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Search Results: 1 - 10 of 3508 matches for " Mehmet Tekinalp "
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P-wave Dispersion for Predicting Paroxysmal Atrial Fibrillation in Acute Ischemic Stroke
Umuttan Dogan, Ebru Apaydin Dogan, Mehmet Tekinalp, Osman Serhat Tokgoz, Alpay Aribas, Hakan Akilli, Kurtulus Ozdemir, Hasan Gok, Betigul Yuruten
International Journal of Medical Sciences , 2012,
Abstract: Background: Detection of paroxysmal atrial fibrillation (PAF) in acute ischemic stroke patients poses diagnostic challenge. The aim of this study was to predict the presence of PAF by means of 12-lead ECG in patients with acute ischemic stroke. Our hypothesis was that P-wave dispersion (Pd) might be a useful marker in predicting PAF in patients with acute ischemic stroke. Methods: 12-lead resting ECGs, 24-hour Holter recordings and echocardiograms of 400 patients were analyzed retrospectively. PAF was detected in 40 patients on 24-hour Holter monitoring. Forty out of 360 age and gender matched patients without PAF were randomly chosen and assigned as the control group. Demographics, P-wave characteristics and echocardiographic findings of the patients with and without PAF were compared. Results: Maximum P-wave duration (p=0.002), Pd (p<0.001) and left atrium diameter (p=0.04) were significantly higher in patients with PAF when compared to patients without PAF. However, in binary logistic regression analysis Pd was the only independent predictor of PAF. The cut-off value of Pd for the detection of PAF was 57.5 milliseconds (msc). Area under the curve was 0.80 (p<0.001). On a single 12-lead ECG, a value higher than 57.5 msc predicted the presence of PAF with a sensitivity of 80% and a specificity of 73%. Conclusion: Pd on a single 12-lead ECG obtained within 24 hours of an acute ischemic stroke might help to predict PAF and reduce the risk of recurrent strokes.
Broadbent’s Cognitive Approach and Its Effect on Motor Performance in Sports  [PDF]
Mehmet Koyuncu
Psychology (PSYCH) , 2011, DOI: 10.4236/psych.2011.25073
Abstract: This study aimed to test Broadbent’s attentional filtering theory in the perceptual motor task of dart throwing. Dart board size was manipulated in order to reduce the amount of information to be filtered in the participants’ field of view. Sample consisted of 122 college students (63 males and 59 females) ranging in age from 17 to 36. Participants’ task was to throw 18 darts at the center of targets 45 cm, 30 cm and 15 cm in diameter. Performance was measured as radial distance from the bulls-eye of each dart. One way ANOVA, Repeated Measure of ANOVA was used in the analysis of the obtained data. The results of our study showed that dart throwing performance gave better results in cases where target’s field of view was reduced, compared to the ones in which target’s field of view was increased. Consistent with Broadbent’s central claim, results showed that fewer stimuli in the field of view required less processing, thus, better performance. Also, those subjects that were exercising regularly did better than the ones that were not exercising. This study provides evidence that reducing target’s field of view in dart throwing increases the chances to obtain better results.
A Survey on Geometric Dynamics of 4-Walker Manifold  [PDF]
Mehmet Tekkoyun
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.211163
Abstract: A Walker n-manifold is a semi-Riemannian n-manifold, which admits a field of parallel null r-planes, with r ≤ 2/n . It is well-known that semi-Riemannian geometry has an important tool to describe spacetime events. Therefore, solutions of some structures about 4-Walker manifold can be used to explain spacetime singularities. Then, here we present complex and paracomplex analogues of Lagrangian and Hamiltonian mechanical systems on 4-Walker manifold. Finally, the geometrical-physical results related to complex (paracomplex) mechanical systems are also discussed.
Embryo and Protoplast Isolation from Barlia robertiana Seeds (Orchidaceae)  [PDF]
Mehmet Aybeke
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.46A001

In the present study, it is aimed to investigate embryo and protoplast isolation from orchid seeds, because of know-how deficiency. As material Barlia robertiana seeds were subjected enzymatic process. Globular embryos with suspensor were fully removed by enzymatic maceration for between 100-180 min of incubation. The highest obtained embryo yields were found in Rapidase EX Color and Rapidase Vino Super, with degree of 89.2-90.3 × 103·g-1 MF and 86.4-91.3 × 103·g-1 MF, respec

Quantitative Phase Analysis Based on Rietveld Structure Refinement for Carbonate Rocks  [PDF]
Mehmet Tamer
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.48154

QPA (Quantitative Phase Analysis) of carbonate rocks bearing calcite and dolomite using X-ray diffractometry (XRD) can be performed using the combined Rietveld Structure Refinement (RSR) and semiquantitative Reference Intensity Ratio (RIR) methods, providing an estimation of crystalline phase in a mixture. Different ratios of five samples were prepared by mixing these crystal minerals with high sensitively. The scan speeds, adequate to determine mineral phases in rock samples, were used as 6 degrees per minute with 0.08 steps. The XRD analysis with commercial TOPAS 3.0 program, defined by a new generation of profile and structure analysis software, based on RSR provides Bragg reflection profiles and the dimension of the unit cell of a phase. The weight fractions of each phase were found by Le Bail and Pawley methods in RSR using a pseudo-Voigt peak shape model. The samples were also characterized by using X-ray fluorescence (XRF) and atomic absorption spectrometer (AAS). These analyses were conducted to compare these results with those obtained from the RSR. In addition to these, RSR of phases is very important to improve the goodness of fit (GOF). Therefore, the discussions of refinement of the carbonate mixing were made and a refinement procedure was given for these mixing in detail. Taking advantage of the RSR with the addition of an internal standard, the phase fraction of all the crystalline phases as well as the amorphous component, has been accurately determined. RSR technique offers a valid support for the characterization of marble in the light of industrial products.

