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Search Results: 1 - 10 of 549103 matches for " A. F. Ozer "
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A Novel Approach to the Surgical Treatment of Lumbar Disc Herniations: Indications of Simple Discectomy and Posterior Transpedicular Dynamic Stabilization Based on Carragee Classification
A. F. Ozer,F. Keskin,T. Oktenoglu,T. Suzer,Y. Ataker,C. Gomleksiz,M. Sasani
Advances in Orthopedics , 2013, DOI: 10.1155/2013/270565
Abstract: Surgery of lumbar disc herniation is still a problem since Mixter and Barr. Main trouble is dissatisfaction after the operation. Today there is a debate on surgical or conservative treatment despite spending great effort to provide patients with satisfaction. The main problem is segmental instability, and the minimally invasive approach via microscope or endoscope is not necessarily appropriate solution for all cases. Microsurgery or endoscopy would be appropriate for the treatment of Carragee type I and type III herniations. On the other hand in Carragee type II and type IV herniations that are prone to develop recurrent disc herniation and segmental instability, the minimal invasive techniques might be insufficient to achieve satisfactory results. The posterior transpedicular dynamic stabilization method might be a good solution to prevent or diminish the recurrent disc herniation and development of segmental instability. In this study we present our experience in the surgical treatment of disc herniations. 1. Introduction The surgical treatment of lumbar disc herniation is performed when the conservative treatment is recalcitrant and only ten percent of all lumbar disc herniations cases are candidates to surgery [1]. The main problem with the surgery is that the lumbar pain of the patients does not necessarily relieved following surgery and even they might become worse. For this reason, there are serious anxiety and suspicion against the surgical treatment of lumbar disc herniations. This phenomenon is also valid for some spine surgeons who will perform the operation. Even on their own series of Mixter and Barr, who first performed the discectomy of lumbar disc herniations, the success and failure rates compete head to head [2]. Later Caspar and Yasargil introduced the microscope into the disc surgery and allowed minimal anatomic damage; however, no significant rise was achieved in satisfactory results [3, 4]. Carragee et al. revealed that the occurrence of disc herniation, the type of surgery, and the rates of reherniation are in a close relation with the defect on posterior annulus [5]. Lumbar disc herniation is not a separate illness but a part of a degenerative process, so the treatment should be designed in this manner. It is known that if the defect on the annulus is small, annulus has capacity to repair itself after fragmentectomy with both operative techniques: endoscopy and microdiscectomy. On the other hand, if the defect is large, problem arises at that time [6, 7]. In this paper, we discussed our results in the light of literature. We
Biomechanics of Posterior Dynamic Stabilization Systems
D. U. Erbulut,I. Zafarparandeh,A. F. Ozer,V. K. Goel
Advances in Orthopedics , 2013, DOI: 10.1155/2013/451956
Biomechanics of Posterior Dynamic Stabilization Systems
D. U. Erbulut,I. Zafarparandeh,A. F. Ozer,V. K. Goel
Advances in Orthopedics , 2013, DOI: 10.1155/2013/451956
Abstract: Spinal rigid instrumentations have been used to fuse and stabilize spinal segments as a surgical treatment for various spinal disorders to date. This technology provides immediate stability after surgery until the natural fusion mass develops. At present, rigid fixation is the current gold standard in surgical treatment of chronic back pain spinal disorders. However, such systems have several drawbacks such as higher mechanical stress on the adjacent segment, leading to long-term degenerative changes and hypermobility that often necessitate additional fusion surgery. Dynamic stabilization systems have been suggested to address adjacent segment degeneration, which is considered to be a fusion-associated phenomenon. Dynamic stabilization systems are designed to preserve segmental stability, to keep the treated segment mobile, and to reduce or eliminate degenerative effects on adjacent segments. This paper aimed to describe the biomechanical aspect of dynamic stabilization systems as an alternative treatment to fusion for certain patients. 