – and compared with the control group. Urine albumin was analyzed using the immunoturbidimetric method (Architect C16000, Abbott Diagnostics). uKIM-1 was determined using a commercially available enzyme-linked immunosorbent assay test kit (USCN Life Science, Hankou, Wuhan, China). One-sample Kolmogorov–Smirnov test, Spearman correlation and Kruskal–Wallis non-parametric tests were performed. Post hoc comparisons were made using Bonferroni-corrected Mann–Whitney U tests. Results The differences between the controls and normalbuminuric, microalbuminuric and albuminuric groups were highly significant for KIM-1. Positive correlation was found between KIM-1 and urine microalbumin–urine microalbumin/creatinine (r = 0.479 P < 0.001; r = 0. 400, P < 0.001; respectively). Conclusion In our study, KIM-1 levels were significantly different suggesting that urinary KIM-1 levels may be an early marker in patients with diabetic nephropathy. J. Clin. Lab. Anal. 00:1–6, 2016.
- Published
- 2016
15. Lower Bounds on the LTE-A Average Random Access Delay Under Massive M2M Arrivals
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Mehmet Koseoglu
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Mathematical optimization ,Computer science ,05 social sciences ,Real-time computing ,050801 communication & media studies ,020206 networking & telecommunications ,02 engineering and technology ,Term (time) ,LTE Advanced ,Orders of magnitude (bit rate) ,Base station ,0508 media and communications ,Random-access channel ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Random access - Abstract
Rapid growth of machine-to-machine (M2M) communications necessitates the reevaluation of the Long Term Evolution-Advanced (LTE-A) performance, since the current standard is not optimized for intensive M2M traffic. A serious issue is that massive M2M arrivals can overload the LTE-A random access channel, resulting in a significant access delay. There have been a number of proposals to control this overload; however, there are no studies on the mathematical characterization of delay bounds to the best of our knowledge. Here, we derive lower bounds for the LTE-A average random access delay for both a regular traffic pattern (uniformly distributed arrivals) and for a traffic pattern, indicating a serious congestion (beta-distributed arrivals). The proposed delay bounds, which predict the minimum delay with less than 6% error, present the fundamental limits of delay that can be achieved by a practical load-balancing algorithm. This paper is also one of the first attempts toward the mathematical analysis of beta-distributed arrivals. We also analyze the effect of estimation accuracy, frequency of random access opportunities, and the number of preambles on the access delay. We show that it is possible to reduce the access delay by several orders of magnitude using an appropriate configuration of these system parameters.
- Published
- 2016
16. Nurture
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Bo-Jhang Ho, Mehmet Koseoglu, Mani Srivastava, and Bharathan Balaji
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Computer science ,05 social sciences ,020206 networking & telecommunications ,Context (language use) ,02 engineering and technology ,Nature versus nurture ,Personalization ,Human–computer interaction ,Push technology ,0202 electrical engineering, electronic engineering, information engineering ,Reinforcement learning ,0501 psychology and cognitive sciences ,Mobile device ,050107 human factors - Abstract
User interaction is an essential part of many mobile devices such as smartphones and wrist bands. Only by interacting with the user can these devices deliver services, enable proper configurations, and learn user preferences. Push notifications are the primary method used to attract user attention in modern devices. However, these notifications can be ineffective and even irritating if they prompt the user at an inappropriate time. The discontent is exacerbated by the large number of applications that target limited user attention. We propose a reinforcement learning-based personalization technique, called Nurture, which automatically identifies the appropriate time to send notifications for a given user context. Through simulations with the crowd-sourcing platform Amazon Mechanical Turk, we show that our approach successfully learns user preferences and significantly improves the rate of notification responses.
- Published
- 2018
17. Optimization vs. reinforcement learning for wirelessly powered sensor networks
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Mani Srivastava, Ayca Ozcelikkale, and Mehmet Koseoglu
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FOS: Computer and information sciences ,Optimization problem ,Computer science ,Computer Science - Information Theory ,Real-time computing ,050801 communication & media studies ,Signalbehandling ,02 engineering and technology ,Communications system ,0508 media and communications ,0202 electrical engineering, electronic engineering, information engineering ,Computer Science::Networking and Internet Architecture ,Reinforcement learning ,Wireless ,business.industry ,Information Theory (cs.IT) ,05 social sciences ,Communication Systems ,020206 networking & telecommunications ,Channel state information ,Signal Processing ,business ,Energy harvesting ,Wireless sensor network ,Energy (signal processing) ,Kommunikationssystem - Abstract
We consider a sensing application where the sensor nodes are wirelessly powered by an energy beacon. We focus on the problem of jointly optimizing the energy allocation of the energy beacon to different sensors and the data transmission powers of the sensors in order to minimize the field reconstruction error at the sink. In contrast to the standard ideal linear energy harvesting (EH) model, we consider practical non-linear EH models. We investigate this problem under two different frameworks: i) an optimization approach where the energy beacon knows the utility function of the nodes, channel state information and the energy harvesting characteristics of the devices; hence optimal power allocation strategies can be designed using an optimization problem and ii) a learning approach where the energy beacon decides on its strategies adaptively with battery level information and feedback on the utility function. Our results illustrate that deep reinforcement learning approach can obtain the same error levels with the optimization approach and provides a promising alternative to the optimization framework.
- Published
- 2018
18. Cross-Layer Energy Minimization for Underwater ALOHA Networks
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Mehmet Koseoglu, Ezhan Karasan, Lin Chen, Graphes, Algorithmes et Combinatoire (LRI) (GALaC - LRI), Laboratoire de Recherche en Informatique (LRI), and Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Engineering ,Optimization problem ,Computer Networks and Communications ,02 engineering and technology ,Energy minimization ,Cross-layer design ,01 natural sciences ,PHY ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,[INFO]Computer Science [cs] ,Multiple access control (MAC) ,Electrical and Electronic Engineering ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,010505 oceanography ,business.industry ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,Bandwidth (signal processing) ,Physical layer ,020206 networking & telecommunications ,Energy consumption ,Computer Science Applications ,ALOHA ,Control and Systems Engineering ,Aloha ,Underwater networks ,business ,Information Systems ,Efficient energy use - Abstract
Underwater networks suffer from energy efficiency challenges due to difficulties in recharging underwater nodes. In addition, underwater acoustic networks show unique transmission characteristics such as frequency-dependent attenuation, which causes the transmission power to significantly depend on the bandwidth and the distance. We here investigate the cross-layer energy minimization problem in underwater ALOHA networks considering the unique transmission properties of the underwater medium. We first analyze the separate optimization of the physical (PHY) and multiple access control (MAC) layers to minimize energy consumption. We analytically obtain the energy-optimum channel access rate for the ALOHA MAC layer, which minimizes the energy consumption per successfully transmitted bit. We then formulate a cross-layer optimization problem, which jointly optimizes PHY and MAC layers to minimize energy consumption. We show that such cross-layer optimization reduces the energy consumption per bit as much as 66% in comparison with separate optimization of both layers. Cross-layer optimization achieves this energy efficiency by assigning higher MAC-layer resources to the nodes that have a longer distance to the base station, i.e., which experience a less efficient PHY layer. Moreover, cross-layer optimization significantly increases the amount data transferred until first node failure since it results in a more homogeneous energy consumption distribution among the nodes.
- Published
- 2017
19. Battery-powered AUV network lifetime under energy constraints
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Mehmet Koseoglu, Alper Bereketli, Ilkay Yazgi, and Burcu Yeni
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Engineering ,business.industry ,Wireless ad hoc network ,Network packet ,Software deployment ,Continuous monitoring ,Real-time computing ,Key (cryptography) ,Submarine ,Energy consumption ,business ,Energy (signal processing) ,Simulation - Abstract
With the recent advances in autonomous underwater vehicle (AUV) technology, it has become feasible to deploy AUV fleets as ad hoc networks for coordinated missions such as remote intelligence, area mapping, and tactical surveillance. In these unattended missions, AUVs are typically sent by a central node, such as a submarine, and they move autonomously. Although there is no need for continuous monitoring of AUV nodes, the central node may occasionally need to broadcast a message to all nodes in the fleet to announce any mission change, such as re-routing or ordering them to return back to the base. However, maximum duration of the mission depends on the lifetime of the AUV network, which is limited by the size and capacity of on-board batteries. This necessitates the detailed analysis of energy consumption characteristics and lifetime constraints in order to avoid operational failure. Here we study the connectivity properties of an energy-constrained ad-hoc AUV network through broadcast simulations. We obtained results with respect to the number of packets transmitted, the total number of nodes, and their mobility characteristics. Our results provide key parameters that must be taken into account in the design and deployment of AUV networks.
