289 research outputs found
Oxidative/antioxidative status, lymphocyte DNA damage, and urotensin-2 receptor level in patients with migraine attacks
No full textMehmet Yigit,1 Ozgur Sogut,1 Özlem Tataroglu,1 Adnan Yamanoglu,1 Eda Yigit,2 Eray Metin Güler,3 Omer Faruk Ozer,3 Abdurrahim Kocyigit3 1Department of Emergency Medicine, Haseki Training and Research Hospital, University of Health Sciences, 2Department of Emergency Medicine, Sisli Hamidiye Etfal Training and Research Hospital, University of Health Sciences, 3Department of Biochemistry, Faculty of Medicine, Bezmialem Vakif University, Istanbul, Turkey Background: The present study investigated the potential roles of plasma lymphocyte DNA damage, the urotensin-2 receptor (UTS2R), and oxidative changes in patients with varying degrees of migraine-related disability who were in the ictal phase and presented to our emergency department. Methods: This study enrolled 40 consecutive adult patients with migraine attack and 40 age- and sex-matched healthy controls. The same health care professional determined the headache-related disability of each patient’s migraine attack using the Migraine Disability Assessment Scale (MIDAS); patients were divided into three groups based on MIDAS score. Plasma lymphocyte DNA damage; UTS2R, malondialdehyde (MDA), and catalase (CAT) levels; total oxidant status (TOS); total antioxidant status (TAS); and the oxidative stress index (OSI) were used as predictors of early oxidative changes. Results: Plasma lymphocyte DNA damage, TOS, MDA levels, and OSI values were significantly higher in patients with migraine compared to controls. Conversely, TAS and CAT and UTS2R levels were markedly lower in patients with migraine compared to controls. Comparisons of the patient groups by MIDAS score revealed significant differences in plasma lymphocyte DNA damage and CAT levels but no differences in TOS, MDA levels, OSI, TAS, or UTS2R levels. MIDAS scores were positively correlated with the degree of lymphocyte DNA damage, but neither of these factors was significantly related to CAT levels. Conclusion: The present data suggest that lymphocyte DNA damage and changes in oxidative/antioxidative status may reflect an enhanced oxidative damage and an ineffective antioxidant defense system in migraineurs during headache attacks. In addition, lymphocyte DNA damage levels may be an indicator of the degree of migraine-related disability as assessed by MIDAS score. Keywords: migraine attack, oxidative/antioxidative changes, lymphocyte DNA damage, urotensin-2 receptor, Migraine Disability Assessment Scal
Dilaceration of Mandibular Central Incisor: a case report
No full textDilaceration of teeth can ocur as a result of trauma to its primary predecessors. Crown dilaceration is more rare than root dilacerations. This report describes a rare case of crown dilaceration of the mandibular central incisor caused by trauma. Periapical radiography and cone beam computed tomography scans revealed a severe crown dilaceration in the labial direction. After conventional root canal treatment, a glass fiber-reinforced post was placed and the tooth was restored using the original crown which was removed from the root before root canal obturation. One year after the treatment, the tooth was clinically intact without mobility and there was no sensitivity during percussion. Radiographic examination revealed that the periodontal tissues were healthy and there was no sign of root resorption. It was concluded that correct diagnosis and prompt treatment help to achieve desirable esthetics and function for crown dilecaration
Efficacy of Two Different Nickel-Titanium Rotary Systems in Retreatment Procedure With or Without Laser-Activated Irrigation: An in Vitro Study
No full textYigit Ozer, Senem/0000-0002-2360-3942Objective: the aim of this study was to compare the efficacy of HyFlex EDM (Coltene/Whaledent, Altstatten, Switzerland) and ProTaper Universal Retreatment Nickel-Titanium (NiTi) Systems [The ProTaper Universal Retreatment (PTR), Dentsply Maillefer, Ballaigues, Switzerland] in the removal of the root canal filling materials with or without laser activated irrigation. Materials and methods: the root canals of 60 human mandibular premolars were instrumented with K files up to size 35 at a working length; the step-back procedure was performed in 1mm increments up to size 50. Next, the teeth were obturated using the lateral compaction technique with gutta-percha and resin-based sealer, and they were randomly divided into two groups (n=30) according to the retreatment systems: PTR and HyFlex EDM NiTi rotary files. Then, each group was divided into two subgroups (n=15), laser [photon-induced photo-acoustic streaming (PIPS); Fotona, Ljubljana, Slovenia] activated irrigation and conventional needle irrigation group. Following these procedures, the specimens were evaluated using micro-computed tomography. Results: There was no significant difference between the instrumentation systems regarding the cleaning efficacy (chi(2)=0.754; p=0.86). Additionally, PIPS method did not have a significant effect on the removal of the filling material compared to conventional needle irrigation. Conclusions: Both instrumentation systems were effective in removing the filling material, but neither was able to remove the filling material completely. PIPS method did not show a significant additional effect regarding the removal of filling material.Adnan Menderes University Research FoundationAdnan Menderes University [DHF-15004]This study was supported by the Adnan Menderes University Research Foundation (DHF-15004). the Foundation had no role in performing the study, including its design or analysis, or in our decision to publish the findings
Experimental testing of high-rate GNSS precise point positioning (PPP) method for detecting dynamic vertical displacement response of engineering structures
No full text© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. The fundamental dynamic property of the structures is the oscillation frequency, which can be derived from the response measurements. The structures with a short/medium/long span (e.g. suspended or cable bridges) vibrate vertically rather than horizontally. The potential of GNSS precise point positioning (PPP) for detecting the dynamic response of vibrating structures has been the focus of recent studies. In this study, the usability of GNSS PPP in detecting the dynamic displacement response of a vertically vibrating structure was experimentally investigated. A number of experiments on cantilever beam structures were conducted and four cases with different vibration frequencies, ranging from 0.94 to 2.90 Hz, were selected to compare the PPP and precise relative methods in the time, position and frequency domain. In addition, the effects of the ultra-rapid and final precise orbit product on the kinematic PPP solution were examined in terms of detecting vertical oscillation. The results clearly show that a high-rate kinematic PPP method can detect the fundamental frequency of vertical vibration to evaluate the dynamic movement of long/medium/short-span suspended bridges and highway viaducts
