Background and Objective: One of the most important factors in the success of anterior composite restorations is color stability in different situations in mouth. The aim of this study was to ...evaluate the color stability of four anterior composites in the staining solutions (tea and coffee) and under Ultra-Violette (UV) accelerated aging using spectrophotometer. Methods: This in-vitro study was conducted on 80 samples of four composites (Grandio, G-aenial, Kalore and Estelite Σ quick). Samples were divided into four subgroups (5 samples in each subgroup): immersion in coffee (for 48 hours), tea (for 48 hours), distilled water (as the control group) and exposure to UV for 168 hours. The color of the samples was evaluated by the spectrophotometer before and after the various conditions using the CIE Lab system and color changes (ΔE*ab) were calculated. Findings: In all composites, the maximum and minimum levels of color changes were related to the groups immersed in coffee and distilled water, respectively. The significant color change was observed in all subgroups (ΔE*ab>3.3), except for the control groups and tea-Estelite Σ quick (ΔE*ab=2.79). The highest color change was related to immersion in coffee-Grandio (ΔE*ab=9.084) and the lowest observed in immersion in distilled water-Estelite Σ quick (ΔE*ab=0.836). In coffee immersion subgroups of Grandio and Kalore, higher color change was seen compared to Estelite Σ quick (p=0.02 and p=0.028, respectively). Conclusion: Long-term exposure to tea and coffee and UV accelerated aging leads to clinical color change in Grandio, G-aenial, Kalore and Estelite Σ quick composites.
Background and Aim: Data regarding the efficacy of universal adhesives are limited. This study aimed to assess the durability of a universal adhesive bond to superficial dentin using etch and rinse ...and self-etch modes. Materials and Methods: In this in vitro, experimental study, 32 sound molars were randomly divided into two groups of Scotchbond Universal adhesive with two-step etch and rinse mode and Scotchbond Universal adhesive with one one-step self-etch mode as recommended by the manufacturer. Coronal part of teeth was restored with composite. The teeth were mounted in acrylic blocks and prepared according to the trimming protocol. The specimens were then randomly divided into two groups of immediate and 5000 thermal cycles and were then subjected to tensile load at a crosshead speed of 1mm/minute. Data were analyzed using two-way ANOVA. Results: The interaction effect of the two independent variables on microtensile bond strength was not significant (P=0.957). Bond strength in etch and rinse group was significantly higher than that of self-etch group (P<0.001). Bond strength in thermocycling subgroups was significantly higher than that of immediate subgroups (P=0.034). Conclusion: Etch and rinse mode was superior to self-etch mode for use of Scotchbond Universal, and thermocycling increased the bond strength of this adhesive.
Aim: This study was done to evaluate the rate of microleakage in class V amalgam restorations in which the dental bonding agent (DBA) Excite was used as a sealer beneath the restorations. Methods: ...four amalgam restorative materials with commercial names of Dentam, Cinalux, Tytin and SDI (GS-80) were used. Seventy sound human premolars were selected and randomly divided into 4 groups of 15 teeth and 2 groups of 5 teeth as negative and positive control groups). Class V cavities were prepared on the buccal surface of each tooth, Excite was applied on the surface of all cavities and then teeth were cured and restored with four selected amalgam restorative materials. Then teeth were thermocycled (500 cycles) and immersed in 2% methylen blue solution for 24 hours. After immersion, teeth were thoroughly washed with tap’s water, and sectioned using a diamond disk. Conclusion: Based on microscopic evaluation and Kruskal-wallis test, Cinalux (An amalgam filling material manufactured in Iran) showed maximum of microleakage in comparison to other amalgam filling materials used in this study, however it’s value was not significant.
Embodiment of infinity in mathematics Khatin-Zadeh, Omid; Farsani, Danyal; Eskandari, Zahra
Frontiers in psychology,
01/2024, Letnik:
14
Journal Article
Recenzirano
Odprti dostop
In this article, we discuss the embodiment of infinity as one of fundamental concepts in mathematics. In contrast to the embodiment of many other mathematical concepts, the embodiment of infinity is ...an endless dynamic process. In embodying +∞, an object moves rightward toward a previously-set limit and passes it. Then, a new limit is set on the right side of the moving object. The moving object continues its movement and passes it as well. The moving object can pass any limit. In other words, there is no impassable limit for it. In embodying -∞, a similar process happens but the movement is leftward. Embodiment of infinitely small quantities has a basic similarity to the embodiment of infinitely large quantities, although it is different in some respects. We call the embodiment of infinity as
. It is iterative because the process of setting a new limit and passing it is repeated endlessly. Finally, it is suggested that in the process of embodying infinitely large and infinitely small quantities, the visual system and the motor system play important roles, as this process involves spatial concepts and movement.
This article discusses perspective and frame of reference in the metaphorical description of mathematical concepts in terms of motions, gestures, and embodied actions. When a mathematical concept is ...described metaphorically in terms of gestures, embodied actions, or fictive motions, the motor system comes into play to ground and understand that concept. Every motion, gesture, or embodied action involves a perspective and a frame of reference. The flexibility in taking perspective and frame of reference allows people to embody a mathematical concept or idea in various ways. Based on the findings of past studies, it is suggested that the graphical representation of a mathematical concept may activate those areas of the motor system that are involved in the production of that graphical representation. This is supported by studies showing that when observers look at a painting or handwritten letters, they simulate the painter’s or writer’s hand movements during painting or writing. Likewise, the motor system can contribute to the grounding of abstract mathematical concepts, such as functions, numbers, and arithmetic operations.