- Published
- 2017
20. Performance Analysis Of Small Data Transmission Schemes For Cellular M2M Communications
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Mehmet Koseoglu
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Small data ,business.industry ,Computer science ,05 social sciences ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,050801 communication & media studies ,020206 networking & telecommunications ,Throughput ,02 engineering and technology ,Preamble ,0508 media and communications ,Transmission (telecommunications) ,0202 electrical engineering, electronic engineering, information engineering ,Wireless ,Overhead (computing) ,business ,Protocol (object-oriented programming) ,Communication channel ,Computer network - Abstract
Channel access procedures of the state-of-the-art cellular standards create a significant overhead for small messages transmitted by Internet of Things (IoT) devices. As IoT becomes a major source of traffic for next-generation wireless communications, there are recent efforts to design low-overhead access schemes. Here we present the delay and capacity analysis of two low-overhead access protocols in a setting similar to LTEM which is recently standardized for IoT communications. The first protocol that we evaluate is an ALOHA-like immediate transmission scheme where the data is transmitted without channel reservation. The second protocol is a preamble-initiated contention-based access scheme where a frequency/time resource is imperfectly reserved by the transmission of a random preamble. Our results show that preamble-initiated contention-based access improves small message throughput 86% both with respect to the ALOHA-like scheme and the conventional LTE channel access. On the other hand, the ALOHA-like scheme provides 62% lower delay in comparison to the preamble-initiated contention-based scheme at low traffic load conditions. Conventional LTE channel access does not provide any improvement in throughput or delay over these two schemes for small message transmissions.
- Published
- 2017
21. Connectivity analysis of an AUV network with OFDM based communications
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Burcu Yeni, Alper Bereketli, Mehmet Koseoglu, Ilkay Yazgi, Tolga M. Duman, and Muharrem Tumcakir
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0106 biological sciences ,Modulation schemes ,Orthogonal frequency-division multiplexing ,Computer science ,Real-time computing ,Word error rate ,Data_CODINGANDINFORMATIONTHEORY ,01 natural sciences ,Frequency-division multiplexing ,Commercial vehicles ,Vehicle to vehicle communications ,Low density parity check coding ,Underwater acoustics ,Frequency division multiplexing ,Electronic engineering ,Autonomous underwater vehicle ,Low-density parity-check code ,0105 earth and related environmental sciences ,Connectivity ,Orthogonal frequency division multiplexing ,Quadrature phase shift keying ,010505 oceanography ,010604 marine biology & hydrobiology ,Satellite communication systems ,AUV network ,OFDM communication ,Doppler compensations ,Cyclic prefix ,Bit error rate ,Connectivity analysis ,Communication channel ,Phase-shift keying - Abstract
Date of Conference: 21-24 February 2017 Conference Name: IEEE Underwater Technology, UT 2017 Autonomous underwater vehicle (AUV) networks play a crucial role in tactical, commercial, and scientific applications, where reliable and robust communication protocols are needed due to the challenging characteristics of the channel. With this motivation, connectivity of AUV networks in different regions with varying transducer characteristics are analyzed through simulations based on real-life orthogonal frequency division multiplexing (OFDM) based communication experiments over noisy and Doppler-distorted channels. Doppler compensation is performed according to the autocorrelation using the cyclic prefix. Using binary and quadrature phase shift keying (BPSK and QPSK) modulation schemes in conjunction with low density parity check (LDPC) coding, error rate levels are investigated through shallow water pond and at-sea experiments. It is shown that, the utilized transmission scheme is capable of correcting all bit errors among nearly one million bits transmitted up to a distance of 1 km, yielding a payload rate of 15.6 kbps with 4096 subcarriers and QPSK modulation. The simulations provide key parameters that must be taken into account in the design of scalable and connected AUV networks.
- Published
- 2017
22. Procalcitonin and C-Reactive Protein Levels According to Blood Culture Results in Intensive Care Unit Patients
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Ozgur Aslan, Mehmet Koseoglu, Metin Demir, Asl Gamze Sener, and Ilhan Afsar
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Microbiology (medical) ,medicine.medical_specialty ,medicine.diagnostic_test ,biology ,business.industry ,C-reactive protein ,Intensive care unit ,Procalcitonin ,law.invention ,Infectious Diseases ,law ,medicine ,biology.protein ,Blood culture ,Intensive care medicine ,business - Published
- 2014
23. Spatio-Temporal Analysis of Throughput for Single-Hop CSMA Networks
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Ezhan Karasan and Mehmet Koseoglu
- Subjects
Computer science ,Throughput ,Spatio-temporal analysis ,Upper and lower bounds ,Base station ,Non-persistent CSMA ,Computer Science::Networking and Internet Architecture ,Model results ,Electrical and Electronic Engineering ,Carrier sense multiple access ,Single-hop ,Throughput modeling ,Throughput (business) ,Single hop ,business.industry ,Spatio-Temporal Analysis ,Single-hop Csma ,Propagation delay ,Propagation delays ,Expression (mathematics) ,Computer Science Applications ,Computer Science::Performance ,Spatiotemporal analysis ,Modeling and Simulation ,Throughput analysis ,Packet transmissions ,business ,Algorithm ,Computer network - Abstract
Cataloged from PDF version of article. Throughput model for non-persistent CSMA networks which was proposed by Kleinrock and Tobagi has been widely used, although it provides a loose lower bound when nodes are distributed in a large area because the analysis assumes that the propagation delay between each pair of users equals to the largest propagation delay in the network. We present a throughput analysis which considers the spatial distribution of nodes. We obtain a simple throughput expression which predicts throughput with an 8% maximum error whereas the earlier model results in a 44% error when the maximum propagation delay equals to the packet transmission time.
- Published
- 2014
24. HOW DO HEALTHCARE PROFESSIONALS USE KNOWLEDGE MANAGEMENT?: EVIDENCE FROM AN EMERGING ECONOMY
- Author
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Gary Ross, Yildirim University, Mehmet Koseoglu, and Saffet Ocak
- Subjects
Knowledge management ,Health professionals ,business.industry ,Business ,Emerging markets - Published
- 2014
25. Prognostic and Predictive Value of Hematologic Parameters in Patients with Metastatic Renal Cell Carcinoma: Second Line Sunitinib Treatment Following IFN-alpha
- Author
-
Murat Akyol, Ahmet Alacacioglu, Ahmet Dirican, Mehmet Koseoglu, Alper Can, Yuksel Kucukzeybek, Mustafa Oktay Tarhan, Lutfiye Demir, Yasar Yildiz, Isil Somali, Ibrahim Vedat Bayoglu, Kadriye Bahriye Payzin, and Cigdem Erten
- Subjects
Adult ,Male ,Cancer Research ,medicine.medical_specialty ,Pathology ,Indoles ,Neutrophils ,Epidemiology ,medicine.drug_class ,Alpha interferon ,Angiogenesis Inhibitors ,Neutropenia ,urologic and male genital diseases ,Antiviral Agents ,Gastroenterology ,Tyrosine-kinase inhibitor ,Renal cell carcinoma ,Internal medicine ,Biomarkers, Tumor ,Sunitinib ,medicine ,Humans ,Pyrroles ,Lymphocytes ,Neoplasm Metastasis ,Mean platelet volume ,Carcinoma, Renal Cell ,Aged ,Neoplasm Staging ,Retrospective Studies ,Hematologic Tests ,business.industry ,Public Health, Environmental and Occupational Health ,Interferon-alpha ,Cancer ,Middle Aged ,Sunitinib malate ,Prognosis ,medicine.disease ,Kidney Neoplasms ,Survival Rate ,Oncology ,Female ,business ,Follow-Up Studies ,medicine.drug - Abstract
Background: Long-term survival is a problem with locally advanced and metastatic renal cell carcinomas. Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor, but data on sunitinib use as a second line treatment in metastatic renal cell carcinoma (mRCC) are limited. Prognostic and predictive value of peripheral blood markers has been shown for many cancers. Materials and Methods: Efficacy and safety profiles of sunitinib after interferon alpha (IFN-α) were evaluated based on retrospective data for 23 patients with mRCC. Hematological parameters (neutrophils, lymphocytes, platelets, mean platelet volume, neutrophil/lymphocyte ratio, platelet/lymphocyte ratio) were recorded at the time of metastasis. It was evaluated whether hematological parameters were prognostic and predictive factors. Results: Median progression-free survival (PFS) time was 16.5 months (95%CI: 0-34.5). Median overall survival (OS) time was 25.7 months (95%CI: 10.8-40.0). Most common side effects were neutropenia (52.2%), stomatitis (26.1%) and hand-food syndrome (26.1%). PFS was found 3.13 vs 17.1 months in patients with neutrophil / lymphocyte ratio (NLR)>3 vs NLR≤3 (p:0.012). Median OS was 6.96 vs 27.1 months in patients with NLR>3 vs NLR≤3 (p:0.001).While 75% of patients who responded to sunitinib had NLR≤3, in 72% of patients with no response to sunitinib NLR>3 was detected (p:0.036). The association between the Memorial Sloan-Kettering Cancer Center (MSKCC) criteria and NLR was statistically significant (p:0.022). Conclusions: Data on second line sunitinib treatment following cytokine in mRCC are limited. In our study, we observed second line sunitinib treatment following IFN-α to be effective and tolerable. NLRappeared to have prognostic and predictive value.
