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Effect of plastic rotation on the concrete contribution to shear strength of RC beams
Aydemir, Cem,Aydemir, Muberra Eser,Arslan, Guray Techno-Press 2021 Advances in concrete construction Vol.11 No.6
This paper provides an analytical model to predict the concrete contribution to shear strength of reinforced concrete (RC) beams that fail in flexure. In the RC members subjected to cyclic loading, the stiffness and hysteretic energy dissipation decreases with diagonal web cracking in the plastic hinge region. The proposed method takes into account plastic rotation in the plastic hinge region by means of critical shear crack theory. To verify the concrete contribution to shear strength predicted by the proposed method, six normal- and high-strength RC beams having various shear span-to-effective depth ratios are tested under cyclic loading. The predictions by the proposed equation and various researchers' equations are compared to the test results. It is found that the proposed method is in good agreement with the test results.
Postdural puncture subdural hematoma or postdural puncture headache? -two cases report-
Aydemir Kale,Hakan Emmez,Özcan Pişkin,Emre Durdağ 대한마취통증의학회 2015 Korean Journal of Anesthesiology Vol.68 No.5
Spinal anesthesia is widely used for many obstetric, gynecological, orthopedic, and urological operations. Subdural hematomas may occur after trauma and are associated with high morbidity and mortality rates. Postdural puncture headache (PDPH) is a benign condition and the most frequent complication of spinal anesthesia. The high rate of headache after spinal anesthesia may mask or delay the diagnosis of subdural hematoma. The true incidence of postdural puncture subdural hematoma (PDPSH) is unknown because most affected patients are probably managed without investigation. Therefore, the true incidence of PDPSH may be greater than suggested by previous reports. The differentiation of headache associated with subdural hematoma from PDPH is crucial. We herein report two cases of bilateral subdural hematoma after epidural anesthesia and emphasize the importance of suspicion for PDPSH and careful evaluation of patients with headache after spinal anesthesia.
Aydemir, Fatih,Cekinmez, Melih,Kardes, Ozgur,Kayaselcuk, Fazilet The Korean Neurosurgical Society 2016 Journal of Korean neurosurgical society Vol.59 No.2
Ganglion cell tumors (GCT) are divided into two subtypes : gangliocytoma and ganglioglioma. Intramedullary gangliocytomas are extremely rare. A 20-year-old male patient with pain of neck, who also had a previously known neuroendocrine tumor of lung, was operated for mass found in the cervicomedullary junction with a presumptive diagnosis of metastases. Only partial resection could be performed. Pathological diagnosis had been reported as gangliocytoma. Only ten cases of intramedullary gangliocytoma have been reported in the literature. Although association with scoliosis and Von Recklinghausen;s disease were previously reported in the literature, no gangliocytoma case concomitant with endocrine tumor of lung have been published. Pathological study is the most important diagnostic method for gangliocytomas. Surgical excision is the primary treatment, but difficulty in total surgical tumor resection is the most important problem.
Massive Calcified Cerebellar Pilocytic Astrocytoma with Rapid Recurrence : A Rare Case
Aydemir, Fatih,Kardes, Ozgur,Kayaselcuk, Fazilet,Tufan, Kadir The Korean Neurosurgical Society 2016 Journal of Korean neurosurgical society Vol.59 No.5
Pilocytic astrocytomas (PAs) are World Heath Organization Grade I tumors and are most common in children. PA calcification is not a common finding and has been reported more frequently in the optic nerve, hypothalamic/thalamus and superficially located cerebral tumors. We present a cerebellar PA in a 3-year-old male patient with cystic components and massive calcification areas. The residual tumor grew rapidly after the first operation, and the patient was operated on again. A histopathological examination revealed polar spongioblastoma-like cells. Massive calcification is not a common feature in PAs and can lead to difficulties in radiological and pathological differential diagnoses.
