The effect of silver nanoparticles on composite shear bond strength to dentin with different adhesion protocols

In Dentistry, restorative materials and oral bacteria are believed to be responsible for restoration failure. To make long-lasting restorations, antibacterial agents should be made. Inorganic nanoparticles and their nano composites are applied as good antibacterial agents. Objective The purpose of this study was to investigate the effect of silver nanoparticles on composite shear bond strength using one etch and rinse and one self-etch adhesive systems. Material and Methods Silver nanoparticles were prepared. Transmission electron microscope and X-ray diffraction were used to characterize the structure of the particles. Nanoparticles were applied on exposed dentin and then different adhesives and composites were applied. All samples were tested by universal testing machine and shear bond strength was assesed. Results Particles with average diameter of about 20 nm and spherical shape were found. Moreover, it was shown that pretreatment by silver nanoparticles enhanced shear bond strength in both etch and rinse, and in self-etch adhesive systems (p≤0.05). Conclusions Considering the positive antibacterial effects of silver nanoparticles, using them is recommended in restorative dentistry. It seems that silver nanoparticles could have positive effects on bond strength of both etch-and-rinse and self-etch adhesive systems. The best results of silver nanoparticles have been achieved with Adper Single Bond and before acid etching

A 2-DOF microstructure-dependent model for the coupled torsion/bending instability of rotational nanoscanner

It has been well established that the physical performance of nanodevices might be affected by the microstructure. Herein, a two-degree-of-freedom model base on the modified couple stress theory is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nanoscanner. Effect of microstructure dependency on the instability parameters is determined as a function of the microstructure parameter, bending/torsion coupling ratio, van der Waals force parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the scanners especially those with long rotational beam elements. Impact of microstructure on instability voltage of the nanoscanner depends on coupling ratio and the conquering bending mode over torsion mode. This effect is more highlighted for higher values of coupling ratio. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nanoscanners. © 2016, Springer-Verlag Berlin Heidelberg

Modeling the effect of microstructure on the coupled torsion/bending instability of rotational nano-mirror in Casimir regime

t has been well-established that the physical performance of nano-devices might be affected by the microstructure. Herein, a 2-degree-of-freedom model based on the modified couple stress elasticity is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nano-electromechanical mirror. The governing equation of the mirror is derived incorporating the effects of electrostatic Coulomb and corrected Casimir forces with the consideration of the finite conductivity of interacting surfaces. Effect of microstructure-dependency on the instability parameters are determined as a function of the microstructure parameter, bending/torsion coupling ratio, vacuum fluctuation parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the mirrors especially those with long rotational beam elements. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nano-mirror

The size-dependent electromechanical instability of double-sided and paddle-type actuators in centrifugal and Casimir force fields

The present research is devoted to theoretical study of the pull-in performance of double-sided and paddle-type NEMS actuators fabricated from cylindrical nanowire operating in the Casimir regime and in the presence of the centrifugal force. D'Alembert's principle was used to transform the angular velocity into an equivalent static, centrifugal force. Using the couple stress theory, the constitutive equations of the actuators were derived. The equivalent boundary condition technique was applied to obtain the governing equation of the paddle-type actuator. Three distinct approaches, the Duan-Adomian Method (DAM), Finite Difference Method (FDM), and Lumped Parameter Model (LPM), were applied to solve the equation of motion of these two actuators. This study demonstrates the influence of various parameters, i.e., the Casimir force, geometric characteristics, and the angular speed, on the pull-in performance. (C) 2017 Sharif University of Technology. All rights reserved

Dynamic instability analysis of U-shaped electromechanical nano-sensor operated in vdW regime

U-shape nanoelectromechanical systems (NEMS) are potential for developing miniature sensors. While the electro-mechanical performance of conventional beam-type NEMS has been exclusively addressed in the literature, few works have considered this phenomenon in U-shaped systems. Herein, the static and dynamic pull-in instability of the U-shaped NEMS is investigated under the presence of vdW force. Based on the recently developed consistent couple stress theory (CCST), the size-dependent constitutive equation is derived. Two types of the beam cross-sections including rectangular and circular geometries are considered. The nonlinear equations are solved by employing Ray-leigh-Ritz solution method. The developed model is validated by comparison with the results presented in literature. The effect of various parameters on the static and dynamic pull-in parameters, phase plans and stability threshold of the system is discussed. The obtained results reveal that the vdW attraction decreases the pull-in voltage while the size dependency enhances the instability voltage. On the other hand, the presented model demonstrates that characteristics of the tip-plate can change the pull-in parameters significantly

The effect of organizational and extra-organizational factors on the empowerment of employees with the role of organizational learning moderator (Case of Study: Nezaja Artillery and Missile Training Center)