- Published
- 2013
26. Prognostic Significance of Circulating Tumor Cells and Serum CA15-3 Levels in Metastatic Breast Cancer, Single Center Experience, Preliminary Results
- Author
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Isil Somali, Serap Cuhadar, Aysenur Atay, Mehmet Koseoglu, Ahmet Dirican, Seyran Yigit, Lutfiye Demir, Ataman Gönel, Yuksel Kucukzeybek, Cigdem Erten, and Mustafa Oktay Tarhan
- Subjects
Adult ,CA15-3 ,Oncology ,Cancer Research ,medicine.medical_specialty ,Epidemiology ,Metastasis ,Breast cancer ,Circulating tumor cell ,Neoplasms ,Internal medicine ,Biomarkers, Tumor ,medicine ,Humans ,Neoplasm Metastasis ,Survival rate ,Aged ,business.industry ,Carcinoma, Ductal, Breast ,Mucin-1 ,Public Health, Environmental and Occupational Health ,Cancer ,Middle Aged ,Neoplastic Cells, Circulating ,Prognosis ,medicine.disease ,Adenocarcinoma, Mucinous ,Metastatic breast cancer ,Survival Rate ,Carcinoma, Lobular ,Adenocarcinoma ,Female ,Neoplasm Grading ,business ,Follow-Up Studies - Abstract
Background: Breast cancer is the second leading cancer causing death in women. Circulating tumor cells are among the prognostic factors while tumor markers are of diagnostic value and can be used for follow-up. The aim of this study was to investigate the correlation between the prognostic significance of the serum CA15-3 levels, number of circulating tumor cells and histopathological tumor factors. Materials and Methods: Thirty patients recently diagnosed with breast cancer were included in the study. Number of circulating tumor cells and serum CA15-3 level were assessed when metastasis was detected and diagnostic value was assessed. Presence of associations with estrogen and progesterone receptors, c-erbB2, Ki-67 proliferation index and histological grade were also evaluated. Results: Median overall survival of the patients with serum CA15-3 levels of >108 ng/dl was 19 months whereas for those with a low serum level it was 62 months. Median overall survival for CTC ≥5vs CTC
- Published
- 2013
27. The effect of storage time and freeze-thaw cycles on the stability of serum samples
- Author
-
Mehmet Koseoglu, Aysenur Atay, Serap Cuhadar, and Ahmet Dirican
- Subjects
Serum ,Time Factors ,Bilirubin ,Clinical Biochemistry ,storage ,chemistry.chemical_compound ,Lactate dehydrogenase ,Freezing ,preanalytical phase ,Humans ,serum ,stability ,temperature ,Blood urea nitrogen ,Blood Specimen Collection ,Original Paper ,Creatinine ,Chromatography ,biology ,Cholesterol ,Biochemistry (medical) ,Albumin ,chemistry ,Biochemistry ,Blood Preservation ,biology.protein ,Uric acid ,Creatine kinase - Abstract
INTRODUCTION Optimal storage of serum specimens in central laboratories for a long period for multicenter reference interval studies, or epidemiologic studies remains to be determined. We aimed to examine the analytical stability of chemistry analytes following numerous freeze-thaw and long-term storage. MATERIALS AND METHODS Serum samples were obtained from 15 patients. Following baseline measurement, sera of each subject were aliquoted and stored at -20 degrees C for two experiments. A group of sera were kept frozen for up to 1, 2 and 3 months and then analyzed for stability. The other experiment consisted of one to ten times of freeze and thaw cycles. Total of 17 chemistry analytes were assayed at each time point. The results were compared with those obtained from the initial analysis of fresh samples. Median or mean changes from baseline (T(0)) concentrations were evaluated both statistically and clinically according to the desirable bias. RESULTS Of the analytes studied, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), gamma-glutamyl transferase (GGT), direct bilirubin, glucose, creatinine, cholesterol, triglycerides, high density lipoprotein (HDL) were stable in all conditions. Blood urea nitrogen (BUN), uric acid, total protein, albumin, total bilirubin, calcium, lactate dehydrogenase (LD) were changed significantly (P < 0.005). CONCLUSIONS As a result, common clinical chemistry analytes, with considering the variability of unstable analytes, showed adequote stability after 3 months of storage in sera at -20 degrees C, or up to ten times of freeze-thaw cycle. All the same, such analysis can only be performed for exceptional cases, and this should be taken into account while planning studies.
- Published
- 2013
28. Probabilistic broadcast for dense AUV networks
- Author
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Ilkay Yazgi, Burcu Yeni, Mehmet Koseoglu, and Alper Bereketli
- Subjects
Engineering ,010505 oceanography ,business.industry ,Continuous monitoring ,Probabilistic logic ,Probabilistic broadcast ,Submarine ,020206 networking & telecommunications ,02 engineering and technology ,Energy consumption ,01 natural sciences ,Flooding (computer networking) ,0202 electrical engineering, electronic engineering, information engineering ,Underwater ,business ,Broadcast radiation ,Simulation ,0105 earth and related environmental sciences ,Computer network - Abstract
As the technology behind autonomous underwater vehicles (AUV) becomes more feasible, it is possible to use fleets of AUVs for coordinated missions such as area mapping, surveillance, etc. The AUVs are typically sent by a central node such as a submarine and move autonomously. Although there is no need for continuous monitoring of AUV nodes, the central node may occasionally need to send a broadcast message to all nodes in the fleet to announce a change in mission; e.g. ordering nodes to return back to the base. To address this need, reliable and low-latency broadcast algorithms for underwater networks are needed. Here we investigate the performance of probabilistic broadcast for AUV networks where the AUVs are not aware of locations of their neighbors. Our results indicate that probabilistic broadcast significantly improves average and maximum delay along with energy consumption in comparison to simple flooding especially for dense networks.
- Published
- 2016
29. Stability studies of common biochemical analytes in serum separator tubes with or without gel barrier subjected to various storage conditions
- Author
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Mehmet Koseoglu, Serap Cuhadar, Aysenur Atay, Ahmet Dirican, and Aysel Hur
- Subjects
Adult ,Male ,Time Factors ,Bilirubin ,Clinical Biochemistry ,Centrifugation ,Biochemistry ,Specimen Handling ,storage ,chemistry.chemical_compound ,Reference Values ,Lactate dehydrogenase ,blood specimen collection ,enzyme stability ,serum ,temperature ,Humans ,Blood Specimen Collection ,Creatinine ,Chromatography ,biology ,Biochemistry (medical) ,Temperature ,Albumin ,Venous blood ,Middle Aged ,Original Papers ,chemistry ,biology.protein ,Uric acid ,Alkaline phosphatase ,Female ,Creatine kinase ,Gels - Abstract
Introduction: The collected and shipped blood samples are exposed to a various extra-analytical factors prior to analysis. The aim of the study was to determine the stability of analytes in serum gel tubes and plain tubes exposed to a range of storage temperatures and times after centrifugation. Materials and methods: Fifteen healthy volunteers were recruited and venous blood was collected into four tubes, two with and two without gel separator. Analyzing the baseline samples in 30 min, all were stored at 4oC or 24oC for 6, 12, 18, 24, 30, 36, 48 and 72 hours and 1 week. Sixteen biochemical anaytes were measured on each sample. Variations remained under the desirable bias considered as clinically insignifi cant. Results: On day three, most analytes remained stable including albumin, protein, creatinine, cholesterol, triglycerides, gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine aminotransferase (ALT), creatine kinase (CK), lactate dehydrogenase (LD) regardless of tube types. Glucose concentration decreased markedly (P = 0.001) beginning from the fi rst hours of storage in plain serum. The stability ma ximized for the analytes including glucose, total bilirubin, urea nitrogen (BUN), uric acid stored at 4 oC in gel tubes. Aspartate aminotransferase (AST) activity increased signifi cantly (P = 0.002) up to 48-h, however bias was no t signifi cant clinically. High density lipoprotein (HDL) concentr ation was stable in gel tubes at 24 oC, in plain tubes at 4 oC stored up to 36-h. Conclusion: Serum gel or non-gel tubes might be used interchangeably for 11 analytes chilled or at 24 oC, whereas some restrictions must be applied for glucose, AST, BUN, HDL, and uric acid.
