Manisa Celal Bayar Üniversitesi Akademik Arşiv Sistemi
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Microshear Bond Strength and Finite Element Analysis of Resin Composite Adhesion to Press-on-Metal Ceramic for Repair Actions after Various Conditioning Methods
No full textPurpose: This study evaluated the repair bond strength of differently surface-conditioned press-on-metal ceramic to repair composites and determined the location of the accumulated stresses by finite element analysis. Materials and Methods: Press-on-metal ceramic disks (IPS InLine PoM, lvoclar Vivadent) (N = 45, diameter: 3 mm, height: 2 mm) were randomly divided into 3 groups (n = 15 per group) and conditioned with one of the following methods: 9.5% hydrofluoric acid (HF) (Porcelain etch), tribochemical silica coating (TS) (CoJet), and an unconditioned group acted as the control (C). Each group was divided into three subgroups depending on the repair composite resins: a) Arabesk Top (V, a microhybrid; VOCO), b) Filtek Z250 (F, a hybrid;3M ESPE); c) Tetric Evo-Ceram (T, a nanohybrid; lvoclar Vivadent) (n = 5 per subgroup). Repair composites disks (diameter: 1 mm, height: 1 mm) were photopolymerized on each ceramic block. Microshear bond strength (MSB) tests were performed (1 mm/min) and the obtained data were statistically analyzed using 2-way ANOVA and Tukey's post-hoc test (alpha = 0.05). Failure types were analyzed under SEM. Vickers indentation hardness, Young's modulus, and finite element analysis (FEA) were performed complementary to MSB tests to determine stress accumulation areas. Results: MSB results were significantly affected by the surface conditioning methods (p = 0.0001), whereas the repair composite types did not show a significant effect (p = 0.108). The interaction terms between the repair composite and surface conditioning method were also statistically significant (p = 0.0001). The lowest MSB values (MPa +/- SD) were obtained in the control group (V = 4 +/- 0.8; F = 3.9 +/- 0.7; T = 4.1 +/- 0.7) (p 0.05). The control group presented exclusively adhesive failures. Cohesive failures in composite followed by mixed failure types were more common in HF and TS conditioned groups. Elasticity modulus of the composites were 22.9, 12.09, and 10.41 GPa for F, T, and V, respectively. Vickers hardness of the composites were 223, 232, and 375 HV for V, T, and F, respectively. Von Mises stresses in the FEA analysis for the V and T composites spread over a large area due to the low elastic modulus of the composite, whereas the F composite material accumulated more stresses at the bonded interface. Conclusion: Press-on-metal ceramic could best be repaired using tribochemical silica coating followed by silanization, regardless of the repair composite type in combination with their corresponding adhesive resins, providing that no cohesive ceramic failure was observed
Optimal perturbation iteration technique for solving nonlinear Volterra-Fredholm integral equations
No full textIn this work, the optimal perturbation iteration method is briefly presented and employed for solving nonlinear Volterra-Fredholm integral equations. The classical form of the optimal perturbation iteration method is modified, and new algorithms are constructed for integral equations. Comparing our new algorithms with some earlier papers proved the excellent accuracy of the newly proposed technique
Review Spam Detection Based on Psychological and Linguistic Features
No full textWith the advances in information and communication technologies, the immense quantity of review texts have become available on the Web. Review text can serve as an essential source of information for individual decision makers and business organizations. Some of the reviews shared on the Web may contain deceptive information to mislead the existing decision making process. In this study, we have presented a supervised learning based scheme for review spam detection. In the presented study, psychological and linguistic feature sets and their combinations are taken into consideration. In the study, the predictive performances of four conventional supervised learning methods (namely, Naive Bayes classifier, K-nearest neighbor algorithm, support vector machines and C4.5 algorithm) are evaluated on the different feature sets
Features of chronic inflammation at the gastric cardia and the relationship with Helicobacter pylori infection and oesophagitis
No full textBackground: The etiopathogenesis of chronic inflammation at the gastric cardia is still debated. It is suggested that carditis may be a finding of gastro-oesophageal reflux disease (GORD) or it may occur as a result of the gastritis caused by Helicobacter pylori (H. pylori) infection. Aim : To examine morphological features of carditis, as well as the associations of carditis with Helicobacter pylori gastritis and oesophagitis as a marker of gastro-oesophageal reflux disease. Patients and methods : Endoscopic biopsy specimens obtained systematically from oesophagus, cardia, corpus and antrum of 135 dyspeptic patients were retrospectively evaluated. In biopsies, we have searched for any correlations between clinical, endoscopic, and histological features. Results : Carditis was detected in 123 (91.1%) of the cases. The mean age of the carditis group was 47.9 years and the male-to-female ratio was 1.08:1. The relation of carditis with age and sex was not significant (p = 0.19 and p = 0.24, respectively). All cases of the carditis group had concomitant chronic gastritis. In these cases, chronic inflammation, degree of neutrophil-mediated activity and H. pylori colonisation were significantly correlated in cardia, corpus and antrum (p < 0.001). Intestinal metaplasia was observed in 14 cases (11.3%) and, was associated with H. pylori colonisation (p < 0.001). Microscopic oesophagitis detected in 37.7% cases also showed correlation with reflux symptoms and endoscopic oesophagitis but not carditis. When all cases with carditis were evaluated for H. pylori infection and oesophagitis, which are presumed risk factors for carditis, H. pylori infection appeared to be an independent risk factor for carditis (p = 0.012), while oesophagitis did not. Conclusions : This study suggests that carditis is commonly found in patients presenting with dyspepsia and the histological features of carditis were similar to those seen in H. pylori gastritis in antrum and corpus. In addition, our data have also shown that carditis was significantly associated with H. pylori infection but not with symptoms or signs of GORD
Patient Presenting with Hemoptysis: A Case of Hughes-Stovin Syndrome