1. Introduction Lower back pain is one of the major health problems around the world. One of the leading causes of lower back pain is considered to be degeneration of intervertebral disc. Disc herniation, spondylolisthesis, spondylosis, and spinal stenosis may follow intervertebral disc degeneration. Back pain occurs when posterior disc bulges out and impinges the nerve roots due to herniated disc. Another nerve root impingement may be seen in the condition of spinal stenosis, which is a reduction of the diameter of the spinal canal. The treatment options of lower back pain may vary depending on the severity of the case. They include conservative treatment or surgical techniques. Conservative treatments include exercise, medications, physiotherapy, and rehabilitation. Surgical treatment is considered for the patients when the back pain limits their daily activities and when the condition does not respond to other therapies. Surgical methods include decompression with spinal fusion or nonfusion devices. Spinal fusion supported by rigid instrumentation is widely used in the treatment of various spinal disorders. Since the procedure was first introduced by Albee and Hibbs in 1911, fusion has played an important role in the lumbar spine employed operations. The ideal result in performing fusion is to gain the necessary therapeutic goals with the minimal disruption of normal structure and function of the spinal column [1, 2]. However, usage of the rigid instrumentation results in a considerable amount of morbidity and of
Neurovascular branching in the tarsal tunnel
Bilge O,Ozer MA,Govsa F
Neuroanatomy , 2003,
Abstract: The diagnosis and therapy of the tarsal tunnel syndrome, various surgical procedures at tarsal region and especially tibial nerve blocks requires a well understanded relationship and anatomy of the tibial nerve. For this purpose medial tarsal regions of 50 feet of embalmed human cadavers were investigated. The bifurcation level of the tibial nerve, the distance of the medial and lateral plantar nerves to the tip of the medial malleolus and the medial tubercle of calcaneus and the diameters of the nerves at the branching point were measured. The bifurcation point of the posterior tibial artery was also noted. We classified the bifurcations of the tibial nerve and posterior tibial artery as type I, II and III respect to the reference line between medial malleolus and calcaneus. While type I was the common type for tibial nerve (n=42, 84%), type III was common for posterior tibial artery (n=23, 46%). Knowledge of the variations in locations of bifurcation level of the tibial nerve and the posterior tibial artery may prevent to damage any neurovascular structure during some procedures like pin insertion and nerve blocks.
Land Cover Dynamics (1990-2002) in Binh Thuan Province, Southern Central Vietnam
Hountondji YC,De Longueville F,Ozer P
International Journal of Asian Social Science , 2012,
Abstract: This paper describes the use of satellite imageries and GIS data for identifying key environmental characteristics of Binh Thuan Province in south central Vietnam and for detecting the major changes patterns within this region. Landsat TM (1990) and Landsat ETM+ (2002) imageries were used to classify the study area into seven land use and land cover (LULC) classes. A post-classification comparison analysis was used to quantify and illustrate the various LULC conversions that took place over the 12-year span of time. Results showed that a steady growth in population has caused extensive changes of land cover throughout the area. The maps also indicate that the loss of woody land (forest) and the extension of wetlands (irrigated area), combined with built-up encroachment, remains one of the most serious environmental problems facing the Binh Thuan Province today. The post-classification change detection analysis showed that critical habitats accounted for nearly 38.5% of the intensive study area between 1990 and 2002 while 61.5% remained stable. Results also showed over the 12-year span, approximately 1151.2 km2 (115.120 ha) forest were converted respectively to brush, irrigated area (wetlands), cropland and built-up. This is an overall average decrease of 9594 hectares of forested area per year. Throughout the study area, districts most affected by forest conversion to another land cover are: Bac Bihn (2798 ha/year), Than Linh (2717 ha/year), Ham Thuan Nam (1601 ha/year) and Ham Thuan Bac (1524 ha/year). Based on the identified causes of these changes, we made policy recommendations for better management of land use and land cover.