- Published
- 2012
30. Smart pricing for service differentiation and load control of the LTE-A IoT system
- Author
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Mehmet Koseoglu
- Subjects
Service (business) ,LTE Advanced ,Broadcasting (networking) ,Transmission (telecommunications) ,business.industry ,Computer science ,Control (management) ,business ,Computer network ,Communication channel - Abstract
The current LTE-Advanced (LTE-A) standard has been designed for human-generated traffic but it has to be adapted for machine-to-machine (M2M) communications due to the expanding Internet of Things (IoT) market. Although most M2M devices infrequently connect to the network and transmit small messages, a serious congestion may occur during the initial channel access phase if a massive number of devices activate near-simultaneously. To address this issue, previous studies have proposed load control methods based on broadcasting an access probability to all nodes or groups of nodes at times of congestion. Such approaches, however, are inadequate in satisfying the wide range of service requirements of IoT applications. Here we propose a pricing-based load control and service differentiation method for M2M traffic over LTE-A which is based on charging M2M devices for each successful channel access and subsequent short message transmission. By increasing the price during congestion, the proposed method effectively controls the access load. It also operates as a service differentiation mechanism providing delay-sensitive nodes a shorter access delay and charging higher prices from them. Simulation results show that the delay performance of the proposed method is close to an optimum load controller; and, it provides service differentiation unlike previous load-control approaches.
- Published
- 2015
31. Serum Leptin Levels in Epileptic Patients Treated with Topiramate and Valproic Acid
- Author
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Uludag, Irem Fatma, Sener, Ufuk, Zoriu, Yasar, mehmet koseoglu, and Aydin, Tugba Kantaroglu
- Subjects
Leptin ,obesity ,topiramate ,valproic acid ,epilepsy ,Medicine ,lipids (amino acids, peptides, and proteins) ,Neurology. Diseases of the nervous system ,RC346-429 - Abstract
OBJECTIVE: Leptin is considered to be a signal factor that regulates body weight and energy expenditure, and there is a strong correlation between serum leptin concentrations, body mass index, and body fat mass in humans. Our aim in this study was to evaluate the role of leptin in valproic acid (VPA) and topiramate (TPM) related weight changes in epileptic patients. METHODS: Body mass index is calculated and serum leptin and insulin levels are measured in 56 patients with epilepsy (40 patients taking VPA and 16 patients taking VPA and TPM) and in 40 healty control subjects. RESULTS: Obesity was seen in 21 patients (52.5%) in VPA treated group, in 15 patients (37.5%) in the control group and in only one male (6.3%) in VPA and TPM treated group. Body mass index was lower in the group treated with VPA and TPM (p
- Published
- 2011
32. Effects of hemolysis interference on routine biochemistry parameters
- Author
-
Serap Cuhadar, Aysenur Atay, Mehmet Koseoglu, and Aysel Hur
- Subjects
medicine.medical_specialty ,Clinical Biochemistry ,Hemolysis ,chemistry.chemical_compound ,Internal medicine ,Lactate dehydrogenase ,medicine ,Humans ,Gamma-glutamyltransferase ,Blood Specimen Collection ,biology ,Chemistry ,Biochemistry (medical) ,Albumin ,Blood Physiological Phenomena ,medicine.disease ,hemolysis ,preanalytical errors ,interference ,analytes ,Endocrinology ,Chemistry, Clinical ,biology.protein ,Uric acid ,Alkaline phosphatase ,Creatine kinase ,Hemoglobin ,Blood Chemical Analysis - Abstract
Introduction: Hemolysis is still the most common reason for rejecting samples, while reobtaining a new sample is an important problem. The aim of this study was to investigate the effects of hemolysis in different hemolysis levels for mostly used biochemical parameters to prevent unnecessary rejecti-ons. Materials and methods: Sixteen healthy volunteers were enrolled in the study. Four hemolysis levels were constituted according to hemoglobin concentrations and they were divided into five groups: Gro-up I: 0-0.10 g/L, Group II: 0.10-0.50 g/L, Group III: 0.51-1.00 g/L, Group IV: 1.01-2.50 g/L, Group V: 2.51-4.50 g/L. Lysis was achieved by mechanical trauma. Results: Hemolysis interference affected lactate dehydrogenase (LD) and aspartate aminotransfera-se (AST) almost at undetectable hemolysis by visual inspection (plasma hemoglobin < 0.5 g/L). Clinically meaningful variations of potassium and total bilirubin were observed in moderately hemolyzed samples (hemoglobin > 1 g/L). Alanine aminotransferase (ALT), cholesterol, gamma glutamyltransferase (GGT), and inorganic phosphate (P) concentrations were not interfered up to severely hemolyzed levels (hemoglobin: 2.5-4.5 g/L). Albumin, alkaline phosphatase (ALP), amylase, chloride, HDL-cholesterol, creatine kinase (CK), glucose, magnesium, total protein, triglycerides, un-saturated iron binding capacity (UIBC) and uric acid differences were statistically significant, but re-mained within the CLIA limits. Conclusion: To avoid preanalytical visual inspection for hemolysis detection, improper sample rejec-tion, and/or rerun because of hemolysis, it is recommended in this study that, routine determination of plasma or serum free hemoglobin concentrations is important. For the analytes interfered with hemolysis, new samples have to be requested.
- Published
- 2011
33. An important role for VCAM-1, but not for ICAM-1 in restenosis following coronary stent implantation
- Author
-
Abdülaziz Taş, Erdinç Arıkan, Nursen Postaci, Serdar Bayata, Murat Yeşil, and Mehmet Koseoglu
- Subjects
medicine.medical_specialty ,medicine.medical_treatment ,Vascular Cell Adhesion Molecule-1 ,Coronary Disease ,Angina Pectoris ,Coronary Restenosis ,Lesion ,Restenosis ,Internal medicine ,Coronary stent ,medicine ,Humans ,Prospective Studies ,Treatment Failure ,Prospective cohort study ,business.industry ,Percutaneous coronary intervention ,Stent ,Equipment Design ,Intercellular Adhesion Molecule-1 ,medicine.disease ,Radiography ,Conventional PCI ,Mann–Whitney U test ,Cardiology ,Stents ,medicine.symptom ,Cardiology and Cardiovascular Medicine ,business ,Biomarkers ,Follow-Up Studies - Abstract
Objective In this study, we evaluated the possibility that, levels of circulating adhesion molecules following direct stent implantation may be a marker of restenosis. Methods This prospective, observational study investigated levels of circulating intercellular (ICAM-1), and vascular cell (VCAM-1) adhesion molecules in 15 patients with stable angina pectoris before and after coronary stent implantation for single vessel-single lesion disease in proximal left anterior descending artery. All patients received bare-metal stents. Patients underwent repeat coronary angiography for detection of restenosis at 6 month. Continuous data between patients with and without restenosis were compared using Mann-Whitney U test. Repeated measurements were compared using Wilcoxon T test. Categorical data were compared using Chi-square statistics. Results Baseline ICAM-1 and VCAM-1 concentrations before percutaneous coronary intervention (PCI) were 4.89±2.28 and 46.35±22.96 ng/ml respectively. Levels of ICAM and VCAM increased nonsignificantly 24 hours after PCI (5.01±2.35 ng/ml and 52.57±19.40 ng/ml, respectively). Six patients (40%) developed restenosis within 6 months. Mean stent length, mean stent diameter, and mean dilatation pressure were comparable in patient groups with and without restenosis. Levels of plasma VCAM-1 measured before and after PCI did not change significantly in patients without restenosis. However, these levels increased significantly in the group of restenosis. At 6 months, patients who developed restenosis, had higher VCAM-1 levels, as compared to baseline values (from 45.1±21.0 to 57.2±14.3 ng/ml, p=0.05). Plasma levels of pre and post PCI ICAM-1 did not differ significantly between groups with and without restenosis. Conclusion These results suggest a more dominant role for VCAM-1, but not for ICAM-1 in development of restenosis following coronary stent implantation.