Transcriptomic analysis of endoplasmic reticulum stress in roots of grapevine rootstock
Aydemir Birsen Çakır,Ergül Ali 한국식물생명공학회 2021 Plant biotechnology reports Vol.15 No.5
Grapevine roots are largely subjected to adverse environmental stresses. To maintain cellular hemostasis during different environmental conditions, cells develop reponse known as endoplasmic reticulum (ER) stress response. However, the cel- lular mechanism of grapevine rootstocks roots has not been studied in detail under conditions of ER stress. In this study, transcriptome analysis has been performed to determine ER-related transcripts in grapevine rootstock induced with tunica- mycin (TM) or dithiothreitol (DTT), causing proteins misfolding in ER, and consequently triggers ER stress. According to the results, 640 genes were expressed differently in the two treatment groups. Out of these, 397 transcripts were found to be associated with tunicamycin treatment. Among tunicamycin-responsive genes increased expression profiles were recorded for 287 genes while the remaining and 110 genes showed decreased expression profile. In contrast, in DTT-treated plants, a total of 557 genes were differentially expressed, 345 of which were upregulated, and 212 were downregulated. In addition, we identified 50 transcripts common to both TM and DTT treatments. TM and DTT treatments increased the expression of transcription factors, the hormone biosynthesis pathway genes. Gene ontology classified genes in groups involving protein folding, oxidative stress, protein phosphorylation, transmembrane transport, transcription and proteolysis regulation. Gene transcripts results revealed genes that may play a significant effect in the response to ER stress of rootstocks root. Considering the results reported here explaining the possible mechanisms of how plants adapt to environmental stresses, an important information gap has been bridged by providing new insights into the ER stress mechanisms in plant roots.
Role of explosive instabilities in high-<i>β</i> disruptions in tokamaks
Aydemir, A.Y.,Lee, H.H.,Lee, S.G.,Seol, J.,Park, B.H.,In, Y.K. International Atomic Energy Agency 2016 Nuclear fusion Vol.56 No.5
<P>Intrinsically explosive growth of a ballooning finger is demonstrated in nonlinear magnetohydrodynamic calculations of high-<I>β</I> disruptions in tokamaks. The explosive finger is formed by an ideally unstable <I>n</I> = 1 mode, dominated by an <I>m</I>/<I>n</I> = 2/1 component. The quadrupole geometry of the 2/1 perturbed pressure field provides a generic mechanism for the formation of the initial ballooning finger and its subsequent transition from exponential to explosive growth, without relying on secondary processes. The explosive ejection of the hot plasma from the core and stochastization of the magnetic field occur on Alfvénic time scales, accounting for the extremely fast growth of the precursor oscillations and the rapidity of the thermal quench in some high-<I>β</I> disruptions.</P>
Aydemir, Muberra Eser Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.5
In this study, strength reduction factors and inelastic displacement ratios are investigated for SDOF systems with period range of 0.1-3.0 s considering soil structure interaction for earthquake motions recorded on soft soil. The effect of stiffness degradation on strength reduction factors and inelastic displacement ratios is investigated. The modified-Clough model is used to represent structures that exhibit significant stiffness degradation when subjected to reverse cyclic loading and the elastoplastic model is used to represent non-degrading structures. The effect of negative strain - hardening on the inelastic displacement and strength of structures is also investigated. Soil structure interacting systems are modeled and analyzed with effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. New equations are proposed for strength reduction factor and inelastic displacement ratio of interacting system as a function of structural period($\tilde{T}$, T) ductility (${\mu}$) and period lengthening ratio ($\tilde{T}$/T).
Aydemir, Muberra Eser Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.6
In this study, inelastic displacement ratios are investigated for existing systems with known lateral strength considering soil structure interaction. For this purpose, SDOF systems for period range of 0.1-3.0 s with different hysteretic behaviors are considered for a number of 18 earthquake motions recorded on soft soil. The effect of stiffness degradation on inelastic displacement ratios is investigated. The Modified Clough model is used to represent structures that exhibit significant stiffness degradation when subjected to reverse cyclic loading and the elastoplastic model is used to represent non-degrading structures. Soil structure interaction analyses are conducted by means of equivalent fixed base model effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. A new equation is proposed for inelastic displacement ratio of system with SSI with elastoplastic or degrading behavior as a function of structural period ($\tilde{T}$), strength reduction factor (R) and period lengthening ratio ($\tilde{T}$/T). The proposed equation for $\tilde{C}_R$ which takes the soil-structure interaction into account should be useful in estimating the inelastic deformation of existing structures with known lateral strength.