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Search Results: 1 - 10 of 149745 matches for " Obay H. Sabrie "
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Fast Handoff for 802.11 Wireless Network  [PDF]
Obay H. Sabrie, Hasan S. Hasan, Rosli Salleh
Communications and Network (CN) , 2011, DOI: 10.4236/cn.2011.34029
Abstract: Whenever the mobile station moves from the range of one access point and comes to the range of another access point a handoff process is occurred. This process takes a long time when using the IEEE 802.11 standard handoff and this delay affect the real time and multimedia applications. This paper provides a layer 2 handoff process for the IEEE 802.11 that is able to eliminate the scanning delay and reduce the total handoff delay.
Enhancing Handoff Process using IAPP with Caching Techniques
Obay H. Sabrie,Rosli Salleh
Journal of Applied Sciences , 2009,
Abstract: This study propose a layer 2 method to enhance the handoff process through eliminating the scanning delay and reduce the time taken to perform a handoff by using Inter Access Point Protocol (IAPP) neighbor’s discovery with access point and station caching techniques, in order to build a List of Neighbors and provide the station with the next possible AP to authenticate directly.
Iloprost, a prostacyclin (PGI2) analogue, reduces liver injury in hepatic ischemiareperfusion in rats
Gedik, Ercan;Girgin, Sadullah;Obay, Basra Deniz;Ozturk, Hayrettin;Ozturk, Hulya;Buyukbayram, Huseyin;
Acta Cirurgica Brasileira , 2009, DOI: 10.1590/S0102-86502009000300012
Abstract: purpose: to evaluate the effects of iloprost a prostacyclin analogue on the hepatic ir injury in rats. methods: forty male sprague-dawley rats (250-300 g) were divided into four groups each containing 10 rats;(1)- controls: data from unmanipulated animals; (2) sham group: rats subjected to the surgical procedure, except for liver i/r, and given saline; (3) i/r group: rats that underwent liver ischemia for 45 min followed by reperfusion for 45 min; (4) ir/ iloprost group: rats pretreated with iloprost (10 μg kg-1, i.v). liver tissues were taken to determine sod, cat, gsh, and mda levels and for biochemical and histological evaluation. results: the plasma alt and ast levels were increased in group 3 than in group 4. mda values and the liver injury score decreased, while the sod, cat, and gsh values increased in group 4 compared to group 3. in group 3, hepatocytes were swollen with marked vacuolization. in group 4, there were regular sinusoidal structures with normal morphology without any signs of congestion. conclusion: we demonstrated hepatoprotective effects of iloprost against severe ischemia and reperfusion injury in rat liver.
The Changes in Status of Antioxidant Defence System on Temporary Cerebral Ischemia and the Protective Effect of Vitamin E and C
Basra Obay Deniz,Abdurrahman ?ermet,Cemil Tümer,Yüksel Ko?yi?it
Dicle Medical Journal , 2004,
Abstract: Time-dependent changes in antioxidant defence system and the effect ofvitamin C and E supplementation on temporary cerebral ischemia wasinvestigated in this study. This study was performed in 140 male Wistaralbino rats weighting 300-400g. Before 30 minutes cerebral ischemiavitamin E (α-tocopherol) 10 mg/kg/day and vitamin C 30 mg/kg/day wereapplied intraperitoneally for a week period. Animals were sacrifiedfollowing 24 h and 72 h ischemia and the brain was removed as quick aspossible. Brain water content, süperoxide dismutase (SOD) ) and catalase(CAT) activities and the level of nonenzymatic antioxidant, reduced vitaminC and α-tocopherol levels were measured. Moreover the level ofmalondialdehyde (MDA) as an indicator of lipid peroxidation wasdetermined. At 24 h of reperfusion superoxide dismutase (SOD) andcatalase (CAT) activities, vitamin C and E level decreased significantly inischemic brain area (p<0.05, p<0.05, p<0.01 and p<0.01 respectively). After72 h of reperfusion SOD and CAT activities surpassed the pre-ischemiclevel (p<0.01 and p<0.05 respectively). The level of vitamin C and Eincreased significantly at 72 hours after ischemia but, did not reach preischemiclevels (p<0.01 and p<0.01 respectively). Administration of vitaminC and E a week before cerebral ischemia prevented the decrease in SODand CAT activities after 24 hours of reperfusion (p<0.01 and p<0.01respectively). Furthermore, the increase in ischemia induced lipidperoxidation and cerebral edema were decreased significantly byadministration of these vitamins (p<0.01 and p<0.01 respectively). Invitamins applied groups, increase in SOD and catalase activities at 72 hoursafter ischemia was similar to control. The results indicated that there isnegative correlation between vitamin C or E level and lipid peroxidation orcerebral edema. Similar relationship was found between SOD or CATactivitiy and lipid peroxidation or cerebral edama.Temporary cerebral ischemia changed the state of anti-oxidant defencesystem and these changes were significantly prevented by treatment with Cand E vitamins before ischemia.