- Published
- 2010
34. Relationship between severity of coronary artery disease and apolipoprotein E gene polymorphism
- Author
-
Mehmet Koseoglu, Aysenur Atay, Erdal Deveci, F. Demet Arslan İnce, and Murat Yeşil
- Subjects
Adult ,Male ,Apolipoprotein E ,medicine.medical_specialty ,Apolipoprotein B ,Apolipoprotein E2 ,Apolipoprotein E4 ,Apolipoprotein E3 ,Blood lipids ,Coronary Disease ,Severity of Illness Index ,Gastroenterology ,Coronary artery disease ,Apolipoproteins E ,Internal medicine ,Genotype ,medicine ,Humans ,Allele ,Allele frequency ,Aged ,Polymorphism, Genetic ,biology ,business.industry ,Middle Aged ,medicine.disease ,Genotype frequency ,Sample Size ,Cardiology ,biology.protein ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
OBJECTIVE To explore the possible contribution of the apolipoprotein (apo) E polymorphisms to the extent and severity of coronary artery disease (CAD) related to lipid metabolism. METHODS Overall, 53 Turkish patients, aged 54+/-11 years defined by coronary angiography were included in this cross-sectional study. Reardon's coronary artery scoring was used. Serum lipids were measured with enzymatic colorimetric methods. Apolipoproteins were measured with nephelometry. Apolipoprotein E gene polymorphisms were determined by the reverse hybridization method. Statistical analyses were performed using one-way ANOVA, Kruskal-Wallis and Chi- square tests. RESULTS The genotype frequencies were 7.5% for E2/E3, 77.4% for E3/E3 and 15.1% for E3/E4. The E2 allele frequency was slightly lower than E4 allele. There were no significant differences between apo E2/E3, E3/E3 and E3/E4 genotypes for severity scorings (26, 41 and 32 respectively, p=0.30) and extent scorings (3.2, 5.5, 4.5, p=0.17). It was found that the most of patients who had E2/3 and E3/4 alleles had low severity scores. On the other hand, there were no significant score difference for patients who had E3/3 alleles. Lipids were not significantly different among the different genotypes. The E3 allele was associated with high apo B levels compared with E2 and E4 genotypes. It was found that severity and extent of disease were not related with lipid metabolism. CONCLUSION We concluded that there were no statistically significant differences between genotypes for extent and severity scorings, but the apo E3 allele is associated with more severe disease than E2 allele. These associations with severity were mediated not only by changes in lipid metabolism but may be also by other mechanisms in CAD patients.
- Published
- 2010
35. Joint resource and network scheduling with adaptive offset determination for optical burst switched grids
- Author
-
Mehmet Koseoglu and Ezhan Karasan
- Subjects
Network scheduling ,Offset (computer science) ,Computer Networks and Communications ,Computer science ,Real-time computing ,Burst loss ,Data-communication ,Offset time ,Optical burst switching ,computer.software_genre ,Scheduling (computing) ,Grid network provisioning ,Quality of service ,Packet switching ,Completion time ,Optical switches ,Wireless telecommunication systems ,Optical communication ,Job completion ,Grid resource provisioning ,Network congestions ,Switching networks ,Scheduling ,business.industry ,Adaptive mechanism ,Provisioning ,Computer simulation ,Grid ,Loss probability ,Network congestion ,Grid computing ,Hardware and Architecture ,Grid scheduling ,Grid resource ,Optical bursts ,business ,Network provisioning ,computer ,Software ,Computer network - Abstract
Optical burst switching (OBS) is a promising technology for optical grids with short-lived and interactive data communication requirements. On the other hand, burst losses are in the nature of the OBS protocol and these losses severely affect the grid job completion times. This paper first proposes a joint grid resource and network provisioning method to avoid congestion in the network in order to minimize grid job completion times. Simulations show that joint provisioning significantly reduces completion times in comparison to other methods that perform network provisioning after grid scheduling. An adaptive extra offset based quality of service (QoS) mechanism is also proposed in order to reduce grid burst losses in case of network congestion. Results show that this adaptive mechanism significantly reduces grid completion times by exploiting the trade-off between decreasing loss probability and increasing delay introduced by the extra offset time. (C) 2009 Elsevier B.V. All rights reserved.
- Published
- 2010
36. Serum hyaluronan levels in patients with knee osteoarthritis
- Author
-
Alev Gürgan, Serpil Bal, Mehmet Koseoglu, Hatice Topac, and Yasemin Turan
- Subjects
Male ,medicine.medical_specialty ,WOMAC ,Osteoarthritis ,Serum Hyaluronic Acid ,Gastroenterology ,chemistry.chemical_compound ,Rheumatology ,Internal medicine ,Hyaluronic acid ,medicine ,Humans ,Hyaluronic Acid ,Aged ,medicine.diagnostic_test ,business.industry ,Case-control study ,Liter ,General Medicine ,Middle Aged ,Osteoarthritis, Knee ,medicine.disease ,Surgery ,C-Reactive Protein ,chemistry ,Case-Control Studies ,Erythrocyte sedimentation rate ,Female ,business - Abstract
We examined the association between clinical parameters of disease activity and serum hyaluronic acid (HA) level in patients with knee osteoarthritis (OA). Fifty-eight patients with knee OA and 40 healthy individuals were included in this study. Demographic data were noted. The radiological evaluation was done according to Kellgren/Lawrence Grading System. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used in evaluating the clinical disability caused by OA. Erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) level were determined in laboratory evaluations. Serum HA levels (in nanogram per milliliter) of both groups were measured by enzyme-linked immunosorbent assay. The mean ages of patients in OA group and control group were 57.58 (9.55) and 43.3(10.2) years, respectively. There was a significant difference between HA levels of both groups (p=0.02). Also, there was a significant correlation between HA level and disease duration (p=0.04), ESR (p=0.001), and CRP level (p0.001). However, there was no significant correlation between HA levels with WOMAC and radiological grade (p0.05). There is no satisfactory amount of data regarding HA level in OA. In our study, we demonstrated that HA was in high levels in the serum of patients with OA. We suggest that serum HA levels may be used as a marker to determine the disease activity.
- Published
- 2007
37. The Acute Effects of Postprandial Hypertriglyceridemia on Coagulation Parameters in Normal and Overweight Individuals
- Author
-
Aysenur Atay, Fatma Demet Arslan Ince, Yavuz Yigit, Mehmet Koseoglu, Hamit Yasar Ellidag, and Köseoğlu, Mehmet Hicri
- Subjects
Prothrombin time ,Hypertriglyceridemia ,medicine.medical_specialty ,Coagulation ,medicine.diagnostic_test ,Triglyceride ,business.industry ,Cholesterol ,Postprandial ,Clinical Biochemistry ,Overweight ,medicine.disease ,Fibrinogen ,chemistry.chemical_compound ,Endocrinology ,High-density lipoprotein ,chemistry ,Internal medicine ,Medicine ,business ,Partial thromboplastin time ,medicine.drug - Abstract
WOS: 000217526200008 Postprandial hypertriglyceridemia may have a procoagulant effect and cause an activation of coagulation system. The measurement of postprandial triglyceride concentrations and coagulation parameters may give additional useful data besides the fasting measurement. Thus, we investigated the acute effects of hypertriglyceridemia after the meal in normal and overweight individuals. Fourteen overweight (Group I) and sixteen normal weight (Group II) voluntary participants were given fat-rich meal (700 kcal). Blood samples were obtained at fasting, 3rd and 6th hours. In both groups, total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride (TG), fibrinogen, prothrombin time (PT), activated partial thromboplastin time, factor VII (FVII), factor IX (FIX), protein C and, protein S activities were measured. As might be expected, TG levels were higher in the postprandial state than the fasting state in both groups and also Group I subjects had higher levels rather than Group II at all states. One of our important finding finding was that PT levels were shorter in Group I at the fasting, postprandial 3rd and 6th hours than Group II (P = 0.007, P = 0.033, P = 0.047 respectively). Moreover, FVII and FIX activities were found as higher in Group I at the postprandial 3rd hour (P = 0.047, P = 0.008 respectively). In conclusion, the high activities of FVII and FIX and short PT levels may predispose to thrombosis in Group I, especially at postprandial states.
