Hasanov A.,Izmir University
International Journal of Non-Linear Mechanics | Year: 2011
Three classes of inverse coefficient problems arising in engineering mechanics and computational material science are considered. Mathematical models of all considered problems are proposed within the J2-deformation theory of plasticity. The first class is related to the determination of unknown elastoplastic properties of a beam from a limited number of torsional experiments. The inverse problem here consists of identifying the unknown coefficient g(2) (plasticity function) in the non-linear differential equation of torsional creep -(g(∇u2)ux1) x1-(g(∇u2)ux2)x2=2φ, x∈Ω⊂R2, from the torque (or torsional rigidity) T(φ), given experimentally. The second class of inverse problems is related to the identification of elastoplastic properties of a 3D body from spherical indentation tests. In this case one needs to determine unknown Lame coefficients in the system of PDEs of non-linear elasticity, from the measured spherical indentation loading curve P=P(α), obtained during the quasi-static indentation test. In the third model an inverse problem of identifying the unknown coefficient g(2(u)) in the non-linear bending equation is analyzed. The boundary measured data here is assumed to be the deflections wi[τk]:=w(λi;τk), measured during the quasi-static bending process, given by the parameter τk, k=1,K, at some points λi=(x1(i),x2(i)), i=1,M of a plate. An existence of weak solutions of all direct problems are derived in appropriate Sobolev spaces, by using monotone potential operator theory. Then monotone iteration schemes for all the linearized direct problems are proposed. Strong convergence of solutions of the linearized problems, as well as rates of convergence is proved. Based on obtained continuity property of the direct problem solution with respect to coefficients, and compactness of the set of admissible coefficients, an existence of quasi-solutions of all considered inverse problems is proved. Some numerical results, useful from the points of view of engineering mechanics and computational material science, are demonstrated. © 2011 Elsevier Ltd. All rights reserved.
Hasanov A.,Izmir University
International Journal of Heat and Mass Transfer | Year: 2012
Inverse problems of identifying the unknown spacewise and time dependent heat sources F(x) and H(t) of the variable coefficient heat conduction equation u t = (k(x)u x) x + F(x)H(t) from supplementary temperature measurement (u T(x)u(x, T f)) at a given single instant of time T f > 0, are investigated. For both inverse source problems, defined to be as ISPF and ISPH respectively, explicit formulas for the Fréchet gradients of corresponding cost functionals are derived. Fourier analysis of these problems shows that although ISPF has a unique solution, ISPH may not have a unique solution. The conjugate gradient method (CGM) with the explicit gradient formula for the cost functional J 1(F) is then applied for numerical solution of ISPF. New collocation algorithm, based on the piecewise linear approximation of the unknown source H(t), is proposed for the numerical solution of the integral equation corresponding to ISPH. The proposed two numerical algorithms are examined through numerical examples for reconstruction of continuous and discontinuous heat sources F(x) and H(t). Computational results, with noise free and noisy data, show efficiency and high accuracy of the proposed algorithms. © 2011 Elsevier Ltd. All rights reserved.
Hasanov A.,Izmir University
Journal of Mathematical Chemistry | Year: 2010
This article presents an analytical approach for identification problems related to ion transport problems. In the first part of the study, relationship between the flux ΦL:= (D(x)ux(0,t)x=0 and the current response I(t) is analyzed for various models. It is shown that in pure diffusive linear model case the flux is proportional to the classical Cottrelian Ic(t). Similar relationship is derived in the case of nonlinear model including diffusion and migration. These results suggest acceptability of the flux data as a measured output data in ion transport problems, instead of nonlocal additional condition in the form an integral of concentration function. In pure diffusive and diffusive-convective linear models cases, explicit analytical formulas between inputs (diffusion or/and convection coefficients) and output (measured flux data) are derived. The proposed analytical approach permits one to determine the unknown diffusion coefficient from a single flux data given at a fixed time t1 > 0, and unknown convection coefficient from a single flux data given at a fixed time t2 > t1 > 0. Linearized model of the nonlinear ion transport problem with variable diffusion and convection coefficients is analyzed. It is shown that the measured output (flux) data can not be given arbitrarily. © 2010 Springer Science+Business Media, LLC.