Resveratrol attenuates oxidative stress and histological alterations induced by liver ischemia/reperfusion in rats
Ercan Gedik, Sadullah Girgin, Hayrettin Ozturk, Basra Deniz Obay, Hulya Ozturk, Huseyin Buyukbayram
World Journal of Gastroenterology , 2008,
Abstract: AIM: To investigate the effects of resveratrol on liver ischemia/reperfusion (I/R) injury in rats.METHODS: A total of 40 male Sprague-Dawley rats weighing 240-290 g were randomized into four groups of ten: (1) controls: data from unmanipulated animals; (2) sham group: rats subjected to the surgical procedure, except for liver I/R, and given saline; (3) I/R group: rats underwent liver ischemia for 45 min followed by reperfusion for 45 min; (4) I-R/Resveratrol group: rats pretreated with resveratrol (10 μmol/L, iv). Liver tissues were obtained to determine antioxidant enzyme levels and for biochemical and histological evaluation.RESULTS: Plasma aminotransferase activities were higher in the I/R group than in the I-R/Resveratrol group. Malondialdehyde levels and the hepatic injury score decreased, while superoxide dismutase, catalase, and glutathione peroxidase levels increased in group 4 compared to group 3. In group 4, histopathological changes were significantly attenuated in resveratrol-treated livers.CONCLUSION: These results suggest that resveratrol has protective effects against hepatic I/R injury, and is a potential therapeutic drug for ischemia reperfusion-related liver injury.
Euler-Lagrange Elasticity: Differential Equations for Elasticity without Stress or Strain  [PDF]
H. H. Hardy
Journal of Applied Mathematics and Physics (JAMP) , 2013, DOI: 10.4236/jamp.2013.17004

Differential equations to describe elasticity are derived without the use of stress or strain. The points within the body are the independent parameters instead of strain and surface forces replace stress tensors. These differential equations are a continuous analytical model that can then be solved using any of the standard techniques of differential equations. Although the equations do not require the definition stress or strain, these quantities can be calculated as dependent parameters. This approach to elasticity is simple, which avoids the need for multiple definitions of stress and strain, and provides a simple experimental procedure to find scalar representations of material properties in terms of the energy of deformation. The derived differential equations describe both infinitesimal and finite deformations.

Euler-Lagrange Elasticity with Dynamics  [PDF]
H. H. Hardy
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.213138
Abstract: The equations of Euler-Lagrange elasticity describe elastic deformations without reference to stress or strain. These equations as previously published are applicable only to quasi-static deformations. This paper extends these equations to include time dependent deformations. To accomplish this, an appropriate Lagrangian is defined and an extrema of the integral of this Lagrangian over the original material volume and time is found. The result is a set of Euler equations for the dynamics of elastic materials without stress or strain, which are appropriate for both finite and infinitesimal deformations of both isotropic and anisotropic materials. Finally, the resulting equations are shown to be no more than Newton's Laws applied to each infinitesimal volume of the material.
Linear Algebra Provides a Basis for Elasticity without Stress or Strain  [PDF]
H. H. Hardy
Soft (Soft) , 2015, DOI: 10.4236/soft.2015.43003
Abstract: Linear algebra provides insights into the description of elasticity without stress or strain. Classical descriptions of elasticity usually begin with defining stress and strain and the constitutive equations of the material that relate these to each other. Elasticity without stress or strain begins with the positions of the points and the energy of deformation. The energy of deformation as a function of the positions of the points within the material provides the material properties for the model. A discrete or continuous model of the deformation can be constructed by minimizing the total energy of deformation. As presented, this approach is limited to hyper-elastic materials, but is appropriate for infinitesimal and finite deformations, isotropic and anisotropic materials, as well as quasi-static and dynamic responses.
Spectral resolution in hyperbolic orbifolds, quantum chaos, and cosmology
H. Then
Physics , 2007,
Abstract: We present a few subjects from physics that have one in common: the spectral resolution of the Laplacian.
Arithmetic quantum chaos of Maass waveforms
H. Then
Mathematics , 2003,
Abstract: We compute numerically eigenvalues and eigenfunctions of the quantum Hamiltonian that describes the quantum mechanics of a point particle moving freely in a particular three-dimensional hyperbolic space of finite volume and investigate the distribution of the eigenvalues.
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