- Published
- 2015
38. Bulgarian Education Mobilization and Teachers with Bulgarian School in Thessaloniki Province
- Author
-
Mehmet KÖSEOĞLU
- Subjects
History of Civilization ,CB3-482 ,Language and Literature - Published
- 2022
- Full Text
- View/download PDF
39. Energy-Optimum Throughput and Carrier Sensing Rate in CSMA-Based Wireless Networks
- Author
-
Mehmet Koseoglu and Ezhan Karasan
- Subjects
Energy utilization ,Computer Networks and Communications ,Computer science ,Energy Efficiency ,Energy budgets ,Budget control ,Throughput ,Analytical Models ,Operating regimes ,High throughput ,Computer Science::Networking and Internet Architecture ,Carrier Sense Multiple Access ,Wireless ,Electrical and Electronic Engineering ,Throughput (business) ,Multihop networks ,business.industry ,Wireless network ,Node (networking) ,Single-hop network ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,Energy consumption ,Energy budget ,Carrier communication ,Carrier sensing ,Spread spectrum ,Computer Science::Performance ,Performance Analysis ,Maximum throughput scheduling ,business ,Maximum through-put ,Software ,Computer network ,Communication channel ,Efficient energy use - Abstract
Cataloged from PDF version of article. We propose a model for the energy consumption of a node as a function of its throughput in a wireless CSMA network. We first model a single-hop network, and then a multi-hop network. We show that operating the CSMA network at a high throughput is energy inefficient since unsuccessful carrier sensing attempts increase the energy consumption per transmitted bit. Operating the network at a low throughput also causes energy inefficiency because of increased sleeping duration. Achieving a balance between these two opposite operating regimes, we derive the energy-optimum carrier-sensing rate and the energy-optimum throughput which maximize the number of transmitted bits for a given energy budget. For the single-hop case, we show that the energy-optimum total throughput increases as the number of nodes sharing the channel increases. For the multi-hop case, we show that energy-optimum throughput decreases as the degree of the conflict graph corresponding to the network increases. For both cases, the energy-optimum throughput reduces as the power required for carrier-sensing increases. The energy-optimum throughput is also shown to be substantially lower than the maximum throughput and the gap increases as the degree of the conflict graph increases for multi-hop networks. © 2002-2012 IEEE.
- Published
- 2014
40. The anti-inflammatory and antioxidant effects of pravastatin and nebivolol in rat aorta
- Author
-
Serap Cuhadar, Safiye Aktaş, Mehmet Koseoglu, Seyhun Dursun, and Aysenur Atay
- Subjects
medicine.medical_specialty ,Coronary Artery Disease ,medicine.disease_cause ,Nebivolol ,chemistry.chemical_compound ,High-density lipoprotein ,Internal medicine ,Hyperlipidemia ,medicine ,Animals ,Rats, Wistar ,Aorta ,Triglycerides ,Pravastatin ,Inflammation ,Triglyceride ,business.industry ,Ceruloplasmin ,nutritional and metabolic diseases ,Arteriosclerosis ,medicine.disease ,Adrenergic beta-1 Receptor Antagonists ,Rats ,Uric Acid ,Disease Models, Animal ,Cholesterol ,NG-Nitroarginine Methyl Ester ,Endocrinology ,chemistry ,Low-density lipoprotein ,Cardiology ,Female ,lipids (amino acids, peptides, and proteins) ,Hydroxymethylglutaryl-CoA Reductase Inhibitors ,Cardiology and Cardiovascular Medicine ,business ,Oxidative stress ,medicine.drug - Abstract
The aim of this study was to investigate the effects of pravastatin and nebivolol in the atherosclerotic process including inflammation and oxidative stress in rat aorta.This experimental randomized controlled study comprised of 35 Wistar albino rats. Nω-nitro-L-arginine methyl ester (L-NAME) - induced vascular inflammation and arteriosclerosis were treated with both of the pharmacologic agents. All were divided into 5 equal groups: the control, group I: L-NAME -15 days, group II: L-NAME 30+ nebivolol, group III: L-NAME -30+ pravastatin, group IV: L-NAME - 30 days. Serum ceruloplasmin, uric acid, total antioxidant capacity (TAC), total cholesterol (T.Chol), low density lipoprotein (LDL), high density lipoprotein (HDL), triglyceride (TG) were analyzed. Medial thickening and leukocyte infiltration status were examined histopathologically. The results were compared with control group and with each other using Kruskal Wallis and Mann-Whitney U test.Pravastatin diminished the rise of ceruloplasmin, which was taken as an index of inflammation (p=0.002). Pravastatin and nebivolol decreased the L-NAME induced oxidative stress (p =0.001, 0.002, respectively). Nebivolol diminished the rise of LDL (p=0.04). Pravastatin lowered T.Chol, LDL and TG levels (p=0.001, 0.008, 0.040, respectively). HDL values were not changed significantly.In conclusion, 15 days of statin therapy attenuated vascular inflammation and lowered the rised lipid levels (LDL, T.cholesterol and TG). Both the nebivolol and pravastatin exhibited antioxidant property. These documented beneficial effects of both of the drugs may improve the clinical outcomes of patients with hypertension or hyperlipidemia by additional studies.AMAÇ: Bu çalışmanın amacı pravastatin ve nebivololün aterosklerotik süreçteki inflamasyon ve oksidatif strese olan etkilerinin sıçan aortunda araştırılmasıydı. YÖNTEMLER: Bu deneysel randomize kontrollü çalışma 35 adet Wistar albino sıçanları ile yapılmıştır. Nω-nitro-L-arginine methyl ester (L-NAME) verilerek oluşturulan vasküler inflamasyon ve arterioskleroz her iki farmakolojik ajanla tedavi edilmiştir. Sıçanlar 5 eşit gruba ayrılmışlardır: grup I: L-NAME-15 gün, grup II: II: L-NAME 30+ nebivolol, grup III: L-NAME -30+ pravastatin, grup IV: L-NAME - 30 gün. Serum serüloplazmin, ürik acid, total antioksidan kapasite (TAC), total kolesterol (T.kol), düşük dansiteli lipoprotein (LDL), yüksek dansiteli lipoprotein (HDL), trigliserid (TG) düzeyleri ölçüldü. Damar medial tabakasının kalınlığı ve lökosit infiltrasyonu histopatolojik olarak değerlendirildi. Sonuçlar kontrol grubu ile ve gruplar birbiriyle karşılaştırılarak değerlendirildi ve Kruskal Wallis, Mann-Whitney U testleri kullanıldı.Pravastatin, enflamasyon indeksi olarak değerlendirilen serüloplazminin yükselmiş olan düzeyini düşürdü (p=0,002). Pravastatin ve nebivolol L-NAME etkisi ile artmış olan oksidatif stresi azalttı (0,001, 0,002, sırasıyla). Nebivolol yükselmiş olan LDL’yi düşürdü (p=0,04). Pravastatin T.kol, LDL ve TG düzeyini düşürdü (p=0,001, 0,008, 0,040, sırasıyla). HDL düzeyinde anlamlı değişiklik görülmedi. SONUÇ: Sonuç olarak, 15 günlük statin tedavisi vasküler inflamasyonu azalttı ve yükselmiş olan lipid düzeyini düşürdü (LDL, T.kol ve TG). Nebivolol ve pravastatin antioksidan etki gösterdiler. Bu çalışmada belgelediğimiz her iki ilacın faydalı etkileri hipertansiyon ve hiperlipidemi hastalarının klinik yararlılığı için ek çalışmalarla desteklenebilir.