Ozturk H.,Izmir University
Journal of Endourology | Year: 2014
Purpose: To evaluate gastrointestinal tract complications of percutaneous nephrolithotomy (PCNL), to determine risk factors, and to develop strategies for diagnosis and treatment. Material and Methods: A literature review was conducted for the studies published in the English language in the databases of PubMed and Scopus between July 1985 and June 2013. The key words for digital literature search were limited to the following: "percutaneous nephrolithotomy complications, ([splenic injury, liver injury, gallbladder injury and biliary peritonitis, colonic injury] during/after [percutaneous nephrolithotomy]), complication, Clavien, Clavien-Dindo classification, management, review, PNL, PCNL." Results: A total of 16 articles on splenic injury were reviewed. There was no consensus in the literature regarding the management of splenic injuries. A conservative approach with new treatment modalities is the most widely accepted method in the literature. A total of seven articles on gallbladder injury were reviewed. All gallbladder injuries resulted in cholecystectomy. The time of diagnosis is the most significant parameter determining choice between laparoscopy and laparotomy. A total of seven articles on liver injury were reviewed. The liver injury generally provides the best response to a conservative approach among other solid organ injuries. A total of 11 articles on bowel injury were reviewed. Bowel injury mostly results in exploratory laparotomy. Unlike colon injuries, bowel injuries are more complex to manage with conservative measures because of the challenges in diagnosis and the fact that the injury is located in the intraperitoneal area. A total of 28 articles, which comprised a large case series with colon injuries, consisted of collaborative reviews and meta-analyses were reviewed. In total, 51 colon injuries (0.5%) were evaluated occurring in 13,424 patients in supine and prone PCNL series. Conservative approaches have proven to be effective in colon injuries in the absence of large perforations and intraperitoneal involvement. Conclusion: There is a downward trend in gastrointestinal complications from PCNL because of the technologic advances that guide the diagnosis and treatment. Paradoxically, the rate of complications is higher in complex kidney stones such as those in a horseshoe kidney and pelvic and malrotated kidney that represent anatomic challenges for intervention. The most important point is to determine the risk factors for preoperative planning of the procedure and to diagnose the complications for proper management early. © Mary Ann Liebert, Inc. 2014.
Hasanov A.,Izmir University |
Pektas B.,Izmir University
Computers and Mathematics with Applications | Year: 2013
The inverse problem of identifying the unknown time-dependent heat source H(t) of the variable coefficient heat equation ut=( k(x)ux)x+F(x)H(t), with separable sources of the form F(x)H(t), from supplementary temperature measurement h(t):=u(0,t) at the left end of the rod, is investigated. The Fourier method is employed to illustrate the comparison of spacewise (F(x)) and time-dependent (H(t) heat source identification problems. An explicit formula for the Fréchet gradient of the cost functional J(H)=∥u(0,ṡ;H)-h∥L2(0,Tf)2 is derived via the unique solution of the appropriate adjoint problem. The Conjugate Gradient Algorithm, based on the gradient formula for the cost functional, is then proposed for numerical solution of the inverse source problem. The algorithm is examined through numerical examples related to reconstruction of continuous and discontinuous heat sources H(t), when heat is transferred through non-homogeneous as well as composite structures. Numerical analysis of the algorithm applied to the inverse source problem in typical classes of source functions is presented. Computational results, obtained for random noisy output data, show how the iteration number of the Conjugate Gradient Algorithm can be estimated. Based on these results it is shown that this iteration number plays a role of a regularization parameter. Numerical results illustrate bounds of applicability of the proposed algorithm, and also its efficiency and accuracy. © 2012 Elsevier Ltd. All rights reserved.
Zengin M.O.,Izmir University |
Cinar E.,Izmir University |
Kucukerdonmez C.,Izmir University
British Journal of Ophthalmology | Year: 2014
Purpose To investigate the effect of nicotine on choroidal thickness using optical coherence tomography (OCT). Design Prospective, case-control study. Methods Sixteen young, healthy subjects and 16 age and gender matched control cases were included in this study; 4 mg nicotine gum was given to the study group and placebo gum to the control group. All participants underwent OCT scanning with a high-speed and resolution spectral-domain OCT device (3D OCT 2000, Topcon, Japan) at baseline, and 1 h following nicotine or placebo administration. The measurements were taken in the morning (10:00-12:00 hours) to avoid diurnal fluctuation. Results The median foveal choroidal thickness at baseline was 337.00 μm (IQR 84.50), which decreased to 311.00 μm (IQR 78.00) at 1 h following oral nicotine intake ( p=0.001). The median choroidal thickness was also significantly decreased at five other extrafoveal points (p≤0.05 for all). In the control group, the median baseline choroidal thickness at the fovea was 330.50 μm (IQR 104.25), and was 332.00 μm (IQR 103.75) at 1 h (p=0.271). Conclusions Nicotine causes a significant decrease in choroidal thickness following oral intake. This acute decrease might be a result of reduced ocular blood flow due to the vasoconstrictive effect of nicotine.
Nilufer Yonguc G.,Izmir University
Molecular biology reports | Year: 2012
Dichlorvos (DDVP) is an organophosphate compound that causes neurotoxicity. Apoptosis plays an important role in neurotoxic cell death in the brain. The aim of this study was to examine caspase 1, caspase-3 and also cell apoptosis related genes as p53, Tumor Necrosis Factor-alpha, Hypoxia Inducible Factor 1-alpha expressions in hippocampus, cerebellum, cortex, and to estimate total hippocampal neuron number in DDVP treated rats. Ten female albino rats were divided into control (n:5) and dose (n:5) groups. In dose group, single dose of DDVP (25 mg/kg) was administered to the animals via oral gavage. A week later, brains were removed and total neuron number was estimated in the left hippocampus using by optical fractionator method. The right part of the brain was used for gene expression analysis. In dose group, total hippocampal neuron number was significantly decreased compared to control group (p = 0.008). Caspase 1 and TNF-alpha gene expression were increased in all brain tissues and p53 gene expression was decreased in only hippocampus tissue in dose group. Short-term exposure to dichlorvos leads to neuronal loss in hippocampus and TNF-alpha rapidly and potently induces apoptosis and also several caspases as possible participants in the apoptotic cascade.