Optimisation of Effective Design Parameters for an Automotive Transmission Gearbox to Reduce Tooth Bending Stress  [PDF]
Mehmet Bozca
Modern Mechanical Engineering (MME) , 2017, DOI: 10.4236/mme.2017.72004
Abstract: Optimisation of effective design parameters to reduce tooth bending stress for an automotive transmission gearbox is presented. A systematic investigation of effective design parameters for optimum design of a five-speed gearbox is studied. For this aim contact ratio effect on tooth bending stress by the changing of contact ratio with respect to pressure angle is analysed. Additionally, profile modification effects on tooth bending stress are presented. During the optimisation, the tooth bending stress is considered as the objective function, and all the geometric design parameters such as module, teeth number etc. are optimised under two different constraints, including tooth contact stress and constant gear centre distance. It can be concluded that higher the contact ratio results in a reduced tooth bending stress, while higher the pressure angle caused an increase in tooth bending stress and contact stress, since decreases in the contact ratio. In addition, application of positive profile modification on tooth reduces tooth bending stress. All of the obtained optimum solutions satisfy all constraints.
Helix Angle Effect on the Helical Gear Load Carrying Capacity  [PDF]
Mehmet Bozca
World Journal of Engineering and Technology (WJET) , 2018, DOI: 10.4236/wjet.2018.64055
Abstract: The aim of this study is to investigate the helix angle effect on the helical gear load carrying capacity, including the bending and contact load carrying capacity. During the simulation, the transverse contact ratio is calculated with respect to the constant pressure angle. By changing the helix angle, both the overlap contact ratio and total contact ratio are calculated and simulated. The bending stress and contact stress of a helical gear are calculated and simulated with respect to the helix angle. Solid (CAD) modelling of a pinion gear was obtained using SOLIDWORKS software. The analytically obtained results and finite elements method results are compared. It is observed that increasing the helix angle causes an increase of the contact ratio of the helical gear. Furthermore, increasing the contact ratio reduces the bending stress and contact stress of the helical gear. However, with a constant transverse contact ratio, it is possible to improve the total contact ratio depending on the helix angle. It is concluded that a higher helix angle increases the helical gear bending and contact load carrying capacity.
Properties of Apricot Kernel and Oils as Fruit Juice Processing Waste  [PDF]
Mehmet Musa ?zcan
Food and Nutrition Sciences (FNS) , 2010, DOI: 10.4236/fns.2010.12006
Abstract: Recently, more attention has been focused on the utilization of food processing by products and wastes, as well as under-utilization agricultural products. Some physical and chemical properties, mineral contents and fatty acid composition of apricot kernel and oils were determined. The oil yields from kernels changed from 42.2% to 57.2%. The crude fibre contents ranged between 4.06% and 7.63%. In addition, crude protein contents ranged between 15.1% and 24.2%. While the peroxide values of kernel oils change between 0.834 meq/Kg and 8.294 meq/Kg, acidity values ranged between 0.279% and 0.700%. The main fatty acids in apricot kernel oils were oleic, linoleic and palmitic acids. Oleic acid contents of kernel oils varied between 53.06% and 70.90%. On the other hand, linoleic acid contents ranged between 21.43% and 35,67%. As a result, the present study showed the apricot kernels of the researched species of apricot kernels from Turkey are a potential source of valuable oil which might be used for edible and other industrial applications.
Effect of Low Velocity Impact Damage on Buckling Properties  [PDF]
Ahmet YAPICI, Mehmet METIN
Engineering (ENG) , 2009, DOI: 10.4236/eng.2009.13019
Abstract: The work described herein consists of experimental measurement of the post-impact buckling loads of E- glass/epoxy laminates. Composite samples with stacking sequence of [+45/?45/90/0]2s were subjected to low-velocity impact loading at energy levels of 36, 56.13, 79.95, 110.31 and 144 J. The impact tests were conducted with a specially developed vertical drop weight testing machine. Impact parameters like peak load, absorbed energy, deflection at peak load and damage area were evaluated and compared. Damaged specimens were subjected to compressive axial forces and buckling loads of the specimens were obtained. The relation between energy levels and buckling loads is investigated.
Electronically Tunable Minimum Component Biquadratic Filters for Interface Circuits  [PDF]
Mehmet Sa?ba?
Circuits and Systems (CS) , 2011, DOI: 10.4236/cs.2011.23033
Abstract: In this paper, two new electronically tunable filter configurations are proposed. The proposed filters operate current-mode (CM), voltage-mode (VM), transimpedance-mode (TIM) and transadmittance-mode (TAM). The first configuration realizes second-order VM band-pass and TAM high-pass filter characteristics from the same configuration. The second one realizes second-order TIM band-pass and CM low-pass filter characteristics from the same configuration. They also use minimum number of electronic components (two capacitors and one active component namely; current controlled current difference transconductance amplifier). The workability of the proposed structures has been demonstrated by simulation results.
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