Experimental assessment of post-processed kinematic Precise Point Positioning method for structural health monitoring
No full textMonitoring the response of engineering structures, such as tall buildings, tower and large-scale bridges, under severe loading conditions, such as strong earthquake or wind storm, is an important requirement to verify their design and construction and to evaluate structural condition and reliability. In the last two decades, high-rate real-time or post-processed kinematic differential Global Positioning System (DGPS) has been widely used in dynamic displacement measurements of civil engineering structures. In recent years, interest has increased for Precise Point Positioning (PPP) due to its capability to generate positioning solutions as accurate as DGPS. In this study, the potential of post-processed kinematic PPP in terms of monitoring dynamic displacement response of a structure has been explored based on free damped oscillation events obtained from a model structure, which is able to vibrate in the fundamental and higher modes of vibration. A number of experiments have been carried out and five events, each of which is different character, have been selected to compare PPP results with DPGS results in the time and frequency domain. The results clearly demonstrate that the PPP method, like the DGPS method, offers great potential for the measurement of horizontal and vertical dynamic movement of structures. The impact of a short period (one minute) of observation length on the result of the kinematic PPP method was also investigated in terms of sensing the dynamic movement of a structure. Twenty selected one-minute data-sets extracted from a one-hour original data-set were processed by Canadian spatial reference system PPP and each one-minute PPP solution was compared with the corresponding segment obtained from the one-hour PPP solution. The results show that the one-minute PPP solution is able to extract the fundamental natural frequency of the oscillation in the horizontal and vertical component just like the one-hour PPP solution after the offset is removed and the lower frequency trend component is filtered out
Multi-element ducts for ducted wind turbines: A numerical study
No full textMulti-element ducts are used to improve the aerodynamic performance of ducted wind turbines (DWTs). Steady-state, two-dimensional computational fluid dynamics (CFD) simulations are performed for a multi-element duct geometry consisting of a duct and a flap; the goal is to evaluate the effects on the aerodynamic performance of the radial gap length and the deflection angle of the flap. Solutions from inviscid and viscous flow calculations are compared. It is found that increasing the radial gap length results in an augmentation of the total thrust generated by the DWT, whereas a larger deflection angle has an opposite effect. Reasonable to good agreement is seen between the inviscid and viscous flow calculations, except for multi-element duct configurations characterized by large flap deflection angles. The viscous effects become stronger at large flap deflection angles, and the inviscid calculations are incapable of taking this phenomenon into account.</p
Stability Formulation for Integrated Opto-mechanic Phase Shifters
No full textAbstractStability of opto-mechanical phase shifters consisting of waveguides and non-signal carrying control beams is investigated thoroughly and a formula determining the physical limitations has been proposed. Suggested formulation is not only beneficial to determine physical strength of the system but also advantageous to guess the response of the output to the fabrication errors. In the iterative analysis of cantilever and double-clamped beam geometrical configurations, the stability condition is revealed under the strong inter-dependence of the system parameters such as input power, device length and waveguide separation. Numerical calculations involving effective index modifications and opto-mechanic movements show that well-known cantilever beams are unstable and inadequate to generate φ = 180° phase difference, while double-clamped beam structures can be utilized to build functional devices. Ideal operation conditions are also presented in terms of both the device durability and the controllability of phase evolution.</jats:p
A comparative design study for MWIR HgCdTe detectors
No full textHigh performance multi-layer MWIR HgCdTe detector design requires detailed analysis considering the interaction between layers and the nonlinear effects. For this purpose, an in-house numerical model is utilized so that electrical and optical parameters are manipulated to eliminate the undesired performance limits. An ideal detector with perfect crystal quality is expected to have diffusion limited dark current. However, for low operating temperatures (<120K), which is usually the case for the high performance applications, SRH mechanism may dominate dark current especially for alternative substrate detectors and low crystal quality resulting in a short SRH lifetime (similar to 200ns). Here, physical sizes, composition and doping profiles are optimized to suppress generation-recombination (GR) dark current so that cooling burden can be minimized. We numerically achieve similar to 30K (from similar to 85K to similar to 115K) increase on the operating temperature without degrading the system performance parameters for the detection of near room temperature object (300K) by placing a wide bandgap layer inside the bandgap
Physical Stability Analysis for Optical MEMS Phase Shifters
No full textStability and switching performance of light force driven opto-mechanical phase shifters are examined and a formula determining the stability condition has been proposed for various structures. The analysis showed that cantilever beams are inadequate to generate 180 phase difference
Physical Stability Analysis for Optical MEMS Phase Shifters
No full textStability and switching performance of light force driven opto-mechanical phase shifters are examined and a formula determining the stability condition has been proposed for various structures. The analysis showed that cantilever beams are inadequate to generate 180 phase difference
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