Yilmaz N.T.,Izmir University
Journal of Cosmology and Astroparticle Physics | Year: 2014
For the massive gravity, after decoupling from the metric equation we find a broad class of solutions of the Stückelberg sector by solving the background metric in the presence of a diagonal physical metric. We then construct the dynamics of the corresponding FLRW cosmologies which inherit effective matter contribution through the decoupling solution mechanism of the scalar sector.
Kobak S.,Izmir University
Therapeutic Advances in Musculoskeletal Disease | Year: 2015
Sarcoidosis is a systemic disorder of unknown etiology, which may involve various tissues and organs and is characterized by a noncaseating granuloma reaction. While pathogenesis is not yet clear, cellular immune system activation and nonspecific inflammatory response occur secondarily to several genetic and environmental factors. T helper 1-cells and macrophage-derived pro-inflammatory cytokines stimulate the inflammatory cascade and formation of granuloma occurs as a result of tissue permeability, cell influx, and local cell proliferation. The different prevalence, clinical results, and disease course observed in different races and ethnic groups, is an indicator of the heterogeneous nature of the disease. Sarcoidosis may mimic and/or may occur concomitantly with numerous primary rheumatic diseases. This disease most commonly presents with bilateral hilar lymphadenopathy, pulmonary infiltrations, and skin and eye lesions. Locomotor system involvement is observed at a range of 15% and 25%. Two major joint involvements have been described: acute and chronic form. The most common form, the acute form, may be the first sign of sarcoidosis and present with arthralgia, arthritis, or periarthritis. Chronic sarcoid arthritis is usually associated with pulmonary parenchymal disease or other organ involvement and occurs rarely. While asymptomatic muscular involvement is reported between 25% and 75%, symptomatic muscular involvement is very rare. Symptomatic myopathy may present as three different types: chronic myopathy, palpable nodular myositis, or acute myositis. Even if rare, 2–5% of cases may exhibit osseous involvement and it is frequently associated with lupus pernio, chronic uveitis, and multisystemic disease. Sarcoidosis was reported together with different rheumatologic diseases. There are studies showing that sarcoidosis may mimic the clinical and laboratory findings of these disorders. Nonsteroidal anti-inflammatory drugs and corticosteroids are used for treating the symptoms of rheumatologic findings. In patients who are unresponsive to corticosteroids, immunosuppressive and anti-tumor necrosis factor alpha drugs may be used. In this review, the incidence of rheumatologic symptoms, the clinical findings, and the treatment of rheumatologic manifestations of sarcoidosis are discussed. © 2015, © The Author(s), 2015.
Tarlaci S.,Izmir University |
Pregnolato M.,University of Pavia
International Journal of Psychophysiology | Year: 2015
The concepts of quantum brain, quantum mind and quantum consciousness have been increasingly gaining currency in recent years, both in scientific papers and in the popular press. In fact, the concept of the quantum brain is a general framework. Included in it are basically four main sub-headings. These are often incorrectly used interchangeably. The first of these and the one which started the quantum mind/consciousness debate was the place of consciousness in the problem of measurement in quantum mechanics. Debate on the problem of quantum measurement and about the place of the conscious observer has lasted almost a century. One solution to this problem is that the participation of a conscious observer in the experiment will radically change our understanding of the universe and our relationship with the outside world. The second topic is that of quantum biology. This topic has become a popular field of research, especially in the last decade. It concerns whether or not the rules of quantum physics operate in biological structures. It has been shown in the latest research on photosynthesis, the sense of smell and magnetic direction finding in animals that the laws of quantum physics may operate in warm-wet-noisy biological structures. The third sub-heading is quantum neurobiology. This topic has not yet gained wide acceptance and is still in its early stages. Its primary purpose is directed to understand whether the laws of quantum physics are effective in the biology of the nervous system or not. A further step in brain neurobiology, towards the understanding of consciousness formation, is the research of quantum laws' effects upon neural network functions. The fourth and final topic is quantum psychopathology. This topic takes its basis and its support from quantum neurobiology. It comes from the idea that if quantum physics is involved in the normal working of the brain, diseased conditions of the brain such as depression, anxiety, dementia, schizophrenia and hallucinations can be explained by quantum physical pathology. In this article, these topics will be reviewed in a general framework, and for the first time a general classification will be made for the quantum brain theory. © 2015 Elsevier B.V.