- Published
- 2014
41. The effects of iodixanol and iopamidol on adhesion molecule serum levels in patients with angina pectoris undergoing coronary angiography: a randomized study
- Author
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Tuna Semerci, Selcen Yakar Tülüce, Filiz Akyıldız Akçay, Oguzhan Toklu, Erdinç Arıkan, İdil Gökçen Koçağra Yağız, Mehmet Koseoglu, Murat Yeşil, and Serdar Bayata
- Subjects
Male ,medicine.medical_specialty ,Randomization ,Contrast Media ,Vascular Cell Adhesion Molecule-1 ,Coronary Artery Disease ,Coronary Angiography ,Gastroenterology ,Iopamidol ,Angina Pectoris ,Angina ,Internal medicine ,Triiodobenzoic Acids ,Medicine ,Humans ,Clinical significance ,Prospective Studies ,Prospective cohort study ,business.industry ,Unstable angina ,Middle Aged ,medicine.disease ,Intercellular Adhesion Molecule-1 ,Iodixanol ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,business ,Complication ,medicine.drug - Abstract
OBJECTIVE To compare intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) serum levels between patients with stable (SAP) and unstable angina pectoris (USAP) undergoing coronary angiography (CAG), investigate effects of CAG on ICAM-1, VCAM-1 levels in SAP, USAP patients; probable different effects of non-ionic radiocontrast media (RCM), iso-osmotic iodixanol and low osmolar iopamidol, on these adhesion molecules (AM). METHODS In this randomized, prospective study, 2 groups consisting of patients with SAP (n=22) and USAP (n=22) undergoing CAG were included. For halves of each group iopamidol, for the other halves iodixanol were used as RCM, in turn for randomization. The patients were divided into 4 subgroups according to clinical presentations and used RCM(SAP-iodixanol, SAP-iopamidol USAP-iodixanol, USAP-iopamidol). ICAM-1, VCAM-1 levels were measured just before and 12 hours after CAG. Repeated measurements were compared with two-way ANOVA test. RESULTS Baseline VCAM-1 concentration was higher in USAP group than SAP group (p=0.001). ICAM-1, VCAM-1 concentrations increased significantly following CAG in SAP, USAP groups. ICAM-1, VCAM-1 concentration increments; didn't reach statistical significance in SAP-iodixanol subgroup, reached a borderline significance in SAP-iopamidol subgroup (p=0.06). In USAP-iodixanol subgroup; only VCAM-1 (p
- Published
- 2014
42. Throughput modeling of single hop CSMA networks with non-negligible propagation delay
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Ezhan Karasan and Mehmet Koseoglu
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Transmission delay ,Computer science ,Unfairness problem ,Packet networks ,Markov process ,Multiaccess communication ,Throughput ,Topology ,Channel capacity ,symbols.namesake ,Performance improvements ,Multiaccess Communication, Carrier Sense Multiple Access (csma) ,Computer Science::Networking and Internet Architecture ,Back-off mechanisms ,Electrical and Electronic Engineering ,Carrier sense multiple access ,Throughput modeling ,Carrier sense multiple access (CSMA) ,Wireless Networks ,business.industry ,Wireless network ,Node (networking) ,Markov processes ,Large Propagation Delay ,Propagation delay ,Carrier communication ,Multi-access communications ,Benchmarking ,symbols ,Large propagation delays ,Packet transmissions ,business ,Computer network ,Communication channel - Abstract
Cataloged from PDF version of article. We analyze the performance of the CSMA protocol under propagation delays that are comparable with packet transmission times. We propose a semi-Markov model for the 2-node CSMA channel. For the 2-node case, the capacity reduces to 40% of the zero-delay capacity when the one-way propagation delay is 10% of the packet transmission time. We then extend this model and obtain the optimum symmetric probing rate that achieves the maximum network throughput as a function of the average propagation delay, d¯, and the number of nodes sharing the channel, N. The proposed model predicts that the total capacity decreases with d¯−1 as N goes to infinity when all nodes probe the channel at the optimum rate. The optimum probing rate for each node decreases with 1/N and the total optimum probing rate decreases faster than d¯−1 as N goes to infinity. We investigate how the short-term unfairness problem in CSMA worsens as the propagation delay increases and propose a back-off mechanism to mitigate this issue. The theoretical results presented in this paper can be used as a benchmark for the performance improvements provided by algorithms that have already been developed.
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- 2013
43. Cardiovascular risk factors in young male adults: impact of physical activity and parental education
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Aysenur Atay, Gulcan Saglam, Serap Cuhadar, Mehmet Koseoglu, and Levent Çuhadar
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Gerontology ,Turkey ,Cardiovascular risk factors ,Blood lipids ,Social class ,smoking ,educational status ,chemistry.chemical_compound ,physical education and training ,medicine ,Family history ,Young adult ,medicine.diagnostic_test ,Triglyceride ,business.industry ,Research ,lcsh:Public aspects of medicine ,lcsh:RA1-1270 ,General Medicine ,lipoproteins ,chemistry ,Household income ,social class ,Lipid profile ,business ,Demography - Abstract
Background: This study was conducted to assess whether choices of physical activity, smoking status, and parental education and income were correlated with the health status of young adult males which are important for preventive health policy. Methods: 491 18-29-year old males from lower socioeconomical districts in Turkey participated in this study. Information about demographic characteristics, parental education, household income, smoking status, and physical activity was obtained by means of a standardized questionnaire. BMI and metabolic parameters (serum lipid profile) were assessed. Results: Mean total cholesterol, LDL, HDL and triglyceride levels were in the normal range. The physically active group displayed a better lipid profile. No relationship was found between parental education and serum lipids. Smoking was slightly correlated with household income (r=103, p=0.022). Conclusion: Young adult males who participate in relatively high levels of physical activity are at lower CHD risk than less active ones. The present study also showed that lower socioecnomic status does not always correlate with higher levels of cardiovascular risk factors. In conclusion, data supports that while family history cannot be changed, HDL levels can be modulated by lifestyle factors as in other populations and that with the determined benefits of increasing physical activity and thus, HDL levels, policy reform in schools to promote physical activity are warranted.
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- 2013
44. Effect of epidural anesthesia on anastomotic leakage in colonic surgery: experimental study
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Tayfun Adanir, Murat Aksun, Gulsah Yilmaz Karaoren, Turker Karabuga, Okay Nazli, Atilla Sencan, and Mehmet Koseoglu
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Anesthesia, Epidural ,Male ,Wound Healing ,Anastomosis, Surgical ,Lidocaine ,Anastomotic Leak ,Colonic Diseases ,Disease Models, Animal ,Anesthesiology and Pain Medicine ,Postoperative Complications ,Emergency Medicine ,Animals ,Surgery ,Laparoscopy ,Rabbits ,Anesthetics, Local - Abstract
The association between the infusion of continuous epidural anesthesia and the anastomotic strength of colonic anastomosis was examined in an animal model.Fourteen white male New Zealand rabbits were included in the study and randomly assigned to two groups. Group 1 (n=7) had continuous epidural 0.9% NaCl infusion (0.4 ml kg-1 bolus and 0.2 ml kg-1 h-1 infusion) and Group 2 (n=7) had continuous epidural 1% lidocaine infusion (0.4 ml kg-1 bolus and 0.2 ml kg-1 h-1 infusion). Infusions started at the beginning of the operation and were continued for six hours postoperatively. All experimental animals underwent right colon resection and colo-colonic anastomosis under general anesthesia. On the fourth postoperative day, relaparotomy was applied and the bursting pressures of the anastomosis (BPA) were measured in situ. Segments 1-cm long consisting of the complete suture lines were excised, and the levels of hydroxyproline and collagen were measured.BPAs were statistically higher in the epidural lidocaine group (median: 248 mmHg; min 117 - max 300) than in the saline group (median: 109 mmHg; min 47 - max 176) (p=0.006). There was no difference between the groups in terms of hydroxyproline and collagen levels in the sample tissues (p0.05).We concluded that the strength of colonic anastomosis may be increased by epidural lidocaine infusion.
- Published
- 2012
45. Effect of Network Density and Size on the Short-Term Fairness Performance of CSMA Systems
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Murat Alanyali, Mehmet Koseoglu, and Ezhan Karasan
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Vertex (graph theory) ,Computer Networks and Communications ,Computer science ,Acceptable limit ,Throughput regions ,Throughput ,Long range correlations ,Spectrum management ,Fairness measure ,Computer Science::Networking and Internet Architecture ,Optimal random-access ,Carrier sense multiple access ,Spectrum access ,Delay ,Degree (graph theory) ,Routers ,business.industry ,Wireless network ,Grid ,Fairness performance ,Computer Science Applications ,Efficient ,Max-min fairness ,Signal Processing ,Grid deployment ,Statistical physics ,business ,Unlicensed spectrum ,Computer network - Abstract
As the penetration of wireless networks increase, number of neighboring networks contending for the limited unlicensed spectrum band increases. This interference between neighboring networks leads to large systems of locally interacting networks. We investigate whether the short-term fairness of this system of networks degrades with the system size and density if transmitters employ random spectrum access with carrier sensing (CSMA). Our results suggest that (a) short-term fair capacity, which is the throughput region that can be achieved within the acceptable limits of short-term fairness, reduces as the number of contending neighboring networks, i.e., degree of the conflict graph, increases for random regular conflict graphs where each vertex has the same number of neighbors, (b) short-term fair capacity weakly depends on the network size for a random regular conflict graph but a stronger dependence is observed for a grid deployment. We demonstrate the implications of this study on a city-wide Wi-Fi network deployment scenario by relating the short-term fairness to the density of deployment. We also present related results from the statistical physics literature on long-range correlations in large systems and point out the relation between these results and short-term fairness of CSMA systems. © 2012 Koseoglu et al; licensee Springer.