Depth of processing vocabulary has been the subject of heated discussion among vocabulary researchers. Yet, current literature lacks research comparing different tasks to investigate the acquisition ...of vocabulary knowledge among adult learners of English as a foreign language (EFL). To fill the gap, we designed five task-based groups based on Technique Feature Analysis (TFA) as a framework to predict the effectiveness of different vocabulary learning tasks with similar or different TFA rankings on L2 vocabulary knowledge gain. The participants were 130 EFL learners (mean age = 21.7, female 61.5%) randomly assigned to the vocabulary learning tasks: reading and multiple-choice items (TFA = 6), reading and choosing definitions (TFA = 6), reading and fill-in-the-blanks (TFA = 7), reading and rewording the sentences (TFA = 6) and composition writing (TFA = 8). The results of the study revealed that tasks with the same TFA scores led to similar vocabulary knowledge gains. While predictions of the TFA are partially supported, composition writing and sentence rewording tasks supersede other tasks in terms of their effectiveness in vocabulary acquisition.
•An integrated approach of hydrochemical, isotopic, and cluster-based methods.•CA approaches including HCA, KM, FCM, and GKM clustering methods were deployed.•Well-developed karst system, low ...δ13C-DIC, depleted isotopic content (δ2H and δ18O)•Karst aquifer with meteoric water with high elevation precipitation origin.
In this work, a combination of isotopic and hydrogeochemical data of a karstic region was clustered with four distinct clustering analysis (CA) methods to study water evolution in a vulnerable karstic region to improve protection, sustainability, and enhanced water resource management. Four CA methods, including hierarchical cluster analysis (HCA), K-means (KM), and fuzzy logic CA methods, fuzzy C-mean (FCM), and genetic K‐means (GKM), have been utilized to analyze hydrochemical, chemical, and isotopic datasets, including dissolved inorganic carbon (DIC), δ13C-DIC, δ18O, and δ2H datasets of water resources of Paveh-Javanrud (PV-JR) karstic region, located at the western border of Iran and Iraq countries. The utilized dataset contains 34 water samples with varied origination to evaluate the performance of each model and find the best method based on a meaningful categorization of geological, hydrogeochemical, and isotopic characteristics. Finally, the best model results were matched graphically with developed geospatial graphs to visualize the correlation between the region's water resources. Accordingly, the FCM and GKM methods represent the same, yet meaningful results and have the best performance among the four methods. It was also identified that the PV-JR water resources could be generally categorized into five distinct clusters, including FC1 to FC5 and GK1 to GK5, of which two clusters that have mixing, two clusters with solo-origination and no sign of mixing, and finally, a seasonal spring which is categorized as a separate cluster. Potentially, studying water resources via theoretical methods combined with considering isotope hydrology is of particular interest since solving the environmental issues related to karstic regions and their water resource management are shared concerns in most arid and semi-arid countries, especially in the Middle East as this study, thus could lay a basis for the following scientific attempts involving hydrogeochemical studies and advanced statistical analysis.
In recent years, there has been a growing research interest in layout design optimization of satellite systems. The layout design optimization of a satellite system is a complex process having a ...large number of design variables and constraints. This paper presents a hybrid optimization algorithm, which globally explores the design search space using Particle Swarm Optimization (PSO) and gradient-based Sequential Quadratic Programming (SQP) to rapidly locate optimum design point. The majority of the previous research works mainly focused on finding reasonable placement of components in satellite layout design, with some specific requirements, which are essential for the satellite stability, control and performance such as attitude control, non-interference and overlap constraints. In this study, additional requirements such as structural stiffness and natural frequency constraints are also considered. The proposed approach is employed on a simplified international global communication satellite. The obtained results indicate that the consideration of natural frequency and attitude control constraints in the configuration layout design of a satellite system can significantly improve the stability and control of the satellite and thus frequency coupling between satellite and launcher can be prevented. In addition, the results indicate that the proposed method provides an effective way of solving layout design optimization problem of satellite systems.
This article looks at metaphor aptness from the perspective of the class-inclusion model of metaphor comprehension and those models that assume a componential nature for the meanings of concepts. ...When the metaphor X is a Y is processed, the concept of X is included in a metaphorical class that is represented by Y, which is usually the most typical member of the metaphorical class. Degree of saliency of the defining feature in the vehicle and the extent to which this feature matches a relevant dimension of topic is the key factor in the degree of aptness of the metaphor. Degree of aptness becomes more complex in those metaphors that describe an abstract concept in terms of another concept. These metaphors include X into a metaphorical class through the mediation of those concepts that are associated to the abstract concept. If the associated concepts have a high degree of typicality in the metaphorical class, they could be better mediators for including the abstract concept into the metaphorical class. The variations of abstract concepts across individuals and their dependency on contexts and cultures could explain why such metaphors may have different degrees of aptness for different people.
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