Objective: One of the most important tasks of human resources management in the army is to cultivate efficient and capable forces that can provide the defense needs of the country in the field of human resources according to the existing threats. In this sense, the quality of the trained forces in this organization, which indicates the proportionality of these resources with threats, is an important factor in determining the effectiveness of the organization. This study was conducted with the aim of investigating the effect of organizational and extra-organizational factors on employee empowerment, and the organizational learning variable played a moderating role in the causal relationship between organizational factors and empowerment.Method: The target population of this research includes all the employees of the Artillery and Missile Training Center of the Islamic Republic of Iran Army, 178 of whom were selected and studied through three questionnaire tools: organizational factors, organizational learning, and empowerment. For data analysis, descriptive correlation strategy and structural equation model were used with the help of SPSS and Smart PLs3 statistical software.Findings: Based on the findings, the variable of organizational learning strengthens the causal relationship between the variable of organizational factors and empowerment, which shows the importance of this variable in adjusting the relationship between organizational and external factors and empowering employees.Conclusion: The result of the research indicates the confirmation of the effect of organizational factors on empowerment and the rejection of the effect of non-organizational factors on the empowerment of the studied employees. Meanwhile, the moderator of organizational learning has strengthened the causal relationship between the two variables of organizational factors and empowerment, which shows the importance of this moderator in the process of improving employee empowerment. Has i

Effect of the centrifugal force on the electromechanical instability of U-shaped and double-sided sensors made of cylindrical nanowires

The U-shaped and double-sided nanostructures are promising for developing miniature angular speed sensors. While the electromechanical instability of conventional beam-type nanostructures has been extensively addressed in the literature, few researchers have investigated this phenomenon in the double-sided and U-shaped sensors. In this regard, the present work demonstrates the effect of the centrifugal force on the pull-in performance of the double-sided and U-shaped sensors fabricated from cylindrical nanowire and operated in the van der Waals (vdW) regime. Based on the modified couple stress theory, the size-dependent constitutive equations of the sensors are derived. The governing equations are solved by two different approaches, i.e. the analytic Duan–Adomian method and the numerical differential quadrature method. The influences of the vdW and centrifugal forces, geometric parameters and the size phenomenon on the pull-in parameters are demonstrated

Cell Adhesion Molecules and Cancer

Theodor Boveri in 1914 recognized the significance of changes in the adhesion of tumor cells to the development of cancer. Cell adhesion is essential in all aspects of in verte-brate cells such as cell growth, cell migration and cell differentiation. The majority of adhesion molecules fall into one of four families: cadherins, integrins, immunoglobulin superfamily (IgSF) and selectins. The cadherins are a family of homophilic CAMs (cell adhesion moleculs), Ca2+ dependent. The most important members of cadherins are E-cadherins (epithelial), P-cadherins (placental) and N-cadherins (neural). Immunoglobu-lin superfamily CAMs (IgSF CAMs) are either homophilic or heterophilic and bind in-tegrins, growth factor receptors cadherins or different IgSF CAMs. The integrins are a family of heterophilic CAMs that bind IgSF CAMs or the extracellular matrix. The se-lectins are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g. mu-cins. They are calcium-dependent. The three family members are E-selectin (endothelial (, L-selectin (leukocyte) and P-selectin (platelet). Recent experimental results indicate that, as well as mediating intercellular and cell–matrix interactions, cell-adhesion mole-cules also directly modulate signal transduction. Changes in the expression or function of cell-adhesion molecules can therefore contribute to tumor progression via altering the adhesion status of the cell or affecting cell signaling. The ability to colonize a specific organ has been correlated with the preferential adhesion of the cancer cells to endotheli-al cells derived from the target organ. This review summarizes recent findings about role of adhesion molecules in the tumor progression

Dynamic instability analysis of U-shaped electromechanical nano-sensor operated in vdW regime

U-shape nanoelectromechanical systems (NEMS) are potential for developing miniature sensors. While the electro-mechanical performance of conventional beam-type NEMS has been exclusively addressed in the literature, few works have considered this phenomenon in U-shaped systems. Herein, the static and dynamic pull-in instability of the U-shaped NEMS is investigated under the presence of vdW force. Based on the recently developed consistent couple stress theory (CCST), the size-dependent constitutive equation is derived. Two types of the beam cross-sections including rectangular and circular geometries are considered. The nonlinear equations are solved by employing Ray-leigh-Ritz solution method. The developed model is validated by comparison with the results presented in literature. The effect of various parameters on the static and dynamic pull-in parameters, phase plans and stability threshold of the system is discussed. The obtained results reveal that the vdW attraction decreases the pull-in voltage while the size dependency enhances the instability voltage. On the other hand, the presented model demonstrates that characteristics of the tip-plate can change the pull-in parameters significantly

Bone marrow-derived mesenchymal stem cell and simvastatin treatment leads to improved functional recovery and modified c-Fos expression levels in the brain following ischemic stroke

Objective(s): The beneficial outcomes of bone marrow-derived mesenchymal stem cell (BMSC) treatment on functional recovery following stroke has been well established. Furthermore, 5-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors have also been shown to increase neuronal survival and promote the movement of BMSCs towards the sites of inflammation. However, the precise mechanisms mediating the improved neurological functional recovery in stoke models following a combination treatment of Simvastatin and BMSCs still remained poorly understood. Materials and Methods: Here, an embolic stroke model was used to experimentally induce a focal ischemic brain injury by inserting a preformed clot into the middle cerebral artery (MCA). Following stroke, animals were treated either with an intraperitoneal injection of Simvastatin, an intravenous injection of 3 ×106 BMSCs, or a combination of these two treatments.Results: Seven days after ischemia, the combination of Simvastatin and BMSCs led to a significant increase in BMSC relocation, endogenous neurogenesis, arteriogenesis and astrocyte activation while also reducing neuronal damage when compared to BMSC treatment alone (PConclusion: These results further demonstrate the synergistic benefits of a combination treatment and help to improve our understanding of the underlying mechanisms mediating this beneficial effect