No full textHughes-Stovin syndrome (HSS) is a very rare autoimmune clinical disorder that has been described as the presence of thrombophlebitis and multiple aneurysms in pulmonary and/or bronchial arteries. The pathogenesis is still unknown, but this syndrome is often thought of as a manifestation of Behcet disease. Herein, we describe a 59-year-old male patient who was admitted to massive hemoptysis. HSS was diagnosed on the basis of imaging pulmonary artery aneurysms and a history of lower extremity thrombosis. It differs in terms of the occurrence of this rare syndrome in an elderly patient. In this syndrome, which has a high mortality, the results are satisfactory when the treatment is started with a rapid diagnosis
Characterization of two natural zeolites for geotechnical and geoenvironmental applications
No full textThis paper reports the findings of experimental studies on two natural zeolitic soils. Engineering properties (e.g., grain size, specific gravity, compressibility, hydraulic conductivity, swelling behavior and shear strength) were determined in order to assess their suitability for geotechnical and geoenvironmental applications. The two zeolite-rich tuff samples investigated were mainly composed of clinoptilolite. The results show that the cation exchange capacities are 60.5 and 57.2 mEq/100 g, which are below the theoretical reported values. Compression index values obtained reveal that the zeolitic soils are not highly compressible. The modified free swell indexes of the zeolitic samples are around 2.0, suggesting that they have low swelling potential. The drained residual friction angles indicate that the zeolitic soils have relatively high internal friction angles (34 degrees and 36.5 degrees for Z-1 and Z-2, respectively). Based on the results obtained, it was concluded that zeolites are mechanically stable materials that are suitable for embankment materials and landfill liner applications. (C) 2010 Elsevier B.V. All rights reserved
Nursing students' classroom climate perceptions: A longitudinal study
No full textBackground: As a versatile and dynamic process, classroom climate directly affects the learning levels of students and their quality of life while in school. Objectives: The study was conducted to explore and compare nursing students' perceptions of classroom climate throughout four years of university education and to evaluate the influencing factors. Design and settings: The longitudinal study was conducted between 2017 and 2020 in the nursing department of a university in Turkey. Participants: The study was carried out with 134 nursing students who enrolled in their first year and agreed to participate in the study. Methods: The data were collected at the end of the fall semester of each of the four years using the Student Information Form and the Classroom Climate Inventory. Results: The mean score of students' perceptions of classroom climate was 2.88 +/- 0.83 for all academic years. The classroom climate inventory mean scores of fourth-year students were statistically significantly higher than their scores in the first and third years (p = 0.000). The students' classroom climate levels were statistically significantly affected by the positive classroom communication among students in all academic years in a positive direction. Statistically significant effective factors in students' classroom climate perceptions by year were as follows: the sense of belongingness to the class in the second and third years (although significantly lower in the first year), socio-cultural activities organized at school the second and fourth years (p < 0.05), instructors' attitudes supporting classroom communication in the first year, and opportunities supporting communication in the school environment in the fourth year (p < 0.05). Conclusions: Students' perception of the classroom climate was moderate overall and affected by positive classroom communication among students in all academic years. School administrators and educators can develop strategies and organize activities to increase positive communication in the classroom
Statistical investigation of the angular momentum dependence of the nuclear level density parameter
No full textThe nuclear level density (NLD) parameter is crucial for calculating cross-sections in nuclear physics, astrophysics, reactor design, and medical physics. Spin and parity, along with excitation energy, are fundamental properties of an excited nuclear level. Previous investigations into the NLD's dependence on spin and parity have primarily used approximate methods like parity equidistribution and Gaussian distribution of spins. However, the specific impact of spin and parity on the NLD parameter, a key component in NLD formulation, has not been extensively studied. We examined the spin and parity dependence of the NLD parameter. Our findings demonstrate that the NLD parameter's dependency on both excitation energy and angular momentum can be accurately characterized by a Laplace distribution, highlighting the complex interplay of these factors in nuclear physics
Observation of the Decay Bc+ → Bs0π+
No full textThe result of a search for the decay B-c(+) -> B-s(0)pi(+) is presented, using the B-s(0) -> D-s(-)pi(+) and B-s(0) -> J/psi phi channels. The analysis is based on a data sample of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1 fb(-1) taken at a center-of-mass energy of 7 TeV, and 2 fb(-1) taken at 8 TeV. The decay B-c(+) -> B-s(0)pi(+) is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is inverted right perpendicular sigma(B-c(+))/sigma(B-s(0))inverted left perpendicular x B(B-c(+) -> B-s(0)pi(+)) = inverted right perpendicular2.37 +/- 0.31 (stat) +/- 0.11 (syst)(-0.13)(+0.17) (tau(Bc+))inverted left perpendicular x 10(-3) the pseudorapidity range 2 < eta(B) < 5, where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the B-c(+) lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction
Dynamics of Axially Accelerating Beams With an Intermediate Support
No full textThe transverse vibrations of an axially accelerating Euler-Bernoulli beam resting on simple supports are investigated. The supports are at the ends, and there is a support in between. The axial velocity is a sinusoidal function of time varying about a constant mean speed. Since the supports are immovable, the beam neutral axis is stretched during the motion, and hence, nonlinear terms are introduced to the equations of motion. Approximate analytical solutions are obtained using the method of multiple scales. Natural frequencies are obtained for different locations of the support other than end supports. The effect of nonlinear terms on natural frequency is calculated for different parameters. Principal parametric resonance occurs when the velocity fluctuation frequency is equal to approximately twice of natural frequency. By performing stability analysis of solutions, approximate stable and unstable regions were identified. Effects of axial velocity and location of intermediate support on the stability regions have been investigated. [DOI: 10.1115/1.4003205