- Published
- 2012
46. Joint Path and Resource Selection for OBS Grids with Adaptive Offset Based QoS Mechanism
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Mehmet Koseoglu and Ezhan Karasan
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- 2007
47. Serum leptin levels in rheumatoid arthritis and relationship with disease activity
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Mehmet Koseoglu, Rezzan Günaydin, Aysenur Atay, Neşe Ölmez, Taciser Kaya, and Aysel Hur
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Leptin ,Male ,medicine.medical_specialty ,Arthritis ,Enzyme-Linked Immunosorbent Assay ,Severity of Illness Index ,Body Mass Index ,Arthritis, Rheumatoid ,Internal medicine ,Immunopathology ,Medicine ,Humans ,Autoimmune disease ,Immunoradiometric assay ,medicine.diagnostic_test ,business.industry ,Tumor Necrosis Factor-alpha ,General Medicine ,Middle Aged ,medicine.disease ,Endocrinology ,Rheumatoid arthritis ,Erythrocyte sedimentation rate ,Disease Progression ,Female ,Immunoradiometric Assay ,business ,Body mass index - Abstract
OBJECTIVES This study was performed to evaluate serum leptin levels in rheumatoid arthritis (RA) patients and investigate the correlation with serum tumor necrosis factor alpha (TNF-alpha) levels and clinical and laboratory parameters of disease activity. METHODS Fifty patients with RA and 34 control subjects were included. Disease activity score 28 (DAS28) was calculated for each patient. Laboratory activity was assessed by examining erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Immunoradiometric assay was used for measuring serum leptin levels (ng/mL). Serum TNF-alpha levels (pg/mL) were measured by sandwich enzyme-linked immunosorbent assay method in 41 of 50 RA patients and in 24 control subjects. RESULTS Age, sex and body mass index (BMI) did not show a statistically significant difference between RA and control subjects (P > 0.05). Serum leptin levels were higher in RA (P = 0.000). In RA patients, there were no correlations between serum leptin levels and disease duration, swollen and tender joint counts, DAS28, CRP, ESR, serum TNF-alpha levels, oral glucocorticoid and methotrexate usage (P > 0.05). There was no statistically significant serum leptin level difference between patients with high disease activity and mild and low disease activity (P = 0.892). Serum leptin levels positively correlated with BMI in both patient and control groups (P < 0.05). In both groups, mean serum leptin levels were higher in women than men. CONCLUSIONS Even though serum leptin levels were found to be significantly higher in RA patients than in control subjects in this study, there was no correlation between serum leptin levels and TNF-alpha levels, clinical and laboratory parameters of disease activity. However serum leptin levels positively correlated with BMI in both patient and control groups. In RA, circulating leptin levels do not seem to reflect disease activity.
- Published
- 2006
48. The effect of storage time and freeze-thaw cycles on the stability of serum samples
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Serap Cuhadar, Mehmet Koseoglu, Aysenur Atay, Ahmet Dirican, Serap Cuhadar, Mehmet Koseoglu, Aysenur Atay, and Ahmet Dirican
- Abstract
Introduction: Optimal storage of serum specimens in central laboratories for a long period for multicenter reference interval studies, or epidemiologic studies remains to be determined. We aimed to examine the analytical stability of chemistry analytes following numerous freeze-thaw and long term storage. Materials and methods: Serum samples were obtained from 15 patients. Following baseline measurement, sera of each subject were aliquoted and stored at -20 ˚C for two experiments. A group of sera were kept frozen for up to 1, 2 and 3 months and then analyzed for stability. The other experiment consisted of one to ten times of freeze and thaw cycles. Total of 17 chemistry analytes were assayed at each time point. The results were compared with those obtained from the initial analysis of fresh samples. Median or mean changes from baseline (T0) concentrations were evaluated both statistically and clinically according to the desirable bias. Results: Of the analytes studied, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), gamma-glutamyl transferase (GGT), direct bilirubin, glucose, creatinine, cholesterol, triglycerides, high density lipoprotein (HDL) were stable in all conditions. Blood urea nitrogen (BUN), uric acid, total protein, albumin, total bilirubin, calcium, lactate dehydrogenase (LD) were changed significantly (P < 0.005). Conclusions: As a result, common clinical chemistry analytes, with considering the variability of unstable analytes, showed adequote stability after 3 months of storage in sera at -20 °C, or up to ten times of freeze-thaw cycle. All the same, such analysis can only be performed for exceptional cases, and this should be taken into account while planning studies.
- Published
- 2013
49. Stability studies of common biochemical analytes in serum separator tubes with or without gel barrier subjected to various storage conditions
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Serap Cuhadar, Ayşenur Atay, Mehmet Koseoglu, Ahmet Dirican, Aysel Hur, Serap Cuhadar, Ayşenur Atay, Mehmet Koseoglu, Ahmet Dirican, and Aysel Hur
- Abstract
Introduction: The collected and shipped blood samples are exposed to a various extra-analytical factors prior to analysis. The aim of the study was to determine the stability of analytes in serum gel tubes and plain tubes exposed to a range of storage temperatures and times after centrifugation. Materials and methods: Fifteen healthy volunteers were recruited and venous blood was collected into four tubes, two with and two without gel separator. Analyzing the baseline samples in 30 min, all were stored at 4ºC or 24ºC for 6, 12, 18, 24, 30, 36, 48 and 72 hours and 1 week. Sixteen biochemi-cal anaytes were measured on each sample. Variations remained under the desirable bias conside-red as clinically insignificant. Results: On day three, most analytes remained stable including albumin, protein, creatinine, choles-terol, triglycerides, gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine aminot-ransferase (ALT), creatine kinase (CK), lactate dehydrogenase (LD) regardless of tube types. Gluco-se concentration decreased markedly (P = 0.001) beginning from the first hours of storage in plain serum. The stability maximized for the analytes including glucose, total bilirubin, urea nitrogen (BUN), uric acid stored at 4 ºC in gel tubes. Aspartate aminotransferase (AST) activity increased significantly (P = 0.002) up to 48-h, however bias was not significant clinically. High density lipoprotein (HDL) con-centration was stable in gel tubes at 24 ºC, in plain tubes at 4 ºC stored up to 36-h. Conclusion: Serum gel or non-gel tubes might be used interchangeably for 11 analytes chilled or at 24 ºC, whereas some restrictions must be applied for glucose, AST, BUN, HDL, and uric acid.
- Published
- 2012
50. Effects of hemolysis interference on routine biochemistry parameters
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Mehmet Koseoglu, Aysel Hur, Aysenur Atay, Serap Cuhadar, Mehmet Koseoglu, Aysel Hur, Aysenur Atay, and Serap Cuhadar
- Abstract
Introduction: Hemolysis is still the most common reason for rejecting samples, while reobtaining a new sample is an important problem. The aim of this study was to investigate the effects of hemolysis in different hemolysis levels for mostly used biochemical parameters to prevent unnecessary rejecti-ons. Materials and methods: Sixteen healthy volunteers were enrolled in the study. Four hemolysis levels were constituted according to hemoglobin concentrations and they were divided into five groups: Gro-up I: 0-0.10 g/L, Group II: 0.10-0.50 g/L, Group III: 0.51-1.00 g/L, Group IV: 1.01-2.50 g/L, Group V: 2.51-4.50 g/L. Lysis was achieved by mechanical trauma. Results: Hemolysis interference affected lactate dehydrogenase (LD) and aspartate aminotransfera-se (AST) almost at undetectable hemolysis by visual inspection (plasma hemoglobin < 0.5 g/L). Clinically meaningful variations of potassium and total bilirubin were observed in moderately hemolyzed samples (hemoglobin > 1 g/L). Alanine aminotransferase (ALT), cholesterol, gamma glutamyltransferase (GGT), and inorganic phosphate (P) concentrations were not interfered up to severely hemolyzed levels (hemoglobin: 2.5-4.5 g/L). Albumin, alkaline phosphatase (ALP), amylase, chloride, HDL-cholesterol, creatine kinase (CK), glucose, magnesium, total protein, triglycerides, un-saturated iron binding capacity (UIBC) and uric acid differences were statistically significant, but re-mained within the CLIA limits. Conclusion: To avoid preanalytical visual inspection for hemolysis detection, improper sample rejec-tion, and/or rerun because of hemolysis, it is recommended in this study that, routine determination of plasma or serum free hemoglobin concentrations is important. For the analytes interfered with hemolysis, new samples have to be requested.
- Published
- 2011
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