Modeling an elastic beam with piezoelectric patches by including magnetic effects
A. O. Ozer,K. A. Morris
Physics , 2014, DOI: 10.1109/ACC.2014.6858862
Abstract: Models for piezoelectric beams using Euler-Bernoulli small displacement theory predict the dynamics of slender beams at the low frequency accurately but are insufficient for beams vibrating at high frequencies or beams with low length-to-width aspect ratios. A more thorough model that includes the effects of rotational inertia and shear strain, Mindlin-Timoshenko small displacement theory, is needed to predict the dynamics more accurately for these cases. Moreover, existing models ignore the magnetic effects since the magnetic effects are relatively small. However, it was shown recently \cite{O-M1} that these effects can substantially change the controllability and stabilizability properties of even a single piezoelectric beam. In this paper, we use a variational approach to derive models that include magnetic effects for an elastic beam with two piezoelectric patches actuated by different voltage sources. Both Euler-Bernoulli and Mindlin-Timoshenko small displacement theories are considered. Due to the magnetic effects, the equations are quite different from the standard equations.
Modeling and stabilizability of voltage-actuated piezoelectric beams with magnetic effects
K. A. Morris,A. O. Ozer
Mathematics , 2013, DOI: 10.1137/130918319
Abstract: Models for piezoelectric beams and structures with piezoelectric patches generally ignore magnetic effects. This is because the magnetic energy has a relatively small effect on the overall dynamics. Piezoelectric beam models are known to be exactly observable, and can be exponentially stabilized in the energy space by using a mechanical feedback controller. In this paper, a variational approach is used to derive a model for a piezoelectric beam that includes magnetic effects. It is proven that the partial differential equation model is well-posed. Magnetic effects have a strong effect on the stabilizability of the control system. For almost all system parameters the piezoelectric beam can be strongly stabilized, but is not exponentially stabilizable in the energy space. Strong stabilization is achieved using only electrical feedback. Furthermore, using the same electrical feedback, an exponentially stable closed-loop system can be obtained for a set of system parameters of zero Lebesgue measure. These results are compared to those of a beam without magnetic effects.
Output Control of Smart Beams under Uncertain Dynamic Loads through Non-Collocated Sensors and Actuators
M. A. Pinsky,A. O. Ozer
Mathematics , 2014,
Abstract: A problem of vibration control of smart beams was addressed in various publications which primarily utilize collocated sensors and actuators and neglect the effect of measurement noise in the observer design. This paper develops a natural design of an output controller which utilizes an eigenfunction approximation of initial continuous model, eliminates control spillover, and consequently leads to an efficient controller which marginalizes effect of bounded system and measurement disturbances while reducing beam vibrations. It is demonstrated that this control approach can be attained by a non-collocated actuator and a point-sensor of velocity located nearly anywhere on the beam. We show in simulations that the proposed methodology leads to an efficient reduction of beam vibrations enforced by unknown bounded disturbances.
Electroweak Theory and Noncommutative Geometry
A. Catal-Ozer,T. Dereli
Physics , 2001, DOI: 10.1088/0264-9381/18/16/315
Abstract: The noncommutative generalisation of the standard electroweak model due to Balakrishna, Gursey and Wali is formulated in terms of the derivations Der_2(M_3) of a three dimensional representation of the su(2) Lie algebra of weak isospin. A light Higgs boson of mass about 130 GeV, together with four very heavy scalar bosons are predicted.
Exact boundary controllability results for a multilayer Rao-Nakra sandwich beam
A. Ozkan Ozer,Scott W. Hansen
Mathematics , 2014, DOI: 10.1137/120892994
Abstract: We study the boundary controllability problem for a multilayer Rao-Nakra sandwich beam. This beam model consists of a Rayleigh beam coupled with a number of wave equations. We consider all combinations of clamped and hinged boundary conditions with the control applied to either the moment or the rotation angle at an end of the beam. We prove that exact controllability holds provided the damping parameter is sufficiently small. In the undamped case, exact controllability holds without any restriction on the parameters in the system. In each case, optimal control time is obtained in the space of optimal regularity for $L^2(0,T)$ controls. A key step in the proof of our main result is the proof of uniqueness of the zero solution of the eigensystem with the homogeneous boundary conditions together with zero boundary observation.
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